Dissertations and theses

 

Digital dissertations and theses from the University of Helsinki. Contains both open access theses as well as metadata records.

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  • Kontula, Keiju (Helsingin yliopisto, 2022)
    Bloodstream infections (BSI) are a major global health burden. Mortality of BSI has remained high despite advances in antimicrobial therapy and intensive care. A notable proportion, up to one third of BSI-associated deaths occur early, already within 2 days after the first positive blood culture specimen. Overall, limited population-based data are available regarding the incidence and outcome of BSIs, as well as the timing of death and factors related to early fatal outcome. The aims of the study were to analyze patient characteristics, causative pathogens, and accuracy of treatment of BSIs leading to early death and to assess the effect of comorbidity, underlying factors, and microbial etiology on the outcome and timing of death of both community-acquired BSIs (CA-BSI) and healthcare-associated BSIs (HA-BSI), and of nosocomial BSIs. In addition, nationwide temporal trends in the incidence, mortality and causative agents of BSIs were explored. For studies I, III and IV, BSIs were identified from the National Infectious Diseases Register. Data on death within 2 days (i.e., early death) and 1 month after the positive blood culture were gathered from the Population Information System (Studies I–IV). Study I included all patients with BSI residing in the Hospital District of Helsinki and Uusimaa in 2007 who died within 2 days of the blood culture specimen. Study II consisted of nosocomial BSIs reported by hospitals taking part in national surveillance in Finland during 1999–2014. Studies III and IV comprised all BSIs in Finland during 2004–2018. Data on the origin of BSI and patients’ underlying diseases were gathered from the National Hospital Discharge Register. In study I, Streptococcus pneumoniae (29%) and Escherichia coli (24%) were the most common causative microbes of CA-BSIs leading to early death, while Pseudomonas aeruginosa (24%) and Staphylococcus aureus (18%) among HA-BSIs. Initial antimicrobial treatment was more often inappropriate in HA-BSIs leading to early death compared to CA-BSIs (50% vs. 12%). Treatment delays tended to be longer in CA-BSIs. In total, 17,767 nosocomial BSIs were identified of which 3% were fatal within 2 days and 14% within 1 month (Study II). Of the fatal nosocomial BSIs, 23% led to early death. The patients who died early were older and their BSIs were more frequently caused by gram-negative bacteria (39% vs. 27%) and related to intensive care, as compared to those who were alive at 1 month. In study III, 173,715 BSIs were identified in the nationwide surveillance of BSIs during 2004–2018. The annual incidence rose from 150 to 309 BSI episodes/100,000 population, and the rise was most prominent in the elderly. The 1-month case fatality declined slightly, from 13.0% to 12.6%, while the all-cause mortality increased from 20 to 39 deaths/100,000. The proportion of E. coli BSIs of all BSIs rose from 26% to 30% and those caused by multidrug-resistant microbes from 0.4% to 2.8%, mostly due to a rise in extended-spectrum β-lactamase-producing E. coli. An increase from 67% to 78% was observed in the proportion of CA-BSIs and from 14% to 23% in patients with severe comorbidity. Of all BSIs, 13% were fatal within 1 month and of these fatal episodes, 28% occurred early (Study IV). The 2-day and 1-month case fatalities of HA-BSIs (5.4% and 21%) were higher compared to those of CA-BSIs (3.0% and 9.8%). Compared to BSI patients who were alive at day 3, those who died early were older and had more severe underlying comorbidities. Furthermore, BSIs leading to early death were more often polymicrobial (12% vs. 6.3%) and caused by P. aeruginosa (6.2% vs. 2.0%), fungi (2.9% vs. 1.4%) and multi-drug resistant (MDR) microbes (2.2% vs. 1.8%), compared to other BSIs. In conclusion, the incidence and mortality of BSIs increased considerably in Finland over time. Despite a rising proportion of aged and comorbid patients, the case fatality of BSIs did not increase possibly reflecting advancements in recognition and treatment of BSIs. The rising trend in CA-BSIs and in resistance of E. coli causes concern and calls for preventive measures and guidance of antimicrobial therapy. Nearly 30% of BSI-associated deaths occurred early. Polymicrobial, fungal, P. aeruginosa and MDR etiology were overrepresented among BSIs with early fatal outcome. These causative agents are a challenge for clinicians with respect to the choice of empiric antimicrobial regimen. The findings underline the importance of preventive interventions and prompt identification of infection and initiation of effective antimicrobial treatment according to the origin of infection and local resistance pattern.  
  • Maroni, Marta (Unigrafia, 2022)
    This dissertation looks at the right to access the Internet through a conceptual analysis, which considers the normativity of the Internet. It points out how the question of inclusion and exclusion is determined by the mediating power of internet technologies. Based on internet governance studies, this thesis moves beyond a techno deterministic understanding of access to the Internet (framed as access/non-access) and identifies major problematic trends transforming and shaping the use of the Internet. In particular, it focuses on the incremental centralization of the Internet into the hands of a few transnational private companies, and as a result, how these actors are in a position to determine not only what is accessible or not, but also our societal values. Further, the dissertation underscores how none of these private actors operates in a lawless way and it traces back how the legal system has been constitutive of the abovementioned dynamics and is at the same time being transformed by them. By applying systems theory, this dissertation argues that the right to access the Internet should be understood as based on an organizational principle for the Internet aiming to maintain equal access and a diverse and plural ecosystem. Different facets of access to the Internet are discussed and analysed in three case studies: ICANN, network neutrality, and platform content moderation. Each case uncovers constitutional problems relating to the practices and procedures of different private companies. While recognizing these actors as new constitutional subjects, this dissertation questions the vocabulary of digital constitutionalism when conceived merely as a way of reacting to and limiting the power of private companies. Building on the sociology of constitutions, this dissertation looks at the institutive and legitimizing function of constitutions and examines the question of which and whose order is being constituted while promoting the language of constitutionalism. Methodologically, the dissertation uniquely combines systems theory, legal analysis, transnational constitutionalism, media theories, science and technology studies and brings to light democratic problems arising from the interplay between law and internet technologies. The thesis thus sets up a theoretical background for further research on internet regulation and related constitutional issues.
  • Pakarinen, Emmi (Helsingin yliopisto, 2022)
    Protein homeostasis is essential for the whole cell function. Therefore, cells monitor protein synthesis, folding, and degradation closely. Disturbances in secretory and membrane protein folding can cause accumulation of misfolded and unfolded proteins in the endoplasmic reticulum (ER). This condition, called ER stress, can predispose for manifestation of various diseases including neurodegenerative diseases such as Parkinson’s disease. Cells activate the unfolded protein response (UPR) to alleviate ER stress and restore homeostasis. Members of a novel neurotrophic factor family, cerebral dopamine neurotrophic factor (CDNF) and mesencephalic astrocyte-derived neurotrophic factor (MANF), are components of the UPR machinery. They are small proteins widely expressed in mammalian tissues and mostly localized to the ER lumen. CDNF and MANF can reduce ER stress with a mechanism that is not fully understood. In addition, they also promote survival of neuronal and non-neuronal cells in different animal disease models. In animal models of Parkinson’s disease, they both protect and even restore the function of midbrain dopamine neurons. However, the involvement of endogenous CDNF and MANF in the maintenance and regulation of dopamine neurons in mice is not known. The aim of this thesis was to examine the role of endogenous CDNF and MANF deletion in UPR regulation in vivo. We also aimed to investigate the role of their deficiency in the maintenance and function of midbrain dopamine neurons as knockdown of MANF results in changes in the dopamine system in fruit fly and zebrafish. In this thesis, we characterized CDNF and MANF knockout mice and analyzed their UPR gene expression and the midbrain dopamine system by gene expression analyses, immunohistochemical methods, and behavioral tests. Compensation between CDNF and MANF was investigated in the third study where we developed and characterized mice lacking both CDNF and MANF. This study demonstrates that MANF ablation causes an increase in UPR gene expression in the developing, adult, and aged brain in vivo and in cortical neurons in vitro. In particular, the inositol-requiring enzyme 1 α (IRE1α) pathway of UPR is persistently activated in the MANF-deficient brain. CDNF ablation, instead, induces UPR gene upregulation in the skeletal muscle, which is aggravated by MANF ablation. This indicates that MANF can functionally compensate for CDNF. We show that vice versa, CDNF cannot compensate for MANF function in the tissues studied. Furthermore, this thesis addresses the role of CDNF and MANF in the function and maintenance of the midbrain dopamine system. We investigated the integrity of dopamine fibers and dopamine neurons in aged mice lacking CDNF, MANF, or both. Furthermore, motor behavior of these mice was investigated to measure the function of the dopamine system. Our data indicated that these mice did not show degeneration of the midbrain dopamine system upon aging although CDNF-deficient mice display functional changes in dopamine neurons. In conclusion, this thesis work elucidates the importance of CDNF and MANF in regulating the UPR with tissue specificity in vivo. In addition, we provide data about the role of endogenous CDNF and MANF in the maturation and maintenance of the midbrain dopamine system.  
  • Niemi, Riitta (Helsingin yliopisto, 2022)
    The nonlactating period is a critically important time for dairy cow health and optimal subsequent milk yield. Regarding udder health, at the beginning and end of this period, cows are most susceptible to new intramammary infections. In addition, dry-off is also the optimal time to cure any existing mammary-gland infections. Hence, intramammary-infused antibiotic dry cow therapy (DCT) after final milking is an important and widely used mastitis control measure. DCT can be administered either to all quarters of all cows or only to infected cows or quarters. The global antibiotic resistance problem causes an increasing need to reduce antibiotic use in livestock, but a shift in management should not harm animal welfare or impair farm profitability. Although selective treatment of only infected cows is a more sustainable approach, accurate and cost-effective identification of cows or quarters in need of medication is a challenge. The objective of this epidemiologic study was to determine ideal drying-off practices to maintain good udder health and productivity while implementing prudent use of antibiotics. The specific focus of interest was on DCT, and an additional aim was to examine risk factors for post-calving udder health problems and reduced milk yield. The three cohort studies comprised retrospective herd- and cow-level dairy-herd-recording data registered from conventional, commercial Finnish dairy farms. The first study evaluated herd-level associations between milk somatic cell count (SCC), milk yield, and various farm characteristics, with an emphasis on antibiotic usage at dry-off. The second study investigated whether the herd-level DCT practice was associated with cow-level udder health in early lactation. The third study determined cow-level milk yield and SCC differences within the first half of lactation between selectively DCT-treated and -untreated cows. Results show that herd-level selective-DCT strategy, even with a very moderate proportion of medicated cows, is no hindrance to maintenance of low herd-average SCC and good milk yield. Regardless of the farm’s DCT practice, average milk yield increased over time, while average SCC remained rather constant. However, the large variation between farms in average yield and SCC over DCT practices suggests the need for farm-specific protocols. The practice of treating all cows in a herd was associated with lower test-day SCC within early lactation compared with the selective-DCT practice. Moreover, a DCT-treated cow on a selective-DCT farm had lower SCC after calving than did an untreated cow. This indicates that DCT continues to be an effective mastitis control practice. Most selective-DCT farms administered DCT to only one-third of their cows, or less. The DCT effect on milk yield differed depending on late-lactation SCC, so that a higher SCC near dry-off led to an increased difference in yield between treated and untreated cows within the first half of lactation. A missed DCT for a high-SCC cow thus had an adverse effect on subsequent lactation milk yield and on SCC, highlighting the need for accurate selection of cows to be treated. Risk factors associated with higher post-calving SCC included high late-lactation SCC, lactational mastitis treatment, high parity, high preceding-lactation average SCC, and high milk yield near dry-off. Rising awareness of the selective-DCT approach currently is emerging in those countries where it is common to treat all cows at the end of lactation. The successful implementation of selective DCT on Finnish farms will hopefully encourage these countries to gradually reduce antibiotic use in dairy livestock. Such a development would perhaps have a positive effect on consumer confidence in the dairy industry. On Finnish dairy farms, rapid structural change in agriculture continues, and therefore maintaining the current low consumption of antibiotics requires optimal farm management, professional advice, and active monitoring.
  • Laaksonen, Topi (Helsingin yliopisto, 2022)
    Distal radial metaphysis is the most common fracture location in children. Fracture morphology varies from stable incomplete torus fractures to complete fractures with different degrees of angulation and shortening. Completely displaced fractures in an overriding position represent the end of the spectrum and reduction of these fractures have been traditionally recommended. Pin fixation has been advocated, because retaining satisfactory fracture alignment with a cast has been proven difficult. On the other hand, it has been suggested that distal metaphyseal radial fractures in an overriding position (DMRFOP) in children under 10 years of age could be treated without reduction. The first aim was to calculate the incidence of DMRFOP in children under 16 years of age in Helsinki, and to assess retrospectively the overall management and quality of treatment of DMRFOP in New Children’s Hospital. The second aim was to outline the current treatment praxis of DMRFOP in patients under 10 years of age. The third aim was to find out retrospectively whether treatment of DMRFOP in a cast without reduction had obtained results similar to the reduction and pin fixation in prepubertal children and the fourth aim was to design a randomized controlled trial (RCT) comparing casting and percutaneous pin fixation of DMRFOP in children under 11 years of age. A total of 113 DMRFOPs in patients during 2014–19 were gathered from Kids’ Fracture Tool, Helsinki. Of these 113 children, 81 were residents of Helsinki. Prescribed treatment, outcome, and adverse events were recorded from the patients’ files. Fracture morphology of both radius and ulna were registered. Guardians of 100/112 patients replied to a telephone survey to assess their satisfaction to the prescribed treatment. The SurveyMonkey™ website was used as a platform for the survey for surgeons treating fractures in the children. The questionnaire included radiographs of three different DMRFOPs in children under the age of 10. Through multiple-choice questions, respondents (213) were asked to choose their preferred treatment and follow-up protocol. The outcomes of 12/13 children, whose DMRFOPs were treated at our institution during 2015–17 by cast immobilization, leaving the fractures in bayonet position, were assessed at 2–4 years from the fracture. Twelve age-matched children, whose DMRFOPs were reduced, and pin fixed, were chosen as controls. A noninferiority RCT comparing casting in finger-trap traction without reduction in the emergency department (ED) with the reduction and pin fixation under anesthesia in the treatment of DMRFOP, in children under 11 years of age, was designed. The mean annual incidence of DMRFOP in the pediatric census population in Helsinki was 1.42/10.000 in 2014–19. Most (73%) DMRFOPs were sustained by children under the age of 11. Reduction in the ED failed in nearly half (46%) of the cases and the rate of secondary intervention was high (56%). Impaired function at follow-up was reported by 6% of the guardians, and forearm asymmetry by 11%. Overall satisfaction to the given treatment was 6.2 on a scale from 1 to 7. The vast majority (176/213, 83%) of respondents to the web-based survey chose reduction for treatment, whereas 2% chose casting in overriding position in all three presented cases. Pin fixation would have been performed by half (49%) of the surgeons who preferred reduction. There was no consensus regarding treatment and follow-up. None of the 24 patients in the case control study had visible deformity at follow-up. Forearm and wrist range of motion (ROM) showed no differences between the method of treatment in both injured and uninjured sides, with mean ratios varying between 0.98 and 1.02. All 24 patients had returned to their preinjury activities. Of the 12 surgically treated children, one developed a superficial pin-track infection, and another had a corrective osteotomy. DMRFOPs are rare, and most of them are sustained by children under 11 years of age. Reduction in the ED is difficult, but functional and cosmetic outcome is generally satisfactory regardless of the treatment method. Treatment of DMRFOP in prepubertal children with reduction and pin fixation does not appear superior to cast immobilization without reduction, although most surgeons still prefer to reduce DMRFOP. A randomized controlled trial, between reduction and pin fixation and the casting treatment, is warranted to verify the results of these studies.
  • Kemp, Kirsi (Helsingin yliopisto, 2022)
    The purpose of acuity assessment, or triage, in the emergency department (ED) is to recognize critically ill patients and to allocate resources according to need. Evidence of validity regarding currently used triage instruments is limited, especially regarding older adults. With a rapidly ageing population and crowded ED’s, more precise acuity assessment instruments for older ED patients are needed. The main objective of this thesis was to assess the accuracy of the Emergency Severity Index (ESI) for older adults and to see if it can be improved by age adjustment. The secondary objectives were to explore the associations of an early warning score and local three level triage instrument with outcomes for older ED patients and to summarize and review current knowledge regarding patients presenting to the ED with nonspecific complaints. Study I compares the accuracy of the ESI for adults under 65 and 65 years or over in a Finnish ED. Results suggest that the ESI is associated with high dependency unit/intensive care unit (HDU/ICU) admission and 3-day mortality for older ED patients. Study II explores the effect of age adjustment on two triage methods for patients presenting in three Finnish ED’s. According to the results, age adjustment improves accuracy in predicting 30-day mortality and hospital admission. Study III assesses the accuracy of an early warning score (NEWS2) and a local three-level triage methods for frail older ED patients. Both methods were poor to moderate in predicting ED outcomes for older adults. Study IV is a systematic review and meta-analysis of patients presenting to the ED with nonspecific complaints. These patients have a higher in-hospital mortality rate, and their care require more time and resources than patients presenting with a specific complaint (SC). Yet NSC patients are triaged less often as urgent than SC patients. In conclusion, the ESI seems to be sufficiently accurate in our population in all age groups. Its predictive performance was superior to our local three-level method. Age adjustment improved the performance of both tools without excessive overtriage. These findings indicate that the ESI can be used in our population, including for older adults, to improve standards of acuity assessment. Patients presenting to the ED with an NSC have a higher risk of mortality and their care requires more time and resources than patients presenting with an SC. Increasing awareness and knowledge about this common syndrome can be utilized when creating treatment protocols and patient pathways for these patients.
  • Ramezanian, Sara (Helsingin yliopisto, 2022)
    Digital technologies have become an essential part of our lives. In many parts of the world, activities such as socializing, providing health care, leisure and education are entirely or partially relying on the internet. Moreover, the COVID-19 world pandemic has also contributed significantly to our dependency on the on-line world. While the advancement of the internet brings many advantages, there are also disadvantages such as potential loss of privacy and security. While the users enjoy surfing on the web, service providers may collect a variety of information about their users, such as the users’ location, gender, and religion. Moreover, the attackers may try to violate the users’ security, for example, by infecting the users’ devices with malware. In this PhD dissertation, to provide means to protect networking we propose several privacy-preserving protocols. Our protocols empower internet users to get a variety of services, while at the same time ensuring users’ privacy and security in the digital world. In other words, we design our protocols such that the users only share the amount of information with the service providers that is absolutely necessary to gain the service. Moreover, our protocols only add minimal additional time and communication costs, while leveraging cryptographic schemes to ensure users’ privacy and security. The dissertation contains two main themes of protocols: privacy-preserving set operations and privacy-preserving graph queries. These protocols can be applied to a variety of application areas. We delve deeper into three application areas: privacy-preserving technologies for malware protection, protection of remote access, and protecting minors.
  • Lehtoranta, Suvi (Helsingin yliopisto, 2022)
    Due to the growing need for phosphorus and nitrogen in food production, more attention needs to be paid for the efficient recovery and safe recycling of wastewater nutrients and organic matter back to agriculture. Source separation of household wastewaters has emerged as an efficient way to recover these nutrients. This can be accomplished by collecting and treating nutrient-rich and nutrient-poor wastewater separately. The nutrients can be recovered in a plant-available form without being mixed with harmful substances from sources other than toilet water. In addition, nutrient recovery is technically easier when the nutrients are undiluted and thus present in higher concentrations. The objective of this dissertation was to analyze the life cycle environmental impacts, advantages and drawbacks, of wastewater management to improve nutrient recovery by source separation in urban, peri-urban and rural areas. Moreover, the limitations of life cycle assessment (LCA) in assessing the environmental impacts of nutrient recovery and recycling were analyzed. The results indicate a substantial increase in the nutrient recovery potential with source separation of wastewaters in urban, peri-urban and rural areas compared to conventional wastewater treatment systems. In urban areas, the source separation of wastewater would allow up to ten times higher nitrogen recovery compared to the conventional system. In rural areas, the source separation of wastewater would bring even greater benefits. Phosphorus recovery could be improved 3-5 times and nitrogen recovery over 30 times. Moreover, improved recovery and recycling of nutrients by source separation would reduce the climate impact of wastewater treatment in urban areas by about half, but the climate impact in rural areas would remain at the same level. Source separation of wastewater would also reduce eutrophication of water bodies, especially in rural areas. Instead, acidifying emissions may increase. However, the actual environmental benefits of improved nutrient recovery and recycling require the realization of avoided emissions, which rely strongly on the decisions made in the planning and design of the system and on the policies and decisions made in the society. LCA offers a good tool to support planning, decision making, and policy related to nutrient recycling. However, the LCA methodology still needs further development and accepted rules to take into account the impacts of carbon content of organic matter in recycled nutrients. Tackling the inefficiencies of nutrient recovery and recycling promotes the transition towards circular economy and carbon neutrality in wastewater management. Source separation of wastewaters offers one way to accomplish these. Source separation allows for more efficient nutrient recycling and supports the self-sufficiency of fertilizers. This requires that the nutrients are recovered and processed into safe end products. To realize the nutrient potential and environmental benefits of the agricultural use of wastewater-based nutrients, policy support and careful planning from a life-cycle perspective are needed.
  • Kanto, Kari (Helsingin yliopisto, 2022)
    Background: Subacromial pain syndrome (SAPS) is the most common diagnosis among patients with atraumatic shoulder pain. The pain experienced while lifting the arm has been attributed to mechanical impingement of the rotator cuff (RC) tendons between the humeral head and the undersurface of the acromion. On the basis of this rationale, arthroscopic subacromial decompression (ASD), the most commonly performed shoulder surgery, is believed to decompress tendon passage through the subacromial space and consequently, relieve symptoms. Aims: The aim of this thesis was to assess the efficacy of ASD in patients with SAPS. The second aim of this thesis was to determine the minimal important differences (MIDs) and patient acceptable symptom state (PASS) for the outcomes used in this trial. We also estimated the annual rate of ASD surgeries in Finland between 1997-2020. Methods: This thesis is based on the FIMPACT trial, a multicentre, three-group, randomised, double-blind, placebo-surgery controlled trial that assessed the efficacy of ASD by comparing it with diagnostic arthroscopy (DA; a placebo surgical intervention) and with a non-operative alternative (exercise therapy; ET) in a more pragmatic setting. We enrolled 210 patients aged 35 to 65 years with clinical findings consistent with SAPS that was deemed unresponsive to non-operative treatment. Participants were randomly allocated to ASD, DA (placebo control), or ET. The two primary outcomes were shoulder pain at rest and on arm activity. Patient outcomes were assessed at 24 months and 5 years after randomisation. We used 2-year follow-up data from the FIMPACT trial to estimate MID and PASS for the outcomes used in this trial. The ASD rate was estimated from reliable nationwide data and the study population was the entire population of Finland. Results: The patients assigned to ASD had no clinically relevant improvement over those assigned to DA at either 24 months or 5 years after randomisation. In the secondary comparison between ASD and ET groups, the ASD group was not superior to ET. Conclusions: The results presented here indicate that ASD provides no clinically relevant benefit over placebo surgery (or exercise therapy) in patients with SAPS. The findings do not support the current practice of performing subacromial decompression in patients with subacromial pain.
  • Lähde, Marianne (Helsingin yliopisto, 2022)
    Colorectal cancer (CRC) is the third leading diagnosed malignancy and the fourth most common cause of cancer-related mortality globally. CRC burden has been expected to increase by 60% within the next decade. Up to every third of the patients die from the disease despite the improvements in the CRC therapy. However, knowledge gained in understanding the molecular subtypes of the CRC has improved the ability to target CRC treatment strategies and to predict the treatment outcomes. Aberrant activation of the Wnt//B-catenin pathway drives intestinal tumorigenesis, often as a result of loss-of-function mutation of the tumor suppressor adenomatous polyposis coli (APC) gene. APC inactivation leads to disrupted proteasomal degradation of cytoplasmic B-catenin, which accumulates in the cytoplasm. This leads to dislocation of B-catenin into the nucleus, where it binds to transcription factors of the TCF/LEF family and initiates the transcription of target genes related to augmented cell cycle and tumorigenesis, such as Prospero homeobox protein 1 (PROX1), which has been shown to induce dysplasia and an invasive phenotype in CRC. R-spondins (RSPO1-3) are ligands that bind to leucine-rich G-protein-coupled receptors (LGR4-6) that promote Wnt signaling. Most of the RSPOs enhance the growth of intestinal stem cells (ISCs) in healthy mice. Furthermore, RSPO gene fusions were recently identified in human (h)CRC. Thus, inhibition of RSPOs was considered to suppress intestinal tumorigenesis. However, a recent report suggested that RSPO2 expression level negatively correlates with intestinal tumor cell differentiation, size, and metastasis. RSPO2 expression was also downregulated via promoter hypermethylation in hCRC, suggesting that RSPO2 would have a tumor-suppressive role in hCRC. One study suggested that LGR5 could enhance transforming growth factor B (TGFB)/SMAD signaling pathway upon RSPO1 stimulation in two tested hCRC cell lines. In general, the role of TGFB/SMAD signaling in CRC is exceptionally complex, as it can turn from tumor suppressive to pro-metastatic throughout the progression of adenomas to carcinomas. Thus, the role of RSPO in intestinal tumorigenesis remains controversial. I was interested in analyzing if exogenous Wnt-signals, especially RSPO1, could affect PROX1 expression induced by B-catenin activation in the early phase of intestinal tumorigenesis. For this analysis, we generated adeno-associated virus vectors (AAV) to induce systemic RSPO1 expression in mice. I then used Apc-deficient ApcMin/+ mice to investigate the effect of exogenous RSPO1 on intestinal adenomas, and surprisingly found that instead of enhancing intestinal tumorigenesis, RSPO1 functions as a suppressor of Wnt/-catenin signaling in Apc mutant adenoma cells and concomitantly activates the TGFB/SMAD signaling pathway, leading to apoptosis and growth inhibition of the adenoma cells. Thus, RSPO1 treatment leads to regression of intestinal adenomas in the ApcMin/+ mice, resulting in significantly increased survival of the mice. My thesis provides a novel insight into the regulation of intestinal stem cells in intestinal adenomas. Our data reveal a dual role of RSPO1 in modulating Wnt signaling, proliferation, and apoptosis in the intestinal stem cells. Furthermore, RSPO1 regulates the competition equilibrium between healthy intestinal stem cells and Apc-mutated tumor stem cells. These findings revise and expand our knowledge on the signaling pathways that regulate tumor progression and they could provide possibilities for the development of novel cancer treatment strategies.
  • Barmaki, Samineh (Helsingin yliopisto, 2022)
    The decreased oxygen availability activates the cells' hypoxia- inducible factor (HIF) pathway. HIF is a critical mediator of physiological responses in acute and chronic hypoxia. Conventional hypoxia chambers, which are widely employed to study hypoxia, are cumbersome and require large gas supply volumes. The high diffusivity of gases makes it impossible to control the local gaseous microenvironments in hypoxia chambers. In this study, microfluidic chips were utilized to create oxygen gradients in nano and micro scales to act as gaseous microenvironments for cell cultures. It was observed that by pumping an oxygen scavenger solution in the microfluidic channels, the hypoxia response increased in the adherent cells on the microchip system. A simultaneous cellular gaseous microenvironment for hypoxia and nitric oxide was created by utilizing a microfluidic channel architecture with two sets of microchannels. One of the channels was filled with the oxygen scavenger solution and the other with a nitric oxide donor (sodium nitroprusside, SNP). The channels then guided these treatments to selected areas of the cell culture. We showed that microfluidics could target the specific region in the chip and modify microenvironmental gases in the cells. At the same time, the other cultural area remained unchanged. A simultaneous cellular response to hypoxia and nitric oxide was obtained after 100 min pumping with a flowrate of 1.6 μl/min. Preeclampsia (PE) is a pregnancy disorder where hypoxia plays a crucial role in the pathophysiology. To mimic a preeclampsia (PE) microenvironment, an oxygen scavenger solution was pumped through the microfluidic channels of a Myogel-coated microchip on which JEG-3 choriocarcinoma cells were cultured as a human trophoblast model for 24h. RNAseq data of the cells from the microchip showed gene expression differences and pathways that were affected by hypoxia; among those were MYC targets, E2F targets, G2-M checkpoint, and the unfolded protein response. Based on our data, the hypoxia created by the microchip caused significant transcriptional changes in JEG-3 cells.
  • Zini, Jacopo (Helsingin yliopisto, 2022)
    Biopharmaceutical products are composed of complex or ordinate combinations of proteins, lipids, sugars, and nucleic acids or living cells or tissues. Due to the intrinsic variability of biological systems and the complexity of the bioprocesses involved in the production of these products, new technologies are required to monitor and characterize, the production processes and the final products. Biophotonic techniques, particularly Raman and Infrared (IR) spectroscopy are rapid, robust, operator independent, non-destructive and label free, thus particularly suitable for these purposes. This dissertation first investigates the use of biophotonic techniques in research of Extracellular Vesicles (EVs). EVs act as intercellular messengers and therefore have considerable potential in drug delivery system, diagnostic biomarker, or therapeutic agent. Subsequently highlighting the need and potential of a new kind of time gated Raman spectrometer to be created. Raman and IR spectroscopy are methods able to characterize and assess the quality of EV suspensions with different degree of purity. These vibrational spectroscopic techniques show different intrinsic advantages, as they are label free and operator independent methods. Particularly, Raman might be the most suitable technology since it is less sensitive to water compared to IR. Raman spectroscopy reveals the information on the chemical composition and physical status of the analyte. However, it does not provide information of the analyte environment which the spectrofluorometer can gather. EVs studied by spectrofluorometer are required to be labelled with a fluorescent dye. Results obtained by fluorescence lifetime imaging spectroscopy underline that the cell uptake of the fluorescently labelled EVs is feasible. Attention must be paid to the efficacy of the labelling and further to the elimination of the unbound dye since the labelling may severely compromise the results or lead to wrong conclusions on EV functionality. The combined advantage of Raman spectroscopy and fluorescence decay are obtained by a previously in-house developed time resolved Raman spectrometer. Thanks to the peculiar sensor of the spectrometer, the width of the time gate can be modified which is used to separate the Raman signal from the fluorescence tail. The modifications can be done even in the data post-processing phase, to obtain the best possible Raman signal-to-noise ratios. The simultaneously detected Raman spectra and time-resolved fluorescence decay curves are used to study the diffusion of small molecular drugs in a hydrogel. The data reveal the chemical composition, physical status, and the interaction with the environment of the samples. Taken together the obtained results suggest that the quality of EV suspensions can be assessed by Raman spectroscopy and their cell uptake detected by fluorescence lifetime spectroscopy. Both Raman spectra and fluorescence decay can be measured simultaneously by a second generation of time-resolved Raman spectrometer.
  • Enroth, Joonas (Helsingin yliopisto, 2022)
    The urban atmosphere is affected by many pollution sources, such as traffic, residential wood combustion and various industrial activities. The spatial accumulation of pollution sources in urban areas results typically in high local concentrations of both gaseous and particle pollution. The meteorological condition prevalent during wintertime are likely to increase the concentrations, due to higher heating needs and lesser atmospheric mixing. In turn this means higher human exposure to aerosol particles, and increased health concerns. The particles produced from the ubiquitous pollution sources of the urban areas have two-fold effects. First, they affect the global climate and local weather conditions, and second, they have significant health impacts, and reduce the average lifetime of the exposed human population. Therefore, it is important to study the urban area and its pollution sources and ensure that we have the tools needed to carry out this research. The urban environment is highly transient, with strong temporal and spatial variations in the aerosol particle concentration. Aerosol particles are emitted among other sources from combustion processes. These processes release both particles directly and indirectly, as precursor gases that can later form large numbers of the minutest of particles in the air. In this thesis I study the properties of urban air quality during wintertime, with a special focus on the aerosol component, and more specifically the counting and sizing technology. The first portion of the thesis describes our finding regarding the urban atmosphere in two European cities, Helsinki and Budapest. In Helsinki we present findings of the different sources of pollution including strong regional sources, such as long-range transport as well as localized sources, like residential wood combustion and highways. We also describe how the pollutants disperse rapidly from local highways to background concentrations and attempt to quantify some of the traffic emissions. In Budapest we show how the local particle population consists of two distinct modes: one corresponding to non-hygroscopic fresh traffic emissions, and the other to more aged aerosol with both higher hygroscopicity and volatility. The latter part of the thesis discusses the state of current particle counting and sizing technology. The particle population in urban areas, tends to evolve rapidly, exhibit high particle number concentrations, and comprises of extremely small particles. To meet these measurement needs, we present the time response characterization of numerous commercial particle counters and discuss the metrology of response time measurement. We go on to compare some of the novel sub-3 nm particle counters developed in recent years and their properties, and finally describe the development and field testing of a purpose-built particle sizer for the sub-10 nm size range. Our findings show how in the sub-3 nm size range, the particle composition can influence the detection efficiency of condensation particle counters.
  • Toijonen, Anna (Helsingin yliopisto, 2022)
    Approximately 5% of neonates are born preterm in Finland, and 20% of these are in breech presentation at the time of birth. Thesis included register linkage studies that examined the predictors for preterm breech presentation and the safety of preterm breech labor in 2004–2018 in Finland. The study demonstrated that the number of predisposing factors for breech presentation increase with increasing gestational age. Some of the predisposing factors for breech presentation are already noticeable at 28–32 weeks, such as maternal preeclampsia / high blood pressure, preterm premature rupture of membranes, and fetal growth restriction. The predisposing factors for breech presentation in late preterm were advanced maternal age, primiparity, a history of a cesarean section, preterm premature rupture of membranes, oligohydramnios, fetal growth restriction, female sex, and congenital anomaly. The risk factors for neonatal morbidity and mortality in vaginal preterm breech labor were assessed. Neonatal morbidity in a trial of vaginal preterm breech labor associated with maternal obesity, smoking, congenital anomalies, preterm premature rupture of membranes, oligohydramnios, and fetal growth restriction. Third study evaluated whether vaginal breech labor at 32 – 37 weeks is associated with an increased risk of short-term neonatal morbidity or mortality compared to cesarean section. Severe neonatal adverse outcomes (neonatal death, an arterial umbilical pH < 7.00, 5 min Apgar < 4) were not increased after vaginal breech labor. Still, the risk of having a 5 min Apgar < 7 was higher among fetuses with vaginal breech labor than fetuses born by cesarean section. The need for neonatal antibiotic therapy, neonatal intensive care unit, and neonatal respiratory distress syndrome were decreased after vaginal breech labor compared to non-urgent cesarean sections. Lastly, the impact of fetal presentation on neurodevelopmental outcomes in a trial of preterm vaginal labor was examined. The incidences of cerebral palsy, epilepsy, intellectual disability, autism spectrum disorder, attention-deficit/hyperactivity disorder, and speech, visual, and auditory disabilities were evaluated at the age of four years according to the fetal presentation at the time of delivery. No association between a trial of vaginal breech delivery at 24– 32 weeks and neurodevelopmental delay was found. Yet, the risks of visual defects and autism spectrum disorders were higher after late preterm breech labor than among controls who were born in a cephalic presentation. The findings demonstrate that previous results on term breech deliveries could not be fully applied to preterm breech deliveries.
  • Kytöjoki, Samu (Helsingin Yliopisto, 2022)
    Testataan väitöskirjojen riiputusta.
  • Tang, Zhipeng (Helsingin yliopisto, 2022)
    Gap-filling is an important preprocessing step in remote sensing applications because it enables successful sensor-based studies by greatly recovering the Earth’s surface records lost due to sensor failures and cloud cover. To date, a great number of methods have been proposed to reconstruct missing data in remote sensing images, but methods that deliver satisfactory performance in handling large-area gaps over heterogeneous landscapes are scant. To address this problem, this thesis proposes two methods—Missing Observations Prediction based on Spectral-Temporal Metrics (MOPSTM) and Spectral and Temporal Information for Missing Data Reconstruction (STIMDR)—that are capable of recovering small and large-area gaps in Landsat time series. Machine learning algorithms are used to implement MOPSTM and STIMDR. MOPSTM applies the k-Nearest Neighbors (k-NN) regression to the target image (i.e. image that is to be reconstructed) and spectral-temporal metrics (STMs, e.g. statistical quantiles) derived from a 1-year Landsat time series. Improved from MOPSTM, STIMDR achieves more powerful performance by employing an effective mechanic that excludes dissimilar data in a longer time series (e.g., changes in land cover). The proposed methods are compared site-to-site with six state-of-the-art gap-filling methods including three temporal interpolation methods and three hybrid methods. With higher accuracy in four study sites located in Kenya, Finland, Germany, and China, MOPSTM and STIMDR have indicated more robust performance than other methods, with STIMDR yielding higher accuracy than MOPSTM. Although gap-filling methods are proposed with increasing frequency, their necessity and effects are rarely evaluated, so this has become an unsolved research gap. This thesis addresses this research gap using land use and land cover (LULC) classification and tree canopy cover (TCC) modelling with the assistance of machine learning algorithms. Random forest algorithm is used to examine whether gap-filled images outperform non-gap-filled (or actual) images in LULC and TCC applications. The results indicate that (i) gap-filled images achieve no worse performance in LULC classification than the actual image, and (ii) gap-filled predictors derived from the Landsat time series deliver better performance on average than non-gap-filled predictors in TCC modelling. Therefore, we conclude that gap-filling has positive effects on LULC classification and TCC modelling, which justifies its inclusion in image preprocessing workflows.
  • Frestadius, Tero (Helsingin yliopisto, 2022)
    The research examines the legacy of segregation at the center of urban America in 2017. It looks at artistic images on walls and in galleries to explore how people maneuver with difference in the segregated urban landscape of Los Angeles now forecast to vanish. The research asks, how did the open-ended processes of art – especially public art – work in the hierarchical spatial order where past housing policies appeared to assure that a given territory came with a population and a culture attached? The answer is a dense and detailed ethnography of engagements around public art in long-marginalized neighborhoods that were self-consciously preparing for the impending change brought by the expansion of public transit and the growth of Downtown. Following the people fighting for fair housing in Los Angeles the study asserts that gentrification in the city was firmly anchored in the unequal segregated urban geography created by racist housing policies. But why were people in opposite ends of the spatial hierarchy rallying for the preservation of the compartmentalized landscape and why had art and culture emerged in some neighborhoods as means of claiming ownership to places and branding them into cultural districts? To make sense of this tangle of culture, designated territories, home ownership, family relations, and racialized categories the study visits the distinction drawn by Marilyn Strathern (2011) between manners of understanding relations by resemblance or by structure. Were peoples’ perspectives in the transforming city based on relations of similarity perceived from outside or did points of view emerge from the relational contexts people occupied? The question resonated with the paradoxical capacity of art to simultaneously give tangible form to social formations and to offer its audience and makers an intimate means for self-reflection and change (Mazzarella 2004). The research examines these issues in practice through detailed ethnographic description. It helps to understand social complexities in a place where built-in spatial divisions coexisted with more open-ended experiences and understandings of urbanity. Sensitive to the divergent social worlds and logics at play the research colors in the gray area between well-known discussions around identity, space, race, representation, gentrification, and writing culture and it does so by means of conventional urban ethnography.
  • Uusitalo, Ruut (Helsingin yliopisto, 2022)
    Emerging vector-borne infectious diseases pose one of the most significant global threats to human health. The outbreaks and burden of vector-borne infectious diseases are estimated to rise in the face of climate warming. Many emerging infectious diseases, such as COVID-19 and Ebola virus disease, are zoonoses; diseases caused by an agent transmitted between animals and humans, but these diseases are also followed by human-to-human transmission. In this thesis, we consider arthropod-borne infectious diseases, which are also zoonoses but in which humans are most commonly infected as dead-end hosts. Mosquitoes and ticks are vectors for numerous pathogens causing infectious diseases and are globally responsible for millions of human deaths each year. Most vector-borne diseases emerge in the subtropics and tropics, but endemic diseases are present also in northern latitudes. Due to climate warming, numbers of disease cases, and disease severity and also variety are expected to increase especially in Northern Hemisphere which become more suitable for vectors to spread. To avoid costs from the loss of human lives or money, there is a strong need to assess impacts on vector species and their habitats. It is a global responsibility to focus on improving vector control strategies, and disease prevention, first, to “ensure healthy lives and promote well-being for all at all ages” (The United Nations’ Sustainable Development Goal 3), but also to understand that human health is closely connected to animal health and environment (One Health- approach). As such, it is vital to produce new information on vectors’ and vector-borne disease’ (VBD) distributions and the influential factors on their emergence, particularly, in understudied regions. In this thesis, environmentally suitable areas for the mosquito and tick species of medical importance in boreal and tropical landscapes, and the risk areas for two endemic VBDs in Finland were identified for the first time. We utilized climate, vegetation, host and vector data known to affect emergence of these vectors and VBDs at varying spatial scales. To our knowledge, this is the first species distribution modelling (SDM) study on vector species which uses good quality host data, and there are only a handful of earlier studies which included suitability data of vectors to predict VBD occurrence. We used SDM approach with a suite of predictive modelling techniques in two different platforms to explore correlations in species-host-disease-environment relationships and to predict spatial patterns of vector distributions and VBD risk in Finland, and in Kenya. Although SDM approaches are widely used by international and national health agencies such as European Centre for Disease Prevention and Control (ECDC), Centers for Disease Control and Prevention (CDC) and World Health Organization (WHO) in their vector control strategy and disease prevention programs, it is a new study approach in Finland with no earlier research. In tropical regions, including Kenya, where the need for vector control and disease prevention is highest, rural regions, particularly, remain understudied. Using data on mosquito collections in the Taita Hills region in Kenya, we found that Stegomyia (St., Aedes) and Culex (Cx.) genera, of which species are vectors of many significant pathogens in the tropics, are widely distributed across the region, both in villages and rural areas with rich and sparse vegetation. In Finland, we identified high-risk areas for tick-borne-encephalitis (TBE), one of the most severe endemic infectious disease in the country, based on environmental and host data, and under current and future climate. Future climate forecasts indicated a wider geographical extent of TBE risk especially in southern and western coast, and southern Lapland. We also identified environmentally suitable areas for the potential SINV vectors Aedes (Ae.) cinereus/geminus, Cx. pipiens/torrentium and Culiseta (Cs.) morsitans in Finland, and estimated the risk areas for SINV infections on environmental, host and produced habitat suitability data on vectors. Municipalities with an increased risk for SINV infections were characterized by high environmental suitability for Ae. cinereus/geminus, high densities of black grouse, capercaillie and hazel grouse, a high proportion of mixed forest in peatlands, and a high number of lakes. The risk of transmission was predicted to be greatest in eastern and central Finland, along the western coast up to southern Lapland in latitudes between 61–64°N. Two tick species; Ixodes (I.) ricinus and Ixodes (I.) persulcatus are responsible of transmitting TBE virus (TBEV) in Finland, and we estimated their distributions utilizing historical data, and newly collected ticks, of which we also screened pathogens TBEV and Borrelia burgdorferi sensu lato (b.s.l.). In these ticks, we found none positive for TBEV, but ≈ 47 % of the tick pools were positive for Borrelia b.s.l. High suitability areas for I. ricinus occurred throughout southern and central Finland up to Central Ostrobothnia (64°N), excluding the narrow areas in Ostrobothnia and Pirkanmaa. For I. persulcatus, the regions northwards from Ostrobothnia along the northern coast up to southern Lapland (66°N), Kainuu, North Savo, North Karelia, and areas in Pirkanmaa and Päijät-Häme were estimated to be suitable areas. Based on the predictions, locations with higher air temperature, higher relative humidity, higher precipitation sum and middle infrared reflectance (MIR) levels, and higher densities of white-tailed deer, European hare and red fox were suitable for I. ricinus. For I. persulcatus, higher mean precipitation, higher densities of white-tailed deer, roe deer and mountain hare indicated higher probability of occurrence. Together, these results have implications for improving knowledge on disease prevention, applying geographic information systems (GIS) and SDM approaches for identifying risk areas and environmental determinants, optimizing the use of limited resources for mitigation strategies, and improving public health outcomes. This data is vital for better understanding of the current and future threats, and will help to find facts which assist the authorities in decision-making on correct and effective actions. The results can be applied to other regions located in similar environmental conditions to study regions. Within this work, we also created a framework in which multidisciplinary and multi-organizational data were combined to the same database. With the produced data, we researchers can prioritize the research topics and funding to correct targets and actions in future studies. During the ongoing and following decades, further actions and research are needed to combat new emergences of vectors and VBDs. Vector surveillance, vector distribution studies in space and time, and mapping risks of VBDs under current and future climate, are essential to gain deeper insights into the spatial nature of recent and future global threats for which we have a shared responsibility to combat.
  • Celikkayalar, Ercan (Helsingin yliopisto, 2022)
    The thesis had the following three objectives: I. To develop and validate a medication safety self-assessment tool (MSSA) in secondary care hospital wards (Study I: organizational level); II. To use clinical pharmacist-conducted collaborative medication reviews (CMRs) in an emergency department (ED) short-term ward to identify inappropriate prescribing (IP) in pre-admission medications; (Study II: health care unit and clinical practice level); III. To investigate how well older people are aware of the major potential risks of benzodiazepines and related drugs (BZD) they are taking and whether the risk awareness changed between 2004 and 2015 (Study III: patient care and medication use level). In Study I (2008-2011), the original MSSA tool (231 items under ten components) was first modified preliminarily and then by the Delphi expert panel (14 panelists) with four rounds. The modified MSSA tool was then pilot tested on 8 hospital wards of various specialties in a regional secondary care hospital. Several safety recommendations were documented, including the development of clinical pharmacy services. In Study II (2016), pre-admission medications of patients were reviewed by the pharmacist. BZD (29%) and antidepressants (28%) were involved in over half of the confirmed IP events. In Study III (2004 and 2015), patients were personally interviewed to determine how well they were aware of the potential risks of the BZD they were taking and whether the risk awareness had changed in the years between the two study periods. The study found that awareness of dependence (p=0.047), interaction with alcohol (p=0.001), dizziness (p=0.002), and developing tolerance (p=0.002) had improved, while awareness of the other potential risks remained unchanged. This thesis found that the modified and validated MSSA tool can be used to support building up safe medication practices in health care organizations, particularly establishing ward-based pharmacotherapy plans (Study I). The pharmacist-led CMR practice was found helpful in ED admissions for older residents (>65 years) in ED admissions (Study II). Older BZD users’ awareness of potential risks related to BZD use was improved between 2004 and 2015. Despite improved patient awareness, no significant change was found in their willingness to discontinue BZD therapy (Study III). National-level coordination is needed to integrate the modified MSSA tool for hospitals as a part of national patient safety policies in Finland (Study I). More research is required to assess whether CMR practice in the ED could impact preventable ED re-admissions (Study II). Future research should also investigate patients’ risk awareness of different high-risk medications, especially in older users (Study III).
  • Wachiye, Sheila (Helsingin yliopisto, 2022)
    Land-use changes account for three-quarters of Africa's anthropogenic greenhouse gas (GHG) emissions, yet little is known about these emissions from a wide variety of land uses, especially from the savanna in Sub-Saharan Africa. To address this gap, I conducted four studies (2018 - 2021) to quantify soil GHG emissions from dominant land use types (LUTs) in the Taita Taveta county, southern Kenya. Three studies were carried out in the lowland under savanna grassland (private conservation and community grazing), bushland, maize cropland (Zea mays L.), and sisal plantation. The fourth study was in the highlands under indigenous forest, pine and eucalyptus plantations, woodland, and maize cropland. Each study covered a whole year. Soil GHG concentrations were measured with static GHG chambers and analysed by gas chromatography over eight one-week and weekly campaigns. Environmental factors including soil temperature, volumetric soil moisture content, vegetation, soil physicochemical characteristics and grazing intensity were evaluated. Daily CO2 emissions varied between 5 – 360 mg C m-2 h-1 and differed between sites. In the lowland, grassland under conservation land had the highest CO2 emissions, while cropland and bushland had the lowest. In the highlands, the pine plantation and indigenous forest emitted higher CO2 than eucalyptus and woodland, while cropland emitted the least. Overall, soil organic carbon accounted for 50% variation in CO2 emissions between the LUTs, while grazing accounted for 60% variation between grassland under conservation and the community grazing. In the sisal plantation, the oldest and youngest stands emitted higher CO2 than mature stands, which is consistent with root respiration since soil organic carbon did not differ between stands. During each study year, CO2 emissions were highest in the wet than in the dry season due to the higher soil moisture and vegetation cover. In the lowland, soil moisture alone explained 20 – 70% seasonal variation in CO2 emissions, while vegetation (based on EVI and NDVI; proxies of vegetation status) explained 18 – 82%. The combined influence of soil moisture and vegetation dynamics proved to be a greater control accounting for 75 – 96% of seasonal variation in CO2 emissions. The indigenous forest and pine plantation were affected by soil temperature rather than moisture, but the relationship was very weak (< 20%). In the lowland, soil N2O (-7.7 – 17 µg N m- 2 h-1) and CH4 (-0.4 – 1.9 mg C m-2 h-1) emissions were very low throughout each study period. Most CH4 values were below the limit of detection (LOD; ±0.03 mg C m-2 h-1) and the ones above were sinks rather than sources, and they did not differ between seasons or sites. N2O emissions were highest in cropland and lowest in bushland but did not vary with season. In the maize cropland, manure application was very low and had no effect on N2O emissions. Due to low soil carbon, nitrogen, and moisture content at all LUTs, N2O and CH4 emissions were of minor significance. Among the assessed LUTs, soil carbon content, moisture, and vegetation characteristics were key drivers for soil GHG emissions. The findings of this study address a significant gap in the spatial and temporal variability of soil GHG emissions in Sub-Saharan Africa, which can be used to improve current estimates, thereby improving climate change mitigation measures when identifying and quantifying national contributions.

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