Browsing by Subject "fysiologi och neurovetenskap"

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  • Andersson, Oliver (Helsingin yliopisto, 2020)
    This study focused on the spectral sensitivity of two Norwegian lake populations of opossum shrimp (Mysis relicta), with a common implantation history and a temporal separation of about 50 years. Previous findings have indicated a difference in the absorption maximum (λmax) between sea and lake populations of Nordic mysids that have been separated about 9 000 years. Between the population groups, the spectral sensitivity correlates to the Wavelength of Maximal Transmission (WLMT) in the habitats. This may be considered a form of adaptive tuning. It is not known if the species-specific mechanism is based on chromophore shift or opsin modification or a combination of both, neither is the timescale of the adaption well understood. The intent was to determine λmax of both populations, what chromophore(s) they use and possible variations of the opsin gene. By comparison to spectrometric data of the habitats, the study aimed to broaden the insight into the mentioned unknowns. The light conditions of the lakes were determined by spectrometry down to depths of three and five meters. As predicted a positive, lake-bound correlation between the attenuation coefficient (k) and WMLT was found. Single-rhabdom microspectrophotometry (MSP) was used to determine λmax of the visual pigment in situ. Absorbance spectra were analysed by manual fitting to mathematical pigment templates and by script-based automation. Neither the chromophore nor differences in λmax could be determined, due to a small sample size that limited the statistical power of the results. The opsin genes from both populations were sequenced. No differences expected to have an effect on spectral sensitivity were found. Spectral tuning could not be demonstrated to have occurred in the populations due to the limited sample size. Nor did the results give support for any new findings on the mechanism or the time scale of spectral tuning among mysids. To answer the proposed questions of the study, additional sampling of both populations is needed.
  • Pitkänen, Stina (Helsingin yliopisto, 2018)
    The arylhydrocarbon receptor (AHR) is known for its xenobiotic role. In the last decades we have realized it has an important role even in normal physiology. Earlier studies have shown different circadian behavior in mice and rats when AHR is activated with the environmental toxoid TCDD. Also, AHR knock-out (AHRKO) mice have shown to adapt quicker to new lighting conditions. The aim of this study was to chart AHRs role on the circadian behavior in rats, by comparing daily eating and drinking habits under normal lighting condition for 7 days and for 7 days after a 12-hour light shift. Tissue samples to be used in continuing studies were taken after the 14 days long follow up. These studies will chart how the circadian timekeeping genes are expressed in the central (suprachiasmatic nucleus) and periphery (liver) cells in AHRKO rats after an adaptation to phase shift compared to wild type rats. This way the study will provide information that will help us understand the role of AHR in different species regarding behavior and in continuing studies gene expression. In our study no differences in drinking and eating activity could be seen between AHRKO and wild type rats. Both groups adapted to new lighting conditions equally fast.
  • Fredrikson, Linda (Helsingin yliopisto, 2019)
    The consumption of omega (n-) 3 polyunsaturated fatty acids (PUFA) from fish has been associated with lower rates of cardiovascular diseases with one mechanism being lowering LDL cholesterol levels in blood. When incorporated into LDL particle n-3 PUFAs can modify the lipid composition and reduce atherogenicity of the particle, e.g. by influencing inflammatory processes. The effects of n-3 PUFA of plant origin are less studied. This study investigated the effects of Camelina sativa oil (CSO), a rich source of alpha-linolenic acid (ALA), on lipid species of human LDL including phosphatidylcholines (PC), lysophosphatidylcholines (LPC), sphingomyelin (SM), triacylglycerols (TAG) and cholesterol esters (CE). A total of 38 subjects with a history of impaired fasting glucose, were randomly divided into two groups; CSO (ALA 10 g/day) and the control group (limited fish and ALA intake) for 12 weeks. Blood samples were collected from the subjects at the beginning and at the end of the experiment after 12 weeks. LDL particles were isolated from blood and the lipids were analyzed by mass spectrometry. The CSO affected more the LDL core lipids (TAG and CE) than lipid species of the shell (PC, LPC, SM). CSO is high in ALA and linoleic acid (LA). Thus, the diet reduced mole fractions of lipid species containing saturated acyl chains while acyl chains in the core lipids with ALA, LA and EPA, that is formed in the body from ALA, were increased. Based on the results, having CSO in the diet changed the LDL particle lipid composition in a favorable direction for cardiovascular health.
  • Karvonen, Eira (Helsingin yliopisto, 2020)
    APECED (Autoimmune-Polyendocrinopathy-Candidiasis-Ectodermal-Dystrophy) is a severe, multiorgan autoimmune disease caused by mutations in the AIRE (autoimmune regulator) gene. APECED is a rare disease, however in Finland the frequency is significantly high (1:25 000) and APECED belongs to the ‘Finnish Disease Heritage’. The most common mutation worldwide is the so-called Finn-major mutation R257X that results in a truncation of the AIRE protein, which disrupts the indispensable functions of AIRE. Immune reactions towards body’s own components are typically prevented with various central and peripheral immune tolerance mechanisms. AIRE is essential for the proper development of central and peripheral tolerance and the absence of functional AIRE leads to a loss of immune tolerance and various autoimmune manifestations. Recent studies have suggested that AIRE also has functions in stem cells and actively contributes to the regulation network of pluripotency. Currently, the development of induced pluripotent stem cell (iPSC) technology has opened opportunities for precision medicine and for defining the cure for genetic diseases, such as APECED. The ultimate objective of our research group is to examine whether APECED could be cured via autologous, gene-corrected cell transplants with the use of induced pluripotent stem cells (iPSCs). As a requirement for such later therapeutic use and iPSC differentiation, the APECED patient-derived iPS cells needed to be characterized in detail. To assess, whether AIRE R257X mutation, present in APECED patients’ iPSCs, would cause defects in their stemness properties, the expression of AIRE and classical stem cell markers were examined with qPCR and immunocytochemistry and compared to healthy control iPSCs. The iPSC cells were also treated with spontaneous differentiation -inducing dimethyl sulfoxide (DMSO) to study, whether AIRE R257X mutation would affect the spontaneous differentiation of iPS cells. To further investigate the stemness and early developmental phase properties of APECED patient derived iPSCs, self-aggregated embryoid bodies (EBs) were generated and cultured. Immunocytochemistry was used to examine whether APECED EBs differ in stemness, proliferation or apoptosis from healthy individual’s EBs. The comparative Ct method (ΔΔCt) i.e. fold change revealed that APECED iPSC clones expressed all the classical stem cell markers similarly to healthy control iPSCs. DMSO treatment reduced the expression of stem cell markers in both healthy and APECED-derived iPSCs. The immunostaining results of iPSCs were consistent with the qPCR analysis. The overall growth properties as well as the immunocytochemical assays of stemness, proliferation and apoptosis markers did not show any significant difference between the APECED patient and healthy control derived EBs. Together the results indicate that the R257X mutation of the APECED patients does not affect stem cell properties such as stem cell marker expression and colony or the EB formation of the iPSCs. The results are contrary to previous studies in mice demonstrating the interspecific difference between mouse and human and denoting the importance of human samples completing the studies with animal models. As the APECED patient derived iPSCs did not exhibit any defects in their stemness properties, the later iPS differentiation and therapeutic use could be accomplished without hindrance. However, future work is still needed, as the small sample size in this preliminary test might introduce some biases to the results and hindered a relevant statistical analysis. Nevertheless, this thesis project was the first time APECED patient-derived iPSCs were characterized and has provided new information about the effect of AIRE mutation in APECED patient derived iPSCs.
  • Moliner, Rafael (Helsingin yliopisto, 2019)
    Classical and rapid-acting antidepressant drugs have been shown to reinstate juvenile-like plasticity in the adult brain, allowing mature neuronal networks to rewire in an environmentally-driven/activity-dependent process. Indeed, antidepressant drugs gradually increase expression of brain-derived neurotrophic factor (BDNF) and can rapidly activate signaling of its high-affinity receptor TRKB. However, the exact mechanism of action underlying drug-induced restoration of juvenile-like plasticity remains poorly understood. In this study we first characterized acute effects of classical and rapid-acting antidepressant drugs on the interaction between TRKB and postsynaptic density (PSD) proteins PSD-93 and PSD-95 in vitro. PSD proteins constitute the core of synaptic complexes by anchoring receptors, ion channels, adhesion proteins and various signaling molecules, and are also involved in protein transport and cell surface localization. PSD proteins have in common their role as key regulators of synaptic structure and function, although PSD-93 and PSD-95 are associated with different functions during development and have opposing effects on the state of plasticity in individual synapses and neurons. Secondly, we investigated changes in mobility of TRKB in dendritic structures in response to treatment with antidepressant drugs in vitro. We found that antidepressant drugs decrease anchoring of TRKB with PSD-93 and PSD-95, and can rapidly increase TRKB turnover in dendritic spines. Our results contribute to the mechanistic model explaining drug-induced restoration of juvenile-like neuronal plasticity, and may provide a common basis for the effects of antidepressant drugs.
  • Jenkins, Cherie (Helsingin yliopisto, 2020)
    Reptiles have long been studied in search of the mechanisms behind neuronal regeneration. This thesis delves into the regenerative areas of two emerging model species to the field of regenerative research: Pogona vitticeps (bearded dragon) and Pantherophis guttatus (corn snake). This fluorescent immunohistochemical study maps out and compares the constitutive proliferative zones in these two species to better define the focus of future comparative neurodegenerative experiments. A BrdU pulse chase experiment in conjunction with PCNA reveals proliferative zones in the lateral ventricular ependyma of both species. Stem cell niches were found in the ependymal lining adjacent to the medial cortex and dorsal ventricular ridge in both species, however, the nucleus sphericus ependyma was an active proliferative zone only in Pantherophis. Imaging of further markers in this study support the findings of the pulse chase experiment. High levels of the stem cell marker Sox2 was found in lateral ventricular ependymal cells in both species. The glial marker GFAP reveals a highly ordered array of radial glia in the cortical areas of Pogona, which is significantly reduced or absent in Pantherophis. And lastly the neuronal marker HU was found in the same cells that were BrdU positive and had migrated a short distance from the proliferative zones, which shows that the proliferative areas in the lateral ventricular lining do indeed produce neurons. The BrdU and PCNA marked cells were quantified in both species, and a brief comparison between the species showed that Pogona had a significantly higher number and concentration of proliferative cells in the proliferative zones than Pantherophis. Scattered BrdU positive cells that were neither neuronal nor positive for any other marker were also found scattered throughout the parenchyma of Pogona, and these cells remain uncharacterized. Differences between these two species are not surprising, as lizards are known to have better regenerative capabilities than snakes, however, more comparative research between these species is needed to gain further insight into the mechanisms behind their contrasting regenerative capabilities.
  • Ollonen, Joni (Helsingin yliopisto, 2020)
    The skull represents the most highly diversified and evolutionarily adapted anatomical aspect of metazoans, and its development and evolution have been a major driving force in the expansion of vertebrates. The evolution of skull and lower jaw bones have led to the adaptive radiation of jawed vertebrates, and skull tissues have changed rapidly over time and were finely tuned to meet functional and ecological demands with tremendous precision. Because of the long-lasting interest in conventional animal models, there is no general genetic or developmental model of skull evolution and diversity in vertebrates. Squamate reptiles represent the best model to study those aspects because of their key basal phylogenetic position within amniotes (i.e., mammals, birds, reptiles) and their exceptionally high levels of morphological variation (including their kinetic skulls). In particular, their lower jaw bones display tremendous variation. In order to assess this variation and the ecological and developmental factors connected to it, several methods from different fields of biology have to be used. In this study, morphometric, embryology and developmental approaches are used to investigate the ecological and developmental factors associated with the diversification of lower jaw bones in snakes and lizards. The shape diversity of squamate lower jaw bones was approached in a systematic way, using geometric morphometrics. Embryological methods were used to compare the embryonic stage of available squamate model animals at oviposition and to assess the order of ossification of embryo with earliest developmental stage at oviposition (bearded dragon, Pogona vitticeps). In addition, expression of major conserved candidate genes at different stages of lower jaw development (pharyngeal arches, mesenchyme patterning, ossification) were assessed in this species. The results indicate that the lower jaw bones of snakes versus lizards but also of fossorial squamates versus other habitats are significantly different. Heterochrony was also detected at both early stages (pharyngeal arche development at oviposition) and at the onset of ossification in lizards and snakes. Coherent with that, alterations in the expression pattern of Dlx genes in pharyngeal arches were observed in bearded dragon in comparison to earlier studies with mice, while other conserved markers of skeletogenesis were rather conserved. This analysis of the genotype and phenotype map of the reptilian skull provides some new insights into the development, origin and divergence of vertebrate tissues. The results will establish a good basis for future studies involving comparative developmental biology of bearded dragon. Future studies will offer excellent new opportunities to link craniofacial morphology, genetics/genomics and development to both ecological adaptation and evolutionary biology.
  • Sundman, Elina (Helsingin yliopisto, 2020)
    Hypothyroidism affected 337 370 people in Finland in 2019. The hypothalamus-pituitary negative feedback loop is used in the diagnostics of hypothyroidism. TSH, a pituitary hormone, is the most used diagnostic tool with the free thyroxine (T4) in a supporting role. L-T4 has been the main treatment option, since the discovery of peripheral deiodination. Biochemical and clinical euthyroidism is the aim of L-T4 therapy. There are no nationwide official treatment guidelines for hypothyroidism in Finland. The Finnish Endocrine Society has published their recommended guidelines in 2019. Studies have shown that 5–15 % of levothyroxine treated patients continue to report symptoms when they are biochemically euthyroid. The symptoms consist of typical symptoms of hypothyroidism: fatigue, cognitive symptoms, depression, anxiety and weight gain. The molecular basis of the symptoms is not yet known. These symptoms have notbeen studied in Finnish population. The aim of this study was to find out what symptoms levothyroxine treated patients report on Finnish social media support groups and view the current treatment of hypothyroidism and guidelines of treatment. This study was conducted by surveying patient-reported information from social media hypothyroidism related support groups. The posts were divided into two groups: hypothyreotic and athyreotic. The biochemical data and symptoms were collected from 137 posts in the athyreotic group and 191 in the hypothyreotic group. Only posts with TSH under or within the refence range and free T4 within the reference range wereincluded in the study. The results show that patients reported symptoms in 74 % of the posts viewed. 81 % of patients reported symptoms in the hypothyroidism group and 64.2 % in the athyreotic group. The most reported symptom in both groups was fatigue. Symptoms were reported within the normal TSH range (0.5-4 mU/l) and below the normal range (<0.5 mU/l). In asymptomatic patients the median TSH was 0.38 mU/l in the athyreotic group and 0.54 mU/l in the hypothyreotic group. Free T4 seems to be a little higher in the asymptomatic patients in both groups. 16.6-25 % the patients reported that they had had Free T3 measured. Free T3 seem to be higher in relation to free T4 in the athyreotic group that reported having no symptoms. L-T4 is the recommended treatment modality for hypothyroidism. Other options are synthetic combination treatment with L-T4 + L-T3 and desiccated thyroid extract (DTE).This study supports the view that hypothyroidism patients can have symptoms on levothyroxine treatment
  • Harmoinen, Katri (Helsingin yliopisto, 2019)
    New Zealand is an isolated landmass laying in the Southwest Pacific waters, far away from any major islands or continents. It was the last major landmass to be colonized by people, discovered by the first Polynesian explorers around a thousand years ago. Historically, New Zealand lacked all native mammals (apart from three species of bats) and so has developed a plethora of bird species and other endemic wildlife. The absence of mammalian predators, combined with the continuous isolation for millions of years, has led the evolution of some very unique and charismatic species. One of these species is the iconic symbol of New Zealand – the kiwi (Apteryx spp). The biggest challenge to the New Zealand wildlife has been the introduction of mammalian species to the New Zealand ecosystem. There are 25 species of introduced mammals in New Zealand today that are regarded as pests. The devastation caused by these species is the main cause for the dramatic decline of the endemic New Zealand wildlife, including the iconic kiwi. Nationally, kiwi continue to decline by more than 2% annually and there are estimates of the species going extinct from the wild within 50 years. Since the first more permanent human settlement, more than 50% of the New Zealand breeding birds have gone extinct. In this thesis, the relation between kiwi and introduced mammalian species around the township of Whakatāne, New Zealand, was studied. During summer 2018-2019, three out of eight monitored kiwi chicks were predated by a suspected mustelid/mustelids and DNA swabs were obtained from the bite sites. Volunteer pest trappers were then asked to bring in all their catches in an attempt to catch the individual/individuals responsible for the predations. Molecular tools including microsatellites were used to create ID profiles in an attempt to match the profiles to those obtained from the kiwi chicks. In the second part of the study, the stoats’ stomachs were analysed as part of a diet study. A new, kiwi specific DNA probe was trialled and the remaining stomach contents were sequenced for other native wildlife species. Out of the three predated kiwi chicks, all of them were confirmed to be stoat predations. Unfortunately, none of the stoat ID profiles obtained matched the profile of the kiwi chick Ranui who was the only chick a good micro-satellite profile was obtained for. This confirmed that the stoat/stoats responsible for the predation of Ranui was not caught as part of this study. In the diet part of this thesis, we trialled the kiwi specific probe but could not identify any kiwi DNA in the stoat stomach contents. The DNA sequencing however revealed five other species: tomtit (lat. Petroica macrocephala, 100%), common chaffinch (lat. Frigilla coelebs, 100%), tui (lat. Prosthemadera novaseelandiae, 96%), European hare (lat. Lepus europaeus,100%) and copper skink (lat. Cyclodina aenea, 100%). These findings shed new light on the extent introduced mammalian species contribute to the species loss taking place in the New Zealand forests today. The use of molecular techniques and tools in conservation offers an often faster, cost-efficient and more reliable alternative to traditional monitoring methods of introduced species. The rapid development of these tools has seen New Zealand taking critical steps towards one day becoming predator free. The ambitious goal to rid New Zealand of target introduced species (mustelids, possums and rats) by year 2050 (Predator Free 2050), has been compared as the New Zealand equivalent of putting the man on the moon.
  • Lankinen, Tuuli (Helsingin yliopisto, 2020)
    Our hearing perception is based on the ability to discriminate mechanical sound waves and to amplify and transduce them into electrical stimuli.This function is based on the complex cellular organization of the cochlea, the hearing organ. The sensory epithelium in the organ of Corti spirals along the cochlear duct in a tonotopic arrangement: every sound frequency elicits the strongest response at allocation along this duct. Sound stimulus is detected by three rows of outer hair cells (OHCs) which amplify- and tone-discriminate the sound stimulus, and by one row of inner hair cells (IHCs), which transduce the mechanical stimulus into electric impulses. Basal regions of the cochlea detect high- frequency sounds and apical regions detect low- frequency sounds. The complexity and sensitivity of the cochlea is linked with its vulnerability to various traumas. Most kinds of damage to the mammalian hair cells is irreversible, because these cells are not capable of regeneration. Hearing impairment has many etiologies. Common to them is that damage is permanent and no pharmacotherapy is available. Hearing impairment is often a disabling condition and it has vast societal consequences. The number of hearing impaired people is constantly increasing and the WHO has estimated that 10% of the world`s population will suffer from disabling hearing loss in 2050. Mesencephalic astrocyte- derived neurotrophic factor (MANF) is an unconventional, ER-resident protein that promotes ER- homeostasis. It has been associated with cytoprotective functions in many neurodegenerative disease- models and shown to promote recovery after ischemic trauma. MANF expression has been previously found in many cell-types in the cochlea, including OHCs and IHCs. Its deficiency in a mouse model led to upregulation of ER-stress markers and a robust, tonotopic base –to apex gradient loss of outer hair cells and severe hearing loss. This study examines the role of MANF in noise-induced trauma in the hair cells of the cochlea. In a conditionally inactivated (Manf -/- cKO) mouse model in the C57BL/6J – background, where Manf has been inactivated from most of the cochlear cells, I studied, if Manf -deficiency sensitizes the cells to noise-induced cell death in two age-groups. I also examined the basic and noise- induced MANF expression, using two mouse- strains, C57BL/6J and CBA/Ca. I also examined OHC stereociliary bundle morphology to find out if noise induces morphological changes in Manf cKO-mice that differ from noise-exposed C57BL/6j wild type mice. This study found that OHCs have a low MANF- expression, whereas in IHCs the expression is strong. MANF is expressed in a base- to apex gradient in the OHCs of the two mouse-strains examined, in a uniform pattern, that correlates with vulnerability, implicating that low levels of MANF predispose basal OHCs to vulnerability. MANF expression in the IHCs was non-gradiental. Noise did not induce upregulation, as was expected, but instead noise induced downregulation of MANF in the basal region of the OHCs by an unknown mechanism in both mouse-strains.This suggests that noise-induced trauma induces ER dyshomeostasis, possibly independent of ER stress response pathways ,unfold protein response (UPR). This study also demonstrates that MANF deficiency sensitizes the OHCs to noise- induced trauma, resulting in more elevated OHC loss and hearing thresholds. This sensitization is mainly caused by a progressive degenerative changes seen in the OHC stereociliary bundles of Manf cKO-mice, and is associated with more severe noise-induced hearing loss. The results of my study suggest that MANF has an important, yet unknown, protective role in noise-induced trauma in OHCs. These results support the possible role of MANF as a therapeutic agent in a noise-induced trauma.
  • Saarnisalo, Ona (Helsingin yliopisto, 2019)
    Lack of Ectodysplasin (EDA), caused by a mutated Eda gene, leads to a syndrome called hypohidrotic ectodermal dysplasia (XLHED) with defects in ectodermal organs such as teeth, hair and sweat glands. The molar teeth of Eda knock out (Eda KO) mice are absolutely and relatively smaller and have fewer cusps than the wild type (WT) molar teeth. In the absence of the EDA protein, the receptor of the EDA signalling pathway (EDAR) remains functional, and therefore EDA-protein therapy can rescue the development of ectodermal organs. The aim of this study was to determine EDA sensitivity windows and to describe the Edar expression pattern in developing mouse lower molars. Eda KO mouse skulls treated with EDA for 24 hours at different stages of development were imaged using x-ray microtomography. The response was studied by analysing the cusp patterns and size proportions of lower molars. In situ hybridisation was used to detect the Edar expression in the developing Eda KO and WT molars at different stages. The results show that molars are sensitive to EDA at the early stages of crown patterning, at the time when Edar is expressed in the primary enamel knot and the secondary enamel knots. The Edar expression pattern suggests that EDA signalling regulates molar size and cusp development through these signalling centres. EDA-treatment during a sensitivity window enhances the growth of the EDA sensitive molar, thereby breaking the previously reported inhibitory cascade –rule. The results of this study provide information for optimising the EDA therapy for XLHED patients.
  • Rydgren, Emilie (Helsingin yliopisto, 2018)
    Kainate receptors (KARs) are glutamate receptors that modulate neurotransmission and neuronal excitability. They assemble from five subunits (GRIK1-5 or GluK1-5) present at both pre- and postsynaptic membranes. KAR function is regulated by neuropilin and tolloid-like (NETO) proteins, which also regulate postsynaptic GRIK2 abundance. Some KAR subunit gene variants associate with psychiatric disorders. Moreover, Grik1, Grik2 and Grik4 knock-out (KO) mice display changes in anxiety- and fear-related behaviours. In previous work, Neto2 KO mice expressed higher fear and impaired fear extinction in the fear conditioning paradigm. We hypothesised that this phenotype could be due to reduced KAR subunit abundance in fear-related brain regions, i.e. ventral hippocampus, amygdala and medial prefrontal cortex (mPFC). We specifically investigated GRIK2/3 and GRIK5 levels in the subcellular synaptosomal (SYN) fraction using western blot. We did not observe any difference between genotypes in any of the brain regions. However, our statistical power may have been insufficient, particularly for amygdala and mPFC. Also, an effect on synaptic KAR subunit abundance might be specific to either pre- or postsynaptic compartment, and thus more difficult to detect in SYN fractions. Alternatively, NETO2 absence may affect KAR actions instead of their subunit levels in fear-related brain regions, which could be examined through electrophysiological recordings. Ultimately, unravelling how a molecular system without NETO2 gives rise to fear behaviour in mice may lead to a better understanding of fear-related disorders in human and to new therapeutic strategies.
  • Huovelin, Suvi (Helsingin yliopisto, 2019)
    Citizen science is a research method in which data collection, analysis or other stages of research is distributed to a large number of volunteers. Citizen science enables collection of large-scale data. In addition, in few cases Citizen science has been integrated into formal school education. It has been found to attract students' interest in the subject and research and to teach students about scientific research. However, the real benefits of citizen science for schools have been just scarcely studied. This study explored the experiences of middle school and high school students on the Helsinki Urban Rat Project (Kaupunkirottatutkimus). The research questions were: (1) How do the middle school and high school students who participated in the Urban Rat Project experience citizen science as part of biology teaching? (2.) How do the students who participated in the Urban Rat Project feel about urban rats and how does the Project affect students’ perception of rats? The data was collected by group theme interviews from middle school and high school students who participated in the City Rat Project. The data consisted of nine recorded interviews with a total of 29 interviewees. The interviews were transcribed and analyzed by content analysis. The Urban Rat Project aroused situational interest towards urban rats and research project. Main factors for aroused interest were novelty and specialty of the project, the involvement created by hands-on activities and the meaningfulness created by contextualism of an authentic research. Learning experiences were categorized by Bloom’s revised taxonomy and the results revealed a number of knowledge types and cognitive process categories, suggesting that the project developed a diverse range of students' thinking. Students were able to develop deeper research skills, critically explore research and its outcomes, and learn about practical challenges and constraints of scientific research. Urban rats gave rise to both negative, positive and neutral feelings among students. The negative emotions were caused by a variety of causes, such as the appearance and behavior of rats, culture created attitudes and students own experiences. Positive feelings were caused by interest toward rats and good experiences with pets. The knowledge learned in the study about urban rats generally reduced negative feelings and in one case aroused them, but many interviewees also felt that the study had no effect on their attitude towards rats, because interaction with rats was not concrete enough during the project and the students were disappointed that they did not see rats or rat footprints. The authentic research context of citizen science such as Urban Rat Project can increase meaningfulness to studying biology, which is not necessarily achieved by other teaching methods and may teach the realities of scientific research better than traditional practical work. In addition, citizen science can provide knowledge and nature experiences that allow learners to reflect on their relationship with nature. In order to achieve nature-related learning goals of the school education, citizen science projects should pay particular attention to the concreteness of the interaction between learners and nature and to the students' experiences in nature during citizen science.