Browsing by Subject "seasonal variation"

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  • Cannistraci, Carlo Vittorio; Nieminen, Tuomo; Nishi, Masahiro; Khachigian, Levon M.; Viikilä, Juho; Laine, Mika; Cianflone, Domenico; Maseri, Attilio; Yeo, Khung Keong; Bhindi, Ravinay; Ammirati, Enrico (2018)
    Background-ST-elevation acute myocardial infarction (STEMI) represents one of the leading causes of death. The time of STEMI onset has a circadian rhythm with a peak during diurnal hours, and the occurrence of STEMI follows a seasonal pattern with a salient peak of cases in the winter months and a marked reduction of cases in the summer months. Scholars investigated the reason behind the winter peak, suggesting that environmental and climatic factors concur in STEMI pathogenesis, but no studies have investigated whether the circadian rhythm is modified with the seasonal pattern, in particular during the summer reduction in STEMI occurrence. Methods and Results-Here, we provide a multiethnic and multination epidemiological study (from both hemispheres at different latitudes, n= 2270 cases) that investigates whether the circadian variation of STEMI onset is altered in the summer season. The main finding is that the difference between numbers of diurnal (6:00 to 18:00) and nocturnal (18:00 to 6:00) STEMI is markedly decreased in the summer season, and this is a prodrome of a complex mechanism according to which the circadian rhythm of STEMI time onset seems season dependent. Conclusions-The "summer shift" of STEMI to the nocturnal interval is consistent across different populations, and the sunshine duration (a measure related to cloudiness and solar irradiance) underpins this season-dependent circadian perturbation. Vitamin D, which in our results seems correlated with this summer shift, is also primarily regulated by the sunshine duration, and future studies should investigate their joint role in the mechanisms of STEMI etiogenesis.
  • Atashi, Nahid; Rahimi, Dariush; Al Kuisi, Mustafa; Jiries, Anwar; Vuollekoski, Henri; Kulmala, Markku; Vesala, Timo; Hussein, Tareq (2020)
    In this study, we performed model simulations to investigate the spatial, seasonal, and annual dew yield during 40 years (1979-2018) at ten locations reflecting the variation of climate and environmental conditions in Jordan. In accordance with the climate zones in Jordan, the dew formation had distinguished characteristics features with respect to the yield, seasonal variation, and spatial variation. The highest water dew yield (an overall annual mean cumulative dew yield as high as 88 mm) was obtained for theMountains Heights Plateau, which has a Mediterranean climate. The least dew yield (as low as 19 mm) was obtained inBadia, which has an arid climate. The dew yield had a decreasing trend in the past 40 years due to climate change impacts such as increased desertification and the potential of sand and dust storms in the region. In addition, increased anthropogenic air pollution slows down the conversion of vapor to liquid phase change, which also impacts the potential of dew formation. The dew yield showed three distinguished seasonal patterns reflecting the three climates in Jordan. TheMountains Heights Plateau(Mediterranean climate) has the highest potential for dew harvesting (especially during the summer) thanBadia(semi-arid climate).
  • Elovaara, Samu; Degerlund, Maria; Franklin, Daniel J.; Kaartokallio, Hermanni; Tamelander, Tobias (Springer Link, 2020)
    Hydrobiologia 847 11 (2020)
    Cell death drives the magnitude and community composition of phytoplankton and can result in the conversion of particulate organic carbon to dissolved organic carbon (DOC), thereby affecting carbon cycling in the aquatic food web. We used a membrane integrity probe (Sytox Green) to study the seasonal variation in the percentage of viable cells in the phytoplankton population in an estuary in the northern Baltic Sea for 21 months. The associated dissolved and particulate organic matter concentrations were also studied. The viable fraction of phytoplankton cells varied from < 20% to almost 100%, with an average of 62%. Viability was highest when a single phytoplankton group (diatoms or dinoflagellates) dominated the community. Viability of sinking phytoplankton cells, including some motile species, was in general as high as in surface water. Changes in viability were not closely related to nutrient concentrations, virus-like particle abundance, seawater temperature or salinity. There was a weak but significant negative correlation between viability and DOC, although at this location, the DOC pool was mainly influenced by the inflow of riverine water. This study demonstrates that cell viability, and its relationship with carbon export, is highly variable in the complex microbial populations common within estuarine and coastal marine ecosystems.
  • Lähdesmäki, Pekka; Pietiläinen, Pekka (Suomen metsätieteellinen seura, 1988)
  • Virta, Leena; Soininen, Janne; Norkko, Alf (2020)
    The global biodiversity loss has raised interest in the different facets of diversity, and the importance of diversity for ecosystem functions has been recognized. However, our knowledge on seasonal and inter-annual variation in the composition and diversity of communities is still poor. Here, we investigated the seasonal and inter-annual changes in taxonomic and functional community composition and diversity of benthic diatoms in a coastal habitat of the northern Baltic Sea, where seasonal and inter-annual variation of climate is pronounced. We found that the taxonomic and functional alpha diversity remained stable at seasonal and inter-annual level despite strong changes in community composition. However, alpha diversity decreased during an exceptionally warm winter possibly due to disturbances induced by the lack of ice. This may suggest that climate warming and consequently limited ice cover will affect the diversity of benthic communities.
  • Taka, Antti-Mathias; Sulkava, Sonja; Kantojärvi, Katri; Pölkki, Pirjo; Morales‐Muñoz, Isabel; Milani, Lili; Porkka-Heiskanen, Tarja; Saarenpää-Heikkilä, Outi; Kylliäinen, Anneli; Paavonen, Juulia; Paunio, Tiina (Helsingin yliopisto, 2019)
    Melatonin is a circadian regulatory hormone with neuroprotective properties. We have previously demonstrated the association of genetic variant rs12506228 near the melatonin receptor 1A gene (MTNR1A) with intolerance to shift work. Furthermore, this variant has been connected to Alzheimer’s disease. Because of the previously suggested role of melatonin signalling in foetal neurocognitive and sleep development, we studied here the association of rs12506228 with early development. The study sample comprised 8-month-old infants from the Finnish CHILD-SLEEP birth cohort (n=1301). Parental questionnaires assessed socioemotional, communication and motor development, as well as sleep length and night awakenings. The A allele of rs12506228 showed an association with slower socioemotional (P=0.025) and communication (P=0.0098) development but no direct association with sleep. However, the association of the Finnish seasons with infant sleep length interacted with rs12506228. Taken together, rs12506228 near MTNR1A, which has been previously linked to adult and elderly traits, is shown here to associate with slower early cognitive development. In addition, these results suggest that the darker seasons associate with longer infant sleep time, but only in the absence of the rs12506228 AA genotype. Since the risk allele has been connected to fewer brain MT1 melatonin receptors, these associations may reflect the influence of decreased melatonin signalling in early development.
  • Sulkava, Sonja M; Taka, Antti-Mathias; Kantojärvi, Katri; Pölkki, Pirjo; Morales-Munoz, Isabel; Milani, Lili; Porkka-Heiskanen, Tarja; Saarenpää-Heikkilä, Outi; Kylliäinen, Anneli; Paavonen, E. Juulia; Paunio, Tiina (2020)
    Melatonin is a circadian regulatory hormone with neuroprotective properties. We have previously demonstrated the association of the genetic variant rs12506228 near the melatonin receptor 1A gene (MTNR1A) with intolerance to shift‐work. Furthermore, this variant has been connected to Alzheimer's disease. Because of the previously suggested role of melatonin signalling in foetal neurocognitive and sleep development, we studied here the association of rs12506228 with early development. The study sample comprised 8‐month‐old infants from the Finnish CHILD‐SLEEP birth cohort (n = 1,301). Parental questionnaires assessed socioemotional, communication and motor development, as well as sleep length and night awakenings. The A allele of rs12506228 showed an association with slower socioemotional (p = .025) and communication (p = .0098) development, but no direct association with sleep. However, the association of the Finnish seasons with infant sleep length interacted with rs12506228. Taken together, rs12506228 near MTNR1A, which has been previously linked to adult and elderly traits, is shown here to associate with slower early cognitive development. In addition, these results suggest that the darker seasons associate with longer infant sleep time, but only in the absence of the rs12506228 AA genotype. Because the risk allele has been connected to fewer brain MT1 melatonin receptors, these associations may reflect the influence of decreased melatonin signalling in early development.