Seasonal variations of physiological responses to heat of subtropical and temperate natives

In an attempt to compare the physiological responses of subtropical natives to heat with those of temperate natives, seasonal variations in physiological responses to heat were observed in young male residents of Okinawa who were born and raised in Okinawa, subtropical zone (group O) and young male residents of Okinawa who were born and raised on the Japan mainland, temperate zone, but moved to Okinawa in less than two years (group M). In both seasons, group O showed less sweat loss, lower Na concentration in sweat, lower rise in rectal temperature and less increase in heart rate during heat exposure than group M. In both groups, greater sweat loss, lower Na concentration in sweat and lower rise in rectal temperature in summer than in winter were observed. Seasonal differences in Na concentration in sweat, rise in rectal temperature and increase in heart rate for group O were smaller than those for group M. It was assumed the efficiency of sweat for cooling the body for group O was better than that for group M, and heat tolerance for group O was superior to that for group M.     

Role of temperate phage in bacterial dissociation

The analysis of literary and own data testifies that the dissociants may appear in bacteria population from spontaneous mutations and transfer of genetic material (conjugation, transformation, transduction). The phage conversion and different DNA reorganizations within a cell where prophage plays an active role, probably introduce the largest contribution into the dissociative transitions of variants which occur with high frequency (about 10(-2)-10(-4). The dissociation of various bacteria has been studied with different degree. The role of temperate phage has been shown in splitting of bacteria into variants in the genera Mycobacterium, Corynebacterium, some Bacillus, Clostridium, Staphylococcus, some enterobacteria, Yersinia, Vibrio Pseudomonas, Rhizobium, Nostoc; the participation of prophage in dissociation of bacteria of the genera Xanthomonas, Erwinia, Bacteroides is proposed. A method for obtaining the nondissociating S-variants for stability of biologically active substances synthesized by cells has been suggested.     

Seasonal succession and strategies of phytoplankton development in two lakes of different trophic states

This study describes the metabolism and structure of phytoplanktoncommunities during seasonal periodicity and discusses strategiesof development adopted by species during succession. The studywas conducted in two trophically different lakes. Each lakedemonstrates a different degree of the ecological succession,which prescribes an increasingly complex taxocenose. In oligomesotrophicLake Pavin the autogenic succession lasts from spring overturnuntil mid-summer. In eutrophic Lake Aydat the autogenic successionis strictly limited to spring. The seasonal changes of the communityproductivity, turnover rate (P/B) and adenylate energy chargeconfirm the hypothesis of a change of the ‘metabolic orientation’of phytoplankton cells during seasonal succession. The autogenicsuccession represents the progression from a growth-orientedstrategy to an equilibrium-oriented one.     

Phenotypic variations in re-lysogenization ofBacillus licheniformis with temperate phage

A bacitracin-producing strainBacillus licheniformis ATCC 10716 harbors two types of inducible phages (LP52 and DLP 10716). 156 strains re-lysogenized with phage LP52 were independently isolated from a cured strain UM12 ofB. licheniformis. Those strains were divided into 12 groups based on colony morphology and pigment production. Some of the re-lysogenized strains grew faster than UM12 and others produced more bacitracin than the cured strain. For example, the production of bacitracin by one of the relysogenized strains, L89, was enhanced by about 70% in comparison with UM12. The phenotypic variations observed with re-lysogenized strains might be due to the re-insertion of the phage genome at different sites of the chromosome in addition to the pleiotropic effect assumed.Abbreviations ATCC American Type Culture Collection - DNA Deoxyribonucleic acid - MC Mitomycin C - OD Optical density - PFU Plaque forming unit - rpm Revolutions per minute - UOD Unit of optical density - UV Ultraviolet Definition Specific growth rate (h^-1) - t time (h) - X cell concentration (g/l)     

Ultraviolet and temperature effects on planktonic rotifers and crustaceans in northern temperate lakes

1. Anthropogenic stressors such as climate change, ozone depletion and acidification may act in concert to alter ultraviolet (UV) light and temperature regimes in freshwater ecosystems. These physical and chemical changes will inevitably affect zooplankton community dynamics, but little is known about their relative effects on different species in natural communities. During spring, species that migrate to surface waters to take advantage of warmer temperatures may be especially vulnerable as UV levels can be high. 2. The objective of this study was to investigate the in situ effects of UV and temperature on a natural assemblage of planktonic rotifers and crustaceans during the spring. We performed in situ exposure experiments in two lakes with different surface temperatures. 3. Exposure to UV had a significant effect on the abundance and/or reproduction of four rotifers: Gastropus spp., Kellicottia bostonensis, Kellicottia longispina, Keratella spp.; two cladocerans: Holopedium gibberum, Daphnia catawba, and one copepod: Leptodiaptomus minutus. Incubation under cooler temperatures had a negative effect on K. longispina and H. gibberum. Temperature and UV had a significant interactive effect on abundance and/or reproduction of L. minutus and Ploesoma truncatum. Our results indicate that changes in underwater UV and temperature can significantly influence the composition of the zooplankton community and ultimately food web dynamics.     

Active bacteria (CTC+) in temperate lakes: temporal and cross-system variations

The temporal variation in the abundance and proportion of highlyrespiration-active bacteria in the eutrophic lakes Esrum andFrederiksborg Slotssø was determined with the redox dye5-cyano-2,3-ditolyl tetrazolium chloride (CTC). In addition,a comparative late summer study was undertaken across a gradientof nutrient enrichment in Danish lakes. The purpose was to investigatethe importance of substrate (chlorophyll) and temperature forthe control of CTC-active cells (CTC+). The abundance of CTC+cells was much lower and more variable than the total numberof cells counted after 4',6-diamidino-2-phenylindole (DAPI)staining. The proportion of CTC+ cells in Lake Esrum and FrederiksborgSlotssø was normally <5%, and between 2.5 and 20%in 14 other lakes. The abundance as well as the proportion ofCTC+ cells increased with chlorophyll in Lake Esrum and FrederiksborgSlotssø, and chlorophyll explained 43% of the variabilityin CTC+ abundance. In the comparative study, the abundance ofCTC+ cells increased along the chlorophyll gradient, which explained49% of the variability. The results showed that the abundanceand, to a lesser degree, the proportion of CTC+ bacteria werecontrolled by substrate supply. One consequence of the low abundanceof active bacteria is that in situ growth rates scaled to CTC+cells are 3- to 7-fold higher than those scaled to DAPI counts.It is suggested that studies on factors controlling bacterioplanktonactivity at the single-cell level should be investigated scaledto active cells.     

Seasonal and physiological variations in serum chemistry and mineral concentrations in cattle

The present study reports the seasonal and physiological variations of copper, zinc, magnesium, iron sodium chlorine, potassium, calcium, phosphorus, urea, alkaline phosphatase (ALP), creatinine (CR), aspartate aminotransfrase (AST), alanine aminotransferase (ALT), cholesterol, albumin, globulin, lactate dehydrogenase (LDH), and total protein concentrations in cattle. Two groups of mated (n=14) and nonmated (n=10), healthy cows were selected for the study. Serum samples were collected at each of four periods: (1) early pregnancy (May), (2) midpregnancy (August), (3) late pregnancy (October), and (4) lactation (February). Physiological variations result in changes of cholesterol, calcium, LDH, and total protein concentrations. Phosphorus varies only with seasonal but not physiological changes, whereas ALP, copper, magnesium, and potassium concentrations change with physiological and seasonal conditions. The copper concentration is increased through the pregnancy. Neither the seasonal nor the physiologic variations affect zinc, iron, sodium, chlorine, calcium, urea, creatinine, albumin, and globulin values in both groups in all periods. Thus, these values can be used as reference for both mater and nonmated bovines. The measured total protein might not reflect its true value because of dehydration during the hot season. These observations suggest that seasonal and physiologic variations have to be taken into consideration for the correct interpretation of serum chemistry and elements status in cattle. Nutritional supplements are required for cattle during certain periods to avoid a decline of their performance, which would then represent consequent economic loses.     

Winter phytoplankton community structure in three shallow temperate lakes during ice cover

The general model of seasonal phytoplankton succession in temperate lakes suggests that winter phytoplankton growth is minimal under ice-cover. However, some studies have found diverse phytoplankton communities during winter. The primary objectives of this study were to determine the species composition and the changes in the winter phytoplankton community structure under the ice. For 2 consecutive winters, phytoplankton samples were collected under ice-cover at 4 sites on 3 lakes in Arrowwood National Wildlife Refuge (ANWR), near Pingree, North Dakota. Ninety taxa were identified and enumerated. Densities of several of these taxa frequently exceeded 10⁶ cells l^–1. The winter phytoplankton communities in these lakes were dominated by flagellates, principally cryptomonads, a synurophyte (Synura uvella), small chrysophytes (Chrysococcus spp., Kephyrion spp.) and a dinoflagellate (Peridinium aciculiferum), as well as non-flagellate microchlorophytes (Monoraphidium spp., Ankistrodesmus spp., and Pseudodictyosphaerium sp.), a cyanobacterium (Gloeocapsa aeruginosa) and centric diatoms (Stephanodiscus minutulus, S. parvus and Cyclotella meneghiniana).     

Seasonal variations of phytoplankton photosynthate partitioning in two lakes of different trophic level

The aim of this study was to compare vertical and seasonal variationsof inorganic carbon allocation into macromolecules by the phytoplanktonpopulation in a eutrophic lake (Lake Aydat) and an oligo-mesotrophiclake (Lake Pavin). Biochemical fractionation was conducted byconsecu tive differential extractions in order to separate proteins,polysaccharides, lipids, and low molecular weight compounds(LMW). The ratio of light absorption at480 and 665 nm by acetoneextracts of phytoplankton pigments was used as an indicatorof the nutritional statusof natural phytoplankton populations.Our results show that in Lake Aydat, the main photosyntheticend productswere poly saccharides, whereas in Lake Pavin, radioactivitywas predominantly incorporated into the protein fraction. Moreover,the seasonal cycles of mixing and stratification in these twolakes affected the pattern of ¹⁴C incorporation into LMW andmacromolecules. An increase in the relative synthesis of proteinsoccurred during stratification periods. It was linked to anincrease in temperature and nutrient limitation further complicatedby the shift in species composition of the populations. Differences recorded both between the two lakes of different trophicstatus and between seasons confirm that the proportion of carbonincorporated into proteins might be a useful indicator of thephysio logical status of phvtoplankton communities.     

Seasonal variations in physiological parameters of phytoplankton across the North Atlantic

Variations in the shapes of the action and absorption spectra,and the physiological parameters of phytoplankton [^B, the biomass(B)-specific initial slope of the photosynthesis-irradiancecurve; the plateau of the curve; _m), themaximum quantum yield of photosynthesis], were studied. Datawere collected in the North Atlantic in five biogeochemicalprovinces for two seasons: in fall of 1992 and spring of 1993.Further, some nine independent variables were tested for theirability to predict the physiological parameters, using linearregression analyses. It was found that the parameters were morevariable between seasons than between provinces, although thedifferences in the spectral shapes between provinces were significant.It was also shown that several independent variables (aloneor in combination) were able to predict a significant fractionof the total variance in the parameters. However, the correlationbetween variables and parameters differed unsystematically bothbetween provinces and seasons. The results suggest that predictinga parameter from an independent variable would have to be carriedout at a province level: the relationship changed or disappearedwhen data from two or more provinces were pooled.     

Seasonal variations in PCR-DGGE fingerprinted viruses infecting phytoplankton in large and deep peri-alpine lakes

Double-stranded DNA viruses infecting eukaryotic algae (e.g., phycodnaviruses) and cyanobacteria (e.g., cyanophages) are now recognized as widespread and ubiquitous in aquatic environments. However, both the diversity and functional roles of these viruses in fresh waters are still poorly understood. We conducted a year-long study in 2011 of the community structure of planktonic virus groups in the upper lit layer of two important freshwater natural ecosystems in France, Lake Annecy (oligotrophic) and Lake Bourget (oligo-mesotrophic). Using PCR-DGGE to target a number of different structural and functional signature genes, i.e.,g20, g23, psbA, polB, and mcp, the phytoplankton viruses were shown to display temporal and spatial variability. There were marked seasonal changes in community structure for all viral groups in Lake Bourget, but only for T4-like myoviruses and psbA-containing cyanophages in Lake Annecy. The multivariate statistical analyses revealed that (1) various environmental factors can directly or indirectly explain the community structure observed for each phytoplankton viral group, and (2) temporal patterns of T4-like myovirus community structure were similar between the two lakes. In general, our results (1) suggest that the observed algal virus patterns were associated with significant shifts in phytoplankton biomass and/or structure, which in turn were shaped by the abiotic environment, and (2) support the Bank model proposed by Breitbart and Rohwer (Trends Microbiol 13:278–284, 2005). This study provides new evidence that freshwater lakes contain a significant diversity of algal viruses, and that the distribution of these viruses strongly mirrors that of their hosts.     

Seasonal variations in physiological indices of adult female white-tailed deer in Texas

Seasonal variations in blood chemistry, urine chemistry, fat reserves, and crude protein levels of rumen contents were determined for free-ranging adult female white-tailed deer (Odocoileus virginianus Zimmermann) in central Texas. Seasonal variations (P less than 0.05) existed for serum total protein, albumin, globulin, albumin/globulin ratios, blood urea nitrogen (BUN), cholesterol, alkaline phosphatase, creatinine, phosphorus, and sodium; and urinary urea/creatinine (U/C) ratios, rumen crude protein, the kidney fat index (KFI), femur marrow fat (FMF), and dressed weights. Variations in BUN, urinary U/C ratios, dressed weights, KFI, and FMF were attributed partially to the nutritional demands of late gestation and lactation.     

Seasonal variations and balanced polymorphisms in the reproductive potential of temperate D. Melanogaster populations

Flies from the first generation of isofemale lines of D. melanogaster founded by wild flies collected in spring, summer and autumn in two French populations have been studied for 4 successive years. Cyclical seasonal variations occur in various genetically determined characteristics involved in reproductive potential.The number of ovarioles of the females and female capacity to control oviposition are subject to variation consisting of an increase in frequency of genotypes controlling large number of ovarioles and strong oviposition blocking control in spring and autumn samples. The opposed genotypes (low number of ovarioles and weaker blocking of oviposition control) are favored in summer generations.This balancing selection, induced by temperature variations, modifies temporarily the genetic equilibrium of the population. This enhances the frequency of better adapted genotypes when conditions become less favorable.

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Résumé L'étude pendant 4 ans de lignées isofemelles, fondées par des mouches capturées dans la nature, au printemps, en été et en automne, dans deux population françaises de D. melanogaster, a mis en évidence des variations saisonnières cycliques portant sur différents caractères liés au potentiel reproducteur. Les individus observés appartenaient à la première génération de laboratoire, élévée en conditions standard; les fluctuations observées correspondaient donc à des variations d'ordre génétique.Le nombre d'ovarioles des femelles et leur capacité à controler leur ponte en présence d'un substrat peu favorable sont soumis à ce type de variations cycliques. Il consiste en une augmentation de la fréquence de certains phénotypes (nombre d'ovarioles élevé et forte capacité de blocage de l'oviposition) au printemps et en automne, tandis que les génotypes opposés (faible nombre d'ovarioles et faible capacité de blocage) sont favorisés pendant les générations estivales.Ces variations correspondent à une sélection balancée induite par les fluctuations de la température. Elles conduisent à une modification temporaire de l'équilibre génétique de la population et à un accroissement de la fréquence des génotypes considérés comme mieux adaptés au climat tempéré, lorsque les conditions environnementales deviennent moins favorables.

     

Evidence for structuring of bacterial community composition by organic carbon source in temperate lakes

Water entering lakes from the surrounding watershed often delivers large amounts of terrestrial-derived dissolved organic carbon (DOC) that can contribute to aquatic bacterial production. However, research suggests that phytoplankton-derived DOC is more labile than its terrestrial counterpart, owing to microbial processing of terrestrial-derived DOC along its flow path to surface waters. The ratio of water colour (absorbance at 440 nm) to chlorophyll a has been suggested as a simple measure of the relative contribution of terrestrial and aquatic primary production to aquatic secondary production. To explore the correlation between primary DOC source and the occurrence of bacterial taxonomic groups, we conducted a survey of bacterial 16S rRNA gene composition in 15 lakes positioned along a water colour : chlorophyll a gradient. Our goal was to identify bacterial taxa occurrence patterns along the colour : chlorophyll a gradient that may indicate a competitive advantage for bacterial taxa using terrestrial or aquatic carbon. We observed a large number of bacterial taxa occurrence patterns suggestive of carbon substrate niche partitioning, especially when relatively highly resolved taxonomic groups were considered. Our survey supports the hypothesis that bacterial taxa partition along a carbon substrate source gradient and highlights carbon source–bacterial interactions that should be explored further.     

Seasonal and interannual variation in carbon dioxide exchange and carbon balance in a northern temperate grassland

Net ecosystem carbon dioxide (CO₂) exchange (NEE) was measured in a northern temperate grassland near Lethbridge, Alberta, Canada for three growing seasons using the eddy covariance technique. The study objectives were to document how NEE and its major component processes—gross photosynthesis (GPP) and total ecosystem respiration (TER)—vary seasonally and interannually, and to examine how environmental and physiological factors influence the annual C budget. The greatest difference among the three study years was the amount of precipitation received. The annual precipitation for 1998 (481.7 mm) was significantly above the 1971–2000 mean (± SD, 377.9 ± 97.0 mm) for Lethbridge, whereas 1999 (341.3 mm) was close to average, and 2000 (275.5 mm) was significantly below average. The high precipitation and soil moisture in 1998 allowed a much higher GPP and an extended period of net carbon gain relative to 1999 and 2000. In 1998, the peak NEE was a gain of 5 g C m^?2 d^?1 (day 173). Peak NEE was lower and also occurred earlier in the year on days 161 (3.2 g C m^?2 d^?1) and 141 (2.4 g C m^?2 d^?1) in 1999 and 2000, respectively. Change in soil moisture was the most important ecological factor controlling C gain in this grassland ecosystem. Soil moisture content was positively correlated with leaf area index (LAI). Gross photosynthesis was strongly correlated with changes in both LAI and canopy nitrogen (N) content. Maximum GPP (A_max: value calculated from a rectangular hyperbola fitted to the relationship between GPP and incident photosynthetic photon flux density (PPFD)) was 27.5, 12.9 and 8.6 µmol m^?2 s^?1 during 1998, 1999 and 2000, respectively. The apparent quantum yield also differed among years at the time of peak photosynthetic activity, with calculated values of 0.0254, 0.018 and 0.018 during 1998, 1999 and 2000, respectively. The ecosystem accumulated a total of 111.9 g C m^?2 from the time the eddy covariance measurements were initiated in June 1998 until the end of December 2000, with most of that C gained during 1998. There was a net uptake of almost 21 g C m^?2 in 1999, whereas a net loss of 18 g C m^?2 was observed in 2000. The net uptake of C during 1999 was the combined result of slightly higher GPP (287.2 vs. 272.3 g C m^?2 year^?1) and lower TER (266.6 vs. 290.4 g C m^?2 year^?1) than occurred in 2000.     

Seasonal variations in bacterial communities in adirondack streams exhibiting pH gradients

Measurements of microbial biomass, bacterial numbers, and microbial production were determined for three small woodland streams located in the Adirondack Mountain region of New York State, USA. These streams exhibited spatial and temporal gradients in water pH ranging from a high of 7.0 to a low of 4.5. Twelve sites along these streams were used for comparative analyses of the effects of pH and related water chemistry parameters on the planktonic, sedimentary, and epilithic bacterial communities. The planktonic bacterial communities were not influenced by water pH or related water chemistry parameters. For sedimentary populations, the organic content of the sediment was more important than the chemistry of the overlying water. The epilithic bacterial communities, however, were influenced significantly by the pH of the water column, showing decreased bacterial production at lower pH.     

Seasonal variations of physiological characteristics and thermal sensation under identical thermal conditions

Seasonal variations of human thermal characteristics were inspected in thermal comfort and when constantly indoors. Metabolic rate, tympanic temperature, skin temperature, body fat, body weight and thermal sensation were measured under identical thermal conditions in a chamber over the course of one year. Experiments were carried out for each subject in both summer and winter. Six subjects were measured 35 times in summer and 45 times in winter. one subject was measured weekly for 14 months. Measurements for analyses were taken 40-60 min after entrance into the chamber. Results revealed the following. 1) For all subjects, the metabolic rate, tympanic temperature and body fat were lower in summer than in winter; thigh skin temperatures were higher in summer than in winter. The averaged individual ratio of seasonal difference was 11.9% for metabolic rate, 14.9% for body fat, 1.8% for thigh temperature and 0.53% for tympanic temperature. Seasonal differences of about 10% in metabolic rate were maintained in this study. 2) Seasonal variations of the variables were examined for phase relationships against the outdoor temperature. 2-1) Metabolic rate, thermal sensation, body weight and body fat changed in reverse phase, whereas skin temperature was in-phase. 2-2) Skin temperature lagged by about one month in both summer and winter. Body fat also lagged by about one month in summer, but corresponded to the phase in winter. Metabolic rates were also in-phase in winter but led about three months in summer. Thermal sensations lagged by about three months in winter but were in-phase in summer. Body weight was in-phase in summer and winter. 2-3) Summer disorders were observed particularly in seasonal variations of metabolic rates, tympanic temperature, skin temperatures, and thermal sensation, thereby suggesting that the effect of temperature exposure was altered by air-conditioner use.     

Nutrient enrichment experiments in three central Florida lakes of different trophic states

Seasonal nutrient enrichment experiments (short-term bioassays) were conducted in three Florida lakes of different trophic states to determine the effects of addition of various nutrient combinations upon chlorophyll a and phytoplankton standing crops. Nutrient enriched surface water samples with crustacean zooplankton removed were incubated in situ in clear polyethylene bags for 3 to 6 days. The 2⁵ factorial design employed two levels (ambient and enriched) of each of five nutrients [NH₄ ⁺, PO _inf4 ^sup3− , Fe⁻ -EDTA, SiO _inf3 ^sup2− and a cation (Ca²⁺ or K⁺) or trace elements]. Ammonium produced significant increases in chlorophyll a and phytoplankton standing crops in all experiments. Phosphate produced similar results in the mesotrophic lake, but the eutrophic lakes had both positive and nonsignificant responses which varied seasonally between lakes. Iron increased chlorophyll a in most experiments but affected total phytoplankton standing crop only during the summer and fall. Silicon had negative effects in some experiments. Cations and trace elements produced marked differences between lakes for chlorophyll a, but total phytoplankton standing crop showed few significant responses. Synergistic responses to two- and three-factor interactions were observed in all lakes. Differences in the responses of phytoplankton taxonomic divisions to enrichment may be responsible for much of the between lake variation in chlorophyll a and total phytoplankton volume responses. Nutrient limitations in these lakes are discussed and related to limnological factors and predictive models.     

Establishing the pattern of heterotrophic bacterial activity in three Central Amazonian lakes

Three lakes of the Central Amazon were studied in depth for a year. Patterns of heterotrophic activity were seen to develop as the result of a variety of factors in the three lakes. Primary mechanisms that appear to control the heterotrophic activity were the water levels, the nutrient concentrations, including labile carbon, and the chlorophyll-a levels. Heterotrophic activity (V_max) in the three lakes varied from values comparable to extreme oligotrophic to eutrophic in each of the lakes studies. The large range (0.045–9.644 µg 1^–1 h^–1) of V_max is viewed as a part of the cycle of growth and renewal which is characteristic of the Central Amazonian Ria and Varzea lakes.     

Electron microscope study of DNA-containing plasms. II. Vegetative and mature phage DNA as compared with normal bacterial nucleoids in different physiological states

The nucleoids of Escherichia coli, independently of the physiological state of the bacteria, are shown to be preserved as a fine-stranded fibrillar nucleoplasm by an OsO(4) fixation under defined conditions: acetate-veronal buffer pH 6, presence of Ca(++) and amino acids, stabilization with uranyl-acetate before dehydration. The same fixation procedure applied to the DNA of vegetative phage reveals a pool of homogeneous fibrillar structure very similar to the nucleoplasm. The "versene test," which produces a coarse coagulation of these plasms, emphasizes the similar behaviour of the pool and the nucleoids. The heads of mature phage are preserved in their true polyhedral shape by the standard fixation procedure, although they may be badly distorted when fixed under different conditions. Lanthanum nitrate and uranyl-acetate are shown to increase markedly the contrast of both phage and cytoplasm. The consequences of the fibrillar structure of the genetic material are discussed in relation to the probable division process.