Seasonal variation in the total volume of Leydig cells in stallions is explained by variation in cell number rather than cell size

Stereological methods were employed in two studies with stallions 1) to determine if seasonal variation in the total volume of Leydig cells is a function of cell number or cell size and 2) to characterize the annual cycle of the Leydig cell population. In the first study, numbers of Leydig cells were calculated for 28 adult (4-20 yr) stallions in the breeding or nonbreeding seasons from nuclear volume density (percentage of the decapsulated testicular volume), parenchymal volume (decapsulated testicular volume), and the volume of individual Leydig cell nuclei. The average volume of the individual Leydig cells was calculated as the total Leydig cell volume/testis (volume density of Leydig cells in the parenchymal volume times parenchymal volume) divided by the number of Leydig cells. The average volume of an individual Leydig cell varied within each season, but means were almost identical for the nonbreeding (6.94 +/- 0.61 picoliter) and breeding (6.91 +/- 0.45 picoliter) seasons. However, Leydig cell numbers per testis were 57% higher in the breeding season, which also had a 58% higher total volume of Leydig cells per testis. In the second study, the numbers of Leydig cells were determined for 43-48 adult horses in each 3-mo period for 12 mo. The number of Leydig cells per testis in May-July was higher (p less than 0.05) than in August-October or February-April, and higher (p less than 0.01) than in November-January. Thus, seasonal fluctuations in the total volume of Leydig cells in adult stallions is a function of the number of Leydig cells that cycle annually.     

Seasonal variation in testicular volume and sexual behavior of Chios and Serres rams

The seasonality of testicular volume and sexual behavior in two Greek breeds of sheep, Chios and Serres, was studied using 10 mature rams of each breed. The rams were kept out of breeding during 2 consecutive years. Live weight was recorded at monthly intervals. Testicular volume was measured at 2-week intervals using an orchidometer. Sexual behavior was recorded at 4-week intervals by exposing rams to oestradiol-treated ovariectomized ewes. The total number of mounts and matings, and the reaction time to first mount and mating were recorded. Chios rams were heavier than Serres rams (87.4 +/- 2.0 kg versus 76.4 +/- 1.9 kg, respectively). All traits varied significantly with month but only testicular volume exhibited a clear seasonal trend in both breeds, with a maximum volume in July-August and a minimum in February-April. Number of mounts showed clear seasonal trend in the Chios breed, with maximum in November. Number of mounts was significantly correlated with length of daylight (-0.18 and -0.21 for Chios and Serres, respectively; P < 0.01) and relative humidity (0.14 and 0.17 for Chios and Serres, respectively; P < 0.05). Testicular volume was positively correlated with air temperature (0.28; P < 0.01) and relative humidity (-0.23; P < 0.01) in the Serres breed only. Results of this study suggest that the testicular volume and number of mounts exhibit seasonal variation in the Chios and Serres rams.     

Seasonal variation in hippocampal volume in a food-storing bird,the black-capped chickadee

Black-capped chickadees (Parus atricapillus) in upstate New York show a peak in food-hoarding intensity in October. We caught chickadees at six different times of the year and measured the volume of several brain structures. We found that the hippocampal formation, which is involved in spatial memory for cached food items, has a larger volume, relative to the rest of the brain, in October than at any other time of the year. We conclude that there is an association between the intensity of food hoarding and the volume of the hippocampal formation and suggest that the enhanced anatomy might be caused by the increased use of spatial memory. © 1995 John Wiley & Sons, Inc.     

Seasonal variation in the abundance and heterotrophic activity of suspended bacteria in two lowland rivers

SUMMARY. 1. Water samples were collected over two years from the Yorkshire Ouse and Yorkshire Derwent and the following were measured: (i) concentration of directly-counted bacteria (free-living and particle-bound), (ii) concentration of colony-forming units, (iii) bacterial heterotrophic activity (turnover rate for glucose assimilation), (iv) specific activity (turnover rate per bacterium), (v) a range of environmental variables.
2. The abundance and activity of suspended bacteria showed similar seasonal periodicities in both rivers.
3. Free-living bacteria were usually more numerous than particle-bound bacteria; low concentration of free-living bacteria and maxima of particle-bound bacteria usually occurred in winter.
4. Concentration of colony-forming units varied irregularly, but lowest levels were found in summer.
5. Turnover rate and turnover rate per bacterium showed distinct summer maxima.
6. Multiple-regression analysis was used to relate bacterial variables to subsets (chosen by factor analysis) of environmental variables; up to 89% of variation in bacterial variables was related to the combined effects of variation by variables in the chosen subsets.     

The impact of zooplankton feeding on the epilimnetic bacteria of a eutrophic lake

SUMMARY. The members of the zooplankion eat bacteria in natural systems, but the impact of this mechanism of removal of bacterial biomass on the bacterioplankton of freshwaters is unknown. Zooplankton abundance and biomass were followed for 2 years in Lake Mendota. Bacterial biomass and heterotrophic production were also assessed. Feeding of zooplankton on bacteria was measured by a cell counts method in 1979 and using radioactively labelled natural assemblages of bacteria in 1980. Total feeding was calculated and was found to account for l-60% of the bacterial biomass daily. Annually, it accounted for 1–10% of the bacterial heterotrophic production. Since bacterial biomass does not change significantly from year to year and yet bacterial production is very high compared to feeding by zooplankton, mechanisms other than feeding must exist which remove biomass from the epilimnetic bacteria in larger amounts.     

Seasonal variation in the testicular volume of capuchin monkeys (Cebus apella) in captivity

The study of the reproductive strategy developed by different species in order to adapt to their environmental conditions and their meaning in an evolutionary perspective is essential for understanding the mechanisms involved in the process of reproduction. Non-human primates are very interesting models for this purpose. Some species show a typical seasonal reproductive pattern, such as rhesus macaques (Macaca mulatta) [Sade, 1964; Conaway and Sade, 1965] and ring-tailed lemurs (Lemur catta) [Zuckerman, 1953], while others, such as gorillas (Gorilla gorilla) and chimpanzees (Pan troglodytes) [Puschmann, 1975], show relative independence of the environment. Neotropical primates display many different breeding strategies. Female capuchin monkeys (Cebus apella), for instance, having reached puberty, have fertile cycles year-round [Hamlett, 1939; Nagle and Denari, 1983]. Interestingly, there are reports of a clear peak of births in free-living [Hamlett, 1939] and captive colonies [Welker et al., 1983] in the dry season, i.e. May-June in the southern hemisphere. Some authors suggest that a seasonal variation in spermatogenesis could explain the birth peak [Freese and Oppenheimer, 1981]. The aim of this study was to investigate this theory, measuring seasonal variation in total testicular volume in a captive group of male capuchin monkeys and assessing its temporal correlation with the birth season as an indirect indication of variation in male fertility.     

Long-term trends of epilimnetic and hypolimnetic bacteria and organic carbon in a deep holo-oligomictic lake

We analysed the long-term dynamics (1980–2007) of hypolimnetic and epilimnetic bacterial abundances and organic carbon concentrations, both dissolved (DOC) and particulate (POC), in the deep holo-oligomictic Lake Maggiore, included in the Southern Alpine Lakes Long-Term Ecological Research (LTER) site. During the 28 years of investigation, bacterial abundance and POC concentrations did not decrease with declining phosphorus concentrations, while DOC concentrations showed a pronounced decrease in the epi- and hypolimnion. We used the annual mean total lake heat content and total annual precipitation as climate-related variables, and in-lake total phosphorus as a proxy for trophic state. The model (forward stepwise regression, FSR) showed that reduced anthropogenic pressure was more significant than climate change in driving the trend in DOC concentrations. Bacterial dynamics in the hypolimnion mirrored the fluctuations observed in the epilimnion, but average cell abundance was three times lower. The FSR model indicates that bacterial number variability was dependent on POC in the epilimnion and DOC in the hypolimnion. In the hypolimnion, cell biovolumes for rod and coccal morphotypes were significantly larger than in the epilimnion.     

Seasonal variation in human births

During the first half of this century, the seasonal pattern of births in European countries showed a major peak in the spring and a minor peak in the autumn. In contrast, the pattern in the US was of a minor peak in spring and a major peak in autumn. Over the last 20 years, the pattern in England and Wales has changed to resemble the US pattern, and the same seems to be true of several other European countries. A hypothesis is offered to account for the difference between the European and the US patterns and for the change from one to the other in some countries. The magnitude of seasonality correlates positively with latitude: it is suggested that this is partially consequent on variation in luminosity.     

Seasonal variation in non-disjunction of sex-chromosomes

Summary There was a significant deviation, from the expected seasonal variation, in the births of 53 patients with Klinefelter's syndrome, 47,XXY (P<0.05). There was a comparatively high frequency of patients with Klinefelter's syndrome born in March–April and October.     

Seasonal variation of suicide in Brazil

Most of what is known about the seasonal variation in suicide rate originates from studies conducted in the northern hemisphere; very few studies have been done in the southern hemisphere. The purpose of the present study was to explore the possibility that in Brazil, the seasonal variation of suicides is a function of photoperiod. This was accomplished by analyzing monthly suicide data for a 12 yr period (1979 to 1990), within latitudes ranging from 2°N to 33°S. Single cosinor analyses with periods of 12 or 6 months were applied to time series of monthly total and suicidal deaths, separated by gender and state. Significant spring or early summer peaks of suicide were found only in the south of Brazil for both men and women, except for the latter in one state. These peaks did not coincide with those found for total deaths, which occurred in the autumn or winter in all areas. No significant six-month period was found. In the present study, the chance of a suicide was typically 10-17% higher during the peak period than during the other months of the year. Although this moderate seasonal effect might not be sufficient to justify planning large scale prophylactic interventions, those dealing with patients who have suicide ideation should be aware of this high risk time.     

Seasonal variation of necrospermia in man

Abstract

We have investigated the variability of the necrozoospermia in human semen, over three periods of nine months from the end of October to July, during the last three years. The donors are twenty young men in good health who have given regular specimens of sperm once of twice monthly for a period of only one or two years. Analysis of the mean curves shows a maximum during winter and a minimum in the beginning of spring, for the three years considered.     

天梯山石窟壁画保存环境中空气细菌的季节性变化

【背景】微生物侵蚀是古代壁画常见生物病害,影响壁画的长久保存和安全陈展。空气微生物作为壁画病害菌的主要来源,近年在文物赋存环境监测和预防性保护中引起广泛重视。【目的】对天梯山石窟壁画的2处保存地,即天梯山原址和武威西夏博物馆壁画保存环境中的空气细菌浓度、群落结构及其季节变化规律进行分析。【方法】利用生物气溶胶采样器,在2016年春、夏、秋、冬4季分别采集各位点空气样品;基于传统培养方法获得空气中细菌浓度及纯培养菌株;通过提取细菌基因组DNA、扩增其16S rRNA基因、测序和系统发生关系分析等技术研究不同位点细菌群落时空动态变化规律;结合环境监测数据,分析影响文化遗产地空气细菌群落变化的主要因素。【结果】空气可培养细菌的总浓度在16.7-1 451.8 CFU/m3范围内变动。原址第18窟和第13窟,各季节细菌浓度无显著性差异,且呈明显季节性变动规律,总体特征为夏秋季低,冬春季高。西夏博物馆外空气细菌浓度在各季节均高于库房内,冬季最高。本研究共鉴定出19个细菌属,隶属于4个门;其中不动杆菌属(Acinetobacter)、节杆菌属(Arthrobacter)、芽孢杆菌属(Bacillus)、考克氏菌属(Kocuria)、短波单胞菌属(Brevundimonas)、肉食杆菌属(Carnobacterium)、 Pseudoclavibacter和薄层菌属(Hymenobacter)为优势属。【结论】天梯山石窟空气细菌群落结构具有明显的时空分布特征;相对湿度、温度及季节性降水均会影响其变化;鉴定得到部分种属具备引起壁画生物腐蚀的潜势;本研究可为当地开展遗址和馆藏环境中文物预防性保护提供本底资料。     

Seasonal variation in cell cycle during early development of the mouse embryo.

Studies of the cell cycle of mouse embryos before implantation were conducted using Giemsa and DAPI stains. The time of embryo recovery did not affect the success rate of cultures during the winter, but embryos cultured during the summer showed the 'two-cell block' phenomenon at the early two-cell stage, 30-37 h after the injection of human chorionic gonadotrophin. There was no significant difference in the number of embryos collected per mouse between summer and winter, but cleavage from the two-cell to the four-cell stage occurred later in the summer than in the winter. Cell cycle of mouse embryos may therefore show seasonal variation.     

Seasonal variation in serum testosterone, testicular volume and semen characteristics in coatis (Nasua nasua)

The objective was to characterize seasonal changes in serum testosterone concentration, testicular volume and sperm quantity and quality in captive coatis (Nasua nasua) from Pantanal, MT, Brazil. Sampling was done once monthly for 1 y. Mean (± SEM) serum testosterone concentrations (767.37 ± 216.2 ng/ml) and total and progressive sperm motility (79.6 ± 3.9%; 3.8 ± 0.3, on a scale of 0 to 5) peaked in July. The highest combined testis volume (10.3 ± 0.4 cm³) and sperm concentration (403 million ± 102 sperm/ml) occurred in August, at the peak of the winter breeding season. No seasonal effects on percentages of morphologically normal sperm, acrosome integrity, or live sperm were detected; however, the percentage of secondary sperm defects was higher in the winter. In conclusion, intricate relationships between testosterone concentration, testis volume, semen concentration and total and progressive sperm motility with high levels of breeding activity were observed during the dry season in the winter (June, July, August), followed by a subsequent decline in these activities during the wet season (i.e., summer: December, January, February). There was no seasonal pattern for production of functionally intact and morphologically normal sperm.     

Changes in cell volume of bacteria and heterotrophic nanoflagellates in a hypereutrophic pond

Changes in cell volume of planktonic bacteria and heterotrophic nanoflagellates (HNF) were examined in a hypereutrophic pond from April to October, 1997. There were marked changes in the abundance of bacteria, HNF and ciliates and in protistan bacterivory during this period. The cell volume of free-living bacteria (0.121 ± 0.031 m³, mean ± SD) was large relative to that reported in the literature. The cell volumes of HNF was 71.1 ± 24.8 m³. Both cell volumes did not follow a seasonal trend. The dominant size class of bacteria was seasonally variable, whereas density of filamentous bacteria was relatively high between August and September. Biomass of filamentous bacteria accounted for up to 33.6% of total bacterial biomass. A correlation analysis for cell volume of bacteria and HNF, density of filamentous bacteria and some microbial variates was performed. The positive correlations detected (p<0.05) were between density of bacteria and cell volume of HNF, and between density of filamentous bacteria and cell volume of HNF.     

Seasonal nutrient variation in trembling aspen

Summary Variation in concentrations of N, K, Mg, and Ca in vegetative-buds, leaves, twigs, and male catkins of trembling aspen (Populus tremuloides Michx.), determined throughout a growing season in central Minnesota, reflected the different physiological roles of the nutrients. Practical implications are discussed.     

Mind the cell: Seasonal variation in telomere length mirrors changes in leucocyte profile

Leucocytes are typically considered as a whole in studies examining telomere dynamics in mammals. Such an approach may be precarious, as leucocytes represent the only nucleated blood cells in mammals, their composition varies temporally, and telomere length differs between leucocyte types. To highlight this limitation, we examined here whether seasonal variation in leucocyte composition was related to variation in telomere length in free‐ranging mandrills (Mandrilllus sphinx). We found that the leucocyte profile of mandrills varied seasonally, with lower lymphocyte proportion being observed during the long dry season presumably because of the combined effects of high nematode infection and stress at that time of the year. Interestingly, this low lymphocyte proportion during the long dry season was associated with shorter telomeres. Accordingly, based on longitudinal data, we found that seasonal changes in lymphocyte proportion were reflected by corresponding seasonal variation in telomere length. Overall, these results suggest that variation in lymphocyte proportion in blood can significantly affect telomere measurements in mammals. However, lymphocyte proportion did not entirely explain variation in telomere length. For instance, a lower lymphocyte proportion with age could not fully explain shorter telomeres in older individuals. Overall, our results show that telomere length and leucocyte profile are strongly although imperfectly intertwined, which may obscure the relationship between telomere dynamics and ageing processes in mammals.