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PubMed2004

Seasonal variation of genotype-specific fertility and adaptation to endemic diseases: a study in past malarial areas of Italy.

Cyclic seasonal variation of genotype-specific fertility could interact with endemic diseases characterized by seasonal variation of severity resulting in changes of gene frequencies in the course of generations. Assuming that a given allele A has a frequency pw in infants conceived in the cold season and a frequency of ps in those conceived in the warm season and assuming that general fertility is the same in the two seasonal periods, the gene frequency in the population is pm = (pw + ps)/2; this frequency remains constant over the course of generations. The introduction of an endemic disease bearing negatively on general fertility and characterized by a seasonal pattern of severity could result in variations of the A allele frequency. If the maximum of endemicity coincides with the maximum value of the allele A frequency, the frequency of allele A will progressively decrease. A simple mathematical algorithm has been applied to two polymorphic enzymes (ACP1 and G6PD) correlated with past malarial morbidity in Sardinia and the Po River delta. The two systems show differences in gene frequency in relation to season of conception. The theoretical changes fit quite well with the data observed in Sardinian and Po delta populations, thus suggesting a mechanism that is an alternative to or concurrent with the classical mechanism that assumes a direct connection between the genetic systems and the biology of the malarial parasite.

Adaptation, Physiological↗
PubMed1994

Testicular and epididymal sperm content in grazing Cashmere bucks: seasonal variation and prediction from measurements in vivo.

Each month, for 15 months, the testes and epididymides were recovered from five Australian cashmere bucks selected at random from a group of mature bucks (initial n = 116) at pasture (location 29 degrees S, 153 degrees E). The extent of seasonal change in testicular and epididymal sperm reserves was determined and indirect methods for predicting these reserves were developed. Paired testicular weight exhibited clear seasonal variation from 137 g in August to 269 g in February. The total elongated spermatid content of the testes, determined by homogenization, showed a very similar seasonal pattern, ranging from 13.8 x 10(9) in September to 36.2 x 10(9) in March. Seasonal changes of similar timing were observed for paired epididymal weight and sperm content. Although changes in total testicular spermatid content were largely the result of change in testicular weight (R2 = 0.72, P < 0.001), the elongated spermatid content of testicular parenchyma (mean, 127 x 10(6) g-1) exhibited significant seasonal variation with elevated values between February and June, suggestive of an increase in the efficiency of spermatogenesis. Daily sperm production, calculated by means of a spermatogenic time divisor for sheep, ranged from 2.76 x 10(9) in September to 7.23 x 10(9) in February. Scrotal circumference, scrotal volume and testicular length x diameter2 were identified as accurate predictors of testicular weight (R2 > or = 0.87) and sperm content (R2 > or = 0.70). The results demonstrate that: (a) cashmere bucks exhibit considerable seasonal variation in spermatogenesis associated primarily with changes in testicular mass but also with changes in the efficiency of spermatogenesis; and (b) indirect measures of testicular size are good predictors of testicular elongated sperm content. When the correct spermatogenic time divisor for goats is determined, such indirect measures may be used to predict daily sperm production.

Animals↗
PubMed2000

Seasonal variation in plasma levels of endothelin-1 and nitric oxide.

BACKGROUND: There is a seasonal variation in the incidence of stroke and coronary heart disease with admissions to hospital being higher in the colder months of the year. The mechanism whereby this winter prevalence of vascular disease occurs is still not fully understood. The aim of our study was to measure plasma levels of vasoactive compounds throughout the year to establish whether or not there were any fluctuations which could play a part in the higher winter incidence. METHODS: We measured plasma levels of the vasoconstrictive endothelin-1 (ET) and the vasorelaxant nitric oxide (NO) throughout the year. Blood samples were collected from 176 normal individuals. Samples were collected between 8.00 and 10.00 hours after an overnight fast of at least 12 hours. RESULTS: Results were divided into two-monthly intervals and analysed using a Kruskal-Wallis one-way analysis of variance and Mann-Whitney U tests (SPSS). We found a significant seasonal variation in both parameters. Mean levels of endothelin were highest in January/February (4.0 pg/ml) and lowest in May/June (2.3 pg/ml), whereas plasma 5 nitric oxide levels were lowest in January/February (5.7 microM) and highest in September/October (9.9 microM); p values were <0.0001 (Jan/Feb vs May/June) and 0.049 (Jan/Feb vs Sept/Oct), respectively. CONCLUSIONS: The high levels of the vasoconstrictor endothelin combined with low levels of vasorelaxant nitric oxide may account in part for the increased incidence of stroke and coronary heart disease seen in these months.

Aged↗
PubMed2002

Misclassification due to body hair and seasonal variation on melanin density estimates for skin type using spectrophotometry.

Recent advances have enabled quite accurate estimations of cutaneous melanin density by spectrophotometry using reflectance of light at wavelengths 400 and 420 nm. Our purpose was to assess the effect of body hair and seasonal variation at the upper inner arm and buttock on measurements of melanin density. We estimated melanin density of 104 volunteers at 3-monthly intervals over 12 months both before and after shaving. Removing body hair at the upper inner arm had no effect, but substantially reduced melanin estimates at the buttock in men. Significant seasonal variation was only observed at the upper inner arm, with highest readings in summer-autumn. In case-control studies, misclassification due to body hair at the buttock and seasonal variation at the upper inner arm could affect the observed odds ratio substantially. However, both sources of error can be reduced by careful attention to key aspects of study design.

Adult↗
PubMed1985

Seasonal variations of metacercarial density of Clonorchis sinensis in fish intermediate host, Pseudorasbora parva.

The seasonal variations of the rate and intensity of metacercarial infection of C. sinensis in P. parva were observed. The fish were collected at Sun-Am river which located in Kim-Hae City, Kyong-Sang-Nam Do(=Province), Korea, from March 1983 to February 1984 every month. A total of 788 fish was examined. The number of metacercariae in each fish was individually counted after the individual digestion by artificial gastric juice. The result was as follows: During one year, 513(65.1%) out of 788 fish were infected with metacercariae. In May, June, July and September, the infection rates ranged from 82. 0 % to 98. 6% whereas the rates was relatively low in March, April, November and February raning from 11. 4% to 64.7%. The intensity of infection was similar with those of infection rates. The mean intensity per infected fish was 103.0 and standard deviation was 118.9 throughout one year. The highest mean intenstiy was in June(294. 8) and the lowest in Novebmver(11.1). The observed frequency of fish with certain intensities of metcercariae were fitted to theoretical equations derived from negative binomial distribution in March, April, November and February(p > 0.05). Meanwhile, the equation of lognormal distribution were fitted with the observed frequencies in May, June, July and September(p > 0.05, p > 0.75). The variance/mean ratio varied by month. The value was the highest in July(814.3) and the lowest in November(158.8). Unlike our hypothesis, the metacercarial density of Clonorchis sinensis in its the most favourable fish host, Pseudorasbora parva showed considerable seasonal variations in the hyperendemic area. The possible factors were discussed.

Journal Article↗
PubMed2004

Seasonal variations in polyhydroxysteroids and related glycosides from digestive tissues of the starfish Patiria (=Asterina) pectinifera.

Seasonal variations in the concentrations of individual polyhydroxysteroids and related low molecular weight glycosides in pyloric caeca and stomach of the starfish Patiria (=Asterina) pectinifera collected at one location near Vladivostok have been studied. HPLC analysis on the fractions containing these substances showed a fairly constant composition of steroids in digestive tissues of P. pectinifera in spite of small seasonal variations in the relative concentrations of individual compounds.

Animals↗
PubMed1976

Seasonal variation in the incidence of mania.

The seasonal variation of admissions to hospital with a diagnosis of mania (296.1) in England and Wales was examined. The results indicated that for females there was a significant seasonal trend, the peak being in August-September, while for males there was no significant seasonal pattern. The possible reasons for these findings are discussed.

Bipolar Disorder↗
PubMed2004

[Seasonal variations in admissions for acute myocardial infarction. The PRIMVAC study].

INTRODUCTION AND OBJECTIVES: Some authors have described seasonal variations in the incidence of acute myocardial infarction. The aim of this study was to determine the existence of seasonal rhythms in admissions for acute myocardial infarction to coronary care units, and in mortality, and to analyze the influence of age on environmental factors. PATIENTS AND METHOD: The study included a total of 8400 consecutive patients with acute myocardial infarction admitted to 12 coronary care units in the PRIMVAC registry from January 1995 to December 1999. Seasonal rhythms were analyzed with the time series method and the Cosinor regression equation. The influence of age was analyzed with the chi 2 test. RESULTS: The total number of admissions increased in winter and decreased in summer. The highest peak (acrophase) occurred in winter, with 2183 cases (r2=0.91), specifically in February, with 742 cases (r2=0.66). The age of the patients conditioned seasonal variations (P=.006), and the influence was statistically significant for patients over 65 years of age. Changes in mortality with time did not reach statistical significance. CONCLUSIONS: A seasonal rhythm in admissions for acute myocardial infarction was found, with an increase in winter and a decrease in summer. Age conditioned the effect of environmental factors on acute myocardial infarction, and patients aged 65 years or older were more sensitive to mechanisms that led to increases in admissions in winter.

Age Distribution↗
PubMed2003

Diurnal and seasonal variations in the onset of primary intracerebral hemorrhage in individuals living in Izumo City, Japan.

OBJECT: Little is known about the temporal patterns of primary intracerebral hemorrhage (ICH) among the general population. The aim of this study was to examine diurnal and seasonal variations in the onset of ICH in a community-based series. METHODS: The study population consisted of 350 patients who presented with primary ICH for the first time and were treated between 1991 and 1998 in Izumo City, Japan. Among the entire patient population, the onset of hemorrhage was rarely observed during the night and a peak was observed in the late afternoon. In men 69 years of age or younger, the onset of ICH exhibited a bimodal distribution, with an initial high peak between 8:00 and 10:00 a.m. and a second, lower peak between 6:00 and 8:00 p.m. In contrast, in men 70 years of age or older and in women regardless of age, only a single evening peak, between approximately 6:00 and 10:00 p.m., was found, and no morning peak was observed. For the entire patient population (for both sexes), and for men alone, seasonal variations--a peak in winter and a trough in summer-were significant for all age groups combined. This factor was significant for patients 69 years of age or younger, during the daytime hours (8:00 a.m.-8:00 p.m.), and for patients with untreated hypertension; however, it was not significant for patients 70 years of age or older, during nighttime hours (10:00 p.m.-8:00 a.m.), or for treated hypertensive and normotensive patients. In women, no significant seasonal patterns were found, regardless of patient age, time of day at onset of ICH, or the presence of risk factors. Seasonal variations were statistically significant for patients with hematomas larger than 5 ml, but not for those with hematomas 5 ml or smaller. CONCLUSIONS: Temporal distributions in the onset of ICH seem to be influenced by patient sex and age. The seasonal patterns of ICH occurrence may result mainly from changes that occur during the daytime, and may also be modified by the presence of untreated hypertension and by the volume of the hematoma.

Adult↗
PubMed1992

Incidence of neonatal hip instability: are there seasonal variations?

We wanted to establish whether the season of birth affected the incidence of neonatally diagnosable hip instability in Eastern England. Data relating the numbers of maternities to the numbers of cases of congenital displacement of the hip diagnosed in neonates were analyzed month by month over a period of 8 years. The study covered 185,744 maternities and 154 cases of displaced hips during the period 1979-1986. While there were wide fluctuations in the monthly incidence, there was a striking excess of the malformation in late winter and early spring, i.e. in January, February, March and April, and a progressive decline in the succeeding months. The cause or causes of the seasonal variation are unknown.

Birth Rate↗
PubMed1998

Eclampsia: is there a seasonal variation in incidence?

OBJECTIVE: To clarify whether seasonal variation of temperature and humidity has any effect on the incidence of eclampsia. Eclampsia is the second major cause of maternal mortality in Pakistan. METHODS: Data was collected monthwise for the year 1996 from 4 large Govt. teaching hospitals of 4 provincial metropolis of Pakistan. Each province has diverse climate with considerable variation of air temperature and humidity. RESULTS: There were 395 cases of eclampsia amongst 18,483 deliveries in 1996, giving an incidence of 2.14%. In Karachi (Sindh Province) with mild hot and humid climate and mild winter months, there was increase in eclampsia cases from April-July and in September. Otherwise the incidence remained stable. In Rawalpindi (Punjab Province) with moderately hot summer and cold winter, it was highest in hot season from May to September but was stable in winter. In Peshawar (N.W.F.P) and Quetta (Baluchistan Province) with more severe cold and dry winter the incidence peaked in winter and summer months both. CONCLUSIONS: The pattern of eclampsia cases showed variations in extremes of temperature but it was stable in mild weather. However, the statistical analysis revealed non-significant relationship of incidence of eclampsia with temperature when analysed by linear regression analysis.

Eclampsia↗
PubMed2005

Regional and seasonal variations in facial sebum secretions: a proposal for the definition of combination skin type.

BACKGROUND/AIMS: Facial sebum secretions are known to change under various circumstances. Facial skin types have been categorized as oily, normal, dry, and combination types. However, these have been evaluated subjectively by individuals to date, and no objective accepted standard measurement method exists. The combination skin type is most common, but its definition is vaguer than the definitions of the other skin types. METHODS: We measured facial sebum secretions with Sebumeter. Sebum secretions were measured at five sites of the face seasonally for a year, in the same volunteers. Using the data obtained we developed a set of rules to define the combination skin type. RESULTS: Regional differences in sebum secretion were confirmed. Sebum secretions on forehead, nose, and chin were higher than on both cheeks. Summer was found to be the highest sebum-secreting season, and seasonal variations were found in the T- and U-zones. A mismatch of skin type in the T- and U-zones in more than two seasons appears to be close to subjective ratings of what is described as the 'combination' skin type. CONCLUSION: We showed that the face shows definitive regional and seasonal variations in sebum secretion. To define the combination skin type, seasonal variations in sebum secretion should be considered in addition to regional variations.

Face↗
PubMed2006

Seasonal variations in water relations in current-year leaves of evergreen trees with delayed greening.

We investigated seasonal patterns of water relations in current-year leaves of three evergreen broad-leaved trees (Ilex pedunculosa Miq., Ligustrum japonicum Thunb., and Eurya japonica Thunb.) with delayed greening in a warm-temperate forest in Japan. We used the pressure-volume method to: (1) assess the extent to which seasonal variation in leaf water relations is attributable to leaf development processes in delayed greening leaves versus seasonal variation in environmental variables; and (2) investigate variation in leaf water relations during the transition from the sapling to the adult tree stage. Leaf mass per unit leaf area was generally lowest just after completion of leaf expansion in May (late spring), and increased gradually throughout the year. Osmotic potential at full turgor (Psi(o) (ft)) and leaf water potential at the turgor loss point (Psi(w) (tlp)) were highest in May, and lowest in midwinter in all species. In response to decreasing air temperature, Psi(o) (ft) dropped at the rate of 0.037 MPa degrees C(-1). Dry-mass-based water content of leaves and the symplastic water fraction of total leaf water content gradually decreased throughout the year in all species. These results indicate that reductions in the symplastic water fraction during leaf development contributed to the passive concentration of solutes in cells and the resulting drop in winter Psi(o) (ft). The ratio of solutes to water volume increased in winter in current-year leaves of L. japonicum and E. japonica, indicating that osmotic adjustment (active accumulation of solutes) also contributed to the drop in winter in Psi(o) (ft). Bulk modulus of elasticity in cell walls fluctuated seasonally, but no general trend was found across species. Over the growing season, Psi(o) (ft) and Psi(w) (tlp) were lower in adult trees than in saplings especially in the case of I. pedunculosa, suggesting that adult-tree leaves are more drought and cold tolerant than sapling leaves. The ontogenetic increase in the stress resistance of I. pedunculosa may be related to its characteristic life form because I. pedunculosa grows taller than the other species studied.

Cell Wall↗
PubMed1998

Seasonal variation of endogenous uveitis in south-western Finland.

PURPOSE: To evaluate if there is a seasonal pattern to the incidence of endogenous uveitis in south-western Finland with special reference to acute anterior uveitis. METHODS: The incidence rates per month of the 414 new uveitis cases from years 1980-82 and 1988 in the district of Turku University Hospital were calculated. The months of the year were grouped into warm (June to September), transitional (April, May, October, November), and cold (December to March) seasons based on the mean air temperature of the months in Turku. RESULTS: We observed a statistically significant increase in the incidence of all uveitis cases in the warm and transitional seasons compared with the cold season (p=0.030 and p=0.008 respectively). A similar seasonal trend was found among anterior uveitis cases, but not among the intermediate, posterior or panuveitis cases. The incidence of acute anterior uveitis cases was higher in the transitional than in the cold season (p=0.025). No seasonal variation of the incidence was found in the subgroup of acute anterior uveitis where ankylosing spondylitis had been confirmed (p=0.70). CONCLUSION: The present data suggests that there is seasonal variation of the incidence of uveitis in south-western Finland.

Acute Disease↗
PubMedDate not supplied

Effects of seasonal variations, acute hypothermia and physostigmine on cardiac acetylcholine, tissue glycogen and blood sugar concentrations in frogs.

The effects of seasonal variations and the effects of acute hypothermia (8.0 degrees) and/or physostigmine (PHY) in different seasons have been studied on the tissue glycogen, cardiac acetylcholine (ACh) and blood sugar contents in frogs. Seasonal variations had no significant effect on cardiac cholinergic activity. However, cardiac ACh concentration was significantly reduced by hypothermia in all seasons. The extents of increase in cardiac ACh in PHY pretreated hypothermic frogs indicate that hypothermia depresses cardiac cholinergic acitity much more in summers than in rainy and winter seasons. The tissue glycogen contents and blood sugar concentrations were significantly lower in winter season than those in summer and rainy seasons. Hypothermia produced marked tissue glycogenolysis and hyperglycaemia during summer and rainy seasons and not during winters. In general PHY had no effect on tissue glycogen contents in any season, but it produced hyperglycaemia during rainy and winter seasons. PHY pretreatment increased cardiac, hepatic and muscle glycogen contents and produced hyperglycaemia in hypothermic winter frogs, and it increased ventricular and muscle glycogen contents during summer and hepatic glycogen during rainy seasons, there being no significant effects on blood sugar.

Acetylcholine↗
PubMed1984

Seasonal variations in plasma retinol and carotenoid levels in rural Gambian women.

Plasma carotenoid levels exhibited a major seasonal variation in pregnant and lactating women in Keneba, a rural Gambian village. This is probably due mainly to the seasonally related contribution of mangoes, which are a major dietary component during May and June, but are essentially unavailable for the remainder of the year. Plasma retinol levels, on the other hand, exhibited much less seasonal variation, although a trend towards higher levels in May and June was just discernible. Plasma retinol levels were significantly lower than those observed in a group of pregnant and lactating women living in the UK.

Carotenoids↗
PubMed2002

Seasonal variations of 222Rn concentrations in the air of a tunnel located in Nagano city.

The seasonal variation of 222Rn concentrations in the air of tunnels constructed during World War II at Nagano City has been investigated. The determination of 222Rn concentrations in tunnel air was performed using a solid-state nuclear track detector technique. The monthly radon concentrations changed smoothly, decreasing towards winter and increasing towards summer, and it was found that the concentrations strongly correlate with the temperature difference between the inside and the outside of the tunnel. In the innermost areas of the tunnel, the maximum concentration was observed in July, its value being about 6500 Bq m (-3). The concentrations of radon in the tunnel air decrease exponentially towards the openings of the tunnel, which indicates that the radon concentration in the tunnel is basically governed by diffusion and mixing of radon gas with air. These observations lead to the conclusion that the seasonal variation of the radon concentration in the tunnel air is mainly caused by a convection current due to a stack effect induced by the temperature difference between the tunnel air and the outside air.

Air Movements↗
PubMedDate not supplied

Seasonal variation in affective disorders. A case register study.

This paper reports the results of a study on seasonal variation in new episodes of affective disorders, conducted using the South-Verona psychiatric case register. We found evidence for a cyclical pattern in the occurrence of affective psychosis, but this was statistically significant only for the males: there was no cyclical variation in depressive neurosis. The advantages are discussed of case register data over hospital admission statistics for the study of seasonal variation. These are particularly marked in case register areas where community psychiatric care is well developed, as in South-Verona.

Adolescent↗