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PubMedDate not supplied

Rearing management of rabbit males selected by high growth rate: the effect of diet and season on semen characteristics.

A total of sixty-six young males were used to evaluate the effect of low (L), medium (M) and high (H) concentrations of dietary digestible energy received during the rearing seasons (autumn and spring) on the performance and main semen characteristics of males for artificial insemination selected by a high growth rate. Males reared during the spring season presented a significantly higher weight at weaning than those reared during the autumn season (P < 0.001), and these differences were maintained until the end of the trial. The requirements of the males were easily covered as a general rule. In the autumn group, the males were unable to intake the digestible protein recommended only during their 3rd month of life, especially with low concentrate diets (P < 0.05). H males showed higher semen concentration and production during the autumn season, while L males showed a higher semen concentration and production than M males during the spring season, the H group showed intermediate values (P < 0.001). Males reared during the spring season showed significantly higher values of sperm concentration (P < 0.01) and production (P < 0.01). H males presented a lower percentage of spermatozoa with cytoplasmic droplets than the L group (P < 0.05) and the lowest values for sperm abnormalities during the autumn season, while the L group presented higher values for percentage abnormalities, especially during the last month controlled (P < 0.05). As a general rule, the main motility parameters controlled were not affected by the rearing diet received nor the season. These results seem to indicate that the management of rabbit males during the growing and rearing periods seem to significantly affect their subsequent performance and semen production.

Animal Feed↗
PubMed2001

Seasonal pattern of early mortality and infectious complications in liver transplant recipients.

Seasonal variation has been documented in the frequency and attributable mortality of a number of medical illnesses and infections in the nontransplantation setting. Whether similar trends exist in transplant recipients is not known. Seasonal rates of overall and early mortality and contributory variables stratified by season were assessed in 190 consecutive liver transplant recipients who underwent transplantation over a 10-year period. The frequency of infectious complications and rejection was also assessed and stratified by season of transplantation. Early (deaths occurring in the first year posttransplantation), but not overall, mortality correlated significantly with seasonality. Of patients with early mortality, 43% (13 of 30 patients) died in winter; 23% (7 of 30 patients), in spring; 13% (4 of 30 patients), in summer; and 20% (6 of 30 patients), in fall. The frequency of deaths in winter was significantly greater than for all other seasons (P = .022). The high wintertime mortality could not be explained by previously recognized risk factors portending a poor outcome, e.g., United Network for Organ Sharing status, Child-Pugh score, surgical time, blood loss, pretransplantation and posttransplantation dialysis, infections, rejection, or increased immunosuppression. Strong trends toward a higher rate of cytomegalovirus disease in patients who underwent transplantation in fall (P = .09) and bacterial infections in those who underwent transplantation in winter were documented (P = .09). There was no correlation between seasonality and rejection. Early mortality in winter in liver transplant recipients was significantly greater than if the deaths were totally random. Whether the seasonal clustering of deaths and infections is triggered by respiratory viruses, yet unrecognized viruses, or unknown exogenous factors remains to be determined.

Adult↗
PubMed2003

Seasonal intestinal inflammation in patients with birch pollen allergy.

BACKGROUND: The pathophysiologic interactions of inflammatory reactions between the mucosa of the respiratory tract and that of the gastrointestinal tract in individuals with allergy are poorly studied, despite the fact that allergic symptoms in the airways and the gastrointestinal tract might arise in the same patient. OBJECTIVE: The objective of this study was to examine the inflammatory response histologically by enumerating eosinophils, IgE+ cells, and T cells in duodenal biopsy specimens in adult patients with IgE-mediated birch pollen allergy during the birch pollen season and off-season. METHODS: Nine patients with birch pollen allergy verified by skin prick test and serum IgE antibodies were investigated toward the end of the birch pollen season and again 6 months later (off-season). Duodenal biopsy specimens were obtained and studied by immunostaining for the eosinophil major basic protein (MBP), IgE, and CD3+ T cells. RESULTS: Oral allergy syndrome to birch-associated foods was present in all patients as indicated by questionnaire. Duodenal increases of MBP+ eosinophils and IgE-bearing cells were found in the patients during the birch pollen season as compared with off-season. No seasonal differences in the T-cell numbers in these patients were seen. Off-season, there was no significant difference between the patients and the control subjects regarding the intestinal frequencies of MBP+ eosinophils, mucosal IgE+ cells, and T cells. CONCLUSION: Birch pollen exposure triggered a local inflammation with an increase in duodenal eosinophils and IgE-carrying mast cells in patients with allergy. Our study gives evidence for the interplay between immunologically active cells in the airways and the gut.

Adult↗
PubMed1986

Seasonal variations in the nutritional status of urban Gambian children.

1. Children aged 6-35 months in an urban community in The Gambia, West Africa, were weighed and their lengths measured at four surveys over an 18-month period, twice towards the end of the rains, and twice during the dry season. 2. Relative to international standards, height-for-age deteriorated steadily with age, while weight-for-age fell sharply in the second-half of infancy but showed no further deterioration from 12 to 35 months of age. 3. Height-for-age showed little seasonal variation, but weight-for-age and weight-for-height were lower at the end of the rains than during the dry season. Weight and height velocities were much lower during the rains than in the dry season, with more than 20% of the children losing weight during the rains. Possible reasons for these seasonal variations are discussed. Compensatory weight gain in the dry season exceeded the velocity expected from the standards in children aged 12 months or more, but height velocity fell below the standards all year. 4. The results are compared with previous findings from Keneba, a rural Gambian village. Weight velocity during the dry season was similar in the two communities, but the village children experienced a sharper decline in weight gain during the rains. 5. These results suggest that seasonal ecological factors may seriously influence the nutritional status of children living in an urban environment with adequate availability of food.

Body Height↗
PubMed2001

Seasonal aspects of weight-for-age in young children in Zimbabwe.

OBJECTIVE: To identify the season with the highest prevalence of underweight among young children and to examine geographical variation in seasonality of underweight. DESIGN: This analysis is based on monthly data from a clinic-based growth monitoring programme that forms part of the National Health Information System. A regression-based technique is used to identify seasonal patterns in both underweight prevalence and attendance nationally and in 60 different districts. SETTING: The analysis covers the period 1988-1995 and is based in Zimbabwe. SUBJECTS: The analysis is based on weight-for-age measurements of Zimbabwean children less than 5 years old, who attended health centres as part of a growth monitoring programme. RESULTS: Nationally, a small but significant increase in levels of underweight takes place during January-March. Participation in growth monitoring also varies seasonally and could account for the increase observed. No evidence of seasonal variation in underweight prevalence is found in the majority of districts studied, although 11 of the districts showed a similar pattern to the national data set. This peak in the incidence of poor nutritional status also coincides with the period of food scarcity before harvest, which is also associated with higher prevalence of diarrhoea and malaria. No differences in seasonality of under-nutrition were found between districts with predominantly subsistence agriculture and those with more commercial forms of agriculture. CONCLUSIONS: Seasonal variation in child weight-for-age exists in some parts of Zimbabwe, but its effects on cross-sectional prevalence studies are likely to be small. There are no readily discernible differences between areas that show evidence of seasonality in levels of underweight and those that do not.

Age Factors↗
PubMedDate not supplied

Seasonality in twin and triplet births.

A study has been made of the twin births in England and Wales 1952-59 and 1963-75. There is good evidence that the incidence of opposite-sexed (and by inference, dizygotic) twin births is seasonal, being about 5% higher in December than June. Triplet births seen to show a seasonal variation at about the same location and with double the amplitude. It seems likely that this seasonal variation of polyzygotic maternities is due to seasonal variation in the rates of multiple ovulation rather than to seasonal variation in any of the other reproductive parameters which could, in principle, be responsible (coital rate, spontaneous abortion, probability of fertilization). It is possible that such an hypothesized variation is due to seasonal variation in food consumption. Evidence in regard to seasonal variance in monozygotic twinning rates is equivocal but a number of considerations suggest that they too are subject to seasonal variation. If this is so, the peak incidence of MZ twin births occurs around November.

Abortion, Spontaneous↗
PubMed2004

Community-based surveillance in the united states of macrolide-resistant pediatric pharyngeal group A streptococci during 3 respiratory disease seasons.

BACKGROUND: In 2001, a total of 48% of pharyngeal group A streptococci (GAS) from Pittsburgh children were macrolide resistant. We assessed macrolide resistance, resistance genes, and emm types among GAS in the United States. METHODS: In prospective, multicenter, community-based surveillance of pharyngeal GAS recovered from children 3-18 years old during 3 respiratory seasons (the 2000-2001 season, the 2001-2002 season, and the 2002-2003 season), GAS were tested for macrolide resistance and underwent emm gene sequencing. Macrolide-resistant GAS were tested for resistance to clindamycin, and resistance genes were determined. RESULTS: Erythromycin resistance was observed in 4.4% of isolates from the 2000-2001 season, 4.3% from the 2001-2002 season, and 3.8% from the 2002-2003 season (P=.80). Clindamycin resistance was found in 1.04% of isolates; annual rates of clindamycin resistance were stable (P=.75). The predominant resistance genotype each year was mef A (65%-76.9%; overall, 70.3%). Resistant isolates included strains representing 8-11 different emm types each year. Heterogeneity of emm subtypes, resistance genes, and clindamycin resistance was evident among resistant isolates within some emm types. Geographic variability in resistance rates was present each year. CONCLUSIONS: The macrolide resistance rate among pharyngeal GAS was <5% and was stable over the 3 seasons. However, rates varied among sites each year. There was no evidence of spread of a specific resistant clone, increasing clindamycin resistance, or escalation in median erythromycin MICs.

Child↗
PubMed2004

Season of birth is not associated with risk of early adult death in rural Senegal.

BACKGROUND: In a rural area of the Gambia, West Africa, young adults born in the 'hungry' season had a high excess of deaths (mortality ratios (MR): 3.7 from 14.5 years and 10.3 from 25 years, P < 0.0001). Among several potential causal factors, fetal undernutrition was considered the most plausible. This study is a similar analysis of children and young adults living in rural Senegal, close to the Gambia. METHODS: A cohort of 9192 subjects born 1962-2001 with prospectively collected dates of birth and death was analysed. MR by season of birth (July-December/January-June) was estimated using Cox's proportional hazards analysis. The nutritional status of non-pregnant women was analysed at monthly intervals 1990-1996. RESULTS: MR by season of birth was slightly greater than 1 during infancy, and close to 1 from 1-5 years and from 5-14.5 years. From 14.5 years old the MR was 0.77 (95% CI: 0.47, 1.25, P = 0.29), compared with 0.53 (95% CI: 0.28, 1.02, P = 0.056) from 20 years and 0.33 (95% CI: 0.09, 1.25, P = 0.10) from 25 years. The weight of women varied strongly by season: means were 3.0-3.9 kg lower at the end of the rainy season (September-November) than during the dry season (February-May, P < 0.001 for each year). CONCLUSIONS: This study found no increased risk of death among young adults born during the hungry season in a rural West African area despite large seasonal variations in women's nutritional status. The strongly increased risk in adult Gambians is probably not explained by fetal undernutrition.

Adolescent↗
PubMed2005

Seasonal pattern of tuberculosis in Hong Kong.

BACKGROUND: Summer predominance of tuberculosis (TB) was reported previously in temperate regions. No consistent data were available for lower latitudes. METHOD: The monthly TB notification data in Hong Kong from 1991 to 2002 were examined for seasonal fluctuation. A seasonal model was then developed after standardization by period, sex, age, history of TB, form of disease, and bacteriological status. RESULTS: The raw monthly counts showed remarkably consistent seasonal fluctuation across different periods, sexes, and age groups. A sine model was fitted for 82 104 notifications (adjusted R(2) = 0.373, P < 0.001). A summer peak was observed with seasonal fluctuation of 18.4% (P < 0.001), which was substantially higher than that reported previously for temperate regions. The amplitudes of fluctuation were 35.0, 15.0, 19.0, and 20.2% for those aged < or =14, 15-34, 35-64, and >/=65 years, respectively (all P < 0.001). No gender difference was noted (18.2% vs 19.0%, P = 0.790). Seasonal pattern was detected among new cases (18.6%, P < 0.001), but not retreatment cases (5.2%, P = 0.333). Culture-positive cases showed greater fluctuation than culture-negative cases (29.4% vs 6.4%, P < 0.001). No significant difference was found between pulmonary and extrapulmonary cases (16.8% vs 21.6%, P = 0.356). TB cases notified in summer were more likely to be smear-positive [odds ratio (OR) 1.100, 95% confidence interval (CI) 1.045-1.158, P < 0.001] and culture-positive (OR 1.175, 95% CI 1.121-1.232, P < 0.001) than those notified in winter, even after stratification by other key variables. CONCLUSION: A consistent seasonal pattern was found, with variable amplitudes of fluctuation in different subgroups and differing disease characteristics in different seasons. These observations are suggestive of the presence of a seasonal disease-modifying factor.

Age Distribution↗
PubMed1996

Seasonality in the clinical onset of insulin-dependent diabetes mellitus in Finnish children. Childhood Diabetes in Finland (DiMe) Study Group.

Seasonal patterns in the incidence of insulin-dependent diabetes based on 2,062 cases diagnosed at age 14 years or under in Finland are described for the years 1987-1992. Seasonal patterns were estimated presenting the data as short Fourier series up to three harmonics together with a possible linear trend. This method allows an arbitrary shape for the seasonal effect. Likelihood ratio tests and Akaike's information criterion were used to determine the number of harmonics necessary to model the seasonal pattern and to test differences among age- and sex-specific subgroups in the population. Seasonal patterns in incidence were compared between sexes and between the three 5-year age groups with each controlling for the other's effect. A significant seasonal pattern in the incidence of insulin-dependent diabetes was found for the sexes combined and for two age groups (0-9 and 10-14 years). A statistically significant seasonal pattern could be confirmed for males, but not for females. During a calendar year, one cycle with a decreased incidence of insulin-dependent diabetes in June was found among younger boys. Among older boys, there were two distinct cycles with a decreased incidence, the first in June and the second during November-December. The most visible seasonal pattern was a lower number of cases diagnosed in June, while during the rest of the year the incidence remained relatively stable and high. The average annual incidence was 35.6 per 100,000 persons without any upward peaks.

Adolescent↗
PubMed2006

Seasonal patterns of leaf gas exchange and water relations in dry rain forest trees of contrasting leaf phenology.

Diurnal and seasonal patterns of leaf gas exchange and water relations were examined in tree species of contrasting leaf phenology growing in a seasonally dry tropical rain forest in north-eastern Australia. Two drought-deciduous species, Brachychiton australis (Schott and Endl.) A. Terracc. and Cochlospermum gillivraei Benth., and two evergreen species, Alphitonia excelsa (Fenzal) Benth. and Austromyrtus bidwillii (Benth.) Burret. were studied. The deciduous species had higher specific leaf areas and maximum photosynthetic rates per leaf dry mass in the wet season than the evergreens. During the transition from wet season to dry season, total canopy area was reduced by 70-90% in the deciduous species and stomatal conductance (g(s)) and assimilation rate (A) were markedly lower in the remaining leaves. Deciduous species maintained daytime leaf water potentials (Psi(L)) at close to or above wet season values by a combination of stomatal regulation and reduction in leaf area. Thus, the timing of leaf drop in deciduous species was not associated with large negative values of daytime Psi(L) (greater than -1.6 MPa) or predawn Psi(L) (greater than -1.0 MPa). The deciduous species appeared sensitive to small perturbations in soil and leaf water status that signalled the onset of drought. The evergreen species were less sensitive to the onset of drought and g(s) values were not significantly lower during the transitional period. In the dry season, the evergreen species maintained their canopies despite increasing water-stress; however, unlike Eucalyptus species from northern Australian savannas, A and g(s) were significantly lower than wet season values.

Australia↗
PubMed1984

Seasonal variation in hypothalamic content of gonadotropin-releasing hormone (GnRH), pituitary receptors for GnRH, and pituitary content of luteinizing hormone and follicle-stimulating hormone in the mare.

Seasonal changes in the hypothalamic-hypophyseal axis were investigated using tissue from 49 light-horse mares, of mixed breeding. Hypothalamic and pituitary tissues were collected at 5 intervals throughout the years 1981 and 1982, representing midbreeding season (July, n = 10), transition out of the breeding season (October, n = 11), midanestrus (December, n = 8), transition into the breeding season (March, n = 10), and again in the following midbreeding season (July, n = 10). The hypothalamic region was dissected into preoptic area, body and median eminence. Gonadotropin-releasing hormone (GnRH) was extracted from hypothalamic samples with methanol-formic acid and quantified by radioimmunoassay. The anterior pituitary was homogenized and receptors for GnRH were quantified in a crude membrane fraction. Concentrations of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) were measured in the resulting supernatant. Content of GnRH in each of the 3 hypothalamic areas varied with season (P less than 0.01) and was lowest during midanestrus (P less than 0.05). There was no effect of season (P greater than 0.01) on either concentration or total number of receptors for GnRH, or concentration of FSH in the anterior pituitary. Concentrations of LH in the anterior pituitary varied with season (P less than 0.001). Means (+/- SEM) for the 5 collection times were 15.5 +/- 2.7, 9.7 +/- 2.4, 2.3 +/- 0.5, 2.7 +/- 0.4 and 11.7 +/- 1.5 microgram LH/mg anterior pituitary, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

Age, social rank and lactational status influence ovulatory patterns in seasonally breeding rhesus monkeys.

Rhesus monkeys housed outdoors exhibit a distinct breeding season limited to the fall and winter months. Four groups of female rhesus monkeys, multiparous nonlactating (MNL; n = 8), multiparous lactating (ML; n = 6), primiparous lactating (PL; n = 3) and nulliparous first-time ovulators (N; n = 6) were studied to investigate the influence of age, parity, and social dominance rank on the parameters of the breeding season. MNL exhibited the longest season (146 days), and PL the shortest (70 days), with N (106 days) and ML (89 days) intermediate. PL females also had a significantly reduced percentage of normal ovulations compared to other groups. Neither body weight nor estimates of body fat were related to either the timing of the ovulatory season or the quality of ovulations within the season. Parity and social dominance rank were significantly related to the percentage of normal ovulations (r = 0.85), with low-ranking, primiparous females exhibiting the fewest normal ovulations. These data indicate that the presence of a suckling infant acts synergistically with environmental factors to determine the parameters of the breeding season. Furthermore, postpubertal females may be more responsive to those factors that terminate the breeding season, and some factor independent of body weight but associated with low social dominance rank and/or primiparity renders females less capable of normal luteal function during the breeding season.

Age Factors↗
PubMed1993

Seasonal changes in gonadotropin-releasing hormone secretion in the ewe: alteration in response to the negative feedback action of estradiol.

Two experiments were performed to test the hypothesis that there is a seasonal change in the negative feedback effect of estradiol on episodic secretion of GnRH in the ewe. The first experiment identified a specific estradiol treatment (delivered by s.c. Silastic implant) that produced a 50% decrease in the frequency of pulsatile secretion of LH in ovariectomized ewes during the anestrous season. In the second experiment, this estradiol treatment was administered to ovariectomized ewes during the mid-breeding and anestrous seasons. Separate groups of ovariectomized ewes not treated with estradiol were included during each season to test for a seasonal difference in the effect of estradiol on episodic GnRH and LH secretion. Samples of hypophyseal portal blood (for GnRH) and jugular blood (for LH) were obtained at 5-min intervals approximately one month after placement of the estradiol implants. During the breeding season, no effect of estradiol was observed on either the frequency or size of GnRH and LH pulses. During anestrus, however, estradiol produced a profound suppression of the frequency of GnRH and LH pulses, and an increase in GnRH pulse size. No significant seasonal change was observed in the characteristics of GnRH and LH pulses in ovariectomized ewes in the absence of estradiol treatment. These findings lead to the conclusion that there is a marked seasonal change in the negative feedback effect of estradiol on episodic GnRH secretion in the ewe, with the steroid being maximally effective during anestrus.

Anestrus↗
PubMed1996

Seasonal variation in the time to pregnancy: avoiding bias by using the date of onset.

To study seasonality in human fecundability, measured indirectly by time to the first pregnancy, we used data from 18,970 French-Canadian women who married for the first time during the 17th or 18th century. The time to pregnancy was approximated by the interval between marriage and first birth minus 38 weeks. We used the week of marriage and the week of conception as references to study seasonality. We found a minor seasonal pattern in time to pregnancy when using the week of marriage as a reference. The proportions of women with a short time to pregnancy were highest during December-January and June-July, indicating that these may be the most fecund periods. In contrast, we found an obvious seasonal pattern when using the date of conception as a reference. This pattern can be largely explained by a strong seasonal pattern in pregnancy planning (in this case, in marriages). When studying seasonal variation in the time to pregnancy, the date of onset of the time to pregnancy should be used as reference, not the date of conception. Otherwise, results will be biased owing to seasonality in pregnancy planning. The same is true for studies on seasonally bound exposures in relation to time to pregnancy.

Adolescent↗
PubMed2007

Variation in incidence of neurodevelopmental disorders with season of birth.

BACKGROUND: The etiologies of autism spectrum disorder and many neurodevelopmental disorders are largely unknown. The detection of a seasonal variation of birth of children diagnosed with a certain disorder could suggest etiological factors that follow a seasonal pattern. We examined the seasonal variation of births of children diagnosed with any of 4 common childhood neuropsychiatric disorders: autism spectrum disorder, hyperkinetic disorder, Tourette syndrome, and obsessive-compulsive disorder. METHODS: The study cohort consisted of all children born in Denmark from 1990 through 1999 identified in the Danish Medical Birth Register (n = 669,995). Outcome data consisted of both inpatient and outpatient diagnoses reported to the Danish National Psychiatric Registry from 1995 through 2004 using the International Classification of Diseases, 10th edition, diagnostic coding system. Logistic regression combined with spline (a smoothing method) was used to estimate the variation with season of birth for each disorder. Estimates of risk of each disorder with season of birth were adjusted for differences in follow-up time and change in incidence over time. RESULTS: No convincing variations in season of birth were observed for any of the 4 disorders, or for the autism-spectrum-disorder subtypes. CONCLUSION: Although we cannot rule out the possibility of seasonal variation of birth for a range of childhood neurodevelopmental disorders, we find little evidence that seasonal environmental factors are related to these disorders.

Attention Deficit Disorder with Hyperactivity↗
PubMed2005

Pathogen adaptation to seasonal forcing and climate change.

Many diverse infectious diseases exhibit seasonal dynamics. Seasonality in disease incidence has been attributed to seasonal changes in pathogen transmission rates, resulting from fluctuations in extrinsic climate factors. Multi-strain infectious diseases with strain-specific seasonal signatures, such as cholera, indicate that a range of seasonal patterns in transmission rates is possible in identical environments. We therefore consider pathogens capable of evolving their 'seasonal phenotype', a trait that determines the sensitivity of their transmission rates to environmental variability. We introduce a theoretical framework, based on adaptive dynamics, for predicting the evolution of disease dynamics in seasonal environments. Changes in the seasonality of environmental factors are one important avenue for the effects of climate change on disease. This model also provides a framework for examining these effects on pathogen evolution and associated disease dynamics. An application of this approach gives an explanation for the recent cholera strain replacement in Bangladesh, based on changes in monsoon rainfall patterns.

Adaptation, Physiological↗
PubMed2006

Seasonal infectious disease epidemiology.

Seasonal change in the incidence of infectious diseases is a common phenomenon in both temperate and tropical climates. However, the mechanisms responsible for seasonal disease incidence, and the epidemiological consequences of seasonality, are poorly understood with rare exception. Standard epidemiological theory and concepts such as the basic reproductive number R0 no longer apply, and the implications for interventions that themselves may be periodic, such as pulse vaccination, have not been formally examined. This paper examines the causes and consequences of seasonality, and in so doing derives several new results concerning vaccination strategy and the interpretation of disease outbreak data. It begins with a brief review of published scientific studies in support of different causes of seasonality in infectious diseases of humans, identifying four principal mechanisms and their association with different routes of transmission. It then describes the consequences of seasonality for R0, disease outbreaks, endemic dynamics and persistence. Finally, a mathematical analysis of routine and pulse vaccination programmes for seasonal infections is presented. The synthesis of seasonal infectious disease epidemiology attempted by this paper highlights the need for further empirical and theoretical work.

Animals↗