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PubMed1986

Seasonal variation in tumor size at diagnosis and immunologic responses in human breast cancer.

Seasonal variations were observed in tumor size and a number of immunologic responses among patients entered in the Breast Cancer Prognostic Study. A significantly larger number of cases were diagnosed with smaller tumors, less than 2 cm, during December through February. It was also noted that elevated inflammatory reactions were seen in breast tumors removed during November, December and January. Seasonal changes were also observed in the serum IgM and IgE concentrations at the time of the patient's mastectomy. Elevated fall-winter leukocyte migration inhibition response to MCF-7 extracts correlated with the same seasonal elevations observed with serum IgM response. Implications of seasonal variation as a reflection of immune events are considered.

Analysis of Variance↗
PubMedDate not supplied

Seasonal variation in the dietary adequacy of highland Pwo and Sgaw Karen (Thailand).

The present report describes seasonal variability (postharvest, preharvest, harvest) in the dietary adequacy of highland Karen farmers (38 Pwo and 51 Sgaw mother-weaned child pairs) in Thailand. Both the Pwo and Sgaw exhibit little functionally significant seasonal variation in either energy or protein intakes, although there is significant seasonal variation in other nutrients. Sgaw Karen mothers and their weaned children had significantly higher intakes of energy, protein, and seven nutrients than their Pwo counterparts during all three study seasons. The cause of this difference appears to be related to the better socioeconomic status of the Sgaw, as well as to differences in belief systems that result in a greater utilization of wild resources by the Sgaw. There were no significant differences in energy intakes between mothers and their children in either ethnic group, while children tended to have significantly greater intakes of protein but significantly lower intakes of other nutrients. These differences in dietary patterns appear to be due to differences in dietary density and dietary preferences, rather than to foods being differentially directed towards adults.

Adolescent↗
PubMed2000

Seasonal variation in suicides: diminished or vanished. Experience from England and Wales, 1982-1996.

BACKGROUND: Seasonal variation in suicidal death has been observed in many countries. In particular, a cyclic variation was found for both men and women in England and Wales in the 1960s and 1970s. Men showed a single 12-month cycle whereas women showed two cycles. AIMS: To re-examine the seasonal variation in suicides in England and Wales for the period 1982-1996. METHOD: A harmonic analysis was used to detect the seasonality of the suicide data. RESULTS: The seasonal effect on suicide is greatly diminished in England and Wales. This is shown by the reduced amplitude and smaller proportion of variance accounted for by the season. CONCLUSIONS: The seasonal effect on suicide has either diminished or vanished.

Adolescent↗
PubMed2006

Seasonal variation in stroke and stroke-associated mortality in patients with a hospital diagnosis of nonvalvular atrial fibrillation or flutter. A population-based study in Denmark.

AIM: There are few data on seasonal variation in stroke and seasonal variation in mortality after stroke in patients with atrial fibrillation. We examined the seasonal pattern in stroke occurrence and the effect of the season on mortality after stroke in patients with a history of nonvalvular atrial fibrillation. METHODS: We identified all individuals, aged 40-89 years, with an incident diagnosis of stroke of any nature (ischemic or hemorrhagic) in the 1980-2002 period and no history of heart valve disease and a previous or concomitant diagnosis of atrial fibrillation or flutter in the Danish National Registry of Patients. Subjects were followed in the Danish Civil Registration System for emigration and vital status. We used periodic regression models to estimate the peak-trough ratio stratified by sex, age and comorbid medical conditions. Seasonal effect on mortality after stroke was analyzed in a Cox proportional hazards model. RESULTS: The relative incidence of stroke estimated as the ratio of the incidence in the month of the peak (January) to the incidence in the month of the trough (July) was 1.11 (95% confidence interval: 1.07-1.15). The relative incidence of stroke was similar for men and women, did not differ by age (stratified by age 75 years) and was essentially similar for comorbid conditions considered. There was no seasonal effect on mortality after stroke. CONCLUSIONS: The occurrence of stroke in patients with atrial fibrillation is modestly higher during the winter. Stroke-associated mortality does not vary by season.

Adult↗
PubMed1997

Seasonal variation in the prevalence of Down syndrome at birth: a review.

STUDY OBJECTIVE: Many studies on seasonality in Down syndrome (DS) have been performed and have come to different conclusions. It is suggested that seasonal variation in hormone production by the hypothalamus-pituitary-ovarian axis just before ovulation leads to seasonality in conception rates of DS. This study aimed to determine whether there is seasonal variation in the prevalence of DS at birth as a proxy for seasonality in DS at conception. DESIGN: All the English and Dutch articles on this topic were reviewed. Articles published between 1966 and January 1996 were traced by Medline, and by the reference lists. MAIN RESULTS: Twenty articles met the criteria for inclusion. Although seven of these studies reported seasonality in DS prevalence, no consistent seasonal pattern was found in DS at birth in these studies, or in the remaining studies. A seasonal pattern could not have been masked by the effects of maternal age, induced abortions, shortened gestation, or misclassification of DS. CONCLUSION: Seasonality in the prevalence of DS at birth does not exist. Evidence did not support the suggestion that DS occurrence is related to seasonality in hormone production.

Down Syndrome↗
PubMed1990

[Seasonal variation in disseminated sclerosis].

Forty-five patients with clinically definite multiple sclerosis (DS) with onset in the period studied, were reviewed retrospectively. The time of the first exacerbation after the onset, but not the time of onset exhibited seasonal variation (p = 0.003), as 76% of the exacerbations occurred in the winter months. On review of all 148 cases of clinically definite DS in the department's records, a seasonal variation was found of both the time of onset (p = 0.047) and the time of the next exacerbation (p = 0.0004). In previous studies different seasons of peak disease activity were found. These differences may be caused by different methods or by differences in the local factors, which influence the course of the disease. The seasonal variation of the frequency of the disease manifestations is probably caused by a variation in environmental factors. In this study, the importance of infections could not be evaluated.

Adolescent↗
PubMedDate not supplied

Breed and seasonal variation of plasminogen activator activity and plasminogen activator inhibition in spermatozoa and seminal plasma of the ram in correlation with testosterone in the blood.

Plasminogen activator activity (PAA) and plasminogen activator inhibition (PAI), against t-PA (t-PAI) or u-PA (u-PAI), in spermatozoa and seminal plasma as well as testosterone in the blood of Friesland, Chios, and Karagouniki rams all showed a seasonal variation with the highest values during the corresponding breeding season of the ewes (Autumn-Winter). The seasonal variation of PAA and PAI in spermatozoa or seminal plasma as well as blood testosterone was different among the three breeds studied. Increased spermatozoal PAA was observed in November and May in Friesland rams, in October and November in Chios rams, and in October in Karagouniki rams. Spermatozoal t-PAI was increased in December and June in Friesland rams, in November and December in Chios rams, and in November in Karagouniki rams. Spermatozoal u-PAI was increased in December in Friesland rams, in October and December in Chios rams, and in November and December in Karagouniki rams. Plasminogen activator activity and PAI in seminal plasma also showed similar seasonal variations. Plasminogen activator activity and PAI in spermatozoa and seminal plasma showed a positive correlation with blood testosterone. The results of the present study support our previous findings on the possible role of spermatozoal PAA and PAI in the fertilizing ability of spermatozoa.

Animals↗
PubMed2000

Seasonal variation of depression and other moods: a longitudinal approach.

The present study examined the effect of season of the year on depression and other moods. Previous work, primarily cross sectional or retrospective in design and involving clinically depressed or seasonally affective disordered samples, has suggested that mood changes as a function of season. However, the literature also shows conflicting and/or inconsistent findings about the extent and nature of this relationship. Importantly, these prior studies have not adequately answered the question of whether there is a seasonal effect in nondepressed people. The present study employed a longitudinal design and a large sample drawn from a normal population. The results, based on those participants for whom mood measures were collected in each season, demonstrated strong seasonal effects. Beck Depression Inventory (BDI) scores were highest in winter and lowest in summer. Ratings on scales of hostility, anger, irritability, and anxiety also showed very strong seasonal effects. Further analyses revealed that seasonal variation in BDI scores differed for females and males. Females had higher BDI scores that showed strong seasonal variation, whereas males had lower BDI scores that did not vary significantly across season of the year.

Adult↗
PubMedDate not supplied

Seasonal variation of Titan's atmospheric structure simulated by a general circulation model.

The seasonal variation of Titan's atmospheric structure with emphasis on the stratosphere is simulated by a three-dimensional general circulation model. The model includes the transport of haze particles by the circulation. The likely pattern of meridional circulation is reconstructed by a comparison of simulated and observed haze and temperature distribution. The GCM produces a weak zonal circulation with a small latitudinal temperature gradient, in conflict with observation. The direct reason is found to be the excessive meridional circulation. Under uniformly distributed opacity sources, the model predicts a pair of symmetric Hadley cells near the equinox and a single global cell with the rising branch in the summer hemisphere below about z = 230 km and a thermally indirect cell above the direct cell near the solstice. The interhemispheric circulation transports haze particles from the summer to the winter hemisphere, causing a maximum haze opacity contrast near the solstice and a smaller contrast near the equinox, contrary to observation. On the other, if the GCM is run under modified cooling rate in order to account for the enhancement in nitrites and some hydrocarbons in the northern hemisphere near the vernal equinox, the meridional cell at the equinox becomes a single cell with rising motions in the autumn hemisphere. A more realistic haze opacity distribution can be reproduced at the equinox. However, a pure transport effect (without particle growth by microphysics, etc.) would not be able to cause the observed discontinuity of the global haze opacity distribution at any location. The stratospheric temperature asymmetry can be explained by a combination of asymmetric radiative heating rates and adiabatic heating due to vertical motion within the thermally indirect cell. A seasonal variation of haze particle number density is unlikely to be responsible for this asymmetry. It is likely that a thermally indirect cell covers the upper portion of the main haze layer. An artificial damping of the meridional circulation enables the formation of high-latitude jets in the upper stratosphere and weaker equatorial superrotation. The latitudinal temperature distribution in the stratosphere is better reproduced.

Atmosphere↗
PubMed1983

Seasonal variations of carbon monoxide-induced polycythemia in rats.

Fluctuations of the extent of polycythemia in rats due to repeated exposure to carbon monoxide prompted us to study whether the differences were caused by seasonal variations. Data from 18 independent experiments involving the hemoglobin values of 206 CO-exposed and 208 control rats over a period of nearly 3 years were available. Because the experiments were not designed for chronobiological studies, several methods of quasilinear and nonlinear regression analysis were applied to fit periodic models to the data. The best fit was obtained by a single cosine function with a period of nearly 12 months and with maximum values in winter and minimum values in summer. Experiments to elucidate mechanism(s) of seasonal variations showed that following a single CO exposure to the nocturnally active rodents, the rate of CO release from the body was higher in the dark span, that reduced food supply produced a potentiation of the CO-induced hemoglobin increase, and that the adaptive CO response was not affected by testosterone or thyroidectomy, but inhibited by L-thyroxine. Thus it seems that influences of light, CO elimination rate, food intake, metabolic rate and related hormones play a role for seasonal variations.

Animals↗
PubMed2006

Seasonal variations in 228Ra/226Ra ratio within coastal waters of the Sea of Japan: implications for water circulation patterns in coastal areas.

In this study, low-background gamma-spectrometry was used to determine the (228)Ra/(226)Ra ratio of 131 coastal water samples from various environments around Honshu Island, Japan (mainly around Noto Peninsula) at 1-3 month intervals from April 2003 until September 2005. Spatial variation in (228)Ra/(226)Ra ratios was also assessed by analyzing 34 coastal water samples from five areas within the Sea of Japan during May and June 2004. The (228)Ra/(226)Ra ratio of coastal water from all sites around Noto Peninsula shows seasonal variation, with minimum values during summer ((228)Ra/(226)Ra=0.7) and maximum values during autumn-winter ((228)Ra/(226)Ra=1.7-2). This seasonal variation is similar to that recorded for coastal water between Tsushima Strait and Noto Peninsula. The measured lateral variation in (228)Ra/(226)Ra ratios within coastal water between Tsushima Strait and Noto Peninsula is only minor (0.5-0.7; May-June 2004). Coastal waters from two other sites (Pacific shore and Tsugaru Strait, north Honshu) show no clear seasonal variation in (228)Ra/(226)Ra ratio. These measured variations in (228)Ra/(226)Ra ratio, especially the temporal variations, have important implications for seasonal changes in patterns of coastal water circulation within the Sea of Japan.

Environmental Monitoring↗
PubMed1983

Seasonal variations in admissions to a tropical paediatric unit.

The monthly admissions over the last 10 years (1972-1981) of children with common illnesses to the Department of Paediatrics, National University of Singapore, were analyzed to ascertain if there were any significant seasonal patterns. The method used (developed by Walter and Elwood) consists of estimating the amplitude of seasonal variations and the time at which the maximum occurs in a postulated simple harmonic fluctuation. Six out of the 9 diagnostic groups studied were found to have significant seasonal variations in at least 5 out of 10 years or 3 out of the last 5 years: pharyngitis, bronchitis, broncho-pneumonia, bronchial asthma, gastro-enteritis, and febrile convulsions. Febrile convulsions showed the best correlation (in terms of the number of monthly admissions) with the other illnesses showing seasonal fluctuations. Admissions for bronchial asthma were negatively correlated with the others. No consistent pattern in the time of peak number of admissions was discernable. The seasonal variations demonstrated are probably related to outbreaks of viral infections which tend to occur round the year in the tropics.

Asthma↗
PubMed2003

Seasonal variation in the incidence of wrist and forearm fractures, and its consequences.

We have used the All Wales Injury Surveillance System (AWISS) in a population-based study of wrist and forearm fractures. We examined seasonal variation in the incidence of these injuries, and looked at resulting pressures on outpatient and inpatient trauma services. AWISS collected data from eight Accident and Emergency (A&E) departments which between them serve a total of 1.2 million people in South Wales. During a single year, we identified all 5013 people who presented with a wrist or forearm fracture. Seasonal variation in wrist/forearm fracture incidence was apparent, but showed a different pattern in different age groups. Overall incidence figures were dominated by an increase in children's fractures in spring and summer. Children under the age of 15 suffered a total of 360 wrist and forearm fractures during the three winter months; an incidence of 5.9/1000 per year that was only about half that observed during the remainder of the year (10.7/1000 per year). In contrast, older people showed a higher incidence in the winter. During the winter months people aged over 75 sustained a total of 160 wrist/forearm fractures; an incidence of 8.2/1000 per year, significantly higher than the incidence observed in other months (5.8/1000 per year). Seasonality of incidence was not apparent in other age groups. Children presenting during the spring and summer months were significantly more likely to need admission to hospital; 22.8% were admitted compared with just 10.3% of those presenting during the winter months (P<0.001, chi(2)-test). Other age groups showed no significant seasonal variation in the likelihood of hospital admission.

Adolescent↗
PubMed2006

Seasonal variation of ventricular tachycardia registered in 24-hour Holter monitoring.

OBJECTIVE: To evaluate the seasonal variation of ventricular arrhythmias and its correlation with ambient temperature in patients submitted to 24-hour Holter monitoring in the city of Porto Alegre, southern Brazil. METHODS: Holter monitoring reports of 3,034 patients from 1996 to 2002 were analyzed. Ventricular tachycardia (VT) was defined as the presence of 3 or more consecutive ventricular beats, at a rate equal to or higher than 100 beats per minute. Percentage distribution of patients presenting VT by seasons and its correlation with ambient temperature were analyzed. RESULTS: Mean age was 59.2 +/- 17.4 years, with a predominance of the female sex (61.9%). Patient distribution by season of the year was: 561 (18.5%) in summer, 756 (24.9%) in fall, 843 (27.8%) in winter and 874 (28.8%) in spring. Fifty-two patients (9.3%) presented VT episodes in summer, 39 (5.2%) in autumn, 56 (6.6%) in winter and 60 (6.9%) in spring (p = 0.035). There was a 40% relative increase in the proportion of patients presenting VT during summer in comparison to winter. There was a trend of increase in the proportion of patients presenting VT with rising temperatures (r = 0.57; p = 0.052). CONCLUSION: The occurrence of VT presents seasonal variations in southern Brazil, with a higher proportion of episodes occurring in summer. There is an association trend between VT and temperature increase.

Electrocardiography, Ambulatory↗
PubMed1984

Seasonal variations of total and free thyroid hormones in healthy men: a chronobiological study.

The seasonal variations of iodothyronines and TSH serum concentrations were evaluated in 24 healthy subjects of both sexes. Using a 12 month cosine function, a significant circannual rhythm was found in T3, T4 and free T4 whose maximal values were found in September for T3, in August for T4 and in October for free T4. No significant seasonal variations in free T3 or TSH were found. Some circannual but not sinusoidal changes were found for reverse T3 and TBG. A positive linear correlation between T4, T3 and reverse T3 changes was observed, indicating that the sinusoidal oscillations of these hormones were in phase with each other. Relative weight was significantly lower in summer than in winter, though spontaneous caloric intake and physical activity did not change. A slight but significant correlation was found between relative weight and T4, free T4 and reverse T3 values measured during the period of study.

Acclimatization↗
PubMed1990

Seasonal variation of cold-induced vasooscillation on rabbit ear central artery.

We studied the seasonal variation of vasooscillation of a rabbit ear central artery induced by exposure of the earlobes to - 7 degrees C liquid. The data were collected over a period of 10 years and analyzed by month. a) The index of arterial temperature fluctuation (IATF), i.e., activation index of cold-induced vasooscillation (CIVO), ranged from 114.5 +/- 26.7 (mean +/- SE) in January to 386.7 +/- 36.1 in June. A significant variation over all 12 months was revealed by analysis of variance (P less than 0.01). The values measured in May (317.1 +/- 47.3), June (386.7 +/- 36.1), and July (315.1 +/- 36.0) were significantly larger than those of other months. b) The monthly IATFs were correlated with the open air temperatures (r = 0.7017, P less than 0.05); however, the peak IATF occurred in June, while the peak open air temperature was in August. c) There was no seasonal variation of the arterial temperature either before or at 18-20 min after -7 degrees C immersion. Arterial temperature was not related to IATF during -7 degrees C exposure. d) When measuring-site temperature was steady, the thermistor temperature changed in parallel with the output from a laser blood volume meter. e) The CIVO was independent of systemic blood pressure and heart rate, which suggested that the occurrence of CIVO was regulated by changes in local vascular resistance.

Animals↗
PubMed1999

Seasonal variation of peroxisomal enzyme activities and peroxisomal structure in mussels Mytilus galloprovincialis and its relationship with the lipid content.

Variations in structure and function of peroxisomes in digestive tissues of marine mussels have been proposed to be valid biomarkers of environmental contamination by organic xenobiotics. The aim of the present work was to study the seasonal variations in peroxisomal enzyme activities, catalase, palmitoyl-CoA oxidase (AOX) and D-amino acid oxidase (DAOX) and peroxisomal structure in mussels. Peroxisomal changes were related to the seasonal variation in the contents of neutral lipids in the digestive gland as the lipid metabolism in mussels is subjected to seasonal variations linked to the reproductive cycle and food intake. Significant higher catalase activities were recorded from April to June when compared to the rest of the year and AOX activity was also markedly induced during the late winter and spring (February to May) with maximal activities in April. DAOX activity did not vary seasonally, the highest activities being measured in November, February and May. Stereological studies of peroxisomes in digestive tubule cells revealed significantly higher volume, surface and numerical densities in animals collected in spring and summer. Changes in peroxisomal volume density were found to be significantly and positively correlated with changes in AOX and catalase activities. The peroxisomal structure and enzyme activities were negatively correlated with the lipid contents of digestive tubules. In April, the volume density occupied by neutral lipids was higher in duct epithelia while previously it was higher in digestive tubule epithelia. This trend was maintained during the period in which peroxisomes were more abundant until July. In the following September, digestive tubules recovered their lipid load. It is concluded that seasonal changes related to food intake and reproductive cycle induce changes in peroxisomal parameters that can be compared to typical peroxisome proliferation, with a 25-fold increase in AOX activity and an 8-fold increase in the peroxisomal numerical density in early spring.

Animals↗
PubMed2002

Baclofen prevents morphine withdrawal irrespective of seasonal variation.

In previous studies we have demonstrated a possible interaction between the gamma-aminobutyric acid (GABA)ergic and opioid systems involved in the antinociceptive effect of the GABAB agonist, baclofen (BAC). In addition, we have demonstrated that BAC was able to prevent the morphine (MOR) withdrawal syndrome in female, as well as male mice. On the other hand, seasonal variations have been observed in some MOR effects. In the present study, we analysed the effects of BAC on naloxone (NAL)-precipitated withdrawal, during two different seasons. The experiments were performed during two seasons: spring-summer (SS) and autumn-winter (AW) for two years, on male Swiss-Webster albino mice (27-33 g). Mice were rendered dependent by intraperitoneal (i.p.) injection of MOR (2mg/kg), twice daily for 9 days. On the tenth day the dependent animals were divided into two groups: one received NAL (6mg/kg, i.p.) 60 min after the last dose of MOR, to develop the NAL-precipitated withdrawal; the other group received BAC (2mg/kg, i.p.) followed by NAL (6mg/kg, i.p.), injected 30 and 60 min after the last dose of MOR, respectively. Behavioural signs were recorded in the open field for 30 min. Although there were seasonal variations in the MOR withdrawal syndrome, we found that BAC prevents MOR withdrawal irrespective of seasonal variation.

Animals↗