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PubMed2005

Impact of influenza vaccination on seasonal mortality in the US elderly population.

BACKGROUND: Observational studies report that influenza vaccination reduces winter mortality risk from any cause by 50% among the elderly. Influenza vaccination coverage among elderly persons (> or =65 years) in the United States increased from between 15% and 20% before 1980 to 65% in 2001. Unexpectedly, estimates of influenza-related mortality in this age group also increased during this period. We tried to reconcile these conflicting findings by adjusting excess mortality estimates for aging and increased circulation of influenza A(H3N2) viruses. METHODS: We used a cyclical regression model to generate seasonal estimates of national influenza-related mortality (excess mortality) among the elderly in both pneumonia and influenza and all-cause deaths for the 33 seasons from 1968 to 2001. We stratified the data by 5-year age group and separated seasons dominated by A(H3N2) viruses from other seasons. RESULTS: For people aged 65 to 74 years, excess mortality rates in A(H3N2)-dominated seasons fell between 1968 and the early 1980s but remained approximately constant thereafter. For persons 85 years or older, the mortality rate remained flat throughout. Excess mortality in A(H1N1) and B seasons did not change. All-cause excess mortality for persons 65 years or older never exceeded 10% of all winter deaths. CONCLUSIONS: We attribute the decline in influenza-related mortality among people aged 65 to 74 years in the decade after the 1968 pandemic to the acquisition of immunity to the emerging A(H3N2) virus. We could not correlate increasing vaccination coverage after 1980 with declining mortality rates in any age group. Because fewer than 10% of all winter deaths were attributable to influenza in any season, we conclude that observational studies substantially overestimate vaccination benefit.

Age Distribution↗
PubMed2002

Illness among schoolchildren during influenza season: effect on school absenteeism, parental absenteeism from work, and secondary illness in families.

BACKGROUND: High attack rates of Influenzavirus among school-aged children tend to be expected to cause significant disruption of usual activities at school and at home. OBJECTIVE: To quantify the effect of influenza season on illness episodes, school absenteeism, medication use, parental absenteeism from work, and the occurrence of secondary illness in families among a cohort of children enrolled in an elementary school during the 2000-2001 influenza season. DESIGN: Prospective survey study. SETTING: Kindergarten through eighth grade elementary school in Seattle, Wash. PATIENTS OR OTHER PARTICIPANTS: All children enrolled in the school were eligible for the study. Study participants were 313 children in 216 families. MAIN OUTCOME MEASURES: The primary outcome measure was missed school days. Secondary outcomes measures included total illness episodes, febrile illness episodes, medication usage, physician visits, parental workdays missed, and secondary illnesses among family members of children in the study cohort. Differences between the rates of study events among participants when influenza was circulating and the event rates during the winter season when influenza was not circulating were used to calculate influenza-attributable excess events. RESULTS: Total illness episodes, febrile illness episodes, analgesic use, school absenteeism, parental industrial absenteeism, and secondary illness among family members were significantly higher during influenza season compared with the noninfluenza winter season. For every 100 children followed up for this influenza season, which included 37 school days, an excess 28 illness episodes and 63 missed school days occurred. Similarly, for every 100 children followed up, influenza accounted for an estimated 20 days of work missed by the parents and 22 secondary illness episodes among family members. CONCLUSION: Influenza season has significant adverse effects on the quality of life of school-aged children and their families.

Absenteeism↗
PubMed1999

Sexual dimorphisms in a neuromuscular system regulating courtship in the green anole lizard: effects of season and androgen treatment.

During the breeding season, male green anoles (Anolis carolinensis) court females by extending a red throat fan called a dewlap. Motoneurons controlling this sexually dimorphic behavior are located in two portions of the brain stem: (a) the vagal portion of nucleus ambiguus (AmbX), and (b) the region containing the glossopharyngeal portion of nucleus ambiguus and the ventral motor nucleus of the facial nerve (AmbIX/VIImv). These motoneurons project to the ceratohyoideus muscle via the ramus pharyngo-laryngeus IX+X. To investigate the effects of season on and androgen regulation of neural and peripheral structures controlling dewlap extension, two experiments were conducted: (a) During the breeding and nonbreeding seasons, motoneuron number, soma size, and nucleus size were investigated in intact males and females and in castrated males treated with a testosterone propionate (TP) or a blank Silastic capsule. (b) Cross-sectional area of the nerve and muscle fiber size, number, and density were investigated in the four treatment groups during the breeding season only. No significant differences were found in motoneuron number. In the breeding season, subtle male-biased sex differences existed in both AmbX and AmbIX/VIImv soma size. Nerve cross-sectional area and muscle fiber size and number were substantially larger in males than females. Muscle fiber density was higher in females. No consistent effects due to season or androgen treatment were detected, although characteristics of motoneurons were in some cases slightly larger in the nonbreeding season. These results suggest that, while parallels to behavior exist between the sexes, morphological changes in adulthood in the dewlap motoneurons and muscle do not normally regulate courtship behavior in the male green anole.

Animals↗
PubMed2000

Season of birth and bulimia nervosa.

OBJECTIVE: Previous studies suggest season of birth variation in eating disorders akin to those of psychoses. We studied season of birth variation in bulimia nervosa. METHOD: Season of birth variation in 935 patients was examined after adjustment for population trends. Variation was also examined for subgroups by age and previous anorexia nervosa. RESULTS: Season of birth did not differ significantly from population norms among bulimics (p >.30), contrasting with studies of other eating disorders. With a history of anorexia nervosa (n = 227), peak season of birth was in March (p <.05). This is consistent with previous studies and also with seasonal birth variation for psychoses. DISCUSSION: Overall, we find no evidence of season of birth variation in bulimia nervosa, and suggest any positive findings be treated with caution. We discuss a number of confounding influences and argue that one explanation remains shared trait vulnerability between anorexia nervosa and psychoses.

Adolescent↗
PubMed2000

Seasonal changes in the hypothalamo-pituitary-testes axis of the Japanese wood mouse (Apodemus speciosus).

Seasonal changes in the hypothalamo-pituitary-testes axis of the Japanese wood mice (Apodemus speciosus) were studied. The testes, epididymis, pituitary and hypothalamus were compared between mice in the breeding season (July) and non-breeding season (October) using morphological techniques, and the plasma testosterone level was evaluated by enzyme immunoassay. Significant differences in these tissues were observed between the breeding season and the non-breeding season. Specifically, differences in the non-breeding season included 1) a decline in testicular and epididymal weights, arrest of spermatogenesis and decrease of serum testosterone concentration; 2) a decrease in the number of luteinizing hormone (LH)-, follicle stimulating hormone (FSH)-, prolactin (PRL)-, and growth hormone (GH)-immunoreactive cells, and decrease in the size of FSH, PRL, and GH-immunoreactive cells; and 3) an increase in the size of gonadotropin-releasing hormone (GnRH)-immunoreactive neurons. Our findings indicate that the male adult Japanese wood mouse exhibits unique seasonal changes in the hypothalamo-pituitary-testes axis which are not found in laboratory mice.

Animals↗
PubMed2002

Seasonal changes in the densities of alpha(2) noradrenergic receptors are inversely related to changes in testosterone and the volumes of song control nuclei in male European starlings.

The functions of song and the contextual cues that elicit song change seasonally in parallel with testosterone (T) concentrations in male European starlings. T is high in spring when at least one function of male song is that of immediate mate attraction, and low outside the context of breeding, when starlings primarily use song for dominance or flock maintenance. Several brain nuclei that control song contain high densities of alpha(2)adrenergic receptors. T can regulate the density of alpha(2)adrenergic receptors in the avian brain, indicating that the density of alpha(2) adrenergic receptors within the song system might change seasonally. Although the function of seasonal brain variation is not entirely clear, in many songbirds the volumes of song nuclei are largest when T is high and males sing most. Male starlings, however, sing both when T is high and when T is low. Therefore, exploring seasonal changes in T and the volumes of song nuclei could provide insight into the function of these changes. The present study was performed to explore the relationships among T, the volumes of song nuclei, and the densities of alpha(2) adrenergic receptors within the song system of male starlings. Song nuclei (the high vocal center [HVc], robust nucleus of the archistriatum [RA], and Area X) were largest, T was highest, and the density of alpha(2) adrenergic receptors (within HVc and RA) was lowest during the breeding season. The reverse pattern was observed outside of the breeding season. These results suggest that changes in T, volumes of song nuclei, and alpha(2) receptor densities might regulate seasonal changes in song behavior or the context that will elicit song in male starlings.

Adrenergic alpha-Antagonists↗
PubMed2005

Seasonal change in neuron size and spacing but not neuronal recruitment in a basal ganglia nucleus in the avian song control system.

Neural plasticity in the song control system of seasonally breeding songbirds accompanies seasonal changes in singing behavior. The volume of Area X, a song control nucleus that forms a portion of the avian basal ganglia, is 75% larger in the spring than it is in the fall. The neuronal basis of the seasonal plasticity in Area X is largely unknown, however. We examined neuronal attributes of Area X in wild adult male song sparrows (Melospiza melodia) captured during the spring and the fall after being implanted for 30 days with osmotic pumps containing [3H]thymidine. We measured the volume of Area X from thionin-stained sections, and neuronal density and number, and average area of the soma from sections labeled with an antibody against Hu, a neuron-specific protein. We sampled two neuron classes: "small" neurons that were most likely striatal-like spiny neurons and "large" neurons, which most likely included pallidal-like projection neurons. We also analyzed seasonal patterns of neuronal recruitment to Area X. The average area of the soma and neuronal spacing for both neuronal classes were greater in breeding birds. There was no difference in total neuron number for both neuronal classes between seasons. The average area of the soma and density and number of newly recruited neurons did not vary across seasons. These results demonstrate that seasonal plasticity in Area X includes changes in neuron size and neuronal density, but not changes in the rate at which new neurons are recruited.

Animals↗
PubMedDate not supplied

Changes in serum levels of LH, FSH, prolactin, testosterone, and cortisol associated with season and mating in male pygmy goats.

Four male pygmy goats were used in a study designed to determine the effects of season on serum hormone (luteinizing hormone, follicle stimulating hormone, prolactin, testosterone, and cortisol) levels, testis size and libido, and the effects of mating on serum hormone profiles. Seasonal peaks were observed for prolactin in July, luteinizing hormone and follicle stimulating hormone in September, and testosterone in October. Luteinizing hormone peak frequency was greatest in September and was increased by mating activity in the months immediately preceding the breeding season. Scrotal circumference did not vary with season and libido showed no consistent seasonal pattern. Mating appeared to raise all hormone levels except during the months when these hormones were seasonally elevated. When episodic releases of luteinizing hormone occurred, they were associated with subsequent rises in serum testosterone levels. On some mating days, when episodic releases of luteinizing hormone were absent, changes in testosterone levels were highly correlated with changes in cortisol levels. It was concluded that both season and mating influence reproductive hormone levels in male pygmy goats.

Animals↗
PubMed2002

Sexual dimorphism and seasonal variation in submandibular gland histology of Bolomys lasiurus (Rodentia, Muridae).

Wild rodents (Bolomys lasiurus) of both sexes were caught in a cerrado grassland area during the dry (July-September) and rainy (January-March) seasons of Brazil. Fasted animals were perfused with Karnovsky fixative through the left ventricle, under ether anesthesia, and the submandibular gland was processed for embedding in historesin. Histological and histometric data show sexual dimorphism at both seasons. In the volume percentage of the granular convoluted tubules (GCT) and their secretory granules, the males exhibited higher values. The absolute volume occupied by these structures, however, was dimorphic only in the rainy season. The diameter of the GCT, the height of its epithelium, and its total length were also greater in males during the rainy season. The absolute volumes of the acini and of the ductal tree were identical in both sexes in the dry and rainy seasons but the acinar diameter increased in the males and females during the rainy season. The sexual dimorphism and the seasonal variations now described in the B. lasiurus submandibular glands could be explained by the augmented reproductive activity of the males in the rainy period.

Animals↗
PubMed2000

Seasonal variations in cytokine expression and cell-mediated immunity in male rhesus monkeys.

Our objectives in this study were to examine seasonal changes in immune responses including cytokine profiles of male rhesus monkeys housed under natural lighting conditions. We also monitored circannual changes in the secretion of several immunomodulatory hormones as potential mediators of the seasonal shifts in immune status. Retrospectively, the medical records of a large group of rhesus monkeys were examined to determine whether a common disease (campylobacteriosis) in this species shows a seasonal pattern of prevalence. Results of the study showed that there was a seasonal shift in the frequency of cells expressing TH1 cytokines (interleukin-2 and interferon-gamma) versus the TH2 prototype cytokine (interleukin-4) by peripheral blood mononuclear cells (PBMC) collected during the winter and summer. The frequency of TH1-type cytokine synthesis in the summer was markedly greater than in the winter whereas TH2-type cytokine expression did not vary between the two seasons. The proliferative response of PBMC to mitogens and natural killer cell activity of PBMC also varied with the season. Several hormones (testosterone, leptin, and prolactin) that modulate immune function exhibited circannual patterns of secretion. The prevalence of Campylobacter infections was higher in the spring than during the summer, fall, or winter. The data suggest that seasonal fluctuations in immune system status may alter the ability of primates to successfully respond to pathogens, and this may be related to circannual patterns of secretion of immunomodulatory hormones.

Animals↗
PubMed2000

Seasonal changes in plasma glucocorticosteroids of free-living female yellow-pine chipmunks: effects of reproduction and capture and handling.

We measured plasma levels of cortisol and corticosterone in female yellow-pine chipmunks (Tamias amoenus) while observing seasonal reproductive and life-history events by live-trapping a natural population during the active (nonhibernating) season. Both glucocorticosteroids (GCs) varied significantly from March through September, starting with minimal values at the time of mating (cortisol approximately 900 ng/ml, corticosterone approximately 50 ng/ml), rising to a peak by late lactation (cortisol approximately 1600 ng/ml, corticosterone approximately 175 ng/ml), and then declining prior to hibernation. Following their emergence from natal burrows, young of the year had GC levels indistinguishable from those of adults. Body mass also varied significantly over the season, increasing after mating and again after parturition to a peak in lactation, after which it declined steadily until hibernation. In addition to the use of standard trapping to describe seasonal hormonal patterns, we also trapped chipmunks using a special protocol to examine the effects of capture and handling on GCs; we obtained an initial (basal) blood sample immediately, within 1-3 min of observing a capture, and then a second sample 30 min after holding the animal in the trap. Chipmunks consistently increased GCs above the initial (basal) level during the 30 min after capture and initial handling; these significant increases in GCs ranged approximately 70-130% for cortisol and 50-190% for corticosterone, depending on season and reproductive state. GC levels at 30 min after capture and handling were similar to those obtained from samples drawn from our standard trapping and blood sampling. We conclude that although capture and handling increase the absolute level of plasma GC hormones, that effect does not obscure natural patterns of seasonal variation in GCs. Overall, our observations suggest an important role of adrenocortical activity in the energy balance of these free-living rodents in two different contexts: (1) the seasonal regulation of physiological state, including body mass, energy reserves, and reproductive function, and (2) an acute response to stimulatory events, encompassing physiological stress, as represented here by capture and handling.

Aging↗
PubMed2000

Daily and seasonal variation in response to stress in captive starlings (Sturnus vulgaris): glucose.

We investigated the seasonal and daily variation in plasma glucose levels in response to stress in captive wild starlings. Starlings were captured from the wild during the winter, held on short days (11L:13D, mimicking winter), and then shifted to long days (19L:5D, mimicking summer). Birds were maintained on long days until they began a prebasic molt, the energetically costly replacement of feathers. Throughout the daily cycle we took a basal blood sample within 3 min of disturbance and took subsequent blood samples at 15 and 30 min. Birds were kept in cloth bags (restraint) between bleeds. Experiments were repeated during all three seasons (short day, long day, and molt). Starlings showed no sexual difference in circulating glucose levels at any time of the day or in any season. Both basal and stress-induced glucose levels, however, showed a significant effect of season, with birds held on long days exhibiting the highest levels, molting birds showing intermediate levels, and birds held on short days exhibiting the lowest levels. Basal glucose levels also showed a circadiel rhythm in all three seasons. Regardless of season, however, the daily peak in basal levels occurred at midday with nadir in the middle of the scotophase. This trend was paralleled in the overall weights of the birds. Although stress-induced glucose levels showed no circadiel rhythm, the stress-induced elevation of glucose above baseline showed a significant daily rhythm, indicating that stress elevated plasma glucose levels only during the scotophase in all three seasons.

Animals↗
PubMed2001

Dehydroepiandrosterone in songbird plasma: seasonal regulation and relationship to territorial aggression.

Many male animals are territorial in the breeding season, when plasma testosterone (T) levels are high, and nonterritorial in the nonbreeding season, when plasma T levels are basal. In contrast to this common pattern, male song sparrows (Melospiza melodia morphna) are territorial year-round, except briefly during molt. Song sparrows are highly aggressive in the nonbreeding season (autumn and winter), even though plasma T, 5 alpha-dihydrotestosterone, androstenedione (AE), and 17beta-estradiol levels are undetectable (<or=0.1 ng/ml). Castration has no effect on nonbreeding territoriality. However, aromatase inhibitors decrease aggression in the nonbreeding season, indicating a role for estrogens in winter. The androgenic substrate for brain aromatase in winter is unclear, because plasma T and AE levels are basal. Here, we measured plasma levels of dehydroepiandrosterone (DHEA). DHEA is a precursor to AE and T, and the avian brain can convert DHEA into sex steroids. In nonbreeding male song sparrows, plasma levels of DHEA were detectable and several times higher than plasma AE and T levels. Plasma DHEA levels were similar in the breeding and nonbreeding seasons, but significantly lower during molt, which parallels seasonal changes in male aggression. Adrenal glands and testes from nonbreeding males had high concentrations of DHEA, suggesting that both tissues may secrete DHEA. However, stress and gonadotropin-releasing hormone (GnRH) did not increase plasma DHEA in nonbreeding birds. We hypothesize that in the nonbreeding season, circulating DHEA, possibly of adrenal origin, is converted into active sex steroids by steroidogenic enzymes in the brain. This mechanism would create high local levels of sex steroids in the brain to support winter aggression.

Adrenal Glands↗
PubMed1996

Seasonal testicular function in male rhesus monkeys.

Some studies report seasonal patterns of testicular function in male rhesus monkeys even when they are housed away from females, while others suggest that exposure to sexually active females is essential for male seasonality. We conducted the present experiment (1) to test claims that seasonal testicular activation occurs in the absence of females and (2) to determine whether regular exposure to and copulation with females enhances, or is without effect upon, seasonal increases in testicular function. We studied two groups of male monkeys housed in a colony room containing no females. Males in the Female Exposure group (n = 7) were paired twice weekly with estradiol-implanted females and copulated vigorously. Males in the second group (n = 7) were placed in the same test chamber (at least 16 h after it had been scrubbed with disinfectant) but were never exposed to females. Serum testosterone levels and testis volume were monitored for both groups. Each group displayed a seasonal pattern of testosterone and of testis volume comparable in timing and magnitude to seasonal increases previously reported in group-housed males, but the two groups did not differ from each other. Our findings confirm that seasonal changes in testosterone and testis size occur in the absence of sexual interaction and demonstrate that moderate levels of sexual activity do not enhance this response.

Animals↗
PubMed2000

Seasonal changes in courtship song and the medial preoptic area in male European starlings (Sturnus vulgaris).

In male starlings (Sturnus vulgaris) courtship song plays a critical role in mate attraction. During the breeding season courtship song occurs prior to copulation and appears to reflect male sexual arousal. Outside the breeding season starlings sing, but song appears unrelated to reproduction. The aromatization of testosterone (T), likely within the medial preoptic nucleus (POM), is critical for the expression of male sexual arousal. The present study was performed to determine whether seasonal changes in the POM might relate to seasonal changes in courtship singing behavior in male starlings. T concentrations, the volume of the POM, and aromatase within the POM were examined both during and outside of the breeding season in male starlings. Song was also recorded at these times both with and without a female present. The POM was largest and contained dense aromatase immunostaining only during the spring breeding season, when T concentrations were highest and males responded to a female with an increase in courtship song. Outside the breeding season the volume of the POM was small, T concentrations were low, and males displayed no changes in song expression in response to female conspecifics. Song bout length was positively related to POM volume, and males sang longer songs in spring. Only males with nestboxes in spring responded to a female, and the POM tended to be larger in these males, suggesting that nestbox possession might influence neuroplasticity within the POM. Overall, the findings suggest that T-dependent plasticity and aromatase activity within the POM might regulate courtship singing in a wild songbird.

Animals↗
PubMed1994

Seasonal distribution of Theileria in Hyalomma anatolicum anatolicum ticks of an endemic area of Haryana, India.

The effect of season on the capacity of Hyalomma anatolicum anatolicum ticks to transmit Theileria was studied by detecting Theileria sporoblasts in the salivary glands of 647 adult ticks moulted in winter (November 1990 to March 1991) and 677 adult ticks moulted in the summer-rainy season (June to August 1991). The intensity (number of infected acini per infected tick) and abundance (number of infected acini per tick examined) of Theileria sporoblasts were significantly (P < 0.05) higher in winter moulted ticks (10.75 and 2.23 respectively) than the summer-rainy season moulted ticks (7.31 and 1.77 respectively). The prevalence of infected moulted ticks was not significantly higher in the summer-rainy season (24.22%) than in the winter (20.71%). A higher percentage of winter moulted ticks had high numbers of infected acini (> or = 11/infected tick) than the summer-rainy season moulted ticks, while the trend was reversed for low numbers of infected acini(5/infected tick), being 47.76% for winter and 73.78% for the summer-rainy season. It was concluded that the winter of Haryana is more favourable to the developing theilerial stages in the ticks than the summer-rainy season.

Animals↗
PubMed1986

Influence of season of birth on weight for age in two genetic groups of cattle.

Body weights from birth to 756 days of age for calves of Mpwapwa cattle (12% Bos taurus inheritance) and backcrosses (34% Bos taurus) born in the wet or the dry season were analysed. The calves were weaned at 75 days of age and after that fed entirely on pasture. Backcrosses were heavier than Mpwapwa at birth and at 252 days of age but not at subsequent ages. Calves born in the dry season had slightly larger birth weights than calves born in the wet season. Weight differences were reversed from 252 to 504 days reflecting the seasonal fluctuations in grass growth. The effect of season of birth on long term rate of gain was negligible. No significant interaction between genetic group (Mpwapwa vs backcrosses) and season of birth (wet vs dry) was observed at any of the ages. The study thus did not confirm the hypothesis that backcrosses because of their higher proportion of Bos taurus genes were more sensitive to the nutritional stress of the dry season than were pure Mpwapwa calves.

Animal Nutritional Physiological Phenomena↗
PubMed2006

Relationships between biochemical bone turnover markers, season, and inflammatory status indices in prepubertal Gambian boys.

Seasonal and interindividual differences in food availability and illnesses cause variations in growth, including bone growth, in children in developing countries. We investigated seasonal differences in biochemical (serum) markers of bone metabolism and relationships between these markers (procollagen type I N propeptide [P1NP], serum C-terminal telopeptide of type 1 collagen [S-CTX]) and serum markers of inflammation (alpha(1)- antichymotrypsin [ACT], C-reactive protein [CRP], sialic acid) in prepubertal Gambian boys. Three seasonal time points were chosen: August, mid-rainy season; October, late rainy season (both are associated with decreased food supply, increased prevalence of infection, reduced weight gain, and stunting); and April, late dry season, when environmental conditions are better and rates of weight gain are higher. The prevalence of raised inflammatory markers was high: 29% of ACT values >0.40 g/L in August, 42% >0.40 g/L in October, and 18% >0.40 g/L in April. Of CRP values, 92-96% were >0.47 mg/L and 30%, 46%, and 18% were >3.95 mg/L in August, October, and April, respectively. Also, 42-52% of sialic acid values were >648 mg/L. Of the bone markers, S-CTX exhibited the highest values in August; P1NP did not vary with season. Inverse relationships between each bone marker and the acute phase markers occurred, with the strongest relationships between P1NP and ACT or sialic acid. We conclude that bone collagen synthesis and turnover are reduced during inflammation in rural Gambian boys. Biochemical indices can provide powerful, single-time point evidence of infection and growth-faltering episodes.

Acute-Phase Proteins↗