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Results for “seasonal selection”

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At least 19 recordsLinked to original sources
PubMed2015

Variation in Drosophila melanogaster central metabolic genes appears driven by natural selection both within and between populations.

In this report, we examine the hypothesis that the drivers of latitudinal selection observed in the eastern US Drosophila melanogaster populations are reiterated within seasons in a temperate orchard population in Pennsylvania, USA. Specifically, we ask whether alleles that are apparently favoured in northern populations are also favoured early in the spring, and decrease in frequency from the spring to autumn with the population expansion. We use SNP data collected for 46 metabolic genes and 128 SNPs representing the central metabolic pathway and examine for the aggregate SNP allele frequencies whether the association of allele change with latitude and that with increasing days of spring-autumn season are reversed. Testing by random permutation, we observe a highly significant negative correlation between these associations that is consistent with this expectation. This correlation is stronger when we confine our analysis to only those alleles that show significant latitudinal changes. This pattern is not caused by association with chromosomal inversions. When data are resampled using SNPs for amino acid change the relationship is not significant but is supported when SNPs associated with cis-expression are only considered. Our results suggest that climate factors driving latitudinal molecular variation in a metabolic pathway are related to those operating on a seasonal level within populations.

Adaptation, Physiological↗
PubMed1978

Selection among males for the genetic improvement of female fertility.

The quantitative physiological study of genetic variation in reproductive performance has shown that differences in the litter size and incidence of lambing in sheep are associated with variation in the release of LH. This variation is detectable in young animals of both sexes, and the injection of LHRH may aid its recognition. In the male it is associated with variation in mating behavior and testis growth. The ovarian activity of both sheep and mice has been shown to change following selection for testis growth. The use of measures of testis growth as criteria for selection to improve the reproductive performance of females is discussed.

Animals↗
PubMed1975

Distribution and seasonal prevalence of bovine lungworms in selected areas in western Montana.

In a survey (Oct, 1967, through Aug, 1969) of the distribution and seasonal prevalence of bovine lungworms in beef herds in 3 western Montana counties (Park, Gallatin, and Ravalli), infected cattle were detected in 27 of 35 herds. Results of 2,125 fecal examinations indicated that 7.8% of all cattle were infected with Dictyocaulus viviparus. Lungworms were found in 6.6% of 1,038 calves (less than 12 months old), 11.5% of 755 yearlings (1 to 2 years old), and 3.3% of 332 cows (more than 2 years old). A distinct seasonal pattern existed in calf infections, with initial passage of larvae beginning in late July or August and persisting until November or December. Exposure of calves in 1 portion of the study area apparently was delayed until November, with patent infections continuing through March. Spontaneous loss of infections normally occurred after 3 to 4 months of patency. The mean rate of larval excretion in the feces of all infected cattle was 0.37 larvae per gram of feces (l/g). Larval output was relatively uniform within each geographic area regardless of host age, but varied considerably from one portion of the study area to another. The potential role of wild ruminants (deer, elk, and moose) in the epizootiology of D viviparus is discussed with respect to western range utilization practices.

Animals↗
PubMed1978

Reproduction and breeding of goats.

Reproduction and genetics of the goat are reviewed with a view of increasing their contribution to mankind. The goat contributes most in tropical regions (within 30 degrees of the equator). The most important product from the goat is milk with meat a close second. Other products are minor. Reproductive rate is a problem only with the Angora goat, but increased reproduction with any type of goat would contribute to improved efficiency. Also, a knowledge of the reproductive phenomenon is necessary for effective management. Genetic studies of goats are limited, but this should not limit improvement programs. Excellent genotypes for producing milk and fiber are available, but adaptation to tropical conditions is needed. Even within temperature regions, there is little evidence of progress in breeding for milk production. Little has been done on the development of the goat as a meat animal. Also, research on crossbreeding for milk or meat production is limited.

Abortion, Veterinary↗
PubMed1978

Leucocyte ascorbic acid and pregnancy.

1. Leucocyte ascorbic acid concentrations have been measured in 1147 females during early pregnancy and in smaller numbers of women before conception, throughout pregnancy and at 6 months post partum. 2. The leucocyte concentration in the 1st trimester was found to be affected by season, social class and smoking. Selecting individuals by extremes of social class, season and smoking produced two small populations with almost separate ascorbic acid distributions and mean concentrations of 21.7 and 45.1 microgram/10(8) leucocytes. 3. Early pregnancy had little effect on leucocyte ascorbic acid concentrations but values decreased in the second trimester. However, this was associated with a leucocytosis so that the total leucocyte ascorbic acid content of blood was unchanged. 4. Low ascorbic acid concentrations during the 1st trimester were not associated with subsequent spontaneous abortions, still-births or neonatal deaths, but there was an increased frequency of low values in women who gave birth to infants smaller than 3250 g. 5. The adequacy of ascorbic acid reserves in early pregnancy is discussed.

Adult↗
PubMed1979

Tympanometry in three-year-old children. II. Seasonal influence on tympanometric results in non-selected groups of three-year-old children.

Screening tympanometry was performed in January 1976 and in August 1978 on 938 healthy 3-year-old children (1 868 ears), constituting more than 95% of the total population of 3-year-olds living in a Danish provincial municipality at the time of testing. Seasonal influence upon the occurrence of middle ear effusion and tubal dysfunction, not previously quantitated by systematic studies on pre-school children, was thus elucidated by comparing the prevalence of these conditions in winter and in summer. There was a statistically significant preponderance of pathological tympanometry in winter, but the difference was not overwhelming. The findings emphasize that problems relating to a disturbed middle ear function in early childhood are of great practical importance throughout the year.

Acoustic Impedance Tests↗
PubMed1979

Air pollution analysis used in operating an environmental control unit.

A simple, fast and reliable method was developed to measure the origin and daily and seasonal variations of selected air pollutants in the Brookhaven Environmental Unit. None of the pollutants that were measured surpassed its threshold limit value. The average concentrations of the pollutants that were measured could be considered as preliminary standard for environmental units in hospitals as long as material analysis for outgassing is used simultaneously.

Air Pollutants↗
PubMedDate not supplied

HLA and pollinosis.

Sixty-two patients were selected who suffered from seasonal pollen-induced bronchial asthma and rhinitis. Histocompatibility antigen typing was carried out with a panel of 70 antisera (Behringwerke) of 33 HLA specificities. The results obtained at locus A of the most representative by percent phenotypic frequency of the HLA studies shows a decreased frecuency of HLA-A11. The phenotyic frequencies of the most representative HLA of B locus in the group of patients shows an increase in the frequency of HLA-B8. This represents 22.6% compared with 9.1% of the controls, which is definitely significant. The results obtained in a study of the haplotype frequency of three combinations of HLA antigens, in a group of allergic patients compared with the controls shows that the frequency of the haplotype A1 B8 is greater in the allergic patients than in the control group, a statistically significant finding. As regards the other two haplotypes A2 B12 and A3 B7, the respective results of the comparison were not significant in the first and marginally significant in the second. Even these few studied cases demonstrate the predominance of HLA-B8 in atopic or hyperreactive states. As regards the A1 B8 haplotype, we also find a slightly increased occurrence, in agreement with the literature. This suggests that the hyperergic response might be associated with the presence of the A1 B8 haplotype.

Female↗
PubMed2026

Seasonal fluctuations in fitness result in severe reductions in effective population size.

Genetic evidence for fluctuating selection has begun to accumulate for different species over the past few decades, especially for the Drosophila genus where studies have reported hundreds of loci undergoing putatively adaptive oscillations across successive seasons. However, most theoretical and simulation studies of fluctuating selection have relied on abstract or weakly parameterized models, making it difficult to assess their relevance for natural populations. In this study, we simulate multilocus seasonally fluctuating selection acting on standing genetic variation under a recently developed model and examine its effect on the variance effective population size (Ne) at a genome-wide scale. By recapitulating genomic, demographic, and evolutionary parameters from natural Drosophila populations in our simulations, we were able to reproduce allele frequency oscillations reported in recent studies and show that these lead to ∼50% genome-wide reductions in Ne. We also demonstrate that Ne reductions are well predicted by the maximum frequency amplitude among all adaptively fluctuating loci, and that the frequency amplitudes are largely determined by the number of adaptively fluctuating loci and the strength of their epistatic interactions. Our results demonstrate that fluctuating selection can substantially reduce effective population size and underscore the importance of temporally variable selection in shaping genome-wide patterns of variation beyond classical models.

Drosophila melanogaster↗
PubMed2026

Seasonal fluctuations in fitness result in severe reductions in effective population size.

Genetic evidence for fluctuating selection has begun to accumulate for different species over the past few decades, especially for the Drosophila genus where studies have reported hundreds of loci undergoing putatively adaptive oscillations across successive seasons. However, most theoretical and simulation studies of fluctuating selection have relied on abstract or weakly parameterized models, making it difficult to assess their relevance for natural populations. In this study, we simulate multilocus seasonally fluctuating selection under a recently developed model and examine its effect on the variance effective population size (Ne ) at a genome-wide scale. By recapitulating genomic, demographic, and evolutionary parameters from natural Drosophila populations in our simulations, we were able to reproduce allele frequency oscillations reported in recent studies and show that these lead to ~50% genome-wide reductions in Ne . We also demonstrate that Ne reductions are well predicted by the maximum frequency amplitude among all adaptively fluctuating loci, and that the frequency amplitudes are largely determined by the number of adaptively fluctuating loci and the strength of their epistatic interactions. Our results demonstrate that fluctuating selection can substantially reduce effective population size and underscore the importance of temporally variable selection in shaping genome-wide patterns of variation beyond classical models.

Drosophila melanogaster↗
PubMed2024

Genotypic and phenotypic characterisation of respiratory syncytial virus after nirsevimab breakthrough infections: a large, multicentre, observational, real-world study.

BACKGROUND: Nirsevimab, a long-acting monoclonal antibody, has been approved for the prevention of respiratory syncytial virus (RSV) infection in infants. In France, more than 210&#x2009;000 single doses were administered in infants younger than 1 year during the 2023-24 season. In this context, the selection and spread of escape variants might be a concern. Here, we aimed to characterise RSV associated with breakthrough infection. METHODS: We did a multicentre, national, observational study in France during the 2023-24 RSV season in RSV-infected infants (aged <1 year) who either received or did not receive a dose of nirsevimab before their first RSV season. We excluded infants with insufficient information about nirsevimab treatment or without parental consent. We used respiratory samples collected in each laboratory for full-length RSV RNA sequencing to analyse changes in the nirsevimab binding site &#xd8;. We tested clinical RSV isolates for neutralisation by nirsevimab. We analysed F candidate substitutions by fusion-inhibition assay. FINDINGS: Of the 695 RSV infected infants, we analysed 545 (78%) full-length RSV genome sequences: 260 (48%) from nirsevimab-treated breakthrough infections (236 [91%] RSV-A and 24 [9%] RSV-B) and 285 (52%) from untreated RSV-infected infants (236 [83%] RSV-A and 49 [17%] RSV-B). Analysis of RSV-A did not reveal any substitution in site &#xd8; known to be associated with resistance to nirsevimab. Two (8%) of 24 RSV-B breakthrough infections had resistance-associated substitutions: F:N208D (dominant resistance-associated substitution) and a newly described F:I64M plus F:K65R combination (minority resistance-associated substitution), both of which induced high levels of resistance in the fusion-inhibition assay. INTERPRETATION: This study is, to the best of our knowledge, the largest genotypic and phenotypic surveillance study of nirsevimab breakthrough infections to date. Nirsevimab breakthrough variants remain very rare despite the drug's widespread use. The detection of resistance-associated substitutions in the RSV-B F protein highlights the importance of active molecular surveillance. FUNDING: ANRS Maladies Infectieuses Emergentes and the French Ministry of Health and Prevention.

Humans↗
PubMed1978

The effects of a collegiate wrestling season on body composition, cardiovascular fitness and muscular strength and endurance.

The purposes of this investigation were: (1) to study the body composition, cardiovascular fitness and muscular strength and endurance of collegiate wrestlers during the course of a season; (2) to determine if selected regression equations used to predict minimal wrestling weight were accurate; (3) to determine if the wrestlers who participated in the study had an accurate perception of their ideal minimal wrestling weights. Body composition (body densitometry), aerobic power (Vo2 max), and muscular strength and endurance (isokinetic) were measured during pre, peak, and post-seasons. The fact that very few significant changes occurred in these measurements during the course of the study appears to be the result of year-round training on the part of the athletes studied. Their peak-season percent body fat (8.36%) was very similar to that reported in other studies involving mature wrestlers. Rapid weight loss through dehydration appeared to be the preferred method of weight reduction among these athletes.

Adult↗
PubMed1976

[Genetics and phenogenetics of the hormonal characteristics of animals. II. Changes in the reactivity of the pituitary-adrenal system and influence of the sex glands in selection of silver-black foxes by behavior].

Seasonal changes in the reactivity of adrenal cortex to ACTH and of the pituitary-adrenal system to psychic stress in intact and castrated domesticated (tame) and non-domesticated (non-tame) silver foxes of both sexes were studied. It is demonstrated that in tame foxes there are differences among the intact and castrated animal in their reaction to ACTH and psychic stress. These differences are maifested especially in autumn (September, October) which is the period of extra-seasonal sexual activity for domesticated animals. This points to the fact that the sex glands exert a great influence on the condition of central regulating mechanisms of the pituitary-adrenal complex and that the selection of silver foxes for tame behaviour changes the functional state of these mechanisms through the change of the functional state of the sex glands.

Adrenal Cortex↗
PubMed1979

Nutrition and ice hockey performance.

Muscle glycogen is a major fuel for ice hockey. About 60% of the muscle glycogen in quadriceps muscle is utilized during a single game. When hockey games are played on successive days, studies reveal that muscle glycogen utilized during the second game is less than that of the first game. The diet of seven professional hockey players was studied for one week during the playing season to determine whether food selection could pose a problem for hockey performance. The data reveal that most players have a high protein intake, but that vegetables and fruit intakes were low. The problem of fuel supply for young hockey players is examined during tournament situations where up to three or more games may be played in a single day.

Adult↗
PubMed1978

[Diagnosis of Bacillus larvae --the causative agent of American foulbrood].

The authoress studied the growth of Bacillus larvae on different nutrient media and its ability of decomposing hydrogen peroxide and reducing nitrates. There are also instructions for rapid cultivation and biochemical diagnosis of Bacillus larvae. It can be performed in any microbiological laboratory, the culture medium can be prepared from available commercially produced preparations, and B. larvae can be detected in suspected material even out of the season, if the method of selective cultivation and repeated pasteurizing is used. Catalase test is proposed to be added to the examination; the result of this test was negative in all 96 strains studied. Photographic documentation of different developmental stages of B. larvae can serve as an aid in microbiological examination.

Animals↗