Postponed reproduction as an adaptation to winter conditions in Drosophila melanogaster: evidence for clinal variation under semi-natural conditions. (41/740)

Patterns of climatic adaptation in drosophila and other insects have largely been inferred from laboratory comparisons of traits that vary clinally. Here, we extend this research to comparisons under semi-natural conditions. To test for clinal variation in reproductive patterns and survival over winter, Drosophila melanogaster populations were initiated from seven collection sites along the eastern coast of Australia, ranging from tropical to temperate regions. The fecundity and survival of these populations were monitored in field cages at a temperate location until all adults had died more than 5 months later. Total fecundity showed a curvilinear relationship with latitude, due to higher egg production by high- and low-latitude populations. Adults from temperate locations survived winter conditions better than those from subtropical populations but not tropical ones. There was a linear cline in the timing of egg production: temperate populations produced eggs later than populations from lower latitudes. This cline is likely to be adaptive because egg-to-adult viability experiments indicated that only eggs laid in spring developed successfully to the adult stage. There was no evidence for climatic adaptation in the immature stages. The adult mortality rate increased gradually over winter, and in some populations was also correlated with the minimum ambient temperature. These results indicate that adaptation to winter conditions in D. melanogaster has involved shifts in reproductive patterns.  (+info)

Predictors of incidence and prevalence of green tobacco sickness among Latino farmworkers in North Carolina, USA. (42/740)

STUDY OBJECTIVE: The characteristics of some populations make epidemiological measurement extremely difficult. The objective of this study is to identify risk factors that explain variation among incidence densities and proportions of one occupational illness, green tobacco sickness, within one such special population, Latino migrant and seasonal farmworkers in the United States. DESIGN: Prospective cohort study. SETTING: 37 farmworker residential sites located in Granville and Wake Counties, North Carolina, USA. PARTICIPANTS: 182 migrant and seasonal farmworkers that included 178 Latino men, three Latino women, and one non-Hispanic white man. MAIN RESULTS: Green tobacco sickness had a prevalence of 0.082, and an incidence density of events per 100 days of 1.88 among the farmworkers. Prevalence and incidence density increased from early to late agricultural season. Major risk factors included lack of work experience, work activities, and working in wet clothes. Tobacco use was protective. CONCLUSION: Green tobacco sickness has a high incidence among migrant and seasonal farmworkers. Because workers have little control over most risk factors, further research is needed to identify ways to prevent this occupational illness.  (+info)

Factors associated with pilot fatality in work-related aircraft crashes, Alaska, 1990-1999. (43/740)

Work-related aircraft crashes are the leading cause of occupational fatality in Alaska, with civilian pilots having the highest fatality rate (410/100,000/year). To identify factors affecting survivability, the authors examined work-related aircraft crashes that occurred in Alaska in the 1990s (1990-1999), comparing crashes with pilot fatalities to crashes in which the pilot survived. Using data from National Transportation Safety Board reports, the authors carried out logistic regression analysis with the following variables: age, flight experience, use of a shoulder restraint, weather conditions (visual flight vs. instrument flight), light conditions (daylight vs. darkness), type of aircraft (airplane vs. helicopter), postcrash fire, crash location (airport vs. elsewhere), and state of residence. In the main-effects model, significant associations were found between fatality and postcrash fire (adjusted odds ratio (AOR) = 6.43, 95% confidence interval (CI): 2.38, 17.37), poor weather (AOR = 4.11, 95% CI: 2.15, 7.87), and non-Alaska resident status (AOR = 2.10, 95% CI: 1.05, 4.20). Protective effects were seen for shoulder restraint use (AOR = 0.40, 95% CI: 0.21, 0.77) and daylight versus darkness (AOR = 0.50, 95% CI: 0.25, 0.99). The finding that state of residence was associated with survivability offers new information on pilot survivability in work-related aircraft crashes in Alaska. These results may be useful in targeting safety interventions for pilots who fly occupationally in Alaska or in similar environments.  (+info)

Weather conditions and Bell's palsy: five-year study and review of the literature. (44/740)

BACKGROUND: Climatic or meteorological condition changes have been implicated in the pathogenesis of Bell's palsy (BP). We evaluate the influence of meteorological parameters, such as temperature, humidity, and atmospheric pressure, and their variation and covariation on the incidence of BP and present a review of the literature on the effect of meteorological conditions on facial nerve function. METHODS: A total of 171 cases of BP admitted to our Department over a five-year period were studied. The meteorological database included daily values of 13 distinct parameters recorded at the meteorological station of the University of Ioannina during this period. A relationship between each meteorological variable and the incidence of BP was investigated by applying (Chi2) test on data from 13 contingency tables. In addition, the influence of different weather types on the incidence of BP was also investigated. For this purpose Cluster Analysis was used to create eight clusters (weather types) for the Ioannina prefecture and (Chi2) test was applied on the contingency tables consisting of the days of BP cases for each cluster. RESULTS: No significant correlation was found either between BP and each distinct meteorological parameter or between BP and any specific weather. CONCLUSIONS: Meteorological conditions, such as those dominating in the Northwestern Greece, and/or their changes have little effect on the incidence of BP. Multicenter studies taking into account atmospheric pollution, and climatic differences between countries, are necessary to scrutinize the environmental effects on facial nerve function.  (+info)

Dairy calf mortality rate: the association of daily meteorological factors and calf mortality. (45/740)

The number of dairy heifer calves born each day, the number of these calves which died prior to 36 days of age and the actual date of death were recorded and analyzed for possible associations with weather factors. The demographic data on dairy calves were supplied by 16 farms in Tulare County, California for the months of July to December 1973. High temperatures in the summer and low temperatures in the winter were associated with an increased risk of death. Calves born during the periods of extreme temperatures had a higher risk of death than those born on more temperate days, while death, when it occurred was temporally related to days of extreme temperatures. Periods of increased risk of death often were associated with large temperature fluctuations irrespective of the absolute temperature. Nonmeteorological factors specific to invidual farms also appeared to influence daily calf mortality rates.  (+info)

The effect of weather on some infectious diseases. (46/740)

For several years the Royal College of General Practitioners has been collecting data supplied by local doctors throughout Britain on some infectious diseases seen in their practices. We describe a method of computerisation of this information and statistical analyses. We are investigating the influence of external factors such as climate on the infectiousness of some diseases. A model is fitted involving a non homogeneous two-state Markov chain whose transition probabilities are governed by the explanatory data.  (+info)

Reported morbidity and the weather. (47/740)

Some observations have been made about the influence of the weather on the use of the general-practitioner service. It is difficult to disentangle the biological and behavioural components of these findings, but in general extremes of weather-low temperatures and sunshine in winter and high temperatures and sunshine in summer-appeared to increase the numbers of reported episodes of respiratory illness.  (+info)

Effects of weather on daily body mass regulation in wintering dunlin. (48/740)

We investigated the influence of changes in weather associated with winter storms on mass balance, activity and food consumption in captive dunlin (Calidris alpina) held in outdoor aviaries, and compared the aviary results with weather-related body mass differences in free-living dunlin collected at Bolinas Lagoon, California. Captive birds fed ad libitum increased their body mass at higher wind speeds and lower temperatures, suggesting regulation of energy stores, whereas free-living birds exhibited patterns suggesting thermoregulatory limits on body mass regulation. Daily energy expenditure in aviary dunlin was 2.85 kJ g d(-1), or 2.8x basal metabolic rate (BMR), with thermostatic costs averaging 59 % of daily expenditure. Slight but significant increases in body mass and energy expenditure in captive birds on rainy days, adjusted for possible external water mass, suggested rainfall as a proximate cue in regulating daily body mass. Body mass changes under artificial rainfall indicated similar results, and field masses suggested that free-living birds have greater body mass on days with measurable rainfall. Increased activity costs under artificial rainfall were associated with an increase in maintenance activities, relative to controls. Whether activity costs increased on days with natural rates of rainfall was unclear. Our results are consistent with current hypotheses regarding the role of body mass regulation in providing insurance against increased starvation risk during deteriorating thermal or foraging conditions, or in reducing the costs of extra mass as conditions improve.  (+info)