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PubMed1993

The evolutionary history of Drosophila buzzatii. XXVII. Thorax length is positively correlated with longevity in a natural population from Argentina.

The correlation between body size and longevity was tested in an Argentinian natural population of Drosophila buzzatii. Mean thorax length of flies newly emerging from rotting cladodes of Opuntia vulgaris was significantly smaller than that of two samples of flies caught at baits. The present results which might be interpreted as directional selection for longevity favoring larger flies are in agreement with previous results achieved in a Spanish natural population of D. buzzatii. Flies emerging from different substrates showed significant differences in thorax length, suggesting that an important fraction of phenotypic variance can be attributed to environmental variability. However, laboratory and field work in different populations of D. buzzatii showed a significant genetic component for thorax length variation.

Animals↗
PubMed1987

Multiple vital functions of the daughterless (da) gene in Drosophila melanogaster and factors influencing its expression.

Multiple sub-vital effects, here designated as reductions in fitness S1-S5, for the second chromosome gene 'daughterless' (da) of Drosophila melanogaster were described as (S1) a recessive maternal lethality for daughters, (S2) a reduced fertility of da/da females, (S3) a recessive sub-vital zygotic effect, (S4) a recessive female-specific zygotic effect and (S5) a recessive maternal interaction effect on sons. (For S1-3 see also: Bell, 1954; Sandler, 1972; Cline, 1976). These five distinct effects were initially quantified from estimates of viability in single generation crossing experiments. Dynamic estimates of these fitness parameters were obtained by fitting the elimination rate of da from a series of large random mating cage populations to a recurrence equation by the method of minimum chi-square. The stability of these estimates discerns those effects which are truly pleiotropic versus those due to linked genes. The dynamic estimates supported only S1 and S4 effects. Evidence for S2 and S5 was indeterminate, but the S3 effect was rejected (P less than 0.01). The observed reduction in fitness, supposedly due to this recessive zygotic effect for da, was most likely the result of linked deleterious genes. These results indicate that pleiotropic vital effects observed in single generation test-cross matings may be caused by linked genes rather than the specific mutant per se. This problem is of particular importance when the mutant allele has been maintained with a balancer chromosome. Experiments on the rescue of daughters from da/da mothers with low temperatures during embryogenesis and with dechorionation of eggs were described in which the findings failed to confirm previously reported actions of the da gene. Modifying genes rather than environmental variables were cited as the probable cause for these conflicting results.

Animals↗
PubMed1992

Genetic aspects of susceptibility to obesity and related dyslipidemias.

Obesity has a multifactorial origin. However, although environmental variables undoubtedly play a role in the development of obesity, it is now clear that genetic variation is also involved in the determination of an individual's susceptibility to body fat accumulation. In addition, it is also widely accepted that obesity is not a single homogeneous phenotype. It is also heterogeneous regarding its causes and metabolic complications. The regional distribution of body fat appears to be an important correlate of the metabolic complications that have been related to obesity. Due to their higher accumulation of abdominal fat, men are generally more at risk for the metabolic complications of obesity than women whereas some obese women, with large gluteal-femoral adipose depots may have a cosmetic problem which may not necessarily require medical intervention. Several studies have been conducted to understand the mechanisms by which abdominal obesity is related to diabetes, hypertension and cardiovascular disease. It appears that the increased risk of abdominal obesity is the result of complex hormonal and metabolic interactions. Studies in genetic epidemiology have shown that both total body fatness and the regional distribution of body fat have a significant genetic component. Standardized intervention studies using an identical twin design have shown that individuals that have the same genetic background tend to show similar changes in body fat and in plasma lipoprotein levels when exposed to standardized caloric excess or energy restriction. Finally, although abdominal obesity is a significant risk factor for cardiovascular disease, not every abdominal obese subject will experience metabolic complications, suggesting that some obese individuals may be more susceptible than others. Variation in several genes relevant to lipid and lipoprotein metabolism may alter the relation of abdominal obesity to dyslipoproteinemias. Abdominal obesity should therefore be considered as a factor that exacerbates an individual's susceptibility to cardiovascular disease.

Adipose Tissue↗
PubMed1989

A nonautonomous model of population growth.

With x = population size, the nonautonomous equation x = xf(t, x) provides a very general description of population growth in which any of the many factors that influence the growth rate may vary through time. If there is some fixed length of time (usually long) such that during any interval of this length the population experiences environmental variability representative of the variation that occurs in all time, then definite conclusions about the population's long-term behavior apply. Specifically, conditions that produce population persistence can be distinguished from conditions that cause extinction, and the difference between any pair of solutions eventually converges to zero. These attributes resemble corresponding features of the related autonomous population growth model x = xf(x).

Animals↗
PubMed1983

Effect of environmental novelty and electroconvulsive shock on the tail flick reflex after placebo or morphine pellet implants.

After implantation of either a placebo or morphine pellet, different groups of rats were either assessed or not assessed on the nociceptive tail-flick test. After 1 week, latencies of placebo-implanted rats were significantly increased if the animals were inexperienced with the nociceptive test or if they were unfamiliar with the environment in which the test was administered. Latencies were not altered by an electroconvulsive shock (ECS) administered 1 week before the reflex test. In contrast, latencies of morphine-pretreated rats were not altered by prior experience with the nociceptive test per se. However, latencies of animals with prior test experience were modified by environmental novelty and ECS. Rats who became tolerant to morphine in a familiar environment were hyperalgesic when subsequently tested in unfamiliar surroundings. The latencies of rats who received a single ECS during the development of tolerance were unchanged 1 week later, whereas the latencies of rats who did not receive ECS showed a significant decline during this interval. These data demonstrate the mutual contribution of pharmacological and environmental variables in nociceptive behavior.

Animals↗
PubMed1989

Economic analysis of age at first marriage.

A subject of great interest to demographers is to relate the timing of demographic events to individual characteristics and environmental variables. Static models of marriage tend to give corner solutions, the choice of marriage, or remaining single. This article develops an economic model of marriage which gives interior solutions to the optimum age at 1st marriage and which does not include an explicit argument about the age at marriage in the utility function. In theoretical analysis, the life cycle model is modified to capture different aspects of the decision of when to get married. Results from empirical analysis support implications derived from the theoretical analysis.

Americas↗
PubMed1990

Nonlatitudinal environmental correlations for alcohol dehydrogenase in southern African populations of Drosophila melanogaster.

The relation between alcohol dehydrogenase (ADH) allozyme frequencies and several environmental variables, as well as latitude and longitude, was examined in 17 natural populations of Drosophila melanogaster in Namibia, South Africa, and Zimbabwe. Unlike several other studies, we found no latitudinal allele-frequency clines and no significant correlation with temperature. We found that the frequency of the most common allele (AdhS) was positively correlated with an increase in rainfall. We suggest that substrate-induced toxicity may explain the geographic variability in our results.

Africa, Southern↗
PubMed1980

Task force report: the social climate of mental health.

This paper focuses on the contributions the field of social ecology can make to understanding and assessing the social environment, with special reference to the prevention of mental illness. Intervention in the social environment for mental illness prevention calls for an adequate concept of the environmental effects of mental health; a classification method for measuring and comparing different environments; a knowledge of the relationships between environmental variables and behavioral or psychological outcomes; and a way of determining the most effective interventions.

Ecology↗
PubMed1979

Life stress and maladaptation of children.

Social environmental variables differentiating maladapting children from matched controls in four inner-city elementary schools were investigated. Teacher selection was used to identify the maladapting children. Identified maladapting children were more likely to have been on welfare and to have experienced significantly more stressful life events during the previous year than the matched control children. The maladapting group was subdivided into welfare and non-welfare groups. Comparisons between groups on the life stress event measures indicated that the nonwelfare maladapting group experienced more life events than either the nonwelfare controls or the maladapting welfare children. The measures of life events correlated with parent ratings of behavior problems for the nonwelfare maladapting group but not for the welfare maladapting or the control groups.

Adaptation, Psychological↗
PubMed1977

Calcite growth under controlled diffusion.

The growth of calcite was studied in a gelatin-gel medium under variable environmental conditions by 2 different methods. The results suggest that the organic matrix, the temperature, the diffusion fluctuation depending on ionic concentrations, and the presence of additives exert a fine control on the evolution of single crystals, polycrystalline aggregates, and highly structured concretions of calcite.

Calcification, Physiologic↗
PubMed1976

Genetic variation in constant environments.

Allozymic variation in proteins encoded by 32 gene loci was analyzed electrophoretically in 64 specimens from 6 localities representing 2 species of the spadefoot toads Pelobates syriacus and P. cultripes from Israel and Portugal, respectively. Out of the 32 loci examined, Esterase-1 was the only locus that proved strongly polymorphic in all 6 localities and in the 2 species. The pattern of genetic variation in Pelobates is best explained by the environmental variability model. Selection for homozygosity as an adaptive strategy seems to operate in the relatively constant and narrow subterranean niche.

Alleles↗
PubMed1988

Descriptive epidemiology of perinatal and infant mortality in various Italian geographic areas.

On the basis of the number of livebirths, stillbirths and deaths within the first year of life published annually by the Central Institute of Statistics and data on demographic, environmental variables, general indicators of health organization, and reproductive habits, the descriptive epidemiology of perinatal and infant mortality in Italy between 1955 and 1984 has been reviewed. Although a marked reduction in Italian stillbirth (from 28.4 in 1955 to 7.1/1,000 births in 1984), perinatal (from 46.2 to 14.5/1,000 births) and infant mortality rate (from 51.0 to 11.3/1,000 live births) was observed, still broad differences between geographical areas within the country remained largely unchanged in proportional terms, since perinatal and infant mortality remained substantially lower in Northern, richer areas. Strong correlation coefficients emerged between perinatal and infant mortality rates and general indicators of health care organization such as number of hospital beds/1,000 inhabitants (and less strongly with number of obstetric beds) or per capita health expenditure. If rates from Northern Italy for the year 1984 were applied to the whole of the country, over 1,000 deaths in the first year of life could be avoided.

Data Interpretation, Statistical↗
PubMed1988

Environmental influences on the development of tolerance to the effects of physostigmine on schedule-controlled behavior.

The influence of environmental variables on the development of tolerance to physostigmine's effects in rats was examined using multiple fixed-ratio, extinction schedules of food presentation. Initial administration of physostigmine (0.4 mg/kg) produced nearly maximal decreases in the number of food pellets delivered, running response rate, and overall response rate, under multiple FR 10, EXT and multiple FR 50, EXT schedules. With repeated administration, tolerance to physostigmine's effects was observed when 10 responses were required to produce reinforcement but was not observed when 50 responses were required to produce reinforcement. Tolerance under the multiple FR 10, EXT schedule of reinforcement was also observed when physostigmine was administered post-session. When tolerance was acquired, it was retained for up to 25 drug-free days. These results suggest that tolerance to physostigmine's effects on schedule-controlled behavior is strongly influenced by response requirement, independently of physostigmine-induced reinforcement loss. Additionally, tolerance is not dependent on experience with the schedule while under the effects of physostigmine, and is retained for a substantial period of time in the absence of continued physostigmine administration.

Animals↗
PubMed1994

Modulation of drug reinforcement by behavioral requirements following drug ingestion.

Eight volunteers with histories of drug abuse participated in two experiments examining the modulation of drug choice by behavioral requirements following drug ingestion. Each morning subjects ingested color-coded capsules containing triazolam (0.25 mg), d-amphetamine (15 mg), or placebo and then engaged in a relaxation or a computer vigilance activity. Experiment 1 involved two phases (i.e. a triazolam and a d-amphetamine phase), presented in counterbalanced order. Within each phase, subjects were first exposed to each of two compounds (placebo and either triazolam or d-amphetamine) once with each activity. Then every other day for 20 days subjects chose which compound they ingested with the vigilance and relaxation activities, with the restriction that they could not choose the same compound with both activities. Seven of eight subjects reliably chose d-amphetamine with the vigilance activity; all subjects always chose triazolam with the relaxation activity. In experiment 2 (5 days' duration), after re-exposure to the color-coded compounds used in experiment 1, subjects chose which compound (placebo, d-amphetamine or triazolam) they ingested with the vigilance activity, and on another occasion (in counterbalanced order), which they ingested with relaxation activity. Seven of eight subjects chose d-amphetamine with the vigilance activity; all subjects chose triazolam with the relaxation activity. The relaxation and vigilance activities modulated triazolam and d-amphetamine reinforcement, thereby demonstrating a new class of environmental variable that can influence drug self-administration.

Adult↗
PubMed1995

Effects of morphine on different aspects of social play in juvenile rats.

To clarify the influence of opioids on social play, the effects of morphine on playful and non-playful social behavior in juvenile rats was investigated under different conditions. Environmental variables employed were different (dim and intense) levels of illumination during testing, familiarity to the test cage, and different periods of social isolation prior to testing. Under dim light conditions, morphine markedly increased playful social behavior, such as pinning, boxing/wrestling and following/chasing, whereas non-playful social behavior such as social exploration and contact behavior was hardly affected. This effect of morphine was independent of duration of previous isolation and dose-dependent, with a maximal effect at 1.0 mg/kg. The mechanism of this effect is interpreted as an action on the rewarding aspects of play. A dose of 0.1 mg/kg of morphine abolished the initial suppression of play induced by unfamiliarity to the test cage, without influencing total levels of play. This may be an effect of morphine on the integration of sensory stimuli. Under intense light conditions, whereas playful behavior was completely suppressed, morphine itself hardly affected such behavior, but decreased some aspects of non-playful social behavior. These results suggest that in juvenile rats playful and non-playful forms of social behavior are differentially regulated. In addition, opioid systems may be involved at different levels in the regulation of social play.

Animals↗
PubMed1993

In a drug discrimination procedure isolation-reared rats generalize to lower doses of cocaine and amphetamine than rats reared in an enriched environment.

Rats with different behavioral histories, defined by rearing and housing in either an enriched condition (EC) or an isolation condition (IC), were trained in a two-lever operant procedure to discriminate 5.0 mg/kg cocaine from saline. In cocaine dose-generalization tests, the IC rats exhibited an ED50 (1.01 mg/kg) significantly lower than the EC rats (ED50: 1.55 mg/kg). The cocaine-appropriate responding was emitted when the rats were treated with d-amphetamine, and for the d-amphetamine test doses the ED50 (0.19 mg/kg) was again significantly lower for the IC rats compared to the ECs (ED50: 0.33 mg/kg). These data suggest that IC rats are more sensitive to the stimulus properties of indirect dopaminergic agonists than EC rats and highlight the importance of environmental variables in governing an organism's response to the stimulus properties of abused drugs.

Animals↗
PubMed1978

The effects of a simulated refinery effluent on the grass shrimp, Palaemonetes pugio.

Duplicate static bioassays were conducted using a simulated refinery effluent on the grass shrimp (Palaemonetes pugio, Hippolyte sp.) with the LC-50 values recorded at 4-, 8-, 24-, 48-, and 96-hr intervals. The stimulated refinery effluent contained phenol (0.10 mg/L), sulfide (0.17 mg/L), chromium (0.25 mg/L), ammonia (10 mg/L), No. 2 fuel oil (10 mg/L), and kaolinite (20 mg/L). This arbitrary reference mixture (ARM) contains approximately the concentration of compounds recommended by EPA for 1977. Of the six ARM components, No. 2 fuel oil was the most toxic followed in decreasing order by sulfide, ammonia, phenol, chromium, and kaolinite. Temperature was the most important environmental variable affecting short term toxicity of the ARM to the grass shrimp. Light intensity, photo-period, and salinity had no significant effect. There was no difference in sensitivity of grass shrimp collected from five locations along the gulf and eastern coasts of the United States. Similarly, there was no difference in the response of two grass shrimp genera, Palaemonetes and Hippolyte to the ARM and there was no differences among the three species of Palaemonetes tested. In comparing the sensitivities of the two genera of grass shrimp and the pinfish (Lagodon rhombroides) to the ARM, the grass shrimp were more sensitive.

Animals↗