Energy conservation in acidophilic bacteria.
Explore the source record for details and available documents.
Bacillus↗
SEARCH · Search PubMed
Results for “Microclimate”
Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Thermoregulatory responses of dystrophic hamsters to changes in ambient temperatures.
The ability of dystrophic hamsters to maintain their body temperature despite abnormal muscle and brown adipose tissue, two organs involved in thermoregulation, was evaluated. Dystrophic hamsters (CHF 146) between the ages of 30 and 160 days kept at 21 degrees C had core (rectal) temperatures (TR) that were 0.5-1.5 degrees C lower than Golden Syrian controls. The reduced core temperatures of dystrophic hamsters were unlikely the result of an incapacity to generate heat since the dystrophic hamsters were able to maintain their TRs during 3 h of acute cold stress (4 degrees C) and to adapt to prolonged cold exposure. However, TRs of cold-acclimated dystrophic hamsters were still 1 degree C below TRs of cold-acclimated control animals. By contrast, increasing the ambient temperature raised TRs of both normal and dystrophic hamsters. When kept at 32 degrees C overnight, the TRs of dystrophic hamsters remained significantly below those of control animals. When heat-exposed dystrophic hamsters were returned to 21 degrees C, their TRs returned to values significantly lower than those of control hamsters. Thus, dystrophic hamsters showed a capacity to thermoregulate, like control hamsters, but appeared to do so at a lower temperature. The reduced core temperatures of dystrophic hamsters kept at 21 degrees C cannot be explained by a reduction in metabolic activity since newborns and 30- and 140-day-old dystrophic hamsters had rates of oxygen consumption (VO2) and carbon dioxide production (VCO2) that were similar to those of controls. These results suggest that the thermoregulatory set point may be altered in dystrophic hamsters.
Aging↗
Renal ammonia excretion and production in goldfish, Carassius auratus, at low environmental pH.
Renal ammonia excretion and production were investigated in normal and acidotic goldfish (Carassius auratus). Goldfish were made acidotic by exposure to a low pH environment (pH 4.0), which caused a lowering of blood pH from 7.88 to 7.61. Environmental acidification resulted in an increase in total renal ammonia excretion (from 0.43 to 1.00 mueq X 100 g-1 X h-1) and urinary concentration (from 0.58 to 0.76 mM), as well as a rise in renal titratable acid output (from -0.57 to +0.62 mueq X 100 g-1 X h-1). The acidotic fish showed a rise in urine flow that was due to an increased glomerular filtration rate. In vitro studies demonstrated the capacity for renal ammonia formation from aspartate, alanine, glutamine, glutamate, and glycine. The relatively high level of glutamate in the renal tissue suggested that the generation of ammonia from these amino acids occurs via the formation of glutamate, either by deamidation of glutamine or transdeamination of aspartate and alanine. Both ammonia production by isolated renal tubules and individual enzyme assays in kidney homogenates indicated that aspartate has the greatest potential as a renal ammonia precursor in vitro. The purine nucleotide cycle, investigated with the use of the inhibitor coformycin, does not appear to contribute to ammonia production in the kidney of this species.
Acidosis↗
Naturalistic studies of human light exposure.
For 24 h, 10 volunteers wore an apparatus that recorded their exposure to light at eye level and at the wrist. Activity was also recorded from the head, both wrists, and an ankle. Most of the subjects were exposed to daylight illumination intensities for only brief and scattered episodes during the 24 h. Some experienced the brightest illumination in the morning and others in the evening. Illuminations at eye level and at the wrist were correlated 0.76, while eye-level illumination was correlated 0.25, 0.44, 0.39, and 0.44 with head, wrists, and ankle activity, respectively. Because human biologic rhythms are probably well synchronized only by illumination approaching daylight intensities, inadequate illumination could be a source of sleep disturbance, chronobiologic disorders, or depression.
Adult↗
Metabolic response to ambient temperature and hypoxia in sinoaortic-denervated rats.
We tested the hypothesis that the sinoaortic afferents may contribute to normoxic thermogenesis and to the magnitude of the hypometabolic response to hypoxia. Adult rats were either sinoaortic denervated (SAX; n = 20) or sham operated (Sham; n = 20). A few days after the operation, gaseous metabolism [O2 uptake (VO2) and CO2 production (VCO2)] was measured with an open-flow system at ambient temperatures (Tamb) of 20, 25, 30, and 35 degrees C as the animal was resting awake. At thermoneutrality (Tamb 30 degrees C) or higher Tamb there was no difference in VO2 or VCO2. Below thermoneutrality, metabolic rate was significantly lower in SAX than in Sham animals (-14 and -16% at 20 and 25 degrees C, respectively). Colonic temperature and arterial PO2 were also slightly less, whereas arterial PCO2 and pH, mean arterial pressure, and heart rate did not differ significantly between the two groups. Exposure to acute hypoxia (10% inspired O2, 20-30 min) at Tamb 20 and 25 degrees C significantly reduced VO2 in both groups to a similar value; hence, at either Tamb, the metabolic drop during hypoxia in Sham animals was larger than that in SAX animals. Hypercapnia (5% CO2 breathing) did not change VO2 in either group. We conclude that in the rat at Tamb slightly below thermoneutrality, the sinoaortic afferents 1) provide a small but significant contribution to normoxic thermogenesis and 2) are not required for the manifestation of the drop in metabolism during hypoxia.
Animals↗
Environmental induction of photononresponsiveness in the Siberian hamster, Phodopus sungorus.
In seasonally breeding rodent species, a fraction of the population is unresponsive to short day lengths (DL) and remains reproductively competent during winter. We previously observed that incidence of nonresponsiveness to short days was affected by photoperiodic history. Here we tested whether exposure to long DL (18 h light/day; 18L) renders animals unresponsive to short DL (10L). Hamsters, maintained from birth in 10L, were transferred at week 6 to 18L or 14L. Ten weeks later (week 16), groups were transferred to 10L for 10 wk. All hamsters maintained in short DL from birth had undeveloped testes at week 6. At week 26, however, 92% of hamsters previously kept in 18L failed to undergo complete gonadal regression in 10L, compared with only 10% of hamsters previously in 14L. Entrainment of locomotor activity in 10L in nonresponsive hamsters resembled that typically observed under long DL. Exposure to 18L may induce nonresponsiveness by altering interactions of component circadian oscillators that mediate gonadal regression in short DL.
Aging↗
Marking behaviour in two lemur species (L. fulvus and L. macaco): relation to social status, reproduction, aggression and environmental change.
The influence of social status, reproductive and agonistic contexts and environmental change on scent-marking and allomarking rates were studied in captive groups of Lemur fulvus and Lemur macaco. No evidence of female social dominance over males appeared in either species. In L. fulvus, intrasexual relationships were characterized by the dominance of one adult male over another and by the existence of female affiliative association ('central' vs. 'peripheral' females). In L. macaco, no intrasexual dominance relationships were apparent except for a brief ostracism of one female. In both species, (1) intrasexual differences in social status were related to differences in marking rates, (2) no direct relation appeared between marking rates and aggression or reproduction, (3) allomarking was not differentially directed towards specific individuals and (4) physical environmental factors clearly influenced scent-marking and allomarking rates. These results are discussed in relation to the possible functions of marking behaviour in intragroup relations.
Aggression↗
Colostrum intake and thermoregulation in the neonatal pig in relation to environmental temperature.
Colostrum consumption and rectal temperature (RT) have been measured on piglets kept at 18-20 degrees C (CG = cold group) and at 30-32 degrees C (WG = warm group) during the first day of life. At an ambient temperature of 18-20 degrees C, piglets consumed 36.8% less (p less than 0.01) colostrum than their littermates at 30-32 degrees C. There was a positive correlation between birth weight and colostrum intake in both groups of piglets. From birth weight and weight gain measurements, colostrum intake could be accurately predicted (R2 = 0.75). RT of piglets significantly dropped after birth and subsequently rose, the extent of the initial fall and the rate of the subsequent rise birth and subsequently rose, the extent of the initial fall and the rate of the subsequent rise depended on the environmental temperature. RT of CG remained significantly lower than that of WG, and a further significant decrease was found from 15 h after birth in CG. At 18-20 degrees C, a progressive decline of the effect of birth weight and a concomitant increase in the effect of colostrum intake. 5 of the 39 CG died within 3 days after birth, while all 41 WG survived. Results provide evidence for cold stress as a major cause of mortality and morbidity in the neonatal pigs.
Animals↗
Health effects and sources of indoor air pollution. Part I.
Since the early 1970s, the health effects of indoor air pollution have been investigated with increasing intensity. Consequently, a large body of literature is now available on diverse aspects of indoor air pollution: sources, concentrations, health effects, engineering, and policy. This review begins with a review of the principal pollutants found in indoor environments and their sources. Subsequently, exposure to indoor air pollutants and health effects are considered, with an emphasis on those indoor air quality problems of greatest concern at present: passive exposure to tobacco smoke, nitrogen dioxide from gas-fueled cooking stoves, formaldehyde exposure, radon daughter exposure, and the diverse health problems encountered by workers in newer sealed office buildings. The review concludes by briefly addressing assessment of indoor air quality, control technology, research needs, and clinical implications.
Air Pollutants↗
The thermal comfort of sedentary workers.
Explore the source record for details and available documents.
Adult↗
Outdoor and indoor air pollution in China.
Explore the source record for details and available documents.
Air Pollutants↗
MalariaSphere: a greenhouse-enclosed simulation of a natural Anopheles gambiae (Diptera: Culicidae) ecosystem in western Kenya.
BACKGROUND: The development and implementation of innovative vector control strategies for malaria control in Africa requires in-depth ecological studies in contained semi-field environments. This particularly applies to the development and release of genetically-engineered vectors that are refractory to Plasmodium infection. Here we describe a modified greenhouse, designed to simulate a natural Anopheles gambiae Giles ecosystem, and the first successful trials to complete the life-cycle of this mosquito vector therein. METHODS: We constructed a local house, planted crops and created breeding sites to simulate the natural ecosystem of this vector in a screen-walled greenhouse, exposed to ambient climate conditions, in western Kenya. Using three different starting points for release (blood-fed females, virgin females and males, or eggs), we allowed subsequent stages of the life-cycle to proceed under close observation until one cycle was completed. RESULTS: Completion of the life-cycle was observed in all three trials, indicating that the major life-history behaviours (mating, sugar feeding, oviposition and host seeking) occurred successfully. CONCLUSION: The system described can be used to study the behavioural ecology of laboratory-reared and wild mosquitoes, and lends itself to contained studies on the stability of transgenes, fitness effects and phenotypic characteristics of genetically-engineered disease vectors. The extension of this approach, to enable continuous maintenance of successive and overlapping insect generations, should be prioritized. Semi-field systems represent a promising means to significantly enhance our understanding of the behavioural and evolutionary ecology of African malaria vectors and our ability to develop and evaluate innovative control strategies. With regard to genetically-modified mosquitoes, development of such systems is an essential prerequisite to full field releases.
Animals↗
Spatio-temporal analysis of the role of climate in inter-annual variation of malaria incidence in Zimbabwe.
BACKGROUND: On the fringes of endemic zones climate is a major determinant of inter-annual variation in malaria incidence. Quantitative description of the space-time effect of this association has practical implications for the development of operational malaria early warning system (MEWS) and malaria control. We used Bayesian negative binomial models for spatio-temporal analysis of the relationship between annual malaria incidence and selected climatic covariates at a district level in Zimbabwe from 1988-1999. RESULTS: Considerable inter-annual variations were observed in the timing and intensity of malaria incidence. Annual mean values of average temperature, rainfall and vapour pressure were strong positive predictors of increased annual incidence whereas maximum and minimum temperature had the opposite effects. Our modelling approach adjusted for unmeasured space-time varying risk factors and showed that while year to year variation in malaria incidence is driven mainly by climate, the resultant spatial risk pattern may to large extent be influenced by other risk factors except during high and low risk years following the occurrence of extremely wet and dry conditions, respectively. CONCLUSION: Our model revealed a spatially varying risk pattern that is not attributable only to climate. We postulate that only years characterized by extreme climatic conditions may be important for developing climate based MEWS and for delineating areas prone to climate driven epidemics. However, the predictive value of climatic risk factors identified in this study still needs to be evaluated.
Bayes Theorem↗
Thermoregulation is the pits: use of thermal radiation for retreat site selection by rattlesnakes.
Pitvipers (Viperidae: Crotalinae) possess unique sensory organs, the facial pits, capable of sensing subtle fluctuations in thermal radiation. Prey acquisition has long been regarded as the sole function of the facial pits. However, the ability to sense thermal radiation could also direct thermoregulatory behavior by remotely sensing nearby surface temperatures. Using a series of behavioral arenas of varying spatial complexity and ecological relevance, we surveyed the ability of the western diamondback rattlesnake Crotalus atrox to direct successful thermoregulatory movements with either functional or disabled facial pits. We found that western diamondback rattlesnakes could base thermoregulatory decisions on thermal radiation cues when their pits were functional, but not when blocked. Our results indicate that the facial pit is part of a generalized sense, and suggest thermoregulation as an alternative hypothesis to prey acquisition for the origin of facial pits.
Animals↗
Use of portable filter units to control the animal house environment.
The application of portable recirculating filter units to the control of laboratory animal house environments was investigated. Under practical conditions such a unit effected reductions in the ammonia level and bacterial content of the atmosphere of a room housing rats.
Ammonia↗
Critical issues in air pollution epidemiology.
The epidemiological studies which have had significant impact on the setting of National Ambient Air Quality Standards (NAAQSs) were performed more than twenty years ago. Most of the more recent studies have been seriously flawed in their design and/or execution because they neglected to account for important variables such as: pollutant exposures other than those from ambient air; the influence of personal activity on pollutant uptake; host responsiveness; and the separate contributions of recent transient peak exposures and long-term chronic exposures on the effects endpoints. For particulate pollutants, the influence of composition and size distribution has also received too little consideration. In order to address these deficiencies, research and methods development are needed on: indices for particulate exposures; identification of exposures relevant to the effects; improved indices of effects; acquisition of response data; identification of exposed populations; and identification of susceptible subgroups. Approaches to these needs are discussed, along with brief reviews of several recent studies that have focused on critical issues of concern, made the necessary efforts to characterize the relevant exposures of the populations being studied, and demonstrated human responses to ambient pollutants at current exposure levels.
Adult↗
The status of indoor air pollution.
Indoor air pollution, specifically restricted in its meaning to chemicals in home indoor air environment, presents a new and probably an important challenge to the researchers of the air pollution field. The general overview of this topic suggests that the voluminous data generated in the past ten or so years have only defined the rudiments of the problem, and significant areas of research still exist. Among the important areas where information is lacking, the exposures to contaminants generated by the use of consumer products and through hobbies and crafts represent perhaps the most urgent need for substantial research.
Air Pollution↗
Potential health effects of indoor radon exposure.
Radon-222 is a ubiquitous noble gas arising from decay of radium-226 normally present in the earth's crust. Alpha radiation from inhaled short-lived daughters of radon readily irradiates human bronchial epithelium, and there is now good evidence of excess risk of lung cancer in underground miners exposed to higher concentrations. In homes, radon levels are highly variable, showing approximately log-normal distributions and often a small fraction of homes with high concentrations of radon and radon daughters. Factors affecting indoor concentrations include type of bedrock under dwellings, house foundation characteristics, radon dissolved in artesian water, and ventilation and degree of air movement in living spaces. Despite much recent work, exposures to radon daughters by the general public are not well defined. From application of risk assessments in miners to home conditions, it appears that about 25% or more of lung cancers among nonsmokers over the age of 60, and about 5% in smokers, may be attributable to exposure to radon daughters at home. It may be necessary to take remedial action to reduce this hazard in those dwellings with elevated levels of radon, and new construction should take account of this problem.
Adult↗