Search PubMed⌕ Search

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.

At least 847 records · Page 47Linked to original sources
PubMed1985

The mechanism of intestinal transport of sulfamethoxazole and the effect of chlorpromazine in rat everted intestine.

The mechanism of the intestinal transport of sulfonamides and the effect of chlorpromazine (CPZ) on it were studied using rat everted intestine in vitro. Sulfamethoxazole (SMZ) was accumulated in the serosal solution in the everted sac obeying the pH partition theory, while sulfisoxazole (SIX) was not accumulated despite the presence of the pH difference between the serosal and mucosal solutions. The reason was suggested that the microclimate pH on the mucosal surface of the intestine so decreased the amount of the unionized molecules of SIX that the transport rate of SIX was decreased to show no accumulation in the serosal solution within the sampling period. CPZ as well as metabolic inhibitors blocked the SMZ accumulation by inhibiting the growth of the pH difference. This effect was caused by the inhibition of the serosal alkalinization.

Animals↗
PubMed1999

The effect of cage size and enrichment on core temperature and febrile response of the golden hamster.

The aim of this study is to determine the effect of cage size and cage enrichment. Golden hamsters were individually housed in standard cages of four different sizes and in enriched cages of three different sizes since 3 weeks of age. Each of the seven housing groups consisted of 12 hamsters. After 14 weeks of housing in their respective environments the measurements started. The mean baseline rectal temperature was significantly higher in hamsters housed in small cages than in hamsters housed in large cages. After the injection of fever-inducing lipopolysaccharide rectal temperature increased by 1 to 2 degrees C. The increase of rectal temperature and the fever index were the highest in animals housed in large cages and the smallest in animals housed in small cages. Through cage enrichment and increasing cage size the mean febrile response increased while the mean baseline rectal temperature decreased. Cage size and cage enrichment had no effect on the dispersion of the measured values. The differences in microclimate between large and small cages were too small to have an effect on thermoregulation. The results indicate that housing in small cages induce chronic stress which obviously affects thermoregulation. The findings demonstrate that the results of some physiological experiments are significantly influenced by the pre-experimental housing conditions.

Animals↗
PubMed2005

The highs and lows of plant life: temperature and light interactions in development.

Plants must constantly respond to changes in the environment whilst maintaining developmental and growth processes if they are to survive into the next generation. A complex network of signals from temperature and light must correctly converge to achieve successful development, through vegetative to reproductive growth. Temperature can be thought of as an environmental factor that provides both 'inductive' and 'maintenance' signals in development. It can stimulate developmental processes such as seed dormancy release, germination and vernalization. However, when temperature is not regarded as inductive, an accommodating network of genes work in concert to ensure growth responses occur regardless of fluctuating microclimate conditions. Many of the temperature-regulated developmental pathways are intimately linked with light signaling. For example, light-temperature interactions are major determinants in the timing of reproductive development. Indeed, the ability to process and react to complex environmental cues is crucial for both normal and adaptive development in a changing environment. These responses are frequently mediated by manipulating the phytohormone network, which serves as a powerful, yet adaptable controller of development. This paper illustrates the influential role temperature perception plays throughout plant development and the close interaction between temperature, light and hormone signaling.

Circadian Rhythm↗
PubMed1998

[Model for simulation of heat loss by premature infants].

A prerequisite for the further improvement in the quality of warming therapy is an accurate knowledge of the interactions between the microclimate in warming therapy devices and the thermal balance of the infant. For generating this knowledge, thermal manikins can be helpful. Suitable models capable of also simulating evaporative heat loss in preterm infants have, however, not been available to date. A thermal manikin representing an infant weighing 530 g and capable of simulating convective, radiative and also evaporative heat loss has now been developed. It comprises an outer shell made of porous, anatomically shaped clay, and is divided into six compartments each of which can be heated individually. Water-filled Gore-Tex bags located immediately beneath the shell are provided to simulate evaporation. In a clinical study, temperature profiles of 8 very small preterm infants were measured thermographically. Measurements in the manikin showed that highly comparable temperature profiles with only minor differences could be obtained. Total heat and water losses by the manikin were in good agreement with clinical values. Using the model described here it is possible to simulate the heat exchange of premature infants under extreme and accurately reproducible environmental conditions. This manikin may thus serve as a tool for comparative studies, for the development of warming therapy equipment, or for training purposes.

Body Temperature Regulation↗
PubMed2001

Questionnaire assessment of the welfare of pigs.

A questionnaire study was performed involving 76 farms with a total of 380,207 pigs to assess the welfare of pigs kept in Hungary based on the animal welfare legislation of the European Union. Most significant deficiencies were found in the fulfillment of the provisions relating to space requirements, the stall microclimate and the behavioural needs of the animals.

Animal Husbandry↗
PubMedDate not supplied

Plant responses to current solar ultraviolet-B radiation and to supplemented solar ultraviolet-B radiation simulating ozone depletion: an experimental comparison.

Field experiments assessing UV-B effects on plants have been conducted using two contrasting techniques: supplementation of solar UV-B with radiation from fluorescent UV lamps and the exclusion of solar UV-B with filters. We compared these two approaches by growing lettuce and oat simultaneously under three conditions: UV-B exclusion, near-ambient UV-B (control) and UV-B supplementation (simulating a 30% ozone depletion). This permitted computation of "solar UV-B" and "supplemental UV-B" effects. Microclimate and photosynthetically active radiation were the same under the two treatments and the control. Excluding UV-B changed total UV-B radiation more than did supplementing UV-B, but the UV-B supplementation contained more "biologically effective" shortwave radiation. For oat, solar UV-B had a greater effect than supplemental UV-B on main shoot leaf area and main shoot mass, but supplemental UV-B had a greater effect on leaf and tiller number and UV-B-absorbing compounds. For lettuce, growth and stomatal density generally responded similarly to both solar UV-B and supplemented UV-B radiation, but UV-absorbing compounds responded more to supplemental UV-B, as in oat. Because of the marked spectral differences between the techniques, experiments using UV-B exclusion are most suited to assessing effects of present-day UV-B radiation, whereas UV-B supplementation experiments are most appropriate for addressing the ozone depletion issue.

Atmosphere↗
PubMed2006

What determines the current presence or absence of permafrost in the Torneträsk region, a sub-arctic landscape in northern Sweden?

In a warming climate, permafrost is likely to be significantly reduced and eventually disappear from the sub-Arctic region. This will affect people at a range of scales, from locally by slumping of buildings and roads, to globally as melting of permafrost will most likely increase the emissions of the powerful greenhouse gas methane, which will further enhance global warming. In order to predict future changes in permafrost, it is crucial to understand what determines the presence or absence of permafrost under current climate conditions, to assess where permafrost is particularly vulnerable to climate change, and to identify where changes are already occurring. The Torneträsk region of northern sub-Arctic Sweden is one area where changes in permafrost have been recorded and where permafrost could be particularly vulnerable to any future climate changes. This paper therefore reviews the various physical, biological, and anthropogenic parameters that determine the presence or absence of permafrost in the Torneträsk region under current climate conditions, so that we can gain an understanding of its current vulnerability and potential future responses to climate change. A patchy permafrost distribution as found in the Torneträsk region is not random, but a consequence of site-specific factors that control the microclimate and hence the surface and subsurface temperature. It is also a product of past as well as current processes. In sub-Arctic areas such as northern Sweden, it is mainly the physical parameters, e.g., topography, soil type, and climate (in particular snow depth), that determine permafrost distribution. Even though humans have been present in the study area for centuries, their impacts on permafrost distribution can more or less be neglected at the catchment level. Because ongoing climate warming is projected to continue and lead to an increased snow cover, the permafrost in the region will most likely disappear within decades, at least at lower elevations.

Animals↗
PubMed2002

Recent advances in the stabilization of proteins encapsulated in injectable PLGA delivery systems.

Injectable controlled-release systems based on biodegradable copolymers of lactic and glycolic acids (PLGAs) have become widely used for delivery of protein therapeutics and vaccine antigens. Over the last five years, great strides have been made toward overcoming the difficulty of stabilizing PLGA-encapsulated proteins. In addition to stabilizing proteins during encapsulation with anhydrous methods, two approaches have proven highly effective to stabilize proteins during 1-month release incubation under physiological conditions: protein complexation with zinc and control of PLGA microclimate pH with antacid excipients. Described here are recent advances in the stabilization of proteins encapsulated in PLGA delivery systems.

Biocompatible Materials↗
PubMed2006

Thermal ecology of the neotropical army ant Eciton burchellii.

I explored the thermal ecology of Eciton burchellii, a New World army ant, in primary forest and forest fragments in the Atlantic lowlands of Costa Rica in 2002 and 2003. My primary objective was to determine whether high surface temperatures in pastures surrounding forest fragments posed a thermal barrier to ant colonies within those fragments; secondarily, I assessed whether thermal gradients within continuous moist forest were sufficient to elicit avoidance reactions from foraging colonies. E. burchellii colonies in forest fragments avoided entering open pasture in full sun (51.3 degrees C) on 100% of all edge interactions; however, edges were readily crossed where artificial shaded areas had previously been installed. Ant raids in primary forest avoided artificially established temperatures >43 degrees C but tolerated 45.5 degrees C in the presence of prey baits. Captive ants held at 43 degrees C survived 18.5 min; at temperatures of 51.3 degrees C survival time was only 2.8 min. Ants running on established foraging trails increased running velocity by 18% when substrate temperature was raised from 28.4 degrees to 38.0 degrees C, and they abandoned trails at temperatures >43 degrees C. The standard deviation (s) of temperatures on active raid trails in continuous forest was 2.13 degrees C, while nearby systematic sampling revealed a greater background standard deviation of 4.13 degrees C. E. burchellii colonies in this region appear to be living surprisingly near their upper limits of thermal tolerance. The heat of open pastures alone is sufficient to prevent their exiting forest fragments, or entering similarly hot areas within continuous forest. Shaded vegetative corridors are sufficient to permit mobility between isolated fragments, and their preservation should be encouraged. Despite views that tropical lowland moist forests have an essentially homogenous microclimate, army ants appear to avoid local hot spots on the forest floor, steering daily foraging trails to follow cooler routes than would be expected by chance. As deforestation remakes tropical landscapes worldwide, it is important to consider the thermal consequences of these actions and their effect on keystone organisms such as army ants. Changes in global climate patterns are likely to affect even evergreen tropical systems whose organisms may be sensitive to finer microclimatic variation than previously suspected.

Animals↗
PubMed2006

Survival and growth of under-planted trees: a meta-analysis across four biomes.

The transformation of natural forest regeneration processes by human activities has created the need to develop and implement new models of forest management. Alternative silvicultural systems such as variable retention harvest, partial and patch cuts, and older forest management practices such as under-planting, are used in many forests around the world, particularly in North American oak stands, the boreal and coastal temperate rain forests of Canada and the United States, and in many degraded tropical regions of Asia and the Americas. Specific objectives are pursued in each of these biomes, but some are common to most regions, such as preservation of cover and structure and their associated benefits for natural or artificial regeneration due to moderation of the microclimate, development of optimal light and competition conditions, and reduced predation by herbivores. Shelterwoods are often presented as an alternative to clear-cutting to improve the survival of planted trees. A meta-analysis of published results with randomization tests was performed to test the relationship between overstory density and planted seedling growth and survival. Multiple comparisons were also used to reveal optimal levels of overstory density, if they exist. A majority of studies show that survival and growth improve as stand density decreases to an intermediate level, below which they either drop or stabilize. This level seems optimal in most conditions, as it is also more apt to fulfill other objectives imposed on today's forest activities, such as the conservation of forest processes and structures, and the reconstruction of degraded stands through the accelerated return of mid- to late-successional species.

Climate↗
PubMed2006

Dyslipidemia in industrial workers in hot environments.

The aim of the study was to follow the rate and manifestation of dyslipidemia in industrial workers exposed to heat. One hundred and two male industrial workers exposed to heat and a control group of 102 male workers were studied. The microclimate components were followed and Wet Bulb Globe Temperature (WBGT) was calculated. The mean WGBT was 35.4 degrees C (28.4-41.7 degrees C) for the studied heat exposed work places. The lipid indices: total cholesterol (TC), high density lipoprotein cholesterol (HDL-C), low density lipoprotein cholesterol (LDL-C) and triacylglycerols were assayed with enzymatic tests. TC/HDL-C ratio was calculated, too. Arterial pressure, anthropometric variables, smoking, alcohol use were followed and no significant differences between the studied groups were found. Significantly higher TC, LDL-C and TC/HDL-C were found with the heat exposed industrial workers. Odds ratio indicated higher risk in heat exposed industrial workers of becoming dyslipidemic [for TC OR = 1.481 (1.097-2.002) and for LDL-C OR = 1.539 (1,123-2.111)]. Regular screening of lipid profile in heat exposed workers is recommended.

Adult↗
PubMed1993

Effects of two kinds of sports shoes with different structure on thermoregulatory responses.

The present experiments were carried out to clarify the effects of two different kinds of shoes, i.e., the standard shoes and the mesh shoes, on thermophysiological responses and clothing microclimates (temperature and humidity) in five female students during rest and walking in the field conditions. Main results were summarized as follows: 1) Skin temperatures in instep, sole and leg were kept lower in the mesh shoes than in the standard shoes. 2) Rectal temperature and heart rates were also kept lower in the mesh shoes than in the standard shoes. 3) Questionnaires disclosed that the subjects wearing the mesh shoes felt less damp. These findings were discussed in terms of thermal physiology. The mesh shoes seemed to be more effective for both the dry and wet heat loss from the feet to the surroundings, resulting in the inhibition of increase in the core temperature.

Adult↗
PubMed1996

Is endurance performance of handgrip exercise influenced by the two different clothing ensembles?

The purpose of this study was to investigate the effects of wearing two different clothing ensembles on endurance performance of handgrip exercise in eight female subjects in the climatic chamber (25 +/- 1 degrees C, 50 +/- 10% RH). The experimental clothing ensembles were HALF and LONG. The clothing ensemble HALF consisted of half-sleeved shirts, knee-length trousers and sandals; LONG of long-sleeved shirts, long-trousers, socks and walking shoes. The subjects carried out the preliminary exercise for 1 hr as scheduled which was composed of slow running on the horizontal treadmill for 25 min, rest for 10 min and running again for 25 min the same as the first running. After the preliminary exercise, the subject exercised with a hand ergometer lifting a weight of 15% of maximal voluntary contraction at the rate of 35 contractions per min until volitional exhaustion. Rectal temperature, skin temperatures, heart rate, body weight loss, clothing microclimate, number of contractions were measured during the experiment and compared between two clothing ensembles. An important result was that the endurance performance of handgrip exercise was significantly greater in HALF than in LONG, for which the lower maintenance of core temperature and mean skin temperature in HALF during the 1 hr preliminary exercise might be responsible. Our present and former results indicate a significant participation of clothing for the endurance performance of handgrip exercise.

Adult↗
PubMedDate not supplied

[Occupational stress and arterial hypertension].

INTRODUCTION: Arterial hypertension is an important medical, social and economic problem in the working population. Factors of occupational exposure lead to a much faster and more frequent occurrence of this disease and its consequential complications. Among these factors the following take an important place: noise, carbon monoxide, job dissatisfaction, microclimate conditions, chemical agents, shift work night work monotonous work and so on. The purpose of this study was to analyze working conditions, working environment, work demands and identification of occupational stressors and their influence on development of arterial hypertension. MATERIAL AND METHODS: This investigation included 3470 workers and it examined technological processes, working time, job sastisfaction, interpersonal relations and physical and chemical hazards of their workplaces. The exposed group consisted of 2270 workers occupationally exposed to stressors. Control group included 1200 workers whose workplaces were without stressors. Workers of exposed group were divided into 14 subgroups in regard to presence of occupational hazards. RESULTS: Arterial hypertension was established in 39.9% of workers of exposed group, which is statistically significantly more than in controls (25.7%). The highest prevalence of arterial hypertension was at workers who were dissatisfied with the job and who were at the same time occupationally exposed to noise and carbon monoxide. Family predisposition and smoking have cumulative effects with occupational hazards. DISCUSSION: Possible mechanisms of arterial hypertension development include activation of adrenergic nervous system, renin-angiotensin aldosterone system, higher concentrations of steroids, catecholamines and free radicals caused by occupational hazards. CONCLUSION: Occupational stressors are significant factors in development of arterial hypertension of exposed workers. The most important stressors are noise, carbon monoxide and job dissatisfaction.

Adult↗
PubMed1990

Measuring physiological responses of animals to environmental stressors using a microcomputer-based portable datalogger.

The microcomputer-based datalogger system described in this report provides excellent flexibility for accurate recording of signals from a variety of sensors at programmable intervals. The small size of the unit permits applications in many research situations in which physiological and microclimate records are required from unrestrained animals. Data presented from two experiments with cattle with ad libitum access to feed demonstrate the utility of the system. The high resolution and frequent measurements illustrate the fine detail of thermoregulatory responses of cattle (as represented by tympanic temperature) to sequential moderate and hot environments, the association of feeding activities with tympanic temperature at moderate conditions, and the disruptions in thermoregulatory function and feeding activities in hot conditions. A comparison of four anatomical sites (two internal, two sub-dermal) for measuring body temperature also illustrates shortcomings in using sub-dermal measures to reflect responses to dynamic ambient environments.

Animals↗
PubMed2005

Effects of increasing temperatures on physiological changes in pigs at different relative humidities.

The effects of relative humidity (RH) and high ambient temperature (T) on physiological responses and animal performance were studied using 12 groups (10 gilts per group) in pens inside respiration chambers. The microclimate in the chamber was programmed so that T remained constant within a day. Each day, the T was increased by 2 degrees C from low (16 degrees C) to high (32 degrees C). Relative humidity was kept constant at 50, 65, or 80%. The pigs' average initial BW was 61.7 kg (58.0 to 65.5 kg), and their average ending BW was 70.2 kg (65.9 to 74.7 kg). Respiration rate (RR), evaporative water (EW), rectal temperature (RT), skin temperature (ST), voluntary feed intake (VFI), water-to-feed ratio (rW:F), heat production (HP), and ADG were analyzed. The animals had free access to feed and water. We determined the T above which certain animal variables started to change: the so-called inflection point temperature (IPt) or "upper critical temperature." The first indicator of reaction, RR, was in the range from 21.3 to 23.4 degrees C. Rectal temperature was a delayed indicator of heat stress tolerance, with IPt values ranging from 24.6 to 27.1 degrees C. For both these indicators the IPt was least at 80% RH (P < 0.05). Heat production and VFI were decreased above IPt of 22.9 and 25.5 degrees C, respectively (P < 0.001). For each degree Celsius above IPt, the VFI was decreased by 81, 99, and 106 g/(pig.d) in treatments 50, 65, and 80% RH, respectively. The ADG was greatest at 50% RH (P < 0.05). Ambient temperature strongly affects the pigs' physiological changes and performance, whereas RH has a relatively minor effect on heat stress in growing pigs; however, the combination of high T and high RH lowered the ADG in pigs. The upper critical temperature can be considered to be the IPt above which VFI decreased and RT then increased. Temperatures of the magnitude of both these IPt are regularly measured in commercial pig houses. We conclude that the upper critical temperatures for 60-kg, group-housed pigs fed ad libitum are between 21.3 and 22.4 degrees C for RR, between 22.9 and 25.5 degrees C for HP and VFI, and between 24.6 and 27.1 degrees C for RT. It is clear that different physiological and productive measurements of group-housed, growing-finishing pigs have different critical temperatures.

Animals↗
PubMed2006

Cold acclimation and overwintering of female Aedes albopictus in Roma.

Eight years after the introduction and establishment of Aedes albopictus in Roma, females of the species extended their trophic activity to the coldest months of the year. Winter monitoring carried out from December 2003 to March 2004 in the urban area of the capital city of Italy recorded a weekly rate of positive ovitraps constantly around 30%, for the entire period of surveillance (14 wk). Eggs from ovitraps did not hatch when stimulated in laboratory with a wet and dry procedure. The hypothesis that long-lived female Ae. albopictus, belonging to the last seasonal generation, could have continued their trophic activity for 3 months, or that 1 or more cycles of reproduction have occurred in peculiar breeding sites, where a favorable microclimate may have allowed the development of at least 1 larval generation, are discussed and compared with the existing literature.

Acclimatization↗
PubMed1981

Measurement of water transport through the skin.

A method for measuring water exchange through human skin has been developed. It is based on estimation of the vapour pressure gradient immediately above the surface of the skin and permits the skin area investigated to be exposed to the ambient air during the entire period of measurement. Influence on the microclimate above the skin, with respect to humidity and temperature, is thereby minimized. An instrument for measuring small amounts of water evaporated from or absorbed by a surface per unit time and area is described and its accuracy discussed. The instrument has a high degree of accuracy and better sensitivity than previously described devices used for this purpose. It has been used primarily to investigate the rate of evaporation from the skin surface in newborn infants and from the skin in patients with burns.

Biological Transport↗