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At least 595 records · Page 33Linked to original sources
PubMed2006

Effects of warming conditions in eastern North American forests on red-backed salamander morphology.

Several studies have reported climate-associated changes in phenotypically plastic traits of amphibians, yet it remains unknown whether amphibians can manifest an evolutionary response to global climate change at the rate and magnitude that it is occurring. To assess this issue, we examined temporal change in the morphology of the red-backed salamander (Plethodon cinereus), a small, abundant woodland salamander distributed widely in eastern North America with two distinct morphotypes: striped individuals associated with cooler microclimates and unstriped individuals associated with warmer microclimates. We compiled morph frequencies for 50,960 individual salamanders from 558 sites as recorded in the published literature and in unpublished field notes of herpetologists between 1908 and 2004. We observed that striping probability increased with increasing latitude, longitude, and elevation and decreased (from 80% to 74% range wide) with time. The combined forces of regional climate warming and, particularly, forest disturbance have evidently been sufficient to cause morphological evolution in this amphibian over the last century.

Animals↗
PubMed1996

Raindrop Momentum Triggers Growth of Leaf-Associated Populations of Pseudomonas syringae on Field-Grown Snap Bean Plants.

Observational and microclimate modification experiments were conducted under field conditions to determine the role of the physical environment in effecting large increases in phyllosphere population sizes of Pseudomonas syringae pv. syringae, the causal agent of bacterial brown spot disease of snap bean (Phaseolus vulgaris L.). Comparisons of daily changes in population sizes of P. syringae on three plantings of snap bean cultivar Cascade and one of cultivar Eagle with weather conditions indicated a strong association of rainfalls with periods of 1 to 3 days in duration during which increases in bacterial population sizes were greater than 10-fold and up to 1,000-fold. The effects of rain on populations of P. syringae were explored further by modifying the microclimate of bean plants in the field with polyethylene shelters to shield plants from rain and fine-mesh inert screens to modify the momentum of raindrops. After each of three separate intense rains, the greater-than-10-fold increases in population sizes of P. syringae observed on plants exposed to the rains did not occur on plants in the shelters or under the screens. The screens decreased the velocity and, thus, the momentum of raindrops but not the volume or quality of rainwater that fell on plants under the screens. Thus, the absence of increases in population sizes of P. syringae on plants under the screens suggests that raindrop momentum plays a role in the growth-triggering effect of intense rains on populations of P. syringae on bean plants under field conditions.

Journal Article↗
PubMed1994

Heat strain in the Canadian Forces chemical defence clothing: problems and solutions.

The Canadian Forces chemical defence protective clothing can induce an overwhelming strain on one's ability to regulate body temperature. Recently a number of investigations have been completed at the Defence and Civil Institute of Environmental Medicine that focused initially on understanding the interaction of metabolic rate, ambient temperature, and ambient vapour pressure on the severity of heat strain associated with wearing the protective clothing. This paper presents a summary of these initial studies together with an overview of different attempts to reduce heat strain during exercise in a hot environment. Factors such as improved aerobic fitness or a period of dry heat acclimation have little if any benefit on tolerance time while wearing the clothing during light or moderate exercise. The best solution to the problem of heat strain remains the use of microclimate conditioning (personal cooling), and these techniques have been successful for Naval and Air Force personnel. For our Land Forces, however, microclimate conditioning is not feasible until a lightweight high-energy power source is developed.

Acclimatization↗
PubMed1993

Lipid absorption: passing through the unstirred layers, brush-border membrane, and beyond.

Lipids are components of our diet and luminal secretions, with physicochemical characteristics that determine their digestion and absorption in the gastrointestinal tract. Lipids include triglycerides, phospholipids, and cholesterol. Dietary lipids contain approximately 97% triglycerides, with small amounts of phospholipids and cholesterol. These components are important in cell membrane composition, fluidity, peroxidation, prostaglandin and leukotriene synthesis, and cellular metabolic processes. Lipids are implicated in the mechanisms of brain development, inflammatory processes, atherosclerosis, carcinogenesis, aging, and cell renewal. Duodenal hydrolysis of dietary lipids and biliary phospholipids and cholesterol is carried out by pancreatic lipase, colipase, phospholipase A2, and cholesterol esterase. Bile acid solubilization results in mixed micelles and liposomes, in gel and liquid crystal phases. Lipid digestion products pass across the intestinal unstirred water layer. For long-chain fatty acids and cholesterol, passage across the unstirred water layer is rate limiting, whereas passage of short- and medium-chain fatty acids is limited by the brush-border membrane. Within the unstirred water layer, an acidic microclimate aids micellar dissociation so that protonated, and to a lesser extent, nonprotonated monomers then pass across the intestinal brush-border membrane. Absorptive mechanisms have been studied extensively in relation to lipid composition, fatty acid chain length, degree of unsaturation, essential fatty acid content, phospholipid components, and cholesterol. Enterocytes may take up lipids from the intestinal lumen or from lipoproteins of the bloodstream, but these pools are likely to be functionally distinct. Recent advances are reviewed, including recent advances in the area of microclimates, compartmentation, lipid binding proteins, intracellular trafficking, intestinal lipoproteins, release of lipids across the basolateral membrane, and dietary effects.

Bile Acids and Salts↗
PubMed1978

Folic acid transport by mammalian small intestine.

The unidirectional influx of folic acid across the mucosal border of hamster duodenum and rat jejunum was determined. Influx follows saturation kinetics, is sodium-dependent, and is inhibited by methotrexate and is sodium-dependent, and is inhbited by methotrexate and folinic acid in the mucosal bathing solution. In hamster duodenum, the maximal influx is 1.2 nmol/(cm2.h), and the folic acid concentration required to give a half maximal influx (Km) is 7.2 micron.. At mucosal folic acid concentration of 1.5 micron, influx is reduced at least 65% by removal of sodium from the bathing solution. The influx process is significantly inhibited by cyanide and 2,4-dinitrophenol. The possibility was evaluated that the acidic microclimate at the brush border regulates the rate of folic acid transport and that inhibition of transmural transport by sodium-free media, ouabain, and methotrexate is brought about indirectly by an increase in pH of the microclimate. The data favor the alternative concept of a sodium-dependent carrier mechanism for entry of folic acid into the cells. The information presented is consistent with active transport of folic acid by a sodium-gradient mechanism, but additional information will be necessary to substantiate such a model.

Animals↗
PubMed1972

The role of intraluminal sodium in glucose absorption in vivo.

Active glucose absorption is thought to depend on a gradient of sodium ion concentration across the brush border membrane of intestinal epithelial cells. This concept is generally accepted, although its validity has never been adequately evaluated in the human small intestine in vivo. According to this hypothesis, the rate of glucose absorption should decrease markedly if the luminal sodium concentration is markedly reduced, and glucose absorption against a concentration gradient should cease entirely if luminal sodium is lower than intracellular sodium concentration. In the present series of experiments we were not able to show an important role of intraluminal sodium concentration in the active absorption of glucose from the human, rat, and dog ileum in vivo. Specifically, glucose absorption was minimally reduced or not reduced at all when intraluminal sodium concentration was reduced from 140 to as low as 2.5 mEq/liter. The discrepancy between our results and those of previous workers whose data suggest that removal of intraluminal sodium should markedly inhibit active glucose absorption is not entirely clear, but there are a number of differences in experimental design between most previous studies and our own. Although our data show that active glucose absorption proceeds at a near normal rate even when lumen sodium concentration is reduced below 3 mEq/liter, our results do not disprove the sodium gradient theory because of the theoretic possibility that the microclimate adjacent to the brush border has a high concentration of sodium even when luminal sodium concentration is markedly reduced. The validity of the sodium gradient hypothesis would appear to be critically dependent on such a microclimate.

Adult↗
PubMed2006

Seasonal variations in plant species effects on soil N and P dynamics.

It is well established that plant species influence ecosystem processes, but we have little ability to predict which vegetation changes will alter ecosystems, or how the effects of a given species might vary seasonally. We established monocultures of eight plant species in a California grassland in order to determine the plant traits that account for species impacts on nitrogen and phosphorus cycling. Plant species differed in their effects on net N mineralization and nitrification rates, and the patterns of species differences varied seasonally. Soil PO4- and microbial P were more strongly affected by slope position than by species. Although most studies focus on litter chemistry as the main determinant of plant species effects on nutrient cycling, this study showed that plant species affected biogeochemical cycling through many traits, including direct traits (litter chemistry and biomass, live-tissue chemistry and biomass) and indirect traits (plant modification of soil bioavailable C and soil microclimate). In fact, species significantly altered N and P cycling even without litter inputs. It became particularly critical to consider the effects of these multiple traits in order to account for seasonal changes in plant species effects on ecosystems. For example, species effects on potential rates of net N mineralization were most strongly influenced by soil bioavailable C in the fall and by litter chemistry in the winter and spring. Under field conditions, species effects on soil microclimate influenced rates of mineralization and nitrification, with species effects on soil temperature being critical in the fall and species effects on soil moisture being important in the dry spring. Overall, this study clearly demonstrated that in order to gain a mechanistic, predictive understanding of plant species effects on ecosystems, it is critical to look beyond plant litter chemistry and to incorporate the effects of multiple plant traits on ecosystems.

Nitrogen↗
PubMed1995

Sweat responses to pesticide-proof clothing influenced by textile materials.

Themoregulatory responses were compared at an ambient temperature of 30 degrees C and a relative humidity of 50% between two kinds of protective clothing for pesticide spraying. One was made of nylon with wet coating polyurethane (A) and another was made of cotton with water repellent finish (B). The clothing ensemble was composed of a short-sleeved cotton shirt, long cotton underpants, cotton socks, shoes and the protective clothing. Five young female adults served as subjects. They took a rest with protective clothing ensemble for 15 min and then walked on a motor-driven treadmill (80m/min, 5% uphill grade) for 40 min, followed by 20-min rest. The increase of forearm sweat rate was higher in clothing A than in clothing B in 4 out of 5 subjects, although the average values were not significantly different. The total sweat rate of the whole body was also significantly larger in clothing A. Mean skin temperature and local skin temperatures in the arm, the chest and the thigh were significantly higher in clothing A than in clothing B. Clothing microclimate humidity was significantly higher in clothing A, while clothing microclimate temperature tended to be higher in clothing A. Individual observations about thermal, humidity and comfort sensation disclosed that the sensation was improved as a whole in clothing B. Local sweat rate was linearly related to mean body temperature and the regression line for clothing A was located above that for clothing B in 4 out of 5 subjects.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1997

Thermal comfort properties of cotton and nonwoven surgical gowns with dual functional finish.

The purpose of this study was to evaluate thermal comfort properties of surgical gowns made of dual functional finish cotton and nonwoven fabrics which have barrier properties of blood and micro-organism. Four types of surgical gowns, which were made of nonwoven fabrics with finish or without and were made of cotton with finish or without, were tested. The thermal insulations of four surgical gowns were measured with thermal manikin. Subjective experiments on thermal comfort, skin temperature and clothing microclimate were conducted. Six male subjects, between 26 and 28 years age old, participated in the wear trials tests. Typical activities for surgeons in the operation theater were simulated during the experimental sessions. Air temperature in a climate chamber was kept at 22 degrees C and its humidity was 60% RH. Air velocity was controlled at less than 0.15 m/s. Inner radiant temperature was almost equal to the air temperature. Basic thermal insulation of the dual functional finished nonwoven surgical gown was 0.87 clo, which was slightly higher than that of untreated (0.84 clo). However, the skin temperature of the subject wearing a dual functional finished surgical gown was significantly lower at P < .05. When the subject wears the dual functional finished gown, the amount of sweating was less than that when wearing untreated. Microclimate temperature and humidity of dual functional finished surgical gown were lower than untreated and it was statistically significant. There was no significant difference in subjective humid and overall comfort sensation between finished and untreated ones. Thermal sensation of dual functional finished one was significantly different from untreated one only during the first exercise. The results of this study indicate that the dual functional finish surgical gown allowed heat to be transferred from the skin of subject to the atmosphere better than untreated. The nonwoven surgical gown showed no difference in comfort properties from cotton one.

Adult↗
PubMed1995

Comparison of calf housing types and tympanic temperature rhythms in Holstein calves.

During fall, 30 Holstein calves were randomly assigned to three housing treatments from birth to weaning: conventional wooden hutches, enclosed molded polyethylene domes, and thermomolded opaque polymer hutches with ridge-top ventilation systems. The wooden and polymer hutches had outdoor pens. Fifteen calves, 5 in each housing type, were fitted with portable data loggers to record ambient (calf microclimate) and tympanic temperatures. Additional data collected included weekly girth, BW, and feed intake; blood samples were collected within 24 h of birth and at weaning (8 wk); and behavioral observations were made at 1, 4, and 7 wk of age. Polyethylene domes had the warmest microclimate, followed by wooden and polymer hutches. Feed intake, growth measurements, blood physiology, and behavior were unaffected by housing type. Diurnal tympanic temperature rhythms of neonatal dairy calves in this study were monophasic: maximums were at 1200 to 1700 h, and minimums were at 0600 to 0900 h. Computed fractal dimensions of tympanic temperature by week indicated a gradual diminishing of stress as the calves became older and acclimated to their environment. This objective characterization provides a basis for further evaluation of physiological stress and a means of improving environmental management.

Animals↗
PubMedDate not supplied

[Strategy and tactics of radiation protection of the personnel in light of future work on stabilization and reorganization of the "Shelter" compound into radiologically safe system].

The research aim is to analyze the "Shelter" personnel work conditions and to estimate how these conditions specify radiological defense. "Shelter" object remains to be an accumulation of the open radiotoxic materials. It is expected that the usage of standard technologies in such conditions will be connected with the great dose-expense of external and internal irradiation. The significant quantity of the fuel dust (more 30 tonne according to uranium) and the extremely harmful microclimate conditions such as: aggressive radiochemical aerosols, exclusively artificial and obviously insufficient illumination, high humidity, discomfortable temperature regime, high ability of many working places to induce the emotional stress reaction in personnel are the specificity of "Shelter" object. The synergetic influence of radiofactor and "Shelter" object microclimate is very dangerous because of its ability to deteriorate significantly the personnel health up to acute stress reaction. In these cases there appear the episodes of the short disorders of orientation in the surrounding situation, paroxysmal consciousness disturbances which may become the nondirect reason of the overirradiation and growth of work traumatism. That's why the methods of the stress-reaction prophylaxis and improvement of the individual defense become extremely improvement for the "Shelter" object personnel. It was shown that the following medicines are perspective due to their adaptogenic and radioprotective abilities, such as: alpha-2-recombinant interferon, antiinflammatory, steroid, antioxidant and enterosorbtive preparations of biological nature.

Humans↗
PubMed2002

[Characteristics of the human thermal state and environment in long-term space flight].

Summarized are data of many-year studies of thermal loading and thermal state of humans in different microclimates. Comparative analysis of various approaches to thermal monitoring of cosmonauts in space suits was performed with the conclusion about advantages of parotid thermometry. To set microclimate standards for long-term space flight, a complex index of the environment cooling potential (ECP) based on the use of an electrical dynamic catathermometer has been proposed. A correlation between ECP values and cosmonaut's thermal sensations was elicited. For the most part, the proposed recommendations have been verified or introduced in the space crew medical care system.

Astronauts↗
PubMed1991

[Risk factors of ischemic heart disease in various occupational groups. II. Complex analysis of risk factors].

Four hundred four men aged 30 to 59 years, belonging to one of 4 occupational groups were investigated in a standard clinical conditions. Two from those groups were characteristic for steel mill professions: 121 blast furnace workers; exerting strenuous physical effort and working in hot microclimate. 131 operators (the second group) performed work in comfort microclimate conditions not demanding much effort. The third group comprised 73 executives of industry. The fourth group consisted of 79 monks. For all subjects of investigations 8 selected risk factors of ischemic heart disease were evaluated. They included: age, sex, family history, habit of smoking, systolic blood pressure, fasting blood cholesterol level, obesity index and professional physical activity. The level of each risk factor had numerical value in a span from "0" to "8". The sum of all points was decisive to which of 3 groups of risk given man should be accounted. Those 3 groups were arbitrary divided into "low, intermediate and high risk". The highest risk was found for the executives group, and the lowest for blast furnace workers. From the risk factors under investigation highest overall influence on incidence of ischemic heart disease had habit of smoking and obesity. Described here point classification system seems to be very simple and useful for estimation of risk of ischemic heart disease in a given population.

Adult↗
PubMed1991

[Evaluation of psychological readiness of the administrators of medical institutions for possible changes in the management functions].

A questionnaire survey of the staff of curative and preventive institutions on the subject of management style, business and personal qualities of their leaders was conducted. The diversity of psychological features was detected in the microclimate of the collectives surveyed naturally conditioned by the interaction between the leader and the collective. The resulting psychological microclimate determines the different degree of willingness to welcome a new economic mechanism: from the possibility of complete realization of its principles by the entire collective to the complete declination.

Attitude of Health Personnel↗
PubMed1995

[Work conditions in concentration of tungsten-molybdenum ore].

Manifold hygienic studies carried out at Tyrnaouz tungsten-molybdenum enterprise served as example to characterize work conditions, microclimate, chemical load, levels of dust, noise, vibration and radiation at modern concentration enterprises. The factors leading in intensity were dust load in air during preparation of ores processing (grinding, grist, etc.), noise, and microclimate especially during cool season. Hygienic importance of occupational factors is shown by data on morbidity with transitory disablement and outpatient medical examinations.

Female↗
PubMed1993

[Experimental rationale for the use of drugs to increase the resistance of the human body to the combined action of carbon monoxide and hyperthermia].

A group of volunteers was exposed to coaction of carbon dioxide (concentration 300 mg/cu m) and heating microclimate (ambient temperature +50 +/- 2 degrees C, relative humidity 20 +/- 5%), simultaneously they received one of the medicines: placebo, bemitil (0.5 g), bromantane (0.25 g) or bemitil (0.5 g) combined with bromantane (0.25 g). Bromantane (0.25 g) or bemitil (0.5 g) combined with bromantane (0.25 g) were proved to be the most effective method to increase stability of the human body against co-action of carbon dioxide and heating microclimate.

Amantadine↗
PubMed2003

Carbon dioxide effects on stomatal responses to the environment and water use by crops under field conditions.

Reductions in leaf stomatal conductance with rising atmospheric carbon dioxide concentration ([CO2]) could reduce water use by vegetation and potentially alter climate. Crop plants have among the largest reductions in stomatal conductance at elevated [CO2]. The relative reduction in stomatal conductance caused by a given increase in [CO2] is often not constant within a day nor between days, but may vary considerably with light, temperature and humidity. Species also differ in response, with a doubling of [CO2] reducing mean midday conductances by <15% in some crop species to >50% in others. Elevated [CO2] increases leaf area index throughout the growing season in some species. Simulations, and measurements in free air carbon dioxide enrichment systems both indicate that the relatively large reductions in stomatal conductance in crops would translate into reductions of <10% in evapotranspiration, partly because of increases in temperature and decreases in humidity in the air around crop leaves. The reduction in evapotranspiration in crops is similar to that in other types of vegetation which have smaller relative reductions in stomatal conductance, because of the poorer aerodynamic coupling of the canopy to the atmosphere in crops. The small decreases in evapotranspiration at elevated [CO2] may themselves be important to crop production in dry environments, but changes in climate and microclimate caused by reduced stomatal conductance could also be important to crop production.

Air↗
PubMed2006

The role of below-ground competition during early stages of secondary succession: the case of 3-year-old Scots pine (Pinus sylvestris L.) seedlings in an abandoned grassland.

In abandoned or extensively managed grasslands, the mechanisms involved in pioneer tree species success are not fully explained. Resource competition among plants and microclimate modifications have been emphasised as possible mechanisms to explain variation of survivorship and growth. In this study, we evaluated a number of mechanisms that may lead to successful survival and growth of seedlings of a pioneer tree species (Pinus sylvestris) in a grass-dominated grassland. Three-year-old Scots pines were planted in an extensively managed grassland of the French Massif Central and for 2 years were either maintained in bare soil or subjected to aerial and below-ground interactions induced by grass vegetation. Soil temperatures were slightly higher in bare soil than under the grass vegetation, but not to an extent explaining pine growth differences. The tall grass canopy reduced light transmission by 77% at ground level and by 20% in the upper part of Scots pine seedlings. Grass vegetation presence also significantly decreased soil volumetric water content (Hv) and soil nitrate in spring and in summer. In these conditions, the average tree height was reduced by 5% compared to trees grown in bare soil, and plant biomass was reduced by 85%. Scots pine intrinsic water-use efficiency (A/g), measured by leaf gas-exchange, increased when Hv decreased owing to a rapid decline of stomatal conductance (g). This result was also confirmed by delta 13C analyses of needles. A summer 15N labelling of seedlings and grass vegetation confirmed the higher NO3 capture capacity of grass vegetation in comparison with Scots pine seedlings. Our results provide evidence that the seedlings' success was linked to tolerance of below-ground resource depletion (particularly water) induced by grass vegetation based on morphological and physiological plasticity as well as to resource conservation.

Carbon Dioxide↗