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PubMed1985

Mechanisms maintaining a low-pH microclimate in the intestine.

The presence of an unequilibrated region adjacent to the mucosal surface of the small intestine has long been suggested. Controversy remains as to the characteristics of this region. This study was designed to further define these characteristics. Our studies demonstrated by two independent methods, pH electrode measurement and dye indicator, that a low-pH compartment does exist at the surface of the intestine. The thickness of this microclimate was estimated to be 700 microns, comparable with that described for the unstirred water layer. Maintenance of the low-pH compartment is due to the presence of a mucus coating rather than hydrogen ion secretion. We postulate that the mucus functions as an ampholyte and restricts hydrogen ion movement in its matrix. The acidic microclimate, unstirred water layer, and the mucus coating might in fact represent a common phenomenon.

Animals↗
PubMed2003

Factors affecting the microclimate pH of the rat jejunum in ringer bicarbonate buffer.

General characteristics of the microclimate layer on the mucosal surface of the rat jejunum incubated in bicarbonate buffers were investigated in vitro using pH sensitive flat membrane microelectrode. Jejunal surface microclimate (JSM) pH changed from 7.30+/-0.03 to 5.83+/-0.04 when the incubation buffer pH decreased from 8.03+/-0.02 to 6.12+/-0.01. Treatment of the mucosal side with mucolytic substances L-cysteine (1% (wt/v)) and 1,4-dithio-DL-threitol (2 mM) significantly (p<0.01) increased JSM pH. Respiratory chain inhibitor, sodium azide (10 mM) also significantly (p<0.05) increased JSM pH. D-Glucose (10 mM) at the mucosal side markedly (p<0.05) decreased JSM pH, which was attenuated by Na(+)/H(+) exchange inhibitor, amiloride (1 mM). Amiloride had no effect on JSM pH when D-glucose was not present at the mucosal side. In contrast to previous observations using bicarbonate free incubation buffers, we have demonstrated that JSM pH is not a constant value, but is dependent on pH of the incubation buffer. Additionally, Na(+)/H(+) exchanger does not contribute to acidic properties of JSM, when there is no D-glucose in the bicarbonate incubation buffer at the mucosal side of the tissue. In conclusion, we suggest that the bicarbonate buffers which are more close to in vivo situation than bicarbonate free buffers should be preferable incubation media when examining JSM.

Amiloride↗
PubMed1992

[The effect of a heat-producing industrial microclimate on the rate of biological aging of the body].

While detecting the biological and cardiopulmonary age the authors have demonstrated that the long-term work under the conditions of the heating industrial microclimate promotes acceleration of biological body aging. In the intensification of the aging process, of great importance is the time at which one starts working under the heating microclimate conditions. Based on the data obtained the conclusion is drawn that employment of the persons over 40 years may be restricted in relation to so-called "hot" occupations.

Adult↗
PubMed2005

[Evaluating influence of individual protective means on heat state of individuals working in heating microclimate].

The authors evaluate working clothes protecting against electromagnetic waves and chemical pollution to exemplify that the clothes use in heating surroundings deteriorates human heat state due to disordered heat-mass exchange with environment and higher physical exertion caused by the clothes weight. The article demonstrates necessity to correct requirements to microclimate parameters, if using working clothes deteriorating heat-mass exchange with environment in heating microclimate. For adequate evaluation of work conditions, the materials include temperature modification values in accordance with some working clothes types.

Adult↗
PubMed1991

[Effect of heating microclimate and noise on the morbidity of female weavers].

The article contains results of research of the complex action of noise and heating microclimate on female weavers and on morbidity with temporary disability in this professional group. The group of medically examined weavers was divided into three parts: Cr. 1 - exposed to noise levels at 98.6 +/- 0.8 dB(A) and t degrees at 25.6 +/- 0.6 degrees C; Gr. 2-93.3 +/- 0.4 dB(A) and t degrees at 24.4 +/- 0.11 degrees C; Gr. 3-93.0 +/- 0.7 dB(A) and t degrees at 26.7 +/- 0.1 degrees C. The specific differences between the 3 groups of female weavers in morbidity with temporary disability caused by hypertension can be explained by the complex action heating microclimate and extensive noise.

Acute Disease↗
PubMed1986

Intestinal surface acid microclimate in vitro and in vivo in the rat.

The presence of the intestinal surface acid microclimate (ISAM) has long been suggested. Controversy, however, still exists as to the existence, general characteristics, and requirements of this microclimate. We examined the existence and distribution of the ISAM along the rat small intestine and colon and determined its general characteristics. The results clearly demonstrate the existence of the ISAM in vitro and in vivo. Glucose and sodium in the incubation medium, as well as normal intracellular metabolism, are essential requirements for the formation and maintenance of the ISAM. We conclude that the ISAM is a normal physiologic phenomenon of the luminal surface of the intestine.

2,4-Dinitrophenol↗
PubMed1985

[The effect of the microclimate in the insemination facility on conception in sows after the first insemination].

In the course of the year, the temperature and relative humidity of the insemination hall of a large pig farm were studied in ten three-week periods. The results were compared with the conception rate of sows inseminated in these periods. The macroclimatic conditions were also studied, and the influence of macroclimate (including temperature and relative humidity) on the microclimate of insemination hall was evaluated. The studied microclimate parameters were found to influence the conception of sows in the first three weeks after insemination. Highly significant differences (significance level of alpha = 0.01) were recorded in the conception of sows after the first insemination, in the occurrence of optimum and increased temperatures, in the occurrence of optimum and increased relative humidity in the summer and winter months. A significant difference at the significance level of alpha = 0.05 was found when the occurrence of increased relative humidity was compared. A high temperature was recorded only in the summer months. In summer and in the first half of autumn (from the 9th of June to the 13th of October) when increased to high temperatures and increased to high relative humidity prevailed in the insemination hall (optimum temperature only in 2.0 to 23.3% of the period; optimum relative humidity in 11.1 to 50.0% of the period), the sow conception rate after the first insemination was low (45.5 to 49.7%). In autumn the microclimatic conditions in the insemination hall returned to the optimum. From the 4th of November to the 16th of February the optimum temperature (optimum in 71.6 to 89.7% of the period) and optimum relative humidity (optimum in 74.2 to 90.7% of the period) prevailed in the insemination hall, enabling an improvement in the conception of sows after the first insemination (71.4 to 80.1%). The temperature inside the insemination hall was influenced by changes in outside temperatures whereas the relative humidity inside the insemination hall was influenced mainly by internal factors.

Animals↗
PubMed1998

[Physiological-clinical evaluation of combined impact of local vibrations, noise and warming microclimate on miners].

Chamber experiments covered 3 groups--miners of surface mine levels, those of the deep levels and examinees having no adaptation to mine--to evaluate combined effects of local vibration, noise and heating microclimate. Human resistance against the stated above factors appeared to be a nonlinear system. Induced by vibration and heating, divergent changes of sensitivity to vibration and dyastolic blood pressure appeared only in the examinees having no adaptation to mine, but not in the miners. The studied occupational factors were not antagonistic. The results obtained necessitate different regulation of microclimate for surface and deep mine levels, in order to consider adaptational peculiarities of miners.

Adult↗
PubMed1992

Studies on the fish gill microclimate.

An isolated and perfused fish gill filament preparation has been developed to facilitate investigations on the fish gill microclimate. Measurements have been made of the concentration of sodium at the lamellar surface and in the mixed-exit water, and of the maximum interlamellar velocity. When the external water has a sodium concentration of 0.10 mmol.l-1, water at the gill surface has a mean sodium concentration of 0.146 mmol.l-1. Mixed-exit water, 50 microns behind the perfused filament, has a mean sodium concentration of 0.118 mmol.l-1. When the water flowing over the filament has a maximum velocity of 18 cm.s-1, the maximum velocity between secondary lamellae is 1.5 cm.s-1. These measurements have been used to support the development of a velocity-modified diffusion model which describes ion movement in the interlamellar space. The analysis and observations on the preparation suggest that substantial unstirred layers do not exist at the lamellar surfaces in this preparation. Simple diffusion to and from the tissue surfaces, in conjunction with parabolic velocity profiles within the interlamellar spaces adequately explain net sodium movements.

Animals↗
PubMed1990

Effect of antisecretory factor on Escherichia coli STa enterotoxin-induced alkalinisation of pig jejunal acid microclimate.

The effect of challenge by Escherichia coli STa enterotoxin on pig jejunal mucosal surface pH was investigated in vivo. Exposure to STa resulted in a rapid and reversible alkalinisation (P less than 0.001) of the jejunal mucosa from 6.27 +/- 0.11 (5) to 6.89 +/- 0.03 (5). This action of STa is probably mediated through cyclic 3'5'-guanosine monophosphate (cGMP) since the 8-bromo analogue of cGMP induced the same effect as that observed after STa challenge. The action of STa on mucosal pH was partially inhibited by pre-administration of an antisecretory factor (ASF) preparation. The action of 8-bromo cGMP was unchanged by the presence of ASF. This implies that ASF inhibition occurs during the early stages of STa action prior to stimulation of guanylate cyclase. This effect of STa on the pig jejunal mucosal surface pH, or acid microclimate, may explain why weak acid supplementation of oral rehydration solutions can be ineffective in certain types of diarrhoeal disease.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1996

Clothing microclimate temperatures during thermal comfort in boys, young and older men.

To examine the effects of age-related differences in thermoregulatory function on the clothing microclimate temperature (Tm) and Tm fluctuations while maintaining thermal comfort in daily life, 5 boys (group B, 10-11 years), 5 young men (group Y, 20-21 years) and 5 older men (group O, 60-65 years) volunteered to take part in this study. The subjects were asked to maintain thermal comfort as closely as possible in their daily lives. Tm (temperatures between the skin surface and the innermost garment) at four sites (chest, back, upper arm, and thigh), skin temperature on the chest (Tchest) and ambient temperature (Ta) were measured over a period of 8-12 h from morning to evening on one day in each of the seasons, spring, summer, autumn, and winter. Records of ability to maintain thermal comfort and of adjustment of their clothes were kept by each subject. Ta during periods of thermal comfort did not differ among the groups in any of the seasons. In group Y, Tm was significantly lower at the thigh than at the other sites in spring, autumn, and winter (P < 0.05) and fluctuations (CV) of Tm were significantly larger at the thigh than at other sites in autumn and winter (P < 0.05). Similar tendencies were observed for Tm and CV of Tm in group B. However, Tm and CV of Tm in group O did not differ by site except for the autumn Tm. Group O had a smaller CV at the thigh in winter (P < 0.05), compared to groups B and Y, suggesting a smaller regional difference in Tm fluctuation in group O. Group O adjusted their clothes even on the lower limbs (together with upper body) in order to maintain thermal comfort in accordance with changes in Ta, while groups B and Y did so only on their upper bodies. These results suggest that compared to boys and young men, lower thermoregulatory function in older men may affect Tm and CV of Tm as a result of clothing on lower limbs being adjusted differently in order to maintain thermal comfort.

Adult↗
PubMed1992

Influence of season and microclimate on fertility of dairy cows in a hot-arid environment.

Records were obtained over a 3 year period from six Holstein dairy farms of 300 to 500 cows each in the Phoenix, Ariz. area. Dairies were selected on the basis of similar management practices, herd size, milk production and facilities (with the exception of cooling systems). Microclimatic modifications (two dairies each) were shade only (approximately 3.7 m2/cow), evaporative-cooled shades and low-pressure water foggers under the shades. Data were categorized by season of calving (spring, Feb.-May; summer, June-Sept.; and fall, Oct.-Jan.). Traits evaluated were calving interval, days open and services/conception. Calving interval was shortest for cows calving in the spring (378 days), intermediate in fall (382 days) and longest in summer (396 days). Similar seasonal trends were observed for days open (103, 103 and 119 days, respectively) and services/conception (1.54, 1.81 and 1.93, respectively). All differences between spring and summer were significant (P less than 0.05). Calving interval and days open were less for evaporative-cooled groups (374 and 98 days, respectively), with no difference between shade only and foggers (391 and 392 days, 112 and 116 days, respectively). Services/conception were similar for all groups (1.72 to 1.79). A significant interaction between microclimate and season for services/conception could be interpreted as (i) smaller season differences for evaporative-cooled groups than for shade or foggers, or (ii) a change in the ranking of control and fogger groups during summer versus fall. Evaporative cooling was more effective than fogging for reducing the detrimental effects of seasonal high temperatures on fertility.

Animals↗
PubMed2004

The effect of urban ground cover on microclimate, growth and leaf gas exchange of oleander in Phoenix, Arizona.

We assessed how small patches of contrasting urban ground cover [mesiscape (turf), xeriscape (gravel), concrete, and asphalt] altered the microclimate and performance of adjacent oleander (Nerium oleander L.) plants in Phoenix, Arizona during fall/winter (September-February) and spring/summer (March-September). Ground-cover and oleander canopy surface temperatures, canopy air temperatures and pot soil temperatures tended to be lowest in the mesiscape and highest in the asphalt and concrete. Canopy air vapor pressure deficits were lowest in the mesiscape and highest in the asphalt plot. Rates of net photosynthesis of all oleander plants were highest in October and May, and declined through mid-summer (June-July), when rates tended to be highest in the cooler mesiscape, particularly when water was limiting. During fall/winter, oleanders in the mesiscape produced 20% less biomass, 13% less leaf area, and had 12% lower relative growth rates (R(G)) than those in the other ground covers. Lower nighttime temperatures in the mesiscape in December led to oleander frost damage. During spring/summer, oleanders in the mesiscape produced 11% more biomass, 16% more leaf area, and had 3% higher R(G) than those in the other cover types. The effects of urban ground cover on oleander performance were season-specific; while oleander growth was greatest in the mesiscape during spring/summer, it was lowest during fall/winter and these plants experienced frost damage. Because all oleander plants produced >10 times as much biomass during the spring/summer, on an annual basis oleanders in the mesiscape produced 5-11% more biomass than plants in the warmer ground covers.

Arizona↗
PubMed2006

Microclimate influence on mineral and metabolic profiles of grape berries.

The grape berry microclimate is known to influence berry quality. The effects of the light exposure of grape berry clusters on the composition of berry tissues were studied on the "Merlot" variety grown in a vineyard in Bordeaux, France. The light exposure of the fruiting zone was modified using different intensities of leaf removal, cluster position relative to azimuth, and berry position in the cluster. Light exposures were identified and classified by in situ measurements of berry temperatures. Berries were sampled at maturity (>19 Brix) for determination of skin and/or pulp chemical and metabolic profiles based on (1) chemical and physicochemical measurement of minerals (N, P, K, Ca, Mg), (2) untargeted 1H NMR metabolic fingerprints, and HPLC targeted analyses of (3) amino acids and (4) phenolics. Each profile defined by partial least-square discriminant analysis allowed us to discriminate berries from different light exposure. Discriminant compounds between shaded and light-exposed berries were quercetin-3-glucoside, kaempferol-3-glucoside, myricetin-3-glucoside, and isorhamnetin-3-glucoside for the phenolics, histidine, valine, GABA, alanine, and arginine for the amino acids, and malate for the organic acids. Capacities of the different profiling techniques to discriminate berries were compared. Although the proportion of explained variance from the 1H NMR fingerprint was lower compared to that of chemical measurements, NMR spectroscopy allowed us to identify lit and shaded berries. Light exposure of berries increased the skin and pulp flavonols, histidine and valine contents, and reduced the organic acids, GABA, and alanine contents. All the targeted and nontargeted analytical data sets used made it possible to discriminate sun-exposed and shaded berries. The skin phenolics pattern was the most discriminating and allowed us to sort sun from shade berries. These metabolite classes can be used to qualify berries collected in an undetermined environment. The physiological significance of light and temperature effects on berry composition is discussed.

Amino Acids↗
PubMed2006

Intermittent microclimate cooling during exercise-heat stress in US army chemical protective clothing.

The effectiveness of intermittent, microclimate cooling for men who worked in US Army chemical protective clothing (modified mission-oriented protective posture level 3; MOPP 3) was examined. The hypothesis was that intermittent cooling on a 2 min on-off schedule using a liquid cooling garment (LCG) covering 72% of the body surface area would reduce heat strain comparably to constant cooling. Four male subjects completed three experiments at 30 degrees C, 30% relative humidity wearing the LCG under the MOPP 3 during 80 min of treadmill walking at 224 +/- 5 W . m(-2). Water temperature to the LCG was held constant at 21 degrees C. The experiments were; 1) constant cooling (CC); 2) intermittent cooling at 2-min intervals (IC); 3) no cooling (NC). Core temperature increased (1.6 +/- 0.2 degrees C) in NC, which was greater than IC (0.5 +/- 0.2 degrees C) and CC (0.5 +/- 0.3 degrees C) ( p < 0.05). Mean skin temperature was higher during NC (36.1 +/- 0.4 degrees C) than IC (33.7 +/- 0.6 degrees C) and CC (32.6 +/- 0.6 degrees C) and mean skin temperature was higher during IC than CC ( p < 0.05). Mean heart rate during NC (139 +/- 9 b . min(-1)) was greater than IC (110 +/- 10 b . min(-1)) and CC (107 +/- 9 b . min(-1)) ( p < 0.05). Cooling by conduction (K) during NC (94 +/- 4 W . m(-2)) was lower than IC (142 +/- 7 W . m(-2)) and CC (146 +/- 4 W . m(-2)) ( p < 0.05). These findings suggest that IC provided a favourable skin to LCG gradient for heat dissipation by conduction and reduced heat strain comparable to CC during exercise-heat stress in chemical protective clothing.

Adult↗
PubMed2006

Textiles and human skin, microclimate, cutaneous reactions: an overview.

This article overviews research in the interdisciplinary area of textile/skin interaction and related cutaneous intolerance. Microclimate in the skin/clothing system and especially the skin responses relates to the moisture and heat transfer within this system and plays a critical role in skin irritation from textiles. A discussion is then given on skin irritation reactions to textiles, including intolerance caused by chemicals (dyes and finishes) and physical contact/friction. Finally, two skin injuries, blisters and pressure ulcers, which are caused by physical contact, pressure, and friction, are documented. Despite the prevalent problems caused by ill textile/skin interactions, minimal efforts have been devoted to this field. In addition, the in vivo experimental studies infrequently lead to a solid conclusion. The cause may lie in the dramatic variation of skin conditions among individuals as well as among different anatomic sites of the same person. Another reason might be the lack of communications between researchers in the areas of textiles and dermatology.

Blister↗
PubMedDate not supplied

Microclimates and energetics of free-living box turtles, Terrapene carolina, in South Carolina.

We measured microclimate, field metabolic rates (FMRs), water flux, and activity patterns of telemetered box turtles (Terrapene carolina) in South Carolina from September 1987 to October 1988. Turtles were inactive for most of the winter and were active only sporadically during the rest of the year. Using the doubly labeled water method, we found that water flux averaged 8.8, 18.9, and 26.4 mL kg(-1) d(-1) in winter, spring, and summer/fall, respectively. FMR for the same periods averaged 0.028, 0.065, and 0.124 mL CO(2) g(-1) h(-1). Differences in FMR among seasons were significant but not between sexes. Using operative temperatures, we predicted standard and maximum metabolic rates of turtles. In winter, FMR was elevated above standard metabolic rates and close to maximum metabolic rates, whereas in spring and summer/fall, FMR fell midway between standard and maximum metabolic rates. We used a model to predict metabolic rates, geographical distribution, and potential reproductive output of box turtles across latitudes in eastern North America. Low FMR and low annual reproductive output may allow box turtles to survive and flourish in unpredictable resource environments by minimizing costs and risks, thereby maintaining greater lifetime reproductive success.

Activity Cycles↗
PubMed1999

Impact of microclimate on immature tick-rodent host interactions (Acari: Ixodidae): implications for parasite transmission.

Rodents play a significant role in enzootic cycles of tick-borne pathogens, notably, in the northern hemisphere, tick-borne encephalitis virus and Lyme borreliosis spirochaetes. The relative numbers of nymphal and larval ticks feeding on rodents are crucial variables in determining the probability of rodent infection and the degree of amplification of infection prevalence in the tick population. Manipulation of the microclimate within quasinatural experimental arenas revealed that under increasingly dry conditions the numbers of unfed nymphal Ixodes ricinus L. questing in upper layers of the herbage decreased, whereas the rate of fat use and the numbers of nymphs feeding on small rodents, both increased. This is consistent with nymphs descending to the moist lower vegetation layers for water replenishment, where they would come into contact with small hosts. Very few larvae quested or fed on rodents under the dry conditions, but many more did so once the humidity increased, suggesting that larvae escape desiccation by becoming quiescent. The ratio of larvae to nymphs feeding on rodents thus increases with increasing humidity, contributing to the seasonal and geographical variation in disease transmission dynamics.

Animals↗