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At least 145 records · Page 8Linked to original sources
PubMed2001

Epidermal proliferative response induced by sodium dodecyl sulphate varies with environmental humidity.

BACKGROUND: Previous studies have suggested that susceptibility of skin to external agents increases in the dry winter season. OBJECTIVES: To test the hypothesis that environmental humidity affects skin sensitivity to irritants. METHODS: The epidermal hyperplasia induced by sodium dodecyl sulphate (SDS) under various humidity conditions was evaluated on the skin of hairless mice. RESULTS: Mice kept under low humidity for 2 days showed more obvious epidermal proliferation 24 h after topical application of SDS than those kept under high or normal humidity for 2 days. In contrast, mice kept under high humidity for 2 weeks showed more obvious epidermal proliferation 24 h after topical application of SDS than those kept under low or normal humidity. The transepidermal water loss was altered significantly in the animals kept under high humidity for 2 weeks, although it was not altered during the first 7 days under either low or high humidity. CONCLUSIONS: These results suggest that environmental humidity influences the sensitivity of skin to topical application of SDS and that increased sensitivity is not always associated with alteration of the water impermeability of the stratum corneum.

Analysis of Variance↗
PubMed2000

A wireless, remote query magnetoelastic CO2 sensor.

This paper presents a wireless, passive, remote query CO2 sensor comprising a ribbon-like magnetoelastic thick-film coated with a mass-changing CO2 responsive polymer synthesized from acrylamide and isooctylacrylate. In response to a magnetic field impulse, the magnetostrictive magnetoelastic sensor vibrates at a characteristic resonant frequency that is inversely dependent upon the mass of the attached CO2 responsive polymer. The mechanical vibrations of the magnetostrictive sensor launch magnetic flux, which can be detected remotely using a pickup coil. By monitoring the resonant frequency of the passive sensor, the atmospheric CO2 concentration can be determined without the need for physical connections to the sensor or specific alignment requirements. The effect of humidity and the CO2 responsive copolymer composition on the measurement sensitivity are reported. Greatest sensitivity is achieved with a polymer comprising a 1:1 mole ratio of acrylamide to isooctyl acrylate. A 0.7% change in atmospheric CO2 concentration can be detected for a 20 microns thick polymer coated sensor.

Acrylamide↗
PubMed1988

Responses of older and younger women to exercise in dry and humid heat without fluid replacement.

Eight older (52 to 62 yr old) post-menopausal and 8 younger (20 to 30 yr old) women were matched with respect to body size, fatness, and maximal oxygen consumption, heat-acclimated, and then exercised at 35 to 40% maximal oxygen consumption in a warm-humid (37 degrees C, 60% relative humidity) environment. Results were compared with similar data from a hot-dry (48 degrees C, 15% relative humidity) environment. No fluid replacement was provided during either of these sessions. In each environment, the older women stored more heat as evidenced by a higher rectal temperature response, but there were no inter-group differences in skin temperature or percent maximal heart rate. Four of the older women were unable to complete either the hot-dry or the warm-humid exposure, although they completed the full 2 h during acclimation sessions when water was provided ad libitum. In the hot-dry environment, the younger women's whole body and local sweat rates were significantly higher than those of the older women; in the warm-humid environment, there was no age-related difference in sweat rate. When local skin temperature and wettedness were artificially elevated, both groups exhibited the same pattern and rate of sweating. Percent decrease in plasma volume was greater for the older women in both conditions, but significantly so only in the warm-humid environment.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1986

Stomatal responses to light and leaf-air water vapor pressure difference show similar kinetics in sugarcane and soybean.

Stomatal responses to light and humidity (vapor pressure difference, VPD) are important determinants of stomatal conductance. Stomatal movements induced by light are the result of a transduction of the light stimulus into modulated ion fluxes in guard cells and concomitant osmotic adjustments and turgor changes. It is generally assumed that this transduction process is a general stomatal property, with different environmental stimuli integrated into guard cell metabolism through their modulation of ion fluxes. In contrast with this notion, the VPD response, which is unique because both its triggering signal and the turgor changes required for aperture modulations involve water molecules, has been considered to be hydropassive and thus independent of guard cell metabolism. We used a kinetic approach to compare the light and VPD responses in order to test the hypothesis that hydropassive changes in guard cell turgor could be faster than the metabolism-dependent light responses. Changes in stomatal conductance in intact leaves of sugarcane and soybean were measured after application of step changes in VPD and in light. In spite of a 5-fold difference in overall rates between the two species, the response rates following light or VPD steps were similar. Although a coincidental kinetic similarity between two mechanistically different responses cannot be ruled out, the data suggest a common mechanism controlling stomatal movements, with the VPD stimulus inducing metabolic modulations of ion fluxes analogous to other stomatal responses.

Journal Article↗
PubMed1983

Measurement of sweating rate with capacitance sensors.

A new forced-evaporation type skin capsule for measuring local sweat gland activity in humans is described and details of its construction and problems of calibration are presented. The capsule is self-contained, portable, and inexpensive making it well suited for use in arrays to make multiple simultaneous determinations on adjacent skin areas. Sweat is evaporated from the skin surface by a stream of dry nitrogen gas; subsequent changes in capsule relative humidity and temperature are measured by a commercially available thin-film capacitance sensor and a solid-state current regulating device, respectively. These changes are measured within the capsule itself so no external water vapor analyzer is needed. Data acquisition and evaporation rate calculations are handled by an on-line microcomputer.

Body Temperature↗
PubMed1980

Heat injuries among recreational runners.

With the increasing popularity of jogging and competitive running, more people are participating in races, particularly during the warm months. In the Southeastern United States, the combination of high temperatures and high relative humidity appears to be responsible for many heat-associated injuries. We studied the training, racing, and selected personal characteristics of heat-injured and age- and sex-matched uninjured recreational runners at four races. The major differences between the two groups were that injured runners had not been running as long, ran fewer miles per week, ran fewer miles per training run, and were more likely to be caught up in the excitement of the event.

Athletic Injuries↗
PubMed1989

Electrical determination of water content and concentration profile in a simulation model of in vivo stratum corneum.

Because of its efficient water-holding capacity, healthy stratum corneum (SC) can stay soft and flexible under any environmental conditions. There may be, however, a great difference in water content within the SC between the lowermost layer that faces the wet underlying living tissue and the superficial portion of the SC that is exposed to the relatively dry ambient atmosphere. To better understand the water profile of the SC and also to verify the accuracy of measurements of high frequency conductance used to evaluate the hydration state of the skin surface, we devised a simple and convenient in vitro model of the SC that stimulates the in vivo setting of the SC. It consists of an isolated sheet of SC whose lower surface covers a pad of water-saturated filter paper, and its upper surface is exposed to the ambient atmosphere. By placing this model in environments with different relative humidities (RH), we confirmed that the recorded conductance values correlated well with the actual water content of the SC (r = 0.94). Using a model having five layers of SC sheets, the water content of the innermost portion of the SC was estimated to be equivalent to about 90% of its dry weight; this level of water content remaining relatively constant over a wide range of ambient RH except in extraordinarily humid environments above 90% RH when water began to accumulate excessively in the whole SC. Using this five SC-sheet model, it was clearly demonstrated that there was an almost straight water concentration gradient from the lowermost layer to the uppermost layer of the SC. We also confirmed that the skin conductance of the high frequency current correlated well with the water content of the superficial portion of the SC as well as with that of the whole SC, therefore, it is a good parameter of the hydration state of the superficial layer of the SC.

Body Water↗
PubMed1981

Heat acclimatization, its decay and reinduction in young Caucasian females.

The loss of heat acclimatization and the number of days necessary for reinduction to the acclimatized state as a function of length of the decay period were studied for periods of four, eight, and twelve days. Six females between 18 and 30 years of age (mean VO2 max = 38.7 mL/kg/min) were concurrently heat acclimatized for ten days by treadmill walking at 5.0 km/hr for 100 minutes per day in an environment of 33.5 degree C WBGT. Both 35% and 75% relative humidities were utilized to achieve at 33.5 degree C WBGT with half the subjects exposed to each condition. Physiological measurements included heart rate, sweat rate, core temperature, and mean skin temperature. Of these measurements, only the sweat rate proved not to be affected by any of the independent variables. Predictive equations were developed for heart rate, core temperature and mean skin temperature for decay periods of four through twelve days in length and end of work values attainable for one through four days of successive work after decay. Significant relationships were found in all cases, with the correlation coefficients ranging from 0.73 to 0.86. Both levels of humidity created the same physiological responses from the subjects, suggesting that the ability of WBGT to evaluate heat stress is independent of the humidity level.

Acclimatization↗
PubMed2003

Adverse airway events during brief nasal inhalations of volatile anaesthetics: the effect of humidity and repeated exposure on incidence in volunteers preselected by response to desflurane.

Twelve volunteers known to have airways that responded adversely to 2.0 MAC desflurane were recruited. Each volunteer inhaled three single breaths of each of 0.5, 1.0 and 2.0 MAC of sevoflurane, halothane, isoflurane, desflurane and balance air, with breaths of air between, whilst breathing nasally through a face mask attached to one of three filters that provided three different levels of humidification. The incidence of any adverse airway events was recorded. The anaesthetic inhaled significantly affected the incidence of adverse airway events (p < 0.001), with the least to most irritant being sevoflurane, halothane, isoflurane and desflurane. Increasing the concentration of anaesthetic also significantly increased the incidence of adverse airway events (p < 0.001). The filter used, and hence the level of humidification, did not affect the incidence of adverse airway events (p = 0.09), but repeated exposure caused a significant reduction in the incidence of adverse airway events (p < 0.001).

Adult↗
PubMed1966

Stomatal density and responsiveness of banana fruit stomates.

Determination of stomatal densities of the banana peel (Musa acuminata L. var Hort. Valery) by microscopic observations showed 30 times fewer stomates on fruit epidermis than found on the banana leaf. Observations also showed that peel stomates were not laid down in a linear pattern as on the leaf.It was demonstrated that stomatal responses occurred in banana fruit. Specific conditions of high humidity and light were necessary for stomatal opening: low humidity and darkness were necessary for closure. Responsiveness of the stomates continued for a considerable length of time after the fruit had been severed from the host.

Journal Article↗
PubMed1999

Warming of feet elevates nasal mucosal surface temperature and reduces the early response to nasal challenge with allergen.

BACKGROUND: We have previously shown that hot, humid air partially reduces the early allergic response. Mechanisms for this effect have been suggested, but none has gained universal acceptance. The most likely explanations are a modification of mucosal temperature or a reduction in nasal secretion osmolality. OBJECTIVE: We sought to investigate whether increasing the nasal mucosal surface temperature by immersing feet in warm water (WW) could decrease the immediate nasal response to challenge with allergen. METHODS: We performed a randomized, 2-way crossover study on 14 subjects with seasonal allergic rhinitis outside of their allergy season. They immersed their feet in either WW (42 degrees C) or room-temperature water (RW; 30 degrees C) for 5 minutes before and during nasal challenge with diluent for the allergen extract, followed by 2 increasing doses of allergen. RESULTS: There was a statistically significant increase in nasal mucosal temperature from baseline after warming of feet (WW, 1.9 +/- 0.1 degrees C, vs RW, 0.2 +/- 0.1 degrees C; P =. 001), but there were no significant differences in body temperature (WW, 0.1 +/- 0.1 degrees C, vs RW, 0.4 +/- 0.1 degrees C; P =.1). Net changes from diluent challenge for all parameters were compared between immersion of feet in WW and RW. Immersion of feet in WW significantly inhibited allergen-induced sneezes (WW, 5.7 +/- 1.1, vs RW, 11.6 +/- 3.2; P <.01), human serum albumin levels (WW, 941.7 +/- 172.2 microg/mL vs RW, 1524.8 +/- 220.6 microg/mL; P <.01), and secretion weights (WW, 30.5 +/- 7.2 mg, vs RW, 41.8 +/- 6.8 mg; P <. 01). CONCLUSION: Our data show that warming of feet decreases the early response to nasal challenge with antigen. This inhibitory effect is probably related to the increase in the nasal mucosal temperature.

Adolescent↗
PubMed1988

Interactions of climatic factors affecting milk yield and composition.

Objectives were to evaluate effects of interactions of maximum temperature, minimum relative humidity, and solar radiation on milk yield and constituent traits. Effects of climate variables and their interactions were significant but small in most cases. Second order regression models were developed for several variables. Six were examined in detail: Holstein and Jersey milk yields, Holstein fat and Feulgen-DNA reflectance percent, and Jersey protein percent and yield. Maximum temperature had greatest influence on each response, followed by minimum relative humidity and solar radiation. Optimum conditions for milk production were at maximum temperatures below 19.4 degrees C, increasing solar radiation, and minimum relative humidity between 33.4 and 78.2% (cool sunny days, moderate humidity). Maximum Holstein fat percent of 3.5% was predicted for maximum temperatures below 30.8 degrees C, minimum relative humidity below 89%, and solar radiation below 109 Langleys; actual mean Holstein fat percent was 3.35%. Optimum climatic conditions for Jersey protein percent were at maximum temperature of 10.6 degrees C with solar radiation at 300 Langleys and relative humidity at 16% (cool sunny days, low humidity). Because noteworthy interactions existed between climate effects, response surface methodology was suitable for determining optimum climatic conditions for milk production.

Animals↗
PubMed2000

Female Pied Flycatchers fail to respond to variations in nest humidity.

We examined the possibility that a cavity-nesting passerine, the Pied Flycatcher (Ficedula hypoleuca), can modify the permeability of its eggs to water vapor facultatively in response to variations in nest humidity (P(N)). We found no significant relationship between the water-vapor conductance (G(E)) of flycatcher eggs and P(N). In addition, incubating female flycatchers failed to change their patterns of incubation when we modified P(N) experimentally. These data, coupled with large variations that occur in the G(E) of the eggs within individual clutches, suggest that Pied Flycatchers do not alter the structure of their eggs as they lay them and may not be aware of differences in P(N). It is more likely that G(E) is determined genetically and has been established by natural selection for eggs with high degrees of hatchability.

Adaptation, Physiological↗
PubMed2003

Projection neurons originating from thermo- and hygrosensory glomeruli in the antennal lobe of the cockroach.

Most insects are equipped with specialized thermo- and hygroreceptors to locate a permissible range of ambient temperature and distant water sources, respectively. In the cockroach, Periplaneta americana, cold, moist, and dry receptor cells in the antennae send axons to particular sets of two or three glomeruli in the dorsocentral part of the antennal lobe (primary olfactory center), designated DC1-3 glomeruli. However, it is not known how thermo- and hygrosensory signals from these glomeruli are represented in higher-order centers, the protocerebrum, in any insect species. With the use of intracellular recording and staining techniques, we identified a new class of interneurons with dendrites almost exclusively in the DC1, DC2, or DC3 glomeruli and axons projecting to the protocerebrum in the cockroach. Remarkably, terminals of all these projection neurons (PNs) covered almost identical areas in the lateral protocerebrum (LP), although their termination areas outside the LP differed from neuron to neuron. The termination areas within the LP were distinct from, but close to, those of uniglomerular and macroglomerular PNs that transmitted signals concerning general odors and female sex pheromones, respectively. PNs originating from DC1, DC2, and DC3 glomeruli exhibited excitatory responses to cold, moist, and dry stimuli, respectively, probably due to excitatory synaptic input from cold, moist, and dry receptor cells, respectively, whereas their responses were often modulated by olfactory stimuli. These findings suggested that dorsocentral PNs participate in neural pathways that lead to behavioral responses to temperature or humidity changes.

Animals↗
PubMed1992

Pulmonary responses of asthmatic and normal subjects to different temperature and humidity conditions in an environmental chamber.

Determining the possible adverse health effects of air pollutants can be complicated by differences in the environmental conditions of temperature and humidity. To evaluate the potentially confounding effects of differences in temperature and humidity, we exposed 8 normal male subjects and 8 male subjects with asthma to the extremes in temperature and humidity that could be maintained in an environmental chamber. We performed serial pulmonary function tests for these subjects before and during 6 hr exposure periods on 5 separate occasions: cold, dry (10 degrees C, 10% relative humidity); cold, humid (10 degrees C, 50% relative humidity); normal ambient (22 degrees C, 40% relative humidity); hot, dry (37 degrees C, 15% relative humidity); and hot, humid (37 degrees C, 60% relative humidity). The exposure period included a 12 min exercise on a cycle ergometer. We found no significant change in spirometry, airways resistance, or diffusing capacity for either group of subjects at rest alone over the 6 hr period of exposure for any exposure condition. However, there were changes in spirometry and airways resistance as a result of the 12 min period of exercise. The subjects with asthma had significant decreases in forced expiratory volume in 1 sec (FEV1) (20-21%) and increases in specific airways resistance when exercising in conditions of cold and dry, cold and humid, and hot and dry. The normal subjects had an average increase in FEV1 of approximately 6% when exercising in the hot and humid conditions. We found significant correlations for the changes in FEV1 with the water content of the exposure conditions for both groups of subjects. We also found that the work performance (expressed as the external work performed divided by the oxygen consumed) was decreased for the subjects in both groups at the conditions of the higher temperature (37 degrees C) compared with the lower temperature (10 degrees C). These results confirm that controlling for the conditions of temperature and humidity is essential in chamber studies, field studies, or epidemiologic evaluations determining the adverse effect of an air pollutant.

Adult↗