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PubMed1980

Effect of ambient temperature and humidity on urine output in sheep.

Urine output, respiratory rate, water intake, plasma and urine osmolalities, and PCV of 6 sheep exposed to 4 weeks of each of hot-humid, hot-dry, and cool-humid environments alternated with 3 weeks each of cool-dry control environments were determined. Compared with urine output during the control environment, urine output increased during hot-humid, hot-dry, and cool-humid exposure, but was 70% greater during the hot-humid environment than during hot-dry exposure. Water intake increased 37% to 45% during hot-dry exposure but decreased 35% during the first 2 weeks of cool-humid exposure. Urine osmolality decreased 38%, 22%, and 44% during hot-humid, hot-dry, and cool-humid exposure, respectively, whereas plasma osmolality values only increased 3% during hot-dry exposure. Respiratory rates increased on exposure to both hot environments, but decreased during cool-humid exposure. The PCV decreased 3% after 1 week of hot-humid exposure, 8% after 4 weeks of hot-dry exposure, and 5% after 4 weeks of cool-humid exposure. Urine output, and probably plasma volume, increased during these periods because evaporative heat loss was reduced due to the lack of adequate air convection and mobility. Heat loss through increased urine output was not significant (P less than 0.2). Enclosed sheep should be kept with short fleeces and should be maintained in conditions of low temperature and adequate convection if representative physiologic, biochemical, and pharmacologic assessments are desired.

Animals↗
PubMed1996

Association between duration of humid season and geographical distribution patterns of different species of chewing lice (Mallophaga:Insecta) infesting domestic chickens in Nigeria.

In a countrywide study of the geographical distribution patterns of chicken lice in Nigeria, 3 species, Menacanthus pallidulus (Neumann 1912), Goniodes dissimilis Denny, 1842, and Menopon gallinae (Linnaeus, 1758), were completely restricted to within areas with a long humid season (6-12 humid mo per yr). In constrast, 4 species, Cuclotogaster occidentalis Tendeiro, 1954, Menacanthus cornutus (Schommer, 1913), Amyrsidea powelli (Bedford, 1920), and Goniodes gigas (Taschenberg, 1879), thrived only in areas where the humid season was of a short duration (< or = 5 mo). The last 3 named species extended also into the fringes of areas with a long humid season (6-8 humid mo) at significantly reduced numbers. They were entirely absent in areas with a particularly protracted humid season (9-12 humid mo). Three other species. Numidilipeurus tropicalis (Peters, 1931), Goniocotes gallinae (DeGeer, 1778), and Lipeurus caponis (Linnaeus, 1758), were just as abundant in areas of a long humid season as they were in areas with a short humid season. It was concluded that there was an association between duration of the humid season and the geographical distribution patterns of certain species of chicken lice in Nigeria. The duration of the humid season might thus provide a means of predicting the potential occurrence of some species of chicken lice in a particular area.

Analysis of Variance↗
PubMed1972

Flowering and Growth Response of Peanut Plants (Arachis hypogaea L. var. Starr) at Two Levels of Relative Humidity.

Peanut plants (Arachis hypogaea L. var. Starr) grown under two different relative humidities were used in all experiments. All plants were germinated and grown to flowering in the greenhouse. At this time, one group was moved to a growth room under 95% relative humidity. After 50 days the humidity of the growth room was lowered to 50%. The second group was moved into a growth room at 50% relative humidity and after 50 days the humidity was raised to 95%.Flowering rates of plants under high humidity were greater than rates of those plants under low humidity. Flowering was stimulated by transfer from low to high humidity, and these plants set the largest percentage of pegs, maintained a high rate of ethylene production by 2-centimeter peg sections, a high growth rate of intact pegs, and they had a higher mean content of gibberellins than plants transferred from a high to a low humidity. The plants in the high to low transfer had the least number of flowers, formed the lowest percentage of pegs, had about 50% less ethylene production by 2-centimeter peg sections, and the peg growth rate declined about 50%.Maximum ethylene production occurred during initial stages of peg growth (1- to 5-millimeter sections), and gibberellin content was generally higher in these peg sections. Thus, high humidity enhanced flowering, peg formation, and peg growth rate. A causal relationship between these effects of high humidity and the growth regulator status of the developing fruit is indicated.

Journal Article↗
PubMed2004

Thermoregulation by rhesus monkeys at different absolute humidities.

The effect of relative humidity on thermoregulation has been well examined. Because the same relative humidity represents very different absolute humidities at different ambient temperatures, the present study was designed to examine the interaction of temperature and absolute humidity on the thermal balance of rhesus monkeys, Macaca mulatta. Thermal balance was examined in six unacclimated, unanesthetized, female rhesus monkeys at ambient temperatures of 25, 30, 35, and 40 degrees C and absolute humidities of 6, 22, and 40 torr. Monkeys were capable of achieving thermal balance under all conditions except at 40 degrees C with 40 torr absolute humidity, where experiments were stopped after rectal temperature exceeded 40.5 degrees C. At 40 degrees C, monkeys increased evaporative heat loss through both respiration and sweating; the slope of the relationship between evaporative heat loss and core temperature was attenuated by increases in absolute humidity. In contrast, absolute humidity had no direct effect on metabolic rate. The rise in body temperature under the conditions of high heat/high humidity was therefore most attributable to humidity-dependent decreases in evaporative heat loss.

Analysis of Variance↗
PubMed2001

Effect of humidity on cuticular water permeability of isolated cuticular membranes and leaf disks.

The effects of humidity on water permeability of astomatous, isolated cuticular membranes and leaf disks of Citrus aurantium L., Vinca major L., Prunus laurocerasus L., Hedera helix L. and Forsythia intermedia (Thunb.) Vahl. were investigated by a new method using 3H2O. With isolated cuticular membranes of P. laurocerasus the isotope method resulted in values similar to those obtained by a well-established gravimetric method. Cuticular water permeability significantly increased by factors of 2 to 3 when air humidities increased from 2 to 100%. Plots of permeances vs. air humidity were non-linear and the slope increased with increasing air humidity. Permeances of intact leaf disks showed a response to increasing humidity similar to those of isolated cuticular membranes. When cuticular water permeability was measured using wax-free, isolated polymer matrix membranes that had been methylated, the effect of air humidity was significantly suppressed compared to non-methylated polymer matrix membranes. From this observation it is concluded that non-esterified, free carboxyl groups present in the cutin polymer matrix significantly contribute to the effect of humidity on cuticular water permeability. These and other polar groups sorb water, which in turn increases the water permeability of polar domains of the cuticle. This humidity-sensitive, polar path of cuticular water permeability is arranged in parallel with the major, dominating and humidity-independent, non-polar path of cuticular water permeability formed by the lipophilic wax components of the cuticle. This conclusion is supported by the fact that cuticular transpiration can be increased by orders of magnitude upon (i) wax extraction, (ii) increase in temperature or (iii) the action of plasticizers, none of which influenced or only marginally influenced the permeability of inorganic ions penetrating plant cuticles across humidity-sensitive polar pores.

Biological Transport↗
PubMed2006

Leaf strategies and soil N across a regional humidity gradient in Patagonia.

We analyzed leaf traits related to carbon-fixation, nutrient conservation strategies, and decomposability and their relationships with potential N-mineralization and microbial N in soil in 19 species of 5 dominant life forms growing in 40 sites across a regional humidity gradient in northern Patagonia. We hypothesized that (1) the shifting of species and life forms across the humidity gradient is related to a shifting in traits of green and senesced leaves with some overlapping among life forms, and (2) leaf traits associated with litter decomposition are related to the potential dynamics of soil-N across the humidity gradient. LMA in green leaves and P-resorption efficiency decreased with humidity while concentrations of lignin and total phenolics in green and senesced leaves and P concentration in senesced leaves increased with humidity. Soil C and N concentrations were positively correlated to humidity. Increasing soil N concentration was related to increasing rates of absolute (per unit soil mass) potential net N-mineralization and microbial-N flush. Relative (per unit N mass) potential net N-mineralization and microbial-N flush decreased with soil N and were inversely correlated to lignin concentration and C/N ratio in senesced leaves. We found overlapping in N concentration and C/N ratio in green and senesced leaves, P concentration in green leaves, and N resorption among species and life forms across the humidity gradient. We concluded that (1) leaf traits related to carbon fixation and the decomposition pathway significantly varied with humidity and were not overlapped between plant life forms from dry and humid habitats, (2) the largest overlapping among species and plant life forms across the gradient occurred in those leaf traits related to N conservation in the plant, and (3) life forms from humid habitats produce more recalcitrant litter that induce lower rates of relative potential net N mineralization (per unit N) than those of dry habitats.

Argentina↗
PubMed2003

Changes in environmental humidity affect the water-holding property of the stratum corneum and its free amino acid content, and the expression of filaggrin in the epidermis of hairless mice.

BACKGROUND: Seasonal changes affect the condition of skin and may trigger various cutaneous disorders. OBJECTIVE: To clarify the effects of the environmental humidity on the skin pathology, we studied the effects of the humidity on a water-holding function of the stratum corneum. METHODS: We evaluated the skin surface conductance, amino acid in the stratum corneum, and immunoreactivity of filaggrin of the epidermis of hairless mice kept in different environmental humidity. RESULTS: Skin surface conductance in the stratum corneum of hairless mice 3-7 days after transfer from a humid environment (>80% relative humidity) to a dry (<10% relative humidity) environment, was significantly lower than that of the mice transferred from a normal environment (relative humidity=40-70%) to a dry environment. The free amino acid content in the stratum corneum significantly decreased 24 h after we transferred the mice from a normal to a dry condition, then it recovered to the original level within 3 days, while the mice transferred from a humid to a dry condition showed a significantly lower amino acid content even 7 days after the transfer. No obvious change was observed in the relative composition of the major components of the free amino acids during the experiments. Immunoreactivity of filaggrin, which is the main precursor of free amino acids in the stratum corneum, also became faint in the epidermis of the mice transferred from a humid or normal to a dry environment. CONCLUSION: These results suggested that a drastic decrease in the environmental humidity reduced the total free amino acid generation and consequently induced skin surface dryness in the stratum corneum.

Amino Acids↗
PubMed2002

Abrupt decreases in environmental humidity induce abnormalities in permeability barrier homeostasis.

Previous reports demonstrated that long-term exposure to extremes in humidity influence permeability barrier homeostasis. Here the effects of a sudden shift from a high humidity to a dry environment were studied. Mice were initially maintained in either a humid (> 80% relative humidity) or normal environment (relative humidity = 40-70%), and then transferred to a dry environment (< 10% relative humidity). Within 2 d of transfer from a humid to a dry environment a 6-7-fold increase in transepidermal water loss occurred that returned to normal within 7 d. No increase in transepidermal water loss occurred in response to a switch from a normal to a dry environment. At a time when barrier function was abnormal, both stratum corneum hydration and pH were normal, indicating that the mechanisms that regulate these functions differ. Following transfer from a humid to dry environment, electron microscopy revealed a marked decrease in: (i) lamellar bodies in the outermost stratum granulosum; (ii) deposition of lamellar body contents at the stratum granulosum-stratum corneum interface; and (iii) the quantity of intercellular lamellae in the stratum corneum, which together could account for the barrier abnormality. Transfer of mice from a normal to a dry environment rapidly stimulated epidermal proliferation, whereas animals switched from a humid to a dry environment displayed a delayed increase in proliferation that might also contribute to the barrier abnormality. The present study demonstrates that sudden changes from a high to a low humidity environment results in abnormal barrier function, which could adversely influence the incidence and/or severity of skin disorders.

Animals↗
PubMed1999

The effect of humidity on samples of microcrystalline cellulose taken from the extrusion/marumerization process.

The purpose of this work was to examine the sorption and desorption of water by various samples of microcrystalline cellulose, MCC (Avicel PH-101), taken from the extrusion/marumerization process, and to provide data that may explain how water affects the MCC polymer matrix during the formation of beads. Two isopiestic (humidity) studies were conducted: the first used samples exposed directly to controlled humidity conditions, whereas the second used samples that were freeze-dried before being exposed to controlled humidity conditions. Water sorption and desorption were determined gravimetrically. When both sets of samples were initially exposed to low-humidity conditions, they reached equilibrium by desorbing water. When these samples were initially exposed to high-humidity conditions, the high moisture content samples desorbed water, whereas the low moisture content and the freeze-dried samples sorbed water to reach equilibrium. When the first set of samples was initially exposed to high- and then to low-humidity conditions, they reached the same water content achieved by being equilibrated directly at the low-humidity condition. However, samples that were initially exposed to low- and then to high-humidity conditions had equilibrium water contents that were lower than those achieved by being equilibrated directly at the high-humidity condition. The original MCC systems exhibit a hysteretic effect above 85%, whereas the freeze-dried systems have a broader range hysteretic effect starting at 20% relative humidity. The results suggest that the internal structure of the MCC polymer fibers must change with the sorption and desorption of water, supporting the autohesion theory.

Adsorption↗
PubMed1970

Response of airborne Mycoplasma pneumoniae to abrupt changes in relative humidity.

The effect of an abrupt change in the relative humidity on the viability of airborne Mycoplasma pneumoniae has been examined. When the microbial aerosols were permitted to equilibrate in air held at either low or high humidities and were then subjected to a sudden shift to a mid-range humidity, a significant loss (>90%) of the colony-forming units per liter of aerosol occurred within 8 min. In contrast, a change in the relative humidity of more than 18% in either direction from a lethal mid-range humidity noticeably decreased the rate of biological decay. Double humidity shifts (i.e., from dry to a mid-range level and then to a high humidity range) were very detrimental, with very few survivors after 8 min. These results indicate that the biological stability of airborne M. pneumoniae may be easily modified by a sudden change in the relative humidity, such as occurs in natural atmospheres. This increased sensitivity brought about by producing changes in relative humidity through the lethal humidity range may provide a method whereby the control of these organisms in naturally contaminated indoor air environments may be eventually achieved.

Aerosols↗
PubMed1987

Effects of eggshell cuticle removal and incubation humidity on embryonic development and hatchability of broilers.

The effects of eggshell cuticle removal and two levels of incubation humidity 28.3 C [50% relative humidity (RH)] and 30.0 C (55% RH) wetbulb temperature (WB) on embryonic mortality and hatchability were determined from broiler hatching eggs laid during 38, 42, 48, and 54 weeks of age. Variables measured were: egg weight loss during the first 17 days of incubation, hatch at Days 19.5 and 20.5 of incubation, hatch of fertile eggs, stage of embryonic mortality, and chick weight at 21.5 days of incubation. Day 0 to 17 percentage egg weight loss was increased when the incubation humidity was lowered and the loss was greater than that observed after cuticle removal. A greater percentage of chicks hatched on Day 19.5 at 28.3 C than at 30.0 C WB. The percentage hatch of 38-week fertile eggs was improved at the higher humidity; the higher humidity also decreased late dead and increased pipped embryonic mortalities. Cuticle removal decreased early dead and increased late dead mortality. At Week 38 cuticle removal and lower humidity resulted in a decrease in chick weight at 21.5 days of incubation. For Weeks 42, 48, and 54 combined, pipped mortality was increased by higher humidity and late dead mortality was increased by cuticle removal. Water loss from the egg was increased by cuticle removal or by lowering incubation humidity from 30.0 C to 28.3 C WB, or by both, but lowering humidity was more effective. Changes in humidity and cuticle removal may affect vital gas exchange to different degrees.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2003

Mycotoxin production in wheat grains by different Aspergilli in relation to different relative humidities and storage periods.

Four different Aspergilli (Aspergillus oryzae, A. parasiticus, A. terreus and A. versicolor) were grown on wheat grains underdifferent degrees of relative humidity 14, 50, 74, 80 and 90%. Samples of wheat grains were taken monthly for a period of six months and examined for mycotoxin production. A. oryzae was found to produce aflatoxins B1, B2, zearalenone, DON and T-2 toxins under elevated degrees of humidity and prolonged periods of storage. A. parasiticus produced aflatoxins B1, G1, NIV, DON and T-2 toxins in high concentrations during a period of not more than three months storage at 14% relative humidity; at an increased level of relative humidity of 74% ochratoxin A, zearalenone and sterigmatocystin were also produced at high levels. The isolate was drastic in toxin production. A. terrus produced toxins at 14% relative humidity (aflatoxin G2 and DON) at levels much higher than any other prevalent degrees of humidity. A. versicolor is highly sensitive to relative humidity and grain moisture content It produced aflatoxins B1, G1, NIV and DON at a relative humidity of 50% and another toxins (aflatoxin G2, ochratoxins A, B and zearalenone) at 74%. The microorganism can be considered a trichothecene producer under suitable relative humidity.

Aflatoxins↗
PubMed2006

Do honeybees, Apis mellifera scutellata, regulate humidity in their nest?

Honeybees are highly efficient at regulating the biophysical parameters of their hive according to colony needs. Thermoregulation has been the most extensively studied aspect of nest homeostasis. In contrast, little is known about how humidity is regulated in beehives, if at all. Although high humidity is necessary for brood development, regulation of this parameter by honeybee workers has not yet been demonstrated. In the past, humidity was measured too crudely for a regulation mechanism to be identified. We reassess this issue, using miniaturised data loggers that allow humidity measurements in natural situations and at several places in the nest. We present evidence that workers influence humidity in the hive. However, there are constraints on potential regulation mechanisms because humidity optima may vary in different locations of the nest. Humidity could also depend on variable external factors, such as water availability, which further impair the regulation. Moreover, there are trade-offs with the regulation of temperature and respiratory gas exchanges that can disrupt the establishment of optimal humidity levels. As a result, we argue that workers can only adjust humidity within sub-optimal limits.

Animals↗
PubMed2005

Intraocular humidity immediately after fluid-air exchange in pars plana vitrectomy.

PURPOSE: To study vitreous cavity humidity during fluid-air exchange in pars plana vitrectomy. METHODS: Intraocular humidity in the vitreous cavity was recorded for 2 min in six artificial eyes, six enucleated pig eyes, and ten patient eyes, after the eyes had been filled with either humidified air (75% humidity) or dry air (8% humidity). RESULTS: In artificial eyes the humidity levelled off at a value that was approximately equal to the humidity of the infused air, i.e., a mean of 71.9% when humidified air was used and a mean of 14.4% when dry air was used. In enucleated pig eyes humidity increased slightly with humidified air and remained stable with dry air. In patients intraocular humidity increased to over 90%, regardless of whether humidified or dry air was used. CONCLUSION: In the living eye, dry air deprives the retinal tissue of humidity, which is lost into the vitreous cavity. This effect can be reduced by using humidified air.

Acetates↗
PubMed2001

Epidermal interleukin-1 alpha generation is amplified at low humidity: implications for the pathogenesis of inflammatory dermatoses.

BACKGROUND: We have previously reported that low humidity amplifies the hyperproliferative and inflammatory response to barrier disruption. Other reports suggest that epidermal interleukin (IL)-1 alpha is stimulated by various factors related to epidermal inflammation and that it may induce other proinflammatory molecules. OBJECTIVES: To evaluate the generation of IL-1 alpha in the skin of hairless mice kept under various conditions of environmental humidity. METHODS: We carried out an immunohistochemical study, and evaluated epidermal IL-1 alpha mRNA and protein levels, and release of IL-1 alpha from skin after tape stripping, in hairless mice kept under low or high humidity. RESULTS: The immunohistochemical study showed that the amount of IL-1 alpha in the epidermis was higher in animals kept in a low-humidity environment than in a high-humidity one. The epidermal IL-1 alpha mRNA and protein levels increased significantly when the animals were kept under low humidity. Moreover, the release of IL-1 alpha from skin immediately after tape stripping was significantly higher in animals kept in a low-humidity environment than in a high-humidity one. CONCLUSIONS: These results suggest that IL-1 alpha is an important factor in mediating the relationship between environmental humidity and epidermal pathology.

Animals↗
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↗
PubMed1998

Low humidity stimulates epidermal DNA synthesis and amplifies the hyperproliferative response to barrier disruption: implication for seasonal exacerbations of inflammatory dermatoses.

Although seasonal changes in humidity are thought to exacerbate various skin diseases, whether these flares can be attributed to prolonged exposure to extremes in environmental humidities has not been studied systematically. We recently showed that prolonged exposure to high versus low humidities induced profound changes in epidermal structure and permeability barrier homeostasis. Therefore, we asked here whether comparable extremes in humidity could initiate not only homeostatic, but also potentially pathophysiologic alterations. We showed first that exposure to low humidity increases epidermal DNA synthesis in normal murine epidermis. Moreover, exposure to a low humidity for 48 h further amplifies the DNA synthetic response to barrier disruption, resulting in marked epidermal hyperplasia. Additionally, exposure to a dry environment for 48 h prior to barrier disruption results in dermal mast cell hypertrophy, degranulation, as well as histologic evidence of inflammation. To demonstrate the role of changes in external moisture on these phenomena, we applied either an occlusive, water-impermeable plastic membrane, Petrolatum, or a nonocclusive humectant, both to nonperturbated and to perturbed skin. All three forms of treatment prevented the epidermal hyperplasia and dermal mast cell hypertrophy and degranulation induced by exposure to low humidity. These studies indicate that (i) exposure to changes in environmental humidity alone induces increased keratinocyte proliferation and markers of inflammation, and (ii) that these changes are attributable to changes in stratum corneum moisture content. Finally, these studies provide evidence that changes in environmental humidity contribute to the seasonal exacerbations/amelioration of cutaneous disorders, such as atopic dermatitis and psoriasis, diseases which are characterized by a defective barrier, epidermal hyperplasia, and inflammation.

Acetone↗
PubMed1980

Humidity in children and adults using the controlled partial rebreathing anesthesia method.

The authors examined inspired humidity using a controlled partial rebreathing anesthesia method (CPRAM) and a circle system in 16 healthy adults and five healthy children. The patients were divided into five study groups (A-E). All patients except those in Group E were anesthetized with fentanyl, pancuronium, nitrous oxide-oxygen, 66-33 per cent, and their lungs were mechanically ventilated; patients in Group E received halothane and nitrous oxide-oxygen, 66-33 per cent, with spontaneous ventilation. Group A (five children) had inspired hummidity measured within a modified coaxial (Bain) anesthesia circuit using CPRAM. Groups B and C (five adults each) had humidity measured within the modified coaxial circuit and at the end of a non-modified coaxial circuit using CPRAM. Groups D and E (three adults each) had humidity measured in the semi-closed and closed circle systems, respectively. Initial, mid-, and end-inspired humidity were measured in all groups for two hours by interrupting the controlled ventilation at 30-min intervals, except in patients of Group E, who had humidity measured at similar intervals for two hours during spontaneous ventilation. No significant difference was found among initial, mid-, or end-inspired humidity, nor was there a significant difference between inspired humidities in children and in adults using CPRAM. The humidity measured in adults within the circuit near the endotracheal tube was not significantly different from that measured distal to the fresh gas flow. The humidities in all CPRAM patients exceeded those of both the semiclosed and closed circle systems, stabilizing within 30 min and remaining constant between 24 and 26 mg H2O/1.

Adult↗