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At least 37 records · Page 2Linked to original sources
PubMed1991

Influence of humidity and temperature on the diel periodicity of oviposition of Toxorhynchites moctezuma (Diptera: Culicidae) in the field.

The diurnal pattern of oviposition by Toxorhynchites moctezuma (Dyar & Knab), ambient relative humidity, and ambient air temperature were monitored hourly between 0600 and 1800 hours for 46 consecutive d in a tropical rainforest in Trinidad, West Indies. The mean number of eggs per ovitrap per hour was correlated negatively with mean ambient relative humidity and positively with air temperature. Partial correlation coefficients among these variables and contingency table analysis indicated a stronger relationship between the oviposition rate and relative humidity than between oviposition rate and temperature. We suggest that this relationship is further evidence of the ability of female Tx. moctezuma to detect suitable oviposition sites using humidity gradients.

Animals↗
PubMed1990

Do ambient temperature and humidity influence the breast-milk intake of babies?

This study explored the possible effect of ambient temperature and humidity on the breast-milk intakes of Australian infants (n = 35) aged 6-12 weeks. Over a 24 h period, each baby was fed only on milk from the breast; milk intakes, temperature and humidity were monitored. Milk intakes--determined by test-weighing the baby, with a correction for evaporative losses during feeds--showed a mean of 830 g/24 h, with median 818 and s.d. 152. The mean correction for evaporative losses was 46 g/24 h; omission of this correction would have led to an average underestimate of 5.5% in 24 h intakes. Ambient conditions varied substantially between subjects: 24 h mean temperatures ranged from 14 to 28 degrees C, and humidities from 48 to 97%. Over these ranges, breast-milk intakes did not appear to be significantly influenced by ambient temperature or ambient humidity; however, the rate of evaporative losses increased by 0.008 g/min for each 1 degree C rise in ambient temperature.

Australia↗
PubMed1979

Air humidity and carotid rete function in thermoregulation of the goat.

1. The effects of air humidity on respiratory rate have been studied in conscious goats exposed to an air temperature of + 33 degrees C. Before the experiments the animals had been chronically implanted with hypothalamic thermodes and intravascular heat exchangers to manipulate hypothalamic and general body core temperatures.2. Raising air humidity from 37 to 96% at constant air temperature resulted in a rise of respiratory rate, an immediate increase in hypothalamic temperature and a delayed smaller increase in general body core temperature.3. The rise of respiratory rate was smaller when general body core temperature was clamped at its control level and was absent when hypothalamic and general body core temperatures were clamped at their control levels during the humid air phase.4. It is concluded that the effect of high air humidity on respiratory rate in goats is predominantly the result of a rise in hypothalamic temperature acting on local thermosensitive structures. The carotid rete heat exchanger is thought to provide the thermal link between the evaporating surfaces of the upper respiratory tract and the hypothalamus.5. This function of the carotid rete heat exchanger is restricted to heat stressed animals. In animals subject to central cooling no local effects on hypothalamic temperature could be observed when the temperature of the inspired air was altered from + 33 to - 17 degrees C.

Animals↗
PubMed1976

Influence of relative humidity on functional effects of an inhaled SO2-aerosol mixture.

Lightly anesthetized guinea pigs were exposed to 1 ppm of sulfur dioxide (SO2) and 1 mg per m3 of sodium chloride aerosol, individually and in combination, at low and high relative humidities. At low relative humidity (less than 40 per cent) the aerosol was a crystal, at high relative humidity (greater than 80 per cent) a droplet. Exposures lasted one hour. Changes in pulmonary mechanical function characterized by an increase in flow resistance and decrease in compliance were seen only when the mixture was administered at high relative humidity. The effect is ascribed to absorption of the highly soluble SO2 into the droplet before inhalation.

Aerosols↗
PubMed1991

Aerosol, humidity and oxygenation.

Patients with artificial airways frequently need aerosol or humidity therapy. For this study, we used aerosols generated from a heated Puritan all-purpose nebulizer and humidity generated from a heated Bennett cascade humidifier to determine the effects of these therapies in spontaneously breathing neurosurgical patients with nasal endotracheal tubes and normal lungs. Crossover comparison of oxygenation status before and after aerosol or humidity therapy was done by analyzing P(A-a)O2 in these patients. We found that aerosols have a detrimental effect on the patient's oxygenation status, suggesting that humidity is preferable in maintaining adequate oxygenation in a patient with a normal lung plus artificial airway. The arterial pH and PaCO2 were not affected by aerosol therapy. Care should be exercised with regard to the adverse hypoxemic effect of bland aerosols when a large-reservoir jet nebulizer is used in an intubated patient who already has impaired cardiopulmonary function or borderline PaO2.

Aerosols↗
PubMed1976

Relationship of temperature and humidity to conception rate of Holstein cows in Hawaii.

Weather data and breeding records for a Holstein herd of 1300 cows in Hawaii were evaluated to determine effects of climate on reproductive performance. The dairy is in a coastal climate near latitude 21 degrees N. Average maximum temperature, relative humidity, and resulting temperature-humidity index for the warmest month of the year were 31 C, 44%, and 79. Average minimum temperature and attending values for the same period were 20 C, 96%, and 68. From late April to November, conception rates were correlated negatively with the average temperature-humidity index of each day of the estrous cycle beginning 11 days prior to breeding. Slopes of regression lines differed, suggesting varying sensitivity of conception rate to heat stress on different days of the cycle. The temperature-humidity index of the 2nd day prior to breeding was most closely correlated with conception rate. Conception rates declined from 66% to 35% as the index increased from 68 to 78. Only the temperature-humdity index of the 2nd day prior to breeding had a significant partial correlation coefficient when the index of the 2nd and 1st day prior to breeding, the day of breeding, and the day following breeding were each evaluated with the index of the others held constant.

Animals↗
PubMed1978

[Changes in the biochemical and morphological indices of broiler chickens depending on the temperature and humidity conditions].

A varying temperature and humidity regime was tested on a total of 200 hybrid birds (White Plymouth Rock x Cornish crosses). Investigated were some indices of the carbohydrate metabolism and the deposition of vitamins in the organism as well as the effect of the temperature and humidity regime on the growth and development of broilers. It was established that the content of glycogen in the liver and the muscles in birds raised first at 32 degree C and relative air humidity of 65--70 per cent was higher than in birds raised at 36 degree C and relative air humidity of 45--50 per cent. Besides, these observations were coupled with some changes in the content of blood sugar and the amount of A and E vitamins in the liver. The body weight of the test broilers by the end of the experiment was 30 grams higher than that of the control group broilers.

Age Factors↗
PubMed1990

Responses of young and older men during prolonged exercise in dry and humid heat.

Eight young, sedentary men (aged 34 years, SD 3) and six older moderately active, unacclimated men (aged 57 years, SD 2) walked on a treadmill at 30% of their maximum oxygen consumption up to 3.5 h in a thermoneutral [dry bulb temperature (Td) 21 degrees C, relative humidity (r.h.) 43%)], a warm humid (Tdb 30 degrees C, r.h. 80%) and a hot dry (Tdb 40 degrees C, r.h. 20%) environment while wearing ordinary working clothes (0.7 clo). Their oxygen consumption, heart rate (fc), rectal (Tre) and mean skin temperature (Tsk), sweat rate (SR), and evaporative rate (ER) were measured during the tests. The ratings of thermal sensation (TS) and perceived exertion (RPE) were assessed using standard scales. In the heat stress tests, the number of experiments discontinued did not significantly differ between the two groups. The mean levels and end-exercise values of Tre, Tsk, fc, TS and RPE were not significantly different between the young and older subjects in any of the environments. In the warm humid environment, however, the Tre and RPE of the older subjects increased continuously (P less than 0.05) during the test compared to the young subjects. No significant difference between the groups was observed in SR or in ER. In the hot dry environment, however, the ER of older men increased more slowly compared to the young men. In spite of some time-related differences observed in Tre, RPE, and ER, the older subjects did not exhibit higher fc during exercise in the heat, they were not more hyperthermic and their performance times were similar to the young subjects.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

The effects of elevated temperature and humidity on rectal temperature and respiration rate in the New Zealand white rabbit.

In 2 replicated factorial experiments, 7-h climate chamber exposures were used to study the responses of adult NZW rabbits to a range of elevated temperatures and humidities. At 18 mm Hg water vapour pressure, 23.8 degrees C was well tolerated, rectal temperature (RT) and respiration rate (RR) averaging 38.6 +/- 0.3 degrees C and 82.9 +/- 15.5 breaths/min, respectively. Both parameters were elevated (P less than 0.001) at 32.2 degrees, 37.8 degrees and 43.3 degrees C. RT and RR reached plateau levels of 39.5-40.1 degrees C and 410-460/min at 32.2 degrees C, which was tolerated for the full 7-h test period. Test temperatures of 37.8 degrees and 43.3 degrees C, on the other hand, could be tolerated for only 80 and 40 min respectively, before RT reached the safe upper limit of 41.7 degrees C. Final RR values at 37.8 degrees and 43.3 degrees C were 701.6 +/- 42.7 and 812 +/- 55.1/min, respectively. In a 34.5 degrees C atmosphere a humidity of 21 mm Hg water vapour pressure was classified as "dry", and was tolerated for 323 +/- 123 min. RT and RR increased by 0.6 degrees C and 316/min during the first 20 min of exposure (P less than 0.05). Thereafter both parameters increased progressively, but with no significant differences between successive recording periods, until RR reached 550.3 +/- 88.8/min at 41.7 degrees C RT. Humidities of 25, 29 and 33 mm Hg water vapour pressure were, on the other hand, classified as "wet" and were tolerated for only 92 +/- 22, 81 +/- 16 and 119 +/- 50 min, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Effects of temperature and humidity on ovipositional biology and egg development of the tropical horse tick, Dermacentor (Anocentor) nitens.

The ovipositional biology and egg development of the tropical horse tick, Dermacentor (Anocentor) nitens (Neumann), was observed at four temperatures (20, 25, 30, and 35 degrees C) and relative humidities (40, 61, 75, and 91% RH). Relative humidity had little effect on length of preoviposition and oviposition periods. With increased rearing temperatures, there was a decrease in both preoviposition and oviposition periods. Oviposition rate increased with temperature and was not affected by relative humidity. Instantaneous rates of oviposition were calculated for each temperature by fitting the data to the logistic growth function. High percentage egg hatch was observed in low saturation deficit environments, and decreased when saturation deficit was increased.

Animals↗
PubMed1976

Effects of hypoxia, heat, and humidity on physical performance.

The effects of hot, humid environment were compared with the effects of high altitude on the physical performance capacity of Ne-palese residents by measuring oxygen uptakes and heart rates at various work rates. The following groups of men were selected: 66 residents of a hot and humid environment in the Terai at sea level; 24 residents and 16 sojourners at 3,8000 m. The maximal oxygen uptake of the sea-level residents was, on the average, 2.55 1.min-1, at which a maximal heart rate of about 200 beats/min was reached. The sojourners at 3,800 m showed a higher maximal oxygen uptake (2.94 1. min-1) at their maximal heart rate of about 175 beats/min. The residents of 3,800 m achieved a similiar oxygen uptake as the sojourners, but did not show a similar maximal heart rate limitation, suggesting that they were capable of achieving a higher maximal oxygen uptake. This study shows that hot, humid environment at sea level is as much incapacitating as is hypoxia at high altitude.

Adult↗
PubMed1976

A new method of measuring skin humidity.

A device suitable for the long-time measurement of relative skin humidity is described. This is a simple circuit with a resistance bridge for lithium chloride sensors connected to a digitally steered logic circuit, which causes dried air to stream intermittently through a measuring chamber placed on the skin in such a way that the relative humidity over the skin is maintained at a constant level. The number of switching time periods is proportional to the relative humidity (secretion performance) of the skin and can be counted, recorded, or directly fed into a digital calculator. The apparatus, including a two-channel version with skin temperature recording, has proved useful in sleep investigations under extreme climatic conditions.

Electronics↗
PubMed1975

Effects of low humidity on small premature infants in servocontrol incubators. I. Decrease in rectal temperature.

19 small premature infants in servocontrol incubators, whose abdominal skin temperature was 36.0 +/- 0.3 degrees C, were subjected to alternate high- and low-humidity environments. With low humidity, rectal temperature dropped significantly below abdominal skin temperature. Skin was the predominant site of evaporative heat loss. The temperature was lower on naked skin than on an area covered by adhesive tape. Thus, servocontrol with low humidity increases evaporative heat loss and engenders a cycle of events that results in paradoxical body temperature decrease as the incubator temperature increases.

Abdomen↗
PubMed1991

Effect of humidity on the deswelling function of the human cornea.

The present study determined the effect of the full range of humidities on the deswelling function of the human cornea. The closed-eye deswelling function and the open-eye deswelling responses for five different levels of humidity (0%, 25%, 60%, 85%, and 100%) were assessed for 8 normal, young-adult subjects. Open-eye corneal deswelling for the 8 subjects was unaffected by relative humidities from 0 to 100%. Therefore, osmotically-driven corneal thinning effect of tear evaporation does not significantly contribute to the deswelling function of the human cornea. We conclude, contrary to recent reports, that the endothelial pump is the primary mechanism that maintains normal corneal thickness and provides recovery from stromal edema.

Adult↗
PubMed1992

Study of lipid changes in freeze-dried fish during storage. I. The interaction of relative humidity and tissue lipids.

Several studies on lipid stability of freeze-dried fish pointed out the relationship between relative humidity (RH) and autoxidation of highly unsaturated fatty acids. The present study shows the changes of tissue lipids in two different fish, freeze-dried and stored under various RH conditions. Fillets of Scomber scomber L and Sardina pilchardus sardina were freeze-dried and stored for 1, 3, 6 and 9 months. periodically, the sample of both fish were analyzed to evaluate the autoxidation of lipids. The results show that the autoxidation of lipids is quicker during 1st-3rd month of storage, while in a high humidity environment the tissue lipids change slower. According to these results both time of storage and relative humidity must be controlled to maintain the nutritive value of freeze-dried fish.

Animals↗
PubMed1992

Heat stress in protective clothing: validation of a computer model and the heat-humidity index (HHI).

Ability to work while wearing protective clothing is often limited by rising body temperature. Peterson analyzed the combined effects of heat, humidity and workload using the Texas Model of Thermoregulation and suggested that environmental heat load imposed on a person wearing heavy, semipermeable clothing could be predicted using the Heat-Humidity Index (HHI = 0.5 Tdb + 0.5 Twb), where Tdb = dry bulb temperature and Twb = wet bulb temperature. Our study was designed to: 1) test the validity of this computer model; and 2) evaluate the applicability of the HHI to heavily clothed subjects working in a variety of thermal environments. Nine men wearing chemical defense clothing were each studied under eight conditions over the range Tdb = 20 - 40 degrees C, Tbg = Tdb + 5 degrees C, relative humidity = 9-75%, and oxygen uptake = 14-27 ml.kg-1 x min-1. Variables analyzed included tolerance time (TT), rectal temperature (Tre), skin temperature, heart rate (HR), weight loss, sweat rate, evaporation rate, and evaporative efficiency. Experiments were designed to last 30-180 min, and continued until Tre = 39 degrees C except when subjective tolerance limits occurred first (12 of 72 experiments). The observed time to reach Tre = 39 degrees C bracketed the predicted time in the more severe conditions, but the model seriously underestimated heat storage in the milder conditions.(ABSTRACT TRUNCATED AT 250 WORDS)

Acclimatization↗
PubMed1992

Impact of tropical conditions on thin layer chromatography in analytical toxicology: high temperatures and moderate humidities.

The impact of high temperatures (24 to 39 degrees C) and low to moderately high humidities (20 to 70%) on the applicability of TLC systems for drug identification was studied during a 6 month climatologic cycle in Burkina Faso (West Africa). In general, the Rf values as observed on the plates were found to be substantially affected as compared with values obtained at temperate climates. Some TLC systems were more affected than others and the largest deviations of up to 30 Rf units were at low humidities. Tropical conditions also had a negative effect on the reproducibility of Rf values. However, when an Rf-correction procedure was applied, using reference mixtures of known drugs on each plate, accuracy as well as reproducibility of the resulting Rfc values were drastically improved and data thus corrected were found to be compatible with existing TLC data bases developed under moderate climatological conditions. The impact of high to extremely high humidities (70 to 100%) remains to be investigated.

Burkina Faso↗