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PubMed2005

Effects of increasing temperatures on physiological changes in pigs at different relative humidities.

The effects of relative humidity (RH) and high ambient temperature (T) on physiological responses and animal performance were studied using 12 groups (10 gilts per group) in pens inside respiration chambers. The microclimate in the chamber was programmed so that T remained constant within a day. Each day, the T was increased by 2 degrees C from low (16 degrees C) to high (32 degrees C). Relative humidity was kept constant at 50, 65, or 80%. The pigs' average initial BW was 61.7 kg (58.0 to 65.5 kg), and their average ending BW was 70.2 kg (65.9 to 74.7 kg). Respiration rate (RR), evaporative water (EW), rectal temperature (RT), skin temperature (ST), voluntary feed intake (VFI), water-to-feed ratio (rW:F), heat production (HP), and ADG were analyzed. The animals had free access to feed and water. We determined the T above which certain animal variables started to change: the so-called inflection point temperature (IPt) or "upper critical temperature." The first indicator of reaction, RR, was in the range from 21.3 to 23.4 degrees C. Rectal temperature was a delayed indicator of heat stress tolerance, with IPt values ranging from 24.6 to 27.1 degrees C. For both these indicators the IPt was least at 80% RH (P < 0.05). Heat production and VFI were decreased above IPt of 22.9 and 25.5 degrees C, respectively (P < 0.001). For each degree Celsius above IPt, the VFI was decreased by 81, 99, and 106 g/(pig.d) in treatments 50, 65, and 80% RH, respectively. The ADG was greatest at 50% RH (P < 0.05). Ambient temperature strongly affects the pigs' physiological changes and performance, whereas RH has a relatively minor effect on heat stress in growing pigs; however, the combination of high T and high RH lowered the ADG in pigs. The upper critical temperature can be considered to be the IPt above which VFI decreased and RT then increased. Temperatures of the magnitude of both these IPt are regularly measured in commercial pig houses. We conclude that the upper critical temperatures for 60-kg, group-housed pigs fed ad libitum are between 21.3 and 22.4 degrees C for RR, between 22.9 and 25.5 degrees C for HP and VFI, and between 24.6 and 27.1 degrees C for RT. It is clear that different physiological and productive measurements of group-housed, growing-finishing pigs have different critical temperatures.

Animals↗

PubMed2001

Recovery from transport and acclimatisation of competition horses in a hot humid environment.

The aims of the present field-based study were to investigate changes in fit horses undergoing acclimatisation to a hot humid environment and to provide data on which to base recommendations for safe transport and acclimatisation. Six horses (age 7-12 years) were flown from Europe to Atlanta and underwent a 16 day period of acclimatisation. Exercise conditions during acclimatisation (wet bulb globe temperature index 27.6+/-0.0 [mean +/- s.e.]) were more thermally stressful compared with the European climate from which the horses had come (22.0+/-1.8, P<0.001). Following the flight, weight loss was 4.1+/-0.8% bodyweight and took around 7 days to recover. Water intake during the day was significantly increased (P<0.05) compared with night during acclimatisation. Daily mean exercise duration was 72+/-12 min and the majority of work was performed with a heart rate below 120 beats/min. Respiratory rate (fR) was increased (P<0.05) throughout acclimatisation compared with in Europe, but resting morning (AM) and evening (PM) rectal temperature (TREC), heart rate (fC) and plasma volume were unchanged. White blood cell (WBC) count was significantly increased at AM compared with in Europe on Days 4 and 10 of acclimatisation (P<0.01), but was not different by Day 16. In conclusion, horses exposed to hot humid environmental conditions without prior acclimatisation are able to accommodate these stresses and, with appropriate management, remain fit and clinically healthy, without significant risk of heat illness or heat-related disorders, provided they are allowed sufficient time to recover from transport, acclimatisation is undertaken gradually and they are monitored appropriately.

Acclimatization↗

PubMedDate not supplied

The influence of varying air humidity on mucociliary activity.

The influence of varying humidity levels in the air surrounding the mucous membrane of rabbit tracheae has been investigated in vitro at 34 degrees C, 37 degrees C and 40 degrees C. The following results were obtained: (1) The average mucociliary wave frequency was linearly reduced following decreasing levels of relative humidity (r.h.) from 90% to 20%. (2) A temperature of 40 degrees C was more detrimental to the mucociliary function than that of 34 degrees C and 37 degrees C (body temperature) at decreasing levels of r.h. (3) At decreasing levels of r.h. the duration of experiments with preservation in recordable activity ("mucociliary survival time") was significantly shorter (p smaller than 0.05) between 50% and 40% r.h. than between 60% and 50% r.h.

Air↗

PubMed1977

Better epoxy resin embedding for electron microscopy at low relative humidity.

In the absence of other factors known to influence sectioning properties, high environmental relative humidity is shown to yield poorly embedded tissue. Humidity-related effects are avoided if the following embedding precedure is used; impregnate tissues using the following solutions 1) 70% alcohol - 5 minutes, 2) 95% alcohol - 2 x 15 minutes, 3) absolute alcohol - 3 x 20 minutes, 4) acetone - 2 x 15 minutes, 5) 1:1 mixture of acetone-epoxy resin (DDSA, 63.4 g; Araldite 502, 5.6 g; Epon 812, 39.4 g; DMP-30, 2.6 g) - 1 hour, 6) acetone-epoxy resin 1:3 - 1 hour, 7) epoxy resin - 1 hour; complete the preparation of blocks as follows 8) when tissues have been oriented in epoxy resin in flat embedding molds, place molds in one evacuated vacuum desiccator 10 cm above a 2 cm layer of Drierite for 24 hours at room temperature, 9) raise temperature to 60 C and maintain for 3 days to cure resin.

Animals↗

PubMed1991

Effects of bovine somatotropin on physiologic responses of lactating Holstein and Jersey cows during hot, humid weather.

Thirty-one lactating Holstein and Jersey cows were used to determine the effects of daily injections of 0 or 20 mg of recombinant bST on physiologic responses during hot, humid weather. Body temperature was determined by measuring milk temperature at each milking. Jugular blood was sampled for serum analysis of selected hormones, blood metabolites, and fatty acids, and arterial blood was sampled for blood pH and blood gas analysis. Milk was characterized for fatty acid composition. Blood pH was unchanged, but partial pressure of blood CO2, blood bicarbonate, base excess, and total CO2 declined with administration of bST. Serum triglycerides increased 89% in cows receiving bST. Blood urea nitrogen tended to decline in cows receiving bST. Serum cortisol, triiodothyronine, and thyroxine did not change, but insulin-like growth factor-1 increased 128% with bST use. Reduced milk short-chain fatty acids, increased milk long-chain fatty acids, and increased blood serum C18:1 fatty acid content occurred in cows administered bST and probably reflected tissue mobilization. Cows administered bST in hot weather had higher milk temperatures. Alterations in physiologic and metabolic measures in association with higher milk temperature suggest an interaction of bST use with hot, humid weather and reflect the need to minimize the effects of heat stress.

Acid-Base Equilibrium↗

PubMed1989

Effect of air humidity on spinability and transport capacity of canine airway secretions.

The effect of varying the inspired air humidity on a rheological property (spinability) and transport capacity of airway mucus has been analyzed in 10 mongrel dogs. Tracheal mucus was collected in anesthetized dogs inspiring through an endotracheal tube the air of a climate chamber maintained at constant temperature (T degrees:20 degrees C). In one test, the dogs inspired air at an absolute humidity (AH) of 9 g water/m3 air directly through the endotracheal tube. In the other test, the dogs inspired through an artificial nose connected to the endotracheal tube giving a AH of 30 g water/m3 air. Tracheal mucus was collected at the external distal end of the endotracheal tube. The spinability (Sp) or thread-forming properties of mucus was measured. The relative mucociliary transport rate (TR) of mucus was analyzed on a frog palate epithelium preparation. The transport rate was significantly (p less than 0.01) lower (range: 0.59-0.80) when the AH of the inspired air was low in comparison to that obtained with high AH (range: 0.70-1.13). The variations in mucus Sp due to changing AH were positively and significantly correlated (r = 0.80, p less than 0.01) with the corresponding variations in TR. These results suggest that lowering the AH of air induces a decrease in the transport capacity which appears to be dependent on the change of spinability that occurs in the mucus.

Air↗

PubMed1980

Effects of microwave and various combinations of ambient temperature and humidity exposures on off-host survival of northern fowl mites.

When northern fowl mites, Ornithonyssus sylviarum (Canestrini and Fanzago), were removed from their host and exposed to ambient temperatures ranging from -15 to 49 C with uncontrolled relative humidity (RH) or to temperatures ranging from .3 to 38 C with an RH of ca. 75%, mites lived longest at 4 C. However, temperatures between .3 and 26 C were also conducive to survival. Temperatures above 43 C killed the mites in less than 5 hr; mites exposed to -15 C lived up to 5 days. A constant humidity of ca. 75% was most beneficial to the mites when temperatures ranged from 33 to 38 C. Manipulation of ambient temperature and RH would be effective in exterminating the northern fowl mites on inanimate objects. Mites exposed for different periods to microwave energy at a net power ranging between 165 to 430 kw/m2 were not selectively heated to temperatures above the temperatures of the containers, nor did the irradiation have any other lethal effects on the mites.

Animals↗

PubMed1984

Increasing hatchability of turkey eggs by matching incubator humidity to shell conductance of individual eggs.

One of the most important factors determining hatchability of avian eggs is the proper water balance of the eggs during incubation. In turkey eggs, a total diffusive water loss (F) of 12 +/- 1% SD initial egg mass in 28 days, yielded maximal hatchability irrespective of the combination of eggshell water vapor conductance (G) and incubator humidity (PI), which brought about this water loss. A good correlation was found between G as obtained at the beginning of incubation and the final F in a given PI. The G in a random sample of 1256 fresh turkey eggs was normally distributed around the mean of 18.70 +/- 2.87 SD milligrams (100 g X day X torr)-1 (Coefficient of variation = 15.3%). The distribution of G in eggs with dead in the shell embryos had, in addition, two more peaks of G values [around 22.5 and 13.0 mg (100 g X day X torr)-1]. When eggs were sorted into low (less than 17), medium (17 to 20), and high (greater than 20) G categories, and incubated at low (19.4), medium (26.6), and high (33.9) torr PI, respectively, hatchability increased by a factor of 1.08. Poor hatchabilities were obtained in mismatching humidities and conductances. It seems that hatchability success may be experimentally improved if a correct rate of water loss is fitted to sorted eggs during incubation.

Animals↗

PubMed2000

Effects of xylazine on acid-base balance and arterial blood-gas tensions in goats under different environmental temperature and humidity conditions.

The effects of acute exposure to 3 different temperature and humidity conditions on arterial blood-gas and acid-base balance in goats were investigated after intravenous bolus administration of xylazine at a dose of 0.1 mg/kg. Significant (P<0.05) changes in the variables occurred under all 3 environmental conditions. Decreases in pH, partial pressure of oxygen and oxyhaemoglobin saturation were observed, and the minimum values for oxygen tension and oxyhaemoglobin saturation were observed within 5 min of xylazine administration. The pH decreased to its minimum values between 5 and 15 min. Thereafter, the variables started to return towards baseline, but did not reach baseline values at the end of the 60 min observation period. Increases in the partial pressure of carbon dioxide, total carbon dioxide content, bicarbonate ion concentration, and the actual base excess were observed. The maximum increase in the carbon dioxide tension occurred within 5 min of xylazine administration. The increase in the actual base excess only became significant after 30 min in all 3 environments, and maximal increases were observed at 60 min. There were no significant differences between the variables in the 3 different environments. It was concluded that intravenous xylazine administration in goats resulted in significant changes in arterial blood-gas and acid-base balance that were associated with hypoxaemia and respiratory acidosis, followed by metabolic alkalosis that continued for the duration of the observation period. Acute exposure to different environmental temperature and humidity conditions after xylazine administration did not influence the changes in arterial blood-gas and acid-base balance.

Acid-Base Equilibrium↗

PubMedDate not supplied

[Influence of temperature and humidity on the reproductive efficiency of Ixodes ricinus (Linnaeus, 1758) and Hyalomma marginatum Koch, 1844 (Ixodoidea, Ixodidae)].

Laboratory studies have been carried out on two species of ticks, I. ricinus and H. marginatum, showing different seasonal activity and different geographical distribution in nature. The purpose of the present study has been to investigate the effect of different combinations of temperature and humidity on the oviposition of I. ricinus and H. marginatum. An index of reproduction efficiency (no. eggs/wt female), established to relate the capacity of the females to produce eggs to their body weight, has been calculated; for I. ricinus 5 temperatures (18-20-25-27 and 30 degrees C) have been studied (Fig. 1), for H. marginatum 3 (25-30 and 32 degrees C) (Fig. 2) and for both species 2 R.H. (75-95%). An optimal range of temperature, within which the value of such an index doesn't change, has been demonstrated for both species by statistical testing (Table 1). A critical weight value as the minimum engorged female weight required for egg deposition has been identified with the weight of first female which has laid eggs. This weight, different in each species, is influenced by temperature and humidity.

Animals↗

PubMed2000

Light scattering characteristics of aerosols at ambient and as a function of relative humidity: Part II--A comparison of measured scattering and aerosol concentrations using statistical models.

The eastern United States national parks experience some of the worst visibility conditions in the nation. To study these conditions, the Southeastern Aerosol and Visibility Study (SEAVS) was undertaken to characterize the size-dependent composition, thermodynamic properties, and optical characteristics of the ambient atmospheric particles. It is a cooperative three-year study that is sponsored by the National Park Service and the Electric Power Research Institute and its member utilities. The field portion of the study was carried out from July 15 to August 25, 1995. The study design, instrumental configuration, and estimation of aerosol types from particle measurements is presented in a companion paper. In the companion paper, we compare measurements of scattering at ambient conditions and as functions of relative humidity to theoretical predictions of scattering. In this paper, we make similar comparisons, but using statistical techniques. Statistically derived specific scattering associated with sulfates suggest that a reasonable estimate of sulfate scattering can be arrived at by assuming nominal dry specific scattering and treating the aerosols as an external mixture with ammoniation of sulfate accounted for and by the use of Tang's growth curves to predict water absorption. However, the regressions suggest that the sulfate scattering may be underestimated by about 10%. Regression coefficients on organics, to within the statistical uncertainty of the model, suggest that a reasonable estimate of organic scattering is about 4.0 m2/g. A new analysis technique is presented, which does not rely on comparing measured to model estimates of scattering to evoke an understanding of ambient aerosol growth properties, but rather relies on measurements of scattering as a function of relative humidity to develop actual estimates of f(RH) curves. The estimates of the study average f(RH) curve for sulfates compares favorably with the theoretical f(RH) curve for ammonium bisulfate, which is in turn consistent with the study average sulfate ammoniation corresponding to a molar ratio of NH4/SO4 of approximately one. The f(RH) curve for organics is not significantly different from one, suggesting that organics are weakly to nonhygroscopic.

Aerosols↗

PubMed1984

Effects of relative humidity and root temperature on calcium concentration and tipburn development in lettuce.

Growth chamber studies were undertaken with a tipburn-sensitive cultivar of romaine lettuce (Lactuca sativa L. cv. Lobjoits Green Cos) grown under a photosynthetic photon flux density of 320 micromoles s-1 m-2 for 16 hours; light and dark temperatures were 26.0 degrees and 12.5 degrees C, respectively. As the relative humidity (RH) during the light period was decreased from 74% to 51%, growth was retarded, Ca concentration increased, and the onset of tipburn delayed. Decreasing RH during the dark period from 95% to 90% reduced growth and resulted in lower Ca concentrations and earlier tipburn development. Further decreases from 90% to 65% caused no additional change in growth or tipburn response. Root temperatures of 23.5 degrees, compared with 15.0 degrees, slightly increased Ca concentration but induced earlier tipburn development. Ca concentrations were increased and tipburn delayed by humidity conditions which provided large diurnal fluctuations in water potential in the plant and which encouraged root pressure flow during the dark period. Elevated root temperatures did not provide expected increases in Ca accumulation in young leaves.

Calcium↗

PubMed2000

[Effects of temperature, relative humidity and pH on germination of chalkbrood fungus, Ascosphaera apis spore].

Studies on the effects of environmental temperature, relative humidity and pH-value on the germination of Ascosphaera apis spore at the stages of activation, enlargement and germ-tube production showed that the germination was found to be independent of temperature within the range of 15-40 degrees C was and 25-40 degrees C, respectively at the stage of activation and enlargement, but closely correlated with the temperature within the range of 25-37 degrees C at the stage of germ-tube production, with the optimum range of 31-35 degrees C. Relative humidity below 80% inhibited spore germination. pH value within the range of 5-7.8 did not affect the spore germination significantly, but pH < 5 reduced the enlargement and germ-tube production drastically. The results indicated that A. apis is a highly specialized pathogen for the life in honeybee larvae.

Humidity↗

PubMedDate not supplied

[Bacterial diversity in microcosms of soils with various humidity].

The succession analysis of bacterial diversity in the A horizons (rich in organic matter) of three contrasting types of soil--burozem, soddy gley soil, and chernozem--showed that the bacterial diversity of soil microcosms in humid regions can be adequately evaluated only if soil samples are incubated at different soil moisture contents. A complete account of actinobacteria and proteobacteria requires the levels of soil moisture corresponding to the maximum capillary-sorption moisture and capillary moisture, respectively. The bacterial diversity, whose value was maximum on the 40th day of succession, was higher in soddy gley soil than in burozem. The taxonomic structures of the bacterial communities of these two types of soil were different. After wetting chernozem samples from arid regions, the soil bacterial community changed insignificantly with time and drastically differed from that of soils from humid regions. The difference in the bacterial diversity of soils was the most distinct when it was evaluated by measuring the proportion between proteobacteria and actino-bacteria.

Bacteria↗

PubMed2002

[The use of thermoelectric modules (Peltier elements) in the relative humidity control of a hyperbaric environment].

The author considers an option for automatic relative humidity control of a hyperbaric environment demonstrated in a pressure chamber for small animals. To achieve the purpose, a device has been developed to cool off gas mixture using the Peltier effect and then remove condensate. Experiments were performed with two different gas mixtures: O2-N2-He at 25.5 x 10(5) Pa and 30 degrees C and air at 6.9 x 10(5) Pa and 22 degrees C. The device enabled stabilization of relative humidity in the chamber at 30-40% without bio-objects and at 35-46% with bio-objects (Wistar rats).

Animals↗

PubMed2002

Indoor air quality assessment of daycare facilities with carbon dioxide, temperature, and humidity as indicators.

Poor indoor air quality (IAQ) in daycare facilities affects both attending children and care providers. Incident rates of upper-respiratory-tract infections have been reported to be higher in children who attend daycare. Excessive carbon dioxide (CO2) exposure can cause several health effects and even sudden infant death. For this study, 26 facilities were randomly selected in a Midwestern county of the United States. CO2, room temperature, and relative humidity were used as indicators for IAQ and comfort levels. These IAQ parameters were continuously monitored for eight hours at each facility by a direct-reading instrument that was calibrated before each measurement. More than 50 percent of the facilities had an average CO2 level over the American Society of Heating, Refrigerating and Air Conditioning Engineers (ASHRAE) standard of 1,000 parts per million (ppm). For temperature and relative humidity, respectively, 42.3 percent and 15.4 percent of facilities were outside of the ASHRAE-recommended comfort zones. The nap-time average CO2 level was about 117 ppm higher than the non-nap-time level. The increment of the nap-time CO2 level in the sleeping-only room over the level in multipurpose rooms was statistically significant (p < .05). According to stepwise multiple regression analysis, nap-time CO2 level was predicted by CO2 level before occupancy, nap-time average temperature, carbon monoxide, and child density (R2 = .83). It is recommended that an appropriate IAQ standard for daycare facilities be established and that children should not be placed in a completely isolated room during nap time.

Air Conditioning↗

PubMed2003

Survival of mice with gamma-ray irradiation in hot and humid environments.

OBJECTIVE: To study the survival of the mice with gamma-ray irradiation in hot and humid environments (HHE) and determine the median lethal dose in 30 days (LD50/30). METHODS: One hundred mice were randomly divided into 2 groups (n=50 each) to receive gamma-ray irradiation at the dosage of either 7 or 9 Gy, and were then immediately transferred to the chambers simulating HHE for treatment for 30, 60, 90 or 120 min respectively, leaving one group at room temperature (n=10 in each group). The death rates of the mice within 30 days were observed. For LD50/30 determination, another 180 mice in 3 equal groups were subjected to irradiation at 5, 7 or 9 Gy, respectively and after further division of each group into 3 equal subgroups, the mice underwent treatment in HHE for 60 or 90 min respectively or at room temperature to observe their death rates within 30 days and calculate the LD50/30. RESULTS: Compared to the mice treated at room temperature, earlier onset and more cases of infections with much severity were observed in all the HHE groups, with reduced average survival time and obviously shortened median survival time (P<0.05), and LD50/30 tended to also decrease in the HHE groups. CONCLUSION: The survival indexes of irradiated mice are significantly decreased in hot and humid environments.

Animals↗

PubMedDate not supplied

The influence of relative humidity and temperature on stability of moexipril hydrochloride in solid phase.

Kinetic and thermodynamic parameters of the decomposition of moexipril hydrochloride in solid phase in the absence and presence of humidity were calculated. The evaluation of stability of moexipril hydrochloride was followed by the HPLC method. The applied method was validated (evaluation of the following parameters: selectivity, linearity, precision, limit of detection (LOD), limit of quantification (LOQ) and repeatability). The effect of humidity on the stability of MHCl in solid phase at 363 K was described by the equation: In ki = ax + b = (0.0676 +/- 0.016) . RH% - (15.53+/-0.78). Identification of degradation products of MHCl were carried out by the HPLC-MS method.

Chromatography, High Pressure Liquid↗