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PubMed1980

Stability of solid drugs: degradation of ergocalciferol (vitamin D2) and cholecalciferol (vitamin D3) at high humidities and elevated temperatures.

Ergocalciferol and cholecalciferol powders were studied at 25 and 40 degrees and at different humidities. Ergocalciferol decomposed rapidly at 25 and 40 degrees when stored in dry air. Decomposition of ergocalciferol led to the formation of products of higher polarity. Cholecalciferol was not as labile under dry conditions, but decomposed rapidly at high temperature.

Cholecalciferol↗

PubMed2004

Quantification of hydrogen cyanide in humid air by selected ion flow tube mass spectrometry.

Following our recent observation that Pseudomonas bacteria in vitro emit hydrogen cyanide, we have found it necessary to investigate the ion chemistry of this compound and to extend the kinetics database for selected ion flow tube mass spectrometry (SIFT-MS) to allow the accurate quantification of HCN in moist air samples, including exhaled breath. Because of the proximity of the proton affinities of HCN and H2O molecules, the presence of water vapour can significantly distort HCN analysis in the presence of water vapour and a more sophisticated analytical procedure has to be developed. Thus, the reactions of H3O+(H2O)0,1,2,3 ions with HCN molecules have been studied in the presence of varying concentrations of water vapour, reactions on which SIFT-MS analysis of HCN relies. The results of these experiments have allowed an analytical procedure to be developed which has extended the kinetics database of SIFT-MS, such that HCN can now be quantified in humid air and in exhaled breath.

Air↗

PubMed2006

The analysis of 1-propanol and 2-propanol in humid air samples using selected ion flow tube mass spectrometry.

Following the observation that propanol is present in the breath samples of cystic fibrosis (CF) patients infected by Pseudomonas aeruginosa (PA), a study of the reactions of H(3)O(+), NO(+) and O(2) (+.) with 1-propanol and 2-propanol has been conducted using selected ion flow tube mass spectrometry (SIFT-MS). In this study the number and the distribution of the product ions from NO(+) reactions with the two propanol isomers under humid air conditions were able to differentiate between the two isomers. The reaction mechanisms and the structures of the product ions for these reactions, especially those with H(3)O(+) and NO(+), have been proposed. As an example, 2-propanol was shown to be present in a breath sample from one CF patient infected with PA, and also in a PA isolate from another CF patient grown on Pseudomonas-selective media. The results of this study allow an analytical procedure to be advanced for the analysis of the two propanol isomers, which can also be utilised in other applications.

1-Propanol↗

PubMed1999

Effect of relative humidity on viability of primary conidia of Zoophthora radicans.

Four isolates of the entomopathogenic fungus Zoophthora radicans were compared in a laboratory study to evaluate the effect of relative humidity (RH) on duration of primary conidial viability. Primary conidia were showered onto agar-coated glass microscope slides within an enclosed chamber equilibrated to one of five test RH levels (60, 75, 80, 95, or 100%). Target RH levels were achieved by recirculating air through a glycerin/water solution, of controlled specific gravity, contained in a reservoir within the chamber. Conidial samples of each isolate incubated for 5, 10, 30, 60, 120, 180, or 240 min at each RH were removed and inspected using a technique of simultaneous vital fluorochrome staining to determine percentage conidial viability. At 60% RH, isolates did not differ significantly and average viability dropped to less than 10% within the first 60 min. At 75% RH, viability did not change significantly over 4 h. However, average viabilities at 75% RH differed significantly for the four isolates and ranged from 24 to 63%. At 80% RH, viability differed significantly among isolates and declined slowly over time, remaining above 80% for 2 h and above 50% for 4 h. At 95 and 100% RH, average viability was near 95% and did not vary significantly with time or isolate. These data can be used to assist selection of appropriate isolates for biological control.

Fungi↗

PubMed2001

Sporulation by Entomophthora schizophorae (Zygomycetes: Entomophthorales) from housefly cadavers and the persistence of primary conidia at constant temperatures and relative humidities.

The duration of discharge of Entomophthora schizophorae (Zygomycetes: Entomophthorales) conidia from house fly (Musca domestica, Diptera) cadavers was measured at 7, 18, and 25 degrees C. The higher the temperature, the shorter the duration of conidia discharge. Significantly more conidia were produced per cadaver at 7 degrees C over a period of 120 h than at 18 and 25 degrees C. At 25 degrees C, the initial discharge over the first 10 h was much larger than at the other temperatures, and at 7 degrees C, no peak in discharge was observed. The persistence of E. schizophorae primary conidia was measured on fabricated non-host surfaces typically found in stables (straw, wood, plaster, and glass) at 7, 18, and 25 degrees C or constant relative humidities of 45, 65, and 85%. Persistence, as measured by the subsequent ability to infect flies, was usually only a few days and depended on the temperature and type of surface. It was greatest on straw, followed by wood, glass, and plaster, and at 7 degrees C, followed by 18 and 25 degrees C. Limited transmission took place between flies exposed to conidia and previously unexposed mates.

Animals↗

PubMed1980

Effect of hidromeiosis on sweat drippage during acclimation to humid heat.

Sweat rate and the rate of change in sweat drippage were studied during the acclimation of eight healthy male subject during exposure to heat during 10 consecutive days. During acclimation to hot humid conditions, the increase in total body sweat rate results in an increase in the rate of sweat drippage. We found, however, that on each day the drippage rate markedly decreased with time after the 1st h of heat exposure. This hidromeiosis was investigated as a function of the heat exposure time. No shortening of the onset time of hidromeiosis occurred with acclimation. With repeated heat exposures, the initial sweat rates in response to stress increased, and the subsequent decline became larger with higher sweat rates at the time of onset of hidromeiosis. Hidromeiosis appears to be a function of the degree of skin wettedness reached in the various local skin areas which determine the overall body skin wettedness upon which evaporative adjustments depend. Thus, the observed overshoot in total sweat rate as indicated by sweat drippage, and the subsequent hidromeiosis, result from initial oversweating in the poorly ventilated areas of skin. This sweat decline seems to be due to a reduction in output of the active sweat glands rather than to a reduction in active sweat gland number.

Acclimatization↗

PubMed1985

Efficiency of sweat evaporation in unacclimatized man working in a hot humid environment.

A method is devised where evaporation and dripping sweat rates can be continuously determined during work. 6 unacclimatized men performed work on a bicycle ergometer at 3 different workloads and in 3 humidities. Ambient temperatures were always equal to mean skin temperatures, thus eliminating all sensible heat transfer. Evaporation rates ranged between 6.8 and 11.2 g X min-1. Rates of dripping sweat ranged from a mean of 2.2 to 10.4 g X min-1. One subject dripped 20.3 g X min-1 in condition H3 (70% RH, 100 W). The fully wet skin in condition H3 corresponded to an evaporative heat transfer coefficient of 99 W X m-2 kPa. Efficiency of sweating, defined as the ratio between secreted and evaporated sweat, ranged from 87 (50% RH, 50 W) to 51% (70% RH, 100 W). Corresponding values of wettedness were 0.56 and 1.0. Efficiency fell to 51% for fully wet skin (H3), and in some subjects the efficiency values were remarkably low. One subject displayed an efficiency of 31% in condition H3. The reduction in efficiency at a given level of wettedness was higher than previously reported.

Acclimatization↗

PubMed1991

Seasonal influence on the reproductive performance of swine in the humid zone of Ghana.

Relationships between month and climatic factors (ambient temperature, relative humidity, RH, and rainfall) with litter size, conception rate, days from weaning to conception and mortalities at birth and preweaning were studied in large white pigs under research station (RS) and commercial farm (CF) conditions. In RS and CF 868 and 572 farrowing records, respectively, were involved. Litter size was almost evenly distributed in all months of the year, at both farms, despite significant (P less than 0.05) negative but low correlations between litter size and maximum (r = -0.272, RS) and minimum (r = -0.233, CF) temperatures in the month after conception. There were no significant differences in conception rate between months. However under RS conditions there were significant (P less than 0.05) correlations between minimum temperature and conception rate in the months prior to (r = -0.362) and at conception (r = -0.221). Days from weaning to conception were bimodally distributed with peak values occurring between January and June and October and December. Significant mortality at birth (P less than 0.05) and preweaning was generally highest in the cold rainy months of May to October. However, only under CF conditions were there significant correlations between minimum temperature in the month of birth and percentage mortalities at birth (r = -0.217) and preweaning (r = -0.250). Rainfall and RH had no significant (P greater than 0.05) correlation with birth and preweaning mortalities.

Animals↗

PubMed1987

Effects of temperature and relative humidity on development times and mortality of eggs from laboratory and wild populations of the European house-dust mite Dermatophagoides pteronyssinus (Acari: Pyroglyphidae).

As part of a study on passive physical control of house-dust mites, a total of 6000 eggs from a population of Dermatophagoides pteronyssinus (Trouessart, 1897) from 17-year-old laboratory cultures were incubated at 60 temperature and relative humidity combinations between 10-35 degrees C and 55-100% RH. Eggs hatched at every combination, although mortality and development time increased between 10-20 degrees C and 30-35 degrees C and below 65% RH. Optimum conditions were 35 degrees C and 80-85% RH. In temperate dry conditions, eggs from a wild population were found to be more resistant to mortality: they developed faster, with 7 times lower mortality than eggs from the laboratory population. This may have been because the laboratory population had become acclimated to the constant near-optimum conditions at which it was kept. Therefore it has been suggested that where laboratory cultures have been used in studies relating to passive physical control, caution should be taken in applying the conclusions to wild populations in the natural house-dust environment.

Animals↗

PubMed1992

The influence of thermal conditions on rectal temperature, respiration rate and pulse rate of lactating Holstein-Friesian cows in the humid tropics.

The effect of minimum, maximum and mean ambient air temperatures and the temperature-humidity index (THI) of the same and the previous day on morning (a.m.) and afternoon (p.m.) rectal temperatures (RT), respiration rates (RR) and pulse rates (PR) were studied in 17 Holstein-Friesian cows over the first 125 days in the 3rd and 4th lactations. Physiological responses showed a diurnal pattern, being lower in the mornings than the afternoons: 38.6 vs 39.0 degrees C for RT, 52.2 vs 60.7 breaths/min for RR and 58.1 vs 64.1 beats/min for PR. Correlations between RT and RR (r = -0.043 to -0.046) and RT and PR (r = -0.178 to -0.261) were low (P greater than 0.05). Correlations between RR and PR (r = 0.353 to 0.365) were moderate (P less than 0.05). Weather variables, especially ambient temperature of the previous day, were more important and influenced physiological responses to a greater extent than other thermal factors the same day. Generally, physiological responses were influenced to a greater extent by ambient temperature than THI. Weather variables explained variations in RT (5.1-59.6%), in RR (13.0-17.8%) and in PR (22.1-25.4%). Relationships between weather variables the previous day and physiological responses were contradictory, with minimum and maximum values showing a negative relationship in contrast with a positive relationship for mean values.

Animals↗

PubMed1976

Survival of airborne influenza virus: effects of propagating host, relative humidity, and composition of spray fluids.

Influenza A virus, strain WSNH, propagated in bovine, human and chick embryo cell cultures and aerosolized from the cell culture medium, was maximally stable at low relative humidity (RH), minimally stable at mid-range RH, and moderately stable at high RH. Most lots of WSNH virus propagated in embryonated eggs and aerosolized from the allantoic fluid were also least stable at mid-range RH, but two preparations after multiple serial passage in eggs showed equal stability at mid-range and higher RH's. Airborne stability varied from preparation to preparations of virus propagated both in cell culture and embryonal eggs. There was no apparent correlation between airborne stability and protein content of spray fluid above 0.1 mg/ml, but one preparation of lesser protein concentration was extremely unstable at 50 to 80 per cent RH. Polyhydroxy compounds exerted a protective effect on airborne stability.

Aerosols↗

PubMed1983

Breed and sex influences on porcine haematological picture under hot humid climatic conditions.

An investigation was undertaken of some haematological characteristics of one indigenous and five exotic breeds of pigs kept on a farm in the hot, humid climate of Ibadan, Nigeria. The total white blood cell counts were not affected by breed and sex but the other parameters exhibited various degrees of response to these two variables, the males of each breed tending to have higher values than the females. The indigenous pigs generally had higher values than the exotic breeds. Of the latter, only the Landrace and Large White had haematological values somewhat similar to those of the West African indigenous pig. This suggests that the Landrace and Large White breeds may be more suited than the other exotic breeds investigated to the climatic conditions prevalent in Ibadan.

Age Factors↗

PubMed1996

Resumption of ovarian activity in zebu cows (Bos indicus) in the humid tropics: influence of body condition and levels of certain blood components related to nutrition.

This study investigated the relationship between resumption of ovarian activity and body condition in a herd of 20 zebu cows in the humid tropics. Blood chemistry profiles to monitor nutritional status were also evaluated. Plasma progesterone was used to determine ovarian activity. During the study, which lasted 18 weeks post partum, 7 of the animals resumed ovarian activity while 13 remained in the anoestrous stage. The beginning of the first luteal phase was registered on day 87 +/- 19 (range 60 to 106). The animals which resumed cyclicity were in significantly better body condition and had significantly higher mean body weight than anoestrous cows. In the group which resumed ovarian activity, calcium levels decreased significantly from 3 weeks before until the first rise of progesterone in the first normal cycle. The study was divided into 2 periods corresponding to weeks 0 to 8 (I) and 9 to 18 (II) based on the finding that until week 8 all animals were reproductively inactive. During period I there were no significant differences between the groups in blood concentrations of albumin, glucose, urea, cholesterol, calcium and phosphorus. During period II albumin was significantly higher and urea significantly lower in the cows resuming ovarian activity. The results suggest that cows able to maintain their body condition from calving through the early post-partum period will have shorter intervals to first post-partum oestrus than cows which have lost body weight. The lower urea and higher albumin levels in the cyclic animals probably reflected a better feed efficiency--the demands of lactation were compensated by an altered nitrogen metabolism.

Animals↗

PubMed1997

Nutritional and economic benefits of Leucaena and Gliricidia as feed supplements for small ruminants in humid West Africa.

Considering leguminous trees Leucaena and Gliricidia as good sources of quality food, on-station and on-farm studies were conducted in the humid zone of West Africa to establish animal responses to levels, times and forms of browse supplementation, to develop alternative feeding strategies for utilising limited feed supply and to assess the economic benefits of feed supplements as against the use of tree foliage as mulch for crop production. Results indicate that at any level of supplement, sheep grew twice as fast as goats. The main benefits of supplementation came through increased growth and survival. Form and level of supplementation had significant effect on intake. Economic analyses showed that crop response to mulching was the principal competing determinant of whether the use of tree foliage as feed supplement was economic.

Africa, Western↗

PubMed2004

Mucociliary function deteriorates in the clinical range of inspired air temperature and humidity.

OBJECTIVE: To test whether a reduction in air temperature within the clinical range [37 degrees C to 30, 100% relative humidity (RH)] altered mucus transport velocity (MTV) and ciliary beat frequency (CBF) in an in vitro ovine tracheal model. DESIGN: Controlled laboratory study. SETTING: University research laboratory. SUBJECTS: Farm-reared sheep. INTERVENTIONS: Tracheae were mounted flat in an organ bath. Krebs Henseleit bathed the serosal surface and air at 100% (RH) was passed over the mucosal surface at 4 l/min. Cilial beat frequency (CBF) was measured photo-electrically and mucus transport velocity (MTV) by timing movement. After 2 h at 37 degrees C (100% RH) the tissue was either maintained with those settings (controls), or the air temperature reduced to 34 degrees C or 30 degrees C. Tissue was taken for histology before and after each experiment. MEASUREMENTS AND RESULTS: CBF was 19.8+/-2.7 beats/s and MTV 5.7+/-2.6 mm/min in tissue exposed to air at 37 degrees C. Cilial activity continued for up to 6 h in the controls but mucus transport was more fragile. Reduction of the air temperature to either 34 degrees C or 30 degrees C led to a decrease in both CBF and MTV and, frequently, total mucociliary failure. There was a reduction in epithelial mucous cell numbers in all preparations. Tissues exposed to low temperature had additional abnormal histology. CONCLUSIONS: Delivery of inspired gas at 30 degrees C, or even 34 degrees C, with 100% RH may not be sufficient to prevent epithelial damage occurring during 6 h exposure.

Air↗

PubMedDate not supplied

Evidence for neuromuscular fatigue during high-intensity cycling in warm, humid conditions.

The purpose of this study was to examine and describe the neuromuscular changes associated with fatigue using a self-paced cycling protocol of 60-min duration, under warm, humid conditions. Eleven subjects [mean (SE) age 21.8 (0.8) years; height 174.9 (3.0) cm; body mass 74.8 (2.7) kg; maximum oxygen consumption 50.3 (1.8) ml.kg.min-1] performed one 60-min self-paced cycling time trial punctuated with six 1-min "all out" sprints at 10-min intervals, while 4 subjects repeated the trial for the purpose of determining reproducibility. Power output, integrated electromyographic signal (IEMG), and mean percentile frequency shifts (MPFS) were recorded at the mid-point of each sprint. There were no differences between trials for EMG variables, distance cycled, mean heart rate, and subjective rating of perceived exertion for the subjects who repeated the trial (n = 4). The results from the repeated trials suggest that neuromuscular responses to self-paced cycling are reproducible between trials. The mean heart rate for the 11 subjects was 163.6 (0.71) beats.min-1. Values for power output and IEMG expressed as a percentage of that recorded for the initial sprint decreased during sprints 2-5, with normalised values being 94%, 91%, 87% and 87%, respectively, and 71%, 71%, 73%, and 77%, respectively. However, during the final sprint normalised power output and IEMG increased to 94% and 90% of initial values, respectively. MPFS displayed an increase with time; however, this was not significant (P = 0.06). The main finding of this investigation is the ability of subjects to return power output to near initial values during the final of six maximal effort sprints that were included as part of a self-paced cycling protocol. This appears to be due to a combination of changes in neuromuscular recruitment, central or peripheral control systems, or the EMG signal itself. Further investigations in which changes in multiple physiological systems are assessed systematically are required so that the underlying mechanisms related to the development of fatigue during normal dynamic movements such as cycling can be more clearly delineated.

Adolescent↗

PubMed1999

Advantages of a smaller bodymass in humans when distance-running in warm, humid conditions.

Using a 65-kg athlete running a 2 h 10 min marathon as an example, we estimated that imbalances between approximately 1400 W of heat production and dissipation would occur in ambient temperatures of 17 degrees C at 90% relative humidity (rh) to 37 degrees C at 50% rh. Because heat production during running depends on body mass and heat loss depends on surface area, intercepts between predicted heat production and maximal heat loss with increasing speeds depend on an athlete's body mass. At 35 degrees C and 60% rh, a 45-kg athlete could maintain thermal balance by running a 2 h 13 min marathon at 19.1 km x h(-1) but a 75-kg athlete would only be able run a 3 h 28 min marathon at 12.2 km x h(-1). In both cases, the production of 970-1020 W of heat would necessitate the evaporation of at least 1.5-1.6 l of sweat per hour. A lower metabolic heat production in lighter runners at any given speed may be one reason why smallness of stature is an asset in distance running.

Adult↗

PubMed1999

Glycerol hyperhydration improves cycle time trial performance in hot humid conditions.

Eight competitive cyclists [mean peak oxygen consumption, (VO2(peak)) = 65 ml x min(-1) x kg(-1)] undertook two 60-min cycle ergometer time trials at 32 degrees C and 60% relative humidity. The time trials were split into two 30-min phases: a fixed-workload phase and a variable-workload phase. Each trial was preceded by ingestion of either a glycerol solution [1 g x kg(-1) body mass (BM) in a diluted carbohydrate (CHO)-electrolyte drink] or a placebo of equal volume (the diluted CHO-electrolyte drink). The total fluid intake in each trial was 22 ml x kg(-1) BM. A repeated-measures, double blind, cross over design with respect to glycerol was employed. Glycerol ingestion expanded body water by approximately 600 ml over the placebo treatment. Glycerol treatment significantly increased performance by 5% compared with the placebo group, as assessed by total work in the variable-workload phase (P < 0.04). There were no significant differences in rectal temperature, sweat rate or cardiac frequency between trials. Data indicate that the glycerol-induced performance increase did not result from plasma volume expansion and subsequently lower core temperature or lower cardiac frequencies at a given power output as previously proposed. However, during the glycerol trial, subjects maintained a higher power output without increased perception of effort or thermal strain.

Adult↗