Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Temperature environment”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 577 records · Page 32Linked to original sources
PubMed1995

[Effect of environmental temperature, cryopreservation and aging on Plasmodium vivax sporozoites developing into exoerythrocytic stages].

After Anopheles stephensi mosquitoes with salivary infection of Plasmodium vivax were put in environments with temperatures of 30 +/- 1 degrees C, 26 +/- 1 degrees C or 13 +/- 1 degrees C for 5 d, their glands were aseptically dissected and sporozoites were collected and inoculated into HepG2-A16 cell monolayers. Seven days post-inoculation the cultured materials were harvested and the exoerythrocytic schizonts and hypnozoites were observed under the microscope by using immunoperoxidase staining technique. The results showed that the sporozoite developing rate of 30 +/- 1 degrees C group and 13 +/- 1 degrees C group was significantly lower than that of 26 +/- 1 degrees C group (0.33%, 0.35% and 0.75% respectively). The proportion of hypnozoites in the total number of EE forms was the highest in the low temperature group (62.5%) compared with 26 +/- 1 degrees C and 30 +/- 1 degrees C group (40.1% and 42.7% respectively). Suggesting that the low environmental temperature first affected the viability of tachysporozoites or the phenotype of sporozoites and thus resulted in heightened hypnozoite rate. This is parallel to the epidemiological data that in the regions of high latitute vivax malaria with long incubation period was more frequently observed. When the sporozoites within the body of mosquito were cryopreserved at -70 degrees C or in liquid nitrogen for 24 h or 5 d respectively, the proportion of hypnozoite increased 87.4% and 82.4%, respectively. However, cryopreservation did not inactivate all of the tachysporozoites, indicating that the resistance to ultralow temperature in bradysporozoite was much greater than that in tachysporozoites. Aging of sporozoites decreased their developing rate and the exoerythrocytic (EE) schizonts were found to grow sluggishly and asynchronously, indicating that the size of EE schizont and the age of sporozoites are in negative correlation. Meantime, proportion of the hyponozoite decreased significantly.

Aging↗
PubMed1991

Behavioral thermoregulation of the toad, Bufo marinus: effects of air humidity.

Two experiments were performed. The first tested the hypothesis that the toad, Bufo marinus, will select a lower ambient temperature under dry environmental conditions. This behavioral response would reduce evaporative water loss and facilitate survival on land. The second experiment measured the effects of temperature on evaporative water loss. In the first experiment, toads were placed in a thermal gradient (11-40 degrees C) for 3 days. On days 1 and 3, water-filled dishes were placed along the temperature gradient and humid air was circulated through the chamber. On day 2, water dishes were removed, and dry air was circulated through the chamber. Body temperature (Tb) was recorded with a cloacal thermistor. Selected Tb was approximately 8.6 degrees C lower during the dry conditions than during the humid conditions. The behavioral hypothermia took about 6 h to develop. In the second experiment, a reduction in Tb from 17.7 to 12 degrees C reduced evaporative water loss by 42%. Consequently, behavioral hypothermia of the toad is an important adaptation to dry environmental conditions.

Animals↗
PubMed2005

Preferred temperature correlates with evaporative water loss in hylid frogs from northern Australia.

We measured temperature preferences of 12 species of hylid frogs (Litoria and Cyclorana) from northern Australia in a laboratory thermal gradient. These species represented a range of ecological habitat use (aquatic, terrestrial, arboreal), adult body size (0.5-60 g), and cutaneous resistance to water loss (Rc=0.6-63.1 s cm-1). We found significant differences among species in selected skin temperature and gradient temperature but not in the variances of these measures (an index of precision of temperature selection). The species' differences correlated significantly with cutaneous resistance to water loss, with more-resistant frogs selecting higher skin and substrate temperatures in the thermal gradient, even after phylogenetic relationships are taken into account. Because cutaneous resistance to water loss also correlates with ecological habit (arboreal>terrestrial>aquatic), we suggest that their higher resistance to water loss allows arboreal and terrestrial species better ability to tolerate high temperatures, where growth or locomotory speed may be higher, without the associated risk of desiccation.

Adaptation, Physiological↗
PubMed1993

Positive correlation between the blood pressure and heart rate response to the cold pressor test and the environmental temperature in older hypertensives.

The aims of our study were to evaluate whether there is any relationship between the environmental temperature and the response to the cold pressor test and if this relationship is different in younger and older hypertensive patients. We studied 100 mild-to-moderate hypertensives, aged 21 to 75 years. In the > or = 45 years group (46 patients) a significant positive correlation between the environmental temperature and the heart rate and blood pressure response to the cold pressor test was found. The relative humidity was not correlated with the response to the cold pressor test, but multiplying the mean temperature and the mean relative humidity enhanced the correlations of the environmental temperature. An increase in the mean temperature for the 20 days before the cold pressor test (the best correlated period) by 10 degrees C correlated with increases in the systolic blood pressure response by 10.5 mm Hg (P = .0195), the diastolic blood pressure response by 8 mmHg (P = .0079), the mean blood pressure by 9 mmHg (P = .0058), and the heart rate response by 3.8 beats/min (P = .0134). In < 45 years patients no environmental relationship of the response to cold pressor test was found. A chronic exposure to low temperatures is correlated with higher blood pressure levels--as previously reported--and, in contrast (but only in elderly), with a lower blood pressure response to acute cold stress. Our findings confirm the higher meteorological dependence of hemodynamics in the elderly, and suggest that the research protocols using the cold pressor test should adjust the response for the previous environmental temperature.

Adult↗
PubMed1984

Effects of postmortem delay and temperature on neurotransmitter receptor binding in a rat model of the human autopsy process.

Studies of neurotransmitter and drug receptor alterations in neurodegenerative disorders have contributed to our understanding of the pathophysiology of these conditions. The effect of postmortem delay in freezing tissue after death and prolonged storage of tissue prior to analysis on receptor binding assays are potential artifacts that may limit interpretation of the effects of disease on receptor populations. We used a rat model of the human autopsy process to study the effects of increasing postmortem delay and storage time on N-methylscopolamine (NMS), p-aminoclonidine (PAC), flunitrazepam (FLU), and spiperone binding in a variety of rat brain regions. The rat brains were cooled using a temperature-controlled environment and thermistor probe to follow cooling curves obtained in human brain. Brains were cooled to either room temperature (22 degrees C) or refrigerator temperature (4 degrees C). For three of the four receptors, receptor binding decreased as postmortem delay before freezing increased, particularly in tissue cooled to room temperature. Unlike binding at other receptor sites, FLU binding increased with increasing postmortem delay to freezing. Different effects on KD and Bmax were noted for each ligand studied. No effects of the freezing process itself or storage at -80 degrees C were detectable.

Animals↗
PubMed2005

Thermal sensation and comfort during exposure to local airflow to face or legs.

The present study examined the contribution of local airflow temperature to thermal sensation and comfort in humans. Eight healthy male students were exposed to local airflow to their faces (summer condition) or legs (winter condition) for 30 minutes. Local airflow temperature (Tf) was maintained at 18 degrees C to 36 degrees C, and ambient temperature (Ta) was maintained at 17.4 degrees C to 31.4 degrees C. Each subject was exposed to 16 conditions chosen from the combination of Tf and Ta. Based on the results of multiple regression analysis, the standardized partial regression coefficient of Tf and Ta were determined to be 0.93 and 0.13 in the summer condition, and 0.71 and 0.36 in the winter condition at the end of the exposure. Also, thermal comfort was observed to depend closely on the interrelation between Tf and Ta. The present data suggested that local airflow temperature is an important thermal factor regarding thermal sensation and comfort.

Adult↗
PubMed2005

Work in artificial cold environments.

The physiological characteristics of work in cold stores, as a typical artificial cold environment, are reviewed mainly from our various field and experimental studies. There are about 4,000 cold stores in Japan, and 85% of them are kept at temperatures below -20 degrees C. Although the duration of cold exposure per stay in a cold store was very short, forklift workers entered the cold stores very frequently. Cold stress and the decrease in workers' performance were the same as for continuous exposure to cold. Since the peripheral skin temperature of subjects at night is higher than that in the afternoon, they are less likely to feel cold or pain sensation at night. However, there was a marked decrease in rectal temperature and in manual performance. There is an increased risk of both hypothermia and accidents for those who work at night. The cold store workers, however, had adapted to cold through daily repeated cold exposures.

Adult↗
PubMed1978

Huddling by rat pups: group behavioral mechanisms of temperature regulation and energy conservation.

Body heat loss was attenuated and oxygen consumption was reduced by huddling in litters of developing rats. Rat pups derive physiological benefits from huddling similar to those enjoyed by adult mammals; these findings contrast with previous characterization of the altricial rat as poikilothermic. Huddling insulates by lessening the explosed body surface area of the participants, thus retarding heat loss and enhancing the efficiency of thermogenesis. These physical mechanisms of the clump are actively regulated by the pups. A novel quantitative measure of huddle size revealed a form of group regulatory behavior in rat pups whereby the surface expanded and contracted with increases and decreases in ambient temperature. The individual basis of this group regulatory activity was investigated by marking individual pups and observing them in huddles by means of time-lapse videography. It was found that individual animals circulate throught the huddle, frequently exchanging locations in the group. By studying the huddle positions of an anesthetized pup and a marked control sibling, dynamics of the pup flow were clarified. Ordinarily, the direction of movement was actively downward, into the pile; immobile pups "floated" on the surface. When the nest temperature was raised to thermoneutral, the direction of pup flow reversed and an immobile animal sank to the depths of the huddle. Through individual competitive adjustments the huddle behaves as a self-regulating unit which provides warmth and insulation to all its active members.

Age Factors↗
PubMed2003

Extent of fungal growth on fiberglass duct liners with and without biocides under challenging environmental conditions.

Eight brands of fiberglass duct liners, including three that contained biocides, were exposed to challenging environmental conditions that would promote fungal growth. Twenty-four rectangular sheet metal ducts in three groups of eight ducts per group were lined with the eight selected liners. Each group of ducts was exposed to one of the three test conditions within an environmental chamber for a period of 15 days. These conditions were a) 75 percent RH, b) 75 percent RH plus water spray, c) 75 percent RH plus dry nutrient, and d) 75 percent RH plus water plus nutrient. Viable spores of Aspergillus niger were aerosolized into each duct as seed. On the 16th day, air and surface samples for fungal spores were collected from inside ducts. The results of air sampling using N6 sampler and visual inspection indicated that two out of three biocide-containing liners, Permacote and Toughgard, inhibited fungal growth but only under condition A. The third biocide-containing liner, Aeroflex Plus, was effective even when it was wet (conditions A and B). All three biocide-containing liners failed to inhibit fungal growth under conditions C and D. Among the five other types of liners that did not contain biocides, ATCO Flex with a smooth Mylar coating was more preferable, exhibiting lower fungal activity during conditions A, B, and C. All liners failed under condition D when nutrient and water were added together. Surface sampling using adhesive tape failed to produce representative results, apparently due to rough/porous surface of duct liners. It was concluded that duct liners with biocide treatment could be less promoting to microbial growth under high humidity as long as their surfaces remain clean and water-free. A liner with an impermeable and smooth surface seems to be less subject to microbial growth under most conditions than biocide-containing liners having porous and/or rough surfaces.

Air Pollution, Indoor↗
PubMed2006

Isolation and characterization of a myo-inositol-1-phosphate synthase gene from yellow passion fruit (Passiflora edulis f. flavicarpa) expressed during seed development and environmental stress.

BACKGROUND AND AIMS: Myo-inositol-1l-phosphate synthase (MIPS) catalyses the conversion of d-glucose 6-phosphate to 1-l-myo-inositol-1-phosphate, the first and rate-limiting step in the biosynthesis of all inositol-containing compounds. Inositol phospholipids play a vital role in membrane trafficking and signalling pathways, auxin storage and transport, phytic acid biosynthesis, cell wall biosynthesis and production of stress-related molecules. In the present study, an MIPS cDNA from developing Passiflora edulis f. flavicarpa seeds was characterized and an investigation made into its spatial and differential expression, as well as changes in its transcription during exposure of growing plants to cold and heat stresses. METHODS: The MIPS-encoding gene was isolated by polymerase chain reaction (PCR) methods, and transcript levels were examined using semi-quantitative reverse transcription-PCR (RT-PCR) during seed development and in response to heat and cold stress. In addition, the copy number of the cloned PeMIPS1 gene in the genome of Passiflora edulis, P. eichleriana, P. caerulea, P. nitida and P. coccinea was determined by Southern blot analyses. KEY RESULTS: A full-length cDNA clone of the PeMIPS1 from P. edulis was isolated and characterized. Southern blot analyses indicated that the genomic DNA might have diverse sequences of MIPS-encoding genes and one copy of the cloned PeMIPS1 gene in the genomes of P. edulis, P. eichleriana, P. caerulea, P. nitida and P. coccinea. RT-PCR expression analyses revealed the presence of PeMIPS1 transcripts in ovules, pollen grains and leaves, and during the seed developmental stages, where it peaked at 9 d after pollination. The PeMIPS1 gene is differentially regulated under cold and heat stress, presenting a light-responsive transcription. CONCLUSIONS: Experimental data suggest that PeMIPS1 transcription plays an important role in the establishment of developmental programmes and during the response of plants to environmental changes. The PeMIPS1 is differentially transcribed during cold and heat stress, presenting a light response pattern, suggesting that it is important for environmental stress response.

Cloning, Molecular↗
PubMedDate not supplied

Temperature changes during exercise stress testing in children with burns.

It has been postulated that because of the extensive destruction of the skin and appendages after thermal injury, the thermoregulatory control mechanism would be impaired, and these patients would be intolerant to prolonged work. Preview studies demonstrate evidence that during work in a hot climate, patients with an extensively healed burn react with an excessive rise in body temperature. This study was designed to investigate the thermoregulatory response to exercise in pediatric patients with burns and to study changes in body temperature during exercise testing. Cardiopulmonary stress tests were completed in 32 children with a mean postburn time of 2.3 +/- 1.5 years and a mean burn size of 44% +/- 23% total body surface area. Exercise variables included expired volume, tidal volume, respiratory rate, tidal/dead space rate, heart rate, and work stage achieved. Temperature monitoring included external auditory canal temperature, burn scar, and normal skin temperature. Values were measured at baseline during and at maximum exercise. Our data indicate all patients reached the same endurance level regardless of the size of the total body surface area burn. Additionally, in a temperature-controlled environment, adequate heat dissipation in children with burns can be maintained during exercise testing without an excessive rise in body temperature.

Body Temperature↗
PubMed1978

The effect of aggregation on the lethality of morphine in mice.

Morphine was more lethal to mice housed in groups (aggregated) than to mice housed individually (isolated). The aggregation effect on morphine lethality was increased when ambient temperature was increased to 29 degrees C and abolished when ambient temperature was lowered to 19 degrees C. At 29 degrees C morphine produced hypothermia in isolated mice and hyperthermia in aggregated mice. Both isolated and aggregated mice were hypothermic after morphine administration at 19 degrees C. At 29 degrees C the locomotor activity of morphine-treated aggregated mice was significantly greater than that of morphine-treated isolated mice, whereas at 19 degrees C no significant difference was found. The locomotor activity time course of morphine-treated aggregated mice at 29 degrees C closely resembled the rectal temperature time course, which suggests that the hyperthermia in those animals involves an increase in heat production via an increase in locomotor activity. However, the hyperthermia observed was not sufficient to explain the increased lethality in aggregated mice. Differences between the aggregation effect on morphine lethality and that previously reported for amphetamine were discussed.

Animals↗
PubMed1983

The hand and environment (5):--Physiological changes of digital functions in two age groups studied by three stress tests under three environmental conditions.

Our serial physiological studies on "the hand and environment" have been reported these last three years. As a stressor to the hand, cold water immersion was the most effective, and the lower the room temperature was, each stressor became the more effective. As a detector for the function of the hand, the digital temperature was the most valuable. However, for studying the digital temperature, the room temperature should be set at more than 20 degrees C. The counting numbers were reduced by aging and colder temperatures. The nerve conduction velocity SCV or MCV became slower in a colder room, but showed no differences between the two age groups in this study.

Adult↗