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At least 55 records · Page 3Linked to original sources
PubMed2002

Host-pathogen interactions in a varying environment: temperature, behavioural fever and fitness.

We demonstrate how variable temperatures, mediated by host thermoregulation and behavioural fever, critically affect the interaction between a host (the desert locust, Schistocerca gregaria) and a pathogen (the fungus Metarhizium anisopliae var. acridum). By means of behavioural thermoregulation, infected locusts can raise their body temperatures to fever levels. The adaptive value of this behaviour was examined using three thermal regimes wherein maximum body temperatures achievable were: (i) below, or (ii) at normally preferred temperatures, or were (iii) unrestricted, allowing heightened fever temperatures. All infected locusts ultimately succumbed to disease, with median survival times of 8, 15 and 21 days post-infection, respectively. Crucially, only those locusts able to fever produced viable offspring. This represents, to our knowledge, the first demonstration of the adaptive value of behavioural fever following infection with a naturally occurring pathogen. By contrast, although normal host thermoregulation moderately reduced pathogen reproduction (by 35%), there was no additional negative effect of fever, resulting in an asymmetry in the fitness consequences of fever for the host and the pathogen. The dependency of the host-pathogen interaction upon external abiotic conditions has implications for how virulence and resistance are treated both theoretically and in the management of pests and diseases.

Adaptation, Physiological↗
PubMed1998

Phylogenetic analysis of nonthermophilic members of the kingdom crenarchaeota and their diversity and abundance in soils

Within the last several years, molecular techniques have uncovered numerous 16S rRNA gene (rDNA) sequences which represent a unique and globally distributed lineage of the kingdom Crenarchaeota that is phylogenetically distinct from currently characterized crenarchaeotal species. rDNA sequences of members of this novel crenarchaeotal group have been recovered from low- to moderate-temperature environments (-1.5 to 32 degreesC), in contrast to the high-temperature environments (temperature, >80 degreesC) required for growth of the currently recognized crenarchaeotal species. We determined the diversity and abundance of the nonthermophilic members of the Crenarchaeota in soil samples taken from cultivated and uncultivated fields located at the Kellogg Biological Station's Long-Term Ecological Research site (Hickory Corners, Mich.). Clones were generated from 16S rDNA that was amplified by using broad-specificity archaeal PCR primers. Twelve crenarchaeotal sequences were identified, and the phylogenetic relationships between these sequences and previously described crenarchaeotal 16S rDNA sequences were determined. Phylogenetic analyses included nonthermophilic crenarchaeotal sequences found in public databases and revealed that the nonthermophilic Crenarchaeota group is composed of at least four distinct phylogenetic clusters. A 16S rRNA-targeted oligonucleotide probe specific for all known nonthermophilic crenarchaeotal sequences was designed and used to determine their abundance in soil samples. The nonthermophilic Crenarchaeota accounted for as much as 1.42% +/- 0.42% of the 16S rRNA in the soils analyzed.

Journal Article↗
PubMed1996

[Changes in thermoregulation and age. Hypothermia and hyperthermia].

The author presents a review of changes in thermoregulation in various ages. The changes at infant and older ages are compared in contrast to thermoregulation in healthy adults. Hypothermia occurs in all age groups, especially in the aged. Then it is determined by both low temperature of environment and impairment in production and expenditure of heat despite the normal environment temperature. A special form of hypothermia is represented by intraoperative hypothermia in the course of surgical performance under general anaesthesia. Hyperthermia occurs most frequently as heatstroke in consequence of high environmental temperature. The author presents etiopathogenesis and pathomechanisms, possible treatment and prevention in thermoregulation disturbances. (Tab. 6, Ref. 79.).

Adolescent↗
PubMed1982

Human exposure to sulfur dioxide and ozone in a high temperature-humidity environment.

In order to examine the role of high temperature and humidity in the possible synergistic action of ozone and sulfur dioxide on human pulmonary function previously reported by some investigators and repudiated by others, we randomly exposed eight healthy young male nonsmokers to filtered air, 0.4 ppm SO2, 0.4 ppm O3, and 0.4 ppm SO2 plus 0.4 ppm O3 at 35 degrees C--85% rh for 2 hours. Subjects exercised for 15 minutes of each half hour at a workload sufficient to elicit a minute ventilation of 30 liters (BTPS). Pulmonary function tests were performed prior to, during, and following exposure. Observed alterations in pulmonary functions in the SO2 + O3 exposure reflected the changes occurring during the O3 exposure, clearly indicating that no synergistic effects related to the additional presence of SO2 were evident in this study. We considered factors suggested as causes for a potential synergism in comparing the conflicting studies on O3 and SO2, and suggest that factors other than temperature-humidity and/or sulfate aerosol production must be sought.

Adult↗
PubMed1987

Hypothermia and poikilothermia induced by a kappa-agonist opioid and a neuroleptic.

When an opioid acting selectively at the kappa opioid receptor is administered subcutaneously to rats along with a neuroleptic at an ambient temperature of 20 degrees C a marked hypothermia ensues. The combination of U-50,488H (a kappa agonist) and chlorpromazine (a neuroleptic) caused a drop in body temperature amounting to as much as 11 degrees C, with all animals recovering after 24-48 h. Naloxone partially reversed the hypothermia. Similar, but less dramatic, decreases in body temperature occurred with other neuroleptics and weaker kappa agonists. The induction of poikilothermia was indicated when the body temperature approached the environment temperature and lethality resulted in 100% of the animals at ambient temperatures of 5 degrees C or 35 degrees C. The potential utility of this or similar combinations of drugs lies in such diverse applications as cardiac surgery, treatment of the near-drowning syndrome and space travel.

3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cycloh↗
PubMed1998

[Effects of opium peptide system on the temperature regulation of mice under dry-hot environment with different temperature].

The Kunming mice were selected as subjects. Animals were allowed to move and drink freely. The Naloxone(0.02 mg/g) was injected by abdominal cavity. The ability to body temperature stable by mice under the environment with high temperature (41 degrees C, 43 degrees C) was observed. The results showed that after obstructing opium receptor by Naloxone, the ability mentioned above was reduced obviously.

Animals↗
PubMed1996

Changes in the ultrastructure of human cells related to certain biological responses under hyperthermic culture conditions.

It has been reported that human cancer cells are more sensitive to high temperatures than normal human cells, and that cell proliferation and viability are affected by the temperature environment. In this study, we proceeded further, and turning our attention to the close relationship between cell morphology and temperature, used two human cancer cell lines and two normal cell strains to investigate how intracellular fine structure changes in a high temperature environment. The results showed that 1) both of the human cancer cell lines were more sensitive to high temperature than the normal human cell strains, and a difference between the temperature sensitivity of the human cancer cell lines was also confirmed. 2) There is no clear difference between the manner in which normal human cells and malignant human cells are affected by hyperthermia. 3) Among other cell structures, effects on the membrane system were observed as early changes in cell structure. The mitochondria were particularly affected, followed by the rER. 4) Changes in the nucleoplasm, as well as the nuclear membrane (inner membrane), and then the intranuclear chromatin, etc., were observed as late changes. 5) Changes in mitochondria were observed in the early stage, but temporarily tended to recover, and were then fatally affected again in the late stage. We discuss the relationship between cell proliferation, cell viability, and cell ultrastructure based on the above results.

Adult↗
PubMed2005

Host-parasite and genotype-by-environment interactions: temperature modifies potential for selection by a sterilizing pathogen.

Parasite-mediated selection is potentially of great importance in modulating genetic diversity. Genetic variation for resistance, the fuel for natural selection, appears to be common in host-parasite interactions, but responses to selection are rarely observed. In the present study, we tested whether environmental variation could mediate infection and determine evolutionary outcomes. Temperature was shown to dramatically alter the potential for parasite-mediated selection in two independent laboratory infection experiments at four temperatures. The bacterial parasite, Pasteuria ramosa, was extremely virulent at 20 degrees C and 25 degrees C, sterilizing its host, Daphnia magna, so that females often never produced a single brood. However, at 10 degrees C and 15 degrees C, the host-parasite interaction was much more benign, as nearly all females produced broods before becoming sterile. This association between virulence and temperature alone could stabilize coexistence and lead to the maintenance of diversity, because it would weaken parasite-mediated selection during parts of the season. Additionally, highly significant genotype-by-environment interactions were found, with changes in clone rank order for infection rates at different temperatures. Our results clearly show that the outcome of parasite-mediated selection in this system is strongly context dependent.

Animals↗
PubMed1998

Genotype-environment interaction at quantitative trait loci affecting sensory bristle number in Drosophila melanogaster.

The magnitude of segregating variation for bristle number in Drosophila melanogaster exceeds that predicted from models of mutation-selection balance. To evaluate the hypothesis that genotype-environment interaction (GEI) maintains variation for bristle number in nature, we quantified the extent of GEI for abdominal and sternopleural bristles among 98 recombinant inbred lines, derived from two homozygous laboratory strains, in three temperature environments. There was considerable GEI for both bristle traits, which was mainly attributable to changes in rank order of line means. We conducted a genome-wide screen for quantitative trait loci (QTLs) affecting bristle number in each sex and temperature environment, using a dense (3.2-cM) marker map of polymorphic insertion sites of roo transposable elements. Nine sternopleural and 11 abdominal bristle number QTLs were detected. Significant GEI was exhibited by 14 QTLs, but there was heterogeneity among QTLs in their sensitivity to thermal and sexual environments. To further evaluate the hypothesis that GEI maintains variation for bristle number, we require estimates of allelic effects across environments at genetic loci affecting the traits. This level of resolution may be achievable for Drosophila bristle number because candidate loci affecting bristle development often map to the same location as bristle number QTLs.

Animals↗
PubMed1995

Pulmonary arteriole hypertrophy in broilers with pulmonary hypertension syndrome (ascites).

Two experiments were conducted to determine the effect of low ventilation or cool temperature environments on pulmonary arteriole hypertrophy. Male broilers were maintained under control or low ventilation conditions in Experiment 1, whereas male broiler breeder by-product chicks were exposed to cool temperature conditions in Experiment 2. Birds were randomly selected for histological evaluation of lung tissue in both experiments. In Experiment 1, birds that had pulmonary hypertension syndrome (PHS+) exhibited a greater degree of inflammation of lung tissue at 5 and 7 wk of age than controls or birds that did not have PHS (PHS-). These PHS+ birds also had higher numbers of cartilaginous osseous nodules at 3 and 7 wk of age than controls. Morphometric analyses revealed that PHS+ birds in Experiment 1 had a thicker medial layer associated with 100 to 200 microns diameter pulmonary arterioles at 7 wk of age, and 50 to 100 microns arterioles at 3 and 7 wk of age than PHS- or control birds. In Experiment 2, PHS+ birds exhibited a thicker medial layer in pulmonary arterioles at 7 wk of age than did PHS- birds, but there were no differences in medial layer thickness at 5 wk of age nor were there differences in the degree of inflammation or amount of osseous nodule formation between PHS+ and PHS- birds at 5 and 7 wk of age. Thus, pulmonary arteriole hypertrophy was observed in birds having PHS in response to both low ventilation and cool temperature environments and this hypertrophy occurred with or without a coincident inflammatory response in lung tissue.

Animals↗