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PubMed2006

RNA helicases and abiotic stress.

RNA helicases function as molecular motors that rearrange RNA secondary structure, potentially performing roles in any cellular process involving RNA metabolism. Although RNA helicase association with a range of cellular functions is well documented, their importance in response to abiotic stress is only beginning to emerge. This review summarizes the available data on the expression, biochemistry and physiological function(s) of RNA helicases regulated by abiotic stress. Examples originate primarily from non-mammalian organisms while instances from mammalian sources are restricted to post-translational regulation of helicase biochemical activity. Common emerging themes include the requirement of a cold-induced helicase in non-homeothermic organisms, association and regulation of helicase activity by stress-induced phosphorylation cascades, altered nuclear-cytoplasmic shuttling in eukaryotes, association with the transcriptional apparatus and the diversity of biochemical activities catalyzed by a subgroup of stress-induced helicases. The data are placed in the context of a mechanism for RNA helicase involvement in cellular response to abiotic stress. It is proposed that stress-regulated helicases can catalyze a nonlinear, reversible sequence of RNA secondary structure rearrangements which function in RNA maturation or RNA proofreading, providing a mechanism by which helicase activity alters the activation state of target RNAs through regulation of the reaction equilibrium.

Animals↗
PubMed1984

Profiles of luteinizing hormone, follicle-stimulating hormone, testosterone and prolactin in rams of diverse breeds: effects of contrasting short (8L:16D) and long (16L:8D) photoperiods.

Mature rams of Polled Dorset, Finnish Landrace, Rambouillet and Suffolk breeding were maintained in a temperature-controlled environment and exposed to two consecutive cycles of short (8L:16D) followed by long (16L:8D) days. Serum hormone concentrations were determined in weekly samples and in 24-h profiles characterized at the end of each lighting schedule (i.e., 12, 24, 36 and 48 weeks). In all four breeds, the pituitary-testicular axis was more active during short days as compared with long days and the magnitudes of changes in serum luteinizing hormone (LH), follicle-stimulating hormone (FSH) and testosterone concentrations were greater for the two most seasonal breeds, Finnish Landrace and Suffolks. In comparison to other breeds, Finnish Landrace rams had significantly (P less than 0.05) higher mean LH levels, showed the greatest number of LH peaks/24 h, and had the highest mean testosterone levels at the end of both periods of short days, while Rambouillet rams had significantly (P less than 0.05) lower testosterone. Rambouillets also showed the smallest changes in pulsatile LH and testosterone secretion and displayed the least number of LH peaks/24 h following short days. Serum FSH levels were significantly (P less than 0.05) higher in Finnish Landrace and Suffolk rams than in Polled Dorsets and Rambouillets after 12 weeks of short days. Breed differences in serum LH, FSH and testosterone were not apparent following long days. Prolactin levels in Rambouillet rams were significantly (P less than 0.05) lower than in the other breeds following both periods of long days. These results indicate that breed differences exist in mature rams with regard to hormone secretory profiles. Breed differences in serum gonadotropin and testosterone are only apparent during short days when the hypothalamo-pituitary-testicular axis in rams is considered most active. Likewise, breed differences in prolactin are noticeable only during long days when secretion of this hormone is enhanced. Breed differences in LH, FSH and testosterone secretion in rams during short days might be related to seasonality of mating and/or fecundity of breed types.

Animals↗
PubMed1995

222Rn progeny surface deposition and resuspension--residential materials.

The radiological hazard of radon gas to occupants in residential environments is from the particulate progeny 218Po, 214Pb, 214Bi, and 214Po, rather than 222Rn itself. Attachment to aerosols, plateout, and resuspension impact on the progeny airborne concentrations. Plateout rate and resuspension factors were measured for air change (ventilation) rates, 0.01 to 1.0 h-1, in a 0.28 m3 test chamber for interior residential materials of wallboard, drapery, carpet, ceiling tile, and concrete, and from 0.05 to 2.5 h-i for hardwood and glass. The overall accuracy of the plateout rate values is estimated to be +/- 13% standard deviation. For the different materials, the plateout rates for 218Po progeny varied by a factor of nearly six. Drapery gave the largest plateout rates. Resuspension rate factors, R, were measured for hardwood, wallboard, drapery, carpet, and glass by a new time-dependent measurement method based on the difference in buildup rate of 214Po to equilibrium caused by resuspension. Values for R obtained for hardwood, wallboard, drapery, carpet and glass were 0.31, 0.29, 0.44, 0.55, and 0.36, respectively ( +/- 30% standard deviation). All measurements were made in a continuous air conditioned interior environment maintaining temperature at 22.2 +/- 1.1 degrees C and relative humidity of 30% +/- 10%. Computations were made of equivalent plateout rates and equilibrium fractions for a standard 5 m x 5 m x 3 m high room to provide values to compare with other work.

Construction Materials↗
PubMedDate not supplied

The burned patient's response to the environment: the 1991 Everett Idris Evans Memorial Lecture.

Homeostatic reflexes are believed to supply the means by which the body adapts to changes in the environment (posture, temperature, etc.) and, hence, it might be expected that their importance would increase when the body is disturbed by trauma. In fact, these reflexes are largely abandoned in the response to danger (the defense-arousal reaction), and it is only after simple fluid loss that a limited improvement is seen, that is, an increase in the sensitivity of the baroreflex. Whenever tissue damage generates nociceptive C fiber afferent impulses, there is serious and relatively long-lasting inhibition of the baroreflex and of all aspects of neural thermoregulation. Significant changes occur after quite moderate injuries and do not depend on any reduction in tissue oxygenation. In children with burns in whom early pyrexia is common, central thermoregulation may also be affected by cytokine pyrogens. These changes have implications for the management of patients with all types of injuries. However, further analysis is needed if we are to understand these responses and their role in the body's defense; without this knowledge, we shall not be able to modulate them effectively.

Animals↗
PubMed1997

Improved running performance in hot humid conditions following whole body precooling.

On two separate occasions, eight subjects controlled speed to run the greatest distance possible in 30 min in a hot, humid environment (ambient temperature 32 degrees C, relative humidity 60%). For the experimental test (precooling), exercise was preceeded by cold-water immersion. Precooling increased the distance run by 304 +/- 166 m (P < 0.05). Precooling decreased the pre-exercise rectal and mean skin temperature by 0.7 degrees C and 5.9 degrees C, respectively (P < 0.05). Rectal and mean skin temperature were decreased up to 20 and 25 min during exercise, respectively (P < 0.05). Mean body temperature decreased from 36.5 +/- 0.1 degrees C to 33.8 +/- 0.2 degrees C following precooling (P < 0.05) and remained lower throughout exercise (P < 0.01) and at the end of exercise (by 0.8 degrees C; P < 0.05). The rate of heat storage at the end of exercise increased from 113 +/- 45 to 249 +/- 55 W.m-2 (P < 0.005). Precooling lowered the heart rate at rest (13%), 5 (9%), and 10 min (10%) exercise (P < 0.05) and increased the end of exercise blood lactate from 4.9 +/- 0.5 to 7.4 +/- 0.9 mmol.L-1 (P < 0.01). The VO2 at 10 and 20 min of exercise and total body sweating are not different between tests. In conclusion, water immersion precooling increased exercise endurance in hot, humid conditions with an enhanced rate of heat storage and decreased thermoregulatory strain.

Adult↗
PubMed1997

Environmental and genetic effects on circadian clock-regulated gene expression in Arabidopsis.

Expression patterns of the cold-circadian rhythm-RNA binding (CCR) and chlorophyll a/b binding (CAB) protein genes have circadian rhythms with phases that are different from each other and are affected differently by cold (4 degrees C) treatment. Cycling of CCR and CAB RNA levels was observed in Arabidopsis seedlings grown for 5 days at 4 degrees C under a light/ dark photoperiod, although the cycling had reduced amplitude compared with normal growth conditions (20 degrees C). CCR RNA levels were elevated in the cold, whereas CAB RNA levels were reduced in the cold relative to levels in control seedlings. Cold pulses (4 degrees C for 12 or 20 hr) under continuous light affected the rhythms of CCR and CAB RNA levels in similar ways. The 12-hr cold pulse caused a 4-hr phase delay in both rhythms, whereas the 20-hr cold pulse resulted in a 12-hr phase delay in both rhythms. The timing of CAB expression 1 (toc1) mutation shortened the period of the CCR rhythm, matching previous results for the regulation of the CAB-luciferase (CAB-luc) transgene in this mutant. The results suggest that CCR and CAB share clock machinery but are regulated by downstream components that are affected differently by the cold. Also, the circadian clock regulating these genes in Arabidopsis has a cold-sensitive phase under continuous light conditions.

Arabidopsis↗
PubMed1977

An analysis of factors influencing the isolation rate of herpes simplex virus.

Attempts were made to improve the rate of isolation of herpes simplex virus (HSV) from clinical specimens by minimizing loss of virus infectivity during transportation and employing the most sensitive cells for isolation. Basical analyses using standard strains of type 1 and type 2 HSV indicated that virus titer decrease was marked even at low temperatures in environments free of proteinous stabilizer such as normal serum or tissue extract, negating the generally held concept that HSV is stable in distilled water. YLE (Earle-lactalbumin HYDROLYSATE-YEAST EXTRACT) medium containing 20% inactivated calf serum was determined to be a transport medium of choice, because degradation of suspended virus during storage and freeze-thawing was negligible and loss of virus during Millipore filtration was minimal. Special coating of the membrane could also be obviated by the use of this solution. In a cell susceptibility test using clinical specimens, secondary rabbit kidney (SRK) cells were the most sensitive, showing a quick development of cytopathic effect. Vero and RK-13 cells were the second best, whereas monkey kidney, HeLa and L cells were far less sensitive. A total of 136 specimens from suspected cases, sent by dermatologists, were tested using SRK cells, and 99 strains of type 1 and 15 strains of type 2 HSV were isolated. Excluding one case from which vaccinia virus was isolated, the isolation rate of HSV was 84.4%.

Animals↗
PubMed2006

Characterization of the Arabidopsis thermosensitive mutant atts02 reveals an important role for galactolipids in thermotolerance.

Plants are constantly challenged with various abiotic stresses in their natural environment. Elevated temperatures have a detrimental impact on overall plant growth and productivity. Many plants increase their tolerance to high temperatures through an adaptation response known as acquired thermotolerance. To identify the various mechanisms that plants have evolved to cope with high temperature stress, we have isolated a series of Arabidopsis mutants that are defective in the acquisition of thermotolerance after an exposure to 38 degrees C, a treatment that induces acquired thermotolerance in wild-type plants. One of these mutants, atts02, was not only defective in acquiring thermotolerance after the treatment, but also displayed a reduced level of basal thermotolerance in a 30 degrees C growth assay. The affected gene in atts02 was identified by positional cloning and encodes digalactosyldiacylglycerol synthase 1 (DGD1) (the atts02 mutant was, at that point, renamed dgd1-2). An additional dgd1 allele, dgd1-3, was identified in two other mutant lines displaying altered acquired thermotolerance, atts100 and atts104. Expression patterns of several heat shock proteins (HSPs) in heat-treated dgd1-2 homozygous plants were similar to those from identically treated wild-type plants, suggesting that the thermosensitivity in the dgd1-2 mutant was not caused by a defect in HSP induction. Lipid analysis of wild-type and mutant plants indicated a close correlation between the ability to acquire thermotolerance and the increases in digalactosyldiacylglycerol (DGDG) level and in the ratio of DGDG to monogalactosyldiacylglycerol (MGDG). Thermosensitivity in dgd1-2 and dgd1-3 was associated with (1) a decreased DGDG level and (2) an inability to increase the ratio of DGDG to MGDG upon exposure to a 38 degrees C sublethal temperature treatment. Our results suggest that the DGDG level and/or the ratio of DGDG to MGDG may play an important role in basal as well as acquired thermotolerance in Arabidopsis.

Acclimatization↗
PubMed1993

Bacterial solute transport proteins in their lipid environment.

The cytoplasmic membrane of bacteria is a selective barrier that restricts entry and exit of solutes. Transport of solutes across this membrane is catalyzed by specific membrane proteins. Integral membrane proteins usually require specific lipids for optimal activity and are inhibited by other lipid species. Their activities are also sensitive to the lipid bilayer dynamics and physico-chemical state. Bacteria can adapt to changes in the environments (respective temperature, hydrostatic pressure, and pH) by altering the lipid composition of the membrane. Homeoviscous adaptation results in the maintenance of the liquid-crystalline phase through alterations in the degree of acyl chain saturation and branching, acyl chain length and the sterol content of the membrane. Homeophasic adaptation prevents the formation of non-bilayer phases, which would disrupt membrane organization and increase permeability. A balance is maintained between the lamellar phase, preferring lipids, and those that adopt a non-bilayer organization. As a result, the membrane proteins are optimally active under physiological conditions. The molecular basis of lipid-protein interactions is still obscure. Annular lipids stabilize integral membrane proteins. Stabilization occurs through electrostatic and possibly other interactions between the lipid headgroups and the charged amino acid residues close to the phospholipid-water interface, and hydrophobic interactions between the fatty acyl chains and the membrane-spanning segments. Reconstitution techniques allow manipulation of the lipid composition of the membrane in a way that is difficult to achieve in vivo. The physical characteristics of membrane lipids that affect protein-mediated transport functions have been studied in liposomal systems that separate an inner and outer compartment. The activity of most transport proteins is modulated by the bulk physical characteristics of the lipid bilayer, while specific lipid requirements appear rare.

Bacteria↗
PubMed2005

Verification of the exponential model of body temperature decrease after death in pigs.

The authors have conducted a systematic study in pigs to verify the models of post-mortem body temperature decrease currently employed in forensic medicine. Twenty-four hour automatic temperature recordings were performed in four body sites starting 1.25 h after pig killing in an industrial slaughterhouse under typical environmental conditions (19.5-22.5 degrees C). The animals had been randomly selected under a regular manufacturing process. The temperature decrease time plots drawn starting 75 min after death for the eyeball, the orbit soft tissues, the rectum and muscle tissue were found to fit the single-exponential thermodynamic model originally proposed by H. Rainy in 1868. In view of the actual intersubject variability, the addition of a second exponential term to the model was demonstrated to be statistically insignificant. Therefore, the two-exponential model for death time estimation frequently recommended in the forensic medicine literature, even if theoretically substantiated for individual test cases, provides no advantage as regards the reliability of estimation in an actual case. The improvement of the precision of time of death estimation by the reconstruction of an individual curve on the basis of two dead body temperature measurements taken 1 h apart or taken continuously for a longer time (about 4 h), has also been proved incorrect. It was demonstrated that the reported increase of precision of time of death estimation due to use of a multiexponential model, with individual exponential terms to account for the cooling rate of the specific body sites separately, is artifactual. The results of this study support the use of the eyeball and/or the orbit soft tissues as temperature measuring sites at times shortly after death. A single-exponential model applied to the eyeball cooling has been shown to provide a very precise estimation of the time of death up to approximately 13 h after death. For the period thereafter, a better estimation of the time of death is obtained from temperature data collected from the muscles or the rectum.

Animals↗
PubMed1973

Elevation in set point for body temperature regulation after prolonged exercise.

1. In nine healthy men, after prolonged exercise (approximately 37 km walk and 2.5 km ascent and descent in 9 hr) deep body temperature at rest stabilized at a higher level than in the absence of previous exercise.2. The increase, approximately 0.36 degrees C, was recorded at both oral and rectal sites. It persisted while the subjects rested in warm and in cool surroundings, and disappeared about 11 hr after the end of exercise.3. The increase in body temperature after exercise was accompanied by a similar increase in the body temperature at which sweating started during body heating.4. After exercise the subjects' metabolic response to cold air (13.6 degrees C) was normal or increased in spite of the elevation in body temperature.5. Blood glucose concentration was never lower than 3.1 mM during these experiments.6. The temperature changes are most easily explained by mild pyrexia due to the release of endogenous pyrogen associated with minor tissue damage.

Adult↗
PubMed1973

Failure of thermoregulation in the cold during hypoglycaemia induced by exercise and ethanol.

1. After young men had exercised for approximately 2 hr at 70% maximum O(2) uptake, and taken 28 ml. ethanol by mouth, their mean blood glucose fell to 2.17 mM. It fell further to 1.77 mM during a 30 min exposure to air at 14.5 degrees C. Plasma lactate, glycerol, beta-hydroxybutyrate and free fatty acid concentrations increased.2. Rectal temperature fell to reach a mean level of 34.49 degrees C by the end of the cold exposure; oesophageal temperature fell to as low as 33.00 degrees C in one case.3. Virtually no increase in metabolic rate and no visible shivering occurred during the cold exposure.4. Administration of glucose (mean 60.4 g) prevented the falls in temperature, and restored metabolic response to the cold to the size found in control experiments without exercise or ethanol.5. Neither exercise without ethanol or ethanol without exercise significantly lowered the blood glucose or impaired the maintenance of body temperature in the cold.6. One obese subject showed almost as great a fall in blood glucose and depression of metabolic response to cold as the thinner men, but no fall in body temperature.

Adult↗
PubMed1974

Behavioral thermoregulation in lizards: importance of associated costs.

The Puerto Rican lizard Anolis cristatellus behaviorally regulates body temperature in an open habitat but passively tolerates lower and more variable temperatures in an adjacent forest where basking sites are few and distant. Thermoregulation may be adaptive only when costs resulting from associated losses of time and energy are low.

Adaptation, Physiological↗
PubMed1995

Venus reconsidered.

The Magellan imagery shows that Venus has a crater abundance equivalent to a surface age of 300 million to 500 million years and a crater distribution close to random. Hence, the tectonics of Venus must be quiescent compared to those of Earth in the last few 100 million years. The main debate is whether the decline in tectonic activity on Venus is closer to monotonic or episodic, with enhanced tectonism and volcanism yet to come. The former hypothesis implies that most radioactive heat sources have been differentiated upward; the latter, that they have remained at depth. The low level of activity in the last few 100 million years inferred from imagery favors the monotonic hypothesis; some chemical evidence, particularly the low abundance of radiogenic argon, favors the episodic. A problem for both hypotheses is the rapid decline of thermal and tectonic activity some 300 million to 500 million years ago. The nature of the convective instabilities that caused the decline, and their propagation, are unclear.

Elements↗