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PubMed1976

Changes in muscle lipid composition and resistance adaptation to temperature in the freshwater crayfish, Austropotamobius pallipes.

The phospholipid and fatty acid composition of muscle lipid extracts from crayfish acclimated to 4 C and 25 C (18 hr-light photoperiod) were analyzed. The phospholipid content and class distribution, and cholesterol content were unaffected by the acclimation treatment. Unsaturation of muscle phosphoglycerides was higher in cold acclimated crayfish. Serine/inositol phosphoglycerides from cold-acclimated animals showed somewhat higher proportions of mono- and polyunsaturated fatty acids, whereas choline and ethanolamine phosphoglycerides were less affected. This was correlated with a decreased resistance of cold-acclimated crayfish to lethal high temperature. Acclimation at 4 C under an 8 hr-light photoperiod caused an increased fatty acid unsaturation of the total phospholipid fraction compared to the 4 C, 18 hr-light photoperiod acclimated animals. The resistance of 4 C acclimated crayfish to lethal high temperature, however, was unaffected by daylength treatment. The resistance of freshwater crayfish to lethal high temperature is not simply related to the degree of saturation of the muscle phospholipids. It is suggested that a breakdown in the integrity of a bulk-lipid bilayer is not involved in the process of heat death; rather, that a membrane-bound protein factor, whose thermal sensitivity is modified by changes in its phospholipid environment during temperature adaptation but not during photoperiod adaptation, is the primary site of heat injury.

Acclimatization↗
PubMed2006

Endemic mycoses: blastomycosis, histoplasmosis, and sporotrichosis.

The endemic mycoses are diverse group of fungi that share several characteristics. They are able to cause disease in healthy hosts, they each occupy a specific ecologic niche in the environment, and they exhibit temperature dimorphism, existing as molds in the environment at temperature of 25 degrees C to 30 degrees C, and as yeasts, or spherules in the case of coccidioidomycosis, at body temperatures. This article discusses histoplasmosis and blastomycosis. Sporotrichosis, which differs in that it is usually a localized lymphocutaneous infection, is included because it shares the characteristics of endemic mycoses.

Antifungal Agents↗
PubMed1975

The membrane of giant molluscan neurons: electrophysiologic properties and the origin of the resting potential.

The molluscan neuron, because of its large size and accessibility, has been an important model for studying the electrophysiology of nerve cells. This review catalogs data about specific molluscan neurons, but the greater importance of this material is in the broad picture of how a neuronal membrane maintains internal potential and is responsive to changes in the environment. Electrical properties of the membrane. The mechanisms which contribute to the resting potential in molluscan neurons can be separated into ionic and metabolic components. When the electrogenic sodium pump is eliminated experimentally, the ionic component of the potential follows the constant field equation quite closely. Many of the "constants" and "parameters" which characterize the membrane of molluscan neurons are actually variables which depend upon temperature, ionic environment, and membrane potential. The evaluation of the electrical parameters is complicated by extensive infoldings of the somatic membrane, and by large axons which drain current from the soma. Most molluscan neurons have a very high specific membrane resistance and a correspondingly low potassium permeability. Membrane capacitance is close to the 1 microF/cm2 value which characterizes biological membranes. The current-voltage relation of molluscan neurons may be complicated by inward-going rectification, but if that is inhibited the I-V curve follows the prediction of either the constant field equation or a simple electrical model. Factors which modify membrane behavior. The resting potential of molluscan neurons is very sensitive to changes in temperature and Ko, through a combination of effects upon the electrogenic sodium pump, inward-going rectification, and the membrane "parameters". Inward-going rectification depends upon a rectifying K conductance, and can be eliminated by cold or the removal of Ko. Strong or prolonged currents have time-dependent effects upon the membrane, and excessive polarization leads to a "high conductance state". The underlying (non-rectifying) K permeability of the membrane is relatively insensitive to temperature and ionic changes, whereas the Na permeability increases with warming. Membrane resistance varies with both temperature and ions (because the I-V curve is sensitive to these conditions) but membrane capacitance is relatively insensitive to external factors. Electrogenic sodium transport. Sodium transport is electrogenic in molluscan neurons. It can be stimulated by warm temperatures and an excess of substrate (e.g. high Nai); it can be inhibited by cold, by an absence of substrate (e.g. low Ko), or by pharmacologic agents such as cyanide or ouabain.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1979

Within-species variation in the development of ultrasonic signaling of preweanling rats.

The development of litter and individual differences in the rate of ultrasonic signaling of neonatal rats was studied. Systematic variations among litters and individuals emerged, without differential treatment. These differences were not correlated with variations in general development as indexed by body weight. Two experiments using a cross-fostering design showed that litter differences developed independently of variations in postnatal environment. These results indicate that the variations among litters in ultrasound rate have a prenatal, possibly genetic, etiology and may represent reliable indicants of response to environmental stress.

Animals↗
PubMed1972

The upper temperature limit for eukaryotic organisms.

An upper temperature limit near 60 degrees for eukaryotic organisms is documented by results of a systematic search for fungi able to grow at higher temperatures. Samples from hot springs, thermal soils, self-heating coal waste piles, and other natural and man-made heated habitats did not yield fungi when enrichments were done at 62 degrees , whereas fungi able to grow at 55-60 degrees can be readily isolated from such habitats. Earlier work had shown that eukaryotic algae are also absent from environments with temperatures above 55-60 degrees . It is suggested that the failure of eukaryotes to evolve members able to grow at higher temperatures is due to their inability to form organellar membranes that are both thermostable and functional.

Biological Evolution↗
PubMed2006

Changing body temperature affects the T2* signal in the rat brain and reveals hypothalamic activity.

This study was designed to determine brain activity in the hypothalamus-in particular the thermoregulatory function of the hypothalamic preoptic area (PO). We experimentally changed the body temperature in rats within the physiological range (37-39 degrees C) and monitored changes in blood oxygenation level-dependent (BOLD) MR signal. To explore PO activity we had to deal with general signal changes caused by temperature-dependent alterations in the affinity of oxygen for hemoglobin, which contributes to BOLD contrast because it is partly sensitive to the amount of paramagnetic deoxyhemoglobin in the voxel. To reduce these overall temperature-induced effects, we corrected the BOLD data using brain-specific correction algorithms. The results showed activity of the PO during body warming from 38 degrees C to 39 degrees C, supported by an increased BOLD signal after correction. This is the first fMRI study on the autonomous nervous system in which hypothalamic activity elicited by changes in the internal environment (body temperature) was monitored. In this study we also demonstrate 1) that any fMRI study of anesthetized small animals should guard against background BOLD signal drift, since animals are vulnerable to body temperature fluctuations; and 2) the existence of a link between PO activity and the sympathetically-mediated opening of the arteriovenous anastomoses in a parallel study on the rat tail, a peripheral thermoregulatory organ.

Animals↗
PubMed2006

Insect eggs at a transition between diffusion and reaction limitation: temperature, oxygen, and water. art.woods@mso.umt.edu.

In diverse animal taxa, eggs and embryos are incapable of transporting oxygen by convection. In such cases, internal oxygen distributions are determined jointly by rates of oxygen consumption and diffusive transport. Here we develop a mathematical model of oxygen consumption and transport in insect eggs, with the goal of understanding-for eggs in variable-temperature environments-the interactive effects of the two processes on development. We fit the model to previously published data on development time of eggs of a sphingid moth, Manduca sexta. The fitted coefficients suggest that eggs develop at a transition point between reaction- and diffusion-limitation. We test then this conclusion with independent data on development times of eggs distributed across a set of temperatures generated by a thermal gradient bar. Finally, we develop an extension of the model that considers tradeoffs between oxygen transfer to eggs versus water loss from them. The model results provide both a rationale for why development is often mass-transfer limited and a set of new predictions about oxygen-water tradeoffs.

Animals↗
PubMed2000

Extinction transition in bacterial colonies under forced convection.

We report the spatiotemporal response of Bacillus subtilis growing on a nutrient-rich layer of agar to ultraviolet (UV) radiation. Below a crossover temperature, the bacteria are confined to regions that are shielded from UV radiation. A forced convection of the population is effected by rotating a UV radiation shield relative to the Petri dish. The extinction speed at which the bacterial colony lags behind the shield is found to be qualitatively similar to the front velocity of the colony growing in the absence of a hostile environment as predicted by the model of Dahmen, Nelson, and Shnerb. A quantitative comparison is not possible without considering the slow dynamics and time-dependent interaction of the population with the hostile environment.

Bacillus subtilis↗
PubMed1993

Effect of the prenatal maternal environment on the control of breathing during non-rapid-eye-movement sleep in the developing lamb.

This study examines the effects of altering the prenatal maternal metabolic and hormonal environment via chronic cold exposure of under-fed ewes on developmental changes in breathing control of developing lambs. Breathing frequency and timing were measured during non rapid-eye-movement (non-REM) sleep in lambs born from either shorn or unshorn ewes after being maintained for at least one hour at warm (28-19 degrees C) and cool (14-5 degrees C) ambient temperatures at 1, 4, 14 and 30 days of age. Breathing frequency and oxygen consumption were significantly higher in 1 day old lambs born from shorn ewes compared with those lambs born from unshorn ewes, at both warm and cool ambient temperatures. In the shorn group breathing frequency decreased between 1 and 4 days of age and continued decreasing upto 30 days of age, during which period inspiratory and to a greater extent expiratory time, lengthened. Laryngeal "braking" of expiratory airflow was observed in more than 50% of lambs born from shorn ewes during non-REM sleep in the warm at 4, 14 and 30 days of age, and in the cold at 14 and 30 days of age. In contrast, lambs born from unshorn ewes showed no change in breathing frequency between 1 and 4 days of age, but a decrease was observed between 4 and 14 days of age, whilst laryngeal "braking" of expiratory airflow was rarely observed at any age.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1983

Effect of thiouracil on response to heat stress of White Leghorn lines selected for fast and slow gain in two temperatures.

Four lines of White Leghorns previously selected for fast and slow gain from 5 to 9 weeks of age in a hot (32.2 C) and in a cold (21.1 C) selection environment were grown from 5 to 9 weeks in the same two temperature environments. Samples of 32 females from each line of the third generation grown in each temperature environment from 5 to 9 weeks of age were divided into two groups; one received .2% thiouracil in the diet for a 5-day period and the other did not. The temperature was then increased to 40.6 C until 52.8% of all birds had died. The percentages of mortality of lines, rearing environments, and thiouracil treatments were then analyzed. An increase of 64.8% mortality from acute heat stress for birds reared in the cold environment was significant, but the differences among the four selected lines were not. The presence of thiouracil in the diet significantly reduced mortality from heat stress by 16.4%. There were no significant interactions between thiouracil treatments and selected lines or rearing environments.

Acclimatization↗
PubMed1983

Evaluation of an affinity chromatographic procedure for the determination of glycosylated hemoglobin (HbA1).

An affinity chromatographic method for the determination of glycosylated hemoglobin (HbA1) was evaluated. The procedure was shown to be precise, the within- and between-assay coefficients of variation being less than 5%. It was also shown to correlate well with electrophoresis (r = 0.968) and ion-exchange chromatography (r = 0.916). An inverse relationship was shown to exist between increasing temperature and HbA1 levels measured by affinity chromatography. A statistically significant difference was found for samples run at 20 degrees C and 25 degrees C respectively, suggesting that the method should be run in a temperature-controlled environment. The affinity procedure was also shown not to be affected by the type of anticoagulant, the concentration of hemoglobin in the hemolysate, and acetylation.

Acetylation↗
PubMed2003

Paludification and forest retreat in northern oceanic environments.

Examination of temperature variations over the past century for Europe and the Arctic from northern Norway to Siberia suggests that variations in the North Atlantic Oscillation are associated with an increase in oceanicity in certain maritime regions. A southward depression of the tree line in favour of wet heaths, bogs and wetland tundra communities is also observed in northern oceanic environments. The physiological basis for this change in ecological succession from forest to bog is discussed in relation to the long-term effects of flooding on tree survival. The heightened values currently detected in the North Atlantic Oscillation Index, together with rising winter temperatures, and increased rainfall in many areas in northern Europe, presents an increasing risk of paludification with adverse consequences for forest regeneration, particularly in areas with oceanic climates. Climatic warming in oceanic areas may increase the area covered by bogs and, contrary to general expectations, lead to a retreat rather than an advance in the northern limit of the boreal forest. High water-table levels are not automatically detrimental to forest survival as can be seen in swamp, bottom land and mangrove forests. Consequently, the inhibitory effects of flooding on tree survival and regeneration in northern regions should not be uncritically accepted as merely due to high water levels. Evidence is discussed which suggests that physiological and ecological factors may interact to inhibit forest regeneration in habitats where there is a risk of prolonged winter-flooding combined with warmer winters and cool moist summers.

Atlantic Ocean↗
PubMed1998

Occurrence of Vibrio vulnificus biotypes in Danish marine environments.

During the unusually warm summer in Denmark in 1994, 11 clinical cases of Vibrio vulnificus infection were reported. These reports initiated an investigation of the occurrence of V. vulnificus biotypes in Danish marine environments. Samples of coastal water, sediment, shellfish, and wild fish were analyzed by preenrichment in alkaline peptone water amended with polymyxin B (2.0 x 10(4) U/liter) followed by streaking onto modified cellobiose-polymyxin B-colistin agar. V. vulnificus-like colonies were tested with a V. vulnificus-specific DNA probe. Low densities of V. vulnificus were detected in water (0.8 to 19 CFU/liter) from June until mid-September and in sediment (0.04 to > 11 CFU/g) from July until mid-November. The presence of V. vulnificus was strongly correlated with water temperature. However, we isolated V. vulnificus from water from a mussel farm at a lower temperature than previously reported (7 degrees C). In 1 of the 13 locations studied, V. vulnificus was found in mussels in 7 of 17 samples analyzed; this is the first report of V. vulnificus in European shellfish. V. vulnificus was also isolated from gills, intestinal contents, and mucus from wild fish. Although biotyping of 706 V. vulnificus strains isolated during our investigations revealed that the majority of the strains (99.6%) belonged to biotype 1, biotype 2 was detected in seawater at a low frequency (0.4%). Our findings provide further evidence that seawater can serve as a reservoir and might facilitate spread of V. vulnificus biotype 2 to eels, with subsequent spread to persons handling eels. In conclusion, our data demonstrate that V. vulnificus is ubiquitous in a temperature marine environment and that V. vulnificus biotype 2 is not strictly confined to eels.

Animals↗
PubMed1984

The detection of interstellar methylcyanoacetylene.

A new interstellar molecule, methylcyanoacetylene (CH3C3N), has been detected in the molecular cloud TMC-1. The J = 8 --> 7, J = 7 --> 6, J = 6 --> 5, and J = 5 --> 4 transitions have been observed. For the first three of these, both the K = 0 and K = 1 components are present, while for J = 5 --> 4, only the K = 0 line has been detected. The observed frequencies were calculated by assuming a value of radial velocity VLSR = 5.8 km s-1 for TMC-1, typical of other molecules in the cloud. All observed frequencies are within 10 kHz of the calculated frequencies, which are based on the 1982 laboratory constants of Moises et al., so the identification is secure. The lines are broadened by hyperfine splitting, and the J = 5 --> 4, K = 0 transition shows incipient resolution into three hyperfine components. The rotational temperature determined for these observations is quite low, with 2.7 K < or = Trot < or = 4 K. the total column density is approximately 5 x 10(12) cm-2.

Acetylene↗
PubMed2005

CVD growth of N-doped carbon nanotubes on silicon substrates and its mechanism.

In the present study, we report the chemical vapor deposition (CVD) of nitrogen-doped (N-doped) aligned carbon nanotubes on a silicon (Si) substrate using ferrocene (Fe(C5H5)2) as catalyst and acetonitrile (CH3CN) as the carbon source. The effect of experimental conditions such as temperature, gaseous environment, and substrates on the structure and morphology of N-doped carbon nanotubes arrays is reported. From XPS and EELS data, it was found that the nitrogen content of the nanotubes could be determined over a wide range, from 1.9% to 12%, by adding the addition of hydrogen (H2) to the reaction system. It was also shown by SEM that N-doped carbon nanotube arrays could be produced on Si and SiO2 substrates at suitable temperatures, although at different growth rates. Using these concentrations, it was possible to produce three-dimensional (3D) carbon nanotubes architectures on predetermined Si/SiO2 patterns. The mechanism underlying the effect of nitrogen containing carbon sources on nanotube formation was explored using X-ray photoelectron spectroscopy (XPS).

Acetonitriles↗
PubMed2005

Modeling physiological responses to military scenarios: initial core temperature and downhill work.

INTRODUCTION: Previous field studies suggested that a thermoregulatory model developed by the U.S. Army Research Institute of Environmental Medicine (USARIEM) needed an adjustment of initial core temperature (Tcr) for individual variation and a metabolic (M) correction during downhill movements. This study evaluated the updated version of the model incorporating these new features using a dataset collected during U.S. Marine Corps marksmanship training at Quantico, VA. METHODS: Individual anthropometrics, physiological, and environmental time series data were obtained from five Marine men. The study focused on the marksmanship training for approximately 2 h, then 30-min marching including uphill and downhill movements in a moderately hot environment (air temperature: approximately 30 degrees C; dew point: approximately 21 degrees C). The predicted and observed heart rate (HR) and Tcr measurements were compared by root mean square deviations (RMSD). RESULTS: Overall, the current model improved predictions of physiological measures (HR RMSD = 23 bpm, Tcr RMSD = 0.46 degrees C), particularly for marching in the heat (HR RMSD = 21 bpm, Tcr RMSD = 0.32 degrees C). The model under-predicted both HR and Tcr during marksmanship training, indicating that a greater solar effect or non-thermal factors may have required higher M rates during these periods. CONCLUSIONS: Updated features of the model significantly improved physiological predictions. However, accurate M estimates are required for slow movements of subjects under heat stress, such as movements on the firing range. Such improvement should result in more accurate simulations of physiological status and better risk assessment, thereby reducing heat injuries and improving performance of deployed military personnel.

Adult↗
PubMed1992

[The survival ability of salmonella, coccidia oocysts and ascarid eggs in laying hen feces from different housing systems].

The time of survival of Salmonella typhimurium, coccidia oocysts and ascaris eggs in manure of layer was determined in 5 different housing systems and 2 storing places for litter. The experiments were carried out in a stable of experimental station Frankenforst of the university of Bonn with a flock of 2200 hens. The effects of the environment conditions temperature, dry matter content, pH-value and intestinal microflora of the manure have also been studied. The time of survival was different depending on the housing system. A recovery of viable coccidia oocysts was possible after 13-370 days, ascaris eggs 53-347 days and Salmonella typhimurium 2-175 days. The tenacity of the investigated test organism mainly depend on the dry matter content of the manure. The longest period of survival of salmonellas was found in dry environment conditions, were as coccidia oocysts and ascaris eggs have been observed with the shortest period of survival. The possibility of the examined resistant parasite stages to develop was disturbed. Only few of them were able to develop and with a longer development time than those examined in the control suspension. The results of this study indicate that chicken manure, before using it in plant production, should be stored long enough to prevent men or animals from possible infections.

Animals↗