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At least 127 records · Page 7Linked to original sources
PubMed2003

Muscle metabolism and growth in Antarctic fishes (suborder Notothenioidei): evolution in a cold environment.

The radiation of notothenioid fishes (order Perciformes) in the Southern Ocean provides a model system for investigating evolution and adaptation to a low temperature environment. The Notothenioid fishes comprising eight families, 43 genera and 122 species dominate the fish fauna in Antarctica. The diversification of the clade probably began 15-20 million years ago after the formation of the Antarctic Polar Front. The radiation was, therefore, associated with climatic cooling down to the present day temperature of -1.86 degrees C. Origins and Evolution of the Antarctic Biota Geological Society Special Publication No. 47, Geological Society of London. pp. 253-268). The success of the group has been closely linked with the evolution of glycopeptide and peptide antifreezes, which are amongst the most abundant proteins in blood and interstitial fluid. The radiation of the clade has been associated with disaptation (evolutionary loss of function) and recovery. For example, it is thought that the icefishes (Channichyidae) lost haemoglobin through a single mutational event leading to the deletion of the entire beta-globin gene and the 5' end of the linked alpha-globin gene, resulting in compensatory adaptations of the cardiovascular system. Phylogenetically based statistical methods also indicate a progressive and dramatic reduction in the number of skeletal muscle fibres (FN(max)) at the end of the recruitment phase of growth in basal compared to derived families. The reduction in FN(max) is associated with a compensatory increase in the maximum fibre diameter, which can reach 100 microm in slow and 600 microm in fast muscle fibres. At -1 to 0 degrees C, the oxygen consumption of isolated mitochondria per mg mitochondrial protein shows no evidence of up-regulation relative to mitochondria from temperate and tropical Perciform fishes. The mitochondria content of slow muscle fibres in Antarctic notothenioids is towards the upper end of the range reported for teleosts with similar lifestyles, reaching 50% in Channichthyids. High mitochondrial densities facilitate ATP production and oxygen diffusion through the membrane lipid compartment of the fibre. Modelling studies suggest that adequate oxygen flux in the large diameter muscle fibres of notothenioids is possible because of the reduced metabolic demand and enhanced solubility of oxygen associated with low temperature. At the whole animal level size-corrected resting metabolic rate fits on the same temperature relationship as for Perciformes from warmer climates. It seems likely that the additional energetic costs associated with antifreeze synthesis and high mitochondrial densities are compensated for by reductions in other energy requiring processes: a hypothesis that could be tested with detailed energy budget studies. One plausible candidate is a reduction in membrane leak pathways linked to the loss of muscle fibres, which would serve to minimise the cost of maintaining ionic gradients.

Animals↗
PubMed1995

Age-dependent sensitivity of rats to the long-term effects of the serotonergic neurotoxicant (+/-)-3,4-methylenedioxymethamphetamine (MDMA) correlates with the magnitude of the MDMA-induced thermal response.

The effects of developmental age on (+/-)-3,4-methylenedioxymethamphetamine (MDMA)-induced reductions in 5-hydroxytryptamine (5-HT) content and 5-HT reuptake sites were investigated in conjunction with the effects of developmental age on MDMA-induced thermoregulatory responses. MDMA was administered to rats at postnatal days (PND) 10, 40 and 70 in a range of ambient temperature environments (10 degrees C, 25 degrees C and 33 degrees C). Animals were monitored for alterations in body temperature and sacrificed 1 week after MDMA administration. MDMA administration at PND 10 did not result in persistent reductions in 5-HT content or 5-HT reuptake sites in frontal cortex, nor could a hyperthermic response be elicited. In contrast, MDMA administration at PND 40 and PND 70 resulted in a hypothermic response in cold environments (10 degrees C) and a hyperthermic response in warm environments (> or = 25 degrees C). When hypothermia was observed after MDMA (10 degrees C environment), long-term reductions in 5-HT content and 5-HT reuptake sites were significantly attenuated or abolished. Conversely, when a hyperthermic response was observed (25 degrees C and 33 degrees C environments), long-term MDMA-induced reductions in 5-HT content and 5-HT reuptake sites were significantly enhanced. Thus, thermal responses significantly correlated with MDMA-induced reductions in 5-HT content and 5-HT reuptake sites. These experiments demonstrate a role for hyperthermia in the expression of serotonergic neurotoxicity after MDMA administration.

Aging↗
PubMed1991

Hypothermia is critical for survival during prolonged insulin-induced hypoglycemia in rats.

Hypothermia is a well-known concomitant of hypoglycemia in mammals. We tested the hypothesis that this hypothermia is an important adaptive response to hypoglycemia in 11 normal Sprague-Dawley rats. Twelve-hour fasted, conscious animals received primed, continuous insulin infusions for up to 8 hours. Plasma glucose was clamped between 30 and 40 mg/dL and core body temperature was monitored continuously during the insulin infusions. Five of the animals were maintained in a room temperature environment (22 to 24 degrees C) during the hypoglycemia; all became hypothermic (mean +/- SE nadir core temperature, 31 +/- 0.5 degrees C). Spontaneous activity was reduced in these animals, but they remained conscious and responsive to external stimuli. All five returned to normal behavior after euglycemia was restored at the end of the insulin infusions. In the remaining six animals, hypothermia was prevented during hypoglycemia by warming of the air in their cages (mean of hourly core temperatures, 37 +/- 0.1 degrees C). None of these animals survived more than 7 hours. The severity of the hypoglycemia was no greater in the euthermic than in the hypothermic group, as judged by the mean of individual nadir plasma glucose levels (25 +/- 1 v 24 +/- 1 mg/dl, respectively) and by the mean number of glucose values per animal that were less than 30 mg/dL (2 +/- 1 v 7 +/- 1). Plasma osmolality did not change significantly in either group during the period of hypoglycemia, suggesting that dehydration was not the cause of death in the euthermic animals.(ABSTRACT TRUNCATED AT 250 WORDS)

3-Hydroxybutyric Acid↗
PubMed1980

[Thermoregulation changes in secondary vocational and technical school students during the summer job experience].

Ninety pupils from a secondary polytechnical school for non-ferrous metallurgy, studying locksmith-mounter specialty, were examined during their summer industrial practice. The changes in body temperature, skin temperature and skin-electric resistance (SER) were studied. It was found that the diurnal and weekly variations in body and skin temperature and SER follow the diurnal and weekly biorhythm of these parameters and directly reflect the environment temperature changes and the duration and intensity of the work performed.

Adolescent↗
PubMed1998

The story of the internal carotid artery of mammals: from Galen to sudden infant death syndrome.

Some anatomical aspects of the blood supply of the brains of mammals have been examined to illuminate their functions. A fundamental explanation of sudden infant death syndrome (cot death) is suggested following experimental observations. Speculative contributions have been made to comparative physiological ideas concerning mammals of pronograde and erect habitus, their vascular pressure adaptations and temperature management. Neuro- and interventional radiologists may make some significant future applications of these ideas. Of immediate practical interest is the possibility of influencing the well-being of human embryos' neural tube development in utero by a comprehensive study of their temperature environment.

Adaptation, Physiological↗
PubMedDate not supplied

The effect of environment on body site temperatures in full-term neonates.

The effect of environment on temperature was examined by comparing tympanic, rectal, inguinal, and axillary temperatures for 63 term infants in three environments: incubator, bassinet, and radiant warmer. Tympanic temperatures were collected with a FirstTemp (Intelligent Medical Systems, Carlsbad, CA) infrared thermometer in the cal-tympanic mode. Rectal, inguinal, and axillary temperatures were collected with an IVAC digital thermometer (San Diego, CA) in the predictive mode. There were moderate correlations between the body site temperatures. The environment significantly influenced temperature readings at the different sites. Temperatures assessed in the superheated environments of the radiant warmer and the incubator were consistently higher than temperatures in the bassinet.

Analysis of Variance↗
PubMed2005

Microclinal variation for ovariole number and body size in Drosophila melanogaster in 'Evolution Canyon'.

Sites that display strong environmental contrasts in close proximity, such as 'Evolution Canyon' on Mt. Carmel, Israel, are natural theatres for investigating adaptive evolution in action. We reared Drosophila melanogaster from collection sites along altitudinal transects on the north- and south-facing canyon slopes in each of three temperature environments, and assessed genetic variation in ovariole number and body size between and within collection sites, and temperature plasticity. Both traits exhibited significant genetic variation within collection sites and phenotypic plasticity in response to temperature, but not genetic variation for plasticity. Between-site genetic variation in ovariole number was negatively correlated with altitude on both slopes of the canyon, and collections from the north- and south-facing slopes were genetically differentiated for male, but not female, body size. Genetic variation between sites within easy dispersal range is consistent with the action of strong natural selection, although neither the selective agent(s) nor the direct targets of selection are known.

Adaptation, Biological↗
PubMed2003

Effects of hyperthermia on rat hippocampal pyramidal cell apoptosis in vitro.

OBJECTIVE: To investigate the changes in the morphology and biochemistry of neonatal rat hippocampal pyramidal cells (HPCs)apoptosis in high-temperature environment. METHODS: In vitro culture of HPCs was established and then subjected to environmental stimulation with high temperatures (37, 40, and 42 degrees Celsius respectively) for 1 h. All the cells were collected at different time points after the treatment and examined by flow cytometery, fluorescence staining, agarose gel electrophoresis and in situ cell apoptosis detection kit. RESULTS: The apoptotic rate and the number of apoptotic bodies increased as the temperature was elevated. DNA ladder was presented on agarose gel electrophoresis, and the germination of the apoptotic body was observed by fluorescence microscope. CONCLUSIONS: Hyperthermia may induce the apoptosis in HPCs in vitro, and the extend of apoptosis and apoptotic behavior may vary with the temperature and treatment duration.

Animals↗
PubMed1988

Effect of changes in local skin temperature on postural vasoconstriction in man.

1. The effects of locally induced alterations in skin temperature on the postural changes in skin blood flow of the foot were assessed in 38 healthy subjects in a constant-temperature environment (22 +/- 0.5 degrees C, mean +/- SD). 2. Moderate local cooling and warming of the foot (26-36 degrees C) was induced by blowing cold or hot air. Higher ranges of temperature (38-44 degrees C) were achieved by a thermostatically controlled disc heater. 3. Skin blood flow was measured before and during each change in local skin temperature using a laser Doppler flowmeter with the foot maintained at heart level, and placed passively 50 cm below the heart. Blood flow was measured in two skin areas: (i) the dorsum on the foot, where arteriovenous anastomoses are absent, and (ii) the pulp of the big toe, where these anastomoses are relatively numerous. 4. It was found that within the physiological temperature range of 26-36 degrees C the normal postural fall in foot skin blood flow was preserved, whereas it was markedly attenuated or totally abolished at higher temperatures (38-44 degrees C). The pattern of response was quite similar in areas having or lacking arteriovenous anastomoses. 5. It is suggested that the failure of postural vasoconstriction observed at the higher skin temperatures might contribute to some of the problems of cardiovascular adaptations seen in a hot environment.

Adult↗
PubMed1986

Effect of temperature on the kinetics of the yeast AMP deaminase.

The temperature dependence of the kinetics of the yeast AMP deaminase was examined using the purified enzyme and the permeabilized yeast cells. The increase in the enzyme affinity for the substrate AMP was accompanied by the decrease in the maximal velocity with the decreasing temperature in the absence and presence of ATP. The apparent Km for AMP was lowest at 15-20 degrees C, and the affinity was decreased below and above this temperature. The rate of the AMP deaminase reaction remained constant over a wide range of temperature in the presence of physiological AMP concentrations. The temperature dependent change in kinetic properties of AMP deaminase may contribute to the control of the yeast glycolytic flux under the condition of lower temperature environments.

AMP Deaminase↗
PubMed2003

Expression of cellular antigens of Listeria monocytogenes that react with monoclonal antibodies C11E9 and EM-7G1 under acid-, salt- or temperature-induced stress environments.

AIMS: To study the expression of cellular antigens of Listeria monocytogenes that react with monoclonal antibodies (MAbs) C11E9 and EM-7G1 under acid-, salt- or temperature-induced stress environments. METHODS AND RESULTS: The reaction patterns of antibodies to L. monocytogenes held in stressful environments for a short duration (3 h) or grown for extended periods (16-72 h) were investigated. During both short or prolonged exposure to stress environments of high temperature (45 degrees C) and NaCl (>1.5%, w/v), reactions of whole cells of L. monocytogenes to antibodies were severely affected as determined by ELISA and by the reduced expression of the antibody-reactive 66 kDa antigen in the Western blot assay. Conversely, cold (4-15 degrees C) or acid (pH 2-3) stress environments had very little effect on antigen expression or antibody reaction. Additionally, heat-killed cells showed reduced reactions to these antibodies when compared with unheated cells. Artificially created stress environments in hotdog slurry also affected the antigen expression in L. monocytogenes. Immunoelectron microscopy revealed that the antibody-reactive antigens were uniformly present on the surface of the cells. Morphological characteristics following growth in stressed environments revealed that heat stress at 45 degrees C caused L. monocytogenes cells to be elongated and to form clumps; whereas, osmotic stress (5.5% NaCl, w/v) caused filamentous appearance with multiple septa along the length of the cell. CONCLUSIONS: These results indicated that MAb C11E9 or EM-7G1 could detect L. monocytogenes from cold or acid-stress environments; however, they may show weaker reactions with heat or osmotically stressed cells or cells grown at 4 degrees C. SIGNIFICANCE AND IMPACT OF THE STUDY: Bacteria in food are routinely subjected to various stresses, induced by cold, heat, salt or acid during processing and storage. Whether stresses would modify the expression of cellular antigens of L. monocytogenes is of a great concern for immunodetections in food products.

Antibodies, Monoclonal↗
PubMed2002

Modeling the lag phase of Listeria monocytogenes.

An estimate of the lag phase duration is an important component for predicting the growth of a bacterium and for creating process models and risk assessments. Most current research and data for predictive modeling programs initiated growth studies with cells grown to the stationary phase in a favorable pH, nutrient and temperature environment. In this work, Listeria monocytogenes Scott A cells were grown in brain heart infusion (BHI) broth at different temperatures from 4 to 37 degrees C to the exponential growth or stationary phases. Additional cells were suspended in a dilute broth, desiccated or frozen. These cells were then transferred to BHI broth at various temperatures from 4 to 37 degrees C and the lag phase durations were determined by enumerating cells at appropriate time intervals. Long lag phases were observed for cells initially grown at high temperatures and transferred to low temperatures. In general, exponential growth cells had the shortest lag phases, stationary phase and starved cells had longer, frozen cells had slightly longer and desiccated cells had the longest lag phases. These data were from immediate temperature transitions. When a computer-controlled water bath linearly changed the temperature from 37 to 5 degrees C over a 3.0- or 6.0-h period, the cells had short lags and grew continuously with declining growth rates. Transitions of 0.75 or 1.0 h had 20-h lag phases, essentially that of immediate transitions. When the transition was 1.5 h, an intermediate pattern of less than 1 log of growth followed by no additional growth for 20 h occurred.

Food Microbiology↗
PubMed2004

Relationship of critical temperature to macromolecular synthesis and growth yield in Psychrobacter cryopegella.

Most microorganisms isolated from low-temperature environments (below 4 degrees C) are eury-, not steno-, psychrophiles. While psychrophiles maximize or maintain growth yield at low temperatures to compensate for low growth rate, the mechanisms involved remain unknown, as does the strategy used by eurypsychrophiles to survive wide ranges of temperatures that include subzero temperatures. Our studies involve the eurypsychrophilic bacterium Psychrobacter cryopegella, which was isolated from a briny water lens within Siberian permafrost, where the temperature is -12 degrees C. P. cryopegella is capable of reproducing from -10 to 28 degrees C, with its maximum growth rate at 22 degrees C. We examined the temperature dependence of growth rate, growth yield, and macromolecular (DNA, RNA, and protein) synthesis rates for P. cryopegella. Below 22 degrees C, the growth of P. cryopegella was separated into two domains at the critical temperature (T(critical) = 4 degrees C). RNA, protein, and DNA synthesis rates decreased exponentially with decreasing temperatures. Only the temperature dependence of the DNA synthesis rate changed at T(critical). When normalized to growth rate, RNA and protein synthesis reached a minimum at T(critical), while DNA synthesis remained constant over the entire temperature range. Growth yield peaked at about T(critical) and declined rapidly as temperature decreased further. Similar to some stenopsychrophiles, P. cryopegella maximized growth yield at low temperatures and did so by streamlining growth processes at T(critical). Identifying the specific processes which result in T(critical) will be vital to understanding both low-temperature growth and growth over a wide range of temperatures.

Bacterial Proteins↗
PubMed2001

Enhancement of short-term synaptic plasticity by prior environmental stress.

All chemical synapses can rapidly up- or downregulate the strength of their connections to reshape the postsynaptic signal, thereby stressing the informational importance of specific neural pathways. It is also true that an organism's environment can exert a powerful influence on all aspects of neural circuitry. We investigated the effect of a prior high-temperature stress on the short-term plasticity of a neuromuscular synapse in the hindleg tibial extensor muscle of Locusta migratoria. We found that the prior stress acted to precondition the synapse by increasing the upper temperature limit for synaptic transmission during a subsequent stressful exposure. As well, preexposure to a stressful high-temperature environment increased short-term facilitation of excitatory junction potentials concurrent with a decrease in excitatory junction potential amplitude and a reduction in its temporal parameters. We conclude that a stressful environment can modify synaptic physiological properties resulting in an enhancement of short-term plasticity of the synapse.

Analysis of Variance↗
PubMedDate not supplied

[Influence of ambient storage temperature on radiographic density and contrast of dated and outdated film].

The authors studied the influence of storage conditions of date and outdated films and the action of environment temperature over the same films. Four groups of films were studied: twenty-five outdated and twenty-five date films were under refrigeration; twenty-five date and twenty-five outdated films were under 36 degrees C temperature and 70% hygrometric for thirty days. Afterward, the films were exposed to radiation X at standardized conditions, together with an AI stepwedge penetrometer, to measure optical density; also the processing conditions were standardized. The results showed that temperature action and films date and outdated produced changes in the optical density and radiographic contrast.

Humidity↗
PubMed1975

[Influence of mediopreoptic stimulation on temperature regulation in rats before and after serotonin injection].

The effects of electrical stimulation of the Area praceoptica medialis (APM) and intraventricular serotonine injection were investigated in thirty Wistar rats tested under normo-, hypo- and hyperthermic conditions. Temperature responses such as oxygen consumption and rectal temperature were measured and heat loss was calculated. The effects of the first stimulation before serotonine injection were compared with those of the second one after serotonine application in order to prove the influence of serotonine on temperature responses due to APM stimulation. On the other hand, the influence of stimulation on changes produced by serotonine injection should be shown by the recordings of the second serotonine responses with stimulation effects and by comparison of these with those of the first serotonine responses without stimulation effects. The first APM stimulation depending on the rectal temperature before stimulation resulted in decreasing oxygen consumption in hypothermic rats while increasing that of hyperthermic animals. There was a little decrease of rectal temperature under hyper- and normothermic conditions. while under hypothermic conditions animals showed marked depression. The increase in heat loss, however, was least in hyperthermic rats and most pronounced in hypothermic animals. The second APM stimulation did almost not affect the temperature responses after serotonine application in normothermic rats, while causing supercooling agin under hypothermic conditions and insignificant cooling at hyperthermic environment temperature. Comparison of the first and second stimulation effects revealed statistical significant differences at normo-, hypo- and hyperthermic temperatures. The results are discussed under consideration of the different starting conditions before the first and second stimulation. These findings do not indicate that serotonine would shift the sensibility of mediopraeoptic structures and thus unequivocally modifies stimulation effects.

Animals↗
PubMed1980

[Average weight and temperature rhythms of fasting chickens from hatching to death].

We have compared the weight and the bodily temperature of some chicks during fasting from hatching till death with the values obtained from regularly nourished chicks at the environment temperature of 34 degrees. The medium period of survival during fasting is 7,4 d while the chicks of 7 d generally survive 3,9 d. The reserve of the vitelline sac (17,8%) is not sufficient to cover the basal metabolism of the chick. Its net weight generally diminishes of 33,6%. Nourished chicks lose weight on the 1st d and then regularly grow up. The chicken temperature from the 14th day on is about 41,8 degrees in the morning and increases in the evening. The temperature during fasting is lower than normal temperature of nourished chicks progressively increases and after 3 d is higher in the evening than in the morning, as it is for the grown-up ones. We are trying to found out the factors which determine the modifications of thermic oscillations during fasting, which are not a circadian rhythm.

Animals↗