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At least 217 records · Page 12Linked to original sources
PubMed2007

Properties of the alpha subunit of a Chaperonin from the hyperthermophilic Crenarchaeon Aeropyrum pernix K1.

The gene encoding for a putative thermosome from the hyperthermophilic crenarchaeon Aeropyrum pernix K1 (ApcpnA) was cloned and the biochemical characteristics of the resulting recombinant protein were examined. The gene (accession no. APE0907) from A. pernix K1 showed some homology with other group II chaperonins from archaea. The recombinant ApcpnA protein has a molecular mass of 60 kDa, determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and exhibited ATPase activity with an optimum temperature and pH of 90 degrees C and 5.0, respectively. The ATPase activity was found to be dependent on manganese and potassium ions, but not magnesium ion. The K(m) for ATP at pH 5.0 and 90 degrees C was 10.04 (+/- 1.31) microM, and k(cat) was determined to be 2.21 (+/- 0.11) min(-1) for the ApcpnA monomer. The recombinant ApcpnA prevents thermal aggregation of bovine rhodanese and enhances the thermal stability of alcohol dehydrogenase in vitro, indicating that the protein is suitable as a molecular chaperonin in the high-temperature environment.

Aeropyrum↗
PubMed2007

Perfusion flow bioreactor for 3D in situ imaging: investigating cell/biomaterials interactions.

The capability to image real time cell/material interactions in a three-dimensional (3D) culture environment will aid in the advancement of tissue engineering. This paper describes a perfusion flow bioreactor designed to hold tissue engineering scaffolds and allow for in situ imaging using an upright microscope. The bioreactor can hold a scaffold of desirable thickness for implantation (>2 mm). Coupling 3D culture and perfusion flow leads to the creation of a more biomimetic environment. We examined the ability of the bioreactor to maintain cell viability outside of an incubator environment (temperature and pH stability), investigated the flow features of the system (flow induced shear stress), and determined the image quality in order to perform time-lapsed imaging of two-dimensional (2D) and 3D cell culture. In situ imaging was performed on 2D and 3D, culture samples and cell viability was measured under perfusion flow (2.5 mL/min, 0.016 Pa). The visualization of cell response to their environment, in real time, will help to further elucidate the influences of biomaterial surface features, scaffold architectures, and the influence of flow induced shear on cell response and growth of new tissue.

Animals↗
PubMed1984

An apparatus for sequentially combining microvolumes of reagents by infrasonic mixing.

A method employing high-speed infrasonic mixing for obtaining timed samples for following the progress of a moderately rapid chemical reaction is described. Drops of 10 to 50 microliter each of two reagents are mixed to initiate the reaction, followed, after a measured time interval, by mixing with a drop of a third reagent to quench the reaction. The method was developed for measuring the rate of denaturation of covalently closed, circular DNA in NaOH at several temperatures. For this purpose the timed samples were analyzed by analytical ultracentrifugation. The apparatus was tested by determination of the rate of hydrolysis of 2,4-dinitrophenyl acetate in an alkaline buffer. The important characteristics of the method are (i) it requires very small volumes of sample and reagents; (ii) the components of the reaction mixture are pre-equilibrated and mixed with no transfer outside the prescribed constant temperature environment; (iii) the mixing is very rapid; and (iv) satisfactorily precise measurements of relatively short time intervals (approximately 2 sec minimum) between sequential mixings of the components are readily obtainable.

Biochemistry↗
PubMed1989

Occupational hot exposures: a review of heat and mass transfer theory.

The assessment and control of hot working environments is based on an appraisal of the thermal interaction between an individual and the surroundings. This paper examines in detail the processes of convection, radiation and evaporation which constitute the principal mechanisms for this interaction. The defining equations are discussed with particular attention given to the appropriate numerical values of body heat and mass transfer coefficients. The use of the heat-mass transfer analogy for the prediction of the mass transfer coefficient is introduced and verified. Finally, recommendations are given as to the most appropriate set of energy exchange equations for use in the analysis of high-temperature environments. The physiological criteria involved in hot working conditions, and the generation of a suitable assessment procedure based on the energy exchange equations, are the subject of a companion paper.

Body Surface Area↗
PubMed2005

The WD-40 repeat motif of Lgl tumor suppressor proteins associated with salt tolerance and temperature sensitivity.

We have recently identified mammalian homologues of lethal giant larvae (Lgl) tumor suppressor gene, rat Rgl-1 and bovine Bgl-1, and demonstrated that they can complement yeast double mutants lacking Sop1 and Sop2, yeast homologues of Lgl. These gene products are capable of regulating cellular viability in restrictive salt and temperature environments. Since Lgl family members contain the WD-40 repeat motif, we investigated its cellular functions using mouse homologue Mgl-1 in the absence of Sop1 and Sop2 in yeasts by complementation. Interestingly, mutant forms of Mgl-1 at the conserved glycine at position 450 and aspartic acid at position 453 in the most conserved WD-40 repeat motif were not able to complement, indicating that these amino acids are critical for regulating salt tolerance and temperature sensitivity in yeast. These results shed light on the important regulation of cytoskeletal complex for cellular polarity within eukaryotic cells.

Adaptation, Physiological↗
PubMed1976

Immune response of channel catfish under different environmental conditions.

Channel catfish were maintained under conditions of low (15.4 C) and fluctuating (15.4 to 26.9 C/24 hours) temperatures, low (126 mg/L NO3-N) and high (289 mg/L NO3-N) nitrate in recirculating systems, crowding (171 g body mass/L), and fasting. They were vaccinated with formalin-killed enteric red-mouth bacterium, and antibody titers were monitored weekly for 10 weeks. Only those fish maintained in low or fluctuating temperature environments had significant (P less than 0.01) immunosuppression. The other environmental conditions studies, which are commonly encountered in intensive fish culture operations, did not compromise the humoral immune response of channel catfish.

Animals↗
PubMed1992

The effects of heating and devitrification on the structure and biological activity of aluminosilicate refractory ceramic fibres.

Three grades of ceramic fibre have been examined for their composition, structures and biological effect in several in vitro assay systems. The fibres were examined in the 'as-manufactured' state and after heating at 1200 and 1400 degrees C. Devitrification of the fibres at 1200 degrees C probably gave mullite crystals on the surface and caused the formation of the high-temperature form of cristobalite and, in zirconia grade fibres, the high-temperature, tetragonal form of zirconia as well. Further heating changed surface structure and led to zircon production in the zirconia fibres. Heating reduced the affinity of the fibres for the surface of V79-4 cells and lowered fibre toxicity toward these cells and towards macrophage-like cells. These changes in toxicity were not due to a reduction in the fibrous nature of the materials although they did become more brittle and powders prepared from them contained more isometric particles than those from as-manufactured materials. This suggests that the devitrification occurring during the use of these materials in high-temperature environments will not necessarily enhance their adverse biological activities despite the production of one phase of crystalline silica.

Aluminum Silicates↗
PubMed2003

Moritella cold-active dihydrofolate reductase: are there natural limits to optimization of catalytic efficiency at low temperature?

Adapting metabolic enzymes of microorganisms to low temperature environments may require a difficult compromise between velocity and affinity. We have investigated catalytic efficiency in a key metabolic enzyme (dihydrofolate reductase) of Moritella profunda sp. nov., a strictly psychrophilic bacterium with a maximal growth rate at 2 degrees C or less. The enzyme is monomeric (Mr=18,291), 55% identical to its Escherichia coli counterpart, and displays Tm and denaturation enthalpy changes much lower than E. coli and Thermotoga maritima homologues. Its stability curve indicates a maximum stability above the temperature range of the organism, and predicts cold denaturation below 0 degrees C. At mesophilic temperatures the apparent Km value for dihydrofolate is 50- to 80-fold higher than for E. coli, Lactobacillus casei, and T. maritima dihydrofolate reductases, whereas the apparent Km value for NADPH, though higher, remains in the same order of magnitude. At 5 degrees C these values are not significantly modified. The enzyme is also much less sensitive than its E. coli counterpart to the inhibitors methotrexate and trimethoprim. The catalytic efficiency (kcat/Km) with respect to dihydrofolate is thus much lower than in the other three bacteria. The higher affinity for NADPH could have been maintained by selection since NADPH assists the release of the product tetrahydrofolate. Dihydrofolate reductase adaptation to low temperature thus appears to have entailed a pronounced trade-off between affinity and catalytic velocity. The kinetic features of this psychrophilic protein suggest that enzyme adaptation to low temperature may be constrained by natural limits to optimization of catalytic efficiency.

Amino Acid Sequence↗
PubMed1999

Regulation of ischemic cell death by glucocorticoids and adrenocorticotropic hormone.

Transient global ischemia results in delayed selective neuronal death of hippocampal CA1 pyramidal cells. Glucocorticoids increase and adrenalectomy decreases the rate of neuronal death; however, they also produce changes in brain temperature, serum glucose and adrenocorticotropic hormone levels. In order to understand the role of glucocorticoids in regulating ischemic cell death, we studied RU 38486, a glucocorticoid receptor blocker, and Org 2766, a non-steroidogenic adrenocorticotropic hormone 4-9 analog. Male Mongolian gerbils were subjected to 5 min of bilateral carotid artery occlusion under a controlled temperature environment (37.0-38.0 degrees C). Animals were injected with either physiological saline, Org 2766 (10 microg/kg/24 h) or RU 38486 (50 mg/kg/8 h), beginning just prior to the occlusion until killing at either day 4 or 7. Blood was collected for serum glucose and cortisol analysis. Damage was evaluated by blinded counts of CAI neurons. Both RU 38486 and Org 2766 treatment significantly (P<0.004) reduced hippocampal CA1 damage at day 4, but not on day 7. While RU 38486 raised serum cortisol and adrenocorticotropic hormone levels, neither treatment affected temperature or serum glucose. The fact that RU 38486 mimicked adrenalectomy without changing temperature suggests that the decreased rate of cell death resulted from either removal of glucocorticoids or increases in adrenocorticotropic hormone. The ability of Org 2766 to affect this rate strongly suggests that adrenocorticotropic hormone is the active regulatory hormone rather than glucocorticoids. While both RU 38486 and Org 2766 prolong the survival of CA1 neurons after transient global ischemia, only RU 38486, which is available and tested in both animals and humans, can block the detrimental effects of post-ischemia glucocorticoid elevations. Thus, the administration of RU 38486 may be a practical adjunct to other neuroprotective agents for victims of cardiac arrest, anesthetic accidents or drowning.

Adrenalectomy↗
PubMed2001

Crystal structures of mutants of Thermus thermophilus IPMDH adapted to low temperatures.

Random mutagenesis on thermophilic 3-isopropylmalate dehydrogenases (IPMDH; EC 1.1.1.85) produced mutant enzymes which adapt to low temperatures. These mutants had higher activity at lower temperatures than the wild-type enzyme without losing high thermostability. Here we report three structures of the mutants of Thermus thermophilus IPMDH determined by X-ray diffraction which was adapted to a low-temperature environment. Two of them have unstable coenzyme binding states and the other one probably has a stable substrate binding state. The present research suggests that the adaptation is correlated with the binding of either coenzyme or the substrate.

3-Isopropylmalate Dehydrogenase↗
PubMed2007

Enhancement of acid amylase production by an isolated Aspergillus awamori.

AIMS: Evaluation of the influence of fermentation components on extracellular acid amylase production by an isolated fungal strain Aspergillus awamori. METHODS AND RESULTS: Eight fungal metabolic influential factors, viz. soluble starch, corn steep liquor (CSL), casein, potassium dihydrogen phosphate (KH(2)PO(4)) and magnesium sulfate (MgSO(4) x 7H(2)O), pH, temperature and inoculum level were selected to optimize amylase production by A. awamori using fractional factorial design of Taguchi methodology. Significant improvement in acid amylase enzyme production (48%) was achieved. The optimized medium composition consisted of soluble starch--3%; CSL--0.5%; KH(2)PO(4)--0.125%; MgSO(4) x 7H(2)O--0.125%; casein--1.5% at pH 4.0 and temperature at 31 degrees C. CONCLUSION: Optimization of the components of the fermentation medium was carried out using fractional factorial design of Taguchi's L-18 orthogonal array. Based on the influence of interaction components of fermentation, these could be classified as the least significant and the most significant at individual and interaction levels. Least significant factors of individual level have higher interaction severity index and vice versa at enzyme production in this fungal strain. The pH of the medium and substrate (soluble starch) showed maximum production impact (60%) at optimized environment. Temperature and CSL were the least influential factors for acid amylase production. SIGNIFICANCE AND IMPACT OF THE STUDY: Acid amylase production by isolated A. awamori is influenced by the interaction of fermentation factors with fungal metabolism at individual and interaction levels. The pH of the fermentation medium and substrate concentration regulates maximum enzyme production process in this fungal strain.

Amylases↗
PubMed1990

Postural vasoconstriction in women during the normal menstrual cycle.

1. Postural vasoconstriction in the foot was examined in 15 women during the menstrual, follicular and luteal phases of the menstrual cycle, and in 13 age-matched men on two separate occasions, in a constant-temperature environment (22 degrees C). 2. Skin blood flow was measured using laser Doppler flowmetry with the subject lying down, first with the foot maintained at heart level, then with the foot lowered passively 50 cm below the heart. In six of the women, at the time of experiment, serum oestradiol and progesterone were determined by radioimmunoassay. In four women and three men, foot swelling rate was also measured in the dependent foot using a strain gauge plethysmograph in addition to the postural changes in flow. At each visit, in all subjects, arterial blood pressure, heart rate, body temperature, foot skin temperature and body weight were also recorded. 3. The men showed no significant changes in all the variables assessed. In contrast, in women during the luteal phase diastolic and mean arterial pressures were significantly reduced, whereas heart rate, body temperature, foot skin temperature and body weight were significantly increased, as compared with the follicular and menstrual phases of the cycle. 4. During the follicular phase, when oestradiol concentration was high, there were significant reductions in dependent flow and foot swelling rate associated with a significantly augmented postural fall in flow, whereas during the luteal phase, when both oestradiol and progesterone levels were high, there were significant increases in dependent flow and foot swelling rate associated with a significantly impaired postural fall in flow.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed2002

Low-temperature extremophiles and their applications.

Psychrophilic (cold-adapted) organisms and their products have potential applications in a broad range of industrial, agricultural and medical processes. In order for growth to occur in low-temperature environments, all cellular components must adapt to the cold. This fact, in combination with the diversity of Archaea, Bacteria and Eucarya isolated from cold environments, highlights the breadth and type of biological products and processes that might be exploited for biotechnology. Relative to this undisputed potential, psychrophiles and their products are under-utilised in biotechnology; however, recent advances, particularly with cold-active enzymes, herald rapid growth for this burgeoning field.

Adaptation, Biological↗
PubMed2006

History of discovery of the first hyperthermophiles.

Hyperthermophiles, growing optimally at 80 degrees C and above had been discovered in 1981. They represent the upper temperature border of life and are found within high temperature environments. In their basically anaerobic surroundings, they gain energy mainly by inorganic redox reactions. Within the phylogenetic tree, hyperthermophiles occupy all the short deep branches closest to the root. The earliest archaeal phylogenetic lineage is represented by the extremely tiny members of the novel kingdom of Nanoarchaeota.

Anaerobiosis↗
PubMed1997

[The effect of climatic factors on the onset of acute myocardial infarction].

The results of the single-relative analysis on the three climatic factors of air temperature, pressure and relative humidity to the attack of acute myocardial infarction in Shenyang city located in the cold Northeastern China area, showed that the attack was more frequent in summer time with high temperature, humidity and low air pressure. The attack was positively related to temperature (r = 0.7463 P < 0.01) and humidity (r = 0.6466 P < 0.01) while is negatively related to air pressure (r = -0.7300 P < 0.05). And specifically, in Shenyang area the incidence was obviously increased with average temperature > 20 degrees C, air pressure < 1010, and relative humidity > 70%. Patients should reduce the activities in high or low temperature environment. Proper precautions should be taken well in advance to avoid the attack on the patients in a particular season. And different nursing measures should be taken in different seasons to comply with changes of climate, for averting the attacks caused by the climate.

Aged↗
PubMed2025

Expansion of the functional genomics GRACE library reveals genes relevant for temperature-dependent fitness in Candida albicans.

A small percentage of species in the fungal kingdom can cause devastating infections in humans, with Candida albicans reigning as a leading cause of systemic disease. One of the key virulence phenotypes for pathogenic fungi is the ability to survive at host body temperature; however, a comprehensive understanding of the mechanisms that orchestrate thermal adaptation in fungi remains incomplete. In this study, we expand the largest functional genomics resource in C. albicans, reaching 71.3% coverage of the entire genome, and perform screens under six different temperatures to identify genes important for temperature-dependent fitness. We describe the function of genes involved in translation (GAR1), splicing (C1_11680C or YSF3), and cell cycle progression (C6_00110C or RHT1) in enabling fungal survival at both low and high temperatures. Through experimental evolution, we also show that C. albicans can rapidly overcome deleterious mutations and adapt to extreme temperature environments. Overall, our study highlights the transformative potential of genome-wide functional genomics to uncover critical vulnerabilities in pathogenic fungi.

Genomics↗
PubMed2000

Delayed, spontaneous hypothermia reduces neuronal damage after asphyxial cardiac arrest in rats.

OBJECTIVE: Core temperature is reduced spontaneously after asphyxial cardiac arrest in rats. To determine whether spontaneous hypothermia influences neurologic damage after asphyxial arrest, we compared neurologic outcome in rats permitted to develop spontaneous hypothermia vs. rats managed with controlled normothermia. INTERVENTIONS: Male Sprague-Dawley rats were asphyxiated for 8 mins and resuscitated. After extubation, a cohort of rats was managed with controlled normothermia (CN) by placement in a servo-controlled incubator set to maintain rectal temperature at 37.4 degrees C for 48 hrs. CN rats were compared with permissive hypothermia (PH) rats that were returned to an ambient temperature environment after extubation. Rats were killed at either 72 hrs (PH72hr, n = 14; CN72hr, n = 9) or 6 wks (PH6wk, n = 6, CN6wk, n = 6) after resuscitation. PH72 rats were historic controls for the CN72 rats, whereas PH6 and CN6 rats were randomized and studied contemporaneously. MEASUREMENTS: A clinical neurodeficit score (NDS) was determined daily. A pathologist blinded to group scored 40 hematoxylin and eosin -stained brain regions for damage by using a 5-point scale (0 = none, 5 = severe). Quantitative analysis of CA1 hippocampus injury was performed by counting normal-appearing neurons in a defined subsection of CA1. MAIN RESULTS: Mean rectal temperatures measured in the PH6wk rats (n = 6) were 36.9, 34.8, 35.5, 36.7, and 37.4 degrees C at 2, 8, 12, 24, and 36 hrs, respectively. Mortality rate (before termination) was lower in PH compared with CN (0/20 vs. 7/15; p < .005). PH demonstrated a more favorable progression of NDS (p = .04) and less weight loss (p < .005) compared with CN. Median histopathology scores were lower (less damage) in PH72hr vs. CN72hr for temporal cortex (0 vs. 2.5), parietal cortex (0 vs. 2), thalamus (0 vs. 3), CA1 hippocampus (1.5 vs. 4.5), CA2 hippocampus (0 vs. 3.5), subiculum (0 vs. 4), and cerebellar Purkinje cell layer (2 vs. 4) (all p < .05). There was almost complete loss of normal-appearing CA1 neurons in CN72hr rats (6 +/- 2 [mean +/- SD] normal neurons compared with 109 +/- 12 in naïve controls). In contrast, PH72hr rats demonstrated marked protection (97 +/- 23 normal-appearing neurons) that was still evident, although attenuated, at 6 wks (42 +/- 24 normal-appearing neurons, PH6wk). CONCLUSION: Rats resuscitated from asphyxial cardiac arrest develop delayed, mild to moderate, prolonged hypothermia that is neuroprotective.

Animals↗
PubMed1997

Sulfur and hydrogen isotope anomalies in meteorite sulfonic acids.

Intramolecular carbon, hydrogen, and sulfur isotope ratios were measured on a homologous series of organic sulfonic acids discovered in the Murchison meteorite. Mass-independent sulfur isotope fractionations were observed along with high deuterium/hydrogen ratios. The deuterium enrichments indicate formation of the hydrocarbon portion of these compounds in a low-temperature environment that is consistent with that of interstellar clouds. Sulfur-33 enrichments observed in methanesulfonic acid could have resulted from gas-phase ultraviolet irradiation of a precursor, carbon disulfide. The source of the sulfonic acid precursors may have been the reactive interstellar molecule carbon monosulfide.

Alkanesulfonic Acids↗