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At least 721 records · Page 40Linked to original sources
PubMed1994

Temperature dependence of lipoxygenase heat inactivation; evaluation with linearly increasing temperature profiles.

A non-isothermal kinetic method for evaluating the temperature dependence of enzyme heat inactivation has been developed from theoretical considerations. By using a non-linear regression software programme and enzyme activity data obtained along linearly increasing temperature profiles, z values of lipoxygenase were obtained in single experiments, substantially reducing time, cost, and labour. The z values so obtained were slightly dependent on heating rate, varying from 4.11 degrees C at a rate of heating of 2.56 degrees C/min to 4.66 degrees C at a heating rate of 1.48 degrees C/min.

Hot Temperature↗
PubMed1995

Evaluation of non-radioactive temperature gradient SSCP analysis and of temperature gradient gel electrophoresis for the detection of HPV 6-variants in condylomata acuminata and Buschke-Loewenstein tumours.

A modified non-radioactive single strand conformation polymorphism analysis incorporating a temperature gradient (TG-SSCP) and temperature gradient gel electrophoresis (TGGE) were evaluated for the detection of human papillomavirus type 6 (HPV 6)-variants in 41 condylomata acuminata and 5 Buschke-Loewenstein tumours. TG-SSCP and TGGE analysed part of the transforming ORF E6 of HPV 6 spanning nucleotides 10 to 495. TG-SSCP distinguished between 8 HPV 6-variants whereas TGGE demonstrated 6 different DNA-species. HPV 6-strains found in Buschke-Loewenstein tumours did not vary in the analysed portion of the E6 ORF as compared to ordinary condylomata acuminata. TG-SSCP and TGGE further showed absence of double infection with different HPV 6-strains in the analysed samples. Our results demonstrated that both methods may be successfully used for the detection of different strains of microbiological agents, although TG-SSCP seemed to provide easier execution and to confer a higher degree of flexibility than TGGE.

Condylomata Acuminata↗
PubMed1986

Effect of temperature and cell density on cellular protein content in temperature-sensitive mutants of rat 3Y1 diploid fibroblasts.

We examined cellular protein content in four temperature-sensitive (ts) mutants of rat 3Y1 fibroblasts (3Y1tsD123, 3Y1tsF121, 3Y1tsG125, and 3Y1tsH203) under various conditions of culture that affect cell proliferation. When proliferation of the ts mutants was inhibited at a nonpermissive temperature (39.8 degrees C) in the G1 phase, prominent accumulation of cellular protein occurred in three mutants (3Y1tsF121, 3Y1tsG125, and 3Y1tsH203) but not in 3Y1tsD123. The over-accumulation of protein at 39.8 degrees C in the former three mutants was inhibited at high cell densities. At low cell densities there was an upper limit in the protein accumulation at 39.8 degrees C. When the three mutants, proliferation-arrested at high cell densities at 33.8 degrees C, were replated sparsely in fresh medium and shifted to 39.8 degrees C, proliferation was completely inhibited, whereas over-accumulation of protein occurred. These results indicating dissociation of protein accumulation and cell proliferation suggest that the two events are regulated by different mechanisms.

Animals↗
PubMed1997

Vigilance state episodes and cortical temperature in the Djungarian hamster: the influence of photoperiod and ambient temperature.

The electroencephalogram, electromyogram and cortical temperature (TCRT) were recorded in seven Djungarian hamsters adapted to a short photoperiod at 16 degrees C ambient temperature (TA; SP16). A baseline day was followed by 4 h sleep deprivation (SD) and 20 h recovery. The analysis included data obtained in earlier experiments at 22 degrees C TA in a long (LP22) and short photoperiod (SP22). In all three conditions the changes in TCRT during vigilance state episodes were a function of episode duration and, for waking and non-rapid eye movement (NREM) sleep, of TCRT at episode onset. The increase in TCRT during REM sleep became progressively larger from LP22 to SP22 to SP16. After SD the mean TCRT decreased below baseline in the LP22 and stayed above baseline in the SP22. This difference in the effect of SD on TCRT was reflected in its increase during REM sleep, which was attenuated during recovery in LP22, but was enhanced in SP22. The time course of TCRT during NREM sleep or waking episodes was unaffected by SD. Therefore, the overall difference in TCRT between baseline and recovery in the LP22 and SP22 is due to changes in the increase in TCRT during REM sleep.

Animals↗
PubMed1990

EPR spectra of ferric cytochromes c' from five strains of Achromobacter xylosoxidans at low temperature and their temperature dependence.

The EPR spectra at low temperature (6 K) and their temperature dependence (10-93 K) for five ferric cytochromes c' isolated from chemoheterotrophic bacteria, Achromobacter xylosoxidans NCIB 11015 (formerly Alcaligenes sp. NCIB 11015), GIFU 543, GIFU 1048, GIFU 1051, and GIFU 1764 are reported. The EPR spectral results indicate that the ground state of the heme iron(III) of cytochromes c' from these chemoheterotrophic bacteria can appear to be in an admixed spin state which consists of predominant S = 5/2 with a slight S = 3/2 character. The EPR spectra were compared with those for ferric cytochromes c' from photosynthetic bacteria and the other ferric hemoproteins.

Alcaligenes↗
PubMed1992

Maintenance of repression control of the ilvGMEDA operon in a temperature-sensitive leucyl-transfer RNA synthetase mutant of Escherichia coli K-12 at a restrictive temperature.

The mechanism of L-leucine regulation of ilvGMEDA is thought to be by ribosome-mediated attenuation that is dependent upon the concentration of Leu-tRNA(Leu) which results from leucyl-tRNA synthetase (LeuRS) activity. The requirement for LeuRS activity in attenuation control was tested in an Escherichia coli K-12 strain containing a temperature-sensitive LeuRS and the ilvGMEDA operon with an active ilvGM. Growth of this strain at 30 degrees C followed by a shift to 37 degrees C to inactivate the LeuRS revealed that ilvGM expression decreased at the restrictive temperature whereas the downstream gene expression was slightly elevated. We suggest that ilvGM does not respond to a deattenuation signal, and that, possibly, a secondary repression/derepression mechanism exists.

Amino Acid Sequence↗
PubMed1990

Influence of ambient temperature on sleep and body temperature after phentolamine in rats.

Phentolamine, an alpha-adrenoceptor antagonist, both decreases rapid-eye-movement sleep (REMS) and causes a dose- and ambient temperature (Ta)-dependent drop in body temperature (Tb). The purpose of this paper was to examine the correlation between changes in sleep and changes in Tb after phentolamine at various Ta's. Tb and sleep were recorded in male rats for 4 h after i.p. injection of either saline or phentolamine (1 mg/kg at Ta 20 degrees C; 5 mg/kg at 20, 30 and 32 degrees C; 10 mg/kg at 20, 30, 32, and 34 degrees C). Changes in sleep were highly correlated with changes in Tb: when Tb dropped, amounts of sleep, especially REMS, also were decreased. The largest effects were seen at Ta 20 degrees C. After 5 mg/kg, Tb was below normal for 2 h and latency to REMS increased 82 +/- 27 min (P less than 0.025). After 10 mg/kg Tb was decreased for 3 h, and latency to REMS increased 91 +/- 19 min (P less than 0.001). While Tb was lower amounts of REMS were also decreased. Smaller effects were observed on slow wave sleep. At those conditions where phentolamine had no effect on Tb (i.e. Ta 20 degrees C, 1 mg/kg, and Ta 32 degrees C, 5 and 10 mg/kg) no differences were found in any measure of sleep. These results demonstrate that the effects of phentolamine on sleep are not caused by direct action on sleep mechanisms, but rather by its actions on thermoregulatory and possibly other mechanisms that modulate sleep.

Animals↗
PubMed1983

Ambient temperature dependence of the body temperature and of the duration of the hibernation periods in the garden dormouse, Eliomys quercinus L.

Hibernation pattern in the garden dormouse (Eliomys quercinus) was studied at TA's of 0, 4, 6.5, and 9 degrees C during 6 months in each study winter. The animals were kept in darkness without food or water. Body temperature and the mean duration of the hibernation periods were ambient temperature dependent. The comparison of hibernation at different TA's was based on three features: the mean duration of the hibernation periods during the midwinter plateau, the existence of the initial and terminal phases with the changing length of the hibernation periods, and the differences between the sexes. The TA of 4 degrees C was the optimal TA for long-term hibernation. The difference between 4 degrees C and other TA's was greater in males. The TA's of 0 and 9 degrees C were near the lower and higher TA limits for long-term hibernation. Signs of the existence of a circannual rhythm were detected in the males toward the end of the hibernation season.

Animals↗
PubMed1994

Application of temperature-induced phase partitioning at ambient temperature for enzyme purification.

Aqueous two-phase partition and temperature-induced phase separation using a non-ionic, random copolymer composed of 20% ethylene oxide, 80% propylene oxide (EO20 PO80) has been used for purification of glucose-6-phosphate dehydrogenase, hexokinase and 3-phosphoglycerate kinase from bakers' yeast. This EO20PO80 copolymer has a cloud point of 18 degrees C, at which temperature it phase separates from water. Enzymes were first partitioned at 4 degrees C in an initial EO20PO80-dextran T500 aqueous two-phase system. This system had an upper copolymer-rich phase and a lower dextran-rich phase. After phase separation had occurred the upper EO20PO80-rich phase was removed and placed at 24 degrees C. This resulted in formation of a new two-phase system with an upper water phase and a lower phase containing 98% copolymer and 2% water. Enzymes were recovered exclusively in upper water phase leaving a polymer-rich lower phase free of contamination. The phase diagram for the system EO20PO80 and dextran T500 at 4 degrees C has been determined.

Chemical Phenomena↗
PubMed1987

Pirenperone effects on temperature preference and body temperature in maturing mice.

Thermoregulatory effects of the selective 5-HT2 antagonist pirenperone were studied 1 hr after IP injection in mice aged 1, 3, 5, 7 and 10 days postpartum. Compared with vehicle injected littermates, a dose of 0.16 mg/kg decreased temperature preference (T pref) on a thermal gradient at all ages. No significant effects were observed on body temperature (Tb) at any of the ages. An increased dose (0.48 mg/kg) caused no greater effect on T pref and no significant effect on Tb. These results indicate that Tb and T pref are separable on the basis of receptor pharmacology, and are discussed in relation to drug effects on 5-HT2 receptors.

Animals↗
PubMed1983

Selection for temperature-sensitive mutations in specific vaccinia virus genes: isolation and characterization of a virus mutant which encodes a phosphonoacetic acid-resistant, temperature-sensitive DNA polymerase.

Seven temperature-sensitive mutants of vaccinia virus have been isolated after preselection for virus resistant to phosphonoacetic acid (PAA). In all seven mutants, the PAA-resistant (PAAr) and ts lesions represent separate mutations. In one mutant, NG26, the PAAr (NG26-PAAr) and ts (NG26-ts) mutations are very closely linked. Both NG26-ts and NG26-PAAr map in the HindIII E DNA fragment. NG26 has a DNA-negative phenotype at 40 degrees. NG26-ts is in the same complementation group as ts42, another DNA-negative mutant which maps in the HindIII E DNA fragment (R. C. Condit, A. Motyczka, and G. Spizz, Virology 128, 000-000, 1983). The order of the mutations is (NG26-ts)-(NG26-PAAr)-ts42. The virus-coded DNA polymerase has been partially purified from wt- and NG26-infected cells. The DNA polymerase encoded by NG26 is temperature sensitive and PAA resistant in vitro as compared to the wt enzyme.

DNA, Viral↗
PubMed1983

Temperature-sensitive mutants of influenza A/Udorn/72 (H3N2) virus. III. Genetic analysis of temperature-dependent host range mutants.

One hundred thirty-three ts mutants of influenza A/Udorn/72 virus were arranged into eight complementation groups, A-H, on Madin-Darby canine kidney (MDCK) monolayer cultures at the restrictive temperature of 40 degrees. The eight complementation groups, A-H, on MDCK cells corresponded to the eight recombination groups, A-H, on rhesus monkey kidney (RMK) cells, respectively, and this suggested that each MDCK complementation group represented one of the eight influenza A RNA gene segments. These ts viruses were used to identify the locus of the ts mutation in temperature-dependent host range (td-hr) mutants of the A/Udorn/72 virus. Sixteen of the 133 ts mutants exhibited distinct host (MDCK)-dependent restriction of plaque formation at 40 degrees but not at 34 degrees and were referred to as td-hr mutants. These 16 td-hr mutants were ts+ (not ts) on RMK cells but ts on MDCK cells. The td-hr mutants did not share a common lesion and the ts lesions were distributed among the eight complementation groups, A-H, when tested on MDCK cells. An analysis of one of the td-hr mutants indicated that an extrageneic RMK-dependent suppressor mutation did not account for the td-hr phenotype. These data suggested that a host-dependent ts mutation was responsible for the td-hr restriction of this mutant. Representation of td-hr mutations in each of the eight complementation groups indicates that the influenza A virus genome can undergo mutation leading to an altered host range in any of its eight RNA segments.

Animals↗
PubMed1992

Authentic temperature-regulation of a heat shock gene inserted into yeast on a high copy number vector. Influences of overexpression of HSP90 protein on high temperature growth and thermotolerance.

Heat shock protein HSP90 is relatively abundant in eukaryotic cells even in the absence of heat shock. Its precise function is still unclear, although it is apparently required in higher levels for growth at high temperatures. In this study Saccharomyces cerevisiae transformants were constructed with 50-150 copies of the homologous heat-inducible gene for HSP90 (HSP82) present on a high copy number episomal vector. These transformants were then used to demonstrate: (i) that this heat shock gene displays essentially normal regulation when present in yeast at high copy numbers; (ii) that yeast is an expression host suitable for the high level synthesis of HSP90; and (iii) that increasing normal cellular levels of HSP90 affects a number of physiological properties. The HSP82 gene is normally single-copy in the haploid yeast genome, yet even at 50 to 150 copies per cell it displayed almost normal basal and heat shock-induced levels of expression. Proper regulation of the heat shock element sequence controlling HSP82 is therefore not lost at high gene copy levels. In unstressed cultures in exponential growth at 25 degrees C the low basal expression of the multiple HSP82 gene copies caused a 3 to 7-fold HSP90 overproduction, but HSP90 levels increased 10-fold to 30-40% of total cell protein following temperature upshift to 39 degrees C for 75 min. Heat induction of the chromosomal genes for other heat shock proteins in the same cells was not suppressed relative to cells which were isogenic but for the possession of just a single HSP82 gene, this constituting further evidence that yeast can authentically regulate a large number of heat shock genes. HSP90 overproduction was not protective against heat killing, causing strain-dependent reductions in growth at 37.5 degrees C and in thermotolerance.

Autoradiography↗
PubMed2004

Development of a stabilized low temperature infrared absorption cell for use in low temperature and collisional cooling experiments.

We have constructed a stabilized low temperature infrared absorption cell cooled by an open cycle refrigerator, which can run with liquid nitrogen from 250 to 80K or with liquid helium from 80K to a few kelvin. Several CO infrared spectra were recorded at low temperature using a tunable diode laser spectrometer. These spectra were analyzed taking into account the detailed effects of collisions on the line profile when the pressure increases. We also recorded spectra at very low pressure to accurately model the diode laser emission. Spectra of the R(2) line in the fundamental band of 13CO cooled by collisions with helium buffer gas at 10.5K and at pressures near 1 Torr have been recorded. The He-pressure broadening parameter (gamma(0) = 0.3 cm(-1) atm(-1)) has been derived from the simultaneous analysis of four spectra at different pressures.

Argon↗
PubMed1987

Emergence temperature indices and relative retention times of pesticides and industrial chemicals determined by linear programmed temperature gas chromatography.

Emergence temperature indices and relative retention times of nearly 600 pesticides and industrial chemicals are sequentially tabulated to provide a basis for the identification of unknowns detected on methyl silicone columns when programmed temperature gas chromatography is used. A technique of normalizing column parameters is described to enable duplication of the tabulated data on columns which have different dimensions, amount of stationary phase, and/or other operating parameters. Suggestions for enhancing the precision with which these data can be reproduced on other equipment are presented.

Chromatography, Gas↗
PubMed1986

Optimization by isochronal analysis. II. Changes in mobile phase velocity and temperature, and in mobile phase composition and temperature.

The theory of resolution optimization by isochronal analysis is further extended to the cases involving simultaneous changes in mobile phase velocity and column temperature, and in mobile phase composition and temperature. In each case, the resolution equation, when written in terms of isochronal conditions, shows that improvements can be obtained without sacrificing analysis time. Several subcases, which relate to the dependence of the selectivity factors on the changed parameters, are described. For each system, the contributions of the various parameters to the resolution are examined. The results of these discussions are plotted as resolution surfaces, on which lines of constant analysis time are indicated. The experimental routes that chromatographers must take in order to apply isochronal analysis are described.

Chemical Phenomena↗
PubMed1984

On temperature factor and the effect of viscosity on blood temperature in the arteries.

A mathematical theory which could be used to explain a clinical observation in some sickle-cell anemia patients is proposed. It is shown that if the energy stored in the elastic walls of the artery of such a patient is accompanied by thermal effects, then the existence of a local hot spot on the body of a sickle-cell anemia patient could be due to shock formation even when the viscosity of the blood is zero. On the other hand, if the energy stored is not accompanied by thermal effects, then a jump in the temperature can only occur if the viscosity is not zero. We give the location of such a jump in the temperature and the time of its occurrence in both cases.

Anemia, Sickle Cell↗