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PubMed1984

Noncoordinate histone synthesis in heat-shocked Drosophila cells is regulated at multiple levels.

Transferring Drosophila tissue culture cells from 25 to 37 degrees C (heat shock) causes histone protein synthesis to become noncoordinate. To determine the level at which this is controlled, the synthesis, degradation, and translation of individual histone mRNAs was studied under both heat shock and control conditions. The increased synthesis of histone H2b protein during heat shock appears to be controlled primarily at the level of translation. During heat shock, H2b mRNA is transcribed at about the same level as in the control. However, H2b mRNA is more stable under heat shock than under control conditions and is predominantly found in polysomes. The reduction in synthesis of H2a, H3, and H4 protein during heat shock appears to be controlled at both the transcriptional and translational levels. Although transcription of H2a, H3, and H4 mRNAs is reduced during heat shock, like H2b mRNA, they are more stable. However, unlike H2b mRNA, these mRNAs are not predominantly associated with polysomes during heat shock. Regulation of H1 synthesis during heat shock is completely different from that of the other histones. During heat shock, H1 mRNA is not transcribed, and unlike all of the other Drosophila mRNAs studied to date, its mRNA is not stable in heat-shocked cells. Results from in vitro translation studies support the conclusion that noncoordinate synthesis of the core histone proteins during heat shock is controlled at the level of translation.

Animals↗
PubMedDate not supplied

Heated intraoperative intraperitoneal mitomycin C and early postoperative intraperitoneal 5-fluorouracil: pharmacokinetic studies.

PURPOSE: The purpose of this study was to report the pharmacokinetics of heated intraoperative intraperitoneal mitomycin C (MMC) and to analyze the impact of heat, extent of peritoneal resections, and effect of intraoperative hyperthermic chemotherapy on the pharmacological properties of the peritoneal plasma barrier. METHODS: Sixty patients with peritoneal carcinomatosis were included in a phase I/II study combining cytoreductive surgery with 2 h of heated intraperitoneal mitomycin C in an intraoperative lavage technique and one cycle of early postoperative 5-fluorouracil (5-FU) given on postoperative days 1-5. Three pharmacokinetic analyses were performed: (1) pharmacokinetics of heated intraoperative intraperitoneal MMC was determined for 18 patients by sampling peritoneal fluid, plasma, and urine during the 2-h procedure; (2) impact of peritoneal resections on MMC pharmacokinetics was assessed by comparing a group of patients who underwent < or = 1 peritonectomy procedure (minimal surgery) to a group of patients who underwent > or = 2 peritonectomy procedures (extensive surgery), and (3) effects of heated intraoperative intraperitoneal chemotherapy on the pharmacokinetics of early postoperative intraperitoneal 5-FU by comparing a group of patients treated with heated intraoperative intraperitoneal MMC to a control group who did not receive heated intraoperative intraperitoneal chemotherapy. RESULTS: The mean dose of heated intraoperative intraperitoneal MMC per patient was 22.5+/-7.1 mg (12.9+/-3.8 mg/m2). Drug absorption from perfusate was 14.3+/-2.7 mg. The mean aeras under the curve (AUC) for perfusate and plasma were, respectively, 340+/-138 and 15+/-4 microg/ml x min. The mean AUC peritoneal fluid/plasma ratio was 23.5+/-5.8. Patients who underwent extensive peritoneal resections exhibited a significantly (p = 0.037; Wilcoxon rank test) increased peak plasma concentration of MMC, a significantly (p = 0.029) increased AUC of plasma concentrations and a significantly (p = 0.034) decreased peritoneal fluid/plasma AUC ratio. Pharmacokinetic studies of early postoperative intraperitoneal 5-FU showed no significant difference in plasma AUC, perfusate AUC and AUC ratio between patients who received and those who did not receive heated intraoperative intraperitoneal MMC. CONCLUSIONS: Heated intraoperative intraperitoneal chemotherapy achieves high peritoneal concentrations of MMC with limited systemic absorption. Systemic drug absorption during heated intraoperative intraperitoneal chemotherapy is increased when extensive peritoneal resections are performed, but such slight increases are unlikely to change the risk of systemic drug toxicities. Heated intraoperative intraperitoneal chemotherapy does not alter the pharmacokinetics of early postoperative intraperitoneal 5-FU.

Antibiotics, Antineoplastic↗
PubMed1982

Heat production during hypoxic contracture of rat myocardium.

Contracture due to hypoxia, to both oxygen and glucose deficiency, and to potassium chloride was induced in rat left ventricular papillary muscle preparations. Under contracture conditions, the sum of resting heat plus contracture heat was measured using Hill-type, planar vacuum-deposited thermopiles. On the basis of the measured total and initial heat output and the corresponding tension-time integral during single twitches under control conditions (Lmax, 21 degrees C, stimulus frequency 12/min), the expected heat output during contracture was calculated, assuming that the contracture tension is maintained by the same calcium-induced cross-bridge cycling as occurs in the single twitch response. With potassium chloride, the contracture tension was 1.33 +/- 0.27 g/mm2, a value which is similar to those found in hypoxic contracture and in contracture due to both oxygen and glucose deficiency. There was no significant difference between measured and calculated values for resting heat plus contracture heat (8.40 +/- 2.84 mW/g measured, 8.55 +/- 2.50 mW/g calculated); there was a linear correlation (r = 0.99) between predicted and measured values (P less than 0.05). The measured value for resting plus contracture heat in hypoxic contracture was 1.88 +/- 0.37 mW/g, whereas a value of 4.80 +/- 1.09 mW/g (P less than 0.005) was calculated on the basis of the twitch heat per tension-time integral and contracture tension (1.09 +/- 0.31 g/mm2). Contracture tension was 1.80 +/- 0.78 g/mm2 in contracture due to oxygen and glucose deficiency, whereas the value for resting plus contracture eat was 1.61 +/- 0.56 mW/g. The calculated resting plus contracture heat value for this preparation was significantly higher (7.45 +/- 3.75 mW/g; P less than 0.05). There was no significant regression between predicted and measured resting heat plus contracture heat in the hypoxic contracture preparations (slope not different from zero). In contracture due to oxygen and glucose deficiency, the linear regression had a slope of 6.06 (P less than 0.05). The results suggest that the potassium chloride contracture relies on cross-bridge cycling as in a twitch contraction, whereas hypoxic contracture and that due to oxygen and glucose deficiency may be explained by cross-bridge formations with no, or very low, heat production, i.e., contracture tensions due to hypoxia and to oxygen and glucose deficiency are maintained by rigor-like cross-bridge formation or by slowly cycling cross-bridges with a long time of cross-bridge attachment.

Animals↗
PubMed2004

Conductive heat exchange with a gel-coated circulating water mattress.

The use of forced-air warming is associated with costs for the disposable blankets. As an alternative method, we studied heat transfer with a reusable gel-coated circulating water mattress placed under the back in eight healthy volunteers. Heat flux was measured with six calibrated heat flux transducers. Additionally, mattress temperature, skin temperature, and core temperature were measured. Water temperature was set to 25 degrees C, 30 degrees C, 35 degrees C, and 41 degrees C. Heat transfer was calculated by multiplying heat flux by contact area. Mattress temperature, skin temperature, and heat flux were used to determine the heat exchange coefficient for conduction. Heat flux and water temperature were related by the following equation: heat flux = 10.3 x water temperature - 374 (r(2) = 0.98). The heat exchange coefficient for conduction was 121 W . m(-2) . degrees C(-1). The maximal heat transfer with the gel-coated circulating water mattress was 18.4 +/- 3.3 W. Because of the small effect on the heat balance of the body, a gel-coated circulating water mattress placed only on the back cannot replace a forced-air warming system.

Adult↗
PubMed2005

Digestive state influences the heart rate hysteresis and rates of heat exchange in the varanid lizard Varanus rosenbergi.

To maximize the period where body temperature (Tb) exceeds ambient temperature (Ta), many reptiles have been reported to regulate heart rate (fH) and peripheral blood flow so that the rate of heat gain in a warming environment occurs more rapidly than the rate of heat loss in a cooling environment. It may be hypothesized that the rate of cooling, particularly at relatively cool Tbs, would be further reduced during postprandial periods when specific dynamic action (SDA) increases endogenous heat production (i.e. the heat increment of feeding). Furthermore, it may also be hypothesized that the increased perfusion of the gastrointestinal organs that occurs during digestion may limit peripheral blood flow and thus compromise the rate of heating. Finally, if the changes in fh are solely for the purpose of thermoregulation, there should be no associated changes in energy demand and, consequently, no hysteresis in the rate of oxygen consumption (V(O2)). To test these hypotheses, seven individual Varanus rosenbergi were heated and cooled between 19 degrees C and 35 degrees C following at least 8 days fasting and then approximately 25 h after consumption of a meal (mean 10% of fasted body mass). For a given Tb between the range of 19-35 degrees C, fh of fasting lizards was higher during heating than during cooling. Postprandial lizards also displayed a hysteresis in fh, although the magnitude was reduced in comparison with that of fasting lizards as a result of a higher fh during cooling in postprandial animals. Both for fasting and postprandial lizards, there was no hysteresis in V(O2) at any Tb throughout the range although, as a result of SDA, postprandial animals displayed a significantly higher V(O2) than fasting animals both during heating and during cooling at Tbs above 24 degrees C. The values of fh during heating at a given Tb were the same for fasting and postprandial animals, which, in combination with a slower rate of heating in postprandial animals, suggests that a prioritization of blood flow to the gastrointestinal organs during digestion is occurring at the expense of higher rates of heating. Additionally, postprandial lizards took longer to cool at Tbs below 23 degrees C, suggesting that the endogenous heat produced during digestion temporarily enhances thermoregulatory ability at lower temperatures, which would presumably assist V. rosenbergi during cooler periods in the natural environment by augmenting temperature-dependent physiological processes.

Animals↗
PubMed1999

Heat transfer from starlings sturnus vulgaris during flight

Infrared thermography was used to measure heat transfer by radiation and the surface temperature of starlings (Sturnus vulgaris) (N=4) flying in a wind tunnel at 6-14 m s-1 and at 15-25 degrees C. Heat transfer by forced convection was calculated from bird surface temperature and biophysical modelling of convective heat transfer coefficients. The legs, head and ventral brachial areas (under the wings) were the hottest parts of the bird (mean values 6.8, 6.0 and 5.3 degrees C, respectively, above air temperature). Thermal gradients between the bird surface and the air decreased at higher air temperatures or during slow flight. The legs were trailed in the air stream during slow flight and when air temperature was high; this could increase heat transfer from the legs from 1 to 12 % of heat transfer by convection, radiation and evaporation (overall heat loss). Overall heat loss at a flight speed of 10.2 m s-1 averaged 11. 3 W, of which radiation accounted for 8 % and convection for 81 %. Convection from the ventral brachial areas was the most important route of heat transfer (19 % of overall heat loss). Of the overall heat loss, 55 % occurred by convection and radiation from the wings, although the primaries and secondaries were the coolest parts of the bird (2.2-2.5 degrees C above air temperature). Calculated heat transfer from flying starlings was most sensitive to accurate measurement of air temperature and convective heat transfer coefficients.

Journal Article↗
PubMed1983

Dependence of shortening heat on sarcomere length in frog muscle and fiber bundles.

The relation between shortening heat and sarcomere length was studied using fiber bundles from frog semitendinosus muscles as well as using whole muscles. The initial sarcomere length was varied between 2.0 and 3.66 micron. Shortening heat was estimated as the excess heat produced after a rapid isovelocity release in a 3 sec tetanus at 0 degrees C. The isometric control heat was measured in the same tetanus, before and after the period of shortening. The unstimulated whole muscles showed a large thermoelastic absorption of heat when released at sarcomere lengths longer than 2.5 micron, and the apparent shortening heat was negative at very long sarcomere lengths. The apparent shortening heat was corrected by subtracting the thermoelastic heat absorption by assuming that the thermoelastic effect was also present in releases of active muscles. The corrected shortening heat decreased linearly with increasing sarcomere length in the range 2.29-3.66 micron, intersecting the length axis at 3.73 +/- 0.21 micron. The thermoelastic heat absorption at long sarcomere lengths was substantially reduced in fiber bundles, suggesting that the parallel elasticity responsible for the thermoelastic effect is mainly present outside muscle cells. The corrected shortening heat in fiber bundles also decreased linearly with increasing sarcomere length, intersecting the length axis at 3.84 +/- 0.25 micron. Thus the results on fiber bundles, also based on correction but the extent of which is substantially smaller than in whole muscles, are in agreement with the results on whole muscles. The results are interpreted to mean that shortening heat is produced by the interaction of thick and thin filaments in contracting muscle.

Animals↗
PubMed2006

Changes in heat production by mature cows after changes in feeding level.

We hypothesized that adaptation of heat production in the realimented cow would occur over an extended period, and the length of time would be influenced by the level of feed. Our objectives were to quantify the changes in heat production of cows after feed restriction and to quantify the effect of level of realimentation on the dynamics of heat production in lightweight cows. Forty 4-yr-old nonpregnant, nonlacting cows (4-breed composite: 1/4 Hereford, 1/4 Angus, 1/4 Red Poll, and 1/4 Pinzgauer) were randomly assigned to receive 1 of 4 levels of a common alfalfa hay source. All cows were feed-restricted [50.0 g of DM/metabolic body size (MBS, kg of BW(0.75)); period 1], and individual fed heat production measurements were taken 0, 7, 13, 28, 56, and 91 d after feed restriction (period 1). In period 2, cows were fed their assigned feed level for their treatment after d 91 of restriction: 50.0 (T50.0), 58.5 (T58.5), 67.0 (T67.0), and 75.5 (T75.5) g of DM/MBS. Measures were taken at 7, 13, 28, 42, 56, 91, 119, and 175 d. In period 3, all cows were fed 75.5 g of DM/MBS after their 175-d measurement, and measures were taken at 7, 14, 28, 56, and 112 d later. In period 1, heat production decreased rapidly during the first 7 d of feed restriction, and heat production continued to decrease during the 91-d restriction. Heat production increased rapidly within the first 7 d, but chronic adaptation continued for T75.5 and T67.0 cows. In period 3, heat production increased rapidly during the first 7 d. Heat production scaled for metabolic body size tended to differ among treatments (P = 0.11). Daily heat production increased by 2.5 kcal/d. These data suggest that there is not a lag in heat production during realimentation and that increased recovered energy is associated with a rapid increase in heat production.

Animal Feed↗
PubMed1987

Effects of different heat treatments during processing on nutrient digestibility of soybean meal in growing swine.

Four soybean meals (SBM) were prepared in a commercial solvent-extraction plant to give a much wider range in heat treatment than is usually found among commercially available SBM. The meals were designated in ascending order of heat treatment as Under, Normal, Over and Rumen Escape. The Normal meal was processed using standard operating conditions. The Under meal received less heat treatment by reducing the steam pressure and retention time in the desolventizer-toaster. Over and Rumen Escape meals received further heat treatment in an additional four-compartment toaster. The Over meal received less heat treatment than the Rumen Escape meal by reducing steam pressure and retention time in both toasters. Crude protein content was similar for the four meals, but lysine tended to decrease with increasing heat treatment. In general, urease activity, trypsin inhibitor, protein dispersibility index and nitrogen solubility index decreased with increasing heat treatment. The +a Hunterlab color values increased as heat treatment increased. Apparent ileal digestibility of N and amino acids were similar for all meals (P greater than .05); however lysine digestibility for the Rumen Escape meal was 3.3 percentage units lower than the average of the lesser-heated meals. Energy digestibilities and nitrogen balance data were also similar (P greater than .05) for the four meals, but the apparent biological value of the Rumen Escape meal was 4.5 percentage units lower than the average of the other meals. There were no differences in nutritional value among the Under, Normal and Over meals, which represent the range in heat treatment usually found among SBM. The Rumen Escape meal, which received more severe heat treatment, tended to have lower nutritional value than the lesser-heated meals.

Animal Feed↗
PubMedDate not supplied

Factors of importance for the development of the step-down heating effect in a C3H mammary carcinoma in vivo.

The effect of step-down heating (SDH) was investigated in a C3H mammary carcinoma inoculated into the feet of CDF1 mice. The SDH effect was evaluated by comparing slopes of time versus growth delay curves of SDH-heated with the curve for single-heated controls. The effect was quantified by a ratio: 'step-down ratio' (SDR), defined as slope (SDH-heated)/slope (single-heated). Step-down heating resulted in thermosensitization in contrast to step-up heating which did not affect the heat sensitivity. The kinetics of the step-down heating effect was investigated by inserting an interval between a 44.5 degrees C/10 min sensitizing treatment (ST) and a 42.0 degrees C test treatment (TT). The effect of SDH was maximal with no interval between ST and TT (SDR = 2.3), decayed within 2 h and turned into thermotolerance. This thermotolerance was maximal after 12 h and decayed within 120 h. The effect of varying the TT temperature was investigated in the range 39.0-44.5 degrees C (ST = 44.5 degrees C/10 min). Below 42.5 degrees C the SDR value increased exponentially, and even a 39 degrees C TT produced a significant heat damage. An Arrhenius analysis was made showing a straight line in the whole temperature range with an activation energy of 526 kJ/mol and an increased activation entropy. These data show that thermosensitization can be induced by SDH in C3H mammary carcinomas in vivo. The effect seems to decay within 2 h, and by decreasing the heat activation energies the effect of low temperature heating is increased.

Animals↗
PubMedDate not supplied

Influence of tonicity and chloramphenicol on hyperthermic cytotoxicity and cell permeability under various heating rates.

The cell lethality and permeability induced in Escherichia coli B/r, Escherichia coli Bs-1 and Zygosaccharomyces bailii cells by high temperature (52 degrees C) after heating at different rates (mean s 0.015, 0.25 and 1.50 degrees C per s) and in media of different tonicity and content (isotonic YEP broth versus 0.01 M phosphate buffer, pH 7.0 containing different concentrations of NaCl) and with versus without chloramphenicol (10 micrograms/ml) have been investigated. Hyperthermic treatment in YEP broth of isotonic 0.01 M phosphate buffer resulted in markedly reduced cytotoxicity with decreasing heat rate. The heating rate effect was larger when the cells were treated in YEP broth. Chloramphenicol, which is known to inhibit expression of heat shock proteins in bacteria, did not affect the viability of cells or the development of thermotolerance in cells heated at different heating rates in isotonic phosphate buffer but prevented the development of an additional degree of thermotolerance in cells heated slowly in YEP broth. In contrast, the differential effect of heating rate on cytotoxicity and cell permeability was not demonstrated when cells were heated in hypertonic solution (1M NaCl in phosphate buffer, pH 7.0). It is proposed that heat destabilization of the osmotic cell homeostasis, which is more profound after rapid heating, plays a major part in heat induced cellular lethality.

Cell Membrane Permeability↗
PubMed1976

The effects of moderate heat stress on patients with ischemic heart disease.

With the use of a climate chamber, the effects of a 3-h exposure to moderate heat stress (23 to 29 degrees C) on the physiology, comfort, and performance of 20 subjects, 10 with slight (group I) and 10 with moderate (group II) ischemic heart disease (IHD), were studied. Twenty matched control subjects were similarly exposed. All of the subjects performed sedentary, mental work throughout the exposure. Humidity was 9 mm Hg; air velocity, 10+/-3 cm per second; and thermal resistance of the clothing, 0.7 clo. Under identical conditions no significant differences in rectal, skin, and finger temperatures or weight loss existed between the three groups, but during heat stress the temperatures and weight loss were always significantly higher than under the control conditions, except for rectal temperatures during the first 2 h. There was no difference between the groups or the two sets of conditions in respiration rate and diastolic blood pressure, but the patients had a significantly lower systolic blood pressure in the third hour of heat stress than under the control conditions. Heart rate and the rate-pressure-product during heat stress were significantly higher in the controls than in the patients. A few patients experienced a slight retrosternal oppression during heat stress, but only one had ECG changes, and none of these symptoms or signs were present under control conditions. Under both sets of temperature conditions the patients were uncomfortable during a longer period of time than the controls, and they were more sensitive to temperature changes, group II being more sensitive than group I. The comfort distribution curve was very narrow for group II. The performance tests were numerical addition, card punching, cue-utilization and creative association. In numerical addition no temperature effect could be shown on the speed of working, but for the patients in group II during heat stress the level of accuracy in the second hour was lower than under control conditions; the trend was the opposite for control subjects. No differences occurred in the first or third hour. In card punching the patients in group II worked significantly more slowly during heat stress than did the control subjects, who improved their performance in heat, as did the paracy with which this task was performed, the patients in group II making significantly more errors in the heat than patients in group I. Cue-utilization did not differ between groups or conditions. Patients performing the creative association test under heat stress supplied significantly fewer unique answers than did patients working under control conditions; no such effect of heat was observed for control subjects. We conclude that patients with IHD are more sensitive to moderate heat stress than healthy control subjects in terms of mental performance and comfort. There are some differences in cardiopulmonary function but no differences in thermoregulation.

Body Temperature Regulation↗
PubMed1990

[Clinical research on hyperthermia of cancer using microwave heating equipment of lens applicator type].

Ninety cases with 96 tumors were treated by the 430 MHz microwave heating systems, HTS-100, at Tokyo Metropolitan Komagome Hospital, Kyoto University and Aichi Cancer Center. The results of treatment were analyzed, and the following have been clarified. Three cases are demonstrated showing feature of HTS-100. 1) The results of 383 sessions of heating by HTS-100 were analyzed, and it has been clarified that even the larger tumors, more than 5 cm both in size and depth, can be heated satisfactorily to temperatures higher than 42 degrees C. This system is capable of heating remarkably wider areas compared with the conventional microwave heating systems. 2) Hyperthermia by HTS-100 and radiotherapy were combined for treatment. The success rate (total percentage of CR plus PRa) of 89 cases analyzed was as high as 66.3%. Furthermore, local heating was successful for 60.7% of tumors, larger than 5 cm and deeper than 4 cm. 3) Combination of microwave heating and RF wave heating is a new method which is helpful for expansion of indications. 4) The frequencies of side effects of HTS-100 heating were: pain, 15.6%; sensation of heat, 6.3%; burns, 3.6%. Most of side effects were transient and slight. The higher frequency of pain than the conventional microwave heating is attributable to expansion of heating area.

Adenocarcinoma↗
PubMed1989

Macroscopic changes seen in human erythrocytes heated in a suspension and the resulting effect on their blood group activity.

Changes in the macroscopic appearance and in the activity of various erythrocyte antigens were observed by heating human erythrocytes of known blood groups at 60-260 degrees C for 15, 30, and 60 min in a suspension that was sealed in an airtight test tube. While the erythrocytes underwent severe hemolysis after heating at 60 degrees C, this phenomenon was not macroscopically observed on heating at 80 and 100 degrees C and the cellular sludge in the tested became brown in color. With further temperature increases, the supernatant became pale yellow at 120-140 degrees C, brown at 160 degrees C and dark brown at 180 degrees C and above, whereas the sediment hardened and became darker in tone. Both A and B activity in the cellular sludge remained active until a 30-min heating at 240 degrees C, as did the O(H) activity until a 15-min heating at 220 degrees C. Both Lewis type activity was detected until a 30-min heating at 200 degrees C and a 15-min heating at 220 degrees C. The P1 activity remained specific after a 30-min heating at 180 degrees C and false-positive reactions were observed after 60 min at 180 degrees C. Among the Rh antigen activity, D activity remained until a 60-min heating at 140 degrees C, C and E until a 30-min heating at 140 degrees C, c until a 15-min heating at 140 degrees C and e until a 30-min heating at 100 degrees C.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Group Antigens↗
PubMed1994

Interaction of heat and hypoxia in modulating transcription of DT diaphorase in human colon adenocarcinoma cells.

To study the regulation of the human detoxicating enzyme DT diaphorase (DTD) under hypoxic conditions, we examined the effects of heat and hypoxia, and their interaction, on the steady-state levels of mRNA and DTD enzyme activity in human colon adenocarcinoma HT29 cells. We found that a 1-h heat treatment (42.5 degrees C) markedly increased the specific activity of DTD. Elevated enzyme activity was observed within 30 min, peaked at 6 h, and had almost returned to baseline by 36 h. The effect of hypoxia alone on DTD enzyme activity developed more slowly, with a maximal response at 24 h, and return to baseline at 72 h. The effect of a 1-h heat treatment was not inhibited by subsequent hypoxic exposure for 8 h. The effect of hypoxia was also not inhibited by heat in any schedule. However, a 1-h exposure to heat during 8 h hypoxic exposure induced the transcriptional effects of heat treatment much earlier. Heat shock followed by hypoxic stress resulted in prolonged elevation of DTD activity similar to that observed with hypoxia alone. We found that DTD mRNA content was elevated with a time course concordant with that of the enzyme activity. These data suggest that hypoxia and heat shock induce expression of the DTD gene independently. The mechanism of heat effect on DTD gene expression was investigated. Gel retardation assays demonstrated the induction of a binding activity of heat-induced transcription factor(s) to heat shock elements following both heat and hypoxia.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenocarcinoma↗
PubMed2000

Effect of heat stress on serotonin-2A receptor-mediated intracellular calcium mobilization in rat C6 glioma cells.

This study was conducted to investigate an effect of heat stress at 44 degrees C for 30 min on intracellular Ca2+ signaling system and on heat shock protein (HSP)-70 expression. 5-HT-induced Ca2+ mobilization was reduced 1, 3 and 6 hrs after heat stress, and recovered to the control level 12 and 24 hrs after heat stress. One hr after heat stress, Ca2+ rise was significantly decreased when the cells were stimulated by any concentration of 5-HT. Thrombin-induced Ca2+ increase was also markedly reduced 1 hr after heat stress. HSP-70 level was increased 6 and 9 hr after heat stress. In HSP synthesis inhibitor quercetin-treated cells, HSP-70 expression was not enhanced after heat stress, and Ca2+ rise in response to 5-HT did not return to the control level. However, the Ca2+ rise induced by 5-HT was not restored to the control level after stress in Ac-Asp-Glu-Val-Asp-H (DEVD)-exposed cells while DEVD had little effect on heat stress-induced synthesis of HSP-70. Dexamethasone did not alter the change in HSP-70 expression or Ca2+ response after heat stress. These results indicate that heat stress attenuated 5-HT-induced Ca2+ mobilization and that HSP-70 expression played an important role in recovery from Ca2+ impairment, possibly via protease activity in C6 cells.

Animals↗
PubMed2006

Heat-induced hormesis in longevity of two sibling Drosophila species.

Previous work showed that mild-heat stress induces longevity hormesis in a model organism, D. melanogaster. Here we compared the possible heat-induced hormesis in longevity of other species of Drosophila, D. buzzatii and its sibling species D. koepferae, in a single-sex environment. Possible correlations between longevity and heat-stress resistance were also tested by measuring longevity, heat-knockdown resistance and the heat-induced Hsp70 expression for each species in a common environment. D. buzzatii was longer lived than D. koepferae at benign temperature. Knockdown resistance to heat stress was positively correlated to longevity within species. However, the shorter-lived species was more resistant to knockdown by heat stress than the longer-lived species. The heat-induced Hsp70 expression was similar between species. A heat-shock treatment (37 degrees C for 1 h at 4 days of age) extended mean longevity in the longer lived species but not in the shorter lived species. In D. koepferae, the demographic rate of senescence decreased but the baseline mortality rate increased by heat-shock, resulting in no extension of mean longevity. Sympatric populations of closely related species can be differentially sensitive to temperature and exhibit different patterns of 37 degrees C-induced hormesis in demographic senescence and longevity. The results also show that positive correlations between stress resistance and life span within species can shift in sign across closely related species. Finally, this study shows that heat-induced hormesis in longevity can be found across different Drosophila species, as hormetic effects are not limited to the previously studied D. melanogaster.

Aging↗
PubMed2003

Light plays a key role in the modulation of heat shock response in the cyanobacterium Synechocystis sp PCC 6803.

The heat shock response is generally characterized by an immediate, intense, and transient activation of gene expression, resulting in the elevated synthesis of heat shock proteins. We found that light modulates these characteristics of the heat shock response in cyanobacteria. Light accelerated the heat induction of htpG, groESL1, groEL2, and hspA, in Synechocystis sp. PCC 6803. In the dark, heat shock response of all the heat shock genes except hspA was not as intense as in the light and no transient peak was detected within 3h after heat shock over the time course of the hspA and groESL1 mRNA accumulation. There was an apparent relationship between the enhancement of the heat shock gene transcription in the light and the level of reduced plastoquinone in the photosynthetic electron transport system. Light affected the transcription, but not the stability of the mRNA of heat shock genes, although the stability was quite different, depending on the heat shock gene. Light also enhanced both the accumulation of GroEL under heat stress and the acquired thermo-tolerance.

Bacterial Proteins↗