A meta-analysis of nausea and vomiting following maintenance of anaesthesia with propofol or inhalational agents

Methamphetamine (m-AMPH) administration injures both striatal dopaminergic terminals and certain nonmonoaminergic cortical neurons. Fluoro-Jade histochemistry was used to label cortical cells injured by m-AMPH in order to identify factors that contribute to the cortical cell body damage. Rats given four injections of m-AMPH (4 mg/kg) at 2-h intervals showed hyperthermia (mean = 40.0 +/- 0.10 degrees C) and increased behavioral activation relative to animals given saline (SAL). Three days later, m-AMPH-treated animals showed indices of injury to striatal DA terminals (depletion of tyrosine hydroxylase immunoreactivity) and parietal cortical cell bodies (appearance of Fluoro-Jade stained cells). Pretreatment with a dopamine (DA) D1, D2, or N-methyl-D-aspartate (NMDA) receptor antagonist, or administration of m-AMPH in a 4 degrees C environment, prevented or attenuated m-AMPH-induced hyperthermia, behavioral activation, and injury to striatal DA terminals and parietal cortical cell bodies. Animals pretreated with a DA transport inhibitor prior to m-AMPH showed hyperthermia, behavioral activation, and parietal cortical cell body injury, but they did not show striatal DA terminal injury. Pretreatment with a 5HT transport inhibitor failed to prevent m-AMPH-induced damage to striatal DA terminals or parietal cortical cell bodies. Animals given four injections of SAL in a 37 degrees C environment became hyperthermic, but showed no injury to striatal DA terminals or cortical cell bodies. The ability of the DA transport inhibitor to block m-AMPH-induced striatal DA damage, but not cortical injury, and the inability of hyperthermia alone to cause the cortical cell body injury suggests that m-AMPH-induced behavioral activation and hyperthermia may both be necessary for the subsequent parietal cortical cell body damage.     

Angiotensin II tachyphylaxis in the guinea pig ileum and its prevention: a pharmacological and biochemical study

Angiotensin II (AII) tachyphylaxis occurs in the guinea pig ileum, but is not induced by analogs lacking the N-terminal amino group or the Arg2 guanidino group. Both AII and Lys2AII increased cell inositol trisphoshate content in cultured intestinal smooth muscle cells. Protein kinase C inhibition by staurosporine or downregulation by prolonged incubation with phorbol reverted tachyphylaxis of the inositol trisphoshate response, but not that of the Na+ uptake response, indicating that the uncoupling of the phosphoinositide signal system by protein kinase C did not involve all processes distal to receptor activation. Tachyphylaxis of the Na+ uptake response was prevented when receptor internalization was blocked by reduction of the temperature (4 degrees C) or by pretreatment of the cells with phenylarsine oxide. Acid washings, which prevented tachyphylaxis of the 24Na+ influx response, also prevented tachyphylaxis of the contractile response of the guinea pig ileum to AII. Although these findings suggest that sequestration or internalization of the AII receptor might be involved in AII tachyphylaxis, binding of [125I]AII and of [125I]Lys2AII to the cells was equally unaffected by repeated administrations of the peptides. The results suggest that conformational change of the AII-receptor complex within the plasma membrane, but not internalization, is the most important factor responsible for tachyphylaxis.     

Role of semicarbazide-sensitive amine oxidase on glucose transport and GLUT4 recruitment to the cell surface in adipose cells

The previous characterization of an abundant population of non-adrenergic imidazoline-I2 binding sites in adipocytes and the recent demonstration of the interplay between these binding sites and amine oxidases led us to analyze the amine oxidase activity in membranes from isolated rat adipocytes. Adipocyte membranes had substantial levels of semicarbazide-sensitive amine oxidase (SSAO). SSAO activity and immunoreactive SSAO protein were maximal in plasma membranes, and they were also detectable in intracellular membranes. Vesicle immunoisolation analysis indicated that GLUT4-containing vesicles from rat adipocytes contain substantial levels of SSAO activity and immunoreactive SSAO protein. Immunotitration of intracellular GLUT4 vesicles indicated that GLUT4 and SSAO colocalize in an endosomal compartment in rat adipocytes. SSAO activity was also found in GLUT4 vesicles from 3T3-L1 adipocytes and rat skeletal muscle. Benzylamine, a substrate of SSAO activity, caused a marked stimulation of glucose transport in isolated rat adipocytes in the presence of very low vanadate concentrations that by themselves were ineffective in exerting insulin-like effects. This synergistic effect of benzylamine and vanadate on glucose transport was totally abolished in the presence of semicarbazide, a specific inhibitor of SSAO. Subcellular membrane fractionation revealed that the combination of benzylamine and vanadate caused a recruitment of GLUT4 to the plasma membrane of adipose cells. The stimulatory effects of benzylamine and vanadate on glucose transport were blocked by catalase, suggesting that hydrogen peroxide production coupled to SSAO activity plays a crucial regulatory role. Based on these results we propose that SSAO activity might contribute through hydrogen peroxide production to the in vivo regulation of GLUT4 trafficking in adipose cells.     

Genistein exerts estrogen-like effects in male mouse reproductive tract

The 'retention analysis method', which is based on size-exclusion chromatography (SEC) in conjunction with an arsenic-specific detector (graphite furnace atomic absorption spectrometer, GFAAS), was used to study the effect of pH (range 2.0-10.0), temperature (4, 25 and 37 degrees C), and the concentration of glutathione in the mobile phase (0.5-7.5 mM) on the formation of arsenic-glutathione species after injection of sodium arsenite using phosphate-buffered saline solutions as mobile phases. The formation of arsenic-GSH species was facilitated by low temperatures (4 degrees C), pH 6.0-8.0 and high concentrations of glutathione (7.5 mM) in the mobile phase. Simulating the physicochemical parameters found inside human red blood cells (approximately 3.0 mM glutathione, 37 degrees C, pH 7.4) and hepatocytes (approximately 7.5 mM glutathione, 37 degrees C, pH 7.4), SEC-GFAAS provided evidence for the formation of arsenic-glutathione species under these conditions. In addition, the 'chelating agent', sodium DL-2,3-dimercapto- -propanesulfonate (1.0 and 2.0 mM) was demonstrated to bind arsenous acid stronger in the presence of glutathione (7.5 mM) under these conditions (PBS buffer, pH 7.4, 37 degrees C).     

Tyramine and vanadate synergistically stimulate glucose transport in rat adipocytes by amine oxidase-dependent generation of hydrogen peroxide

Nonadrenergic imidazoline I2-binding sites colocalize with monoamine oxidase (MAO) in various tissues. As white adipocytes from various species have been reported to be very rich in I2-sites, the authors consider whether these cells show a substantial MAO activity and explore its functional role. Oxidation of [14C]tyramine by rat adipocyte membranes was dependent on both MAO and semicarbazide-sensitive amine oxidase (SSAO). Tyramine oxidation was identical in membranes and in intact adipocytes (Vmax: 11-12 nmol/min/mg protein). A similar effect of MAO and SSAO inhibitors was obtained in both the intact cells and the membranes: half of the activity was sensitive to semicarbazide and the other half more easily inhibited by MAO-A than by MAO-B inhibitors. As the reaction catalyzed by amine oxidases generates H2O2, which mimicks certain insulin effects in adipocytes, we tested whether tyramine oxidation influences glucose transport in adipocytes. One mM tyramine weakly stimulated glucose transport. A clear potentiation of tyramine effect occurred in the presence of 0.1 mM vanadate, ineffective by itself, reaching half-maximal insulin stimulation. This stimulation was sensitive to MAO and SSAO inhibitors and to catalase. The 5-fold activation of glucose transport was accompanied by translocation of GLUT4 transporters to the plasma membrane. This shows that tyramine is readily oxidized by adipocytes and potentiates the effects of vanadium on glucose transport through release of hydrogen peroxide. The role of the amine oxidases, which are highly expressed in adipocytes, allows them to be considered as more than mere scavengers of circulating amines.     

Lesbians and cancer support: clinical issues for cancer patients

Unidirectional, ouabain-insensitive K+ influx rose steeply with warming at temperatures above 37 degreesC in guinea pig erythrocytes incubated in isotonic medium. The only component of ouabain-insensitive K+ influx to show the same steep rise was K-Cl cotransport (Q10 of 10 between 37 and 41 degrees C); Na-K-Cl cotransport remained constant or declined and residual K+ influx in hypertonic medium with ouabain and bumetanide rose only gradually. Similar results were obtained for unidirectional K+ efflux. Thermal activation of K-Cl cotransport-mediated K+ influx was fully dependent on the presence of chloride in the medium; none occurred with nitrate replacing chloride. The increase of K+ influx through K-Cl cotransport from 37 to 41 degrees C was blocked by calyculin A, a phosphatase inhibitor. The Q10 of K-Cl cotransport fully activated by hydroxylamine and hypotonicity was about 2. The time course of K+ entry showed an immediate transition to a higher rate when cells were instantly warmed from 37 to 41 degrees C, but there was a 7-min time lag in returning to a lower rate when cells were cooled from 41 to 37 degrees C. These results indicate that the steepness of the response of K-Cl cotransport to mild warming is due to altered regulation of the transporter. Total unidirectional K+ influx was equal to total unidirectional K+ efflux at 37-45 degrees C, but K+ influx exceeded K+ efflux at 41 degrees C when K-Cl cotransport was inhibited by calyculin or prevented by hypertonic incubation. The net loss of K+ that results from the thermal activation of isosomotic K-Cl cotransport reported here would offset a tendency for cell swelling that could arise with warming through an imbalance of pump and leak for Na+ or for K+.     

Endurance performance in humans: the effect of a dopamine precursor or a specific serotonin (5-HT2A/2C) antagonist

In this study we examined the effect of a dopamine (DA) precursor (L-DOPA) or a serotonin (5-HT) antagonist (Ritanserin) on time to exhaustion. The study had a double-blind, randomised, placebo controlled and cross-over design. Seven moderately trained men performed three tests to exhaustion at 65% Wattmax. Each test was separated by two weeks to allow washout of the drugs (dose: 4 mg/kg Sinemet, and 0.3 mg/kg Ritanserin). Blood lactate, hematocrit, glucose, ammonia, free fatty acids (FFA), growth hormone (GH) and catecholamines were determined before and after exercise. Time to exhaustion did not differ between the three trials. Most of the parameters measured in this study responded as predicted during cycling to exhaustion in man. DA agonism significantly increased heart rate, lactate, and plasma DA values at rest, while other parameters such as FFA, lactate, plasma noradrenaline (NA) and adrenaline (A), and plasma GH showed the highest absolute levels at exhaustion. Ritanserin did not influence basal glucose and heart rate at rest, but this group showed a much lower increase in plasma catecholamine levels. We conclude that under the present conditions, neither a metabolic precursor of DA nor a specific centrally acting 5-HT2A/2C antagonist, when given in two single doses 24 h and immediately before the experiments, influences the time to exhaustion on a bicycle trial at 65% Wattmax.     

Mechanism of differential potencies of isothiocyanates as inducers of anticarcinogenic Phase 2 enzymes

Isothiocyanates occur in many edible plants and are consumed in substantial quantities by humans. A number of isothiocyanates block chemical carcinogenesis in a variety of animal models by inhibiting Phase 1 enzymes involved in carcinogen activation and by inducing Phase 2 enzymes that accelerate the inactivation of carcinogens. There are large but unexplained potency differences among individual isothiocyanates. When murine hepatoma (Hepa 1c1c7) and several other cell lines were exposed to low concentrations (1-5 microM) of certain isothiocyanates, the intracellular isothiocyanate/dithiocarbamate concentrations (measured by cyclocondensation with 1,2-benzenedithiol) rose rapidly (30 min at 37 degrees C) to very high levels (e.g., 800-900 microM). The intracellular accumulation of isothiocyanates/dithiocarbamates was temperature, structure, and glutathione dependent and could not be saturated under experimentally achievable conditions. When murine hepatoma cells were exposed to nine isothiocyanates (5 microM for 24 h at 37 degrees C) that differed considerably in structure and Phase 2 enzyme inducer potencies, the intracellular concentrations (area under curve) correlated closely and linearly with their potencies as inducers of the Phase 2 enzymes: NAD(P)H:quinone reductase and glutathione S-transferases. Isothiocyanates that did not accumulate to high levels were not inducers. These observations suggest strongly that induction of Phase 2 enzymes depends on intracellular levels of isothiocyanates/dithiocarbamates. Depletion of glutathione by treatment of Hepa cells with buthionine sulfoximine increased the inducer potencies of several isothiocyanates but could not be directly related to changes in intracellular isothiocyanate/dithiocarbamate concentrations, suggesting that glutathione may play several roles in the induction process.     

Effects of 6-hydroxydopamine and pimozide on temperature maintenance by the chicken

Intraventricular implants of pimozide in adult white leghorn hens were used to block dopamine (DA) receptors, and 6-hydroxydopamine (6-OHDA) was injected intraventricularly to destroy the noradrenergic system locally. The hens were exposed to ambient temperatures of 5 and 35 degrees C, and their core temperature was measured. One hundred micrograms of 6-OHDA significantly reduced the norepinephrine (NE) but not the DA content of the hypothalamus and reduced the uptake of [3H]NE but not of [3H]DA by synaptosomes in vitro. Neither of the drug treatments nor their combination affected average core body temperature (Tb) at either 5 or 35 degrees C. Pimozide treatment caused a lower maximum Tb at 35 degrees C and a higher maximum Tb at 5 degrees C than the control treatment. No evidence was obtained that 6-OHDA treatment affected body temperature regulation. It is concluded that neither the DA nor the NE system is essential for normal temperature maintenance in the hen exposed to either 5 or 35 degrees C.     

Synaptic-like microvesicles of neuroendocrine cells originate from a novel compartment that is continuous with the plasma membrane and devoid of transferrin receptor

We have characterized the compartment from which synaptic-like microvesicles (SLMVs), the neuroendocrine counterpart of neuronal synaptic vesicles, originate. For this purpose we have exploited the previous observation that newly synthesized synaptophysin, a membrane marker of synaptic vesicles and SLMVs, is delivered to the latter organelles via the plasma membrane and an internal compartment. Specifically, synaptophysin was labeled by cell surface biotinylation of unstimulated PC12 cells at 18 degrees C, a condition which blocked the appearance of biotinylated synaptophysin in SLMVs and in which there appeared to be no significant exocytosis of SLMVs. The majority of synaptophysin labeled at 18 degrees C with the membrane-impermeant, cleavable sulfo-NHS-SS-biotin was still accessible to extracellularly added MesNa, a 150-D membrane-impermeant thiol-reducing agent, but not to the 68,000-D protein avidin. The SLMVs generated upon reversal of the temperature to 37 degrees C originated exclusively from the membranes containing the MesNa-accessible rather than the MesNa-protected population of synaptophysin molecules. Biogenesis of SLMVs from MesNa-accessible membranes was also observed after a short (2 min) biotinylation of synaptophysin at 37 degrees C followed by chase. In contrast to synaptophysin, transferrin receptor biotinylated at 18 degrees or 37 degrees C became rapidly inaccessible to MesNa. Immunofluorescence and immunogold electron microscopy of PC12 cells revealed, in addition to the previously described perinuclear endosome in which synaptophysin and transferrin receptor are colocalized, a sub-plasmalemmal tubulocisternal membrane system distinct from caveolin-positive caveolae that contained synaptophysin but little, if any, transferrin receptor. The latter synaptophysin was selectively visualized upon digitonin permeabilization and quantitatively extracted, despite paraformaldehyde fixation, by Triton X-100. Synaptophysin biotinylated at 18 degrees C was present in these subplasmalemmal membranes. We conclude that SLMVs originate from a novel compartment that is connected to the plasma membrane via a narrow membrane continuity and lacks transferrin receptor.     

Formation of ring-shaped structures on erythrocyte membranes after treatment with botulinolysin, a thiol-activated hemolysin from Clostridium botulinum

Damage to erythrocyte membranes by botulinolysin (BLY) was studied by electron microscopy, which revealed ring-shaped structures with inner diameters and widths of approximately 32 and 6.7 nm, respectively. BLY bound to membranes at 0 degrees C, but subsequent treatment with glutaraldehyde prevented ring formation during further incubation at 37 degrees C. Zn2+ ions inhibited ring formation but not binding of BLY to membranes.     

Cholinergic modulation of the release of [3H]acetylcholine from synaptosomes of the myenteric plexus

The purpose of these experiments was to determine if cholinergic agents affected the release of acetylcholine (ACh) from a synaptosomal preparation of the guinea pig ileum myenteric plexus. The synaptosomal preparation was first incubated with the precursor [3H]choline; subsequently, release of the stored [3H]ACh was measured. The release was decreased by oxotremorine or exogenous ACh plus hexamethonium and increased by exogenous ACh plus evoked release that was inhibited by nicotinic antagonists or muscarinic agonists. Release was stimulated half-maximally by approximately 2 microM- and maximally by 10 microM-DMPP. Either in the absence of calcium or at 0 degrees C, DMPP was without effect. The effect of 10 microM-DMPP was brief, a significant stimulation occurring only within the first 2 min at 37 degrees C. Tetrodotoxin also inhibited excitation by DMPP but not completely. Thus, the release of [3H]ACh appears to be presynaptically modulated, negatively by muscarinic agonists and positively by nicotinic agonists.     

An increase in cytosolic protease activity during liver preservation. Inhibition by glutathione and glycine

Degradative cytosolic proteolysis contributes to cell injury following ATP depletion. Although ATP depletion is a salient feature of ischemic liver storage for transplantation, information regarding cytosolic protease activity during liver storage is lacking. Thus our aim was to measure liver cytosolic protease activity following ischemic storage. A progressive increase in total cytosolic protease activity was observed over time at both 37 degrees C and 4 degrees C, but the increase was greater at 37 degrees C. Total cellular proteolysis was also temperature-dependent during anoxia (37 degrees C > 4 degrees C), demonstrating a physiologic correlation between cellular proteolysis and measurements of cytosolic protease activity. The stimulation of total cytosolic protease activity was due to an increase in metallo- and aspartate protease activity. Of particular interest, glutathione (GSH) inhibited both metalloprotease and aspartate protease activity from cytosol of stored livers. Glycine, the carboxyl-terminal amino acid of GSH, also inhibited both metalloprotease and aspartate protease activity. In addition to being an antioxidant, GSH may exert its protective effects during organ preservation by inhibiting cytosolic proteases--perhaps via its glycine moiety. These experiments support the hypothesis that degradative proteolysis contributes to liver injury during organ preservation.     

Local non-synaptic modulation of aldosterone production by catecholamines and ATP in rat: implications for a direct neuronal fine tuning

In addition to hypophyseal control, steroid synthesis and secretion in the adrenal cortex is also under direct local neural modulation. We obtained morphological and neurochemical evidence that a substantial proportion of the noradrenergic nerve endings lie in close proximity to zona glomerulosa cells without making synaptic contact, thus providing evidence for a direct local modulatory role of catecholamines in steroid secretion. These noradrenergic neurones, like other noradrenergic neurones in the central nervous system, are able to take up dopamine (DA), convert it partly into noradrenaline (NA) and to release both NA and DA together with the co-transmitter ATP when neuronal activity drives them to do so. These catecholamines and ATP may reach zona glomerulosa cells via diffusion in a paracrine way and modulate the synthesis of aldosterone. The presence of ecto-Ca-ATPases, enzymes that may terminate the effect of ATP, was demonstrated around the nerve profiles indicating that not only ATP but its metabolites (ADP, AMP, adenosine) can also influence the production of aldosterone. These data strongly support the possibility of a paracrine, non-synaptic modulatory role of catecholamines and ATP in the regulation of adrenocortical steroid secretion.     

Effect of environmental temperature on glucose-induced insulin response in the newborn rat

Blood glucose and plasma insulin and glucagon concentrations were determined in full-term rats delivered by cesarean section and exposed to 37 degrees C. or 24 degrees C. environmental temperature during the first hours of extrauterine life. When newborn rats were maintained at thermal neutrality (37 degrees C.), a transient period of hypoglycemia of two hours occurred, associated with a rapid fall in plasma insulin and a rise in plasma glucagon concentrations. During cold exposure (24 degrees C.), the blood glucose level remained stable over the four hours studied; the decrease of plasma insulin was sluggish while the rise of plasma glucagon was unchanged. In newborn rats maintained at 37 degrees C., an intraperitoneal glucose load one hour after delivery produced a marked rise in blood glucose and plasma insulin concentrations one hour later. The distribution of experimental points suggested a sigmoidal dose-response curve. By contrast in newborn rats kept at room temperature (24 degrees C.) the same glucose load did not induce any increase in plasma insulin in spite of hyperglycemia. However, phentolamine resulted in pronounced plasma insulin rise in hypothermic newborns in response to glucose administration. From these observations it is concluded that the in-vivo unresponsiveness of the beta cells to glucose at birth, reported by others, is mainly due to the experimental conditions.     

The reactivity of selected acrylate esters toward glutathione and deoxyribonucleosides in vitro: structure-activity relationships

Acrylate esters are alpha,beta-unsaturated esters used as plastic monomers whose toxicity may involve reaction with tissue nucleophiles via Michael addition. Structure-activity relationships for reactivity of selected esters with glutathione (GSH) and deoxyribonucleosides were investigated in the present studies. The esters investigated were methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, butyl methacrylate, tetraethyleneglycol diacrylate, tetraethyleneglycol dimethacrylate, and ethyleneglycol dimethacrylate. To compare their reactivities toward GSH, esters were incubated for up to 1 hr at 37 degrees C and pH 7.4 with either GSH or red blood cells in phosphate-buffered saline followed by measurement of free thiol. In both systems acrylate electrophilic reactivity decreased with alpha-methyl substitution; however, the decrease in electrophilic reactivity was more evident in the cell-free system than in the red blood cell model. Increased alcohol chain length moderately affected the apparent second-order rate constant for the spontaneous reaction of acrylate esters with GSH, but did not affect potency relative to cellular GSH depletion. The apparent second-order rate constants of bifunctional esters are more than twice the rate constants of the much smaller monofunctional esters. Ethyl acrylate, a reactive acrylate ester based upon glutathione alkylation, has been designated a class 2B (suspect human) carcinogen by the International Agency for Research on Cancer. To detect possible DNA alkylation by acrylate esters in vitro, ethyl acrylate was incubated with deoxyribonucleosides for up to 24 hr at pH 6.7 or 7.4 and 37 degrees C or up to 8 hr and 50 degrees C. HPLC analysis revealed no detectable adduct formation.(ABSTRACT TRUNCATED AT 250 WORDS)     

Modeling the growth of Yersinia enterocolitica in donated blood

BACKGROUND: Sepsis and death subsequent to the transfusion of blood containing Yersinia enterocolitica is an increasing problem. The organisms probably originate from bacteremia in the donor and can subsequently multiply at low temperature. STUDY DESIGN AND METHODS: Reported here are experiments with a strain of Y. enterocolitica associated with a case of transfusion-associated bacteremia. RESULTS: It was found that the rapid early killing of Y. enterocolitica injected into donated blood does not require viable phagocytes and can be explained by complement-mediated killing. Complement resistance in Y. enterocolitica is known to be plasmid-coded. It is expressed at 37 degrees C, but not at 20 degrees C, and is favored by calcium-deficient culture media. Y. enterocolitica organisms induced to express complement resistance were still killed in donated blood, though the initial rate was slower. Such organisms multiplied in plasma at 37 degrees C, but were killed after 6 hours of incubation at 20 degrees C, presumably because complement resistance genes are switched off at this temperature. CONCLUSION: This experiment is thought to reflect the natural history of Y. enterocolitica contamination of blood, in which complement-resistant organisms in the donor blood encounter lower temperatures after donation. These observations suggest that the practice of plasma depletion may have contributed to the increased incidence of mortality due to Y. enterocolitica contamination of donated blood.     

Radioimmunoassay of thyrotropin releasing hormone in plasma and urine

A sensitive and specific radioimmunoassay has been developed capable of measuring thyrotropin releasing hormone (TRH) in extracted human plasma and urine. All of three TRH analogues tested had little cross-reactivity to antibody. Luteinizing hormone releasing hormone, lysine vasopressin, rat growth hormone and bovine albumin were without effect, but rat hypothalamic extract produced a displacement curve which was parallel to that obtained with the synthetic TRH. Sensitivity of the radioimmunoassay was 4 pg per tube with intraassay coefficient of variation of 6.2-9.7%. Synthetic TRH could be quantitatively extracted by methanol when added to human plasma in concentration of 25, 50 and 100 pg/ml. TRH immunoreactivity was rapidly reduced in plasma at 20 degrees C than at 0 degrees C, but addition of peptidase inhibitors, FOY-007 and BAL, prevented the inactivation of TRH for 3 hr at 0 degrees C. The TRH in urine was more stable at 0 degrees C than 20 degrees C, and recovered 75 +/- 4.6% hr after being added. The plasma levels of TRH were 19 pg/ml or less in normal adults and no sex difference was observed. The rate of disappearance of TRH administered i.v. from the blood could be represented as half-times of 4-12 min. Between 5.3-12.3% of the injected dose was excreted into urine within 1 hr as an immunoreactive TRH. These results indicate the usefulness of TRH radioimmunoassay for clinical investigation.     

Induction of tolerance to hypothermia and hyperthermia by a common mechanism in mammalian cells

Pretreatment by hypothermic (25 degrees C) cycling (PHC) of attached exponential-phase V79 Chinese hamster cells by Method 4 (24 hr at 25 degrees C + 1.5 hr at 37 degrees C + 24 hr at 25 degrees C + trypsin + 3 hr at 37 degrees C) or by Method 3 (48 hr at 25 degrees C + trypsin + 3 hr at 37 degrees C) make mammalian V79 cells significantly more resistant to 43 degrees C hyperthermia. There is no significant difference in the 43 degrees C curves whether Method 3 or 4 is used for pre-exposure. If pre-exposure at 15 or 10 degrees C, the resistance to hyperthermia is significantly reduced. PHC by Method 4 significantly increases survival of cells exposed to 5 degrees C and, to a lesser extent, to 10 degrees C. The increase in hyper- and hypothermic survival after PHC cannot be accounted for by changes in cell cycle distribution. Heat-shock protein synthesis is not induced by PHC; hence, protection does not result from newly synthesized proteins. When cells are made tolerant to hyperthermia by a pretreatment in 2% DMSO for 24 hr at 37 degrees C (Method 8), the cells are not more resistant to subsequent exposures to hypothermia, either at 5 or 10 degrees C. The results imply that there may be two mechanisms of inducing resistance to hyperthermia, only one of which also confers resistance to hypothermia.     

Altered cytotoxicity of (2-chloroethyl)-3-sarcosinamide-1-nitrosourea in human glioma cell lines SK-MG-1 and SKI-1 correlates with differential transport kinetics

Resistance to (2-chloroethyl)-3-sarcosinamide-1-nitrosourea (SarCNU), an experimental anticancer compound, was investigated in the chloroethylnitrosourea-sensitive Mer- SK-MG-1 and -resistant Mer- SKI-1 human glioma cell lines. The transport of [3H]SarCNU was examined in suspension. The uptake of [3H]SarCNU was found to be temperature dependent in SK-MG-1 and SKI-1, but less so in SKI-1. At 37 degrees C, uptake of 50 microM [3H]SarCNU was linear up to 4 s in both cell lines, with uptake being significantly faster in SK-MG-1 than in SKI-1 under initial rate conditions. There was no significant difference in the rate of influx at 22 degrees C between both cell lines. Equilibrium was approached after 1 min at 22 and 37 degrees C. At 37 degrees C, steady state accumulation of SarCNU at 30 min was reduced significantly (35%) in SKI-1 cells compared with SK-MG-1 cells, although accumulation was similar at 22 degrees C. In SK-MG-1 cells, uptake of [3H]SarCNU at 37 degrees C was found to be saturable, but uptake in SKI-1 cells was not saturable over a 1000-fold range of concentrations. Analysis of efflux in cells preloaded with 50 microM [3H]SarCNU revealed that the rate of efflux was equivalent in both cell lines but that the efflux rate was more rapid at 37 degrees C compared with 22 degrees C. Metabolism of SarCNU at 37 degrees C was not different in either cell line after a 60-min incubation, as determined by thin layer chromatography. SKI-1 cells, compared with SK-MG-1 cells, were 3-fold more resistant to SarCNU at 37 degrees C but only 2-fold more resistant at 22 degrees C, a temperature at which SarCNU accumulation was similar in both cell lines. The 2-fold resistance at 22 degrees C was similar to that of 1,3-bis(2-chloroethyl)-1-nitrosourea at 37 and 22 degrees C. These findings indicate that increased cytotoxicity in SK-MG-1 cells is associated with a greater accumulation of SarCNU via an epinephrine-sensitive carrier that is not detectable in SKI-1 cells. However, part of the chloroethylnitrosourea resistance in SKI-1 cells is not secondary to decreased accumulation.