Reversal of insulin resistance by ATP in hemorrhagic shock.

Hemorrhagic shock was produced by bleeding rats to a mean arterial pressure of 40 mm Hg (1 mm Hg = 133 N/m2), which was maintained for 2 h. Muscles from these animals ('shock' muscles) showed resistance to the stimulation of glucose uptake by insulin. Addition of 1 mM ATP-MgCl2 to the medium had no effect on basal glucose uptake in either group of muscles, but it permitted insulin to exert its stimulatory effect in 'shock' muscles. An optimal insulin effect on glucose uptake in 'shock' muscles incubated without ATP was observed at an insulin concentration of 0.2 Unit/ml. When 1 mM ATP-MgCl2 was added to the medium, optimal insulin effect in 'shock' muscles was observed at an insulin concentration of 0.007 Unit/ml. Increasing the concentration of ATP-MgCl2 to 2.5 mM in the medium resulted in an optimal insulin effect at an insulin concentration of ATP-MgCl2 to 2.5 mM in the medium resulted in an optimal insulin effect at an insulin concentration of 0.001 Unit/ml in 'shock' muscles. Following 1 h cubation in Krebs-HCO3 medium, intracellular ATP contents of 'shock' muscles were approximately 50% lower than in control muscles. Addition of 1 mM ATP-MgCl2 to the incubation medium had no effect on the intracellular ATP contents of either group of muscles following incubation; however, 2.5 mM ATP-MgCl2 elevated intracellular ATP contents of 'shock' muscles but had no effect in control muscles. Possible mechanisms for this reversal of insulin resistance by ATP-MgCl2 in shock are discussed.     

Transient extreme insulin resistance in shock during diabetic ketoacidosis.

Transient extreme insulin resistance was encountered during an episode of diabetic ketoacidosis (DKA) in an insulin-treated diabetic patient. On admission, the plasma glucose level was 1241 mg dl-1 and arterial blood pH 6.895 with HCO3- 4.7 mEql-1. An intravenous bolus injection of 20 units, followed by continuous infusion of 20 units h-1 of short-acting regular human insulin, was instituted. Ischemic myocardial changes were noted on the initial electrocardiogram, therefore fluid replacement was limited to 1,000 ml of 0.9% saline solution in the first hour. As the plasma glucose level declined by only 203 mg dl-1 (41 mg dl-1 h-1) in the first 5 h, the insulin dose was doubled every 2 h. At hour 4, the patient developed circulatory shock which required vasopressor support and respiratory assistance. A plasma glucose level of 300 mg dl-1 was not achieved until the total dosage of insulin amounted to 91,580 units at hour 25. Insulin resistance was not observed from that point on. The patient had neither insulin antibodies nor anti-insulin receptor antibodies in serologic testing. The insulin binding characteristics of the patient's erythrocytes were similar to those from healthy controls both with and without experimental acidosis and with a high level of beta-hydroxybutyrate. Among multiple potential factors, the severe shock associated with DKA has been considered as a primary cause of the transient severe insulin resistance in this case.     

Heat shock affects permeability and resistance of Bacillus stearothermophilus spores.

Heat shock of dormant spores of Bacillus stearothermophilus ATCC 7953 at 100 or 80 degrees C for short times, the so-called activation or breaking of dormancy, was investigated by separating the resulting spores by buoyant density centrifugation into a band at 1.240 g/ml that was distinct from another band at 1.340 g/ml, the same density as the original spores. The proportion of spores at 1.240 g/ml became larger when the original dormant spores were heated for a longer period of time, but integument-stripped dormant spores were quickly and completely converted to spores with a band at 1.240 g/ml. The spores with bands at both 1.240 and 1.340 g/ml were germinable faster than the original dormant spores and thus were considered to be activated. The spores with a band at 1.240 g/ml, which were considered to be fully activated, were apparently permeabilized, with a resulting complete depletion of dipicolinic acid, partial depletion of minerals, susceptibility to lysozyme action, permeation of the gradient medium, changed structural appearance in electron micrographs of thin-sectioned spores, and partly decreased heat resistance (D100 = 453 min) compared with the original dormant spores (D100 = 760 min). However, the fully activated spores with a band at 1.240 g/ml, although devoid of dipicolinic acid, still were much more resistant than germinated spores or vegetative cells (D100 = 0.1 min). The spores with a band at 1.340 g/ml, which were considered to be partly activated, showed no evidence of permeabilization and were much more heat resistant (D100 = 1,960 min) than the original dormant spores.(ABSTRACT TRUNCATED AT 250 WORDS)     

Elevation of the heat resistance of Salmonella typhimurium by sublethal heat shock

The survival of Salmonella typhimurium after a standard heat challenge at 55 degrees C for 25 min increased by several orders of magnitude when cells grown at 37 degrees C were pre-incubated at 42 degrees, 45 degrees or 48 degrees C before heating at the higher temperature. Heat resistance increased rapidly after the temperature shift, reaching near maximum levels within 30 min. Elevated heat resistance persisted for at least 10 h. Pre-incubation of cells at 48 degrees C for 30 min increased their resistance to subsequent heating at 50 degrees, 52 degrees, 55 degrees, 57 degrees or 59 degrees C. Survival curves of resistant cells were curvilinear. Estimated times for a '7D' inactivation increased by 2.6- to 20-fold compared with cells not pre-incubated before heat challenge.     

Elevation of the heat resistance of Salmonella typhimurium by sublethal heat shock

The survival of Salmonella typhimurium after a standard heat challenge at 55°C for 25 min increased by several orders of magnitude when cells grown at 37°C were pre-incubated at 42°, 45° or 48°C before heating at the higher temperature. Heat resistance increased rapidly after the temperature shift, reaching near maximum levels within 30 min. Elevated heat resistance persisted for at least 10 h. Preincubation of cells at 48°C for 30 min increased their resistance to subsequent heating at 50°, 52°, 55°, 57° or 59°C. Survival curves of resistant cells were curvilinear. Estimated times for a '7D' inactivation increased by 2.6- to 20-fold compared with cells not pre-incubated before heat challenge.     

Strain-dependent induction by heat shock of resistance to ultraviolet light inEscherichia coli

Heat shock induces resistance to killing by ultraviolet light inEscherichia coli JE1011. When cells growing at 30°C were transferred to 42°C, maximum resistance to ultraviolet radition was reached after 30–45 min, but no change in heat resistance occurred. The effect was dependent on growth or protien synthesis. In contrast,E. coli B becomes more sensitive to the radiation and more heat resistant after a similar treatment. Thus, ultraviolet resistance and thermal resistance are not induced together in these two strains and may arise by independent mechanisms. It is also possible that thelon gene is involved in the effect of heat shock on ultraviolet resistance.     

Heat shock applied early in sporulation affects heat resistance of Bacillus megaterium spores.

Cells of Bacillus megaterium 27 were challenged by a 30-min heat shock at 45 degrees C during various sporulation stages and then shifted back to a temperature permissive for sporulation (27 degrees C), at which they developed spores. Heat shock applied at 120 min after the end of the exponential phase induced synthesis of heat shock proteins (HSPs) in the sporangia and delayed the inactivation of spores at 85 degrees C. Several HSPs, mainly HSP 70, could be detected in the cytoplasm of these spores. An analogous HSP, the main HSP induced by increased temperature during growth, belongs to the GroEL group according to its N-terminal sequence. The identity of this protein was confirmed by Western blot (immunoblot) analysis with polyclonal antibodies against B. subtilis GroEL. Sporangia treated by heat shock immediately or 240 min after exponential phase also synthesized HSPs, but none of them could be detected in the spores in an appreciable amount. These spores showed only a slightly increased heat resistance.     

Effect of prior heat shock on heat resistance of Listeria monocytogenes in meat.

The effect of prior heat shock on the thermal resistance of Listeria monocytogenes in meat was investigated. A sausage mix inoculated with approximately 10(7) L. monocytogenes per g was initially subjected to a heat shock temperature of 48 degrees C before being heated at a final test temperature of 62 or 64 degrees C. Although cells heat shocked at 48 degrees C for 30 or 60 min did not show a significant increase in thermotolerance as compared with control cells (non-heat shocked), bacteria heat shocked for 120 min did, showing an average 2.4-fold increase in the D64 degrees C value. Heat-shocked cells shifted to 4 degrees C appeared to maintain their thermotolerance for at least 24 h after heat shock.     

Heat shock resistance conferred by expression of the human HSP27 gene in rodent cells

Heat shock induces in cells the synthesis of specific proteins called heat shock proteins (HSPs) and a transient state of thermotolerance. The putative role of one of the HSPs, HSP27, as a protective molecule during thermal stress has been directly assessed by measuring the resistance to hyperthermia of Chinese hamster and mouse cells transfected with the human HSP27 gene contained in plasmid pHS2711. One- and two-dimensional gel electrophoresis of [3H]leucine- and [32P]orthophosphate-labeled proteins, coupled with immunological analysis using Ha27Ab and Hu27Ab, two rabbit antisera that specifically recognize the hamster and the human HSP27 protein respectively, were used to monitor expression and inducibility of the transfected and endogenous proteins. The human HSP27 gene cloned in pHS2711 is constitutively expressed in rodent cells, resulting in accumulation of the human HSP27 and all phosphorylated derivatives. No modification of the basal or heat-induced expression of endogenous HSPs is detected. The presence of additional HSP27 protein provides immediate protection against heat shock administered 48 h after transfection and confers a permanent thermoresistant phenotype to stable transfectant Chinese hamster and mouse cell lines. Mild heat treatment of the transfected cells results in an induction of the full complement of the endogenous heat shock proteins and a small increase in thermoresistance, but the level attained did not surpass that of heat-induced thermotolerant control cells. These results indicate that elevated levels of HSP27 is sufficient to give protection from thermal killing. It is concluded that HSP27 plays a major role in the increased thermal resistance acquired by cells after exposure to HSP inducers.