Regulation of the permeability of the gonococcal cell envelope by the mtr system

The mtrR gene of Neisseria gonorrhoeae controls the level of susceptibility to hydrophobic antibiotics and detergents. The mtrR gene was cloned and shown to encode a putative transcriptional repressor. The mtr region was homologous to the envCD and acrAB regions of Escherichia coli, which are also involved in susceptibility to hydrophobic compounds. A homologous repressor protein was encoded by a previously unrecognized open reading frame within both the envCD and acrAB regions. Deletion of mtrR resulted in increased resistance to antibiotics and detergents: the mtrR mutations in two penicillin-resistant clinical isolates resulted in a change of His-105 to Tyr. We propose that the mtrR repressor allows gonococci to regulate the permeability of its cell envelope in response to environmental signals, so that they can grow in the presence of toxic faecal lipids in the rectum as well as in the genital tract.

Alterations in renal gluconeogenesis and blood flow during hemorrhagic shock

The role of renal gluconeogenesis following hemorrhagic shock was studied. Hemorrhagic shock was induced in fasted, anesthesized rats by reduction of blood pressure to 40 mm Hg for either 30 or 150 min. Plasma samples were obtained for plasma glucose determination, and right renal arterial blood flow was determined with the help of an ultrasonic transit time blood flowmeter in hemorrhagic shock and control rats. The kidney was perfused via the renal artery with 37 degrees C oxygenated, glucose-free Krebs-Henseleit solution in the presence of 100 microM phloridzin to inhibit the cellular reuptake of glucose. Renal glucose production was determined by measuring glucose in both renal vein effluent and urine. After 30 min of equilibration, 5 mM lactate and 0.5 mM pyruvate were added to the perfusate as a gluconeogenic substrate, and effluent samples were collected after 5, 10, and 15 min. Moderate hyperglycemia was observed in vivo following 30 min of hemorrhagic shock, and significant hypoglycemia (P < .05) was observed following 150 min of hemorrhagic shock. Renal arterial flow was significantly decreased at 30 min (P < .05) and 150 min (P < .05) of hemorrhagic shock. Renal glucose production with and without substrate after 30 min of hemorrhagic shock was similar compared to control. Renal glucose production after 150 min of hemorrhagic shock was significantly decreased (P < .05) compared to control.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of diltiazem on altered glucose regulation during endotoxic shock

Endotoxic shock is associated with profound metabolic alterations including hypoglycemia and hyperlactiacidemia. We studied hepatic glucose production and the role of diltiazem in affecting these metabolic alterations in a rat model of endotoxic shock. Fasted rats were intravenously injected with saline, endotoxin (20 mg/kg), endotoxin (20 mg/kg) plus diltiazem (1.2 mg/kg), or saline plus diltiazem. Five hours after the injections, the rats were anesthetized and blood samples were obtained for plasma glucose and lactate. The livers of all rats were then perfused in situ with an oxygenated 37 degrees C glucose-free Hanks' balanced salt solution at a rate of 30 ml/min via the portal vein and effluent was collected from the inferior vena cava. After 30 min equilibration, 5 mM lactate was added to the perfusate as a gluconeogenic substrate. Endotoxic groups exhibited hypoglycemia (64.5 +/- 12.7 mg/dl) and hyperlacticacidemia (4.3 +/- 0.63 mM). Diltiazem administration improved the hypoglycemia (96.9 +/- 9.1 mg/dl) and attenuated the hyperlacticacidemia (2.2 +/- 0.7 mM) in the endotoxic group. Gluconeogenic stimulation with lactate was demonstrated in both the control (18.1 +/- 2.3 vs 12.8 +/- 1.86 microns/g/hr, P < .05) and endotoxic (16.6 +/- 2.3 vs 9.8 +/- 1.1, P < .05) groups. However, stimulation in the endotoxic groups was significantly less compared with control. Gluconeogenic stimulation in the endotoxic group was unaffected after diltiazem administration. These data suggest that diltiazem treatment in endotoxic shock improves hypoglycemia and attenuates hyperlacticacidemia. These metabolic alterations are not associated with an improvement in substrate-specific stimulation of gluconeogenesis.

Altered cellular calcium regulation and hepatic glucose production during hemorrhagic shock

The relationship between intracellular Ca2+ and glucose production in the liver during early and late states of hemorrhagic shock was studied. Rats were anesthetized with intraperitoneal sodium pentobarbital and both femoral arteries and one femoral vein were cannulated. Rats were divided into two groups. One group was subjected to hemorrhagic shock by rapid withdrawal of blood to a mean arterial pressure of 40 mm Hg and maintained in shock for either 30 or 150 min. Rats in the control group were observed for the same time period. Hepatic glucose production was evaluated in both groups by a nonrecirculating liver perfusion model with and without lactate as a substrate. Intracellular free Ca2+ in hepatocytes was measured using the Ca2+ selective indicator Fura-2, under basal and epinephrine-stimulated conditions. Hyperglycemia and hyperlacticacidemia were observed in vivo at 30 min of hemorrhagic shock, whereas hypoglycemia and hyperlacticacidemia were observed at 150 min of shock. Hepatic glucose production in isolated perfused livers was significantly depressed at 30 min in animals subjected to shock (P less than 0.05). Lactate-induced glucose production was significantly attenuated at 30 and 150 min (P less than 0.05). Basal Ca2+, in isolated hepatocytes, at 30 and 150 min of hemorrhagic shock was significantly (P less than 0.05) higher than in controls. The hemorrhagic shock rat hepatocytes failed to evaluate intracellular free Ca2+ upon stimulation with 10(-5) M epinephrine. These results demonstrate that hemorrhagic shock is associated with an increase in hepatocyte intracellular Ca2+ concentration along with attenuation of hormone-mediated mobilization of calcium and substrate specific stimulation of hepatic glucose production.

Overexpression of the c-erbB-2/neu–encoded p185 protein in primary lung cancer

The c-erbB-2/neu gene encodes a transmembrane protein of 185 kDa (p185) with tyrosine kinase activity and extensive sequence homology to epidermal growth factor receptor. Amplification and overexpression of the c-erbB-2/neu gene has been shown in certain human tumors and is postulated to be important in human carcinogenesis. High levels of expression of the c-erbB-2/neu gene have been reported in non-small-cell lung cancer (NSCLC) cell lines and primary tumors from the United States. Since geographical and cultural factors may contribute to the development of certain types of cancer, we examined p185 examined p185 expression in 120 tumors from Chinese patients with lung cancers of different cell types and used immunohistochemical staining to determine the extent and general significance of p185 expression in human primary lung cancer. Our results demonstrate that 58.8% of the NSCLCs expressed p185 and that expression of p185 was observed only in NSCLC and not in small-cell lung cancers. Thirty-three of 41 adenocarcinomas and 24 of 55 squamous cell carcinomas among the NSCLCs examined were found to express p185 at levels different from those of normal lung. For the squamous cell carcinomas, p185 expression was correlated with lymph node metastasis (P less than 0.01), but for the adenocarcinomas, it was not (P greater than 0.05). In addition, expression of p185 in NSCLC was significantly more frequent in patients in advanced clinical stages. Our findings indicate that p185 expression is a frequent event and a general phenomenon in NSCLC and is correlated with poor clinical prognostic indicators, suggesting that expression of p185 may be of potential prognostic importance in NSCLC.

Optimizing the performance of Doppler blood-flow probes in extra-corporeal circuits

A theory is developed to improve the signal-to-noise (S/N) ratio of clamp-on Doppler blood-flow probes by optimizing their operating frequency for the tubing utilized in extra-corporeal blood circuits. The theoretical results can be used to increase the magnitude of both the S/N and Doppler frequency shift and to produce a greater tolerance of S/N to variations in the dimensions and acoustic parameters of Tygon tubes. It is shown that thin tube walls improve the S/N and reduce the effect of temperature variations on the magnitude of the S/N. Measurements were performed on various Tygon tubes and their acoustic attenuations obtained. These values were used to predict an optimum operating frequency of 1.78 MHz for the de facto standard tubing having 3/32-in wall thickness. If a 1/16-in wall thickness were substituted, then the optimum operating frequency would be 2.67 MHz and the S/N would increase by 14.54 dB.

Desensitization of adenosine A2 receptors in the striatum of the rat following chronic treatment with diazepam

Following prolonged treatment (7 days) with diazepam (10 mg/kg/day, using ALZET mini-osmotic pumps) in rats, the function of adenosine receptors was assessed in specific structures of the brain, using both agonist ligand binding and adenylate cyclase assays. Binding to A1 receptors was quantified using [3H]N6-[(R)-1-methyl-2-phenylethyl] adenosine, a selective ligand at A1 receptors. Differences in the binding of this ligand and that of [3H]5'-N-ethylcarboxamide adenosine, which binds to both A1 and A2 subtypes of receptors with similar affinities, were used to quantify A2 receptors. Treatment with diazepam failed to alter the binding of [3H]N6-[(R)-1-methyl-2-phenylethyl] adenosine in all areas of the brain studied. However, the binding of A2 receptors and A2 receptor-mediated stimulation of adenylate-cyclase were significantly attenuated in striatal membranes from diazepam-treated rats. Thus, the present study indicated that functional adenosine A2 receptors were desensitized after prolonged treatment with diazepam, since decreased agonist binding to A2 receptors paralleled an attenuation in the stimulation by adenosine of the activity of adenylate cyclase, an effect mediated by the A2 receptor. These results further indicate that the changes in adenosine A2 receptors correlated with significant short-lasting alterations in the sleep-wake cycle during the withdrawal of diazepam. The alterations in sleep-wakefulness did not correlate with the effect of diazepam on benzodiazepine receptors since no changes were observed in the binding of benzodiazepine receptors.

Lysosome-associated membrane proteins: characterization of LAMP-1 of macrophage P388 and mouse embryo 3T3 cultured cells

Lysosome-associated membrane protein (LAMP)-1, a major glycoprotein of mouse embryo 3T3 cells and specifically associated with the lysosomal membrane, has been identified in P388 macrophage cells and compared with the homologous glycoprotein of NIH 3T3 cells. Immunofluorescence microscopy with anit-LAMP-1 monoclonal antibodies shows that the antigen was distributed throughout P388 cells including the ruffled edges or pseudopodia, identical to the pattern of acridine orange accumulation. LAMP-1 was purified from P388 cells by affinity chromatography with 1D4B monoclonal antibody, yielding a homogeneous glycoprotein comprising 0.1% of the total detergent-extracted cell protein. The apparent mass of P388 LAMP-1 was 130,000 to 150,000 compared to the 3T3 glycoprotein of 105,000 to 115,000. Analysis of tryptic peptides indicated that the two purified glycoproteins were highly homologous. Protein synthesis was analyzed in a variety of cell lines by pulse-chase labeling with [35S]methionine; in every case, LAMP-1 was synthesized as a precursor of apparent Mr 92,000, and then converted to heterogeneous mature forms differing in average Mr from 110,000 to 140,000. The basis for these apparent differences in mass was examined by studies of the biosynthesis and oligosaccharide composition of the glycoprotein. Core polypeptides of 45,000 Da were obtained from both HaNIH and P388 cells by treating immunoprecipitates of [35S]methionine pulse-labeled molecules with endoglycosidase H. Cells treated with monensin contained heterogeneous molecules of 80,000 to 85,000 Da. Isoelectric heterogeneity of mature LAMP-1 was markedly reduced by treatment with neuraminidase whereas there was little effect on the apparent molecular weight of the molecules or the differences between the various cell lines. beta-D-Xyloside inhibition of glycosaminoglycan synthesis had little effect on the apparent mass of LAMP-1.