Monosodium glutamate (MSG)-obese rats develop glucose intolerance and insulin resistance to peripheral glucose uptake

Different levels of insulin sensitivity have been described in several animal models of obesity as well as in humans. Monosodium glutamate (MSG)-obese mice were considered not to be insulin resistant from data obtained in oral glucose tolerance tests. To reevaluate insulin resistance by the intravenous glucose tolerance test (IVGTT) and by the clamp technique, newborn male Wistar rats (N = 20) were injected 5 times, every other day, with 4 g/kg MSG (N = 10) or saline (control; N = 10) during the first 10 days of age. At 3 months, the IVGTT was performed by injecting glucose (0.75 g/kg) through the jugular vein into freely moving rats. During euglycemic clamping plasma insulin levels were increased by infusing 3 mU.kg-1.min-1 of regular insulin until a steady-state plateau was achieved. The basal blood glucose concentration did not differ between the two experimental groups. After the glucose load, increased values of glycemia (P < 0.001) in MSG-obese rats occurred at minute 4 and from minute 16 to minute 32. These results indicate impaired glucose tolerance. Basal plasma insulin levels were 39.9 +/- 4 microU/ml in control and 66.4 +/- 5.3 microU/ml in MSG-obese rats. The mean post-glucose area increase of insulin was 111% higher in MSG-obese than in control rats. When insulinemia was clamped at 102 or 133 microU/ml in control and MSG rats, respectively, the corresponding glucose infusion rate necessary to maintain euglycemia was 17.3 +/- 0.8 mg.kg-1.min-1 for control rats while 2.1 +/- 0.3 mg.kg-1.min-1 was sufficient for MSG-obese rats. The 2-h integrated area for total glucose metabolized, in mg.min.dl-1, was 13.7 +/- 2.3 vs 3.3 +/- 0.5 for control and MSG rats, respectively. These data demonstrate that MSG-obese rats develop insulin resistance to peripheral glucose uptake.     

The CD40-CD154 system in anti-infective host defense

Research in the past few years has documented significant advances in our understanding of the CD40-CD40 ligand (CD154) system in diverse immune functions. This system influences many T cell mediated inflammatory immune responses and effector functions, unmasking a previously unexpected role for CD40-CD154 in cell mediated immunity. Manipulation of CD154 in animal models of infection by the use of CD154-deficient mice or anti-CD154 antibodies has shown the importance of this system in the initiation of the inflammatory response, in the activation of antigen-presenting cells and in resistance to infections.     

Induction of neutralizing antibody in mice by immunization with recombinant 56 kDa protein of Orientia tsutsugamushi

Anti-oriential antibody inhibits Orientia tsutsugamushi attachment to, and penetration of, host cells. However, O. tsutsugamushi antigens that induce the production of a neutralizing antibody have not been identified. The authors immunized mice and rabbits with the recombinant 56 kDa protein of O. tsutsugamushi fused to the maltose binding protein of Escherichia coli (MBP-Bor56) and analysed their effect on O. tsutsugamushi attachment to or penetration of L929 cells. O. tsutsugamushi attachment and penetration were measured by using an indirect immunofluorescent antibody assay (IFA). O. tsutsugamushi growth in L929 cells was determined by [3H]thymidine uptake assay. By IFA, we observed a 96% reduction of attachment or penetration of O. tsutsugamushi treated with rabbit anti-MBP-Bor56 sera. [3H]thymidine uptake showed that mouse anti-MBP-Bor56 sera caused a 91% reduction in O. tsutsugamushi growth, when compared to mouse anti-MBP sera. These results suggest that the 56 kDa protein of O. tsutsugamushi plays an important role in O. tsutsugamushi attachment to or penetration of cells.     

Rate-dependent hemodynamic responses during incremental atrial pacing in chronic constrictive pericarditis before and after surgery

Chronic constrictive pericarditis is a frequent cause of diastolic dysfunction, and results in impaired ventricular filling. Unlike in normal subjects, ventricular filling in constrictive pericarditis occurs almost entirely in the initial one third of diastole, and cardiac output is dependent predominantly on heart rate. Tachycardia impairs ventricular filling in normal subjects, but its effects in patients with constrictive pericarditis have not been studied. The effect of increasing heart rate alone with atrial pacing on the central and peripheral hemodynamics of patients with untreated chronic constrictive pericarditis before and after pericardiectomy was evaluated. Increased heart rate with atrial pacing increased cardiac output, whereas stroke volume remained unchanged up to heart rates of 140 beats/min. Further increases in heart rate resulted in reductions of cardiac output and stroke volume. There were no significant changes in ventricular filling pressures. Infusion of 300 ml of saline solution at peak pacing rates did not improve cardiac output. After successful surgical pericardiectomy, the hemodynamic effects of atrial pacing returned to normal. It is concluded that moderate tachycardia improves the hemodynamic profile of patients with constrictive pericarditis.     

Taste-potentiated odor aversion learning based on amphetamine

This study sought to determine whether a taste can potentiate a conditioned odor aversion based on amphetamine as well as those based on lithium. A taste-potentiated odor aversion (TPOA) based on lithium was obtained in Experiment 1 only with a low concentration of an almond odor. This concentration was used in Experiment 2 where the taste, 0.1% saccharin, potentiated an odor aversion based on 1 mg/kg d-amphetamine. This was replicated in Experiment 3 where potentiation was found with doses of both 1 and 3 mg/kg amphetamine, and no effect of dose was detected. It was concluded that TPOA learning is not restricted to drugs such as lithium that produce conditioned unpalatability as well as conditioned aversions to a taste, because amphetamine does not produce conditioned unpalatability at the doses used here. Furthermore, because in Experiment 3 postconditioning extinction of the saccharin aversion removed the potentiation effect, it appears that this form of TPOA may depend on an association between the odor and taste, as proposed by within-compound theory.     

Hemin: levels in experimental subarachnoid hematoma and effects on dissociated vascular smooth-muscle cells

Although hemin is known to exert toxic effects on a variety of cell types, its possible participation in the genesis of cerebral vasospasm has received little attention. The authors measured the concentration of hemin in experimental subarachnoid clot and studied its effects on the morphology and 45Ca++ uptake of vascular smooth-muscle cells dissociated from canine carotid artery. Craniectomies were performed in five dogs under general anesthesia, and 3 to 5 ml of autologous whole blood was deposited in the supraclinoid subarachnoid compartment. The concentration of hemin recovered by Folch extraction from clotted material removed 7 days after surgery was 390 +/- 247 microM (mean +/- standard error of the mean). Mean vascular smooth-muscle cell length after 40 minutes of exposure to 50 microM hemin was 37.3 +/- 1.2 microns (control 51.6 +/- 1.6 microns) (p < 0.01). The mean percent permeation of 45Ca++, measured by a dual label technique, of cells exposed to hemin was 200.9% +/- 23% (control 102.9% +/- 4.3%) (p < 0.01). These findings indicate that hemin accrues in subarachnoid hematoma, that it exerts a constrictive effect on vascular smooth-muscle cells, and that this effect is associated with an increased uptake of Ca++. This study demonstrates that hemin should be included in the list of potential agents that participate in the development of cerebral vasospasm.     

Stochastic model for a wavelike exothermal reaction in condensed heterogeneous systems

The labile protons of two 32-base-pair, four-arm models of immobile Holliday junctions have been studied by two-dimensional 1H nuclear magnetic resonance (NMR) spectroscopy. Overlap of resonances in the imino-imino region of two-dimensional nuclear Overhauser enhancement (NOE) spectra necessitates the use of a multi-pathway approach for obtaining sequence-specific assignments wherein all possible NOE connectivities to the labile protons are utilized, including those from the 2H of adenine, 5CH3 of thymine, and 5H of cytosine. Resonance assignments are obtained for all slowly exchanging imino and cytosine amino protons. Base-pairing up to and including the junction point is found in all four arms of both Holliday junctions. Several cross-arm NOE connectivities are identified and can be used to infer the geometry of the helical stacking domains. The two Holliday junctions studied, which differ only by the exchange of two base pairs at the branch point, appear to have opposite arm stacking geometries. These assignments form an important part of the critical background for detailed NMR analysis of Holliday junction structure and dynamics.     

Human gamma-interferon expression in the mammary gland of transgenic mice

Transgenic mice carrying a hybrid gene consisting of ovine beta-lactoglobulin gene sequences and human gamma-interferon (hIFN-g) cDNA were produced. hIFN-g expression in the mammary gland of two lactating transgenic founder females was found. The concentration of active hIFN-g in the milk was estimated as being ca. 1800 IU/ml. The hIFN-g ability to express in the mammary gland was found in the progeny of transgenic founder male.     

The evaluation of the cytotoxicity of preparations with anticarcinogenic action in human cell cultures

An approach for determination of cytotoxicity of chemical and biological drugs which combine the estimation of quality and quantity of cells after their treatment are proposed by the authors. The visual control of cellular minicultures permits one: 1) to register specific and pathologic alterations of cell morphology, 2) to trace their development in dynamics under the action of individual or complex drugs and 3) to choose the optimum time for the experiment fixation. The special staining of the treated cells and measurement of the optical density of absorbed histological dye permits one to make a conclusion about the changing of the cells quantity. A combined method of double estimation gives the opportunity to detect the artefacts taking place after staining the cells treated by some drugs and extracts of natural origin in high concentrations.     

Inhibition of sodium/calcium exchange and calcium channels of heart cells by volatile anesthestics

BACKGROUND: Volatile anesthetics exert profound effects on the heart, probably through their effect on Ca2+ movements during the cardiac cycle. Ca2+ movements across the sarcolemma are thought to involve mainly Ca2+ channels and the Na+/Ca2+ exchanger. We have therefore investigated the action of halothane, isoflurane, and enflurane on Na+/Ca2+ exchange and Ca2+ channel activity to assess the contribution of these pathways to the observed effect of the anesthetics on the myocardium. METHODS: Sarcolemmal ion fluxes were investigated using radioisotope uptake by isolated adult rat heart cells in suspension. Na+/Ca2+ exchange activity was measured from 45Ca2+ uptake by Na(+)-loaded cells. Ca2+ channel activity was measured from verapamil-sensitive trace 54Mn2+ uptake during electric stimulation. RESULTS: Halothane, isoflurane, and enflurane inhibited Na+/Ca2+ exchange completely, with similar potency when concentrations were expressed in millimolar units in aqueous medium but not when expressed as minimum alveolar concentration (MAC). The inhibition by enflurane was particularly strong, > 50%, at 2 MAC. In contrast, the three anesthetics inhibited Ca2+ channels with similar potency when concentrations were expressed as MAC but not when expressed in millimolar units in aqueous medium. Hill plots of pooled data with all three anesthetics showed a slope of -3.87 +/- 0.50 for inhibition of Na+/Ca2+ exchange and -1.73 +/- 0.19 for inhibition of Ca2+ channels. CONCLUSIONS: Halothane, isoflurane, and enflurane inhibit both Na+/Ca2+ exchange and Ca2+ channels at concentrations relevant to anesthesia, although they exhibit differences in potency and number of sites of action. At 1.5 MAC, halothane inhibits Ca2+ channels more than Na+/Ca2+ exchange, whereas enflurane inhibits Na+/Ca2+ exchange more than Ca2+ channels. Isoflurane inhibited both systems equally. The inhibition of Ca2+ influx by these agents is likely to contribute to their negative inotropic effect in the heart. The inhibition of Na+/Ca2+ exchange by enflurane may account for its observed action of delaying relaxation in species lacking sarcoplasmic reticulum.