Insulin-like growth factor I (IGF-I)-stimulated pancreatic beta-cell growth is glucose-dependent. Synergistic activation of insulin receptor substrate-mediated signal transduction pathways by glucose and IGF-I in INS-1 cells

Nutrients and certain growth factors stimulate pancreatic beta-cell mitogenesis, however, the appropriate mitogenic signal transduction pathways have not been defined. In the glucose-sensitive pancreatic beta-cell line, INS-1, it was found that glucose (6-18 mM) independently increased INS-1 cell proliferation (>20-fold at 15 mM glucose). Insulin-like growth factor I (IGF-I)-induced INS-1 cell proliferation was glucose-dependent only in the physiologically relevant concentration range (6-18 mM glucose). The combination of IGF-I and glucose was synergistic, increasing INS-1 cell proliferation >50-fold at 15 mM glucose + 10 nM IGF-I. Glucose metabolism and phosphatidylinositol 3'-kinase (PI 3'-kinase) activation were necessary for both glucose and IGF-I-stimulated INS-1 cell proliferation. IGF-I and 15 mM glucose increased tyrosine phosphorylation mediated recruitment of Grb2/mSOS and PI 3'-kinase to IRS-2 and pp60. Glucose and IGF-I also induced Shc association with Grb2/mSOS. Glucose (3-18 mM) and IGF-I, independently of glucose, activated mitogen-activated protein kinase but this did not correlate with IGF-I-induced beta-cell proliferation. In contrast, p70(S6K) was activated with increasing glucose concentration (between 6 and 18 mM), and potentiated by IGF-I in the same glucose concentration range which correlated with INS-1 cell proliferation rate. Thus, glucose and IGF-I-induced beta-cell proliferation were mediated via a signaling mechanism that was facilitated by mitogen-activated protein kinase but dependent on IRS-mediated induction of PI 3'-kinase activity and downstream activation of p70(S6K). The glucose dependence of IGF-I mediated INS-1 cell proliferation emphasizes beta-cell signaling mechanisms are rather unique in being tightly linked to glycolytic metabolic flux.     

Plasma concentrations of risperidone and its 9-hydroxy metabolite and their relationship to dose in schizophrenic patients: simultaneous determination by a high performance liquid chromatography with electrochemical detection

A simple, sensitive and accurate method for the simultaneous determination of risperidone (RSP) and its 9-hydroxy metabolite (9-OH-RSP) in human plasma is described. The relationship between dose of RSP and the plasma concentration of RSP and 9-OH-RSP in a clinical situation is discussed. Both compounds were isolated from plasma by a simple one-step liquid-liquid extraction with 15% methylene chloride in pentane. High-performance liquid chromatography separations were made on a cyano column and the compounds were detected by electrochemical detector. The method had sufficient sensitivity to determine RSP and 9-OH-RSP accurately at concentrations as low as 0.25 ng/ml when 1 ml of plasma is used for the analysis. The assay determinations were accurate, precise and consistent with a coefficient of variation less than 15%. Commonly co-administered drugs and other antipsychotics did not interfere with the analysis of either RSP or 9-OH-RSP There were large variations in inter- and intra-individual values of plasma concentrations of RSP and 9-OH-RSP. The 9-OH-RSP appears to be the major circulating active moiety and its plasma concentrations were, on the average 22 fold higher than that of RSP in schizophrenic patients treated with RSP. The ratio of RSP/9-OH-RSP concentrations suggested that three of the patients may have deficiency in cytochrome P450 enzyme CYP 2D6. The plasma concentrations of RSP showed a weak relationship with the administered daily oral dose (r = 0.4684, p = 0.01, n = 215). However, there was a good relationship between the daily dose of RSP and the plasma concentration of 9-OH-RSP (r = 0.6654, p = 0.01, n = 280) or the total active moiety, sum of RSP and 9-OH-RSP concentrations (r = 0.7041, p = 0.0005, n = 280). The measurement of the total active moiety in plasma of schizophrenic patients may be useful for assessing the relationship between dose and plasma concentration and dose and clinical outcome of patients rather than measuring RSP alone.     

Epidemiological studies in children of a low-endemic region, a high-endemic region, and dwellers of a leprosy colony: evaluation of anti-ND-BSA antibodies and lepromin response

Children residing in a low-endemic region (LER), a high-endemic region (HER), and a leprosy colony contact population (CP) were evaluated for lepromin response as well as reactivity to the Mycobacterium leprae-specific synthetic antigen, ND-BSA. The mean reactivity to ND-BSA in the LER group (OD 0.03 +/- 0.03, N = 71) was significantly lower (p < 0.001) than that in the contact population (OD 0.14 +/- 0.09, N = 140) as well as the population residing in the HER (OD 0.09 +/- 0.08, N = 1340). ELISA-positive results were the highest (21.4%) with the CP group and lowest (0.0%) in the LER group, suggesting that it was a measure of the extent of exposure of M. leprae. In the contact population, females showed a preponderance for ELISA positivity over males (p < 0.005), a finding not observed with the HER population. The Mitsuda responses showed a Gaussian-type distribution in all of the three populations examined with the mean response being highest in the LER (6.0 mm +/- 2.9) and lowest in the HER (4.5 mm +/- 2.0) groups. The percent positivity for the Mitsuda reaction was found to be highest in the LER (93.0%) and lowest in the HER (88.3%) groups. The Mitsuda response thus appears to be independent of M. leprae exposure, and its interpretation in a given population needs consideration of several factors, such as nutritional, environmental, etc.(ABSTRACT TRUNCATED AT 250 WORDS)     

A dual thrombin receptor system for platelet activation

Platelet-dependent arterial thrombosis triggers most heart attacks and strokes. Because the coagulation protease thrombin is the most potent activator of platelets, identification of the platelet receptors for thrombin is critical for understanding thrombosis and haemostasis. Protease-activated receptor-1 (PAR1) is important for activation of human platelets by thrombin, but plays no apparent role in mouse platelet activation. PAR3 is a thrombin receptor that is expressed in mouse megakaryocytes. Here we report that thrombin responses in platelets from PAR3-deficient mice were markedly delayed and diminished but not absent. We have also identified PAR4, a new thrombin-activated receptor. PAR4 messenger RNA was detected in mouse megakaryocytes and a PAR4-activating peptide caused secretion and aggregation of PAR3-deficient mouse platelets. Thus PAR3 is necessary for normal thrombin responses in mouse platelets, but a second PAR4-mediated mechanism for thrombin signalling exists. Studies with PAR-activating peptides suggest that PAR4 also functions in human platelets, which implies that an analogous dual-receptor system also operates in humans. The identification of a two-receptor system for platelet activation by thrombin has important implications for the development of antithrombotic therapies.     

Chemokine receptor CCR2 expression and monocyte chemoattractant protein-1-mediated chemotaxis in human monocytes. A regulatory role for plasma LDL

The subendothelial accumulation of macrophage-derived foam cells is one of the hallmarks of atherosclerosis. The recruitment of monocytes to the intima requires the interaction of locally produced chemokines with specific cell surface receptors, including the receptor (CCR2) for monocyte chemoattractant protein-1 (MCP-1). We have previously reported that monocyte CCR2 gene expression and function are effectively downregulated by proinflammatory cytokines. In this study we identified low density lipoprotein (LDL) as a positive regulator of CCR2 expression. Monocyte CCR2 expression was dramatically increased in hypercholesterolemic patients compared with normocholesterolemic controls. Similarly, incubation of human THP-1 monocytes with LDL induced a rapid increase in CCR2 mRNA and protein. By 24 hours the number of cell surface receptors was doubled, causing a 3-fold increase in the chemotactic response to MCP-1. The increase in CCR2 expression and chemotaxis was promoted by native LDL but not by oxidized LDL. Oxidized LDL rapidly downregulated CCR2 expression, whereas reductively methylated LDL, which does not bind to the LDL receptor, had only modest effects on CCR2 expression. A neutralizing anti-LDL receptor antibody prevented the effect of LDL, suggesting that binding and internalization of LDL were essential for CCR2 upregulation. The induction of CCR2 expression appeared to be mediated by LDL-derived cholesterol, because cells treated with free cholesterol also showed increased CCR2 expression. These data suggest that elevated plasma LDL levels in conditions such as hypercholesterolemia enhance monocyte CCR2 expression and chemotactic response and potentially contribute to increased monocyte recruitment to the vessel wall in chronic inflammation and atherogenesis.     

Labor and delivery in a pregnancy involving fetal macrosomia

The alleged connection between fetal magalosomia and the increased risk of maternal and perinatal morbidity justifies the lively discussion that has developed about the management problems caused by a big unborn child. The aim of this study is to offer a contribution to the definition of the more or less peculiar problems associated with labour and delivery in a pregnant women with a megalosomic fetus. The study was retrospectively carried out on a sample of 45 women who, during the period 1190-1993, delivered a fetus weighing at least 4 kg. This sample was statistically compared with a numerically identical standard sample, selected at random. The main characteristics of labour and delivery were examined in the two groups under study. The most considerable differences observed concern the length of the labour, greater in the sample than in the standard group, and the frequency of dystocic events, similarly more considerable in the pregnant women with a megalosomic fetus. Maternal and perinatal outcomes, in spite of the small number of cesarean sections performed, were anyway very good in both the examined groups. In our experience, the risks associated with fetal megalosomia were rather limited, but this is not a reason to minimize beyond measure the problem we are talking about.     

Developmental modulation of mouse hypoglossal nerve inspiratory output in vitro by noradrenergic receptor agonists

The ontogeny of the noradrenergic receptor subtypes modulating hypoglossal (XII) nerve inspiratory output was characterized. Noradrenergic agents were locally applied over the XII nucleus of rhythmically active medullary slice preparations isolated from mice between zero and 13 days of age (P0-P13) and the effects on XII inspiratory burst amplitude quantified. The alpha1 receptor agonist phenylephrine (PE, 0.1-10 microM) produced a dose-dependent, prazosin-sensitive (0.1-10 microM) increase in XII nerve inspiratory burst amplitude. The magnitude of this potentiation increased steadily from a maximum of 15+/-8% in P0 mice to 134+/-4% in P12-P13 mice. The beta receptor agonist isoproterenol (0.01-1.0 mM) produced a prazosin-insensitive, propranolol-sensitive potentiation of XII nerve burst amplitude. The isoproterenol-mediated potentiation increased with development from 27+/-5% in P0-P1 slices, to 37+/-3% in P3 slices and 45+/-4% in P9-P10 slices. The alpha2 receptor agonist clonidine (1 mM) reduced XII nerve inspiratory burst amplitude in P0-P3 slices by 29+/-5%, but had no effect on output from P12-P13 slices. An alpha2 receptor-mediated inhibition of inspiratory activity in neonates (P0-P3) was further supported by a 19+/-3% reduction in XII nerve burst amplitude when norepinephrine (NE, 100 microM) was applied in the presence of prazosin (10 microM) and propranolol (100 microM). Results indicate that developmental increases in potentiating alpha1 and, to a lesser extent, beta receptor mechanisms combine with a developmentally decreasing inhibitory mechanism, most likely mediated by alpha2 receptors, to determine the ontogenetic time course by which NE modulates XII MN inspiratory activity.     

Ataxic hemiparesis: critical appraisal of a lacunar syndrome

BACKGROUND and PURPOSE: Ataxic hemiparesis is a well-recognized lacunar syndrome involving homolateral ataxia with accompanying corticospinal tract impairment. Despite 30 years of clinical experience there continues to be some doubt as to the defining clinical characteristics, precise neuroanatomic localization of the syndrome, and etiologic mechanisms. METHODS: We now present 45 new cases that have been analyzed for clinico-radiologic correlation and etiology. Also, all published cases from the English literature known to the authors are reviewed. RESULTS: We found that the clinical syndrome of ataxic hemiparesis accurately predicts a small deep infarction, generally in the pons or internal capsule. Sensory loss is highly associated with a capsular localization. We found that 47% of the cases were attributed to small-vessel disease, 11% to cardioembolism, and only 7% to artery-to-artery embolism (all in the basilar artery); 1 case was attributed to thrombocytosis, 1 to multiple sclerosis, and the rest either had negative or incomplete evaluation. Approximately two thirds of the infarctions occurred in patients with neuroimaging evidence of other ischemic brain lesions. CONCLUSIONS: Ataxic hemiparesis is a distinct clinical syndrome that accurately predicts a small deep infarction, most commonly in the pons or internal capsule. Only sensory loss accurately predicts a capsular localization. Etiology in nearly half of the cases can be attributed to small-vessel disease. Furthermore, ataxic hemiparesis appears to be a good marker for generalized asymptomatic cerebrovascular disease.     

Infraorbital nerve transection alters serotonin transporter expression in sensory pathways in early postnatal rat development

OBJECTIVE: To determine the relationship between sperm motility and sperm morphology parameters and IVF and pregnancy rates. DESIGN: Pre- and postpreparation analysis of semen samples from infertile couples undergoing IVF-ET. SETTING: Andrology Laboratory, Royal Maternity Hospital, Belfast, Northern Ireland. PATIENT(S): One hundred fifty couples undergoing IVF-ET treatment at the Regional Fertility Centre. INTERVENTION(S): None. MAIN OUTCOME MEASURE(S): The ability of human sperm to achieve IVF and pregnancy was investigated in relation to motility parameters (assessed with computer-aided sperm analysis [Integrated Visual Optical System] and percent normal morphology (determined with the strict criteria). RESULT(S): Significant differences were observed in motility parameters and percent normal morphology in samples that achieved > or =50% fertilization compared with < or =50% fertilization and between samples that achieved a pregnancy compared with those that did not. Significant positive correlations were observed between percent progressive motility, the velocity of sperm movement, and morphology parameters and both IVF and pregnancy. CONCLUSION(S): Both sperm motility parameters and percent normal morphology are significant factors in predicting fertilization and pregnancy rates in IVF.