Because of the vaccine-related decline in meningitis due to H. influenzae type b, bacterial meningitis in the United States is now a disease predominantly of adults rather than of infants and young children.

The sulphonylurea drug glibenclamide is a widely used inhibitor of the cystic fibrosis transmembrane conductance regulator (CFTR). To investigate how glibenclamide inhibits CFTR, we studied CFTR Cl− channels using excised inside‐out membrane patches from cells expressing wild‐type human CFTR. Addition of glibenclamide (10–100 μM) to the intracellular solution caused a concentration‐dependent decrease in the open time of CFTR Cl− channels, but closed times did not change. This suggests that glibenclamide is an open‐channel blocker of CFTR. Glibenclamide is a weak organic acid. Acidification of the intracellular solution relieved glibenclamide inhibition of CFTR, suggesting that the anionic form of glibenclamide inhibits CFTR. To begin to identify the glibenclamide binding site in CFTR, we investigated whether glibenclamide competes with either MgATP or Cl− ions for a common binding site. Glibenclamide inhibition of CFTR was unaffected by nucleotide‐dependent stimulation of CFTR, suggesting that glibenclamide and intracellular MgATP interact with CFTR at distinct sites. Glibenclamide inhibition of CFTR was voltage dependent and enhanced when the external Cl− concentration was decreased. The data suggest that glibenclamide and Cl− ions may compete for a common binding site located within a large intracellular vestibule that is part of the CFTR pore.

Young children, elderly persons, and black persons of all ages are disproportionately affected by invasive pneumococcal disease. Current ACIP recommendations do not address a subset of persons aged 18 to 64 years but do include those at highest risk for death from invasive pneumococcal disease.

Adiponectin is an adipokine first described just over a decade ago. Produced almost exclusively by adipocytes, adiponectin circulates in high concentrations in human plasma. Research into this hormone has revealed it to have insulin-sensitizing, anti-inflammatory and cardioprotective roles. This review discusses the history, biology and physiological role of adiponectin and explores its role in disease, with specific focus on adiponectin in inflammation and sepsis. It appears that an inverse relationship exists between adiponectin and inflammatory cytokines. Low levels of adiponectin have been found in critically ill patients, although data are limited in human subjects at this stage. The role of adiponectin in systemic inflammation and critical illness is not well defined. Early data suggest that plasma levels of adiponectin are decreased in critical illness. Whether this is a result of the disease process itself or whether patients with lower levels of this hormone are more susceptible to developing a critical illness is not known. This observation of lower adiponectin levels then raises the possibility of therapeutic options to increase circulating adiponectin levels. The various options for modulation of serum adiponectin (recombinant adiponectin, thiazolidinediones) are discussed.

Sustained hyperglycemia induces insulin resistance, but the mechanism is still incompletely understood. Glucosamine (GlcN) has been extensively used to model the role of the hexosamine synthesis pathway (HSP) in glucose-induced insulin resistance. 3T3-L1 adipocytes were preincubated for 18 h in media ± 0.6 nmol/l insulin containing either low glucose (5 mmol/l), low glucose plus GlcN (0.1-2.5 mmol/l), or high glucose (25 mmol/l). Basal and acute insulin-stimulated (100 nmol/l) glucose transport was measured after re-equilibration in serum and insulin-free media. Preincubation with high glucose or GlcN (1-2.5 mmol/l) inhibited basal and acute insulinstimulated glucose transport only if insulin was present during preincubation. However, only preincubation with GlcN plus insulin inhibited insulin-stimulated GLUT4 translocation. GLUT4 and GLUT1 protein expression were not affected. GlcN

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In addition to microvascular abnormalities, neuronal apoptosis occurs early in diabetic retinopathy, but the mechanism is unknown. Insulin may act as a neurotrophic factor in the retina via the phosphoinositide 3-kinase/Akt pathway. Excessive glucose flux through the hexosamine biosynthetic pathway (HBP) is implicated in the development of insulin resistance in peripheral tissues and diabetic complications such as nephropathy. We tested whether increased glucose flux through the HBP perturbs insulin action and induces apoptosis in retinal neuronal cells. Exposure of R28 cells, a model of retinal neurons, to 20 mM glucose for 24 h attenuated the ability of 10 nM insulin to rescue them from serum deprivation-induced apoptosis and to phosphorylate Akt compared with 5 mM glucose. Glucosamine not only impaired the neuroprotective effect of insulin but also induced apoptosis in R28 cells in a dose-dependent fashion. UDP-N-acetylhexosamines (UDP-HexNAc), end products of the HBP, were increased ϳ2-and 15-fold after a 24-h incubation in 20 mM glucose and 1.5 mM glucosamine, respectively. Azaserine, a glutamine:fructose-6-phosphate amidotransferase inhibitor, reversed the effect of 20 mM glucose, but not that of 1.5 mM glucosamine, on attenuation of the ability of insulin to promote cell survival and phosphorylate Akt as well as accumulation of UDP-HexNAc. Glucosamine also impaired insulin receptor processing in a dose-dependent manner but did not decrease ATP content. By contrast, in L6 muscle cells, glucosamine impaired insulin receptor processing but did not induce apoptosis. These results suggest that the excessive glucose flux through the HBP may direct retinal neurons to undergo apoptosis in a bimodal fashion; i.e. via perturbation of the neuroprotective effect of insulin mediated by Akt and via induction of apoptosis possibly by altered glycosylation of proteins. The HBP may be involved in retinal neurodegeneration in diabetes. Diabetic retinopathy (DR)1 is usually considered a disease of the microvasculature, but significant involvement of neuronal components has been implicated as well. Previous studies by us and others (1, 2) indicate that neuronal cells in the retina, including ganglion cells, undergo apoptosis both in rats and humans with early diabetes. The pro-apoptotic BAX protein was also reported to be induced in neuronal as well as vascular components of the retina in patients with diabetes (3). However, the mechanism of the neurodegeneration in DR remains open to debate. Because insulin administration reduced the rate of apoptosis in streptozotocin-diabetic rats (2), systemic metabolic compromise such as hyperglycemia or defective insulin action, or both, adversely affects neuronal survival in the retina.Insulin is known to act as a neurotrophic factor in cultured neuronal cells including retinal ganglion cells (4, 5). Insulin exerts a broad array of biological responses by binding to its specific receptors and activating the intracellular signaling cascades such as the IRS-1/PI3K/Akt pathway. Our recen...

Succinate dehydrogenase (EC 1.3.99.1) in the yeast Saccharomyces cerevisiae is a mitochondrial respiratory chain enzyme that utilizes the cofactor, FAD, to catalyze the oxidation of succinate and the reduction of ubiqinone. The succinate dehydrogenase enzyme is a heterotetramer composed of a flavoprotein, an iron-sulfur protein, and two hydrophobic subunits. The FAD is covalently attached to a histidine residue near the amino terminus of the flavoprotein. In this study, we have investigated the attachment of the FAD cofactor with the use of an antiserum that specifically recognizes FAD and hence, can discriminate between apo- and holoflavoproteins. Cofactor attachment, both in vivo and in vitro, occurs within the mitochondrial matrix once the presequence has been cleaved. FAD attachment is stimulated by, but not dependent upon, the presence of the iron-sulfur subunit and citric acid cycle intermediates such as succinate, malate, or fumarate. Furthermore, this modification does not occur with C-terminally truncated flavoprotein subunits that are fully competent for import. Taken together, these data suggest that cofactor addition occurs to an imported protein that has folded sufficiently to recognize both FAD and its substrate.