Host response toBothrops asper snake venom

As part of the characterization of the host reactivity to the venom ofBothrops asper, we investigated the inflammatory responses in the mouse footpad model. The subcutaneously injected venom induced a rapid increase of serum IL-6 concentration, which peaked between 3 and 6 h and returned to normal values at 12 h. In contrast, serum TNF- and IL-1 were not detectable at any time point studied. A myotoxic phospholipase A₂ isoform purified from this venom, myotoxin II, was also able to induce a systemic IL-6 release when injected into the footpad. Both venom and myotoxin induced local edema and a leukocyte infiltrate accumulating in the muscle and subdermal tissue within 6 h. The infiltrate consisted predominantly of neutrophils at 6 and 24 h, but at later times, mononuclear cells also appeared. The edema, leukocyte infiltration, and IL-6 responses did not depend on the hemorrhagic activity of venom, since all three effects were seen after injection of (1) preneutralized venom, devoid of hemorrhagic activity, and (2) purified myotoxin II. Circulating platelet numbers were significantly decreased 30 min after venom injection and returned to normal after 12 h. The venom also induced a rapid inversion in the ratio of neutrophils to lymphocytes in peripheral blood, which did not normalize until 12 h later. The present observations suggest that venom, besides its cytotoxic properties, induces early hematologic and immunologic alterations. These findings may be of relevance in future treatment modalities.     

Treatment with an anti-CD18 monoclonal antibody in rabbits inhibits pneumococcal-induced leukocyte recruitment in the skin,but not in the meninges

Inflammatory recruitment of leukocytes into the cerebrospinal fluid (CSF) during bacterial meningitis has been shown to contribute to the neurological damage commonly associated with this disease. In this study we tested whether inhibition of firm leukocyte adhesion to vascular endothelium could reduce leukocyte recruitment into the subarachnoid space (SAS) and into the skin in rabbits challenged with pneumococcal cell wall (PCW) antigen. PCW was given either as an intracisternal or an intradermal (i.d.) injection. Intravenous (i.v.) treatment with a monoclonal antibody (mAb), IB4, against the leukocytic adhesion molecule CD18 has previously been documented to attenuate leukocyte CSF accumulation in experimental bacterial meningitis. In the present study, i.v. treatment with anti-CD18 mAbs (IB4) only tended to inhibit CSF leukocyte influx in animals with PCW-induced meningitis. However, if the antigen was injected i.d., treatment i.v. with the same mAb (IB4) dramatically reduced leukocyte accumulation in the skin. Our findings indicate that the mechanisms responsible for PCW-induced inflammatory accumulation of leukocytes in skin and meninges are different.     

Potentiation of human alpha4beta2 neuronal nicotinic receptors by a Flustra foliacea metabolite

The effects of various Flustra foliacea metabolites on different types of human neuronal nicotinic acetylcholine receptors (nAChRs) expressed in Xenopus oocytes were investigated. Whereas most of the compounds tested had a small blocking effect, one of them, deformylflustrabromine, selectively increased the current obtained in alpha4beta2 receptors when co-applied with acetylcholine (ACh). The current increase was reversible and concentration-dependent. This potentiating effect was still present at saturating concentrations of acetylcholine, and no changes in single-channel conductance or reversal potential were observed, thus suggesting a modification in the gating of alpha4beta2 receptors. Dwell time analysis of single channel records indicates that the mechanism of action of deformylflustrabromine could be both an increase of the opening rate constant and a decrease of the closing rate constant on alpha4beta2 receptors. Thus, deformylflustrabromine may constitute an excellent starting point for the future development of related agents able to potentiate human neuronal nicotinic receptor function.     

Improvement in histological diagnosis of primary hyperparathyroidism with a monoclonal antiparathyroid antibody

The monoclonal antiparathyroid antibody E11 reacts with a glycoprotein of high molecular weight, which acts as a calcium receptor on the surface of parathyroid cells and mediates calcium regulation of parathyroid hormone (PTH) release. Reduced expression of the calcium receptor has been implicated as a cause of the defect in PTH regulation in the pathological parathyroid parenchyma of patients with hyperparathyroidism (HPT). The present study evaluated the efficacy of immunostainings with the E11 antibody in comparison with routine histopathological methods including staining by the oil red O technique for histological discrimination between normal and pathological parathyroid glands. Parathyroid tissue from euparathyroid individuals invariably presented intense and homogeneous surface staining, with the antibody on virtually all chief cells, while the pathological glands from patients with HPT consistently showed heterogeneous and reduced immunostaining. Even minimally enlarged pathological glands from individuals with mild hypercalcemia and the normal-sized glands associated with adenomas displayed parathyroid chief cells with reduced antibody reactivity. The monoclonal antiparathyroid antibody should constitute a useful tool in parathyroid histopathology not only by its ability to identify the parathyroid tissue, but also by directly demonstrating the functionally normal and abnormal cells within the parathyroid tissue.     

Characterization of an IgA receptor from group B streptococci: specificity for serum IgA

Some strains of group B streptococci express a cell surface protein which binds IgA. This report describes some properties of such an IgA receptor and compares it with a previously described IgA receptor from group A streptococci. The group B receptor was released in an almost pure form from bacteria incubated at elevated pH, and could be isolated by IgA-Sepharose affinity chromatography. The sequence of the N-terminal 19 amino acid residues was unique. The receptor preferentially binds IgA of human origin, as shown in immunoblotting experiments with purified IgA from nine different species. The affinity constant of the purified receptor for serum IgA was determined to be 3.5 x 10(8) M-1, but for secretory IgA it was too low to allow determination. This result indicates that secretory component and/or J chain interferes with the binding of IgA to this type of bacterial receptor, which may be one of the physiological functions of these polypeptides. A reduction in affinity was also observed for another complexed form of IgA, alpha 1-microglobulin-IgA. The group B receptor is antigenically unrelated to the IgA receptor from group A streptococci (protein Arp), but competitive inhibition experiments indicate that they bind to the same region in IgA. The implications of these findings, and the biological role of bacterial IgA receptors, are discussed.     

Variations in attachment ofNeisseria gonorrhoeae to vaginal epithelial cells during the menstrual cycle and early pregnancy

An in vitro system was used to study the ability of virulent gonococci to adhere to vaginal epithelial cells obtained from healthy donors during the pre- and postmenstrual phases, and from those in early pregnancy. It was found that more gonococci adhered to the cells from donors in the postmenstrual phase than to cells from those in the premenstrual one. This difference was statistically highly significant. The attachment rate of gonococci to vaginal epithelial cells was similar in early pragnancy and in the premenstrual phase.     

Metabolic functions of duplicate genes in Saccharomyces cerevisiae

The roles of duplicate genes and their contribution to the phenomenon of enzyme dispensability are a central issue in molecular and genome evolution. A comprehensive classification of the mechanisms that may have led to their preservation, however, is currently lacking. In a systems biology approach, we classify here back-up, regulatory, and gene dosage functions for the 105 duplicate gene families of Saccharomyces cerevisiae metabolism. The key tool was the reconciled genome-scale metabolic model iLL672, which was based on the older iFF708. Computational predictions of all metabolic gene knockouts were validated with the experimentally determined phenotypes of the entire singleton yeast library of 4658 mutants under five environmental conditions. iLL672 correctly identified 96%-98% and 73%-80% of the viable and lethal singleton phenotypes, respectively. Functional roles for each duplicate family were identified by integrating the iLL672-predicted in silico duplicate knockout phenotypes, genome-scale carbon-flux distributions, singleton mutant phenotypes, and network topology analysis. The results provide no evidence for a particular dominant function that maintains duplicate genes in the genome. In particular, the back-up function is not favored by evolutionary selection because duplicates do not occur more frequently in essential reactions than singleton genes. Instead of a prevailing role, multigene-encoded enzymes cover different functions. Thus, at least for metabolism, persistence of the paralog fraction in the genome can be better explained with an array of different, often overlapping functional roles.     

The Effects of a Gastric Inhibitory Substance on Gastric Secretion in the Pylorus Ligated Rat1

An extract was prepared from juice secreted by vagally denervated isolated pouches of the gastric antrum in the dog, by dialyzing against water and lyophilization. This gastric inhibitory substance (GIS) was assayed in pylorus ligated rats. Three groups of rats served as controls. One group received no injections, while the two other were injected with saline (1 ml/100 g rat) intravenously (i.v.) or intraperitoneally (i.p.). Two different types of gastric secretion were studied: (a) basal or spontaneous gastric output, and (b) gastric acid response to exogenous gastrin. GIS lowered significantly the basal or spontaneous output of acid, but did not alter the basal output of pepsin significantly. When GIS was injected into animals stimulated by gastrin, there was a highly significant lower output of both acid and pepsin.     

Intermittent preventive sulfadoxine-pyrimethamine treatment of primigravidae reduces levels of plasma immunoglobulin G, which protects against pregnancy-associated Plasmodium falciparum malaria

Pregnancy-associated malaria (PAM) is an important cause of maternal and neonatal suffering. It is caused by Plasmodium falciparum capable of inhabiting the placenta through expression of particular variant surface antigens (VSA) with affinity for proteoglycans such as chondroitin sulfate A. Protective immunity to PAM develops following exposure to parasites inhabiting the placenta, and primigravidae are therefore particularly susceptible to PAM. The adverse consequences of PAM in primigravidae are preventable by intermittent preventive treatment (IPTp), where women are given antimalarials at specified intervals during pregnancy, but this may interfere with acquisition of protective PAM immunity. We found that Kenyan primigravidae receiving sulfadoxine-pyrimethamine IPTp had significantly lower levels of immunoglobulin G (IgG) with specificity for the type of parasite-encoded VSA-called VSA(PAM)-that specifically mediate protection against PAM than did women receiving a placebo. VSA(PAM)-specific IgG levels depended on the number of IPTp doses received and were sufficiently low to be of clinical concern among multidose recipients. Our data suggest that IPTp should be extended to women of all parities, in line with current World Health Organization recommendations.