Immunization of Aotus monkeys with recombinant Plasmodium falciparum hybrid proteins does not reproducibly result in protection from malaria infection

Plasmodium falciparum antigens SERP, HRPII, MSAI, and 41-3 have shown promise as vaccine components. This study aimed at reproducing and extending previous results using three hybrid molecules. Antibody responses were reproduced in Aotus monkeys, but solid protection from a P. falciparum blood-stage challenge that showed an unintendedly enhanced pathogenicity was not observed.     

Evolution of malaria in Africa for the past 40 years: impact of climatic and human factors

MOTIVATION: Prediction methods for identifying binding peptides could minimize the number of peptides required to be synthesized and assayed, and thereby facilitate the identification of potential T-cell epitopes. We developed a bioinformatic method for the prediction of peptide binding to MHC class II molecules. RESULTS: Experimental binding data and expert knowledge of anchor positions and binding motifs were combined with an evolutionary algorithm (EA) and an artificial neural network (ANN): binding data extraction --> peptide alignment --> ANN training and classification . This method, termed PERUN, was implemented for the prediction of peptides that bind to HLA-DR4(B1*0401). The respective positive predictive values of PERUN predictions of high-, moderate-, low- and zero-affinity binders were assessed as 0.8, 0.7, 0.5 and 0.8 by cross-validation, and 1.0, 0.8, 0.3 and 0.7 by experimental binding. This illustrates the synergy between experimentation and computer modeling, and its application to the identification of potential immunotherapeutic peptides. AVAILABILITY: Software and data are available from the authors upon request. CONTACT: vladimir@wehi.edu. au     

Violent emergence from anesthesia: is it a pharmacological or psychological reaction?

A violent emergence from deep sedation is an uncommon reaction in the daily practice of anesthesia in the oral and maxillofacial surgery office. We present a case of a 22-yr-old male with a severe violent emergence from deep sedation that we attribute to a psychological rather than a pharmacological cause. A differential diagnosis is discussed, as are methods of treatment.     

Propagation of mechanically induced intercellular calcium waves via gap junctions and ATP receptors in rat liver epithelial cells

Mechanical stimulation was used to initiate Ca2+ waves in rat liver epithelial cells in order to ascertain the degree to which gap junctional intercellular communication (GJIC) is involved in communication of Ca2+ to adjacent cells and to assess alternative Ca2+ signaling pathways that may be present between these cells. In both WB-F344 cells, which show a high degree of GJIC, and WB-aB1 cells, which are GJIC deficient, mechanical stimulation of a single cell induced a Ca2+ wave which propagated away from the point of stimulation, across cell borders, to neighboring cells directly or indirectly in contact with the stimulated cell. In addition, the Ca2+ wave was transmitted to nearby isolated cells that exhibited no direct or indirect contact with the stimulated cell. Treatment of cells with 18beta-glycyrrhetinic acid, a compound that has been shown to block GJIC, did not significantly affect propagation of the Ca2+ wave. In contrast, treatment with suramin, a P2-purinergic receptor inhibitor, significantly reduced both the rate and the extent of Ca2+ wave propagation in WB-F344 cells and completely blocked its propagation in WB-aB1 cells. Cotreatment with suramin and glycyrrhetinic acid was found to completely block the mechanically induced Ca2+ wave in both cell lines. These studies indicate that mechanically induced cell injury in rat liver epithelial cells initiates signaling through at least two pathways, involving intercellular communication via gap junctions and extracellular communication via ATP activation of purinergic receptors.     

Improved biochemical variables, nutrient intake, and hormonal factors in slow nocturnal hemodialysis: a pilot study

OBJECTIVE: To determine whether slow nocturnal hemodialysis (SNHD) can be safely performed in patients with end-stage renal disease to improve the biochemical and clinical outcome. MATERIAL AND METHODS: We conducted an 8-week pilot study in nondiabetic adult patients, who underwent dialysis 6 nights per week for 8 hours each night. A dialysate flow rate of 300 mL/min and a blood flow rate of 250 mL/min, through an internal jugular dual-lumen venous catheter, were used. The equipment used was a COBE Centry System 3 dialysis machine and Fresenius F-80 (1.8 m2) or Baxter CT 190 (1.9 m2) dialyzers. Five patients were enrolled in the study. RESULTS: Two patients did not complete the study because of catheter-related infections--one at day 7 and one after 4 weeks of SNHD. All patients had improved blood pressure control, and no intradialytic adverse events occurred. Dietary intake improved, urea and creatinine levels significantly decreased, and weekly delivery of dialysate increased on SNHD. Potassium, chloride, beta 2-microglobulin, phosphorus, calcium, and high-density lipoprotein cholesterol all improved on SNHD. Serum testosterone increased in the three men on SNHD, but parathyroid hormone, luteinizing hormone, and follicle-stimulating hormone remained unchanged. Erythropoietin levels increased on SNHD, despite no change in exogenous erythropoietin doses in three patients and discontinuation of administration of erythropoietin in one. The following biochemical factors did not change significantly: serum sodium, bicarbonate, vitamin B12, folate, alkaline phosphatase, total cholesterol, triglycerides, and albumin. CONCLUSION: Higher doses of hemodialysis benefit nutrition, improve biochemical variables, and may improve many hormonal systems.     

Competition between folding and glycosylation in the endoplasmic reticulum

Using carboxypeptidase Y in Saccharomyces cerevisiae as a model system, the in vivo relationship between protein folding and N-glycosylation was studied. Seven new sites for N-glycosylation were introduced at positions buried in the folded protein structure. The level of glycosylation of such new acceptor sites was analysed by pulse-labelling under two sets of conditions that are known to reduce the rate of folding: (i) addition of dithiothreitol to the growth medium and (ii) introduction of deletions in the propeptide. A variety of effects was observed, depending on the position of the new acceptor sites. In some cases, all the newly synthesized mutant protein was modified at the novel site while in others no modification took place. In the most interesting category of mutants, the level of glycosylation was dependent on the conditions for folding. This shows that folding and glycosylation reactions can compete in vivo and that glycosylation does not necessarily precede folding. The approach described may be generally applicable for the analysis of protein folding in vivo.     

Reporting of industrial accidents in The Netherlands

Using an acetylcholine receptor-specific T-cell clone (TCC) from a myasthenia gravis patient, we have compared the induction of unresponsiveness by three agents: an anti-V beta monoclonal antibody (mAb), complexes of MHC class II with specific peptide (DR4:peptide) and free peptide. Pretreatment with each agent without antigen-presenting cells specifically rendered the TCC unresponsive to a subsequent optimal stimulus. A substantial proportion of the DR4:peptide pretreated cells underwent apoptosis and the remainder were profoundly unresponsive. Apoptosis was less prominent after pretreatment with free peptide and was not significant with anti-V beta mab; with both, the unresponsiveness was transient in the survivors. These diverse effects of engaging the T-cell receptor in the absence of costimulation suggest that these agents act via different mechanisms, and give insights to the potential for specific immunotherapy.     

Development of a narrow water-immersion objective for laserinterferometric and electrophysiological applications in cell biology

The immunity repressor (Rep) of bacteriophage Mu establishes and maintains lysogeny by shutting down transposition functions needed for phage DNA replication. Although Rep is stable in vivo, an altered immunity repressor (Vir) encoded by virulent, trans-dominant Mu mutants is rapidly degraded by Escherichia coli ClpXP protease. Rep and Vir are degraded at approximately the same maximal velocity (Vmax) by ClpXP, but the Km for Rep (3.6 microM) is over 20-fold higher than the Km for Vir (0.15 microM). Rep is also highly resistant to degradation in the presence of DNA whereas Vir is not. Vir increases the rate of Rep degradation by reducing its Km and imparts to Rep ClpXP sensitivity in the presence of DNA. Vir can drive at an accelerated rate the complete degradation of Rep molecules that outnumber Vir by eightfold or more. So long as Vir is present at a concentration of 0.1 microM or higher, Rep is degraded with a Km that is indistinguishable from that of Vir. These characteristics of repressor may be an important means of transducing physiological signals that induce Mu transposition in response to growth conditions or environmental stress, ClpXP hypersensitivity being disseminated among Rep molecules for the induction of Mu transposition.     

The control of Ca release from the cardiac sarcoplasmic reticulum: regulation versus autoregulation

This review discusses the mechanism and regulation of Ca release from the cardiac sarcoplasmic reticulum. Ca is released through the Ca release channel or ryanodine receptor (RyR) by the process of calcium-induced Ca release (CICR). The trigger for this release is the L-type Ca current with a small contribution from Ca entry on the Na-Ca exchange. Recent work has shown that CICR is controlled at the level of small, local domains consisting of one or a small number of L-type Ca channels and associated RyRs. Ca efflux from the s.r. in one such unit is seen as a 'spark' and the properties of these sparks produce controlled Ca release from the s.r. A major factor controlling the amount of Ca released from the s.r. and therefore the magnitude of the systolic Ca transient is its Ca content. The Ca content depends on both the properties of the s.r. and the cytoplasmic Ca concentration. Changes of s.r. Ca content and the Ca released affect the sarcolemmal Ca and Na-Ca exchange currents and this acts to control cell Ca loading and the s.r. Ca content. The opening probability of the RyR can be regulated by various physiological mediators as well as pharmacological compounds. However, it is shown that, due to compensatory changes of s.r. Ca, modifiers of the RyR only produce transient effects on systolic Ca. We conclude that, although the RyR can be regulated, of much greater importance to the control of Ca efflux from the s.r. are effects due to changes of s.r. Ca content.