Potential-dependent action ofAnemonia sulcata toxins III and IV on sodium channels in crayfish giant axons

Effects of toxins III and IV (ATX III and IV) from the sea anemoneAnemonia sulcata on the Na current of crayfish giant axons were studied. Both toxins slowed the inactivation of Na channels, producing a maintained Na current during a depolarizing voltage pulse. Using the intensity of the toxin-induced maintained current as an index for the fraction of Na channels to which toxin is bound, the toxin association and dissociation kinetics were analyzed. The dissociation rate of ATX III was increased by two orders of magnitudes by depolarizing the membrane from –70 to –40mV. This increase of the dissociation rate caused a marked decrease in the binding rate of ATX III to Na channels in the same potential range. ATX IV exhibited association and dissociation kinetics that had a potential dependency quite similar to that of ATX III in spite of different ionic charge distribution in these two toxins. The results support the view that the potential-dependent kinetics of these toxins are not due to an electrostatic interaction between the ionic charges of toxins and the membrane potential but result from a modulation of the binding energy depending on the gate configuration of the Na channel.     

A fatal case of necrotizing sinusitis due to toxigenic Corynebacterium ulcerans

A 77-year-old farmer developed cough with sputum production, fever, bloody nasal discharge and a mass in his right maxillary sinus leading to necrotic ulceration of the sinus. Corynebacterium ulcerans, carrying the beta-phage for the diphtheria toxin and secreting the toxin, was detected microscopically and by culture from the sinusoidal and ulcer discharge. Despite immediate antimicrobial chemotherapy the patient died of pulmonary failure associated with the production of large amounts of very viscous sputum. Identification of the causative agent, pathophysiological aspects and risk factors of this unusal infection are discussed.     

Live varicella vaccine polarizes the mucosal adjuvant action of cholera toxin or its B subunit on specific Th1-type helper T cells with a single nasal coadministration in mice

This study was undertaken to determine whether the specific Th1- or Th2-cell response to varicella-zoster virus was induced predominantly by a mucosal adjuvant, cholera toxin, in mice. A commercially available live varicella vaccine (Oka strain) and cholera toxin or its B subunit were administered simultaneously via the nasal route. Delayed-type hypersensitivity to the Oka vaccine was induced, but the systemic neutralizing antibody response was low. The delayed-type hypersensitivity evoked after a single administration was relatively higher than that on administration three times. When spleen cells from mice immunized once with the vaccine and cholera toxin or its B subunit were restimulated with the live vaccine in vitro, there was greater thymidine uptake and production of interleukin- 2 (IL-2) than controls, but only a low level of IL-4 production. The production of IL-2 induced by the B subunit of cholera toxin was less than that by cholera toxin and a mutant of Escherichia coli enterotoxin on co-immunization with the vaccine in mice. Cholera toxin and its B subunit have been reported to induce predominantly a specific Th2-type T-cell response to various antigens. However, the Oka vaccine is an antigen that polarizes the activation of specific Th1/Th2-type T cells by cholera toxin or its B subunit to the Th1-type side. Cholera toxin and its B subunit are thus useful mucosal adjuvants for inducing cellular immunity to the Oka vaccine similar to Escherichia coli enterotoxin.     

Tissue cages for study of experimental streptococcal infection in rabbits. II. Humoral and cell-mediated immune response to erythrogenic toxins

Infection of rabbits with erythrogenic toxin producing streptococcal strains caused a marked increase of humoral antibodies, which was detected by immunoprecipitation and ELISA. An antibody response directed towards the erythrogenic toxin type A was demonstrated by fused rocket immunoelectrophoresis. All toxinogenic reference strains produced ET type A under in vivo conditions despite that this toxin was not always demonstrated under in vitro conditions. The infection resulted in an increase of mitogenic response of peripheral lymphocytes to the initial nonspecific mitogenic erythrogenic toxins, whereas the Con A stimulation was depressed starting 14 days after infection and lasting during a period of 90 days. Since a normal antibody response was evoked, it seems likely that the T helper cell function was not affected.     

Tissue cages for study of experimental streptococcal infection in rabbits. I. Production of erythrogenic toxins in vivo

Tissue cages implanted subcutaneously were used to infect rabbits with erythrogenic toxin (ET) producing streptococci. The in-vivo production of ET was followed during the infection by immunoprecipitation analyses of the tissue cage fluid (TCF). ET types A and C were mainly detected during the first week of infection, but, as late as 4 weeks after the inoculation, ET was occasionally found in TCF. The nonspecific mitogenic activity of ET on human lymphocytes was also used as a biological marker to recognize ET in TCF. Mitogenic activity was detected in 90% of samples during the first week. In order to characterize the mitogenic material released by growing streptococci, TCF was electrofocused in polyacrylamide gel. The eluates of sliced gels were checked for mitogenic activity and compared with a purified ET preparation containing ET types A and C. It could be verified that ET type A was produced under in-vivo conditions by strains NY-5 and SF130, while ET type C was produced by strain T18. Differences between production of toxins in vitro and in vivo might be of significance for the understanding of the pathogenetic mechanisms in streptococcal infection.     

Effect of tetanus toxin on protein composition of synaptic structures of the rat brain and spinal cord

It was shown by electrophoresis on polyacrylamide gel that the content of proteins with low electrophoretic mobility rises in a Triton extract of the fractions of synaptic structures from the spinal cord tissue of rats with local tetanus, whereas no change was found in the protein spectrum in the dodecyl sulfate extract. In experiments in vitro tetanus toxin stimulated the incorporation of lysine-H³ into total proteins of cortical synaptosomes.Laboratory of General Pathology of the Nervous System, Institute of General Pathology and Pathological Physiology, Academy of Medical Sciences of the USSR, Moscow. Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 79, No. 4, pp. 19–22, April, 1975.     

The set of naturally processed peptides displayed by DR molecules is tuned by polymorphism of residue 86

The response to tetanus toxoid (TT) was studied in immune donors that carry two alleles of DR5 that differ only at DRβ residue 86: DRB1*1101 (G86, abbreviated 1101) and DRB1*1104 (V86, abbreviated 1104). A large number of TT-specific T cell clones was isolated and the epitopes recognized in association with 1101 and 1104 were mapped. We found that two epitopes (p2 and p32) can be recognized in association with both 1101 and 1104 while three epitopes (p23, p27 and p30) are recognized in association with 1101, but never in association with 1104. The sets of naturally processed self peptides displayed by 1101 and 1104 were characterized using alloreactive T cell clones. We found that all 1104 alloreactive clones recognize both 1104 and 1101, while ?30% of the alloreactive 1101 clones fail to recognize 1104. Thus it is apparent that both naturally processed TTand self peptides displayed on 1104 molecules represent a fraction of those displayed on 1101 molecules. The mechanism responsible for this differential presentation was investigated by comparing the capacity of 1101 and 1104 antigen-presenting cells to present TTor synthetic peptides to specific T cells and by measuring the binding of these peptides to DR molecules. Three sets of results suggest that V86 acts as a constraint to the binding of naturally processed peptides: (i) all 1104-restricted or alloreactive T cell clones recognize TT- or allo-epitopes presented by 1101 as well, thus ruling out a major effect of V86 as a residue determining T cell restriction specificity; (ii) presentation of naturally processed peptides correlates in general with the capacity of long synthetic peptides to bind to 1101 or 1104 and (iii) while the naturally processed p30 epitope discriminates between 1101 and 1104, a short synthetic peptide binds equally well to and is comparably recognized in association with both 1101 and 1104. Taken together these results suggest that the natural polymorphism at residue 86 might be a molecular switch that finely tunes the complexity of the peptide collection presented on DR molecules.     

Synthesis of polyetherurethanes containing L-serine dipeptide and their use as materials for biomedical films

Prepolymers, which were produced by the polyaddition reaction of polytetramethylene glycol (PTMG) or polyethylene glycol (PEG) and 4,4'-diphenylmethane diisocyanate (MDI) or hexamethylene diisocyanate (HMDI), were chain-extended with a linear dipeptide of L-serine (Z-Ser-Ser-OMe) or a cyclic dipeptide of L-serine [c-(Ser)2] to yield novel polyetherurethanes containing dipeptide segments. The relationship between the surface morphology and the biomedical properties of the film of the novel polyetherurethanes was investigated. The surface of PU(PTMG,Z-Ser-Ser-OMe,MDI) film was smooth, but fibrous structures were developed in the bulk of the film with increasing molecular weight of the PTMG segment. The antithrombogenicity of the film containing the low molecular weight PTMG segment was better than that of the usual polyetherurethane film without the dipeptide segments. The partial hydrolysis of the ester groups involved in the dipeptide segment improved the antithrombogenicity. In the surface and the bulk of PU[PTMG,c-(Ser)2,MDI] film, spherulite structures were developed when the molecular weight of the PTMG segment was high, while single crystals with a length of 3-4 microns were produced when the molecular weight of the PTMG segment was low. The antithrombogenicity of the film containing the high molecular weight PTMG segment was better than that of the usual polyetherurethane film without the dipeptide segments. PU(PTMG/PEG,Z-Ser-Ser-OMe,MDI) film and PU[PTMG/PEG,c-(Ser)2,MDI] film were permeated by uraemic toxins. The permeation was accelerated with increasing water content of the film and decreasing molecular weight of the solute. The oxygen permeability of the film of the polyetherurethane containing the linear or cyclic dipeptide segments was greater than that of polyetherurethane film which does not contain the dipeptide segments.     

Co-stimulation of T cells via CD28 inhibits human IgE production; reversal by pertussis toxin.

In lymphocyte cultures, IgE production was achieved by stimulating T cells with anti-CD2 and IL-2. Here we show that anti-CD28, in the presence or absence of IL-2, reduces this IgE production approximately 10-fold. This inhibition of IgE production was almost completely reversed by Pertussis toxin (PT). PT had no effect on IgE production when the cells were stimulated in the absence of anti-CD28. No major effects of PT were found on IgM production. PT had no effect on purified B cells, stimulated with IL-4 and anti-CD40. In the presence of saturating amounts of rIL-4 similar results were obtained, albeit the absolute amounts of IgE produced were higher in all situations. Furthermore, PT-induced IgE production was still dependent on IL-4, as was evident from experiments in which anti-IL-4 was added to the culture. The IgE enhancing effect was dependent on the adenosine diphosphate (ADP)-ribosyltransferase activity of PT, because a mutant molecule lacking this activity was not able to restore anti-CD28-induced inhibition of IgE synthesis. Thus, we show that co-stimulation with anti-CD28 causes an inhibition of T cell-dependent IgE production by B cells, which inhibition can be specifically overcome by PT. An analysis of the molecular pathways underlying this phenomenon may contribute to our understanding of the regulation of IgE synthesis in (patho)physiological conditions.