Characteristics of interaction between central neurons and abdominal stretch receptors in the crayfish

Spontaneous activity of slow- and fast-adapted abdominal stretch receptor (SAR and FAR) of the crayfish and their activity evoked by adequate stimulation were investigated in the presence of efferent regulation. Activity of the receptors was shown to be under effective inhibitory control of two central neurons, principal and accessory; activity of these neurons, in turn, is determined by the current receptor activity. The closest interaction is found between SAR and the principal inhibitory neuron. Two types of efferent regulatory action of this neuron were discovered: grouped and continuous. Its powerful discharges (up to 361 spikes) arising in response to only one SAR afferent impulse are described. The character of synaptic connections between the peripheral and central neurons is discussed.I. P. Pavlov Institute of Physiology, Academy of Sciences of the USSR, Leningrad. Institute of Zoology, Academy of Sciences of the Moldavian SSR, Kishinev. Translated from Neirofiziologiya, Vol. 4, No. 3, pp. 317–327, May–June, 1972.     

Stabilization of the amplification convertase of complement by monoclonal antibodies directed against human factor B

Three IgM mouse monoclonal antibodies (MoAb), 5B5-A, 2D2-B, and 5B12-A, were prepared by fusion of spleen cells from mice immunized with human B with the SP 2/0 myeloma cell line. They were assessed for their effect on cell-bound and fluid-phase amplification convertases of complement (C) with purified proteins in vitro. 5B5-A and 2D2-B were similar in their effects on cell-bound preformed C3bBb in that they bound to cell-bound C3bBb, stabilized the C3bBb convertase, and rendered the C3bBb convertase relatively resistant to the plasma protein H. These two MoAb were also able to enhance C3 consumption in vitro in reaction mixtures containing C3b, C3, B, and D. At the same time, they presumably stabilized the C3 convertase and caused relative sparing of B hemolytic activity in the reaction mixtures. In contrast, 5B12-A, which also bound to Bb and C3bBb, did not induce any stabilization, but rather caused accelerated decay of cell-bound C3bBb. These results indicate that MoAb against B can have C3NeF-like activity. On the other hand, not all MoAb against B have stabilizing activity on the C3bBb convertase.     

Ligand-dependent secretion of rat retinol-binding protein expressed in HeLa cells.

A minigene encoding rat retinol-binding protein (RBP) was transfected into HeLa cells, which do not express endogenous RBP, transthyretin, or cellular retinol-binding protein. The HeLa cells manufactured and secreted the transfected gene product, demonstrating that RBP-transthyretin assembly is not a requirement for the secretion of RBP. When HeLa cells were grown under vitamin A-deficient conditions, RBP accumulated in the endoplasmic reticulum. Both serum and retinol stimulated secretion of RBP in a concentration-dependent manner. The retinol-regulated secretion occurred also after protein synthesis had been blocked by cycloheximide. Addition of holo-RBP or retinal, but not retinoic acid, stimulated secretion of RBP. Thus, an in vitro model system that resembles the rat hepatocyte in vivo with regard to the known regulation of RBP secretion has been established in a human cell line of extrahepatic origin. It can be concluded that cellular retinol-binding protein is not required for the transfer of retinol to RBP and that the mechanism whereby retinol controls the intracellular transport of RBP is neither specific for tissues synthesizing RBP nor species-specific. To investigate the structural properties responsible for the endoplasmic reticulum retention of RBP in the absence of its ligand, a cDNA encoding chicken purpurin, a protein that is 50% identical to RBP and that binds retinol, was expressed in HeLa cells. In contrast to RBP, purpurin was not retained in vitamin A-deficient HeLa cells.     

Immunolocalization of abscisic acid by monoclonal antibodies in Lavandula stoechas L. leaves

A monoclonal antibody was used to localize abscisic acid in Lavandula stoechas L. plants treated with 1 M abscisic acid. ABA localization was performed using EDC as the only fixative, which preserves antigenicity and improves the specificity of monoclonal antibodies. A relationship was observed between the effect of abscisic acid on chloroplast ultrastructure and ABA accumulation. Gold particles accumulated on swollen chloroplasts. Our findings provide cytochemical evidence that the chloroplast is a trapping compartment, and yield valuable information on the relation between chloroplast ultrastructure and ABA accumulation.Abbreviations ABA abscisic acid - BSA bovine serum albumin - EDC 1-(3-dimethyl-aminopropyl)-3 ethyl carbodiimide - IgG immunoglobulin G - mAB monoclonal antibodies - pAB polyclonal antibodies     

Activity of Lentinus edodes intracellular lectins at various developmental stages of the fungus

We studied changes of the hemagglutinating activity of intracellular lectins of the basidiomycete Lentinus edodes (shiitake) at various stages of its morphogenetic development depending on erythrocyte type, growth medium, and lectin purification degree. Under certain experimental conditions, the specific lectin activity at the brown mycelium film stage exceeded the corresponding value for nonpigmented mycelium. The sensitivity of the lectins towards trypsin-treated rabbit erythrocytes was no less than a hundredfold higher than towards any other erythrocyte type studied. The general regularities of specific activity change did not depend on nutrient medium composition. With purification of intracellular shiitake lectins, their sensitivity to human erythrocytes decreased seventyfold or more, whereas their sensitivity to rabbit erythrocytes increased by the same factor.     

Tumor necrosis factor alpha-induced activation of c-jun N-terminal kinase is mediated by TRAF2.

Tumor necrosis factor alpha (TNF alpha) a pro-inflammatory cytokine is an endogenous mediator of septic shock, inflammation, anti-viral responses and apoptotic cell death. TNF alpha elicits its complex biological responses through the individual or cooperative action of two TNF receptors of mol. wt 55 kDa (TNF-RI) and mol. wt 75 kDa (TNF-RII). To determine signaling events specific for TNF-RII we fused the extracellular domain of the mouse CD4 antigen to the intracellular domain of TNF-RII. Crosslinking of the chimeric receptor using anti-CD4 antibodies initiates exclusively TNF-RII-mediated signals. Our findings show that: (i) TNF-RII is able to activate two members of the MAP kinase family: extracellular regulated kinase (ERK) and c-jun N-terminal kinase (JNK); (ii) TRAF2, a molecule that binds TNF-RII and associates indirectly with TNF-RI, is sufficient to activate JNK upon overexpression; (iii) dominant-negative TRAF2 blocks TNF alpha-mediated JNK activation and (iv) TRAF2 signals the activation of JNK and NF-kappaB through different pathways. Our findings suggest that TNF alpha-mediated JNK activation in fibroblasts is independent of the cell death pathway and that TRAF2 occupies a key role in TNF receptor signaling to JNK.     

Preparation and partial characterization of a Lactobacillus lactis bacteriophage

High-titer lysates of a bacteriophage active against Lactobacillus lactis were prepared from liquid cultures as well as from areas of confluent lysis in soft-agar overlayers. Phage concentration and purification were accomplished by means of polyethylene glycol precipitation, differential centrifugation, and cesium chloride gradient centrifugation. The buoyant density of this phagein cesium chloride was 1.4795 g/ml. Characterization of phage growth cycle by one-step growth experiments under optimal conditions showed that the latent period was about 120 min, that the rise period lasted approx. 130 min, and that the average burst-size was about 80.Abbreviations p.f.u. plaque forming units - m.o.i. multiplicity of infection - PEG polyethylene glycol - SSC standard saline citrate solution