Molecular evidence for the expression of nicotinic acetylcholine receptor alpha-chain in mouse thymus.

The presence and structure of nicotinic acetylcholine receptor (nAChR) in the thymus has been a subject of interest for many years because of its possible role in the pathogenesis of the autoimmune disease myasthenia gravis. Using the polymerase chain reaction with primers specific for the alpha-chain of nAChR (nAChR-alpha), an 880-bp homologous band was found after amplification of cDNA prepared from mouse thymus, thymic medullary and cortical epithelial cell lines, but not from thymocytes or kidney. Sequencing of the polymerase chain reaction product from the thymus and thymic medullary and cortical epithelial lines showed identity with skeletal muscle nAChR-alpha over the region examined. This region includes the domains of the molecule on which B cell and T cell autoantigenic targets have been described. No evidence was found in mouse tissue for the exon 3A, which has been described in human muscle and the human rhabdomyosarcoma cell line TE671. Our results provide evidence at the RNA level for the expression of the nAChR-alpha on stromal cells but not on thymocytes in normal murine thymus and are consistent with a role for intrathymic autoantigen expression in the pathogenesis of myasthenia gravis.     

Interaction of ethanol with opiate receptors

Addition of ethanol to rat brain homogenate containing opiate receptors inhibits at a concentration of 50 mM the stereospecific binding of 3H-naloxone at 37 degrees C but not at 0 degree C, with the ID50 being 462 mM under these conditions. The temperature-dependent inhibition of the ligand binding suggests that ethanol does not compete with naloxone for specific binding sites of opiate receptors and changes the structure of lipids in biological membranes. Scatchard's analysis has demonstrated that apart from a decrease in the number of highly affinity binding sites of 3H-naloxone, the total amount of the binding sites remains unchanged both in the presence and absence of ethanol and constitutes 453 and 549 fmol/mg protein. It is assumed that ethanol might interconvert highly and low-affinity binding sites. Analysis of the effect of ethanol on 3H-naloxone binding with opiate receptors contained by synaptic membranes obtained from animals with varying predisposition to voluntary alcoholization has shown that ethanol inhibits to a greater degree ligand binding with membranes obtained from rats predisposed to alcoholization. The possibility of the involvement of receptors in the biochemical mechanisms by which the initial alcoholic motivation is effected is under discussion.     

Effect of adrenaline on kidney lysosome function in rats during prolonged soft tissue crushing

The total and unsedimentable activity of acid DNase, RNase, phosphatase and arylsulfatases A and B was examined in the rat kidneys during long-term compression of soft tissues in the presence of high excitability of the sympathoadrenal system. Injection of adrenalin to rats with trauma reduced the total activity of DNase, acid phosphatase and arylsulfatases A and B, particularly at the late periods of soft tissue compression, whereas the total activity of acid RNase slightly increased as compared with control. Compression of soft tissues after adrenalin preinjection was accompanied by a substantial rise of unsedimentable activity of the lysosomal enzymes under study in the kidneys. The activity of the enzymes in cytosol progressively ascended as the time of soft tissue injury increased.     

Cyclic AMP is not detectable in Clostridium perfringens

Cyclic AMP was not detected (less than 5 X 10(-9) M intracellular concentration) at any stage of growth or sporulation of two strains of Clostridium perfringens grown with or without methylxanthines. Only Bacillus and Lactobacillus, genera belonging to the same phylogenetic cluster, have previously exhibited undetectable levels of cyclic AMP.     

Comparative greenhouse study of Eucalyptus grandis in vitro plantlets and half-sib seedlings,II. Dry matter accumulation and relative distribution

In vitro directly micropropagated plantlets from three selected five-year-old Eucalyptus grandis Hill ex. Maiden hybrids were compared to their related half-sib seedlings for growth and growth pattern parameters under greenhouse conditions used for operational seedling production. The oven dry weights were determined from stem, leaf, and root samples collected every 40 days for four times. Relative growth rate, net assimilation rates and shoot:root ratio were calculated. Survival was 98% and 95% for plantlets and seedlings, respectively. Significant differences were observed between parents in terms of shoot and root dry weights and their ratios with similar ranking among plantlets and seedlings, suggesting genetic control over these traits. Plantlets started with significantly higher root: shoot ratios and stem, leaf, root, and total dry weight. Although seedlings had higher relative growth and net assimilation rates, all the initial differences decreased sharply over time.     

The histology and calcification of regenerating scales in the blackspotted topminnow, Fundulus olivaceus (Storer)

The regenerating scale and tissues comprising the scale pocket of Fundulus olivaceus were examined microscopically at specific intervals. Scale removal resulted in a thickening of the epidermis which persisted through the early stages of regeneration. This thickening was due in part to the appearance of columnar basal cells which divided producing cells that became mucous cells and squamous cells. The scale regenerated as a relatively large plate of bone which first appeared between layers of scleroblasts on the floor of the scale pocket and then grew producing circuli and radii. By the fourth day of regeneration, calcium was observed in the cytoplasm of the scleroblasts and at randomly distributed foci in the osseous portion of the scale. The osseous layer was completely calcified by 15 days of regeneration.     

Effect of specific antibodies on active immunity development in those inoculated with an antirabies vaccine

The study of the effect of gamma globulin introduced in different doses (0.5 and 0.25 ml/mg) in combination with Fermi rabies vaccine (observations on humans were made) and with cerebral rabies vaccine inactivated by UV irradiation (in animal experiments) demonstrated that the injection of the higher doses of gamma globulin resulted in lower geometrical mean of antibody titers. Therefore, in combined administration of rabies vaccine and gamma globulin for postexposure rabies prevention it is advisable to reduce the dose of gamma globulin by one-half.