The main immunogenic region (MIR) of the nicotinic acetylcholine receptor and the anti-MIR antibodies

Myasthenia gravis (MG) is caused by autoantibodies against the nicotinic acetylcholine receptor (AChR) of the neuromuscular junction. The anti-AChR antibodies are heterogeneous. However, a small region on the extracellular part of the AChR alpha subunit, called the main immunogenic region (MIR), seems to be the major target of the anti-AChR antibodies, but not of the specific T-cells, in experimental animals and possibly in MG patients. The major loop of the overlapping epitopes for all testable anti-MIR monoclonal antibodies (MAbs) was localized within residues 67-76 (WNPADYGGIK for Torpedo and WNPDDYGGVK for human AChR) of the alpha subunit. The N-terminal half of alpha 67-76 is the most critical, Asn68 and Asp71 being indispensable for binding. Yet anti-MIR antibodies are functionally and structurally quite heterogeneous. Anti-MIR MAbs do not affect channel gating, but they are very potent in mediating acceleration of AChR degradation (antigenic modulation) in cell cultures and in transferring experimental MG in animals. Fab fragments of anti-MIR MAbs bound to the AChR prevent the majority of the MG patients' antibodies from binding to and causing loss of the AChR. Whether this inhibition means that most MG antibodies bind on the same small region or is a result of broad steric/allosteric effects is under current investigation.     

Ligninolytic enzyme activity: A comparison of the veratryl alcohol and Azure B assay systems

Summary Ligninolytic enzyme activities in cell-free culture filtrates of Coriolus versicolor, Fusarium solani and Phanaerochaete chrysosporium were assessed using a veratryl alcohol oxidation assay system and results compared with those obtained using a relatively new assay system based on the oxidation of Azure B.     

Features of changes in bioelectric reactions of the cerebral cortex in rats with deafferentation pain syndrome]

In rats with pain syndrome after sciatic nerve section the authors studied spontaneous and evoked bioelectric activity in sensomotor cerebral cortex of both hemispheres. Electrocorticogram showed the presence of hyper-synchronic discharges and paroxysmal peak-wave (700-800 mV) activity in contralateral hemisphere. While stimulating the injured limb the threshold of evoked potentials (EP) was observed to decrease, its amplitude to increase and focus maximum EP activity to extend.     

The effect of interleukin-2 on experimental emotional hypertension]

The effect of human recombinant interleukin-2, one of the potent mediators of the immune system, on the course of emotional hypertension in non-linear white rats has been investigated. A significant and prolonged hypotensive action of a single injection of interleukin-2 in hypertensive rats has been revealed. The data obtained can be a new evidence of participation of immune system in the development of hypertension in experimental animals.     

Effects of 4-methyluracil and carnosine on healing of skin wounds in rats

In experiments in vivo and in vitro the authors studied antioxidative properties of 4-methyluracil and carnosine, their capacity to inhibit sex and accelerate healing of skin wounds. 4-methyluracil and carnosine discover almost the same capacity to decrease in the tissues of the wound and the blood serum in the formation of various intermediate products of free radical oxidation. Data are given on the study of the dynamics of wound healing after a 5-day treatment with equimolar quantities.     

A histochemical analysis of the oxidative-reductive enzymes in the cardiomyocytes of mature and old rats following low-dose external gamma irradiation

The effect of gamma rays in low dose (0.5 Gy) on enzymes activity of glycolysis, tricarboxylic acid cycle, diaphorases in cardiomyocytes of adult and old albino rats at 3-, 10- and 30-day after irradiation was studied. It was established that the diaphorases activity decreased, the lactate dehydrogenase activity increased whereas that of other tricarboxylic acid cycle enzymes underwent phase changes. In result discoordination of redox enzymes in cardiomyocytes of rats hypoxic state develops. The question of the age sensitivity of heart to irradiation in low dose is discussed.     

The epidemiological importance of Vibrio cholerae isolated from different ecological systems

The analysis of the data on the isolation of V. cholerae from different ecological systems indicates that V. eltor do not constantly inhibit the rivers and sea at the territory under control. Hemolytically active V. cholerae without the vct gene, found to be faintly virulent and avirulent when studied on suckling rabbits used as a model and when evaluated by the complex method, show no tendency towards epidemic spread in the presence of conditions for the realization of the transmission of vibrios by the water route.     

Effect of Temperature, Light, Nutrients and Dehardening on Abscisic Acid Induced Cold Hardiness in Bromus inermis Leyss Suspension Cultured Cells

The effects of culture conditions on abscisic acid (ABA)-inducedfreezing tolerance were determined in smooth bromegrass Bromusinermis Leyss cv. Manchar) cell suspension cultures. Bromegrasscultures initiated with 2 g fr wt of cells achieved maximumfreezing tolerances (greater than –32?C) at 25 to 30?Cin the presence of 75 to 100 µM ABA. High levels of freezingtolerance induced by ABA were correlated with high growth ratesat 25 and 30?C. In control cells, incubation at 10?C inducedoptimum levels of hardiness with minimal growth. Prolonged exposure(6 weeks) of cells to 3?C, with or without ABA, increased freezingtolerance only by several degrees. Exogenous ABA concentrationsgreater than 100 µM were not inhibitory to growth. Repeatedexposure to ABA, however, retarded growth and made the cellstolerant to temperatures below –40?C. Removal of ABA fromthe medium resulted in dehardening of the cells both at 25 and3?C. Nitrogen had a marginal effect on ABA-induced hardeningat 25?C, but inhibited age-dependent hardening of control cellcultures. Light had no effect on the freezing tolerance of culturedcells. Addition of 10% sucrose, 30 min prior to freezing, tobromegrass cells treated with ABA for 4 days increased freezingtolerance more than 15?C. These observations are discussed inrelation to the contrasting behaviour of the low temperatureand photoperiod dependent cold acclimation of plants (Received July 14, 1989; Accepted October 23, 1989)