Content of red blood-cell sialic acid in BW 35 blood donors. Relation to magnesium concentration and pyruvate kinase activity

Previous studies have shown that the concentration of red blood cell (RBC) magnesium is significantly lower in subjects carrying an HLA-BW 35 antigen (p less than 0.001) than in non-carriers. As this finding might be related to modifications of the RBC membrane sialoglycoconjugates, RBC sialic acid was comparatively determined in BW 35+ and BW 35- subjects. Pyruvate-kinase activity mean RBC volume, and reticulocyte count have also been determined in order to estimate whether some significant variations in the level of these age markers could be detected between the HLA BW 35+ and BW 35- subjects. A significant negative correlation between sialic acid and RBC magnesium concentrations was observed for the whole population tested (n 57, p less than 0.005), 61% of the BW 35+ and only 25% of the BW 35- individuals having sialic acid values above, and magnesium values below the overall mean (p less than 0.01). The variance of mean RBC volume was also larger for the BW 35+ group. Other determinations did not show any significant variations, suggesting that the results are not related to RBC age.     

Isoquinoline alkaloids from cell suspension cultures of Fumaria capreolata

Fumaria capreolata was taken into cell suspension culture. The culture yielded a biomass of about 12 g dry weight per liter of medium; the dried cells contained ca. 0.1% of alkaloids. Besides choline, the following ten known isoquinoline alkaloids were isolated from the cell extract in crystalline form: coptisine, dehydrocheilanthifoline; (+)-isoboldine; magnoflorine; N-methylcoclaurine; (+)-reticuline; (–)-pallidine; protopine; sanguinarine; (–)-scoulerine. This is the most diverse isoquinoline alkaloid spectrum thus far published for a cell suspension culture.     

Effects of EEG of the osmotic opening of the blood-brain barrier in rats

EEG activity was recorded in rats submitted to osmotic opening of the BBB by intracarotid mannitol infusion.This procedure produced an immediate short-lasting depression of the EEG and a tardive paroxysmal EEG activity. Both these phenomena were more relevant on the ipsilateral hemisphere. In some instances a tonico-clonic seizure was recorded.Pre-treatment with diazepam abolished the occurrence of the tardive EEG and behavioral modifications.In accord with previous findings, focal seizure activity is likely to be responsible for the metabolic abnormalities associated with osmotic opening of the BBB. This preparation therefore produces in the brain unphysiological states in respect to local metabolism and electrical function.     

Contribution to catalysis and stability of the five cysteines in Escherichia coli aspartate aminotransferase. Preparation and properties of a cysteine-free enzyme.

The five cysteines, at positions 82, 191, 192, 270, and 401, of Escherichia coli aspartate aminotransferase (AATase) were, individually and in some combinations, converted to alanine by site-directed mutagenesis (C82A, C191A, C192A, C270A, C401A). Cys-191, which is conserved in all AATase isozymes, was mutated to serine as well (C191S). A quintuple mutant, with all cysteines converted to alanines (Quint), was also constructed. The effects of these single and multiple mutations were examined by steady-state kinetics and urea denaturation. The thermal stabilities of Quint and of the wild-type enzyme (WT) were determined by differential scanning calorimetry. The mutants had kcat values up to 50% greater than that of WT and KMAsp and KM alpha-KG values up to 1.5- and 3.3-fold higher than that of WT. The mutants C82A and C191A exhibit nearly the same CM in urea denaturation experiments as WT, while the other single mutants and Quint are less stable, with CM differences of up to 0.7 M urea. Quint is also less thermostable than WT, with a delta TM of 3.3-4.4 degrees C. Thus the five cysteine replacements yield small, but significant, changes in catalytic and denaturation parameters, but none of the cysteines was found to be essential. The changes manifested in the mutation of the conserved Cys-191 to alanine are no greater than those observed with the four nonconserved cysteines. We consider the evolutionary implications of these findings.     

Influence of exogenous NO donator and variations in the Ca<Superscript>2+</Superscript> content on transport activity related to tonoplast proton pumps in ontogenesis and under hyperosmotic stress

The changes in transport activity of tonoplast proton pumps under the influence of exogenous NO donator and modulation of Ca²⁺ concentration jointly and separately were investigated at different stages of ontogenesis and under hyperosmotic stress. The results suggest that both exogenous NO donator and Ca²⁺ ions can influence the activity of transport processes related to tonoplast and this influence is especially evident in the period of growth and accumulation of metabolites. Under hyperosmotic stress, H⁺-pyrophosphatase plays a more important role than H⁺-ATPase: the activity of the former increases 2.3-fold compared to the control osmotic conditions, whereas the activity of H⁺-ATPase is practically unchanged. H⁺-pyrophosphatase was more responsive to the presence of exogenous NO donator and to variations in Ca²⁺ concentration. The effects of exogenous NO donator on tonoplast proton pumps depended on the concentration of Ca²⁺, which apparently can mediate NO action.     

Structure–antimicrobial activity of some natural isocoumarins and their analogues

Three naturally occurring isocoumarins (paepalantine, paepalantine 9-O-beta-D-glucopyranoside and paepalantine 9-O-beta-D-allopyranosyl(1 --> 6) glucopyranoside) and two semi-synthetic analogues, 9,10-acylated compound and 9-OH-10-methylated compound, structurally similar to paepalantine, were evaluated for antimicrobial activity using a spectrophotometric microdilution technique. The paepalantine was active against S. aureus, S. epidermidis, and E. faecalis while the other four compounds proved ineffective against all microorganisms tested at concentrations of 500 microg/ml. Variations in phenolic substitution at OH-9 and/or OH-10 in the paepalantine molecule resulted in compounds without antimicrobial activity. A combination of structural features, two phenolic groups as cathecolic system, forms an oxygenated system arrangement that may reflect the potentially antimicrobial properties of paepalantine.     

Repair mechanisms involved in muscle regeneration following partial excision of the rat gastrocnemius muscle

The sequential cytological events of the regeneration process, after partial excision of the gastrocnemius muscle in the rat, were followed by light and electron microscopy. During the first 2 days after injury leukocytes and macrophages infiltrate into the traumatized area. Myogenic regeneration is then characterized by mainly two repair mechanisms. Mononucleated cells, that populate the excised area, most probably fuse together to give rise to newly formed multinucleated myotubes that further develop to striated myofibers. Another mechanism involves the repair of injured muscle fibers by the possible fusion of mononucleated cells with their necrotic cut ends. Consequently, by addition of nuclei and new muscular material, sarcoplasmic outgrowths from the injured fibers are formed. It is concluded that mainly two repair mechanisms are involved in the regeneration process following partial excision of a muscle: addition of new muscle fibers in a process similar to that of embryonic myogenesis and also meristic growth from the injured fibers.