Influence of orotic acid upon post-excitatory facilitation released by stimulation of the tooth pulp]

The influence of orotic acid on post-excitatory facilitation of evoked potentials released by electric stimulation of the tooth pulp in the sensomotor cortex was studied. 15-360 min following application of 100 mg/kg orotic acid, increase in amplitude of potentials released by stimulation of the tooth pulp, reinforcement of the post-excitatory facilitation observable 5 msec after stimulation occurred.     

Characterization of the pH 4.0 endonuclease from adenovirus-type-2-infected KB cells.

The properties of the pH 4.0 endonuclease from adenovirus-type-2-infected KB cells were determined. The enzyme has a molecular weight of approximately 40000. Its pH optimum is at pH 4.0, it is not inhibited by ethylenediaminetetraacetate (EDTA), and it is active at temperatures up to 60 degree C. The enzyme cleaves adenovirus DNA in a stepwise manner. The limit digestion product has a molecular weight of 120000-200000. There is evidence that the cleavage reaction proceeds via an initial single-strand nick. Under the conditions tested the endonuclease did not seem to reveal a high degree of specificity as to the recognition of cleavage sites, or else the sites recognized occurred very frequently.     

Homologies between paraflagellar rod proteins from trypanosomes and euglenoids revealed by a monoclonal antibody

A Nonidet P 40 insoluble fraction was isolated from Trypanosoma brucei and was used to raise a monoclonal antibody (5E9). The antigen was localized by indirect immunofluorescence in the flagellum of T. brucei and of two species of euglenoids, Euglena gracilis and Distigma proteus. In immunoblot analysis, 5E9 appeared to bind to paraflagellar rod proteins PFR1 and PFR2 of T. brucei (72000 and 75000 mol. wt.) and of E. gracilis (67000 and 76000 mol. wt.). The presence of a common epitope in paraflagellar rod proteins from species of trypanosomes and euglenoids shows that despite distinct structures of the rods some identical domain exists in the proteins that could be involved in their supramolecular assembly into a similar organelle. The antigenic determinant defined by 5E9 was also shown to be present in a 87000 molecular weight polypeptide located in the proximal part of the flagellum of Crithidia oncopelti in which a paraflagellar rod is not detectable at the ultrastructural level.     

Resistivity of Red Blood Cells Against High-Intensity, Short-Duration Electric Field Pulses Induced by Chelating Agents

The interaction of human red blood cells (RBCs) with diethylenetriamine-pentaacetic acid (DTPA) or its Gd-complex (Magnevist, a widely used clinical magnetic resonance contrast agent containing free DTPA ligands) led to the following, obviously interrelated phenomena. (i) Both compounds protected erythrocytes against electrohemolysis in isotonic solutions caused by a high-intensity DC electric field pulse. (ii) The inhibition of electrohemolysis was observed only when cells were electropulsed in low-conductivity solutions. (iii) The uptake of Gd-DTPA by electropulsed RBCs was relatively low. (iv) (Gd-) DTPA reduced markedly deformability of erythrocytes, as revealed by the electrodeformation experiments using high-frequency electric fields. Taken together, the results indicate that (Gd-) DTPA produce stiffer erythrocytes that are more resistant to electric field exposure. The observed effects of the chelating agents on the mechanical properties and the electropermeabilization of RBCs must have an origin in molecular changes of the bilayer or membrane-coupled cytoskeleton, which, in turn, appear to result from an alteration of the ionic equilibrium (e.g., Ca²⁺ sequestration) in the vicinity of the cell membrane. Received: 19 January 1999/Revised: 1 April 1999     

The chemical-transformation products of 1,6-dibromo-1,6-dideoxygalactitol and 1,2:5,6-dianhydrogalactitol in aqueous solution

After hydrolysis of 1,6-dibromo-1,6-dideoxygalactitol (1) and 1,2:5,6-dianhydrogalactitol (2), 11 compounds were isolated, three of them as tritylated derivatives. Their structures were established on the basis of chemical evidence and, for four compounds, by X-ray diffraction. The main product of the hydrolysis of 1 was 3,6-anhydro-1-bromo-1-deoxy-dl-galactitol; the end-products of the hydrolysis of 2 were 1,5-anhydro-dl-galactitol, 2,5-anhydro-dl-altritol, and galactitol.     

Functional anatomy of the musculature of the trachea.

The smooth musculature of the human trachea was studied and compared with earlier observations in the rabbit. The results may be summarized as follows: 1. The annular m. constrictor tracheae, previously observed in the rabbit, has also been identified in the human trachea. 2. Longitudinal muscle fibers outside the constrictor musculature were observed in man. These fibers are rudimentary and appear to be of no functional importance. 3. From a functional point of view, it appears justified to regard the outer tracheal musculature largely as a constrictor musculature. 4. The main function of the outer musculature of the trachea and the elastic cartilaginous arches is to maintain the stability of the tracheal wall. 5. The variation of the lumen of the trachea is mainly controlled by the m. trachealis in the pars membranacea.     

Collagen crosslinking and cartilage glycosaminoglycan composition in normal and scoliotic chickens

The amounts of lysine-derived crosslinks in collagens from tendon, cartilage, intervertebral disc, and bone and changes in the composition of sternal cartilage glycosaminoglycans were estimated in two lines of chickens, a control-isogenic line and a line that develops scoliosis. In the scoliotic line, scoliosis first appears at 3-4 weeks and progressively increases in severity and incidence so that 90% of the birds express the lesion by week 10. We have reported previously that cartilage, tendon, and bone collagens from scoliotic birds are more soluble than corresponding collagens from normal birds. Herein, collagen crosslinking and altered proteoglycan metabolism are examined as possible mechanisms for the differences in collagen solubility. At 1 week of age there were fewer reducible crosslinking amino acids (hydroxylysinonorleucine, dihydroxylysinonorleucine, and lysinonorleucine) in collagens from sternal cartilage and tendon in the scoliotic line than in the isogenic line. However, by week 3 and at weeks 5 or 7 values were similar in both groups. The amounts of hydroxypyridinium in vertebral bone and intervertebral disc collagen were also similar in both groups of birds. Consequently, differences in collagen crosslinking do not appear to be a persistent developmental defect underlying the expression of scoliosis in the model. However, differences were observed in cartilage proteoglycans and glycosaminoglycans from the scoliotic line that were not present in cartilage from the isogenic line. The average molecular weight of the uronide-containing glycosaminoglycans was 30% less in the scoliotic line than in the isogenic line, i.e., 12,000 compared to 18,000. The size distribution of cartilage proteoglycans from the scoliotic line also differed from that of proteoglycans from the isogenic line.(ABSTRACT TRUNCATED AT 250 WORDS)     

Statistical evidence for remnants of the primordial code in the acceptor stem of prokaryotic transfer RNA

Summary The specificity of interaction of amino acids with triplets in the acceptor helix stem of tRNA was investigated by means of a statistical analysis of 1400 tRNA sequences. The imprint of a prototypic genetic code at position 3–5 of the acceptor helix was detected, but only for those major amino acids, glycine, alanine, aspartic acid, and valine, that are formed by spark discharges of simple gases in the laboratory. Although remnants of the code at position 3–5 are typical for tRNAs of archaebacteria, eubacteria, and chloroplasts, eukaryotes do not seem to contain this code, and mitochondria take up an intermediary position. A duplication mechanism for the transposition of the original 3–5 code toward its present position in the anticodon stern of tRNA is proposed. From this viewpoint, the mode of evolution of mRNA and functional ribosomes becomes more understandable.Offprint requests to: W. Moller     

Regulation of enzymes and isoenzymes of carbohydrate metabolism in the yeast Saccharomyces cerevisiae

An electrophoretic method has been devised to investigate the changes in the enzymes and isoenzymes of carbohydrate metabolism, upon adding glucose to derepressed yeast cell. (i) Of the glycolytic enzymes tested, enolase II, pyruvate kinase and pyruvate decarboxylase were markedly increased. This increase was accompanied by an overall increase in glycolytic activity and was prevented by cycloheximide, an inhibitor of protein synthesis. (ii) In contrast, respiratory activity decreased after adding glucose. This decrease was clearly shown to be the result of repression of respiratory enzymes. A rapid decrease within a few minutes of adding glucose, by analogy with the so-called ‘Crabtree effect’, was not observed in yeast. (iii) The gluconeogenic enzymes, fructose-1,6-bisphosphatase and malate dehydrogenase, which are inactivated after adding glucose, showed no significant changes in electrophoretic mobilities. Hence, there was no evidence of enzyme modifications, which were postulated as initiating degradation. However, it was possible to investigate cytoplasmic and mitochondrial malate dehydrogenase isoenzymes separately. Synthesis of the mitochondrial isoenzyme was repressed, whereas only cytoplasmic malate hydrogenase was subject to glucose inactivation.