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Biomedical subjects

H Betz

Publications and source records attributed to H Betz.

At least 271 records · Page 15Linked to original sources
PubMed1981

Choline acetyltransferase activity in chick retina cultures: effect of membrane depolarizing agents.

The activity of choline acetyltransferase (CAT) was investigated in primary cultures of retina from 8-day-old chick embryos. After the second day in culture, the total and specific activities of the enzyme decreased by more than 50%. Cultivation of the cells in 56 mM K+ or 59 microgram/ml of veratrine retarded the loss of CAT activity up to days 3-5 in vitro. If the addition of 56 mM K+ or 59 microgram/ml of veratrine was delayed until the third day of culture, these agents had no effect on the remaining CAT activity. These results suggest that the survival in culture of a part of the cholinergic retinal neurons requires membrane depolarization.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1981

Spontaneous pneumatocele during radiation of a giant meningosarcoma.

A man, aged 66 years, sustained a pneumatocele after radiotherapy for a frontabasal meningeal sarcoma. There was improvement initially, but a fall was experienced without injury to the head and the condition worsened. X-rays of the skull revealed a pneumatocele which was treated conservatively and disappeared within 4 weeks. The literature on spontaneous pneumatocele is reviewed briefly and the etiology discussed.

Aged↗
PubMed1981

Characterization of the alpha-bungarotoxin receptor in chick-embryo retina.

Primary cultures and membranes fractions from chick embryo retina bind iodinated alpha-bungarotoxin, a highly selective ligand for nicotinic acetylcholine receptors from skeletal muscle and fish electric organ. The binding is saturable with an equilibrium dissociation constant (Kd) of 0.75 +/- 0.09 nM. The pseudo-first-order rate constant (k+1) for binding at 37 degrees C is 1.76 +/- 10(5) M-1 s-1, the dissociation rate constant (k-1) at 37 degrees C is 1.15 x 10(-4) s-1. Nicotinic cholinergic ligands and local anaesthetics inhibit alpha-bungarotoxin binding. In the case of carbamoylcholine, the inhibition of binding depends on the time of exposure to this cholinergic agonist. alpha-Bungarotoxin has no effect on the carbamoylcholine-induced stimulation in sodium permeability of cultured retinal neurons. On sucrose density gradients containing Triton X-100, the toxin binding site sediments with an apparent sedimentation coefficient of 10.5-11 S. Detergent-solubilized alpha-bungarotoxin receptor cross reacts with antisera raised against nicotinic acetylcholine receptors from Torpedo marmorata. These results are interpreted as indicating that alpha-bungarotoxin binds to retinal nicotinic acetylcholine receptors without affecting cholinergic receptor function.

Animals↗
PubMed1980

Evolution of cholinergic proteins in developing slow and fast skeletal muscles in chick embryo.

1. The cholinergic differentiation of two phenotypically muscles of the chick, the slow multiply innervated anterior latissimus dorsi (a.l.d.) and the fast focally innervated posterior latissimus dorsi (p.l.d.), was investigated during embryonic life and after hatching using both autoradiographical and biochemical methods. 2. The contents in total protein and in acetylcholinesterase activity follow similar development patterns in both muscles, but, after the 15th day in ovo, the accumulation of choline acetyltransferase activity and of acetylcholine nicotinic receptor sites as determined by alpha-bungarotoxin binding occurs at a faster rate in a.l.d. than in p.l.d. 3. In muscle of the p.l.d., a rapid increase of the total number of acetylcholine receptor clusters takes place after the 11th day of embryonic life although some clusters could be observed on myofibres as soon as the 4th day in ovo. 4. The rate of degradation of cholinergic receptor sites in chick muscle is constant around 28 hr up to the 10th day after hatching; thus the different rates of accumulation of acetylcholine receptor in a.l.d. and p.l.d., respectively, after the 15th day of embryonic life must be due to different rates of receptor synthesis. 5. The role of muscle activity in the biochemical differentiation of the developing motor end-plate was investigated in chick embryos which had been paralysed by repeated injections into the yolk sac of a curare-like agent, Flaxedil (May & Baker). 6. The total content in acetylcholinesterase of both a.l.d. and p.l.d. muscles is not significantly modified by paralysis. However, the histochemical staining of end-plates for acetylcholinesterase as well as the heavy form of this enzyme (19 . 5 S) are consistently reduced after Flaxedil injection. 7. In muscles from Flaxedil-treated embryos, the total content in acetylcholine receptor sites as determined by alpha-bungarotoxin binding is higher than in those from control embryos, whereas the rate of degradation of these sites is not significantly altered. 8. The localization of the acetylcholine receptors under the motor nerve terminals is not prevented by blocking muscle activity at the postsynaptic level. Clusters of receptor are still present, and there is no significant change in the number and distribution of these clusters along the myofibres of a.l.d. and p.l.d. muscles. 9. These results are discussed with respect to motor end-plate formation in multiply and focally innervated embryo muscles, and in relation to the control of cholinergic proteins distribution and synthesis by muscle activity.

Acetylcholine↗
PubMed1978

[Effects of chronic paralysis of chick embryo by flaxedil on the development of the neuromuscular junction].

Chronic paralysis of Chick embryos by the cholinergic antagonist flaxedil blocks the subsynaptic accumulation of acetylcholinesterase but not the formation of acetylcholine receptor cluster. Flaxedil paralysis also causes an increase of the total muscle content of acetylcholine receptor without altering the half-life of the receptor protein. The spontaneous activity of the embryon therefore "shuts off" the synthesis of extrasynpatic acetylcholine receptor.

Acetylcholinesterase↗
PubMed1977

Protein degradation during the differentiation of eukaryotic cells: studies on the sporulation of Saccharomyces cerevisiae and on the formation of the neuromuscular junction in the chick embryo.

The role of protein degradation in cell and tissue differentiation has been investigated during the sporulation of Saccharomyces cerevisiae and during endplate formation in developing avian muscle. The results suggest that a variety of proteolytic processes as enzyme inactivation, degradation of mitochondrial membrane constituents and removal of embryonic cell surface proteins exert stringent controls over the sequence of differentiation in eukaryotic cells.

Animals↗
PubMed1976

Protein degradation during yeast sporulation. Enzyme and cytochrome patterns.

The levels of several enzymes have been studied during sporulation of Saccharomyces cerevisia. The specific activities of ribonuclease and aminopeptidase I raised several-fold after transfer of the cells to sporulation medium, whereas the specific activities of phosphofructokinase, glucose-6-phosphate dehydrogenase, tryptophan synthase and pyruvate decarboxylase were not significantly altered. The specific activities of NAD-dependent glutamate dehydrogenase, isocitrate lyase, malate dehydrogenase and fructose bisphosphatase all decreased from the onset of sporulation. The inactivation of these latter enzymes was inhibited by cycloheximide and by inhibitors of energy metabolism. Hexokinase, alcohol dehydrogenase and glutamate oxaloacetate transaminase were partially lost from the cells during the period of ascus maturation. None of the enzyme changes observed proved to be 'sporulation-specific' in that it occurred exclusively in sporulating diploid yeast cells. Therefore it is postulated that the meiotic events and the metabolic changes required for ascospore formation are under separate genetic control in this organism. During sporulation, the cellular content of cytochromes b, c, and aa3 was reduced to 20% or less of that present in vegetative derepressed cells. Since the relative percentage of total to cycloheximide-insensitive mitochondrial protein synthesis was not significantly altered throughout sporulation, and the pattern of mitochondrially synthesized polypeptides was rather similar both in vegetative and in sporulating cells, it appeared that not only degradation but also synthesis and therefore turnover of the mitochondrially coded polypeptides of cytochromes b and aa3 took place during sporulation. The activity ratio of cytochrome c oxidase to F1-ATPase in submitochondrial particles isolated from vegetative cells and from purified asci was almost identical. This indicates that the loss of membrane-bound mitochondrial cytochromes during sporulation is probably due to a nonselective degradation of inner mitochondrial membrane proteins.

Aminopeptidases↗
PubMed1976

Protein degradation and proteinases during yeast sporulation.

During ascospore formation in Saccharomyces cerevisiae, at least 60-70% of the pre-existing vegetative protein was broken down at a rather constant rate until the time mature asci appeared. Under the same conditions in a non-sporulating haploid derived from the same strain the rate of protein degradation, although initially comparable to that of sporulating cells, decreased much more rapidly. Proteins synthesized at different times during sporulation had approximately the same degradation rates as the vegetative proteins. Similar rates of degradation were observed for the vegetative proteins in all fractions obtained from cell homogenates by differential centrifugation. Protein breakdown after transfer to sporulation medium was blocked by uncouplers and inhibitors of energy metabolism, and was partially inhibited by cycloheximide. Polyacrylamide gel electrophoresis, in the presence of sodium dodecylsulfate, of the proteins extracted from vegetative cells and from isolated asci and ascospores revealed that ascus formation was accompanied by a shift of the cellular proteins to a lower molecular weight. From several proteinase inhibitors tested, only tosyl-p-lysine chloromethylketone slightly reduced the rate of ascus formation. During sporulation the total activity of proteinase A increased more than twofold with a maximum at 18 h after transfer to sporulation medium. Total proteinase B activity showed a striking increase in the first hours after transfer to sporulation medium and after that remained constant throughout sporulation. The levels of carboxypeptidase Y and of the proteinase B inhibitor were not significantly altered during sporulation. The proteinases and the proteinase B inhibitor were present within the mature ascospore. The proteinases from both vegetative and sporulating cells were eluted with the same ionic strength from DEAE-Sephadex, and they were undistinguishable in their sensitivity to different proteinase inhibitors. No additional proteolytic activities could be detected in sporulating cells using 3H-labelled denatured yeast protein as a substrate.

Carboxypeptidases↗
PubMed1976

[Congenital skull changes in Recklinghausen's neurofibromatosis].

Congenital skull changes in neurofibromatosis are uncommon. Maybe for this reason, they are often misinterpreted, consequently resulting in expensive examinations and unnecessary treatments. However, if correctly evaluated, the corresponding radiological findings represent characteristic and pathognomonic signs of the disease. Three cases of neurofibromatosis are reported, the symptoms presented in detail and the pertinent differential diagnosis discussed.

Adolescent↗
PubMed1975

Levels and turnover of the proteinase B inhibitors in yeast.

The ratio of the proteinase B inhibitors IB1 and IB2 from baker's yeast was shown to depend on the yeast strain by specific immunoprecipitation from boiled yeast extract and subsequent electrophoresis of the heat-dissociated precipitates on polyacrylamide gels. Bothe IB1 and IB2 were found, IB2 being by far predominant. Saccharomyces carlsbergensis NCYC 74 contained IB1, whereas in Saccharomyces cerevisiae X 2180 only IB2 was present. When cells of the latter strain were labelled with [14C] leucine from the beginning of growth and pulsed with [3H] leucine during the stationary phase, no short-lived IB1 could be detected. However, the peak of IB2 resolved on the gel showed an increased 3H/14C ratio in comparison to the majority of the other cellular proteins. The increased 3H/14C ratio was found to be the result of catabolite repression of inhibitor synthesis during exponential growth: cells growing on glucose as carbon source contain high inhibitor levels only during the stationary phase of growth, whereas during growth on acetate high amounts of inhibitor are present even in exponentially growing cells. During the stationary phase of growth the inhibitor is degraded with the same half-life as the total cellular proteins (about 50 h).

Fungal Proteins↗