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Biomedical subjects

H Holzer

Publications and source records attributed to H Holzer.

At least 163 records · Page 9Linked to original sources
PubMed1977

Effects of glucose and nitrogen source on the levels of proteinases, peptidases, and proteinase inhibitors in yeast.

In Saccharomyces cerevisiae harvested from early exponential growth on glucose-containing media, the specifc activities of proteinases A and B, carboxypeptidase Y, and the inhibitors IA, IB, IC of these three proteinases, respectively, are found to be 10-30% of the specific activities observed in media without glucose, containing acetate as a carbon source; the activities of two aminopeptidases in glucose-grown cells were 30-50% of those in acetate-grown cells. In contrast to fructose-biphosphatase, phosoenolpyruvate carboxykinase, and cytoplasmic malate dehydrogenase, which are inactivated after the addition of glucose to derepressed cells, the proteinases and inhibitors are not inactivated after glucose addition, but appear to be repressed. Growth of the yeast on poor nitrogen sources or starvation for nitrogen results in 2-3 fold increases in the levels of most proteinases and peptidases, but this effect is not observed with glucose as the carbon source.

Acetates↗
PubMed1977

Characteristics and functions of proteinase A and its inhibitors in yeast.

A purification and some properties of proteinase A from yeast are described. A specific macromolecular inhibitor of proteinase A from yeast cytosol has been isolated and shown to be a protein (molecular weight 7,700) consisting of a majority of polar amino acids. Proline, arginine, cysteine and tryptophan were not detected in the inhibitor. Possible biological functions of proteinase A and the proteinase A-inhibitor (and of other yeast proteinases and their inhibitors) in the following processes are discussed: general protein turnover, catabolite inactivation of enzymes, enzyme degradation at starvation and at transition to spore formation, and activation of pre-enzymes and precursor proteins by limited proteolysis.

Amino Acids↗
PubMed1976

Studies on the proteinase-A inhibitor I3A from yeast.

The purification and some properties of the two inhibitors I2A and I3A of proteinase A from yeast have previously been described [Saheki et al, (1974) Eur. J. Biochem. 47, 325]. An improved method for the preparation of I3A which is less time-consuming and leads to higher yields is presented. Based on amino acid analysis, I3A contains 68 amino acids per molecule. The molecular weight was 7676. The inhibitor contained no proline, no arginine, no cysteine and no tryptophan, but did contain a large number of the polar amino acids glutamate + glutamine, aspartate + asparagine and lysine. Neither by dansylation nor by Edman degradation could an N-terminal amino acid be detected. Changes in the circular dichroism upon transition from pH 6.9 to 3.0 suggest different tertiary structures at these pH values. Experiments on the kinetics of inhibition of proteinase A revealed an apparent Ki value of 5.5 X 10(-8) M for I3A and 1.6 X 10(-8) M for pepstatin. A "non-stoichiometric inhibition" of a "pseudo-irreversible" type is concluded from the kinetic data. A hydrophobic type of binding of I3A to yeast proteinase A is suggested from experiments demonstrating a large decrease in the percentage of inhibition caused by addition of 2 M urea, 2 M guanidine hydrochloride, 0.125% Triton or 0.125% cholic acid.

Amino Acids↗
PubMed1976

Inactivation of yeast enzymes by proteinase A and B and carboxypeptidase Y from yeast.

Changes in the activities of 15 different enzymes during incubation of a crude yeast extract with the purified yeast proteinases A and B, and carboxypeptidase Y, respectively, have been measured. The spectrum of action of the three proteinases on the enzymes measured differs significantly, increasing or decreasing their activities or having no effect. Incubation of purified cytoplasmic malate dehydrogenase or purified mitochondrial malate dehydrogenase with proteinases A and B results in selective inactivation of the cytoplasmic enzyme, whereas the mitochondrial activity is not affected. Carboxypeptidase Y has no effect on the activity of either dehydrogenase. The results support the idea of selective proteolysis as the mechanism of the earlier observed inactivation of cytoplasmic malate dehydrogenase, initiated by the addition of glucose to intact yeast cells grown on acetate as carbon source ("glucose effect").

Carboxypeptidases↗
PubMed1976

Effects of yeast proteinase A, proteinase B and carboxypeptidase Y on yeast phosphofructokinase.

Incubation of a crude yeast extract containing phosphofructokinase with proteinase A, proteinase B or carboxypeptidase Y gave the following results: Proteinase B and carboxypeptidase Y did not change the activity of phosphofructokinase during incubation. On the other hand, incubation with proteinase A resulted in a 40-100% activation; continued incubation, however, led to an inactivation of the enzyme. Addition of allosteric effectors did not change the activation or inactivation process. The activated phosphofructokinase was not changed with respect to pH optimum and ATP inhibition. Molecular weight determination of phosphofructokinase in crude extracts in the presence of inhibitors of proteinase A indicated a molecular weight of 700000. Without inhibitors of proteinase A, the molecular weight was determined to be 600 000, while after 40-100% activation by proteinase A, a molecular weight of 500 000 was obtained. The activity profile of proteinase A in density gradients indicated that this enzyme is bound to variety of cellular proteins.

Adenosine Triphosphate↗
PubMed1976

[Hemofiltration in the treatment of generalized edema].

9 fluid overloaded patients, 8 of them with congestive heart failure and 1 patient with acute renal failure, were treated by ultrafiltration without hemodialysis. Using Gambro-major- and Rhone-Poulenc-6-dialysers the patients were deprived of 6,907.14+/-3,586.13 ml or 652.83 ml/h of extracellular fluid, on an average. During the withdrawal of fluid the plasma volume and central venous pressure decreased, whereas the cardiac output slightly increased. After the ultrafiltration, which did not show any undesirable side effects, the patients could be held in a compensative state by conservative therapy (digitalis and diuretics).

Aged↗
PubMed1976

[Hemodynamic long-term effects of a beta-receptor blockader (Pindolol) in primary essential hypertension].

1. Pindolol lowers blood pressure both, immediately after administration by a reduction of cardiac output and heart rate and after long-term administration by reducing peripheral resistance. Cardiac index, initially decreased, reached the control value after 8 weeks of treatment. 2. The persistent reduction in heart rate and increase of the cardiac index during exercise after prolonged treatment together with the increase of right and left heart filling pressures seems to be due to augmentation of the Starling mechanism. The increase of the stroke volume at rest and during exercise diminished the blood-pressure lowering effect of the drug. 4. The exercise-induced increase of noradrenalin was abolished by acute administration of pindolol. After long-term treatment, however, we found a consistent and significant elevation of the plasma-catecholamines. This may reflect the development of heart failure [1], a tyramin- or cocain-like action of pindolol [2] or an indirect sympathicomimetic effect of this drug at low doses (10--15 mg/day orally ) [3]. 5. The elevation of plasma-noradrenalin reflects increased sympathetic tone and may be responsible for the increase in stroke volume and plasma renin activity observed by several authors. 6. Since there was no evidence for a hemodynamic mode of action, the lowering of blood rpessure by pindolol may be a central effect.

Blood Pressure↗
PubMed1976

[Serum levels of LH and FSH in patients with adreno-genital syndrome (AGS) (author's transl)].

Serum levels of LH, FSH, testosterone and 17beta-estradiol were estimated by radioimmunoassay in 13 children suffering from AGS. Hormone levels were determined during and after substitution therapy and were compared with values registered in normal subjects. After therapy was stopped a statistically significant rise of testosterone and 17beta-estradiol was observed, but no changes in the serum levels of LH and FSH was noted. The discrepancies between the two observations are discussed.

Adrenal Hyperplasia, Congenital↗
PubMed1976

[Plasma aldosterone in childhood].

According to a radioimmunological method modified in our laboratory we determined plasma aldosterone levels under standardized conditions in children of different age from 2 weeks to 14 years, in women undergoing uncomplicated vaginal delivery, and in the cord blood of the corresponding newborn babies. Furthermore, the effect of different stimulating factors (ACTH, salt restriction, severe vomiting, fever) in children was studied. In mothers and cord blood we found 68.6 +/- 39.3 ng/100 ml and 75.5 +/- 37.4 ng/100 ml, respectively. In the first two years of life there is a decrease in plasma aldosterone levels to the relatively constant concentration at the age of 2 to 14 years (7.3 +/- 4.7 ng/100 ml). The age groups 2 weeks to 1 year, 1 to 2 years and 2 to 14 years all show significant differences. A correlation of age (first two years of life) and plasma aldosterone level could be shown (correlation coefficient -0.50 according to Pearson). The stimulation results are comparable with literature data concerning adults. The mechanism of stimulation by vomiting and fever is discussed.

Adolescent↗
PubMed1975

[The clinical value of the cortisol secretion rate determination in paediatric endocrinology (author's transl)].

The cortisol secretion rate was determined in 18 children according to a modified and simplified method. In 7 cases the determination was repeated after stimulation with synthetic ACTH. 12 of these children suffered from diseases which may affect glucocorticoidsteroid production and the remaining 6 children served as normal controls. In some cases the plasma 11-hydrocorticoid level and urinary excretion of 17-ketogenic steroids were additionally determined. Differences in adrenal function were noted in 2 patients with congenital adrenal hyperplasia (one of the salt-losing type, the other nonsalt-losing type) and 5 patients with adrenal insufficiency. A normal cortisol secretion rate was found in 3 children with diverse disturbances of carbohydrate metabolism, as well as in a child with subtotal adrenalectomy. The clinical value of the determination of the cortisol secretion rate is discussed and was found to be a more reliable indicator of glucocorticoid activity than other parameters.

11-Hydroxycorticosteroids↗
PubMed1975

Proteolytic activities in yeast.

Studies on the mechanism and time course of the activation of proteinases A (EC 3.4.23.8), B (EC 3.4.22.9) and C (EC 3.4.12.--) in crude yeast extracts at pH 5.1 and 25 degrees C showed that the increase in proteinase B activity is paralleled with the disappearance of proteinase B inhibitor. Addition of purified proteinase A to fresh crude extracts accelerates the inactivation of the proteinase B inhibitor and the appearance of maximal activities of proteinases B and C. The decrease of proteinase B inhibitor activity and the increase of proteinase B activity are markedly retarded by the addition of pepstatin. Because 10-minus 7 M pepstatin completely inhibits proteinase A without affecting proteinase B activity, this is another indication for the role of proteinase A during the activation of proteinase B. Whereas extracts of yeast grown on minimal medium reached maximal activation of proteinases B and C after 20 h of incubation at pH 5.1 and 25 degrees C, extracts of yeast grown on complete medium had to be incubated for about 100 h. In the latter case, the addition of proteinas A results in maximal activation of proteinases B and C and disappearance of proteinase B inhibitor activity only after 10--20 h of incubation. With the optimal conditions, the maximal activities of proteinases A, B and C, as well as of the proteinase B inhibitor, were determined in crude extracts of yeast that had been grown batchwise for different lengths of time either on minimal or on complete medium. Upon incubation, all three proteinases were activated by several times their initial activity. This reflects the existence of proteolytically degradable inhibitors of the three proteinases and together with the above mentioned observations it demonstrates that the "activation" of yeast proteinases A, B and C upon incubation results from the proteolytic digestion of inhibitors rather than from activation of inactive zymogens by limited proteolysis.

Culture Media↗