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Biomedical subjects

H Brandt

Publications and source records attributed to H Brandt.

At least 73 records · Page 4Linked to original sources
PubMed1976

Effects of two ionizing groups on the active site of human carbonic anhydrase B.

Investigation of some pH-dependent properties of human erythrocyte carbonic anhydrase B indicate that the active site is influenced by at least two charged groups. The properties studied include the pH dependence of inhibition of native, monocarboxamidomethyl, and monocarboxymethyl enzymes by iodide ion and the pH dependence of the visible spectra of the cobalt derivatives of these enzymes. One ionizing group has a pKa of about 7.3 in the native enzyme, 8.2 in the carboxyamidomethyl enzyme, and 9.0 in the carboxymethyl enzyme. It has a major influence on activity and anion inhibition, and on the visible spectra of the cobalt enzymes. A second group has a pKa of about 6.1 in native and modified enzymes. When zinc is at the active site, the secondary group in its acidic form decreases the Ki for I-. With the carboxyamidomethyl and carboxymethyl enzymes, the Ki decreases by about an order of magnitude. However, if cobalt is substituted for zinc in the modified enzymes, this group does not influence the Ki for I- and the binding of I- does not influence the pKa of the spectral transitions caused by ionization of this secondary group. In the case of nonalkylated Co2+-enzyme, another ionizing group with a pK of about 6.2 prevents the binging of I- at low pH. These results show that the active site is altered when cobalt is substituted for zinc in carbonic anhydrase B.

Binding, Competitive↗
PubMed1976

Evidence for the coordinate control of activity of liver glycogen synthase and phosphorylase by a single protein phosphatase.

Homogeneous rabbit liver phosphorylase phosphatase (Brandt, H., Capulong, Z. L., and Lee, E. Y. C. (1975) J. Biol. Chem. 250, 8038-8044) also dephosphorylates glycogen synthase b. During purification, phosphorylase phosphatase and glycogen synthase phosphatase co-purified with a constant ratio of activities. The two activities co-migrated on disc gel electrophoresis. Both substrates competed with each other for the phosphatase, and both phosphatase activities were inhibited by lysine ethyl ester. It is concluded that liver phosphorylase phosphatase and glycogen synthase phosphatase have a common identity and that coordinate regulation of the phosphatase-catalyzed activation of glycogen synthase and inactivation of phosphorylase occurs in vivo. This provides a parallel and opposing mechanism to that mediated by adenosine 3':5'-monophosphate-dependent protein kinase, which coordinately inactivates glycogen synthase and, via phosphorylase kinase, activates phosphorylase. Maximal glycogen synthase phosphatase activity was observed near neutrality. Mg2+ and glucose-6-P activated the glycogen synthase phosphatase reaction and this activation was pH-dependent. The Km for glycogen synthase b was 0.12 muM.

Animals↗
PubMed1976

[A suggestion for the evaluation of the antepartal cardiotocogram (author's transl)].

An evaluation scale for the antepartal cardiotocogram is suggested which is intentionally based on the Apgar scale. Five criteria were evaluated: three characteristics of the basal fetal heart rate and two characteristic, recognized alterations in heart rate. In regard to the interpretation of the basal heart rate, level, range and number of flat readings per minute are significant for the prognosis. Alterations in heart rate permit a prognostic statement depending on the form and type of the acceleration and deceleration 0-2 points are given for every characteristic so that the index can vary from 0 to 10 points. The condition of the fetus is physiologic when the index is between 8-10, the prognosis is questionable when the index is between 5 and 7 and the condition of the fetus is critical when it is 4 or lower.

Apgar Score↗
PubMed1975

Purification and properties of rabbit liver phosphorylase phosphatase.

A procedure for the purification of rabbit liver phosphorylase phosphatase is described. The specific activity of the preparation is 2,100 units/mg of protein, representing a 25,000-fold purification. During the initial steps of the purification a large activation of enzyme activity was observed. The molecular weight of the purified enzyme was estimated by Sephadex G-75 chromatography to be 35,000, and by sucrose density ultracentrifugation to be 34,000 (2.9 S). On Na dodecyl-SO4 polyacrylamide disc gel electrophoresis a single component with a molecular weight of 34,000 was observed. The pH optimum is 6.9 to 7.4, and the Km for rabbit muscle phosphorylase alpha is 2 muM. The same procedure is also applicable to the extensive purification of phosphorylase phosphatase from rabbit muscle.

Animals↗
PubMed1975

[The effects of elevated calcium concentrations in artificial cerebrospinal fluid on pial arteries during perivascular microperfusion and the Ca++-antagonistic effect of bencyclane (author's transl)].

The influence of artificial cerebrospinal fluid (CSF) containing 6, 9 and 18 mEq/l Ca++, respectively, on 145 pial arteries of nine anesthetized cats was investigated by the perivascular microperfusion technique. The higher the concentration of Ca++ in the perivascular space and the longer these high Ca++ concentrations acted on the vascular wall, the more pronounced were the constrictions of the arteries. If N-[3-(1-benzyl-cycloheptyloxy)-propyl]-N,N-dimethyl-amine (bencyclane-hydrogenfumarate, Fludilat) (10 mg/100 ml) was added to the CSF, dilatations occurred, even if the concentrations of Ca++ were higher than in normal CSF (3 meq/l). The degree of dilatation, however, was dependent on the Ca++ concentration in the CSF. With high Ca++ in the CSF the dilatatory action of bencyclane was inhibited when K+ and H+ in the CSF were kept constant. The reaction can be described as Ca++ antagonism, the possible mechanisms of which are discussed.

Animals↗
PubMed1975

[Blood circulation, oxygen pressure and pH of the cerebral cortex under the influence of bencyclane].

The effect of N-[3-(1-benzyl-cycloheptyl-oxy)-propyl]-N,N-dimethyl-amine (bencyclan-hydrogenfumarate, Fludilat¿ on the cerebral vascular system was studied by means of the following methods: 1. In pigs regional cerebral cortical blood flow was continuously recorded with a heat conduction device, cortical pH with a glass electode in which the flat measuring surface and the reference were close together. Cortical pO2 was recorded with a multiwire platinum electrode. Systemic arterial blood pressure was monitored by means of a Statham transducer. 2. In a second series in cats the perivascular space of small pial arteries or arterioles was perfused with cerebro-spinal fluid (CSF) to which bencyclan had been added. The perfusion was performed by means of micropipettes. Local cortical blood flow increased slightly for some minutes after slow infusion of 1--3 mg/kg bencyclan. Rapid injection caused initially a significant decrease in arterial blood pressure, which was accompanied by a transient decrease in CBF and in cortical pH. After the return of the arterial blood pressure to its initial value, CBF increased. Cortical pO2 and cortical pH returned to initial values. After slow infusion of the substance the pH variation was usually very slight or it was missed completely. Perivascular microperfusion wtih CSF containing bencyclan caused dilatation of those pial sections which were in contact with the drug. High concentration of the drug caused stronger dilatations than did low concentrations. It is concluded that the substance causes dilatations of the cerebral vessels and that this dilatation occurs also during constant perivascular pH.

Animals↗