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Biomedical subjects

R Geiger

Publications and source records attributed to R Geiger.

At least 127 records · Page 7Linked to original sources
PubMed1979

Similarity between a kininogenase (kallikrein) from human large intestine and human urinary kallikrein.

A human colon kininogenase (kallikrein) was isolated by gel filtration on Sephacryl S-200 and affinity chromatography on Trasylolbound Sepharose, yielding a material with a specific activity of 1.3 U/mg (substrate: AcPheArgOEt). The molecular weight of the enzyme as estimated by gel filtration is approximately 70 000. After reduction with mercaptoethanol two bands were obtained in dodecyl sulfate eletrophoresis with molecular weights of 27 000 and 70 000. The bimolecular velocity constant for the inhibition by diisopropyl fluorophosphate was determined as 4 l x mol-1 x min-1. The preparation was characterized by immunological and enzymatic methods. Using the radioimmumoassay for human urinary kallikrein cross-reactivity and parallel binding curves were obtained. Kinin liberation from human high Mr-kininogen was totally inhibited by antibodies directed against human urinary kallikrein. Trasylol and diisopropyl fluorophosphate, but not by antibodies directed against human trypsin and plasma kallikrein. The effect on dog blood pressure was comparable to that obtained with human urinary kallikrein. The amino acid composition of human large intestine kallikrein is very similar to that of human urinary kallikrein.

Animals↗
PubMed1978

[Improvement of pathological glucose tolerance by bradykinin in diabetics and in surgical patients (author's transl)].

Intravenous glucose tolerance tests (GTT) were performed in 13 metabolically healthy patients at the first and second day after abdominal surgery. GTT were carried out during an additional infusion of bradykinin (BK) (80 microgram/h) in six of these patients at the first day (group A) and in seven patients at the second day (group B). Furthermore, GTT were performed in six patients with chemical diabetes with and without BK-infusion. In addition, the effect of BK on blood glucose concentration in the postabsorptive state was investigated in nine maturity onset diabetics and in five healthy volunteers. As a control, another nine diabetics received physiological saline. In both groups of surgical patients BK improved glucose tolerance (k-values: group A without BK 1.03 +/- 0.12, with BK 1.31 +/- 0.07; group B without BK 0.85 +/- 0.18, with BK 1.25 +/- 0.21). This was also true in chemical diabetics (without BK 0.81 +/- 0.03, with BK 1.08 +/- 0.04). While BK did not change blood glucose concentration in healthy volunteers, it reduced that of diabetics by 12.2 +/- 1.4% continuously during 100 min. No spontaneous drop of blood glucose was observed in diabetics receiving saline. These results are in good accord with the present view that kinins may play a role within the regulation of carbohydrate metabolism.

Blood Glucose↗
PubMed1978

Human plasma kallikrein: purification, enzyme characterization and quantitative determination in plasma.

Human plasma kallikrein was isolated from a plasma fraction related to Cohn fraction IV4 by affinity- and Sephadex G-150 chromotography yielding a material with 17.3 TAME-U/A280 unit. The preparation was characterized by immunological and enzymatic methods. Complex formation with alpha2-macroglobulin, C1-inactivator and aprotinin was demonstrated by immunoelectrophoresis. The bradykinin release from high-molecular weight kininogen and its inhibition by antibodies to kallikrein, AT III and AT III-heparin complex were measured using a biological test system (rat uterus). Time dependent inactivation of kallikrein by AT III, and AT III-heparin complex was shown by means of a synthetic kallikrein substrate: Bz-Pro-Phe-Arg-pNan. The same substrate was used to measure the activation of prekallikrein in plasma by kaolin and F XII a. Antibodies raised against kallikrein were shown to inhibit the reaction specifically. A quantitative determination of plasma prekallikrein by electroimmunodiffusion according to Laurell was developed: the plasma concentration in normal individuals was found to be 1.8 - 2.2 TAME-U/ml related to kallikrein activity; this corresponds approximately to 9 - 11 mg antigen/100 ml plasma.

Animals↗
PubMed1978

Peptide esters and nitroanilides as substrates for the assay of human urinary kallikrein.

Ac-Phe-ArgOMe is hydrolyzed much faster than are Bz-ArgOEt, Z-ArgOMe, or Ac-Gly-ArgOMe by the kallikrein from human urine. The synthesis of Ac-Phe-ArgOEt is described. Hydrolysis of this substrate can be conveniently monitored by a coupled spectrophotometric procedure. Increase in absorbance is linear with time and proportional to the amount of kallikrein up to a deltaA366 of at least 0.22/10 min. This assay for human urinary kallikrein is 46-fold more sensitive than that based on Bz-ArgOEt and 38-fold more sensitive than that with D-Val-Leu-Arg-p-nitroanilide. A number of other arginine p-nitroanilides are hydrolyzed by this enzyme at still lower rates. The assay of human urinary kallikrein with D-Val-Leu-ArgOEt is about a factor of two less sensitive than the assay with Ac-Phe-ArgOEt. This also holds for Z-TyrONp, which displays a rapid spontaneous hydrolysis. Furthermore, the rate of the enzymic reaction with Z-TyrONp drops off rapidly.

Anilides↗
PubMed1977

B1-3,5-diiodotyrosine insulin: a valid tracer for insulin.

Insulin, specifically substituted at the PheB1 position with 3,5-diiodotyrosine, has been tested in several biological and immunological systems. Immunoreactivity was assessed using antisera specific for different parts of the insulin molecule. Biological activity in vitro was estimated on isolated rat fat cells. In vivo bioactivity (hypoglycaemia) and metabolism (metabolic and urinary clearance rates, half-life, apparent distribution space) were measured by infusion of the material into greyhounds. The results indicated that this B1-labelled insulin preparation was biologically fully active and, unlike randomly labelled preparations of iodoinsulin, was metabolised with kinetics indistinguishable from those of the unlabelled hormone. We suggest that this material is a valid tracer for insulin, fulfilling the criteria of high specific activity and biological identity to the native hormone.

Adipose Tissue↗
PubMed1977

Synthesis and properties of [11-serine]alpha-melanotropin.

[Ser11]alpha-melanotropin has been prepared and its melanotropic activity compared with that of alpha-melanotropin and several known analogues. Full activity does not depend on the positive charge of 11-lysine in alpha-melanotropin but on the hydrophilic character of the amino group or a corresponding residue. A shift, or even more, a loss of such a group decreases the melanotropic activity.

Amino Acid Sequence↗
PubMed1977

Isolation of human urinary kallikrein by affinity chromatography. Determination of human urinary kallikrein, I.

Human urinary kallikrein (EC 3.4.21.8) was purified to electrophoretically homogeneity by gel filtration on Sephadex G-100, followed by affinity chromatography on aprotinin-Sepharose. The molecular weight, estimated by gel filtration, is 64,000 Daltons, by dodecyl sulfate electrophoresis 45,000 Daltons and 29,000 Daltons, and it is microheterogeneous on electrofocusing, yielding isoelectric point values of 3.8, 3.9 and 4.05. The kinetic constants for hydrolysis of BZArgOEt, TosArgOMe, CbzTyrONp, and human HMW-kininogen were determined. Benzamidine and aprotinin are competitive inhibitors of human urinary kallikrein.

Chromatography, Affinity↗
PubMed1977

Chemical and biological properties of porcine secretin and secretin analogues modified in positions 3 and 4.

The synthesis of secretin does not offer fundamental difficulties any longer. The problem of the stability of the hormone seems to be solved from a practical point of view. However, the mechanism of the inactivation of secretin in solution is not yet satisfactorily explained, alpha-beta Rearrangement of the Asp-Gly bond may play a role, but some observations indicate that inactivation is not a straight reaction. Like secretion [Ala-4] secretin shows beta-sympathomimetic activity. The availability of a suitable depot preparation permits physiological studies with secretin and its analogues after subcutaneous administration.

Animals↗