Biomedical subjects
Publications and source records attributed to P Friberger.
A chromogenic peptide substrate H-D-Val-Leu-Arg-pNA (S-2266) has been used for the determination of glandular kallikrein derived from pancreas, urine and saliva. The conditions used have been optimized. The methods developed are simple and shown to have good reproducibility.
The mechanism of the prolonged effect of dextran on the duration of local anaesthesia has been studied. Using radio-active mepivacaine it was found that dextran prolonged the duration of infiltration anaesthesia in guinea-pigs by delaying the absorption of the local anaesthetic agent. Experiments in vitro indicate that molecular complexes between the local anaesthetic and dextran may be formed and it is assumed that the delayed absorption might be due to the formation of such molecular complexes. This hypothesis was strengthened by experiments in which dental infiltration anaesthesias were performed in healthy volunteers.
Chromogenic peptide substrates for serine proteases have been designed by using two approaches: (1) by using the natural substrate as a model and (2) by structure-activity correlations obtained through screening of a large number of tripeptides. Some recent examples, substrates for kallikreins and urokinase are given.
New chromogenic tripeptide substrates have been used for the determination of kallikreins and urokinase. The conditions have been optimized. It is possible to determine prekallikrein in plasma after activation with Cephotest. No significant loss in activity caused by plasma kallikrein inhibitors is observed at the dilutions used.
The factor Xa-sensitive substrate BZ-Ile-Glu-Gly-Arg-p-nitroanilide has been made more sensitive by making ester and amide derivatives of the gamma-carboxyl group of the glutamyl residue. The morpholinyl and piperidyl amides react 2.5 times more rapidly with factor Xa.
The chromogenic substrate S-2251 (H-D-Val-Leu-Lys-pNA), a selective and sensitive substrate for plasmin activity, has made it possible to develop simple and reproducible methods for the determination of antiplasmin and plasminogen in human plasma. These methods have been optimized and studied in detail and found to be very specific for the respective factors.
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A method for determination of antiplasmin activity is presented. Plasmin and plasma are incubated, and the remaining plasmin activity is measured spectrophotometrically by means of the plasmin specific tripeptide substrate H-d-Val-l-Leu-l-Lys-p-nitroanilide. The method is simple, rapid and easily automatized. By the immunoadsorption technique, and with the aid of purified substances it is shown that the measured activity is mainly due to a new antiplasmin [2,4] and possibly to some extent to alpha1-antitrypsin and C1-esterase inhibitor have no antiplasmin activity in the method. Heparin and epsilonaminocaproic acid interfered with the assay.
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The relationship between pH and fluoride uptake in intact enamel of permanent premolars was investigated by using: (1) a sodium fluoride dentifrice, (2) a potassium fluoride + manganese chloride dentifrice, and (3) a sodium fluoride solution of the same fluoride concentration. The first part of this paper deals with the in vitro uptake of fluoride from dentifrice slurries and from sodium fluoride solutions of different pH ranging from 7.1 to 4.5. This investigation showed that there was no significant difference between the agents but that the effect of the pH was significant. The uptake of fluoride in the form of fluorapatite was more than five times larger at the lower pH level. The second part of the paper deals with the rate of fluoride uptake (increase in fluoride content) from dentifrices in the same pH range. It was shown that the three agents gave the same initial rate of fluoride uptake (about 50 parts/10(6)/min) at pH 6 and that the rate of fluoride uptake in the outer layer of the enamel was proportional to the hydrogen ion activity.
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