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Biomedical subjects

F Bergmann

Publications and source records attributed to F Bergmann.

At least 109 records · Page 6Linked to original sources
PubMed1977

Influence of 8-substitutes on the oxidation of hypoxanthine and 6-thioxopurine by bovine milk xanthine oxidase.

1. The influence of 8-substituents was studied on the rate of oxidation of hypoxanthine and 6-thioxopurine by bovine milk xanthine oxidase (EC 1.2.3.2). 2. An 8-methyl group does not alter the rate of oxidation of hypoxanthine materially, but an 8-phenyl substituent reduces it markedly. This is ascribed to inhibition of the tautomerisation process, responsible for substrate activation, prior to oxidation. 3. In contrast, the 8-phenyl group in 3-methyl-8-phenylhypoxanthine enhances the rate, presumably by binding to a hydrophobic site near the enzymaic center. 4. An 8-phenyl group in 6-thioxopurine markedly increases the rate of enzymaic oxidation. Probably the aromatic substituent diverts anion formation to the imidazole ring. In contrast, ionisation of 8-methyl-6-thioxopurine involves the pyrimidine moiety, thus rendering enzymic attack at position 2 more difficult.

Animals↗
PubMed1976

Oxidation of N-methyl substituted hypoxanthines, xanthines, purine-6,8-diones and the corresponding 6-thioxo derivatives by bovine milk xanthine oxidase.

1. The oxidation of six series of purines (hypoxanthines, xanthines, purine-6,8-diones and the corresponding 6-thioxo derivatives) by a highly purified bovine milk xanthine oxidase (EC 1.2.3.2) has been studied, using a variety of N-methyl derivatives. 2. N-Methyl substituents can either enhance or reduce enzymic rates. Enhancement is ascribed to blockade of groups which mediate unfavorable modes of binding of substrate to enzyme. Introduction of N-methyl groups can also inhibit enzymic oxidation, either by occluding essential binding groups or by preventing spontaneous or enzyme-induced tautomerisation processes, which create suitable binding sites in the substrates. 3. In all purines which are rapidly attacked by xanthine oxidase, proper attachment to the active center is mediated by the groupings (3) NH, (9) N or (3) N, (9) NH. 4. Reduced rates usually express lowered substrate affinity, which finds its expression in weak competitive inhibition of xanthine oxidation.

Animals↗
PubMed1976

Dual action of morphine and related drugs on compulsive gnawing of rats.

Rats received daily i.p. injections of p-chlorophenylalanine (PCPA) for 3 days, before morphine and related drugs were implanted into the lateral thalamus or injected systemically. PCPA enhanced the stereotyped response to morphine, methadone, and apomorphine, as expressed by compulsive gnawing, but abolished the antagonistic effect of large doses of i.p. morphine. Thus, suppression of gnawing by large doses of systemic morphine and related analgesics may be mediated by a serotoninergic pathway. PCPA also brought to light the ability of pethidine to cause gnawing, which is otherwise suppressed by the strong antagonistic effect of this drug. Morphine and related analgesic drugs exert a dual effect: stimulation of gnawing via a catecholaminergic mechanism and inhibition of gnawing by a serotoninergic mechanism.

Animals↗
PubMed1976

Fractures of the tibia in children.

A total of 102 children, aged 1-15 years, treated for fissures, infractions, and fractures of the tibia were studied to elucidate the influence of age, type of fracture, and mechanism of trauma upon the course of union. In addition, an assessment was made of the possibilities the child has of correcting deformities of the diaphysis during continued growth. Eight-five of the children were followed up clinically and radiologically. The time taken for union to occur increased with increasing age. The "high energy" injuries were found to be more apt to cause transverse and comminuted fractures, with injury to the skin, than the "low energy" fractures. At the time of union, 25 patients had angular deformities. The mean correction of this deformity up to the time of follow-up was only 10 per cent. The tendency to correct the deformity ceased 18 months after the accident, and was independent of the child's age at the time of the accident.

Adolescent↗
PubMed1976

[Surgery for chronic non neoplastic diseases of the pancreas (author's transl)].

The authors analyze the surgical indications and procedures for cases of chronic pancreatites. There were but few cases and the procedures were chosen for minimal harm ; there were : 4 external marsupialisations, 1 resection of a true cyst, 5 cystoanastomoses, 2 biliary bypasses, 4 left pancreatectomies. Postoperative courses were normal in 12 patients; 2 had recurrent pancreatitis because of alcoholism. Our attitude towards chronic pancreatic lesions is thus as follows: 1. Cautions and reserved indications. 2. Ad minima procedures.

Adult↗
PubMed1974

Compulsive gnawing in rats after implantation of drugs into the ventral thalamus. A contribution to the mechanism of morphine action.

1 Implantation of morphine into various parts of the corpus striatum of rats evokes only weak gnawing responses.2 Deposition of apomorphine, morphine or methadone in the region of the nucleus ventralis thalami produces a biphasic response, i.e. general excitation, followed by a period of intense gnawing.3 The effect of both apomorphine and morphine is blocked by chlorpromazine, haloperidol and pimozide. However, pretreatment with alpha-methyltyrosine methyl ester or alpha-methyldopa prevents only the gnawing response to morphine, but not to apomorphine.4 Systemic nalorphine, morphine or pethidine suppress the gnawing response, evoked by thalamic implants of apomorphine or morphine.5 Systemic amphetamine potentiates the effect of thalamic deposits of morphine.6 Compulsive gnawing, following implantation of morphine into the ventral region of the thalamus, probably results from enhanced production and release of catecholamines.

Amphetamine↗