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Biomedical subjects

F Bergmann

Publications and source records attributed to F Bergmann.

At least 91 records · Page 5Linked to original sources
PubMed1980

On the mechanism of action of 2-amino-4-methylpyridine, a morphine-like analgesic.

2-Amino-4-methylpyridine (2-AMP), when implanted into the ventral lateral thalamus of rats, does not cause stereotyped behavior. On the other hand, when compulsive biting and gnawing was evoked by thalamic implants of morphine (via stimulation of type 1 opiate receptors, which activate a dopaminergic mechanism) or of apomorphine, systemic application of 2-AMP suppressed this response. The anti-gnawing effect of 2-AMP was abolished by naloxone, indicating that the inhibitory action of 2-AMP involves activation of another, viz. type 2 receptor. The antagonistic influence of 2-AMP could also be suppressed by pretreatment of the rats with p-chlorophenylalanine. It is concluded that 2-AMP has only a weak effect on type 1 opiate receptors, linked to a dopaminergic mechanism, but it possesses high affinity to type 2 opiate receptors, which are connected with serotonergic pathways.

Analgesics↗
PubMed1979

Behavior of N-methylated allopurinols and related 4-thioxopyrazolo [3,4-d]pyrimidines towards bovine milk xanthine oxidase.

1. All available N-mono- and N,N'-dimethylallopurinols and the corresponding 4-thioxo derivatives have been tested as substrates or inhibitors of bovine milk xanthine oxidase (xanthine: oxygen oxidoreductase, EC 1.2.3.2). 2. None of the compounds tested revealed any inhibitory activity towards the enzyme. 3. All compounds were resistant to enzymic oxidation, with the exception of 7-methylallopurinol and its 4-thioxo analog. Both these compounds were attacked at position 6. 7-Methylallopurinol was oxidised nearly ten times faster than the isomeric 3-methylhypoxanthine. 4. These observations can be explained by assuming that for attack at C-6, the enzyme must bind both to N-1 and N-2 in the pyrazole ring and causes tautomerisation, which places a double bond at position 5,6 in the pyrimidine ring. This activation process resembles the activation of hypoxanthine.

Allopurinol↗
PubMed1978

Effects of propylbenzilylcholine mustard on injection into the liquor space of cats.

In unanaesthetized cats the effects were examined of propylbenzilylcholine mustard (PrBCM) on injection into the cannulated cerebral ventricles and cisterna magna. Extreme motor excitation, vocalization, shivering leading to fever, tachypnoea, panting, piloerection and salivation were produced on ventricular, vigorous scratching bouts on cisternal, injections. The sites of these actions are discussed. None of the effects was produced by atropine similarly injected. All effects were suppressed by anaesthetizing doses of pentobarbitone sodium injected intraperitoneally.

Animals↗
PubMed1977

Oxidation of hypoxanthines, bearing 8-aryl or 8-pyridyl substituents, by bovine milk xanthine oxidase.

1. Hypoxanthines, bearing at position 8 aryl or pyridyl substituents, are converted by bovine milk xanthine oxidase (xanthine: oxygen oxidoreductase, EC 1.2.3.2) into the corresponding xanthines at low rates. Oxidation is accelerated considerably when the 8-pyridyl substituents are quaternised. 2. In the enzymic oxidation of quaternary 8-pyridylhypoxanthines a lag phase precedes the attainment of a constant, maximal reaction rate. It is assumed that the delay is due to a relatively slow conformational change in the active enzymic center. 3. In 8-(3'-N-methylpyridinio)xanthine betaine, also the pyridinium moiety is attacked at high pH (9-11) to yield an N-methyl-2-pyridone. The analogous pyridone is the only oxidation product of 1-methyl-8-(3'-N-methylpyridinio)-hypoxanthine betaine, which is not attacked in the pyrimidine ring. 4. The cationic substrates are attracted to the enzyme by an anionic group, which probably forms an ion pair with a protonated amino group in or near the active center.

Animals↗
PubMed1977

Enzymic oxidation of 3-hydroxyxanthine to 3-hydroxyuric acid.

1. Bovine milk xanthine oxidase (xanthine:oxygen oxidoreductase, EC 1.2.3.2) oxidises 3-hydroxyxanthine slowly to 3-hydroxyuric acid; the 1-methyl derivative of 3-hydroxyxanthine is attacked about twice as fast. 2. The pH optimum for the reaction of 2-hydroxyxanthine is near 5, i.e. the neutral form of this substrate is attacked much faster than the anion. Probably in the "active" form of the latter, the negative charge is located mainly in the imidazole ring, thus inhibiting nucleophilic attack at C-8.

Animals↗
PubMed1977

Oxidation of methyl derivatives of pteridin-4-one, lumazine and related pteridines by bovine milk xanthine oxidase.

1. Pteridin-4-ones, methylated at nitrogen or carbon, N-methylated lumazines and related oxopteridines were studied as substrates of a highly purified bovine milk xanthine oxidase (xanthine : oxygen oxidoreductase, EC 1.2.3.2). 2. The enzyme can oxidise at high rates both uncharged and anionic substrates. Variation of enzymic activity with pH is mainly due to pH-dependent changes in the active enzymic center. 3. Milk xanthine oxidases at different stages of purification convert pteridin-4-one into the 4,7-dione (compound 13 in this article). 4. Methylation at C-6 in the pyrazine moiety enhances enzymic attack at C-2 in the pyrimidine ring. N-Methylation may increase or reduce rates of oxidation. 5. For oxidation at C-2, the most favorable form of the substrate bears a double bond at C(2) = N(3). Attack at C-7 is enhanced strongly in structures bearing a double bond at C(6) = C(7). 6. In general, pteridines react with xanthine oxidase as non-hydrated molecules. However, oxidation of 8-methyllumazine at C-7 may take place by dehydrogenation of the 7-CHOH group of the covalently hydrated molecule.

Animals↗
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↗