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Biomedical subjects

C Simon

Publications and source records attributed to C Simon.

At least 343 records · Page 19Linked to original sources
PubMed1979

Effect of antimitotic drugs on tubulin GTPase activity and self-assembly.

Microtubule inhibitors can be classified into two categories: 1) those which inhibit the polymerization-dependent GTPase activity of phosphocellulose-purified tubulin, but induce a significant polymerization-independent GTPase activity (e.g. colchicine, griseofulvine, daunorubicine); 2) those which inhibit the GTPase activity associated with tubulin polymerization and that induced by inhibitors of the first class (e.g. the vincaalkaloids and podophyllotoxin). The colchicine-stimulated GTPase activity of tubulin appears to be due to the tubulin.colchicine complex. This suggests that colchicine inhibits tubulin assembly by binding to a tubulin-tubulin interaction site required for the polymerization-dependent GTPase activity and induces by itself a tubulin conformational change that leads to polymerization-independent GTPase activity. Stoichiometry of inhibition by vinblastine of the colchicine-stimulated GTPase activity is 1:2. On the other hand, the inhibition by vinblastine of the tubulin self-assembly and of the polymerization-dependent GTPase activity is strongly substoichiometric at the beginning of the polymerization reaction, 1 vinblastine molecule inhibiting the ability of 10 tubulin dimers to polymerize and to hydrolyze the GTP. However, at the polymerization plateau, the inhibition effect by vinblastine appears to be lower, suggesting a selective action of vinblastine on the early stages of the polymerization reaction.

Animals↗
PubMed1979

[Assay of cefaclor in serum and urine (including stability test) using high pressure liquid chromatography (author's transl)].

Using high pressure liquid chromatography (reverse phase method) a study was made of the stability of cefaclor dissolved in sodium citrate buffer, normal serum and urine and stored for different periods of time at 4 degrees C and 37 degrees C. In sodium citrate buffer (pH 4.0) and in urine (pH 6.0) no appreciable loss of activity of cefaclor occurred at either 4 degrees C or 37 degrees C, even after longer periods of storage (up to 24 h). Serum containing cefaclor stored at 37 degrees C lost about 4% of the active cefaclor after 30 min, 13% after 1 h and 20% after 2 h; no cefaclor could be detected after 24 h. The loss was lower during storage of serum containing cefaclor at 4 degrees C, and after 24 h 60% of the initial concentration of active cefaclor was found. Using a lichrosorb-NH2 column, it could be demonstrated that after 24 h storage of serum containing cefaclor, only phenylglycine, but not amino-chloro-cephem-carboxylic acid or cefaclor was present. After oral administration of 1 g cefaclor, cefaclor was present in the serum and urine of adult volunteers and only small amounts of phenylglycine and amino-chloro-cephem-carboxylic acid.

Adult↗
PubMed1979

The follicular iodide pool as a two-compartment system: evidence from the unstimulated thyroid gland.

The isotopic equilibrium method was used for a 60-day period to follow iodine turnover in control and hypophysectomized rats. After the suppression of TSH by hypophysectomy, only the captured iodide is used for iodination of thyroglobulin, the iodide recycling being abolished. In unstimulated gland, two metabolically distinct iodide compartments do exist which differ either in their chemical form or in their morphological distribution, or both.

Animals↗
PubMed1979

[Possible indications for recently developed antibiotics [author's transl)].

Properties and possible indications of recently developed antibiotics are described. For the treatment of pseudomonas aeruginosa infections of all penicillins azlocillin is the most favourable drug (instead of carbenicillin), for treatment of esch. coli infections it is mezlocillin (instead of ampicillin). Becampicillin and equally amoxycillin are more than ampicillin suitable for oral application (because of almost complete absorption). Cefaclor has a broader spectrum and stronger activity than cefalexin and will replace cefalexin in future. Sisomicin is similar to gentamicin and has no essential advantages. Netilmicin seems to be less oto-and nephrotoxic than gentamicin and may be used with less risk of side-effects in patients with renal insufficiency. Amikacin is reserved for infections by gentamicin-resistant bacteria.

Amikacin↗
PubMed1979

[Reference values of lipid metabolism in childhood (author's transl)].

Sera of 949 children were analyzed for cholesterol and triglycerides by enzymatic methods and for lipoprotein pattern by electrophoresis. For the first time all ages were examined. Two independent collectives were compared: healthy pupils and sick children without disturbances of lipid metabolism. The values of these groups showed no significant difference. In infancy cholesterol and triglycerides levels heavily depend on age, while later in childhood values change little. Highest reference values are 6.36 mmol/l (= 246 mg/dl) for cholesterol and 1.74 mmol/l (= 154 mg/dl) for triglycerides.

Adolescent↗
PubMed1979

Serum and sputum levels of cefaclor.

In a cross-over study, 10 healthy adult volunteers received 1 g cefaclor and 1 g cephalexin orally 1 hour after a standard breakfast. Serum levels of cefaclor rose somewhat faster and were higher than those of cephalexin in the first 60 minutes. At the end of the second hour the serum concentration of cephalexin was 50--100% higher. The area under the serum level curve averaged 45 hr-micrograms/ml for cefaclor and 60 hr-micrograms/ml for cephalexin. Calculated pharmacokinetic constants indicate that the absorption rate of cefaclor was nearly the same as that of cephalexin. The serum half-life of cefaclor was 1 hr. The urine recovery of cefaclor for 9 hours averaged 65%, whereas cephalexin resulted in a urine recovery of 85%. To evaluate sputum levels, 15 adult patients with bronchial carcinoma and secondary bronchitis or pneumonia were treated with 0.5 g of cefaclor orally 4 times daily. The mean individual sputum levels were 0.44 micrograms/ml (after the first dose) and 0.54 micrograms/ml (after repeated administration). In 10 other patients, after a single 1 g dose of cefaclor mean sputum levels after 1 hour and 3 hours doubled, whereas peak concentrations in sputum after 2 hours did not differ significantly. These results suggest that cefaclor will be useful in respiratory tract infections caused by sensitive bacteria.

Adult↗
PubMed1979

[Studies on the competition of several antibiotics for binding sites to serum protein (author's transl)].

Protein binding of benzylpenicillin, acidocillin, ampicillin, oxacillin, tetracycline and clindamycin was determined in vitro by equilibrium dialysis with and without combination. Concentrations of labelled drugs were measured by scintigraphy, of non-labelled drugs by agar diffusion technique using a test strain resistant against the second antibiotic of the combination. Percentage of protein binding of the different penicillins decreased somewhat in higher concentrations, whereas with tetracycline there was found a significant increase of protein binding in higher concentrations. There was no inhibition of protein binding when combining two penicillins or tetracycline with clindamycin at lower concentrations. If very high concentrations of oxacillin of flucloxacillin were used in combination with benzylpenicillin protein binding of benzylpenicillin was reduced by about 20%.

Anti-Bacterial Agents↗
PubMed1978

[Cefuroxim, a new beta-lactamase stable cephalosporin].

In vitro activity of cefuroxime, a new cephalosporin stable to bacterial beta-lactamases, was compared with that of cefalothin and other cephalosporins by serial dilution test in more than 600 bacterial strains. Cefuroxime was more active than cefalothin on most strains of Gram negative bacilli (except Salmonella species) and also on most strains of cefalothin-resistant bacteria. In comparison to cefalothin, cefoxitin and cefamandol, cefuroxime exerted the strongest activity on meningococci, streptococci of group A and B and also on Citrobacter freundii. It was as active as cefamandol and more active than cefalothin and cefoxitin on Haemophilus influenzae (also in ampicillin-resistant strains). Pharmacokinetic studies were performed in 10 healthy adult volunteers after i.v. injection of 0.75 g, 1 g, and 1.5 g cefuroxime and of 1 g cefalothin. Cefuroxime was superior to cefalothin by slower renal excretion, longer half-life, lesser or no metabolization and better tissue penetration. Cefuroxime is well tolerated and should be administered in adequate doses corresponding to the severity of the disease and the susceptibility of the causative agent.

Adult↗
PubMed1978

[Clinical pharmacology of Bacampicillin in comparison to Ampicillin (author's transl)].

Equimolecular doses of Ampicillin and Bacampicillin were administrated orally, of Ampicillin also by i.v. injection to 10 healthy adult volunteers (cross over study). By comparison of areas under serum level curves after i.v. and oral administration absorption rate of Bacampicillin which is hydrolysed rapidly to Ampicillin in the body was determined as 95%. Peaks of serum levels after 0.8 g. Bacampicillin administered orally were higher (15,9 microgram/ml) and earlier (after 60 min) than after 0.556 g. Ampicillin administered orally (3.5 microgram/ml after 150 min). Concentrations of Ampicillin in skin blister fluid 1 h after i.v. injection of Ampicillin were 20 times higher than after oral administration of Ampicillin and 3-4 times higher than after oral administration of Bacampicillin; after 3 and 4 hours skin blister levels after i.v. injection were only a half of skin blister levels after oral administration of Bacampicillin. Determination of antibiotic concentrations in saliva and tears showed similar relations. Since higher peaks in serum resulted in higher concentrations in the extravascular space Bacampicillin which is absorbed compeltely and more rapidly should be prefered for oral administration.

Administration, Oral↗