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Biomedical subjects

A Polak

Publications and source records attributed to A Polak.

At least 109 records · Page 6Linked to original sources
PubMed1976

Renal stones and urinary infection: a study of antibiotic treatment.

Twenty-two patients in whom renal calculi and urinary infection were closely associated were studied over two to five years. Four patients had previously had stones surgically removed, and five underwent pyelolithotomy during the course of the study. Urinary infection was treated with an appropriate antibacterial agent, and treatment was followed by long-term prophylaxis, usually with cotrimoxazole. A sterile urine was maintained for long periods in all these patients. In four patients, however, apparent stone growth occurred while the urine was sterile. On entering the study 21 of the 22 patients complained of symptoms. After treatment 19 of the 20 patients who were still attending were symptom-free. Six of the 22 patients entered the study with raised levels of serum creatinine; levels fell in four and remained raised in two. This antibacterial regimen, either alone or after surgery, will usually relieve symptoms and may prevent deterioration of renal function.

Adult↗
PubMed1976

Metabolic studies with 5-fluorocytosine-6-14C in mouse, rat, rabbit, dog and man.

Metabolism of 5-fluorocytosine-6-14C (5-FC) was studied in mice, rats, rabbits and dogs after oral and subcutaneous, single and repeated administration. In the urines of all species, intact 5-FC accounted for more than 90% of the total radioactivity at any time of the various treatment schedules. The average proportion of the urinary metabolites was around 5% in dogs, 3% in rabbits, 2.5% in rats, and 2% in mice of the total radioactivity. At repeated dosage, there was an increase of metabolites in mice but a decrease in rats treated subcutaneously. Neither increase nor decrease was observed in rabbits (treated orally) and dogs. Two metabolites were identified, alpha-fluoro-beta-ureido-propionic acid (FUPA) and alpha-fluoro-beta-alanine, the latter occurring mainly after oral treatment. These compounds represent probably that part of 5-FC which was deaminated to 5-fluorouracil (5-FU) or directly to 5-fluorodihydrouracil. FUPA was the only metabolite found in the urines collected from 4 out of 5 human volunteers during the first 12 h after single oral administration of 3.5 g of the radiolabelled drug. Its maximum proportion was 1.1% of the total radioactivity. No metabolites were detected in the urine neither of the 5th volunteer nor in those of 3 mycosis patients who were given the radioactive dose after they had received regular chemotherapy with unlabelled 5-FC (150 mg/kg/day) for at least 2 weeks. The sensitivity threshold of the method was 0.1-0.4% of the total radioactivity. One of the patients had developed thrombocytopenia which was probably due to 5-FC chemotherapy. The symptoms of 5-FC intolerance were in most of the examined species similar to those observed with 5-FU [9]. However, no quantitative correlation between proportion of metabolites and 5-FC toxicity is apparent except that man is the species in which both metabolism and toxicity are the lowest. It has not been proved yet that 5-FC intolerance occurring in a small percentage of patients receiving 5-FC chemotherapy (mainly leukopenia, thrombocytopenia) results in fact from conversion to 5-FU.

Administration, Oral↗
PubMed1975

Mode of action of 5-fluorocytosine and mechanisms of resistance.

Mode of action of 5-fluorocytosine (5-FC) and mechanisms of resistance to the drug are discussed on the basis of experiments performed with Candida albicans ATCC 26790 and with 50 selected clinical isolates of C. albicans belonging to serological type A or B and representing various degrees and models of 5-FC resistance (sensitivity). Incorporation of 5-fluorouridylic acid into RNA appeared as a prerequisite to antifungal activity, although at a given incorporation rate, growth inhibition varied considerably from one strain to the other. The amino acid pool was unbalanced, and there was evidence for disturbance of protein synthesis. These dysfunctions of RNA probably account for growth inhibition and cell death, whereas up to the present, there was no proof of formation of 5-fluorodeoxyuridylic acid nor of subsequent inhibition of thymidylate synthetase. Incorporation of fluorinated pyrimidine into RNA was lower in normally sensitive type B strains than in normally sensitive ones of type A, whereas the frequency of 5-FC-resistant mutants was the same. The two serological types did not differ in the activity of cytosine permease nor in that of cytosine deaminase. Among 29 clinical isolates with 6-FC resistance (or impaired sensitivity) no instance of cytosine permease deficiency was found. Two isolates (belonging to the serological type A) were deficient in cytosine deaminase, whereas the majority was probably deficient in uridine monophosphate pyrophosphorylase or had a surplus of de novo synthesis of pyrimidines. Relative 5-FC resistance was more common than complete resistance.

Candida albicans↗