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Biomedical subjects

B Schmid

Publications and source records attributed to B Schmid.

At least 91 records · Page 5Linked to original sources
PubMed1983

A comparative study of digoxin levels by radioimmunoassay micromethod in capillary and venous blood samples in children.

In a group of 30 digitalized children, we compared the digoxin levels in capillary and venous plasma samples, both of which were obtained simultaneously from each child. We statistically concluded that the venous plasma samples could surely be replaced by capillary plasma samples for measurements of plasma digoxin levels without any significant difference. Additionally, we showed that storing the capillary plasma samples at room temperature for 3 days did not lead to any significant change in digoxin levels. This is an important point for the hospitals and practitioners who do not have their own possibilities for digoxin determination.

Blood Preservation↗
PubMed1980

Biological assessment of chemical DNA damage in germ cells of male rabbits.

DNA damage represents a key step in mutagenesis and carcinogenesis. Excision repair has been described to be the major pathway restoring damaged DNA. Assaying DNA repair may thus illuminate the mechanism of mutagenesis and carcinogenesis and serve as an indicator of the mutagenic and carcinogenic potential of environmental chemicals and drugs. The paper demonstrates a practical application of these concepts. DNA damage induced by chemical substances in male germ cells of rabbits was assessed by the demonstration of DNA repair synthesis in meiotic and post-meiotic maturation stages. Incorporation of tritium-labeled thymidine was monitored in spermatozoa obtained by serial ejaculation. The test was validated with several standard mutagens and carcinogens, and its usefulness was demonstrated with a study on 3 suspected genotoxic drugs, i.e. hycanthone, isoniazid, and metronidazole.

Animals↗
PubMed1979

Unscheduled DNA synthesis in male rabbit germ cells induced by methylmethane sulfonate, cyclophosphamide and adriamycin.

Male rabbit germ cells were labelled by intratesticular injection of [3H]-thymidine (3H-T). In sperms of control animals, radioactivity was first demonstrated between the 40th and 43rd day after labelling, corresponding to preleptotene spermatocytes. In rabbits treated with 22.5 mg/kg methylmethane sulfonate (MMS), significant radioactivity was shown in sperms collected from day 19 ownwards. These cells derived from spermatocyes and early spermatids at the time of labelling. 3H-T incorporation into these cell populations represents unscheduled DNA synthesis (UDS), a repair process initiated after chemical damage of germ cell DNA. After i.v. injection of 20 mg/kg cyclophosphamide, an alkylating agent that must be activated, labelled sperms were found 28--37 days after treatment. This shows that UDS took place in spermatocytes during the pachytene and zygotene stages. Adriamycin (1.0 and 3.0 mg/kg) induced UDS during pachytene and zygotene stages of spermatogenesis. Sperm counts decreased during spermatogonial stages by a factor of about ten in cyclophosphamide and adriamycin treated rabbits. It was not changed after MMS-treatment.

Animals↗
PubMed1978

DNA repair processes in germ cells demonstrated in ejaculated sperms of rabbits treated with methyl methane sulfonate.

Male rabbits were treated with a single i.v. injection of 22.5 mg/kg methyl methane sulfonate (MMS). 0--24 h later [3H]-thymidine was injected in both testicles. Incorporation of the isotope in germ cell DNA was demonstrated in ejaculated sperms. In controls labeled sperms were demonstrated first on day 40--43. These cells were in the preleptotene spermatocyte phase at the time of [3H]-thmidine injection. In rabbits treated with MMS significant radioactivity occurred in sperms collected from day 19 onwards. These cells were in late spermatocyte and early spermatid phase of maturation when [3H]-thymidine was injected. Incorporation of thymidine in these cell populations is interpreted as an expression of unscheduled DNA synthesis, a repair process initiated after chemical damage of germ cell DNA by MMS. The usefulness of the rabbit test system within the framework of conventional mutagenicity screening tests is discussed.

Animals↗
PubMed1977

A simplified method for the isolation of sperm heads from the caput epididymidis of rodents and from ejaculated rabbit seminal plasma.

The present report describes a simple and rapid procedure to isolate highly purified sperm heads from mouse, rat and rabbit. The isolation procedure involves mincing of the caput epididymidis (CPE) of mice and rats to obtain a crude CPE suspension. This suspension is filtered to remove tubular fragments. The filtrate containing sperms and cellular contaminants is trypsinized, followed by sonication. To obtain rabbit sperm head suspension, ejaculated spermatozoa are briefly exposed to the cationic detergent CTAB-D, followed by trypsinization. Trypsin treatment of the suspension yields sperm heads and tails. The suspension containing sperm heads and tails is separated by discontinuous sucrose density gradient centrifugation. Highly purified and enriched sperm heads are recovered from the bottom of 2.5 M sucrose of the gradient. Enriched sperm heads contain less than 1% sperm tails.

Animals↗
PubMed1976

[Resistance to beta-lactam antibiotics and aminoglycosides in gram negative bacteria. 1. Molecular and genetic characterization of R-factors (author's transl)].

With frequent use of aminoglycoside antimicrobials and beta-lactam antibiotics in hospitals in the last few years, the number of bacterial strains resistant to these chemotherapeutics increased. Lately, strains of E. coli, Klebsiella, Enterobacter, Serratia, Proteus and Pseudomonas resistant to many antimicrobials (ampicillin, carbenicillin, cephalothin, chloramphenicol, gentamycin, tobramycin, sisomycin, neomycin, paromomycin, kanamycin, streptomycin, spectinomycin, tetracycline, sulphonamides) were isolated from patients of the university hospital in Zuerich. The resistant phenotype of two representative strains (Klebsiella pneumoniae 1 and Serratia marcescens 2) could be transferred by mixed cultivation to E. coli K-12. Multiple resistance of strain 1, and addition, could be transferred to Salmonella typhimurium, Serratia marcescens, Providencia, Proteus mirabilis and Klebsiella pneumoniae in varying frequencies. Transfer to Pseudomonas aeruginosa, however, could not be achieved. Spontaneous instability of resistance was observed in 0.15% of the cells of an overnight brothe culture and in 90% of the cells of a three months old culture. Conjugation, instability and the response to the sex phages MS-2 and If-1 suggested that resistance was mediated by a monomolecular R-factor, belonging to the fi+-type. This suggestion was confirmed by molecular characterization of the resistance plasmids. After transfer of the R-factors of K. pneumoniae 1 (R-FK 1) and Serratia marcescens 2 (R-FK2) into E. coli K-12, plasmid DNA was labelled with (methyl-3H) thymidine, and isolated by isopycnic centrifugation in cesiumchlorid-ethidium-bromide. Analysis of plasmid DNA then was carried out by sedimentation in a 5-20% neutral sucrose gradient together with reference plasmids of known molecular weights and sedimentation constants. The analysis revealed that R-FK1 had a molecular weight of 54 X 10(6) and R-FK2 of 50 X 10(6) daltons. The values were confirmed by contour length measurements of open circular forms with an electron microscope. A comparison of the sedimentation profile of labelled plasmid DNA from strain 1 and 14C-labelled DNA of E. coli K-12 (R-FK1) showed that the wild-type strain contained, besides the large resistance plasmid, at least two smaller "cryptic" plasmids. These smaller plasmid molecules were also found in antibiotic susceptible variants of strain 1, which did not contain the 54 X 10(6) dalton plasmid molecule, responsible for the resistant phenotype. The number of copies of R-FK1 in E. coli K-12 was determined to be 2, indicating stringent control of replication. It is discussed that the growing number of isolations of strains of Escherichia, Klebsiella, Serratia, Proteus, Providencia and Pseudomonas, exhibiting the same resistance phenotype, results from the spread of the R-factor described above among the hospital bacterial flora.

Aminoglycosides↗
PubMed1976

[Resistance to beta-lactam antibiotics and aminoglycosides in gram negative bacteria. 2. Mechanism of resistance (author's transl)].

In a preceding paper the genetics of resistance of 2 representative strains exhibiting resistance to beta-lactam antibiotics (ampicillin, catbenicillin, cephalothin) to aminoglycosides (kanamycin, neomycin, paromomycin, gentamycin, sisomycin, tobramycin, streptomycin, spectinomycin) and further antimicrobials (tetracycline, chloramphenicol, suphonamides) were described. This paper reports about the mechanism of resistance to beta-lactam antibiotics and aminoglycosides in these strains. Enzymatic extracts from K. pneumoniae 1 and Serratia marcescens 2 were produced by the osmotic shock procedure. Incubation of these extracts with aminoglycoside antibiotics, to which the strains are resistant, and ATP resulted in the total inactivation of the antimicrobials, as measured with a Bacillus subtilis assay. Analysis of this inactivation with the radioactive methods of Davies and his colleagues revealed that the kanamycins, neomycins, paromomycin and gentamycin A were phosphorylated. Because butirosin was not a substrate for the phosphorylating enzyme, it was concluded that the strain produced the neomycin/kanamycin phosphototransferase I. Furthermore, it was found that streptomycin and spectinomycin were adenylylated by the enzymatic extracts as well as gentamycin C1a, C1, C2, A, tobramycin, sisomycin and the kanamycins. This substrate profile indicated the presence of two adenylylating enzymes: streptomycin/spectinomycin-adenylyl-transferase and gentamycin-adenylyltransferase. After transfer of multiple drug resistance by conjugation from both strains into C. coli K-12, sonified extracts were prepared and examined for enzymatic activity splitting beta-lactam antibiotics. The relative rates of inactivation of benzylpenicillin, ampicillin and cephaloridine as well as the inhibitory effect of cloxacillin, but not of p-chloro-mercuri-benzoate on the inactivation of cephaloridine indicated that both strains produced a class III/type a (TEM type) beta-lactamase. It is discussed that the increasing frequency of gram-negative organisms form the university hospital with identical resistant phenotypes as the strains examined is the result of the spread of an R-factor among the hospital bacterial flora.

Aminoglycosides↗
PubMed1975

[Some thoughts on the assessment of work capacity during therapy (author's transl)].

The "Gesetz über die Angelichung der Leistungen zur Rehabilitation" (Act on the Harmonisation of Rehabilitation Services) requires that during the implementation of any medical rehabilitation measure the possibilities be examined as to whether vocational rehabilitation services (training, assistance in job finding, assistance at work in the present job, occupational change within the company) can contribute to maintaining, improving or restoring the earning capacity. It is neither expected nor possible to make an accurate assessment of all occupational abilities. The evaluation can be made only for particular functions and skills. Also, it is not necessary that precise concepts concerning goals and type of vocational rehabilitation measures already be developed during the medical phase of rehabilitation. However, it is imperative to know whether the previous occupation can be maintained without jeopardizing the earning capacity, or whether vocational rehabilitation services are needed. In the latter case, the financially responsible agency for the rehabilitation process needs to be informed on work performance limitations, occupational risks and skills existing for a particular job. Furthermore, professionals working in facilities with psychological and vocational therapeutic units can give their opinion on the suit-ability of particular rehabilitation measures. View-points are discussed, which contribute to a clarification of the employment history and performance picture. The patient has to be informed of the effects of his disability and the progress which can be achieved, in order to motivate him to undergo vocational rehabilitation.

Disability Evaluation↗