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Biomedical subjects

T Hermann

Publications and source records attributed to T Hermann.

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

Preparation, properties and biological activity of natural and semisynthetic urethanes of monensin.

Conversion of the monovalent polyether antibiotic monensin into a series of urethane derivatives substituted at C-26 causes a ten-fold increase in the cation transporting properties of the antibiotic as well as making the resulting semisynthetic urethanes divalent ionophores. These changes must in part account for the enhanced antimicrobial activities of the urethanes. The most active derivatives are the phenylurethanes which are ten times more active in vitro against Gram-positive bacteria and unlike monensin are active against Candida albicans and Penicillium digitatum. Another novel activity exhibited by four of the urethanes was against Plasmodium berghei, the causative agent for malaria.

Anti-Bacterial Agents↗
PubMed1982

[Use of a new rheometer for the study of the filtrability of a suspension of sickled red cells as a function of PO2].

The filtration time of a small volume (0.1 ml) of red cell suspension from normal (AA), heterozygous (AS) and homozygous (SS) subjects for sickle cell disease was investigated as a function of PO2 The curve of filtration time of AS and SS red cell suspensions was biphasic. At high values of PO2, the progressive reduction of filtrability of sickle cell suspensions with decreasing PO2 occurred without new change in morphology of most of the cells. In contrast, at lower PO2 the apparent filtrability was improved and the cells were sickled." However the red blood cells were retained by the filter and the "solvent" filtrability was improved because rigid and highly deformed sickled cells did not clogged completely the pores of the filter. This study allowed to distinguish a new concept of apparent filtrability for red blood cells in sickle cell disease.

Anemia, Sickle Cell↗
PubMed1981

RBC filterability, oxygen saturation, ATP intracellular stock, and cerebral microcirculation.

The filterability of erythrocytes through Nucleopore filters of 5 micrometer has been studied with a new device (Hemorheometer SPO1). A reliable and reproducible index of filterability (IF) can be obtained which depends only on the red blood cell deformability. The results showed an alteration of red blood cell deformability in some pathological circumstances like smoking and that deformability depends on the nature of haemoglobin, the ATP intracellar stock and the saturation of haemoglobin by oxygen. The cerebral microcirculatory consequences of alterations of red blood cell deformability has been studied in vitro by measuring whole blood filterability on 5 micrometer Nucleopore filters with the classical technic of Reid & Dormandy and in vivo by 99mTc cineangioscintigraphy and by determination of the regional cerebral blood flow by the 133Xenon inhalation technic. The results showed an increase of cerebral ascensional time and mean transit time of the cineangioscintigraphy and a decrease of regional cerebral blood flow in patients presenting with a decrease of whole blood filterability flow.

Adenosine Triphosphate↗
PubMed1980

Microbial products. IV. X-14847, a new aminoglycoside from Micromonospora echinospora.

Micromonospora echinospora strain X-14847 produces gentamicin A as the major antibiotic together with a new aminoglycoside, termed X-14847, and identified as a 2-amino-2-deoxy-alpha-D-glucopyranosyl myo-inositol. This report describes the taxonomy of the culture, fermentation conditions, the isolation and the identification of X-14847.

Aminoglycosides↗
PubMed1977

Feedback inhibition of the synthesis of an antibiotic: aurodox (X-5108).

The effect of aurodox on its own biosynthesis by Streptomyces goldiniensis was studied. It was found that addition of exogenous aurodox inhibits further accumulation of aurodox by the antibiotic-producing culture. Both long term fermentation studies with aurodox-14C and precursor incorporation studies over short time periods indicated that aurodox synthesis was regulated by feedback inhibition. The concentration of aurodox required to completely block further synthesis of the antibiotic was about 400 microng/ml. This is the same as the maximum concentration of aurodox normally accumulated by the culture used in this study. Antibiotic synthesis was inhibited not only by aurodox but also by some structural analogs of aurodox including several having no antibacterial activity. This effect was immediate and readily reversible, indicating that it could be due to inhibition of an enzyme(s) involved in the biosynthesis of aurodox.

Aurodox↗
PubMed1976

Studies on a new polyether antibiotic, Ro 21-6150.

A new polyether antibiotic, Ro 21-6150, has been isolated from culture broths of Streptomyces hygroscopicus, strain X-14563. Ro 21-6150 has ionophore properties and is active in vitro against gram-positive bacteria.

Animals↗
PubMed1976

Kinetics and mechanism of degradation of some 5-allylbarbituric acid derivatives. Part 3: Kinetics of solvolysis of major intermediates of 5.5-diallylbarbituric acid degradation.

Solvolysis of N-diallylacetylurea and 5.5-diallylmalonuric acid was investigated in the pH range ca. 8--12 by means of spectrophotometric and t.l.c. methods. Their log k--pH profiles were constructed from the experimental results obtained by degradation at 70 degrees C. Therefore, specific catalytic rate constants and pKa's were derived. The kinetic mechanism of N-diallylacetylurea solvolysis, resulting among other things from the so-called kinetic salt effect, depends on hydroxyl-ion attack on its undissociated and monoanionic forms. However, the degradation of alpha.alpha-diallylmalonuric acid in the pH range 10--12 is an example of specific base catalysis which can be explained by hydroxyl-ion attack on its monoanionic species. The degradation of alpha.alpha-diallylmalonuric acid below pH=10 does not follow a theoretical equation postulated, because the spectrophotometric method does not allow monitoring the formation of N-diallylacetylurea in the presence of the above acid. Thin-layer chromatography was used to check different pathways of transformations of the intermediate studies.

Allyl Compounds↗
PubMedDate not supplied

Angiogenesis as a target for tumor treatment.

Angiogenesis is a key step in tumor growth, invasion and metastasis. Thus, antiangiogenic therapy was postulated to be an attractive approach for antitumor treatment. Based on today's knowledge, at least three strategies for inhibition of angiogenesis are feasible: (1) inhibition of release of angiogenic factors from tumor cells and/or neutralization of angiogenic molecules that have already been released: (2) inhibition of vascular endothelial cell proliferation and migration, and (3) inhibition of the synthesis and turnover of vessel basement membrane. To date, a number of antiangiogenic agents have been identified. In animal models, treatment with angiogenesis inhibitors has proven antitumor effects. Early clinical experience with angiogenic inhibitors indicates that optimal antiangiogenic therapy in the future is likely to be based on the long-term administration to cancer patients in adjunct to surgery, radiotherapy and conventional chemotherapy.

Animals↗