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Biomedical subjects

C Ebert

Publications and source records attributed to C Ebert.

45 records · Page 3Linked to original sources
PubMed1978

[Fluorescence-analytical studies of the reaction of several psychoactive drugs with membrane structures of the CNS].

The use of 1-anilino-8-naphthalene sulfonate (ANS) as an indicator of membrane conformational perturbations induced by psychoactive drugs was tested with regard to its specificity considering both chemical structure (phenothiazine, butyrophenone, phenylalkylhydrazine) and pharmacological activity (major transquilizers, antidepressants, antihistamines), on the one hand, and brain region (cortex, striatum, hippocampus) and subcellular structure of membranes (mitochondria, microsomes, synaptosomes), on the other. Not only a weak strengthening of ANS affinity to membrane constituents by chlorpromazine and promethazine (haloperidol and phenelzine were without effect), but also the alteration of membrane structure in such a way as to create additional ANS binding sites by chlorpromazine and to a smaller degree also by promethazine and haloperidol (phenelzine was without effect) resulting in a manifold increase in fluorescence indicated any relation to functional characteristics of biological material or properties of drugs. Apparent dissociation constants and membrane ANS binding sizes are reported.

Anilino Naphthalenesulfonates↗
PubMed1977

On the introduction of disulfide crosslinks into fibrous proteins and bovine serum albumin.

Hydroxyl groups in serine side chains of collagen, silk fibroin, and bovine serum albumin (BSA) were converted to SH by tosylation. In collagen film, 50% of the serine OH groups could be thiolated at most. In fibroin, only 13% because of its compact beta-pleated sheet structure and low susceptibility to swelling. The SH groups introduced are near enough together to form -S-S- bonds by oxidation. The residual SH content after oxidation was 0.1% in collagen and 0.03 to 0.25% in fibroin. Disulfide crosslinking increased the shrinkage temperature of collagen and fibroin and decreased the amount of shrinkage. BSA was crosslinked to dimers (MBSA) according to gel permeation chromatography and sedimentation analysis by the analytical centrifuge. Because these crosslinked proteins can be metabolized by the usual processes, in contrast to those crosslinked by artificial, nonphysiological bridges, they may be used for biological or medical purposes.

Amino Acids↗
PubMed1977

The formation and cleavage of lysinoalanine crosslinks.

Treatment of lysinoalanine (LAL) with methyl iodide at pH-values above 8 leads to cleavage to dehydroalanine (DHA) and Nepsilon-di- or/and trimethyllysine, as was shown by ultraviolet spectra and amino acid analysis. This reaction is due to methylation of the crosslinking NH group of LAL to the quaternary ammonium compound; nucleophilic beta-elimination follows. By this reaction, the epsilon-amino groups of polylysine and its copolymers can be methylated to form di- and/or trimetryl-lysine residues. Chemically modified polypeptides containing Nepsilon-dimethyllysine can be made in this way.

Alanine↗
PubMed1977

On the specific cleavage of cysteine containing peptides and proteins.

Addition of cysteine to the double bonds of polydehydroalanine and copolymers of dehydroalanine (DHA) and methylcysteine, alanine, leucine or gamma- methyl-L-glutamate is accompanied by increased solubility and decreased molecular weight. This result is due to a peptide bond cleavage caused by formation of a thiazolidine as a consequence of nucleophilic attack by the sulfur atom on the preceding C=O group and subsequent splitting of the peptide bond by nucleophilic attack of an OH ion. This mechanism is predominant in alkaline media; in acid another mechanism is favoured; carbonyl-oxygen attacks the carbonyl-C-atom of the cysteine residue, forming a second ring system. Addition of one water molecule then yields two peptide fragments, one of them a terminal cysteine residue. Both mechanisms could be confirmed in the case of gamma-L-glutamyl-dehydroalanyl-glycine by adding cysteine. Furthermore, it could be shown that SH-glutathione is decomposed at alevated temperatures according to the two mechanisms mentioned. This SH-induced peptide bond cleavage can be used for selective peptide chain splitting of cysteine-containing polypeptides and proteins under relatively mild conditions.

Alanine↗
PubMed1975

Intra-aortic balloon counterpulsation: potential for therapy in hemorrhagic shock with associated myocardial failure.

After attaching appropriate monitoring devices enabling the measurement of the slope of the left ventricular function curve, left atrial pressure, mean aortic pressure, peak left ventricular pressure, and tension time index, three groups of ten dogs were subjected to varying periods of hemorrhagic shock until a slope of their ventricular function curve was reduced to either 75% (Group I), 50% (Group II), or 25% (Group III) of their baseline value. Resuscitation was attempted in all dogs by the intravenous infusion of shed blood plus additional balanced salt solution. This infusate was administered to maintain either the mean aortic pressure within 15 mm Hg of the baseline value or a left atrial pressure of 15 mm Hg, whichever occurred forst. One half of the dogs received, in addition, intra-aortic balloon counterpulsation. All dogs not receiving counterpulsation expired within two hours. There was no apparent effect of counterpulsation on Group I animals. Three of five animals (Group II) and four of five animals (Group III) receiving counterpulsation survived to the end of the experiment with significant (p smaller than .01) improvement in the parameters monitored. The utilization of counterpulsation as an adjunct to treatment in hemorrhagic shock is suggested.

Animals↗
PubMedDate not supplied

Control of sulfatase and sulfotransferase activities by medrogestone in the hormone-dependent MCF-7 and T-47D human breast cancer cell lines.

In the present study, we explored the effect of the progestin medrogestone on the sulfatase and sulfotransferase activities in the hormone-dependent MCF-7 and T-47D human breast cancer cell lines. After 24 h incubation at 37 degrees C of physiological concentrations of estrone sulfate ([3H]-E1S: 5x10(-9) mol/l), it was observed that this estrogen was converted in a great proportion to E2 in both cell lines. Medrogestone significantly inhibits this transformation, at all the concentrations tested (5x10(-8) to 5x10(-5) mol/l), in both cell lines. The IC50 values were 1.93 micromol/l and 0.21 micromol/l in MCF-7 and T-47D cells, respectively. In another series of studies, after 24 h incubation at 37 degrees C of physiological concentrations of estrone ([3H]-E1: 5x10(-9) mol/l), the sulfotransferase activity was detectable in both cell lines. Estrogen sulfates (ES) are found exclusively in the culture medium, which suggests that as soon as they are formed they are excreted into the medium. Medrogestone has a biphasic effect on sulfotransferase activity in both cell lines. At low doses: 5x10(-8) and 5x10(-7) mol/l, this compound stimulates the enzyme by +73.5 and 52.7%, respectively, in MCF-7, and by 84.5 and 62.6% in T-47D cells. At high concentrations: 5x10(-6) and 5x10(-5) mol/l, medrogestone has no effect on MCF-7 cells, but inhibits the sulfotransferase activity in T-47D cells by -31.4% at 5x10(-5) mol/l. In conclusion, the inhibitory effect provoked by medrogestone on the enzyme involved in the biosynthesis of E2 (sulfatase pathway) in estrogen-dependent breast cancer, as well as the stimulatory effect on the formation of the inactive ES, support a probable anti-proliferative effect of this progestin in breast tissue. Clinical applications of these findings can open new therapeutic possibilities for this disease.

Antineoplastic Agents, Hormonal↗