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Biomedical subjects

M Marshall

Publications and source records attributed to M Marshall.

At least 235 records · Page 13Linked to original sources
PubMed1981

[Acute effects of low carbon monoxide concentrations on blood rheology, platelet fuction, and the arterial wall in the minipig (author's transl)].

While investigating the initial effects of low carbon monoxide concentrations on haemorheology and the arterial wall, minipigs were exposed to CO-air mixtures with 160, 185, and 420ppm CO. The daily exposure time was 4h. Exposure to 160 and 185 ppm CO led to a significant increase of platelet aggregation. Four hundred twenty parts per million CO caused an increase in haematocrit, blood and plasma viscosity, and in platelet aggregation. When examined by light microscopy, there were no changes in the arterial wall, whereas scanning electron-microscopic examinations revealed adhesions of shape-changed platelets on the arterial endothelium in some cases already after a single 4-h exposure to 160 or 185 ppm CO. After 4 x 4-h exposures to 420ppm CO there were mixed microthrombi on the arterial endothelium. According to preliminary transmission electron-microscopic studies these adhesions of platelets and also adhesions of mononuclear elements can always be related to foci of degeneration in the endothelial cells. These examinations showed that low concentrations of carbon monoxide can cause both haemorheological and morphological changes in the arterial wall. The further development of these changes under chronic CO exposure and a possible significance of the environmental hygiene beyond cigarette smoking has to be clarified by long-term experiments.

Animals↗
PubMed1980

Ornithine transcarbamylases. Ordering of S-cyano peptides and location of characteristically reactive cysteinyl residues within the sequence.

The peptides produced by cleavage of the S-cyano derivatives of the ornithine transcarbamylases (ornithine carbamoyltransferase, 2.1.3.3) from bovine liver, Streptococcus faecalis ATCC 11,420, and Streptococcus faecium ATCC 8043 have been isolated and aligned. Their amino acid compositions and COOH-terminal sequences are reported. The COOH-terminal peptide (51 residues in the bovine enzyme; 66 residues in the bacterial enzymes) contains the essential sulfhydryl group.

Amino Acid Sequence↗
PubMed1980

The essential sulfhydryl group of ornithine transcarbamylases. Reaction with anionic, aromatic disulfides and properties of its cyano derivative.

The essential sulfhydryl group of the ornithine transcarbamylases (ornithine carbamoyltrasferase, 2.1.3.3) from bovine liver and Streptococcus faecalis reacts slowly with aromatic disulfides at alkaline pH. But at pH 4.5, the apparent second-order rate constant for the reaction of this group in the S. faecalis enzyme with 5,5'-dithiobis(2-nitrobenzoic acid) (Nbs2) is 40-fold that for the reaction of 2-mercaptoethanol. This enhanced reactivity at acid pH, because it occurs only with anionic, aromatic disulfides and results in rates greater than those for low molecular weight thiols, must be due to a specific interaction with these reagents. The Nbs derivatives of both enzymes are inactive; the cyano derivatives prepared from them by cyanolysis are active but with greatly increased Kmorn. The slow rates of cyanolysis and thiolysis suggest that access to the Nbs residue is limited. Also, the red shift of the spectrum of the Nbs residue in the enzymes from that of Nbs2 implies that its microenvironment is different from that of the bulk medium. Deprotonation of a residue in the S. faecalis enzyme causes a further red shift. Since even the small, uncharged cyano group interferes with the binding of ornithine to both enzymes, the essential sulfhydryl group may actually be a part of the binding site for ornithine.

Animals↗
PubMed1980

The essential sulfhydryl group of ornithine transcarbamylases. pH dependence of the spectra of its 2-mercuri-4-nitrophenol derivative.

The essential sulfhydryl group of the ornithine transcarbamylases (ornithine carbamoyltransferase, 2.1.3.3) from bovine liver and Streptococcus faecalis reacts preferentially with 2-chloromercuri-4-nitrophenol. The spectra of this derivative between pH 4.4 AND 8.8 HAVE BEEN RESOLVED INto the spectrum of the nitrophenolate ion (III) and two species of phenol (I and II). The lambda max of I and II (both enzymes) and III (bovine) are red shifted from those of the comparable species in the same derivative of 2-mercaptoethanol. Deprotonation of a residue on the enzyme must be responsible for the transition from I to II. The pK values of the phenolic group are 7.1 (mercaptoethanol), 7.7 (bovine), and 8.8 (S. faecalis). The red shift in the lambda max of III and the modest increase in the pK of the phenolic group are consistent with a relatively hydrophobic environment for the nitrophenolate ion in the bovine enzyme. Since deprotonation of the residue in the bovine enzyme perturbs the pK of the phenolic group only slightly, its effect may be indirect. Interaction with a neighboring carboxyl group (pK 5.3) would account for the large increase in the pK of the phenolic group in the S. faecalis enzyme, which is not accompanied by an appreciable shift in the lambda max. Carbamyl-P increases the pK of the phenolic group in both enzymes, a result consistent with its binding site being close to the essential sulfhydryl group.

Animals↗
PubMed1980

Fluidised-bead bed in the intensive-therapy unit.

The fluidised-bead bed is a novel way of managing patients in the intensive-therapy unit (ITU) with various nursing problems. It is particularly suitable for the management of pressure areas and for patients at the extremes of weight range. Theoretically, the bed is a way of reducing catabolism, but this has so far not been properly investigated.

Adult↗
PubMed1980

Early micro- and macro-angiopathy in the streptozotocin diabetic minipig.

Streptozotocin diabetes in the minipig constitutes an outstanding model for the study of diabetic angiopathies. Changes which are classified as macroangiopathy are evident after 6 months, while the first changes indicative of microangiopathy appear already after about 18 months. The degree of pronouncement of the microangiopathy depends on the duration and severity of the induced diabetes. These results constitute a cogent argument in favour of the "metabolic theory" of the development of diabetic microangiopathy.

Animals↗