Biomedical subjects
Publications and source records attributed to K Macek.
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Tropoelastin and elastin preparations obtained from aortae of spontaneously hypertensive rats (SHR) show an increased proportion of polar amino acids (aspartic acid, glutamic acid, arginine and tyrosine). The content of these amino acids is 1.43-3.04 times higher in SHR rats than in similar elastin or tropoelastin preparations obtained from normotensive animals. On the other hand elastin and tropoelastin preparations obtained from SHR rats show a lower frequency of the Val-Pro sequence; this was found to be 35.93 per 1000 amino acid residues in SHR rats as compared to 51.04 per 1000 amino acids in the preparations obtained from control animals. Since similar differences were found not only in elastin preparations but also in tropoelastin, contamination of these preparations with an acidic protein seems unlikely. In general the results obtained are similar to those seen in animals kept on a long term high fat diet. It appears feasible to suggest that these differences are caused by a changed proportion of two different elastin type.
Some important facts about the chromatographic separation of a number of selected categories of drugs are summarized. The data refer to the chromatographic method of choice, stationary phase, mobile phase (carrier gas), detection procedure and (where available) method sensitivity. Also, fundamental instrumental parameters, namely injector, column and detector temperature, carrier gas and mobile phase flow-rate and gradient set-up are reported here. In all cases also the source material used for analysis is specified. The data are presented in table form, each table dealing with a particular category of drugs. The following categories of drugs are being dealt with: anthelmintics, antiarteriosclerotics, antibacterials, anticholinergics and cholinergics, anticoagulants, antidiabetics, antiemetics, antimycotics, antihistamines, antimalarials, antiparasitics, antiparkinsonics, antitussives, antiulcer drugs, antiviral compounds, appetite depressants and immunosuppressives.
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A distinct age dependence was observed in the occurrence of the gamma-carboxyglutamic acid containing proteins obtained from kidney cortex, liver and femoral bone. In the femoral bone, a stepped increase was seen when comparing animals 60, 350 and 700 days old. In the liver and mainly in the kidney cortex there was no change during the first year of life, but a distinct increase in the gamma-carboxyglutamate containing proteins was seen between day 350 and 700. It was also established that the increased level of gamma-carboxyglutamate at least in kidney cortex is due to a more intense carboxylation reaction in older animals as increased incorporation of labelled bicarbonate was observed in the microsomal fraction. In accordance with our previous results the occurrence of the carboxyglutamic acid containing proteins was shown to be vitamin D dependent; in vitamin D deprived animals supplemented with this vitamin the reappearance of gamma-carboxylate is more distinct in situations where higher levels of gamma-carboxyglutamic acid occur physiologically.
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It has been shown that in the skin of chronically irradiated rats the proportion of collagen type III as compared to collagen type I is increased; on the other hand, no changes in the overall proportion to collagen were observed in the skin. It appears that the increased proportion of collagen type III in chronically irradiated rats is responsible for the decreased solubility of cutaneous collagen in these animals. Concomitantly, indirect evidence was accumulated for the presence of an additional cross-link in type III collagen, present only when irradiated animals served as the collagen source. This cross-link is located subterminally as long as it is not removed by limited pepsin digestion. It was concluded that the physiological decrease in solubility and the decrease in solubility observed in chronically irradiated animals have a different molecular background.
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It was demonstrated that 50% food restriction for a period of two years causes a considerable increase in gamma-chain polymers of rat skin collagen. The polymerization reaction occurs in both main skin collagen types, e.g. collagen type I and III. Concomitantly increased amounts of alpha-aminoadipic acid were found in preparations of food deprived rats as compared to the controls. It appears that this unusual amino acid arises from the oxidative stabilization of dehydro hydroxylysinonorleucine, the main intermolecular collagen cross-link present in the skin. It is suggested that the degree of polymerization of skin collagen in fasted animals is the result of reutilization of more soluble collagen forms.
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Feeding of animals with high fat diets results in a distinct increase in the stability of the collagen structure as reflected by its higher resistance towards proteolytic cleavage. It appears that covalent cross links are formed when the experimental animals are fed a diet containing a high proportion of unsaturated fatty acids, i.e. when the chance of the formation of reactive intermediates is increased. This is based on the observation of the presence of non-reducible high molecular weight collagenous material in pepsin treated collagen. This high molecular weight fraction exhibited a typical 390/460 nm fluorescence and a distinct decrease of lysine content. It is suggested that the observed phenomena result from the action of in vivo present potential cross-linking agents.