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Biomedical subjects

M A Paz

Publications and source records attributed to M A Paz.

At least 55 records · Page 3Linked to original sources
PubMed1977

Crosslinking profiles of elastin from anatomically defined regions of the lung.

Elastin was isolated and purified by a procedure which sequentially removed lipids, collagen, structural glycoproteins and the microfibrillar proteins. Crosslinking profiles were obtained by column chromatography either after reduction with 3[H]NaBH4 or after reaction with 14[C]NaCN and NH3. Examination of the crosslinking profiles of the elastins from various tissue regions revealed differences in the type, distribution and quality of crosslinks.

Animals↗
PubMed1977

Collagen prolyl hydroxylation in WI-38 fibroblast cultures: action of hydralazine.

The action of hydralazine on collagen prolyl hydroxylation was studied in a cell culture system using WI-38 fibroblasts. The prolyl hydroxylation level was determined by a method involving the digestion of collagen by bacterial collagenase and the examination of specific peptides. The presence of low concentrations of hydralazine (0.2 mM) in both "young" and "old" fibroblast cultures strongly inhibited collagen prolyl hydroxylation. The degree of inhibition was greater in serum-deficient cultures. No significant improvement in the degree of hydroxylation was observed by increasing either ascorbate or iron levels in the hydralazine-containing cultures in which hydroxylation was inhibited. Some of the reported side effects of hydralazine seen in patients might be related to its inhibitory effects on mixed function oxidative (MFO) hydroxylation systems. While the ascorbate dependence of the prolyl hydroxylase system of WI-38 decreased with the "age" of the culture, hydralazine inhibition of hydroxylation was dramatic with cultures of all "ages".

Ascorbic Acid↗
PubMed1977

The effect of diphenylhydantoin on fibroblasts in vitro.

It was found that 0.02 mM was the higher concentration of drug which is not toxic and is compatible with normal cell morphology and growth over a period of a week. Using this concentration of drug there was no consistent stimulation of cell growth. A small increase in cell number was noted, however, in some cultures during the first 24 hours of culture. DpH at a concentration of 0.02 mM in the presence of ascorbic acid decreased collagen prolyl hydroxylation in "old" W1-38 cultures but a concentration of 0.1 mM was required to decrease the values to a similar extent in "young" cultures. A concentration of 0.02 mM DpH had no effect on hydroxylation in an "old" HGF culture. It is speculated that in a responsive individual a reduction of collagen prolyl hydroxylation may play a role in the etiology of DpH-induced gingival enlargement and congenital malformations.

Cell Line↗
PubMed1976

Isolation, purification, and cross-linking profiles of elastin from lung and aorta.

Elastin from anatomically defined regions of young calf lung and dog aorta was isolated and purified by a procedure which sequentially removed lipids, collagen, structural glycoproteins, and the microfibrillar proteins without apparent damage to the cross-linking residues, which have been shown to be sensitive to autoclaving and hot alkali treatment. One of the methods described was effective in obtaining pure elastin from lung parenchyma. Visceral pleura was found to be the richest source (25% dry weight) of elastin in the lung tissues examined. The amino acid compositions of the elastins purified by different methods were compared for purity and for the detection of possible damage to cross-linking compounds. Cross-linking profiles were obtained by column chromatography either after reduction with 3[H]NaBH4 or after reaction with 14[C]NaCN and NH3. The 3[H]NaBH4 method, under carefully controlled conditions, proved not to be quantitatively reproducible. The reaction of elastin with 14[C]NaCN and NH3 appeared preferable due to its reproducibility; this procedure required one type of hydrolysis for the analysis of all the cross-linking compounds. Examination of the cross-linking profiles of the elastins from various tissue regions revealed differences in the type, distribution, and quality of cross-links.

Amino Acids↗
PubMed1975

Posttranslational protein modifications, with special attention to collagen and elastin.

It is apparent that significant progress has been made in our understanding of the biosynthesis, modifications, and maturation of collagen and elastin. We now recognize and partially understand special reactions involved in hydroxylations within the cell and complex cross-linking processes occurring outside the cell. Recent experiments (191) have shown that in human diploid fibroblast cultures of limited doubling potential (191) the hydroxylation of collagen prolyl residues appears to be "age" or passage-level dependent. With increasing passage level of these cultures, both the ascorbate requirements and the extent of collagen hydroxylation decrease. "Young" cell cultures have a strong requirement for complete hydroxylation and without ascorbate there is only about 50% of the normal level. "Middle-aged" cultures show higher hydroxylation without and full hydroxylation with ascorbate, whereas "old" (or cultures close to "senescence") are incapable of full hydroxylation with or without ascorbic acid. Although the overall system may show some deterioration with increasing passage levels, it appears that with increasing passage levels other components in the cell replace the ascorbate dependence of the hydroxylase system to a greater exten. In some ways, aging WI-38 cultures begin to resemble some transformed cells in their biochemical reactions, although they continue to remain diploid and eventually lose the ability to replicate. It is not yet known whether old animals can produce collagen, which may now be underhydroxylated, perhaps contributing to certain senescent changes. Careful examination of the hydroxylation index of collagen produced in organoid cultures of tissue biopsies as a function of donor age might be informative, particularly if one looks at the quality of collagen by employing collagenase and other proteolytic digests with collagen (191). One could comare the levels of frequent and characteristic peptide triplet sequences such as Gly-Pro-Hyp to Gly-Pro-Pro, Gly-Ala-Hyp to Gly-Ala-Pro, or Gly-Pro-Hyl to Gly-Pro-Lys and others for evaluation of hydroxylation throughout the entire molecule or at selected sequences.

Amino Acid Sequence↗