Biomedical subjects

L Klein

Publications and source records attributed to L Klein.

At least 271 records · Page 15Linked to original sources

PubMed1969

Reversible transformation of fibrous collagen to a soluble state in vivo.

Metabolic pathways of pre-existing and newly synthesized collagen fractions from skin and induced connective tissue were studied in rats that had been labeled with (3)H-L-proline 6 and 20 weeks previously. The distribution of specific radioactivity was determined for soluble and insoluble collagens. Multiple extractions of neutral salt-soluble and citrate-soluble collagen demonstrated constant specific radioactivities which indicated the achievement of an isotopic steady state. Citrate-soluble collagen was four times more radioactive than neutral salt-soluble collagen, which indicated a large difference in biological age (months) between fractions. Different levels of specific radioactivity in collagen fractions from implanted sponge indicated that both pre-existing (citrate-soluble) and newly synthesized collagen (salt-soluble) contributed to the insoluble collagen of induced connective tissue in normal and hypophysectomized rats. The isotopic data indicated that pre-existing fibrous collagen could be solubilized in vivo and translocated from skin to sponge via citrate-soluble collagen.

Animals↗

PubMed1969

The quantitative relationship of urinary peptide hydroxyproline excretion to collagen degradation.

To determine the quantitative relationship of urinary hydroxyproline peptide excretion to collagen breakdown, known quantities of radioactive hydroxyproline peptides were administered to unlabeled animals and excertion of radioactivity in respiratory carbon dioxide, urine, and feces was measured. The major routes of excretion of collagen peptide metabolites were respiratory carbon dioxide (75%) and urine, as hydroxyproline-containing peptides (25%). Since the predominant urine hydroxyproline peptide linkage is proly-hydroxyproline, L-prolyl-L-hydroxyproline-(3)H was administered to unlabeled animals. Greater than 80% of the administered dipeptide was excreted in urine, suggesting that this peptide linkage is not hydrolyzed to a significant extent in vivo. These data suggest that urinary hydroxyproline excretion is a "fairly" sensitive indicator of collagen breakdown and can be used at the clinical level to quantitate changes in collagen breakdown.

Animals↗

PubMed1969