Biomedical subjects

G Quintarelli

Publications and source records attributed to G Quintarelli.

At least 19 recordsLinked to original sources

PubMed1979

Fibrogenesis and biosynthesis of elastin in cartilage.

This study presents direct evidence that dissociated chondroblasts from rabbit ear cartilage grown in vitro are capable of synthesizing insoluble elastin. Ultrastructural examination indicated that at an early stage of tissue development, elastogenesis is initiated producing a form of primary fibrils which later condense into an electron dense amorphous material which, unlike other elastin-containing tissues, is heavily stained by metal cations and lacks peripheral microfibrils. Native elastic fibrils and the mature elastic fiber bundles are both susceptible to elastase digestion. Transmission electronmicroscopy demonstrated the presence of many intracellular filaments all showing a substructural organization and localized in close proximity to the nucleus. Their possible contractile nature is discussed. Amino acid analysis of cartilage elastin and of the elastin synthesized in vitro revealed a close chemical similarity between the two molecules. Ultrastructural analysis of the in vitro elastin demonstrated a substructural organization quite similar to that of the elastin observed in an in vivo system.

Amino Acids↗

PubMed1978

Role of hyaluronic acid in the in vivo aggregation of cartilage proteoglycans.

From studies of isolated cartilage proteoglycans in solution it has been inferred that they occur in the tissue as aggregates of high molecular weight which consist of proteoglycan monomers, hyaluronic acid and specific link proteins. The present investigation provides direct evidence for the existence of hyaluronic acid-containing aggregates in vivo, as indicated by the following observations: Treatment of sections of coastal cartilage from newborn rabbits with Streptomyces hyaluronidase led to complete disappearance of the electron dense granules, which have been previously identified as chondroitin sulfate proteglycans, from the extracellular matrix. Similar results were obtained on digestion with leech hyaluronidase which, like the Streptomyces enzyme, specifically degrades hyaluronic acid. Proteoglycan aggregation occurs not only in the extracellular compartment but intracellularly as well, since a portion of the hyaluronidase-senstive, electron dense proteoglycan granules are found in intracellular vesicles. It is concluded that the ability of proteoglycan monomers to form aggregates is a true reflection of the in vivo organization of these molecules and that aggregate formation is an important factor in the maintenance of the normal physiological function of cartilage tissue.

Animals↗

PubMed1977

The effects of acetylation on the binding region of cartilage proteoglycans to hyaluronic acid.

Proteoglycans in cartilage are found as aggregates and as monomers. Evidence has been obtained indicating that hyaluronic acid, normally present in this tissue, binds together monomers into large molecular weight aggregates. In this investigation, the interacting region of the protein backbone has been studied. The results unequivocally demonstrated that the epsilon amino groups of lysine are involved in hyaluronic acid binding to proteoglycans and that their blocking by acetylation either prevents reaggregation or disaggregates the high mol.w aggregates.

Acetylation↗

PubMed1975

Age-dependent changes on the state of aggregation of cartilage matrix.

The state of aggregation of cartilage matrix and its variations with age have been studied by biochemical, cytochemical, and ultrastructural methods. Determination of proteoglycans and collagen in costal cartilage from newborn, 4-week-, and 4-year-old rabbits showed that marked changes occurred during the first 4 weeks, i.e., a 30 percent decrease in proteoglycan content and a 3-fold increase in collagen. No significant changes were observed thereafter. The extractability of the proteoglycans after treatment with 4 M guanidinium chloride varied drastically, depending upon the age of the animal. Whereas 73 per cent of the proteoglycans was extracted from the neonatal tissue, the yield from old tissue was only 10 per cent. It is suggested that the decrease in extractability with age is related to the increase in collagen content. Cytochemical observations demonstrated that, in the neonatal tissue, metachromatic staining of the matrix was lost after guanidinium chloride treatment, with the exception of chromotropic granules still present in the lacunae. In the 1-month-old animals, a general decrease in the staining reaction ensued, except in the perilacunar areas. In the extracted tissues, instead, the picture changed drastically in that metachromasia was decreased in the interterritory but was not modified, as in the neonatal tissue, in the areas adjacent to the cell nests. In the old tissue, the patchy and irregular staining, typical of the cartilage of this age, was not modified by extraction with the guanidium salt. At the ultrastructural level, the proteoglycans in the neonatal tissue appeared as granules of different size, the largest having dimensions of about 900 A, In the 1-month-old animals, degenerative changes were already observed in the chondrocytes, including loss of the perilacunar space, reduction of the endoplasmic reticulum, and an increase of intracellular glycogen and lipids. The proteoglycan droplets, so prominent at the neonatal stage, were no longer evident. In the older animals, apart from the many foci of mineralization, the chondrocytes were almost all degenerated and showed signs of extensive vacuolation and lipid infiltration.

Aging↗

PubMed1974