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Biomedical subjects

D Volpin

Publications and source records attributed to D Volpin.

At least 55 records · Page 3Linked to original sources
PubMed1979

X-ray diffraction study of bovine lens capsule collagen.

The wide angle X-ray diffraction pattern of air-dried lens capsule collagen under tension is the same as the tendon collagen diffraction pattern with regard to the main reflections, and indicates that lens capsule collagen has the characteristic three-stranded helical structure with an axial repeat of 0.29 nm as tendon collagen. The low angle X-ray diffraction pattern shows several weak diffraction maxima corresponding to the meridional reflections of capsule collagen which show orders of 63.0 nm periodicity. This is an evidence of quarter staggered molecular assembly typical of tendon collagen even if less ordered. The results are consistent with the existence in lens capsule collagen of clearly defined molecular units, which can be oriented by stress and are packed in a poor-ordered fibrillar assembly.

Animals↗
PubMed1978

Structural organization of collagen fibrils in media aortic wall.

Small-angle X-ray diffraction patterns of bovine, human and porcine media aortic wall show meridional reflections corresponding to a periodicity which suggest a molecular packing typical of tendon collagen. However the meridional intensity distribution of stretched air dried aortic samples appears different from that of air-dried tendon, probably because of the presence of a large amount of type III collagen with the environment, which are specific for aortic tissue. The stretched wet aortic samples show a marked decrease in intensity, revealing an extensive disorder in the axially-projected structure of the fibrils. When a loading system simulating the effect of blood pressure is applied to a ring of aorta, no evidence of orientation of collagen is seen by X-ray diffraction, as would be expected if collagen fibrils had an isotropic distribution inside the aorta media. Scanning electroni microscopy supports the existence of a network of collagen fibrils surrounding elastic lamellae.

Adult↗
PubMed1977

Age-related changes in the reducible cross-links of human dermis collagen.

Samples of normal human dermis of different ages are reduced with tritiated sodium borohydride and changes of major reducible cross-links are compared as a function of chronological age. While lysinorleucine practically remains constant, reduced desmosine changes slightly, hydroxylysinoroleucine and dihydroxylysinonorleucine display a marked decrease with age. An unknown compound is shown to increase with aging. The data suggest a correlation between the change of aldimine cross-links and the structural and/or biochemical changes occurring with increase in age.

Adult↗
PubMed1977

Ultrastructure of elastin coacervates.

Electron micrographs of negatively stained coacervates of supernatant from sonicated-elastin showed the presence of filamentous structure with the center to center distance typical of tropoelastin, synthetic polypentapeptide as in peptide T1 of tropoelastin, and alpha-elastin. Electron micrographs of negatively stained coacervates of the polypentapeptide, alpha-elastin and sonicated elastin exhibit banded fibers when coacervates are formed, stained and dried at temperatures greater than 50 degrees C.

Elastin↗
PubMed1976

Banded figers in high temperature coacervates of elastin peptides.

Electron micrographs of negatively stained coacervates of the synthetic polypentapeptide of propoelastin and of alpha-elastin exhibit banded fibers when the coacervates are formed, stained, and dried at temperatures greater than 50 degrees. This apparent increase in order occurs at the same temperature as an increase in order in aqueous solution and as a change in the volume expansion coefficient of fibrous elastin.

Elastin↗
PubMed1976

Optical diffraction of tropoelastin and alpha-elastin coacervates.

Optical diffraction applied to micrographs of coacervated tropoelastin and alpha-elastin show an equatorial repeat around 50 A. This confirms a 50 A center-to-center distance of parallel aligned filaments to be a fundamental property of the tropoelastin and alpha-elastin coacervates. This periodicity is similar to that of mature cross-linked elastin. These results allow the conclusion that hydrophobic association is the predominant driving force for formation of filamentous elastin in vitro. It is suggested that the coacervate is a model for relaxed fibrous elastin.

Elastin↗
PubMed1975

The extraction of phosphoproteins from bovine dentin.

The phosphoprotein obtained by the neutral pH tris buffer extraction of acetic acid demineralized bovine dentin has been compared with the phosphoprotein extracted directly during the neutral pH EDTA demineralization process. The phosphoproteins isolated by DEAE-cellulose chromatography from the neutral pH EDTA demineralization extract are not identical to those isolated by the same procedure from the dentin which had been subjected to acid demineralization. The two demineralization procedures yield phosphoproteins different in amino acid content and in presence of 260 nm UV absorbing moiety. Even after sequential acid demineralization, trisbuffer extraction and EDTA extraction, the residual dentin contains phosphoprotein. A peptide fragment containing both collagen and phosphoprotein moieties has been isolated following digestion and cleavage of the insoluble dentin collagen with cyanogen bromide. The acid demineralization process appears to be accompanied by degradation which removes both protein and non-protein components from the phosphoprotein.

Acetates↗