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Biomedical subjects

D Herbage

Publications and source records attributed to D Herbage.

At least 91 records · Page 5Linked to original sources
PubMed1982

Composition, cross-linking and thermal stability of bone and skin collagens in patients with osteogenesis imperfecta.

The composition, cross-linking, and thermal stability of the collagens were determined in bone and skin biopsies from 4 patients with moderate to severe forms of osteogenesis imperfecta (OI). The major modification observed with respect to control subjects was an overhydroxylation of lysine in type I bone collagen (hydroxylysine content doubled in three patients and increased by 50% in the last patient). This overhydroxylation is confirmed by a similar increase in the dihydroxylated cross-link of bone collagen: the dehydrodihydroxylysinonorleucine. The type II collagen from cartilage and the pepsin-soluble collagens from the skin of these patients contained the normal amount of hydroxylysine. A small amount of type III collagen has been found in three patients, while only in one patient a slight increase in the type III/type I collagen ratio was observed in skin. In all patients the thermal stability of the collagen triple helix, measured by differential scanning calorimetry, was normal in both bone and skin. Although in at least three patients the clinical features allowed us to classify our patients into two different groups (Sillence et al., 1979 classification--groups I and III), the biochemical results are similar, suggesting that the overhydroxylation of the lysine in type I bone collagen is a common feature of severe forms of osteogenesis imperfecta.

Adolescent↗
PubMed1981

Biochemical characterization of the cuticle collagen of the nematode Caenorhabditis elegans.

Proteins of purified cuticles from adults of the small free-living nematode Caenorhabditis elegans are solubilized by reduction in the presence of a strong denaturing agent and then carboxymethylated. As in the large parasitic nematode Ascaris lumbricoïdes, these soluble proteins appeared to be collagens by their amino acid compositions. C. elegans cuticle collagen is separated into seven major components with different apparent molecular weights by molecular sieve chromatography and sodium dodecyl sulphate-polyacrylamide gel electrophoresis. The two main components, which together account for more than 64% of the total cuticle collagen, were extracted from gel after electrophoresis and analyzed. They differ in their amino acid compositions and would seem to represent genetically distinct collagen chains. The results presented lead to the hypothesis of the presence in this collagen of at least two different chains.

Amino Acids↗
PubMed1980

Cockroach collagen: isolation, biochemical and biophysical characterization.

Collagen fibrils from the mesenteric connective sheath of the adult cockroach Periplaneta americana were extracted by enzymatic digestion with pepsin and were purified. Chromatographic studies and sodium dodecylsulfate electrophoresis revealed the presence of a single chain. It was demonstrated that the structure of this collagen could be represented by the formula (alpha)3. The amino acid composition is typical of collagens (one-third glycine, and a high imino acid content) and similar to that of type II. The carbohydrate content was high (8.8%), and the cyanogen bromide pattern was different from that of known collagens. The chains were linked by the stable intermolecular bond dihydroxylysinonorleucine. The banding patterns of the segment-long-spacing crystallites and of the reconstituted fibrils were similar to type I collagen. The molecular weight (Mr 280,000) and length (285 nm) were typical, but the denaturation temperature was high (38.5 degrees C). It was concluded that cockroach mesenteric collagen showed the characteristic features of invertebrate mesodermal collagens, except that of the thermal stability of the triple-helical structure.

Amino Acids↗
PubMed1980

Collagen immunotyping in human liver: light and electron microscope study.

Types I, III, IV, and AB collagens have been extracted from human cirrhotic livers and specific antibodies have been raised in rabbits and purified. Histological immunofluorescent staining of collagen types in normal and fibrotic human livers reveals the respective distribution of the various collagens among the hepatic connective matrix and the modification of the normal pattern in fibrosis: types I and III appear to be the main components of the fibrotic connective matrix in enlarged portal spaces and of the Dissian reticulin framework; type IV collagen deposits are thickened around portal vessels and ducts and outline lobular capillarized sinusoids; type AB collagen appears as thin punctual deposits in portal and Dissian fibrotic connective matrix. Ultrastructural immunoperoxidase labeling of type I and III collagen makes it possible to identify the typical collagen fibers, using 65 nm periodicity, as type I collagen and the fibrillar associated network as type III collagen. Fibers of type I collagen are preferentially organized in large dense bundles in Dense Connective Matrix Organization (DCMO), since fibrillar type III collagen network is predominant in Loose Connective Matrix Organization (LCMO) surrounding vascular and biliary tracts.

Collagen↗
PubMed1978

Intermolecular interaction studies on native and enzyme-treated acid-soluble collagen.

The aggregative properties of acid-soluble collagen, native or enzyme treated, have been studied by electric birefringence and low shear rate viscosity. A unique type of aggregate has been found, about 700 nm long for native collagen and 530 nm for pepsin treated, regardless of the acetic acid concentration in the range 1--100 mM. The number of aggregates increases with collagen concentrations, as could be expected for electrostatic interactions. On the contrary, pepsin-extracted cartilage collagen forms aggregates of covalent nature, the number of which is independent of concentration. Viscosity measurements show two different interaction mechanisms: a short distance one which can be identified with the electric birefringence-detected aggregation, and a long distance superstructure which disappears when salt is added to the solution.

Acetates↗
PubMed1977

Biochemical and physiochemical characterization of pepsin-solubilized type-II collagen from bovine articular cartilage.

Solubilization of collagen from bovine articular with pepsin requires the preliminary extraction of proteoglycans from the ground substance. Biochemical and physiochemical properties of this pepsin-solubilized collagen are independent of the pretreatment (extraction with 1.5M-CaCl2, 5M-guanidinium chloride or 0.2M-NaOH) and of the age range (2-4-year-old and 2-month-old animals). Characterization of the de-natured components, of the CNBr peptides and of the amino acid and cross-link composition shows that the collagen of the hyaline cartilage is all type II. Electrical birefringence measurements showed the presence of tropocollagen molecules (length 280nm) and molecules whose length is slightly less than twice that of the tropocollagen molecules. This latter molecule may be a dimer composed of two monomers linked by intermolecular head-to-tail bonds and whose theoretical length (530nm), according to the quarter-stagger theory, is in good agreement with our measured values (510-530nm). We have verified that the beta-components of this collagen are formed of two alpha-chains linked by the stable intermolecular bond, dehydrodihydroxylysinonorleucine. These dimeric molecules are absent from solutions of skin collagen whose beta-components possess only aldol-type intramolecular cross-links. Although reconstituted fibres from solutions of skin and cartilage collagen are similar, the segment-long spacing crystallites formed with pepsin-solubilized cartilage collagen present a symmetrical and dimeric form corresponding to the lateral aggregation of two monomers with an overlap (90nm) of the C-terminal ends.

Amino Acids↗
PubMed1976

Collagen heterogeneity in pig heart valves.

For the first time, it has been possible to solubilize a significant amount of heart valve collagen from 6 month old pigs by pepsin treatment. Chromatographic and electrophoretic analysis of this pepsin-soluble collagen gives evidence for the presence of two types of collagen molecules: type I collagen and another type which has properties similar to those of type III collagen. For example, this collagen, present as a gamma component, gives rise, when reduced by dithiothreitol, to two bands by SDS-acrylamide gel electrophoresis: a beta band and an alpha band. Furthermore, the collagenic web of this tissue is highly polymerized, which explains the inability to solubilize all of the collagen molecules and the presence of high-molecular-weight molecules in the pepsin-soluble fractions.

Animals↗
PubMed1976

High-angle electron diffraction of frozen hydrated collagen.

By using the techniques developed by Taylor et al. [(1975) J. Mol. Biol. 92, 165-167] (freezing of the hydrated specimen before its insertion into the electron microscope and keeping it frozen throughout the diffraction experiment), it was possible to obtain a high-angle electron-diffraction pattern from collagen fibrils. This pattern is in good agreement with that obtained by high-angle X-ray diffraction. Electron diffraction will be very useful to study collagen, because the diffraction pattern from a carefully selected area of one fibril is now feasible.

Animals↗