Search PubMed⌕ Search

Biomedical subjects

R L Trelstad

Publications and source records attributed to R L Trelstad.

At least 55 records · Page 3Linked to original sources
PubMed1982

Type I collagen segment long spacing banding patterns. Evidence that the alpha 2 chain is in the reference or A position.

Densitometric scans of electron micrographs of type I collagen segment long spacing crystallites stained with uranyl acetate or phosphotungstic acid and uranyl acetate have been correlated with computer-synthesized scans derived from the sequence of the alpha 1(I) and alpha 2 chains. Three models that differ in the location of the alpha 2 chain were used in the computer synthesis; Models A, B, and C have the alpha 2 chain in the A, B, and C chain positions, respectively. For all 13 experimental scans, the order of decreasing correlation with the models was found to be A,B,C. The probability of getting the same order of decreasing correlation all 13 times is 6/6(13). It was also determined at the 0.99 confidence level that the mean of the differences in the correlation coefficients among the models is greater than 0, supporting the conclusion that sequence-derived models best fit the experimental data when the alpha 2 chain is in the A position. Our results also agree with recent studies that show that uranyl ions bind to both positively and negatively charged residues on collagen type I.

Animals↗
PubMed1982

Glutamate-induced cellular injury in isolated chick embryo retina: Müller cell localization of initial effects.

The neurotoxic and gliotoxic effects of glutamate and several glutamate analogues were studied in isolated chick embryo retinas. To facilitate examination of initial pathological events, a short-term incubation system was developed and used for light microscopic and autoradiographic investigation. Low-dose, short-term glutamate treatment of 12-day retinas resulted in a glial-specific lesion in the Müller cells, characterized by extensive cellular edema; at higher concentrations and/or longer treatment times, neurotoxic as well as gliotoxic effects were seen. The early glial damage was identical in appearance to that seen after incubation with DL-alpha-aminoadipate and other reported gliotoxins. No evidence of a similar glial-specific action was seen after administration of kainic acid, although extensive neuronal degeneration did result. Incubation of retinas with tritiated glutamate (3H-glu) revealed a selective uptake of the label by Müller cells. Autoradiographic grains were localized over Müller foot processes at the inner limiting membrane, and by 30 minutes labeled the entire glial system. Prior treatment with neurotoxic levels of glutamate did not alter the autoradiographic localization to glial cells. Possible glial-neuronal interactions and their effect on cytotoxic patterns are discussed.

Animals↗
PubMed1982

Nanophthalmic sclera. Ultrastructural, histochemical, and biochemical observations.

Scleral tissue from two cases of nanophthalmos was examined by amino acid analysis, light microscopy, histochemistry, and transmission electron microscopy. Perifibrillar aggregates, similar to proteoglycans, were prominent in the nanophthalmic sclera. The sclerae were thicker than normal and the bundles of collagen fibrils were less ordered. The clinical features of vortex vein compression seem causally related to the disordered and thickened sclera, which, in turn, may be caused by dysfunctional proteoglycans, or interaction with the scleral collagen, or both.

Adult↗
PubMed1982

Omphalocele and multiple severe congenital anomalies associated with osteodysplasty (Melnick-Needles syndrome).

Osteodysplasty (Melnick-Needles syndrome, MNS), a severe bone dysplasia with presumed autosomal dominant inheritance, has now been described in 24 individuals, with a predominance of females (21:3). We report an affected woman who gave birth to a male infant with omphalocele, hypoplastic kidneys, and the skeletal changes of this disorder; he died soon after birth. Histologic studies of the calvaria and long bones showed normal maturational sequences, but suggest that remodeling was not normal. This is the second known instance of a male infant with omphalocele and this skeletal dysplasia born to a woman with MNS. We suggest that the gene for the MNS may also cause a syndrome of multiple abnormalities that can be lethal and that this more severe phenotype in males may account for the altered sex ratio among reported cases. Both X-linked dominant and autosomal-dominant sex-limited inheritance are feasible interpretations of the existing information.

Abnormalities, Multiple↗
PubMed1982

Age-dependent effects of glutamate on photoreceptor cells of the isolated chick embryo retina.

Neurotoxic and gliotoxic effects of glutamate were studied in isolated chick embryo retinas of various ages. Employing a short-term incubation system, we found that initial cellular changes in retinas from 15- and 21-day chick embryos were localized to glial Müller cells as previously shown in retinas from 12-day embryos. In the older retinas, however, an additional selective lesion was consistently found in the presumptive photoreceptor cells. Similar photoreceptor damage was not seen in 12-day retinas, even after treatment with relatively high glutamate doses. Autoradiographic uptake of tritiated glutamate in retinas at 12 and 14 days was localized to the glial Müller cells; in the 14-day retinas, however, there was also uptake of the labeled amino acid into the developing inner segments. Uptake of tritiated glutamate in retinas at younger (8-day) and older (21-day) ages did not show any obvious localization of the label.

Age Factors↗
PubMed1982

Collagen fibrillogenesis in tissues, in a solution and from modeling: a synthesis.

Collagen fibril formation has been studied in tissues by light and electron microscopy; in solution by light scattering and microscopy; and from modeling based on the amino acid sequence of type I collagen. Taken together these studies indicate that collagen fibril assembly involves a stepwise formation of intermediate aggregates in which each intermediate is formed from earlier aggregates. In this sequence, monomeric collagen contributes only to the formation of early aggregates; and fibrils grow in length by the addition of intermediate aggregates to the end of a subfibril and in width by lateral wrapping of subfibrils. Modeling based on amino acid sequence data of possible intermolecular charge-charge interactions indicate 2 different kinds, one which promotes linear aggregation and the other which promotes linear aggregation. The effects of different collagens and coprecipitants such as glycoproteins and proteoglycans can begin to be explained by their influence on the character of intermediate subassemblies. Ultrastructural data from 2 tissues, embryonic cornea and tendon, indicate that the site of fibril growth and assembly is at the cell surface.

Animals↗
PubMed1981

Nonenzymatic hydroxylations of proline and lysine by reduced oxygen derivatives.

The biosynthesis of trans-3- and trans-4-hydroxyprolines and 5-hydroxylysine in animal cells requires polypeptide proline or lysine, enzymes and cofactors including iron, and possibly involves peroxidatic intermediates. Several laboratories have reported the presence of low-molecular-weight hydroxyproline and hydroxylysine peptides in cell and organ cultures. We found that these small peptides contained the trans-3 and cis-4 isomers of hydroxyproline as well as trans-4 ones and that their production was not completely inhibited by alpha, alpha-dipyridyl, and iron chelator and effective inhibitor of enzyme-mediated hydroxylations. It is known that oxygen or hydrogen peroxide in the presence of metal can hydroxylate proline and other aromatic compounds. We show here that reduced oxygen derivatives can hydroxylate both free and polypeptide-bound proline and lysine, and that scavengers of hydroxyl radicals suppress, but do not completely inhibit, this reaction. Reduced oxygen derivatives can be generated in normal and pathological circumstances, and some of the low-molecular-weight hydroxyproline and hydroxylysine peptides found in cell and organ cultures might be derived from these derivatives and therefore do not reflect collagen turnover, but rather some other cellular activity.

Free Radicals↗
PubMed1981

Type V collagen from the chick embryo: biochemical, physicochemical and ultrastructural characteristics.

Two collagen alpha chains have been isolated from whole 17 day chick embryos which are similar to the B chain or alpha 1(V) and the A chain or alpha 2(V) recently described in mammalian and avian tissues. A non-collagenous acidic protein was co-purified with the Type V collagen which was resistant to pepsin digestion. The molecular weight, circular dichroism spectrum, melting temperature and diffusion coefficient of the native Type V collagen and isolated alpha chains were similar to values obtained for other chick collagen types. The SLS crystallite of Type V collagen had a distinct pattern of banding as identified by electron microscopy. We consistently observed more alpha 2(V) than alpha 1(V) following both CM-cellulose and QAE-Sephadex ion exchange chromatography of denatured Type V collagen, but unusual solubility properties and recoveries of the alpha 1(V) chain may have diminished its relative amount. In addition we have found that the alpha 1(V) chains are chemically heterogeneous and one component electrophoreses as an alpha 2(V) chain on SDS gels.

Animals↗
PubMed1980

Type I collagen in solution. Structure and properties of fibril fragments.

We have measured the diffusion coefficient and weight average molecular weight of type I collagen fibril fragments obtained by acid extraction of rat tail tendons and neutral extraction of lathyritic chick skin, using laser light scatttering techniques. The molecular weight and translational diffusion coefficient were found to be 8.05 +/- 0.40 x 10(5) and 0.450 +/- 0.04 x 10 (-7) cm2/s, respectively, for preparations which contain aggregates in 0.01 M HCl, and 2.82 +/- 0.20 x 10 (5) and 0.780 +/- 0.04 x 10 (-7) cm(2)/s for collagen single molecules. Using these data, as well as the theoretical diffusion coefficient for a single collagen molecule, models for various staggering modes and aggregate mixtures were developed in an attempt to understand the structure of the fibril components present in solution. It was found that several models with 1 to 4 D (D = 67 nm) staggers fit the experimental data for the aggregated preparations. Analysis of the end-to-end distance of negatively stained segment long spacing crystallites prepared from solutions containing fibril fragments and the banding pattern of positively stained segment long spacing crystallites suggest that collagen solutions contain linear aggregates with 4 D and possibly 4.4 D staggers in agreement with light scattering data. Thermal denaturation studies demonstrate that the apparent melting point of cross-linked linear aggregates, 33.5 +/- 0.5 degrees C, is identical with that of single molecules at pH 2.0. We conclude that a linear filament with predominant 4 D stagger is a basic unit of type I collagen fibrillar structure.

Animals↗
PubMed1980

Biochemical characterization of collagens synthesized by intestinal epithelial cell cultures.

Rat intestinal epithelial cells in culture synthesize and secrete several different collagens as identified by biochemical and ultrastructural criteria. These collagens were labeled with [U-14C]proline, separated by DEAE- and CM-cellulose chromatography, and at least four different collagen chains were identified. Two of them, present almost exclusively as fully processed collagens, were alpha 1(I) and alpha 2 chains. The presence of a large excess of alpha 1 (I) chains over the normal ratio for type I collagen indicated that both type I collagen [alpha 1(I)]2 alpha 2 and [alpha 1(I)]3 or type I trimer were present both in the culture medium and in the extracellular matrix. The labeled alpha 1(I) chain had a CNBr peptide pattern superimposable on that of a standard alpha 1(I) chain from rat skin, but the intact radiolabeled chain differed from the standard in its migration on sodium dodecyl sulfate gels and elution position on CM-cellulose column and had a much higher hydroxylysine content. The other two collagen chains were present in the culture medium exclusively as partially processed procollagens. They constituted 60 to 70% of the collagenous proteins and had features corresponding to none of the known collagen types. They were separated by CM-cellulose chromatography and further characterized. Both contained interchain disulfide bonds in the pepsin-resistant portion of the molecule and, after pepsin digestion, eluted from CM-cellulose at lower salt concentrations than standard alpha 1(I) chain. One of them was characterized by a low hydroxyproline content and a high hydroxylysine content, with all the hydroxylysine present as glycosylgalactosyl derivative. The CNBr peptide patterns of these two unknown chains differed from each other, and did not correspond to those of any standard collagen chain examined. They may represent new collagen types specifically present in the intestinal basement membrane.

Animals↗