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Biomedical subjects

S R Pinnell

Publications and source records attributed to S R Pinnell.

At least 55 records · Page 3Linked to original sources
PubMed1986

Degradation of porcine dermal connective tissue by collagenase and hyaluronidase.

Selective destruction of connective tissue may be a useful therapeutic tool in conditions associated with abnormal deposition of scar tissue. We have investigated intradermal injections of clostridial collagenase and bovine testicular hyaluronidase alone and in combination in Yucatan miniature hairless pigs. Collagenase in combination with hyaluronidase was quite efficient at destroying the connective tissue matrix, although elastic tissue appeared to be completely spared. Collagenase alone at higher doses degraded collagen, but hyaluronidase had little effect on connective tissue architecture.

Animals↗
PubMed1985

A paradoxical effect of hydralazine on prolyl and lysyl hydroxylase activities in cultured human skin fibroblasts.

The effect of hydralazine on several parameters of collagen biosynthesis has been studied in cultured human skin fibroblasts. Cells treated with hydralazine synthesized procollagen which was severely deficient in hydroxyproline and hydroxylysine, indicating inhibition of prolyl and lysyl hydroxylase reactions in the cell. Assays of prolyl and lysyl hydroxylase activities, however, revealed markedly increased levels in hydralazine-treated cells. The stimulatory effect of hydralazine could not be simulated in cell extracts, demonstrating its requirement for intact cells. The effect occurred slowly over a period of 96 h and was dependent on hydralazine concentration between 10 and 100 microM. This phenomenon was also observed in lysyl hydroxylase-deficient mutants. In both normal and mutant cells the relative magnitude of the hydralazine effect could be modified by ascorbic acid in the culture medium. Ascorbic acid increased the response of prolyl hydroxylase to hydralazine from 1.5- to 2-fold to 3- to 7-fold, whereas it decreased the response of lysyl hydroxylase to hydralazine from 4- to 8-fold to 2- to 3-fold. Total collagen synthesis was substantially reduced in hydralazine-treated cells; the time course and the dose-response relationship were similar to those observed for the hydroxylases. alpha, alpha'-Dipyridyl, an iron chelator, mimicked these effects of hydralazine. The studies suggest the existence in cultured cells of a compensatory mechanism for overproduction of these crucial enzymes in collagen biosynthesis, a mechanism which remains functional in cells derived from patients afflicted with hydroxylysine-deficient collagen disease.

Ascorbic Acid↗
PubMed1985

Topical minoxidil in early male pattern baldness.

One-hundred twenty-six healthy men with early male pattern baldness completed a 12-month double-blind, controlled trial of 2% and 3% topical minoxidil. Subjects were initially randomly assigned to use placebo or 2% or 3% topical minoxidil. After 4 months of study, the placebo group was crossed over to 3% topical minoxidil. Both objective measurement of hair growth by counting of vellus, terminal, and total hairs in a vertex target balding area and subjective assessment by subject and investigator were done. Treatment of subjects with topical minoxidil for 4 months resulted in a statistically significant increase in terminal hair growth in comparison with placebo therapy. In addition, subjects initially treated with placebo, when crossed over to topical minoxidil, showed a significant increase in the number of terminal hairs. No subject had a net hair loss in the target area during the study. These results indicate that topical minoxidil can increase terminal hair growth in early male pattern baldness.

Administration, Topical↗
PubMed1985

Serum stimulation of lysyl hydroxylase activity in cultured human skin fibroblasts.

In the absence of ascorbic acid, confluent human skin fibroblasts incubated in 0.5% serum-supplemented medium had one-third of the level of lysyl hydroxylase activity of cells incubated in media containing high serum concentrations (5-20%). This difference appeared to be due to a decline in the enzyme activity following serum deficiency, and was largely abolished by addition of ascorbic acid to the medium. The effect of serum deficiency was slow, manifesting in 48 h at the earliest, and was completely reversed by replenishing the medium with serum. Prolyl hydroxylase activity was independent of serum concentration, both in the absence and in the presence of ascorbic acid in the culture medium.

Blood↗
PubMed1984

Isolation and characterization of a human pro alpha 2(I) collagen gene segment.

Over 20 kilobase pairs of the human pro alpha 2(I) collagen gene have been isolated and characterized by restriction endonuclease mapping, cell-free translation of hybrid-selected RNA, and DNA sequence analysis. We have sequenced an exon and determined its length to be 108 base pairs (bp). This is consistent with the organization of chick and sheep collagen genes in that exons are multiples of 9 bp in length, frequently being 54 and 108 bp. The sequenced exon was bordered by a GT (guanine-thymine) at its 3' end and an AT (adenine-thymine) at its 5' end. This pattern has been found at all normal intron-exon junctions in eukaryotic cells. The amino acid sequence derived from DNA sequencing of this 108 bp exon revealed 88% homology compared to the amino acid sequence of bovine pro alpha 2(I). The bases encoded 12 Gly-X-Y triplets characteristic of the helical portion of collagen. A unique sequence Gly-Gly-Lys-Gly-Glu-Lys identified this fragment as alpha 2(I) collagen.

Amino Acid Sequence↗
PubMed1983

A comparison of lysyl hydroxylation in various types of collagen from type VI Ehlers-Danlos syndrome fibroblasts.

Type I, type III, and type V collagens were isolated from type VI Ehlers-Danlos syndrome fibroblasts. Five different alpha chains were separated and their degrees of prolyl and lysyl hydroxylations were determined. Lysyl hydroxylation in all collagen types was low in the mutant fibroblasts compared to age-matched controls, with no significant change in prolyl hydroxylation. The degrees of lysyl hydroxylation in type I, type III, and type V collagens were 52%, 73%, and 76% of controls, respectively.

Adult↗
PubMed1983

Collagen synthesis in cultured human skin fibroblasts: effect of ascorbic acid and its analogs.

In confluent human skin fibroblasts maintained in 0.5% serum-supplemented medium. L-ascorbate specifically stimulated the rate of incorporation of labeled proline into total collagenase-sensitive protein, without changing the specific activity of the intracellular free proline. This influence of ascorbate reached a maximum at 30 microM and continued for at least 4 days, resulting in a 4-fold increase. The ascorbate effect occurred in cells at both confluent and subconfluent densities and was evident at all serum concentrations from 0.5-20%. The effect was independent of duration of the radioactive pulse between 2-6 h. D-Ascorbate, D-isoascorbate, and L-dehydroascorbate also stimulated collagen synthesis but at considerably higher concentrations, i.e., 250-300 microM. The stimulation of collagen synthesis by ascorbate and its analogs was accompanied by a decline in prolyl hydroxylase activity and a rise in lysyl hydroxylase activity; again L-ascorbate was found to be most effective. Dimethyltetrahydropterine and L-lactate failed to produce these effects.

Ascorbic Acid↗
PubMed1982

Regulation of collagen synthesis.

Collagen synthesis is a complex orchestration of intracellular and extracellular events. In addition to synthesis of the polypeptide chains more than a dozen modifications of the molecule occur; most of these are enzymatic and specific for collagen. Regulational control of collagen synthesis promises to be equally complex. Examples are described to 4 specific regulatory influences. Ascorbic acid markedly stimulates collagen synthesis without affecting synthesis of other proteins. This effect appears to be unrelated to its cofactor roles for hydroxylation of lysine and proline. Glucocorticoids at microM concentration specifically inhibit collagen synthesis. Tissues treated with glucocorticoids have diminished levels of mRNA for collagen. During collagen synthesis the aminoterminal propeptide of procollagen is cleaved by a specific protease. This peptide appears to be a feedback inhibitor of collagen synthesis. This effect can be demonstrated in cells and in cell-free synthesizing systems. A membrane receptor system may permit the peptide to be recognized and subsequently act as a translational control mechanism. Viral transformation of fibroblasts results in selectively decreased synthesis of collagen. Levels of cytoplasmic and nuclear mRNA are likewise selectively diminished consistent with transcriptional control.

Animals↗
PubMed1982

Molecular defects in the Ehlers-Danlos syndrome.

Several abnormalities in collagen biosynthesis have been described in patients with Ehlers-Danlos syndrome. Examples of collagen structural mutations as well as post-translational enzymatic defects have been detected. Patients with hydroxylysine-deficient collagen disease (Ehlers-Danlos type VI) have diminished lysyl hydroxylase activity. One mutant enzyme has been characterized which is thermally labile and had an altered affinity for ascorbate. Another mutant enzyme had a normal requirement for cofactors but activity was diminished. Type VII Ehlers-Danlos syndrome is associated with altered processing of procollagen to collagen. Most often the disorder is associated with deficient procollagen aminoprotease activity. One patient appears to represent a structural mutation of pro alpha 2 (I) resulting in incomplete cleavage of the amino terminal propeptide. One family with x-linked Ehlers-Danlos syndrome (type V) has been described with altered lysyl oxidase activity. Other patients with this disorder have had normal lysyl oxidase activity. The ecchymotic form of Ehlers-Danlos syndrome (type IV) has defective type III collagen-synthesis. Patients have been described with absent synthesis, diminished synthesis and diminished secretion.

Collagen↗
PubMed1982

The structure and function of dermal connective tissue in normal individuals and patients with inherited connective tissue disorders.

Normal, human dermis is a dense, interwoven collagen and elastic matrix organized into papillary and reticular regions. the papillary dermis is a narrow zone beneath the epidermis which includes an even narrower subepidermal connective tissue band beneath the basal lamina. The reticular dermis has superficial intermediate and deep reticular zones. Each region is distinguished by the organization of the fibrous connective tissue. In this review, the structure, composition and function of each region of the normal dermis is surveyed and alterations in the tissue that have been recognized ultrastructurally in skin from patients with inherited connective tissue diseases are discussed. A molecular defect in a connective tissue molecule can be expressed phenotypically at one or more levels of dermal organization and can modify the structure of other matrix components. In some cases, the entire interwoven pattern of the dermis is altered; in others, the dermis retains the interwoven pattern and alterations are expressed as defects in the association of fibrils into fibers and fiber bundles. Abnormalities in the size, packing and relationships of fiber bundles also can occur. These changes involve the collagen matrix primarily. Depletion or exaggeration of elastin, or of the amorphous ground substance can also influence the organization of collagen and of the overall dermal architecture. The alterations described are illustrated with scanning electron micrographs of skin from patients with inherited connective disorders and are discussed in terms of the mechanical abnormalities of the tissue.

Collagen↗
PubMed1981

Keloids: a review.

Keloids are predominantly fibrous tumors which appear as firm, variably pruritic or tender growths near a site of injury. Usually appearing between the ages of 10 and 30, most keloids are located on the upper back, shoulders, earlobes, and anterior portion of the chest. The etiology remains unknown, but the accumulated fibrous tissue is associated with increased cellularity and increased metabolic activity of keloid fibroblasts. Isolated keloid fibroblasts demonstrate normal growth characteristics along with increased collagen and proteoglycan synthesis. Numerous keloid treatments have been attempted, but variable success has followed either single use or combinations of intralesional corticosteroid injection, surgery, pressure devices, radiation, cryosurgery, and systemic chemotherapy.

Adolescent↗
PubMed1981

Regulation of collagen synthesis by ascorbic acid.

After prolonged exposure to ascorbate, collagen synthesis in cultured human skin fibroblasts increased approximately 8-fold with no significant change in synthesis of noncollagen protein. This effect of ascorbate appears to be unrelated to its cofactor function in collagen hydroxylation. The collagenous protein secreted in the absence of added ascorbate was normal in hydroxylysine but was mildly deficient in hydroxyproline. In parallel experiments, lysine hydroxylase (peptidyllysine, 2-oxoglutarate:oxygen 5-oxidoreductase, EC 1.14.11.4) activity increased 3-fold in response to ascorbate administration whereas proline hydroxylase (prolyl-glycyl-peptide, 2-oxoglutarate:oxygen oxidoreductase, EC 1.14.11.2) activity decreased considerably. These results suggest that collage polypeptide synthesis, posttranslational hydroxylations, and activities of the two hydroxylases are independently regulated by ascorbate.

Ascorbic Acid↗
PubMed1981

Collagen synthesis by human skin fibroblasts in culture: studies of fibroblasts explanted from papillary and reticular dermis.

Matched human skin fibroblast cultures were established from papillary and reticular dermis. Papillary dermal fibroblasts exhibited increased plating efficiency, exponential growth, and confluent density when compared with their matched reticular dermal cultures. Collagen synthesis by these cells, however, was essentially similar regardless of their origin. Relative collagen synthesis was similar at confluent densities. No differences in type specific collagen synthesis could be detected; relative amounts of types I and III collagens in culture media and types I, III, and AB collagens in the cellular pellet were similar. Type I pC collagen was consistently elevated in culture media from reticular dermal fibroblasts when compared to papillary dermal fibroblasts. The significance of this difference in procollagen processing is unknown.

Adult↗
PubMed1980

A familial cutis laxa syndrome with ultrastructural abnormalities of collagen and elastin.

A familial cutis laxa syndrome is reported in a mother and son. In addition, the son had Klippel-Tranaunay-Weber syndrome, which may be related to his underlying disorder. Ultrastructural examination of skin revealed previously recognized abnormalities of elastic tissue. In addition, abnormalities in collagen structure are demonstrated. The underlying defect in this disorder appears to result in abnormalities in both elastic tissue and collagen structure.

Adolescent↗
PubMed1980

Prolyl and lysyl hydroxylase activities of human skin fibroblasts: effect of donor age and ascorbate.

Prolyl and lysyl hydroxylase activities in cultures of human skin fibroblasts from fetal to 94-yr-old donors were measured. In contrast to earlier studies with whole skin, neither prolyl nor lysyl hydroxylase activity was found related to donor age. Prolyl hydroxylase activity increased 3- to 6-fold when cell extracts were incubated with ascorbate and other hydroxylation cofactors before assay. A similar increase in prolyl hydroxylase activity occurred when cells were incubated with ascorbate. Lysyl hydroxylase activity remained unaltered under these conditions.

Adolescent↗