Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

---

Query: T20B12 .5
956,342 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Human endothelial cell monolayers prepared from umbilical veins have been incubated with aspirin (1--2 mM) dissolved in Hepes modified solution and in platelet-rich plasma. They have also been incubated with plasma prepared from subjects before and after intake of aspirin giving a mean plasma concentration of 0.5 mM. The effects of the endothelial cells on ADP and collagen-induced platelet aggregation and malondialdehyde production in platelet-rich plasma have been tested. The endothelial cells had a spontaneous inhibitory effect on all three parameters. This effect was abolished when the cells were incubated with aspirin dissolved in MHS for 20 min and the increase in effect observed when platelet-rich plasma was incubated with endothelial cells for a period of 30 min was similarly inhibited when aspirin was dissolved in plasma or when plasma prepared from subjects who had taken aspirin were used. Aspirin had no inhibitory effect on prostacyclin (PGI2) with regard to the effect of PGI2 on platelets. On the contrary, the two compounds had an additive inhibitory effect on platelet aggregation induced by ADP and collagen. These findings should be considered with regard to the use of aspirin as an antithrombotic agent.
...
PMID:The inhibitory effect of aspirin on human endothelial cells. 36 62

Cloned bovine endothelial cells were grown on a preformed layer of cultured rat smooth muscle cells that contained large amounts of connective tissue proteins. The successful growth of the endothelial cells was dependent upon the addition of more than 2.5 x 10(4) cells per cm2, and the final density reached was approximately 2.5 times higher than that obtained for the same cells growing on plastic. The endothelial cells anchored more firmly to the smooth muscle cells than to plastic, and electron microscopy showed the existence of an irregular, dense, basal lamina-like structure between the two cell types. Biochemical analysis of the lamina produced by the endothelial cells in isolation demonstrated the presence of collagen and two fucosylated glycoproteins. The structure produced, which has some of the characteristics of a blood vessel wall, was stable for several months in culture and has many potential applications.
...
PMID:Construction of an artificial blood vessel wall from cultured endothelial and smooth muscle cells. 37 89

A combination of dodecylsulphate/polyacrylamide gel electrophoresis and fluorography has been used to quantify the synthesis of type I and type III collagens by periodontal ligament in situ and periodontal-ligament fibroblasts in vitro. The separation of 14C-labelled collagen alpha chains was achieved by introducing an interrupted reduction step, and the total radioactivity in the alpha-chain bands related to the fluorographic response by a series of standard curves. From these curves an accurate assessment of the relative amounts of type I and III collagen synthesized could be made. The same system also allowed the synthesis and processing of the respective procollagens to be analyzed. For the study in vivo, 200-g male rats were injected with 2 mCi [14C]glycine and killed 0.5-6 h later. Periodontal ligament was dissected from the mandibular molars and the newly-synthesized collagens extracted with 0.45 M sodium chloride. In the study in vitro, confluent monkey periodontal-ligament fibroblasts were cultured in the presence of [14C]proline and [14C]glycine. Analysis of labelled collagens showed a rapid conversion of type I procollagen to collagen but type III collagen was recovered as a procollagen intermediate both in vitro and in vivo. Analysis of duplicate samples after pepsin digestion showed type III collagen synthesis to comprise 15% of the total collagen synthesized in vivo and 20% in early subcultures in vitro. However, the proportion of type III synthesized by the fibroblasts decreased on subculturing. The data demonstrate that fibroblasts in vitro retain the basic characteristics of collagen synthesis and procollagen processing found in vivo, but the overall phenotypic expression of the cells is not stable in culture.
...
PMID:Procollagen synthesis and processing in periodontal ligament in vivo and in vitro. A comparative study using slab-gel fluorography. 38 26

Alveoli and ducts isolated from virgin rat mammary glands synthesize basement membrane collagen (typeIV) in primary culture. Using purified antibodies to type IV collagen, prominent intracellular and extracellular fluorescence is observed in the epithelium. No fluorescence is observed with antibodies to collagen type I and III. From quantitation of the incorporation of [14c]proline-labeled proteins, 1.5 to 2.5 per cent of the newly synthesized proteins are collagen. Type IV collagen from these cultures was biochemically identified on the basis of (1) the high ratio of labeled 3-hydroxyproline to 4-hydroxyproline (1:10), (2) the gel electrophoretic pattern of the collagenase-sensitive proteins precipitated with 1.7 M NaCl, (3)the failure of the collagen to bind to diethylaminoethyl-cellulose, and(4)the immunologic cross-reactivity with mouse tumor type IV is identical with that of type IV collagen from other sources. When the supportive hormones, insulin, prolactin, hydrocortisone, progesterone, and estradiol are removed from the cultures, there is a 90 per cent reduction in the amount of [3H]proline recovered in collagen synthesis coincides with only a 30 percentdrop in the growht rate and a 20 per cent drop in total protein synthesis of the sells over the 24-hour period without hormones. Pulse-chase experimout hormones. Pulse-chase experiments revealed an enhanced turnover of collagen following hormone withdrawal. This system may be an in vitro model of collagen turnover in mammary gland in involution.
...
PMID:Hormonal requirements for basement membrane collagen deposition by cultured rat mammary epithelium. 39 Feb 39

Endothelial cells isolated from bovine aorta synthesize and secrete type III procollagen in culture. The procollagen, which represents the major collagenous protein in culture medium, was specifically precipitated by antibodies to bovine type III procollagen and was purified by diethyl-aminoethylcellulose chromatography. Unequivocal identification of the pepsin-treated collagen was made by direct comparison with type III collagen isolated by pepsin digestion of bovine skin, utilizing peptide cleavage patterns generated by vertebrate collagenase, CNBr, and mast cell protease. The type III collagen was hydroxylated to a high degree, having a hydroxyproline/proline ratio of 1.5:1.0. Pulse-chase studies indicated that the procollagen was not processed to procollagen intermediates or to collagen. Pepsin treatment of cell layers, followed by salt fractionation at acidic and neutral pH, produced several components which were sensitive to bacterial collagenase and which comigrated on sodium dodecyl sulfate-polyacrylamide gel electrophoresis with alpha A, alpha B, and type IV collagen chains purified from human placenta by similar techniques. Bovine aortic endothelial cells also secreted fibronectin and a bacterial collagenase-insensitive glycoprotein which, after reduction, had a molecular weight of 135,000 on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (using procollagen molecular weight standards) and which was not precipitable by antibodies to cold-insoluble globulin or to alpha 2-macroglobulin. Collagen biosynthesis by these cells provides an interesting model system for studying the polarity of protein secretion and the attachment of cells to an extracellular matrix. The presence of type III collagen in the subendothelium and the specific interaction of this protein with fibronectin and platelets suggest the involvement of this collagen in thrombus formation following endothelial cell injury.
...
PMID:Collagen synthesis by bovine aortic endothelial cells in culture. 39 Dec 67

Urimary excretion of hydroxyprolin (Hyp) is one index of total collagen degradation, from all sources. Since some of the Hyp released from collagen may be further metabolized before it is excreted, other markers are necessary to measure collagen breakdown. Excretion of the glycosides of hydroxylysine (Hyl), glucosyl galactosyl hydroxylysine (Hy1[Gl)cGa1]), and galactosyl hydroxylysine (Hyl[Ga)]), more accurately reflects collagen metabolism since these products occur in specificratios in different tissue collagens and are themselves metabolized only to a minor degree. The ratios of total Hy1/Hyp and Hyl(GlcGal)/Hyl(Ga1) were measured in the urine of norma. subjects and of patients with Paget's disease of bone, hyperphosphatasia, and extensive thermal burns. In patients with extensive thermal burns the pattern of urinary Hy1 and its glycosides was consistent with degradation of collagen in dermis and fascia. When bone collagen degradation was dominant, the pattern of urinary metabolites reflected that source. Pagetic bone collagen has an amino acid composition similar to normal bone and Hy1(G1cGa1/Hyl(G1) of 0.396-0.743,vs. normal of 0.474+/-0.088. In untreated patients with severe Paget's disease of bone or hyperphosphatasia (urinary Hyp greater than 2.0 micronmol/mg creatinine) urinary Hyl/Hyp averaged 0.052+/-0.042 (0.042+/-0.009 in normal bone) and Hy1(G1cGa1)/Hy1(Ga1) 0.601+/-0.017 (0.47+/-0.009 in normal bone). When bone resorption was decreased sufficiently with calcitonin or disodium etidronate in these patients, both the urinary ratios of Hy1/Hyp and Hy1(G1cGa1)/Hyl(Gal) rose. In normal subjects treated with calcitonin and excreting relatively little Hyp, the ratio of Hy1/H)P approached 0.7 and Hy1(G1ycGa1)/Hy1(Ga1) approached 3.5. There increased ratios reveal the existence of a source of collagen breakdown other than skin or bone. The first subcompoent of complement, Clq, which has collagen-like sequences, relatively high amounts of Hy1, and most of the glycosylated Hy1 as Hy1(G1cGa1), could be the source of these metabolites.
...
PMID:Urinary excretion of hydroxylysine and its glycosides as an index of collagen degradation. 40 21

Homogentisic acid inhibits the in vitro activity of chick embryo lysyl hydroxylase, a microsomal enzyme which catalyzes the transformation of certain lysyl residues in collagen to hydroxylysine. Chick embryo lysyl hydroxylase activity was measured as specific tritium release as tritium water from a [4,5-(3)H]lysine-labeled unhydroxylated collagen substrate prepared from chick calvaria. Kinetic studies revealed a linear, noncompetitive type of inhibition with respect to collagen substrate with a Ki of 120-180 muM. The inhibition by homogentisic acid was reversible in that enzyme activity could be restored after dialysis of preincubated mixtures of homogentisic acid with enzyme or substrate. The inhibition by homogentisic acid was competitive with respect to ascorbic acid, and the addition of reducing agents, such as ascorbic acid or 1,4-dithiothreitol, protected lysyl hydroxylase activity from homogentisic acid inhibition.In organ cultures of embryonic chick calvaria, biosynthesis of hydroxylysine-derived intermolecular collagen cross-links was inhibited in a dose-dependent manner by 0.5-5 mM homogentisic acid. Because homogentisic acid inhibits the formation of hydroxylysine in a cell-free assay and in organ cultures, this compound must pass into the cells of calvaria to inhibit intracellular hydroxylysine formation and subsequently to diminish the reducible intermolecular cross-links of the newly synthesized collagen. We propose that the inhibition of lysyl hydroxylase and the resulting hydroxylsine-deficient, structurally modified collagen may be clinically significant in the defective connective tissue found in alkaptonuric patients.
...
PMID:In vitro inhibition of chick embryo lysyl hydroxylase by homogentisic acid. A proposed connective tissue defect in alkaptonuria. 40 2

Light and electron microscopic analyses were carried out on the stimulated and unstimulated paravermal cortices of six rhesus monkeys that had electrodes implanted on their cerebella for 2 months. The electrodes and the stimulation regime (10 p.p.s.: 8 min on, 8 min off) were similar to those used to stimulate the human cerebellum for treatment of certain neurological disorders. Mere presence of the electrode array in the posterior fossa for 2 months resulted in some meningeal thickening, attenuation of the molecular layer, and loss of Purkinje cells immediately beneath the electrode array. There was no evidence of scarring. After 205 hours of stimulation (7.35 X 10(6) pulses) over 18 days, a charge of 0.5 muC/ph or estimated charge density of 7.4 muC/sq cm/ph resulted in no damage to the cerebellum attributable to electrical stimulation per se. Such a charge/phase is about five times the threshold for evocation of cerebellar efferent activity, and might be considered "safe" for stimulation of human cerebellum. Charge density/phase and charge/phase were directly related to increased cerebellar injury in the six other cerebellar cortices stimulated. Leptomeningeal thickening increased with increased charge density. Injury included severe molecular layer attenuation, ongoing destruction of Purkinje cells, gliosis, ongoing degeneration of myelinated axons, collagen intrusion, and increased levels of local polysaccharides. In all cases, even with damage that destroyed all conducting elements beneath the electrodes, there was no damage further than 1 to 2 mm from the edges of the electrode arrays.
...
PMID:Tissue reactions to long-term electrical stimulation of the cerebellum in monkeys. 40 68

The functional, biochemical, and histological changes in a severed median nerve, 9 months after epineurial repair, were studied in 14 monkeys. In seven the mesoneurium had been stripped 5 cm proximal and 5 cm distal to the site of repair, and in seven the nerve had been stripped only over a 0.5 cm area, just enough to allow repair. In the first group the mean muscular strength in the abductor pollicis brevis was 197 gm, as compared to 257 gm in the second group. The amount of collagen in the perineurium was 57 microgram/mg, as compared to 43 microgram/mg, and the incidence of the h-l-h-nl cross-link was 16% to 21%, as compared to 9% to 11%. If the regeneration of the lacerated nerve was compromised by the deposition of collagen resulting from mobilization of the distal segment, as suggested by the decrease in the strength of the abductor pollicis brevis muscle, then any mobilization of a nerve necessary to obtain a sutured junction with minimum tension should be limited to the proximal segment.
...
PMID:The effect of devascularization on the regeneration of lacerated peripheral nerves: an experimental study. 41 69

A patient is described with congenital hypotonia, lax joints, friable skin, hemorrhagic scars, high-arched palate, and borderline microcornea. Acid hydrolyzed whole skin collagen had a reduced hydroxylysine content of 0.5 residues per 1,000 as compared to 5.1 +/- 0.7 in control skin. Collagen lysyl hydroxylase in dialyzed subcellular fractions of cultured skin fibroblasts required L-ascorbate as a principal cofactor. Activity of this enzyme in cultured skin fibroblasts derived from this patient, his father, and mother were 17%, 66%, and 39% of control values, respectively. Collagen prolyl hydroxylase activity was normal. Pharmacologic amounts of oral vitamin C (4 gm/day) produced an increase and withdrawal resulted in abrupt diminution of urinary excretion of hydroxylysine. Over a two-year period the patient's wound healing and muscle strength improved and corneal diameter increased. Hydroxylysine content of the skin did not increase.
...
PMID:Inherited human collagen lysyl hydroxylase deficiency: ascorbic acid response. 41 88


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>

---