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Biomedical subjects

W Y Li

Publications and source records attributed to W Y Li.

At least 91 records · Page 5Linked to original sources
PubMed1987

Reduction of inositol triphosphate in retinal microvessels by glucose and restimulation by myo-inositol.

The formation of inositol phospholipids (IPLs) and inositol phosphate esters (IPEs) in response to glucose was studied in isolated retinal microvessels from porcine eyes. Retinal microvessels incubated from 60 hr with myo-[3H]inositol were sequentially extracted to obtain IPLs and IPEs. [3H]Inositol-labelled IPLs were deacylated to produce the corresponding glycero derivatives. Both deacylation products and water-soluble IPEs were monitored by anion-exchange chromatography. In the presence of high glucose (30 mM) the labelling in inositol triphosphate (IP3) was reduced to 77% and was restimulated by adding myo-inositol (final concentration 0.4 mM) to 158% of the control under physiological conditions of glucose (5 mM) and myo-inositol (0.04 mM). With a fixed glucose concentration (5 mM), IPE accumulation was observed with increasing concentrations of exogenous myo-inositol. Under physiological conditions (glucose 5 mM, myo-inositol 0.04 mM) the distribution (percentage) of radioactivity in phosphatidylinositol (PI), phosphatidylinositol 4-phosphate (PIP) and phosphatidylinositol 4,5-phosphate (PIP2) was 63:19:18. The myo-inositol concentration dependence of IPL formation was also demonstrated. A decrease in IP3 in response to high glucose without changing PIP2 but with a reduction in PI indicated that PI may act as a reservoir to replace a possible loss of PIP2. These findings suggest that availability of myo-inositol by retinal microvessels may be essential to maintain the normal signal transduction and cell proliferation associated with IPL turnover under high glucose concentration.

Animals↗
PubMed1986

Actin in cultured bovine retinal capillary pericytes: morphological and functional correlation.

Actin in cultured bovine retinal capillary pericytes was identified and partially characterized biochemically. The filamentous actin was localized in bovine retinal capillary pericytes using a fluorescent mushroom toxin (nitrobenzoxadiazole-phallacidin) specific for actin. One-dimensional SDS-polyacrylamide-gel electrophoresis of urea-extracted proteins from bovine retinal capillary pericytes revealed a 46,000 MW protein band corresponding to an actin standard, which comprised 7.3% of the total urea-soluble proteins. Actin-activated skeletal muscle myosin Mg2+-ATPase assay, using [gamma-32P]-ATP as substrate, demonstrated functional actin in bovine retinal capillary pericyte extracts after DEAE-cellulose anion-exchange chromatography. The actin-containing protein fractions were eluted at ionic strengths between 0.25 and 0.35 M KCl. The presence of functional actin in pericytes indicated the ability to generate contractile force. This contraction-generating ability may allow pericytes to regulate microvessel caliber and to maintain the integrity of the capillary wall. A lack of this function when pericytes are preferentially lost in diabetic retinal microangiopathy could destabilize the microvessel wall and predispose the capillary to further pathologic changes.

Actins↗
PubMed1986

Kinetics of ascorbate transport by cultured retinal capillary pericytes. Inhibition by glucose.

Accumulation of radioactive L-[carboxyl-14C]-ascorbic acid by cultured bovine retinal capillary pericytes was studied. Kinetic analysis of the transport showed a time-dependent, saturable system with an apparent Km of 76.0 microM and a Vmax of 42 pmole/micrograms DNA/min. A facilitated carrier diffusion process was established on the basis that the system was not sensitive to 2,4-dinitrophenol, ouabain, or reduced sodium concentration in the incubation media, and that the carrier system demonstrated stereospecificity for an ascorbate analogue, dehydroascorbate, and for sugar analogues such as alpha-D-glucose and 3-0-methyl-D-glucose (3-0-MG), but not for beta-D-fructose or L-glucose. Transport of ascorbate by cultured pericytes was insulin-insensitive. 3-0-Methyl-D-glucose inhibited ascorbate transport into pericytes in a non-competitive manner with a Ki of 22 mM. These results indicate that, in cultured retinal capillary pericytes, a common facilitated carrier diffusion system is involved in the transport of ascorbate and sugar analogues such as alpha-D-glucose or 3-0-MG.

Animals↗
PubMed1985

Translation of type IV procollagen messenger RNA from cultured cat retinal pigment epithelial cells.

The activity of type IV procollagen mRNA was detected in the total cytoplasmic RNA prepared from normal feline retinal pigment epithelial cells in culture. The translation products contained two distinct bands in the pro alpha chain region on SDS-PAGE, which were sensitive to collagenase digestion. Corresponding bands were identified in the immunoprecipitate of the translation products after reaction with an anti-type IV collagen antiserum and separation by protein A-Sepharose column chromatography.

Animals↗
PubMed1985

Induction of class II (Ia) alloantigen expression on corneal endothelium in vivo and in vitro.

Class II (DR or Ia) alloantigens are potent inducers of cell-mediated immune responses. However, the expression of Class II alloantigens on corneal cells, except for Langerhans cells within the limbal epithelium, has not previously been described. We have induced Ia expression on cultured rabbit corneal endothelial cells with human immune interferon, and have demonstrated numerous Ia-positive cells in the endothelium during primary immunogenic uveitis in vivo. Cultured endothelial cells which had been treated with immune interferon in vitro functioned as stimulator cells in a mixed leukocyte reaction. Induction of Class II alloantigen expression by lymphokines may potentiate corneal allograft rejection.

Animals↗
PubMed1984

Examination of the interrelationship between aliphatic group dipole moment and polar substituent constants.

The relationships between 210 aliphatic group dipole moments (mu) and Taft polar constants (sigma *) are explored, and they are shown to be correlated by a general equation: mu = -a X sigma * -b X n' -c, where a, b, and c are constants. The value n' is a parameter reflecting the attenuating factor due to the number and electronic nature of the interval atoms between the most electronegative atom and the first atom connected to the acetate in the measurement of sigma *. The mu and sigma * values of over 214 aliphatic substituents are compiled for future correlation studies. Comparative examples using sigma * and mu in quantitative structure-activity relationships are presented.

Anticonvulsants↗
PubMed1984

Increased solubility of newly synthesized collagen in retinal capillary pericyte cultures by nonenzymatic glycosylation.

The effect of increasing glucose concentration on the solubility of newly synthesized collagen was studied in bovine retinal capillary pericyte (BRCP) cultures. Synchronized pericytes were labeled with [3H]-proline in media containing either 5, 10, 20 or 40 mM glucose, or 5 mM glucose and 100 micrograms/ml beta-aminopropionitrile fumarate (BAPN). The relative rate of collagen synthesis in the medium (soluble collagen) was significantly increased, and the rate in the cell layer (insoluble collagen) was decreased, by an elevated glucose concentration. The increase in collagen solubility with 20 and 40 mM glucose (over normal, 5 mM glucose) was 14 and 42%, respectively, of that obtained with BAPN. BAPN and 4-deoxypyridoxine inhibited BRCP lysyl oxidase activity, but elevated glucose concentrations did not. Increased nonenzymatic glycosylation of newly synthesized collagen was demonstrated in BRCP cultures co-labeled with L-[14C]-glucose and L-[3H]-proline. The increase in collagen solubility with elevated glucose concentrations therefore appears to be the result of the inhibition of lysyl-derived cross-link formation because of an increased nonenzymatic glycosylation of the epsilon-amino groups of lysyl residues of newly synthesized collagen in culture.

Aminopropionitrile↗
PubMed1982

Nucleotide sequence of 7 S RNA. Homology to Alu DNA and La 4.5 S RNA.

7 S RNA, a component of normal higher eukaryotic cells and several oncornaviruses, was shown to be conserved in evolution (Erikson, E., Erikson, R. L., Henry, B., and Pace, N. R. (1973) Virology 53, 40-46). Recently, 7 S RNA was shown to be partially complementary to Alu family DNA sequences (Weiner, A. (1980) Cell 22, 209-218). In the present study the nucleotide sequence of Novikoff hepatoma 7 S RNA was determined to be: (formula, see text) Comparison of 7 S RNA, Alu and B1 family DNA, and La 4.5 S RNA sequences for homologies showed that 1) one-third of 7 S RNA, mainly the 5'-end, was homologous to Alu and B1 family sequences; 2) one 300-nucleotide long Alu family sequence contained two binding sites for 7 S RNA; and 3) the 5'-ends of 7 S RNA and La 4.5 S RNA also had extensive (60%) homologies. A model for the secondary structure of 7 S RNA based on maximal base pairing and preferential nuclease cleavage sites is also presented.

Animals↗