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W W Chen

Publications and source records attributed to W W Chen.

At least 55 records · Page 3Linked to original sources
PubMed1987

Biosynthesis of myelin-associated proteins in simian virus 40 (SV40)-transformed rat Schwann cell lines.

In order to study the biosynthesis of myelin-associated proteins in Schwann cells, we have induced proliferation of cultured Schwann cells from neonatal rat sciatic nerve by transformation with Simian Virus 40 (SV40). Homogeneous transformed Schwann cell lines were established by single cell cloning. The transformed phenotype of these Schwann cell lines was determined by both integration of SV40 viral DNA sequences into the cellular genome and active synthesis of the large T antigen of SV40. In addition, similar transformations with SV40 virus containing a temperature-sensitive mutation in the large T gene yielded Schwann cell lines with transformed phenotype which were temperature-sensitive. In this report, we demonstrate that these SV40-transformed Schwann cells actively synthesize myelin-specific sulfatide, myelin-associated glycoprotein (MAG) and the glial cell marker 2':3'-cyclic nucleotide 3'-phosphodiesterase (CNPase). Despite the expression of MAG and CNPase, these Schwann cells did not synthesize PO the major protein of peripheral myelin. Since a substantial amount of normal size PO mRNA was present in these transformed Schwann cells, the lack of PO synthesis was apparently not the result of a deficiency of transcription. These results are consistent with the possibility that the regulation of PO synthesis differs from that of MAG and CNPase synthesis and that PO synthesis may be controlled at the post-transcriptional level.

2',3'-Cyclic-Nucleotide Phosphodiesterases↗
PubMed1987

Effect of dimethyl sulfoxide on transformed rat Schwann cells.

Cultured rat Schwann cells transformed by Simian Virus 40 (SV40) have previously been shown to retain their ability to synthesize myelin-associated galactosylceramide and sulfatide. Little is known about the mechanism regulating galactosphingolipid synthesis in Schwann cells. We have found that growing the transformed Schwann cells in the presence of dimethyl sulfoxide (DMSO) markedly inhibits the incorporation of [35S]sulfate into sulfatide, in a time- and dose-dependent manner. The concentration of DMSO which resulted in a half-maximal inhibition after 6 days of incubation was 0.5%, and the incubation time required for a half-maximal effect at 1.0% DMSO was approximately 4 days. In contrast, DMSC did not affect the incorporation of [35S]sulfate into glycosaminoglycans. In addition, DMSO treatment has little effect on the synthesis of cellular DNA, proteins and lipids. When transformed Schwann cells were treated with DMSO, a substantial decrease in the incorporation of [3H]galactose into galactosylceramide was observed. The concentration of DMSO which resulted in a half-maximal inhibition of galactosylceramide synthesis was approximately 0.5%, similar to the concentration required for a similar effect on sulfatide synthesis. However, the incubation time required for a half-maximal inhibitory effect on galactosylceramide synthesis at 1.0% DMSO was less than 1 day, which was substantially shorter than the time required for the inhibition of sulfatide synthesis at this concentration. This finding is consistent with the interpretation that treatment with DMSO inhibits the synthesis of galactosylceramide, a precursor of sulfatide, which results in a decrease in the synthesis of sulfatide during a prolonged incubation of DMSO.

Animals↗
PubMed1987

Peroxisomal beta-oxidation enzyme proteins in adrenoleukodystrophy: distinction between X-linked adrenoleukodystrophy and neonatal adrenoleukodystrophy.

Very long chain fatty acids, which accumulate in plasma and tissues in X-linked adrenoleukodystrophy (ALD), neonatal ALD, and the Zellweger cerebrohepatorenal syndrome, are degraded by the peroxisomal beta-oxidation pathway, consisting of acyl-CoA oxidase, the bifunctional enoyl-CoA hydratase/3-hydroxyacyl-CoA dehydrogenase, and beta-ketothiolase. A marked deficiency of all three enzyme proteins was reported in livers from patients with the Zellweger syndrome, a disorder in which peroxisomes are decreased or absent. Peroxisomes are not as markedly decreased in neonatal ALD and appear normal in X-linked ALD. Immunoblot analysis of the peroxisomal beta-oxidation enzymes revealed an almost complete lack of the bifunctional enzyme in neonatal ALD liver, similar to the finding in Zellweger tissue. In contrast, acyl-CoA oxidase and beta-ketothiolase were present in neonatal ALD liver, although the thiolase appeared to be in precursor form (2-3 kDa larger than the mature enzyme) in neonatal ALD. Unlike either neonatal ALD or Zellweger syndrome, all three peroxisomal beta-oxidation enzymes were present in X-linked ALD liver. Despite the absence in neonatal ALD liver of bifunctional enzyme protein, its mRNA was detected by RNA blot analysis in fibroblasts from these patients. These observations suggest that lack of bifunctional enzyme protein in neonatal ALD results from either abnormal translation of the mRNA or degradation of the enzyme prior to its entry into peroxisomes.

3-Hydroxyacyl CoA Dehydrogenases↗
PubMed1986

Effects of lysosomotropic agents on lipogenesis.

Chloroquine, quinine, and NH4Cl are lysosomotropic agents which inhibit lysosomal function, apparently by raising the intralysosomal pH. We found that preincubation of cultured human skin fibroblasts with these lysosomotropic agents under serum-free conditions induced about a 10-fold stimulation of lipogenesis. A similar stimulatory effect on the incorporation of 3H2O, [14C]acetate, [14C]pyruvate, [14C]palmitate, and [14C]choline into cellular lipids was observed. The effect was both time and dose dependent, and was reversible. The concentrations of chloroquine, quinine, and NH4Cl resulting in half-maximal stimulation were about 3 microM, 30 microM, and 9 mM, respectively. At these concentrations, stimulation of lipogenesis correlated with impairment of lysosomal function. At a concentration of 10 microM chloroquine, the half-time for maximal stimulation was about 4 h. Most of the [14C]acetate was incorporated into phosphatidylcholine and other cellular lipids; less than 10% was found in cholesterol and cholesterol ester. Nevertheless, incorporation of [14C]acetate into cholesterol showed a chloroquine-induced stimulation parallel to that observed for phospholipids, suggesting that stimulation of both lipogenesis and cholesterogenesis occurred. The stimulatory effect of lysosomotropic agents on lipogenesis appeared to depend on active synthesis of cellular proteins. In the presence of cycloheximide, an inhibitor of protein synthesis; the stimulation was completely abolished.

Acetates↗
PubMed1985

Percutaneous transfemoral catheterization in aortic stenosis with a USCI Sones catheter curve A type 1 (7540).

We report our experience with the use of a USCI Sones catheter curve A type 1 (7540) to cross the aortic valves of 45 patients with clinically significant aortic stenosis. The technique was successful in all our patients with a fluoroscopic time of less than 3 min. A gradient of up to 200 mmHg across the aortic valve area was recorded, and the smallest valve area calculated was less than 0.2 cm2. The method obviated the need for a guidewire and satisfactory left ventriculograms were obtained. No major complication was observed. We conclude that the technique is a simple, rapid, and safe means of obtaining left ventricular hemodynamic and angiographic information in patients with aortic stenosis of various degrees of severity.

Adult↗
PubMed1984

Lysosomal involvement in cellular turnover of plasma membrane sphingomyelin.

At least two isoenzymes of sphingomyelinase (sphingomyelin cholinephosphohydrolase, EC 3.1.4.12), including lysosomal acid sphingomyelinase and nonlysosomal magnesium-dependent neutral sphingomyelinase, catalyse the degradation of sphingomyelin in cultured human skin fibroblasts. A genetically determined disorder of sphingomyelin metabolism, type A Niemann-Pick disease, is characterized by a deficiency of lysosomal acid sphingomyelinase. To investigate the involvement of lysosomes in the degradation of cellular membrane sphingomyelin, we have undertaken studies to compare the turnover of plasma membrane sphingomyelin in fibroblasts from a patient with type A Niemann-Pick disease, which completely lack acid sphingomyelinase activity but retain nonlysosomal neutral sphingomyelinase activity, with turnover in fibroblasts from normal individuals. Plasma membrane sphingomyelin was labeled by incubating cells at low temperature with phosphatidylcholine vesicles containing radioactive sphingomyelin. A fluorescent analog of sphingomyelin, N-4-nitrobenzo-2-oxa-1,3-diazoleaminocaproyl sphingosylphosphorylcholine (NBD-sphingomyelin) is seen to be readily transferred at low temperature from phosphatidylcholine liposomes to the plasma membranes of cultured human fibroblasts. Moreover, when kinetic studies were done in parallel, a constant ratio of [14C]oleoylsphingosylphosphorylcholine ( [14C]sphingomyelin) to NBD-sphingomyelin was taken up at low temperature by the fibroblast cells, suggesting that [14C]sphingomyelin undergoes a similar transfer. The comparison of sphingomyelin turnover at 37 degrees C in normal fibroblasts compared to Niemann-Pick diseased fibroblasts shows that a rapid turnover of plasma membrane-associated sphingomyelin within the first 30 min appears to be similar in both normal and Niemann-Pick diseased cells. This rapid turnover appears to be primarily due to rapid removal of the [14C]sphingomyelin from the cell surface into the incubation medium. During long-term incubation, an increase in the formation of [14C]ceramide correlating with the degradation of [14C]sphingomyelin is observed in normal fibroblasts. In contrast, the level of [14C]ceramide remains constant in Niemann-Pick diseased cells, which correlates with a higher level of intact [14C]sphingomyelin remaining in these cells compared to normal cells.(ABSTRACT TRUNCATED AT 250 WORDS)

4-Chloro-7-nitrobenzofurazan↗
PubMed1984

Iron overload in thalassaemic patients in Hong Kong.

Body iron status, as measured by serum ferritin, was studied in 101 adult Chinese thalassaemic patients, 46 males and 55 females. Thirty of them had mild disease (beta thalassaemia trait), 56 disease of intermediate severity (haemoglobin H disease) and 15 severe disease (homozygous beta thalassaemia, Hb E-beta thalassaemia and delta beta-beta thalassaemia). The extent of iron overload correlated with the severity of disease. In severe thalassaemia, iron overload occurred early in life and was independent of multiple transfusions. While significant impairment of left ventricular function was present in only one of six patients studied, evidence of decreased pituitary (especially gonadotrophic) function was observed in six out of seven. Hypocalcaemia, probably due to hypoparathyroidism, was seen in one.

Adolescent↗
PubMed1983

Efficacy of low-dose, subcutaneously administered heparin in treatment of pregnant women with artificial heart valves.

Between 1979 and 1982, the efficacy of fixed low-dose heparin, administered subcutaneously as thromboembolic prophylaxis, was studied during 14 pregnancies in 10 patients with mechanical heart valves. Calcium heparin (5000 units every 12 hours) was substituted for warfarin during the first trimester and the last month of pregnancy. Although the regimen was well tolerated and was associated with only 14% of first-trimester abortions, five episodes of thromboembolism occurred in four patients. Thus, this fixed, low-dose heparin regimen did not provide adequate thromboembolic prophylaxis in patients with prosthetic heart valves during pregnancy.

Abortion, Spontaneous↗
PubMed1983

Aortic catheterisation via percutaneous left ventricular puncture.

When retrograde catheterisation and angiography of the ascending aorta from the brachial or femoral approach is not possible, this can be accomplished by direct percutaneous left ventricular puncture. The haemodynamic and angiographic information obtained was essential to surgical correction of aortic arch anomalies as illustrated in two patients.

Adult↗