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W Chao

Publications and source records attributed to W Chao.

66 records · Page 4Linked to original sources
PubMed1989

Metabolism of platelet-activating factor (PAF; 1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine) and lyso-PAF (1-O-alkyl-2-lyso-sn-glycero-3-phosphocholine) by cultured rat Kupffer cells.

The metabolism of platelet-activating factor (PAF; identified as AGEPC: 1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine) and lyso-PAF (lyso-GEPC: 1-O-alkyl-2-lyso-sn-glycero-3-phosphocholine) was investigated in cultured rat Kupffer cells. The rat Kupffer cells accumulated [3H]AGEPC and deacetylated this compound to the corresponding [3H]lyso-GEPC, which was the major metabolic product of [3H]AGEPC. [3H]Lyso-GEPC was distributed primarily in the supernatant fraction of incubated cells throughout the experimental interval. Only a very small portion of the [3H]lyso-GEPC was further converted to 1-O-alkyl-2-acyl-sn-glycero-3-phosphocholine (alkylacyl-GPC), indicating that this acylation process was not particularly active in these cells. When [3H]lyso-GEPC was incubated with Kupffer cells, the conversion of lyso-GEPC to AGEPC via the acetyltransferase reaction increased up to 30 min and declined thereafter. Bovine serum albumin (BSA) had a substantial influence on both the cellular uptake and the metabolism of [3H]AGEPC. An increase in the BSA concentration in the incubation media reduced the cellular uptake of [3H]AGEPC and the subsequent formation of lyso-GEPC. The results of this study suggest that the hepatic Kupffer cells play an important role in the metabolism of PAF. Moreover, these results infer that the regulation of the PAF level in certain hepatic pathophysiological situations may be a consequence of the production and subsequent metabolism of this potent lipid autacoid in the Kupffer cells of the liver.

Animals↗
PubMed1989

Biosynthesis of platelet-activating factor by cultured rat Kupffer cells stimulated with calcium ionophore A23187.

Cultured rat Kupffer cells synthesize and release platelet-activating factor (PAF) when stimulated with calcium ionophore A23187. The production of PAF is concentration- and time-dependent and, based upon [3H]serotonin release assays, approx. 1.0 pmol of PAF is formed per 8 x 10(6) cells during 10 min of ionophore stimulation. It is suggested that Kupffer cells are important cellular components which produce and release PAF in order to facilitate communication between hepatic sinusoidal and parenchymal cells. Further, it is suggested that such mediator production in response to reticulo-endothelial cell stimulation causes the hepatic glycogenolytic response previously in the isolated perfused rat liver.

Acetyl Coenzyme A↗
PubMed1987

An enhancer element in the far upstream spacer region of rat ribosomal RNA gene.

To determine whether far upstream 5'-flanking sequences control rat rDNA transcription, we constructed plasmids containing several 5' and 3' deletions within the nontranscribed spacer region. In vitro transcription of these plasmids identified three enhancer regions, designated A, B, and C, which can dramatically stimulate transcription from the core promoter. Further analysis of region B showed that the enhancer element lies between -2.183 and -2.357 kilobase pairs upstream of the initiation site. The plasmid containing the 174-base pair enhancer element could stimulate rRNA gene transcription as much as 10-20-fold relative to transcription of the plasmid containing only the core promoter. This enhancer was not another promoter domain and could function irrespective of its orientation or distance from the promoter or when inserted downstream of the initiation site. Computer analysis of known sequences of enhancer regions A and C did not reveal any significant homology between these DNA segments and the 174-base pair enhancer element. Competition assay demonstrated that the enhancer element B forms a stable complex with the transcription factor(s) and that interaction between the enhancer and the factor(s) was essential for the stimulation of rDNA transcription. This is the first report of a mammalian ribosomal rDNA enhancer element that exhibits the characteristics of an RNA polymerase II enhancer.

Animals↗
PubMed1986

Decreased methylation of the major mouse long interspersed repeated DNA during aging and in myeloma cells.

Sequences of DNA that hybridize on Southern blots with cloned EcoR1 1.3 kb (ER1) of long interspersed repeated sequence (L1Md) of mouse have been examined in genomic DNA of neonatal mice, livers and brains of adult mice (3, 10, 27, and 30 mo old), and the solid myeloma tumor MOPC-315. The isoschizomers Hpa II (CCGG or mCCGG) and Msp I (CCGG or CmCGG) were used to assess methylation. We found that the L1Md sequence is fully methylated in young animals but demethylated in myeloma. Demethylation of L1Md sequence also occurred in aged animals. By scanning the autoradiogram, we found that approximately 8% of the 10(4)-10(5) copies have been demethylated in 27-mo-old liver.

Aging↗
PubMed1985

Conformational restrictions of the retinoid skeleton.

A series of conformationally restricted retinoids has been synthesized and assayed for biological activity. These compounds have aromatic rings in place of selected double bonds of the tetraene side-chain of retinoic acid and could be considered as analogues of retinoic acid in which some of the double bonds possess s-cis topology. Thus far, analogues in which the bonds corresponding to the (5,7E)-, (7,9E)-, (9,11,13E)- and (11,13E)-double bond systems of retinoic acid are restricted to a cisoid conformation have been studied. Analogues were screened for their ability to reverse keratinization in hamster tracheal organ culture and to inhibit the induction of ornithine decarboxylase in mouse epidermis. Selected compounds were also screened in the antipapilloma assay in mice. The toxicity of some analogues on intraperitoneal injection in mice was determined.

Animals↗
PubMed1980

Peripheral lymphocyte subpopulations in patients with herpes genitalis.

Peripheral blood samples from 52 women including 16 with herpes genitalis and 36 healthy persons were studied to enumerate subpopulations of lymphocytes. T lymphocyte counts were done by SRBC rosette tests and B lymphocytes by immunobead rosette tests using antibody-coated polyacrylamide beads. It was found that the mean percentage of "active T lymphocytes was significantly less in the patients with herpes genitalis than in the controls (herpes genitalis; 13.9 +/- 6.8%, controls; 25.0 +/- 8.3%, p less than 0.001). No difference was noted in the percentage of "total" T lymphocytes, "total" B lymphocytes and subsets of B lymphocytes (IgG-, IgA- and IgM-bearing lymphocytes) between the patients and controls. The present findings suggest that cell-mediated immune function associated with "active" T lymphocytes is suppressed in patients with herpes genitalis.

B-Lymphocytes↗
PubMed1979

Alteration of early T lymphocyte count in patients with herpes genitalis.

Peripheral blood samples from 52 women, including 16 with herpes genitalis and 36 healthy persons, were studied to enumerate subpopulations of lymphocytes. It was found that the mean percentage of 'active' T lymphocytes was significantly less in the patients with herpes genitalis than in the controls.

Female↗
PubMed1977

Determination of B lymphocyte population using antibody-coated polyacrylamide beads.

The present study describes a method for the determination of the human B cell population by the use of polyacrylamide beads which are coated with antibody specific for each of the immunoglobulin classes. This method provides a simpler determination of the B cell count than the EA or EAC rosette tests. The antibodycoated beads also have the potential of being used to quantify the subpopulations of B cells bearing specific classes of immunoglobulins.

Acrylamides↗