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Biomedical subjects

W Song

Publications and source records attributed to W Song.

At least 145 records · Page 8Linked to original sources
PubMed1996

Nucleotide homologies in genes encoding members of the S100 protein family.

Members of the S100 protein family exhibit a unique pattern of cell/tissue-specific expression and approx. 50% similarity at the amino-acid level. The cDNAs encoding many of these proteins from a variety of species are now available making a comparison of these family members at the nucleotide level possible. With few exceptions, family members exhibited less nucleotide identity than amino-acid similarity. Furthermore, the pattern of divergence calculated on the basis of nucleotide identity did not always agree with that calculated on the basis of amino-acid similarity. The majority of sequence diversity occurred in the nontranslated regions suggesting that these regions may be involved in directing the expression of particular members of the family to specific cell types. When comparisons of individual family members were made across species, the following order of species diversity was observed: rat/mouse < human/bovine < porcine < rabbit/avian < Xenopus laevis. The structure of the gene loci encoding these proteins was remarkably conserved both within family members of a given species as well as in individual family members from different species. Although there appears to be great diversity in the 5' flanking regions of these genes, members of the family share at least one common potential regulatory element-the S100 protein element. Thus, membership in the S100 family could be ascertained on the basis of gene organization and the presence of an SPE. Although functional data are limited, the available data indicate that the regulation of the expression of S100 family members is complex and involves both positive and negative regulatory elements. Additional nucleic acid sequences and complimentary functional studies will be required to dissect the mechanisms which target the expression of the members of this family to specific cell types during development.

Animals↗
PubMed1996

Expression of the rat S100A1 gene in neurons, glia, and skeletal muscle.

Using a rat S100A1 cDNA probe, S100A1 expression has been documented in rat C6 glioma cells, a cell line previously thought to express only the S100B protein. To identify the molecular mechanisms which target S100A1 gene expression to specific cell types, the rat S100A1 gene was cloned, and functional analysis of the 5' flanking region of the gene was performed. The rat S100A1 gene was located in an 8.5 kb BamHI genomic fragment which contained 3 exons plus 1.6 kb of 5'-upstream and 0.37 kb of 3'-downstream flanking sequence. A single transcription initiation start site and a single polyadenylation signal were identified in this gene. A number of potential regulatory consensus sequences were identified in the rat S100A1 gene including general transcription factor binding sequences (TATA box, GC box and CCAAT box), cAMP regulated sequences (CRE), skeletal muscle specific sequences (E-box and M-CAT), an S100 protein element, and a (GCT) trinucleotide repeat. Analysis of an S100A1 promoter-CAT construct by ribonuclease protection assay demonstrated that this gene is functional in three S100A1 expressing cell lines, C6 cells, PC12 cells and L6 cells. CAT constructs containing progressive deletions of the S100A1 promoter region revealed a positive regulatory element in skeletal muscle (L6) cells between -1600/-1081. The fact that these same sequences were negative in glial (C6) cells and neutral in neuronal (PC12) cells suggests that this region plays a major role in targeting S100A1 expression to specific cell types. The -1081/+10 region contained both positive and negative elements, some of which were cell-type specific. Thus, S100A1 expression is under complex transcriptional control which involves positive and negative elements as well as cell type specific elements.

Animals↗
PubMed1996

Endogenous 7-oxocholesterol is an enzymatic product: characterization of 7 alpha-hydroxycholesterol dehydrogenase activity of hamster liver microsomes.

Previously, we described a new metabolite derived from endogenous cholesterol in the presence of hamster liver microsomal protein and NADPH (Song et al., 1991, Biochem. Pharmacol. 41, 1439-1447). Through gas chromatography/mass spectral analysis of the metabolite and its methoxime-3-dimethyl-t-butylsilyl ether derivative, this metabolite has been definitively identified as 7-oxocholesterol. Isotope incorporation experiments using molecular 18O2 demonstrated that no oxygen atoms from molecular oxygen were incorporated into the product, 7-oxocholesterol, when 7 alpha-hydroxycholesterol was used as substrate. In contrast, one atom of 18O was incorporated into cholesterol from 18O2 during its metabolism to form 7 alpha-hydroxycholesterol. Formation of 7-oxocholesterol was dependent upon the presence of NADP+, 7 alpha-hydroxycholesterol, and hamster liver microsomes. This enzyme appears to be a membrane-bound protein and its activity was most abundant in liver microsomal fractions and to a lesser extent in mitochondrial fractions; little or no activity was observed in nuclei or cytosol. The enzyme activity was present in highest content in the livers of hamsters and was also observed in human and bovine liver microsomes, but not those of mouse, rabbit, or rat. The reaction was inhibited by 2'-AMP, but not by anti-NADPH:cytochrome-P450 oxidoreductase globulin, carbon monoxide, metyrapone, nor miconazole. In contrast to the previously characterized 3 beta-hydroxy-delta 5-C27-steroid oxidoreductase activity, NAD+ did not serve as an effective cofactor for 7-oxocholesterol formation. The ability of NADPH to partially serve as a cofactor in this reaction was shown to be due to a high NADPH-oxidase activity of hamster liver microsomes, thereby providing sufficient NADP+ to serve as the oxidizing pyridine nucleotide for the reaction. These results document the existence of a non-P450, NADP(+)-dependent 7 alpha-hydroxycholesterol dehydrogenase in liver microsomes which catalyzes this reaction. The product, 7-oxocholesterol, is produced enzymatically in the livers of hamsters and other mammals and may regulate bile acid metabolism or other processes due to its action as an oxysterol.

Animals↗
PubMed1996

Effects of dietary cholesterol on hepatic production of lipids and lipoproteins in isolated hamster liver.

The effect of 2-week 2% cholesterol vs. chow feeding on regulation of hepatic lipoprotein, lipids and apoprotein (Apo), and biliary lipids production was evaluated by the isolated perfused hamster liver model. Cholesterol feeding did not change very-low-density lipoprotein (VLDL), low-density lipoprotein (LDL), and high-density lipoprotein (HDL) particle size but significantly increased the hepatic production of VLDL-cholesterol fourfold, VLDL-triglyceride two and one-half-fold but not phospholipid in VLDL. It also increased LDL-cholesterol fourfold but not triglyceride or phospholipid in LDL, whereas lipids in HDL remained unchanged. Gradient sodium dodecyl sulfate-polyacrylamide gel electrophesis (SDS-PAGE) and Western blot analysis (density of apoprotein/density of albumin/g liver) indicated that cholesterol feeding enhanced Apo B tenfold, Apo A-I fivefold but not Apo E in VLDL. Apo E and Apo B did not change in LDL. Apo E but not Apo A-I increased (threefold) in HDL by cholesterol feeding. Cholesterol feeding decreased bile salt secretion 28% but increased cholesterol secretion 118% in bile, whereas phospholipid and bile volume remained unchanged. Increased Apo A-I in VLDL suggested that Apo A-I is involved in enhanced hepatic export of cholesterol and triglyceride. Different patterns of lipid and Apos in VLDL and LDL after cholesterol feeding also suggested separate VLDL and LDL export mechanisms. Elevated Apo E but not lipids in HDL after cholesterol feeding suggests that hepatic HDL may function as a carrier of newly synthesized hepatic Apo E into the circulation for transfer to other lipoproteins (chylomicron [CM], CMr) to facilitate hepatic cholesterol uptake and clearance.

Animals↗
PubMed1996

Cloning of a second Arabidopsis peptide transport gene.

Previously, we reported the isolation of a peptide transport gene designated AtPTR2 from Arabidopsis thaliana by functional complementation of a yeast peptide transport mutant. We now report the isolation of a second peptide transport gene (AtPTR2-B) from Arabidopsis using the same approach. Similar to the effects of transferring AtPTR2-A (previously called AtPTR2), transfer of AtPTR2-B to yeast peptide transport mutants restored the ability to grow on di- and tripeptides but not peptides four residues or longer. However, unlike yeast mutants complemented with either the yeast PTR2 gene or the AtPTR2-A gene, transformants expressing AtPTR2-B were only partially sensitive to toxic peptides. Northern analysis showed that AtPTR2-B was constitutively expressed in all plant organs. Studies of the kinetics indicated that AtPTR2-A and AtPTR2-B have Km values of 47 and 14 microM, respectively, with Vmax values of 0.061 and 0.013 nmol mg-1 cell dry weight s-1, respectively, when dileucine was used as a substrate. AtPTR2-B is encoded on a 2.0-kb cDNA corresponding to a 585-amino acid protein (64.4 kD). Hydropathy analysis indicates that the protein is highly hydrophobic and suggests that there are 12 putative transmembrane segments. AtPTR2-B, like AtPTR2-A, shares significant similarity to a number of other proteins involved in transport of peptides into cells.

Amino Acid Sequence↗
PubMed1996

Delayed protection against ischaemia-induced ventricular arrhythmias and infarct size limitation by the prior administration of Escherichia coli endotoxin.

1. Bacterial endotoxin (lipopolysaccharide derived from Escherichia coli) was injected intraperitoneally in conscious rats in doses ranging from 0.5 to 2.5 mg kg-1. At various times afterwards the animals were anaesthetized and subjected to a 30 min period of left coronary artery occlusion. 2. Under these conditions the severity of ventricular arrhythmias was markedly suppressed, in comparison with saline-injected controls, but this was particularly marked with the higher doses (1.5 and 2.5 mg kg-1); the number of ventricular premature beats was reduced from 1687 +/- 227 over the 0.5 h coronary artery occlusion period to 190 +/- 46 in those rats administered 2.5 mg kg-1 endotoxin 8 h previously (P < 0.05). The duration of ventricular tachycardia was also significantly reduced (138 +/- 26 s to 8.9 +/- 4.2 s; P < 0.01) and there was a reduction in the incidence of ventricular fibrillation (from 56% to 10%). 3. The time course of this protection was studied following the administration of a single dose of 2.5 mg kg-1 of endotoxin by anaesthetizing rats 4, 8 or 24 h later. Protection was apparent at each time but was particularly marked at 8 h. 4. No rat given the highest dose of endotoxin (32 in all) died as a result of ventricular fibrillation, or from any other cause, during an occlusion, in contrast to a 26% mortality in the controls (P < 0.01). 5. Infarct size, measured following a 30 min period of coronary artery occlusion followed by a 3 h reperfusion period, was reduced both 8 and 24 h after the administration of 2.5 mg kg-1 endotoxin (reductions of 24.3 and 23.1% respectively; P < 0.05). Endotoxin had no significant effect on the area at risk. 6. The beneficial effects of endotoxin on infarct size and on ventricular arrhythmias were markedly attenuated by the prior administration of dexamethasone, 3 mg kg-1 given 1 h prior to endotoxin administration. Dexamethasone itself reduced infarct size (P < 0.05) but had no direct effect on arrhythmia severity following coronary artery occlusion. 7. The mechanisms of this "cross-tolerance' induced by bacterial endotoxin against ischaemia-reperfusion injury remain to be elucidated but the most likely mechanisms appear to be the induction of protective enzymes or proteins (e.g. nitric oxide synthase, cyclo-oxygenase (COX) 2) probably mediated by cytokine release.

Animals↗
PubMed1996

SSN genes that affect transcriptional repression in Saccharomyces cerevisiae encode SIN4, ROX3, and SRB proteins associated with RNA polymerase II.

The RNA polymerase II of Saccharomyces cerevisiae exists in holoenzyme forms containing a complex, known as the mediator, associated with the carboxyl-terminal domain. The mediator includes several SRB proteins and is required for transcriptional activation. Previous work showed that a cyclin-dependent kinase-cyclin pair encoded by SSN3 and SSN8, two members of the SSN suppressor family, are identical to two SRB proteins in the mediator. Here we have identified the remaining SSN genes by cloning and genetic analysis. SSN2 and SSN5 are identical to SRB9 and SRB8, respectively, which encode additional components of the mediator. Genetic evidence implicates the SSN genes in transcriptional repression. Thus, these identities provide genetic insight into mediator and carboxyl-terminal domain function, strongly suggesting a role in mediating transcriptional repression as well as activation. We also show that SSN4 and SSN7 are the same as SIN4 and ROX3, respectively, raising the possibility that these genes also encode mediator proteins.

Base Sequence↗
PubMed1996

Protein phosphatase type 1 interacts with proteins required for meiosis and other cellular processes in Saccharomyces cerevisiae.

Protein phosphatase type I (PP1) is involved in diverse cellular processes, and its activity toward specific substrates is thought to be controlled by different regulatory or targeting subunits. To identify regulatory subunits and substrates of the Saccharomyces cerevisiae PP1, encoded by GLC7, we used the two-hybrid system to detect interacting proteins. Among the many proteins identified were Gac1, a known glycogen regulatory subunit, and a protein with homology to Gac1. We also characterized a new gene designated GIP1, for Glc7-interacting protein. We show that a Gip1 fusion protein coimmunoprecipitates with PP1 from cell extracts. Molecular and genetic analyses indicate that GIP1 is expressed specifically during meiosis, affects transcription of late meiotic genes, and is essential for sporulation. Thus, the Gip1 protein is a candidate for a meiosis-specific substrate or regulator of PP1. Finally, we recovered two genes, RED1 and SCD5, with roles in meiosis and the vesicular secretory pathway, respectively. These results provide strong evidence implicating PP1 function in meiosis. In addition, this study indicates that the two-hybrid system offers a promising approach to understanding the multiple roles and interactions of PP1 in cellular regulation.

Amino Acid Sequence↗
PubMed1996

[The effects of retinoic acid on the ultrastructure of cultured fibroblasts].

The paper reports the effects of retinoic acid on the ultrastructure of cultured fibroblasts. Electron microscopic observation (SEM and TEM) showed that fibrous substances on the cell surface and outside the cell had decreased. The results indicated that retinoic acid inhibits collagen synthesis of fibroblasts. The possible mechanism of the effect of retinoic acid in the treatment of scar is discussed.

Collagen↗
PubMed1996

Active expression of G gamma globin gene on chromosome 11 with Yunnanese A gamma delta beta)0-thalassemia deletion in MEL cells.

A permanent lymphocyte cell line of a heterozygote with Yunnanese (A gamma delta beta)0-thalassemia deletion, associated with an increased production of G gamma globin in adult, was founded using Epstein-Barr virus transformation. The hybrids of the lymphocyte cell and mouse erythroleukemia cell (MEL) were achieved and the hybrids containing human chromosome 11 were selected with the monoclonal antibody 53/6. The subclones containing only either the normal or the abnormal human chromosome 11 were separated and the expression of the human globin genes was studied. Expression of the beta-globin gene, but not the G gamma and A gamma, was observed in the hybrids containing only the normal human chromosome 11, while active expression of the G gamma globin gene was observed in the hybrids containing only the abnormal human chromosome 11. These results have confirmed that the DNA deletion in the beta-globin gene cluster is the cause of persistent active expression of the G gamma globin gene in the Yunnanese mutant.

Adult↗
PubMed1996

Role of endogenous cholecystokinin in the regeneration of pancreatic tissue after acute hemorrhagic pancreatitis in rats.

The aim of this study was to investigate the effect of endogenous cholecystokinin (CCK) on pancreatic regeneration after acute hemorrhagic pancreatitis. Acute hemorrhagic pancreatitis was induced in rats by two intraperitoneal cerulein injection (20 micrograms/kg BW) with 5h water-immersion stress once a day for successive 3 days. After the cessation of repetition of acute pancreatitis the rats were treated with successive feeding with 0.1% camostat-containing diet or SC injection of CR-1505 (CCK receptor antagonist, 50 mg/kg BW x 2/day) for 7 days. Zymogen enzymes and protein contents per DNA in pancreatic tissue were significantly higher in rats treated with camostat compared with control rats, and plasma CCK level was elevated. To the contrary, pancreatic regeneration was retarded in the rats treated with CR 1505. It is concluded that endogenous CCK has a trophic effect during regeneration after acute hemorrhagic pancreatitis.

Acute Disease↗
PubMed1996

Increased expression of PDGF and c-myc genes in lungs and pulmonary arteries of pulmonary hypertensive rats induced by hypoxia.

The role of growth factors and proto-oncogene in pulmonary vascular structural remodelling is not well known. The present study examined gene expression of platelet-derived growth factor (PDGF)-A and -B chain and proto-oncogene, c-myc, in lung tissue and pulmonary artery of rats exposed to hypoxia and compared to those levels of gene expression in normal rats. Normal lungs and pulmonary artery expressed PDGF-A chain transcript of 1.7 kb and PDGF-B chain transcript of 3.5 Kb. The c-myc transcript of 2.2 kb was expressed as well. After hypoxic exposure for 7 and 14 days mRNA levels of PDGF-B chain and c-myc were elevated significantly compared with those of control rats. PDGF-A chain mRNA increased after hypoxia for 7 days, and then declined. These results suggest that activation of autocrine and/or paracrine is important in proliferation mechanism of pulmonary artery smooth muscle cells in hypoxic pulmonary hypertensive rats.

Animals↗
PubMed1996

[Evaluation for therapeutic efficacy of decompression of optic nerve canal in 121 cases].

OBJECTIVE: To evaluate the therapeutic efficacy of decompression of optic nerve canal in the eye with indirect nerve injury in the optic nerve canal. METHODS: 121 patients with indirect injury of optic nerve in the canal were selected and decompression of optic nerve canal was performed on them. Then the outcomes were reviewed and analyzed. RESULTS: Visual acuities of 76 patients (62.81%) were improved. CONCLUSION: It is obvious that decompression of optic nerve canal is associated with significant improvement in cases with good preoperative vision. In cases without light perception, treatment of steroids and dehydrant should be firstly applied, afterwards according to the patient's individual situation, selectively the case is to perform the operation. Thus the therapeutic effectiveness can be greatly elevated. Decompression of optic nerve canal is safe and reliable.

Adolescent↗
PubMed1995

Entry of B cell antigen receptor and antigen into class II peptide-loading compartment is independent of receptor cross-linking.

The processing and presentation of Ag by B lymphocytes are initiated by Ag binding to the B cell Ag receptor (BCR). Using subcellular fractionation, we recently identified a compartment in B cells in which functional, processed Ag-class II complexes are formed following BCR-mediated Ag internalization, referred to as the peptide-loading compartment. These studies, however, did not address the transport of Ag or BCR from the cell surface to the peptide-loading compartment. In this work, we describe the intracellular trafficking of Ag and surface Ig (sIg) in B cells and evaluate the effect of cross-linking sIg on this intracellular movement. We show that sIg constitutively transports Ag from the plasma membrane, through endosomes, to the MHC class II peptide-loading compartment. The cross-linking of the BCR increases the rate of internalization of sIg and bound Ag, but does not alter the trafficking pathway. Thus, the delivery of Ag to the class II peptide-loading compartment by the sIg is independent of BCR cross-linking, but can be influenced by BCR cross-linking.

Animals↗
PubMed1995

Intracellular transport of invariant chain-MHC class II complexes to the peptide-loading compartment.

Th cells recognize peptide fragments of foreign Ags bound to MHC class II molecules. Upon synthesis in the endoplasmic reticulum, the alpha- and beta-chains of the class II molecules rapidly associate with invariant chains (li). The dissociation of li from class II molecules precedes binding of processed Ag and the formation of SDS-stable alpha beta dimers. We previously showed that functional, processed Ag-class II complexes are assembled in a dense lysosome-like compartment that contains stable class II molecules, but no li, referred to in this work as the peptide-loading compartment. We also identified a separate compartment that contains predominantly SDS-unstable li-class II complexes. Because we were unable to identify known organelle markers associated with this compartment, we refer to it as the X compartment. In this work, we provide results that indicate that the X compartment is composed of transport vesicles that move li-class II complexes to the peptide-loading compartment, where all events in the assembly of processed Ag-class II complexes occur.

Antigens, Differentiation, B-Lymphocyte↗