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Biomedical subjects

Y Wei

Publications and source records attributed to Y Wei.

At least 199 records · Page 11Linked to original sources
PubMed1999

Peripheral tissue distribution of orphanin FQ precusor mRNA in stroke-prone spontaneously hypertensive rats.

The heptadecapeptide orphanin FQ (OFQ) is a recently discovered neuropeptide that exhibits structural features reminiscent of the opioid peptides and that is an endogenous ligant to a G protein-coupled receptor sequentially related to the opioid receptors. OFQ was originally isolated from brain, but the presence of OFQ in peripheral tissues, especially in cardiovascular system, has not been clarified. The present study was designed to investigate the peripheral tissue distribution of OFQ precusor mRNA in stroke-prone spontaneously hypertensive rats (SHRSP) and compare the difference of OFQ precusor mRNA expression in aorta or cultured vascular smooth muscle cells (VSMCs) between SHRSP and wistar-Kyoto normotensive (WKY) rats. By using quantitative reverse transcription-polymerase chain reaction (RT-PCR), OFQ precusor mRNA was detected in aorta and ovary at high levels comparable with the amounts found in brain. Moderate expression was found in testis, while a little OFQ precusor mRNA could be detected in atrium. All other peripheral tissues examined from SHRSP, including ventricle, liver, lung and kidney, showed no expression of OFQ precusor mRNA. In the vascular system, OFQ precusor mRNA was expressed in aorta, pulmonary artery, renal artery and vein at high levels comparable with the amounts found in brain. We also found that OFQ precusor mRNA levels were much higher in aorta or cultured VSMCs from SHRSP than those from WKY rats. In conclusion, the present study has shown that OFQ precusor mRNA is present in some peripheral tissues, especially in cardiovascular and reproductive system, suggesting that OFQ possibly involves in the regulation of cardiovascular and reproductive functions.

Animals↗
PubMed1998

Cloning and functional characterization of PACAP-specific receptors in zebrafish.

Two PACAP receptors were isolated from total zebrafish cDNA library prepared from 6-day old fish by a homology-based cloning strategy. The two zebrafish PACAP receptors have the same topology as the one found in other members of this class of seven membrane-spanning G-protein-coupled receptors. Each of the two zebrafish PACAP receptors shares about 70% sequence identity at the amino acid level with the human PACAP-type 1 receptor, and about 50% amino acid identity with PACAP/VIP R-1 and PACAP/VIP R-2 receptors. One of these zebrafish receptors contains the hop2 configuration found in the human and rat PACAP-type 1 receptors. On the basis of these structural characteristics the zebrafish PACAP receptors were classified as PACAP-type 1 and PACAP-type 2 receptors. In competitive binding experiments zebrafish PACAP-type 1 and PACAP-type 2 receptors showed similar binding specificity for zebrafish and human PACAP-38 and PACAP-27. Furthermore, the specificity of PACAP-type 1 and PACAP-type 2 receptors for zebrafish and human PACAPs is about 1,000-fold higher than for human VIP. These results demonstrate that zebrafish PACAP-type 1 receptor is a structural and pharmacological homolog of the mammalian PACAP-type 1 receptor. Additional pharmacological characterization is needed in order to classify the zebrafish PACAP-type 2 receptor.

Amino Acid Sequence↗
PubMed1998

A photoactivated prodrug.

A photolabile derivative (1) of the anticancer drug, 5-fluorodeoxyuridine (2), was designed and synthesized as a model prodrug. Photolysis of 1 with long-wavelength UV light rapidly released 2 in solution. While compound 1 alone is nontoxic to cells, the presence of both 1 and UV irradiation (lambda = 350 nm) resulted in potent inhibition of cell growth.

Antimetabolites, Antineoplastic↗
PubMed1998

Age and liver transplantation: a report of the Liver Transplantation Database.

BACKGROUND: The average age of liver transplant recipients has increased steadily during the last decade. The effects of recipient age on outcome of liver transplantation were evaluated in a large prospective database. METHODS: A total of 735 adult recipients of single-organ liver transplants for nonfulminant liver disease enrolled in a large prospective database between 1990 and 1994 were analyzed for associations of patient age with outcomes. Patients were categorized into two groups: younger being <60 and older being > or = 60 years of age. RESULTS: Older liver transplant recipients were more likely to be female, white, and have the diagnoses of primary biliary cirrhosis or cryptogenic cirrhosis than younger recipients, who were more likely to have the diagnosis of alcoholic liver disease. Disease severity was similar between the two groups. After transplantation, the durations of stay in the intensive care unit and hospital were longer for older than for younger transplant recipients, but episodes of acute rejection were less frequent. The quality of life at 1 year was similar among older and younger recipients. Patient survival was lower for older than for younger recipients (81% vs. 90% at 1 year; P=0.004), whereas graft survival was not different (80% vs. 85% at 1 year; P=0.163). The excess mortality among older recipients was largely due to nonhepatic causes, including infectious, cardiac, and neurological diseases occurring within 6 months after transplantation. CONCLUSIONS: Although patient survival was significantly lower among liver transplant recipients above the age of 60 years, the excess mortality was due to nonhepatic, largely age-related problems. The overall success of liver transplantation and improvement in quality of life for older recipients is excellent.

Adult↗
PubMed1998

Phosphorylation of histone H3 at serine 10 is correlated with chromosome condensation during mitosis and meiosis in Tetrahymena.

H3 phosphorylation has been correlated with mitosis temporally in mammalian cells and spatially in ciliated protozoa. In logarithmically growing Tetrahymena thermophila cells, for example, H3 phosphorylation can be detected in germline micronuclei that divide mitotically but not in somatic macronuclei that divide amitotically. Here, we demonstrate that micronuclear H3 phosphorylation occurs at a single site (Ser-10) in the amino-terminal domain of histone H3, the same site phosphorylated during mitosis in mammalian cells. Using an antibody specific for Ser-10 phosphorylated H3, we show that, in Tetrahymena, this modification is correlated with mitotic and meiotic divisions of micronuclei in a fashion that closely coincides with chromosome condensation. Our data suggest that H3 phosphorylation at Ser-10 is a highly conserved event among eukaryotes and is likely involved in both mitotic and meiotic chromosome condensation.

Amino Acid Sequence↗
PubMed1998

Endothelin-induced conversion of embryonic heart muscle cells into impulse-conducting Purkinje fibers.

A regular heart beat is dependent on a specialized network of pacemaking and conductive cells. There has been a longstanding controversy regarding the developmental origin of these cardiac tissues which also manifest neural-like properties. Recently, we have shown conclusively that during chicken embryogenesis, impulse-conducting Purkinje cells are recruited from myocytes in spatial association with developing coronary arteries. Here, we report that cultured embryonic myocytes convert to a Purkinje cell phenotype after exposure to the vascular cytokine, endothelin. This inductive response declined gradually during development. These results yield further evidence for a role of arteriogenesis in the induction of impulse-conducting Purkinje cells within the heart muscle lineage and also may provide a basis for tissue engineering of cardiac pacemaking and conductive cells.

Animals↗
PubMed1998

Characterization of a novel cis-syn and trans-syn-II pyrimidine dimer glycosylase/AP lyase from a eukaryotic algal virus, Paramecium bursaria chlorella virus-1.

Endonuclease V from bacteriophage T4, is a cis-syn pyrimidine dimer-specific glycosylase. Recently, the first sequence homolog of T4 endonuclease V was identified from chlorella virus Paramecium bursaria chlorella virus-1 (PBCV-1). Here we present the biochemical characterization of the chlorella virus pyrimidine dimer glycosylase, cv-PDG. Interestingly, cv-PDG is specific not only for the cis-syn cyclobutane pyrimidine dimer, but also for the trans-syn-II isomer. This is the first trans-syn-II-specific glycosylase identified to date. Kinetic analysis demonstrates that DNAs containing both types of pyrimidine dimers are cleaved by the enzyme with similar catalytic efficiencies. Cleavage analysis and covalent trapping experiments demonstrate that the enzyme mechanism is consistent with the model proposed for glycosylase/AP lyase enzymes in which the glycosylase action is mediated via an imino intermediate between the C1' of the sugar and an amino group in the enzyme, followed by a beta-elimination reaction resulting in cleavage of the phosphodiester bond. cv-PDG exhibits processive cleavage kinetics which are diminished at salt concentrations greater than those determined for T4 endonuclease V, indicating a possibly stronger electrostatic attraction between enzyme and DNA. The identification of this new enzyme with broader pyrimidine dimer specificity raises the intriguing possibility that there may be other T4 endonuclease V-like enzymes with specificity toward other DNA photoproducts.

Binding Sites↗
PubMed1998

Structure of a microbial homologue of mammalian platelet-activating factor acetylhydrolases: Streptomyces exfoliatus lipase at 1.9 A resolution.

BACKGROUND: Neutral lipases are ubiquitous and diverse enzymes. The molecular architecture of the structurally characterized lipases is similar, often despite a lack of detectable homology at the sequence level. Some of the microbial lipases are evolutionarily related to physiologically important mammalian enzymes. For example, limited sequence similarities were recently noted for the Streptomyces exfoliatus lipase (SeL) and two mammalian platelet-activating factor acetylhydrolases (PAF-AHs). The determination of the crystal structure of SeL allowed us to explore the structure-function relationships in this novel family of homologous hydrolases. RESULTS: The crystal structure of SeL was determined by multiple isomorphous replacement and refined using data to 1.9 A resolution. The molecule exhibits the canonical tertiary fold of an alpha/beta hydrolase. The putative nucleophilic residue, Ser131, is located within a nucleophilic elbow and is hydrogen bonded to His209, which in turn interacts with Asp177. These three residues create a triad that closely resembles the catalytic triads found in the active sites of other neutral lipases. The mainchain amides of Met132 and Phe63 are perfectly positioned to create an oxyanion hole. Unexpectedly, there are no secondary structure elements that could render the active site inaccessible to solvent, like the lids that are commonly found in neutral lipases. CONCLUSIONS: The crystal structure of SeL reinforces the notion that it is a homologue of the mammalian PAF-AHs. We have used the catalytic triad in SeL to model the active site of the PAF-AHs. Our model is consistent with the site-directed mutagenesis studies of plasma PAF-AH, which implicate Ser273, His351 and Asp296 in the active site. Our study therefore provides direct support for the hypothesis that the plasma and isoform II PAF-AHs are triad-containing alpha/beta hydrolases.

1-Alkyl-2-acetylglycerophosphocholine Esterase↗
PubMed1998

Ergosteroids. II: Biologically active metabolites and synthetic derivatives of dehydroepiandrosterone.

An improved procedure for the synthesis of 3 beta-hydroxyandrost-5-ene-7,17-dione, a natural metabolite of dehydroepiandrosterone (DHEA) is described. The synthesis and magnetic resonance spectra of several other related steroids are presented. Feeding dehydroepiandrosterone to rats induces enhanced formation of several liver enzymes among which are mitochondrial sn-glycerol 3-phosphate dehydrogenase (GPDH) and cytosolic malic enzyme. The induction of these two enzymes, that complete a thermogenic system in rat liver, was used as an assay to search for derivatives of DHEA that might be more active than the parent steroid. Activity is retained in steroids that are reduced to the corresponding 17 beta-hydroxy derivative, or hydroxylated at 7 alpha or 7 beta, and is considerably enhanced when the 17-hydroxy or 17-carbonyl steroid is converted to the 7-oxo derivative. Several derivatives of DHEA did not induce the thermogenic enzymes whereas the corresponding 7-oxo compounds did. Both short and long chain acyl esters of DHEA and of 7-oxo-DHEA are active inducers of the liver enzymes when fed to rats. 7-Oxo-DHEA-3-sulfate is as active as 7-oxo-DHEA or its 3-acetyl ester, whereas DHEA-3-sulfate is much less active than DHEA. Among many steroids tested, those possessing a carbonyl group at position 3, a methyl group at 7, a hydroxyl group at positions 1, 2, 4, 11, or 19, or a saturated B ring, with or without a 4-5 double bond, were inactive.

Animals↗
PubMed1998

Ergosteroids III. Syntheses and biological activity of seco-steroids related to dehydroepiandrosterone.

The unusual activity of some D-ring-seco estrogens led us to prepare several seco steroids related to dehydroepiandrosterone (DHEA) and to test for their ability to mimic thyroid hormone and 7-oxo-DHEA (1) as inducers of thermogenic enzymes in rats' livers. Only one, 3 beta-acetoxy-17a-oxa-androst-5-ene-7,17-dione (17), was capable of inducing both mitochondrial glycerophosphate dehydrogenase and malic enzyme. The closely related 3 beta-hydroxy-17a-oxa-androsta-5,15-diene-7,17-diones (both 14 alpha and 14 beta, 14 and 15) induce the formation of malic enzyme but not of glycerophosphate dehydrogenase. The 3 beta-propionyl ester of the above 14 alpha steroid was not active, presumably because it was not deacylated in vivo. The 16,17 dicarboxylic acid (9) produced by opening the D-ring also induced the formation of malic enzyme but not of glycerophosphate dehydrogenase. 3 beta-Acetoxyandrost-5-ene-7,16,17-trione, an intermediate in the synthesis of D-ring seco compounds enhanced the formation of both enzymes. Twelve other D-ring seco compounds were not active. Seco androstanes oxygenated at position 7 and with expanded A or B rings were not active.

Animals↗
PubMed1998

An epidermis/papilla-specific oxalate oxidase-like protein in the defence response of barley attacked by the powdery mildew fungus.

A cDNA clone of a defence response transcript was isolated from a library prepared from barley leaves expressing papilla resistance towards the powdery mildew fungus, Blumeria (syn. Erysiphe) graminis f.sp. hordei (Bgh). The 904 bp sequence encodes a 229 amino acid polypeptide with a putative signal peptide of 23 amino acids. After cleavage, the protein has a mass of 22.3 kDa and exhibits up to 60% amino acid identity to certain dicot proteins, and 46% amino acid identity to barley oxalate oxidase; therefore we designated it HvOxOLP (for Hordeum vulgare oxalate oxidase-like protein). Single-base substitutions among several cDNA and RACE clones demonstrate a gene of many copies. Both the transcript and protein accumulate from 3 h after inoculation with Bgh. The transcript level peaks at 18-24 h and subsequently decreases, whereas the protein level is stable from 24 h after inoculation. The accumulation patterns are independent of the outcome of the barley/powdery mildew interaction, unlike that of PR proteins, for example. The transcript accumulates specifically in the inoculated epidermal tissue. This temporal and spatial expression pattern suggests a very close relationship to papilla formation. Immunoblot analyses have facilitated a demonstration that HvOxOLP, like oxalate oxidase, is a water-soluble 100 kDa oligomeric protein. The oligomer is heat-stable and SDS-tolerant, and it can be denatured into a 25 kDa monomer. Attempts to demonstrate oxalate oxidase activity for this protein have failed. However, the relationships to oxalate oxidase suggests that HvOxOLP may be involved in H2O2 generation necessary for, for example, cross-linking of cell wall components during formation of papillae.

Amino Acid Sequence↗
PubMed1998

Activation of heterologous gene expression by the large isoform of hepatitis delta antigen.

Hepatitis delta virus (HDV) encodes two isoforms of its principal gene product, hepatitis delta antigen (HDAg). These two forms play distinctive and complementary roles in viral replication. Here we report that the large (LHDAg), but not the small (SHDAg), isoform of HDAg has the capacity to activate the expression of cotransfected genes driven by a variety of promoters, including the pre-S, S, and C promoters of hepatitis B virus. Mutational analysis of the C-terminal 19 amino acids unique to LHDAg shows that changing prolines to alanines in the two PXXP motifs in this region specifically ablates the activation function without abolishing another activity of LHDAg, namely, its ability to inhibit HDV RNA synthesis. However, C-terminal truncations that also disrupt these PXXP motifs only slightly diminished the activation function, indicating that the proline mutations were not acting by inactivating potential SH3 interactions that could be mediated by these motifs. Mutation of the isoprenylated cysteine to serine decreases but does not abolish the activation activity, and overexpression of SHDAg does not interfere with the transactivation function of LHDAg. Although the mechanism and biological significance of this activity of LHDAg remain unknown, the presence of this activity serves as yet another marker that functionally distinguishes this protein from the closely related isoform SHDAg.

Amino Acid Sequence↗
PubMed1998

In vivo effects of mutations in woodchuck hepatitis virus enhancer II.

Woodchuck hepatitis virus (WHV) enhancer II (EnII) is located upstream of the major pregenomic RNA promoter and is thought to play an important role in the insertional activation of the N-myc2 gene during WHV hepatocarcinogenesis. WHV EnII is recognized by at least three host transcription factors: HNF-1, HNF-4, and Oct-1. Here, the roles of these EnII-binding factors in viral transcription and replication have been further examined. In HepG2 cells transiently transfected with a chloramphenicol acetyltransferase (CAT) gene whose expression is dependent upon EnII, mutations in either the HNF-1 or the HNF-4 site strongly reduced CAT activity, while ablation of the Oct-1 site decreased CAT expression only twofold. Mutations in more than one site completely abolished reporter expression. These same mutations were also tested in an overlength WHV genome for their impact on viral replication and gene expression. In transfected HepG2 cells, lesions in the HNF-1 site inactivated pregenomic RNA expression and viral reverse transcription, with only minimal effects on the expression of other viral mRNAs. By contrast, Oct-1 site lesions had no effect on either viral RNA synthesis or DNA replication, and HNF-4 site lesions produced a modest reduction of pregenomic RNA but had no impact on viral DNA synthesis. Testing of the mutants in susceptible woodchucks revealed that, as expected, viruses with lesions in the HNF-1 site were nearly noninfectious, while mutants with lesions at the Oct-1 site were fully replication competent. HNF-4 site mutants were replication competent but may display reduced levels of replication in the intact animal host. We conclude that (i) EnII is primarily devoted to the regulation of pregenomic RNA in WHV, (ii) HNF-1 is essential for EnII function in vivo, and (iii) HNF-4 plays a demonstrable but adjunctive role in EnII function.

Animals↗
PubMed1998

Menhaden oil prevents but does not reverse sucrose-induced insulin resistance in rats.

Although fish oil supplementation may prevent the onset of diet-induced insulin resistance in rats, it appears to worsen glycemic control in humans with existing insulin resistance. In the present study, the euglycemic, hyperinsulinemic (4x basal) clamp technique with [3-3H]glucose and 2-deoxy-[1-14C]glucose was used to directly compare the ability of fish oil to prevent and reverse sucrose-induced insulin resistance. In study 1 (prevention study), male Wistar rats were fed a purified high-starch diet (68% of total energy), high-sucrose diet (68% of total energy), or high-sucrose diet in which 6% of the fat content was replaced by menhaden oil for 5 wk. In study 2 (reversal study), animals were fed the high-starch or high-sucrose diets for 5 wk and then the sucrose animals were assigned to one of the following groups for an additional 5 wk: high starch, high sucrose, or high sucrose with 6% menhaden oil. Rats fed the high-starch diet for 10 wk served as controls. In study 3 (2nd reversal study), animals followed a similar diet protocol as in study 2; however, the reversal period was extended to 15 wk. In study 1, the presence of the fish oil in the high-sucrose diet prevented the development of insulin resistance. Glucose infusion rates (GIR, mg.kg-1.min-1) were 17.0 +/- 0.9 in starch, 10.6 +/- 1.7 in sucrose, and 15.1 +/- 1.5 in sucrose with fish oil animals. However, in study 2, this same diet was unable to reverse sucrose-induced insulin resistance (GIR, 16.7 +/- 1.4 in starch, 7.1 +/- 1.5 in sucrose, and 4.8 +/- 0.9 in sucrose with fish oil animals). Sucrose-induced insulin resistance was reversed in rats that were switched back to the starch diet (GIR, 18.6 +/- 3.0). Results from study 3 were similar to those observed in study 2. In summary, fish oil was effective in preventing diet-induced insulin resistance but not able to reverse it. A preexisting insulin-resistant environment interferes with the positive effects of menhaden oil on insulin action.

Animals↗
PubMed1998

Adipose tissue-derived tumor necrosis factor activity correlates with fat cell size but not insulin action in aging rats.

Adipose tissue-derived tumor necrosis factor (AT-TNF) protein and messenger RNA (mRNA) has been shown to correlate with insulin resistance in some studies. However, in a study using different aged Fischer 344 rats, AT-TNF activity correlated more strongly with cell size than with fasting plasma insulin. The present study was undertaken to more carefully examine the relationship among AT-TNF, adipose cell size, and insulin action using more precise measures of insulin action. Basal and hyperinsulinemic, euglycemic clamps were performed in male Sprague Dawley rats at four different ages (8, 13, 21, and 61 weeks old). [3-(3)H]glucose and 2-deoxy-D-[1-(14)C]glucose were used to assess glucose kinetics and tissue-specific glucose uptake. Because TNF activity represents the summation of TNF synthesis, secretion, and the amount of soluble inhibitors present, TNF activity was measured using a bioassay, in addition to measuring TNF protein and mRNA levels. AT-TNF activity increased significantly with age, as did the glucose infusion rate, a measure of whole body insulin resistance. However, AT-TNF activity did not correlate with any parameter of insulin action measured during the hyperinsulinemic, euglycemic clamps. In epididymal fat, AT-TNF activity correlated with: glucose infusion rate: r = -0.50, P = 0.17; rate of appearance: r = -0.19, P = 0.35; rate of disappearance: r = 0.08, P = 0.69. As was noted before, AT-TNF activity correlated well with fat cell size (r = 0.76, P < 0.001 in epididymal fat; r = 0.58, P = 0.007 in SUB fat). These data suggest that although AT-TNF activity and insulin resistance increase with age, the two are not functionally related. These data do not eliminate the potential role of nonadipose TNF in the regulation of insulin action.

Adipocytes↗