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Biomedical subjects

W Shi

Publications and source records attributed to W Shi.

At least 91 records · Page 5Linked to original sources
PubMed2000

Endothelial responses to oxidized lipoproteins determine genetic susceptibility to atherosclerosis in mice.

BACKGROUND: Oxidized LDL has been found within the subendothelial space, and it exhibits numerous atherogenic properties, including induction of inflammatory genes. We examined the possibility that variations in endothelial response to minimally modified LDL (MM-LDL) constitute one of the genetic components in atherosclerosis. METHODS AND RESULTS: By a novel explant technique, endothelial cells (ECs) were isolated from the aorta of inbred mouse strains with different susceptibilities to diet-induced atherosclerosis. Responses to MM-LDL were evaluated by examining the expression of inflammatory genes involved in atherosclerosis, including monocyte chemotactic protein-1 (MCP-1) and macrophage-colony-stimulating factor (M-CSF), an oxidative stress gene, heme oxygenase-1 (HO-1), and other, noninflammatory, genes. ECs from the susceptible mouse strain C57BL/6J exhibited dramatic induction of MCP-1, M-CSF, and HO-1, whereas ECs from the resistant strain C3H/HeJ showed little or no induction. In contrast, ECs from the 2 strains responded similarly to lipopolysaccharide. CONCLUSIONS: These data provide strong evidence that genetic factors in atherosclerosis act at the level of the vessel wall.

Animals↗
PubMed2000

Association between initial diagnostic procedure and hysteroscopy and abnormal peritoneal washings in patients with endometrial carcinoma.

BACKGROUND: Hysteroscopy has been implicated in the finding of positive peritoneal washings (PW) in patients with endometrial carcinoma in several case reports. The current study was designed to evaluate whether there was an increased incidence rate of positive peritoneal washings in patients after hysteroscopy compared with patients who did not undergo hysteroscopy. METHODS: Two hundred eighty-four women with endometrial carcinoma were treated by hysterectomy with intraoperative PW at the Memorial Sloan-Kettering Cancer Center between 1995-1998. They were diagnosed by either endometrial biopsy (EMB) or dilatation and curretage (D & C) with or without hysteroscopy during the same period. RESULTS: Of 173 patients diagnosed by EMB, 16 had abnormal PW (9.2%). Of 111 patients diagnosed by D & C, 11 had abnormal PW (9.9%). There was no significant difference between the two groups (P = 0.85). Of 23 patients who were diagnosed by D & C with hysteroscopy, 3 had abnormal PW (13.0%). Of 177 patients who did not undergo hysteroscopy, 17 had abnormal PW (9.6%). Of 84 patients for whom information regarding hysteroscopy was not available, 7 had abnormal PW (8.3%). The incidence rates among the three groups were not significantly different (P = 0.79). CONCLUSIONS: The initial diagnostic procedure, including hysteroscopy, does not appear to be associated with a high incidence rate of abnormal PW in patients with endometrial carcinoma.

Adult↗
PubMed2000

Crystal structures of Giardia lamblia guanine phosphoribosyltransferase at 1.75 A(,).

Giardia lamblia, the protozoan parasite responsible for giardiasis, requires purine salvage from its host for RNA and DNA synthesis. G. lamblia expresses an unusual purine phosphoribosyltransferase with a high specificity for guanine (GPRTase). The enzyme's sequence significantly diverges from those of related enzymes in other organisms. The transition state analogue immucillinGP is a powerful inhibitor of HGXPRTase from malaria [Li, C. M., et al. (1999) Nat. Struct. Biol. 6, 582-587] and is also a 10 nM inhibitor of G. lamblia GPRTase. Cocrystallization of GPRTase with immucillinGP led unexpectedly to a GPRTase.immucillinG binary complex with an open catalytic site loop. Diffusion of ligands into preformed crystals gave a GPRTase.immucillinGP.Mg(2+).pyrophosphate complex in which the open loop is stabilized by crystal contacts. G. lamblia GPRTase exhibits substantial structural differences from known purine phosphoribosyltransferases at positions remote from the catalytic site, but conserves most contacts to the bound inhibitor. The filled catalytic site with an open catalytic loop provides insight into ligand binding. One active site Mg(2+) ion is chelated to pyrophosphate, but the other is chelated to two conserved catalytic site carboxylates, suggesting a role for these amino acids. This arrangement of Mg(2+) and pyrophosphate has not been reported in purine phosphoribosyltransferases. ImmucillinG in the binary complex is anchored by its 9-deazaguanine group, and the iminoribitol is disordered. No Mg(2+) or pyrophosphate is detected; thus, the 5'-phosphoryl group is needed to immobilize the iminoribitol prior to magnesium pyrophosphate binding. Filling the catalytic site involves (1) binding the purine ring, (2) anchoring the 5'-phosphate to fix the ribosyl group, (3) binding the first Mg(2+) to Asp125 and Glu126 carboxyl groups and binding Mg(2+).pyrophosphate, and (4) closing the catalytic site loop and formation of bound (Mg(2+))(2). pyrophosphate prior to catalysis. Guanine specificity is provided by two peptide carbonyl oxygens hydrogen-bonded to the exocyclic amino group and a weak interaction to O6. Transition state formation involves N7 protonation by Asp129 acting as the general acid.

Animals↗
PubMed2000

Determinants of atherosclerosis susceptibility in the C3H and C57BL/6 mouse model: evidence for involvement of endothelial cells but not blood cells or cholesterol metabolism.

Lipids, monocytes, and arterial wall cells are primary components involved in atherogenesis. Using the inbred mouse strains C57BL/6J (B6) and C3H/HeJ (C3H), which have been extensively studied as models of the genetic control of diet-induced atherosclerosis, we examined which of these components determine genetic susceptibility. To test whether dietary responsiveness is involved, a congenic strain of C3H carrying an apoE-null allele (apoE(-/-)) was constructed. Although C3H.apoE(-/-) mice had higher plasma cholesterol levels, they developed much smaller lesions than their B6.apoE(-/-) counterpart on either chow or Western diets. Reciprocal bone marrow transplantation between the strains, with congenics carrying the same H-2 haplotype, was performed to examine the role of monocytes. The atherosclerosis susceptibility was not altered in the recipient mice, indicating that variations in monocyte function were not involved. Endothelial cells isolated from the aorta of B6 mice exhibited a dramatic induction of monocyte chemotactic protein-1, macrophage colony-stimulating factor, vascular cell adhesion molecule-1, and heme oxygenase-1 in response to minimally modified LDL, whereas endothelial cells from C3H mice showed little or no induction. In a set of recombinant inbred strains derived from the B6 and C3H parental strains, endothelial responses to minimally modified LDL cosegregated with aortic lesion size. These data provide strong evidence that endothelial cells, but not monocytes or plasma lipid levels, account for the difference in susceptibility to atherosclerosis between the 2 mouse strains.

Animals↗
PubMed2000

Electron paramagnetic resonance and electron nuclear double resonance spectroscopic identification and characterization of the tyrosyl radicals in prostaglandin H synthase 1.

The tyrosyl radicals generated in reactions of ethyl hydrogen peroxide with both native and indomethacin-pretreated prostaglandin H synthase 1 (PGHS-1) were examined by low-temperature electron paramagnetic resonance (EPR) and electron nuclear double resonance (ENDOR) spectroscopies. In the reaction of peroxide with the native enzyme at 0 degrees C, the tyrosyl radical EPR signal underwent a continuous reduction in line width and lost intensity as the incubation time increased, changing from an initial, 35-G wide doublet to a wide singlet of slightly smaller line width and finally to a 25-G narrow singlet. The 25-G narrow singlet produced by self-inactivation was distinctly broader than the 22-G narrow singlet obtained by indomethacin treatment. Analysis of the narrow singlet EPR spectra of self-inactivated and indomethacin-pretreated enzymes suggests that they reflect conformationally distinct tyrosyl radicals. ENDOR spectroscopy allowed more detailed characterization by providing hyperfine couplings for ring and methylene protons. These results establish that the wide doublet and the 22-G narrow singlet EPR signals arise from tyrosyl radicals with different side-chain conformations. The wide-singlet ENDOR spectrum, however, is best accounted for as a mixture of native wide-doublet and self-inactivated 25-G narrow-singlet species, consistent with an earlier EPR study [DeGray et al. (1992) J. Biol. Chem. 267, 23583-23588]. We conclude that a tyrosyl residue other than the catalytically essential Y385 species is most likely responsible for the indomethacin-inhibited, narrow-singlet spectrum. Thus, this inhibitor may function by redirecting radical formation to a catalytically inactive side chain. Either radical migration or conformational relaxation at Y385 produces the 25-G narrow singlet during self-inactivation. Our ENDOR data also indicate that the catalytically active, wide-doublet species is not hydrogen bonded, which may enhance its reactivity toward the fatty-acid substrate bound nearby.

Animals↗
PubMed2000

The tetraspanin CD9 associates with transmembrane TGF-alpha and regulates TGF-alpha-induced EGF receptor activation and cell proliferation.

Transforming growth factor-alpha (TGF-alpha) is a member of the EGF growth factor family. Both transmembrane TGF-alpha and the proteolytically released soluble TGF-alpha can bind to the EGF/TGF-alpha tyrosine kinase receptor (EGFR) and activate the EGFR-induced signaling pathways. We now demonstrate that transmembrane TGF-alpha physically interacts with CD9, a protein with four membrane spanning domains that is frequently coexpressed with TGF-alpha in carcinomas. This interaction was mediated through the extracellular domain of transmembrane TGF-alpha. CD9 expression strongly decreased the growth factor- and PMA- induced proteolytic conversions of transmembrane to soluble TGF-alpha and strongly enhanced the TGF- alpha-induced EGFR activation, presumably in conjunction with increased expression of transmembrane TGF-alpha. In juxtacrine assays, the CD9-induced EGFR hyperactivation by transmembrane TGF-alpha resulted in increased proliferation. In contrast, CD9 coexpression with transmembrane TGF-alpha decreased the autocrine growth stimulatory effect of TGF-alpha in epithelial cells. This decrease was associated with increased expression of the cdk inhibitor, p21(CIP1). These data reveal that the association of CD9 with transmembrane TGF-alpha regulates ligand-induced activation of the EGFR, and results in altered cell proliferation.

Animals↗
PubMed2000

The Electric Dipole Moment of the B(1)Pi State of ZrO.

A laser ablation source combined with a time-of-flight mass spectrometer has been constructed. The static electric field in the mass spectrometer gives rise to a first-order Stark effect splitting from which the permanent electric dipole moment of the B(1)Pi state (v = 0) of (90)ZrO is determined and found to be 3.43 +/- 0.07 D. The X(1)Sigma and B(1)Pi states are further investigated and comparisons with the results from ab initio calculations are made. Copyright 2000 Academic Press.

Journal Article↗
PubMed2000

Favorable short-term and long-term outcome after elective radical rectal cancer resection in patients 75 years of age or older.

PURPOSE: Because the elderly population in Western countries is rapidly increasing, as is their life expectancy, studies aimed at determining the impact of major surgery for primary rectal cancer in this group are warranted. The purpose of this study was to compare perioperative morbidity and mortality and long-term disease-specific and overall survival in primary rectal cancer patients, older and younger than 75 years of age, subject to major pelvic surgery. METHODS: From September 1986 to December 1996, the Prospective Colorectal Service Database identified 1,120 consecutive patients who underwent major pelvic surgery for primary rectal cancer. Of these, 157 (15 percent) were 75 years of age or older and comprise the elderly group. From the remaining 963 patients younger than 75 years of age, a representative random sample of 174 was selected and constitutes the younger group. Data were obtained from computerized databases and confirmed via chart review and telephone interviews. RESULTS: Perioperative complications were observed in 53 (34 percent) elderly and 63 (36 percent; P = not significant) younger patients. Perioperative deaths occurred in two (1.3 percent) elderly and one (0.6 percent; P = not significant) younger patient. The median follow-up time was 48 months. Although the overall survival was lower in the elderly group (P = 0.02; the 5-year overall survival rates were 51 and 66 percent), the disease-specific survival rate was similar in the two groups (P = 0.75; the 5-year disease-specific survival rates were 69 and 71 percent). CONCLUSION: In select individuals 75 years of age or older, major pelvic surgery for primary rectal cancer can be done with perioperative morbidity and mortality rates comparable to those obtained in younger individuals, while achieving excellent disease-specific and overall long-term survival.

Aged↗
PubMed2000

Prokinetic effect of erythromycin after colorectal surgery: randomized, placebo-controlled, double-blind study.

PURPOSE: Nausea and vomiting three to seven days after an elective operation on the colon and rectum remain a persistent clinical problem. Erythromycin, a safe, inexpensive drug that stimulates intestinal motilin receptors, has previously been shown to accelerate gastric emptying significantly after upper gastrointestinal surgery. We aimed to evaluate the effect of postoperative intravenous erythromycin on postoperative ileus in patients undergoing elective surgery for primary colorectal cancer. METHODS: Between May 1998 and April 1999, 150 patients undergoing primary resection of colon or rectal cancer were enrolled in this prospective, randomized, placebo-controlled trial. One hundred thirty-four patients completed the study. Patients were excluded if they had extensive metastatic disease, were taking medications known to interact with erythromycin, or if they required an ileostomy. Patients received either 200 mg of intravenous erythromycin or placebo every six hours. Clinical endpoints were recorded and continuous end-points are presented as mean +/- standard deviation. RESULTS: There were no significant complications related to erythromycin. The erythromycin (n = 65) and placebo (n = 69) groups were comparable regarding demographic and operative factors. The erythromycin group had a slightly shorter length of time to passage of flatus (4.1 +/- 1.3 vs. 4.4 +/- 1.1 days; P = 0.03). There was no significant difference between erythromycin and placebo in time to first solid food (5.6 +/- 1.9 vs. 5.4 +/- 1.8 days), time to first bowel movement (5.2 +/- 1.9 vs. 5.4 +/- 1.3 days), or time to discharge from hospital (7.5 +/- 2.0 vs. 7.6 +/- 2.8 days). There was no difference in the rate of clinically significant nausea (26 vs. 26 percent; P = 0.99), vomiting (17 vs. 16 percent; P = 0.88), or nasogastric tube placement (9 vs. 7 percent; P = 0.68). CONCLUSIONS: Erythromycin does not seem to alter clinically important outcomes related to postoperative ileus in patients undergoing resection for colorectal cancer.

Aged↗
PubMed2000

The Myxococcus xanthus wbgB gene encodes a glycosyltransferase homologue required for lipopolysaccharide O-antigen biosynthesis.

Myxococcus xanthus is a gram-negative soil bacterium that initiates a complex developmental program in response to starvation. A transposon insertion (Tn5-lac omega109) mutant with developmental deficiencies was isolated and characterized in this study. A strain containing this insertion mutation in an otherwise wild-type background showed delayed developmental aggregation for about 12 h and sporulated at 1-2% of the wild-type level. Tn5-lac omega109 was found to have disrupted the M. xanthus wbgB gene, which is located 2.1 kb downstream of the M. xanthus lipopolysacharide (LPS) O-antigen biosynthesis genes wzm wzt wbgA. The deduced polypeptide sequence of WbgB shares significant similarity with bacterial glycosyltransferases including M. xanthus WbgA. The wbgB::Tn5-lac omega109 mutant was found to be defective in LPS O-antigen synthesis by immunochemical analysis. Further mutational analysis indicated that the defects of the wbgB::Tn5-lac omega109 mutant were not the result of polar effects on downstream genes. Various motility assays demonstrated that the Tn5-lac omega109 mutation affected both social (S) and adventurous (A) gliding motility of M. xanthus cells. The pleiotrophic effects of wbgB mutations indicate the importance of LPS O-antigen biosynthesis for various cellular functions in M. xanthus.

Amino Acid Sequence↗
PubMed2000

Genetics of atherosclerosis: the search for genes acting at the level of the vessel wall.

Recent studies in mice have revealed genetic factors contributing to atherosclerosis that are independent of known risk factors. These factors appear to act locally, at the level of the vessel wall. In this review, we discuss these studies and summarize some of the cellular and molecular interactions that may be involved. We also outline the approaches for the identification of such factors in humans.

Animals↗
PubMed2000

Identification of CD72 as a lymphocyte receptor for the class IV semaphorin CD100: a novel mechanism for regulating B cell signaling.

We have identified the lymphocyte semaphorin CD100/Sema4D as a CD40-inducible molecule by subtractive cDNA cloning. CD100 stimulation significantly enhanced the effects of CD40 on B cell responses. Administration of soluble CD100 markedly accelerated in vivo antigen-specific antibody responses. CD100 receptors with different binding affinities were detected on renal tubular cells (K(d) = approximately 1 x 10(-9)M) and lymphocytes (K(d) = approximately 3 x 10(-7)M). Expression cloning revealed that the CD100 receptor on lymphocytes is CD72, a negative regulator of B cell responsiveness. CD72 thus represents a novel class of semaphorin receptors. CD100 stimulation induced tyrosine dephosphorylation of CD72 and dissociation of SHP-1 from CD72. Our findings indicate that CD100 plays a critical role in immune responses by the novel mechanism of turning off negative signaling by CD72.

Animals↗
PubMed2000

The class IV semaphorin CD100 plays nonredundant roles in the immune system: defective B and T cell activation in CD100-deficient mice.

The class IV semaphorin CD100/Sema4D differentially utilizes two distinct receptors: plexin-B1 in nonlymphoid tissues, such as brain and kidney, and CD72 in lymphoid tissues. We have generated CD100-deficient mice and demonstrated that they have functional defects in their immune system, without apparent abnormalities in other tissues. The number of CD5(+) B-1 cells was considerably decreased in the mutant mice, whereas conventional B cells and T cells appeared to develop normally. In vitro proliferative responses and immunoglobulin production were reduced in CD100-deficient B cells. The humoral immune response against a T cell-dependent antigen and in vivo priming of T cells were also defective in the mutant mice. These results demonstrate nonredundant and essential roles of CD100-CD72 interactions in the immune system.

Animals↗
PubMed2000

Analysis of gene expression in Treponema denticola with differential display polymerase chain reaction.

Treponema denticola is an oral spirochete associated with the periodontal diseases. A great deal of the molecular components of T. denticola will be learned soon since its genome sequence project is on the way. One of the most important works after genome sequence is to analyze the function of these genes and their regulation. However, like many other oral pathogens, there are currently a very limited number of molecular and genetic tools available to study gene expression in T. denticola. In this article, we describe a method of adapting differential display polymerase chain reaction (ddPCR) for use in the T. denticola system. To test for effectiveness of this protocol, we used three different temperature conditions, 4 degrees C, 25 degrees C and 42 degrees C, to test for differential gene expression. With various ddPCR conditions, we found a number of genes that were expressed differentially. Some of these differentially expressed genes were cloned and sequenced and found to be homologous with the known temperature-regulated genes, including HtrA. The study indicates that the ddPCR method can be effectively used in T. denticola for analyzing gene expression under various conditions.

Bacterial Proteins↗
PubMed2000

Hormonal regulation of sodium/sulfate co-transport in renal epithelial cells.

Serum sulfate concentrations are elevated in infants, young children, and pregnant women due, at least in part, to increased renal sulfate reabsorption. Little is known about the effects of hormones, particularly those involved in growth, development, and pregnancy, on renal sulfate reabsorption. The objective of this investigation was to examine the effects of growth hormone (GH), insulin-like growth factor 1 (IGF-1), progesterone (PG), and 17beta-estradiol (EST) on renal sodium/sulfate co-transport. 35S-sulfate uptake was determined in Madin-Darby canine kidney (MDCK)/NaSi-1 cells (MDCK cells that have been stably transfected with rat sodium/sulfate co-transporter (NaSi-1) cDNA) and in opossum kidney (OK) cells. NaSi-1 mRNA was determined by RT-PCR and protein levels by ELISA. GH (0.1 nM) significantly increased the sodium/sulfate co-transport in MDCK/NaSi-1 cells up to 35%. IGF-1 induced a concentration-related stimulation of the sodium/sulfate co-transport with a maximal response observed at 1000 nM (59% increase). Sodium-dependent sulfate uptake was significantly increased when cells were preincubated with 10 nM PG, 10 nM EST, or 10 nM PG/10 nM EST up to 41%, 46%, or 39%, respectively. OK cells exhibited endogenous sodium-dependent sulfate transport; significantly increased sodium/sulfate co-transport was also observed in OK cells that were preincubated with GH, IGF-1, and PG/EST, although not with EST alone. The NaSi-1 mRNA and NaSi-1 protein levels were significantly increased in MDCK/NaSi-1 cells treated with 0.1 nM GH, 100 nM IGF-1, 10 nM PG, and/or 10 nM EST compared with control. These results suggest that the increased renal sulfate reabsorption that occurs in neonates, young and pregnant humans, and animals could be mediated by the increased steady-state levels of NaSi-1 mRNA produced by the higher plasma concentrations of GH, IGF-1, or PG/EST.

Animals↗
PubMed2000

SOS3 function in plant salt tolerance requires N-myristoylation and calcium binding.

The salt tolerance gene SOS3 (for salt overly sensitive3) of Arabidopsis is predicted to encode a calcium binding protein with an N-myristoylation signature sequence. Here, we examine the myristoylation and calcium binding properties of SOS3 and their functional significance in plant tolerance to salt. Treatment of young Arabidopsis seedlings with the myristoylation inhibitor 2-hydroxymyristic acid caused the swelling of root tips, mimicking the phenotype of the salt-hypersensitive mutant sos3-1. In vitro translation assays with reticulocyte showed that the SOS3 protein was myristoylated. Targeted mutagenesis of the N-terminal glycine-2 to alanine prevented the myristoylation of SOS3. The functional significance of SOS3 myristoylation was examined by expressing the wild-type myristoylated SOS3 and the mutated nonmyristoylated SOS3 in the sos3-1 mutant. Expression of the myristoylated but not the nonmyristoylated SOS3 complemented the salt-hypersensitive phenotype of sos3-1 plants. No significant difference in membrane association was observed between the myristoylated and nonmyristoylated SOS3. Gel mobility shift and (45)Ca(2)+ overlay assays demonstrated that SOS3 is a unique calcium binding protein and that the sos3-1 mutation substantially reduced the capacity of SOS3 to bind calcium. The resulting mutant SOS3 protein was not able to interact with the SOS2 protein kinase and was less capable of activating it. Together, these results strongly suggest that both N-myristoylation and calcium binding are required for SOS3 function in plant salt tolerance.

Adaptation, Physiological↗