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Biomedical subjects

W Guo

Publications and source records attributed to W Guo.

At least 235 records · Page 13Linked to original sources
PubMed1995

Expression of cDNA fragment encoding sperm membrane peptide in E. coli.

A secretory high-level expression cloning vector designated as pSBC-20 was constructed by inserting a DNA fragment encoding the signal peptide of ompA protein into pBV 220 vector. Any foreign DNA fragment can be inserted into the polylinker cloning sites located after the secretion signal sequence. The cloned foreign gene is under the control of the PR-PL promoter while the expression of the gene is regulated by the cI-gene product. The products are secreted into the periplasmic space of bacteria or into the medium. A recombinant plasmid (pRSD-220) was constructed by inserting the 210 bp from RSD-2, a cDNA encoding a peptide fragment of human sperm protein, into the EcoRI site of pSBC-20. The E. coli cells transformed with pRSD-220 were propagated at 30 degrees C, then incubated at 42 degrees C for several hrs. The cloned gene product was secreted into the culture medium at a high rate. The yield was about 60 mg of gene product per liter of cultured medium.

Base Sequence↗
PubMed1995

bFGF promotes functional expression of transient outward currents in cultured neonatal rat ventricular cells.

To investigate the effect of basic fibroblast growth factor (bFGF) on ion channel expressions in developing cardiac cells, a short-term primary culture of ventricular myocytes isolated from day-old newborn rats was established. Functional expressions of the transient outward currents (Ito) were measured by whole-cell voltage-clamp method. Addition of 40 ng/ml bFGF to the serum-free culture medium for 72 hours increased the Ito density without influences on membrane capacitance of the myocytes, an estimate of cell size. bFGF also promoted expressions of the steady-state outward currents. Methyl 2,5-dihydroxycinnamate (3 microM), a tyrosine kinase inhibitor, showed preferential inhibition of the bFGF-stimulated increase in Ito density. These results suggest that bFGF may play a role in regulating ion channel expressions of developing cardiac cells via activation of bFGF receptor tyrosine kinase activity.

Animals↗
PubMed1995

Effect of intraamniotic dexamethasone administration on intestinal absorption in a rabbit gastroschisis model.

Infants with gastroschisis experience delayed intestinal motility and absorption for several weeks after birth. This intestinal dysfunction is believed to occur primarily in the third trimester and to be largely caused by the prolonged exposure of the intestine to amniotic fluid. Previous studies have shown that prenatal steroid administration will enhance mucosal disaccharidase activity and nutrient uptake. The present study evaluates the effects of dexamethasone on intestinal function in a rabbit fetal gastroschisis model. Thirty-four fetuses from 10 New Zealand white rabbits were divided into three groups: (1) gastroschisis group (GSC, n = 10), gastroschisis was created on gestational day (GD) 24 (term = 31 to 33 days); (2) dexamethasone group (GSD, n = 10), after the creation of gastroschisis, a small osmotic pump was placed into the rabbit doe for dexamethasone infusion into the fetal amniotic cavity for 7 days (0.2 microgram/g/d); (3) normal group (NF, n = 10), unoperated littermates from the GSC group. There were no maternal deaths, and fetal survival rate was 85%. The fetal small intestinal disaccharidase enzyme, lactase (UE/g protein), was markedly decreased in GSC fetuses. It was increased 70% in the GSD group but lower than in normal fetuses (GSC = 10.0 +/- 1.6; GSD = 17.3 +/- 1.6 [GSD versus GSC, P < .05]; NF = 48.0 +/- 6.7). Maltase activity in the GSD group was significantly increased (GSC = 7.2 +/- 1.1; GSD = 13.9 +/- 1.8 [GSD versus GSC, P < .05]; NF = 12.2 +/- 1.3).(ABSTRACT TRUNCATED AT 250 WORDS)

Abdominal Muscles↗
PubMed1995

Adaptation of rabbit small intestinal brush-border membrane enzymes after extensive bowel resection.

Short lengths of small intestine may be resected without significantly affecting the digestive and absorptive capacity; however, extensive resection produces varying degrees of malnutrition. This study was undertaken to define the adaptive changes in the remaining small intestine of two of the jejunal and ileal mucosal brush-border membrane enzymes after extensive small bowel resection in rabbits. Thirty adult New Zealand White rabbits underwent a 50% to 60% jejuno-ileal-enterectomy with end-to-end anastomosis. Maltase activity (UE/g protein) increased from 152 (preoperative) to 392 at 3 weeks in the proximal segment and from 85 to 259 in the distal segment; these levels decreased to 222 and 155 in the respective segments at 6 weeks. AOP activity (UE/g protein) increased from 154 (preoperative) to 171 in the proximal segment and 171 to 256 in the distal segment at 3 weeks, and was 131 and 288 in the respective segments at 6 weeks. This marked increase in the mucosal brush-border enzymatic activities at 3 weeks postoperatively was associated with a 28% increase in bowel length. By 6 weeks the enzyme levels had decreased slightly; however, there was a persistent 41% increase in bowel length over that immediately postoperation. The mucosal surface area increased from 295 mm2 immediately postoperation to 5,337 mm2 at 3 weeks and 7,635 mm2 at 6 weeks, a 250% increase. The authors conclude that there is an immediate compensatory increase in villus length as well as brush-border enzymatic expression in the remaining intestine that gradually declines as the small intestinal surface area continues to increase and the bowel lengthens with time.

Adaptation, Physiological↗
PubMed1995

Reticuloendothelial system function in acute liver injury induced by D-galactosamine.

AIMS/METHODS: Reticuloendothelial system function, as assessed by clearance of radiolabelled bacteria, was evaluated in acute liver injury induced by D-galactosamine in rats, and compared with that after 70% liver resection model. RESULTS: Reticuloendothelial system function was significantly impaired in both instances, but the extent and the pattern of reticuloendothelial system impairment differed in the two models. While the elimination rate of the radiolabelled bacteria (k-value) decreased in both the liver resection and D-galactosamine groups (19% and 52%, respectively), the corrected phagocytic index (alpha) increased in 70% liver resection (247%), indicatine increased activity among the remaining reticuloendothelial system cells of the liver. Estimation of subserosal organ blood flow showed decreased flow to the cecum and distal small intestine (correction of intesting) in both groups, whereas it was significantly increased (477%) in the remaining parts of the liver in the liver resection group. CONCLUSIONS: These findings show that reticuloendothelial system activity is deranged in both these groups, which may explain the increased occurrence of bacterial complications observed in corresponding clinical conditions.

Animals↗
PubMed1995

ORDMKV: a computer program fitting proportional odds model for multi-state Markov process.

ORDMKV is a computer program designed to fit a multi-state discrete-time Markov model for k-stages disease processes having an ordinal structure. The model consists of k transient states representing the increasing severity of the disease process, and the final state can be optionally chosen to be an absorbing state in cases such as death. The ordinal structure of the stages of the disease is modelled by using ordinal response models. Each row of the one-step transition probability matrix is modelled using a proportional odds model based on the cumulative transition probabilities. By using these ordinal response models, the number of parameters used to model the disease process can be reduced significantly not only with respect to a general discrete-time model, but also compared with a parsimonuos continuous-time model. A restricted model can be fitted by assuming that the effect of the covariables in the cumulative probability has common regression coefficients in all stages of the disease process. This assumption, if it holds, reduces the number of regression coefficients associated with each covariate to only one. The regression coefficients of this model are estimated via the method of maximum likelihood, using a quasi-Newton optimization algorithm. When the last state is considered as an absorbing state, it is possible to compute survival curves from the transient states of the process. The program was written in standard FORTRAN 77 and is illustrated using a four-state model to determine factors influencing diabetic retinopathy in young subjects with insulin-dependent diabetes mellitus.

Diabetes Mellitus, Type 1↗
PubMed1995

MARKOV: a computer program for multi-state Markov models with covariables.

This paper discusses a computer program, called MARKOV, designed to fit a multi-state Markov model with covariables, with a particular emphasis on the analysis of survival data. The Markov model consists of k-1 transient disease states and one absorbing state. The exact transition times are not observed, except in situations such as death. Baseline transition intensities and regression coefficients are estimated via the method of maximum likelihood using a quasi-Newton optimization algorithm. The program's output includes the parameter estimates, the standard error of the estimates, the matrix of the correlation of the estimates and minus two times the log-likelihood function, evaluated at the initial values and at the maximum likelihood estimates. Optionally, survival curves can be generated from each transient state, for one or more combination of covariable values and simple tests about the parameters. The program is illustrated by using a four-state model to determine factors influencing diabetic retinopathy in young subjects with insulin-dependent diabetes mellitus.

Algorithms↗
PubMed1995

Molecular organization and motions of crystalline monoacylglycerols and diacylglycerols: a C-13 MASNMR study.

Six saturated acylglycerols (1-myristoyl-sn-glycerol, 1-palmitoyl-sn-glycerol, 1,2-dimyristoyl-sn-glycerol, 1,2-dipalmitoyl-sn-glycerol, 1,2-dipalmitoyl-rac-glycerol, and 1,3-dimyristoylglycerol) were studied in their various polymorphic forms (sub-alpha, alpha, beta') by natural abundance C-13 nuclear magnetic resonance (NMR) with magic angle spinning (MASNMR). C-13 MASNMR does not require single crystals and can observe relatively disordered crystals, distinct advantages over crystallographic diffraction methods. Well resolved spectra were obtained for each acylglycerol, and the chemical shifts of corresponding carbons were different for each crystalline phase and the isotropic liquid phase; moreover, in the case of monoacylglycerols, the symmetrically nonequivalent molecules in the same crystalline structure gave distinct C-13 resonances for the same carbon. The C-13 chemical shifts corresponding to each polymorphic phase were interpreted in terms of differences in intramolecular bond distances, intermolecular interactions (such as H bonding), and molecular motions. Mobilities of the glycerol backbone and acyl chains were assessed by the C-13 linewidths and the C-H dipolar relaxation rates. The chemical shift anisotropy(ies) (delta sigma) of the carbonyl group(s) of each acylglycerol was determined from slow-spinning MAS spectra, and was discussed in terms of the conformational and/or motional changes for the carbonyl carbon(s).

Anisotropy↗
PubMed1995

Phase behavior and crystalline structures of cholesteryl ester mixtures: a C-13 MASNMR study.

Cholesteryl esters are a transport and storage form of cholesterol in normal physiology but also a significant lipid in atherosclerotic plaques. To understand better the molecular properties of cholesteryl esters in tissues and plaques, we have studied the polymorphic and mesomorphic features of pure and mixed cholesteryl esters by solid state C-13 NMR with magic angle sample spinning (MASNMR). The temperature-dependent properties of two single components (cholesteryl linoleate (CL, C18:2) and cholesteryl linolenate (CLL, C18:3)), four binary systems (cholesteryl palmitate (CP, C16:0) with CL, CLL or cholesteryl oleate (CO, C18:1), and CO/CL), one ternary system (CO/CP/CL), and one quaternary system (CO/CP/CL/CLL) were studied. The mixing ratios were based on the composition of an atherosclerosis plaque dissected from a cholesterol-fed New Zealand white rabbit. C-13 MASNMR determined the phase transition temperatures, identified the phases present in all systems, and provided novel information about molecular structures. For example, solid CL exhibited a disordered structure with multiple molecular conformations, whereas pure CLL had a crystalline structure different from the three most commonly characterized forms (MLII, MLI, BL). In binary mixtures, the crystalline structure of each cholesteryl ester species was identified by its own characteristic resonances. It was found that CP always existed in its native BL form, but CL and CO were influenced by the composition of the mixture. CL was induced to form MLII crystals by the coexisting CP (55 wt%). When CO was cooled from the isotropic phase, it existed as a mixture of MLII and an amorphous form. The presence of CP significantly accelerated the conversion of the amorphous form to the MLII form. For the ternary mixture co-dried from chloroform, CL cocrystallized with CO in the MLII form and CP existed in BL form. Addition of a small amount of CLL slightly increased the heterogeneity of the solid mixture, but had little effect on the crystal structures or the phase transitions. C-13 MASNMR represents a powerful method for physical characterization of cholesteryl ester mixtures reflecting the composition of biological samples.

Animals↗
PubMed1995

Effect of nutrition intervention on intermediate endpoints in esophageal and gastric carcinogenesis.

A nutrition intervention trial involving > 3000 participants was conducted in Linxian, China, where the esophageal and stomach cancer mortality rates are among the highest in the world and suspicion exists that chronic deficiencies of multiple nutrients are etiologically involved. The trial was randomized, double-blind, and placebo-controlled and tested the effect of multivitamin and multimineral supplements in reducing cancer incidence and mortality in adults with cytologically detected esophageal dysplasia. Endoscopic and cytologic examinations of samples of trial participants during the intervention allowed evaluation of intermediate endpoints in esophageal and gastric carcinogenesis, including asymptomatic histologic precancerous lesions and early invasive cancer, epithelial proliferation, and cytologic abnormalities. Results from these ancillary studies suggest that multivitamin and multimineral supplementation may decrease proliferation and enhance cytologic reversion to nondysplasia.

Adult↗
PubMed1995

The Linxian trials: mortality rates by vitamin-mineral intervention group.

Two randomized nutrition intervention trials were conducted in Linxian, an area of north central China with some of the world's highest rates of esophageal and stomach cancer and a population with a chronically low intake of several nutrients. One trial used a factorial design that allowed us to assess the effects in nearly 30,000 participants of daily supplementation with four nutrient combinations: retinol and zinc; riboflavin and niacin; vitamin C and molybdenum; and beta-carotene, alpha-tocopherol, and selenium. The second trial provided daily multiple vitamin-mineral supplementation or placebo in 3318 persons with esophageal dysplasia, a precursor to esophageal cancer. After supplements were given for 5.25 y in the general population trial, small but significant reductions in total [relative risk (RR) = 0.91] and cancer (RR = 0.87) mortality were observed in subjects receiving beta-carotene, alpha-tocopherol, and selenium but not the other nutrients. The reductions were greater in women than men, and in those under compared with over the age of 55; however, differences by sex or age were not significant. After multiple vitamin and mineral supplements were given for 6 y in the smaller dysplasia trial, reductions in total (RR = 0.93) and cancer (RR = 0.96) mortality were observed but these were not significant. The largest reductions were for cerebrovascular disease mortality, but the effects differed by sex: a significant reduction was observed in men (RR = 0.45) but not women (RR = 0.90). Restoring adequate intake of certain nutrients may help to lower the risk of cancer and other diseases in this high-risk population.

Adult↗
PubMed1995

Possible immunologic involvement of antioxidants in cancer prevention.

The people of Linxian County, China have one of the world's highest rates of esophageal cancer. Two intervention trials were conducted to determine whether supplementation with specific vitamins and minerals could lower mortality from or incidence of cancer in this population and whether supplementation with multiple vitamins and minerals would reduce esophageal and gastric cardia cancer in persons with esophageal dysplasia. About 30,000 general population (GP) subjects in the GP trial were randomly assigned to one of eight intervention groups according to a one-half replicate of a 2(4) factorial experimental design and were supplemented for 5.25 y with four combinations of micronutrients at doses from one to two times the US recommended dietary allowance (RDA). About 3000 subjects in whom dysplasia was diagnosed in the dysplasia trial were randomly assigned to groups receiving daily supplementation with 14 vitamins and 12 minerals at two to three times the US RDA or placebo for 6 y. Results of the dysplasia trial indicate that in individuals with esophageal dysplasia, micronutrient supplementation had little effect on T lymphocyte responses. In contrast, male participants in the GP trial who were supplemented with beta-carotene, vitamin E, and selenium showed significantly (P < 0.05) higher mitogenic responsiveness of T lymphocytes in vitro than those not receiving these micronutrients.

Adult↗
PubMed1995

Cloning of a novel constitutively expressed pectate lyase gene pelB from Fusarium solani f. sp. pisi (Nectria haematococca, mating type VI) and characterization of the gene product expressed in Pichia pastoris.

Since plant-pathogenic fungi must penetrate through pectinaceous layers of the host cell wall, pectin-degrading enzymes are thought to be important for pathogenesis. Antibodies prepared against a pectin-inducible pectate lyase (pectate lyase A [PLA]) produced by a phytopathogenic fungus, Fusarium solani f. sp. pisi (Nectria haematococca, mating type VI), was previously found to protect the host from infection. The gene (pelA) and its cDNA were cloned and sequenced. Here we report the isolation of a new pectate lyase gene, pelB, from a genomic library of F. solani f. sp. pisi with the pelA cDNA as the probe. A 2.6-kb DNA fragment containing pelB and its flanking regions was sequenced. The coding region of pelB was amplified by reverse transcription-mediated PCR, using total RNA isolated from F. solani pisi culture grown in the presence of glucose as the sole carbon source. The predicted open reading frame of pelB would encode a 25.6-kDa protein of 244 amino acids which has 65% amino acid sequence identity with PLA from F. solani f. sp. pisi but no significant homology with other pectinolytic enzymes. The first 16 amino acid residues at the N terminus appeared to be a signal peptide. The pelB cDNA was expressed in Pichia pastoris, yielding a pectate lyase B (PLB) which was found to be a glycoprotein of 29 kDa. PLB was purified to homogeneity by using a two-step procedure involving ammonium sulfate precipitation followed by Superdex G75 gel filtration chromatography. Purified PLB showed optimal lyase activity at pH 10.0. A rapid drop in the viscosity of the substrate and Mono Q anion-exchange chromatography of the products generated by the lyase showed that PLB cleaved polygalacturonate chains in an endo fashion. Western blotting (immunoblotting) with antibodies raised against PLA showed that PLB and PLA are immunologically related to each other. The 5' flanking regions of both pelA and pelB were translationally fused to the beta-glucuronidase gene and introduced into F. solani f. sp. pisi, and beta-glucuronidase activities of the transformants were measured. Expression of the marker gene by the transformants showed that pelA expression is induced by pectin and repressed by glucose, whereas expression of pelB is constitutive and is not subject to glucose repression. Reverse transcription-mediated PCR showed that both pelA and pelB are expressed when F. solani f. sp. pisi infects pea epicotyl.

Base Sequence↗
PubMed1995

Alterations in intestinal bacterial flora modulate the systemic cytokine response to hemorrhagic shock.

To test the hypothesis that the resident gut flora plays an active role in modulating the cytokine response to hemorrhagic shock, plasma levels of interleukin-6 (IL-6) and tumor necrosis factor (TNF) were measured from the following three groups of rats before, immediately after, and 3, 8, or 24 h post-hemorrhagic shock (90 min at 30 mmHg)/sham shock: 1) rats with a normal gut flora (NF), 2) rats whose gut flora had been decontaminated with oral antibiotics (AD), and 3) rats with intestinal overgrowth with E. coli. In all three groups, portal and systemic TNF and IL-6 levels were 2- to 10-fold higher in the shock than the sham-shock rats (P < 0.05), with the highest TNF and IL-6 levels observed in the rats that were colonized with Escherichia coli (P < 0.05 vs. AD and NF). TNF levels were higher in the NF than the AD groups at 3 and 8 h postshock. The present study suggests that changes in the gut microflora modulate the systemic cytokine response to hemorrhagic shock with intestinal bacterial overgrowth leading to the greatest increase in plasma IL-6 and TNF levels.

Animals↗
PubMed1995

Effect of chronic hypoxia on ion channel development in cultured cardiac cells.

In order to investigate mechanisms underlying the postnatal development of the transient outward current (Ito) in the rat heart, we established a primary culture of neonatal rat ventricular myocytes and studied the modulated expressions of Ito under normoxic (21% O2) and hypoxic (7.5% O2) growth conditions. During development from day 5 to day 15 in the normoxic cultures, Ito density doubled without any changes to the kinetics of current inactivation. Chronic hypoxia from day 6 to day 15 prevented this increase in Ito density. The reduced expression of Ito under hypoxic conditions was due to the loss of the fast inactivating component of Ito (Ito,f) These observations suggest that ion channels in neonatal rat cardiomyocytes in primary culture are not constitutively expressed but can be regulated by extrinsic factors. The postnatal increase in Ito density among newborn rats is closely associated with an alteration in oxygen tension.

Action Potentials↗
PubMed1995

[A preliminary study on the mechanism of against human tongue cancer cell line].

Inverted phase contrast microscope and transmission electron microscope examination reveals that, tumor-draining lymphnode lymphocytes (DNL) conjugated with tumor cells very tightly at 12 hours co-culture. The DNL cell nucleus was seen positioned away from the target cells, whereas the cell mitochondria granules were oriented toward the point of contact with the target cells. The injured target cell had a highly condensed cytoplasm and chromatin and formation of cytoplasmic blebs, which were consistent with an apoptotic cell death rather than with a lytic or necrotic cell death. The mechanism was exocytosis of granules containing a pore-forming protein. Holes formed in the target cell's membrane may allow a lethal substance to enter and to induce its death via an apoptotic mechanism.

Apoptosis↗