Biomedical subjects

W Guo

Publications and source records attributed to W Guo.

At least 19 recordsLinked to original sources

PubMed1995

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

Antibodies prepared against a pectate lyase (PLA) produced by a phytopathogenic fungus Fusarium solani f. sp. pisi (Nectria haematococca, mating type VI) were previously found to protect the host against infection. The cDNA and gene (pelA) for PLA were cloned and sequenced. A new pectate lyase gene, pelC, was isolated from a genomic library of F. solani pisi with pelA cDNA as a probe. A 1.3-kb DNA fragment containing the pelC gene and its flanking regions was identified and sequenced. The coding region of pelC was amplified by reverse transcription-polymerase chain reaction using total RNA isolated from a pectin-induced F. solani pisi culture as template. The open reading frame of pelC was predicted to encode a 23.3-kDa protein of 219 amino acid residues, which shares 51% identity with PLA from F. solani pisi. No typical fungal leader peptide sequence could be identified at the N-terminus of the predicted protein sequence. The amplified pelC cDNA was expressed in Pichia pastoris yielding a pectate lyase C (PLC) with a molecular mass of 26.0 kDa and containing carbohydrates. PLC was purified to homogeneity using Mono Q anion-exchange chromatography. Purified PLC required Ca2+ for its activity and showed optimal lyase activity at pH 9.5 and 55 degrees C. Rapid drop in the viscosity of the substrate and Mono Q anion-exchange chromatography of the products generated by the lyase showed that PLC cleaved polygalacturonate chains in an endo fashion. Western blot using antibodies raised against PLA and PLC showed that PLC and PLA are immunologically related to each other.

Amino Acid Sequence↗

PubMed1995

A multinuclear solid-state NMR study of phospholipid-cholesterol interactions. Dipalmitoylphosphatidylcholine-cholesterol binary system.

Multinuclear (1H, 13C, 31P) MASNMR and static solid-state 31P NMR were used to study the molecular interactions between dipalmitoylphosphatidylcholine (DPPC) and free cholesterol (CHOL) in multilayers of DPPC containing 0-65 mol % CHOL with respect to total lipid at temperatures between 25 and 55 degrees C. 13C chemical shifts and line shapes for DPPC and CHOL resonances were measured in 13C MASNMR spectra. The apparent chemical shift anisotropy (CSA) of the DPPC acyl methylene resonances [(CH2)n] was calculated from the 1H MASNMR spectra. CSA and line shape changes were recorded as a function of CHOL content by 31P static solids and MASNMR. The presence of CHOL significantly changed the 13C chemical shifts and line shapes of DPPC carbonyl carbons below or above the main transition temperature of pure DPPC. Chemical shift changes were also observed for CHOL carbons as a function of the mixing ratio, signifying a changing local environment of CHOL. For mixtures with CHOL > 50 mol %, 13C MASNMR detected crystalline CHOL in the monohydrate form. When the excess CHOL was in a submicroscopic crystalline form that was not readily detected by differential scanning calorimetry, or optical microscopy (but readily observed by 13C MASNMR), the 31P powder pattern was affected, suggesting interaction of the excess CHOL with the aqueous interface of the bilayer. These results suggest the potential of 13C MASNMR for detection of crystalline CHOL in biological samples.

1,2-Dipalmitoylphosphatidylcholine↗

PubMed1995

Identification of a putative steroidogenic factor-1 response element in the DAX-1 promoter.

The nuclear hormone receptor, DAX-1, is responsible for X-linked adrenal hypoplasia congenita and hypogonadotrophic hypogonadism. We recently cloned the 5' flanking region of the human DAX-1 gene and in this report we describe the identification of a putative steroidogenic factor 1 (SF-1) response element approximately 110 bases upstream of the TATA box. Both DAX-1 and SF-1 are expressed in similar tissues including the adrenal cortex, gonads, hypothalamus, and the pituitary gland. Like DAX-1, SF-1 expression has been shown to be essential for the development of the adrenal cortex. We demonstrate that SF-1 is able to efficiently bind to the putative SF-1 response element found in the DAX-1 promoter in vitro. This suggests that SF-1 may directly regulate the expression of DAX-1 and that these two transcription factors may be components of a cascade required for development of steroidogenic tissues.

Base Sequence↗

PubMed1995

Diagnosis of X-linked adrenal hypoplasia congenita by mutation analysis of the DAX1 gene.

OBJECTIVE: To develop a rapid diagnostic approach to individuals with the X-linked cytomegalic form of adrenal hypoplasia congenita (AHC) and hypogonadotropic hypogonadism (HH) due to mutations in DAX1, a new member of the nuclear hormone receptor gene superfamily. DESIGN: Molecular genetic diagnostic investigations of individuals with AHC and their relatives included polymerase chain reaction amplification of DAX1 for identification of intragenic mutations and fluorescence in situ hybridization with a cosmid containing the DAX1 gene for evaluation of larger deletions. PARTICIPANTS: Families that had males affected with AHC were evaluated for mutations involving the DAX1 gene. RESULTS: DAX1 mutations were identified in four families that had males affected with AHC. Two apparently independent pedigrees had an identical frame-shift mutation due to a single base pair deletion, and a third had a larger deletion involving the entire DAX1 locus. The fourth family was evaluated by fluorescence in situ hybridization for prenatal diagnosis, and both the DAX1 locus and the contiguous glycerol kinase region were deleted. CONCLUSIONS: Molecular genetic and molecular cytogenetic techniques represent rapid and complementary approaches to the diagnosis of mutations in the DAX1 gene responsible for AHC and the associated HH. Specific diagnosis of the cause of adrenal insufficiency in these boys permits anticipatory management of the HH and prenatal counseling for parents of the affected child and other members of their families.

Adrenal Insufficiency↗

PubMed1995

Association of triadin with the ryanodine receptor and calsequestrin in the lumen of the sarcoplasmic reticulum.

Triadin is a major membrane protein that is specifically localized in the junctional sarcoplasmic reticulum of skeletal muscle and is thought to play an important role in muscle excitation-contraction coupling. In order to identify the proteins in the skeletal muscle that interact with triadin, the cytoplasmic and luminal domains of triadin were expressed as glutathione S-transferase fusion proteins and immobilized to glutathione-Sepharose to form affinity columns. Using these affinity columns, we find that triadin binds specifically to the ryanodine receptor/Ca2+ release channel and the Ca(2+)-binding protein calsequestrin from CHAPS (3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonic acid)-solubilized skeletal muscle homogenates. The luminal but not the cytoplasmic domain of triadin-glutathione S-transferase fusion protein binds [3H]ryanodine receptor, whereas neither the cytoplasmic nor the luminal portion of triadin binds [3H]PN-200-100-labeled dihydropyridine receptor. In addition, the luminal domain of triadin interacts with calsequestrin in a Ca(2+)-dependent manner and is capable of inhibiting the reassociation of calsequestrin to the junctional face membrane. These results suggest that triadin is the previously unidentified transmembrane protein that anchors calsequestrin to the junctional region of the sarcoplasmic reticulum, and is involved in the functional coupling between calsequestrin and the ryanodine receptor/Ca2+ release channel.

Animals↗

PubMed1995

The effect of epidermal growth factor on mucosal function after ileal resection.

Since epidermal growth factor (EGF) enhances gut mucosal regeneration, the present study was undertaken to evaluate the effect of EGF on brush-border membrane enzyme activity and glutamine uptake in the intestinal remnant following extensive small bowel resection. Twenty-four adult male New Zealand White rabbits were divided into three groups: Group 1 (n = 12) served as controls. Groups 2 and 3 (n = 6 each) underwent a 50-60% mid-jejunoileal resection with anastomosis of the remaining intestine, leaving 90 cm between the pylorus and the ileocecal valve. Group 3 rabbits had a subcutaneous osmotic pump implanted to deliver EGF for 7 days at 0.3 micrograms/kg/hr. Rabbits from Groups 2 and 3 were sacrificed 3 weeks postoperation. Mucosa from the proximal and distal segments of the remaining intestine was analyzed for wet/dry weight, maltase and aminooligopeptidase activity, and glutamine uptake. There was a twofold increase in mucosal dry weight/cm of intestine in rabbits without EGF at 3 weeks (Group 2) and a fourfold increase in those given EGF (Group 3). The maltase enzyme capacity (UEnzyme/rabbit) increased from 37 +/- 10 in controls (Group 1) to 167 +/- 30 without EGF and 207 +/- 30 with EGF. The aminooligopeptidase enzyme capacity (UEnzyme/rabbit) increased from 55 +/- 10 to 147 +/- 20 and 226 +/- 30 in Groups 1, 2, and 3, respectively. Glutamine uptake capacity (microM glutamine/min) also increased significantly, from 63 +/- 19 in Group 1 to 88 +/- 6 without EGF and 162 +/- 18 with EGF (P < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

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

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

[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↗

PubMed1995

[Protective effect of semen Ziziphi spinosae on superoxide dismutase reduction in mice with endotoxin fever].

An animal model with decreasing SOD was established by fever from intravenous injection of endotoxin. The SOD level was measured by RIA in the animal serum and liver tissues. The results indicated that the SOD level of the model group was obviously lower than that of the normal group (P < 0.05), but the level of the group treated with Semen Ziziphi Spinosae was higher than that of the model group. The study shows that Semen Ziziphi Spinosae can protect mice with endotoxin fever from SOD decrease.

Animals↗

PubMed1995

Comparison of plasma cytokine levels in rats subjected to superior mesenteric artery occlusion or hemorrhagic shock.

The overall goal of this study was to compare the effects of systemic hypotension (hemorrhagic shock) versus local gut ischemia (superior mesenteric artery (SMA) occlusion) on cytokine production and bacteria/endotoxin translocation. Sham or actual SMA occlusion led to an increase in tumor necrosis factor (TNF), which was greatest at the end of the occlusion period, while the IL-6 response peaked 3 h post-SMA occlusion. The TNF and IL-6 response after hemorrhagic shock differed from that observed after SMA occlusion in that the peak response occurred later and was of lower magnitude (p < .05). Although the animals subjected to SMA occlusion had a significantly increased incidence of bacterial translocation to both the mesenteric lymph nodes and systemic organs compared to rats subjected to hemorrhagic shock, in neither group was the blood level of endotoxin elevated and there was no association between bacterial translocation and cytokine levels. These results suggest that different models of intestinal ischemia have different cytokine profiles and that the early TNF response associated with SMA occlusion model is primarily due to the laparotomy.

Animals↗