Biomedical subjects

S Wang

Publications and source records attributed to S Wang.

At least 883 records · Page 49Linked to original sources

PubMed1998

Monitoring spinal-cord injury intraoperatively and attempting prognosis by cortical somatosensory evoked potentials: experimental study.

In order to monitor spinal-cord injury intraoperatively and to evaluate prognosis by cortical somatosensory evoked potentials (CSEP), the spinal-cord function of 42 dogs, whose cords were injured by air-sac pressure or various striking trauma, was monitored by CSEP intraoperatively and 1 to 3 months postoperatively. Although amplitude declined by 100 percent, compared with preoperative readings, spinal-cord injury by air-sac pressure had no lasting effects. If the pressure was removed in a timely fashion, the function of the spinal cord recovered after 1 to 3 months postoperatively. As for the effect of various striking traumas, safe limits, according to intraoperative CSEP monitoring, were that the prolonged P1 wave latency was less than 1.5 times, and that the declining P1-N1 wave amplitude was less than 50 percent. The change in amplitude was quite sensitive and its recovery was earlier than morphologic changes and functional recovery. Results indicated that CSEP monitoring of spinal-cord injury intraoperatively is accurate and reliable and that it can also predict an accurate prognosis for the injured spinal cord in this canine model.

Animals↗

PubMed1998

Pharmacophores in drug design and discovery.

Compounds containing a specific pharmacophore--the minimum structural features necessary for enzyme binding--can be retrieved from a database such as the National Cancer Institute repository by means of three-dimensional (3D) searching, which allows the retrieval of all compounds possessing a specified set of atoms with a given 3D geometry. The ways in which pharmacophores can be found and characterized and the details of the 3D searching methods are described. Elaboration of compounds found in such searches and their subsequent development as lead drugs is also discussed.

Animals↗

PubMed1998

HMG CoA lyase deficiency: identification of five causal point mutations in codons 41 and 42, including a frequent Saudi Arabian mutation, R41Q.

The hereditary deficiency of 3-hydroxy-3-methylglutaryl (HMG) CoA lyase (HL; OMIM 246450 [http://www3.ncbi.nlm.nih. gov:80/htbin-post/Omim/dispmim?246450]) results in episodes of hypoketotic hypoglycemia and coma and is reported to be frequent and clinically severe in Saudi Arabia. We found genetic diversity among nine Saudi HL-deficient probands: six were homozygous for the missense mutation R41Q, and two were homozygous for the frameshift mutation F305fs(-2). In 32 non-Saudi HL-deficient probands, we found three R41Q alleles and also discovered four other deleterious point mutations in codons 41 and 42: R41X, D42E, D42G, and D42H. In purified mutant recombinant HL, all four missense mutations in codons 41 and 42 cause a marked decrease in HL activity. We developed a screening procedure for HL missense mutations that yields residual activity at levels comparable to those obtained using purified HL peptides. Codons 41 and 42 are important for normal HL catalysis and account for a disproportionate 21 (26%) of 82 of mutant alleles in our group of HL-deficient probands.

Base Sequence↗

PubMed1998

Immunogenicity of live attenuated SA14-14-2 Japanese encephalitis vaccine--a comparison of 1- and 3-month immunization schedules.

Live attenuated SA14-14-2 Japanese encephalitis (JE) vaccine has been safe and effective in >100 million immunized children, but its current administration schedule of two doses given a year apart does not lend itself to inclusion in established Expanded Program of Immunization (EPI) schedules of childhood immunization. Immune responses to immunization at shorter intervals were compared in middle-school-aged children immunized with two doses separated by 1 month (n = 116) or 2.5 months (n = 115). Two vaccine lots were compared. Seroconversion to the vaccine was observed in 100% of vaccinees immunized in the 1-month schedule and in 94% (lot 2) and 100% (lot 1) of vaccinees immunized in the 2.5-month schedule. Geometric mean titers were almost 2-fold higher with the longer schedule. The routine administration of JE SA14-14-2 vaccine to infants in an EPI schedule should be possible using either interval.

Adolescent↗

PubMed1998

A composite regulatory element in the first intron of the estrogen-responsive very low density apolipoprotein II gene.

During periods of egg laying in the chicken, when circulating levels of estrogen are increased, the liver-specific estrogen-dependent very low density apolipoprotein II (apoVLDLII) gene is expressed. This expression takes place primarily at the level of transcription, driven by two estrogen response elements that reside in the promoter. In transient transfection assays, expression is increased fourfold when the first intron is added to the promoter construct, indicating that 75% of the regulation comes from intron A. Using in vitro DNase I footprinting, six protein-binding sites were revealed throughout the first intron. The functional significance of these binding sites was evaluated by mutation and transient transfection. Two of the protein-binding regions were shown to increase transcription. Site-specific mutations introduced at either the +66 to +86 or +112 to +129 sites disrupted trans-factor binding and reduced the estrogen-dependent expression by 45% and 34%, respectively. A plasmid containing both mutations resulted in a 43% decrease in expression, indicating that the contributions of these regions are not additive. Competition with known sequences in electrophoretic mobility shift assays suggested that the +66 to +86 site binds a chicken member of the nuclear receptor transcription factor family.

Animals↗

PubMed1998

Hepatic export of glutathione and uptake of constituent amino acids, glutamate and cysteine, in broilers in vivo.

This study was conducted to document the glutathione (GSH) cycle (interorgan circulation of GSH) in broilers in vivo. Two experiments were conducted on 36 anesthetized male broilers (n = 6 per treatment) implanted with cannulae in the carotid artery, hepatic portal, and hepatic veins. Plasma GSH, glutamate, cysteine, cystine, and cysteinylglycine levels in each vessel were monitored following a bolus injection [Experiment (Exp.) 1] or 30 min continuous infusion (Exp. 2) of GSH, or a gamma-glutamyltranspeptidase inhibitor (AT125) into the hepatic portal vein. Controls received saline alone. The GSH and AT125 treatments were used to determine the effect of increasing the prehepatic GSH load and of inhibiting systemic GSH degradation, respectively, on the GSH cycle. Hepatic export of GSH was clearly evident in all three treatment groups in both experiments (Exp.). The GSH and AT125 treatments raised amino acid levels in some or all of the vessels, whereas cysteinylglycine was elevated by AT125 and depressed by the GSH treatment compared to Controls. Hepatic uptake of glutamate, cysteine, and/or cystine was observed in Controls and GSH-treated birds, but not in birds given AT125 (Exp. 2). Neither hepatic export nor uptake of cysteinylglycine was observed in any treatment group. The results clearly demonstrate the ability of the avian liver to export GSH into the general circulation despite alterations that might arise from changes in extra-hepatic ability to utilize GSH or its constituent amino acids.

Animals↗

PubMed1998

Heat conditioning induces heat shock proteins in broiler chickens and turkey poults.

Peripheral leukocyte heat shock proteins (HSP: HSP90, HSP70, and HSP23) from broiler chickens and turkey poults were induced by in vitro and in vivo high temperature exposure. Heat conditioning, via a daily 1 h exposure to 41 C, enhanced in vitro HSP expression in leukocytes from chickens heat-conditioned for 1 to 2 wk, and a similar response was found in turkey poults with 3 wk of heat conditioning causing the greatest HSP expression. In vivo heat exposure trials caused maximization of HSP expression after 1 wk of daily heat conditioning exposures in broilers, but no additional enhancement was seen in chickens heat conditioned for 2 wk. Enhancement in HSP expression was evident for periods up to 4 wk after termination of the daily heat conditioning episodes.

Acclimatization↗

PubMed1998

Lung lining fluid antioxidants in male broilers: age-related changes under thermoneutral and cold temperature conditions.

The purpose of this study was to determine age-related changes in lung lining fluid antioxidants in broilers reared under thermoneutral or cold temperature conditions. Male broilers (Cobb 500) were placed in floor pens within environmental chambers and fed a standard commercial starter diet. The thermoneutral Control chamber was maintained at 32, 30, 27, and 22 to 25 C for Weeks 1, 2, 3, and 4 to 7, respectively, whereas temperature in the Cold chamber was lowered to 18 C during Week 3 and maintained between 15 and 18 C for the rest of the study. At 2, 4, and 7 wk, four to six birds per chamber were selected randomly. The lungs were lavaged with heparinized saline (2 mL/g lung) to obtain lung lining fluid. Antioxidants [reduced (GSH), oxidized (GSSG), and total (TGSH) glutathione, uric acid, ascorbic acid, and alpha- and gamma-tocopherol] in lung lining fluid were determined by HPLC; protein was determined colorimetrically. In Controls, levels of alpha- and -gamma-tocopherol, uric acid, and GSH in lung lining fluid decreased between 2 and 7 wk of age. Birds in the Cold chamber exhibited higher protein, a higher GSSG:TGSH ratio, and a decrease in ascorbic acid (7 wk) in lung lining fluid relative to Controls. Lung lining fluid antioxidants were not correlated with antioxidants in plasma. To determine the effect of vitamin E supplementation on lung lining fluid antioxidants, birds were given a supplement of 200 IU alpha-tocopherol per day for 7 d. Alpha-tocopherol supplementation elevated alpha-tocopherol levels in lung lining fluid, but lowered ascorbic acid, GSH, and GSSG and had no effect on uric acid in lung lining fluid. The results of this study suggest that antioxidant protection in lung lining fluid may diminish with age, that cold conditions in this study produced an oxidative stress in lung lining fluid in broilers, and that oral supplementation of alpha-tocopherol elevated lung lining fluid alpha-tocopherol.

Aging↗

PubMed1998

Antioxidant defenses in lung lining fluid of broilers: impact of poor ventilation conditions.

Lung lining fluid antioxidants represent a potentially important protective barrier of lung epithelial cells to damaging effects of air pollutants, yet no information is apparently available concerning lung lining fluid antioxidants in broilers. Therefore, goals of this study were to establish uric acid, ascorbic acid, reduced (GSH) and oxidized (GSSG) glutathione, and protein concentrations in lung lining fluid obtained from male broiler chickens maintained for 6 to 7 wk within environmentally controlled rooms (Control) or chronically exposed to high levels of dust and ammonia within a broiler rearing house (House). The entire respiratory tract was carefully removed following an overdose of anesthetic and lavage fluid was collected after flushing the lungs with heparin-saline (10 mL per lung). There was no difference in GSH, but GSSG, uric acid, and protein concentrations were higher in House birds than in Controls. An increase in the GSSG to total glutathione (GSx) ratio, an indicator of oxidative stress, was also observed in birds maintained in the House environment. Ascorbic acid was not detected in House-reared birds and detected in only 4 of 12 Controls. Regression analysis revealed positive correlations between lung lining fluid protein and uric acid (r = 0.71; P < 0.01), protein and GSSG (r = 0.73; P < 0.01), and uric acid and GSSG concentrations (r = 0.69, P < 0.01). Additionally, GSSG was positively correlated (r = 0.66; P < 0.01) with the right ventricular weight ratio, an index commonly used in identifying the development of pulmonary hypertension syndrome in broilers. These data, the first to document lung lining fluid antioxidants in avian species, indicate an oxidative stress can be detected in fluid of broilers exposed to high levels of dust and ammonia in a simulated poultry house environment.

Animals↗

PubMed1998

Age-related changes of plasma glutathione and cysteine in broilers: effect of dithiothreitol reduction vitro on free and bound pools.

A study was conducted to determine free and protein-bound pools of glutathione and cysteine in the plasma of male broiler chicks. Birds were brooded in battery cages and provided ad libitum access to a starter diet and water. Plasma was treated with a reducing agent, dithiothreitol (DTT), or left untreated, and analyzed by HPLC to determine free and protein bound pools of reduced (GSH) and oxidized (GSSG) glutathione, cysteine (Cys), and cystine (Cyss). With respect to total plasma pools of GSH and Cys, between 0 and 21 d of age; 1) free GSH increased from 30 to 90% with a reciprocal decrease in protein-bound GSH, but GSSG was not detected; and 2) free Cys decreased from 20 to 10%, free Cyss increased from 24 to 45%, and protein-bound Cys decreased from 55 to 44%. The majority of the GSH plasma pool in this study was present in a free, acid-soluble form, whereas most of the total Cys pool was present as Cyss or bound to protein.

Aging↗

PubMed1998

TR1, a new member of the tumor necrosis factor receptor superfamily, induces fibroblast proliferation and inhibits osteoclastogenesis and bone resorption.

A newly identified member of the tumor necrosis factor receptor (TNFR) superfamily shows activities associated with osteoclastogenesis inhibition and fibroblast proliferation. This new member, called TR1, was identified from a search of an expressed sequence tag database, and encodes 401 amino acids with a 21-residue signal sequence. Unlike other members of TNFR, TR1 does not contain a transmembrane domain and is secreted as a 62 kDa glycoprotein. TR1 gene maps to chromosome 8q23-24.1 and its mRNA is abundantly expressed on primary osteoblasts, osteogenic sarcoma cell lines, and primary fibroblasts. The receptors for TR1 were detected on a monocytic cell line (THP-1) and in human fibroblasts. Scatchard analyses indicated two classes of high and medium-high affinity receptors with a kD of approximately 45 and 320 pM, respectively. Recombinant TR1 induced proliferation of human foreskin fibroblasts and potentiated TNF-induced proliferation in these cells. In a coculture system of osteoblasts and bone marrow cells, recombinant TR1 completely inhibited the differentiation of osteoclast-like multinucleated cell formation in the presence of several bone-resorbing factors. TR1 also strongly inhibited bone-resorbing function on dentine slices by mature osteoclasts and decreased 45Ca release in fetal long-bone organ cultures. Anti-TR1 monoclonal antibody promoted the formation of osteoclasts in mouse marrow culture assays. These results indicate that TR1 has broad biological activities in fibroblast growth and in osteoclast differentiation and its functions.

Animals↗

PubMed1998

Postsurgical surveillance of colon cancer: preliminary cost analysis of physician examination, carcinoembryonic antigen testing, chest x-ray, and colonoscopy.

OBJECTIVE: This study is the first to examine the relative and absolute costs of physician examination, carcinoembryonic antigen (CEA) assessment, chest x-ray, and colonoscopy in detecting recurrent disease in patients who have undergone surgical resection for primary colon carcinoma. METHODS: Of the 1356 Eastern Cooperative Oncology Group patients in Intergroup Protocol 0089 who underwent surgical resection for Dukes' B2 and C colon carcinoma, 421 patients who developed recurrent disease were reviewed. Follow-up testing was performed according to protocol guidelines, with the cost of each test equal to 1995 Medicare reimbursement. Follow-up was defined as the time to recurrence for the 421 patients in whom disease recurred (mean 18.6 months) or up to 5 years for the additional 930 patients in whom disease did not recur (mean 38.6 months). Patients were divided into three categories: nonrecurrent, recurrent but not resectable, and recurrent but resectable with curative intent. The estimated mean cost of each test in detecting group 3 (recurrent but resectable) patients was calculated. RESULTS: Of the 421 patients who developed recurrent disease, 96 underwent surgical resection of their disease with curative intent (group 3). For group 3 patients, the first indication of recurrent disease was CEA testing (30), chest x-ray (12), colonoscopy (14), and other (40). Of the 40 "other" patients, 24 presented with symptoms. Routine physician examination, however, failed to identify a single resectable recurrence, and the total cost for physician examination was $418,615. The detection rate for CEA testing was 2.2%, the total cost was $170,880, and the cost per recurrence was $5,696. The detection rate for chest x-ray was 0.9%, the total cost was $120,934, and the cost per recurrence was $10,078. The detection rate of colonoscopy was 1%, the total cost was $641,344, and the cost per recurrence was $45,810. CONCLUSIONS: CEA measurement was the most cost-effective test in detecting potentially curable recurrent disease. Physician visits were useful only in the evaluation of symptoms; a routine physician examination had no added benefit.

Antineoplastic Agents↗

PubMed1998

Study of toxin production by isolates of Stachybotrys chartarum and Memnoniella echinata isolated during a study of pulmonary hemosiderosis in infants.

A cluster of cases of pulmonary hemosiderosis among infants was reported in Cleveland, Ohio, during 1993 and 1994. These unusual cases appeared only in infants ranging in age from 1 to 8 months and were characterized by pulmonary hemorrhage, which caused the babies to cough up blood. A case-control study identified major home water damage (from plumbing leaks, roof leaks, or flooding) as a risk factor for development of pulmonary hemorrhage in these infants. Because of an interest in the possibility that trichothecene mycotoxins might be involved in this illness, a number of isolates of Stachybotrys chartarum were grown in the laboratory on rice, and extracts were prepared and analyzed both for cytotoxicity and for specific toxins. Two isolates of Memnoniella echinata, a fungus closely related to S. chartarum, were also included in these studies. S. chartarum isolates collected from the homes were shown to produce a number of highly toxic compounds, and the profiles of toxic compounds from M. echinata were similar; the most notable difference was the fact that the principal metabolites produced by M. echinata were griseofulvins.

Animals↗

PubMed1998

Delineating the specific influence of virus isoelectric point and size on virus adsorption and transport through sandy soils.

Many of the factors controlling viral transport and survival within the subsurface are still poorly understood. In order to identify the precise influence of viral isoelectric point on viral adsorption onto aquifer sediment material, we employed five different spherical bacteriophages (MS2, PRD1, Q beta, phi X174, and PM2) having differing isoelectric points (pI 3.9, 4.2, 5.3, 6.6, and 7.3 respectively) in laboratory viral transport studies. We employed conventional batch flowthrough columns, as well as a novel continuously recirculating column, in these studies. In a 0.78-m batch flowthrough column, the smaller phages (MS2, phi X174, and Q beta), which had similar diameters, exhibited maximum effluent concentration/initial concentration values that correlated exactly with their isoelectric points. In the continuously recirculating column, viral adsorption was negatively correlated with the isoelectric points of the viruses. A model of virus migration in the soil columns was created by using a one-dimensional transport model in which kinetic sorption was used. The data suggest that the isoelectric point of a virus is the predetermining factor controlling viral adsorption within aquifers. The data also suggest that when virus particles are more than 60 nm in diameter, viral dimensions become the overriding factor.

Adsorption↗

PubMed1998

Protective CD4+ and CD8+ T cells against influenza virus induced by vaccination with nucleoprotein DNA.

DNA vaccination is an effective means of eliciting both humoral and cellular immunity, including cytotoxic T lymphocytes (CTL). Using an influenza virus model, we previously demonstrated that injection of DNA encoding influenza virus nucleoprotein (NP) induced major histocompatibility complex class I-restricted CTL and cross-strain protection from lethal virus challenge in mice (J. B. Ulmer et al., Science 259:1745-1749, 1993). In the present study, we have characterized in more detail the cellular immune responses induced by NP DNA, which included robust lymphoproliferation and Th1-type cytokine secretion (high levels of gamma interferon and interleukin-2 [IL-2], with little IL-4 or IL-10) in response to antigen-specific restimulation of splenocytes in vitro. These responses were mediated by CD4+ T cells, as shown by in vitro depletion of T-cell subsets. Taken together, these results indicate that immunization with NP DNA primes both cytolytic CD8+ T cells and cytokine-secreting CD4+ T cells. Further, we demonstrate by adoptive transfer and in vivo depletion of T-cell subsets that both of these types of T cells act as effectors in protective immunity against influenza virus challenge conferred by NP DNA.

Animals↗

PubMed1998

Lagging-strand, early-labelling, and two-dimensional gel assays suggest multiple potential initiation sites in the Chinese hamster dihydrofolate reductase origin.

There is general agreement that DNA synthesis in the single-copy and amplified dihydrofolate reductase (DHFR) loci of CHO cells initiates somewhere within the 55-kb spacer region between the DHFR and 2BE2121 genes. However, results of lagging-strand, early-labelling fragment hybridization (ELFH), and PCR-based nascent-strand abundance assays have been interpreted to suggest a very narrow zone of initiation centered at a single locus known as ori-beta, while two-dimensional (2-D) gel analyses suggest that initiation can occur at any of a large number of potential sites scattered throughout the intergenic region. The results of a leading-strand assay and two intrinsic labelling techniques are compatible with a broad initiation zone in which ori-beta and a second locus (ori-gamma) are somewhat preferred. To determine how these differing views are shaped by differences in experimental manipulations unrelated to the biology itself, we have applied the lagging-strand, ELFH, neutral-neutral, and/or neutral-alkaline 2-D gel assays to CHOC 400 cell populations synchronized and manipulated in the same way. In our experiments, the lagging-strand assay failed to identify a template strand switch at ori-beta; rather, we observed a gradual, undulating change in hybridization bias throughout the intergenic spacer, with hybridization to the two templates being approximately equal near a centered matrix attachment region. In the ELFH assay, all of the fragments in the 55-kb intergenic region were labelled in the first few minutes of the S phase, with the regions encompassing ori-beta and ori-gamma being somewhat preferred. Under the same conditions, neutral-neutral and neutral-alkaline 2-D gel analyses detected initiation sites at multiple locations in the intergenic spacer. Thus, the results of all existing replicon-mapping methods that have been applied to the amplified DHFR locus in CHOC 400 cells are consistent with a model in which two somewhat preferred subzones reside in a larger zone of multiple potential initiation sites in the intergenic region.

Animals↗

PubMed1998

Numb-associated kinase interacts with the phosphotyrosine binding domain of Numb and antagonizes the function of Numb in vivo.

During asymmetric cell division, the membrane-associated Numb protein localizes to a crescent in the mitotic progenitor and is segregated predominantly to one of the two daughter cells. We have identified a putative serine/threonine kinase, Numb-associated kinase (Nak), which interacts physically with the phosphotyrosine binding (PTB) domain of Numb. The PTB domains of Shc and insulin receptor substrate bind to an NPXY motif which is not present in the region of Nak that interacts with Numb PTB domain. We found that the Numb PTB domain but not the Shc PTB domain interacts with Nak through a peptide of 11 amino acids, implicating a novel and specific protein-protein interaction. Overexpression of Nak in the sensory organs causes both daughters of a normally asymmetric cell division to adopt the same cell fate, a transformation similar to the loss of numb function phenotype and opposite the cell fate transformation caused by overexpression of Numb. The frequency of cell fate transformation is sensitive to the numb gene dosage, as expected from the physical interaction between Nak and Numb. These findings indicate that Nak may play a role in cell fate determination during asymmetric cell divisions.

Amino Acid Sequence↗

PubMed1998

Novel regulatory factors interacting with the promoter of the gene encoding the mRNA cap binding protein (eIF4E) and their function in growth regulation.

Regulation of the mRNA cap binding protein (eIF4E) is critical to the control of cellular proliferation since this protein is the rate-limiting factor in translation initiation and transforms fibroblasts and since eIF4E mutants arrest budding yeast in the G1 phase of the cell cycle (cdc33). We previously demonstrated regulation of eIF4E by altered transcription of its mRNA in serum-stimulated fibroblasts and in response to c-myc. To identify additional factors regulating eIF4E transcription, we used linker-scanning constructs to characterize sites in the promoter of the eIF4E gene required for its expression. Promoter activity was dependent on sites at -5, -25, -45, and -75; the site at -75 included a previously described myc box. Electrophoretic mobility shift assays identified DNA-protein interactions at -25 and revealed a binding site (TTACCCCCCCTT) that is unique to the eIF4E promoter. Proteins of 68 and 97 kDa bound this site in UV cross-linking and Southwestern experiments. Levels of 4E regulatory factor activities correlated with c-Myc levels, eIF4E expression levels, and protein synthesis in differentiating U937 and HL60 cells, suggesting that these activities may function to regulate protein synthesis rates during differentiation. Since the eIF4E promoter lacked typical TATA and initiator elements, further studies of this novel initiator-homologous element should provide insights into mechanisms of transcription initiation and growth regulation.

Animals↗