Search PubMed⌕ Search

Biomedical subjects

Y Zeng

Publications and source records attributed to Y Zeng.

At least 163 records · Page 9Linked to original sources
PubMed1996

Inhibition of glycoprotein processing by L-fructose and L-xylulose.

A number of unusual and rare carbohydrates were tested as potential inhibitors of various glycosidases, as well as inhibitors of N-linked oligosaccharide processing. The best inhibitors of several arylglycosidases and of glucosidase I were L-xylulose and L-fructose. Both of these sugars showed some inhibitory activity towards yeast alpha-glucosidase but were inactive against beta-glucosidase and other arylglycosidases. The inhibition of yeast alpha-glucosidase by L-xylulose was of a competitive nature and required a concentration of 1 x 10(-5) M for 50% inhibition. Both L-xylulose and L-fructose also inhibited the purified soybean glucosidase I, with 50% inhibition occurring at about 1 x 10(-4) M, but showed no inhibitory activity against soybean glucosidase II. When influenza virus-infected MDCK cells were raised in the presence of L-xylulose, there was a dose-dependent inhibition in the formation of complex types of oligosaccharides on the viral glycoproteins consistent with the inhibition of the processing glucosidase I. This inhibition resulted in the occurrence of oligosaccharides on the viral glycoproteins that were characterized as Glc3Man9(GlcNAc)2 structures. L-Fructose also inhibited glycoprotein processing in cell culture, and the inhibition resulted in the formation of similar oligosaccharides to those seen with L-xylulose. However, L-fructose was a poorer inhibitor than L-xylulose and required much higher concentrations for the same degree of inhibition. Neither of these compounds inhibited protein synthesis or the formation of lipid-linked saccharides in culture MDCK cells, even when tested at concentrations of 5 mg/ml (about 30 mM) of culture media.

Animals↗
PubMed1996

[Determination of flavonol glycosides in the leaf of Ginkgo biloba L. by TLC scanning].

A TLC scanning method for the determination of flavonol glycosides in the leaf of Ginkgo biloba has been established. The method includes hydrolysis of the flavonoids and subsequent quantitative TLC scanning assay of the aglycones obtained. Determinations were carried out with a Shimadzu CS-930 scanner, with lambda(S) = 370 nm and lambda(R) = 650 nm. The recoveries were 96.0%-99.6% with RSD of 1.03%-2.08%.

Antiviral Agents↗
PubMed1996

[A study of the variation of the (AT)xTy motif-530bp 5' to the beta-globin gene in the Chinese population].

The repeated purine-pyrimidine motif (AT)xTy at the region -530bp 5' to the beta-globin gene is regarded as the binding site for BP1, a transcriptionally repressive nuclear protein. In present study, the rearrangement patterns of the -530 motif in the Chinese population, including 43 patients with various hemoglobinopathies and part of their relatives (34), as well as 20 hematologically normal individuals, were investigated with the method of ds-DNA cycle sequencing. The results showed that the -530 motif in Chinese people had three major variation types-(AT)8T5, (AT)7T7 and (AT)9T5. Besides, a novel rearrangement type, (AT)10T3, was found in a hematologically normal family. Furthermore, the analysis of haplotype between the beta-globin structural loci and the -530 motif rearrangement indicated that linkage disequilibrium existed between three mutant beta-globin genes (i.e., IVS-II-654(C-->T), CD41-42(-4bp) and HbE), and three -530 motif rearrangement types (i.e., (AT)8T5, (AT)7T7 and (AT)9T5)7 respectively.

Asian People↗
PubMed1996

[Prediction of the level of continuous positive airway pressure in the management of obstructive sleep apnea syndrome via nasal mask].

OBJECTIVE: To predict and optimal level of continuous positive airway pressure (CPAP) in the menagement of obstructive sleep apnea syndrome (OSAS) by relating certain parameters of respiratory disturbance and sleep hypoxemia. METHODS: 18 patients with OSAS (all male, aged 48 +/- 11 yrs) were enrolled in the study. Their actual levels of CPAP (Pm) were determined by a RHK-5500 mode polysomnographic system plus BiPAP (ST/D) system. The actuual Pm was related to the respiratory disturbance index (RDI) or total time of SaO2 < or = 90% (T S90). The correlation regression equations were calculated. 6 patients with OSAS (Group A) were treated with the predicted nasal CPAP (predicted Pm) which was derived from the regression equation, 8-10 hours per night, for 5-7 nights. 13 patients (Group B) receiving nasal CPAP treatment using the actually measured Pm served as control. RESULTS: There was a close positive linear correlation between RDI or T S90 and actual Pm. Symptoms and polysomnographic parameters improved significantly after one course of CPAP treatment in Group A. The efficacy showed no signifcant different as compared with that in Group B. CONCLUSIONS: It was suggested that RDI or T S90 are of value and simple in predicting the pressuure level of CPAP in the management of OSAS with nasal CPAP.

Adult↗
PubMed1995

Inhibition of transplant rejection following treatment with anti-B7-2 and anti-B7-1 antibodies.

Antigen-specific T cell activation depends initially on the interaction of the T cell receptor (TCR) with peptide/MHC. In addition, a costimulatory signal, mediated by distinct cell surface accessory molecules, is required for complete T cell activation leading to lymphokine production and proliferation. CD28 has been implicated as the major receptor on T cells responsible for delivering the costimulatory signal. Although two distinct ligands for CD28, B7-1 and B7-2, have been identified on antigen-presenting cells (APC), the co-stimulatory role of each molecule during a physiological immune response remains unresolved. In the present study, the relative roles of B7-1 and B7-2 interactions were evaluated in an allogeneic pancreatic islet transplant setting. In isolation, anti-B7-2 mAbs and, to a much lesser degree, anti-B7-1 mAbs suppressed T cell proliferative responses to allogeneic islets or splenic APC in vitro. Maximal inhibition of the allogeneic response was observed using a combination of the anti-B7-1 and anti-B7-2 mAbs. Administration of anti-B7-2 but not anti-B7-1 mAbs prolonged C3H allograft survival in B6 recipients, with a combination of both mAbs significantly prolonging rejection beyond either mAb alone. The immunosuppressive effects of the in vivo mAb treatment were not manifested in in vitro analyses as T cells isolated from suppressed mice responded normally to allogeneic stimuli in terms of both proliferation and lymphokine production. However, combined mAb therapy in vivo selectively delayed CD4+ T lymphocyte infiltration into the graft. These data suggest that both B7-1 and B7-2 costimulatory molecules are active in vivo, although B7-2 plays a clearly dominant role in this allograft model. The mechanism of immune suppression in vivo remains unresolved but may occur at sites distinct from the allograft.

Abatacept↗
PubMed1995

Genomic organization and chromosomal location of the human dsRNA adenosine deaminase gene: the enzyme for glutamate-activated ion channel RNA editing.

The structure of the human gene encoding the double-stranded RNA (dsRNA) adenosine deaminase (DRADA) was characterized. This nuclear localized enzyme is involved in the RNA editing required for the expression of certain subtypes of glutamate-gated ion channel subunits. The DRADA gene span 30 kb pairs and harbors 15 exons. The transcription of the DRADA gene driven by the putative promoter region, which contains no typical TATA or CCAAT box-like sequences, is initiated at multiple sites, 164 to 216 nucleotides upstream of the translation initiation codon. The three dsRNA binding motifs (DRBM), 70 amino acid residues long, are each encoded by two exons plus an intervening sequence that interrupts the motif at the identical amino acid position. This finding is consistent with the notion that the dsRNA binding domains may be composed of two separate functional subdomains. Fluorescent in situ hybridization localized the DRADA gene on the long arm chromosome 1, region q21. The gene structure and sequence information reported in this study will facilitate the investigation of involvement of DRADA in hereditary diseases that may be the result of malfunction of glutamate-gated ion channels.

Adenosine Deaminase↗
PubMed1995

UDP-N-acetylglucosamine:dolichyl-phosphate N-acetylglucosamine-1-phosphate transferase is amplified in tunicamycin-resistant soybean cells.

A tunicamycin-resistant soybean cell line was developed by gradually increasing the concentration of tunicamycin in the growth medium. At the final stage, the resistant cells could survive in media containing 60 micrograms/ml of tunicamycin, whereas normal cells show a greatly retarded growth rate at 0.5 microgram/ml of antibiotic. The tunicamycin-resistant cells had a greater than 40-fold increase in the activity of the enzyme UDP-GlcNAc:dolichyl-P GlcNAc1P transferase, a 2-3-fold increase in the activity of dolichyl-P-mannose synthase, but no increase in the activities of other enzymes of the lipid-linked saccharide pathway such as dolichyl-P-glucose synthase or mannosyl transferases. There was also no change in the activities of the glycoprotein-processing enzymes, glucosidase I or glucosidase II, as compared to wild-type cells. The increase in GlcNAc1P transferase was due to an increased production of enzyme, as seen by a dramatic increase in the amount of a 39-kDa protein, which is presumed to be this enzyme protein. The GlcNAc1P transferase from tunicamycin-resistant cells was equally sensitive to tunicamycin as was the wild-type enzyme, but was considerably more labile to temperatures above 30 degrees C. The activity in tunicamycin-resistant cells was greatly stimulated by exogenous dolichyl-P. The spectrum of oligosaccharides from labeled lipid-linked oligosaccharides was similar in wild-type and tunicamycin-resistant soybean cells, but the resistant cells had significantly greater amounts of the shorter and much lower amounts of the larger-sized oligosaccharides.

Anti-Bacterial Agents↗
PubMed1995

Production of antigen-specific human antibodies from mice engineered with human heavy and light chain YACs.

Our paper describes the introduction of large fragments of both the human heavy and light chain Ig genes into the mouse germline to create a mouse strain capable of producing a broad repertoire of antigen-specific, fully human antibodies. The human immunoglobulin gene sequences were functional in the context of the mouse machinery for antibody recombination and expression, either in the presence or absence of functional endogenous genes. This was demonstrated by their ability to undergo diverse rearrangement, to be expressed at significant levels, and to exclude expression of mouse immunoglobulins irrespective of their copy number or site of integration. The decrease in susceptibility to influence by adjacent genomic sequences may reflect the greater size, variable gene content, or structural integrity of the human Ig YACs and/or the presence of unidentified but important regulatory elements needed for optimal expression of the human immunoglobulin genes and their correct regulation. Our results show that mouse B cells coexpressing human heavy and kappa chains, upon immunization, can produce antigen-specific, fully human antibodies. Furthermore, the human heavy and kappa chain YACs induced differentiation and maturation of the growth-arrested B-cell lineage in mice with inactivated endogenous Ig genes, leading to the production of a diverse repertoire of fully human antibodies at levels approaching those in normal serum. These results suggest the potential value of these mice as a source of fully human antibodies for human therapy. Furthermore, it is expected that such mice would lack immunological tolerance to and thus readily yield antibodies to human proteins, which may constitute an important class of targets for monoclonal antibody therapy. Our findings suggest that the introduction of even larger portions of the human heavy and light chain loci, which should be achievable with the ES cell-yeast spheroplast fusion technology described, will result in strains of mice ultimately capable of recapitulating the full antibody repertoire characteristic of the human humoral response to infection and immunization. The present and future mouse strains may prove to be valuable tools for studying the molecular mechanisms and regulatory sequences influencing the programmed assembly and expression of human antibodies in the normal immune response, as well as the abnormal response characteristic of autoimmune disease and other disorders. The strategy we have described for the introduction of large segments of the human genome into mice in conjunction with the inactivation of the corresponding mouse loci may also have broad applicability to the investigation of other complex or uncharacterized loci.

Animals↗
PubMed1995

Isocitrate dehydrogenase from bovine heart: primary structure of subunit 3/4.

Bovine NAD(+)-dependent isocitrate dehydrogenase was shown previously to contain four subunits of approx. 40 kDa (subunits 1-4) possessing different peptide maps and electrophoretic properties [Rushbrook and Harvey (1978) Biochemistry 17, 5339-5346]. In this study the heterogeneity is confirmed using enzyme purified by updated methods and from single animals, ruling out allelic variability. Subunits 1 and 2 were differentiated from each other and from subunits 3 and 4 by N-terminal amino acid sequencing. Subunits 3 and 4 (subunits 3/4) were identical in sequence over 30 residues. The N-terminal residues of subunits 1 and 2 were homologous but not identical with the beta- and gamma-subunits respectively of the comparable pig heart enzyme. Subunits 3/4 were identical over 30 residues with the N-terminus of the pig heart alpha-subunit. Full-length sequence, including that for mitochondrial import, is presented for a protein with the processed N-terminus of subunits 3/4, deduced from cloned cDNA obtained utilizing the N-terminal sequence information. The derived amino acid sequence for the mature protein contains 339 amino acids and has a molecular mass of 36,685 Da. Complete identity with N-terminal and Cys-containing peptides totalling 92 residues from the alpha-subunit of the pig heart enzyme [Huang and Colman (1990) Biochemistry 29, 8266-8273] suggests that maintenance of a particular three-dimensional structure in this subunit is crucial to the function of the enzyme. An electrophoretic heterogeneity within the pig heart alpha-subunit, similar to that shown by bovine subunits 3/4, was demonstrated. One reordering of the Cys-containing peptides of the pig heart alpha-subunit is indicated. Sequence comparison with the distantly related NADP(+)-dependent enzyme from Escherichia coli, for which the three-dimensional structure is known [Stoddard, Dean and Koshland (1993) Biochemistry 32, 9310-9316] shows strong conservation of residues binding isocitrate, Mg2+ and the NAD+ moiety of NADP+, consistent with a catalytic function.

Amino Acid Sequence↗
PubMed1995

Long-term (> 3-year) insulin independence in a patient with pancreatic islet cell transplantation following upper abdominal exenteration and liver replacement for fibrolamellar hepatocellular carcinoma.

In the University of Pittsburgh experience, the most successful setting for human islet allografts is in patients undergoing upper abdominal exenteration with total pancreatectomy and liver transplantation for the indication of malignancy (cluster). In this group of patients 6/11 were insulin-independent for long periods. We report herein the metabolic course or the longest survivor (> 3 years). This patient has been free of exogenous insulin since the third postoperative month and has sustained her body weight without total parenteral nutrition since the 4th postoperative month. The patient has some postprandial hyperglycemia but average capillary glucoses are near-normal to normal as are glycosylated hemoglobin values. The clearance of glucose during the administration of an intravenous glucose load has been well preserved and is currently normal. C-peptide stimulates significantly in response to intravenously injected glucose. The absolute levels of stimulation during the test have declined possibly related to improvements in renal function, decreased immunosuppression or the natural history of cells transplanted into the portal site. The kinetics of the C-peptide response to intravenously injected glucose shows a persistent abnormality of first-phase insulin release and a prolonged second phase release. Basal glucagon levels are low but stimulate to a mixed meal. This patient's results demonstrate long-term function of islet cells from a single donor transplanted into the portal vein using FK506 as an immunosuppressant agent.

Abdominal Neoplasms↗
PubMed1995

Sperm membrane potential: hyperpolarization during capacitation regulates zona pellucida-dependent acrosomal secretion.

Membrane potential (VM) was investigated in mouse and bovine sperm populations. VM was determined from the fluorescence emission of the lipophilic anion, bis(1,3-diethylthiobarbituric acid)trimethine oxonol (DiSBAC2(3)), and from the lipophilic cation, 3,3'-dipropylthiodicarbocyanine iodide (DiSC3(5)). Fluorescent signals were corrected for contributions of mitochondrial potentials and apparent VM values were obtained by calibrations in sperm selectively permeabilized with valinomycin or with gramicidin D. The calculated VM values of uncapacitated mouse and bovine sperm were approximately -35 and -30 mV, respectively. In contrast, capacitated populations of mouse and bovine sperm have VM values of -50 to -60 mV. Membrane hyperpolarization is due in part to an enhanced K+ permeability. The development of zona pellucida-activated signal transducing mechanisms during capacitation is dependent upon hyperpolarization. It is suggested that VM alterations regulate the activation state of sperm, thereby suppressing premature acrosome reactions in uncapacitated sperm and permitting capacitated sperm to respond to zona pellucida stimuli.

Acrosome↗
PubMed1995

Fertility of rural China: effects of local family planning and health programs.

"The rationing of births in China after the 1979 announcement of the 'one child family policy' has been held responsible for the rapid decrease in Chinese fertility, whereas other observers have noted that parallel fertility declines occurred with voluntary behavior in other East and Southeast Asian countries. This paper assesses the joint contribution of local family planning and health programs, individual characteristics of women, and the development of their communities, as explanatory variables for Chinese fertility in rural areas of three provinces in 1985. Given the explicit quantitative reproductive goals of the government, an ordered Probit model for cumulative fertility is estimated for women age 15-34 and 35-49."

Asia↗
PubMed1995

A case for bone canaliculi as the anatomical site of strain generated potentials.

We address the question of determining the anatomical site that is the source of the experimentally observed strain generated potentials (SGPs) in bone tissue. There are two candidates for the anatomical site that is the SGP source, the collagen-hydroxyapatite porosity and the larger size lacunar-canalicular porosity. In the past it has been argued, on the basis of experimental data and a reasonable model, that the site of the SGPs in bone is the collagen-hydroxyapatite porosity. The theoretically predicted pore radius necessary for the SGPs to reside in this porosity is 16 nm, which is somewhat larger than the pore radii estimated from gas adsorption data where the preponderance of the pores were estimated to be in the range 5-12.5 nm. However, this pore size is significantly larger than the 2 nm size of the small tracer, microperoxidase, which appears to be excluded from the mineralized matrix. In this work a similar model, but one in which the effects of fluid dynamic drag of the cell surface matrix in the bone canaliculi are included, is used to show that it is possible for the generation of SGPs to be associated with the larger size lacunar-canalicular porosity when the hydraulic drag and electrokinetic contribution of the bone fluid passage through the cell coat (glycocalyx) is considered. The consistency of the SGP data with this model is demonstrated. A general boundary condition is introduced to allow for current leakage at the bone surface. The results suggest that the current leakage is small for the in vitro studies in which the strain generated potentials have been measured.

Biomechanical Phenomena↗
PubMed1995

Stokes problems for moving half-planes.

New exact solutions of the Navier-Stokes equations are obtained for the unbounded and bounded oscillatory and impulsive tangential edgewise motion of touching half-infinite plates in their own plane. In contrast to Stokes classical solutions for the harmonic and impulsive motion of an infinite plane wall, where the solutions are separable or have a simple similarity form, the present solutions have a two-dimensional structure in the near region of the contact between the half-infinite plates. Nevertheless, it is possible to obtain relatively simple closed-form solutions for the flow field in each case by defining new variables which greatly simplify the r- and theta- dependence of the solutions in the vicinity of the contact region. These solutions for flow in a half-infinite space are then extended to bounded flows in a channel using an image superposition technique. The impulsive motion has application to the motion near geophysical faults, whereas the oscillatory motion has arisen in the design of a novel oscillating half-plate flow chamber for examining the effect of fluid shear stress on cultured cell monolayers.

Animals↗
PubMed1995

[Pathological findings of proximal tubal occlusive infertility].

Exicised tubal segments (including interstial and isthmic portions) from 33 women with proximal tubal occlusive infertility were examined pathologically. We found that pathologic entities included chronic tubal inflammation (70.59%), tubal endometriosis (9.80%), obliterative fibrosis (7.84%), salpingitis isthmica nodosa (5.88%), tubal tuberculosis (3.92%). Only one of the tubes (1.96%) showed no obvious pathological change. These observations on proximal tubal occlusion in combination with clinical features and pelvic changes indicate that: (1) These are multiple distinct pathologic patterns, and pelvic findings do not predict the pathologic changes of the tubes. (2) Induced abortion and uterine curetage is an important factor for the proximal tubal occlusive infertility. Pelvic inflammatory disease and intrauterine device are other factors.

Abortion, Induced↗
PubMed1995

[Androgen receptors and effects of sex hormones on growth of a human ovarian carcinoma cell line].

Previous study had showed that ovarian carcinoma cell line (HO-8910 cells) contained estrogen receptors (ER) and progesterone receptors (PR). In this experiment, androgen receptors (AR) in these cells were determined by a whole cell binding assay with a synthetic nonmetabolizable androgen-methyltrienolone (3H-R1881). The results showed that there existed high affinity and low capacity, specific binding sites for 3H-R1881 in these cells, the apparent maximum binding capacity and dissociation constant of these binding sites revealed by scathchard analysis being 6.52 fmol/10(6) cells and 2.96 nmol/L respectively, indicating the presence of AR in addition to ER and PR in HO-8910 cells. Furthermore, the effects of sex hormones, i.e., estrodiol, progesterone and testosterone on the growth of HO-8910 cells were also investigated. The results showed that testosterone at 10 nmol/L slightly increased the number of HO-8910 cells, but the increase was not dose-dependent and not statistically significant. Estrodiol and progesterone had no growth-stimulatary or inhibitary effects on these cells.

Cell Division↗