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B Wang

Publications and source records attributed to B Wang.

At least 487 records · Page 27Linked to original sources
PubMed1998

High-resolution structure of an archaeal zinc ribbon defines a general architectural motif in eukaryotic RNA polymerases.

BACKGROUND: Transcriptional initiation and elongation provide control points in gene expression. Eukaryotic RNA polymerase II subunit 9 (RPB9) regulates start-site selection and elongational arrest. RPB9 contains Cys4 Zn(2+)-binding motifs which are conserved in archaea and homologous to those of the general transcription factors TFIIB and TFIIS. RESULTS: The structure of an RPB9 domain from the hyperthermophilic archaeon Thermococcus celer was determined at high resolution by NMR spectroscopy. The structure consists of an apical tetrahedral Zn(2+)-binding site, central beta sheet and disordered loop. Although the structure lacks a globular hydrophobic core, the two surfaces of the beta sheet each contain well ordered aromatic rings engaged in serial edge-to-face interactions. Basic sidechains are clustered near the Zn(2+)-binding site. The disordered loop contains sidechains conserved in TFIIS, including acidic residues essential for the stimulation of transcriptional elongation. CONCLUSIONS: The planar architecture of the RPB9 zinc ribbon-distinct from that of a conventional globular domain-can accommodate significant differences in the alignment of polar, non-polar and charged sidechains. Such divergence is associated with local and non-local changes in structure. The RPB9 structure is distinguished by a fourth beta strand (extending the central beta sheet) in a well ordered N-terminal segment and also differs from TFIIS (but not TFIIB) in the orientation of its apical Zn(2+)-binding site. Cys4 Zn(2+)-binding sites with distinct patterns of polar, non-polar and charged residues are conserved among unrelated RNAP subunits and predicted to form variant zinc ribbons.

Amino Acid Sequence↗
PubMed1998

T cell-mediated pathology in two models of experimental colitis depends predominantly on the interleukin 12/Signal transducer and activator of transcription (Stat)-4 pathway, but is not conditional on interferon gamma expression by T cells.

The requirements for interleukin (IL)-12/signal transducer and activator of transcription (Stat)-4 signaling and induction of T cell-specific interferon (IFN)-gamma expression in the development of T helper cell (Th)1-type pathology were examined in two different models of experimental colitis. In each model, abnormal reconstitution of the T cell compartment in immunodeficient mice by adoptive cell transfer leads to a wasting syndrome and inflammation of the colon, induced by IFN-gamma and tumor necrosis factor (TNF)-alpha-producing T cells. We show here that treatment with anti-IL-12 antibodies in one of the models, or reconstitution with T cells from Stat-4-deficient (Stat-4(null)) mice in both models resulted in a milder disease in the majority of recipient animals, compared with those that were left untreated or that had been reconstituted with wt cells. Protected mice in each group also harbored lower frequencies of IFN-gamma-producing T cells than did diseased mice, suggesting that effects on wasting and colitis resulted from the attenuation of IFN-gamma expression by T cells. To test whether the development of pathogenic T cells in the two colitis models was directly dependent on T cell-specific IFN-gamma expression, IFN-gammanull donors were used for T cell reconstitution in each system. Surprisingly, large numbers of IFN-gammanull-reconstituted mice developed wasting and colitis, which in many cases was of comparable severity to that seen in animals reconstituted with wt cells. Furthermore, T cells from these animals expressed TNF-alpha, demonstrating that they had retained the ability to produce another proinflammatory cytokine. Taken together, these results demonstrate that in some forms of chronic experimental colitis the development of pathogenic T cells is influenced predominantly, though not exclusively, by IL-12 via the actions of Stat-4 proteins. Furthermore, our data suggest that in the models of colitis studied here the effects of IL-12/Stat-4 or other Th1 promoting pathways are not limited to the induction of IFN-gamma gene expression in T lymphocytes.

Animals↗
PubMed1998

Development of highly selective SH3 binding peptides for Crk and CRKL which disrupt Crk-complexes with DOCK180, SoS and C3G.

Many Src Homology 3 (SH3) domains function as molecular adhesives in intracellular signal transduction. Based on previous ultrastructural studies, short motifs which bind to the first SH3 domains of the adapters Crk and CRKL were selectively mutagenised to generate Crk/CRKL SH3-binding peptides of very high affinity and selectivity. Affinities were increased up to 20-fold compared to the best wildtype sequences, while the selectivity against a similar SH3 domain [Grb2SH3(N)] was not only retained, but sometimes increased. Blot techniques with GST-fusion peptides and in solution precipitation assays with biotinylated high affinity Crk binding peptides (HACBPs) were subsequently used to analyse the binding of these sequences to a large panel of SH3 domain-containing fusion proteins. Only those proteins which contained the CrkSH3(1) or CRKLSH3(1) domains bound efficiently to the HACBPs. A GST-HACBP fusion protein precipitated Crk and CRKL proteins out of 35S-labelled and unlabelled cell lysates. Very little binding of other cellular proteins to HACBP was detectable, indicative of a great preference for Crk and CRKL when compared to the wide variety of other endogenous cellular proteins. Moreover, HACBP disrupted in vitro preexisting Crk-complexes with DOCK180 and the exchange factors SoS and C3G, which are known targets of Crk adapters, in a concentration dependent manner. HACBP-based molecules should therefore be useful as highly selective inhibitors of intracellular signalling processes involving Crk and CRKL.

Adaptor Proteins, Signal Transducing↗
PubMed1998

Targeted disruption of the ubiquitous CNC-bZIP transcription factor, Nrf-1, results in anemia and embryonic lethality in mice.

The CNC-basic leucine zipper (CNC-bZIP) family is a subfamily of bZIP proteins identified from independent searches for factors that bind the AP-1-like cis-elements in the beta-globin locus control region. Three members, p45-Nf-e2, Nrf-1 and Nrf-2 have been identified in mammals. Expression of p45-Nf-e2 is largely restricted to hematopoietic cells while Nrf-1 and Nrf-2 are expressed in a wide range of tissues. To determine the function of Nrf-1, targeted disruption of the Nrf-1 gene was carried out. Homozygous Nrf-1 mutant mice are anemic due to a non-cell autonomous defect in definitive erythropoiesis and die in utero.

Amino Acid Sequence↗
PubMed1998

Engraftment of bone marrow from severe combined immunodeficient (SCID) mice reverses the reproductive deficits in natural killer cell-deficient tg epsilon 26 mice.

A large, transient population of natural killer (NK) cells appears in the murine uterine mesometrial triangle during pregnancy. Depletion of uterine (u) NK cells, recently achieved using gene-ablated and transgenic mice, results in pathology. Pregnancies from matings of homozygous NK and T cell-deficient tg epsilon 26 mice have <1% of normal uNK cell frequency, no development of an implantation site-associated metrial gland, and an edematous decidua with vascular pathology that includes abnormally high vessel walls/lumens ratios. Fetal loss of 64% occurs midgestation and placentae are small. None of these features are seen in pregnant T cell-deficient mice. To confirm the role of the NK cell deficiency in these reproductive deficits, transplantation of tg epsilon 26 females was undertaken using bone marrow from B and T cell-deficient scid/scid donors. Engrafted pregnant females have restoration of the uNK cell population, induced metrial gland differentiation, reduced anomalies in the decidua and decidual blood vessels, increased placental sizes, and restoration of fetal viability at all gestational days studied (days 10, 12, and 14). Thus, uNK cells appear to have critical functions in pregnancy that promote decidual health, the appropriate vascularization of implantation sites, and placental size.

Animals↗
PubMed1998

Saccharomyces cerevisiae Cdc6 stimulates Abf1 DNA binding activity.

In budding yeast Saccharomyces cerevisiae, an ARS binding factor 1 (Abf1) binds to the sequence-specific DNA element involved in DNA replication and transcription. We describe in this study how yeast Cdc6 protein stimulates Abf1 protein DNA binding activities. The Abf1 binding activity was reduced approximately 20-fold in a cdc6-1 mutant than in the wild-type strain. Introducing a copy of the wild-type CDC6 gene into the cdc6-1 mutant strain restored the Abf1 DNA binding activity. We demonstrated that recombinant Abf1 binds to ARS1 in vitro, and its DNA binding activity can be highly stimulated by the addition of a fusion glutathione S-transferase (GST)-Cdc6 protein. Deletion analysis revealed that the stimulating region is located at the amino terminus of the Cdc6 protein. However, we could not find the direct physical interaction between Cdc6 and Abf1. Instead, we found that the GST-Cdc6 can compete with distamycin A for binding to the DNA molecule. As distamycin A is a specific reagent that binds noncovalently to DNA at (A + T)-rich tracks, the stimulation of Abf1 DNA binding activity may be mediated by the Cdc6/DNA interaction. Our results favor a hypothesis that Cdc6 may function as an architectural factor in the assembly of a functional initiation replication complex.

Antiviral Agents↗
PubMed1998

Unique HIV type 1 V3 region sequences derived from six different regions of brain: region-specific evolution within host-determined quasispecies.

HIV type 1 viral quasispecies were amplified by polymerase chain reaction (PCR) in the hypervariable V3 region of gp120 from six different regions of the brain (right and left frontal; right and left parietal; and right and left occipital) and from the peripheral blood mononuclear cells (PBMCs) of a patient who died of AIDS dementia complex (ADC). Cloning and sequencing of the entire V3 region suggested the presence of genetically unique sequences in different regions of the brain. In contrast, the blood-derived viral quasispecies carried homogeneous sequences that were characterized by a single octapeptide crest motif (HLGPGSAF), a motif important in viral fusion. The brain-derived viral strains showed extensive sequence heterogeneity and the presence of seven different octapeptide and four different tetrapeptide crest motifs (HIGPGRAF, RIGPGRAF, HIGPGSAI, HLGPGSAF, HIGPESAI, HLGPESAI, and YLRPGSAF). In addition, the brain-derived strains were also characterized by variable net V3 loop charge and hydrophilicity, along with distinct amino acid changes specific to different brain regions. Together, the sequence and phylogenetic analyses are unique in identifying the complexity of a viral quasispecies and its independent regional evolution within the brain compartment. Uniquely divergent viral strains were identified in the frontal regions and their presence was further supported by the presence of multinucleated giant cells (characteristic of HIV encephalopathy) predominantly in the left and right frontal regions. In summary, these analyses suggest that genetically different populations of HIV-1 may be present in different brain compartments and confirm that specific neurotropic variants may exist.

Acquired Immunodeficiency Syndrome↗
PubMed1998

Dependence of cardiac cell Ca2+ permeability on sialic acid-containing sarcolemmal gangliosides.

The specific removal of negatively-charged sialic acid by neuraminidase produces a large increase in cardiac myocyte Ca uptake (17.3 +/- 1.1 mmol Ca/kg dry weight) and marked cell contracture. Importantly, the insertion of the negatively-charged amphiphile dodecyl sulfate in the sarcolemma eliminates the increased calcium uptake and preserves contractile function. In the present study, we further examine the role of sialic acid-Ca interaction and, specifically, the role of gangliosides (sialic acid-containing glycolipids) in cardiac cells' Ca permeability. Neonatal cell culture and adult ventricular myocytes were used. The major findings of this study are: (1) while dodecyl sulfate inhibits cellular calcium uptake and contracture development induced by sialic acid removal, cationic and neutral amphiphiles are without effect. (2) Ca channel blockers (nifedipine and protamine) and the Na/Ca exchange inhibitor Ni do not modify the effect of sialic acid removal. (3) A non-classical-channel related whole-cell current appears and increases after 21 +/- 2.2 min treatment with 0.02 U/ml neuraminidase (n = 4). Incubation with neuraminidase in the presence of dodecyl sulfate greatly delays the appearance of these currents to 44.4 +/- 6.1 min (n = 4). (4) The use of a specific probe for GM1 ganglioside, the cholera toxin B subunit (3 micrograms/ml), induces a moderate but clear increase in cellular Ca (1.63 +/- 0.3 mmol Ca kg dry weight; n = 8). However, this increase was not modified by treatment with dodecyl sulfate. (5) Finally, 50 mU/ml endoglycoceramidase, an enzyme which specifically cleaves the link between the sialic acid-containing oligosaccharide and ceramide of gangliosides, induced a significant increase in Ca uptake (4.4 +/- 0.9 mmol Ca kg dry weight, n = 4). These results indicate the importance of negatively charged sialic acid-containing gangliosides in the maintenance of cardiac cell physiological Ca permeability. The increase in Ca uptake induced by the removal of sialic acid seems to be mediated by development of a Ca "leak" via other than classical cation channels.

Animals↗
PubMed1998

Alternative splicing of human NrCAM in neural and nonneural tissues.

Neural cell adhesion molecule NrCAM exists in a variety of isoforms as a result of alternative splicing of individual exons during RNA processing. In this report we demonstrate that many of the alternative splicing events described for chick are conserved in man and describe a novel variant of NrCAM cDNA. Furthermore, we show that NrCAM is expressed at significant levels outside the nervous system; in particular in pancreas, adrenal glands, and placenta and that expression in both brain and other tissues is accompanied by a very variable pattern of exon utilization in fetal and adult cells.

Adrenal Glands↗
PubMed1998

Consequences of Fas-ligand and perforin expression by colon T cells in a mouse model of inflammatory bowel disease.

BACKGROUND & AIMS: We describe a type of colitis that develops after transplantation of nonallogeneic wt bone marrow cells into T cell- and natural killer cell-deficient Tg26 mice (BM-->Tg26). In these animals, severe wasting and inflammation of the colon correlates with the expansion of mucosal T lymphocytes that displays cytotoxic activity. The aims of this study were to determine the relative contribution of perforin and Fas ligand (Fas-L) expression to the cytotoxic action of these T cells and to examine the influence of each pathway in this model of colitis. METHODS: Colonic T cells were tested for their ability to mediate Fas- and perforin-dependent killing in redirected cytotoxicity assays. Bone marrow cells from donor mice lacking either Fas-L (gld mice) or perforin (PFPnull mice) or both molecules were used to reconstitute Tg26 mice. RESULTS: Colon cytotoxic T lymphocyte displayed both Fas- and perforin-dependent killing. Deficiency in perforin, but not Fas-L, resulted in reduced incidence of wasting and, to a lesser extent, severe colitis in BM-->Tg26 animals. CONCLUSIONS: Colon T cells from BM-->Tg26 mice express both perforin and Fas-L. Although neither pathway is critical in the development of colitis, perforin does have a measurable influence on disease in the BM-->Tg26 colitis model.

Animals↗
PubMed1998

Induction of pulmonary immunity in cattle by oral administration of ovalbumin in alginate microspheres.

Respiratory infectious diseases are an important cause of economic losses to the cattle industry. There is a need for an effective, easy to administer vaccine to the critical bacterial pathogens that cause pneumonia in cattle. An orally administered vaccine could be given to a large number of animals without significant stress to the animals and with minimal labor. The purpose of this study was to determine whether the oral administration of a model antigen (ovalbumin) in alginate microspheres could induce pulmonary immunity in cattle. Calves were vaccinated orally with ovalbumin (OVA) following either a subcutaneous (s.c.) or oral priming dose of OVA. Calves primed and boostered by oral administration (oral/oral) of OVA encapsulated in alginate microparticles had increased numbers of antigen-specific IgA ASCs (ASCs) in bronchoalveolar lavage (BAL) fluids. Calves that received a s.c. priming followed by an oral booster inoculation (s.c./oral) of OVA in alginate microspheres had a greater number of anti-OVA IgA, IgG1 and IgG2 ASCs in BALF. S.c./oral calves also had increased numbers of anti-OVA IgG1 ASCs in peripheral blood whereas oral/oral calves had none. S.c./oral calves had increased anti-OVA IgG1, IgG2, and IgA titers in BALF, and IgG1 and IgG2 in serum compared to both oral/oral and sham vaccinated calves. These results indicate that oral administration of antigen encapsulated in alginate microspheres results in a mucosal immune response in the respiratory tract of cattle. Furthermore, s.c. priming both enhanced the IgA response and stimulated an IgG1 and IgG2 response not seen in oral/oral calves. The difference in antibody isotype results suggest that design of the vaccination protocol can direct antibody responses as needed for a specific immunization program.

Administration, Oral↗
PubMed1998

Coumarin-based prodrugs. Part 3: Structural effects on the release kinetics of esterase-sensitive prodrugs of amines.

To study the structural effects on the release kinetics of a coumarin-based esterase-sensitive prodrug system, two series of compounds with varying structural features of the ester 'trigger' part and the amine 'drug' part were synthesized. The half-lives of the nine model prodrugs in the presence of porcine liver esterase ranged from about 2 min to 190 min. The steric bulkiness of the acyl group seems to have only a very minor effect on the half-lives of the esterase-triggered release of amines from the model prodrugs. The rate of the lactonization depends on the steric and electronic properties of the amine moiety.

Amines↗
PubMed1998

Blood pressure at age 3-24 years in a rural community in Anhui, China.

PURPOSE: This community-based study in Anhui, China examined the sex-specific pattern of blood pressure (BP) and its major determinants between age 3 and 24 years. METHODS: BP, height, weight, and related covariates were obtained from all eligible subjects by consistent methods. A generalized additive model was used to explore independent relations between BP and covariates. The sample for analyses included a total of 14,277 subjects (7244 males and 7033 females). RESULTS: Systolic blood pressure (SBP) increased linearly with age to an apparent plateau around the age of 15 years in girls and 20 years in boys. Diastolic blood pressure (DBP) essentially paralleled SBP. Until the age of 10, both SBP and DBP were similar in boys and girls; thereafter, values for boys surpassed those for girls with an average difference of 9 mmHg and 4 mmHg for SBP and DBP, respectively, at 20 years of age. This sex difference appeared to persist into early adulthood. The independent relation between BP and each of the three major determinants (age, height, and weight) was nonlinear over the age range studied. Sex-specific regression models with linear terms for age, height and weight were developed for each of four age groups (3-9, 10-14, 15-19, 20-24 years). The 5th, 10th, 90th, and 95th percentiles based on the percentage of predicted values can serve as the cutoffs for low, normal-low, normal-high, and high BP. The predicted values were derived from the above regression models that take into account an individual's sex, age, height, and weight. CONCLUSIONS: This analysis provided important basis for classification of hypertension status and subsequent investigation of environmental risk factors in this population.

Adolescent↗
PubMed1998

Sialic acid concentration of brain gangliosides: variation among eight mammalian species.

Sialic acid is a vital component of brain gangliosides which play an essential role in the transmission and storage of information in the brain. The concentration of bound sialic acid in gangliosides and free sialic acid in the brain cortex of eight different mammals [human, chimpanzee (Pan troglodytes), rat (Rattus norvegicus), mouse (Mus musculus), rabbit (Oryctolagus cuniculus), sheep (Ovis aries), cow (Bos indicus) and pig (Sus scrofa)] were compared. Total sialic acid concentration (890+/-103 microg/g wet weight tissue, mean+/-SE, n = 6) was 2-4 times higher in the human brain compared with the other species studied (0.001 < p < 0.05). There was no significant difference between human males and females. The rank order of adult brain sialic acid after humans (in microg/g) was rat (493+/-23, n = 12), mouse (445+/-29, n = 16), rabbit (380+/-18, n = 6), sheep (323+/-43, n = 6), cow (304+/-14, n = 6) and pig (252+/-14, n = 6). Apart from the cow vs the sheep, the differences between species were statistically significant (p < 0.05). In the mouse, cow and sheep, total sialic acid concentration increased during maturation by 18-32% (p < 0.05). In a 2-year-old chimpanzee, the sialic acid concentration in the left lobe of the brain cortex was 25% higher than that of right lobe at 6 weeks of age (p < 0.05). Free sialic acid was higher in the human brain cortex (41+/-3 microg/g) than that of the rat and mouse (32+/-3 and 25+/-5 microg/g respectively) and absent from other species. Variation in brain sialic acid concentration among different animals has implications for the evolution of the brain and may affect learning ability in animals.

Aging↗
PubMed1998

A comparison of the bioconversion rates and the Caco-2 cell permeation characteristics of coumarin-based cyclic prodrugs and methylester-based linear prodrugs of RGD peptidomimetics.

PURPOSE: To compare the bioconversion rates in various biological media and the Caco-2 cell permeation characteristics of coumarin based cyclic prodrugs (3a, 3b) and methylester-based linear prodrugs (1b, 2b) of two RGD peptidomimetics (1a, 2a). METHODS: Bioconversion rates of the prodrugs to the RGD peptidomimetics were determined in Hank balances salt solution (HBSS), pH 7,4, at 37 degrees C and in various biological media (human blood plasma, rat liver homogenate, Caco-2 cell homogenate) known to have esterase activity. Transport rates of the prodrugs and the RGD peptidomimetics were determined using Caco-2 cell monolayers, an in vitro cell culture model of the intestinal mucosa. RESULTS. In HBSS, pH 7,4, the coumarin-based cyclic prodrugs 3a and 3b degraded slowly and quantitatively to the RGD peptidomimetics 1a and 2a, respectively (3a, t1/2 = 630+2-14 min; 3b, t1/2 = 301 +/-12 min). The methylester-based linear prodrugs 1b and 2b were more stable to chemical hydrolysis (1b and 2b, t1/2 > 2000 min). Both the coumarin-based cyclic prodrugs and the methylester-based linear prodrugs degraded more rapidly in biological media containing esterase activity (e.g., 90% human blood plasma: 1b, t1/2 < 5 min; 2b, t1/2 < 5 min; 3a, t1/2 < 91+/-1 min; 3b, 1/2 < 57+/-2 min). When the apical (AP)-to-basolateral (BL) permeation characteristics were determined using Caco-2 cell monolayers, it was found that the methylester prodrugs 1b and 2b underwent esterase bioconversion (>80%) to the RGD peptidomimetics 1a and 2a, respectively, In contrast, the cyclic prodrugs 3a and 3b permeated the cell monolayers intact. Considering the appearance of both the prodrug and the RGD peptidomimetic on the BL side, the methylester prodrugs 1b and 2b were approximately 12-fold more able to permeate than were the RGD peptidomimetics 1a and 2a. When similar analysis of the transport data for the coumarin prodrugs 3a and 3b was performed, they were shown to be approximately 6-fold and 5-fold more able to permeate than were the RGD peptidomimetics 1a and 12a, respectively. CONCLUSION: The coumarin-based cyclic prodrugs 3a and 3b were chemically less stable, but metabolically more stable, then the methylester based linear prodrugs. The esterase stability of the cyclic prodrugs 3a and 3b means that they are transported intact across the Caco-2 cell monolayer in contrast to the methylester prodrugs 1b and 2b, which undergo facile bioconversion during their transport to the RGD peptidomimetics. However, both prodrug systems successfully delivered more (5-12-fold) of the RGD peptidomimetic and/or the precursor (prodrug) than did the RGD peptidomimetics themselves.

Animals↗
PubMed1998

Anti-asparaginase antibodies following E. coli asparaginase therapy in pediatric acute lymphoblastic leukemia.

Asparaginase is an effective antileukemic agent and is included in most front-line protocols for pediatric acute lymphoblastic leukemia (ALL) worldwide; however, allergic reactions to asparaginase may be dose-limiting. We evaluated plasma anti-asparaginase antibody concentrations in a cohort of children with newly diagnosed ALL, who did and who did not exhibit clinical hypersensitivity, after Escherichia coli (E. coli) asparaginase therapy. Thirty-five children who received asparaginase 10000 IU/m2 i.m. three times weekly for nine doses as part of both multiagent induction and reinduction chemotherapy, and seven monthly doses during the first 7 months of continuation treatment, were studied. Twenty-two patients experienced initial allergic reactions to asparaginase during continuation (n=20) or reinduction (n=2) phases and 13 children did not exhibit any reaction. An enzyme-linked immunosorbent assay (ELISA) was used to measure anti-asparaginase antibodies in plasma samples, diluted 1:3200, using E. coli asparaginase as the antigen. The median anti-asparaginase antibody concentration (OD at 1:3200 dilution) increased from 0.039 at induction to 0.506 at reinduction in patients who exhibited clinical hypersensitivity (P = 0.0002). By comparison, median antibody level increased from 0.011 to 0.032 OD at identical time points in patients who did not react to asparaginase (P = 0.02). Both post-induction and post-reinduction anti-asparaginase antibody levels were higher in reacting than in nonreacting patients (P = 0.004 and P = 0.01, respectively). Antibody levels were inversely related to the time elapsed between the reaction and sampling (P = 0.011). Although anti-asparaginase antibody levels increased from the post-induction plasma sample to the post-reinduction sample in 28 of 35 patients regardless of whether they exhibited clinical hypersensitivity, patients with hypersensitivity reactions had higher antibody levels than did identically treated control patients at comparable time points in therapy. Therefore, antibody analysis may be of clinical value in predicting future hypersensitivity.

Adolescent↗