Search PubMed⌕ Search

Biomedical subjects

B Xu

Publications and source records attributed to B Xu.

At least 289 records · Page 16Linked to original sources
PubMed1995

[Evaluation of presurgical orthodontic correction of the mandibular prognathism].

The aim of this study was to evaluate the effects of presurgical orthodontic correction of the mandibular prognathism. The sample consisted of two groups of surgical cases. The cases of the mandibular prognathism in group I with lower anterior dental compensation received presurgical orthodontic decompensation, and the cases in group II without lower anterior dental compensation did not receive presurgical orthodontic decompensation. The results showed that before presurgical orthodontic treatment, significantly differences existed between the two groups variable ILi/OL and ANB. After presurgical orthodontic correction lower incisors position in group I was very close to that in the group II, this means that the presurgical orthodontic treatment significantly changed the position of the lower incisors.

Adolescent↗
PubMed1995

[The role of intestinal permeability in the pathogenesis of ankylosing spondylitis].

By use of low molecular weight polyethlene glycol (PEG400) as tracer, a revised Chedwick method with capillary gas chromatography was used to examine the intestinal permeability in 49 subjects including patients with ankylosing spondylitis (AS) and rheumatoid arthritis (RA) and healthy controls. Recovery percentage, maximal recovery percentage [Rmax(%)] and Rmax(w) were used to find the effect of bowel permeability in the pathogenesis and disease flare up of AS, as well as the role of HLA-B27 for the bowel permeability. The results showed that in AS group, the recovery of first component (242D) was higher and the Rmax(%) was lower than those in the controls. No statistical difference was found with other indexes. The results indicated that bowel permeability is not elevated in AS. The passage of enteral bacteria antigen into the host may not result from the process of nonspecific penetration. We postulate that there may somehow be a process of "active transportation" in the pathogenesis of AS. More studies of the process are necessary to clarify its importance in the early stage of AS.

Adult↗
PubMed1995

[The inhibitory effects of immune sera against two recombinant hybrid antigens on the growth of Plasmodium falciparum in vitro].

The inhibitory effects of rabbit immune sera against two recombinant hybrid antigens (C and CAC) of Plasmodium falciparum to the multiplication and development of in vitro cultured P. falciparum parasites were tested. Although both of anti-C and anti-CAC immune sera had inhibitory effect on parasites, the anti-CAC serum showed much greater effect than that of anti-C serum (P < 0.05). The inhibitory capacities in the sera to parasites were enhanced with the increase in the serum concentration as well as with the prolongation of the incubation time of the sera with the parasites. It was shown that after 72 h incubation of the anti-CAC serum with the parasites at the concentration of 1%, 10% and 20%, the inhibition rates were 15%, 54% and 82%, respectively. The immune sera caused the dispersion of parasite cytoplasm, atrophy of parasites, agglutination of free merozoites and degeneration of schizonts, suggesting that the hybrid antigen could produce multi-functional protective antibodies against antigens of Plasmodium falciparum.

Animals↗
PubMed1995

Four outbreaks of human trichinellosis in Henan Province.

Four outbreaks of human trichinellosis caused by eating pork together had occurred successively in two rural areas and two cities of Henan Province, where the disease is endemic. Of the 110 persons involved, 54 had the onset. All of them had the history of eating pork. In the outbreak of Dengzhou, in those persons who dined together, men were all uninfected and 13 women were infected. The difference found between sexes was suggested to be related with spirit drinking. In these 54 patients, the latent period ranged from 3 to 28 days. The relevant clinical symptoms and signs were fever, edema, myalgia, rash, headache, nausea, abdominal pain and diarrhea. Vomiting was uncommon. Most patients were hospitalized and all cases recovered in two weeks after proper treatment with albendazole.

Animals↗
PubMed1995

[Mechanism of resistance to mitomycin C in a human bladder cancer cell line].

This study was undertaken to determine the mechanism of resistance of a human bladder cancer cell line SCaBER to mitomycin C (MMC). The IC50 value for MMC in SCaBER cells was higher by 2.7 fold by 1-h drug exposure colony formation assay as compared to another bladder cancer cell line J82. NADPH cytochrome P450 reductase and DT-diaphorase activities were significantly lower in SCaBER cells as compared to those of J82 suggesting that relatively resistance of SCaBER cells to MMC may be due to inefficient drug activation. Further support for this conclusion derives from the observation that sensitivities of J82 and SCaBER cells to BMY25282, a MMC analogue with lower quinone reduction potential, were similar. MMC dependent lipid peroxidation (an indicator of oxygen free radical formation) was higher in SCaBER cells than in J82. The activities of anti-oxsidative enzymes GSH peroxidase and catalase did not differ significantly in these cells. These results suggest that resistance of SCaBER cells to MMC may not be due to the reduced free radical formation in these cells. MMC induced DNA interstrand cross-link (ISC) formation was markedly lower in SCaBER cells than in J82. Taken together, these results suggest that SCaBER cell resistance to MMC may be due to the reduced drug activation and ISC formation in these cells.

Antibiotics, Antineoplastic↗
PubMed1995

[Preparation of oral berberine bisulfate liposomes].

The co-precipitate has been made from berberine bisulfate and polyvingyl pyrrolidone (PVP) with the ratio of 1 : 5. The liposomes entrapped berberine bisulfate have been prepared with the ration of drug to lipid 1 : 20 and the ratio of cholesterol to soy phosphatide 2 : 7. The percentage of encapsulation is 48.72%. The test in vivo of small intestinal absorption in rats shows that liposomes can increase the absorption by 4-fold odd compared with free ber-berine bisulfate.

Animals↗
PubMed1995

The hypothalamo-neurohypophyseal system in birds.

The hypothalamus is the central integrative structure for the neuroendocrine regulation of body fluid homeostasis. Despite many different modulatory endocrine and peptidergic inputs there are three main neuroendocrine 'channels' involved in osmoregulation: 1. corticotropin releasing hormone (CRH)-adrenocorticotropic hormone (ACTH)-adrenal steroids (aldosterone, corticosterone); 2. renin-angiotensin; 3. arginine-vasotocin (AVT). In this paper the important role of the AVT synthesizing hypothalamo-neurohypophysial system (HNS) in the control of osmoregulation is described. Although the onset of AVT gene expression and peptide synthesis is as early as around day 6 of embryonal life in the chick, osmoregulatory function may not occur before the end of the second week of incubation. Rapid maturational processes during the last week of embryonal development lead to a 'close-to-mature' response of the AVT secretory system to physiological (osmotic) stimulation in the one-day-old chicken. Stable AVT plasma concentrations imply continuous secretion and/or degradation of this peptide in the blood of the chicken. Osmotic challenge causes not only an increase in plasma osmolality, plasma sodium and AVT concentration, but also AVT gene expression is upregulated. The AVT system participates in adaptational] processes during the perihatching period and its secretory activity depends on modulatory effects caused by suboptimal humidity during incubation.

Amino Acid Sequence↗
PubMed1995

Presurgical orthodontic decompensation of mandibular incisors.

The effects of presurgical orthodontic decompensation on lower incisor inclination and angle ANB were studied using a modified Pancherz method of cephalometric analysis. Two groups of patients with mandibular hyperplasia were studied: one group (Group 1) of nineteen cases which required orthodontic decompensation and another (Group 2) of twenty-one cases which did not. The cephalometric changes which occurred in Group 1 were compared with the significant cephalometric differences existing between the two groups with respect to incisor inclination (ILi/OL; P < .001) and the sagittal relation (ANB; P < 0.05). After orthodontic treatment the average lower incisal angulation of the treated group was the same as that in the untreated group; the variations (S.D) being 3.6 degrees and 7.4 degrees respectively indicating that the clinical assessment of the orthodontic treatment effect was quite high.

Adaptation, Physiological↗
PubMed1994

c-fos expression in the rat brain following central administration of neuropeptide Y and effects of food consumption.

Administration of neuropeptide Y (NPY) intracerebroventricularly (i.c.v.) results in the release of a number of hypothalamic and pituitary hormones and stimulation of feeding and suppression of sexual behavior. In this study, we sought to identify cellular sites of NPY action by evaluating perikaryal Fos-like immunoreactivity (FLI), a marker of cellular activation, in those hypothalamic and extrahypothalamic sites previously implicated in the control of neuroendocrine function and feeding behavior. Additionally, we compared the topography of FLI in these brain sites when food was either available ad libitum or withheld after NPY injection (1 nmol/3 microliters, i.c.v.). The results showed that one hour after NPY injection a larger number of cells in the parvocellular region of the paraventricular nucleus (PVN) were FLI-positive in the absence of food consumption. However, in association with food intake, a significant number of cells were intensely stained in the magnocellular region of the PVN. An analogous increase in FLI in association with feeding was apparent in the supraoptic nucleus (SON), the dorsomedial nucleus and the bed nucleus of the stria terminalis in the hypothalamus. Among the extrahypothalamic sites, feeding facilitated FLI in a large number of cells located in the lateral subdivision of the central amygdaloid nucleus and the lateral subdivision of the solitary tract. FLI was observed in a moderate number of cells in the hypothalamic arcuate nucleus (ARC) and ventromedial nucleus, and this response was not changed by feeding.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Primary leukemia cells resistant to alpha-interferon in vitro are defective in the activation of the DNA-binding factor interferon-stimulated gene factor 3.

Cells from one-third of chronic lymphocytic leukemia (CLL) patients are resistant to alpha-interferon (alpha-IFN) as measured by induction of blast transformation. We have previously shown that all CLL clones express alpha/beta-IFN receptors, but that the resistant cells are defective in the induction of the enzyme 2',5'-oligoadenylate synthetase (2',5-A synthetase). Thus, the deficiency in IFN sensitivity is localized somewhere between the interaction of the IFN molecule with its receptor and induction of 2',5'-A synthetase. We have now further characterized the resistance of CLL clones to IFN by investigating whether it is associated with a defect in the activation of IFN-stimulated gene factor 3 (ISGF3), which is involved in the activation of alpha-IFN-stimulated genes (ISGs). A defect induction of ISGF3 after alpha-IFN treatment was found in 4 of 12 CLL patients. There was a close correlation between defective induction of ISGF3 and a lack of enhancement of 2',5'-A synthetase as well as induction of blast transformation. Pretreatment with gamma-IFN and mixing experiments with extracts from IFN-sensitive cells indicate that a lack of the gamma-component of ISGF3 was the reason for defect in activation in 2 of the patients. We conclude that a defect in activation of ISGF3 is a possible cause for resistance in CLL cells to IFN-induced blast transformation in vitro.

2',5'-Oligoadenylate Synthetase↗
PubMed1994

Analysis of sequence transfers resembling gene conversion in a mouse antibody transgene.

The role of gene conversion in murine immunoglobulin gene diversification is unclear. An antibody gene construct designed to provide the homologous donor and acceptor sequences required for conversion mechanisms was produced and used to generate transgenic mice. When these transgenic mice were immunized, DNA sequence transfers between tandem transgene VDJ regions were detectable and resembled gene conversion events. There is a strong link between these conversion-like sequence transfers and transgene somatic hypermutation, suggesting that both processes might occur at the same stage of B cell differentiation.

Animals↗
PubMed1994

Insulin synthesis, secretory competence, and glucose utilization are sensitized by transgenic yeast hexokinase.

Glucokinase regulates insulin secretion by controlling the rate of glucose phosphorylation. In this report we utilize islets transgenic for high affinity yeast hexokinase to examine the role of glucose phosphorylation on other beta cell functions. Normal pancreatic islets responded to culture in low glucose by lowering insulin synthetic rates, becoming depleted of insulin and insulin mRNA, losing competence to respond to glucose with increased insulin secretion, and lowering glucokinase levels by one-half. In transgenic islets, increased high affinity hexokinase activity provided significant protection against reductions in all parameters of insulin synthesis and helped preserve the competence of beta cells to secrete insulin. The transgenic hexokinase also increased the rate of glucose utilization. These results demonstrate that glucose phosphorylation and presumably glucokinase mediate these glucose regulated responses. Of the parameters measured, only the change in glucokinase activity did not show an effect of the yeast hexokinase transgene. We also found that yeast hexokinase transgene expression was regulated 10-fold by glucose. This is the first demonstration of glucose inducibility of the insulin promoter in transgenic mice.

Animals↗
PubMed1994

Evidence that neuropeptide Y is a physiological signal for normal food intake.

Neuropeptide Y is the most potent orexigenic signal known. To test the hypothesis that NPY is a physiological messenger molecule for normal food intake in rats, we studied the effects of passive immunization against endogenous NPY on cumulative daily food intake in non-fasted spontaneously feeding rats. The results show that continuous central infusion of NPY antibodies markedly suppressed the nighttime and the cumulative 24 h food intake in a dose-dependent fashion. These results support the hypothesis that NPY may be a physiological signal involved in the stimulation of ingestive behavior in rats.

Animals↗
PubMed1994

Amphibian allantoinase. Molecular cloning, tissue distribution, and functional expression.

The chain of enzymes necessary to convert uric acid to its metabolic products urea and glyoxylic acid in vertebrates is truncated through the successive loss of allantoicase, allantoinase, and urate oxidase during phylogenetic evolution. Previous studies have assigned the localization of both urate oxidase and allantinase to the peroxisome in the amphibian liver. This study reports the cloning of a cDNA encoding bullfrog (Rana catesbeiana) allantoinase, an enzyme that converts allantoin to allantoic acid. The cDNA is 2112 base pairs in length containing a 1449-base pair open reading frame which corresponds to a 483-residue protein (53,296 Da). Structural analysis of the deduced protein suggested two potential transmembrane segments and the presence of a putative mitochondrial localization sequence in the amino terminus. Immunocytochemical analysis revealed that allantoinase is localized to mitochondria and not to peroxisomes. On Northern blotting, a single mRNA species was detected in the liver and kidney of frog but not in other tissues; this distribution was confirmed by immunoblotting. The hepatic- and renal-specific expression of allantoinase coincides with the distribution of urate oxidase in these tissues in the frog. The allantoinase expressed in Saccharomyces cerevisiae and in Spodoptera frugiperda (Sf9) insect cells exhibits catalytic activity and is antigenically identical to the native frog enzyme.

Amidohydrolases↗
PubMed1994

Growth hormone (GH) induces tyrosine-phosphorylated proteins in mouse L cells that express recombinant GH receptors.

Porcine and bovine GH receptor (GHR) cDNAs were stably expressed in mouse L cells, which normally do not possess detectable levels of mouse GHR. Expression of the GHR cDNAs resulted in specific binding of 125I-labeled GH by these cell lines. To study GHR-related signaling events in these cells, protein tyrosine phosphorylation was examined. In GH-treated cells, a tyrosine-phosphorylated protein with a molecular mass of approximately 95 kDa (pp95) was increased dramatically (approximately 100-fold) relative to non-GH-treated cells. The amount of pp95 within the cells after GH treatment was positively correlated with the number of GHRs on the cells. Tyrosine phosphorylation of pp95 could not be induced by prolactin, insulin, insulin-like growth factor I, interleukin 2, epidermal growth factor, platelet-derived growth factor, or fibroblast growth factor. Phosphorylation of pp95 was found to be a rapid event that could be observed 60 sec after GH treatment. Also, pp95 appears to exist as a complex of two proteins, i.e., pp95 and pp96. The GH-induced response by these cells may be of use in screening GH analogs for biological activity.

Animals↗
PubMed1994

Probing the metal binding sites of Escherichia coli isoleucyl-tRNA synthetase.

The metal binding properties of isoleucyl-tRNA synthetase (IleRS) from Escherichia coli were studied by in vivo substitution of the enzyme-bound metals. Purified E. coli IleRS was shown to have two tightly bound zinc atoms per active site. Cobalt- and cadmium-substituted IleRS were also found to contain two tightly bound Co2+ and Cd2+ atoms per polypeptide chain, respectively. The d-d transitions in the low energy absorption spectrum of Co(2+)-substituted IleRS were characteristic of that expected for two tetrahedrally coordinated Co2+ metals. Apo-IleRS was found to be inactive in both the aminoacylation of tRNA(Ile) and in the isoleucine-dependent ATP-pyrophosphate exchange reactions. Both Co(2+)- and Cd(2+)-substituted IleRS were found to have kcat/Km values in the isoleucine-dependent ATP-pyrophosphate exchange assay approximately 5-fold lower than the native Zn2+ enzyme. A single enzyme-bound Zn2+ or Co2+ atom per polypeptide chain could be removed by dialysis of Zn(2+)- or Co(2+)-substituted IleRS against 1,10-phenanthroline. Removal of one of the two enzyme-bound Zn2+ atoms per polypeptide chain with 1,10-phenanthroline was found to decrease (kcat/Km)Ile by approximately 130-fold. The dependence of the kinetic parameters on the identity and number of enzyme-bound metals in the isoleucine-dependent ATP-pyrophosphate exchange reaction suggests that at least one enzyme-bound metal is indirectly involved in aminoacyladenylate formation. Metal substitution or removal of one of the two enzyme-bound metals in IleRS was found to have little effect on the Km value for tRNA(Ile) or the kcat value for aminoacylation of tRNA(Ile).(ABSTRACT TRUNCATED AT 250 WORDS)

Acylation↗