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Biomedical subjects

J Xu

Publications and source records attributed to J Xu.

At least 973 records · Page 54Linked to original sources
PubMed1996

[Experience of laparoscopic vagotomy for the treatment of chronic duodenal ulcer].

Ten patients with chronic duodenal ulcer underwent posterior truncal vagotomy combined with anterior seromyotomy of lesser curvature of the stomach (Taylor's procedure). Perioperative acid secretory studies (Horlland test) and gastric emptying tests were performed. Postoperative recovery was uneventful in all patients. The acid secretory studies showed decreased BAO, MAO and PAO (P < 0.01). The postoperative gastric emptying was significantly delayed, and the patients are all symptom free. Follow up gastroscopy revealed ulcer healing in 7 patients.

Adult↗
PubMed1996

[Assay of anti-corneal endothelial antibody after penetrating keratoplasty].

OBJECTIVE: To study the effective materials in the immune response and the humoral immunity in graft rejective reaction in the host after penetrating keratoplasty (PKP). METHODS: PK was performed on 2 groups of monkeys with a 5.5 mm button in a 5.0 mm bed. The heterogroup (human to monkey) had 4 monkeys, and homo-group (monkey to monkey) also 4. Nelken's method was modified. Two kinds of antigens, corneal endothelial and stromal antigens, had been made the first time. Enzyme linked immunosorbent assay (ELISA) was used to detect the anti-corneal endothelial antibody (ACEAb) in the serum and aqueous humor of the host. RESULTS: After PKP, the anti-corneal stromal antibody did not increase obviously, while the increase of ACEAb was distinct. CONCLUSION: Humoral immune response can occur in the host after PK, and the effective material is ACEAb.

Animals↗
PubMed1996

[The analysis of clinical dental crown of primary molar teeth].

For providing the anatomical data of primary molar teeth in China and using for the reference of clinical orthodontics, we measured and analysed the clinical crown of first and second primary molar teeth in 167 children of 4-6 years old finely. Each tooth was measured for 7 items with 9,228 in total. The heights of teeth crowns on buccal site were much taller than that on glossopalatal site except E. The mesial, distal and buccoglossal lenths were much longer on the enlarged part of crown than on the occlusive part. The mean values of symmetric teeth on both sites almost were of no difference. The mean values were not different in age groups (4.5 or 6 years old) either.

Anthropometry↗
PubMed1996

A population-based study of lens opactities.

PURPOSE: Age-related lens opacity is the main cause of vision disability in elderly population all over the world. This study was designed to investigate the prevalence and incidence of lens opacity. METHODS: 1817 eyes of 932 adults over 45 years-old were sampled randomly from 4 villeges within Doumen, a county located in the south of Guangdong provience, China. The procedure of the examination was performed by ophthalmologists. The lens opacities were graded according to a standarized photo of the Lens Opacities Classification System II (LOCS-II). RESULTS: The prevalence of lens opacities in nuclear color, nuclear opacity, cortical opacity and subcapsular opacity was 16.1%, 28.6%, 30.3% and 8.7%, respectively. The frequency of all four types of opacities increased with age. The prevalence of lens opacities in four types was higher in female than that in male. CONCLUSION: The data we got are important for prevalence of lens opacities of population-based study as well as basic information for cohort study in the future.

Aged↗
PubMed1996

The etiology of vision impairment in target population.

PURPOSE: research the etiology of vision impairment in target persons over 45 years old in Doumen county, Guangdong province. METHODS: Depending on the prevalences of the blindness among the person aged over 50 years, the theoretic sample rate is 1,000/4,8733 x 100% = 2.05%. The 8 districts were divided into 3 parts according to the local economic situation and the proportion of the population in the areas. In fact, the sampling rate is 932/10055 = 88.34%. RESULTS: We found that impairment < 0.3 accounted for 10.94%. The prevalence of bilateral blindness and low vision was 1.61% and 3.22%, respectively. Both prevalences of blindness and low vision were increased with age. The leading cuase of blindness was cataract (45.2%). The second was corneal opacity (16.7%). Prevalences of the low vision and the blindness were higher in females than in males (P < 0.005). CONCLUSIONS: Curable and preventable diseases were the leading cause for the blindness (70%). Prevalences of blindness and the low vision increase with age. We will continually follow up the population over 50 years of age in Doumen county.

Age Factors↗
PubMed1996

[Dynamic changes in soluble interleukin-2 receptor levels after rat corneal allograft].

PURPOSE: To evaluate the diagnostic utility of serum IL-2R level test in corneal allograft rejection. METHODS: Serum soluble IL-2R was detected by radioimmunoassay in rat corneal allograft model. RESULTS: Levels of soluble IL-2R were markedly elevated prior to the clinical diagnosis of rejection. CONCLUSIONS: Marked elevations of soluble IL-2R are associated with rejection, measurement of soluble IL-2R may have a useful value in the early diagnosis of corneal allograft rejection.

Animals↗
PubMed1996

[Studies on the chemical constituents of Dregea sinensis Hemsl].

Two new compounds named dresigenin B and dresioside I were isolated from the root of Dregea sinensis Hemsl. Their structures were demonstrated as 20-O-(2-methylbutyryl) tomentogenin and dihydrosarcostin 3-O-beta-D-thevetopyranosyl (1-4)-beta-D-oleandropyranosyl (1-4)-beta-D-cymaropyranoside by spectral evidence.

Drugs, Chinese Herbal↗
PubMed1995

Impairment of antigen-specific T-cell priming in mice lacking CD40 ligand.

Lack of functional expression of CD40 ligand (CD40L) on T cells results in hyper-IgM syndrome (HIGM1), a human immunodeficiency associated with a severely impaired humoral immune response that is consistent with defects in B-cell responses. Patients also succumb to recurrent opportunistic infections such as Pneumocystis carinii and Cryptosporidial diarrhoea, suggesting that T-cell functions are also compromised in these individuals, but so far this has not been explained. We have previously shown that mice deficient for CD40L, like HIGM1 patients, show grossly abnormal humoral responses. Here we report that CD40L-deficient mice are defective in antigen-specific T-cell responses. Adoptively transferred antigen-specific CD4+ T cells lacking CD40L failed to expand upon antigen challenge of the recipients, showing that expression of CD40L on T cells is required for in vivo priming of CD4+ T cells and therefore for the initiation of specific T-cell immune responses.

Animals↗
PubMed1995

Rapid induction of a novel costimulatory activity on B cells by CD40 ligand.

BACKGROUND: T cells and B cells communicate by direct cell--cell interaction that is crucial to the functioning of the immune system. It is well established that the interaction between B-cell-expressed CD40 and T-cell-expressed CD40 ligand (CD40L) is critical for T-cell-dependent antibody responses, but the role of this interaction in T-cell responses is less clear. In this study, we have used mice with targeted mutations in the genes encoding CD40L or CD28 to investigate how the CD40-CD40L interaction induces on B cells a costimulatory activity that acts in addition to antigen to trigger T-cell growth. RESULTS: We show that T cells from Cd40L-deficient mice induce a substantially reduced costimulatory activity on B cells compared to wild-type T cells, particularly at early time points. Surprisingly, T cells, from CD40L-deficient mice induce similar levels of B7-1 and B7-2 as do wild-type T cells. We further show that the CD40L-mediated induction of costimulatory activity precedes the induction of B7-1, B7-2 and the heat-stable antigen (HSA). CD4 T cells isolated from the CD28-deficient mice can receive costimulatory activity from CD40L-induced B cells, demonstrating that the induced molecules can costimulate T cells by a CD28-independent mechanism. We have generated a novel monoclonal antibody that inhibits the CD40L-induced costimulatory activity. Expression of the epitope detected by this monoclonal antibody correlates with the induction of the costimulatory activity, and the molecule recognized by the monoclonal antibody is a single chain of around 85 kDa, distinct from B7-1, B7-2, ICAM-1, ICAM-2, ICAM-3, HSA CD5, integrin and 4-1BB ligand. CONCLUSIONS: Our results demonstrate that CD40L is both necessary and sufficient for rapid, T-cell-mediated induction of costimulatory activity on B cells. This costimulatory activity is distinct from B7-1 and B7-2, and is independent of CD28.

Animals↗
PubMed1995

Assembly of voltage-gated potassium channels. Conserved hydrophilic motifs determine subfamily-specific interactions between the alpha-subunits.

Voltage-gated potassium (K+) channels are assembled by four identical or homologous alpha-subunits to form a tetrameric complex with a central conduction pore for potassium ions. Most of the cloned genes for the alpha-subunits are classified into four subfamilies: Kv1 (Shaker), Kv2 (Shab), Kv3 (Shaw), and Kv4 (Shal). Subfamily-specific assembly of heteromeric K+ channel complexes has been observed in vitro and in vivo, which contributes to the diversity of K+ currents. However, the molecular codes that mediate the subfamily-specific association remain unknown. To understand the molecular basis of the subfamily-specific assembly, we tested the protein-protein interactions of different regions of alpha-subunits. We report here that the cytoplasmic NH2-terminal domains of Kv1, Kv2, Kv3, and Kv4 subfamilies each associate to form homomultimers. Using the yeast two-hybrid system and eight K+ channel genes, two genes (one isolated from rat and one from Drosophila) from each subfamily, we demonstrated that the associations to form heteromultimers by the NH2-terminal domains are strictly subfamily-specific. These subfamily-specific associations suggest a molecular basis for the selective formation of heteromultimeric channels in vivo.

Amino Acid Sequence↗
PubMed1995

Genetic susceptibility to asthma--bronchial hyperresponsiveness coinherited with a major gene for atopy.

BACKGROUND: Bronchial hyperresponsiveness, a risk factor for asthma, consists of a heightened bronchoconstrictor response to a variety of stimuli. The condition has a heritable component and is closely related to serum IgE levels and airway inflammation. The basis for these relations is unknown, as is the mechanism of genetic susceptibility to bronchial hyperresponsiveness. We attempted to define the interrelation between atopy and bronchial hyperresponsiveness and to investigate the chromosomal location of this component of asthma. METHODS: We studied 303 children and grandchildren of 84 probands with asthma selected from a homogeneous population in the Netherlands. Ventilatory function, bronchial responsiveness to histamine, and serum total IgE were measured. The association between the last two variables was evaluated. Using analyses involving pairs of siblings, we tested for linkage between bronchial hyperresponsiveness and genetic markers on chromosome 5q31-q33, previously shown to be linked to a genetic locus regulating serum total IgE levels. RESULTS: Serum total IgE levels were strongly correlated (r = 0.65, P < 0.01) in pairs of siblings concordant for bronchial hyperresponsiveness (defined as a > or = 20 percent decrease in the forced expiratory volume in one second produced by histamine [threshold dose, < or = 16 mg per milliliter]), suggesting that these traits are coinherited. However, bronchial hyperresponsiveness was not correlated with serum IgE levels (r = 0.04, P > 0.10). Analyses of pairs of siblings showed linkage of bronchial hyperresponsiveness with several genetic markers on chromosome 5q, including D5S436 (P < 0.001 for a histamine threshold value of < or = 16 mg per milliliter). CONCLUSIONS: This study demonstrates that a trait for an elevated level of serum total IgE is coinherited with a trait for bronchial hyperresponsiveness and that a gene governing bronchial hyperresponsiveness is located near a major locus that regulates serum IgE levels on chromosome 5q. These findings are consistent with the existence of one or more genes on chromosome 5q31-q33 causing susceptibility to asthma.

Adolescent↗
PubMed1995

Structure of two cecropin B-encoding genes and bacteria-inducible DNA-binding proteins which bind to the 5'-upstream regulatory region in the silkworm, Bombyx mori.

Two genomic DNAs encoding cecropin B (CecB), an antibacterial protein from Bombyx mori, were cloned and sequenced. The number of CecB genes was estimated to be more than four copies per haploid by genomic Southern blotting. Two genes, CecB1 and CecB2, were located tandemly within 12 kb in the same orientation. These two genes encoded identical amino acids, though 15 nucleotides (nt) were different in the coding region and the intron size varied. About 90% of the nt spanning 800 bp in the 5'-untranslated region (UTR) were identical between the two genes. This 5'-flanking region contained characteristic sequences such as a repetitive element of B. mori (Bm1), an interleukin-6 response element (IL-6 RE), and two putative lipopolysaccharide (LPS) response elements (LPS RE). An electrophoretic mobility shift assay (EMSA) showed that the fat body contains at least three different nuclear proteins inducible by bacteria which bind to the 5'-UTR, suggesting that these proteins may be involved in CecB expression triggered by bacteria.

Amino Acid Sequence↗
PubMed1995

Blockage of the early events of mitogenic signaling by interferon-gamma in macrophages in response to colony-stimulating factor-1.

Inhibition of cell proliferation is an important biologic function of interferons (IFNs), which has been exploited in therapeutic treatment of certain hematologic malignancies. However, the molecular mechanism was not clear. We have recently shown that IFNs (alpha/beta and gamma) inhibit protein kinase C (PKC)-dependent (such as PDGF and phorbol ester) but not PKC-independent (such as epidermal growth factor) activation of Raf-1 and mitogen-activated protein kinases (MAPK/ERKs) in fibroblasts (Xu et al, Mol Cell Biol 14:8018, 1994), suggesting a novel mechanism by which IFNs execute their antiproliferative function. Monocytes/macrophages are primary targets in vivo for IFN-gamma, the major activity of macrophage-activating factor. In the present study, mechanism of IFN-gamma-induced antiproliferative action in macrophages in response to colony-stimulating factor-1 (CSF-1) has been investigated. Our results show that antiproliferative effect of IFN-gamma overrode mitogenic effect of CSF-1 and phorbol ester, as measured by early gene expression, DNA synthesis and cell proliferation. Although activation, phosphorylation, and turnover of the CSF-1 receptor and CSF-1-induced increase in diacylglycerol production remained normal, IFN-gamma blocked CSF-1-stimulated activation of mitogen-activated protein kinases, Raf-1 kinase, increase in GTP-bound Ras and tyrosine phosphorylation, and activation of protein kinase C delta (PKC-delta). PKC-delta was required for CSF-1-induced mitogenic signaling and a primary target for IFN-gamma-induced inhibition. Interestingly, although phorbol myristate acetate stimulated Ras activation, PKC-delta did not appear to be an upstream activator of Ras. These studies clearly indicated that IFN-gamma specifically inhibits PKC-delta activation, resulting in blockage of the early events of mitogenesis in macrophages in response to CSF-1.

Animals↗
PubMed1995

Point mutations in awdKpn which revert the prune/Killer of prune lethal interaction affect conserved residues that are involved in nucleoside diphosphate kinase substrate binding and catalysis.

The awd gene of Drosophila melanogaster encodes a nucleoside diphosphate kinase. Killer of prune (Kpn) is a mutation in the awd gene which substitutes Ser for Pro at position 97 and causes dominant lethality in individuals that do not have a functional prune gene. This lethality is not due to an inadequate amount of nucleoside diphosphate (NDP) kinase activity. In order to understand why the prune/Killer of prune combination is lethal, even in the presence of an adequate NDP kinase specific activity level, and to understand the biochemical basis for the conditional lethality of the awdKpn mutation, we generated second site mutations which revert this lethal interaction. All of the 12 revertants we recovered are second site mutations of the awdKpn gene. Three revertants have deletions of the awdKpn protein coding region. Two revertants have substitutions of the initiator methionine and do not accumulate KPN protein. Seven revertants have amino acid substitutions of conserved residues that are likely to affect the active site: five of these have no enzymatic activity and two have a very low level of specific activity. These data suggest that an altered NDP kinase activity is involved in the mechanism underlying the conditional lethality of the awdKpn mutation.

Amino Acid Sequence↗
PubMed1995

Hypermetaphase fluorescence in situ hybridization for quantitative monitoring of Philadelphia chromosome-positive cells in patients with chronic myelogenous leukemia during treatment.

Using Philadelphia chromosome-positive (Ph+) chronic myelogenous leukemia (CML) as a model, our aim has been to develop a molecular cytogenetic method of high resolution analysis for monitoring the frequency of cells with nonrandom chromosome rearrangements in the bone marrow of patients receiving treatment for hematologic malignancies. Long-term exposure (24 hours) of bone marrow cultures to colcemid (0.1 microgram/mL) maximized a high frequency of metaphase collection. Such preparations were subjected to fluorescence in situ hybridization (FISH) using a 5 Mb probe that overlapped the region of the translocation at chromosome 9q34. This detected the Ph translocation in the resultant large number of overly contracted chromosome spreads. The procedure was validated and verified by studying 70 double-blind marrow samples from patients in different stages of Ph+ CML and from patients with Ph- hematologic malignancies (controls). This hypermetaphase FISH (HMF) method clearly identified Ph+ metaphases and allowed the analysis of 500 hypermetaphases per sample in less than 1 hour after FISH. HMF (1) identified statistically significant differences between the frequencies of Ph+ cells in samples that differed by less than 4%; (2) resolved such differences among patient samples that were all judged 100% Ph+ by standard G-band cytogenetics (CG); (3) resulted in the reclassification of response status in 23% of the patients initially classified by CG; (4) recognized Ph+ cells in 16% of patients characterized as having a complete cytogenetic response and in one patient with an original diagnosis of Ph- CML; and in one patient with an original diagnosis of Ph- CML; and (5) was informative where insufficient metaphases were obtainable for analysis by CG. HMF appears to be uniquely suitable for monitoring the status of patients with CML receiving treatment. It should also be applicable for patients with any hematologic diseases where chromosomal alterations are known and appropriate FISH probes are available.

Azure Stains↗
PubMed1995

cDNA cloning and gene expression of lebocin, a novel member of antibacterial peptides from the silkworm, Bombyx mori.

A cDNA encoding lebocin, a novel member of insect antibacterial peptides, was isolated from the fat body cDNA library of Bombyx mori larvae immunized with Escherichia coli. The cDNA was 844 bp long and had an open reading frame (ORF) containing a probable signal peptide (16 amino acids), a putative prosegment (104 amino acids) and a mature peptide (32 amino acids) followed by 27 additional amino acids at its carboxyl-terminus. Northern blot analysis showed that lebocin gene expression was inducible by bacterial injection, occurred tissue-specifically in the fat bodies and continued at least for 48 h post-infection. These results suggest that lebocin has a unique precursor structure and shows typical gene expression pattern as insect antibacterial peptide.

Amino Acid Sequence↗