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Biomedical subjects

M Xia

Publications and source records attributed to M Xia.

At least 55 records · Page 3Linked to original sources
PubMed1996

Searching eye movement, smooth pursuit eye movement and schizophrenia.

OBJECTIVE: To detect whether the smooth pursuit eye movement (SPEM) and searching eye movement (SEM) could be considered as a biological marker of schizophrenia, and used as a tool in helping diagnosis of schizophrenia. METHODS: 88 schizophrenics, 77 patients with mood disorders, 32 with "neurosis", and 74 normal healthy controls were examined for SPEM and SEM individually. The authors verified the results in all the first-visit 150 outpatients in March 1993 by comparing the examination results with the clinical diagnoses after a 6-month follow-up. RESULTS: Significant differences were found in the number of eye fixation (NEF) and total eye scanning length (TESL) of SEM between schizophrenics and normal controls or patients with other disorders. Less NEF and shorter TESL could be helpful in differential diagnosis, and the agreement rate, Kappa coefficient was 0.62. No significant differences were found in SPEM in this investigation between non-medicated schizophrenics and normal controls. CONCLUSION: Searching eye movement (SEM) might be considered as a biological marker of schizophrenia and might be used as a supplementary tool in its diagnosis.

Adult↗
PubMed1995

Megakaryocyte growth and development factor and interleukin-3 induce patterns of protein-tyrosine phosphorylation that correlate with dominant differentiation over proliferation of mpl-transfected 32D cells.

Recently, the ligand for c-mpl, a member of the family of cytokine receptors, was cloned and found to be a physiologic regulator of platelet homeostasis. We report that megakaryocyte growth and development factor (MGDF, thrombopoietin [TPO], c-mpl ligand ) induces differentiation in a majority of mpl-transfected 32D cells, while interleukin (IL)-3 is exclusively mitogenic in this system. MGDF differentiation, as measured by decreased proliferation, changes in cellular morphology, increased adherence, and downregulation of very late antigen (VLA)-4, is dominant over IL-3 proliferation. MGDF induces tyrosine-phosphorylation of mpl, JAK2, SHC, SHPTP-1 (HCP, motheaten) and SHPTP-2 (Syp, PTP-1D) within 30 seconds of stimulation, as well as of vav and MAPK with slightly delayed kinetics. A fraction of mpl and JAK2 is preassociated, and the stoichiometry of this complex is unaltered by cytokine stimulation. After MGDF stimulation, we detect interactions among SHC, grb2, SHPTP-1, SHPTP-2, and the mpl/JAK2 complex. IL-3 induces phosphorylation of the above proteins with the exception of mpl and also causes weak JAK1 phosphorylation. Although similar in composition, the MGDF- and IL-3-induced complexes of signal transducers appear to be assembled in different configurations, especially with respect to SHPTP-2. Both MGDF and IL-3 induce tyrosine phosphorylation of STAT3 (APRF) and STAT5 (MGF), with MGDF favoring STAT3 while IL-3 predominantly causes STAT5 phosphorylation. In addition, some proteins become tyrosine-phosphorylated in response to MGDF only, suggesting that we may have detected differentiation-specific signal transducers. These include a number of high-molecular-weight proteins (140 to 200 kD) and one 28-kD protein that becomes tyrosine-phosphorylated only briefly.

Amino Acid Sequence↗
PubMed1995

Chronic exposure to retroviral vector encoded MGDF (mpl-ligand) induces lineage-specific growth and differentiation of megakaryocytes in mice.

Megakaryocyte growth and development factor (MGDF) has recently been identified as a ligand for the c-mpl receptor. Using retroviral-mediated gene transfer, MGDF has been overexpressed in mice to evaluate the systematic effects due to chronic exposure to this growth factor. MGDF overexpressing mice had more rapid platelet recovery than control mice after transplantation. Following this recovery, the platelet levels continued increasing to fourfold to eightfold above normal baseline levels and remained elevated (five-fold above control mice) in these animals, which are alive and well at more than 4 months posttransplantation. Increased megakaryocyte numbers were detected in a number of organs in these mice including bone marrow, spleen, liver, and lymph nodes. Prolonged overexpression of MGDF led to decreased marrow hematopoiesis, especially erythropoiesis, with a shift to extramedullary hematopoiesis in the spleen and liver. All the MGDF overexpressing mice analyzed to date developed myelofibrosis and osteosclerosis, possibly induced by megakaryocyte and platelet produced cytokines. No significant effect on other hematopoietic lineages was seen in the MGDF overexpressing mice, showing that the stimulatory effect of MGDF in vivo is restricted to the megakaryocyte lineage.

Animals↗
PubMed1995

Interleukin-3 signals through multiple isoforms of Stat5.

The interleukin (IL)-3 family of cytokines mediates its numerous effects on myeloid growth and maturation by binding a family of related receptors. It has been shown recently that IL-3 induces the activation of two distinct cytoplasmic signal transducing factors (STFs) that are likely to mediate the induction of immediate early genes. In immature myeloid cells, IL-3 activates STF-IL-3a, which comprises two tyrosine-phosphorylated DNA binding proteins of 77 and 80 kDa. In mature myeloid cells, IL-3 and granulocyte-macrophage colony-stimulating factor activate STF-IL-3b, which consists of a 94 and 96 kDa tyrosine-phosphorylated DNA binding protein. Peptide sequence data obtained from the purified 77 and 80 kDa proteins (p77 and p80) indicate that they are closely related but are encoded by distinct genes. Both peptide and nucleotide sequence data demonstrate that these two proteins are the murine homologs of ovine mammary gland factor (MGF)/Stat5. The peptide data also indicate that p77 and p80 are phosphorylated on tyrosine 699, a position analogous to the tyrosine that is phosphorylated in Stat1 and Stat2 in response to interferon. Additionally, antiserum raised against bacterially expressed p77/p80 recognizes the 94 and 96 kDa protein components of STF-IL-3b, suggesting that these may be additional isoforms of Stat5. These studies indicate that the IL-3 family of ligands is able to activate multiple isoforms of the signal transducing protein Stat5.

Amino Acid Sequence↗
PubMed1995

Cloning, sequencing and analysis of a gene encoding Escherichia coli proline dehydrogenase.

Using a genomic subtraction technique, we cloned a DNA sequence that is present in wild-type Escherichia coli strain CSH4 but is missing in a presumptive proline dehydrogenase deletion mutant RM2. Experimental evidence indicated that the cloned fragment codes for proline dehydrogenase (EC 1.5.99.8) since RM2 cells transformed with a plasmid containing this sequence was able to survive on minimal medium supplemented with proline as the sole nitrogen and carbon sources. The cloned DNA fragment has an open reading frame of 3942 bp and encodes a protein of 1313 amino acids with a calculated Mr of 143,808. The deduced amino acid sequence of the E. coli proline dehydrogenase has an 84.9% homology to the previously reported Salmonella typhimurium putA gene but it is 111 amino acids longer at the C-terminal than the latter.

Amino Acid Sequence↗
PubMed1995

Detection of two groups of 25.2 MDa Tet M plasmids by polymerase chain reaction of the downstream region.

Forty-four Neisseria gonorrhoeae, 12 N. meningitidis, four Kingella denitrificans and one Eikenella corrodens carrying 25.2 MDa Tet M plasmids were analysed using polymerase chain reaction (PCR) to the downstream region of the incomplete Tet M transposon. From each isolate, one of two different PCR fragments of approximately 700 or 1600 bp were obtained. The two different sized PCR fragments had > or = 90% DNA sequence identity with Ureaplasma urealyticum Tet M downstream sequences. The difference between the large PCR fragment and the smaller PCR fragment was a deletion of over 800 bp in the smaller fragment. Both PCR fragments were found in plasmids isolated from N. gonorrhoeae and K. denitrificans. The smaller PCR fragment was found in N. meningitidis plasmids and the larger PCR fragment was found in the E. corrodens plasmid.

Bacterial Proteins↗
PubMed1995

Pulsed-field gel electrophoresis for genomic analysis of Neisseria gonorrhoeae.

Pulsed-field gel electrophoresis (PFGE) is a technique for analyzing large DNA fragments. PFGE was compared to auxotyping and Por serovar (A/S) classification to determine its utility in the study of gonococcal infection, subtyping A/S classes, and clone identification. PFGE patterns were stable in vitro after 2 isolates were passaged 50 times, and those from sex partners were indistinguishable with both enzymes. Fourteen proline-requiring IA-6 isolates from Kenya produced 8 NheI and 7 XbaI patterns; these included 6 Tet M-carrying isolates, all producing the same NheI pattern. PFGE patterns of 14 arginine-, hypoxanthine-, and uracil-requiring IA-1,2 isolates, from the US Pacific Northwest and Hawaii in 1993, were less diverse with both enzymes. PFGE analysis represents a potentially useful addition to the current gonococcal classification system.

Contact Tracing↗
PubMed1994

Human vasoactive intestinal peptide1 receptors expressed by stable transfectants couple to two distinct signaling pathways.

Vasoactive intestinal peptide (VIP) is a potent neuropeptide mediator of central and peripheral nervous system function. A human VIP1 receptor (HVR) cDNA clone was previously obtained from HT29 intestinal epithelial cells and lung tissue. Stably-transfected human embryonic kidney 293 cells and chinese hamster ovary (CHO) cells expressing about 10(6) HVRs per cell that bind [125I]VIP with a Kd of 0.2-0.8 nM, and specifically recognized by anti-HVR antibodies, were established and characterized. VIP induced increases in intracellular cAMP levels ([cAMP]i) dose-dependently with an EC50 of 0.2 nM in 293 and CHO stable transfectants and concurrently evoked dose-dependent increases in intracellular calcium concentrations ([Ca2+]i), as determined by fluorescence-dye spectroscopy. Untransfected 293 and CHO cells showed minimal binding or intracellular effects of VIP; however, native VIP1 receptors of HT29 cells also increased [cAMP]i and [Ca2+]i in dose-dependent responses to VIP. Thus recombinant and native human VIP1 receptors both couple to two distinct signal transduction pathways within a single cell type.

Animals↗
PubMed1994

Cloning and expression of the EP3-subtype of human receptors for prostaglandin E2.

Prostaglandin E2 (PGE2) is a potent mediator in many human tissues that is recognized by three distinct subtypes of receptors (Rs), designated EP1, EP2 and EP3. A cDNA from a human kidney library encodes a 367 amino acid protein, of 85% homology with the mouse EP3R, that is expressed predominantly in kidney tissue. Human EP3Rs of transfectants bound [3H]-PGE2 with a mean Kd of 2.6 nM and native specificity. In contrast to the reliance of EP2Rs on increases in the intracellular concentration of cyclic AMP ([cAMP]i) for cellular signaling, EP3Rs transduce both decreases in [cAMP]i and modest increases in [Ca++]i.

Amino Acid Sequence↗
PubMed1994

Parthenogenesis in the genus Schistosoma: electrophoretic evidence for this reproduction system in S. japonicum and S. mansoni.

Mixed infections with Schistosoma japonicum and S. mansoni were carried out in mice. S. japonicum females paired with S. mansoni males developed normally and produced numerous viable eggs; very little sperm was found in the female genital tract. The eggs yielded many miracidia infective to Oncomelania hupensis, the host of S. japonicum. Cercariae arising from miracidia developed into male worms with an electrophoretic pattern of malate dehydrogenase (MDH) corresponding only to the maternal species S. japonicum. S. mansoni females paired with S. japonicum produced few viable eggs; sperm was found in the female genital tract. Miracidia hatched from some of these eggs were infective to Biomphalaria glabrata, the host of S. mansoni. Cercariae arising from miracidia developed into female worms with an electrophoretic pattern of MDH typical of the maternal species S. mansoni. It was concluded that S. japonicum females paired with S. japonicum males reproduce parthenogenetically. Parthenogenesis in schistosomes is discussed.

Animals↗
PubMed1994

Risk factors for HIV infection among drug users in Yunnan province, China: association with intravenous drug use and protective effect of boiling reusable needles and syringes.

OBJECTIVES: To characterize the prevalence and correlates of HIV infection among drug users in southwestern China. METHODS: Drug users in Longdao village, Yunnan Province underwent standardized interview and voluntary HIV serologic testing in a cross-sectional study. Analyses of potential risk and protective factors were stratified by method of drug use. RESULTS: Of 182 participants, 79 (43%) were HIV-1-seropositive. HIV seropositivity was found in 51 (80%) of the 64 intravenous drug users (IVDU) and 28 (24%) of the 118 who acknowledged use of drugs only by smoking [odds ratio (OR), 12.6; 95% confidence interval (CI), 5.7-28.5]. Among IVDU, reported sterilization of reusable injection equipment by boiling before intravenous drug use was associated with significant protection (adjusted OR, 0.16; 95% CI, 0.03-0.87). This protective association was also significant among the subset of IVDU who shared reusable injection equipment. CONCLUSIONS: HIV infection among drug users in Yunnan Province was highly correlated with intravenous drug use. The protective effect of sterilization of reusable injection equipment by boiling could be easily integrated into health education programs among IVDU in China and other rural Asian settings where reusable injection equipment is used.

Adult↗
PubMed1993

Cloning and expression of the EP2 subtype of human receptors for prostaglandin E2.

Prostaglandin E2 (PGE2) is a potent mediator in many human tissues, that is recognized by three distinct subtypes of receptors, designated EP1, EP2 and EP3. A cDNA from a human lung library encodes a 53 kDa protein of 88% homology with the mouse EP2 receptor. Human EP2 receptors in COS-7 cell transfectants bound [3H]-PGE2 with a mean Kd of 2.2 nM and native specificity, and transduced increases in the intra-cellular concentration of cyclic AMP, but not of Ca++. That most EP2 receptor mRNA is in lung, kidney, intestinal, glandular and immune tissues, is consistent with functional responses.

Amino Acid Sequence↗
PubMed1993

Insulin secretion, myo-inositol transport, and Na(+)-K(+)-ATPase in glucose-desensitized rat islets.

Glucose-induced insulin secretion is desensitized during long-term exposure of pancreatic islet beta-cells to elevated glucose levels. This study characterizes an in vitro model of glucose-induced desensitization in cultured isolated islets of the rat. Insulin secretion in desensitized islets cultured with 11 mM glucose for 4-7 days was progressively reduced compared with the normal freshly isolated (fresh) islets. When desensitized islets were returned to a basal concentration of glucose (5.5 mM) for up to 2 h, the glucose sensitivity of insulin secretion was restored to normal (recovered islets). Carbachol and L-arginine also reversed the effects of desensitization. However, basal insulin release was elevated in desensitized and recovered islets. Sodium-dependent myo-inositol uptake was reduced during desensitization by up to 49% within 4 days. myo-Inositol uptake was restored to normal in a time-dependent manner during recovery of islets at 5.5 mM glucose. The recovery of myo-inositol uptake paralleled that of insulin release. The apparent transport constant for myo-inositol uptake was significantly increased during desensitization, whereas the maximum uptake was not changed. myo-Inositol supplementation (35 or 250 microM) during islet culture did not alter myo-inositol uptake or insulin secretion in desensitized islets. Na(+)-K(+)-ATPase activity, but not 5'-nucleotidase activity, in desensitized islets was also inhibited by 65 and 47% when compared with fresh islet and recovered islet Na(+)-K(+)-ATPase activity, respectively. Thus, cultured islets represent an appropriate model to study biochemical parameters associated with the onset and reversibility of glucose desensitization of insulin secretion.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

A study and analysis of the deaths due to advanced Schistosoma japonicum infection in the Dongting Lake area of China.

This study collected records of 245 cases of death due to advanced schistosomiasis japonica in the eastern Dongting Lake area between 1985 and 1990. The mean survival of the patients was 5.16 years. The patients with ascitic type had a shorter expected life while the life span of splenomegalic type patient markedly improved after splenectomy. The HBsAg positive rate was 43.64%; the rate of those complicated with carcinoma of liver was 19.18%. The latter group had a HBV infection rate as high as 61.70%.

Adolescent↗
PubMed1990

Expression of a T cell receptor gamma-chain (V gamma 1.1J gamma 4C gamma 4) transgene in mice influences T cell receptor ontogeny and thymic architecture during development.

In this report, we have characterized T cell ontogeny in mice transgenic for the V gamma 1.1J gamma 4C gamma 4 (TcR gamma 4) TCR chain gene by analyzing the T cell surface phenotype and microarchitecture of the transgenic lymphoid organs during development. The first wave of V gamma 3J gamma 1C gamma 1 TCR+ thymocytes that appear in the thymus at day 14 of gestation were virtually absent in the TCR gamma 4 transgenic mice. However, comparable levels of total gamma delta+ thymocytes were present in the TCR gamma 4 transgenic mice, suggesting that these thymocytes expressed a transgene receptor. In addition, the appearance of significant numbers of TCR alpha beta+ T cells occurred earlier (day 17 of fetal development) in the transgenic thymus. After birth, thymuses from TCR gamma 4 transgenic mice were characterized by a consistent increase in the number of TCR gamma delta+ thymocytes and a transient increase (between 2 and 4 wk of age) in the absolute number of TCR+ thymocytes (2- to 4-fold) compared with thymuses from normal mice. Immunohistologic analysis of the thymus, spleen, and lymph nodes from 2-day and 3-wk-old transgenic mice showed significant differences to controls only in regions harboring mature, functional T cell subsets which may be the result of bidirectional signaling between lymphocyte subsets (influenced by transgene expression) and stromal elements. The results demonstrate that striking differences, leading to the earlier appearance of mature T cells, occurred in both the fetal and neonatal thymus and periphery of mice that expressed a TCR gamma 4 transgene. These findings are consistent with the hypothesis that expression of the TCR gamma 4 chain gene, early in ontogeny, has a positive influence on the development of the T cell compartment.

Animals↗