Search PubMed⌕ Search

Biomedical subjects

X Qian

Publications and source records attributed to X Qian.

At least 55 records · Page 3Linked to original sources
PubMed2000

Timing of CNS cell generation: a programmed sequence of neuron and glial cell production from isolated murine cortical stem cells.

Multipotent stem cells that generate both neurons and glia are widespread components of the early neuroepithelium. During CNS development, neurogenesis largely precedes gliogenesis: how is this timing achieved? Using clonal cell culture combined with long-term time-lapse video microscopy, we show that isolated stem cells from the embryonic mouse cerebral cortex exhibit a distinct order of cell-type production: neuroblasts first and glioblasts later. This is accompanied by changes in their capacity to make neurons versus glia and in their response to the mitogen EGF. Hence, multipotent stem cells alter their properties over time and undergo distinct phases of development that play a key role in scheduling production of diverse CNS cells.

Animals↗
PubMed2000

Expression of GC-C, a receptor-guanylate cyclase, and its endogenous ligands uroguanylin and guanylin along the rostrocaudal axis of the intestine.

Members of the receptor-guanylate cyclase (rGC) family possess an intracellular catalytic domain that is regulated by an extracellular receptor domain. GC-C, an intestinally expressed rGC, was initially cloned by homology as an orphan receptor. The search for its ligands has yielded three candidates: STa (a bacterial toxin that causes traveler's diarrhea) and the endogenous peptides uroguanylin and guanylin. Here, by performing Northern and Western blots, and by measuring [125I]STa binding and STa-dependent elevation of cGMP levels, we investigate whether the distribution of GC-C matches that of its endogenous ligands in the rat intestine. We establish that 1) uroguanylin is essentially restricted to small bowel; 2) guanylin is very low in proximal small bowel, increasing to prominent levels in distal small bowel and throughout colon; 3) GC-C messenger RNA and STa-binding sites are uniformly expressed throughout the intestine; and 4) GC-C-mediated cGMP synthesis peaks at the proximal and distal extremes of the intestine (duodenum and colon), but is nearly absent in the middle (ileum). These observations suggest that GC-C's activity may be posttranslationally regulated, demonstrate that the distribution of GC-C is appropriate to mediate the actions of both uroguanylin and guanylin, and help to refine current hypotheses about the physiological role(s) of these peptides.

1-Methyl-3-isobutylxanthine↗
PubMed2000

Aberrant DNA methylation of cyclin D2 and p27 genes in rodent pituitary tumor cell lines correlates with specific gene expression.

We previously reported that increased DNA methylation was an important mechanism of silencing the p27 gene in some pituitary tumor cell lines [1]. DNA methylation correlated inversely with p27 gene expression. The p27 and cyclin D2 genes are located in the same region of mouse chromosome 6, rat chromosome 4, and human chromosome 12p13. Because both genes are located in the same gene cluster, we investigated whether methylation was a principal mechanism regulating cyclin D2 as well as p27 expression in rodent pituitary cell lines. Bisulfite genomic sequencing showed that the normally unmethylated cytosines of the p27 gene in normal pituitary (NP) were extensively methylated in GH3 and GHRH-CL1 cells, but not in AtT 20, alphaT3-1 and LbetaT2 cells; but cyclin D2 was extensively inactivated in various pituitary tumor cell lines by increased DNA methylation. These abnormalities of methylation in p27 and cyclin D2 genes occurred with different frequencies in five pituitary tumor cell lines with 100% (5/5) methylation of the cyclin D2 gene and 40% (2/5) methylation of the p27 gene. Treatment with the methyl transferase inhibitor 5'-aza-2'-deoxycytidine (AZAdC) increased expression of cyclin D2 and p27 in GH3 and GHRH-CL1 pituitary tumor cells. There was a correlation between hypermethylation and gene expression. GH3 tumors implanted into Wistar-Furth rats in vivo did not change the methylation status of the p27 and cyclin D2 genes. These data indicate a coordinately reduced expression of these two linked genes in most rodent pituitary tumor cell lines and suggest that methylation of cyclin D2 and p27 might occur in a "hot spot" in this gene-rich cluster.

Journal Article↗
PubMed2000

Antinociceptive activity of [beta-methyl-2', 6'-dimethyltyrosine(1)]-substituted cyclic [D-Pen(2), D-Pen(5)]Enkephalin and [D-Ala(2),Asp(4)]Deltorphin analogs.

Research in our laboratories involves the development of selective opioid agonists and antagonists as: 1) pharmacological tools to elucidate the mechanisms of opioid antinociception, and 2) potential analgesics that possess therapeutic advantages over currently available drugs. We hypothesized that the selectivity of peptide agonists toward the opioid receptor types and subtypes is topographically dependent. The current results assess the antinociceptive activity and opioid receptor selectivity of a series of beta-methyl-2',6'-dimethyltyrosine (TMT)-substituted cyclic [D-Pen(2),D-Pen(5)]enkephalin (DPDPE) and [D-Ala(2), Asp(4)]deltorphin (DELT I) analogs. Compounds were injected via the intracerebroventricular route into male ICR mice, and antinociception was assessed using the 55 degrees C warm water tail-flick test. Antinociceptive A(50) values ranged from 0.35 to 17 nmol for the DELT I analogs and from 7.05 to >100 nmol for the DPDPE analogs. To test for receptor selectivity, mice were treated with selective mu- and delta-opioid antagonists. In general, mu [beta-funaltrexamine (beta-FNA)]- and delta(1) ([D-Ala(2),Leu(5), Cys(6)] enkephalin)-antagonists blocked the antinociceptive actions of [TMT(1)]DPDPE analogs, whereas the antinociceptive actions of [TMT(1)]DELT I analogs were more sensitive to antagonism by the delta(2)-selective antagonist [Cys(4)]deltorphin and the mu-antagonist beta-FNA. The antinociceptive actions of the [(2R, 3S)-TMT(1)]DELT I analog was suppressed by both [D-Ala(2),Leu(5), Cys(6)]enkephalin and beta-FNA. These results are in contrast to those found with the parent molecules DPDPE (primarily a delta(1) agonist) and DELT I (a mixed delta(1)/delta(2) agonist). These results demonstrate that topographical modification in position 1 of the DPDPE and DELT I peptides affects antinociceptive potency and opioid receptor selectivity.

Analgesics, Opioid↗
PubMed2000

[Bone marrow transplantation for beta-thalassemia major].

OBJECTIVE: To examine the feasibility of bone marrow hematopoietic stem cell transplantation for thalassemia major. METHODS: Bone marrow transplantation was performed on a 4-year-old patient with beta-thalassemia major, whose gene mutation was CD41-42/654. The donor was his brother. In the 850ml bone marrow, the nucleated cells were 5.6x10(8)/kg, CD(+)(34) cells 7.8 x 10(6)/kg, and colony-forming-unit-granulocyte-macrophages(CFU-GM) 5.7x10(5)/kg. HLA was one site mismatched, while RBC type matched. Pre-transplant conditions included Busulfan 16mg/kg, cyclophosphamide 200mg/kg and lymphoglobuline 88mg/kg. Cyclosporine and methotrexate were used for prevention of graft-versus-host disease(GVHD). RESULTS: After transplantation, the patient had grade II acute GVHD and cytomegalovirus(CMV) interstitial pneumonia; he was cured. White blood cells(WBC) and neutrophil granulocytes recovered to 1.1 x 10(9)/L and 0.4 x10(9)/L respectively on day 14 post transplantation. WBC was 4.5 x 10(9)/L on day 18, and descended for a time during treating interstitial pneumonia with Ganciclovir. Platelet(Plt) exceeded 50 x 10(9)/L on day 86 and recovered to normal 5 mothers and a half post transplantation. Hb reached 106g/L on day 128. The patient received the last blood transfusion on day 103. Before transplantation, the patient had to receive 200ml blood infusion per month for maintaining Hb 60-90g/L; after transplantation, his Hb kept up >110g/L for 6 months without blood transfusion. The gene type had changed to donor's CD41-42/N heterozygen. CONCLUSION: This is the first report on successful transplantation of bone marrow stem cell for thalassemia major in China, suggesting a new way to treat the disease and to expand the use of BMT. For treatment of CMV interstitial pneumonia post-transplantation, Ganciclovir should be dose enough and be used for at least 2 months.

Child, Preschool↗
PubMed2000

Cloning and sequence analysis of a Phytophthora cinnamomi gene which encodes for cinnamomin, a toxin with implications in root rot of cranberry.

We used a polymerase chain reaction (PCR) based cloning strategy to isolate cinnamomin genes from Phytophthora cinnamomi 8601, a pathogen responsible for cranberry root rot. Complete DNA sequence analysis of nine recombinant clones revealed two different classes of genes, each class consisting of genes with identical DNA sequences. Both classes of genes (Cin-1 and Cin-2) contained an open reading frame encoding a protein of 122 amino acid residues. The encoded proteins, named cinnamomin-1 and cinnamomin-2 (Cin-1 and Cin-2), were highly homologous to other proteins of the elicitin family and contained a 19 amino acid residue long signal peptide sequence. Both Cin-1 and Cin-2 proteins showed higher degree of sequence homology to the alpha-elicitins than beta-elicitins; moreover, a Val residue was found at position 13 of the putative mature Cin-1 and Cin-2 proteins. Because alpha-elicitins and beta-elicitins are known to contain a Val and a Lys residue, respectively, at this position, we concluded that both Cin-1 and Cin-2 genes from P. cinnamomi 8601 encode for alpha cinnamomins, Cin-1 and Cin-2.

Algal Proteins↗
PubMed2000

Cryptorchidism induces mouse testicular germ cell apoptosis and changes in bcl-2 and bax protein expression.

Up to half of the germ cells die during their development. The mechanism involved in their death is still unclear. We investigated the possibility that the testicular germ cell loss may be due to a change in the testicular temperature and apoptosis through the interplay of bcl-2 and bax proteins. To investigate the effect of temperature on apoptosis and the role of bcl-2 and bax proteins in apoptosis in adult mouse testis, we used the experimental unilateral cryptorchidism model. We found that the weight of the affected testis decreases in 6 to 15 days after operation (p < 0.05). H&E staining showed vacuolization of the seminiferous epithelium and the appearance of multinucleated giant cells with loss of germ cells. The terminal deoxynucleotidyl transferase-mediated dUTP nick-end-labeling method (TUNEL) showed positive staining germ cells scattered in normal testicles that increased significantly 6 to 15 days after experimental cryptorchidism (p < 0.05). Positive cells were mainly primary spermatocytes and round spermatids. DNA ladder was seen in 1.5% agarose gel electrophoresis in 6 to 15 days-operated testicles. Biotin-avidin DCS system indirect immunofluorescence technique indicated that the bcl-2 protein was chiefly distributed in the cytoplasm of germ cells in normal testicles, whereas the bax protein was chiefly expressed in the cytoplasm of germ cells in 6 to 15 days-operated testicles. Western blot analysis showed that the bcl-2 protein down-regulated and the bax protein up-regulated apoptosis. Our data indicated that cryptorchidism-induced testicular cell degeneration was mediated by apoptosis probably as the result of increased temperature in the testicle; bcl-2 and bax proteins played important roles in male germ cell apoptosis.

Animals↗
PubMed2000

[Biological characteristics and occurrence regularity of Phassus excrescens Bulter].

The biological characterisitics and occurrence regularity of Phassus excrescens were studied from 1997 to 2000 in the eastern part of Heilongjiang Province and Jilin Province. In this area, most of its individuals took two years to finish one generation, and over-wintered two times with eggs and larvae, respectively. At the end of June or the first ten days of July, larvae transferred to damage Fraxinus mandshurica. Feeding with artificial diet indoor, the larvae finished 6 instars before pupation. In artificial Manchurican ash forest, the larva mainly damaged the truck basal(below 20 cm) or truck of 2 to 20 years old Fraxinus mandshurica. The occurrence amount of this species was closely related to the forest age and the stand structure. Usually, pure artificial Fraxinus mandshurica stands and Fraxinus mandshurica-Pinus koraiensis mixed stands were damaged seriously, while Fraxinus mandshurica-Larix mixed forests were damaged lightly.

Animals↗
PubMed2000

[Effect of adenovirus type 5 E1A gene on proliferation and metastasis of human lung adenocarcinoma cells].

OBJECTIVE: To investigate the effects of E1A gene on proliferation and metastasis of human lung adenocarcinoma cells. METHODS: A mammalian E1A-expressing recombinant constructed in our laboratory, named pcDNA3-E1A, was introduced into human lung adenocarcinoma cell line(Anip 973) by lipofectamine. The cells resistant to G418 were selected. The characteristics of the E1A-expressing Anip 973(Anip 973-E1A) cells were studied in vitro and in vivo, including cell growth rate and doubling-time, colony-forming efficiency on soft agarose, tumorigenicity and metastasis. RESULTS: The growth rate of E1A-Anip 973 cells was diminished and their colony-forming efficiency was inhibited significantly. The tumorigenicity in nude mice of the E1A-expressing Anip 973 was markedly suppressed. CONCLUSION: E1A suppresses the malignant phenotype of human lung adenocarcinoma cell line. This study provides experimental data for gene therapy of lung cancer with E1A.

Adenocarcinoma↗
PubMed2000

[127 cases of pulmonary fungal infection].

OBJECTIVE: To find out the clinical features, therapeutic outcome, prognosis and the major predisposing diseases of pulmonary fungal infection(PFI). METHOD: 127 cases with PFI were retrospectively analyzed. RESULTS: Various predisposing diseases were found in 95% of total cases, among them, COPD, systemic lupus erythromatus(SLE), leukemia and chronic renal disease were main predisposing diseases. Primary pulmonary fungal infection was rare. All the clinical manifestations of PFI were not specific, reontgenographic features showed mainly bronchitis type(61%). Monilia (Candida) was ranked the first pathogen (79.5%). The mortality of PIF was high. Chronic renal and hematological diseases might be the risk factors for mortality (RR, relative rate, 5.14). CONCLUSIONS: PFI is an important cause of the secondary infection in many diseases. The clinical features of PFI is non-specific and the morbidity is rising. Clinicians should pay more attention to it.

Bronchitis↗
PubMed2000

[Multiple types of chemokines expressed in mouse thymic stromal cell lines].

OBJECTIVE: To investigate semi-quantitative mRNA expression of SDF-1 alpha, IP-10, KC, MCP-1, and RANTES in thymic stromal cell lines of MTEC1, MTDC, D2SC, MTECB, TEC 1C8, TNC as well as in the primary thymic stromal cell cultures. The chemotactic activities of recombinant SDF-1 alpha, IP-10, MCP-1, and RANTES to mouse thymocytes were detected. METHODS: Using beta-actin as internal control, the mRNA of the chemokines listed above were amplified for 30 cycles with RT-PCR. The amplified products were observed by agarose electrophoresis, and each band was analyzed with integrated optical density. With the method of Boyden chamber assay, the chemotactic activities of recombinant SDF-1 alpha, IP-10, MCP-1, and RANTES were detected to thymocytes, and the chemotactic indices were calculated. RESULTS: The expression intensity of SDF-1 alpha, IP-10, KC, MCP-1, and RANTES varied from each other in the stromal cell lines detected. The PCR products of SDF-1 alpha and MCP-1 were not seen in D2SC or TEC 1C8, nor was the band of KC observed in TEC 1C8 either. The chemotactic indices of recombinant SDF-1 alpha, IP-10, MCP-1, and RANTES to thymocytes were 3.7, 4.5, 6.2, and 2.6, respectively. CONCLUSIONS: Different thymic stromal cell lines could express different types of chemokines with different expression intensities. To thymocytes, recombinant SDF-1 alpha, MCP-1, and IP-10 showed strong chemotactic activities, while the chemotactic activity of RANTES was very weak.

Animals↗
PubMed2000

[Change of angiotensin system activity and the effects of corticosteroid on it in asthmatic guinea pigs].

OBJECTIVE: To investigate the role of angiotensin system(ATs) and effect of corticosteroid on ATs activity at the onset of asthma. METHODS: After establishing asthmatic model of guinea pig by intraperitoneal injection with ovalbumin to sensitize and inhalation with the same sensitizer 3 weeks later to induce asthma attack, the levels of angiotensin(AT) I and AT II and the activity of angiotensin converting enzyme(ACE) were measured respectively in extractive fluid of chopped lung tissue, bronchial alveolar lavage fluid (BALF) and plasma (ACE activity in serum) in three groups of experimental guinea pigs including asthmatic group, control group and corticosteroid group. RESULTS: In the chopped lung tissue and BALF, the AT I, AT II levels and the ACE activity in the asthmatic group were significantly higher than that in the control group(P < 0.01), however, they did not differ significantly each other in plasma in three groups(P > 0.05). In corticosteroid group, the levels of AT I, AT II and ACE activity were significantly decreased in the BALF compared with that in the asthmatic group(P < 0.01). CONCLUSION: The results suggest that the lung tissue may have a local angiotensin system that may be activated and play a role in asthma attack, and the inhibition of ATs activity may be one of the mechanisms in the effects of inhaled corticosteroid on prevention and control of asthma.

Adrenal Cortex Hormones↗
PubMed1999

Direct analysis of the products of sequential cleavages of peptides and proteins affinity-bound to immobilized metal ion beads by matrix-assisted laser desorption/ionization mass spectrometry.

Consecutive enzymatic reactions on analytes affinity-bound to immobilized metal ion beads with subsequent direct analysis of the products by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry have been used for detecting protein synthesis errors occuring at the N-terminus. The usefulness of this method was demonstrated by analyzing two commercially available recombinant HIV proteins with affinity tags at the N-terminus, and histatin-5, a peptide with multiple histidine residues. The high specificity, sensitivity, and speed of analysis make this method especially useful in obtaining N-terminal sequencing information of histidine-tagged recombinant proteins.

Amino Acid Sequence↗
PubMed1999

Induction of the Tat-binding protein 1 gene accompanies the disabling of oncogenic erbB receptor tyrosine kinases.

Conversion of a malignant phenotype into a more normal one can be accomplished either by down-regulation of erbB family surface receptors or by creating inactive erbB heterodimers on the cell surface. In this report, we report the identification and cloning of differentially expressed genes from antibody-treated vs. untreated fibroblasts transformed by oncogenic p185(neu). We repeatedly isolated a 325-bp cDNA fragment that, as determined by Northern analysis, was expressed at higher levels in anti-p185(neu)-treated tumor cells but not in cells expressing internalization defective p185(neu) receptors. This cDNA fragment was identical in amino acid sequence to the recently cloned mouse Tat binding protein-1 (mTBP1), which has 98.4% homology to the HIV tat-binding protein-1 (TBP1). TBP1 mRNA levels were found to be elevated on inhibition of the oncogenic phenotype of transformed cells expressing erbB family receptors. TBP1 overexpression diminished cell proliferation, reduced the ability of the parental cells to form colonies in vitro, and almost completely inhibited transforming efficiency in athymic mice when stably expressed in human tumor cells containing erbB family receptors. Collectively, these results suggest that the attenuation of erbB receptor signaling seems to be associated with activation/induction or recovery of a functional tumor suppressor-like gene, TBP1. Disabling erbB tyrosine kinases by antibodies or by trans-inhibition represents an initial step in triggering a TBP1 pathway.

3T3 Cells↗