Biomedical subjects

L Geng

Publications and source records attributed to L Geng.

At least 55 records · Page 3Linked to original sources

PubMed1998

The expression in vivo of a second isoform of pT alpha: implications for the mechanism of pT alpha action.

A second isoform of pT alpha, "pT alpha(b)," is derived from the pT alpha locus by tissue-specific, alternative splicing. pT alpha(b) is coexpressed in the thymus with the previously characterized form of pT alpha (which we term pT alpha(a)) and is also expressed in peripheral cells without pT alpha(a). While pT alpha(a) acts to retain most TCR beta-chains intracellularly, pT alpha(b) permits higher levels of cell surface TCR beta expression and facilitates signaling from a CD3-TCR beta complex.

Alternative Splicing↗

PubMed1998

Search for human T-lymphotropic virus type I carriers among northeastern Chinese.

Human T-lymphotropic virus type I (HTLV-I) is thought to be the causative agent of adult T-cell leukemia/ lymphoma (ATL). This virus infection is endemic in southwestern Japan, parts of Africa and the Caribbean Islands. We examined sera of 1645 subjects of Liaoning province, northeastern China to detect HTLV-I carriers in an effort to reveal the migratory route taken by the early Japanese (Jomon people). As a result, all sera were found to be negative as tested by particle-agglutination (PA), immunofluorescence (IF), enzyme-linked immunoabsorbent (ELISA) and Western blotting methods. This suggests that the Jomon people, who are thought to have brought HTLV-I to the Japan archipelago tens of thousands of years ago, did not come from northeast China.

Adult↗

PubMed1998

Fibronectin is chemotactic for CT 26 colon carcinoma cells: sub-lines selected for increased chemotaxis to fibronectin display decreased tumorigenicity and lung colonization.

CT 26 murine colon carcinoma cells demonstrated directional migration (chemotaxis) in response to fibronectin (FN). Sub-lines were derived by positive and negative selection to FN across Transwell filters of 8 microm pore size. The FL6 sub-line (positively selected) demonstrated a significantly increased chemotactic response (P<0.01) to FN compared with parental CT 26 cells, while the FU7 sub-line (negatively selected) showed a reduced chemotactic response to FN (P<0.01). Comparable levels of alpha4, alpha5, alphav and beta1 integrins, which mediate FN attachment, were expressed on positively and negatively selected sub-lines and parental CT 26 cells. Activation of integrins with Mn2+ suggested that the integrins expressed on FL6 cells were in the fully activated state; in contrast FU7 cells displayed only partially activated integrins. Cell attachment and integrin activation status of the sub-lines correlated with their chemotactic response to FN. In vivo FL6 cells showed a significantly reduced tumour growth rate s.c. and a reduction in the number of lung colonies formed following i.v. injection compared with parental CT 26 and FU7 cells. In contrast FU7 cells displayed a significant increase in s.c. tumour growth and the number of lung colonies when compared with the parental line and FL6 sub-line. The results indicate that interaction between integrin receptors expressed on cancer cells and FN plays a central role in the chemotactic response of CT 26 colon carcinoma cells, and that in this model cells selected for chemotaxis to FN displayed a reduced malignant potential.

Adenocarcinoma↗

PubMed1998

Major histocompatibility complex class II alleles in an Uygur population in the Silk Route of Northwest China.

HLA class II (DRB1, DQA1, DQB1 and DPB1) genotyping was performed in 57 unrelated Uygur individuals inhabiting the northwestern China area by the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method. Among 98 DRB1 alleles tested, 23 alleles were detected, and DRB1*0701 (16.7%) and DRB1*0301 (14.0%) were the most and the second most common alleles, respectively. In 8 DQA1 alleles detected, DQA1*05 (26.3%), DQA1*03 (21.9%) and DQA1*0201 (21.1%) were very frequent. Of 21 DQB1 alleles tested, 13 were observed. Among them, DQB1*02 was highly predominant with the gene frequency of 32.5%. Of 46 DPB1 alleles tested, 15 were detected, among which DPB1*0401 (31.6%) was the most frequent. Two haplotypes predominate clearly; DRB1*0701-DQA1*0201-DQB1*02 (15.5%) and DRB1*0301-DQA1*05-DQB1*02 (12.6%). The dendrogram constructed by the neighbour-joining (NJ) method based on the allele frequencies of the DRB1, DQA1, DQB1 and DPB1 genes of 13 representative populations all over the world suggested that Uygur belonged to the Asian group and lay at the closest genetic distance to a Kazak population inhabiting the same area.

Alleles↗

PubMed1998

[A molecular and epidemiology study in patients with ventilator-associated pneumonia].

OBJECTIVE: To evaluate causative agents in patients with ventilator-associated (VA) pneumonia epidemiologically, then to provide useful suggestion for diagnosis and treatment of VA pneumonia. METHOD: Prospectively, a protected specimens brush was used to obtain the secretion of lower respiratory tract of 65 patients, who had been receiving mechanical ventilation or tracheostomy for more than 72 hours. At the same time, other samples were collected from the relevant places, including pharyngeal and gastric juice of patients as well as other persons, ward's air. The secretion obtained were cultured with a quantitative method. Then all bacteria isolated were studied with the analysis of pattern of plasmids and chromosomal restriction endonuclease. RESULT: It was showed that the route of infection of the Gram-negative bacilli in VA pneumonia (19 cases) was intrinsic, a retrograde colonization from patient's stomach, that was the pattern of clonization from stomach to pharynx, then into lower respiratory tract, and the Gram-positive staphylococcus spread mainly through the ward's air, then directly into lower respiratory tract, or extrinsic (20 cases). CONCLUSION: The Gram-positive staphylococcus is also major disease-producing germs in VA pneumonia, and the infection routes of G+ and G- bacteria might be different.

Adult↗

PubMed1998

[Effect of rotundine on gastric acid and pepsin activity in rats].

A test was made on the effect of rotundine on the secretion of gastric acid and pepsin activity in rats. Compared with the control group, rotundine(> or = 17.1 mg/kg) inhibited gastric acid and decreased secretion of gastric juice(P < 0.01), but had no influence on pepsin activity. There was a negative relationship between total acidity and pH of gastric juice (r = -0.9818).

Animals↗

PubMed1998

Transfection of a vector expressing wild-type p53 into cells of two human glioma cell lines enhances radiation toxicity.

Replication-deficient adenovirus (Adv5)-based vectors containing either wild-type p53 or the beta-gal marker gene were introduced into cells of the T98G (p53 mutant) and U87MG (p53 wild-type) human glioma cell lines. The wild-type p53 gene was successfully expressed in each cell line as shown by flow cytometry and Western blotting. The presence of the p53-expressing vector was toxic in both cell lines compared to control cells or to those containing the beta-gal vector. At levels of Adv5p53 vector that produced detectable toxicity, the effect of irradiation was enhanced, producing a twofold increase in cell killing. In the T98G cells, the presence of the p53 vector resulted in an increase in the number of cells undergoing apoptosis after irradiation, whereas a smaller and only additive response was observed in the U87MG cells. Conversely, an increase in micronucleus formation, indicating corrupt mitotic activity, was observed in irradiated Adv5p53-positive U87MG cells but not in T98G cells. These data suggest that p53-expressing vectors effectively enhance radiation lethality in these human glioma cell lines, but that the mechanism of action cannot be simply related to activation of the p53-dependent pathway to apoptosis.

Apoptosis↗

PubMed1997

Characterization of colorectal-cancer-related cDNA clones obtained by subtractive hybridization screening.

In an attempt to seek out new factors that are related to colorectal carcinogenesis at the molecular level, subtractive hybridization between cDNA of normal mucosal tissues and mRNA of colorectal carcinoma tissues was performed. Subsequent screenings of the cDNA libraries, constructed from normal mucosal tissues, using the "subtractive probes" generated a total of 46 clones that were expressed in normal mucosa but were either expressed at a significantly reduced level or not expressed at all in cancer tissues. Partial nucleotide sequences of all of these cDNA clones were determined, and sequence homology analyses were performed with the Genbank database. Of the 46 cDNA samples, 44 contained substantial sequence homologies with 32 immunoglobulin gene fragments, a helix-loop-helix basic phosphoprotein gene, an acidic ribosomal phosphoprotein P2 gene, a BLR1 gene for Burkitt's lymphoma receptor 1 gene, D5S419 DNA segment containing (C-A) repeats, a glucokinase (GCK) gene, a Na+, K+-ATPase alpha-subunit gene, a histocompatibility system HLA-DR heavy-chain gene, a dystrophic gene, a mucin (MUC2) gene, a mu-glutathione S-transferase gene, a Menkes disease protein gene, and a 40-kDa keratin intermediate filament precursor gene. The remaining two cDNA clones (now registered under GenBank accession numbers U17714 and U20428) showed few (less than 60%) sequence homologies with any known sequences in the GenBank database and, therefore, may represent novel genes whose expression was down-regulated in human colorectal carcinomas. The possible clinical significance of these findings and the involvement of these two genes in the carcinogenesis of colorectal as well as other cancers are being investigated.

Base Sequence↗

PubMed1997

Gamma delta cells regulate autoimmunity.

Gamma delta cells are attractive candidates for mediators of autoimmune disease. They can expand in germ-free mice, probably through recognition of autoantigens, and gamma delta-cell-deficient mice, unlike mice deficient in alpha beta T cells or B cells, show no severe defects in the immune response to foreign antigen challenge. A capacity of gamma delta cells to effect or regulate tissue damage is also plausible, given their ready localization to tissues, and their myriad of effector functions. Added to this, attempts to reconstruct the physiological course of autoimmune diseases with only autoreactive alpha beta T cells seem invariably to fall short for lack of other unidentified players. Gamma delta cells and their putative ligands have been linked to autoimmune conditions, and recent experiments confirm that gamma delta cells play a significant role in autoimmune disease in vivo.

Animals↗

PubMed1997

Perinatal lethality with kidney and pancreas defects in mice with a targetted Pkd1 mutation.

PKD1 is the most common site for mutations in human autosomal dominant polycystic kidney disease (ADPKD). ADPKD is characterized by progressive replacement of kidney tissue by epithelial cysts and eventual renal failure. Hepatic and pancreatic cysts are also common. The PKD1 protein, polycystin, is a cell-surface protein of unknown function that is widely expressed in epithelia and in vascular smooth muscle and myocardium. None of the genetic forms of murine polycystic disease map to the murine Pkd1 locus. We introduced into mice by homologous recombination a Pkd1 truncation mutation, Pkd1-, that mimics a mutation found in ADPKD. Pkd1- heterozygotes have no discernible phenotype, whereas homozygotes die during the perinatal period with massively enlarged cystic kidneys, pancreatic ductal cysts and pulmonary hypoplasia. Renal cyst formation begins at embryonic day 15.5 (E15.5) in proximal tubules and progresses rapidly to replace the entire renal parenchyma. The timing of cyst formation indicates that full-length polycystin is required for normal morphogenesis during elongation and maturation of tubular structures in the kidney and pancreas.

Abnormalities, Multiple↗

PubMed1997

Major histocompatibility complex class II alleles in Kazak and Han populations in the Silk Route of northwestern China.

Genetic polymorphism of the HLA class II loci including the DRB1, DQA1, DQB1 and DPB1 genes was investigated by the polymerase chain reaction-restriction fragment-length polymorphism (PCR-RFLP) method in a Kazak population inhabiting the most northwestern part of China, Urümqi in the Xinjiang Uygur Zizhiqu as well as in a Han population in the same area. Forty-two Kazak and 59 Han unrelated volunteers were enrolled in this study. Among 51 DRB1 alleles tested, 29 alleles were detected, and DRB1*0301 (13.1%) and DRB1*07 (10.7%) in Kazak and DRB1*0901 (11.9%), DRB1*1501 (11.0%) and DRB1*07 (11.0%) in northwestern Han were highly predominant. In 8 DQA1 alleles detected, DQA1*0501 (29.8%) and DQA1*0301 (23.8%) in Kazak, and DQA1*0301 (28.8%) and DQA1*0102 (19.5%) in northwestern Han were the most and the second most common alleles, respectively. Of 18 DQB1 alleles tested, 14 were observed, among which DQB1*0201 and DQB1*0301 were very frequent both in Kazak (23.8% and 21.4%, respectively) and northwestern Han (18.6% and 16.9%, respectively) populations. Of 37 DPB1 alleles tested, 14 were detected. Among them, the frequencies of DPB1*0401 (21.4%), DPB1*0501 (20.2%), DPB1*0402 (19.0%) and DPB1*0201 (16.7%) in Kazak, and those of DPB1*0501 (38.1%) and DPB1*0201 (16.1%) in northwestern Han were highly increased. Several three-locus haplotypes were recognized to predominate significantly, namely DRB1*0301-DQA1*0501-DQB1*0201 (13.1%) and DRB1*0701-DQA1*0201-DQB1*0201 (8.3%) in Kazak; and DRB1*0901-DQA1*0301-DQB1*0303 (11.9%) and DRB1*0701-DQA1*0201-DQB1*0201 (10.2%) in northwestern Han. The dendrogram constructed by the neighbor-joining (NJ) method based on the allele frequencies of the DRB1, DQA1, DQB1 and DPB1 genes of 12 representative populations all over the world including northern Han, southern Han, Manchu and Japanese suggested that Kazak and northwestern Han were the closest to each other, but Kazak was a little farther from the Asian ethnic groups than northwestern Han.

Alleles↗

PubMed1997

Distribution and developmentally regulated expression of murine polycystin.

PKD1, the gene that is mutated in approximately 85% of autosomal dominant polycystic kidney disease (ADPKD) cases in humans, has recently been identified (Eur. PKD Consortium. Cell 77: 881-894, 1994; also, erratum in Cell 78: 1994). The longest open-reading frame of PKD1 encodes polycystin, a novel approximately 460-kDa protein that contains a series of NH2-terminal adhesive domains (J. Hughes, C. J. Ward, B. Peral, R. Aspinwall, K. Clark, J. San Millan, V. Gamble, and P. C. Harris. Nat. Genet. 10: 151-160, 1995; and Int. PKD Consortium. Cell 81: 289-298, 1995) and several putative transmembrane segments. To extend studies of polycystin to an experimentally accessible animal, we have isolated a cDNA clone encoding the 3' end of Pkd1, the mouse homologue of PKD1, and raised a specific antibody to recombinant murine polycystin. This antibody was used to determine the subcellular localization and tissue distribution of the protein by Western analysis and immunocytochemistry. In the mouse, polycystin is an approximately 400-kDa molecule that is predominantly found in membrane fractions of tissue and cell extracts. It is expressed in many tissues including kidney, liver, pancreas, heart, intestine, lung, and brain. Renal expression, which is confined to tubular epithelia, is highest in late fetal and early neonatal life and drops 20-fold by the third postnatal week, maintaining this level into adulthood. Thus the temporal profile of polycystin expression coincides with kidney tubule differentiation and maturation.

Aging↗

PubMed1997

[Assignment of a novel colorectal cancer-associated gene HSU17714 gene to human chromosome band 22q13 by in situ hybridization].

OBJECTIVE: To identify the chromosomal localization of novel colorectal cancer-related gene HSU17714. METHODS: Enhanced fluorescence in situ hybridization technique was applied with tyramine as the enhancer. RESULTS: 80%(128/160) interphase and 60% (104/174) metaphase cells showed obvious hybridization signals of HSU17714. 85%(40/47) metaphase cells showed hybridization signals at 22q13 in the fluorescence R-banding assay. CONCLUSION: HSU17714 is assigned to human chromosome 22q13.

Chromosomes, Human, Pair 22↗

PubMed1997

[The discovery of pituitary adenylate cyclase activating polypeptide (PACAP) and its research progress].

Pituitary adenylate cyclase activating polypeptide(PACAP) is a new bioactive polypeptide originally isolated from ovine hypothalamus. It is widely distributed in the central and peripheral nervous systems, and some non-nervous tissues as well. Mediated by PACAP receptors, it stimulates adenylate cyclase and subsequently increases the cAMP level in target cells. PACAP is not only a new type of hypophysiotropic hormone, but also functions as a neurotransmitter and neuromodulator. In addition, it plays a role in paracrine and autocrine regulation of certain types of cells.

Amino Acid Sequence↗

PubMed1997

Screening and identification of down-regulated genes in colorectal carcinoma by subtractive hybridization: a method to identify putative tumor suppressor genes.

OBJECTIVE: To search for new putative tumor suppressor genes in colorectal carcinoma. METHODS: Subtractive hybridization technologies were applied to screen and select genes, the expression of which was down-regulated in colorectal carcinoma. mRNAs uniquely expressed in normal cells but not in colorectal carcinoma were recovered as cDNA (sub-cDNA) after two rounds of subtractive hybridization with mRNA prepared from colorectal carcinoma. The sub-cDNAs were then used as probes to screen a normal human colon cDNA library constructed in lambda-Zap II phage. The DNAs of positive clones were in vivo excised, and partial DNA sequences were analyzed and compared with DNA sequence database Genbank. RESULTS: A total of 46 different clones with an average of about 1 kilobases in transcript size was recovered. Among these 46 down-regulated genes in colorectal carcinoma were genes encoding immunoglobulin (n = 32), 40-kDa keratin intermediate filamentous protein or IFP (n = 1), major histocompatibility complex-related protein (n = 1), unrelated structural proteins (n = 10) and gene products yet to be identified (n = 2). RNA dotblot hybridizations confirmed that all 46 clones contained genes that were down-regulated and have not been reported before in colorectal carcinoma. CONCLUSION: The results of this study suggested that the 46 clones were down-regulated in colorectal carcinoma, they should be further studied as new putative tumor suppressor genes and could be used as new tumor markers of colorectal carcinoma.

Colorectal Neoplasms↗

PubMed1996

Identification and localization of polycystin, the PKD1 gene product.

Polycystin, the product of autosomal dominant polycystic kidney disease (ADPKD) 1 gene (PKD1) is the cardinal member of a novel class of proteins. As a first step towards elucidating the function of polycystin and the pathogenesis of ADPKD, three types of information were collected in the current study: the subcellular localization of polycystin, the spatial and temporal distribution of the protein within normal tissues and the effects of ADPKD mutations on the pattern of expression in affected tissues. Antisera directed against a synthetic peptide and two recombinant proteins of different domains of polycystin revealed the presence of an approximately 400-kD protein (polycystin) in the membrane fractions of normal fetal, adult, and ADPKD kidneys. Immunohistological studies localized polycystin to renal tubular epithelia, hepatic bile ductules, and pancreatic ducts, all sites of cystic changes in ADPKD, as well as in tissues such as skin that are not known to be affected in ADPKD. By electron microscopy, polycystin was predominantly associated with plasma membranes. Polycystin was significantly less abundant in adult than in fetal epithelia. In contrast, polycystin was overexpressed in most, but not all, cysts in ADPKD kidneys.

Antibodies↗

PubMed1996

Seroepidemiological studies on Silk Road ethnic groups.

To clarify the origin of the Japanese, the Jomom and/or Yayol, we screened for HTLV-1 and -II antibodies among inhabitants of the Silk Road, the Han, Uygur and Kazaks. We also screened for HIV, HBV, and HCV. The HTLV-I, -II, HIV, and HCV antibody tests were uniformly negative in all the studied groups. In contrast, a significantly higher incidence of HBs antigen was observed in all the groups tested (Northern Han: 11.9%, Uygur: 6.0%, Kazak: 9.1%). These results indicate that these ethnic groups are not the origin of the indigenous Japanese (the Jomon), and that HBV is prevalent in the various groups along the Silk Road.

Antigens, Viral↗

PubMed1995

The relative radiosensitivity of TK6 and WI-L2-NS lymphoblastoid cells derived from a common source is primarily determined by their p53 mutational status.

The lymphoblastoid cell lines WI-L2-NS and TK6 were derived from a non-clonal pool of cells taken from a human spleen. Despite their common background they exhibit marked differences in radiosensitivities; D0 values of 93 and 67 cGy have been reported for WI-L2-NS and TK6 cells respectively. We show here that this differential radiosensitivity is due to a decreased ability of the WI-L2-NS cell line to undergo radiation-induced apoptosis. Further, the WI-L2-NS cell line overexpresses the p53 gene product as a result of a mutation in codon 237 of the p53 gene. These data indicate that WI-L2-NS cells through disruption of normal p53 function are unable to engage the radiation-induced apoptosis program and so are relatively radioresistant.

Apoptosis↗