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Biomedical subjects

X Ding

Publications and source records attributed to X Ding.

At least 109 records · Page 6Linked to original sources
PubMed1998

Pancreatic cancer cells selectively stimulate islet beta cells to secrete amylin.

BACKGROUND & AIMS: Patients with pancreatic adenocarcinoma have a high incidence of diabetes, profound insulin resistance, and high circulating amylin concentrations. It was hypothesized that pancreatic cancer cells produce a factor that stimulates islets to secrete amylin but not insulin. METHODS: Amylin and insulin secretion were measured after coculture of pancreatic cancer cells with beta cells (BRIN-BD11). The factor responsible was characterized by exposing beta cells to cancer cell-conditioned medium. RESULTS: Coculture with pancreatic (PANC-1 HPAF, and MiaPaCa2) but not colonic cancer cells (Colo 320) significantly increased amylin secretion but did not change insulin output. This effect was both time and cell number dependent. Coculture with PANC-1 or HPAF cells significantly decreased intracellular amylin, but not insulin, content. PANC-1 or HPAF cell-conditioned medium also increased amylin secretion and decreased intracellular amylin content. The factor responsible was extracted under both neutral and acidic conditions, was heat labile, and had a molecular weight of approximately 1500. CONCLUSIONS: A soluble factor from pancreatic cancer cells selectively stimulates amylin secretion from islet cells, explaining the excessive amylin secretion found in pancreatic cancer. Because elevation of amylin concentration is an early feature of pancreatic cancer, characterization and measurement of the tumor-derived amylin-releasing factor might be valuable in the early detection of this disease.

Adenocarcinoma↗
PubMed1998

Role of corticotropin-releasing factor and substance P in pressor responses of nuclei controlling emotion and stress.

The wide distribution of corticotropin-releasing factor (CRF) and substance P (SP)-immunoreactive cell bodies, nerve terminals and corresponding receptors in pressor nuclei controlling emotion and stress implies that CRF and SP may play important roles in pressor responses of these nuclei; hence CRF or SP was microinjected into these nuclei respectively in Wistar male rats anesthetized with urethane to test this possibility. Microinjection of CRF into nucleus amygdaloideus centralis, nucleus paraventricularis, nucleus ventromedialis, lateral hypothalamus-perifornical region, periaqueductal gray matter, nucleus parabrachialis, locus coeruleus or rostral ventrolateral medulla respectively could evoke pressor responses (but CRF injection into nucleus dorsomedialis could not elicit significant pressor responses). Injection of substance P into all the above nuclei could also elicit hypertensive responses of different magnitudes, whereas normal saline injection into these nuclei had no effect. These results indicate that both CRF and SP in the above mentioned nuclei may play important roles in hypertension induced by prolonged emotional stress.

Animals↗
PubMed1998

Pre-MBT patterning of early gene regulation in Xenopus: the role of the cortical rotation and mesoderm induction.

Patterning events that occur before the mid-blastula transition (MBT) and that organize the spatial pattern of gene expression in the animal hemisphere have been analyzed in Xenopus embryos. We present evidence that genes that play a role in dorsoventral specification display different modes of activation. Using early blastomere explants (16-128-cell stage) cultured until gastrula stages, we demonstrate by RT-PCR analysis that the expression of goosecoid (gsc), wnt-8 and brachyury (bra) is dependent on mesoderm induction. In contrast, nodal-related 3 (nr3) and siamois (sia) are expressed in a manner that is independent of mesoderm induction, however their spatially correct activation does require cortical rotation. The pattern of sia and nr3 expression reveals that the animal half of the 16-cell embryo is already distinctly polarized along the dorsoventral axis as a result of rearrangement of the egg structure during cortical rotation. Similar to the antagonistic activity between the ventral and the dorsal mesoderm, the ventral animal blastomeres can attenuate the expression of nr3 and sia in dorsal animal blastomeres. Our data suggest that no Nieuwkoop center activity at the blastula stage is required for the activation of nr3 and sia in vivo.

Animals↗
PubMed1998

Macromolecular organization and genetic mapping of a rapidly evolving chromosome-specific tandem repeat family (B77) in cotton (Gossypium).

Isolation and characterization of the most prominent repetitive element families in the genome of tetraploid cotton (Gossypium barbadense L; [39]) revealed a small subset of families that showed very different properties in tetraploids than in their diploid progenitors, separated by 1-2 million years. One element, B77, was characterized in detail, and compared to the well-conserved 5S and 45S rRNA genes. The 572 bp B77 repeat was found to be concentrated in several discontinuous tandem arrays confined to a single 550 kb SalI fragment in tetraploid cotton. Genetic mapping based on the absence of the pentameric 'rung' in the G. barbadense 'ladder' showed that B77 maps to a D-subgenome chromosome. In situ hybridization supports the contention that the array is confined largely to a single chromosomal site in the D-subgenome. The B77 repeat has undergone a substantial increase in copy number since formation of tetraploid cotton from its diploid relatives. RFLPs observed among tetraploid cotton species suggest that amplification and/or rearrangement of the repeat may have continued after divergence of the five tetraploid cotton species. B77 contains many short direct repeats and shares significant DNA sequence homology with a Nicotiana alata retrotransposon Tna1-2 integrase motif. The recent amplification of B77 on linkage group D04 suggests that the D-subgenome of tetraploid cotton may be subject to different evolutionary constraints than the D-genome diploid chromosomes, which exhibit few genome-specific elements. Further, the abundance of B77 in G. gossypioides supports independent evidence that it may be the closest extant relative of the D-genome ancestor of cotton.

Base Sequence↗
PubMed1998

Insect resistance of transgenic tobacco expressing an insect chitinase gene.

Chitinase expression in the insect gut normally occurs only during moulting, where the chitin of the peritrophic membrane is presumably degraded. Thus, insects feeding on plants that constitutively express an insect chitinase gene might be adversely affected, owing to an inappropriately timed exposure to chitinase. This hypothesis was tested by introducing a cDNA encoding a tobacco hornworm (Manduca sexta) chitinase (EC 3.2.1.14) into tobacco via Agrobacterium tumefaciens-mediated transformation. A truncated but enzymatically active chitinase was present in plants expressing the gene. Segregating progeny of high-expressing plants were compared for their ability to support growth of tobacco budworm (Heliothis virescens) larvae and for feeding damage. Both parameters were significantly reduced when budworms fed on transgenic tobacco plants expressing high levels of the chitinase gene. In contrast, hornworm larvae showed no significant growth reduction when fed on the chitinase-expressing transgenics. However, both budworm and hornworm larvae, when fed on chitinase-expressing transgenic plants coated with sublethal concentrations of a Bacillus thuringiensis toxin, were significantly stunted relative to larvae fed on toxin-treated non-transgenic controls. Foliar damage was also reduced. Plants expressing an insect chitinase gene may have agronomic potential for insect control.

Animals↗
PubMed1998

A secretory cellulose-binding protein cDNA cloned from the root-knot nematode (Meloidogyne incognita).

A cDNA encoding a secretory cellulose-binding protein was cloned from the root-knot nematode (Meloidogyne incognita) with RNA fingerprinting. The putative full-length cDNA, named Mi-cpb-1, encoded a 203 amino acid protein containing an N-terminal secretion signal peptide. The C-terminal sequence of the putative MI-CBP-1 was similar to a bacterial-type cellulose-binding domain, whereas the N-terminal sequence did not show significant similarity to any proteins in data bases. Recombinant MI-CBP-1 lacked cellulase activity, but bound to cellulose and plant cell walls. In Southern blot hybridization, Mi-cbp-1 hybridized with genomic DNA from M. incognita, M. arenaria, and M. javanica, but not M. hapla, Heterodera glycines, or Caenorhabditis elegans. Polyclonal antibodies raised against recombinant MI-CBP-1 strongly labeled secretory granules in subventral gland cells of second-stage juveniles in indirect immunofluorescence microscopy. Enzyme-linked immunosorbent assay detection of MI-CBP-1 in stylet secretions of second-stage juveniles with the polyclonal antibodies indicated MI-CBP-1 could be secreted through the nematodes' stylet, suggesting that the cellulose-binding protein may have a role in pathogenesis.

Amino Acid Sequence↗
PubMed1998

GB virus C/hepatitis G virus infection among Colombian native Indians.

To elucidate the prevalence of GB virus C/hepatitis G virus (GBV-C/HGV) infection in Colombian native Indians, serum GBV-C/HGV RNA was assayed in 163 native Indians and 67 members of the general population in Colombia. The native Indians (males:females = 40:123) and the members of the general population (males:females = 20:47) were tested by reverse transcription-semi-nested polymerase chain reaction. Of the 163 native Indians, 10 (6.1%) were positive for GBV-C/HGV RNA, compared with one (1.5%) of 67 from the general population. All Indians were negative for hepatitis B surface antigen and antibody to hepatitis C virus. Of 10 Indians with GBV-C/HGV RNA, the genotype of nine subjects was the Asian type. These data indicated that 1) the prevalence of GBV-C/HGV RNA in Colombian native Indians is high, and 2) GBV-C/HGV was probably brought from Asia and inherited for generations in some native Indian groups.

Adolescent↗
PubMed1998

[Analysis of 25 episodes of acute occupational poisoning accidents and studies on its preventive strategy].

OBJECTIVE: To study the causes of the occurrence of severe acute occupational poisoning and its first-aid, and to improve its prevention and management. METHODS: Data of labor health conditions in 25 episodes of poisoning during the past 13 years were collected and analyzed statistically according to industries, enterprises and toxicals. RESULTS: Twenty-five episodes of poisoning accidents involved 131 persons, with 22 deaths. The incidence rate of occupational poisoning accidents in township and town enterprises exceeded that in state-owned ones. Ten kinds of toxicants were involved in the poisoning, with the hydrogen sulfide, benzene, carbon monoxide, phosgene and organophosphorus pesticide at the top five places in the number of cases with poisoning they caused. There were another 131 persons intoxicated during their emergency action and eight deaths, with a higher incidence and mortality rates due to poisoning than those in the operation workers. CONCLUSION: The major causes of the poisoning accidents were lack of knowledge of prevention and protection from them. It laid a good foundation for the establishment of emergency rescuing system in the grassroots.

Accidents, Occupational↗
PubMed1998

[Expression of p53 and ras p21 gene products in malignant transformed V79 cell induced by various organic components of DEPs].

The effect of various fractions of diesel exhausted particles on the expression of mutant p53 antigen product and ras oncogene p21 product was examined by immunohistochemical method in malignant transformed V79 cell. The result showed that all fractions of diesel exhausted particles (DEPs) could significantly increase the expression of p53 products (P < 0.01). It demonstrated that the organic fractions of DEPs could induce the mutation of p53 suppressor gene in malignant transformed cells. But the expression levels of ras oncogene p21 product were not changed under the same experimental conditions (P > 0.05).

Animals↗
PubMed1998

[Chemical constituents of Phyllanthus urinaria L. and its antiviral activity against hepatitis B virus].

Studies on the chemical constituents of Phyllanthus urinaria and its antiviral activity against hepatitis B virus were completed. Eleven compounds have been isolated. Two of them are new compounds methyl ester dehydrochebulic acid and methyl brevifolin carboxylate. Antiviral experiments on HBsAg in vitro and liver damage caused by CCl4 have shown that. Phyllanthus urinaria possesses antiviral activities against HBV.

Animals↗
PubMed1998

[Optimization of non-gel sieving capillary electrophoretic separation of DNA fragments of hundreds of base pairs].

Non-gel sieving capillary electrophoresis has been employed in the biological sciences for the size-based separation of macromolecules such as nucleic acids. In this paper, four factors i.e. electric field strength, capillary length, capillary diameter and hydroxy-propylmethylcellulose (HPMC) concentration were integratively evaluated to select the optimal condition of separating DNA fragments of a few hundreds of base pairs through orthogonal analysis. Conclusion was made through comprehensive analysis: better separation could be achieved in longer capillary, smaller inside diameter of capillary and less field strength. In practical application, effective separation in short time is important. We preferred to employ 8 g/L HPMC in coated capillary (37 cm x 75 microns i.d.) and electric field strength of 324 V/cm in separating DNA fragments of hundreds of base pairs. From sampling to getting results only a few more than ten minutes were needed in capillary electrophoresis. It needs less amount of sample (a few nanoliters) and shows higher sensitivity (0.1 pmol in UV detection) than polyacrylamide gel electrophoresis (PAGE). pBR322/Msp I fragments were completely resolved in both capillary electrophoresis and PAGE, and four-bases resolution was obtained. When the concentration of the PCR product is too low (< 20 mg/L), PCR reaction system is used as a negative control to make sure of the peak generated by the unpurified PCR products, avoiding interference made by PCR buffer and polymerase.

Apolipoprotein B-100↗
PubMed1998

[Studies on diterpenoids from the roots of Euphorbia ebracteolata].

Euphorbia ebractolata has been used as insecticide and tuberculocide. Four crystalline compounds were isolated from the root of this plant. They were characterized by their physico-chemical properties and spectral data as: 3-acety alpha-amyrin (I), Jolkinolide B (II), ebracteolatanolide A (III) and ebracteolatanolide B (IV). I and II were isolated for the first time from E. ebracteolata Hayata. III and IV are new compounds.

Diterpenes↗
PubMed1998

Purification and characterization of heterologously expressed mouse CYP2A5 and CYP2G1: role in metabolic activation of acetaminophen and 2,6-dichlorobenzonitrile in mouse olfactory mucosal microsomes.

The metabolic activation of two known olfactory mucosal (OM) toxicants, acetaminophen (AP) and 2,6-dichlorobenzonitrile (DCBN), was examined with mouse liver and OM microsomes and purified, heterologously expressed mouse CYP2A5 and CYP2G1. In reconstituted systems, both isoforms were active in metabolizing DCBN and AP to metabolites that formed protein adducts. The formation of DCBN- or AP-protein adducts and other AP metabolites, including 3-hydroxy-AP and, in the presence of glutathione, AP-glutathione conjugate, was also detected in OM microsomal reactions and to a much greater extent than in liver microsomes. Evidence was obtained that CYP2A5 and CYP2G1 play major roles in mouse OM microsomal metabolic activation of DCBN and AP. Immunoblot analysis indicated that CYP2A5 and CYP2G1 are abundant P450 isoforms in OM microsomes. OM microsomal AP and DCBN metabolic activation was inhibited by 5- and 8-methoxsalen, which inhibit both CYP2A5 and CYP2G1, and by an inhibitory anti-CYP2A5 antibody that also inhibits CYP2G1. In addition, the roles of CYP1A2 and CYP2E1 in the OM bioactivation of AP and DCBN were ruled out by comparing activities of acetone-treated mice or Cyp1a2(-/-) mice with those of control mice. Thus, CYP2A5 and CYP2G1 may both contribute to the known OM-selective toxicity of AP and DCBN. Further analysis of the kinetics of AP and DCBN metabolism by the purified P450s suggested that CYP2A5 may play a greater role in OM microsomal metabolism of AP, whereas their relative roles in DCBN metabolism may be dose dependent, with CYP2G1 playing more important roles at low substrate concentrations.

Acetaminophen↗
PubMed1998

[Investigation of the genetic instability of tumor cells by transfection of RER+ cell lines with exogenous microsatellite sequence].

OBJECTIVE: Frequent alterations of microsatellite sequence of cancer cells were found recently in a substantial fraction of human cancers including hereditary non-polyposis colon cancer. This paper aimed to investigate the genetic instability of tumor cells by using microsatellite instability(MI) as the marker in vitro. METHODS: Two RER+ cell lines (replication error phenotype), RKO and HCT116 and one RER- cell line, sw480, were used as the hosts for transfection with an episomal plasmid, pCMV-CAR, containing an exogenous (CA)14 repeat which was inserted within the coding sequence of lacZ reporter gene and thus made lacZ misreading. The transfectant clones were selected and established by hygromicin. Expression and production of lacZ reporter gene of restored reading frame were detected with X-gal staining assay. RESULTS: After hygromicin selection, stable pCMV-CAR transfectant clones were established. It was shown that mutation of deletion of insertion within(CA)14 occurred in the transfectant RER+ cells but not in the RER-cells. The mutation restored normal reading frame of lacZ gene, and resulted in expression and production of bio-active beta galactosidase which was detected with X-gal staining. This feature of the transfectant clones was maintained during culture passages. CONCLUSION: The alterations of the exogenous(CA)14 repeat in the transfectant RER+ clones revealed genetic instability and complicated mutation status of cancer cells. It is suggested that the exogenous (CA)14 in transfectant clones could be a useful target sequence for monitoring the effects of environmental agents on MI of human cancer cells.

Cell Line↗
PubMed1998

Differential xenobiotic induction of CYP2A5 in mouse liver, kidney, lung, and olfactory mucosa.

The effects of pyrazole, which is known to induce hepatic cytochrome P4502A5 (CYP2A5) through posttranscriptional mechanisms, on the level of CYP2A5 in liver and extrahepatic tissues were examined in this study. Intraperitoneal administration of pyrazole at 200 mg/kg for 3 days induced CYP2A4/5 mRNAs and proteins and microsomal coumarin 7-hydroxylation activity in liver and kidney of C57BL/6 mice. A marginal increase (30%) in CYP2A4/5 mRNAs was also observed in the olfactory mucosa but not in the lung, and no increase in CYP2A4/5 proteins or microsomal coumarin 7-hydroxylation activity was observed in either the olfactory mucosa or lung. CYP2A4/5 proteins were not detected on immunoblots in other tissues examined, including breast, bone marrow, testis, prostate, ovary, and uterus from control or pyrazole-treated mice. On the other hand, pyrazole treatment induced CYP2E1 in the olfactory mucosa as well as in liver and kidney, indicating that the olfactory mucosa was exposed to pyrazole. The lack of CYP2A inducibility in the olfactory mucosa was also observed for several other known inducers of hepatic CYP2A5, including cobaltous chloride, stannous chloride, griseofulvin, thioacetamide, and aminotriazole. These results suggest that the mechanisms involved in the induction of hepatic and renal CYP2A5 by pyrazole and other xenobiotic compounds may be tissue-specific.

Amitrole↗
PubMed1998

Insulin secretion is inhibited by subtype five somatostatin receptor in the mouse.

BACKGROUND: Recently five somatostatin receptor subtypes (SSTRs) were cloned, allowing the development of highly specific agonists to these SSTRs. Previous studies have shown a species specificity phenomenon with respect to the inhibition of insulin secretion by these selective agonists. This study was undertaken to determine which SSTR (2 or 5) is responsible for the inhibitory effect of somatostatin on glucose-stimulated mouse insulin secretion. METHODS: Intact mouse islets (n = 10) were stimulated with D-glucose in the presence or absence of receptor-specific somatostatin agonists. RESULTS: D-glucose (16.7 mmol/L) augmented insulin secretion by 158% above that seen with 3.9 mmol/L D-glucose. In the presence of DC 32-92 (SSTR5) selective agonist, D-glucose (16.7 mmol/L) augmented insulin secretion by 64% above that seen with 3.9 mmol/L D-glucose. The presence of SSTR 5 selective agonist resulted in a significant (P < .05) inhibition of glucose-stimulated insulin secretion. The identification of SSTR5 within the mouse pancreas was established by reverse transcriptase polymerase chain reaction and confirmed by Southern blot analysis. CONCLUSIONS: These results suggest that the inhibitory effect of somatostatin on insulin secretion is mediated through the subtype 5 receptor within the mouse islet.

Animals↗
PubMed1998

GB virus C/hepatitis G virus infection among patients with hepatocellular carcinoma in the inshore area of the Yangtze River, China.

To investigate the association between GB virus C/hepatitis G virus (GBV-C/HGV) infection and the development of hepatocellular carcinoma (HCC) in H city, in the inshore area of the Yangtze River, where high prevalence of HCC has been reported, we determined hepatitis B virus (HBV) and hepatitis C virus (HCV) markers, GBV-C/HGV-RNA and GBV-C/HGV E2 antibody (anti-HG E2) among 114 HCC patients and the same number of age- and sex-matched controls. There were no significant differences in the clinical and demographic characteristics between them, except for serum alanine aminotransferase level and history of liver diseases. There was a significant difference of hepatitis B virus surface antigen (HBsAg) prevalence between the HCC patients (75.4%) and the controls (20.2%; P<0.01). Hepatitis C virus antibody was detected in 4.4% of the HCC patients, compared with 1.7% of the controls. GB virus-C/HGV-RNA and anti-HG E2 were detected in 14.9 and 1.7% of the HCC patients, respectively, compared with 7.0 and 1.7% of the controls, respectively. Nucleotide sequences and molecular evolutionary analysis showed the strains of GBV-C/HGV-RNA were classified into genotype 2 and 3 (HG and ASIA type). An effect analysis showed an odds ratio (OR) for developing HCC from GBV-C/HGV infection among HBsAg-positive subjects was 14.9, with a 95% CI of 4.9-45.4. HBsAg infection alone was 13.83 (95% CI 7.4-25.9) and GBV-C/HGV infection alone, 3.74 (95% CI 1.1-13.1), respectively. These data indicate that HBV infection is considered to be one of the major risk factors in patients with HCC and although GBV-C/HGV infection was observed in both the HCC and the control groups, it might not play an important role in the development of HCC in this area.

Adult↗