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Biomedical subjects

X Feng

Publications and source records attributed to X Feng.

At least 181 records · Page 10Linked to original sources
PubMed1996

[Endothelin-1 induces chemotaxis of pulmonary artery smooth muscle cells].

Migration of pulmonary artery smooth muscle cells (PASMC) and their precorsors might be an important mechanism of pulmonary vascular structural remodelling associated with hypoxic pulmonary hypertension (HPH). Endothelin-1 (ET-1) plays an important role in the pathogenesis of HPH. This study observed that ET-1 induced chemotaxis of PASMC in a dose dependent manner. The maxium chemotactic response of PASMC to ET-1 occured at a concentration of 10(-9) mol/L. The chemotactic activity of ET-1 is weakened, when its concentration is higher than 10(-9) mol/L. BQ123, a specific antagonist of ETRA, significantly inhibited the chemotaxis of PASMC induced by ET-1, which indicates that the chemotactic activity of ET-1 may be mediated by ETRA. Hypoxia enhanced the chemotaxis of PASMC induced by ET-1. This study suggests that ET-1 and hypoxia might stimulate the migration of PASMC and/or its precorsor. The further mechanism is under study.

Animals↗
PubMed1995

Cooperative medical schemes in contemporary rural China.

Improvements in rural health care in China in the 1950s, 1960s and 1970s were largely due to the development of cooperative medical schemes (CMSs) and the establishment of a three-tier rural health network. Since the economic reforms were instituted in the late 1970s, the financing and delivery of rural health services have seen many changes, some positive, others not. Most CMSs have collapsed. In the absence of CMSs, the rural population has to pay for health care out-of-pocket and poor families have greater difficulty in getting access to essential health care. In the meantime, emphases of health services have tended to shift from lower to higher levels, from preventive to curative services, and from planning and management to market forces. This paper outlines the evolution of CMSs, reasons for their collapse, and their likely impact on rural health services. The main focus is on the development of a new generation of rural cooperative health care schemes, given their importance in the process of consolidating the rural three-tier health network after the impact of the economic reforms: the characteristics of some schemes, the apparent conditions for success, and government policy towards the development of cooperative health care financing are presented.

China↗
PubMed1995

Intracranial germ cell tumors: detection of p53 gene mutations by single-strand conformation polymorphism analysis.

Using polymerase chain reaction-single-strand conformation polymorphism (PCR-SSCP) analysis, p53 gene mutation was examined in 12 intracranial germ cell tumors (5 yolk sac carcinomas and 7 germinomas), many of which were derived from young patients in the first to the second decade. A total of 10 mutations were detected in 4 of the 12 cases and, in 3 of them, the mutations were multiple or tandem. Among the 10 mutations, 7 were missense, 1 was splicing and 2 were silent. The 7 missense mutations were located at previously proposed hot spot codons or in their vicinity or, when outside the hot spots, at a codon encoding an amino acid conserved in most vertebrates. These findings suggested that all 7 missense mutations may actually give rise to functional alteration of the p53 protein. The splicing mutation was considered to be a germ-line mutation, though its biological effect was equivocal, since the neoplastic tissue contained an additional mutation. The pattern of the mutations was predominancy of G:C-A:T transition with frequent involvement of the CpG site. These mutations were more frequently detected in yolk sac carcinomas (60%; 3/5 cases) than in germinomas (14%; 1/7 cases), suggesting that the contribution of the p53 mutation to carcinogenesis differed with the histological type of the intracranial germ cell tumor.

Adolescent↗
PubMed1995

Studies on kinetics of substrate utilization of hydrogen production from wastewater with immobilized cells of photosynthetic bacteria.

The kinetic characteristics of substrate utilization by immobilized cells of Rhodopseudomonas capsulata 386 and Rhodopseudomonas sp. D for H2 production was investigated. The results showed that substrate utilization did not proceed simultaneously with H2 evolution, H2 producing capacity of immobilized cells with agar was higher than that of alginate immobilized cells, but the appearance of maximum H2 producing activity was later than the last one. The kinetics of substrate utilization (glucose) by immobilized cells of strain D followed the first-order reaction, rate constant k value was 1.2 x 10(-2) L/h, analysis of macrokinetics indicated that substrate utilization by immobilized cells in H2 evolution process was governed by biochemical reaction other than diffusion transfer limitation, because of the Thiele modulus were 0.125 and 0.154 for immobilized cells with D = 3.6 mm and 4.4 mm particles, the corresponding effective factor were determined as 0.998 and 0.988, respectively. An immobilized cell bioreactor, fed by glucose and lactate, was employed for continuous H2 evolving system. It was found that hydrogen production were 0.659 L/d and 0.477 L/d in immobilized cells system of strain 386 and D when lactate used as H2 evolving substrate, while the volumetric H2 rate were all up to 1.0 L/L.d.

Diffusion Chambers, Culture↗
PubMed1995

[Application of Plasmodium falciparum DNA extract from dried blood spot of falciparum malaria patient in polymerase chain reaction].

Polymerase chain reaction (PCR) primered with primers 3,4 and 5,6 was performed using DNA extracted from dried blood spot of a falciparum malaria patient from Mengpeng Township, Yunnan using four different methods, including STE-proteinase K-SDS, methanol-proteinase K-SDS, Chelex-100 and Chelex-100-proteinase K to amplify DNA of apical membrane antigen 1 (AMA-1). A 900 bp DNA band could be seen on the ethidium bromide-stained agarose gel electrophoresis of the PCR products when DNA was extracted using all the above-mentioned methods except STE-proteinase K-SDS method. DNA extracted with Chelax-100 was recommended.

Animals↗
PubMed1995

[Preliminary studies on the effects of tumor necrosis factor gene transfer on the growth of human hepatocellular carcinoma cells in nude mice].

An eukaryotic expression vector containing tumor necrosis factor alpha (TNF alpha) gene (psVK3-tnf) was transduced into hepatocellular carcinoma (HCC) cell line, SMMC7721, by calcium phosphate coprecipation method. The TNF-gene-transduced SMMC7721 cell began to secrete TNF after 24h (50 0/ml), reached peak level at 48-72h (90U/ml), and declined after 96h (40U/ml). Three weeks after the pSVK3-tnf DNA entrapped with calcium phosphate was introduced directly into subcutaneous nodules of human HCC in nude mice (treated mice), the growth of HCC was significantly delayed as compared to the pSVK3 group (control mice) (2.5 +/- 1.6 cm vs. 3.2 +/- 1.8 cm, n = 6, P < 0.05). There was a transient increase in TNF alpha level in peripheral blood in the treated but not in the control mice. The survival time of the treated mice was markedly prolonged as compared to the control (44.0 +/- 3.3d vs. 28.2 +/- 2.0d, n = 6, P < 0.01). The above results suggest that TNF alpha gene transfer might be a hopeful therapy for HCC.

Animals↗
PubMed1995

[Sequence analysis of apical membrane antigen I from a Plasmodium falciparum isolate collected from Mengpeng Township, Yunnan Province].

Genomic DNA from a Plasmodium falciparum isolate (CMP-1) collected from a falciparum malaria patient at Mengpeng Township, Mengla County, Yunnan Province was used as the template for PCR amplification primered with oligonucleotides from the conserved regions of the apical membrane antigen I (AMA-1) as reported. PCR products recovered from the low melting-point agarose gel electrophoresis were digested with BamHI and EcoRI to generate fragments approximately 420, 445 and 900 bp which were used as the inserts to insert into the M13 mp8 and M13 mp9 vectors for sequencing using 373 sequencer. 1773 bases were read out, among which 17 point mutations were found to result in substitutions of 15 codens which were non-synonymous mutations except for one as compared with that of the consensus. In particular, a relatively hot region of variation was apparent between amino acids 160 and 210.

Amino Acid Sequence↗
PubMed1995

[Clinical evaluation of serum collagen type IV in diagnosing liver fibrosis].

UNLABELLED: Serum collagen type IV (CIV) levels determined by one step sandwich EIA kit were compared with the serum procollagen type III (PCIII) and hyaluronic acid (HA) in 114 patients with various liver diseases, 30 patients without liver diseases (NL) and 30 controls. RESULTS: serum CIV was significantly increased in chronic active hepatitis, liver cirrhosis and primary hepatic carcinoma. So were PCIII and HA. Serum CIV PCIII and HA were found to be closely related to the degree of fibrosis in 69 patients' liver biopsy studies, but no correlation could be found between these 3 markers. The sensitivity of CIV, PCIII, HA in detecting liver fibrosis were 73.9%, 67.4%, 67.4% with specificity of 95.7%, 91.3%, 100.0% respectively. The early diagnostic value of CIV is better than PCIII and HA; their combination could further raise the diagnostic sensitivity to more than 90.0%.

Collagen↗
PubMed1995

[Study on the effect of endothelin and nitric oxide on DNA synthesis of pulmonary artery smooth muscle cells and modulation of hypoxia].

Increasing vasoconstriction and vascular remodeling of pulmonary vasculature are main characteristics of hypoxic pulmonary hypertension (HPH). Basal pulmonary circulatory tone is maintained by a dynamic balance of vasoconstrictors and vasodilators acting on the pulmonary vascular smooth muscle cells. Endothelin-1 (ET-1) and nitric oxide (NO) are the most important endothelium-derived vasoconstrictor (EDCF) and vasodilator (EDRF). In this report, we studied the effect of ET-1 and NO on hypoxic pulmonary vascular remodeling. We observed that ET-1 dose dependently increased DNA synthesis of pulmonary artery smooth muscle cells (PASMC), SNP, a NO generating drug, inhibited DNA synthesis of PASMC and its inhibitory effect was mediated by cGMP. Hypoxia increased the proliferative response of PASMS to ET-1 by stimulating autocrine of PASMC and decreased the inhibitory effect of SNP by reducing the activity of intra-cellular soluble guanylate cyclase. Based on the result, it is suggested that the balance of ET-1 and NO and regulation of hypoxia play important roles in hypoxic pulmonary vascular remodeling.

Animals↗
PubMed1994

Isotopic analyses of nitrogenous compounds from the Murchison meteorite: ammonia, amines, amino acids, and polar hydrocarbons.

The combined volatile bases (ammonia, aliphatic amines, and possibly other bases), ammonia, amino acids, and polar hydrocarbons were prepared from the Murchison meteorite for isotopic analyses. The volatile bases were obtained by cryogenic transfer after acid-hydrolysis of a hot-water extract and analyzed by combined gas chromatography-mass spectrometry of pentafluoropropionyl derivatives. The aliphatic amines present in this preparation comprise a mixture that includes both primary and secondary isomers through C5 at a total concentration of > or = 100 nmoles g-1. As commonly observed for meteoritic organic compounds, almost all isomers through C5 are present, and the concentrations within homologous series decrease with increasing chain length. Ammonia was chromatographically separated from the other volatile bases and found at a concentration of 1.1-1.3 micromoles g-1 meteorite. The ammonia analyzed includes contributions from ammonium salts and the hydrolysis of extractable organic compounds, e.g., carboxamides. Stable isotope analyses showed the volatile bases to be substantially enriched in the heavier isotopes, relative to comparable terrestrial compounds delta D < or = +1221%; delta 13C = +22%; delta 15N = +93%). Ammonia, per se, was found to have a somewhat lower delta 15N value (+69%) than the total volatile bases; consequently, a higher delta 15N (>93%) can be inferred for the other bases, which include the amines. Solvent-extractable polar hydrocarbons obtained separately were found to be enriched in 15N (delta 15N = +104%). Total amino acids, prepared from a hydrolyzed hot-water extract by cation exchange chromatography, gave a delta 15N of +94%, a value in good agreement with that obtained previously. Nitrogen isotopic data are also given for amino acid fractions separated chromatographically. The delta 15N values of the Murchison soluble organic compounds analyzed to date fall within a rather narrow range (delta 15N = +94 +/- 8%), an observation consistent with their formation, or formation of their precursors, by interstellar chemistry.

Amines↗
PubMed1994

Electrochemical therapy for intermediate and advanced liver cancer: a report of 50 cases.

Fifty cases of primary liver cancer were treated by electrochemical therapy (ECT). Tumour size ranged from 3.5 to 21.0 cm. ECT was performed by administration of 6-10 V, 50-100 mA and an electric quantity of 300-1000 C. Duration of treatment was one and a half to four hours. There was an inverse relationship between tumour size and curative effect. There was no death within three months of treatment. Six- and 12-month survival was 88% and 69%, respectively. In conclusion, ECT is an effective treatment which prolongs the patients' life. We have found the method to be of practical value in the management of liver cancers in the intermediate or advanced stage.

Adult↗
PubMed1994

[Detection of Plasmodium falciparum by polymerase chain reaction (PCR)].

A pair of primers were designed and synthesized based on the DNA fragment coded erythrocyte-binding antigen (EBA-175) of Plasmodium falciparum (P.f.) and polymerase chain reaction (PCR) was performed to detect P.f. cultured in vitro. The amplified products were analysed by agarose gel electrophoresis and a specific 492 bp DNA band was showed in P.f. infected blood sample, but no band showed in P. vivax, P. cynomolgi, P. yoelii and P. berghei infected blood samples, nor in normal one. The parasite densities detected by this method could be as minimal as 10 parasites/20 microliters blood. The PCR technique showed high sensitivity and specificity.

Animals↗
PubMed1993

p53 gene mutations in pontine gliomas of juvenile onset.

Using polymerase chain reaction-single strand polymorphism(PCR-SSCP) and nucleotide analyses, p53 gene mutation was examined in 13 pontine gliomas many of which were of juvenile onset. A total of 15 mutations were detected in 8 cases, of which 5 revealed multiple or tandem mutations. The mutations included 6 G:C-A:T and 4 A:T-G:C transitions and 4 G:C-T:A and 1 A:T-T:A transversions. There was only 1 transition at the CpG site. Normal tissues of the same patients revealed no mutation, suggesting that these mutations were somatic, but not of germ line, in nature. The pattern of mutation characterized by frequent multiple or tandem occurrence, predominancy of transition at non-CpG sites and relatively frequent transversions suggested that pontine glioma might be related with some mutagenic or carcinogenic agents.

Amino Acid Sequence↗
PubMed1993

Neuron-specific enolase (NSE) and non-neuronal enolase (NNE) mRNAs are co-expressed in neurons of the rat cerebellum: in situ hybridization histochemistry.

Using in situ hybridization histochemistry, we analysed the localization of mRNAs for neuron-specific enolase (NSE) and non-neuronal enolase (NNE) in the rat cerebellum at various postnatal developmental stages. Synthetic 45 meric oligonucleotides corresponding to partial sequences of the non-coding region of rat NSE or NNE mRNA were 35S-labeled to approximately the same specific activity and used as hybridization probes. On examination of the adult rat cerebellum, both NSE and NNE signals were detected in all identified and presumed neurons which included Purkinje cells, internal granule cells and presumed stellate/basket cells in the cerebellar cortex and neurons of the dentate nucleus. Examination of the cerebellum during postnatal development also revealed coexistence of NSE and NNE signals in these neurons from early stages. During development, both signals coincidentally increased in Purkinje cells and neurons of the dentate nucleus, while only NSE signals showed a gradual increase in the internal granule cells in which NNE signals remained at the same level from early postnatal to adult stages. The external granule cells showed NNE signals until postnatal day 7 but thereafter the signals became less distinct, especially in cells if the inner zone of the external granule cell layer. Thus, it was shown that NSE and NNE were commonly coexpressed at the mRNA level in various neurons of the cerebellum except for very undifferentiated external granule cells which expressed only NNE mRNA.

Aging↗