Biomedical subjects

Y Feng

Publications and source records attributed to Y Feng.

At least 325 records · Page 18Linked to original sources

PubMed1996

2-Aminofluorene-DNA adduct levels in tumor-target and nontarget organs of rapid and slow acetylator Syrian hamsters congenic at the NAT2 locus.

DNA adduct formation is an important initial event in chemical carcinogenesis. Metabolic activation and deactivation pathways are involved in aromatic amine carcinogenesis, and genetic polymorphism in the N-acetyltransferase 2 (NAT2) gene is associated with differential susceptibility to cancer from aromatic amine chemicals. In the present study, aromatic amine-DNA adduct levels were measured in rapid (Bio. 82.73/H-Patr) and slow (Bio. 82.73/H-Patr) acetylator Syrian hamsters congenic at the NAT2 locus following a single injection of 2-aminofluorene (60 mg/kg). The major DNA adduct, N-(deoxyguanosin-8-yl)-2-aminofluorene (C8-AF), was detected and quantitated by 32P-postlabeling assay at 6, 18, 24, 36, and 48 hr postinjection. Peak levels of C8-AF were achieved at 18-36 hr post-injection in both rapid and slow acetylators. C8-AF levels were significantly higher in tumor-target organs (liver and urinary bladder) than in nontarget organs (heart, colon, and prostate). Significant differences in C8-AF levels between rapid and slow acetylators in liver, heart, colon, and prostate were not observed. However, C8-AF levels in urinary bladder were significantly (four-fold) higher in rapid versus slow acetylators. These results suggest that 2-aminofluorene forms significantly higher levels of DNA adducts in tumor-target organs than in non-target organs and that acetyltransferase polymorphism plays a significant role in 2-aminofluorene-DNA adduct formation in urinary bladder of Syrian hamster.

Acetylation↗

PubMed1996

Effects of tetrandrine on cardiac noradrenaline release evoked by electrical stimulation.

The effects of tetrandrine (TD) on endogenous cardiac noradrenaline (NA) release evoked by electrical stimulation were investigated in perfused guinea pig hearts. The overflow of cardiac NA and its intraneuronal metabolite 3,4-dihydroxyphenylethyleneglycol (DOPEG) were determined by high pressure liquid chromatography (HPLC). In the presence of TD, the release of NA evoked by either nerve ganglion-stimulation or cardiac field-stimulation was significantly reduced (P < 0.01). The overflow of DOPEG was markedly enhanced (P < 0.01). TD inhibited cardiac endogenous NA release resulting from activation of the sympathetic nerve terminals within the myocardium, and increased the release of DOPEG, indicating that TD could result in a loss of NA from storage vesicles or activate monoamine oxidase in axoplasma, which could be detected by markedly increased DOPEG release. These effects of TD may be associated with its property of calcium antagonist.

Alkaloids↗

PubMed1996

The effect of eicosanoids on the expression of MHC genes in cultured human colon cancer cells and mouse colonocytes in vivo.

Eicosanoids have been implicated in the pathogenesis of cancer and are known to regulate the expression of antigens of the major histocompatibility complex (MHC). In human colon cancer, we have recently observed that: (a) the expression of MHC class I and II antigens are markedly reduced; and (b) the levels of PGE2, but not of PGF2 alpha and LTB4, are elevated compared to histologically normal mucosa. Therefore, we investigated the effect of PGE2, PGF2 alpha and LTB4 on the regulation of MHC class I antigens in two human colon adenocarcinoma cell lines and in a murine model of colon cancer. None of these eicosanoids had any significant effect on the expression of MHC class I antigens in the human colonocytes or the transcription rate of class I genes, with the exception of LTB4 which only modestly suppressed the transcription rate. Similarly, 16, 16-dimethyl-PGE2 had no effect on the expression of MHC class I genes in the colonocytes of BALB/c mice treated with the carcinogen dimethylhydrazine. We conclude that PGE2, PGF2 alpha and LTB4 did not affect the expression of MHC class I antigens in cultured human colon adenocarcinoma cells, and 16, 16-dimethyl PGE2 did not affect their expression in mice, even when mice were treated with a colon carcinogen. Thus, these eicosanoids are an unlikely regulator of the observed underexpression of MHC class I antigens in human colon cancer.

16,16-Dimethylprostaglandin E2↗

PubMed1996

The fragile X mental retardation protein is a ribonucleoprotein containing both nuclear localization and nuclear export signals.

Fragile X syndrome is a frequent cause of mental retardation resulting from the absence of FMRP, the protein encoded by the FMR1 gene. FMRP is an RNA-binding protein of unknown function which is associated with ribosomes. To gain insight into FMRP function, we performed immunolocalization analysis of FMRP truncation and fusion constructs which revealed a nuclear localization signal (NLS) in the amino terminus of FMRP as well as a nuclear export signal (NES) encoded by exon 14. A 17 amino acid peptide containing the FMRP NES, which closely resembles the NES motifs recently described for HIV-1 Rev and PKI, is sufficient to direct nuclear export of a microinjected protein conjugate. Sucrose gradient analysis shows that FMRP ribosome association is RNA-dependent and FMRP is found in ribonucleoprotein (RNP) particles following EDTA treatment. These data are consistent with nascent FMRP entering the nucleus to assemble into mRNP particles prior to export back into the cytoplasm and suggests that fragile X syndrome may result from altered translation of transcripts which normally bind to FMRP.

Amino Acid Sequence↗

PubMed1996

High- and low-bar squatting techniques during weight-training.

Eight Swedish national class weightlifters performed "high-bar" squats and six national class powerlifters performed "low-bar" squats, with a barbell weight of 65% of their 1 RM, and to parallel- and a deep-squatting depth. Ground reaction forces were measured with a Kistler piezo-electric force platform and motion was analyzed from a video record of the squats. A computer program based on free-body mechanics was designed to calculate moments of force about the hip and knee joints. EMG from vastus lateralis, rectus femoris, and biceps femoris was recorded and normalized. The peak moments of force were flexing both for the hip and the knee. The mean peak moments of force at the hip were for the weightlifters 230 Nm (deep) and 216 Nm (parallel), and for the powerlifters 324 Nm (deep), and 309 Nm (parallel). At the knee the mean peak moments for the weightlifters were 191 Nm (deep) and 131 Nm (parallel), and for the powerlifters 139 Nm (deep) and 92 Nm (parallel). The weightlifters had the load more equally distributed between hip and knee, whereas the powerlifters put relatively more load on the hip joint. The thigh muscular activity was slightly higher for the powerlifters.

Adolescent↗

PubMed1996

Direct cDNA selection with DNA microdissected from mouse chromosome 16: isolation of novel clones and construction of a partial transcription map of the C3-C4 region.

A group of cDNA segments was selected by direct hybridization of mouse cerebellar cDNAs against genomic DNA pools generated by microdissection of the mouse chromosome 16 (MMU16) C3-C4 region. After elimination of repetitive sequences and adjustment for redundancy among clones, 34 novel cDNA fragments were isolated. The MMU16 origin of clones was confirmed by genetic linkage mapping. Reverse transcription PCR indicated that approximately 68% of the cDNAs represent transcripts that are expressed in adult mouse cerebellum. Northern blotting showed that some of these are predominantly or solely expressed in brain. This work demonstrates that DNA microdissected from banded MMU16 can be used for direct cDNA selection, thus enabling construction of a new, region-specific partial transcription map. This selected cDNA library should be a useful reagent for further molecular neurobiological studies.

Animals↗

PubMed1996

Microbial metabolism of pyridine, quinoline, acridine, and their derivatives under aerobic and anaerobic conditions.

Our review of the metabolic pathways of pyridines and aza-arenes showed that biodegradation of heterocyclic aromatic compounds occurs under both aerobic and anaerobic conditions. Depending upon the environmental conditions, different types of bacteria, fungi, and enzymes are involved in the degradation process of these compounds. Our review indicated that different organisms are using different pathways to biotransform a substrate. Our review also showed that the transformation rate of the pyridine derivatives is dependent on the substituents. For example, pyridine carboxylic acids have the highest transformation rate followed by mono-hydroxypyridines, methylpyridines, aminopyridines, and halogenated pyridines. Through the isolation of metabolites, it was possible to demonstrate the mineralization pathway of various heterocyclic aromatic compounds. By using 14C-labeled substrates, it was possible to show that ring fission of a specific heterocyclic compound occurs at a specific position of the ring. Furthermore, many researchers have been able to isolate and characterize the microorganisms or even the enzymes involved in the transformation of these compounds or their derivatives. In studies involving 18O labeling as well as the use of cofactors and coenzymes, it was possible to prove that specific enzymes (e.g., mono- or dioxygenases) are involved in a particular degradation step. By using H2 18O, it could be shown that in certain transformation reactions, the oxygen was derived from water and that therefore these reactions might also occur under anaerobic conditions.

Acridines↗

PubMed1996

Effects of repeated administration of a kappa-opioid agonist on phorbol ester binding to membrane-bound protein kinase C in rat brain.

The dissociation constant (KD) of [3H]phorbol 12,13-dibutyrate (PDBu) binding to protein kinase C (PKC) in membranes of rat cortex and midbrain was significantly decreased with no change in the receptor density (Bmax) following 7-d treatment with a kappa-opioid agonist, U-50,488 (20 mg/kg/d, i.p.). Neither the Bmax nor KD values in pons/medulla were altered by repeated U-50,488 treatment. These results suggest that repeated administration of a kappa-opioid agonist increases the affinity for PDBu binding to the membrane-bound PKC in rat cortex and midbrain, but not in pons/medulla.

3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cycloh↗

PubMed1996

Novel anti-inflammatory compounds prevent CD11b/CD18, alpha M beta 2 (Mac-1)-dependent neutrophil adhesion without blocking activation-induced changes in Mac-1.

Leumedins are small organic molecules with anti-inflammatory properties in vivo. We report here that leumedins inhibit the CD11b/CD18 alpha M beta 2 (Mac-1)-dependent adherence of neutrophils to serum proteins. The activation of neutrophils leading to adherence via Mac-1 is associated with an increase in cell surface Mac-1 level, and with an increased affinity of Mac-1 for adhesion partners. Inhibition of neutrophil adherence by leumedins does not require blocking the recruitment of Mac-1 from intracellular granules to the cell surface. Furthermore, leumedins do not block the expression on Mac-1 of the epitope for an "activation-specific" antibody (CBRM1/5). Time course studies show that leumedins inhibit adherence by targeting an event which occurs concurrently with changes in Mac-1 level and induction of the CBRM1/5 epitope. Therefore, leumedins block an unknown process which is permissive for Mac-1-dependent adherence.

Amino Acid Sequence↗

PubMed1996

Effects of gypenosides on cellular immunity of gamma-ray-irradiated mice.

OBJECTIVE: To investigate the effects of gypenosides (Gs) on cellular immunocompetence in the gamma-ray-irradiated mice. MATERIALS AND METHODS: Tested mice of ICR strain were treated continuously with Gs for 10 days before or after 4 Gy gamma-irradiation. Body weight and splenic weight of mice were measured. The blastogenic response of splenocytes to mitogens, such as PHA, Con A and LPS were also detected. The cellular immunocompetence was measured by 3H-thymidine incorporation in each tested mouse. RESULTS: Body weight as well as splenic weight decreased in gamma-ray-irradiated mice. The blastogenic responses of splenocytes to mitogens were inhibited after gamma-ray irradiation. To treat with Gs was effective to enhance the recovery of body weight, splenic weight and immunocompetence in gamma-ray-irradiated mice from radiation damage. CONCLUSIONS: Four Gy gamma-ray irradiation could decrease splenic weight and cellular immunocompetence of mice. Gs could help the recovery of the splenic weight and cellular immunocompetence in gamma-ray-irradiated mice.

Animals↗

PubMed1996

[Gonadotropins stimulate the proliferation of human epithelial ovarian cancer cell].

OBJECTIVE: To observe the effect of FSH and LH on the proliferation of human epithelial ovarian cancer cell. METHOD: Human epithelial ovarian cancer AO cells were incubated with follicle stimulating hormone (FSH) and luteinizing hormone (LH) (2U/L and 2.5U/L respectively). They were detected for proliferation by the use of the immunohistochemical technique and morphology. RESULTS: The positive rate of proliferating cell nuclear antigen expressed in the cancer cell was increased significantly (p < 0.05) indicating its proliferation stimulating effect by FSH. The mitosis of cancer cells was increased by FSH and by LH (35%, 16% respectively). CONCLUSIONS: It is suggested that FSH and LH can stimulate the proliferation of epithelial ovarian cancer cell, and they may play an important in the development of epithelial ovarian cancer.

Cell Division↗

PubMed1996

Secretory expression of a single-chain insulin precursor in yeast and its conversion into human insulin.

A synthetic single-chain porcine insulin precursor (PIP) gene and an alpha-mating factor leader sequence (alpha MFL) gene obtained by the PCR method are inserted between the promoter and 3'-terminating sequence of the alcohol dehydrogenase gene ADH1 in plasmid pVT102-U to form plasmid pVT102-U/alpha MFL-PIP. The single-chain insulin precursor is expressed and secreted to the culture medium by Saccharomyces cerevisiae transformed by pVT102-U/alpha MFL-PIP. The precursor is purified and converted into human insulin by tryptic transpeptidation. The purified human insulin is fully active and can be crystallized. The overall yield of human insulin is 25 mg per liter of culture medium.

Base Sequence↗

PubMed1996

Effects of hydrazine, phenelzine, and hydralazine treatment on rat hepatic and renal drug-metabolizing enzyme expression.

The hepatic and renal toxicity associated with hydrazine treatment has been linked to free radical damage resulting from oxidative metabolism by cytochrome P4502E1 (CYP2E1). Despite this association, there has been little characterization of the effects of hydrazine treatment on the expression of hepatic and renal CYP2E1 or glutathione-S-transferase-alpha (GST-alpha), an enzyme responsible for catalyzing the conjugation of free radicals with reduced glutathione. Therefore, the effects of treatment with hydrazine or one of the therapeutic hydrazines phenelzine and hydralazine on rat hepatic and renal CYP2E1 and GST-alpha expression were investigated. Adult male Sprague-Dawley rats were treated with 0.9% saline vehicle (1 dose ip), hydrazine (100 mg/kg ip), phenelzine (100 mg/kg ip), or hydralazine (25 mg/kg ip). CYP2E1 mRNA and protein levels were monitored by Northern and immunoblot analyses, respectively, and GST-alpha Ya and Yc subunit levels were determined by immunoblot analysis. Hydralazine administration caused a significant (approximately 159%) increase in renal GST-alpha subunit expression. In addition, hydrazine and phenelzine treatment produced substantial elevations (approximately 464% and 566%, respectively) in renal CYP2E1 protein, whereas hydralazine administration did not alter renal CYP2E1 expression. Changes in rat hepatic GST-alpha Ya or Yc subunit levels after treatment with hydrazines phenelzine, or hydralazine were not statistically significant. Similarly, hepatic CYP2E1 levels were not significantly altered after treatment with hydrazine, phenelzine, or hydralazine. Northern blot analysis revealed that the observed increases in renal CYP2E1 protein levels after treatment with hydrazine or phenelzine were not accompanied by concomitant increases in CYP2E1 mRNA. These results suggest that treatment with hydrazine or the therapeutic hydrazine phenelzine significantly increases the expression of rat renal CYP2E1 protein, and that the molecular mechanism responsible for these effects are posttranscriptional in nature.

Animals↗

PubMed1996

[Effects of recombinant human tumor necrosis factor on the development of ascitic tumor and expression of c-erbB2 in the nude mouse models of ovarian cancer].

OBJECTIVE: To investigate the effects of recombinant human tumor necrosis factor (rhTNF) on the growth of ascitic tumor and expression of c-erbB2 in the nude mouse models of ovarian cancer. METHODS: By intraabdominal injection, rhTNF was delivered to the peritoneal cavity of nude mouse with ovarian cancer as well as control group, after 6 days treatment, tumor cell counting and expression of c-erbB2 were detected by indirect fluorescence flow cytometry. RESULTS: There is a significant difference in tumor cell counting between the study group and control group (P < 0.01). Expression of c-erbB2 in study group was lower than that in control group. CONCLUSION: rhTNF was demonstrated to have effects on both inhibition of ascitis tumor development and down regulation of c-erbB2 expression in nude mouse with ovarian cancer.

Animals↗

PubMed1996

Effect of carboplatin based combination chemotherapy on ovarian cancer.

OBJECTIVE: To investigate the effect of carboplatin based combination chemotherapeutic regimen given intraperitoneally and intravenously on ovarian epithelial cancer. MATERIALS AND METHODS: Carboplatin based combination chemotherapy was given intraperitoneally and intravenously to 48 patients with epithelial ovarian cancer. Of them, 10 cases with ascites had received no treatment before, and 38 patients had undergone cytoreductive surgery prior to the study. RESULTS: The results of this study showed that carboplatin based combination chemotherapy could not only reduce the tumor mass but also decrease the amount of ascites (P < 0.05) in patients with ascites. The response rate was 80% (clinical complete response rate was 10%) in untreated patients with ascites. The 3-year survival rate of patients with ovarian epithelial cancer was 92.3% in stage I, and 30% in stage III patients after the cytoreductive surgery. Tumor recurrence occurred during the course of chemotherapy in 15% of stage I patients and 53.3% of stage III patients. CONCLUSION: Carboplatin based combination chemotherapy given intraperitoneally and intravenously has potent effect on untreated ovarian cancer with ascites. But carboplatin based chemotherapy could not overcome the problem of drug resistance. To improve the prognosis of ovarian cancer, much more researches on the mechanisms of drug resistance need to be carried out.

Antineoplastic Combined Chemotherapy Protocols↗

PubMed1996

[Antimicrobial properties of Flos Lonicerae against oral pathogens].

The antimicrobial effect of Flos Lonicerae on oral pathogens was studied. The results showed that 73.9% of the tested pathogens were inhibited at a concentration below 6.25mg/ml. Streptococci mutants, actinomyces viscosus and bacteroides melaninogenicus were comparatively more sensitive to Flos Lonicerae.

Actinomyces viscosus↗

PubMed1996

[The regulation of the secretion of transforming growth factor-beta 1 by estrogen on ovarian cancer AO, 3AO cell lines and its relationship with cell proliferation].

OBJECTIVE: To investigate the regulatory effect of the secretion of transforming growth factor-beta 1 (TGF-beta 1) by estrogen on ovarian cancer AO, 3AO cell lines and on cell proliferation. METHOD: The secretion of TGF-beta 1 was investigated by using western dot blot and the cell proliferation by 3H-thymidine uptake. RESULT: In vitro, AO cells under the effect of estrogen can secreted TGF-beta 1, and there was cell proliferation, but both gave dose-dependent responses. Estrogen significantly promoted the secretion of TGF-beta 1 of AO cells at low (10(-13) mol/L) and high (10(-5)mol/L) concentrations, but the level of cell proliferation showed inhibition. In contrast, in the 3AO cells under the same conditions, no difference in TGF-beta 1 secretion was found from those of the control groups, dose-dependent response was seen in cell proliferation and there was no significant correlation between the expression of TGF-beta 1 and cellular proliferation. CONCLUSION: The results suggest that there may be TGF-beta 1 autocrine loop in AO ovarian cancer cell line, which, when estrogen regulated may be associated with the cell proliferation. In 3AO cell line, under the same conditions, TGF-beta 1, autocrine is not regulated by estrogen, nor is it related to cell proliferation regulation.

Cell Division↗

PubMed1996

[Interventional treatment for partial stenosis or occlusion type of Budd-Chiari syndrome].

It is difficult to deal with interventional management of partial stenosis or occlusion type of Budd-chiari syndrome and manage the hepatic veins associated with inferior vena cave occlusion. Puncture, PTA and vascular stent plant were used to treat 12 patients with partial stenosis or occlusion of Budd-chiari syndrome. The procedures were successful. Either the symptoms or signs disappeared or relieved after operation. No severe side effects occurred. Follow-up for 1.5 through 26 months (average 8.5 months) revealed that the early or middle results were gratifying. There may be danger during operation, but perfect skills and adequate clinical anatomic knowledge help avoid severe side effects.

Adult↗