Biomedical subjects

C Chen

Publications and source records attributed to C Chen.

At least 541 records · Page 30Linked to original sources

PubMed1999

[Studies on allozyme of Gammatricula].

AIM: To furnish molecular genetic evidences for taxonomy of Gammatricula. METHODS: A total of 24 enzymes of 6 populations of Gammatricula songi and 1 population of Gammatricula chinensis collected from Kaihua County and Chunan County of Zhejiang Province were studied using horizontal starch gel electrophoresis. RESULTS: 29 loci were found. The percentages of polymorphic loci of G. songi populations were 6.9%-13.8%. All loci of G. chinensis were monomorphic. The Nei's distance among G. songi populations did not exceed 0.12. The Nei's distance between G. songi and G. chinensis was 0.73. CONCLUSION: The allozyme variations of inter-G. songi are limited, but the allozyme variation between G. songi and G. chinensis is significant.

Alleles↗

PubMed1999

[Studies on allelic zymogram of periodic Brugia malayi from Zhejiang Province].

AIM: To study the allelic zymogram of periodic B. malayi from Zhejiang Province. METHODS: 180 adult worms(male 60, female 120), 32,000 microfilaria and 1,500 infective larvae of periodic B. malayi were examined for the isoenzymes of 14 enzymes by horizontal starch gel electrophoresis with 14 different isomyme. RESULTS: Twenty-seven allelic loci were found in three developing stages of B. malayi, most of them were homozygotes, however, two of them(MPI,MDH) were heterozygotes(7.4%). 17, 19 and 9 loci were presented in adult worms, microfilariae and infective larvae, respectively. At the same time, the allelic zymogram of B. malayi from Guizhou Province was also examined. CONCLUSION: The allelic zymogram of periodic B. malayi from Zhejiang Province was similar to that of periodic B. malayi from Guizhou Province but passaged in the laboratory.

Animals↗

PubMed1999

[Preparation of the high-titer retroviral viruses for transducting PDGF-A gene].

OBJECTIVE: To prepare high-titer recombinant retrovirus for transducting platelet-derived growth factor A chain(PDGF-A) gene, which will pave the way for future research in vitro and in vivo on biological function of autocrine and paracrine of PDGF-A gene expression product. METHODS: The cDNA fragment of human PDGF-A was inserted into the polyclonal sites of retroviral vector GINa containing cytomegalovirus (CMV) promotor. The constructed recombinant plasmid was transformed into PA317 packaging cell line. The positive clones were obtained by selection in G418-medium and amplified. The supernatant virus was used to infect NIH3T3 cells and titrated. After drug resistance selection, NIH3T3 cell clones were amplified, and a histochemical analysis was performed. SDS-PAGE electrophoresis and Western blot as well as 3H-TdR incorporation methods were adopted to assay the presence and the mitogenic activity of the PDGF in the conditioned medium. RESULTS: The highest titer of the virus was 1.4 x 10(5) CFU/ml. The PDGF-A expression was verified with SDS-PAGE electrophoresis and Western blot and immunofluorescent staining. The cell mitogenic activitiy in the media was up to 51.2 U/(10(6).d). CONCLUSIONS: We had made high-titer recombinant retrovirus for transducting human PDGF-A gene. The gene was expressed with high efficiency. The expressed product has significant mitogenic effect on NIH3T3 cell line.

Cytomegalovirus↗

PubMed1999

[Studies of Echinopsis multiplex on antineoplastic effects].

Fresh Echinopsis multiplex decoction(p.o. 30 g/kg and 60 g/kg) could inhibit the growth of solid tumour S180 and Lewis pulmonary carcinoma, prolong the survival date of the mice with the tumours. In vitro, the serum of animal, which took the herb, significantly suppressed the proliferation of EAC tumour cells and inhibited the YAC-1 tumour cell DNA synthesis when compared with the serum of normal animal. The decoction did not reduce the WBC, but increased the number of PFC of spleen cells at the effective dose in mice with tumour, indicating that it did not impair the immune system, but enhance the immune function.

Animals↗

PubMed1999

[Flotation spectrophotometric determination of copper on isochromatic dye ion pair with crystal violet and bromopnenol blue].

Bromophenol blue (BPB) was produced and entered into the aqueous phase when NaOH solution of pH = 10 was added to Cu(biq)2BPB by trichloromethane and isoamyl alcohol (20:1) extractive. And then CV x BPB was floated by crystal violet (CV) with benzene solution. The flotation was dissolved in ethanol and the absorbance of the solution measured at 590 nm. The sensitivity was raised because of the two dyes assistant effect. The molar absorptivity was 1.45 x 10(5) L x mol(-1) x cm(-1). Copper in the sample was separated first by extracting the Cu(biq)2BPB complex with trichloromethane and isoamyl alcohol, thus achieving a high selectivity. Beer's law was obeyd in the range of 0-0. 4 mg/L with a relative standard deviation of 3.6%. For 4.8 x 10(-8) g/mL copper solution, the recoveries were 97.8%-101.7%.

Bromphenol Blue↗

PubMed1999

[Study on laser flash spectroscopy of laser-induced interaction of DNA and polynucleotides with SO4*-].

The interactions of DNA and polynucleotides (poly[G],poly[A] and poly[C]) with SO4*- were investigated by 248 nm laser flash photolysis. The results show that, the reactions of poly[G] or poly[A] with SO4*- yield predominantly the corresponding one-electron-oxidated base radicals. With poly[C], it is suggested that SO4*- radical reacts predominantly by addition to the base moiety to produce C5-yl and C6-yl sulphate radical adducts,and subsequently H-abstraction yields C2'-sugar radical. The predominant species resulting from the reaction of DNA with SO4*- is DNA guanyl radical.

DNA↗

PubMed1999

[Determination of 14 elements in chromium-rich brewer's yeast by ICP-AES].

An ICP-AES method was established for the determination of 14 elements in chromium-rich and normal brewer's yeast. The RSDs of two standard reference materials were 0. 5%-3.2% and 0.4%-3.4%, respectively. The results showed that chromium contents could affect the concentrations of other elements in chromium-rich brewer's yeast. The concentrations of K, Mn, P, V, Mg and Ca in chromium-rich brewer's yeast were significantly lower than those in normal brewer's yeast.

Chromium↗

PubMed1999

[Floatation spectrophotometric determination of metals with isochromatic dye ion-pairs tetrabromofluorescein-rhodamine 6G system].

The floatation spectrophotometric determination of germanium, platinum and ferrum with isochromatic dye ion-pairs formed by tetrabromofluorescein (TBF) and rhodamine 6G (R6G) is described. The association complexes of these metallic ions with rhodamine 6G floated with organic solvent were first allowed to react on basicity, and then on tetrabromofluorescein which is of the same color as rhodamine 6G. The isochromatic dye ion-pairs of R6G x TBF were floated with toluene. The floatation R6G x TBF in acetone was dissolved and the absorbance of the solution at 530 nm was measured. The sensitivity is raised because of the 2 m dyes. The molar absorptivities for Ge, Pt and Fe are greater than 10(5) L mol(-1) cm(-1).

English Abstract↗

PubMed1999

[Study on laser flash spectroscopy of processes of photoionization of tyrosine: pH effects].

The processes of photoionization of tyrosine on three different pH value solutions were investigated by 248 nm laser flash photolysis. The results showed that the processes of photoionization of tyrosine were affected by pH value of the solution. With pH value increasing, the molecule number of photoionization increases via a monophotonic process, and decreases via a biphotonic process. Furthermore, the pH effect of photoionization of tyrosine resulting from deprotonation of phenolic hydroxyl group in alkaline solution was demonstrated.

Hydrogen-Ion Concentration↗

PubMed1999

[Studies on the infrared spectra of mico2-OR or micro2-SR-bridged double-cubane-like clusters containing MoFe3S4 cores].

The IR spectra of micro2-OR or micro2-SR- bridged double-cubane-like clusters containing MoFe3S4 cores (Et4N)3 [Mo2Fe6S8Cl6 (OMe)3] (1), (Et4N) [Mo2Fe6S8 (SPh)6 (OMe)3 (2), (Bu4N)3 Mo2Fe6S (SPh)6 (OMe)3] (3), (Et4N)3 [Mo2Fe6S8 (SBu(t))6(OMe)3](4), (Et4N)3[Mo2Fe6S8 (SPh)9](5) have been investigated. Their characteristic frequencies (v)Mo-micro2O(R), (v)Mo-micro2S(R), (v)Mo-S, (v)Fe-S*, (v)Fe-SR, (v)Fe-Cl were assigned by comparing their vibrational frequencies with their structural parameters and by comparing the IR spectra of them with that of the linear clusters. The electrophilic induced effects in different way and the relationship between deltav (i.e. (v)Mo-S* (v)Fe-S*) and Fe --> Mo charge transfer have been discussed. Finaly, the sameness and difference between the double-cubane-like and linear Mo-Fe-S clusters were demonstrated.

English Abstract↗

PubMed1999

Colorectal adenomatous and hyperplastic polyps: smoking and N-acetyltransferase 2 polymorphisms.

Arylamine N-acetyltransferase 2 (NAT2) is involved in both the detoxification and bioactivation of carcinogenic arylamines and other mutagens. This enzyme is polymorphic, and the fast and slow phenotypes are thought to be risk factors for colon and bladder cancer, respectively. Here, we report on a case-control study of adenomatous and hyperplastic polyps, with particular attention to tobacco smoking, a known risk factor for adenomas, and polymorphisms of NAT2. All participants underwent complete colonoscopy and were subsequently divided into case and control groups on the basis of pathology. Cases were diagnosed with confirmed adenomas (n = 527) or hyperplastic polyps (n = 200); controls (n = 633) had no history of colonic neoplasia and no polyps at colonoscopy. NAT2 genotype was determined using an oligonucleotide ligation assay and fast, intermediate, or slow phenotype imputed. Multivariate-adjusted odds ratios (ORs) and 95% confidence intervals were computed using logistic regression adjusting for age, sex, nonsteroidal anti-inflammatory drug use, and hormone replacement therapy use. Smoking was associated with an increased risk of adenomas [current versus never smoking OR = 2.0 (95% confidence interval, 1.4-2.9)] and hyperplastic polyps [current versus never smoking OR = 4.1 (2.6-6.5)]. NAT2 status among adenomatous polyp patients and hyperplastic polyp patients, respectively, showed ORs of 1.1 (0.8-1.4) and 1.2 (0.8-1.6; intermediate versus slow) and 1.1 (0.6-1.9) and 0.9 (0.4-1.9; fast versus slow). There were no differences in risk when adenoma patients were stratified on multiplicity, size, or histopathological subtype of polyps. Never-smokers showed no variation in risk across acetylator status for either species of polyp, whereas current smokers showed ORs of 2.0 (1.2-3.2) and 2.3 (1.4-3.9) for adenomas and 3.9 (2.1-7.1) and 4.9 (2.6-9.4) for hyperplastic polyps for slow and intermediate/fast NAT2, respectively, compared with slow-NAT2 never-smokers. Risks of both multiple [OR = 4.3 (2.1-8.8)] and large [OR = 3.8 (1.9-7.5)] adenomas were somewhat elevated in current smokers with an intermediate/fast phenotype compared with smokers with a slow NAT2 phenotype, but the interaction was not statistically significant. Risk of hyperplastic polyps and adenomatous polyps is strongly related to smoking. There is little suggestion of interaction between NAT2 status and smoking and no relationship with NAT2 genotype alone.

Adenomatous Polyps↗

PubMed1998

Palmitoylation of the rat mu opioid receptor.

We examined whether the mu opioid receptor was palmitoylated and attempted to determine sites of palmitoylation. Following metabolic labeling with [3H]palmitic acid and immunoaffinity purification of the mu opioid receptor, SDS-PAGE and fluorography revealed a broad labeled band with Mr of approximately 80 kDa in CHO cells stably expressing the rat mu receptor, but not in CHO cells transfected with the vector alone, indicating that the mu receptor is palmitoylated. Activation of the receptor with morphine did not affect the extent of palmitoylation. Hydroxylamine or dithiothreitol treatment removed most of the radioactivity, demonstrating that [3H]palmitic acid is incorporated into Cys residue(s) via thioester bond(s). Surprisingly, mutations of the only two Cys residues in the C-terminal domain did not reduce [3H]palmitic acid incorporation significantly. Thus, unlike many G-protein coupled receptors, the palmitoylation site(s) of the rat mu opioid receptor do(es) not reside in the C-terminal domain.

Amino Acid Sequence↗

PubMed1998

A dielectric omnidirectional reflector

A design criterion that permits truly omnidirectional reflectivity for all polarizations of incident light over a wide selectable range of frequencies was used in fabricating an all-dielectric omnidirectional reflector consisting of multilayer films. The reflector was simply constructed as a stack of nine alternating micrometer-thick layers of polystyrene and tellurium and demonstrates omnidirectional reflection over the wavelength range from 10 to 15 micrometers. Because the omnidirectionality criterion is general, it can be used to design omnidirectional reflectors in many frequency ranges of interest. Potential uses depend on the geometry of the system. For example, coating of an enclosure will result in an optical cavity. A hollow tube will produce a low-loss, broadband waveguide, whereas a planar film could be used as an efficient radiative heat barrier or collector in thermoelectric devices.

Journal Article↗

PubMed1998

A snake toxin inhibitor of inward rectifier potassium channel ROMK1.

Mamba snake dendrotoxins have been used extensively in biochemical and physiological studies of K+ channels of the brain. Their known targets of inhibition have been limited to the family of voltage-gated K+ channels. We report the isolation of a dendrotoxin inhibitor of ROMK1, a channel belonging to the inward rectifier family of K+ channels. The inhibitory activity, fractionated to purity with FPLC and HPLC, is identical to a previously identified delta-dendrotoxin. To verify that delta-dendrotoxin blocks ROMK1 channels, a cDNA encoding the toxin was synthesized and recombinant toxin expressed in Escherichia coli. Electrophysiological recordings reveal that recombinant delta-dendrotoxin has a half-maximal inhibition constant (Kd) of 150 nM when applied to ROMK1 channels expressed in Xenopus laevis oocytes. That the delta-dendrotoxin binding site exists on separate K+ channel classes is shown by its high affinity for two of the voltage-gated family of channels, Kv1.1 (Kd < 0.1 nM) and Kv1.6 (Kd = 23 nM). Single amino acid substitutions in ROMK1 indicate that delta-dendrotoxin binds to the pore region of ROMK1 even though it does not completely block conduction through the pore. These results suggest that dendrotoxins inhibit K+ channels by recognizing the structurally conserved pore region of these channels.

Amino Acid Sequence↗

PubMed1998

[Studies on the Ras p21 levels in workers exposed to coal tar pitch and coke oven volatiles].

To study the effects of serum p21 levels on the health of coal tar pitch(CTP) and coke oven volatiles (COV) workers recognized as the high risk population of pulmonary carcinoma, serum p21 levels among 24 cases of CTP workers, 25 cases of COV workers and 12 cases of normal control were detected with the method of Western Blotting. The results showed that the mean serum p21 level in exposed group was significantly higher than that in the normal control (366.8 vs 1270.7, P < 0.001). In the COV workers, serum p21 level in coke furnace workers was remarkably higher than that in the workers with other types of work. There were no differences for p21 among workers with different work years and between workers with or without smoking history. It indicates that CTP and COV can cause the p21 protein level increase in the occupational population.

Adult↗

PubMed1998

[Epidemiological study of airway responsiveness on the patients with asthma].

The analysis of date on 641 nuclear families with asthma declared that the sensity and specify of the airway responsiveness with Methecholone(MTCH) Challenge Test for the clinical diagnosis of asthma is 72 percent and 70 percent. The population with airway hyperresponsiveness was 6.01 times higher risk to asthma than one of negative airway responsiveness. The OR of male and female for asthma was 4.97, 5.06, respectively, and was statistically significant (P < 0.01). Moreover, the risk of asthma was been increasing with MTCH concentration was increased (i.e. degree of airway responsiveness decreased) step by step, as well showed the lineage trend between the asthma and airway responsiveness significantly (P < 0.01). The Measurement of airway responsiveness play an important role in clinic and prevent medicine.

Adolescent↗

PubMed1998

Expression of beta1,4-galactosyltransferase in the development of mouse brain.

Beta1,4-galactosyltransferase (GalTase, EC 2.4.1.38) transfers galactose to the terminal N-acetylglucosamine of complex-type N-glycans, which have great importance for cell-cell interactions during fertilization and early embryogenesis. In this study, the activity of beta1,4-galactosyltransferase in mouse brain during development was measured with the method of reverse HPLC using a fluorescence-labeled biantenary sugar chain, GlcNAcbeta1-2Manalpha1-6(GlcNAcbeta1-2Manalpha1- 3) Manbeta1-4GlcNAcbeta1-4GlcNAc-PA. The level of messenger RNA of this enzyme during the development of mouse brain was also investigated with Northern blot analysis. The results showed that: (1)beta1,4-galactosyltransferase showed similar branch specificity and kinetics for the biantenary substrate during development; (2) GalTase activity in fetal mouse brain was four times higher than that in adult mouse brain and decreased gradually in the course of development; (3) messenger RNA level was highest in fetal mouse and decreased dramatically after birth. However, the contents of mRNA were not parallel to the enzyme activity.

Animals↗

PubMed1998

Developmental enhancement of secretory response to isoproterenol coupled with increases in beta-adrenoceptor density and Gs protein function in rat parotid tissues.

The beta-adrenergic agonist, isoproterenol (IPR), stimulated more significantly and sensitively amylase secretion from both the tissues of 7- and 56-day-old rats than a cholinergic agonist, carbachol, at the same concentration. The EC50 value of amylase secretion with IPR decreased significantly during development but that with carbachol did not change. Estimation by measuring bindings of [3H]dihydroalprenolol and [3H]quinuclidynylbenzylate indicated the marked increases in the numbers of both beta-adrenoceptors and muscarinic receptors in the tissues during development. The affinity of beta-adrenoceptors for the agonist was also enhanced during development, but that of muscarinic receptors for the agonist was not. These developmental changes in the number and affinity of beta-adrenoceptors and muscarinic receptors paralleled those in amylase secretory response of the tissues to their agonists. The response of adenylate cyclase (AC) of the tissues to 1 microM IPR was steadily enhanced after birth. In contrast, the response of AC to 1 microM forskolin was high until 14 days old, but markedly decreased at 28 days old and thereafter maintained this level. The increase in cholera toxin-catalyzed ADP-ribosylation (AR) of stimulatory GTP binding proteins (Gs proteins) in the tissues was apparent at 14 days old, reaching a maximum at 56 days old and thereafter decreasing with age. On the other hand, pertussis toxin-catalyzed AR of inhibitory GTP binding proteins (Gi proteins) did not change after birth. Thus, the ratio of apparent levels of Gs to Gi proteins increased significantly after birth, reaching a maximum at 56 days old, but decreased rapidly till 84 days old and thereafter maintained this level. These changes in the ratio paralleled those in the response of AC to IPR. These results showed that the rapid and marked increases in the number and affinity of beta-adrenoceptors and the ratio of apparent levels of Gs to Gi proteins in rat parotid tissues during development had a key role in the enhancement of the secretory response of the tissues to beta-agonists.

Adenosine Diphosphate Ribose↗