PubMed Health⌕ Search

Biomedical subjects

D M Zhou

Publications and source records attributed to D M Zhou.

15 recordsLinked to original sources
PubMed2001

Catalytic effect of soil colloids on the reaction between CrVI and p-methoxyphenol.

Adsorption of CrVI and p-methoxyphenol (PMP) on soil colloids at different pH media was studied. The resulting k1 and n of 1.89 x 10(2) and 0.53 (r2 = 0.99) and k2 and b of 0.13 and 1.25 x 10(3) (r2 = 0.96) were obtained from Freundlich (Q = k1Caqn) and Langmuir [Q = k2bCaq/(1 + k2Caq)] simulation equations, respectively, for CrVI adsorption on soil colloids (pH 4.20). The adsorption of PMP on soil colloids in pH 5.72 media was simulated by five different equations and the results indicated that the Fritz-Schluender one (r2 = 1.00) was the most suitable among them. Adsorption quantity of CrVI and PMP on colloids increased with increasing acidity in the pH range of 3.5-9.0. Study of CrVI adsorption kinetics indicated that the adsorption equilibrium of CrVI was reached rapidly within 2 h. In pure aqueous solution, CrVI reduction by PMP was observed only when the media's pH was lower than 4.0. Oxidation and reduction reaction between CrVI and p-methoxyphenol obviously occurred when soil colloids were involved in this system, even at pH > or = 7.0, which strongly suggested that minerals in soil colloids acted as catalysts to speed the reaction of CrVI and PMP. The oxidized product of PMP by CrVI, extracted by chloroform in acid media and analyzed by gas chromatography-mass spectrometry, was identified as benzoquinone. The reaction included two steps of one electron process.

Adsorption↗
PubMed2001

Interaction of Cd and citric acid, EDTA in red soil.

Adsorption and desorption process of cadmium in red soil (Ferrisols) as well as the influence by media's pH were investigated in detail with and without citric acid and EDTA. Experimental results clearly showed that Cd adsorption in red soil was affected significantly by the coexisted organic chemicals. In the presence of citric acid and EDTA, Cd adsorption in red soil increased with pH in acid media but decreased in high pH one. Further studies placed stress on the adsorbed Cd in red soil which was found to be existed mainly as exchangeable one at pH < 5.5, and desorption rate by 0.10 mol/L NaNO3 gave a peak-shaped curve due to the difference of specifically and nonspecifically adsorbed Cd with pH's change.

Adsorption↗
PubMed2001

[HLA-DRB1 gene polymorphism of Naxi ethnic group of Yunnan Province, China and its ethnological evolution analysis].

The HLA-DRB1 gene polymorphism of Naxi ethnic group of Yunnan Province, China was investigated for the first time using high resolution PCR-SBT method, which is based on sequences of HLA-DRB1 Intron 1 and Intron 2 with our improvement. From 60 individuals of Naxi 37 DRB1 alleles were detected. The distribution of allele frequencies is evenly spread for most of alleles detected in Naxi. However, the gene frequency for HLA-DRB1 * 12021 is 17.50%. The other common alleles (> 5%) were HLA-DRB1 * 1404(7.50%), 1504(5.83%), 04051(5.83%), 08032(5.83%), 09012(5%), 03011(5%), and they covered 35% of the total alleles detected from Naxi, and 52.49% after adding the frequency of HLA-DRB1 * 12021. HLA-DRB1 * 0305, 0438, 1123, 1132, 1310, 0812 were detected in Chinese for the first time, and were very rare in other ethnic groups worldwide. Using the HLA-DRB1 gene frequencies of various ethnic groups, we constructed the phylogenetic tree by Fitch-Margoliash and Least-Squares Distance Methods and Cavalli-Sforza's chord measure of genetic distance. In our dendrogram, the South China populations were clustered together, and Siberian, Japanese and Minority of North China were clustered together, in which two big clusters we thought represented the ancient Southern and Northern Mongolian. Our results showed Naxi was clustered with Lahu and Yao ethnic groups, which were in the cluster of South China population. Obviously Naxi belongs to the South China ethnic groups and can't trace its origin from northern ethnic groups with the HLA-DRB1 genetic data. But based on Naxi's historical folklore, it was down to Southern China from Northwest China. The preliminary analysis about its origin conundrum was discussed in this paper based on our genetic data in relationship with its history and ethnology studies.

China↗
PubMed2001

[Immunity against Schistosoma japonicum induced by phage display peptides mimicking antigenic epitopes of Trichinella spiralis].

OBJECTIVE: To obtain the short peptides mimicking antigenic epitopes of Trichinella spiralis (T. s.), and explore their cross protective immunity against Schistosoma japonicum (S.j.) in mice. METHODS: IgG antibodies were purified from sera of mice infected with T.s.. The purified IgG was used to immunoscreen a phage random peptide library of 7 amino-acid residues displayed as a fusion to protein of filamentous phage. Positive clones were obtained by affinity selection, the reactivity of each clone binding to specific IgG was detected by ELISA. Kunming mice were immunized subcutaneously three times with mixed phage clones. The mice were sacrificed 45 days after challenge. The worms and the liver eggs were counted. RESULTS: After three rounds of panning, the relevant phages had been enriched approximately 150 times in production as compared to those from the first round. Of 24 phage clones randomly selected from the third round biopanning, 21 clones were shown to actually bind to the specific IgG. As compared with the control group, the worm and the liver egg reduction rates in vaccination group were 42.8% and 66.3% (P < 0.001), respectively. CONCLUSION: The above results demonstrate that antigenic epitopes of T. s. can be prepared by immunoscreening phage random peptide library and a significant protective immunity against S. j. can be induced by these epitopes in mice.

Animals↗
PubMed2001

[Cloning and characterization of three novel genes encoding transmembrane proteins of Schistosoma japonicum].

OBJECTIVE: To clone and analyze novel antigen molecules of Schistosoma japonicum (Sj), and to provide effective vaccine candidate antigens against schistosomiasis japonica. METHODS: Sj adult cDNA library was screened using sera of mice infected with Trichinella spiralis (Ts) and the inserts of positive clones were specifically amplified by PCR. The positive clones were sequenced and the sequence data were analyzed using Nucleotide BLAST software of NCBI and Expert Protein Analysis System of Swiss Institute of Bioinformatics. RESULTS: Nine positive clones were obtained after three rounds of immunoscreening. The size of these inserts ranged from 0.6 kb to 2.1 kb. Among five novel genes, Sj-Ts1, Sj-Ts3 and Sj-Ts5 (GenBank accession number: AY005816, AF299080 and AY024352, respectively) encode trans-membrane proteins with 83, 83 and 233 amino acids, respectively. Sj-Ts1 protein predicted contains one possible trans-membrance helix, one N-myristoylation site, two phosphorylation sites for protein kinase C and one for tyrosine kinase, Sj-Ts3 protein contains two possible transmembrance helices and one casein kinase II phosphorylation site, whereas Sj-Ts5 protein has five possible transmembrance helices, one N-glycosylation site, one N-myristoylation site, two phosphorylation sites for cAMP- and cGMP-dependent protein kinase and four for protein kinase C and one for casein kinase II. CONCLUSION: Three novel genes encoding three transmembrane proteins might be developed as new vaccine candidates against Sj infection.

Amino Acid Sequence↗
PubMed2000

[Immunoscreening of Schistosoma japonicum adult worm cDNA library by sera from rabbits vaccinated with ultraviolet-attenuated cercariae].

OBJECTIVE: To find out the major antigenic molecules of radiation-attenuated cercariae, and provide some useful candidate antigens for developing schistosomiasis vaccine. METHODS: Schistosoma japonicum (Sj) adult worm cDNA library was screened by sera of rabbits vaccinated with ultraviolet-attenuated cercariae, and the inserts of positive clones were specifically amplified by PCR and sequenced. RESULTS: Ten positive clones were obtained after three rounds of screening, and the size of Sj cDNA fragments of the positive clones ranged from 1.5 kb to 1.8 kb. Five partial sequences were got after preliminary sequencing. Two of them had significantly homology with Sj dynein light chain 5(DLC 5) gene and Sj mitochondrial gene, respectively, and the others were identified as partial sequences of novel genes for they showed only partial homology with non-schistosome genes or other organism in the database. CONCLUSIONS: The positive clones may be the genes encoding the antigens that can elicit protective immunity against Sj.

Animals↗
PubMed2000

[Research on mental health status of 726 adolescents and its influential factors].

Mental health status of 726 adolescents and their backgrounds were investigated with Symptom Check List(SCL-90) and self-designed questionnaire. The results showed that the prevalence rate of psychological problems ranged from 6.34% to 24.93%. Among these problems, obsession led all the others. Females had higher scores in interpersonal sensitivity, depression, anxiety, phobia than males. Logistic regression analysis indicated that the major factors contributed to mental health status of adolescents were the relationship between teacher and student, father's concern with his child, only child or not, parents' expectations, personality and sex. The study provides reference source for improving the mental health status of adolescents.

Adolescent↗
PubMed1998

Explanation by a putative triester-like mechanism for the thio effects and Mn2+ rescues in reactions catalyzed by a hammerhead ribozyme.

Divalent metal ion-dependent hammerhead ribozymes can cleave any RNA with a NUX triplet, wherein the N can be any residue and X can be C, U or A. In recent literature on the mechanism of action of hammerhead ribozymes, one important role of divalent metal ions is generally suggested to be an electrophilic catalyst by directly coordinating with the pro-Rp oxygen of the scissile phosphate to stabilize the transition state. This proposal was made on the basis of thio effects and the proposed electrophilic catalyst is very attractive as an explanation for the catalytic activity of metalloenzymes. Reexamination of thio effects with substrates having a GUA triplet at the cleavage site shows that, in agreement with the previous finding, the cleavage rate, in the presence of Mg2+ ions, is significantly reduced in the case of the phosphorothioate substrate (RpS), wherein the pro-Rp oxygen at the scissile phosphate is replaced by sulfur, while the cleavage rate is reduced to a much lesser extent for the other isomer (SpS), wherein the pro-Sp oxygen at the scissile phosphate is replaced by sulfur. However, more careful examination of the rescue ability of Mn2+ ions with these isomers demonstrates that more thiophilic Mn2+ ions rescue the reaction not only with the RpS isomer but also with the SpS isomer and, importantly, to a greater extent for the SpS isomer. These results argue against the previous conclusion that a metal ion is directly coordinating with the pro-Rp oxygen of the scissile phosphate to stabilize the transition state. In this paper we try to elucidate the possible origin of the thio effects and propose a 'triester-like' mechanism in reactions catalyzed by hammerhead ribozymes.

Catalysis↗
PubMed1997

Explanation by the double-metal-ion mechanism of catalysis for the differential metal ion effects on the cleavage rates of 5'-oxy and 5'-thio substrates by a hammerhead ribozyme.

In a previous examination using natural all-RNA substrates that contained either a 5'-oxy or 5'-thio leaving group at the cleavage site, we demonstrated that (i) the attack by the 2'-oxygen at C17 on the phosphorus atom is the rate-limiting step only for the substrate that contains a 5'-thio group (R11S) and (ii) the departure of the 5' leaving group is the rate-limiting step for the natural all-RNA substrate (R11O) in both nonenzymatic and hammerhead ribozyme-catalyzed reactions; the energy diagrams for these reactions were provided in our previous publication. In this report we found that the rate of cleavage of R11O by a hammerhead ribozyme was enhanced 14-fold when Mg2+ ions were replaced by Mn2+ ions, whereas the rate of cleavage of R11S was enhanced only 2.2-fold when Mg2+ ions were replaced by Mn2+ ions. This result appears to be exactly the opposite of that predicted from the direct coordination of the metal ion with the leaving 5'-oxygen, because a switch in metal ion specificity was not observed with the 5'-thio substrate. However, our quantitative analyses based on the previously provided energy diagram indicate that this result is in accord with the double-metal-ion mechanism of catalysis.

Animals↗
PubMed1997

Selection of RNA aptamers that bind specifically to the NS3 protease of hepatitis C virus.

The RNA genome of human hepatitis C virus (HCV) is translated into a large precursor polyprotein. The NS3 protease of HCV has a crucial role in the processing of the polyprotein into functional viral proteins. We have used an in vitro genetic-selection strategy to isolate high-affinity RNA aptamers that bind to the NS3 protein, especially to its protease domain. Starting from a RNA pool that had a random sequence core of 12-18 nucleotides, aptamers that bind specifically to the NS3 protein were selected after 10 rounds of selection and amplification. A single aptamer, 10G-1, was found predominantly (71%) in the selected pool. This aptamer could bind to the NS3 protein with a binding constant of 650 nM and inhibit the proteolytic activity in vitro. By phosphate-modification-interference analysis we showed that the phosphate residues that are critical for the binding of 10G-1 to NS3 lie within the selected regions of the aptamer and that binding involves electrostatic contacts with the phosphates of regions G28-U34 and A47-A55. The NS3-binding region in 10G-1 can serve as a basis for designing more potential inhibitors of the NS3 protein.

Base Sequence↗
PubMed1994

A first look at biosensors.

This is a very elementary guide to biosensors, outlining the principles of operation of some optoelectronic and current measuring biosensors. Factors which can influence successful translation to the marketplace are addressed.

Journal Article↗
PubMed1992

Peritoneal reflections of left perihepatic region: radiologic-anatomic study.

To clarify the anatomy of the peritoneal reflections of the left perihepatic region, the authors examined 95 cadavers. Thirty-eight were studied radiographically, 37 with sagittal dissection, and 20 with transverse dissection. In over 80% of the cadavers, the left triangular ligament of the liver separated the left suprahepatic space into anterior and posterior sections. The lesser omentum extended to the diaphragm, where its anterior layer reflected and continued as the posterior layer of the left triangular ligament. Thus, the posterior left suprahepatic space and the lesser sac were clearly separated by the lesser omentum and the stomach and over-lapped each other in three dimensions. The posterior left suprahepatic space was located anterosuperior to the lesser sac and in turn was continuous with the gastrohepatic space inferiorly. Carefully researched diagrams of both the midline sagittal and left parasagittal perihepatic spaces were developed. This information has clinical value when the radiologist is called on to drain a left perihepatic abscess.

Humans↗
PubMed1991

Chimeric and truncated gCap39 elucidate the requirements for actin filament severing and end capping by the gelsolin family of proteins.

gCap39 is an actin filament end-capping protein which has a threefold repeated domain structure similar to the N-terminal half of gelsolin. However, unlike gelsolin, gCap39 does not sever actin filaments and dissociates completely from filament ends after calcium removal. We have capitalized on these differences to explore the structural basis for actin filament capping, severing, and their regulation. Using truncated gCap39, generated by limited proteolysis or deletion mutagenesis, we found that actin filament capping requires multiple gCap domains, and almost the entire molecule is necessary for optimal activity. gCap39 domain I, like the equivalent domain in gelsolin, contains an actin monomer binding site. gCap39 domains II-III are, however, different from gelsolin in that they do not bind to the side of actin filaments. Since filament side binding is hypothesized to be the first step in severing, lack of side binding may explain why gCap39 does not sever. This is confirmed directly by swapping gCap39 domains II-III for the side-binding gelsolin domains to generate a chimera which severs actin filaments. The chimera is Ca2+ independent in actin filament severing and capping, although gCap39 domain I itself is regulated by Ca2+.

Actins↗
PubMed1989

Time-resolved fluorescence studies on NADH bound to mitochondrial malate dehydrogenase.

Time-resolved fluorescence studies on the emission of NADH bound to porcine heart mitochondrial malate dehydrogenase [S)-malate:NAD+ oxidoreductase, EC 1.1.1.37), in the presence and absence of saturating levels of hydroxymalonate, were carried out. The lifetime of NADH bound in the ternary complex was determined to be 9.5 ns compared to 1.74 ns as reported in the literature. Steady-state and dynamic polarization data indicated a Debye rotational relaxation time in the range of 106-109 ns for the dimeric enzyme. This value is significantly larger than that calculated for a spherical protein and is consistent with the asymmetric dimer found by crystallographic studies.

Animals↗