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Biomedical subjects

W Yan

Publications and source records attributed to W Yan.

At least 163 records · Page 9Linked to original sources
PubMed1995

tinman, a Drosophila homeobox gene required for heart and visceral mesoderm specification, may be represented by a family of genes in vertebrates: XNkx-2.3, a second vertebrate homologue of tinman.

tinman is a Drosophila Nk-homeobox gene required for heart and visceral mesoderm specification. Mutations in tinman result in lack of formation of the Drosophila heart, the dorsal vessel. We have isolated an Nk-homeobox gene from Xenopus laevis, XNkx-2.3, which appears by sequence homology and expression pattern to be a homologue of tinman. The expression pattern of XNKx-2.3 both during development and in adult tissues partially overlaps with that of another tinman homologue, Csx/NKx-2.5/XNkx-2.5. We have found that embryonic expression of both XNkx-2.3 and XNkx-2.5 is induced at a time when cardiac specification is occurring. XNkx-2.3 is expressed in early cardiac primordia before the expression of a marker of cardiac differentiation. XMLC2, as well as in pharyngeal endoderm. In adult tissues, XNkx-2.3 is expressed in the heart and several visceral organs. As the helix-loop-helix factor Twist is thought to regulate tinman expression in Drosophila, we have compared the expression of XNkx-2.3 and Xtwist during embryonic development in Xenopus. There appears to be no overlap in expression patterns of the two RNAs from the neurulae stages onward, the first time at which the RNAs can be visualized by in situ hybridization. The overlapping expression patterns of XNkx-2.3 and mNkx-2.5/XNkx-2.5 in conjunction with evidence presented here that other Nk-homeodomains are expressed in adult mouse and Xenopus heart suggests that tinman may be represented by a family of genes in vertebrates.

Alleles↗
PubMed1995

[Constituents of lignanoids in Siphonostegia chinensis Benth].

A trace monomeric compound was isolated from the aerial part of Siphonostegia chinensis, and determined by X-ray diffraction as a lignanoid compound named syringaresinol. It is obtained from this plant as well as from Scrophulariaceae for the first time.

Drugs, Chinese Herbal↗
PubMed1995

tRNA selection by a class II aminoacyl-tRNA synthetase: the role of accessory domains and inter-domain communication in RNA recognition.

We have used a secondary site suppression approach to investigate the basis of tRNA selection by the E. coli histidyl-tRNA synthetase. This enzyme recognizes a unique G-1:C73 base pair located in the acceptor stems of prokaryotic histidyl-tRNAs. A genetic selection system was constructed in which growth on glycerol was dependent on histidine specific amber suppression of a triose phosphate isomerase (tpi) gene containing an amber codon at His 95. Three independent revertants linked to hisS were isolated and sequenced, and the resulting mutant proteins were characterized biochemically. These studies are interpreted in light of the x-ray structure of the E. coli HisRS adenylate complex, and show that the C-terminal domain and its interactions with the catalytic domain play a biologically significant role in tRNA selection.

Binding Sites↗
PubMed1995

[A study on behavioural characteristics of staying on the mountain and its relationship with malaria infection in Li and Miao minorities in Hainan Province].

A study of sociology combined with epidemiology was conducted in Li Minority's two villages and Miao Minority's two villages nearby the foot of mountain in a historically malaria hyperendemic area, Nanqiao Township of Wanning County in August, 1993. The results showed that malaria infection was closely correlated to the behaviour of staying overnight on the mountain of Li and Miao Minorities during farming seasons. Most of Li people stayed overnight on the mountain for planting areca were adults, accounting for 21.6% of the whole population, the duration of stay was about half a year; Miao people stayed overnight on the mountain planting and harvesting upland rice, always with their family member, so the percentage of people who had stayed on the mountain was as high as 82.1%, the duration of stay was about one and half a month. Blood smear examination showed that the malaria parasite rates in both Li and Miao villages were 11.1% and 24.1%, respectively, the positive rate of P. falciparum was 1.0% and 9.1%, respectively, the positive rate of IFA (titer >or= 1 : 40) was 31.2% and 46.5%, respectively. It is indicated that both the rate of parasitaemia and the P. falciparum infection were much higher in Miao Minority than those in Li Minority (P < 0.001). A cohort analysis showed that the malaria parasite rate of population who having not stayed, having ever stayed and being stayed on the mountain was 6.5%, 27.4% and 42.1%, respectively, of them the rate of P. falciparum infection was 0.5%, 8.8% and 18.4%, respectively. The results suggest that malaria acquired from mountainous forest referring to "up-mountain infection" is a major source of malaria infection and a significant risk factor in determining the prevalence of malaria (especially falciparum malaria) in Hainan Province. This behavioural risk factor has become the main obstacle for malaria control in Hainan Province. Therefore, controlling "up-mountain infection" and adopting appropriate anti-malaria measures to protect the risk population who have to work and stay on the mountain should be strengthened in the malaria control program.

China↗
PubMed1994

Cytosine 73 is a discriminator nucleotide in vivo for histidyl-tRNA in Escherichia coli.

The acceptor helix of histidine tRNAs in Escherichia coli is capped by a unique base pair in which the cytosine at the discriminator position is paired with an extra guanosine at -1. In previous in vitro studies, the presence of the G-1:C73 base pair was found to be required to obtain both optimal histidylation by histidyl-tRNA synthetase and accurate 5' processing by RNase P. We investigated the role of G-1:C73 in histidine tRNA identity and found that nucleotide substitutions conferred mischarging by other amino acids in a pattern that correlated with the discriminator base and not with the extra nucleotide at -1. As shown by primer extension experiments, the relatively minor role of the -1 nucleotide in vivo could be attributed to altered RNase P processing. These studies show that interactions of tRNAs in vivo both with RNase P during tRNA biosynthesis and with the pool of aminoacyl-tRNA synthetases can modulate the effects of substitutions at recognition nucleotides, eliciting changes in transfer RNA identity.

Base Composition↗
PubMed1993

Effects of hyaluronic acid on the release of proteoglycan from the cell matrix in rabbit chondrocyte cultures in the presence and absence of cytokines.

OBJECTIVE: To investigate the effects of hyaluronic acid (HA) on the release of proteoglycan by cultured rabbit chondrocytes. METHODS: Articular cartilage chondrocytes were isolated from the knee joints of New Zealand white rabbits. Proteoglycan synthesis after incubation with HA was determined by measuring 35S-sulfate incorporation. Cells incubated with HA were labeled with 3H-glucosamine and applied to a Sepharose CL-2B column. After incubation of confluent cells with 35S-sulfate and then with HA in various concentrations in the presence or absence of cytokines, proteoglycan release from the cell matrix layer was measured. RESULTS: HA (M(r) 3 x 10(5) to 19 x 10(5)), at 10 micrograms/ml to 1 mg/ml, had little effect on the incorporation of 35S-sulfate or 3H-glucosamine into cartilage matrix proteoglycans, or on the hydrodynamic size of proteoglycan monomers, in rabbit chondrocyte cultures. However, at 10-1,000 micrograms/ml, HA suppressed the release of 35S-proteoglycans from the cell matrix layer into the medium in the presence and absence of interleukin-1, tumor necrosis factor alpha, or basic fibroblast growth factor. CONCLUSION: These results suggest that HA is a potent inhibitor of the displacement of matrix proteoglycan into culture medium.

Animals↗
PubMed1993

The interferon-induced double-stranded RNA-activated human p68 protein kinase potently inhibits protein synthesis in cultured cells.

The role of the interferon-induced double-stranded RNA (dsRNA)-activated human p68 protein kinase as an inhibitor of protein synthesis has been inferred from work with cell-free systems, but direct proof in animal cells is lacking. To document the action of p68 protein kinase in vivo, we have used an infection-transfection system where expression of p68 is driven by a vaccinia virus promoter regulated by the lacl repressor/operator controlling elements. In cultured cells infected with vaccinia virus and transfected with a plasmid containing the p68 gene, there is synthesis of p68 when lacl repressor is inhibited with isopropyl-beta-D-thiogalactoside. When infection-transfections are carried out with the p68 gene together with the luciferase (LUC) reporter gene, a strong inhibition of LUC expression developed with time postinfection. This inhibition was not observed with a mutant form of the kinase (Lys-->Arg at position 296) and it was reversed by antisense expression of the p68 gene. During inhibition of LUC expression the protein kinase was phosphorylated, possibly as a result of autophosphorylation activated by the dsRNA forms which are known to accumulate in vaccinia virus-infected cells. Inhibition of LUC expression was at the level of translation. Our findings demonstrate that expression and activation of the human p68 protein kinase in vivo potently inhibits protein synthesis.

Cells, Cultured↗
PubMed1993

A multidrug resistance regulatory chromosomal locus is widespread among enteric bacteria.

Constitutive expression of the mar operon (marRAB) in Escherichia coli produces a multiple antibiotic resistance phenotype mediated by the expression of multiple genetic loci in response to regulatory proteins in the operon. A mar-specific DNA probe was used to search for the operon in bacterial strains representing 53 species and 27 genera. Among these, 6 other Enterobacteriaceae, Salmonella, Shigella, Klebsiella, Citrobacter, Hafnia, and Enterobacter species, contained DNA sequences that hybridized to the probe under high-stringency conditions. By use of a selection protocol developed to obtain multiple antibiotic resistant mutants of E. coli, multiply resistant mutants that showed increased expression of mar-specific RNA were obtained from Enterobacter agglomerans and Salmonella species.

Blotting, Northern↗
PubMed1993

In vitro oocyte maturation in the zebra fish, Brachydanio rerio, and the fertilization and development of the mature egg.

The in vitro maturation process of zebra fish oocytes was investigated. When incubated with medium EM-199 containing 0.5 microgram/ml of 17 alpha-hydroxyprogesterone in an incubator with 80% O, 25 degrees C, the germinal vesicles of the oocytes in stage IV migrated from middle between the center and the periphery to the periphery in 40 min, and the oocytes went into stage V 30 min later, undergoing germinal vesicle breakdown (GVBD) with a GVBD% of 59%. Two hours were needed for such oocytes to complete their final maturation. The mature eggs cannot come off the follicle layer surrounding them naturally (ovulation). By removing the follicle and adding active sperm for insemination, we can cause the mature eggs to become fertilized. The chorion elevated and blastoderm formed on the animal pole. The cleavage and development of the fertilized eggs followed are the same as naturally matured fertilized eggs. Using blastula as the criterion for a successful fertilization of the in vitro maturated egg, the fertilization rate is 78%. This is the first report on the successful oocyte final maturation in vitro in zebra fish. The establishment of an oocyte in vitro maturation technique has given grounds for the further investigation on the transfer of foreign genes in the germinal vesicles of the oocytes.

17-alpha-Hydroxyprogesterone↗
PubMed1993

Localization of juvenile, but not late-infantile, neuronal ceroid lipofuscinosis on chromosome 16.

The neuronal ceroid lipofuscinoses (NCL) are a group of progressive neurodegenerative disorders characterized by the deposition of autofluorescent proteinaceous fingerprint or curvilinear bodies. We have found that CLN3, the gene underlying the juvenile form of NCL, is very tightly linked to the dinucleotide repeat marker D16S285 on chromosome 16. Integration of D16S285 into the genetic map of chromosome 16 by using the Centre d'Etude du Polymorphisme Humain panel of reference pedigrees yielded a favored marker order in the CLN3 region of qtel-D16S150-.08-D16S285-.04-D16S148-.02-D16S 67-ptel. The most likely location of the disease gene, near D16S285 in the D16S150-D16S148 interval, was favored by odds of greater than 10(4):1 over the adjacent D16S148-D16S67 interval, which was recently reported as the minimum candidate region. Analysis of D16S285 in pedigrees with late-infantile NCL virtually excluded the CLN3 region, suggesting that these two forms of NCL are genetically distinct.

Adolescent↗
PubMed1993

Variation of Cmax and Cmax/AUC in investigations of bioequivalence.

In order to enable the setting of regulatory criteria for the equivalence of absorption rates on a sound scientific basis, the variation of Cmax/AUC and Cmax was evaluated. Under most conditions, the variation of Cmax/AUC was 10-25% higher than that of AUC independently of the variability of the extent of absorption. By contrast, the variation of Cmax was 50-60% higher than that of AUC and was strongly dependent on the variability of the extent of absorption. Therefore, it is recommended that for establishing the equivalence of absorption rates, the 90% confidence limits for the percentage ratio of the Cmax/AUC values of two drug products should be (based on their logarithmic averages or medians) between 75 and 133%. Regulatory decisions based on Cmax, while not favored, should expect that the 90% confidence limits for the percentage ratio of the Cmax values of two drug products be (based on their logarithmic averages or medians) between 70 and 143%. These recommendations parallel and are contingent upon the internationally harmonized criterion for the equivalence of extents of absorption which requires that the 90% confidence limits for the percentage ratio of two AUC values (based on their logarithmic averages or medians) be between 80 and 125%.

Absorption↗
PubMed1992

Hormonal profile of the menstrual cycle in Chinese women after tubal sterilization.

Ten women after tubal sterilization were studied for the hormonal profile of the menstrual cycle. They had undergone sterilization procedures, on the average 5.3 years (range 1.5-10 years) earlier. The serum concentrations of LH, FSH, prolactin, estradiol and progesterone were measured by RIA in daily blood samples of a complete menstrual cycle. Another ten normal women were studied at the same time and were used as the control group. There were no significant differences in the hormonal patterns of the menstrual cycle between the two groups. There was a significantly lower LH level in the early luteal phase of the tubal ligation group compared to the control group. Also, a significantly lower E2 luteal peak compared to the preovulatory peak was observed in the tubal ligation group. The physiological significance of these minor changes is not clear. Only one out of ten women in the tubal ligation group, who had undergone sterilization 1.5 years prior, showed a deficiency in luteal function, but her ovulatory function and menstrual cycle appeared normal. This study indicates that normal hormonal profiles are retained after tubal sterilization.

Adult↗
PubMed1992

Genome maps of Campylobacter jejuni and Campylobacter coli.

Little information concerning the genome of either Campylobacter jejuni or Campylobacter coli is available. Therefore, we constructed genomic maps of C. jejuni UA580 and C. coli UA417 by using pulsed-field gel electrophoresis. The genome sizes of C. jejuni and C. coli strains are approximately 1.7 Mb, as determined by SalI and SmaI digestion (N. Chang and D. E. Taylor, J. Bacteriol. 172:5211-5217, 1990). The genomes of both species are represented by single circular DNA molecules, and maps were constructed by partial restriction digestion and hybridization of DNA fragments extracted from low-melting-point agarose gels. Homologous DNA probes, encoding the flaAB and 16S rRNA genes, as well as heterologous DNA probes from Escherichia coli, Bacillus subtilis, and Haemophilus influenzae, were used to identify the locations of particular genes. C. jejuni and C. coli contain three copies of the 16S and 23S rRNA genes. However, they are not located together within an operon but show a distinct split in at least two of their three copies. The positions of various housekeeping genes in both C. jejuni UA580 and C. coli UA417 have been determined, and there appears to be some conservation of gene arrangement between the two species.

Bacterial Proteins↗
PubMed1992

Detection of circulating antigen by McAb-AST for evaluating the efficacy of anti-Leishmania chemotherapy.

We have adapted the simple and sensitive McAb-antigen spot test (AST) for evaluating the efficacy of anti-Leishmania chemotherapy. Serum samples from 37 kala-azar patients were tested by McAb-AST, and all showed definite positive reactions before treatment. After a course of antimony treatment, 20 turned negative, coupled with the disappearance of clinical symptoms; another 12 cases responded with weak positivity accompanied by an improvement of clinical manifestations; and the remaining 5 antimony-resistant patients showed strong positive reactions, with their conditions gradually worsening. Furthermore, all 6 cases in which the diagnosis was missed by the bone marrow smear method turned McAb-AST negative after chemotherapy. These results suggest that McAb-AST can be used to evaluate the efficacy of chemotherapy as well as to avoid missed diagnosis by the bone marrow smear method.

Adolescent↗
PubMed1991

Sizing and mapping of the genome of Campylobacter coli strain UA417R using pulsed-field gel electrophoresis.

Agarose-immobilized chromosomal DNA from the nalidixic-acid-resistant Campylobacter coli strain UA417 and its streptomycin-resistant (StrR) derivative, UA417R, were digested with the restriction enzymes SalI (GTCGAC) and SmaI (CCCGGG). The sizes of the resulting fragments were determined using pulsed-field gel electrophoresis. The two genomes showed similar restriction patterns of seven and 13 fragments for the two respective enzymes and the total genome size was determined to be approx. 1.7 Mb. Analysis of partial digestion fragments, as well as Southern-blot hybridization, were used to construct a physical map of the C. coli UA417R genome. Natural transformation studies using DNA fragments extracted from UA417R, as well as the erythromycin-resistant (EryR) C. coli strain UA585, were used to locate the StrR and EryR resistance markers on the genomic map.

Blotting, Southern↗
PubMed1991

Pulsed-field gel electrophoresis of Campylobacter jejuni and Campylobacter coli genomic DNA and its epidemiologic application.

Genomic DNA from 12 different Campylobacter jejuni and 10 Campylobacter coli isolates was digested with SmaI and analyzed by pulsed-field gel electrophoresis (PFGE) and 16S rRNA hybridization studies. Although the two Campylobacter species displayed species-specific restriction and hybridization patterns, significant intraspecies differences were observed. Combined PFGE and hybridization pattern analysis failed to provide any more epidemiologic information than was obtained from PFGE restriction profiles alone. Therefore, results from these studies indicate that PFGE analysis of SmaI-restricted genomic DNA provides a reliable means of differentiating C. jejuni from C. coli and may represent a more practical approach to epidemiologic studies than combining conventional DNA restriction digestion pattern with RNA hybridization procedures.

Animals↗