Biomedical subjects

R Yao

Publications and source records attributed to R Yao.

66 records · Page 4Linked to original sources

PubMed1993

Construction of new Campylobacter cloning vectors and a new mutational cat cassette.

We have developed new Campylobacter shuttle vectors which are 6.5-6.8-kb plasmids carrying Campylobacter and Escherichia coli replicons, a multiple cloning site (MCS), the lacZ alpha gene, oriT and either a kanamycin or chloramphenicol resistance-encoding gene (KmR or CmR) from Campylobacter which functions in both hosts. These vectors can be mobilized efficiently from E. coli into C. jejuni or C. coli, and stably maintained in these hosts. Plasmids pRY107 and pRY108 carry a KmR marker and 17 unique cloning sites in two different orientations in lacZ alpha, allowing easy blue/white color selection. Plasmids pRY111 and pRY112 contain a CmR gene and 17 unique sites in both orientations. In addition, MCS are flanked by T7 and T3 late promoters and M13 forward and reverse primer sites, facilitating expression in T7 or T3 expression systems and sequence analysis. A Campylobacter CmR gene cartridge, bracketed by six restriction sites, has been developed for use in site-specific mutagenesis of Campylobacter genes.

Base Sequence↗

PubMed1993

Isolation and characterization of a DNA fragment containing various kinds of repetitive sequences located on human chromosome 21.

In order to investigate the repetitive sequences located on human chromosome 21, we have isolated DNA fragments containing Alu sequences. One of the clones, p1, was chosen for further study, because it contained repetitive sequences different from the Alu sequence. Nucleotide sequence analysis of p1 indicates that p1 contains L1 and O-family sequences. Interestingly, when the L1 sequence was used as a probe, a discrete band of 5 kb was seen in HindIII-digested DNA from somatic cell hybrids containing human chromosome 21 as the sole human chromosome. The L1 sequence was rearranged and was interrupted by O-family sequence, which was flanked by 6 bp target site duplications. Since all three repetitive sequences are known to act as retroposons, these results imply that there is an integration hot spot on human chromosome 21. The sequence was mapped within 21q11-21.

Animals↗

PubMed1992

Adhesion and junction molecules in embryonic and adult lens cell differentiation.

The expression of the neural cell adhesion molecule NCAM and its polysialic acid (PSA) moiety was documented during embryonic development and adult differentiation of chicken lens cells. In both the embryo and adult, NCAM is predominantly found in the epithelium and the zone of young elongating cells of the annular pad. NCAM abundance drops markedly in the cortical fibers and is further reduced in the lens nucleus. Epithelial cell NCAM is more highly poly-sialylated in the adult than in the embryonic lens. Three isoforms of NCAM at 180, 140, and 120 kDa were detected in the lens and predominantly associated with the unit membrane-enriched plasma membranes of fiber cells. The distribution of NCAM relative to MP26 and the adherence junction-associated glycoprotein N-cadherin suggests that NCAM could influence the formation of fiber cell gap junctions and adherence junctions.

Animals↗

PubMed1992

Nucleotide sequence and transcriptional regulation of a positive regulatory gene of Shigella dysenteriae.

A 1,937 bp PstI-HindIII fragment containing the ipaR locus was cloned from the large invasion plasmid of Shigella dysenteriae CG097, and its nucleotide sequence was completely determined. The IpaR protein (35 kDa, calculated from the DNA sequence) was synthesized in Escherichia coli chi 1411 minicells containing the 1,937-bp PstI-HindIII fragment. To determine the regulatory role of ipaR for ipa genes, we applied genetic complementation experiments using chloramphenicol acetyltransferase (CAT) as reporter. Analyses of CAT activity of the recombinant plasmids containing the 5' flanking sequences of the 24-kDa-protein gene and the ippI, ipaB, ipaC, and ipaD genes defined strong promoters upstream of the 24-kDa-protein gene and ipaD gene, weak promoters upstream of the ippI and ipaB genes, and the absence of any promoter activity for the ipaC gene. Complementation analyses showed that the CAT activity only under direction of the ippI promoter region increased 1.8-fold in the presence of IpaR protein. On the basis of our data, we suggest that an operon comprising ippI, ipaB, and ipaC is positively regulated by IpaR protein which has a trans effect on a DNA sequence upstream of the ippI promoter.

Amino Acid Sequence↗

PubMed1992

Immunochemical differences among Methanosarcina mazei S-6 morphologic forms.

Methanosarcinae are the only archaeobacteria known to undergo major morphologic changes during growth involving unicellular and multicellular forms, and Methanosarcina mazei S-6 is the only strain for which three distinct forms, packets, single cells, and lamina, have so far been observed. It is reported that two pairs of these forms, either packets and single cells or single cells and lamina, grew and interconverted in medium with the same composition, Ca2+ and Mg2+ concentrations, and growth substrate, and that the two forms in each pair displayed distinctive differences revealed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and immunoblotting, the same growth medium-substrate notwithstanding.

Antigens, Bacterial↗

PubMed1991

Nucleotide sequence of the ipaBCD structural genes of Shigella dysenteriae.

A 9 kb EcoRI and two PstI fragments from the virulence plasmid of Shigella dysenteriae CG097 were shown to contain all ipa genes by probing with Shigella flexneri ipaB, -C, -D and -A gene probes. The DNA sequences of S. dysenteriae ipaBC genes were very similar to those of S. flexneri M90T and S. flexneri YSH6000, but ipaD differed by 22 codons from that of S. flexneri. The differences in ipaD may account for the different in vitro host specificities shown by S. dysenteriae and S. flexneri. The nucleotide composition of ipa genes revealed an unusually large number of codons that are rarely used in Escherichia coli chromosomal genes, indicating a different origin.

Amino Acid Sequence↗

PubMed1990

Immunohistochemistry of superoxide dismutase-1 in developing human brain.

The developmental changes in superoxide dismutase (SOD)-1 were studied in brains ranging in age from human fetuses to adults by immunohistochemistry. SOD-positive neurons and glial cells appeared with maturation in each region, and increased progressively with gestational and postnatal age. This phenomenon implies a relationship between SOD-1 gene expression and the anti-oxidant defence mechanism in developing neurons and glia.

Adult↗

PubMedDate not supplied

Alphamethrin-impregnated bed nets for malaria and mosquito control in China.

A community-based intervention trial was carried out to evaluate the effectiveness of alphamethrin-impregnated bed nets for control of Plasmodium vivax malaria and its vector in an area of moderate endemicity in southern Henan province, central China in 1990. Malaria incidence was significantly lower in the intervention group than in the comparison group (2.03 vs. 3.57 per 100 person-years at risk). The protective efficacy for malaria incidence was 43%. The prevalence of malaria parasitaemia among children under 10 years old in the intervention group was about one-quarter of that in the comparison group (0.93% vs. 3.25% and 0.71% vs. 1.96% after one and 4 months use of impregnated nets, respectively). Alphamethrin-impregnated bed nets had a mass killing effect on vector mosquitoes. The outdoor person-biting density of Anopheles anthropophagus and A. sinensis decreased by 70.3% and 29.3% respectively. The density of these 2 mosquito species found resting inside treated nets was close to zero. No side effect was found among users of impregnated bed nets. Impregnation with alphamethrin was more effective on polyester than on cotton netting and residual effects lasted at least one year. Use of alphamethrin is less expensive than permethrin and deltamethrin.

Animals↗

PubMedDate not supplied

The effect of DDT spraying and bed nets impregnated with pyrethroid insecticide on the incidence of Japanese encephalitis virus infection.

A retrospective investigation was conducted to evaluate the effectiveness of DDT residual indoor spraying and bed nets impregnated with pyrethroid insecticide for Japanese encephalitis control in southern Henan province, China. DDT residual indoor spraying had no effect on the incidence of Japanese encephalitis, but it was greatly reduced after the introduction of pyrethroid-impregnated bed nets. Only a small effect on outdoor biting densities of Culex tritaeniorhyncus was found, although the number of mosquitoes resting inside bed nets decreased markedly after the introduction of bed net impregnation.

Animals↗

PubMedDate not supplied

The protective effect of bed nets impregnated with pyrethroid insecticide and vaccination against Japanese encephalitis.

A population-based case-control study to evaluate the protective effect of bed nets impregnated with pyrethroid insecticide and of vaccination against Japanese encephalitis was carried out in Gusi county, Henan province, China from June to September 1991; 50 cases and 100 matched controls were studied. Bed nets impregnated with pyrethroid insecticide greatly decreased the risk of infection among children under 10 years old, and vaccine efficacy was 78% (95% CI 16%-94%). We suggest that impregnated bed nets could be used as a quick response during outbreaks of Japanese encephalitis.

Bedding and Linens↗

PubMedDate not supplied

The effects of a binary mixture of benzo(a)pyrene and 7H-dibenzo(c,g)carbazole on lung tumors and K-ras oncogene mutations in strain A/J mice.

Polycyclic aromatic hydrocarbons (PAH) and N-heterocyclic aromatic hydrocarbons (NHA) are environmental pollutants formed during the incomplete combustion of organic materials. Benzo(a)pyrene (BaP) and 7H-dibenzo(c,g)carbazole (DBC) are well-characterized representatives of the PAH and NHA classes of compunds, respectively. Both are demonstrated carcinogens that frequently co-occur in environmental mixtures. This preliminary study was conducted to investigate the effects of a binary mixture of BaP and DBC on lung carcinogenicity in the strain A/J mouse as manifested by tumor development and mutations in the K-ras gene. Male A/J mice were administered the following single intraperitoneal dose (mg/kg) combinations of BaP and DBC dissolved in a 0.2-mL volume of tricaprylin--10 DBC:10 BaP; 2 DBC:10 BaP; 2 DBC:100 BaP; and 10 DBC: 100 BaP, and each of the compounds alone at the same doses. Mice were sacrificed 8 months after carcinogen treatment and lung tumor multiplicity and K-ras mutations determined (high-dose combination). The combination of DBC and BaP produced fewer tumors than the sum of all tumors produced by each compound acting alone. The frequency of tumors with K-ras mutations was also less in a sample of the 10 DBC:100 BaP treatment group than in the same-dose, single compound-treated animals. The dominant mutations produced by BaP and DBC were expressed in tumors from animals treated with the mixture.

Animals↗

PubMedDate not supplied

Extract from Arca granosa L. inhibits proliferation of human tumour cell lines with kidney and lung origin.

Marine organisms are being considered increasingly as sources of anti-tumour agents. The extract from Arca granosa L. has been shown to decrease the growth of tumours and this study was undertaken to determine its ability and mechanism of inhibition. The extract inhibited the proliferation of six human tumour cell lines from different origins with varying sensitivity. The cell lines Ketr-3, A549 and NCl-H460 with kidney or lung origins were more sensitive to the extract than those of the HepG-2, MCF-7 and MGC-803 cells from other origins. In the three sensitive cell lines (Ketr-3, A549 and NCI-H460) the extract was shown to block different phases of the cell cycle progression and inhibit DNA synthesis in a concentration-dependent manner. It was concluded that the extract from A. granosa is potentially a novel anti-tumour agent, especially on kidney and lung tumour cell lines.

Animals↗