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Biomedical subjects

B Dai

Publications and source records attributed to B Dai.

At least 91 records · Page 5Linked to original sources
PubMed1990

[Detection of the microquantity DNA of Leptospira interrogans by polymerase chain reaction].

Leptospirosis is a severe zoonosis in the world. The methods for detecting leptospira are not sensitive and specific so far. The problems in early diagnosis and epidemiological identification of Leptospirosis remain unsolved. Two recombinant DNA fragments of serogroup Icterohaemorrhagiae, Leptospira were selected by repeated molecular cloning and screening in this study firstly. One of them can hybridize with the DNA of various serogroups of Leptospira interrogans; the other can only hybridize with the DNA of serogroup Icterohaemorrhagiae. After the nucleotides sequence analysis, from these 2 recombinant DNA fragments, 2 pairs of polymerase chain reaction (PCR) oligonucleotide primers were synthesized, named primer B 1, 2 and primer B 3, 4 PCRs were carried out with these 2 primers for detecting the microquantity (0.1 ng) of various serovars, serogroup of leptospires. All the DNA of Leptospira interrogans can be amplified by primer B 1, 2, and only the DNA of serogroup icterohaemorrhagiae, Leptospira reacted specially with primer B 3, 4. The DNA of non-pathogenetic Leptospira and some other microbes, however, had no amplification at all. This study is first reported at home and abroad. The results demonstrate that PCR is a very sensitive and specific technique of DNA amplification, which can be used as a powerful tool in the early diagnosis and epidemiological identification of leptospirosis.

Animals↗
PubMed1990

[The study on homology of leptospires with molecular hybridization].

Homology of leptospires from different genus, different serogroups were studied with molecular hybridization. Leptospiral DNAs were extracted and purified with phenolchloroform-isoamylalcohol method. Alpha 32P-dCTP was used to label DNA from L. interrogans serogroup icterohaemorrhagiae serovar lai strain 017 as a DNA probe, and hybridized with DNAs of 2 genus, 5 serogroups of leptospires represented by 6 strains on NC filter. Four serogroups of pathogenic leptospires which caused endemic disease in Sichuan Province were also detected by the probe. The results showed that L. interrogans serogroup icterohaemorrhagiae, serogroup autumnalis and serogroup hebdomadis had a high degree of homology while there was a low degree of homology between L. interrogans and L. biflexa and Leptonema illini. Four major serogroups of pathogenic leptospires in Sichuan Province, with their high degree of homology, could be detected by a radiolabelled probe from serogroup icterohaemorrhagiae. Hybridization may be used as a tool for diagnosis of leptospirosis in human beings and animals.

DNA Probes↗
PubMed1990

[Investigation on the immunoprotection of monoclonal antibodies against outer envelopes of serogroup Icterohaemorrhagiae serovar lai strain 017 leptospires].

BALB/c mice were immunized intraperitoneally with outer envelopes of serogroup icterohaemorrhagiae lai serovar strain 017 leptospires. Monoclonal antibodies against outer envelopes (IgG, agglutinating titre 1:25,600) were produced by hybridoma technique. The monoclonal antibodies ascites (diluted 1:100) 1 ml administered intraperitoneally 1 hour before the intraperitoneal injection of 2 x 10(8) leptospires of strain 017 and the subsequent daily administration of McAb in similar doses for five days protected 80% of guinea pigs. Survival rates of three control groups which received physiological saline, ascites of BALB/c mouse myeloma cell lines SP2/0, and monoclonal antibodies against Pseudomonas aeruginosa in place of monoclonal antibodies against outer envelopes of strain 017 leptospires were 10%, 20% and 10% respectively. When killed 20 days after challenge, guinea pigs of experiment group were normal at autopsy. Old pulmonary haemorrhage were present in the animals of three control groups. Passive immunoprotection experiments have demonstrated immunoprotection of monoclonal antibodies against outer envelopes of strain 017 leptospires. It will be valuable for separating protective antigen fraction of outer envelopes and studying new vaccine of leptospira.

Animals↗
PubMed1990

[DNA hybridization and identification of Leptospira serogroup icterohaemorrhagiae with Leptospira recombinant DNA probes].

Two recombinant DNA probes-PLIpso1 (15kb) and PLIEc34 (4kb), derived from Leptospira serovaricterohaemorrhagiae genomic libraries, were applied for the hybridization and identification of 13 strains of Leptospira in serogroup icterohaemorrhagiae. Difference in hybridization signal in combination with the banding pattern provide a good way for identification of serovars and strains. The recombinant DNA, specific to L. serogroup icterohaemorrhagiae, hybridized with a limited number of DNA fragments which had been digested by several restriction endonucleases. The less complex banding pattern and higher sensitivity facilitate characterization of various serovars and strains in serogroup icterohaemorrhagiae. In general the DNA patterns recognized by both probes have extensive genomic homology in same serovar (but still can distinguish strains in same serovar by some unique bands) and apparent difference in various serovars (especially serovars naam, nanxi and honghe). The results indicated that Southern blotting with recombinant DNA probe might provide tools for identification, characterization and analysis of leptospira.

Blotting, Southern↗
PubMed1990

[The study on genome size of leptospires].

Determination of genome size is very important in genetic studies and the molecular cloning of leptospires. With pulsed field gel electrophoresis (PFGE), which can be used in the analysis of large DNA molecules, we studied the genome size of leptospires and analysed it with rare cutter restrict endonuclease Not I. The PFGE system used was CHEF-DR II which produced parallel bands in agarose gel. The results showed that the genome size of leptospires was 2000kb and there was no dramatic difference between the 5 strains of 2 genus leptospira. Rare cutter Not I digestion of genome DNA of leptospira resulted in 11 bands and its bands pattern was quite different from that of E. coli, S. choleraesuis, S. typhimurium, and S. dysenteriae genome DNA. It is thought that more information can be obtained about leptospiral DNA with PFGE technique.

Cloning, Molecular↗
PubMed1990

[Purification and identification of antimicrobial peptides of rabbit neutrophils].

Five antimicrobial peptides were extracted from the cytoplasmic granules of rabbit neutrophils with 0.01 mol/L citric acid. SDS-PAGE gel densitometric analysis of the citric acid extract showed that they accounted for 34%-42% of the total extract proteins. When subjected to acid urea polyacrylamide gel electrophoresis, five peptides migrated much further to the cathode than lysozyme. Beginning with the most cathodal component, they were in turn referred to as NP1, NP2, NP3, NP4, and NP5. They were purified from the citric acid extract by virtue of preparative polyacrylamide gel electrophoresis. Each of them was of low molecular weight (2,500-6,000) as determined by SDS-PAGE. Three of the peptides were tested in vitro for fungicidal activity. When Candida albicans (10(7)/ml) were incubated with 12.5 micrograms/ml of NP1 or NP2 at 37 degrees C for 2 h, the death rates of the organisms were 96.6% and 93.3% respectively. NP3 was shown to be active against Candida albicans although less potent than NP1 and NP2.

Animals↗
PubMed1990

[Study on the characteristics of agglutination reaction of McAb with Leptospira interrogans outer envelope].

Three McAb were produced against an outer envelope preparation from Leptospira, interrogans, serovar Lai by fusion of SP2/0 myeloma cells with immune BALB/c mice spleen cells. The fusion rate was 96% and the antibody positive rate was 50%. One of the hybridomas, E4B11C9, reacted with 13 of the 13 serovars of the Icterohaemorrhagiae serogroup in microscopic agglutination test (MAT) but did not react with the 18 representative serovars of L. interrogans and L. biflexa serovar patoc and Leptonema illini. For all non-reactive serovars the MAT titres were greater than 1:25. The McAb, E4B7G5, reacted similarly with all serovars except smithi and tonkini. E4B7D4 reacted also similarly with all serovars except serovars birkini, ndambari, bogvere, smithi and tonkini. Therefore, 3 McAb showed serogroup specificity and partial serogroup specificity by agglutination. The agglutination titres were high and hybridomas were stable, so it might be useful in providing a simple, rapid method for the classification and identification of clinical isolates such as pathogenic L. interrogans in place of the complicated and time-consuming conventional methods.

Agglutination Tests↗
PubMedDate not supplied

Reliable procedure for closing the duodenal stump for bleeding posterior duodenal ulcer.

Bleeding posterior duodenal ulcers is a critical problem especially in patients of advanced age. Surgical treatment should obtain efficient and stable hemostasis and avoid digestive fistulas due to leakage of the duodenal stump. The main difficulty lies in the closure of the duodenal stump. A procedure using intramural dissection of the duodenum and closure by means of a stapler is reported for a series of 40 patients without recurrent bleeding or duodenal fistula. Seven patients (17%) died from associated diseases, especially respiratory insufficiency (3 patients) and cirrhotic liver failure (2 patients).

Adult↗
PubMedDate not supplied

[Anorectal malignant melanomas. Apropos of 2 new cases].

Clinical and therapeutic characteristics of anorectal melanoma have been studied about 2 new cases. The initial symptoms were often misdiagnosed with hemorrhoids disease. This cancer carries a bad prognosis but the best treatment seems to be abdominoperineal resection (APR) when the thickness of the melanoma is under 3 mm. Over this limit, APR alone will not cure this disease. Curative treatment will probably involve a combined therapy with local and systemic therapies.

Anus Neoplasms↗