Biomedical subjects

B Dai

Publications and source records attributed to B Dai.

At least 73 records · Page 4Linked to original sources

PubMed1992

[The production and identification of partial serogroup--specific monoclonal antibodies against leptospires hebdomadis serogroup].

Hebdomadis is one of the major serogroups found in China. In Sichuan, this serogroup appears to have a close relationship with local outbreak of leptospirosis. BALB/c mice were immunized intrasplenically with outer envelope of serogroup Hendomadis serovar hebdomadis strain 245. Spleen cells were fused with SP2/0 myeloma cells, two monoclonal antibodies Af2 and Bb2 were produced by hybridoma technique. McAb Af2 and McAb Bb2 were identified to be IgG1 and IgG3 by immunodiffusion respectively. Specificities of these two McAbs were determined by MAT; both reacted to 8 serovars (hebdomadis, nona, kambale, kremastos, worsfoldi, jules, maruborincana) of Hebdomadis serogroup. The agglutination titres of McAb Af2 and McAb Bb2 were 1:640-1:2,500,000 and 1:320-1:2,500,000, respectively. The two McAbs did not agglutinate with serovar kabura of Hebdomadis serogroup, they did not agglutinate with 11 serovars of Sejroe serogroup, 4 serovars of Mini serogroup, 18 representive serovars of L. interrogans in 18 serogroups, L. biflexa strain Patoc I and Leptonema illini. So it was found that McAb Af2 and McAb Bb2 showed partial serogroup specificity for Hebdomadis by agglutination.

Animals↗

PubMed1992

[The detection and analysis of leptospiral DNA in patients' serum of early leptospirosis by polymerase chain reaction and DNA hybridization with digoxigenin-AMPPD].

We have detected and analysed the leptospiral DNA in serum of patients with early Leptospirosis from the epidemic area of China by PCR and DNA hybridization with Digoxigenin (Dig)-3-(2'-Spiroadamantane)-4-methoxy-4-(3"-phosphoryloxy)- phenyl-1,2-dioxetane (AMPPD) to develop a sensitive, specific and reliable technique for the early diagnosis of leptospirosis, and full satisfactory results have obtained. Fourteen serum specimens from patients with leptospirosis proven by blood culture and serological test were prepared according to Boom's methods for PCR test, and oligonucleotide primers, named G1 G2, were obtained from a genomic library of leptospira interrogans. PCR amplification with serum specimens was performed. Each cycle of amplification consisted of denaturation at 94 degrees C for 1 min, annealing at 55 degrees C for 1 min and elongation at 72 degrees C for 2 min. Each sample was subjected to 32 cycles. The amplified DNA were separated by electrophoresis with 2% agarose gel and hybridized with the homologous DNA probe labelling with Dig-AMPPD by means of Southern blotting. All of 14 samples revealed the presence of leptospira and the strong signals were visualized with homologous DNA probe hybridization by Southern blotting. Negative and positive controls appeared correctly. The DNA fragment generated from PCR amplification homologically hybridized with the DNA of 16 strains which are from Yasudas' genomic species and represent the different genomic groups of leptospires. The single recognized band (about 400 bps) from 6 out of the 16 strains has come out which are representative of the principal strains in Sichuan, China.(ABSTRACT TRUNCATED AT 250 WORDS)

Adamantane↗

PubMed1992

[Detection of leptospiral DNA in the serum of 175 patients with early leptospirosis by polymerase chain reaction].

We have developed a sensitive assay for leptospira, using the polymerase chain reaction (PCR). On the basis of the published nucleotides sequence of 23S rRNA gene from Leptospira interrogans serovar canicola strain Moulton, primers were chosen to produce an amplified fragment of 123 bp. Primer A: 5'GAT CTA ATT CGC TGT AGC AGG3' and primer B: 5'ACT TTC ACC CTC TAT GGT CGG3' Eight different svs. of Leptospira interrogans could all be detected by PCR, but the DNAs from L. biflexa. Leptonema bacteria, virus and human could not produce the specific amplified fragment. The assay detected approximately 10 fg of purified leptospiral DNA and 1 microliter serum of experimental animal. Positive results were obtained from simulated positive samples containing a single organism leptospiral DNA. The diagnostic test (proved by "gold standards": Clinical diagnosis; blood culture and MAT) showed that the sensitivity was 92.00%; the specificity 94.35%; the accuracy 92.54%; the positive predictive value 98.17%; the negative predictive value 78.13%; the positive likelihood ratio 16.25; and the negative likelihood ratio 0.0848. The diagnosis of early leptospirosis by using PCR may become a significant addition to diagnostic means.

Animals↗

PubMed1992

[Study on the frequency of primary rubella infection among early pregnant women].

Rubella virus is the common agent of prenatal infection. Congenital malformation rate is very high among pregnant women who are infected rubella primarily during the first trimester of pregnancy. Sera were taken from 10412 early pregnant women in 4 cities and 4 countries of 6 Provinces in 4 districts of China from April 1990 to October 1991 for detection of special IgM antibodies against rubella with Capture-EIA test. The results showed that the primary infection rate was 0.318% of those women without clinical symptoms of rubella during their early pregnant period. A high infection rate of 1.477% was found in those women with clinical symptoms, 4.7 times the former rate. The total infection rate of 10,412 women was 0.461%. By this rate at least some 40 thousand CRS infants will be born each year in China. This figure is more than the sum of patients suffering from poliomyelitis and Japanese encephalitis, and much more than the number disabled from these two infectious diseases. Some suggestions to prevent CRS were put forward in this paper.

Antibodies, Viral↗

PubMed1992

[Marking and detection of DNA of leptospires in the dot-blot and situ hybridization with digoxigenin-labelled probes].

DNA of Leptospira interrogans sv. lai strain 017 was labelled with digoxigenin or alpha 32P or biotin and used as probes to detect DNA of leptospires. Probes labelled with digoxigenin were able to detect 0.1-1 pg of homologous DNA and 10(2) of L. interrogans sv. lai strain 017. Probes alpha 32P and biotin detected 1 pg and 10 pg of homologous DNA and 10(3), 5 x 10(3) of L. interrogans sv. lai strain 017 respectively. These three probes couldn't detect L. biflexa sv. patoc strain Patoc I, L. illini strain 3055, Escherichia coli. Bacillus aerogenes capsulalus, Salmonella anatis, K-DNA of Leishmania, and of human WBC. Comparison of digoxigenin-, alpha 32P- and Biotin-labelled probes in the dot-blot hybridization assay on different serogroup sv. of leptospires revealed that digoxigenin-labelled probes were more sensitive than alpha 32P and biotin-labelled probes. The results indicate that digoxigenin-labelled probes DNA can be used for detection of leptospires in field and clinic. We also report procedures in situ hybridization with leptospira in tissues smear and plasma sediment of an experimentally infected guinea pig. It offers the advantage of recognizable of leptospiral morphology in combination with a hybridization signals. The results indicate that digoxigenin-labelled DNA probes of 017 strain might provide tool for routine diagnosis and classification in cases of leptospiral interrogans infection.

Animals↗

PubMed1992

Advances in research on leptospira and human leptospirosis in China.

Leptospirosis exists in 26 of 30 provinces (exclusive of Taiwan province) in China. Up to now, a total of 18 serogroups and 70 serovars of pathogenic leptospires have been identified, including 35 serovars first found in China. A great deal of work has gone into the study of the leptospires and leptospirosis, and the present paper reviews these works, concentrating on serovar lai (the major serovar in China) and pulmonary diffuse hemorrhage (PDH), a traumatic consequence of leptospirosis.

Animals↗

PubMed1992

[Homology study of leptospires by molecular hybridization].

Nick translation and random primer labelling method were applied to prepare three genomic DNA probes from Leptospira interrogans strain 017, Leptospira biflexa strain Patoc I and Leptonema illini strain 3055, and then hybridized with DNA of 17 strains leptospires from different genus, species, serogroup and serovar. The results showed no homology between Leptospira and Leptonema, and only a low degree of homology between L. interrogans and L. biflexa but it showed a high degree of homology among L. interrogans. The study also proved the possibility to establish a DNA probe prepared from a single leptospira strain to detect different serovars.

Blotting, Southern↗

PubMed1992

[Observation of monoclonal antibody E4B7D5 inhibitory effect on leptospiral adherence using scanning electron microscope].

BALB/c mice were immunized intraperitoneally with outer envelopes of serogroup icterohaemorrhagiae lai serovar strain 017 leptospires. Monoclonal antibody (McAb) E4B7D5 against outer envelopes (IgG1, agglutinating titre 1:25,600) was produced by hybridoma technique. Passive immunoprotection experiments have demonstrated the immunoprotection of McAb E4B7D5 against strain 017 leptospires. Effect of McAb E4B7D5 on leptospiral adherence to the surface of normal human pulmonary embryonic fibroblasts was observed by using scanning electron microscope. The results indicated that the leptospiral adherence noted in various agglutinating titre McAb E4B7D5 groups was less frequent than that in the three control groups. It was concluded that the inhibitory effect of McAb E4B7D5 on leptospiral adherence may play a role in the immunoprotection.

Animals↗

PubMed1992

[Assay of genomic DNA homology among strains of different virulent leptospira by DNA hybridization].

Nick translation labelling technique was applied to the preparation of two 32P labelled genomic DNA probes from L. interrogans serovar Lai strain 017 and Leptonema illini strain 3055, respectively. Dot-blotting and Southern-blotting with DNA of five strains leptospira from different genus and species were performed. The results showed that certain differences among the L. interrogans, L. biflexa and Leptonema illini could be detected by endonuclease assay. L. interrogans strain 017 with L. biflexa strain Patoc I and Leptonema illini 3055 strain exhibited very little homology. L. interrogans strains 017, 601, and 245 from different serogroup and serovar had a high degree of homology. Leptonema illini strain 3055 showed little homology with L. interrogans and L. biflexa. Therefore DNA hybridization may be used as a tool for the identification and classification of leptospira.

Blotting, Southern↗

PubMed1992

[Detection of leptospira by dot blot hybridization with photobiotin- and 32P-labelled DNA].

Photobiotin- and 32P-labelled DNA probes of L. interrogans sv. lai strain 017 were produced and the DNA and leptospires were dotted on the NC filter and hybridized. The results showed that photobiotin and 32P-labelled DNA probes could detect DNAs of homology. The smallest amount of DNA that could be detected with the probes were 5pg and 1pg, and the smallest numbers of pathogenic leptospires were 5 x 10(3) and 10(3), respectively. Nonpathogenic leptospires. L. biflexa sv. patoc strain Patoc 1, L. illini strain 3055, Escherichia coli, Bacillus aerogenes capsulatus, and Salmonella anatis, could not be detected by the probes. The study demonstrates that leptospires DNA probe could be produced by labelling the DNA with photobiotin. It has higher sensitivity and specificity and can be used for detection of leptospires in the field and clinic.

Affinity Labels↗

PubMed1992

[Value of a "floppy" Nissen in the treatment of gastroesophageal reflux. Apropos of 117 cases].

The Nissen fundoplication is the most widely used antireflux procedure. However this operation is associated with several specific complications. To prevent these complications, an alternative antireflux procedure ("floppy" Nissen) has been designed. This investigation was conducted to investigate the effects of the floppy Nissen performed on 117 patients, between 1978 and 1990. Indication for surgery was the endoscopic discovery of stage I and II oesophagitis (59 cases), III and IV oesophagitis (25 cases) or an associated disease (gallstones: 25 cases, duodenal ulcer: 8 cases), pH monitoring used preoperatively in 47 cases showed an important reflux in 33 cases (70%). Preoperative manometry exploration (71 cases) showed a low pressure of the low oesophageal sphincter (LOS) in 63 cases (89%). The "floppy" Nissen procedure was performed over a length 4 to 6 cm. The folds of the diaphragm were closed back behind the oesophagus in 40 cases. During the postoperative period the pH-data were restored to normal range in 73% (18/26 cases), and the value of the LOS was restored in 74% (19/26 cases). The mean duration of clinical follow-up study of 99 patients was 3.22 years. Improvement in clinical symptoms was noted for 86%; 13% had specific Nissen complications (9 gall-bloat syndrome, 4 intermittent dysphagia). Six patients had to be reoperated. This technique allowed good control of the reflux symptoms, with a low incidence of mechanical complications.

Adult↗

PubMed1991

[Analysis of leptospiral deoxyribonucleic acids by restriction endonucleases].

For the application of restriction endonuclease analysis in typing and identifying leptospira, we selected some serovars and isolates, and analysed preliminarily their DNA with four restriction enzymes, EcoR I, Bgl II, Hha I, and Hind III. The DNA samples were isolated from the reference strains and isolates as follows: Serovar lai 56601, 017 (the virulent strain for PDH model of guinea pig), Serovar autumnalis 56606, Serovar manhao II 67020, and isolates 87112 and 87369. Each 2 micrograms of DNA was digested with 20mu of restriction enzyme at 37 degrees C for 2h and electrophoresed in 0.8% agarose gel. The gels were stained in ethidium bromide and photographed with UV light. In our experiments, apparently different restriction patterns of serovar lai 017 were observed with four restriction enzymes. Serovar lai, serovar autumnalis and serovar manhao II showed different patterns with EcoR I, especially in high molecular regions. We also observed in serovar lai 017 a distinct 10.5kb band which was obscure in 56601, the reference strain of serovar lai, after EcoR I digestion. The three serovars showed some delicate differences in Hind III restriction pattern. The two isolates from Apodemus agrarius in Sichuan (1987) 87112 and 87369 had patterns identical to those of serovar lai 56601, 017 with EcoR I, and 87112 also had a pattern identical to 56601, 017 with Hind III. Our results indicate that selected three serovars can be identified by analysis of their DNA with EcoR I and Hind III. It is suggested that restriction endonuclease analysis be a good method in typing and identify leptospira and in studying the differences of special DNA molecules.

DNA Restriction Enzymes↗

PubMed1991

[Preparation of SOKT1-RTA immunotoxin and its specific cytotoxic effect on human T lymphocytes].

An immunotoxin, SOKT1-RTA, was prepared successfully by conjugating a murine anti-human T lymphocyte monoclonal antibody (McAb) SOKT1 and the ricin toxin A chain (RTA) with the heterobifunctional linker SPDP. At the presence of 20 mmol/L NH4Cl, the SOKT1-RTA conjugate killed 82% of the human peripheral blood T cells (PBT), and decreased their 3H-Leu incorporation to 6.2% of the untreated controls. The toxic effect of the immunotoxin can be partially blocked by unconjugated SOKT1, but not by an irrelevant McAb D51. These results indicated that the SOKT1-RTA conjugate still retains both functions of its component parts:binding to human PBT specifically, and inhibiting protein synthesis. It may be an effective reagent for in vitro depletion of immunocompetent T cells from human bone marrows.

Antibodies, Monoclonal↗

PubMed1991

[Construction of gene bank of L. interrogans serovar lai and cloning of homological sequences of virulent leptospirosis].

A gene bank of the main pathogen of pulmonary diffuse haemorrhage type leptospirosis (PDH), L. interrogans serovar lai strain 017, was first constructed with plasmid vector pUC9, which contained 610 recombinant clones and laid the foundation for further investigation of molecular characteristics of leptospires with strong virulence. Recombinant plasmids which have homological sequences of pathogenic leptospires were screened from the gene bank. A recombinant plasmid, designated pCX7, could detect 1.7 kb fragment of strain 017, 9.0 kb of strain 601 and 30.0 kb of strain 610 respectively without cross hybridization with nonvirulent leptospires such as L. biflexa strain Patoc I and Leptonema illini. pCX9, another recombinant plasmid, could detect 1.9 kb fragment of strain 017 and had no hybridization with other pathogenic or nonpathogenic leptospires. The results showed that the degree of homology between pathogenic and non-pathogenic leptospires was very low and the degree of homology was very high among the pathogenic leptospires.

Cloning, Molecular↗

PubMed1991

[Liver injuries].

Explore the source record for details and available documents.

Abdominal Injuries↗

PubMed1991

[Influences of an anti-pan-T cell ricin A-chain immunotoxin on generation of human immunocompetent T cells and hematopoietic progenitor cells].

SOKT1 -RTA immunotoxin, which consisted of an anti-pan-T cell monoclonal antibody SOKT1 and ricin toxin A-chain, decreased the peripheral blood lymphocyte transformation in response to PHA and to alloantigen by 92.9% and 84.7%, respectively. The generation of allocytotoxic T cell was also dramatically inhibited by this immunotoxin. After treatment of human bone marrow mononuclear cells with the immunotoxin, erythroid proliferation in CFU-E test preserved 62.9%. Based on these findings, we concluded that SOKT1-RTA immunotoxin can effectively inactivate human T lymphocytes in vitro without serious toxic effect on the hematopoietic progenitor cells. It may be an effective agent in aGVHD prophylaxis.

Antibodies, Monoclonal↗

PubMed1991

Duration of immunity following immunization with live measles vaccine: 15 years of observation in Zhejiang Province, China.

The duration of immunity following measles vaccination of 2882 immunized children has been investigated in a closed region of China for 15 years. A total of 1002 of the children were treated as primary immunization subjects, and 1547 as reimmunization subjects. These two cohorts were not in contact with known wild measles virus over the whole observation period, and the results obtained probably reflected the antibody responses to measles vaccine alone. The remaining 333 vaccinees came into contact with wild measles virus, and this permitted evaluation of the protective effect of the measles vaccines tested: 4 children experienced very mild clinical measles, and 329 experienced subclinical infection, including 12 who had had undetectable haemagglutination-inhibition antibodies for 9-10 years. These results indicate that the immunity induced by successful primary immunization may persist for at least 15 years. Within this period, a second dose of vaccine only induces low antibody responses which decrease rapidly to their original levels. This provides strong evidence that the immunity produced by primary immunization is long-lasting. However, there were some indications that reimmunization might produce better effects if live attenuated measles virus were used with a longer interval between doses.

Adolescent↗

PubMed1990

[Study on the production, identification of serogroup-specific monoclonal antibodies against leptospires of Australis serogroup and detection of its antigen].

Spleen cells of BALB/c mice immunized with whole Leptospira interrogans serogroup Australis serovar australis strain 620 were fused with myeloma cells line SP2/0. Specificities of four McAbs determined by MAT. 2E1 McAb (IgG3) reacted with 11 serovars, of the Australis serogroup, but did not react with 22 representative serovars of L. interrogans in 20 serogroups, L. biflexa strain patoc I and Leptonema illini strain 3055. 2E1 McAb showed serogroup specificity for Australis by agglutination and the other 3 McAbs showed partial serogroup specificity. We compared the outer envelope (OE) protein profiles of serovar australis strain 620 with those of two pathogenic L. interrogans serovar lai strain 601 and serovar hebdomadis strain 156 by SDS-PAGE. 63kd protein profile was only found in the OE of strain 620, and the quantity of 42kd protein of strain 620 was greater than that of strain 601 and 156. The immunoblotting revealed that 2E1 McAb reacted with a 34kd band in the OE preparation of serovar australis strain 620, but did not react with that of other two L. interrogans. 2E1 McAb also did not react with OE of non-pathogenic leptospires. It was suggested that 34kd protein might contain the antigenic determinants which were shared by leptospires of Australis serogroup.

Animals↗