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Biomedical subjects

J Zhao

Publications and source records attributed to J Zhao.

At least 703 records · Page 39Linked to original sources
PubMed1992

Electrochemical enzyme immunoassay for detection of toxic substances.

Sensors that provide reliable, rapid measurement of toxic substances are needed to solve significant human health and safety problems. We developed a new biosensor design that combines the advantages of immunoassay with electrochemical response. We established that this enzyme-linked immunosensor measures toxic substances in biological samples. The biosensor consists of two major elements: (1) an electrical conducting layer having immobilized enzyme, polyclonal or monoclonal antibodies, and other necessary reagents, and (2) the electronic components used in the signal readout. The result is an amperometric immunoassay based on coupling the immunochemical reaction to the enzyme electrode response by using a soluble, electrochemically active mediator. The specific question addressed was: Does the system's immunochemical detection reliably respond at sufficiently low analyte concentrations? We present our results in these areas: (1) enzyme immobilization on colloidal gold; (2) colloidal gold-enzyme deposition on the electrode surface; (3) mediator-antigen conjugate synthesis; (4) antibody incorporation at the electrode surface; (5) bioelectrode characterization and optimization; and (6) immunosensor demonstration to detect antigen. Sensors that employ immunochemical detection will have broad applicability to detect/diagnose toxic substances in biological samples such as blood and urine and in environmental samples such as wastewater and drinking water.

Biosensing Techniques↗
PubMed1992

The prophylactic effect of thyroxin on kanamycin ototoxicity in guinea pigs.

Guinea pigs receiving intramuscular kanamycin sulfate 400 mg/kg daily and thyroxin 10 mg/kg orally every other day for 9 days were studied to determine whether thyroxin prevents toxic damage to the cochlea from kanamycin. The auditory brainstem response thresholds of wave IV evoked by tone pip stimuli at 4 and 8 kHz were found to be 19.1 dB and 27.2 dB poorer, respectively, for the kanamycin-only animals. Less than 10% of outer hair cells were damaged in 80% of basal turns but without any involvement in the rest turns in animals given thyroxin. Over 50% of outer hair cells were damaged in 65.4% of basal turns and over 50% of the second and third turns were also involved in the kanamycin-only group. Our study suggests that thyroxin reduces the accumulation of kanamycin in the perilymph and prevents the ototoxicity of kanamycin.

Animals↗
PubMed1992

Cloning and nucleotide sequence analysis of a chloramphenicol acetyltransferase gene from Vibrio anguillarum.

The chloramphenicol resistant gene (cat) encoding chloramphenicol acetyltransferase (CAT) in a transferable R plasmid (pJA7324) isolated from the fish pathogen Vibrio anguillarum strain PT24 was cloned into the plasmid vector pUC19. The nucleotide sequence analysis of 1,348 base pair DNA identified an open reading frame encoding a protein of 216 amino acid residues with a calculated molecular mass of 25,471 daltons. The predicted amino acid sequences for this cat gene are 37-69% homologous with other CAT proteins of both Gram-negative and -positive bacteria. Colony hybridization performed with a PvuII-BamHI fragment including this cat gene as a probe, revealed that the same or similar chloramphenicol resistance genes existed among V. anguillarum isolates.

Amino Acid Sequence↗
PubMed1992

Nucleotide sequence analysis of the class G tetracycline resistance determinant from Vibrio anguillarum.

The nucleotide sequence of the class G tetracycline resistance determinant previously isolated from Vibrio anguillarum has been determined. Two open reading frames of divergent polarity were identified. A resistance gene (tet A) encodes a protein of 393 amino acid residues (deduced molecular mass of 40.9 kDa), and a repressor gene (tet R) encodes a protein consisting of 210 amino acids with a calculated molecular mass of 23.6 kDa. Based on the deduced amino acid sequences, the proteins of tet A(G) and tet R(G) are about 60% homologous with those of RP1/Tn1721 (class A) and pSC101/pBR322 (class C), and about 50% homologous with Tn10 (class B). The relationship of the tet (G) sequence to five known tetracycline resistance determinants (class A to E) is discussed.

Amino Acid Sequence↗
PubMed1992

Beat-to-beat changes in AV nodal refractory and recovery properties during Wenckebach cycles.

The roles of changes in refractory and recovery properties of the atrioventricular node as affected by facilitation and fatigue in the genesis of Wenckebach periodicity were studied in isolated rabbit heart preparations. The contribution of nodal recovery time, facilitation, and fatigue to beat-to-beat changes in nodal conduction time (NCT) and effective (ERPN) and functional refractory periods of node (FRPN) occurring during stable 4:3 Wenckebach cycles was determined with premature stimulation protocols performed during these cycles. Fatigue prolonged, equally for each beat, NCT, ERPN, and FRPN, and therefore did not contribute to Wenckebach periodicity. Beat-to-beat increases in facilitation broadened the range of recovery times for which conduction was successful and decreased NCT, ERPN, and FRPN below the values expected from fatigue alone. However, ERPN and NCT increased overall from beat to beat because of NCT-induced (effects of NCT on ensuing refractoriness) increases in nodal refractoriness and consequent shortenings of the recovery time. These findings establish a complementary role for the recovery and refractory properties in generating the Wenckebach periodicity and demonstrate the modulating roles of facilitation and fatigue on this phenomenon.

Animals↗
PubMed1992

Metabolic effects of treadmill exercise training on the diabetic heart.

This study determined whether exercise training in rats would prevent the accumulation of lipids and depressed glucose utilization found in hearts from diabetic rats. Diabetes was induced by intravenous streptozotocin (60 mg/kg). Trained diabetic rats were run on a treadmill for 60 min, 27 m/min, 10% grade, 6 days/wk for 10 wk. Training of diabetic rats had no effect on glycemic control but decreased plasma lipids. In vivo myocardial long-chain acylcarnitine, acyl-CoA, and high-energy phosphate levels were similar in sedentary control, sedentary diabetic, and trained diabetic groups. The levels of myocardial triacylglycerol were similar in sedentary control and diabetic rats but decreased in trained diabetic rats. Hearts were perfused with buffer containing diabetic concentrations of glucose (22 mM) and palmitate (1.2 mM). D-[U-14C] glucose oxidation rates (14CO2 production) were depressed in hearts from sedentary diabetic rats relative to sedentary control rats. Hearts from trained diabetic rats exhibited increased glucose oxidation relative to those of sedentary diabetic rats, but this improvement was below that of the sedentary control rats. [9,10(-3)H]palmitate oxidation rates (3H2O production) were identical in all three groups. These findings suggest that exercise training resulted in a partial normalization of myocardial glucose utilization in diabetic rats.

Animals↗
PubMed1992

Fusion of a scid pre-B cells with a wild type (myeloma) B cell results in correct rearrangement of a V(D)J recombination substrate.

Mice with the scid mutation have a defect in the V(D)J recombinase. In order to determine whether the SCID product is normally present in mature B cells that do not have the recombinase activity, scid pre-B cells were fused with myeloma cells. It was found that in the hybrid cells, a rearrangement test gene was correctly joined immediately after fusion. The same test gene was aberrantly rearranged in the scid pre-B cells. Stable hybrids between the scid pre-B and the myeloma cells had lost the expression of RAG-1 and RAG-2 genes, supporting the previous finding of an inhibitor of rearrangement in myeloma cells that acts shortly after fusion. Thus, mature B cells apparently contain the SCID product, the wild type SCID function is not competitively interfered with by products present in scid pre-B cells, and the SCID product seems not to be a target for the recombinase inhibitor.

Animals↗
PubMed1992

[Study on the infections of U. urealyticum, M. hominis, and C. trachomatis in patients with venereal diseases and healthy controls in three areas of China].

Two hundred and thiry-nine patients with venereal diseases and 264 healthy controls, from Yichang, Liuzhou, and Beijing, were detected for the antibodies to Ureaplasma urealyticum (Uu). Mycoplasma hominis (Mh), and Chlamydia trachomatis (Ct) by indirect hemagglutination (IHA) in 1990. The results showed that: 1) in patients with venereal diseases, the positive rates was the highest in Ct (27.62%), higher in Uu (17.57%), and lower in Mh (4.18%); 2) the levels of antibody to Ct and Uu were significantly higher in the patients than in the healthy controls; 3) in the patients, the positive rate of antibody to Ct was the highest in Beijing (55.88%), whereas, the lowest in Yichang (15.28%); the prevalence rate of antibody to Uu was the highest in Liuzhou (26.23%), whereas, the lowest in Beijing (5.88%); the level of antibody to Mh was not significantly different in the areas mentioned; and 4) the patients with venereal diseases were commonly complicated with infections caused by Ct, Uu, and Mh, there was a new problem to control and treat venereal diseases.

Adolescent↗
PubMed1992

[An outbreak of rubella with a cinema as source].

An outbreak of rubella occurred in four primary schools at jiu-bao town Yuhang county from twentieth Dec. 1989 to twelfth Feb. 1990. Attack rate was 37.46%. The patients had typical clinical features, and its prognosis was good. Average latent period was 17.8 days. The outbreak was suggested to related to a cinema, the first generation of 196 cases had the history of going to the movies. There was no case among those who had not gone to the same cinema at the same period. The highest attack rate was 56.97% in a primary school. The highest attack rate of age group was at 10-15 year group (48.40%), the rubella IgM positive rate at 2-5 days and 6-20 days were 52.63% and 76.66% respectively. 30 days later, no positive result was found.

Adolescent↗
PubMed1992

Overexpression of H-ras oncogene induces resistance to the growth-inhibitory action of transforming growth factor beta-1 (TGF-beta 1) and alters the number and type of TGF-beta 1 receptors in rat intestinal epithelial cell clones.

In this report, we utilize rat intestinal cell (IEC-18) clones expressing an activated human H-ras gene to investigate the relationship between malignant transformation and growth control by transforming growth factor beta (TGF-beta). We demonstrate that clones expressing high levels of H-ras oncogene lose sensitivity to the growth inhibitory action of TGF-beta. The loss of sensitivity is related to the degree of H-ras expression and is shown to be a direct consequence of H-ras expression through the use of a clonal cell line with inducible expression of activated H-ras. Co-incident with the loss of growth inhibition, ras-expressing clones display an altered expression of TGF-beta-binding proteins as detectable by [125I]TGF-beta cross-linking. While IEC-18 cells express type II (92 kDa) binding protein predominantly, H-ras expression induces a shift to predominantly type I (69 kDa) binding protein expression.

Animals↗
PubMed1992

[Immunological identification of tiger-bone].

Anti-tiger sera were prepared by using tiger serum proteins to immunize the rabbits. Tiger-bone can be identified by the specific serological reaction between the anti-tiger sera and the tiger-bone proteins.

Animals↗
PubMed1992

Strain- and age-associated differences in lymphocyte phenotypes and immune responsiveness in C4-deficient and Albany strains of guinea-pigs.

Spleen lymphocytes from C4-deficient (C4D) and Albany strains of guinea-pigs, 1-7 days, 3-6 and 12-16 months old, genetically related to inbred strains 13 and 2 respectively, were analysed in terms of their expression of cell surface markers, allogenic and T- and B-cell mitogenic responses, and interleukin-1 (IL-1) and IL-2 production. There were strain- and age-associated differences in phenotypic expression and immune responsiveness levels. In both strains a significant shift in immunocompetence apparently occurs postnatally before 3-6 months of age, with no further significant changes noticed in animals 12-16 months old. Phenotypic changes in cell surface markers did not always correlate with functional capability of lymphoid cells. H159+ (pan T) and H155+ (CD4) lymphocyte number and levels of T-cell responsiveness (mitogenic and allogenic responses, and IL-2 production) were higher in C4D neonates compared with age-matched Albany guinea-pigs or with young animals of the same strain. On the other hand, 31D2+ (B) lymphocytes in a significantly higher proportion in Albany neonates compared with similarly aged C4D, did not correlate at this age or at any other time with their proliferative response to lipopolysaccharide (LPS) or dextran sulphate (DS), two B-cell-specific mitogens.

Aging↗
PubMed1992

[A control study of intravenous versus oral clomipramine in major depression].

Intravenous clomipramine (n = 105) and oral clomipramine (n = 64) were compared in a control study of 169 inpatients with major depression. The therapeutic effects were evaluated with four-degree scale and the rating scales of HDS and CGI. The results showed intravenous group has earlier response and better antidepressive effects than oral group within treatment period of 2 weeks. No significant differences between two groups were found in anticholinergic side-reaction. Clinical useful values of intravenous clomipramine were discussed.

Administration, Oral↗
PubMed1991

Amplified gene expression in CD59-transfected Chinese hamster ovary cells confers protection against the membrane attack complex of human complement.

Protection against the pore-forming activity of the human C5b-9 proteins was conferred on a nonprimate cell by transfection with cDNA encoding the human complement regulatory protein CD59. CD59 was stably expressed in Chinese hamster ovary cells using the pFRSV mammalian expression vector. After cloning and selection, the transfected cells were maintained in media containing various concentrations of methotrexate, which induced surface expression of up to 4.2 x 10(6) molecules of CD59/cell. Phosphatidylinositol-specific phospholipase C removed greater than 95% of surface-expressed CD59 antigen, confirming that recombinant CD59 was tethered to the Chinese hamster ovary plasma membrane by a lipid anchor. The recombinant protein exhibited an apparent molecular mass of 21-24 kDa (versus 18-21 kDa for human erythrocyte CD59). After N-glycanase digestion, recombinant and erythrocyte CD59 comigrated with apparent molecular masses of 12-14 kDa, suggesting altered structure of asparagine-linked carbohydrate in recombinant versus erythrocyte CD59. The function of the recombinant protein was evaluated by changes in the sensitivity of the CD59 transfectants to the pore-forming activity of human C5b-9. Induction of cell-surface expression of CD59 antigen inhibited C5b-9 pore formation in a dose-dependent fashion. CD59 transfectants expressing greater than or equal to 1.2 x 10(6) molecules of CD59/cell were completely resistant to human serum complement. By contrast, CD59 transfectants remained sensitive to the pore-forming activity of guinea pig C8 and C9 (bound to human C5b67). Functionally blocking antibody against erythrocyte CD59 abolished the human complement resistance observed for the CD59-transfected Chinese hamster ovary cells. These results confirm that the C5b-9 inhibitory function of the human erythrocyte membrane is provided by CD59 and suggest that the gene for this protein can be expressed in xenotypic cells to confer protection against human serum complement.

Animals↗
PubMed1991

Inhibition of homologous complement by CD59 is mediated by a species-selective recognition conferred through binding to C8 within C5b-8 or C9 within C5b-9.

The capacity of the human complement regulatory protein CD59 to interact with terminal complement proteins in a species-selective manner was examined. When incorporated into chicken E, CD59 (purified from human E membranes) inhibited the cytolytic activity of the C5b-9 complex in a manner dependent on the species of origin of C8 and C9. Inhibition of C5b-9-mediated hemolysis was maximal when C8 and C9 were derived from human (hu) or baboon serum. By contrast, CD59 showed reduced activity when C8 and C9 were derived from dog or sheep serum, and no activity when C8 and C9 were derived from either rabbit or guinea pig (gp) serum. Similar specificity on the basis of the species of origin of C8 and C9 was also observed for CD59 endogenous to the human E membrane, using functionally blocking antibody against this cell surface protein to selectively abrogate its C5b-9-inhibitory activity. When E bearing human CD59 were exposed to C5b-8hu, CD59 was found to inhibit C5b-9-mediated lysis, regardless of the species of origin of C9, suggesting that the inhibitory function of CD59 can be mediated through recognition of species-specific domains expressed by human C8. Consistent with this interpretation, CD59 was found to bind to C5b-8hu but not to C5b67hu or C5b67huC8gp. Although CD59 failed to inhibit hemolysis mediated by C5b67huC8gpC9gp, its inhibitory function was observed for C5b67huC8gpC9hu, suggesting that, in addition to its interaction with C5b-8hu, CD59 also interacts in a species-selective manner with C9hu incorporated into C5b-9. Consistent with this interpretation, CD59 was found to bind both C5b67huC8gpC9hu and C5b-8huC9gp, but not C5b67huC8gpC9gp. Taken together, these data suggest that the capacity of CD59 to restrict the hemolytic activity of human serum complement involves a species-selective interaction of CD59, which involves binding to both the C8 and C9 components of the membrane attack complex. Although CD59 expresses selectivity for C8 and C9 of human origin, this "homologous restriction" is not absolute, and this human complement regulatory protein retains functional activity toward C8 and C9 of some nonprimate species.

Antigens, Differentiation↗