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Biomedical subjects

R Jin

Publications and source records attributed to R Jin.

At least 109 records · Page 6Linked to original sources
PubMed1992

Thermodynamics and structure of a DNA tetraplex: a spectroscopic and calorimetric study of the tetramolecular complexes of d(TG3T) and d(TG3T2G3T).

We report a combined thermodynamic and structural characterization of a DNA tetraplex. Using spectroscopic and calorimetric techniques, we demonstrate that d(TG3T) and d(TG3T2G3T), in the presence of K+, form stable tetramolecular complexes. From differential scanning calorimetry measurements, we obtain the following thermodynamic profiles for formation of each tetraplex at 25 degrees C: delta G degrees = -6.9 kcal/mol of tetraplex (or -2.3 kcal/mol of tetrad; 1 cal = 4.184 J), delta H degrees = -62.6 kcal/mol of tetraplex (or -20.9 kcal/mol of tetrad), and delta S degrees = -186.9 cal.K-1.mol-1 of tetraplex (or -62.3 cal.K-1.mol-1 of tetrad) for the d(TG3T) tetraplex; and delta G degrees = -20.2 kcal/mol of tetraplex (or -3.4 kcal/mol of tetrad), delta H degrees = -123.2 kcal/mol of tetraplex (or -20.5 kcal/mol of tetrad), and delta S degrees = -346.0 cal.K-1.mol-1 of tetraplex (or -57.7 cal.K-1.mol-1 of tetrad) for the d(TG3T2G3T) tetraplex. These data demonstrate that at 25 degrees C a G-tetrad can exhibit considerable stability, comparable to or even exceeding that of most Watson-Crick nearest-neighbor interactions, with this stability resulting from a very favorable enthalpy of formation. Temperature-dependent CD measurements reveal that the melting temperatures of both tetraplexes exhibit unusually low salt dependences. This unexpected behavior may reflect a diminished charge density due to bound K+ ions. For each complex, the Na+ and K+ forms exhibit drastically different isothermal and temperature-dependent CD profiles, with the K+ forms of each tetraplex melting more sharply and at a higher temperature than the Na+ forms. Using one- and two-dimensional NMR techniques, we show that the strands in the tetramolecular complex of d(TG3T), K+ are all parallel and that the guanine glycosidic conformations are all anti.

Base Sequence↗
PubMed1992

[Effects of artificial cultured Panax notoginseng cell on cardiovascular system].

Alcoholic extract from artificial cultured Panax notoginseng cell (SCC) ip has been found conducive to increasing the resistance of mice to anoxia. In vitro it helps to increase the outflow of coronary vessels, decrease the heart rate, inhibit the constriction of aortic strip stimulated by nor-epinephrine and relax spasmodic constriction of ileum smooth muscles markedly. SCC powder suspension on po administration can contract bleeding and coagulation time. The pharmacologic activities of SCC are similar to those of crude Panax notoginseng.

Animals↗
PubMed1991

Characterization by 1H NMR of glycosidic conformations in the tetramolecular complex formed by d(GGTTTTTGG).

We have conducted two dimensional NOESY studies on the molecule d(G2T5G2) to characterize the structure of the tetramolecular complex previously identified by calorimetric and spectroscopic studies (1). Analysis of the NOE and exchange cross peaks observed in the NOESY spectra establishes the formation of structured conformations at low temperature (5 degrees C). Significantly, within each strand of these structured conformations, the G1 and G8 residues adopt syn glycosidic torsion angles, while the G2 and G9 residues adopt anti glycosidic torsion angles. Consequently, any structure proposed for the tetramolecular complex of d(G2T5G2) must have alternating G(syn) and G(anti) glycosidic torsion angles within each strand. The implications of this observation for potential structures of the tetramolecular complex of d(G2T5G2) are discussed.

Base Sequence↗
PubMed1991

Monoclonal antibody-defined epitope map of expressed rubella virus protein domains.

An expanded library of murine monoclonal antibodies (MAbs) was generated by infecting BALB/C mice with the Therien strain of rubella virus (RV) and selecting secreting hybrids by enzyme-linked immunosorbent assay (ELISA) using purified virion targets. A panel of plasmids containing specified RV cDNA fragments was also constructed by using a variety of strategies with pGE374- and pGE374-derived expression vectors. Hybrid RecA-RV-beta-galactosidase (LacZ)- or RecA-RV-truncated LacZ-containing proteins collectively representing the entire open reading frame of the structural proteins of RV were overexpressed in Escherichia coli. Bacterial lysates were then probed by ELISA with selected MAbs and by immunoblot following separation by electrophoresis under denaturing conditions. With this approach, MAbs that appeared to react with linear determinants defined epitopes localized within the following domains: MAbs C-1, C-2, and C-8 bind epitopes within the predicted amino-terminal 21 amino acids of the capsid region C9 to C29; MAb C-9 binds to a domain bounded by C64 and C97; MAbs E2-1 through E2-6 bind to the E2 glycoprotein backbone region from E2(1) to E2(115); MAbs E1-18 and E1-20 bind to the E1 glycoprotein region from E1(202) to E1(283). MAb E1-18 neutralizes RV infectivity; MAb E1-20 neutralizes infectivity and modestly inhibits hemagglutination. Analyses with selected synthetic peptides have confirmed several of the molecular domains deduced with the expressed proteins. These plasmid constructions and peptides have proven useful in beginning to unravel the molecular organization of several antigenic sites of this human pathogen.

Animals↗
PubMed1991

[Textual and herbal studies on shashen and qini (Adenophora spp.)].

This paper reports the origins of the Chinese traditional drugs nanshashen and beishashen, as well as the original plants of shashen, xingyeshashen, xiyeshasen and qini recorded in the bencaological works of the past dynasties. Our study shows that shashen is Adenophora stricta, both xingyeshashen and qini are A. hunanensis and xiyeshashen is A. paniculata.

Drugs, Chinese Herbal↗
PubMed1989

Growth-associated shedding of a tumor antigen (CE7) detected by a monoclonal antibody.

A monoclonal antibody was developed against an antigen, termed CE7, which was highly expressed on the surface of rat fibrosarcoma KMT-17 cells (clone A3) cultured in low serum medium (A3-1% FCS). The CE7 antigen was not detectable on A3 cells cultured in ordinary high serum medium (A3-10% FCS), on in vivo passaged A3 cells, or on parental in vivo KMT-17 cell line. However, immunoelectron microscopy and Western blot analyses indicated that CE7 antigen was produced by these tumor cells in all circumstances but was shed from their surfaces in vesicular form into the surrounding tissue culture medium or ascites, unless low serum concentration prevailed and disappeared from their cell surfaces. We have previously reported that the immunogenicity of A3 cells was increased when the serum concentration was lowered from 10% to 1% and the phenomenon paralleled the CE7 antigen expression on the A3 cells. These results suggest that the CE7 antigen could be a tumor-associated rejection antigen and that the expression of the CE7 antigen on A3-1% FCS cells (which is shed by high serum culture or in vivo transplantation and disappears from the cell surface) may play a role in immunological responses against the tumor cells.

Animals↗
PubMed1988

Characterization of the minor groove environment in a drug-DNA complex: bisbenzimide bound to the poly[d(AT)].poly[d(AT)]duplex.

We compare the fluorescence properties of bisbenzimide (also known as Hoechst 33258) bound to the minor groove of the poly[d(AT)].poly[d(AT)] duplex with the corresponding fluorescence properties of bisbenzimide dissolved in neat organic solvents and mixed organic/aqueous solvents. Based on these comparisons, we conclude that the minor groove of the bisbenzimide-poly[d(AT)].poly[d(AT)] complex is quite nonpolar and exhibits a local dielectric constant of approximately 20 D. We discuss how this insight influences our understanding of the molecular forces that dictate and control the binding affinities and specificities of minor groove-directed DNA binding ligands.

Benzimidazoles↗
PubMed1986

Influence of mixing technique on some properties of PMMA bone cement.

PMMA bone cements (Refobacin-Palacos R, Sulfix 6, AKZ, and CMW bone cement, types I and II), from six different clinics, were investigated in three stages. In the first stage, studies of density, hardness, flexural strength, and compressive strength were made, as well as molecular weight measurements and microscopic investigations. These studies reflected the current state of techniques of application used in operating theaters. They revealed wide variations in the properties of the materials studied. Secondly, a comprehensive study of the process-technology in the laboratory was performed. The following variables were investigated or discussed: mixing vessel, order of the individual components, mixing time, rate of mixing, pressure application on the mixed bone cement, kneading, cement thickness, pouring into the syringe, contact force during polymerization, and preparation quantity. The third stage involved the development and clinical testing of an improved mixing technique. Using this improved mixing technique, all three selected clinics achieved far better results with reduced variability. A comparison between a centrifuging technique after mixing and our improved, but conventional, mixing technique, displays advantages for the latter. The question regarding a correlation between cement specimens of high porosity and early implant loosening could not be answered on the basis of the 43 PMMA bone cement explants investigated (implanted 6 months to 15 years). In some cases, the studies revealed that the bone cement manufacturers should be required to revise and quantify existing instructions for use. The users, on the other hand, should give more consideration to the mixing technique and its consequences.

Bone Cements↗
PubMedDate not supplied

Toluene diisocyanate protein adducts in the bronchoalveolar lavage of guinea pigs exposed to vapors of the chemical.

To investigate the process of toluene diisocyanate (TDI) sensitization, studies were conducted to identify TDI-protein adducts in the bronchoalveolar lavage (BAL) fluid of guinea pigs exposed to a sensitizing atmosphere of the commercially used 4:1 mixture of 2,4- and 2,6-TDI. Animals were exposed to 2 ppm TDI for 3 h. Immediately thereafter lungs were lavaged. TDI-modified proteins in the lavage fluid were identified by immunologic staining with a highly sensitive and specific rabbit antiserum raised to a TDI-keyhole limpet hemocyanin (TDI-KLH) conjugate. The sensitivity of the antiserum was demonstrated by its ability to identify TDI-guinea pig serum albumin (GSA) adducts with as few as 0.7 mol of TDI/mol of protein. The antiserum did not react with GSA nor with a GSA adducted with another aromatic diisocyanate, diphenylmethane 4,4'-diisocyanate. TDI-protein adducts in the BAL fluid were identified by sodium dodecyl sulfate-polyacrylamide gel electrophoresis followed by immunoblotting with use of the rabbit anti TDI-KLH antiserum. At least 5 protein bands were recognized by the antiserum. Electrophoretic mobilities indicated molecular sizes equivalent to 10.5, 38, 45, 66, and 148 kDa. Employing a murine anti-GSA antibody in immunoaffinity chromatography, one of the proteins in the 66-kDa band was identified as serum albumin. Attempts to purify the TDI-albumin adduct using a Cibacron-Sepharose column were unsuccessful. Studies with a model TDI0.7-GSA conjugate (which contained an average of 0.7 mol of TDI/mol of GSA) indicated that the TDI-albumin was not retained by the triazine dye column unless the adducted protein was first reduced by incubation with mercaptoethanol.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMedDate not supplied

In vivo and in vitro reactions of toluene diisocyanate isomers with guinea pig hemoglobin.

Guinea pig hemoglobin (Hb) adducts of 2,4- and 2,6-toluene diisocyanate (2,4- and 2,6-TDI) were individually prepared, each at a Hb tetramer to diisocyanate ratio of 1:1, and compared with adducts of Hb from animals exposed to 1 ppm 2,4-TDI vapor. Each Hb sample was subjected to C4 HPLC chain/heme separation with UV detection. Survey of the LC fractions using an antiserum prepared to a heterologous TDI-protein indicated a difference in chain specificity and product types formed in vitro by the two isomers. Ionspray mass spectrometry (MS) revealed the chemistry of the adduction products. Carbamoylated products, formed from adduction by one TDI molecule (with one isocyanato group hydrolyzed to an amino group), were detected by MS with 2,4-TDI on each chain and with 2,6-TDI on the beta chain. Additionally, a quasi-molecular ion of a bis carbamoylation adduct was noted by MS in the in vitro 2,4-TDI-Hb adduct in the form of TDI-cross-linked alpha and beta chains. Ionspray MS analysis of the Hb isolated from guinea pigs exposed in vivo to 2,4-TDI indicated carbamoylation products with both the alpha and beta chains in which one of the two original isocyanato groups had been hydrolyzed to the amine. We also found evidence of an amine-nitroso adduct on the alpha chain in the in vivo sample. These results indicate that at least one of the isocyanato moieties (or a masked derivative) of 2,4-TDI survived passage through the lung, into the serum, and through the erythrocyte membrane to form adducts with Hb that were stable to dialysis, gel filtration, and reversed phase HPLC separation under acidic conditions. The presence of an apparent amine-nitroso adduct indicated in vivo formation of 2,4-diaminotoluene, a recognized animal carcinogen.

Administration, Inhalation↗
PubMedDate not supplied

Physician asthma management practices in Canada.

OBJECTIVES: To establish national baseline information on asthma management practices of physicians, to compare the reported practices with the Canadian Consensus recommendations and to identify results potentially useful for interventions that improve physician asthma management practices. DESIGN: National, stratified cross-sectional survey. SETTINGS: The 10 provinces and two territories of Canada, from 1996 to 1997. PARTICIPANTS: Questionnaires were sent to 4489 physicians stratified by province/territory and specialty group (family/general practice, respirology, internal medicine, pediatrics and allergy/immunology); 2605 responses were received. OUTCOME MEASURES: Methods for the diagnosis, treatment, education and follow-up of patients with asthma ('asthma management practices'). RESULTS: Significant variations existed among the five specialty groups in asthma management practices. A low use of objective measures of airflow limitation to assist with diagnosis was found among some respondents (mostly family physicians). Up to 40% of physicians regarded the daily fixed dosing (three or four times a day) of inhaled, short acting beta2-agonist as 'first-line therapy' for moderate to severe asthma. A minority of physicians reported using written action plans for patients or referring them to other health professionals for asthma education. Insufficient time during appointments and a perceived lack of appropriate educational materials were frequently cited as reasons for not providing asthma education. The perceived knowledge of the Canadian Consensus recommendations varied among physicians but was lowest among nonspecialists. CONCLUSIONS: The survey showed variations in certain aspects of the management of asthma by physicians. The findings will help to target specific areas for future physician education programs and other behavioural change strategies.

Asthma↗