Search PubMed⌕ Search

Biomedical subjects

H Jiang

Publications and source records attributed to H Jiang.

At least 649 records · Page 36Linked to original sources
PubMed1991

Effect of epinephrine or cAMP on cAMP-bound protein kinase holoenzymes in rat heart.

Nonperfused or epinephrine-perfused rat hearts were used to examine the relative amounts of adenosine 3',5'-cyclic monophosphate (cAMP)-free and cAMP-bound holoenzymes of type II cAMP-dependent protein kinase (cAK). Crude tissue extracts of nonperfused hearts were chromatographed in the absence or presence of [3H]cAMP using DEAE-high-performance liquid chromatography. A partially resolved cAMP-free peak of cAK eluted at 0.17 M NaCl, and an asymmetric peak containing bound [3H]cAMP eluted at a slightly higher NaCl concentration. The first peak contained a tetrameric holoenzyme [2 regulatory (R) subunits and 2 catalytic (C) subunits]. From analysis of R-to-C ratios, the [3H]cAMP-bound peak contained a mixture of tetrameric and trimeric (R2C) forms. Both cAMP-free and cAMP-bound holoenzyme forms were virtually inactive without added cAMP under the conditions used. [3H]cAMP dissociation rate studies revealed that the bound cAMP in the peak fraction was equally distributed in the two different binding sites of the enzyme. Compared with the cAMP-free form, the cAMP-bound enzyme in the peak fraction exhibited enhanced binding in nonequilibrium [3H]cAMP binding assays. The cAMP-bound holoenzymes were estimated to represent at least 64% of the total type II cAK in control extracts, and the cAMP-free form was largely converted to the cAMP-bound forms by perfusing hearts with epinephrine.

Animals↗
PubMed1991

Normalization of force generated by canine airway smooth muscles.

A variety of normalizations have been employed to compare maximal isometric force (Po) produced by smooth muscles at different locations and stages of maturation. Because these procedures have not always been based on rigorous principles, confusion has resulted. To obtain a less ambiguous index of force production, we measured in vitro Po from mongrel canine tracheal (TSM) and bronchial (BSM) smooth muscle with an electromagnetic lever and normalized it to force per unit cross-sectional area of whole tissue (tissue stress), to force per unit cross-sectional area of muscle in the cross section of total tissue (muscle stress), and to force per fractional unit of myosin in the tissue cross section (myosin stress). Proportion of myosin in cross-sectional area of tissue was deduced from data obtained by sodium dodecyl sulfate gel electrophoresis of crude muscle extracts. For TSM, tissue stress was 1.499 X 10(5) N/m2 +/- 0.1 (SE), whereas it was only 0.351 X 10(5) N/m2 +/- 0.05 (SE) for BSM, representing a 4.27-fold difference (P less than 0.01). There was a 1.60-fold difference (P less than 0.05) in muscle stress, which was correlated to the morphometric finding that 79 +/- 1.4% (SE) of the tracheal strip cross section was muscle, whereas only 30 +/- 1.0% (SE) of bronchial tissue was occupied by muscle. Average myosin content was the same in smooth muscle cells of TSM and BSM, indicating that total amount of myosin in tissue cross sections was essentially a function of proportional area of muscle cells in total tissue cross sections.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Effect of FK-506 on heart allograft survival in the highly sensitized recipient rats as compared with ciclosporin and 15-deoxyspergualin.

The effect of FK-506 on allograft survival in unsensitized recipients has been established in several animal experimental models. In this present study, we investigated the immunosuppressive capacity of FK-506, in comparison with ciclosporin (Cs) and 15-deoxyspergualin (DSG), on heart allograft in presensitized rats. Heart grafts from male ACI rats were heterotopically transplanted to male LEW rats. All recipient rats were sensitized with donor-type whole blood admixed with immunoadjuvant (adjuvant complete Freund) 7 days prior to transplantation. FK-506, Cs and DSG were administered from day 0 to day 14 posttransplantation. The results showed that both FK-506 and Cs significantly prolonged heart allograft survival of presensitized recipients in a dose-dependent manner. The minimum effective dose in the treatment was less for FK-506 than for Cs. However, DSG showed almost no effect of prolongation in this experiment.

Animals↗
PubMed1991

Inhibitory regulation of serum factor(s)-caused ornithine decarboxylase induction by the protein kinase C system in A431 human epidermoid carcinoma cells.

Replacement of the culture medium with fresh medium containing 10% fetal calf serum caused ornithine decarboxylase (ODC) induction in A431 human epidermoid carcinoma cells. Two peaks of ODC activity were observed at 5 and 14 hr after the medium replacement. The peak activity observed at 5 hr was more prominent than that at 14 hr. The first peak of ODC induction was suppressed by a potent protein kinase C activator, 12-O-tetradecanoylphorbol-13-acetate (TPA), in a concentration-dependent manner. The second peak, however, was not suppressed by TPA. Other potent protein kinase C activators, such as mezerein and 12-O-retinoylphorbol-13-acetate, also suppressed the first peak of ODC induction. Synthetic diacylglycerols, 1,2-dioctanoyl-sn-glycerol and 1-oleoyl-2-acetylglycerol, did not inhibit the serum factor(s)-caused ODC induction. Phorbol-13-acetate, an inactive phorbol ester, also failed to inhibit the ODC induction. The growth of A431 cells was slightly suppressed by TPA. In protein kinase C down-regulated cells, TPA failed to inhibit the serum factor(s)-caused ODC induction. These results suggest that the serum factor(s)-caused ODC induction in A431 cells is negatively regulated by the protein kinase C system, which may not be activated by exogenous diacylglycerols.

Blood↗
PubMed1991

In vitro kinetic study of the immunosuppressive effect of deoxymethylspergualin on human peripheral blood mononuclear cells.

The immunosuppressive mechanism of Deoxymethylspergualin (MeDSG) was investigated in human subjects by in vitro assay. In an allogeneic mixed lymphocyte reaction (MLR), MeDSG was added at different times. A moderate immunosuppressive activity against allogeneic blastogenesis was seen even when MeDSG was added on the 4th day from the initiation of culture. In the cell-mediated lymphocytolysis (CML) assay, MeDSG was added to bulk MLR in CML in the same manner. For the strong suppression of CML, however, MeDSG should be added to bulk MLR within 2 days from the initiation of culture. There was a difference in immunosuppressive kinetic pattern of MLR and CML induced by MeDSG. In the study of the effect of MeDSG on the interleukin-2 (IL-2) production of allogeneic blast cells, MeDSG showed only a slight suppression. In the MeDSG induced regulator cell assay, these cells induced no suppression of fresh CML, even when they were adoptively transferred to fresh bulk MLR in CML at different times. In the subset analysis of surface phenotypes of allogeneic blast cells in MLR, IL-2R+ cells and CD8+ LFA1+ cells treated with MeDSG, were significantly decreased. These results indicate that MeDSG acts on a comparatively early stage of the afferent phase in allogeneic stimulation and suppresses development of cytotoxic lymphocytes strongly, without inhibition of IL-2 production or suppressive regulator cell induction.

Cytotoxicity, Immunologic↗
PubMed1991

Survival of cardiac allograft in highly sensitized and nonsensitized rats treated with FK506.

The effect of FK506 was studied in sensitized and nonsensitized recipients using a rat cardiac allograft model. Heart grafts from Male ACI rats were heterotopically transplanted to Male LEW rats. The sensitized rat models were established by using donor type blood, admixed with immunoadjuvant (Adjuvant Complete Freund), seven days prior to transplantation. FK506 was administrated from day 0 to day 14 posttransplantation. The results showed that FK506 could prolong allograft survival in both sensitized and nonsensitized rat recipients in a dose-dependent manner, although, the dose required in sensitized recipients was higher than in nonsensitized recipients. The minimal effective dose of FK506 was 0.32 mg/kg/day in sensitized recipients and 0.1 mg/kg/day in nonsensitized recipients.

Animals↗
PubMed1991

Defined chemically cross-linked oligomers of human C-reactive protein: characterization and reactivity with the complement system.

Chemically cross-linked C-reactive protein (CRP) oligomers were prepared and characterized, and C1q binding and C activation were investigated. Purified human CRP was polymerized in the presence of both non-cleavable and cleavable cross-linking agents and further separated by Superose 12 analytical FPLC column chromatography into fractions of 110 KDa (pentameric monomers), 220 KDa (dimers) and 330 KDa (trimers); virtually no larger oligomers were formed under a variety of experimental conditions. CRP subunits were cross-linked both within and between CRP pentamers. CRP trimers retained native CRP antigenicity without expression of neo-CRP epitopes. CRP trimers showed maximal binding and CRP dimers showed partial binding of solid phase C1q while CRP monomers bound virtually no C1q at all; CRP trimers also bound to fluid phase C1q. Binding was Ca++ independent and increased as the ionic strength or pH were lowered, characteristics comparable to binding of aggregated IgG to C1q; it was not inhibited by phosphorylcholine. CRP trimers consumed total C, C1 and C2 haemolytic activities upon incubation in fresh human serum, but much less efficiently than did CRP-protamine complexes or Agg-IgG. CRP trimers failed to deplete alternative C pathway haemolytic activity at all. The stable, chemically defined CRP oligomers described in this report, which bind C1q efficiently but display poor ability to activate the classical C pathway in the absence of an appropriate ligand, should be valuable in further studies of the interactions between CRP and the C system.

C-Reactive Protein↗
PubMed1991

[Determination of tetracyclines by flow injection analysis].

An accurate, convenient and fast method was proposed for the determination of tetracyclines (tetracycline, chlortetracycline, oxytetracycline, doxycycline and methacycline) and their preparations by flow injection detector based on tetracycline flow-through sensor. The parameters affecting the measurement were discussed. The detector can respond to tetracycline, chlortetracycline, oxytetracycline, doxycycline and methacycline, at the same time. Their slopes are 51-55 mV/decade over the concentration range of 10(-2)-5 x 10(-5) mol/L at pH 1.5-3.5. The results obtained are in good agreement with those by biological assay (less than 3% deviation). One hundred samples can be determined in an hour.

Electrochemistry↗
PubMed1991

[Effect of endothelin on rat mesenteric microvessels].

By video microscope, it was observed that endothelin (ET) caused constriction of the mesenteric microvessels of pentobarbital-anesthetized Wistar rats in a dose-dependent manner. With the consequence of causing a decrease of rate of blood flow and even some microcirculation disorder, the action was long lasting. The constrictive effect of ET on microvessel was much stronger than norepinephrine. The results suggest that ET is a potent vasoconstrictor for microvessel and may play an important role in causing microcirculatory disorder.

Animals↗
PubMed1990

The carriage of Escherichia coli resistant to antimicrobial agents by healthy children in Boston, in Caracas, Venezuela, and in Qin Pu, China.

BACKGROUND AND METHODS: The healthy members of a community represent its largest reservoir of bacteria resistant to antimicrobial agents. We compared the resistance to eight agents of Escherichia coli in stool samples from untreated, healthy children in cities on three continents. RESULTS: When screened by a selective method that detected 1 resistant colony in 10,000 colonies, nearly half the children in Boston (18 of 39) had no resistant colonies--a finding consistent with the findings of other surveys performed in developed countries. However, all but 1 of 41 children screened in Caracas, Venezuela, and all but 2 of 53 in Qin Pu, China, carried resistant strains. Only 1 child in Boston but 25 in Caracas and 34 in Qin Pu carried strains resistant to trimethoprim. None of the children in Boston or Caracas but 17 in Qin Pu carried strains resistant to gentamicin. Among 10 colonies selected randomly from each stool sample, the average frequency of resistance in Caracas was 3.6 times greater than in Boston, and that in Qin Pu was 5.3 times greater. There was resistance to five or more antimicrobial agents in 20 percent of the Qin Pu strains and in 6 percent of the Caracas strains but in none of the Boston strains. CONCLUSIONS: In addition to clinical isolates, as reported previously, the bacteria that colonize health children in the community may be resistant far more often in some regions than in others. A low rate of carriage of antimicrobial resistance in the community should become a public health goal.

Anti-Bacterial Agents↗