Biomedical subjects

J F Wang

Publications and source records attributed to J F Wang.

At least 127 records · Page 7Linked to original sources

PubMed1996

Distinct deactivation and desensitization kinetics of recombinant GABAA receptors.

The functional role of the large heterogeneity in GABAA receptor subunit genes and its role in setting the properties of inhibitory synapses in the CNS is poorly understood. A kinetic comparison between currents elicited by ultra-rapid application with a piezoelectric translator of 1 mM GABA to mammalian cells transfected with cDNAs encoding distinct GABAA receptor subunits revealed that the intrinsic deactivation and desensitization properties depend on subunit combination. In particular, receptors containing alpha 6 with beta 2 gamma 2 subunits were endowed with a significantly slower deactivation as compared to those receptors containing alpha 1 with beta 2 gamma 2 subunits. While desensitization produced by prolonged GABA applications on alpha 1 beta 2 gamma 2 receptors was characterized by a rapid exponential decay followed by a slower decay and a steady state response, alpha 6 beta 2 gamma 2 receptors lacked desensitization. Furthermore, GABAA receptors lacking the gamma 2 subunit were characterized by a much larger non-desensitization component and a very rapid deactivation. Lastly, analysis of GABA-activated currents in cells cotransfected with alpha 1 and alpha 6 together with beta 2 gamma 2 subunit revealed unique kinetic properties. Our results suggest that distinct subunit composition confers specific deactivation and desensitization properties that may profoundly affect synaptic decay kinetics and the capability to sustain high frequency synaptic inputs.

Cell Line↗

PubMed1996

Using factor analysis to explore nurses' fear of AIDS in the United States of America.

The purpose of this study was to create a reliable research instrument to test the fear of AIDS (FOA) and to explore the dimension of FOA among nurses. We hypothesized that certain factors, such as physical closeness to AIDS patients or HIV-positive blood and nontolerance of homosexuals, increase fear of AIDS among nurses. A sample of 365 nurses in a mid-Atlantic state of the United States was surveyed with an 82-item Knowledge, Attitudes, and Practice (KAP) questionnaire to examine the fear of AIDS among nurses in the United States. Using correlation, item and factorial analysis, a 23-item FOA Scale II (alpha = 0.826) was created and seven FOA factors were identified. Factor analysis was used to help understand the dimensions of FOA as measured by FOA Scale II. Principal components analysis was used to analyse the correlation matrix because some items were on a five-point scale and some were on a three-point scale. The varimax rotation was used, because if one were to define dimensions then these dimensions should be as independent of each other as possible. The coefficient alpha of 0.826 obtained from using FOA Scale II indicated that FOA could be considered to be a general factor; but the general factor could be exhibited through several avenues. It was determined that FOA could be represented by four or by seven dimensions, and if one uses the eigenvalue of 1 for a cut-off point then one would argue that there were seven factors. If one used the screen test, then one could assume that there were four factors of interest. Our decision for the analysis of this paper was to attempt the interpretation of the seven factors. We used both the factor loadings-the correlation of the item score with the linear combination-and the factor score coefficients (the weights of the items to form the linear combinations) to interpret the factor. The factor analysis thus seems to give insight into the dimensions of FOA as measured by FOA Scale II. Fear of AIDS seems to be exhibited in the following seven ways: (a) support for policies which would protect me from AIDS, (b) fear of contact with blood and bodily fluids of AIDS patient, (c) turning against those who have AIDS, (d) only care for those who deserve to be helped, (e)concern that I would have no help if I had AIDS, (f) concern about the financial burden of AIDS, and (g) loss of self-worth for one who has AIDS.

Acquired Immunodeficiency Syndrome↗

PubMed1996

Alpha 6 and gamma 2 subunit antisense oligodeoxynucleotides alter gamma-aminobutyric acid receptor pharmacology in cerebellar granule neurons.

To characterize the role of the alpha 6 subunit in gamma-aminobutyric acid (GABA) receptors in cerebellar granule cells, primary cerebellar cultures were treated with antisense oligodeoxynucleotides (ODNs) complementary to and overlapping the initial codon of the alpha 6 subunit cDNA. The specific reduction in the expression of the alpha 6 receptor subunit protein after a 48-hr antisense ODN treatment was assessed with the use of immunoblot assays. Sister cultures were treated in parallel with mismatched (scrambled) ODNs. Inhibition of GABA-gated currents by furosemide, a selective inhibitor of GABAA receptors containing alpha 6 subunits, was attenuated after the alpha 6 antisense treatment. Furosemide was tested in parallel in transfected cells expressing various combinations of the alpha 1 and alpha 6 subunits, which showed that the relative abundance of these subunit mRNAs determines the extent of furosemide-induced inhibition of GABA-gated currents. Compared with control or mismatched ODN-treated cell cultures, treatment of granule neurons with alpha 6 antisense ODNs caused a decrease in GABA-induced maximal current density and increased the half-maximal concentration derived from GABA dose-response curves. Furthermore, the depletion of alpha 6 subunits from cerebellar granule cells enhanced flunitrazepam-induced potentiation of GABA-activated currents. In contrast, gamma 2 antisense ODN treatments of cell cultures increased the receptor sensitivity to GABA and potently decreased the response to flunitrazepam. Our results show that alpha 6 and gamma 2 subunit expression can be blocked with the use of synthetic ODNs and that these subunits are crucial determinants of the pharmacological properties of native GABAA receptors in cerebellar granule cells.

Allosteric Regulation↗

PubMed1996

[Molecular epidemiology of meningococcal meningitis in Mali: isolation of a new class 1 protein variant (P1.y)].

The study deals with 570 strains of Neisseriaceae isolated between 1989 and 1994 in Mali: 396 of the strains were isolated from samples of cerebrospinal fluid and 174 from the throat. Serogroup C accounted for 55% of all strains. Antigenic structure was determined by ELISA, SDS-PAGE and transfer to nitrocellulose membrane for immunoblotting with monoclonal antibodies produced at the Max Planck Institute for Molecular Genetics. For serogroup A, the class 1 protein types found were P1.7 for strains isolated prior to 1994 and P1.9 for strains isolated in 1994. P1.7 is specific to clone IV-1 and P1.9 to clone III-1, which was responsible for the 1994 epidemic. All strains of serogroup C isolated from fluid CSF and most strains isolated from the throat exhibit a new type of class 1 protein which the authors have designated P1.y. P1.y is characteristic of Malian strains of serogroup C; it is rare or absent in strains from other countries (Burkina Faso, Ghana, Italy, USA). The nucleotide sequence of the gene expressing P1.y and the corresponding amino acid sequence were determined at the National Institute for Biological Standards and Control, England.

Bacterial Proteins↗

PubMed1995

Isolation of virus-neutralizing RNAs from a large pool of random sequences.

RNA and ribonuclease-resistant RNA analogs that bound and neutralized Rous sarcoma virus (RSV) were isolated from a large pool of random sequences by multiple cycles of in vitro selection using infectious viral particles. The selected RNA pool of RSV-binding sequences at a concentration of 0.16 microM completely neutralized the virus. Of 19 sequences cloned from the selected pool, 5 inhibited RSV infection. The selected RNA and RNA analogs were shown to neutralize RSV by interacting with the virus, rather than by adversely affecting the host cells. The selection of the anti-RSV RNA and RNA analogs by intact virions immediately suggests the potential application of this approach to develop RNA and RNA analogs as inhibitors of other viruses such as human immunodeficiency virus.

Antiviral Agents↗

PubMed1995

Modulation of megakaryocytopoiesis by thrombopoietin: the c-Mpl ligand.

We have further characterized the biological activities, mechanism of action, and target cell populations of recombinant human and murine thrombopoietin (rhTPO and rmTPO) in in vitro human and murine model systems. Alone, hTPO or mTPO stimulated the maturation of immature murine megakaryoblasts as measured in a single cell assay. The combination of hTPO or mTPO and interleukin-6 (IL-6) resulted in a further increase in megakaryocyte differentiation in this system. Murine TPO stimulated mouse megakaryocyte progenitor development. Human megakaryocyte progenitor development was potentiated by hTPO alone and further augmented in the presence of the early-acting cytokines (IL-3) or kit ligand/stem cell factor (KL/SCF). To further define the mechanism of action of TPO, neutralization studies were performed with antisera to IL-3, granulocyte-macrophage colony-stimulating factor (GM-CSF), IL-1 beta, and IL-11. No diminution in TPO activity was observed in the presence of these antisera. Moreover, because adhesive interactions are known to modulate hematopoiesis, we studied whether hTPO might alter such interactions between human bone marrow (BM) megakaryocytes and human BM stromal fibroblasts. No changes were observed in either megakaryocyte expression of the surface molecules lymphocyte function-associated antigen-1, very late activation antigen-4, or intercellular adhesion molecule-1 or the adhesion of megakaryocytes to stromal fibroblasts after treatment with the growth factor. Furthermore, no induction of secretion of the cytokines IL-1 alpha, IL-1 beta, GM-CSF, IL-6, granulocyte-CSF, tumor necrosis factor-alpha, transforming growth factor-beta 1, or transforming growth factor-beta 2 by primary human BM megakaryocytes was noted after treatment of the cells with hTPO. To address whether TPO affects very primitive hematopoietic progenitors, we studied the residual cells from the BMs of mice treated with high doses of 5-fluorouracil. Although no effect of mTPO alone was noted on the viability or replication of such primitive murine progenitor populations, the triple combination of IL-3 + KL/SCF + TPO stimulated growth of megakaryocyte progenitors. These results indicate that TPO is a highly lineage-specific growth factor whose primary biological effects are likely to be direct modulation of the growth and maturation of committed megakaryocyte precursors and immature megakaryoblasts.

Animals↗

PubMed1995

Clinical significance of intratumoral blood flow in cervical carcinoma assessed by color Doppler ultrasound.

BACKGROUND: Much evidence has suggested that vascular density reflects the clinical behavior of cancer. In this study, the intratumoral blood flow in cervical carcinomas was assessed by transvaginal color Doppler ultrasound, and its clinical significance was evaluated. METHODS: Sixty-five patients with Stage Ib-IIb cervical carcinoma exhibiting visible cervical tumor by transvaginal ultrasound were enrolled. All patients were scheduled for radical hysterectomy and pelvic lymph node dissection. Transvaginal color Doppler ultrasound was performed before surgery to search for blood flow signals from the tumor and the main uterine artery. The corresponding arterial resistance index (RI) was calculated. Clinical and pathologic data were recorded. A cytokinetic study was performed by propidium iodide staining and flow cytometry. The human papillomavirus (HPV) status was assessed by polymerase chain reaction. RESULTS: Intratumoral blood flow was detected by color Doppler ultrasound in 46.2% (30/65) of the tumors. Patients with detectable intratumoral blood flow exhibited significantly more pelvic lymph node metastasis (10/30 vs. 2/35, P = 0.005), a higher percentage of cancer cells in the S- + G2M-phase (30.02 +/- 18.54% vs. 19.35 +/- 11.21%, P < 0.005), and a higher prevalence of HPV infection (30/30 vs. 25/35, P = 0.001) when compared with those without intratumoral blood flow. No significant difference was observed concerning the patient's age, tumor size, clinical staging, histologic type, and DNA ploidy status between these two groups. Regression analysis of the intratumoral RI value on the S- + G2M-phase fraction showed linear regression (n = 30, r2 = 0.501, P < 0.01). The RI values of the main uterine artery showed no significant difference between these two groups. CONCLUSION: The intratumoral blood flow by transvaginal color Doppler ultrasound correlated well with a higher proliferation index, higher incidence of HPV infection, and pelvic lymph node metastasis in cervical carcinoma.

Adult↗

PubMed1995

Electron paramagnetic resonance investigations of nitrosyl complex formation during endotoxin tolerance.

The prior administration of low dose endotoxin induces a state of hyporesponsiveness or tolerance to the lethal effects of endotoxin. It is generally accepted that macrophages are main cellular components in the development of tolerance, hence, nitric oxide (.NO) as one of the macrophage mediators may play a role in host defense mechanisms during tolerance. In this study, we utilized EPR spectroscopy to directly detect nitrosyl complexes as products of .NO in whole blood, livers and intestines of lipopolysaccharide (LPS)-tolerant rats. Male Sprague-Dawley rats were injected with a "low dose" LPS (0.5 mg/kg) 12-168 h prior to a "high dose" LPS (3 mg/kg), then sacrificed 6 h later. EPR signals of nitrosyl hemoprotein complexes were detected in specimens after high dose LPS. The post-LPS EPR signals of nitrosyl complexes from all samples were attenuated by a prior injection of low dose LPS. The signals of dinitrosyl-iron-dithiolate became apparent in samples from tolerant rats as signals of nitrosyl hemoprotein decreased. The maximal tolerance in terms of diminished .NO production was observed when low dose LPS was given 48-96 h prior to high dose LPS. Hemoglobin concentrations in the intestine used as biomarkers of hemorrhagic damage, were concomitantly attenuated in the jejunum of tolerant rats. These results together with our previous studies indicate that suppression of .NO production may contribute to the amelioration of hepatic and intestinal injury during endotoxin tolerance.

Amino Acid Oxidoreductases↗

PubMed1995

Nitro containing L-arginine analogs interfere with assays for nitrate and nitrite.

We evaluated the effect of in vivo and in vitro administration of nitro-containing and nitro-deficient L-arginine-derived nitric oxide (NO) synthase inhibitors on the measurement of NO in plasma, urine and HEPES buffered physiologic salt solution (PSS) by ozone chemiluminescence and by the modified Griess reaction. In vivo administration of 1, 5, 25, 40 or 50 mg/kg of NG-nitro-L-or D-arginine methyl ester (LNAME, DNAME), NG-nitro-L-arginine (LNA) or aminoguanidine (AG) to rats and mice increased NO in urine and plasma as determined by chemiluminescence using 2.3% vanadium chloride in 2N HCI at 100 degrees C as the redox reagent. In vivo administration of 1 and 10 mg/kg/day of NG-imino-ethyl-L-ornithine (LNIO) or 3 amino-1,2,4 triazine (AT) reduced plasma and urine NO. Addition of LNAME, DNAME and LNA (100 nM to 1 mM) to the redox solution produced a concentration response curve for NO in the chemiluminescence assay similar to that produced by standard solutions of sodium nitrite and nitrate. LNMMA produced a small NO signal but only at concentrations equal to or exceeding 0.1 mM. LNIO, AT and AG did not give any NO signal even at concentrations exceeding 1 mM. Conversion of plasma or urine nitrate to nitrite with cadmium gave elevated values of plasma nitrite by the Greiss assay when LNAME or LNA was the NO synthase inhibitor. We conclude that in vivo and in vitro use of LNAME and LNA and in vivo use of high doses of aminoguanidine interfere with the assay of NO2- and NO3- with the modified Griess reaction and with chemiluminescence. We suggest that LNAME and LNA not be used in vivo or in vitro when total RNI is measured with these assays.

Animals↗

PubMed1995

Mu-opioid agonist enhancement of prostaglandin-induced hyperalgesia in the rat: a G-protein beta gamma subunit-mediated effect?

Guanine nucleotide-binding regulatory protein stimulation of adenylyl cyclase has been shown to be an important second messenger system for many processes, including mechanical hyperalgesia. Recently, interactions between guanine nucleotide-binding regulatory protein subunits and adenylyl cyclase affecting the level of cyclic adenosine 3',5'-monophosphate accumulation have been demonstrated. In this study we evaluated such an interaction by measuring paw-withdrawal thresholds to mechanical stimuli in Sprague-Dawley rats in the presence of two direct-acting hyperalgesic agents, prostaglandin E2 and the adenosine A2-agonist, CGS21680. The effects of two agents expected to liberate inhibitory guanine nucleotide-binding regulatory protein subunits were also studied: [D-Ala2,N-Me-Phe4,Gly5-ol]enkephalin (a mu-opioid receptor agonist) and N6-cyclopentyladenosine (an A1-adenosine agonist). Injection of [D-Ala2,N-Me-Phe4,Gly5-ol]enkephalin immediately before prostaglandin E2 or CGS21680 significantly attenuated the hyperalgesia subsequently induced by these agents, i.e. the sensitivity to these hyperalgesic agents was decreased. On the other hand, injection of [D-Ala2,N-Me-Phe4,Gly5-ol]enkephalin 5 min after prostaglandin E2 or CGS21680 significantly enhanced the hyperalgesia observed. Injection of the adenosine A1-agonist N6-cyclopentyladenosine immediately before and 5 min after prostaglandin E2 or CGS21680 had a similar effect to [D-Ala2,N-Me-Phe4,Gly5-ol]enkephalin. The decrease in sensitivity to prostaglandin E2- and CGS21680-induced hyperalgesia by preadministration of [D-Ala2,N-Me-Phe4,Gly5-ol]enkephalin or N6-cyclopentyladenosine and the enhancement by postadministration were all reversed by pertussis toxin, an inhibitor of inhibitory guanine nucleotide-binding regulatory protein, suggesting the involvement of an inhibitory guanine nucleotide-binding regulatory protein.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine↗

PubMed1995

Changed central and peripheral catecholamines and indoleamines in one-way crossed-intestine rats: relationship to changes in feeding behavior and metabolism.

The involvement of central and peripheral catecholamines and serotonin (5-HT) in regulation of feeding and energy metabolism was examined in one-way crossed intestine rats that show large and sustained changes in daily food intake. Five to six weeks after the crossed-intestinal surgery, catecholamines and indoleamines in dissected major brain regions and in the heart, intrascapular brown adipose tissue (IntBAT), pancreas, and serum were determined using HPLC with electrochemical detection. The food-losing rats increased daily food intake from 70.8 to 126.3 g, whereas their partners decreased daily food intake from 67.1 to 38.7 g (p < .001). Compared with the partners and sham-operated controls, the food-gaining rats had increased 5-hydroxy-indoleacetic acid (5-HIAA) throughout the brain [hypothalamus, 442.9 vs. 383.5 (p < .05) and 404.2 ng/g (p < .05), Lateral cortex plus amygdala (LC + A), 236.6 vs. 216.8 (p < .05) and 212.0 ng/g (p < .05), brain stem, 282.9 vs. 238.7 (p < .05) and 245.1 ng/g (p = .05), cerebellum, 56.7 vs. 49.6 (p < .05) and 44.4 ng/g (p < .05)]. Higher 5-HIAA in food-gaining rats that were undereating are consistent with serotonin's role in inhibiting food intake. Peripherally, the rats gaining food showed significantly lower NE, 5-HT, and 5-HIAA in IntBAT compared with their partners (NE, 994.2 vs. 1236 ng/g, 5-HT 338.0 vs. 527 ng/g, and 5-HIAA, 39 vs. 51 ng/g). Because NE and 5-HT have been shown to exert stimulating effects on BAT-mediated thermogenesis, lower levels of NE, 5-HT, and 5-HIAA in IntBAT of food gaining rats are compatible with the lower metabolic rate observed in these animals. The results show that both central and peripheral catecholamines and serotonin are involved in regulation of food intake and energy metabolism.

Analysis of Variance↗

PubMed1995

Genomic localization of tomato genes that control a hypersensitive reaction to Xanthomonas campestris pv. vesicatoria (Doidge) dye.

Xanthomonas campestris pv. vesicatoria causes bacterial spot, one of the most serious diseases of tomatoes. The lycopersicon esculentum accession 'Hawaii 7998' is the only reliable source of resistance to race 1 strains of the pathogen. This resistance is associated with a hypersensitive reaction controlled by multiple nondominant genes. The inoculated area becomes fully necrotic 24 hr after inoculation in 'Hawaii 7998,' whereas full necrosis is observed 5 and 4 days after inoculation in the susceptible species L. pennellii (LA 716) and their F1, respectively. An interspecific backcross population, using 'Hawaii 7998' as the recurrent parent, was analyzed to determine the linkage relationships between the resistance genes and 135 molecular marker loci. The range of responses of the BC1 population included those of the parents. Linkage to a hypersensitive response factor was assessed by comparing the rates of necrosis development between homozygous and heterozygous plants at 8 hr-intervals. Three factors that affect the hypersensitive response of 'Hawaii 7998' were detected. One factor is on the short arm of chromosome I, another on the long arm of chromosome I, and a third on the long arm of chromosome 5. These factors appeared to act independently and to have additive effects.

Chromosome Mapping↗

PubMed1995

Chronic alcohol administration stimulates nitric oxide formation in the rat liver with or without pretreatment by lipopolysaccharide.

This study examines the effect of chronic alcohol consumption on nitric oxide release from the liver of rats with or without lipopolysaccharide (LPS) (Escherichia coli) treatment. Reactive nitrogen intermediates (RNIs) in plasma were monitored with an NOx Analyzer, and nitric oxide (NO) production was measured as nitrite or nitrite + nitrate accumulation in perfusates of the perfused liver, and in supernatants of the freshly isolated hepatic cells after incubation for 3 hr in Hank's balanced salt solution buffer containing 1 mM L-arginine. RNI concentration in plasma of control rats was 32.0 +/- 3.4 microM (mean +/- SE). Livers from diet-fed control rats produced RNIs at the barely detectable rate of 7.8 +/- 1.5 nmol/hr x g wet liver. Six hr after administration of LPS (1 mg/kg, i.v.), plasma RNI levels in diet-fed control rats increased to 426.9 +/- 29.4 microM, and RNI release from the perfused liver was also markedly elevated to 97.7 +/- 7.7 nmol/hr x wet g liver, indicating hepatic NO release as a potentially important source for the increased RNI in plasma. The presence of NG-monomethyl-L-arginine (0.5-1 mM) or the absence of L-arginine in the perfusate inhibited LPS-induced stimulation of RNI release. EGTA (1 mM) had little effect, indicating that the increased RNI release was likely to be due to inducible NO synthase activity. The release of RNIs by freshly isolated Kupffer cells increased 13-fold, and this small cell mass contributed almost half of the hepatic RNI production under these conditions. Plasma ALT concentration was elevated after LPS administration, indicating incipient liver damage.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Oxidoreductases↗

PubMed1995

Caregiver-child interactions in Japan, Taiwan, and the United States.

This study reports the results of an investigation of the contact stimulation between caregivers and their children in 409 dyads (38 in Japan; 100 in Taiwan; and 271 in the United States). An instrument was used to record quantitative and qualitative data of the dyads in the three countries. A time-sampling procedure of 1 minute of observation and 1 minute of recording, with a minimum of 15 minutes and a maximum of 30 minutes, per dyad was used for data collection. The findings indicate significant differences at the p = 0.0001 level among the three cultural groups on the following variables: proximity, clothing, soothing, playing with the child, reading to the child, holding the child, and behavior toward a sleeping child.

Analysis of Variance↗

PubMed1995

Alterations of energy and substrate metabolism in rats with large and sustained changes in daily food intake.

Energy expenditure was measured in one-way crossed-intestine rats by use of indirect calorimetry to examine the role of energy metabolism in body weight control. The intestinal surgery was done according to Koopmans (Brain Res. Bull. 14: 595-603, 1985). The food-losing rats increased daily food intake from 70.8 to 126.3 g/day, whereas their partners decreased intake from 67.1 to 38.7 g/day (P < 0.001). Compared with levels before surgery, the food-losing rats showed slightly increased O2 consumption (1.31 vs. 1.28 1.h-1.kg-1) and metabolic rate (6.62 vs. 6.39 kcal.h-1.kg-1) and largely increased CO2 production (1.31 vs. 1.22 l.h-1.kg-1, P < 0.01), whereas in their food-gaining partners O2 consumption (1.12 vs. 1.25 l.h-1.kg-1, P < 0.01) and metabolic rate (5.76 vs. 6.26 kcal.h-1.kg-1) were significantly decreased. Respiratory quotients were higher in the food-gaining rats than in their partners (1.076 vs. 0.999, P < 0.01), indicating more fatty acid synthesis. These results suggest that daily food intake and energy expenditure increase and decrease together, despite the fact that about the same amount of food has been absorbed from the intestines of each rat.

Animals↗

PubMed1995

Comparison of three human-murine heteromyeloma cell lines for formation of human hybridomas after electrofusion with human peripheral blood lymphocytes from meningococcal cases and carriers.

Peripheral blood lymphocytes from meningitis patients and healthy meningococcal carriers were fused by electrofusion with the three human-murine heteromyeloma cell lines CB-F7, K6H6B5 and H7NS. 934 hybridomas producing human immunoglobulins were obtained in 30 fusions. Heteromyeloma K6H6B5 yielded a significantly higher proportion of hybridomas producing IgG antibodies than did the two other cell lines. CB-F7 and K6H6B5 yielded comparable numbers of hybridomas whose supernatants reacted with homologous bacteria, whereas the cell line H7NS was less efficient.

Animals↗

PubMed1995

Effect of hypoxia on angiotensin II content and its receptor in guinea pig aorta.

AIM: To study the effects of hypoxia on the vasoconstrictive response and the angiotensin II (Ang II) content and its receptor. METHODS: Hypoxia was induced in isolated aorta of guinea pig by gassing N2. The vasoconstrictive response of aorta to Ang II was recorded. Ang II content and its receptor were measured by radioimmuoassay. RESULTS: Ang 3-3000 nmol L-1 increased the contractile response of aorta. Hypoxia amplified the vasoconstrictive effect of Ang II. The concentration of Ang II were 44 +/- 24 and 50 +/- 17 pg/g wet wt (n = 10), respectively in non-hypoxic and hypoxic aortae. The receptor density in non-hypoxic aorta was 17 +/- 3 fmol mg-1, and that in hypoxia was 33 +/- 5 fmol mg-1 (P < 0.01). CONCLUSION: The enhancement of the vasoconstrictive action of Ang II by hypoxia is due to the increase in the angiotensin receptor density, but not associated with the changes in the Ang II content in hypoxic aorta of guinea pig.

Angiotensin II↗

PubMed1995

Effects of Panax notoginseng saponin Rg1 on cardiac electrophysiological properties and ventricular fibrillation threshold in dogs.

AIM: To study the effects of Rg1 isolated from saponins of Panax notoginseng on cardiac electrophysiological properties and ventricular fibrillation threshold (VFT). METHODS: Seventeen open-chest dogs were randomly allocated into a Rg1 group (20 mg kg-1, iv) and a control group. The electrophysiological variables and VFT were evaluated by standard electric stimuli and monophasic action potential (MAP) recording. RESULTS: Rg1 prolonged sinus node recovery time (SNRT) by 19.1%, AV conduction Wenckebach cycle length (AVWCL) by 7.1%, and ventricular effective refractory period (VERP) by 7.9%. It prolonged ventricular MAPD30, MAPD50, and MAPD90 by 25.5%, 24.2%, and 13.5%, respectively. VFT was increased by 19.2%. CONCLUSION: Rg1 prolonged ventricular refractoriness and repolarization, and increased VFT. It was indicated that cardiac electrophysiological effects of Rg1 were similar to those of amiodarone.

Action Potentials↗