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Biomedical subjects

L S Liu

Publications and source records attributed to L S Liu.

At least 37 records · Page 2Linked to original sources
PubMed1995

[Cardiac function in isolated working rat heart with pressure overload hypertrophy: correlation with myocardial angiotensin II].

Using the isolated working rat heart model, we recorded cardiac function of the hypertrophied hearts induced by abdominal aortic banding and determined the myocardial angiotensin II level. Compared with the sham-operated control hearts, the maximal diastolic rate (-dp/dt) and coronary flow rate (per gram of left ventricular weight) were decreased, while the myocardial angiotensin II content was increased in the hypertrophied hearts. Correlation analysis revealed that both coronary flow rate (r = -0.8097, P < 0.001) and -dp/dt (r = -0.5463, P < 0.01) were negatively correlated to myocardial angiotensin II. We conclude that the activated cardiac renin-angiotensin system may be responsible for the decreased diastolic function and coronary reserve in the hypertrophied hearts.

Angiotensin II↗
PubMed1994

Enhanced protein blotting from PhastGel media to membranes by irradiation of low-intensity ultrasound.

A novel approach to protein blotting based on application of ultrasound is proposed. Three minutes of ultrasound exposure (1 MHz, 2.5 W/cm2) was sufficient for a very clear transfer of proteins from a polyacrylamide gel (PhastGel) to nitrocellulose or nylon 66 Biotrans membranes. The proteins evaluated were prestained sodium dodecyl sulfate-polyacrylamide gel electrophoresis standards (18,500-106,000 Da) and 14C-labeled Rainbow protein molecular weight markers (14,300-200,000 Da). In control experiments, which were performed following similar procedures without turning the ultrasonic generator on, no protein blotting could be seen. For comparable blotting results, 30 min for electroelution or 240 min for elution by convection blotting was required.

Electrophoresis, Polyacrylamide Gel↗
PubMed1994

[Functional and histological evidence of insulin resistance in spontaneously hypertensive rat].

In order to confirm the existence of insulin resistance in spontaneously hypertensive rat (SHR), rich musculature glucose tolerance test (GTT) and histological method examination of the insulin receptor were carried out in SHR and the normotensives (WKY). The basal serum insulin level was higher and the area under insulin curve during GTT was also higher in SHR than those in WKY, while the basal serum glucose level and the area under glucose curve during GTT in SHR were similar to those in WKY. As compared with WKY, SHR displayed a significantly lower percentage of insulin sensitive slow-twitch fiber of plantaris and medial head of gastrocnemius (type I fiber). There were strong positive correlations between blood pressure (BP) and insulin as well as between BP and the area under insulin curve, but the correlation between insulin and percentage of type I fiber was negative. In conclusion, the present study provides both functional and structural evidence of insulin resistance in SHR.

Animals↗
PubMed1993

Blood pressure and life style in the People's Republic of China: three samples in the INTERSALT Study.

In INTERSALT, the International Cooperative Study on Electrolytes and Blood Pressure, three centres located in the People's Republic of China (PRC) had distinctive patterns of BP and of life style variables that, in INTERSALT overall, were found to relate to BP. The PRC centres had low body mass index (BMI) and alcohol consumption but high urinary sodium and sodium/potassium ratio (Na/K). Compared with 45 other INTERSALT centres, average BMI was 22.7 vs. 25.4 and alcohol consumption was 32% vs. 61%, with heavy drinking 3% vs. 14%. However, Na/K in the PRC was 6.7 vs. 3.2 in the other centres. This combination of factors may underlie the BP pattern observed. While mean BP in the PRC was lower than in the 45 centres (-7.0 mmHg SBP, -5.6 mmHg for DBP), this was counterbalanced by other findings. Upward slope of systolic pressure with age was 45% greater for the PRC than the other centres and 24% greater for diastolic pressure. As a result, although percentage hypertensive for ages 20-49 years for the PRC was half that in the 45 centres (6% vs. 12%), by age 50-59 years the prevalence was 31% in the PRC and 38% in the other centres. Hypertension prevalence in Tianjin, with highest Na/K in INTERSALT (7.6) was 40% for ages 50-59 years. While sample size in individual centres does not provide power to demonstrate aetiological relationships, these findings permit formulation of the following hypothesis: although lower body mass and lower alcohol intake may counteract to some degree impact of high salt intake, such intake over decades eventually takes its toll on BP.

Adult↗
PubMed1993

Endothelium-derived nitric oxide: role in vascular regulation and interaction with norepinephrine, endothelin and superoxide anion.

Endothelium-derived nitric oxide (EDNO) is an important vasodilator substance produced by the vascular endothelium. The present in vivo and in vitro study is aimed at evaluating its role in vascular regulation and its interactions with norepinephrine (NE), endothelin-1 (ET) and superoxide anion. In male anesthetized wistar rats, inhibition of the in vivo EDNO pathway with L-NAME (an established specific inhibitor of EDNO synthesis, 1-4 (mg/kg, iv bolus) provoked sustained, dose-dependent hypertensive responses (mean arterial pressure increased 45 +/- 1.5% over baseline for more than 60 minutes at a dose of 4 mg/kg, mean +/- Sx, which was completely reversed by L-arginine, the normal substrate for EDNO synthesis). In the in vitro study on rat aortic rings, blocking the endothelial production of EDNO with L-NAME (10(-4) M), caused the most prominent enhancement of the contractile responses to NE (increased maximal responses and lowered EC50), a smaller enhancement of contraction to ET and minimal modification of the vasoconstrictive effects of superoxide anion. L-arginine (10(-4) M), on the contrary, slightly attenuated the contraction to NE and ET but without the contraction to superoxide anion. The present study confirms that EDNO system represents one of the most important physiological depressor mechanisms in vivo, and indicates that EDNO is an important, differential antagonistic mechanism against the vasoconstrictors. It is also demonstrated that L-arginine availability is generally not the rate-limiting step in the in vivo generation of EDNO. The implications of the results were discussed.

Animals↗
PubMed1992

Synthesis and nonthrombogenicity of polymer membrane with surface-graft polymers carrying thrombin inhibitor.

An acrylamide derivative of a thrombin inhibitor was synthesized and graft polymerized to the surfaces of polymer membranes. The thrombin-inhibitor activity was unaffected by the introduction of an acryloyl group. The surface-graft membrane deactivated thrombin markedly and suppressed adhesion of platelets, resulting in a high nonthrombogenicity. Immersion of polymer membranes blended with the thrombin inhibitor in phosphate-buffered saline for 10 d resulted in the loss of nonthrombogenicity, while the polymer membranes grafted with the thrombin inhibitor derivative maintained the nonthrombogenicity over a long period.

Acrylamides↗
PubMed1992

Interaction of thrombin with synthetic fluorescent substrate immobilized on polymer membrane.

Synthetic fluorescent substrates for thrombin were immobilized on a polyurethane membrane. The interaction of thrombin with the immobilized substrates was investigated. Upon hydrolysis of immobilized substrates by thrombin, fluorescence was emitted, intensity increasing linearly with time. From a Lineweaver-Burk plot, kinetic parameters of the enzyme reaction on the membrane surface were determined. The dissociation constant (K) was increased and the catalytic constant (k) decreased markedly by immobilization. More reactive thrombin substrates in solution were also more reactive in the immobilized state. More thrombin was adsorbed and adsorbed thrombins were inactivated more strongly on the surface with more reactive substrates when immobilized. The immobilization of thrombin substrate markedly suppressed fibrin formation on the membrane surface and made the membrane non-thrombogenic.

Adsorption↗
PubMed1992

Effects of atrial natriuretic factor on patients with renovascular hypertension.

Previous studies have shown the effects of atrial natriuretic factor (ANF) on rats with renovascular hypertension (RVH). In the present study low dose alpha-hANF (0.025 microgram/kg/min) was administered intravenously for 60 minutes to seven RVH patients. Results demonstrated an inhibition of renin-angiotensin-aldosterone system (RAAS), reduction of plasma catecholamine and arginine vasopressin(AVP), diuresis and natriuresis, increase of hematocrit and creatinine clearance, and slight decrease of blood pressure. These results showed that most factors involved in the establishment and maintenance of RVH are affected by ANF infusion.

Adult↗
PubMed1992

[Acute and chronic hypotensive effect of m-nifedipine].

Three groups of adult stroke--prone spontaneously hypertensive rats (SHRsp) were treated with m-nifedipine (m-Nif) 2.5, 5 and 10 mg.kg-1 by intraperitoneal injection. The systolic blood pressure (SBp) decreased significantly. The hypotensive effect persisted for 2-4, 6-8, and 12 h respectively and the peak effect appeared in 1 h. The range of hypotension was markedly greater than that of nifedipine (Nif). In SHPsp, treatment with m-Nif 10 or 30 mg.kg-1.d-1 for 4 weeks reduced significantly the SBp, but the hypotensive action is about the same as Nif.

Animals↗
PubMed1991

Interaction of poly(sodium vinyl sulfonate) and its surface graft with antithrombin III.

Poly(sodium vinyl sulfonate) (PVS) was found to be 1/14 times as active as heparin in inducing the conformational change and activation of antithrombin III. The conformational change of antithrombin III was investigated in terms of the intrinsic fluorescence of tryptophan residue, the extrinsic fluorescence using 1,6-diphenyl-1,3,5-hexatriene as fluorescent probe, and Fourier-transform infrared spectroscopy. It was evident in the experiment using 2,4,6-trinitrobenzene sulfonate that PVS elicited the activity of antithrombin III by interacting with amino groups of the protein as does heparin. Sodium vinyl sulfonate was graft-polymerized onto polyetherurethane (PEU) film that was treated with glow discharge in advance. PVS-grafted PEU film adsorbed antithrombin III easily and, like ungrafted PVS, induced conformational change and activation of antithrombin III. However, the mechanism of interaction of the PVS graft with antithrombin III did not seem to be completely the same as that of ungrafted PVS in solution.

Antithrombin III↗
PubMed1991

Synthesis and antithrombogenicity of heparinized polyurethanes with intervening spacer chains of various kinds.

Heparin was immobilized to polyetherurethaneurea membrane by covalent or ionic bondings with intervening spacer chains having different lengths and different terminal functional groups. The amount of immobilization of heparin and the release rate of immobilized heparin were controlled by the nature and the mode of bonding of spacer chains. The heparinized polyetherurethaneurea membranes became more in vitro antithrombogenic and suppressed more strongly the adhesion and activation of platelets, as the amount of immobilization increased. It was also shown that the membrane to which the low-molecular-weight fraction of heparin was immobilized was less stimulating to platelets.

Animals↗
PubMed1991

Biological activity of urokinase immobilized to cross-linked poly(2-hydroxyethyl methacrylate).

The fibrinolytic enzyme urokinase was immobilized by encapsulation or cross-linking to poly(2-hydroxyethyl methacrylate) networks. The immobilized urokinase was more thermally stable, more stable against pH change and more resistant to inactivation by plasma protease inhibitors. These stabilities were improved with increasing degree of cross-linking. On the other hand, the enzymatic activity of immobilized urokinase decreased with increasing degree of cross-linking. A suitable degree of cross-linking is needed for the maintenance of high biological activity of immobilized urokinase over a long period.

Antithrombin III↗