Biomedical subjects

D X Li

Publications and source records attributed to D X Li.

32 records · Page 2Linked to original sources

PubMed1992

Preliminary human trial of inactivated golden hamster kidney cell (GHKC) vaccine against haemorrhagic fever with renal syndrome (HFRS).

An inactivated golden hamster kidney cell culture (GHKC) vaccine against haemorrhagic fever with renal syndrome (HFRS) has been developed in recent years. A monovalent GHKC vaccine (lot 88-17) was prepared with L99 strain of the rat-type hantavirus, adapted in suckling mouse brain, cultivated in GHKC, and inactivated with 0.025% formalin, and a preliminary trial of the vaccine was carried out in a small number of human volunteers with the approval of the Ministry of Public Health, PRC, in order to identify safety and antibody response of the vaccine. Three inoculations were made on days 0, 7 and 28 respectively, by the intramuscular route with 1 ml vaccine each time for every volunteer. No obvious side effect was observed in vaccinees within 3 days after each inoculation. All 12 vaccinees (10 received three inoculations, and two received two inoculations of the vaccine) showed positive seroconversion of IgG antibody (by IFAT and ELISA) and neutralizing antibody (by enzyme focus reduction neutralization test, EFRNT), and 10 of them were still seropositive 180 and 360 days after the first inoculation. These results suggest that this vaccine would be safe for human use, and could effectively induce IgG and neutralizing antibody responses.

Adult↗

PubMed1992

Effects of microinjection of picrotoxin into posterior hypothalamus on ventricular electric stability.

Ventricular fibrillation threshold (VFT), serum potassium, and monophasic action potentials (MAP) have been assessed before and after microinjection of picrotoxin (Pic) into posterior hypothalamus in rabbits. Pic (2 and 3 micrograms) brought about a biphasic effect on VFT, an initial decrease followed by a notable increase. Pretreatment with spinal cord transection almost abolished the descending phase, whereas pretreatment with vagotomy depressed the ascending phase significantly. Following the microinjection of Pic, serum potassium rose up to 5.0 mmol.L-1 at 30 min. The amplitude of MAP (MAPA) and Vmax were lessened in rabbits, while in vagotomized rabbits, the changes of MAP were aggravated, and the duration of MAP was shortened. Phentolamine counteracted the changes of MAP induced by Pic. These results suggested that the initial decrease of VFT caused by Pic derived mainly from the direct action and myocardial ischemia of sympathetic activation, while its subsequent elevation was caused by vagal activation and hyperkalemia.

Action Potentials↗

PubMed1992

[Protective effects of tetrahydroprotoberberines on experimental myocardial infarction in rats].

The protective effects of tetrahydroprotoberberines (THPB), viz., l-tetrahydropalmatine (THP), l-stepholidine (SPD), and tetrahydroberberine (THB) on experimental myocardial infarction by ligating the left coronary artery were estimated in rats. The myocardial infarction size (MIS) was determined by nitro-blue tetrazolium technique. THP, SPD, and THB, as well as propranolol, played a remarkable role in diminishing the MIS within 24 h and decreasing the rise of creatine kinase (CK) and aspartate aminotransferase (AST) in the serum within 4 h after the ligation of the coronary artery. Among these drugs, SPD provided the myocardium with the best protective benefit. Systolic and diastolic blood pressures (SBP and DBP) were rapidly lowered after SPD 2.5 mg.kg-1 iv by 39.5% and 48.5%, respectively. The value of the MBP x HR x LVET was concomitantly decreased by 35.1% in the anaesthetized rats. The myocardial contractility and diastolic compliance were not implicated during the experimental regimen. The prophylactic administration of SPD 2.5 mg.kg-1 improved the cardiac hemodynamic alterations caused by ligating the left coronary artery. SPD depressed the elevation of T and LVEDP, and reduction of +dP/dtmax, Vpm, and Vmax besides complete resistance to the reduction of -dP/dtmax and LVSP, underlying the precautions against the damage of the myocardial contractility and diastolic compliance, especially the latter.

Alkaloids↗

PubMed1991

Stress-induced changes of central GABAergic function in rats.

The effects of acute and repeated immobilization stress on central GABAergic function were examined in rats by evaluating the changes of the cardiovascular responses to intracerebroventricular injection of GABA. The depressor and bradycardia responses of GABA were attenuated significantly by immobilization stress for 6 h (from -5.5 +/- 0.7 kPa and -75 +/- 25 bpm to -2.3 +/- 0.9 kPa and -27 +/- 16 bpm respectively, for GABA 200 micrograms). These effects of stress were neither mimicked by administration of hydrocortisone, nor abolished by pretreatment with adrenalectomy or diazepam, but they were attenuated significantly by pretreatment with isoniazid. These results indicated that immobilization stress for long duration causes subsensitivity of central GABA receptors, in which the down-regulation mechanism may be involved.

Adrenalectomy↗

PubMed1991

[The effect of tetrandrine on rat myocardial ATPases].

The effect of tetrandrine (Tet) on Na+,K(+)-ATPase and Mg(2+)-ATPase in rat myocardial microsomes was investigated in vitro. Under optimal condition, Tet did not influence Na+,K(+)-ATPase activity but concentration-dependently inhibited Mg(2+)-ATPase with an IC50 of 179 mumol/L. At 10 or 100 mumol/L, Tet caused the concentration-inhibition curves for ouabain a parallel shift to the right. Tet 100 mumol/L markedly increased the activity of Na+,K(+)-ATPase under suboptimal K+ or excessive Ca2+ condition. However, it did not significantly increase the enzyme activity when the Na+ concentration was lower. A kinetic analysis showed that Tet increased the affinity of Na+,K(+)-ATPase to ATP, but did not change the maximal velocity of the enzyme reaction.

Alkaloids↗

PubMed1990

Induction and purification of kievitone hydratase from Fusarium solani f. sp. phaseoli.

Fusarium solani f. sp. phaseoli is capable of detoxifying the major isoflavonoid phytoalexins produced by its host plant Phaseolus vulgaris. One of the enzymic activities involved is kievitone hydratase (KHase), a secreted glycoprotein which catalyses the conversion of kievitone to the less fungitoxic derivative, kievitone hydrate. Even under conditions of substrate induction, the enzyme is expressed at levels that are too low for satisfactory purification. Therefore, several other isoflavonoids were tested as inducers in culture. Among the phytoalexins produced by the host plant, phaseollinisoflavan was the best inducer, elevating the level of secreted enzyme eight-fold. Treatment with biochanin A, a product of chickpea, resulted in a 16-fold increase of secreted activity. The maximum rate of induction was observed 9-24 hr after addition of biochanin A, during which time several metabolites of the inducer were also present. KHase was purified from filtrates of biochanin A-induced cultures. Denaturing gel electrophoresis indicated that two species of Mr 47,000 and 49,000 copurified with the activity. N-Terminal sequence analysis indicated that the two species possessed related, or identical, polypeptide moieties. Comparison with the size of the non-denatured enzyme, previously determined to be ca 100,000, indicates that its native state is a dimer.

Amino Acid Sequence↗

PubMed1990

Ventricular arrhythmia evoked by microinjection of picrotoxin into brain areas in rabbits.

To explore the main areas of brain responsible for arrhythmia evoked by icv picrotoxin (Pic), a very small dose of Pic (3 micrograms) was injected into different areas of brain in anesthetized rabbits. The short latency of arrhythmia was found after microinjection of Pic into posterior hypothalamus (PH, 5.6 +/- 0.9 min) and the medial part of tuberal region (7.5 +/- 2.9 min). The ventricular arrhythmia was abolished by vagotomy, iv phentolamine or diazepam, or pretreatment with adrenalectomy or vagotomy. Microinjection of phentolamine or diphenhydramine into PH prior to Pic postponed the arrhythmia. The results indicate that PH and the medial part of tuberal region are the most effective areas for Pic to induce arrhythmia, activations of both sympathoadrenomedullary and parasympathetic systems are involved in the genesis of arrhythmia.

Adrenalectomy↗

PubMed1989

[Inhibitory action of intracerebroventricular injections of norepinephrine and clonidine on ventricular extrasystoles induced by stimulating hypothalamus in rabbits].

The effects of bilateral intracerebroventricular (icv) injections of norepinephrine (NE) and clonidine on hypothalamic stimulation-induced ventricular extrasystoles (VE) were investigated in alpha-chloralose and urethane anaesthetized rabbits. NE and clonidine reduced the number of HVE. The effects of NE were antagonized by pretreatment with phentolamine and yohimbine, but unaffected by pretreatment with prazosin. Pretreatment with yohimbine could also abolish the effects of clonidine. It is concluded that the effects of reduction in VE induced by NE and clonidine may be mediated by activating central alpha 2-adrenoceptors rather than alpha 1-adrenoceptors.

Animals↗

PubMed1989

[Effects of l-tetrahydropalmatine on isolated rabbit arterial strips].

The effects of l-tetrahydropalmatine (THP) on isolated rabbit aortic, renal and superior mesenteric arterial strips were studied in comparison with verapamil (Ver). THP and Ver shifted the KCl, CaCl2, norepinephrine (NE) and 15-methyl prostaglandin F2 alpha dose-response curves to the right in a non-parallel fashion, and decreased the maximal response, showing noncompetitive antagonism. THP was less potent in dilating arterial strips than Ver. THP and Ver obviously inhibited the intracellular Ca2+-dependent component of NE-induced contraction of the aorta, but only slightly decreased the extracellular Ca2+-dependent component when the concentration of THP or Ver was very high (THP 0.1 mmol/L, Ver 10 mumol/L). The results suggest that THP, similar to Ver, mainly inhibits potential-operated calcium channels. THP and Ver were more potent in dilating renal and superior mesenteric arterial strips than aortic strips. The results indicate that the vasodilation effect of THP is similar to that of Ver and that THP probably has a calcium antagonistic effect.

Alkaloids↗

PubMed1989

[Inhibitory effects of gamma-aminobutyric acid and diazepam on ventricular arrhythmias induced by hypothalamic electric stimulation].

The experiments were carried out on rabbits with ventricular arrhythmias (VA) induced by hypothalamic electric stimulation. The effects of GABA or diazepam (Dz) and picrotoxin on VA were observed. After GABA 0.25, 0.5, 1 mg/rabbit were injected into cerebral ventricle (icv) or cisterna magna (icm), the VA was dose-dependently reduced, the similar effect was seen after Dz 0.1 mg was injected into subarachnoid cavity (sac) or icm. The effect was not induced by GABA sac or Dz icv. Picrotoxin 20 micrograms icv or 30 micrograms icm obviously increased VA, and this effect was partly antagonized by pretreatment with GABA 0.5 mg icv or icm and Dz 0.1 mg icm. The results suggest that central GABAergic system plays an important role in development of arrhythmias, and that increasing activity in this system may inhibit VA.

Animals↗

PubMed1987