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Biomedical subjects

J H Li

Publications and source records attributed to J H Li.

At least 127 records · Page 7Linked to original sources
PubMed1992

Comparison of the in vitro effects of K+ channel modulators on detrusor and portal vein strips from guinea pigs.

The effects of K+ channel openers and blockers on smooth muscles of vascular and nonvascular origin from guinea pigs have been investigated. Cromakalim, pinacidil, nicorandil and minoxidil sulfate all abolished the spontaneous myogenic activity of the guinea pig portal vein and the KCl-evoked activity of detrusor strips with the same rank order of ptoency. Whereas both apamin and charybdotoxin stimulated myogenic activity of the detrusor strips, they produced insignificant effects on spontaneously active portal vein strips and failed to antagonize the mechanoinhibitory effects of cromakalim in the two tissues. Glibenclamide, on the other hand, only stimulated the myogenic activity of portal vein strips but antagonized the mechanoinhibitory effects of cromakalim, pinacidil, nicorandil and minoxidil sulfate in both tissues. Rubidium, at millimolar concentrations, stimulated the myogenic activity, and antagonized the actions of cromakalim in both tissues. The data indicate that there are definite functional dissimilarities as exhibited by the differential response of the two tissues to K+ channel modulators. These findings may be exploited in the design of new drugs with tissue selectivity.

Animals↗
PubMed1992

[Immunohistochemical localization and histochemical observation of antigens in Pagumogonimus skrjabini].

Using immunohistochemical method, the antigens were shown to be mainly located in the cecum, tegument, esophagus, pharynx, excretory bladder, uterus and oral sucker of Pagumogonimus skrjabini. Histochemical analyses showed that antigens contained enzymes such as acid phosphatase (ACP), alkaline phosphatase (AKP), and acetylcholinesterase (AChE). Other chemical substances, for example, alkaline protein, basic protein, glycogen and acid mucopolysaccharides were also detected in the antigens of P. skrjabini.

Acetylcholinesterase↗
PubMed1992

Renal and antihypertensive effects of a novel eukalemic diuretic, ICI 207,828.

ICI 207,828, an aminomethylphenol pyrazine derivative, produces water diuretic effects with only minimal alterations in kaliuresis in dogs and rats after oral and parenteral administration. In the dog, ICI 207,828 reached maximum activity at a dose of 10 mg/kg, p.o. This was comparable to that of hydrochlorothiazide (HCTZ) at a dose of 5 mg/kg, p.o. or higher. In the rat, a dose of 30 mg/kg, p.o. of ICI 207,828 was comparable to the maximum of water diuretic and saluretic response obtained with HCTZ at a dose of 10 mg/kg, p.o. Based upon studies using in vitro amphibian models of the mammalian nephron, ICI 207,828 appeared to act on both the thick ascending limb of the loop of Henle and the late distal nephron. In the toad bladder preparation, ICI 207,828 inhibited Na+ transport when placed on either the mucosal (amiloride-like) or serosal (thiazide-like or loop diuretic-like) sides. This compound also inhibited Cl- transport in the toad cornea preparation (loop diuretic-like). ICI 207,828 did not change plasma K+ significantly in dogs dosed for 14 days at doses having diuretic effects (5 and 10 mg/kg, p.o., daily). In contrast, HCTZ consistently decreased plasma K+, whereas amiloride increased it significantly. ICI 207,828 demonstrated antihypertensive effects in spontaneously hypertensive rats. At 30 mg/kg, p.o., b.i.d., ICI 207,828 and HCTZ produced approximately equal antihypertensive activities during a 3 1/2-day treatment period. The pharmacological profile of ICI 207,828 indicates that this compound is a potent eukalemic diuretic and antihypertensive agent in animals.

Amiloride↗
PubMed1991

Comutagenesis of sodium arsenite with ultraviolet radiation in Chinese hamster V79 cells.

Solar ultraviolet radiation has been associated with the induction of skin cancer. Recent studies have indicated that near-ultraviolet, especially UVB, is mutagenic. Exposure to trivalent inorganic arsenic compounds has also been associated with increased skin cancer prevalence. Trivalent arsenic compounds are not mutagenic per se, but are comutagenic with a number of cancer agents. Here, we test the hypothesis that arsenite enhances skin cancer via its comutagenic action with solar ultraviolet radiation. Irradiation of Chinese hamster V79 cells with UVA (360 nm), UVB (310 nm) and UVC (254 nm) caused a fluence-dependent increase in mutations at the hprt locus. On an energy basis, UVC was the most mutagenic and UVA the least. However, when expressed as a function of toxicity, UVB was more mutagenic than UVC. Nontoxic concentrations of arsenite increased the toxicity of UVA, UVB and UVC. Arsenite acted as a comutagen at the three wavelengths; however, higher concentrations of arsenite were required to produce a significant (P less than 0.05) comutagenic response with UVB. The increased mutagenicity of UVB and UVA by arsenite may play a role in arsenite-related skin cancers.

Animals↗
PubMed1991

Influence of pentobarbital and chloralose anesthesia on quinidine-induced effects on atrial refractoriness and heart rate in the dog.

The effects of pentobarbital and chloralose on the atrial effective refractory period (AERP), atrial and ventricular rates, and mean blood pressure and also on the effects of quinidine on the same parameters were investigated in dogs with chronic atrioventricular block and implanted atrial pacing electrodes. Pentobarbital (30 mg/kg) increased the AERP by up to 12%, atrial and ventricular rates by 39 and 40%, respectively, and after initial lowering (48%) it increased the mean blood pressure (46%). Chloralose (100 mg/kg) increased the AERP (less than 30 min) by up to 7%, the atrial rate by 49%, the ventricular rate (less than 5 min) by 18%, and the mean blood pressure by 47%. In conscious dogs, quinidine at cumulative doses of 2, 4, and 8 mg/kg, i.e., at plasma levels between 2.7 +/- 0.6 and 6.3 +/- 1.3 micrograms/ml, increased the AERP by up to 21, 28, and 46%, the atrial rate by 49, 65, and 72%, and the ventricular rate (less than or equal to 5 min) by 17, 14, and 14%, and lowered the mean blood pressure by 19, 33, and 43%, respectively. Pentobarbital increased the quinidine-induced lengthening of the AERP by up to 10, 21, and 25 ms, respectively, and reduced the corresponding atrial (38, 53, and 67 beats/min) and ventricular (4, 4, and 5 beats/min) chronotropic effects. In contrast, chloralose reduced the quinidine-induced lengthening of the AERP (5, 12, and 22 ms, respectively), but did not modify the corresponding atrial and ventricular chronotropic effects. Neither pentobarbital nor chloralose altered quinidine plasma levels or the hypotensive effects of this drug.(ABSTRACT TRUNCATED AT 250 WORDS)

Anesthetics↗
PubMed1991

The effects of atropine on pharmacokinetics of theophylline in rabbits.

The effects of atropine on serum concentrations and pharmacokinetics of theophylline were studied in six rabbits (2.07 +/- 0.11 kg). Theophylline serum concentration was determined by ultraviolet spectrophotometry. After i.v. administration of aminophylline 12.5 mg/kg, i.m. atropine 1 mg/kg decreased significantly the maximal serum concentration of theophylline from 23.6 +/- 1.1 to 19.6 +/- 1.1 mg/l, and increased that of theophylline at the time of 6 and 8 hours after injection. After i.v. aminophylline administration without or with atropine, the pharmacokinetic parameters of theophylline calculated using a one compartment open model were: K (elimination rate constant) = 0.23 +/- 0.03, 0.19 +/- 0.02/h; t1/2 (half life) = 3.04 +/- 0.40, 3.66 +/- 0.40 h; Cl (clearance) = 0.26 +/- 0.04, 0.23 +/- 0.03 l/kg/h, respectively (P less than 0.01). But there was no significant variation in modification of volume of distribution (Vd). The results suggested that there is a significant drug interaction between atropine and theophylline.

Animals↗
PubMed1991

[Changes in serum LDH isozymogram in burn shock].

The changes in LDH isozymogram of 36 burned patients in shock period are reported. The results show as follows: 1. The characteristics of LDH isozymogram spectrum are: A. LDH1 greater than LDH2; B. The activity of LDH5 is enhanced. C. The 3 main types of LDH isozymogram spectrum are: LDH1 greater than LDH2 greater than LDH3 greater than LDH4 greater than LDH5 LDH1 greater than LDH2 greater than LDH3 greater than LDH5 greater than LDH4 LDH1 greater than LDH2 greater than LDH5 greater than LDH3 greater than LDH4 2. In the severe and extensive cases, the incidence of LDH1 greater than LDH2 is higher.

Adolescent↗
PubMed1990

Separation and characterization of the metabolic products of lappaconitine in rat urine by high-performance liquid chromatography.

The separation and characterization of the metabolic products of lappaconitine in rat urine by high-performance liquid chromatography with electrochemical and ultraviolet detection are described. Urine samples from rats intravenously administered lappaconitine hydrobromide were extracted with chloroform and then purified on a Sep-Pak C18 cartridge. The subsequent resolution into individual compounds was achieved by high-performance liquid chromatography. Identification of these compounds was based on comparisons of the chromatographic behaviour and the detector response with those of authentic samples. Changes in the ratio of lappaconitine to its metabolites in rat urine with time after dosing led to a proposal for one of the probable metabolic pathways of lappaconitine in the rat.

Aconitine↗
PubMed1990

Studies on the metabolism of lappaconitine in humans. Identification of the metabolites of lappaconitine in human urine by high performance liquid chromatography.

The metabolites of lappaconitine in the urine of humans having been previously administered intramuscularly with lappaconitine hydrobromide were studied using high performance liquid chromatography with electrochemical and ultraviolet detection. The urine was extracted by means of liquid- and solid-phase extractions. Each of the metabolites of lappaconitine was purified by high performance liquid chromatography on a reversed phase column and identified on the basis of the chromatographic behaviour and the detector response. It was proved that lappaconitine, N-deacetyl-16-O-demethyllappaconitine and N-deacetyllappaconitine were excreted in urine from humans receiving lappaconitine.

Aconitine↗
PubMed1990

Effects of protease inhibitors on c-myc expression in normal and transformed C3H 10T1/2 cell lines.

In the present study, the effect of protease inhibitors on c-myc expression in normal and transformed C3H 10T1/2 cells was examined. Steady-state c-myc RNA levels were reduced in normal proliferating C3H 10T1/2 cells grown in medium containing antipain, leupeptin, and Bowman Birk inhibitor (BBI). These protease inhibitors have been shown previously to suppress transformation yields in carcinogen-exposed cells. A lesser reduction in c-myc RNA levels was observed when cells were grown in the presence of protease inhibitors that do not suppress carcinogenesis and when transformed C3H 10T1/2 cell populations were grown in the presence of the anticarcinogenic protease inhibitors. Studies to determine the effects of antipain on the stability of the c-myc message and on c-myc transcription rates were also performed. The half-life of the c-myc message increased from 10 to 40 min when cells were grown in antipain; cycloheximide further stabilized the c-myc message. Interestingly, nuclear run-off experiments showed that antipain had no effect on c-myc transcription rates. These data suggest that proteases may be involved in the regulation of c-myc RNA expression in normal C3H 10T1/2 cells, possibly by a posttranscriptional mechanism.

Animals↗
PubMed1990

Photodynamic therapy in the treatment of malignant tumours: an analysis of 540 cases.

Malignant tumours (540 cases), including tumours of the lung, oesophagus, cardia, stomach, rectum, bladder, other urinary genital organs, face and mouth, eyes, ear, nose and throat (ENT), head and neck, breast and skin, were treated using photodynamic therapy (PDT) between 1982 and 1985 in Beijing. All of the cases were identified pathologically and the patients received haematoporphyrin derivative (HPD) (5 mg kg-1) intravenously 48-72 h prior to PDT. An argon-pumped dye laser emitting at 630 nm was used for the treatment. The results were as follows: complete response (CR) was obtained in 227 cases (42.1%), partial response (PR) was obtained in 114 cases (21.1%), mild response (MR) was obtained in 120 cases (22.2%) and 79 cases (14.6%) showed no response (NR). The effectiveness of PDT in the different organs was compared. HPD fluorescence was examined in 409 cases of malignant tumours: 344 lesions (84.1%) revealed red fluorescence (positive reaction), 32 gave an equivocal response and 33 gave a negative reaction. Positive fluorescence was seen in all types of malignant tumour in our study. Indications and limitations of PDT for the different organs are discussed and compared.

Argon↗
PubMed1989

[Nd-YAG laser treatment of tracheobronchial lesions].

From January 1987 to May 1988, 32 cases with tracheobronchial lesions were treated with Nd-YAG laser. Complete restoration of the airway was achieved in one case of leiomyoma, adenoma, carcinoid and mucous epithelioma each, 2 cases of polyp and 7 cases of granuloma. Significant restoration was seen in one case of granuloma, 2 cases of hematoma and papilloma, each, 3 cases of amyloidosis and partial restoration in one case of granuloma. The remaining 10 cases with squamous cell carcinoma and adenocarcinoma with severe airway obstruction were treated by Nd-YAG laser for palliative purpose only. Four of them revealed significant remission and 6 responded with partial remission. No severe complication was observed during or after the procedures. Nd-YAG laser treatment provides a new curative method avoiding resection of the lung in benign lesions and a palliative therapy for unresectable obstructive malignant tumors.

Adult↗
PubMed1989

Inhibition of DNA ligase activity by arsenite: a possible mechanism of its comutagenesis.

We have previously shown that the inhibition of MNU-induced DNA repair by arsenite occurs after the incision step in Chinese hamster V79 cells. We now report that nuclear DNA ligase activity is inhibited after arsenite treatment and that the inhibited activity is mostly DNA ligase II. Both constitutive and MNU-inducible levels of DNA ligase II are inhibited. The addition of arsenite in vitro also indicates that DNA ligase II is more sensitive to arsenite inhibition than DNA ligase I. Since DNA ligase II is reported to be involved in the ligation step of excision repair, its inhibition by arsenite is a likely mechanism for the inhibition of DNA repair by arsenite and may account for the fact that arsenite acts as a comutagen with a number of different types of mutagens. The carcinogenicity of arsenite may also be a result of ligase inhibition.

Animals↗
PubMed1989

[Changes in metallothionein content of the heart and liver during acute myocardial infarction in rats].

Metallothionein (MT) is an important endogenous anti-injury substance involved in the defensive system. In myocardial infarction model produced by left coronary artery occlusion in-rat, the content of left ventricular myocardial MT was significantly increased to a maximum on 4th day by 6-fold compared with preoperative value, and the content of hepatic MT increased by 3.5-fold on the 2nd day. During the whole experimental period (seven days) the MT content in heart and liver was significantly higher than those in the pre-operation period (P less than 0.01). Pretreatment with reserpine did not alter the dynamic changes of cardiac and liver MT content during myocardial infarction. The above results suggest that this increase in tissue MT is not influenced by catecholamine.

Animals↗