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Biomedical subjects

J F Liu

Publications and source records attributed to J F Liu.

At least 55 records · Page 3Linked to original sources
PubMed1995

[Determination of N-demethyldiazepam and its metabolite oxazepam in plasma by HPLC and their pharmacokinetics in rats].

A simple rapid and sensitive HPLC method for simultaneous determination of N-demethyldiazepam and its metabolite oxazepam in both human and rat plasma was described. A reversed phase C18 column equipped with a 240 nm detector were selected. Diazepam was used as internal standard. The mobile phase consisted of acetonitrile--0.01 mol.L-1 sodium acetate buffer (pH 3.8, 33.3: 66.6 v/v). The retention time for N-demethyldiazepam, oxazepam and internal standard were 4.85 min, 2.8 min and 8.5 min, respectively. The lower detection limits for oxazepam and N-demethyldiazepam were 10 ng.ml-1 and 7 ng.ml-1, respectively. The precisions (RSD%, n = 5) of within-day and day-to-day were less than 6% and 10% and their absolute recoveries were 74% and 86%, respectively. The pharmacokinetic characteristics of N-demethyldiazepam in Sprague-Dawley rats after a single oral dose of 2.5 mg.kg-1 was investigated by this method. The concentration-time curve was fitted to a two-compartment open model. Its main pharmacokinetic parameters were: Tmax = 0.24 h, Cmax = 1211.78 ng.ml-1, T1/2 beta = 2.84 h, AUC = 1264 ng.ml-1.h-1.

Animals↗
PubMed1995

Coping with culture-based conflict: implications for counseling research and practice.

Interpersonal conflict related to sociocultural group membership was examined with a multicultural university sample. The Social Group Conflict Scale (SGCS), collective self-esteem (CSE), and Bradburn affect scale were administered to 248 university students. The current study attempted to replicate and extend the findings on social group-based conflict recently proposed by Dunbar, Sue, and Liu. Results indicated that 51% of the subjects reported encountering interpersonal conflict attributable to their social group memberships, with ethnicity being the most frequently attributed group category. Significant gender and ethnic differences were noted in coping approach employed in responding to the conflict event. The current findings are considered in regard to effectively assessing and responding to intercultural conflict for mental health practice.

Adolescent↗
PubMed1994

Selective involvement of central 5-HT2 receptors in the maintenance of tolerance to ethanol by arginine8-vasopressin.

Arginine8-vasopressin (AVP) has been shown repeatedly to affect learning and memory and to maintain tolerance to ethanol if the brain serotonin and catecholamine systems are intact. In the present study, 5,7-dihydroxytryptamine (5,7-DHT) was injected intracerebroventricularly to disrupt serotonergic projections from the raphe to the forebrain. This resulted in a marked decrease in 5-hydroxytryptamine (5-HT) immunoreactivity in the terminal areas of the septum and the hippocampus, but not in the serotonin-containing neuronal cell bodies in the raphe nuclei. In control rats, tolerance to the motor-impairing effects of ethanol lasted for only 5 days after the cessation of ethanol treatment but could be maintained indefinitely for as long as AVP was given. In the 5,7-dihydroxytryptamine-lesioned rats, AVP was unable to maintain the tolerance. Continuous intracerebroventricular infusion of 5-HT restored the ability of AVP to maintain ethanol tolerance in the lesioned rats. A selective 5-HT2 agonist (alpha-methylserotonin) was equally effective, and a 5-HT3 receptor agonist (2-methylserotonin) was slightly less effective, but the 5-HT1A agonist dipropylaminotetralin (8-hydroxy-dipropylaminotetralin) was totally ineffective in this respect. The results indicate selective involvement of brain 5-HT2 and possibly 5-HT3 receptors in mediating AVP maintenance of tolerance to ethanol but do not pinpoint their specific loci or roles.

5,7-Dihydroxytryptamine↗
PubMed1994

[Studies on the anticonvulsive activity of pyrazolidinones].

The anticonvulsive activity of three kinds of pyrazolidinones: 5-benzyl-substituted-3-pyrazolidinones; 5-benzyl-1-alkyl substituted and 1-alkyl substituted-3-pyrazolidinones were studied. Fourteen substitutes of these three kinds of pyrazolidinones were found to be potent anticonvulsants. In doses less than TD50, they were found to be able to protect mice and rats from seizures produced by maximal electroshock seizure (MES), such action appeared rapidly and lasted for a short period. II-f was shown to be the most potent anti-MES agent among these three kinds of pyrazolidinones. It also showed therapeutic effect in treating experimental epilepsy produced by intrahippocampal injection of zinc sulfate in rabbits and audiogenic seizures in rats. The third kind of pyrazolidinones also showed anti-metrazol induced seizures in mice.

Acoustic Stimulation↗
PubMed1993

Influence of low density lipoproteins on cytosolic free Ca2+ concentration and dense tubular system in human platelets.

The cytosolic free Ca2+ concentration [Ca2+]i and dense tubular system (DTS) of washed human platelets were affected by low density lipoproteins (LDL) of 25 micrograms/ml at 37 degrees C for 10 minutes. After the incubation with LDL, the [Ca2+]i increased from 115 +/- 29 nM to 141 +/- 24 nM. LDL promoted the increase of [Ca2+]i (471 +/- 31 nM) induced by thrombin (0.03 U/ml) as compared to that which thrombin did alone (240 +/- 11 nM) (p < 0.05). The increased Ca2+ influx from the extracellular space is thought to be the reason of the increase in [Ca2+]i, since the effect of LDL was abolished by removal of external Ca2+ by EGTA. The DTS changed primarily from thin elongated forms to rounded vesicles. No evidence was noticed that LDL caused a mobilization of Ca2+ from the DTS.

Biological Transport↗
PubMed1993

A comparison of corneal endothelial changes after use of Healon or Viscoat during phacoemulsification.

We conducted a prospective, randomized trial comparing the endothelial protective effects of Healon (Kabi Pharmacia Ophthalmics, Inc., Monrovia, California) and Viscoat (Alcon Surgical, Inc., Ft. Worth, Texas) in 59 eyes of 59 patients undergoing iris-plane or posterior-chamber phacoemulsification with posterior-chamber lens implantation. We evaluated postoperative central and superior changes in corneal thickness and corneal endothelial cell density, coefficient of variation in cell size, and percentage of hexagons. In the overall series, at one day postoperatively, corneal thickness increased 17% centrally and superiorly in eyes receiving Healon compared to 12% centrally and 11% superiorly in eyes receiving Viscoat (P < .05). Sixteen weeks postoperatively, superior endothelial cell loss was 11.6% in eyes receiving Healon compared to 2.1% in eyes receiving Viscoat (P < .01). In the iris-plane phacoemulsification group, superior cell loss at week 16 was 13.8% in eyes receiving Healon and 0.5% in eyes receiving Viscoat (P < .04). In the posterior-chamber phacoemulsification group, there were no significant differences between the Healon and Viscoat subgroups. Comparing the surgical techniques, in the Healon group, central cell loss at week 16 was 13.8% in the iris-plane phacoemulsification subgroup and 0.6% in the posterior-chamber phacoemulsification subgroup (P < .03), and coefficient of variation in cell size increased 3.7% in the iris-plane subgroup and decreased 6.8% in the posterior-chamber subgroup (P < .04). In the Viscoat group, there were no significant differences between surgical techniques at week 16. Viscoat provided greater corneal endothelial protection than Healon during iris-plane phacoemulsification. In eyes receiving Healon, posterior-chamber phacoemulsification resulted in less corneal endothelial trauma than the iris-plane technique.

Aged↗
PubMed1993

Blockade of chronic tolerance to ethanol by the NMDA antagonist, (+)-MK-801.

Previous studies indicated that learning and memory play important roles in the development of tolerance to ethanol. (+)-MK-801 has been shown to impair learning and might thus also block the development of tolerance to ethanol. To test this possibility, rats were trained to criterion on the moving belt, a complex motor coordination test. Acute i.p. injection of (+)-MK-801 (a non-competitive NMDA channel blocker) produced dose-related impairment on this test. A dose of 0.1 mg/kg, that had negligible effect by itself, potentiated the acute effects of ethanol. In a chronic experiment with different animals, half of the rats received (+)-MK-801 or saline daily, followed 30 min later by ethanol (1.8 g/kg i.p.) and three practice runs on the belt, and 1 h later a second dose of (+)-MK-801 or saline. The other half received the same drugs but ethanol followed the practice. (+)-MK-801 blocked the functional tolerance to ethanol in both groups when the pre-ethanol dose was 0.25 mg/kg, but not when it was 0.1 mg/kg. Tolerance to the effects of (+)-MK-801 itself did not occur over 2 weeks of treatment. These results suggest that NMDA receptors are involved in development of chronic tolerance to ethanol as shown previously with rapid tolerance.

Animals↗
PubMed1993

[Antipyretic and anti-inflammatory effects of Artemisia annua L].

The antipyretic, heat-resisting anti-inflammatory analgesic and bacteriostasis effects of water extracts ethyl-acetate and n-butyl alcohol extracts of Artemisia annua are reported. Animal experiment has demonstrated that qinghao acid is one of the actively bacteriostatic constituents. Scopoletin is one of the anti-inflammatory constituents of Artemisia annua.

Animals↗
PubMed1993

Involvement of membrane glycophorins in human erythrocytes invaded by Plasmodium falciparum.

The extent of participation and changes of glycophorins (GPs) and membrane proteins in the merozite-human erythrocyte interaction during the invasion of Plasmodium falciparum (Pf) were studied by immunoblotting techniques. Polyclonal antisera to alpha GP and to its C-terminal fragment (residues 82-131) as well as M and N specific monoclonal antibodies (MoAbs) were used. We examined the GPs in the parasite-free saponin lysates, saponin pellets and the culture supernatants of the infected erythrocytes in comparison with the mock cultured normal RBC. Excepting the usual GP patterns, a GP with molecular weight of 77.5 K (band 1') existed in the parasitized erythrocytes and their saponin pellets and several GP bands ranging from 28K to 54K were present in saponin pellets when probed with anti-GP and anti-peptide C sera. This reflected the disintegration of erythrocyte membrane alpha GP through the invasion of Pf. The alpha 2 GP in the saponin pellets of the parasitized MM erythrocytes surprisingly cross-reacted with the N MoAb, implying that it may have come from the intermingling of the host alpha GP in MM erythrocytes with the parasite alpha GP reacting to N MoAb. The saponin pellets of parasitized erythrocytes preserved a considerable amount of ankyrin, band 3, protein 4.1 and 4.2, while the GP bands were densely mixed with the parasite proteins and the disintegrated products of membrane proteins. Four erythrocyte-binding antigens (EBA) of 143 K, 135 K, 115 K and 107 K recognized by malaria hyperimmune serum were detected in the culture supernatants of Pf, some of them appeared in the infected erythrocytes, their saponin lysates and pellets.

Animals↗
PubMed1992

Elliptocytosis associated with an abnormal alpha glycophorin.

A case of elliptocytosis associated with an undescribed abnormal alpha glycophorin (alpha GP) is reported. Using immunoblotting techniques, a clear-cut minor band 6' was detected emerging just behind the monomer of delta GP (band 6) when probed with anti-alpha GP antiserum. It also reacted with anti-peptide C antiserum, suggesting that this new band with a molecular weight of 24 K is related to the structural alteration of alpha GP and not delta GP. The erythrocyte membrane proteins of the patient exhibited a quite normal pattern, with a normal alpha spectrin/beta spectrin ratio, but the reaction with anti-protein 4.1 serum confirmed the increase in proteolytic susceptibility of her protein 4.1. The results of DNA mapping implied that the abnormality may be due to a short deletion of the heterozygote. The significance of deviation involving the alpha GP and protein 4.1 to the elliptocytic change of erythrocyte shape is briefly discussed.

Aged↗
PubMed1992

Quantitation of particulate microemboli during cardiopulmonary bypass: experimental and clinical studies.

An electronic particle-size analyzer (Coulter Counter ZM) was used to quantitate particulate microemboli 15 to 80 microns in size during cardiopulmonary bypass. Through both laboratory studies and clinical research, we confirmed three main causes of microemboli: (1) infusion of banked blood stored for more than 3 days; (2) use of cardiotomy reservoirs; and (3) use of bubble oxygenators. The regression equation between number of particles and blood storage time was Y = 3.7262X + 10.244 (r = 0.886; p < 0.01). The number of microemboli from cardiotomy reservoirs was 2.8 to 5.1 times that from other sources (p < 0.01). The number of solid particles from bubble oxygenators was 1.8 to 3.2 times that from membrane oxygenators (p < 0.01). Electron microscopy showed that a large number of solid particles more than 20 microns in size were formed during heart-lung bypass. They obstructed the microcirculation and damaged pulmonary capillary endothelial and alveolar epithelial cells. The degree of histological damage was related to the number and size of microemboli and the duration of pulmonary microcirculatory obstruction.

Animals↗
PubMed1992

Arginine-8-vasopressin potentiates acute ethanol intoxication.

AVP maintains ethanol (EtOH) tolerance after cessation of chronic EtOH treatment. However, the acute interaction of AVP and EtOH has not been well characterized. Rats were trained on a moving belt and the EtOH dose-response relationship (range 1.0-2.0 g/kg) was determined after pretreatment with saline, AVP (2.5-40 micrograms SC or 10 ng ICV), the AVP-V1 receptor antagonist [Des-Gly9,d(CH2)5(1),O-Et-Tyr2, Val4,Arg8]-vasopressin (10 ng ICV), or AVP in combination with the V1 antagonist. AVP produced a 16% decrease in the EtOH ED50 when given either SC or ICV; this decrease, which appears to represent true potentiation rather than additivity, was prevented by the preadministration of the V1 antagonist. Other rats were made EtOH-tolerant by 7 daily injections of either EtOH alone (1.8 g/kg IP) or EtOH (1.5 g/kg IP) + AVP (10 micrograms SC), followed by a practice session on the moving belt. In both sets of tolerant animals, AVP potentiation of acute EtOH effects was still seen on day 6. The mechanism of AVP potentiation of EtOH-induced impairment is unknown, but the failure of the V1 antagonist alone to alter the effect of EtOH suggests that endogenous AVP is not involved directly in modulating EtOH intoxication.

Alcoholic Intoxication↗
PubMed1992

Role of the gamma-aminobutyric acid receptor/chloride channel complex in tolerance to ethanol and cross-tolerance to diazepam and pentobarbital.

The role of the gamma-aminobutyric acid (GABA) receptor/chloride channel complex in the development of tolerance to ethanol and cross-tolerance to diazepam and pentobarbital was assessed. Rats given a low (1.8 g/kg) dose of ethanol before daily practice on the moving belt test of motor incoordination, and those given a high daily dose (3.6 g/kg) not paired with practice, showed tolerance to ethanol and cross-tolerance to diazepam and pentobarbital, whereas rats receiving 1.8 g/kg of ethanol after practice did not. Control rats were trained on the moving belt, but received no ethanol treatment. No differences were seen among the treatment groups in the abilities of GABA or ethanol to increase 36Cl uptake into cerebral cortical microsacs. However, diazepam potentiation of GABA-mediated chloride flux was significantly lower in rats receiving daily intoxicated practice, but only if they received an i.p. injection of ethanol 1 hr before sacrifice. The degree of pentobarbital potentiation of the effect of GABA did not correlate with the behavioral cross-tolerance observed. The results indicate that behaviorally augmented cross-tolerance from ethanol to diazepam correlates incompletely with changes on the biochemical level.

Animals↗
PubMed1992

[Studies on genetic engineering of human insulin-purification and characterization of human proinsulin and insulin].

E. coli DH 5 alpha cells harboring a plasmid pWR 590-BCA 4 for fused human proinsulin production were cultured. The fused human proinsulin was isolated from the fermented cells and then subjected it to cleavage with BrCN. The cleaved product was then converted to crude proinsulin-S-sulfonate using oxidative sulfitolysis. The isolation of human proinsulin-S-sulfonate was accomplished by ion exchange chromatography on QAE-sephadex A-25, followed by gel filtration on sephadex G-50. The purified human proinsulin-S-sulfonate was folded using a disulfide interchange method. The folding mixture was then chromatographed on sephadex G-50 and purified proinsulin was obtained. The proinsulin was then converted to human insulin and C-peptide by a combination cleavage with trypsin and carboxypeptidase B. The total yield of human insulin was about 5 mg/L The Zinc insulin crystals were obtained with amorphous human insulin using citrate method. The amino acid composition N-terminal sequences as well as C-terminal amino acid residues are in agreement with expected results. The hypoglycemic activity of purified human insulin is 26-27 U/mg, as judged by mouse convulsion assay, and the RIA activity is about 99% of that of porcine insulin.

Cloning, Molecular↗
PubMed1991

[Experimental studies on the concurrent infections with Entamoeba histolytica and Schistosoma japonicum].

The mongolian gerbil (Merious unguiculatus) was used as an experimental animal model for studying the concurrent infections and pathogenicities with Entamoeba histolytica (E. h.) and Schistosoma japonicum (S. j.) by the cutaneous infection with 20 fresh cercariae of S. j. and the intracaecal inoculation of 5 x 10(5)/0.5 ml amebic suspension. Light and electron microscopy were used to observe the pathological changes of the caecal wall in the concurrent infections. The results showed that S. j. infection could promote the development of caecal amoebiasis, and stimulate symbiotic E. h. infection to develop invasive caecal amoebiasis. The pathological characteristics of the concurrent two infections not only exhibited the characteristics of the single E. h. or S. j. infection, but also showed its own specialty. Immunological effect of the host was apparently involved in the pathogenic process. In addition, the trophozoites of E. h. were usually observed to adhere closely to the egg shell of S. j. at the site of tissues necrosis. From the adherence phenomenon observed in our studies, there might exist an affinity mechanism between the E. h. trophozoite and S. j. ovum.

Animals↗
PubMed1990

Resistance to receptor-mediated degradation of a murine epidermal growth factor analogue (EGF-Val-47) potentiates its mitogenic activity.

In most cell types two classes of epidermal growth factor (EGF) receptors can be found: a major class that binds EGF with relatively low affinity and a minor class that binds with very high affinity. Structure-function studies have shown that mutations at amino acid 47 in the EGF molecule severely reduce its affinity for the EGF receptor but do not cause preferential binding to one or the other subclass of receptors. Using three EGF derivatives with a mutation at amino acid 47 (Ser-47, Leu-37-Tyr-47, and Val-47), we have investigated the relative contribution of the two receptor subclasses to the EGF-dependent mitogenic response. We show that mitogenicity correlates exclusively with occupancy of the high-affinity receptor and that full occupancy of this subclass is required for maximal stimulation. In addition we demonstrate that for the EGF-Val-47 analogue this requirement can be abrogated and half-maximal biological activity reached with a high-affinity receptor occupancy of only 8%. While the rate of internalization did not significantly differ between EGF-Val-47 and native mEGF, the analogue was much more resistant to degradation by cellular proteases and, after binding and receptor-mediated internalization, was released into the medium predominantly in an intact form. We propose that the increased mitogenicity of EGF-Val-47 is due to its prolonged half-life, resulting in continued occupancy of the high-affinity EGF receptor.

Animals↗