Biomedical subjects

Q X Chen

Publications and source records attributed to Q X Chen.

50 records · Page 3Linked to original sources

PubMed1991

Hysteroscopic hydrotubation for treatment of tubal blockage.

In order to increase the effectiveness of hydrotubation, a plastic cannula was inserted into the fallopian tube under hysteroscopic control. Fifty women with tubal blockage confirmed by HSG were selected for treatment. Hydrotubation solution consisted of hydrocortisone (20 mg), gentamicin (160,000 IU) and procaine (80 mg) in 20 ml distilled water. Repeat HSG was performed. After three treatments, tubal patency (one or both tubes) was achieved in 20 women (40%), and seven pregnancies resulted within 1-18 months. Hysteroscopic hydrotubation may be an alternative treatment for tubal blockage.

Adult↗

PubMed1991

Intracellular Ca2+ suppressed a transient potassium current in hippocampal neurons.

The effects of intracellular Ca2+ (Ca2+i) on K+ currents in hippocampal cells were examined using acutely isolated cells obtained from adult guinea pigs. Whole-cell voltage-clamp recordings were carried out in a configuration that allowed a continuous perfusion of the intracellular medium. Recording media were made to block inward currents and allowed selective activation of K(+)-dependent outward currents. Voltage-dependent outward currents consisted of an initial rapidly decaying component followed by a sustained component. The time constant of decay of the transient current was about 25 msec, and previous studies (Numann et al., 1987) showed that the kinetic and pharmacological properties of this current closely resembled the A current recorded in invertebrate neurons (Connor and Stevens, 1971; Thompson, 1982). Intracellular perfusion of hippocampal cells with a solution containing elevated Ca2+ (about 4.5 x 10(-4) M) elicited outward currents at the holding potential (-45 to -55 mV) and produced changes in voltage-dependent K+ currents. The transient outward current (IA) activated by depolarization was suppressed with increases in Ca2+i. Delayed, sustained K+ currents were greatly potentiated. Data also showed that, among the 3 effects elicited by Ca2+i, suppression of IA was most sensitive to Ca2+i elevation. Previous results (Numann et al., 1987) showed that IA had a lower threshold (about -45 mV) than sustained currents (about -40 mV). By using low levels of depolarization (-40 mV), IA can be selectively activated, and the suppressive effect of Ca2+i on IA was confirmed on the kinetically isolated IA.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1990

GABAA receptor function is regulated by phosphorylation in acutely dissociated guinea-pig hippocampal neurones.

1. Current mediated by GABAA receptors was examined in pyramidal cells acutely dissociated from the hippocampus of mature guinea-pigs. Current responses were measured using whole-cell voltage-clamp recordings. An internal perfusion technique was used to change the intracellular contents during recording. 2. Application of GABA (100-300 microM) by short duration pressure pulses produced outward current responses at a holding potential of -10 mV. When recordings were made with intracellular solutions which did not contain Mg-ATP, GABA responses progressively decreased to less than 10% of their initial values after 10 min. This 'run-down' of the GABA response could not be accounted for by desensitization since the rate of run-down was not dependent upon agonist application. 3. The run-down of the GABAA response was reversed when Mg2+ (4 mM) and ATP (2 mM) were introduced into the intracellular perfusate. In addition to the presence of Mg-ATP, buffering of Ca2+ in the intracellular solution to low levels (approximately 10(-8) M) was also necessary to stabilize the GABAA response. 4. The role of a phosphorylation process in regulating the GABAA receptor was tested. After the GABA response stabilized, introduction of alkaline phosphatase (100 micrograms/ml) to the intracellular perfusate caused a complete run-down of the GABA response. 5. Stable GABA responses were obtained when ATP was replaced by ATP-gamma-S (adenosine 5'-O-(thiotriphosphate), an analogue of ATP that donates a thiophosphate group resulting in a product that is more resistant to hydrolysis. Following such treatment GABA responses declined more slowly after the introduction of intracellular alkaline phosphatase. 6. Run-down of GABA responses accelerated when intracellular Ca2+ concentration ([Ca2+]i) was elevated to about 5 x 10(-4) M. The run-down caused by elevated [Ca2+]i could be stopped and reversed by reducing [Ca2+]i to about 10(-8) M. 7. The introduction of ATP-gamma-S to the intracellular medium retarded the run-down of GABA responses caused by elevation of [Ca2+]i. 8. N-(6-Aminohexyl)-5-chloro-1-naphthalenesulphonamide (W-7), a calmodulin inhibitor, reduced the rate of run-down induced by elevated [Ca2+]i. 9. These results suggest that the function of the GABAA receptor is maintained by phosphorylation of the receptor or some closely associated regulatory molecule. Elevation of [Ca2+]i destabilizes the function of the GABAA receptor, probably by activating a Ca2+/calmodulin-dependent phosphatase.

Adenosine Triphosphate↗

PubMed1989

Fetal lamb 3 beta, 20 alpha-hydroxysteroid oxidoreductase: dual activity at the same active site examined by affinity labeling with 16 alpha-(bromo[2'-14C]acetoxy)progesterone.

3 beta,20 alpha-Hydroxysteroid oxidoreductase was purified to homogeneity from fetal lamb erythrocytes. The Mr 35,000 enzyme utilizes NADPH and reduces progesterone to 4-pregnen-20 alpha-ol-3-one [Km = 30.8 microM and Vmax = 0.7 nmol min-1 (nmol of enzyme)-1] and 5 alpha-dihydrotestosterone to 5 alpha-androstane-3 beta, 17 beta-diol [Km = 74 microM and Vmax = 1.3 nmol min-1 (nmol of enzyme)-1]. 5 alpha-Dihydrotestosterone competitively inhibits (Ki = 102 microM) 20 alpha-reductase activity, suggesting that both substrates may be reduced at the same active site. 16 alpha-(Bromoacetoxy)progesterone competitively inhibits 3 beta- and 20 alpha-reductase activities and also causes time-dependent and irreversible losses of both 3 beta-reductase and 20 alpha-reductase activities with the same pseudo-first order kinetic t1/2 value of 75 min. Progesterone and 5 alpha-dihydrotestosterone protect the enzyme against loss of the two reductase activities presumably by competing with the affinity alkylating steroid for the active site of 3 beta,20 alpha-hydroxysteroid oxidoreductase. 16 alpha-(Bromo[2'-14C]acetoxy) progesterone radiolabels the active site of 3 beta,20 alpha-hydroxysteroid oxidoreductase wherein 1 mol of steroid completely inactivates 1 mol of enzyme with complete loss of both reductase activities. Hydrolysis of the 14C-labeled enzyme with 6 N HCl at 110 degrees C and analysis of the amino acid hydrolysate identified predominantly N pi-(carboxy[2'-14C]methyl)histidine [His(pi-CM)].(ABSTRACT TRUNCATED AT 250 WORDS)

Affinity Labels↗

PubMed1989

[Studies on synthetic new drug SC1001-sodium against epilepsy induced by coriaria lactone in rabbits].

In the present experiment, SC1001Na synthesized by West China University of Medical Sciences was used for studying to resist epilepsy induced by coriaria lactone. Forty-two normal male rabbits weighing 1.7-2.5 kg were randomly divided into four groups. The animals of the control group received coriaria lactone (3 mg/kg, i.m.). The animals in each of the experimental groups were injected separately with SC1001Na (100, 200 and 300 mg/kg, i.p.), but the control animals were not injected with SC1001Na. Thirty minutes later, the animals of the experimental groups were injected with the same dose of coriaria lactone as the control animals. The behavior of all animals before and after injection were observed continuously in 4-5 hours. The ECoG of eight animals of them were observed at the same time with telemetric method. The results of experiments indicated that SC1001Na is effective on epilepsy induced by coriaria lactone, in decreasing seizure rate, lengthening latent period, reducing seizure degree, as well as in decreasing mortality.

Animals↗

PubMed1989

[An experimental observation on the calmative and antiepileptic effects of a new synthetic drug SC1001-aminum intupaias].

In this experiment, the calmative and anti-epileptic effects of SC1001A were observed in fifty-five tupaias (Tupaia belangeri Yunalis), both male and female, were divided into four groups. The animals of the first group were perfused with SC1001A (400mg/kg) into their stomach. The animals of the second group were injected with coriaria lactone (5mg/kg, i.m.) for inducing seizures. The remaining two groups received SC1001A 100 and 400 mg/kg respectively by the same way as that of the first group, and 1 min later, they were injected immediately with coriaria lactone (5 mg/kg, i.m.). After the drug being perfused, the behaviors of all the experimental animals were observed continuously for 2-3 h. The results of the experiment indicated that SC1001A was possessed of a calmative effect which appeared shortly after drug (mean 12.88 min) and did not sustain a long time (mean 98 min). In addition, SC1001A was obviously effective on epilepsy induced by coriaria lactone in tupaias, in reducing the seizure rate, the times of petit mal and grand mal, as well as the duration of grand mal.

Animals↗

PubMed1989

[Effects of synthetic new drug SC1001-sodium on respiratory frequency, heart rate, rectal temperature and electrocorticogram in rabbits].

Seventeen normal male rabbits weighing 1.7-2.8 kg were randomly divided into 2 groups. The experimental group (ten rabbits) was injected with SC1001Na (200 mg/kg, i.p.). The control group (seven rabbits) was injected with normal saline of the same volume. Continuous observations for 6 hours were made after injection, with reference to respiratory frequency (RF), heart rate (HR), rectal temperature (RT) and ECoG of these rabbits. The results of experiments indicate that SC1001Na has a slight inhibitory effect on RF and RT, an obvious inhibitory effect on the activity of central nervous system, and an accelerating effect on HR in rabbits.

Animals↗

PubMed1987

Isolation of 3 beta,20 alpha-hydroxysteroid oxidoreductase from sheep fetal blood.

3 beta,20 alpha-Hydroxysteroid oxidoreductase has been isolated from ovine fetal blood by a 2,370-fold purification scheme of ammonium sulfate fractionation, calcium phosphate gel adsorption, affinity chromatography, and fast performance liquid chromatography. A new high performance liquid chromatography-based assay for measuring 20 alpha-reductase activity is described. The enzyme is a monomer with a molecular weight of 35,000 and uses NADPH as a cofactor for reductase activity. It reduces progesterone to 4-pregnen-20 alpha-ol-3-one or 5 alpha-dihydrotestosterone to 5 alpha-androstan-3 beta,17 beta-diol with kinetic characteristics of Km = 30.8 microM and Vmax = 0.7 nmol min-1 (nmol of enzyme)-1 or Km = 74 microM and Vmax = 1.3 nmol min-1 (nmol of enzyme)-1, respectively. 5 alpha-Dihydrotestosterone competitively inhibits 20 alpha-reductase activity with a Ki value of 102 microM.

Animals↗

PubMed1987