PubMed Health⌕ Search

Biomedical subjects

X H Xie

Publications and source records attributed to X H Xie.

14 recordsLinked to original sources
PubMed1997

[Integration of visual signals in the brain: mechanisms and functional significance of synchronous oscillation].

How are the functions performed by one part of the nervous system integrated with those of others? One possible way is by synchronous oscillation. We have reviewed recent advances in visual system, where synchronous oscillations have been intensively observed and investigated. This article is concentrated on discussing theoretical reasoning, experimental evidence, possible mechanisms underlying the generation and the functional significance of visual synchronous oscillations. Predictions on several prosperous areas were also outlined.

Animals↗
PubMed1995

Reduction of GABA-mediated inhibitory postsynaptic potentials in hippocampal CA1 pyramidal neurons following oral flurazepam administration.

Oral administration of the benzodiazepine, flurazepam, for one week results in tolerance in vivo and in vitro and in a reduction in recurrent and feedforward inhibition in vitro in the CA1 pyramidal cell region of hippocampus. In the present study CA1 pyramidal cells were examined intracellularly in vitro in rat hippocampal slices (500 microns) from rats sacrificed two or seven days after cessation of oral flurazepam treatment. Following drug treatment, the membrane characteristics of CA1 pyramidal cells were not significantly different from control neurons. GABAA-mediated, early inhibitory postsynaptic potentials were significantly reduced in amplitude (60%) in pyramidal neurons from rats killed two days, but not in those killed seven days, after the end of drug administration. The decrease in early inhibitory postsynaptic potential amplitude was observed using just-subthreshold, threshold and supramaximal orthodromic stimulation as well as following antidromic activation. The magnitude of the decrease in the early inhibitory postsynaptic potential amplitude was similar in the presence of the GABAB antagonist, CGP 35348, and could not be attributed to differences in the strength of afferent stimulation between flurazepam-treated and control groups. The size of the GABAB-mediated, late inhibitory postsynaptic potentials was also significantly decreased (45%) in comparison to control cells. Reversal potentials for both the early (-72 mV) and late (-92 mV) hyperpolarizations were not significantly different between groups. Following high intensity orthodromic stimulation, in the presence of an intracellular sodium channel blocker (QX-314) which also blocks the GABAB-mediated late hyperpolarization, a bicuculline-sensitive late depolarizing potential was unmasked in neurons from FZP-treated rats, but never from control cells. Excitatory postsynaptic potential amplitude was significantly increased in flurazepam-treated neurons and the threshold for the synaptically-evoked action potential was significantly increased. Following depolarizing current injection, the duration and frequency of pyramidal cell discharges and the action potential threshold were not altered by oral flurazepam treatment. The amplitude of the fast afterhyperpolarization was also not changed. Overall, the findings indicate an impairment of transmission at GABAergic synapses onto hippocampal CA1 pyramidal cell neurons after chronic benzodiazepine treatment at a time when rats are tolerant to the anticonvulsant effects of the benzodiazepines in vivo.

Acetates↗
PubMed1994

Impairment of feedforward inhibition in CA1 region of hippocampus after chronic benzodiazepine treatment.

The strength of feedforward inhibition was assessed in the CA1 region of in vitro hippocampus of benzodiazepine tolerant rats 2 and 7 days after 1 week oral flurazepam (FZP) administration. Feedforward inhibition was activated with a Schaffer collateral stimulation just-subthreshold for a population spike followed at intervals of 10-100 ms by test population spikes elicited from the subicular side of the recording electrode. The amplitude of test spike was reduced to a lesser degree 2 days, but not 7 days, after FZP treatment, suggesting a decrease feedforward inhibition in treated rats coinciding with the time course for reversal of anticonvulsant tolerance in vivo.

Animals↗
PubMed1992

Reduction in potency of selective gamma-aminobutyric acidA agonists and diazepam in CA1 region of in vitro hippocampal slices from chronic flurazepam-treated rats.

The potency and efficacy of selective gamma-aminobutyric acidA (GABAA) agonists (GABA, muscimol, isoguvacine and 4,5,6,7-tetrahydroisoxazolo-[5,4-c]-pyridin-3-ol), the GABAB agonist, baclofen, and the benzodiazepine agonist, diazepam, were examined using extracellular recording techniques in in vitro hippocampal slices from rats sacrificed 2 days after 1 week of flurazepam treatment. Population spikes elicited by stimulation of Schaffer collaterals were recorded in the CA1 pyramidal cell region with NaCl-containing glass micropipettes. GABA agonists were superfused in increasing concentrations for 5 min. Drug responses, averaged over the last 2 min for each concentration, were compared to the predrug base line. GABAA agonists, but not baclofen, showed a significant, 2-fold, decrease in potency, but not efficacy, to reduce CA1-evoked responses in treated vs. control slices. The benzodiazepine effect was evaluated by the shift in the isoguvacine dose-response curve in the absence, then presence, of diazepam. A reduction in diazepam potency was demonstrated in vitro by a significantly reduced shift in the isoguvacine curve by 300 nM, but not 1 microM, diazepam after chronic but not acute in vivo pretreatment. The results indicated a selective GABAA agonist subsensitivity and diazepam tolerance in hippocampus after 1 week of flurazepam treatment and establish the hippocampal slice preparation as a valuable substrate for investigating synaptic mechanisms of benzodiazepine tolerance.

Animals↗
PubMed1991

Chronic benzodiazepine treatment of rats induces reduction of paired-pulse inhibition in CA1 region of in vitro hippocampus.

Paired-pulse inhibition was studied extracellularly in in vitro hippocampal slices from rats sacrificed 48 h or 7 days after 1 week flurazepam (FZP) treatment. Population spikes and field excitatory postsynaptic potentials (EPSPs) were recorded with NaCl-containing glass micropipettes in the stratum pyramidale and stratum radiatum, respectively, of the CA1 region. Conditioning pulses were delivered by stimulating Shaffer collaterals (orthodromic) or the alveus (antidromic). Orthodromic test pulses were delivered with interpulse intervals of 10-200 ms. There was a significant reduction in paired-pulse inhibition in slices from treated vs control rats in both the orthodromic-orthodromic and antidromic-orthodromic paradigms. Reduced inhibition was evident 48 h, but not 7 days, after the end of FZP treatment. Furthermore, there was a significant prolongation of the half decay time of the field EPSP, without a significant change in the initial slope or maximum amplitude. The results may suggest an impairment of endogenous gamma-aminobutyric acid function in the hippocampus after chronic benzodiazepine (BZ) treatment and may provide a basis for a mechanism of BZ tolerance.

Action Potentials↗
PubMed1991

Anti-pentylenetetrazol effect of intranigral 2-amino-7-phosphonoheptanoate attenuated by muscimol.

Bilateral injection of 2-amino-7-phosphonoheptanoate (2-APH), a selective N-methyl-D-aspartate (NMDA) receptor antagonist, into substantia nigra pars reticulata (SNpr) significantly and dose-dependently suppressed tonic pentylenetetrazol (PTZ) seizures (100 mg/kg, i.p.). The results confirm the anticonvulsant effectiveness of 2-APH and the capacity of SNpr to modulate PTZ seizure activity. The anti-PTZ effect of 2-APH was significantly attenuated by muscimol, co-infused into SNpr. This result supports the hypothesis, drawn from earlier studies, that intranigral muscimol can interfere with the anti-PTZ actions of other intranigral treatments.

2-Amino-5-phosphonovalerate↗
PubMed1991

[Study on targeting drug delivery system--the animal behavior in vivo after hepatic arterial embolization of methotrexate microsphere].

The cross-linked MTX-gelatin microsphere was chosen as an experimental model. Pharmacokinetics and biodegradable period of the microsphere were studied after hepatic arterial embolization in vivo in dogs. After hepatic arterial infusion, the concentration of MTX-ms in peripheral vein blood increased rapidly and declined slowly. In contrast, the peak time of the drug concentration of infused MTX solution appeared at once and decreased rapidly. The half-life of MTX-ms in vivo was 2.14 times as much as that of MTX solution. During the assay period of sixteen hours the drug concentration of MTX-ms in hepatic vein blood was constantly higher than that of MTX solution. The follow-up angiography revealed that microsphere is a kind of peripheral embolic agent and its degradable time in vivo is about one month. Both sustained release and embolization effectiveness of microsphere will be significant in treatment of hepatic cancer.

Animals↗
PubMed1991

[Study on targeting drug delivery system--the characteristics of methotrexate microsphere and experimental treatment of hepatic tumor in rats by arterial embolization].

Preparation of methotrexate microsphere (MTX-ms) by emulsion-freezing technique was introduced and the experimental results proved that MTX entrapped in the microspheres exhibited good stabilities towards temperature, cobalt-60 radiation and light. The dissolution and inflation rate of the microspheres in pH 7.4 buffer solution at different times measured by Coulter counter was presented. Antitumor activity of MTX-ms after hepatic arterial embolization was examined in a model of liver tumor in Wistar rats. The group of rats treated with MTX-ms showed a rather significant reduction in tumor growth and more extended tumor necrosis as compared with the other groups, e.g. normal saline solution, MTX solution, placebo gelatin-ms and the results demonstrate that the effect of arterial chemoembolization used by MTX-ms is superior to that of the groups either using arterial chemotherapy or arterial embolization alone in treating rat liver cancer.

Animals↗
PubMed1990

Adenosine triphosphate liposomes: encapsulation and distribution studies.

Four methods for encapsulating adenosine triphosphate (ATP) in liposomes were evaluated. Optimum entrapment required emulsifying ATP with the lipids used to form the liposome membrane in a high-speed homogenizer followed by evaporating the organic solvent with vigorous stirring. Under these optimum conditions ATP entrapment was 38.9%; i.e., the dosage form contained 38.9 g of ATP per 100 g of lipid. The distribution of positively charged liposomes loaded with ATP was studied in dogs with experimentally induced myocardial infarction. Intravenous injection of positively charged ATP liposomes caused accumulation of ATP in myocardial infarct tissue. Myocardial infarct tissue has reduced blood flow; since positively charged liposomes accumulated in infarct tissue, liposomes may be a drug delivery system for this disease state.

Adenosine Triphosphate↗
PubMed1989

The cervix-ripening effect of 15-methyl-prostaglandin F2 alpha methyl ester before vacuum aspiration for termination of early pregnancy in primigravidae.

A double blind clinical trial on prostaglandin for cervix ripening prior to vacuum aspiration for termination of early pregnancy in primigravidae was carried out in 68 patients with 6-11 week's gestation. The patients were randomly treated with either 1.0 mg of 15-methyl-prostaglandin F2 alpha methyl ester vaginal suppository or a placebo suppository. A mean cervical dilation to 6.6 mm was achieved with minimal side effects in the prostaglandin group as against 4.3 mm in the placebo group. The 15-methyl-prostaglandin F2 alpha methyl ester suppository technique seems to be effective, safe and simple in ripening the cervix for termination of early pregnancy in primigravidae.

Adult↗
PubMed1989

[Studies on the preparation of adenosine triphosphate (ATP) liposomes].

In this paper, a method--improved emulsification vesicles (IEV) was proposed for the preparation of adenosine triphosphate (ATP) liposome. The ATP entrapment ratio reached 38.9% (w/w), which was much greater than that reported in the literature. Thus, IEV is an excellent method which has never been presented. Together with ultrafiltration for removing unentrapped drugs and radiation sterilization, these methods are most meaningful for the production of liposomes in large scale.

Adenosine Triphosphate↗