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C L Zhang

Publications and source records attributed to C L Zhang.

At least 73 records · Page 4Linked to original sources
PubMed1992

Effects of the triazole derivative loreclezole (R72063) on stimulus induced ionic and field potential responses and on different patterns of epileptiform activity induced by low magnesium in rat entorhinal cortex-hippocampal slices.

Effects of loreclezole (R72063), a triazole derivative with anticonvulsant properties, were studied on field potentials in rat hippocampal slices and on different patterns of low Mg(2+)-induced epileptiform activity in combined entorhinal cortex-hippocampal slices. Lowering extracellular Mg2+ induced recurrent (10-60/min), short (40-80 ms) discharges in hippocampal areas CA1 and CA3. In the entorhinal cortex (EC) up to 90 s long ictaform events associated with large negative field potential and changes in the neuronal microenvironment were generated. These seizure like events changed their characteristics after one to two hours to recurrent discharges of 0.8 to 10 s. 20 microM loreclezole blocked the seizure like events in the entorhinal cortex completely 30-80 min after onset of application. The recurrent short discharges in the hippocampus were reliably blocked by 40 muM loreclezole 60-90 min after bath application with incomplete recovery after washout of several hours. The recurrent discharges in the entorhinal cortex were reliably blocked by 80 microM loreclezole applied for 80-100 min. Decreases in [Ca2+]o and associated slow field potentials evoked by repetitive stimulation of the stratum radiatum were depressed in a dose dependent manner, while similar changes induced by alvear stimulation remained almost unaffected. A paired pulse stimulus paradigm used to test for effect of loreclezole on synaptically evoked transient field potentials in normal medium revealed interference with mechanisms involved in frequency potentiation. While responses to alvear stimulation were largely unaffected, the response to a paired pulse stimulus to stratum radiatum was depressed over the whole range of tested stimulus intervals (15 to 150 ms). The findings suggest that loreclezole has effects on different patterns of epileptiform activity induced by extracellular low Mg2+ possibly by interfering with processes leading to frequency potentiation.

Animals↗
PubMed1992

Comparison of the effects of losigamone and its isomers on maximal electroshock induced convulsions in mice and on three different patterns of low magnesium induced epileptiform activity in slices of the rat temporal cortex.

Losigamone (AO-33) is a recemate of a tetronic acid derivative. The effects of losigamone and its three isomers (AO-242, AO-294 and AO-23) were compared on maximal electroshock (MES) induced convulsions in mice and on different patterns of extracellularly recorded, low Mg2+ induced epileptiform activity in slices of the rat temporal cortex. Lowering Mg2+ induced recurrent short discharges in areas CA3 and CA1 while ictaform events that lasted for many seconds were induced in the entorhinal cortex. In the hippocampus the activity stayed stable over a number of hours. In contrast, the ictaform events in the entorhinal cortex changed their characteristics after one to two hours to recurrent discharges of 0.8 to 10 s. Afterdischarges and interictal events were absent. 50 microM AO-242 showed a similar efficacy to 50 microM AO-33 in reducing and blocking epileptiform discharges in areas CA1 and CA3 while 50 microM AO-294 and 50 microM AO-23 had weaker effects than 50 microM AO-33. Concentrations of 50 microM and 100 microM AO-242 showed a similar efficacy to AO-33 on ictaform events in the entorhinal cortex. Late recurrent discharges were also blocked by AO-33 and AO-242 although at higher concentrations (300 microM). The in vitro observations are with respect to order of efficacy in accordance with the in vivo data obtained in the maximal electroshock test in mice. The order of potency in the MES test was AO-242 greater than AO-33 much greater than AO-294 much greater than AO-23.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

The dentate gyrus as a regulated gate for the propagation of epileptiform activity.

Properties of the interaction between the entorhinal cortex (EC) and the dentate gyrus were studied in a combined EC hippocampal slice preparation in which most of the fiber connectivity within this structure is intact. Epileptiform activity was induced by lowering extracellular Mg2+ concentration. This caused short recurrent discharges in the hippocampus while seizure-like events (SLE) slowly spread from the site of initiation to neighboring areas. At the end of a SLE, the EC, the subiculum and the neocortical area Te2 discharged in synchrony. This activity could develop into a state of recurrent tonic discharges highly synchronized between the different areas. These discharges were insensitive to treatment with currently available antiepileptic drugs. Although the SLE increased neuronal firing and extracellular potassium concentration in the dentate gyrus, this activity had only moderate effects on the activity generated in areas CA3 and CA1. Removing GABAergic inhibition with baclofen and bicuculline caused the spread of SLE from the EC to the dentate gyrus. Slow inhibitory postsynaptic potentials and intrinsic properties of dentate gyrus granule cells appear to underlie the filtering function of the dentate gyrus.

Afferent Pathways↗
PubMed1992

[Prospective study of intrauterine fetal resuscitation with aminophylline].

80 cases of fetal distress were divided at random into group A and B. Group A was treated with the traditional three drugs combination treatment. Group B was treated with intravenous injection of aminophylline slowly. FHR CTG and BPS were monitored and analysed. The results were as follows: (1) The differences before and after treatment in group B were significant. (2) Only FHR in group A showed difference before and after treatment. (3) The changes after treatment between group A and B were significant. These suggested that the effect of aminophylline on intrauterine fetal resuscitation is better method.

Aminophylline↗
PubMed1992

[Effect of intraventricular injection of 6-hydroxydopamine on the initiation of hibernation in ground squirrels].

The effect of forced depletion of brain norepinephrine (NE) on the onset of hibernation was observed in the ground squirrel (Citellus dauricus) by intraventricular injection of 6-hydroxydopamine (6-OHDA). The results showed: (1) Intraventricular injection of 100-200 micrograms 6-OHDA, which depleted 50-60% NE, markedly facilitated the onset of hibernation, i.e. the average induction period for hibernation in the treated animals was significantly shorter than that of the natural hibernating animals. (2) The average total torpor time in the treated animals was longer than that of natural hibernating animals. (3) All hibernating animals treated with 6-OHDA were able to wake up from deep hibernation spontaneously and undergo normal hibernation bouts. The results indicate the decrease of NE system activity in brain is one important factor in triggering the onset of hibernation.

Animals↗
PubMed1991

Human aortic proteoglycans of subjects from districts of high and low prevalence of atherosclerosis in China.

The contents of three species of proteoglycans (PGs), heparan sulfate PG(HSPG), chondroitin sulfate PG(CSPG) and dermatan sulfate chondroitin sulfate PG(DSCSPG), in human thoracic aortas of subjects from districts of high (Beijin, in North China) and low (Nanning, in South China) prevalence of atherosclerosis in China were quantitated. Higher aortic HSPG and DSCSPG (but lower DS) in samples from Nanning than those from Beijing might be implicated in the lower prevalence of atherosclerosis in the former.

Adolescent↗
PubMed1991

Neuropeptides and neurotransmitters in human placental villi.

The human placenta contains many kinds of bioactive substances which are more or less similar to those from the hypothalamic-pituitary-gonadal axis. Most of the studies were carried out mainly with term placenta. The present study, therefore, was attempted to identify, quantify and characterize these substances in the human placenta at the early pregnancy. Using the RIA, immunohistochemistry, HPLC, tissue culture and intrauterine injection methods, we have found that: (1) many kinds of neuropeptides and neurotransmitters are present in the placental villi; (2) LH-RH, NT and SRIF positive immunoreactive granules are localized in the cytotrophoblast and those of beta-EP, 5-HT positive granules in the syncytiotrophoblast; (3) synthetic LH-RH and dynorphin (Dyn) stimulate the hCG secretion of the early placental villi in vitro, and (4) the antisera of LH-RH, NT, Dyn and NE antagonist-alpha-MPT significantly reduced the number of blastocyst implantations in the early pregnant rat. These results indicate that in the human placenta there possibly exists a self-regulation mechanism for the synthesis and secretion of placental hormones and neurotransmitters. Therefore, the human placenta can be regarded as a neuroendocrine organ.

Animals↗
PubMed1991

Identification and characterization of viral polypeptides from type-II avian adenoviruses.

The polypeptides of serologically related viruses of hemorrhagic enteritis (HE) in turkeys, marble spleen disease (MSD) in pheasants, and splenomegaly in chickens (SMC) were separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and analyzed by protein immunoblotting with polyclonal antibodies to HE virus (HEV). The viral polypeptides II, III, IV, V, VI, and VII were detected on SDS-PAGE with the size range from 18 to 97 kDa in HEV. Viral polypeptides II, III, V, VI, and VII were detected in MSD virus and virus of SMC. Protein immunoblotting of viral proteins with anti-HEV serum revealed antigenic differences between the 3 viruses of avian adenovirus type-II examined. The differences were that the polypeptides II, III, IV, V, VI, and VII were identified in HEV and the polypeptides II, V, VI, and VII were identified in MSD virus and virus of SMC. The bands of penton base (polypeptide III) and fiber (polypeptide IV) were seen in HEV only by protein immunoblotting.

Adenoviridae Infections↗
PubMed1991

[Drug evaluation of huperzine A in the treatment of senile memory disorders].

Huperzine A is an alkaloid which was first isolated from Huperzia serrata (Thumb) Trev by Zhejiang Academy of Medical Sciences and Shanghai Institute of Materia Medica, Chinese Academy of Sciences. It exhibits a significant anticholinesterase activity and has been used on myasthenia gravis patients. The therapeutic effects were studied by random, match and double-blind method on 56 patients of multi-infarct dementia or senile dementia and 104 patients of senile and presenile simple memory disorders. The curative effects were evaluated by Wechsler memory scale. The im dose for multi-infarct dementia was 0.05 mg bid for 4 wk, whereas that for senile and presenile simple memory disorders was 0.03 mg bid for 2 wk. Saline was used on control group. The result showed that the curative effect of huperzine A was significant. Only a few patients felt slight dizziness and this did not affect the therapeutic effects.

Aged↗
PubMed1991

Correlation of annual change of luteinizing hormone-releasing hormone (LH-RH) with gonadal development in amphioxus.

The present study demonstrates for the first time by RIA that LH-RH is present in the heads as well as the bodies of the amphioxuses of both sexes. Gonadoliberin increases gradually during the course of gonadal development. At the time of gonadal maturity, LH-RH content reaches a maximum. The annual change of LH-RH correlates well with gonadal development and the gonadosomatic index (GSI). The reproductive season of the amphioxus covers about three months from May to July, and LH-RH content starts to increase in May (66.89 +/- 5.26 ng) and reaches the peak in June (158.57 +/- 3.17 ng), indicating that LH-RH is likely also to be involved in the reproductive activity of the chordate. This finding is of significance in understanding the evolutionary process of the reproductive endocrine in the vertebrate.

Animals↗
PubMed1990

Pulmonary artery involvement in aorto-arteritis. An analysis of DSA.

Angiographic features of the pulmonary artery were studied in 24 patients with aortoarteritis (Takayasu's arteritis) by digital subtraction angiography. The pulmonary artery involvement was found in nine cases (37.5%). The right side was involved in eight and the left side in five cases. The right pulmonary artery was involved in two cases, the lobar artery in six, the segmental artery in six, and subsegmental as well as peripheral branches in four. The angiographic features were stenosis and/or occlusion as were the changes of the systemic arteries in aorto-arteritis. The aorta and its main branches were involved in all nine patients, but the severity of pulmonary vascular changes was not always related to the systemic vascular changes. Bronchial angiography demonstrated enlarged and tortuous bronchial arteries in four cases. Lung ECT revealed abnormalities in four cases.

Adolescent↗
PubMed1990

[Determination of two major metabolites of A-OT-Fu in mice serum by 4th order derivative UV spectrophotometry].

A 4th order derivative UV spectrophotometric method was developed for the determination of two major metabolites (TFu and 5-Fu) of A-OT-Fu in mice serum following per os of 290 mg/kg of the drug. TFu and 5-Fu were extracted from mice serum by ethyl acetate. The amplitudes of 252 and 289 nm for axle are linear with concentration of TFu and 5-Fu within the range of 5-50 micrograms/ml. Under the given experimental condition the recovery of TFu and 5-Fu were over 95%. The maximum concentration of TFu and 5-Fu appeared at 1 h and 2 h respectively after administration.

Animals↗
PubMed1990

[A simple method for predicting equality of absorption and elimination rate constants].

A new method is proposed by which one can predict whether absorption rate constant (Ka) and elimination rate constant (Ke) are equal in the one-compartment open model with first-order processes. The method used only blood drug concentration-time data in the terminal segment of concentration versus time curve is described as follows. We defined Ai as Ai = 2/(tn + 1 + tn) + ln(cn/cn + 1)/(tn + 1 - tn) (i = 1,2,3,...) where n is the number of sampling sequence, cn and cn + 1, tn and tn + 1 are any two consecutive blood drug concentration (c)-time (t) data in the terminal segment of c-t curve, respectively. If Ai was equal or approximate, Ka and Ke might be equal or approach each other. In addition, both Ka and Ke were equivalent to the arithmetic mean of Ai. If Ai was reduced gradually while (tn + 1 + tn)/2 was increased, Ka might not be equal to Ke.

Absorption↗
PubMed1989

[Pharmacodynamics of dihydroartemisinine against Plasmodium berghei in mice].

Dihydroartemisinine (DHA) is a derivative of qinghaosu(artemisine), which is an antimalarial drug. DHA was given to mice inoculated with Plasmodium berhgei ANKA strain by intramuscular injection. Within proper dose range, the dose-effect and time-effect curves of DHA against the malaria can be described by y = 4.9960 + 2.9536 x and y = 7.2654 - 0.3414 t, respectively, where y is the estimated value of parasitemia suppressing rate in probit; x is log dose; t is the period since drug administration im. Accordingly, the ED50 = 1.00 +/- 0.13 mg/kg and the time of half-effect was 6.6 h, when the dose was 5.0 mg/kg im. The elimination rate constant of the effective dose in vivo was 0.2662h-1 with a half-life of 2.6 h.

Animals↗