Biomedical subjects

M Y Li

Publications and source records attributed to M Y Li.

At least 37 records · Page 2Linked to original sources

PubMed1997

Effect of quinine on autoreceptor-regulated serotonin release in the rat hippocampus.

The involvement of K+ channels in the autoregulation of terminal serotonin (5-hydroxytryptamine, 5-HT) release was investigated by microdialysis in the hippocampus of conscious rats. Extracellular 5-HT was increased concentration-dependently by the K+ channel blocker quinine (10, 100 and 1000 microM in perfusate), and tetrodotoxin (10 microM) but not fluoxetine (5 microM) exerted a partially attenuating influence. The 5-HT1/2/6 receptor antagonist methiothepin (50 microM) increased dialysate 5-HT, most likely through 5-HT1B autoreceptors tonically activated in the hippocampus of awake rats as opposed to the previously reported lack of effect 5-HT1B autoreceptor blockade in anesthetized rats. The effect of methiothepin was greatly reduced by preperfusion with quinine (100 microM), consonant with a role for quinine-sensitive K+ channels in the autoregulation of 5-HT release in the hippocampus by 5-HT receptor antagonism. In contrast, the reduction in dialysate 5-HT induced by the 5-HT1 receptor agonist RU 24969 (1 microM), in the presence of fluoxetine (5 microM), persisted in the co-presence of quinine, consonant with the involvement of (extrasynaptic?) 5-HT autoreceptors not coupled with quinine-sensitive K+ channels.

Animals↗

PubMed1997

Carbamazepine increases extracellular serotonin concentration: lack of antagonism by tetrodotoxin or zero Ca2+.

Carbamazepine administration causes large increases in extracellular serotonin concentration and dose-related anticonvulsant effects in genetically epilepsy-prone rats (GEPRs). In order to determine the generality of the effect on serotonin, we determined the anticonvulsant ED50 for carbamazepine against maximal electroshock seizures in outbred, non-epileptic Sprague-Dawley rats. We then administered anticonvulsant carbamazepine doses to Sprague-Dawley rats and observed extracellular serotonin concentration in hippocampi by way of microdialysis. We found that administration of carbamazepine, either systemically or through the dialysis probe, resulted in significant and dose-related increases in extracellular serotonin concentration. Basal serotonin release was decreased by tetrodotoxin administration through the dialysis probe. Tetrodotoxin administration through the dialysis probe did not decrease the effect of systemically or focally administered carbamazepine on extracellular serotonin concentration. Similarly, elimination of Ca2+ from the dialysate did not alter the release of serotonin caused by carbamazepine. These findings suggest that the serotonin releasing effect of carbamazepine does not take place by exocytosis and does not require action potentials in the brain area in which the release takes place. Further they suggest that the effect is mediated by an action of carbamazepine directly on serotonergic nerve terminals.

Animals↗

PubMed1997

Anticonvulsant doses of carbamazepine increase hippocampal extracellular serotonin in genetically epilepsy-prone rats: dose response relationships.

The antiepileptic drug carbamazepine produces dose related anticonvulsant effects in genetically epilepsy-prone rats (GEPRs) and most other animal seizure models. Carbamazepine releases serotonin as part of the pharmacodynamic action by which it suppresses convulsions in GEPRs and it releases serotonin in non-epileptic Sprague-Dawley rats. The two strains which make up the GEPR seizure model (moderate seizure GEPR-3s and severe seizure GEPR-9s) experience anticonvulsant effects in response to different doses of carbamazepine (GEPR-3 ED50 = 25 mg/kg; GEPR-9 ED50 = 3 mg/kg). The present study determined that carbamazepine produces a dose related increase in extracellular serotonin in each of the two GEPR strains. The doses of carbamazepine required to increase extracellular serotonin are similar to the doses required for an anticonvulsant effect in each of the strains. This result provides further support for the hypothesis that release of serotonin by carbamazepine is an important part of the pharmacodynamic action by which this drug suppresses seizures.

Analysis of Variance↗

PubMed1997

Extracellular dopamine, norepinephrine, and serotonin in the ventral tegmental area and nucleus accumbens of freely moving rats during intracerebral dialysis following systemic administration of cocaine and other uptake blockers.

Extracellular levels of dopamine (DA), serotonin (5-HT), and norepinephrine (NE) were measured by microdialysis in conscious rats equipped with dual probes, one in the ventral tegmental area (VTA) and another one in the contralateral nucleus accumbens (NACC). Dialysate content of all amines in both regions was essentially abolished by local infusion of tetrodotoxin (1 microM) or Ca2+-free buffer. Injection of the selective DA uptake blocker GBR 12935 (15 mg/kg i.p.) increased DA, as well as NE and, to a lesser extent, 5-HT in the VTA; it increased DA more than 5-HT in the NACC. The selective NE uptake blocker desipramine (10 mg/kg i.p.) increased NE but also 5-HT in the VTA and NACC; the DA level was persistently enhanced in the VTA, whereas in the NACC it initially rose and then fell below baseline value. The selective 5-HT uptake blocker citalopram (15 mg/kg i.p.) was generally more effective in elevating dialysate level of 5-HT than that of other amines in both regions. Cocaine (20 mg/kg i.p.) was non-selective in enhancing all three amines in both regions. There is considerable crosstalk between monoamine systems occurring upon systemic administration of uptake blockers, and the VTA and NACC are notably different in the time course of the DA effect (long-lasting versus transient).

Animals↗

PubMed1997

[The sterilization effect of formaldehyde fumigating on the catheter place vertically].

UNLABELLED: The aim of this paper is to investigate the effect of formaldehyde fumigating on the sterilization of catheters with different diameters and placed in different positions. The lumen of cleaned catheters with different diameters was filled with a solution of live bacilli coil. The catheters were then dried by a drier and divided into 3 groups for formaldehyde fumigating sterilization. A segment of 5 cm of the middle section of the sterilized catheters was cut and incubated at 36 degrees C for 48 h with bouillon medium. For those segments with positive culture, bacteriologic identification was done. RESULTS: Group A, U = 6.85 and P < 0.01; Group B, chi 2 = 8 and P < 0.01; Group C, chi 2 = 13, P < 0.01. CONCLUSIONS: in the same conditions, fumigating in vertical direction is better than fumigation in horizontal direction and save time; in the same conditions, the positive culture rate is inversely related to the diameter of the catheters; for catheter with a diameter greater than 0.75 cm, fumigating vertically for 2 h is enough to obtain satisfactory sterilization effects.

Catheters, Indwelling↗

PubMed1997

[Effect of intrathecal or intracerebroventricular administrition of OFQ on pain threshold and acpuncture analgesia in rats].

Orphanin FQ (OFQ) is a newly discovered 17-amino-acid peptide capable of inducing hyperalgesia. In the present study, the effects of OFQ on basal pain threshold and acupuncture anlgesia (AA) in rats were observed using the tail-flick test. It was found that intrathecal (i.t.) or intracerebroventricular (i.c.v.) administrition of 0.1 microgram OFQ had no effect on basal pain threshold of rats, while 1 microgram OFQ could lower the threshold. However, OFQ at both the doses (0.1 or 1.0 microgram) administered by either i.t. or i.c.v. injection could antagonize AA with that occuring in the brain being more prominent then in the spinal cord. When the rats were repeatedly treated with antisense oligonucleotide to block synthesis of OFQ receptor, pain threshold increased significantly. At such instance, when the OFQ was combined with acupuncture, the effect of AA showed no obvious change. The above results show that the OFQ at small dose has no effect on pain threshold but can lower it at larger dose; while in both cases OFQ can antagonize AA.

Acupuncture Analgesia↗

PubMed1996

Extracellular dopamine, norepinephrine, and serotonin in the nucleus accumbens of freely moving rats during intracerebral dialysis with cocaine and other monoamine uptake blockers.

Monoamine-uptake blockers were applied focally (0.1-1,000 microM) through a dialysis probe in the nucleus accumbens of freely moving rats, and the extracellular concentrations of dopamine, norepinephrine, and serotonin were measured. The selective dopamine-uptake blocker GBR 12935 increased dopamine preferentially with only a small effect on norepinephrine, whereas the selective serotonin-uptake blocker fluoxetine increased serotonin output preferentially. In contrast, the selective norepinephrine-uptake blockers desipramine and nisoxetine enhanced not only norepinephrine, but also serotonin and dopamine appreciably. Cocaine increased all three amines with the greatest effects on dopamine and serotonin. As in our previous study on the ventral tegmental area, there was a positive association between dopamine and norepinephrine output when all blocker data were taken together. The present results suggest a contribution of the increase in norepinephrine, but not serotonin, to the enhancement of dopamine after cocaine applied focally in the nucleus accumbens.

Animals↗

PubMed1996

[Influence of green tea polyphenols varnish on saliva]

This study observed the inhibitory effect of green tea polyphenols varnish on the activity of humman saliva.We found 0.78 and 1.56mg/ml green tea polyphenols varnish is the best.We also observed the release of green tea polyphenols from liquid varnish is more than that from membraniform vanish.The release quantities of green tea polyphenols from membraniform is limited,suggest the influence of green tea polyphenols varnish on the activity of human saliva is small.

Journal Article↗

PubMed1996

[Air analysis of the doctor and nurse offices in tall hospital buildings].

O2, PO2, CO2, total number of bacteria were detected in doctor-nurse offices which are at the same side on the 6 and 7th floor in the first affiliated hospital of China Medical University. The results showed that the detected O2 and PO2 in doctor-nurse office were conformed to the normal range of country's indoor standard. The average value of bacteria detection was above the standard Which is less than 500/m3 in ordinary ward given by the Ministry of Health of China. The average CO2 detection was below 0.07%, but sometimes above 0.07% during the 8:30 detection in the morning, total number of bacteria was a little higher too, which suggested that more attention are needed.

Air Microbiology↗

PubMed1995

Global stability for the SEIR model in epidemiology.

The SEIR model with nonlinear incidence rates in epidemiology is studied. Global stability of the endemic equilibrium is proved using a general criterion for the orbital stability of periodic orbits associated with higher-dimensional nonlinear autonomous systems as well as the theory of competitive systems of differential equations.

Epidemiology↗

PubMed1995

Centromere spreading and centromeric aberrations in ovarian tumors.

Centromere spreading (CS) of chromosomes and high occurrence of aberrations at centromeric region were observed in two papillary serous cystadenocarcinomas and one borderline papillary serous cystadenoma of the ovary. In the borderline tumor, CS of chromosome 12, trisomy of which had been reported as the sole abnomaly in benign ovarian tumors, was seen in three metaphases. It is suggested that CS may be an early event in the carcinogenesis of epithelial ovarian tumors. Centromeres of some chromosomes in tumor cells may be unstable and thus bring about premature centromere separations and breakages at centromeric regions, followed by some numerical and structural chromosomal aberrations.

Centromere↗

PubMed1995

[Central mechanism of inhibitory effect of histamine H1-receptor agonists PEA on gastric acid secretion].

The present experiment is undertaken to study the central mechanism of the inhibitory effect of 2-pyridylethylamine (PEA, i.c.v.) on the gastric acid secretion. Gastric acid was continuously washed out with 37 degrees C saline by means of a perfusion pump in male adrenalectomized wistar rats. Drugs were injected into the third ventricle to examine the effect on pentagastrin-induced (160 micrograms/kg, s.c.) gastric acid secretion. The results were as follows: (1) Pretreatment with CRF-antiserum (2.5 microliters, 1:20,000, i.c.v.) blocked the inhibitory effect of PEA (10 micrograms, i.c.v.) on gastric acid secretion. (2) Administration of CRF (1 and 2 micrograms, i.c.v.) or beta-endorphin (0.94 and 1.25 micrograms, i.c.v.) markedly inhibited the gastric acid secretion. (3) Pretreatment with naloxone (5 micrograms, i.c.v.) blocked the inhibitory effect of CRF (1 microgram, i.c.v.), but the inhibitory effect of beta-endorphin (0.94 microgram, i.c.v.) was not changed by pretreatment with CRF-antiserum (1:20,000, 2.5 microliters, i.c.v.). These results suggest that PEA stimulates the release of hypothalamic CRF which stimulates the release of hypothalamic endogenous opioid peptides. The peptides again induces vagus nerve-mediated inhibitory effect on gastric acid sceretion.

Adrenalectomy↗

PubMed1995

[Effects of morphine on monosodium glutamate neurotoxicity and its mechanism].

The enhancing effects of morphine on monosodium glutamate (MSG) neurotoxicity and its blocking by naloxone were studied through morphological observation, together with detection of concentrations of intracellular free Ca2+ ([Ca2+]i) by Ca2+ indicator Fura-2/AM and lactate dehydrogenase (LDH) efflux in the bathing medium in primary cultures from 14-17 d old mouse fetal cortex. It was found that 10 min pre-incubation of young cortical neurons (7 day in vitro) with morphine 10(-7) or 10(-6) mol.L-1 substantially increased LDH release from 105.7% +/- 19.0% (treated with MSG alone) to 194.5% +/- 17.7% and 214.0% +/- 9.5% respectively after exposure to MSG 0.1 mmol.L-1, but pre-incubation with morphine (10(-7) or 10(-6) mol.L-1) plus naloxone (0.1 mmol.L-1) reversed the LDH release after treatment with the same concentration of MSG. Morphine (10(-7) or 10(-6) mol.L-1) produced little elevation of [Ca2+]i. However, when combined with MSG (0.1 mmol.L-1) morphine elevated the [Ca2+]i level much more than MSG alone. These results suggest that morphine markedly enhances excitotoxic neuron damage, which can be reversed by naloxone. Overloading of intracellular Ca2+ may be a simultaneous pathological mechanism underlying the neuronal damage and death that occur in excitatory toxicity.

Animals↗

PubMed1994

The effect of calcitonin gene-related peptide on ischemic reperfusion-induced arrhythmias in rats.

Thirty-six wistar rats (150-250 g body weight) were randomly divided into two groups. There were equal numbers of male and female rats in each group. Each group of rats was given either 0.5 ml normal saline or calcitonin gene-related peptide (CGRP, 20 micrograms/kg dissolved in 0.5 ml normal saline) intravenously within 5 min. Coronary arteries of these rats were occluded 5 min after administration. The coronary artery was then released from ligation 5 min later. The heart beat of all rats was monitored for 30 min. An electrocardiogram was recorded using limb leads and below-xiphoid leads. There was no ischemic reperfusion-induced arrhythmia in the first minute of reperfusion in CGRP group, while 13 rats occurred ischemic reperfusion-induced arrhythmia (ventricular tachycardia and fibrillation) in the normal saline group (P < 0.05). Average onset time of ischemic reperfusion-induced arrhythmia was 377.5 +/- 141.0 s/sim. In the CGRP group, compared with 42.7 +/- 55.4 s/sim. for the normal saline group (P < 0.01). The duration of ischemic reperfusion-induced arrhythmia was 15.0 +/- 30.6 s/sim. In the CGRP group compared with 104.4 +/- 143.8 s/sim. in the normal group (P < 0.05). There was no death in the CGRP group, but six rats in the normal saline group died (P < 0.05). The results showed that CGRP could reduce and delay the occurrence of ischemic reperfusion-induced arrhythmia such as ventricular tachycardia and fibrillation, especially in the early period, and decrease the mortality. The mechanism is not clear and needs to be studied further.

Animals↗

PubMed1994

Flow dependence of metoprolol elimination in isolated perfused rat liver.

The effect of blood flow rates on hepatic elimination of metoprolol (Met) was studied in a recirculating isolated perfused rat liver system with a constant infusion of Met into the reservoir. This design ensures that, at a steady state, the elimination rate of Met is a constant. The results showed that at flow rates of 10, 20, and 30 ml.min-1, the concentrations of Met entering the liver (Cin) were 7.6, 5.0, and 3.4 micrograms.ml-1 and the concentrations leaving the liver (Cout) were 1.2, 2.0, and 2.7 micrograms.ml-1, while the logarithmic average concentrations in hepatocytes (C) were 3.4, 3.2, and 3.0 micrograms.ml-1, respectively. It is concluded that the hepatic elimination of Met is flow-dependent, which is in accordance with the 'parallel tube' model.

Animals↗

PubMed1994

[A study on the structure of human lamina cribrosa sclerae].

The lamina cribrosa of 15 normal adult human eyes were observed by scanning electron microscopy and their images were analyzed by a computerized system to study the distribution of pores and the proportion of connective tissue in different regions of the lamina cribrosa. The results revealed that there are significantly more large pores (> or = 3,000 microns2) in the superior and inferior than those in the nasal and temporal quadrants, especially in the peripheral regions, however, in terms of area the percentages of connective tissue in the nasal and temporal quadrants are the highest. In addition, the histological study of the lamina cribrosa disclosed that the collagenous fibers, various in calibre, are arranged in bundles and tangentially around each pore. Since the nerve fiber damage in glaucoma initially occurs at the superior and inferior parts of the optic nerve, the above anatomical characteristics possibly can explain the cause of the visual field defects in early glaucoma.

Adult↗

PubMed1994

[A report of the quantitative determination of relative afferent pupillary defect in central retinal vein occlusion].

Relative afferent pupillary defect (RAPD) indicates injury to the afferent pupillary nerve fibers anterior to the optic chiasma. The light attenuator composed of 2 optical polarizers was utilized to determine the RAPD quantitatively in 32 cases of central retinal vein occlusion (CRVO). In 13 cases with ischemic CRVO, 77% manifested an RAPD of 0.9 log unit or over and none less than 0.75 log unit. In contrast, among 19 cases with non-ischemic CRVO, 84% showed an RAPD of 0.65 log unit or less and none over 0.75 log unit, suggesting that RAPD was a sensitive index for differentiating ischemic from non-ischemic CRVO.

Humans↗

PubMed1993

[Purification and characterization of lipoteichoic acid from Streptococcus Sobronus]

Lipoteichoic acid (LTA) is amphipathic molecule found in cell surface of gram-positive bacteria.Although there were some hypothese about adhesion of LTA,the role of LTA in bacterial pathogenicety is still unclear.For this reason,a seria studies of LTA were carried out.In this study LTA was extracted by hot aqueous phenol from Strptococcus Sobronus 6715 grown in tryptic soy both supplemented with 5% sucrose for 17 hours,and was purfied on gel filtration by Sepharose 6B,chloroform-methanol precipitation and chromtography on DEAE-Sephacel.The purified LTA was characterized by FT-IR and 1H-NMR with standard sample of LTA (Sigma Co) as control.The results showed that LTA contains alanine ester and glycosyl residues which take important role in the amphipathic molecule.

Journal Article↗