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Biomedical subjects

M Shao

Publications and source records attributed to M Shao.

17 recordsLinked to original sources
PubMed1999

Enhancement of GABA-activated current by muscarine in rat dorsal root ganglion neurons.

The modulation of GABA-gated ion channel responses to GABA, pentobarbital and diazepam by muscarine was studied in freshly isolated rat dorsal root ganglion neurons using a whole-cell patch-clamp technique. Muscarine enhanced current activated by 5 microM GABA dose-dependently with an EC50 of 40 +/- 2 microM. This potentiation was not blocked by pirenzepine, gallamine and atropine, the specific and non-specific muscarinic receptor antagonists. Muscarine shifted the GABA dose-response curve to the left, with the GABA EC50 decreased from 45 +/- 2 to 13 +/- 2 microM. The maximal response to GABA was suppressed to 89.3 +/- 4.6% as compared with the control (100%) by 80 microM muscarine. Muscarine potentiated GABA (1-100 microM)-activated current in a voltage-independent manner. Muscarine shifted the dose-response curve for pentobarbital enhancement of GABA-activated current to the left, and the enhancement of GABA-activated current by muscarine was additive to that of pentobarbital over all pentobarbital concentrations. Muscarine shifted the dose-response curve for diazepam (1-100 nM) enhancement of GABA-activated current to the left. However, muscarine attenuated the facilitatory effect of saturating concentrations of diazepam (> 100 nM). The potentiating effect of muscarine was blocked by 1 nM ethyl-beta-carboline-3-carboxylate, the inverse agonist of benzodiazepine receptors. These results suggest that GABA-gated ion channel responses to GABA and pentobarbital were potentiated by muscarine and the binding site(s) for muscarine might be related to those for diazepam.

Acetylcholine↗
PubMed1998

[Association between the debrisoquine hydroxylase gene polymorphism and the genetic susceptibility of Parkinson's disease].

OBJECTIVE: To clarify the relation of the debrisoquine hydroxylase gene polymorphism with the genetic susceptibility of Parkinson's disease. METHODS: The debrisoquine hydroxylase gene polymorphisms were analyzed with the polymerase chain reaction-restriction fragment length polymorphism methods in 100 cases of Parkinson's disease and 100 age-,sex-matched normal controls. RESULTS: It was found that the frequencies of A and B mutation of debrisoquine hydroxylase gene in group of patients were higher than those in the controls, and the risk of suffering Parkinson's disease increased 2 times. In group of the patients, the frequencies of C188-->T, G4268-->C and C2938-->T were also higher than those in the controls. Especially in those with C2938-->T mutation, the risk of suffering the disease increased 2.58 times. CONCLUSION: The result suggested that the defect of the detoxifying enzymes might be a factor contributing to the genetic susceptibility of Parkinson's disease.

Adult↗
PubMed1998

X-ray studies on cross-linked lysozyme crystals in acetonitrile-water mixture.

Tetragonal crystals of hen egg white lysozyme were cross-linked and subjected to X-ray diffraction study in acetonitrile-water media with different acetonitrile concentrations. Crystals in neat acetonitrile did not scatter X-ray well. Structures of crystals in neat water, in 90% and 95% acetonitrile, and crystal back-soaked from acetonitrile to water, were determined to about 2 A resolution. For crystals in both 90% acetonitrile, and crystal back-soaked from acetonitrile to water, were determined to about 2 A resolution. For crystals in both 90% and 95% acetonitrile, only one protein-bond acetonitrile molecule is found in the active site cleft, and its location and binding-protein mode is similar to the C subunit of polysaccharide. The alteration in conformation and hydrogen-bond pattern involving water as solvent causes the reduction of the protein's flexibility in organic media. The back-soaked crystal regained its ordinary three-dimensional structure in water.

Acetonitriles↗
PubMed1998

Determination of the amino acid neurotransmitters in the dorsal root ganglion of the rat by capillary electrophoresis with a laser-induced fluorescence-charge coupled device.

A sensitive, rapid and accurate analysis of the amino acid neurotransmitters in dorsal root ganglion (DRG) of rat was accomplished by capillary electrophoresis with a laser-induced fluorescence-charged coupled device (LIF-CCD) and fluorescein isothiocyanate (FITC) derivatization. Since the CCD is an image detector with a matrix array of photoelements, the photogenerated charge generated from single photoelements was summed up by on-chip charge binning, and used to improve the detection sensitivity. A self-compiled data processing program was used to calculate digitally the summation of the multiwavelength data and transform three-dimensional electropherograms into two-dimensional electropherograms. Use of this program improved the detection sensitivity, the extraction of useful statistical data and the performance of the quantitative analysis. Owing to its excellent detectability and the unique characteristic of its two-dimensional format, which allows to perform analog and digital summation, high detection sensitivity with detection limits ranging from 1.2 to 17.2 nM was obtained for the amino acid neurotransmitters by LIF-CCD. This method was demonstrated to be a powerful tool for analyzing the complex biological samples through quantitative determination of the six amino acid neurotransmitters in the DRG of rat.

Animals↗
PubMed1997

Statistical framework for ultrasonic spectral parameter imaging.

This study examines the statistics of ultrasonic spectral parameter images that are being used to evaluate tissue microstructure in several organs. The parameters are derived from sliding-window spectrum analysis of radiofrequency echo signals. Calibrated spectra are expressed in dB and analyzed with linear regression procedures to compute spectral slope, intercept and midband fit, which is directly related to integrated backscatter. Local values of each parameter are quantitatively depicted in gray-scale cross-sectional images to determine tissue type, response to therapy and physical scatterer properties. In this report, we treat the statistics of each type of parameter image for statistically homogeneous scatterers. Probability density functions are derived for each parameter, and theoretical results are compared with corresponding histograms clinically measured in homogeneous tissue segments in the liver and prostate. Excellent agreement was found between theoretical density functions and data histograms for homogeneous tissue segments. Departures from theory are observed in heterogeneous tissue segments. The results demonstrate how the statistics of each spectral parameter and integrated backscatter are related to system and analysis parameters. These results are now being used to guide the design of system and analysis parameters, to improve assays of tissue heterogeneity and to evaluate the precision of estimating features associated with effective scatterer sizes and concentrations.

Carcinoma↗
PubMed1996

Solid-phase synthesis, metal binding and folding properties of caulimovirus-related 'zinc finger'.

A 17-residue peptide containing the caulimovirus-related "zinc finger' was prepared by solid-phase peptide synthesis. Fluorescence measurements showed that the tryptophan quantum yield was Zn(2+)-dependent, allowing a 1:1 a stoichiometry for the complex to be determined. The structure of the peptide was characterized using circular dichroic spectroscopy, which indicates that the peptide exhibits a random coiled conformation in the absence of zinc but appears to form an ordered structure in the presence of zinc.

Amino Acid Sequence↗
PubMed1994

[Auto-analysis of corneal endothelium with photoelectrical scans and computer].

A quantitative analysis of corneal endothelial cells was made with photoelectrical scans and computer in 67 eyes. No difference was found as regards to the mean cell area and density between the endothelial analysis system and routine square counting. On the other hand, we analyzed corneal endothelial cells between 30 eyes wearing hard contact lens and 30 eyes of age- and sex-matched nonwearing control. The parameters, including cell density individual cell area, area, mean cell area, standard deviation, coefficient of variation of cell size (CV), maximum cell, minimum cell, the ratio of the maximum to minimum cell, and percentage of the hexagoal cells, were automatically displayed. The cell density and mean cell area also showed no significant difference (P > 0.05) between the wearers and nonwearing control, but the CV and the frequency of the hexagonal cells showed significant difference (P < 0.01). The ratio of maximum to minimum cell, the polymegethism and pleomorphism were obviously increased in the wearers. It is highly suggested that computer analysis system is of great value in evaluating corneal endothelial cells.

Adolescent↗
PubMed1991

Experimental study on the corneal endothelium of traumatic cataract.

The cell morphology of corneal endothelium in 84 mice with experimental traumatic cataract was investigated with stained corneal buttons. In the experimental group, the boundaries between adjacent corneal endothelial cells were significantly distorted, some cell boundaries manifested degenerative changes that led to coalescence of the cells. The mean density and mean area of endothelial cells of the controls showed significant difference from those of the experimental group during the 12 weeks of observation. The density of endothelial cells decreased from 3,312 +/- 337/mm2 of the control group to 2,944 +/- 418/mm2 in the group of partially opaque lenses and 2,713 +/- 472/mm2 in the group of totally opaque lenses. Meanwhile, the area of endothelial cells and the coefficient of variation also significantly changed correspondingly, and the degree of damage in the corneal endothelium correlated with the degree of the lens opacity.

Animals↗
PubMed1991

[Survey of fungi and bacterinum of the conjunctival sac in Guangzhou area].

This paper presents the results of fungal culture from healthy conjunctival sac in 178 eyes. The rate of positive culture of the fungi was 25% in farmers, 11.1% in cleaners, and 8.8% in city residents respectively. Culture for aerobic was carried out in the samples from conjunctival sacs of 137 eyes. The rate of positive culture was 71.9% in farmers, 80.6% in cleaners, and 23.2% in city residents respectively. On the other hand, the rate of fungal positive culture was 9.7% and that of aerobic was 30% in the patients managed with steroid eyedrops for more than one month. The aspergillus and penicillium were the most commonly seen species among the isolated fungal strain, whereas the staphylococci and streptococcus pneumonia were the most common among the isolated aerobic. The results run parallel to the fact that the main pathogens of ocular infection seen clinically are fungi and aerobics. The authors emphasize that the conjunctival sac should be disinfected to prevent infections caused by opportunistic pathogens.

Adolescent↗
PubMed1991

[Dynamics of endothelial cells of the peripheral area of cornea].

Clinical corneal buttons of 150 cases were stained with try-pan blue and alizalin red S, so as to compare the relative density of endothelial cells and to analyse the forms of the cell nuclei. The result showed that cell densities of fetal corneal endothelium of 25 cases with fetal period from 19 to 34 weeks, had no significant difference (P > 0.05) between the central and peripheral areas of cornea. However, the cell densities of corneal endothelium of 19 cases, aged from newborn to 53 years, showed a significant difference (p < 0.01). The cell nuclei of the fetal corneal endothelium have elliptic forms mainly, which are similar between central and peripheral area of corneal endothelium. However, the forms show an unstable nucleus morphological structure. From newborn to adult cornea, the nucleus forms of corneal endothelial cells tend to be stable and circular, but there are unstable forms of endothelial cell nuclei dispersed in corneal periphery. This emphasize that the endothelial cells in corneal periphery still keep its cell differential function of development in some degree.

Adolescent↗
PubMed1990

[Clinical effects of magnesium sulfate in the treatment of supraventricular tachyarrhythmia].

The obvious effects of magnesium sulfate are noticed not only in ventricular tachyarrhythmia but also in supraventricular tachyarrhythmia (SVTA) which include paroxysmal supraventricular tachycardia (PSVT), chaotic atrial tachycardia (CAT), atrial fibrillation (AF) with rapid heart rate and nonparoxysmal junctional tachycardia (NPJT). This paper reports the effects of magnesium sulfate treatment in 25 cases of SVTA in a self-controlled before and after study. Among 10 cases of PSVT, 6 cases were treated by injection of 25% magnesium sulfate 5-10 ml. Except 2 cases with W-P-W and aberrant ventricular condition, the PS-VT were terminated immediately after half a dose of magnesium sulfate i.v. in 2 cases, other 2 cases were terminated by 5-10 min after a dose of magnesium sulfate i.v.. Some improvements were observed in these 4 cases. The rest 4 cases were prevented by 12 days' intravenous infusion of 1% magnesium sulfate 250 ml per day, 3 cases of them recovered. Three cases of CAT recovered within an hour to two days by infusion of 1% magnesium sulfate 250 ml. Four cases of AF with rapid heart rate were collected, even though it is difficult to determine whether it is due to overdose or inadequacy of digitalis. The heart rates were reduced by magnesium sulfate injection in those 4 cases. Eight cases of NPJT due to heart failure with digitalis intoxication recovered after infusion of 1% magnesium sulfate 250ml within 10 hours to two days. Finally, the mechanism of the effect of magnesium sulfate treatment in SVTA was discussed.

Adult↗
PubMed1985

Effects of occupational lead exposure.

Fifty-three workers in a battery factory, 52 solderers in a television factory, and 50 embroidery workers (a reference group) were studied. The average air lead levels of the three workplaces were 0.578 mg/m3, 0.002 mg/m3, and 0.001 mg/m3, respectively. Adverse effects in terms of clinical manifestations and biochemical criteria were evident among the battery factory workers. A significant dose-response relationship existed between the toxic effects and the air lead levels. The solderers showed no apparent abnormalities in comparison with the embroidery workers. The early clinical manifestations were dysfunction of the central nervous system, indigestion, arthralgia, and myalgia in the extremities. A positive association was observed between the prevalence of fatigue, mild abdominal pain, and arthralgia and the blood lead (PbB), urinary lead (PbU), and zinc protoporphyrin (ZPP) levels. The symptomatic threshold values of PbB, PbU, and ZPP were 30 micrograms/dl (1.5 mumol/l), 0.045 mg/l (0.2 mumol/l), and 40 micrograms/dl (0.7 mumol/l), respectively. The PbB, PbU, free erythrocyte protoporphyrin, and ZPP levels and the blood aminolevulinic dehydratase ratio could be used as indicators of lead exposure, although ZPP is preferred for a preventive monitoring program. The motor and sensory conduction velocities of the median nerve were slower in the exposed groups than in the reference group. No effects on behavioral function were observed among the solderers.

Central Nervous System Diseases↗
PubMed1984

The role of hepatic biotransformation in mediating the acute toxicity of the phosphorothionate insecticide chlorpyrifos.

The apparent (app) Km and app Vmax for mouse hepatic microsomal oxidative detoxification of chlorpyrifos to 3,5,6-tricholoro-2-pyridinol were 16.10 +/- 6.8 microM and 263.2 +/- 22.5 nmol/liver/min, respectively. The app Km and app Vmax for the oxidative activation of chlorpyrifos to chlorpyrifos oxon were 20.0 +/- 6.5 microM and 126.1 +/- 14.6 nmol/liver/min, respectively, whereas the app Km and app Vmax for hepatic microsomal hydrolysis of chlorpyrifos oxon to 3,5,6-trichloro-2-pyridinol were 1.87 +/- 0.36 mM and 89,450.7 +/- 12,087.3 nmol/liver/min, respectively. Under first-order conditions the capacity of mouse hepatic microsomes to detoxify chlorpyrifos oxon exceeded their capacity to generate this potent cholinesterase inhibitor from chlorpyrifos by a factor of 7.6. Pretreatment of mice with phenobarbital (70 mg/kg daily for 4 days) resulted in a 2.5-fold increase in the app Vmax's for oxidative activation and detoxification of chlorpyrifos, and a 1.6-fold increase in the app Vmax for hydrolysis of chlorpyrifos oxon. The app Km's were not altered by phenobarbital pretreatment. Administration of beta-naphthoflavone (80 mg/kg/daily for 2 days) to mice resulted in a slight decrease in the app Vmax's for oxidative activation and detoxification of chlorpyrifos, without altering the app Km's of the same reactions, or the hydrolysis of chlorpyrifos oxon. Phenobarbital and beta-naphthoflavone increased and decreased, respectively, the predicted hepatic clearance of chlorpyrifos. The acute toxicity of chlorpyrifos was slightly antagonized by phenobarbital pretreatment, but was potentiated by beta-naphthoflavone administration. These pretreatments did not affect cholinesterase, nonspecific esterase, or plasma A-esterase activities. Collectively, these results suggest that chlorpyrifos oxon formed within the liver does not escape hydrolysis by the liver, and that extrahepatic sites of activation are important in directly mediating the acute toxicity of chlorpyrifos.

Animals↗
PubMed1984

Chronic administration of an organophosphorus insecticide to rats alters cholinergic muscarinic receptors in the pancreas.

Male rats were treated for 10 days with the organophosphorus insecticide, acetylcholinesterase inhibitor, O,O-diethyl S-[2-(ethylthio)ethyl] phosphorodithioate (disulfoton, 2 mg/kg/day by gavage). At the end of the treatment, binding of [3H]quinuclidinyl benzilate ( [3H]QNB) to cholinergic muscarinic receptors and cholinesterase (ChE) activity were assayed in the pancreas. Functional activity of pancreatic muscarinic receptor was investigated by determining carbachol-stimulated secretion of alpha-amylase in vitro. ChE activity and [3H]QNB binding were significantly decreased in the pancreas from disulfoton-treated rats. The alteration of [3H]QNB binding was due to a decrease in muscarinic receptor density with no change in the affinity. Basal secretion of amylase from pancreas in vitro was not altered, but carbachol-stimulated secretion was decreased. The effect appeared to be specific since pancreozymin was able to induce the same amylase release from pancreases of control and treated rats. The results suggest that repeated exposures to sublethal doses of an organophosphorus insecticide lead to a biochemical and functional alteration of cholinergic muscarinic receptors in the pancreas.

Animals↗
PubMed1984

The interaction of the phosphorothioate insecticides chlorpyrifos and parathion and their oxygen analogues with bovine serum albumin.

The distribution and subsequent toxicity of hazardous chemicals can be influenced by their interactions with plasma proteins. In the present study reversible binding of the phosphorothioate insecticides chlorpyrifos and parathion to fatty acid-free bovine serum albumin (BSA) was examined using the technique of equilibrium dialysis. Computer analyses of the binding data revealed that chlorpyrifos and parathion each bound reversibly to a single class of binding sites on BSA, with apparent KD values of 3.4 +/- 0.1 and 11.1 +/- 0.3 microM, respectively. Additionally, the maximal number of binding sites for each insecticide per molecule of BSA was one. Displacement studies using both chlorpyrifos and parathion indicated that each was a competitive inhibitor of the other's binding, suggesting that they were bound to the same site. Incubation of chlorpyrifos oxon or paraoxon with a 1% solution of BSA resulted in limited, EDTA-insensitive formation of 3,5,6-trichloro-2-pyridinol or p-nitrophenol, respectively. Pretreatment of BSA with 5 mM paraoxon, chlorpyrifos oxon, or 1 mM diisopropylfluorophosphate did not alter this activity, suggesting that these reactions resulted from an esterase-like capacity of BSA, and not from phosphorylation of BSA by these oxons.

Animals↗