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Biomedical subjects

L Peng

Publications and source records attributed to L Peng.

At least 109 records · Page 6Linked to original sources
PubMed1997

[Determination of amino acid contents in cotton-seed-cake powder].

In this work, the contents of amino acids in three kinds of cotton-seed-cake powder from domestic and abroad were determined by using Waters Automatic Amino Acid Analyzer with post-column derivatization and fluorescence detection. The operating conditions were cation exchange resin column, 250 mm x 4.6 mm i.d., gradient elution, detection wavelength lambda(ex) = 338 nm and lambda(em) = 425 nm. The results showed that contents of amino acids from both domestic cotton seed cakes were less than those from abroad.

Amino Acids↗
PubMed1997

Intraocular pressure in inbred mouse strains.

PURPOSE: To develop a protocol to measure the intraocular pressure (IOP) of living mice and to determine the IOP of genetically different mouse strains. METHODS: Eyes of anesthetized animals were cannulated with a very fine fluid-filled glass microneedle. The microneedle was connected to a pressure transducer, and the pressure signal was analyzed with a computer system. Intraocular pressures of male C3H/He iota, C57BL/ 6 iota, A/iota, and BALB/c iota mice were determined. RESULTS: Differences in IOP were detected between genetically distinct mouse strains maintained in virtually identical environments. C3H/He iota was the strain with the highest average IOP (13.7 +/- 0.8 mm Hg). This strain average was 1.4 mm Hg higher than that for C57BL/6 iota (12.3 +/- 0.5 mm Hg; P = 0.14), 4.3 mm Hg higher than that for A/iota (9.4 +/- 0.5 mm Hg; P < 0.001), and 6 mm Hg higher than that for BALB/c iota (7.7 +/- 0.5 mm Hg; P < 0.001). CONCLUSIONS: The authors have developed an accurate and reliable procedure for measuring intraocular pressure in living mice. This procedure can detect IOP differences between groups of mice that differ by genotype.

Animals↗
PubMed1997

Angiotensin-converting enzyme gene and atherosclerosis.

Common variants of the angiotensin-converting enzyme (ACE) gene (ACE ie humans, Ace in mice) associated with changes in circulating ACE activities have been suggested to confer differential risks for atherosclerosis. Using a mouse model of atherosclerosis induced by heterozygosity for apolipoprotein E gene disruption and an atherogenic diet, we have studied the impact on atherogenesis of a mutation that changes the level of function of Ace. We find that this genetically determined change does not influence the size or complexity of atherosclerotic lesions. Ace genotype was not a significant determinant of lesion size in female (+/+ = 12.9 +/- 1.5 and +/- = 11.7 +/- 1.6 microns2 x 10(4)) or male (+/+ = 0.95 +/- 0.25 and +/- = 1.83 +/- 0.59 microns2 x 10(4)) mice; however, lesions were significantly larger (P < .001) in female than male mice. Ace genotype also did not affect lesion complexity; however, lesions in females showed significantly increased frequency of cholesterol clefts, acellular cores, fibrous caps, and calcifications compared with those in males. The hypothesis that genetic variation in the level of ACE gene expression affects the development of atherosclerosis is not supported by these findings.

Animals↗
PubMed1997

A novel method for quantitative analysis of apoptosis.

In the present study, we describe a method of quantifying DNA fragmentation. This assay is based on saturation labeling 3'-ends of DNA fragments with alpha(32)PdCTP in the presence of 2',3'-dideoxy-cytidine-5'-triphosphate (ddCTP) by terminal deoxynucleotidyl transferase (TdT). The saturation labeling of 3'-ends of DNA fragments was performed by adding different concentrations of alpha(32)PdCTP to a DNA sample, from which a maximal labeling (Lmax) and a kinetic parameter (Km) of the TdT reaction are calculated. The saturated labeling gives true quantitation that makes it possible to accurately compare quantities of DNA fragments among different samples. This method requires as little as 5 ng of DNA and increases the sensitivity of apoptotic DNA detection by at least 200-fold relative to the widely used ethidium staining method. The application of this method in an apoptosis study showed that (a) a time- and dose-dependent increase in the number of DNA strand breaks in apoptotic lymphocytes was induced by dexamethasone, and (b) age-dependent apoptosis occurred in the cardiac tissues of spontaneously hypertensive rats. Results of this assay were confirmed by the DNA ladder pattern exhibited after electrophoresis as well as the morphologic changes of apoptosis observed under electron microscopy and were very consistent with results obtained in quantifying apoptotic cells by flow cytometric analysis (r = 0.98, p = 0.002). Thus, this assay is quantitative, simple, sensitive, and useful for assessing apoptosis.

Animals↗
PubMed1997

[Packing drainage of transmastoid approach for treatment of otogenic brain abscess: a report of 30 cases].

Thirty cases of patients with otogenic brain abscess (OBA) who received mastoid radical operations were treated simultaneously by means of packing drainage via the appoach of the mastoid operative cavity. 26 cases of those were cured. The results showed that the therapeutical method gave satisfactory effectiveness and had many advantages. It provided an effective montitor for retraction and had many vomica, and gave ample drainage for retraction in that it made OBA seldom recur. The operative procedure is fit for the great majority of OBA. The paper also discussed intraoperative and postoperative complications and other problems pertinent to the operation.

Adolescent↗
PubMed1996

Biochemical evaluation of photolabile precursors of choline and of carbamylcholine for potential time-resolved crystallographic studies on cholinesterases.

Acetylcholinesterase and butyrylcholinesterase both rapidly hydrolyze the neurotransmitter acetylcholine. The unusual three-dimensional structure of acetylcholinesterase, in which the active site is located at the bottom of a deep and narrow gorge, raises cogent questions concerning traffic of the substrate, acetylcholine, and the products, choline and acetate, to and from the active site. Time-resolved crystallography offers a promising experimental approach to investigate this issue but requires a suitable triggering mechanism to ensure efficient and synchronized initiation of the dynamic process being monitored. Here we characterize the properties of two photolabile triggers which may serve as tools in time-resolved crystallographic studies of the cholinesterases. These compounds are 2-nitrobenzyl derivatives of choline and of carbamylcholine, which generate choline and carbamylcholine, respectively, upon photochemical fragmentation. Both photolabile compounds are reversible inhibitors, which bind at the active sites of acetylcholinesterase and butyrylcholinesterase with inhibition constants in the micromolar range, and both photofragmentation processes occur rapidly and with a high quantum yield, without substantial photochemical damage to the enzymes. Photolysis both of acetylcholinesterase and of butyrylcholinesterase, complexed with a 2-nitrobenzyl derivative of choline, resulted in regeneration of enzymic activity. Photolysis of acetylcholinesterase complexed with the 2-nitrobenzyl derivative of carbamylcholine led to time-dependent inactivation, resulting from carbamylation of acetylcholinesterase, which could be reversed upon dilution, due to decarbamylation. Both sets of experiments demonstrated release of choline within the active site. In the former case, choline was produced photochemically at the active site. In the latter case, choline was generated enzymatically, within the active site, concomitantly with carbamylation of the acetylcholinesterase. The two photolabile compounds may thus serve as complementary probes for time-resolved studies of the route of product release from the active sites of the cholinesterases.

Acetylcholinesterase↗
PubMed1996

Immunohistochemical analysis of growth factor expression and localization in gastric coronary vein of cirrhotic patients.

This study was designed to investigate the expression and localization of PDGF, bFGF, EGF, and TGF alpha in gastric coronary vein of cirrhotic (n = 30) and non-cirrhotic patients (n = 10) using immunohistochemical technique. The strongly positive immunostaining rate were 93%, 89%, 70% and 68% respectively in cirrhotic patients. The immunostaining was negative in non-cirrhotic patients. The damage to endothelium, hypertrophy and hyperplasia of vascular smooth muscle cells and vascular remodeling were seen in gastric coronary vein of cirrhotic patients. These results suggested that gastric coronary vein could produce growth factor during cirrhosis, the growth factor can act on the vascular function and/or structure via autocrine-paracrine mechanism.

Adult↗
PubMed1996

Astrocyte-neuron interaction during one-trial aversive learning in the neonate chick.

During two specific stages of the Gibbs-Ng model of one-trial aversive learning in the neonate chick, we have recently found unequivocal evidence for a crucial involvement of astrocytes. This evidence is metabolic (utilization of the astrocyte-specific energy store, glycogen, during normal learning and inhibition of memory formation by the astrocyte specific metabolic inhibitors, fluoroacetate and methionine sulfoximine) as well as physiological (abolition of memory formation in the presence of ethacrynic acid, an astrocyte-specific inhibitor of cellular reaccumulation of potassium ions). These findings are discussed in the present review in the framework of a more comprehensive description of metabolic and physiological neuronal-astrocytic interactions across an interstitial (extracellular) space bounded by minute processes from either cell type.

Animals↗
PubMed1996

Development and validation of an LC-MS-MS method for the determination of terfenadine in human plasma.

A sensitive LC-MS-MS method capable of quantifying terfenadine at levels down to 100 pg ml-1 in human plasma is reported. The method was validated over a linear range from 0.1 to 5.0 ng ml-1 using a liquid-liquid extraction with a deuterium-labelled internal standard. The between-run precision and accuracy of the calibration standards were 2.6-6.0% RSD and -2.0 to +2.2% relative error (RE). The between-run and within-run precision and accuracy of quality control samples (0.3, 1.5 and 3.5 ng ml-1) were 1.0-5.9% RSD and +1.7 to +6.3% RE. This method was applied to the analysis of human plasma samples.

Chromatography, Liquid↗
PubMed1996

Blood pressure and fluid-electrolyte balance in mice with reduced or absent ANP.

Atrial natriuretic peptide (ANP)-gene knockout mice of three genotypes (+/+, +/-, and -/-) were maintained on a low-salt diet (0.008% NaCl). They were then fed either the same low-salt diet or a high-salt diet (8% NaCl) for 1 wk. No differences were found among genotypes in daily food and water intakes or in urinary volume and electrolyte excretions. Arterial blood pressures measured in anesthetized animals at the end of the dietary regimen were significantly and similarly increased in -/- compared with +/+ mice on each diet. Renal excretion of fluid and electrolytes was measured in anesthetized mice before and after acute blood volume expansion. No genotype differences were observed before volume expansion. After volume expansion the wild-type (+/+) mice had much greater saluretic responses than either the heterozygous (+/-) or the homozygous mutant (-/-) animals on the low-salt diet but not on the high-salt diet. We conclude that ANP lowers blood pressure in the absence of detected changes in renal function; ANP is not essential for normal salt balance, even on high-salt intake; and ANP is essential for the natriuretic response to acute blood volume expansion on a low-salt but not high-salt intake.

Animals↗
PubMed1996

Pharmacological and developmental evidence that the potassium-induced stimulation of deoxyglucose uptake in astrocytes is a metabolic manifestation of increased Na(+)-K(+)-ATPase activity.

There is disagreement in the literature whether or not deoxyglucose accumulation, a measure of glycolytic activity, is increased in astrocytes during exposure to elevated concentrations of the potassium ion (K+). In the present work we have confirmed our previous finding that deoxyglucose accumulation in primary cultures of well-differentiated mouse astrocytes shows a robust increase when the K+ concentration in the incubation medium is raised to or above 12 mM. This response is inhibited by ouabain (with a half-maximum effect at approximately 0.1 mM), indicating that it is a metabolic manifestation of the activity of an Na(+)-K(+)-ATPase. The stimulation at this high level of K+ indicates a remarkably low K+ affinity of the Na(+)-K(+)-ATPase involved, enabling it to be activated by above-normal concentrations of K+. At a resting concentration of K+ (5.4 mM), at least one half of the deoxyglucose accumulation is also a reflection of Na(+)-K(+)-ATPase activity, as shown by its susceptibility to inhibition by ouabain. Ouabain has some effect even at a concentration of 0.1 microM, indicating participation of not only the alpha 1 isoform which has a low affinity to ouabain, but also of the alpha 2 isoform, which has a high affinity. The stimulatory effect of elevated K+ is absent in immature astrocytes and only develops after prolonged time in culture. It could not be evoked in a seemingly similar culture of rat astrocytes, which has previously been shown to lack Na(+)-K(+)-ATPase activity as well as the alpha 2 isoform of the ATPase. This isoform has unequivocally been found to be expressed by astrocytes in situ.

Animals↗
PubMed1996

[Experimental study of human micro-urokinase gene therapy].

OBJECTIVE: To determine the feasibility and efficiency of gene therapy to thrombotic disease. METHODS: The retroviral vectors containing 982 bp mUKcDNA were constructed and transfected into PA317 viral packaging cells. Recombinant retroviral particles collected from media of PA317 cells were injected into mice subcutaneous tissue, abdominal cavity and quadriceps muscle, respectively. mUK activity of plasma was measured with a synthetic substrate S-2390. Six mice were sacrificed after injection for immunofluorohistochemical staining. RESULTS: The mUK activity in plasma was obviously increased (P < 0.01) and the expression of mUKcDNA was observed at local sites of injection by immunofluorohistochemical staining. The mUK activity was raised for 4 months. CONCLUSION: The injection of recombinant viral particles containing transcriptional unit of mUKcDNA might be applied to the prevention and treatment of thrombotic disease.

Animals↗
PubMed1996

Effect of 764-3 on aggregation and calcium movements in aequorin-loaded human platelets.

Washed human platelets were loaded with the Ca(2+)-sensitive photoprotein, aequorin, using hypoosmotic shock treatment-technique. Then aggregation and cytoplasmic ionized calcium concentration ([Ca2+]i) changes in response to collagen or thrombin were measured simultaneously in the aequorin-loaded human platelets with a Platelet Ionized Calcium Aggregometer. 764-3, an active component isolated from the Chinese medicinal herb Salvia Miltiorrhiza Bge, inhibited platelet [Ca2+]i rise as well as aggregation evoked by collagen or thrombin in the presence of extracellular Ca2+. After the extracellular Ca2+ was removed by addition of EGTA, collagen or thrombin, causing no aggregation, still elicited platelet [Ca2+]i rise which reflected Ca2+ mobilization from intraplatelet stores. Under this condition, 764-3 could also suppress platelet [Ca2+]i rise. Analysis shows that 764-3 inhibits platelet Ca2+ influx and Ca2+ mobilization with similar potency, which accounts for its suppression of platelet [Ca2+]i rise, and must contribute to its inhibition of platelet aggregation.

Biological Transport, Active↗
PubMed1995

Structural differences in the cerebral cortex of healthy female and male subjects: a magnetic resonance imaging study.

There are both reproductive and nonreproductive behavioral differences between men and women. Brain regions involved in determining sexual behavior have been reported to differ between the sexes. Nonreproductive, cognitive functional differences between sexes might be reflected in higher-order cortical structural dimorphisms, which have not previously been studied. We hypothesized that cortical regions involved in verbal behavior (which is sexually dimorphic) would differ between sexes. Using magnetic resonance imaging, we assessed gray matter volumes in several cortical regions in 17 women and 43 men. Women had 23.2% (dorsolateral prefrontal cortex) and 12.8% (superior temporal gyrus) greater gray matter percentages (corrected for overall brain size and age) than men in a language-related cortical region, but not in a more visuospatially related cortical region. These data seem to establish sexually dimorphic structural differences in the cerebral cortex, consistent with prior cerebral blood flow reports.

Adult↗
PubMed1995

Further evidence that fluoxetine interacts with a 5-HT2C receptor in glial cells.

It is generally believed that the antidepressant drug fluoxetine (Prozac) exerts all its effects by inhibition of serotonin uptake into neurons and an ensuing increase in the extracellular concentration of serotonin. However, these studies have confirmed and expanded our previous observation that fluoxetine on its own exerts agonist effects on astrocytes (a glial cell type), which resemble those exerted by serotonin. Fluoxetine appears to act on a different subtype of receptor (the 5-HT2C receptor [in original terminology the 5-HT1C receptor]) than the one on which micromolar concentrations of serotonin are known to act in astrocytes (the 5-HT2A receptor [in original terminology the 5-HT2 receptor]). However, this study has shown that application of serotonin to these cells stimulates glycogenolysis and causes an increase in free cytosolic concentration of calcium that is not inhibited by the 5-HT2A selective antagonist, ketanserin. Moreover, both effects are pronounced at the low nanomolar level of serotonin and, therefore, by definition, act on the 5-HT2C receptor. The concentration/response correlation is identical for the serotonin effects on free cytosolic calcium concentration and on glycogenolysis. Fluoxetine exerts similar effects, but low nanomolar concentrations have no effect, and the concentration required to obtain half-maximum response is 1-3 microM, a concentration dependence that is consistent with the plasma levels of fluoxetine during treatment with this drug.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

Morphometric analysis of spinous cell in oral submucous fibrosis. Comparison with normal mucosa, leukoplakia and squamous cell carcinoma.

The morphometric analysis of the spinous cell in 16 specimens of oral submucous fibrosis (OSF) was made by using interactive image analysis system (IBAS-II). 19 parameters of the size and shape were chosen, and compared with normal mucosa, leukoplakia, dysplasia and carcinoma. The results indicated that the cell dimensions (area, perimeter, all kinds of diameter) and nuclear cytoplasmic ratio in OSF were between normal mucosa and dysplasia as well as carcinoma. The former showed a progressive decrease (P < 0.01), and the latter showed a progressive increase (P < 0.01). The dimensions of the nuclei did not show considerable differences among the groups (P < 0.05). A series of discriminant functions had been developed with stepwise discriminant analysis, the agreement ratio for OSF was 93.75%. The decrease of cell area and the increase of nuclear cytoplasmic ratio could reflect a malignant progress. The cell morphometric model could discriminate OSF well from other groups, suggesting that the change of the epithelium in OSF appearing in the spinous cell is specific itself.

Carcinoma, Squamous Cell↗
PubMed1995

[Characterization of platelet activation induced by CD9 McAbs].

The platelet activation induced by two anti-human platelet P24/CD9 McAbs was investigated. The results showed that the pathways of platelet aggregation induced by the two McAbs (HI117 and SJ9A4) were different and HI117 and SJ9A4 induced the phosphorylation of platelet proteins (40,000 and 20,000) when platelets were activated. However, HI117 did not cause a rise in intracellular Ca2+ concentration in activated platelets in comparison with SJ9A4 and the epitope recognized by HI117 and SJ9A4 was different and this might explain why the two CD9 McAbs played different roles in platelet activation in addition, McAbs HI117 and SJ9A4 could not promote associations of other proteins (eg: GP II b/III a) with P24/CD9 on activated human platelets. All these results indicate that the mechanisms of platelet activation induced by HI117 or SJ9A4 are different from each other. It suggests that CD9 antigen plays an importent and complex role in platelet activation.

Antibodies, Monoclonal↗