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Biomedical subjects

D Xu

Publications and source records attributed to D Xu.

At least 19 recordsLinked to original sources
PubMed1992

Ethanol and glycogen synthesis in cardiothoracic and skeletal muscles following glucose re-feeding after starvation in the rat.

The pattern of glycogen deposition in individual cardiothoracic and skeletal muscles in response to oral and intraperitoneal glucose administration was examined in 40 h-starved rats. Rates of glycogen synthesis were consistently higher in oxidative muscles than in non-oxidative muscles. Intragastric ethanol administration was associated with an impaired glycaemic response and the almost total abolition of glycogen deposition in oxidative muscles in response to oral or intraperitoneal glucose re-feeding. This effect was dose-dependent and differential, in that ethanol produced no equivalent impairment in glycogen deposition in non-oxidative muscles. Ethanol treatment also selectively promoted glycogenolysis in oxidative muscles in the starved state. There was positive correlation (P < 0.001) between the decrease in glycogen levels in soleus and diaphragm muscles in response to increasing ethanol doses and blood glucose and lactate concentrations after intraperitoneal glucose administration, implying that the basis for the impairment in glycogen synthesis may be diminished glucose availability. The mechanism whereby ethanol may differentially compromise carbohydrate metabolism in oxidative muscles is discussed.

Animals↗
PubMed1992

Extracellular matrix in the rat spiral limbus.

The matrix of the spiral limbus is obviously a special form of the intercellular substance. In the present study, the rat's spiral limbus was investigated by electron microscopy after fixation with ruthenium red and tannic acid and immunofluorescence to demonstrate matrix components. Collagen types I, II, V, VI, VII, IX and XI and fibronectin were not observed. Collagen type II and cartilage-specific proteoglycans, however, occurred in large quantities. The basal lamina of interdental cells and inner sulcus cells did not contain any collagen type IV, while the basal lamina of the capillaries had only minor amounts. Laminin and nidogen appeared in large amounts in the basal lamina. After fixation with tannic acid, the matrix between the interdental cells and the capillaries contained 20- to 22-nm-thick single and irregularly running fibrils as well as plaques of a fine granular material. After fixation with ruthenium red, 30- to 60-nm-thick, electron-dense granules occurred and most probably consisted of proteoglycans. These findings indicate that the composition of the matrix of the spiral limbus is similar to that of cartilage but not identical.

Animals↗
PubMed1992

Expression and pharmacological characterization of a stimulatory subtype of adenosine receptor in fetal chick ventricular myocytes.

Ventricular and atrial myocytes cultured from chick embryos 14 days in ovo were used as model systems to study cardiac adenosine receptors. In membranes of ventricular cultures, blocking of the A1-adenosine receptor pathway by the A1-selective antagonist 8-cyclopentyl-1,3-dipropylxanthine (DPCPX) or by pertussis toxin treatment of the myocyte resulted in a significant adenosine agonist-mediated stimulation of the adenylate cyclase activity. The maximal increases in adenylate cyclase activity caused by the equipotent or the A2-adenosine receptor-selective agonists (from 52.1 +/- 3% to 63 +/- 10% [mean +/- SEM]) were significantly greater than those caused by the A1-selective agonists (from 11 +/- 5% to 34.6 +/- 7%) (p less than 0.01, by t test, n = 4-8). However, in membranes of atrial myocytes, when A1-subtype had been blocked, the various adenosine agonists had no effect on the adenylate cyclase activity. Whether the stimulatory adenylate cyclase-coupled adenosine receptor is also capable of stimulating contractility in the intact ventricular myocyte was next investigated. In ventricular but not in atrial cells, the various adenosine agonists caused an increase in the contractile amplitude in the presence of DPCPX or in myocytes preexposed to pertussis toxin. The increase in contraction amplitude caused by each agonist was expressed as percent of maximum (maximum is the increase in contractility caused by 2.4 mM calcium). In the pertussis toxin-treated myocyte, the maximal increases caused by the equipotent or A2-agonists (NECA, MECA, CV-1808, and CGS21680, from 49.6 +/- 3% to 52.5 +/- 6%, n = 8-12) were significantly greater than those elicited by the A1-agonists (2-CADO, S-PIA, R-PIA, and DCCA, from 12 +/- 4% to 37 +/- 3%, n = 8) (p less than 0.05, by t test). These data demonstrated that a stimulatory adenosine receptor, likely the A2-adenosine receptor, was present on the ventricular but not the atrial myocytes and was linked directly to a stimulation of the cardiac contractility. The functional effects mediated by the A1-subtype became manifested in the presence of isoproterenol, as evidence by an inhibition of the isoproterenol-stimulated increases in adenylate cyclase activity and in cardiac contractility by adenosine agonists. Thus, both subtypes of adenosine receptors, each mediating opposing responses, were present on the ventricular myocytes, whereas only the A1-subtype was found in the atria. The presence of a stimulatory functional A2-adenosine receptor may help explain the absence of a direct negative inotropic response to adenosine in the ventricle.

Adenylate Cyclase Toxin↗
PubMed1992

A new effective and non-harmful chemical adjuvant for the induction of experimental autoimmune uveoretinitis.

The induction of T cell mediated disease models in animals is usually dependent on the use of complete Freund's adjuvant (CFA). In order to avoid the painful side effects of CFA on the animals, we tested the capacity to induce experimental autoimmune uveoretinitis (EAU) with Hunter's adjuvant (HA). This new adjuvant makes use of nonionic copolymer surfactants, and does not cause deleterious effects to animals. We have found that EAU could be efficiently induced in rats with low doses of S-Ag (10 micrograms) in very small quantity of HA (10 microliters). The biologic parameters of EAU induction showed a potent stimulation of lymphocytes proliferation maximal 11 days after immunization, as well as high levels of antibody production.

Adjuvants, Immunologic↗
PubMed1992

[Application of the regression orthogonal design to the fertilization of Psoralea corylifolia L. for optimum yield].

This paper probes into the determination of the optimum amount of fertilization by applying regression orthogonal design. After a significance test by regression equation, a regression equation can be set up, i. e. Y = 25.21 + 9.18 Xn + 15.68 Xp - 0.4 Xn2 - 0.98 Xp2 + 0.062 Xn Xp. This equation can be used to describe the relationship between yield and amount of fertilization.

Fertilizers↗
PubMed1992

Impaired attachment of hepatocytes to extracellular matrix components after chronic ethanol administration.

BACKGROUND: Previous studies have shown that the assembly and properties of the hepatocyte plasma membrane are altered by ethanol administration, indicating possible changes in the receptor-mediated binding of the plasma membrane to extracellular matrix substrates. In the present study, the effects of chronic ethanol consumption on the ability of hepatocytes to attach to various components of the extracellular matrix were investigated. EXPERIMENTAL DESIGN: Rats were pair-fed for 5 weeks with a liquid diet containing either ethanol (as 36% of total calories) or isocaloric carbohydrate. The effects of ethanol treatment on hepatocyte-extracellular matrix interactions was ascertained by determining the ability of isolated hepatocytes to attach to various extracellular matrix substrates. RESULTS: The attachment of hepatocytes, isolated from the ethanol-fed rats, to laminin-coated plates was significantly decreased compared with hepatocytes from chow-fed or pair-fed controls. Greater decreases in attachment were seen when higher numbers of hepatocytes were seeded in the plates. Similar inhibitions of attachment were also observed when fibronectin or type I collagen were used as matrices. Time-course cell attachment assays indicated that the maximum extent of attachment rather than the rate of attachment was primarily altered by chronic ethanol feeding. Hepatocytes from the ethanol-fed rats also detached more readily from the matrix-coated plates than those from the controls. A reduced number of functional surface receptors for matrix components is likely the most important factor that accounts for the ethanol-induced impairment of hepatocyte attachment. CONCLUSIONS: These results indicate that chronic ethanol administration impairs the interactions of hepatocytes with their extracellular matrix and that this defect could lead to alterations of hepatocyte structure and function.

Animals↗
PubMed1992

[Isolation and identification of Leclercia adecarboxylate in clinical isolates in China].

1987, 3 strains of gram-negative straight rods were examined from 3 cases of patients with diarrhea. It's producing yellow pigment, fermentative metabolism of carbohydrates, oxidase test negative and motility with the help of peritrichous flagella. Through systematic biochemical identification, calculation of G+C mol% and homology of DNA/DNA, the species of Leclercia adecarboxylate are identified. While the susceptibility to certain antibiotics and the pathogenicity for white mice are tested, and relation of these microorganisms to clinical diarrhea is discussed.

Animals↗
PubMed1991

Clinical experience with triphasic oral contraceptive (Triquilar) in 527 women in China.

From October 1987 to May 1989, a total number of 527 women completed a total of 6,291 treatment cycles in 6 centers in China for the study of a triphasic oral contraceptive - Triquilar. The mean age of subjects was 30.21 +/- 2.84 years. There were 7 pregnancies during the study period. Among them, five were patient failures because of missed pill or incorrect intake; one had taken barbiturates along with Triquilar. Only one woman became pregnant in the 11th treatment cycle without any reason being found. In most cases, menstrual flow decreased and dysmenorrhea improved as treatment continued. Of the total treatment cycles, the incidence of missed withdrawal bleeding was 0.25%, spotting 0.97%, and breakthrough bleeding 0.48%. Nausea and vomiting was the most common side effect and accounted for 6.4% of the total treatment cycles. This was followed by breast tenderness (3.7%), dizziness (2.4%) and headache (1.6%). Most of the side effects occurred during the first few cycles and were alleviated later. By the end of one year, the total dropout was 64 cases. The reasons for discontinuing treatment were: pregnancy 1.33 (per hundred women), menstrual disturbances 0.76, side effects 3.80, other medical reasons 2.09, and personal reasons 4.18. The results confirm that Triquilar is an effective oral contraceptive with good cycle control and low incidence of side effects. No serious reaction has been reported. It has been well accepted by the Chinese women. However, due to the low dosage of steroids, it is of utmost importance to avoid errors in its use.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

Phosphotyrosine phosphatase activity in human platelets.

Using O-phosphotyrosine as a substrate, human platelets were shown to contain a highly active phosphotyrosine phosphatase (PTPase) activity. This activity was potently inhibited by vanadate, molybdate, and HgCl2. About 80% of the PTPase activity was particulate. When Triton-solubilized PTPase activity from whole platelets was applied to a DEAE Sephacel column about 40% came through unbound. The activity that bound was eluted by a NaCl gradient as a broad, heterogeneous peak. The possibility is raised for the existence of multiple forms of phosphotyrosine phosphatases in human platelets. That one or more of these forms may be regulated by activators of platelet aggregation and secretion, such as thrombin and collagen, is discussed.

Blood Platelets↗
PubMed1991

Formation of DNA adducts in F-344 rats after oral administration or inhalation of [14C]methyl bromide.

The genotoxic effects of methyl bromide were investigated in a DNA-binding study. [14C]Methyl bromide was administered to male and female F-344 rats orally, or by inhalation from a closed exposure system. DNA adducts were detected in the liver, lung, stomach and forestomach. [14C]3-Methyladenine, [14C]7-methylguanine and [14C]O6-methylguanine were identified using a combination of three different methods of hydrolysing DNA, followed by HPLC or gas chromatography-mass spectrometry. After both oral and inhalation exposure, the highest levels of methylated guanines, especially those of [14C]O6-methylguanine, were found in the stomach and forestomach of the rats. These results clearly demonstrate a systemic DNA-alkylating potential of methyl bromide.

Administration, Inhalation↗
PubMed1991

DNA binding of methyl iodide in male and female F344 rats.

The genotoxic potency of methyl iodide was investigated in a DNA binding study. Male and female F344 rats were exposed to 14C-labelled methyl iodide orally or by inhalation in a closed exposure system. DNA adducts were detected in the liver, lung, stomach and forestomach of the exposed animals. [14C]3-Methyladenine, [14C]7-methylguanine and [14C]O6-methylguanine could be identified by a combination of three different methods of hydrolysing DNA and subsequent HPLC or GC/MS analysis. The highest values of methylated guanines were determined in the stomach and forestomach of the animals following both oral and inhalative exposure. These results demonstrate a systemic genotoxic effect of methyl iodide.

Adenine↗
PubMed1991

Cytogenetic studies on peripheral lymphocytes of members from two multiple familial polyposis coli families.

Cytogenetic studies were carried out on peripheral lymphocytes of 30 members from two typical familial polyposis coli (FPC) families. It was found that, under low folic acid culture conditions, the chromosome aberration rate of FPC family members (10%) was much higher than that of the control group (2.3%). No significant difference in SCE was found between the two groups. We suggest that the chromosome aberration rate under certain conditions may be used as a parameter for the early detection of FPC in certain FPC families. The analysis of fragile sites sensitive to low folic acid in FPC family members revealed that besides the significant increase of 3p14, which is frequently seen in tumor patients, other unique sites (1p22, 1p32 and 6q21) were also present in most of the FPC patients. Fragile sites 1p22, 1p32 and 6q21 are located near certain well known oncogene loci; thus, they may have something to do with the pathogenesis of FPC. The actual relationship between these fragile sites and FPC remains to be elucidated.

Adenomatous Polyposis Coli↗
PubMed1991

Morphology, differentiation and matrix production of liver cells in organoid cultures (high density cultures) of fetal rat livers.

The aim of this study was to demonstrate the morphology and matrix synthesis of embryonic rat liver cells (day 18 of gestation) in organoid cultures (high density cultures) with electron microscopic and immunomorphological techniques. For this purpose the cells of embryonic rat livers were isolated enzymatically and grown in an organoid culture (high density culture) for 3 weeks in a Trowell system. During the first 48 h a sorting-out process took place, i.e. liver and blood-forming cells met to form aggregates. In between mesenchymal cells were seen. Vessel-like cavities developed. Electron microscopic inspection of the hepatocytes did not reveal any lesions of the cell organelles after 14 days in culture. As late as after a 3-week culture period mitochondrial swellings and an increased number of autophagic vacuoles were observed. A rim of collagenous fibrils or fibrillar bundles and granular matrix structures was perceptible as early as after 7 days in culture. Immunofluorescence microscopic techniques revealed collagen types III, IV and VI as well as laminin, nidogen, heparansulfate-proteoglycan and fibronectin in these areas. Thus, the composition of the matrix in this culture system corresponds (apart from the absence of collagen type I) to the embryonic situation. Therefore, the organoid culture appears to be an appropriate technique to study the behaviour of hepatocytes in vitro. It is especially suited to demonstrate the formation of matrix components in liver cells and their extracellular occurrence.

Animals↗