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Biomedical subjects

Q Chen

Publications and source records attributed to Q Chen.

At least 649 records · Page 36Linked to original sources
PubMed1994

Preparation, characterization, and evaluation of a monoclonal antibody against the rabbit platelet glycoprotein IIb/IIIa in an experimental angioplasty model.

The deposition of platelets at the site of balloon angioplasty is thought to play a major role in the pathogenesis of restenosis. The antibody AZ-1, which binds to the rabbit platelet glycoprotein IIb/IIIa receptor and inhibits platelet function both in vitro and in vivo, was produced and tested in an experimental model of angioplasty. Atherosclerosis was induced by desiccation injury of the femoral artery, followed by a 28-day diet with 2% cholesterol and 6% peanut oil. Rabbits were randomized to receive an infusion of saline, a single infusion of 0.5 mg/kg of AZ-1, or an infusion of 0.6 mg/kg AZ-1 before angioplasty. The latter group received a second infusion of 0.6 mg/kg 72 hours later. Functional platelet inhibition was demonstrated by prolongation of the bleeding time in all treated animals. Angiography was performed at baseline, immediately after a standardized angioplasty, and again 28 days after angioplasty on a total of 42 vessels. There were no significant differences between the antibody-treated group and the control group in the mean angiographic minimum luminal diameter at any of the time points. There was also no difference in the initial improvement after angioplasty (acute gain), in the decrease in luminal diameter from immediately after angioplasty to 28 days after angioplasty (late loss), or in the overall improvement from before angioplasty to 28 days after angioplasty. Quantitative histological analysis confirmed the lack of a beneficial effect of AZ-1. There were no significant differences in the area of the intima, the media, or the combined intima and media between the antibody-treated groups and the control group. Thus, potent platelet inhibition for up to 6 days after balloon angioplasty using a monoclonal antibody that inhibits platelet aggregation did not reduce the response to vascular injury after balloon angioplasty in this rabbit model of experimental atherosclerosis.

Angioplasty↗
PubMed1994

Differential inhibition of cyclic AMP-dependent protein kinase, myosin light chain kinase and protein kinase C by azaacridine and acridine derivatives.

A series of 72 acridine and azaacridine derivatives have been tested as inhibitors of Ca(2+)- and phospholipid-activated protein kinase C (PKC), the catalytic subunit of cyclic AMP-dependent protein kinase (cAK) and Ca(2+)-calmodulin-dependent myosin light chain kinase (MLCK). A series of monomethyl derivatives of N-(2-dimethylaminoethyl)-acridine-4-carboxamide that have anti-tumour activity are good inhibitors of MLCK (IC50 values ranging from 4-138 microM) but these same compounds are ineffective or relatively poor inhibitors of PKC or cAK. With only several exceptions, the effective azaacridine inhibitors of PKC and MLCK (IC50 values < 200 microM) have basic or neutral 4-substituents whereas the effective azaacridine inhibitors of cAK have either neutral or acidic 4-substituents. The four exceptions found to this generality are effective inhibitors of all three protein kinases with IC50 values of about 100 microM or less. With several exceptions azaacridine inhibitors of PKC are also inhibitors of MLCK but effective inhibitors of cAK are relatively poor inhibitors of MLCK and PKC and vice versa. 4-N-(2-dimethylaminoethyl)-6-azaacridone-4-carboxamide is a competitive inhibitor of MLCK with respect to both the peptide substrate and ATP. All other acridines and azaacridines examined are non-competitive inhibitors of both MLCK and cAK with respect to both ATP and peptide substrate. All azaacridine PKC inhibitors examined are competitive with respect to ATP and noncompetitive with respect to peptide substrate suggesting that binding of these inhibitors is at or near the enzyme active site. The inhibition of MLCK (but not cAK or PKC) by anti-tumour acridine carboxamides suggests a novel site of in vivo biological action and a useful criterion for the detection of potential antitumour compounds.

Acridines↗
PubMed1994

Absorption and incorporation into tissue lipids of 3H-arachidonic- and 14C-linoleic acid: effects of ethanol in jejunal tissue cultures and in vivo.

The effects of ethanol in the rat on the absorption and incorporation of 3H-arachidonic (20: 4, n-6) and 14C-linoleic acid (18:2, n-6) into tissue lipids was examined in jejunal tissue cultures in vivo. The pattern of incorporation earlier seen in the small intestine in vivo, ie. a preferential incorporation of 3H-20: 4 in comparison to 14C-18: 2 into phospholipids (PL), particularly phosphatidylethanolamine (PE) and phosphatidylinositol (PI) was seen in the jejunal tissue cultures. 10 mM ethanol slightly decreased the incorporation of 3H-20: 4 into PE and PI, but did not change the partitioning of labelled fatty acids into phospholipids and triacylglycerols (TG). Ethanol (100 mM) decreased the incorporation of both 3H and 14C into both PL and TG and caused a moderate increase in the TG/PL radioactivity ratio. Rats were also infused intraduodenally with either 10% ethanol or saline and given 3H-20: 4 and 14C-18: 2 in Intralipid. Radioactivity of tissue lipids were analysed after 1, 2 and 3 h. Ethanol did not significantly influence the absorption or the retention in small intestine, liver or heart of 3H or 14C, or the time course for the 3H- and 14C lipid radioactivity in serum. The distribution of 3H and 14C between total nonpolar lipids and individual PLs was also similar in the two groups, 3H-20: 4 thus exhibiting the same preferential incorporation into PLs, compared to 14C-18: 2, in both groups. Significant amounts of 3H and 14C appeared in phosphatidylethanol (PEth) of the small intestine, heart and liver, when the tissues from the ethanol-infused animals were stored frozen before extraction. When the tissues were extracted immediately after the experiment, the proportions of 3H and 14C migrating as PEth did not exceed 0.5%. Although sufficient amounts of ethanol and the phospholipase D activity necessary for PEth formation were thus present in the tissues examined, little PEth formation thus occurred during the ethanol infusion. In the ethanol treated group about 1% of the 3H and 14C radioactivity of the small intestine was in ethyl ester. Intraduodenal infusion of 10% ethanol in vivo thus has little acute effects on the metabolism of absorbed 18: 2 and 20: 4 in the intestinal mucosal cells. Formation of some ethyl ester occurs, however.

Animals↗
PubMed1994

Post-hospital home health care for Medicare patients.

Medicare patients in five diagnosis-related groups (DRGs) associated with heavy use of post-hospital care discharged from 52 hospitals in 3 cities were followed up at 6 weeks, 6 months, and 1 year to determine the factors associated with their being discharged home with or without home health care and the correlates of improvement in their functional status. Models correctly predicted those discharged home from those going to institutions in a range from 54 to 82 percent of cases. The amount of the variance in the change in function for those who went home (with or without home health care) explained by the models tested ranged from 19 percent to 73 percent. Total Medicare costs for the patients who went home were considerably less in the year subsequent to the hospitalization compared with those discharged to institutional care.

Activities of Daily Living↗
PubMed1994

[Detection of vaginal and cervical human papillomavirus by electronic microscope examination and polymerase chain reaction technique].

UNLABELLED: Forty-seven specimens, biopsied during April-July 1990, pathologically proven to be vaginal or cervical condyloma acuminata (CA) in 34, wart-like lesions in 6, infections in 7, were screened for detection of human papillomavirus (HPV) by electronic microscope (EM) examination and polymerase chain reaction (PCR) technique. HPV type 11 (HPV-11) infections were diagnosed by Dot-blot hybridization in 40 out of these 47 specimens. RESULTS: (1) No typical virus particles was observed in all samples under EM examinations. However, interchromatin and perichromatin granules were found within the nuclei of koilocytes in 88.23% of the vaginal CA specimens. Nuclear bodies were seen in 3 out of 27 vaginal CA and HPV11 positive specimens. Furthermore, koilocytosis was also seen in the basal and parabasal layers of vaginal mucosa. (2) The positive rate for detection of HPV11 and HPV6 DNA by PCR technique in vaginal CA specimens was 92.6%, while positive rate for HPV 11, 6, 16 and 18 DNA was only 3.7%.

Adult↗
PubMed1994

[Role of EcoRI-BclI fragment at the promoter upstream region on the expression of alpha-amylase gene].

A series of plasmids derived from pNL201 with the promoter upstream region of alpha-amylase gene of B. licheniformis have been constructed. In the meantime, a series of plasmids derived from pAmy41 with full alpha-amylase gene have also been constructed and they have different promoter upstream region with the EcoRI-BclI fragment deleted or partial destroyed. The alpha-amylase activity of the engineering strains carrying alone or double plasmids has been determined. The statistical results show that the EcoRI-BclI fragment possesses negative regulation in the expression of alpha-amylase gene in B. subtilis.

Deoxyribonuclease EcoRI↗
PubMed1994

The autocrine regulatory effect of vasoactive intestinal peptide on the growth of human pancreatic carcinoma cells.

In the present study, the effects of VIP on the growth of two human pancreatic carcinoma cell lines PU-PAN-1 and PANC-1 were determined using tritiated thymidine incorporation. VIP receptors, intracellular cAMP and polyamines were investigated. The results indicated that VIP at a concentration of 10(-8) mol/L to 10(-7) mol/L can significantly stimulate the growth of PU-PAN-1 cells but not PANC-1 cells. This effect is dose-dependent and abolished by VIP receptor antagonist, [4-C1-Phe6, Leu17] VIP, suggesting VIP receptors in PU-PAN-1 cells may mediate this effect. VIP can markedly elevate the levels of intracellular cAMP and polyamines in PU-PAN-1 cells, indicating that the growth-promoting effect stimulated by VIP may be via a rapid increase in the biosyntheses of cAMP and polyamines. In addition, the VIP-antibody inhibited the growth of PU-PAN-1 cells in serum-free culture medium. The results above suggested that VIP has an autocrine regulatory effect on this pancreatic carcinoma cell line (PU-PAN-1).

Biogenic Polyamines↗
PubMed1994

[Study on red blood cell immune adherence function in coriaria lactone-induced epileptic seizure rats].

The immune adherence function of red blood cells in 17 rats was studied. It was found that the rosette rate of red blood cell C3b receptor (RBC-C3bRR) was 7.45 +/- 1.36% in the epilepsy group (8 rats), and 10.84 +/- 1.77% in the control group (9 rats); and that the rosette rate of red blood cell immune complex (RBC-ICR) was 7.42 +/- 2.62% in the epilepsy, and 10.80 +/- 1.72% in the control. As compared with the control group, the rosette rate of red blood cell C3b receptor was remarkably decreased in the epilepsy group (P < 0.05). There was no significant difference between the two groups in RBC-ICR. The results from this study demonstrated that the CL-induced seizures might result in decrease in red blood cell immune adherence function of the epilepsy rats.

Animals↗
PubMed1994

[Reference values for blood, hair, and organ selenium levels in adults of Beijing].

Two hundred and four blood specimens and 202 hair specimens, and 72 tissue specimens of heart, liver, spleen, lung, kidney, muscle and skeleton from adults living in Beijing suddenly died were collected during 1990-1991. Selenium levels were determined by 2,3-diamine naphthalene fluorescence method with serum, human hair and calf liver as standard references to assure the quality of determination, and their reference values for adults in Beijing were established. Selenium nutritional status of the adults was evaluated preliminarily. Dietary selenium intake was estimated based on serum selenium levels, and the body total selenium content was estimated by biological monitoring.

Adolescent↗
PubMed1994

[A new concept and method of standardizing predictive value].

A new concept and method of standardizing predictive value was put forward. The theoretical predictive value which was not affected by prevalence rate or different component in normal and abnormal groups and was gotten under the appointed standardizing condition that made the cases in the two groups to be same with each other and to be called standardizing component was defined as standardizing predictive value. The value will change only with the change of sensitivity and specificity of diagnostic test. By the new concept and method, the value of diagnostic test can be explained, judged and expressed in unique standard.

False Negative Reactions↗
PubMed1994

[Induction of gastric adenocarcinoma in Wistar rats following neonatal exposure to MNNG and neoplastic transformation assay of DNA of the induced cancer].

Adenocarcinoma, adenoma and dysplasia of the stomach of adult Wistar rats were induced following administration of MNNG for 10 days by gavage when they were new-born. The incidence of the three types of pathological lesions at the dose of 0.4 mg MNNG per rat being 39%, 50% and 100% respectively. Induction of gastric adenocarcinoma is dose-dependent. The incidence of adenocarcinoma in male rats being significantly higher then that of female rats (P < 0.02). 23 of 33 (70%) induced cancers were found in the gastric antrum. By the use of DNA cotransfection technique and the assay of carcinogenicity in the Balb/c nude mice, it was also found that the DNA of 4 of the 6 induced gastric carcinomas could transform NIH/3T3 cells into malignant cells, an indication that the induced cancer DNA contains transforming gene.

3T3 Cells↗
PubMed1994

Metabolism of chylomicron phosphatidylinositol in the rat: fate in vivo and hydrolysis with lipoprotein lipase and hepatic lipase in vitro.

Phosphatidylinositol (PI), mainly stearoyl-arachidonyl PI, occurs as a minor phospholipid constituent in both chyle and plasma lipoproteins. The kinetics and the pathway by which plasma and chyle PI is metabolized have not been investigated. The role of lipoprotein PI in the supply of arachidonic acid (20:4) and inositol lipid components to different tissues is thus unknown. In this study we examined the fate of chyle PI in vivo and its hydrolysis by lipoprotein lipase (LPL), hepatic lipase (HL), and postheparin plasma in vitro. Chyle and chylomicrons were labeled in the PI portion by feeding [3H]myo-inositol and in the phosphatidylcholine (PC) portion by feeding [14C]choline in a linoleate-rich fat meal (Intralipid) to mesenteric duct-cannulated rats. After intravenous injection of doubly labeled chyle into normal rats, [3H]PI disappeared from plasma at a slower rate than [14C]PC; after 60 min 41.6 +/- 2.7% 3H and 24.3 +/- 1.8% 14C (means +/- SEM, n = 4, P < 0.01) remained in plasma lipids. About 15% of both isotopes were in liver lipids after 60 min. Previous injection of a blocking antiserum against rat HL did not significantly influence the serum and liver radioactivity after 60 min. Radioactive PI was rapidly transferred to high density lipoproteins (HDL) during the metabolism of chylomicrons. Analysis of 3H and 14C in different molecular species of PI and PC in chyle and in serum indicated that there was no significant difference in disappearance rates between various species, stearoyl-arachidonyl PI thus disappearing at the same rate as total [3H]PI. Both lipoprotein lipase (LPL) and HL catalyzed formation of lyso-PI in vitro, the rate being increased by the addition of serum. About 60% of the lyso-PI formation catalyzed by postheparin plasma in 60 min could be blocked by antiserum to HL, which almost completely blocked the hydrolysis occurring after the first 10 min. The study thus shows that both LPL and HL hydrolyze chylomicron PI in vitro. LPL and HL may, however, be of limited importance for the clearance of chyle PI in vivo, most of the chylomicron PI being transferred to HDL, and thereafter eliminated from plasma at a slow rate mainly by other mechanisms.

Animals↗
PubMed1994

Interconversion of alpha-linolenic acid in rat intestinal mucosa: studies in vivo and in isolated villus and crypt cells.

The desaturation-elongation of [14C]linolenic acid (n-3) in the rat small intestine was examined in homogenates of villus and crypt cells in vitro and in mesenteric lymph duct cannulated rats in vivo, using high performance liquid chromatography of fatty acid methyl esters with continuous flow measurement of 14C. Desaturation-elongation of [14C]18:3 to [14C]18:4, [14C]20:4, and [14C]20:5 (n-3) could be demonstrated in both villus and crypt cell homogenates, the rate of interconversion generally being highest in the villus cell fraction. For example, during incubation with 20 nmol [14C]linolenic acid (n-3), the average rates of delta 6 desaturation were 1.35 pmol/min per mg protein in villus and 0.93 pmol/min per mg protein in crypt cell homogenates. The acylation of [14C]linolenic acid (n-3) into phospholipids in crypt cells was twofold higher than in villus cells. Addition of 1-palmitoyl-sn-glycero-3-phosphocholine (20-240 microM) increased the incorporation of [14C]linolenic acid (n-3) into phosphatidylcholine, and decreased the interconversion of [14C]linolenic acid (n-3) to delta 6 and delta 5 desaturation products in both villus and crypt cells. 1-Palmitoyl-sn-glycero-3-phosphocholine also decreased the incorporation of 14C into triacylglycerols and phosphatidic acid, the decrease being more pronounced in the crypt cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Acylation↗
PubMed1994

[Effect of the changes of amino acids on both signal peptide C-terminal and mature protein N-terminal region to the secretion of alpha-amylase in B. subtilis].

By site-directed mutagenesis, G and C have taken the place of T and G at nucleotide sequence 287 and 291 of B. licheniformis alpha-amylase gene to generate pAm-y413B and the N-terminal sequence of mature protein have been changed from 7Leu 8Met to 7Arg8Ile. By the insertion of polylinker into the C-terminal of the signal sequence of alpha-amylase gene of pAmy413, the signal peptide of alpha-amylase produced by pAmy413L is 13 amino acids more than the pAmy413 (which is 29 amino acids long) and also, a new recognition cleavage sequence for signal peptidase I (Ala-Gln-Ala decreases Ser) is created; The secondary structure of the signal peptide has been analyzed by computer programs. The alpha-amylase relative activity of the two mutant strains is 3% and 36% of pAmy413, respectively. The molecular weight of extracellular alpha-amylase is the same as pAmy413. Terminal analysis shows that the N-terminal amino acid of mature protein is Ala, not Ser, and suggests that SPase I prefers to cleavage at the wild type recognition site (Ala-Ala-Ala decreases Ala). Therefore, all of the above results show that the secretion of alpha-amylase in B. subtilis is in accordance with the co-translational transportation model.

Amino Acid Sequence↗
PubMed1994

[Characterization of receptor-mediated binding of 99mTc-NGA in vitro].

This paper reports results of an assay of the binding of 99mTc-galactosylneoglycoalbumin (NGA) and plasma membranes of the rat liver in vitro. The data showed that 99mTc-NGA could be bound to the membrane receptor with high affinity. Specificity and saturability, and that the amount of membrane-bound 99mTc-NGA varied linearly with the amount of membrane within each reaction tube. The biphasic curve of scatchard plot revealed that 99mTc-NGA was bound to two sites of the receptor with different affinity and concentration (K1 8.4089 x 10(9) L/mol, R1 1.7350 x 10(-12) mol/mg); K2 2.0827 x 10(8) L/mol, R2 6.9530 x 10(-12) mol/mg). Therefore, the authors consider that 99mTc-NGA is a promising hepatic receptor agent for imaging.

Albumins↗
PubMed1993

Desaturation and chain elongation of n - 3 and n - 6 polyunsaturated fatty acids in the human CaCo-2 cell line.

Human CaCo-2 cells were incubated with [14C]linoleic (18:2(n - 6)), [14C]linolenic (18:3(n - 3)) and [3H]eicosapentaenoic acid (20:5(n - 3)), and the interconversion of the radioactive fatty acids to higher homologues and their acylation into triacylglycerols (TG) and phospholipids were examined. An active conversion of [14C]18:3 to [14C]20:5 and [14C]docosapentaenoic acid (22:5(n - 3)) and of [3H]20:5 to [3H]22:5, but not to [3H]docosahexaenoic acid (22:6(n - 3)) was observed. In relation to the amounts that had been incorporated into cellular phospholipids and TG, the interconversion of [14C]18:3 clearly exceeded that of [14C]18:2. Addition of 10-100 microM 18:2 or 10-50 microM arachidonic acid (20:4(n - 6)) increased the percent interconversion of [14C]18:2 to [14C]20:4. E.g., addition of 50 microM 20:4 increased the formation of [14C]20:4 from 4.4 +/- 0.1% to 5.9 +/- 0.8%, decreased the incorporation into phospholipids from 64.8 +/- 6.3% to 31.4 +/- 1.2% and increased the incorporation into TG from 8.8 +/- 0.4% to 28.8 +/- 1.1%. In contrast, addition of 10-100 microM 18:3 or 20:5 significantly decreased the interconversion of both [14C]18:2 and [14C]18:3. E.g., addition of 50 microM 20:5 decreased the formation of [14C]20:4 from [14C]18:2 from 4.4 +/- 0.1% to 0.9 +/- 0.1%, whereas the effects on the acylation reactions were very similar to those of 20:4. 20:5 also decreased the formation of interconversion products from [14C]18:3. 18:2 and 20:4 caused a smaller decrease in the formation of [14C]20:5 and actually increased percent conversion to [14C]22:5. The percent conversion of [3H]20:5 to [3H]22:5 was also increased by the addition of 50-100 microM unlabeled 20:5. [14C]18:2 and [14C]18:3 were predominantly incorporated into phosphatidylcholine (PC) whereas more of the radioactive 20:4, 20:5 and 22:5 was incorporated into phosphatidylethanolamine (PE). An active fatty acid interconversion catalyzed by delta 6 and delta 5 desaturases thus occurs in the human CaCo-2 cell line, whereas conversion of 20:5(n - 3) to 22:6(n - 3) could not be demonstrated. The desaturation-elongation pathway has a preference for 18:3(n - 3) and is subjected to an efficient feedback regulation by 20:5(n - 3). Formation of 22:5 increases with available 20:5 mass and by the presence of other polyunsaturated fatty acids competing with 20:5 for acylation into phospholipids.

Carbon Radioisotopes↗
PubMed1993

Synthesis, conformational analysis, and the glycosidic coupling reaction of substituted 2,7-dioxabicyclo[4.1.0]heptanes: 1,2-anhydro-3,4-di-O-benzyl-beta-L- and beta-D-rhamnopyranoses.

1,2-Anhydro-3,4-di-O-benzyl-alpha-L-rhamnopyranose was synthesized from L-rhamnose, while the D-enantiomer was synthesized from methyl 6-deoxy-2,3-O-isopropylidene-alpha-D-mannopyranoside. For both of the syntheses, the key intermediates were 2-O-acetyl-3,4-di-O-benzyl-alpha-D- and -alpha-L-rhamnopyranosyl chlorides that were quantitatively prepared from the corresponding diacetates by chlorination. Ring closure of the chlorides was carried out readily with potassium tert-butoxide in oxolane, and crystalline 1,2-anhydro-3,4-di-O-benzyl-beta-D- and beta-L-rhamnopyranose were obtained in high yields. Conformational calculations, which were carried out using vicinal proton-proton coupling constants by the modified Karplus equation, suggested that the conformations of the pyranose rings of the title compounds were basically a half chair (4H5) with some flattening at C-4. Force-field calculations (MMP2) confirmed the experimental conformation with good agreement. The coupling reaction of the 1,2-anhydro-L-rhamnose ether with 1,2;3,4-di-O-isopropylidene-alpha-D-galactopyranose was effected in oxolane by catalysis by a Lewis acid, and only the alpha-linked disaccharide was obtained.

Antigens, Bacterial↗