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Biomedical subjects

Q Zhou

Publications and source records attributed to Q Zhou.

At least 379 records · Page 21Linked to original sources
PubMed1991

The effect of cholesterol on the accumulation of intracellular calcium.

Cholesterol/egg phosphatidylcholine (PC) liposomes (1:1 or 4:1, M/M), in which the absolute amount of PC was adjusted to be the same, were incubated with cultured bovine arterial smooth muscle cells for up to 8 h at 37 degrees C. The effect of increased cellular cholesterol on the accumulation of intracellular calcium in these cells was studied. The results indicate that the intracellular calcium content, measured by Fura-2/AM, was increased 2.3-fold by incubation with 4:1, cholesterol/PC liposomes. Kinetic analysis using 45Ca2+ indicated that the increased calcium influx was due to increase of pool size, not from a change of rate constant. (Ca2+ + Mg2+)-ATPase activity was decreased by 4:1, cholesterol/PC liposomes. The molar ratio of cholesterol/phospholipids in the cell membranes was directly proportional to that in liposomes. No change in phospholipid composition was noted. We suggest that the accumulation of intracellular calcium was a composite result due to the altering effect of inserted cholesterol on surface area, and to direct interactions between cholesterol and the proteins of the Ca2+ channel and (Ca2+ + Mg2+)-ATPase.

Animals↗
PubMed1991

Reduced absolute rate of myo-inositol biosynthesis of cultured bovine retinal capillary pericytes in high glucose.

De novo biosynthesis of myo-inositol (MI) by permeabilized cultured bovine retinal capillary pericytes (BRCP) and feline retinal pigment epithelial cells (FRPE), grown in different concentrations of glucose, were studied. After incubation with a physiological concentration of [14C]glucose 6-phosphate (G6P), the radioactive G6P derivatives were quantitated by a single HPLC column. Based on the determined specific activity of [14C]G6P, activities of inositol 1-phosphate synthase (MI synthase) were calculated. The activity of MI synthase was reduced 48% by growing BRCP in a high-glucose medium (20 mM) in comparison with that in the normal medium (glucose 5 mM). In contrast, the de novo MI biosynthesis by FRPE was not changed with increasing concentrations of glucose in the medium. As compared with MI uptake previously studied, the synthesized MI contributes a substantial proportion of cellular MI pool in BRCP. Therefore, in BRCP growing in high glucose the reduced MI biosynthesis aggravates the low MI content resulting from the inhibited MI uptake, and thus leads to altered inositol phospholipid metabolism.

Animals↗
PubMed1991

The effect of 25-hydroxycholesterol on accumulation of intracellular calcium.

Liposomes prepared with 25-hydroxycholesterol and egg phosphatidylcholine (PC) were incubated with bovine arterial smooth muscle cells for 8 h at 37 degrees C. Cells incubated in the absence of liposomes or with liposomes containing cholesterol and PC were used as controls. The results indicated that calcium accumulated in the smooth muscle cells incubated in the presence of 25-hydroxycholesterol containing liposomes in an amount proportional to the time of incubation. The calcium accumulation, as indicated by kinetic analysis, resulted from an increased compartment size. (Ca(2+)+Mg2+)-ATPase exhibited decreased activity after pretreatment with 25-hydroxycholesterol containing liposomes and the increased intracellular calcium content was directly proportional to the decreased (Ca(2+) + Mg2+)-ATPase activity. When lipids in the cell membrane were examined, a failure to change the cholesterol/phospholipids ratio in the membrane was noted. The 25-hydroxycholesterol content in the membrane determined by HPLC did not increase. An increase in sphingomyelin and a decrease in phosphatidylethanolamine and acidic phospholipids in the membrane was noted. We suggest that the accumulation of intracellular calcium comes from both an increase of calcium influx and a decrease of (Ca(2+) + Mg2+)-ATPase activity, which may be the consequence of changes in membrane phospholipid composition.

Animals↗
PubMed1991

The selectin GMP-140 binds to sialylated, fucosylated lactosaminoglycans on both myeloid and nonmyeloid cells.

Granule membrane protein-140 (GMP-140) is an inducible receptor for myeloid leukocytes on activated platelets and endothelium. Like other selectins, GMP-140 recognizes specific oligosaccharide ligands. However, prior data on the nature of these ligands are contradictory. We investigated the structural features required for ligand interaction with GMP-140 using purified GMP-140, cells naturally expressing specific oligosaccharides, and cells expressing cloned glycosyltransferases. Like the related selectin endothelial leukocyte adhesion molecule-1 (ELAM-1), GMP-140 recognizes alpha(2-3)sialylated, alpha(1-3)fucosylated lactosaminoglycans on both myeloid and nonmyeloid cells, including the sequence Neu5Ac alpha 2-3Gal beta 1-4(Fuc alpha 1-3)GlcNac beta-R (sialyl Lewis x). Recognition requires sialic acid, because cells expressing large amounts of Lewis x, but not sialyl Lewis x, do not interact with GMP-140. Although sialyl Lewis x is expressed by both myeloid HL-60 cells and CHO cells transfected with an alpha 1-3/4 fucosyltransferase, GMP-140 binds with significantly higher affinity to HL-60 cells. Thus, the sialyl Lewis x tetrasaccharide may require additional structural modifications or specific presentations in order for leukocytes in flowing blood to interact rapidly and with high affinity to GMP-140 on activated platelets or endothelium.

Amino Sugars↗
PubMed1991

A monoclonal antibody (SZ-53) against thrombomodulin inhibits thrombin-mediated release of t-PA and PGI2 from endothelial cells.

Monoclonal antibodies against thrombomodulin have become a useful means to study the structure and function of thrombomodulin. In this study, we used a monoclonal antibody against human thrombomodulin, named SZ-53, to investigate the function of thrombomodulin on the surface of cultured human umbilical vein endothelial cells. Preincubation of endothelial cells with SZ-53 before addition of thrombin not only inhibited thrombomodulin mediated activation of protein C, but also inhibited thrombin mediated release of t-PA and PGI2 from endothelial cells. The inhibitory effects depended on the concentration of SZ-53 IgG. According to our experimental results, we suggest that thrombomodulin on the surface of endothelial cells could participate in the regulation of thrombin mediated release of t-PA and PGI2 from these cells.

Antibodies, Monoclonal↗
PubMed1991

[Plasma PGI2 and TXA2 levels on a model of PDH in leptospirosis].

Guinea pigs were intravenously injected with icterhemorrhagiae serogroup Lai serovar strain 017 leptospirosis to model the pulmonary diffuse hemorrhage (PDH) in leptospirosis. Thirty-eight hours after the injection, the jugular arteries were catheterized to collect blood sample. The plasma was prepared for radioimmunoassay of TXB2 and 6-keto-PGF1a, the stable metabolites of TXA2 and PGI2 respectively. The plasma level of TXB2 in the experimental group, 107.15 +/- 41.65 pg/ml (n = 7), almost doubled that of the control, 54.05 +/- 12.93 pg/ml (n = 7), with significant difference (P less than 0.01); meanwhile, no significant difference was observed of 6-keto-PGF1a, 67.97 +/- 16.89 pg/ml (n = 6) vs. 98.06 +/- 40.63 pg/ml (n = 9) with P greater than 0.1. The fact that TXA2 causes vasoconstriction and increases vessel permeability suggests that TXA2 elevation should play a role in the mechanism of PDH in leptospirosis.

6-Ketoprostaglandin F1 alpha↗
PubMed1991

[Central norepinephrine and angiotensin II contents in the brain regions of spontaneously hypertensive rats (SHR) and the interaction between them].

The norepinephrine (NE) and angiotensin II (A II) contents in the brain regions of SHR and WKY (Wistar Kyoto) rats at different ages were determined by fluorospectrophotometry and radioimmunoassay. The systolic blood pressure (SBP) of the rats was measured indirectly with a tail cuff technique in conscious state. The results were as follows: There was no significant difference in the central A II and NE contents between SHR and WKY rats at 8-week age. Since 12th week age the SBP of SHR has increased gradually, up to 16th to 20th week and then maintained steady level. Whereas there was no significant change of SBP in WKY rats in the same span of age. In the early and late states of hypertension the A II contents in the medulla oblongata, pons, hypothalamus and nucleus caudatus of SHR were markedly higher than those of the age-matched WKY rats. But the change of NE content of SHR in the early stage showed a different picture as compared with that of WKY rats, i.e., NE decreased in medulla oblongata and anterior hypothalamus but increased in pons, posterior hypothalamus and nucleus caudatus. However, in the late stage there was no such significant difference between SHR and WKY rats. Consequently, it is suggested that the central A II and NE participated in the development of hypertension of SHR, and that the maintenance of hypertension is mainly dependent upon the increased A II content. Microinjection of captopril or 6-OHDA in the lateral cerebroventricle of SHR elicited a decrease of BP and reduction of both A II and NE contents in the medulla and hypothalamus.(ABSTRACT TRUNCATED AT 250 WORDS)

Angiotensin II↗
PubMed1991

Studies on breeding of antibiotic-producing strain 5102 by protoplast fusion. IV: Verification of fusant FR-008, and isolation and characterization of the new antimicrobial substance.

On the basis of the high performance liquid chromatography (HPLC) of Antibiotic 5102-1, the principal components of this antibiotic were isolated from the cultures of starting strain 10-22 and the fusant FR-008. The result further verified that FR-008 was a recombinant of intraspecific fusion of Streptomyces hygroscopicus subsp. yingchengensis. A new antimicrobial substance was isolated and purified from the fermented product of fusant FR-008, which could not be produced by the starting strain. The color reactions of the new substance with concentrated sulphuric acid or concentrated hydrochloric acid and the UV-VIS absorptions indicated that it was a haptene macrolide antibiotic. The liquid chromatography for aromatic moiety showed that this antibiotic contained p-amino-acetophenone moiety. The amino acid analysis of the antibiotic revealed that it contained an aminosugar moiety, which was different from that in any other haptene macrolide antibiotic. The detailed chemical structure of the aminosugar moiety has yet to be identified.

Anti-Bacterial Agents↗
PubMed1990

The S-type lectin from calf heart tissue binds selectively to the carbohydrate chains of laminin.

We report that the S-type lectin in calf heart tissue, termed calf heart agglutinin (CHA), binds to immobilized mouse laminin in ligand blotting and solid-phase radioligand binding assays. When compared with other glycoproteins, radioiodinated CHA binds preferentially to immobilized laminin. The binding is saturable with a Kd of 9.2 x 10(-7) M and is competitively inhibited by nonradiolabeled CHA as well as a similar lectin from porcine heart tissue. Both lactose and N-acetyllactosamine are good inhibitors of binding to laminin but binding is not inhibited by heparin. Exoglycosidase treatments demonstrated that the binding of radioiodinated CHA to laminin is not dependent on terminal sialyl-, fucosyl-, beta- or alpha-linked galactosyl residues, whereas treatment of laminin with endo-beta-galactosidase significantly decreases the lectin binding. Thus, CHA binds selectively to the poly-N-acetyllactosamine chains on complex-type Asn-linked oligosaccharides in laminin.

Animals↗
PubMed1990

Cloning of a transcriptionally active human TATA binding factor.

Transcription factor IID (TFIID) binds to the TATA box promoter element and regulates the expression of most eukaryotic genes transcribed by RNA polymerase II. Complementary DNA (cDNA) encoding a human TFIID protein has been cloned. The human TFIID polypeptide has 339 amino acids and a molecular size of 37,745 daltons. The carboxyl-terminal 181 amino acids of the human TFIID protein shares 80% identity with the TFIID protein from Saccharomyces cerevisiae. The amino terminus contains an unusual repeat of 38 consecutive glutamine residues and an X-Thr-Pro repeat. Expression of DNA in reticulocyte lysates or in Escherichia coli yielded a protein that was competent for both DNA binding and transcription activation.

Amino Acid Sequence↗
PubMed1990

[Measurement of left ventricular ejection fraction in myocardial infarction by 2-dimensional echocardiography--comparison with radionuclide angiography].

Left ventricular ejection fraction (LVEF) with 4 different algorithms (biplane and single-plane Simpson's rule and ellipsoid area-length method) was measured by 2-dimensional echocardiography (2 DE) in 42 patients with myocardial infarction (MI), and the results were compared with those with equilibrium radionuclide angiography (ERNA). The correlation coefficients were 0.98 for biplane Simpson's rule (apical 4 and 2 chamber view), 0.96 for biplane area-length method (apical 4 and 2 chamber view), 0.81 for single-plane Simpson's rule (apical 4 chamber view), and 0.77 for single-plane area-length method (apical 4 chamber view). The results indicated that biplane method is superior to single-plane method. Biplane area-length method is an alternative simple method for LVEF measurement in patients with MI.

Echocardiography↗
PubMed1990

Intramural pericyte degeneration in early diabetic retinopathy study in vitro.

An experimental model of diseased pericytes was established by using cultured bovine retinal capillary pericytes in high--glucose medium. The high glucose stimulated polyol pathway, reduced cellular myo-inositol content and disturbed inositol phospholipid metabolism which resulted in a decrease in inositol trisphosphate (IP3) level. The correlation of suppressed IP3 levels with reduced DNA synthesis was evident. These findings suggested the biochemical mechanism by which retinal pericytes degenerate in high glucose. To supplement myo--inositol and/or an aldose reductase inhibitor to the high--glucose medium largely reversed the suppressed IP3 level and the decreased DNA synthesis. Therefore, these two manipulations may be considered as in vitro therapy to treat sick pericytes induced by high glucose.

Animals↗
PubMed1990

[Preliminary studies on the relationship between the blood pressure and renin-angiotensin system in brain and blood vessels in SHRSP].

This work analyzed the relationship between A I concentration in aorta tissue and systolic blood pressure (SBP) in stroke-prone spontaneously hypertensive rats (SHRSP) at different ages. The SBP of SHRSP increased progressively with the age until the age of 20 weeks, when the SBP of SHRSP no longer elevated but sustained at a relatively high and stable level. The A I concentration in aorta of SHRSP was much higher than that of Wistar Kyoto rats at all of the three different ages. Perfusion of captopril into the lateral cerebroventricle of SHRSP for four weeks evoked a considerable decrease of A I concentration in brain as well as a significant reduction of SBP accompanied by a decrement of A I concentration in aorta and concentration of norepinephrine and epinephrine in aorta tissue and plasma. The results further confirm the close relationship between the changed activity of renin-angiotensin system localized in blood vessels during hypertension and the pathogenesis of hypertension, and indicate the possible regulative control of A I generated from central nervous system over the production of A I from blood vessels by means of facilitating the activity of peripheral sympathetic nerve system.

Angiotensin II↗
PubMed1990

[Effect of the overactivated central renin-angiotensin system on the concentration of brain norepinephrine and epinephrine in stroke-prone spontaneously hypertensive rats and its significances].

The content of norepinephrine (NE) and epinephrine (E) in the brain of spontaneously hypertensive rats has proved abnormal, but the cause remained unknown. It was shown in the recent work that NE content in pons, posterior hypothalamus, nucleus caudatus and E concentration in medulla oblongata, anterior and posterior hypothalamus of 12-week old stroke-prone spontaneously hypertensive rats (SHRSP) were much higher than those of age-matched Wister-Kyoto rats (WKY). SHRSP also showed higher levels of systolic blood pressure (SBP) and brain angiotensin II (A II) than WKY. Intracerebroventricular (icv) perfusion of angiotensin-converting enzyme inhibitor captopril (20 micrograms for each time and three times for each day for four weeks) inhibited the synthesis of brain A II and reduced SBP and NE, E contents in all examined brain areas in SHRSP and WKY. However, the effects of chronically perfused captopril on SBP and brain NE, E levels in SHRSP were much more significant than in WKY. The results indicate that the modulatory effects of central renin-angiotensin system (RAS) on central adrenergic and noradrenergic system might be overactivated in SHRSP, which might partially responsible for the abnormally high levels of NE, E in some of the brain areas of SHRSP.

Angiotensin II↗
PubMed1989

Characterization of an S-type lectin purified from porcine heart.

We have purified a carbohydrate-binding protein from porcine heart by affinity chromatography on asialofetuin-Sepharose and have characterized this protein with respect to its size, amino acid composition, partial amino acid sequence, and carbohydrate-binding specificity. Porcine heart lectin (PHL) has a subunit molecular mass of 14,700 and is immunologically cross-reactive with a polyclonal antibody raised against a lectin isolated from calf heart. The amino acid composition of PHL is similar to that of lectins that have been isolated from calf heart, bovine brain, and rat lung. Moreover, the primary sequences of four tryptic fragments (52 amino acids total) derived from PHL are closely related to sequences previously determined for 10 other vertebrate-derived lectins. The ability of PHL to agglutinate rabbit erythrocytes was inhibited only by oligosaccharides containing terminal beta-galactosyl residues. These data indicate that PHL is a vertebrate "S-type" lectin and provide further evidence that the structures and carbohydrate-binding specificities of these lectins are highly conserved across diverse vertebrate genera.

Amino Acid Sequence↗
PubMed1989

The entry of gossypol across the blood-testis barrier in rats.

This paper presents the experimental data about how different formulations of gossypol enter the blood-testis barrier following intravenous administration in acute experiments on rats. It was found that gossypol encapsulated by liposomes crossed the blood-testis barrier more readily than free gossypol, without affecting its pharmacokinetic pattern in the circulating blood, suggesting that liposomes may be useful as drug carriers and may facilitate the entry of encapsulated gossypol into the seminiferous tubule from the blood.

Animals↗