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Biomedical subjects

Y Z Cao

Publications and source records attributed to Y Z Cao.

At least 19 recordsLinked to original sources
PubMed2001

Increased 15-HPETE production decreases prostacyclin synthase activity during oxidant stress in aortic endothelial cells.

Selenium (Se) is an integral component of glutathione peroxidase and is able to detoxify peroxides that can affect arachidonic acid (AA) metabolism, thereby influencing eicosanoid biosynthesis. This study investigated the effects of oxidant stress, a consequence of Se deficiency, on eicosanoid formation and important key enzyme expression in bovine aortic endothelial cells (BAEC). Bovine aortic endothelial cells cultured in Se-deficient media and stimulated with tumor necrosis factor alpha or H2O2 produced significantly less prostacyclin (PGI(2)) and more 15-hydroxyeicosatetraenoic acid, 15-hydroperoxyeicosatetraenoic acid (15-HPETE), and thromboxane than Se-supplemented BAEC. Additionally, reverse transcription polymerase chain reaction and immunoblotting determined that the mRNA and protein levels of the eicosanoid forming enzymes cyclooxygenase-1 (COX1), cyclooxygenase-2 (COX2), and PGI synthase were not significantly changed. The addition of 15-HPETE to Se-supplemented BAEC inhibited the production of PGI(2) suggesting that the accumulation of lipid hydroperoxides during Se-deficiency may be the underlying factor in the altered eicosanoid production during Se deficiency. Furthermore, inhibition of COX and addition of PGH(2) to Se-deficient or Se-supplemented BAEC still resulted in lower PGI(2) formation by Se-deficient cells. Together, these results suggest that Se deficiency modifies eicosanoid production by affecting the activity of key enzymes, particularly PGI synthase, rather than their transcription or translation.

Animals↗
PubMed2000

Determination of clopidol residues in chicken tissues by high-performance liquid chromatography-mass spectrometry.

A high-performance liquid chromatographic-mass spectrometric (HPLC-MS) method has been developed for determination of clopidol residues in chicken tissues. Samples are extracted with acetonitrile. The extracts are cleaned up on an alumina column followed by an anion-exchange column. The clopidol is separated on a column (150 cmx4.6 mm) of Intertsil by using acetonitrile-water (20:80) as mobile phase. The clopidol was qualitatively identified by molecule mass and determined quantitatively by selected ion monitoring mode at 190 m/z. The recoveries with RSDs ranged from 91.6+/-10.1 to 97.3+/-5.7 at 0.010 to 10.0 mg/kg by spiking three matrices (chicken muscle, liver, and kidney). The limit of detection was 0.005 mg/kg, and the limit of quantification was 0.010 mg/kg.

Chromatography, High Pressure Liquid↗
PubMed2000

Altered eicosanoid biosynthesis in selenium-deficient endothelial cells.

Selenium (Se) is an integral part of the Se-dependent glutathione peroxidase (Se-GSH-Px) catalytic domain. By modulating the cellular levels of fatty acid hydroperoxides, Se-GSH-Px can influence key enzymes of arachidonic acid cascade, in this case cyclooxygenase (COX) and lipoxygenase (LOX). To investigate this phenomenon, the effects of cellular Se status on the enzymatic oxidation of arachidonic acid were investigated in bovine mammary endothelial cells (BMEC), which were cultured in either Se-deficient (-Se) or Se-adequate (+Se) media. When stimulated with calcium ionophore A23187, BMEC produced eicosanoids of both COX and LOX pathways. Compared with the Se-adequate cells, the production of prostaglandin I(2) (PGI(2)), prostaglandin F(2) (PGF(2alpha)), and prostaglandin E(2) (PGE(2)) was significantly decreased in Se-deficient cells, whereas the production of thromboxane A(2) (TXA(2)) was markedly increased in the -Se BMEC cultures. Although the enzymatic oxidation of arachidonic acid by the LOX pathway was found to be relatively less than by the COX pathway, the BMEC cultured in -Se media produced significantly more 15-hydroperoxyeicosatetraenoic acid (15-HPETE) than the +Se cells produced. Based on these results, we postulate that cellular Se status plays an important regulatory role in the enzymatic oxidation of arachidonic acid by the COX and LOX pathways. The altered eicosanoid biosynthesis, especially the overproduction of 15-HPETE, in -Se BMEC may be one of the underlying biochemical phenomena responsible for vascular dysfunction during Se deficiency.

Animals↗
PubMed2000

A PARAFAC algorithm using penalty diagonalization error (PDE) for three-way data array resolution.

A modified parallel factors analysis (PARAFAC) algorithm with the penalty diagnolization error (PDE) was developed. This algorithm can overcome the slow convergence problem of the traditional PARAFAC method and is insensitive to the number of components, i.e., it is much faster than PARAFAC and insensitive to overestimation of the dimensionality of the model. The characteristic performance was demonstrated by treating simulated and real excitation-emission fluorescence data for samples of naphthalene, 1-naphthol and 2-naphthol with satisfactory results.

Journal Article↗
PubMed1996

Evidence for G-protein-dependent and G-protein-independent activation of phospholipase D in lymphocytes.

Previously we reported that tumor-promoting phorbol esters stimulate phospholipase D (PLD) independent of protein kinase C (PKC) activation in bovine lymph node lymphocytes. (Cao et al., Biochem. Biophys. Res. Commun. 171, 955-962, 1990; 217, 908-915, 1995). In the present study, we examined the effects of prostagladins (PGs), E2, F2 alpha, D2, and H2 on PLD activity as measured by conversion of [1-14C] arachidonic acid-labeled phospholipids into phosphatidylethanol (PEt) in bovine lymph node lymphocytes. Prostaglandins stimulated the formation of PEt at an optimal concentration of 10 microM with relative stimulatory effect on the order of PGE2 > PGF2 alpha > PGH2 > PGD2. The PGE2-stimulated formation of PEt was dose-dependent in the range of 0.1 to 10 microM and was not inhibited by PKC inhibitors staurosporine and K252a. When both PGE2 and 12-0-tetradecanoylphorbol-13-acetate (TPA) were included, their effect on the PLD activation was additive. Furthermore, NaF, a G-protein activator, stimulated the PEt formation. Interestingly, the stimulatory effects of PGE2 and NaF were not additive; however, the formation of PEt by NaF and TPA was additive. These results suggest that similar to TPA, PGs increase PLD activity independent of PKC and the stimulation by PGs and TPA in lymphocytes may involve both G-protein-dependent and G-protein-independent signaling pathways.

Animals↗
PubMed1995

The mechanism of sphingosine enhancement of phorbol ester-mediated phospholipase D activation in lymphocytes.

Tumor-promoting phorbol esters stimulate the production of phosphatidylethanol (PEt) in bovine lymph node lymphocytes through the activation of Phospholipase D (PLD). Sphingosine enhanced the 12-O-tetradecanoylphorbol-13-acetate (TPA)-mediated formation of PEt in lymphocytes, while it had no effect by itself. Interestingly, the incorporation of labeled arachidonic acid into phospholipids was increased by sphingosine. Examination of the effect of sphingosine along with TPA on the incorporation of [1-14C]labeled-arachidonic acid into individual phospholipids revealed that they enhanced significantly the specific activity of only PC and lyso-PC fractions. These observations indicate that sphingosine does not activate PLD directly as TPA does. It appears that sphingosine increases the specific radioactivity of the substrate pool for PLD which results in an apparent increase in PEt when both sphingosine and TPA are present.

Animals↗
PubMed1992

Selenium deficiency alters the lipoxygenase pathway and mitogenic response in bovine lymphocytes.

We investigated the effect of altered selenium (Se) nutrition on arachidonic acid oxidation in immune cells. Experiments were conducted with peripheral blood lymphocytes obtained from dairy cattle fed diets either supplemented with or deficient in Se. The results indicate that the concanavalin A-stimulated lymphocyte proliferation was significantly lower in Se-deficient cows. When stimulated by calcium ionophore A23187, the lymphocytes derived from Se-deficient cows produced significantly less 5-hydroxyeicosatetraenoic acid (5-HETE) and leukotriene B4 (LTB4) than those obtained from Se-supplemented cows. When included in cell cultures from animals fed +Se diets, 5-HETE and LTB4 elicited a partial reversal of the inhibition of lymphocyte proliferation by either hydrocortisone or nordihydroguaiaretic acid. Based on this information, we postulate that dietary Se status, which in turn determines tissue Se concentration, plays an important role in the regulation of arachidonate metabolism by way of the 5-lipoxygenase pathway. This may be one of the biochemical mechanisms underlying the inhibition of lymphocyte proliferation and the decrease in resistance to infectious diseases observed in Se-deficient animals.

Animals↗
PubMed1992

Identification and quantitation of HIV-1 in the liver of patients with AIDS.

OBJECTIVE: To detect and quantify HIV-1 in the liver in vivo. DESIGN: Fourteen liver biopsy samples and corresponding blood lymphocytes and monocytes from patients with AIDS were studied for HIV-1 using quantitative polymerase chain reaction (PCR). In addition, expression of HIV-1 antigen and messenger (m) RNA in 10 autopsy liver specimens was examined by immunohistochemistry and in situ hybridization. RESULTS: The amount of HIV-1 DNA in nine liver samples ranged from 850 to 27,000 copies per 10(6) cells, with mean and median values of 8150 and 3500 copies per 10(6) cells, respectively. Five other samples had no detectable HIV-1 DNA by PCR. Intracellular expression of HIV-1 antigen and mRNA was also detected in both Kupffer cells and hepatocytes by in situ studies. CONCLUSION: These findings strongly indicate that HIV-1 could replicate in the liver of a majority of patients with AIDS.

Acquired Immunodeficiency Syndrome↗
PubMed1991

Increased 12-HETE production in bovine lymphocytes during selenium deficiency.

When peripheral blood lymphocytes were incubated with arachidonic acid in the presence of Ca++ ionophore (A23187), the cells from the selenium-deficient dairy cows produced significantly greater quantities of 12-hydroxyeicosatetraenoic acid (12-HETE) than the cells from the selenium-supplemented animals. The major product of reaction was verified as 12-HETE by cochromatography with a 12-HETE standard on an HPLC and structural analysis by GC-MS. Additionally, concanavalin A-stimulated lymphocyte proliferation was significantly decreased in cells from the Se-deficient cows. Furthermore, 12-HETE generated by the A23187-stimulated lymphocytes inhibited lymphocyte proliferation when added to Se-supplemented cell cultures. These observations suggest that self-regulation of lymphocyte proliferation might be mediated by 12-HETE production, especially during an altered nutritional state such as Se deficiency.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗
PubMed1991

Another discontinuous epitope on glycoprotein gp120 that is important in human immunodeficiency virus type 1 neutralization is identified by a monoclonal antibody.

To define the domains in the envelope glycoprotein important for antibody neutralization of the human immunodeficiency virus type 1 (HIV-1), monoclonal antibodies (mAbs) were generated by immunizing mice with purified glycoprotein gp120 of the IIIB isolate. One mAb, G3-4, reacted with the gp120 of homologous (IIIB) and heterologous (RF) isolates. In addition, mAb G3-4 efficiently neutralized both IIIB and RF viruses in vitro, as well as four of nine primary HIV-1 isolates. In competition immunoassays, mAb G3-4 and soluble CD4 were found to inhibit one another in binding to gp120. However, no competition was seen between mAb G3-4 and mAbs directed to the third variable region or the fourth conserved region of gp120. In particular, mAb G3-4 did not compete with our human mAb 15e, which identifies a discontinuous epitope on gp120 involved in group-specific neutralization of HIV-1 and in gp120-CD4 binding. Epitope-mapping studies on mAb G3-4 with synthetic or unglycosylated recombinant peptides were negative, suggesting that its epitope may be discontinuous. Indeed, this hypothesis was confirmed by showing the loss of mAb G3-4 serologic reactivity when gp120 was first denatured. We conclude that the site recognized by mAb G3-4 represents another discontinuous epitope on gp120 important for neutralization of HIV-1.

Animals↗
PubMed1990

Evidence for protein kinase C independent activation of phospholipase D by phorbol esters in lymphocytes.

Recently it was reported that tumor-promoting phorbol esters stimulate the production of phosphatidylethanol (PEt) in lymphocytes through the activation of phospholipase D (PLD). However, it remains unclear whether this activation is mediated through protein kinase (PKC). The study reported here shows that tumor promoters 12-0-tetradecanoylphorbol-13-acetate (TPA), phorbol dibutyrate (PDBU), 12-deoxyphorbol-13-phenylacetate (DOPP), 12-deoxyphorbol-13-phenylacetate-20-acetate (DOPPA) and mezerin activated PLD, as measured by the formation of PEt, whereas Concanavalin A (ConA) had no effect. Inhibitors of PKC, sphingosine (2 x 10(-6) M - 5 x 10(-6) M), H-7, HA1004 (5 x 10(-7) - 5 x 10(-6) M) and K252a (1 x 10(-7) - 1 x 10(-6) M) failed to block the PEt synthesis induced by TPA. In fact, sphingosine increased it. Other PKC activators, 1-oleoyl-2-acetylglycerol (OAG) and dioctanoylglycerol (DiC8) had no effect on lymphocyte PLD activity. Analysis of the phospholipid contents after stimulation by TPA showed that only phosphatidylcholine (PC) was significantly decreased. Interestingly, TPA activated PLD in intact cells but not in lysates or subcellular fractions. These observations suggest that stimulation of PLD-catalyzed PEt synthesis by TPA is not solely mediated through PKC activation.

Animals↗
PubMed1990

CD4-independent, productive human immunodeficiency virus type 1 infection of hepatoma cell lines in vitro.

Five hepatoma cell lines, including CZHC/8571, PLC/PRF/5, Hep3B, HepG2, and HUH7, were inoculated with three diverse isolates of human immunodeficiency virus type 1 (HIV-1). Productive infection was noted in all hepatoma cell lines, and expression of viral p24 antigen lasted for over 3 months, but its level decreased in proportion to the number of viable cells. HIV-1 antigens were also found in the cells by immunohistochemical staining and radioimmunoprecipitation assay, as were viral RNA by in situ hybridization and HIV-1-like particles by electron microscopy. Virus yield assays were also positive on supernatant fluids collected from hepatoma cultures inoculated with HIV-1. Despite their susceptibility to infection, all five hepatoma cell lines were negative for CD4 by immunofluorescence and for CD4 mRNA by slot-blot hybridization. In addition, HIV-1 infection of hepatoma cell lines was not blocked by anti-CD4 monoclonal antibody or soluble CD4. Together, these findings clearly demonstrate that all five hepatoma cell lines were susceptible to productive infection by HIV-1 in vitro via a CD4-independent mechanism.

CD4 Antigens↗
PubMed1990

HIV-1 neutralizing antibodies in urine from seropositive individuals.

HIV-1 neutralizing activity was demonstrated in serum and 200-fold concentrated urine from individuals who were HIV-1 antibody positive in both their serum and urine, including AIDS-KS, AIDS-OI, ARC, and asymptomatic patients. Virus neutralization activity was detected in 23 of 56 (41.1%) of the serum samples and in 19 of 56 (33.9%) of the urine samples tested, with titers ranging from 1:8 to 1:256 and 1:1 to 1:4, respectively. The highest frequency of HIV-1 neutralizing activity (87.5%) and the highest mean neutralization titers (1:65) were found in the ARC patients. A high prevalence of p24 antigen in serum and low numbers of T4-lymphocytes correlated with a low frequency of neutralizing activity in either serum or urine in the infected individuals. HIV-1 neutralizing activity in the urine was shown to be due to immunoglobulins using a Sephadex G-100 filtration gel. All 19 urine samples with neutralizing activity contained antibodies reactive with envelope glycoproteins gp160, gp120, and gp41 by Western blot, similar to that seen with serum. The frequency of HIV-1 neutralizing activity in the urine concentrates was generally associated with high titers of neutralizing antibody in the corresponding serum. These findings suggest that HIV-1 neutralizing antibodies are lost in the urine by an as yet unknown mechanism.

AIDS-Related Complex↗
PubMed1989

Megakaryocytes of human immunodeficiency virus-infected individuals express viral RNA.

The pathogenesis of thrombocytopenia associated with human immunodeficiency virus (HIV) infection is not fully understood. Immune mechanisms provide a partial explanation but fail to account for a lack of compensatory megakaryocytosis, the rapid reversal after treatment with azidothymidine, and the ultrastructural aberrations seen in the megakaryocytes of patients with acquired immunodeficiency syndrome. Therefore, a direct effect of HIV on megakaryocytes was investigated. The bone marrow of HIV seropositive individuals was analyzed ultrastructurally, and the megakaryocytes of 10 thrombocytopenic patients were subjected to in situ hybridization with a HIV RNA probe. The structural aberrations in HIV megakaryocytes were distinct from those in HIV-negative immune thrombocytopenias, and the megakaryocytes of 10 of 10 patients examined by in situ hybridization unambiguously expressed viral RNA. Therefore, it is likely that direct infection of megakaryocytes with HIV-1 is one mechanism for the decrease in platelet production.

Acquired Immunodeficiency Syndrome↗
PubMed1989

Antibodies to human immunodeficiency virus type 1 in the urine specimens of HIV-1-seropositive individuals.

Specific antibodies to human immunodeficiency virus type 1 (HIV-1) were detected in 200-fold concentrated urine samples, but none were detected in unconcentrated urine specimens, from 100 randomly selected HIV-1--seropositive individuals by enzyme-linked immunosorbent assay (ELISA) and Western blot techniques using the manufacturer's recommended procedures. Using modified methods for both the ELISA and Western blot tests, antibodies to HIV-1 have also been detected in the unconcentrated urine specimens from the same HIV-1--seropositive individuals. No difference in the frequency of antibodies to HIV-1 were found between unconcentrated and 200-fold concentrated urine samples when tested by the modified methods. HIV-1 core antigen (p24) was not detected in either the concentrated or the unconcentrated HIV-1--seropositive adult urine samples; none of these individuals showed overt clinical or laboratory evidence of renal dysfunction. The titer of the antibodies to HIV-1 found in the urine specimens was found to be parallel with the titer of antibodies to HIV-1 in the corresponding individual's serum. Further elucidation of the pathophysiology and the nature of the specific antibodies to HIV-1 observed in the urine of HIV-1--seropositive individuals is under investigation in our laboratories.

Adolescent↗
PubMed1987

The purification and characterization of a phospholipase A in hamster heart cytosol for the hydrolysis of phosphatidylcholine.

Phospholipases A1 and A2 catalyze the hydrolysis of acyl groups of phospholipids at C-1 and C-2, respectively. These phospholipases are important in phospholipid catabolism and the remodeling of the acyl groups of phospholipids. Phospholipase A from hamster heart cytosol was purified by a combination of ion-exchange and gel filtration chromatography. The purity of the enzyme was assessed by nondenaturing polyacrylamide gel electrophoresis, two-dimension polyacrylamide gel electrophoresis, and immunological studies. The purified enzyme exhibited both phospholipase A1 and A2 activities toward phosphatidylcholine and had the ability to hydrolyze the acyl groups of phosphatidylethanolamine. However, the enzyme was not active toward lysophosphatidylcholine, diacylglycerol, or triacylglycerol. By Sepharose 6B chromatography, the molecular weight of the purified enzyme was estimated to be 140,000. Analysis of the purified enzyme by sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed that the enzyme was composed of identical Mr 14,000 subunits. At least six subunits in the native enzyme could be cross-linked by dimethyl suberimidate. Both phospholipase A1 and A2 activities showed similar pH profiles, exhibited no absolute requirements for divalent metallic cations, but displayed a high degree of specificity for the acyl groups of phosphatidylcholine at both C-1 and C-2. The Km of phospholipases A1 and A2 for 1-palmitoyl-2-arachidon-ylglycerophosphocholine was found to be identical (0.5 mM).

Animals↗