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Biomedical subjects

J Gu

Publications and source records attributed to J Gu.

At least 19 recordsLinked to original sources
PubMed1992

Total metabolic flow of glycosphingolipid biosynthesis is regulated by UDP-GlcNAc:lactosylceramide beta 1-->3N-acetylglucosaminyltransferase and CMP-NeuAc:lactosylceramide alpha 2-->3 sialyltransferase in human hematopoietic cell line HL-60 during differentiation.

We have previously reported that ganglioside GM3 was remarkably increased during monocytoid differentiation of human myelogenous leukemia cell line HL-60 cells and that neolacto series gangliosides (NeuAc-nLc) were enriched during granulocytoid differentiation. In addition, HL-60 was differentiated into monocytic lineage by exogenous GM3 and into granulocytoid by NeuAc-nLc. In the present report, the enzymatic bases of glycosphingolipid biosynthesis in HL-60 during differentiation induced by 12-O-tetradecanoylphorbol-13-acetate and all-trans-retinoic acid were investigated. The following results were of particular interest. (i) Lactosylceramide alpha 2-->3 sialyltransferase (GM3 synthase) was remarkably up-regulated during monocyte differentiation, while the GM3 synthase level did not change in granulocytic differentiation. (ii) By contrast, lactosylceramide beta 1-->3N-acetylglucosaminyltransferase (Lc3Cer synthase) was down-regulated during monocytic differentiation, while the activity of Lc3Cer synthase was found to increase in granulocytic differentiation. (iii) The activities of four downstream glycosyltransferases (for synthesis of NeuAc-nLc) were found to increase or to remain unchanged during monocytic and granulocytic differentiation. These results strongly suggested the following. The dramatic GM3 increase and the decrease of NeuAc-nLc during monocytic differentiation are the consequences of the up-regulation of GM3 synthase and the down-regulation of Lc3Cer synthase, although the downstream enzymes are ready to catalyze their enzyme reactions. The notable increase of NeuAc-nLc and the relative decrease of GM3 during granulocytic differentiation are the results of the unchanged level of GM3 synthase and the up-regulation of Lc3Cer synthase together with the activation of the downstream glycosyltransferases. These results suggest that these two key upstream glycosyltransferases, GM3 synthase and Lc3Cer synthase, play critical roles in regulating the glycosphingolipid biosynthesis in HL-60 cells during differentiation. This switching mechanism of these two glycosyltransferases, together with our previous findings, might be one of the most important parts of the determining system of differentiation direction in human myeloid cells into monocytic or granulocytic lineages.

Antibodies, Monoclonal↗
PubMed1992

Biosynthesis of blood group I and i antigens in rat tissues. Identification of a novel beta 1-6-N-acetylglucosaminyltransferase.

The beta-galactoside beta 1-6- and beta 1-3-N-acetylglucosaminyltransferases (beta 1-6GnT and beta 1-3GnT) that synthesize blood group I and i antigens were identified in rat tissues, using pyridylaminated lacto-N-neotetraose (Gal beta 1-4GlcNAc beta 1-3Gal beta 1-4Glc-PA) as an acceptor. The products of the transferase reactions were separated on high performance liquid chromatography. The products of the transferase reactions were identified by 1H NMR as (formula; see text) and GlcNAc beta 1-3Gal beta 1-4GlcNAc beta 1-3Gal beta 1-4Glc-PA. The product for beta 1-6GnT was also identified by methylation analysis. Kinetic experiments were carried out using rat serum for beta 1-3GnT and partially purified enzyme from rat intestine for beta 1-6GnT. beta 1-3GnT has a pH optimum of 7.5 and requires Mn2+ for optimal activity. beta 1-6GnT has a pH optimum of 7.0 and does not require Mn2+. Studies on the substrate specificity of each enzyme indicated that the preferred substrate for beta 1-3GnT had the general structure Gal beta 1-4GlcNAc-OR and, for beta 1-6GnT, Gal beta 1-4GlcNAc beta 1-3Gal-OR where R = sugar. This is the first demonstration that the beta 1-6GnT acts on an internal galactose of lacto-N-neotetraose and paragloboside, and the enzyme appears to be a novel enzyme in terms of substrate specificity.

Animals↗
PubMed1992

Deficiency of beta 1-6 N-acetylglucosaminyltransferase involved in the biosynthesis of blood group I antigen in the liver of LEC rats.

The activities of the beta 1-6 and beta 1-3 N-acetylglucosaminyltransferase, which synthesize blood group I and i antigens, respectively, were measured in various tissues of hepatitis- and hepatoma-predisposed rats (LEC rats). In LEC rats the beta 1-6 N-acetylglucosaminyltransferase activity was barely detectable in the liver, while substantial enzyme activity was found in other tissues. In the control LEA rats the enzyme was expressed in most tissues, including the liver. Immunochemical studies using a monoclonal antibody which recognizes I antigen indicated that the expression of I antigen was less prominent in hepatocytes of LEC rats than in hepatocytes of LEA rats. The level of beta 1-3 N-acetylglucosaminyltransferase activity was constant in most of the tissues during the development. These results indicate that the biosynthesis of I antigen does not occur in the livers of the LEC rats.

Aging↗
PubMed1992

Reticuloendotheliosis type C and primate type D oncoretroviruses are members of the same receptor interference group.

The reticuloendotheliosis viruses (REVs), originally isolated from avian species, constitute a group of retroviruses which are more closely related to mammalian retroviruses than to other avian retroviruses. The envelope glycoproteins of members of the REV group display a striking amino acid sequence identity with a group of primate oncoretroviruses which belong to a single receptor interference group and include all of the type D and some type C primate oncoretroviruses. Members of the REV group also have a broad host range which covers most avian cells and some mammalian cells, including those of simian and human origin. In view of this broad host range and the envelope sequence similarities, we investigated the cross-interference pattern between REV and primate virus groups to determine whether they utilized the same receptor. Superinfection experiments using a vector virus containing an Escherichia coli lacZ gene showed that reticuloendotheliosis and simian oncoretroviruses constitute a single receptor interference group on both human and canine cells and indicate that the viruses bind to the same receptor to initiate infection. These results suggest that this receptor binding specificity has been maintained over a wide range of retroviruses and may be responsible for the broad spread of these retroviruses between different orders of vertebrates.

Amino Acid Sequence↗
PubMed1992

Tumor necrosis factor mediates experimental pulmonary edema by ICAM-1 and CD18-dependent mechanisms.

(TNF alpha)-induced sequestration of neutrophils (PMN) in lungs and of the resultant PMN-dependent pulmonary edema. Guinea pig lungs perfused with Ringers-albumin were challenged with TNF alpha (1,000 U/ml) for 90 min, followed by addition of fresh perfusate containing 2 x 10(7) human PMN. TNF alpha challenge caused sequestration of PMN in the pulmonary vascular bed as indicated by a threefold increase in lung tissue myeloperoxidase activity (MPO). The activation of the sequestered PMN with phorbol 12-myristate 13-acetate (PMA; 5 x 10(-9) M) produced threefold increases in pulmonary artery (Ppa) and pulmonary capillary hydrostatic (Pcap) pressures, and twofold increases in lung wet-to-dry weight (W/D) ratio and capillary filtration coefficient (Kf,c) over baseline. TNF alpha prestimulation was required for these responses since activation of PMN with PMA in control lungs produced smaller increases in Ppa and Pcap (P less than 0.01) and did not change the W/D and Kf,c. TNF alpha prestimulation also induced the expression of intercellular adhesion molecule (ICAM-1) on pulmonary vascular endothelial cells. Monoclonal antibodies (mAbs) to the neutrophil CD18 integrin (beta-chain of CD11/CD18 complex) (mAb IB4) and to its endothelial cell ligand ICAM-1 (mAb RR1/1) were used to examine the role of PMN adhesion in the TNF alpha-induced responses. Pretreatment of PMN with mAb IB4 prevented PMN uptake and increases in Ppa, Pcap, Kf,c, and W/D ratio. Addition of mAb RR1/1 to the perfusate reduced PMN uptake by 58%, and prevented the increases in Ppa, Pcap, Kf,c, and W/D ratio, as with mAb IB4. The findings indicate that TNF alpha prestimulation of lungs mediates PMN uptake and that this requires the expression of ICAM-1 and its interaction with CD18 integrin on PMN. The activation of PMN sequestered by ICAM-1-dependent mechanism contributes to the development of pulmonary vascular injury and edema.

Animals↗
PubMed1992

Physical manipulation of subcutaneously implanted cardiac muscle in rat increased plasma atrial natriuretic peptide concentration.

UNLABELLED: To examine the effects of physical stretch on cardiac muscle endocrine activity, the authors transplanted whole neonatal hearts subcutaneously into the back and the ears of the correspondent mother (n = 9). Seven days later, physical manipulation was applied on the implanted heart by stretching the skin and the subcutaneous tissue encasing the implanted cardiac muscle, for a period of five to ten minutes. Such manipulation was repeated approximately every seven days postoperatively for a total of two to four times for each rat. The plasma atrial natriuretic peptide (ANP) levels were measured by radioimmunoassay prior to and immediately following manipulation. Postmanipulation plasma ANP levels were found to increase from the premanipulation levels. At two weeks postimplant, the average increase was 290% with the highest single-specimen increase being nearly twelvefold. The increases observed at two and three weeks following implantation had Signed Rank Test p values of 0.015 and 0.042 respectively. The viability of the implanted hearts was confirmed by cell culture. Light microscopic immunocytochemistry detected ANP immunoreactivity in the implanted cardiocytes. The elevated plasma ANP concentration induced by the manipulation appeared to be correlated with the functional status of the implanted cardiocytes. IN CONCLUSION: (1) Subcutaneously transplanted neonatal myocardiocytes survived for at least three to four weeks while retaining the ability to produce ANP. (2) Physical manipulation of implanted heart induced ANP release. Therefore, cardiac ANP production and release is indeed stimulated by physical stretching.

Animals↗
PubMed1992

Effect of adenosine triphosphate on the postischemic left ventricular function of the immature myocardium.

In this study, the effect of exogenous adenosine triphosphate (ATP) on the immature myocardium was evaluated. Isolated working neonatal rabbit hearts were perfused aerobically for 15 min with Krebs-Henseleit buffer (KHB) at 37 degrees C, and then arrested with St. Thomas solution (STS) in group 1 and STS containing 500 mumol/L of ATP in group 2 at 4 degrees to 6 degrees C and maintained at 10 degrees to 14 degrees C for 60 min. Hearts were reperfused with KHB aerobically at 37 degrees C for 15 min. Each heart served as its own control before and after arrest. Systolic function was significantly depressed in group 1 compared with group 2. There was a significant decrease in the peak left ventricular (LV) systolic pressure in group 1 (preischemia mean [PIM] 54 mm Hg to postischemia mean [PoIM] 42 mm Hg, Student's t test p = 0.007) than in group 2 (PIM 66 to PoIM 62 mm Hg, p = 0.5). The LV pulse pressure decreased in group 1 (PIM 72 to PoIM 54 mm Hg, p = 0.02) but not in group 2 (PIM 84 to PoIM 86 mm Hg, p = 0.9) and the rate of rise of LV pressure (dP/dT) in group 2 improved (PIM 5718 to PoIM 6926 mm Hg, p = 0.4) compared with group 1 (PIM 7021 to PoIM 4125 mm Hg, p = 0.008). The PoIM LV flow (LVF) was greater in group 2 than group 1 (LVF group 1 = 2.7 ml/min, group 2 = 4.5 ml/min). Diastolic pressures were not significantly different in the two groups. Our findings suggest that the incorporation of ATP in STS has a significant effect in improving postischemic LV systolic function in neonatal rabbit hearts.

Adenosine Triphosphate↗
PubMed1992

[Preliminary use of recombinant glycoprotein 52kd as an antigen in the diagnosis of human cytomegalovirus infection].

Interest in the human cytomegalovirus (HCMV) mainly derives from its associations with congenital malformations, mental retardation, and severe or fatal infections in immunosuppressed individuals such as transplant patients, tumor and AIDS patients. It is evidenced that there has been a need for a rapid and sensitive methods to detect an ongoing acute infection. The recent studies showed that high titers of antibody to the glycoprotein 52kd are present in sera of patients undergoing acute HCMV infection. However, purification of individual glycoprotein from HCMV-infected cells is a daunting prospect. HCMV glycoprotein 52 kd expressed via recombinant DNA techniques are a promising approach to solve this problem. In order to evaluate the diagnostic value of the recombinant glycoprotein 52 kd antigenic code region for HCMV infection, we have used the polymerase chain reaction (PCR) and recombinant DNA techniques to construct successfully the high-level expression plasmid pHCMV containing the HCMV GP-52 kd antigenic code region, with the predicted protein at levels up to 20% in total bacterial protein. The expressed protein was purified from SDS-PAGE, used as an antigen in Western-blot, and reacted with 12 cases of the positive sera, 4 cases of the negative sera, following by reaction with HRP-labelled horse IgG antibody against human. The results indicated that the approach we are using to detect antibody to HCMV acute infection are as sensitive as general serological methods such as ELISA, with the advantages of easy preparation of antigen with high quantity, and clinical practicability.

Antibodies, Viral↗
PubMed1992

Construction of an Rb gene expression plasmid.

We obtained an 844 bp Bg1II fragment from an Rb cDNA clone and inserted it into the expression vector pWR-13 to construct an Rb gene expression plasmid. When the Rb Bg1II fragment was fused in-frame into pWR-13, it was operated by a Lac Z promoter and produced a fusion protein which consisted of expressed Rb protein and a small peptide from Lac Z. The recombinants were transformed into E. coli with the CaCl2 method, screened by in situ hybridization, and restriction mapped. Total cellular protein of transformed clones was analyzed by SDS-PAGE and Commassie blue staining. The sense clones showed a unique band at 28,000. On Western blot, this band specifically reacted with 125I-labelled antibody against synthetic Rb peptide. This protein comprised more than 5% of total bacterial protein.

Amino Acid Sequence↗
PubMed1991

A new biological membrane for pericardial closure.

In an attempt to develop a new and better biological membrane for the pericardium, we evaluated the use of glutaraldehyde treated human amniotic membrane (AM) and compared it to polytetraflouroethylene (PTFE) membrane as a pericardial substitute. Four dogs underwent a right thoracotomy. Two 4 x 3-cm portions of pericardium, 3-4 cm apart, were excised in each animal and both sites replaced with a similar sized patch of 0.8% glutaraldehyde-treated AM and 0.2-mm PTFE membrane respectively. The AM was sutured to the pericardial defect with its smooth surface facing the epicardium. After 18 weeks, the materials were evaluated. The AM patches revealed minimal extrapericardial and no epicardial adhesion. The PTFE patches had moderate to severe epicardial adhesions and severe extrapericardial adhesions. Histopathological examination of AM patches revealed that the integrity of the AM was preserved, however, neovascularization and slight lymphocytic infiltration were observed. In the PTFE patches, there were severe inflammatory infiltration and fibroblast proliferation into both surfaces. AM patches by virtue of their low immunogenicity evoke very minimal host to graft reaction. These AM grafts, however, tear easily unless carefully sutured. Improved methods of treatment may improve suturing strength. We conclude that AM performs satisfactorily and is superior to PTFE as a pericardial substitute.

Amnion↗
PubMed1991

Determination of infundibular innervation and amine receptor content in cyanotic and acyanotic myocardium: relation to clinical events in tetralogy of Fallot.

Right ventricular myocardium was assessed for cholinergic and adrenergic innervation, as well as alpha-adrenergic, beta-adrenergic, and muscarinic receptors, in 18 cyanotic patients with tetralogy of Fallot (TOF) and four acyanotic control patients with ventricular septal defect, each of whom underwent a cardiac repair from June through December 1987. Neurons containing acetylcholine (ACH), neuron-specific enolase (NSE), S-100 protein, neuropeptide-Y (NPY), dopamine-beta-hydroxylase (DBH), and calcitonin gene-related polypeptide (CGRP) were detected surrounding arterioles and myocytes in all specimens. NSE and S-100 immunoreactivities were also identified in the cytoplasm of TOF cardiocytes, possibly indicating a neuroendocrine origin of these cells. Cardiocyte size was increased in TOF (p = 0.05). Acetylcholine (cholinergic) (p = 0.04) and CGRP (cholinergic) positive neurons (p = 0.07) were decreased in the TOF as compared to controls. Adrenergic fiber content (p = 0.15) and beta receptors (p = 0.21) were similar in both groups. There was an increase in muscarinic receptors in the controls (p = 0.002), and a marked increase in alpha receptors in TOF (p = 0.019). There were no intragroup differences in the TOF patients according to degree of cyanosis. In conclusion, there were important differences in neuronal and amine receptor content between TOF and control patients. Increased alpha receptors in TOF could account for differences in clinical and hemodynamic events.

Acetylcholine↗
PubMed1991

Detection of endothelin-like immunoreactivity in epithelium and fibroblasts of the human umbilical cord.

We studied tissue sections of freshly obtained full-term and premature human umbilical cords using polyclonal antibody to endothelin and immunocytochemistry. Endothelin immunoreactivity was detected in the cytoplasm of epithelial cells and primitive fibroblasts, but not in the endothelial cells of both full-term and premature umbilical cords. Immunoelectron microscopy using indirect immunogold staining technique localized endothelin immunoreactivity to the cytoplasm of the epithelial cells and fibroblasts but not confined to any particular structures. No endothelin immunoreactivity was detected in the nucleus or on the cell membrane. Pre-absorption tests with synthetic endothelin-1, -2, and -3 independently established that the immunoreactivity represented endothelin-1 and -2, but not -3. The presence of endothelin-1 and -2-like immunoreactive materials in epithelial cells and fibroblasts of human umbilical cord suggests a role of endothelin in parturition.

Cytoplasm↗
PubMed1991

A case of basophilic leukemia bearing simultaneous translocations t(8;21) and t(9;22).

We report a case of basophilic leukemia with simultaneous translocations of t(8;21) and t(9;22). The patient's clinical and hematologic findings were characteristic only of t(9;22) but not of t(8;21). This unusual cytogenetic phenomenon raises a challenge to the current concepts of primary chromosomal abnormalities in cancer.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1991

The cryopreserved stented pulmonary homograft valve in the tricuspid position.

This study was designed to evaluate the early phase events occurring in a stented pulmonary homograft valve implanted in the tricuspid position. A human pulmonary homograft was sterilized in antibiotic solution for 48 hours and cryopreserved in liquid nitrogen (-176 degrees C). Following thawing and trimming, the pulmonary valve was mounted on a Dacron cloth-covered Delrin stent and implanted into the tricuspid position in 3-month-old sheep, for a mean of 95 +/- 5 days. Seven animals were studied. Morphological assessment indicated good structural tissue preservation despite a decrease in viable fibroblasts noted in the distal part of the leaflets. The collagen fibers remained unchanged, and no tissue calcification was found. Viability of the mounted homograft was evaluated using an in vitro tissue culture method, and the viable cells underwent chromosomal analysis to identify whether they originated from the donor or host. Cells with 56 chromosomes, a number intrinsic to sheep cells, were cultured from the donor recipient junctional area. Hemodynamic and angiographic data, which were collected at the time of both implantation and explantation, revealed no functional deterioration of the implanted valve over 3 months. At the time of explantation, six of the seven valves were competent and no cusp retraction or thickening was noted. The seventh valve had deteriorated due to endocarditis. We conclude that stented cryopreserved pulmonary homografts may be useful as bioprostheses in the tricuspid position.

Animals↗
PubMed1991

Role of ICAM-1 in neutrophil-mediated lung vascular injury after occlusion and reperfusion.

We examined the role of intracellular adhesion molecule 1 (ICAM-1 or CD54) in the development of pulmonary edema in rabbits after pulmonary artery occlusion and reperfusion using a monoclonal antibody (MAb) RR1/1 directed against ICAM-1, a ligand for the CD18 leukocyte adhesion glycoprotein complex. A vascular clamp was placed around the left pulmonary artery for 24 h and then released to allow reperfusion for 2 h. Lungs subjected to 24 h of unilateral pulmonary artery occlusion showed increased binding of 125I-labeled RR1/1 and immunocytochemical evidence of ICAM-1 expression in pulmonary vascular endothelial cells compared with the contralateral lung. MAbs RR1/1 (0.5 mg/kg) or IB4 (1.0 mg/kg) (MAb directed against an epitope on the CD18 adhesion glycoprotein) was infused 45-60 min before the start of reperfusion to assess the roles of ICAM-1 and CD18 in the response. After reperfusion, the lungs were removed, suspended from one end of a weighing balance, and perfused with Ringer-albumin (0.5 g/100 ml), and the changes in lung weight were monitored for 60 min. Lung tissue myeloperoxidase (MPO) content (a marker of neutrophil sequestration) was determined after reperfusion. The increases in lung weight gain in the RR1/1- and IB4-treated groups of 960 +/- 100 and 865 +/- 110 mg, respectively, were less (P less than 0.05) than in untreated controls (3,550 +/- 725 mg).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Physical overdistension converts ventricular cardiomyocytes to acquire endocrine property and regulate ventricular atrial natriuretic peptide production.

Atrial natriuretic peptide (ANP) is present in adult atria but at very low concentrations in normal adult mammalian ventricles. In the atria, the production of ANP is regulated by physical distension of the atrial wall. The same phenomenon was investigated in the ventricles of rats and men. Cardiac tissues from human ventricular aneurysm (n = 5), spontaneously hypertensive rats (n = 30), and rats that had overloaded left ventricles induced by surgery (n = 84) were studied with the methods of light microscopic immunocytochemistry, electron microscopic immunogold staining, and RNA-RNA tissue in situ hybridization. It was found that the levels of ANP gene expression, ANP immunoreactivity, and ANP-containing specific granules in the overburdened ventricles were elevated and their degrees of fluctuation were directly proportional to the force of physical distension applied to the ventricular cardiomyocytes. In rats, ANP mRNA and ANP immunoreactivity returned to the control level seven days after the ventricular overload was surgically released. The changes of ANP and its mRNA in the ventricles were related more closely to the changes of intraventricular pressure than to cardiocytic hypertrophy. In addition, ANP immunoreactivity was demonstrated in Purkinje cells and periarteriolar cardiomyocytes in the ventricles of normotensive rats. In conclusion, physical overstretch of the ventricle wall is likely to be the triggering factor affecting ventricular cardiomyocytes to acquire endocrine property, and also to regulate the production of ventricular ANP, thereby contributing to the control of the blood volume and the blood pressure.

Animals↗