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Biomedical subjects

S M Jung

Publications and source records attributed to S M Jung.

At least 37 records · Page 2Linked to original sources
PubMed2000

Involvement of activated integrin alpha2beta1 in the firm adhesion of platelets onto a surface of immobilized collagen under flow conditions.

Recently, we demonstrated that agonist-induced activation of the platelet surface collagen-receptor integrin alpha1beta2 converts it to an active form that can bind soluble collagen with high affinity (Jung, SM, Moroi, M: J Biol Chem 1998; 273: 14827-37). Here, the involvement of alpha2beta1 activation and the high affinity binding property of activated alpha2beta1 in platelet adhesion to a collagen surface under flow conditions were analyzed. Platelet adhesion to immobilized collagen was measured in the presence of TS2/16, an activating anti-integrin alpha2beta1 antibody, and inhibiting antibodies, Gi9 and 6F1. TS2/16 decreased the moving velocity of platelets on the collagen surface, but Gi9 and 6F1 increased it, indicating that alpha2beta1 activation induces the tight binding of platelets to immobilized collagen under flow. Platelet adhesion, expressed as the surface area occupied by adhered platelets, in the presence of TS2/16 was similar to that in its absence. In contrast, adding Gi9 or 6F1 caused biphasic adhesion composed of a first phase, a lag phase whose length differed in each experiment, and a second phase adhesion with a rate similar to that of the control. This biphasic adhesion indicates that alpha2beta1 activity is inhibited and also suggests that some other factor(s) may contribute to the adhesion under flow. At concentrations where neither 6F1 nor Gi9 affected collagen-induced aggregation, these antibodies inhibited soluble collagen binding to thrombin-activated platelets. Only at much higher concentration did 6F1 inhibit collagen-induced aggregation. TS2/16 had no effect on the aggregation. The present results are evidence against the major involvement of integrin alpha2beta1 in platelet aggregation; instead, they indicate that integrin alpha2beta1 would be mainly associated with the tight binding of platelets to collagen.

Antibodies, Monoclonal↗
PubMed1998

Integrin-mediated platelet adhesion.

Adhesion of platelets to the damaged subendothelium is a prerequisite reaction for the initiation of hemostasis in vivo. Platelet membranes contain high concentrations of integrins and other glycoproteins (GPs) that are involved in the platelet adhesion to the extracellular matrix. In the present review, we focus on two platelet integrins, integrin alphaIIb beta3 (GPIIb/IIIa) and integrin alpha2 beta1 (GPIa/IIa) because these integrins are major components of the platelet membrane proteins and are known to contribute to platelet adhesion to fibrin(ogen) and collagen surfaces, respectively. These integrins bind soluble ligands (fibrinogen or collagen) after platelets are activated but only have low affinity towards these ligands when platelets are in the resting state. We describe the binding properties of these integrins and discuss the mechanism for the activation of these integrins. Platelets can adhere to fibrin(ogen) or collagen immobilized on a surface. When platelets adhere to a collagen- or fibrin-coated surface, they become activated and form aggregates; this is especially prominent under flow conditions. We discuss the contribution of these integrins and non-integrin proteins, GPIb and GPVI, to the platelet adhesion on to the collagen surface, especially under flow conditions, a system that most closely approximates platelet adhesion in vivo.

Animals↗
PubMed1998

Platelets interact with soluble and insoluble collagens through characteristically different reactions.

Platelet interaction with soluble and insoluble collagens was characterized through binding studies. In contrast to resting platelets, cells reacted with activators, TS2/16 (integrin alpha2 beta1-activating antibody), thrombin, collagen-related peptide, or ADP, exhibited specific soluble collagen binding that is Mg2+-dependent, but inhibited by prostaglandin I2, Ca2+, and Gi9 (anti-integrin alpha2 beta1 antibody). Each platelet has 1500-3500 soluble collagen binding sites, with a dissociation constant of 3. 5-9 x 10(-8) M. This is the first study to show the specific binding of soluble collagen to platelets; our data strongly suggest that the receptor is integrin alpha2 beta1 after it becomes activated upon platelet activation. These results suggest that activation of platelets transforms integrin alpha2 beta1 to a state with higher affinity binding sites for soluble collagen. The soluble collagen-platelet interaction was compared with the platelet interaction with fibrillar collagen, which has until now not been demonstrated to bind specifically to platelets. Here, we demonstrated specific, biphasic fibrillar collagen binding. One phase is rapid and metal ion-independent, and accounts for most of the binding. The other phase is slow and Mg2+-dependent. The characteristic differences in the specific bindings of soluble and fibrous collagens demonstrate the different contributions of two different collagen receptors.

Animals↗
PubMed1998

Induction of V3-specific cytotoxic T lymphocyte responses by HIV gag particles carrying multiple immunodominant V3 epitopes of gp120.

Effort to develop a vaccine to prevent infection of human immunodeficiency virus (HIV) have focused on the induction of neutralizing antibodies. In our previous study, we reported that chimeric gag-env virus-like particles (VLPs) induce neutralizing antibodies which block HIV infection. In addition to the neutralizing antibodies, the cytotoxic T-lymphocyte (CTL) response is considered to be another major immune defense mechanism required for recovery from many different viral infections. In the present study, we have constructed chimeric fusion proteins using HIV-2 gag precursor protein with (1) four neutralizing epitopes from HIV-1 gp160; (2) three tandem copies of consensus V3 domain, which have been derived from 245 different isolates of HIV-1 and carries both the principal neutralizing determinant (PND) and CTL epitopes; and (3) V3 domains from HIV-1IIIB, HIV-1MN, HIV-1RF, and HIV-1SF2. These chimeric fusion proteins were expressed in a large quantity within insect cells, and released as VLPs into the cell culture medium. The purified gag-env VLPs from all three constructs appear to be spherical particles similar to immature HIV but slightly larger than the gag VLPs. Immunoprecipitation analysis showed that the chimeric proteins were recognized not only by HIV-1 positive patient sera, but also by monoclonal and polyclonal antisera raised against V3 peptides of HIV-1IIIB, HIV-1MN, HIV-1RF, and the gp120 antiserum against HIV-1SF2. Balb/C mice immunized with these chimeric VLPs successfully induced CTL activity against V3 peptide-stimulated target cells. In addition, a high degree of cross-reactivity was observed among the four different strains of HIV-1 V3 domain, indicating that the tandem multiple consensus V3 peptide sequence carried by HIV-2 gag can be used as a potential HIV vaccine against various HIVs.

Animals↗
PubMed1998

Granulocytic sarcoma presenting as a giant breast tumor in a pregnant woman: a case report.

We report a case of granulocytic sarcoma (chloroma) presenting as a giant breast tumor in a pregnant woman with no history of leukemia. The case was initially diagnosed as medullary carcinoma on a biopsy specimen and a modified radical mastectomy was performed. The diagnosis of granulocytic sarcoma requires the pathologist's high index of suspicion. The presence of immature eosinophils was an important clue. Leder's chloroacetate esterase stain; immunostaining for myeloperoxidase, CD34, CD43, CD68, and lysozyme; and ultrastructural finding of cytoplasmic lysosomal granules and Auer bodies all aided in confirming the diagnosis. It is imperative to recognize granulocytic sarcoma to avoid unnecessary surgery. Granulocytic sarcoma should be included in the differential diagnosis of breast tumors, especially in tumors with diffuse proliferation of small tumor cells.

Adult↗
PubMed1997

Analysis of the involvement of the von Willebrand factor-glycoprotein Ib interaction in platelet adhesion to a collagen-coated surface under flow conditions.

The requisite initial reaction for in vivo thrombus formation in flowing blood is platelet adhesion to the exposed surface of the extracellular matrix. The contribution of von Willebrand factor (vWF ) in plasma and glycoprotein (GP) Ib on the platelet membrane to platelet adhesion has been well-documented. We have recently developed a procedure (the "flow adhesion assay") for measuring platelet adhesion under flow conditions that allowed us to characterize platelet adhesion to a collagen-coated surface. Here, we apply our method to analyze platelet adhesion to a vWF-coated surface to determine how this might differ from adhesion to a collagen-coated surface. Platelet adhesion to the vWF-coated surface was monitored as the linear increase in the area occupied by adherent platelets. The fluorescence image showed that platelets adhering to the vWF surface were mainly single platelets, and if any were present, the platelet aggregates were small, this being the primary difference from the adhesion to a collagen surface, where adherent platelets were mostly in aggregates. The flow adhesion assay detected the movement of platelets on the vWF surface, suggesting the reversible binding of vWF with platelets. The velocity of the platelets increased at higher shear rates or at lower vWF densities on the surface. Treatment of the vWF-coated surface with the aggregating agent botrocetin before initiation of blood flow increased platelet adhesion while dramatically decreasing the velocity of platelet movement. The present observations on the adhesion of platelets to the vWF-pretreated collagen surface and measurements of the velocity of platelets moving on the collagen surface suggest that the first interaction on the collagen-coated surface is the binding of vWF molecules to the collagen surface. This small number of vWF molecules would serve to attract and slow platelets flowing near the surface. This would facilitate the actual adhesion to the collagen surface that is mainly generated by the interaction between platelet collagen receptors, including GP Ia/IIa and GP VI, with collagen.

Adsorption↗
PubMed1997

Platelet receptors for collagen.

The interaction of platelets with collagen is a complex reaction because collagen monomer does not have any affinity to platelets, but collagen fibrils and immobilized collagen bind strongly to platelets. It was postulated that a platelet would have multiple binding sites for collagen that would encompass several collagen molecules polymerized to each other. The mechanism for how these collagen fibrils or immobilized collagen bind to and activate platelets is still unknown. Two platelet glycoproteins, GP Ia/IIa (integrin alpha 2 beta 1) and GP VI, fulfill the following requirements for a physiological collagen receptor: 1) antibodies against these proteins inhibit the platelet aggregation induced by collagen and platelet adhesion to collagen under both static and flow conditions, and 2) patients whose platelets are deficient in either GP Ia/IIa or GP VI have been found, and their platelets show no interaction with collagen. Under flow conditions, which closely approximate physiological conditions under which thrombus formation occurs, platelets interact with vWf molecules bound to immobilized collagen and then the adhered platelets would react with collagen through their collagen receptors, resulting in activation of the platelets and subsequent formation of platelet aggregates. Although the details of the interaction of GP Ia/IIa with collagen have been investigated in recent years, the mechanism of the reaction between GP VI and collagen remains to be explored.

Blood Platelets↗
PubMed1997

Cyclopia in one of discordant twins: a case report.

Cyclopia is an uncommon congenital anomaly resulting from arrest of the development of the anterior end of the neural plate. It is always associated with abnormalities of the brain. Cyclopia has never been reported in one twin only. In this report, we describe a case of cyclopia in a female infant with normal karyotype who was one of discordant twins. The infant died perinatally. The parents were healthy and not sanguineously related. Prenatal imaging studies revealed cyclopia, holoprosencephaly and hypognathia. Postmortem examinations revealed one orbit, one eyeball and absence of the nose. The central nervous system included rudimentary cerebral hemispheres with fusion of the two lateral ventricles and the third ventricle forming a single large cavity. The superior aspect of each cerebral hemisphere consisted of only a transparent membrane. The olfactory bulb nad tract was absent. The optic nerves were not identified.

Adult↗
PubMed1996

Analysis of platelet adhesion to a collagen-coated surface under flow conditions: the involvement of glycoprotein VI in the platelet adhesion.

Platelet adhesion to the exposed surface of the extracellular matrix in flowing blood is the first and critical reaction for in vivo thrombus formation. However, the mechanism of this in vivo platelet adhesion has yet to be studied extensively. One of the reasons for this is the lack of a practical assay method for assessing platelet adhesion under flow conditions. We have devised an assay method (the fluorescent adhesion assay) that is based on the technique originally reported by Hubbell and McIntire (Biomaterials 7:354, 1986) with some modifications to make it more amenable for assaying small samples and have developed an analysis method to quantify the extent of platelet adhesion and aggregation from fluorescence images by using a computer-assisted image analysis system. In our assay, platelet adhesion, expressed as the percentage of the area covered by adhered platelets, was found to increase biphasically as a function of time. In the first phase, platelets interacted with the coated collagen, transiently stopping on the surface; we called this reaction the temporary arrest. In the second phase, platelets adhered much more rapidly and permanently on the surface, and this adhesion was dependent on the shear rate; platelets formed aggregates in this phase. We used our assay to analyze the effects of platelet aggregation inhibitors on platelet adhesion. All three examined inhibitors, EDTA (10 mmol/L), antiglycoprotein (GP) IIb/IIIa, and GRGDS peptide (1 mmol/L), inhibited the second phase adhesion in flowing blood. Furthermore, GPVI-deficient platelets also showed defective second-phase adhesion under the same conditions. These results suggested that GPIIb/IIIa activation and GPVI contribute to the reaction inducing the second phase. The second-phase adhesion has been extensively investigated, and the consensus is that this reaction is mainly attributable to the platelet-platelet interaction. In this report, we were able to detect an earlier reaction, the temporary arrest. This temporary arrest would reflect the fast and weak interaction between platelet GPIb/IX and collagen-von Willebrand factor complexes on the collagen-coated surface.

Blood Platelets↗
PubMed1996

MRI in presumed cervical anterior spinal artery territory infarcts.

We report the MRI findings in two patients with presumed cervical spinal cord infarcts in the anterior spinal artery territory. MRI revealed abnormal signal intensities and/or band-like enhancement in the anterior two-thirds of the cervical spinal cord, corresponding to the vascular territory of the anterior spinal artery. Clinically there was an anterior spinal cord syndrome.

Aged↗
PubMed1993

Phorbol ester treatment of two megakaryoblastic cell lines, CMK and UT-7, induces specific protein composition changes with non-coincident time-courses.

The expressions of platelet-specific glycoprotein(GP)s Ib, IIb and IIIa were analyzed in 2 megakaryoblastic cell lines: CMK and UT-7. Phorbol-12 myristate 13-acetate (PMA) treatment of CMK induced expressions of GPs IIb and IIIa that peaked on the 4th day post-treatment, while treated UT-7 cells showed maximal levels of these GPs during the 6-8th days. Antibody staining to detect the formation of GPIb alpha after PMA induction showed the presence of the intact GP in UT-7 and the degraded form in CMK. In UT-7, synthesis of GPIIb mRNA increased on days 4-6 after PMA treatment, in parallel with the increase of GPIIb. PMA increased the cytoskeletal protein (actin and myosin) contents in both lines, but in contrast to the two GPs, the increase in these proteins started immediately after PMA addition to the cells. Cell surface proteins of CMK and UT-7 cells were rapidly modified after PMA induction. Especially notable were the degradations of 93-kDa and 140-kDa proteins that occurred on days 1-2 after PMA treatment. These studies demonstrate that the expression of platelet-specific proteins shows a different time dependency than the increment of cytoskeletal proteins, indicating that the syntheses of these two classes of proteins are most likely induced through different mechanisms.

Cell Differentiation↗
PubMed1992

Platelet adhesion to collagen-coated wells: analysis of this complex process and a comparison with the adhesion to matrigel-coated wells.

The mechanisms of platelet adhesion to collagen type III-coated wells and Matrigel-coated wells were analyzed. The adhesion of 51Cr-labeled platelets to collagen-coated wells showed a biphasic pattern. The early stage of adhesion was inhibited by antibodies against platelet glycoprotein(GP)s Ia/IIa and VI. The later stage of platelet adhesion was inhibited by an antibody against the GPIIb/IIIa complex and a concomitant release of 14C-labeled serotonin was observed. The percentage of adhered platelets was increased when a higher platelet concentration was added in the reaction medium. These results indicated that the adhesion assay of platelets to collagen-coated wells was composed of two reactions: the first one is the platelet-collagen interaction that depends on GPIa/IIa and GPVI on the platelet surface; and the second reaction is the platelet-platelet interaction, platelet aggregation, which depends on GPIIb/IIIa. The adhesion of platelets to Matrigel-coated wells was indicated to involve platelet-Matrigel interactions that were partly dependent on the laminin in the Matrigel solution.

Antibodies, Monoclonal↗
PubMed1992

Molecular basis for Glanzmann's thrombasthenia (GT) in a compound heterozygote with glycoprotein IIb gene: a proposal for the classification of GT based on the biosynthetic pathway of glycoprotein IIb-IIIa complex.

The genetic basis for Glanzmann's thrombasthenia (GT) was elucidated on a compound heterozygote with glycoprotein (GP)IIb gene: an opal mutation at the end of exon 17 (CGA----TGA) results in only a trace amount of GPIIb mRNA, and a splicing mutation at the acceptor site of exon 26 (CAG----GAG) causes an in-frame, exon skipping process from exon 25 to 27. This aberrant transcript encodes a single-chain polypeptide characterized by a 42-amino acid deletion, which includes the proteolytic cleavage site(s) and a unique, proline-rich region at the location corresponding to the carboxyl-terminal of the normal GPIIb alpha-chain. These characteristics are shared by a previously reported defective GPIIb molecule, which is neither assembled with GPIIIa nor transported to the cellular surface. Despite its normal transcription level, expression of the present defective GPIIb molecule was significantly decreased (approximately 6% of the control level). Because the precursor GPIIb molecule is assembled with GPIIIa in the endoplasmic reticulum (ER) and its processing, as well as stability, is dependent on the GPIIIa subunit, the defective GPIIb molecule may be rapidly degraded by the intrinsic quality control system of the ER due to its inability to form a stable heterodimer complex as a consequence of its misfolded structure. Although we did not confirm that the GPIIIa genes of this individual were normal, GPIIIa may be secondarily decreased (approximately 11% of control), because a large part of it could not be complexed, making it vulnerable to proteolysis. To elucidate the molecular basis for GT, we propose here a classification of GT based on the biosynthetic pathway of the GPIIb-IIIa complex.

Base Sequence↗
PubMed1992

[Platelet membrane glycoproteins and the molecular mechanisms of hereditary platelet dysfunction].

Glycoproteins, present on the outer surface of platelets, function in the aggregating and releasing reactions of these cells. Some of the hereditary diseases of platelet dysfunction, such as, thrombasthenia and Bernard-Soulier syndrome, have been shown to result from defects in some of these glycoproteins. Recent advances in molecular biology have enabled us to analyze the genes which encode the defective glycoproteins in these patients. The information from these studies also helps us to understand in detail the function of the glycoproteins. At present, the major glycoproteins, GP II b/IIIa and GP I b/IX, have been studied extensively and we know the details of the mechanisms through which they function. However, as to the minor glycoproteins, GP I a/II a, GP IV and GP VI, details remain to be elucidated.

Bernard-Soulier Syndrome↗
PubMed1991

Analysis of a variant form of platelet glycoprotein (GP) IIb: a second patient with abnormal molecular weight GPIIb.

In 1988, we reported a thrombasthenic patient whose platelets contained an abnormal molecular weight GPIIb (Blood, 71, 915, 1988). Here we describe another patient whose platelets contain a variant GPIIb with properties similar to the previously reported abnormal GPIIb. This patient has a small amount of the abnormal GPIIb and was suggested to be a heterozygote characterized by deficient and abnormal GPIIb genes. The abnormal GPIIb was suggested to be related to the precursor form of GPIIb because the molecular weights of both proteins are the same. The abnormal GPIIb may lack a peptide region around the cleavage site of the two chains, as suggested from its lack of reactivity towards antibodies against these epitopes.

Antibodies, Monoclonal↗
PubMed1989

A patient with platelets deficient in glycoprotein VI that lack both collagen-induced aggregation and adhesion.

Molecular level studies on platelets deficient in collagen-induced aggregation provide evidence for identifying possible platelet collagen receptors. We investigated platelets from a patient with mild bleeding time prolongation, but otherwise normal coagulation data. Her platelets lacked collagen-induced aggregation and adhesion, but retained normal aggregation and release by other agonists. Labeling her platelets with 125I or 3H and analysis by SDS-PAGE/autoradiography showed normal levels of glycoproteins Ia, Ib, IIa, IIb, IIIa, and IV. However, there were significantly decreased incorporations of both radioactivities into a 61-kD membrane glycoprotein (GP), which was identified as GPVI from its mobility on unreduced-reduced, two-dimensional SDS-PAGE. Sugiyama et al. (1987. Blood. 69: 1712) reported that the serum from an idiopathic thrombocytopenic purpura (ITP) patient contained an antibody against a 62-kD platelet protein. Our patient's platelets lacked the antigen for the ITP patient's antibody, demonstrating that the ITP serum contains a specific antibody against GPVI. The patient's parents' platelets contained approximately 50% the normal amount of GPVI, but still had normal collagen-induced aggregation and adhesion. The patient's platelets did not bind to types I and III collagen fibrils. Our results suggest that GPVI functions as a collagen receptor.

Adult↗