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Biomedical subjects

T N Vlasik

Publications and source records attributed to T N Vlasik.

At least 19 recordsLinked to original sources
PubMed2005

Phospholipid hydrolysis with phospholipases A2 and C impairs apolipoprotein B-100 conformation on the surface of low density lipoproteins by reducing their association resistance.

Modification of apolipoprotein B-100 conformation on the surface of LDL isolated from human blood was demonstrated by enzyme immunoassay with a panel of monoclonal antibodies to this protein. The study by the light transmission fluctuation method showed that incubation of LDL with phospholipases A2 or C led to association of LDL particles. This lipolytic modification seems to impair LDL surface properties inducing association of these particles, which can play an important role in lipid accumulation in the vascular wall and at early stages promote the development of atherosclerosis.

Apolipoprotein B-100↗
PubMed2005

Proteolysis of apoprotein B-100 impairs its topography on LDL surface and reduces LDL association resistance.

Serine proteinases (trypsin and chymotrypsin) cause destruction of apolipoprotein B-100 on the surface of human blood LDL. Incubation of LDL with these enzymes increases the mean size of LDL particles. Proteolysis of apolipoprotein B-100 induces changes in surface structure, destabilizes LDL particles, and reduces their association resistance. Presumably, this proteolytic modification of LDL with subsequent association of these particles plays an important role in accumulation of cholesterol in the vascular wall and in the development of early stages of atherosclerosis.

Agglutinins↗
PubMed2005

Cloning and characterization of the human FCRL2 gene.

We report cloning and characterization of FCRL2, a novel human gene that belongs to the FcR family. The gene is closely linked and structurally similar to the recently identified FCRL/FREB/FcRX gene. The encoded protein is composed of three Ig-like domains and a C-terminal mucin-like domain containing a conserved alpha-helical motif with dileucine signals. Intraexonic splicing may generate two alternative transcripts, coding for isoforms with the third and fourth domains replaced by entirely different amino acid sequences. Like FCRL, the full-length isoform of FCRL2 is expressed intracellularly in transfected 293T cells. Expression analysis revealed FCRL2 mRNA only in placenta. The gene transcripts were not detected in lymphoid tissues or in the main leukocyte subsets isolated from peripheral blood. However, we found that FCRL2 is differentially expressed by transformed B cell lines. Of interest is also the finding that the gene expression may be up-regulated in the progression of melanocytic tumors.

Alternative Splicing↗
PubMed2005

[Results of clinical trials of a novel glycoprotein IIb-IIIa antagonist framon in high-risk coronary angioplasty].

New glycoprotein (GP) IIb-IIIa antagonist preparation framon (Monafram), is the F(ab')(2) fragment of a monoclonal antibody FRaMon directed against GP IIb-IIIa. This preparation blocks GP IIb-IIIa binding with fibrinogen and inhibits platelet aggregation both in vitro and upon intravenous administration. Safety and ability of framon to prevent thrombotic complications in high risk coronary angioplasty (CA) was evaluated in the present study. FRAMON was injected intravenously into 153 patients just before the start of procedure as a single bolus at the dose of 0.25 mg/kg. Control group was formed of 126 patients who underwent angioplasty without GP IIb-IIIa blockers. After framon administration there were no allergic reactions or major bleedings, deep thrombocytopenia (< 50000/microl) developed in 1 patient (< 1%), and antibodies against framon were detected in less than 5% of patients. Number of unfavorable outcomes (cardiovascular death, myocardial infarction, angina recurrence) within 1 month after CA was 3 times higher in control group than in the group of patients treated with framon (11.4% and 3.3%, respectively, p = 0.018). The effect of framon was most strongly pronounced within the first day after procedure -- administration of the drug reduced number of acute thromboses from 6.5% to 0.7% (p = 0.013). Significant differences between numbers of end points was still preserved at 6 months after procedure (25.7 and 14.2% in control and framon groups, respectively, p = 0.023). The data obtained proved safety and clinical efficacy of framon administration in coronary angioplasty with high risk of thrombotic complications.

Angioplasty, Balloon, Coronary↗
PubMed2004

Antigenic differences between apo-B in native and circulating modified low-density lipoproteins.

The state of apo-B in native and circulating modified low-density lipoproteins was studied by solid-phase enzyme immunoassay. We studied the interaction of these particles with monoclonal antibodies to apo-B of low-density lipoproteins. Native and circulating modified low-density lipoproteins had different affinity for the studied antigens. Our results illustrate conformational changes in apo-B of circulating modified low-density lipoproteins compared to native low-density lipoproteins. These changes probably contribute to increased accumulation of particles in vascular cells and their transformation into foam cells giving way to atherosclerotic vascular lesions.

Antibodies, Monoclonal↗
PubMed2004

Development of antibody to human GM3 synthase and immunodetection of the enzyme in human tissues.

Polyclonal antibody was raised to a cloned fragment of human GM3 synthase. Affinity purified R27C1 antibody to the tagged recombinant protein inhibited GM3 synthase activity in human liver and HL-60 cells in a dose-dependent manner. However, the R27C1 antibody did not affect liver sialyltransferase activity towards asialofetuin. We are the first to measure GM3 synthase activity in human liver (194 +/- 60 pmol NeuAc/h per mg protein), which was about 10-fold lower than in phorbol myristate acetate-stimulated HL-60 cells (1353 +/- 573 pmol NeuAc/h per mg protein). On immunoblotting the R27C1 antibody recognized a common protein band in a number of human tissues (liver, brain, atherosclerotic aortic intima, HL-60 cells) with molecular mass of about 60 kD, which is similar to that of the purified GM3 synthase from rat liver. In human liver and aortic intima, the 60-kD band was almost a single band, which makes possible the use of the R27C1 antibody for immunohistochemical studies in these tissues.

Animals↗
PubMed2004

[Antiplatelet effects of glycoproteins IIb-IIIa antagonist monafram].

First Russian glycoprotein (GP) IIb-IIIa antagonist, preparation Monafram, is the F(ab')2 fragment of anti-GP IIb-IIIa monoclonal antibody FRaMon. In in vitro experiments it was shown that Monafram blocked platelet aggregation induced by ADP and thrombin; reduced secretion from platelet granules; and due to simultaneous interaction with two GP IIb-IIIa molecules almost irreversibly bound to platelet surface. Monafram clinical trials were performed in healthy volunteers (n = 10) and in patients with ischemic heart disease undergoing high risk coronary angioplasty (n = 153). Monafram intravenous bolus administration at 0.25 mg/kg decreased ADP-induced platelet aggregation by more than 90, 80, 60 and 30% at 1, 12, 24 and 72 h after injection, respectively. No significant differences were detected between antiaggregatory effects of Monafram and ReoPro introduced at 0.25 mg/kg bolus + 12 h infusion at 0.125 microg/kg per min. Durable inhibition of aggregation after Monafram administration was mediated by platelet-bound preparation--free Monafram was cleared from plasma within 12 h, while platelet-bound preparation occupied more than 90, 70-80 and 40-50% of GP IIb-IIIa at 1, 12-24 and 72 h after injection, respectively. Major bleedings and allergic reactions were detected in none of patients, deep thrombocytopenia--in one patient and antibodies against Monafram--in 5% of patients. Within one month after coronary angioplasty Monafram decreased the number of end points (fatal and nonfatal myocardial infarction and angina recurrence) from 11.4 to 3.3%.

Antibodies, Monoclonal↗
PubMed2003

[Use of polymerase chain reaction for determining T-cell clonality].

AIM: To distinguish T-cell lymphomas and reactive T-cell proliferation it is important to confirm the ability of T-cells to be cloned. Conventional histological and immunophenotypic methods fail to determine the ability of T-cells to be cloned. An experience in the use of detection of T-cell receptor gene gamma-chain (TCRy) rearrangement for determining T-cellular clonality is described. MATERIAL AND METHODS: Polymerase chain reaction (PCR) and single strand conformational polymorphism (SSCP) were used to determine T-cell clonality. Twenty healthy donors, 28 patients with T-lymphomas, and 26 patients with various non-T-cell lymphoproliferative disorders or reactive processes were studied. RESULTS: T-cell monoclonality was detected in 23/28 (82%) T-cell lymphoma cases, whereas in all the samples from normal subjects a polyclonal pattern of rearrangements TCRy was found. The sensitivity of the method was estimated as 2.5%, 7%, and 10% was demonstrated for bone marrow, spleen, and peripheral blood, respectively. CONCLUSION: PCR-SSCP for TCRy was found to be a useful supplement to routine histological and immunophenotypic methods in the diagnosis of T-cell lymphomas.

Clone Cells↗
PubMed2002

Safety, inhibition of platelet aggregation and pharmacokinetics of Fab'2 fragments of the anti-glycoprotein IIb-IIIa monoclonal antibody FRaMon in high-risk coronary angioplasty.

The purpose of the study was to evaluate safety, effects on platelet aggregation and pharmacokinetics of F(ab')(2) fragments of anti-glycoprotein (GP) IIb-IIIa murine monoclonal antibody FRaMon (F(ab')(2) FRaMon) upon its intravenous administration in patients undergoing high-risk coronary angioplasty. Patients were treated before angioplasty with F(ab')(2) FRaMon at 0.2 mg/kg (n = 17) and 0.25 mg/kg (n = 12) bolus or with abciximab at 0.25 mg/kg bolus + 12 h infusion at 0.125 microg/kg per min (n = 29). F(ab')(2) FRaMon at both doses decreased platelet aggregation induced by 20 microM ADP to <10, <20, <40 and <70% of the predrug level at 1, 12, 24 and 72 h after injection, respectively. No significant differences were observed between F(ab')(2) FRaMon and abciximab antiaggregatory effects. In none of the patients did F(ab')(2) FRaMon cause allergic reactions, major bleedings or deep thrombocytopenia. Antibodies against F(ab')(2) FRaMon were detected in one patient. Free F(ab')(2) FRaMon was cleared from plasma within 12 h, while platelet-bound preparation occupied >95, 70-80 and 40-50% of GP IIb-IIIa at 1 and 12-24 h and 3 days after injection, respectively. Thrombotic complications within the first month after angioplasty in groups treated with F(ab')(2) FRaMon and abciximab were observed in one and two patients, respectively. The data obtained have shown that F(ab')(2) FRaMon at bolus administration to patients undergoing coronary angioplasty caused no serious side effects and at comparative dosage inhibited platelet aggregation with the same efficacy as abciximab at bolus + infusion administration.

Abciximab↗
PubMed2002

[Pharmacodynamics, safety, and clinical effects of a novel glycoprotein IIb/IIIa antagonist framon during high risk coronary angioplasty].

Preparation framon [F(ab')2 fragments of the anti-glycoprotein (GP) IIb/IIIa monoclonal antibody (FRaMon)] blocks fibrinogen binding to GP IIb/IIIa and platelet aggregation. Dynamics of platelet aggregation inhibition, safety, and clinical effects of framon were studied in high-risk coronary angioplasty. Twenty seven patients underwent angioplasty with framon, 29 - with abciximab and 28 - with no GP IIb/IIIa antagonists. Framon at 0.2 mg/kg (n=16) and 0.25 mg/kg (n=11) bolus administration inhibited platelet aggregation induced by 20 mcM ADP by more than 90%, 80%, 60% and 30% in comparison with the predrug level 1, 12, 24 and 72 h after injection, respectively. Almost the same dynamics of aggregation inhibition was observed upon abciximab administration at 0.25 mg/kg bolus + 0.125 mcg/kg/min infusion for 12 h. No signs of individual intolerance and side effects including allergic reactions and bleedings were detected in patients treated with framon. Slight decrease of platelet count (15-20%) was observed on the first day after framon administration. Antibodies against framon were detected in 1 out of 22 tested patients. Free (nonbound to platelets) framon was completely removed from the circulation 12 h after injection. The number of endpoints (death, myocardial infarction and indications for repeat revascularization) within 1 year after angioplasty was approximately the same in the groups with framon and abciximab - 7 of 25 (28%) and 7 of 28 (25%), respectively, and more than 1.5 fold higher in the group without GP IIb/IIIa blockers - 12 of 27 (44,4%).

Angioplasty, Balloon, Coronary↗
PubMed2001

[Inhibition of thrombocyte aggregation by F(ab')2-fragments of monoclonal antibodies FraMon (CRC64) to glycoproteins IIb-IIIa].

AIM: To study the effects of F(ab')2 fragments of the monoclonal antibody (monAB) FRaMon against glycoproteins (GP) IIb-IIIa on platelet aggregating activity in vitro and after injection to healthy volunteers. MATERIAL AND METHODS: In vitro experiments were performed to study effects of F(ab')2 and Fab fragments of FRaMon on platelet aggregation (PA) and 14C-serotonin secretion and characteristics of 125I-labelled F(ab')2 and Fab FRaMon binding to platelets. In vivo effects of F(ab')2 FRaMon (preparation FRAMON) were studied upon its bolus i.v. injection to 10 healthy volunteers at the doses of 0.025-0.2 mg/kg. PA was registered before and 1, 6, 12, 24 hours and 3 and 12-15 days after FRAMON injection. FRAMON binding to platelets in the vascular bed was evaluated by inhibition of 125I-FRAMON in vitro binding to platelets obtained from volunteers. Development of antibodies against FRAMON was evaluated by ELISA two weeks after FRAMON injection. RESULTS: In vitro F(ab')2 FRaMon completely blocked PA induced by ADP and thrombin at the concentrations < 4 and < 7.5 mcg/ml, respectively, and revealed higher inhibitory capacity than Fab FRaMon. F(ab')2 FRamon also inhibited 14C-serotonin secretion from ADP-activated platelets. F(ab')2 FRamon interacted with two GP IIb-IIIa molecules on one platelet and bound to platelets more tightly than Fab FRaMon. F(ab')2 FRaMon (preparation FRAMON) bolus i.v. injection to healthy volunteers at the doses of 0.025-0.2 mg/kg did not induce any signs of individual intolerance, including allergic reactions, bleeding and thrombocytopenia. FRAMON at 0.2 mg/kg almost completely inhibited ADP-induced PA of volunteer's platelets 1 h after injection and by more than 70% at 12 h and by more than 50% at 24 h after injection. PA ability recovered to normal 3 days after injection. Antibodies against FRAMON were detected in 1 out of 10 volunteers. CONCLUSION: F(ab')2 fragments of monAB FRaMon effectively inhibited aggregating ability both in vitro and after injection to healthy volunteers and could be suggested as a basis for development of a new GP IIb-IIIa antagonist.

Animals↗
PubMed1999

Identification of 130 kDa cell surface LDL-binding protein from smooth muscle cells as a partially processed T-cadherin precursor.

Atypical cell surface lipoprotein-binding proteins of 105 kDa and 130 kDa are present in membranes of vascular smooth muscle cells. We recently identified the 105 kDa protein from human aortic media as T-cadherin, an unusual glycosylphosphatidylinositol (GPI)-anchored member of the cadherin family of cell adhesion proteins. The goal of the present study was to determine the identity of 130 kDa lipoprotein-binding protein of smooth muscle cells. We applied different approaches that included protein sequencing of purified protein from human aortic media, the use of human T-cadherin peptide-specific antisera, and enzymatic treatment of cultured cells with trypsin and GPI-specific phospholipase C. Our results indicate that the 130 kDa protein is a partially processed form of T-cadherin which is attached to the membrane surface of smooth muscle cells via a GPI anchor and contains uncleaved N-terminal propeptide sequence. Our data disclose that, in contrast to classical cadherins, T-cadherin is expressed on the cell surface in both its precursor (130 kDa) and mature (105 kDa) forms.

Aorta↗
PubMed1998

Immunoreactivity of apolipoprotein B-100 and binding to LDL-receptor of phospholipase A2-treated low density lipoproteins.

Lipid--protein particles were obtained by treatment of low density lipoproteins (LDL) with phospholipase A2 from bee venom. Under these conditions, half of the phosphatidylcholine (PC) of LDL was changed to lysophosphatidylcholine (LPC). At the same time, the composition of other lipids and the apoprotein structure were unaffected. Three monoclonal antibodies (MAbs) against various apo B epitopes were used to test immunoreactivity of phospholipase A2-treated LDL (pl-LDL). The apo B epitope interacting with MAb 4C11 (amino acid residues 2377-2658) showed significantly decreased immunoreactivity. Increase in MAb 4C11 binding was demonstrated to depend on oxidation degree of LDL. Thus, changing of half of PC to LPC modified apo B translocation in the lipoprotein globule in an opposite manner as compared with changes induced by oxidative modification. A minor increase in immunoreactivity of pl-LDL with 1D1 MAb against a large middle part of apo B (residues 1297-3249) may be due to the effect of the change of surface lipid composition on the extent of immersion of apo B into the hydrophobic phase. No changes in the interaction of pl-LDL with MAb 2G8 (residues 3748-4306) were observed in comparison with native LDL. This fact demonstrates that 50% phospholipolysis of LDL does not affect the expression of apo B C-terminal residues in pl-LDL. Twofold increase in pl-LDL affinity to immobilized LDL-receptor was shown in contrast to LDL. The data indicate that LPC accumulation in LDL results in better elimination of LDL from the blood stream than in case of accumulation of oxidative products.

Antibodies, Monoclonal↗
PubMed1996

Monoclonal antibody directed to a fibrinogen A alpha #529-539 epitope inhibits alpha-chain crosslinking by transglutaminases.

A monoclonal antibody (5A2) recognizing a segment near the C-terminus of the fibrin(ogen) A alpha-chain (A alpha #529-539) was found to inhibit alpha-chain crosslinking catalyzed by coagulation factor XIIIa and by tissue-transglutaminase. The rapid gamma-chain cross-linking by factor XIIIa was not affected by the antibody. Results obtained from direct binding and competitive immunoassay established that the antigenic determinant recognized by 5A2 was included within the CNBr fragment referred to as CNBr X (A alpha #518-584), and that it survived trypsin digestion but was destroyed by treatment with Staph V-8 protease or chymotrypsin. Reverse-phase (C-18) high performance liquid chromatography (HPLC) was employed to obtain a CNBr X tryptic fingerprint, which was subsequently characterized by compositional and NH2-terminal analysis. Assay of the HPLC column effluent revealed a single peak of 5A2 immunoreactivity that coincided with elution of the eleven-residue tryptic peptide, A alpha #529-539. When this isolated peptide and its parent CNBr fragment were employed as solution phase competitors in the 5A2 immunoassay, the relative cross-reactivities (18.3%, peptide: fragment) indicated that a significant proportion of the 5A2 epitope was preserved within the small peptide. This is a region that is released from fibrinogen early in its degradation by plasmin. Thus, the antibody can be used as a probe for intact fibrin(ogen) and C-terminal (A) alpha-chain fragments, in addition to assessing roles of the A alpha-chain C-terminus in cross-linking.

Animals↗
PubMed1993

Detection of an epitope specific for the dissociated form of glycoprotein IIIa of platelet membrane glycoprotein IIb-IIIa complex and its expression on the surface of adherent platelets.

Glycoproteins (GPs) IIb and IIIa form a Ca(2+)-dependent complex in platelet membrane and change their conformation upon platelet activation and dissociation of the complex. A new anti-GPIIIa monoclonal antibody (mAb), CRC54, is described which could distinguish different conformational states of GPIIIa. This antibody (i) precipitated GPIIb-IIIa from platelet Triton X-100-lysate, (ii) recognized the GPIIIa band in Western blotting of platelet SDS-lysate, and (iii) did not react with platelets from a Glanzmann's thrombasthenia patient lacking GPIIb-IIIa. Immunoblotting of chymotryptic digestion products of purified GPIIb-IIIa has shown that CRC54 epitope is located within residues 1-100 at the N-terminus of GPIIIa. CRC54 bound weakly to platelets in the presence of Ca2+ and Mg2+, 2.34 +/- 0.28 x 10(3) molecules per platelet at saturation. The same level of binding was observed without any divalent cations in the medium. However, binding of CRC54 was increased by several times after treatment of platelets with EDTA, 10.04 +/- 0.28 x 10(3) molecules per platelet. Increase of CRC54 binding correlated with the dissociation of GPIIb-IIIa complex which was followed by the decrease of the binding of another mAb, CRC64, directed against complex-specific epitope of GPIIb-IIIa. Binding of CRC54 to platelets was changed neither by platelet activation in suspension with thrombin or ADP nor by the occupancy of GPIIb-IIIa ligand binding site with GRGDSR peptide. However, binding was significantly stimulated by platelet adhesion to polystyrene plastic. As measured using 51Cr-labelled platelets, binding of 125I-CRC54 to adherent platelets in the presence of divalent cations was about 4 times higher than to platelets in suspension, 8.68 +/- 0.48 x 10(3) per platelet. This increase was not due to the dissociation of GPIIb-IIIa since complex-specific antibody CRC64 still bound effectively to the surface of adherent platelets. The data obtained indicated that: (1) CRC54 recognized an epitope specific for the dissociated form of GPIIIa; (2) the CRC54-reactive epitope of GPIIIa is also expressed on the surface of adherent platelets.

Antibodies, Monoclonal↗