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D Meyer

Publications and source records attributed to D Meyer.

At least 415 records · Page 23Linked to original sources
PubMed1988

Analysis of von Willebrand factor mRNA from the lung of pigs with severe von Willebrand disease by using a human cDNA probe.

To examine the control of porcine von Willebrand factor (vWF) biosynthesis we cloned human vWF complementary DNA (cDNA) and investigated the expression of the vWF gene in lungs from normal pigs and pigs with severe von Willebrand's disease (vWD). Recombinant clones spanning approximately 90% of human vWF cDNA were identified in a lambda gt10 human lung cDNA library by screening with oligonucleotides. One clone spanning nucleotides 960 to 3,240 of human vWF cDNA was used to investigate the steady-state levels of vWF mRNA in lungs from normal pigs and from pigs phenotypically determined to be homozygous for vWD. This clone hybridized with genomic DNA from pig leukocytes when Southern blots were processed under very stringent conditions; therefore, human cDNA clones were considered valid probes to detect porcine mRNA. Northern blot analysis of total RNA from normal pig lung and human umbilical vein endothelial cells identified the vWF mRNA as a molecular species of approximately 9.0 kilobases (kb). A very faint to undetectable band at 9.0 kb in total RNA from lungs of vWD pigs suggested a decreased rate of transcription of the vWF gene. Sucrose density gradient centrifugation of RNA from the vWD pigs confirmed by Northern analysis that the high-molecular weight fractions contained vWF mRNA and at the same size as normal pig mRNA. Dot blot hybridization analysis of vWF and actin mRNA processed under stringent conditions demonstrated that the relative ratio of vWF mRNA to actin mRNA in the vWD pigs varied from 21% to 41% of the ratio observed in normal pigs. Because the amount of vWF mRNA is not correlated to the amount of vWF activity or antigen in plasma of vWD pigs we conclude that posttranscriptional events are also probably involved in abnormal expression of vWF in these animals.

Animals↗
PubMed1987

Purification and further characterization of antithrombin III Milano: lack of reactivity with thrombin.

The functional abnormality of Antithrombin III "Milano", a previously described variant with monomeric and dimeric forms of abnormal AT III, has been further characterized. Affinity chromatography on heparin-Sepharose led to the separation and purification of two distinct fractions: fraction I is identical to normal AT III; fraction II (abnormal AT III) reproduces the abnormalities of the AT III "Milano", i.e. lack of thrombin inhibition, increased mobility by two-dimensional immunoelectrophoresis in the absence of heparin and migration as two bands with molecular weights of 60 K and 120 K by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). The interaction of both fractions with purified alpha-thrombin was studied by the formation of complexes as well as by affinity chromatography on thrombin-Sepharose. No thrombin-AT III complexes could be demonstrated with either the monomeric or dimeric forms of purified variant AT III at both concentrations of thrombin used. Similarly, no binding to thrombin-Sepharose was observed, thus indicating that the molecular defect of AT III Milano is related to its absence of reactivity with thrombin.

Antithrombin III↗
PubMed1987

Light-regulated methylation of chloroplast proteins.

Protein carboxyl methyltransferases, which catalyze transfer of methyl groups from S-adenosyl-L-methionine to the free carboxyl groups of acidic amino acids in proteins, can be divided into two classes based on several characteristics, such as the stoichiometry of substrate protein methylation, base stability of the incorporated methyl group, specificity for substrate, and participation in a regulatory system with which methylesterases are associated. The presence of such an enzyme in a photosynthetic system was demonstrated in the present work. The extent of methylation of chloroplast proteins was stimulated 30% by light and then decreased by the same amount in the presence of the electron transport inhibitor 3-(3',4'-dichlorophenyl)-1', 1'-dimethylurea or uncouplers of phosphorylation, indicating a dependence of the methyltransferase activity on photosynthetic electron transport and the trans-membrane delta pH. The light-independent, as well as the light-dependent, activity is probably of chloroplast origin since the extent of light stimulation in the purified thylakoid membranes and the stromal fraction was similar, and at low concentrations of S-adenosyl-L-methionine the small subunit of ribulose-1,5-bisphosphate carboxylase:oxygenase was found to be the predominant substrate. The labeling pattern of chloroplast proteins and labeling of an exogenous nonchloroplast protein indicated that the methyltransferase activity was not substrate-specific, although at low concentrations of the methyl donor, the small subunit of ribulose-1,5-bisphosphate carboxylase:oxygenase was labeled almost exclusively. Based on the low stoichiometry (less than 100 pmol/mg protein) of the methylation, its base lability, irreversibility, and the lack of substrate specificity except at very low concentrations of methyl donor, it was inferred that the chloroplast methyltransferase is best classified as a class II system that may function as part of a repair mechanism to replace racemized amino acids.

Chloroplasts↗
PubMed1987

Multicenter comparison of five functional and two immunological assays for protein C.

Five functional assays and two immunoassays for protein C (PC) were evaluated in parallel for the same plasma samples collected from healthy subjects, patients with congenital and acquired PC deficiencies or patients with conditions associated with high PC levels. For 7 patients starting warfarin therapy and for 15 patients during stabilized warfarin therapy, there were significant between-assay differences. For these groups immunoassays gave higher values than most functional assays and the latter also gave varied results, probably depending on their respective capacity for recognizing a carboxylated PC. On the other hand, there were no significant between-assay differences nor discrepancies between PC activity and antigen levels for healthy subjects (n = 39), patients with congenital PC deficiency (n = 10), myocardial infarction (n = 25), chronic liver disease (n = 19), disseminated intravascular coagulation (n = 35), in the post-operative period (n = 20) or in women taking oral contraceptives (n = 20). This comparison of PC assays indicates that PC levels measured by different functional or immunological assays are very close in the majority of clinical conditions, but not for patients on oral anticoagulants.

Blood Coagulation Tests↗
PubMed1987

Role of platelet membrane glycoproteins and von Willebrand factor in adhesion of platelets to subendothelium and collagen.

Development of in vitro perfusion systems and quantitative methods to evaluate various aspects of platelet-surface interactions have helped to elucidate some complex interactions in platelet adhesion and platelet-platelet cohesion. The importance of platelet GPs in these interactions was soon evident, and rapid progress in biochemistry and immunology has made it possible to study the roles of these GPs in more detail. From our studies, which made use of platelets with GP deficiencies, MAbs, purified vWF, proteolytic fragments of vWF, a synthetic peptide, and in vitro perfusion systems, it appeared that GPIb and GPIIb/IIIa function as receptors for vWF, which binds platelets to connective tissue at sites of vascular lesions (FIGURE 8). More detailed information about these interactions is expected in the near future when bioengineered products are available for testing in flow models and in other experimental approaches.

Antibodies, Monoclonal↗
PubMed1987

Cell cycle variations of dinucleoside polyphosphates in synchronized cultures of mammalian cells.

Zajdela hepatoma culture cells (ZHC) and mouse embryo fibroblasts (Swiss 3T3) were synchronized in G1 or S phase by serum deprivation and aphidicolin treatment, respectively, to study the variations in adenylyl nucleotide (Ap4X) pool size during the progress of the cell cycle. Only minor variations, which never exceeded a factor of 2, were observed when the Ap4X concentrations were expressed on a cellular basis. The variations were found to be strictly parallel to the ATP variations. Upon release from an aphidicolin block, the minor variations of Ap4X followed DNA synthesis and preceded cytokinesis. When the nucleotide content was compared with the amount of proteins, the faint specific cell cycle changes were almost completely damped when the cells were synchronized by serum deprivation, but remained practically unchanged in the case of aphidicolin synchronization. These results suggest that the observed variations could reflect the accumulation of some nucleotides before cell division. It is not clear yet whether the variation in Ap4X concentration is significant by itself or is simply a phenomenon resulting from changes in the ATP pool.

Adenine Nucleotides↗
PubMed1987

Post-irradiation leiomyosarcoma. Case report with immunohistochemical studies.

We report here one case of post-irradiation leiomyosarcoma. The diagnosis of this was confirmed using anti-intermediate filament antibodies: tumor cells were positive for anti-vimentin and anti-desmin but negative for anti-prekeratin and anti-epithelial membrane antigen. The positive staining with anti-desmin clearly indicates a muscular origin although the tumor cells were not stained by two anti-actin antibodies, one directed against alpha-smooth muscle actin and the other against alpha-striated muscle actin. Irradiation was motivated by a wrong diagnosis of breast carcinoma when the patient was 13 year-old. The laps of time separating irradiation and the occurrence of the leiomyosarcoma was 13 years. The total dose was 6,000 rads. This is the ninth case of post-irradiation leiomyosarcomas reported in the literature.

Actin Cytoskeleton↗
PubMed1987

Localization of a collagen-interactive domain of human von Willebrand factor between amino acid residues Gly 911 and Glu 1,365.

A collagen-binding domain of von Willebrand factor (vWF) has been identified in the central part of the molecule by comparing the binding properties of vWF and Staphylococcus aureus V-8 protease-generated vWF fragments with collagen. The binding of purified human vWF to human type III collagen was found to be specific. At saturation, 38 to 50.2 micrograms of vWF bound per milligram of collagen. Scatchard plots derived from binding isotherms demonstrated the presence of at least two classes of binding sites. Purified vWF was digested with S aureus V-8 protease into two complementary fragments (SpIII and SpII). SpII, the C-terminal end of vWF (amino acid residues 1,366 to 2,050), was totally devoid of affinity for collagen. Contrarily, purified SpIII, the N-terminal part of vWF (residues 1 to 1,365), totally displaced vWF binding and specifically bound to collagen. At saturation, 25 to 45 micrograms of SpIII bound per milligram of collagen. Scatchard plots demonstrated the presence of a single class of binding sites. SpIII was further digested with the same enzyme to generate SpI, a 52-kilodalton fragment from the C-terminal part of SpIII (residues 911 to 1,365). Spl induced a dose-dependent inhibition of both vWF and SpIII binding to collagen. A series of six monoclonal antibodies against SpIII that completely abolished vWF and SpIII interaction with collagen also bound to SpI. In conclusion, SpI extending between amino acid residues 911 and 1,365 of vWF contains a specific site that interacts with human type III collagen.

Antibodies, Monoclonal↗
PubMed1987

Localization of a factor VIII binding domain on a 34 kilodalton fragment of the N-terminal portion of von Willebrand factor.

Factor VIII (F.VIII) was tested for its ability to bind in solid phase system to von Willebrand Factor (vWF) or fragments obtained with Staphylococcus aureus V-8 protease, ie, SpIII (N-terminal), SpI (central), and SpII (C-terminal). Bound F.VIII was estimated in situ by clotting and chromogenic assays. F.VIII bound in a dose-dependent manner to immobilized vWF and SpIII but not to SpII or SpI. Binding was inhibited by 0.25 mol/L CaCl2 as well as by an excess of vWF or SpIII. Accordingly, immobilized F.VIII specifically bound 125I-vWF and SpIII but not SpII or SpI. Twelve monoclonal antibodies (MoAbs) directed towards SpIII, specifically blocking binding of F.VIII to vWF or SpIII, were used for the mapping of plasmic or tryptic fragments of vWF or SpIII. We thus established that a F.VIII binding domain of vWF is located on a 34 kilodalton (kd) fragment of the N-terminal portion of vWF, between residues 1 and 910, and that it is distinct from the GPIb and collagen binding domains.

Antibodies, Monoclonal↗
PubMed1987

Binding of human von Willebrand factor to collagen and to collagen-stimulated platelets.

Binding of von Willebrand factor (vWF) to collagen and to "collagen-stimulated platelets" was studied. Purified human iodine 125-labeled vWF binds to collagen. Binding was rapid, dependent on collagen and vWF concentration, independent of divalent ion concentration, and inhibited by unlabeled vWF as well as by high concentrations of fibronectin and fibrinogen. It was blocked by six monoclonal antibodies (MAbs) to human vWF (B200 through B205). Conversely, binding of 125I-vWF to platelets in the presence of collagen (collagen-treated platelets) was time dependent, saturable, and dependent on collagen, vWF, and divalent ion concentration. It was also inhibited by unlabeled vWF, fibronectin, or fibrinogen as well as by MAbs to vWF B200 through B205. In addition, binding of vWF to collagen-treated platelets was blocked by MAb to vWF 9 previously shown to inhibit binding of vWF to glycoprotein (GP) IIb-IIIa as well as by a MAb to GPIIb-IIIa. This binding was also strikingly decreased with use of patient platelets deficient in either GPIIb-IIIa or GPIa, whereas it was normal in the presence of a MAb to GPIb or when testing patient platelets deficient in GPIb. In conclusion, binding of vWF to platelets in the presence of collagen appeared to be a three-step phenomenon, including: binding of vWF to collagen; interaction of collagen with its receptor on the platelet membrane (GPIa ?), leading to activation of platelets and exposure of GPIIb-IIIa; and binding of vWF to GPIIb-IIIa.

Antibodies, Monoclonal↗
PubMed1987

Platelet von Willebrand factor: evidence for its involvement in platelet adhesion to collagen.

Although it is well established that plasma von Willebrand Factor (vWF) is essential to platelet adhesion to subendothelium at high shear rates, the role of platelet vWF is less clear. We studied the respective role of both plasma and platelet vWF in mediating platelet adhesion to fibrillar collagen in a parallel-plate perfusion chamber. Reconstituted blood containing RBCs, various mixtures of labeled washed platelets and plasma from controls or five patients with severe von Willebrand disease (vWD), was perfused through the chamber for five minutes at a shear rate of 1,600 s-1. Platelet-collagen interactions were estimated by counting the radioactivity in deposited platelets and by quantitative morphometry. When the perfusate consisted of normal platelets suspended in normal plasma, platelet deposition on the collagen was 24.7 +/- 3.6 X 10(6)/cm2 (mean +/- SEM, n = 6). Significantly less deposition (16 +/- 2.3) was observed when vWD platelets were substituted for normal platelets. In mixtures containing vWD plasma, significantly greater deposition (9 +/- 2.2) was obtained with normal than with vWD platelets (1 +/- 0.4) demonstrating a role for platelet vWF in mediating the deposition of platelets on collagen. Morphometric analysis confirmed these data. Our findings indicate that platelet, as well as plasma, vWF mediates platelet-collagen interactions at a high shear rate.

Antibodies, Monoclonal↗
PubMed1987

Treat or refer: patients' interest in family physician involvement in their psychosocial problems.

Seven hundred fifteen patients entering three family practice clinics (rural private practice, urban private practice, urban residency) completed a questionnaire assessing their interest in their family physicians' involvement in four representative psychosocial problems: spouse abuse or neglect, lack of exercise, a dying family member, and a sexual problem. A majority of the patients (57 to 78 percent) wanted help for the four problems from their family physicians either independently or in conjunction with a specialist, whereas only 4 to 21 percent wanted referral to specialists exclusively. Desired level of family physician involvement was predicted (R2 = .291) by a series of reason for involvement variables representing the following conceptual areas: perception of value in talking about personal problems; perception of family physician background, time, and interest; and the Health Belief Model. This study supports the conclusion that family physicians need skills in managing psychosocial problems so they can provide the type of care that most patients want.

Adult↗
PubMed1986

An enzyme immunoassay (ELISA) for the quantitation of human factor VII.

A new solid phase enzyme-linked immunosorbent assay (ELISA) was developed for the quantitation of human Factor VII antigen (F VII Ag), using a monospecific rabbit anti-F VII antiserum. Anti-F VII F(ab')2 fragments were adsorbed to polystyrene plates. The binding of serial dilutions of control or test plasma, containing F VII, was detected by incubation with peroxidase-labeled anti- FV II IgG followed by the addition of hydrogen peroxyde and O-phenylenediamine. This ELISA is specific, sensitive (detection limit: 0.05%) and accurate (coefficient of variation: 1.5-4% for within- and 1.6-9% for between-assays). F VII coagulant activity (F VII C) and F VII C) and F VII Ag were determined in large populations of controls and patients. In normal plasma (n = 38), F VII Ag ranged from 83 to 117% and the correlation coefficient between F VII Ag and F VII C was 0.94. In patients with severe (F VII C inf. 1%) congenital F VII deficiency (n = 5), F VII Ag was undetectable in two cases (inf. 0.05%) and markedly reduced (0.35 to 5.6%) in the three other cases. In patients with liver cirrhosis (n = 15), F VII Ag ranged from 21% to 59% and was in good correlation with F VII C (r = 0.84). In dicoumarol treated patients (n = 15), the levels of F VII Ag ranged from 51% to 79% and a poor correlation (r = 0.52) with F VII C was observed.(ABSTRACT TRUNCATED AT 250 WORDS)

Antibody Specificity↗