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Biomedical subjects

R Bach

Publications and source records attributed to R Bach.

At least 73 records · Page 4Linked to original sources
PubMed1989

[Hemodilution in patients with multiple morbidity and peripheral arterial occlusive disease].

The treatment of multi-morbid patients suffering from peripheral arterial occlusive disease (PAOD) is rendered difficult due to concomitant diseases such as coronary heart disease, chronic obstructive pulmonary affection, arterial hypertension or diabetes mellitus. Haemodilution can be a clinically efficient therapy for some of the concomitant diseases as well. It is, however, necessary to use a weak colloidal solution which has no additional volume effect as an iso-oncotic substance. Hydroxyethyl starch 200/0.5 6% meets all these demands. In a double-blind, placebo-controlled study over a period of 6 weeks a marked and significant increase of almost 40% in painfree walking distance was achieved for 19 of 37 multi-morbid patients with PAOD II by moderate hypervolaemic haemodilution with venesections. Besides the clinical improvement, blood fluidity also increased through a reduction in haematocrit, plasma viscosity, and erythrocyte aggregation.

Adult↗
PubMed1989

Tissue factor gene expression in acute myeloblastic leukemia.

We have studied tissue factor gene expression in the leukocytes of 22 patients with acute myeloblastic leukemia (AML). Total RNA from peripheral blood or bone marrow cells depleted of monocytes was analyzed by Northern blot analysis using a 32P-labeled tissue factor cDNA probe. Cells from 10 cases expressed tissue factor mRNA and positive cases were distributed among the myeloblastic, myelomonocytic, and monocytic subtypes of AML. Tissue factor transcripts were not detected in cells derived from normal bone marrow. The expression of this gene product on the surface of leukemic cells could contribute to the excessive thrombin generation that has been observed in some individuals with this disorder.

Blood Coagulation Factors↗
PubMed1989

Enhanced responsiveness of endothelium in the growing/motile state to tumor necrosis factor/cachectin.

Some in vivo observations have suggested that growing or perturbed endothelium, such as that which occurs during angiogenesis, is more sensitive to the action of cytokines (TNF/cachectin, TNF, or IL-1) than normal quiescent endothelial cells. This led us to examine the responsiveness of endothelium to TNF as a function of the growth/motile state of the cell. TNF-induced modulation of endothelial cell surface coagulant function was half-maximal at a concentration of approximately 0.1 nM in subconfluent cultures, whereas 1-2 nM was required for the same effect in postconfluent cultures. Perturbation of endothelial cell shape/cytoskeleton was similarly more sensitive to TNF in subconfluent cultures. Consistent with these results, radioligand binding studies demonstrated high affinity TNF binding sites, Kd approximately 0.1 nM on subconfluent cultures, whereas only lower affinity sites (Kd approximately 1.8 nM) were detected on postconfluent cultures. The mechanisms underlying this change in the affinity of endothelium for TNF were studied in four settings. Crosslinking experiments with 125I-TNF and endothelium showed additional bands corresponding to Mr approximately 66,000 and approximately 84,000 with subconfluent cultures that were not observed with postconfluent cultures. Experiments with X-irradiated endothelium, whose growth but not motility was blocked, indicated that proliferation was not required for induction of high affinity TNF sites. Postconfluent endothelium, triggered to enter the proliferative cycle by microbutuble poisons, expressed high affinity TNF binding sites together with changes in cell shape/cytoskeleton well before their entry into S phase. Using wounded postconfluent monolayers, cells that migrated into the wound and those close to the wound edge displayed enhanced TNF binding and modulation of coagulant properties. These results suggest a model for targetting TNF action within the vasculature; regulation of high affinity endothelial cell binding sites can direct TNF to activated cells in particular parts of the vascular tree.

Animals↗
PubMed1989

Tumor necrosis factor enhances expression of tissue factor mRNA in endothelial cells.

We have examined the effect of recombinant tumor necrosis factor on the expression of tissue factor activity and tissue factor mRNA levels in vascular endothelial cells. Following exposure of human umbilical vein endothelial cells to this cytokine, the appearance of tissue factor procoagulant activity was detected following cell disruption, and was maximal at 6 hours. Northern blot analysis of cytokine-treated cells demonstrated a similar increase in the synthesis of tissue factor mRNA, followed by a gradual decline to the basal level by 18 hours. Cycloheximide by itself induced the accumulation of high levels of tissue factor mRNA in these cells. This result suggests that the proteins necessary for transcription of the tissue factor gene are present in the endothelial cell prior to cytokine stimulation, and synthesis of the tissue factor mRNA may be controlled, in part, by a labile repressor protein.

Cells, Cultured↗
PubMed1989

Serum stimulation of quiescent human fibroblasts induces the synthesis of tissue factor mRNA followed by the appearance of tissue factor antigen and procoagulant activity.

Expression of the gene for tissue factor, the cell-surface initiator of blood coagulation, was examined by stimulating growth-arrested human fibroblasts with serum and measuring changes in the cellular content of tissue factor mRNA, antigen, and activity. Maximum tissue factor mRNA levels were reached within 1 h following serum induction and slowly declined to basal levels from 24 to 48 h after stimulation. The appearance of the tissue factor mRNA was followed by an increase in tissue factor antigen and activity. The parallel rise in antigenically positive protein and procoagulant activity was first observed about 2 h after serum stimulation with a peak at 12 h followed by a slow decline during the next 36 h. The serum-induced synthesis of the tissue factor mRNA was independent of de novo protein synthesis as demonstrated by the increased tissue factor mRNA levels generated in the presence of cycloheximide. The results of this study suggest that the synthesis of tissue factor in human fibroblasts is regulated principally at the level of transcription. In one strain of fibroblasts the activity/antigen ratio, during the period of maximum synthesis, was indistinguishable from that of tissue factor which had been immunoaffinity purified from human brain and reconstituted into phospholipid vesicles. However, during serum starvation the activity/antigen ratio in these cells was significantly reduced. Western blot analysis revealed that in serum-starved cells there was an accumulation of truncated forms of the tissue factor antigen while in the serum-stimulated cells only the full-length antigen was observed.

Blood↗
PubMed1989

Multiple cutaneous myxomas coinciding with repeated cardiac myxomas. A syndrome.

We report on a 31-year-old woman who underwent surgery for two metachronous cardiac myxomas - 7 and 9 years after excision of several cutaneous myxomas. Our observation is a further case of a syndrome-like complex of cardiac and cutaneous myxoma(s), pigmentation anomalies and endocrine disorders described only recently. As modern investigative methods and the development of cardiovascular surgery have brought about an essential improvement in diagnostics and prognosis of cardiac myxomas, the knowledge of this syndrome-like complex is of great therapeutic importance. Therefore, in our opinion, echocardiographic investigations are strongly recommended even in asymptomatic patients, once several cutaneous myxomas are diagnosed histologically.

Adult↗
PubMed1989

Effects of fish oil capsules in two dosages on blood pressure, platelet functions, haemorheological and clinical chemistry parameters in apparently healthy subjects.

The effects of a fish oil concentrate with an omega-3 fatty acid content of 42% was determined in two dosages in a double-blind, placebo-controlled study with a parallel group comparison over a period of 5 weeks with 30 healthy subjects. The daily intake chosen was four and eight capsules corresponding to 1.26 or 2.52 g omega-3 fatty acids. Plasma viscosity, erythrocyte rigidity and systolic blood pressure were significantly decreased (p less than 0.01) after a 5-week administration of 2.52 g omega-3 fatty acid daily. The reduction in vitamin E concentration was significant (p less than 0.01) only in the low-dose fish oil group. Lipids and lipoproteins remained unchanged throughout this experiment.

Adult↗
PubMed1988

Human tissue factor contains thioester-linked palmitate and stearate on the cytoplasmic half-cystine.

The state of the five half-cystine residues in human tissue factor (TF) has been characterized. The results indicate that the four half-cystines in the extracellular domain of TF form two disulfide bonds and the half-cystine in the cytoplasmic region is acylated by palmitic acid and stearic acid. The extracellular disulfide cross-links, Cys49-Cys57 and Cys186-Cys209, were deduced from the analysis of tryptic peptides. Acylation of the cytoplasmic half-cystine was demonstrated by purifying and characterizing fibroblast TF from cells labeled with [3H]palmitic acid. Radiolabeled fibroblast TF was observed by autoradiography following sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The tritiated material covalently bound to the protein was identified as [3H]palmitate and [3H]stearate by reverse-phase high-pressure liquid chromatography. Deacylation of TF with hydroxylamine resulted in the spontaneous generation of disulfide-linked TF dimers. This result suggests that the disulfide-linked TF dimer, a minor component of most TF preparations, and the recently described heterodimeric form of TF are artifacts produced by deacylation of Cys245 and subsequent interchain disulfide bond formation.

Autoradiography↗
PubMed1988

Local abnormalities of coagulation and fibrinolysis and alveolar fibrin deposition in sheep with oleic acid-induced lung injury.

Extravascular, primarily intra-alveolar, fibrin deposition is a histologic hallmark of acute lung injury in humans and experimental animals, but the mechanisms leading to this finding are poorly understood. To determine whether local abnormalities in the fibrinolytic-procoagulant balance contribute to alveolar fibrin deposition in acute lung injury, we studied bronchoalveolar lavage (BAL) fluids of anesthetized sheep that received intravenous oleic acid. Prominent alveolar fibrin deposition was observed within 2 h after oleic acid-induced lung injury. Procoagulant and fibrinolytic activities were determined in BAL samples of anesthetized, mechanically ventilated sheep before and 2 h after intravenous oleic acid or saline. BAL procoagulant activity was found to be due mainly to tissue factor associated with Factor VII. In baseline BAL samples, we found relatively low levels of procoagulant activity and relatively high levels of fibrinolytic activity. After induction of oleic acid-induced lung injury, the procoagulant activity of BAL was markedly increased, whereas fibrinolytic activity was either depressed or undetectable. Antiplasmin activity was detectable in BAL of sheep after oleic acid-induced lung injury, which contributed at least in part to the depressed fibrinolytic activity observed. These perturbations occurred with the appearance of extensive alveolar fibrin deposition. In control sheep, BAL fibrinolytic activity was decreased, and antiplasmin activity increased modestly after 2 h of mechanical ventilation, but procoagulant activity was unchanged and alveolar fibrin was not observed. Procoagulant activity in lung lymph and plasma after lung injury did not differ from baseline values, and fibrinolytic activity was undetectable in lymph or plasma samples. These data indicate that increased procoagulant activity and concurrent disruption of the balance of coagulation and fibrinolysis establish local conditions that promote acute fibrin deposition in the alveoli of mechanically ventilated, oleic acid-injured sheep.

Animals↗
PubMed1988

[Isovolemic hemodilution in patients with coronary heart disease].

In the age of cellsavers patients suffering from coronary heart disease are diluted to a hematocrit of 20% or even less during a surgical intervention in the coronaries and they leave the operating room with a hematocrit of 30%. On the other hand, a hemodilution to a level of 30% in patients with coronary heart disease represents a contraindication due to the limited coronary reserve. On the occasion of the collection of autologue blood, before vascular surgery or for therapeutical hemodilution, the hematocrit was reduced from 45 to 35% by means of an isovolemic hemodilution with 500 ml of Haes 200/0.5 10% in 50 patients. In the load-ECG the pressure X frequency-product and the dyspnoe decreased significantly. The microcirculation in the nailfold and the systemical blood fluidity increased significantly. As in 22% of the patients a deterioration was stated, we propose to dilute all the patients who have to undergo a coronary vessel operation without exclusion criteria once isovolemically and to stress them before and afterwards. The patients having a clinical defict should be diluted intraoperatively only to 30% and postoperatively not under 35%.

Angina Pectoris↗
PubMed1987

Isolation of cDNA clones coding for human tissue factor: primary structure of the protein and cDNA.

Tissue factor is a membrane-bound procoagulant protein that activates the extrinsic pathway of blood coagulation in the presence of factor VII and calcium. lambda Phage containing the tissue factor gene were isolated from a human placental cDNA library. The amino acid sequence deduced from the nucleotide sequence of the cDNAs indicates that tissue factor is synthesized as a higher molecular weight precursor with a leader sequence of 32 amino acids, while the mature protein is a single polypeptide chain composed of 263 residues. The derived primary structure of tissue factor has been confirmed by comparison to protein and peptide sequence data. The sequence of the mature protein suggests that there are three distinct domains: extracellular, residues 1-219; hydrophobic, residues 220-242; and cytoplasmic, residues 243-263. Three potential N-linked carbohydrate attachment sites occur in the extracellular domain. The amino acid sequence of tissue factor shows no significant homology with the vitamin K-dependent serine proteases, coagulation cofactors, or any other protein in the National Biomedical Research Foundation sequence data bank (Washington, DC).

Amino Acid Sequence↗
PubMed1987

An inhibitory monoclonal antibody against human tissue factor.

We obtained a hybridoma using immune spleen cells from a mouse injected with human brain tissue factor that had been purified on a factor VII-agarose affinity column. This monoclonal IgG1, HTF1-7B8, inhibits tissue factor procoagulant activity. The concentration of HTF1-7B8 producing half-maximal inhibition is influenced by the concentration of factor VIIa, suggesting that the antibody and enzyme compete for the cofactor. The antibody was successfully used to detect both human and bovine tissue factor on nitrocellulose dot blots, indicating that the epitope recognized by this antibody is conserved in both species. This antibody clearly reveals tissue factor on a Western blot. An HTF1-7B8 affinity column was used to purify tissue factor from both human brain and placenta. The electrophoretic mobilities in polyacrylamide gels in the presence of sodium dodecyl sulfate (SDS) and the amino acid compositions of the purified tissue factor from brain and placenta are indistinguishable, as are their specific procoagulant activities in reconstituted systems. This antibody will be useful for immunopurification and characterization of tissue factor structure and mechanism.

Amino Acids↗
PubMed1986

[Predictor function of hemorheologic parameters with reference to the incidence of manifest circulatory disorders: Concept of the Aachen study].

The prevention of cardiovascular disease has up till now generally been limited to control of the classical risk factors. The primary problem of the risk factor model is, that although a statistically verified relationship exists between risk factors and vascular disease, an individual prognosis is presently impossible. Surveys that show a relation between risk factors and impaired blood fluidity support the conception that a change in blood fluidity could be considered an early detection screening of vascular diseases. Prospective studies have shown that the hematocrit is related to circulatory disturbances. The main aim of the present study was to determine the clinical relevance of rheological parameters (hematocrit, plasma viscosity, erythrocyte rigidity, thrombocyte aggregation, erythrocyte aggregation), and the importance of altered blood fluidity as a predictor of manifest cerebral, cardiac or peripheral vascular disturbance.

Blood Viscosity↗
PubMed1986

Factor VII binding to tissue factor in reconstituted phospholipid vesicles: induction of cooperativity by phosphatidylserine.

The binding of factor VII and tissue factor produces a membrane-associated proteolytic complex which may be the primary biological initiator of coagulation. Homogeneous tissue factor, a glycoprotein purified from bovine brain, was reconstituted into phospholipid vesicles ranging from neutral (100% phosphatidylcholine) to highly charged (40% phosphatidylserine) with octyl glucoside. The vesicles were characterized with respect to size and tissue factor content and orientation. Employing data from protease digestion, we deduced that tissue factor is randomly oriented; thus, its effective concentration in these vesicles was half its total concentration. In all binding experiments, 1 mol of enzyme was bound per mole of available activator at saturation. This stoichiometry was not affected by the form of the enzyme employed or the phospholipid composition of the vesicles. With tissue factor incorporated into phosphatidylcholine vesicles, the Kd was 13.2 +/- 0.72 nM for factor VII and 4.54 +/- 1.37 nM for factor VIIa. Thus, the one-chain zymogen binds to the activator with only slightly less affinity than the more active two-chain enzyme. Active-site modification of factor VII and factor VIIa with diisopropyl fluorophosphate resulted in tighter binding of the derivatized molecules. Inclusion of phosphatidylserine in the vesicles altered the binding both quantitatively and qualitatively. With increasing acidic phospholipid, the concentration of enzyme required to occupy half the activator sites was decreased. In addition, positive cooperativity was observed, the degree of which depended on the vesicle charge and the form of the enzyme. An explicit two-site cooperative binding model is presented which fits these complex data. In this model, tissue factor is at least a dimer with two interacting enzyme binding sites.

Animals↗
PubMed1986

Affinity purification of human tissue factor: interaction of factor VII and tissue factor in detergent micelles.

Tissue factor, a known initiator of blood coagulation, was found to be active in Triton X-100. A system consisting of tissue factor, factor VIIa, calcium ions, and coagulation factor X generated activated factor X at an appreciable rate. Based on this observation, we coupled human and bovine factor VII to a solid support. Each column bound tissue factor, solubilized in Triton X-100, in a species-specific manner. These interactions required calcium ions; when the columns were washed with detergent containing calcium ions, no tissue factor was eluted. When calcium ions were omitted from the eluant, tissue factor emerged as a sharp peak. Human tissue factor was extracted from an acetone brain powder into 2% Triton X-100. This extract, made 10 mM in CaCl2, was passed over a factor VII column. Human factor VII (1.2 mg) was coupled to 30 ml of Affi-Gel 15. This column bound approximately equal to 15 micrograms of human tissue factor. The eluted material was approximately equal to 25% pure. Final purification was achieved by gel filtration after chymotryptic digestion of contaminants. The tissue factor activity was stable to this treatment. The molecular weight determined by sodium dodecyl sulfate/PAGE (approximately equal to 46,000) was also unchanged by chymotrypsin. The final material was a single band on PAGE, demonstrated similar resistance to tryptic and chymotryptic digestion as bovine tissue factor, and had approximately the same specific coagulant activity as the previously purified bovine material. Tissue factor was also purified from human placenta, yielding a similar protein. A partial 28-residue sequence of the latter has been obtained.

Biological Assay↗
PubMed1985

Cellular requirements for tissue factor generation by bovine aortic endothelial cells in culture.

Cultured bovine aortic endothelial cells acquired the ability to initiate coagulation after treatment with endotoxin or phorbol ester. The acquired procoagulant activity was identified as tissue factor since cells treated with endotoxin or phorbol ester activated factor X only in the presence of factor VIIa, and factor X activation could be completely blocked by a specific antibody to bovine tissue factor apoprotein. The generation of tissue factor activity was evident after 6 hours of incubation and was dependent on RNA and protein synthesis, as indicated by the inhibitory effects of actinomycin D and cycloheximide. Endotoxin and phorbol ester are toxic to cultured endothelial cells as evidenced by release of LDH and detachment from the culture dish. Surviving endothelial cells lose their stress fibers and assume a cytoskeletal organization characteristic of mobility or radial extension. Because these changes in cell shape occurred parallel with the acquisition of procoagulant activity, the effects of drugs interfering with organization of the cytoskeleton were tested. Cytochalasins B and D, vinblastine, and colchicine, each decreased the generation of tissue factor activity when cells were exposed to endotoxin or phorbol ester. Trifluoperazine, a calmodulin antagonist, also prevented the generation of tissue factor activity in a dose-dependent fashion. Thus, perturbation of endothelial cells by treatment with phorbol ester or endotoxin induces potent tissue factor procoagulant activity. This cellular response appears to require protein and RNA synthesis, normal cytoskeletal functions, and the Ca++-calmodulin system.

Animals↗