Feedforward correction of nonlinearities in piezoelectric scanner constructions and its experimental verification.

Piezoelectrical actuators widely used in scanning devices for highly resolved displacement generation exhibit a number of known nonlinear effects as hysteresis and creep. This article describes an attempt to minimize those nonlinearities by recognizing the relation between scan range and voltage magnitude in a scanner specific function. In addition, by utilizing a strain gauge sensor system, a forward displacement correction is realized. The mathematical procedure behind the hysteresis correction is described in detail. The dependence of the higher order correction factors on parameters such as scan speed, scan range, or center position is studied carefully to extract their influence on the result. Finally, integral nonlinearities of about 1% are proven in experiments with an atomic force microscope.

Purification and properties of staphylocoagulase.

Staphylocoagulase, an exoprotein of coagulase-positive Staphylococci, has been purified to a state in which only trace amounts of contaminating proteins are detectable. Aspartic acid was found as a single N-terminal amino acid in this preparation. The molecular weight is 61 000; the isoelectric point lies as pH 4.53. The amino acid composition was determined.

Activation of a pro-enzyme by a stoichiometric reaction with another protein. The reaction between prothrombin and staphylocoagulase.

The reaction between prothrombin and staphylocoagulase was investigated and the following conclusions were drawn: (a) Optimal amounts of the active reaction product (coagulase-thrombin) are found when equimolar amounts of prothrombin and staphylocoagulase are added together. (b) The molecular weight of coagulase-thrombin equals the sum of the molecular weights of staphylocoagulase and prothrombin when estimated both by gelfiltration and by sodijm dodecylsulphate-polyacrylamide gel electrophoresis. (c) The amino acid composition of coagulase-thrombin cannot be distinguished from the sum of the amino acid compositions of prothrombin and staphylocoagulasd. (d)in a preparation of coagulase-thrombin the N-terminal amino acids are those of prothrombin (alanin) and staphylocoagulase (aspartic acid). (e) An antibody against coagulase-thrombin precipitates prothrombin and staphylocoagulase but not thrombin. (f) We put forward the hypothesis that the thrombin activity in coagulasethrombin is the result of a stoichiometric reaction between one molecule of prothrombin and one molecule of staphylocoagulase, and limited proteolysis does not play a role in this mechanism.

Protection by endoscopy against death from colorectal cancer. A case-control study among veterans.

BACKGROUND: Although several clinical and epidemiologic studies suggest that timely diagnostic procedures of the large bowel may reduce mortality from colorectal cancer, the evidence for this relationship is primarily circumstantial. METHODS: A case-control study was conducted among hospitalized US military veterans to investigate whether diagnostic procedures of the large bowel were performed in the period preceding the diagnosis of colorectal cancer less frequently in patients dying of colorectal cancer than in control patients. Data files of a total of 4411 veterans dying of colorectal cancer between 1988 and 1992 were extracted from the records of the US Department of Veterans Affairs, Washington, DC. Data of four living control patients and four dead control patients without colorectal cancer were matched by age, sex, and race to each case patient. The case and the two control populations were compared by conditional logistic regression, calculating odds ratios, and their 95% confidence interval. RESULTS: Diagnostic procedures of the large bowel reduced mortality from colorectal cancer, the odds ratio being 0.41 (range, 0.33 to 0.50) for the comparison with living control patients. The protective effects of proctosigmoidoscopy, colonoscopy, and polypectomy lasted for 5 years. The procedures were protective against death from cancer of the colon, as well as cancer of the rectum. The most protective influence was associated with removal of tissue through biopsy, fulguration, and polypectomy. Similar influences were found comparing case patients with dead control patients. CONCLUSION: Removal of tissue represents the most effective means to reduce mortality from cancers of the large bowel. It retains its efficacy over a time period of 5 years.

Cytomegalovirus alters the von Willebrand factor content in human endothelial cells.

Cultured human endothelial cells were infected with human cytomegalovirus AD 169 and Kerr. The infection resulted in the appearance of viral antigens in the nuclei of about 10% of the endothelial cells and in the concomitant disappearance of vWF from the infected cells. No differences were observed between endothelial cells from different sources (umbilical cord veins or arteries, adult veins).

The procoagulant response of cytomegalovirus infected endothelial cells.

The report describes the effect of an in vitro infection of human umbilical vein endothelial cells with human Cytomegalovirus (CMV). The parameters studied are cellular procoagulant activity, secretion of plasminogen activator inhibitor (PAI-1) and urokinase-type plasminogen activator (u-PA), activation and internalization of factor X and Merocyanine 540 staining. The infection does not result in an increase in PAI-1 and u-PA secretion, but it brings about a procoagulant response, which is relatively rapid compared to the tissue factor mediated response induced by inflammatory mediators. The time course and the coagulation factor dependency suggest a facilitated interaction of coagulation factors on the surface of infected cells. Chromogenic activity measurements after the addition of purified factor X and electron microscopic examination of the cells after addition of colloidal gold-factor X conjugates both point to an internalization of factor X and/or Xa after interaction with the endothelial cell surface. Merocyanine 540 staining suggests that CMV infection leads to membrane perturbations.

Effect of a moderate fish intake on haemostatic parameters in healthy males.

This article describes the results of a dietary intervention study performed in three different centers. In the study the effect of a diet enriched with fish on the coagulation tendency of blood was investigated. Two groups of 40 volunteers were given a dietary supplement consisting of 135 g of canned mackerel or meat paste (control) for a 6 weeks period. Compliance, monitored by measuring the urinary excretion of lithium, added to the supplements, was about 80%. Before, during and at the end of the experimental period a number of hemostatic parameters, reflecting the coagulation tendency of blood and the procoagulant activity of monocytes, were measured. The fish supplement did not cause a significant effect on the prothrombin time and on the levels of factor VII, activated factor VII, antithrombin III, von Willebrand factor, fibrinogen, plasminogen and alpha 2-antiplasmin. A slight but transient prolongation in the activated partial thromboplastin time was observed as well as a significant increase in the factor X level, which became more pronounced with prolongation of the experimental period; no activated factor X was found. A tendency towards a stimulation of monocyte procoagulant activity was noticed.

Hemostatic factors and platelet aggregation after a fish-enriched diet or fish oil or docosahexaenoic acid supplementation.

The effects of a fish-enriched diet or dietary supplements consisting of either fish oil or a docosahexaenoic acid-rich oil (DHA-oil) on platelet aggregation and hemostatic factors were studied in healthy male students. After an experimental period of 15 weeks, the levels of tissue factor pathway inhibitor, prothrombin fragment 1+2 and fibrinogen as well as factor VII activity were not changed. Factor X activity was slightly decreased by the fish diet (P < 0.05). Collagen but not ADP-induced maximum platelet aggregation decreased in the fish diet and the fish oil groups (P < 0.05 in both). In the DHA-oil group there was a slight, statistically insignificant, increase of platelet aggregation which correlated significantly with the decrease of plasma triglycerides. Platelet aggregation measured 4 h after a standardized fat meal was lower than in the fasting state and this decrease correlated with the increase of plasma triglycerides. These results show that a fish diet and fish oil, but not DHA-oil, inhibit in vitro platelet aggregation and that hemostatic factors are not affected by moderate n-3 fatty acid supplementation.

Clotting factors secreted by monocytes and macrophages: analytical considerations.

The secretion of clotting factors by rat spleen macrophages and human peripheral blood monocytes has been studied. The results show that the amount of clotting factors measured depends critically upon the characteristics of the assay system used. The presence of warfarin, salicylic acid or thrombin in the culture medium is shown to decrease the vitamin K dependent clotting factor activity in the supernatant after in vitro culture of rat spleen macrophages and human peripheral blood monocytes.

The vitamin K-antagonism of salicylate and warfarin.

When administered in high dosages, salicylate acts as a vitamin K-antagonist: it induces a decrease of the plasma concentration of the Gla-containing coagulation factors and an accumulation of microsomal substrates for vitamin K-dependent carboxylase in the liver and in the lung. In vitro the drugs inhibit the DTT-dependent reductases which mediate the reduction of vitamin K epoxide and vitamin K quinone. NADH-dependent reductase and vitamin K-dependent carboxylase are not inhibited.

Induction of endothelial cell procoagulant activity by cytomegalovirus infection.

Endothelial cells isolated from rat aorta were infected in vitro with rat cytomegalovirus. Viral antigens appeared in nucleus and cytoplasma and newly made extracellular virus was detected in the supernatant. Furthermore, the viral infection caused the appearance of procoagulant activity on the endothelial cells.

Evaluation of dyspepsia and functional gastrointestinal disorders: a cost-benefit analysis of different approaches.

OBJECTIVE: To establish a decision rule for diagnostic testing in patients with dyspepsia. DESIGN: Medical decision analysis using a decision-tree model. METHODS: Costs and benefits associated with two alternative strategies are compared. In the first strategy, empirical therapy alone is provided. The second strategy also includes tests to diagnose the cause of dyspepsia. RESULTS: It is more beneficial to test than to employ empirical treatment alone if the a-priori probability P of an organic disease is larger than the ratio of the costs T of testing to the costs C of a missed diagnosis: P > T/C. In most clinical situations, the costs of a missed diagnosis outweigh the costs of testing by a factor of 5-10, for which the cost ratio is 10-20%. CONCLUSION: Diagnostic tests should be performed in patients with dyspepsia, whenever the probability of finding organic disease exceeds the ratio of the cost of testing to the cost of missing this diagnosis.

Prevention of colorectal cancer by flexible endoscopy and polypectomy. A case-control study of 32,702 veterans.

OBJECTIVE: To determine whether patients with colorectal cancer are less likely than unaffected controls to have had one or more endoscopic procedures (flexible sigmoidoscopy, colonoscopy, or polypectomy) before being diagnosed with cancer. DESIGN: Case-control study. SETTING: Hospitals of the Department of Veterans Affairs. PATIENTS: 8722 and 7629 case-patients with colon and rectal cancer, respectively, and age-, sex-, race-matched controls who were discharged at the same time as the corresponding case-patients. MEASUREMENTS: Number and type of endoscopic procedures of the large bowel done from 1981 until the development of colorectal cancer in each case-patient. The influence of endoscopic procedures on the development of colorectal cancer was tested by conditional multiple logistic regression analysis. RESULTS: Compared with controls, patients with colorectal cancer were less likely to have had an endoscopic procedure of the large bowel before being diagnosed with cancer (odds ratio for colon cancer, 0.51 [95% CI, 0.44 to 0.58]; odds ratio for rectal cancer, 0.55 [CI, 0.47 to 0.64]). In patients who had flexible sigmoidoscopy, colonoscopy, and polypectomy, the odds ratios were even smaller. When analyzed by separate 1-year intervals, patients with cancer had significantly fewer procedures during periods of up to 6 years before their onset of their cancer. Similarly, fewer inpatient and outpatient procedures were done in patients than in controls. CONCLUSIONS: Endoscopic procedures of the large bowel reduce the risk for developing colon and rectal cancer by 50%, their protective influence lasting 6 years.

Constipation and cathartics as risk factors of colorectal cancer: a meta-analysis.

Since individual case-control studies have failed to resolve the question whether constipation and use of cathartics represent significant risk factors of colorectal cancer, a meta-analysis was performed. The method by Peto was used to calculate pooled odds ratios of the cancer risk among exposed and unexposed subjects. The analysis of 14 previously published case-control studies revealed statistically significant risks for colorectal cancer associated with both constipation and use of cathartics, the pooled odds ratios and their 95 percent confidence intervals being 1.48 (1.32-1.66) and 1.46 (1.33-1.61), respectively. The increased risk applied similarly to both sexes, it was higher in cancer of the colon than rectum. Since constipation and cathartics are associated with much lower odds ratios than various dietary components, such as fat, meat, alcohol, and low-vegetable or low-residue diets, it appears that their risk reflects the confounding influence of underlying dietary habits.

Diseases preceding colon cancer. A case-control study among veterans.

Patients with regular use of nonsteroidal antiinflammatory drugs (NSAIDs) appear to have a reduced mortality from colon cancer. As NSAID use is associated with gastrointestinal bleeding, endoscopic exploration of patients on NSAID may lead to more efficient screening and frequent detection of colon cancer. A case-control study was conducted among 12,304 veterans with a colon cancer diagnosed between 1988 and 1992. Four controls were matched by age, sex, and race to each case. The frequency distributions of previous discharge diagnoses in cases and controls were compared. Arterial embolism and thrombosis, spondylosis, peripheral vascular disease, angina, osteoarthrosis, and ischemic heart disease protected against future development of colon cancer. On the other hand, atrial fibrillation and flutter, as well as phlebitis and thrombophlebitis, were associated an increased occurrence of colon cancer after 5-10 years. The study contrasts diseases that are treated with aspirin with those that are treated with other anticoagulants. Both cause bleeding, but the reduced risk of colon cancer was seen only in conditions treated with aspirin. The difference between the two disease groups from the same VA patient population suggests that chronic use of NSAID truly protects against future development of colon cancer.

Simple screening techniques for the detection of hypercoagulation. A study of 53 children suffering from familial hypercholesterolemia type IIa.

A number of new screening techniques to detect the tendency to hypercoagulability in children with familial hypercholesterolemia is presented. The use of Thrombokinetics (TKG) and the introduction of a quotient as a new parameter are discussed. The new techniques are compared with the conventional methods. The link of an increased quotient with the activated stage of factor VII has been shown in a pilot study. For the definition of normal values there is a need of a normal pool which has been critically prepared.