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Biomedical subjects

R Kaufmann

Publications and source records attributed to R Kaufmann.

340 records · Page 19Linked to original sources
PubMedDate not supplied

Why does the cardiac force-velocity relationship not follow a Hill hyperbola? Possible implications of feedback loops involved in cardiac excitation-contraction coupling.

1. If cardiac force-velocity (PV) relationships are determined in a rhythmically beating isolated preparation by progressively changing afterloads, the PV curves obtained exhibit a characteristic nonhyperbolic shape with an upward convexity in the force domain close to P0. It was suggested by others that this might be due to contractile element (CE) shortening against series elastic component (SEC) and/or the early decay of the active state at isometric peak tension. 2. The present investigation performed in isolated cat papillary muscles demonstrates that neither CE shortening against SEC nor the variation of the intensity of the active state can fully account for the nonhyperbolic shape of cardiac PV curves. 3. On the other hand large parts of the remaining deviation could be eliminated if the "progressive loading sequence" (PLS) was replaced for an "interpolated loading sequence" (ILS). Here, the muscle contracts under steady state conditions either isometrically or isotonically (zero load). Single afterloaded test contractions are interpolated after every 10th beat. 4. It is concluded that the nonhyperbolic shape of cardiac PV curves, determined by progressively changing afterloads, is the expression of at least four factors: (i) the existence of displacement dependent variation of excitation-contraction coupling (including the contraction-excitation-contraction recoupling loop), (ii) CE shortening against non CE bound SEC, (iii) a variable active state and (iiii) a fourth unknown mechanism.

Animals↗
PubMedDate not supplied

Prevention of deep vein thrombosis in patients with hip fractures: low molecular weight heparin versus dextran.

A randomized open trial was undertaken to compare the antithrombotic efficacy of a low molecular weight heparin (LMWH; Sandoparin) with that of dextran 70 in patients undergoing surgery for hip fracture. One hundred thirteen patients received LMWH once daily subcutaneously at a fixed dosage while 103 patients received intravenous dextran 70. Postoperative deep vein thrombosis (DVT) was assessed by a diagnostic algorithm using the 125Iodine fibrinogen uptake test as screening and Duplex ultrasonography and/or ascending venography as confirming techniques for suspected DVT. The frequency of DVT was significantly lower in the LMWH group than in the dextran group (15.5 versus 32.6%, p less than 0.005). Proximal DVT was rare in both groups (LMWH: 2%, Dextran: 1%). Only one case of fatal fat pulmonary embolism was observed during the 10 day prophylaxis period in a patient receiving Dextran. Three cases of pulmonary embolism occurred later; one fatal event in the dextran group on day 14, and two cases in the LMWH group (one fatal and one non-fatal event) on day 14 and 17, respectively. There was no major bleeding complication in either group. We conclude that the LMWH we used is safe, was well tolerated, and has a significantly better thromboprophylactic effect than dextran 70.

Adult↗
PubMedDate not supplied

Multiple agminated Spitz nevi arising on a café au lait macule: review of the literature with contribution of another case.

The majority of Spitz nevi are acquired solitary lesions. Multiple Spitz nevi are rare and may develop on hyperpigmented skin. We report a 16-year-old girl with multiple Spitz nevi arranged on a café au lait macule. Immunohistochemistry showed positivity for S-100 and HMB-45. Of interest, expression of Polo-like kinase (PLK), a novel proliferation marker that recently proved to be positive in up to 98% of malignant melanoma cells, showed positivity in 40% of the nevus cells. The clinical development of multiple Spitz nevi is not yet clear, as they are preferentially excised. Reviewing 70 cases in the literature we found that multiple agminated Spitz nevi occur more frequently than reported previously. In about one-third of these cases Spitz nevi arose on congenitally hyperpigmented skin.

Adolescent↗
PubMedDate not supplied

Melanocytes in vitro: how do they undergo mitosis?

Human melanocytes of the adult skin are slow-cycling cells with a highly dendritic morphology. Nevertheless in vitro proliferation can be achieved using adequate stimulators. Time lapse studies revealed the morphologic changes during melanocyte mitosis: dendrites are drawn back into the cell body, the cell becomes spherical and detaches from the support. Cell division takes place while the cell is suspended. Consecutively the two cells reattach to the support and form new dendrites. About 1% cells per culture are detached from the support and ca. 70% of these cells are viable and putative within mitosis. By every medium change mitotic cells become withdrawn supporting selection of G0-cells, Therefore we recommend centrifugation of exhausted medium in order to add mitotic cells back to the culture.

Adult↗
PubMedDate not supplied

Is an imbalanced calcium-homeostasis responsible for the experimentally induced endolymphatic hydrops?

The target of the investigations were the presumably ion-transporting cells of the vestibular organ, i.e. the area of 'dark cells' of the semicircular canal and utriculus. Those cells have been assayed for structural changes by LM and EM and for alterations of the ionic content (LAMMA) in coloured guinea pigs with unilaterally induced endolymphatic hydrops. Characteristically changed structures of the secretory epithelium and disordered pigmentation in the vestibular organ were noted. Those cellular alterations were accompanied by intracellular ionic changes, especially an increased level of Ca2+ in the light cells and melanocytes. Our investigations show that, at least for experimental hydrops, an imbalanced homeostasis of Ca exists that may be responsible for the enlargement of the endolymphatic space.

Animals↗
PubMedDate not supplied

Meizothrombin, an intermediate of prothrombin cleavage potently activates renal carcinoma cells by interaction with PAR-type thrombin receptors.

Recently, meizothrombin (MT), an intermediate enzyme in the prothrombin cleavage cascade has been shown to activate cells of a brain tumor cell line by interaction with PAR-1-type thrombin receptors with a potency comparable to that of thrombin. In this study, we investigated the effect of recombinant human MT (rMT) on calcium mobilization in primary cultures established from surgically resected human renal cell carcinomas. Meizothrombin induced very rapidly transient calcium mobilization in RCC cells comparable to that observed with thrombin. RCC cells stimulated with thrombin after rMT challenge were unable to elicit a new calcium response and vice versa. Therefore, rMT and thrombin seem to activate calcium signaling in primary RCC cultures by similar mechanisms including PAR-1- and PAR-3-type thrombin receptors as shown by using PAR-type specific antibodies. Our results demonstrate rMT as a potent activator of human RCC cells suggesting a function of not only thrombin but also of this catalytically active thrombin precursor enzyme in human renal cell carcinoma.

Calcium↗
PubMedDate not supplied

Human sperm motility--enhancement and inhibition measured by laser Doppler spectroscopy.

Laser Doppler spectroscopy is an excellent instrument to measure motility parameters of human spermatozoa. Experiments have been performed by the aid of a now commercially available instrumental setup called LAZYMOT to study enhancement and inhibition as well as influences of different physical treatments on the motility of human spermatozoa. The motility enhancing influence of Kallikrein (up to 40% with 4 KU/ml) and prostaglandin E2 could be proven, thereby verifying some sort of mechanism of action within the Kallikrein-Kinin system. Furthermore tested substances in this context were bradykinin (no effect), caffeine (enhancement), salicylic acid (slight decrease), and other prostaglandins (no effect). The influence of washing, centrifugation, resuspension liquid, and temperature has been examined. It turned out that the lowest motility degradation is to be achieved by washing twice at a pH value of 7.4 at forces of 200 g for 10 min each time. The optimal temperature during this process and the measurements thereafter was found to be 36 degrees C. Unsaturated fatty acids like arachidonic acid have been found to be very strong motility inhibiting substances, which can totally block any movement of spermatozoa.

Bucladesine↗
PubMedDate not supplied

[Care of aged psychiatric patients in a multidisciplinary center].

On the basis of recent German, English and French publications dealing with the increasing numbers of emotionally disturbed old persons the measures required to master that problem are discussed. The out-patient center in Lausanne (CH) is described as a successfully working model. Finally the attempt is made to estimate the extent of supplementary therapeutic intervention required in the near future.

Aged↗
PubMedDate not supplied

A novel implantable electromechanical ventricular assist device. First acute animal testing.

A novel ventricular assist device (HIA-EMLVAD-AT1, Helmholtz Institute Aachen-Electromechanical Left Ventricular Assist Device-Animal Test Version 1), driven by a uniformly and unidirectionally rotating actuator and a patented hypocycloidic pusherplate displacement gear unit, was developed and tested in an acute animal experiment. The excellent free filling behavior of the pump chamber with a stroke volume of 65 ml is obtained by a 2:3 ejection-filling time relationship. The uniform motor rotation facilitates simple sensorless pre and afterload detection by motor current analysis. In contrast to common apical cannulation, the inlet cannula was placed via the left atrium through the mitral valve into the left ventricle. This connection mode is preferable for left ventricular recovery and preservation. Left atrial, left ventricular, and aortic pressure curves, as well as pulmonary artery flow data, were obtained. The data show very effective unloading of the natural ventricle and demonstrate the feasibility of this novel assist device. Directions for further improvement of technical features were also identified.

Animals↗