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Biomedical subjects

D Westphal

Publications and source records attributed to D Westphal.

At least 19 recordsLinked to original sources
PubMed1999

Platelet function and hemolysis in centrifugal pumps: in vitro investigations.

The effects of centrifugal pumps on blood components other than erythrocytes, namely platelets and their interaction with the coagulation system, are not very well known. In a comparative study with three centrifugal pumps (BioMedicus BP-80, St. Jude Isoflow, and Sarns Delphin) and the Stockert roller pump hemolysis, platelet counts, thromboplastin and partial thromboplastin times, as well as resonance thrombography (RTG) parameters for the assessment of platelet and coagulation function were evaluated in vitro. Normalized indices of hemolysis (NIH) with ACD anticoagulation after 360 minutes were 0.008+/-0.004 (Isoflow), 0.018+/-0.017 (BP-80), 0.085+/-0.051 (Delphin), and 0.049+/-0.010 g/1001 (roller pump). Plasmatic coagulation was activated in all circuits. Platelet function was severely inhibited by the BP-80, indicated by increase in RTG platelet time to 358%+/-150% of initial values compared to 42%+/-29% (Isoflow), 40%+/-20% (Delphin), and 12%+/-10% (roller pump). Fibrin polymerization was affected similarly. The large surface area of the BP-80 leads to an extensive activation of platelets and plasminogen.

Blood Coagulation↗
PubMed1998

The implementation of a quality-net as a part of the European project DIABCARE Q-Net.

DIABCARE Q-Net is a European project with a consortium of partners in healthcare, industry, and research, which has the overall target of improvement in diabetes care by aggregation, evaluation, and feedback of anonymized patient data with the tools of modern telematics, resulting from the initiative of the St. Vincent-Declaration, St. Vincent, Italy. Based on standardized tools for quality improvement in diabetes care, i.e., the Basic Information Sheet (BIS) and recently developed data entry and feedback software (DIABCARE Data for Windows), DIABCARE Q-Net as a part of the Telematics Applications Program of the European Commission will improve diabetes care and disease management by the implementation of a quality network. Therefore, the project implements regional, national, and central nodes for processing of diabetes quality indicators. All participating centers (GP's and clinics in Europe) get feedback by standardized benchmarking. The pilot testing and the state of implementation of our network confirm the importance of improving the quality of life of diabetic patients in all participating countries.

Computer Communication Networks↗
PubMed1996

Acute inhalation toxicity testing: considerations of technical and regulatory aspects.

The EU regulatory statute for the acute hazard identification of chemicals requires selection of the two most appropriate routes of administration. Testing employing the oral route is mandatory, whereas selection of the dermal or inhalation route requires expert judgement, i.e. considerations of structural alerts with regard to the inherent acute inhalation toxicity as well as the likelihood of dermal and inhalation exposure, respectively. Currently, testing of chemicals requires acute inhalation exposure of 4-h and 1-h durations according the EU classification and labelling and UN Transport Guidelines, respectively. The analysis made revealed that 1-h exposures appear to add little knowledge in addition to existing 4-h LC50 values and a default value of 4 should be used for conversion of 4-h to 1-h LC50 values, independently of the physical state of the chemical. Therefore, also the unit of concentration of exposure atmospheres should be independent of nominal features of the test substance. Hence, the preferred dose metric is mass (mg/liter air) rather than volume (ppm). Taking into account the overall variability of acute toxicity data the recommendations given are classification into the following groups of 4-h LC50 values: < or = 0.05, > 0.05-0.2, > 0.2-1, > 1-5 and > 5.0 mg/l. No distinction should be made concerning vapours and aerosols with regard to units and conversion factors from 4-h to 1-h LC50 values and the default factor of 4 appears to be most suitable. Further differentiation of classification is not indicated due to technical variability of acute inhalation testing and resolution of the acute bioassay.

Administration, Inhalation↗
PubMed1993

Incorporation of oleic acid and eicosapentaenoic acid into glycerolipids of cultured normal human fibroblasts.

Confluent skin fibroblasts from normal humans were incubated in serum free medium with up to 100 nmole/mL eicosapentaenoic acid (EPA; bound to albumin in a 4.6:1 ratio) and compared with cells incubated with oleic acid (OA) at similar concentrations. The rate of [14C]OA incorporation into triacylglycerol (TG) (nmol/mg/h) was approximately 5-fold greater than that of [14C]EPA. The mass of TG formed after incubation of fibroblasts with EPA was also significantly lower than that formed with OA (43.2 +/- 9.3 vs. 59.5 +/- 6.6 micrograms/mg cell protein, respectively, P = 0.006). The addition of excess, unlabeled EPA reduced the rate of incorporation of [14C]OA into TG whereas unlabeled OA stimulated incorporation of [14C]EPA into TG. When the cells were preincubated with human serum basic proteins (BP I, II and III), the mass of TG formed (compared to baseline) was significantly higher with the basic proteins whether OA or EPA was studied. Only BP I significantly stimulated the mass of cell phospholipids, an effect that occurred with either OA or EPA in the medium. The results suggest that in cultured normal human fibroblasts, OA is a better substrate for TG synthesis than EPA and that this effect may be accentuated by the presence of the basis proteins.

Binding, Competitive↗
PubMed1992

Two-dimensional color-mapping of turbulent shear stress distribution downstream of two aortic bioprosthetic valves in vitro.

Since artificial heart valve related complications such as thrombus formation, hemolysis and calcification are considered related to flow disturbances caused by the inserted valve, a thorough hemodynamic characterization of heart valve prostheses is essential. In a pulsatile flow model, fluid velocities were measured one diameter downstream of a Hancock Porcine (HAPO) and a Ionescu-Shiley Pericardial Standard (ISPS) aortic valve. Hot-film anemometry (HFA) was used for velocity measurements at 41 points in the cross-sectional area of the ascending aorta. Three-dimensional visualization of the velocity profiles, at 100 different instants during one mean pump cycle, was performed. Turbulence analysis was performed as a function of time by calculating the axial turbulence energy within 50 ms overlapping time windows during the systole. The turbulent shear stresses were estimated by using the correlation equation between Reynolds normal stress and turbulent (Reynolds) shear stress. The turbulent shear stress distribution was visualized by two-dimensional color-mapping at different instants during one mean pump cycle. Based on the velocity profiles and the turbulent shear stress distribution, a relative blood damage index (RBDI) was calculated. It has the feature of combining the magnitude and exposure time of the estimated shear stresses in one index, covering the entire cross-sectional area. The HAPO valve showed a skewed jet-type velocity profile with the highest velocities towards the left posterior aortic wall. The ISPS valve revealed a more parabolic-shaped velocity profile during systole. The turbulent shear stresses were highest in areas of high or rapidly changing velocity gradients. For the HAPO valve the maximum estimated turbulent shear stress was 194 N m-2 and for the ISPS valve 154 Nm-2. The RBDI was the same for the two valves. The turbulent shear stresses had magnitudes and exposure times that might cause endothelial damage and sublethal or lethal damage to blood corpuscules. The RBDI makes comparison between different heart valves easier and may prove important when making correlation with clinical observations.

Aortic Valve↗
PubMed1990

Estimation of turbulent shear stresses in pulsatile flow immediately downstream of two artificial aortic valves in vitro.

Measuring turbulent shear stresses is of major importance in artificial heart valve evaluation. Bi- and unidirectional fluid velocity measurements enable calculation of Reynolds shear stress [formula: see text] and Reynolds normal stress [formula: see text]. tau is important due to the relation to hemolysis and thrombus formation, but sigma is the only obtainable parameter in vivo. Therefore, determination of a correlation factor between tau and sigma is pertinent. In a pulsatile flow model, laser Doppler (LDA) and hot-film (HFA) anemometry were used for simultaneous bi- and unidirectional fluid velocity measurements downstream of a Hall Kaster and a Hancock Porcine aortic valve. Velocities were registered in two flow field locations and at four cardiac outputs. The velocity signals were subjected to analog signal processing prior to digital turbulence analysis, as a basis for calculation of tau and sigma. A correlation factor of 0.5 with a correlation coefficient of 0.97 was found between the maximum Reynolds shear stress and Reynolds normal stress, implying [formula: see text]. In vitro estimation of turbulent shear stresses downstream of artificial aortic valves, based on the axial velocity component alone, seems possible.

Aortic Valve↗
PubMed1988

In vitro stress measurements in the vicinity of six mechanical aortic valves using hot-film anemometry in steady flow.

Based on hot-film anemometry, point velocity measurements in the total cross sectional area 1 and 2 diameters downstream of: Björk-Shiley Standard, Convex-Concave and Monostrut, Hall-Kaster (Medtronic-Hall), St. Jude Medical and Starr-Edwards Silastic Ball aortic valves were made. The spatial distribution of Reynolds Normal Stresses (RNS) was visualized three-dimensionally in order to point out where and to what extent the highest RNSs were found. The measurements were made in steady flowing glycerol mixture at flow rates 10, 20 and 30 l. min-1 corresponding to mean velocities of 27, 54 and 81 cm s-1. The highest maximum RNS values were around 250 Nm-2 and were found downstream of the Björk-Shiley Monostrut and Starr-Edwards Ball valves. The lowest maximum RNSs were found downstream of the St. Jude Medical and Hall-Kaster (Medtronic-Hall) valves (125-140 Nm-2). The Starr-Edwards valve had the highest mean RNS (117 Nm-2) followed by the Björk-Shiley Monostrut (87 Nm-2). These simplified measurements of artificial heart valve performances concerning RNS, enhance the interpretation of results in more complicated flow models not to say in vivo.

Aortic Valve↗
PubMed1987

Three-dimensional visualization of axial velocity profiles downstream of six different mechanical aortic valve prostheses, measured with a hot-film anemometer in a steady state flow model.

Hot-film anemometry was used for in vitro steady-state measurements downstream of six mechanical aortic valve prostheses at flow rates 10, 20 and 30 l.min-1. Three-dimensional visualizations of velocity profiles at two downstream levels were made with the valves rotated 0 and 60 degrees in relation to the sinuses of valsalvae. The velocity fields downstream of the disc valves were generally skew with increasing velocity gradients and laminar shear stresses with increasing flow rates. Furthermore, increased skewness of the velocity profiles was noticed when the major orifices of the disc valves were towards the commissure than when approaching a sinus of valsalvae. The velocity profiles downstream of the ball valve were generally flat but with considerably more disturbed flow, consistent with the findings in turbulent flow.

Aortic Valve↗
PubMed1984

[Biotransformation of monolinuron (N-(4-chlorophenyl)-N'-methyl-N'methoxyurea) in isolated perfused chicken liver].

The biotransformation of radioactively labelled monolinuron (N-(4-chloro[U-14C]phenyl)-N'-methyl-N'-methoxyurea) was studied in the isolated perfused liver of the chicken. After a 4-hr perfusion, 83.1% of the added radioactivity was recovered, 56.6% in the perfusion medium and 26.5% in the liver and bile. The fraction of radioactivity extractable from the perfusion medium into ethyl acetate amounted to 47.8% of the added dose. In addition to monolinuron, five breakdown products were identified in this extract, namely N-(4-chlorophenyl)-N'-hydroxymethyl-N'-methoxyurea, N-(4-chlorophenyl)-N'-methoxyurea, N-(4-chlorophenyl)-N'-methylurea, 4-chlorophenylurea and 4-chloroacetanilide. Of particular interest was the absence of arylhydroxylated monolinuron derivatives, since in monolinuron-metabolism studies in the laying hen 2-hydroxy-4-chlorophenylurea and 3-hydroxy-4-chlorophenylurea were both detected. This differing metabolism corresponds to earlier findings in the rat, in which arylhydroxylated breakdown products were detected only in in vivo studies and not in rat-liver perfusion. Possible reasons for the differing metabolism of monolinuron in vivo and in vitro are discussed.

Animals↗
PubMed1979

[Delayed infections after foreign body inclusion in the maxillofacial region].

Nine cases of so-called late infections following foreign body inclusions due to trauma as well as possible developmental mechanisms were discussed. The question arises as to whether a nonirritating incorporated foreign body should be surgically removed as early as possible to eliminate the possibility of late infection.

Abscess↗
PubMed1979

[Bulbus motility in early and late surgery of orbital floor fractures (author's transl)].

Among 638 patients with fractures of the middle third of the facial skeleton 139 were found to have clinically relevant fractures of the orbital floor. 74 of them were followed up ophthalmologically and by x-ray examination. In 49 patients the results of the operative treatment were judged from a detailed questionnaire. Operation within 2 weeks after the accident yielded better results than later operation. Persisting motility disturbances concerned mainly the upper field of gaze.

Eye Movements↗
PubMed1978

Hypoxemia following the administration of sublingual nitroglycerin.

Nitroglycerin, 0.6 mg sublingually, was given to 27 nonasthmatic subjects with varying degrees of airways dysfunction to determine the effect on arterial oxygenation. In six normal subjects, the partial pressure of oxygen in arterial blood (Pao2) transiently decreased by 9 mm Hg (p less than 0.05) and in eight subjects with only small airways dysfunction, the Pa02 decreased by 14 mm Hg (p less than 0.0001). The alveolar-arterial oxygen gradient on oxygen increased by only 11 mm Hg indicating that the decrease in room air Pao2 was primarily due to worsening ventilation-perfusion mismatch and not to an increase in shunt. Thirteen subjects with advanced obstructive or restrictive lung disease experienced a much lesser decrease in Pao2 of 4 mm Hg. Data are presented on xenon perfusion studies of a dog model of unilateral alveolar hypoxia that suggest the worsening ventilation-perfusion ratio seen in the human subjects after the administration of nitroglycerin could be due to loss of the lung's ability to vasoconstrict in regions of alveolar hypoxia and shift perfusion to better ventilated regions of the lung.

Adult↗
PubMed1978

Testing in vitro of an indirect mutagen (cyclophosphamide) with human leukocyte cultures: Activation by liver perfusion and by incubation with crude liver homogenate.

The indirect mutagen cyclophosphamide was tested in human whole blood cultures with respect to chromosome-breaking activities and suppression of mitotic indices after activation by liver perfusion and crude liver homogenates with and without cofactors. Both methods produced nearly the same effects, with the exception of liver homogenate without cofactors which had only weak metabolic activities.

Animals↗