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Biomedical subjects

A Seifert

Publications and source records attributed to A Seifert.

At least 19 recordsLinked to original sources
PubMed2006

Technique for backward particle tracking in a flow field.

A numerical method to determine the history of particle paths is presented and its application for mixing quantification is illustrated. When more than one source exists in a flow field, the current technique can reveal the particle's identity found in any time and place in the field, by backward tracking its origin. Since the particle position at a preceding time is not known, the velocity vector is implicit. To resolve this uncertainty, a three-stage iterative procedure is developed and implemented. The current particle velocity is multiplied by the time increment and the product is used to estimate the previous time increment particle position. Two velocity matrices are generated on a mesh around the estimated position. The first matrix is the Eulerian velocity field interpolated on the mesh. The second matrix contains velocity vectors that point to the current particle position. A correlation matrix is calculated from the two velocity matrices in order to resolve the actual particle position in the previous time increment. Determination of the time increments' size is performed by checking the maximum of the correlation matrix. The new algorithm was validated using a numerical solution of the confined twin-jet flow at low Reynolds number. This flow performs a Hopf bifurcation at a Reynolds number of about 30, therefore chaotic trajectories might exist in the flow. First, the convergence of the backward particle path to the streamlines in steady flow was demonstrated. Convergence of the particle paths for various time increments was achieved also at the unsteady two-dimensional confined twin-jet flow. When the flow has more than one source, the proposed tracking method can be applied to generate complete and ordered particle source images in any desired position and time in the flow field. Maps of particle sources are used to visualize the flow patterns and the stretched interface between the two fluid sources. Those maps are demonstrated as a powerful tool for mixing quantification and can be implemented also for pollution source detection and many other fluid dynamics applications.

Journal Article↗
PubMed2004

[Mitigated erysipelas after implantation of foreign material].

When an infection occurs in the incisional area following surgery where foreign materials (i. e. endoprostheses, metal plates or plastic meshes) are implanted, a revision may become necessary because an infection in the area of the implant and involvement of the implant itself cannot be ruled out. In the case of a mitigated erysipelas, cultures taken during the revision seldom show bacterial growth. The disease progresses because surgery does not solve the problem of a weakened immune system and lymph stasis; on the contrary, it usually deteriorates the situation. A high dose antibiotic regimen is recommended as therapy for the mitigated erysipelas instead of an operative revision orally given. levofloxacin has proven to be successful reducing the recurrence rate. The course of two patients with mitigated erysipelas is represented for example in form of case studies. The patients were underwent several surgical revisions. But we had not to explant the endoprostheses at all. Finally both patients were treated with levofloxacin without further relapses.

Aged↗
PubMed2002

Thrombin as a survival factor for cancer cells: thrombin activation in malignant effusions in vivo and inhibition of idarubicin-induced cell death in vitro.

OBJECTIVES: The aim of the experiments shown here, is to demonstrate exemplarily that thrombin can be a survival factor for malignant cells. METHODS: Activation of the coagulation system has been examined in patients with acute myeloid leukemia (AML) and non-Hodgkin lymphoma (NHL) before and after chemotherapy as well as in malignant effusions of heavily pretreated patients with solid tumors. Thrombin receptor expression (PAR-I) has been examined on HL-60 cells; the effect ofthrombin on the proliferation of the cells and inhibition of apoptosis induction by idarubicin has been shown. RESULTS: Using fibrinopeptide A as an indirect parameter for thrombin activation, we found elevated levels in patients with AML and NHL before and a significant 2-fold increase after chemotherapy (p < 0.02 for the AML group; p < 0.0006 for the NHL group). Apparently, this does not only affect patients with hematological diseases, but also with solid tumors. In order to find out if the tumor cells directly activate thrombin, we examined malignant effusions of patients with different solid tumors. Comparing prothrombin fragment 1 + 2 in ascites and pleural effusions with the patients' serum levels, we found it significantly increased in all cases (mean of 1.96 +/- 0.5 nmol/l in the serum vs. 12.1 +/- 3.6 nmol/l in effusions; p < 0.001). The majority of patients presented elevated serum levels. Additionally, we incubated HL-60 cells (human promyelocytic leukemia) with thrombin prior to treatment with idarubicin. Expression of thrombin receptor (PAR-1) could be verified by FACS-analysis using a monoclonal antibody. HL-60 cells responded with increased proliferation to thrombin exposure with concentrations between 0.3 and 3 U/ml. This effect could be abolished by the addition of hirudin, demonstrating thrombin specificity. In these concentrations, thrombin was able to abrogate the induction of apoptosis by idarubicin completely (p < 0.005). CONCLUSIONS: Here we give evidence for the role of thrombin as a resistance factor for tumor cells towards chemotherapy. In the light of the fact that thrombin is regularly activated in cancer patients, these findings indicate that thrombin is a clinically relevant cellular resistance factor. A number of pre-clinical and clinical studies imply that inhibition of the coagulation system, e.g. by low-molecular weight heparins or warfarin, increases the effect of chemotherapy.

Apoptosis↗
PubMed1998

Role of fiberoptic bronchoscopy in conjunction with the use of double-lumen tubes for thoracic anesthesia: a prospective study.

BACKGROUND: Fiberoptic bronchoscopy has been recommended to verify the position of double-lumen tubes (DLT), but this remains controversial. The authors studied the role of bronchoscopy for placing and monitoring right- and left-sided DLTs after blind intubation and after positioning the patient. METHODS: Two hundred patients having thoracic surgery requiring DLT insertion were prospectively studied. "Blind" tracheal intubations were done with 163 left-sided and 37 right-sided disposable polyvinyl chloride Robertshaw tubes. Bronchoscopy was performed by a different anesthesiologist after intubation and conventional clinical verification of correct placement and after patient positioning for thoracotomy. A DLT was considered malpositioned when it had to be moved >0.5 cm to correct its position. Critical malpositions were those that might have affected patient safety or influenced the surgical procedure if left uncorrected. RESULTS: After "blind" DLT intubation, clinical evidence of malpositioning was found in 28 patients. This was confirmed by fiberoptic assessment. In 172 patients in whom placement was judged correct by clinical assessment, malpositioning was detected by bronchoscopy in 79 cases, 25 of which were critical. After patient positioning, DLTs were found to be displaced in 93 patients, 48 of which were critical. Right-sided DLTs were significantly more likely to be malpositioned than were left-sided DLTs. Two complications were related to unsatisfactory lung separation in the 200 patients studied. CONCLUSIONS: After blind intubation and patient positioning, more than one third of DLTs required repositioning. Routine bronchoscopy is therefore recommended after intubation and after patient positioning.

Adolescent↗
PubMed1996

Physico-chemical characterization of legumin-T from faba bean (Vicia faba L).

Legumin-T, the high-molecular mass product of limited tryptic hydrolysis of faba bean legumin, was investigated using hydrodynamic methods, static light scattering, fluorescence and ultraviolet spectroscopy. The following physico-chemical parameters were determined in a high-ionic strength buffer system: molecular mass, 2.4 x 10(5) g/mol; sedimentation coefficient, SO20 = 10.8 x 10(-13)Si; diffusion coefficient, DO20 = 4.1 x 10(-7) cm2 s-1; intrinsic viscosity, [eta] = 3.51 mL/g; partial specific volume, v = 0.719 mL/g; frictional ratio, f/f0 = 1.22; shape factor, beta = 2.17 x 10(6). Conformational changes during the formation of legumin-T can be deduced from the fluorescence emission and UV spectra.

Fabaceae↗
PubMed1991

[Time-limited contacts with psychosomatic-psychotherapeutic ambulatory care. I. Retrospective evaluation by patients].

Despite of the relevance of psychosomatic-psychotherapeutic outpatient services there is a lack of empirical studies concerning their effectiveness and compliance from the patients' point of view. This study describes the retrospective judgements of a maximum of three outpatient consultations, given by 125 patients after a mean follow-up period of 14 months. These patients completed a comprehensive questionnaire, comparable with instruments used in follow-up studies of longterm psychotherapies. The questionnaire covered demographic data, a detailed description of the consultations (including the atmosphere of the contact and the therapeutic alliance), their consequences as well as the present life situation and -quality. The results first indicate that patients who refused their participation in the study received more unspecific recommendations by the therapist, and were more commonly referred by other clinics. The judgements of the consultations were predominantly negative. Patients criticized for example a lack of activity by the therapist and of practical advice. The overall rate of compliance (i.e. number of patients who followed the therapist's recommendations) was 49%. Compliance was higher with respect to individual therapy and lowest with respect to inpatient psychotherapy. As far as the present life situation was concerned, the patients answers indicate a slight decrease of their complaints as well as an increase of life quality as compared to the time of the consultation. Potential reasons for the negative view of time limited contacts with a psychosomatic outpatient unit are finally discussed.

Adolescent↗
PubMed1991

[Time-limited contacts with psychosomatic-psychotherapeutic ambulatory care. II. Potential determinants of compliance with therapeutic recommendations].

In a detailed analysis of the data from a follow-up study with 125 patients of a psychosomatic outpatient unit, possible determinants of the utilization of therapeutic recommendations (which was seen as an indicator of compliance) have been analysed. The overall compliance-rate in the sample was 49%. Comparisons of the patients who were compliant or noncompliant (61 vs 37) revealed that demographic as well as diagnostic characteristics hardly differentiated between the two groups. The compliance-rate seems to be higher in patients who had been judged as motivated by their therapist during the time of their contacts with the unit. Besides that, the perception of the atmosphere of the contacts as well as the therapeutic alliance during a maximum of three consultations differed between both groups. Patients who were compliant assessed their life quality more positively at the time of the follow up than the other group. In a second step of the analysis, an attempt was made, by means of cluster analyses, to investigate the relationship between the compliance-rates, and the mode of referral as well as diagnostic characteristics on the one, the judgement of qualitative aspects of the consultations on the other hand. The analysis of the first relationship indicated a tendency for noncompliance in older patients and those suffering from addictions, whereas compliance seemed to be high in younger patients who came to the consultation of their own accord. Multivariate analyses further confirmed the significance of the therapeutic alliance for the prediction of compliance-rates and the importance of several other qualitative aspects of the contacts.(ABSTRACT TRUNCATED AT 250 WORDS)

Adaptation, Psychological↗
PubMed1989

[Keratoacanthoma and its clinical variants. Review of the literature and histopathologic analysis of 90 cases].

Current knowledge about the etiology and histogenesis of keratoacanthoma (KA) is first reviewed, after which the various clinical and histological patterns of this tumor are presented. The differential diagnosis, particularly against spinocellular carcinoma (SCC), and possible forms of therapy are discussed. A series of 90 KAs seen in the period 1976-1986 were investigated histopathologically with reference to the overall architecture, the epithelial differentiation, the behavior towards the adjacent tissue, and the extent and composition of the cellular infiltrate. In addition to routine staining with hematoxylin-eosin and Giemsa, several files have been subjected to immunohistological analysis by means of the peroxidase-antiperoxidase method (PAP) (keratin, lysozyme, epithelial membrane antigen, tissue polypeptide antigen). In 79 cases (88%) the overall architecture found was that of an endo-exophytic, dome-shaped structure with a central crater filled with a plug and with epithelial "lips" at the margins. In 3 KA (3%) a more endophytic picture was seen though no ulceration was observed. In 2 tumors in the very early stages (2%), there was no formation of horn crater and no epithelial lips. Similarly, 5 flat, plaque-like KA (6%) also showed no horn crater. With the exception of 3 aggregated (and/or multicentric) KA (3%), no solitary or multiple types were found. In 88 cases (98%), proliferation of the epidermis was observed mainly in the lateral and basal parts. In 86 KA (96%) there was a relatively well-demarcated, sharp border to the basal tumor portions. In 4 cases (4%) a less precise definition of the outer tumor margins was observed, because of a considerable pseudocarcinomatous, though not truly infiltrative, growth pattern. In 24 KA (27%) there was a strong tendency to formation of one or more sequesters. In the majority of cases, maturation of the epithelial cells was normal. Abnormal multipolar mitoses (7 cases; 8%) and relatively pronounced cellular atypies (8 cases; 9%) were occasionally observed. There was a clear correlation between the composition and extent of the inflammatory infiltrate and the tumor growth stage. In 78 KA (87%) large numbers of intraepithelial neutrophilic microabscesses were shown. In only 13 cases (14%) were substantial numbers of eosinophilic leukocytes observed, and 3 of these tumors (3%) later developed eosinophilic microabscesses.(ABSTRACT TRUNCATED AT 400 WORDS)

Diagnosis, Differential↗
PubMed1988

Fibrin monomer complexes (SFMC) after substitution of antithrombin III (AT III) in consumption coagulopathy.

The report refers to substitution therapy of 33 patients who suffered consumption coagulopathy. Various blood coagulation and fibrinolytic variables were measured. After successful AT III donation to patients suffering DIC, soluble fibrin monomer complexes (SFMC) disappeared within 0.5-12 hours. If AT III decreases SFMC proves positive again. In addition to analysis of AT III we recommend to analyse SFMC to detect thrombin induced consumption reaction (DIC). Furthermore we found the fibrin split product D-dimer was a particularly sensitive indicator of DIC in case of hyperfibrinolysis (D-dimer was analysed in six patients). The reactions of fibronectin and SFMC proved inversely proportional.

Adolescent↗
PubMed1988

[Behavior of respiratory tract, esophagus and pulmonary artery pressure in bronchoscopies in normofrequent jet ventilation in comparison with Friedel's ventilation technics].

The dynamics of selected physiological respiratory parameters were studied in a total of 29 patients. During slight hyperventilation and good oxygenation by both Friedel's and jet ventilation (driving pressure 0.3 and 0.4 MPa, respectively), comparably low respiratory tract pressures were observed. Transmission to intrathoracic (44-46%) and mean pulmonary artery pressure (11-13%) indicates only a low-grade ventilation-induced hemodynamic influence. By contrast, clear increases in pulmonary artery pressure due to intubation were recorded. Thus, the employed normofrequent jet ventilation with its continuous open-tube ventilation which is independent of the undisturbed bronchological examination possesses beneficial properties from a cardiorespiratory view.

Adult↗
PubMed1987

Extragonadal germ cell tumor: the preoperative urological evaluation.

Primary extragonadal germ cell tumors were diagnosed in 4 patients in whom surgical or postmortem examination of the testis failed to reveal germ cell tumor. A fifth patient underwent serial examination with testicular ultrasound without evidence of any abnormalities and he remains free of disease following chemotherapy. Based on our experience and a literature review, it is our opinion that orchiectomy is not indicated unless there is a palpable testicular abnormality, recent change in testicular size or consistency, abnormal testicular ultrasound or history of cryptorchidism, or if the primary tumor is choriocarcinoma.

Adult↗
PubMed1987

Iron overload, but not treatment with desferrioxamine favours the development of septicemia in patients on maintenance hemodialysis.

During a 19-month period we determined the incidence of bacterial infection among 39 patients treated with desferrioxamine who had end-stage renal disease and were undergoing maintenance hemodialysis. Twenty-three received desferrioxamine because of aluminum-related bone disease, and 16 because of iron overload. A control group of 193 patients on maintenance hemodialysis but without desferrioxamine was used. No difference was found in the incidence of septicemia or of all bacterial infections between the patients with aluminum-related bone disease treated with desferrioxamine and the control patients (0.12 vs. 0.12 septicemia per patient-therapy-year, p greater than 0.05; 0.23 vs. 0.26 bacterial infections per patient-therapy-year, p greater than 0.05). The incidence of septicemia in patients treated with desferrioxamine for iron overload, however, was almost three times that in the control patients (0.36 vs. 0.12 septicemia per patient-therapy-year, p less than 0.01). To assess the effect of iron overload itself, we determined the frequency of bacterial infection in patients on regular hemodialysis who have never received desferrioxamine. These were subdivided into three groups according to serum ferritin level which indicated normal or low iron stores (Group I: serum ferritin 10-330 micrograms/l, n = 125), moderate (Group II: serum ferritin 331-1000 micrograms/l, n = 49) or more advanced iron overload (Group III: serum ferritin 1001-2000 micrograms/l, n = 10). Compared to patients with normal or low serum ferritin levels (Group I), we found a significantly higher rate of bacterial infection among patients in Group II compared with Group I (0.18 vs. 0.34 infections per patient-therapy-year, p less than 0.05) and Group III compared with Group I (0.18 vs. 0.58 infections per patient-therapy-year, p less than 0.01). These results suggest that treatment with desferrioxamine does not favour the development of septicemia or bacterial infection independently of iron overload and that iron overload itself may predispose patients on regular hemodialysis to bacterial infection.

Aged↗