Biomedical subjects
G Feifel
Publications and source records attributed to G Feifel.
Rectal endosonography.
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Angiogenesis and hemodynamics of microvasculature of transplanted islets of Langerhans.
Transplantation of isolated islets of Langerhans is frequently followed by early loss of islet function. Because whether this is caused by insufficient vascularization or graft rejection is unknown, angiogenesis and microvascularization of islet grafts were studied in vivo by means of intravital microscopy. After transplantation of syngeneic islets in hamster dorsal skin-fold chambers, 97% (n = 66) of the islets exhibited the first signs of angiogenesis at days 2-4, characterized by sinusoidal sacculations and capillary sprouts. After 10 days, angiogenesis was completed, consisting of a microvascular network similar to those of islets in situ: arterial supply, afferent and efferent capillary loops, and venular drainage. Functional density of microvessels was 700.1 +/- 127.0 cm-1, and erythrocyte velocity was 0.58 +/- 0.35 mm/s. Intracellular insulin was demonstrated immunohistochemically. Electron-microscopic studies revealed normal fine structure of the capillary wall. The model allows in vivo analysis of microvascular phenomena occurring in host-vs.-graft reaction after allogeneic and xenogeneic islet transplantation. Furthermore, it may be used to quantitatively assess immunosuppressive regimens.
[Current significance of retrospective studies].
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Highly sensitive assays of autoantibodies to thyroglobulin and to thyroid peroxidase.
These highly sensitive assays are based on the interaction between thyroid autoantibodies and 125I-labeled autoantigens. Serum samples are incubated with labeled thyroid peroxidase (TPO) or thyroglobulin (Tg) to allow the formation of antibody-labeled antigen complexes. The complexes are then precipitated by addition of solid-phase Protein A. In the presence of high concentrations of TPO antibody or Tg antibody, more than 50% of the respective labeled antigen was precipitated, whereas only 1-2% was precipitated in the absence of autoantibody. Interassay CVs were 3.2% and 5.7%, respectively, for the anti-TPO and anti-Tg assays. There was no cross-reactivity between Tg antibody and TPO antibody. Results correlated highly significantly with results from other assay systems based on antigen-coated cells or plastic supports, but the assays described here were considerably more sensitive. Scatchard analysis of the assay data provided information on the affinity and serum concentration of TPO autoantibodies (ka approximately 10(9) L/mol and concentrations up to 1 g/L) and Tg autoantibodies (ka approximately 4 x 10(10) L/mol and concentrations up to 1 g/L). Overall, these assays provide a sensitive, precise, and convenient system for measuring and investigating the properties of thyroid autoantibodies.
Tissue PO2 and functional capillary density in chronically ischemic skeletal muscle.
In order to study changes in functional capillary density and tissue PO2 in chronically ischemic skeletal muscle, a new model, using the Syrian golden hamster was developed. In the hamster dorsal skin fold, which receives its vascular supply from two cranial and two caudal feeding arteries, a double frame chamber was implanted and ischemia was induced in the cranial part by heat coagulation of the cranial arteries outside of the chamber. This technique allows for analysis of microvascular hemodynamics and local tissue PO2 prior to and during a prolonged period of ischemia in skin muscle. As result of ischemia the diameters of the arterioles increased (p less than 0.001) over the whole 11 day observation period. Functional capillary density decreased significantly (p less than 0.01) during the first 7 days, while capillary RBC-velocity was reduced throughout the 11 days of observation. RBC-velocity in collecting venules was diminished significantly throughout the postischemic observation period. The diameters of the collecting venules first increased upon ischemia (p less than 0.001) but were found decreased at 4, 7 and 11 days. Measurements of tissue PO2 demonstrated a marked decrease from a mean PO2 of 20.5 mmHg prior, to 9.5 mmHg following induction of ischemia. The model allows for induction of chronic ischemia and is suitable to study the effect of therapeutic measures on the microcirculation in chronically ischemic skeletal muscle in vivo.
[How have recent results concerning transfusion-induced immunosuppression and danger of transmission of AIDS changed indications for the transfusion of blood and blood components?].
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Quantitative analysis of microcirculatory disorders after prolonged ischemia in skeletal muscle. Therapeutic effects of prophylactic isovolemic hemodilution.
Reperfusion injury following prolonged ischemia is thought to be caused primarily by microvascular failure. The aim of the present study was to investigate whether prophylactic isovolemic hemodilution with Dextran 60 (hct 30%) could improve microvascular perfusion after 4 h of pressure-induced ischemia in skeletal muscle. In 28 Syrian golden hamsters (6-8 weeks/60-80 g b. wt.) a dorsal skinfold chamber and permanent arterial and venous catheters were implanted under Nembutal anesthesia (50 mg/kg b. wt.). Following a recovery period of 48 h pressure-induced ischemia was applied to the skeletal muscle within the skinfold chamber by means of a transparent stamp. Quantitative analyses of microhemodynamics were performed in the awake animal prior to and 15 min, 1, 2, 4 and 24 h after ischemia using vital fluorescence microscopy. In non-treated animals, functional capillary density decreased after 4 h of ischemia to 30% of the initial values (P less than 0.001); after 24-h reperfusion only 50% of the initially perfused capillaries were reperfused (P less than 0.001). The heterogeneity of functional capillary density increased after ischemia to a maximum of 2.19 +/- 0.94 as compared to 0.48 +/- 0.11 prior to ischemia. Capillary RBC-velocity suffered a marked reduction in the early reperfusion phase and did not recover up to the 24-h observation time. In contrast, prophylactic isovolemic hemodilution was associated with only a small and reversible reduction of functional capillary density after 4-h ischemia. At 24-h reperfusion 90% of the initially perfused capillaries were reperfused. Capillary RBC-velocity was reduced in the early reperfusion phase, but returned to normal values within 24 h. Thus, prophylactic isovolemic hemodilution resulted in a marked reduction of microvascular reperfusion failure in skeletal muscle. A hematocrit lower than normal prior to ischemia provides better conditions for capillary reperfusion after prolonged ischemia.
[Pre- and postoperative quantitative flow measurements (electromagnetic and sonographic) in the assessment of surgical results in carotid stenoses].
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[Diagnostic strategies of the small and large intestine].
The selection and sequence of different diagnostic procedures, such as abdominal X-ray, contrast roentgenography, ultrasonography, endoscopy and angiography, depend on the presenting symptoms and the presumptive diagnosis. In addition, the acuteness of the disease and the requirements for planning the operation determine the diagnostic time course. Novel image processing devices, such as endosonography and computerized tomography, may improve diagnosis, especially in rectal diseases. Successful outcome of diagnostic examinations can be achieved only by differentiated use of radiologic and endoscopic methods.
[Local therapy of rectal cancer].
Curative local excision or segmental resection can be performed in 10-15% of patients with rectal carcinoma, avoiding colostomy. Local treatment of early, microinvasive carcinoma is the procedure of choice. The most important problem is patient selection. With the endosonographic assessment of the tumor invasion, preoperative staging is possible with high accuracy. In a small series 10 patients were found to be tumor-free 4-46 months after local treatment.
Prolongation of graft survival in allogeneic islet transplantation by (-) 15-deoxyspergualin in the rat.
The effect of 15-Deoxyspergualin, a novel drug which has been described to have anti-tumour activity, on allogeneic graft survival (Dark Agouti----Lewis rats) after pancreatic islet transplantation was tested. A marked prolongation of graft survival could be shown using doses of 1.0, 2.5 and 5.0 mg Deoxyspergualin/kg on day 0 until day +9 post transplantation. A maximum of 55.6 days (average) survival time was observed using 2.5 mg/kg Deoxyspergualin compared to 5.2 +/- 0.6 days without immunosuppression. Using the chemiluminescence reaction of recipient monocytes after islet transplantation, a marked suppression of the monocyte system exceeding the treatment period could be observed. Since, in contrast to cyclosporin, B-cell toxicity could not be shown, the new drug seems to be a hopeful step towards successful allogeneic islet transplantation for treatment of diabetes.
Assessment of depth of invasion in rectal cancer by endosonography.
Pre-operative staging of rectal cancer could be significantly improved by the imaging method of endorectal ultrasound. Using high-frequency transducers a complex rectal wall pattern was demonstrated. Depending on in vitro or in vivo examinations and on US probes of different frequency the current interpretation is not uniform. Agreement exists on the interpretation of the muscularis propria which is of clinical importance. Objective and precise criteria for lymph node differentiation have yet to be worked out.
Prolongation of graft survival in allogeneic pancreas and liver transplantation by (-)15-deoxyspergualin.
(-)15-Deoxyspergualin, originally discovered as an antitumoral drug, was shown to have different immunosuppressive effects, when pancreas and orthotopic allogeneic liver transplantations in rats were compared. In the strong rejection model dark agouti----Lewis (RT1a----RT1(1)) we could only show a minor immunosuppressive effect, as far as pancreaticoduodenal and pancreas segment transplantations are concerned: graft survival was prolonged by 9 days in pancreas segment allografts (p less than 0.01) and by 6 days in pancreaticoduodenal allografts (p less than 0.01), when recipients were treated by ten doses of 2.5 mg/kg deoxyspergualin. Pretreatment of recipients with 15-deoxyspergualin was not efficient. On the contrary, in orthotopic liver transplantation done by the cuff technique, a remarkable prolongation of allograft survival could be demonstrated: about half of the animals showed prolongation of allograft survival for more than 80 days, compared with about 11 days in the control group (p less than 0.01). The substance is considered to be valuable for clinical application.
Deoxyspergualin induces tolerance in allogeneic kidney transplantation.
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[The effect of metamizole on gastric emptying and small intestine transit in the rat].
The effect of the pyrazolone derivative metamizole on the motility of the upper gastrointestinal tract of the rat was investigated. An animal model for simultaneous quantification of gastric emptying and small intestinal transport was used. A test meal with different radioactive labels was administered by means of previously implanted tubes both to the stomach (1.0 ml; 51Cr) and to the duodenum (0.25 ml; 99mTc), and the spatial distribution of both isotopes in a gastrointestinal preparation was determined after a transport time of 30 min. It has been shown that intravenously administered metamizole reduces significantly the percentage of the test meal discharged by the stomach (control: 70.9 +/- 2.8; 50 mg/kg metamizole: 26.3 +/- 6.9, p less than 0.001; 250 mg/kg metamizole: 3.8 +/- 1.5, p less than 0.001); 1250 mg/kg metamizole: 1.1 +/- 0.3; p less than 0.001). The 50- and 250-mg/kg doses had no negative effect on the propulsion of the small intestine. A dose of 1250 mg/kg induced a significant reduction in small intestinal transport (p less than 0.001).
[Pseudo-obstruction of the intestine].
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[Therapy of peptic ulcer: when long-term drug therapy, when surgical treatment?].
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