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Biomedical subjects

U Windberger

Publications and source records attributed to U Windberger.

27 records · Page 2Linked to original sources
PubMed1993

Dissociation of hemodynamic and renal effects of i.v. alpha-hANF (99-126) in conscious calves.

The effects of i.v. human atrial natriuretic factor (alpha-hANF [99-126]) was investigated in 5 conscious calves (age 4 months, weight 94 +/- 14kg) with constant fluid (300 ml/h) and sodium intake over a period of 24 hours before and during the 3 hours of experimentation. We administered 200 micrograms, 400 micrograms and 800 micrograms ANF at hourly intervals. Immediately (+2 min) after the i.v. injection the peptide's serum-concentration rose from, basal 13 +/- 3 to 802 +/- 191 (200 micrograms), 1707 +/- 419 (400 micrograms) and 3483 +/- 878 pmol/l (800 micrograms) (p < 0.0001), respectively. Mean arterial pressure decreased from, basal, 108 +/- 18 to 85 +/- 17, 76 +/- 16 and 69 +/- 18 mmHg (p < 0.0001), and central venous pressure decreased from, basal, 5.1 +/- 3 to 1.2 +/- 1, 0.4 +/- 1 and 0.8 +/- 2 mmHg (p < 0.001). Heart rate increased from, basal, 66 +/- 5 to 84 +/- 23, 111 +/- 29 and 114 +/- 13 b/min (p < 0.001). Following the administration of ANF the urine volume decreased from, basal, 261 +/- 145 to 195 +/- 72, 121 +/- 41 and 102 +/- 33 ml/h (p < 0.0041). The urinary sodium excretion rates decreased from, basal, 50 +/- 17 to 30 +/- 13, 22 +/- 10 and 19 +/- 10 mmol/h (p < 0.007), and the potassium excretion rates decreased from, basal, 43 +/- 19 to 39 +/- 16, 26 +/- 11 and 23 +/- 10 mmol/h (p < 0.0047). Endogenous clearance of creatinine (basal: 182 +/- 30 ml/min) did not change (260 +/- 84, 218 +/- 66 and 224 +/- 76 ml/h) following i.v. ANF. Inspite of this marked fluid retention, the hematocrit, expressed as relative change, was increased by 7.5%, 11.8% and 10.4%. In 2 calves we additionally measured an increased whole blood and plasma density possibly indicating increased liquid permeation to an extravascular compartment. Thus, in calves the hemodynamic effects of ANF are comparable to those seen in man. However, the failure of ANF to stimulate diuresis and natriuresis indicates a dissociation of hemodynamic and renal effects of ANF in calves.

Animals↗
PubMed1993

[Laparoscopic colon surgery--from experiment to initial clinical experience].

The technique of Laparoscopic resection of the colon sigmoideum was practised in an experimental model before starting a clinical program of laparoscopic colonic surgery. Until now, two resections of the colon sigmoideum, one ileocecal resection, one right colectomy, one Hartmann's procedure and one transversostomy have been performed laparoscopically. Three patients had colonic carcinoma. One sigmoid resection had to be converted to open surgery and this patient underwent relaparotomy because of postoperative ileus. The postoperative course of the other patients was uncomplicated. The promising initial experience demonstrates that laparoscopic colonic surgery is feasible, although further studies have to prove advantages and indications, especially with respect to oncology.

Adolescent↗
PubMed1992

Cardiac function, morphology and chromosomal aberrations in a calf with ectopia cordis cervicalis.

A male calf with ectopia cordis cervicalis inferior was investigated clinically, hemodynamically, and morphologically from the 3rd day of age until slaughter at the age of 22 months. Arterial hypertension (mean AOP 140 mm Hg), concentric myocardial hypertrophy and good ventricular contractility with normal valve function were found. Normal clinical condition at rest (cardiac output 48 l/min in the 600 kg bullock), but cyanosis and dyspnea during physical exercise were observed. Variations in the large vessels, such as persistence of the right cranial caval vein and one common pulmonary vein emptying into the left atrium, were found. Abrupt caliber differences of large arterial vessels together with a right angled aortic arch were observed, presumably contributing to increased afterload. The cytogenetic analysis showed the presence of a small marker chromosome leading to a chromosome number of 61 in a fraction of metaphases (mosaicism). Moreover, chromosome breakages were observed in many cells. From the 5 cows which were inseminated, 3 became pregnant. Ectopia cordis was not observed in any offspring. We conclude that in this animal compensated cardiac insufficiency with peripheral hypertension was established.

Animals↗
PubMed1992

Diminished release of atrial natriuretic factor in calves with a total artificial heart.

Venous hypertension after total artificial heart (TAH) replacement, a common problem in humans as well as experimental animals, is thought to be related to reduced release of atrial natriuretic factor (ANF) due to atrial damage. To verify this hypothesis, we stimulated the release of ANF in 6 calves before (-7 days) and after TAH replacement (+25, +50, +80, and +100 days) by the rapid (+ = 10 min) infusion of 2 L of Ringer's solution. In normal calves (-7 days) this procedure induced a rise in plasma concentration of ANF from 18.5 +/- 12 to 31.6 +/- 12 pmol/L (p < 0.05). After TAH the ANF release continuously decreased (analysis of variance, p < 0.02). Thus, ANF increased by 9.8 +/- 9.3, 6.8 +/- 17.5, 0.4 +/- 5.2, and 0.5 +/- 3.2 pmol/L at days 25, 50, 80, and 100, respectively. The central venous pressure increased by 3.4 +/- 1.5 mm Hg (before TAH) and by 6 +/- 2.9 mm Hg (after TAH) during this procedure. A decrease in plasma concentrations of aldosterone, most likely due to extracellular volume expansion and a decrease in total protein plasma concentrations and in hematocrit due to the dilution of blood, was seen in each experiment. Necropsy demonstrated massive atrial dilatation and myocardial dystrophy with atrial fibrosis. ANF granules were present to a small extent in every calf. We conclude that rapid intravenous infusion is an adequate stimulus to release ANF in normal calves. After TAH implantation the release of ANF by high venous pressure declines although ANF granules are still present in the damaged atrial stumps. Therefore, the loss of stimulated ANF could contribute to the observed increase in venous pressure in TAH calves although other pathophysiologic mechanisms cannot be excluded.

Aldosterone↗
PubMed1991

Mesh-constricted varicose and dilated veins used as arterial bypass grafts.

To avoid non-autogenous vascular prostheses in coronary and peripheral vascular procedures, otherwise unusable dilated, varicose or thin-walled veins can be implanted as naturally endothelialized grafts after being calibrated by insertion into mesh tubes. In six sheep the 14 mm diameter jugular vein was inserted into a 12 cm long, 6 mm diameter Dacron mesh tube and implanted as a femoropopliteal graft. On the contralateral side the femoral vein with a maximal diameter of 7 to 8 mm was implanted. At control angiography after two months all grafts were patent, none of the wrapped grafts showed wrinkles or signs of anastomotic hyperplasia. Segments of wrapped veins were casted in paraffin under physiological pressure and cut transversely. In all cases the vein wall was pressed against the mesh tubes without forming folds. Mesh-wrapped varicose veins were used for three femorocrural and seven femoropopliteal reconstructions. All grafts showed a smooth flow surface at control angiography. Indentations occurred only at sites where thick-walled side branches had been ligated rather than oversewn. One popliteo-pedal reconstruction occluded after two months and one patient with a crural reconstruction died two months after surgery with a patent graft. The remaining grafts were patent after 11 (2-32) months. Oversized veins can be considerably constricted by tubes without forming wrinkles. By this technique varicose veins can be used as bypass grafts and in general vein grafts can be matched in size to the recipient vessel.

Aged↗
PubMed1990

A method for constricting large veins for use in arterial vascular reconstruction.

A satisfactory biologic graft can be created if dilated, but otherwise unusable veins are wrapped with a constrictive mesh tube. The purpose of this study was to determine whether a resorbable constrictive tube creates an appropriately sized vascular graft by induction of neoarterial wall growth. In 8 sheep a 5 cm segment of the carotid artery was resected and the external jugular vein inserted as a tubular graft. The vein was either wrapped with a polydioxanon (PDS) reinforced polyglactin (Vicryl) mesh (n = 4), a Vicryl mesh (n = 4), or a Dacron mesh tube (n = 3) to achieve a diameter reduction to 7 mm. Or the vein was used without reinforcement (n = 3). At angiography after 6 months the unreinforced veins had a diameter of 19 mm (range 15-22). The Vicryl reinforced veins measured 9.4 (8.5-10) mm, but 3 of 4 developed aneurysmatic dilatations at sites of valve sinuses with a mean diameter of 19 (15-21) mm. PDS reinforced veins measured 7.4 mm (7.1-7.9). Two of 4 had minor aneurysms of 13 and 16 mm. The two remaining PDS reinforced grafts were indistinguishable from the native artery. Dacron tubes reduced the vein size reliably to 7.6 (7.5-7.9) mm, but showed narrowing at the proximal anastomoses (PDS 7.2 +/- 0.4, Dacron 6.1 +/- 0.4, p = 0.016). PDS wrapping reduced maximal graft diameter to 10.9 +/- 4 mm as compared to that of the native vein, 18.7 +/- 3.5 (p less than 0.05). Resorbable meshes can reduce the diameter of a venous graft by strengthening the vessel wall.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMedDate not supplied

Sustained heart failure induced by repeated microsphere injections for left ventricular assist device testing.

A subacute to chronic heart failure model was established to test left ventricular assist device (LVAD) systems. Five calves were anesthetized and instrumented. Heart failure was induced by daily injection of polystyrene microspheres (37-70 microns) into a left coronary catheter. The last three animals had an atrio-aortic pulsatile LVAD implanted. Cardiac output (CO) decreased from 12 to 5.5 L/min, and SV from 120 to 60 ml, whereas left atrial pressure (LAP) increased from 12 to 25 mmHg within 10 to 20 days in the two animals without LVAD support. Both animals stopped eating and drinking. The LVAD experiments were terminated after 5, 10, and 11 days. Cardiac function was determined during daily pump-off tests. After repeated microsphere injections, LAP increased to 30 and 50 mmHg, and CO decreased to 4 and 6 L/min without pump support. Daily stepwise microsphere injections induce a sclerotic cardiomyopathy in a safe and reliable manner.

Animals↗
PubMedDate not supplied

Improved biocompatibility by postfixation treatment of aldehyde fixed bovine pericardium.

Long-standing release of locally cytotoxic aldehyde concentrations is responsible for lack of spontaneous endothelialization and increased calcification of glutaraldehyde fixed bovine pericardium. Postfixation treatment with amino acids made in vitro endothelialization of bioprosthetic heart valves possible. Such treated pericardium calcified significantly less (13 +/- 4 micrograms/mg dry weight) than did conventionally processed pericardium (114 +/- 25 micrograms/mg) after 63 days of subcutaneous implantation in rats. To test the ability for spontaneous in vivo endothelialization, 5 sheep had 6 mm grafts made from postfixation treated pericardium (PTP) implanted into the carotid artery, compared to PTFE grafts on the contralateral side, which spontaneously endothelialize in animal models. In a pregnant animal, both grafts occluded. All remaining pericardial grafts remained patent, but one additional PTFE graft occluded and another one was stenosed. The area covered with red thrombus was significantly smaller in the PTP grafts (3.05 +/- 3.9%) than in the PTFE grafts 42 +/- 14% (p = 0.0036); TEM and SEM showed endothelial cells growing directly on the PTP, but only on myofibroblasts in PTFE grafts. Postfixation treatment of glutaraldehyde fixed pericardium aids spontaneous endothelialization and decreases tissue calcification.

Animals↗