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Biomedical subjects

J Weinmann

Publications and source records attributed to J Weinmann.

12 recordsLinked to original sources
PubMed1998

Interruption of bronchial circulation leads to a severe decrease in peribronchial oxygen tension in standard lung transplantation technique.

OBJECTIVE: In clinical practice lung transplantation is the only procedure where the transplanted organ is left without its own arterial perfusion. With the interruption of the bronchial arteries the nutritive support is dependent on collateral flow by the pulmonary artery and the oxygen tension of desaturated central venous blood, representing an abnormal physiology. METHODS: To analyze this problem systematically, we used a standard single left lung transplantation model in the pig (n = 12). In accordance with the clinical standard, lung preservation was performed with modified Euro-Collins solution with addition of prostacycline. The duration of ischemia was set to 4 h. Before and after single left lung transplantation tissue oxygen tension in the peribronchial tissue was measured with Licox tissue pO2 microprobes. For validation, the myocardial tissue oxygen tension was recorded simultaneously. The hemodynamic assessment included continuous flow measurement of the left and right pulmonary artery using Transsonic ultrasound flow probes. After transplantation the animals were observed for 4 h. For hypothetic augmentation of collateral blood flow to the peribronchial tissue we administered Nitric oxide (10 ppm) to the ventilation in six pigs (group B). Six pigs (group A) served as a control without the addition of nitric oxide (NO). All pigs were ventilated with a FiO2 of 0.5 resulting in paO2 values between 160 and 200 mmHg. RESULTS: In both groups single lung transplantation led to a significant decrease in peribronchial tissue oxygen tension throughout the observation period. Pre-Tx values of peribronchial tissue oxygen tension (38.31 +/- 6.56 mmHg) decreased to 9.72 +/- 2.55 mmHg in group A and 10.3 +/- 3.61 mmHg in group B after 4 h, which could not be altered by a FiO2 of 1.0 (P < 0.0001). The addition of NO in group B led to a significantly augmented flow in the left pulmonary artery (0.63 +/- 0.31 l/min in group B vs. 0.46 +/- 0.26 l/min group A, P < 0.001) representing 67 vs. 49% of the pre-Tx flow in groups B and A, respectively, but the peribronchial tissue oxygen tension was not influenced (P > 0.05). In both groups A and B, the central venous pO2 did not differ in the postoperative period (41.83 +/- 3.27 mmHg group A vs. 43.26 +/- 2.98 mmHg group B) and was kept in a comparable range to the pretransplantation values (45.23 +/- 3.41 mmHg pre-Tx). CONCLUSIONS: The persistence of a very low peribronchial tissue oxygen tension in the early phase after lung transplantation cannot be influenced by improved pulmonary artery flow and solely relates to the central venous pO2, which cannot be augmented by the addition of NO. This mechanism might be a trigger for anastomotic healing problems, infectious complications and later development of obliterative bronchiolitis (OB).

Animals↗
PubMed1989

The regulation of expression of mouse mammary tumor virus DNA by steroid hormones and growth factors.

Mouse mammary tumor virus (MMTV) expression is associated with hyperplastic alveolar growth and subsequent development of mammary cancers in the mouse. The expression of this virus is also controlled by factors involved in the normal proliferation and differentiation of the mammary epithelium. During pregnancy when the mammary gland undergoes massive proliferation, MMTV expression is increased. Steroid hormones and growth factors that play an important role in the proliferation of mammary gland cells are responsible for the increased MMTV expression. In sarcomatous transformation of mouse mammary epithelial cells, MMTV expression is repressed. This repression is due to negative control of MMTV expression by transforming growth factor-beta (TGF beta). This growth factor is produced in high amounts when mammary epithelial cells progress into the transformed state. The expression of MMTV is therefore under multiple control by steroid hormones and growth factors.

Animals↗
PubMed1988

DNA sequences outside the receptor-binding sites differently modulate the responsiveness of the mouse mammary tumour virus promoter to various steroid hormones.

Glucocorticoids, progestins and androgens all induce the transcription of the mouse mammary tumour virus (MMTV) DNA upon binding of their respective receptors to the hormone response element (HRE). This element is located between -202 and -59 5' upstream of the start of transcription on the MMTV long terminal repeat (LTR) region. The HRE contains four repeats of the hexanucleotide 5'-TGTTCT-3' to which the steroid hormone receptors are thought to bind. To investigate the contribution of the individual receptor-binding sites and neighbouring sequences to the steroid hormone action at the MMTV LTR promoter, we mutated various regions of the HRE and studied their response in transfection experiments. Each of the four receptor-binding sites was found to contribute substantially to the overall induction of transcription by all the various steroid hormones tested. This indicates that each individual receptor-binding site on the HRE is important for maximum hormone response. Additionally, we identified four separate sequences outside the receptor binding sites that differentially modulated the response of the MMTV LTR promoter to various steroids. One of these sequences binds the cellular factor, NFI. Thus the interaction of trans-acting factors with sequences outside the hormone receptor-binding sites controls the hormone response of the MMTV LTR promoter.

Acetyltransferases↗
PubMed1988

Mineralocorticoid regulation of transcription of transfected mouse mammary tumor virus DNA in cultured kidney cells.

Renal cells contain two corticosteroid-binding entities defined on the basis of hormone-binding selectivity as type I (mineralocorticoid) and type II (glucocorticoid). The mineralocorticoid, aldosterone can bind to both type I and type II receptors. This poses problems in defining the characteristics of a true mineralocorticoid regulated expression of specific genes. We have used chimaeric constructs bearing the mouse mammary tumor virus (MMTV) promoter to study aldosterone action in the feline renal cell line CRFK. We have shown that in these cells aldosterone induces MMTV transcription through its own receptor (type I). This induction of MMTV transcription by aldosterone is a primary response to the hormone. We have shown that the DNA sequences that mediate the aldosterone response overlap the hormone response element (HRE) required for the glucocorticoid, progestin, and androgen induction of transcription at the MMTV long terminal repeat region. Thus the aldosterone regulation of MMTV long terminal repeat transcription is identical to the mode of action of the other steroid hormones at this promoter.

Aldosterone↗
PubMed1987

Effect of digitoxin on cardiac arrhythmias in hemodialysis patients.

Digitoxin is considered a risk factor for ventricular arrhythmias in hemodialysis patients. In a randomized, crossover controlled study, 55 hemodialysis outpatients with sinus rhythm were prospectively investigated in two 48-h periods of electrocardiographic monitoring, one on and one off digitoxin or vice versa. The frequency of ventricular ectopic beats (mean +/- SD) which were found in 31 of 55 patients (56%), was slightly higher on hemodialysis (10 +/- 28 beats/h) than in the following 20 h (5.4 +/- 10 beats/h) and the next day off hemodialysis (3.6 +/- 6.6 beats/h); however, no difference was seen in patients on digitoxin during hemodialysis (10 +/- 29 beats/h), in the following 20 h (4.8 +/- 15 beats/h) and on the next day off hemodialysis (1.2 +/- 6.6 beats/h). The frequency of ventricular bigemini, polymorphous ectopies, couplets, more than 30 ectopies/h, salvos and tachycardias (10 vs 9 patients) on and off digitoxin was about the same (n.s., Fisher test). Supraventricular bigemini, salvos, tachycardias, and atrial fibrillation, however, occurred in significantly fewer patients on digitoxin (3 vs 13) than in those off digitoxin (P = 0.01, Fisher test). It is concluded that digitoxin does not increase the risk of ventricular arrhythmias in hemodialysis patients. Digitoxin, however, may have a beneficial effect on the supraventricular arrhythmias frequently observed in these patients.

Adult↗
PubMed1984

[Trial for digitalis withdrawal in hemodialysis patients].

The indication for digitalis treatment was investigated in a controlled and prospective study lasting 12 months in 110 patients on long-term haemodialysis. In ten patients, digitalis was needed because of tachyarrhythmia due to atrial fibrillation and in five because of recurrent pulmonary edema. In 57 patients receiving digitoxin, therapy was discontinued for 4 to 6 weeks, whereas 13 patients not yet treated with digitalis, received digitoxin for 4 weeks. Without digitoxin, trial fibrillation occurred in 4 patients, while no patient experienced atrial fibrillation with digitoxin (P = 0.002). In 13 patients, radiological findings (heart enlargement, pulmonary congestion) were better with digitoxin than without. Thus digitoxin appeared to be clearly indicated in 29% of the haemodialysed patients. Additionally, digitalis was indicated in 31 patients because of heart enlargement, pulmonary congestion and (or) previous pulmonary edema. Initially, 76% of the patients were receiving digitoxin, whereas, after the investigation, the rate was only 57% (P less than 0.001). The prospective frequency of clinically apparent digitoxin intoxication was low (3%) and so were the overall toxic plasma digitoxin levels (5%). Digitalis should be given deliberately but not restrictively to haemodialysis patients, since atrial fibrillation (13%) and heart failure (50%) are frequent and often concealed.

Adult↗
PubMed1979

[Digoxin concentrations in plasma and tissue. A postmortal investigation (author's transl)].

Postmortal tissue digoxin concentration and prefinal and postmortal plasma digoxin concentrations from 9 patients were determined using the 125J-digoxin radioimmunoassay. The concentration of digoxin in the myocardium of the left ventricle was 61.44 +/- 45.17 ng/g. In the right ventricle the concentration was 36.78 +/- 33.11 ng/g. Higher digoxin concentrations were found in the right atrium (34.93 +/- 21.86 ng/g) than in the left atrium (25.43 +/- 14.57 ng/g). In plasma samples taken after death approximately 62% higher digoxin concentrations were found than in samples of patients in prefinal state. Histological examination revealed positive correlation between in the high varying digoxin concentrations and the pathological conditions of the tissue structure.

Aged↗
PubMed1978

[Suicide with beta-methyldigoxin (author's transl)].

A 50-year-old woman committed suicide by taking an overdose of beta-methyldigoxin. The interval between swallowing the tablets and death was about 60 minutes. Plasma and tissue samples, taken 163 hours after death, were analysed for glycosides by radioimmunoassay. The plasma-glycoside level was 75.1 ng/ml, in the left ventricular myocardium it was 143.2 ng/g wet-weight. and in the right ventricular myocardium 159.7 ng/g wet-weight. The tissue-plasma ratio for the various parts of the heart varied from 0.8 to 2.1. Death occurred in the early distribution stage.

Digoxin↗
PubMed1978

Human myocardium and plasma digoxin concentration in patients on long-term digoxin therapy.

Digoxin concentration of 14 left ventricular papillary muscles and 36 right atrial appendages of 45 patients undergoing cardiac surgery were determined by the NEN 125J-radioimmunoassay. Blood specimens for digoxin assay were withdrawn immediately before operation, 12 to 16 hr after the last digitalis dose. Mean papillary muscle digoxin concentration was 76.1 ng/g +/- 25.5; mean ratio to plasma digoxin level, 36.8:1. The mean concentration of right atrial appendages was 41.8 ng/g; mean ratio, 29.9:1. Most of the tissue specimens were examined histologically using Hematoxylin-Eosin and van Gieson stains. No clear relation between tissue digoxin concentration and hisological alteration, i.e., the degree of fibrosis or lipomatosis, could be found, although most severe alterations were found in right atrial appendages corresponding to a higher variation in tissue concentrations and a poorer correlation to plasma digoxin (r = 0.47, respectively for papillary muscle r = 0.73).

Adult↗