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Biomedical subjects

A Röckel

Publications and source records attributed to A Röckel.

At least 19 recordsLinked to original sources
PubMed1992

Low-molecular-weight protein-permeable cuprammonium rayon haemofilter.

Searching for a dialyser membrane with a cut-off similar to that of the human glomerulus, a modified cuprammonium rayon (AM-75-UP) and a polyacrylonitrile (PAN-15-DX) haemofilter were tested in vivo for the ability to eliminate substances of a molecular weight (MW) of 10-65 kilodaltons (kDa). Endogenous marker substances of a defined MW (beta-2-microglobulin 11.8 kDa; retinol binding protein 21 kDa; alpha-1-microglobulin 26.7 kDa; alpha-1-glycoprotein 41 kDa; alpha-1-antitrypsin 54 kDa; albumin 66.3 kDa) were measured by laser nephelometry or immunosorbent assay; sieving coefficients (SC) and protein elimination (PE) per 20 l haemofiltration were calculated for each low-MW protein. The PAN haemofilter shows elimination characteristics comparable to those of earlier tested haemofilters (polysulphone, AN69, cellulose triacetate) with a sharp cut-off in the MW range of 10-15 kDa. The cuprammonium rayon haemofilter is permeable for proteins with a higher MW; especially for alpha-1-microglobulin a relevant removal (SC 0.2; PE 0.56 g/20 l) was established. This membrane has a cut-off more similar to that of the human glomerulus; but far from the demanded quality with a relevant removal of substances in the MW range up to 60 kDa. Calculated albumin loss (2.4 +/- 0.2 g/20 l) seems to be tolerable for stable haemodialysis patients.

Acrylic Resins↗
PubMed1989

Allergy to dialysis materials.

One hundred and six unselected patients were screened for allergic symptoms, specific IgE against ethylene oxide (ETO), isocyanates (ISO), formaldehyde (FA), phthalates (PHT), total IgE and eosinophil count. Complement activation was measured during cellulosic dialysis in atopic patients and in a control group. Sixteen patients demonstrated mild allergic symptoms during dialysis treatment. Ten of them had IgE elevation and eosinophilia. Eight of these patients had positive RASTs (ETO: n = 5, ETO-ISO(?)-FA: n = 2, ISO-PHT: n = 1) against dialysis material. All eight had an eosinophilia and seven showed an IgE elevation. An amelioration of symptoms could be obtained in three patients with elevated (greater than 15%) ETO-binding values after switching to ETO-free dialysers; avoiding PHT- and ISO-containing dialysis materials allergic symptoms remained constant. Cuprammonium rayon-induced complement activation had a more rapid onset and was more pronounced in atopic patients. The study confirms the role of ETO, but not of the other dialysis materials in the allergic sensitisation of haemodialysis patients.

Complement Activation↗
PubMed1989

Transmembranous transport and adsorption of beta-2-microglobulin during hemodialysis using polysulfone, polyacrylonitrile, polymethylmethacrylate and cuprammonium rayon membranes.

Beta-2-microglobulin (b2M) was identified as a causative agent of amyloidosis associated with long-term hemodialysis (HD). Therefore, we examined handling of b2M during a 4-hour hemodialysis session. We compared b2M adsoprtion and diffusive/convective elimination between high-flux membranes such as polysulfone (PS; F 60, Fresenius), polyacrylonitrile (AN 69; Filtral, Hospal) and polyacrylonitrile (PAN, PAN 12CX2, Asahi) and less permeable membranes such as cuprammonium rayon (CR; AM 160 H, Asahi) and polymethylmethacrylate (PMMA; BK-1.6 U, Toray). To calculate total elimination, arterio-venous differences of b2M were measured at 0, 5, 20, 60 and 240 minutes; dialysate concentration was analyzed to evaluate diffusive/convective transport. Differences between recovery in dialysate and total removal were regarded as amount removed by adsorption. Total elimination per 4-hour hemodialysis session and per m2 membrane surface was 154.7 +/- 12.3 mg for the PS, 137.8 +/- 28.4 mg for the AN 69, 179.8 +/- 47.5 mg for the PAN, 130.8 +/- 11.8 mg for the PMMA and 14.4 +/- 16.0 mg for the CR membrane. Diffusive/convective transport was 128.0 +/- 18.1 mg for PS, 54.7 +/- 8.1 mg for AN 69 and 106.5 +/- 20.8 mg for PAN and insignificant for PMMA and CR. Adsorption was 26.7 +/- 4.3 mg for PS, 83.1 +/- 29.0 mg for AN 69 and 59.8 +/- 17.2 mg for PAN. Besides transmembranous transport sorption is an important mode of elimination. Weekly endogenous generation rate is about twice as high as b2M elimination.

Acrylic Resins↗
PubMed1986

Regulation of parotid kallikrein secretion-role of the alpha 2- and beta-adrenergic system.

The effects of pharmacologically induced alterations of alpha 1, alpha 2 and beta-adrenergic system on kallikrein secretion - measured as amidolytic activity - in rat parotid gland were tested in vivo. Beta and alpha 1/2-adrenergic stimulation (Orciprenaline, alpha-methylnorepinephrine) caused a comparably significant increase of parotid kallikrein secretion. Alpha 2-receptor blockade (yohimbine) but not the alpha 1-antagonist prazosin, partly abolished the effect of alpha-methylnorepinephrine. The effects of the alpha 1-adreno-receptor agonist norfenephrine on kallikrein secretion were significantly lower compared to alpha 1/2-adreno-receptor-stimulation.

Adrenergic alpha-Agonists↗
PubMed1985

Parotid kallikrein secretion in the rat after alterations of electrolyte transport and cAMP activity.

The effects of pharmacologically induced alterations of electrolyte transport and cAMP activity on kallikrein secretion - measured as amidolytic activity - in rat parotid gland were tested in vivo. Changes in transepithelial sodium/potassium transport caused a significant alteration of parotid kallikrein handling. Amidolytic activity was inhibited by sodium channel blockade (via amiloride) and stimulated by an increased sodium influx (via the sodium ionophore monensin). Enhanced intracellular cAMP activity (via dibutyryl cAMP and theophylline) caused a significant increase of ductal kallikrein and potassium secretion. Alterations of intracellular calcium-ion concentration (via A 23187 and verapamil) did not influence parotid kallikrein secretion. Parotid kallikrein secretion seems to be dependent on intracellular sodium and cAMP concentration.

Amiloride↗
PubMed1979

Salivary kallikrein excretion in hypertension.

According to immunohistochemical investigations kallikrein in the majors salivary glands is located predominantly at the apical border of the striated duct cells and as a luminal rim in the main excretory ducts. Comparatively the highest concentrations are observed in the submandibular gland of rats and cats in the cytoplasmic granules of the granular tubules. In normal humans and rats the kallikrein activity of parotid saliva is inversely related to flow rate and sodium concentration. An increased salivary kallikrein concentration is found in human essential hypertension and renoparenchymal hypertension associated with impaired kidney function. Furthermore in rats with various forms of hypertension (genetic hypertension, DOCTMA salt and renovascular hypertension) the salivary kallikrein secretion - as determined by the BAEE-esterase activity - is enhanced. In contrast to the kallikrein secretion the flow dependent sodium concentration of parotid saliva is reduced in human essential and renoparenchymal hypertension as well as in rats with various forms of experimental and genetic hypertension, which indicates an enhanced sodium reabsorption in the glandular duct system. Furthermore in most forms of hypertension, there is a tendency of higher potassium levels in the saliva. The pathogenesis of the enhanced glandular kallikrein secretion in hypertension is discussed with regard to a counterregulatory mechanism in hypertension as well as to a sympathicoadrenergic activation. The enhanced sodium reabsorption in the duct system in the various forms of hypertension could be the cause as well as a consequence of the enhanced kallikrein secretion.

Absorption↗
PubMed1979

[Saralasin in resistant hypertensive crisis (author's transl)].

4 patients with hypertensive crisis (glomerulonephritis [n = 2], phaeochromocytoma [n = 1], reno-vascular hypertension [n = 1] combined with encephalopathy, showed a normalisation of blood-pressure up to 18 days during angiotensin-II-blockade with saralasin. Prior, blood pressure was treated insufficiently by intravenous diazoxide and Na-nitroprusside. Increased plasma-renin-activity and plasma levels of catecholamines pointed to an activation of the renin-angiotensin- and sympathico-adrenergic system. A trial of therapy with saralasin--especially, if blood-pressure response to diazoxide and sodium-nitroprusside is insufficient--could be indicated. Side-effects like pressor-reactions are excluded by very low priming doses (0,1 microgram/kg/min); rebound-hypertension at the end of the therapy is avoided by an overlapping therapy with renin suppressing drugs (beta-receptor blockers, clonidine, guanfacinum).

Adrenergic beta-Antagonists↗
PubMed1979

Effects of acute hemodialysis-induced changes in sodium balance on the renin-angiotensin system in renovascular and spontaneously hypertensive rats.

In two-kidney Goldblatt hypertensive, spontaneously hypertensive, and normotensive control rats the activity of the renin-angiotensin system was tested during variation of sodium balance. Acute, exactly calculable and selective changes of total body sodium were achieved by hemodialyzing the conscious rats using dialysate with either high or low sodium content. The activity of the RAS was evaluated by blood pressure response to AT II blockade (saralasin bolus injection; 25 micrograms/kg b.w., i.v.) and the plasma-renin activity. During sodium depletion blood pressure maintenance became renin-dependent; sodium loading caused a decrease of renin-angiotensin activity in renovascular hypertension. A weak direct correlation between deprssor response to saralasin and the PRA could be established in the different sodium-depleted and -loaded states.

Angiotensin II↗
PubMed1979

Uraemic sympathetic neuropathy after haemodialysis and transplantation.

Autonomic function in patients with uraemia treated conservatively, by haemodialysis, and by transplantation was evaluated by the pupillary reaction to tyramine, the Valsalva manoeuvre and a postural tolerance test. The pupillary reaction to tyramine is diminished in haemodialysis patients compared with control subjects. Renal transplantation improves, but does not correct the pupillary reaction to tyramine. The frequency of the diminished response roughly correlates with the degree of renal insufficiency, with results of a Valsalva manoeuvre, and with postural tolerance tests. Our data show that uraemic autonomic dysfunction is improved by successful renal transplantation, but not by adequate haemodialysis.

Adult↗
PubMed1978

Beta-adrenergic blockade in stress protection. Limited effect of metoprolol in psychological stress reaction.

In a model system the influence of mental stress on blood pressure and heart rate was studied in normal persons and in patients with hypertension (WHO grade III). Metoprolol was employed to investigate the preventive effect of beta-adrenergic blockade on the response to stress. In all groups blood pressure increased significantly during mental stress. The effect was not inhibited by metoprolol. The rise in heart rate, however, was depressed by beta-blockade. Reaction time, opticomotor coordination and concentration ability were studied as parameters of vigilance, but no significant difference between the metoprolol and control groups were observed. Thus, metoprolol only influenced the heart rate in mental stress and it did not affect vigilance.

Adult↗
PubMed1978

A simplified method for measurement of Ca++-activity in serum, using serum-monovettes and a Ca++-selective disk-electrode.

A simplified method for the anaerobic measurement of ionized calcium in serum of venous blood by use of ion-selective electrodes--the monovette-technique--is described. For estimation of Ca++ a new electrode type--the disk-electrode (11, 12, 13, 14)--charged with a synthetic, electrically neutral Ca++-carrier of the octandioic acid-type (1), is tested.

Blood Chemical Analysis↗
PubMed1978

[Transfemoral embolus aspiration from both renal arteries].

In a 50-year-old female patient who had suffered from coronary heart disease for about 3 years, a cerebral embolus resulted in left-sided hemiparesis. Four days later she became anuric. Acute thromboembolis occlusion of the renal arteries was assumed and renal angiography was performed. The angiography showed complete obstruction of the left renal artery and partial obstruction of the right renal artery. Due to the poor general condition of the patient it was not possible to carry out renovascular surgery or streptokinasetherapy. An attempt was therefore made to remove the emboli from the renal arteries by a new technique (transfemoral embolus aspiration). The subsequent angiography showed normal circulation in the right kidney and improved circulation in the left kidney. Ten days of dialysis treatment were required until urine production started again. Death then occurred from other causes. The autopsy confirmed free permeable renal vessels and absence of permanent sequelae in the parenchyma.

Aortography↗
PubMed1978

Haemodialysis in rats.

A plate dialyser requiring an extracorporeal blood volume of 1.5 ml was developed to dialyse conscious rats. In experiments in vitro and in vivo its function was tested. The in vitro clearances of urea, creatinine and potassium were 126+/-9 ml/min/m2, 70.5+/-9 ml/min/m2, and 132.5+/-13 ml/min/m2, respectively. The method appears to be suitable for pharmacological and toxicological studies.

Animals↗
PubMed1978

[Investigations on the performance of calcium selective disc-electrodes with electrically charged and neutral ligands in anaerobic serum measurements (author's transl)].

Anaerobically prepared serum samples from healthy subjects were simultaneously analysed for Ca++ in a flow-through-system of three ion selective disc-electrodes (electrochemical multimeasurementsystem). Two of the sensors contained electrically charged ligands, the third contained a neutral carrier. With neutral carriers an improvement of performance was noted in that there was a large increase in selectivity toward H+- and NH+4-ions and a distinct enhancement of reproducibility.

Anaerobiosis↗