Holger Baumgartner

Synthesis of nucleotides in adrenal medulla and their uptake into chromaffin granules

Abstract Perfused bovine adrenal glands were labelled with 3 H-adenosine or 32 P-phosphate. The time course of the labelling and the nature of the labelled products in the various subcellular fractions were investigated. The catecholamine storing vesicles (chromaffin granules) took up labelled ATP, but significant amounts of 3 H-ATP did not appear until 30 min after the injection of the isotope. Four hours after the injection of the isotope the predominantly labelled nucleotide in adrenal medulla was 3 H-ATP which was specifically confined to chromaffin granules. There was no evidence that chromaffin granules accumulated significant amounts of 3 H-ADP and 3 H-AMP. Similar results were obtained with 32 P-phosphate as a precursor. Inhibitors of mitochondrial oxidative phosphorylation (cyanide, dinitrophenol) almost completely prevented the uptake of 3 H-ATP in chromaffin granules, whereas iodoacetic acid was less effective. It is concluded that in intact cells chromaffin granules obtain newly synthesized ATP mainly from a mitochondrial pool. The mechanism of ATP uptake into chromaffin granules now warrants a detailed study on isolated granules incubated in vitro .

Effect of sodium nitroprusside on myocardial performance and venous tone

The action of sodium nitroprusside upon the mechanical performance of the isolated, working rat heart and on isolated bull veins has been studied. Cumulative concentrations of 1--1000 ng sodium nitroprusside per ml had no effect on left ventricular pressure, end-diastolic left ventricular pressure, dp/dtmax, cardiac output and calculated wall stiffness of isolated rat hearts with constant rate, preload and afterload. Isolated strips of bull veins contracted with noradrenaline showed a dose dependent relaxation by sodium nitroprusside in concentrations of 5--1000 ng per ml. This study shows that sodium nitroprusside has no direct effect on myocardial contractility and causes venous relaxation.

Electrophysiological findings in a case of severe intrathecal baclofen overdose

Multimodality evoked potentials were examined in a case of serious accidental intrathecal baclofen overdose in a patient who suffered from severe spasticity due to a traumatic brain lesion. Electrophysiological findings during, before and after the intoxication were compared. Transcranial electrical stimulation up to 750 V did not evoke any responses in thenar muscles on the first day of intoxication. An improvement to normal values was observed within 3 days, paralleled by an amelioration of the patients clinical condition. Cervical electrical stimulation was largely unaffected by baclofen. Median nerve somatosensory and brain-stem acoustic evoked potentials revealed few or no differences during intoxication compared to pre- and post-intoxication responses.

Isolated chromaffin granules maintenance of ATP content during incubation at 31°C

Abstract Chromaffin granules incubated at 31°C, lose 30% of their catecholamines and nucleotides in 4 hr. However, in the presence of ATP and Mg 2+ less than 10% of the catecholamines and nucleotides are released. Apparently the ATP-stimulated uptake of catecholamines prevents both the loss of catecholamines and that of nucleotides.

Clonidine and Hyperhidrosis

Excerpt To the editor: Because emotional sweating is under sympathetic control (1), clonidine, known to inhibit sympathetic tone (2), could be useful in the treatment of excessive emotional sweatin...