PubMed Health⌕ Search

Biomedical subjects

H Assmann

Publications and source records attributed to H Assmann.

At least 19 recordsLinked to original sources
PubMed2000

Inhibition by adenosine A(2A) receptors of NMDA but not AMPA currents in rat neostriatal neurons.

Whole-cell patch clamp experiments were used to investigate the transduction mechanism of adenosine A(2A) receptors in modulating N-methyl-D-aspartate (NMDA)-induced currents in rat striatal brain slices. The A(2A) receptor agonist 2-p-(2-carboxyethyl)phenethylamino-5'-N-ethylcarboxamidoadenosine (CGS 21680) inhibited the NMDA, but not the (S)-alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) current in a subset of striatal neurons. Lucifer yellow-filled pipettes in combination with immunostaining of A(2A) receptors were used to identify CGS 21680-sensitive cells as typical medium spiny striatal neurons. Dibutyryl cyclic AMP and the protein kinase A activator Sp-cyclic AMPs, but not the protein kinase A inhibitors Rp-cyclic AMPS or PKI(14 - 24)amide abolished the inhibitory effect of CGS 21680. The phospholipase C inhibitor U-73122, but not the inactive structural analogue U-73343 also interfered with CGS 21680. The activation of protein kinase C by phorbol 12-myristate 13-acetate or the blockade of this enzyme by staurosporine did not alter the effect of CGS 21680. Heparin, an antagonist of inositol 1, 4,5-trisphosphate (InsP(3)) and a more efficient buffering of intracellular Ca(2+) by BAPTA instead of EGTA in the pipette solution, abolished the CGS 21680-induced inhibition. The calmodulin antagonist W-7 and cytochalasin B which enhances actin depolymerization also prevented the effect of CGS 21680; the calmodulin kinase II inhibitors CaM kinase II(281 - 309) and KN-93 but not the inactive structural analogue KN-92 were also effective. The calcineurin inhibitor deltamethrin did not interfere with CGS 21680. It is suggested that the transduction mechanism of A(2A) receptors to inhibit NMDA receptor channels is the phospholipase C/InsP(3)/calmodulin and calmodulin kinase II pathway. The adenylate cyclase/protein kinase A and phospholipase C/protein kinase C pathways do not appear to be involved.

Adenylyl Cyclases↗
PubMed1998

Adenosine A2A receptors inhibit the conductance of NMDA receptor channels in rat neostriatal neurons.

Whole-cell patch clamp experiments were carried out in rat striatal brain slices. In a subset of striatal neurons (70-80%), NMDA-induced inward currents were inhibited by the adenosine A2A receptor selective agonist CGS 21680. The non-selective adenosine receptor antagonist 8-(p-sulphophenyl)-theophylline and the A2A receptor selective antagonist 8-(3-chlorostyryl)caffeine abolished the inhibitory action of CGS 21680. Intracellular GDP-beta-S, which is known to prevent G protein-mediated reactions, also eliminated the effect of CGS 21680. Extracellular dibutyryl cAMP, a membrane permeable analogue of cAMP, and intracellular Sp-cAMPS, an activator of cAMP-dependent protein kinases (PKA), both abolished the CGS 21680-induced inhibition. By contrast, Rp-cAMPS and PKI 14-24 amide, two inhibitors of PKA had no effect. Intracellular U-73122 (a phospholipase C inhibitor) and heparin (an inositoltriphosphate antagonist) prevented the effect of CGS 21680. Finally, a more efficient buffering of intracellular Ca2+ by a substitution of EGTA (11 mM) by BAPTA (5.5 mM) acted like U-73122 or heparin. Hence, A2A receptors appear to negatively modulate NMDA receptor channel conductance via the phospholipase C/inositoltriphosphate/Ca2+ pathway rather than the adenylate cyclase/PKA pathway.

Adenosine↗
PubMed1993

Mutants with substitutions for Glu171 in the catabolite activator protein (CAP) of Escherichia coli activate transcription from the lac promoter.

Single amino acid substitutions for residue Glu171 in helix E of the catabolite gene activator protein (CAP) of Escherichia coli have been reported to abolish activation of transcription without impairing binding to the CAP site of the lac promoter. The negative charge of Glu171 was proposed to transmit the activating signal from CAP to RNA polymerase. However, this idea has been challenged by later work. We set up a system to re-examine this issue. We analysed the ability of mutant CAP-E171L and CAP-E171K proteins to bind a near-consensus CAP site in vivo and found it to be diminished fourfold relative to wild type in each case. Activation of lac transcription by these mutant proteins remains the same as with wild-type CAP. Thus our results confirm that Glu171 in helix E of CAP is not involved directly in the activation of transcription. Yet CAP-E171K does not activate transcription as well as wild-type CAP under all circumstances. Possible reasons for this absence of activation are discussed.

Amino Acid Sequence↗
PubMed1992

[Preoperative computer tomography and postoperative classification of brain tumors].

Imaging of different brain tumor types by computed tomography (CT) or contrast-enhanced CT scans is often very similar. Therefore, the exact preoperative CT diagnosis of intracranial neoplasms is difficult. Among 100 cases (88 primary brain tumors, 12 brain metastases), the preoperative classification by CT was correct in 51 and partially correct in 22 cases. A corresponding presumptive CT diagnosis was made in 22 brain neoplasms. 5 cases were misinterpreted. Examples of CT scans and histological pictures are compared and analysed according to the literature.

Brain Neoplasms↗
PubMed1989

[Pulmonary alveolar microlithiasis (disease in 2 siblings--case report)].

This article presents case reports on brother and sister suffering from microlithiasis alveolaris pulmonum. Diagnosis was established by means of the course of the disease, the relatively typical x-ray film and the findings on performing scintigraphy of the skeleton and also by computed tomography. Findings confirmed that the course of the disease is symptom-free for a long time; that it occurs in both sexes; and that it becomes manifest with considerable incidence in some families. Pulmonary alveolar microlithiasis is not a generalised metabolic disease, since it affects the lungs only. If the aetiology remains unclear, no causal treatment can be effected.

Adult↗
PubMed1987

[Ergotism within the scope of the postoperative prevention of thromboembolism].

Vasospastic reactions (ergotism), a complication in postoperative prophylaxis against thrombo-embolism, using heparin-dihydroergotamine, are assessed in this paper on the basis of the authors' own observations and following evaluation of 19 literature references. The authors feel that the above combination of active substances may be recommended also for the future in routine prophylactic medication to prevent thrombo-embolism.

Dihydroergotamine↗
PubMed1987

[Diagnosis and differential diagnosis of primary empty sella].

A report is given on 12 patients (6 men, 6 women) presenting primary Empty Sella who were admitted as inpatients with a provisional diagnosis of a hypophyseal tumour. The most frequent first symptom was uncharacteristic cephalgia. Visual disturbances and an impairment of potency/libido were only mentioned in the second place. 5 of the 12 patients were adipose and overweight, 2 of them additionally showed hypertensive blood pressure values. 2 female patients suffered from galactorrhoea. The typical "Empty Sella Patient" frequently described in the literature - the overweight medium-aged woman was an exception among our patients. Besides the ascertainment of the ophthalmological findings and the performance of a complete endocrinological function diagnosis the respective radiological diagnosis was established: native sellar picture, sella tomography, computer tomography, angiography and pneumocephalography. A high informative value in the differential-diagnostic demarkation from a hypophyseal tumour has until now been attributed to pneumoencephalography with an intracellar accumulation of air being considered to prove the presence of an empty sella. Under modern examination conditions, however, a computer-tomographic clearing will in most cases be possible.

Adult↗
PubMed1987

[Recurrent cystic "hypophyseal abscess"].

A report is given on a primary hypophyseal abscess with an acute chiasmal syndrome, the only case among 426 hypophyseal interventions. In spite of two pterional exposures a relapse occurred, so that in the third operation a transethmoideo-sphenoid access was chosen. In this procedure--as the method of choice--a drainage into the paranasal sinuses is reached. The genesis is discussed on the basis of the histological findings, assuming differential-diagnostically a Rathke's cyst as the starting point.

Adult↗
PubMed1984

[Metallic mercury poisoning. Case report].

Intoxications by metallic mercury are extremely rare. Report of a patient, who tried to commit suicide by subcutaneous injection of 500 g of metallic mercury. He died 16 months later in the course of the intoxication. A short review is given of effects and reactions of metallic mercury in the human organism.

Humans↗