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Biomedical subjects

R Walz

Publications and source records attributed to R Walz.

64 records · Page 4Linked to original sources
PubMed1991

Memory facilitation by post-training intraperitoneal, intracerebroventricular and intra-amygdala injection of Ro 5-4864.

Post-training i.p. (2.0 or 5.0 mg/kg), i.c.v. (2.5 micrograms/rat), or intra-amygdala (1.6-40 ng/amygdala) administration of Ro 5-4864 causes memory facilitation of step-down inhibitory avoidance in rats. The effect is expressed as an increased latency to step down in a retention test carried out 24 h after training. Ro 5-4864 is a blocker of the Cl(-)-channel associated with GABAA receptors, at a site sensitive to the antagonist, PK11195, and different from that sensitive to picrotoxin. PK11195, given i.c.v. (2.5 micrograms/rat) or into the amygdala (8 ng/amygdala), antagonized the effect of Ro 5-4864. Intra-amygdala picrotoxin administration (80 ng/amygdala) also caused retrograde memory facilitation, but its effect was not antagonized by PK11195. At a higher dose (40 ng/amygdala), PK11195 had an amnestic effect of its own, which suggests that it might be acting against an endogenous ligand of receptor to Ro 5-4864 in the Cl(-)-channel. These findings support the hypothesis that there is a GABAA mechanism in the amygdala normally involved in the modulation of the post-training memory processing of aversive learnings.

Amygdala↗
PubMed1991

Posttraining presentation of a flashing light alters retrieval of a two-way active avoidance task in rats.

Rats were trained and tested in a two-way active avoidance task (30 trials, 0.4-mA footshock, 24-h training-test interval). Exposure to an open field with flashing light (60-W lamp, 30 Hz, for 7 min, OFL) 2 h after training caused a retrieval impairment for the avoidance task, a phenomenon called retroactive interference. Animals familiarized with the OFL 24 h before training showed no retrieval impairment when exposed to the OFL 2 h after training. Both adrenal medullectomy (performed 7 to 14 days before training) and dexamethasone treatment (2 mg/kg, injected IP 24 h and 12 h before training) prevented the OFL interfering effect. Time-course experiments revealed that OFL presented either 1 or 4 h after training caused no retrieval deficit, and that animals exposed to the OFL 2 h after training and receiving another OFL presentation 1 or 2 h, but not 4 h, prior to testing had normal retrieval performance. These results suggest: 1) that the retroactive interference caused by presentation of OFL 2 h after training is due to failure of retrieval of the avoidance task since it is counteracted by the pretest presentation to the OFL, 2) that the OFL-induced retrieval interfering effect partly depends on the novelty of the OFL situation, and on the functional integrity of pituitary ACTH and adrenomedullar-dependent mechanisms and 3) that there are different mechanisms involved in posttraining and pretest OFL effects since they present distinct time-courses.

Adrenal Medulla↗
PubMed1991

Effect of post-training injections of flumazenil into the amygdala, hippocampus and septum on retention of habituation and of inhibitory avoidance in rats.

Adult rats were submitted to two different behavioral tasks using the same apparatus: the habituation of exploration of the apparatus considered as a novel environment as measured by the decrease in number of rearings and of ambulation between training and testing, and step-down inhibitory avoidance as measured by the increase in the latency to step down from a start platform onto an electrified grid between the training and the test session. The training-test interval for both tasks was 20 h. The immediate post-training injection of the benzodiazepine receptor antagonist flumazenil (10 nmol) bilaterally into the hippocampus enhanced retention of the two tasks. Application of the same drug, at the same dose to the septum or amygdala had no effect on habituation but enhanced retention of the avoidance task. The data are consistent with previous findings showing that both tasks are accompanied by the release of benzodiazepine-like immunoreactivity in the three structures and that this release is greater after the avoidance task. The present findings suggest a differential regional involvement of endogenous benzodiazepine-mediated mechanisms in memory modulation, according to the task undertaken.

Amygdala↗
PubMed1990

Post-training down-regulation of memory consolidation by a GABA-A mechanism in the amygdala modulated by endogenous benzodiazepines.

In rats, amygdala benzodiazepine-like immunoreactivity decreases by 29% immediately after the animals step down from the platform of an inhibitory avoidance apparatus and decreases by a further 45% immediately after they receive a training footshock. The decrease is attributable to a release of diazepam or diazepam-like molecules. The immediate post-training intraamygdala injection of the central benzodiazepine antagonist flumazenil (10 nmole/amygdala) causes memory facilitation, and that of the GABA-A agonist muscimol (0.005 to 0.5 nmole) causes retrograde amnesia. Pretraining ip flumazenil administration (2.0 and 5.0 mg/kg) attenuates the effect of post-training muscimol by a factor of at least 100. The higher dose of pretraining flumazenil also causes memory facilitation. The data suggest that post-training consolidation is down-regulated by a GABA-A mechanism in the amygdala modulated by endogenous benzodiazepines released during training and at the time of consolidation.

Amygdala↗
PubMed1990

Malignant pleural mesothelioma: some aspects of epidemiology, differential diagnosis and prognosis. Histological and immunohistochemical evaluation and follow-up of mesotheliomas diagnosed from 1964 to January 1985.

64 diffuse pleural mesotheliomas diagnosed between 1964 and January 1985 at the Institute of Pathology of the University of Freiburg were analyzed. Since 1980 an increase from one case to 10 cases per year has been observed. The tumor was 3 to 4 times more frequent in men than in women. The age distribution showed a peak between the age of 50 and 60. In 26 cases evidence of exposure to asbestos was detected. In one patient radiotherapy of Hodgkin's disease may have been of etiological significance. The median survival time was 13 months. The five-year survival rate was only 4%. Histologic reevaluation was only possible in cases diagnosed after 1975. Of 43 cases thus evaluated 26 were pure mesothelial, 15 biphasic and 2 of the spindle-cell subtype. A median survival time of 23 months for pure mesothelial mesothelioma in comparison to 13 months for the biphasic mesothelioma indicated a better prognosis for pure mesothelial mesothelioma. Although no other primary tumors were detected, in 10 cases the differential diagnosis of adenocarcinoma had to be considered, and in 3 cases tumors of non-epithelial origin had to be excluded. 35 of 43 mesothelioma were CEA-negative, 38 out of 43 cytokeratin-positive, and 33 out of 43 were EMA-positive. Factor-VIII-related antigen was not demonstrated. 12 of 43 mesotheliomas showed PAS-positive staining, 29 of 43 were stained with Alcian blue. 7 of these 29 showed a positive digestion with hyaluronidase. Although CEA may not be negative in every mesothelioma, this marker seems to be a valid tool for the differential diagnosis of adenocarcinoma. In order to safeguard against a mistaken diagnosis of pleural mesothelioma, the exclusion of other tumors is always indispensable.

Adult↗
PubMed1990

[Massive hemorrhage from an "esophageal tumor": thoracic aortic aneurysm rupturing into the esophagus].

We report on an arteriosclerotic aneurysm of the descending aorta penetrating into the esophagus. On endoscopy it mimicked a bleeding esophageal tumour. The typical clinical course of aortoesophageal fistulas (AEF) exhibits Chiari's triad of midthoracic pain, sentinel arterial hemorrhage, usually hematomesis, and final exsanguination after a symptom-free interval. The various causes of AEF are discussed together with the respective diagnostic and therapeutic problems.

Aged↗
PubMed1989

[Effect of laser irradiation on atherosclerosis vascular segments in relation to wave length and pulse width].

The interaction of pulsed Nd:YAG laser radiation and atherosclerotic vessel wall is reported. The effects in the area of radiation were examined at an infrared, green, and ultraviolet wavelength at variable pulsewidths. The laser beam was focused directly on the plane surface of the tissue. The macroscopic and histologic examinations demonstrate that thermal damage of tissue is higher at an infrared wavelength than at a green wavelength and respectively at an ultraviolet wavelength. With increasing pulsewidth an increase of coagulation and necrosis of plaque material and adjacent vessel wall can be noted. The results show that for the precise ablation of plaque without adjacent vessel wall injury short pulsed ultraviolet radiation is preferable.

Angioplasty, Balloon, Coronary↗