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K Braun

Publications and source records attributed to K Braun.

152 records · Page 9Linked to original sources
PubMedDate not supplied

Differential emotional experience leads to pruning of dendritic spines in the forebrain of domestic chicks.

Auditory filial imprinting induces quantitative changes of synaptic density in the forebrain area mediorostral neostriatum/hyperstriatum ventrale of the domestic chick. The aim of the present study was to examine the time window and the extent and quality of experience that is required for the induction of these synaptic changes. We found that a brief (30 min) experience with the imprinting situation (tone stimulus + mother surrogate) is sufficient to induce spine elimination, which is detectable on postnatal day 7, but not 80 min after the presentation of the imprinting stimuli. This synaptic reorganization requires the association of the acoustic imprinting tone with an emotional reward (mother surrogate); acoustic stimulation alone does not lead to detectable synaptic changes. The results of the present study provide further evidence that juvenile emotional learning events, such as filial imprinting, lead to a selective synaptic reorganization.

Acoustic Stimulation↗
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Passive avoidance training and recall are associated with increased glutamate levels in the intermediate medial hyperstriatum ventrale of the day-old chick.

In the young chick, the intermediate medial hyperstriatum ventrale is involved in learning paradigms, including imprinting and passive avoidance learning. Biochemical changes in the intermediate medial hyperstriatum ventrale following learning include an up-regulation of amino-acid transmitter levels and receptor activity. To follow the changes of extracellular amino acid levels during passive avoidance training, we used an in vivo microdialysis technique. Probes were implanted in chicks before training the animals, either on a methylanthranylate- or water-coated bead. One hour later, recall was tested in both groups by presenting a similar bead. An increase of extracellular glutamate levels accompanied training and testing in both groups; during training, glutamate release was higher in methylanthranylate-trained than in water-trained chicks. When compared with the methylanthranylate-trained chicks during testing, the water-trained chicks showed enhanced extra-cellular glutamate levels. No other amino acid examined showed significant changes. After testing, the chicks were anesthetized and release-stimulated with an infusion of 50 mM potassium. Extracellular glutamate and taurine levels were significantly increased in both methylanthranylate- and water-trained chicks. The presentation of methylanthranylate as an olfactory stimulus significantly enhanced glutamate levels, especially in methylanthranylate-trained chicks. The results suggest that such changes in extracellular glutamate levels in the intermediate medial hyperstriatum ventrale accompany pecking at either the water- or the methylanthranylate-bead. The taste of the aversant may be responsible for the greater increases found in methylanthranylate-trained birds.

Amino Acids↗
PubMedDate not supplied

Endothelin plasma levels in acute graft rejection after heart transplantation.

BACKGROUND: Endothelin is an oligopeptide of endothelial origin with potent vasoconstrictive and mitogenic properties, implicated in the pathogenesis of cyclosporine-induced hypertension, graft vasculopathy, and renal failure. Experimental animal data suggest a role for endothelin in allograft rejection also. METHODS: To determine the role of endothelin in acute graft rejection after heart transplantation, we determined endothelin plasma levels in 165 blood samples from 79 cardiac allograft recipients (2 to 81 months after the operation) with normal graft function and correlated our findings with the histologic severity of acute graft rejection according to International Society for Heart and Lung Transplantation grading. For comparison endothelin levels were determined in 30 healthy controls and in 22 early postoperative transplant recipients (< 2 months after the operation). RESULTS: Endothelin plasma levels were significantly higher in transplant recipients than in controls (early postoperative: 7.97 = 7.53 pg/ml; late postoperative: 3.68 +/- 1.72 pg/ml; controls: 1.55 +/- 0.89 pg/ml). Endothelin plasma levels were not significantly different between groups of rejection grades 0 to 4. In the comparison of two groups of no rejection or lower (International Society for Heart and Lung Transplantation grade 0 and 1, n = 134) and higher (International Society for Heart and Lung Transplantation grade > or = 2, n = 31) rejection severity or comparing patients requiring rejection therapy (n = 20) with those not requiring therapy (n = 145), endothelin levels did not differ significantly between the groups. In 22 patients with three to six available consecutive biopsy scores and endothelin levels, intraindividual longitudinal analysis did also not show any significant correlation. The only positive correlation of endothelin levels with other laboratory parameters was found with serum creatinine concentrations (p < 0.001). In the early postoperative recipients, no correlation of endothelin plasma levels with rejection severity was seen; furthermore the only significant association was found with time after operation. CONCLUSIONS: In this study endothelin plasma levels were not influenced by acute allograft rejection after heart transplantation. Therefore endothelin levels do not appear to be a useful marker for noninvasive rejection diagnosis. Furthermore, a relevant pathogenetic role of endothelin in the rejection process cannot be derived from these data.

Acute Disease↗