Ralf Herz

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We investigated whether the difference in infarction volume after occlusion of a long proximal segment of the middle cerebral artery between Wistar and Fischer-344 rats, is caused by differences in collateral blood flow rate through leptomeningeal anastomoses. In view of the retrograde direction of collateral blood flow into the middle cerebral artery(More)
We hypothesized that the interstrain difference between Wistar and Fischer-344 (F344) rats in cerebral infarction volume after proximal middle cerebral artery (MCA) occlusion might be explained by differences in excitotoxicity between both rat strains. Using microdialysis we measured during a 5 h period after MCA occlusion the release of aspartate,(More)
Vector quantization (VQ) is known to be an optimal compression method for a stationary and ergodic source, provided that arbitrarily large vector dimension and codebook size are employed. In practical VQ encoding schemes of images and video sequences, hardly one of these assumptions is fulfilled; the dimension and codebook are limited in size and, perhaps(More)
In L 1-distortion limited compression each single pixel value is only changed by maximal grey values. In this paper we present a theoretical framework for L 1-distortion limited compression that covers several recently proposed methods. The basics of each of these methods are described. We give a comparison of coding results for the Lenna test image, a(More)
We compared in Wistar rats collateral blood flow through leptomeningeal anastomoses after middle cerebral artery occlusion using craniotomy ('extravasal occlusion'), which results in a small volume of cerebral infarction, and after intraluminal thread occlusion ('intravasal occlusion'), which produces a large volume of cerebral infarction. Simultaneous(More)
In £ ¥ ¤-distortion limited compression each single pixel value is only changed by maximal ¦ ¨ § grey values. In this paper we present a theoretical framework for £ ¤-distortion limited compression that covers several recently proposed methods. The basics of each of these methods are described. We give a comparison of coding results for the Lenna test(More)
We observed that the pro-opiomelanocortin-derived neuropeptide, gamma 2-melanocyte-stimulating hormone (gamma 2-MSH), has various peripheral and central hemodynamic effects in the rat, including a marked enhancing effect on cerebral blood flow. This hemodynamic profile might be of interest in the pharmacotherapeutic approach to acute cerebral ischemia.(More)
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