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At least 1,279 records · Page 71Linked to original sources
PubMed1986

Automated comparison of scintigraphic images.

New algorithms for automated comparison of scintigraphic images have been developed and are described here. The first step presented here is the registration of the images, performed by optimizing, with respect to the registration parameters (two translational shifts, one angle of rotation, the two parameters of a linear transformation of the gray levels), the stochastic sign change (SSC) criterion. The optimization of this criterion is demonstrated to be efficiently performed using the adaptative random search strategy; a more limited but less time-consuming method is also presented. The second step described is the point-by-point comparison of the registered images. The pixel-by-pixel application of Poisson variable statistical tests permits the generation of the significant image differences. From such images it is possible to detect modifications which escape visual inspection. Examples of applications are given in controlled and routine conditions. These algorithms are useful for the processing of many investigations and are proposed for implementation on all nuclear medicine data processing systems.

Bone and Bones↗
PubMed2000

Role of climbing fibers in determining the spatial patterns of activation in the cerebellar cortex to peripheral stimulation: an optical imaging study.

The spatial patterns of activation in the rat cerebellar cortex evoked by ipsilateral face stimulation were mapped using optical imaging based on the pH sensitive dye, Neutral Red. The aims of the study were to characterize the optical responses evoked by peripheral stimulation and test the hypothesis that the resultant parasagittal banding is due to climbing fiber activation. In the anesthetized rat Crus I and II of the cerebellar cortex were stained with Neutral Red. Epi-fluorescent changes produced by a train of stimuli (5-10s and 4-20 Hz) to the ipsilateral face were monitored in time using a fast, high resolution charge-coupled device camera. The patterns of activation were quantified using a two-dimensional fast Fourier transform analysis that removed signals with high spatial frequencies and minimized the contribution of horizontal structural elements (i.e. blood vessels). The dominant spatial pattern of activation evoked by face stimulation was that of parasagittal bands. The bands were highly frequency-dependent and were elicited most strongly by stimulus frequencies in the range of 6-8 Hz. There was a large fall-off in the response for frequencies above and below. The optical signal evoked by face stimulation built up over a period of 10s and then gradually decayed. Within a folium the individual parasagittal bands exhibited some frequency and temporal specificity. Stimulation of the contralateral inferior olive also resulted in the activation of parasagittal bands with characteristics similar to the bands evoked by face stimulation, including a preferred stimulus frequency which peaked at 10 Hz. Injection of lidocaine into the contralateral inferior olive blocked the parasagittal bands evoked by ipsilateral face stimulation, while control injections of saline had no effect. The results confirm that a parasagittal banding pattern is a dominant feature of the functional architecture of the cerebellar cortex. The parasagittal banding pattern observed with Neutral Red is due primarily to the activation of climbing fiber afferents. The frequency tuning of the responses, with the preference for peripheral stimuli of 6-8 Hz, is in agreement with previous findings that the inferior olive is inherently rhythmic. These observations support the hypothesis that inferior olivary neurons are dynamically coupled into groups that activate parasagittal bands of Purkinje cells in the cerebellar cortex. The frequency tuning also supports the hypothesis that the climbing fiber system is involved with timing. Activation of this afferent system may require stimuli with appropriate frequency content and stimuli synchronized to the rhythmicity of the inferior olive.

Action Potentials↗
PubMed1994

Light- and electronmicroscopic distribution of taurine, an organic osmolyte, in rat renal tubule cells.

Several lines of evidence suggest that taurine acts as an organic osmolyte in the kidney. We investigated the cellular and subcellular distribution of this amino acid in rat renal tubule cells. Semi- and ultrathin sections of plastic-embedded rat kidney were incubated with an antiserum against conjugated taurine, using peroxidase-antiperoxidase and immunogold procedures, respectively. Extensive control tests confirmed the selectivity of the antiserum. Our immunocytochemical preparations revealed a highly differentiated labeling pattern. Strong labeling (judged visually or by computer-aided calculation of gold particle densities) was found in collecting duct cells throughout cortex and medulla, in proximal straight tubule cells, and in cells of the descending thin limbs of Henle's loop. Intermediate gold particle densities occurred in proximal convoluted tubule cells and intercalated cells of the collecting ducts (the gold particle in the latter being 30% of that in the collecting duct cells). The distal convoluted tubules, and thick and thin ascending limbs were almost immunonegative. It cannot be excluded that the proportion of free taurine that is retained by the fixative varies somewhat among the different cell types. Yet the highly differentiated labeling pattern that was obtained suggests that taurine is heterogeneously distributed among different populations of tubule cells, and that its level varies substantially even among cells that are exposed to the same osmotic stress.

Animals↗