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4 recordsLinked to original sources

PubMed1976

The length of parallel fibers in the cat cerebellar cortex. An experimental light and electron microscopic study.

Experimental light and electron microscopic studies were carried out to determine the length of parallel fibers in the cat cerebellar cortex. Using a fine surgical knife, vermal and hemispheral folia were cut perpendicular to their long axis. The animals were sacrificed 1-10 days after the operation. Sections of the transected folia were then stained with a Fink-Heimer procedure. The resulting degeneration appeared as fine dots that extended lateral to the lesion, as predictable from the course of the parallel fibers. Densitometer readings indicate that the density of degeneration declines gradually lateral to the lesion. The specificity of the silver impregnation was checked by processing silver stained sections for electron microscopy. This confirmed the location of the silver precipitate on degenerating parallel fibers. The pattern of parallel fiber degeneration in the molecular layer has a trapezoidal configuration centered on the lesion. The shorter parallel fibers are located at the base of the molecular layer and extend for 5 mm. The parallel fibers become progressively longer as they approach the pial surface where they attain a maximum length of 7 mm. Our studies suggest that in folia longer than 7 mm parallel fibers are 6 mm long on the average. In addition, it was determined on Golgi sections that the average center-to-center distance between en passant boutons of individual parallel fibers is 5.2 mum. The data indicate that an average parallel fiber, 6 mm long, forming approximately 1100 boutons, may synapse with each Purkinje dendritic tree it traverses.

Animals↗

PubMed2026

Partial enumeration of extreme rays in metabolic networks using bit pattern trees.

Extreme ray analysis of metabolic networks, even though very powerful, is currently limited to smaller metabolic networks. Some approaches to generating partial sets of extreme rays exist, but the computational efficiency of the so-called double-description method is yet to be exploited. Previous work highlighted the possibility of sampling within its iterations, enabling partial enumeration for double-description based methods. However, these approaches severely lack computational efficiency to be a suitable alternative. In this work, the highly efficient bit pattern trees are used within the sampling framework to significantly enhance its output and speed. Combined with the recent revision of the Canonical Basis Approach (CBA), our approach outperforms the other tested methods under the reported benchmark conditions even for a full enumeration study, requiring only half the computation time. In addition, a filter setting allows the memory demand to be scaled down while retaining high efficiency. However, some issues with the combinatorial explosion of candidates still persist and are further investigated. This study therefore puts forward a novel, double description-based alternative to partial enumeration of extreme rays. Further improvements in memory efficiency would allow this promising approach to scale powerful extreme ray-based analyses to genome-scale metabolic networks.

constraint-based modelling↗

PubMed1978

Arterial collateral vessels in legs with obliterative arteriosclerosis.

A method for assessment of arterial collateral vessels and corresponding stenoses on arteriograms of arteriosclerotic legs is presented. The method is based on the concept that compensatory collateral vessels, by-passing stenoses of the conductive arterial segments, have to cross a plane traversing the distal part of each segment (common iliac artery, external iliac/common femoral artery and superficial femoral artery). The number of collateral vessels was counted and the minimum diameter within the corresponding conductive arterial segment was measured (three locations in each leg). There was a close correlation between the sum of remaining lumen diameters and the sum of corresponding collaterals in thirty-four legs (r = -0.77, P less than 0.001). Maximum lower leg blood flow during exercise (thermodilution) was better correlated to arteriosclerotic changes in the pelvic arterial tree than to changes in the femoral arteries, and the must abundant collateral vessels were found in individuals having central stenoses or occlusions.

Adult↗

PubMed1991

Crossed and uncrossed projections to cat sacrocaudal spinal cord: II. Axons from muscle spindle primary endings.

The terminal fields of primary afferent fibers from tail muscle spindle primary endings were mapped within cat sacrocaudal spinal cord (S3-Ca7), using intra-axonal recording and horseradish peroxidase staining techniques. We sought to determine the ipsilateral and contralateral projection patterns and to relate these to the fibers' muscles of origin. Fifty-three group Ia fibers were successfully stained. Segmental collaterals originated from either the ascending or descending branch within the dorsal columns. Collaterals coursed rostromedially within the dorsal columns and traversed the medial aspect of the dorsal horn. Ipsilateral terminations were similar for all fibers. Within the ventral horn, boutons were consistently observed in the medial or central portions of lamina VII. In lamina VIII, a variable number of boutons was seen on fine branches emerging from larger fibers coursing ventrally. Clusters of terminals were plentiful in the regions of motoneurons, i.e., lamina IX and the nucleus commissuralis. Terminals were found in the adjacent white matter. In addition to ipsilateral terminations, some group Ia fibers (20 of 53) had collateral branches that crossed ventrally to the central canal, terminating within the midline ventral gray commissure and/or the contralateral ventral horn. Crossed projections always originated in medial (dorsal or ventral), but not lateral, muscles of the tail. These data suggest that ipsilateral projections of group Ia fibers make connections on sacrocaudal motoneurons, on neurons mediating segmental reflex functions and on neurons conveying ascending information. It is speculated that crossed and uncrossed connections between group Ia fibers from medial muscles and bilateral dendritic trees of motoneurons subserve synchronized co-contraction of synergistic muscles located on the two sides of the body, such as with dorsal or ventral flexion of the tail. Group Ia projections from lateral muscles, that are entirely ipsilateral, would be involved with lateral movements of the tail.

Afferent Pathways↗