Growth cones and axon trajectories of a sensory pathway in the amphibian spinal cord

Central axons of sensory ganglion (SG) neurons of the Xenopus tail enter the spinal cord via the ventral roots and travel dorsally and rostrally following a diagonal course within the lateral marginal zone (LMZ) to reach the dorsolateral fasciculus (DLF) (Nordlander et al.: Brain Res., 440:391-395, 1988). Axons are dispersed as they cross the cord. At the DLF they turn and travel together rostrally, sharing the fascicle with axons of primary sensory neurons (Rohon-Beard cells) already present in the tract. In this paper we analyze the growth patterns of the central projections of SG axons in the tail by using HRP applied to proximal branches of tail spinal nerves. Growth cones of the diagonal route are variable in configuration, often bearing processes that spread within the LMZ. Once the DLF, growth cones change shape, becoming distinctly linear. While growth cones navigating the diagonal part of the route never contact or fasciculate with other diagonal SG axons, SG growth cones and axons of the DLF are more closely associated with their fellows. Measurements of the slopes of SG axons in the diagonal route indicated a limited range with a mean of 23 degrees with respect to the cord axis. On the basis of these observations, we conclude that 1) navigational patterns for growth cones of this pathway differ for the diagonal versus the DLF part of its course, and 2) fasciculation is not a mechanism used by SG axons to reach the DLF, but that instead, each axon is able to find its way independently.     

Ameloblastoma after surgical removal of an impacted mandibular molar. A case report

A case of an ameloblastoma diagnosed about 3 1/2 years after removal of an impacted mandibular 3rd molar is presented. The pre-operative radiographs, though poor in quality, showed an ill-defined radiolucency in relation to the tooth. This feature was not apparent to the examiners at the time of first presentation. Despite unfavourable working conditions in developing countries, a high level of suspicion should be maintained to avoid serious sequelae at a later stage.     

Radioimmunoassay for amatoxins by use of a rapid, 125I-tracer-based system

In this new radioimmunoassay system for determination of amatoxins in urine and plasma, a novel chemical approach is used for antigen and 125I-tracer production, based on a detoxified alpha-amanitin derivative (aldoamanitin). Total assay time, including data processing, is less than 100 min. The lowest detectable concentration is 1 microgram/L for urine, 0.1 microgram/L for plasma. In the clinically significant range, within-run CVs are less than 8%. This new 125I-based assay is a significant improvement over existing 3H technology in terms of speed, precision, and freedom from interference.     

Role of pylorus in mediating cholecystokinin-stimulated satiety in the Zucker rat

Obese Zucker rats are less responsive than their lean littermates to the effects of cholecystokinin-octapeptide on satiety and pancreatic growth and exocrine function. We hypothesized that the hyperphagia observed in obese Zucker rats may be caused by a decreased pyloric contractile response to cholecystokinin, resulting in an increased rate of gastric emptying, decreased postprandial gastric distention, and thus decreased satiety. Pyloric muscle strips from six obese Zucker rats and six lean littermates were mounted in separate tissue baths and isometric contraction was measured in response to acetylcholine and cholecystokinin-octapeptide. The dose-response curves for acetylcholine-and cholecystokinin-octapeptide-stimulated pyloric muscle contraction were similar for both the obese and the lean rats. (For cholecystokinin, D₅₀ obese=4.0±0.6 nM, D₅₀ lean=3.4±0.2 nM;P=0.16). We conclude that the decreased satiety response to cholecystokinin-octapeptide observed in obese Zucker rats is not secondary to a decreased pyloric responsiveness to cholecystokinin.This work was supported by NIH grant AM28303-03.     

Lumbar spondylolysis and spondylolisthesis in college football players. A prospective study

A prospective study was done on Indiana University freshman football players to determine if the incidence of lumbar spondylolysis and spondylolisthesis followed the pattern of previous studies. Using x-ray film evaluation, 145 freshman players were followed through their careers from 1978 to 1983. As in previous studies, a higher percentage (15.2%) of the defect was found than exists in the general population. However, only 2.4% of these players developed the problem in college, a much lower figure than previously found. Affected team members played a variety of positions. In addition to spondylolysis, some other problems, such as spina bifida occulta, were found. Theories on the cause of spondylolysis and spondylolisthesis are reviewed, and preventive suggestions such as more careful training and weight lifting are presented.