Myelination of the corpus callosum in the cat: time course, topography, and functional implications

The parameters of myelin development were ascertained in two specific regions of the corpus callosum in a series of cats aged 12 postnatal days through adult. The posteriormost portion of the splenium and the anterior-most portion of the genu were examined in cross section by using the electron microscope. Measurements were made to determine the age at which myelin first appeared, the number and distribution of myelinated fibers, the number and distribution of myelin lamellae, and cross-sectional area of ensheathed axons during development. The results indicate that myelination begins and ends earlier in the anterior region of the callosum. Measurements of myelin lamellae indicate similarities between anterior and posterior regions of the callosum, although development occurs earlier in the genu than in the splenium. No evidence was found for a sequence in the size of axons acquiring myelin sheaths, except that extremely small fibers are the last to begin myelinating. Myelination of the splenium of the corpus callosum begins at the very end of the behavioral and physiological critical period for the corpus callosum's role in visual functional development (Elberger: Behav. Brain Res. 11:223-231, '84; Elberger and Smith: Exp. Brain Res. 57:213-223, '85). Since myelination of a pathway is used as an index of functional reliability, this indicates that the basis for the callosal role in developing visual functions is probably not based on its physiological input to visual cortex.     

Molecular and mechanical property changes during aging of bone cement in vitro and in vivo

The changes in mechanical properties and free radical concentration of curing Simplex P Radiopaque Bone Cement in vivo and in vitro conditions were studied. Samples were prepared so that each in vivo sample that cured and aged in the canine femoral intramedullary cavities had an in vitro counterpart that was cured and aged in a constant-temperature saline bath at 37 degrees C. An electron paramagnetic resonance (EPR) spectrometer was used to measure the growth and decay (curing) of polymerization radicals. The results of EPR measurements showed that the curing (disappearance of free radicals) of in vivo samples takes a much longer time (more than 4 weeks) than in vitro curing (less than 2 weeks). The mechanical tests indicate that, whether aged in vivo or in vitro, the strength increased rapidly for the first 1-2 weeks and then slight increases were seen for up to 6 months.     

A leg ulcer as manifestation of metastatic squamous cell vaginal carcinoma

Cutaneous metastasis of vaginal carcinoma is extremely rare. So far, the total number of reported skin metastasis of vaginal carcinoma is only one. We present another case with an unusual manifestation of vagina carcinoma metastasis: skin metastasis presenting as a leg ulcer on the lower leg.