Kunji Shirahama

The time course and extent of motor neuron loss following spinal cord compression in rats

Motor deficits after spinal cord injury arise from damages to the descending spinal pathways and ventral motoneurons (VMN). In contrast to data on damages to the white matter or the descending spinal pathways, few quantitative data on damages to VMN after injury are available currently. The purpose of this study was to examine quantitatively the temporal and spatial pattern of VMN loss after spinal cord compression. Two groups of adult female Wistar rats were used in this study: rats which were subjected to spinal cord compression in short duration with an aneurysm clip (experimental group) and rats which were subjected to a sham-operation (control group). Using serial cross-sections of the spinal cord, VMN were counted up to the 7th day after surgical intervention at 0, 1, 2, and 3 mm rostral and caudal to the lesion epicenter (experimental group) or to the median of the serial sections (control group). At 15 minutes after the compression, VMN were lost only at the epicenter section and no VMN were observed there. By 8 hours, VMN loss had spread to next 1 mm rostral and caudal section to the epicenter. Virtually, no further loss was detected between 8 hours and later time points. This study showed that compression to the adult rat spinal cord in short duration led to VMN loss, which progressed acutely and expanded modestly. Our findings could be used to develop effective treatment and provide a better understanding of VMN loss after spinal cord injury.

Time course of influence by ovariectomy and calcium diet on bone properties in mice.

This study was investigated the influence by ovariectomy (OVX) and calcium diet on bone properties in eighty-one female ICR strain mice with age of 5 weeks. The animals were randomly assigned to sham operation (SHAM), OVX, SHAM+low Ca intake (L.Ca) and OVX+L.Ca group. They were euthanized with lethal dose of pentobarbital sodium at day 50, 100 and 140 post-operatively. For determining the bone properties, both femur and tibial bones were excised from the hind limb, and removed off surrounding tissues. Thereafter, bone length, bone dry weight, and also mechanical strength and ash content of the bones were determined. The bone length on both femur and tibia was significantly longer in OVX group than in the other groups after 50 day of experiment, this situation was continued to the end of the experiment. Bone dry weight, mechanical strength, and ash content were significantly decreased by OVX and L.Ca over the time of the experiment, and those of OVX+L.Ca group were the lowest in all groups. OVX and L.Ca have a great potential for weakening the mechanical strength and have an additive effect when combined. OVX and L.Ca block the gain of bone mass.