SCHWANN CELL PROLIFERATION IN DEVELOPING MOUSE SCIATIC NERVE : A Radioautographic Study

Proliferation of Schwann cells in neonatal mouse sciatic nerve was studied radioautographically in 1-µ glycol methacrylate sections. 28 mice were injected with thymidine-3H, 4 µc/g, 48 hr after birth, and were killed serially over the next 4 days. For the cell cycle following injection, the generation time was approximately 24 hr as determined by grain-count halving data; the duration of synthesis phase was 8 hr as determined from a curve constructed from the per cent of mitotic figures containing label; and the labeling index was 9% at 2 hr after injection. With these estimates, the per cent of Schwann cells proliferating was calculated to be 27%. In addition, roughly 25% of dividing cells appeared to cease division during the cell cycle under study. The relationship of these findings to other events during maturation of nerve is discussed

Dynamics of an inchworm nano-walker

An inchworm processive mechanism is proposed to explain the motion of dimeric molecular motors such as kinesin. We present here preliminary results for this mechanism focusing on observables like mean velocity, coupling ratio and efficiency versus ATP concentration and the external load F.Comment: 6 pages, 2 figure

Behavioural Plasticity in an Ecological Generalist: Microhabitat Use by Western Fence Lizards

Question: What is the basis for geographic variation in microhabitat use in fence lizards? Hypothesis: Population differences in microhabitat use reflect behavioural plasticity rather than genetic or experiential differences. Organisms: Western fence lizards (Sceloporus occidentalis). Field site: Three sites (desert, valley, and mountain) in southern California, USA. Methods: We compared habitat use by free-ranging lizards in three field populations. We also collected lizards from these three populations and studied their microhabitat use in experimental enclosures at a single field site. Results: In the wild, lizards chose higher and shadier perches at the hottest (desert) site, lower and sunnier perches at the coolest (mountain) site, and intermediate perches at the thermally intermediate valley site. However, lizards collected from the three source populations did not differ in microhabitat use in experimental enclosures at a common field site, supporting our hypothesis. Microhabitat choice is an important thermoregulatory mechanism in this species