Anatomic and clinical significance of the first and most medial deep transverse metatarsal ligament

A review of the related literature revealed ambiguity and inconsistency as to the location of the first and most medial deep transverse metatarsal ligament in relation to the adjacent soft tissue and osseous structures. Seventy right sided, mid-thigh cadaveric dissections were completed by the investigators. The results consistently identified the ligament as bifurcate, bearing a common stem with the medial aspect of the second metatarsophalangeal joint capsule and a split attachment to the lateral aspect of the first metatarsophalangeal joint capsule and sesamoidal apparatus. The conjoined tendon of the adductor hallucis muscle was consistently identified as passing between this bifurcation. Knowledge of the location of this anatomic structure bears importance in the podiatric surgeon's attempt to restore the alignment of the first metatarsophalangeal joint by means of soft tissue or osseous procedures.     

NMDA Receptor Activation Triggers Voltage Oscillations, Plateau Potentials and Burstinq in Neonatal Rat Lumbar Motoneurons ln Vitro

Whole-cell recordings of lumbar motoneurons in the intact neonatal rat spinal cord in vitro were undertaken to examine the effects of Kmethyl-D-aspartate (NMDA) receptor activation on membrane behaviour. Bath application of NMDA induced rhythmic voltage oscillations of 5.9 ± 2.1 mV (SD) at a frequency of 4.4 ± 1.5 Hz. Amplitude, but not frequency, of the voltage oscillations was membrane potential-dependent. Voltage oscillations could recruit action potentials and/or plateau potentials with or without superimposed bursting. Blockade of synaptic transmission with tetrodotoxin (TTX) sometimes resulted in a loss of oscillatory activity which could then be restored by increasing the NMDA concentration. After application of TTX, the trajectory of NMDA-induced oscillations was similar to the trajectory induced in the presence of intact synaptic networks, although the mean oscillation duration was longer and the oscillation frequency was slower (1.8 ± 1.1 Hz). Current ramps delivered after bath application of NMDA demonstrated bistable membrane properties which may underlie the plateau potentials. Injection of intracellular current pulses could initiate, entrain and terminate individual plateau potentials. The results suggest that membrane depolarization produced by oscillations may activate other intrinsic conductances which generate plateau potentials, thereby providing the neuron with enhanced voltage sensitivity, compared to that produced by NMDA receptor activation alone. These oscillatory events may have a role in the regulation of motor output in a variety of rhythmic behaviours including locomotion.     

Lymphotoxin but not tumor necrosis factor functions to maintain splenic architecture and humoral responsiveness in adult mice

To compare the function of the tumor necrosis factor (TNF) and lymphotoxin (LT)α/β systems in the mature immune system, these two pathways were blocked with soluble receptor-immunoglobulin (R-Ig) fusion proteins in normal adult mice. Inhibition of LTα/β signaling using LTβR-Ig or a blocking monoclonal antibody against murine LTβ had profound effects. The spleen lacked discrete B cell follicles and the marginal zone was altered. Less marked changes were detected in lymph nodes. LTα/β inhibition also prevented germinal center formation in the spleen and impaired Ig production in response to sheep red blood cells (SRBC) immunization. These results show that the LTα/β system is required for the maintenance of splenic architecture and normal immune responses, and not simply for the development of peripheral immune organs during ontogeny. In contrast, inhibition of the TNF/LTα pathway with TNF-R55-Ig did not affect the splenic architecture or the anti-SRBC response. Splenic defects and impaired antibody responses are seen in TNF-deficient mice, suggesting that TNF is important during development. Therefore relative to TNF, the LT system has the dominant influence on splenic organization and anti-SRBC Ig formation in the adult mouse.