Postnatal maturational properties of rat parafascicular thalamic neurons recorded in vitro.

Thalamic relay neurons have homogeneous, adult-like firing properties and similar morphology by 12 days postnatally (PN 12). Parafascicular (Pf) neurons have a different morphology compared with typical thalamic relay neurons, but the development of their electrophysiological properties is not well studied. Intracellular recordings in PN 12-50 Pf neurons revealed several heterogeneous firing patterns different from those in thalamic relay neurons. Two types of cells were identified: Type I cells displayed a fast afterhyperpolarization (AHP) followed by a large-amplitude, slow AHP; whereas Type II cells had only a fast AHP. These cell types had overlapping membrane properties but differences in excitability. Some properties of Pf neurons were adult-like by PN 12, but, unlike thalamic relay neurons, there were significant maturational changes thereafter, including decreased action potential (AP) duration, increased fast AHP amplitude and increased excitability. Pf neurons did not exhibit rhythmic bursting and generally lacked low-threshold spike (LTS) responses that characterize thalamic relay neurons. Pf neurons exhibited nonlinear I-V relationships, and only a third of the cells expressed the time and voltage-dependent hyperpolarization activated (Ih) current, which declined with age. These results indicate that the morphological differences between Pf neurons and typical thalamic relay neurons are paralleled by electrophysiological differences, and that Pf membrane properties change during postnatal development.

Post-cesarean section cecal volvulus.

Cecal volvulus after cesarean section is rare. Symptoms include abdominal pain, nausea, vomiting, constipation, cystic abdominal mass, and high-pitched bowel sounds. Abdominal x-ray photography is often diagnostic, revealing a dilated cecum with a single fluid level and distended loops of small bowel. The main differentiating factors in post-cesarean large bowel distention are sigmoid volvulus and pseudo-obstruction of the colon. Treatment should accomplish derotation, decompression, and anchoring to prevent recurrence.

Arterial insufficiency in hemodialysis access procedures: reconstruction by an interposition polytetrafluoroethylene graft conduit.

The interposition polytetrafluoroethylene graft conduit has found many uses in the armamentarium of the surgeon who performs vascular access for hemodialysis: when resection of aneurysm or pseudoaneurysm is required, or when an extension loop is required, either to simply lengthen the amount of graft or to circumvent an infected segment after resection. Herein, we have presented yet another use for the interposition polytetrafluoroethylene graft conduit, based on physiologically sound principles and a now proved successful outcome, namely as a surgical alternative for the patient with a hemodynamically unstable hemodialysis fistula resulting in arterial insufficiency. Poiseuille's Law regarding flow of liquids through a tube supports the concept on which our interposition graft is based: v = pi X P X R4/8 X 1 X n where v is the volume escaping per second, P the difference of pressure at the ends of the tube, R its radius, l the length of the tube, and n the coefficient of viscosity. Given the maintenance of all other parameters, if one increases the length of the tube through which blood is flowing, the volume of flow through said tube is simultaneously decreased, and the ischemic symptoms caused by arterial insufficiency are thereby ameliorated.