Transcranial Doppler identifies a malfunctioning extraventricular drain.

Transcranial Doppler (TCD) is an invaluable tool allowing real-time monitoring of physiologic blood flow velocity changes. We present a case where TCD monitoring for vasospasm after subarachnoid hemorrhage identified blood flow velocity changes consistent with sudden increased intracranial pressure (ICP) due to a malfunctioning extraventricular drain. The primary team was alerted to these findings, and immediately revised her shunt with normalization of ICP and TCD. Serial TCD monitoring allowed identification of an imminently fatal complication in time to allow a life saving intervention. TCD is a portable, inexpensive, real-time tool providing important physiologic data regarding blood flow velocities and intracranial pressure that is crucial to the care of critically ill patients.

Nerve cross-sectional area in extremes of age.

INTRODUCTION: Nerve cross-sectional area reference values have been reported for many nerves, but there have been few studies in pediatric and geriatric populations. This study was conducted to determine the influence of age on nerve cross-sectional area. METHODS: Thirty-two children (3 months to 16 years) and 20 geriatric adults (67-92 years) without known neurologic conditions underwent bilateral ultrasound to measure the area of the following nerves: median at the wrist and forearm; ulnar at the wrist and elbow; radial in the spiral groove; sciatic in the distal thigh; fibular at the knee; tibial at the knee and ankle; and sural at the ankle. RESULTS: In general, nerve cross-sectional area increased with age. Nerve size correlated most closely with age, but a correlation was also seen with body mass index. CONCLUSIONS: Nerve cross-sectional area increases with age, which is important to note when using ultrasound to evaluate children and geriatric patients.

Mutations within the C-terminus of the gamma subunit of the photosynthetic F1-ATPase activate MgATP hydrolysis and attenuate the stimulatory oxyanion effect.

Two highly conserved amino acid residues near the C-terminus within the gamma subunit of the mitochondrial ATP synthase form a "catch" with an anionic loop on one of the three beta subunits within the catalytic alphabeta hexamer of the F1 segment [Abrahams, J. P., Leslie, A. G. W., Lutter, R., and Walker, J. E. (1994) Nature 370, 621-628]. Forming the catch is considered to be an essential step in cooperative nucleotide binding leading to gamma subunit rotation. The analogous residues, Arg304 and Gln305, in the chloroplast F1 gamma subunit were changed to leucine and alanine, respectively. Each mutant gamma was assembled together with alpha and beta subunits from Rhodospirillum rubrum F1 into a hybrid photosynthetic F1 that carries out both MgATPase and CaATPase activities and ATP-dependent gamma rotation [Tucker, W. C., Schwarcz, A., Levine, T., Du, Z., Gromet-Elhanan, Z., Richter, M. L. and Haran, G. (2004) J. Biol. Chem. 279, 47415-47418]. Surprisingly, changing Arg304 to leucine resulted in a more than 2-fold increase in the kcat for MgATP hydrolysis. In contrast, changing Gln305 to alanine had little effect on the kcat but completely abolished the well-known stimulatory effect of the oxyanion sulfite on MgATP hydrolysis. The MgATPase activities of combined mutants with both residues substituted were strongly inhibited, whereas the CaATPase activities were inhibited, but to a lesser extent. The results indicate that the C-terminus of the photosynthetic F1 gamma subunit, like its mitochondrial counterpart, forms a catch with the alpha and beta subunits that modulates the nucleotide binding properties of the catalytic site(s). The catch is likely to be part of an activation mechanism, overcoming inhibition by free mg2+ ions, but is not essential for cooperative nucleotide exchange.