A Six-Coordinate Silicon Dihydride Embedded in a Porphyrin: Enhanced Hydride-Donor Properties and the Catalyst-Free Hydrosilylation of CO2.

The catalyst-free hydrosilylation of CO2 under mild conditions remains limited. Herein, we report the synthesis, characterization, and reactivity of 5,10,15,20-tetraphenylporphyrinato(dihydrido)silicon(IV) (1) as a six-coordinate silicon dihydride. The Si-H moiety of 1 reacts with polar double bonds and CO2 in the absence of a catalyst to afford hydrosilylated products. Combining the hydrosilylation with subsequent transformation furnishes formic acid from CO2 . Computational studies indicate that the hydride-donor properties of 1 are exceptionally high for a neutral silicon hydride, and that the direct hydride transfer from silicon to carbon is a pivotal step in the hydrosilylation of CO2 with 1.

L233P mutation in the bovine leukemia virus Tax protein depresses endothelial cell recruitment and tumorigenesis in athymic nude mice.

Bovine leukemia virus (BLV) can be divided into two categories based on the amino acid at position 233 in the Tax protein, which probably plays a crucial role in leukemogenesis. We show here that a rat fibroblast cell line stably expressing L233-Tax formed significantly larger tumors than P233-Tax-expressing cells in a murine xenograft study. Although the microvessel density was comparable in both tumors, visible blood vessel invasion was observed only on tumors from L233-Tax-expressing cells. Endothelial cell tube formation assays using human umbilical vein endothelial cells showed no significant difference in angiogenic activity between conditioned medium from L233- and P233-Tax-expressing cells, whereas in vitro chemotaxis assays revealed that only L233-Tax-expressing cells produced a chemoattractant for endothelial cells. Since pathological neovascularization can occur from the recruitment of endothelial progenitor cells, these results suggest that L233-Tax-expressing cells recruit murine endothelial progenitor cells and promote neovascularization to support tumor growth. BLV-infected lymphoma cells may also recruit bovine endothelial progenitor cells to promote neovascularization. The findings of this study are consistent with our previous observation that BLV carrying P233-Tax has a significantly longer incubation period for developing tumors than the virus carrying L233-Tax and provide insight into the function of Tax in leukemogenesis by BLV.

Effects of therapeutic gait training using a prosthesis and a treadmill for ambulatory patients with hemiparesis.

OBJECTIVE: To examine the short-term effects of a newly developed hemiparetic gait training in which patients walk with a prosthesis applied to the nonparetic leg in the flexed knee position. DESIGN: Pre-post nonrandomized controlled trial. SETTING: Rehabilitation center and gait laboratory of a university hospital. PARTICIPANTS: Community-dwelling ambulatory volunteers (N=22) with chronic hemiparesis caused by a unilateral stroke. INTERVENTION: Study subjects participated in a gait training program using either a below-knee prosthesis or a treadmill. Treadmill gait training was performed at a speed approximating the maximum gait velocity for each patient. The 3-week program consisted of a 5-minute gait training session 2 to 3 times a day. MAIN OUTCOME MEASURES: The ground reaction forces, stance time, step length and cadence during walking at a comfortable speed, and maximum gait speed, as well as the Berg Balance Score, were estimated before and after each training program. RESULTS: In comparison with changes after the treadmill gait training, analyses of covariance demonstrated a significant increase of the fore-aft ground reaction forces during the paretic propulsion phase and a significant increase in the relative durations of the paretic and nonparetic single stance involved in a gait cycle after the prosthetic gait training (P<.05). CONCLUSIONS: Prosthetic gait training would have different effects on a hemiparetic gait than treadmill gait training. The gait-related task inducing the dominant use of the paretic leg to support the body may be useful as a rehabilitative treatment to improve the kinetic abilities in the paretic stance period.

A method for estimating noise variance of CT image.

Rank et al. have proposed an algorithm for estimating image noise variance composed of the following three steps: the noisy image is first filtered by a difference operator; a histogram of local signal variances is then computed; and, finally the noise variance is estimated from a statistical evaluation of the histogram. We have verified the accuracy of this algorithm on a CT image by indirect methods, and have shown that this method is able to estimate CT image noise variance with reasonable accuracy, regardless of whether or not the noiseless image is uniform. Further, we have proposed a simple alternative method for the last two steps of the Rank et al. method. However, one must pay attention to the fact that the estimated noise variance will be biased when the nearest two pixels are correlated and that this algorithm does not work well if the assumption of stationarity of noise components is violated.