Mechanical properties and microstructure of AZ31 Mg alloy containing Ca element fabricated by various rolling speeds.

It was reported that the yield strength (YS) of a rolled Mg-3 wt%, Al-1 wt%, Zn-0.3 wt%, Ca alloy reached 340 MPa. The YS value of a rolled Mg-Al-Zn alloy decreases with increasing the rolling speed but that of a rolled Mg-Al-Zn-Ca alloy remains unchanged until the rolling speed of 5 m/min. Static recrystallization behavior in Mg-Al-Zn alloy occurred as a function of rolling speeds; on the other hand, it did not happen in Mg-Al-Zn-Ca alloy. A number of fine precipitates were observed in the grain of the latter alloy, suggesting that they restrain the dislocations from moving during rolling processes and keep the high strength. From the result of boss-forming test, the Mg-Al-Zn-Ca alloy shows more boss-formability than Mg-Al-Zn alloy.

Motor branch block of the rectus femoris: its effectiveness in stiff-legged gait in spastic paresis.

OBJECTIVE: To verify the efficacy of motor branch block of the rectus femoris for stiff-legged gait in spastic patients. DESIGN: Before-after treatment trial. SETTING: University hospital physical medicine and rehabilitation department outpatient clinic. PATIENTS: Thirty-one adult spastic patients with stiff-legged gait. INTERVENTION: Motor branch block of the rectus femoris with 2% lidocaine and 5% phenol. OUTCOME MEASURES: Subjective assessment of gait performance by patients themselves and objective assessment of gait speed and sagittal knee kinematics. RESULTS: Seventy-four percent (23/31) of patients felt an improvement (improved knee bending, disappeared toe dragging) after nerve block with lidocaine. Sixteen of 17 patients with an abnormal swing phase activity of the rectus femoris without that of the vastus medialis or lateralis and 20 of 23 patients with a sufficient hip flexor strength expressed an improvement subjectively. Gait analysis showed increased maximal knee flexion at swing phase and increased slope of knee flexion curve at toe off (p < .05). Phenol block was performed in 19 of 23 patients who had had a subjective improvement in their gait performance after nerve block with lidocaine. Gait speed, maximal knee flexion angle at swing phase, and slope of knee flexion curve at toe off increased significantly after phenol block (p < .05). CONCLUSION: Motor branch block of the rectus femoris can be an effective treatment in stiff-legged gait. Its effect is varied with hip flexor strength and dynamic electromyographic findings of quadriceps.

Purification and characterization of GTP cyclohydrolase I from Streptomyces tubercidicus, a producer of tubercidin.

GTP cyclohydrolase I catalyzing the first reaction in the biosynthesis of pterin moiety of folic acid in bacteria, was purified from Streptomyces tubercidicus by at least 203-fold with a yield of 32% to apparent homogeneity, using ammonium sulfate fractionation, DEAE-cellulose, Sepharose CL-6B, and hydroxylapatite column chromatography. The molecular weight of the native enzyme was estimated to be 230,000 daltons by gel permeation chromatography. The purified enzyme gave a single band on sodium dodesyl sulfate-polyacrylamide gel electrophoresis and its molecular weight was apparently 58,000 daltons. These results indicate that the enzyme consists of four subunits with the same molecular weight. The K(m) and Vmax values for GTP of the purified enzyme were determined to be 80 microM and 90 nmol/min (mg protein), respectively. The optimum pH and temperature for the enzyme reaction were pH 7.5-8.5 and 40-42 degrees C, respectively. Coenzyme or metal ion was not required for the enzyme activity. The enzyme activity was inhibited by most divalent cations, while it was slightly activated by potassium ion. In case of nucleotides, CTP, GMP, GDP, and UTP inhibited enzyme activity, among which GDP exhibited the strongest inhibitory effect.