Effect of gamma-aminobutyric acid treatment on plasma substance P and calcitonin gene-related peptide levels in children with asthma / 中国当代儿科杂志

<p><b>OBJECTIVE</b>To study the changes in plasma substance P (SP) and calcitonin gene-related peptide (CGRP) levels in children with acute asthma before and after gamma-aminobutyric acid (GABA) treatment.</p><p><b>METHODS</b>Seventy-five children with asthma were randomly assigned to GABA treatment (n=36) and control groups (n=39). Both groups were given conventional treatment for asthma. Besides the conventional treatment, the treatment group was administered with oral GABA (25-30 mg/kg•d). Plasma content of SP and CGRP was measured using ELISA before treatment and after remission.</p><p><b>RESULTS</b>There were no significant differences in plasma content of SP and CGRP between the GABA treatment and control groups (P＞0.05) before treatment. Plasma content of SP and CGRP in the GABA treatment group was significantly lower than the control group (SP: 57±15 pg/mL vs 127±12 pg/mL; CGRP: 23±10 pg/mL vs 42±8 pg/mL) after remission (P<0.01). Plasma content of SP and CGRP after remission was significantly lower than before treatment (P<0.01) in both groups. There was a significantly positive correlation between plasma SP and CGRP content in asthmatic children (r=0.792, P<0.01).</p><p><b>CONCLUSIONS</b>GABA can significantly decrease plasma levels of SP and CGRP in children suffering from acute asthma.</p>

Ultra-high cycle fatigue behaviors of implanted Ti-6Al-4V in high frequency after subjection to simulated body fluid / 医用生物力学

Objective To study the ultra-high cycle fatigue behaviors of the Ti-6Al-4V alloy implant after subjection to simulated body fluid (SBF) environment exceeding 107 cycles, and to predict its service life. Method The Ti-6Al-4V alloy specimens were subjected to SBF in two groups for two days and six days respectively; using the ultrasonic fatigue testing technique, the ultra high cycle fatigue properties of Ti-6Al-4V alloy after subjection to SBF in body temperature were studied and the initiation mechanisms of fatigue cracks were investigated and analyzed with scanning electron microscopy (SEM) and energy dispersive atomic X-ray (EDA X ray). Then, a comparison with corresponding behaviors of the normal Ti 6Al 4V alloy was made. Results The S~N curve of the Ti-6Al-4V alloy after subjection had the similar tendency as that of the normal one, showing that they descended continuously during 104 and 108 cycles and the descending tendency was lower in the region of 107～108 cycles; the life of the specimens after subjection dropped before the fatigue life of 107 cycles and was smaller after the fatigue life of 107 cycles than that of the normal ones; the life of the specimens subjected for six days had little difference with that subjected for two days; fracture could still occur beyond 107 cycles, showing that there was no fatigue limit as the traditional fatigue conception described. Fatigue cracks mainly initiated from the surface of specimen before the fatigue life of 107 cycles and some specimens had multiple crack initiation sites; fatigue failure initiated from internal inclusion where mostly the element Al aggregated after the fatigue life of 108 cycles. Conclusions The ultra high cycle fatigue properties of the Ti-6Al-4V alloy decreas a little with SBF subjection; the initiation site of the fatigue crack changes from the surface to the internal defect with the increase of the number of cycle.