Changes in energy metabolism in the quadriceps femoris after a single bout of acute exhaustive swimming in rats: a ³¹P-magnetic resonance spectroscopy study / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>Little is known about the value of (31)P-magnetic resonance spectroscopy ((31)P-MRS) in in vivo assessment of exhaustive exercise-induced injury in skeletal muscle. We aimed to evaluate the value of a (31)P-MRS study using the quadriceps femoris after a single bout of acute exhaustive swimming in rats, and the correlation between (31)P-MRS and histological changes.</p><p><b>METHODS</b>Sixty male Sprague-Dawley rats were randomly assigned to control, half-exhaustive, and exhaustive exercise groups. (31)P-MRS of the quadriceps femoris of the right lower limb was performed immediately after swimming exercise to detect Pi, PCr, and β-ATP. The Pi/PCr, Pi/β-ATP, PCr/β-ATP, and PCr/(PCr+Pi) were calculated and pH measured. Areas under the receiver operating characteristic curve (AUCs) were calculated to evaluate the diagnostic potential of (31)P-MRS in identifying and distinguishing the three groups. HE staining, electron microscopy and desmin immunostaining after imaging of the muscle were used as a reference standard. The correlation between (31)P-MRS and the mean absorbance (A value) of desmin staining were analyzed with the Pearson correlation test.</p><p><b>RESULTS</b>Pi, PCr, Pi/PCr, and PCr/(PCr+Pi) showed statistically significant intergroup differences (P < 0.05). AUCs of Pi, PCr, Pi/PCr, and PCr/(PCr+Pi) were 0.905, 0.848, 0.930, and 0.930 for the control and half-exhaustive groups, while sensitivity and specificity were 90%/85%, 95%/55%, 95%/80%, and 90%/85%, respectively. The AUCs of Pi, PCr, Pi/PCr and PCr/(PCr+Pi) were 0.995, 0.980, 1.000, and 1.000 for the control and exhaustive groups, while sensitivity and specificity were 95%/90%, 100%/90%, 100%/95%, and 100%/95%, respectively. The AUCs of Pi, PCr, Pi/PCr, and PCr/(PCr+Pi) were 0.735, 0.865, 0.903, and 0.903 for the half-exhaustive and exhaustive groups, while sensitivity and specificity were 80%/60%, 90%/75%, 95%/65%, and 95%/70%, respectively. In the half-exhaustive group, some muscle fibers exhibited edema in HE staining, and the unclear Z-discs and the mitochondria with vacuolar degeneration under electron microscopy. Compared with the half-exhaustive group, muscle fiber edema was increased in the exhaustive group, and the Z-discs were broken and the mitochondria exhibited marked vacuolar degeneration under electron microscopy. There were significant difference in A values of desmin staining in the right vastus lateralis among the control, half-exhaustive, and exhaustive groups with 0.58 ± 0.06, 0.30 ± 0.04, and 0.21 ± 0.02, respectively (P < 0.05). Histological examination also showed injury-induced changes in the vastus lateralis among the different intensities groups. Statistically a moderate correlation between (31)P-MRS and desmin was observed, the correlation coefficients of Pi, PCr, Pi/PCr, and PCr/(PCr+Pi) were -0.706, 0.709, -0.726, and 0.791, respectively (P < 0.01).</p><p><b>CONCLUSIONS</b>(31)P-MRS can effectively reflect the changes in energy metabolism in the skeletal muscle after a single bout of acute exhaustive swimming in rats. Based on the significant correlation between (31)P-MRS parameters and histological changes, the changes of Pi, PCr, Pi/PCr, and PCr/(PCr+Pi) can indirectly reflect the degree of exercise-induced injury.</p>

Diffusion weighted imaging for quantification of liver fibrosis in patients using normalized apparent diffusion coefficient values at 3.0 T MR / 中华放射学杂志

ObjectiveThe purpose of this study is to discuss the diagnostic accuracy of nornalized liver ADC using the spleen and renal cortex as reference organs for the diagnosis of liver fibrosis.Methods Forty three patients with liver disease (chronic liver disease group) at compensated stage and 10 healthy volunteers (control group) were retrospectively assessed with diffusion-weighted imaging at a 3.0 T MR unit.Liver ADC,spleen ADC,renal ADC and normalized ADC (defined as the ratio of liver ADC to spleen ADC or renal cortex ADC,S-ADC and R-ADC for short) were measured in patients stratified by fibrosis stage.Spearman analysis was used to see the correlation between fibrosis stages and ADC,one-way ANOVA was used to compare the ADCs in different fibrosis stages.Logistic regression analysis was used to determine the performance of ADC for prediction of liver fibrosis,and show the area under the curve ( AUC),sensitivity and specificity choosing the optimal cutoff value that maximized the Youden index.ResultsTen volunteers belonged to SO stage.From SO to S4 stage,there were 2,5,9,12 and 15 patients,correspondingly,liver ADCwere (1.37±0.13) ×10-3,(1.33±0.16) ×10 -3,(1.17±0.16) ×10-3,(1.23±0.14) ×10-3and ( 1.12 ±0.11 ) × 10-3mm2/s,S-ADC were 1.86 ±0.18,1.68 ±0.12,1.34 ±0.14,1.48 ±0.15 and 1.34±0.10,R-ADC were 0.71 ±0.08,0.68 ±0.12,0.61 ±0.09,0.64 ±0.11 and 0.60 ±0.08respectively,and the differences among them were significant ( F =6.48,18.70 and 3.04,P ＜0.05 ).The correlation between fibrosis stage and S-ADC was stronger than between fibrosis stage and liver ADC,R-ADC (r =- 0.71,- 0.51,- 0.41 ;P ＜ 0.01 ).S-ADC was superior to liver ADC and R-ADC for detection of S2,S3 and S4 fibrosis stage (Youden index:0.91,0.58,and 0.59).ConclusionSpleen normalized liver ADC improves diagnostic accuracy for detection of liver fibrosis than liver ADC and renal normalized liver ADC.