[Research on the reliability and validity of postural workload assessment method and the relation to work-related musculoskeletal disorders of workers].

OBJECTIVE: To form a new assessment method to evaluate postural workload comprehensively analyzing the dynamic and static postural workload for workers during their work process to analyze the reliability and validity, and to study the relation between workers' postural workload and work-related musculoskeletal disorders (WMSDs). METHODS: In the study, 844 workers from electronic and railway vehicle manufacturing factories were selected as subjects investigated by using the China Musculoskeletal Questionnaire (CMQ) to form the postural workload comprehensive assessment method. The Cronbach's α, cluster analysis and factor analysis were used to assess the reliability and validity of the new assessment method. Non-conditional Logistic regression was used to analyze the relation between workers' postural workload and WMSDs. RESULTS: Reliability of the assessment method for postural workload: internal consistency analysis results showed that Cronbach's α was 0.934 and the results of split-half reliability indicated that Spearman-Brown coefficient was 0.881 and the correlation coefficient between the first part and the second was 0.787. Validity of the assessment method for postural workload: the results of cluster analysis indicated that square Euclidean distance between dynamic and static postural workload assessment in the same part or work posture was the shortest. The results of factor analysis showed that 2 components were extracted and the cumulative percentage of variance achieved 65.604%. The postural workload score of the different occupational workers showed significant difference (P<0.05) by covariance analysis. The results of nonconditional Logistic regression indicated that alcohol intake (OR=2.141, 95%CI 1.337-3.428) and obesity (OR=3.408, 95%CI 1.629-7.130) were risk factors for WMSDs. The risk for WMSDs would rise as workers' postural workload rose (OR=1.035, 95%CI 1.022-1.048). There was significant different risk for WMSDs in the different groups of workers distinguished by work type, gender and age. Female workers exhibited a higher prevalence for WMSDs (OR=2.626, 95%CI 1.414-4.879) and workers between 30-40 years of age (OR=1.909, 95%CI 1.237-2.946) as compared with those under 30. CONCLUSION: This method for comprehensively assessing postural workload is reliable and effective when used in assembling workers, and there is certain relation between the postural workload and WMSDs.

Ex-vivo MR imaging of liver intracellular contrast agents.

The objective is to evaluate whether an ex-vivo model can be used to test intracellular contrast agents for MR imaging of the liver. T1 weighted inversion recovery, proton density spin echo and T2* weighted gradient echo images of the liver were acquired at 0.5 T in 10 rats before and 30 min after intravenous injection of 0.075 mmol/kg Gadolinium benzyloxypropionictetraacetate (Gd-BOPTA, n = 5) or 0.015 mmol/kg dextran magnetite (DM, n = 5), Four additional animals served as controls. After exsanguination and perfusion with saline and formalin, specimens of the liver and brain were embedded in an agar gel and examined with MR imaging one to three weeks later using the same protocol. In-vivo, the mean liver signal enhancement caused by Gd-BOPTA in T1, proton density and T2* weighted images was +23%, +28% and -70%, respectively. The mean liver signal enhancement caused by DM was -71%, -76% and -94%. In-vitro, no signal change was seen in the brain of animals injected with Gd-BOPTA and DM as compared to controls. Liver signal was increased by Gd-BOPTA and decreased by DM. Mean liver enhancement rate induced by Gd-BOPTA was +22%, +5% and +27% for T1, proton density and T2* weighted images, respectively. Mean liver enhancement rate induced by DM was -27%, -19% and -31%. MR imaging signal changes induced by liver intracellular contrast agents are still appreciable in an ex-vivo model. The latter might be useful for for preliminary investigation of intracellular contrast agents for MR imaging of the liver.

Liver and spleen enhancement after intravenous injection of carboxydextran magnetite: effect of dose, delay of imaging, and field strength in an ex vivo model.

It has been predicted that liver and spleen enhancement after administration of superparamagnetic contrast agents may be different, depending on the strength of the main magnetic field. With the use of an ex vivo model, we investigated at 0.3, 0.5, and 1.5 T the effects on liver and spleen signal intensity of 5, 15, and 45 mumol/kg body weight of dextran magnetite (SHU 555A) in 54 rats. Nine rats served as controls. At different time delays since injection, the animals were killed, and after perfusion with saline, the liver, brain, and spleen were fixed in formalin. The specimens were embedded in an agar gel matrix and imaged with inversion recovery T1-weighted, proton density spin echo, and T2*-weighted gradient recalled echo (GRE) sequences. At each magnetic field strength, peak liver and spleen signal loss increased with increasing dose of the contrast medium. Signal loss was significantly more conspicuous after a dose of 15 than 5 mumol/kg body weight, but not after a dose of 45 compared with 15 mumol/kg. No signal change was observed in the brain. GRE images showed higher enhancement than proton density-weighted spin echo and inversion recovery images but were noisier. The enhancement showed a plateau between 30 min and 24 hours. Only the signal decrease of the liver after a low dose of contrast medium on GRE images was significantly higher (p < 0.01) at 1.5 than at 0.5 and 0.3 T. Other differences in respect to the field strength were less significant (p < 0.05) or nonsignificant. Differences in the spleen enhancement were nonsignificant. SHU 555A at a dose of 15 mumol/kg is an efficient intracellular contrast agent for liver and spleen at low, mid, and high field strength. Proton density spin echo images are probably the sequence of choice to exploit SHU 555A contrast effects and a wide time window for imaging after its intravenous injection does exist.

[The effect of vanillin on the fully amygdala-kindled seizures in the rat].

The anticonvulsive action of vanillin, an antiepileptic agent structurally related to vanillyl alcohol isolated from Gastrodia elata Blume, on the fully amygdala-kindled seizures was investigated. Fully kindled seizures were produced by repeated application of low intensity electrical stimulation to the basolateral amygdala once per day. Fifteen consecutive stimulations were needed to reach the first stage 5 seizures at which animals showed behavioral convulsions and electroencephalographic abnormalities. The stage 5 seizures were suppressed by vanillin ip 1 h before stimulation with the ED50 of 286 mg/kg. Meanwhile, the epileptic afterdischarge duration was significantly shortened. Phenytoin at a nontoxic dose 50 mg/kg ip obviously reduced the stage 5 seizures. The present study provides a very useful experimental model of chronic epilepsy to detect anticonvulsants.