Individual and combined impacts of biomechanical and work organization factors in work-related musculoskeletal symptoms

BACKGROUND: Investigations of work-related low back (LB) and upper extremity (UE) disorders have increasingly utilized multivariable models that include biomechanical/physical and work organization factors. However, the nature of any interactive effects is not well understood. METHODS: Using questionnaires, high and low exposure groups for biomechanical/physical factors, cognitive demands, cognitive processing, interpersonal demands, participatory management, skill discretion, and time pressure for 289 individuals (U.S. Marines) were identified. Musculoskeletal symptom status was also determined by questionnaire. Individual and biomechanical-psychosocial combinations were examined in adjusted multivariable logistic regression analyses. RESULTS: Time pressure was associated with both LB and UE symptoms (odds ratio(s) (OR) range = 2.13-3.09), while higher biomechanical exposures were risk factors for LB symptoms (OR = 2.07; 95% confidence intervals (CI): 1.00-4.35) and concurrent LB and UE symptoms (OR = 2.80; CI: 1.35-5.83). Greater risks for concurrent LB and UE symptoms were indicated for combinations involving higher biomechanical exposure and: time pressure (OR = 2.21; CI: 1.19-4.10); cognitive demands (OR = 2.25; CI: 1.23-4.09); cognitive processing (OR = 2.08; CI: 1.16-3.75); interpersonal demands (OR = 2.44; CI: 1.35-4.41); participatory management (OR = 2.50; CI: 1.30-4.81). Results did not suggest any interaction between biomechanical and work organization factors. CONCLUSIONS: While no synergism was indicated, the present findings emphasize the need to consider both biomechanical factors and specific work organization factors, particularly time pressure, in reducing musculoskeletal-related morbidity.     

Role of conditioned taste aversion in the development of activity anorexia

Activity anorexia (AA) occurs when rats are restricted to one meal period (60-90 min) each day and have unlimited access to a running wheel the rest of the time. This AA procedure also contains the conditions necessary for conditioned taste aversion (CTA). The food eaten during the meal period is the conditioned stimulus paired with the unconditioned stimulus produced by wheel running. Thus, CTA to food may account in part for the decreased eating in AA. To test this possibility, male rats were subjected to the AA procedure. They had daily 90-min exposures to their familiar chow and spent the rest of the day in running wheels (experimental condition) or home cages (control condition). A second, concurrent experiment had the same procedure except that novel, rather than familiar, food was used. In both experiments, AA occurred; the rats allowed to wheel run ate less than those in the control condition. Several days after AA training, a two-food preference test assessed whether CTA occurred. Wheel running induced CTA when food was novel but not when it was familiar. Since AA is typically studied with procedures using familiar food, the present findings indicate that CTA plays little or no role in AA.     

Short-term exposure of Chinook salmon (Oncoryhnchus tshawytscha) to o,p-DDE or DMSO during early life-history stages causes long-term humoral immunosuppression

We evaluated the effect of short-term exposures to a xenobiotic chemical during early life-history stages on the long-term immune competence of chinook salmon (Oncoryhnchus tshawytscha). Immersion of chinook salmon eggs in a nominal concentration of o,p-dichlorodiphenyldichloroethylene (o,p-DDE; 10 ppm) for 1 hr at fertilization followed by immersion in the same dose for 2 hr at hatch resulted in a significant reduction in the ability of splenic leukocytes from fish 1 year after treatment to undergo blastogenesis upon in vitro stimulation with lipopolysaccharide. We also observed that the vehicle, dimethyl sulfoxide (DMSO), caused a significant reduction in the ability of the splenic leukocytes to express surface immunoglobin M (SIgM) at this time. The concentration of o,p-DDE in a pooled sample of whole fry from this treatment was 0.53 microg/g lipid 1 month after first feeding but was undetectable in all other treatments. Mortality rate, time to hatch, fish length, and weight were unaffected by treatment with o,p-DDE. Similarly, sex ratios, gonadal development, and concentrations of plasma estradiol and 11-ketotestosterone were not affected by the treatment. In addition, we found no evidence that plasma lysozyme concentrations or the mitogenic responses of splenic leukocytes to concanavalin A or polyinosinic-polycytidylic acid were influenced by the treatment. In this experiment, a brief period of exposure to o,p-DDE or DMSO during early development was able to induce long-term effects on humoral immune competence of chinook salmon. Such immunosuppression may increase susceptibility to disease, which may in turn be critical to regulating the population.     

Air following splenic embolization: infection or incidental finding?

The use of splenic embolization for nonoperative management has increased. With increased use of this adjunct, a new and frequent finding has been air within the areas of infarction in patients with or without clinical signs of infection. The purpose of this study was to determine if air within areas of splenic infarction is pathologic of infection or rather an incidental finding. A retrospective review over the past 3 years of inpatients undergoing splenic embolization and having pre- and postembolization abdominal computed tomography scans were reviewed for the findings of free air as well as any clinical signs of infection. A total of 96 consecutive patients were included. Of these, 12 had evidence of infarction with air. Six of these patients had undergone distal embolization with intraparenchymal air, but no symptoms. These were successfully observed. Two patients demonstrated subcapsular air/fluid levels, which underwent drainage with splenic preservation. Cultures were negative for infection. The remaining 4 underwent splenectomy. Of these, all had large collections of air. Two of these 4 spleens were infected: 1 with alpha-hemolytic Streptococcus and one with Clostridia perfringens. The remainder was sterile. This gave an overall infection rate of 17 per cent of patients with evidence of air. This yield increased to 33 per cent if the patient had symptoms and 50 per cent in those with large amounts of air and symptoms. Overall, we feel that air following embolization is a concern, but does not constitute infection. Patients with large amounts of air and signs and symptoms of infection will have a far higher infectious rate, 50 per cent in this limited series. In these patients, evaluation for infection is indicated; that being percutaneous sampling versus splenectomy.