Perception of task duration affects metabolic cost during split-belt adaptation.

Humans continuously adapt locomotor patterns. Whether metabolic cost reduction is the primary objective or a by-product of the observed biomechanical changes during adaptation is not known. The main goal of our study is to determine if perception of task duration affects the adaptation of locomotor patterns to reduce energetic cost during split-belt walking. We tested the hypothesis that individuals who believe they will sustain a locomotor adaptation task for a prolonged time will reduce metabolic cost by adapting toward a walking pattern associated with lower mechanical work. N=14 participants walked on a split-belt treadmill for 10 minutes with knowledge of task duration (group K), while N=15 participants performed the task under the assumption that they would walk for 30 minutes (group U). Both groups walked for 10 minutes with the belts moving at 1.5 and 0.5 m/s, followed by 6 minutes of walking with both belts at 1.0 m/s. We observed a significant main effect of Time (p<0.001, observed power 1.0) and the interaction of Time×Group (p=0.004, observed power 0.84) on metabolic cost. Participants in the U group had a metabolic cost that was 12% lower during adaptation compared to the K group, which did not reduce metabolic cost during adaptation. The metabolic cost reduction observed in group U was not associated with biomechanical changes during adaptation. Our results indicate that metabolic cost reduction has a primary role in tasks that need to be sustained for a prolonged time, and this reduction is not only related to biomechanical factors.

Quantification of multidrug-resistant M. tuberculosis bacilli in sputum during the first 8 weeks of treatment.

SETTING: Mulago Hospital, Kampala, Uganda.OBJECTIVE: To quantify Mycobacterium tuberculosis in sputum during the first 8 weeks of pulmonary multidrug-resistant TB (MDR-TB) treatment.DESIGN: We enrolled consecutive adults with pulmonary MDR-TB treated according to national guidelines. We collected overnight sputum samples before treatment and weekly. Sputum samples were cultured on Middlebrook 7H11S agar to measure colony-forming units per mL (cfu/mL) and in MGIT™ 960™ media to measure time to detection (TTD). Linear mixed-effects regression was used to estimate the relational change in log10 cfu/mL and TTD.RESULTS: Twelve adults (median age: 27 years) were enrolled. Half were women, and two-thirds were HIV-positive. At baseline, median log10 cfu/mL was 5.1, decreasing by 0.29 log10 cfu/mL/week. The median TTD was 116.5 h, increasing in TTD by 36.97 h/week. The weekly change was greater in the first 2 weeks (-1.04 log10 cfu/mL/week and 120.02 h/week) than in the remaining 6 weeks (-0.17 log10 cfu/mL/week and 26.11 h/week).CONCLUSION: Serial quantitative culture measures indicate a slow, uneven rate of decline in sputum M. tuberculosis over 8 weeks of standardized pulmonary MDR-TB treatment.

Wastewater reclamation for use in snow-making within an alpine resort in Australia--resource rather than waste.

The Mt Buller Alpine Resort is located approximately 200 km north of Melbourne, in Victoria, Australia. A wastewater treatment plant services the resort and currently treats to advanced nutrient removal standards. The treated effluent is presently discharged into the Howqua River. Most Australian ski resorts are not blessed with abundant snow cover on a regular basis. Artificial snow allows most of the popular ski runs to operate for the whole of the season. At the Mt Buller resort, snow-making is presently limited by lack of water supply in the catchment. The conditions at Mt Buller resort present a unique opportunity to utilise reclaimed wastewater to allow increased snow-making capacity. It is one of the unique opportunities where the wastewater is valued as a resource rather than merely viewed as a waste problem. Wastewater reclamation for snow-making will require additional treatment for pathogen removal. It is proposed that following advanced nutrient removal, the effluent will require further treatment, including membrane ultrafiltration, so as to ensure a minimum of four barriers for pathogen removal. Pilot plant operation of a membrane ultrafiltration system commenced in June 2000 and will continue until the end of 2001, to primarily demonstrate the extent of pathogen removal.

A novel intermediate filament-associated protein: further characterization of the G.3.5 antigen.

Several novel intermediate filament-associated proteins (IFAPs) have been discovered using hybridoma technology on multiple sclerosis plaque tissue. One of these, designated the G.3.5 antigen, is a desmin-binding IFAP in skeletal and cardiac muscle. It has been suggested that because of sequence similarities to alpha-actinin the G.3.5 antigen is an alpha-actinin-like protein which may cross-link actin and intermediate filaments in the cytoskeleton. In this study, it is reported that (1) the G.3.5 antigen is present in hepatocytes in addition to the previously described astrocytes, skeletal and cardiac myocytes, fibroblasts, and several other non-nervous tissues; (2) in myocytes and hepatocytes, the G.3.5 and alpha-actinins do not co-localize; (3) by transmission electron microscopy the G.3.5 antigen appears to be a rod-shaped dimer similar to alpha-actinin; (4) isolation of the G.3.5 antigen does not simultaneously isolate alpha-actinin; and (5) limited proteolysis of the G.3.5 antigen and alpha-actinin generates dissimilar maps. In binding studies, alpha-actinin cross-links actin but has no effect on desmin; the G.3.5 antigen does not appear to cross-link actin, desmin or mixtures of both under the assay conditions. These results support the hypothesis that the G.3.5 antigen is a novel IFAP related to alpha-actinin, but do not support a role for the antigen as a cross-linker between intermediate filaments and actin.