Contribution of limb momentum to power transfer in athletic wheelchair pushing.

Pushing capacity is a key parameter in athletic racing wheelchair performance. This study estimated the potential contribution of upper limb momentum to pushing. The question is relevant since it may affect the training strategy adopted by an athlete. A muscle-free Lagrangian dynamic model of the upper limb segments was developed and theoretical predictions of power transfer to the wheelchair were computed during the push phase. Results show that limb momentum capacity for pushing can be in the order of 40J per push cycle at 10m/s, but it varies with the specific pushing range chosen by the athlete. Although use of momentum could certainly help an athlete improve performance, quantifying the actual contribution of limb momentum to pushing is not trivial. A preliminary experimental investigation on an ergometer, along with a simplified model of the upper limb, suggests that momentum is not the sole contributor to power transfer to a wheelchair. Muscles substantially contribute to pushing, even at high speeds. Moreover, an optimal pushing range is challenging to find since it most likely differs if an athlete chooses a limb momentum pushing strategy versus a muscular exertion pushing strategy, or both at the same time. The study emphasizes the importance of controlling pushing range, although one should optimize it while also taking the dynamics of the recovery period into account.

Urinary lysosomal enzymes for detection of acute renal allograft rejection.

Six patients who received renal transplants were closely monitored to compare the sensitivity of urine levels of beta-galactosidase and N-acetyl-beta-glucosaminidase with conventional clinical and laboratory parameters in the detection of impending rejection. A rapid (60 minute), simple, accurate fluorometric assay was used to measure activities of both enzymes. Eighty per cent of ten rejection episodes were accompanied by a two- to sixfold increase in enzyme release. Parallel changes in serum creatinine levels and urinary volume occurred in six rejection episodes, but in two episodes, elevated urinary enzyme levels were observed two and four days prior to clinical evidence of rejection. It is concluded that urinary lysosomal enzyme measurements by fluorometric assay are valuable indicators of acute renal rejection, particularly when the diagnosis is not clearly established by conventional criteria that show only minimal changes. Continuing studies in a large group of renal transplant recipients are under way to evaluate the validity of this conclusion and to determine whether enzyme measurements, will, indeed, be indicative of early rejection.

Disturbance type and gait speed affect fall direction and impact location.

Since falling to the side and impacting on or near the hip increase hip fracture risk, we examined the fall direction and pelvis impact location resulting from four disturbances (faint, slip, step down, trip) at three gait speeds (fast, normal, slow) in 14 young adults instructed not to attempt recovery. We hypothesized that certain disturbances such as faints and slips and slow walking speed were more likely to result in an impact on the hip. For each trial, the fall direction, impact location and pelvis impact velocity were measured. The results showed that both disturbance type and gait speed significantly affected fall direction and impact location (analysis of covariance with repeated measures, p< or =0.0001) with a significant interaction (p<0.05). Trips and steps down usually resulted in forward falls, with frontal impacts regardless of gait speed. At fast gait speed, slips and faints also usually resulted in forward falls, with frontal impacts. As gait speed decreased, however, slips usually resulted in sideways or backward falls, with impact on the hip or buttocks, and faints resulted in a greater number of sideways falls, with impact near the hip. Therefore, compared to other disturbances and gait speeds, slipping or fainting while walking slowly was more likely to result in an impact on the hip, suggesting a greater risk for hip fracture. Furthermore, 56% of the impact velocities generated were within one standard deviation of the estimate of the mean impact velocity needed to fracture an elderly femur.

The threshold trip duration for which recovery is no longer possible is associated with strength and reaction time.

The recovery of young adults from trips of increasing severity was studied. Our null hypothesis was that lower extremity strength, and reaction time, step time, step distance and step velocity measured in a volitional stepping task would not explain a significant portion of the variance in the magnitude of the threshold trip duration for which recovery is no longer possible. Ten males and 11 females (average age 26.8 and 28.4 years old, respectively) were subjected to trips of increasing duration until recovery was no longer possible with a single step. The average threshold trip duration for which subjects were no longer able to recover with a single step was 681+/-169ms. The threshold trip duration significantly increased as lower extremity strength increased and volitional reaction time decreased (multiple stepwise linear regression: R(2)=0.52, p=0.001). The other volitional step parameters and the subject characteristics were not significantly associated with the magnitude of the threshold trip duration. These results suggest that some trip-related falls may be due to slower reaction times and/or reduced lower extremity strengths.

Clinical pancreas transplantation: a learning curve of its management.

In this evolving experience, acceptable patient and graft survival after PTX appear best secured by the use of whole duodenopancreatic grafts, enteric drainage, triple immunosuppression induced by OKT3, and the monitoring of postprandial blood glucose and serum amylase for detection of rejection.

[Hypertrichosis and gingival hypertrophy regression in renal transplants following the substitution of cyclosporin by tacrolimus]. / Régression de l'hypertrichose et de l'hypertrophie gingivale chez des greffés rénaux suite à la substitution de la cyclosporine par le tacrolimus.

Gingival Hyperplasia (GH) and hypertrichosis (HT) are two sides effects associated with the usage of cyclosporine (CyA) but not with tacrolimus (FK 506). The aim of this study is to evaluate the efficacy and security of the conversion from CsA to FK 506 to treat those two complications. From August 1996 to May 1997, 15 patients (9 males, 6 females) aged from 23 to 63 years old (38 +/- 14, mean +/- SD) were switched from CsA to FK 506, 12 for GH, 2 for HT and one for combined presentation. FK 506 was first initiated at a dose of 0.15 mg/kg/day and then adjusted to a level target of 8 ng/ml. The conversion was done on an out patient basis at average 35 (5-83) months after transplantation. Patients were followed prospectively for 12 months. There was a significant reduction in GH in all patients within 3 months. Five out 13 patients had a complete resolution of GH within three months of conversion, 9/12 within 6 months and all by 12 months. HT resolved completely within 6 months. No rejection episode occurred and the serum creatinin remain stable over one year post conversion. Conversion from CsA to FK 506 is thus a safe and valid option to treat CsA induced GH and HT.

Comparative toxicity of adriamycin and adriamycin-DNA in rats.

Adriamycin (ADR) can be linked to DNA without loss of its antitumoral activity while reducing the acute toxicity of free ADR (Deprez--DeCampeneere et al., 1979, 1980). However, the potential chronic toxic effects of both forms of ADR are poorly documented. For such a study, it is necessary to establish the sequence of treatment allowing the administration of a sufficient amount of drugs to induce chronic toxicity and a schedule leading to prolonged survival of animals. In this study, 24 Lewis rats were injected twice a week during four weeks with either free or DNA-linked ADR, and three dose levels were tested: 4, 2 and 1 mg/kg. Our results indicated that the total cumulative dose of ADR should not exceed 8 mg/kg over one month, if prolonged survival is desired. The binding of ADR to DNA seemed also to reduce the acute toxic effects induced by free ADR, in rats. However, such a beneficial effect was not observed when the chronic nephrotoxicity was considered since characteristic renal lesions were observed in all long-term survivors, whatever the dose and the form of ADR received.

Adriamycin and adriamycin-DNA nephrotoxicity in rats.

The early nephrotoxicity of free and DNA-bound adriamycin (ADR) was compared in left nephrectomized rats. Free ADR induced progressive renal failure within 3 weeks, in association with renal changes characterized by severe tubular distention and vacuolization of podocytes in glomeruli. On the contrary, renal function remained normal and renal lesions were discrete in animals treated with ADR bound to DNA. Thus, the binding of ADR to DNA seems to reduce the early nephrotoxicity of free ADR.