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.

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.

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.

[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.

Simultaneous liver and whole pancreas harvesting in the multiorgan cadaveric donor.

Simultaneous harvesting of the liver and whole pancreas is usually not performed because it is believed that the shared vascular supply of both organs is incompatible with safe grafting. A careful review of the vascular anatomy, however, shows that simultaneous removal of the two organs is feasible, and a technique is described by which the liver is revascularized in the recipient through the celiac axis or the common hepatic artery and the pancreas is revascularized through the superior mesenteric and splenic arteries. When the vascular supply is abnormal, reconstruction of the vascular tree of one or both organs may be needed. The results of this technique used on 10 recipients are analysed.

One-stage hepatectomy in the dog.

This report describes a technique for total hepatectomy in the dog. The procedure maintains the integrity of the gastrointestinal tract and the pancreas in the normothermic, anesthetized animal. The technique involves (i) a mesentericocaval shunt, (ii) a temporary external bypass between the femoral and jugular veins, and (iii) a permanent internal bypass between the abdominal and thoracic inferior vena cava through the tendinous area of the diaphragm. This 60- to 70-min procedure yields a preparation useful for short-term metabolic studies in nonhepatic tissues.

[Immunosuppressive effect of cyclosporin A incapsulated into liposomes]. / Effet immunosuppresseur de la cyclosporine A incorporée dans les liposomes.

A preparation of cyclosporine A (CsA) in small liposomes (300 nm) was tested in a rat model of heterotopic cardiac allograft. At a daily dose of 1,5 mg/kg during 14 days, the graft survival rate was 30.4 +/- 2.8 days with a liposome-CsA solution versus 16 +/- 2.3 days with a Cremophore-CsA solution (p less than 0.01). Animals treated with the liposome-CsA preparation exhibited less weight loss than animals treated with cremophore-CsA solution (p less than 0.01). It is likely that the up-take of CsA by macrophages, when incapsulated into liposomes is dramatically enhanced; these cells have been pointed out at targets for IL2 inhibition by CsA.

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.

Adverse effect of blood transfusions on patient survival after resection of rectal cancer.

Studies have shown that the number of units of blood transfused perioperatively in patients operated on for colonic cancer has a progressively strong negative influence on survival. The present study, involving 198 patients with rectal cancer, was done to determine if perioperative blood transfusions had any prognostic significance. Multivariate regression analysis was applied to these patients, operated for cure of Dukes' stage A, B or C disease. Other variables analysed were age, sex, preoperative hemoglobin, albumin and lymphocyte values and the timing of transfusion. Perioperative deaths, pre- and post-operative immunodepression, neoplasia in situ, nonresections and stage D disease were excluded. It was found that the number of units of blood transfused perioperatively had a negative effect on patient survival, that was independent of the other analysed variables. It is suggested that blood transfusion perioperatively exerts an immunosuppressive effect on patients with rectal cancer.

Efficacy of incorporating cyclosporine into liposomes to reduce its nephrotoxicity.

A preparation of cyclosporine (CsA) in liposomes was tested in the rat to evaluate its effectiveness in reducing CsA nephrotoxicity. The drug was injected intravenously in unilaterally nephrectomized Lewis rats at a daily dose of 25 mg/kg for 14 days, either in a cremophore solution (eight rats) or in a preparation of liposomes (eight rats). Another group of four animals received the cremophore solution alone. Overall, rats treated with the CsA-liposome preparation had reduced toxicity, exhibiting better survival rates and less weight loss than those treated with the CsA-cremophore. Incorporating CsA into liposomes induced a statistically significant (p less than 0.05) reduction in the otherwise progressive increase of serum creatinine during week 2 of the experiment. Following administration of CsA-liposome preparation, epithelial cells of the proximal renal tubules appeared morphologically normal, without evidence of vacuolization, which is characteristic of CsA nephrotoxicity and was seen in the CsA-cremophore group. Although the exact mechanism is not clearly understood, it is likely that the tissue distribution of CsA, when incorporated into liposomes, is modified in favour of the reticuloendothelial cells, thereby sparing highly sensitive, but non-target organs such as the kidneys.

Hemolytic uremic syndrome in renal allografted patients treated with cyclosporin.

The classical triad of hemolytic uremic syndrome (microangiopathic hemolytic anemia, severe thrombopenia, and renal failure) developed de novo in three of our renal transplanted patients under cyclosporin A treatment. The predominant morphologic findings in the grafts consisted of glomerular and arteriolar thrombosis as well as arteriolonecrosis, all features of the syndrome. In one instance, ischemic bowel disease supervened after graft removal and was associated with persistent low grade microangiopathic process. De novo hemolytic uremic syndrome has been reported in patients treated with cyclosporin A following bone marrow or liver transplantation as well as in a few renal graft recipients. This peculiar form of cyclosporin A nephrotoxicity should not be confused with acute rejection of the renal transplant.