An analysis of the temperature dependence of force, during steady shortening at different velocities, in (mammalian) fast muscle fibres

We examined, over a wide range of temperatures (10–35°C), the isometric tension and tension during ramp shortening at different velocities (0.2–4 L0/s) in tetanized intact fibre bundles from a rat fast (flexor hallucis brevis) muscle; fibre length (L0) was 2.2 mm and sarcomere length ~2.5 μm. During a ramp shortening, the tension change showed an initial inflection of small amplitude (P1), followed by a larger exponential decline towards an approximate steady level; the tension continued to decline slowly afterwards and the approximate steady tension at a given velocity was estimated as the tension (P2) at the point of intersection between two linear slopes, as previously described (Roots et al. 2007). At a given temperature, the tension P2 declined to a lower level and at a faster rate (from an exponential curve fit) as the shortening velocity was increased; the temperature sensitivity of the rate of tension decline during ramp shortening at different velocities was low (Q10 0.9–1.5). The isometric tension and the P2 tension at a given shortening velocity increased with warming so that the relation between tension and (reciprocal) temperature was sigmoidal in both. In isometric muscle, the temperature T0.5 for half-maximal tension was ~10°C, activation enthalpy change (∆H) was ~100 kJ mol−1 and entropy change (∆S) ~350 J mol−1 K−1. In shortening, these were increased with increase of velocity so that at a shortening velocity (~4 L0/s) producing maximal power at 35°C, T0.5 was ~28°C, ∆H was ~200 kJ mol−1 and ∆S ~ 700 J mol−1 K−1; the same trends were seen in the tension data from isotonic release experiments on intact muscle and in ramp shortening experiments on maximally Ca-activated skinned fibres. In general, our findings show that the sigmoidal relation between force and temperature can be extended from isometric to shortening muscle; the implications of the findings are discussed in relation to the crossbridge cycle. The data indicate that the endothermic, entropy driven process that underlies crossbridge force generation in isometric muscle (Zhao and Kawai 1994; Davis, 1998) is even more pronounced in shortening muscle, i.e. when doing external work

Bilateral giant renal angiomyolipoma associated with hepatic lipoma in a patient with tuberous sclerosis Angiomiolipomas renais gigantes bilateralmente associados a lipoma hepático em pacientes com esclerose tuberosa

OBJECTIVE: To report a case of bilateral giant renal angiomyolipoma associated with tuberous sclerosis, with successful treatment, and to review the literature concerning angiomyolipoma treatment. CASE REPORT: Patient with tuberous sclerosis and angiomyolipoma diagnosed by ultrasonography during her pregnancy. At that time, the angiomyolipoma on the right side was 9 cm in diameter. Conservative management was selected during her pregnancy. The patient returned 7 years later, with a 24.7 x 19.2 x 10.7 cm tumor on the right side and another of 13 x 11.5 x 6.5 cm on the left side, in addition to multiple small angiomyolipomas. A nephron-sparing surgery with tumoral enucleation was performed on the right side, and after 3 months, the tumor on the left side was removed. Renal function in the post-operative period was preserved, and contrast medium progression was uniform and adequate in both kidneys. CONCLUSION: We conclude that an angiomyolipoma larger than 4 cm should be removed surgically, since they have a greater growth rate and pose a risk of hemorrhage. Resection of smaller tumors is safe and has decreased morbidity. Tumoral enucleation is an effective treatment method that preserves kidney function.<br>OBJETIVO: Relatar um caso de angiomiolipoma gigante, bilateral, associado a esclerose tuberosa, tratado com sucesso e revisar a literatura concernente ao tratamento do angiomiolipoma. RELATO DO CASO: Paciente portadora de esclerose tuberosa, com diagnóstico de angiomiolipoma realizado por ultra-sonografia durante gestação. O tumor apresentava 9cm de diâmetro, à direita. Optou-se por conduta conservadora durante a gestação, e a paciente retornou somente 7 anos após, com tumor de 24,7 x 19,2 x 10,7 cm à direita e outro à esquerda de 13 x 11,5 x 6,5 cm, além de múltiplos angiomiolipomas pequenos. Realizada inicialmente ressecção tumoral à direita, por enucleação, com preservação do parênquima renal, e 3 meses após à esquerda. A função renal pós-operatória se manteve inalterada, e ambos os rins apresentaram uniformidade e progressão do contraste adequados. CONCLUSÃO: Concluímos que os angiomiolipomas maiores que 4cm devem ser tratados cirurgicamente porque têm maior risco de crescimento e hemorragias. As ressecções de tumores menores são mais seguras e têm menor morbidade. A enucleação dos tumores é forma eficaz de ressecção dos mesmos, com preservação de parênquima renal