The effect of aminophylline on function and intracellular pH of the rat diaphragm

Abstract

We studied the effect of aminophylline on twitch tension (TT) and intracellular pH (pHi) in isolated rat diaphragm strips that were fatigued, hypercapnic, or hypoxic. Superfused muscles were directly stimulated at 0.5 Hz. The pHi was measured from distribution volumes of dimethyl-oxazolidinedione. Fatigue was induced by intermittent tetanic stimulation. Hypercapnia and hypoxia were produced by altering superfusate carbon dioxide tension (PCO2) or oxygen tension (PO2). Aminophylline (1.0 mmol.l-1) reversed the twitch decay seen during fatigue or hypercapnic acidosis, and caused partial recovery of twitch depression during hypoxia. Muscle fatigue was not due to an intracellular acidosis. Both hypercapnia and hypoxia lowered pHi. Aminophylline did not alter pHi in unstimulated muscles, but caused a significant fall in pHi in stimulated muscles that were fatigued or hypoxic. High dose aminophylline improved twitch tension in diaphragm strips that were fatigued, acidotic, or hypoxic. Twitch potentiation was not due to an intracellular alkalosis. Aminophylline lowered pHi in stimulated muscle, and thus, theoretically, could sometimes be harmful in the treatment of muscle fatigue.

Application strategy of finite element analysis in artificial knee arthroplasty

“…Current tibial components consist of two main material options, all-polyethylene tibial components and metal-backed tibial components, which differ in material and component method, resulting in differences in prosthesis-bone and component-component stresses. It was found that while a significant increase in measured strain was observed for both the all-polyethylene and metal-backed tibial components in the simulated load distribution, the all-polyethylene tibial component showed a more pronounced stress rise at the proximal tibia ( Small et al, 2010 ). Brihault et al (2016) compared the stress distribution and fretting of tibial plateau prostheses made of different materials when the knee joint flexed 120°.…”

“…This strategy has the advantages of causing less injury and allowing quick recovery ( Scott and Santore, 1981 ; Berend et al, 2005 ). However, UKA is a technically demanding surgical method, and attention must be paid to the size of the components, the osteotomy and postoperative alignment because overcorrection or overloosening may lead to adverse results, these include primarily bearing dislocations (in mobile-bearing designs), aseptic mechanical loosening, polyethylene wear (in fixed-bearing designs), progression of osteoarthritis in unreplaced compartments, periprosthetic fractures and unexplained pain ( Shee et al, 1990 ; Kim et al, 2016 ). Resulting in a typical 10-year survival rate of 80% to 85% for the prosthesis ( Crawford et al, 2020 ), and ways to reduce these adverse events to improve prosthesis longevity need to be continuously explored.…”