Differential effects of caffeine on skinned fibers from control and hypertrophied ferret hearts

Ferret thoracic anatomy by 2-deoxy-2-(18F)fluoro-D-glucose (18F-FDG) positron emission tomography/computed tomography (18F-FDG PET/CT) imaging

The domestic ferret (Mustela putorius furo) has been a long-standing animal model used in the evaluation and treatment of human diseases. Molecular imaging techniques such as 2-deoxy-2-(¹⁸F)fluoro-D-glucose (¹⁸F-FDG) positron emission tomography (PET) would be an invaluable method of tracking disease in vivo, but this technique has not been reported in the literature. Thus, the aim of this study was to establish baseline imaging characteristics of PET/computed tomography (CT) with ¹⁸F-FDG in the ferret model. Twelve healthy female ferrets were anesthetized and underwent combined PET/CT scanning. After the images were fused, volumes of interest (VOIs) were generated in the liver, heart, thymus, and bilateral lung fields. For each VOI, standardized uptake values (SUVs) were calculated. Additional comparisons were made between radiotracer uptake periods (60, 90, and >90 minutes), intravenous and intraperitoneal injections of ¹⁸F-FDG, and respiratory gated and ungated acquisitions. Pulmonary structures and the surrounding thoracic and upper abdominal anatomy were readily identified on the CT scans of all ferrets and were successfully fused with PET. VOIs were created in various tissues with the following SUV calculations: heart (maximum standardized uptake value [SUV_Max] 8.60, mean standardized uptake value [SUV_Mean] 5.42), thymus (SUV_Max 3.86, SUV_Mean 2.59), liver (SUV_Max 1.37, SUV_Mean 0.99), right lung (SUV_Max 0.92, SUV_Mean 0.56), and left lung (SUV_Max 0.88, SUV_Mean 0.51). Sixty- to 90-minute uptake periods were sufficient to separate tissues based on background SUV activity. No gross differences in image quality were seen between intraperitoneal and intravenous injections of ¹⁸F-FDG. Respiratory gating also did not have a significant impact on image quality of lung parenchyma. The authors concluded that ¹⁸F-FDG PET and CT imaging can be performed successfully in normal healthy ferrets with the parameters identified in this study. They obtained similar imaging features and uptake measurements with and without respiratory gating as well as with intraperitoneal and intravenous ¹⁸F-FDG injections. ¹⁸F-FDG PET and CT can be a valuable resource for the in vivo tracking of disease progression in future studies that employ the ferret model.

Is contractility depressed in the failing human heart?

Is contractility depressed in the failing human heart? The question must be approached in a stringent manner. Myocardium from failing human hearts has been shown to generate normal physiological force under the ideal conditions of low stimulation and an adequate energy supply. Nevertheless, even when subjected to physiologically conducive conditions, failing myocardium experiences a slowed relaxation, adversely affecting the diastolic properties of the heart. In addition, experiments have shown that increasing the contraction rates of failing hearts clearly results in lowered force and pressure evolution. This information indicates a decrease in contractile reserve in both a systolic and diastolic sense. Not surprisingly, the term end-stage heart failure becomes questionable when applied to myocardium obtained from patients undergoing cardiac transplantation. A number of studies involve such myocardium from feasible regions of the heart perfused within ideal physiological conditions yielding, at times, nonfailing performance. Therefore, it becomes imperative to bear in mind the role of such myocardium within the framework of the entire diseased heart.

Effect of haemodynamic pressure overload of the adult ferret right ventricle on inotropic responsiveness to external calcium and rest periods

The inotropic effects of external calcium concentration ([Ca2+]o] and rest periods have been compared in papillary muscles isolated from control (n = 4) and pressure-overloaded right (n = 5) ventricles of adult ferrets. Hypertrophy was induced by pulmonary artery clipping for 30-45 days. Under control conditions (3 mM [Ca2+]o, 0.1 Hz), the isometric twitch force of hypertrophied muscles was decreased by 75%, time to peak was increased by 30% and time to half-relaxation was increased by 50% compared with non-hypertrophied preparations. The sensitivity of contraction to [Ca2+]o was decreased in hypertrophied muscles compared with control ([Ca2+] required for half-maximal contraction: 4.1 mM vs 1.7 mM) and the maximal contraction reached at high [Ca2+]o was smaller in pressure-overloaded muscles compared with control (8.3 +/- 2.0 mN mm-2 vs 19.0 +/- 2.1 mN mm-2 respectively). In both groups, rest periods longer than the steady-state interval were initially accompanied by a potentiation of the first post-rest contraction compared with steady-state. Peak potentiation occurred after a rest of 120 s in hypertrophied muscles and after a rest of 60 s in control. The maximal relative potentiation, i.e. compared with the steady-state twitch, was higher in hypertrophied muscles (+75%) than in control (+20%). After peak potentiation, the amplitude of the first post-rest contraction progressively decreased with increasing periods of rest, although at a slower rate in hypertrophy compared with control. The time constants of post-rest decay were 1203 +/- 99 s and 528 +/- 24 s respectively.(ABSTRACT TRUNCATED AT 250 WORDS)