Lombari, Theresa R

Background: Myocardial reperfusion following prolonged ischemia may paradoxically cause additional injury, including edema and microvascular damage. These structural alterations augment tissue echogenicity measurable by integrated backscatter (IB). We sought to characterize alterations of myocardial IB in an ischemic and then reperfused region of the rat heart. Methods: Myocardial IB in 12 adult male Sprague-Dawley rats was studied at baseline, 60 minutes after left anterior descending coronary artery occlusion, and chronologically after coronary reopening. Short-axis scans of the mid left ventricle were acquired at a frequency of 8 MHz. Mean±SD values of IB were measured in the region of interest at baseline, ischemia, and reperfusion, and assessed by a paired t-test. Results: See figure and table. IB did not significantly change between baseline and ischemia. However, within 1 minute of reperfusion, IB significantly increased, as compared to both baseline and ischemia, and continued to increase until 10 minutes after reperfusion, when a plateau was reached. Conclusions: Myocardial reperfusion following acute prolonged ischemia in a rat heart significantly augments tissue echogenicity. A continuing increase of IB within minutes of the reperfusion onset and the subsequent plateau of elevated IB values suggest progression and completion, respectively, of reperfusion injury, detectable by a high-frequency transducer.

Pharmacokinetics of drugs may differ between small and large mammals (including humans); therefore, drug testing in animal models must be carefully designed. Sprague–Dawley rats were used in cardiac experiments, during which the lopinavir concentration in serum had to match human therapeutic levels (4–10 μg/mL). Lopinavir was administered as a co-formulated drug of lopinavir and ritonavir. It was found that after a single administration of a standard human peroral dose (lopinavir 13.3 mg/kg of body weight), the serum concentration of lopinavir was only one-tenth of the target level. It remained below the minimum target level even after 10-fold the standard dose was administered. After initial pilot tests, a dose escalation study was conducted with oral doses 10- and 15-fold the standard clinical dose of lopinavir (i.e. 133 and 200 mg/kg, respectively). A second administration 2 h later effectively increased and maintained higher concentrations during the experimental ischaemia and reperfusion periods. A dose-dependent increase in serum concentration of the drug was observed. Thus, the target therapeutic serum level of lopinavir in the rats was achieved by administrating 10- to 15-fold the standard human dose twice, separated by a 2 h interval.

Abstract Tumor-associated eosinophilia has been observed in numerous human cancers and several tumor models in animals; however, the details surrounding this eosinophilia remain largely undefined and anecdotal. We used a B16-F10 melanoma cell injection model to demonstrate that eosinophil infiltration of tumors occurred from the earliest palpable stages with significant accumulations only in the necrotic and capsule regions. Furthermore, the presence of diffuse extracellular matrix staining for eosinophil major basic protein was restricted to the necrotic areas of tumors, indicating that eosinophil degranulation was limited to this region. Antibody-mediated depletion of CD4+ T cells and adoptive transfer of eosinophils suggested, respectively, that the accumulation of eosinophils is not associated with T helper cell type 2-dependent immune responses and that recruitment is a dynamic, ongoing process, occurring throughout tumor growth. Ex vivo migration studies have identified what appears to be a novel chemotactic factor(s) released by stressed/dying melanoma cells, suggesting that the accumulation of eosinophils in tumors occurs, in part, through a unique mechanism dependent on a signal(s) released from areas of necrosis. Collectively, these studies demonstrate that the infiltration of tumors by eosinophils is an early and persistent response that is spatial-restricted. It is more important that these data also show that the mechanism(s) that elicit this host response occur, independent of immune surveillance, suggesting that eosinophils are part of an early inflammatory reaction at the site of tumorigenesis.