Validation of the use of long-term indwelling jugular catheters in a rat model of cardiotoxicity.

Doxorubicin administered to rats induces a dose-dependent cardiomyopathy. Both doxorubicin administration and the presence of indwelling catheters have been associated with thrombus formation. We sought to determine feasibility of drug delivery and degree of thrombogenesis related to long-term indwelling catheter use in a cardiotoxicity model. Rats receiving doxorubicin or saline via jugular catheters coated with end-point immobilized heparin were compared to rats receiving similar treatments via direct jugular intravenous injection (venotomy). Onset of cardiotoxicity, defined by reduction in fractional shortening to 45% or less, was determined by echocardiography. Thrombogenesis was assessed by observation of atrial thrombi and pulmonary emboli as determined by post-mortem and histologic examination. Significantly more of the doxorubicin-treated and catheterized group (87.5%) developed cardiotoxicity relative to the doxorubicin-treated-venotomized group (28.6%), as indicated by an earlier and more precipitous decline in fractional shortening in the doxorubicin-treated-catheterized rats. Despite this change, rats from catheterized groups demonstrated improved weight maintenance relative to venotomy groups. Although the number of pulmonary emboli did not differ significantly between groups, 50% of the doxorubicin-treated-catheterized animals developed vegetative endocarditis. Despite alteration of the model-induced cardiac disease, we submit that the more reliable and early induction of the desired endpoint, in addition to improved weight maintenance, represent model refinements. The ease of drug delivery with minimal restraint and no anesthesia is an additional and important benefit. The development of vegetative endocarditis represents an opportunity to study the formation and prevention of this condition.

Role of reactive nitrogen species in development of hepatic injury in a C57bl/6 mouse model of human granulocytic anaplasmosis.

Human granulocytic anaplasmosis (HGA), caused by the granulocytic rickettsia-like organism Anaplasma phagocytophilum, is the 3rd most frequent vector-borne infection in North America. To understand the disease mechanisms of HGA, we developed a murine model that lacks clinical disease yet exhibits characteristic histopathologic and immunologic changes. Because the degree of hepatic histopathology is unrelated to high bacterial numbers, tissue injury in HGA is thought to occur due to products of innate immunity, such as nitric oxide (NO) and reactive nitrogen species (RNS) from cytokine-activated macrophages. To test the hypothesis that RNS cause hepatic tissue damage, mice received either water treated with a nonspecific inhibitor of inducible nitric oxide synthase, L-NAME, or untreated water for 7 to 10 d before infection and continuing thereafter. Mice were euthanized for tissue harvest at 0, 7, 14, or 21 d after infection to assess differences in histopathology, hepatic bacterial load, RNS quantity in urine and liver, and serum chemistry values. Overall, L-NAME treatment had a beneficial effect, resulting in lower histopathology scores and RNS levels compared with those of untreated mice. There were no significant differences in hepatic bacterial load among treatment groups of infected mice. The observed increases in serum glucose and alanine aminotransferase levels on day 14 appear to be unexpected side effects of L-NAME administration. HGA is best characterized as an immunopathologic disease rather than one caused by direct bacterial injury to the host. Therefore, human and animal patients with HGA likely would benefit from therapy targeting reduced inflammation to supplement anti-infective modalities.

Insulin-like growth factor-I improves cerebellar dysfunction but does not prevent cerebellar neurodegeneration in the calcium channel mutant mouse, leaner.

The effects of insulin-like growth factor-I (IGF-I) on cerebellar dysfunction and neurodegeneration were investigated in leaner mice, which exhibit cerebellar ataxia and neurodegeneration related to P/Q-type calcium channel mutations. Leaner mice showed significantly reduced serum and cerebellar IGF-I concentrations compared to wild-type mice at postnatal day 30. Behavioral assessment of leaner mice injected with IGF-I subcutaneously for 4 weeks showed partially improved cerebellar function. Histological analysis of IGF-I treated leaner cerebella showed no difference in the number of dying Purkinje cells compared to control leaner cerebella. These results further support potential use of IGF-I as a therapeutic aid for cerebellar ataxia related to calcium channel mutations. Nonetheless, IGF-I administration does not rescue dying cerebellar neurons, which suggests that the beneficial effects of IGF-I may have been achieved through surviving cerebellar neurons.