The maintenance of bone mass results from a delicate balance between bone formation by osteoblasts and bone resorption by osteoclasts. Understanding these processes is essential for the development of effective treatments for skeletal diseases. Mechanical bone marrow ablation provides a unique animal model to study bone repair and the roles of specific genes in this process. Ablation of marrow induces the formation of intramembranous bone in the medullary cavity, which is subsequently resorbed by osteoclasts. We used this model to ask whether mitogen-activated protein kinase (MAPK) phosphatase 1 (MKP1) affects the bone formed in response to marrow ablation. MKP1 is a negative regulator of MAPK signaling, which is essential for a wide variety of cellular mechanisms, including those critical for osteoblast and osteoclast function. At 10 d after mechanical bone marrow ablation, the femurs of male mkp1^+/+ and mkp1^–/– mice were compared with those of unoperated baseline mice by using radiography, peripheral quantitative computed tomography, and microcomputed tomography. Both genotypes developed increased bone mass after marrow ablation, but the increase was more pronounced in mkp1^–/– mice compared with mkp1^+/+ mice. These results indicate that MKP1 affects the bone formed in response to marrow ablation and suggest encouraging possibilities for the use of inhibitors of MKP1 to modulate bone repair.

Moxidectin has been used safely as an antiparasitic in many animal species, including for the eradication of the mouse fur mite, Mycoptes musculinus. Although no side effects of moxidectin have previously been reported to occur in mice, 2 strains of the senescence-accelerated mouse (SAMP8 and SAMR1) sustained considerable mortality after routine prophylactic treatment. To investigate the mechanism underlying this effect, moxidectin toxicosis in these mice was evaluated in a controlled study. Moxidectin was applied topically (0.015 mg), and drug concentrations in both brain and serum were analyzed by using HPLC coupled with mass spectrometry. The moxidectin concentration in brain of SAMP8 mice was 18 times that in controls, and that in brain of SAMR1 mice was 14 times higher than in controls, whereas serum moxidectin concentrations did not differ significantly among the 3 strains. Because deficiency of the blood–brain barrier protein P-glycoprotein leads to sensitivity to this class of drugs in other SAM mice, Pgp immunohistochemistry of brain sections from a subset of mice was performed to determine whether this commercially available analysis could predict sensitivity to this class of drug. The staining analysis showed no difference among the strains of mice, indicating that this test does not correlate with sensitivity. In addition, no gross or histologic evidence of organ toxicity was found in brain, liver, lung, or kidney. This report shows that topically applied moxidectin at a standard dose accumulates in the CNS causing toxicosis in both SAMP8 and SAMR1 mice.

Accurate, rapid, and noninvasive health assessments are required to establish more appropriate endpoints in mouse cancer models where tumor size is not easily measured. We evaluated potential endpoints in mice with experimentally induced peritoneal lymphoma, an abdominal tumor model, by comparing body weight, body condition, and behavior with those of a control group of mice not developing lymphoma. Our hypothesis was that body weight would increase or plateau, whereas body condition and behavioral scores would decrease, as disease progressed. Results indicated that body weight did not differ significantly between the control and experimental groups, but the experimental group experienced significant decreases in both body condition and behavioral scores. Our results support the use of body condition and behavioral scoring as adjunctive assessment methods for mice involved in abdominal lymphoma tumor studies in which health may decline despite an increase or plateau in body weight.

Obesity-associated cardiovascular disease exerts profound human and monetary costs, creating a mounting need for cost-effective and relevant in vivo models of the complex metabolic and vascular interrelationships of obesity. Obesity is associated with endothelial dysfunction and inflammation. Free fatty acids (FFA), generated partly through β-adrenergic receptor-mediated lipolysis, may impair endothelium-dependent vasodilation (EDV) by proinflammatory mechanisms. β-Adrenergic antagonists protect against cardiovascular events by mechanisms not fully defined. We hypothesized that β antagonists may exert beneficial effects, in part, by inhibiting lipolysis and reducing FFA. Further, we sought to evaluate the fat-fed rat as an in vivo model of obesity-induced inflammation and EDV. Control and fat-fed rats were given vehicle or β antagonist for 28 d. Serum FFA were measured to determine the association to serum IL6, TNFα, and C-reactive protein and to femoral artery EDV. Compared with controls, fat-fed rats weighed more and had higher FFA, triglyceride, leptin, and insulin levels. Unexpectedly, in control and fat-fed rats, β antagonism increased FFA, yet inflammatory cytokines were reduced and EDV was preserved. Therefore, reduction of FFA is unlikely to be the mechanism by which β antagonists protect the endothelium. These results reflect the need for validation of ex vivo models of obesity-induced inflammation and endothelial dysfunction, concurrent with careful control of dietary fat composition and treatment duration.

We established an inbred rat strain with unilateral urogenital anomalies from an incidentally identified male rat with unilateral renal agenesis and an undescended left testis. These rats were characterized by unilateral renal agenesis in both sexes, undescended testes with agenesis and hypoplasia of the accessory sex organs in male rats, and complete and partial agenesis of the uterine horn in female rats. All of these urogenital anomalies were unilateral and restricted to the left side; we named this phenotype unilateral urogenital anomalies (UUA). Breeding tests showed that these abnormalities were inherited as polygenic traits. The weight of right kidneys of affected rats was 1.7-fold higher than that of normal rats; histologically, glomerulosclerosis, tubular dilations, and tubular casts were detected at 30 wk of age. These alterations may have resulted from compensatory renal adaptation to the lack of 1 kidney. The cryptorchid left testes of affected male rats showed atrophy of seminiferous tubules and degeneration of spermatocytes and spermatids. These results indicate that the UUA rat may be a good model to study the etiology of unilateral renal agenesis accompanied by agenesis of the reproductive tract and to study compensatory alterations resulting from the congenital loss of 1 kidney.

Bacillus anthracis, the causative agent of anthrax, is a category A priority pathogen that causes extensive damage in humans. For this reason, B. anthracis has been the focus of numerous studies using various animal models. In this study, we explored physiologic parameters in Dutch belted rabbits with inhalation anthrax to characterize the disease progression in this model. To this end, we infected Dutch belted rabbits with 100 LD₅₀ B. anthracis Ames spores by nasal instillation and continuously recorded various physiologic parameters by using telemetry. In addition, samples were collected at selected times for serum chemistry, hematology, and blood gas analysis. The animals exhibited hemodynamic and respiratory changes that coincided with those reported in human cases of inhalational anthrax infection, including hypotension, altered heart rate, and respiratory distress. Likewise, hematology, serum chemistry, and blood gas analysis revealed trends comparable to human anthrax-related pathophysiology. The Dutch belted rabbit model of inhalational anthrax exhibited most of the physiologic, hematologic, and biochemical sequelae noted in human cases. Therefore, this rabbit model fulfills several of the criteria of a useful animal model for studying disease pathogenesis and evaluating therapeutics during inhalational anthrax.

The objective of this work was to demonstrate that the New Zealand White (NZW) rabbit intramuscular model can be used for detecting calcification in bioprosthetic tissue and to compare the calcification in the rabbit to that of native human valves. The rabbit model was compared with the commonly used Sprague–Dawley rat subcutaneous model. Eighteen rabbits and 18 rats were used to assess calcification in bioprosthetic tissue over time (7, 14, 30, and 90 d). The explanted rabbit and rat tissue discs were measured for calcium by using atomic absorption and Raman spectroscopy. Calcium deposits on the human valve explants were assessed by using Raman spectroscopy. The results showed that the NZW rabbit model is robust for detecting calcification in a shorter duration (14 d), with less infection complications, more space to implant tissue groups (thereby reducing animal use numbers), and a more metabolically and mechanically dynamic environment than the rat subcutaneous model . The human explanted valves and rabbit explanted tissue both showed Raman peaks at 960 cm^–1 which is representative of hydroxyapatite. Hydroxyapatite is the final calcium and phosphate species in the calcification of bioprosthetic heart valves and rabbit intramuscular implants. The NZW rabbit intramuscular model is an effective model for assessing calcification in bioprosthetic tissue.

Current guidelines recommend β blockers for patients after myocardial infarction (MI). Novel therapies for heart failure should be tested in combination with this medication before entering clinical trials. In this methodologic study, we sought to describe the time course of systolic and diastolic parameters of cardiac performance over a 6-wk period in closed-chest model of swine MI treated with a β blocker. Myocardial infarction in pigs (n = 10) was induced by 90-min balloon occlusion of the left anterior descending coronary artery. Echocardiography and pressure–volume data were collected before and at 1 and 6 wk after MI; histopathology was assessed at 6 wk. Left-ventricular (LV) volume increased significantly over 6 wk, with significant decreases in ejection fraction, wall motion index, stroke work, rate of pressure development (dP/dt_max), preload recruitable stroke work, and mechanical efficiency. Impairment of diastolic function was manifested by a significant increase in the exponential β coefficient of the LV end-diastolic pressure–volume relation and reduction of LV pressure decay. At 6 wk, histopathologic analysis showed that the size of the infarct area was 16.3% ± 4.4%, and the LV mass and myocyte cross-sectional area in both the infarct border and remote zones were increased compared with those of noninfarcted pigs (n = 5). These findings suggest a dynamic pattern of remodeling over time in a closed-chest ischemia–reperfusion swine model of acute MI on β-blocker therapy and may guide future studies.

Large animal models for acute pulmonary hypertension (PHT) show distinct differences between species and underlying mechanisms. Two embolic procedures and continuous infusion of a stable thromboxane A₂ analogue (U46619) were explored for their ability to induce PHT and their effects on right ventricular function and pulmonary and systemic circulation in 9 pigs. Injection of small (100 to 200 μm) or large (355 to 425 μm) polystyrene beads and incremental dosage (0.2 to 0.8 μg kg^–1 min^–1) of U46619 all induced PHT. However, infusion of U46619 resulted in stable PHT, whereas that after bead injection demonstrated a gradual continuous decline in pressure. This instability was most pronounced with small beads, due to right ventricular failure and consecutive circulatory collapse. Furthermore, cardiac output decreased during U46619 infusion but increased after embolization with no relevant differences in systemic pressure. This result was likely due to the more pronounced effect of U46619 on pulmonary resistance and impedance in combination with limited effects on pulmonary gas exchange. Coronary autoregulation and adaption of contractility to afterload increase was not impaired by U46619. All parameters returned to baseline values after infusion was discontinued. Continuous infusion of a thromboxane A2 analogue is an excellent method for induction of stable, acute PHT in large animal hemodynamic studies.

In the oxidative stress hypothesis of aging, the aging process is the result of cumulative damage by reactive oxygen species. Humans and chimpanzees are remarkably similar; but humans live twice as long as chimpanzees and therefore are believed to age at a slower rate. The purpose of this study was to compare biomarkers for cardiovascular disease, oxidative stress, and aging between male chimpanzees and humans. Compared with men, male chimpanzees were at increased risk for cardiovascular disease because of their significantly higher levels of fibrinogen, IGF1, insulin, lipoprotein a, and large high-density lipoproteins. Chimpanzees showed increased oxidative stress, measured as significantly higher levels of 5-hydroxymethyl-2-deoxyuridine and 8-iso-prostaglandin F_2α, a higher peroxidizability index, and higher levels of the prooxidants ceruloplasmin and copper. In addition, chimpanzees had decreased levels of antioxidants, including α- and β-carotene, β-cryptoxanthin, lycopene, and tocopherols, as well as decreased levels of the cardiovascular protection factors albumin and bilirubin. As predicted by the oxidative stress hypothesis of aging, male chimpanzees exhibit higher levels of oxidative stress and a much higher risk for cardiovascular disease, particularly cardiomyopathy, compared with men of equivalent age. Given these results, we hypothesize that the longer lifespan of humans is at least in part the result of greater antioxidant capacity and lower risk of cardiovascular disease associated with lower oxidative stress.