Using non-invasive neuroimaging to enhance the care, well-being and experimental outcomes of laboratory non-human primates (monkeys)

Over the past 10-20 years, neuroscience witnessed an explosion in the use of non-invasive imaging methods, particularly magnetic resonance imaging (MRI), to study brain structure and function. Simultaneously, with access to MRI in many research institutions, MRI has become an indispensable tool for researchers and veterinarians to guide improvements in surgical procedures and implants and thus, experimental as well as clinical outcomes, given that access to MRI also allows for improved diagnosis and monitoring for brain disease. As part of the PRIMEatE Data Exchange, we gathered expert scientists, veterinarians, and clinicians who treat humans, to provide an overview of the use of non-invasive imaging tools, primarily MRI, to enhance experimental and welfare outcomes for laboratory non-human primates engaged in neuroscientific experiments. We aimed to provide guidance for other researchers, scientists and veterinarians in the use of this powerful imaging technology as well as to foster a larger conversation and community of scientists and veterinarians with a shared goal of improving the well-being and experimental outcomes for laboratory animals.

Pharmacokinetics and toxicity of intravitreal chemotherapy for primary intraocular lymphoma

OBJECTIVE

To investigate the pharmacokinetics and toxicity of intravitreal chemotherapeutic agents in the rabbit eye for the potential treatment of primary intraocular lymphoma and other intraocular malignancies.

METHODS

The ocular pharmacokinetics of intravitreal methotrexate sodium (400 microg) was studied in 10 New Zealand white rabbits, and a single-compartment, first-order elimination model was used to calculate the drug half-life. With the use of these data, a treatment schedule using serial injections of intravitreal methotrexate and single injections of fluorouracil and dexamethasone sodium phosphate was developed. This schedule was studied in 4 New Zealand white rabbits to explore the combined toxicity of these agents.

RESULTS

Methotrexate vitreous levels, following a 400-microg intravitreal injection, remained therapeutic (>0.5 microM) in the rabbit eye for 48 to 72 hours. Intravitreal methotrexate, combined with fluorouracil and dexamethasone, showed no evidence of drug toxicity as determined by electroretinography and histopathologic examination.

CONCLUSIONS

A treatment schedule for primary intraocular lymphoma consisting of methotrexate intravitreal injections every 48 to 72 hours provides therapeutic drug concentrations in the vitreous and, in combination with fluorouracil and dexamethasone, appears to be safe in the rabbit eye.

CLINICAL RELEVANCE

Although responsive to conventional chemotherapy or radiotherapy, recurrence of ocular involvement with primary central nervous system lymphoma occurs in more than 50% of treated cases. Anecdotal reports of the use of intravitreal chemotherapy for primary intraocular lymphoma have been encouraging. However, animal data on the pharmacokinetics and toxicity of combined intravitreal agents for the treatment of this disease are lacking.

Effects of dietary soybean estrogens on the reproductive tract in female rats

The estrogenic actions of dietary phytoestrogens have raised concerns regarding the potential DES-like developmental effects on the female genital tract, but the growing evidence of cardioprotective benefits of dietary soybean estrogens provides the impetus to assess the effects of these compounds in adult female models of the menopause. We conducted an experiment in ovariectomized rats to determine the independent effects of dietary soybean estrogens (SBE) and the interactions of these agents with the commonly used pharmaceutical estrogen preparation (conjugated equine estrogens, CEE) in the vagina and uterus. We looked at the effects of SBE and CEE, alone and in combination, on uterine weight, body weight, vaginal cytology, uterine luminal epithelial height, and immunohistochemical staining for proliferating cell nuclear antigen (PCNA), lactoferrin (Ltf), and apoptosis. Ovariectomized rats were fed diets containing casein or soybean protein (SBE, low dose = 11.6 mg isoflavones/ 1800 cal; high dose = 117.8 mg/1800 cal), with no CEE, low dose CEE (0.313 mg/1800 cal), or high dose CEE (0.625 mg/1800 cal) added. In this study, SBE did not demonstrate estrogenic activity for uterine weight or vaginal cytology. We also found no estrogenic effects of these doses of SBE for PCNA, apoptosis, Ltf staining, or for LEH measurements. In addition, our results regarding the interactions of SBE and CEE do not show any evidence that the combination is additive in effect. On the contrary, the LEH response induced by low levels of CEE, was reduced by high levels of SBE. Furthermore, the Ltf response induced by CEE also was reduced by high levels of SBE. This suggests that high doses of SBE may antagonize the estrogen-agonist actions of low doses of CEE in the rat uterus. Our results in the ovariectomized rat model of menopause suggest that dietary soybean estrogens will not elicit a pattern of effects that simply recapitulates those of steroidal estrogens.

Acute pneumonia in a Syrian hamster: isolation of a Corynebacterium species

A respiratory tract illness was detected in a 1-year-old male Syrian hamster; after it failed to respond to antibiotic therapy, the hamster was euthanized by CO2 administration. Postmortem examination revealed acute edematous pneumonia, and Corynebacterium paulometabulum was isolated from the lungs.