One of the principal challenges facing a toxicologic pathologist is to determine and differentiate a true adverse effect from a non-adverse or an adaptive response. Recent publications from the Society of Toxicologic Pathology (STP) and the European STP provide guidance for determining and communicating adversity in nonclinical toxicology studies. In order to provide a forum to inform and engage in a discussion on this important topic, a continuing education (CE) course was held during the 2016 STP Annual meeting in San Diego, CA. The lectures at this course provided guidance on determining and communicating adversity using case studies involving both clinical pathology and anatomic pathology. In addition, one talk also focused on data quality, study design and interpretation of artifacts that could hinder the determination of adversity. The CE course ended with a talk on understanding adversity in preclinical studies and engaging the regulatory agencies in the decision making process. This manuscript is designed to provide brief summaries of all the talks in this well received CE course.

Abstract.A rare, multisystemic intravascular proliferative disorder was identified postmortem in eight cats. The majority of these cats died or were euthanized following episodes of dyspnea, lethargy, and anorexia. Microscopic examination revealed occlusive, intraluminal proliferations of spindle cells within small vessels. The heart was consistently involved, and myocardial dysfunction was the probable cause of illness in all cats. Immunohistochemically, the majority of intravascular cells expressed von Willebrand factor, and a smaller number expressed smooth muscle actin, compatible with a dual population of endothelial cells and pericytes, suggesting a reactive rather than a neoplastic process. Four cases of a similar feline vascular disorder from the veterinary literature are reviewed. The histopathology resembles reactive angioendotheliomatosis in humans, a benign cutaneous intravascular endothelial and pericytic proliferative condition. However, in contrast, this feline disease is multisystemic and fatal. We propose the name ''feline systemic reactive angioendotheliomatosis'' for this unique, idiopathic disorder of domestic cats.

In support of a clinical trial in the pediatric population, available nonclinical and clinical data provide input on the study design and safety monitoring considerations. When the existing data are lacking to support the safety of the planned pediatric clinical trial, a juvenile animal toxicity study is likely required. Usually a single relevant species, preferably a rodent, is chosen as the species of choice, while a nonrodent species can be appropriate when scientifically justified. Juvenile toxicology studies, in general, are complicated both conceptually and logistically. Development in young animals is a continuous process with different organs maturing at different rates and time. Structural and functional maturational differences have been shown to affect drug safety. Key points to consider in conducting a juvenile toxicology study include a comparative development of the organ systems, differences in the pharmacokinetics/absorption, distribution, metabolism, excretion (PK/ADME) profiles of the drug between young animal and child, and logistical requirement in the juvenile study design. The purpose of this publication is to note pertinent points to consider when designing and conducting juvenile toxicology studies and to aid in future modifications and enhancements of these studies to enable a superior predictability of safety of medicines in the pediatric population.

Although purification from 31% to 2% low-MW Hb content significantly decreased vasoactive responses, further purification to 0.4% had no additional clinically measurable effects in severe HS. If further diminution in HBOC vasoactivity is desired for use in HS, additional technical approaches may be required.