Abstract
There is an identified need by the regulatory agencies for pharmaceutical safety assessment in pediatric or juvenile populations. Many chronic toxicity/carcinogenicity studies now capture the early life exposure period through perinatal dosing. Targeted juvenile toxicity studies help identify postnatal developmental toxicities that are not adequately assessed in reproductive toxicity assessments and may not be adequately or safely tested in pediatric clinical trials. As a result, the need to identify the normal histological changes that occur during the postnatal period is increasing. The Academic Press publication, Atlas of Histology of the Juvenile Rat, edited by George Parker and Catherine Picut, should be a necessary part of that evaluation. This atlas is a strikingly beautiful color pictorial of rat postnatal day (PND) development through PND 42. The illustrations and accompanying text are arranged in 14 chapters according to organ systems. The 448-page hardcover book is also available online at http://www.sciencedirect.com/science/book/9780128026823, with pdf versions of each chapter. This is a true atlas with more than 700 high-resolution photomicrographs and is based on the extensive experience of 15 veterinary pathologists.
The authors state that the impetus for this atlas was an identified personal need from performing pathology evaluations on nonclinical safety assessment studies that involved immature rats. There are a variety of publications on the histologic alterations and variations in organs and tissues of mature rats but little is published on normal rat postnatal development. Also, very few pathologists have training and expertise in the recognition and interpretation of organ and tissue alterations in immature rats. The authors rightly state that challenges can occur when a pathologist must interpret histologic alterations in unscheduled death animals because age-matched untreated control animals are typically not available for comparison. This color atlas provides the needed histology data for such reviews and interpretations.
The authors had three stated goals for this atlas. The first goal was to “provide an atlas of postnatal development for use by toxicologic pathologists, pathology trainees, and research scientists.” The second goal was to “provide age-matched normal tissue sections for comparison” for times when a pathologist has to interpret early deaths, when the study does not include age-matched tissues from nondosed control animals. The third goal was to “assist with the design of time-targeted juvenile toxicity studies.” The authors have, in my opinion, been successful in meeting all of their goals.
Each chapter has a short introduction and each organ/tissue is briefly discussed and well illustrated. The authors have provided information and images of organs/tissues from the Sprague-Dawley (Crl:CD) rat for PND 0/1, 7, 14, 21, 28, 35, and 42 in order to capture the postnatal developmental stages of neonate, infantile, juvenile, peripubertal, and late puberty. These time periods loosely correlate with similar developmental stages in humans. The summary narratives were not intended to be comprehensive but are well written and concise and provide enough information to give an overview of development. When needed, details of the organ or tissue structure are provided in the figure legends. Each section is well referenced, so those seeking additional information will know where to go. But what stands out most about this book are the images. The editors, individual chapter authors, and illustrations editor, Cynthia Swanson, have done a wonderful job providing low- and high-magnification images that are well annotated with clear, informative figure legends. Each color figure was digitally scanned and is very large, 5¾ inches wide and
When interpreting postnatal changes in the developing rat, the pathologist will no longer need to rely solely on personal experience when animals die or are euthanized prior to the scheduled study endpoint and age-matched controls are unavailable. Just pick up this book and you will most likely find what you are looking for. One must note, however, that each juvenile study has its own controls, which are the most appropriate for comparison with the treated animals. When designing targeted studies, especially juvenile toxicity studies, this atlas can provide the expected schedule of postnatal organ/tissue development and thus allows the pathologist to provide valuable input during the study design phase. Surely, this book will find its way into the libraries and onto the desktops of many pathologists, trainees, and research scientists where it will be an invaluable reference tool for years to come.