A Practical Approach, Second Edition=Ronald D. Ho.pdf

476 DEVELOPMENTAL REPRODUCTIVE TOXICOLOGY: A PRACTICAL APPROACH, SECOND EDITIONand then released. Rat and hamster pups are held approximately 38 cm above the surface; mousepups are held 17 to 20 cm above the surface. The pup must land on all four limbs to meet thecriterion. This usually occurs between PND 8 164,165 and 18 in Sprague-Dawley rats, with the averageacquisition around PND 16 169 or 17. 166 The use of videotape to record the response will allow moreinformation to be obtained, such as response speed, character, and progression. 174,1759. Forelimb Grip Test (Categorical)Each pup is tested for forelimb grip on PND 21. A thin rod (approximately 2 to 3 mm in diameter)is supported by a ring stand suspended horizontally above the padded surface. The pup is held soit can grasp the thin rod with its forepaws and is then released. It must remain suspended for atleast 1 sec to meet the criterion. The number of pups that met the criterion, divided by the totalnumber of pups tested, is recorded.10. Pupil Constriction ReflexAll pups in each litter are examined once on PND 21 for direct and consensual pupillary constrictionof both eyes in response to the beam from a penlight. This test evaluates the autonomic componentof cranial nerve reflexes. Each nesting box is transferred from the study room to a quiet isolatedtesting room, sufficiently dim to dilate the pupils of the eyes of the pups. Each pup is testedindividually, with the following requirements to meet the criterion:The pup is removed from the nesting box and the penlight is directed into one eye. Immediateconstriction of the pupil of the eye being tested is the initial requirement.Without turning the light off, it is immediately directed into the contralateral eye, the pupil of whichshould already be constricted.The light is turned off for a minimum of 5 sec. This sequence is then repeated for the other eye.Responses should be identical to meet the criterion.D. Examination of Rodents for HypospadiasIn males, hypospadias is defined as an opening of the urethra at an abnormal location on the ventralsurface of the penis. In normal males, the urethral opening is located at the tip of the penis. Inaffected males, the urethral opening extends a variable distance from the base of the penis. Otherphysical characteristics that may be seen in the affected males are inability to fully extend thepenis, distended preputial glands, undescended testes, and decreased anogenital distance. In females,hypospadias is defined as an opening of the urethra into the vagina rather that at the urinary apertureadjacent to the vaginal opening.1. In-life Procedure for Male RodentsMale rodents are examined beginning on PND 39 (rat) or PND 22 (mouse). Each male is removedfrom its cage and held in a supine position. Gentle digital pressure is applied to the sides of therodent’s prepuce. The ventral surface of the penis is examined for the location of the urethralopening. The presence of hypospadias is documented as follows: If the prepuce has not separatedand the location of the urethral opening is not apparent, the observation is documented as “hypospadiasnot determined” (this observation is continued daily until it is determined whether hypospadiasis present); if the urethral opening is located at the tip of the penis, the observation is recordedas “hypospadias absent”; or if the urethral opening is located ventrally anywhere along the shaft of thepenis, the observation is recorded as “hypospadias present.” Severity scores, if required, are assigned.If the penis can be extended and the urethral opening is located approximately one-half to two-thirdsthe distance from the base of the penis, then the severity is recorded as “slight.” If the penis cannot befully extended and the urethral opening is located approximately one-quarter to one-half the distance© 2006 by Taylor & Francis Group, LLC