Structural and functional abnormality of ectopic testes in rats.

Some males of a mutant strain of King-Holtzman rats exhibit an anomalous heritable defect manifested as either unilateral or bilateral ectopic testes. In the adult, these testes contain seemingly immature Sertoli and Leydig cells, seminiferous tubules greatly reduced in diameter, and exhibit arrested spermatogenesis. Thus, the affected testis is essentially sterile. An inability to produce normal amounts of testosterone and androstenedione by these gonads is probably a reflection of changes that have been effected in their Leydig cells. Thus, this study suggests that abnormal function of the Leydig and Sertoli cells and seminiferous tubule failure in these mutant animals result from the physiologically cryptorchid condition.

Ectopic testes: a heritable mutation in the King-Holtzman rat: androgen-binding protein in testes and epididymides.

Assays of androgen-binding protein (ABP) were carried out on testes, and epididymal heads and tails. This strain of rat exhibits a heritable mutation physically manifested as unilateral or bilateral maldescended (ectopic) testes. When present, they are found immediately cranial to the external inguinal ring in the superficial connective tissue on the ventral body wall. Charcoal-extracted cytosols were preincubated with 16 nM tritiated 5 alpha-dihydrotestosterone ( [3H] DHT) for 16-20 h at 4 degrees C and ABP was separated by polyacrylamide gel electrophoresis under steady-state conditions in the presence of 2 nM [3H] DHT. The gels were transversely cut into 2.1-mm thick slices and serially counted in a liquid scintillation counter. Binding of [3H] DHT to ABP was assumed to be 1:1 and the sum dpm of the ABP-containing slices corrected for background was expressed as pmol DHT bound/mg protein. Compared to normal male siblings, cytosol ABP levels on the ectopic side in unilateral ectopic rats were 78% and 93% lower than normal in epididymal heads and tails, respectively; whereas similar values for either side in bilateral ectopic rats were 88% and 99%. The above differences indicated in the cytosol ABP levels were significant at P less than 0.0001. On the other hand, in no case were differences in ABP levels in normal and ectopic testes in bilateral ectopic, unilateral ectopic and normal male rats significant. Also, epididymal heads and tails on the descended side of unilateral ectopic rats demonstrated no significant difference when compared to corresponding tissues in normal male siblings.(ABSTRACT TRUNCATED AT 250 WORDS)

Androgen receptors in the brain of neonatal normal male and androgen insensitive rats.

Androgen binding was investigated in the cytosol of brains from neonatal normal and tfm rats using sucrose gradient and charcoal assay. The neonatal normal rat brain contains androgen receptors which sediment at 8S in a sucrose gradient at low ionic strength and at 4S in the presence of 0.5M KC1. These receptors have a high affinity (Kd = 1.2 X 10(-9)M) for dihydrotestosterone (DHT), with a binding capacity of 7.3 X 10(-15) moles/mg cytosol protein. By contrast, there is very little, if any, high affinity androgen receptors in the neonatal tfm rat brain. Apparently, metabolism of testosterone does not affect androgen binding in the neonatal rat brain. The presence of these receptors and the occurrence of aromatization in the brain of neonatal rats are discussed in relation to their possible roles in sexual differentiation of the brain.

An anatomical study of the brains of Dipodomys (Mammalia: Rodentia: Heteromyidae).

Whole brains and Nissl-stained serial sections of 3 species of kangaroo rat (Dipodomys spectabilis, D. ordii, D. merriami) were compared for interspecific differences. Neuroanatomical variations were conservative in nature. Examination of the cerebellum revealed possible differences in locomotion and ecology. Dipodomys ordii exhibited more neurological evidence for increased specialization of the hindlimbs, while D. merriami had the least differentiated cerebellar surface, thereby suggesting more stereotyped movements of the hindlimbs. Dipodomys spectabilis had abilities that lie somewhere between those of D. ordii and D. merriami. Stereological analysis demonstrated little difference in the percent of total brain volume comprising the telencephalon, diencephalon, cerebellum, and brain stem; and it revealed the relative position of the cranial nerve nuclei.