Mutations in the androgen receptor (AR) gene cause a range of phenotypic abnormalities of male sexual development. At one end of the spectrum are individuals with complete androgen insensitivity (complete testicular feminization) who exhibit normal breast development and female external genitalia. At the other extreme are individuals with male phenotypes that are characterized by either subtle undervirilization or infertility. Studies in a number of different laboratories have identified mutations of the AR gene in subjects with androgen resistance syndromes. Defects that interrupt the AR open-reading frame have been traced to a number of distinct types of genetic alterations, have been identified in widely separated segments of the AR gene, and are invariably associated with the phenotype of complete androgen insensitivity. By contrast, mutations that cause single amino acid substitutions within the AR are localized to the DNA-or ligand-binding domains of the receptor protein and have been associated with the full range of androgen-resistant phenotypes. Regardless of the nature of the mutation, functional studies and assays of AR abundance suggest that the phenotypic abnormalities that result from mutation of the AR are the result of the impairment of receptor function, decreases in receptor concentration, or both.

Lesions to the mature mammalian central nervous system cause irreversible degeneration, in which neurons have been previously thought to be passive victims. In this study, axon-lesioned adult rat neurons are shown instead to actively degrade themselves through the process of apoptosis: a programmed type of cell death in which the cellular apparatus is actively involved in the degradation process. To investigate whether retinal ganglion cells of an adult mammal follow an apoptotic type of death when their axons are severed, DNA breaks in nuclei were labeled in situ, using a method that specifically incorporates biotinylated deoxynucleotides by exogenous terminal deoxynucleotidyl transferase on the 3'-OH ends of DNA. The active nature of the death mechanism was demonstrated by the reduction in biotin-labeled nuclei after administering the protein synthesis inhibitor cycloheximide. Our results suggest that retinal ganglion cells of the adult rat die through apoptosis when axotomized. This raises new possibilities in the treatment of CNS injuries, by the potential interruptibility of a program for neuronal death.

Growth of ovarian follicles involves regulated proliferation and differentiation of granulosa cells (1, 2). Exponential growth of granulosa cells in preovulatory follicles is followed by their terminal differentiation and formation of the corpus luteum, a transition initiated by the ovulatory surge of luteinizing hormone (LH).1 This transition of proliferating granulosa cells to non-dividing luteal cells is associated with specific changes in the expression of cell cycle regulatory molecules that control specific kinase cascades. The cell cycle activators, cyclin D2 and cyclin E, are increased by FSH and steroids in rapidly growing preovulatory follicles but are rapidly turned off by the surge of LH that terminates follicular growth (1, 2). Conversely, the cell cycle inhibitors, p27 KIP1 and p21 CIP1 , are induced by the LH surge (1, 2). Thus, the gonadotropins impact cell cycle progression at multiple steps depending on the stage of granulosa cell differentiation.The effects of the gonadotropins on ovarian cell proliferation and differentiation are mediated by changes in intracellular cAMP that activates cAMP-dependent protein kinases (protein kinase A) (3), as well as several other kinases (4, 5). Known targets of protein kinase A are the cAMP regulatory element (CRE)-binding protein CREB and the CREB-binding protein CBP (6). CREs are essential for transcriptional activation of aromatase (7) and inhibin ␣ (8), as well as the AP1 factors, c-fos (9) and fra2 (10). AP1 factors, in turn, mediate FSH-regulated expression of inhibin ␤A by binding to a variant CRE in the promoter of the ␤A gene (11). Members of the AP1 transcription factor superfamily are proto-oncogenes that regulate cell proliferation and transformation (12). They have also been associated with differentiation (13, 14). These observations suggest that specific AP1 factors or the combination of specific AP1 factors may regulate different sets of functions at specific stages of granulosa cell differentiation. Despite the intense research efforts that have analyzed the function of the Jun/Fos family in many different cell types, relatively few studies have analyzed how hormones regulate the expression of AP1 factors in granulosa cells or how these factors might impact FSH or LH activation of specific genes. Therefore, it becomes imperative to know which AP1 factors are present in granulosa cells and which might be regulated or activated by FSH and LH.

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In mammals, dihydroorotase is part of a trifunctional protein, dihydroorotate synthetase, which catalyzes the first three reactions of de novo pyrimidine biosynthesis. Dihydroorotase catalyzes the formation of a peptide-like bond between the terminal ureido nitrogen and the beta-carboxyl group of N-carbamyl-L-aspartate to yield heterocyclic L-dihydroorotate. A variety of evidence suggests that dihydroorotase may have a catalytic mechanism similar to that of a zinc protease [Christopherson, R. I., & Jones, M. E. (1980) J. Biol. Chem. 255, 3358-3370]. Tight-binding inhibitors of the zinc proteases, carboxypeptidase A, thermolysin, and angiotensin-converting enzyme have been synthesized that combine structural features of the substrates with a thiol or carboxyl group in an appropriate position to coordinate a zinc atom bound at the catalytic site. We have synthesized (4R)-2-oxo-6-thioxohexahydropyrimidine-4-carboxylate (L-6-thiodihydroorotate) and have found that this analogue is a potent competitive inhibitor of dihydroorotase with a dissociation constant (Ki) in the presence of excess Zn2+ ion of 0.17 +/- 0.02 microM at pH 7.4. The potency of inhibition by L-6-thiodihydroorotate in the presence of divalent metal ions decreases in the order Zn2+ greater than Ca2+ greater than Co2+ greater than Mn2+ greater than Ni2+; L-6-thiodihydroorotate alone is less inhibitory and has a Ki of 0.85 +/- 0.14 microM. 6-Thioorotate has a Ki of 82 +/- 8 microM which decreases to 3.8 +/- 1.4 microM in the presence of Zn2+. Zn2+ alone is a moderate inhibitor of dihydroorotase and does not enhance the potency of other inhibitors.(ABSTRACT TRUNCATED AT 250 WORDS)