Browsing by Author "ARRAU, J"

Now showing 1 - 8 of 8
  • No Thumbnail Available
    Item
    CYTOGENETIC AND REPRODUCTIVE STUDIES OF 2 NOMINAL SUBSPECIES OF PHYLLOTIS-DARWINI AND THEIR EXPERIMENTAL HYBRIDS
    (1984) WALKER, LI; SPOTORNO, AE; ARRAU, J
    P. darwini vaccarum and P. d. darwini live contiguously in central Chile, the former in the high Andes an the latter in the Central Valley and on the coast. All individuals examined of both kinds had 38 chromosomes of similar shape, but P. d. vaccarum always showed large paracentromeric C-bands on all chromososmes: P. d. darwini showed none or only small ones. Pairings (56) between the 2 forms were made in the laboratory. They resulted in 23 hybrids produced by 4 P. d. vaccarum females and 4 P. d. darwini females. A higher incidence of aggression and mortality was observed in the cross-pairings, as well as a lower incidence of birth (14.3%) and a lower mean litter size (2.9), in comparison with 117 pairings within forms (65.0% and 4.2%, respectively). C-banded hybrid metaphases showed 19 chromosomes with large paracentromeric C-bands and 19 with none or only small ones. In the G-banded hybrid karyotypes, it was possible to identify 8 chromosome pairs with total correspondence of band patterns, 5 pairs with correspondence only at their long arms and 10 autosomes and the X chromosomes with no correspondence at all. Hybrids were completely sterile; adults had incomplete germinal lines and a lack of differentiated gametes in their gonads. There results and the presence of individuals of both chromosomal forms in the same trap line with no traces of mixing, provide strong evidence of complete genetic isolation of the 2 forms; they should be considered as separate species. Gene flow is suggested between P. d. vaccarum and the other Andean forms living in northern Chile and probably with those from southern Chile; the oldest species-group name available for all of these is P. d. xanthopygus.
  • No Thumbnail Available
    Item
    EFFECT OF CASTRATION AND TESTOSTERONE ON NOREPINEPHRINE STORAGE AND ON THE RELEASE OF [H-3]NOREPINEPHRINE FROM RAT VAS-DEFERENS
    (1985) LARA, H; GALLEGUILLOS, X; ARRAU, J; BELMAR, J
    Norepinephrine and dopamine-.beta.-hydroxylase, used as noradrenergic vesicle markers, were decreased in the rat vas deferens 10 days after castration. Five days of testosterone administration to castrated animals increased the enzyme activity over that of controls but did not modify norepinephrine content. In tissue fractions obtained by differential centrifugation, the highest activities of the noradrenergic markers appeared in the vesicular fraction of controls and in the soluble fraction of castrated animals. Testosterone reversed the effect of castration: it increased dopamine-.beta.-hydroxylase activity in the vesicular and soluble fractions, while norepinephrine increased only in the vesicular fraction. Results obtained after continuous sucrose gradient centrifugation of vesicular fractions suggested that these changes principally affected the number of light noradrenergic vesicles while testosterone increased the number of vesicles reduced by castration. Hormonal manipulations also modified some functional properties of nerve endings: norepinephrine depletion after transmural stimulation in the presence of tetraethylammonium, as well as the release of the neurotransmitter, were decreased after castration. These effects were reversed by testosterone. A modulatory effect of testosterone on the norepinephrine storage system and on the functional properties of the adrenergic innervation of vas deferns is suggested.
  • No Thumbnail Available
    Item
    EFFECT OF EXOGENOUS SEX STEROIDS UPON THE NUMBER OF GERM-CELLS AND THE GROWTH OF FETAL OVARIES GRAFTED UNDER THE KIDNEY CAPSULE OF ADULT OVARIECTOMIZED HAMSTERS
    (1983) ARRAU, J; ROBLERO, L; CURY, M; GONZALEZ, R
    Effect of estradiol (E), progesterone (P) and testosterone propionate (T) upon growth and germ cell population of fetal ovaries transplanted under the kidney capsule of adult ovariectomized hamsters was examined. Fetal ovaries were obtained 15 days postcoitum and the host received daily s.c. injections of E (1 .mu.g/day), P (5 mg/day), T (500 .mu.g/day) or E + P in 0.1 ml oil for 25 days beginning 5 days before grafting. One day after the last injection, the size of the ovary, the germ cell population and plasma steroid levels were assessed. Results of hormone assays indicate that daily steroid administration was able to maintain continuously elevated plasma levels of the corresponding hormone. Interconversions or steroid secretion by the graft, if any, were not reflected in the peripheral circulation. Growth of the graft was stimulated by T and inhibited by P, in comparison with E and oil-treated controls. All germ cells were at the stage of primary-oocyte-forming part of a primordial or growing follicle. Their absolute number was significantly increased by T and E and significantly decreased by P and E + P. The number of oocytes per mm3 of ovary was increased 80, 48 and 40% with E, T and E + P, respectively. In the hamster, exogenous sex steroids given to the host can exert specific effects upon the growth and oocyte population of a grafted fetal ovary. Whether or not the action of steroids upon the graft is a direct one and whether they influenced oogonial mitosis, the evolution of the meiotic prophase or atresia of primary oocytes remains to be determined.
  • No Thumbnail Available
    Item
    INHIBITION OF GROWTH AND DIFFERENTIATION OF FETAL HAMSTER GONADS GRAFTED INTO THE ADULT TESTIS
    (1988) ARRAU, J; BUSTOSOBREGON, E; CABELLO, R
    A cytomorphological analysis of the effect of adult testes on growth and differentiation of grafted fetal testis or ovaries was performed in hamsters. Fetal gonads, taken at 14 days post-coital age, were grafted for 30 days either under the renal capsule or testicular capsule of scrotal or cryptorchid tests of adult hamsters (weight 15 .+-. 23 g). Renal grafts were also performed in males castrated 30 days prior to receiving the fetal gonads. Growth and differentiation of the fetal gonads (testis or ovary) was totally inhibited by the scrotal testis. When the cryptorchid testis was the recipient of fetal gonads, inhibition was correlated inversely with the degree of spermatogenic damage elicited in the cryptorchid testis. No inhibition was observed in fetal gonads grafted under the kidney capsule, nor in castrated, normal or cryptorchid animals. As normal growth and differentiation of both testis and ovary occurred when grafted under the kidney capsule, the inhibitory effect of adult gonads seems to be unrelated to plasma testosterone levels in the host, as levels were undetectable in castrated hamsters and reduced drastically in cryptorchid animals. At the same time, the testicular-inhibiting substance in normal animals did not act at a distance, since it effect was restricted to fetal gonads grafted under the testicular capsule. This inhibitory subtance may correspond to the spermatogonial chalone, known to be produced by differentiating spermatogenic cells (mainly spermatocytes and round spermatids in the rat and mouse); these chalones prevent spermatogonial proliferation and, consequently, the critical number of spermatogonia needed to enter meiosis is not attained. It is doubtful if the same substance has the ability to differentiate the fetal ovary or if this effect can be ascribed to a more complex situation involving other testicular peptides of paracrine action and/or locally levels of androgens.
  • No Thumbnail Available
    Item
  • No Thumbnail Available
    Item
  • No Thumbnail Available
    Item
    SEX-RATIO OF HAMSTER FETUSES ASSESSED BY GONADAL MORPHOLOGY - EFFECT OF MOTHERS AGE
    (1987) ARRAU, J; CURY, M; MADRID, F
    This paper describes the assessment of phenotypic sex in hamster fetuses 12-15 days postcoitum. External morphometric parameters such as body weight, crown-rump length and anus-genital distance did not permit the differentiation of males from females. The sex was determined easily by inspection of the internal genital structures under low power magnification on Days 13-15 postcoitum. The size, shape and location of the gonads and the presence of a conspicuous blood vessel on the testis were the most useful criteria. An inverse relationship was found between the age of the mother at conception and the number of fetuses in mothers 2 to 7 months old. The decrease in the number of fetuses with increasing age of the mothers affected preferentially the population of phenotypic males.
  • No Thumbnail Available
    Item