Experiments were conducted with littermate gilts maintained in stainless steel metabolism cages within environmentally controlled rooms and consuming a corn-soybean meal based diet. The objectives of these studies were to investigate the impact of different dietary levels of manganese (Mn) and/or stage of the reproductive cycle on mineral metabolism and more specifically Mn metabolism in primigravid gilts and rats. Nutritional status was assessed using conventional balance studies, the analyses of physiological fluids (urine, plasma, colostrum, milk), tissues of the dam and offspring, and by a radioisotope dilution-balance technique. Trace element retention in the first-litter gilt was not significantly altered by dietary Mn restriction (11 $ mu$g/g DM) or by different stages of the reproductive cycle. In contrast, among the macro elements, phosphorus and perhaps calcium retention were improved in late gestation, whereas magnesium and nitrogen retention were unchanged. The weight of the litter at birth from dams consuming the low Mn (LMn) diet was significantly less than high Mn (HMn) gilts (96 $ mu$g/g DM). The Mn concentration in the liver and kidney of HMn gilts were significantly higher than in LMn gilts at the end of lactation. Likewise, the bones from HMn piglets contained higher concentrations of Mn at birth, and the liver and kidney concentrations were greater at weaning. Dietary Mn intake did not influence the rate of $ sp{54}$Mn excretion by the gilt during late gestation. The endogenous fecal Mn component was of similar magnitude, averaging 0.26 and 0.21 mg/d for the HMn and LMn gilts, respectively. However, the endogenous contribution to total fecal Mn was almost 8 fold different, representing 0.12% and 0.82% of total fecal Mn for the HMn and LMn gilts, respectively. The biological half-life of Mn in the body of the gilt was not influenced by dietary Mn within the intake range of 26 to 210 mg/d and averaged 54 days. The turnover rate (TR) of Mn was es

Factors affecting bovine ovarian responsiveness to stimulation by pregnant mare's serum gonadotropin (PMSG) were studied. Initially, the effects of plasma progesterone concentration on the response were considered using a progesterone-releasing intravaginal device (PRID) to provide an artificial source of the hormone. Due to inherent biological variation in vivo, in vitro methods were developed in which cAMP and progesterone production by granulosa cells were measured. Regardless of the size of the follicles from which the cells originated, PMSG stimulated significant cAMP accumulation. Cyclic AMP production was similar between aspirated granulosa cells and those scraped from the follicle wall, between ovaries with and without a corpus luteum from the same animal, and between follicles from animals early ( 10 days) in their estrous cycles. The PMSG failed to stimulate bovine granulosa cells to synthesize significantly more progesterone than untreated cells. Unlike porcine granulosa cells, bovine cells from antral follicles of any size appeared to luteinize spontaneously in culture. / Hormonal changes in the preovulatory follicle were measured using the PMSG/hCG-treated prepubertal gilt as a model. After hCG administration, follicular fluid levels of cAMP peaked at 4 hr followed 24 hr later by a rise in prostaglandins F and E (PGF, PGE) concentrations which peaked near the expected time of ovulation. Indomethacin injection blocked ovulation and the prostaglandin rise, although the inhibition could be reversed by the administration of PGF(,2)(alpha). Temporal changes in estrone, estradiol-17(beta), progesterone, androstenedione, testosterone and 5 (alpha)-dihydrotestosterone were also measured. / In an effort to decrease endogenous levels of inhibin, thereby increasing endogenous FSH and thence follicular development, heifers, ewes and does were actively immunized against porcine follicular fluid or proteinaceous fractions of bovine seminal plasma. In some animals, plasma FSH concentrations were elevated although ovulation rates and estrous cycle lengths were not altered. / A culdoscopy technique was developed for repeated monitoring of ovarian morphological changes in cows.

Five experiments were undertaken to identify metabolites and hormones that could mediate the effect of dietary energy status on reproduction, particularly pulsatile secretion of luteinizing hormone (LH) postpartum dairy cows. / In the first two experiments, the concentration of progesterone (P4) in tailhead adipose tissue and plasma in 12 cows at different stages of pregnancy and lactation was determined as was P4 produced in vitro by explants of tailhead adipose tissue. Concentration of P4 in adipose tissue was correlated with that of plasma P4 near estrus and during the luteal phase of the estrous cycle, and P4 was released in vitro by fat mobilization. / In the third and fourth experiments, blood was collected continuously for 16 h from four ovariectomized cows offered maintenance or restricted energy diets after priming with P4 or estradiol (E2) using a crossover experimental design. The results indicated that P4 released during body fat mobilization is minor and is not related to LH secretion. Dietary energy restriction influenced plasma LH concentration and pulse amplitude but the effect was modulated by P4 and E2 priming. Dietary energy restriction decreased glucose concentration but did not influence plasma non-esterified fatty acids (NEFA), cortisol, P4 and insulin levels. Cortisol was negatively related to LH pulse frequency. Glucose and insulin were positively and negatively correlated with LH pulse amplitude, respectively. Cortisol, NEFA and glucose jointly had a negative correlation with LH concentration. / In the fifth experiment, blood samples were collected daily for 60 d and every 10 min for 8 h on 18, 36 and 54 d postpartum from 24 cows (12 ovariectomized) fed low (1.4 Mcal/kg DM) (L) or high (1.7 Mcal/kg DM) (H) energy in a 2 x 2 factorial treatment design. LH pulse frequency was reduced at 18 d postpartum in ovariectomized cows, but not in intact cows, fed L. First postpartum ovulation occurred later in intact cows fed L compared to those fed H. Energy balance and plasma glucose concentration were lower, but plasma NEFA, $ beta$-hydroxybutyrate (BHB) and E2 concentrations higher, in cows fed L compared to those fed H. E2 concentration in intact cows fed L was elevated for a prolonged period prior to first ovulation. Diet had no influence on plasma P4 and insulin concentrations. Plasma E2 and BHB concentrations were positively correlated with LH pulse frequency in intact cows across diets and ovariectomized cows fed L, respectively. NEFA were negatively correlated with LH pulse amplitude in ovariectomized cows fed L. Glucose, NEFA and P4 were negatively, but BHB, E2 and insulin positively correlated, individually or in association, with LH concentration. / Overall, the results suggest that the effect of dietary energy status on LH patterns and timing of onset of postpartum ovulation is modulated by priming with or presence of ovarian steroids. The relationships of metabolites and hormones with LH patterns appear to change with dietary energy level, ovarian status and mutual associations among the metabolites and hormones. These parameters, especially glucose and BHB, may be potential mediators of the effect of dietary energy status on LH patterns. (Abstract shortened by UMI.)

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Includes bibliography / 1 v. (various pagings) : ill ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Biochemistry, 1988

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Texte remanié de: Th. Ph. D.--University of Chicago, 1984.

Les neurones à Kisspeptine (Kp) de l'AVPV sont essentiels pour la survenue du pic de LH. Celle-ci est conditionnée par les concentrations circulantes d'oestrogènes (E2) et le moment du jour. Nous avons étudié si les neurones à Kp de l'AVPV étaient le lieu d'intégration de deux messages chez des souris sauvages intactes : un message E2, et un message temporel. Nous voulions savoir si ces neurones hébergeaient une horloge secondaire impliquée dans la temporalité du pic de LH. Durant l'après-midi du proestrus, une baisse drastique de l'immunoréactivité (ir) de Kp apparaît 2h avant la survenue du pic de LH au moment où l'expression de l'ARNm Kiss1 est élevée. Au contraire durant le diestrus, Kpir,l'expression de l'ARNm Kiss1 et les concentrations circulantes de LH restent basses. Les neurones à Kp de l'AVPV expriment une protéine horloge PER1 avec un rythme journalier exhibant un retard de phase de 2.8 h en diestrus comparativement au proestrus. Des explants d'AVPV exprimant les Kp provenant de souris PER2::LUCIFERASE dévoilent des oscillations circadiennes soutenues avec une période de 23.2h, significativement plus courte que celle observée dans les NSC. L'incubation des explants d'AVPV en présence d'E2 (10nM) rallonge la période d'une heure. En conclusion, cette étude indique que les neurones à Kp de l'AVPV présentent un rythme journalier dépendant des E2, qui pourrait être piloté par la présence d'une horloge secondaire au sein de ces neurones. / The kisspeptin (Kp) neurons in the anteroventral periventricular nucleus (AVPV) are essential for the preovulatory LH surge, which is gated by circulating estradiol (E2) and the time of day. We investigated whether AVPV Kp neurons in intact female mice may be the site in which both E2 and daily signals are integrated and whether these neurons may host a circadian oscillator involved in the timed LH surge. In the afternoon of proestrous day, Kp immunoreactivity displayed a marked and transient decrease 2 hours before the LH surge. In contrast, Kp content was stable throughout the day of diestrus, when LH levels are constantly low. AVPV Kp neurons expressed the clock protein period1 (PER1) with a daily rhythm that is phase delayed compared with the PER1 rhythm measured in the main clock of the suprachiasmatic nuclei (SCN). PER1 rhythm in the AVPV, but not in the SCN,exhibited a significant phase delay of 2.8 hours in diestrus as compared with proestrus. Isolated Kp expressing AVPV explants from PER2::LUCIFERASE mice displayed sustained circadian oscillations of bioluminescence with a circadian period (23.2 h) significantly shorter than that of SCN explants(24.5 h). Furthermore, in AVPV explants incubated with E2 (10 nM to 1 μM), the circadian period was lengthened by 1 hour, whereas the SCN clock remained unaltered. In conclusion, these findings indicate that AVPV Kp neurons display an E2-dependent daily rhythm, which may possibly be driven by an intrinsic circadian clock acting in combination with the SCN timing signal.

M.Sc. / A general introduction provides the foremost morphological characteristics of the genus. A breeding colony of Argulus japonicus was kept under laboratory conditions in order to study sperm transfer. Pairs in copula were studied with histology and scanning electron microscopy. Sections of copulating pairs revealed sperm on the accessory copulatory structures of the male; and scanning electron microscopy showed that sperm transfer occurs in three phases which can be differentiated to ten different stages. Sperm transfer occurs via a spermatophore in A. japonicus. This is the first observation of a spermatophore in Argulus. For the second part of this study, seven specimens of an unknown freshwater ectoparasitic crustacean were collected from red tilapia fish, kept for consumption at the “Langat Fishing, Seafood and Beer Garden” Restaurant just off the Langat River in Selangor, Malaysia. Initial investigation showed that the specimens were of the genus Argulus. Light and scanning electron microscopical studies were subsequently used to identify the species. A comparison with all Argulus species formerly described from Asia and the surrounding islands was conducted. The species was identified as Argulus coregoni, due to the presence of the roughly triangular shaped anterior respiratory areas and the kidney bean shaped posterior respiratory areas. Additionally, the abdomen with sharply pointed terminal ends as well as the presence of characteristic accessory protrusions on the second ii swimming leg of the male specimens confirmed this identification. This species has not previously been described from Malaysia. The final chapter of this dissertation contains an overall summative discussion of the different parts of this study and highlights future possible research avenues.

Lake Victoria, the largest tropical lake, has faced an unprecedented assault on its ecosystem through a variety of anthropomorphic causes that include the introduction of Nile perch Lates niloticus and over-fishing. As a result there have been species extinctions and declining fish population trends. This thesis explores options for reversing these declining population trends and the restoration of collapsed fisheries based on indigenous non-cichlid species. A candidate species was chosen - the cyprinid fish Labeo victorianus. This thesis studied various aspects of L. victorianus' reproductive biology in two geographically distant populations. These included general reproductive patterns in relation to proximate environmental conditions, gonadal development and recrudescence, sex development, characterisation of genetic and morphological diversity, and induced spawning. Fish from both populations were found to be potamodrometic, and highly fecund, iteroparous spawners. L. victorianus was also shown to be an undifferentiated gonochorist, where all individuals pass through an intersexual juvenile stage prior to differentiation, and maturation to either sex. Sexual maturity was attained at a significantly larger size within the Kagera River than that of Sio River fish – possibly as a response to genotypic and/or phenotypic differences. Spawning seemed to be synchronised with rainfall in Kagera River - a pattern that was not strictly adhered to with the Sio River. Thorough microscopic investigation of recrudescence patterns indicated there was uninterrupted spawning in fish from the Kagera River followed by Type I oocyte atresia. In contrast, there was a 90% spawning failure, as characterised by Type II oocyte atresia, within the Sio River population. Aspects of spermatogenesis and sperm ultrastructure using light- and ultramicrotomic methods are described. Although the populations had varying reproductive biology parameters and were morphologically distinct, they remained undifferentiated at the mitochondrial level. Both populations were characterised by low nucleotide diversity – a feature attributed to a bottleneck event. The option of captive breeding was explored by conducting induced spawning experiments. Success was only achieved with a decapeptide Gonadotropic Releasing Hormone ([D-Arg⁶, Pro⁹-NEt])-sGnRH) in combination with a water-soluble dopamine receptor antagonist metoclopramide. This thesis stresses the importance of a research-oriented approach in the conservation of Lake Victoria's indigenous fish resources. It was concluded that information needed for the development of management policies can be generated within a reasonably short time period, of approximately three years, with modest levels of funding support.