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    Effects of photoperiod on some reproductive organs and endocrine glands of young rams : a thesis presented in partial fulfilment of the requirements for the degree of Master of Agricultural Science at Massey University
    (Massey University, 1968) Zweng, Martin John
    Following Marshall's (1937) observation that ewes transported from one hemisphere to another reversed their oestrous and anoestrous seasons to conform to a new seasonal environment, it was hypothesized that daylength (photoperiod) had some effect on the reproductive activity of the ewe. Sykes and Cole (1944) exposed ewes to an experimental decrease in daylength of 6 hours over a period of 5 weeks. The experiment commenced in the Spring when daylength was 11.5 hours. Breeding occurred earlier that normal and lambs were produced four to five months before the usual time. Criticism of this work arose because of the use of only a limited number of animals, and the fact that the animals were of Ramboiillet stock, a breed known to show oestrous activity, under natural conditions, in the Spring and early Summer. These preliminary observations seemed to indicate that the ewe exhibited sexual activity in response to a "short" or "shortening" daylength. From these initial experiments, other observations of natural breeding seasons and more sophisticated photoperiod experiments have followed.
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    Reproductive and metabolic endocrinology in rams selected for high or low plasma IGF-1 concentrations : a thesis presented in partial fulfilment of the requirements for the degree of Master of Animal Science at Massey University
    (Massey University, 2007) Park, Eun-Kuk
    The objectives of this study were to define reproductive and metabolic endocrinology in Romney rams selected at the time of weaning for high or low peripheral IGF-1 concentrations with particular relevance to the annual changes in the relationships between GH, IGF-I and insulin and the relationship between that system and the activity of the reproductive endocrine axis. Parameters examined in detail included testis function, the response of IGF-I and insulin to GRF, and expression of IGF-I and its binding proteins in the testis. A preliminary experiment (December 2005 and March 2006) examined semen sample high, low and unsclccted IGF-I rams. In the main experiment, blood and semen samples were collected in July, September and November 2006 and March 2007 from yearling rams (high or low IGF-I concentrations). Scrotal circumference and inguinal skin were recorded. Blood samples were collected via jugular venipuncture. After a collection of the control samples, rams were given 50 ug hGRF and 1,000 IU hCG. Second blood samples were collected 40 min (testosterone) and 10 h later (insulin and 1GF-I). Seasonal differences from July to March were evident in the percentage of abnormal sperm, scrotal circumference and sperm motility, and concentrations of testosterone, IGF-I and insulin. IGF-I line differences were also found in scrotal circumference and IGF-I and insulin concentrations. Testosterone concentrations did not differ between lines, but, when actual IGF-I concentrations were taken into consideration, exhibited different secretion patterns between lines. In the experiment 3, samples of liver and testis tissue were collected from four animals for expression of mRNA for IGF-I, Type I IGF receptor and IGF binding proteins. It was found that genes foi IGF-I, Types I IGF receptor and IGF binding proteins -2, -3, -4, -5 and -6 were expressed in the testis. Significant high expression of Type I IGF receptor and IGFBP-3 in the testis was found in the low line, with different levels of high and low expression of IGF-I in the liver of the two lines. These studies suggested that circulating concentrations IGF-I are associated with gonadotropin-stimulated steroidogenesis that affects scrotal circumference, but differences in IGF-I status between lines are modulated by the different expression of mRNA for IGF-1R and IGFBPs and by negative feedback between lines.
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    The effect of nutritional fetal programming on post-pubertal male reproduction in sheep : a thesis presented in partial fulfilment of the requirements for the degree of Master of Veterinary Studies at Massey University, Palmerston North, New Zealand
    (Massey University, 2013) Fermin, Lisanne M
    There is evidence that the in utero environment affects or programmes postnatal development and performance of offspring. Previous investigations have been conducted to establish the effects of dam nutrition on the development and reproductive performance of rams following various nutritional regimes of the ewe during pregnancy. This study further examines the effect of nutritional treatments of ewes during pregnancy on post-pubertal male reproductive performance. Sixty-two ram offspring, obtained from twin-bearing ewes that were fed at one of three different nutritional treatments in early pregnancy (Day 21-50, Low (LD21-50) vx. Maintenance (MD21-50) vs. High (HD21-50)), and one of two different nutritional treatments in mid to late pregnancy (Day 51-140), Maintenance (MD51-140) vs. High (HD51-140), were utilised in this study. Reproductive performance was measured using the accepted indicators of scrotal circumference, and semen quality and quantity (visual density, motility, quantitative sperm density and morphology) to establish if there was any effect of maternal nutrition on these parameters. The influence of seasonality was also investigated. Ewe nutrition during D 21-50 or D 51-140 had no effect on scrotal circumference, semen quality nor quantity. The rams in this study generally conformed to previously described seasonal patterns of reproductive activity. In conclusion, the present study demonstrates that under these conditions, post-pubertal male reproductive function and capacity and therefore fertility appear to be unaffected by prenatal maternal nutrition, and that rams maintain their cyclical reproductive response to seasonal cues.
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    Some aspects of meiosis in normal and Robertsonian translocation-carrying rams : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Veterinary Science at Massey University
    (Massey University, 1974) Chapman, Helen Margaret
    SOME ASPECTS OF MEIOSIS IN NORMAL AND ROBERTSONIAN TRANSLOCATION-CARRYING RAMS A study was made of the meiotic chromosomes in air-dried preparations from 35 genitally sound rams (Ovis aries). The quantity and quality of dividing cells were best when testicular material was obtained by castration under local anaesthesia from rams during their breeding season. Sodium tri-citrate solution was used as hypotonic treatment and the cells were fixed in suspension with glacial acetic acid and absolute alcohel plus a trace of chloreform. Slides were stained either with aceto-orcein or with Giemsa for a "C-banding" technique. Fourteen of the rams bad a normal mitotie karyetype (54,xy) and the remainder were heterozygous or homozygous carriers of a Massey I, Massey II or Massey III Robertsonian translocation and had the following mitotic karyotypes: 53,xy,t(5q26q); 52,xy, t(5q26q) t(5q26q); 53,xy,t(8q11q); 53,xy,t(7q25q); 52,xy, t(7q25q) t (7q25q). One ram was heterozygous for both the Massey I and Massey III Robertsonian translocations. Analysis of primary spermatocyte cells showed that a modal number of 27 chromosomal elements was present in normal rams, while in both heterozygous and homozygous Robertsonian translocation-carriers, a modal number of 26 chromosomal elements was recorded. Heterozygous carriers of the three types of Robertsonian translocations, which involved non-homologous chromosomes, were characterized by the presence of a trivalent in cells at the diplotene, diakinesis and metaphase I stages. The modal number of chromosomal elements was recorded in over 80 per cent of the cells at diakinesis and metaphase I in the heterozygous and normal rams while over 77 per cent of the cells in the Massey I homozygote and 90 per cent of the cells in the Massey III homozygote had modal counts. An association between the sex bivalent and a small autosomal bivalent was recorded in 7.5 per cent of the diakinesis-metaphase I cells from normal rams and in between 3.4 and 4.7 per cent of the cells from the translocation-carrying rams. Separation of the sex chromosomes was observed in 0.5 to 1.5 per cent of the diakinesis-metaphase I cells in both Robertsonian translocation-carrying and normal rams. However no evidence at metaphase II of the sex chromosome aneuploidy expected if the two univalents disjoined at random at first anaphase whs observed. Eighty seven metaphase II figures from normal rams and 1,146 metaphase II figures from Robertsonian translocation-carrying rams were recorded. Detailed analysis of 1,131 cells showed that over 80 per cent of the non-polyploid metaphase II figures from the normal and homozygous rams had euploid chromosome arm counts. In contrast between 54 and 67 per cent of the metaphase II figures from the heterozygous rams were euploid. No hypermodal cells were recorded at metaphase II in either the normal or homozygous rams but from 4.5 to 9.2 per cent of the metaphase II cells in the three types of heterozygous ram were hypermodal. The results obtained in this thesis showed that the proportion of cells with chromosome arm counts of 29 was higher in the heterozygotes than in the normal or homozygous Robertsonian translocation-carrying rams. There were significantly greater numbers of cells with 29 chromosome arms than with 31 chromosome arms in the three heterozygote classes which suggested that chromosome loss due to lagging at first anaphase or technical manipulation, must have occurred in addition to non-disjunction. Statistically significant differences in chromosome arm distributions were shown to exist between rams which were heterozygous for a particular translocation and rams which were homozygous for the same translocation or normal rams. In addition to differences between individual rams, a significant difference between the Massey II Robertsonian translocation and the Massey I and III Robertsonian translocations occurred. Fewer balanced translocation X-bearing metaphase II cells were recorded than expected in three of the four Massey II Robertsonian translocation heterozygotes. Non-translocation bearing X and Y cells predominated at metaphase II in the three translocation types when total metaphase II counts were considered, and greater than expected numbers of X-bearing cells were found in both the euploid and aneuploid classes in the Massey III Robertsonian translocation heterozygotes. Since the majority of normal ewes mated with Robertsonian translocation heterozygous rams conceived to their first service, and because no lambs with unbalanced karyotypes associated with a Robertsonian translocation have been recorded, it is suggested that only chromosomally balanced (euploid) spermatozoa are involved in fertilization. It is further suggested that the absence of unbalanced karyotypes in progeny is explicable on the basis of a degeneration of aneuploid spermatocytes occurring prior to their maturation. The three translocations in the homozygous state behaved as normal autosomal bivalents at meiosis with regular segregation at anaphase I. It is suggested that the lowered fertility seen in matings involving heterozygous rams and heterozygous ewes cannot be attributed to any deficiencies in the spermatogenic function of the ram.
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    Studies of neuroendocrine mechanisms influencing seasonal variations in semen production and plasma hormone levels in rams : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy at Massey University
    (Massey University, 1976) Barrell, Graham Keith
    Many workers have shown that sheep are seasonal breeders with peak reproductive activity occurring during the autumn months. The initial experiment in this thesis was designed to define the seasonality of reproduction in rams of the N.Z. Romney breed as determined by repeated measurements of semen characteristics and of plasma hormone levels. These parameters were studied for 16 months in six N.Z. Romney rams on pasture, with five Merino and four Polled Dorset rams included for comparison. Semen from all three breeds showed relatively regular seasonal changes in ejaculate volumes and seminal fructose levels with peak values being recorded during March. Likewise, monthly hormone levels varied in a regular manner with plasma LH, testosterone and prolactin concentration being elevated during the summer months. Many of the other semen parameters measured showed little tendency for seasonal variations, however a change in semen collection technique, from predominantly artificial vagina to entirely electro-ejaculation, may have masked some seasonal changes. All three breeds showed similar seasonal changes in the parameters studied although semen from the Polled Dorsets did not exhibit regular seasonal variations in fructose levels. Further experiments were carried out to define the neuroendocrine mechanisms which regulate the seasonal reproductive changes in N.Z. Romney rams. Three olfactory bulbectomized rams, three cranial cervical ganglionectomized rams and four rams which had undergone both of these surgical modifications, were grazed together with the rams mentioned above. These surgical treatments disrupted the regular seasonal changes in plasma levels of LH and prolactin, but not, of testosterone. Spermatozoal concentrations in ejaculates from operated rams were higher than those from unoperated controls, whereas mean fructose concentrations were lower; however the pattern of seasonal changes in seminal fructose levels was similar in all groups of rams. Cranial cervical ganglionectomy reduced hydroxyindole-O-methyl transferase activity and cell volumes in the pineal glands, so it was concluded that disrupted seasonal patterns of changes in plasma LH and prolactin levels, plus the altered semen production in the surgically treated rams, resulted from modified pineal gland and/or olfactory system activity. A preliminary investigation into the role of changes in daily photoperiod as the stimulus for seasonality of reproduction, was carried out by placing rams in light-controlled rooms at the time of the March equinox. Over the following nine months rams exposed to a phase-reversed annual lighting cycle showed earlier elevations of seminal fructose and plasma testosterone levels than rams on either the normal annual or a constant equinoctial lighting regime. In all three groups plasma prolactin levels were directly related to the length of daily photoperiod. The findings of the above experiments were extended by a final study in which both pinealectomized and sham-operated rams were exposed to normal or reversed annual lighting cycles. Effects of lighting on plasma testosterone and prolactin levels, and on seminal fructose levels, were diminished by pinealectomy. Autopsy data related to gonadal and accessory sex gland function showed significant operations x lighting regimes interactions, which supported the conclusion that in rams pineal gland function mediates endocrine and gonadal responses to changes in daily photoperiod. Three short-term investigations of hormonal secretion profiles conducted during the latter experiment, showed that major fluctuations in the release of LH, testosterone, prolactin and cortisol occurred irregularly during the day. A nocturnal elevation of plasma prolactin levels was abolished by pinealectomy. These acute studies tended to confirm the findings of the latter experiment, but in particular they highlighted the pulsatile nature of hormonal secretion.
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    Studies of testicular and reproductive endocrine parameters in the ram with particular reference to sexual maturation : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy at Massey University
    (Massey University, 1977) Wilson, Peter Raymond
    Experiments in this thesis were designed to establish short-term and longitudinal patterns of secretion of LH, testosterone and prolactin, responses to GnRH administration, testicular and reproductive endocrine changes associated with sexual maturation in the ram, and to study endocrine factors which may influence reproductive development. 24 hour hormonal secretion profile studies employing 20 min sample collection intervals in 9 adult rams, and 8 h secretion profile studies in eight prepubertal, pubertal and early post-pubertal rams confirmed that LH was secreted in a pulsatile manner. Testosterone was secreted quantitatively following each episodic LH elevation in pubertal and older rams, but a consistent qualitative and quantitative secretory response was not observed in prepubertal rams. Plasma prolactin levels were stable and high during the summer, but low basal levels interspersed with pulsatile fluctuations occurred in winter sampling periods. Prolactin secretion profiles of prepubertal and sexually maturing rams were similar, and levels fluctuated markedly at each stage of development. No circadian rhythms of LH, testosterone or prolactin secretion were evident in adult or sexually developing rams, but data was produced which supported the existence of a sampling-induced elevation of LH and prolactin in young rams: higher levels of both hormones were observed in early samples of sequential sampling studies employing venepuncture techniques. Study of hormone levels of ram lambs bled each two weeks from birth to approximately 8 months of age showed that plasma LH content was low at birth, rose to a peak at approximately 6 weeks of age, and declined during the period of major testicular development (10 - 18 weeks); plasma testosterone concentrations were low at birth and increased steadily throughout the period of study; while prolactin levels were low at birth, Increased rapidly to reach a plateau from approximately 6 to 20 weeks, then gradually decreased to low levels by 32 weeks. Testicular and epididymal development, seminiferous and epididymal tubule growth, and the onset of spermatogenesis during puberty followed patterns similar to those reported by previous authors. Regression analyses failed to distinguish major correlations between these developmental parameters and endocrine changes associated with sexual maturation. Responses to intravenous GnRH injection and Infusion to adult rams showed that LH output occurred in a dose-dependent manner but subsequent testosterone elevations were not significantly different. The LH responses of prepubertal rams to intravenous injections of GnRH (1 μg/Kg) were high, but progressively decreased at consecutive four-weekly injection and sampling routines from 6 to 32 weeks of age. Peak LH responses were progressively delayed during this period. Testosterone output following GnRH-induced LH elevations were low in prepubertal rams and increased progressively during sexual maturation. Maximal responses to repeated GnRH injections were observed in pubertal (14 week old) rams. Weekly treatment of ram lambs with GnRH failed to alter any of the testicular or endocrine parameters assessed during sexual development whereas weekly androgen treatment depressed mean testis and epididymal weights, seminiferous and epididymal tubular diameters and epididymal spermatozoal reserves, as well as basal and GnRH-stimulated testosterone output. Prenatal androgenization of female lambs resulted in masculinization of external genitalia. Postnatal basal levels of LH were depressed in both males and females from androgenized ewes, while LH responses to GnRH were unaltered. It was concluded that prenatal androgenization depressed hypothalamic hypophysiotrophic function.
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    Studies on pubertal development in boars and rams : effects of hemicastration and artificial cryptorchidism on hormone secretory patterns and development of reproductive organs : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy at Massey University
    (Massey University, 1981) Kuruwita, Vijitha Yasasee
    Experiments described in this thesis were designed to reinvestigate longitudinal patterns of secretion of LH and testosterone in boars and rams; also to determine the effects of hemicastration of boars and the effects of hemicastration and artificially induced cryptorchidism of rams on longitudinal and acute hormone secretion patterns, as well as some parameters of reproductive organ development. Plasma LH and testosterone levels of spring and autumn born Large White x Landrace boars were relatively high at birth, but declined from about the 4th postnatal week. Autumn born boars showed a distinct prepubertal LH peak, but in spring born animals there was no such peak. LH concentrations of barrows were high throughout the period of study. Plasma testosterone levels were low between 4 and 12 weeks of age then increased progressively until the end of study. Season of birth had little influence on the longitudinal profiles of secretion of either hormone. Intensive bleeding experiments with entire and hemicastrated boars confirmed that LH and testosterone were secreted in a pulsatile manner; hemicastration had no significant effect on pulsatile secretion, mean hormonal concentrations, nor LH or testosterone responses following injection of GnRH. On the other hand, while LH responses to GnRH administration were not affected by advancing age, the subsequent testosterone output increased with sexual maturation. Compensatory hypertrophy in testicular and epididymal weights and in seminiferous tubular diameters was noted in organs recovered from hemicastrates. However, qualitative histological analyses of testicular samples revealed that the cellular changes observed in all animals were of maturational nature and entirely age-related. From these observations it was concluded that hemicastration of developing boars did not result in any acceleration of the onset of spermatogenesis nor any advancement of puberty. In ram lambs LH concentrations were low at birth, increased to peak levels at around 10 weeks of age, then declined to low values between 16 and 30 weeks of age when the experiment ended. In contrast plasma testosterone values were low at birth but increased steadily, particularly from about 18 weeks of age. Mean LH and testosterone concentrations recorded from longitudinal, acute profile and pre-GnRH plasma samples of hemicastrated ram lambs confirmed the observations recorded from hemicastrated boars that the remaining testes were capable of secreting near normal quantities of testosterone and hence maintaining virtually unchanged plasma LH levels. On the other hand, a transient but significant increase in plasma FSH levels was detected following hemicastration of ram lambs. Conversely, cryptorchidism caused an elevation of LH and FSH secretion throughout the period of study. Neither surgical treatment had any influence on longitudinal or acute prolactin or testosterone secretory patterns. Mean plasma prolactin levels recorded from all animals were high initially then declined steadily throughout the period of study. That decline in prolactin levels coincided with the seasonal decrease in daily photoperiod. Plasma testosterone levels recorded from all three treatment groups increased steadily from birth to reach peak concentrations at 30 weeks of age. Short term profile studies with entires, hemicastrates and cryptorchids confirmed the episodic mode of secretion of LH, prolactin and testosterone, and to less extent FSH. Hemicastration had no significant effect on episodic secretion of any of these hormones. Cryptorchidism caused a significant increase in number of LH peaks and a decrease in number of testosterone peaks, but had no effect on patterns of prolactin or testosterone secretion. GnRH administration caused an increase in plasma LH, FSH and testosterone secretion in entires and responses were unaffected by hemicastration. However, exaggerated gonadotrophin responses were noted from cryptorchids, while the testosterone responses recorded from these animals tended to be lower (but not significantly so) than those of entires and hemicastrates. Mean plasma gonadotrophin levels recorded from each group were reduced by testosterone propionate pre-treatment; that result gave support to the concept that hypoandrogenism may have been the major reason for the elevation of plasma LH levels in cryptorchids. while total LH responses declined with age and maximal FSH responses of all three treatment groups were noted at 24 weeks of age, testosterone responses increased with sexual maturation. Testicular and epididymal weights and seminiferous tubular diameter data obtained from hemicastrate rams confirmed that this treatment resulted in compensatory hypertrophy of the remaining organs. As recorded from hemicastrated boars there was no major alteration in cell populations of the germinal epithelium or Leydig cells. The changes observed were entirely of a maturational nature and age-related. Testes and epididymides obtained from cryptorchids showed no increase in weight during the experiment and thus were smaller than those of age-matched entires. It was apparent that intra-abdominal temperature prevented normal development of these organs. Qualitative histological examination showed that there was complete arrest of all maturational changes, both in the germinal epithelium and interstitial tissue of cryptorchid testes. On the basis of hormonal and organ data obtained from experiments described in this thesis it was concluded that LH, FSH and possibly testosterone were responsible for compensatory hypertrophy of the remaining testes of hemicastrates. The transient elevation of plasma FSH levels which occurred following this treatment probably was due to an overall decrease in production of testicular inhibin, the major regulator of FSH secretion. Presumably the remaining testis subsequently produced sufficient inhibin to reduce FSH secretion back to normal levels. These observations add weight to the hypothesis that following hemicastration, the compensatory increase in testicular androgen secretion occurs more rapidly than does the increase in rate of secretion of FSH inhibitory products. In contrast the increased secretion of LH and FSH in the cryptorchids resulted from reduced testicular production of androgens and inhibin, respectively. Those changes in testicular secretion persist throughout the period of cryptorchidism.
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    Studies on the vaccination of sheep against Brucella ovis infection : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy at Massey University
    (Massey University, 1986) Bailey, Karen Marie
    A study was made of the efficacy and adverse effects of an inactivated Brucella ovis saline-in-oil vaccine administered either once or twice by either the subcutaneous or the intraperitoneal route. Seven Brucella ovis isolates from various sources, including the two used in the manufacture of the Brucella ovis vaccine, were subjected to Bacterial Restriction Endonuclease Analysis and no genetic differences were found. It was concluded that there is probably only one strain of the organism. It was found that rams vaccinated by the subcutaneous route in the neck invariably developed a palpable inflammatory lesion at the site of injection. The lesions had a mean diameter of approximately 3cm, about one-third of them discharged, and the majority persisted for at least one year after vaccination. These lesions were chronic granulomatous inflammatory reactions arranged around droplets of the oily Brucella ovis vaccine. The intraperitoneal route of vaccination has been advocated in the past as a way of avoiding visible lesions. Necropsy of vaccinated animals revealed that in over 50% of cases, at least some of the vaccine administered by this technique failed to reach the cavity and was deposited either beneath the parietal peritoneum or between the muscles of the abdominal wall. Regardless of the site of deposition, however, the vaccine always provoked a chronic granulomatous inflammation of the tissues with which it came into contact. Changing from a subcutaneous to an intraperitoneal vaccination technique merely moved the reaction to a site where it was less visible. Serological studies using the Brucella ovis complement fixation test, gel diffusion test and enzyme linked immunosorbent assay demonstrated a consistent difference in the antibody response of rams vaccinated by the subcutaneous technique in comparison with those vaccinated by the intraperitoneal technique. Those vaccinated by the subcutaneous route generally developed antibody titres more rapidly and often had higher peak titres. In the same way, animals vaccinated twice by either route generally had greater and more persistent antibody titres than those vaccinated once by the same method. The differences in the serological response of rams to different vaccination techniques vere reflected by similar differences in resistance to experimental infection. The administration of an inactivated Brucella ovis saline-in-oil vaccine by any of the techniques studied significantly increased resistance to challenge by the intravenous route. However, two spaced doses of vaccine appeared to be more effective than a single dose, and the subcutaneous technique appeared to be more effective than the intraperitoneal method. Using intravenous inoculation, the number of bacteria required to infect 50% of unvaccinated animals was estimated to be 9.5 x 104 organisms. The administration of a single dose of vaccine by the intraperitoneal technique raised that figure to approximately 6.7 x 106, and the administration of two doses of vaccine by the subcutaneous route raised it to approximately 6.8 x 107. A viable count of the number of Brucella ovis bacteria present in the semen of an infected ram showed that at least 3 x 109 organisms could be excreted in a single ejaculate. This was over 31,000 times the number required to infect 50% of unvaccinated rams after intravenous inoculation and 44 times that required to infect 50% of animals vaccinated twice by the subcutaneous route. There is therefore a real possibility that natural challenge through homosexual activity may result in the infection of even vaccinated rams. It vas concluded that if vaccination is to be used as a means of controlling the spread of ovine brucellosis, a programme of two doses of vaccine administered at an interval of at least four weeks should he employed. The second dose of vaccine should be administered at least four weeks before the anticipated period of risk. If this method of control is adopted, a palpable lesion at the site of injection which is likely to persist for over a year should be expected. It should also be understood that rams vaccinated in this way may not be totally resistant to Brucella ovis and may still become infected.
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    A study of meiosis in rams carrying multiple Robertsonian translocations : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Veterinary Science at Massey University
    (Massey University, 1982) Scott, Ian Stewart
    A study was made of meiotic chromosomes in air-dried preparations from 30 genitally sound rams (Ovis aries). Three of the rams had a normal mitotic karyotype (2n = 54) and the remainder were carriers of the t1, t2 and t3 Robertsonian translocations in various heterozygous and homozygous combinations. The studies on the primary spermatocytes showed that the normal rams had a modal number of 27 chromosomal elements and the translocation-carrying rams were recorded with a modal number of either 24 or 25. The translocation in the heterozygous state was characterized by the presence of a trivalent in cells at the diplotene, diakinesis and metaphase I stages, while in the homozygous state it was characterized by the presence of a bivalent. The modal number of chromosomal elements was recorded in 90.5 to 97.3 percent of the cells at diakinesis and metaphase I in the translocation-carrying rams. The modal number of chromosomal elements was recorded in 88.3 percent of the cells in the normal rams. An association between the sex bivalent and a small autosomal bivalent was recorded in 3.5 to 5.3 percent of the cells at diakinesis and metaphase I in the translocation-carrying rams. Eight percent of the cells in the normal rams were seen with a sex bivalent association. The sex chromosomes were separated in 0.0 to 1.1 percent of the cells at diakinesis and metaphase I in the translocation-carrying rams, while 0.7 percent of the cells in the normal rams had separated sex chromosomes. However, aneuploidy involving the sex chromosomes was not observed in the secondary spermatocytes from the normal and translocation-carrying rams. A total of 1,757 secondary spermatocytes were counted from 27 translocation-carrying rams and 103 secondary spermatocytes from 3 normal rams. The studies on the secondary spermatocytes showed that the modal number of 30 chromosome arms was recorded in 87.3 to 96.0 percent of the non-polyploid cells in the translocation-carrying rams and 95.2 percent of the cells in the normal rams. No hypermodal cells were found in the normal rams. Hypermodal cells were recorded in 0.0 to 3.6 per cent of the non-polyploid cells in the translocation-carrying rams. There were individual variations in the percentage of hypermodal cells recorded in rams with identical karyotypes. There were also significantly greater numbers of cells with 29 chromosome arms than with 31 chromosome arms in the translocation-carrying rams. This suggested that chromosome loss due to lagging at anaphase I or technical manipulation, must have occurred in addition to non-disjunction. A significant surplus of secondary spermatocytes of normal karyotype and a deficit of 25, t1 t3 were found in the metaphase II figures from the triple heterozygous rams. Significantly uneven distributions of segregation products were also found in the multiple translocation-carrying rams with karyotypes of 50,xy,t1t2t2t3 and 49,xy,t1t2t2t3tx. The translocation-carrying sheep have been shown to have good conception rates and an average breeding performance. This would suggest that only balanced (euploid) spermatozoa are involved in fertilization and the unbalanced (aneuploid) spermatocytes fail to mature into spermatozoa and are selected against or degenerate during spermatogenesis. The evidence indicates that the fertility of the ram is unaffected by the presence of the translocation chromosomes and consequently these sheep should not be eliminated arbitrarily from our animal populations.
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    Studies on the innervation of the ovine pineal and the regulation of melatonin secretion : a thesis in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Physiology at Massey University
    (Massey University, 1991) Mockett, Bruce George
    The studies described in this thesis were designed to investigate the neural regulation of melatonin secretion from the ovine pineal gland. Initial studies sought to establish the effects of a range of anaesthetics on the nocturnal rise in plasma melatonin levels in Romney rams and to identify the anaesthetic treatment most suitable for use in future acute studies; this was found to be halothane induction and maintenance. To investigate the neural mediation of melatonin secretion from the ram pineal, a series of experiments was performed in which the pre-ganglionic sympathetic innervation was stimulated electrically. Acute stimulation during the night or day resulted in an immediate, sustained rise in plasma melatonin levels, with nighttime responses being significantly greater than daytime responses (P<0.05). Similar studies in conscious rams were subsequently made possible by the development of a cuff electrode which could be implanted around the CST's and remain functional for at least six weeks. In these studies it was demonstrated that photoperiod (16L:8D of 8L:16D) did not influence melatonin output, while responsiveness to stimulation was highest during the middle, rather than at the beginning or end, of the photoperiod. The second study employing chronically implanted electrodes was designed to evaluate the influence of various parameters of continuously applied CST stimulation on the pineal's melatonin secretory response. Unexpectedly, it was found that only small rises in plasma melatonin levels resulted from stimulation with any of the combinations of stimulus parameters tested and that no one combination was significantly more effective than any other in promoting increases in plasma melatonin levels. These findings appear to have resulted from inadequate performance of the electrodes and/or nerve damage. The final study undertaken in this thesis was designed to identify the innervation of ovine pineal by immunocytochemically localizing the neuropeptides NPY & VIP, and the enzymes NSE & PNMT. All four antigens were observed in intrapineal nerve fibres, while NSE was also present in pinealocytes. SCGX reduced, but did not eliminate, this immunoreactivity suggesting that both central and peripheral regions innervate the pineal and that partial denervation initiates a neural compensatory mechanism.