Bibliography: leaves 172-214. Interleukin-12 (IL-12) is a heterodimeric cytokine composed of two disulphide-linked subunits, p35 and p40, which form biologically active p70. IL-12 is able to induce IFN-y production from T and NK cells, and promote the proliferation of mitogen-activated T cells. It is thought that IL-12 may be an important cytokine in the initiation and progression of allograft destruction. This thesis describes the characterisation of ovine IL-12.

No description available.

Bibliography: leaves 172-214. / 214 leaves, [41] leaves of plates : ill. (some col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Interleukin-12 (IL-12) is a heterodimeric cytokine composed of two disulphide-linked subunits, p35 and p40, which form biologically active p70. IL-12 is able to induce IFN-y production from T and NK cells, and promote the proliferation of mitogen-activated T cells. It is thought that IL-12 may be an important cytokine in the initiation and progression of allograft destruction. This thesis describes the characterisation of ovine IL-12. / Thesis (Ph.D.)--University of Adelaide, Dept. of Medicine, 2000

The feeding of 2.5 mgm. of diethylstilbestrol (DES) per head per day to growing wethers fed a dehydrated grass meal ration increased dry matter intake by 6 per cent and decreased dry matter digestibility by 2.4 per cent. The DES-treated lambs digested 5.4 cent (P<.05) more crude protein, 9.2 per cent (P<.20) more ether extract, 15 per cent (P< .01) less crude fibre, and 3.5 per cent (P<.01) less nitrogen-free extract. The use of a two stage in vitro digestion technique did not reveal any influence of a wide range of DES levels upon dry matter digestibility. The implantation of 12 mgm. DES in growing ewes and wethers increased pituitary and adrenal gland weights by 46 per cent (P<.005) and by 23 per cent respectively. The thyroid gland weights were decreased 21 per cent (P<.005). The gross histology of the pituitary gland was not found to be changed by DES treatment The use of I¹³¹ did not reveal changes in the activity of the thyroid gland following the feeding of 1.0, 2.0, and 2.5 mgm. DES per day to growing wethers. Lambs fed an all-concentrate ration and implanted with 12 mgm. DES gained more rapidly and efficiently than their controls The DES-treated lambs had a lower dressing percentage, and required less time to reach market weight. These results indicate that the action of DES in enhancing growth rate and efficiency of gain in the ruminant appears to be mediated by one or more mechanisms. First, DES may alter the digestive activities of the rumen microflora by selectively promoting their proteolytic activity and inhibiting their cellulolytic activity. It may, nevertheless, allow for an increased absorption of the degradation products of protein metabolism. These products may be present in a more readily digested form or may be more readily passed through the intestinal tract wall. Secondly, DES may stimulate growth of the anterior pituitary, resulting in an altered production of a number of the tropic hormones arising from this gland. With an increased growth of the anterior pituitary, an increased level of STH could account for a more efficient feed utilization. Control and DES-treated lambs utilize approximately the same amount of apparent digestible energy, however DES-treatment resulted in an increased growth rate. This must be due to an increased utilization of net energy, possibly associated with an alteration in tropic hormone production. / Land and Food Systems, Faculty of / Graduate

Pressure changes and myoelectrical activity in the ovine rumen were investigated following the surgical implantation of fluid filled balloon-tipped tygon tubes and paired fine needle platinum electrodes. The correlations among rumen pressure change and myoelectrical spike burst duration, frequency and magnitude data from 447 7 one minute periods were determined in order to select a single reliable quantitative measurement of rumen motility. The results showed that all these parameters accurately reflect activity changes in the rumen. Myoelectrical spike burst duration was shown to be the most sensitive indicator and was used as the criterion for examination of lactic acid induced motility changes. Rumen motility was not affected by intraruminal introduction of 1000 ml of 0.15 or 0.7 M lactic acid at pH 2.0 via permanently implanted cannulae. Intravenous infusion of 2 concentrations of sodium lactate which increased blood lactate levels by approximately 20 mg% and 180 mg% respectively, also had no effect on rumen motility. Infusion of lactic acid solutions (250 ml) 0.15 or 0.7 M (pH 2.0, 4.0 and 6.0) intraduodenally via polyethylene cannulae exerted profound effects on rumen motility. Immediately following ( 1 min) the commencement of the infusion of lactic acid (pH 2.0), a short period of total inhibition of motility occurred which was followed by a rapid recovery of motility to near normal levels despite the continuation of the infusion. These initial short periods of inhibition and recovery continued for up to one hour following termination of infusion. Similar yet somewhat reduced responses were observed upon intraduodenal infusion of the lactic acid solutions at pH 4.0 and 6.0. These results suggest that inhibition of rumen motility in lactic acidosis may be caused primarily by lactic acid produced in the rumen entering the intestine and causing a stimulation of the enterogastric reflexes. / Land and Food Systems, Faculty of / Graduate

No description available.

Includes bibliographical references (leaves 198-223) Examines the metabolism of plasma lipoprotein triacylglyceride in sheep (Ovis aries) under normal fed conditions, fasting and alloxan diabetes.

Call number: LD2668 .T4 1979 B76 / Master of Science

Call number: LD2668 .T4 1958 C46 / Master of Science

Spring-born ram lambs were used to examine: (1) sexual maturational changes in LH, FSH and prolactin (PRL) secretion, testicular gonadotropin receptors, and testicular size and function; (2) predictability of yearling ram reproductive function from juvenile testicular size and reproductive hormone measurements. Despite continuous increases in testis size, serum LH-profile characteristics became greatest between 2 and 4 months and declined thereafter. However, LH-peak frequency increased by about 2-fold between 6 and 7 months; this was associated with marked increases in testosterone (T) secretion and spermatogenic function. Mean FSH and PRL levels were maximum at 2 months and 3 to 5 months, respectively, and decreased thereafter. Increases in steroidogenic and spermatogenic function were due partly to increases in testicular content of LH and FSH receptors. Yearling ram testis size and spermatogenic function were predictable from testis size at 5 to 6 months, neonatal (50 days) secretion of LH and T, and pubertal (150 days) secretion of T. However, combinations of testicular size and reproductive hormone measurements provided greater predictive power.