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LD2668 .T4 1941 P41 / Master of Science

Call number: LD2668 .T4 1984 W43 / Master of Science

Sixty-two newborn Holstein-Friesian calves were used to study the role of colostrokinin, serum cortisol, and serum thyroxine in the absorption of maternal immunoglobulin. Calves were removed from their dams prior to suckling and assigned one of four rations: colostrum, whole milk, milk plus colostral immunoglobulin, and milk plus immunoglobulin plus colostrokinin. Calves were fed their assigned ration either at birth or after twelve hours inanition. All calves were fed pooled colostrum at 24 hours postpartum. Blood samples were collected at seventeen times during the first 32 hours postpartum. Calves were born with high cortisol concentrations (88 ng/ml) which decreased (P < .05) within two hours postfeeding. Serum cortisol levels increased (P < .05) between two and three hours after calves ingested a colostral source of immunoglobulin. Time of initial feeding had no effect on the cortisol surge. No such increase was observed in neonates consuming an immunoglobulin-free milk ration. These results demonstrate that the immunoglobulin fraction of colostrum is responsible for initiating an increase in cortisol secretion by the adrenal cortex. Within four hours postpartum, serum thyroxine concentrations increased (P < .05) at least 50% in all treatment groups regardless of whether the calves were fed or fasted. After peaking at 18 μg/dL, the serum thyroxine concentrations fell gradually throughout the duration of the collection period. Colostrokinin exhibited a biphasic effect on serum immunoglobulin concentrations which was dependent on the initial time of feeding. Calves exposed to colostrokinin in 0 hour feedings had serum immunoglobulin G concentrations significantly higher (P < .05) after 16 hours postpartum than animals not fed colostrokinin. Fasted calves, exposed to colostrokinin at 12 hours postpartum, had no increase in serum immunoglobulin G concentrations following a colostrum feeding at 24 hours postpartum. Fasted calves fed a ration not containing colostrokinin exhibited a two-fold increase in serum immunoglobulin G concentrations after the 24 hour colostrum feeding. Colostrokinin did not have an immediate effect on serum immunoglobulin G concentrations, but required an approximate twelve hour period to manifest its regulatory function. The presence or absence of colostrokinin in the experimental rations did not have any effect on the cortisol or thyroxine profiles. The variable serum immunoglobulin G profiles suggest that colostrokinin is involved in the acquisition of passive immunity by the calf, but colostrokinin may have more than one physiological role.

Removal of the pineal gland from partially parathyroidectomized rats produces stereotyped violent seizures. Inasmuch as the neurotransmitter norepinephrine (NE) has been implicated in this experimental paradigm, the purpose of this study was to investigate the effect of specific alterations in catecholamine function on convulsions produced by pinealectomy (PinX). Additionally, the role of various pineal substances, sex differences and the caging paradigm in the convulsive response was studied. Male and female rats (grouped five per cage) were found to respond similarly to the convulsive stimulus of parathyroidectomy followed by PinX. Neither implants of melatonin nor ventricular injections of arginine vasotocin in isolated and grouped rats, respectively, produced consistent changes in convulsions from PinX. The method of caging the rats after PinX, however, dramatically influenced seizures. Isolated rats (one per cage) convulsed significantly later after PinX and did so less often than grouped (five per cage) controls. NE neurotransmission appears to play a strong role in influencing PinX-induced seizures. Augmenting NE function with desipramine suppressed seizures. Convulsions were enhanced by the (beta)-receptor antagonist timolol, while neonatal injections of the catecholamine neurotoxin 6-OHDA potentiated seizures so markedly that many rats died from just one convulsion. NE levels were significantly reduced in the telencephalons and increased in the brain stems of sham-pinealectomized rats which had also received neonatal 6-OHDA; telencephalic levels of DA were elevated by 6-OHDA. Both the proconvulsant effects of 6-OHDA and the alterations it produced in central catecholamine levels were prevented, for the most part, by pretreatment with DMI. Altering both NE and DA function with L-dihydroxyphenylalanine, (alpha)-methyl-p-tyrosine, FLA-63 or reserpine did not significantly affect PinX-induced seizures in isolated rats. NE appears to play a strong role in modulating PinX-induced seizures; however, a deficit in NE function per se does not seem to be the fundamental cause of the seizures since sham-pinealectomized rats having lowered NE and/or DA function did not convulse.

No description available.

Application of power MOSFETs in spaceborne power converters was simulated by exposing devices to low-dose-rate ionizing radiation. Both radiation-hardened and nonhardened devices were tested with constant and switched gate biases during irradiation. In addition, some of the devices were under load. The threshold-voltage shifts were strongly bias dependent. The threshold-voltage shift of the nonhardened parts was approximately dose-rate independent, while the hardened parts exhibited significant dose-rate dependence. A pre-anneal dose-rate dependence was found for the interface-state buildup of the switched and positively biased devices, but the results for the switched devices were qualitatively different than those for the positively biased devices. The buildup of interface trapped charge was found to be the primary contributor to mobility degradation, which results in reduced drive capability and slower operation of the devices. These results indicate that new methods need to be utilized to accurately predict the performance of power MOSFETs in space environments.

This research is designed to test how sublethal exposure to copper affects tadpole predator-escape behavior and how quickly tadpoles recover. After exposure, tadpoles were separated. Escape behavior was recorded for two-thirds of exposed tadpoles while one-third of the exposed population was measured weekly to determine growth and recovery. Control tadpoles were consumed within 15 minutes whereas those exposed to higher concentrations were consumed at a slower rate, which does not support the hypotheses. Although the rate of predation was lower, tadpoles exposed to higher Cu concentrations were on average, 1.47 cm in total body length. Those exposed to 0.93 mg/L averaged 0.86 cm. After being placed into clean water, treatment tadpoles recovered after 20 days.

To help address the knowledge gap between science and practice this study explores the possible positive benefits of using a more pedagogical effect size estimate when presenting statistical relationships. Traditional presentation has shown limitations with major downsides being that scientific findings are misinterpreted or misunderstood even by professionals. This study explores the possible effects of the non-traditional effect size estimate Common Language Effect Size (CLES) on different training outcomes for HR professionals. This study also explores the possible effect of cognitive system preference on training outcomes. Results show no overall effect of CLES on either training outcomes or cognitive system. A positive effect of CLES on training outcome is found at the subfactor level showing a significant effect. The results can be interpreted that non-traditional effect size estimates have a limited effect on training outcomes. This small but valuable piece to bridge the gap of knowledge is discussed.

Fung Chun Kit. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2005. / Includes bibliographical references (leaves 117-139). / Abstracts in English and Chinese. / Declaration of Originality --- p.i / Acknowledgements --- p.ii / Abstract --- p.iii / 摘要 --- p.v / List of figures --- p.vi / List of tables --- p.viii / List of abbreviations --- p.ix / Chapter Chapter I --- General introduction --- p.1 / Chapter 1.1 --- Different fish habitats with various salinities --- p.1 / Chapter 1.2 --- Osmotic challenges faced by teleosts --- p.2 / Chapter 1.3 --- High ionic strength results in DNA damage and excess water gain --- p.3 / Chapter 1.4 --- Osmoregulatory organs and mechanisms for osmotic balance --- p.4 / Chapter 1.5 --- Different tolerance to salinity changes --- p.8 / Chapter 1.6 --- Effective communication among osmoregulatory organs --- p.9 / Chapter 1.7 --- Introduction to GH and PRL --- p.9 / Chapter 1.8 --- Structure of the GHR and PRLR --- p.10 / Chapter 1.9 --- Hypoosmoregulatory action of GH/IGF-I axis in teleosts --- p.11 / Chapter 1.10 --- Hyperosmoregulatory action of PRL in teleosts --- p.11 / Chapter Chapter II --- Research rationale --- p.13 / Chapter 2.1 --- Physiological importance of osmoregulation in fish --- p.13 / Chapter 2.1.1 --- Energy metabolism --- p.13 / Chapter 2.1.2 --- Growth --- p.14 / Chapter 2.1.3 --- Immunity --- p.14 / Chapter 2.1.4 --- Reproduction --- p.15 / Chapter 2.2 --- Aquaculture importance --- p.15 / Chapter 2.3 --- Unknown molecular regulatory mechanism of hormones during salinity changes in fish --- p.16 / Chapter 2.4 --- Animal model --- p.17 / Chapter Chapter III --- In vivo studies of sbGHR and sbPRLR expression in osmoregulatory organs in response to salinity changes --- p.18 / Chapter 3.1 --- Introduction --- p.18 / Chapter 3.1.1 --- Dynamic change of GH level during salinity changes --- p.18 / Chapter 3.1.2 --- Dynamic change of PRL level during salinity changes --- p.19 / Chapter 3.1.3 --- In vitro studies of GH and PRL release from teleost pituitary in response to extracellular osmolality changes --- p.20 / Chapter 3.1.4 --- Biological actions of GH and PRL through the GHR and PRLR --- p.21 / Chapter 3.2 --- Materials and methods --- p.23 / Chapter 3.3 --- Results --- p.28 / Chapter 3.4 --- Discussion --- p.36 / Chapter 3.4.1 --- Plasma osmolality change during salinity changes --- p.36 / Chapter 3.4.2 --- Gene expression after HSW exposure --- p.38 / Chapter 3.4.3 --- Ionic mediators of the gene expression --- p.43 / Chapter 3.4.4 --- Gene expression after BW exposure --- p.44 / Chapter 3.4.5 --- Dynamic changes of the GHR and PRLR in response to salinity changes --- p.45 / Chapter 3.4.6 --- Regulation of the gene expression in response to salinity changes --- p.46 / Chapter Chapter IV --- Gene expression of sbGHR in liver during salinity changes --- p.49 / Chapter 4.1 --- Introduction --- p.49 / Chapter 4.1.1 --- Responses of the somatotropic axis to salinity changes in fish --- p.49 / Chapter 4.2 --- Materials and methods --- p.52 / Chapter 4.3 --- Results --- p.56 / Chapter 4.4 --- Discussion --- p.60 / Chapter 4.4.1 --- Inhibition of GHR and IGF-I gene expression in liver during HSW exposure --- p.60 / Chapter 4.4.2 --- Downregulation of GHR gene expression by hyperosmotic stress --- p.62 / Chapter 4.4.3 --- Growth retardation of fish during hyperosmotic environment --- p.64 / Chapter Chapter V --- Gene expression studies of sbPRLR in gill organ culture --- p.68 / Chapter 5.1 --- Introduction --- p.68 / Chapter 5.1.1 --- Functions of gill in fish osmoregulation --- p.68 / Chapter 5.1.2 --- Gill culture as a model for osmoregulation studies --- p.69 / Chapter 5.2 --- Materials and methods --- p.70 / Chapter 5.3 --- Results --- p.71 / Chapter 5.4 --- Discussion --- p.73 / Chapter Chapter VI --- Regulation of gene expression of sbGHR in liver during hyperosmotic stress: promoter studies --- p.75 / Chapter 6.1 --- Introduction --- p.75 / Chapter 6.1.1 --- What is a promoter? --- p.75 / Chapter 6.1.2 --- Promoter studies of GHR gene --- p.76 / Chapter 6.2 --- Materials and methods --- p.78 / Chapter 6.3 --- Results --- p.85 / Chapter 6.4 --- Discussion --- p.104 / Chapter Chapter VII --- General discussion and future perspectives --- p.111 / References --- p.117