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Typescript / 191 leaves / 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 and General Physiology, 1965

Diss. (sammanfattning) Linköping : Univ., 2001. / Härtill 5 uppsatser.

Diss. (sammanfattning) Stockholm : Karol. inst. / Härtill 5 uppsatser.

Diss. (sammanfattning) Stockholm : Karol. inst. / Härtill 5 uppsatser.

The regulation of calcium (Ca²⁺) was examined during long-term changes of neuronal excitability in the mammalian CNS. The preparations under investigation included the kindling model of epilepsy, a genetic form of epilepsy and long-term potentiation (LTP) of neuronal activity. The study also includes a discussion of the possible roles of a neuron-specific calcium-binding protein (CaBP). The findings are summarized as follows: 1) The distribution of CaBP was determined in cortical areas of the rat using a specific radioimmunoassay. The protein was found to have an unequal distribution in various cortical areas with preponderence in ventral structures. 2) Extending previous studies on the role of CaBP in kindling-induced epilepsy, its decline was correlated to the number of evoked afterdischarges (AD's) during the process of kindling. 3) Marked changes in CaBP levels were also found in the brains of the epileptic strain of mice (El). The hippocampal formation and the dorsal occipital cortex contained significantly lower CaBP than the control (CF-1) strain. The induction of seizures further decreased the levels of CaBP in the El mice. These findings are indicative of a possible genetic impairment of neuronal Ca²⁺ homeostasis in the El strain. 4) The levels of total hippocampal Ca²⁺ and Zn²⁺ were measured by atomic absorption spectrophotometry in control and commissural-kindled animals. While no change was found in the total Ca²⁺ content of the region, hippocampal Zn²⁺ of kindled preparations was found to be significantly elevated. 5) To measure Ca²⁺ -homeostasis, the kinetic analysis of ⁴⁵Ca uptake curves was undertaken in the in vitro hippocampus. This technique was found to be a valid method for assessment of Ca²⁺-regulation in the CNS under both physiological and pathophysiological conditions. The effect of various extracellular Ca²⁺ concentrations, 2,3-dinitrophenol (DNP), calcitonin, nifedipine and 3-isobutyl-1-methylxanthine (IBMX) on ⁴⁵Ca uptake curves was examined in order to identify the two exchangeable Ca²⁺ pools derived through kinetic analysis. 6) The kinetic analysis of ⁴⁵Ca uptake curves revealed that Ca²⁺-regulation of the hippocampus is impaired following amygdala- and commissural kindling. The changes reflect an enhancement of a Ca²⁺ pool that includes free cytosolic Ca²⁺ and a concomitant decrease in the amount of buffered calcium probably as a result in the decrease of hippocampal CaBP levels. 7) A novel form of long-term potentiation (LTP) of neuronal activity in the CA1 region of the hippocampus is described. Perfusion of 100 uM of IBMX in the hippocampal slice preparation induced a long lasting increase in the amplitude of the stratum radiatum evoked population spike and EPSP responses with changes in synaptic efficacy as indicated by the altered input/output relationships. Intracellular correlates of IBMX-induced LTP included lowering of synaptic threshold and enhancement of the rate of rise of the EPSP with no alterations in the passive membrane characteristics of CA1 pyramidal neurons. The fact that IBMX was able to exert its effect even in the presence of the calcium-blocker cation Co²⁺, taken together with the drug's action on hippocampal exchangeable Ca²⁺, raises the possibility that the Ca²⁺ necessary for induction of LTP may be derived from an intraneuronal storage site. These studies indicate the significance of intracellular Ca²⁺ -regulatory mechanisms in long-term changes of neuronal excitability which occur in experimental models of epilepsy and long-term potentiation. / Medicine, Faculty of / Cellular and Physiological Sciences, Department of / Graduate

published_or_final_version / Zoology / Master / Master of Science

Bibliography: leaves 179-231. / xv, 234 leaves : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / The aim of this thesis is to characterise the oophorectomised rat model for post menopausal bone loss by determining the effect of oophorectomy on calcium balance and the components of calcium balance in young and adult rats. The study utilises the metabolic calcium balance technique for this purpose. Many of the characteristics of the animal model are described particularly in terms of the effects of oophorectomy on bone histomorphometry and metabolic markers of bone turnover. The study characterises the changes in calcium balance and its components through the growth period. / Thesis (Ph.D.)--University of Adelaide, Dept. of Physiology, 1996

A series of three balance experiments were conducted to study the effect of the addition of animal fat to the diet on the utilization of calcium by growing chicks. In two experiments, the chicks were fed diets containing four levels of calcium, 0.75%, 1.0%, 1.25% and 1.50%, with a calcium: phosphorus ratio of 1.7:1. A fifth treatment was fed in which the top calcium level was adjusted to provide a calcium:phosphorus ratio of 2.5:1. All diets fed contained an excess of Vitamin D. Each of the five mineral treatments was fed as a control diet, to which no supplemental fat was added, and as a high fat diet, in which 8% of ground cellulose was replaced by 8% animal fat. In one experiment the diets contained 24% protein. In the other, the protein level was reduced to 20.6%. In the third experiment, to clarify the effect of adjusting the calcium:phosphorus ratio in the diet, three levels of calcium were fed with calcium:phosphorus ratios of approximately 1.5:1 and 2:1. As in the previous experiments, the different mineral levels were fed as low fat diets, and as high fat diets containing 8% animal fat. The diets fed in this experiment contained 23.6% protein. Criteria of calcium utilization used in all these experiments were rate of growth, feed efficiency, calcium balance (% of calcium retained) and calcium retention (calcium retained per 100 grams of gain in body weight). In addition, in the first two experiments, the percentage of bone ash was determined on a sample of chicks from each group at the conclusion of the experiment. It was found that: 1. The calcium requirement for growth and feed efficiency was not affected by the addition of 8% animal fat to the diet. The calcium requirement for maximum growth when the diet contained 24% protein appeared to be between 1.0 and 1.25% of the diet. All levels of calcium fed provided equal growth with diets containing 20.7% protein. 2. The addition of 8% fat to the diet significantly impaired bone calcification when the diet contained 24% protein. No impairment was evident at the 20.7% protein level. Diets containing 1% calcium provided calcification equal to that provided by diets containing 1.25% or 1.5% calcium. 3. Calcium balance (% of calcium retained) was found to be influenced excessively by differences in feed efficiency. A more useful index of calcium utilization was calcium retention, expressed in terms of body weight. 4. The addition of 8% animal fat to the diet impaired calcium retention (expressed as calcium retained per unit gain in weight) when the diet contained 1% to 1.5% calcium. In the case of the low fat diets, calcium retention rose as the level of calcium in the diet was increased to 1.25%, and remained constant as the calcium level was increased further to 1.5%. When fat was added to the diet, calcium retention rose more slowly as the calcium level was increased, and failed to reach the maximum retention of the low fat diets. The degree to which calcium retention was reduced was not sufficient to affect growth, in the presence of vitamin D above the usual allowance. 5. The addition of 8% animal fat to diets containing 24% protein increased the rate of growth and improved feed efficiency. The addition of fat to diets containing 20.7% protein did not affect the rate of growth and had little, if any, effect on feed efficiency. 6. Adjusting the calcium:phosphorus ratio of the diet within the limits tested did not affect growth, calcification, or calcium retention. / Land and Food Systems, Faculty of / Graduate

This study has shown that season, salinity, temperature and intertidal height all affect the rate up calcium uptake by mussels. For summer-adapted mussels, calcium uptake was found to be temperature dependent over the range of acute temperatures measured (1°-23°C). When subjected to a range of salinities over a three week period, summer-adapted mussels showed calcium-uptake rates which were salinity dependent from 25%-75% SW, and which did not show any increase in uptake rate in salinities greater than 75% SW. For winter-adapted mussels, calcium uptake was temperature independent over a temperature range from 5°-l7°C. At higher and lower temperatures, uptake was reduced. When subjected to a range of salinities over a three-week period, winter-adapted mussels were also unable to compensate for the lower concentration of calcium in the seawater, and did not show any increase in the uptake rate in salinities greater than 75% SW. It was found that high and low intertidal mussels had different calcium uptake rates, and that transplantation could alter the uptake rate of transplanted mussels to the uptake rate of untransplanted controls. In the intertidal zone a gradient of shell size was found, which could be associated with the change in uptake range over the intertidal range. Differences in immersion time between the two. sites could not explain all of the differences in uptake rate, but high intertidal mussels were found to have less total dry weight of soft parts than low mussels, and correcting for this difference accounted for the the remainder of the difference in calcium-uptake rate between the two sites. The soft parts of the mussel were found to become saturated with ⁴⁵Ca after four hours, while the shell accumulated calcium for the duration of the experiment. The mantle and gill tissue held the same amount of calcium when corrected for differences in weight, while the viscera held a greater pool of calcium. Accounting for real increases in the amount of calcium accumulated by the shell showed that the uptake rates reported in this study are about 59% of the absolute uptake rates. / Science, Faculty of / Zoology, Department of / Graduate