No description available.

No description available.

No description available.

No description available.

No description available.

The in vitro rate and cationic composition of the fluid secreted by the Malpighian tubules of the African migratory locust, Locusta migratoria migratoroides L, was investigated in this study. The concentrations of the elements Na, K, P, S, CI, Mg and Ca within Locusta Malpighian tubule type 1 cells, and the surrounding basement membrane, were quantified. Inhibitors and stimulators of fluid production were used to perturb the normal secretory state of the tubule cells. The rate of fluid secretion under control conditions was between 1.82 and 1.33. nl min(^-1) The fluid [K(^+)] was approximately 126mM, and [Na(^+)] 51 mM. The basement membrane was characterised by high [Na] and [CI] whilst a gradient of [K](_i) was observed. [K](_i) rose from approximately 193 mmol Kg(^-1) d.w. at the basal infoldings to 481 mmol Kg(^-1) d.w. at the apical microvillar border. The central cytoplasmic [K](_i) was 348 mmol Kg(^-1) d.w., estimated as 116mM. [Na](_i) and [Cl](_i) were generally lower, being 57mM and 29mM respectively in the central cytoplasm. Only K assumed a concentration gradient. Intracellular mass dense concretions were observed. Three types were present, the first rich in P and Ca, the second, rich in S, Na and K, and the third, rich in Mg, K and Na. The fluid production inhibitors furosemide (1mM) and bafilomycin A(_1) (1µM) raised the [N(^+)] in the secreted fluid, and altered [K](_i), [Na](_i) and [CI](_i). Furosemide lowered [K](_i) but increased [Na](_i) and [Cl](_i). Bafilomycin lowered [K(^+)] in the secreted fluid, though [K](_i) increased. Both inhibitors abolished the [K](_i) gradient. Replacing K(^+) with Rb(^+) in the bathing saline slowed fluid secretion and lowered [K](_i) and [Cl](_i), though a gradient of [K](_i) was retained. Rb adopted an intracellular gradient which mirrored that of K. Rate of secretion data suggests Rb enters the cell basolaterally primarily via the Na(^+)-K(^+)-ATPase. The fluid secretion stimulator cAMP (1mM) lowered [K](_i), and raised [Na](_i) and [Cl](_i), but corpora cardiaca extract left these elements' concentrations largely unchanged. Stimulation with both corpora cardiaca extract and cAMP maintained the [K](_i) gradient. These stimulators changed the content and number of mass dense concretions present, in manner which suggested that these structures were important in ion transport. These findings support the current model of ionic transport in these cells, including the basolateral presence of an Na(^+)-K(^+)-2Cr cotransporter, and an apical proton-pumping V-type ATPase / K(^+)/nH(^+) antiport complex.

This dissertation examined the phenotypic plasticity of endothermic, flight and respiratory physiology in response to developmental oxygen exposure in the moth Manduca sexta. Development in both 10% O2 hypoxia and 30% O2 hyperoxia treatments were used to look at the physiological consequence on both ends of the oxygen spectrum. Hypoxic insects reached smaller sizes as adults and had longer pupation lengths than controls. Hyperoxic insects were larger at the end of the larval stage, had increased larval growth rates, but also had longer developmental larval developmental times and pupation lengths than controls. There was a decrease in both metabolic rate and thorax temperatures of hypoxic reared insects at normoxic levels. In flight trials hypoxic insects had the lowest critical flight PO2, and the hyperoxic insects had the highest PO2. There was an increase in hypoxic insect flight muscle mitochondria oxygen consumption in permeabilized fibers, but this did not translate to the isolated flight muscle mitochondria metabolic rates. Rearing oxygen level did not significantly affect mitochondrial density and size; myofibril density and size, or tracheal density and size in flight muscle. Overall, I found that higher levels of organization were more susceptible to the effects of chronic oxygen exposure and found more effects of hypoxia than hyperoxia.

No description available.

The hemlock woolly adelgid (HWA), Adelges tsugae Annand (Hemiptera: Sternorrhyncha: Adelgidae) is a small invasive insect that frequently causes hemlock (Tsugae spp.) mortality in the eastern United States. Studies have shown that once healthy hemlocks become infested by the adelgid, nutrients are depleted from the tree, leading to both tree decline and a reduction of the adelgid population. Since A. tsugae is dependent on hemlock for nutrients, feeding on trees in poor health may affect the insect's ability to obtain necessary nutrients and consequently affect their population and physiological health. A cluster analysis, based on quantitative and qualitative tree health measurements, grouped sample trees into categories of lightly and moderately impacted trees. The A. tsugae population health on each tree was determined by measuring insect density, survival from aestivation, and peak fecundity. A. tsugae physiological health was determined similarly by measuring insect biomass, total carbon, carbohydrate, total nitrogen, and amino nitrogen. A. tsugae from moderately impacted trees exhibited significantly greater fecundity; however, A. tsugae from lightly impacted hemlocks contained significantly greater levels of carbohydrates, total nitrogen, and amino nitrogen. All A. tsugae physiological parameters increased significantly over time as the insects matured and reproduced regardless of tree health classification. While the results of the physiological analysis generally support our hypothesis that A. tsugae on lightly impacted trees are healthier than those on moderately impacted trees, this was not reflected in the population fitness measurements of the insects. Further examination of A. tsugae egg health may elucidate this apparent contradiction. / Master of Science in Life Sciences

No description available.