Browsing by Subject "carbohydrate"
Now showing 1 - 4 of 4
Results Per Page
Sort Options
Item Diet-mixing in a Generalist Herbivore: Trade-offs Between Nutrient and Allelochemical Regulation(2014-05-07) Le Gall, MarionDespite decades of research, many key aspects related to the physiological processes and mechanisms insect herbivores use to build themselves remain poorly understood, and we especially know very little about how interactions among nutrients and allelochemicals drive insect herbivore growth processes. Understanding the physiological effects of these interactions on generalist herbivores is a critical step to a better understanding and evaluation of the different hypothesis that have been emitted regarding the benefits of polyphagy. I used both lab and field experiments to disentangle the respective effect of protein, carbohydrates and allelochemicals on a generalist herbivore, the grasshopper Melanoplus differentialis. The effect of protein and carbohydrates alone were examined using artificial diets in choice and no-choice experiments. Results were plotted using a fitness landscape approach to evaluate how protein-carbohydrate ratio and/or concentration affected performance and consumption. Growth was best near the self-selected ratio obtained from the choice experiment, most likely due to the fact that the amount of food digested was also higher on that ratio. By contrast, development time was not best near the preferred ratio most likely due to the trade-off existing between size and development time. These results illustrate how nutrient availability can shape an ecological trade-off: growing big or growing fast. When an allelochemical (gramine, an alkaloid commonly found in grass) was introduced to the artificial diets, it had an interactive effect with protein and carbohydrates on performance and consumption and performance were generally improved on diets that contained higher amount of protein. Host plants of two wild populations were determined by gut content analysis and fed in choice and no-choice experiment. First the plant material was dried and ground and its protein, carbohydrate, terpenoid and phenolic content analyzed. Both populations regulated for the same protein-carbohydrate intake. However performance was different, due to variation in plant allelochemical content. This demonstrated for the first time that nutrient regulation, not toxin dilution, is directing food selection behavior in a generalist herbivore. Finally the role of macronutrients was analyzed in a context of cost of detoxification by measuring microsomal p450 production in the presence/absence of gramine. In the presence of choice, nutrient regulation was altered when gramine was present in the protein-biased diet. In the absence of choice, insects performed better on carbohydrate biased diet. I found that gramine elevated the level of microsomal protein in the fat body.Item Effects of Higher Carbohydrate or Higher Protein Diets with Exercise on Individual Risk Factors of Metabolic Syndrome in Women(2014-03-18) Lockard, BrittanieThe purpose of this analysis was to determine whether following a higher protein (HP) diet for 10-weeks promotes a reduction of MetS and the individual NCEP ATP III MetS risk factors better than a higher carbohydrate (HC) diet, when combined with an exercise program. 633 women (age 46.2?11.4 yrs, height 163?7 cm, weight 92.7?18 kg, BMI 34.8?6 kg/m^(2)) were assigned either a HP or HC diet in conjunction with 30 minutes of circuit-style exercise 3x/wk for 10-weeks. Participants consumed 1,425?355 kcal/day while the HP group (N=371) consumed 1.14?0.5, 1.41?0.7, and 0.63?0.3 g/kg/d CHO, PRO, fat and the HC group (N=292) consumed 0.78?0.3, 2.20?0.7, and 0.60?0.2 g/kg/d. Participants were retrospectively categorized as apparently healthy (N=377) or metabolic syndrome (?3 MetS risk factors, N=286). Body composition, anthropometrics, resting energy expenditure, lipid profiles, markers of glucose homeostasis, and fitness parameters were assessed at 0 and 10 weeks. Data were analyzed using ANOVA or MANOVA for repeated measures. The HP group experienced a greater decrease in scanned mass (HP -3.9?3.5, HC -3.0?3.5 kg, p=0.002), fat mass (HP-3.1?2.7, HC -2.4?2.8 kg, p=0.003), weight (HP -4.3?3.6, HC -3.2?3.4 kg, p<0.001), and body mass index (HP -1.6?1.3, HC -1.2?1.3 kg/m^(2), p<0.001), and tended to experience a greater decrease in waist circumference (HP -4.0?5.7, HC -3.2?5.7 cm, p=0.07). Individuals with MetS experienced greater decreases in weight (AH -3.6?3.4, MS -4.2?3.6 kg, p=0.054), body mass index (AH -1.3?1.3, MS -1.6?1.3 kg/m2, p=0.046), systolic blood pressure (AH -0.5?13.3, MS -5.9?16.0 mmHg, p<0.001), diastolic blood pressure (AH -0.4?8.9, MS -4.1?10.5 mmHg, p<0.001), triglycerides (AH -0.00?0.47, -0.23?0.73 mmol/L, p<0.001), and glucose (AH +0.01?0.73, MS -0.24?1.19 mmol/L, p=0.001) and a trend towards a greater decrease in scanned mass (AH -3.3?3.5, MS -3.8?3.5 kg, p=0.07) and lean mass (AH -0.56?2.0, MS -0.89?2.0 kg, p=0.07). Results indicate that participants following the HP diet experienced more favorable changes in body composition and triglyceride levels, and that participants with MetS have greater room for improving markers of health on a diet and exercise protocol.Item Influence of exogenous effectors of invertase activity on rice physiology and growth(2009-05-15) Rounds, Elliott WilsonCarbon flow into developing ovaries has been reported to be important in seed retention and seed size. Invertase, which cleaves sucrose into glucose and fructose has been shown to be important in rapidly expanding tissue, such as early root growth or during tiller expansion. The manipulation of invertase activity with over-the-top applications of agrochemicals may prevent the detrimental effects of abiotic stress by altering the source/sink relationship. These experiments examined economically important tissues in rice production during critical developmental stages under abiotic stress. Field and greenhouse studies were conducted under normal growing conditions using local management practices. Plants were treated with exogenous chemicals that affect the activity of invertase during the early-grain fill stage on field grown plants. Other plants were exposed to elevated nighttime temperature of 30?C for 4 d using a free-air, infrared heating device in the greenhouse. Rice was also treated at mid- to late-grain fill stage of the main crop to identify the impact of the exogenous chemicals on developing ratoon tiller buds. The activity of soluble acid invertase (SAI), concentrations of glucose, fructose, sucrose, and starch were determined in penultimate leaves, panicles, and main-crop stem segments during ratoon tiller bud expansion, using the enzyme-coupled stoichiometric production of NADH measured spectrophotometrically at 340nm. The results suggest SAI, carbohydrates, and agronomic characters are influenced by exogenous chemicals at the applied rates. The thidiazuron treatment caused an unidentified stress event. The stress was confirmed by increased hexose concentration and the proportion of hexose concentration to sucrose concentration. This stress reduced the main-crop grain yield, but not the ratoon yield or total grain yield. An interaction between the ammonium molybdate treatment and high nighttime temperature was seen in the panicle. The ranked difference was reduced by the high nighttime temperature from the ambient nighttime temperature for the SAI activity, TSC content, starch content, and TNC content. The tested chemicals and rates are not appropriate for commercial rice production because the effect of the exogenous chemicals do not appear to consistently aid rice plants to counteract the detrimental effects of abiotic stress.Item Insect Herbivore Stoichiometry: The Effect of Macronutrient Quantity, Ratio, and Quality (Orthoptera: Acridae, Schistocerca americana)(2011-02-22) Boswell, Andrew William PayneThe field of ecological stoichiometry has been dominated by studies focusing on aquatic & benthic microinvertabrates with less attention given to herbivorous insects. These organisms rely on their food source(s) to supply all of the building blocks (elements) they need in order to complete their life cycle. Since insect herbivores do not have the same elemental composition as the plants they use for food the question arises; of how they go about building themselves. We investigated what happened when grasshoppers were fed diets with various macronutrient profiles, their total amounts, and when the protein quality varied. We discovered that under controlled conditions when using a high quality protein source that grasshoppers are able to maintain a strict level of elemental homeostasis, but that the elements directly related to manipulations made in the food seem to vary (carbon, which is associated with carbohydrates and nitrogen, associated with protein). We also discovered that when the quality of protein changes an immature grasshoppers elemental stoichiometry loses some of this strict homeostatic regulation.