Browsing by Subject "glucose"
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Item Application and modeling of frequency-domain lifetime spectroscopy for microsphere-based optical glucose sensors(2009-05-15) Liang, FengA new glucose affinity sensor based on a homogeneous fluorescence resonance energy transfer (FRET) assay system was developed to monitor the competitive binding between concanavalin A (ConA) and dextran. The FRET quenching kinetics of the donor were analyzed from frequency-domain (FD) measurements as functions of both glucose and acceptor-protein concentrations using a F?rster-type decay kinetics model. The results showed that the FD measurements and donor decay kinetics can indicate quantitative changes in the presence of glucose at concentrations ranging from 0 to 224 mg/dL. The second set of experiments proved the feasibility of performing analyte sensing with FD lifetime spectroscopy using microsphere-based sensors in multiple scattering solutions. A well characterized pH-sensitive fluorophore was entrapped in poly(ethylene glycol) microspheres. The particles were then immersed in a buffered polystyrene solution of various pH. Measurements of phase shift and modulation of the generated and multiply scattered fluorescent light were acquired as the modulation frequency of the incident excitation light varied from 10 to 120 MHz. After the measured data were analyzed with the coupled diffusion equations, the obtained lifetimes from the scattering measurements matched values from non-scattering measurements. Lastly, a new two-speed Monte Carlo (MC) simulation was developed to predict light propagation through the sensors and thus was used to evaluate these sensors and to design these sensors for implantation. The model used random packing structure and considered geometric optics and two light propagation speeds. Experimental measurements of phase-shift and modulation of excitation light were made on a cubic phantom with non-fluorescent resin microspheres of 74 ?m diameter, and compared to those computed from the MC simulation. The results showed that the mean phase shift (PS) deviation was 0.736? and the mean amplitude deviation was 42%. Quantitative changes in detected fluorescence phase-shift and modulation were investigated for microsphere diameter, volume fraction, refractive index, and fluorophore lifetime. We also found that even though the sensitivity of PS change in the presence of scattering was the same as the value without scattering, the values of PS were magnified due to the scattering effects.Item Design and Verification of an Optical System to Interrogate Dermally-implanted Microparticle Sensors(2012-07-16) Long, RuiqiDiabetes mellitus affects 25.8 million Americans (8.3%) and over 300 million people worldwide. Clinical trials indicate that proper management of blood glucose levels is critical in preventing or delaying complications associated with diabetes. Thus, there is a common need to monitor and manage blood glucose properly for people with diabetes. However, the patients? compliance for recommended monitoring frequency is low due to the pain and inconvenience of current standard finger-pricking tests. To promote patient adherence to the recommended self-monitoring frequency, non-invasive/ minimally invasive glucose testing approaches are needed. Luminescent microparticle sensor is an attractive solution. For these sensors to be deployed in vivo, a matched optical system is needed to interrogate dermally-implanted sensors. This research project investigated the light propagation in skin and the interaction with implants using Monte Carlo modeling. The results of the modeling were used to design an optical system with high interrogation and collection efficiency (40~300 times improvement). The optical system was then constructed and evaluated experimentally. A stable skin phantom mimicking the optical properties of human skin was developed as a permanent evaluation medium to minimize the use of animals. The optical properties of the skin phantom matched the maximum published values of human skin in scattering and absorption over the spectral range of 540~700nm in order to avoid overestimation of the capability of the system. The significant photon loss observed at the connection between the designed system and a commercial spectrometer was overcome using two optimized designs: a two-detector system and a customized low-resolution spectrometer system. Both optimization approaches effectively address the photon loss problem and each showed good SNR (>100) while maintaining a sufficient system resolution for use with fluorescent materials. Both systems are suitable for luminescence measurement, because broad bands of the luminescent spectrum are of interest. In the future, either system can be easily modified into a more compact system (e.g. handheld), and it can be directly coupled to an analog-to-digital converter and integrated circuits offering potential for a single compact and portable device for field use with luminescent diagnostic systems as well as implanted sensors.Item Effects of carbohydrate applications on growth and vitality of live oak (Quercus virginiana)(2009-05-15) Martinez Trinidad, TomasUrban forests grow in stressful environments that can have negativerepercussions on tree energy reserves. The goal of this research was to evaluate theimpact of exogenously applied carbohydrates on growth and vitality of live oaks(Quercus virginiana P. Miller). An initial study focused on carbohydrate partitioningrevealed that annual mean glucose concentration in leaf tissues (49.55 mg?g-1 DW) wasalmost double that in twigs, trunks, or roots. Starch concentrations in roots and trunks(38.98 and 38.22 mg?g-1 DW of glucose, respectively) were higher during the dormantseason and approximately three times the concentrations found in other tissues. Aninvestigation of the effects of exogenous soil applications of glucose and starch on soilmicrobial activity revealed no significant differences using recoverable viable microbes.However, soil respiration was significantly increased (P<0.05) by glucose a week afterapplication, while higher starch concentrations (120 g?L-1) significantly increased(P<0.05) soil respiration after the fourth week. Although tree soil drenched withcarbohydrates in a different study showed significantly (P<0.05) greener leaf color, higher chlorophyll fluorescence, and increased soil respiration at higher concentrationsof starch (120 g?L-1), no significant differences were observed in photosynthesis or trunk,canopy, or root growth. Analysis of 13C signatures was unable to detect uptake ofexogenous carbohydrates. For trunk-injected trees with glucose and sucrose, trunkgrowth was significantly (P<0.05) increased by carbohydrate supplementation.Differences were also found in twig glucose content, root starch content, and chlorophyllfluorescence among overall concentration means. A study to compare field diagnostictools with carbohydrate laboratory analysis established that a portable blood glucosemeter can be used to measure glucose content in trees. However, ohmmeter,refractometer, chlorophyll fluorescence spectrometer, and iodine staining results did notcorrelate well with laboratory analysis of carbohydrate concentrations. Results fromthese studies reveal that soil applied carbohydrates can greatly increase soil microbialactivity, provide evidence that trunk-injected carbohydrates may improve growth andvitality of live oaks, and provide a new field diagnostic tool to increase the efficiency ofmeasuring carbohydrates in trees.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 Effects of Maternal Nutrition Manipulation on Mares and Their Foals(2013-03-14) Winsco, Kelly NPrevious research documented the fetus is sensitive to nutrition of the dam, but this has not been thoroughly investigated in horses. Objectives of the current studies were to determine effect of manipulation of maternal nutrition during the last third of pregnancy on mare performance, intake, hormones, foaling parameters, colostrum, and foal passive transfer of immunity and growth, and effects of supplemental arginine. Plane of nutrition influenced mare performance, and DMI was influenced by time with the first trial finding all mares consumed less in the 10th month of pregnancy compared to the 11th month, and the second trial finding all mares consumed less during the 11th month. Additionally, the second study determined arginine supplementation has no detrimental effects on DMI. Both studies indicated the dual marker system was sufficient at estimating DMI. Neither trial found an influence of treatment on foaling parameters or physical measurements obtained following parturition, and the second study determined arginine supplementation also did not affect foaling or measurements. The first study determined maternal nutrition did not affect foal growth or ADG. When colostrum quality was evaluated, the first study determined mares consuming only hay had increased specific gravity and Brix% indicating higher quality. This was confirmed by IgG analysis finding a tendency for increased IgG concentration. However, colostrum volume was not affected by nutrition, nor was total g IgG. The second study found contrasting results with greater specific gravity in mares on a high plane of nutrition, and a tendency for moderate plane of nutrition mares to have greater volume. Additionally, the second study determined that arginine supplementation does not influence colostrum volume or quality (measured by specific gravity or Brix %). In the first trial, maternal diets affected glucose and insulin AUC in mares, which altered insulin dynamics in the resulting foals. Foal insulin AUC and peak insulin concentration were greater in foals from mares supplemented with concentrate compared to foals from mares fed hay alone. These studies have provided a wealth of information to help elucidate the impact of maternal nutrition in late gestation on mares and their foals.Item Enhancement of a fluorescent sensor for monitoring glucose concentration in diabetic patients(Texas A&M University, 2007-04-25) Ibey, Bennett LukeThe need for overnight and continuous monitoring of glucose levels in diabetic patients is profound, especially among juveniles. Implantation of a chemical assay which responds optically to changes in glucose concentration shows promise as a technology capable of continuously monitoring blood sugar with little invasion into the body. Previous fluorescent chemical assays, based on the affinity binding reaction between Concanavalin A protein and dextran, performed well but suffered from limited dermal penetration. In this work, a novel replacement for the dextran molecule (glycosylated dendrimer) was fabricated and tested to determine if it would improve the overall response of the sensing chemistry to glucose. Experiments were carried out and it was found that the assay??????s functionality was based on the controlled aggregation of the Con A protein and the modified dendrimer molecule. This new assay proved to be specific to glucose, reversible, and independent of fluorophore dye attached to the protein. This research was furthered by encapsulation of the new assay into a PEG hydrogel which showed response to glucose but, due to leeching, did not perform well under repeated exposures. A new method for encapsulation was proposed based on poration of the hydrogel to create micropores capable of holding the assay chemistry and allowing it to react to incoming glucose, while the surrounding polymer restricted leeching. Preliminary results with previous assays proved the potential of a mannitol based poration procedure, but unforeseen complications in lyophilization of the new sensor assay restricted its completion. Due to instability of Con A in solution, it was hypothesized that the immobilization of it onto the surface of an active substrate would increase its stability overtime as seen in previous works. The immobilization procedure was performed on Con A for both polystyrene spheres and gold (nanoshells and colloid). Both results showed an adequate amount of protein on the surface of the particles, but little binding activity was demonstrated. Overall, the improvements to the sensor chemistry response were notable and the potential for stabilization and enhancement of the response through the use of an active substrate is promising.Item Glucose oxidation in heart-type fatty acid binding protein null mice(Texas A&M University, 2006-10-30) Adhikari, SeanHeart-type fatty acid binding protein (H-FABP) is a major fatty acid binding factor in skeletal muscles. Genetic lack of H-FABP severely impairs the esterification and oxidation of exogenous fatty acids in soleus muscles isolated from chow-fed mice (CHOW-solei) and high fat diet-fed mice (HFD-solei), and prevents the HFD-induced accumulation of muscle triglycerides. Here, we examined the impact of H-FABP deficiency on the relationship between fatty acid utilization and glucose oxidation. Glucose oxidation was measured in isolated soleus muscles in the presence or absence of 1 mM palmitate (simple protocol) or in the absence of fatty acid after preincubation with 1 mM palmitate (complex protocol). With the simple protocol, the mutation slightly reduced glucose oxidation in CHOW-muscles, but markedly increased it in HFDmuscles; unexpectedly, this pattern was not altered by the addition of palmitate, which reduced glucose oxidation in both CHOW- and HFD-solei irrespective of the mutation. In the complex protocol, the mutation first inhibited the synthesis and accumulation of triglycerides and then their mobilization; with this protocol, the mutation increased glucose oxidation in both CHOW- and HFD-solei. We conclude: (i) H-FABP mediates a non-acute inhibition of muscle glucose oxidation by fatty acids, likely by enabling both the accumulation and mobilidoes not mediate the acute inhibitory effect of extracellular fatty acids on muscle glucose oxidation; (iii) H-FABP affects muscle glucose oxidation in opposing ways, with inhibition prevailing at high muscle triglyceride contents.zation of a critical mass of muscle triglycerides; (ii) H-FABPItem Heart- and liver-type fatty acid binding proteins in lipid and glucose metabolism(Texas A&M University, 2004-11-15) Erol, ErdalHeart-type Fatty Acid-Binding Protein (H-FABP) is required for high rates of skeletal muscle long chain fatty acid (LCFA) oxidation and esterification. Here we assessed whether H-FABP affects soleus muscle glucose uptake when measured in vitro in the absence of LCFA. Wild type and H-FABP null mice were fed a standard chow or high fat diet before muscle isolation. With the chow, the mutation increased insulin-dependent deoxyglucose uptake by 141% (P<0.01) at 0.02 mU/ml of insulin, but did not cause a significant effect at 2 mU/ml insulin; skeletal muscle triglyceride and long chain acyl-CoA (LCACoA) levels remained normal. With the fat diet, the mutation increased insulin-dependent deoxyglucose uptake by 190% (P<0.01) at 2 mU/ml insulin, thus partially preventing insulin resistance, and completely prevented the threefold (P<0.001) diet-induced increase of muscle triglyceride levels; however, muscle LCACoA levels showed little or no reduction. With both diets, the mutation reduced the basal (insulinindependent) soleus muscle deoxyglucose uptake by 28% (P<0.05). These results establish a close relationship of FABP-dependent lipid pools with insulin sensitivity, and indicate the existence of a non-acute, antagonistic, and H-FABP-dependent fatty acid regulation of basal and insulin-dependent muscle glucose uptake. Liver fatty acid binding protein (L-FABP) has been proposed to limit the availability of chain LCFA for oxidation and for peroxisome proliferator-activated receptor (PPAR-alpha), a fatty acid binding transcription factor that determines the capacity of hepatic fatty acid oxidation. Here, we used L-FABP null mice to test this hypothesis. Under fasting conditions, this mutation reduced β-hydroxybutyrate (BHB) plasma levels as well as BHB release and palmitic acid oxidation by isolated hepatocytes. However, the capacity for ketogenesis was not reduced: BHB plasma levels were restored by octanoate injection; BHB production and palmitic acid oxidation were normal in liver homogenates; and hepatic expression of key PPAR-alpha target (MCAD, mitochondrial HMG CoA synthase, ACO, CYP4A3) and other (CPT1, LCAD) genes of mitochondrial and extramitochondrial LCFA oxidation and ketogenesis remained at wild-type levels. These results suggest that under fasting conditions, hepatic L-FABP contributes to hepatic LCFA oxidation and ketogenesis by a nontranscriptional mechanism.Item Influence of Maternal Plane of Nutrition and Arginine Supplementation on Mares and Their Foals: Glucose and Insulin Dynamics(2012-10-19) Hanson, AndreaThirty-two Quarter horse mares (468 to 668 kg BW; 3 to 19 yr) were utilized in a randomized complete block design. Animals were blocked by expected foaling date and randomly assigned to treatments within block. Treatments began 110 d prior to expected foaling date and were arranged as a 2 x 2 factorial consisting of two planes of nutrition, moderate (Mod; 0.5% BW as fed grain/d) or high (High; 1% BW as fed grain/d) and two levels of L-arginine supplementation, 0.21 g/kg BW/d (Arg) or no supplemental Arg (Con; L-alanine to maintain isonitrogenous diets). Mares were housed by block, allowed ad libitum access to water and coastal bermudagrass (Cynodon dactylon) hay, and fed commercial grain twice daily in individual stalls. A modified frequent sampling i.v. glucose tolerance test (FSIGT) was performed on mares during the 11th month gestation and on foals at 5 and 30 d of age. Jugular catheters were placed 1 h before FSIGT, and horses were allowed ad libitum access to bermudagrass hay and water throughout. After a baseline plasma sample was collected, a glucose bolus of 0.3 g/kg BW was administered. Blood samples were collected at 1, 2, 3, 4, 5, 6, 7, 8, 10, 12, 14, 16, and 19 min. At minute 20, an insulin bolus of 30 mU/kg BW was administered. Blood samples continued to be collected at 22, 23, 24, 25, 27, 30, 35, 40, 50, 60, 70, 80, 90, 100, 120, 150, and 180 min. Samples were placed into tubes containing sodium heparin, immediately placed on ice, and centrifuged within 20 min. Plasma was then collected, placed in microtubes and frozen at -20 degrees C for later analysis. Glucose concentrations were analyzed using a colorimetric assay and insulin concentrations determined using a commercial RIA kit. There was no influence of dietary treatment on mare glucose area under the curve (AUCg) or peak glucose (PG) and insulin (PI) concentrations (P >= 0.55). Mare insulin area under the curve (AUCi) tended to be influenced by the interaction between nutritional plane and ARG supplementation (P <= 0.06) with HighCon mares having greater AUCi than ModCon (P <= 0.05), and HighCon mares having greater AUCi than mares fed HighArg (P <= 0.05). Foal AUCg, AUCi, and PI were not influenced by maternal diet. However, PG concentration in foals tended to be influenced by mare AA supplementation with foals from Con mares having higher concentrations compared to Arg (P <= 0.09) An influence of age was observed on foal AUCg and AUCi. Foal AUCg was greater at 5 d compared to 30 d (P <= 0.003). Foal AUCi tended to be greater at 30 d compared to 5 d (P <= 0.08). Data suggest maternal plane of nutrition and arginine supplementation can alter mare and foal glucose and insulin dynamics.Item Insulin Sensitivity in Tropically Adapted Cattle With Divergent Residual Feed Intake(2012-10-19) Shafer, GentrieResidual feed intake (RFI) is one method to identify feed efficient animals; however, this method is costly and time consuming therefore, identifying an indirect measure of RFI is important. Evaluating the glucoregulatory mechanisms in cattle selected for divergent RFI may provide insight into metabolic processes involved in feed efficiency. This study evaluated the effect of a glucose (GLUC) challenge on efficient (LRFI) and inefficient (HRFI) tropically adapted bulls and heifers. Insulin (INS) secretion was determined by radioimmunoassay (RIA) and GLUC was determined by colorimetry. Insulinogenic index (IIND) was calculated as the ratio of INS to GLUC (I/G). Bonsmara heifers were evaluated in two experiments. Similar results were observed in both experiments. RFI affected (P < 0.05) INS response; with LRFI heifers having a greater INS response than HRFI heifers. Similarly, RFI affected (P < 0.05) IIND; with LRFI heifers having a greater IIND than HRFI heifers. In Santa Gertrudis bulls, RFI did not affect (P > 0.05) GLUC conc. or Ins. response; however, numerically HRFI bulls had a greater INS response than LRFI bulls. RFI affected (P < 0.05) IIND; with LRFI bulls having a lower IIND than HRFI bulls. In Brahman heifers (Exp 1), RFI did not affect (P > 0.05) GLUC concentration or INS. response; however, numerically HRFI heifers had a greater INS response than LRFI heifers. RFI affected (P < 0.05) IIND; with LRFI heifers having a lower IIND than HRFI heifers. In Brahman bulls (Exp 2), RFI affected (P > 0.05) INS response; with HRFI bulls having a greater INS response than LRFI bulls. RFI affected (P < 0.05) IIND; with LRFI bulls having a lower IIND than HRFI bulls. Bonsmara cattle evaluated for RFI had a response to an influx of exongenous glucose that was opposite to that observed in the Brahman and Santa Gertrudis cattle evaluated for RFI. Insulinogenic index was significantly different between RFI groups in each experiment. The lower amount of INS required for clearance of the GLUC from the circulation of the Brahman and Santa Gertrudis cattle fits with our hypothesis that more efficient cattle would require less INS than the less efficient cattle. Further research and studies need to establish glucoregulatory differences between breeds and sexes of cattle evaluated for RFI.