Browsing by Subject "Starch"
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Item Circadian clock gene expression and growth vigor in arabidopsis hybrids and mRNA stability in arabidopsis allotetraploids(2010-12) Kim, Eun Deok; Chen, Z. JeffreyHybrids and polyploids are very common in plants and some animals. Although hybrid vigor or heterosis has been widely adopted in agricultural practices, the underlying mechanisms are poorly understood partly because of their multigenic nature and the lack of a good model system for the study. Allotetraploidy is an emerging model system for investigating molecular mechanisms of hybrid vigor. An allotetraploid is formed by interspecific hybridization followed by chromosome doubling or hybridization between two autotetraploid parents and is genetically stable. A previous study showed nonadditive expression (different from the mid-parent value) of over 5% of genes in the allotetraploids, suggesting altered transcriptional and post-transcriptional regulation. Here oligo-gene microarray analysis of mRNA stability in allotetraploids was carried out to investigate how nonadditive gene regulation upon allopolyploidization is achieved at the posttranscriptional level. Approximately 1% of annotated genes were identified as unstable transcripts, and their estimated half-life is less than 60 minutes. The unstable transcripts in Arabidopsis allotetraploids are associated with nonadditive gene expression and with stress and environmental responses. The nonadditively expressed genes identified in the previous study include those encoding proteins involved in energy and metabolic pathways, which are putative targets of circadian clock regulators. To test how circadian clock genes affect downstream genes and pathways, expression of CIRCADIAN CLOCK ASSOCIATED1 (CCA1) was up- or down-regulated by overexpressing CCA1 or cca1(RNAi) driven by the promoter of TIMING OF CAB EXPRESSION 1 (TOC1). Upregulation of CCA1 was associated with repression of downstream genes in chlorophyll biosynthesis and starch metabolism, whereas down-regulation of CCA1 correlated with upregulation of these downstream genes. As a result, chlorophyll and starch content was ~10% higher in the TOC1::cca1(RNAi) transgenic plants than the controls, while the growth vigor is lower in the TOC1::CCA1 transgenic plants. To further test the effects of clock genes in growth vigor, CCA1 expression was examined in reciprocal hybrids of A. thaliana ecotypes. The maternal effect on starch content was observed in several combinations of hybrids, which was correlated with preferential expression of maternal CCA1 during early stages of seed development. Although the cause of parent-of-origin effects is still unclear, the data have clearly documented parent-of-origin effects on circadian clock gene expression and starch metabolism in hybrids.Item Development of a simplified process for obtaining starch from grain sorghum(Texas Tech University, 1969-05) Marshall, James TildenNot availableItem Raman studies of iodine-doped poly(vinyl alcohol) thin films(Texas Tech University, 1996-08) Sengupta, ArchitaNot availableItem Ruminant pancreatic exocrine function and influence of protein quality and quantity on intestinal starch assimilation(Texas Tech University, 1993-08) Castlebury, Ronald E.The primary goal of animal nutritionists working with animals used for human consumption is to meet nutritional requirements of the animal while at the same time trying to maximize gain and feed efficiency for obvious economical reasons. One nutritional factor that limits feed efficiency in ruminants, as compared to nonruminants, is their apparent inability to digest large quantities of starch in the small intestine. Numerous factors are involved in the extent and site of digestion of dietary starch in ruminants.Item Starch acetate as a film forming excipient in controlled drug delivery(Texas Tech University, 2004-08) Nutan, Mohammad Tawhidul HaqueThe present investigation highlighted the prospect of using starch acetate as an excipient for coating multi-particulate beads for controlled drug delivery. Starch acetate with high degree of substitution (dS) was synthesized from native com starch using the aqueous paste disintegration method followed by acetylation in pyridine. The dS value as determined by the saponification-titration method was about 2.9. The synthesized polymer was compared with the raw material, starch, by Fourier transform infrared (FTIR), X-ray and molecular mass analysis. The reaction showed high yield and was found to be almost complete The rheologic and interfacial properties of starch acetate solution in chloroform were performed. The solution appeared to be a pseudoplastic system, especially at higher concentrations (1.5-5.0 %). The surface tension of the solution (28.36-33.31 dyne/cm) was relatively unaffected by polymer concentration (0.5- 5%) at 20 °C. Free films obtained from starch acetate solution in the presence of 17 different plasticizers were characterized. Triacetin and triethyl citrate were the best among all common plasticizers tested in terms of physical appearance, mechanical strength and glass transition temperature of the films. Permeation of tritiated water through the films with triacetin was dependent on the extent of plasticization. It increased from 3.15x10"^ to 4.15x10"^ cm^/s when triacetin concentration was increased from 50 to 80%. Scanning electron microscopic (SEM) photographs revealed clear differences between smooth plasticized and rough unplasticized films. Prepared starch acetate was utilized to coat beads containing the model drug. The model drug, dyphylline was compatible with the core, Nu-pareil® inert beads, the binder, Opadry® and the anticaking agent, talc through thermal, FTIR and content analyses. Dmg loading was performed in a fluid bed coater with a bottom spray system. Drug-loaded beads were coated using starch acetate solution containing triacetin in the fluid bed coater. Seven formulation and process variables were screened by a Plackett- Burman statistical design. Coating weight gain, plasticizer concentration and curing temperature had greater influence than other factors on the in vitro drug release in a USP type-II dissolution apparatus over 12 h. A further optimization procedure was carried out using response surface methodology (RSM). A three factor, three level Box-Behnken design was employed for this purpose The three factors studied, coating weight gain (X\). Plasticizer concentration (X2) and curing temperature (X3), were found to correlate (R^2=99.61) with cumulative percent drug released after 12 h (Y5) by the regression equation, Y5 = 89.83 - 11.98X1 + 2.82X2 - 4.31X1^2 + 1 .90X1X2. Contour and response surface plots explained the interaction effects. Optimization was done by maximizing drug release over 12 h and placing constraints at dissolution time points of 0.5, 1, 4 and 8 hours. The optimized formulation (Xi=10%,X ^2=55%, X3=45 °C) showed a first-order release and was close to the predicted model in terms of the two commonly used fit factors, f1 and f2 values. A properly trained artificial neural network (ANN) was utilized as an alternative for optimization. A set of designed data were used as the input. Very low system error and more than 99% of train and test R^2 values indicated the strength of the procedure. The observed optimized data were in close agreement with the expected values with f1 and f2 values of 0.67 and 97.18, respectively. This showed that if properly utilized, ANN can compete with the popular experimental designs used in pharmaceutical study. Thermal, X-ray and infrared analyses suggested absence of any significant interaction of the drug with the excipients used in the optimized formulation. SEM photographs showed a continuous film over the bead covering the drug layer. Surface roughness of starch acetate coated beads at different coating level was used to determine the completion of coating. Minimum roughness was found at 3% coating level. The optimized bead also had low values of roughness parameters. The drug release pattern from the optimized formulation was unaffected by acidic environment or a-amylase An in vivo study in male Sprague-Dawley rats showed more sustained plasma dyphylline level as compared to drug powder, used as the control. The mean Cmax, Tmax andAUC for the formulation were calculated to be 5.70+0.56 μg/ml 4 h and 47.08+5.15 μg.h/ml, respectively, compared to 11.10±0.20 μg/ml, ≤1 h and 64.40±I0.63μg.h/ml for the control (n=6). The mean residence time of the drug increased significantly (p<0.05) for the controlled release product (6.2 versus 4.4 h). These results show that starch acetate with dS 2.9 may serve as a valuable addition to the list of polymeric excipients for controlled drug delivery of small organic molecules such as dyphylline.Item Synthesis and mobilization of carbohydrate in xylem parenchyma cells of cotton during water deficiency(2009-05) Roper, Becky Jo; Holaday, A. Scott; Payton, Paxton R.; Tissue, David T.; Zak, JohnThe aim of this study was to determine whether water deficiency affected the carbohydrate content of cotton xylem parenchyma cells and the total extractable activity of key enzymes associated with starch synthesis and mobilization and sucrose synthesis. Wild-type cotton (Gossypium hirsutum L. cv Coker 312) were subjected to well-watered, water-deficit, and re-watered treatments along with SPS+ cotton to determine whether the total sucrose phosphate synthase (SPS) activity and sucrose content of xylem parenchyma cells increased when the spinach gene for SPS is overexpressing in cotton. Cotton plants were grown to certain periods of development (seedling, flowering, or boll developing) and subjected to a gradual water deficit. Once these stages were determined and showed significant effect by water deficiency, the process was repeated on flowering cotton in the summer and autumn, and with boll developing cotton in the autumn. In these single stage experiments, half of the water deficient treated cotton were left to be re-watered for four days and sampled to determine the extent of the recovery of sink metabolism and photosynthate production. Leaf CO2-exchange measurements were conducted the day before sampling with pre-dawn leaf water status taken the day of sampling. Nodal xylem tissue with the bark removed were sampled, frozen, and stored in -85C until extraction analysis could be preformed. Activities of SPS, ADP-glucose pyrophosphorylase (AGPase), sucrose synthase (SucSyn), and amylase (fall boll only) from xylem tissue samples were determined and compared with the contents of hexose, sucrose, and starch. The results indicated that stored starch in the xylem parenchyma cells of cotton is catabolized (“mobilizedâ€) to hexose, glucose and fructose, for sucrose synthesis or other uses during water deficit stress. Water deficit stress in both types of cotton in all major stages of growth caused a decline in SucSyn and an increase in beta-amylase. This supports the hypothesis that sink carbohydrate metabolism can be downregulated and carbohydrate metabolism using stored reserves as a source of soluble sugars can be upregulated in xylem parenchyma cells during environmental stress. The information gained here will provide further insight on the possibility that starch reserves in xylem parenchyma cells can be modified to serve as sources of soluble carbohydrate for osmotic adjustment and growth of strong sinks (e.g., bolls) during water deficit stress.Item The effect of enzymes and starch damage on wheat flour tortilla quality(Texas A&M University, 2007-04-25) Arora, SapnaSpecific enzymes have been used to improve flour quality for bread but enzyme action in tortilla flour has not been investigated. Two different wheat flours were prepared into tortillas using laboratory-scale, commercial equipment with fixed processing parameters. Dough and tortilla properties were evaluated using subjective and objective methods. Tortillas were stored in plastic bags at 22????C for evaluation. The effects of nine enzymes (amyloglucosidase 1, amyloglucosidase 2, bacterial 1, bacterial 2, fungal, maltogenic 1, maltogenic 2, malted barley and xylanase) on quality of wheat flour tortillas were evaluated. Dough absorption was adjusted to attain uniform dough for tortillas. Enzyme addition to tortilla flour did not significantly affect tortilla weight, moisture and pH. Bacterial 2 amylase extended shelf stability while maltogenic 1 and xylanase exhibited smaller improvements in shelf stability and other tortilla properties. Addition of 0.05 activity unit bacterial 2 amylase improved tortilla diameter and improved tortilla shelf life from 12 to 28 days. Maltogenic 1 at 280 ppm improved tortilla diameter, opacity and shelf life. Addition of 100 ppm of xylanase effectively improved tortilla diameter and shelf life. Bacterial 1 amylase at 60 ppm improved tortilla diameter but did not improve shelf stability. Amyloglucosidase 2, maltogenic 2 and malted barley amylase did not improve tortilla quality at any of the evaluated levels. Amyloglucosidase 1 and fungal amylase reduced overall tortilla quality at all the evaluated levels. Bread-making quality of wheat flour is correlated with the damaged starch present in the flour. Damage was induced by grinding the samples for 0, 1, 4 and 8 hr to determine the effects of starch damage on tortilla quality. Processing increased starch damage of control tortilla flour from 5.4% to 12.6%. Damage starch increased dough water absorption, toughness and press rating and reduced diameter and opacity of tortillas. Damage starch improved tortilla rollability at higher levels but did not improve tortilla properties in combination with bacterial 2 amylase. Overall tortilla quality was not improved due to additional starch damage. Improved tortilla quality using bacterial 2 amylase at very low levels could be commercialized.