• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 1
  • Tagged with
  • 4
  • 4
  • 3
  • 3
  • 3
  • 2
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Developmental Gene Expression in the Small Intestine of Chickens from Lines Divergently Selected for High or Low Juvenile Body Weight

Miller, Carin R. 23 October 2007 (has links)
Nutrient transporters in the small intestine are responsible for dietary nutrient assimilation and therefore the expression of these transporters can influence the overall nutrient status as well as the growth and development of the animal. This thesis examined correlated responses to selection in the developmental gene expression of the peptide transporter PepT1, the glutamate/aspartate transporter EAAT3, the sodium-dependent glucose transporter SGLT1, and the fructose transporter GLUT5 in the small intestine of chickens from lines divergently selected for high (HH) or low (LL) eight-week body weight and their reciprocal crosses, (HL and LH). Chicks were weighed and killed on embryonic day 20 (E20), day of hatch (DOH with no access to feed), and days 3 (D3), 7(D7), and 14 (D14) post hatch. Duodenum, jejunum, ileum and liver were collected. DNA extracted from liver was used to sex birds by PCR. RNA was extracted from the intestinal segments of four males and four females from each mating combination (MC) and time point except E20 HL males (n = 3) and D7 LL females (n = 2). Expression of nutrient transporters was assayed by real-time PCR using the relative quantification method. In comparing HH and LL males and females there was a line by segment interaction in PepT1 gene expression, with no segment difference in HH and greatest expression in the ileum of the LL (P < 0.05). There was also a MC by age by sex interaction for PepT1 gene expression (P < 0.0001) with peak gene expression occurring on DOH for LL females, on D7 for HH females, on D7 for LL males and D14 for HH males. Overall, females had greater EAAT3 expression (P < 0.03). Gene expression of EAAT3 was greatest in the ileum, intermediate in the jejunum, and least in the duodenum (P < 0.0007). There was an age by segment interaction for EAAT3 expression (P = 0.0002) and a MC by segment interaction (P < 0.02), with LL having greater expression than HH in the ileum. Females had greater SGLT1 expression than males (P < 0.0001). There was a sex by age interaction for the expression of SGLT1 (P < 0.0001). Females induced SGLT1 expression on DOH and maintained this level through D14, while males gradually increased expression through D7 and decreased expression by D14. These results indicate that expression of PepT1, EAAT3, SGLT1 are differentially expressed in male and female chickens regardless of selection for high or low juvenile body weight. These results also show a sexual dimorphism in the capacity to absorb peptides, anionic amino acids, and glucose from the intestine, which has implications for the poultry industry with regard to diet formulations for straight-run and sex-separate grow-out operations. In comparing male HH, HL, LH, and LL chicks, overall LL had the greatest level of expression (P <0.06), HH had the least level of expression (P < 0.006) and HL and LH had intermediate levels of expression (P < 0.06). Greatest PepT1 gene was expression in the ileum (P < 0.0003) and there was a MC by segment interaction with expression increasing from duodenum to ileum in LL, but there was no segment difference in any other MC (P < 0.08). Within each intestinal segment there was a MC difference (P < 0.02). There was an effect of sire for PepT1 expression, with progeny from low weight selected sires (LWS) having greater expression than progeny from high weight selected (HWS) sires (P = 0.0008). There was no difference between intestinal segments in progeny from HWS sires, however, greatest PepT1 gene expression was seen in the ileum of progeny from LWS sires (P < 0.0001). Overall, expression of EAAT3 was greatest in the ileum, intermediate in the jejunum and least in the ileum (P < 0.0001) and there was a segment by age interaction for EAAT3 expression (P < 0.0001). In all MCs except HH, EAAT3 gene expression increased from duodenum to ileum (P < 0.08). Within the ileum, the LL had greatest EAAT3 gene expression, LH and HL had intermediate gene expression, and HH had least expression (P < 0.08). Expression of SGLT1 gradually increased through D7 and decreased by D14 (P < 0.0001) and overall, was greatest in the distal small intestine (P < 0.0001). There was a MC by segment interaction, with SGLT1 gene expression being greatest in the distal small intestine in LL, LH, and HL, but greatest in the jejunum of HH (P < 0.04). Within the ileum, LL had greater SGLT1 gene expression than HH (P < 0.06). Overall, greatest GLUT5 expression was in the distal small intestine (P < 0.0001) and there was a MC by segment interaction, with expression being greatest in the distal small intestine in LL and HL (P < 0.02), greatest in the ileum of LH (P < 0.08), and greatest in the jejunum of HH (P < 0.09). Within the ileum there was a MC difference (P < 0.07). These results indicate that selection for high or low juvenile body weight may have influenced the gene expression pattern of these nutrient transporters in the small intestine, which may contribute to the overall differences in the growth and development of these lines of chickens. / Master of Science
2

EXPRESSION OF PORCINE INTESTINAL NUTRIENT TRANSPORTERS ALONG CRYPT-VILLUS AXIS AND DURING POSTNATAL DEVELOPMENT

Yang, Chengbo 08 January 2011 (has links)
This research was conducted to investigate the expression of porcine intestinal nutrient transporters along the neonatal crypt-villus axis and during the postnatal development. First, we examined the transport kinetics of Na+-glucose co-tranporter 1 (SGLT1) and Na+-dependent neutral amino acid (AA) transporter B0AT1 and then the protein and mRNA abundances of SGLT1, B0AT1 and Na+-dependent neutral AA exchanger ASCT2 along the jejunal crypt-villus axis in the neonatal pig and the potential mechanisms associated with their regulations. Our results suggested that: 1) high levels of apical maximal SGLT1 and B0AT1 uptake activities were shown to exist along the entire jejunal crypt-villus axis in the neonatal pig; 2) there were no significant differences in the SGLT1, B0AT1 and ASCT2 protein abundances in spite of their different mRNA abundances among the crypt-villus axis, suggesting unique posttranscriptional regulatory mechanisms; and 3) global protein translational efficiency, as assessed by examining some of the key protein translational initiation and elongation factors, was higher in the crypt cells than in the upper villus cells, likely playing a regulatory role for maintaining apical nutrient transporter abundances in crypt cells of the neonate. Second, we further examined the protein and mRNA abundances of jejunal neutral AA transporters B0AT1 and ASCT2 and acidic AA transporter EAAC1 during the postnatal development in pigs at the ages of d 1, 4, 6, 12, 20, 28 (1-wk post-weaning), and 70 (mature gut at grower phase), respectively. Our results showed that the jejunal apical B0AT1, ASCT2 and EAAC1 protein abundances were dramatically decreased during the postnatal development and were likely regulated at both the transcriptional and post-transcriptional levels. These substantial decreases in the small intestinal apical Na+-dependent AA transporter abundances may contribute to increased intestinal microbial catabolism of AA, which may be partially responsible for the reduced whole body efficiency of nitrogen utilization during the postnatal growth in pigs. Collectively, our results suggest that apical nutrient transporters SGLT1, B0AT1 and ASCT2 are abundantly expressed along the entire jejunal crypt-villus axis in the neonatal pig, whereas abundances of jejunal apical AA transporters EAAC1, B0AT1 and ASCT2 declined substantially during the postnatal growth in pigs.
3

Dietary and Developmental Regulation of Nutrient Transporter Gene Expression in the Small Intestine of Two Lines of Broilers

Gilbert, Elizabeth R. 04 September 2008 (has links)
To better understand the digestive and absorptive capacities of the chick intestine so that we may feed diets that better meet the nutritional needs of the chick, it is important to understand how expression of nutrient transporter genes changes in response to various factors. A series of feeding trials were conducted to evaluate the dietary and developmental regulation of nutrient transporter mRNA abundance in the small intestine of two lines of broilers selected on corn-based (Line A) or wheat-based (Line B) diets. Abundance of mRNA was quantified in all experiments using real time PCR and the absolute quantification method. The objective of the first study was to investigate intestinal nutrient transporter and enzyme mRNA in Line A and B broilers at embryo day 18 and 20, day of hatch, and d 1, 3, 7, and 14 posthatch. Genes evaluated included the peptide transporter, PepT1, 10 AA transporters (rBAT, bo,+AT, ATBo,+, CAT1, CAT2, LAT1, y+LAT1, y+LAT2, BoAT and EAAT3), four sugar transporters (SGLT1, SGLT5, GLUT5, and GLUT2), and a digestive enzyme, APN. For PepT1, Line B had greater quantities of mRNA compared with Line A (P = 0.001), suggesting a greater capacity for absorption of AA as peptides. Levels of PepT1 mRNA were greatest in the duodenum (P < 0.05), whereas the abundances of SGLT1, GLUT5 and GLUT2 mRNA were greatest in the jejunum (P < 0.05). Abundances of EAAT3, bo,+AT, rBAT, BoAT, LAT1, CAT2, SGLT5 and APN mRNA were greatest in the ileum (P < 0.05). Quantities of PepT1, EAAT3, BoAT, SGLT1, GLUT5, and GLUT2 mRNA increased linearly (P < 0.01), while CAT1, CAT2, y+LAT1, and LAT1 mRNA decreased linearly (P < 0.05) with age. The objective of the second study was to evaluate the effect of dietary protein quality on intestinal peptide, AA, and glucose transporter, and digestive enzyme mRNA abundance in Line A and B broilers. At day of hatch (doh), chicks from both lines were randomly assigned to corn-based diets containing 24% crude protein (CP) with either soybean meal (SBM) or corn gluten meal (CGM) as the supplemental protein source, ad libitum. Groups of chicks from both lines were also assigned to the SBM diet at a quantity restricted to that consumed by the CGM group (SBM-RT). Abundance of PepT1, EAAT3, and GLUT2 mRNA was greater in Line B (P < 0.03), while APN and SGLT1 were greater in Line A (P < 0.04). When feed intake was equal (CGM vs restricted SBM), a greater abundance of PepT1 and bo,+AT mRNA was associated with the higher quality SBM (P < 0.04), while a greater abundance of EAAT3 and GLUT2 mRNA was associated with the lower quality CGM (P < 0.01). When feed intake was restricted (SBM vs SBM-RT), a greater abundance of PepT1 mRNA was associated with the restricted intake (P < 0.04). The objective of the third study was to determine the effect of dietary protein composition on mRNA abundance of peptide and AA transporters, and a digestive enzyme. From day 8 to day 15 posthatch, Line A and B broilers were fed equal amounts of 1 of 3 diets (24% CP). Dietary protein sources included whey protein concentrate (whey), a partial whey hydrolysate (hydro), or a mixture of free amino acids (AA) similar to the composition of whey. Intestine was collected at days 8, 9, 11, 13, and 15. Expression of all genes except LAT1 was greater (P < 0.05) in Line B compared with A. Abundance of PepT1, EAAT3, y+LAT2, CAT1, bo,+AT, and APN mRNA varied little across diets in Line A but for CAT1 mRNA was greatest (P = 0.005) in Line A birds that consumed the AA diet. Expression of these genes was greatest (P < 0.006) in Line B birds consuming the hydro diet. A greater (P < 0.05) age response of bo,+AT, EAAT3, CAT1, and APN mRNA was observed in birds consuming the hydro or AA diets relative to the whey diet. Results from these studies collectively demonstrate that nutrient transporter gene expression is responsive to a variety of factors, including developmental stage, dietary manipulation, and genetic selection. Information from these studies can be used to improve dietary formulation so that nutrient utilization is enhanced, resulting in improved growth of the broiler. / Ph. D.
4

Distribution and Relative Abundance of Nutrient Transporter mRNA in the Gastrointestinal Tract of Black Bears

Gilbert, Elizabeth R. 18 August 2005 (has links)
Black bears are omnivorous, and tend to be opportunistic feeders, in that they will eat what is readily abundant or available. The end-products of intestinal digestion are absorbed by the body through the action of transporter proteins expressed on the brushborder membrane of small intestinal epithelial cells. The goal of this study was to increase the understanding of the physiological processes associated with nutrient assimilation by black bears. Distribution and relative abundance of mRNA of a peptide transporter (PepT1), a glucose transporter (SGLT1), two AA transporters (NBAT, bo,+AT), and a digestive enzyme, aminopeptidase N (APN), in the intestinal tract of black bears were investigated. Ten bears were used for this study. For tissue collection, the intestine was removed from the animal and divided into five sections. Each collected section was opened longitudinally, rinsed in ice-cold PBS, and the mucosal scrapings were stored at -80&#61616;C. Total RNA was extracted and quantified by spectrophotometry. Abundance of PepT1, SGLT1, NBAT, bo,+AT, and APN mRNA was determined by performing Northern blots, using bear cDNA probes. Northern blot data were quantified by densitometric analysis, with the abundance of each gene expressed relative to GAPDH. Abundance of PepT1 (P < 0.05), APN (P < 0.05), and SGLT1 (P < 0.0001) changed quadratically from the proximal to the distal intestine with abundance being greatest in the midregion. Abundance of bo,+AT mRNA increased linearly (P < 0.05) from the proximal to distal intestine. Abundance of NBAT mRNA did not change among intestinal segments.The absolute number of molecules of mRNA/ng of total RNA for each gene was determined using Real-Time PCR. Similar to the Northern results, abundance of PepT1 (P < 0.0003), SGLT1 (P < 0.0003), and APN (P < 0.02) changed quadratically from the proximal to distal intestine with abundance being greatest in the mid-region, and bo,+AT mRNA increased linearly (P < 0.0001) from the proximal to distal intestine. NBAT mRNA abundance also increased linearly (P < 0.0001) from proximal to distal intestine. PepT1 mRNA was present at tenfold or greater levels than AA transporter mRNA in all segments of the intestine, suggesting that di- and tripeptides constitute the major form in which AAs are absorbed. NBAT and bo,+AT mRNA abundance was greater towards the distal portion of the intestine, suggesting their importance in salvaging remaining unabsorbed AAs.These results indicate that the mRNA of nutrient transporters examined and APN are differentially expressed throughout the gastrointestinal tract of black bears, suggesting their involvement in nutrient assimilation. / Master of Science

Page generated in 0.1476 seconds