The splanchnic bed is a group of organs (liver, intestines, stomach, pancreas and spleen) which are active in the metabolism of amino acids. However, the impact of this group of organs on the dietary requirements of humans has yet to be determined. The focus of this research will be the requirements of two indispensable amino acids, threonine and lysine, and the impact of the splanchnic bed on amino acid kinetics. Threonine is an indispensable amino acid which is critical in the production of mucins in the gut and contributes significantly to collagen, elastin and tooth enamel formation in mammals. The first study was designed to determine the threonine requirement for the parenterally-fed, stable, post-surgical neonate. The mean threonine parenteral requirement, as experimentally derived in human neonates, was 32.8 mg•kg-1•d-1 which was less than the recommended enteral intake of 76 mg•kg-1•d-1 suggesting a splanchnic uptake in humans of 57%. Lysine is an indispensable amino acid used primarily, in the mammalian body, for protein synthesis but it also acts as a precursor for carnitine synthesis. The second study was devised to determine the lysine requirement for the parenterally-fed, stable, post-surgical neonate. The mean lysine parenteral neonatal requirement as experimentally determined in human neonates, was 104.9 mg•kg-1•d-1 which was less than the recommended enteral intake of 119 mg•kg-1•d-1 suggesting a splanchnic uptake in humans of 12%. The third study was intended to increase our knowledge of the metabolism of threonine and lysine by the splanchnic bed. Adult humans were fed isotopic threonine and lysine both enterally and parenterally. We determined that retention of threonine and lysine by the splanchnic bed was 16.7% and 17.1% respectively, which were not significantly different. The conclusion was that, in healthy human adult males, there was no difference in the extraction of threonine and lysine by the splanchnic bed which was different from our findings in parenterally fed piglets and human neonates.

The splanchnic bed is a group of organs (liver, intestines, stomach, pancreas and spleen) which are active in the metabolism of amino acids. However, the impact of this group of organs on the dietary requirements of humans has yet to be determined. The focus of this research will be the requirements of two indispensable amino acids, threonine and lysine, and the impact of the splanchnic bed on amino acid kinetics. Threonine is an indispensable amino acid which is critical in the production of mucins in the gut and contributes significantly to collagen, elastin and tooth enamel formation in mammals. The first study was designed to determine the threonine requirement for the parenterally-fed, stable, post-surgical neonate. The mean threonine parenteral requirement, as experimentally derived in human neonates, was 32.8 mg•kg-1•d-1 which was less than the recommended enteral intake of 76 mg•kg-1•d-1 suggesting a splanchnic uptake in humans of 57%. Lysine is an indispensable amino acid used primarily, in the mammalian body, for protein synthesis but it also acts as a precursor for carnitine synthesis. The second study was devised to determine the lysine requirement for the parenterally-fed, stable, post-surgical neonate. The mean lysine parenteral neonatal requirement as experimentally determined in human neonates, was 104.9 mg•kg-1•d-1 which was less than the recommended enteral intake of 119 mg•kg-1•d-1 suggesting a splanchnic uptake in humans of 12%. The third study was intended to increase our knowledge of the metabolism of threonine and lysine by the splanchnic bed. Adult humans were fed isotopic threonine and lysine both enterally and parenterally. We determined that retention of threonine and lysine by the splanchnic bed was 16.7% and 17.1% respectively, which were not significantly different. The conclusion was that, in healthy human adult males, there was no difference in the extraction of threonine and lysine by the splanchnic bed which was different from our findings in parenterally fed piglets and human neonates.

Thesis (Ph. D.)--Cornell University, January, 2009. / Vita. Includes bibliographical references (leaves 102-118).

Supplementation with graded levels of threonine to an all barley-lysine diet (0.75% total lysine) improved the daily gain, feed efficiency and carcass quality of growing-finishing pigs. An addition of 0.10% threonine produced the optimum growth response in the experimental animals. No additional improvement was obtained with higher levels of threonine or threonine plus methionine supplementation of the diet. The 0.10% level of threonine supplementation gave performance criteria which were comparable to those obtained with the barley-soybean control diet, except the former diet resulted in significantly higher backfat measurements. Threonine added at levels of 0.15% resulted in higher nitrogen retention than the other barley-lysine-threonine diets. Nitrogen retention on this diet did not differ significantly from the control diet. Barley-amino acid diets resulted in better protein ultilization than barley-soybean control diets. Feeding trials and metabolism trials indicated that methionine was not limiting in barley and that threonine was the second limiting amino acid. Growth trials with weanling rats confirmed the results obtained in the pig nutritional experiments. Rat experiments indicated that no additional beneficial effects were obtained when lysine levels were increased from 0.75% to 0.90% even when supplemented with additional threonine. Results indicated that supplementation with lysine to a total level of 0.75% and threonine at a level of 0.10% resulted in a highly balanced amino acid ratio for rats, and gave growth rates which approached those obtained on the control diet. Supplementation of the barley-lysine diet with 0.20% threonine and all other essential amino acids resulted in growth rates and nitrogen retentions which resembled the results obtained with the control diet. The replacement of the essential amino acid mixture with glycine on an equal nitrogen basis did not result in adequate nitrogen retention or growth rates. / Land and Food Systems, Faculty of / Graduate

<p> N-[(9-β-D-ribofuranosyl-9H-purin-6-yl)carbamoyl]- threonine, a hypermodified nucleoside found in transfer RNA represents the archetype structure of a group of synthetic ureidopurines which promote cell division in plants. L-threonine was shown to be incorporated into this nucleoside in Tobacco tissue and Rhizopogon roseolus transfer RNA. Also, this nucleoside was isolated as a free molecule in Rhizopogon roseolus growth medium.</p> <p> Chromatographic analysis of an enzymic hydrolysate of 3 g of yeast transfer RNA failed to indicate the presence of a lipophilic derivative of PCT riboside. It is concluded that PCT riboside occurs in transfer RNA with a free carboxyl group.</p> / Thesis / Master of Science (MSc)

The period gene determines biological rhythmicity in Drosophila melanogaster. The X-linked gene is 7.4kb, containing 8 exons and 7 introns from which a 4.5kb message is translated. A striking feature of the protein encoded by per is a series of alternating threonine-glycine residues in the fifth exon. Moreover, this string of residues is polymorphic for length variation in natural populations, the most frequent variants having 17, 20 or 23 Thr-Gly pairs. In the present study, a geographic analysis of this polymorphism within North American populations was conducted, the results of which indicate significant variation of allele frequency with latitude. The use of spatial autocorrelation analysis and Mantel tests clearly show that the most common variant, encoding 17 Thr-Gly pairs, exhibits a clinal pattern in its distribution along a north-south axis. Furthermore, DNA sequence analysis of several variants has uncovered a novel new variant which encodes 22 Thr-Gly pairs whose nucleotide sequence differs from any published data. Similar statistical analysis conducted on seven allozymes for populations collected along the same transect shows that several have monotonic clinal patterns in their allele frequency distributions which also show correlation with latitude. A previous study of morphological traits on the same populations showed the existence of a non-monotonic clinal pattern. Comparison of the results observed for the molecular and morphological markers indicates that they are subject to different evolutionary forces. The results highlight the importance of comparing patterns of geographic variation using different genetic elements. / Thesis / Master of Science (MS)

Thesis (Ph. D.)--University of Washington, 1999. / Vita. Includes bibliographical references (leaves [157]-179).

Ziel der vorliegenden Arbeit war es festzustellen, ob die unterschiedliche Versorgung mit Protein (XP), Threonin (Thr) und Glycin (Gly) bei einer limitierten Threoninversorgung einen Einfluss auf die Threonindehydrogenase-Aktivität (TDG-Aktivität) in der Leber von Küken und Laborratten hat. Dazu wurden 7 Versuche mit federgesexten männlichen Cobb-Küken und weißen Wistar-Ratten in verschiedenen Altersstufen und Lebendmassebereichen durchgeführt: Versuch 1: Küken vom 15. - 25. Lebenstag bei unterschiedlichen Rohproteingehalten. Die kalkulierten XP-Gehalte lagen bei 5,5%; 11,0%; 16,5%; 22,0%; 27,5% und 33,0%. Versuch 2: Küken vom 17. - 30. Lebenstag bei XP-Gehalten von 18,5% und 22,5% mit jeweils 2 Threoninstufen von 0,45% und 0,60% wahr fäcal verdaulichem Threonin. Versuch 3: Küken vom 10. - 20. Lebenstag bei XP-Gehalten von 16,5% und 22,0% und einer Steigerung des Threoningehaltes von 0,65% auf 0,79% Threonin bei 16,5% XP und 0,86% auf 1,05% Threonin bei 22,0% XP. Versuch 4: Küken vom 1. - 49. Lebenstag in Bodenhalten bei praxisnaher Phasenfütterung. Die Prüfung der Leber-Threonindehydrogenase erfolgte am 7., 21., 35. und 49. Lebenstag. Versuch 5: Küken vom 5. - 15. Lebenstag bei einem XP-Gehalt von einheitlich 22,0% und Glycingehalten von 0,64% und 0,98% und wahr fäcal verdaulichen Threoningehalten von 0,45% und 0,60% bei 0,64% bzw. 0,98% Glycingehalt. Die Gly+Ser-Gehalte betrugen insgesamt 1,55% bzw. 1,90%. Versuch 6: Weiße Wistar-Ratten im Lebendmassebereich von 106 - 140 g bei XP-Gehalten von 0%, 6,0%, 12,0%, 18,0% und 24,0%. Vesuch 7: Weiße Wistar-Ratten im Lebendmassebereich von 149 - 167 g und XP-Gehalten von 12,0% und 18,0% mit unterschiedlichen Threoningehalten von 0,28%, 0,42% und 0,72% bei 12,0% XP bzw. 0,42%, 0,52% und 0,72% bei 18,0% XP. Am Ende des jeweiligen Vesuches wurden die Lebern von jeweils 6 Tieren entnommen und für die Bestimmung der TDG-Aktivität in vitro aufbereitet. Die Threoninwirksamkeiten wurden aus N-Bilanzversuchen mit einem exponentiellen N-Verwertungsmodell abgeleitet. Folgende Ergebnisse wurden erzielt: 1. Durch die Erhöhung der XP-Gehalte stieg die TDG-Aktivität in der Kükenleber ab 22,0% XP in der Futtermischung trotz limitierter Threoninversorgung signifikant an. Die Threoninwirksamkeit war unverändert bis zu einem XP-Gehalt von 27,5% und fiel bei 33,0% XP signifikant ab. D. h. durch einen verstärkten Abbau von Threonin durch die TDG erfolgte eine Verminderung der Thr-Wirksamkeit bei der Futtermischungen mit hohem XP-Gehalt. 2. Bei einem XP-Gehalt von 18,5% und einem Anstieg der Thr-Konzentration von 0,45% auf 0,60% dThr zeigte sich kein Einfluss auf die TDG-Aktivität in der Kükenleber, wohl aber bei einem XP-Gehalt von 22,5% und einem Gehalt von 0,60% dThr war die TDG-Aktivität in der Kükenleber erhöht. Das könnte den Bereich angeben, in dem Threonin nicht mehr limitierend wirkt. 3. Bei einem Gehalt von 16,5% XP und einem Anstieg der Thr-Konzentration von 0,65% auf 0,79% wurde kein Einfluss auf die TDG-Aktivität in der Kükenleber ermittelt, dagegen stieg die TDG-Aktivität bei einem Gehalt von 22,0% XP und einer Erhöhung des Thr-Gehaltes von 0,86% auf 1,05% signifikant an. 4. Im Verlauf des Phasenfütterungsversuches zeigten sich altersabhängige Veränderungen der TDG-Aktivität, die mit Phasen eines besonders hohen metabolischen Bedarfes an Glycin erklärt weden können. 5. Bei einem XP-Gehalt von 22,0% (Gly + Ser-Gehalt 1,55%) führte die Erhöhung des Thr-Gehaltes von 0,45% auf 0,60% dThr zu einer mehreren Akkumulation von Gly in den Lebermitochondrien, jedoch nicht signifikantem Anstieg der TDG-Aktivität. Bei 1,90% Gly+Ser und 22,0% XP stieg die TDG-Aktivität nach Thr-Zulage signifikant an. Dieser Befund weist auf das Ende des Thr-Limitierungsbereiches hin. 6. Bei Laborratten lag die TDG-Aktivität bei einer proteinfreien Ration am niedrigsten, erhöhte sich bei einer XP-Steigerung bis 12,0% XP, verringerte sich geringfügig bis 18,0% XP und stieg von 18,0% bis 24,0% XP tendenziell an. Insgesamt beeinflusste das XP-Niveau die TDG-Aktivität aber nur zufällig. 7. Der Anstieg des Thr-Gehaltes von 0,28% auf 0,72% bei 12,0% XP bewirkte einen allmählichen Anstieg der TDG-Aktivität in den Rattenlebermitochondrien. Das trifft ebenfalls für die Futtermischung mit 18,0% XP zu, allerdings auf einem etwas höheren Niveau. Die TDG-Aktivität wurde nahezu ausschließlich durch die Aminoacetonakkumulierung moduliert. TDG-Aktivität und Thr-Wirksamkeit zeigten das Ende des Thr-Limitierungsbereiches an. Die in vitro TDG-Aktivitäten der Leber von Küken und Laborratten wird demnach nicht nur durch die Thr-Konzentrationen im Futter sondern auch vom XP-Gehalt und damit dem Angebot anderer Aminosäuren sowie vom Alter beeinflusst. Da offensichtlich Zusammenhänge zur unspezifischen Katabolisierungsrate anderer Aminosäuren bestehen, wird die Interpretation von TDG-Veränderungen (in vitro) erschwert. Bezüge zum Parameter Thr-Wirksamkeit sind mit Einschränkungen deutlich geworden und müssen, bevor quantitative Aussagen möglich sind, weiter erforscht werden.

Sarcopenia is a condition that is most common in aged animals, and is characterized by the loss of skeletal muscle mass and integrity, and can lead to physical disability and poor quality of life. Since skeletal muscle protein synthesis can be limited by the availability of amino acids, supplementation of limiting amino acids to ameliorate the progression of sarcopenia has become a topic of interest in companion animal research. Although there is some data to support the idea that amino acid supplementation improves maintenance of muscle mass in aged horses, the cellular mechanisms behind that improvement have yet to be elucidated. Therefore, the objective of this study was to examine the effect of amino acid supplementation in aged horses on markers of whole body and muscle protein metabolism. In a cross-over design, six old horses were studied while receiving each of three treatments in a replicated Latin square design. For all three treatments, horses received 1.8% BW/d of timothy hay cubes and 0.5% BW/d of experimental concentrate. The three treatments included a control (CON) treatment concentrate that was designed to meet all requirements of mature horses when fed in combination with the timothy hay cubes, and two supplemented concentrates, LYS/THR with additional lysine and threonine (40 mg/kg BW/d and 31 mg/kg BW/d, respectively), and LYS/THR/MET with additional lysine, threonine, and methionine (40 mg/kg BW/d, 31 mg/kg BW/d and 11mg/kg BW/d respectively). In each 15 d period, following a 9-day adaptation, horses were fitted with a collection harness, and total urine and feces were collected for 72 hours for assessment of nitrogen balance and creatinine output. Blood samples were taken directly before feeding and 30, 60, 90, 120, 150, 180, 210, and 240 minutes post-feeding for analysis of plasma urea nitrogen (PUN), glucose, insulin, and plasma amino acid concentrations. Muscle biopsy samples were taken for analysis of proteins in the mTOR pathway. Additionally, horses underwent stable isotope infusion procedures, and comparisons of phenylalanine kinetics were used to determine whole-body rates of protein synthesis and degradation. There was no significant effect of treatment on creatinine output (P=0.58), relative abundance of proteins in the mTOR pathway (P>0.05), nitrogen retention (P=0.70), or phenylalanine kinetics (P>0.05). PUN concentrations were significantly (P=0.0058) higher for LYS/THR and LYS/THR/MET than for CON. Atrogin-1 activation was significantly higher for the pre-feeding CON sample compared to the post-feeding CON sample. Lack of significant difference in creatinine output suggests that there were not significant differences in muscle mass between treatments. Lack of significant differences in mTOR protein activation suggests that amino acid supplementation did not result in improvements in protein synthesis. Lack of significant differences in nitrogen retention and phenylalanine kinetics suggests that whole-body protein metabolism was not improved. Additionally, higher PUN concentrations in the supplemented diets suggests that the supplemented amino acids being provided were catabolized. However, increased activation of Atrogin-1 in the pre-feeding CON samples, but not the pre-feeding samples of supplemented treatments, suggests amino acid supplementation may have reduced protein degradation in the post-absorptive state. Data from the present study suggests that amino acid availability may not have been limiting protein synthesis in the sedentary aged horses in the present study.

The amino acid requirements of growing horses are currently unknown, and studies suggest that threonine is a limiting amino acid in common horse diets. Thus, the objective of this study was to determine the threonine requirement of growing horses fed two different forage to concentrate ratios using the indicator amino acid oxidation method. The study consisted of a high concentrate phase (HC; 60% concentrate and 40% forage) and a high forage phase (HF; 25% concentrate and 75% forage). Within each phase, 6 female yearling Thoroughbred horses were randomly assigned each of 6 dietary treatments in a 6 x 6 Latin square design. All 6 treatments were identical, apart from varying equimolar ratios of threonine to glutamate. After 6 days of adaptation, blood samples were collected before and after the morning meal for plasma urea nitrogen (PUN) and amino acid analysis. On day 7, horses underwent the IAAO protocol, during which regular breath and blood samples were collected. Phenylalanine flux, oxidation, non-oxidative disposal, and release from body protein, as well as total carbon dioxide production were calculated using plateau enrichment of samples. There was a significant linear effect of threonine intake on plasma threonine concentrations, and PUN had a significant linear response during the HC phase. There was no significant effect of treatment on phenylalanine oxidation during either phase (P ≥ 0.05). It is unlikely that threonine was limiting in the experimental diets.