Ultra-low-loss nanofiber Fabry-Perot cavities optimized for cavity quantum electrodynamics.

We demonstrate the fabrication of ultra-low-loss, all-fiber Fabry-Perot cavities that contain a nanofiber section, optimized for cavity quantum electrodynamics. By continuously monitoring the finesse and fiber radius during the fabrication of a nanofiber between two fiber Bragg gratings, we were able to precisely evaluate taper transmission as a function of radius. The resulting cavities have an internal round-trip loss of only 0.31% at a nanofiber waist radius of 207 nm, with a total finesse of 1380, and a maximum expected internal cooperativity of ∼1050 for a cesium atom on the nanofiber surface. Our ability to fabricate such high-finesse nanofiber cavities may open the door for the realization of high-fidelity scalable quantum networks.

Measurement of microresonator frequency comb coherence by spectral interferometry.

We experimentally investigate the spectral coherence of microresonator optical frequency combs. Specifically, we use a spectral interference method, typically used in the context of supercontinuum generation, to explore the variation of the magnitude of the complex degree of first-order coherence across the full comb bandwidth. We measure the coherence of two different frequency combs and observe wholly different coherence characteristics. In particular, we find that the observed dynamical regimes are similar to the stable and unstable modulation instability regimes reported in previous theoretical studies. Results from numerical simulations are found to be in good agreement with experimental observations. In addition to demonstrating a new technique to assess comb stability, our results provide strong experimental support for previous theoretical analyses.

Efficiency of dispersive wave generation from a dual-frequency beat signal.

The emission of dispersive waves (DWs) by temporal solitons can be described as a cascaded four-wave mixing process triggered by a pair of monochromatic continuous waves (CWs). We report experimental and numerical results demonstrating that the efficiency of this process is strongly and nontrivially affected by the frequency detuning of the CW pump lasers. We explain our results by showing that individual cycles of the input dual-frequency beat signal can evolve as higher-order solitons whose temporal compression and soliton fission govern the DW efficiency. Analytical predictions based on the detuning dependence of the soliton order are shown to be in excellent agreement with experimental and numerical observations.

Generalized dispersive wave emission in nonlinear fiber optics.

We show that the emission of dispersive waves in nonlinear fiber optics is not limited to soliton-like pulses propagating in the anomalous dispersion regime. We demonstrate, both numerically and experimentally, that pulses propagating in the normal dispersion regime can excite resonant dispersive radiation across the zero-dispersion wavelength into the anomalous regime.

Dietary protein composition influences abundance of peptide and amino acid transporter messenger ribonucleic acid in the small intestine of 2 lines of broiler chicks.

This study evaluated the effect of dietary protein composition on mRNA abundance of a peptide transporter (peptide transporter 1, PepT1), amino acid (AA) transporters [Na(+)-independent cationic and zwitterionic AA transporter (b(o,+)AT), excitatory AA transporter 3 (EAAT3), Na(+)-independent cationic and Na(+)-dependent neutral AA transporter 2 (y(+)LAT2), L-type AA transporter 1 (LAT1), and cationic AA transporter 1 (CAT1)], and a digestive enzyme (aminopeptidase N) in 2 lines (A and B) of broilers that differentially express PepT1 mRNA (line B > line A). From d 8 to 15 posthatch, birds were fed 1 of 3 diets. Protein sources included whey protein concentrate, a whey partial hydrolysate (WPH), or a mixture of free AA (AA) identical to the composition of whey. Quantities of mRNA were assayed by real-time PCR in the small intestine of males at d 8, 9, 11, 13, and 15. For all genes except LAT1, abundance of mRNA was greatest in line B birds that consumed the WPH diet (P < 0.006). When mRNA abundance was normalized to beta-actin quantities, this effect disappeared, demonstrating a generalized effect on gene expression in line B birds that consumed the hydrolysate. There was a greater villus height:crypt depth ratio (P < 0.05) in line B birds fed the WPH diet as compared with line A. In conclusion, line B birds, which express greater PepT1, displayed enhanced intestinal mucosal absorptive surface area and differential regulation of PepT1, AA transporters, and aminopeptidase N in response to dietary protein composition.

Gene expression of nutrient transporters in the small intestine of chickens from lines divergently selected for high or low juvenile body weight.

Nutrient transporters in the small intestine are responsible for dietary nutrient assimilation; therefore, the expression of these transporters can influence overall nutrient status as well as the growth and development of the animal. This study examined correlated responses to selection in the developmental gene expression of PepT1, EAAT3, SGLT1, and GLUT5 in the small intestine of chickens from lines divergently selected for 48 generations for high (HH) or low (LL) 56-d BW and their reciprocal crosses (HL and LH). Duodenum, jejunum, and ileum were collected from male and female chicks on embryonic d 20, day of hatch with no access to feed, and d 3, 7, and 14 posthatch. Total RNA was extracted, and nutrient transporter expression was assayed by real-time PCR using the relative quantification method. In comparing male and female HH and LL chicks, there was a mating combination x age x sex interaction for PepT1 expression (P < 0.001), a main effect of sex for EAAT3 (P < 0.05) and SGLT1 (P < 0.001) expression, and an age x sex interaction for SGLT1 expression (P < 0.001). These results demonstrate a sexual dimorphism in the capacity to absorb nutrients from the intestine, which has implications for the poultry industry with regard to diet formulations for straight-run and sex-separate grow-out operations. Results from comparing male LL, LH, HL, and HH chicks indicate that selection for high or low juvenile BW may have influenced the gene expression profiles 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.

Expression profiling of the solute carrier gene family in chicken intestine from the late embryonic to early post-hatch stages.

Intestinal development during late embryogenesis and early post-hatch has a long-term influence on digestive and absorptive capacity in chickens. The objective of this research was to obtain a global view of intestinal solute carrier (SLC) gene family member expression from late embryogenesis until 2 weeks post-hatch with a focus on SLC genes involved in uptake of sugars and amino acids. Small intestine samples from male chicks were collected on embryonic days 18 (E18) and 20 (E20), day of hatch and days 1, 3, 7 and 14 post-hatch. The expression profiles of 162 SLC genes belonging to 41 SLC families were determined using Affymetrix chicken genome microarrays. The majority of SLC genes showed little or no difference in level of expression during E18-D14. A number of well-known intestinal transporters were upregulated between E18 and D14 including the amino acid transporters rBAT, y(+)LAT-2 and EAAT3, the peptide transporter PepT1 and the sugar transporters SGLT1, GLUT2 and GLUT5. The amino acid transporters CAT-1 and CAT-2 were downregulated. In addition, several glucose and amino acid transporters that are novel to our understanding of nutrient absorption in the chicken intestine were discovered through the arrays (SGLT6, SNAT1, SNAT2 and AST). These results represent a comprehensive characterization of the expression profiles of the SLC family of genes at different stages of development in the chicken intestine and lay the ground work for future nutritional studies.

Board-invited review: Peptide absorption and utilization: Implications for animal nutrition and health.

Over the last 50 yr, the study of intestinal peptide transport has rapidly evolved into a field with exciting nutritional and biomedical applications. In this review, we describe from a historical and current perspective intestinal peptide transport, the importance of peptides to whole-body nutrition, and the cloning and characterization of the intestinal peptide transporter, PepT1. We focus on the nutritional significance of peptide transport and relate these findings to livestock and poultry. Amino acids are transported into the enterocyte as free AA by a variety of AA transporters that vary in substrate specificity or as di- and tripeptides by the peptide transporter, PepT1. Expression of PepT1 is largely restricted to the small intestine in most species; however, in ruminants, peptide transport and activity is observed in the rumen and omasum. The extent to which peptides are absorbed and utilized is still unclear. In ruminants, peptides make a contribution to the portal-drained visceral flux of total AA and are detected in circulating plasma. Peptides can be utilized by the mammary gland for milk protein synthesis and by a variety of other tissues. We discuss the factors known to regulate expression of PepT1 including development, diet, hormones, diurnal rhythm, and disease. Expression of PepT1 is detected during embryological stages in both birds and mammals and increases with age, a strategic event that allows for the immediate uptake of nutrients after hatch or birth. Both increasing levels of protein in the diet and dietary protein deficiencies are found to upregulate the peptide transporter. We also include in this review a discussion of the use of dietary peptides and potential alternate routes of nutrient delivery to the cell. Our goal is to impart to the reader the nutritional implications of peptide transport and dietary peptides and share discoveries that shed light on various biological processes, including rapid establishment of intestinal function in early neonates and maintenance of intestinal function during fasting, starvation, and disease states.

Uptake of zinc from zinc sulfate and zinc proteinate by ovine ruminal and omasal epithelia.

Uptake and transport of Zn from (65)Zn-labeled ZnSO(4) and Zn proteinate (ZnProt) by ruminal and omasal epithelia were examined by using a parabiotic chamber system. Uptake was measured during a 4-h incubation with 10, 20, or 200 microM Zn as ZnSO(4) or ZnProt in the mucosal buffer (pH 6.0, Krebs-Ringer phosphate). Zinc uptake and transport were also evaluated after simulated ruminal digestion. Buffered ruminal fluid contained a feed substrate and 10 or 200 microM added Zn as ZnSO(4) or ZnProt. In a preliminary experiment, uptake of Zn by omasal tissue was low; thus, the remaining experiments were conducted solely with ruminal epithelium. Incubations to determine the effect of time on Zn uptake from mucosal buffer containing 20 microM added Zn as ZnSO(4) or ZnProt resulted in increased (P < 0.01) Zn uptake as incubation time increased from 30 to 240 min. Zinc uptake was also greater (P = 0.02) from mucosal buffer containing ZnProt compared with ZnSO(4). Zinc uptake from incubations containing 10 or 200 microM was affected by source x concentration (P = 0.05) and concentration x time (P < 0.01) interactions. With 10 microM Zn, uptake was not influenced by Zn source, whereas when 200 microM Zn was added, Zn uptake from ZnProt was greater than from ZnSO(4). Increasing incubation time resulted in increased Zn uptake with 200 microM Zn in the mucosal buffer; however, with 10 microM Zn, uptake did not change after 30 min. After simulated ruminal fermentation, the proportion of Zn in a soluble form was influenced by a source x concentration interaction (P = 0.03). After 18 h of incubation, the proportion of Zn that was soluble was not different between ZnProt and ZnSO(4) in buffered ruminal fluid that contained 10 microM added Zn, but was greater for ZnProt compared with ZnSO(4) with 200 microM Zn in the incubation. Zinc uptake from the aqueous fractions of simulated ruminal digestions containing 200 microM added Zn was greater (P < 0.01) than from those containing 10 microM added Zn. Zinc transport, based on detection of (65)Zn in serosal buffer, did not occur in any of the experiments. The results of the current experiments suggest that absorption of Zn into the bloodstream does not occur from the ruminant foresto-mach; however, Zn uptake occurs in ruminal tissue and is greater from ZnProt than from ZnSO(4).

Developmental regulation of nutrient transporter and enzyme mRNA abundance in the small intestine of broilers.

The objective of this study was to investigate intestinal nutrient transporter and enzyme mRNA in broilers selected on corn- and soybean-based (line A) or wheat-based (line B) diets. We investigated the peptide transporter PepT1, 10 amino acid transporters (rBAT, b(o,+)AT, ATB(o,+), CAT1, CAT2, LAT1, y(+)LAT1, y(+)LAT2, B(o)AT, and EAAT3), 4 sugar transporters (SGLT1, SGLT5, GLUT5, and GLUT2), and a digestive enzyme (aminopeptidase N). Intestine was collected at embryo d 18 and 20, day of hatch, and d 1, 3, 7, and 14 posthatch. The mRNA abundance of each gene was assayed using real-time PCR and the absolute quantification method. For PepT1, line B had greater quantities of mRNA compared with line A (P = 0.001), suggesting a greater capacity for absorption of amino acids 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, b(o,+)AT, rBAT, B(o)AT, LAT1, CAT2, SGLT5, and aminopeptidase N mRNA were greatest in the ileum (P < 0.05). Quantities of PepT1, EAAT3, B(o)AT, SGLT1, GLUT5, and GLUT2 mRNA increased linearly (P < 0.01), whereas CAT1, CAT2, y(+)LAT1, and LAT1 mRNA decreased linearly (P < 0.05) with age. Abundance of y(+)LAT2 mRNA changed cubically (P = 0.002) with peaks of expression at day of hatch and d 7, and aminopeptidase N and SGLT5 mRNA changed quadratically (P = 0.005) with age. These results provide a comprehensive profile of the temporal and spatial expression of nutrient transporter mRNA in the small intestine of chicks.

Growth performance and intestinal morphology responses in early weaned pigs to supplementation of antibiotic-free diets with an organic copper complex and spray-dried plasma protein in sanitary and nonsanitary environments.

The objective of this study was to determine the effects of addition of spray-dried plasma protein (SDPP) and Cu to nonmedicated diets on growth performance and intestinal morphology in weaned pigs reared in sanitary or nonsanitary environments. Weanling pigs (n = 192, 18 +/- 2 d of age, 6.0 +/- 0.2 kg of BW) were assigned to 8 treatments arranged factorially, including 2 dietary levels of SDPP (0 or 6% for the initial 10 d), 2 levels of added dietary Cu (0 or 200 ppm for the entire 35-d experiment), and 2 pen sanitation conditions (sanitized or nonsanitized before pig placement). The nonsanitary pen condition was created by 3 applications of swine manure slurry to all pen surfaces in 1 room and not washing or disinfecting. In an identical adjacent room, sanitary pens were washed and disinfected before weaning. There were 4 pigs per pen, and feed and water were available ad libitum. Growth performance was determined at the end of each diet formulation phase (d 10, 20, and 35 after weaning). On d 10, 1 pig per pen was euthanized, and cross sections of duodenum, jejunum, and ileum were collected for microscopic assessment of mucosal morphology. During the initial postweaning period, SDPP, and Cu supplementation improved ADG and ADFI (P < 0.001). A trend for an interaction of sanitation x dietary SDPP (P = 0.07) was observed for G:F, with a positive response to the supplement in nonsanitary pens but no response in sanitary pens. There were no interactions of SDPP and Cu for any performance variables (P > 0.30). By d 35, there were no main or interaction effects of treatment on ADG or G:F (P > 0.17). Pen sanitation condition produced morphological effects, with shorter villous length and less crypt depth observed in each intestinal segment for pigs reared in the nonsanitary pens (P < 0.05), but these effects must be considered conditional based on the potential confounding influence of separate nursery rooms. In the duodenum, reduced crypt depth with Cu supplementation (P = 0.01) and a tendency for greater villous length with SDPP supplementation (P = 0.09) were observed. In this study, SDPP and Cu supplementation improved pig growth performance during the initial 10-d postweaning. These modifications to nonmedicated diets acted independently with regard to their impacts on postweaning performance and, therefore, could have additive effects.

Effects of body weight and nutrition on mammary protein expression profiles in Holstein heifers.

A proteomics approach was used to characterize biochemical and cellular mechanisms governing effects of peripubertal feeding on heifer mammary development. Mammary parenchymal tissue from 24 Holstein heifers randomly assigned to treatments arranged in a 2 x 2 factorial design was used to generate 2-dimensional protein maps of mammary tissue extracts. Heifers were reared on 1 of 2 dietary treatments, restricted (650 g/ d of daily gain) or elevated (950 g/d of daily gain) and killed at 1 of 2 body weights (BW, 200 or 350 kg). Cytosolic mammary gland extracts were prepared from frozen mammary parenchyma. Proteome maps of extracts were constructed using PDQuest software. Densities of 820 protein spots were analyzed using the MIXED procedure of SAS. Protein spots were characterized by changes in profiles of expression in response to increased BW, dietary treatment, or both. Dietary treatment influenced the expression of 131 protein spots, whereas heifer BW influenced the expression of 108 spots. The 22 most highly influenced (statistically) spots were excised and submitted for mass spectrometric analyses. Returned protein names and accession numbers were used in National Center for Biotechnology Information database searches to obtain information on the identified proteins. For example, one of the proteins that differed by dietary treatment, transferrin, a binding protein of insulin-like growth factor binding protein-3, was identified via these methods. Possible roles of this and other proteins in mammary development are described. We concluded that a proteomic approach is an effective tool for identifying the proteins involved in bovine mammary development.

Broiler performance and intestinal alterations when fed drug-free diets.

A study was carried out to investigate the effects of a drug-free feeding program on broiler performance and intestinal morphology. Chicks vaccinated against coccidia were randomly assigned to 4 dietary treatments: 1) negative control (NC), basal diet; 2) positive control (PC), diet 1 + Lincomycin; 3) program 1 (PG1); diet 1 + Bio-Mos, Vegpro, MTB-100, Acid Pak 4-Way, and All-Lac XCL; 4) and program 2 (PG2), diet 1 + Bio-Mos and All-Lac XCL, each of which were assigned to 13 pens (48 birds in each of 52 pens). Growth traits (BW, feed intake, yield, mortality, BW gain, and feed conversion rate) were obtained through 49 d. At d 14, 3 chicks per pen were challenged with coccidia. Segments of duodenum, ileum, and ceca were removed to measure intestinal morphology at d 14, 28, 35, and 49. Final BW gain of broilers on PC (2.736 kg) was numerically higher than those for NC (2.650 kg). Cumulative feed conversion rate at d 49 was improved (P < 0.05) in birds consuming PC and PG2 compared with NC. Overall, mortality was higher for birds consuming the NC (P < 0.05) than the PC, PG1, and PG2 diets. Interaction of dietary treatments with age and age alone were evident (P < 0.0001) for morphology of duodenum, ileum, and ceca. Lamina propria in ceca was thicker (P < 0.008) in broilers consuming the NC than PG1 and PG2 diets. The results of this study indicated that feeding birds without growth promoters resulted in higher mortality and decreased growth performance than did feeding a diet with an antibiotic, and the combination of Bio-Mos and All-Lac XCL helped to reduce negative effects.

Developmental regulation of a turkey intestinal peptide transporter (PepT1).

A cDNA encoding a turkey intestinal peptide transporter, tPepT1, was isolated from a turkey small intestinal cDNA library. The tPepT1 cDNA encodes a 714-amino acid protein with 12 predicted transmembrane domains. The amino acid sequence of tPepT1 is 94.3% identical to chicken PepT1 and approximately 60% identical to PepT1 from rat, sheep, rabbit, and human. Using a 2-electrode voltage-clamp technique in Xenopus oocytes expressing tPepT1, Gly-Sar transport was pH dependent but was independent of Na+ and K+. For the dipeptides Gly-Sar and Met-Met, the evoked inward currents indicated that the transporter was saturable and had high affinity (0.69 +/- 0.14 mM and 0.23 +/- 0.04 mM, respectively) for these substrates. However, transport of the tetrapeptide, Met-Gly-Met-Met, exhibited apparent substrate inhibition at high substrate concentrations. To study developmental regulation of PepT1 mRNA in turkey embryos, embryos (6 males and 6 females) were sampled daily from 5 d before hatch to the day of hatch (d 0). The abundance of PepT1 mRNA in the small intestine was quantified densitometrically from Northern blots after hybridization with full-length tPepT1 cDNA as probe. A 3.2-fold increase in PepT1 mRNA was observed in intestinal tissue from 5 d before hatch to d 0. This increase in PepT1 mRNA abundance indicates that the PepT1 gene is developmentally regulated and that there may be an important role for PepT1 in the neonatal poult.

Parental IQ and cognitive development of malnourished Indonesian children.

A cross-sectional study of children in West Kalimantan, Indonesia, was conducted to examine the relationship between malnutrition history, child IQ, school attendance, socioeconomic status, parental education and parental IQ. In unadjusted analyses, severely stunted children had significantly lower IQ scores than mild-moderately stunted children. This effect was significant when stunting, school attendance and parental education were included in multivariable models but was attenuated when parental IQ was included. Our research underscores the importance of accounting for parental IQ as a critical covariate when modeling the association between childhood stunting and IQ.

Functional characterization of a cloned pig intestinal peptide transporter (pPepT1).

Absorption of dietary protein can be mediated through the uptake of AA as free AA or small peptides. A H(+)-coupled, peptide transport protein, PepT1, is responsible for the absorption of small peptides arising from digestion of dietary proteins in the small intestine. The magnitude of peptide absorption and the nutritional significance of PepT1 are unknown for many food-producing animals; thus, the objective of this study was to clone and determine the functional characteristics of the pig PepT1 (pPepT1). Two cDNA-encoding pPepT1 were isolated, which contain alternative polyadenylation sites. The predicted pPepT1 is a 708-AA protein, which shows 82.8, 85.7, and 64.7% AA identity to human, sheep, and chicken PepT1, respectively. On northern blots, two pPepT1 mRNA of approximately 2.9 and 3.5 kb were detected in the duodenum, jejunum, and ileum of the small intestine and are presumed to result from alternative polyadenylation. Uptake of [(3)H]-Gly-Sar was measured in Chinese hamster ovary cells transiently transfected with a pPepT1 expression vector to study the functional expression of pPepT1. Peptide transport was H(+)-dependent, with an optimal pH of 6.0 to 6.5. The ability of pPepT1 to transport various peptides was assayed by calculating the concentration of unlabeled peptide that inhibited 50% of [(3)H]-Gly-Sar uptake (IC(50)) in transfected cells. Eleven dipeptides and two tripeptides had IC(50) values that ranged from 0.004 to 0.53 mM. Three peptides, Lys-Lys, Arg-Lys, and Lys-Trp-Lys, had IC(50) values greater than 1. 38 mM and seem to be poor substrates for pPepT1. For all three tetrapeptides examined, uptake of Gly-Sar was too small to measure, even at a concentration of 10 mM tetrapeptide; therefore, IC(50) values could not be calculated. These results demonstrate that pPepT1 can transport a variety of dipeptides and tripeptides but not tetrapeptides.

Splanchnic and mammary nitrogen metabolism by dairy cows fed dry-rolled or steam-flaked sorghum grain.

Objectives were to determine net release or uptake of alpha-amino N, ammonia N, and urea N across portal-drained viscera, liver, splanchnic, and mammary tissues of lactating Holstein cows (n = 8, 86 +/- 8 d in milk) fed alfalfa hay-based total mixed rations containing 40% dry-rolled or steam-flaked sorghum grain. The total mixed rations were offered at 12-h intervals in a crossover design. Blood samples were obtained from indwelling catheters in the portal, hepatic, and mammary veins and mesenteric or costoabdominal arteries, every 2 h for each cow and diet. Steam-flaking increased in vitro rate of starch hydrolysis compared with dry-rolled sorghum (66 vs. 25%). Diet did not alter dry matter intake (18.2 +/- 0.3 kg). Daily milk yield (27.6 +/- 0.8 kg), efficiency of production, and most milk components did not differ between diets, but fat yield was reduced (0.86 vs. 0.91 kg/d) by steam-flaked sorghum, and lactose concentration was increased (4.99 vs. 4.82%). Blood flows in portal and hepatic veins did not differ between diets. Steam-flaking tended to increase urea N cycling to the gut (162 vs. 95 g/d) compared with dry-rolling of sorghum, whereas net absorption of ammonia N and alpha-amino N across portal-drained viscera were decreased. Net mammary uptake of a-amino N increased more than 20% (83 vs. 67 g/d), resulting in a higher mammary extraction ratio (15 vs. 11%) for steam-flaked versus dry-rolled sorghum. Flaking of sorghum improved the efficiency of postabsorptive N metabolism by increasing urea N cycled to the gut and alpha-amino N uptake by the mammary gland.

Splanchnic and mammary nitrogen metabolism by dairy cows fed steam-rolled or steam-flaked corn.

Objectives were to determine net release or uptake of a-amino N, ammonia N, and urea N across portal-drained viscera, liver, splanchnic, and mammary tissues of lactating Holstein cows (n = 6; 109 +/- 9 d in milk) fed alfalfa hay-based total mixed rations (TMR) containing 40% steam-rolled or steam-flaked corn grain. The TMR were offered at 12-h intervals in a crossover design. Blood samples were obtained from indwelling catheters in portal, hepatic, and mammary veins and mesenteric or costo abdominal arteries, every 2 h for each cow and diet. Steam-flaked compared with steam-rolled corn greatly increased in vitro starch hydrolysis (56 vs. 34%). Daily intake of dry matter (18.4 +/- 0.4 kg/d), starch, N, and net energy for lactation by cows were not altered by processing corn; neither were daily yield of milk (29.1 +/- 0.7 kg/d), fat-corrected milk, nor fat-corrected milk per dry matter intake. Steam-flaking tended to increase percent milk protein (2.97 vs. 2.82%; P = 0.07), but not yield, and decrease percent lactose (4.83 vs. 4.94) but not yield. Portal and hepatic blood flows were not affected by diet, nor were net absorption of alpha-amino N and ammonia N. Steam-flaking compared with steam-rolling increased urea N cycling to portal-drained viscera (212 vs. 87 g/d) by 140%, estimated mammary uptake and extraction ratio of alpha-amino N. Flaking versus rolling of corn improved N utilization in dairy cows by increasing urea cycling to the gut and uptake of a-amino N by the mammary gland. Higher mammary uptake of alpha-amino N (78 vs. 50 g/d) by dairy cows fed steam-flaked corn tended to increase milk protein content and may explain the previously observed effects of cows fed steam-flaked versus steam-rolled corn.

Expression of a cloned ovine gastrointestinal peptide transporter (oPepT1) in Xenopus oocytes induces uptake of oligopeptides in vitro.

We determined the primary structure, tissue distribution and in vitro functional characterization of a peptide transporter, oPepT1, from ovine intestine. Ovine PepT1 (oPepT1) cDNA was 2829-bp long, encoding a protein of 707 amino acid residues with an estimated molecular size of 78 kDa and an isoelectric point (pI) of 6.57. Transport function of oPepT1 was assessed by expressing oPepT1 in Xenopus oocytes using a two-electrode voltage-clamp technique. The transport process was electrogenic and pH dependent, but independent of Na+, Cl- and Ca2+. The oPepT1 displayed a broad substrate specificity for transport of neutral and charged dipeptides and tripeptides. All dipeptides and tripeptides examined evoked inward currents in a saturable manner, with an affinity constant (Kt) ranging from 27 micromol/L to 3.0 mmol/L. No responses were detected from tetrapeptides or free amino acids. Northern blot analysis demonstrated that oPepT1 was expressed in the small intestine, omasum and rumen, but was not expressed in liver and kidney. The presence of the peptide transporter in the forestomach at such levels could provide nutritionally important amino acid nitrogen to ruminants.

Polymorphisms in the thrombopoietin gene are associated with risk of myocardial infarction at a young age.

Five polymorphisms in the thrombopoietin (TPO) gene were identified, one in the 5' untranslated region (UTR) (C1796T), two within intron 5 (C4830A and A4877C), and two in the 3' UTR (A5713G and A6160T). The allele frequencies were determined in a group of 450 healthy middle aged men from the UK and found to be 0.46 for 1796T, 0.38 for 4830A, 0.004 for 4877C, 0.47 for 5713G and 0.07 for 6160T. Genotypes for the three common polymorphisms were determined in a group of 176 young male Swedish survivors of a myocardial infarction (MI) and 186 age-matched controls and a group of 156 young Italian survivors of an MI and 147 age and sex matched controls. In both the Swedish and the Italian studies polymorphisms were found to be associated with increased risk of MI. In the Swedish sample the frequency of 4830A was significantly higher in controls (0.40) compared with patients (0.29) (P=0.003), with an odds ratio for AA homozygotes of 0.48 (0.25-0.92; P=0.03) compared with CC homozygotes. In the Italian sample the frequency of 5713G was significantly lower in controls (0.31) compared with cases (0.40) (P=0.03), with an odds ratio for GG homozygotes of 2.29 (1.08-4.89; P=0.03) compared with AA homozygotes. These risk associations are consistent since 4830A and 5713A show strong allelic association. After adjusting for other measured risk factors the effect on risk was still significant in the Italian sample 2.39 (1.02-5.58), but not in the Swedish sample 0.46 (0.16-1.32). The observation of frequency differences between cases and controls in two independent samples strongly suggests that the TPO gene is involved as a risk factor for developing MI at a young age, but the identified polymorphisms are probably acting as markers for an unidentified functional mutation elsewhere in the gene locus.