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.

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.

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.

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.

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.

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.

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.

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.

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.

Intestinal absorption of protein hydrolysis products: a review.

Many experimental techniques have allowed researchers to probe the fate of hydrolysis products from proteins in the small intestine. An overview of amino acid and peptide absorption from the small intestine is presented with attention given to historical perspectives that have led to current concepts. Speculation about nutritional significance of these processes is offered. Species differences exist in site of amino acid absorption. Numerous mechanisms are available for the transport of amino acids, including Na(+)-dependent carriers (energy-requiring), Na(+)-independent carriers and diffusion. The relative contribution each transport system makes to absorption is dependent on substrate concentration. Individual amino acids are not absorbed with equal efficiency; methionine usually is absorbed in the greatest proportion. There are interactions among amino acids for transports by specific transport systems. Small peptides (mostly di- and tripeptides) are absorbed from the small intestine more rapidly than are free amino acids; peptides are transported by systems independent of those responsible for transporting free amino acids. Evidence exists that the active transport of these peptides is via a proton gradient. Although the concept that peptides are absorbed intact into the circulation is not universally accepted, evidence supporting the possibility of tissue utilization of these small peptides is accumulating.

Serum proteins as carriers of amino acids to and from the hindlimbs of fed and fasted calves.

Venoarterial differences in the amino acid composition of serum proteins were measured across the hindlimbs of growing Holstein steer calves (147 kg) surgically fitted with abdominal aorta and caudal vena cava cannulae. Steers were maintained in near steady-state metabolism by feeding at hourly intervals in a continuously lighted environment. The steady-state blood samples were obtained 10 d post-surgery; then the steers were fasted and resampled. Arterial and venous serum proteins were chromatographically separated into four fractions and the amino acid composition of each was determined. Under steady-state conditions, there appeared to be a tendency for serum protein amino acids to appear on the venous side of the tissue in either greater or lesser concentrations than on the arterial side, depending upon the protein fraction. However, after the steers had fasted for 72 h, virtually all amino acids from all protein fractions were present in greater concentrations in venous serum than in arterial serum. Furthermore, the quantitative differences were several-fold larger than during steady-state sampling. It appears that serum proteins may contribute to the transport of amino acids to and from peripheral tissues. Data further suggest that all serum proteins do not appear to function in the same manner, and physiological state influences this process.

Vitamin A deficiency: serum cortisol and humoral immunity in lambs.

Serum cortisol and antigen-specific and polyclonal immunoglobulin G (IgG) concentrations were measured to investigate the relationship between vitamin A status and immune function in lambs. Twenty-four 3-mo-old crossbred ewe lambs weighing approximately 10 kg were each fed 900 g/d of a carotene-deficient diet. The 12 control lambs also received a 100,000 IU oral dose of vitamin A palmitate every 2 wk. All lambs were given primary and secondary antigenic challenges. Lambs were slaughtered at the end of the secondary challenge period. Liver vitamin A concentrations were greater (P less than .001) in the control animals (69.5 vs 1.3 micrograms/g wet tissue). Both groups of lambs exhibited a similar growth response until d 105, after which daily gain of the control lambs exceeded (P less than .03) that of the A-deficient lambs. Polyclonal serum IgG concentrations were greater (P less than .05) in the A-deficient lambs on d 49 to 124 and on d 151 (P less than .10). Ovalbumin-specific serum IgG concentrations tended to be greater in the control lambs throughout the primary and secondary challenge periods. Control lambs had greater titers on d 164 (P less than .07) and d 190 (P less than .03). Vitamin A status appeared to have no consistent effects on serum cortisol concentrations. Spleen weights were greater (P less than .002) in the A-deficient lambs. Lungs from 11 of 12 A-deficient lambs contained abscesses, as opposed to 1 of 12 for the control lambs. Both polyclonal and antigen-specific IgG concentrations were affected by vitamin A status. Serum cortisol concentrations did not appear to mediate this effect.

Simultaneous isolation and characterization of brush border and basolateral membrane vesicles from bovine small intestine.

Purified brush border and basolateral membranes were isolated from homogenized intestinal enterocytes of Holstein steers by divalent cation precipitation followed by differential and sucrose density gradient centrifugation. Alkaline phosphatase and Na/K adenosine triphosphatase served as marker enzymes for the brush border and basolateral membranes, respectively. The brush border and basolateral membrane fractions were enriched 5.1- and 10.1-fold, respectively, over the cellular homogenate. Electron micrographs, obtained with transmission electron microscopy, confirmed the vesicular nature of the membranes and revealed that basolateral membrane vesicles generally were smaller and more irregular in shape than brush border membrane vesicles. The vesicular nature of isolated membrane preparations was confirmed with osmotic activity experiments. Enrichment of brush border and basolateral membrane fractions compared to the initial homogenate and the vesicular configuration of both preparations indicate that the isolated brush border and basolateral membrane preparations were suitable models for evaluating nutrient transport properties of bovine small intestine. The number of transport experiments possible per animal using the membrane vesicle technique is many times more efficient than some other in vitro techniques (i.e., intestinal rings or everted sacs).

Nitrogen utilization and digestibility of amino acids by lambs fed a high-concentrate diet with limestone or magnesium oxide.

Effects were evaluated of high dietary levels of magnesium oxide (MgO) or limestone on DM, OM and CP digestibility, N balance and intestinal absorption of amino acids by lambs fed a high concentrate diet. Twelve wether lambs equipped with abomasal and ileal cannulas were blocked by weight and breeding and allotted to treatments in a randomized block design in two consecutive trials. Diets were control (800 g), control plus 1.5% MgO (812 g), control plus 1.5% limestone (812 g) and control plus 3.0% limestone (824 g) fed in two equal portions at 12-h intervals. Ruminal fluid pH differences were small. The pH of ileal digesta was greater (P less than .05) with MgO than with limestone (8.23 vs 7.73). Fecal pH was higher (P less than .01) for lambs fed all mineral treatments (avg 8.75) than for lambs fed the control (7.61) and was higher (P less than .01) when MgO (9.53) rather than limestone (8.36) was fed. Ruminal NH3N was lower (P less than .01) when lambs were fed MgO (11.9 mg/dl) compared with limestone (avg 31.2 mg/dl). Preintestinal DM digestibility was greatest (P less than .10) with limestone (avg 49.5%) feeding compared with feeding MgO (31.2%) or the control (35.4%). About 41.5% more essential (P less than .05) and 48% more nonessential (P less than .03) amino acids reached the small intestine when MgO was fed than when limestone was fed. Partial digestibility of amino acids in the small intestine was reduced (P less than .03) an average of 5 percentage units when MgO or limestone was fed. Feeding high levels of MgO or limestone to lambs did not improve the overall digestibility of DM, OM or CP. In fact, feeding high levels of MgO or limestone appeared to be detrimental, reducing intestinal absorption of amino acids.

Intestinal acid flow, dry matter, starch and protein digestibility and amino acid absorption in beef cattle fed a high-concentrate diet with defluorinated rock phosphate, limestone or magnesium oxide.

Five Angus heifers (285 kg) with duodenal and ileal cannulas were used to study the effects of feeding mineral acid neutralizers on digesta and fecal pH, intestinal acid flow, DM, starch and CP digestion and amino acid absorption in cattle fed a high-concentrate diet (7.5 kg/d). The experimental design was a 5 x 5 latin square. Treatments included control diet alone or control diet with the addition of 1.60% defluorinated rock phosphate-medium (DRP-M, 77% greater than 150 mu but less than 1,180 mu), 1.60% defluorinated rock phosphate-coarse (DRP-C, 85% greater than 850 mu but less than 1,700 mu), 1.28% limestone (92% greater than 150 mu but less than 850 mu) or .50% MgO, (81% greater than 250 mu but less than 1,180 mu), as an as-fed basis. Ileal pH was increased (P less than .05) from 7.49 to 7.85 by MgO. Fecal pH was increased (P less than .05) in this order: MgO (7.18) greater than DRP-M (6.86) = limestone (6.86) = DRP-C (6.75) greater than control (6.54). Liquid flow to the duodenum was increased (P less than .05) an average of 19.7% by the mineral treatments. Duodenal acid concentrations (mEq/liter) were greatest (P less than .05) for DRP-M (65.4) and DRP-C (64.0) vs limestone (55.5) and MgO (54.4). Acid flow to the intestine was increased (P less than .05) to 4.02, 4.53 and 4.82 Eq/d for animals fed limestone, DRP-M and DRP-C, respectively, from 3.51 Eq/d for control animals. Total tract DM, starch and CP digestibilities were similar (P greater than .10) among treatments. Limestone and DRP-M increased (P less than .10) the partial digestibility of most amino acids by about 6.8%. Mineral treatments did not increase total tract digestion of starch or CP. However, cattle fed DRP-M and limestone may have used protein more efficiently.

Glycyl-L-sarcosine absorption across ovine omasal epithelium during coincubation with other peptide substrates and volatile fatty acids.

To define the interactions between the absorption of glycyl-L-sarcosine (Gly-Sar; .1 mM) and glycine, L-methionylglycine, glycyl-L-leucine, L-carnosine, or L-methionylglycyl-L-methionyl-L-methionine (each at 5 mM), ovine omasal epithelium was collected from eight wethers (average BW=69+/-8.2 kg) and mounted in parabiotic chambers. [1,2]-[14C]Glycyl-L-sarcosine was used as a marker to monitor the presence of Gly-Sar. The Gly-Sar concentration in the omasal epithelium after 60 min of incubation was greatest (P < .05; .0055 nmol/mg dry tissue) when only Gly-Sar was present. Glycine inhibited (P < .05) Gly-Sar movement through the tissue by 20%, and peptide substrates inhibited (P < .05) Gly-Sar movement by 60 to 85%. The appearance of Gly-Sar in serosal buffers increased quadratically (P < .001) with time. Numerically, Gly-Sar appearance in serosal buffers was stimulated by the presence of glycine and peptide substrates. In a second experiment, ovine omasal epithelium was collected from four lambs (average BW=47+/-6.0 kg) to determine the interactions of Gly-Sar absorption (.1 mM) alone or when coincubated with either 10 mM butyric acid, or with a mixture of VFA (50 mM acetic acid, 40 mM propionic acid, and 10 mM butyric acid). The movement of Gly-Sar through the omasal epithelium was greatest (P < .05) when only Gly-Sar was present, and the VFA mixture inhibited (P < .05) Gly-Sar movement by 84%. Results from these studies support the idea that peptides can be absorbed across omasal epithelium and that the process involves mediated as well as nonmediated mechanisms, including possibly paracellular transport.