Prenatal and postnatal development of the small intestine in the insectivore Suncus murinus

The development of the small intestine in the insectivore Suncus murinus was noted during the period from 21 days' gestation to 20 days after birth. At 21 days of gestation, the proximal small intestine exhibited the beginning of villus formation, whereas the distal small intestine preserved the stratified epithelium. Stratified epithelium in the distal small intestine changed into a single layer by 24 days' gestation. At 26 days' gestation, each epithelial cell was immature; but by 28 days mature-looking epithelial cells were found. The shape of the villi changed from cuboid to columnar during the same period. The connective-tissue cores of the villi began to develop at 7 days after birth in the proximal small intestine and at 15 days after birth in the distal small intestine. Crypts appeared at 15 days after birth. Endocytosis of epithelial cells took place at 28 days of gestation. In the proximal small intestine, supranuclear vesicle clusters were observed first at birth; they began to decrease both in number and size at 10 days' gestation and then disappeared completely by 20 days after birth. In the distal small intestine, large supranuclear vacuoles were observed first at 28 days of gestation. Although these vacuoles invariably were found up to 15 days after birth, they also disappeared completely by 20 days. Epithelial cells showed a structure similar to those of the adult after weaning.     

Characterization of the outermembrane proteins of Vibrio cholerae expressed in in vivo culture

Two outer membrane proteins (Omps) of Vibrio cholerae O1, expressed in the intestine (in vivo) but not in culture media (in vitro), were investigated. The molecular masses of those proteins were 116 kDa and 15 kDa, and they were not associated with iron-regulated proteins. Convalescent cholera patients' sera reacted with the 15 kDa protein but not with the 116 kDa protein. The N-terminal amino acid sequence of the 15 kDa protein was homologous to V. cholerae OmpT. Anti-serum to the 15 kDa protein caused agglutination of the organisms grown in the intestine, but not the organisms in in vitro culture. The anti-serum was bactericidal, but it did not inhibit the adhesion of the organisms to the intestine and HEp-2 cells. These findings suggest the possibility that the 15 kDa protein could be involved in post-infection immunity.     

Survival after total-body irradiation. I. Effects of partial small bowel shielding

The small intestine of the rat was shielded during total-body irradiation (TBI) to evaluate the effects of radiation dose and length of intestine shielded on survival. Sprague-Dawley rats were anesthetized in groups of 10. Using aseptic surgical procedures 80, 40, 20, or 10 cm, or none of the proximal or distal small intestine were temporarily exteriorized and shielded during irradiation with photons from an 18 MeV linear accelerator. Less than 17% of the dose was delivered to the shielded intestines. In unshielded animals deaths occurred from Days 4 to 6 with 13, 15, or 17 Gy and from Days 8 to 30 with 9, 11, and 12 Gy. However, in all animals exposed to 15 Gy with all or part of the small intestine shielded, survival was increased to between 5 and 9 days. Shielding of the distal small intestine was more effective in prolonging survival than shielding of the proximal small intestine. The previously identified target of radiation damage in the small intestine is the crypt stem cell. In this study, the analysis of histological specimens of shielded and irradiated small intestine suggested that humoral factors also influence intestinal histology and survival after irradiation. These humoral factors are thought to originate from the irradiated body tissues, the shielded proximal intestine, and the shielded distal intestine. Further studies are required to identify these factors and to determine their mode of action and their therapeutic potential after radiation damage to the small intestine.     

Changes in relative organ weights and intestinal transporter gene expression in embryos from white Plymouth Rock and WENS Yellow Feather Chickens

This study was conducted to evaluate the embryonic development of broilers with different growth rates and correlate the differences between the amino acid transporter and peptide transporter gene expression patterns to the growth of the small intestine. The results showed that the body and yolk weights of the White Plymouth Rock (WPR) embryos were higher than those of the WENS Yellow Feather Chicken (WYFC) embryos although the relative embryonic body weights were inversely correlated. We studied nine organs and classified them into four clusters according to their changes in relative weight during the hatching process. The levels of gene expression of SLC7A9, SLC1A1 and SLC15A1 in the small intestine increased during embryo development and were affected by breed. Breed-specific differences in embryonic development were observed for SLC7A9, SLC1A1 and SLC15A1 gene expression. When represented as a function of SLC7A9, SLC1A1 or SLC15A1 gene expression, strong correlations were observed for the weight of small intestine. We conclude that WPR embryos have a higher absolute growth rate but a lower relative growth rate in comparison with WYFC embryos. Moreover, the expression levels of the SLC7A9, SLC1A1 or SLC15A1 genes can be used as indicators for the growth of the small intestine.     

猪小肠移植术供肠的灌洗和保存

目的探讨围手术期移植小肠灌注和保存的方法。方法切取猪供肠后,采用100 cm左右高度、略加压法,经移植肠血管以15 mL/min左右灌洗速度持续灌注4℃ 3%羟乙基淀粉注射液、4℃生理盐水保存移植肠。移植前对保存的移植小肠进行组织学检查。结果供肠总灌注时间为50.5±10.6 min;冷缺血时间为80.24±24.62min。组织学检查显示移植肠组织学没有明显改变。移植肠存活良好。结论采取上述方法在短时间内可以提供质量良好的供肠。     

Stimulation of uracil nucleotide synthesis in mouse liver, intestine and kidney by ammonium chloride infusion

De novo pyrimidine synthesis was studied in mouse liver, intestine, and kidney by intraperitoneal infusion of 15NH4Cl and analysis of 15N incorporation into uracil nucleotide pools. When the dose of a 1-h infusion of 15NH4Cl was increased from 50 mumol to 250 mumol the fraction of the total uracil nucleotide pool formed by de novo synthesis increased 4.0-fold in liver to 8.4% and 2.3-fold in intestine to 13.7%. The increase in intestine was independent of the increase in liver as evidenced by the lack of correlation between the increase observed in the intestine and liver of the same animal and the different distributions of label in the uracil ring nitrogens. A 2.4-fold increase in newly formed uracil nucleotides was observed in kidney when the infusion dose was raised from 150 mumol to 250 mumol. The increase in kidney was correlated with the increase in liver in the same animal and the distribution of label in the uracil ring nitrogens was similar to the distribution in liver. These results suggest that the increase in newly formed uracil nucleotides in intestine is due to increased de novo synthesis of pyrimidines in the intestine, while the increase in the kidney is due to increased salvage synthesis of uracil nucleotides from uridine synthesized in the liver and output to the circulation.     

The response of digestive proteases to abrupt salinity decrease in the euryhaline sparid Sparus aurata L

The response of the digestive proteases to abrupt salinity change was studied in juvenile gilthead sea bream (Sparus aurata) for 15 days after transfer from 33 per thousand to 21 per thousand. Salinity decrease affected significantly neither the activity of total acid proteases in stomach, nor the activities of total alkaline proteases and major serine proteases--trypsin and chymotrypsin--in the alkaline part of the intestine. The activity of the major proteases was significantly different between the alkaline segments of the intestine, with the posterior intestine presenting the highest activities followed by the pyloric caeca. This distribution pattern remained unaffected by salinity decrease. Notably, salinity change led to significant alterations in elastase and carboxypeptidase activity. The changes were more prominent in the upper part of the intestine (pyloric caeca and anterior intestine) than in the posterior intestine. In pyloric caeca significant alteration of carboxypeptidase A and B activities was observed, elastase changes were confined to anterior intestine together with alterations in carboxypeptidase B activity, while in posterior intestine the changes were restricted to carboxypeptidase A activity. The results are discussed in relation to the osmoregulatory action of the intestinal segments and dietary protein digestion.     

Intestine lengths of Southern African savanna rodents and insectivores: intra- and interspecific comparisons

Comparative intestine lengths of 15 Southern African savanna rodents and insectivores are presented. Differences in relative intestine length (ratio between hind gut length to head/body length) between seasons were significant in Aethomys chrysophilus . In various species, breeding females, with their increased energy requirement, had hind gut lengths that were well above average. These females also accounted for the differences between sexes which were significant in two species ( Aethomys chrysophilus and A. namaquensis ). Within species no correlation was found between relative intestine length and body size (length and weight) of the animals. Between species the correlation was significant and the larger species had relatively longer intestines. Three groups can be distinguished according to the different feeding types of the species. The omnivorous Praomys natalensis has by far the longest intestine. It is followed by a group of species that can be considered as granivore/herbivore. The species that are partly or predominantly insectivorous have the shortest intestine. The results of the field study are found to be in agreement with reports from laboratory experiments concerning adaptations of intestine length to different environmental situations.     

Identification of a Core Bacterial Community within the Large Intestine of the Horse

The horse has a rich and complex microbial community within its gastrointestinal tract that plays a central role in both health and disease. The horse receives much of its dietary energy through microbial hydrolysis and fermentation of fiber predominantly in the large intestine/hindgut. The presence of a possible core bacterial community in the equine large intestine was investigated in this study. Samples were taken from the terminal ileum and 7 regions of the large intestine from ten animals, DNA extracted and the V1-V2 regions of 16SrDNA 454-pyrosequenced. A specific group of OTUs clustered in all ileal samples and a distinct and different signature existed for the proximal regions of the large intestine and the distal regions. A core group of bacterial families were identified in all gut regions with clear differences shown between the ileum and the various large intestine regions. The core in the ileum accounted for 32% of all sequences and comprised of only seven OTUs of varying abundance; the core in the large intestine was much smaller (5-15% of all sequences) with a much larger number of OTUs present but in low abundance. The most abundant member of the core community in the ileum was Lactobacillaceae, in the proximal large intestine the Lachnospiraceae and in the distal large intestine the Prevotellaceae. In conclusion, the presence of a core bacterial community in the large intestine of the horse that is made up of many low abundance OTUs may explain in part the susceptibility of horses to digestive upset.     

Energie-, Kohlenstoff-, Stickstoff- und Aminosäurenbilanzversuch mit wachsenden Cornish- Hähnen

The time course of AA digestion, AA balance (sV AS), and AA absorption (wV AS) was estimated on growing rats (Wistar rats, LW= 124 g) in different sections of the intestinal tract using the combination of ¹⁵N tracer and TiO₂ marker techniques. The animals received once a diet of ¹⁵N labelled wheat and yeast as protein sources supplemented by TiO₂ as a marker. Up to 6 h after feeding the amino acid composition the ¹⁵N excess and the TiO₂ content in the digesta of stomach, small and large intestine were determinated in the relation of amino acids resp. of ¹⁵N labelled amino acids to the marker. In addition the content of amino acids and the ¹⁵N excess of these amino acids were estimated in plasma. From these data the disappearance rates and the relation of exogenous to endogenous amino acids as well as the sV and the wV values of the different amino acids were calculated for the different gut sections.

The following results were obtained:

- The relative disappearance rate for N and TiO₂ marker out of the stomach went approximately parallel but with a delay for TiO₂ of about 30 minutes.

- The AA composition of the stomach content, the small and the large intestine content did not vary in dependence of the time.

- The AA composition of the stomach digesta was nearly identical to that of the diet, while that of the small intestine was between exogenous AA composition (feed) and endogenous AA composition (digesta on protein free feeding). AA composition of the large intestine digesta showed quite big differences (bacterial AA break down and AA synthesis).

- Considering a delay time (small intestine: 1 h, large intestine: 4 h) the exogenous portion of the different AA remained constant in both of these intestinal sections during the whole experimental time.

- The exogenous AA part varied for small intestine digesta between 31 and 69% (mean value: 41%), and for large intestine digesta between 13 and 39% (mean value: 22%).

- The sV AS values in the small intestine (AA balance resp. precaecal digestibility) differed from 61% (threonine) to 86% (proline) with an average of 73.4 ± 7.4%, those for wV AS (AA absorption) from 81% (lysine) to 94% (proline) with an average of 88.1±4.1%. There were significant differences between AA, but they are negligible for practical purposes.

- In the small intestine the estimated values for postprandial absorption of the exogenous AA accounted after 1 h, 2 h, 4 h and 6 h for 21%, 33.7%, 46.5%, and 70.7% of the AA intake respectively, mean absorption rate = 9.1 ± 0.5%/h.

- The AA balance in the whole tract (sV AS) was 75 to 94% (on average 82 ± 5.3%) and the wV AS (balance corrected by the ¹⁵N method) ranged from 92 to 99% (on average 96±1.8%). These values correspond to the faecal AA digestibility in conventional experiments.

- In the large intestine the postileal disappearance of the AA (sV) was on average 9.7% with a maximum value of 26% for glycine, and with a minimum for methionine of ‐2.1% caused by bacterial synthesis of methionine. Te postileal wV in the large intestine amounted to 7.5%.

- The time course of the disappearance rate of the ¹⁵N labelled AA in the small intestine and the appearance rate of these AA in the plasma showed an analogous behavior. Both of them characterize the postprandial absorption.

The following conclusion can be drawn:

The method used (combination of ¹⁵N tracer and TiO₂ marker techniques) enables determining the time course of transit and the variation of exogenous AA: endogenous AA proportion in the different intestinal sections and estimating the faecal and precaecal digestibility of the different AA.

The course of secretion and absorption of the different AA should be specified in further experiments using the more precise analysis of ¹⁵N by GC‐MS resp. GC‐C‐IRMS technique. An apply of this method to farm animals (pigs) seems to be possible.     

Regional differences in the appearance of adult-type glycosphingolipids in the small intestine of inbred rats at weaning time

The small intestine of 15- to 33-day-old rats was cut into four segments: duodenum, proximal jejunum, distal jejunum, and ileum. Neutral glycosphingolipids and gangliosides were purified from each segment and analyzed by thin-layer chromatography in order to study the developmental appearance of adult-type glycolipids at each level of the small intestine. Type 1 A-6 glycolipid was first detected in the ileum at 15 days and subsequently in the jejunum and duodenum at 19 days of age. N-Glycolylneuraminic acid was expressed first in the ileum at 17 days, then in the proximal jejunum at 21 days, but only after 29 days in the duodenum. In each region, 6-8 days were required between first detection and full expression of N-glycolylneuraminic acid. The presence of 2-hydroxylated fatty acids in glucosylceramide was found first in the ileum at 19 days, 2-3 days before appearing in the duodenum and proximal jejunum. A period of 2-3 days was necessary to reach full adult-type level of 2-hydroxylated fatty acids in glucosylceramide. These results show that adult-type glycolipids appear earlier in the distal than in the proximal region of the rat small intestine, and that different glycolipids appear at different times and at different rates. The finding that the biochemical differentiation of the whole small intestine expands over a period of 3 days to 2 weeks, depending on the region and the glycolipid, before being fully completed indicates that, in addition to the time lag observed between the distal and the proximal region, the new cells arising from the crypt of Lieberkhün after 15 days of age are not at once fully differentiated.     

饥饿对中间球海胆MYP基因转录表达的影响

应用实时定量PCR技术对主要卵黄蛋白(Major yolk protein,MYP)基因在不同饥饿时期中间球海胆的体腔细胞、性腺、肠、胃中的转录表达差异进行了分析。结果表明,在正常状态下,MYP基因在体腔细胞、性腺、肠、胃等不同组织中的转录表达差异明显,肠中的表达量最高,其他组织中的表达量均较低。随饥饿时间的延长,MYP基因在体腔细胞中的表达量先迅速下降,而后稳定在较低水平,实验结束时下降至对照组的1.58%;在性腺中的表达量持续上升,实验结束时上升至对照组的679.75%;在肠中的表达量持续下降,实验结束时下降至对照组的33.33%;在胃中的表达量呈上升趋势,实验结束时上升至对照组的106.52倍。综合来看,饥饿状况下,中间球海胆肠中的MYP表达量持续下降,但仍是MYP的主要合成部位;性腺中MYP表达量持续上升,致使其MYP表达比重上升;胃、体腔细胞中表达量在饥饿过程中虽有变化,但总表达量很少,对MYP的整体表达影响不大。     

Circadian rhythm of ornithine decarboxylase activity in small intestine of fasted rats.

The aim of this study was to determine whether the circadian changes in ornithine decarboxylase (ODC) activity of different segments of the small intestine were governed by factors other than food intake. First, the effects of fasting on mucosal ODC activity were examined. The results indicate that mucosal ODC activity in 24 hr and 48 hr fasted rats decreased significantly compared with ad libitum-fed rats. Second, the circadian rhythm of mucosal ODC activity was characterized by measuring mucosal ODC activity in fasted rats at four time points (09:00, 15:00, 21:00, and 03:00 hr; light period: 06:00-18:00 hr). The results from this study indicate that there is a detectable baseline ODC activity in different segments of fasting intestine. In duodenum, mucosal ODC activity was highest at 15:00 hr (light period), a time at which the rat was normally not eating. In jejunum and ileum, mucosal ODC activity increased between 21:00 and 03:00 hr (dark period). The observation that small intestine exhibits a distinct circadian rhythm of ODC activity in fasted rats suggests that not only food but also intrinsic factors can modulate physiologic oscillations in mucosal ODC activity.     

Comparative study on the inhibition of acetylcholinesterase activity in the freshwater fish Cyprinus carpio by mercury and zinc.

The effects of sublethal concentrations of mercury (0.1mg/l) and zinc (6 mg/l) on acetylcholinesterase activity and acetylcholine content of gill, kidney, intestine, brain, liver and muscle of the freshwater fish Cyprinus carpio at 1, 15 and 30 days of exposure were studied. A significant suppression in acetylcholinesterase activity was recorded in all the organs from both mercury and zinc intoxicated fish at all the exposure periods. Concurrently, a significant increase in the content of acetylcholine in the organs was observed. These changes observed in the organs of mercury treated fish in different exposure periods were in the order 1 greater than 15 less than 30 days and in zinc treated fish 1 greater than 15 greater than 30 days. Further, these changes were greater in magnitude in the brain, liver and muscle (non-osmoregulatory organs) than in the gill, kidney and intestine (osmoregulatory organs) in both metal media.     

HSP90 mRNA在胃癌和大肠癌中表达的研究

目的为探讨胃癌和大肠癌细胞HSP90 mRNA表达的特点.方法利用核酸原位杂交技术,对79例胃肠癌组织进行检测.结果表明HSP90 mRNA在胃癌和大肠癌中的阳性率分别为55.56%(15/27)和69.23%(36/52).mRNA表达与病理类型、分化程度和有否淋巴结转移有相关性.结论 HSP90 mRNA在胃肠癌中有较高表达,检测HSP90 mRNA可以作为提示预后的重要临床指标.     

Differential patterns of expression of Eps15 and Eps15R during mouse embryogenesis

Eps15 and Eps15R are related tyrosine kinase substrates, which have been implicated in endocytosis and synaptic vesicle recycling. Through the protein:protein interaction abilities of their EH domains, they establish a complex network of interactions with several proteins, including Numb, a protein necessary for neuronal cell fate specification. We analyzed the expression of Eps15 and Eps15R during murine development, at the time of active neurogenesis. The most striking difference was at the level of subcellular localization, with Eps15 present in the cytosol and on the plasma membrane, while Eps15R exhibited mainly a nuclear localization. Interesting topographical differences also emerged. In the 12.5 days post coitum neuroepithelium, Eps15 was expressed in the ventricular zone, which contains proliferating neuroblasts, whereas Eps15R was found only in postmitotic neurons. Conversely, both proteins were expressed in sensory and cranial ganglia. At later times, the expression of Eps15 and Eps15R was widely maintained in neuronal structures. In other tissues, Eps15 was first seen in the liver primordium and at low levels in choroid plexus, lung, kidney and intestine; later on the expression was maintained at high levels in epithelia. Nuclear staining of Eps15R was present in kidney, intestine, lung and liver, as well as in heart and pancreas.     

Purification and characterization of alpha-amylases from the intestine and muscle of ascaris suum (Nematoda)

Alpha-Amylase (EC 3.2.1.1) was purified from the muscle and intestine of the parasitic helminth of pigs Ascaris suum. The enzymes from the two sources differed in their properties. Isoelectric focusing revealed one form of a-amylase from muscles with pl of 5.0, and two forms of amylase from intestine with pI of 4.7 and 4.5. SDS/PAGE suggested a molecular mass of 83 kDa and 73 kDa for isoenzymes of a-amylases from intestine and 59 kDa for the muscle enzyme. Alpha-Amylase from intestine showed maximum activity at pH 7.4, and the enzyme from muscle at pH 8.2. The muscle enzyme was more thermostabile than the intestinal alpha-amylase. Both the muscle and intestine amylase lost half of its activity after 15 min at 70 degrees C and 50 degrees C, respectively. The Km values were: for muscle amylase 0.22 microg/ml glycogen and 3.33 microg/ml starch, and for intestine amylase 1.77 microg/ml glycogen and 0.48 microg/ml starch. Both amylases were activated by Ca2+ and inhibited by EDTA, iodoacetic acid, p-chloromercuribenzoate and the inhibitor of a-amylase from wheat. No significant differences were found between the properties of a-amylases from parasites and from their hosts.     

小鼠小肠四种消化酶活力的胎后发育模式

为明确晚成型小鼠胎后发育肠道消化酶活力的建立过程和发育模式,探讨其与适应性调节假说的关系,测定了从出生后至27日龄小鼠小肠前、中、后段的乳糖酶、蔗糖酶、麦芽糖酶和氨基肽酶的酶活力。结果发现单位组织酶活力方面,乳糖酶活力先增后降,小肠前段在9日龄而中后段在12日龄达到最高,至27日龄时仅中段有微弱的酶活力;蔗糖酶活力12日龄始出现,前段和后段自15日龄迅速升高,至18日龄达最高,但随后显著降低,而中段在15日龄后持续升高至21日龄达到最高,此后维持在较高水平;麦芽糖酶出生时已具有活力,但在15日龄前维持较低水平,此后迅速升高,前后段在18日龄,中段在21日龄达到峰值,此后下降;小肠前段的氨基肽酶活力出生后至27日龄持续下降,而后段和中段从出生到断乳前则持续升高,断乳后略有下降。除乳糖酶总酶活力先增后降,在15日龄达峰值外,其余3种酶的总酶活力均持续增加。在小肠不同位置4种酶活力的分布具有显著差异,且日龄对不同位置酶活力的影响趋势不同。总之,小鼠小肠4种消化酶的酶活力随时间的变化能够与其食物转变的消化需求相匹配,部分地支持适应性调节假说。     

Influence of obestatin on the histological development of the small intestine in piglets during the first week of postnatal life

Obestatin is a gastrointestinal peptide having wide-ranging effects on cell proliferation; however, its mechanism of action remains poorly understood. Thus, the aim of the study was to elucidate the effect of exogenous obestatin on the postnatal structural development of the small intestine. Seven-day-old piglets with an average BW of 1.56 ± 0.23 kg were divided into four groups (n = 10) that received intragastrically obestatin (2, 10 or 15 μg/kg BW) or vehicle. After a 6-day experimental period, morphological analysis of gastrointestinal tract and small intestine wall (mitosis and apoptosis indexes, histomorphometry of mucosa and muscularis layers) was performed. The study revealed a seemingly incoherent pattern of the histological structure of the small intestine among the experimental groups, suggesting that the effect of obestatin is both intestinal segment specific and dose dependent. Histomorphometric analysis of the small intestine showed that higher doses of obestatin seem to promote the structural development of the duodenum while simultaneously hindering the maturation of more distal parts of the intestine. Intragastric administration of obestatin increased the crypt mitotic index in all segments of the small intestine with the strongest pro-mitotic activity following the administration of obestatin at a dose of 10 and 15 μg/kg BW. The significant differences in the number of apoptotic cells in the intestinal villi among the groups were observed only in proximal jejunum and ileum. In conclusion, it seems that obestatin shows a broad-spectrum of activity in the gastrointestinal tract of newborn piglets, being able to accelerate its structural development. However, the varied effect depending on the intestinal segment or the concentration of exogenous obestatin causes that further research is needed to clarify the exact mechanism of this phenomenon.     

Lysine synthesized by the gastrointestinal microflora of pigs is absorbed,mostly in the small intestine

This study used a digesta transfer protocol to determine the site of absorption of lysine synthesized by the gastrointestinal microflora of pigs. Eight pigs were used, four with reentrant cannulas in the terminal ileum, two with simple T cannulas in the terminal ileum, and two intact. All pigs were given, for 5 days, the same low-protein diet that included fermentable carbohydrates. The diet of two pigs with reentrant cannulas (donor) and of the two intact (control) pigs was supplemented with (15)NH(4)Cl. The two other pigs with reentrant cannulas (acceptor pigs) and those with simple cannulas (used to supply unlabeled digesta) were given the same diet but unlabeled NH(4)Cl. Ileal digesta were collected continuously from all of the reentrant cannulas and kept on ice. All digesta from each donor pig were reheated and returned to the distal cannula of its companion acceptor, whose ileal digesta were discarded. Unlabeled ileal digesta from the pigs with simple cannulas were instilled into the distal cannulas of the donor pigs. At the end of the experiment, the average (15)N enrichment in the plasma free lysine of control pigs was 0.0407 atom % excess (APE); that of donor pigs was 0.0322 APE (79% of controls), whereas that of acceptor pigs was only 0.0096 APE (24% of controls). Due to nitrogen recycling, acceptor pigs had labeled lysine in the digesta of the stomach and small intestine, and donor pigs had labeled lysine in the digesta of the large intestine. If account is taken of the higher (15)N enrichment of microbial lysine in the large compared with the small intestine, it can be estimated that >90% of the absorption of microbial lysine took place in the small intestine.