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METABOLISM AND NUTRITION |
* Department of Poultry Science, North Carolina State University, Raleigh 27695; Department of Animal and Dairy Science, University of Guelph, Ontario, Canada, N1G 2W1; and Department of Animal Science, National Chung Hsing University, Taichung, Taiwan, China
2 Corresponding author: Jim_Croom{at}ncsu.edu
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ABSTRACT |
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 TOP ABSTRACT INTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
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Key Words: broiler chicken • direct-fed microbial • scanning electron microscopy • histology
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INTRODUCTION |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
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Lactobacilli and bifidobacteria are the most frequently used DFM genera. Lactobacilli are gram-positive, non-spore-forming rods, usually nonmotile, and do not reduce nitrate. They can be divided into 3 distinct 16S ribosomal RNA groups (Fooks and Gibson, 2002). Bifidobacteria are also gram-positive, nonspore-forming rods, with distinct cellular bifurcations with club-shaped morphologies. They make a significant contribution to carbohydrate fermentation in the colon (Fooks and Gibson, 2002). They possess fructosylfructanosidase, which hydrolyzes the link between the fructose moieties of inulin and oligofructose (Fooks and Gibson, 2002). Both lactobacilli and bifidobacteria have been associated with beneficial effects for the host, such as promotion of gut maturation, gut integrity, antagonism against pathogens, and immune modulation (Lan et al., 2005).
Furthermore, DFM bacteria are believed to have many effects on GI tract histology and ultrastructure (Awad et al., 2006) and on the regulation of mucus synthesis and secretion (Deplancke and Gaskins, 2001). Mucus is secreted by the goblet cells throughout the GI tract and forms an adherent gel on the mucosal surface (Sklan, 2004). The mucous layer acts as a barrier between the luminal contents and intestinal nutrient transporters, and it protects the mucosal surface from exogenous and endogenous luminal irritants, such as bile salts (Yagi et al., 1990). Additionally, several studies have shown that DFM may enhance the integrity of the tight junctions between the intestinal epithelial cells during infections or inflammatory conditions (Montalto et al., 2004; Shen et al., 2006).
The objectives of the present study were to investigate the histological and ultrastructural changes in intestinal architecture as well as the spatial relationship between microorganisms and the epithelial cells lining the GI tract of birds fed a DFM and salinomycin. Salinomycin, an ionophore that alters the transport of ions across biological membranes (Augustine and Danforth, 1999), was of interest because of its common usage as a coccidiostat antimicrobial in poultry production systems.
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MATERIALS AND METHODS |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
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A completely randomized design was used for both trials. Chicks from each treatment were randomly blocked by age for experimental measurements, so the average age of the chicks was 21 d at the time of measurements. Chicks were assigned to one of following treatments: no additives (control), salinomycin (SAL; 50 ppm of feed), and a DFM consortium (PrimaLac, Star Labs, Clarksdale, MO; 0.3% of a diet). PrimaLac was added as a lyophylized mix containing 1 x 108 cfu/g of Lactobacillus casei, Lactobacillus acidophilus, Bifidobacterium thermophilum, and Enterococcus faecium. Salinomycin was chosen because of its widespread use as a coccidiostat within the poultry industry and its antimicrobial properties against gram-negative organisms (Duffy et al., 2005).
Chicks were placed at hatch in Petersime batteries; control and SAL were housed in batteries in a separate room from the live organism DFM treatment with single pass air. To prevent cross-contamination between the control and SAL chicks and the DFM chicks, access to the bird rooms was restricted to essential personnel, with all procedures being performed on the control and SAL room before entering the DFM room. Personnel were required to shower and change clothes before reentering the control room. Chickens were fed their respective treatment diets for 21 d. They were then taken off of feed for 12 h before sample collection on d 21.
Individual bird measurements were regarded as the experimental unit. For the histomorphometric calculations, an average of 10 measurements for each parameter from each bird were statistically analyzed as a 1-way ANOVA using the statistical program Statistix 8 (Analytical Software, Tallahassee, FL). Because sample sizes in these trials were small, Fisher’s least significant difference was used to test differences between means only when the ANOVA indicated significance at P 
0.05 (Motulsky, 2005).
Sample Collection and Analyses
Birds in trials 1 and 2 were killed by cervical dislocation after a 12-h feed deprivation period. Immediately after euthanasia, the middle portion of the ileum, between Meckel’s diverticulum and the ileo-cecal-colonic junction (trial 1) and between the cecal and colonic junction (trial 2), samples were collected from 18 birds (6 per treatment) and flushed with PBS for SELM imaging.
In trial 1, ileal and jejunal samples were collected, and tissue samples were fixed in 10% neutral buffered formalin for 24 h. Trimmed cross-sections placed in biopsy cassettes were rinsed in running tap water and processed into paraffin on a Sakura VIP tissue processor (Sakura Finetek USA Inc., Torrance, CA). A routine overnight process cycle was used. Tissues were embedded in paraffin, and four 1-µm sections were cut on a Leica 2135 microtome (Leica Microsystems, Nussloch, Germany) and placed on slides. Step sections at 200-µm intervals allowed for visualization of different sets of villi and crypts. Slides were stained with hematoxylin and eosin on a Sakura automatic stainer. A computerized microscopic image analyzer (Southern Micro Instruments, Atlanta, GA) was used to determine the histomorphometric parameters, villus height, villus width at its base, villus perimeter length, crypt depth, external muscle layer thickness, and height of enterocytes at midvillus, as previously described (Fan et al., 1997). The criterion for selection of histological sections for examination was based on the presence of an intact lamina propria, and villi were chosen that were perpendicularly sectioned through the mid-line axis.
In the second trial, 10 to 12 one-millimeter pieces from each sample were fixed in a mixture of 3% glutaraldehyde in 0.1 M cacodylate buffer (pH 7.4) for SELM analysis. Tissue specimens were postfixed with 1% osmium tetroxide in ice-cold buffer for 20 min. The specimens were dehydrated in a graded series of ethanol solutions (30, 50, 70, 90, and 100%, twenty minutes each) and were then subjected to critical-point drying (Samdri-795, Tousimis, Rockville, MD) Peabody, MS) using liquid CO2 as the medium. The dried specimens were coated with gold or palladium (Anatech Hummer 6.2, Anatech Ltd., Hayward, CA) and examined with a JEOL 5900 scanning electron microscope (JEOL Ltd., Rockville, MD) at 20 kV.
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RESULTS |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
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. In the jejunum, the DFM-treated broilers had increased villus height and perimeter (P = 0.009 and 0.003, respectively) compared with the SAL-fed chicks (Figure 1). Similarly, jejunal crypt depth and muscle thickness values were greater in the DFM-treated (P = 0.01 and 0.01, respectively) than in the birds treated with SAL. The ilea of the DFM-treated birds had a greater muscle thickness than did the ilea of the control- and SAL-treated birds (P = 0.02; Figure 2). There were no significant differences between treatments for villus height:crypt depth ratio and midvillus enterocyte height in the ileum and jejunum of the 3 treatment groups. More goblet cells were also observed for the DFM-treated birds compared with that observed for the control- and SAL-treated birds (data not shown).
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, panel A). Often the extrusion zones for dead enterocytes at the apex of the villi were wide and contained deep furrows and many shedding cells. Occasionally, at the apex of the villus spaces, extrusion zones for dead enterocytes as well as disintegrating cells were observed between the epithelial cells. They were approximately 2-µm long. The mucous blanket showed a pronounced tendency across all treatments to condense during dehydration and to separate from the tissue surface in specimens prepared for SELM. In most samples, the fibrous polysaccharide glycocalyx of the microvillous surface is easily observed.
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, panels A and B, and Figure 5, panels A and B). The thickness of the mucous blanket observed in the ileal samples from the 21-d-old broiler chickens appeared to be from 10 to 15 µm for the DFM and control groups, respectively (Figure 4, panel A, and Figure 5, panel A). The thicker mucous blanket in the ileum of control birds was apparently able to withstand more damage during sample preparation but was still seen as a discontinuous balled and rolled layered structure rather than as the continuous blanket, which normally covers tissue in vivo (Skrzypek et al., 2005). Although the mucous blanket was usually dehydrated to various extents in the samples from all of the treatment groups, bacteria could always be seen within the mucous layer. A higher bacterial density was apparent in the sample mucous layer of the control birds compared with samples from the DFM birds (Figure 5, panel A). Secondly, the ileal DFM samples had a lower density of segmented filamentous-like bacteria (SFB) compared with the samples from the control birds.
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, panel D). Few SFB coexisted near other microbial organisms (Figure 6, panels A to D). Rod-shaped bacteria (similar to lactobacilli in morphology) were observed on the surface of the ileal, cecal, and colonic mucosa (Figure 5
, Figure 7, panels C and D, and Figure 8, panels C and D). There was clearly a greater number of those microorganisms, however, in broiler chicks treated with the DFM (Figure 3, panel B). Bacteria observed in the ileum of the DFM-treated birds seemed to be associated with goblet cells compared with those observed in control and SAL groups (Figure 7, panel C, and Figure 9). The largest populations of surface-associated bacteria were observed in the colon of DFM-treated birds.
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, panels A to F, and Figure 8, panels A to F). The SELM imaging showed an increase in bacterial attachment to epithelial tissue with DFM supplementation compared with the bacterial attachment in the other treatments. The SAL treatment altered the cecal epithelium, with large areas that were smooth and denuded of mucus, as well as by lowering the number of goblet cells (Figure 5, panels E and F). There were also fewer transversed furrows in the SAL-treated birds in contrast to their abundance in the DFM-treated group. Similar differences were noted in the colon. Bacterial colonization associated with the epithelial surface of the colon was pronounced with DFM as was colonization of the mucous blanket. There were more goblet cells present in the colon of SAL-treated birds than in cecum; however, most of the colonic goblet cells in the SAL-treated birds were not associated with bacterial colonization in their proximal areas. |
DISCUSSION |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
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). Lactobacillus treatment caused similar changes in poultry, as previously described (Dobrogosz et al., 1991). Muscle thickness was also greater in the ileum of DFM-fed than in SAL-fed birds. Increases in the villus height and the villus height:crypt depth ratio are directly correlated with increased epithelial cell turnover (Fan et al., 1997). In the present study, analysis of this parameter did not show any significant differences among the treatments. This suggests that the increases in villus height and perimeter that were observed with the DFM treatment are not associated with enterocyte turnover rates. This observation is in agreement with previous studies from this laboratory, which have shown no differences in protein:DNA ratio of the intact ileum and jejunum (Chichlowski et al., 2006). Increased passive absorption of glucose and proline in 21-d-old chicken broilers fed DFM diet was also observed in those previous studies. Adjustment in the absorptive area from the DFM treatment may be linked to increased passive absorption of nutrients. Skrzypek et al. (2005) coined the term "indifferent absorptive area," which described potential absorptive ability not entirely utilized in the nutrient absorption of growing piglets. In their study, the shift was made from such a state into "effective absorptive area" after the first feeding in synchrony with increases in the local circulation in the gut mucosa. It is possible that DFM treatment in our study triggered a similar shift, increasing the effective absorptive area via alterations in villus size as compared to SAL.
The bacteria in the GI tract are associated with the mucous layer, which is easily removed from the epithelial surface when tissue sections are processed for SELM. In conventional fixation methods, preserving the mucous layer is a challenge, because in most cases, it is washed away or dissolved more quickly than it can be stabilized. However, despite those challenges, some differences were noted in the mucous layers associated with the different dietary treatments (Figure 4, panels A to H). Other investigators have reported this problem as a limiting factor in the interpretation of mucosal integrity with SELM micrographs of intestinal samples (Allan-Wojtas et al., 1997). Extensive damage to the mucous layer during SELM preparation of samples was observed in this study. It is thought that in vivo this structure is likely continuous and covers the microvillous surface almost completely by 21 d (Allan-Wojtas et al., 1997). As the animal matures, the mucous layer thickens, and more microbial flora colonizes within it (Rozee et al., 1982).
Upon examination of samples in the present trial, it was concluded that some microorganisms are firmly attached to the epithelial surface, especially in the DFM treatment. Infrequent occurrence in the ileum and colon suggest that the bacterial colonies might be easily dislodged during preparation of the specimens from those areas. Previous studies have not observed any structural elements, such as filaments, connecting bacteria to the epithelium or microbial penetration of the mucosa, with the exception of SFB in SELM imaging of intestinal villi tissue (Salanitro et al., 1974). Additionally, microbes are able to colonize the mucous matrix within which many different microbial flora exist. Because the mucous blanket is normally very thick, understanding its microbial population dynamics is of considerable importance. Contrary to previous reports, in the present experiment, the majority of the observed bacteria were positioned on the tissue surface rather than imbedded in the mucous blanket (Rozee et al., 1982).
The number of goblet cells per villus increases as the villi grow, but the proportion of goblet cells to enterocytes remains constant with age (Tucker and Taylor-Pickard, 2004). The role of the mucus in absorption and protection against pathogens is not yet fully understood; however, Ikeda et al. (2002) reported that goblet cells may play an important role in epithelial cell repair following damage to the GI mucosa. In the present experiment, there was a visual increase in goblet cell numbers associated with the DFM treatment, as compared with SAL and control treatments as observed through both the light and SELM (data not shown).
In the present experiment, the feeding of SAL greatly altered the epithelial surface in all sections analyzed. The effects of the ionophores on cell and tissue integrity are likely a result of physiological effects on the permeability of the cell membranes to the alkali metal cations, which can also physically change the intracellular osmolality (Zhu and McDougald, 1992). In previous studies, salinomycin markedly disrupted the integrity of merozoite membranes and caused cytoplasmic vacuolization (Augustine and Danforth, 1999). It is possible that in the present study, in which chicks were not exposed to protozoa or bacterial pathogens and in which they were housed in clean conditions, this ionophore could have blocked some of the microbial binding sites by becoming inserted into the intestinal epithelial membranes of the host. The presence of salinomycin in the membranes of the intestinal epithelium would likely have a critical effect upon the epithelial water balance, thereby causing enterocyte damage. Indeed, besides a decreased level of bacterial colonization in the ileum and colon samples from the birds fed SAL, we also observed many areas with dehydrated and damaged tissue (Figure 6, panels E and F, and Figure 8, panels E and F).
Previous studies in this laboratory have suggested that salinomycin, when used as a supplement under clean conditions, can have a low toxicity threshold that decreases BW and increases energetic demands on intestinal tissues as compared with control and DFM (Chichlowski et al., 2007). In the cecum, where bacterial colonization is usually the greatest, the SAL-treated birds had visible indentations in the epithelium and a lower number of goblet cells dispersed within the epithelial tissue. It is possible that decreased BW, ileal glucose and proline absorption, and increased whole-body and intestinal O2 observed with SAL treatment, reported previously in this laboratory (Chichlowski et al., 2006), is linked to the epithelial damage caused by the feeding of SAL.
The control-treated birds contained an abundance of segmented bacteria embedded in the epithelium within the ileum. To date, segmented fusiform bacteria, which are abundant in the intestine of young animals, have not been cultured (Tucker and Taylor-Pickard, 2004). They are known to be nonpathogenic, gram-positive, anaerobic, spore-forming bacteria that inhabit the intestinal tract (Dewhirst et al., 1999; Yamauchi and Snel, 2000) as well as the respiratory tract (Jang and Hirsh, 1994). Yamauchi and Snel (2000) called these organisms simply unclassified SFB, whereas other authors have used the description of fusiform, extremely O2-sensitive bacteria (Dewhirst et al., 1999), or Fusobacterium (Omata, 1953). The genus Fusobacterium currently includes 13 species (Citron, 2002). In this study, we called these organisms SFB. Their function as immune-stimulating agents has been reported (Meyerholz et al., 2002). Furthermore, SFB have been reported to have a potential antagonistic effects against GI bacterial pathogens (Heczko et al., 2000), and they adhere to intestinal epithelial cells with holdfasts and filaments which are usually found only at the ileal villus tip (Davis and Savage, 1974; Glick et al., 1978). The apparent decrease in SFB colonization following the feeding of the DFM, in the present trial, is not understood; however, it is possible that increased colonization with DFM organisms affected this reduction.
The most efficient DFM bacteria will likely be strains that are robust enough to survive the harsh physicochemical conditions present in the GI tract (Fooks and Gibson, 2002). This includes gastric acid, bile secretions, and competition with the resident microflora. Greater numbers of microbial flora associated both with the epithelium (Figure 9) and mucous blanket in the birds fed the DFM in the present trial suggest that the consortium of bacteria contained in the DFM product used in the present trial colonize effectively. The large complement of colonizing microorganisms in the DFM-fed group may inhibit pathogens and other opportunistic microbiota from reaching and colonizing small and large intestinal tissue, as well as the cecum. We suggest that the presence of the DFM bacteria may preclude colonization by opportunistic potential pathogens, even when they are repeatedly introduced into the GI tract.
The action of antibiotics or bacterial toxins may distort the mucous barrier that facilitates the development and attachment of pathogens. It is possible that invading bacteria may depend on the alterations of the mucous layer and its association with the epithelial tissue. Also, changes in the properties of this barrier can alter absorption of both dietary and endogenous macromolecules and ions (Sklan, 2004). In previous studies, increased passive nutrient absorption was observed in the DFM birds compared with control- and SAL-treated birds (Chichlowski et al., 2006). Thus, there exists a potential connection between alterations in the appearance of the mucous layer in the present study and previous reports and nutrient transport. It is possible that the presence of the DFM organisms in the diet of broilers might facilitate nutrient transport in the GI tract that is not dependent on Na transporters. Furthermore, it has previously been demonstrated that bacteria can upregulate a complex of gene action in epithelial cells and by doing so dramatically influence the expression of a diverse array of epithelial products, thereby altering the biochemistry, physiology, and function of the intestinal barrier (Tucker and Taylor-Pickard, 2004).
The results of this study demonstrate that the introduction of DFM into the intestinal tract results in the colonization of a subpopulation of bacteria that alters intestinal microarchitecture. Furthermore, these bacteria establish unique spatial relationships with the intestinal mucosa and epithelial cells. These DFM-evoked changes in intestinal histology and surface architecture may, in part, be responsible for previously described changes in intestinal function with DFM supplementation. Further studies are needed to understand this possible relationship.
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ACKNOWLEDGMENTS |
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FOOTNOTES |
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Received for publication October 17, 2006. Accepted for publication January 28, 2007.
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REFERENCES |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
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Augustine, P. C., and H. D. Danforth. 1999. Influence of betaine and salinomycin on intestinal absorption of methionine and glucose and on the ultrastructure of intestinal cells and parasite developmental stages in chicks infected with Eimeria acervulina. Avian Dis. 43:89–97.[ISI][Medline]
Awad, W. A., J. Bohm, E. Razzazi-Fazeli, K. Ghareeb, and J. Zentek. 2006. Effect of addition of a probiotic microorganism to broiler diets contaminated with deoxynivalenol on performance and histological alterations of intestinal villi of broiler chickens. Poult. Sci. 85:974–979.
Bird, A., W. Croom, and B. McBride. 2002. Dietary management of the intestinal microbiota using probiotics and prebiotics in human and animals. Proc. Aust. Poult. Sci. Symp. 14. Poult. Res. Found., Univ. Sydney, Australia.
Chichlowski, M., W. J. Croom Jr., M. A. Froetschel, M. D. Koci, B. M. McBride, R. Qiu, and L. R. Daniel. 2006. Effect of PrimaLac, direct fed microbial, on ileal absorption, energy expenditure and intestinal microbial fermentation. Poult. Sci. 85(Suppl. 1):33. (Abstr.)
Chichlowski, M., J. Croom, B. W. McBride, L. Daniel, G. Davis, and M. Koci. 2007. Direct-fed microbial PrimaLac and salinomycin modulate whole-body and intestinal oxygen consumption and intestinal mucosal cytokine production in the broiler chick. Poult Sci. 86:1100–1106.
Citron, D. M. 2002. Update on the taxonomy and clinical aspects of the genus Fusobacterium. Clin. Infect. Dis. 35(Suppl. 1):S22–S27.[ISI][Medline]
Davis, C. P., and D. C. Savage. 1974. Habitat, succession, attachment, and morphology of segmented, filamentous microbes indigenous to the murine gastrointestinal tract. Infect. Immun. 10:948–956.
Deplancke, B., and H. R. Gaskins. 2001. Microbial modulation of innate defense: Goblet cells and the intestinal mucus layer. Am. J. Clin. Nutr. 73(Suppl.):1131S–1141S.[ISI][Medline]
Dewhirst, F. E., C.-C. Chien, B. J. Paster, R. L. Ericson, R. P. Orcutt, D. B. Schauer, and J. G. Fox. 1999. Phylogeny of the defined murine microbiota: Altered Schaedler flora. Appl. Environ. Microbiol. 65:3287–3292.
Dobrogosz, W. J., B. L. Black, and L. A. Casas. 1991. Delivery of viable Lactobacillus reuteri to the gastrointestinal tract of poultry. Poult. Sci. 70(Suppl. 1):158. (Abstr.)
Duffy, C. F., G. F. Mathis, and R. F. Power. 2005. Effects of Natustat supplementation on performance, feed efficiency and intestinal lesion scores in broiler chickens challenged with Eimeria acervulina, Eimeria maxima and Eimeria tenella. Vet. Parasitol. 130:185–190.[ISI][Medline]
Fan, Y., J. Croom, V. Christensen, B. Black, A. Bird, L. Daniel, B. McBride, and E. Eisen. 1997. Jejunal glucose uptake and oxygen consumption in turkey poults selected for rapid growth. Poult. Sci. 76:1738–1745.
Fooks, L. J., C. R. Fuller, and G. R. Gibson. 1999. Prebiotics, probiotics and human gut microbiology. Int. Dairy J. 9:53–61.
Fooks, L., and G. Gibson. 2002. Probiotics as modulators of the gut flora. Br. J. Nutr. 88:S39–S49.[ISI][Medline]
Glick, B., K. A. Holbrook, I. Olah, W. D. Perkins, and R. Stinson. 1978. A scanning electron microscope study of the caecal tonsil: The identification of a bacterial attachment to the villi of the caecal tonsil and the possible presence of lymphatics in the caecal tonsil. Poult. Sci. 57:1408–1416.[ISI][Medline]
Heczko, U., A. Abe, and B. B. Finlay. 2000. Segmented filamentous bacteria prevent colonization of enteropathogenic Escherichia coli O103 in rabbits. J. Infect. Dis. 181:1027–1033.[ISI][Medline]
Hong, H. A., L. H. Duc, and S. M. Cutting. 2005. The use of bacterial spore formers as probiotics. FEMS Microbiol. Rev. 29:813–835.[ISI][Medline]
Ikeda, H., C.-L. Yang, J. Tong, H. Nishimaki, K. Masuda, T. Takeo, K. Kasai, and G. Itoh. 2002. Rat small intestinal goblet cell kinetics in the process of restitution of surface epithelium subjected to ischemia-reperfusion injury. Dig. Dis. Sci. 47:590–600.[ISI][Medline]
Jang, S. S., and D. C. Hirsh. 1994. Characterization, distribution, and microbiological associations of Fusobacterium spp. in clinical specimens of animal origin. J. Clin. Microbiol. 32:384–387.
Lan, Y., M. W. A. Verstegen, S. Tamminga, and B. A. Williams. 2005. The role of the commensal gut microbial community in broiler chickens. World’s Poult. Sci. J. 61:95–104.[ISI]
Lin, D. C. 2003. Probiotics as functional foods. Nutr. Clin. Pract. 18:497–506.
Marteau, P., P. Seksik, P. Lepage, and J. Dore. 2004. Cellular and physiological effects of probiotics and prebiotics. Mini Rev. Med. Chem. 4:889–896.[ISI][Medline]
Meyerholz, D. K., T. J. Stabel, and N. F. Cheville. 2002. Segmented filamentous bacteria interact with intraepithelial mononuclear cells. Infect. Immun. 70:3277–3280.
Montalto, M., N. Maggiano, R. Ricci, V. Curigliano, L. Santoro, F. Di Nicuolo, F. M. Vecchio, A. Gasbarrini, and G. Gasbarrini. 2004. Lactobacillus acidophilus protects tight junctions from aspirin damage in HT-29 cells. Digestion 69:225–228.[ISI][Medline]
Motulsky, H. 2005. Intuitive Biostatistics. Oxford Univ. Press, New York, NY.
Omata, R. R. 1953. Studies on the nutritional requirements of the fusobacteria: An active principle present in yeast extract. J. Bacteriol. 65:326–329.
Rozee, K., D. Cooper, K. Lam, and J. Costerton. 1982. Microbial flora of the mouse ileum mucous layer and epithelial surface. Appl. Environ. Microbiol. 43:1451–1463.
Salanitro, J., I. Blake, and P. Muirhead. 1974. Studies on the cecal microflora of commercial broiler chickens. Appl. Microbiol. 28:439–447.[ISI][Medline]
Shen, T. Y., H. L. Qin, Z. G. Gao, X. B. Fan, X. M. Hang, and Y. Q. Jiang. 2006. Influences of enteral nutrition combined with probiotics on gut microflora and barrier function of rats with abdominal infection. World J. Gastroenterol. 12:4352–4358.[ISI][Medline]
Sklan, D. 2004. Early gut development: The interaction between feed, gut health and immunity. Pages 9–32 in Interfacing Immunity, Gut Health and Performance. L. A. Tucker and J. A. Taylor-Pickard, ed. Nottingham Univ. Press, UK.
Skrzypek, T., J. L. Valverde Piedra, H. Skrzypek, J. Wolinski, W. Kazimierczak, S. Szymanczyk, M. Pawlowska, and R. Zabielski. 2005. Light and scanning electron microscopy evaluation of the postnatal small intestinal mucosa development in pigs. J. Physiol. Pharmacol. 56(Suppl. 3):71–87.
Tucker, L. A., and J. A. Taylor-Pickard. 2004. Interfacing Immunity, Gut Health and Performance. 1st ed. Nottingham Univ. Press, UK.
Yagi, T., Y. Miyawaki, A. Nishikawa, S. Horiyama, K. Yamauchi, and S. Kuwano. 1990. Prostaglandin E2-mediated stimulation of mucus synthesis and secretion by rhein anthrone, the active metabolite of sennosides A and B, in the mouse colon. J. Pharm. Pharmacol. 42:542–545.[ISI][Medline]
Yamauchi, K., and J. Snel. 2000. Transmission electron microscopic demonstration of phagocytosis and intracellular processing of segmented filamentous bacteria by intestinal epithelial cells of the chick ileum. Infect. Immun. 68:6496–6504.
Zhu, G., and L. R. McDougald. 1992. Characterization in vitro and in vivo of resistance to ionophores in a strain of Eimeria tenella. J. Parasitol. 78:1067–1073.[Medline]
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