Reduction of population levels of some indigenous bacteria by lactobacilli in the gastrointestinal tract of gnotobiotic rats.

Effects of each of three indigenous Lactobacillus groups on other bacterial populations were separately investigated in gnotobiotic rats. In the wall of the non-glandular part of the stomach, contents of the stomach and contents of the upper part of the small intestine, some pre-associated indigenous bacteria were reduced to conventional population levels by introducing three groups of lactobacilli: Group I (Lactobacillus acidophilus and related strains), Group II (L. fermentum) and the groups mixed. However, no obvious reduction in cell numbers of the pre-associated bacteria occurred in the case of Group III (L. murini).     

Distribution of lactobacilli in the porcine gastrointestinal tract

Abstract Characteristics of the lactobacilli colonizing the various regions of the porcine gastrointestinal tract were investigated. The lumenal contents from the gastric, jejunal, cecal and colonic regions, and biopsies from the gastric non-secreting and secreting regions were homogenized and serial dilutions were spread on Rogosa agar and colonies (50 per region and animal) were randomly sampled. The lactobacillus isolates were grouped according to their protein profiles of lysozyme-treated whole cells. Several different groups of lactobacillus could be detected. Specific groups were associated and often unique for the stomach, jejunal, cecal and colonic regions of the gastrointestinal tract. A few groups were uniformly distributed through the tract. Although published studies of lactobacilli colonizing stomach mucosa have been restricted mainly to the non-secreting region, significant levels were also detected on the secreting stomach tissue. Population densities ranged from 2 × 10⁴ to 2 × 10⁶ CFU per cm² on both the secretory and non-secretory regions. Of the isolates which colonized the gastric secreting epithelium, 26% formed smooth colonies and 74% formed rough colonies. In contrast, the non-secreting epithelium was mainly colonized by lactobacilli forming smooth colonies (67%). From this study, one can suggest that different lactobacilli are associated with specific regions of the gastrointestinal tract, and that some specific groups appear to be restricted to defined regions.     

Colonization of the porcine gastrointestinal tract by lactobacilli

Eight strains of lactobacillus isolated from the porcine gastrointestinal tract were tested for their ability to adhere in vitro to cells collected from stratified squamous epithelium in the digestive tracts of newborn piglets. Piglets were inoculated with individual strains, and their digestive tracts were sampled at intervals to determine the colonizing ability of the lactobacilli. The results of the in vitro test did not predict whether a lactobacillus strain would associate with stratified squamous epithelium in the piglet digestive tract, but epithelial association in vivo appeared to be an important factor in the maintenance of lactobacillus populations in the tract. None of the lactobacillus strains used as inocula was numerically dominant in the tract 7 days after inoculation of the piglets with a single dose of the bacteria.     

Colonization of the porcine gastrointestinal tract by lactobacilli.

Eight strains of lactobacillus isolated from the porcine gastrointestinal tract were tested for their ability to adhere in vitro to cells collected from stratified squamous epithelium in the digestive tracts of newborn piglets. Piglets were inoculated with individual strains, and their digestive tracts were sampled at intervals to determine the colonizing ability of the lactobacilli. The results of the in vitro test did not predict whether a lactobacillus strain would associate with stratified squamous epithelium in the piglet digestive tract, but epithelial association in vivo appeared to be an important factor in the maintenance of lactobacillus populations in the tract. None of the lactobacillus strains used as inocula was numerically dominant in the tract 7 days after inoculation of the piglets with a single dose of the bacteria.     

In vitro adhesion specificity of indigenous Lactobacilli within the avian intestinal tract

In vitro adherence of Lactobacillus strains to cell and tissue types along the chicken alimentary tract and to ileal mucus were determined. Fresh isolates from chickens adhered to the epithelium of crop and, in a strain-dependent manner, to follicle-associated epithelium and the apical surfaces of mature enterocytes of intestinal villi. No adherence to the apical surfaces of undifferentiated enterocytes, the mucus-producing goblet cells, or the ileal mucus was detected.     

Immunocytochemical studies on the distribution pattern of daunomycin in rat gastrointestinal tract

The cancer drug daunomycin is used in treatment of leukemia but possesses severe side effects that involve the gastrointestinal tract. We therefore used a newly developed immunocytochemical procedure to determine the distribution of DM in the gastrointestinal tracts of rats after i.v. injection. Two hours after injection, DM was diffusely distributed in nuclei and most parts of the cytoplasm of intestinal epithelial cells. The cytoplasmic immunoreactivity for DM was most pronounced in small granules of the apical cytoplasm. Sixteen hours after injection, DM immunostaining was by and large absent in the villous epithelium but persisted in the intestinal crypts. In addition, staining was also detected in endothelial cells, scattered cells of the lamina propria and in smooth muscle cells. After 5 days, only little staining for DM remained. Similar findings were made in the colon. In the gastric mucosa, DM accumulation persisted at 16 h in some glandular cells but was lost from the surface epithelium. No staining was detected in saline-injected control rats. The distribution of DM accumulation correlated partially with the distribution of apoptotic cells as detected by the TUNEL procedure. Our results pinpoint that DM may exert prolonged effects on glandular and regenerative cells of the gastrointestinal tract—an observation that may explain the gastrointestinal toxicity of the drug. It seems possible that DM accumulation in surface epithelial cells is rapidly cleared through drug transporters.     

Probiotic properties of human lactobacilli strains to be used in the gastrointestinal tract

AIMS: The study of two human strains of Lactobacillus to be used as probiotics in the gastrointestinal tract. METHODS AND RESULTS: The Lactobacillus acidophilus UO 001 and Lact. gasseri UO 002, were resistant to the gastrointestinal conditions (pH 2 and 3, presence of pepsin, pancreatin or bile salts), the resistance was enhanced in the presence of skimmed milk. Additionally, adhered to Caco-2 cells through glycoproteins in Lact. gasseri and carbohydrates in the case of Lact. acidophilus. These strains are able to inhibit the growth of certain enteropathogens: Salmonella, Listeria and Campylobacter without interfering with the normal microbiota of the gastrointestinal tract, as stated by using the mixed culture and the spot agar test. Finally, strongly adherent Lact. gasseri were found to inhibit the attachment of Escherichia coli O111 to intestinal Caco-2 cells under the condition of exclusion. CONCLUSIONS: These results indicate that the two strains of Lactobacillus from human origin present important properties for survival in, and colonization of, the gastrointestinal tract, that give them potential probiotic. SIGNIFICANCE AND IMPACT OF THE STUDY: Two strains of Lactobacillus isolated from human vagina of healthy premenopausal women could be promising candidates to be used in the preparation of probiotic products and for their use as health-promoting bacteria.     

In vitro studies on methyl mercury distribution in human blood

Studies comparing the methyl mercury (mHg) content of maternal and newborn blood have shown increased levels in the newborn. This has been attributed to facilitated transplacental diffusion because of high fetal hematocrit (Hct). This study shows the converse, that the diffusion of mHg diminishes progressively with increasing Hct. The diffusion of m203Hg across a Millipore membrane (0.45 microns) separating compartments A and B of a diffusion cell was studied. When both compartments contained saline or plasma alone, equilibration from A to B occurred in 5 h. Introduction of human red blood cells (RBC) in saline (Hct 20%) into B resulted in a twofold increase in diffusion of mHg when compared to saline alone. Increasing Hct in saline in compartment B resulted in a progressive decrease in diffusion (r = -0.95, P less than 0.001). The presence of RBC in plasma (Hct 20%) in B resulted in a 70% decrease in diffusion; with increasing Hct, diffusion was further reduced (r = -0.95, P less than 0.001). Direct addition of mHg to RBC in saline resulted in 98% RBC uptake. Increasing concentrations of plasma (at a constant Hct) resulted in a progressive decrease in RBC uptake. In undiluted plasma at Hct 14%, RBC uptake of mHg was 35%. Plasma electrophoresis showed that much of the mHg was associated with a high-molecular-weight lipoprotein fraction. Plasma components appear to be important in the distribution of mHg in blood, and may be a factor in the relatively higher blood levels in the fetus.     

In vitro appraisal of the probiotic value of intestinal lactobacilli

Lactobacilli play a distinctive role in the microbial balance of the chicken gut. In experiments simulating the chicken crop, the antagonism of lactobacilli against Enterobacteriaceae and Salmonella typhimurium was demonstrated and was attributed to lactic acid production. Moreover, adhesion to the crop epithelium was a common characteristic of intestinal lactobacilli. As opposed to salmonellas, lactobacilli were sensitive to deconjugated bile salts at 2.5mm. This sensitivity could lower their chance of proliferation in the small bowel of the chicken tract.The authors are at the Laboratory of Microbial Ecology, Faculty of Agricultural Sciences, State University of Gent, Coupure L., 653, B-9000 Gent, Belgium.     

Relationships between the probiotic and host indigenous lactobacilli under the conditions of mixed cultivation in vitro

Relationships between 5 Lactobacillus manufacturing strains, 458 cultures of indigenous lactobacilli isolated from the human digestive and vaginal tracts and 98 isolates from the feces of white rats and mice were under study. The study demonstrated that under the conditions of mixed in vitro cultivation of paired cultures, probiotic strains inhibited more than 60% of the indigenous lactobacilli isolates. L. acidophilus strain K3 III 24 had the widest spectrum of antagonistic activity. Antagonistic relationships between indigenous lactobacilli depended on the origin, individual features and the anatomical sites of the culture isolation. Based on these results it has to be suggested that probiotic lactobacilli are capable of inducing disbalance in the host indigenous lactoflora. While choosing probiotics the character of relationships between probiotic microorganisms and the indigenous lactobacilli of the future recipient is recommended to be preliminarily tested in vitro.     

Fluorescent histochemical studies on the mucosa of the vertebrate gastrointestinal tract

Summary Fluorescent histochemical studies have been made on the mucosa of the gut of a mammal (guinea-pig) and of some lower vertebrates (trout, eel, toad and lizard). Adrenergic nerves in the mucosa generally occur in perivascular plexuses. There appears to be no adrenergic innervation of the muscularis mucosae.Yellow fluorescent enterochromaffin cells were observed in the mucosal epithelium of all species, including fish. Autofluorescent structures in the mucosa of these animals have also been described and were particularly prominent in the large intestines of teleost fish.     

Molecular approaches for the detection and identification of bifidobacteria and lactobacilli in the human gastrointestinal tract

In this review an overview of various molecular techniques and their application for the detection and identification of bifidobacteria and lactobacilli in the gastrointestinal (GI) tract is presented. The techniques include molecular typing techniques such as amplified ribosomal DNA restriction analysis (ARDRA), randomly amplified polymorphic DNA (RAPD), pulsed field gel electrophoresis (PFGE), ribotyping and community profiling techniques such as PCR coupled to temperature and denaturing gradient gel electrophoresis (PCR-TGGE and PCR-DGGE, respectively). Special attention is given to oligonucleotide probes and primers that target the ribosomal RNA (rRNA) sequences and their use in PCR and different hybridisation techniques such as DNA microarrays and fluorescent in situ hybridisation (FISH). In addition, recent findings based on the molecular studies of bifidobacteria and lactobacilli in the GI-tract are reviewed.     

In vitro characterization of calcium transport along the gastrointestinal tract of freshwater rainbow trout Oncorhynchus mykiss

Using an in vitro gut-sac technique, this study examined the mechanisms of calcium (Ca) uptake along the gastrointestinal tract (GIT) of rainbow trout Oncorhynchus mykiss. Ca uptake into three different compartments (mucous-bound, mucosal epithelium and blood space) of four distinct GIT segments (stomach, anterior intestine, mid intestine and posterior intestine) was monitored after luminal exposure to 10 mM Ca saline (radiolabelled with (45) Ca). Ca transport was determined to be both time-dependent and concentration-dependent. The concentration-dependent kinetics of Ca uptake was investigated using varying luminal concentrations of Ca (1, 10, 30, 60 and 100 mM). In the blood-space compartment, Ca uptake was saturable at high Ca concentrations in the mid intestine (suggesting mediated transport), while linear uptake was found in the other gut segments. In the mucous-bound and mucosal epithelium compartments, however, saturation kinetics were found for most GIT segments, also suggesting mediated transport. Manipulation of serosal saline osmotic pressure with mannitol demonstrated that Ca uptake was not greatly affected by solvent drag. Elevated mucosal cadmium (Cd) did not appear to inhibit Ca uptake into the blood space in any of the GIT sections, and Ca uptake did not appear to be sodium dependent. Maximum transport capacities for Ca and Cd were found to be comparable between the gills and gut, but affinities were much higher at the gills (up to 3000 times).     

Studies on the removal of Cd ions by gastrointestinal lactobacilli

Applied Microbiology and Biotechnology - Accumulation of toxic metal ions in food and water is nowadays a growing health-related problem. One detoxification method involves the use of...     

Contractile effects of ghrelin-related peptides on the chicken gastrointestinal tract in vitro

Ghrelin is an endogenous ligand for growth hormone secretagogue receptor (GHS-R), and it stimulates growth hormone (GH) release, food intake and gastrointestinal motility in mammals. Ghrelin has also been identified in the chicken, but this peptide inhibits food intake in the chicken. We examined the effects of ghrelin and related peptides on contractility of the isolated chicken gastrointestinal tract in vitro. Among ghrelin-related peptides examined (1 microM of rat ghrelin, human ghrelin, chicken ghrelin and growth hormone releasing peptide-6 (GHRP-6)), only chicken ghrelin was effective on contraction of the chicken gastrointestinal tract. Des-acyl chicken ghrelin was ineffective, suggesting that octanoylation at Ser3 residue of chicken ghrelin was essential for inducing the contraction. Amplitude of chicken ghrelin-induced contraction was region-specific: highest in the crop and colon, moderate in the esophagus and proventriculus, and weak in the small intestine. The contractile response to chicken ghrelin in the crop was not affected by tetrodotoxin (TTX), but that in the proventriculus was decreased by TTX and atropine to the same extents. D-Lys3-GHRP-6 (a GHS-R antagonist) caused a transient contraction and inhibited the effect of chicken ghrelin without affecting the high-K+-induced contraction. Chicken ghrelin potentiated electrical field stimulation-induced cholinergic contraction without affecting the responsiveness to bath-applied carbachol in the proventriculus. The location of GHS-R differs in the crop (smooth muscle) and proventriculus (smooth muscle and enteric neurons). These results indicate that ghrelin has contractile activity on gastrointestinal tract in the chicken in vitro, and the effect was region-specific. The action would be mediated through the GHS-R, which is highly sensitive to chicken ghrelin.