Recent advances in human protozoan parasites of the gastrointestinal tract

An attempt was made in this report to present an update on the recent development on intestinal protozoan infections in humans. Except for a few historical references the review covers the period from 1980 to the time of writing, mid-1985. The emphasis was on the more important parasites and an effort made to cover the latest developments in their biology, epidemiology and pathogenesis. During preparation of this paper I was impressed with the plethora of papers published on some parasites and the paucity of reports on others. There are an increasing number of papers on Cryptosporidium sp. and the interest in the organisms should continue. Furthermore, it will be of interest to follow the association between Blastocystis hominis and disease. These are essentially new protozoan parasites of man, and one wonders how many more intestinal protozoan parasitosis are still waiting to be found. Like the Cryptosporidium sp., it may be a matter of finding the right diagnostic technique to detect the unknown organism.Giardiasis continues to be a cause of diarrhea among various groups especially campers who are drinking untreated water and G. lamblia as well as E. histolytica are being found more frequently in homosexuals with and without AIDS. The ability to predict virulence in strains of E. histolytica by enzyme patterns is intriguing but some skeptics still prefer the older test for virulence by cecal scoring in animals. New animal models are being evaluated and new techniques applied to the study of pathogenic protozoa. In the future the use of new biotechnological methods will most certainly lead to a better understanding of intestinal protozoa as well as of other parasitic organisms.     

Glucagon- and glicentin-immunoreactive cells in the human digestive tract

Summary The distribution and cellular location of substances reacting with anti-glucagon or anti-glicentin sera, i.e., glucagon-like and glicentin-like immunoreactivities, were studied in the human digestive tract using the immunofluorescence and immunoperoxidase methods. Both types of immunoreactivity were (1) absent in the antrum, (2) abundant in cells located at the periphery of pancreatic islets, (3) unevenly present in cells scattered in the epithelium of the small intestinal mucosa, the glicentin-immunoreactive cells being particularly abundant in the ileum. In the pancreas, and, when simultaneously present, in the intestine, both glucagon and glicentin immunoreactivities were located in the same cells.The precise ultrastructural location of each immunoreactivity was readily made using colloidal gold and ferritin tracers on ultrathin sections of glutaraldehyde-osmium fixed and epoxy resin-embedded tissues. In the pancreas, both glucagon and glicentin immunoreactivities were found in the granules of the A-type cells; the glucagon immunoreactivity was only present in the core of the granule, whereas the glicentin immunoreactivity was found either in the peripheral halo only, or throughout the entire granule. In the small intestine, both immunoreactivities were located inside the granules of the L-type cells.Quantitative specificity tests suggested that the glucagon- and the glicentin-like substances of the pancreas differ from those found in the intestine.Work supported by INSERM, A.T.P. number: 167539     

Distribution of retinol-binding protein in the human digestive tract.

By employing polyclonal antibodies for retinol-binding protein (RBP), its distribution in the human pancreas and digestive tract mucosa was compared with those of transthyretin (TTR) and various peptide hormones. The materials used included surgically removed pancreas, esophagus, stomach, small and large intestines. Paraffin sections were stained by the indirect immunoenzyme method. The results indicate that RBP-containing cells are found in the pancreas and the gastrointestinal mucosa, but most frequently in the gastric antrum and duodenum. In the pancreas, RBP-containing cells are found in the islets and among acinar and ductal epithelial cells, and consistently stain for chromogranin A. RBP-containing cells in the gastrointestinal mucosa showed typical features of endocrine cells and also stained for chromogranin A. The distribution of TTR in these tissue sites resembled that of RBP, but the immunoreactive intensities of both peptides altered independently. Comparison of the distribution of RBP, TTR, and various gastrointestinal peptide hormones revealed that the distribution of RBP coincided with none of the other peptides, although some of the RBP-containing cells stained for most of the peptides examined and vice versa. These results suggest that RBP may be a consistent component of gastrointestinal endocrine cells.     

Ontogeny of vasoactive intestinal peptide in the human fetal digestive tract

Immunocytochemistry and radioimmunoassay were used to assess the appearance time and tissue distribution of vasoactive intestinal peptide (VIP) in the digestive tract of the human fetus. By radioimmunoassay, VIP was measurable from 10 weeks of gestation. The peptide was abundantly distributed in the jejuno-ileum and colon, where the tissue peptide concentration rose from 9-14 weeks of gestation (18.4 +/- 4.4 and 22.0 +/- 5.0 pmol/g wet weight, respectively) to 15-21 weeks (83.0 +/- 21.1 and 98.6 +/- 36.4 pmol/g, respectively). Lower concentrations were recorded in pancreas from 9-14 weeks of gestation (4.3 +/- 0.8 pmol/g) to 15-21 weeks (13.9 +/- 3.7 pmol/g). The peptide concentration was 15.6 +/- 1.9 pmol/g in fundus and 25.5 +/- 3.2 pmol/g in antrum from 15 to 21 weeks of gestation. The highest concentration was recorded in duodenum from 15 to 21 weeks of gestation (118.4 +/- 40.8 pmol/g wet weight). Tissue VIP concentration and age were positively correlated in the jejuno-ileum. By immunofluorescence, immunoreactive VIP was localized in nervous fibers in the muscularis externa, in the submucosa and in the lamina propria. Scarce cell bodies were also found in the myenteric plexus. No immunofluorescent endocrine cells were observed. These results suggest: (1) the early appearance of immunoreactive VIP in gut, as early as 10 weeks of gestation; (2) the peptide, localized in nervous structures only, follows the same distribution pattern as that in adults; (3) the development of VIPergic structures is a continuous process, initiated during the 3rd month of pregnancy.     

Microflora and internal parasites of the digestive tract of Eurasian griffon vultures (Gyps fulvus) in Croatia

Faecal and vomit samples were collected from 12 griffon vultures (Gyps fulvus) in May 2002 and examined for bacteria, fungi and parasites. Bacteria present included Escherichia coli, Aeromonas salmonicidia, Proteus sp., Escherichia fergusonii, Providencia alcalifaciens, Micrococcus sp. and Streptococcus sp. Mycological examination revealed the presence of Candida sp., yeasts and in one case, Rhodotorula rubra. Strongyle eggs were found in several samples. In most faecal samples, ascarid eggs of Toxocara type were found. Tapeworm eggs of Moniezia type were present in one faecal sample. Both microbiologic and parasitic findings are most likely the result of the feeding habits of griffon vultures.     

Bifidobacteria in the digestive tract of bumblebees

Bifidobacteria and other bacterial groups (lactobacilli, facultative anaerobes, anaerobes) from the digestive tract of three bumblebee species (Bombus lucorum (34 samples), Bombus pascuorum (18 samples) and Bombus lapidarius (9 samples)) were enumerated and characterised. Counts of facultative anaerobic bacteria and lactobacilli (5.41 ± 2.92 and 2.69 ± 3.02 log CFU/g of digestive tract content) were lower than those of anaerobes (7.66 ± 0.86 log CFU/g). Counts of bifidobacteria were determined using two selective media: MTPY (Modified Trypticase Phytone Yeast extract agar) and a new medium with pollen extract. There was no significant difference between the counts of bifidobacteria from both media, 5.00 ± 2.92 log CFU/g on MTPY and 5.00 ± 2.87 on the pollen medium. Subsequently, 187 bacterial strains of the family Bifidobacteriaceae (fructose-6-phosphate phosphoketolase-positive) were isolated from three different localities and from all three species of bumblebees. Bifidobacteria were found in 42 out of 61 specimens (69%). Twenty-three (38%) specimens had counts of bifidobacteria higher than 7.0 log CFU/g. Bifidobacteria represented the dominant group of anaerobes (>70% of total anaerobes), i.e., the principal group of bacteria in the bumblebee digestive tract, in only fourteen specimens (23% of total). For the first time, bifidobacteria were isolated from the digestive tract of bumblebees. In addition, we suggest, on the basis of biochemical tests (API 50 CHL and RAPID ID 32) and genetic methods (PCR and DGGE), that these bacteria may represent new species within the family of Bifidobacteriaceae.     

Survival of Lactobacillus casei in the human digestive tract after consumption of fermented milk

A human trial was carried out to assess the ileal and fecal survival of Lactobacillus casei DN-114 001 ingested in fermented milk. Survival rates were up to 51.2% in the ileum and 28.4% in the feces. The probiotic bacterium has the capacity to survive during its transit through the human gut.     

Homopolymer tract organization in the human malarial parasite Plasmodium falciparum and related Apicomplexan parasites

Background

Homopolymeric tracts, particularly poly dA.dT, are enriched within the intergenic sequences of eukaryotic genomes where they appear to act as intrinsic regulators of nucleosome positioning. A previous study of the incomplete genome of the human malarial parasite Plasmodium falciparum reports a higher than expected enrichment of poly dA.dT tracts, far above that anticipated even in this highly AT rich genome. Here we report an analysis of the relative frequency, length and spatial arrangement of homopolymer tracts for the complete P. falciparum genome, extending this analysis to twelve additional genomes of Apicomplexan parasites important to human and animal health. In addition, using nucleosome-positioning data available for P. falciparum, we explore the correlation of poly dA.dT tracts with nucleosome-positioning data over key expression landmarks within intergenic regions.

Results

We describe three apparent lineage-specific patterns of homopolymeric tract organization within the intergenic regions of these Apicomplexan parasites. Moreover, a striking pattern of enrichment of overly long poly dA.dT tracts in the intergenic regions of Plasmodium spp. uniquely extends into protein coding sequences. There is a conserved spatial arrangement of poly dA.dT immediately flanking open reading frames and over predicted core promoter sites. These key landmarks are all relatively depleted in nucleosomes in P. falciparum, as would be expected for poly dA.dT acting as nucleosome exclusion sequences.

Conclusions

Previous comparative studies of homopolymer tract organization emphasize evolutionary diversity; this is the first report of such an analysis within a single phylum. Our data provide insights into the evolution of homopolymeric tracts and the selective pressures at play in their maintenance and expansion.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2164-15-848) contains supplementary material, which is available to authorized users.     

Carbohydrase activities in the bovine digestive tract

1. The carbohydrase activities of homogenates of mucosa from the abomasum, small intestine, caecum and colon, and of the pancreas of cattle were studied. 2. The disaccharidase activities were located mainly in the small intestine and showed a non-uniform pattern of distribution along the small intestine; trehalase activity was highest in the proximal part, lactase and cellobiase activities were highest in the proximal and middle parts and maltase activity was highest in the distal part. 3. The intestinal lactase and cellobiase activities were highest in the young calf and decreased with age, whereas the intestinal maltase and trehalase activities, which were very low compared with the lactase activity, did not change with age. 4. No intestinal sucrase or palatinase activity was detected in the calf or in the adult cow. 5. Homogenates of intestinal mucosa also exhibited amylase and dextranase activity. 6. Homogenates of the pancreas possessed a strong amylase activity and a weak maltase activity. The maltase activity did not change with age, whereas the amylase activity increased with age. 7. No marked differences were observed between the carbohydrase activities of calves fed solely on milk and those of calves given a concentrate-hay diet from 6 weeks of age.     

Nitric oxide synthase immunoreactivity in the enteric nervous system of the developing human digestive tract

We have investigated indirectly the presence of nitric oxide in the enteric nervous system of the digestive tract of human fetuses and newborns by nitric oxide synthase (NOS) immunocytochemistry and nicotinamide adenine dinucleotide phosphate diaphorase (NADPHd) histochemistry. In the stomach, NOS immunoactivity was confined to the myenteric plexus and nerve fibres in the outer smooth musculature; few immunoreactive nerve cell bodies were found in ganglia of the outer submucous plexus. In the pyloric region, a few nitrergic perikarya were seen in the inner submucous plexus and some immunoreactive fibres were found in the muscularis mucosae. In the small intestine, nitrergic neurons clustered just underneath or above the topographical plane formed by the primary nerve strands of the myenteric plexus up to the 26th week of gestation, after which stage, they occurred throughout the ganglia. Many of their processes contributed to the dense fine-meshed tertiary nerve network of the myenteric plexus and the circular smooth muscle layer. NOS-immunoreactive fibres directed to the circular smooth muscle layer originated from a few NOS-containing perikarya located in the outer submucous plexus. In the colon, caecum and rectum, labelled nerve cells and fibres were numerous in the myenteric plexus; they were also found in the outer submucous plexus. The circular muscle layer had a much denser NOS-immunoreactive innervation than the longitudinally oriented taenia. The marked morphological differences observed between nitrergic neurons within the developing human gastrointestinal tract, together with the typical innervation pattern in the ganglionic and aganglionic nerve networks, support the existenc of distinct subpopulations of NOS-containing enterice neurons acting as interneurons or (inhibitory) motor neurons.     

Impact of intestinal parasites on digestive function in humans

In humans as well as in animals, intestinal parasites can affect key stages of alimentation, digestion, and absorption. Selected examples of the effects of parasitic infection on food intake, intestinal propulsion and motility, organ function, epithelial structure and function, and intestinal circulation are presented. Malabsorption and nutrient loss can result from many of these common infections. Additional data are needed to determine the extent to which alterations in gastrointestinal structure and function vs. effects on appetite mediate the effects of parasites on host nutrition in humans.