Immunochemical evidence for met-enkephalin-like and leu-enkephalin-like peptides in tissues of the earthworm, Lumbricus terrestris

The presence of met- and leu-enkephalin-like immunoreactive materials in nerve, gut, seminal vesicle and body wall tissues of the earthworm Lumbricus terrestris has been demonstrated by means of radioimmunoassay technique. The greatest activity of met- and leu-enkephalin-like immunoreactivity in earthworm gut appears in regions of high digestive enzyme activity and gastrin-like immunoreactivity where it presumably plays a role in regulation of gut function. In all tissues studied the levels of met-enkephalin-like immunoreactivity were higher than that of leu-enkephalin-like immunoreactivity. Dual localization of met- and leu-enkephalin-like immunoreactivity in earthworm gut and nerve tissues follows the pattern observed of peptide hormones in vertebrates which are common to both endocrine and non-endocrine tissues.     

Influence of abdominal temperature and luminal contents on the cauda epididymidis of the rat

In an attempt to determine if changes previously described in the epididymides of cryptorchid testes were related to the elevated environmental temperature or to the absence of normal luminal constituents, rats were divided into four test groups. Group I animals were made unilaterally cryptorchid. Animals in Group II had only the cauda epididymidis of one side maintained within the abdominal cavity (cryptepididymal) while the caput epididymides and testes remained in the scrotum. The testes of animals in Group III remained in the scrotum but had their efferent tubules ligated on one side. Testes of unoperated rats and contralateral testes of the test animals served as controls. The histochemical demonstration of sorbitol dehydrogenase (SDH) was used to determine differences in functional activity and light and electron microscopy were used to determine structural changes. SDH activity could not be demonstrated in the cauda epididymidis of cryptorchid and efferent tubule-ligated animals; animals in which the luminal contents were obviously changed. These same groups of animals showed abnormal folding of the basal surface of the epididymal epithelium at the ultrastructural level. Activity of SDH could be demonstrated in control epididymides and in those that contained normal luminal contents but were maintained at the temperature of the abdominal cavity. The basal surface of the epididymal epithelium was not unusual in these animals. The results indicate that the epididymis is influenced to a greater extent by changes in luminal contents than by temperature elevation.     

Distribution of glutamate dehydrogenase in the intestine of the earthworm (Lumbricus terrestris), and some physiological implications

• 1.1. Intestines of fresh and dehydrated-starved L. terrestris were compared to tissue and anterior-posterior distribution of glutamate dehydrogenase (GDH) and other mitochondrial or cytosol dehydrogenases.
• 2.2. For any dehydrogenase, including GDH, practically all the activity was in the gut epithelium. This distribution of GDH supports Tillinghast (1967, 1968) as to the excretory route for ammonia.
• 3.3. While the distributions of the marker dehydrogenases were reasonably uniform along the intestine, the GDH activity was predominantly (80–90% of the total activity) in the last third of the mid-intestine, indicating a true physiological differentiation of the midgut tube. The GDH activity of the typhlosole was about two times the activity in the peripheral epithelium. The GDH distribution was independent of the physiological state of the worm.
• 4.4. From the distribution of GDH it follows that the mid-intestine, immediately before the hindgut, is the main region both for amino acid uptake and catabolism. As regards amino acids, it typifies the primitive digestive tube by having both the absorptive and the liver functions.

     

Morphology of the epithelium in the alimentary tract of the larval lamprey,Petromyzon marinus L.

The alimentary tract of the ammocoete of the lamprey, Petromyzon marinus L., is divisible into three morphologically distinct regions: the oesophagus, the anterior intestine, and the posterior intestine. The epithelium of the oesophagus possesses mucous, ciliated, and columnar cells and appears to be specialized for movement of food particles. The epithelium of the anterior intestine possesses secretory cells with numerous zymogen granules, ciliated cells, and columnar-absorptive cells. Although some absorption occurs in the anterior intestine, the main function of this region seems to be the release of digestive enzymes and the continued movement of food particles. The epithelium of the posterior intestine is entirely comprised of columnar absorptive cells, namely tall (light and dark) columnar and low columnar, and the primary function of this region is one of absorption. The epithelium of the hindgut resembles that of the archinephric duct (Youson and McMillan, '71). The morphology of the alimentary tract of ammocoetes suggests that some differentiation and renewal of cell types may occur in the epithelium of the three regions. Comparison of the alimentary tract of larval lamprey with that of other vertebrates indicates that the gut of the ammocoete represents a less specialized level of vertebrate development.     

Endodermal secretion of chitin in the 'cuticle' of the earthworm gizzard

The gizzard of earthworms is definitely of endodermal origin. Contrary to the opinion that tissue of endodermal origin is unable to synthesize chitin, the gizzard epithelium secretes large amounts of chitin-containing material which has special properties. 28.7 +/- 5.7% of the dry weight proved to be chitin; the microfibres form a random felt-like texture. They are not arranged in layers comparable to those found in arthropod cuticle. The protein content amounts to 44.9 +/- 7.1% of the dry weight; the remaining material contains at least uronic acids. In the protein matrix large amounts of the enzymes amylase and protease have been demonstrated. As the so-called cuticle is sloughed off at the lumen side, these enzymes are mingled with the gut contents. It might be called a gastric shield, as it closely resembles this structure, widespread among Mollusca. The thickness of the gizzard cuticle varies between 10 and 90 mum in Lumbricus terrestris and 10-50 mum in L. rubellus. Autoradiography has shown that it is replaced at a high rate. In Lumbricus terrestris it is renewed completely in less than 60 hr, and in smaller Lumbricus rubellus, this takes place in about 48 hr. These results are in agreement with the biochemical findings.     

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).     

4种蚯蚓肠道微生物对砷毒性的响应差异研究

蚯蚓肠道是微生物多样性的一个潜在存储库。砷对蚯蚓肠道微生物群落的影响已被证实,但砷在不同蚯蚓肠道菌群中生物转化的差异仍不清楚。为了进一步阐述土壤中广泛存在的低浓度砷(浓度为5,15,25 mg/kg)对不同种类蚯蚓肠道微生物影响的差异,将4种典型蚯蚓暴露于砷污染土壤后,测定其肠道微生物组成变化,并分析砷对不同蚯蚓肠道内砷富集、形态和砷生物转化基因的影响。结果显示,所有蚯蚓组织内均存在明显的砷富集,其富集系数由高到低依次为:安德爱胜蚓(1.93)>加州腔蚓(0.80)>通俗腔蚓(0.78)>湖北远盲蚓(0.52),蚯蚓组织和肠道内砷形态主要以无机砷为主,其中As(III)含量比例> 80%,部分蚯蚓组织内还发现少量有机砷。4种蚯蚓肠道微生物群落在门水平上主要以变形菌、厚壁菌和放线菌为主,并与周围土壤细菌群落组成存在显著差异。同时,在土壤和肠道内共检测到17个砷转化基因,其中蚯蚓肠道内As(V)还原和砷转运相关基因相对丰度较高,而砷(去)甲基化基因丰度较低。此外,低浓度砷污染对蚯蚓生长无显著影响,却能引起蚯蚓肠道微生物群落的紊乱。蚯蚓种类和砷污染是引起蚯蚓肠道微生物...     

The earthworm gut: an ideal habitat for ingested N2O-producing microorganisms

The in vivo production of nitrous oxide (N(2)O) by earthworms is due to their gut microbiota, and it is hypothesized that the microenvironment of the gut activates ingested N(2)O-producing soil bacteria. In situ measurement of N(2)O and O(2) with microsensors demonstrated that the earthworm gut is anoxic and the site of N(2)O production. The gut had a pH of 6.9 and an average water content of approximately 50%. The water content within the gut decreased from the anterior end to the posterior end. In contrast, the concentration of N(2)O increased from the anterior end to the mid-gut region and then decreased along the posterior part of the gut. Compared to the soil in which worms lived and fed, the gut of the earthworm was highly enriched in total carbon, organic carbon, and total nitrogen and had a C/N ratio of 7 (compared to a C/N ratio of 12 in soil). The aqueous phase of gut contents contained up to 80 mM glucose and numerous compounds that were indicative of anaerobic metabolism, including up to 9 mM formate, 8 mM acetate, 3 mM lactate, and 2 mM succinate. Compared to the soil contents, nitrite and ammonium were enriched in the gut up to 10- and 100-fold, respectively. The production of N(2)O by soil was induced when the gut environment was simulated in anoxic microcosms for 24 h (the approximate time for passage of soil through the earthworm). Anoxia, high osmolarity, nitrite, and nitrate were the dominant factors that stimulated the production of N(2)O. Supplemental organic carbon had a very minimal stimulatory effect on the production of N(2)O, and addition of buffer or ammonium had essentially no effect on the initial N(2)O production rates. However, a combination of supplements yielded rates greater than that obtained mathematically for single supplements, suggesting that the maximum rates observed were due to synergistic effects of supplements. Collectively, these results indicate that the special microenvironment of the earthworm gut is ideally suited for N(2)O-producing bacteria and support the hypothesis that the in situ conditions of the earthworm gut activate ingested N(2)O-producing soil bacteria during gut passage.     

An in vitro analysis of intestinal ammonia handling in fasted and fed freshwater rainbow trout (Oncorhynchus mykiss)

Ammonia transport and metabolism were investigated in the intestinal tract of freshwater rainbow trout which had been either fasted for 7 days, or fasted then fed a satiating meal of commercial trout pellets. In vivo, total ammonia concentrations (T _amm) in the chyme were approximately 1 mmol L^?1 across the entire intestine at 24 h after the meal. Highest chyme pH and P _NH3 values occurred in the posterior intestine. In vitro gut sac experiments examined ammonia handling with mucosal (Jm_amm) and serosal (Js_amm) fluxes under conditions of fasting and feeding, with either background (control ≤0.013 mmol L^?1) or high luminal ammonia concentrations (HLA = 1 mmol L^?1), the latter mimicking those seen in chyme in vivo. Feeding status (fasted or fed) appeared to influence ammonia handling by each individual section. The anterior intestine exhibited the greatest Jm_amm and Js_amm values under fasted control conditions, but these differences tended to disappear under typical post-feeding conditions when total endogenous ammonia production (Jt_amm = Js_amm ? Jm_amm, signs considered) was greatly elevated in all intestinal sections. Under fasted conditions, glutamate dehydrogenase (GDH) and glutaminase (GLN) activities were equal across all sections, but the ammonia-trapping enzyme glutamine synthetase (GS) exhibited highest activity in the posterior intestine, in contradiction to previous literature. Feeding clearly stimulated the total rate of endogenous ammonia production (Jt_amm), even in the absence of a high luminal ammonia load. This was accompanied by an increase in GDH activity of the anterior intestine, which was also the site of the largest Jt_amm. In all sections, during HLA exposure, either alone or in combination with feeding, there were much larger increases in endogenous Jt_amm, most of which was effluxed to the serosal solution. This is interpreted as a response to avoid potential cytotoxicity due to overburdened detoxification mechanisms in the face of elevated mucosal ammonia. Thus T _amm of the intestinal tissue remained relatively constant regardless of feeding status and exposure to HLA. Ammonia production by the gut may explain up to 18 % of whole-body ammonia excretion in vivo under fasting conditions, and 47 % after feeding, of which more than half originates from endogenous production rather than from absorption from the lumen.     

Regional metabolic differences in the rat diaphragm

This study characterized the biochemical properties of the rat diaphragm by measuring the activities of selected citric acid cycle and glycolytic enzymes. The diaphragm was removed from 10 female Sprague-Dawley rats (180 days old) and dissected into five discrete anatomic regions: crural (region 1), left posterior costal (region 2), left anterior costal (region 3), right anterior costal (region 4), and right posterior costal (region 5). Sections were assayed for total protein concentration and the activities of succinate dehydrogenase (SDH) and lactate dehydrogenase (LDH). The SDH activity in the crural region was approximately 18% lower (P less than 0.05) than that in any costal region. Furthermore, protein concentration was significantly lower (P less than 0.05) in the crural region compared with all costal regions. In contrast, costal regions 2-5 did not significantly differ from each other in protein concentration or SDH activity. LDH activity did not differ significantly (P greater than 0.05) between regions. Finally, the LDH-to-SDH activity ratio was significantly higher (P less than 0.05) in the crural diaphragm compared with all costal regions. We conclude that the crural region of the rat diaphragm is significantly lower in oxidative capacity than all the costal regions. Investigators who use a rodent model to study diaphragmatic function and plasticity should consider the oxidative heterogeneity of the diaphragm when designing experiments.     

Morphology of the bovine epididymis

The epididymis of the bull was divided into six regions, and morphological differences between regions were studied. The epithelium of all regions contained four cell types: principal and basal epithelial cells, and intraepithelial lymphocytes and macrophages. The epithelium of regions II-V also contained a few apical cells. Principal cells of all regions possessed an endocytotic apparatus including stereocilia underlain by canaliculi, coated vesicles, and subapical vacuoles (up to 1 micron in diameter); however, large vacuoles with a flocculent content and multivesicular bodies (up to 5 microns in diameter) were most numerous in regions II, III, and IV. The unique features of principal cells of region I were the presence of well-developed Golgi bodies, few lipid droplets, and whorls of smooth endoplasmic reticulum in the supranuclear cytoplasm. Numerous mitochondria, distended cisternae of rough endoplasmic reticulum, and dense granules characterized the infranuclear cytoplasm of the principal cells of regions II-VI; however, these features were more developed in region V. Apical cells were characterized by the apical location of the nucleus, many mitochondria in the apical cytoplasm, and few microvilli at the luminal border. Basal cells with few cytoplasmic lipid droplets were present throughout the length of the epididymis but appeared more numerous in region V. Intraepithelial lymphocytes were present at all levels of the epithelium but were never seen in the lumen. Intraepithelial macrophages containing heterogeneous granules, eccentric nuclei, and pseudopods were invariably seen near the basal area of the epithelium in all regions. These observations are discussed in an effort to define the role of each cell type in the epididymal epithelium.     

The Earthworm Gut: an Ideal Habitat for Ingested N2O-Producing Microorganisms

The in vivo production of nitrous oxide (N₂O) by earthworms is due to their gut microbiota, and it is hypothesized that the microenvironment of the gut activates ingested N₂O-producing soil bacteria. In situ measurement of N₂O and O₂ with microsensors demonstrated that the earthworm gut is anoxic and the site of N₂O production. The gut had a pH of 6.9 and an average water content of approximately 50%. The water content within the gut decreased from the anterior end to the posterior end. In contrast, the concentration of N₂O increased from the anterior end to the mid-gut region and then decreased along the posterior part of the gut. Compared to the soil in which worms lived and fed, the gut of the earthworm was highly enriched in total carbon, organic carbon, and total nitrogen and had a C/N ratio of 7 (compared to a C/N ratio of 12 in soil). The aqueous phase of gut contents contained up to 80 mM glucose and numerous compounds that were indicative of anaerobic metabolism, including up to 9 mM formate, 8 mM acetate, 3 mM lactate, and 2 mM succinate. Compared to the soil contents, nitrite and ammonium were enriched in the gut up to 10- and 100-fold, respectively. The production of N₂O by soil was induced when the gut environment was simulated in anoxic microcosms for 24 h (the approximate time for passage of soil through the earthworm). Anoxia, high osmolarity, nitrite, and nitrate were the dominant factors that stimulated the production of N₂O. Supplemental organic carbon had a very minimal stimulatory effect on the production of N₂O, and addition of buffer or ammonium had essentially no effect on the initial N₂O production rates. However, a combination of supplements yielded rates greater than that obtained mathematically for single supplements, suggesting that the maximum rates observed were due to synergistic effects of supplements. Collectively, these results indicate that the special microenvironment of the earthworm gut is ideally suited for N₂O-producing bacteria and support the hypothesis that the in situ conditions of the earthworm gut activate ingested N₂O-producing soil bacteria during gut passage.     

Transdifferentiation in holothurian gut regeneration

It has recently been shown that the whole spectrum of cell types constituting a multicellular organism can be generated from stem cells. Our study provides an example of an alternative mechanism of tissue repair. Injection of distilled water into the coelomic cavity of the holothurian Eupentacta fraudatrix results in the loss of the whole digestive tract, except the cloaca. The new gut reforms from two separate rudiments. One rudiment appears at the anterior end of the body and extends posteriorly. The second rudiment grows anteriorly from the cloaca. In the anterior rudiment, the luminal epithelium (normally derived from endoderm) develops de novo through direct transdifferentiation of the coelomic epithelial cells (mesodermal in origin). In the posterior rudiment, the luminal epithelium originates from the lining epithelium of the cloaca. After 27 days, the two rudiments come into contact and fuse to form a continuous digestive tube lined with a fully differentiated luminal epithelium. Thus in this species, the luminal epithelia of the anterior and posterior gut rudiments develop from two different cell sources-i.e., from the mesodermally derived mesothelium and the endodermally derived epithelium of the cloacal lining, respectively. Our data suggest that differentiated cells of echinoderms are capable of transdifferentiation into other cell types.     

Interactions of earthworms with Atrazine-degrading bacteria in an agricultural soil

In the last 10 years, accelerated mineralization of Atrazine (2-chloro-ethylamino-6-isopropylamino-s-triazine) has been evidenced in agricultural soils repeatedly treated with this herbicide. Here, we report on the interaction between earthworms, considered as soil engineers, and the Atrazine-degrading community. The impact of earthworm macrofauna on Atrazine mineralization was assessed in representative soil microsites of earthworm activities (gut contents, casts, burrow linings). Soil with or without earthworms, namely the anecic species Lumbricus terrestris and the endogenic species Aporrectodea caliginosa, was either inoculated or not inoculated with Pseudomonas sp. ADP, an Atrazine-degrading strain, and was either treated or not treated with Atrazine. The structure of the bacterial community, the Atrazine-degrading activity and the abundance of atzA, B and C sequences in soil microsites were investigated. Atrazine mineralization was found to be reduced in representative soil microsites of earthworm activities. Earthworms significantly affected the structure of soil bacterial communities. They also reduced the size of the inoculated population of Pseudomonas sp. ADP, thereby contributing to the diminution of the Atrazine-degrading genetic potential in representative soil microsites of earthworm activities. This study illustrates the regulation produced by the earthworms on functional bacterial communities involved in the fate of organic pollutants in soils.     

Electron microscopic studies of the digestive tract and absorption from the gut lumen of a feather star,oligometra serripinna (Echinodermata)

Summary The gut of a crinoid echinoderm is described for the first time by transmission electron microscopy. The gut comprises a short esophagus, a relatively long intestine and a short rectum. From the luminal side to the coelomic side, the layers of the gut wall are an inner epithelium, an epineural plexus (much reduced or absent in the intestine and rectum), haemal fluid, smooth muscles mixed with a hyponeural plexus, and a visceral peritoneum. The inner epithelium of the esophagus consists of numerous flagellated enterocytes and some mucous cells containing abundant mucous granules. The luminal surface of the esophagus, but not that of the other gut regions, is covered by a conspicuous cuticle. The inner epithelium of the intestine consists of some exocrine cells, presumably exporting digestive enzymes to the gut lumen, and numerous vesicular enterocytes that are flagellated and contain a few apical mucous granules. The inner epithelium of the rectum is made up entirely of vesicular enterocytes most of which lack a flagellum. The uptake of macromolecules from the gut lumen was demonstrated by feeding the feather stars food mixed with ferritin. By 4 h after feeding, ferritin was identified in presumed secondary lysosomes within the enterocytes of the esophagus and within the vesicular enterocytes of the intestine and rectum. The functional implications of the new fine structural results are discussed.     

Amylase activity in the alimentary tract and salivary glands of Periplaneta americana L

The optimum conditions for amylase activity and the distribution of the enzyme in the salivary glands and various gut regions were investigated. Maximum activity of the enzyme was observed at 7.0 pH and 50 degrees C temperature and the activity increased with increasing time period, and enzyme and substrate concentrations. Amylase from the salivary glands was found to be exceptionally potent and the enzyme concentration decreased from the anterior to the posterior part of the gut in well-fed cockroaches. The findings are discussed with regard to the source of amylase synthesis.     

Regional differences in the morphology of the goat epididymis: a light microscopic and ultrastructural study

The goat epididymis, based on morphological differences, was divided into five regions; regions I and II, and the proximal part of region III constituted the head; the distal part of region III and region IV, the body; and region V, the tail. The epithelium of all regions contained principal and basal epithelial cells and intraepithelial lymphocytes and macrophages. In addition, regions II to IV also contained a few apical cells. Clear cells were absent. The epithelium varied in height from the tallest in region I (88 +/- 33 microns) to the shortest in region V (38 +/- 5 microns). Conversely, the luminal diameter, thickness of smooth muscle wall, and luminal sperm concentration were highest in region V. The irregular epithelial height of regions I and IV accounted for a stellate lumen in contrast to the oval lumen of the other regions. Whereas the lumen of region I contained only a few sperm, those of regions II, III, and IV were filled with sperm. Principal cells were the only cell type that showed striking cytological differences between regions. While they contained absorptive features (canaliculi, pinocytotic and coated vesicles, and subapical vacuoles) in all regions, the principal cells of region II were filled with large, heterogeneous vacuoles (up to 5 microns in diameter), suggesting that they may be preferentially involved in transporting and digesting particulate material. Besides absorptive features, principal cells of all regions contained morphological correlates of protein synthesis such as highly developed Golgi complexes in the supranuclear area and numerous cisternae of RER near the Golgi body and in the infranuclear cytoplasm. The cisternae of RER were more developed in region IV, and in some instances, they were distended with flocculent material resembling newly synthesized protein. Unlike the protein synthesizing organelles, principal cells of all regions lacked morphological correlates of steroid hormone synthesis. These results are compared with previously published data on the regional differences in the epididymis of other species, especially with those of the rat and the bull, in an effort to understand the significance of the epididymis in sperm maturation.     

Regional gene expression in the epithelia of the Xenopus tadpole gut

In recent years much progress has been made in the understanding of the genes and mechanisms involved in specification of the cells of the endoderm, which give rise to the epithelium of the gut and respiratory system. However, little is known about the way in which the gut becomes patterned along its anterior-posterior axis, that is, how boundaries are established between the different epithelia of the gut tube. Here we show that the expression patterns of five genes divide the Xenopus tadpole gut epithelium into at least four regions along this axis in the undifferentiated, 3-day-old gut (stage 41), and that these divisions are maintained until at least 7 days, when cell differentiation is well under way. In addition, the restricted expression patterns of these genes clearly mark the anterior and posterior boundaries of the intestine. Xsox2 is expressed in the anterior gut, spanning the oesophagus and stomach but terminating at the stomach/intestine boundary. Xcad1 and Xcad2, two caudal-type homeobox genes, are expressed in a region with an anterior limit at this boundary and a posterior limit between the colon and proctodeum, therefore covering the whole of the small and large intestines. Intestinal fatty acid binding protein (IFABP) is expressed only in the anterior small intestine, and the even-skipped homeobox gene Xhox3 is expressed in the most posterior part of the gut, the proctodeum.     

Influence of retention time on degradation of pancreatic enzymes by human colonic bacteria grown in a 3-stage continuous culture system

Hydrolytic enzymes were measured in gut contents from four sudden death victims. Pancreatic amylase and total protease activities decreased distally from the small bowel to the sigmoid/rectum region of the large intestine, showing that considerable breakdown or inactivation of the enzymes occurred during gut transit. To determine whether pancreatic enzymes were substrates for the gut microflora, mixed populations of bacteria were grown in a 3-stage continuous culture system on a medium that contained pancreatic extract as the sole nitrogen source. The multichamber system (MCS) was designed to reproduce in vitro , the low pH, high nutrient, fast growth conditions of the caecum and right colon and the neutral pH, low nutrient, slow growth conditions of the left colon. Results showed that pancreatic amylase was resistant to breakdown by intestinal bacteria compared with the peptide hydrolases in pancreatic secretions. Leucine aminopeptidase, trypsin and to a lesser degree, chymotrypsin, were easily degraded by gut bacteria, but pancreatic elastase was comparatively resistant to breakdown. Protein degradation in the MCS, as determined by enzyme activities, protein concentration and ammonia and phenol production, increased concomitantly with system retention time over the range 24–69 h. These results suggest that intestinal bacteria play an important role in the breakdown of hydrolytic enzymes secreted by the pancreas and that this process and protein fermentation in general, is likely to occur maximally in individuals with extended colonic retention times.     

Influence of retention time on degradation of pancreatic enzymes by human colonic bacteria grown in a 3-stage continuous culture system

Hydrolytic enzymes were measured in gut contents from four sudden death victims. Pancreatic amylase and total protease activities decreased distally from the small bowel to the sigmoid/rectum region of the large intestine, showing that considerable breakdown or inactivation of the enzymes occurred during gut transit. To determine whether pancreatic enzymes were substrates for the gut microflora, mixed populations of bacteria were grown in a 3-stage continuous culture system on a medium that contained pancreatic extract as the sole nitrogen source. The multichamber system (MCS) was designed to reproduce in vitro, the low pH, high nutrient, fast growth conditions of the caecum and right colon and the neutral pH, low nutrient, slow growth conditions of the left colon. Results showed that pancreatic amylase was resistant to breakdown by intestinal bacteria compared with the peptide hydrolases in pancreatic secretions. Leucine aminopeptidase, trypsin and to a lesser degree, chymotrypsin, were easily degraded by gut bacteria, but pancreatic elastase was comparatively resistant to breakdown. Protein degradation in the MCS, as determined by enzyme activities, protein concentration and ammonia and phenol production, increased concomitantly with system retention time over the range 24-69 h. These results suggest that intestinal bacteria play an important role in the breakdown of hydrolytic enzymes secreted by the pancreas and that this process and protein fermentation in general, is likely to occur maximally in individuals with extended colonic retention times.