Hindgut Regions Research Articles

The Termite Gut Microflora as an Oxygen Sink: Microelectrode Determination of Oxygen and pH Gradients in Guts of Lower and Higher Termites

Clark-type oxygen microelectrodes and glass pH microelectrodes, each with a tip diameter of <=10 (mu)m, were used to obtain high-resolution profiles of oxygen concentrations and pH values in isolated termite guts. Radial oxygen profiles showed that oxygen penetrated into the peripheral hindgut contents up to about 150 to 200 (mu)m below the epithelial surface in both the lower termite Reticulitermes flavipes (Kollar) and the higher termite Nasutitermes lujae (Wasmann). Only the central portions (comprising less than 40% of the total volume) of the microbe-packed, enlarged hindgut compartments ("paunches") were completely anoxic, indicating that some members of the hindgut microbiota constitute a significant oxygen sink. From the slopes of the oxygen gradients, we estimated that the entire paunches (gut tissue plus resident microbiota) of R. flavipes and N. lujae accounted for 21 and 13%, respectively, of the respiratory activity of the intact animals. Axial oxygen profiles also confirmed that in general, only the paunches were anoxic in their centers, whereas midguts and posterior hindgut regions contained significant amounts of oxygen (up to about 50 and 30% air saturation, respectively). A remarkable exception to this was the posterior portion of an anterior segment (the P1 segment) of the hindgut of N. lujae, which was completely anoxic despite its small diameter ((apprx=)250 (mu)m). Axial pH profiles of the guts of Nasutitermes nigriceps (Haldeman) and Microcerotermes parvus (Haviland) revealed that there were extreme shifts as we moved posteriorly from the midgut proper (pH (apprx=)7) to the P1 segment of the hindgut (pH >10) and then to the P3 segment (paunch; pH (apprx=)7). The latter transition occurred at the short enteric valve (P2 segment) and within a distance of less than 500 (mu)m. In contrast, R. flavipes, which lacks a readily distinguishable P1 segment, did not possess a markedly alkaline region, and the pH around the midgut-hindgut junction was circumneutral. The oxic status of the peripheral hindgut lumen and its substantial oxygen consumption, together with previous reports of large numbers of aerobic and facultatively anaerobic bacteria in the hindgut microflora, challenge the notion that termite hindguts are a purely anoxic environment and, together with the steep axial pH gradients in higher termites, refine our concept of this tiny microbial habitat.

Microspine variation in hindgut regions of four families of cockroaches (Blattaria)

Microspines in the cockroach (Blattaria) hindgut were studied to determine their structure, variation, and potential use in classification. Short spines (1–10 μm) were found in all regions of the hindgut, except for the rectal cuticle in all species, the posterior region of the ileum and colon in C. punctulatus and the posterior portion of the ileum of the blaberoid species. They were also characteristics of the pyloric and other valvular cuticle between areas of the hindgut. Moderate (20–60 μm) and long (over 100 μm) microspinal lengths were associated with bacterial aggregations or plaques in the ileum. Microspinal modifications showed only poor phylogenetic correlations.

An investigation into early placental ontogeny: allantoic attachment to the chorion is selective and developmentally regulated

Culture of postimplantation conceptuses was used in conjunction with microsurgery to investigate the timing, the mechanism and the developmental regulation of chorioallantoic fusion in the mouse. The timing of fusion was determined in both freshly recovered conceptuses and in those that had been cultured from as early as the mid-streak stage. Attachment of the allantois to the chorion was found to have occurred in most conceptuses by the 6-somite stage, irrespective of whether they had been cultured. In investigating the mechanism of fusion, we wished to determine whether it depended on directed growth of the allantoic bud or on its differential adhesion to the chorion. Microsurgery was used to transplant allantoic tissue into the exocoelomic cavity of conceptuses from which the resident allantois had been removed. In synchronous grafting experiments, transplanted allantoises typically attached to the chorion despite loss of their connection with the hindgut region of the fetus. Hence selective attachment of the allantois to the chorion clearly cannot depend simply on its directed growth. While the transplanted allantoic tissue attached to the chorion selectively, it did not attach to it precociously, despite being favourably positioned to do so. These findings argue that the initial attachment of the allantois to the chorion depends on a selective adhesive mechanism that is developmentally regulated. Further grafting experiments in which donor conceptuses were either more or less advanced than hosts revealed that attachment of the allantois to the chorion depends primarily on the stage of the allantois rather than on the stage of the chorion. Collectively, these findings support the hypothesis that the initial stage of chorioallantoic fusion depends on selective adhesion between regionally differentiated mesodermal surfaces which is governed principally by the stage of development of the allantois.

Myoendocrine-like Cells in Invertebrates: Occurrence of Noncardiac Striated Secretory-like Myocytes in the Gut of the Ant Formica polyctena

The occurrence of myoendocrine-like cells investing the ampullar draining region of Malpighian tubules and neighboring midgut and hindgut regions of the ant Formica polyctena is reported. These striated muscle cells show small electron-dense endocrine-like granules (130 ± 0.95 nm) in addition to myofilaments and ordinary organules of the myocytes. Apart from their contractile function, such ultrastructural features suggest a regulatory role for these cells, as is the case of vertebrate myoendocrine cells. As far as we know, the ant secretory myocytes reported here constitute the first description of myoendocrine cells among invertebrates, as well as the first report of secretory, striated muscle cells outside the heart in the animal kingdom.

Lipid digestion in turbot (Scophthalmus maximus). I: Lipid class and fatty acid composition of digesta from different segments of the digestive tract

The lipid content and lipid composition of digesta from the stomach, foregut, hindgut and rectum of juvenile turbot fed a commercial diet were determined in order to examine the process of lipid digestion in this species. The moisture content of the digesta increased along the digestive tract from 71.5% in the stomach to 89.6% in the rectum. The lipid content of the digesta increased initially from 15.7% of the dry weight in the stomach to 36.1% in the foregut but thereafter decreased through 23.2% in the hindgut to 9.1% in the rectum. The proportion of triacylglycerols (TAG) in the total lipid of the digesta decreased from 63% in the stomach to 17.4% in the rectum whereas that of free fatty acids (FFA) increased from 10016 to 48.9%. The highest proportions of monoacylglycerols (MAG), diacylglycerols (DAG) and most phospholipids were observed in the lipid of the hindgut digesta. In addition, a fall in levels of neutral and phospholipid classes as digesta moved from hindgut to rectum signified absorption.Analysis of the fatty acid composition of the lipid classes TAG, DAG and MAG suggest a polyunsaturated fatty acid specificity for hydrolysis may exist. Saturated, monounsaturated and polyunsaturated fatty acids (PUFA) accounted for 17.9%, 45.4% and 37.0%, respectively of the FFA present in the foregut whereas the corresponding values for the rectum were 32.6%, 51.9% and 16.3%. Overall, the results suggest a PUFA specifity for hydrolysis may exist alongside the positional non-specific lipolytic activity associated with the hindgut regions of the digestive tract of turbot and that PUFA, released by lipolysis are more effectively absorbed from the digesta than monounsaturated and saturated fatty acids.

Passive uptake in the small intestine and active uptake in the hindgut contribute to the highly efficient mineral metabolism of the common mole-rat, Cryptomys hottentotus.

Cryptomys hottentotus has no access to dietary or endogenous sources of cholecalciferol (D3). Serum concentrations of calcifediol (25(OH)D3) were undetectable (< 5 ng/ml) and calcitriol (1,25(OH)2D3), although detectable in plasma, was at a low concentration (31.40 (SEM 3.06 pg/ml). Despite their naturally impoverished vitamin D status, these animals exhibited highly efficient mineral absorption processes (Ca apparent fractional absorption efficiency, AFA (%) 95.33 (SEM 1.36); inorganic P (P(i)) AFA (%) 93.49 (SEM 0.81)). Furthermore, plasma mineral content was tightly regulated (Ca 2.57 (SEM 0.08) mmol/l; Mg 1.23 (SEM 0.05) mmol/l; P(i) 2.12 (SEM 0.15) mmol/l). Mode of uptake in C. hottentotus was unlike that in other D3-replete mammals. First, passive (rather than active) uptake occurred in the traditional site of active Ca absorption (with serosal:mucosal (S:M) ratios in the duodenum of 1.32 (SEM 0.13)), and the only site of active Ca uptake was the hindgut (caecum S:M 3.35 (SEM 0.46); proximal colon S:M 2.13 (SEM 0.30)). Despite the presence of active uptake in these hindgut regions, their overall contribution to the daily rate of mineral absorption was small (9.53 (SEM 1.27)%). These underground inhabitants rely upon highly efficient, passive mineral uptake. This is adequate to meet their mineral requirements and maintain mineral homeostasis in the absence of vitamin D.

The effect of chromic oxide (Cr2O3) on aerobic bacterial populations associated with the intestinal epithelial mucosa of Arctic charr, Salvelinus alpinus (L.)

Populations of aerobic heterotrophic bacteria present in the gastrointestinal tract of healthy Arctic charr, Salvelinus alpinus (L.), were estimated using the dilution plate technique. The gastrointestinal bacterial flora of fish fed an unsupplemented diet was dominated by Gram-negative bacteria of the genera Acinetobacter, Aeromonas, Agrobacterium, Alcaligenes, Cytophaga, Flavobacterium, Pseudomonas, and Vibrio, and Gram-positive bacteria of the genera Arthrobacter, Brevibacterium, Corynebacterium, Kurthia, Lactobacillus, Microbacterium, Micrococcus, Staphylococcus, and Streptococcus. The composition of the indigenous aerobic bacterial flora in the digestive tract, and especially the microorganisms isolated from the midgut and hindgut regions, was affected by inclusion of 1% chromic oxide (Cr2O3) in the diet. Many of the Gram-negative bacterial genera and some of the Gram-positive bacterial genera were not detectable in the Cr2O3-fed fish. The midgut and hindgut regions in the Cr2O3-fed fish were dominated by Gram-positive microorganisms of the genera Lactobacillus and Streptococcus. It is suggested that the increased accumulation of Cr2O3 in the alimentary tract, as dietary compounds are removed, affects the attachment sites for the gastrointestinal microflora or affects the gut epithelium directly.Key words: chromic oxide, aerobic bacterial flora, Arctic charr.

At high dietary levels ethanol alters the structure of mid- and hindgut epithelial cells of Drosophila melanogaster larvae.

The midgut of Drosophila melanogaster is a site of alcohol dehydrogenase (ADH) activity, the enzyme that catalyzes the first step in the major pathway for ethanol degradation. The effects of different levels of dietary ethanol on the ultrastructures of the guts of larvae of the Canton-S wild-type strain and the ADH-deficient, Adhn2, strain were ascertained. In wild-type larvae fed an ethanol-free, defined medium, the foregut epithelium was characterized by few glycogen rosettes and sparse microvilli that protruded into the gut's thick lumen lining. The midgut epithelium was typical of cells involved in absorption and active transport with abundant microvilli on the apical surface and membrane infoldings on the basal surface. In place of microvilli, the apical surface of the hindgut had membrane infoldings. The apical surfaces of both the mid- and hindgut epithelium were covered by a thick, electron-dense peritrophic membrane consisting of chitin. In both strains the subcellular damage that was correlated with ethanol levels in the diet was confined to the midgut and hindgut regions. Damage to gut cells in the form of disrupted mitochondria, dilated rough endoplasmic reticulum, low densities of glycogen rosettes and protein granules, high numbers of autophagic vacuoles, and the presence of myelin whirls was extensive in Canton-S strain larvae fed a high ethanol diet. A low dietary concentration of ethanol induced changes in gut ultrastructure of Adhn2 larvae similar to the changes that were observed in wild-type larvae fed the higher ethanol concentrations, but the basal infoldings were more dilated in the Adhn2 larvae. At high dietary concentrations the disruption of mid- and hindgut cells by ethanol appeared great enough to interfere with the digestion and absorption of nutrients.

Catecholaminergic neurons supplying the hindgut of the crayfish Procambarus clarkii

The crayfish hindgut is surrounded by a dense plexus of nerve terminals which are known to contain catecholamines. This plexus is positively stained using a monoclonal antibody to tyrosine hydroxylase, the enzyme that catalyzes the rate-limiting step in catecholamine biosynthesis. Two immunoreactive neurons, whose cell bodies are located in the third and fourth abdominal ganglia, contribute to the nerve plexus. Each of these neurons sends a single axon posteriorly through the ventral nerve cord and into the intestinal nerve, where the axon bifurcates to supply the anterior and posterior hindgut regions. High-performance liquid chromatography, coupled to electrochemical detection, demonstrates the presence of dopamine in the intestinal nerve of Procambarus clarkii. Dopamine increases the motility of the isolated hindgut in a dose-dependent manner. The results suggest that two dopaminergic neurons are involved in the neurogenic coordination of hindgut movements.

Ontogeny of the sodium pump in embryos of rockfish of the genusSebastes

The purpose of the present investigation was to determine at what stages of embryonic development the sodium pump (Na+,K+-activated ATP phosphohydrolase, EC 3.6.1.3) appears and whether the ontogeny of the sodium pump plays a role in the matrotrophic viviparity ofSebastes. Early larval stages (stages 1–14) had embryonic tissues nearly devoid of Na, K-ATPase activity. After epiboly, tissues from embryos taken from both species,S. schlegeli andS. taczanowskii, had significant levels of enzymatic activity coincident with the appearance of neuronal tissue in the head fold (stages 15–20). Maximal levels of specific activities of the enzyme were reached with the onset of the vascular circulation and the opening of the buccal cavity together with maturation of the midgut and hindgut regions of the intestinal tract (stages 26 and 28). Ouabain, a specific inhibitor of Na, K-ATPase, was used to measure survival of embryos placed in different seawater concentrations under in vitro conditions. The most sensitive stages to external ouabain were 26–30. These findings support the hypothesis that the intestinal tract is functional prior to gestation and could be transporting important nutritive material found in maternal ovarian fluid.

Physiological changes associated with sporangiospore extrusion from trichospores of Smittium culisetae

Trichospores of the fungus, Smittium culisetae (Trichomycetes), require a two-phase sequence of stimuli for sporangiospore extrusion: Phase I (20 m M KCl, pH 10) and Phase II (pH 7). Phases I and II correspond to conditions within the respective midgut and hindgut regions of mosquito larval hosts. In this study, trichospore pressure increased 1.0 MPa during Phase I but sporangiospores were not extruded. Potassium uptake was insufficient to account for the pressure increase. Sporangiospore extrusion from trichospores was stimulated by a drop in pH at Phase II. Lowering the osmotic potential of the Phase II solution with sucrose inhibited sporangiospore extrusion to varying degrees, with total inhibition occurring at osmotic potentials ≤ −2.7 MPa. At an osmotic potential of −2.1 MPa, the interwall layer at the trichospore apex swelled at the point of sporangial rupture without emergence of the sporangiospore. Interwall layer swelling during Phase II may rupture the sporangial wall of the trichospore and allow the sporangiospore to be extruded by its Phase I pressure.

On the Early Development of the Vestimentiferan Tube WormRidgeiasp. and Observations on the Nervous System and Trophosome ofRidgeiasp. andRiftia pachyptila

Stages in the development of the vestimentiferan Ridgeia sp., based on lengths of preserved specimens processed for scanning electron microscopy, were examined. Features of the nervous system and trophosome of Riftia pachyptila were studied by light, scanning-, and transmission-electron microscopy. Development proceeds from a trochophore-type larva with an anterior prototrochal ciliary ring and a posterior assemblage of transient larval setae, through intermediate stages, some of which lack endosymbiotic bacteria but all of which display additional transient features such as larval branchial filaments, a ventral medial process, and digestive tract, to a young juvenile stage that possesses endosymbiotic bacteria and exhibits the morphology characteristic of adult vestimentiferans. Larval branchial filaments are resorbed in later developmental stages and replaced by paired rows of ciliated branchial filaments with pinnules. The larval gut is divisible into foregut, midgut, and hindgut regions based on cytol...

Ultrastructural Changes in Trichospores of Smittium culisetae and S. culicis during in Vitro Sporangiospore Extrusion and Holdfast Formation

Ultrastructural changes associated with in vitro sporangiospore extrusion (“germination”) and holdfast formation in Smittium culisetae and S. culicis (Trichomycetes) were examined upon treatment of trichospores with potassium at pH 10 (Phase I) followed by a drop in the pH to 7 (Phase II). Phases I and II correspond to sequential conditions encountered by trichospores during passage through the respective midgut and hindgut regions of the insect larval host. In untreated trichospores of S. culisetae, spore bodies were aligned at the apex of the trichospore. Canals in the sporangiospore wall were also present at the apex, along with an interwall layer interposed between the sporangial and sporangiospore walls. No ultrastructural changes were observed at Phase I. Trichospores extruded sporangiospores apically during Phase II and the interwall layer extended outward with the emerging sporangiospore to form the sleeve. Untreated trichospores of S. culicis contained spore bodies scattered throughout the cytoplasm. Canals and an interwall layer were present at both the apex and base of the trichospore. During Phase I, sporangiospores were extruded apically or basally following migration of the spore bodies to either pole of the trichospore. Holdfast formation was restricted to Phase II in both S. culisetae and S. culicis. Disappearance of the spore bodies suggests that they contain the initial holdfast material for attachment to the gut lining. Sporangiospore canals serve as the probable route for expulsion of holdfast material. Holdfasts of S. culisetae adhered to a diversity of substrates in vitro.

Fine structure of the pyloric region and of the hindgut in the proturan Neocondeellum dolichotarsum (insecta, protura).

The fine structure of the midgut, pyloric region, Malpighian papillae, and hindgut in the proturan, Neocondeellum, was studied. Midgut cells, rich in rough endoplasmic reticulum and mitochondria, are linked to each other by smooth septate junctions. No peritrophic membrane is visible over the microvilli. The posterior cells of the midgut carry short microvilli and are surrounded by a muscular pyloric sphincter. Behind such sphincter is a wide pyloric chamber that has cells with very long microvilli pointing anteriorly toward the midgut. These cells with their microvilli form a kind of stopper that controls the passage of the intestinal content into the hindgut. The Malpighian papillae have an apical globular secretory region producing proteinaceous material, which is then collected in a microvillate cistern at the proximal end of the cell. A peduncle formed by flattened squamous cells joins each papilla to the hindgut epithelium. The hindgut shows two differently organized regions, both engaged in fluid reabsorption. The principal cells of the anterior region show a system of apical subcuticular cavities into which thin microvilli extend. In the cytoplasm of these cells, there are numerous mitochondria associated with infoldings of the plasma membrane. The principal cells of the posterior hindgut region have bundles of long microvilli beneath the cuticle. Also, these cells exhibit at their base an abundant system of infoldings of the plasma membrane and mitochondria. The results are considered in relation to the phylogenetic relationship between Neocondeellum and other proturan genera.

Metabolism in marine flatfish—II. Protein digestion in dover sole ( Solea solea L.)

1. 1. The digestive tracts of adult and juvenile Dover sole were examined for protease activities. 2. 2. A pepsin-like protease with an optimal pH value of 1.7 predominated in the stomach region, but the main endoprotease action in the foregut, midgut and hindgut regions was optimal in the range of pH 9.5–10.5 and showed good activity towards elastin orcein. 3. 3. Experiments using synthetic substrates suggested the presence of chymotrypsin- and trypsin-like activities optimal between pH 7 and 8. Collagenase activity was also shown to exist in this pH region. 4. 4. The presence of enzymes corresponding to carboxypeptidases a and b and leucine aminopeptidase was indicated. 5. 5. The possible significance of these results to the farming of Dover sole is discussed.

Proliferation and renewal of the epithelium in the intestine of young adult anadromous sea lampreys, Petromyzon marinus L.

The pattern of incorporation of [3H]thymidine in the intestinal epithelium of young adults of the anadromous sea lamprey, Petromyzon marinus L., was examined for up to 41 days using autoradiography. Compared with haemopoietic tissue of the fat column and the epithelium of the kidney, the intestinal epithelium does not rapidly incorporate the isotope. The epithelia of the anterior and posterior intestines and the hindgut regions all undergo a proliferation which, based on changes in the labelling index through time, suggest that a renewal of the epithelium takes place in each region. Most of the cells undergoing cell division are specialized absorptive cells but, in the posterior intestine and hindgut, mucous cells also undergo a variable rate of division. Although there is a slightly greater frequency of labelled cells at the bases of the longitudinal folds, there are no definite zones of proliferation in any region of the intestine. Instead, patches of dividing cells appear throughout the height of longitudinal mucosal folds. This is similar to the situation in parts of the intestine of larval lampreys and the intestine of amphibian tadpoles but unlike the case in other fishes.

A Study of the Gastro-intestinal Parasites of domestic Populations of the Cockroach Periplaneta americana Linnaeus at Nsukka, Nigeria

The gastro-intestinal parasites of Cockroaches Peritaneta americana Linnaeus from three domestic sources at Nsukka, Nigeria were studied. Five species of protozoa and six of helminths (including cysts of Entamoeba sp. and eggs of Ascaris sp, and Trichuris sp, ) were found in the insects. Cockroaches from sewage had comparatively the greatest parasite infestations while those from household boxes showed the least infection rates. Successive nymphal stages of the insects showed significant increase in their parasite loads, upwards to the adult stage. Most of the parasites were found in the hindgut region, and practically none in the foregut. Stained histological sections of the insects’ gut revealed close association between the parasites (especially Gregarina blattarum Spraque and Syphacia obvelata Rudolph) and the endothelium. The epidemiology and ecological implications of the types, distribution, and loads of parasites found in the insects are discussed in relation to their common occurrence in and around human homes.

Structural observations on the alimentary canal of Paranthessius anemoniae, a copepod associate of the snakelocks anemone Ammonia sulcata

Light and electron microscopy has shown the alimentary canal of Paranthessius to be composed of clearly defined foregut, midgut and hindgut regions. The spacious foregut is cuticle‐lined and separated from the midgut by a valve. The midgut epithelium is composed of columnar cells with an apparent secretary/absorptive rôle, and amoeboid cells thought to engulf material from the lumen. The amoeboid cells have large electron‐dense central vacuoles containing carbohydrate‐and protein‐staining material. These cells appear to be sloughed off into the lumen to form part of a faecal pellet. Apart from their digestive rôle the midgut cells store lipid and it is considered possible that they have an osmoregulatory function. The hindgut epithelium cell type, lacks a cuticular layer and is thought to be mainly concerned with absorption. The alimentary canal is surrounded by strands of longitudinal and circular muscle.

The Mode of Infection of the Insect Pathogenic Fungus Culicinomyces in Larvae of the Mosquito Culex Fatigans.

The initiation and morphological development of infection by Culicinomyces in C. fatigans larvae was followed by means of observations of dissections and stained histological sections of infected specimens. The infection sites are the foregut and hindgut regions of the digestive tract, unlike those of most other insect-parasitizing fungi, which invade through the exterior integument. The penetration of the gut wall and growth in the haemocoel is described, as well as sporulation of the fungus after death of the larvae. The first stage in infection is the firm adherence of the fungal spore to the gut cuticle. This occurs before the spore germinates, and there is evidence to suggest that it may be excited by a thigmotropic stimulus. The penetration of the gut wall does not involve the formation of an appressorium, though this does not preclude mechanical penetration. The penetration of the exterior cuticle, which occurs after death of the insect and initiates conidiophore formation, involves a typical appressorium and mechanical force.

On a parasitic nematode, Galebiella sp. Basir, 1941, from aquatic beetles in Egypt.

The genus Galebiella Basir, 1941, has been recorded from Hydrous aculeatus Sol. (Coleoptera: Hydrophilidae) in the U.A.R. Female nematodes only were found, in the hindgut of the adult beetles.Worms were especially abundant close to the pyloric valve and were found free in the gut lumen; a few of them were loosely attached to the gut wall.The reaction of the hind- and midgut was almost the same yet the infection was restricted to the hindgut.In many cases of infection the peritrophic membrane in the hindgut region became fragmented into longitudinal fibres. The intima, epithelium and muscle layers showed no changes at all.