Integrin-linked kinase: integrin's mysterious partner

Integrin-mediated cell adhesion regulates a vast number of biological processes including migration, survival and proliferation of cells. It is therefore not surprising that defects in integrin function are often rate-limiting for development and profoundly affect the progression of several diseases. The functions of integrins are mediated through the recruitment of cytoplasmic plaque proteins. One of these is integrin-linked kinase, which connects integrins to the actin cytoskeleton and transduces signals through integrins to the extracellular matrix and from integrins to various subcellular compartments.     

An apparatus for sampling gut contents of large,living fishes

Synopsis Apparatus and methods are described and illustrated for flushing and retaining gut contents from large, living fishes with water supplied by a 12 volt portable pump.     

Neuropeptides in the fish gut. An immunohistochemical study of evolutionary patterns

The presence and distribution of bombesin-, enkephalin-, gastrin/cholecystokinin-, neuropeptide Y-, neurotensin-, somatostatin-, substance P-, and VIP-like immunoreactivities in gut nerves of representatives of nineteen cyclostome, elasmobranch and teleost species have been studied. The results have been correlated to results from previous studies in other species. Nerve plexuses showing bombensin-like, substance P-like and VIP-like immunoreactivity are commonly occurring, while other neuropeptides may have a more varied distribution. Tentative evolutionary patterns, and the possible function and importance of each peptide is discussed.     

Fate of ciliates in the earthworm gut: An in vitro study

The behavior of the ciliateColpidium campylum was unaffected by exposure in vitro to high concentrations of pharyngeal and hindgut fluids from the earthwormLumbricus terrestris, but movement became abnormal and ceased in concentrations of midgut fluid as low as 1.5%. On mixingC. campylum culture with an equal volume of midgut fluid, which often contained resident astomatous ciliates, the.C. campylum cells were immediately immobilized and frequently disintegrated, while the astomatous ciliates continued to behave normally. Possible causes of the hostility of the midgut environment, and implications for earthworm nutrition, are discussed.     

Prostaglandin H synthase immunoreactivity in human gut. An immunohistochemical study.

Prostaglandins exhibit a variety of actions on intestinal smooth muscle depending upon the type, dose and muscle layer studied. As the cellular origin of prostaglandin H (PGH) synthase has not been established with certainty in the human gut wall, we studied the localization of PGH synthase in the human duodenum, jejunum, ileum and colon by immunohistochemistry. PGH synthase immunoreactivity appeared to be similar in all segments of the intestine. Most smooth muscle cells seemed to contain PGH synthase; however, the reaction in the lamina muscularis mucosae was much stronger than in the longitudinal and circular muscle layers. Endothelial cells in capillaries and larger vessels showed a positive reaction. In addition, unidentified cells in subserosa, at the level of Auerbach's plexus and in the submucosa were stained. We concluded that the smooth muscle cells of the human gut has a rather large capacity for PGH synthesis and the present results may provide a basis for a better understanding of both normal physiological functions as well as intestinal disease states involving disorders of prostaglandin synthesis.     

An antioxidant system required for host protection against gut infection in Drosophila

A fundamental question that applies to all organisms is how barrier epithelia efficiently manage continuous contact with microorganisms. Here, we show that in Drosophila an extracellular immune-regulated catalase (IRC) mediates a key host defense system that is needed during host-microbe interaction in the gastrointestinal tract. Strikingly, adult flies with severely reduced IRC expression show high mortality rates even after simple ingestion of microbe-contaminated foods. However, despite the central role that the NF-kappaB pathway plays in eliciting antimicrobial responses, NF-kappaB pathway mutant flies are totally resistant to such infections. These results imply that homeostasis of redox balance by IRC is one of the most critical factors affecting host survival during continuous host-microbe interaction in the gastrointestinal tract.     

The aging gut

A spectrum of changes occurs in the function of the gastrointestinal tract throughout the life of the animal. With aging, there is a decline towards newborn levels of the villus surface area and brush border membrane markers, but the absorption of some nutrients continues to increase (such as glucose and vitamin), whereas the absorption of some nutrients falls (such as cholesterol) and fatty acids). Clearly there is a distinction between age-related alterations in intestinal form and function, and some of the enzyme- or carrier-mediated changes are substrate specific. With aging, the structure and brush border membrane composition of the intestine tends to regress towards newborn levels. It remains to be clarified whether these changes are a benefit to the animal, whether they represent a degeneration of normal function, and whether these changes are the cause or the effect of various age-related alterations in metabolic and physiological function.     

An antimony-silver/silver chloride electrode system for measuring pH in insect gut contents

An electrode system consisting of a cast antimony rod with a silver chloride-coated wire as a reference electrode has been developed to measure pH in insect gut contents. The electrode works well with buffer volumes down to 0.1 μl. Response to pH is linear between pH 4 and 11 and equates to a change of 52.3 mV per pH unit at 18–20°C. Electrical resistance is low (0.25 MΩ), so the electrode can be used with low-impedance meters and does not require shielding from induced currents. Its useful range lies between redox potentials −330 mV (pH 7) and +297 mV to 350 mV, corresponding to a pe + pH range of 1.4 to about 10.8. This covers reported gut pH values for most insects so far examined. Consequently the electrode is suitable for measuring pH of gut contents from many insects that are too small to be analysed with current commercial electrodes.     

An intrinsic gut leptin-melanocortin pathway modulates intestinal microsomal triglyceride transfer protein and lipid absorption

Fat is delivered to tissues by apoB-containing lipoproteins synthesized in the liver and intestine with the help of an intracellular chaperone, microsomal triglyceride transfer protein (MTP). Leptin, a hormone secreted by adipose tissue, acts in the brain and on peripheral tissues to regulate fat storage and metabolism. Our aim was to identify the role of leptin signaling in MTP regulation and lipid absorption using several mouse models deficient in leptin receptor (LEPR) signaling and downstream effectors. Mice with spontaneous LEPR B mutations or targeted ablation of LEPR B in proopiomelanocortin (POMC) or agouti gene related peptide (AGRP) expressing cells had increased triglyceride in plasma, liver, and intestine. Furthermore, melanocortin 4 receptor (MC4R) knockout mice expressed a similar triglyceride phenotype, suggesting that leptin might regulate intestinal MTP expression through the melanocortin pathway. Mechanistic studies revealed that the accumulation of triglyceride in the intestine might be secondary to decreased expression of MTP and lipid absorption in these mice. Surgical and chemical blockade of vagal efferent outflow to the intestine in wild-type mice failed to alter the triglyceride phenotype, demonstrating that central neural control mechanisms were likely not involved in the observed regulation of intestinal MTP. Instead, we found that enterocytes express LEPR, POMC, AGRP, and MC4R. We propose that a peripheral, local gut signaling mechanism involving LEPR B and MC4R regulates intestinal MTP and controls intestinal lipid absorption.     

An essential complementary role of NF-kappaB pathway to microbicidal oxidants in Drosophila gut immunity

In the Drosophila gut, reactive oxygen species (ROS)-dependent immunity is critical to host survival. This is in contrast to the NF-kappaB pathway whose physiological function in the microbe-laden epithelia has yet to be convincingly demonstrated despite playing a critical role during systemic infections. We used a novel in vivo approach to reveal the physiological role of gut NF-kappaB/antimicrobial peptide (AMP) system, which has been 'masked' in the presence of the dominant intestinal ROS-dependent immunity. When fed with ROS-resistant microbes, NF-kappaB pathway mutant flies, but not wild-type flies, become highly susceptible to gut infection. This high lethality can be significantly reduced by either re-introducing Relish expression to Relish mutants or by constitutively expressing a single AMP to the NF-kappaB pathway mutants in the intestine. These results imply that the local 'NF-kappaB/AMP' system acts as an essential 'fail-safe' system, complementary to the ROS-dependent gut immunity, during gut infection with ROS-resistant pathogens. This system provides the Drosophila gut immunity the versatility necessary to manage sporadic invasion of virulent pathogens that somehow counteract or evade the ROS-dependent immunity.     

An amino-terminal fragment of cholecystokinin-58 is present in the gut: evidence for a similar processing site of procholecystokinin in canine gut and brain

Radioimmunoassays using antibodies specific for the carboxyl terminus of cholecystokinin (CCK) and the midportion of CCK-58 (raised against synthetic canine CCK-33-(1-27] revealed the existence of a CCK fragment in canine gut and brain extracts which lacks the biologically active carboxyl terminal immunoreactivity. This material eluted on Sephadex G-50 gel permeation chromatography in the region of CCK-58, on high-pressure liquid chromatography (HPLC) after CCK-39 and before CCK-58, and on cation-exchange FPLC it eluted after CCK-58. The immunoreactive pattern, the ratio of absorbance at 280-220 nm and the chromatographic elution positions suggest that this large CCK-like molecule represents an amino-terminal fragment of CCK-58. This fragment is present in canine gut and brain. Therefore, a similar processing site of procholecystokinin is suggested in both tissues.     

Predator gut state and prey detectability using electrophoretic analysis of gut contents

Abstract. I. An investigation of the effects of position of food in the gut (gut state), time since feeding, meal size and environmental temperature on the detection of prey using the electrophoretic separation of proteins with esterase activity was undertaken. The waterbug Notonecta glauca Linn (Hemiptera/Heteroptera) was used as the model predator.
2. Seven easily recognizable gut states can be identified at different times since commencement of a meal.
3. Specific prey esterase 'fingerprint' bands can be detected whilst food remains in the foregut.
4. Meal size and environmental temperature (affecting digestion and assimilation rates) both affect the rate of filling and emptying of the foregut, and hence the time period over which prey proteins can be detected by electrophoresis following a meal. Small meals and high temperatures lead to quite rapid changes in gut state with time and thus reduce the time period over which prey can be identified from gut contents (20 h). Large meals and low temperatures extend this period (48 h).
5. Predator gut state is the most important parameter in prey detectability from gut contents, and from a visual examination of the gut state it is immediately evident whether or not prey detection by electrophoresis will be possible.
6. There is further evidence in support of a twocompartment food processing model for Nofoonecru , and the significance of this type of processing in relation to gut content analysis of sucking predators is discussed.