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Results for “Digestive System Physiological Phenomena”

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At least 127 records · Page 7Linked to original sources
PubMed2004

Effect of diet on mucin kinetics and composition: nutrition and health implications.

The mucus gel covering the gut epithelium is in dynamic balance between synthesis and secretion of mucin from goblet cells and proteolytic and physical erosion that releases mucin into the lumen. In the lumen, mucin is partially protected from proteolysis by carbohydrate chains, and it contributes to endogenous protein reaching the ileum. Dietary components modulate the contribution of mucin to endogenous protein components and their qualitative composition. In addition, mucin plays a key role in gastrointestinal protection in association with the microflora. In this review, we will attempt to evaluate the consequences of dietary manipulation of mucin on gut health.

Animal Nutritional Physiological Phenomena↗
PubMed2000

Nitric oxide: a molecule of the millennium.

Recognition of Nitric oxide (NO) as the chemical entity of endothelium-derived relaxing factor (EDRF) has renewed the interest of the scientific community in the last decade. The outcome of research the world over is that the dreaded environmental pollutant is found to be a fundamental physiological mediator and effector. NO is synthesized endogenously by enzymes nitric oxide synthase (NOS) in specialized tissues from its precursor L-arginine. The L-arginine-NO biosynthetic pathway is involved in physiological processes such as vasodilation, memory, neuroprotection, peristalsis, penile erection, immune defense, various endocrine and exocrine secretions in various systems such as cardiovascular, CNS, reproductive and immune system. Small quantities of NO produced by constitutive enzymes mediate these physiological effects. The expression of inducible enzyme or overstimulation of constitutive enzymes leading to production of large quantities of NO is implicated in the cytotoxic effects observed in various disorders like AIDS, cancer, Alzheimer's, arthritis etc. In conclusion, NO is a 'double edged sword' and the challenge before the scientific community is to develop strategies for using it to our advantage.

Animals↗
PubMed1987

The physiology of aging.

A knowledge of the physiology of aging is necessary in understanding the medical problems of the elderly. Far-reaching effects results from such diverse changes as increased density and decreased water content of connective tissue, reduced estrogen production, reduced respiratory ciliary function, diminished efficiency of the pulmonary macrophages and decreases in brain and renal mass.

Aging↗
PubMed1995

Amylin/islet amyloid polypeptide: biochemistry, physiology, patho-physiology.

Amylin is a 37 amino-acid peptide mainly produced by the islet beta-cell. Aggregation of amylin is partly responsible for amyloid formation. Amyloid deposits occur both extracellularly and intracellularly and may contribute to beta-cell degeneration. Amylin is packed in beta-cell granules and cosecreted with insulin in response to the same stimuli but, unlike other beta-cell products, it is produced from specific a gene on chromosome 12. Basal, plasma amylin concentrations are around 5 pM, and increase fourfold after meals or glucose. Higher levels are found in cases of insulin resistance, obesity, gestational diabetes and in some patients with NIDDM. Low or absent levels are found in insulin-dependent diabetic patients. There are similarities between amylin and non beta-cell peptides such as calcitonin gene related peptides (CGRP). They may bind to the same receptor, determine similar post-receptor phenomena and qualitatively similar actions but with different degree of potency. The actions of amylin are multiple and mostly exerted in the regulation of fuel metabolism. In muscle, amylin opposes glycogen synthesis, activates glycogenolysis and glycolysis (increasing lactate production). Consequently, amylin increases lactate output by muscle and increases the plasma lactate concentration. In fasting conditions, this lactate may serve as a gluconeogenic substrate for the liver, contributing to replenish depleted glycogen stores and to increase glucose production. In non-fasting conditions, lactate can be transformed by liver in triglycerides. It is not clear at present whether amylin actions on the liver are direct or mediated by changes in circulating metabolites. A probably indirect effect of amylin in muscle is to decrease insulin- (or glucose)-induced glucose uptake, which may contribute to insulin resistance. Other actions include inhibition of glucose-stimulated insulin secretion and, in general, actions mimicking CGRP effects. Some of these actions are seen at supraphysiological concentrations. The physiopathological consequences of amylin deficiency, or excess are under active by investigated.

Amino Acid Sequence↗
PubMed1987

Secretion of somatostatin and its physiologic function.

Somatostatin, initially described as a growth hormone release-inhibitory peptide 14 amino acids in length, has been shown to be one of a family of related peptides. It is ubiquitous in distribution and versatile as a paracrine factor with a potentially important role in the regulation of gut, pancreatic, and nervous system function in addition to its well-recognized influence on the pituitary secretion of growth hormone and thyroid-stimulating hormone. With the development of new super agonists, it has become possible to manipulate the endocrine milieu, to modify gut, pancreatic, and pituitary function, and in the case of several diseases such as acromegaly, intractable diarrhea, and carcinoid, to make a significant advance in therapy.

Animals↗
PubMed1985

Prostaglandins, thromboxanes and leukotrienes in clinical medicine.

Although prostaglandin research began about 50 years ago, many of the most important advances in understanding the biochemistry, physiology and pharmacology have taken place within the past five to ten years. There is great potential for the extension of this research to the clinical practice of medicine. At this time, the most common interaction that clinicians have with the prostaglandin field is in administering nonsteroidal anti-inflammatory drugs, which function by inhibiting prostaglandins. The uses of these drugs include treating not only inflammation, but also dysmenorrhea, some renal disease, thrombotic diseases and some metabolic disorders. Prostaglandin analogs, with their potent effects on uterine contraction, are in common use in obstetrics. Other analogs, with gastric and duodenal cytoprotective effects are useful in treating peptic ulcer disease. Future benefits from prostaglandin and leukotriene research may include new therapy for inflammatory and hypersensitivity diseases such as asthma, inflammatory bowel diseases and dermatitis.

Animals↗
PubMed1985

Gastrointestinal somatostatin: distribution, secretion and physiological significance.

Somatostatin-like immunoreactivity (SLI) has been found throughout the gastrointestinal tract in all species examined. In the stomach it is mainly present in endocrine-type D-cells whereas in the intestine there is also an extensive distribution in enteric neurones. In all regions of the gastrointestinal tract multiple forms of somatostatin exist. A precursor (prosomatostatin) has been partially sequenced, three forms with 20 (SS-20), 25 (SS-25) and 28 (SS-28) amino acids completely sequenced, and somatostatin-14 (SS-14) demonstrated by radioimmunoassay. Both SS-14 and SS-28 exert a wide range of actions on the gastrointestinal tract and there is strong supportive evidence for a role in the regulation of gastric acid and gastrin secretion, gastrointestinal motility and intestinal transport. Both in vivo and in vitro studies on the secretion of gastric SLI into the vasculature have shown that nutrients initiate the process but that subsequent events are regulated by a complex interplay between hormonal and neuronal pathways. GIP is one of the most potent hormonal secretagogues. In the stomach, acetylcholine, opioid peptides and substance P are probably involved in parasympathetic inhibitory pathways and gastrin releasing peptide in stimulatory pathways. The sympathetic nerves are also stimulatory. Regulation of secretion of intestinal SLI has not been so extensively studied. Although SLI is also found in the gastrointestinal lumen the significance is unclear. Despite these advances the exact route of delivery of somatostatin to its target organs is uncertain and paracrine, endocrine and neural pathways may all be involved.

Animals↗
PubMed2004

Influence of method of whole wheat inclusion and xylanase supplementation on the performance, apparent metabolisable energy, digestive tract measurements and gut morphology of broilers.

1. The aim of the present study was to examine the influence of whole wheat inclusion and xylanase supplementation on the performance, apparent metabolisable energy (AME), digesta viscosity, and digestive tract measurements of broilers fed on wheat-based diets. The influence of the method of whole wheat inclusion (pre- or post-pelleting) was also compared. A 3 x 2 factorial arrangement of treatments was used with three diet forms (648 g/kg ground wheat [GW], GW replaced by 200 g/kg of whole wheat before [WW1] or after cold-pelleting [WW2]) and two xylanase levels (0 and 1000 XU/kg diet). 2. Birds given diets containing whole wheat had improved weight gains, feed efficiency and AME compared to those fed on diets containing ground wheat. The relative gizzard weight of birds fed WW2 diets was higher than in those fed GW and WW1 diets. Pre-pelleting inclusion of whole wheat had no effect on relative gizzard weight. Post-pelleting inclusion of whole wheat resulted in greater improvements in feed efficiency and AME than the pre-pelleting treatment. 3. Xylanase supplementation significantly improved weight gain, feed efficiency and AME, irrespective of the wheat form used. Viscosity of the digesta in the duodenum, jejunum and ileum were reduced by xylanase addition. Xylanase supplementation reduced the relative weight of the pancreas. 4. Neither xylanase supplementation nor whole wheat inclusion influenced the relative weight and length of the small intestine. 5. Xylanase supplementation increased ileal villus height. A significant interaction between diet form and xylanase was observed for ileal crypt depth. Xylanase supplementation had no effect on crypt depth in birds fed on diets containing GW, but increased the crypt depth in WW2 diets. No significant effects of diet form and xylanase supplementation were observed for the thickness of the tunica muscularis layer of gizzard or villus height, crypt depth, goblet cell numbers or epithelial thickness in the ileum. 6. Improved performance observed with post-pelleting inclusion of whole wheat was associated with increased size of the gizzard and improved AME. The gizzard development hypothesis, however, will not explain the improvements observed with pre-pelleting inclusion of whole wheat, suggesting the involvement of other factors.

Animal Nutritional Physiological Phenomena↗
PubMed1995

The nutritional significance of endogenous N-losses along the gastro-intestinal tract of farm animals.

In animal production, endogenous protein losses associated with the digestion process are important losses, but difficult to measure. Measuring methods include feeding N-free diets, regression techniques based on amino acid profiles, and separating feed protein and endogenous protein by markers like homoarginine, hydrolysed casein or stable isotopes like 15N. Endogenous losses arise from saliva, digestive enzymes, bile, shedded epithelial cells and mucins and may be extra stimulated by the presence in feeds of antinutritional factors (ANF) such as lectins, trypsin inhibitors (TI), tannins and fibre. The impact of such factors may differ between non-ruminants and ruminants. The magnitude of the effect of the different factors is quantified and some of the consequences for protein deposition and nitrogen losses to the environment are discussed.

Amino Acids↗
PubMed2004

Components of feed efficiency in broiler breeding stock: influence of water intake and gastrointestinal contents.

An experiment was conducted with 3 lines of broilers to evaluate the potential roles of water intake and fill of the gastrointestinal (GI) tract on feed conversion ratio (FCR) as measured in a 1-wk FCR test. Birds were reared to juvenile selection age (41 d) and subsequently selected, with the best 18 to 29% of male chicks placed into cages for FCR testing. Feed and water intake were highly correlated in all lines, with each in turn highly correlated with weight gain on test. Although filling of the GI tract differed between the top and bottom halves of the FCR distribution, FCR as measured and corrected for weight of GI tract contents were highly correlated (r = 0.59 to 0.93). Differences between FCR classes were striking for weight gain, but differences between FCR class groups were subtle for starting weight and feed intake. These subtle differences are difficult to detect in a single generation, but may add up through generations of selection. Based on the results of the current and previous studies, it appears that selection for improved FCR works at multiple levels to improve efficiency of feed conversion in broiler breeding stock.

Animal Feed↗