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PubMed1989

Neuroanatomical substrates involved in the control of food intake.

Five neural pathways were reviewed regarding their specific role in the control of food intake in birds. The five pathways included the trigeminal sensorimotor system, the visual system/basal ganglia pathway, the gustatory system, the olfactory pathway, and the autonomic nervous system/parasympathetic pathway. The trigeminal system is the pathway best understood among the five systems associated with feeding. It begins with sensory nerves innervating the upper and lower mandibles and buccal cavity and ends with nerves projecting to jaw muscles. The function of the pathway is to control the grasping and mandibulation of pellets or seeds. The visual system includes both the tectofugal and thalamofugal pathways. Both visual pathways interact with the avian paleostriatal complex. The latter is equivalent to the mammalian basal ganglia. The second pathway is important in food recognition as well as in orienting the body with respect to its position in three-dimensional space. The third neural circuit involves the sense of taste. Approximately 300 taste buds have been identified within the buccal cavity of the chicken, suggesting that the gustatory system is better developed than once thought. The fourth pathway involves the olfactory system; as in the visual system, more than one pathway has been identified. The dominant pathway appears to project to the piriform cortex, a structure that may play a role in monitoring essential amino acid contents of the brain. The fifth pathway involves an interaction of the hypothalamus and the dorsal motor nucleus of the vagus. This pathway is important in activating the parasympathetic nervous system and in preparing an organism to feed. All five pathways play different roles in controlling food intake in birds.

Animals↗
PubMed2001

Covariation in individuals' sensitivities to bitter compounds: evidence supporting multiple receptor/transduction mechanisms.

People vary widely in their sensitivities to bitter compounds, but the intercorrelation of these sensitivities is unknown. Our goal was to investigate correlations as a function of individual sensitivities to several bitter compounds representative of different chemical classes and, from these correlations, infer the number and variety of potential bitterness transduction systems for these compounds. Twenty-six subjects rated and ranked quinine HCl, caffeine, (-)-epicatechin, tetralone, L-phenylalanine, L-tryptophan, magnesium sulfate, urea, sucrose octaacetate (SOA), denatonium benzoate, and n-propylthiouracil (PROP) for bitterness. By examining individual differences, ratings and rankings could be grouped into two general clusters--urea/phenylalanine/tryptophan/epicatechin, and quinine/caffeine/SOA/denatonium benzoate/tetralone/magnesium sulfate-none of which contained PROP. When subjects were grouped into the extremes of sensitivity to PROP, a significant difference was found in the bitterness ratings, but not in the rankings. Therefore, there are also subjects who possess diminished absolute sensitivity to bitter stimuli but do not differ from other subjects in their relative sensitivities to these compounds.

Adolescent↗
PubMed1998

Inhibition of insulin release by alpha- and beta-D-galactose pentaacetate.

Several monosaccharide polyacetate esters display higher biological efficiency than the corresponding unesterified carbohydrates, this being attributable to their capacity to cross the plasma membrane without requiring the intervention of a specific carrier system and to their subsequent intracellular esterase-catalyzed hydrolysis. Some of these esters, however, also exert a direct effect upon a receptor system apparently displaying analogies with that involved in the identification of bitter compounds by taste buds. For instance, under suitable experimental conditions, esters of non-nutrient monosaccharides, such as L-glucose, D-mannoheptulose or 2-deoxy-D-glucose, unexpectedly stimulate insulin release. The present work reveals that alpha-D-galactose pentaacetate and, to a lesser extent, beta-D-galactose pentaacetate both inhibit leucine-induced insulin release in rat pancreatic islets. This indicates that the postulated receptor system displays anomeric specificity and may participate in a negative modulation of insulin secretion. It is proposed that advantage could be taken of the negative insulinotropic action of D-galactose pentaacetate esters to prevent excessive insulin release in pathological situations.

Animals↗
PubMed2001

A histological and histochemical study of the oesophagus and oesogaster of the Senegal sole, Solea senegalensis.

A histological and histochemical study was performed in the buccal cavity and papillae, which were around the teeth, as well as in the oesophagus and oesogaster of the Senegal sole, Solea senegalensis adult specimens. The oesophagus and oesogaster were made up of four distinct layers: mucosa, submucosa, muscular and serous. Two morphological types of epithelial cells were distinguishable in the oesophageal mucosa: the more numerous type cells possessed an electron-dense cytoplasm, whereas the cytoplasm was electron-clear in the other cells. Mucus-secreting cells were the dominant feature of the epithelium throughout the oesophagus. These goblet cells were filled with numerous mucous droplets of low electron-density. The oesophagus was devoid of taste buds. In the oesogaster mucosa, three types of cells were distinguished: dark, rodlet and light epithelial cells. Dark epithelial cells showed different characteristics from that in the oesophagus: the nucleus was irregular with an electron-dense hyaloplasm, the cytoplasm had a scarce smooth and granular endoplasmic reticulum; a Golgi apparatus consisted of four parallel cisternae, dense granules without membrane, lysosomes and numerous mitochondria. The rodlet cells were elongated, contained rod-like structures and were surrounded by an electron-dense capsule-like structure. The bulk of the rodlet cell was composed of up to 20 extended rodlet units. Light epithelial cells of the oesogaster had the same characteristics as those observed in the oesophagus and contained numerous mitochondria with a dense matrix, abundant smooth endoplasmic reticulum and numerous vesicles. In the goblet cells of the papillae, sulfomucin was recognised, since they showed alcianophilia (alcian blue pH 1.0 and 0.5). These cells were negative to protein reaction (bromophenol blue) and contained -S-S- and SH groups. Enzymatic activities (alkaline phosphatase, acid phosphatase, ATPase (pH 7.2 and 9.4) and lipid reactions were negative in the goblet cells of the buccal cavity. Epithelial cells of oesophagus contained a weak presence of acid and neutral mucopolysaccharides. Oesophageal goblet cells contained carboxylated, sulphated (weakly and strongly ionised) mucosubstances and sialic acid. Most goblet cells did not contain proteins and presented disulphide (-S-S-) and sulphydril (-SH) groups. Proteins in general, and in particular those rich in lysine, tyrosine and arginine were present in the epithelium, lamina propria, submucosa and muscular layer of the oesophagus. Lipids in general and phospholipids were observed in the oesophageal epithelium while unsaturated, acid and neutral lipids were not observed. The lamina propria and submucosa contained a weak presence of phospholipids and unsaturated lipids. Acid phosphatase and ATPase (pH 7.2) activities were observed in the lamina propria, submucosa and muscular regions, while ATPase (pH 9.2) activity was weak in these areas. ATPase activity (pH 7.2 and 9.5) was very weak in the epithelium. Oesophageal goblet cells were negative to lipid and enzymatic reactions.

Acid Phosphatase↗
PubMed2004

General morphology of the oral cavity of the Nile crocodile, Crocodylus niloticus (Laurenti, 1768). II. The tongue.

The heads of nine 2.5 to 3-year-old Nile crocodiles (Crocodylus niloticus) were obtained from a commercial farm where crocodiles are raised for their skins and meat. The animals from which these specimens were obtained appeared clinically healthy at the time they were slaughtered. A description of the macroscopic and microscopic features of the tongue of the Nile crocodile is presented and the results are compared with published information on this species and other Crocodylia. The histological features are supplemented by information supplied by scanning electron microscopy. Macroscopic features of interest were the dome shaped structures grouped in a triangular formation on the posterior two-thirds of the dorsum of the tongue. These structures were identified by light microscopy to contain well-developed branched, coiled tubular glands and associated lymphoid tissue. Other histological features included a lightly keratinised stratified squamous surface epithelium supported by a thick layer of irregular dense fibrous connective tissue. Deep to this region was a clearly demarcated adipose tissue core with a dense mass of striated lingual musculature. Localised thickenings were present in the epithelium which were associated with ellipsoid intra-epithelial structures resembling taste buds.

Alligators and Crocodiles↗
PubMed1976

Studies on the morphology and histology of the digestive tract of Bagarius bagarius (Ham).

1. The alimentary tract of Bagarius bagarius is long in accordance with its omnivorous nature and consists of buccal cavity, pharynx, oesophogus, stomach, intestine, and rectum. 2. The month is terminal and bounded by upper and lower lips, which are provided with many villiform teeth. 3. The buccal cavity and pharynx are dorso-ventrally flattened with smooth lining in the former and folded in the latter. Taste buds and mucous cells are present in these parts which help in selection of food and inlubricating the prey respectively. 4. The oesophagus is small but wide and produced into longitudinal folds. Histologically it is composed of the usual 4 layers viz. serosa, muscularis, submucosa and mucosa. The mucosa is stratified and bears mucous cells. 5. The stomach is large, sac-like and divided into a large cardiac and a small pyloric portion. In the submucosa of the cardiac part, gastric glands are present into the cryps of mucosa. 6. The intestine is distinguished into duodenum, ileum and rectum on the basis of folds. These folds are of honey comb type in duodenum, longitudinal in the ileum, and anatamosing in the rectum to form a honey comb. The muscularis of the duodenum is better developed than that of the ileum and is best formed in the rectum, where the mucosa contains abundant mucous cells. 7. The liver consists of 2 lobes and is formed of polygonal cells. Blood capillaries and hepatic ductules are present in it. The gall bladder lies in between the right lobe of liver and duodenum. It consists of connective tissues lined with columnar cells on inner side and serosa on the outer side. 8. The pancreas is diffused and lies concentrated between the liver, stomach and the coils of intestine. It is composed of polyhedral cells, which are aggregated to form acini. The pancreatic tissue is supplied with the pancreatic ductules and blood capillaries.

Animals↗
PubMedDate not supplied

A field emission SEM and HVTEM study of collagen fiber bundles in the lamina propria of the palatine mucosa in the developing mouse.

The ultrastructural development of the surface belonging to the epithelium-connective tissue interface of the hard and soft palatine mucosa of mouse was studied using field emission scanning electron microscopy and high voltage transmission electron microscopy methods. The tissues were analysed at 18 days of gestation, and, 1, 3, 7, 14, 21, 30 and 90 days after birth. The three-dimensional architecture of the connective tissue in the lamina propria showed different shapes. The papillae began to form on days 7 and 14 but continued to growth until the adult period. Different stages of primary and secondary connective tissue papillae were recognized in the hard palatine mucosa whereas the soft palate showed erect connective tissue papillae, small round formations containing taste buds and several openings of the salivary glands ducts.

Aging↗
PubMed1999

Effects of extracellular pH upon the insulinotropic action of alpha-D-glucose pentaacetate.

The pentaacetate ester of alpha-D-glucose was recently introduced as a new insulin secretagogue. Its insulinotropic action appears mainly attributable to the catabolism of its hexose moiety in islet cells, but a direct effect of the ester itself upon a receptor apparently displaying analogy with that involved in the recognition of bitter agents by taste buds may also be operative. In the present study, the secretory response of rat isolated pancreatic islets to alpha-D-glucose pentaacetate (1.7 mM) was found to be preserved, except in the absence of any other exogenous nutrient, when the extracellular pH was raised from about 7.4 to 8.0. Inversely, however, when the extracellular pH was lowered to about 7.0, alpha-D-glucose pentaacetate inhibited both basal and D-glucose- or L-leucine-stimulated insulin output. These findings are interpreted to support a dual mode of action of alpha-D-glucose pentaacetate upon insulin secretion, a lowering of extracellular pH revealing a negative component of the islet B-cells functional response to such a monosaccharide ester.

Animals↗
PubMed1999

Extraneural organ involvement in human rabies.

Human rabies is a fatal encephalomyelitis. After the development of the central nervous system infection, there is centrifugal spread of the rabies virus to extraneural (systemic) organs. With histochemical staining and localization of rabies virus antigen (RVA) with immunoperoxidase staining, we have examined tissue sections of organs from 14 postmortem pediatric and adult cases of human rabies acquired in Mexico and the People's Republic of China. RVA was found in nerve plexuses in multiple organs, including the gastrointestinal tract. RVA was observed in muscle fibers of the heart, tongue, and larynx. RVA frequently was observed in the adrenal medulla with an associated inflammatory reaction. Minor salivary glands of the tongue contained RVA and major salivary glands showed RVA in plexuses, but not in either acini or ducts. Epithelial cells of the tongue and taste buds were occasionally infected. RVA was observed in hair follicles of the skin and rarely in pancreatic islets. The infection of extraneural organs was sometimes, but not always, associated with an inflammatory reaction. These findings indicate that centrifugal spread of rabies virus to extraneural organs occurs frequently in human rabies.

Adolescent↗
PubMed1975

Normal histology of the human soft palate.

The histology of the human soft palate seen in four whole soft palates and four mucosal biopsies has been described, with an emphasis on the elastic fibres. Striking features were the presence of much fat, thick interglandular connective tissue septa, considerable elastic tissue, and a complete absence of taste buds.

Adult↗
PubMed2000

Sodium taste detectability in rats is independent of anion size: the psychophysical characteristics of the transcellular sodium taste transduction pathway.

There are two known sodium transduction pathways in the rat gustatory system. The transcellular pathway is blocked by amiloride, and the paracellular pathway is limited by the anion gluconate. The contribution of each pathway to sodium detection was assessed. Sodium gluconate (NaGlu) and NaCl thresholds did not differ, implying that the paracellular pathway is not necessary for normal sodium detection. Adding 100 microM amiloride raised both NaCl and NaGlu thresholds but did not abolish all performance to NaGlu, indicating that some chemical cue was present at high concentrations. Rats were also exposed to one of three NaCl diets (0.12%, 1.0%, or 6.0% NaCl) through maternal and ad lib intake from Embryonic Day 1 through testing in adulthood. No differences across dietary groups were found for NaCl or NaGlu threshold with or without amiloride. Thus, this developmental dietary treatment does not appear to affect taste sensitivity to sodium subserved through either transduction pathway. Collectively, these data suggest that the transcellular transduction pathway is both necessary and sufficient for normal sodium detection.

Animals↗
PubMed2001

Surveillance of the gastrointestinal mucosa by sensory neurons.

A dense network of extrinsic and intrinsic sensory neurons supplies the gastrointestinal tract. Intrinsic sensory neurons provide the enteric nervous system with the kind of information that this brain of the gut requires for its autonomic control of digestion, whereas extrinsic afferents notify the brain about processes that are relevant to energy and fluid homeostasis and the sensation of discomfort and pain. The sensory repertoire of afferent neurons is extended by their responsiveness to mediators released from enteroendocrine and immune cells, which act like "taste buds" of the gut and serve as interface between the gastrointestinal lumen and the sensory nerve terminals in the lamina propria of the mucosa. Functional bowel disorders such as non-ulcer dyspepsia and irritable bowel syndrome are characterized by abdominal discomfort or pain in the absence of an identifiable organic cause. It is hypothesized with good reason that infection, inflammation or trauma causes sensory pathways to undergo profound phenotypic and functional alterations that outlast the acute insult. The pertinent changes involve an exaggerated sensitivity of the peripheral afferent nerve fibres as well as a distorted processing and representation of the incoming information in the brain. This concept identifies a number of receptors and ion channels that are selectively expressed by primary afferent neurons as important molecular targets at which to aim novel therapies for functional bowel disorders.

Colonic Diseases, Functional↗