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PubMed2001

Excitotoxic lesions of the hippocampus leave sensory preconditioning intact: implications for models of hippocampal function.

Learning about contextual cues is markedly disrupted in rats with hippocampal lesions. One analysis of this disruption is that it reflects a general failure to form associations between the elements of complex events. A straightforward prediction of this analysis is that sensory preconditioning will be disrupted by hippocampal lesions. This prediction was assessed by presenting rats with flavored solutions composed of 2 elements (A and X) before X was paired with an injection of the emetic, lithium chloride. A subsequent test revealed that rats were less willing to consume Solution A than they were to consume a control solution, B. This was true of rats with sham lesions and those with excitotoxic lesions of hippocampus. These findings fail to support the proposition that the hippocampus-dependent deficit in contextual conditioning is due to a general disruption to the process of associating the elements of complex events.

Animals↗
PubMed1978

Food extrusion.

Extrusion processing has become an important food process in the manufacture of pasta, ready-to-eat cereals, snacks, pet foods, and textured vegetable protein (TVP). An extruder consists of tightly fitting screw rotating within a stationary barrel. Preground and conditioned ingredients enter the screw where they are conveyed, mixed, and heated by a variety of processes. The product exits the extruder through a die where it usually puffs and changes texture from the release of steam and normal forces. Mathematical models for extruder flow and torque have been found useful in describing exclusion operations. Scale-up can be facilitated by the application of these models. A variety of food extruder designs have developed. The differences and similarity of design are discussed. Pertinent literature on the extrusion of cereal/snack products, full-fat soy, TVP, pet foods (dry and semi-moist), pasta, and beverage or other food bases are discussed. In many of these applications, the extruder is a high temperature, short time process which minimizes losses in vitamins and amino acids. Color, flavor, and product shape and texture are also affected by the extrusion process. Extrusion has been widely applied in the production of nutritious foods. Emphasis is placed on the use of extrusion to denature antinutritional factors and the improvement of protein quality and digestibility.

Amino Acids↗
PubMed1998

Comparison of effects of a range of 5-HT receptor modulators on consumption and preference for a sweetened ethanol solution in rats.

This study assessed the effects of a range of serotonergic agents on preference for a slightly sweetened ethanol solution (10% ethanol, 3% glucose) in rats. A two-bottle, free-choice paradigm was used following induction of ethanol consumption. The model used provides a robust and reliable level of ethanol self-administration in normal laboratory rats. Ethanol consumption was significantly and selectively reduced by the 5-hydroxytryptamine-1A (5-HT1A) full agonist 8-OH-DPAT (0.3-1.0 mg/kg) and the 5-HT3 antagonist granisetron (0.1-1.0 mg/kg). Non-specific reductions in fluid consumption were induced by the 5-HT1B agonist RU 24969 (0.1-1.0mg/kg) and the 5-HT2 antagonist ritanserin (1.0-6.0 mg/kg). These studies thus confirm the potential for decreasing ethanol consumption and ethanol preference of 5-HT1A agonists and 5-HT3 antagonists, but failed to find any selective effects for agents acting at 5-HT1B or 5-HT2 receptors.

Alcohol Drinking↗
PubMed2000

"Outings to your taste": a nutrition program for the elderly.

"Outings to Your Taste" is an innovative program that aims to improve the nutritional status and social network of elderly people who receive home-delivered meals. This article examines participation in one of the program's components, outings to community restaurants. Participation data were collected on-site and information about client characteristics was collected in at-home interview surveys of targeted clients (n = 144). While about half of the clients had tried at least one outing, more than 25% of them participated in at least one third of the outings offered to them. Results indicate that the program attracted a variety of clients in terms of sociodemographic, health, and social isolation characteristics.

Activities of Daily Living↗
PubMed2004

Neuroendocrinology of gastric H+ and duodenal HCO3- secretion: the role of brain-gut axis.

Gastric H+ and duodenal HCO3- secretions are precisely regulated by neuro-hormonal mechanisms at central and peripheral levels to match the rate of these secretions with the type of stimulation of sensory receptors in the head area (sight, smell, taste, etc.) and in the gastro-intestinal system. Two-way communication pathways operate between the brain and the gut, each comprising afferent fibers signaling sensory information from the gut to the brain and efferent fibers transmitting signals in opposite direction. Short intramural and long extramural reflexes are triggered as well as various gut hormones are released by feeding that "cooperate" with the "brain-gut axis" in the alteration of exocrine and endocrine gastro-duodenal secretion, motility and blood circulation. The malfunction of gastric or duodenal secretory mechanisms may lead to disturbances of gastric H+-pepsin or duodenal mucus-HCO3- secretion and to gastro-duodenal disorders and diseases. This review presents recent advances in pathophysiological mechanisms underlying gastro-duodenal secretory disorders.

Animals↗
PubMed2005

Lithium-induced gene expression of inducible cyclic adenosine monophosphate early repressor in the rat adrenal gland.

Lithium has acute and chronic effects on the hypothalamic-pituitary-adrenal gland (HPA) axis that are important for both therapeutic (e.g., treatment of mood disorders) and experimental (e.g., as the toxin in conditioned taste aversion studies) applications. We visualized lithium-induced activation of the HPA axis in rats by the adrenal expression of inducible cAMP early repressor (ICER), which is activated by elevated intracellular cAMP. We have shown that 1) intraperitoneal lithium chloride (LiCl) induces transient expression of ICER and c-fos mRNAs in the rat adrenal cortex and increases plasma level of corticosterone; 2) the cortical expression of ICER mRNA by LiCl occurs in a dose-dependent manner; 3) adrenal induction of ICER expression is delayed compared with c-fos expression; 4) dexamethasone pretreatment (4 mg/kg) blocks corticosterone release and adrenocortical ICER induction either by systemic LiCl (76 mg/kg) or by restraint stress; and 5) intracerebroventricular LiCl (127 microg/5 microl) is sufficient for adrenocortical, but not medullary, ICER induction. These results suggest that adrenocortical ICER expression could serve as a reliable marker for lithium-induced activation of the HPA axis. Understanding the activation of immediate-early genes such as c-fos or ICER in response to a single LiCl injection is an important first step in understanding the long-term changes in gene expression elicited by lithium that are involved in its therapeutic and toxic effect. The pattern and mechanism by which lithium stimulates ICER transcription in the adrenal gland would serve as a useful model system in future studies of lithium.

Adrenal Cortex↗
PubMed1999

Solution conformation of brazzein by 1H nuclear magnetic resonance: resonance assignment and secondary structure.

Brazzein is a sweet-tasting protein isolated from the fruit of the West African plant Pentadiplandra brazzeana Baillon. It is the smallest and the most water-soluble sweet protein discovered so far, it is also highly thermostable. The proton NMR study of brazzein at 600 MHz (pH 3.5, 300K) is presented. Complete sequence specific assignment of the individual backbone and sidechain proton resonances were achieved using through-bond and through-space connectivities obtained from standard two-dimensional NMR techniques. The secondary structure of brazzein contains one alpha-helix (residues 21-29), one short 3(10)-helix (residues 14-17), two strands of antiparallel beta-sheet (residues 34-39, 44-50) and probably a third strand (residues 5-7) near the N-terminus.

Amino Acid Sequence↗
PubMed2003

Convergent evolution of cucurbitacin feeding in spatially isolated rootworm taxa (Coleoptera: Chrysomelidae; Galerucinae, Luperini).

Historically, chemical ecologists assumed that cucurbitacin feeding and sequestration in rootworm leaf beetles is a remnant of an ancient association between the Luperini (Coleoptera: Chrysomelidae; Galerucinae) and Cucurbitaceae (ancestral host hypothesis). Under this premise, rootworms that do not develop on cucurbits but undergo pharmacophagous forays for cucurbitacins are thought to do so to supplement novel host diets that lack these bitter compounds. The ancestral host hypothesis is supported from studies of pyrrolizidine alkaloid pharmacophagy in Lepidoptera but has not been subjected to phylogenetic analysis within the Luperini. New evidence that this feeding behavior is better correlated with an adult affinity for pollen than with larval host offers the possibility that Old and New World rootworm species with an affinity for cucurbitacins converged on this behavior through apomorphic taste receptor modifications (loose receptor hypothesis). Here we test the monophyly of cucurbitacin feeding within the Luperini by using nuclear and mitochondrial sequence data to infer phylogenetic relationships among 49 taxa representing tribes of the Galerucinae and subtribes of the Luperini. The resulting phylogenetic hypothesis is mostly concordant with existing tribal and subtribal delineations within the Subfamily Galerucinae sensu stricto (Galerucinae not including the flea beetles). The establishment of ancestry among the subtribes of the Luperini refutes the monophyly of cucurbitacin feeding and cucurbit specialization, with the New World Diabroticina being paraphyletic to the Old World Aulacophorina and cosmopolitan Luperina. These data unambiguously support the convergent evolution of cucurbitacin feeding in rootworms and are inconsistent with the ancestral host hypothesis.

Animals↗
PubMed2000

Rating changes over the course of meals: what do they tell us about motivation to eat?

Detailed analysis of the pattern of change in rated appetite within a meal have proved a useful technique through which to explore appetite control. Variability in individual ratings, and technical difficulties in achieving ratings at equivalent stages of a meal, have lead to the use of curve-fitting techniques to model changes in rated appetite across a meal. These changes could best be described by a quadratic function, in which the three parameters (intercept, linear and quadratic coefficients) represented distinct influences on meal size. In normal subjects, manipulations of palatability and opioid receptor blockade and preloads of alcohol all modified the linear component of this function only, while preloading with maltodextrin reduced appetite at the start of eating (the intercept) but not the pattern of change in ratings within that meal. Thus the linear coefficient appears to measure the degree of stimulation of appetite by the sensory characteristics of the food, while the intercept reflects baseline appetite at the start of a meal. These results suggest that microstructural analyses of rating changes allow some dissociation of the factors underlying motivation to eat, and provide a novel methodology for future experimentation.

Alcohol Drinking↗
PubMed2004

The activation mechanism of class-C G-protein coupled receptors.

Class-C G-protein coupled receptors (GPCRs) represent a distant group among the large family of GPCRs. This class includes the receptors for the main neurotransmitters, glutamate and gamma-aminobutyric acid (GABA), and the receptors for Ca(2+), some taste and pheromone molecules, as well as some orphan receptors. Like any other GPCRs, class-C receptors possess a heptahelical domain (HD) involved in heterotrimeric G-protein activation, but most of them also have a large extracellular domain (ECD) responsible for agonist recognition and binding. In addition, it is now well accepted that these receptors are dimers, either homo or heterodimers. This complex architecture raises a number of important questions. Here we will discuss our view of how agonist binding within the large ECD triggers the necessary change of conformation, or stabilize a specific conformation, of the heptahelical domain leading to G-protein activation. How ligands acting within the heptahelical domain can change the properties of these complex macromolecules.

Allosteric Site↗
PubMed1999

Drug addiction as a disorder of associative learning. Role of nucleus accumbens shell/extended amygdala dopamine.

Conventional reinforcers phasically stimulate dopamine transmission in the nucleus accumbens shell. This property undergoes one-trial habituation consistent with a role of nucleus accumbens shell dopamine in associative learning. Experimental studies with place- and taste-conditioning paradigms confirm this role. Addictive drugs share with conventional reinforcers the property of stimulating dopamine transmission in the nucleus accumbens shell. This response, however, undergoes one-trial habituation in the case of conventional reinforcers but not of drugs. Resistance to habituation allows drugs to repetitively activate dopamine transmission in the shell upon repeated self-administration. This process abnormally facilitates associative learning, leading to the attribution of excessive motivational value to discrete stimuli or contexts predictive of drug availability. Addiction is therefore the expression of the excessive control over behavior acquired by drug-related stimuli as a result of abnormal strenghtening of stimulus-drug contingencies by nondecremental drug-induced stimulation of dopamine transmission in the nucleus accumbens shell.

Amygdala↗
PubMed2001

Activation of rhodopsin: new insights from structural and biochemical studies.

G-protein-coupled receptors (GPCRs) are involved in a vast variety of cellular signal transduction processes from visual, taste and odor perceptions to sensing the levels of many hormones and neurotransmitters. As a result of agonist-induced conformation changes, GPCRs become activated and catalyze nucleotide exchange within the G proteins, thus detecting and amplifying the signal. GPCRs share a common heptahelical transmembrane structure as well as many conserved key residues and regions. Rhodopsins are prototypical GPCRs that detect photons in retinal photoreceptor cells and trigger a phototransduction cascade that culminates in neuronal signaling. Biophysical and biochemical studies of rhodopsin activation, and the recent crystal structure determination of bovine rhodopsin, have provided new information that enables a more complete mechanism of vertebrate rhodopsin activation to be proposed. In many aspects, rhodopsin might provide a structural and functional template for other members of the GPCR family.

Amino Acid Sequence↗
PubMed2006

Model studies on the efficacy of protein homogenates from raw pork muscle and dry-cured ham in binding selected flavor compounds.

The binding of sarcoplasmic and myofibrillar proteins extracted from postrigor pork muscle and from 7 and 12 months dry-cured hams with volatile compounds such as 3-methyl-butanal, 2-methyl-butanal, 2-pentanone, hexanal, methional, and octanal was studied using solid phase microextraction and gas chromatography analysis. The binding ability of sarcoplasmic proteins from pork muscle was higher than the ability shown by 7 and 12 months dry-cured ham sarcoplasmic homogenates and also higher than the binding ability of myofibrillar homogenates. The effect of the ionic strength on the binding was also studied. This effect was more important on myofibrillar proteins due to its ability to produce changes on the protein conformation that affect their binding ability. However, the sarcoplasmic protein binding ability was more related to the small compounds present in this homogenate than with the aqueous phase ionic strength.

Aldehydes↗
PubMed1999

[Determination of inosine 5'-monophosphate and guanosine 5'-monophosphate in taste-enhancers by ion chromatography].

A high performance anion-exchange chromatographic method was developed for the simultaneous determination of two kinds of taste-enhancers, inosine 5'-monophosphate (IMP) and guanosine 5'-monophosphate (GMP), in the presence of monosodium glutamate and chloride (salt). The separation was achieved by using Dionex IonPac AG11 and IonPac AS11 columns, and the determination by ultraviolet absorbance detection at 254 nm. The detection limits (S/N = 3) were 0.21 mg/L and 0.27 mg/L for IMP and GMP, respectively. Good linearities between the concentrations of the two analytes and relevant peak area responses were obtained in the range of 2-100 mg/L. Under the experimental conditions, glutamate, chloride, succinate, benzoate, sorbic acid and citrate did not interfere in the determination of IMP and GMP. The method has been successfully applied to the determination of IMP and GMP in gourmet powder as well as chicken bouillon, and the average recoveries for various samples ranged from 97% to 103%.

Calibration↗
PubMed2002

Alkylpyridiniums. 1. Formation in model systems via thermal degradation of trigonelline.

Trigonelline is a well-known precursor of flavor/aroma compounds in coffee and undergoes significant degradation during roasting. This study investigates the major nonvolatile products that are procured after trigonelline has been subjected to mild pyrolysis conditions (220-250 degrees C) under atmospheric pressure. Various salt forms of trigonelline were also prepared and the thermally produced nonvolatiles analyzed by thin layer chromatography, liquid chromatography-electrospray ionization tandem mass spectrometry, and (1)H and (13)C nuclear magnetic resonance. Results revealed the decarboxylated derivative 1-methylpyridinium as a major product of certain salts, the formation of which is positively correlated to temperature from 220 to 245 degrees C. Moreover, trigonelline hydrochloride afforded far greater amounts of 1-methylpyridinium compared to the monohydrate over the temperature range studied. Investigations into other potential quaternary amine products of trigonelline also indicate nucleophilic substitution reactions that lead to dialkylpyridiniums, albeit at concentration levels approximately 100-fold lower than those recorded for 1-methylpyridinium.

Alkaloids↗
PubMed2000

Flavor release from salad dressings: sensory and physicochemical approaches in relation with the structure.

The effect of process and formulation on sensory perception and flavor release was investigated on salad dressing models. Oil/vinegar emulsions (phi = 0.5, droplet size > 10 microm) with thickeners and a whey protein concentrate were prepared with different fat droplet sizes and different distributions of fat droplet size. The effect of the amount of emulsifier was also tested. Sensory profile analysis was performed by a trained panel and flavor release quantified by dynamic headspace analysis. When the droplet size is increased, the lemon smell and citrus aroma significantly increase, whereas the egg note, mustard, and butter aroma significantly decrease. The concentrations of alcohols and acids significantly increase when droplet size increases, whereas those of other compounds such as limonene or benzaldehyde significantly decrease. The dispersion of the droplet size has a small effect on flavor perception, and the effect of the increase of the amount of emulsifier is noticed only by instrumental analysis.

Dietary Fats↗
PubMed2002

Anxiogenic and depressive-like effects, but no cognitive deficits, after repeated moderate tryptophan depletion in the rat.

The tryptophan (TRP) depletion method has been used as a tool to investigate the effects of acute lowered serotonin levels in the brain. In the present study, the effects of this treatment were investigated in rat models of anxiety (open field test, home cage emergence test), depression (forced swimming test, sucrose preference test) and cognition (spatial discrimination learning, sustained attention). It was found that the repeated TRP depletion increased anxiety-related behaviour in the open field test and increased immobility in the forced swimming test. The other behavioural tests did not reveal effects of treatment. TRP levels were decreased in plasma (34%) and hippocampus (33%) but not in the cortex. Stress-induced corticosterone levels were not affected after TRP depletion. The present findings indicate that repeated moderate TRP depletion leads to anxiogenic and depressive-like behaviour in the rat and corroborates the notion of the involvement of serotonin in these behaviours.

Animals↗
PubMed1982

Schedule-induced self-injection of drugs.

Studies of acquisition and maintenance patterns of drug intake, including dependence, necessitate voluntary intake of drugs. Voluntary intake in animal studies is difficult to achieve because of aversive taste factors associated with most drugs, and involuntary or forced choice methods obscure the behavior which is the object of study. The schedule-induced polydipsia paradigm has been used to induce oral ingestion of large volumes of alcohol, barbiturate and other drug solutions. We have developed a method of schedule-induced self-injection which allows the study of acquisition and maintenance of drug intake behavior with changing environments free from the interference of taste factors or imbalances due to excessive water intake. In this paper we review our findings on the acquisition and maintenance patterns of amphetamine, methadone, heroin, alcohol, nicotine, cocaine, delta 9-THC and haloperidol. For all drugs except amphetamine, the combination of schedule and nutritional deprivation leads to the highest rates of drug intake as compared to controls. The schedule does not appear to be a potent factor at 90% and free feeding weight, and drug intake is the result of interaction of environmental factors and pharmacological properties of the drugs, rather than the effects of drug or environmental factors separately. The maintenance patterns of nicotine, cocaine, heroin and alcohol are also discussed and the advantages of schedule-induced self-injection over schedule-induced polydipsia methods are presented.

Amphetamine↗