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Aims Certain bacteria can produce gamma aminobutyric acid (GABA) from glutamate in the human intestinal tract, leading to the possibility of altering GABA levels through diet. To this end, we assessed the ability of seven commercially available probiotic supplements to produce GABA. Method and results Probiotic strains were compared for GABA production in pure culture. The bacteria were inoculated at a concentration of 107 CFU ml−1 in 10 ml MRS supplemented with monosodium glutamate (1% w/v), both with and without oligofructose-enriched inulin (OFI) (1% w/v). Two strains with the highest production of GABA were further assessed for 48 h in pH-controlled anaerobic batch cultures inoculated with faecal bacteria. Liquid chromatography-mass spectrometry (LC–MS) was used for quantification of GABA and microbiota composition was determined through 16S rRNA gene sequencing. Levilactobacillus brevis LB01 (CGMCC 16921) and Lactiplantibacillus plantarum 299v (DSM 9843) were the most efficient producers of GABA. High GABA levels (28.32 mmol l−1 ± 0.29) were produced by the probiotic strain L. brevis LB01 at pH 5.4–5.6. This was significantly higher than the levels of GABA produced by L. plantarum (4.8 mmol l−1 ± 6.8) and a negative control (2.9 mM ± 3.1). The addition of OFI did not further stimulate GABA production under the conditions tested. The ability of these strains to produce GABA in-vitro was further evaluated in a faecal microbiota environment. Once again, L.brevis LB01 produced the highest levels of GABA (40.24 mmol l−1 ± 20.98). Conclusions L. brevis LB01 was found to be the most efficient probiotic strain, of those tested, for GABA production. [ABSTRACT FROM AUTHOR]

In this study, an effective, simple and rapid high-performance liquid chromatography (HPLC) using fluorescence (FLD) method was developed and validated for the determination of monosodium glutamate (MSG) in 57 various food samples. Besides, HPLC-Evaporate Light Scattering Detection (ELSD) method was carried out for determination of MSG without derivatization. MSG analysis was performed by derivatization with dansyl chloride at excitation 328, emission 530nm with fluorescence detector. HPLC-FLD method was carried out by using C18 (150 mm, 4.6 mm, 2.7 μm) column with the mobile phase consisting of (Water: Methanol:Glacial Acetic Acid)/(54:45:1,v/v/v). The column temperature was set at 25°C and the flow rate was set at 0.5 mL min−1 with an injection volume 20 μL. The results were linear (R2 = 0.9999) with very low quantification limits. The applied method was optimized and the validated parameters such as LOD, LOQ, accuracy, precision, linearity and robustness were calculated. The obtained results were statistically compared with each other. The validated HPLC-FLD method was successfully applied for the analysis of MSG in all of the food samples. Moreover, HPLC-ELSD method was optimized and successfully demonstrated for detect the MSG without derivatization. [ABSTRACT FROM AUTHOR]

Aims: This study aimed to screen the γ‐aminobutyric acid (GABA)‐producing lactic acid bacteria (LAB) from kimchi, and investigate the glutamate decarboxylase (GAD) activity of the highest GABA‐producing strain. Methods and Results: Seven strains of LAB were screened from kimchi with GABA‐producing activity. Strain Levilactobacillus brevis F109‐MD3 showed the highest GABA‐producing ability. It produced GABA at a concentration of 520 mmol l−1 with a 97.4% GABA conversion rate in MRS broth containing 10% monosodium glutamate for 72 h. The addition of pyridoxal 5'‐phosphate had no significant effect on the GAD activity of L. brevis F109‐MD3. The optimal pH range of GAD was 3.0–5.0 and the optimal temperature was 65°C. The D value of GAD at 50, 60 and 70°C was 7143, 971 and 124 min respectively and Z value was 11.36°C. Conclusions: Seven strains isolated from kimchi, especially F109‐MD3, showed high GABA‐production ability even in the high concentrations of MSG at 7.5% and 10%. The GAD activity showed an effective broad pH range and higher optimal temperature. Significance and Impact of the Study: These seven strains could be potentially useful for food‐grade GABA production and the development of healthy foods. [ABSTRACT FROM AUTHOR]

Aims: This research sought to improve the ability of biocontrol yeast to suppress postharvest fungal disease and explore possible mechanisms of action. Methods and Results: The addition of 2% sodium glutamate (SG), which is edible and recognized as safe, enhances the inhibitory effect of Rhodosporidium paludigenum Fell & Tallman on Penicillium expansum in vivo and in vitro. Rhodosporidium paludigenum cells grown in medium with a final concentration of 2% SG, displayed viability under a variety of stress conditions, including sodium chloride (NaCl), calcofluor white (CFW), Congo red (CR) and sodium dodecyl sulphate (SDS). Activity and relative gene expression levels of antioxidant‐related enzymes in R. paludigenum, including peroxisomal catalase (CAT), thioredoxin reductase (TrxR), glutathione peroxidase (GSH‐PX), glutathione reductase (GR) and superoxide dismutase (SOD) were altered in the presence of SG. Levels of reactive oxygen species (ROS) increased in cells grown in the presence of SG as well as the content of several amino acids. Conclusions: In the presence of 2% SG R. paludigenum inhibited P. expansum and exhibited tolerance to a number of stressful conditions which may involve the upregulation of antioxidant enzymes and amino acids. Significance and Impact of the Study: The ability of culture conditions to enhance the fungal suppressive abilities of yeast has the potential to enhance the management of postharvest disease in fruit. [ABSTRACT FROM AUTHOR]

The prototypical stimuli for umami taste is monosodium glutamate (MSG), which is the sodium salt form of glutamic acid. A proportion of the population has a reduced or complete inability to taste l -glutamate independent to the sodium ion. To determine individuals' umami discrimination status, many studies use a series of triangle tests containing isomolar (29 mM) sodium chloride (NaCl) and MSG, requiring participants to correctly identify the odd sample. Across studies, inconsistent categorization criteria have been applied. The aim of this study was to determine the optimal classification criterion based on the number of tests assessed to ascertain an individual's ability to discriminate between MSG and NaCl. Thirty-eight participants attended 3 taste assessment sessions, each involving 24 triangle tests (2 blocks of 12 tests) containing 29 mM NaCl and 29 mM MSG, detection and recognition threshold were measured for MSG, monopotassium glutamate (MPG), and sweet (sucrose) tastes. There was no learning, or fatigue trend over n = 24 (P = 0.228), and n = 12 (P = 0.940) triangle tests across each testing session. Twenty-four triangle tests produced the most consistent categorization of tasters across sessions (68.4%). The test–retest correlation across each testing session was highest for n = 24 triangle tests (ICC = 0.50), in comparison to 12 (ICC = 0.37). Overall, conducting n = 24 compared with n = 12 triangle tests provided the optimal classification to determine an individual's ability to discriminate l -glutamate from NaCl and thus their umami discrimination status, based on the number of tests assessed in this study. [ABSTRACT FROM AUTHOR]

The deficit syndrome is thought to be a more homogenous clinical subgroup within the syndrome of schizophrenia that is characterized by enduring negative symptoms. It is hypothesized that distinct pathophysiological processes underlie the subtypes, where the deficit syndrome reflects an early onset nonprogressive developmental process, and the nondeficit form of the illness is characterized by attenuated neuroplasticity secondary to elevated glutamate levels. We used single-voxel magnetic resonance spectroscopy (PRESS; TE: 30 ms) to measure left frontal white matter neurometabolite levels in 61 antipsychotic-naïve first-episode psychosis patients (39 who did not display deficit features, 22 who did display deficit features, assessed with the Schedule for the Deficit Syndrome) and 59 healthy controls. Metabolite levels were quantified with the LCModel. We used a MANCOVA to determine neurometabolite differences between healthy controls, deficit syndrome patients, and nondeficit patients. We report a significant group difference when all metabolites were considered jointly (F [10,208] = 2.16; P =.02). Post hoc analyses showed that patients presenting without deficit features had higher glutamate levels than patients with deficit features and controls. Patients presenting without deficit features also had significantly higher myoinositol levels than controls; myoinositol levels were trend-level higher in patients presenting with deficit features compared to controls. Our data support the idea that the pathophysiology of patients presenting without deficit features may differ from those presenting with deficit features. [ABSTRACT FROM AUTHOR]

To enable the taste evaluation of many food samples at a time as well as the comparison of taste evaluation data acquired at different times, a standardization method for taste intensities was developed by a combination of a taste sensor system and a standard solution prepared with taste substances. In the case of tomato juices, citric acid, sucrose, and monosodium glutamate were used as standard taste substances for sourness, sweetness, and umami taste, respectively. Each standard point of the taste intensities was determined using only one standard solution including these standard substances. The taste intensity was described as a value on a scale based on discrimination thresholds of human gustation, where intensities of sourness, sweetness, and umami taste of the tomato juices were classified into multiple levels. Organoleptic evaluation supported these results. Validation for the present standardization method revealed that this approach has enough precision for practical tomato taste evaluation. A standard solution prepared with pure chemicals constantly provides high-precision taste sensor outputs. [ABSTRACT FROM AUTHOR]

γ-Glutamyl compounds have unveiled their importance as active substances or precursors of pharmaceuticals. In this research, an approach for enzymatic synthesis of γ-glutamyl compounds was developed using γ-glutamylmethylamide synthetase (GMAS) from Methylovorus mays and polyphosphate kinase (PPK) from Corynebacterium glutamicum. GMAS and PPK were co-recombined in pETDuet-1 plasmid and co-expressed in E. coli BL21 (DE3), and the enzymatic properties of GMAS and PPK were investigated, respectively. Under the catalysis of the co-expression system, l-theanine was synthesized with 89.8% conversion when the substrate molar ratio of sodium glutamate and ethylamine (1:1.4) and only 2 mM ATP were used. A total of 14 γ-glutamyl compounds were synthesized by this one-pot method and purified by cation exchange resin and isoelectric point crystallization with a yield range from 22.3 to 72.7%. This study provided an efficient approach for the synthesis of γ-glutamyl compounds by GMAS and PPK co-expression system. [ABSTRACT FROM AUTHOR]

We explore here the cis-regulatory logic that dictates gene expression in specific cell types in the nervous system. We focus on a set of eight genes involved in the synthesis, transport, and breakdown of three neurotransmitter systems: acetylcholine (unc-17/ VAChT, cha-1/ChAT, cho-1/ChT, and ace-2/AChE), glutamate (eat-4/VGluT), and g-aminobutyric acid (unc-25/GAD, unc-46/LAMP, and unc-47/VGAT). These genes are specifically expressed in defined subsets of cells in the nervous system. Through transgenic reporter gene assays, we find that the cellular specificity of expression of all of these genes is controlled in a modular manner through distinct cis-regulatory elements, corroborating the previously inferred piecemeal nature of specification of neurotransmitter identity. This modularity provides the mechanistic basis for the phenomenon of “phenotypic convergence,” in which distinct regulatory pathways can generate similar phenotypic outcomes (i.e., the acquisition of a specific neurotransmitter identity) in different neuron classes. We also identify cases of enhancer pleiotropy, in which the same cis-regulatory element is utilized to control gene expression in distinct neuron types. We engineered a cis-regulatory allele of the vesicular acetylcholine transporter, unc-17/VAChT, to assess the functional contribution of a “shadowed” enhancer. We observed a selective loss of unc-17/VAChT expression in one cholinergic pharyngeal pacemaker motor neuron class and a behavioral phenotype that matches microsurgical removal of this neuron. Our analysis illustrates the value of understanding cis-regulatory information to manipulate gene expression and control animal behavior. [ABSTRACT FROM AUTHOR]

Aims: Poly‐γ‐glutamic acid (γ‐PGA) is an excellent water‐soluble biosynthesis material. To confirm the rate‐limiting steps of γ‐PGA biosynthesis pathway, we introduced a heterologous Bacillus strain pathway and employed an enzyme‐modulated dismemberment strategy in Escherichia coli. Methods and Results: In this study, we heterologously introduced the γ‐PGA biosynthesis pathway of two laboratory‐preserved strains—Bacillus amyloliquefaciens FZB42 and Bacillus subtilis 168 into E. coli, and compared their γ‐PGA production levels. Next, by changing the plasmid copy numbers and supplying sodium glutamate, we explored the effects of gene expression levels and concentrations of the substrate l‐glutamic acid on γ‐PGA production. We finally employed a two‐plasmid induction system using an enzyme‐modulated dismemberment of pgsBCAE operon to confirm the rate‐limiting genes of the γ‐PGA biosynthesis pathway. Conclusion: Through heterologously over‐expressing the genes of the γ‐PGA biosynthesis pathway and exploring gene expression levels, we produced 0·77 g l−1 γ‐PGA in strain RSF‐EBCAE(BS). We also confirmed that the rate‐limiting genes of the γ‐PGA biosynthesis pathway were pgsB and pgsC. Significance and Impact of the Study: This work is beneficial to increase γ‐PGA production and study the mechanism of γ‐PGA biosynthesis enzymes. [ABSTRACT FROM AUTHOR]

Despite the importance of hedonic reactions in pig's intake, feed palatability has been typically inferred from preference or acceptance measures. However, these measures are influenced by factors beyond palatability, such as energy density and hunger. The aim of this study was to evaluate palatability responses in pigs to sweet and umami taste at different inclusions levels. Pigs (24 per experiment) were video recorded while exposed in pairs to different sucrose (Exp. 1) or monosodium glutamate (MSG, Exp. 2) solutions over seven consecutive 10 min tests (one concentration per day). In both experiments, palatability was estimated through consumption patterns (consumption time per approaches, CT/A), facial expressions (snout openings and tongue protrusions), and consumption during a brief 2 min period. Data were analyzed by sucrose or MSG concentration. Sucrose concentration affected total intake, producing an inverted-U function and a quadratic relationship with sucrose concentration (P = 0.012). In contrast, CT/A and snout openings showed a dose effect (P < 0.005) with a direct correlation between sucrose concentration and CT/A (R = 0.23, P = 0.033) but not for openings (R = 0.18, P = 0.105) where a quadratic relationship appears (P < 0.001). Tongue protrusions and brief consumption time were not affected by sucrose concentration (P = 0.144 and 0.205, respectively). MSG concentration affected consumption, CT/A, snout openings, and brief consumption time (P < 0.001), with significant (P < 0.001) positive correlations (R = 0.59, 0.56, 0.56, and 0.68), respectively. As with rats, CT/A appears to provide a novel and interesting measure reflecting the palatability of preferred ingredients in pigs. However, brief consumption time and orofacial reactions show less similarity between pigs and rodents. Thus further studies are necessary both to better understand the measurement methods themselves and relationship between hedonic reactions and simple consumption in pigs. [ABSTRACT FROM AUTHOR]

The mammalian tastes of sweet, umami, and bitter are initiated by activation of G protein-coupled receptors (GPCRs) of the T1R and T2R families on taste receptor cells. GPCRs signal via nucleotide exchange and hydrolysis, the latter hastened by GTPase-accelerating proteins (GAPs) that include the Regulators of G protein Signaling (RGS) protein family. We previously reported that RGS21, uniquely expressed in Type II taste receptor cells, decreases the potency of bitter-stimulated T2R signaling in cultured cells, consistent with its in vitro GAP activity. However, the role of RGS21 in organismal responses to GPCR-mediated tastants was not established. Here, we characterized mice lacking the Rgs21 fifth exon. Eliminating Rgs21 expression had no effect on body mass accumulation (a measure of alimentation), fungiform papillae number and morphology, circumvallate papillae morphology, and taste bud number. Two-bottle preference tests, however, revealed that Rgs21-null mice have blunted aversion to quinine and denatonium, and blunted preference for monosodium glutamate, the sweeteners sucrose and SC45647, and (surprisingly) NaCl. Observed reductions in GPCR-mediated tastant responses upon Rgs21 loss are opposite to original expectations, given that loss of RGS21--a GPCR signaling negative regulator--should lead to increased responsiveness to tastant-mediated GPCR signaling (all else being equal). Yet, reduced organismal tastant responses are consistent with observations of reduced chorda tympani nerve recordings in Rgs21-null mice. Reduced tastant-mediated responses and behaviors exhibited by adult mice lacking Rgs21 expression since birth have thus revealed an underappreciated requirement for a GPCR GAP to establish the full character of tastant signaling. [ABSTRACT FROM AUTHOR]

Previous studies have reported that the umami taste of monosodium l-glutamate (MSG) and saltysmelling odors (e.g., soy sauce, bacon, sardines) enhance the perception of saltiness. This study aimed to investigate the neural basis of the enhancement of saltiness in human participants using functional near-infrared spectroscopy (fNIRS). University students who had passed a taste panel test participated in this study. Sodium chloride solutions were presented with or without either 0.10% MSG or the odor of soy sauce. The participants were asked to drink a cup of the stimulus and to evaluate only saltiness intensity in Experiment 1, as well as other sensory qualities in Experiment 2, and temporal brain activity was measured using fNIRS. In Experiment 3, the participants were asked to evaluate saltiness intensity using the time-intensity (TI) method, and the response of the parotid salivary glands was measured using fNIRS. The fNIRS data showed that the added MSG and soy sauce enhanced the hemodynamic response in temporal brain regions, including the frontal operculum, but no effect on the hemodynamic salivary responses was detected. These results indicate that the perceived enhancement of saltiness occurs in the brain region that is involved in central gustatory processing. Furthermore, the results of the sensory evaluations suggest that enhancement of saltiness by the addition of MSG is mainly based on fusion of the salty-like property of MSG and saltiness of NaCl, whereas enhancement by the addition of soy sauce odor is mainly based on modulation of the temporal dynamics of saltiness perception. [ABSTRACT FROM AUTHOR]

Umami taste is imparted predominantly by monosodium glutamate (MSG) and 5′-ribonucleotides. Recently, several different classes of hydrophobic umami-imparting compounds, the structures of which are quite different from MSG, have been reported. To obtain a novel umami-imparting compound,N-cinnamoyl phenethylamine was chosen as the lead compound, and a rational structure-optimization study was conducted on the basis of the pharmacophore model of previously reported compounds. The extremely potent umami-imparting compound 2-[[[2-[(1E)-2-(1,3-benzodioxol-5-yl)ethenyl]-4-oxazolyle]methoxy]methyl]pyridine, which exhibits 27,000 times the umami taste of MSG, was found. Its terminal pyridine residue and linear structure are suggested to be responsible for its strong activity. The time taken to reach maximum taste intensity exhibited by it, as determined by the time-intensity method, is 22.0 s, whereas the maximum taste intensity of MSG occurs immediately. This distinct difference in the time-course taste profile may be due to the hydrophobicity and strong receptor affinity of the new compound. Intense umami-imparting molecule11was discovered by structural optimization of natural umami-imparting substance; rubenamine9and rubescenamine10. [ABSTRACT FROM PUBLISHER]

This study was conducted to investigate the sensory characteristics and temporal migration of hydroxyl-sanshool compounds at slight and moderate concentrations after dissolution in ethanol-water, saccharose, NaCl, and MSG via 2-AFC, time intensity (TI) and temporal dominance of sensations (TDS) methods. The pungency detection threshold (DT) was suppressed in saccharose while NaCl and MSG solutions showed no effect on pungency DT. The area under the curve (AUC) of pungency increased in NaCl and MSG solutions and decreased significantly in saccharose solution. /max (maximal intensity) also increased in NaCl and MSG at low concentrations of hydroxyl-sanshool compounds. The temporally dominant sensations and migration of said sensations across the oral cavity differed among different carriers. Low levels of pungency compounds were characterized by tingling first in the tongue tip and ending in the lips, while moderate levels of the compound produced tingling, astringency, vibrating, and numbing from the tongue tip to the bilateral sides of the tongue, lips, palate, cheek mucosa, and surface of the tongue over time. There were significant differences in the maximum rate, peak time, and duration of any dominant sensation, as well as in the duration of sensation in the lips, tongue tip, and bilateral sides of the tongue. This study provides a dynamic profile of consuming pungent food, which provides a reference not only for the design of new food products with desirable pungency, but also as a scientific basis for the application of pungent compounds within the food and catering industry. [ABSTRACT FROM AUTHOR]

Previous research showed that L-alanine and monosodium L-glutamate elicit similar taste sensations in rats. This study reports the results of behavioral experiments designed to compare the taste capacity of C57BL/6J wild type and T1r3- mice for these 2 amino acids. In conditioned taste aversion (CTA) experiments, wild-type mice exhibited greater sensitivity than knockout mice for both L-amino acids, although knockout mice were clearly able to detect both amino acids at 50 mM and higher concentrations. Generalization of CTA between L-alanine and L-glutamate was bidirectionally equivalent for both mouse genotypes, indicating that both substances elicited similar tastes in both genotypes. This was verified by the discrimination experiments in which both mouse genotypes performed at or near chance levels at 75 and 150 mM. Above 150 mM, discrimination performance improved, suggesting the taste qualities of the 2 L-amino acids are not identical. No differences between knockout and wild-type mice in discrimination ability were detected. These results indicate that while the T1r3 receptor is important for tasting L-alanine and L-glutamate, other receptors are also important for tasting these amino acids. [ABSTRACT FROM AUTHOR]

The heterodimeric T1R1 + T1R3 receptor is considered critical for normal signaling of L-glutamate and 5'-ribonucleotides in the oral cavity. However, some taste-guided responsiveness remains in mice lacking one subunit of the receptor, suggesting that other receptors are sufficient to support some behaviors. Here, mice lacking both receptor subunits (KO) and wild-type (WT, both n = 13) mice were tested in a battery of behavioral tests. Mice were trained and tested in gustometers with a concentration series of Maltrin-580, a maltodextrin, in a brief-access test (10-s trials) as a positive control. Similar tests followed with monosodium glutamate (MSG) with and without the ribonucleotide inosine 5'-monophosphate (IMP), but always in the presence of the epithelial sodium channel blocker amiloride (A). Brief-access tests were repeated following short-term (30-min) and long-term (48-h) exposures to MSG + A + IMP and were also conducted with sodium gluconate replacing MSG. Finally, progressive ratio tests were conducted with Maltrin-580 or MSG + A + IMP, to assess appetitive behavior while minimizing satiation. Overall, MSG generated little concentration-dependent responding in either food-restricted WT or KO mice, even in combination with IMP. However, KO mice licked less to the amino acid stimuli, a measure of consummatory behavior in the brief-access tests. In contrast, both groups initiated a similar number of trials and had a similar breakpoint in the progressive ratio task, both measures of appetitive (approach) behavior. Collectively, these results suggest that while the T1R1 + T1R3 receptor is necessary for consummatory responding to MSG (+IMP), other receptors are sufficient to maintain appetitive responding to this "umami" stimulus complex in food-restricted mice. [ABSTRACT FROM AUTHOR]

Aim To evaluate the technological and safety properties of Lactobacillus futsaii CS3 and CS5 isolated from Thai fermented shrimp products ( Kung-Som) in order to develop a valuable gamma-aminobutyric acid ( GABA)-producing starter culture. Methods and Results Both strains showed a high GABA-producing ability (>8 mg ml−1) in MRS broth containing 20 mg ml−1 monosodium glutamate ( MSG) for 120 h. They also exhibited inhibitory activity against foodborne pathogens and spoilage bacteria. Cell surface hydrophobicity and proteolytic activity were observed in both strains. Strain CS3 survived better under simulated gastrointestinal tract conditions with only 1·5 log-units cell decrease over 8 h. Both strains showed the ability to deconjugate taurocholate and taurodeoxycholate acid. Neither virulence genes nor biogenic amine production was detected. Strain CS3 exhibited susceptibility to all tested antibiotics with the exception of vancomycin, while strain CS5 showed resistance to vancomycin, ampicillin and chloramphenicol. Conclusions Based on the results obtained, Lact. futsaii CS3 is very promising as a GABA-producing and potentially probiotic starter culture strain for applications in functional fermented foods. Significance and Impact of the Study This study focuses on the technological and safety characteristics of Lact. futsaii CS3 and CS5 including their high GABA-producing capacity for the first time. This provides a way of replacing chemical GABA by natural GABA using a GABA-producing starter culture candidate, at the same time offering the consumer new attractive food products. [ABSTRACT FROM AUTHOR]

Aims To optimize a protective medium for freeze-dried Pichia membranifaciens and to evaluate biocontrol efficacies of agents against blue and green mould and anthracnose in citrus fruit. Methods and Results Based on the screening assays of saccharides and antioxidants, response surface methodology was used to optimize sucrose, sodium glutamate and skim milk to improve viability of freeze-dried Pi. membranifaciens. Biocontrol assays were conducted between fresh and freeze-dried Pi. membranifaciens against Penicillium italicum, Penicillium digitatum and Colletotrichum gloeosporioides in citrus fruit. Solving the regression equation indicated that the optimal protective medium was 6·06% (w/v) sucrose combined with 3·40% (w/v) sodium glutamate and 5·43% (w/v) skim milk. Pi. membranifaciens freeze-dried in the optimal protective medium showed 76·80% viability, and retained biocontrol efficacy against Pe. italicum, Pe. digitatum and Co. gloeosporioides in citrus fruit. Conclusions The optimal protective medium showed more effective protective properties than each of the three protectants used alone. The viability of freeze-dried Pi. membranifaciens finally reached 76·80%. Meanwhile, the biocontrol efficacies showed no significant difference between fresh and freeze-dried yeast against Pe. italicum, Pe. digitatum and Co. gloeosporioides in citrus fruit. Significance and Impact of the Study The results showed the potential value of Pi. membranifaciens CICC 32259 for commercialization. [ABSTRACT FROM AUTHOR]

The effect of temperature on umami taste has not been previously studied in humans. Reported here are 3 experiments in which umami taste was measured for monopotassium glutamate (MPG) and monosodium glutamate (MSG) at solution temperatures between 10 and 37 °C. Experiment 1 showed that for subjects sensitive to MPG on the tongue tip, 1) cooling reduced umami intensity whether sampled with the tongue tip or in the whole mouth, but 2) had no effect on the rate of umami adaptation on the tongue tip. Experiment 2 showed that temperature had similar effects on the umami taste of MSG and MPG on the tongue tip but not in the whole mouth, and that contrary to umami taste, cooling to 10 °C increased rather than decreased the salty taste of both stimuli. Experiment 3 was designed to investigate the contribution of the hT1 R1-hT1 R3 glutamate receptor to the cooling effect on umami taste by using the T1R3 inhibitor lactisole. However, lactisole failed to block the umami taste of MPG at any temperature, which supports prior evidence that lactisole does not block umami taste for all ligands of the hT1R1-hT1R3 receptor. We conclude that temperature can affect sensitivity to the umami and salty tastes of glutamates, but in opposite directions, and that the magnitude of these effects can vary across stimuli and modes of tasting (i.e., whole mouth vs. tongue tip exposures). [ABSTRACT FROM AUTHOR]

The marker of neuronal activation, c-Fos, can be used to visualize spatial patterns of neural activity in response to taste stimulation. Because animals will not voluntarily consume aversive tastes, these stimuli are infused directly into the oral cavity via intraoral cannulae, whereas appetitive stimuli are given in drinking bottles. Differences in these 2 methods make comparison of taste-evoked brain activity between results that utilize these methods problematic. Surprisingly, the intraoral cannulae experimental conditions that produce a similar pattern of c-Fos activity in response to taste stimulation remain unexplored. Stimulation pattern (e.g., constant/intermittent) and hydration state (e.g., water-restricted/hydrated) are the 2 primary differences between delivering tastes via bottles versus intraoral cannulae. Thus, we quantified monosodium glutamate (MSG)- evoked brain activity, as measured by c-Fos, in the nucleus of the solitary tract (nTS; primary taste nucleus) across several conditions. The number and pattern of c-Fos neurons in the nTS of animals that were water-restricted and received a constant infusion of MSG via intraoral cannula most closely mimicked animals that consumed MSG from a bottle. Therefore, in order to compare c-Fos activity between cannulae-stimulated and bottle-stimulated animals, cannulated animals should be water restricted prior to stimulation, and receive taste stimuli at a constant flow. [ABSTRACT FROM AUTHOR]

Background: Monosodium Glutamate (MSG) is one of the most widely used food-additives in commercial foods. Its application has increased over time and it is found in many different ingredients and processed foods obtainable in every market or grocery store. Besides its flavor enhancing effects, MSG has been associated with various forms of toxicity. Aim of the work: The aim of the present work was to determine the effect of monosodium glutamate on the histology of the ileum of the adult male albino rats and evaluate the protective effect of vitamin E. Material and methods: 30 Adult male albino rats were assigned randomly into three groups; control group, it was further subdivided into three subgroups (IA received no treatment, IB received 2 ml olive oil/day, and IC received 400 IU/kg. BW of Vitamin E dissolved in 2 ml olive oil once daily), MSG group (rats fed 2mg/kg. BW of MSG once daily, orally), and vitamin E treated group (rats fed MSG and received concomitant 400 IU/kg/day vitamin E orally). Weight of rats were measured at the start & end of experiment. At the end of experiment (15 days), rats were euthanized, and ileal specimens were processed into paraffin blocks for light microscopic examination and other specimens were processed into scanning electron microscopic examination. Morphometric study and statistical analysis were done. Results: The present work demonstrated that MSG induced several histopathological changes of the ileum. Broad, fused villi sloughed epithelial cells and pronounced increase in the number of goblet cells. Massive lymphocyte infiltration and hemorrhage was noticed in the lamina propria. Enterocytes lining crypts showed cytoplasmic vacuolation, pale nuclear staining and loss of demarcation between adjacent cells. Increased villus width, goblet cell and lymphocytes numbers was demonstrated by histomorphometry. Vitamin E treated group showed histopathological findings mostly normalized compared with MSG group. Width and length of villi was reduced, enterocytes appeared healthy and well arranged, reduced inflammatory cell infiltrate and vascular congestion and decreased number of goblet cells was observed. Conclusion: The present results demonstrated deleterious effects of MSG on the structure of the mucosa of the ileum. It also suggested a novel and favorable protective effect of vitamin E on mucosa of the ileum. [ABSTRACT FROM AUTHOR]

Previous electrophysiological investigation shows that combinations of compounds classified by humans as umami-tasting, such as glutamate salts and 5'-ribonucleotides, elicit synergistic responses in neurons throughout the rodent taste system and produce a pattern that resembles responses to sweet compounds. The current study tested the hypothesis that a synergistic mixture of monopotassium glutamate (MPG) and inositol monophosphate (IMP) possesses perceptual similarity to sucrose in mice. We estimated behavioral similarity among these tastants and the individual umami compounds using a series of conditioned taste aversion (CTA) tests, a procedure that measures whether a CTA formed to one stimulus generalizes to another. Our primary finding was that a CTA to a synergistic mixture of MPG + IMP generalizes to sucrose, and vice-versa. This indicates umami synergistic mixtures are perceived as having a sweet, or at least sucroselike, taste to mice. Considering other recent studies, our data argue strongly in favor of multiple receptor mechanisms for umami detection, and complexity in taste perception models for rodents. [ABSTRACT FROM AUTHOR]

Aims: Metabotropic glutamate receptors 2 and 3 (mGluR2/3) contribute to control the level of glutamate in the synapse. In rodents, mGluR2/3 agonists attenuate the reinstatement of alcohol-seeking behavior. Linking possible alterations of the mGluR2/3 system to the etiology and type of alcoholism could provide valuable information for the development of novel mGluR2/3 function modulating therapies in addiction treatment. To date, mGluR2/3 binding density has not been studied in human alcoholics. We aimed to investigate the possible differences in mGluR2/3 binding between Cloninger type 1 anxiety-prone and type 2 impulsive alcoholics and controls. Methods: We performed a post-mortem whole-hemisphere autoradiography to study the mGluR2/3 binding density of 9 type 1 alcoholics, 8 type 2 alcoholics and 10 controls. [3H]LY341495, a potent group II metabotropic glutamate receptor antagonist, was used as the radio-ligand with l-glutamate as a displacer. Results: [3H]LY341495 binding density was statistically significantly increased (P = 0.046) in the perigenual anterior cingulate cortex (pACC) of type 2 alcoholics when compared with controls. In other brain areas, no significant difference between the groups was found. Conclusion: This preliminary study suggests that impulsive type 2 alcoholics might have alterations in the mGluR2/3 function in the pACC, a brain area presumed to be involved in the control of drug-seeking behaviors and self-control. [ABSTRACT FROM PUBLISHER]

Aims: To make a comparative evaluation of the effects of different stabilizers and freezing rates on structurally different viruses during lyophilization and storage. Methods and Results: Two virus strains from each of six animal virus families, including both enveloped and nonenveloped viruses, were lyophilized in (i) culture medium, (ii) with the addition of gelatine-sucrose and (iii) skim milk-sodium glutamate. All the virus suspensions were frozen (i) at -80°C or (ii) in liquid nitrogen before lyophilization. Virus titre assay after lyophilization and after 8 months storage at 4°C revealed that the efficacy of stabilizers depended on virus structure. Generally, the best protective quality for enveloped viruses was achieved with gelatine-sucrose, which best maintained their infectivity and envelope morphology. Even additive-free culture medium proved adequate for nonenveloped viruses. Differences in stabilizer efficacy were also found between virus families and were expressed immediately after lyophilization; the activity of stabilizers in the course of storage was very similar. Freezing in liquid nitrogen proved beneficial for picornaviruses. Conclusions: The choice of an appropriate stabilizer with respect to virus type is crucial for effective lyophilization. Significance and Impact of the Study: This study contributes to the establishment of general guidelines for animal virus lyophilization, with particular respect to differences in virus structure. [ABSTRACT FROM AUTHOR]

The flavor of dashi, the broth prepared from dried bonito tuna, is attractive to humans and rodents. The present experiments examined the ability of dashi to serve as an oral and/or postoral rewarding stimulus for conditioned flavor preferences in mice. In Experiment 1, C57BL/6J (B6) mice were infused intragastrically with dashi when they consumed a conditioned stimulus (CS)+ flavor and with water when they drank a CS− flavor on alternate days. Postoral dashi did not condition a CS+ preference. The combined effects of oral and postoral dashi exposure were examined in Experiment 2, in which B6 mice consumed a CS+ flavored dashi solution and CS− flavored water on alternate days. The mice did not prefer the CS+ to CS− when both flavors were presented in water. Yet, the B6 mice in both experiments preferred dashi to water in oral tests. Experiment 3 showed that taste-impaired Trpm5 knockout (KO) mice did not learn to prefer dashi after exposure to it, in contrast to previous findings with the umami prototype monosodium glutamate. This was not due to an inability to taste dashi, because Trpm5 KO mice learned a strong preference for dashi after it was mixed with glucose. The impact of dashi on reward may largely reflect an enhancement of association of oral and postoral effects of food. [ABSTRACT FROM AUTHOR]

The consumption of monosodium glutamate (MSG) solutions has been shown to reinforce preferences for MSG and for MSG–paired flavors in mice. These effects appear to have a strong postoral component, such that MSG detected in the gut is associated with concurrently consumed flavors. Two experiments investigated postoral MSG reward by infusing 400mM MSG intragastrically (IG) to C57BL/6 mice as they consumed a conditioned stimulus (CS+) flavor. An alternate CS− flavor was paired with IG water. In Experiment 1, the grape and cherry CS flavors were unsweetened, and intakes and preferences for the CS+ flavor were modest. Experiment 2 attempted to generate stronger preferences by adding 0.05% saccharin to the CS flavors. Sweet taste did enhance intakes during training and testing but did not significantly increase percent CS+ intake or persistence of the preference. However, only conditioning with the sweet CS+ resulted in the mice expressing a preference for oral MSG in an initial choice test with water. These findings extend recent studies demonstrating postoral MSG conditioning in rats. [ABSTRACT FROM AUTHOR]

The prototypic umami substance monosodium glutamate (MSG) reinforces preferences for its own flavor, as well as preferences for flavors associated with it, by conditioning processes. Mice of 3 inbred strains (C57BL/6J (B6), 129P3/J, and FVB/NJ) and 2 taste-knockout (KO) groups derived from the B6 lineage were initially indifferent to 200mM MSG, but this evaluation was altered by forced exposure to MSG. B6 and KO mice acquired an MSG preference, 129 mice remained indifferent, and FVB mice avoided MSG. The shifts in preference imply a postoral basis for MSG effects, suggesting that it could produce preferences for associated flavors. New mice were trained with a conditioned stimulus (CS+) flavor mixed in 200mM MSG and a CS− flavor in water. Similar to the parent B6 strain, mice missing the T1r3 element of an umami receptor or the downstream signaling component Trpm5 learned to prefer the CS+ flavor and subsequently showed similar preferences for MSG in an ascending concentration series. Consistent with their responses to forced exposure, the 129 strain did not acquire a significant CS+ preference, and the FVB strain avoided the CS+ flavor. The 129 and FVB strains showed little attraction in the ascending MSG concentration series. Together, these data indicate that the postoral effects of MSG can modulate responses to its own and MSG-paired flavors. The basis for strain differences in the responses to MSG is not certain, but the taste-signaling elements T1r3 and Trpm5, which are also present in the gut, are not required for mediation of this flavor learning. [ABSTRACT FROM AUTHOR]

Umami taste is responsible for sensing monosodium glutamate, nucleotide enhancers, and other amino acids that are appetitive to vertebrates and is one of the five basic tastes that also include sour, salty, sweet, and bitter. To study how ecological factors, especially diets, impact the evolution of the umami taste, we examined the umami taste receptor gene Tas1r1 in a phylogenetically diverse group of bats including fruit eaters, insect eaters, and blood feeders. We found that Tas1r1 is absent, unamplifiable, or pseudogenized in each of the 31 species examined, including the genome sequences of two species, suggesting the loss of the umami taste in most, if not all, bats regardless of their food preferences. Most strikingly, vampire bats have also lost the sweet taste receptor gene Tas1r2 and the gene required for both umami and sweet tastes (Tas1r3), being the first known mammalian group to lack two of the five tastes. The puzzling absence of the umami taste in bats calls for a better understanding of the roles that this taste plays in the daily life of vertebrates. [ABSTRACT FROM AUTHOR]

Aims To assess the ability of human intestinally derived strains of Lactobacillus and Bifidobacterium to produce γ-aminobutyric acid ( GABA). Methods and Results Strains of Lactobacillus and Bifidobacterium were grown in medium containing monosodium glutamate ( MSG). Growth of the bacteria and conversion of MSG to GABA were measured. Of 91 intestinally derived bacteria assessed, one Lactobacillus strain and four strains of Bifidobacterium produced GABA. Lactobacillus brevis DPC6108 was the most efficient of the strains tested, converting up to 100% of MSG to GABA. The ability of the cultured intestinal strains to produce GABA was investigated using a simple p H-controlled anaerobic faeces-based fermentation, supplemented with 30 mg ml−1 MSG. The addition of Lact. brevis DPC6108 to a faeces-based fermentation significantly increased the GABA concentration ( P < 0·001), supporting the notion that this biosynthesis could occur in vivo. Conclusions The production of GABA by bifidobacteria exhibited considerable interspecies variation. Lactobacillus brevis and Bifidobacterium dentium were the most efficient GABA producers among the range of strains tested. The addition of Lact. brevis DPC6108 to the culturable gut microbiota increased the GABA concentration in fermented faecal slurry at physiological p H. Significance and Impact of the Study Identification of optimal MSG conversion to GABA by particular cultured elements of the commensal intestinal microbiota and the demonstration that this can occur under simulated in vivo conditions offer new prospects for microbiota modulation to promote health. [ABSTRACT FROM AUTHOR]

Obese people and diabetic patients are known to be high risk of colorectal cancer (CRC), suggesting need of a new preclinical animal model, by which to extensively study the diverse mechanisms, therapy and prevention. The present study aimed to determine whether experimental obese and diabetic mice produced by monosodium glutamate (MSG) treatment are susceptible to azoxymethane (AOM)-induced colon tumorigenesis using early biomarkers, aberrant crypts foci (ACF) and β-catenin-accumulated crypts (BCACs), of colorectal carcinogenesis. Male Crj:CD-1 (ICR) newborns were daily given four subcutaneous injections of MSG (2 mg/g body wt) to induce diabetes and obesity. They were then given four intraperitoneal injections of AOM (15 mg/kg body wt) or saline (0.1 ml saline/10 g body wt). Ten weeks after the last injection of AOM, the MSG-AOM mice had a significant increase in the multiplicity of BCAC (13.83 ± 7.44, P < 0.002), but not ACF (78.00 ± 11.20), when compare to the Saline-AOM mice (5.45 ± 1.86 of BCAC and 69.27 ± 8.06 of ACF). Serum biochemical profile of the MSG-treated mice with or without AOM showed hyperinsulinemia, hypercholesteremia and hyperglycemia. The mRNA expression of insulin-like growth factor-1 receptor (IGF-1R, P<0.01) was increased in the MSG-AOM mice, when compared with the mice given AOM alone. IGF-1R was immunohistochemically expressed in the BCAC, but not ACF, in the AOM-treated mice. Our findings suggest that the MSG mice are highly susceptible to AOM-induced colorectal carcinogenesis, suggesting potential utility of our MSG-AOM mice for further investigation of the possible underlying events that affect the positive association between obese/diabetes and CRC. [ABSTRACT FROM AUTHOR]

The article discusses a study which investigated mice's behavioral and nerve responses to different umami substances. The study examined the taste characteristics of several umami substances including monosodium L-glutamate (MSG), sodium succinate, and betaine. Results revealed that sodium succinate had strong synergy with inosine 5'-monophosphate (IMP). It notes that the synergy of D-MSG with IMP might be weak.

Listeria monocytogenesΔ gadD1 and Δ lisK mutants display enhanced and reduced sensitivity, respectively, to the food preservative nisin in laboratory media. However, the behaviour of these strains in a nisin-containing food has not been assessed. Here we use cottage cheese as a model food to address this issue. Antibiotic-resistant forms of the wild-type and mutant strains were employed to investigate the behaviour of multiple strains in a single food sample, thereby eliminating the problem of intersample variation. Using this approach, it was established that percentage survival of the Δ lisK mutant was greater than the parent strain in the absence of nisin and that this relative difference became even more dramatic in cottage cheese supplemented with nisin. The numbers of the Δ gadD1 mutant decreased more rapidly than the parent in cottage cheese without nisin, but surprisingly this trend was reversed in nisin-supplemented cheese. Upon the addition of 10 mmol l monosodium glutamate, a substrate for the glutamate decarboxylase (GAD) system, the wild-type LO28 strain regained its relative advantage over Δ gadD1. Care needs to be taken when predicting the behaviour of mutants of L. monocytogenes with altered resistance to nisin in food as experiments in laboratory media are not always a good indicator of how the strains will behave in such food environments. This study further emphasizes the importance of utilizing food matrices to confirm observations made using laboratory media. [ABSTRACT FROM AUTHOR]

The article presents a study which examines the influence of oxidized arachidonic acid (AA) or hexanal on the bitter and umami taste perception of mouse. The study determines the mouse licking frequency of mice subjects in a tastant with and without water extract from oxidized AA to a quinine hydrochloride (QHCl). Result shows decrease of mice licking frequency in concentrations having QHCl. Moreover, the study concludes that hexanal affects mouse perception of taste to QHCl.

Aims: To develop solid-state fermentation system (SSF) for hyper production of tylosin from a mutant γ-1 of Streptomyces fradiae NRRL-2702 and its parent strain. Methods and Results: Various agro-industrial wastes were screened to study their effect on tylosin production in SSF. Wheat bran as solid substrate gave the highest production of 2500 μg of tylosin g−1 substrate by mutant γ-1 against parent strain (300 μg tylosin g−1 substrate). The tylosin yield was further improved to 4500 μg g−1 substrate [70% moisture, 10% inoculum (v/w), pH 9·2, 30°C, supplemental lactose and sodium glutamate on day 9]. Wild-type strain displayed less production of tylosin (655 μg of tylosin g−1 substrate) in SSF even after optimization of process parameters. Conclusion: The study has shown that solid-state fermentation system significantly enhanced the tylosin yield by mutant γ-1. Significance and Impact of the Study: This study proved to be very useful and resulted in 6·87 ± 0·30-fold increase in tylosin yield by this mutant when compared to that of wild-type strain. [ABSTRACT FROM AUTHOR]

Statistical methodologies were employed to optimize submerged culture medium for the production of a novel antineoplastic compound aspergiolide A by a marine-derived fungus Aspergillus glaucus HB1-19 for the first time. Orthogonal design was preformed to determine the initial composition. Then Plackett–Burman design was applied to evaluate the influence of related nutrients, and yeast extract paste, soybean powder and sodium glutamate were confirmed as critical factors in the medium. Response surface methodology (RSM) was finally taken as an effective approach to optimize the combination of the obtained three significant factors. The predicted maximal aspergiolide A production of 62.4 mg/L appeared at the region where the concentrations of sodium glutamate, soybean powder, and yeast extract paste were 2, 1, and 1.07 g/L, respectively. Under the proposed optimized conditions, the experimental aspergiolide A production reached 71.2 mg/L. The correlation between predicted value and measured value of these experiments proved the validity of the response model. After optimization, aspergiolide A production increased 4.22 times compared to that of the original medium. Elemental analysis was finally taken into consideration, and carbon–nitrogen ratio in the medium increased from 20.1:1 to 86.6:1. This great difference was inferred as the most important reason for production enhancement by metabolic pathway analysis. [ABSTRACT FROM AUTHOR]

An apparent plasticity in glucose sensitivity was first noted while studying human taste variants, but the experimental design did not rule out regression to the mean. Since then, a human taste induction hypothesis that sensitivity for a taste stimulus increases with repeated exposure to it has been supported first by experience-induced changes in taste identification of monosodium glutamate and, subsequently, in sensory detection of glutaraldehyde, as well as in psychophysical and functional magnetic resonance imaging responses to novel taste stimuli. Yet, whether such plasticity occurs for the highly familiar taste of sugar remained unconfirmed. Therefore, we tested the taste induction hypothesis for sugar using a counterbalanced design, consisting of 3 pretreatment and 2 treatment conditions. The effects over time also were followed with an additional group of participants. The results showed that 1) experience with fructose significantly increases sensitivity for the taste of a sugar, glucose; 2) there are no significant differences in the sugar sensitivity between groups of randomly assigned participants before treatments; 3) a single session of 5 brief tastings of glucose has an effect on glucose sensitivity when tested 11 or 12 days later; and 4) without continued treatment, the increased sensitivity reverses within 33 or 34 days. [ABSTRACT FROM AUTHOR]

To date, only one study has examined responses to monosodium glutamate (MSG) from gustatory neurons in the rat geniculate ganglion and none to free fatty acids. Accordingly, we recorded single-cell responses from geniculate ganglion gustatory neurons in anesthetized male rats to MSG and linoleic acid (LA), as well as to sucrose, NaCl, citric acid, and quinine hydrochloride. None of the 52 neurons responded to any LA concentration. In contrast, both narrowly tuned groups of gustatory neurons (sucrose specialists and NaCl specialists) responded to MSG, as did 2 of the broadly tuned groups (NaCl generalistI and acid generalists). NaCl-generalistII neurons responded only to the highest MSG concentration and only at low rates. No neuron type responded best to MSG; rather, responses to 0.1 M MSG were significantly less than those to NaCl for Na+-sensitive neurons and to sucrose for sucrose specialists. Interestingly, most Na+-sensitive neurons responded to 0.3 M MSG at levels comparable with those to 0.1 M NaCl, whereas sucrose specialists responded to 0.1 M MSG despite being unresponsive to NaCl. These results suggest that the stimulatory effect of MSG involves activation of sweet- or salt-sensitive receptors. We propose that glutamate underlies the MSG response of sucrose specialists, whereas Na+-sensitive neurons respond to the sodium cation. For the latter neuron groups, the large glutamate anion may reduce the driving force for sodium through epithelial channels on taste cell membranes. The observed concentration-dependent responses are consistent with this idea, as are cross-adaptation studies using 0.1 M concentrations of MSG and NaCl in subsets of these Na+-sensitive neurons. [ABSTRACT FROM AUTHOR]

Inosine monophosphate (IMP) and guanosine monophosphate (GMP) elicit an umami taste in humans and synergistically increase the intensity of the umami taste of monosodium glutamate (MSG). Conditioned taste aversion (CTA) studies in rodents indicate that these nucleotides and MSG elicit quite similar tastes, but recent physiological evidence suggests that these nucleotides and MSG may not activate the same population of taste receptors and therefore may not elicit identical taste qualities. This study reports the findings of several behavioral experiments with rats that compared the taste properties of IMP and GMP with each other and with those of MSG. Well-trained rats were able to detect both nucleotides at nanomolar concentrations, but they did not respond to either nucleotide in two-bottle preference tests or brief-access CTA tests at concentrations less than 0.5 mM. Discrimination experiments found that the tastes of these nucleotides could not be discriminated from each other, but both could be discriminated from MSG, even when the taste of Na+ was controlled. Overall, these experiments indicate the taste properties of the two 5′-ribonucleotides are quite similar to each other, and even though they may elicit an umami sensation, these sensations are not identical to the taste of MSG. [ABSTRACT FROM AUTHOR]

Background: The consumption of fast-food is increasing among children, adolescents and adults. Carbonated drinks are widely consumed with fast food that also exists in the form of diet drinks as Diet Coke. One of the thousands of chemicals used in our new high-tech foods is the monosodium glutamate (MSG). Aim of the Study: This study was conducted to investigate the effect of Diet Coke and monosodium glutamate salt either separately or in combination on the cerebellar cortex and kidney of adult male albino rats. Materials and Methods: Twenty five adult male albino rats were divided into four groups. Group I: control group (10 rats) divided equally into two subgroups, subgroup IA in which rats had free access to food and water and subgroup 1B in which each rat administrated 0.5 ml of distilled water once daily by oral gavage. Rats had free access to food and water. Group II (5 rats): in which rats received Diet Coke instead of water throughout the day. Group DI (5 rats): in which each rat received 0.5m1 of MSG salt solution by dose of 3ern MSG/kgm by oral gavage once daily. Group IV (5 rats): in which each rat received Diet Coke instead of water throughout the day and 0.5m1 of MSG salt solution by dose of 3gm MSG/kgm by oral gavage once daily. Cerebella and kidneys were dissected out and processed for histological, immunohistochemical and morphometric studies. Results: Histological examination of the cerebellum and the kidney revealed that both Diet Coke and MSG either separately or in combination resulted in degenerative changes that were more significant in the combination group. The cerebellum showed degeneration of Purkinje cells and vaculations in the molecular layer. The kidney showed shrunken glomeruli, vacuolations of cells lining renal tubules with pyknotic nuclei. Hyaline debris detected in renal sections of combination group. Conclusion: Diet Coke and MSG induced degenerative changes in both the cerebellum and the kidney that was more significant in their combination. [ABSTRACT FROM AUTHOR]

The article discusses the study which investigates how intracellular Ca(2+) increases in the umami transduction pathway. The researchers have measured the changes in the intracellular Ca(2+) levels in response to umami stimuli monosodium glutamate, inosine 5'-monophosphate or both in mouse taste receptor cells (TRCs) by Ca(2+) imaging. Results indicate that umami-responsive TRCs have increased their intracellular Ca(2+) levels through two pathways.

Molecular and behavioral studies have identified heterodimers of the T1R family as receptors for detecting the tastes of sweet (T1R2 + T1R3) and umami (T1R1 + T1R3). However, behavioral studies have reported conflicting findings with T1R3 knockout (KO) mice. One study showed a complete or nearly complete loss of preference for sweet and umami substances by KO mice, whereas KO mice in another study showed only a partial reduction in preferences for sucrose and monosodium glutamate (MSG), the prototypical umami substance. The present experiments used psychophysical methods to assess how sensitive T1R1-KO mice are to sucrose and MSG and discrimination methods to determine if these mice could distinguish between the tastes of sucrose and MSG. Detection thresholds of T1R3-KO mice and wild-type (WT) C57Bl mice were nearly identical for sucrose and MSG. Mice of both genotypes were easily able to discriminate between the tastes of sucrose and MSG. When amiloride (a sodium channel blocker) was added to all solutions to reduce the taste of Na+, discrimination accuracy of both genotypes of mice decreased but more so for the T1R3-KO mice than the WT mice. However, even when the sodium taste of MSG was neutralized, both genotypes could still discriminate between the two substances well above chance performance. These results suggest that sucrose and MSG can be detected by taste receptors other than T1R2 + T1R3 and T1R1 + T1R3 and that the conflicts between the previous studies may have been due to the methodological limitations. [ABSTRACT FROM AUTHOR]

A few studies have reported experience-inducible changes in human taste and olfactory sensitivities. However, no study thus far has systematically characterized the stability of the enhanced sensitivities. In our previous study, we found increases in taste identification ability for monosodium glutamate (MSG) in subjects who had been briefly exposed to MSG in food for 10 days. Here, we tested the temporal stability of the enhanced taste identification ability. First, we exposed a group of 20 subjects to MSG in food and then compared their sensitivities to MSG with those of a control group. When tested on day 11 or 12, the mean MSG taste identification ability of the MSG-exposed group was significantly higher than the control group. Next, 11 of the subjects who were exposed to MSG in food initially, and then stopped being exposed performed significantly poorer in identifying MSG after 10 days of the nonexposure than they did 10 days before. In contrast, nine subjects who were exposed to MSG initially and continued being exposed maintained their high identification levels. These results support earlier finding of the plasticity in the taste identification of MSG and show that the enhanced identification ability can be reversed rapidly when MSG exposure is not sustained. [ABSTRACT FROM AUTHOR]

Aims: Effects of amino acid on morphological development and nucleus formation of arachidonic acid-producing filamentous micro-organism, Mortierella alpina were investigated using flow-through chamber. Methods and Results: Mortierella alpina CBS 754·68 was cultivated in flow through chamber using nutrient-rich, minimal and specific amino acid-containing minimal media. To investigate the effect of amino acid on morphological parameters either 0·28 g l−1 alanine, 0·53 g l−1 sodium glutamate one hydrate or 0·42 g l−1 valine was added to the minimal medium. In a flow-through chamber, the growth of hyphal elements and nucleus formation of arachidonic acid-producing fungus M. alpina were studied on-line, using image analysis techniques. When the Ala- and Val-containing media were used, the hyphal growth units (HGUs) were 90·2 and 86·7 μm per tip, respectively, which were 2·4-fold higher than that in the nutrient-rich medium, indicating that Ala and Val stimulate the elongation of hyphae. The specific nucleus formation rates were Glu->Val-containing media>minimal and nutrient-rich media>Ala-containing medium. The nucleus doubling times in Glu- and Val-containing media were 1·9 and 2 h, respectively, which were not significant different. Conclusions: Ala and Val stimulate the elongation of M. alpina hyphae, and nucleus formation rates were Glu->Val->Ala-containing media. Significance and Impact of the Study: Formation of fungal morphology and nucleus were shown using the flow-through chamber coupled with image analysis, which making possible to discuss the relationship between mycelial morphology and nucleus formation of M. alpina. [ABSTRACT FROM AUTHOR]

The sense of taste provides humans with necessary information about the composition and quality of food. For humans, five basic tastes are readily distinguishable and include sweet, bitter, salty, sour, and savory (or umami). Although each of these qualities has individualized transduction pathways, sweet and umami tastes are believed to share a common receptor element, the T1R3 receptor subunit. The two G-protein–coupled heteromer receptors that comprise an umami stimulus receptor (T1R1–T1R3) and a sweetener receptor (T1R2–T1R3) constitute a potential link between these two qualities of perception. While the role of the individual monomers in each human heteromer has been examined in vitro, very little is known of the implication of this research for human perception, or specifically, how sweet and savory taste perceptions may be connected. Using a psychophysical approach, we demonstrate that lactisole, a potent sweetness inhibitor that binds in vitro to hT1R3, also inhibits a significant portion of the perception of umami taste from monosodium glutamate. Following the molecular logic put forward by Xu et al. (2004, Proc. Natl Acad. Sci. USA, 101, 14258–14263), our psychophysical data support the in vitro hypothesis that the shared T1R3 monomer moderates the activation of both T1R2 and T1R1 in humans and impairs suprathreshold perception, respectively, of sweetness and, to a lesser degree, umaminess in the presence of lactisole. [ABSTRACT FROM AUTHOR]

The article cites a study that investigated the effects of lysine, monosodium glutamate, glycine and alanine with different degrees of polymerization on the gelatinization behavior of potato starch granules. Viscosity and swelling measurements and microscopic observation are used to clarify the contribution of the net charge to the regulatory effects on the gelatinization behavior.

g. zhao and g. zhang. 2005. The effects of protective agents, rehydration media and freezing temperature on the viabilities of Lactobacillus brevis and Oenococcus oeni H-2 when subjected to freeze-drying were investigated. Several protectants and rehydration media were tested to improve the survival after freeze-drying. The cells were also frozen at −65 and −20°C to check the effect of freezing temperature on the viability. The best protectant and rehydration medium to obtain the highest viability after freeze-drying varied with the species of bacteria. Yeast extract (4·0%) and sodium glutamate (2·5% ) gave maximum viability of L. brevis and O. oeni (67·8% and 53·6% respectively). The highest survival of L. brevis and O. oeni were obtained when rehydrated with 10% sucrose and MGY medium respectively. When the bacterial cells were frozen quickly (−65°C) than slowly (−20°C), L. brevis and O. oeni both showed increased viability after freeze-drying. The viabilities of L. brevis and O. oeni after freeze-drying were shown to be strain specific and dependent on protective agents, rehydration media and freezing temperature. [ABSTRACT FROM AUTHOR]

We examined the necessity of α-gustducin, a G protein α-subunit expressed in taste cells, to taste-mediated licking responses of mice to sapid stimuli. To this end, we measured licking responses of α-gustducin knock-out (Gus−/−) mice and heterozygotic littermate controls (Gus+/−) to a variety of ‘bitter’, ‘umami’, ‘sweet’, ‘salty’ and ‘sour’ taste stimuli. All previous studies of how Gus−/− mice ingest taste stimuli have used long-term (i.e. 48 h) preference tests, which may be confounded by post-ingestive and/or experiential effects of the taste stimuli. We minimized these confounds by using a brief-access taste test, which quantifies immediate lick responses to extremely small volumes of sapid solutions. We found that deleting α-gustducin (i) dramatically reduced the aversiveness of a diverse range of ‘bitter’ taste stimuli; (ii) moderately decreased appetitive licking to low and intermediate concentrations of an ‘umami’ taste stimulus (monosodium glutamate in the presence of 100 μM amiloride), but virtually eliminated the normal aversion to high concentrations of the same taste stimulus; (iii) slightly decreased appetitive licking to ‘sweet’ taste stimuli; and (iv) modestly reduced the aversiveness of high, but not low or intermediate, concentrations of NaCl. There was no significant effect of deleting α-gustducin on licking responses to NH4Cl or HCl. [ABSTRACT FROM AUTHOR]

Aims: The aim of the present study was to evaluate the effects of acute and chronic exposure to alcohol on taste responses to a prototypic umami substance, monosodium glutamate (MSG). Methods: The rated intensity and pleasantness of MSG taste (0.03-10.0%) was compared in chronic male alcoholics (n = 35) and control subjects (n = 25). In a separate experiment, the effects of acute exposure of the oral mucosa to ethanol rinse (0.5-4.0%) on MSG taste (0.3-3.0%) were studied in 10 social drinkers. Results: The alcoholic and control group did not differ in terms of the rated intensity and pleasantness of MSG taste. Electrogustometric thresholds were significantly (P < 0.01) higher, i.e. worse, in the alcohol-dependent subjects. The difference remained significant after controlling for between-group differences in cigarette smoking and coffee drinking. Rinsing with ethanol did not alter either intensity or pleasantness of MSG taste in social drinkers. Conclusions: The present results suggest that: (i) neither acute nor chronic alcohol exposure modifies taste responses to MSG; (ii) alcohol dependence may be associated with deficit in threshold taste reactivity, as assessed by electrogustometry. [ABSTRACT FROM AUTHOR]

Recent research has implicated T1R1/T1R3 as the primary taste receptor in mammals for detecting l-amino acids, including l-monosodium glutamate (MSG) and l-alanine. Previous behavioral studies with rodents found only minimal evidence that these two substances share perceptual qualities, but those studies did not control for the taste of sodium associated with MSG. This study used several behavioral methods to compare the perceptual qualities of MSG and l-alanine in rats, using amiloride (a sodium channel blocker) to reduce the sodium component of MSG taste. Detection thresholds of l-alanine in rats ranged between 0.4 and 2.5 mM, with or without amiloride added, which are similar to threshold estimates for MSG. Conditioned taste aversion (CTA) found that rats showed strong cross-generalization of CTA between MSG and l-alanine when mixed with amiloride, indicating the two substances have similar perceptual qualities. Discrimination methods showed that rats easily discriminated between l-alanine and MSG unless the cue function of sodium was reduced. The discrimination became significantly more difficult at concentrations <100 mM when amiloride was added to all stimuli and became even more difficult when NaCl was also added to l-alanine solutions to match the sodium concentrations of MSG. These results indicate that, perceptually, MSG and l-alanine have quite similar taste qualities and support the hypothesis that these two l-amino acids activate a common taste receptor. The differences in perceptual qualities also suggest separate afferent processing of one or both substances may also be involved. [ABSTRACT FROM AUTHOR]