Amino Acid Response Research Articles

Adipocyte amino acid sensing controls adult germline stem cell number via the amino acid response pathway and independently of Target of Rapamycin signaling in Drosophila.

How adipocytes contribute to the physiological control of stem cells is a critical question towards understanding the link between obesity and multiple diseases, including cancers. Previous studies have revealed that adult stem cells are influenced by whole-body physiology through multiple diet-dependent factors. For example, nutrient-dependent pathways acting within the Drosophila ovary control the number and proliferation of germline stem cells (GSCs). The potential role of nutrient sensing by adipocytes in modulating stem cells in other organs, however, remains largely unexplored. Here, we report that amino acid sensing by adult adipocytes specifically modulates the maintenance of GSCs through a Target of Rapamycin-independent mechanism. Instead, reduced amino acid levels and the consequent increase in uncoupled tRNAs trigger activation of the GCN2-dependent amino acid response pathway within adipocytes, causing increased rates of GSC loss. These studies reveal a new step in adipocyte-stem cell crosstalk.

Can bottom ice algae tolerate irradiance and temperature changes?

Sea ice algae are significant primary producers of the ice-covered marine environment, growing under typically cold, dim conditions. During ice break-up they are released to the water column, where temperatures can be several degrees higher and irradiance can increase by orders of magnitude. To determine how sea ice algae respond to such rapid changes, we carried out incubations to examine their tolerance to environmentally realistic levels of change in temperature and PAR, as expressed by photosynthetic response and production of mycosporine-like amino acids (MAAs). The algae were also exposed to a broader range of temperatures, to evaluate their potential to function in warmer seas in the event, for instance, of anthropogenic transfer to locations further north. When subjected to PAR (0–100μmolm−2s−1) at ecologically relevant temperatures (−1°C, 2°C, 5°C), the algae showed tolerance, indicated by a lack of decline in the quantum efficiency of photosystem II (PSII). The data show that bottom ice algae can tolerate increasing temperature and PAR comparable to the changes experienced during and after sea ice melt. MAA production increased at higher PAR and temperature. At ambient PAR levels, increased temperatures resulted in lower ϕPSII. However, as PAR levels were increased, higher temperature reduced the level of stress as indicated by higher ϕPSII values. This result suggests, for the first time in sea ice algal studies, that higher temperatures can ameliorate the negative effects of increased PAR. Exposure to much higher temperatures suggested that the algae were capable of retaining some photosynthetic function at water temperatures well above those currently experienced in some of their Antarctic habitats. However, when temperature was gradually increased past 14°C, the photosystems started to become inactivated as indicated by a decrease in quantum yield, suggesting that the algae would not be viable if transferred to lower latitude cold temperate areas.

Carbon Dioxide Enrichment Restrains the Impact of Drought on Three Maize Hybrids Differing in Water Stress Tolerance in Water Stressed Environments

Three maize genotypes were grown in controlled environment chambers with ambient (38 Pa) or elevated (70 Pa) carbon dioxide and water stress treatments were initiated 17 days after sowing. Shoot dry weight of the drought tolerant hybrid in both CO2 treatments was 44 to 73% less than that of the intermediate and sensitive hybrids when seedlings were well watered. Decreased shoot and root dry weights of the tolerant maize hybrid due to drought were about one-half that of the other two hybrids. Genotypic differences were observed in decreases of soil water content, leaf water potential, net photosynthesis and stomatal conductance in response to drought. Eleven of 19 amino acids measured in this study increased, methionine was unchanged and alanine and aspartate decreased in response to drought in the ambient CO2 treatment. Increased amino acid levels under elevated CO2 were observed at the end of the experiment. Significant genotypic differences were detected for amino acid responses to drought. Effects of drought on all three genotypes were mitigated by CO2 enrichment. Decreased shoot growth likely improved the stress tolerance of a highly drought resistant maize hybrid by reducing moisture loss, improving soil moisture content and increasing leaf water potential.

The amino acid response to a mixed meal in patients with type 2 diabetes: effect of sitagliptin treatment.

Amino acid (AA) metabolism is altered in type 2 diabetes (T2D), and fasting levels of α-hydroxybutyrate (α-HB), a biomarker for insulin resistance, have been suggested to track AA metabolism. We investigated the changes in AA and α-HB induced by a mixed-meal tolerance test (MTT) and the effects of sitagliptin treatment. Forty-seven T2D patients [56 ± 7 years, body mass index (BMI) 29.9 ± 4.2 kg/m(2) ] were randomized to sitagliptin (100 mg/day, 6 weeks) or placebo. Seven age- and BMI-matched non-diabetic subjects served as control (CT). During a 5-h MTT, branched-chain AA (BCAA) peaked earlier in T2D than CT [75(25) vs. 62(3) mmol/l · h over 2 h, median(interquartile range), p = 0.05], and rose higher [5-h increment: 31(23) vs. 19(24) mmol/l · h, p = 0.05]. Fasting α-HB was higher [7.5(2.7) vs. 5.9(1.3) µg/ml, p = 0.04 T2D vs. CT], and its meal-induced increments were larger [24(99) vs. -41(86) µg/ml · h, p = 0.006]. Plasma non-esterified fatty acids (NEFA) declined during MTT, but their increments were greater in patients (53 ± 16 vs. 35 ± 10 mEq/l · h, p = 0.005). Compared to placebo, both BCAA [-6.4(21.1) vs. 0.0(48.0) mmol/l · h, p = 0.01] and α-HB increments [-114(250) vs. 114(428) µg/ml · h, p = 0.002] decreased with sitagliptin, and meal-induced NEFA suppression was improved. Changes in BCAA and α-HB were reciprocally related to changes in insulin sensitivity (ρ = -0.37 and -0.43, p ≤ 0.01). T2D is associated with a hyperaminoacidaemic response to MTT, which circulating α-HB levels track. Sitagliptin-induced glycaemic improvement was associated with reductions in BCAA and α-HB excursions and better NEFA suppression, in parallel with improved insulin sensitivity, confirming that α-HB is a readout of metabolic overload.

Mitochondrial Phosphoenolpyruvate Carboxykinase (PEPCK-M) Is a Pro-survival, Endoplasmic Reticulum (ER) Stress Response Gene Involved in Tumor Cell Adaptation to Nutrient Availability

Mitochondrial phosphoenolpyruvate carboxykinase (PEPCK-M), encoded by the nuclear PCK2 gene, links TCA cycle intermediates and glycolytic pools through the conversion of mitochondrial oxaloacetate into phosphoenolpyruvate. In the liver PEPCK-M adjoins its profusely studied cytosolic isoform (PEPCK-C) potentiating gluconeogenesis and TCA flux. However, PEPCK-M is present in a variety of non-gluconeogenic tissues, including tumors of several origins. Despite its potential relevance to cancer metabolism, the mechanisms responsible for PCK2 gene regulation have not been elucidated. The present study demonstrates PEPCK-M overexpression in tumorigenic cells as well as the mechanism for the modulation of PCK2 abundance under several stress conditions. Amino acid limitation and ER stress inducers, conditions that activate the amino acid response (AAR) and the unfolded protein response (UPR), stimulate PCK2 gene transcription. Both the AAR and UPR lead to increased synthesis of ATF4, which mediates PCK2 transcriptional up-regulation through its binding to a putative ATF/CRE composite site within the PCK2 promoter functioning as an amino acid response element. In addition, activation of the GCN2-eIF2α-ATF4 and PERK-eIF2α-ATF4 signaling pathways are responsible for increased PEPCK-M levels. Finally, PEPCK-M knockdown using either siRNA or shRNA were sufficient to reduce MCF7 mammary carcinoma cell growth and increase cell death under glutamine deprivation or ER stress conditions. Our data demonstrate that this enzyme has a critical role in the survival program initiated upon stress and shed light on an unexpected and important role of mitochondrial PEPCK in cancer metabolism.

Comparative proteomic analysis of different developmental stages of the edible mushroom Termitomyces heimii.

BackgroundTermitomyces heimii is a basidiomycete fungus that has a symbiotic relationship with termites, and it is an edible mushroom with a unique flavour and texture. T. heimii is also one of the most difficult mushrooms to cultivate throughout the world. Little is known about the growth and development of these mushrooms, and the available information is insufficient or poor. The purpose of this study was to provide a base of knowledge regarding the biological processes involved in the development of T. heimii. The proteomic method of 2 dimensional difference gel electrophoresis 2D-DIGE was used to determine and examine the protein profiles of each developmental stage (mycelium, primordium and fruiting body). Total proteins were extracted by TCA-acetone precipitation.ResultsA total of 271 protein spots were detected by electrophoresis covering pH 3–10 and 10–250 kDa. Selected protein spots were subjected to mass spectrometric analyses with matrix-assisted laser desorption/ionisation (MALDI TOF/TOF). Nineteen protein spots were identified based on peptide mass fingerprinting by matching peptide fragments to the NCBI non-redundant database using MASCOT software. The 19 protein spots were categorised into four major groups through KEGG pathway analysis, as follows: carbohydrate metabolism, energy metabolism, amino acid metabolism and response to environmental stress.ConclusionsThe results from our study show that there is a clear correlation between the changes in protein expression that occur during different developmental stages. Enzymes related to cell wall synthesis were most highly expressed during fruiting body formation compared to the mycelium and primordial stages. Moreover, enzymes involved in cell wall component degradation were up-regulated in the earlier stages of mushroom development.

Metabolomic analysis reveals amino-acid responses to an oral glucose tolerance test in women with prior history of gestational diabetes mellitus

ObjectiveAlthough gestational diabetes mellitus (GDM) is associated with an increased risk of type 2 diabetes mellitus (T2DM) compared to normoglycemic pregnancies, the biochemical pathways underlying the progression of GDM to T2DM are not fully elucidated. The purpose of this exploratory study was to utilize metabolomics with an oral glucose tolerance test (OGTT) to examine the amino acid response in women with prior GDM to determine if a relationship between these metabolites and established risk factors for T2DM exists. Materials/methodsThirty-eight non-pregnant women without diabetes but with prior GDM within the previous 3 years were recruited from a community-based population. A 75 g-OGTT was administered; fasting and 2-h plasma samples were obtained. Metabolite profiles of 23 amino acids or amino acid derivatives were measured with gas chromatography-mass spectrometry. Measures of insulin resistance were derived from the OGTT and risk factors for T2DM were obtained by self-report. ResultsTwenty-two metabolite levels decreased significantly in response to the OGTT (p < 0.05). The clinical covariates most powerfully associated with metabolite level changes included race, body mass index (BMI), and duration of prior breastfeeding, (mean ± SD of standardized β-coefficients, β = −0.38 ± 0.05, 0.25 ± 0.08, and 0.44 ± 0.03, respectively, all p < 0.05). Notably, a prior history of breastfeeding was associated with the greatest number of metabolite changes. ConclusionsGreater change in metabolite levels after a glucose challenge was significantly associated with a longer duration of breastfeeding and higher BMI. Further exploration of these preliminary observations and closer examination of the specific pathways implicated are warranted.

The c‐RAF/MEK/ERK MAPK pathway regulates a class of GCN2‐independent amino acid response genes (818.6)

During adaptation to protein/amino acid (AA) limitation, the general control non‐derepressible 2 (GCN2) serine/threonine protein kinase initiates the amino acid response (AAR) by binding uncharged tRNAs, which activates its kinase activity. Subsequently, GCN2 phosphorylates eukaryotic initiation factor 2 (eIF2) leading to suppression of general protein synthesis, but induction of translation for specific mRNA species, including that for the transcription factor ATF4. ATF4 is a major effector of AAR‐induced transcription for many genes involved in restoring homeostasis or inducing apoptosis. GCN2 is currently the only well characterized sensor for AA deficiency in mammalian cells and the GCN2‐eIF2‐ATF4 pathway is considered the predominant AAR signaling mechanism. However, evidence from several laboratories has been published suggesting that GCN2‐independent AAR signaling exists. In this study, HepG2 human hepatoma clonal cell lines, expressing shRNA against GCN2, were generated to investigate the possibility of alternative AAR signaling mechanisms. Based on previous research, the MAPK pathways were likely candidates and therefore, were screened using chemical inhibitors. Using IL‐8 as a model MAPK‐responsive and AA‐responsive gene, it was established that c‐RAF/MEK/ERK signaling contributes to GCN2‐independent regulation of a wide spectrum of genes following AA limitation.Grant Funding Source: Supported by NIH, DK092062 and DK094729

Lactose: a milk‐specific carbohydrate enabling homeostatic regulation of glucose and insulin (623.12)

Lactose, a disaccharide of glucose and galactose, is uniquely present in mammalian milk. Human milk provides the infant with about 40% energy as lactose and 50% from fat. With 6‐7 g/dL lactose, the breast fed infant consumes high carbohydrate/kg body wgt, suggesting carbohydrate induced hepatic lipogenesis would be problematic with a high fat milk diet. However, galactose, unlike glucose is non‐insulinogenic and shows high hepatic clearance. We propose lactose in human milk confers unique metabolic advantage to the infant by delivering non‐insulinogenic carbohydrate which can be slowly metabolized in the liver to glucose or to support fatty acid oxidation. We determined insulin, glucose, triglyceride, free fatty acid and amino acid responses in 16 healthy adult men given in random order 650 mL carbohydrate‐free infant formula reconstituted to contain 50g lactose, glucose, sucrose or corn syrup solids. The milk formula was given 3 hr after a lactose and sucrose‐free meal, then again after 3 hr, to model the carbohydrate load and continuous feeding of breast‐fed infants. Blood was drawn every 15 min, and total and incremental area‐under‐curve change in insulin and glucose determined. Lactose gave a significantly lower rise in plasma insulin and glucose, in the first and particularly second 3 hr following intake, compared to glucose or corn syrup solids (P &lt;0.001). Individual variability in triglyceride responses was high, with no difference due to carbohydrate in this 6 hr study. We show lactose enables maintenance of glucose and insulin equilibrium, avoiding high postprandial peaks achieved with glucose or corn syrups in milk fed at 3 hr intervals. We propose an important metabolic homeostatic role for lactose as carbohydrate source in human milk. Supported by Mead Johnson Nutrition.Grant Funding Source: Mead Johnson Nutrition

Expression of the glycine transporter type 1 (GlyT‐1A) is upregulated by ATF‐4 following physiological stress in human intestinal epithelial cells (1109.14)

Downstream of activating transcription factor 4 (ATF‐4) in Caco‐2 cells in response to stress. In the present study we show that increased expression of the GlyT‐1a gene following stress is dependent on elements contained within the 5’untranslated region (UTR). Caco‐2 cells transfected with plasmid constructs containing sequences representative of the GlyT‐1a proximal promoter and 5’UTR upstream of a beta‐galactosidase reporter showed increased reporter activity following treatment with thapsigargin (Tg), tunicamycin (Tu), amino acid (AA) starvation, tertbutylhydroquinone(tBHQ) or Diethyl maleate (DEM). Short labeled DNA probes containing a potential amino acid response element (AARE) located in exon 1 of the GLYT‐1a gene demonstrated binding by ATF‐4 in gel shift and super shift assays. qPCR assays performed on short genomic DNA fragments isolated from Caco‐2 cells by chromatin immunoprecipitation (ChIP) with antibodies against ATF4 demonstrated 9, 5 and 2‐fold enrichment of the ATF‐4/AARE interaction at the 5’‐UTR region of GlyT1a following Tu, AA starvation and DEM treatment respectively. Our data suggests that response elements within the 5’UTR including exon 1 and the first 85 bases of exon 2 are required for transcriptional induction of GlyT1a. We propose the direct interaction of ATF‐4 at the identified AARE drives transcriptional up‐regulation of GlyT‐1a following nutrient, oxidative and endoplasmic reticulum stress.Grant Funding Source: University of Newcastle

Low protein diet during gestation and lactation induces autophagy‐related gene LC3 in the liver of rat dams (737.5)

Autophagy is essential for the maintenance of cellular homeostasis and is activated in mouse liver cells by amino acid deprivation. A low protein diet during gestation and lactation has been associated with poor fetal development but consequence in mother has not been fully investigated. This study aims to investigate the effects of a low protein diet during gestation and lactation on liver physiology of dams and characterize the associated hepatic autophagy. Timed‐pregnant Sprague‐Dawley rats were fed a control (control, 20 kcal% protein) or a low protein (LP, 8 kcal% protein) diet during gestation and lactation. Dam liver was collected for analysis at weaning. LP dams had significantly lower circulating threonine than control dams, which is accompanied with the hepatic activation of Amino Acid Response pathway. Expression of an autophagy‐related gene, microtubule‐associated protein 1 light chain 3 beta (lc3) was up‐regulated by the LP diet which coincided with increased ATF4 binding at the predicted promoter region of lc3 gene. Also, we observed increased LC3 protein localization outside nucleus by the LP diet. Knocking down of ATF4 by siRNA decreased mRNA and protein expressions of LC3 in a rat hepatoma cell line. In conclusion, our data demonstrate that ATF4 is potentially involved in the autophagy process through regulation of LC3 by a low protein diet during gestation and lactation in the liver of rat dam.

Terahertz time-domain spectroscopy response of amines and amino acids intercalated smectites in far-infrared region

Layered clay minerals from the smectite group with different chemical composition and resulting layer charge (e.g. pyrophyllite, illite, hectorite and montmorillonite) were characterised for their dielectric properties in the far-infrared region using terahertz-time domain spectroscopy (THz-TDS). Samples with distinct cation exchange capacity such as hectorite and montmorillonite were modified using cation exchange reaction with alkylamines or amino acids. The presence of these species in 2D gallery was proved by X-ray diffraction and Fourier transform infrared spectroscopy. The frequency-dependent refractive index of these minerals was determined in the experimentally accessible range of 0.1–3.0 THz (3–100 cm−1) using THz-TDS. Pristine samples revealed their refractive indices to be 1.82–2.15 at about 1 THz while the modified montmorillonite samples had their refractive indices changed by organic molecules used for their modification to 1.70–2.35 for amines and 1.97–2.36 for amino acids. The presence of organic substances in 2D gallery of clays was detectable despite the relatively high absorption of smectites with magnitude of 100 cm−1.

Dietary deprivation of each essential amino acid induces differential systemic adaptive responses in mice

Dietary deprivation of essential amino acids (EAAs) in mammals is known to cause reductions in food intake and body weight. The aim of this study was to determine whether and how mice respond to deprivation of individual EAA species. Dietary deprivation of any single EAA (not non-EAA) in mice led to progressive weight loss in the order of Ile(-) > Val(-) > Thr(-) > Leu(-) > Trp(-) > His(-) > Phe(-) > Met(-) > Lys(-) , which correlated with the reduction in food intake. Decreased levels of the deprived EAAs as well as increased levels of all or some of the other amino acids were detected in the serum, although these levels differed among the diets examined. Serum biochemistry identified significant increases in creatine phosphokinase, blood urea nitrogen, alanine aminotransferase, and aspartate aminotransferase, and decreases in glucose and triglycerides; computed tomography revealed a marked reduction in abdominal/femoral fat and muscle depots; histology identified diffuse myofiber atrophy in the rectus femoris muscle, all in that approximate order. In contrast, amino acid response, autophagy, and ubiquitination marker genes as well as amino acid transporter genes were induced in both deprived EAA-specific and tissue-specific manners. Dietary deprivation of individual EAAs induced systemic adaptive responses that differed in magnitude and molecular machinery.

Targeted metabolomic analysis of amino acid response to L-asparaginase in adherent cells.

L-asparaginase (L-ASP) is a therapeutic enzyme used clinically for the treatment of childhood acute lymphoblastic leukemia. L-ASP’s anticancer activity is believed to be associated primarily with depletion of asparagine, but secondary glutaminase activity has also been implicated in its anticancer mechanism of action. To investigate the effects of L-ASP on amino acid metabolism, we have developed an LC–MS/MS metabolomics platform for high-throughput quantitation of 29 metabolites, including all 20 proteinogenic amino acids, 6 metabolically related amino acid derivatives (ornithine, citrulline, sarcosine, taurine, hypotaurine, and cystine), and 3 polyamines (putrescince, spermidine, and spermine) in adherent cultured cells. When we examined the response of OVCAR-8 ovarian cancer cells in culture to L-ASP, asparagine was depleted from the medium within seconds. Interestingly, intracellular asparagine was also depleted rapidly, and the mechanism was suggested to involve rapid export of intracellular asparagine followed by rapid conversion to aspartic acid by L-ASP. We also found that L-ASP-induced cell death was more closely associated with glutamine concentration than with asparagine concentration. Time-course analysis revealed the dynamics of amino acid metabolism after feeding cells with fresh medium. Overall, this study provides new insight into L-ASP’s mechanism of action, and the optimized analytical method can be extended, with only slight modification, to other metabolically active amino acids, related compounds, and a range of cultured cell types.Electronic supplementary materialThe online version of this article (doi:10.1007/s11306-014-0634-1) contains supplementary material, which is available to authorized users.

Phospholipase C and Diacylglycerol Mediate Olfactory Responses to Amino Acids in the Main Olfactory Epithelium of an Amphibian

The semi-aquatic lifestyle of amphibians represents a unique opportunity to study the molecular driving forces involved in the transition of aquatic to terrestrial olfaction in vertebrates. Most amphibians have anatomically segregated main and vomeronasal olfactory systems, but at the cellular and molecular level the segregation differs from that found in mammals. We have recently shown that amino acid responses in the main olfactory epithelium (MOE) of larval Xenopus laevis segregate into a lateral and a medial processing stream, and that the former is part of a vomeronasal type 2 receptor expression zone in the MOE. We hypothesized that the lateral amino acid responses might be mediated via a vomeronasal-like transduction machinery. Here we report that amino acid-responsive receptor neurons in the lateral MOE employ a phospholipase C (PLC) and diacylglycerol-mediated transduction cascade that is independent of Ca2+ store depletion. Furthermore, we found that putative transient receptor potential (TRP) channel blockers inhibit most amino acid-evoked responses in the lateral MOE, suggesting that ion channels belonging to the TRP family may be involved in the signaling pathway. Our data show, for the first time, a widespread PLC- and diacylglycerol-dependent transduction cascade in the MOE of a vertebrate already possessing a vomeronasal organ.

Response of free amino acids in four legumes plants to air pollution

Response of free amino acids in four legumes plants to air pollution

Cellular responses to individual amino‐acid depletion in antibody‐expressing and parental CHO cell lines

Depletion of two nonessential amino acids, asparagine (Asn) and glutamine (Gln), occurred during a fed-batch production process with a CHO cell line expressing a recombinant antibody. This depletion coincided with growth suppression and the onset of the stationary phase. Experimental withdrawal of Asn led to cell cycle arrest of cell line A in G0/G1 phase. On a mechanistic level, withdrawal of either Asn or Gln stimulated the amino-acid response (AAR) pathway, indicating that depletion of nonessential amino acids can induce AAR in this cell line. Compared to withdrawal of an essential amino acid, leucine (Leu), withdrawal of either Asn or Gln induced fewer changes in downstream effectors of mammalian target of rapamycin (mTOR) signaling involved in regulation of global protein synthesis. Global transcriptional analysis followed by pathway analysis revealed that the cultures experienced a down-regulation of cell-cycle progression, DNA replication and nucleotide biosynthesis in an E2F-dependent manner, as well as a down-regulation of lipid metabolism in a SREBP1/2-dependent manner as a result of individual amino-acid withdrawal. Timing and magnitude of observed phenotypic and transcriptional responses to amino-acid withdrawal differed between essential (Leu) and nonessential (Asn and Gln) amino acids examined. Observed responses were similar in parental (CS9 and CHOK-1) and two other antibody-producing CHO cell lines, but the magnitude of the transcriptional response was both cell-line and amino-acid dependent. Overall, these results suggest that depletion of nonessential amino acids in cell culture plays a role in the onset of the stationary phase of production process and offer mechanistic insights into the observed growth attenuation phenotype.

Short-term cuprizone feeding induces selective amino acid deprivation with concomitant activation of an integrated stress response in oligodendrocytes.

Cuprizone [bis(cyclohexylidenehydrazide)]-induced toxic demyelination is an experimental approach frequently used to study de- and re-myelination in the central nervous system. In this model, mice are fed with the copper chelator cuprizone which leads to oligodendrocyte apoptosis and subsequent microgliosis, astrocytosis, and demyelination. The underlying mechanisms of cuprizone-induced oligodendrocyte death are still unknown. We analysed differences in amino acid levels after short-term cuprizone exposure (i.e., 4 days). Furthermore, an amino acid response (AAR) pathway activated in oligodendrocytes after cuprizone intoxication was evaluated. Short-term cuprizone exposure resulted in a selective decrease of alanine, glycine, and proline plasma levels, which was paralleled by an increase of apoptotic cells in the liver and a decrease of alanine aminotransferase in the serum. These parameters were paralleled by oligodendrocyte apoptosis and the induction of an AAR with increased expression of the transcription factors ATF-3 and ATF-4 (activating transcription factor-3 and -4). Immunohistochemistry revealed that ATF-3 is exclusively expressed by oligodendrocytes and localized to the nuclear compartment. Our results suggest that cuprizone-induced liver dysfunction results in amino acid starvation and in consequence to the activation of an AAR. We propose that this stress response modulates oligodendrocyte viability in the cuprizone animal model.

Responses of free amino acids in rice seedlings during cyanide metabolism

Responses of free amino acids to botanical assimilation of free cyanide were investigated. Young rice seedlings (Oryza sativa L. cv. XZX 45) were grown in nutrient solution amended with free cyanide (KCN). Cyanide was analyzed in solution as well as in plant materials to estimate the phyto-assimilation potential. Free amino acids in different parts of plants were also measured to determine metabolic responses to KCN exposure. Phyto-assimilation of KCN was obvious, and the rates were positively correlated to the concentration supplied. Although changes in total amino acid content in plant materials were negligible during KCN metabolism (p > 0.05), responses of different amino acids to KCN treatments were quite different. All treatments with KCN increased the content of proline (Pro) and isoleucine (Ile) in roots significantly compared with control (p < 0.05), while changes of aspartic acid, lysine, and histidine in roots were more evident at higher KCN treatments (p < 0.05). Results indicate that the content of Pro, Ile, and tyrosine showed pronounced increase in shoots of rice seedlings exposed to KCN at 1.44mg CN/L or higher (p < 0.05). Other amino acids slightly changed in all plant materials exposed to KCN (p > 0.05). Results indicate that specific amino acids in rice seedlings showed positive response to non-toxic concentrations of exogenous KCN. These findings could provide additional insights into the inducible mechanisms underlying the involvement of amino acids in KCN metabolism.

Effects of Antiglutamate Antibodies on the Development of Stress Response and Neurotransmitter Content in the Hippocampus and Hypothalamus of Rats with Different Behavioral Activity

We studied the effects of intranasal administration of antiglutamate antibodies on the development of stress response and level of neurotransmitter amino acids and monoamines in brain structures of rats with different initial behavioral activity. The stress exposure was followed by significant changes in behavioral activity and concentration of neurotransmitters in rat hippocampus and hypothalamus. The changes in the level of neurotransmitter amino acids and monoamines were more pronounced in the hippocampus. Antiglutamate antibodies administered intranasally in a single dose of 250 μg/kg immediately after stress exposure prevented the development of the stress response and normalized the level of neurotransmitters in the brain structures of rats. The effect of antibodies was the most pronounced in behaviorally active rats.