Emission rate of amino acids and ammonia and their role in olfactory preference behaviour of juvenile Arctic charr, Salvelinus alpinus (L.)

The behaviour of juvenile Arctic charr, Salvelinus alpinus (L.) , to an abrupt concentration step of L-amino acids, L-alanine and ammonium chloride was studied by fluviarium technique. The emission rates of these substances were studied. Juvenile Arctic charr emit 8.0 × 10⁻⁴ mol total ammonia-N kg⁻¹ h⁻¹ and 3.3 × I0⁻⁵ mol amino acids kg⁻¹ h⁻¹. In behaviour tests the charr avoided 5.6x 10⁻⁶and 5.6 × 10⁻⁷ M ammonium chloride. The 17 L-amino acid mixture, ranked as observed in the analysis of emission, was avoided at 4.6 × 10⁻⁷ M, while 100 times dilution of this value gave neither avoidance nor attraction. The charr avoided L-alanine tested alone at the concentration of 4.6 × 10 ⁻⁷ M. Anosmic charr showed neither avoidance nor attraction to the mixture of 17 amino acids tested at 4.6 × 10⁻⁷ M. The results indicate that ammonia as well as emitted amino acids are not responsible for the olfactory mediated attraction to conspecific odour shown earlier in Arctic charr. On the contrary, these substances may have a negative effect by reducing the strength of attraction.     

Amino Acids as Nitrogen Sources for the Growth of Euglena gracilis and Astasia longa

SYNOPSIS. Euglena gracilis (bacillaris variety, strain SM-L1, streptomycin-bleached) used the following amino adds (10⁻³ M) as sole nitrogen source for growth on a defined medium: glycine, alanine, valine, leucine, isoleucine, serine, threonine, and glutamic acid. Aspartic acid was used at 10⁻² M. Glutamine and asparagine were used at 10⁻³ M and were better N sources than their parent dicarboxylic amino acids. Not used as sole N source for growth were phenylalanine, tyrosine, tryptophan, cysteine, cystine, methionine, proline, hydroxyproline, histidine, arginine, lysine, and taurine. Astasia longa (Jahn strain) was more restricted than Euglena and used only asparagine and glutamine as N sources for growth.     

凤眼莲根分泌物氨基酸组分对根际肠杆菌属F2细菌的趋化作用

凤眼莲(Eichhornia crassipes)的根分泌物中含有Met等多种氨基酸,其中Met、GABA、Gly、Ala、Asp、Ser、Val和Leu(10^-7～10^-2mol·L^-1)均对凤眼莲的根际肠杆菌属F₂(Enterobacter sp.F₂)细菌有强烈的正趋化作用;Glu、Thr和His(10^-7～10^-3mol·L^-1)也对该菌有一定的正趋化作用;而Lys、Cys、Arg、Tyr、Pro、Asn、Gln、Ile、Phe和Typ则对该菌表现出一定的负趋化作用.对细菌的正趋化作用存在一个趋化物的最适浓度范围.具有正趋化作用的氨基酸在凤眼莲根际的浓度都较高,而具有负趋化作用的浓度则较低,这正是凤眼莲与该根际细菌结合为根际微生态系统的原因之一.     

Behavioural responses of salmonid fry to low amino acid concentrations

The behaviour of start feed brown trout, Salmo trutla , and Atlantic salmon, Salmo salar , fry was observed in response to 5, 50 and 500 nM concentrations of L-alanine, _L-proline, L-arginine and glycine. In addition, salmon fry were tested with dilute concentrations of shrimp extract. Five behaviour patterns (snap, yawn, dart, twitch movements and active swimming) were shown in response to all amino acid and shrimp extract concentrations. Snapping, darting and active swimming increased in both species as a function of amino acid concentration, and in the salmon fry as a function of increasing shrimp extract concentration. Otherwise, the salmon showed twice as much yawning and more twitch movements than the trout, but the trout showed more active swimming than the salmon. Both species showed an increase in activity in response to L-proline at 5 nM, and the salmon also responded to L-arginine and glycine at this concentration. Both species first responded to L-alanine at 50 nM, but the trout did not respond to glycine until a concentration of 500 nM was presented. The salmon fry responded to shrimp extract at c. 10 ¹⁴g l^-1, but no differences in their activity were observed in response to concentrations between c. 10^-12 and 10^-6gl^-1.     

Suppressive effect of l-phenylalanine on manganese peroxidase in the white-rot fungus Phanerochaete chrysosporium

Abstract The effect of added l-amino acids and NH₄⁺ on manganese peroxidase activity in ligninolytic cultures of Phanerochaete chrysosporium were investigated. Among 11 amino acids (0.2 mM) tested, including phenylalanine, glutamate, glutamine, histidine, alanine, iso-leucine, ornithine, glycine, aspartate, proline, and arginine, phenylalanine was the most effective in suppression of manganese peroxidase synthesis. However, all the amino acids tested except proline completely suppressed the enzyme synthesis at 2 mM concentration.     

Histological changes in the gill, kidney and liver of Lahontan cutthroat trout, Salmo clarki henshawi, living in lakes of different salinity-alkalinity

Lahontan cutthroat trout thrive in saline-alkaline lakes, where other trout species often cannot survive. We examined Lahontan cutthroat trout from nine lakes in which salinity and alkalinity ranged from about 90 to 12 000 mg1⁻¹ and 60 to 3500mgl⁻¹ as HCO₃⁻ respectively, for sublethal histological changes in gill, kidney, and liver tissues. Gill chloride cell hyperplasia, gill lamellar epithelial separation, kidney glomerular swelling, blood congestion in kidneys, and deposition of hyalin droplets in kidney glomeruli, tubules, and hemopoietic tissues were the histological alterations statistically associated with differences in lakewater chemistry.
Deposition of hyalin in kidney tubules was the only histological change judged pathological and whose severity appeared sufficient to jeopardize normal organ function. Differences in lakewater chemistry explained nearly 90% of the variability observed in severity of tubular hyalin degeneration, and SO₄²⁻ was the ion most positively correlated with increasing tubular hyalin. Our results suggest that Lahontan cutthroat trout will develop slight to moderate hyalin degeneration in kidney tubules if stocked into lakes where salinity and SO₄²⁻ concentrations equal or exceed 5000 mgl⁻¹ and 2000mgl⁻¹, respectively.     

Glycine release from Y79 retinoblastoma cells

Abstract: Glycine release, induced by a high concentration of potassium chloride (K⁺), was investigated in cultured human Y79 retinoblastoma cells. The cells were labeled by incubation with [2-³H]glycine prior to K⁺ depolarization. Depolarization with 55 m M K⁺ caused an immediate, Ca²⁺-dependent release of approximately 20% of the cellular radiolabeled glycine content. Chemical analysis of the intracellular free glycine content also showed that approximately 20%, 2.4 nmol/mg protein, was released after K⁺ depolarization. Glycine release from labeled Y79 cells was not stimulated by incubation with 55 mM choline chloride. Based on measurements with an amino acid analyzer, it is concluded that of the free amino acids contained in the Y79 cell, only glycine is specifically released into the extracellular fluid by K⁺ depolarization. Although the intracellular content of serine and glutamate decreased, these amino acids were not released from the cells. Further studies with [U-¹⁴C]serine suggest that serine is converted into glycine in Y79 cells. Veratridine also caused an immediate release of [2-³H]glycine from the cells, and this was blocked by tetrodotoxin. This suggests that the Y79 cells possess voltage-dependent Na⁺ channels. These results indicate that K ⁺ - and veratridine-stimulated glycine release occurs in Y79 retinoblastoma cells, providing additional evidence that this continuously cultured line may be a useful model for certain human retinal and central nervous system functions.     

The effects of temperature, pH and water hardness on winter starvation of young-of-the-year smallmouth bass, Micropterus dolomieui Lacepede

Year-class strength in northern populations of smallmouth bass is strongly influenced by winter starvation of young-of-the-year. We examined starvation among young bass under both winter and summer light and temperature conditions. During starvation, body condition declines to a specific level and then the fish dies. Body condition at death is a well defined function of body size that remains relatively constant over a wide range of environmental conditions. Starvation rate varies systematically with body size, temperature, pH and water hardness. Available stored energy increases more rapidly with body size than starvation rate. Therefore, lifetime under starvation conditions tends to increase with increasing body size. The Q₁₀ for starvation rate over the temperature range 2.5-8° C is 2.2. Starvation rate increases as pH declines from 7.0-4.9: the rate at pH 4.9 is ∼ 1.25 times the rate at pH 7 Starvation rate decreases as Ca concentration increases from 1 mgl⁻¹ to 80mgl⁻¹: the rate at 80 mg Ca 1⁻¹ is ∼0.80 times the rate at 1 mgl⁻¹.     

Taste responses of the facial and glossopharyngeal nerves to amino acids in the rainbow trout

No significant differences were noted between responses of rainbow trout Oncorhynchus mykiss facial and glossopharyngeal nerves to 15 amino acids. Nine of these amino acids tested at 10⁻² M were stimulatory, whereas only two tested at 10⁻³ M were effective gustatory stimuli. For both nerve systems, ≤10⁻³ M L-proline was the most stimulatory amino acid, with an estimated threshold of 10⁻⁷ M; however, L-α-amino-β-guanidino-propionic acid (estimated threshold of 3×10⁻³ M), was the most potent compound at 10⁻² M. These results indicate that the same amino acids activate taste buds innervated by facial and glossopharyngeal nerves, respectively, and suggest that the same amino acids can be important in chemosensory feeding behaviour in the rainbow trout.     

Ecomycins, unique antimycotics from Pseudomonas viridiflava

A novel family of peptide antimycotics, termed ecomycins, is described from Pseudomonas viridiflava , a plant-associated bacterium. Ecomycins B and C have molecular masses of 1153 and 1181. They contain equimolar amounts of a β hydroxyaspartic acid, homoserine, threonine, serine, alanine, glycine and one unknown amino acid. Fatty acids were detectable after hydrolysis, methylation and gas chromatography and mass spectroscopy. The ecomycins have significant bioactivities against a wide range of human and plant pathogenic fungi. The minimum inhibitory concentration values for ecomycin B were 4·0 μg ml⁻¹ against Cryptococcus neoformans and 31 μg ml⁻¹ against Candida albicans. Pseudomonas viridiflava also produces what appears to be syringotoxin, an antifungal lipopeptide previously described from Ps. syringae.     

Amino Acid Enhancement of Recovery in Dry-heat Damaged Spores of Bacillus subtilis

Spores of Bacillus subtilis MD2 and var. niger were dry-heat damaged at 150°, 160° and 170°C and recovered on media of increasing complexity. The greater the heat dose the more marked was the effect of amino acid supplements on recovery. For strain MD2 maximum germination and outgrowth of unheated spores could be obtained on a minimal salts + glucose medium with alanine, aspartic acid, glycine and methionine; the latter three amino acids served to enhance growth, not germination. The recovery of heat-damaged spores was significantly increased by adding valine plus isoleucine or arginine or glutamine. The increase was probably due to the use of valine and isoleucine as substrates of NAD-linked dehydrogenases to generate reducing power and serve as NH₃-donor, initiating germination in spores which were unable to germinate as a result of inactivation of alanine dehydrogenase. Valine or isoleucine added singly suppressed recovery by feedback inhibition of the pathways to both these amino acids during outgrowth.     

Unique glycine-activated riboswitch linked to glycine–serine auxotrophy in SAR11

The genome sequence of the marine bacterium ' Candidatus Pelagibacter ubique' and subsequent analyses have shown that while it has a genome as small as many obligate parasites, it nonetheless possesses a metabolic repertoire that allows it to grow as one of the most successful free-living cells in the ocean. An early report based on metabolic reconstruction indicated that SAR11 cells are prototrophs for all amino acids. However, here we report experimental evidence that ' Cand. P. ubique' is effectively auxotrophic for glycine and serine. With glucose and acetate added to seawater to supply organic carbon, the addition of 125 nM to 1.5 μM glycine to growth medium containing all other nutrients in excess resulted in a linear increase in maximum cell density from 1.14 × 10⁶ cells ml⁻¹ to 8.16 × 10⁶ cells ml⁻¹ ( R ² =  0.992). Serine was capable of substituting for glycine at 1.5 μM. ' Cand. P. ubique' contains a glycine-activated riboswitch preceding malate synthase, an unusual genomic context that is conserved in the SAR11 group. Malate synthase plays a critical role in central metabolism by enabling TCA intermediates to be regenerated through the glyoxylate cycle. In vitro analysis of this riboswitch indicated that it responds solely to glycine but not close structural analogues, such as glycine betaine, malate, glyoxylate, glycolate, alanine, serine or threonine. We conclude that ' Cand. P. ubique' is therefore a glycine–serine auxotroph that appears to use intracellular glycine level to regulate its use of carbon for biosynthesis and energy. Comparative genomics and metagenomics indicate that these conclusions may hold throughout much of the SAR11 clade.     

Relationship between osmoprotection and the structure and intracellular accumulation of betaines by Escherichia coli

Abstract Naturally occuring betaines, especially glycine betaine and proline betaine, were accumulated by Escherichia coli from urine. In synthetic hyperosmotic medium, with an homologous series of added betaines, (CH₃)₃N⁺-(CH₂) _n -COO⁻, osmoprotective activity and intracellular accumulation decreased monotonically as n increased from 1 to 5. In contrast, α -substituted glycine betaines were accumulated in a similar manner to glycine betaine, but with different osmoprotective activities. Arsenobetaine, with a quaternary arsonium group, was also accumulated but amino acids which can become negatively charged in a chemically basic environment were not.     

SO2 and assimilatory sulfate reduction in beech leaves

The effect of SO₂ on the extractable activity of ATP sulfurylase (EC 2.7.7.4.). adenosine 5'-phosphosulfate sulfotransferase, ribulosebisphosphate carboxylase, chlorophyll, protein, sulfate, and amino acids was examined in leaves of potted grafts of beech ( Fagus sylvatica L.) treated in outdoor fumigation chambers. Addition of 0.025 and 0.075 μl SO₂ 1⁻¹ to unfiltered ambient air caused a decrease in the extractable activity of adenosine 5'-phosphosulfate sulfotransferase to about 20 to 30% of the controls. Neither the extractable activity of ATP sulfurylase and ribulosebisphosphate carboxylase nor the content in chlorophyll, total amino acids and protein were significantly affected by SO₂, but there was an increase in the sulfate content. Leaves treated with 0.075 μl SO₂ 1⁻¹ contained more alanine and cysteine and less serine than the controls. After transfer of the SO2-treated beech trees to control chambers there was an increase in adenosine 5'-phosphosulfate sulfotransferase activity, but no significant decrease in SO₂₋⁴-sulfur.     

A GC-MS method for determination of amino acid uptake by plants

In this study, we present a rapid, robust and sensitive method for quantification of plant amino acid uptake using universally (U) (¹³C, ¹⁵N)-labelled amino acids and gas chromatography-mass spectrometry (GC-MS). Amino acids were analysed as their tert -butyldimethylsilyl (tBDMS) derivatives and displayed detection limits in the range 10–100 fmol on column, depending on the amino acid. The technique allows for simultaneous detection and quantification of both unlabelled and isotopically labelled species of amino acids. This makes simple quantification of plant amino acid uptake from an isotopically labelled source possible. The analytical variation was low, concerning total amino acid concentrations (relative standard deviation, rsd , less than 5.3%) as well as enrichment of U-¹³C, ¹⁵N-labelled glycine (Gly), arginine (Arg) and glutamic acid (Glu) ( rsd <2.1%). An application of the GC-MS method was conducted on non-mycorrhizal Pinus sylvestris roots supplied with U-¹³C, ¹⁵N-labelled amino acids. Intact, labelled amino acids were traced in root extracts. This provided conclusive evidence of plant root uptake of intact amino acids. Uptake rates of the three amino acids Gly, Glu and Arg in the range 0.5–37.9 μmol g⁻¹ dry weight h⁻¹ were recorded. These rates are comparable with those recorded in earlier studies of amino acid uptake, using other methods, as well as uptake rates measured for nitrate and ammonium.     

Adsorption and release of amino acids from epilithic biofilms in streams

SUMMARY. I. Stream sediment with a natural biofilm generally adsorbed more glycine, aspartic acid, and lysine than sterile sediment. Lysine was adsorbed to a greater extent than the other two amino acids.
2. In the presence of Ca²⁺, adsorption of aspartic acid increased and adsorption of lysine decreased. Glycine was not affected.
3. Stream sediment preferentially removed amino acids with a positive charge or a polar R group from maple leaf leachate.
4. It is estimated that stream invertebrates may have access to a maximum of 7.3% of the amino acids present in epilithic biofilms. More amino acids were available from biofilms exposed to leaf leachate.     

Concentrations and annual loading of dissolved organic matter in a small moorland stream

SUMMARY. 1. Dissolved organic matter (DOM) was measured at 8h intervals over a 1 year period in a stream draining 51 ha of moorland with peaty soils.
2. DOM concentrations increased with increasing stream discharge from low flow values of 0–3 mg 1⁻¹ to maximum values of 30 mg 1⁻¹. There were also seasonal differences of up to 13mgl⁻¹ between August (maximum) and February, and differences of about 2.5 mg l⁻¹ between rising and falling stage samples.
3. Seasonal variation was closely related to mean temperature.
4. Total loss over the year was 168 kg ha⁻¹ DOM (84 kg ha⁻¹ C), larger than previous estimates for upland sites.     

Oxidative Stress, Hypoxia, and Ischemia-Like Conditions Increase the Release of Endogenous Amino Acids by Distinct Mechanisms in Cultured Retinal Cells

Abstract: The aim of this study was to elucidate the mechanisms by which retinal cells release endogenous amino acids in response to ascorbate/Fe²⁺-induced oxidative stress, as compared with chemical hypoxia or ischemia. In the absence of stimulation, oxidative stress increased the release of aspartate, glutamate, taurine, and GABA only when Ca²⁺ was present. Under hypoxia or ischemia, the release of aspartate, glutamate, glycine, alanine, taurine, and GABA increased mainly by a Ca²⁺-independent mechanism. The increased release observed in N -methyl- d -glucamine⁺ medium suggested the reversal of the Na⁺-dependent amino acid transporters. Upon oxidative stress, the release of aspartate, glutamate, and GABA, occurring through the reversal of the Na⁺-dependent transporters, was reduced by about 30%, although the release of taurine was enhanced. An increased release of [³H]arachidonic acid and free radicals seems to affect the Na⁺-dependent transporters for glutamate and GABA in oxidized cells. All cell treatments increased [Ca²⁺]_i (1.5 to twofold), although no differences were observed in membrane depolarization. The energy charge of cells submitted to hypoxia or oxidative stress was not changed. However, ischemia highly potentiated the reduction of the energy charge, as compared with hypoglycemia or hypoxia alone. The present work is important for understanding the mechanisms of amino acid release that occur in vivo upon oxidative stress, hypoxia, or ischemia, frequently associated with the impairment of energy metabolism.     

Cadmium toxicity to the freshwater amphipod Gammarus pulex (L.) during the moult cycle

SUMMARY. 1. The toxicity of cadmium to mature Gammarus pulex at different stages in the moult cycle is described.
2. Immediate post-moult animals are significantly more sensitive than intermoult specimens at cadmium concentrations between 1.0 and 0.1 mg 1⁻¹ but not at 0.03 or 0.01 mg Cd 1⁻¹.
3. At a calcium concentration of 40mgl⁻¹, post-moult animals undergo recalcification within 7 days and thereafter there is little variation in their response to cadmium.
4. External calcium concentrations of 40 and 115mg 1⁻¹ do not affect cadmium toxicity but at 180 mg Ca1⁻¹ the sensitivity of immediate post-moult specimens is significantly reduced.
5. The results are discussed with regard to the protection of G. pulex by present water quality standards.