Ninhydrin-positive Substances Research Articles

Osmoregulatory power influences tissue ionic composition after salinity acclimation in aquatic decapods

Decapod crustaceans show variable degrees of euryhalinity and osmoregulatory capacity, by responding to salinity changes through anisosmotic extracellular regulation and/or cell volume regulation. Cell volume regulatory mechanisms involve exchange of inorganic ions between extra- and intra-cellular (tissue) compartments. Here, this interplay of inorganic ions between both compartments has been evaluated in four decapod species with distinct habitats and osmoregulatory strategies. The marine/estuarine species Litopenaeus vannamei (Lv) and Callinectes danae (Cd) were submitted to reduced salinity (15‰), after acclimation to 25 and 30‰, respectively. The freshwater Macrobrachium acanthurus (Ma) and Aegla schmitti (As) were submitted to increased salinity (25‰). The four species were salinity-challenged for both 5 and 10 days. Hemolymph osmolality, sodium, chloride, potassium, and magnesium were assayed. The same inorganic ions were quantified in muscle samples. Muscle hydration (MH) and ninhydrin-positive substances (NPS) were also determined. Lv showed slight hemolymph dilution, increased MH and no osmotically-relevant decreases in muscle osmolytes; Cd displayed hemolymph dilution, decreased muscular NaCl and stable MH; Ma showed hypo-regulation and steady MH, with no change in muscle ions; As conformed hemolymph sodium but hypo-regulated chloride, had stable MH and increased muscle NPS and ion levels. Hemolymph and muscle ions (especially chloride) of As were highly correlated (Pearson, +0.83). Significant exchanges between hemolymph and muscle ionic pools were more evident in the two species with comparatively less AER regulatory power, C. danae and A. schmitti. Our findings endorse that the interplay between extracellular and tissue ionic pools is especially detectable in euryhaline species with relatively lower osmoregulatory strength.

Methods for assessment of body tissue composition as an indication of the energetic status in bivalve populations: A comparison of biochemical and elemental analysis

Elemental (CHN) and proximate biochemical compositions of body tissues are useful tools among the ecological indices most commonly used in evaluation of the energetic status of animal populations. Gnaiger and Bitterlich (1984) supplied procedures for the interconversion between both these measurements based on stoichiometric relationships, that were further tested using gut contents and body tissue samples of freshwater fishes. Despite a lack of validation studies, the reported conversion factors have been broadly applied in the field of body composition analysis of marine invertebrates, especially bivalve mollusks. The aim of this study was to test the applicability of those conversion equivalents in analysis of the body tissues of two congeneric clam species (Ruditapes decussatus and Ruditapes philippinarum). To this end, proximate biochemical composition, as analyzed by fractionated extraction of tissues samples and quantification using spectrophotometric methods, was converted to elemental composition, and the resulting figures were compared with those of direct CHN analysis. The results of this comparison indicate good agreement within the ranges reported, provided that ninhydrin positive substances (NPS) are incorporated in the biochemical composition analyses. The magnitude of the nonprotein N component in bivalve tissues appears to complicate the reverse computation of biochemical components from elemental composition because no accurate estimation of proteins from N contents might be possible. Additionally, a specific correction of residual water in dried samples of bivalve tissues for CHN analysis should be applied. The absence of broad differences found between species reflects the morphological, evolutionary and functional proximity between them, whereas tissue differences display the differential role that each organ plays in the organism, although other sources of variability such as diet and sex should be addressed in future research.

DEVELOPMENT OF ANALYTICAL METHOD FOR THE DETERMINATION OF NINHYDRIN-POSITIVE SUBSTANCES IN AMINO ACIDS BY HIGH-PERFORMANCE LIQUID CHROMATOGRAPHY

Aim and Objectives: The aim of the work is focused on the optimization of the high-performance liquid chromatography (HPLC) method for the determination of ninhydrin-positive substances in amino acids using HPLC technique in a single method. Since, most of the amino acids are widely used in the determination of Renal and Nutrition drug products exist independently in the monograph for each amino acid either by TLC or HPLC.Methods: The chromatographic separation was performed using sodium amino acid analysis cation exchange column using Sodium Eluent Na 315, Sodium eluent Na 425, and Sodium Eluent Na 640 as Mobile phase, performed by gradient program with detection of wavelength 570 nm using flow rate as 0.4 mL/min. The method has been evaluated using post-column derivatization technique (HPLC/Pinnacle PCX).Results: All the amino acids were eluted correspondingly at the individual retention time and the method shall be validated as per the ICH Q2R1 Guideline.Conclusion: The method has been successfully evaluated and developed for the analytical applications.

Paralarvae of Octopus vulgaris Type II are stenohaline conformers: relationship to field distribution and dispersal

The degree of euryhalinity of cephalopod planktonic paralarvae potentially affects the dispersal capacity and distributional range of species. Herein, we tested the hypothesis that O. vulgaris Type II paralarvae would show some tolerance to seawater dilution, evaluated from integrated field and laboratory experiments. Paralarvae were collected from zooplankton samples (salinities of 30.3–32.6), in the Parana Bay Estuarine Complex (PBEC), Southern Brazil. In the laboratory, they were exposed to salinities of 28, 30, 33, 35 (control), and 37, from 15 min to 24 h. Survival ranged from 60 to 83%, 73–100%, and 100% at salinity of 28, 30, and 33–37, respectively. Body fluid osmolality (BFO), body water content (BWC), and ninhydrin-positive substances (NPS, amino acids) were quantified at salinities of 33, 35, and 37 (with 100% survival). BFO was always isosmotic to the external medium. BWC and the high NPS concentration remained unchanged in all salinities. Thus, these paralarvae tolerate some deviation from seawater salinity, displaying osmoconforming behavior, maintain body hydration, and show high ability of tissue volume/water regulation in short periods of time. Presumably, this physiological capacity of paralarvae might be one factor allowing their dispersal and survival along environments with moderate deviations from seawater salinity.

Hypoosmotic stress in the mussel Perna perna (Linnaeus, 1758): Is ecological history a determinant for organismal responses?

Ecological history of organisms may be related to different responses and adaptations to stressors. This study aims to evaluate whether marine brown mussels (Perna perna Linnaeus, 1758) collected from sites with distinct histories of fluctuations in abiotic parameters, including salinity, respond differently to hypoosmotic stress. Mussels were collected at different sites (a marine site, with no history of salinity variation, and an estuarine site, with usual salinity variations) and exposed in laboratory for 14 days to hypoosmotic stress (salinities 25 and 20). It was observed that mussels collected at the marine site showed increased oxygen consumption (VO2), reduced haemolymph osmolality and concentrations of Na+, Cl−, and K+; increased levels of ninhydrin-positive substances in the haemolymph, and no changes in gill Na+/K+-ATPase activity, as expected for osmoconforming organisms. For animals collected at the estuarine site, except for VO2, this same pattern was only observed on day 1 of hypoosmotic stress. Unexpectedly, on days 4 and 14, VO2 decreased, the osmolality and ionic concentration returned to near baseline values, and mussels gill Na+/K+-ATPase activity increased at day 4. This long-term response detected for estuarine mussels is similar to that observed for osmoregulating organisms, which is very unexpected for marine bivalves. Despite being novel in the relevant literature, these results suggest that in some situations mussels could adopt osmoregulating behavior, such as increasing Na+/K+-ATPase activity and thereby probably reducing water circulating inside valves. In conclusion, these results indicate that ecological history, shown here by differences in organismal origin, influence physiological parameters of mussels in response to a stressful situation.

Pool of phosphoethanolamine and phosphoserine in the brain of the snail Lymnaea stagnalis L. in summer and before winter dormancy

Small amounts of phospholipid metabolites, phosphoethanolamine and phosphoserine, were discovered at a ratio of 1:9 in the brain of a freshwater mollusk, the pond snail Lymnaea stagnalis L., collected both in summer and autumn. The phosphoethanolamine pool increased by 15% in autumn relative to the summer level (up to 625 ± 44 nmol per g of wet tissue), although this value still constituted 6% of the total pool of free amino acids and ninhydrin-positive substances. These findings are in striking contrast with our previous results that showed adaptive modifications of the amino acid and phosphoethanolamine pools in the brain of eurythermal freshwater fish at low temperatures. At the same time, these data demonstrate the presence of phosphoethanolamine and phosphoserine in the central nervous system at comparatively early stages of its evolution.

Phytochemical Changes Initiated by Insects

Abstract The occurrence of leaf galls and the relation between the host plant and the causative insect are discussed. The leaves, galls, and leaves freed from galls of Salix fragilis have been examined by one-way and two-way paper chromatography and a separation of the major constituents achieved on powdered cellulose columns. The galls and leaves freed from galls were compared by band chromatography and the results suggest that one phytochemical change initiated by the sawfly is an accumulation of catechins, leucoanthocyanins and a ninhydrin positive substance.

Compositions of Extractive Nitrogenous Constituents and Their Monthly Variation for Fresh Capsosiphon fulvescens

To elucidate the composition of extractive nitrogenous components in the fresh Capsosiphons fulvescens cultured off the southern coast of Korea, and to determine the monthly variation of these nitrogenous components, extract samples collected monthly from December to March at Jangheung-gun, Jeonnam Province were analyzed for total nitrogen, free and combined amino acids, ATP and related compounds, betaines, trimethylamine oxide (TMAO) and trimethylamine (TMA). The content of extractive nitrogen was 1,090～1,233 ㎎/100 g on dry basis. The number of 21～25 ninhydrin-positive substances was detected in the analysis of free amino acids, and their total amount was 3,710～4,788 ㎎/100 g on dry basis. Among them, free proline, asparagine, glutamic acid, alanine, taurine and glutamine were found to be abundant. The combined amino acids amounted to 1,573～2,121 ㎎/100 g in total and the total amount of ATP and related compound was 33.8～84.0 ㎎/100 g (1.06～2.46 μ㏖/g) on dry basis. Betaine, glycinebetaine, β-alaninebetaine, γ-butyrobetaine, homarine and trigonelline were detected in most of samples. Levels of free and combined amino acids, ATP and related compounds fluctuated from sample to sample, with their contents higher in December and January and lower in March.

Differences in osmotolerance in freshwater and brackish water populations of Theodoxus fluviatilis (Gastropoda: Neritidae) are associated with differential protein expression

The euryhaline gastropod Theodoxus fluviatilis is found in northern Germany in freshwater or in brackish water habitats in the Baltic Sea. Previous studies have revealed that individuals from both habitats are not distinguishable by morphological characters or by sequence comparison of DNA encoding 16S RNA or cytochrome C. As reported in this study, animals collected in the two habitats differ substantially in their physiological ability to adapt to different salinities. Comparison of accumulation rates of ninhydrin-positive substances (NPS) in foot muscle upon transfer of animals to higher medium salinities revealed that brackish water animals were perfectly able to mobilize NPS, while freshwater animals had only limited ability to do so. In an attempt to explore whether this difference in physiology may be caused by genetic differentiation, we compared protein expression patterns of soluble foot muscle proteins using 2D gel electrophoresis and silver staining. Of the 40 consistently detected protein spots, 27 showed similar levels in protein expression in animals collected from freshwater or brackish water habitats, respectively. In 12 spots, however, protein concentration was higher in brackish water than in freshwater animals. In four of these spots, expression levels followed increases or decreases in medium salinities. In a different set of 4 of these 12 spots, protein levels were always higher in brackish water as compared to freshwater animals, regardless of their physiological situation (14 days in artificial pond water or in medium with a salinity of 16 per thousand). The remaining 4 of the 12 spots had complex expression patterns. Protein levels of the remaining single spot were generally higher in freshwater animals than in brackish water animals. These expression patterns may indicate that freshwater and brackish water animals of T. fluviatilis belong to different locally adapted populations with subtle genetic differentiation.

Deregulation of apoptotic volume decrease and ionic movements in multidrug-resistant tumor cells: role of chloride channels

Changes in cell volume and ion gradients across the plasma membrane play a pivotal role in the initiation of apoptosis. Here we explore the kinetics of apoptotic volume decrease (AVD) and ion content dynamics in wild-type (WT) and multidrug-resistant (MDR) Ehrlich ascites tumor cells (EATC). In WT EATC, induction of apoptosis with cisplatin (5 muM) leads to three distinctive AVD stages: an early AVD(1) (4-12 h), associated with a 30% cell water loss; a transition stage AVD(T) ( approximately 12 to 32 h), where cell volume is partly recovered; and a secondary AVD(2) (past 32 h), where cell volume was further reduced. AVD(1) and AVD(2) were coupled to net loss of Cl(-), K(+), Na(+), and amino acids (ninhydrin-positive substances), whereas during AVD(T), Na(+) and Cl(-) were accumulated. MDR EATC was resistant to cisplatin, showing increased viability and less caspase 3 activation. Compared with WT EATC, MDR EATC underwent a less pronounced AVD(1,) an augmented AVD(T), and a delay in induction of AVD(2). Changes in AVD were associated with inhibition of Cl(-) loss during AVD(1), augmented NaCl uptake during AVD(T), and a delay of Cl(-) loss during AVD(2). Application of the anion channel inhibitor NS3728 inhibited AVD and completely abolished the differences in AVD, ionic movements, and caspase 3 activation between WT and MDR EATC. Finally, the maximal capacity of volume-regulated anion channel was found to be strongly repressed in MDR EATC. Together, these data suggest that impairment of AVD, primarily via modulation of NaCl movements, contribute to protection against apoptosis in MDR EATC.

Volume regulation mechanisms in Rana castebeiana cardiac tissue under hyperosmotic stress

Volume changes of cardiac tissue under hyperosmotic stress in Rana catesbeiana were characterized by the identification of the osmolytes involved and the possible regulatory processes activated by both abrupt and gradual changes in media osmolality (from 220 to 280 mosmol/kg H 2O). Slices of R. catesbeiana cardiac tissue were subjected to hyperosmotic shock, and total tissue Na +, K +, Cl − and ninhydrin-positive substances were measured. Volume changes were also induced in the presence of transport inhibitors to identify osmolyte pathways. The results show a maximum volume loss to 90.86±0.73% of the original volume (measured as 9% decrease in wet weight) during abrupt hyperosmotic shock. However, during a gradual osmotic challenge the volume was never significantly different from that of the control. During both types of hyperosmotic shock, we observed an increase in Na + but no significant change in Cl − contents. Additionally, we found no change in ninhydrin-positive substances during any osmotic challenge. Pharmacological analyses suggest the involvement of the Na +/H + exchanger, and perhaps the HCO 3 −/Cl − exchanger. There is indirect evidence for decrease in Na +/K +-ATPase activity. The Na + fluxes seem to result from Mg 2+ signaling, as saline rich in Mg 2+ enhances the regulatory volume increase, followed by a higher intracellular Na + content. The volume maintenance mechanisms activated during the gradual osmotic change are similar to that activated by abrupt osmotic shock.

Osmotic stress and muscle tissue volume response of a freshwater bivalve

The freshwater bivalve, Corbicula fluminea, when submitted to hyperosmotic solutions, behaves as a hyperosmoconformer; we have observed an increase in osmolality and ions in its extracellular fluid. Osmotic and ionic changes in its watery environment represent a challenge for the tissues of this mollusk. Thus we evaluated, in vitro, muscle tissue volume variations (based on wet weight change) under anisosmotic salines, as well the possible regulatory mechanisms involved in the processes. This tissue did not exhibit complete volume regulation under anisosmotic saline solutions, but showed less variation than would be predicted by Van't Hoff's law, and tissue volume remained essentially stable throughout 90 min of exposure. To minimize tissue swelling in hyposmotic situations, C. fluminea muscle mobilizes organic osmolytes (ninhydrin positive substances) and inorganic ions (K+ and Cl−). While under hyperosmotic stimulus, apparently only inorganic osmolytes (Na+ and Cl−) are mobilized by the tissue. Our results indicate ionic accumulation by the Na+–K+–2Cl− cotransporter and the Na+/H+ coupled to Cl−/HCO3− exchangers. Exposure of the muscle tissue to Ca2+-free anisosmotic saline did not result in a detectable inhibition of the mechanisms described above. The Ca2+ gradient that derives from the absence of this ion, even apparently enhances the regulatory mechanisms. These responses of this freshwater mollusk in hyperosmotic solutions, and the muscle tissue under anisosmotic (hypo and hyperosmotic) saline solutions, have not been previously characterized in the manner and approach as reported here. Specifically, we analyze both organic and inorganic osmolytes mobilized under hyposmotic stress, and can infer the participation of Na+ and Cl− pathways stimulated by hyperosmotic stress. From the perspective gained in this study, tissue volume responses may be used as models for toxicological investigations.

Energetics and metabolism of yellowtail kingfish ( Seriola lalandi Valenciennes 1833) during embryogenesis

A study was undertaken to measure changes in oxygen consumption and metabolite concentration (ammonia, free amino acids, glucose, glycogen, ninhydrin positive substances and protein) in embryos of yellowtail kingfish ( Seriola lalandi) incubated at different temperatures (17, 19, 21 and 23 °C). The oxygen uptake at hatch and total oxygen consumed during embryogenesis was negatively correlated with temperature, and resulted in Q 10 values less than 1. This was attributed to the fact that embryos and first hatch larvae have been reported to be smaller at warmer incubation temperatures and therefore consumed less oxygen. Free amino acids were present in high concentrations immediately after spawning (188 ± 15.3 nmol ind − 1 ) and were dominated by the neutral amino acids alanine, glycine, isoleucine, leucine, serine, and valine. The free amino acid pool was rapidly depleted until hatch (20–40 nmol ind − 1 ), after which the pool was dominated by glycine, serine, valine and arginine/taurine (unresolved). The loss of positive buoyancy around the time of hatch was likely to be correlated with the decrease in free amino acid content during embryogenesis. The sequence of metabolic fuel use during embryogenesis is likely to be similar to that observed in other marine fish species with pelagic eggs, namely that carbohydrates, lipid and protein are of relatively minor importance compared to the catabolism of free amino acids for energy. Eggs incubated at 17, 19 and 21 °C had similar profiles of metabolite concentration during embryogenesis, however, eggs incubated at 23 °C were found to have a considerably different pattern of substrate utilisation, possibly indicative of abnormal physiological development at a temperature above that which is routinely encountered in the wild.

Branchial carbonic anhydrase activity and ninhydrin positive substances in the Pacific white shrimp, Litopenaeus vannamei, acclimated to low and high salinities

The Pacific white shrimp, Litopenaeus vannamei, acclimated to 30 ppt salinity, was transferred to either low (15 and 5 ppt), or high (45 ppt) salinity for 7 days. Hemolymph osmolality, branchial carbonic anhydrase activity, and total ninhydrin-positive substances (TNPS) in abdominal muscle were then measured for each condition. Hemolymph osmotic concentration was regulated slightly below ambient water osmolality in shrimp acclimated to 30 ppt. At 15 and 5 ppt, shrimp were strong hyper-osmotic regulators, maintaining hemolymph osmolality between 200 and 400 mOsm above ambient. Shrimp acclimated to 30 ppt and transferred to 45 ppt salinity were strong hypo-osmotic and hypo-ionic regulators, maintaining hemolymph osmolality over 400 mOsm below ambient. Branchial carbonic anhydrase (CA) activity was low (approximately 100 micromol CO(2) mg protein(-1) min(-1)) and uniform across all 8 gills in shrimp acclimated to 30 ppt, but CA activity increased in all gills after exposure to both low and high salinities. Anterior gills had the largest increases in CA activity, and levels of increase were approximately the same for low and high salinity exposure. Branchial CA induction appears to be functionally important in both hyper- and hypo-osmotic regulations of hemolymph osmotic concentrations. Abdominal muscle TNPS made up between 19 and 38% of the total intracellular osmotic concentration in shrimp acclimated to 5, 15, and 30 ppt. TNPS levels did not change across this salinity range, over which hemolymph osmotic concentrations were tightly regulated. At 45 ppt, hemolymph osmolality increased, and muscle TNPS also increased, presumably to counteract intracellular water loss and restore cell volume. L. vannamei appears to employ mechanisms of both extracellular osmoregulation and intracellular volume regulation as the basis of its euryhalinity.

Osmoregulation and tissue water regulation in the freshwater red crab Dilocarcinus pagei (Crustacea, Decapoda), and the effect of waterborne inorganic lead

Inorganic lead has been measured in high concentrations in certain streams in Brazil. This study has evaluated the osmoregulatory effects of lead on the native freshwater red crab Dilocarcinus pagei. In order to probe its osmoregulatory and tissue volume regulatory capabilities and how it would be affected by lead, the crab has been submitted to individual and combined salt and chemical stresses (Pb 2+). Male crabs were exposed for 10 days to either: (1) control (freshwater, FW), (2) brackish water of salinity 15 (BW), (3) inorganic lead in freshwater (FWPb), and (4) inorganic lead in brackish water (BWPb), 2.7 mgPb/L. In vivo, whole crabs lost weight transiently when exposed to Pb 2+, both in FW and in BW. Haemolymph osmolality and ion concentrations increased and remained elevated upon exposure of crabs to BW, with or without Pb 2+, showing a trend to hyper-conformation. In vitro, muscle weight decreased in isosmotic conditions upon exposure to Pb 2+. Na +, Cl −, and ninhydrin positive substances (NPS) were increased in muscle exposed to hyperosmotic saline, well above what would be expected from simple efflux of water, suggesting a partial regulatory volume increase (RVI) capacity. This partial RVI involves the Na +, K +, 2Cl −-cotransporter and the Na +/H + exchanger on Na + and Cl − uptake, as judged from further decreases in muscle weight in the presence of the respective inhibitors. A breakdown of proteins into NPS seems to follow the uptake of inorganic ions. Pb 2+ has affected water and ion movements in D. pagei both in the whole animal and in the isolated tissue. This study has highlighted the relevance of evaluating tissue volume regulation in aquatic animals confronted with metal polluted waters.

Amino acid signaling through the mammalian target of rapamycin (mTOR) pathway: Role of glutamine and of cell shrinkage

Mammalian target of rapamycin (mTOR) mediates a signaling pathway that couples amino acid availability to S6 kinase (S6K) activation, translational initiation and cell growth rate, participating to a versatile checkpoint that inspects the energy status of the cell. The pathway is activated by branched-chain amino acids (BCAA), leucine being the most effective, whereas amino acid dearth and ATP shortage lead to its deactivation. Glutamine- or amino acid-deprivation and hyperosmotic stress induce a fast cell shrinkage (with marked decrease of the intracellular water volume) associated to mTOR-dependent S6K1 dephosphorylation. Using cultured Jurkat cells, we have measured the changes of cell content and intracellular concentration of ATP, of relevant amino acids (BCAA) and of ninhydrin-positive substances (NPS, as measure of NH(2)-bearing organic osmolytes) under conditions that deactivate (leucine-deprivation, glutamine-deprivation, amino acid withdrawal, sorbitol-induced hyperosmotic stress) or reactivate a previously deactivated, mTOR-S6K1 pathway. We have also assessed the mitochondrial function by measurements of mitochondrial transmembrane potential in cells subjected to hypertonic stress. Our results indicate that diverse control signals converge on the mTOR-S6K1 signaling pathway. In the presence of adequate energy resources, the pathway senses the amino acid availability as inward transport of effective amino acids (as BCAA and especially leucine), but its activation occurs only in the presence of an extracellular amino acid complement, with glutamine as obligatory component, and does not tolerate decrements of cell water volume incapable of maintaining adequate intracellular physicochemical conditions.

Changes in some nitrogenous compounds in the blood and tissues of freshwater pikeperch (Sander lucioperca) during salinity acclimation

The effect of ambient salinity changes (0.9, 6 and 12 psu) on the levels of dissolved ammonia (DA), ninhydrin positive substances (NPS), trimethylamine (TMA) and trimethylamine oxide (TMAO) in the blood and tissue of medium-acclimated Sander lucioperca L. (also Stizostedion lucioperca ) were investigated. In freshwater, blood and tissue total free amino acid levels (measured as NPS) were 3.62 mM and 60.61 mM, respectively. The NPS content increased significantly ( P <0.05) in the tissue and blood on acclimation to 6 and 12 psu salinities. The mass-specific tissue TMAO concentration of pikeperch acclimated to normal freshwater was 0.413±0.084 μmol TMAO g −1 . Results reveal that TMAO levels are positively influenced by the external salinity medium where significant differences in mean levels occurred between the groups ( P <0.05). The calculated p[NH 3 ] and [NH 4 + ] gradients reveal that the [NH 3 ] gradient was consistently low (cf. the [NH 4 + ] gradient). The gradient of p[NH 3 ] decreased with the medium increased salinities. The results suggest that freshwater pikeperch may be able to resist salinity changes by manipulation of nitrogen metabolism. Free amino acids and TMAO are involved in mediating response to salinity exposure in freshwater pikeperch.

Changes in some nitrogenous compounds in the blood and tissues of freshwater pikeperch ( Sander lucioperca) during salinity acclimation

The effect of ambient salinity changes (0.9, 6 and 12 psu) on the levels of dissolved ammonia (DA), ninhydrin positive substances (NPS), trimethylamine (TMA) and trimethylamine oxide (TMAO) in the blood and tissue of medium-acclimated Sander lucioperca L. (also Stizostedion lucioperca) were investigated. In freshwater, blood and tissue total free amino acid levels (measured as NPS) were 3.62 mM and 60.61 mM, respectively. The NPS content increased significantly ( P<0.05) in the tissue and blood on acclimation to 6 and 12 psu salinities. The mass-specific tissue TMAO concentration of pikeperch acclimated to normal freshwater was 0.413±0.084 μmol TMAO g −1. Results reveal that TMAO levels are positively influenced by the external salinity medium where significant differences in mean levels occurred between the groups ( P<0.05). The calculated p[NH 3] and [NH 4 +] gradients reveal that the [NH 3] gradient was consistently low (cf. the [NH 4 +] gradient). The gradient of p[NH 3] decreased with the medium increased salinities. The results suggest that freshwater pikeperch may be able to resist salinity changes by manipulation of nitrogen metabolism. Free amino acids and TMAO are involved in mediating response to salinity exposure in freshwater pikeperch.

Combined effect of sepia soaking and temperature on the shelf life of peeled shrimp Penaeus kerathurus

The effects of sepia ink ( Sepia officinalis) extract solutions with concentrations of 0.0%, 0.01%, 0.2% and 2% on the microbial flora and the chemical composition of stored peeled shrimp ( Penaeus kerathurus) were examined at two temperatures (−2 and 0 ° C). The quantification of aerobic and psychotrophic bacteria was performed by a plate count after each 3 days of storage. Results showed that partial freezing and coating treatments had synergistic effects in reducing the aerobic plate counts (APCs) with at least a 10-day extension of shelf life. The inhibition efficacy on the psychotrophic cells in shrimp meat increased with the increase in concentration of the added extract. However, the extract showed no effect after 16 days on the mesophilic bacteria. No detrimental effects of sepia coating on organoleptic parameters such as appearance, odour, and taste were observed. Partial freezing reduced significantly the formation of nitrogenous compounds in all samples, however total volatile bases (TVB) and trimethylamine (TMA) levels were lower in the sepia extract-treated samples. Initially, shrimp tissue ninhydrin positive substances (NPS) level was 9.74 ± 1.05 mM/100 g tissue. No significant change was observed in the treated-samples during the refrigerated storage, conversely, these concentrations increased in the raw shrimps.

Biochemical composition of Mnemiopsis leidyi in the southern Caspian Sea

The biochemical composition of the invasive ctenophore, Mnemiopsis leidyi from the southern Caspian Sea was analysed in terms of total fractions of protein, lipid, ninhydrin-positive substances (NPS), polysaccharides (PS) and low molecular- weight carbohydrates (LMC). The sum of organic substances per gram dry weight was 84.2 mg g−1. Protein was the major organic fraction followed by lipid and NPS. The NPS/ protein and LNC/PS ratio were 0.45 and 0.50 respectively. Starvation of M. leidyi for a 5-day period resulted in a 32.7% reduction of total organic content. These data will be important in evaluating the feeding condition of M. leidyi specimens from the field.