Present and future needs for algae and algal products

A review of the present needs, mainly for production of phycocolloids and food condiments, is given. Supply and demand vary from balanced, in some, to disproportionate in other fields. World-wide shortage of agarophytes contrasts with huge, unexploited beds of brown seaweeds.In future, partly conflicting trends will decide the needs for algae and algal products. Growth in the human population, pollution, overexploitation of land and lack of freshwater will encourage use of seaweeds. Modern biotechnology will favour this development, but will also be a serious threat to industrial exploitation of seaweeds. Future uses of marine algae will be decisively influenced by the effort put into and the results coming out of seaweed research.     

Effects of cod bradykinin and its analogs on vascular and intestinal smooth muscle of the Atlantic cod, Gadus morhua.

The effects of [Arg(0),Trp(5),Leu(8)]-BK (cod [Arg(0)]BK) on vascular preparations from branches of the cod celiac artery and on longitudinal smooth muscle preparations from the cod intestine were investigated. Cod [Arg(0)]BK (3 x 10(-8) M) caused a relaxation of the celiac artery precontracted with adrenaline. The relaxation was abolished by the cyclooxygenase inhibitor indomethacin, suggesting that the effect is mediated through the release of prostaglandins, but there was no evidence for the involvement of leukotrienes or nitric oxide in the response. In the intestinal preparations, cod [Arg(0)]BK produced concentration-dependent contractions (pD(2) = 8.28 +/- 0.16). Experiments with N-terminally and C-terminally truncated analogs and with alanine-substituted analogs of cod [Arg(0)]BK demonstrate that the central amino acid Gly(4) and the C-terminal amino acids Leu(8) and Arg(9) are the most important in determining the conformation of the peptide that interacts with the receptor. The results indicate that the ligand binding properties of the cod BK receptor are considerably different from the receptor present in trout tissues and may resemble those of the mammalian B(2) receptor more closely.     

Analysis of teleost hemoglobin by Adair and Monod-Wyman-Changeux models

Summary The allosteric effects of the erythrocytic nucleoside triphosphates (NTP) and of proton concentrations were investigated by precise measurement of Hb–O₂ equilibria of tench hemoglobin (including extreme, high and low saturation ranges) and analysed in terms of the MWC two state model and the Adair four step oxygenation theory.At low concentrations (NTP/Hb ratio=1.0, and pH>7.3) ATP, GTP and protons decrease Hb–O₂ affinity by increasing the allosteric constantL and reducingK _T, the association constant¹ of the deoxy, tense state of the Hb, without significantly affecting that (K _R) of the oxy state, increasing the free energy of cooperativity (G). High concentrations of these effectors, however, also reduceK _R. The greater sensitivity of the half-saturation O₂ tension (P ₅₀) of the Hb to GTP than to ATP at the same concentration, correlates with greater effects of GTP on bothK _T andK _R. The pH and NTP dependence of the four Adair association constants and the calculated fractional populations of Hb molecules in different stages of oxygenation show that the autochthonous NTP effectors and protons stabilize the T structure and postpone the TR transition basic to cooperativity in fish Hb.The possible implications of the findings for aquatic respiration are discussed.Abbreviations ATP adenosine triphosphate - DPG 2,3-diphosphoglycerate (glycerate-2,3-bisphosphate) - GTP guanosine triphosphate - IHP inositol hexaphosphate - NTP nucleoside triphosphates In this paperK _T andK _R are defined as theassociation equilibrium constants instead of dissociation constants (as originally defined by Monod et al. 1965) to facilitate comparison with the Adair constants     

Influences of exercise-stress and adrenaline upon intra- and extracellular acid-base status,electrolyte composition and respiratory properties of blood in tench (Tinca tinca) at different seasons

Summary Exercise-stress in tench resulted in severe acidoses in both the red cells and the extracellular fluid in vivo. These coincident pH decreases conformed to the in vitro pH_i-pH_e relationship for tench blood in the oxygenated state. The extracellular acidosis was primarily respiratory in winter and metabolic in spring and summer. This was due to more effective buffering of metabolic protons in winter by an elevation in [HCO ₃ ^– ] levels, rather than to differences in the lactic- and carbonic acid loads. A good correspondence was found between buffered metabolic protons and increases in [lactate].There was no evidence for -adrenergic red cell swelling and associated red cell pH changes in tench both after exercise and adrenaline infusion. Arterial O₂ transport was, however, improved in exercise by pronounced increases in .Large increases in plasma potassium concentration and small elevations of chloride and calcium levels occurred in exercise. Hematocrit and blood [Hb] also increased, probably due to an adrenergic release of erythrocytes from the spleen, but these increases were small and appeared unimportant for blood O₂ transport.Seasonal differences were found in exercise-induced changes in [lactate], in the magnitude of electrolyte and changes, as well as in resting values for pH_e, pH_i, [HCO ₃ ^– ], [Cl^–] and [Ca⁺⁺]. The origin and importance of these are discussed.     

Thermodynamic analysis of precisely measured oxygen equilibria of tench (Tinca tinca) hemoglobin and their dependence on ATP and protons

Summary Precise oxygen equilibria including extreme, high and low saturation values were determined for hemoglobin (Hb) from the freshwater teleostTinca tinca at three temperatures, each at two pH levels and in the presence and absence of the erythrocytic cofactor ATP, at twofold molar excess over Hb.Analysis of the data in terms of Adair's successive oxygenation theory shows that in the absence of ATP, each of the four oxygenation steps are exothermic, but that net heat release decreases as pH falls from 8.2 to 7.4. ATP greatly depresses the temperature sensitivity of oxygenation particularly at physiological erythrocytic pH, where endothermic cofactor dissociation finds expression in a reverse temperature sensitivity for binding of the 3^rd oxygen molecule to the tetrameric Hb.Enthalpy (H _i) and entropy (S _i) changes of oxygenation vary with oxygenation step, i, as well as with pH and ATP addition, but the variations of H _i are similar to those of S _i reflecting enthalpy-entropy compensation.The data show that the cooperative effects in tench Hb can be dominated either by entropic or enthalpic contributions, depending on the experimental condition and the oxygenation step.     

Differences in microhabitat,abundance, biomass and body size between oxybiotic and thiobiotic free-living marine nematodes

Summary Analysis of samples from a 15 m deep sandy bottom in the northern part of Øresund, Denmark shows that the nematode fauna comprises 2.9 million individuals per m² down to 20 cm depth which averages of 0.40 g organic carbon. Highest densities are found in the uppermost cm. Biomass attains its highest value at 1–2 cm depth. Three results are discussed: 1) nematodes in the uppermost cm are, on average, three times smaller than those between 1–8 cm depth (60 ng org. C vs. 200 ng org. C ind. weight); 2) a distinct abundance trough is found at 8 cm depth, which correlates with the physical space occupied by the gallery of the lugworm Arenicola marina as well as with its possibly unselective feeding on the interstitial meiofauna at that depth; 3) the thiobiotic (deeper-living) species are significantly more slender than the oxybiotic (surface-dwelling) species, suggesting surface-dependent adaptations to life in oxygen poor and sulphide rich sediments where large amounts of dissolved organic matter occur. This is in contrast to previous assumptions that the body length or body shape reflects adaptations to the physical constraints of interstitial space.     

Phenotypic differentiation of aphidicolin-selected human neuroblastoma cultures after long-term exposure to nerve growth factor

Human neuroblastoma SH-SY5Y (SY5Y) cultures, exposed to murine 7 S nerve growth factor (NGF) for 5 weeks and selected with aphidicolin (Aph) for 1 week, acquire several properties indicative of mature peripheral nerve cells. The mitotic activity of treated cultures decreases prior to Aph selection and ultimately reaches a level approximately 3% that of untreated cultures by Week 4 of treatment. The measured plasma membrane resting potential of the cells increases from -5 mV for untreated cells to -(45-56) mV for NGF/Aph-treated cells. Intracellular stores of monoamines are increased as determined by histochemical staining, and levels of neuron-specific enolase antigen increase as a result of NGF/Aph treatment. The resulting outgrowth of neurites is extensive and large bundles of processes commonly exceed 300 micron in length. NGF/Aph-treated cells acquire a dependence upon NGF for survival; however, with continued administration of NGF, the cultures appear to be capable of surviving indefinitely. Retinoic acid will also promote certain aspects of a differentiated phenotype under similar culture conditions. As judged by these criteria, cells of the SY5Y human neuroblastoma cell line have the potential for phenotypic and irreversible differentiation in vitro and can survive for prolonged periods under these culture conditions.     

Enzymic basis for leakiness of auxotrophs for phenylalanine in Pseudomonas aeruginosa

The dual enzymic routes for phenylalanine biosynthesis that exist in Pseudomonas aeruginosa complicate the isolation of phenylalanine auxotrophs. Mutants blocked in each of the various phenylalanine-pathway steps are essential for full appreciation of the physiological nature and gene-enzyme relationships of this biochemical system. A leaky phenylalanine-requiring mutant of P. aeruginosa (PAT1051) was found to lack the bifunctional P-protein (chorismate mutase-prephenate dehydratase), but retained the monofunctional isozyme species of chorismate mutase (chorismate mutase-F) as well as cyclohexadienyl dehydratase (components of the arogenate 'overflow' route to phenylalanine). This is the first mutant of P. aeruginosa shown to be deficient in any enzyme specific for phenylalanine synthesis. It is concluded that although the arogenate pathway has the demonstrated potential to overproduce phenylalanine, the substrate levels normally available to the arogenate pathway in the wild-type are inadequate to satisfy the full metabolic demand for phenylalanine.     

Glyphosate sensitivity of 5-enol-pyruvylshikimate-3-phosphate synthase from Bacillus subtilis depends upon state of activation induced by monovalent cations

The 5-enol-pyruvylshikimate-3-phosphate (EPSP) synthase from Bacillus subtilis was activated by monovalent cations, catalytic activity being negligible in the absence of monovalent cations. The order of cation effectiveness (NH4+ greater than K+ greater than Rb+ greater than Na+ = Cs+ = Li+) indicated that the extent of activation was directly related to the unhydrated cation radius. Ammonium salts, at physiological concentrations, were dramatically more effective than other cations. Activation by ammonium was instantaneous, was not influenced by the counter ion, and gave a hyperbolic saturation curve. Hill plots did not show detectable cooperativity in the binding of ammonium. Double-reciprocal plots indicated that ammonium increases the maximal velocity and decreases the apparent Michaelis constants of EPSP synthase with respect to both phosphoenol pyruvate (PEP) and shikimate 3-phosphate (S3P). A direct relationship between sensitivity to inhibition by glyphosate and the activation state of EPSP synthase was demonstrated. Hill plots indicated a single value for glyphosate binding throughout the range of ammonium activation. Double-reciprocal plots of substrate saturation data obtained with ammonium-activated enzyme in the presence of glyphosate showed glyphosate to behave as a competitive inhibitor with respect to PEP and as a mixed-type inhibitor relative to S3P. The increased glyphosate sensitivity of ammonium-activated EPSP synthase is attributed to a lowering of the inhibitor constant of glyphosate with respect to PEP. Erroneous underestimates of sensitivities of some bacterial EPSP synthases to inhibition by glyphosate may result from failure to recognize cation requirements of EPSP synthases.     

Effect of lysophosphatidylserine on immunological histamine release

The effect of lysophosphatidylserine on immunological histamine release has been studied in rat peritoneal mast cells actively sensitized with horse serum and in human basophils challenged with anti-IgE. In contrast to other lysophospholipids, lysophosphatidylserine enhances the immunological histamine release in rat mast cells. The effect shows the kinetics of a saturable process with an apparent Km for lysophosphatidylserine of 0.26 microM. A similar Km value (0.21 microM) is found when measuring the non-immunological histamine release activated by lysophosphatidylserine plus nerve growth factor. A comparison with phosphatidylserine shows that a half-maximal response to lysophosphatidylserine occurs at a concentration 4-times lower. In addition, the magnitude of the response is higher. At variance with rat mast cells, lysophosphatidylserine does not influence the histamine release elicited by immunological and non-immunological stimuli in human basophils. The histamine secretion in these cells is instead affected by a calcium ionophore or tetradecanoylphorbolacetate, a compound producing activation of protein kinase C.