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.     

Autoantibodies specific for the cardiac myosin isoform are found in mice susceptible to Coxsackievirus B3-induced myocarditis

Several mouse strains are susceptible to immunopathic myocarditis after infection with Coxsackievirus B3 (CB3). This disease is associated with autoantibodies that are directed against myosin. In this study we characterized sera from CB3-infected mice for their reactivity with three different myosin isoforms (heart, skeletal muscle, and brain myosins) and for autoantibody isotype by using an ELISA. Competitive inhibition assays and absorption studies with various myosins demonstrated the presence of two autoantibody populations in sera of susceptible A.CA and A.SW mice. The first was specific for cardiac myosin and was mainly IgG. The second antibody population cross-reacted with heart, skeletal muscle, and brain myosin and was mainly IgM. B10.PL/SgSf and B10.A/SgSf mice, which do not develop immunopathic myocarditis, produced only the IgM autoantibody population cross-reactive with all three myosin isoforms. Because the heart-specific myosin autoantibodies were found exclusively in the mouse strains that developed immunopathic myocarditis, they can be considered a serologic marker for autoimmune heart disease.     

The 90-kilodalton peptide of the heme-regulated eIF-2 alpha kinase has sequence similarity with the 90-kilodalton heat shock protein

Highly purified preparations of the heme-controlled eIF-2 alpha (eukaryotic peptide initiation factor 2 alpha subunit) kinase of rabbit reticulocytes contain an abundant 90-kilodalton (kDa) peptide that is immunologically cross-reactive with spectrin and that modulates the activity of the enzyme [Kudlicki, W., Fullilove, S., Read, R., Kramer, G., & Hardesty, B. (1987) J. Biol. Chem. 262, 9695-9701]. The amino-terminal sequence of the 90-kDa protein has a high degree of similarity with the known amino-terminal sequences of the Drosophila 83-kDa heat shock protein (20 out of 22 residues) and with other related heat shock proteins. The amino acid sequence of a tryptic phosphopeptide isolated by high-performance liquid chromatography from the eIF-2 alpha kinase associated 90-kDa protein after phosphorylation by casein kinase II is shown to be identical with a 14 amino acid segment of the known sequence of the Drosophila 83-kDa heat shock protein. Results of hydrodynamic studies indicate a highly elongated structure for the reticulocyte protein, characteristic of a structural protein. Additional structural similarities between the eukaryotic heat shock proteins, the reticulocyte eIF-2 alpha kinase associated 90-kDa peptide, and spectrin are discussed.     

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.     

Cholecystokinin-induced residual stimulation of enzyme secretion from mouse pancreatic acini

When dispersed acini from mouse pancreas are first incubated with cholecystokinin octapeptide, washed and then reincubated with no additions there is significant stimulation of amylase secretion during the second incubation (residual stimulation of enzyme secretion). Cholecystokinin-induced residual stimulation of enzyme secretion is modified, but not abolished, by reducing the temperature of the first incubation from 37 degrees C to 4 degrees C. Measurement of binding of 125I-labeled cholecystokinin octapeptide indicated that maximal cholecystokinin induced residual stimulation of enzyme secretion occurs when 12-20% of cholecystokinin receptors are occupied by cholecystokinin octapeptide. Moreover, maximal cholecystokinin-induced residual stimulation of amylase secretion is 25% greater than maximal cholecystokinin-induced direct stimulation of amylase secretion. Cholecystokinin tetrapeptide, which causes the same maximal direct stimulation of amylase secretion as does cholecystokinin octapeptide, causes a maximal residual stimulation of enzyme secretion that is only 30% of that caused by a maximally effective concentration of cholecystokinin octapeptide. Adding dibutyryl cyclic GMP to the second incubation can reverse the residual stimulation caused by adding cholecystokinin to the first incubation. The pattern and extent of the dibutyryl cyclic GMP-induced reversal of residual stimulation varies, depending on the temperature and concentration of cholecystokinin octapeptide in the first incubation. The present results are compatible with the hypothesis that mouse pancreatic acini possess two classes of cholecystokinin receptors. One class has a relatively high affinity for cholecystokinin and produces stimulation of enzyme secretion; the other class has a relatively low affinity for cholecystokinin and produces inhibition of enzyme secretion.     

Changes in gill histology of fathead minnows and yellow perch transferred to soft water or acidified soft water with particular reference to chloride cells

Summary Fathead minnows, Pimephales promelas, and yellow perch, Perca flavescens, were transferred from moderately soft Lake Superior water (hardness 45mg/l as CaCO₃) to very soft diluted Lake Superior water (hardness 4.5mg/l). Sulfuric acid was added in some treatments by means of a multichannel diluter. In very soft water, chloride cells proliferated in the gills, especially in the epithelium of the secondary lamellae. When exposed to acid, chloride cells were damaged and less abundant in the secondary lamellae, and blood osmolality was reduced at pH 5.0 (x = 188 mOsm/kg, 9 days exposure; normal 280 mOsm/kg) for the minnows and pH 4.1 (x = 218 mOsm/kg, 58 days exposure; normal 329 mOsm/kg) for the perch. Certain chloride cells which form gland-like clusters in the primary lamellae of perch gills showed little damage even at pH 4.1. The present study supports the view that chloride cells proliferate in very soft fresh water to help maintain ionic balances, and that damage to these cells in acidified soft water may be related to diminished ionoregulatory capacity. The greater acid tolerance of chloride cells of, and the higher blood osmolality maintained by, perch could help to explain the greater tolerance of this species to low pH. In some cases, a species' ability to acclimate to very soft water and acidified soft water may depend upon the number, distribution, and physiology of its chloride cells.