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Biomedical subjects

M Nikinmaa

Publications and source records attributed to M Nikinmaa.

52 records · Page 3Linked to original sources
PubMed1988

The adrenergic responses of carp (Cyprinus carpio) red cells: effects of PO2 and pH.

Carp (Cyprinus carpio) red cells do not show beta-adrenergic responses when incubated with 10(-5) mol l-1 adrenaline at atmospheric oxygen tension and a pH value close to the in vivo resting pH (approx. 8.1). However, when either the pH or the oxygen tension of the incubation medium is decreased, the adrenergic responses appear, showing that oxygen or an oxygen-linked phenomenon has a direct influence on the response. Once present, the adrenergic red cell response is similar to that of trout: cellular water content, sodium content and intracellular pH all increase. Quantitatively the effect appears to be much smaller in carp than in trout. Adrenaline induces an increase in red cell oxygen content when the oxygen content is plotted as a function of extracellular pH. This effect coincides with the onset of the Root effect and is caused by the adrenaline-induced increase in intracellular pH, since it disappears when the oxygen content is plotted as a function of intracellular pH. The red cell ATP content decreases metabolically during adrenaline incubations. In contrast, cellular GTP content is not metabolically reduced in adrenaline-treated cells, showing that the rapid and selective decrease in red cell GTP concentration, observed in hypoxic cyprinids, is not adrenergically induced.

Adenosine Triphosphate↗
PubMed1987

Anion movements across lamprey (Lampetra fluviatilis) red cell membrane.

Chloride and bicarbonate movements across lamprey red cell membrane were investigated. The halftime for equilibration of radioactive chloride across the red cell membrane was 2.46 h, and apparent permeability for chloride-36 was approximately 10(-9) cm X s-1, a value similar to that observed for lipid bilayers. Chloride movements were not affected by the anion exchange inhibitor, 4,4'-diisothiocyano-stilbene-2,2'-disulfonic acid (DIDS). Furthermore, intracellular buffering is effectively isolated from the extracellular compartment, as shown by the fact that practically no pH recovery occurred in the unbuffered extracellular medium after either acidification or alkalinization. These observations show that lamprey red cell membrane is quite impermeable to bicarbonate and other acid/base equivalents.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMed1987

Effects of plasma proteins on the dehydroabietic acid-induced red cell breakdown.

Since red cell hemolysis may play a role in the development of jaundice in fishes exposed to resin acids, we studied the effects of dehydroabietic acid (DHAA) on rainbow trout red cells in vitro. In incubations with physiological saline DHAA caused red cell breakdown at concentrations above 5 mg/liter within 24 hr. In plasma incubations red cell breakdown was observed only after 48 hr at concentration of 240 mg/liter, and DHAA at concentrations of 60 and 120 mg/liter dissolved lipids from red cell membranes within 24-48 hr. In addition, no changes were seen in 6 hr in red cell function when cells were treated in plasma with 210 mg DHAA/liter. The addition of albumin to saline incubations markedly reduced hemolysis and showed that the protection against DHAA in plasma results from binding of DHAA to plasma proteins.

Abietanes↗
PubMed1987

Ion exchange mechanisms on the erythrocyte membrane of the aquatic salamander, Amphiuma tridactylum.

The effects of different pharmacological agents and incubation media on the intracellular pH and water content of Amphiuma erythrocytes were investigated in vitro. Adrenaline had no significant effect on the intracellular pH or cell water content. DIDS caused an intracellular alkalinization that could be abolished by amiloride, ouabain or removal of sodium from the incubation medium. In addition, amiloride and DIDS both caused a decrease in cell water content. The data indicate that sodium/proton and chloride/bicarbonate exchangers are present on the membrane of Amphiuma erythrocytes and these exchangers are active under steady-state conditions.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMed1987

Red cell function of carp (Cyprinus carpio) in acute hypoxia.

The red cell function of carp, subjected to acute hypoxia, was studied. During hypoxic exposure red cell water content, sodium and chloride concentration and pH increased, whereas plasma sodium and chloride concentrations decreased. Treatment of the animals with a beta-adrenergic antagonist, propranolol, before the onset of hypoxia, largely inhibited the increase in red cell water content, diminished the changes in red cell pH and prevented the changes in red cell and plasma sodium concentration. The red cell chloride concentration increased also in propranolol-treated animals thus illustrating the effect of the deoxygenation of haemoglobin on the ion concentrations of red cells. These data indicate that adrenergic activation of sodium/proton exchange across red cell membrane plays a role in the acute responses of carp to hypoxia.

Animals↗
PubMed1986

Mechanisms of pH regulation in lamprey (Lampetra fluviatilis) red blood cells.

Mechanisms regulating the red cell pH in lamprey (Lampetra fluviatilis) were studied using the ammonium chloride prepulse technique. The cells were initially incubated in a physiological saline containing 20 mmol l-1 ammonium chloride, and intracellular pH measured with the DMO technique. Ammonium chloride was then rapidly removed by centrifugation, and the changes in the intracellular pH followed. The intraerythrocytic pH is primarily regulated by an amiloride-sensitive sodium/proton exchange. When sodium is present in the incubation medium, the intracellular pH rapidly recovers from the acidification associated with the removal of ammonium chloride from the incubation. When sodium is removed from the incubation medium, intracellular pH does not recover, and when the cells are treated with 10(-3) mol l-1 amiloride in the presence of sodium, carbon dioxide and bicarbonate, the intracellular pH recovery is drastically reduced. The movements of carbon dioxide, its consecutive catalysed hydration and dissociation to protons and bicarbonate and, possibly, movements of bicarbonate out of the cell acidify the cell contents. This is shown by the observation that the steady-state intracellular pH is higher in a HEPES-buffered medium than in a CO2/HCO3(-)-buffered medium at the same extracellular pH. The acidification is dependent on cellular carbonic anhydrase activity, present in lamprey red cells, which speeds up the hydration reaction. When the action of carbonic anhydrase is inhibited by acetazolamide, removal of ammonium chloride from the incubation medium does not cause intracellular acidification.

Ammonium Chloride↗
PubMed1985

Sublethal effects of simulated pulp mill effluents on the respiration and energy metabolism of rainbow trout (Salmo gairdneri).

Rainbow trout were exposed to 0.08 X 96-hr LC50 concentration of simulated unbleached (KME-Sa) and bleached (KME-Sa + CP) kraft pulp mill effluents. A sulfate soap preparation (Sa) with and without added chlorophenols (CP) was used as the toxicant mixture. The lipid content of white muscle increased in both test groups, and its protein content decreased in the KME-Sa-treated group. The ammonia excretion rate also decreased in both test groups. These results show that there was a shift from protein to lipid metabolism. On the other hand, apart from a slight hypoglycemia, only minor changes were observed in the carbohydrate metabolism. The overall effects on blood respiratory properties were functionally insignificant. However, the effects of kraft mill effluent with and without chlorophenols were qualitatively dissimilar in several respects.

Animals↗
PubMed1985

Metabolic effects of dehydroabietic acid on rainbow trout erythrocytes.

Oxygen consumption and ATP concentration were measured in rainbow trout erythrocytes incubated in a physiological saline containing 0, 5, 15, 30 or 60 mg/l dehydroabietic acid. DHAA caused a decrease in cellular ATP level and oxygen consumption at concentrations above 15 mg/l. Haemolysis increased markedly, when the cellular ATP concentration decreased below 1 mM. These data suggest that increased breakdown of red cells may be the primary reason for jaundice which is observed in resin acid-toxicated fish.

Abietanes↗
PubMed1984

Shape changes in goose erythrocytes.

Goose erythrocytes were subjected to agents and treatments that produce echinocytosis in human erythrocytes. In the presence of the ionophore A23187 and calcium at greater than micromolar concentrations, goose red cells retained their normal ellipsoidal symmetry, but developed extensive semiregular membrane wrinkles or corrugations. Metabolic NTP (nucleoside triphosphate) depletion, induced either by iodoacetamide or by incubating the cells without a substrate, initially produced a similar cell corrugation, but after prolonged incubation most cells became spherical with the nucleus displaced to the cell periphery. The echinocytic agents indomethacin and dimyristoylphosphatidylcholine had no effect on the gross morphology of goose erythrocytes.

Adenosine Triphosphate↗
PubMed1983

Effects of exercise stress on acid-base balance and respiratory function in blood of the teleost Tinca tinca.

We measured the effects of severe, short-term exercise stress on the acid-base balance, the O2 transporting properties and the cofactors for O2 binding in the blood of tench, Tinca tinca. Short-term severe exercise resulted in a drastic decrease in arterial blood pH which is attributed to a mixed respiratory and metabolic acidosis. Concomitantly arterial PO2 rose in apparent compensation for the detrimental effects of the acidosis on O2 transport by the blood.

Acid-Base Equilibrium↗
PubMed1982

Blood oxygen transport of hypoxic Salmo gairdneri.

The in vivo blood oxygen binding properties of rainbow trout were studied in normoxia and hypoxia (PO2 55-60 mmHg). Owing to hypoxia the in vivo oxygen dissociation curve of blood was shifted to the left; the P50 value decreased from 37 mmHg in normoxia to 27 mmHg in hypoxia. Hypoxia also caused an increase in the erythrocytic volume, a decrease in the concentrations of ATP and hemoglobin inside the cell, and an increase in the intraerythrocytic pH. All these responses are interrelated. The swelling of the erythrocytes decreased the concentrations of ATP and Hb in the cell. This decrease changed the Donnan distribution of protons across the red cell membrane, thus increasing the intraerythrocytic pH. The increase in the intraerythrocytic pH was the main cause of the increase in the blood oxygen affinity. Owing to the increased blood oxygen affinity the oxygen transport from gills to tissues in hypoxia was only slightly decreased from that in normoxia. However, as the venous oxygen tension decreased in hypoxia, the diffusion of oxygen from tissue capillaries to the cells was probably slowed down in hypoxia when compared to normoxia.

Acclimatization↗
PubMed1982

The effects of adrenaline on the oxygen transport properties of Salmo gairdneri blood.

1. An injection of adrenaline into the dorsal aorta of Salmo gairdneri caused an increase in the dorsal aortic O2 content at 7 and 14 degrees C. 2. At 7 degrees C the number of erythrocytes in the dorsal aorta increased as indicated by the increases in both the Hct value and the haemoglobin concentration. 3. At 14 degrees C the erythrocytes in the dorsal swelled owing to the injection of adrenaline; this shifts the O2 dissociation curve to the left and in this way increases the dorsal aortic O2 content.

Animals↗
PubMed1982

Physiological changes in trout (Salmo gairdneri) during a short-term exposure to resin acids and during recovery.

Six rainbow trouts were exposed to a 2 mg/l concentration of resin acids for 24 h. The toxicants influenced respiration by causing a decrease in arterial P02, red cell volume and pH, and an increase in ATP/Hb ratio. These responses were reversible on recovery. A disturbance in hydromineral balance was shown by a decrease in plasma chloride concentration, which was reversible in all but one fish. This fish had additional metabolic difficulties as shown by increases in plasma lactate concentration and enzyme activity. An indication of liver dysfunction was the increase in plasma bilirubin concentration, continuing throughout recovery.

Adenosine Triphosphate↗
PubMedDate not supplied

The lamprey (Lampetra fluviatilis) erythrocyte; morphology, ultrastructure, major plasma membrane proteins and phospholipids, and cytoskeletal organization.

The aim of this study was to characterize the erythrocyte of the lamprey (Lampetra fluviatilis), a primitive vertebrate. The lamprey erythrocyte predominantly has a non-axisymmetric stomatocytelike shape. It has a nucleus and a haemoglobin-filled cytosol with a few organelles and vesicular structures. Surprisingly, there is no marginal band of microtubules. Sodium dodecylsulphate polyacrylamide gel electrophoresis followed by Coomassie blue staining of isolated plasma membranes revealed a single band at the level of the human spectrin doublet. Major bands also occurred at approximately 175 kDa and comigrating with human erythrocyte actin (approximately 45 kDa). The presence of spectrin, actin and vimentin was shown by immunoblotting. Band 3 protein, the anion exchanger in higher vertebrates, seemed to be highly deficient or lacking, as was also the case with ankyrin. Confocal laser scanning microscopy combined with immunocytochemical methods showed spectrin, actin and vimentin mainly to be localized around the nucleus, from where actin- and vimentin-strands extended out into the cytoplasm. Actin also seemed to be present at the plasma membrane. Phospholipid analyses of plasma membrane preparations showed the presence of the same four major phospholipid groups as in the human erythrocyte, although with higher and lower amounts of phosphatidylcholine and sphingomyelin, respectively. The low fluorescein isothiocyanate conjugated annexin V binding, as monitored by flow cytometry, indicated that phosphatidylserine is mainly confined to the inner membrane leaflet in the lamprey erythrocyte plasma membrane.

Animals↗
PubMedDate not supplied

Beta-adrenergic stimulation of volume-sensitive chloride transport in lamprey erythrocytes.

We measured the effects of a beta-adrenergic agonist, isoproterenol, on chloride transport and volume regulation of lamprey (Lampetra fluviatilis) erythrocytes in isotonic (288 mosm L(-1)) and hypotonic (192 mosm L(-1)) medium. Isoproterenol at a high concentration (10(-5) M) did not influence chloride transport in isotonic medium but markedly increased chloride fluxes in hypotonic conditions: unidirectional flux increased from 100 mmol kg dcw(-1) h(-1) in the absence to 350 mmol kg dcw(-1) h(-1) (dcw=dry cell weight) in the presence of isoproterenol. Simultaneously, the half-time for volume recovery decreased from 27 to 9 min. Isoproterenol caused an increase in cellular cyclic AMP (cAMP) concentration. The stimulation of chloride transport in hypotonic conditions could be induced by application of the permeable cAMP analogue, 8-bromo-cyclic AMP, suggesting that the effect of beta-adrenergic stimulation on chloride transport occurs downstream of cAMP production. As isoproterenol did not affect unidirectional rubidium fluxes in hypotonic conditions, the transport pathway influenced by beta-adrenergic stimulation is most likely the swelling-activated chloride channel. Because the beta-adrenergic agonist only influenced the transport in hypotonic conditions despite the fact that cAMP concentration also increased in isotonic conditions, the activation may involve a volume-dependent conformational change in the chloride channel.

Adrenergic beta-Agonists↗