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F B Jensen

Publications and source records attributed to F B Jensen.

44 records · Page 3Linked to original sources
PubMed1987

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

Precise oxygen equilibria including extreme, high and low saturation values were determined for hemoglobin (Hb) from the freshwater teleost Tinca 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 3rd oxygen molecule to the tetrameric Hb. Enthalpy (delta Hi) and entropy (delta Si) changes of oxygenation vary with oxygenation step, i, as well as with pH and ATP addition, but the variations of delta Hi are similar to those of delta Si 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.

Adenosine Triphosphate↗
PubMed1987

Analysis of teleost hemoglobin by Adair and Monod-Wyman-Changeux models. Effects of nucleoside triphosphates and pH on oxygenation of tench hemoglobin.

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 greater than 7.3) ATP, GTP and protons decrease Hb-O2 affinity by increasing the allosteric constant L and reducing KT, the association constant of the deoxy, tense state of the Hb, without significantly affecting that (KR) of the oxy state, increasing the free energy of cooperativity (delta G). High concentrations of these effectors, however, also reduce KR. The greater sensitivity of the half-saturation O2 tension (P50) of the Hb to GTP than to ATP at the same concentration, correlates with greater effects of GTP on both KT and KR. 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 T----R transition basic to cooperativity in fish Hb. The possible implications of the findings for aquatic respiration are discussed.

Animals↗
PubMed1987

Effects of nitrite exposure on blood respiratory properties, acid-base and electrolyte regulation in the carp (Cyprinus carpio).

Adult carp were subjected to 1 mM environmental nitrite for 48 h and nitrite uptake and changes in blood respiratory properties, extracellular electrolyte composition and acid-base status were examined. A constant influx of nitrite caused an accumulation of NO2- in plasma to 5.4 mM in 48 h. The fraction of methaemoglobin rose with plasma [NO2-] to 83%, and the arterial oxygen content decreased to extremely low values. Arterial PO2 increased as a compensation to this O2-shortage, whereas the O2 saturation of the functional (unoxidized) haemoglobin decreased, revealing a reduction in its O2 affinity. Blood haematocrit decreased as a result of red cell shrinkage, which caused very high red cell haemoglobin (Hb) concentrations. The erythrocytic nucleoside triphosphate (NTP) concentration showed a parallel increase whereby NTP/Hb, as well as the relative contributions of ATP and GTP to NTP, remained unchanged. Plasma [Cl-] declined by 15 mM in 48 h, offsetting the plasma [NO2-] increase, minor changes in plasma [HCO3-] and a considerable increase in plasma [lactate]. Arterial pH and [HCO3-] rose slightly during the first 24 h of nitrite exposure, but returned to control values at 48 h. The rise in plasma [lactate] was not reflected in an extracellular metabolic acidosis. Plasma [K+] increased by 94% in 48 h, revealing an uncompensated extracellular hyperkalemia, whereas plasma [Na+] decreased, and plasma [Ca++] was unchanged. Plasma osmolality remained essentially constant.(ABSTRACT TRUNCATED AT 250 WORDS)

Acid-Base Equilibrium↗
PubMed1987

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.

Exercise-stress in tench resulted in severe acidosis in both the red cells and the extracellular fluid in vivo. These coincident pH decreases conformed to the in vitro pHi-pHe 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 [HCO3-] 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 beta-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 PO2. This increase was not of adrenergic origin, as adrenaline alone caused a decrease in arterial PO2. 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 PO2 changes, as well as in resting values for pHe, pHi, [HCO3-], [Cl-] and [Ca++]. The origin and importance of these are discussed.

Acid-Base Equilibrium↗
PubMed1986

Pronounced influence of Hb-O2 saturation on red cell pH in tench blood in vivo and in vitro.

At an extracellular pH of 7.9 the red cell pH in tench blood exhibits a nonlinear, strongly inverse relationship with Hb-O2 saturation, both when investigated in vitro and in vivo (in fish exposed to acid water with and without aluminium). The pHi difference between deoxygenated and oxygenated erythrocytes is large (i.e., 0.35 pH units), which can be accounted for by the Haldane effect and the buffering properties of the blood. The major shift in pHi occurs between 50 and 100% Hb-O2 saturation, indicating an almost full exploitation of the Haldane effect within the normal physiological range of blood O2 saturations.

Animals↗
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↗
PubMed1980

Evidence for the presence of receptors for C3 and IgG Fc on human synovial cells.

The presence of receptors for IgG Fc and fragments of C3 on primary cultures and cryostat sections of normal and rheumatoid synovial tissues was assessed. Significant proportions of large rounded cells with asteroid projections found in such cultures had receptors for both IgG Fc and fragments of C3. Moreover, Gram negative bacteria that had fixed complement, but not EAC, bound in a linear fashion on the superficial layers of synovial cryostat sections. On the basis of morphologic and histochemical criteria, the cultured cells bearing these receptors were tentatively determined to represent a subset of synovial lining cells. The possible role of such receptors on synovial lining cells in the pathogenesis of rheumatoid arthritis is discussed.

Arthritis, Rheumatoid↗