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Biomedical subjects

F B Jensen

Publications and source records attributed to F B Jensen.

At least 37 records · Page 2Linked to original sources
PubMed1998

Effects of exhausting exercise and catecholamines on K+ balance, acid-base status and blood respiratory properties in carp.

The potential role of adrenergic mechanisms in the recovery of potassium balance and acid-base status following 5 min of exhausting exercise was studied in carp. The extracellular metabolic H+ load after exercise matched the lactate load, suggesting similar release rates of H+ and lactate from white muscle. Blockage of alpha-adrenoceptors by phentolamine or beta-adrenoceptors by propranolol neither influenced absolute magnitudes nor recovery kinetics of extracellular H+ and lactate loads. The arterial oxygen tension increased following exercise, but blood oxygen transport was not improved via a red cell beta-adrenergic response or modulation of the red cell nucleoside triphosphate content. Exercise induced an increase in extracellular [K+] which was corrected within 30-60 min of recovery. The recovery of K+ balance was not influenced by blockage of adrenergic receptors. Red cell [K+] changed only insignificantly following exercise, whereby a possible function of the red cells as a temporary depository for K+ during the extracellular hyperkalaemia could not be established. The minimal influence of catecholamines on the measured parameters during recovery from exercise was supported by an absence of change in these parameters upon adrenaline injection in resting carp.

Acid-Base Equilibrium↗
PubMed1998

Carbon dioxide transport in alligator blood and its erythrocyte permeability to anions and water.

Deoxygenation of alligator red blood cells (RBCs) caused binding of two HCO3- equivalents per hemoglobin (Hb) tetramer at physiological pH. At lowered pH, some HCO3- binding also occurred to oxygenated Hb. The erythrocytic total CO2 content was large, and Hb-bound HCO3-, free HCO3-, and carbamate contributed about equally in deoxygenated cells. The nonbicarbonate buffer values of RBCs and Hb were high, and the Hb showed a significant fixed acid Haldane effect. Binding of HCO3- on deoxygenation occurred without a change in RBC intracellular pH, revealing equivalence between oxylabile HCO3- and H+ binding. Erythrocyte volume, plasma pH, and plasma HCO3- concentration also varied little with the degree of oxygenation. Diffusional water permeability was higher in oxygenated than deoxygenated RBCs. The RBCs have rapid band 3-mediated Cl- and HCO3- transport, which was not affected by degree of oxygenation, but net fluxes of Cl- and HCO3- via the anion exchanger are small during blood circulation at rest. Most of the CO2 taken up into the blood as it flows through tissue capillaries is carried within the erythrocytes as Hb-bound HCO3- until CO2 is excreted when blood flows through pulmonary capillaries.

Acid-Base Equilibrium↗
PubMed1998

Interaction between haemoglobin and synthetic peptides of the N-terminal cytoplasmic fragment of trout band 3 (AE1) protein.

Two acidic peptides corresponding to the first 10 and 20 amino acid residues of the N-terminal, cytoplasmic fragment of rainbow trout band 3 (AE1) protein were synthesised in order to study their interaction with trout and human haemoglobin (Hb). The peptides did not influence the oxygen affinity of the main anodic trout Hb component (Hb IV) when tested at surplus peptide concentration ([peptide]/[Hb4]=16), at high and low ionic strength and at pH values ranging from 6.5 to 7.6. With human Hb, however, the 20-mer peptide markedly decreased the oxygen affinity and increased the Bohr effect. These data suggest that the trout band 3 peptide binds preferentially to the deoxy (T) conformation of human Hb, probably at the organic phosphate binding site in the central cavity between the beta-chains, which is known to be the binding site for the acidic N terminus of human band 3. In trout Hb IV, the presence of negatively charged Asp at position NA2 of the beta-chains (in contrast to positive or neutral residues in mammalian Hb) may weaken any interaction with the highly negatively charged peptides.

Amino Acid Sequence↗
PubMed1997

Acid-base regulation in tadpoles of Rana catesbeiana exposed to environmental hypercapnia.

Tadpoles of Rana catesbeiana were exposed to different levels of environmental hypercapnia. The acid-base regulatory response differed from that in adult amphibians in showing a high degree of pH compensation in the extracellular fluid (65-85%) and complete compensation in the intracellular fluid (tail muscle and liver) within 24 h. Hypercapnia induced a massive transfer of HCO3- equivalents and Ca2+ from the tadpoles to the environment, which lasted some 4-6 h. Bicarbonate accumulated in the body fluids came mainly from internal buffer sources (probably CaCO3 in lime sacs and/or skin deposits). It is suggested that the large bicarbonate efflux from the animal is a consequence of the dissolution of CaCO3 stores and the delayed adjustment of bicarbonate-retaining mechanisms. Re-exposure of tadpoles to hypercapnia after 1-3 weeks of normocapnic recovery only affected transepithelial fluxes of acid-base equivalents marginally, suggesting that mobilisable CaCO3 stores were depleted during the first exposure to hypercapnia and that they were not refilled. The CaCO3 stores may normally be mobilised during the slowly developing internal hypercapnia that occurs during metamorphosis.

Acid-Base Equilibrium↗
PubMed1994

[Penile vein surgery. A follow-up study of erectile dysfunction of presumed venous origin].

Forty patients who underwent penile venous surgery (PVS) because of suspected veno-occlusive dysfunction, were evaluated approximately 15 months (median) postoperatively as to their sexual capability. Although 47.5% were able to obtain penile rigidity, this was sufficient for intercourse in only 35%. Short-term subjective improvement was noted in 55% as opposed to long-term improvement in 35%. Analysis for predictive factors was negative. In conclusion, the indication for PVS should be reconsidered, as an insufficient theoretical concept might explain the low long-term success rate.

Adult↗
PubMed1992

Inhibition of adrenergic proton extrusion in rainbow trout red cells by nitrite-induced methaemoglobinaemia.

The effects of nitrite-induced methaemoglobinaemia on adrenergic proton extrusion from rainbow trout red blood cells were studied using the pH-stat method. In control conditions adrenergic proton extrusion was completely inhibited by amiloride and was greater in deoxygenated than in oxygenated erythrocytes. Nitrite-induced methaemoglobinaemia was associated with a pronounced reduction in the catecholamine-stimulated proton efflux from both deoxygenated and oxygenated erythrocytes. In deoxygenated erythrocytes the initial proton efflux upon catecholamine stimulation decreased by 60-70%, while the percentage of methaemoglobin in the red cells increased from the control level of 1-3% to 20%. In oxygenated erythrocytes the decrease was 30% at the same methaemoglobin percentage range. It is suggested that the pronounced influence of nitrite-induced methaemoglobinaemia on adrenergic proton efflux results from an inhibition of the red cell sodium/proton exchanger by the R-like haemoglobin conformations.

Animals↗
PubMed1992

Increased working capacity with hyperoxia in humans.

The purpose of the study was to examine the influence of oxygen-breathing on maximal oxygen uptake (VO2max) and submaximal endurance performance. Six young women and five men rode a cycle-ergometer while breathing compressed air (normoxia, NOX) or a 55% O2 in N2 mixture (hyperoxia, HOX). The VO2max increased significantly by 12% (P less than 0.01) with HOX in the women but not in the men (+4%; nonsignificant). Maximal heart rate was also increased with HOX in the women but not in the men. Endurance time during work to exhaustion at 80% of normoxic VO2max was 41% longer in HOX than in NOX (P less than 0.025) with no significant difference between the men and the women. The variation among individuals was large. The oxygen uptake and respiratory quotient were not different in the two endurance tests, but pulmonary ventilation (VE) and blood lactate concentration were lower in HOX than in NOX, especially during the latter part of the task. Plasma base deficit (BDpl) increased initially by 3.5 mmol.l-1 during HOX and then stabilized. In NOX, a continuous increase was seen and the change was more than twice as large. Relative to BDpl, VE was higher in HOX than in NOX indicating a more efficient ventilatory compensation of the metabolic acidosis. The reduced ventilatory demand and lower metabolic acidosis in HOX in combination with lower relative exercise intensity may have contributed to the longer time to exhaustion. However, the pattern of individual variation suggested that other mechanisms were also involved.

Adult↗
PubMed1990

Non-invasive blood pressure monitoring during head-up tilt using the Penaz principle.

Continuous blood pressure measurement by a non-invasive means is of clinical utility in many situations where changes in cardiovascular hemodynamics and blood volume distribution are likely to occur. We have compared blood pressure measurements using the Penaz principle (Finapres, Ohmeda) to an intra-arterial catheter system during head-up tilt (reverse Trendelenburg's position) which models central hypovolemia. Twelve healthy volunteers were raised to a 60 degree head-up tilt position for 60 min or until presyncope occurred. Seven subjects developed presyncopal symptoms at a mean time of 38 +/- 6 min with blood pressure measured by the Penaz principle falling from 140 +/- 8/72 +/- 4 to 82 +/- 10/54 +/- 6 mmHg (18.7 +/- 1.1/9.6 +/- 0.5 to 10.9 +/- 1.3/7.2 +/- 0.8 kPa) (P less than 0.01), at which point they were returned to a horizontal position with an immediate rise in blood pressure. During the maximal drop in blood pressure, heart rate decreased from 82 +/- 7 to 45 +/- 5 (P less than 0.01). Overall, the non-invasive system had a correlation coefficient of 0.98 as compared to the intra-arterial method and ECG for blood pressure and heart rate in all 12 subjects during rest, tilt, and recovery. We conclude that the Penaz principle apparatus is a useful monitor of symptomatic hypotension during central hypovolemia.

Adult↗
PubMed1990

Heart rate and arterial blood pressure at the onset of static exercise in man with complete neural blockade.

1. We tested the 'muscle-heart reflex' hypothesis for the immediate increases in heart rate and blood pressure at the onset of static exercise in man by performing complete blockade of afferent nerves from the working muscles. Brief (5 s) maximal static hand-grip contractions were performed without performing a Valsalva-like manoeuvre and with no increase in central venous pressure both before and after combined axillary and radial blockade with lidocaine. Muscle strength was reduced to near zero. The effectiveness of the afferent neural blockade was evaluated by recording the heart rate and blood pressure responses and rating the perceived pain during a cold pressor test of the blocked and contralateral unblocked hand. 2. The cold pressor test increased blood pressure but had no effect on heart rate. Afferent neural blockade eliminated the increase in blood pressure and the perceived pain associated with the cold pressor test. Maximal hand-grip contractions resulted in immediate and similar increases in heart rate and blood pressure before and after afferent neural blockade of the arm. 3. The results of this study suggest that the immediate increases in heart rate and blood pressure at the onset of static exercise in man occur when the 'muscle-heart reflex' is inoperable.

Adult↗
PubMed1990

External negative thigh pressure. Effect upon blood flow and pressure in the foot in patients with occlusive arterial disease.

We studied the effect of external application of 35-45 mmHg negative pressure around the thigh on toe blood pressure and skin blood flow in nine patients with occlusion of the superficial femoral artery and rest pain/severe intermittent claudication. The systolic toe blood pressure increased from 32 (range 5-70) mmHg before treatment to 57 (42-75) mmHg (p less than 0.05) during negative thigh pressure and 44 (range 10-88) mmHg after treatment. In addition, the gain in toe blood pressure tended to be greater the lower the pre-test toe pressure was, correlation coefficient r = 0.52 (p greater than 0.05). Relative skin blood flow, measured in the first toe interstice by the 133Xe wash-out method, increased by 304 (range 86-767) percent (p less than 0.05) during the test period compared to the mean wash-out rate obtained before and following the test period. Heart rate, systemic blood pressure, skin temperature, serum protein and haematocrit measured during each phase of the study were similar. We conclude that 35-45 mmHg negative pressure around the thigh in patients with occlusion of the superficial femoral artery induce increased blood perfusion in the foot, possibly due to changes in collateral arterial resistance in the thigh.

Aged↗
PubMed1989

[Continuous non-invasive measurement of blood pressure].

Automatic continuous non-invasive measurement of blood pressure using the Penaz' principle (Finapres) was compared with the blood pressure records using a sphygmomanometer during anaesthesia in 29 patients without significant arteriosclerosis. There were no significant differences between values recorded using the two methods. Furthermore, the changes recorded in systolic, diastolic and mean arterial pressures were not significantly different. Also, the pulse recorded with the Penaz' principle corresponded to the heart rate recorded from ECG. Automatic continuous non-invasive measurement of blood pressure using the Penaz' principle offers a valuable aid for monitoring patients during anaesthesia.

Adult↗
PubMed1989

[Ergotism in migraine. Peripheral vascular complications in 14 patients with migraine].

The general occurrence of subclinical ergotism with reduced peripheral systolic blood pressures in patients taking ergotaminepreparations regularly for migraine and the frequent occurrence of milder symptoms indicates that severe ischaemia of the extremities is not as rare a complication as would appear from the few case reports published. The 14 cases reported here constitute the largest series published of migraine patients with acute ergotism. The patients, all women, were admitted to a vascular department over a period of 14 years. They suffered from severe ischaemia of one or more extremities after consumption of varying doses of ergotamine tartrate. Ten patients had previously exhibited symptoms of acute or chronic ergotism, but only eight were admitted with this diagnosis. Liver enzyme tests were abnormal in five out of six patients examined, while three patients had ECG signs of myocardial ischaemia, regressing during treatment. At the beginning of the period, hyperbaric oxygen at 3 ATAB was the standard treatment. Since 1980, the treatment of choice has been continous i.v. nitroglycerine infusion for 24 hours. Nine patients experienced prolonged postischaemic symptoms; one patient required a forefoot amputation and four patients had permanent ischaemic muscular damage. Increased bioavailability of ergotamine due to hepatic vasospasm is suggested as a cause of sudden reduced tolerance to ergotamine. Peripheral systolic pressures and liver function tests should be controlled in patients taking ergotamine regularly. Subclinical ergotism over a prolonged period may facilitate development of occlusive peripheral vascular disease.

Adult↗
PubMed1989

Hydrogen ion equilibria in fish haemoglobins.

H+ titration studies on oxygenated and deoxygenated haemoglobins from carp, rainbow trout, spiny dogfish and pig are reported, and compared with Hb-H+ equilibria in other species and structural information deduced from amino acid sequences. The buffer values of oxygenated and deoxygenated teleost haemoglobins are low in comparison with elasmobranch and mammalian haemoglobins. This correlates with a much lower content of histidine residues and alpha-amino groups in teleost haemoglobins, than that in elasmobranch, dipnoan, amphibian, reptilian, avian and mammalian haemoglobins. The low total histidine content in teleost haemoglobins is paralleled by a reduced number of titratable histidine residues compared with that in mammals. An inverse relationship is observed between the magnitude of buffer values and the magnitude of fixed-acid Haldane effects. The largest Haldane effect and smallest buffer values are seen in carp, followed by trout, whereas the smallest Haldane effect and largest buffer values are seen in dogfish. The H+ equilibria of pig haemoglobin are intermediate between those of teleost and elasmobranch haemoglobins.

Animals↗
PubMed1988

Effect of electrode temperature on orthostatic changes in forefoot transcutaneous oxygen tension (tc-PO2).

The influence of increasing the temperature of the transcutaneous oxygen tension (tc-PO2) electrode from 37 to 45 degrees C on the orthostatic changes in tc-PO2 was studied in six normal subjects. The tc-PO2 electrode was mounted on the forefoot. The blood pressure of the forefoot was changed by elevating and lowering the forefoot in relation to heart level. At all electrode temperatures tc-PO2 decreased about 35% when the forefoot was elevated. At electrode temperatures between 41 and 45 degrees C tc-PO2 increased about 20% when the electrode was lowered below heart level. This indicates a passive vascular bed in the heated tissue under the electrode. However, at 37 degrees C tc-PO2 decreased about 40% when the forefoot was lowered. This indicates that the local vasoconstrictor response to increased venous transmural pressure is preserved when the tissue under the electrode is heated to 37 degrees C only. The study suggest that tc-PO2 monitoring at 37 degrees C may be used for continuous, non-invasive monitoring of the local vasoconstrictor response, and thus of arteriolar contractility and intact sympathetic innervation.

Adult↗
PubMed1988

Red-cell pH in tench. Interacting effects of cellular nucleoside triphosphates, Hb-oxygenation and extracellular pH.

Experimental adjustments of red-cell pH (pHi) by varying red-cell nucleoside triphosphate (NTP) content, blood oxygenation state and extracellular pH (pHe) demonstrated a tight interdependence of these variables in their influence upon pHi. The increase in pHi with deoxygenation (delta pHi (d--o] is large, but becomes strongly reduced when the NTP content is decreased and when pHe falls. Lowering of red-cell NTP increases pHi, notably at high pHe, but this NTP dependence of pHi (delta pHi/delta(NTP/Hb] is much smaller in deoxygenated than in oxygenated blood. The pHe dependence of pHi (delta pHi/delta pHe) increases upon reduction of red-cell NTP content and upon deoxygenation. The results are consistent with the view that pHi is governed by Donnan-like distribution of protons across the red-cell membrane, and show that a pronounced red-cell swelling accompanies increases in the distribution ratio [H+]e/[H+]i. The data are interpreted in terms of changes in the red-cell non-permeable charge as induced by NTP and its linkage with the haemoglobin proton equilibria.

Acid-Base Equilibrium↗