[Does examination play any role in continuing education? Experiences from clinical chemistry].
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Chemistry, Clinical↗
Biomedical subjects
G Ronquist
Publications and source records attributed to G Ronquist.
Characteristics of membrane-bound 5'-nucleotidase on human prostasomes.
Examination of prostasomes, isolated from human seminal plasma, showed that there was very little remaining paranitrophenylphosphatase activity when assayed in the presence of 10 mmol/l of tartrate and 2 mmol/l of levamisole. Under these conditions it was possible to study the prostasome membrane-bound 5'-nucleotidase activity, which was unaffected by these two inhibitors. The activity was considered to be located at the external surface of the prostasome membrane and a 50-60% increase in activity was obtained by the addition of 0.05% Triton X-100. The prostasome membrane-linked 5'-nucleotidase readily hydrolysed 5'-AMP. Two other 5'-nucleoside monophosphates, 5'-IMP and 5'-GMP, were also hydrolysed, but more slowly; 2'- or 3'-AMP were practically not attacked. The prostasome membrane-linked 5'-nucleotidase obeyed Michaelis-Menten kinetics. Apparent Km for 5'-AMP was 11.2 +/- 2.1 mumol/l and Vmax 64.7 +/- 11.4 nmol/mg protein/min. These figures were somewhat changed in presence of 0.05% Triton X-100, the Km value being reduced by 30% and the Vmax value increased by 60%. Adenosine 5' (alpha, beta methylene) diphosphate (100 mumol/l), Ni2+ (10 mmol/l) and concanavalin A (20 micrograms/ml) were all potent inhibitors of the prostasome membrane-linked 5'-nucleotidase.
5'-Nucleotidase↗
Phosphocreatine turnover and pH balance in forearm muscle of patients with syndrome X.
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Adult↗
[Specialist examination in clinical chemistry. Voluntary examination for higher competence].
The Swedish Society for Clinical Chemistry has now completed its second board examination for voluntary specialist diploma in clinical chemistry. The first day comprised a 6 hour written examination (about 20 essay questions). The second day was an oral examination in front of five clinical chemists representing different aspects of the specialty, firstly as questions on the subject as a whole and secondly in the form of a seminar where original research work carried out by the examinee was discussed.
Chemistry, Clinical↗
Balance of amino acids in the pregnant human uterus at term.
The nutritive and metabolic state of the human uterus at term is evaluated by measuring the uptake and release of amino acids. The subjects are ten healthy women with normal pregnancy undergoing elective caesarean section at term, before onset of labour. Free amino acids in arterial (radial artery) and venous (plexus of the uterine and ovarian veins) blood are determined and arteriovenous (AV) differences in each amino acid across the uterus are calculated. Generally the AV differences are negative, i.e. uterus at term releases amino acids in most cases. The human pregnant uterus at term is characterized by a release of amino acids rather than uptake. This indicates that they are in excess and are not needed in anabolic processes or as a fuel, even when the uterine tissue at term is supposed to be preparing for its grand performance, i.e. the delivery.
Adult↗
Myocardial uptake and release of lactate after high dose neurolept endotracheal intubation in coronary surgery.
To evaluate the relationship between the hemodynamic and ECG variables used in routine surveillance of coronary surgery and myocardial lactate metabolism, 23 middle-aged, male, beta 1-blocked patients about to undergo coronary surgery were monitored before and after endotracheal intubation with high dose (30 micrograms/kg) fentanyl-midazolam anesthesia. The induction of anesthesia was followed by a mean arterial pressure decrease (from 98 +/- 4 to 76 +/- 3 mm Hg) and heart rate increase (from 53 +/- 3 to 66 +/- 2 beats/min). After intubation the hemodynamic variables were stable except for a further, transient increase in heart rate (to 69 +/- 2 beats/min). The myocardial uptake of lactate decreased after intubation, from 48 +/- 5 mumol/min to a lowest level of 24 +/- 3 mumol/min. A lactate release was exhibited in 7/23 patients (30%). No ST-segment changes were observed. The correlation between the myocardial lactate uptake/release and hemodynamic or ECG variables was unimpressive or non-existent (r < or = 0.20). Thus, a reduced uptake and even a release of lactate occurred irrespective of the ST-segment, heart rate, or systemic or pulmonary artery pressures. In conclusion, endotracheal intubation in patients with coronary disease was consistently (17/23 patients) followed by a reduced myocardial uptake of lactate, in spite of high dose neurolept anesthesia and beta 1-blockade. This metabolic event was not consistently related to hemodynamic changes.
Adrenergic beta-Antagonists↗
Coxsackie B3 myocarditis induces a decrease in energy charge and accumulation of hyaluronan in the mouse heart.
Interstitial oedema in chronic inflammation and ischaemia is related to an accumulation of hyaluronan (hyaluronic acid; HA) in the interstitium. As interstitial oedema will affect the oxygen transport in the interstitium we have evaluated whether accumulation of HA is related to signs of myocardial energy depletion in virus induced myocarditis. Myocarditis was induced in Balb/c mice by inoculation of Coxsackie B3 virus. The extractable HA content of the myocardium increased progressively from a baseline value of 153 +/- 26 micrograms g-1 dry weight to a maximum of 286 +/- 78 micrograms g-1 dry weight at day 7, whereafter there was a slight decline. Affinity histochemistry visualized HA in the endo-perimysium in healthy myocardium. At day 5 after Coxsackie B3 inoculation there was a general widening of the endomysium, which exhibited a positive staining for HA. In conjunction with focal inflammatory infiltrates the staining for HA was even more pronounced. The energy rich adenylates were reversibly affected by the Coxsackie B3 infection. There was a slight, but significant decline in EC from 0.74 +/- 0.05 in the control group to a minimum value of 0.64 +/- 0.10 at day 5, whereafter a restitution was observed at days 7 and 10. The total adenine nucleotide pool was similarly decreased from 27.8 +/- 2.9 mumol g-1 dry weight in controls to 24.6 +/- 2.1 micrograms g-1 dry weight at day 5, and normalized at days 7 and 10. The data suggest that virus induced myocarditis is associated with a local accumulation of HA in the myocardium.(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗
Functional and biochemical effects of a K(+)-ionophore on the isolated perfused rat heart.
Valinomycin, a K(+)-specific ionophore, influenced function and metabolism of isolated perfused rat hearts in a dose-dependent fashion. At a concentration of 0.05 micrograms ml-1 in perfusion fluid a 50% reduction of heart rate (HR) and a 90% reduction in max dP/dt were observed. These effects were paralleled by a substantial decrease of myocardial energy charge from about 0.80 to 0.20. A 2.5 fold increase in tissue lactate concentration indicated an increased rate of glycolytic activity. Low ATP combined with high ADP and AMP levels as found in these valinomycin-treated hearts is known to promote phosphofructokinase activity and may explain the elevated lactate levels. A significant increase in the concentrations of adenosine, IMP and inosine was observed as well.
Adenosine↗
Arachidonic acid 15-lipoxygenase and traces of E prostaglandins in purified human prostasomes.
Human spermatozoa are associated with arachidonate 15-lipoxygenase activity. This activity could be due to 15-lipoxygenase in small organelles (prostasomes), which are known to bind hydrophobically to germ cells. This possibility was assessed by separating prostasomes from human spermatozoa by differential centrifugation and purifying them by gel filtration (Sephadex G-200). Purified prostasomes metabolized [1-14C]arachidonic acid to 15(S)-hydroxyeicosatetraenoic acid as determined by reverse phase and by chiral phase HPLC and by gas chromatography-mass spectrometry. Biosynthesis of prostaglandins could not be detected, but the prostasomes contained trace amounts of the four major E prostaglandins of human seminal fluid (3.6 nmol mg-1 of prostasomal protein). Arachidonic acid 15-lipoxygenase has recently been implicated in the acrosome reaction of bull spermatozoa and it may have a similar function in the acrosome reaction of human spermatozoa.
Arachidonate 15-Lipoxygenase↗
alpha-Amino-n-butyric acid methyl ester induces concentrative uptake of L-dopa in human Langerhans' cells normally not operative for L-dopa transport.
We recently reported the existence of two kinds of human epidermal Langerhans' cells (LC), one which can take up and accumulate L-dopa and one which cannot. The dopa(+) LC take up L-dopa by carrier-mediated exchange diffusion, that is, the influx of L-dopa and the outflow of an intracellular substance are linked via the same carrier. The nature of the fundamental difference between L-dopa(+) and L-dopa(-) cells has not been clarified. We have now found that alpha-amino-n-butyric acid methyl ester (ABA-OME) penetrates into intracellular compartments, perhaps endosomes or lysosomes, of all LC, where hydrolysis results in the accumulation of the free amino acid (ABA). This accumulation causes a considerable increase in osmotic pressure of the membrane-limited organelle, leading to influx of water and swelling. Co-incubation with L-dopa revealed an influx of L-dopa into LC which normally cannot take up this amino acid. It is suggested that these LC lack the capacity to synthesize and/or store the counterpart which allows L-dopa to enter the dopa(+) LC, but that ABA in the L-dopa(-) LC can function as an equivalent counterpart.
Adult↗
Ionophore A23187 reduces energy charge by enhanced ion pumping in suspended human erythrocytes.
Washed human erythrocytes were basically incubated in phosphate-buffered saline at 37 degrees C with different concentrations (1-5 mumol l-1) of the divalent cationophore A23187. This ionophore induced a decrease by about 75% of ATP content and energy charge (EC) and a concomitant increase in ADP and AMP contents in a dose-dependent fashion such that an inverse ATP/ADP relationship developed. EGTA at 1 mumol l-1 annihilated the effect of A23187 on energy status. When glucose was added to the basic incubation medium A23187 inclusion resulted in an elevated lactate production concomitantly with a partial restoration of EC. Introduction of Mg2+ to basic incubation medium containing glucose and the ionophore resulted in a sharp increase in lactate production with an energy state that was maintained at a control level. It is concluded that the low EC of erythrocytes obtained by this ionophore is the result of runaway ATPases dissociated from glycolysis. Since human erythrocytes are devoid of organelles other than the plasma membrane it is concluded that the ionophoric effect is exerted in the plasma membrane.
Adenosine Diphosphate↗
Effects of the ionophore gramicidin D on energy metabolism in human erythrocytes.
Washed human erythrocytes were incubated in phosphate-buffered saline at 37 degrees C with different concentrations (2-80 mg l-1) of the monovalent cationophore gramicidin D. The ionophore induced a decrease of ATP content and energy charge (EC) and a concomitant increase in ADP and AMP contents. At a concentration of 10 mg l-1 of the ionophore the reduction of EC and ATP concentration was about 50%. Increasing the concentration of the ionophore resulted in a substantial haemolysis with no further effect on the nucleotide levels. Lowering the concentration of the ionophore to 5 mg l-1 (to avoid haemolysis) lead to a similar effect on the energy status. Ouabain at 0.5 mmol l-1 in incubation medium distinctly blunted the ionophoric effect on EC and adenine nucleotides. Addition of glucose on the contrary reversed these effects by about 80%. Hence, the glucose-induced increase in glycolytic flux as evidenced by an increase in lactate production was not sufficient to restore energy state.
Adenosine Diphosphate↗
Increased activity of 5' nucleotidase in serum of patients with sickle cell anaemia.
Fifty-nine patients with homozygous sickle cell anaemia, 17 heterozygous individuals and 22 controls were investigated in respect to serum (S) 5'nucleotidase (5'NT, EC 3.1.3.5). The patients showed a significantly higher mean value of S-5'NT compared to the controls. However, this rise was heterogeneous as it occurred only among a subgroup of patients. The heterozygous individuals were not different from either the patients or the controls generating a situation which puts the heterozygous individuals in an intermediate position between the patients and the controls. S-5'NT showed significant correlation with S-bilirubin, S-aspartate aminotransferase, S-alanine aminotransferase and especially S-gammaglutamyl transferase. However, it was not correlated with S-alkaline phosphatase, which is another marker for hepatobiliary disease. These results suggest that the liver involvement in a subgroup of patients with sickle cell anaemia is a mixture of hepatocyte damage and the biliary tree involvement.
5'-Nucleotidase↗
Ionophoric interaction with the myocyte sarcolemma: a new insight into the pathophysiology of degenerative myocardial disease.
A certain group of compounds often derived from microbes known as ionophores function as ion channels when incorporated in biological membranes. Different ionophores have a relative specificity for certain cations such as Ca2+ or K+. When such compounds are integrated in the cell membrane of a host cell a leakage of the ion in question is induced and the physiologic ion gradient will be dissipated. This will activate ion pumps at the expense of ATP in order to restore the physiologic ion gradient. This effect is seen for a number of different viruses including Coxsackie B3. Based on own experiments we suggest that this ionophoric effect is important in the pathophysiology of myocarditis. We have shown that mice with Coxsackie B3 myocarditis have low myocardial ATP and high ADP and AMP levels. This pattern of abnormal energy metabolism is also seen in patients with Syndrome X. It is suggested that the ECG and thallium perfusion scintigram suggestive of ischemia in such patients is rather due to the effect of an ionophore leading to an extracellular potassium shift.
Adenine Nucleotides↗
Increased membrane activity of glyceraldehyde 3-phosphate dehydrogenase in erythrocytes of patients with homozygous sickle cell anaemia.
Membrane-bound glyceraldehyde 3-phosphate dehydrogenase activity was measured in erythrocytes from 43 patients with sickle cell anaemia, 24 heterozygous and 27 controls. A significant increase of the activity was found among the patients but no such difference was observed between the heterozygous and the control individuals. The patients showed nearly non Gaussian distribution of the enzyme activity and were subgrouped on the basis of these results, subgroup I had normal values and subgroup II showed markedly increased activities. The patients in subgroup II had significantly lower blood haemoglobin concentrations and significantly higher lactate dehydrogenase activities in serum than subgroup I. The subgroups did not differ in blood reticulocyte counts, serum bilirubin, serum iron concentrations or band 3 protein content of erythrocyte membranes.
Adolescent↗
Membrane transport properties of L-2,4-diaminobutyrate revisited.
We explore here the special structural features of certain diamino acid analogs which may account for their intense accumulation into tumor cells, first observed for the Ehrlich ascites tumor cell for in vitro suspensions. This accumulation, which ordinarily occurs mainly by system A for its dipolar substrates, is so intense for these tripolar diamino acids accompanied by the chloride ion as well as by displacement, especially of the cellular potassium ion, that the cells swell to several times their normal volume and osmotic destruction arises. These structural features receive our reconsideration here toward understanding the energization of amino acid transport into cells, also toward identifying among them possible superior 11C-labeled tracers for imaging tumors in situ by positron emission tomography (PET). The possibility of therapeutic, perhaps osmotic, destruction of inoperable terminal gliomas by topical application of such amino acids by microdialysis has also been considered in preliminary tests by one of us (G.R.) and his associates.
Amino Acids↗
Treatment of malignant glioma by a new therapeutic principle.
L-2, 4 diaminobutyric acid (DAB) is a non-physiological, cationic amino acid transported into cells by System A with potent antitumour activity in vitro against human glioma cells. This activity was the result of the pronounced concentrated uptake of DAB in glioma cells to the extent that a cellular lysis could occur due to osmotic reasons. We describe the treatment of 3 patients with inoperable malignant glioma by direct and continuous administration of DAB in tumour tissue employing a microdialysis technique. One to three microdialysis probes were implanted in the tumour tissue through small dural incisions in 3 patients with inoperable malignant glioma. Micropumps charged with 3 ml a day of a Tris-buffered 0.125 M DAB solution made isotonic at pH 7.55 were adapted to the input channel of the probe and a sampling tube to the output for continuous flowing into tumour tissue. The patients were treated in this way for a total of 14-21 days without side effects assignable to DAB. Massive tumour necrosis occurred as judged by comparison of computed tomography performed before and after DAB treatment. The yield of the dialysis procedure with regard to DAB was estimated to be 40-50%. The dialysate concentration of arginine (a cationic amino acid considered to be transported mainly by system A) was high and increased nearly 4-fold from day 3 to day 6 of treatment. DAB administered in this way into malignant brain tumour tissue was well tolerated and showed promising antitumour activity in the 3 patients with inoperable malignant glioma.(ABSTRACT TRUNCATED AT 250 WORDS)
Aminobutyrates↗
Influence of beta 1-blockade on myocardial substrates early after a coronary operation.
A high adrenergic strain during reperfusion after ischemia impedes functional recovery. Conversely, adrenergic blockade may be beneficial during reperfusion. This study was undertaken to find out if early postoperative high-dose infusion of the selective beta 1-blocking agent metoprolol tartrate has additional effects on metabolic variables related to myocardial energy supply/demand balance compared with those obtained with a late preoperative oral dose. The study included 21 male patients undergoing coronary bypass grafting. All patients received an oral dose of metoprolol before the operation. After the operation, patients were randomized to a control group or a group receiving intravenous infusion of metoprolol. Myocardial uptake of oxygen and substrates was determined before and during atrial pacing. Metoprolol reduced arterial concentrations of free fatty acids, reduced myocardial uptake of free fatty acids, and enhanced myocardial uptake of lactate. During paced tachycardia, the metoprolol concentration correlated negatively with myocardial uptake of free fatty acids (r = -0.80; p < 0.001) and positively with myocardial uptake of lactate (r = 0.53; p < 0.05). It is concluded that postoperative infusion of metoprolol induces myocardial metabolic changes compatible with an improved energy supply/demand balance.
Administration, Oral↗