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Biomedical subjects

G Ronquist

Publications and source records attributed to G Ronquist.

At least 91 records · Page 5Linked to original sources
PubMed1994

Enhanced recruitment of motile spermatozoa by prostasome inclusion in swim-up medium.

Prostasomes, which are prostate-derived organelles, were purified from human seminal plasma for inclusion in Earle's balanced salt solution (EBSS) medium with or without human serum albumin. These media were used for swim-up experiments and the subsequent analyses of sperm motility parameters at different incubation times. The yield of motile spermatozoa after swim-up in EBSS medium enriched with boiled prostasomes was increased by 32% compared with EBSS containing albumin. Native prostasomes were less active. Combinations of albumin and either prostasomes or boiled prostasomes significantly increased the recovery of motile spermatozoa and also increased the percentage of spermatozoa displaying progressive motility after 1 h of incubation. Media lacking albumin showed lower values regarding progressive motility after 22 h of incubation. A beneficial effect of prostasomes was noted on lateral head displacement and percentage of hyperactive spermatozoa during the first 6 h of incubation. These results suggest that inclusion of prostasomes, especially boiled prostasomes, in swim-up media may improve the recovery of hyperactive motile spermatozoa for up to 6 h in cases of established male factor infertility, and consequently increase the opportunities for fertilization.

Hot Temperature↗
PubMed1994

Direct effect of insulin on 45calcium uptake in human erythrocytes.

OBJECTIVE: High blood pressure is prevalent in obesity and non-insulin dependent diabetes mellitus; both conditions, with insulin resistance and essential hypertension, have been associated with increasing intra-erythrocytic levels of calcium ions. We tested the hypothesis of whether insulin itself might be responsible for the abnormal red cell cytosolic free calcium. DESIGN: The ionic effects of insulin were studied on the kinetics of 45calcium uptake in vitro in normal human erythrocytes. SETTING: The study was performed in the outpatient clinic of a central hospital. SUBJECTS: Sixteen healthy, normotensive individuals with normal body mass index were recruited for the study. MAIN OUTCOME MEASURES: Blood from eight individuals was used for time-dependent studies of 45calcium uptake in erythrocytes and blood from another eight individuals was used for dose-dependent studies of insulin effect. RESULTS: The rate of 45calcium influx in red blood cells has two components, a fast component (0-10 min), which measures the initial rate of 45calcium influx, and a slow component (10-60 min) probably reflecting a relatively large backflux of calcium (calcium efflux), which accordingly determines an apparent low rate of 45calcium influx between 10-60 min. The uptake was linear with time between 10-120 min regardless of insulin being present or not. Insulin at a concentration of 120 mU L-1 significantly decreased the 45calcium uptake in a time-dependent fashion between 10-120 min. The uptake was 508 (+/- 59) at 60 min in the presence of insulin vs. a control value of 529 (+/- 59) pmol mL red blood cells-1 (P < 0.001). The corresponding figures at 120 min were 742 (+/- 109) and 767 (+/- 127), respectively (P = 0.02). Inconsistent results were obtained on 45calcium uptake at 60 min by varying insulin concentrations from 40-640 mU L-1 and a dual effect of insulin on 45calcium uptake could not be excluded, one at a fairly low concentration of insulin (40-120 mU L-1) and another at a high concentration (160-640 mU L-1). CONCLUSION: The data indicate a direct role of insulin in the transport process of calcium into normal human erythrocytes.

Calcium Radioisotopes↗
PubMed1994

Dynamic changes of myocardial inositoltrisphosphate and cyclic nucleotides: relationship to contractile response in the perfused working rat heart after adrenergic and muscarinic agonist stimulation.

Initial and late effects by adrenergic and muscarinic agonists on inositol trisphosphate (IP3) and cyclic nucleotide levels were determined and correlated to mechanical response in perfused rat hearts. Forty-three rat hearts were perfused with Krebs-Henseleit buffer in a modified Langendorff apparatus as a working preparation. The hearts were perfused as controls (n = 11), or with noradrenaline (10(-6) mol l-1) (n = 21), or with carbachol (3 x 10(-7) mol l-1) (n = 11) added to the perfusion buffer. The hearts were frozen at 20 s, 30 s and 40 min after addition of noradrenaline and at 20 s and 40 min after addition of carbachol, and after 5 and 45 min of control perfusion. cAMP and cGMP were determined by radioligand methods and IP3 by a combined fast performance liquid chromatography (FPLC)-isotachophoretic method. cAMP increased by 36% within 20 s followed by a decrease (22%) during the 10 s following noradrenaline addition. After 40 min cAMP regained its value near that of 20 s. Noradrenaline perfusion did not influence IP3 levels during the first 30 s although the value at 40 min was significantly higher (59%). IP3 increased (42%) after 20 s of carbachol perfusion followed by a 25% decrease at 40 min. Sustained stimulation of beta-receptors (after 40 min in our model) resulted in a repeated increase in cAMP only, without an increase in contractility.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Treatment of renal anaemia with recombinant human erythropoietin results in decreased red cell uptake of 45Ca.

The ability of erythrocytes to undergo deformation may be of importance to erythrocyte survival and to blood flow resistance. In a previous study a decreased deformability was demonstrated in the erythrocytes of uraemic patients treated with recombinant human erythropoietin (rhEPO). Erythrocyte deformability is, at least partly, determined by the intracellular concentration of free calcium ions. Six patients with renal anaemia (initial haemoglobin 95 +/- 11 g/l) were treated with rhEPO. They were examined with regard to certain erythrocyte characteristics before treatment and after reaching a haemoglobin concentration exceeding 120 g/l. A decrease was noted upon treatment in erythrocyte deformability and uptake of 45Ca in vitro. The blood pressure tended to increase. The individual values of the decrease in 45Ca uptake and the increase in systolic blood pressure were positively correlated to each other (r = 0.87; p < 0.05). No correlation was found between changes in erythrocyte deformability and 45Ca uptake. The decrease in 45Ca uptake may be interpreted in two different ways. It could reflect a reduced membrane permeability to calcium ions, or, which is more probable, it could be the end result of an increase in the intracellular metabolic pool of free calcium ions caused by the rhEPO treatment. We, therefore, conclude that rhEPO treatment has certain effects on calcium homeostasis in erythrocytes which may be related to blood pressure regulation.

Adult↗
PubMed1994

Parasympathetic muscarinic stimulation limits noradrenaline induced myocardial creatine kinase release: a study in the isolated perfused working rat heart.

It has long been known that high concentrations of catecholamines may induce myocardial damage, and aggravate ischaemic injury. It has also been shown that beta-blockade may protect the myocardium from ischaemic damage. Stimulation of muscarinic receptors modulates beta-adrenergic receptor affinity for isoproterenol and attenuates isoproterenol induced adenylyl cyclase activation. Effects of muscarinic receptor stimulation were therefore investigated in isolated anterogradely perfused rat hearts under different experimental conditions. One group of hearts was perfused with noradrenaline, 10(-6) mol l-1 for 45 min, and another group was perfused with different carbachol concentrations (3 x 10(-7)-10(-5) mol l-1) with or without noradrenaline 10(-6) mol l-1, for 45 min. Release of creatine kinase to the perfusion buffer was taken as a sign of cell damage. Heart rate, left ventricular maxdP/dt and left ventricular pressure were measured throughout the perfusion time by insertion of a 20 gauge cannula through the left ventricular wall near the base. Carbachol (3 x 10(-7) mol l-1) alone induced a decrease of heart rate by 25% and maxdP/dt by 13%. Noradrenaline produced a 20% increase in heart rate, whereas the combination of noradrenaline plus carbachol induced a minor decrease in heart rate. Muscarinic receptor stimulation alone decreased myocardial contractility. However, when combined with noradrenaline no decrease in contractility was seen. Also, the release of creatine kinase to the perfusion buffer containing the combination of carbachol plus noradrenaline was reduced. Thus, muscarinic receptor stimulation protected the myocardium from catecholamine induced damage at concentrations where no change in contractility was seen.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Myocardial metabolism 8 hours after coronary surgery: effects of dopamine.

Myocardial substrate metabolism is abnormal in the early period after cardiac surgery. Myocardial uptake of substrates remains restricted 6 hours postoperatively and cannot match the demand during periods of increased energy requirements. We investigated the relationship between myocardial oxidative rate and substrate uptake in 22 men c. 8 hours after coronary surgery. Myocardial energy demand was raised experimentally by infusing dopamine. The influence of selective beta 1-blockade was analyzed. The uptake of free fatty acids dominated (34.74 +/- 8.83 mmol/min*10(-3) and sufficed to explain the oxygen consumption in basal postoperative conditions (0.468 +/- 0.051 mumol/min) and during amplified energy requirements (0.881 +/- 0.117, r = 0.71). Although the capacity to adjust substrate uptake to energy requirements thus was regained, the uptake of glucose and of lactate (6.14 +/- 13.13 and 2.29 +/- 20.31 mmol/min*10(3) respectively) was marginal, which may be important for ischaemic tolerance. Metoprolol influenced oxygen consumption during amplified adrenergic activity, but did not markedly affect substrates.

Coronary Artery Bypass↗
PubMed1993

High adenosine content in human uterine smooth muscle compared with striated skeletal muscle.

We determined the concentrations of adenosine and some of its catabolic products in biopsy specimens from predetermined loci of human myometrium under different functional conditions to compare uterine muscle with rectus abdominis muscle from the same individuals. In order to achieve a good resolution in the separation of nucleosides and purine bases, a preseparation procedure was developed prior to analysis of these compounds on high performance liquid chromatography. Adenosine occurred in a nearly 70-fold higher concentration in smooth uterine muscle in comparison with striated skeletal muscle. Similarly, myometrial inosine and hypoxanthine were 7- and 2.4-times in excess over the rectus muscle, whereas xanthine was scarcely and rather evenly represented in the two types of muscles. The uterine content of adenosine and inosine was distinctly higher in pregnant women compared to non-pregnant ones. A regional difference existed for adenosine, with 3.3 times higher concentration in fundus uteri compared to the isthmic part. A reverse pattern was observed for hypoxanthine and inosine, being 2-3 times more frequent in the isthmic part. The orthophosphate concentration was not stoichiometrically related to the adenosine concentration in a simple way, being 2-3 times lower in uterine muscle compared to the skeletal muscle. A significant correlation existed between uterine contents of AMP and adenosine and similarly, significant inverse correlations were apparent between uterine ATP and ADP contents and energy charge on one hand and adenosine content on the other.

Adenosine↗
PubMed1993

Energy economy in the pregnant human uterus at term: studies on arteriovenous differences in metabolites of carbohydrate, fat and nucleotides.

Metabolic regulation was studied in the pregnant human uterus by determining its uptake and release of various substrates, some of which are commonly used as a fuel and some are markers of disturbed energy status in cells. Ten healthy women with normal pregnancy were examined when undergoing elective Caesarean section at term, before onset of labour. Carbohydrate metabolites (glucose, lactate and pyruvate), fat metabolites (free fatty acids (FFA) and glycerol) and nucleotide metabolites (hypoxanthine, xanthine and urate) were determined in arterial (radial artery) and venous (plexus of the uterine and ovarian veins) blood. In addition the arteriovenous difference in each substance across the uterus was calculated. A distinct uptake of glucose was a typical finding in the pregnant uterus as reflected by a positive difference. On the other hand, glycerol and FFA were released from the pregnant uterus. Similarly, a degradation of adenine-containing nucleotides seemed to be continuously ongoing in the pregnant uterus, since oxypurines displayed a negative difference as well.

Adult↗
PubMed1993

Dissipation of the calcium gradient in human erythrocytes results in increased heat production.

Heat production rates were measured by a microcalorimetric method in suspended human erythrocytes in the absence and presence of different concentrations of the divalent cationophore A23187. Determinations were carried out during 60 min under static conditions on erythrocytes incubated in various isotonic media at 37 degrees C, pH 7.35. In incubations containing the ionophore, time-power curves showed an early peak followed by a descending slope levelling off at a steady state after 30-60 min. In contrast, the controls lacked the early peak, showing hyperbolic ascending curve profiles before reaching steady state. The appearance of the early peak in the presence of ionophore was dependent upon the composition of the medium, both Mg2+ ions and glucose being decisive. Likewise, dose-response relationships concerning heat production at 60 min depended on the composition of the media. In a basic incubation medium lacking Mg2+ and glucose, no effect was seen on heat production by the ionophore (1-3 mumol/l). Rather modest effects were obtained by the ionophore at 2 and 3 mumol/l when Mg2+ was present. A clear-cut dose-response relationship was observed in a Mg2+ and glucose enriched medium for the ionophore from 1-3 mumol/l. The significant increase in heat production observed at 60 min with 2 mumol/l of A23187 in the Mg2+ and glucose enriched medium was abolished by 1 mmol/l EGTA. Calmidazolium, a calmodulin antagonist, could only marginally reduce the ionophoric effect on heat production. It was concluded that the appearance of the early peak was not the result of an increase in glycolytic rate but rather a consequence of the ionophoric action on the Ca2+ gradient.

Adenosine Triphosphate↗
PubMed1993

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↗
PubMed1993

[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↗
PubMed1993

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↗
PubMed1993

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↗
PubMed1993

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↗
PubMed1993

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↗
PubMed1993

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↗