Search PubMed⌕ Search

Biomedical subjects

G Ronquist

Publications and source records attributed to G Ronquist.

At least 73 records · Page 4Linked to original sources
PubMed1995

Association of some hydrolytic enzymes with the prostasome membrane and their differential responses to detergent and PIPLC treatment.

Prostasomes are human prostate derived organelles that were isolated from both prostatic fluid and seminal plasma for the present study. Specific activities were determined for prostasome membrane-associated enzymes, alkaline phosphatase (ALP), 5'-nucleotidase (5'NT), and alkaline phosphodiesterase I (APD). The mode of their membranous anchoring was studied by treatment of prostasomes with phosphoinositol-specific phospholipase C (PIPLC) and different detergents. A substantial amount of ALP (50%) and 5'NT (31%) was released by incubation of prostasomes with 2 U/ml of PIPLC contrary to the small amount of APD (12%) released by the same treatment. After PIPLC treatment, the enzymes were recovered in the aqueous phase after phase repartition in Triton X-114 indicating that PIPLC removed the hydrophobic domain converting the enzymes from membrane-linked to aqueous soluble forms. Octyl glycoside was the most efficient one among different detergents to solubilize the enzymes from the prostasome membrane. Both ALP and 5'NT were resistant to the treatment with Triton X-100 and Triton X-114. These results suggest that ALP, 5'NT, and APD are more or less extensively linked to the prostasome membrane via a glycophosphoinositide anchor.

5'-Nucleotidase↗
PubMed1995

Abundance of guanine, guanosine, inosine and adenosine in human seminal plasma.

Guanine, guanosine, inosine and adenosine were found in large amounts in seminal plasma from 145 men, regardless of whether spermatozoa were present or not. The mean guanine level in 61 normozoospermic men was 89.7 +/- 93.1 mumol/l; this was significantly lower in 32 vasectomized men (18.9 +/- 31 mumol/l) suggesting the involvement of the epididymis in its secretion. Guanine and nucleoside levels were significantly higher in the seminal plasma of oligozoo- and azoospermic than normozoospermic men. Guanine and nucleoside levels were consistently inter-related in the seminal plasma of normozoospermic men with the best correlation between guanine and guanosine.

Adenosine↗
PubMed1995

Prolongation and improvement of prostasome promotive effect on sperm forward motility.

Prostasomes isolated from human seminal plasma stimulated the forward motility of buffer-washed, and therewith immobilised, normal human spermatozoa in a dose- and time-related fashion. Albumin exhibited a similar capacity for stimulation. Combining prostasomes with 5 mmol/l of any of the hexoses fructose, glucose or mannose (but not galactose) resulted in a prolongation and improvement of the effect by prostasomes (or albumin) for the first 150 min. Hence, a dose-response effect at 60 and 120 min was obtained by prostasomes on sperm forward motility provided 5 mmol/l of fructose was present--otherwise not. Many substances besides the hexoses were examined for possible positive effects on sperm forward motility in concert with prostasomes with no additional effect. Enrichment of optimum concentrations of prostasomes and glucose with 2 mmol/l of adenine stimulated further the velocity parameters of the spermatozoa over time. The effect of adenosine was less evident under these conditions. Experiments carried out with prostasomes in the presence of divalent cations or chelators suggested that magnesium ions are essential for sperm forward motility. There appeared to be a safety margin concerning calcium ions, and zinc ions did not seem to be primarily involved in sperm forward motility in the presence of prostasomes.

Hexoses↗
PubMed1995

Energy economy of human uterine muscle strips under different in vitro conditions and its dependence on tissue redox potential.

OBJECTIVE: To study the energy economy of human myometrium in vitro. STUDY DESIGN: Myometric biopsies were kept for 10 min or 4 h in a buffer solution at +4 degrees C before preparation into 'early' and 'late' strips, respectively. The strips were perifused at +37 degrees C for different periods of time. Adenylates, energy charge (EC), adenosine and NAD+ were determined in individual strips. RESULTS: Mean EC and ATP values were low, the 'late' strips displaying 5% and 20% lower values than the 'early' strips, respectively. During perifusion the EC increased slightly, ADP decreased significantly and the strips began to contract. A correlation fitting a multiplicative function was evident between EC and NAD+ (r = 0.89, P < 0.001). CONCLUSION: Human myometrium, being operative at an unusually low EC level, maintained its energy economizing and contractile functions in vitro for 4 h, displaying a tight relationship between EC and NAD+, suggestive of a compromised energy balance.

Adenosine Diphosphate↗
PubMed1995

Different energy metabolite pattern between uterine smooth muscle and striated rectus muscle in term pregnant women.

OBJECTIVE: To study the energy metabolite pattern in term pregnant myometrium and to compare it with that of a striated skeletal muscle. STUDY DESIGN: Metabolites of carbohydrates, triglycerides and nucleotides were determined in biopsies from myometrium and rectus abdominis muscle from ten healthy term pregnant women before onset of labour. The metabolite concentrations in the two types of muscle were compared by two tailed Student's t-test for paired values and correlations were calculated by Pearsson's correlation test. RESULTS: Comparison of the two muscle types revealed a higher concentration of glucose and a higher lactate/pyruvate ratio in the myometrium but a lower concentration of triglyceride metabolites. Adenosine was found in 36-fold higher concentration in the uterine compared with the rectus muscle and an inverse relationship between adenosine and glucose concentrations was observed in the myometrium. CONCLUSION: The results indicated that the pregnant uterine smooth muscle utilized glucose as the principal nutritive metabolite rather than lipids and that the anaerobic pathway of the glucose metabolism was more active in the myometrium compared with the striated rectus muscle. Also, it is suggested that glucose has a critical role as the principal fuel for ATP formation and the involvement of the adenylate kinase and 5'-nucleotidase reactions in any event of glucose shortage.

Adult↗
PubMed1995

Continuous monitoring of energy metabolites using microdialysis during myocardial ischaemia in the pig.

A diagonal branch of the left anterior descending artery was occluded for 80 min. One microdialysis probe was inserted in the ischaemic area and two in the non-ischaemic areas. In six animals radiolabelled microspheres were injected before and during ischaemia and after reperfusion to monitor flow. Arterial and pulmonary artery pressures, pulmonary capillary wedge pressure and cardiac output were followed-up. Radiolabelled microsphere distribution confirmed the reduction of myocardial blood flow during coronary artery occlusion, with flow returning to normal values upon reperfusion. Rate pressure product as an index of heart work was stable throughout the 80 min ischaemic period, but increased at reperfusion. Dialysates from non-ischaemic tissue showed stable baseline values. In ischaemic tissue, lactate increased by 300% and pyruvate levels decreased by 50% within 15 min. Adenosine increased rapidly five-fold, but started to decline after 15 min of ischaemia. Inosine showed a slower but a marked 20-fold increase, decreasing at the end of the ischaemic period. Hypoxanthine increased five-fold during the first 30 min. Finally, guanosine showed a slow increase to about four times above basic values. Microdialysis was an excellent tool for the continuous monitoring of myocardial metabolites during ischaemia. Adenosine appeared to be a more sensitive marker of early ischaemia than lactate, although interestingly, adenosine levels had decreased already after 15 min, most probably due to intracellular accumulation of protons and Pi.

Adenosine↗
PubMed1995

Dynamics of myocardial metabolism in the preconditioned porcine heart studied using continuous microdialysis.

A microdialysis technique was used to measure myocardial catabolism of adenine nucleotides during preconditioning. Following thoracotomy in domestic pigs, a probe was inserted into the ischaemic myocardium and two probes into normal myocardium. Preconditioning was instituted by occluding a diagonal branch of the left anterior descending coronary artery four times over a 10 min period (interspersed with 20 min of reperfusion each time), followed by index ischaemia for 40 min and terminated by 20 min of reperfusion. Non-preconditioned animals, which had been subjected to 40 min ischaemia and 20 min of reperfusion were used as controls. Sham operated animals were additional controls. Following equilibration, the dialysis fluid was continuously pumped and the microdialysate analysed at 5 min intervals. In the dialysate, the amount of lactate, pyruvate, adenosine, inosine, hypoxanthine and guanosine was measured. Circulatory parameters were: rate pressure product, pulmonary artery pressures, cardiac output and pulmonary wedge pressure. There was no significant statistical difference in cardiac work between preconditioned pigs and controls. A sharp rise in adenosine was observed during the first short ischaemic period with attenuation during the following three short ischaemic periods. In the microdialysate, lactate, adenosine, inosine, hypoxanthine and guanosine were significantly lower during index ischaemia in the preconditioned group than in the non-preconditioned group. Pyruvate levels decreased during preconditioning and rose to a higher level after each brief ischaemic period, followed by a decrease, which was proportionally similar in the preconditioned and unpreconditioned animals during index ischaemia. The effect of preconditioning on lactate and catabolite levels indicated a powerful inhibition of adenine nucleotide catabolic processes due to ischaemia.

Adenine Nucleotides↗
PubMed1995

Alzheimer amyloid beta-peptides exhibit ionophore-like properties in human erythrocytes.

There is growing evidence that the amyloid beta-peptide (beta 1-40) is involved in the aetiology of Alzheimer's disease also implicating an altered calcium homeostasis of affected cells. Beta 1-40 has been proposed to form calcium channels in synthetic bilayer membranes [1]. We wanted to investigate in the present study whether beta 1-40 (or fragments thereof) could act as ionophores in a biological membrane like the one in human erythrocytes. Incubation of the cells for 2 h and 4 h at 37 degrees C together with 6 mumol L-1 of beta 1-40 or of fragments beta 1-28 and beta 25-35, resulted in a significantly decreased energy charge qualitatively similar to the one obtained by a known calcium ionophore (A 23187, 0.05 mumol L-1). Moreover, beta 1-40 and its two fragments induced a significant alteration of 45Ca permeability in human red blood cells of the same type as the one achieved by the calcium ionophore. The ionophoric action of beta 1-40 and its two fragments may lead to an increase of the intracellular calcium ion concentration, in turn resulting in enhanced Ca(2+)-ATPase activity and a decrease in energy charge. This may be valid also for neuronal plasma membranes and could, therefore, be a possible aetiological mechanism in Alzheimer's disease.

Adenosine Diphosphate↗
PubMed1995

Disturbed energy balance in skeletal muscle of patients with untreated primary hypertension.

OBJECTIVE: It has been shown that the distribution of Na+ and Ca2+ in various cells is abnormal in patients with untreated primary hypertension, indicating an altered membrane permeability in these cells. This would activate certain ion pumps and thereby enhance ATP turnover. We investigated possible alterations in energy economy of skeletal muscle tissue. DESIGN: Skeletal muscle energetics were studied in vitro and in vivo in patients with untreated primary hypertension. Phosphocreatine (PCr), energy charge (EC) and total adenylate values were assessed. SETTING: The study was performed at the outpatient clinic of a general hospital and at a university clinical chemistry department and at a specialized bioenergetic laboratory. SUBJECTS: Altogether, 17 patients with untreated primary hypertension were examined together with matched, healthy and normotensive controls with normal body-mass index. MAIN OUTCOME MEASURES: Skeletal muscle biopsies were obtained from 10 patients and 10 controls for analysis of high energy phosphate compounds. Another seven patients were enrolled for in vivo NMR spectroscopy. RESULTS: We found a decrease of 30% (P < 0.01) of PCr content in the patients, whilst EC and total adenylates were unchanged. Nuclear magnetic resonance spectroscopy showed an abnormal decrease of PCr during exercise followed by a markedly slower regeneration of PCr during post-exercise recovery parallelled by a slower recovery of pH. This phenomenon was mirrored by a more pronounced decrease of ATP/Pi in patients during exercise and a slower recovery of ATP/Pi. CONCLUSION: The data are compatible with an increased ATP turnover in skeletal muscle cells of patients with untreated primary hypertension although ATP was favoured and kept at a normal resting level at the expense of the PCr store.

Adenosine Triphosphate↗
PubMed1995

Myocardial inositoltrisphosphate is depressed by dibutyryl cAMP. An experimental study in the isolated working rat heart.

A possible interrelation between IP3 and cAMP was studied in rat myocardium through circumvention of the receptor mediated stimulatory step of adenylyl cyclase by the administration of dibutyryl cAMP (db-cAMP). Changes in IP3 and cyclic nucleotide contents were correlated to changes in contractility after 40 min of beta- and alpha-adrenergic stimulation. Rat hearts (n = 23) were perfused with Krebs-Henseleit buffer in a modified Langendorff apparatus as a working preparation. The hearts were allocated to perfusion as control (n = 6); or with phenylephrine (10(-6) mol L-1, n = 6); (-)-isoproterenol (10(-6) mol L-1, n = 6); db-cAMP (2 x 10(-4) mol L-1, n = 5). All hearts were freeze-clamped after 40 min of perfusion. Phenylephrine produced a slow increase in maxdP/dt reaching a maximal value after 10 min (P < 0.05); thereafter it decreased, reaching the control level at 30 min. Isoproterenol perfusion resulted in an early (20 s) increase in maxdP/dt (P < 0.05). Over the next 10s maxdP/dt decreased markedly reaching an inflection point at 30 s. Thereafter only a slow increase during the rest of the perfusion was seen. Dibutyryl cAMP increased maxdP/dt slowly during the whole perfusion period reaching maximum after 40 min. Cyclic-AMP was increased by 21% after 40 min of phenylephrine perfusion while the corresponding increases by isoproterenol and db-cAMP were 131 and 105%, respectively (P < 0.05). Phenylephrine increased IP3 content to the same extent as isoproterenol perfusion (P < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

Carbachol-induced increase in inositol trisphosphate (IP3) content is attenuated by adrenergic stimulation in the isolated working rat heart.

The interrelated responses of concomitant adrenergic and muscarinic receptor stimulation on second messengers and mechanical activity in the isolated perfused working rat heart were studied. The hearts were perfused with Krebs-Henseleit buffer in a modified Langendorff apparatus. The hearts were perfused with noradrenaline (10(-6) mol L-1, n = 20), with carbachol (3 x 10(-7) mol L-1, n = 11) or with noradrenaline plus carbachol (n = 20) in the above-mentioned concentrations. The hearts were frozen at 20 s, 30 s and 40 min after addition of noradrenaline and noradrenaline plus carbachol and at 20 s and 40 min after addition of carbachol. Five hearts were freeze-clamped directly after preperfusion and another five hearts after 40 min of perfusion and used as controls. Myocardial cAMP increased at 20 s and 40 min after noradrenaline perfusion. In contrast to this cAMP was unchanged at 20 s and decreased at 40 min after perfusion with noradrenaline plus carbachol. IP3 content increased after 20 s of carbachol- and after 40 min of noradrenaline perfusion (P < 0.05). However, noradrenaline plus carbachol did not induced any significant increase in IP3 content after 20 s and 30 s, but after 40 min a decrease below basal level was found (P < 0.05). Noradrenaline stimulation attenuated muscarinic agonist induced IP3 formation. A reciprocity existed in that noradrenaline induced IP3 formation was attenuated by carbachol. No direct relationship was observed between the IP3 response and contractility, also valid for cAMP.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Triphosphate↗
PubMed1995

The value of prostate specific antigen in early diagnosis of prostate cancer: the study of men born in 1913.

PURPOSE: We attempt to elucidate the performance of serum prostate specific antigen (PSA) as a screening test for prostate cancer. MATERIALS AND METHODS: We analyzed sera stored since 1980 in a nested case-control study. RESULTS: The 36 patients with prostate cancer had a markedly greater mean serum PSA level than did 68 subjects without cancer (22.71 versus 2.67, respectively, p < 0.0001). Among the controls 24% had a serum PSA of greater than 4.0 micrograms/l. A serum PSA value exceeding 4.0 micrograms/l. in 1980 was associated with a 20-fold excess risk of cancer between 1981 and 1986, and an 8-fold risk between 1987 and 1991. CONCLUSIONS: Diagnosis of clinically significant prostate cancer can be advanced substantially by serum PSA testing. However, the large number of high serum PSA values in men who remained free of clinical disease emphasizes the need for a more specific screening test.

Aged↗
PubMed1995

Multicentre evaluation of a non-wipe system for the rapid determination of total cholesterol in capillary blood, Accutrend Cholesterol on Accutrend GC.

Accutrend Cholesterol, a non-wipe test for the determination of total cholesterol in capillary blood, was evaluated at four clinical centres. Cholesterol determinations with the Accutrend system using capillary blood were compared with results obtained with the cholesterol oxidase/p-aminophenazone (CHOD-PAP) method using the respective capillary sera. Triacylglycerols, uric acid and haematocrit were determined to evaluate potential interference. Imprecision measurements were performed with venous blood. To examine the reproducibility of results from lot to lot, three different lots of test strips were included in these investigations. Results with Accutrend Cholesterol agree with those of the comparison method within systematic differences of +2.5% to -3.2%, depending on the lot. There was no interference by triacylglycerols up to 10.28 mmol/l (900 mg/dl), by uric acid 60 to 400 mumol/l (1 mg/dl to 7 mg/dl), or by haematocrits between 0.35 and 0.54. Impression data show coefficients of variation of generally less than 5%. Thus Accutrend Cholesterol proved to be a reliable system for the determination of total cholesterol.

Blood Chemical Analysis↗
PubMed1994

Low energy charge and high adenosine content in smooth muscle of human bladder in comparison with striated muscle.

This study determined the energy charge, adenosine and inosine content of human bladder smooth muscle in comparison with striated muscle of the same individual. Biopsies were obtained from 21 women who were subjected to urethrocystopexy because of urinary stress incontinence. We found that the ATP content of bladder smooth muscle was only about one-eighth of that of striated muscle. The energy charge of bladder smooth muscle was 0.78 +/- 0.13, which is low compared with striated muscle (0.92 +/- 0.02). The adenosine content of bladder smooth muscle was 6.7 times higher than striated muscle and the adenosine/ATP ratio was 1:9 compared with 1:450 for striated muscle. These findings were in accordance with our previous studies on uterine smooth muscle.

Adenosine↗
PubMed1994

Promotive effect by prostasomes on normal human spermatozoa exhibiting no forward motility due to buffer washings.

Prostasomes, small corpuscular organelles derived from the prostate gland, were isolated from human seminal plasma by means of ultracentrifugation and Sephadex G 200 chromatography to assess objectively their promotive effect on the motility of buffer-washed normal human spermatozoa exhibiting no forward motility. Prostasomes were efficacious in about 70% of these spermatozoa, and a maximum value was obtained with prostasomes at a concentration corresponding to a protein content of 0.7-0.8 g/l followed by a plateau at higher concentrations. Addition of albumin alone resulted in a similar response although at a somewhat lower level and about 50% of the spermatozoa were rendered motile with a maximum effect of albumin at about 2.5 g/l. Albumin concentrations exceeding 3 g/l were less active. At protein concentrations of 0.25 g/l, prostasomes were superior to albumin in every respect concerning the effects on various sperm movement characteristics. These divergent effects were abolished when comparing prostasomes corresponding to a protein concentration of 0.75 g/l with albumin at 2.3 g/l, i.e. at their respective optimum concentration. Heat treatment and ultrasonication of prostasomes did not affect their motility-promoting properties. Some problem of sperm dysfunction has generally been considered to be a major contributory factor to infertility. By supplementing sperm preparations with postasomes in cases of established male factor, the already poor quality spermatozoa may more frequently be rendered capable of fertilization after insemination.

Humans↗
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↗