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W Zidek

Publications and source records attributed to W Zidek.

At least 73 records · Page 4Linked to original sources
PubMed2000

D609-phosphatidylcholine-specific phospholipase C inhibitor attenuates thapsigargin-induced sodium influx in human lymphocytes.

Previously, we reported that the phosphatidylcholine-specific phospholipase C (PC-PLC) inhibitor tricyclodecan-9-yl xanthogenate (D609) potentiates thapsigargin-induced Ca(2+) influx in human lymphocytes. In the present study we examined the effect of D609 on the thapsigargin-induced Na(+) entry. We found that the early phase of the thapsigargin-induced increase in the intracellular Na(+) concentration (approx. 1-2 min after stimulation) was attenuated after preincubation of lymphocytes with D609. By contrast, thapsigargin-induced Na(+) influx was not affected in the presence butan-1-ol, which inhibits phosphatidylcholine-specific phospholipase D (PC-PLD). The thapsigargin-induced Na(+) influx could be mimicked by PC-PLC exogenously added to the lymphocyte suspension, whereas addition of PC-PLD had no effect. In addition, thapsigargin stimulated formation of the physiological PC-PLC products, diacylglycerol. Cell-permeable diacylglycerol analogue, dioctanoyl-glycerol (DOG), produced time- and concentration-dependent increase in the intracellular Na(+) concentration. Both thapsigargin- and DOG-induced Na(+) increases were not affected in the presence of Na(+)/H(+) antiport inhibitor, HOE609, or Na(+)/Ca(2+) antiport inhibitor, dimethylthiourea, as well as in the presence of Co(2+) and Ni(2+), which block store-operated Ca(2+) entry. By contrast, markedly reduced thapsigargin- and DOG-induced Na(+) influx were noted in the presence of flufenamic acid, which blocks the non-selective cation current (I(CRANC)). In conclusion, our results suggest that diacylglycerol released due to the PC-PLC activation contributes to the thapsigargin-induced Na(+) entry.

Biological Transport↗
PubMed2000

Long-term treatment with continuous positive airway pressure improves quality of life in obstructive sleep apnoea syndrome.

Continuous positive airway pressure (CPAP) is an established treatment of obstructive sleep apnoea syndrome (OSAS). While it is known that CPAP reverses the pathological breathing pattern and improves daytime sleepiness, there are no sufficient data on the long-term influence of CPAP on quality of life in patients with OSAS. Thirty-nine patients with polysomnographically verified OSAS (apnoea/hypopnoea index (AHI): (mean+/-SD) 46.8+/-21.8 events x h(-1)) were prospectively studied. All patients answered three quality of life measures (Complaint List, Nottingham Health Profile Part 1 (NHP), and Verbal Analogue-Scale "quality of life") prior to the initiation of CPAP therapy. After a mean of 9 months they were re-evaluated by polysomnography, and completed the questionnaires once again. As expected, CPAP was effective in treating the sleep-related breathing disorder. AHI decreased significantly from (mean+/-SD) 46.8+/-21.8 events x h(-1) to 3.3+/-6.3 events x h(-1), and minimum oxygen saturation increased from 77.1+/-9.3% to 89.9+/-3.4%, while body mass index did not change significantly (31.3+/-5.4 versus 30.8+/-4.8 kg x m(-2)). During long-term treatment with CPAP the Complaint List revealed a significant improvement of the extent of subjective impairment due to physical and general complaints (26.4+/-9.9 versus 20.4+/-11.1), and NHP a significant improvement of emotional reactions (19.8+/-21.7 versus 11.1+/-14.0) and energy (50.8+/-36.6 versus 32.1+/-36.7), but not of pain, physical mobility, sleep, social isolation, and quality of life as assessed by the It is concluded that long-term continuous positive airway pressure therapy is effective in improving not only pathological breathing patterns but also parameters that estimate quality of life in patients with obstructive sleep apnoea syndrome.

Female↗
PubMed2000

Platelet function in patients with obstructive sleep apnoea syndrome.

Patients with obstructive sleep apnoea syndrome (OSAS) are subject to an increased cardiovascular morbidity including myocardial infarction and stroke. Platelets play an important role in the pathogenesis and triggering of acute cardiovascular syndromes. So far, the influence of OSAS on platelet function is not fully understood. Platelet aggregability to epinephrine, collagen, arachidonic acid, and adenosine diphosphate in vitro was measured in 17 consecutive male patients (53.0+/-2.1 yrs) with polysomnographically verified OSAS and compared with that of 15 male controls (50.1+/-3.6 yrs) at 20:00 h, 24:00 h, and 06:00 h. In addition, the long-term effects of continuous positive airway pressure (CPAP) therapy on platelet aggregability was assessed after 6 months. Platelet aggregation in vitro induced by epinephrine showed a slight increase overnight in the untreated OSAS patients (NS) whereas it decreased slightly (NS) in the controls and in the treated OSAS patients. Pretherapeutic platelet aggregability was significantly lowered by CPAP therapy both at 24:00 h (64.0+/-6.5 versus 55.3+/-6.7%, p<0.05) and at 06:00 h (64.1+/-6.5 versus 45.8+/-7.6%; p=0.01). Platelet aggregability during sleep in the controls resembled that found in patients with OSAS during CPAP therapy. The results suggest that obstructive sleep apnoea syndrome contributes, at least in part, to platelet dysfunction and that long-term continuous positive airway pressure treatment may reduce platelet aggregability.

Adult↗
PubMed2000

Increased sodium-proton antiporter activity in patients with obstructive sleep apnoea.

Cytosolic pH (pH(i)) and the activity of the sodium-proton antiporter (Na(+)/H(+) antiporter) were measured in lymphocytes from 22 patients with obstructive sleep apnoea and from 24 age-matched healthy subjects (Controls). The cellular Na(+)/H(+) antiporter was measured spectrophotometrically using a pH-sensitive fluorescent dye after intracellular acidification using sodium propionate. Resting pHi was similar in lymphocytes from patients with obstructive sleep apnoea and from controls (7.36 +/- 0.20, n=22; vs. 7.35 +/- 0.19, n=24; mean +/- SD). The Na(+)/H(+) antiporter activity was significantly higher in patients with obstructive sleep apnoea than in controls (11.87 +/- 3.26 x 10(-3) pH(i)/s vs. 4.38 +/- 1.40 x 10(-3) pH(i)/s; P < 0. 0001). The apparent affinity of the Na+/H+ antiporter was not significantly different between the groups (6.90 +/- 0.23 vs. 6.87 +/- 0.20). In patients with obstructive sleep apnoea the activity of the Na(+)/H(+) antiporter remained stable during the night. The activity of the Na(+)/H(+) antiporter was 13.49 +/- 4.80 x 10(-3) pH(i)/s at 20.00 and 13.26 +/- 6.13 x 10(-3) pH(i)/s at 02.00. From the present results it is concluded that an increased cellular Na(+)/H(+) antiporter activity may be a genetic marker for patients who are predisposed to obstructive sleep apnoea.

Aged↗
PubMed2000

Increased intracellular reactive oxygen species in patients with end-stage renal failure: effect of hemodialysis.

BACKGROUND: Reactive oxygen species (ROS) have been implicated in various forms of cellular injury. ROS may cause cell damage and are involved in the pathophysiology of several diseases, including atherosclerosis and chronic inflammation. METHODS: Disturbances of intracellular ROS levels were investigated in 28 patients with end-stage renal failure. The intracellular ROS levels were measured in lymphocytes before and after hemodialysis using biocompatible membranes and were compared with those from 11 patients with end-stage renal failure, not yet on renal replacement therapy, and 27 healthy control subjects. ROS levels were measured spectrophotometrically using the intracellular dye dichlorofluorescin diacetate. RESULTS: The spontaneous production of ROS was significantly higher in lymphocytes from patients with end-stage renal failure compared with healthy control subjects (P < 0.01). The addition of 100 nmol/L phorbol-myristate-acetate (PMA) produced a significant increase of ROS, both in lymphocytes from patients with end-stage renal failure and healthy control subjects. The PMA-induced ROS increase was significantly higher in lymphocytes from patients with end-stage renal failure compared with healthy control subjects (P < 0.01). In patients with end-stage renal failure, not yet on renal replacement therapy, the PMA-induced ROS was also significantly higher compared with healthy control subjects. The PMA-induced ROS increases were significantly inhibited by catalase, but not by superoxide dismutase or the superoxide dismutase mimetic, tempol. PMA-induced ROS was significantly reduced by tyrphostin A51 in lymphocytes from patients with end-stage renal failure and from healthy control subjects (each P < 0.01), indicating the involvement of a tyrosine kinase-dependent pathway. In patients with end-stage renal failure, the spontaneous and the PMA-induced production of ROS was not significantly different before and after hemodialysis. CONCLUSIONS: Regular hemodialysis sessions using biocompatible membranes have no effect on the elevated intracellular ROS in patients with end-stage renal failure.

Aged↗
PubMed2000

Increased intracellular generation of reactive oxygen species in mononuclear leukocytes from patients with diabetes mellitus type 2.

Since increased cellular production of reactive oxygen species is a source of oxidative stress and thus may contribute to the development of diabetic complications, the baseline and stimulated concentrations of intracellular reactive oxygen species were measured in 16 patients with diabetes mellitus type 2 and 19 healthy control subjects. Reactive oxygen species and cytosolic calcium were monitored spectrophotometrically using dihydrorhodamine-123 and fura-2, respectively, in a suspension of mononuclear leukocytes. Measurements were made in the presence or absence of superoxide dismutase, sodium azide, genistein, or bisindolylmaleimide 1. Baseline reactive oxygen species concentrations were significantly higher in diabetic patients compared with control (p<0.001). Activation of mononuclear leukocytes by formyl-Met-Leu-Phenylalanine and phytohemagglutinin significantly increased reactive oxygen species in diabetic patients compared with control (p<0.05). The formyl-Met-Leu-Phenylalanine-induced increases were unchanged in the presence of superoxide dismutase, but dropped significantly in the presence of sodium azide by 80% and 73% in diabetic patients and control, respectively (each p<0.01). The formyl-Met-Leu-Phenylalanine-induced responses were significantly inhibited by genistein and bisindolylmaleimide 1 (p<0.01), suggesting the involvement of tyrosine kinase and protein kinase C. Resting calcium (p<0.05) and stimulated calcium were significantly greater in diabetic patients than in control. The results show that patients with diabetes mellitus type 2 generate increased reactive oxygen species under stimulated conditions, suggesting increased risk for oxidative stress and associated complications.

Calcium↗
PubMed1999

Identification and characterization of P(1), P(7)-Di(adenosine-5')-heptaphosphate from human platelets.

Diadenosine pentaphosphate and diadenosine hexaphosphate have been isolated in human platelets and have been postulated to play an important role in the control of vascular tone. Here we describe the isolation and identification of diadenosine heptaphosphate from human platelets. Dinucleoside polyphosphates were concentrated by affinity chromatography from a nucleotide-containing fraction from deproteinated human platelets. Dinucleoside polyphosphates were purified by anion-exchange and reversed phase high performance liquid chromatography to homogeneity. Analysis of one of these fractions with matrix-assisted laser desorption/ionization mass spectrometry revealed a molecular mass of 1076.4 (1077.4 = [M + H](+)) Da. UV spectroscopic analysis of this fraction showed the spectrum of an adenosine derivative. Comparison of the postsource decay matrix-assisted laser desorption/ionization mass spectrum of the fraction minus that of diadenosine heptaphosphate (Ap(7)A) demonstrated that the isolated substance was identical to Ap(7)A. The identity of the retention times of the authentic and the isolated compound confirmed this result. Enzymatic analysis demonstrated an interconnection of the phosphate groups with the adenosines in the 5'-positions of the riboses. With thrombin-induced platelet aggregation, Ap(7)A is released from the platelets into the extracellular space. The vasoconstrictive action of Ap(7)A on the vasculature of the isolated perfused rat kidney Ap(7)A was slightly less than that of Ap(6)A. The threshold of the vasoconstrictive action of Ap(7)A was 10(-5) mol/liter. The vasoconstrictive effect was abolished by suramin and pyridoxal phosphate 6-azophenyl-2', 4'-disulfonic acid, suggesting an activation of P(2x) receptors. Furthermore, Ap(7)A inhibits ADP-induced platelet aggregation. Thus, the potent vasoconstrictor Ap(7)A derived from human platelets, like other diadenosine polyphosphates, may play a role in the regulation of vascular tone and hemostasis.

Adenosine Diphosphate↗
PubMed1999

High-performance liquid chromatographic assay of the diadenosine polyphosphates in human platelets.

Diadenosine pentaphosphate (Ap5A) and diadenosine hexaphosphate (Ap6A) were recently identified in human platelets and were shown to be important modulators of cardiovascular function. Here we describe an HPLC assay for quantitating Ap3A, Ap4A, Ap5A, and Ap6A contents in human platelets simultaneously. Di(1,N6-ethenoadenosine) hexaphosphate was used as internal standard. The extraction procedure consists of (a) deproteinization, (b) selective concentration of the diadenosine polyphosphates with a boronate affinity chromatography, and (c) desalting prior to the HPLC analysis. The assay was validated by PSD-MALDI-mass spectrometry and by addition of authentic diadenosine polyphosphate to platelet samples. The assay was carried out by an ion-pair reversed-phase perfusion chromatography. In platelets from human blood the following amounts of diadenosine polyphosphates were determined: Ap3A, 192.5 +/- 151.0 nM; Ap4A, 223.8 +/- 172.3 nM; Ap5A, 100.2 +/- 81.1 nM; Ap6A, 32.0 +/- 19.6 nM (mean +/- SD, n = 105). The described assay can be used with less than 20 ml blood and allows quantitation of the diadenosine polyphosphates in the picomole range.

Blood Platelets↗
PubMed1999

Prevalence of ventricular late potentials in patients with obstructive sleep apnea syndrome.

BACKGROUND: It is known from various cardiac disorders that the presence of ventricular late potentials (VLP) in the signal-averaged electrocardiogram (ECG) is associated with an increased risk of sudden cardiac death. HYPOTHESIS: In view of the increased cardiovascular mortality of patients with obstructive sleep apnea syndrome (OSAS), we assessed the prevalence of VLP in these patients. METHODS: In all, 118 consecutive patients with polysomnographically verified OSAS were prospectively studied; 21 snorers without evidence of a sleep-related breathing disorder served as a control group. Signal-averaged ECG and 24-h Holter ECG were performed in all patients and controls, and left ventricular function was determined by radionuclide ventriculography in the OSAS group. Furthermore, patients and controls were followed for up to 45.5 months for arrhythmic events, syncopes, or sudden cardiac death. RESULTS: An abnormal signal-averaged ECG was seen in seven patients (5.9%) and in one snorer (4.8%). Patients with and without VLP did not differ with respect to age, body mass index, left ventricular ejection fraction, or ectopic activity in the 24-h Holter ECG, but the former had significantly higher mean (standard deviation) apnea/hypopnea indices [55.4 (25.2)/h vs. 37.4 (22.6)/h; p < 0.05]. Of the 118 patients, 110 could be followed for 26.7 (7.9) months. During this period, two patients had syncopes and one patient had sudden cardiac death. The seven patients with VLP remained free of events during the follow-up period, as did the 21 snorers. CONCLUSIONS: Patients with OSAS have a low prevalence of VLP in the signal-averaged ECG, not exceeding that in normal subjects. Moreover, abnormal signal-averaged ECGs do not appear to be useful as a prognostic marker.

Adult↗
PubMed1999

Electron-probe X-ray Microanalysis of Magnesium and Sodium Ion Content in Vascular Smooth Muscle Cells from Spontaneously Hypertensive and Normotensive Rats.

Whereas in blood cells decreased magnesium concentrations and increased sodium concentrations in essential hypertension have often been described, only sparse data exist on cellular magnesium or sodium content in vascular smooth muscle cells. Therefore, in aortic smooth muscle cells from seven spontaneously hypertensive rats (SHR) of the Münster strain and seven normotensive Wistar-Kyoto rats (WKY), the intracellular magnesium and sodium content were measured by electron-probe X-ray microanalysis. Measurements were performed in aortic cryosections 3 µm thick. The magnesium ion content was 0.93 +/- 0.17 g/kg dry weight in SHR vs 1.14 +/- 0.12 g/kg dry weight in WKY (p < 0.05). Vascular smooth muscle sodium ion content was measured at 6.85 +/- 0.59 g/kg dry weight in WKY and 12.47 +/- 1.62 g/kg dry weight in SHR (p < 0.05). In conclusion, aortic smooth muscle cells from SHR are characterized by a markedly lowered intracellular magnesium ion content and increased sodium ion concentrations compared with normotensive cells. The results may be due to genetically determined disturbances in transmembrane magnesium and sodium ion transport. Cellular magnesium and sodium handling may be disturbed in SHR aortic smooth muscle as it is in hypertensive blood cells.

Journal Article↗
PubMed1999

Inositol-1,4,5-trisphosphate increase by diadenosine tetraphosphate in preparations from failing human myocardium.

In human ventricular trabeculae carneae 100 microM AP4A (diadenosine tetraphosphate) increased force of contraction to 162.8+/-15.7% of predrug value (n=9). This positive inotropic effect was accompanied by a prolongation of time parameters: time to peak tension and time of relaxation were prolonged by 7.8+/-1.3% and 14.9+/-3.8%, respectively (P<0.05). In the same trabeculae, AP4A increased IP3 (inositol-1,4,5-trisphosphate) content from 9.0+/-1.3 pmol/mg to 22.9+/-5.4 pmol/mg protein (n=5-9). In conclusion, the positive inotropic effect of AP4A in the human myocardium is likely due to an increase of IP3 mediated probably via Gq-coupled P2Y-purinoceptors. Because of the prominent role of Gq in the development of cardiac disease, these findings may lay the ground to further investigate the possible role of AP4A and/or related ligands (e.g. AP2A and AP3A) in heart failure.

Cardiomyopathies↗
PubMed1999

Na(+)/Ca(2+) exchange inhibitors modulate thapsigargin-induced Ca(2+) and Na(+) influx in human lymphocytes.

Thapsigargin has been shown the elevate intracellular Na(+) concentration in human lymphocytes, but mechanisms underlying thapsigargin-induced Na(+) entry are little understood. In the present study we investigated thapsigargin-induced changes in cytosolic free Na(+) and Ca(2+) concentration in human lymphocytes after inhibition of the Na(+)/Ca(2+) exchange with two structurally unrelated compounds, dimethylthiourea ad bepridil. The intracellular Na(+) increase induced by 5 microM thapsigargin was significantly enhanced in the presence of 5 mM dimethylthiourea or 40 microM bepridil. In contrast, both compounds significantly decreased the thapsigargin-induced intracellular Ca(2+) elevation. No effect of dimethylthiourea or bepridil on thapsigargin-induced Ca(2+) influx was observed in the absence of extracellular Na(+). These observations are consistent with the hypothesis that thapsigargin stimulates Na(+)/Ca(2+ )exchange in human lymphocytes. However, Na(+)/Ca(2+) exchange does not mediate Na(+) influx in human lymphocytes.

Bepridil↗
PubMed1999

Tyrosine and calcium/calmodulin kinases are common signaling components in the generation of reactive oxygen species in human lymphocytes.

This study examined the signaling mechanism involved in the generation of reactive oxygen species (ROS) in human lymphocytes activated by formyl-Met-Leu-Phenylalanine (fMLP; 200 nmol/L) or phorbol-myristate-acetate (PMA; 100 nmol/L). ROS were monitored spectrophotometrically using dichlorofluorescin diacetate. fMLP and PMA significantly increased ROS above the control levels (p<0.05 and 0.001, respectively). These increases were significantly inhibited by catalase, sodium azide, and dimethylsulfoxide but not by superoxide dismutase, suggesting that the ROS apparently included hydrogen peroxide, singlet oxygen and hydroxyl ion but not superoxide anion. PMA-induced responses were reduced by tyrphostin (p<0.01), ST-638 (p<0.05), KN-62 (p<0.001), bisindolylmaleimide (p<0.001), RO-31-8220 (p<0.001), and by LY-83583 (p<0.001), suggesting significant involvement of tyrosine kinase, calcium/calmodulin kinase II, protein kinase C and guanylyl cyclase. fMLP-induced responses were significantly reduced by only tyrphostin (p<0.001), ST-638 (p<0.05), and KN-62 (p<0.01). The results show that tyrosine kinase and calcium/calmodulin kinase II are common signalling components in the production of reactive oxygen species in activated lymphocytes.

Aminoquinolines↗
PubMed1999

Reactive oxygen species in essential hypertension and non-insulin-dependent diabetes mellitus.

To evaluate whether increased levels of reactive oxygen species (ROS) are involved in the pathogenesis of essential hypertension (EH) and non-insulin-dependent diabetes mellitus (NIDDM), both resting and stimulated levels of intracellular ROS were measured in lymphocytes from patients with EH (n = 10), NIDDM (n = 16) and age-matched healthy individuals (control subjects, n = 19). ROS was monitored with the dye, dihydrorhodamine-123 (DHR; 1 micromol/L) in the presence or absence of superoxide dismutase (superoxide scavenger), sodium azide (singlet oxygen/hydrogen peroxide scavenger), genistein (tyrosine kinase inhibitor), or bisindolylmaleimide (protein kinase C inhibitor). Simultaneous monitoring of cytosolic [Ca2+]i was done with fura-2. Resting ROS levels were significantly higher in NIDDM (4.71+/-0.25 nmol/10(6) cells; mean +/- SEM, P<.05) compared with EH (4.03+/-0.22 nmol/10(6) cells) or controls (4.05+/-0.15 nmol/10(6) cells). The formyl-Met-Leu-Phenylalanine-(fMLP)-induced ROS generation was significantly higher in NIDDM (21.92+/-2.23 nmol/10(6) cells; P<.05) compared with EH (14.58+/-1.90 nmol/10(6) cells) or control (16.06+/-1.22 nmol/10(6) cells). The fMLP-induced ROS increase was significantly reduced in the presence of sodium azide in all groups (P<.01) but was largely unaffected in the presence of SOD. Genistein and bisindolylmaleimide significantly inhibited the fMLP-induced ROS in all groups. The fMLP-induced [Ca2+]i increase was significantly higher in NIDDM (71+/-12 nmol/L, P <.01) compared with EH (42+/-4 nmol/L) and control subjects (35+/-3 nmol/L). Phytohemagglutinin was more effective in increasing [Ca2+]i than ROS. It is concluded that ROS may play a role in the metabolic syndrome of NIDDM but not in EH.

Biomarkers↗
PubMed1999

Evidence for two different P2X-receptors mediating vasoconstriction of Ap5A and Ap6A in the isolated perfused rat kidney.

The activation of various P2-receptor subtypes in rat renal vasculature by P1, P5-diadenosine pentaphosphate (ApsA) and P1, P6-diadenosine hexaphosphate (Ap6A) were studied by measuring their effects on perfusion pressure during continuous perfusion in a rat isolated perfused kidney. Permanent perfusion with Ap5A and Ap6A elicited both a transient and sustained vasoconstriction with both vasoconstrictions to be different: the transient vasoconstriction can be elicited with concentrations > or = 10 nM, whereas the sustained vasoconstriction is observed with concentrations > or = 1 nM. ApsA and Ap6A act via the same receptors as alpha,beta-methylene ATP (alpha,beta-meATP). The rank order of potency for transient vasconstriction was alpha,beta-meATP = ApsA>Ap6A>B,gamma-meATP, and for sustained vasoconstriction alpha,beta-meATP = Ap5A > beta,gamma-meATP > or = Ap6A. Suramin, a non-selective P2-receptor antagonist, and pyridoxal-phosphate-6-azophenyl-2;4-disulphonic acid (PPADS) a highly selective P2X-receptor antagonist antagonized both the transient and the sustained vasoconstriction. Taken together the results of the agonist profile of Ap5A and Ap6A and comparing its findings to literature it can be demonstrated that the transient but not the sustained vasoconstriction is mediated via the P2X1-receptor which is present in rat renal vasculature. It is demonstrated that the agonist profile of the sustained vasoconstriction induced by ApsA and Ap6A does not fit to any currently known P2X- or P2Y-receptor subtype. We conclude a yet unidentified P2X-receptor or chimeric P2X-receptor may contribute to the effects on rat renal vasculature produced by Ap5A and Ap6A and which may play an important role in glomerular perfusion pressure and blood pressure control.

Adenosine Triphosphate↗