Biomedical subjects

C Spieker

Publications and source records attributed to C Spieker.

At least 37 records · Page 2Linked to original sources

PubMed1995

Effect of extracellular Mg2+ concentration on agonist-induced cytosolic free Ca2+ transients.

The modulating effects of extracellular Mg2+ concentration ([Mg2+]o) on vascular contraction are well known. In the present study it was tested how the changes in cytosolic free Ca2+ concentration ([Ca2+]i) induced by various agonists are modified by changes in [Mg2+]o. Extracellular Mg2+ deprivation increased the [Ca2+]i response to arginine vasopressin, to angiotensin II and to thapsigargin, but not to 5-hydroxytryptamine and noradrenaline. Withdrawal of extracellular Ca2+ revealed that extracellular Mg2+ deprivation increased Ca2+ influx, but not Ca2+ release from cellular stores. The findings demonstrate that different responses of [Ca2+]i to agonists may underlie the modulating effect of [Mg2+]o on vascular contraction.

Angiotensin II↗

PubMed1995

Coenzyme A glutathione disulfide. A potent vasoconstrictor derived from the adrenal gland.

The adrenal gland is involved in the regulation of vascular tone by secretion of vasoactive agents such as catecholamines, neuropeptide Y, or endogenous ouabain. A further potent vasoconstrictor is isolated from bovine adrenal glands and is identified by chromatography, mass spectrometry, UV spectroscopy, and enzymatic cleavage as coenzyme A glutathione disulfide (CoASSG). CoASSG is found in chromaffin granules of adrenal glands and is released from adrenal medulla slices by carbachol. At a concentration of 10(-12) mol/L CoASSG increases renal vascular resistance. Intra-aortic injection of 5 x 10(-10) mol CoASSG increases blood pressure in the intact animal. Besides its vasopressor properties, this substance potentiates the effects of angiotensin II on vascular tone. It is concluded that CoASSG could play a role in blood pressure regulation not only by direct effects but also by modulation of the action of angiotensin II.

Adrenal Glands↗

PubMed1995

Lymphocytic Na(+)-H+ exchange increases after an oral glucose challenge.

The effects of oral glucose challenge on plasma glucose concentration, plasma insulin concentration, arterial blood pressure, cytosolic pH (pHi), cytosolic free Na+ concentration ([Na+]i), and cellular Na(+)-H+ exchange activity were investigated in 16 healthy subjects. The pHi, [Na+]i, and Na(+)-H+ exchange activity were measured in intact lymphocytes by using the fluorescent dye technique. The oral glucose challenge significantly increased plasma glucose, plasma insulin, and the lymphocytic Na(+)-H+ exchange activity, measured as change of pHi per second (control [0 hours], 5.20 +/- 0.53 x 10(-3) dpHi/s; 1 hour after glucose administration, 8.28 +/- 1.07 x 10(-3) dpHi/s; 2 hours after glucose administration, 8.15 +/- 1.18 x 10(-3) dpHi/s; P = .002). The lymphocytic Na(+)-H+ exchange was significantly correlated with plasma glucose concentration (r = .357, P = .041). During steady state euglycemic hyperinsulinemic clamp, the Na(+)-H+ exchange activity was not significantly changed compared with baseline values. The study shows that changes of blood glucose levels can induce an acute increase in Na(+)-H+ exchange activity. Systolic blood pressure and Na(+)-H+ exchange activity were significantly (P < .001) but weakly correlated during an oral glucose challenge.

Adult↗

PubMed1995

Plasma, cytosolic and membrane magnesium content in renal insufficiency.

Plasma magnesium, cytosolic (lymphocytic) and membrane (erythrocytic) magnesium concentrations were determined in 15 controls with normal renal function compared to 12 patients with renal insufficiency (chronic glomerulonephritis, serum creatinine 2.5 +/- 0.8 mg/dl, mean +/- SD). Plasma magnesium concentrations were determined by atomic absorption spectroscopy (AAS), cytosolic free magnesium with the fluorescent indicator Mag-Fura-2, and membrane magnesium by AAS, referred to membrane protein content which was determined according to Bradford's method. Plasma magnesium was 0.91 +/- 0.08 mmol/litre in controls versus 0.95 +/- 0.09 mmol/litre in renal-insufficient patients. Cytosolic free magnesium content was 2.38 +/- 0.75 mmol/litre in controls and 2.61 +/- 0.35 mmol/litre in the renal-insufficient group. In the renal-insufficient group membrane magnesium concentrations were found to be significantly increased as compared to the control group (2.85 +/- 0.62 vs 0.53 +/- 0.22 mmol/g membrane protein, mean +/- SD, P < 0.05). The results show that cell membranes may be of special importance in renal insufficiency in avoiding magnesium overload of the cell and in keeping free cytosolic magnesium stores stable.

Adult↗

PubMed1995

A multicenter, randomized, double-blind, placebo-controlled, two-year trial to study the effect of nitrendipine on chronic renal transplant function.

The ongoing multicenter, randomized, double-blind, placebo-controlled trial investigates the effect of nitrendipine on kidney function after renal transplantation. Renal transplant recipients (6th-12th postoperative week, serum creatinine < 3 mg/dl) were divided into a normotensive (diastolic blood pressure < 90 mmHg) and a hypertensive group (diastolic blood pressure > or = 90, < 115 mmHg). Normotensive patients are randomly treated for 104 weeks with nitrendipine 2 x 5 mg daily or placebo, hypertensive patients with 2 x 10 mg - 2 x 20 mg nitrendipine daily or placebo and in case of inefficacy with additional antihypertensive drugs. Primary end point of the study is the renal transplant function. The trial was started in June 1990. One hundred and eight patients were included into the normotensive and 138 patients into the hypertensive group. Renal allograft function, cyclosporine trough levels and the donor characteristics were not different between the normotensive and hypertensive groups at entry into the study. After 12 months there was no significant change of renal transplant function in both groups. Cyclosporine trough levels were also similar in the normotensive and hypertensive group after 12 months. As expected, blood pressure decreased significantly after 12 months from 150 +/- 17/95 +/- 11 mmHg to 141 +/- 16/90 +/- 9 mmHg in the hypertensive group (p < 0.01). In contrast, in the normotensive group blood pressure increased significantly from 128 +/- 12/80 +/- 6 mmHg to 135 +/- 15/86 +/- 8 mmHg (p < 0.001). No normotensive but 4 hypertensive patients developed graft failure during the first 12 months of the study.

Adolescent↗

PubMed1995

The impact of lacidipine, a novel dihydropyridine calcium antagonist, on carbohydrate and lipid metabolism.

In an open, multicenter study, the calcium antagonist lacidipine was tested for efficacy and safety, particularly with respect to any influence on lipid and carbohydrate metabolism. The study was performed in 2,127 patients with essential hypertension. The patients were treated orally, with lacidipine in a dosage of 2-6 mg once daily for 48 weeks. Lacidipine significantly reduced both systolic and diastolic blood pressure by 20 +/- 17 mm Hg and 14 +/- 10 mm Hg, respectively, from baseline values (both p < 0.0001). Decreases in blood pressure were achieved without any adverse effects on lipid and carbohydrate metabolism, either in the total group or in subsets of diabetic or hyperlipidemic patients. It is concluded that lacidipine is a safe and effective drug in the long-term antihypertensive treatment of patients with essential hypertension and with concomitant metabolic disorders such as diabetes mellitus or dyslipidemia.

Calcium Channel Blockers↗

PubMed1995

Different effects of hypertension, atherosclerosis and hyperlipidaemia on arterial distensibility.

OBJECTIVE: To investigate the different effects of hypertension, hyperlipidaemia and atherosclerosis on the visco-elastic properties of large arteries. DESIGN: Vessel wall properties were determined in patients who had been subjected for the first time to coronary arteriography. Normotensive patients with no coronary disease (n = 15), one-vessel disease (n = 15) or two- or three-vessel disease (n = 15), 15 treated hypertensive patients (mean +/- SEM duration of hypertension 9.6 +/- 1.7 years) with no coronary disease and normocholesterolaemia and 15 healthy controls were matched for blood pressure, age and sex. METHODS: Arterial distension of the common carotid artery was determined by using a multigate Doppler system. The blood pressure curve was recorded by finger plethysmography. RESULTS: The end-diastolic diameter was significantly higher in the hypertensives (P<0.05) but not significantly different in the normotensives compared with the controls. Arterial distensibility was significantly lower in the hypertensive group [(13.3 +/- 0.8) x 10(-3)/kPa] than in the controls [(19.1 +/- 1.5) x 10(-3)/kP; P<0.01), in the group with no coronary disease [(18.8 +/- 1.3) x 10(-3)/kPa; P<0.01] and in those with one-vessel disease [(17.7 +/- 1.4) x 10(-3)/kPa; P<0.05]. Arterial distensibility was not significantly lower in the hypertensives than in the group with two- or three-vessel disease [(15.0 +/- 1.0) x 10(-3)/kPa; NS). No significant correlation was found between cholesterol or lipoprotein(a) levels and arterial distensibility in the normotensive patients. CONCLUSIONS: Hypertension is the predominant factor affecting the visco-elastic properties of large arteries. Arterial compliance is significantly altered only in extensive atherosclerosis.

Arteriosclerosis↗

PubMed1994

Diadenosine phosphates and the physiological control of blood pressure.

Our understanding of the regulation of vascular tone has been extended since the identification of vasoactive agents such as the atrial natriuretic peptides, endothelial-derived relaxing factor and endothelin. Unidentified vasopressive agents have been found in platelets. Here we isolate these vasopressors and identify them as diadenosine pentaphosphate (AP5A) and diadenosine hexaphosphate (AP6A) by chromatography, mass spectrometry, ultraviolet spectroscopy and enzymatic cleavage. In the vasculature of isolated perfused rat kidney, both diadenosine phosphates were active at a concentration of 10(-9) M; in aortic rings, contractions were elicited at 10(-8) M. Intra-aortic injection in the rat caused a prolonged increase in blood pressure. We conclude that AP5A and AP6A may play a part in local vasoregulation and possibly in the regulation of blood pressure.

5'-Nucleotidase↗

PubMed1994

Studies of the vessel wall properties in hemodialysis patients.

Compliance is an important property of the arterial system and abnormalities in compliance can greatly affect cardiovascular function. The elastic properties of the common carotid artery were therefore studied in 24 normotensive hemodialysis patients and 24 healthy normotensives using a noninvasive technique. The hemodialysis patients and the control subjects were matched for blood pressure. Arterial distension was measured by Doppler analysis of the vessel wall movements and blood pressure was recorded by finger-phlethysmography (Finapres). The vessel wall distensibility (DC: 2.49 +/- 0.23 10(-3)/mm Hg; mean +/- SEM) was significantly reduced and the end diastolic diameter (d: 7.3 +/- 0.3 mm) was significantly increased in younger hemodialysis patients (36.3 +/- 2.0 years) when compared with age-related controls (DC: 3.44 +/- 0.24 10(-3)/mm Hg; d: 6.3 +/- 0.3 mm; mean +/- SEM). In older hemodialysis patients (60.2 +/- 2.3 years), there was no significant difference in vessel wall distensibility (DC: 1.55 +/- 0.15 10(-3)/mm Hg) and vessel diameter (d: 7.8 +/- 0.3 mm) as compared with age-matched controls (DC: 1.77 +/- 0.14 10(-3)/mm Hg; d: 7.2 +/- 0.3 mm). The results show that vessel wall distensibility of the common carotid artery is decreased in younger hemodialysis patients as compared with age-matched healthy subjects. The volume expanded state in hemodialysis patients cannot account for the decreased arterial distensibility, since volume depletion by hemodialysis was not associated with a significant change of arterial distensibility (DC 2.14 +/- 0.44 10(-3)/mm Hg before, DC 2.26 +/- 0.45 10(-3)/mm Hg after ultrafiltration, NS).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1994

Cellular Ca2+ ATPase activity in diabetes mellitus.

Basal and maximal Ca2+ ATPase activity was studied in erythrocytes of 29 healthy controls, 15 patients with insulin-dependent diabetes mellitus (IDDM) and 22 patients with non-insulin-dependent diabetes mellitus (NIDDM). Basal and maximal Ca2+ ATPase activity was significantly decreased in insulin-dependent diabetes mellitus (8.4 +/- 0.5 and 22.5 +/- 1.1 pmol/10(6) RBC/min) and non-insulin-dependent diabetes mellitus (7.3 +/- 1.0 and 18.6 +/- 1.8 pmol/10(6) RBC/min) compared to healthy controls (9.3 +/- 1.0 and 24.6 +/- 1.1 pmol/10(6) RBC/min). Maximal Ca2+ ATPase activity showed a significant correlation to systolic blood pressure in both insulin-dependent diabetes mellitus and non-insulin-dependent diabetes mellitus. There was no significant correlation of maximal Ca2+ ATPase activity to fasting serum glucose concentration and to HbA1 levels. Maximal Ca2+ ATPase activity was significantly correlated to creatinine clearance in non-insulin-dependent diabetes mellitus, but not in insulin-dependent diabetes mellitus. It is concluded that a decreased cellular Ca2+ ATPase activity may predispose to the development of hypertension in diabetes mellitus.

Aged↗

PubMed1994

Effect of lisinopril and metoprolol on arterial distensibility.

Apart from lowering blood pressure, antihypertensive drugs may influence vessel wall function. In a randomized double-blind study, the effect of lisinopril and metoprolol on arterial distensibility was studied in 40 patients with essential hypertension. After a placebo run-in period, the patients were randomly treated with metoprolol (50, 100, or 200 mg) or lisinopril (5, 10, or 20 mg) for 10 weeks. In the lisinopril group, blood pressure decreased after 10 weeks of therapy from 173 +/- 10/102 +/- 5 to 155 +/- 10/85 +/- 3 mm Hg and in the metoprolol group from 167 +/- 12/102 +/- 4 to 153 +/- 8/84 +/- 3 mm Hg. Diameter (millimeters), relative change in diameter (percent), and distensibility (10(-3)/kPa) of the left common carotid artery were determined after the placebo run-in period and after 6 and 10 weeks of antihypertensive therapy. A multigate Doppler system was used to measure the vessel wall movements by Doppler analysis in M-mode; blood pressure was recorded by finger plethysmography (Finapres). Neither lisinopril nor metoprolol influenced the end-diastolic diameter of the common carotid artery after 6 and 10 weeks of treatment. In the lisinopril group, a significant increase of percent change in diameter (P < .05 compared with the baseline value; P < .05 compared with the metoprolol group) and distensibility (P < .01 compared with the baseline value; P < .05 compared with the metoprolol group) was observed. The results show that lisinopril but not metoprolol improves arterial distensibility in essential hypertension. Pressure-independent effects of angiotensin converting enzyme inhibitors may be important modulators of adaptive changes in the arterial wall.

Adult↗

PubMed1994

Increased cytosolic sodium and reduced Na,K-ATPase activity in transgenic rats.

The transgenic rat TGR(mRen2)27 is a new monogenetic model in hypertension research that develops fulminant hypertension after the mouse Ren-2d renin gene has been integrated into its genome. To evaluate the molecular mechanism of development of hypertension in this animal model, we measured cytosolic free sodium concentration in intact lymphocytes from seven transgenic rats and eight age-matched normotensive Sprague-Dawley rats using the novel sodium-sensitive fluorescent dye sodium-binding benzofuranisophthalate. Resting cytosolic sodium was significantly higher in transgenic rats compared with Sprague-Dawley rats (31.7 +/- 2.2 versus 18.2 +/- 0.4 mmol/L, mean +/- SEM, P < .001). Inhibition of Na,K-ATPase by 0.5 mmol/L ouabain for 5 minutes significantly increased lymphocytic cytosolic sodium in Sprague-Dawley rats to 36.5 +/- 3.4 mmol/L (P < .001 compared with resting value), whereas no significant change could be observed in transgenic rats (35.4 +/- 0.6 mmol/L), indicating that Na,K-ATPase is less responsive in transgenic rats. The Na,K-ATPase activity from erythrocytes was measured with an enzyme-linked assay. Na,K-ATPase activity was significantly reduced in transgenic rats compared with Sprague-Dawley rats (4.0 +/- 0.3 versus 8.1 +/- 0.6 U/L, P < .001). We concluded that reduced Na,K-ATPase activity leads to elevated cytosolic sodium in this model of genetic hypertension.

Animals↗

PubMed1994

Effect of Na,K-ATPase inhibition on cytosolic free calcium ions in vascular smooth muscle cells of spontaneously hypertensive and normotensive rats.

OBJECTIVE: To investigate the role of Na(+)-Ca2+ exchange in the regulation of cytosolic free Ca2+ and the pathogenesis of primary hypertension. METHOD: Cytosolic free Ca2+ ([Ca2+]i) in cultured vascular smooth muscle cells from normotensive and spontaneously hypertensive rats of the Münster strain was measured using the fluorescent dye fura-2 after inhibition of Na+,K+ATPase by ouabain and after addition of angiotensin II. RESULTS: [Ca2+]i showed a rapid increase together with a depolarization of membrane potential as measured by merocyanine 540. The ouabain-induced increase in [Ca2+]i was blocked in Ca(2+)-free medium and by nifedipine, but incubation with the inhibitor of the Na(+)-Ca2+ exchange, NiCl2, did not diminish the effect of ouabain. Likewise, in Na(+)-free medium the response to ouabain was not suppressed. The angiotensin II-induced changes in [Ca2+]i were diminished in Ca(2+)-free medium and by nifedipine, but enhanced by NiCl2. CONCLUSION: The increase in [Ca2+]i after Na+,K+ ATPase inhibition is not due to a modulation of Na(+)-Ca2+ exchange, but to a Ca2+ influx through Ca2+ channels. Changes in Na(+)-Ca2+ exchange caused by Na+,K+ ATPase inhibition may not play an important role in vascular smooth muscle cells of spontaneously hypertensive rats.

Animals↗

PubMed1994

Different calcium storage pools in vascular smooth muscle cells from spontaneously hypertensive and normotensive Wistar-Kyoto rats.

OBJECTIVE: To evaluate whether the distribution of intracellular free calcium may be impaired in primary hypertension. DESIGN: Cytosolic free calcium and stored calcium were investigated in cultured vascular smooth muscle cells from spontaneously hypertensive rats (SHR). METHODS: The concentrations of intracellular and stored calcium were investigated in cultured vascular smooth muscle cells from spontaneously hypertensive rats aged 6 months from the Münster strain (SHR) and from age-matched normotensive Wistar-Kyoto (WKY) rats. Vascular smooth muscle cells were grown on coverslips, and fluorescence measurements of the intracellular calcium concentration were performed using fura-2. The different effects of thapsigargin, a selective Ca-ATPase inhibitor, and of angiotensin II (Ang II) on the calcium storage pools were investigated. RESULTS: In the absence of external calcium thapsigargin produced a dose-dependent transient increase in the concentration of intracellular calcium in vascular smooth muscle cells. The thapsigargin-induced maximum peak increase in the concentration of intracellular calcium was not significantly different in SHR and WKY rats. After depletion of the thapsigargin-sensitive calcium pools the addition of 100 nmol/l Ang II produced a rise in the concentration of intracellular calcium in vascular smooth muscle cells from SHR and WKY rats. Using vascular smooth muscle cells from the SHR the Ang II-induced increase in the concentration of intracellular calcium was not significantly different in the presence and absence of thapsigargin, indicating that the calcium pools depleted by thapsigargin and Ang II do not overlap significantly in vascular smooth muscle cells from SHR. In contrast, in the WKY rats the response to Ang II was significantly diminished after depletion of the thapsigargin-sensitive pool. When Ang II and thapsigargin were administered in the reverse order, i.e. Ang II before thapsigargin, the thapsigargin response was diminished in the WKY rats but not in the SHR. CONCLUSION: SHR differ from WKY rats in having vascular smooth muscle cells that contain thapsigargin-sensitive calcium storage pools that are distinct from the Ang II-sensitive calcium pools.

Angiotensin II↗

PubMed1993

[Arterial embolism and thrombocytopenia during heparin therapy].

This is a case report of heparin-associated thrombocytopenia syndrome (white clot syndrome). An 81-Year-old patient was treated with sodium-heparin for proximal deep-venous thrombosis and pulmonary embolism. During administration of heparin, the platelet count decreased to a nadir of 27/nl on day 14 after initiation of this therapy. We also observed a recurrence of pulmonary embolism as well as arterial thromboembolism in the right arm and the right leg. After immediate discontinuation of heparin therapy and change of anticoagulation to oral anticoagulants with overlapping administration of a low molecular weight heparin and application of immunoglobulins, we observed total recanalization of the arterial occlusions, normalization of lung-perfusion scan and rapid recovery of the platelet count.

Aged↗

PubMed1993

Effect of cytokines on cytosolic-free calcium in human platelets from essential hypertensives.

The different effects of cytokines on cytosolic-free calcium concentration ([Ca2+]i) and intracellular stored calcium were investigated in platelets from 35 essential hypertensive patients (HT) and 45 age- and sex-matched normotensive control subjects (NT). Erythropoietin (EPO) and interleukin 2 significantly increased platelet [Ca2+]i, whereas platelet-derived growth factor, and fibroblast growth factor had no significant effect on [Ca2+]i. The EPO-induced rise of [Ca2+]i was significantly higher in HT compared to NT (15.2 +/- 4.3 nmol/L v 1.3 +/- 1.7 nmol/L, P < .01). Preincubation with EPO significantly increased calcium in intracellular stores in platelets from HT and NT. Inhibition of protein kinase C significantly enhanced EPO-induced rise of stored calcium. It is concluded that an increased response of HT to EPO may be associated with essential hypertension.

Adult↗

PubMed1993

Effect of long-term hemodialysis on arterial compliance in end-stage renal failure.

To assess the influence of long-term hemodialysis on arterial compliance, the elastic vessel wall properties of the common carotid artery were determined in 20 normotensive renal transplant recipients (age 44.7 +/- 4.1 years) 8-12 weeks after first transplantation and in 10 healthy controls (age 45.9 +/- 5.2 years). Arterial distension was measured by using a multigate pulsed Doppler system, blood pressure curve was recorded by finger-plethysmography. 10 patients with a prior long-term hemodialysis of 51 +/- 11 months were compared to 10 patients with a prior short hemodialysis of 18 +/- 7 months. The patients and controls had been matched in respect of age, sex and blood pressure. In the long and short-term hemodialysis group, the proportion of patients (n = 10) with a history of mild hypertension was similar--mild hypertension for 25 +/- 10 months (n = 5) and for 27 +/- 9 months (n = 5). In the group with long-term hemodialysis, the cross-sectional compliance and the distensibility coefficient was significantly reduced in comparison to the group with short-term hemodialysis (p < 0.005) and to the control group (p < 0.001). A significant inverse correlation between the hemodialysis period and the distensibility coefficient (r = -0.59; p < 0.005) showed a decrease in arterial compliance with the length of hemodialysis treatment. The results demonstrate that vessel wall elasticity decreases with the length of hemodialysis treatment and is reduced by hemodialysis-dependent factors, which are detached from sustained arterial hypertension. As cause of reduced arterial compliance in long-term hemodialysis hypervolemia, hypercirculation and disturbed calcium-phosphate metabolism is suggested.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1993

Circadian blood pressure variations in endocrine disorders.

Circadian rhythm of blood pressure and of heart rate was studied in patients with hyperthyroidism (n = 10), pheochromocytoma (n = 8), primary hyperaldosteronism (n = 7), and in a control group of essential hypertensive patients (n = 18) and of normotensive healthy subjects (n = 11). 24-hour blood pressure was monitored non-invasively using SpaceLabs (SL 90207) with 8-min intervals in the daytime (8 a.m. to 10 p.m.) and 30-min intervals during night-time (10 p.m. to 8 a.m.). To characterize circadian blood pressure rhythm the difference between the mean blood pressure during daytime and that during night-time was calculated. In patients with hyperthyroidism the day-night difference of the systolic and diastolic blood pressure and of the heart rate was significantly reduced when compared to the normotensive control group (p < 0.05). The day-night difference of the systolic and diastolic blood pressure was significantly lower in the group with pheochromocytoma and hyperthyroidism than in the essential hypertensive controls (p < 0.05); the day-night difference of the heart rate was similar. In the patients with primary hyperaldosteronism the day-night differences of the systolic and diastolic blood pressure and of the heart rate was similar to those in essential hypertensive controls. We conclude that endocrine disorders affecting sympathetic activity like pheochromocytoma or hyperthyroidism influence the circadian blood pressure rhythm, whereas the renin-aldosterone-system has no major impact on the diurnal blood pressure variation. The results therefore support the hypothesis that circadian blood pressure variation is mainly mediated by a modulation of the sympathetic tone.

Adrenal Gland Neoplasms↗