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J Kastrup

Publications and source records attributed to J Kastrup.

At least 19 recordsLinked to original sources
PubMed2004

A simplified cytokine immunoassay using magnetic polymer particles.

Accurate detection of cytokines is essential for understanding their biological role in the immune system. Various methods to detect cytokines have been developed, including sandwich enzyme-linked immunosorbent assay (ELISA) and flow cytometry-based methods. All of the currently available methods have limitations, however. These limitations include time and extensive handling in standard sandwich ELISAs and the need for specialized equipment in flow cytometry-based assays. We have developed a magnetic polymer cytokine immunoassay and demonstrate that this assay is rapid and simple, needs less handling and offers better dynamic range, compared to standard sandwich ELISA. Furthermore, it does not require flow cytometry equipment, which is often used in microparticle-based polymer immunoassays. The magnetic polymer cytokine immunoassay described in this study is as sensitive as a standard sandwich ELISA. Because the method is not limited to the use of magnetic polymer particles, it is versatile and compatible with a number of different solid matrixes.

Animals↗
PubMed2003

Increased cardiac BNP expression associated with myocardial ischemia.

Congestive heart failure is accompanied by increased cardiac brain natriuretic peptide (BNP) gene expression with elevated plasma concentrations of BNP and its precursor, proBNP. We investigated if myocardial ischemia in the absence of overt heart failure may be another mechanism for increased myocardial BNP expression. The BNP expression was examined in hypoxic myocardium of patients undergoing coronary bypass grafting surgery, in patients with coronary artery disease and normal left ventricular function undergoing percutaneous transluminal intervention therapy, and in heart failure patients without coronary artery disease. BNP mRNA was quantified by real-time PCR, and plasma BNP and proBNP concentrations were measured with radioimmunoassays. Quantitative analysis of BNP mRNA in atrial and ventricular biopsies from coronary bypass grafting patients revealed close associations of plasma BNP and proBNP concentrations to ventricular, but not atrial, BNP mRNA levels. Plasma BNP and proBNP concentrations were markedly increased in patients with coronary artery disease but without concomitant left ventricular dysfunction. These results are compatible with the notion that myocardial ischemia, even in the absence of left ventricular dysfunction, augments cardiac BNP gene expression and increases plasma BNP and proBNP concentrations. Thus, elevated BNP and proBNP concentrations do not necessarily reflect heart failure but may also result from cardiac ischemia.

Angioplasty, Balloon, Coronary↗
PubMed2002

In vitro production and characterization of partly assembled human CD3 complexes.

Pairwise assembly of human CD3 chains takes place in the endoplasmic reticulum of T cells. Subsequently, the CD3 heterodimers form complexes with Ti alpha and Tiss chains forming hexameric Ti alpha beta CD3 gamma epsilon delta epsilon complexes. Finally, association with the zeta 2 homodimer occurs in Golgi apparatus before the fully assembled T-cell receptor is transported to the cell surface. To study the structural properties of the human CD3 chains, we have developed new methods to produce and fold the extracellular domains of CD3 gamma, CD3 delta and CD3 epsilon. Proteins were expressed in Escherichia coli as denatured chains and de novo folded in vitro. CD3 gamma and CD3 epsilon folded as soluble monomers, whereas CD3 delta did not yield any soluble proteins. When folding the chains pairwise, soluble CD3 gamma epsilon and CD3 delta epsilon heterodimers could be isolated, whereas CD3 gamma delta heterodimers were not produced. Using antibodies as structural probes, we identified two different types of antigenic epitopes that were dependent on heterodimerization. Our data indicate that CD3 epsilon undergoes a conformational change after dimerization with CD3 gamma or CD3 delta. Furthermore, we demonstrated that the CD3 gamma epsilon heterodimer could be purified using immunoaffinity chromatography.

Antibodies, Monoclonal↗
PubMed2002

Systemic vascular resistance during brief withdrawal of angiotensin converting enzyme inhibition in heart failure.

We tested the hypothesis that moderate increases in endogenous angiotensin II (Ang II) concentrations, induced by withdrawal of angiotensin converting enzyme inhibition (ACE-I) in patients with compensated heart failure (HF) on chronic medical therapy, do not increase or impair control of systemic vascular resistance (SVR). SVR was determined in supine and seated positions in 12 HF patients [NYHA class II-III; ejection fraction=0.29 +/- 0.03 (mean +/- SE)] and 9 control subjects. HF patients were investigated during high (n=11; withdrawal of ACE-I treatment for 24 h) and low (n=9; sustained ACE-I therapy) endogenous plasma Ang II concentrations. Withdrawal of ACE-I therapy in HF caused moderately increased Ang II concentrations of 30 +/- 5 pg/ml compared with 12 +/- 2 pg/ml in controls (p<0.05 vs. HF patients). Despite this, SVR was similar in HF (supine: 1503 +/- 159; seated: 1957 +/- 262 dyn s/cm5, p<0.05 vs. supine) and controls (supine: 1438 +/- 104; seated: 1847 +/- 127 dyn s/cm5, p<0.05 vs. supine). During sustained ACE-I therapy in HF, plasma Ang II concentrations were lower (6 +/- 2pg/ml, p<0.05 vs. withdrawal of ACE-I in HF) with no effect on supine SVR. However, the posture-induced increase in SVR in response to the seated position was attenuated. In conclusion, brief moderate increases in circulating plasma Ang II concentrations in compensated HF do not increase SVR compared to control subjects or impair control of SVR in response to a posture change.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed2001

Predictors of coronary in-stent restenosis: importance of angiotensin-converting enzyme gene polymorphism and treatment with angiotensin-converting enzyme inhibitors.

OBJECTIVES: This study aimed to clarify the role of the angiotensin-converting enzyme (ACE) gene polymorphism in the development of in-stent restenosis. BACKGROUND: In-stent restenosis occurs after treatment of coronary artery stenosis in 12% to 32% of coronary interventions with stents. Experimental and clinical studies have suggested that the deletion/insertion (D/I) polymorphism of the ACE gene plays a role in this. METHODS: Quantitative coronary angiography before, immediately after and six months after stent implantation were compared in 369 patients, in whom D/I typing of the ACE gene was performed. RESULTS: At follow-up we found no differences between the three genotypes in minimal lumen diameter (homozygotes with two deletion alleles in the ACE gene [DD], 2.20 mm; heterozygotes with one deletion and one insertion allele in the ACE gene [DI], 2.19 mm; and homozygotes with two insertion alleles in the ACE gene [II], 2.25 mm). The corresponding diameter stenoses were: DD: 25%, DI: 27%, II: 27% (p = NS), and the frequency of restenosis (>50% diameter stenosis) was: DD: 15.7%, DI: 11.0% and II: 16.4% (p = NS). Logistic regression analysis identified diabetes (odds ratio [OR]: 3.0, 95% confidence interval [CI]: 1.0 to 8.7), lesion length (OR: 1.1, 95% CI: 1.01 to 1.30) and minimal lumen diameter immediately after the intervention (OR: 0.3, 95% CI: 0.14 to 0.85) as predictors of in-stent restenosis. In a post hoc analysis of patients treated versus those not treated with an ACE-inhibitor antagonist or an angiotensin receptor antagonist, we found an increased frequency of in-stent restenosis in the DD genotypes (40% vs. 12%, p = 0.006). CONCLUSIONS: The D/I polymorphism is not an independent predictor of coronary in-stent restenosis in general, but it may be of clinical importance in patients treated with ACE inhibitors or angiotensin receptor antagonists.

Adult↗
PubMed2001

[Abciximab (ReoPro) in the treatment of acute coronary syndromes].

Platelet activation plays a major role in the pathophysiology of acute coronary syndromes (ACS). Inhibition of platelet function is the basic pharmacological treatment of ACS. Platelet membrane glycoprotein IIb/IIIa inhibitors, a new class of potent antiplatelet agents, have been used in the treatment of ACS and in the prevention of complications after percutaneous coronary interventions (PCI). Several large clinical trials have demonstrated the effectiveness of this class of agents. The first of these agents to show beneficial effects after coronary interventions was the mouse/human chimeric Fab fragment antibody c7E3 abciximab (ReoPro). The purpose of this article is to describe the pharmacology of abciximab and to review the results of the clinical trials carried out with the drug in patients with ACS, treated either with or without acute/elective PCI.

Angioplasty, Balloon, Coronary↗
PubMed2001

T-cell receptor downregulation by ceramide-induced caspase activation and cleavage of the zeta chain.

Regulation of T-cell receptor (TCR) cell surface expression levels is probably an important mechanism by which T-cell responsiveness is controlled. Previously, two distinct pathways for TCR downregulation have been described. One is dependent on protein kinase C (PKC) and the leucine-based receptor-sorting motif (L-based motif) of the CD3 gamma chain but independent of tyrosine kinases, whereas the other is dependent on the tyrosine kinase activation but independent of the PKC and the CD3 gamma L-based motif. In this study, we describe a new pathway for TCR downregulation distinct from both the PKC/CD3 gamma L-based motif-dependent and the tyrosine kinase-dependent pathways. This pathway is dependent on ceramide-induced activation of caspases and correlate with caspase-mediated cleavage of the zeta chain. Thus, a 10--15% downregulation of the TCR was induced following the treatment of the T cells with ceramide for 4 h. A close correlation between TCR downregulation, caspase activation, and cleavage of the zeta chain was found. Furthermore, the caspase inhibitors abolished the cleavage of the zeta chain and TCR downregulation in parallel with the inhibition of the caspase activity.

Amino Acid Chloromethyl Ketones↗
PubMed2001

Prolonged QTc interval predicts mortality in patients with Type 1 diabetes mellitus.

AIMS: To evaluate prolonged QTc interval and QT dispersion as predictors of all-cause and cardiovascular mortality after adjustment for well-established risk factors in Type 1 diabetic patients. METHODS: From a cohort of all adult Type 1 diabetic patients, duration of diabetes >or= 5 years, attending the clinic in 1984 and followed in an observational study for 10 years (n = 939), all subjects with resting baseline electrocardiograms were identified (n = 697, 360 males). The QT length was measured and corrected for heart rate (QTc). Maximal QTc length (QTc max) and QT dispersion were determined. RESULTS: At baseline, 431 had normoalbuminuria (< 30 mg/24 h), 138 had microalbuminuria (30-299 mg/24 h) and 128 had macroalbuminuria (>or= 300 mg/24 h) of whom 66 (15%), 35 (25%) and 61 (48%) died during follow-up, respectively (26 (6%), 14 (10%), 21 (16%) from cardiovascular disease). QTc max. was 442 (1.2) ms (mean (SEM)) for survivors and 457 (3.7) in patients who died (P < 0.001). In a Cox proportional hazards model including baseline values of putative risk factors, independent predictors of death were QTc max (P = 0.03), age (P < 0.001), presence of hypertension (P = 0.001), male sex (P < 0.001), log urinary albumin excretion (P < 0.001), smoking (P = 0.04), log serum-creatinine (P < 0.001), height (P < 0.001), low social class (P = 0.04), whereas QT dispersion, heart rate, and HbA1c were not included. In the subgroup with macroalbuminuria, but not for all patients, QTc max was an independent risk factor for cardiovascular mortality. CONCLUSION: QTc prolongation, but not increased QT dispersion, is an independent marker of increased mortality in patients with Type 1 diabetes mellitus.

Adult↗
PubMed2001

Neuroendocrine and renal effects of intravascular volume expansion in compensated heart failure.

To examine if the neuroendocrine link between volume sensing and renal function is preserved in compensated chronic heart failure [HF, ejection fraction 0.29 +/- 0.03 (mean +/- SE)] we tested the hypothesis that intravascular and central blood volume expansion by 3 h of water immersion (WI) elicits a natriuresis. In HF, WI suppressed ANG II and aldosterone (Aldo) concentrations, increased the release of atrial natriuretic peptide (ANP), and elicited a natriuresis (P < 0.05 for all) compared with seated control. Compared with control subjects (n = 9), ANG II, Aldo, and ANP concentrations were increased (P < 0.05) in HF, whereas absolute and fractional sodium excretion rates were attenuated [47 +/- 16 vs. 88 +/- 15 micromol/min and 0.42 +/- 0.18 vs. 0.68 +/- 0.12% (mean +/- SE), respectively, both P < 0.05]. When ANG II and Aldo concentrations were further suppressed (P < 0.05) during WI in HF (by sustained angiotensin-converting enzyme inhibitor therapy, n = 9) absolute and fractional sodium excretion increased (P < 0.05) to the level of control subjects (108 +/- 34 micromol/min and 0.70 +/- 0.23%, respectively). Renal free water clearance increased during WI in control subjects but not in HF, albeit plasma vasopressin concentrations were similar in the two groups. In conclusion, the neuroendocrine link between volume sensing and renal sodium excretion is preserved in compensated HF. The natriuresis of WI is, however, modulated by the prevailing ANG II and Aldo concentrations. In contrast, renal free water clearance is attenuated in response to volume expansion in compensated HF despite normalized plasma AVP concentrations.

Aldosterone↗
PubMed2001

Protein phosphatase 2A isotypes regulate cell surface expression of the T cell receptor.

The mechanisms underlying T cell receptor (TCR) down-regulation have been extensively studied during the last decade. Whereas the importance of phosphorylation in this process has been established, it is less certain whether dephosphorylation plays a role in TCR down-regulation. In this study, we show that inhibition of the serine/threonine protein phosphatase PP2A family had a biphasic effect on TCR expression. Thus, low concentrations of PP2A inhibitors induced TCR down-regulation, whereas higher concentrations of PP2A inhibitors induced TCR up-regulation. The effect of PP2A inhibition was independent of phosphorylation of the CD3gamma endocytosis motif. Whereas TCR down-regulation was caused by a partial inhibition of exocytosis, TCR up-regulation was caused by an inhibition of endocytosis. The effects on exocytosis and endocytosis were not restricted to the TCR, indicating a more general regulatory role for PP2A in both exocytosis and endocytosis.

Amino Acid Sequence↗
PubMed2001

Plasma pro-brain natriuretic peptides are strong biochemical markers in clinical cardiology.

The cardiac natriuretic peptides constitute a family of peptides that regulate fluid homeostasis as well as vascular tonus and growth. Following the fundamental establishment of the heart as an endocrine organ in the early 1980's, the cardiac natriuretic peptides have today been identified as potent biochemical tools in diverse aspects of clinical cardiology including as diagnostic, therapeutic and prognostic markers of cardiac dysfunction as well as potential drug targets. In man, Atrial Natriuretic Peptide (ANP) and Brain Natriuretic Peptide (BNP) are mainly synthesised and secreted by the failing heart, whereas the closely related C-type Natriuretic Peptide (CNP) appears to be a local factor secreted by the endothelium and hence is not considered as a cardiac natriuretic peptide. With the ongoing development of sensitive immunoassays, increased plasma concentrations of ANP and BNP peptides have been associated to a variety of cardiac diseases--but their clinical usefulness as biochemical markers in congestive heart failure is the most promising. In contrast to the large quantity of clinical research on cardiac-derived peptides, the basic understanding of the molecular heterogeneity of these peptides is however still insufficient. Since much clinical work on peptides derived from the proBNP precursor has been published recently, this mini-review will focus on these novel peptides and their potential applications in the clinical setting.

Amino Acid Sequence↗
PubMed2000

beta2-adaptin is constitutively de-phosphorylated by serine/threonine protein phosphatase PP2A and phosphorylated by a staurosporine-sensitive kinase.

Clathrin-mediated endocytosis includes cycles of assembly and disassembly of the clathrin-coated vesicle constituents. How these cycles are regulated is still not fully known but previous studies have indicated that phosphorylation of coat subunits may play a role. Here we describe that beta2-adaptin undergoes cycles of phosphorylation/de-phosphorylation in intact cells. Thus, beta2-adaptin was constitutively de-phosphorylated by serine/threonine protein phosphatase 2A and phosphorylated by a staurosporine-sensitive kinase in vivo. Confocal laser scanning microscopy demonstrated that phosphorylated AP2 complexes were found more evenly distributed at the plasma membrane compared to non-phosphorylated AP2 complexes which were found in aggregates. Finally, we found that phosphorylation of beta2-adaptin correlated with inhibition of clathrin-mediated endocytosis. Our results support the hypothesis that phosphorylation/de-phosphorylation of coat proteins plays a regulatory role in the assembly/disassembly cycle of clathrin-coated vesicles.

Adaptor Protein Complex beta Subunits↗
PubMed2000

Ceramide-induced TCR up-regulation.

The TCR is a constitutively recycling receptor meaning that a constant fraction of TCR from the plasma membrane is transported inside the cell at the same time as a constant fraction of TCR from the intracellular pool is transported to the plasma membrane. TCR recycling is affected by protein kinase C activity. Thus, an increase in protein kinase C activity affects TCR recycling kinetics leading to a new TCR equilibrium with a reduced level of TCR expressed at the T cell surface. Down-regulation of TCR expression compromises T cell activation. Conversely, TCR up-regulation is expected to increase T cell responsiveness. The purpose of this study was to identify and characterize potential pathways for TCR up-regulation. We found that ceramide affected TCR recycling dynamics and induced TCR up-regulation in a concentration- and time-dependent manner. Experiments applying phosphatase inhibitors indicated that ceramide-induced TCR up-regulation was most probably mediated by serine/threonine protein phosphatase 2A. Analyses of T cell variants demonstrated that TCR up-regulation was dependent on the presence of an intact CD3gamma L-based motif and thus acted on TCR engaged in the recycling pathway. Finally, we showed that TCR up-regulation probably plays a physiological role by increasing T cell responsiveness. Thus, by affecting the TCR recycling kinetics, T cells have the potential both to up- and down-regulate TCR expression and thereby adjust T cell responsiveness.

Amino Acid Motifs↗
PubMed2000

Plasma disappearance of albumin and impact of capillary thickness in idiopathic dilated cardiomyopathy and after heart transplantation.

BACKGROUND-The increased plasma disappearance of albumin has previously been described in decompensated congestive heart failure (CHF); this disappearance normalized after diuretic treatment. Cardiac transplantation (HTX) and current medical treatment affect microvascular structure and function. We investigated the plasma disappearance of albumin and the impact of microvascular thickness and electrostatic properties in patients with compensated CHF and after HTX. METHODS AND RESULTS-The fraction of intravascular albumin that passes to the extravascular space per unit time, as determined from the plasma disappearance of intravenously injected (131)I-labeled albumin, was increased to 7.8+/-1.7% in 16 patients with CHF compared with 18 controls (6.5+/-1.9%, P<0.05); these levels normalized after HTX (5.8+/-2.6%, P<0.01, n=17). The change in ratio between (131)I-albumin and simultaneously injected negatively charged glycosylated (125)I-albumin (selectivity index, >1/hour in controls) was lower in patients with HTX (0.993+/-0. 022/hour) than in controls (1.008+/-0.019/hour; P<0.05), which indicated a relatively increased plasma disappearance of negatively charged albumin in HTX patients. Capillary basement membrane thickness was evaluated semiquantitatively from skin biopsies and showed no difference in the 3 groups (control, CHF, and HTX patients). However, in all 3 study groups, subjects with thicker capillary basement membranes had lower albumin escape rates (6.1+/-1. 8%, n=32, versus 7.6+/-2.6% in subjects without thickening of capillary basement membranes, n=19; P<0.05). CONCLUSIONS-The plasma disappearance of albumin increased in patients with compensated CHF and it normalized after HTX. The present normalized capillary basement thicknesses in patients with CHF and the direct association between this parameter and plasma albumin disappearance indicate that previous compensatory microvascular basement membrane growth results in restricted permeability. Microvascular electrostatic properties did not relate to plasma albumin disappearance.

Adult↗
PubMed2000

Plasma clearance of polyfructosan and extracellular body fluid distribution in idiopathic dilated cardiomyopathy and after heart transplantation.

The total extracellular fluid volume and distribution in plasma and interstitial spaces, and the microvascular permeability properties were studied in 16 nonedematous patients with congestive heart failure (CHF) due to idiopathic dilated cardiomyopathy and 17 such patients who underwent heart transplantation (HT) by analyzing the 3-hour plasma disappearance curve of polyfructosan. Eighteen healthy subjects served as controls. Polyfructosan (3.5 kD) is an extracellular marker and inulin analog transported almost solely by diffusion. The initial capillary membrane plasma clearance (i.e., the permeability-surface area product), the interstitial plasma clearance determined at 10 minutes (clearance[10), and the extracellular volume were determined from the polyfructosan curves. I-131-albumin was used as a plasma volume reference. Permeability-surface area product was elevated in both patient groups (6.6 +/- 1.9 ml/ kg/min in the CHF group and 6.7 +/- 2.0 ml/kg/min in the HT group vs 5.1 +/- 1.3 ml/kg/min in controls, p <0.01 for both), whereas clearance(10) was normalized in the HT group (4.5 +/- 0.9 ml/kg/min in the HT group, 4.4 +/- 0.7 ml/kg/min in controls vs 5.0 +/- 0.9 ml/kg/ min in the CHF group, p <0.1 and p <0.05, respectively). The normalization of interstitial plasma clearance of polyfructosan was associated with time since HT (r = 0.49, p <0.05). Plasma volumes were similar in all 3 groups (41 +/- 8 ml/kg in controls, 44 +/- 13 in the CHF group and 39 +/- 8 in the HT group). In contrast, total extracellular volume was elevated in both patients groups (177 +/- 27 ml/kg in the CHF group and 173 +/-27 in the HT group vs 152 +/- 12 in controls, p <0.01). The results strongly suggest a microvascular permeability defect in both patient groups that perhaps plays a role in the extravascular distribution of the excess extracellular fluid volume.

Adult↗
PubMed2000

Assessment of continuous skeletal muscle blood flow during exercise in humans.

The ability to measure regional blood flow from exercising skeletal muscles is of great interest. However, noninvasive techniques such as venous occlusion plethysmography and pulsed Doppler duplex ultrasonography only allow determination of blood flow at rest. The aim of our study was to investigate the influence of position on continuous measured skeletal muscle blood flow response in the upright and supine positions during graded maximal exercise by means of the local (133)Xenon washout technique with portable CdTe(Cl) detectors. Fifteen healthy subjects (8 women and 7 men, mean age 46 +/- 11 years) performed graded maximal bicycle exercise in both supine and upright positions in random order on 2 subsequent days. Blood flow in the musculus tibialis anterior was measured using the local (133)Xenon washout technique. A total of 55-110 MBq of (133)Xenon dissolved in isotonic saline was injected intramuscularly and the gamma emission was registered by light-weight portable CdTe(Cl) detectors. During supine exercise skeletal muscle blood flow increased continuously with increasing work load. However, during upright exercise blood flow increased only at the initial three work loads, then it decreased gradually. Immediately after exercise blood flow returned to preexercise values for both positions. The skeletal muscle blood flow at maximum work load for each subject was 74% (relative flow values) (P < 0.05) higher in the supine compared with the upright position. There was no significant difference in absolute or relative blood flow values at similar time points. Exercise time was longer in the supine (1345 +/- 548 s) compared with the upright position (1148 +/- 453 s) (P < 0.005). The local (133)Xenon washout technique with portable CdTe(Cl) detectors allows continuous determination of skeletal muscle blood flow during graded bicycle exercise in supine and upright positions. Furthermore, blood flow at maximum work load and exercise time was increased in supine compared with upright exercise.

Adult↗