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J Kastrup

Publications and source records attributed to J Kastrup.

At least 55 records · Page 3Linked to original sources
PubMed1998

The phosphorylation state of CD3gamma influences T cell responsiveness and controls T cell receptor cycling.

The T cell receptor (TCR) is internalized following activation of protein kinase C (PKC) via a leucine (Leu)-based motif in CD3gamma. Some studies have indicated that the TCR is recycled back to the cell surface following PKC-mediated internalization. The functional state of recycled TCR and the mechanisms involved in the sorting events following PKC-induced internalization are not known. In this study, we demonstrated that following PKC-induced internalization, the TCR is recycled back to the cell surface in a functional state. TCR recycling was dependent on dephosphorylation of CD3gamma, probably mediated by the serine/threonine protein phosphatase-2A, but independent on microtubules or actin polymerization. Furthermore, in contrast to ligand-mediated TCR sorting, recycling of the TCR was independent of the tyrosine phosphatase CD45 and the Src tyrosine kinases p56(Lck) and p59(Fyn). Studies of mutated TCR and chimeric CD4-CD3gamma molecules demonstrated that CD3gamma did not contain a recycling signal in itself. In contrast, the only sorting information in CD3gamma was the Leu-based motif that mediated lysosomal sorting of chimeric CD4-CD3gamma molecules. Finally, we found a correlation between the phosphorylation state of CD3gamma and T cell responsiveness. Based on these observations a physiological role of CD3gamma and TCR cycling is proposed.

Amino Acid Sequence↗
PubMed1998

Leucine-based receptor sorting motifs are dependent on the spacing relative to the plasma membrane.

Many integral membrane proteins contain leucine-based motifs within their cytoplasmic domains that mediate internalization and intracellular sorting. Two types of leucine-based motifs have been identified. One type is dependent on phosphorylation, whereas the other type, which includes an acidic amino acid, is constitutively active. In this study, we have investigated how the spacing relative to the plasma membrane affects the function of both types of leucine-based motifs. For phosphorylation-dependent leucine-based motifs, a minimal spacing of 7 residues between the plasma membrane and the phospho-acceptor was required for phosphorylation and thereby activation of the motifs. For constitutively active leucine-based motifs, a minimal spacing of 6 residues between the plasma membrane and the acidic residue was required for optimal activity of the motifs. In addition, we found that the acidic residue of leucine-based motifs must be located amino-terminal to the dileucine sequence for proper function of the motifs and that residues surrounding the motifs affect the activity of the motifs. Thus, our observations suggest that the position, the exact sequence, and surrounding residues are major determinants of the function of leucine-based receptor sorting motifs.

Amino Acid Sequence↗
PubMed1998

Two distinct pathways exist for down-regulation of the TCR.

TCR down-regulation plays an important role in modulating T cell responses both during T cell development and in mature T cells. Down-regulation of the TCR is induced by engagement of the TCR by specific ligands and/or by activation of protein kinase C (PKC). We report here that ligand- and PKC-induced TCR down-regulation is mediated by two distinct, independent mechanisms. Ligand-induced TCR down-regulation is dependent on the protein tyrosine kinases p56(lck) and p59(fyn) but independent of PKC and the CD3gamma leucine-based (L-based) internalization motif. In contrast, PKC-induced TCR down-regulation is dependent on the CD3gamma L-based internalization motif but independent of p56(lck) and p59(fyn). Finally, our data indicate that in the absence of TCR ligation, TCR expression levels can be finely regulated via the CD3gamma L-based motif by the balance between PKC and serine/threonine protein phosphatase activities. Such a TCR ligation-independent regulation of TCR expression levels could probably be important in determining the activation threshold of T cells in their encounter with APC.

Amino Acid Sequence↗
PubMed1998

Effects of nisoldipine and lisinopril on microvascular dysfunction in hypertensive Type I diabetes patients with nephropathy.

1. Our objective was to compare the effect of a long-acting calcium antagonist (nisoldipine) compared with an angiotensin-converting enzyme inhibitor (lisinopril) on the non-neurogenic regulation of the microvascular blood flow in hypertensive Type I diabetes patients with diabetic nephropathy.2. We performed a 1-year double-blind, double-dummy randomized controlled study comparing nisoldipine (20-40 mg once daily) with lisinopril (10-20 mg once daily) in 48 hypertensive Type I diabetes patients with diabetic nephropathy. For comparison, 22 age-matched normotensive healthy control subjects were included. Measurements were performed at baseline and after 1 year of antihypertensive treatment. The minimal vascular resistance and distensibility (stiffness) of resistance vessels in skin and skeletal muscle were measured using the local isotope washout method.3. Mean arterial pressure was reduced to the same extent in both groups: nisoldipine, 113+/-2.1 to 105+/-1.6 mmHg (P<0.001); lisinopril, 110+/-2.7 to 101+/-2.1 mmHg (P<0.002) (controls, 88+/-2.2 mmHg; P<0.0001 compared with diabetic patients). Nisoldipine improved the skin vascular distensibility from 28+/-3.3 to 43+/-3.8% (P<0.005) and decreased skin minimal vascular resistance from 16.9+/-1.0 to 13.6+/-0.8 mmHg.ml-1.min.100 g (P<0. 02). Lisinopril had no significant effect on skin vascular distensibility (40+/-4.0% and 41+/-4.4%), but minimal vascular resistance tended to diminish (18.1+/-0.9 to 15.8+/-1.3 mmHg.ml-1. min.100 g (P=0.09). Nisoldipine significantly increased the skin distensibility (P=0.05) after 1 year of antihypertensive treatment compared with lisinopril.4. The control group had a skin vascular distensibility of 54+/-3.2% and a minimal vascular resistance of 10. 8+/-0.7 mmHg.ml-1.min.100 g, both significantly different from the values in the diabetic groups (P<0.0001 for all). Skeletal muscle vascular distensibility was unaltered after 1 year of treatment with both nisoldipine (22+/-3.3% and 19+/-2.7%) and lisinopril (19+/-2.1% and 24+/-2.5%), but was reduced compared with a control value of 43+/-3.7% (P<0.0001 for diabetes patients versus controls). However, neither nisoldipine nor lisinopril had any effect on the increased minimal vascular resistance or the reduced skeletal muscle distensibility.5. Enhanced thickening of the basement membranes of the terminal arteriolar wall was found in skin biopsy specimens in 91% of diabetic patients and 38% only in control subjects (P<0. 000001 both before and after treatment for diabetic patients versus controls). There was no significant effect of antihypertensive treatment on arteriolar hyalinosis.6. The reduction in systemic blood pressure was identical during 1 year of treatment with nisoldipine or lisinopril. The abnormal arteriolar stiffness was more pronounced in the group treated with nisoldipine than with lisinopril and only nisoldipine compared with lisinopril improved the abnormal arteriolar stiffness and minimal vascular resistance in the skin. This suggests that nisoldipine can reverse the peripheral skin perfusion and thereby improve the local protection against development of ischaemic skin lesions in Type I diabetes patients with clinical diabetic nephropathy.

Adult↗
PubMed1998

Beneficial impact of ramipril on left ventricular hypertrophy in normotensive nonalbuminuric NIDDM patients.

OBJECTIVE: To evaluate the effect of the ACE inhibitor ramipril as compared with placebo on left ventricular mass index (LVMI) in normotensive, nonalbuminuric NIDDM patients with left ventricular hypertrophy (LVH). Patients with NIDDM are characterized by excessive cardiovascular morbidity and mortality, and LVH, an independent risk factor for cardiac events, is often present in NIDDM patients. RESEARCH DESIGN AND METHODS: A total of 38 normotensive, nonalbuminuric (albuminuria < 100 mg/24 h) NIDDM patients with LVH (LVMI > 131 g/m2 in men and > 100 g/m2 in women) were enrolled in a 6-month randomized, double-blind parallel group study to compare the effects of ramipril (5 mg/day) with placebo on LVMI (echocardiography, Vingmed CFM725, Diasonics Sonotron), QTc dispersion determined as the interlead variation in QTc interval on standard electrocardiogram (ECG), and 24-h ambulatory blood pressure (A&D TM2420, Tokyo, Japan). A total of 16 ramipril (10 men, 60 +/- 9 years [mean +/- SD]) and 15 placebo-treated (8 men, 55 +/- 10 years) patients completed the study, and their data are presented. RESULTS: Ambulatory blood pressure was almost identical at baseline (132/76 +/- 3/1 vs. 133/74 +/- 5/2 mmHg [mean +/- SEM]) and remained stable during follow-up (134/76 +/- 3/1 vs. 136/74 +/- 6/2 mmHg) in the ramipril and placebo group, respectively. LVMI was comparable at baseline (137.1 +/- 7.0 vs. 129.6 +/- 3.7 g/m2) in the ramipril and placebo group, respectively, and decreased significantly more in the ramipril group as compared with the placebo group (17.6 +/- 3.0 vs. 5.7 +/- 4.6 g/m2, respectively, 11.9 [0.7-23.1] g/m2, mean difference [95% CI]; P = 0.037). QTc dispersion was comparable at baseline (60.2 [5.5] vs. 64.1 [6.5] ms) and did not change significantly during follow-up: -2.5 [7.0] vs. -12.2 [9.5] ms; mean difference 9.8 (-14.2 to 33.8 ms) in the ramipril and placebo group, respectively. CONCLUSIONS: Ramipril induces regression of LVH in normotensive, nonalbuminuric NIDDM patients, independent of reduction in systemic blood pressure.

Aged↗
PubMed1997

Regulation and function of the CD3gamma DxxxLL motif: a binding site for adaptor protein-1 and adaptor protein-2 in vitro.

Several receptors are downregulated by internalization after ligand binding. Regulation of T cell receptor (TCR) expression is an important step in T cell activation, desensitization, and tolerance induction. One way T cells regulate TCR expression is by phosphorylation/dephosphorylation of the TCR subunit clusters of differentiation (CD)3gamma. Thus, phosphorylation of CD3gamma serine 126 (S126) causes a downregulation of the TCR. In this study, we have analyzed the CD3gamma internalization motif in three different systems in parallel: in the context of the complete multimeric TCR; in monomeric CD4/CD3gamma chimeras; and in vitro by binding CD3gamma peptides to clathrin-coated vesicle adaptor proteins (APs). We find that the CD3gamma D127xxxLL131/132 sequence represents one united motif for binding of both AP-1 and AP-2, and that this motif functions as an active sorting motif in monomeric CD4/ CD3gamma molecules independently of S126. An acidic amino acid is required at position 127 and a leucine (L) is required at position 131, whereas the requirements for position 132 are more relaxed. The spacing between aspartic acid 127 (D127) and L131 is crucial for the function of the motif in vivo and for AP binding in vitro. Furthermore, we provide evidence indicating that phosphorylation of CD3gamma S126 in the context of the complete TCR induces a conformational change that exposes the DxxxLL sequence for AP binding. Exposure of the DxxxLL motif causes an increase in the TCR internalization rate and we demonstrate that this leads to an impairment of TCR signaling. On the basis of the present results, we propose the existence of at least three different types of L-based receptor sorting motifs.

Adaptor Protein Complex alpha Subunits↗
PubMed1997

Left ventricular hypertrophy in non-insulin-dependent diabetic patients with and without diabetic nephropathy.

The aim of our cross-sectional case-control study was to evaluate putative mechanisms of the increased cardiac morbidity and mortality in NIDDM patients with or without diabetic nephropathy. Fifty-one NIDDM patients with diabetic nephropathy (38 males, age 61 +/- 8 years, group 1), 53 NIDDM patients with normoalbuminuria (42 males, 61 +/- 7 years, group 2), and 22 non-diabetic control subjects (15 males, 58 +/- 8 years, group 3) were investigated. Previous antihypertensive treatment was withdrawn 2 weeks before the study. Left ventricular mass index (LVMI) and systolic function were determined by echocardiography. LVMI was elevated, mean +/- SE, in group 1: 157 +/- 6 g m(-2), and in group 2: 139 +/- 7 g m(-2), as compared with group 3: 95 +/- 5 g m(-2) (p < 0.001, for both), and in group 1 as compared with group 2 (p = 0.05). The prevalence of left ventricular hypertrophy (LVH) (LVMI > 131 g m(-2) in men and > 100 gm(-2) in women) was much higher in group 1: 75% (95% CI, 60-86), and group 2: 51% (95% CI, 37-65), as compared with group 3: 9% (95% CI, 1-29) (p < 0.001, for both), and in group 1 as compared with group 2 (p < 0.01). Shortening fraction of the left ventricle, % +/- SE, was relatively reduced in group 1: 32.5 +/- 1.1%, and group 2: 33.4 +/- 1.1%, as compared with group 3: 41.2 +/- 1.2% (p < 0.01, for both). In a subgroup of 26 normoalbuminuric normotensive NIDDM patients, LVMI was higher than in 14 normotensive non-diabetic control subjects: 137 +/- 10 g m(-2) vs 96 +/- 7 g m(-2), respectively (p < 0.005). The prevalence of LVH was 42% (95% CI, 23-63) and 14% (95% CI, 2-43) (p = 0.07) in these two groups, respectively. In conclusion, normotensive and hypertensive NIDDM patients with and without diabetic nephropathy frequently suffer from LVH and relatively reduced systolic function which may constitute independent risk factors for fatal and non-fatal cardiac events.

Age Factors↗
PubMed1996

Effects of orthotopic cardiac transplantation on structural microangiopathy and abnormal hemodynamics in idiopathic dilated cardiomyopathy.

To examine whether cardiac transplantation would reverse morphologic and hemodynamic changes in peripheral circulation in idiopathic dilated cardiomyopathy, the structure of terminal arterioles and minimal vascular resistance were measured in skin at the dorsum of the foot in the same 14 patients before and 80 +/- 21 (mean +/- SD) days and 387 +/- 46 days after transplantation. The results were compared with data from a group of 16 healthy subjects. Blood flow was measured by the local technetium-99m pertechnetate washout method in a vascular bed relaxed with histamine. Structural microangiopathy (enhanced thickening of the basement membranes) in the arterioles was disclosed in skin biopsies in 11 of 14 patients before transplant, but in none of the 16 control subjects (p < 0.002). These abnormalities were unchanged 80 days after cardiac transplantation. However, arteriolar wall thickening was significantly reduced over the 1-year period after transplantation (p < 0.05), but this was not complete. Transplantation also led to a significant delayed decrease in minimal vascular resistance: before transplantation, 10.1 +/- 3.2 mm Hg.ml-1.100 g.min (mean +/- SD); 80 days after transplantation, 9.3 +/- 3.1 mm Hg.ml-1.100 g.min (p = NS), and 1 year after transplantation 7.6 +/- 2.4 mm Hg.ml-1 100 g.min (p < 0.01). Minimal vascular resistance before and 80 days after transplantation was significantly increased compared with that in healthy control subjects (6.3 +/- 1.7 mm Hg.ml-1 100g.min [p < 0.0003 and p < 0.003, respectively]). However, 1 year after transplantation, minimal vascular resistance was reduced to comparable levels when compared with that in control subjects (p = NS). These results indicate that structural microangiopathy and minimal vascular resistance in skin are improved slowly and gradually within the first year after orthotopic cardiac transplantation in patients with idiopathic dilated cardiomyopathy, however, the remodeling of histopathology is not accompanied by complete normalization.

Adult↗
PubMed1996

Plasma endothelin in congestive heart failure: effect of the ACE inhibitor, fosinopril.

OBJECTIVES: The study evaluates the influence of treatment with the angiotensin-converting enzyme inhibitor, fosinopril, on the plasma endothelin level in patients with congestive heart failure, and the relationship between plasma endothelin and clinical study parameters (bicycle exercise test, echocardiography, heart failure score and blood pressure). METHODS: Plasma endothelin was measured in 34 patients with moderately severe congestive heart failure at randomisation in the fosinopril/placebo-controlled study 'Fosinopril Efficacy and Safety Trial' and at the end of the 12-week study period. RESULTS: The patients had elevated pre-treatment plasma endothelin concentrations (3.5 +/- 1.2 pg/ml, mean +/- s.d., n = 34) compared with healthy volunteers (2.0 +/- 0.4 pg/ml, n = 21, P < 0.0001). Treatment with fosinopril for 12 weeks lowered plasma endothelin from 3.5 +/- 1.2 to 2.5 +/- 0.7 pg/ml (m = 18, P < 0.005), in contrast to the non-significant increase in the placebo-treated group 3.5 +/- 1.3 to 4.3 +/- 2.4 pg/ml, n = 16). A multiple regression analysis for baseline study parameters, demonstrated a significant relationship between plasma endothelin and exercise test duration and a composite heart failure score classification (r = 0.53, P < 0.001). CONCLUSIONS: Treatment of patients with congestive heart failure with the angiotensin-converting enzyme inhibitor, fosinopril, reduce the elevated plasma endothelin level to normal values. The relation between plasma endothelin and clinical parameters indicates that endothelin may play a pathophysiological role in the progression of congestive heart failure.

Aged↗
PubMed1996

Plasma endothelin in congestive heart failure: a predictor of cardiac death?

BACKGROUND: Endothelin is a potent vasoconstrictor, with growth-promoting and possible cardiotoxic and arrhythmogenic properties. This study investigates the association between increased plasma endothelin in congestive heart failure and prognosis. METHODS AND RESULTS: Forty-four patients with congestive heart failure showed increased plasma endothelin concentrations (mean +/- SD, 3.7 +/- 1.7 pg/mL; n = 44) compared with healthy volunteers (2.0 +/- 0.4 pg/mL, n = 21, P < .00003). Plasma endothelin increased with the severity of the disease. All patients were followed for an average of 17 months (range, 2-25 months). Cardiac mortality was 27% (8 of 30 patients) in the group with plasma endothelin concentrations above 3 pg/mL and 0% (0 of 14 patients) in the group with plasma endothelin concentrations below 3 pg/mL (P < .05). In contrast, separation of patients based on different New York Heart Association groups and ejection fractions revealed no significant difference regarding this endpoint. CONCLUSIONS: Increased plasma endothelin concentrations in patients with congestive heart failure appears to serve as a predictor of cardiac death.

Adult↗
PubMed1996

Subcutaneous blood flow in man during sleep with continuous epidural anaesthesia.

BACKGROUND: Subcutaneous blood flow increases during sleep and we evaluated if this increase is affected by epidural anaesthesia. METHODS: Lower leg subcutaneous blood flow was determined by 133Xenon clearance in ten subjects during continuous epidural anaesthesia at L2-L3 including eight hours of sleep, while the upper abdominal subcutaneous blood flow served as control. RESULTS: Epidural anaesthesia to the level of the umbilicus was followed by an increase in the lower leg subcutaneous blood flow from 3.4 (1.8-6.3) to 7.8 (3.6-16.9) ml min-1 100 g-1 (median and range; P < 0.001) and returned to 3.5 (2.4-7.6) ml min-1 100 g-1 after 88 (45-123) min. In contrast, until the period of sleep the upper abdominal region blood flow remained at 5.2 (3.2-6.4) ml min-1 100 g-1. During sleep, lower leg subcutaneous blood flow did not change significantly, but the upper abdominal flow increased to 6.2 (5.2-7.2) ml min-1 100 g-1 after 34 (29-70) min (P < 0.01), and it remained elevated for 125 (100-164) min. CONCLUSIONS: The results indicate that although epidural anaesthesia induced only a temporary increase in lower leg subcutaneous blood flow, it hindered the rise in subcutaneous blood flow normally manifest during early sleep.

Abdominal Muscles↗
PubMed1995

Insulin-resistant glucose metabolism in patients with microvascular angina--syndrome X.

Studies in patients with microvascular angina (MA) or the cardiologic syndrome X have shown a hyperinsulinemic response to an oral glucose challenge, suggesting insulin resistance and a role for increased serum insulin in coronary microvascular dysfunction. The aim of the present study was to examine whether patients with MA are insulin-resistant. Nine patients with MA and seven control subjects were studied. All were sedentary and glucose-tolerant. Coronary arteriography was normal in all participants, and exercise-induced coronary ischemia was demonstrated in all MA patients. A euglycemic, hyperinsulinemic clamp was performed in combination with indirect calorimetry. Biopsy of vastus lateralis muscle was taken in the basal state and after 4 hours of euglycemia and hyperinsulinemia (2 mU.kg-1.min-1). The fasting level of "true" serum insulin was significantly higher (43 +/- 6 v 22 +/- 3 pmol/L, P < .02) and the rate of insulin-stimulated glucose disposal to peripheral tissues was lower in patients with MA (13.4 +/- 1.0 v 18.2 +/- 1.4 mg.kg fat-free mass [FFM]-1.min-1, P < .02) due to a decrease in nonoxidative glucose metabolism (8.4 +/- 0.9 v 12.5 +/- 1.3 mg.kg FFM-1.min-1, P < .02). No difference was found in glucose or lipid oxidation rates between the two groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1995

Nocturnal temperature and subcutaneous blood flow in humans.

The aim of this study was to investigate the possible relationship between variations in local skin and body temperatures, and a subcutaneous hyperaemia response during sleep in humans. Nocturnal subcutaneous blood flow (SBF) was measured in the lower legs of 9 subjects for 8-12 h under outpatient conditions. The core temperature was measured by a tympanic membrane temperature sensor, and the local skin temperature was measured by a skin temperature sensor. The 133Xe wash-out technique with portable CdTe(Cl) detectors was used for measurement of the SBF. The SBF increased significantly (P < 0.0001) after 1 h sleep, with the hyperaemia persisting for 2 h. During the hyperaemic phase, the local skin temperature increased significantly (P < 0.0001) and then decreased again in the post-hyperaemic phase (P < 0.01). The core temperature decreased significantly during the measurement period (P < 0.01). Separate ordinary linear regression analyses revealed no significant correlations between the measured temperature parameters and the blood flow levels during sleep. The results indicate no governing role of the local skin or body temperatures on the local SBF. The local skin temperature increased significantly secondary to the nocturnal subcutaneous hyperaemia (i.e. active vasodilatation), which is believed to be involved in a thermoregulatory effector mechanism.

Adult↗
PubMed1995

Microvascular distensibility in two different vascular beds in idiopathic dilated cardiomyopathy.

The local isotope-washout technique allows discrimination between blood flow in skin and muscle. Arteriolar constriction, mediated by the sympathetic nervous system, is abolished in a papaverine-histamine-relaxed vascular bed. Microvascular distensibility of relaxed resistance vessels was measured in skeletal muscle and skin of the lower limb in patients with congestive heart failure (CHF) secondary to idiopathic dilated cardiomyopathy and in healthy subjects. Vascular transmural pressure was elevated 40 mmHg by head-up tilt and caused muscle blood flow to increase by 11 +/- 9% in 20 CHF patients compared with 44 +/- 20% in 11 control subjects (P < 0.0003). Also the increase in skin blood flow was significantly reduced: 31 +/- 18% in 42 CHF patients compared with 62 +/- 29% in 25 control subjects (P < 0.001). Regression analysis demonstrated a significant association between microvascular distensibility in skin and skeletal muscle tissue (P = 0.003, r = 0.51, n = 31). Structure of terminal arterioles was determined in skin biopsies, and structural microangiopathy was found in 32 of 42 CHF patients. Multiple regression analysis demonstrated the degree of microangiopathy to be the only parameter significantly associated with microvascular distensibility (P = 0.005, r = 0.42). (There was no association to NY Heart Association functional class, left ventricular ejection fraction, duration of CHF, age of subject, or mean arterial blood pressure.) We conclude that patients with idiopathic dilated cardiomyopathy have similar decreased microvascular distensibility in skeletal muscle and skin. Furthermore, structural alterations in terminal arterioles seem to be associated with decreased distensibility and increased stiffness of the cutaneous microvascular bed.

Adult↗