Biomedical subjects

P B Hansen

Publications and source records attributed to P B Hansen.

At least 19 recordsLinked to original sources

PubMed2005

Vasoconstrictor and vasodilator effects of adenosine in the mouse kidney due to preferential activation of A1 or A2 adenosine receptors.

The present experiments in mice were performed to determine the steady-state effects of exogenous adenosine on the vascular resistance of the whole kidney, of superficial blood vessels, and of afferent arterioles. The steady-state effect of an intravenous infusion of adenosine (5, 10, and 20 microg/min) in wild-type mice was vasodilatation as evidenced by significant reductions of renal and superficial vascular resistance. Resistance decreases were augmented in adenosine 1 receptor (A1AR) -/- mice. Renal vasodilatation by the A2aAR agonist CGS 21680A [2-p-(2-carboxyethyl)phenethyl-amino-5'-N-ethylcarboxamido-adenosine hydrochloride] (0.25, 0.5, and 1 microg/kg/min) and inhibition of adenosine-induced relaxation by the A2aAR antagonist ZM-241385 [4-(2-[7-amino-2-(2-furyl)[1,2,4]triazolo[2,3-a][1,3,5]triazin-5-yl-amino]ethyl)phenol] (20 mg/kg) suggests that the reduction of renovascular resistance was largely mediated by A2aAR. After treatment with Nomega-nitro-L-arginine methyl ester (L-NAME) adenosine was unable to alter superficial blood flow and resistance significantly indicating that adenosine-induced dilatation is NO-dependent. Absence of a dilatory effect in endothelial nitric-oxide synthase (NOS) -/- mice suggests endothelial NOS as the source of NO. When infused into the subcapsular interstitium, adenosine reduced superficial blood flow through A1AR activation. Adenosine (10(-7) M) constricted isolated perfused afferent arterioles when added to the bath but not when added to the luminal perfusate. Luminal adenosine caused vasoconstriction in the presence of L-NAME or the A2AR antagonist 3,7-dimethyl-1-(2-propynyl)xanthine. Our data show that global elevation of renal adenosine causes steady-state vasorelaxation resulting from adenosine 2 receptor (A2AR)-mediated generation of NO. In contrast, selective augmentation of adenosine around afferent arterioles causes persistent vasoconstriction, indicating A1AR dominance. Thus, adenosine is a renal constrictor only when it can interact with afferent arteriolar A1AR without affecting the bulk of renal A2AR at the same time.

Adenosine↗

PubMed2004

Rapid non-genomic effects of aldosterone on rodent vascular function.

The main role of aldosterone is to maintain body sodium homeostasis by promoting salt reabsorption in the collecting ducts of the kidney. In the cardiovascular system, aldosterone may be harmful in a number of disease states by inducing fibrosis and vascular dysfunction. The present review describes novel results from several laboratories, which show that aldosterone also has beneficial effects in the cardiovascular system by stimulating the production of nitric oxide (NO) from the endothelium. The effect of aldosterone is seen within minutes, and is not inhibited by blockers of gene transcription, thus pointing to a non-genomic mechanism. Furthermore, this potentially beneficial effect is observed at low physiological concentrations of aldosterone (0.1-10 pm). The effect is mediated by the classical mineralocorticoid receptor, and it involves heat shock protein 90, phosphatidylinositol (PI)-3 kinase, protein kinase B, endothelial nitric oxide synthase, and liberation of NO. It is proposed that in healthy individuals with a functioning NO system, the detrimental effects of aldosterone on cardiovascular function are balanced by activation of the potentially beneficial effect of NO. However, in situations with endothelial dysfunction, such as congestive heart failure and hypertension, the negative effects of aldosterone are unopposed and inhibition of aldosterone is warranted.

Aldosterone↗

PubMed2004

Plasma renin in mice with one or two renin genes.

AIM: In the present study we have investigated whether the presence of a second renin gene exerts an overriding influence on plasma renin such that mice with two renin genes have consistently higher renin levels than mice with only one renin gene. METHODS: Plasma renin was determined as the rate of angiotensin I generation using a radioimmunoassay (RIA) kit with (plasma renin concentration, PRC) or without (plasma renin activity, PRA) the addition of purified rat angiotensinogen as substrate. RESULTS: In male 129SvJ, DBA/2 and Swiss Webster mice, strains possessing both Ren-1 and Ren-2, PRC (ng Ang I mL(-1) h(-1)) averaged 178 +/- 36, 563 +/- 57 and 550 +/- 43 while PRA was 2.9 +/- 0.5, 3.6 +/- 0.8 and 7.8 +/- 1.2. In male C57BL/6, C3H and BALB/c mice that express only Ren-1, PRC averaged 426 +/- 133, 917 +/- 105 and 315 +/- 72, and PRA was 3.4 +/- 1.0, 6.9 +/- 1.7 and 4.5 +/- 1.2. In the two renin gene A1AR-/- mice compared with the one renin gene A1AR+/+, PRC averaged 538 +/- 321 and 415 +/- 159 while PRA averaged 3.2 +/- 1.1 and 4.4 +/- 1.4 ng Ang I mL(-1) h(-1). Aldosterone levels showed no significant differences between one renin (C57BL/6, C3H and BALB/c) and two renin (129SvJ, DBA/2 and Swiss Webster) gene mice. Furthermore, by quantitative real-time polymerase chain reaction (RT-PCR) we found no correlation between the number of renin genes and whole kidney renin mRNA levels from one and two renin gene mice. CONCLUSION: Our data show that baseline plasma renin is not systematically higher in mice with two renin genes than in one renin gene mice. Thus, the presence of a second renin gene does not seem to be a major determinant of differences in PRC between different mouse strains.

Aldosterone↗

PubMed2004

Anagrelide treatment in 52 patients with chronic myeloproliferative diseases.

In this retrospective multi-centre study, we report our experience with anagrelide in the treatment of thrombocytosis in patients with chronic myeloproliferative diseases. Our study included 52 patients (age 20-78 years). The initial anagrelide dose was, in general, 0.5 mg once daily and mean maintenance dosage was 1.7 mg/day. The overall response rate was 79% including 75% complete remission and 4% partial remission. Forty-two patients (81%) had adverse effects and in 29% of the study population, the adverse effects necessitated cessation of anagrelide. The most common adverse effect was moderate anaemia (50%). Two patients experienced erectile dysfunction which has been described only once previously in association with anagrelide treatment. One patient progressed to acute leukaemia. However, this patient had been pre-treated with two potentially leukaemogenic drugs and had only been in short-term treatment with anagrelide. Furthermore, a total of 13 events were recorded. More than 25% of these events occurred in patients with platelet counts between 400 and 600 x 10(9)/l and almost 40% of all events occurred in patients with platelet counts above 400 x 10(9)/l. This observation supports the hypothesis that aggressive control of thrombocytosis to a platelet count <400 x 10(9)/l might reduce the number of thrombohaemorrhagic events. Anagrelide is safe and effective in reducing the platelet counts, but a high proportion of the patients discontinue treatment because of the adverse effects of the drug.

Adult↗

PubMed2003

Rapid inhibition of vasoconstriction in renal afferent arterioles by aldosterone.

Aldosterone has been suggested to elicit vessel contraction via a nongenomic mechanism. We tested this proposal in microdissected, perfused rabbit renal afferent arterioles. Aldosterone had no effect on internal diameter in concentrations from 10(-10) to 10(-5) mol/L, but aldosterone abolished the ability of 100 mmol/L KCl to induce vascular contraction. The inhibitory effect of aldosterone was observed from 1 pmol/L. The inhibitory effect was significant after 5 minutes and maximal after 20 minutes and was fully reversible. Actinomycin D (10(-6) mol/L) prolonged the effect of aldosterone. The effect was abolished by the mineralocorticoid receptor antagonist spironolactone (10(-7) mol/L) but not by the glucocorticoid receptor antagonist mifepristone (10(-6) mol/L). The K+-mediated increase of intracellular calcium concentration in afferent arterioles was not affected by aldosterone. Mineralocorticoid receptor was detected by reverse transcription-polymerase chain reaction and immunohistochemistry in rat renal vasculature and rabbit endothelial cells. Inhibition of phosphatidylinositol (PI)-3 kinase with LY 294002 (3x10(-6) mol/L) restored sensitivity to K+ in the presence of aldosterone, and afferent arterioles were immunopositive for PI-3 kinase subunit p110alpha. Inhibition of NO formation by L-NAME (10(-4) mol/L) or inhibition of soluble guanylyl cyclase with 1H-(1,2,4)Oxadiazolo[4,3-a]quinoxaline-1-one restored K+-induced vasoreactivity in the presence of aldosterone. Similar to aldosterone, the NO donor sodium nitroprusside inhibited K+-induced vascular contraction. Geldanamycin (10(-6) mol/L), an inhibitor of heat shock protein 90, abolished aldosterone-induced vasorelaxation. We conclude that aldosterone inhibits depolarization-induced vasoconstriction in renal afferent arterioles by a rapid nongenomic mechanism that is initiated by mineralocorticoid receptor activation and involves PI-3 kinase, protein kinase B, and heat shock protein 90-mediated stimulation of NO generation.

11-beta-Hydroxysteroid Dehydrogenase Type 2↗

PubMed2001

Differential expression of T- and L-type voltage-dependent calcium channels in renal resistance vessels.

The distribution of voltage-dependent calcium channels in kidney pre- and postglomerular resistance vessels was determined at the molecular and functional levels. Reverse transcription-polymerase chain reaction analysis of microdissected rat preglomerular vessels and cultured smooth muscle cells showed coexpression of mRNAs for T-type subunits (Ca(V)3.1, Ca(V)3.2) and for an L-type subunit (Ca(V)1.2). The same expression pattern was observed in juxtamedullary efferent arterioles and outer medullary vasa recta. No calcium channel messages were detected in cortical efferent arterioles. Ca(V)1.2 protein was demonstrated by immunochemical labeling of rat preglomerular vasculature and juxtamedullary efferent arterioles and vasa recta. Cortical efferent arterioles were not immunopositive. Recordings of intracellular calcium concentration with digital fluorescence imaging microscopy showed a significant increase of calcium in response to K(+) (100 mmol/L) in isolated afferent arterioles (140+/-25%) and in juxtamedullary efferent arterioles (118+/-21%). These calcium responses were attenuated by the L-type antagonist calciseptine and by the T-type antagonist mibefradil. Intracellular calcium increased in response to K(+) in cortical efferent arterioles (21+/-9%). Mibefradil and nickel concentration dependently blocked K(+)-induced contraction of perfused rabbit afferent arterioles. Calciseptine blocked the contraction mediated by K(+) (EC(50) 8x10(-14)). S-(-)-Bay K 8644 had no effect on vascular diameter in the afferent arteriole. We conclude that voltage-dependent L- and T-type calcium channels are expressed and of functional significance in renal cortical preglomerular vessels, in juxtamedullary efferent arterioles, and in outer medullary vasa recta, but not in cortical efferent arterioles.

Animals↗

PubMed2001

[Clinical use of recombinant human thrombopoietin. Status and perspectives].

Thrombopoietin (TPO) is primarily produced by hepatocytes and regulates the production and differentiation of megakaryocytes and platelets in the bone marrow. The endogenous TPO level is increased when the megakaryocyte count is low, and high in aplastic anaemia and after myeloablative chemotherapy. TPO is cloned and manufactured by a recombinant technique for clinical use. Treatment with recombinant human TPO (rhTPO) after intensive chemotherapy may reduce the need for platelet transfusions. Administration of granulocyte colony-stimulating factor in combination with rhTPO has enhanced the mobilisation and harvest product of haematopoietic stem cells. Whether rhTPO is effective in the treatment of the myelodysplastic syndrome, aplastic anaemia, and other conditions with bone marrow insufficiency (including AIDS) is not yet known. In liver cirrhosis, the endogenous TPO level rapidly increases after liver transplantation. Accordingly, substitution of rhTPO may be indicated in advanced liver failure complicated by thrombocytopenia and bleeding.

Blood Platelets↗

PubMed2001

Localization of prostaglandin E(2) EP2 and EP4 receptors in the rat kidney.

We investigated the localization of cAMP-coupled prostaglandin E(2) EP2 and EP4 receptor expression in the rat kidney. EP2 mRNA was restricted to the outer and inner medulla in rat kidney, as determined by RNase protection assay. RT-PCR analysis of microdissected resistance vessels and nephron segments showed EP2 expression in descending thin limb of Henle's loop (DTL) and in vasa recta of the outer medulla. The EP4 receptor was expressed in distal convoluted tubule (DCT) and cortical collecting duct (CCD) in preglomerular vessels, and in outer medullary vasa recta. Butaprost, an EP2 receptor-selective agonist, dose dependently raised cAMP levels in microdissected DTL and outer medullary vasa recta specimens but had no effect in EP2-negative outer medullary collecting duct segments. Dietary salt intake did not alter EP2 expression in the kidney medulla. These results suggest that PGE(2) may act in the resistance vessels and in the DTL and DCT-CCD segments as a paracrine, cAMP-dependent regulator of vascular resistance and tubular transport, respectively.

Animals↗

PubMed2000

Vascular smooth muscle cells express the alpha(1A) subunit of a P-/Q-type voltage-dependent Ca(2+)Channel, and It is functionally important in renal afferent arterioles.

In the present study, we tested whether the alpha(1A) subunit, which encodes a neuronal isoform of voltage-dependent Ca(2+) channels (VDCCs) (P-/Q-type), was present and functional in vascular smooth muscle and renal resistance vessels. By reverse transcription-polymerase chain reaction and Southern blotting analysis, mRNA encoding the alpha(1A) subunit was detected in microdissected rat preglomerular vessels and vasa recta, in cultures of rat preglomerular vascular smooth muscle cells (VSMCs), and in cultured rat mesangial cells. With immunoblots, alpha(1A) subunit protein was demonstrated in rat aorta, brain, aortic smooth muscle cells (A7r5), VSMCs, and mesangial cells. Immunolabeling with an anti-alpha(1A) antibody was positive in acid-macerated, microdissected preglomerular vessels and in A7r5 cells. Patch-clamp experiments on aortic A7r5 cells showed 22+/-4% (n=6) inhibition of inward Ca(2+) current by omega-Agatoxin IVA (10(-8) mol/L), which in this concentration is a specific inhibitor of P-type VDCCs. Measurements of intracellular Ca(2+) in afferent arterioles with fluorescence-imaging microscopy showed 32+/-9% (n=10) inhibition of the K(+)-induced rise in Ca(2+) in the presence of 10(-8) mol/L omega-Agatoxin IVA. In microperfused rabbit afferent arterioles, omega-Agatoxin IVA inhibited depolarization-mediated contraction with an EC(50) of 10(-17) mol/L and complete blockade at 10(-14) mol/L. We conclude that the alpha(1A) subunit is expressed in VSMCs from renal preglomerular resistance vessels and aorta, as well as mesangial cells, and that P-type VDCCs contribute to Ca(2+) influx in aortic and renal VSMCs and are involved in depolarization-mediated contraction in renal afferent arterioles.

Animals↗

PubMed2000

[Circulatory support with the mechanical heart, "HeartMate"].

Treatment with the mechanical heart, HeartMate, has been introduced in Denmark. Short-term circulatory support can be obtained by intraaortic balloon counterpulsation, an external centrifugal pump and the total artificial heart. Long-term circulatory support can be established by treatment with the HeartMate. The principle of the mechanical heart is simple--a pump is implanted in parallel to the existing heart and connected to external, portable batteries. The patient quickly improves and is brought in an optimal state for transplantation. A few patients have been able to omit the subsequent heart transplantation. The patient's own heart improved during the treatment and the native heart functioned again after the system was explanted. The main complications during treatment are bleeding, infection, thromboembolic events and systemic failure. Permanent, fully implantable mechanical circulatory pumps are under development--which may herald the beginning of a whole new era for treatment of cardiac failure.

Assisted Circulation↗

PubMed2000

[Economic aspects of implementation of the mechanical heart, "HeartMate"].

This economic evaluation was performed to assess the economic consequences for society and for the Danish health care sector of replacing the traditional treatment with Biomedicus assist device with The Mechanical Heart, HeartMate, as a bridge to transplantation for patients with severe cardiac failure. A cost-effectiveness analysis showed that the use of HeartMate is more cost-effective than the use of Biomedicus assist device. Using HeartMate one life-year gained costs DKK 225,000. Using Biomedicus one life-year gained costs DKK 270,000. The use of HeartMate results in an additional expenditure of DKK 615,000 per patient. By this additional expenditure the patients gain 3.6 extra life-years on average. The marginal expenditure by replacing the Biomedicus treatment with HeartMate is DKK 170,000 per extra life-year gained.

Cost-Benefit Analysis↗

PubMed2000

Human immunodeficiency virus-associated malignant lymphoma in eastern Denmark diagnosed from 1990-1996: clinical features, histopathology, and association with Epstein-Barr virus and human herpesvirus-8.

The clinicopathological features of human immunodeficiency virus (HIV)-associated lymphoma were investigated in a retrospective study of 85 adult patients in eastern Denmark diagnosed during the period 1990-1996. The possible pathogenetic role of Epstein-Barr virus (EBV) and human herpesvirus 8 (HHV-8) in these tumours was also studied. Seventy patients (82%) presented with extranodal disease and 26 (31%) had CNS involvement at diagnosis. Diffuse large cell B-cell lymphoma was the most frequent histological subtype, comprising 65 of 79 cases available for microscopic re-evaluation (82%) and including 20 of 23 evaluable patients with CNS lymphoma (87%). EBV RNA was demonstrated by in situ hybridization in 51 of 65 evaluable tumours (79%) and in 14 of 16 cases (88%) with CNS-lymphoma. Three cases showed a T-cell phenotype. The presence of HHV-8 DNA was analysed by PCR in 32 cases. A strong band consistent with tumour cell infection was detected in only one case, weaker bands being seen in 4 cases. None of these patients had primary effusion lymphomas. In conclusion, Danish AIDS-related lymphomas are of predominantly high-grade B-cell type with extranodal localization and atypical presentation. Our results provide further evidence that EBV plays a major role in the pathogenesis of large cell AIDS-related lymphoma, whereas HHV-8 does not appear to contribute significantly to the development of solid lymphomas in this group of patients.

Adult↗

PubMed2000

Exocytosis and endocytosis in juxtaglomerular cells.

The cellular events related to secretion of renin are not well understood. Here we review some of the evidence that has led to the current understanding of renin secretion as a process that involves exocytosis as the predominant mode of secretion. This is based on the observation of occasional fusion events between secretory granules and cell membrane and measurement of intermittent secretion of renin from single afferent arterioles, with a renin content of each secretion episode that corresponds to the renin content of one secretory granule. More recently it has been demonstrated that the afferent arterioles lose a large number of renin granules after acute stimulation without changing the average granular volume. Current electrophysiological techniques have now permitted direct measurements of cell membrane capacitance in juxtaglomerular (JG) cells as a measure of net addition (exocytosis) or removal (endocytosis) of membrane material. With this technique we have shown that cAMP, which is a vasodilator and stimulates renin secretion, enhances net exocytosis at low concentrations, while at higher concentrations membrane retrieval processes are also stimulated. We suggest that both exocytosis and endocytosis are regulated processes in the JG-cells and both may be important for the long-term control of renin secretion at the single cell level.

Animals↗

PubMed2000

The alpha(1G)-subunit of a voltage-dependent Ca(2+) channel is localized in rat distal nephron and collecting duct.

The molecular type and localization of calcium channels along the nephron are not well understood. In the present study, we assessed the distribution of the recently identified alpha(1G)-subunit encoding a voltage-dependent calcium channel with T-type characteristics. Using a RNase protection assay, alpha(1G)-mRNA levels in kidney regions were determined as inner medulla >> outer medulla congruent with cortex. RT-PCR analysis of microdissected rat nephron segments revealed alpha(1G) expression in the distal convoluted tubule (DCT), in the connecting tubule and cortical collecting duct (CT+CCD), and inner medullary collecting duct (IMCD). alpha(1G) mRNA was expressed in the IMCD cell line mIMCD-3. Single- and double-labeling immunohistochemistry and confocal laser microscopy on semithin paraffin sections of rat kidneys by using an anti-alpha(1G) antibody demonstrated a distinct labeling at the apical plasma membrane domains of DCT cells, CT principal cells, and IMCD principal cells.

Animals↗

PubMed1999

Fatal virus-associated hemophagocytic syndrome associated with coexistent chronic active hepatitis B and acute hepatitis C virus infection.

A 28-year-old man was admitted to our department with intermittent fever, hepatosplenomegaly and pancytopenia. Liver parameters and serum ferritin were markedly elevated. Bone marrow biopsy showed hypocellularity, histiocytic hyperplasia, and hemophagocytosis consistent with a virus-associated hemophagocytic syndrome (VAHS). There was serological evidence of chronic active hepatitis B and acute hepatitis C virus infection. The patient died despite aggressive immunosuppressive and supportive treatment. Autopsy revealed signs of acute viral hepatitis with cholestasis. Histiocytes engaged in hemophagocytosis were observed in bone marrow and spleen. The condition was interpreted as VAHS associated with chronic active hepatitis B and acute hepatitis C virus infection. To our knowledge this is the first report of a hemophagocytic syndrome in that setting.

Acute Disease↗

PubMed1999

Do blood levels of neuron-specific enolase and S-100 protein reflect cognitive dysfunction after coronary artery bypass?

BACKGROUND: Neuron-specific enolase (NSE) and S-100 protein have been used as markers for major brain damage. Cognitive dysfunction after cardiac surgery represents subtle brain damage that is detected by neuropsychological testing. We hypothesised that blood levels of NSE and S-100 protein would increase after coronary artery bypass surgery and that the change in blood level would correlate with the change in cognitive function. METHODS: We included 35 elderly patients undergoing coronary artery bypass surgery. Neuropsychological testing was performed before surgery and postoperatively at discharge from hospital and after 3 months using a neuropsychological test battery. Serum levels of NSE and S-100 protein were measured before surgery and postoperatively after 24 h and 48 h. RESULTS: Serum level of both NSE and S-100 protein increased significantly 24 and 48 h after coronary artery bypass. Only the increase in NSE after 24 h was found to correlate with the degree of cognitive dysfunction at discharge from hospital. The increase in S-100 protein after 24 h correlated significantly with the duration of cardiopulmonary bypass. CONCLUSION: NSE seems to be a useful blood marker for early cognitive dysfunction after coronary artery bypass surgery.

Aged↗

PubMed1998

[Virus-associated hemophagocytic syndrome. Diagnosis and treatment].

Virus-associated haemophagocytic syndrome (VAHS) is a rare disease characterized by fever, splenomegaly, cytopenia and histiocytic proliferation with haemophagocytosis in the reticuloendothelial system. The clinical course of VAHS can be dramatic and the prognosis is often poor. The pathogenesis of VAHS is not well understood. Many believe that viral infection provokes an abnormal immune response in predisposed individuals leading to hyperactivation of Th1 helper cells, macrophage proliferation and secretion of large amounts of cytokines. The resultant hypercytokinaemia may be responsible for the clinical and biochemical manifestations of VAHS. In this article the clinical features, presumed pathogenesis, diagnostic criteria and treatment of VAHS are discussed.

Diagnosis, Differential↗

PubMed1998

[Bacterial infections as complications of dog bites].

Dog bites may result in serious bacterial infections with e.g. the gram-negative rods Capnocytophaga canimorsus and Pasteurella multocida. Human disease caused by these microorganisms can be complicated by acute development of septicaemia and/or meningitis followed by disseminated intravascular coagulation syndrome, peripheral gangrene and renal failure. The mortality of C. canimorsus septicaemia is about 23-31%. These severe infections are most often reported in immunocompromised patients and occur a few days after the bite. By reviewing the literature it is concluded that the broadest prophylactic coverage is obtained by amoxicillin/clavulanic acid and that antibiotic prophylaxis should be given to all immunocompromised patients experiencing a dog bite. Moreover, prophylactic treatment should be initiated for all patients with greater penetrating wounds and those involving the hands.

Animals↗