Henrik Ørbæk Andersen

Pressure-pain threshold in human temporal region. Evaluation of a new pressure algometer

A hand-held pressure algometer with a pressure sensitive strain gauge at the tip was used to measure the pressure-pain threshold (PPT) in the temporal region of healthy volunteers. Various sizes of circular tips and various application rates were tested before selecting an area of 0.5 cm2 and a constant application rate of 0.68 N X sec-1 for future use. A highly significant correlation was found between PPT values obtained from the two sides (of the head) (P less than 0.001) and between PPT values obtained with a 3-week interval (P less than 0.001). In a series of 50 immediate consecutive measurements in the same individual, the mean PPT was 171 kPa (N = 6, 2 S.D. 24%). The mean relative change in PPT after a 3-week interval was 0 +/- 51% (N = 11, 2 S.D.). In the course of 5 repeated determinations at weekly intervals there was a significant increase in PPT (ANOVA, P less than 0.05). Subcutaneous lignocaine significantly elevated PPT compared to placebo. Due to the high inter-individual variation, determinations of PPT for group comparisons should include rather large population samples, whereas in paired studies, the intra-individual variation allows the investigation of much smaller groups (10-20 subjects). It is our experience that the pressure algometer is easy to operate in the hands of a skilled laboratory assistant.

Heart allograft vascular disease: an obliterative vascular disease in transplanted hearts.

More than 30 years have passed since the first human heart transplantation was performed. Since then, short-term survival after heart transplantation has been markedly improved, but this development has not been paralleled with a similar improvement in long-term survival. One of the major reasons for this is the subsequent development of heart allograft vascular disease, an obliterative disease in the coronary arteries of the transplanted heart. The dubious effect of re-vascularization in this disease, the less favorable outcome after repeat heart transplantation, and the low donor supply have called for intensified research for new and efficient prophylactic therapies against heart allograft vascular disease. This research has lead to improved knowledge about diagnosis, etiology, pathogenesis, prophylaxis, and treatment possibilities. The most important among these seem to be: (i) the introduction of intravascular ultrasound for early detection of the disease; (ii) evidence to suggest that hyperlipidemia, insufficient immunosuppressive therapy, human leukocyte antigen (HLA)-mismatch, and infection with cytomegalovirus (CMV) all may promote allografts vascular disease; and (iii) the introduction of at least two promising prophylactic therapies in humans namely 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors and calcium entry blockers, and others potentially promising e.g. angiotensin-converting enzyme-inhibitors, angiopeptin, mycophenolate mofetil and rapamycin. This review summarizes present knowledge on the possibilities of inhibiting or treating heart allograft vascular disease incorporating evidence from both human and experimental studies.

Cyclosporin suppresses transplant arteriosclerosis in the aorta-allografted, cholesterol-clamped rabbit. Suppression preceded by decrease in arterial lipoprotein permeability.

The immunosuppressant cyclosporin has been suggested to aggravate as well as retard the development of transplant arteriosclerosis, the major long-term problem for patients with heart transplants. We examined the effect of human therapeutic levels of blood cyclosporin on the development of experimental transplant arteriosclerosis. The thoracic aorta from one rabbit was transplanted as an end-to-side bypass on the abdominal aorta of another rabbit, and plasma cholesterol was clamped at 5 to 7 mmol/L. Cyclosporin markedly suppressed the severity of transplant arteriosclerosis, judged both biochemically and histologically: cholesterol content in aortic transplants was reduced by 70% and 80% after 10 days and 20 days of cholesterol feeding, respectively (both comparisons, P < .01), and after 20 days of cholesterol feeding myointimal proliferation was totally inhibited in grafts from cyclosporin-treated animals, judged from maximal intimal thickness and intimal area on cross sections of grafts (both comparisons, P < .05). In another group of non-cholesterol-fed, aorta-transplanted rabbits, cyclosporin reduced by 90% (P < .01) an otherwise markedly increased permeability to low-density lipoprotein in transplanted aortas. These results suggest that cyclosporin causes a substantial decrease in the severity of transplant arteriosclerosis and that this effect is mediated at least partly via a large decrease in aortic lipoprotein permeability.

Effect of Cyclosporine on Arterial Balloon Injury Lesions in Cholesterol-Clamped Rabbits: T Lymphocyte–Mediated Immune Responses Not Involved in Balloon Injury–Induced Neointimal Proliferation

Restenosis after balloon dilatation of stenosed coronary arteries is a major clinical problem. Because T lymphocytes occur in neointima and because cyclosporine inhibits T-lymphocyte proliferation, we tested the hypothesis that cyclosporine would attenuate neointimal proliferation after balloon dilation injury. Rabbits with a balloon-injured aorta, randomized to cyclosporine in the human therapeutic range (n=13) or vehicle (n=14) were followed up for 5 weeks; as a control for the effect of cyclosporine, half the rabbits received in addition an aorta allograft. Rabbits were clamped at a human plasma cholesterol level of 5 to 7 mmol/L. Cyclosporine did not affect aorta cholesterol accumulation or neointimal proliferation in balloon-injured aortas; however, it attenuated both in transplanted aortas. Likewise, cyclosporine had no effect on endothelial cells at balloon-injured sites, but protected these cells in the transplanted aortas. Infiltration of smooth muscle cells, T lymphocytes, and macrophages were unaffected by cyclosporine in balloon-injured aortas; however, in transplanted aortas, cyclosporine reduced the relative number of T lymphocytes and macrophages but increased the relative number of smooth muscle cells. Finally, in balloon-injured aortas, cyclosporine did not affect expression of vascular adhesion molecule-1, intercellular adhesion molecule-1, or major histocompatibility complex II, but all these cellular activation markers were attenuated by cyclosporine in transplanted aortas. These results suggest that cyclosporine does not attenuate neointimal proliferation after balloon dilatation, and that T lymphocyte--mediated immune responses are not involved in neointimal proliferation after balloon dilatation.

Dose-Dependent Suppression of Transplant Arteriosclerosis in Aorta-Allografted, Cholesterol-Clamped Rabbits: Suppression Not Eliminated by the Cholesterol-Raising Effect of Cyclosporine

Cyclosporine may suppress transplant arteriosclerosis; however, it also raises plasma cholesterol, which could promote the disease. Our aim was to test these hypotheses experimentally. In experiment 1 (n = 34), cholesterol was clamped at a human level of 5 to 7 mmol/L, and rabbits were given either saline or cyclosporine in a low, medium or high dose. In experiment 2 (n = 15), in which dietary cholesterol was fixed at 0.05 g.kg-1.d-1, and experiment 3 (n = 16), in which no dietary cholesterol was added to the chow, rabbits were given either medium-dose cyclosporine, saline, or vehicle. The duration of each experiment was 5 weeks. In experiment 1, cyclosporine attenuated the development of transplant arteriosclerosis dose dependently (trend test: P < .0001). Cyclosporine also suppressed, in a dose-dependent manner, the activation of the immune system (trend test: P < .05) and the presence of T lymphocytes (trend test: P < .0001) and macrophages in the intima (trend test: P < .01). Despite a higher plasma cholesterol level in cyclosporine-treated rabbits compared with saline-treated rabbits in both experiment 2 (4.9 versus 2.9 mmol/L) and experiment 3 (1.6 versus 0.8 mmol/L), transplant arteriosclerosis was significantly reduced by cyclosporine (Mann-Whitney U test; P < .05 and P < .05). These results suggest that cyclosporine suppresses experimental transplant arteriosclerosis dose dependently. Accordingly, in the assessment of the optimal cyclosporine dose to heart-transplanted patients, it should be taken into account that a dose reduction may promote transplant arteriosclerosis.

Effect of oestrogen replacement therapy on development of experimental arteriosclerosis: A study in transplanted and balloon-injured rabbit aortas

The mechanism underlying possible protection of oestrogen replacement therapy against cardiovascular disease appears to go beyond beneficial changes in plasma lipoproteins. A direct action of oestrogen on the metabolism of lipoproteins after entering the arterial wall may occur. The present study evaluated whether oestrogen replacement therapy affects the development of experimental arteriosclerosis in immunologically injured (experiment A + B) and balloon-injured (experiment B) aortas in ovariectomized rabbits maintained at a human level of plasma cholesterol; both models involve severe damage to the endothelium with resulting rapid accumulation of lipoproteins in the arterial intima and therefore appear suitable for studying factors directly affecting subendothelial lipoprotein metabolism. In experiment A, dietary cholesterol required to maintain a human level of plasma cholesterol was significantly higher for the oestrogen group than for the placebo group. Similarly, cholesterol accumulation in the aortic grafts was borderline higher for the oestrogen than the placebo group, whilst intimal hyperplasia was without difference between the groups. Due to a modified schedule of cholesterol feeding in experiment B, oestrogen and placebo groups received the same amount of dietary cholesterol, and cholesterol accumulation and intimal hyperplasia were similar in immunologically injured and balloon-injured parts of the aorta in both groups. These results suggest that in the female rabbit maintained at a human level of plasma cholesterol, oestrogen replacement therapy has no direct action on the development of experimental arteriosclerosis when induced by immunological or mechanical injury to the endothelium.

Relative importance of ischemic injury and immunological injury on the development of transplant arteriosclerosis in rabbit aortic allografts

The development of transplant arteriosclerosis has emerged as a major problem to long-term survival after heart transplantation. The accelerated development of arteriosclerosis in the transplanted arteries, including the aorta, could result either from an ischemic injury in connection with the transplantation, or from an immunological reaction against the transplant, or both. We evaluated histologically and biochemically whether extension of the ischemic period from 1 to 24 hr has any influence on the development of transplant arteriosclerosis, in aorta-allografted rabbits clamped at human levels of plasma cholesterol. One set of rabbits was without immunosuppressive treatment (n = 10 + 9) and another otherwise identical set of rabbits received cyclosporine to achieve blood cyclosporine levels in the human therapeutic range (n = 10 + 12). The number of T lymphocytes in intima suggested that, in the grafts from untreated animals, an immunological injury had arisen, which cyclosporine reduced. A clear trend toward a worsening of the transplant arteriosclerosis was demonstrated as a function of the severity of the ischemic injury, both with and without immunosuppressive treatment. However, the worsening effect of maximal ischemic injury was less than that due to maximal immunological injury. In grafts from cyclosporine-treated animals, the development of transplant arteriosclerosis was significantly less than in grafts from untreated animals exposed to identical periods of ischemia. These results suggest that compared with immunological injury, ischemic injury is of minor importance for the development of experimental transplant arteriosclerosis.

Effect of cyclosporine during initiation of transplant arteriosclerosis. An ultrastructural study in the aorta-transplanted rabbit

The immunosuppressant cyclosporine protects against the development of experimental transplant arteriosclerosis. To investigate the mechanism underlying this effect, aorta-allografted rabbits were randomly assigned to cyclosporine (n = 6) in the human therapeutic range or to its vehicle (n = 5). Perfusion fixation was performed 2 weeks after the transplantation, followed by light, scanning and transmission electron microscopy examination. Intimal proliferation was absent in native aortas, present in all grafts from vehicle-treated animals, and either absent or sparse in grafts from cyclosporine-treated rabbits. The endothelium of native aortas from both vehicle- and cyclosporine-treated rabbits was normal. Aortic allografts from cyclosporine-treated rabbits exhibited a normal endothelium with only a few adhering mononuclear cells, whereas aortic allografts from vehicle-treated rabbits exhibited an endothelial surface ranging from near-normal with only few adhering platelets and mononuclear cells, to an almost destroyed endothelium, lined with lymphocyte-like cells, monocytes/macrophages, platelets, erythrocytes and fibrin; in the subendothelial layer, mononuclear cells and smooth muscle cells were abundant. These results suggest that damage to the endothelial cells as well as invasion of lymphocytes, monocytes/macrophages and smooth muscle cells into the subendothelial space are important events during initiation of transplant arteriosclerosis, and that cyclosporine largely attenuates these early pathological changes.

Urinary apolipoprotein M as a biomarker of acute kidney injury in children undergoing heart surgery.

AIM To investigate whether apoM is excreted in urine of children undergoing heart surgery and the potential of apoM as early biomarker of acute kidney injury (AKI). MATERIALS & METHODS Urine was collected in children undergoing heart surgery. ApoM was measured with ELISA. U-apoM was characterized by gel filtration chromatography and western blotting. RESULTS ApoM was excreted into the urine 0-4 h postoperatively as the full-length apoM in particles smaller than plasma HDL. At 0 h, U-apoM predicted AKI with an area under the receiver-operating characteristics curve of 0.70 (p < 0.018). Sensitivity was 0.71 and specificity was 0.68 at a cutoff level at 1.45 nmol/l. CONCLUSION ApoM is excreted in the urine of children after cardiac surgery. Its potential as biomarker of AKI deserves exploration.