Inhibition of the renin-angiotensin system ameliorates genetically determined hyperinsulinemia.

This study was performed in order to assess the potentially different effects of the angiotensin-converting enzyme inhibitor captopril and of the angiotensin II receptor antagonist irbesartan on the metabolic syndrome in an animal model. Male NZO/BL6 F1 mice were treated with captopril, irbesartan, or placebo for 10 months: Control animals treated with placebo developed a metabolic syndrome with obesity (55.5+/-6.3 g), hypertension (146+/-10 mm Hg), hyperinsulinemia (7.2+/-5.7 ng/ml), hypercholesterolemia (5.1+/-0.7 mmol/l), cardiac hypertrophy (269+/-44 mg) and atherosclerotic plaques in the ascending aorta (3.6+/-1.5 microm(2)). Treatment with angiotensin-converting enzyme inhibitor or angiotensin II receptor antagonist significantly (p<0.001) reduces hypertension (73+/-5 and 78+/-11 mm Hg), cardiac hypertrophy (203+/-26 and 202+/-18 mg) and atherosclerosis (2.2+/-0.9 and 1.8+/-0.8 microm(2)). In addition, they prevented the development of obesity (42.2+/-3.5 and 38.3+/-2.8 g) and hyperinsulinemia (3.6+/-1.5 and 1.8+/-0.4 ng/ml). In conclusion, long-term treatment with an angiotensin-converting enzyme inhibitor or an angiotensin II receptor antagonist can ameliorate obesity and hyperinsulinemia in a genetically determined mouse model.

Tumour-cell-endothelial interactions: free radicals are mediators of melanoma-induced endothelial cell damage.

Damage to vascular endothelium may play an important role during metastasis. We used a three-dimensional model of tumour cell extravasation to test the hypothesis that certain types of tumour cells are able to induce vascular endothelial cell injury. Multicellular tumour spheroids (MCTS) of 14 human cancer cell lines and spheroids from two benign cell lines were transferred onto confluent monolayers of human endothelial cells (EC). MCTS from 4 of 7 melanoma cell lines induced damage of the endothelium which was closely associated with tumour cell attachment. Endothelial cell injury became evident morphologically by loss of cell membrane integrity and sensitivity to shear stress. Similar results were obtained with EC derived from human umbilical veins, umbilical arteries and saphenous veins. Addition of the oxygen radical scavenger catalase showed a dose- and time-dependent inhibition (up to 48 h) of EC damage in the case of the melanoma cell lines ST-ML-11, ST-ML-14 and SK-MEL-28. The scavenging enzyme superoxide dismutase proved to be protective (up to 12 h) in ST-ML-12 MCTS. In contrast, allopurinol, deferoxamine mesylate, ibuprofen, nor-dihydroguaretic acid, soybean trypsin inhibitor or aprotinin had no protective effect. None of the non-melanoma cancer cell lines or benign cells induced endothelial cell damage. Endothelial injury has been shown to enhance the process of metastasis. Our results suggest that free-radical-mediated endothelial cell damage may be one of the mechanisms contributing to the devastating metastatic potential of melanoma.

Effectiveness and safety of ultrasonic atherosclerotic plaque ablation: in vitro investigation.

Ultrasound energy was applied to 137 segments of human cadaver atherosclerotic arteries, 90 with calcified and 47 with noncalcified atheromatous plaque, and to 100 segments of healthy swine aorta. The average depth of penetration was dependent on the forward force of the ultrasonic probe, the duration of treatment, and the degree of atherosclerosis. There was one perforation of a fibrous plaque using a forward force of 2 Newton and 45 sec of application time. Injury of healthy intima was minimal. It is concluded that catheter-delivered ultrasound is effective and safe for the disintegration of atherosclerotic plaques. Presently, the main limitations of the system are the lack of flexibility and steerability.

Idiopathic calcinosis of the scrotum: scanning electron microscopic study with X-ray microanalysis.

In a 31-year-old man 12 nodules up to 1 cm in diameter were observed in the scrotum; these had developed over 3 years. Energy-dispersive x-ray analysis of the dermal foci showed a high content of calcium and phosphorus even in nodules smaller than 1 mm in diameter. No increased mineral deposition was observed in the surrounding connective tissue, however. Scanning electron microscopy revealed finely granulated crystals, and cellular remnants giving rise to development of calcified nodules were disclosed. The results support the hypothesis of a degenerative origin of scrotal calcinosis.

Adhesion and spreading of corneal endothelial cells on collagens type I and IV in vitro: a model to study mechanisms of endothelial repair.

In vitro assays using endothelial cells (EC, bovine corneal) were performed to study adhesion and spreading on collagen types I and IV. Adhesion was quantitatively analyzed by counting the EC under a light microscope. Spreading was determined by measuring cell area using a scanning electron microscope (SEM). Collagen types I, IV, and IV-F, a mixture of 70, 120, and 140 KD fragments of type IV, all promoted EC adhesion, Types IV and IV-F showed evidence of giving a more marked adhesion than type I. A study of cell area, carried out under identical conditions, such as those in the adhesion assay, showed that types I and IV-F, but not type IV, promoted cell spreading. This provides evidence that cell adhesion and spreading are indeed separate biological phenomena. Furthermore, the ability of fragments of type IV collagen to promote both cell adhesion and spreading may represent an inherent repair mechanism in damaged endothelium.

A method to study the interaction between intraocular lens loops and anterior segment vasculature.

Gold-coated plastic casts of the anterior segment ocular microcirculation of the rabbit eye were studied by scanning electron microscopy to define the interaction between ciliary sulcus fixated intraocular lenses and the anterior segment vasculature. A detailed description of the technique is given. Interactions such as loop deformation by the tissue and loop erosion into the vascular tissue are shown. Possible clinical applications of this experimental model are discussed.

Clinical experience with expanded polytetrafluoroethylene Gore-Tex surgical membrane for pericardial closure: a study of 110 cases.

Complete closure of the pericardium after cardiac operations has the advantage of avoiding injury of the heart and great vessels during reoperation. Between 1985 and 1987, the pericardium was closed with Gore-Tex Surgical Membrane (SM) in a selected series of 110 patients 1 month to 76 years of age. Fifty-three patients had congenital heart lesions and 57 patients had acquired heart disease. Overall hospital mortality was 3/110 cases. In no instance was there a relationship between occurrence of death and pericardial closure with SM. There was one episode of cardiac tamponade on the seventh postoperative day. One patient developed fever and leukocytosis due to a mediastinal hematoma. During a mean follow-up of 15 months, four patients had to be reoperated upon three, four, eight weeks, and eight months after primary operation. The anterior wall of the heart had no adhesion with the SM and the other parts of pericardium could be dissected easily. Scanning electron microscopic examination of the explanted SM patches showed neither cellular ingrowth nor immunocompetent cellular elements. The Gore-Tex Surgical Membrane has the advantages of easy availability and lack of reaction between its surface and the epicardium and pericardium. We believe its routine use should be encouraged in patients with high probability of reoperation after repair of complex cardiac anomalies, implantation of bioprostheses, coronary revascularization for one- or two-vessel disease, and repair of degenerative disease of the ascending aorta.

Features of vernix caseosa cells.

In an attempt to collect more information about the features of the vernix caseosa (VC), a relatively unstudied material, some of the histochemical, ultrastructural, and immunological characteristics of VC cells have been investigated. Histochemistry and light microscopy was used to demonstrate the activity of acid and alkaline phosphatase in VC cells, enzymes with a marked increase in activity in the amniotic fluid toward term. Acid phosphatase activity was strongly present either as intracytoplasmic granules or as amorphous material between the cells; alkaline phosphatase activity was absolutely nonexistent. The ultrastructural morphology of the VC cells was analyzed by scanning and transmission electron microscopy (TEM). Significant differences can be demonstrated in the individual surface patterns of the VC keratinocytes. TEM showed irregularly flattened cells in various stages of keratinization. The ultrastructural findings confirm the dissimilarity, which exists between the individual VC cells. Finally, immunofluorescent staining tests of frozen VC smears showed that only immunoglobulin G conjugate gives strong positive reaction at the antigen sites of the VC cells. The special finding in this study is the polymorph appearance of the surface pattern and the cytoplasma structure of the VC cells, as well as the lack of uniform appearance of the acid phosphatase activity in and between the cells. All these suggest that the status of the individual VC cell is not similar in regard to their keratinization and desquamation activities.

Closure of the pericardium using expanded polytetrafluoroethylene GORE-TEX-Surgical Membrane: clinical experience.

Complete closure of the pericardium after cardiac operation would have the advantage of avoiding injury of the heart and great vessels should repeat sternotomy prove to be necessary. In such situations, various pericardial closure techniques have been described. Synthetic materials produced severe scarring, while xenografts appeared to be satisfactory, although fibrous reactions and aseptic cystic formations have been reported recently. Between 1985 and 1986 we closed the pericardium with GORE-TEX-Surgical Membrane in a selected series of 72 patients aging 1 month to 76 years, median 24 years. Overall hospital mortality was 3/72 cases. In no instance was there a relationship between death occurrence and pericardial closure through Surgical Membrane. There were 5 cases each of low cardiac output and rethoracotomy because of bleeding. No cardiac tamponade occurred. Two patients had to be reoperated three and four weeks after primary repair. Surgical Membrane was explanted. Electron microscopy examination showed no cellular ingrowth in the low porosity membrane. No immunocompetent cellular compounds were present on either side of the graft. Follow-up interval averaged 13 months. No complication related to pericardial closure has occurred until now. The Surgical Membrane has the advantages of easy availability, of lack of reactions both between its surface and the underlying epicardium and with the rest of the pericardium. We believe its routine use should be encouraged mainly in patients with high probability of reoperation.

Influence of the lectins and polycation on the configuration of renal podocytes: a scanning electron microscopic study of renal podocytes after micropuncture of the glomerulus in vivo.

The lectins concanavalin A (Con A), wheat germ agglutinin (WGA), Ricinus communis agglutinin (RCA) I+II and the polycation protamine sulfate were applied directly to renal glomerular podocytes by micropuncture techniques in vivo; others received a control solution. To make visible the distribution of lectins, some rats were given fluorescein isothiocyanate-conjugated Con A. The glomeruli undergoing the micropuncture experiments were labeled and then prepared for SEM and TEM observation, in some cases also for histochemical analysis. Comparatively, the effect of application of the Con A and protamine sulfate solution by intraarterial infusion was studied. The glomeruli of a total of 100 Munich-Wistar rats were studied. Con A and WGA cause varying degrees of 'retraction' of the foot processes of the podocytes when applied using the techniques of micropuncture. Intraarterial infusion of a Con A solution, on the other hand, causes no changes in the podocytes. RCA II, applied for 10 min using micropuncture techniques, causes thickening and swelling of the foot processes as well as the formation of intercellular junctions ('agglutination'). RCA I, on the other hand, causes no changes in the podocytes of the rat glomerulus. Glomeruli treated with the micropuncture application of the polycation protamine sulfate demonstrate largely 'agglutination' and only sometimes localized minimal retraction of the foot processes of the podocytes. The intraarterial infusion of protamine sulfate causes almost exclusively 'agglutination' of the podocyte foot processes. Retraction of the podocyte foot processes is probably a result of the active movement of the podocytes, which in turn induced by attachment of lectines to the lectin receptors in glycocalyx of the podocyte cell membrane. Simple reduction of the polyanions in the podocyte cell membrane by protamine sulfate appears to cause only simple electrostatic interaction which then results in 'agglutination' of the podocyte foot processes.

The influence of lectin concanavalin A on the configuration of renal podocytes.

Concanavalin A (ConA) was applied directly to renal glomerular podocytes by micropuncture techniques in vivo. Others received a control solution without ConA. To make visible the distribution of ConA, some rats were given fluorescein-isothiocyanate conjugated ConA. The glomeruli undergoing the micropuncture experiments were labeled and then prepared for SEM observation. Comparatively, the effect of application of the same solutions by intra-arterial infusion was studied. The glomeruli of a total of 33 Munich -rats were studied. Our results show that direct contact of ConA with the podocytes is needed to induce retraction of the podocytic cell processes. The pattern of podocytes treated with ConA is comparable to that of the minimal change nephrotic glomeruli. ConA seems to act by blocking anionic surface charges of the podocytes. This reduction in negative charges along the surface coat of the podocytes could be the key for understanding the combined morphological and functional alterations in podocytes of nephrotic glomeruli: The reduction in negative charges along the surface coat of the podocytes can alter the permselectivity for anionic and cationic proteins and can, at the same time, alter the configuration of the podocytes by changing the potential gradient along the cell membrane.