Incidence of cutaneous malignant melanoma in the Czech Republic: the risks of sun exposure for adolescents.

The Czech Republic reported one of the highest incidence rate in cutaneous melanoma (CM) in Europe and because this incidence has been increasing, mainly among young people, the main goal of our study was to establish sun exposure behavior risk factors for CM formation and to evaluate whether the young generation of Czechs is exposed to a higher risk of CM than the older generation. A questionnaire-based case-control study was conducted. We obtained 978 completed questionnaires: 216 from patients with CM and 762 from healthy respondents. The healthy individuals were further divided to adolescents (n = 460) and older respondents (n = 302). Three logistic regression models were developed: 1. patients with CM vs. healthy older respondents, 2. adolescents vs. healthy older respondents, and 3. patients with CM vs. adolescents. The main risk factors for all three models were the number of sunburn episodes and the use of the sunscreen in the childhood. The most alarming results for adolescents included: all day sun exposure, including times of maximum risk (11 AM to 3 PM), inadequate use of sunscreen in adulthood, and frequent mountain holidays. Our results show that sun-safety in the young generation is satisfactory, when the responsibility for sun exposure behavior is in the hands of their parents; however, when children become adolescents, they become immune to sun-safety and risk prevention campaigns and their behavior becomes much more risky. Our results further suggest the sun-safety campaigns need to be modified in such a way as to have greater impact and influence on adolescent sun-risk behaviors.

The effect of particle size on bioavailability in cyclosporine preparations based on submicron dispersions.

The effect of particle size on bioavailability of 9 different formulations with cyclosporine A was studied. A common feature of all the formulations was the ability to form submicron dispersions under dilution. The composition of individual formulations was chosen in such a way that they were based on same or similar excipients. For each formulation, pharmacokinetic study was carried out in beagle dogs. On groups of 10 dogs, the average AUC was evaluated. Particle size of formulations under dilution in water was measured by laser scattering method. According to the results of particle size measurement, the formulations were sorted out into groups of similar particle size distribution by use of two methods of multivariate statistical analysis. The average AUC within groups and between-groups was compared, and the effect of particle size on bioavailability was evaluated.

Thiazolidinediones--tools for the research of metabolic syndrome X.

The resistance to insulin (insulin resistance, IR) is a common feature and a possible link between such frequent disorders as non-insulin dependent diabetes mellitus (NIDDM), hypertension and obesity. Pharmacological amelioration of IR and understanding its pathophysiology are therefore essential for successful management of these disorders. In this review, we will discuss the mechanisms of action of thiazolidinediones (TDs), a new family of insulin-sensitizing agents. Experimental studies of various models of IR and an increasing number of clinical studies have shown that TDs normalize a wide range of metabolic abnormalities associated with IR. By improving insulin sensitivity in skeletal muscles, the adipose tissue and hepatocytes, TDs reduce fasting hyperglycaemia and insulinaemia. Furthermore, TDs markedly influence lipid metabolism--they decrease plasma triglyceride, free fatty acid and LDL-cholesterol levels, and increase plasma HDL-cholesterol concentrations. Although TDs do not stimulate insulin secretion, they improve the secretory response of beta cells to insulin secretagogues. TDs act at various levels of glucose and lipid metabolism--ameliorate some defects in the signalling cascade distal to the insulin receptor and improve glucose uptake in insulin-resistant tissues via increased expression of glucose transporters GLUT1 and GLUT4. TDs also activate glycolysis in hepatocytes, oppose intracellular actions of cyclic AMP, and increase intracellular magnesium levels. TDs bind to peroxisome proliferator activating receptors gamma (PPAR gamma), members of the steroid/thyroid hormone nuclear receptor superfamily of transcription factors involved in adipocyte differentiation and glucose and lipid homeostasis. Activation of PPAR gamma results in the expression of adipocyte-specific genes and differentiation of various cell types in mature adipocytes capable of active glucose uptake and energy storage in the form of lipids. Furthermore, TDs inhibit the pathophysiological effects exerted by tumour-necrosis factor (TNF alpha), a cytokine involved in the pathogenesis of IR. These effects are most likely also mediated by stimulation of PPAR gamma. In mature adipocytes, PPAR gamma stimulation inhibits stearoyl-CoA desaturase 1 (SCD1) enzyme activity resulting in a change of cell membrane fatty acid composition. Apart from their metabolic actions, TDs modulate cardiovascular function and morphology independently of the insulin-sensitizing effects. TDs decrease blood pressure in various models of hypertension as well as in hypertensive insulin-resistant patients, and inhibit proliferation, hypertrophy and migration of vascular smooth muscle cells (VSMC) induced by growth factors. These processes are considered to be crucial in the development of vascular remodelling, atherosclerosis and diabetic organ complications. TDs induce vasodilation by blockade of Ca2+ mobilisation from intracellular stores and by inhibition of extracellular calcium uptake via L-channels. Furthermore, TDs interfere with pressor systems (catecholamines, renin-angiotensin system) and enhance endothelium-dependent vasodilation. A key role of TDs effects in vascular remodelling is played by inhibition of the mitogen-activated protein (MAP) kinase pathway. This signalling pathway is important for VSMC growth and migration in response to stimulation with tyrosine-kinase dependent growth factors. In addition to the vasoprotective mechanisms mentioned above, troglitazone, the latest representative of this pharmacological group, possesses antioxidant actions comparable to vitamin E. In summary, TDs have the unique ability to attack mechanisms responsible for metabolic alterations as well as for vascular abnormalities characteristic for IR. Therefore, TDs represent a powerful research tool in attempts to find a common denominator underlying the pathophysiology of the metabolic syndrome X. A recently reported link between MAP kinase signalling pathway and PPAR gamma

Insulin bound to chiral polymer with N-acetyl-D-glucosaminyl units. Lacks of mitogenic activity on rat aorta smooth muscle cell proliferation.

Insulin was covalently attached to two terpolymers of N-(2-hydroxypropyl) methacrylamide, N-methacryloyldiglycine and a) R-(-)-1-methyl-2-methacryloylamidoethyl 2-acetamido-2-deoxy-beta-D-glucopyranoside or b) S-(+)-1-methyl-2-methacryloylamidoethyl 2-acetamido-2-deoxy-beta-D-glucopyranoside. The mitogenic effect of both conjugates on vascular smooth muscle cell proliferation was investigated. The results indicated that insulin bound to both carriers with pendant N-acetylglucosaminyl groups possesses hypoglycemic activity but not the mitogenic effect of native insulin. This study shows that for these insulin conjugates, the effect does not depend on the steric configuration of the sugar-containing monomer units incorporated in the terpolymer. A hypothesis is developed that some competition is taking place between N-acetylglucosaminyl groups on the polymeric insulin carrier and the same moieties in the insulin receptor expressed on the surface of smooth muscle cells leading to a lack of mitogenic activity.

Determination of cadmium and copper with ET-AAS after electrochemical deposition on a graphite electrode.

The electrodeposition of cadmium and copper on a special graphite disk electrode has been performed at controlled potential. The electrode with the deposit has been inserted into the graphite atomizer HGA-400 by an adapted automatic sampler for the final determination by ET-ASS. The sensitivity of determination has been 0.371 (microg l(-1))(-1) for cadmium and 0.025 (microg l(-1))(-1) for copper for 2 min electrodeposition and increased linearly with the time of deposition. The limit of detection (3s(bl)) has been 7.9 ng l(-1) Cd(2+) and 0.11 microg l(-1) Cu(2+) for 2 min deposition and it has been improved with increased time of electrodeposition. The technique has been applied to the determination of both metals in seawater and to speciation in the presence of EDTA complexing agent.

The role of myocardial glycogen content for the development of isoprenaline-induced myocardial lesions in different inbred strains of rats.

Two inbred rat strains, differing in their resistance to the induction of myocardial lesions by the administration of isoprenaline (ISO), have been developed. The extent of ISO-induced myocardial lesions (IML) was three to five times lower in the ISO-resistant (IR) strain as compared to that in the ISO-sensitive (IS) strain. The two strains differ also in a number of other genetically determined features, e.g., a higher myocardial glycogen content (MGC) and higher adipose tissue weight in IR rats. Between IML extent and MGC a significant negative correlation has been demonstrated in 2nd filial generation of IR and IS hybrids. By contrast, no correlation has been found between the resistance to the development of IML and the other genetically determined features studied. High resistance to the development of IML and a high MGC were also noted in another inbred strain, the hypertriacylglycerolemic (HTG) rats. Comparison of IML extent in HTG, IR and IS rats has revealed that the extent of IML, while depending on MGC, is independent of triacylglycerolemia. MGC can be raised in IR and IS rats by various interventions (e.g., repeated administration of ISD or fasting). Regardless of the intervention used, it entails a simultaneous increase in resistance to the development of IML. In vivo administration of glucose and insulin, however, exerts only a minimal effect on MGC and on the extent of IML. It may be concluded, therefore, that under our experimental conditions the enhanced resistance to the development of IML, whether genetically determined (IR, HTG rats) or induced by some interventions (fasting, repeated ISO administration), is closely related to an increased MGC.

Hereditary hypertriglyceridemic rat: a new animal model of metabolic alterations in hypertension.

Hereditary hypertriglyceridemic rats (hHTg) were developed as a new genetic model for the study of relationships between blood pressure (BP) and metabolic abnormalities. This strain has been produced by selective inbreeding from Wistar rats according to the rise of plasma triglycerides induced by a high-sucrose diet. Though hHTg rats display hypertriglyceridemia, impaired glucose tolerance, hyperinsulinemia, insulin resistance and increased BP even without nutritional stimuli, high sucrose feeding further aggravates these symptoms. High plasma triglycerides levels in hHTg rats seem to be a consequence of their hyperproduction. Impaired insulin action is responsible for the defective glucoregulation in this strain. The loss of insulin responsiveness might be due to a reduction in the number of glucose transporters. Highly significant relationships among plasma triglycerides, ouabain-resistant Na+ transport and BP were demonstrated in the hHTg rats. Segregating populations (F2 hybrids) should be used for genetic analysis of the primary role of lipid and/or ion transport abnormalities in the pathogenesis of this form of genetic hypertension.

The effect of combination therapy with cyclosporine A and hydrocortisone on glucose metabolism in diabetic rats following pancreatic islet transplantation.

Glucose tolerance, insulin secretion and in vitro insulin action were examined in streptozotocin-induced diabetic rats following pancreatic islet allotransplantation treated with combination of oral cyclosporine A (10 mg/kg) and hydrocortisone (1.5 mg/kg) intramuscularly. 1400 pure islets from multiple donors were implanted either into the portal vein (n = 10) or under the renal capsule (n = 11). Ten sham-operated non-diabetic animals receiving the same immunosuppressive therapy, 8 healthy animals without any treatment and 10 diabetic animals without immunosuppression following islet transplantation were used as controls. In all transplanted animals blood glucose was normalized by day 3 after transplantation with lower levels in those transplanted intraportally (p < 0.05). Non-immunosuppressed animals rejected the graft after 6.5 +/- 1.2 days after transplantation, immunosuppressed animals in both groups remained normoglycaemic till the end of the experiment on day 28. Oral glucose tolerance tests and insulin levels on days 10 and 28 improved dramatically. No differences in glucose and insulin levels between intraportal and subcapsular groups were found. Post-load glucose levels in immunosuppressed non-transplanted animals were higher on day 28 than before treatment and were also higher than in the healthy non-treated group (p < 0.05). In vitro insulin action determined by the incorporation of labelled glucose into adipose tissue was impaired only in animals in which islets were transplanted into the liver (p < 0.05 vs other groups). In conclusion, therapy with cyclosporine A and hydrocortisone prevents allogeneic islet rejection in rats during a short-term experiment. Although glucose tolerance is not completely normalized following transplantation, slight impairment is also demonstrable in healthy animals on the same drug therapy.

Erythrocyte ion transport alterations in hypertriglyceridaemic rats.

1. Hypertension appears to be associated with both abnormalities in ion transport and disturbances in lipid metabolism. The aim of the present study was to search for alterations in erythrocyte ion transport in hereditary hypertriglyceridaemic rats. This strain is characterized by a pronounced elevation of blood pressure which correlates with the plasma triacylglycerol level. 2. Erythrocyte Na+ content was elevated in hypertriglyceridaemic rats due to an increased ouabain-resistant Na+ net uptake. This was caused not only by the acceleration of bumetanide-sensitive Na+ inward co-transport, but also by the augmentation of bumetanide-resistant Na+ inward leak. A moderate enhancement of bumetanide-sensitive Rb+ uptake was seen in hypertriglyceridaemic animals, but there were no changes in bumetanide-resistant Rb+ leak. 3. The plasma triacylglycerol level correlated positively not only with blood pressure (P < 0.001) but also with ouabain-resistant Na+ transport (P < 0.002), bumetanide-sensitive Na+ and K+ (Rb+) co-transport (P < 0.01 and P < 0.001, respectively), bumetanide-resistant Na+ leak (P < 0.02) and erythrocyte Na+ content (P < 0.05). 3. Thus the association of augmented ouabain-resistant Na+ transport with elevated blood pressure in this form of experimental hypertension might be mediated by genetic disorders of lipid metabolism.

Adrenergic overactivity and insulin resistance in nonobese hereditary hypertriglyceridemic rats.

Nonobese, hereditary hypertriglyceridemic (HTG) rats provide an interesting model of hypertriglyceridemia, glucose intolerance, and hypertension. In age-matched 15 HTG and 16 control Wistar rats fed on a high sucrose diet (70 cal%) for 6 weeks, we measured insulin sensitivity in vivo and some parameters of sympatoadrenal system. Using euglycemic clamps with administration of 2-deoxy[1-3H]glucose, we found whole body insulin resistance and decreased glucose metabolic index Rg' in soleus muscle, epitrochlearis muscle, diaphragm, and white adipose tissue in HTG rats. We found higher levels of plasma epinephrine and higher excretion of vanilmandelic and homovanilic acids in HTG rats. The binding of [3H]-dihydroalprenol to the heart membrane fraction was similar in both groups, but the dissociation constant Kd was increased by 75% in the heart of HTG rats.

Effect of a low salt diet on blood pressure and vasoactive hormones in the hereditary hypertriglyceridemic rat.

In hereditary HTG rats, basal systolic blood pressure using tail-cuff sphygmomanometry was significantly higher (122.1 +/- 2.1 mm Hg; n = 16) than that in NTG animals (107.1 +/- 1.52; n = 16). A low salt diet did not influence blood pressure in NTG rats during the consecutive 4 weekly periods. However, in the second week blood pressure in HTG rats rose significantly in both the control rats on a normal salt diet and those on a low salt diet (132.5 +/- 1.89, n = 8, and 132.6 +/- 1.93, n = 8). No further changes were registered in the third and fourth week in control HTG rats. On the other hand, blood pressure fell significantly in HTG rats on a low salt diet in the third week in comparison with the second week (119.5 +/- 3.2, n = 8), and it increased again in the fourth week (123.0 +/- 2.35, n = 8). Hormones in plasma were determined at the end of the experiment. Plasma levels of norepinephrine were not influenced by differences in salt intake and were significantly higher by about 45% in HTG than in NTG animals. The lowest concentration of corticosterone in plasma was found in control HTG rats (1.2 +/- 0.2 vs 4.6 +/- 0.8 micrograms/100 ml in control NTG rats). Nevertheless, corticosterone concentration increased in HTG rats on a low salt diet at comparable values found in NTG rats on a low salt diet (3.1 +/- 0.8 vs 4.3 +/- 1.5). Plasma renin activity and plasma aldosterone concentrations were not different in the NTG and HTG groups and were uninfluenced by the diets (Table 1). We conclude that the elevated blood pressure in HTG rats and its variations during the experiment may reflect more pronounced sympathetic activity in HTG rats rather than blood pressure dependency on different salt intake.

Do preoperative branched-chain amino acids have a beneficial effect on the heart after cardiac surgery?

To verify the hypothesis, formulated on the basis of data emerging from animal experiments, that branched-chain amino acids (BCAA) exert a protective effect on the heart during ischaemia, eight patients immediately before aortocoronary reconstruction were provided 400 ml of a 3% BCAA solution. A control group comprised another eight patients. Per- and postoperative myocardial status and myocardial enzyme levels were assessed. Myocardial biopsy was performed during surgery to determine glycogen levels. Creatine kinase (CK) levels were invariably higher in the BCAA group, with statistically significant differences in samples obtained immediately after surgery (10.6 +/- 3.35 mu kat/l vs. 4.07 +/- 0.59, p < 0.0004), in the evening after surgery (14.2 +/- 5.92 vs. 5.91 +/- 2.21, p < 0.06) and in the morning of the first postoperative day (18.0 +/- 10.1 vs. 7.5 +/- 4.76, p < 0.025) when aspartate aminotransferase (AST) levels were likewise higher (1.35 +/- 0.28 vs. 1.00 +/- 0.26, p < 0.035). There were no differences between the groups in the number of defibrillations after ischaemia, myocardial glycogen content, peroperative ischaemia, incidence of arrhythmia and catecholamine support. We conclude that BCAA at the above indicated doses did not raise myocardial glycogen content or improve myocardial status after cardiac surgery. Their administration resulted in a rise in CK and AST in the postoperative period.