Leptin increases luteinizing hormone secretion of fasting female rats.

PURPOSE: To investigate whether leptin acts directly on the anterior hypophysis by influencing gonadotropin secretion in vivo. MATERIALS AND METHODS: Cycling female rats were catheterised for frequent blood sampling and were either fasted or allowed free access to food. Stereotactic lesion of the medial preoptic area (MPOA) of the hypothalamus was performed in order to eliminate gonadotropin releasing hormone (GnRH) production. Leptin was administered at a dose of one mg/kg i.v. and blood samples were taken just before leptin administration and then after 30, 60, 90, 120, and 180 minutes. Plasma gonadotropin levels were determined. With completion of sampling, the brains were removed and the localisation of the lesions was verified histologically. RESULTS: Leptin at one mg/kg induced an increase in luteinizing hormone (LH) secretion in fasting rats, both in those with a lesion and those with intact medial preoptic area with a peak occurring 90 minutes after infusion. The augmenting effect was more prominent when the hypothalamus was intact. There was no effect in fed animals with or without lesion. Similarly, no effect was observed on follicle stimulating hormone (FSH) levels in any of the experimental groups. CONCLUSIONS: Leptin acts directly on the hypophysis enhancing LH but not FSH secretion. Nutritional state influences leptin's effect on the hypothalamus and the hypophysis.

One heart, two bodies: a simulation study of body surface potential differences between donor and recipient of heart transplantation.

In cardiac transplantation has been recognized some "abnormalities" in recipient ECG. We investigated the influence of heart geometrical position within the chest cavity as well as somatometric parameters on body surface torso potentials. Two control patients with different Body Mass Index (BMI) were undergone a chest MRI scan. Using specific software we created two tetrahedral meshes that could be applied in our study. A post-mortem human heart was undergone a MRI scan and we also created its tetrahedral mesh. Using second software we extracted the heart mesh of control's torsos and we replaced them with the mesh of the post-mortem heart. The last program also assessed the influence of heart (re)positioning within the thorax, on the body surface potentials. The Finite Elements Method (FEM) was used to solve the forward electrocardiographic problem for both torsos, under the assumption that all the ventricular myocardium of the one post-mortem heart was excited. FEM was also applied in simulating Body Surface Potential Mapping (BSPM) on the first thorax torso for nine different heart positions. For BSPM, FEM has been applied on Poison equation. The results show higher BSPM in patient with lower BMI and significant changes in BSPM when heart was rotated round its long axis. Conversely, the heart shifts (long x- or y- axis) didn't cause significant changes on simulated BSPM.

Latest aspects of aldosterone actions on the heart muscle.

The genomic action of aldosterone has already been known to the scientific community and is well-documented to a satisfactory degree. However, the existence of rapid, non-genomic aldosterone actions has repeatedly been proven. These actions are apparent to a lot of tissues, among which the cardiac tissue, with the cardiac cells being responsible for the secretion of endogenous aldosterone. In the genomic pathway, the connection between the hormone and its receptor results increased reabsorption of sodium and water and excretion of potassium. Thus, the genomic procedure reacts indirectly on cardiovascular system by altering the blood pressure. New studies have shed light on unknown aspects of the non-genomic mechanism, which is sometimes performed by means of mineralocorticoid receptor (MR), while others through an MR-independent pathway. It is believed that aldosterone exerts its non-genomic action with the help of a different receptor, probably a G protein coupled receptor. A possible target is protein kinase C (PKC), and PKCε is postulated increase the permeability of the membrane of the cardiac cells to sodium, resulting in delayed repolarization and prolongation of action potential. These findings totally agree with and account for the serendipitous finding of our laboratory, that there is a positive correlation between plasma aldosterone levels and left ventricle (LV) contraction duration. Also, aldosterone has been proven to exacerbate the oxidative stress and induce vasoconstriction by acting on the vascular resistance and the cardiac output. Finally, this article deals with the role of aldosterone in cardiac fibrosis and the latest aspects of aldosterone actions on the heart muscle as well as providing a historical overview of the landmarks pertaining aldosterone's research.

Low dose pioglitazone does not affect bone formation and resorption markers or bone mineral density in streptozocin-induced diabetic rats.

Our study aims to investigate the effect of a low-dose pioglitazone regimen on bone mineral density and bone formation-resorption markers in control and diabetic rats. Wistar rats were divided into 4 groups: non-diabetic controls, control rats receiving pioglitazone (3 mg/kg), streptozocin-treated diabetic rats (50 mg/kg), diabetic rats treated with pioglitazone (3 mg/kg). The duration of the experiment was 8 weeks. Diabetes in our rats was associated with weight loss, increased urinary calcium excretion and reduced plasma osteocalcin levels. Diabetes mellitus did not affect bone mineral density. Pioglitazone administration had no impact on bone formation and resorption markers levels and did not modify bone mineral density in the four studied groups. Pioglitazone at the 3 mg/kg dose was not associated with significant skeletal complications in our experimental model.

A semi-automated approach towards generating three-dimensional mesh of the heart using a hybrid MRI/histology database.

Both the forward and inverse problems of electrocardiography rely on the precise modelling of the anatomic and electrical properties of the thoracic tissues. This, in turn, requires good knowledge of the electrical anisotropy as well as conductivity inhomogeneity of the heart, lungs and the rest of the thorax. Cardiac electrical anisotropy is related to its microstructure (fibre length, density and orientation). We hereby present detailed three-dimensional (3D) meshes of the thorax and heart, using image data from contiguous 2D magnetic resonance (MR) imaging slices as well as a realistic 3D cardiac fibre orientation model that derives its data from high-resolution ex vivo human heart MR images and from histology specimens of heart tissue. Using specific software, we integrated the 3D thorax and heart meshes in one that addresses the related modelling requirements for the solution of the forward and inverse problems of electrocardiography.

The role of endothelium and endogenous vasoactive substances in sepsis.

Sepsis and septic shock are great challenges for the doctors who treat critically ill patients. A big part of the scientific community is performing researches about the pathophysiology and treatment of this clinical problem. The endothelium has a very significant role in the alterations that sepsis causes especially to the circulatory system. The disorders of the normal function of the endothelium include derangement of the vascular tone, increase of endothelium permeability, activation of the endothelial cells, production of various regulators and disorders of coagulation. Nitric oxide is the modulator that mediates the action of most vasodilators. The overproduction of nitric oxide during sepsis is possibly the most important cause of the vasopressor-resistant hypotension which characterizes septic shock. The levels of natriuretic peptides are also increased. These peptides act through several ways on the circulatory system both peripherally and directly on the myocardium. Endothelin, vasopressin, adrenomedullin and prostacyclin are vasoactive substances that have their own role in the regulation of the circulatory system during sepsis.

Red blood cell volume (RBCV) and blood volume (BV) in male albino (NZW) rabbits with 99mTc.

Estimation of red blood cell volume (RBCV) and blood volume (BV) in experimental animals is important for studies concerning pharmaceutical distribution. In this study RBCV was measured, using 99mTc, in 64 male albino New Zealand rabbits with a body weight (BW) of 3.12 +/- 0.37 (SD) kg. The packed cell volume (PCV) was 38.17 +/- 2.37% (SD), the hematocrit (Hct) of the venous blood sample, corrected for trapped plasma, was PCV x 0.97 and the somatic hematocrit (Ho) was calculated as 0.89 x Hct. RBCV was measured using the pretinning method and the BV was calculated according to the formula BV = RBCV x 100/Ho. Labeling efficiency was 96.4% +/- 3.8% (SD). The RBCV was found to be 18.52 +/- 1.96 (SD) mL/kg (BW) and BV 56.12 +/- 4.82 (SD)mL/kg (BW). The correlation of the RBCV and BV to BW is given by the formulae: RBCV = 66.754 ln(BW(g)) - 478.702 (r2 = 0.624, P less than 0.001) and BV = -47.587 + 197.342 ln(BWkg) (r2 = 0.72, P less than 0.001). The 99mTc results do not differ significantly from those of the standard 51Cr procedure, but the 99mTc labeling method permits repetitive measurements at shorter intervals compared to 51Cr.

Cardiovascular effects of aging. Interrelationships of aortic, left ventricular, and left atrial function.

BACKGROUND: Previous studies have shown that elastic properties of the aorta decrease, while left atrial dimensions, the contribution of left atrial systole to left ventricular filling, and left ventricular mass increase with age. In most studies, however, aortic function, and ventricular and atrial parameters were performed in different populations, and thus, the earliest manifestation of aging in the cardiovascular system is not known. The present study was undertaken to define the earliest cardiovascular abnormality(ies) occurring in the cardiovascular system with age. PATIENTS AND METHOD: In 181 normotensive subjects (147 females and 34 males) age 22-64 years, left ventricular mass, volumes, function and work (echocardiography and blood pressure), left atrial volumes and stroke volume (biplane area-length method by echo), pulse wave velocity (PWV) (carotid to femoral artery, Doppler), and left atrial kinetic energy were measured simultaneously: left atrial kinetic energy = 1/2 mv2, where m = left atrial stroke volume x 1.06 (blood specific gravity), v = transmitral A wave velocity. Regression analyses were performed to correlate all measured cardiovascular parameters with age. RESULTS: Pulse wave velocity (r = 0.51), left atrial kinetic energy (r = 0.42), and A wave velocity (r = 0.38) were correlated to age, while left ventricular mass, function and work were not. Multiple regression analysis among ten clinical and echocardiographic parameters demonstrated that only age contributed independently to pulse wave velocity; only age and pulse wave velocity were contributed independently to left atrial kinetic energy; and only age contributed independently to A wave velocity. CONCLUSIONS: The data demonstrate that age-related alterations in aortic function and left atrial work (left atrial kinetic energy) can be defined prior to changes in left ventricular structure and systolic function. Simultaneous studies of left atrial, left ventricular, and aortic function are required to better understand the effect of aging on the cardiovascular system.