Bi-directional actions of estrogen on the renin-angiotensin system

Estrogen stimulates the renin-angiotensin system by augmenting both tissue and circulating levels of angiotensinogen and renin. We show, however, that angiotensin converting enzyme (ACE) activity in the circulation and in tissues is reduced in two animal models of postmenopausal chronic hormone replacement. We observed a reduction of ACE activity in association with a significant increase in plasma angiotensin I (Ang I) and hyperreninemia in ovariectomized monkeys treated with Premarin (conjugated equine estrogen) replacement for 30 months. Plasma angiotensin II (Ang II) levels were not increased in monkeys treated with estrogen, suggesting that the decrease in ACE curtailed the formation of the peptide. The Ang II/Ang I ratio, an in vivo index of ACE activity, was significantly reduced by estrogen treatment, further supporting the biochemical significance of estrogen's inhibition of ACE. In ovariectomized transgenic hypertensive (mRen2)27 rats submitted to estrogen replacement treatment for 3 weeks, ACE activity in plasma and tissue (aorta and kidney) and circulating Ang II levels were reduced, whereas circulating levels of angiotensin-(1-7) (Ang-(1-7) were increased. Ang-(1-7), the N-terminal fragment of Ang II, is a novel vasodilator and antihypertensive peptide. Thus, the net balance of these effects of estrogen on the renin-angiotensin vasoconstrictor/vasodilator system is to promote the antihypertensive effect.

Valores de referência das colinesterases em plasma e eritrócitos / Reference values of plasma and erythrocyte cholinesterases

As atividades colinesterases no sangue säo utilizadas como bioindicadores na exposiçäo aos inseticidas organofosforatos. Neste trabalho foram estudadas as atividades da pseudocolinesterases plasmática (chE-P) e da acetilcolinesterase eritrocitária (chE-E) em 101 indivíduos considerados sadios, näo expostos ocupacionalmente às substâncias anticolinesterásicas, para se estabelecer valores de referência destes indicadores. As atividades enzimáticas foram determinadas pelo método de Ellman e cols. modificado. Para atestar o estado de saúde dos voluntários, foram também realizadas análises de alguns parâmetros bioquímicos e hematológicos. Os valores médios (intervalo de confiança 95 porcento) dos indicadores pesquisados foram de 8,8 DA/min/mL (8,4 - 9,3) e de 54,9 (52,9 - 56,9), respectivamente para a chE-P e a chE-E. Os resultados deste trabalho podem ser utilizados como de referência das atividades enzimáticas, quando valores de pré-exposiçäo individual näo forem disponíveis, situaçäo comum, principalmente, em casos de intoxicaçäo por inseticidas organofosforados. Näo foi notada diferença estatisticamente significativa nos resultados quando a populaçäo foi subdividida de acordo com o sexo e a faixa etária. O uso do tabaco, o local de morada e o tipo de trabalho, entre outros, näo afetaram os níveis enzimáticos da colinesterases

Aspectos bioquímicos do plasma e fluido peritoneal de eqüinos com cólica / Biochemical aspects of plasma and peritoneal fluid from horses with colic

Compararam-se as características do plasma e do fluido peritoneal entre 6 eqüinos clinicamente sadios com as de outros 16 eqüinos com cólica. Encontrou-se uma elevaçäo significante na taxa de proteínas plasmáticas totais e na concentraçäo do fosfato inorgânico nos eqüinos com cólica. Este fato esteve diretamente relacionado a lesöes isquêmicas intestinais. Assim, conclui-se que algumas alteraçöes bioquímicas do plasma e do fluido peritoneal, quando analisadas em conjunto com os dados obtidos no exame clínico, säo bons indicadores da severidade do caso

The ecto-ATPases of endoparasites and of blood cells and vessels

The cells of blood vessel walls and the external surface of all blood cells have an ecto-ATPase which hydrolyzes ATP to ADP and also ADP to AMP. This enzyme has also been called apyrase or ATP-diphosphohydrolase. The enzyme hydrolyzes a broad range of tri-and diphosphate nucleosides such as UTP and UDP, GTP and GDP in additon to the adenine nucleotides and because of that it has also been called a nucleoside triphosphate hydrolase. The possible physiological roles for this ecto-ATPase involve the control of vascular tone by modulation of the levels of ATP and ADP binding to purino-receptors of the vasculature, the modulation of thrombogenesis by controlling the extracellular level of ADP which is known to activate platelet aggregation, and the protection from cytolytic effects of extracellular ATP. An ATP-diphosphohydrolase activity has been characterized on the external surface of Schistosoma mansoni, a parasite that lives in the circulation of the human host, and on the outer surface of Entamoeba histolytica, a parasite that may enter the circulation of the host through ulceration in the intestinal mucosa. The endoparasite Toxoplasma gondii also exhibits a nucleoside triphosphate hydrolase of high activity, although in this case the ecto-localization is still not documented. We raise the possibility that the endoparasites have evolved in a way to possibly mimic some of the conditions on the surface of cells normally present in the host circulation, thus escaping hemostatic defense responses of the host which require extracellular ADP or ATP.

Estudio de pacientes con litiasis urinaria calcica / Study of patients with calcified urinary lithiasis

Se presenta el trabajo relacionado con la litiasis rinaria cronica, se han revisado 863 historias clínicas del Servicio de Nefro-urología del hospital "Jaime Mendoza" dependiente de la Caja Nacional de Salud de la ciudad de sucre, Bolivia, entre los años de 1987 a 1991. Habiendose encontrado 64 pacientes portadores de litiasis urinaria calcica, lo que corresponde al 7,4. Como quiera que el manejo de la litiasis urinaria no es satisfactorio en nuestro medio, las medidas profilacticas practicamente no existen o solo se limitan a la restriccion de la leche y aumentar la ingestion de agua. Motivados por esa realidad, hemos adaptado en nuestro Servicio el protocolo de estudio de la litiasis urinaria calcica propuesto por Pak y Coe. Para ello fue necesario previamente establecer como punto de partida los valores normales del protocolo, el mismo se realizo en un grupo de 20 personas de ambos sexos, sin antecedentes de litiasis. Posteriormente hemos aplicado ese mismo protocolo a 20 de nuestros pacientes portadores de litiasis urinaria calcica habiendose encontrado 18 alteraciones. Finalmente se ofrece un cuadro de la ubicacion de la litiasis en los diferentes segmentos del aparato urinario.

GPI-specific phospholipase D as an apolipoprotein

Glycosylphosphatidylinositol-specific phospholipase D (GPI-PLD) has recently been shown to be associated with high-density lipoproteins (HDL) in bovine serum. To determine the distribution of GPI-PLD among lipoproteins and characterize the GPI-PLD-containing lipoproteins in human plasma, we used dextram sulfate and immunoaffinity chromatography to isolate apolipoprotein-specific lipoproteins. This procedure allowed fractionation of lipoprotein particles into those containing apolipoprotein B (Lp B), apolipoproteins AI and AII (Lp AI/AII), or apolipoprotein AI only (Lp AI). In five plasma samples with HDL cholesterol ranging from 40 to 129 mg/dl, 75 ñ 12 percent (mean ñ SD) of the GPI-PLD activity was associated with LpAI, 11 ñ 13 percent with Lp AI/AII, while only 13 ñ 9 percent was present in plasma devoid of these lipoproteins, suggesting that most of the GPI-PLD in human plasma is associated with apolipoprotein AI. No GPI-PLD activity was detected in Lp B. Further characterization of the GPI-PLD-containing lipoproteins by gel filtration chromatography, nondenaturing poly-acrylamide and agarose gel electrophoresis revealed that GPI-PLD was restricted to an apolipoprotein AI-containing particle or complex that was small (apparent mean Mw of 140 KDa) and distinct from the bulk of HDL. Thus, the majority of plasma GPI-PLD appears to be specifically associated with a small, minor fraction of apoloprotein AI

Antiestrogen U23,469 induced alterations of catecholamine levels on plasma and central nervous system

The effect of antiestrogen U23,469 administration in vivo on the centration of dopamine, norepinephrine and epinephrine in the plasma, cerebral cortex and hypothalamus in ovariectomized rats was investigated. Rats were treated with estradiol benzoate, progesterone and U23,469 in different doses, s.c., daily for 6 days. Control group was injected with sesame oil. Catecholamines were estimated by radioenzymatic assay. Six days of U23,469, estradiol benzoate, progesterone or its combination altered the catecholamine levels compared to the control. Dopamine decreased in plasma with progesterone and U23.469. In the cerebral cortex, progesterone and U23,469 increased significantly and in the hypothalamus all the treatments produced a decrease of catecholamines. The levels of NE were reduced with estradiol benzoate, progesterone and U23,469; there was no significant difference in the norepinephrine levels after different treatments in the cerebral cortex, but the NE levels were significantly decreased inthe hypothalamus. Epinephrine Showed differences related to the treatment, as in plasma, as in cerebral cortex and hypothalamus. These resultas suggest that antiestrogen treatment compared with the estradiol benzoate or progesterone may affect the catecholamine levels of the central nervous system and plasma and support the idea that AE could have an indirect effect on the catecholaminergic system