Influence of Nitric Oxide-Cyclic GMP and Oxidative STRESS on Amyloid-ß Peptide Induced Decrease of Na,K-ATPase Activity in Rat Hippocampal Slices.

Amyloid-ß peptide (Aß) has been shown to cause synaptic dysfunction and can render neurons vulnerable to excitotoxicity and oxidative stress. Na,K-ATPase plays an important role to maintain cell ionic equilibrium and it can be modulated by N-methyl-D-aspartate (NMDA)-nitric oxide (NO)-cyclic GMP pathway. Disruption of NO synthase (NOS) activity and reactive oxygen species (ROS) production could lead to changes in Na,K-ATPase isoforms' activities that may be detrimental to the cells. Our aim was to evaluate the signaling pathways of Aß in relation to NMDA-NOS-cyclic GMP versus oxidative stress on α1-/α2,3-Na,K-ATPase activities in rat hippocampal slices. Aß1-40 induced a concentration-dependent increase of NOS activity and increased cyclic guanosine monophosphate (cGMP), TBARS (thiobarbituric acid reactive substances), and 3-Nitrotyrosine (3-NT)-modified protein levels in rat hippocampal slices. The increase in NOS activity and cyclic GMP levels induced by Aß1-40 was completely blocked by MK-801 (inhibitor of NMDA receptor) and L-NAME (inhibitor of NOS) pre-treatment but changes in TBARS levels were only partially blocked by both compounds. The Aß treatment also decreased Na,K-ATPase activity which was reverted by N-nitro-L-arginine methyl ester hydrochloride (L-NAME) but not by MK-801 pre-treatment. The decrease in enzyme activity induced by Aß was isoform-specific since only α1-Na,K-ATPase was affected. These findings suggest that the activation of NMDA-NOS signaling cascade linked to α2,3-Na,K-ATPase activity may mediate an adaptive, neuroprotective response to Aß in rat hippocampus.

Rat vas deferens SERCA2 is modulated by Ca2+/calmodulin protein kinase II-mediated phosphorylation.

Ca2+ pumps are important players in smooth muscle contraction. Nevertheless, little information is available about these pumps in the vas deferens. We have determined which subtype of sarco(endo)plasmic reticulum Ca2+-ATPase isoform (SERCA) is expressed in rat vas deferens (RVD) and its modulation by calmodulin (CaM)-dependent mechanisms. The thapsigargin-sensitive Ca2+-ATPase from a membrane fraction containing the highest SERCA levels in the RVD homogenate has the same molecular mass (∼115 kDa) as that of SERCA2 from the rat cerebellum. It has a very high affinity for Ca2+ (Ca0.5 = 780 nM) and a low sensitivity to vanadate (IC50 = 41 µM). These facts indicate that SERCA2 is present in the RVD. Immunoblotting for CaM and Ca2+/calmodulin-dependent protein kinase II (CaMKII) showed the expression of these two regulatory proteins. Ca2+ and CaM increased serine-phosphorylated residues of the 115-kDa protein, indicating the involvement of CaMKII in the regulatory phosphorylation of SERCA2. Phosphorylation is accompanied by an 8-fold increase of thapsigargin-sensitive Ca2+ accumulation in the lumen of vesicles derived from these membranes. These data establish that SERCA2 in the RVD is modulated by Ca2+ and CaM, possibly via CaMKII, in a process that results in stimulation of Ca2+ pumping activity.

Rat vas deferens SERCA2 is modulated by Ca2+/calmodulin protein kinase II-mediated phosphorylation

Ca2+ pumps are important players in smooth muscle contraction. Nevertheless, little information is available about these pumps in the vas deferens. We have determined which subtype of sarco(endo)plasmic reticulum Ca2+-ATPase isoform (SERCA) is expressed in rat vas deferens (RVD) and its modulation by calmodulin (CaM)-dependent mechanisms. The thapsigargin-sensitive Ca2+-ATPase from a membrane fraction containing the highest SERCA levels in the RVD homogenate has the same molecular mass (∼115 kDa) as that of SERCA2 from the rat cerebellum. It has a very high affinity for Ca2+ (Ca0.5 = 780 nM) and a low sensitivity to vanadate (IC50 = 41 µM). These facts indicate that SERCA2 is present in the RVD. Immunoblotting for CaM and Ca2+/calmodulin-dependent protein kinase II (CaMKII) showed the expression of these two regulatory proteins. Ca2+ and CaM increased serine-phosphorylated residues of the 115-kDa protein, indicating the involvement of CaMKII in the regulatory phosphorylation of SERCA2. Phosphorylation is accompanied by an 8-fold increase of thapsigargin-sensitive Ca2+ accumulation in the lumen of vesicles derived from these membranes. These data establish that SERCA2 in the RVD is modulated by Ca2+ and CaM, possibly via CaMKII, in a process that results in stimulation of Ca2+ pumping activity.

Lack of evidence for regulation of cardiac P-type ATPases and MAP kinases in transgenic mice with cardiac-specific overexpression of constitutively active á1B-adrenoceptors

The regulatory function of á1B-adrenoceptors in mammalian heart homeostasis is controversial. The objective of the present study was to characterize the expression/activity of key proteins implicated in cardiac calcium handling (Na+/K+-ATPase and Ca2+-ATPases) and growth (ERK1/2, JNK1/2 and p38) in mice with cardiac-selective overexpression of constitutively active mutant á1B-adrenoceptor (CAMá1B-AR), which present a mild cardiac hypertrophy phenotype. Immunoblot assays showed that myocardial plasma membrane Ca2+-ATPase (PMCA) expression was increased by 30 percent in CAMá1B-AR mice (N = 6, P < 0.05), although there was no change in sarco/endoplasmic reticulum Ca2+-ATPase (SERCA2) expression. Moreover, total Ca2+-ATPase activity was not modified, but a significant increase in the activity of the thapsigargin-resistant (PMCA) to thapsigargin-sensitive (SERCA) ratio was detected. Neither Na+/K+-ATPase activity nor the expression of á1 and á2 subunit isoforms was changed in CAMá1B-AR mouse hearts. Moreover, immunoblot assays did not provide evidence for an enhanced activation of the three mitogen-activated protein kinases studied in this stage of hypertrophy. Therefore, these findings indicate that chronic cardiac á1B-AR activation in vivo led to mild hypertrophy devoid of significant signs of adaptive modifications concerning primary intracellular calcium control and growth-related proteins, suggesting a minor pathophysiological role of this adrenergic receptor in mouse heart at this stage of development.

Lack of evidence for regulation of cardiac P-type ATPases and MAP kinases in transgenic mice with cardiac-specific overexpression of constitutively active alpha(1B)-adrenoceptors.

The regulatory function of alpha(1B)-adrenoceptors in mammalian heart homeostasis is controversial. The objective of the present study was to characterize the expression/activity of key proteins implicated in cardiac calcium handling (Na(+)/K(+)-ATPase and Ca(2+)-ATPases) and growth (ERK1/2, JNK1/2 and p38) in mice with cardiac-selective overexpression of constitutively active mutant alpha1B-adrenoceptor (CAMalpha(1B)-AR), which present a mild cardiac hypertrophy phenotype. Immunoblot assays showed that myocardial plasma membrane Ca(2+)-ATPase (PMCA) expression was increased by 30% in CAMalpha(1B)-AR mice (N = 6, P < 0.05), although there was no change in sarco/endoplasmic reticulum Ca(2+)-ATPase (SERCA2) expression. Moreover, total Ca(2+)-ATPase activity was not modified, but a significant increase in the activity of the thapsigargin-resistant (PMCA) to thapsigargin-sensitive (SERCA) ratio was detected. Neither Na(+)/K(+)-ATPase activity nor the expression of alpha(1) and alpha(2) subunit isoforms was changed in CAMalpha(1B)-AR mouse hearts. Moreover, immunoblot assays did not provide evidence for an enhanced activation of the three mitogen-activated protein kinases studied in this stage of hypertrophy. Therefore, these findings indicate that chronic cardiac alpha(1B)-AR activation in vivo led to mild hypertrophy devoid of significant signs of adaptive modifications concerning primary intracellular calcium control and growth-related proteins, suggesting a minor pathophysiological role of this adrenergic receptor in mouse heart at this stage of development.

Schistosoma mansoni infection enhances host portal vein contraction: role of potassium channels and p38 MAP kinase.

Murine Schistosoma mansoni infection is related to an increased contraction of portal vein in response to 5-hydroxytryptamine (5-HT). The present study addressed a putative alteration of ion channels and enzymes involved in vascular contraction. In control group, either inhibition of K+ channels sensitive to ATP (K(ATP)) or Ca2+ (BK(Ca)) increased 5-HT-induced contraction, but the same did not occur in infected mice. On the other hand, inhibition of p38 MAP kinase markedly decreased the vascular contraction to 5-HT in the infected mice with minor effects in the control group. Accordingly, we observed a higher density of phospho-p38 MAP kinase, that refers to the fully active state of the enzyme, in portal veins from infected mice as compared to control animals. These results suggest that the reduced function of K(ATP) and BK(Ca) channels along with an increased contribution of p38 MAP kinase contribute to the increased contraction of portal veins to 5-HT observed in murine schistosomiasis.

Similia similibus curentur: notaçäo histórica da medicina homeopática / Similia Similibus curentur: historical backgrounds of homeopathic medicine

A história da medicina homeopática foi discutida neste artigo, abordando-se as concepçöes de Hipócrates, Galeno, Paracelso e Hahnemann. Pretendemos dar uma idéia da evoluçäo da ciência médica de um modo geral, incluindo, neste contexto, o surgimento gradativo das idéias que levaram Hahnemann a criar a homeopatia.

Mecanismos de imunossupressäo na infecçäo aguda pelo "Trypanosoma cruzi" / Immunosuppression mechanisms in acute infection to \"Trypanosoma cruzy\"

Os autores apresentam consideraçöes gerais sobre a resposta de imunossupressao associada à moléstia de Chagas, com o objetivo de contribuir para o entendimento deste importante e promissor ramo do conhecimento.

Blood pressure response to mils psysical training in normotensive and controlled-hypertensive humans

In order to investigate the effect of mild physical activity on blood pressure (BP), 62 subjects - 21 normotensives (NT) and 41 controlled-hypertensives (CHT) - were submitted to 20 minutes of walking and the evaluation of their systolic, diastolic blood pressure and heart rate (SBP, DBP and HR, respectively) was performed before, during and after exercise. Maximal SBP and DBP values as well as the prevalence of cardiovascular risk factors were also assessed. The results show significant diference between the profile of SBP, DBP and HR response from the NT and CHT, the latter presenting less response than the former (P<0.05). During exercise, maximal SBP and DBP from CHT were not at dangerous levels (mean + - SEM = 148.7 + - 2.5 X 84.7 + - 1.3) corresponding to mild or borderline hypertension. However, other risk factors were detected in the studied group. These findings indicate that hypertension is connected with specific alterations in the control of BP.

Alteraçöes mitocondriais e subcelulares tempo-dependentes após breve oclusäo coronariana seguida de reperfusäo em coraçäo de rato / Time-dependence of mitochondrial abnormality and subcellular changes after brief coronary occlusion followed by reperfusion in rat heart

Após 15 minutos de isquemia, realizada por oclusäo da artéria coronariana, coraçöes de ratos wistar foram reperfundidos por 0-5 hora, 6-11 horas ou 12-17 horas. Apesar das conhecidas características que ocorrem na anoxia miocárdial tal como eosinofilia (acidofilia - dados näo mostrados), edema celular e extracelular, e ondulaçäo das fibras, a alteraçäo mitocondrial foi nosso mais importante achado. A alteraçäo, evidenciada como um alongamento mitocondrial e um aspecto fusiforme, parece ser específi a estas condiçöes experimentais, ou seja, um curto período de hipóxia e um longo período de reperfusäo sanguínea. A razäo deste aspecto näo foi elucidada, mas pode ser devido às trocas peculiares que sofrem as mitocôndrias de tecidos isquêmicos reperfundidos.