PubMed Health⌕ Search

Biomedical subjects

C Hermenegildo

Publications and source records attributed to C Hermenegildo.

At least 19 recordsLinked to original sources
PubMed2006

Alterations in the phenotype and function of immune cells in ovariectomy-induced osteopenic mice.

BACKGROUND: Within the last few years, much evidence has been presented on the involvement of the immune system in certain types of bone loss, such as activated T cells in rheumatoid arthritis and in periodontitis. Estrogen deficiency induces bone loss; however, how this deficiency affects the immune system has not been sufficiently studied. METHODS: To evaluate the effects of estrogen withdrawal on the status and functionality of the immune system, mice were ovariectomized or sham-operated, and 5 weeks after surgery, when osteopenia had developed, several parameters were analysed in spleen and in bone marrow. We analysed bone turnover, cell phenotype by flow cytometry, cell function by cell proliferation assays, and the expression of several genes related to the process. RESULTS: Five weeks after ovariectomy, augmented osteoclastogenesis persisted in the bone marrow. In addition, the ovariectomized mice had more B-cells and CD3+ T-cells expressing the receptor activator of NF-kappaB ligand (CD3+/RANKL+). The ovariectomized mice had lower serum alkaline phosphatase activity, a normal amount of T cells, lower percentages of CD11b+ and CD51+ cells in the bone marrow, and a lower serum interferon-gamma level compared with sham-operated controls. CONCLUSIONS: The data suggest that, 5 weeks after ovariectomy, bone turnover remains imbalanced, with increased osteoclastogenesis and a decreased rate of bone formation. Moreover, there is an increase in B-cell formation, with normal and decreased percentages of T cells and myelomonocytic cells (CD11b+), respectively, in the bone marrow. Decreased serum interferon-gamma levels could be involved in the increased osteoclastogenesis found in the present work.

Alkaline Phosphatase↗
PubMed2006

Cyclooxygenases regulation by estradiol on endothelium.

Estrogen and hormone replacement therapies are being tested to prevent the incidence of cardiovascular disease in postmenopausal women. In spite of the evidence from several epidemiological studies suggesting that estrogens protect against atherosclerosis and associated diseases, controversy exists. Moreover, it is important to develop synthetic compounds that achieve the beneficial effects of estrogens on the cardiovascular system while minimizing such undesirable effects on other tissues as the increased risk of endometrial and breast cancer. Some drugs that modulate estrogen function in a tissue-specific manner (Selective Estrogen Receptor Modulators; SERMs) have been discovered and are currently being used in clinical practice. An example of these is raloxifene. Clinical and experimental data support the consideration of endothelium as a target for estradiol and other sexual hormones. Among other actions, estradiol has been implicated in the control of prostacyclin production through cyclooxygenases (COX) regulation in endothelial cells. Prostacyclins are powerful vasodilators and potent inhibitors of platelet aggregation which are produced from free arachidonic acid through the catalytic activity of two COX: COX-1 and COX-2. Together, these COX represent the main control mechanism for prostacyclin production. Although several non-specific COX inhibitors have been available for decades (aspirin, indomethacin, ibuprofen), COX-2 selective inhibitors have been commercialized only within the last few years, thus making it possible to increase the study and treatment of different disorders. This review will discuss clinical and experimental data that document the endothelial effects of estradiol and SERMs on prostacyclin production and COX regulation, their vascular consequences, and their possible interactions with COX inhibitors.

Animals↗
PubMed2005

Progestogens stimulate prostacyclin production by human endothelial cells.

BACKGROUND: The effects of progestogens on endothelial physiology are poorly studied. Prostacyclin is a potent vasodilator synthesized by two isoforms of cyclooxygenase (COX) in endothelium. We examined the effects of two clinically used progestogens, progesterone and medroxyprogesterone acetate (MPA), on prostacyclin production by cultured human umbilical vein endothelial cells (HUVEC) and the possible role of progesterone receptors and both COX enzymes. METHODS: Cells were exposed to 1-100 nmol/l of either progesterone or MPA and prostacyclin production was measured in culture medium. RESULTS: Both progestogens significantly increased prostacyclin release in a time- and dose-dependent manner, being higher than control after 24 h. Progesterone and MPA, both at 10 nmol/l, increased mRNA expression and protein content of both COX. All these effects were mediated through progesterone receptor activation, since they were abolished by treatment of cells with the progesterone receptor antagonist RU-486. Selective inhibitors of COX-1 and -2 (SC-560 and NS-398 respectively) reduced basal prostacyclin release, and eliminated increased production in response to progestogens. In combination with estradiol, progestogens had an additive effect without eliminating estradiol-induced prostacyclin production. CONCLUSIONS: Our results support the hypothesis that progesterone and MPA increased HUVEC prostacyclin production in a progesterone receptor-dependent manner, by enhancing COX-1 and COX-2 expression and activities.

Cells, Cultured↗
PubMed2004

Effect of delayed breeding on the reproductive performance of female mice.

The aim of the present study was to determine, in the mouse, whether maintaining females as virgins until an advanced reproductive age was associated with decreased reproductive performance and reproductive lifespan compared with females of the same age that were first mated with males at an earlier reproductive age. Randomly selected virgin hybrid (C57BL/6JIco female x CBA/JIco male) female mice were housed individually with a randomly selected 12- to 14-week-old hybrid male either at the age of 28 weeks (normal breeding group; n = 20) or 51 weeks (delayed breeding group; n = 23) for the rest of their reproductive life. Females were checked once daily to determine the day of parturition and to record the litter size and gender of pups at birth for each consecutive litter. At weaning, offspring were weighed and killed. Delayed breeding was associated with smaller litter sizes, both at birth and at weaning, a higher bodyweight of pups at weaning, a higher percentage of litters with at least one newborn pup cannibalised, earlier cessation of female reproductive life and a higher mortality rate of dams during the breeding period. These results show that delayed breeding in the mouse is associated with decreased reproductive performance and a shorter reproductive lifespan compared with females bred at an earlier reproductive age.

Age Factors↗
PubMed2001

The effect of oral hormone replacement therapy on lipoprotein profile, resistance of LDL to oxidation and LDL particle size.

OBJECTIVES: To disclose if oral estradiol (E(2)), alone or in combination with natural progesterone (P) or medroxyprogesterone acetate (MPA), may modify the oxidizability of low density lipoprotein (LDL), and if the effect is achieved at physiological dosages. LDL oxidizability was assessed by the resistance to oxidation by copper and by the particle size profile, since small particles have increased oxidation susceptibility. METHODS: Thirty-three women received two consecutive, two-month length doses of 1 and 2 mg/day of oral E(2). They were then randomly assigned to a fourteen-day treatment of 2 mg/day E(2) plus either 300 mg/day P or 5 mg/day MPA. A parallel group of experiments was performed on a pool of baseline plasma, where hormones were added at the desired concentration. Lipoprotein levels, resistance of LDL to oxidation, and LDL particle diameter, were measured at baseline and after each treatment. RESULTS: Estradiol reduced LDL levels and increased high density lipoprotein (HDL) and triglycerides. P abolished these changes, whereas MPA only reversed the increase of HDL. Estradiol protected LDL from oxidation in a dose-dependent manner, although only at pharmacological concentrations (1 microM or higher). Both P and MPA were inert at either physiological or pharmacological concentrations. The size of the LDL particles remained unaffected except under MPA, in which it was reduced. CONCLUSIONS: Estradiol has a protective effect against LDL oxidation, although only at pharmacological dosages. P and MPA did not limit the E(2) action. The size of the LDL particles remained unaltered after each E(2) dose, but MPA, and not P, was associated with a diminution.

Administration, Oral↗
PubMed2000

Activation of N-methyl-D-aspartate receptors in rat brain in vivo following acute ammonia intoxication: characterization by in vivo brain microdialysis.

Ammonia is considered the main agent responsible for the neurological alterations in hepatic encephalopathy. It was suggested that ammonia toxicity is mediated by activation of N-methyl-D-aspartate (NMDA) receptors. The aim of this work was to assess, by in vivo brain microdialysis in freely moving rats, whether acute ammonia intoxication leads to activation of NMDA receptors in the cerebellum of the rat in vivo. We measured the effects of ammonia intoxication on the neuronal glutamate-nitric oxide-cyclic guanosine monophosphate (cGMP) pathway, by measuring the ammonia-induced increase of extracellular cGMP. Ammonia intoxication increases extracellular cGMP, and this increase is prevented by (5R,10S)-5-methyl-10,11-dihydro-5H-dibenzo[a, d]cyclohepten-5,10-imine hydrogen maleate (MK-801). There is a good correlation between the increase in cGMP and the seriousness of the neurological symptoms elicited by different doses of ammonia. Ammonia doses inducing coma did not affect extracellular glutamate, while doses leading to death increased it by 349%. The time courses of ammonia-induced increases in extracellular ammonia, cGMP, and glutamate indicate that NMDA receptor activation occurs before the increase in extracellular glutamate. Ammonia-induced increase in glutamate is prevented by MK-801. These results indicate that ammonia intoxication leads to activation of NMDA receptors in the animal in vivo, and that this activation is not caused by increased extracellular glutamate. The possible underlying mechanism is discussed.

Ammonia↗
PubMed1999

Chronic exposure to aluminium impairs the glutamate-nitric oxide-cyclic GMP pathway in the rat in vivo.

Aluminium is neurotoxic and is considered a possible etiologic factor in Alzheimer's disease, dialysis syndrome and other neurological disorders. The molecular mechanism of aluminium-induced impairment of neurological functions remains unclear. We showed that aluminium impairs the glutamate-nitric oxide-cGMP pathway in cultured neurons. The aim of this work was to assess by in vivo brain microdialysis whether chronic administration of aluminium in the drinking water (2.5% aluminium sulfate) also impairs the glutamate-nitric oxide-cGMP pathway in the cerebellum of rats in vivo. Chronic exposure to aluminium reduced NMDA-induced increase of extracellular cGMP by ca 50%. The increase in extracellular cGMP induced by the nitric oxide generating agent S-nitroso-N-acetylpenicillamine was higher (240%) in rats treated with aluminium than in controls. Immunoblotting experiments showed that aluminium reduced the cerebellar content of calmodulin and nitric oxide synthase by 34 and 15%, respectively. Basal activity of soluble guanylate cyclase was decreased by 66% in aluminium-treated rats, while the activity after stimulation with S-nitroso-N-acetylpenicillamine was similar to controls. Basal cGMP in the cerebellar extracellular space was decreased by 50% in aluminium-treated rats. These results indicate that chronic exposure to aluminium reduces the basal activity of guanylate cyclase and impairs the glutamate-nitric oxide-cGMP pathway in the animal in vivo.

Aluminum↗
PubMed1999

Long-term effects of postovulatory aging of mouse oocytes on offspring: a two-generational study.

Aims of this study were to analyze the long-term effects of postovulatory aging of mouse oocytes on 1) reproductive traits of parental (F(0)) and first (F(1))-generation females (pregnancy rate, gestation length, litter size, perinatal death, and sex ratio of offspring) and 2) developmental and behavioral variables of F(1) and second-generation (F(2)) offspring (birth weight and weight gain during preweaning development, postnatal day of attainment of immediate righting, spontaneous motor activity, and passive and active conditioned learning ability). Hybrid (C57BL/6JIco x CBA/JIco) females were artificially inseminated at 13 h (control group) or 22 h (oocyte-aged group) after GnRH injection. Experimental (oocyte-aged group) F(0) females exhibited lower pregnancy rate, shortened gestation length, decreased litter size, higher perinatal death of their pups, and increased percentage of male offspring compared to control F(0) females. Postovulatory aging of oocytes was also associated with increased number of growth-retarded pups, delayed development of the righting reflex, and higher spontaneous motor activity and emotionality of F(1) offspring. Postovulatory aging of F(0) oocytes did not affect birth weight, weight gain during preweaning development, passive and active conditioned learning ability of F(1) offspring, or reproductive traits of F(1) females or developmental and behavior variables of F(2) offspring.

Animals↗
PubMed1998

Nitroarginine, an inhibitor of nitric oxide synthase, prevents changes in superoxide radical and antioxidant enzymes induced by ammonia intoxication.

Injection of large doses of ammonium salts leads to the rapid death of animals. However, the molecular mechanisms involved in ammonia toxicity remain to be clarified. We reported that injecting ammonium acetate (7 mmol/kg) to rats increases the production of superoxide and reduces the activities of some antioxidant enzymes in rat liver and brain. We proposed that these effects induced by ammonia intoxication would be mediated by formation of nitric oxide. To test this possibility we tested whether injection of nitroarginine, an inhibitor of nitric oxide synthase, prevents the effects of ammonia intoxication on antioxidant enzymes and superoxide formation. Following injection of ammonia, glutathione peroxidase, superoxide dismutase and catalase activities were decreased in liver by 42%, 54% and 44%, respectively. In brain these activities were reduced by 35%, 46% and 65%, respectively. Glutathione reductase remained unchanged. Superoxide production in submitochondrial particles from liver and brain was increased by more than 100% in both tissues. Both reduction of activity of antioxidant enzymes and increased superoxide radical production were prevented by previous injection of 45 mg/kg of nitroarginine, indicating that ammonia induces increased formation of nitric oxide, which in turn reduces the activity of antioxidant enzymes, leading to increased formation of superoxide.

Ammonia↗
PubMed1998

Carbachol-induced hydrolysis of phospholipids in hippocampal slices may be mediated in part by subsequent activation of metabotropic glutamate receptors.

We observed that AP-3, an antagonist of metabotropic glutamate receptors, reduced carbachol-induced hydrolysis of phospholipids in hippocampal slices. This inhibition could be explained in different ways, e.g.: 1) AP-3 acts also as antagonist of muscarinic receptors mediating the hydrolysis of phospholipids induced by carbachol, 2) Carbachol induces the release of glutamate which, by activating metabotropic glutamate receptors, leads to additional hydrolysis of phospholipids. The aim of this work was to test these possibilities. It is shown that AP-3 reduces carbachol-induced hydrolysis of phospholipids in hippocampal slices but not in cerebellar neurons at 10-14 days of culture, when these cells are not able to induce hydrolysis of phospholipids following activation of metabotropic glutamate receptors. It is also shown that carbachol induces a release of [3H]aspartate in hippocampal slices. The results reported suggest that the hydrolysis of phospholipids induced by carbachol in hippocampal slices would have two components. One part would be due to direct activation by carbachol of muscarinic receptors associated to activation of phospholipase C. This part would not be inhibited by AP-3. The second part would be due to subsequent release of glutamate and activation of metabotropic glutamate receptors. This part would be inhibited by AP-3.

Alanine↗
PubMed1998

Chronic hyperammonemia impairs the glutamate-nitric oxide-cyclic GMP pathway in cerebellar neurons in culture and in the rat in vivo.

The aim of this work was to assess whether ammonia concentrations similar to the increase found in the brain of hyperammonemic rats (100 microM), impair N-methyl-D-aspartate (NMDA) receptor-mediated signal transduction. We first measured glutamate neurotoxicity, which in these neurons is mediated by activation of NMDA receptors, as an initial parameter reflecting activation of NMDA receptor-mediated pathways. Long-term treatment of cultured neurons with ammonia prevents glutamate-induced neuronal death. The EC50 was 20 microM, and at 100 microM the protection was complete. The induction of the protective effect was not immediate, but took several hours. Treatment with 100 microM ammonia did not prevent a glutamate- or NMDA-induced rise of intracellular calcium. Ammonia impaired the glutamate-nitric oxide-cGMP (3',5'-cyclic guanosine monophosphate) pathway in a dose- and time-dependent manner. Glutamate-induced formation of cGMP was reduced by 42%, while activation of nitric oxide synthase was not affected. Ammonia reduced by 31% cGMP formation induced by S-nitroso-N-acetyl-penicillamine (SNAP), a NO-generating agent, confirming that the interference occurs at the level of guanylate cyclase activation by nitric oxide. To assess whether chronic moderate hyperammonemia in vivo also impairs the glutamate-nitric oxide-cGMP pathway, we determined by in vivo brain microdialysis in freely moving rats the formation of cGMP induced by NMDA. In hyperammonemic rats, the formation of cGMP induced by NMDA and SNAP was reduced by ca. 60 and 41%, respectively, indicating that chronic hyperammonemia in the animal in vivo also impairs the glutamate-nitric oxide-cGMP pathway. Impairment of this pathway can contribute to the neurological alterations found in hyperammonemia and hepatic encephalopathy.

Ammonia↗
PubMed1998

Chronic exposure to aluminum impairs neuronal glutamate-nitric oxide-cyclic GMP pathway.

Humans are exposed to aluminum from environmental sources and therapeutic treatments. However, aluminum is neurotoxic and is considered a possible etiologic factor in Alzheimer's disease and other neurological disorders. The molecular mechanism of aluminum neurotoxicity is not understood. We tested the effects of aluminum on the glutamate-nitric oxide-cyclic GMP pathway in cultured neurons. Neurons were exposed to 50 microM aluminum in culture medium for short-term (4 h) or long-term (8-14 days) periods, or rats were prenatally exposed, i.e., 3.7% aluminum sulfate in the drinking water, during gestation. Chronic (but not short-term) exposure of neurons to aluminum decreased glutamate-induced activation of nitric oxide synthase by 38% and the formation of cyclic GMP by 77%. The formation of cyclic GMP induced by the nitric oxide-generating agent S-nitroso-N-acetylpenicillamine was reduced by 33%. In neurons from rats prenatally exposed to aluminum but not exposed to it during culture, glutamate-induced formation of cyclic GMP was inhibited by 81%, and activation of nitric oxide synthase was decreased by 85%. The formation of cyclic GMP induced by S-nitroso-N-acetylpenicillamine was not affected. These results indicate that chronic exposure to aluminum impairs glutamate-induced activation of nitric oxide synthase and nitric oxide-induced activation of guanylate cyclase. Impairment of the glutamate-nitric oxide-cyclic GMP pathway in neurons may contribute to aluminum neurotoxicity.

Aluminum↗
PubMed1997

Modulation of glutamine synthesis in cultured astrocytes by nitric oxide.

1. Previous results suggest that glutamine synthesis in brain could be modulated by nitric oxide. The aim of this work was to assess this possibility. 2. As glutamine synthetase in brain is located mainly in astrocytes, we used primary cultures of astrocytes to assess the effects of increasing or decreasing nitric oxide levels on glutamine synthesis in intact astrocytes. 3. Nitric oxide levels were decreased by adding nitroarginine, an inhibitor of nitric oxide synthase. To increase nitric oxide we used S-nitroso-N-acetylpenicillamine, a nitric oxide generating agent. 4. It is shown that S-nitroso-N-acetylpenicillamine decreases glutamine synthesis in intact astrocytes by approximately 40-50%. Nitroarginine increases glutamine synthesis slightly in intact astrocytes. 5. These results indicate that brain glutamine synthesis may be modulated in vivo by nitric oxide.

Animals↗
PubMed1997

Superoxide production and antioxidant enzymes in ammonia intoxication in rats.

Injection of large doses of ammonium salts lead to the rapid death of animals. However, the molecular mechanisms involved in ammonia toxicity remain to be clarified. We have tested the effect of injecting 7 mmol/kg of ammonium acetate on the production of superoxide and on the activities of some antioxidant enzymes in rat liver, brain, erythrocytes and plasma. Glutathione peroxidase, superoxide dismutase and catalase activities were decreased in liver and brain (both in cytosolic and mitochondrial fractions) and also in blood red cells, while glutathione reductase activity remained unchanged. Superoxide production in submitochondrial particles from liver and brain was increased by more than 100% in both tissues. Both diminished activity of antioxidant enzymes and increased superoxide radical production could lead to oxidative stress and cell damage, which could be involved in the mechanism of acute ammonia toxicity.

Ammonia↗
PubMed1996

NMDA receptor antagonists prevent acute ammonia toxicity in mice.

We proposed that acute ammonia toxicity is mediated by activation of NMDA receptors. To confirm this hypothesis we have tested whether different NMDA receptor antagonists, acting on different sites of NMDA receptors, prevent death of mice induced by injection of 14 mmol/Kg of ammonium acetate, a dose that induces death of 95% of mice. MK-801, phencyclidine and ketamine, which block the ion channel of NMDA receptors, prevent death of at least 75% of mice. CPP, AP-5, CGS 19755, and CGP 40116, competitive antagonists acting on the binding site for NMDA, also prevent death of at least 75% of mice. Butanol, ethanol and methanol which block NMDA receptors, also prevent death of mice. There is an excellent correlation between the EC50 for preventing ammonia-induced death and the IC50 for inhibiting NMDA-induced currents. Acute ammonia toxicity is not prevented by antagonists of kainate/AMPA receptors, of muscarinic or nicotinic acetylcholine receptors or of GABA receptors. Inhibitors of nitric oxide synthase afford partial protection against ammonia toxicity while inhibitors of calcineurin, of glutamine synthetase or antioxidants did not prevent ammonia-induced death of mice. These results strongly support the idea that acute ammonia toxicity is mediated by activation of NMDA receptors.

Ammonia↗
PubMed1996

Carnitine and choline derivatives containing a trimethylamine group prevent ammonia toxicity in mice and glutamate toxicity in primary cultures of neurons.

Carnitine prevents acute ammonia toxicity in animals. We propose that acute ammonia toxicity is mediated by activation of N-methyl-D-aspartate receptors and have shown that carnitine prevents glutamate neurotoxicity. The aim of this work was to assess whether other compounds containing a trimethylamine group are able to prevent ammonia toxicity in mice and/or glutamate toxicity in primary neuronal cultures. It is shown that betaine, trimethylamine-N-oxide, choline, acetylcholine, carbachol and acetylcarnitine prevent ammonia toxicity in mice. They also prevent glutamate but not N-methyl-D-aspartate neurotoxicity. Choline, acetylcholine and acetylcarnitine afford partial (approximately 50%) protection at nanomolar concentrations and nearly complete protection at micromolar concentrations. Trimethylamine-N-oxide, carbachol and betaine afford nearly complete protection at approximately 0.2 mM. The protective effect against glutamate neurotoxicity is prevented by 2-amino-3-phosphonopropionic acid, an antagonist of metabotropic glutamate receptors. Atropine, an antagonist of muscarinic receptors, prevents the protective effect of most of the above compounds against ammonia toxicity in mice and against glutamate toxicity in cultured neurons. These results support the idea that acute ammonia toxicity is mediated by activation of N-methyl-D-aspartate receptors and that glutamate neurotoxicity could be prevented by activating metabotropic glutamate receptors and/or muscarinic receptors.

Ammonia↗
PubMed1993

Decreased glutathione peroxidase activity in sciatic nerve of alloxan-induced diabetic mice and its correlation with blood glucose levels.

The effect of alloxan-induced diabetes on glutathione peroxidase (GSH-Px) activity in sciatic nerve of mice has been studied. We have found, 7 days after alloxan treatment, a significant decrease in this enzymatic activity in the cytosol of sciatic nerve of diabetic mice, and moreover, that these changes remained unaltered up to 21 days after alloxan injection. No modification in the glutathione content of sciatic nerve of diabetic mice was observed throughout the experiment when compared with controls. The decrease in GSH-Px activity in this tissue shows a good correlation with the increase of blood glucose levels throughout the experiment. It is hypothesized whether a combination of mechanisms could be involved in this decrease of GSH-Px activity and if oxygen radicals might be the common mediators of these processes.

Animals↗