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Avaliação do cálcio sérico ionizado em gatos sadios e em gatos com insuficiência renal crônica; Serum ionized calcium evaluation in healthy cats and in cats with chronic renal failure

Giovaninni, Luciano Henrique
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 26/06/2003 PT
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A insuficiência renal crônica (IRC) pode ocasionar uma série de alterações metabólicas no organismo, das quais o comprometimento do metabolismo do cálcio pode acarretar em desmineralização óssea e mineralização de tecidos moles, inclusive renal, favorecendo a perda ainda maior de néfrons. Na rotina, a avaliação do cálcio é geralmente realizada pela mensuração do cálcio sérico total, entretanto, a única fração biologicamente ativa deste mineral é representada pelo cálcio ionizado. Assim, o presente estudo teve como objetivo avaliar o cálcio ionizado em gatos sadios e em gatos com IRC, com o intuito de se obter subsídios para o melhor entendimento da homeostase do cálcio. Foram analisados 25 gatos sadios (grupo controle) e 19 gatos com IRC (grupo de estudo) em que foram determinadas as concentrações séricas de cálcio ionizado, cálcio total, sódio, potássio, cloreto, fósforo inorgânico, albumina, como também do pH sangüíneo e das variáveis da hemogasometria. Não foram observadas diferenças significantes entre os grupos controle e estudo no que se relaciona aos valores de cálcio total (controle = 9,52 ± 0,96; IRC = 9,48 ± 0,96) e cálcio ionizado (controle = 5,24 ± 0,18; IRC = 5,29 ± 0...

Efeito de bloqueadores de canais de íons cálcio sobre espermatozóides e oócitos de hamsters fecundados in vivo e in vitro ; Effects of calcium ion channel blockers on hamster spermatozoa and oocytes in in vivo and in vitro fertilization

Gabaldi, Sandra Helena
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 14/07/2004 PT
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O processo de fertilização está intimamente relacionado ao íon cálcio. Há relatos que bloqueadores de canais de íons cálcio voltagem-dependentes, utilizados na terapia anti-hipertensiva, podem levar à infertilidade masculina, mas poucos relatos são os de seus efeitos sobre o oócito. O objetivo deste experimento foi verificar a influência dos bloqueadores de canais de cálcio voltagem-dependentes do tipo-L, verapamil, nifedipina e diltiazem, sobre os gametas masculino e feminino. Machos e fêmeas hamsters foram utilizados em testes in vivo e in vitro. Foram realizados tratamentos in vitro no Experimento I: espermatozóides foram capacitados em meios contendo três concentrações de bloqueadores de canais de cálcio e avaliados quanto à capacitação espermática, hiperatividade e fertilidade in vitro. Oócitos foram tratados previamente por 30 minutos com quatro concentrações de antagonistas de canais de cálcio e submetidos a teste de fertilização in vitro e à avaliação do comportamento dos grânulos corticais. No Experimento II, os bloqueadores de canais de cálcio foram administrados, duas vezes ao dia, por 60 dias nos machos e por 30 dias nas fêmeas, que foram analisados pela fertilidade in vivo, capacitação e hiperatividade espermáticas...

Relação da ingestão de cálcio com a obesidade e alterações metabólicas em adolescentes pós-púberes; Relation between dietary calcium intake with obesity and metabolic alterations in post-pubertal adolescents.

Santos, Luana Caroline dos
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 13/01/2006 PT
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Introdução: Dentre as inúmeras contribuições nutricionais para a obesidade, alguns estudos evidenciam o cálcio dietético como um fator negativamente relacionado com o Índice de Massa Corporal. Ensaios clínicos e experimentais demonstraram que o mecanismo provável é a maior disponibilidade do cálcio intracelular capaz de promover aumento da lipogênese, inibição da lipólise e hiperinsulinemia. Devido a escassez de dados semelhantes em adolescentes, o presente trabalho avaliou a relação do cálcio com a obesidade nesta população. Métodos: Estudo caso-controle e transversal, envolvendo adolescentes eutróficos (GE) e obesos (GO). Os participantes foram submetidos à avaliação antropométrica (peso e estatura), avaliação da composição corporal (DXA), avaliação bioquímica, incluindo perfil lipídico, glicemia de jejum, insulina e dosagem dos hormônios grelina e leptina (apenas nos obesos) e avaliação alimentar (registro de três dias). A resistência à insulina foi estimada por meio do HOMA-IR. A análise estatística constou de teste t Student, correlação de Pearson, Qui-Quadrado, teste exato de Fisher, ANOVA e Odds Ratio. A ingestão de cálcio foi ajustada pelo consumo energético da dieta por meio do método de nutriente residual. Resultados: Foram avaliados 96 adolescentes...

Influência da remodelação óssea na transferência de cálcio e fósforo durante hemodiálise em pacientes com doença renal crônica; Influence of the bone remodeling in the calcium and phosphorus transfer during hemodialysis in patients with chronic kidney disease

Karohl, Cristina
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 13/12/2010 PT
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A cinética e os fatores determinantes da transferência do cálcio e do fósforo durante a hemodiálise foram pouco avaliados e não são completamente compreendidos até os dias de hoje, apesar de associarem-se ao desenvolvimento e progressão da doença óssea renal, à calcificação vascular e à maior mortalidade. Tanto a transferência de cálcio e a remoção de fósforo durante a diálise afetam o equilíbrio do metabolismo mineral. Este estudo tem por hipótese que o metabolismo mineral e ósseo poderia, por sua vez, afetar a cinética de ambos os íons durante a diálise. No entanto, remodelação óssea não é usualmente considerada quando modelos cinéticos são aplicados para cálcular o balanço do cálcio e do fósforo. OBJETIVO: Avaliar a cinética do cálcio e do fósforo durante a hemodiálise e o papel da remodelação óssea nessa transferência. MÉTODO: Vinte e três pacientes (idade = 43,2 ± 17 anos) com doença renal crônica em hemodiálise no Hospital das Clínicas da USP foram submetidos a 4 sessões de hemodiálise com cada uma das seguintes concentrações de cálcio no dialisato (Cad): 2,0; 2,5; 3,0 e 3,5 mEq/L. Amostras de sangue e de dialisato foram coletadas a cada 30 minutos para calcular a transferência de cálcio e fósforo e avaliar os fatores determinantes desta transferência. RESULTADOS: O balanço de cálcio foi extremamente variável em todas as Cad. A transferência de cálcio foi de 578±389...

Influencia de bloqueadores de canais de calcio no processo de degeneração/regeneração muscular em camundongos ditroficos MDX; The influence iof calcium channel blockers in the process of muscular degeneration/regeneration in mdx mice

Cintia Yuri Matsumura
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 02/06/2008 PT
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A ausência da distrofina em fibras musculares de camundongos mdx e na Distrofia Muscular de Duchenne (DMD) provoca ruptura no sarcolema, aumento no influxo de cálcio e conseqüente degeneração muscular. Neste trabalho verificamos os efeitos dos bloqueadores de canais de cálcio diltiazem e verapamil na degeneração/regeneração do músculo distrófico de camundongos mdx. Camundongos mdx (n=32; 18 dias de vida pós-natal) receberam diariamente injeção intraperitoneal de diltiazem (n=16; 72 mg/kg) ou verapamil (n=16; 25 mg/kg) por 18 dias. Após este período os músculos esternomastóide, diafragma, tibial anterior e coração foram retirados. Animais mdx controle (n=16) foram injetados com solução salina. Ambas drogas diminuíram significativamente os níveis séricos de creatina quinase (mdx tratado com salina: 573±245 U/l, animais tratado com diltiazem: 161±53*U/l e animais tratados com verapamil: 217±57*U/l; média±desvio padrão, *p<0,05 comparados a animais tratados com salina, teste t de Student). A quantificação de cálcio total, por espectrômetro de emissão óptica em plasma, foi 173-475% maior em músculos do mdx comparado a músculos de animais controles não-distróficos C57Bl/10. Verapamil e diltiazem reduziram a concentração de cálcio total apenas no diafragma (diltiazem: 229 mg de cálcio/kg versus salina: 295mg de cálcio/kg; p=0...

Calcium handling in Sparus auratus: effects of water and dietary calcium levels on mineral composition, cortisol and PTHrP levels

Abbink, W.; Bevelander, G. S.; Rotllant, J.; Canario, Adelino V. M.; Flik, G.
Fonte: The Company of Biologists Publicador: The Company of Biologists
Tipo: Artigo de Revista Científica
Publicado em 01/11/2004 ENG
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Juvenile gilthead sea bream (Sparus auratus L.; 10–40·g body mass) were acclimatized in the laboratory to full strength (34‰) or dilute (2.5‰) seawater and fed normal, calcium-sufficient or calcium-deficient diet for nine weeks. Mean growth rate, whole-body calcium and phosphorus content and accumulation rates were determined, as well as plasma levels of ionic and total calcium, cortisol and parathyroid hormone related protein (PTHrP; a hypercalcemic hormone in fish). When confronted with limited calcium access (low salinity and calcium-deficient diet), sea bream show growth arrest. Both plasma cortisol and PTHrP increase when calcium is limited in water or diet, and a positive relationship was found between plasma PTHrP and plasma ionic calcium (R2=0.29, N=18, P<0.05). Furthermore, a strong correlation was found between net calcium and phosphorus accumulation (R2=0.92, N=16, P<0.01) and between body mass and whole-body calcium (R2=0.84, N=25, P<0.01) and phosphorus (R2=0.88, N=24, P<0.01) content. Phosphorus accumulation is strongly calcium dependent, as phosphorus accumulation decreases in parallel to calcium accumulation when the diet is calcium deficient but phosphorus sufficient. We conclude that PTHrP and cortisol are involved in the regulation of the hydromineral balance of these fish...

Mammary-Specific Ablation of the Calcium-Sensing Receptor During Lactation Alters Maternal Calcium Metabolism, Milk Calcium Transport, and Neonatal Calcium Accrual

Mamillapalli, Ramanaiah; VanHouten, Joshua; Dann, Pamela; Bikle, Daniel; Chang, Wenhan; Brown, Edward; Wysolmerski, John
Fonte: Endocrine Society Publicador: Endocrine Society
Tipo: Artigo de Revista Científica
EN
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To meet the demands for milk calcium, the lactating mother adjusts systemic calcium and bone metabolism by increasing dietary calcium intake, increasing bone resorption, and reducing renal calcium excretion. As part of this adaptation, the lactating mammary gland secretes PTHrP into the maternal circulation to increase bone turnover and mobilize skeletal calcium stores. Previous data have suggested that, during lactation, the breast relies on the calcium-sensing receptor (CaSR) to coordinate PTHrP secretion and milk calcium transport with calcium availability. To test this idea genetically, we bred BLG-Cre mice with CaSR-floxed mice to ablate the CaSR specifically from mammary epithelial cells only at the onset of lactation (CaSR-cKO mice). Loss of the CaSR in the lactating mammary gland did not disrupt alveolar differentiation or milk production. However, it did increase the secretion of PTHrP into milk and decreased the transport of calcium from the circulation into milk. CaSR-cKO mice did not show accelerated bone resorption, but they did have a decrease in bone formation. Loss of the mammary gland CaSR resulted in hypercalcemia, decreased PTH secretion, and increased renal calcium excretion in lactating mothers. Finally, loss of the mammary gland CaSR resulted in decreased calcium accrual by suckling neonates...

Mitochondrial-Sarcoplasmic Reticulum Crosstalk: Mitochondrial Subcellular Localization, Calcium Uptake, and Suppression of Local Calcium Release in Fast-Twitch Skeletal Muscle During Postnatal Development

Rossi, Ann Elizabeth ; Dirksen, Robert T.
Fonte: Universidade de Rochester Publicador: Universidade de Rochester
Tipo: Tese de Doutorado
ENG
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Thesis (Ph.D.)--University of Rochester. School of Medicine and Dentistry. Dept. of Pharmacology & Physiology, 2009.; In adult skeletal muscle, mitochondria are primarily located next to calcium release units (CRUs), or triads, the structures formed by the close apposition of sarcoplasmic reticulum (SR) terminal cisternae and transverse tubules (T-tubules). Close SR-mitochondria colocalization and the formation of functional calcium microdomains permit rapid mitochondrial calcium uptake during physiological elevations in myoplasmic calcium. At the same time, exclusive positioning of mitochondria adjacent to CRUs is a prerequisite for inhibition of local calcium release (i.e. Ca2+ sparks). In this way, a structural association of mitochondria with the triad provides a basis for privileged bidirectional SR-mitochondrial communication between the two organelles. However, limited information is available with regard to mitochondrial disposition during skeletal muscle development. To this end, the following research characterized mitochondrial localization in flexor digitorum brevis (FDB) fibers from young (0.5-1 month of age) and adult (2-4 months of age) mice using both confocal and electron microscopy. As expected, adult FDB fibers exhibited mitochondrial staining similar to that of SR proteins located at the SR-T-tubule junction...

Does the response of bone mass to calcium supplements depend on calcium absorption efficiency?

Smith, E.; Need, A.; Schultz, C.; Horowitz, M.
Fonte: Bio Scientifica Ltd Publicador: Bio Scientifica Ltd
Tipo: Artigo de Revista Científica
Publicado em //2004 EN
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OBJECTIVE: Calcium supplements can reduce bone resorption and slow bone loss after the menopause, but these effects may be limited by poor intestinal absorption. Since the increase in blood ionised calcium and decrease in serum parathyroid hormone after a calcium load are diminished in patients with poor calcium absorption, we aimed to see whether the response of bone mineral content (BMC) to calcium is related to initial calcium absorption. DESIGN: We retrospectively examined the changes in forearm BMC in 164 patients (139 women and 25 men) receiving calcium therapy alone for low bone density in a university hospital. METHODS: BMC was measured in a Molsgaard single energy absorptiometer and calcium absorption in a single blood sample 1 h after a dose of 5 microCi (45)Ca in 20 mg calcium carrier. Results were analysed by simple and multiple regression analysis. RESULTS: Mean forearm BMC did not change significantly over the mean 43 (S.D., 33) months of treatment (1.023 (0.247) to 1.017 (0.246) g/cm). The annual percentage of change was positively related to both body weight (r=0.180; P=0.020) and radiocalcium absorption (r=0.185; P=0.017). Multiple linear regression confirmed that both variables contributed to the change in BMC (P=0.023 and 0.019 respectively). The mean annual percentage of change in BMC on calcium therapy was not related to age...

Recalculation of the calcium requirement of adult men

Nordin, B.; Morris, H.
Fonte: Amer Soc Clinical Nutrition Publicador: Amer Soc Clinical Nutrition
Tipo: Artigo de Revista Científica
Publicado em //2011 EN
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Background: There is uncertainty about the calcium requirement with particular respect to age and sex differences and the calculation of skin calcium losses. Objective: We calculated the calcium requirement of adult men from a homogenous set of calcium balances and a robust estimate of calcium loss through the skin. Design: We reviewed available high-quality published calcium balances in men and retrieved 219 balances; we noted a fall in calcium absorption in individuals >60 y of age. Our analysis was confined to 157 men ≤59 y of age with intakes of ≤1100 mg Ca. Results: The mean age of the men was 38 y (range: 17–59 y), and the mean duration of the balances was 107 d (9–480 d). We assumed skin calcium losses of 40 mg Ca/d on the basis of the calcium content of insensible water loss. There was a highly significant correlation between calcium intake and the net absorbed calcium (R2 = 0.59), but inspection and physiologic considerations led us to use the logarithmic transformation of intake, which yielded the equation Ca absorbed = 210 log Ca intake − 1135 mg Ca. The calcium intake at which urine calcium plus skin calcium losses were equal to the net absorbed calcium was rounded to 750 mg Ca as the requirement, which implied a recommended allowance of 900 mg Ca. Conclusion: We conclude that the mean calcium requirement of adult men <60 y of age is 750 mg Ca/d...

Untersuchungen zum Calciumstoffwechsel an humanem Myokard in einer Mikroperfusionkammer; Analysis of calcium homeostasis of human cardiac tissue in a microperfusion chamber

Renovanz, Mirjam
Fonte: Universidade de Tubinga Publicador: Universidade de Tubinga
Tipo: Dissertação
DE_DE
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Inhalt dieser Arbeit war es ein dem Herzmuskelgewebe kongruentes humanes Myokardmodell zu entwickeln und damit fluoreszenzmikroskopisch die intrazellulären Calciumregulationsmechanismen und ihre Rolle beim Reperfusionsschaden bzw. der Apoptoseinduktion zu untersuchen. Dazu wurde eine spezielle Mikroperfusionskammer eingesetzt, in der die Kardiomyozytenzellverbände durch ein Kunststoffnetz schonend fixiert werden konnten. Für eine simultane Untersuchung von mit Fluoreszenzfarbstoff beladenen und nicht beladenen Zellverbänden wurde eine doppelt gekammerte Mikroperfusionskammer entwickelt, in der für die beiden gleichzeitig perfundierten Zellverbände die selben Verhältnisse herrschten. Die Untersuchung der Calciumhomöostase erfolgte zunächst unter Perfusion mit Calcium-haltiger und Calcium-freier Krebs-Henseleit-Lösung. Anschließend wurden Hypoxie- und Reperfusions-Versuche unter Kühlung und Stickoxyd- bzw. Carbogenbegasung durchgeführt. Hierbei erfolgte eine Einteilung in verschiedene Gruppen (Kardioplegie/Hypoxie/Reperfusion, Hypoxie/Reperfusion). Dabei befanden sich in dem unteren Teil der Mikroperfusionskammer nicht mit Fluoreszenzfarbstoff beladene Zellverbände. Diese wurden anschließend zu Kryoschnitten verarbeitet...

Effect of low or high dietary calcium on the morphology of the rat femur

chen, H.; Hayakawa, D.; Emura, S.; Ozawa, Y.; Okumura, T.; Shoumura, S.
Fonte: Murcia : F. Hernández Publicador: Murcia : F. Hernández
Tipo: Artigo de Revista Científica Formato: application/pdf
ENG
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The present study compared the effect of a calcium deficit or surfeit on femurs. Young female rats were fed with the normal (1.18%), low (0.05%), or high (2.00%) calcium diet for 3, 7, 15 or 30 days. Two groups received the low calcium diet for the first 15 days and then were followed by the normal (L-N) or high calcium diets (L-H) for the sequential 15 days. The morphology of the femur was studied together with serum calcium, parathyroid hormone (PTH), calcitonin and bone mineral density (BMD). We did not find any significant changes in the serum PTH level and bone morphology in the high calcium group. In the low calcium group, the serum PTH level increased, BMD of the whole body, the femoral weight and the femoral trabecular bone decreased as compared with the normal calcium group. There was a greater proportion of resorbing surface, less resting surface and larger vascular canal openings in the femoral endosteal surfaces in the low calcium group. In the L-N or L-H group, the femoral trabecular bone increased and the femoral resorbing surface decreased as compared with those of the low calcium group. These findings suggest that high calcium intakes do not affect the bone mass, and low calcium intakes have a deleterious effect on bone status...

Suppression of parathyroid hormone and bone resorption by calcium carbonate and calcium citrate in postmenopausal women

Thomas, S.; Need, A.; Tucker, G.; Slobodian, P.; O'Loughlin, P.; Nordin, B.
Fonte: Springer Publicador: Springer
Tipo: Artigo de Revista Científica
Publicado em //2008 EN
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This study was conducted to compare the suppressive effects of calcium carbonate and calcium citrate on bone resorption in early postmenopause. Calcium citrate is thought to be better absorbed. We therefore tested the hypothesis that calcium as citrate is more effective than calcium as carbonate in suppressing parathyroid hormone (PTH) and C-terminal telopeptide. Twenty-five healthy postmenopausal women were recruited in this double blind crossover study. The subjects were randomly allocated to receive either 1,000 mg of elemental calcium as carbonate or 500 mg of calcium as citrate. They were given the alternate calcium dose 1 week later. Serum measurements of total and ionized calcium, phosphate, PTH, and CrossLaps were repeated 12 hours after each dose. Analysis of variance found no significant difference between measures for the two salts. Tests for equivalence indicated that 500 mg of calcium citrate may be superior to 1,000 mg of calcium carbonate in raising serum total and ionized calcium (P = 0.04 and 0.05, respectively). For all parameters measured, 500 mg of calcium citrate was at least as beneficial as 1,000 mg of calcium carbonate. Calcium citrate is at least as effective as calcium carbonate in suppressing PTH and C-terminal telopeptide cross-links...

Biochemical variables in pre- and postmenopausal women: reconciling the calcium and estrogen hypotheses

Nordin, B.; Need, A.; Morris, H.; Horowitz, M.
Fonte: Springer-Verlag London Limited Publicador: Springer-Verlag London Limited
Tipo: Artigo de Revista Científica
Publicado em //1999 EN
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There is controversy as to whether the rise in urinary calcium at the menopause is the cause or the result of the rise in bone resorption at that time. In an attempt to resolve this issue, we have compared the relevant biochemical variables in 102 premenopausal volunteers (mean age 37 years; range 21-52) and 86 apparently normal postmenopausal women (mean age 55 years; range 40-60). We measured the fasting serum calcium, creatinine, proteins, electrolytes and intact parathyroid hormone (PTH), and the urinary calcium and creatinine both after an overnight fast and in a 24-h collection. We calculated serum calcium fractions, creatinine clearance and the notional tubular maximum reabsorptive capacity for calcium. Creatinine excretion and clearance were lower in the post- than in the premenopausal women after correction for surface area and age. Total serum calcium was higher in the post- than in the premenopausal women but this was accounted for by the higher ligand concentrations in the former. Fasting and 24-h urinary calcium were also higher in the post- than in the premenopausal women due in part to the former's higher filtered load of calcium (due to their higher serum complexed calcium) but mainly to their reduced tubular reabsorption of calcium despite their slightly raised serum PTH. Our analysis resolves the rise in urinary calcium at the menopause into its two components: increased filtered load and reduced tubular reabsorption. The changes in these two variables...

Calcium acetate versus calcium carbonate in the control of hyperphosphatemia in hemodialysis patients

d'Almeida Filho,Eufrônio José; Cruz,Elisa de Albuquerque Sampaio da; Hoette,Marcos; Ruzany,Frederico; Keen,Luana Neves Lopes; Lugon,Jocemir Ronaldo
Fonte: Associação Paulista de Medicina - APM Publicador: Associação Paulista de Medicina - APM
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/11/2000 EN
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CONTEXT: Hyperphosphatemia has an important role in the development of bone and mineral abnormalities in end-stage renal disease (ESRD). OBJECTIVE: To compare the phosphorus binding power and the hypercalcemic effect of calcium acetate and calcium carbonate in hemodialysis patients. TYPE OF STUDY: Crossover, randomized, double-blind study. PLACE: A private hospital dialysis center. PARTICIPANTS: Fifty-two patients who were undergoing regular hemodialysis three times a week ([Ca++] dialysate = 3.5 mEq/L). PROCEDURES: Half of the patients were started on 5.6 g/day of calcium acetate and, after a 2 week washout period, received 6.2 g/day of calcium carbonate. The other half followed an inverse protocol. MAIN MEASUREMENTS: Clinical interviews were conducted 3 times a week to monitor for side effects. Determinations of serum urea, calcium, phosphorus, hematocrit, Kt/V and blood gas analysis were obtained before and after each treatment. RESULTS: Twenty-three patients completed the study. A significant increase in calcium plasma levels was only observed after treatment with calcium carbonate [9.34 mg/dl (SD 0.91) vs. 9.91 mg/dl (SD 0.79), P < 0.01]. The drop in phosphorus levels was substantial and significant for both salts [5.64 mg/dl (SD 1.54) vs. 4.60 mg/dl (SD 1.32)...

Caracterización cuantitativa de señales intracelulares de calcio; Quantitative characterization of intracellular calcium signaling

Sigaut, Lorena
Fonte: Facultad de Ciencias Exactas y Naturales. Universidad de Buenos Aires Publicador: Facultad de Ciencias Exactas y Naturales. Universidad de Buenos Aires
Tipo: info:eu-repo/semantics/doctoralThesis; tesis doctoral; info:eu-repo/semantics/publishedVersion Formato: application/pdf
Publicado em //2011 SPA
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Las señales de calcio son utilizadas por una enorme variedad de células para regular procesos tan distintos como la fertilización o la muerte celular, entre muchos otros. La versatilidad del ión calcio como agente señalizador se basa en la gran diversidad de comportamientos que su concentración puede desplegar dentro de las células. Desentrañar la compleja trama de mecanismos que determinan dichos comportamientos es un enorme desafío que requiere la combinación de estrategias múltiples tanto experimentales como de modelado. En particular, el amplio rango de escalas espaciales y temporales involucradas no puede ser abarcado con un unico tipo de experimentos y es entonces que la elaboración de modelos que permitan conectar observaciones dispares se vuelve indispensable. Por otro lado, para que los modelos puedan cumplir este rol es necesario contar con estimaciones confiables, idealmente obtenidas in situ, de algunas de las cantidades que caracterizan a los fenómenos físicos y químicos involucrados en las señales. El objetivo de esta Tesis ha sido avanzar en la obtención de estas estimaciones realistas realizando experimentos opticos y desarrollando el marco teórico necesario para extraer información cuantitativa de los mismos. Una de las propiedades pobremente caracterizadas es la tasa a la que el calcio se transporta dentro de las células. Existen distintas técnicas opticas para estimar coeficientes de difusión...

Impacto da remodelação óssea sobre a transferência da massa de cálcio durante a hemodiálise: estudo em pacientes com hiperparatireoidismo pré e pós paratireoidectomia; Effects of bone remodelling on calcium mass transfer during hemodialysis: study of patients with hyperparathyroidism pre and post parathyroidectomy

Goldenstein, Patricia Taschner
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 03/09/2015 PT
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Distúrbios do metabolismo mineral e ósseo são altamente prevalentes e considerados como causa relevante da morbidade e mortalidade dos pacientes com doença renal crônica. Diversas estratégias diagnósticas e terapêuticas têm sido estudadas nesses doentes; entretanto, pouco valor é dado ao cálcio do dialisato, apesar do impacto que possa exercer sobre o balanço de cálcio durante a hemodiálise. Os fatores determinantes da transferência de cálcio durante o procedimento são ainda controversos. Nesse estudo prospectivo, avaliamos a influência da remodelação óssea sobre o balanço de cálcio em dez pacientes dialíticos em três situações consecutivas: hiperparatireoidismo grave (Pré paratireoidectomia), durante a \"síndrome de fome óssea\" (Fome óssea) imediatamente após a paratireoidectomia e após estabilização clínica (Paratireoidectomia tardia). Durante cada fase os participantes foram submetidos a três sessões randômicas de hemodiálise com diferentes concentrações de cálcio no dialisato: 2,5; 3,0 e 3,5 mEq/L. Todos os pacientes foram submetidos à biópsia óssea para análise histomorfométrica e quantificação de proteínas ósseas no início do estudo. A transferência de cálcio variou grandemente entre os pacientes em cada fase do estudo mesmo usando o mesmo cálcio no dialisato...

Detection, properties, and frequency of local calcium release from the sarcoplasmic reticulum in teleost cardiomyocytes

Llach Martínez, Anna; Espinosa Molina, Cristina; Alvarez-Lacalle, Enrique; Tort Bardolet, Lluís; Benítez Iglesias, Raúl; Hove-Madsen, Leid
Fonte: Universidade Autônoma de Barcelona Publicador: Universidade Autônoma de Barcelona
Tipo: Artigo de Revista Científica Formato: application/pdf
Publicado em //2011 ENG
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Calcium release from the sarcoplasmic reticulum (SR) plays a central role in the regulation of cardiac contraction and rhythm in mammals and humans but its role is controversial in teleosts. Since the zebrafish is an emerging model for studies of cardiovascular function and regeneration we here sought to determine if basic features of SR calcium release are phylogenetically conserved. Confocal calcium imaging was used to detect spontaneous calcium release (calcium sparks and waves) from the SR. Calcium sparks were detected in 16 of 38 trout atrial myocytes and 6 of 15 ventricular cells. The spark amplitude was 1.45±0.03 times the baseline fluorescence and the time to half maximal decay of sparks was 27±3 ms. Spark frequency was 0.88 sparks µm−1 min−1 while calcium waves were 8.5 times less frequent. Inhibition of SR calcium uptake reduced the calcium transient (F/F0) from 1.77±0.17 to 1.12±0.18 (p = 0.002) and abolished calcium sparks and waves. Moreover, elevation of extracellular calcium from 2 to 10 mM promoted early and delayed afterdepolarizations (from 0.6±0.3 min−1 to 8.1±2.0 min−1, p = 0.001), demonstrating the ability of SR calcium release to induce afterdepolarizations in the trout heart. Calcium sparks of similar width and duration were also observed in zebrafish ventricular myocytes. In conclusion...

Nuclear calcium signaling evoked by cholinergic stimulation in hippocampal CA1 pyramidal neurons

Power, John; Sah, Pankaj
Fonte: Society for Neuroscience Publicador: Society for Neuroscience
Tipo: Artigo de Revista Científica
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The cholinergic system is thought to play an important role in hippocampal-dependent learning and memory. However, the mechanism of action of the cholinergic system in these actions in not well understood. Here we examined the effect of muscarinic receptor stimulation in hippocampal CA1 pyramidal neurons using whole-cell recordings in acute brain slices coupled with high-speed imaging of intracellular calcium. Activation of muscarinic acetylcholine receptors by synaptic stimulation of cholinergic afferents or application of muscarinic agonist in CA1 pyramidal neurons evoked a focal rise in free calcium in the apical dendrite that propagated as a wave into the soma and invaded the nucleus. The calcium rise to a single action potential was reduced during muscarinic stimulation. Conversely, the calcium rise during trains of action potentials was enhanced during muscarinic stimulation. The enhancement of free intracellular calcium was most pronounced in the soma and nuclear regions. In many cases, the calcium rise was distinguished by a clear inflection in the rising phase of the calcium transient, indicative of a regenerative response. Both calcium waves and the amplification of action potential-induced calcium transients were blocked the emptying of intracellular calcium stores or by antagonism of inositol 1...

Action of calcium binders.: Formation of calcium salts in the intestinal tract and the blood circulatory system

Martínez Yaquelo,César
Fonte: Acta bioquímica clínica latinoamericana Publicador: Acta bioquímica clínica latinoamericana
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/06/2006 EN
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Calcium binders are water- soluble substances whose anionic part can possibly react with calcium cations present in any part of the human body. Some examples of calcium binders are phosphoric, oxalic and phytic acids and their alkaline salts present in many natural foods, in some foods containing additives, and in some medicines. There are also uric and lactic acids that are the result of normal metabolism. The first negative action of calcium binders takes place in the intestinal tract when they react with calcium of dairy food. The latter produces a combination of calcium binder anions with calcium cations, and then an insoluble salt that precipitates as small solid particles that cannot be assimilated and which are eliminated in the faeces. The second negative action of calcium binders takes place when soluble calcium binders are assimilated into the blood circulatory system and get in contact with the free ionized calcium in serum, which gives rise to complexed calcium with inorganic and organic anions. Immediately the free ionized normal level of calcium in blood serum decays, and the parathyroid hormone comes into action (secondary hyperparathyroidism) extracting free ionized calcium from bones (bone resorption). The soluble complexed calcium circulates in the serum through the whole blood circulatory system...