Different Sources Of Calcium Research Articles

Calcium-dependent mechanisms involved in the modulation of tyrosine hydroxylase by endothelins in the olfactory bulb of normotensive rats

Endothelins (ETs) are widely expressed in the olfactory bulb (OB) and other brain areas where they function as neuropeptides. In a previous study we reported that in the OB ET-1 and ET-3 participate in the long-term regulation of tyrosine hydroxylase (TH), the key enzyme in catecholamine biosynthesis. ETs stimulate TH activity by increasing total and phosphorylated enzyme levels as well as its mRNA. ET-1 response is mediated by a super high affinity ETA receptor coupled to adenylyl cyclase/protein kinase A and Ca2+/calmodulin-dependent protein kinase II (CaMK-II) activation whereas that of ET-3 through an atypical receptor coupled not only to these signaling pathways but also to phospholipase C (PLC)/protein kinase C pathway. Given the participation of PLC and CaMKII in the regulation of TH by ETs in the OB we sought to establish the contribution of calcium to ETs response. Present findings show that calcium released from ryanodine-sensitive channels and extracellular calcium were necessary to stimulate TH by ETs through CaMK-II. On the other hand, intracellular calcium released by the endoplasmic reticulum partially mediated ETs-evoked increase in TH mRNA but calcium influx and CaMK-II inhibition abolished the response. However calcium mechanisms were not involved in ETs-evoked increase in TH protein content. Present findings support that different sources of calcium contribute to the long-term modulation of TH activity and expression mediated by ETs in the rat OB.

Different Effect of Rho Kinase Inhibition on Calcium Signaling in Rat Isolated Large and Small Arteries

In addition to its role in the regulation of artery contraction, Rho kinase (ROCK) was reported to be involved in the cytosolic calcium response to vasoconstrictor agonists in rat aorta and superior mesenteric artery (SMA). However, it remains to be determined whether ROCK also contributes to calcium signaling in resistance arteries, which play a major role in blood pressure regulation. The investigation of the effect of ROCK inhibition on the calcium and contractile responses of rat resistance mesenteric artery (RMA), in comparison with aorta and SMA, indicated that the calcium response to noradrenaline was inhibited by the ROCK inhibitor Y-27632 in aorta and SMA but not in RMA. The effect of Y-27632 on the calcium signal was unaffected by cytochalasin-D. ROCK activation in noradrenaline-stimulated arteries was confirmed by the inhibition of myosin light chain phosphorylation by Y-27632. Moreover, noradrenaline-induced calcium signaling was similarly inhibited by nimodipine in aorta, SMA and RMA, but nimodipine sensitivity of the contraction increased from the aorta to the RMA, suggesting that the contraction was controlled by different sources of calcium. In pressurized RMA, Y-27632 and H-1152 depressed pressure-induced calcium responses and abolished myogenic contraction. These results stress the important differences in calcium signaling between conductance and resistance arteries.

Role of low and high-voltage activated Ca2+-dependent K+ currents in the control of alpha-motoneuron discharge and its implication in hyperreflexia

Specificity of calcium-activated potassium (K+) currents to different sources of calcium has been noted in many neurons (e.g.1). Recently, in spinal alpha-motoneurons (α-MN), it was shown that the low-voltage activated L-type calcium currents (also known as persistent calcium currents) activate an exclusive subset of small conductance K+ currents (SKL)2. The SKL currents were distinct from the medium after-hyperpolarization (mAHP) producing N/P-type calcium activated K+ currents (SKAHP currents). The same study further suggested that an enhancement of persistent calcium current often observed after chronic spinalization can in part be due to reduced availability of the SKL channels albeit mAHP remained unchanged. While mAHP has been suggested to be integral in controlling motoneuron firing frequencies and grading L-Ca activation, the role of SKL currents in motoneuron discharge is unknown. The goal of this study is to characterize the influence of SKAHP and SKL currents on motoneuron firing frequencies. Here we test the hypothesis that SKAHP and SKL currents play differential roles in the control of persistent inward currents that are key determinants of motoneuron excitability.

Aplicação foliar de cálcio em pessegueiro na Serra Gaúcha: avaliação do teor de nutrientes na folha, no fruto e produção

Na região Sul do Brasil, as aplicações foliares de cálcio têm sido usadas durante o ciclo produtivo do pessegueiro. Entretanto se carece de conhecimentos sobre o teor de cálcio e de outros nutrientes na folha, usada para estimar o estado nutricional da planta, no fruto, utilizado como referência para definir a ocorrência de distúrbio fisiológico e na produção. O trabalho objetivou avaliar o efeito de pulverizações foliares de diferentes fontes de cálcio no seu teor e de outros nutrientes nas folhas, nos frutos e na produção. O trabalho compreendeu dois experimentos e foi conduzido na safra agrícola de 2003/2004, em um pomar comercial de pessegueiro da cultivar Chimarrita, em Pinto Bandeira-RS, sobre um Cambissolo Húmico. O experimento 1 consistiu de uma, duas e três pulverizações foliares de cloreto de cálcio nas concentrações de 0 (água); 0,5; 1,0 e 2,0%. O experimento 2 compreendeu uma, duas e três pulverizações foliares de nitrato de cálcio nas concentrações de 0 (água); 0,5; 1,0 e 2,0%. O delineamento experimental usado nos dois experimentos foi de blocos ao acaso, com três repetições e três plantas por parcela, que foram distribuídas ao longo da linha de plantio. Nas plantas dos dois experimentos, foram coletadas folhas completas (limbo+pecíolo) do terço médio dos ramos do ano, nos diferentes lados da planta, secas, moídas e preparadas para a análise dos teores de cálcio, nitrogênio, potássio e magnésio. Na maturação completa, os frutos foram colhidos e determinados a massa, a produção e os teores de cálcio, nitrogênio, potássio e magnésio. Os resultados mostraram que as aplicações foliares de cloreto de cálcio e nitrato de cálcio durante o ciclo produtivo do pessegueiro aumentaram o teor de cálcio na folha. Porém, não afetaram o teor de nitrogênio, potássio e magnésio na folha, o teor de cálcio, nitrogênio, potássio e magnésio no fruto e na produção.

Oxalates in some Indian green leafy vegetables

The soluble and total oxalate contents of 11 leafy vegetables grown in India were determined. Spinach, purple and green amaranth and colocasia contained high levels of total oxalates, which ranged from 5,138.0±37.6 mg/100 g dry matter up to 12,576.1±107.9 mg/100 g dry matter. Seven other leafy vegetables (curry, drumstick, shepu, fenugreek, coriander, radish and onion stalks) contained only insoluble oxalate, which ranged from 209.0±5.0 mg/100 g dry matter to 2,774.9±18.4 mg/100 g dry matter. In vitro digestion of the samples showed that the gastric available oxalate was 10% lower than the values obtained from acid extraction and that intestinal available oxalate was 20% lower than the values obtained following hot water extraction. The percentage calcium bound in the insoluble oxalate fraction of the dried leafy vegetables ranged from 3.3% to 86.7% of the total calcium. Addition of four different sources of calcium (low fat milk, whole milk, calcium carbonate and calcium sulphate) resulted in a range of 32–100% reductions of intestinal available oxalate in the mixture.

Cinética do fósforo em tecidos de ovinos em crescimento alimentados com diferentes fontes de cálcio

Foram utilizados 12 cordeiros machos, inteiros, com peso médio de 31,6kg. Os cordeiros foram alimentados com dietas à base de milho e farelo de soja, suplementadas com diferentes fontes de cálcio: calcário calcítico (CC), feno de alfafa (FA), polpa cítrica (PC) e farinha de conchas de ostras (FCO). Os animais receberam injeção de 7,4 MBq do radiofósforo (32P) e após sete dias foram abatidos para posteriores análises. Utilizou-se o delineamento em blocos ao acaso, com quatro tratamentos e três repetições. A taxa de retenção de 32P, as atividades específicas relativas e padronizadas, e a quantidade de P inorgânico nos tecidos foram iguais para todos os tratamentos (P>0,05). A comparação entre os tecidos mostrou que a concentração de P inorgânico e a taxa de retenção de 32P (P<0,01) foram mais altas nos ossos em relação aos tecidos moles (P<0,01). A retenção de 32P apresentou a seguinte ordem decrescente: rins, fígado, coração, músculos e ossos (P<0,01). A reabsorção óssea de P foi maior que a deposição de P, levando ao balanço negativo do elemento para a maioria dos animais. Concluiu-se que as diferentes fontes de cálcio não interferiram na cinética do P e que a quantidade de P ingerida não atendeu às exigências de P dos animais.

The effect of dietary calcium source, concentration and particle size on calcium retention, eggshell quality and overall calcium requirement in laying hens

1. Four different sources of calcium in isonitrogenous and isoenergeric diets were fed to laying hens for 2 weeks when they were 56 and 57 weeks old. The calcium source blends were as follows: 29% fine limestone (LF) + 71% large limestone (LG), 32% LF + 68% eggshell, 32% LF + 68% oyster shell, 50% LF + 50% LG. The contents of these blends of calcium in the diets were as follows: 103·3, 93·3, 93·3 and 93·3 g/kg, respectively. 2. The coefficients of calcium retention were significantly higher in 50:50 LF:LG (0·578) and 32:68 LF:eggshell (0·576). The midnight feeding significantly improved the coefficient of calcium retention in all mixtures except 50:50 LF:LG. 3. In the mixtures 29:71 LF:LG and 32:68 LF:oyster shell, there were significantly greater eggshell quality, eggshell weight, eggshell thickness and eggshell strength. Midnight feeding had no significant effect on eggshell quality. 4. In the ration with oyster shells, 96·5% of the retained calcium was deposited in the eggshell, but in rations 32:68 LF:eggshell and 50:50 LF:LG the utilisation was only 73·9 and 78·6%, respectively. 5. To ensure good quality eggshells in the last third of production, the recommendation for calcium is 4·1 g/kg (900 g/kg dry matter, feed intake 110 g/d). As a source of calcium in this stage of production, a feed mixture containing two-thirds large particles should be used (limestone grit or oyster shell).

Study on phosphorus metabolism in growing sheep fed different sources of calcium by using the isotope dilution technique

The close association of calcium and phosphorus in bone, and the narrow relationship between these minerals makes this subject always an important aim of study for researches on animal nutrition (Braithwaite, 1984). The utilization of alternative sources of calcium has been studied in Brazil in the last years however there is a lack of information about the effects of these sources on phosphorus metabolism. The aim of this study was to evaluate phosphorus metabolism in sheep fed four different sources of calcium through determination of true absorption and endogenous faecal loss of phosphorus by using the isotope dilution technique (Vitti et al., 2000).

Appetency and preference in horses offered lucerne or chalk as a source of calcium

Lucerne and chalk are sources of calcium used to supplement horses diets. The voluntary ingestion of lucerne varies with its form (Cuddeford, 1994). The objectives of this study were to compare the appetency for different sources of calcium, measured by kinetic of ingestion and selection behaviour (sorting, refusal) and to evaluate the effect of those different sources of calcium supplements on the preference of diets offered as a simultaneous choice. The sources of calcium studied were chalk and dehydrated lucerne presented in three forms: 6 mm diameter pellets, 18 mm diameter pellets and ground.

Ingestion and metabolic profile in horses offered lucerne or chalk as a source of calcium

When horses are on diets that are predominant in cereals, the combination of low concentrations of calcium in the diet and the binding of calcium by phytates may result in inadequate calcium intake (Rose, 1990). Chalk and dehydrated lucerne are rich in calcium. It has been shown that the voluntary ingestion of lucerne varies with its form (Cuddeford, 1994). The aim of this study was to evaluate the effect of different sources of calcium (chalk vs dehydrated lucerne) and lucerne forms (6 mm diameter pellets, 18 mm diameter pellets and ground lucerne) on the ingestion and on the metabolic profile in horses offered a cereal-based diet.

Distinct muscarinic receptor subbtypes linked to different sources of calcium in guinea-pig gallbladder

Distinct muscarinic receptor subbtypes linked to different sources of calcium in guinea-pig gallbladder

Growth responses to various calcium sources in a yellow earth soil with low calcium status

Different sources of calcium (carbonate, acetate, sulphate and silicate) were investigated with the aim of determining the nature of the response to lime that occurs on the yellow earths of northern Cape York Peninsula. Stylosanthes guianensis cv. Cook was grown in pots as the test plant in a calcium source x phosphorus rate experiment, which was harvested on three occasions. Initially each source, except CaSO4, increased soil pH and decreased extractable aluminium, but during the pot experiment, pH of all treatments decreased below that in the initial soil and extractable aluminium increased. No evidence was found of a calcium x phosphorus interaction, which might have been expected if aluminium was interfering with phosphorus uptake, nor was any effect found of calcium source or rate on phosphate sorption by amended soils. Dry matter yields responded to increased rates of application of calcium, and at the later harvests were closely related to calcium concentration in the dry matter. Aluminium concentrations in the plant tops (60-180 �g g-1) were not excessively high. It is concluded that the major response to 'liming' on this soil is in correcting calcium deficiency and not in overcoming an aluminium toxicity problem.

Cereals and Rickets: XII. The Effect of Calcium and Vitamin D on the Availability of Phosphorus

In feeding experiments with rats the availability of phytic acid phosphorus was markedly affected by the calcium and vitamin D content of the diet. With an optimal intake of phosphorus and a calcium-phosphorus ratio of 1/1 phytic acid phosphorus was almost as readily utilized as the inorganic form. However, with an increase in the calcium-phosphorus ratio to 2/1 the availability of phytic acid phosphorus was markedly decreased. Further increases in the calcium content of the rations decreased the availability of phytic acid phosphorus still more. On the other hand, inorganic phosphorus was not markedly affected by an increase in calcium even up to a ratio of 6/1. Different sources of calcium had a small but definite differential effect on the utilization of phosphorus. Calcium chloride produced a more severe rickets than either the carbonate or the sulfate. Calcium sulfate produced more bone ash than calcium carbonate. Vitamin D improved the utilization of both forms of phosphorus. This effect was more pronounced with phytic acid since the increment of improvement possible within the limits of calcification was less with the inorganic form. Even in the presence of vitamin D phytic acid phosphorus was not so readily available as the inorganic form. The aforementioned relative effects of different sources of calcium were also noted in the presence of vitamin D.