Article Abstract:
The extracellular ionized Ca2+ ((Ca2+)o) functions as a first messenger in many cellular processes, such as blood clotting. The concentration of (Ca2+)o in blood is constant while that in cavities in contact with the external environment shows large fluctuations. The ion-sensing receptor (CaR) is present in the parathyroid, kidney, intestine and lungs. It is capable of sensing minute changes in the (Ca2+)o concentration. Mutations in CaR cause heritable diseases, such as hypocalciuric hypercalcemia and neonatal severe hyperparathyroidism.
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Article Abstract:
The rate of tip growth and the morphology of fungal hyphae are influenced by Ca2+ ionophores, inhibitors of Ca2+ transport, calmodulin, Ca2+ binding dyes variations in extracellular Ca2+ concentration and the introduction of buffers in the cytoplasm. The intermediary for these agents is the tip-high gradient of cytoplasmic free Ca2+ present in the growing tips. This is responsible for the establishment and maintenance of apical organization, the regulation of hyphad morphogenesis through control of apical growth.
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Article Abstract:
Tip-growing cells may have cytoplasmic gradients of Ca(super+) linked to polarized growth. A tip-high Ca(super2+) gradient has been seen in growing fungal hyphae, although its role is unknown. Evidence for functions of a Ca(super2+) gradient is provided using a mathematical model. It is shown that Ca(super2+) may be responsible for apical accumulation of vesicles and an increase in cytogel osmotic pressure.
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