Mast cell activation involves plasma membrane potential- and thapsigargin-sensitive intracellular calcium pools

Summary— The regulation and role of the intracellular Ca²⁺ pools were studied in rat peritoneal mast cells. Cytosolic free calcium concentration ([Ca²⁺]i) was monitored in fura-2 loaded mast cells. In the presence of Ca²⁺ and K+, compound 48/80 induced a biphasic increase in [Ca²⁺]i composed of a fast transient phase and an apparent sustained phase. The sustained phase was partially inhibited by the addition of Mn²⁺. DTPA, a cell-impermeant chelator of Mn²⁺, reversed this inhibition, suggesting that a quenching of fura-2 fluorescence occurs in the extracellular medium. In the absence of extracellular Ca²⁺, the transient phase, but not the sustained one, could be preserved, provided that mast cells were depolarized. The transient phase was completely abolished by thapsigargin, a microsomal Ca²⁺-ATPase inhibitor. Maximum histamine release induced by either compound 48/80 or antigen was obtained in the absence of added Ca²⁺ only when mast cells were depolarized. These histamine releases were inhibited by low doses (< 30 nM) of thapsigargin. Thapsigargin at higher doses induced histamine release which was unaffected by changing the plasma membrane potential, but was completely dependent on extracellular Ca²⁺, showing that a Ca²⁺ influx is required for thapsigargin-induced exocytosis. Together, these results suggest that the mobilization of Ca²⁺ from thapsigargin sensitive-intracellular pools induced by compound 48/80 or antigen is sufficient to trigger histamine release. The modulation of these pools by the plasma membrane potential suggest their localization is close to the plasma membrane.     

Bone and calcium homeostasis.

The principal repository of calcium is bone. Calcium enters bone largely via the trabeculae, with the rate of calcium clearance by bone approximating 50 percent. Calcium enters bone as an ion in solution, but undergoes a phase change to a solid as soon as in contact with the bone surfaces. Calcium removal from and redistribution in bone is mediated by the bone cells, principally osteoblasts and osteoclasts. Calcium enters the body via intestinal absorption, a transport process that is the vectorial result of a saturable and an non-saturable step. Calcium leaves the body in the urine and stool, with a circulating calcium ion having one chance in about four of being lost via excretion. Ions like lead can compete with calcium at the sites of calcium deposition and transport. Their rate in the body should therefore parallel that of calcium, but may be modified by differing binding affinities or interactions with specific sites and molecules.     

CURRENT CONCEPTS IN INFANT NUTRITION

Nutritional needs vary during the first year of life according to the infant's individualized pattern of growth and amount of physical activity. After delivery, the infant must make many physiologic adjustments, develop immunologic defenses, and take in adequate nutrients for survival. The type and consistency of foods change as the gastrointestinal system matures and becomes able to metabolize the components and excrete the needed metabolites of increasingly complex foods. The recommended dietary allowance for infancy is based on the amount of nutrients provided to healthy infants in human milk during the first six months of life and on the consumption of formula and increasing amounts of solid food during the second six months. The introduction of solid foods should parallel the developmental changes that occur within the central nervous system throughout the first year; these provide a level of readiness for the infant to manage foods of various textures from full liquid to soft. Even though significant technologic advances have led to changes in the way infants can be fed, human milk is still the optimal choice. Most women can be encouraged to breast-feed regardless of their own nutritional status or dietary intake. Contraindications can be managed on an individual basis. If women do not elect to breast-feed, suitable commercial formulas are available. The important issue in feeding is that of providing a variety of appropriately prepared foods offered in a nonjudgmental atmosphere so that the foundation is laid for the development of good food habits.     

Einfluss der Diurese auf die Darstellung der Harnwege mit Perabrodil

Zusammenfassung Da die Ausscheidungsgesch windigkeit des Perabrodils von dem Wasserangebot der Nieren offensichtlich weitgehend unabhängig ist, führt eine Wasserdiurese zu Verdünnung des Kontrastmittels und somit zu mangelhaften Pyelogrammen. Die Vorbedingung zur Erreichung guter Ausscheidungspyelogramme ist der Durst-zustand. Unsere Versuche zeigen, daß eine rigorose Trockenlegung des Patienten mit aller Energie anzustreben ist. Es darf auch nicht vergessen werden, daß ein großes Reinigungsklistier kurz vor der Aufnahme zu störend starker Diurese führen kann.