钾通道开放剂降低血管平滑肌细胞内游离钙浓度(英文)

目的:研究PCO—Pin,Nic,Lem及RP对VMSC内[Ca~(2 )]_i的改变及其可能机制。方法:VSMC加入Fura-2 AM 2.5μmol·L~(-1)37℃下孵育50min,[Ca~(2 )]_i用荧光分光光度计检测。结果:4种PCO能较弱地抑制K~ 30 mmol·L~(-1)诱导的[Ca~(2 )]_i增加,但明显抑制ATP 0.1mmol·L~(-1)诱导的[Ca~(2 )]_i峰相及持续相增加,且呈剂量依赖性。格列苯脲完全阻断Pin,Lem及RP的作用,只部分抑制Nic的作用。无钙液中先给4种PCO,能显著抑制ATP诱导的[Ca~(2 )]_i峰相增加。结论:4种PCO均抑制ATP诱导的[Ca~(2 )]_i增加,此作用与减少细胞外钙内流及细胞内钙释放有关。     

Repetitive firing properties in subpopulations of the chick Edinger Westphal nucleus.

The avian Edinger Westphal nucleus, through the ciliary ganglion, controls accommodation, iris constriction, and blood flow through the choroid. In live brainstem slices, the nucleus is easily identifiable as an olive-shaped cluster of neurons dorsal to the oculomotor nerve and nucleus. Intracellular recordings from neurons in the nucleus identified two classes of responses to sustained (300 to 500 ms) injections of depolarizing current. One set of cells fired action potentials for the duration of the pulse while a second set of cells fired action potentials only transiently, during the first 50 to 100 ms, after which they remained silent regardless of the size of the depolarization. Intracellular recordings followed by injections of the fluorescent dye lucifer yellow revealed that repetitively firing cells were located in the lateral half of the nucleus while non-repetitively or transiently firing cells were located in the medial half. These locations correspond to different Edinger Westphal subdivisions which have distinct inputs and target populations. The varying firing patterns are discussed with reference to the known functions of the subdivisions in which they occur. Replacement of calcium by magnesium in the extracellular medium had no effect on the number of action potentials fired by non-repetitively firing cells, suggesting that a calcium-activated potassium current is not responsible for suppressing repetitive firing in these cells. In contrast, in repetitively firing cells removal of extracellular calcium increased the frequency of action potential discharge and decreased the amplitude of afterhyperpolarizations following single action potentials. Addition of cadmium to the bath medium had similar effects.(ABSTRACT TRUNCATED AT 250 WORDS)     

铁骨晶对大鼠钙代谢、骨密度的影响及临床观察

本实验以铁骨晶（多肽钙），进口脱脂奶粉，活性钙冲剂，贝壳钙为钙源添加于大鼠正常饲料中。观察结果表明：上述４组钙的吸收率分别为６４．４％，６９．１％，５９．９％，５１．６％；钙的储留率分别为８９．８％，９３．３％，８５．２％，７９．０％；钙的存留率分别为４３．６％，４９．０％，３２．４％，２６．８％；股骨指数分别为７．０２×１０（－３），６．４３×１０（－３），６．８４×１０（－３）。６．８８×１０（－３）；折断力（牛顿）分别为６０．５４±１２．５５，４６．８１±９．３２，４３．２６±１６．６２，３８．２４±１０．７９。同时以铁骨晶为钙源对７０例（５～６岁）儿童进行了血清Ｃａ，Ｆｅ，Ｚｎ，Ｈｂ及生长发育的检测。铁骨晶组的身高，体重，胸围分别比对照组增加。铁骨晶组血清Ｃａ，Ｆｅ，Ｚｎ，Ｈｂ也均有较好的改善。这表明铁骨晶具有较好的促进钙吸收利用作用，同时能增加骨强度作用。     

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.     

Graves病患者血甲状旁腺激素、钙、磷、碱性磷酸酶基础值的观察

对照观察了28例Graves病患者及29名正常人血浆甲状旁腺激素、(PTH)血钙、血磷、碱性磷酸酶的基础值。Graves病组血碱性磷酸酶明显高于对照组,而PTH、钙、磷无显著差异。Graves病组血钙>2.75mmol/L者占21%,与某些文献大致相符。正常组血钙与PTH基础值间呈负相关,而Graves病组该两值间无相关,提示Graves病时血钙浓度的平衡调节中PTH以外的因素如甲状腺激素等可能对其影响较大。     

Transient Brain Ischaemia Provokes Ca2+, PIP2 and Calpain Responses Prior to Delayed Neuronal Death in Monkeys

To clarify the mechanism of postischaemic delayed cornu Ammonis (CA)-1 neuronal death, we studied correlations among calpain activation and its subcellular localization, the immunoreactivity of phosphatidylinositol 4,5-bisphosphate (PIP₂) and Ca²⁺ mobilization in the monkey hippocampus by two independent experimental approaches: in vivo transient brain ischaemia and in vitro hypoxia-hypoglycaemia of hippocampal acute slices. The CA-1 sector undergoing 20 min of ischaemia in vivo showed microscopically a small number of neuronal deaths on day 1 and almost global neuronal loss on day 5 after ischaemia. Immediately after ischaemia, CA-1 neurons ultrastructurally showed vacuolation and/or disruption of the lysosomes. Western blotting using antibodies against inactivated or activated μ-calpain demonstrated μ-calpain activation specifically in the CA-1 sector immediately after ischaemia. This finding was confirmed in the perikarya of CA-1 neurons by immunohistochemistry. CA-1 neurons on day 1 showed sustained activation of μ-calpain, and increased immunostaining for inactivated and activated forms of μ- and m-calpains and for PIP₂. Activated μ-calpain and PIP₂ were found to be localized at the vacuolated lysosomal membrane or endoplasmic reticulum and mitochondrial membrane respectively, by immunoelectron microscopy. Calcium imaging data using hippocampal acute slices showed that hypoxia-hypoglycaemia in vitro provoked intense Ca²⁺ mobilization with increased PIP₂ immunostaining specifically in CA-1 neurons. These data suggest that transient brain ischaemia increases intracellular Ca²⁺ and PIP₂ breakdown, which will activate calpain proteolytic activity. Therefore, we suggest that activated calpain at the lysosomal membrane, with the possible release of biodegrading enzyme, will cause postischaemic CA-1 neuronal death.     

Calcium intake in the elderly: validation of a dietary questionnaire

Epidemiological studies of calcium and osteoporosis have been hampered by the lack of a suitable tool for assessing calcium intake. This report describes a new frequency and amount questionnaire for measuring present and past calcium intake in the elderly. The validity of the questionnaire was tested against two commonly used standards of dietary assessment, five-day duplicate diets and seven-day weighed dietary inventories. The resulting correlation coefficients were, respectively, r = 0.76 and r = 0.69, while that for repeatability was r = 0.84. Furthermore, the questionnaire categorized subjects into thirds of the distribution of intake with almost no gross misclassification. It is suggested that the present findings may be extended to the majority of normal, healthy elderly subjects, implying wide application for the questionnaire in the assessment of calcium intake in the elderly.     

Insulinoma: Selective arterial calcium injection performed to confirm localization and complete resection

A case of insulinoma is reported in a patient in whom selective arterial calcium injection (SACI) tests were performed both to confirm tumor localization before surgery and to confirm complete tumor removal during surgery. An 18-year-old woman with hypoglycemic episodes was diagnosed with an insulinoma in the pancreatic body demonstrated by celiac arteriography. In a preoperative SACI test, calcium was injected into the splenic artery (SpA), gastroduodenal artery (GDA), and superior mesenteric artery (SMA). Serum immunoreactive insulin (IRI) and proinsulin levels were measured in hepatic venous samples. IRI was markedly increased after the injection of calcium into the GDA and SMA, while there was no response in IRI levels when calcium was injected into the SpA. Therefore, no occult insulinoma was revealed in the distal area fed by the SpA, although the presence of insulinoma was uncertain in the proximal pancreas. In the intraoperative SACI test, calcium was injected into the celiac artery. Insulin (determined by enzyme immunoassay) and proinsulin levels were measured in portal venous samples before and after resection of the tumor. After resection, these levels decreased in response to the calcium stimuli, confirming complete removal of the insulinoma. The SACI test was helpful to localize the insulinoma and was useful to confirm the complete removal of the tumor.     

0～16岁城乡儿童骨骼矿物质含量及影响因素的研究

使用单光子骨矿物测定仪，自１９９４年初到１９９５年底，分别在河南省扶沟县和新乡市测定了３３２名健康的０～１６岁城乡儿童右前臂１／３处桡骨和尺骨的骨矿物质含量（ＢＭＣ），采用逐步多元回归分析了多个独立变量对桡骨ＢＭＣ和测量部位骨宽度的影响。结果显示：桡骨和尺骨的ＢＭＣ、骨宽度（ＢＷ）、ＢＭＣ／ＢＷ和前臂长度均随年龄而增加，０～６岁城市儿童的ＢＭＣ高于农村儿童；桡骨ＢＭＣ与所测量部位的ＢＷ呈正相关，年龄、体重和身高对桡骨ＢＭＣ都显示出显著和独立的正影响；儿童的桡骨ＢＭＣ与年龄呈显著正相关；而桡骨ＢＭＣ与体重的比值与年龄呈显著负相关；测定部位桡骨ＢＷ和前臂长度随年龄的增加呈曲线增加。在以身高和体重调整后，性别、年龄和体重对桡骨ＢＷ的影响变得不显著，只有身高的影响显著。本研究证明儿童在０～１６岁范围，身高（而不是肥胖）是骨骼ＢＭＣ的主要决定因素。在比较儿童骨密度结果时，要参考多个变量，如ＢＭＣ、骨密度，ＢＭＣ／体重、ＢＭＣ／年龄等综合评价指标更有说明力。