Ryanodine: its possible mechanism of action in the caffeine-sensitive calcium store of smooth muscle

The caffeine-sensitive intracellular Ca store was characterized and the mechanism of action of ryanodine in the store was studied using K-depolarized guinea-pig taenia caecum. (1) After incubation of the preparation with CaCl₂ (Ca loading), caffeine was applied in Ca-deprived medium, to produce a transient contraction and to monitor the amount of the stored Ca. As duration of Ca deprivation was prolonged, the amplitude of the caffeine-induced contraction was decreased. When ryanodine was applied during Ca deprivation, the rate of the decrease was remarkably accelerated. (2) The rate of rise of the contraction induced by external Ca ((Ca)o) was slowed by preceding depletion of the stored Ca by caffeine, compared with that observed in the Ca loaded preparation. However, in the presence of ryanodine, even if stored Ca was depleted by caffeine, the rate of rise of the (Ca)o-induced contraction remained at a higher level. (3) These results suggest that ryanodine stimulates a leak of the stored Ca, and that the contraction induced by the transmembrane influxed Ca could be modulated by the amount of Ca in, or leakiness of, the caffeine-sensitive Ca store.     

Physiological responses and manual performance in humans following repeated exposure to severe cold at night

We evaluated human physiological responses and the performance of manual tasks during exposure to severe cold (–25°C) at night (0300–0500 hours) and in the afternoon (1500–1700 hours). Thirteen male students wearing standard cold protective clothing occupied a severely cold room (–25°C) for 20 min, and were then transferred to a cool room (10°C) for 20 min. This pattern of exposure was repeated three times, for a total time of exposure to extreme cold of 60 min. The experiments were started either at 1500 hours or 0300 hours and measurements of rectal temperature, skin temperature, blood pressure, performance in a counting task, hand tremor, and subjective responses were made in each condition. At the end of the experiment at night the mean decrease in rectal temperature [0.68 (SEM 0.04)°C] was significantly greater than that at the end of the experiment in the afternoon [0.55 (SEM 0.08)°C, P<0.01]. After the second cold exposure at night the mean increase in diastolic blood pressure [90 (SEM 2.0) mmHg] was significantly greater than that at the end of the second cold exposure in the afternoon [82 (SEM 2.8) mmHg, P<0.01]. At the end of the second cold exposure at night, mean finger skin temperature [11.8 (SEM 0.8)°C] was significantly higher than that at the comparable time in the afternoon [9.0 (SEM 0.7)°C, P<0.01]. Similarly for the toe, mean skin temperature at the start of the second cold exposure at night [25.6 (SEM 1.5)°C] was significantly higher than in the afternoon [20.1 (SEM 0.8)°C, P<0.01]. The increased skin temperatures in the periphery resulted in increased heat loss. Since peripheral skin temperatures were highest at night, the subjects noted diminished sensations of thermal cold and pain at that time. Manual dexterity at the end of the first cold exposure at night [mean 83.7 (SEM 3.6) times·min^–1] had decreased significantly more than at the end of the first cold exposure in the afternoon [mean 89.4 (SEM 3.5) times·min^–1, P<0.01]. These findings of a lowered rectal temperature and diminished manual dexterity suggest that there is an increased risk of both hypothermia and accidents for those who work at night. Electronic Publication     

钙池操纵的钙通道的调控机制

钙池操纵的钙通道(store-operated calciumchannel,SOC)系存在于细胞膜表面的一种新发现的钙通道,它是非兴奋性细胞Ca2 内流的主要通道。SOC的开启是由钙库耗竭所激发,然而,钙库耗竭如何开启SOC仍不十分清楚。文章综述了SOC开启调控机制的有关研究进展。     

Mechanism of acidic pH‐induced contraction in spontaneously hypertensive rat aorta: role of Ca2+ release from the sarcoplasmic reticulum

Aim: This study was conducted to investigate the mechanism of acidic pH‐induced contraction (APIC) with regard to Ca²⁺ handling using isometric tension recording experiments. Results: Decreasing extracellular pH from 7.4 to 6.5 produced a marked and sustained contraction of spontaneously hypertensive rat (SHR) aorta, that was 128.7 ± 2.0% of the 64.8 mm KCl‐induced contraction. Verapamil, an inhibitor of voltage‐dependent Ca²⁺ channels (VDCC) significantly inhibited the APIC. In Ca²⁺‐deficient solution, sustained contraction induced by acidic pH was abolished completely, while a transient contraction was still observed suggesting the release of Ca²⁺ from intracellular site. Ryanodine (1 μm ), a ryanodine receptor blocker, and 10 μm cyclopiazonic acid (CPA; a sarco/endoplasmic reticulum Ca²⁺ ATPase inhibitor) abolished the transient contraction induced by acidosis. In normal Ca²⁺‐containing solution, ryanodine significantly decreased the rate of rise as well as maximum level of APIC. Interestingly, ryanodine and CPA showed an additive inhibitory effect with verapamil and the combined treatment of ryanodine or CPA with verapamil nearly abolished the APIC. Conclusions: It is concluded that acidic pH induces Ca²⁺ release from ryanodine/CPA‐sensitive store of sarcoplasmic reticulum in SHR aorta. This Ca²⁺ plays an important role in the facilitation of the rate of rise of APIC, as well as contributing to the sustained contraction via a mechanism which is independent of Ca²⁺ influx through VDCC.     

Changes in element concentrations induced by agonist in pig pancreatic acinar cells

 Changes in electrolytes of pig pancreatic acinar cells following application of gastrin-cholecystokinin (CCK) were investigated using the technique of X-ray microanalysis of hydrated and dehydrated sections of freshly frozen pancreas. After stimulation by CCK (10^–9 M), Na and Cl increased significantly in the cytoplasm [Na, from 10 mmol/kg wet wt. (48 mmol/kg dry wt.) to 19 mmol/kg (95 mmol/kg); Cl, from 22 mmol/kg (105 mmol/kg) to 49 mmol/kg (245 mmol/kg)] as well as in the luminal interspace [Na, from 53 mmol/kg (189 mmol/kg) to 65 mmol/kg (283 mmol/kg); Cl, from 65 mmol/kg (232 mmol/kg) to 102 mmol/kg (443 mmol/kg)]. In the secretory granules Cl increased significantly from 30 mmol/kg (86 mmol/kg) to 67 mmol/kg (203 mmol/kg). K decreased significantly from 120 mmol/kg (571 mmol/kg) to 81 mmol/kg (405 mmol/kg) in the cytoplasm, while both increased from 38 mmol/kg (109 mmol/kg) to 58 mmol/kg (176 mmol/kg) in the granules and from 46 mmol/kg (164 mmol/kg) to 48 mmol/kg (209 mmol/kg) in the luminal interspace. Ca increased significantly in the cytoplasm as well as in the luminal interspace, and decreased significantly in the secretory granules. CCK evoked Ca release from secretory granules in the secretory pole of acinar cells. The values were measured from dehydrated sections, and agreed well with those from hydrated sections. The effect of furosemide, an inhibitor of the Na⁺-K⁺-2Cl^–co-transporter, on the ion transport of acinar cell was studied. When furosemide (10^–5 M) was added to the external solution, the cytoplasmic Cl and Ca concentrations decreased significantly, while there was a little decrease in Na and K concentrations under the secretory condition. These results indicate that Na⁺-K⁺-2Cl^–co-transport, and Na⁺, Cl^–and K⁺ exits into the lumen are involved in the mechanism of ion secretion in pig pancreatic acinar cells. Received: 17 January 1996 / Accepted: 12 March 1996     

Heterogeneities in Consumer Diet Quality and Health Outcomes of Consumers by Store Choice and Income

Obesity and other diet-related health conditions have received much attention in the public health literature over the past two decades. This study investigates the relationship between household food budget shares at different food outlets with diet quality and weight-related health outcomes in the United States. Our analysis used event-level food purchase data from the national household food acquisition and purchases survey (FoodAPS). We find that, after controlling for observables, food purchase location is significantly associated with diet quality and body mass index (BMI). Our findings indicate that larger food budget shares at convenience stores and restaurants are linked with poor diet quality based on the healthy eating index-2015 (HEI-2015) scores and higher BMI. We further explored potential heterogeneity on outcomes of interest across income groups. Results suggest heterogeneous effects may exist across income groups: low-income households, who spent a larger share of their food budget at convenience stores and fast-food restaurants are related to poor diet quality and more likely to be obese. Our findings will help improve understanding of the causes of diet-related health problems and may illuminate potential avenues of intervention to address obesity.     

驻店执业药师与医院医师优势合作的SWOT分析

目的 :促进我国驻店执业药师与医院医师的合作。方法 :运用SWOT分析方法 ,分别对驻店执业药师和医院医师各自的优、劣势以及各自所处环境的机会、威胁进行分析。结果与结论 :我国驻店执业药师和医院医师应各司其职、相互交流、共同协作 ,一起服务于我国的卫生保健事业。     

Tubular aggregate myopathy and Stormorken syndrome: Mutation spectrum and genotype/phenotype correlation

Calcium (Ca²⁺) acts as a ubiquitous second messenger, and normal cell and tissue physiology strictly depends on the precise regulation of Ca²⁺ entry, storage, and release. Store‐operated Ca²⁺ entry (SOCE) is a major mechanism controlling extracellular Ca²⁺ entry, and mainly relies on the accurate interplay between the Ca²⁺ sensor STIM1 and the Ca²⁺ channel ORAI1. Mutations in STIM1 or ORAI1 result in abnormal Ca²⁺ homeostasis and are associated with severe human disorders. Recessive loss‐of‐function mutations impair SOCE and cause combined immunodeficiency, while dominant gain‐of‐function mutations induce excessive extracellular Ca²⁺ entry and cause tubular aggregate myopathy (TAM) and Stormorken syndrome (STRMK). TAM and STRMK are spectra of the same multisystemic disease characterized by muscle weakness, miosis, thrombocytopenia, hyposplenism, ichthyosis, dyslexia, and short stature. To date, 42 TAM/STRMK families have been described, and here we report five additional families for which we provide clinical, histological, ultrastructural, and genetic data. In this study, we list and review all new and previously reported STIM1 and ORAI1 cases, discuss the pathomechanisms of the mutations based on the known functions and the protein structure of STIM1 and ORAI1, draw a genotype/phenotype correlation, and delineate an efficient screening strategy for the molecular diagnosis of TAM/STRMK.     

Mitochondrial ligand inhibits store-operated calcium influx and COX-2 production in human microglia

We used calcium sensitive fluorescence microscopy to investigate the actions of PK11195, a ligand for the mitochondrial peripheral benzodiazepine receptor (PBR), to modulate Ca2+ influx through store-operated channels (SOC) in human microglia. PK11195 effectively blocked SOC-mediated Ca2+ influx induced by platelet-activating factor (PAF) in a dose-dependent manner (IC50 of 9 microM). A prolonged SOC-mediated Ca2+ entry was also induced using the sarcoplasmic endoreticulum Ca2+-ATPase (SERCA) inhibitor cyclopiazonic acid (CPA) to deplete intracellular endoplasmic reticulum (ER) stores; a single concentration of PK11195 (at 20 microM) reduced SOC-mediated Ca2+ influx by 78%. RT-PCR and immunocytochemical analysis results showed PK11195 also inhibited the expression and production of cyclooxygenase-2 (COX-2) triggered by PAF stimulation. These results suggest that activation of the PBR in mitochondria is linked to reduced entry of Ca2+ through plasmalemmal SOC and subsequent modulation of cellular functions in human microglia.     

A lentivirally delivered photoactivatable GFP to assess continuity in the endoplasmic reticulum of neurones and glia

The endoplasmic reticulum (ER) is the largest intracellular membranous organelle. Functions of the ER are many and diverse, which include various biosynthetic, transport and signalling roles, central to cellular physiology, such as the biosynthesis of membrane and secretory proteins and the regulation of intracellular calcium. Its continuous lumen also serves as a highway for the distribution of proteins and ions to different regions of the cell, independent of the cytosol. The ER is an excitable organelle, capable of generating a regenerative wave of calcium release, which can propagate along the endomembrane throughout the entire cell, serving as a system of intracelluar communication in polarised cells. Nowhere is this feature of ER function more crucial than in neurones. The extremely polarised nature of nerve cells presents a unique challenge for the global co-ordination of localised physiological events such as growth cone guidance and synaptic plasticity. Clearly, the physical continuity of the neuronal ER lumen is central to its functionality as a conduit for communication. To further probe the continuity of ER in neurones and glia, we developed LV-PA-pIN-KDEL, a photoactivatable analogue of our recently described vector LV-pIN-KDEL, a lentivirally delivered ER-targeting soluble GFP. We demonstrate the ability of this vector to transduce astrocytes and neurones in culture and in cortical explants. Furthermore, we exploit the photoactivatable attributes of the vector together with a focal laser photoactivation protocol to reveal the continuous nature of the ER lumen in these cell types, presenting the first direct evidence of an astrocytic ER luminal continuum and providing more data to support the existence of a single ER lumen in neurones. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.