Nifedipine loaded chitosan microspheres: characterization of internal structure

In the present investigation, a simple technique was employed to obtain cross-sections of unloaded and nifedipine loaded chitosan microspheres. Microspheres, adhering to a polymerized resin block, were cut with an ultramicrotome and viewed with a scanning electron microscope. Unloaded microspheres exhibited a uniform dense matrix structure while crystals of nifedipine were clearly visible in the drug-loaded microspheres. At 2% drug loading, however, no crystals could be seen in the microspheres indicating that either the drug was molecularly dispersed or dissolved in the matrix at this concentration. This was confirmed by powder X-ray diffractometry studies where no peak due to crystalline nifedipine was observed. At high Span 85 concentration (1.5% w/v), the external surface of the microspheres collapsed, but the internal structure remained dense. When the drug was dispersed in the chitosan solution with stirring during preparation, the entrapment was good and the shape of the crystals was changed. The internal structure of the microspheres following dissolution exhibited the presence of pores.     

The Phenomenon of “Pe-ischaemic Conditioning” in the Brain only Partly involves the NMDA Receptor: A Magnetic Resonance Study

We have investigated in more detail our previous observations on a form of ischaemic pre-conditioning “metabolic adaptation”, i.e.—that sequential metabolic insults (hypoxia followed 40 min later by combined hypoxia + hypoglycaemia, or vice versa) are less injurious (monitored by increased [Ca²⁺]_i and decreased PCr) than the immediate combined insult. We have now observed that the “adaptation” occurs between 10 and 20 min. Pre-treatment of the tissues with 10 μM-MK801 showed that it had no effect on the increase in [Ca²⁺]_i caused by the sequential insult and only partially blocked the increase observed by exposure to the immediate combined insult. Exposure to both the delayed and immediate combined insults with low extracellular Ca²⁺ resulted in a two-fold increase in [Ca²⁺]_i, similar to the increase observed with normal extracellular Ca²⁺ in the presence of MK801. The results are discussed in terms of the possible origins of the increases in [Ca²⁺]_i.     

Pycnogenol, French maritime pine bark extract, improves endothelial function of hypertensive patients

A placebo-controlled, double-blind, parallel group study was performed with 58 patients to investigate effects of French maritime pine bark extract, Pycnogenol, on patients with hypertension. Supplementation of the patients with 100 mg Pycnogenol over a period of 12 weeks helped to reduce the dose of the calcium antagonist nifedipine in a statistically significant manner. The intake of Pycnogenol decreased endothelin-1 concentrations significantly compared to placebo while concentrations of 6-keto prostaglandin F1a in plasma were significantly higher compared to placebo. Values for nitric oxide (NO) in plasma increased in both groups, but the differences were not significant. Angiotensin II concentrations in plasma were lowered in the placebo group to a larger extent than in the Pycnogenol group. Heart rate, electrolytes and blood urea nitrogen were not changed during treatment in both groups of patients. Unwanted effects observed in both groups were of mild and transient nature, such as gastrointestinal problems, vertigo, headache and nausea. Differences in rate of side effects were not statistically significant between the two groups. Study results support a supplementation with Pycnogenol for mildly hypertensive patients.     

Gravity-directed calcium current in germinating spores of Ceratopteris richardii

 Gravity directs the early polar development in single cells of Ceratopteris richardii Brogn. It acts over a limited period of time during which it irreversibly determines the axis of the spore cell's development. A self-referencing calcium selective electrode was utilized to record the net movement of calcium across the cell membrane at different positions around the periphery of the spore during the period in which gravity orients the polarity of the spore. A movement of calcium into the cell along the bottom and out of the cell along the top was detected. This movement was specific, polarized, and strongest in a direction that opposed the vector of gravity. Treatment with nifedipine, a calcium-channel blocker, diminished the calcium current and caused the cell to lose its responsiveness to the orienting influence of gravity. Results shown suggest that calcium plays a crucial role in the ability of a single cell to respond to gravity and in the subsequent establishment of its polarity. Received: 13 June 1999 / Accepted: 1 September 1999     

Effects of capacitative calcium entry on agonist-induced calcium transients in A7r5 vascular smooth muscle cells

OBJECTIVE: The purpose of this study was to evaluate the contribution of capacitative calcium influx to intracellular calcium levels during agonist-induced stimulation of vascular smooth muscle cells. METHODS: Aortic vascular smooth muscle cells (A7r5) were loaded with Indo-1 and intracellular calcium transients were measured. Cells were challenged with either arginine vasopressin (0. 5 microM) or thapsigargin (1 microM). Lanthanum (1 mM) was used to block capacitative calcium influx through store-operated channels. Calcium traces were analyzed for basal, peak and plateau responses. Recordings were derivatized and integrated to gain additional information. Nonlinear regression provided a time constant that describes restoration of ionic equilibrium involving both sequestration and extrusion pathways. RESULTS: Stimulation of cells with thapsigargin produced a non-L-type calcium influx that was attenuated by lanthanum. Cells excited with vasopressin exhibited a rapid calcium increase followed by a gradual decrease to a plateau level. Lanthanum pretreatment prior to stimulation caused no significant change in baseline, peak or plateau calcium levels as compared to control. Lanthanum caused no significant change in maximal calcium release rate, calcium integrals or time constant as compared to control. CONCLUSIONS: Capacitative calcium entry can occur in vascular smooth muscle cells, but does not appear to contribute significantly to the vasopressin response.     

VCTDSA联合CT灌乌司他丁联合硝苯地平控释片对ESWL术后肾功能的保护作用

目的：观察乌司他丁（商品名天普洛安）和硝苯地平控释片（商品名拜新同）对体外冲击波碎石术（ESWL）所致急性肾功能损害的保护作用。方法：将80例接受ESWL治疗的肾结石患者,随机分为天普洛安组、拜新同组、天普洛安和拜新同联合组以及对照组,每组20例。检测并比较ESWL前1d和后1、3、5d患者尿丙二醛（MDA）、N-乙酰-β-1）．氨基葡萄糖苷酶／肌酐（NAG／Cr）和24h尿B2-微球蛋白（p2-MG）的变化。结果：EWSL术后第1天,对照组MDA、NAG／Cr和β2-MG水平均明显高于术前（P〈0．05）,且随着术后时间的延长,患者MDA、NAG／Cr和β2-MG水平呈逐渐下降趋势,术后第1、3、5天治疗组MDA、NAG／Cr和132．MG数值均明显低于相同时点对照组（P〈0．05）。术后第1、3天,联合用药组MDA、NAG／Cr和[32-MG水平明显低于单独用药的两组（乌司他丁组和拜新同组）（P〈0．05）,第5天联合用药组MDA、NAG／Cr和β2-MG水平与单独用药的两组（乌司他丁组和拜新同组）比较均无明显差异（P〉0．05）,单独用药的两组（乌司他丁组和拜新N组）之间在相同时点MDA、NAG／Cr和β2-MG水平无明显差异。结论：乌司他丁可显著减轻ESWL所致的肾损伤,与钙离子拮抗剂联合用药效果更佳。     

硝苯地平缓释片联合缬沙坦治疗原发性高血压疗效和 安全性的Meta 分析

摘要目的：系统评价硝苯地平缓释片联合缬沙坦治疗原发性高血压的疗效和安全性。方法：计算机检索PubMed、Cochrane Library 、CBM、CNKI、VIP 等数据库,按照纳入和排除标准纳入依硝苯地平缓释片联合缬沙坦治疗原发性高血压的随机对照试验 （RCT）,并补充检索纳入研究的参考文献;按Cochrane 系统评价方法由两名评价员独立评价纳入文献质量、提取资料并交叉核对 无误后,采用RevMan 5.1 软件进行统计学分析。结果：共纳入4 个RCT,包括共450例患者,其研究质量均为C级。Meta 分析结 果显示：硝苯地平缓释片联合缬沙坦治疗原发性高血压的显效率[RR=1.29, 95%CI(1.08～1.55), P< 0.01]、总有效率[RR=1.19, 95% CI(1.10～1.29), P<0.01]和无效率[RR=0.38, 95%CI(0.24～0.62), P<0.01]与单用硝苯地平缓释片比较,两组差异有统计学意义,两组 有效率差异无统计学意义[RR=1.02, 95%CI(0.97～1.32), P>0.01]。结论：现有证据表明：硝苯地平缓释片联合缬沙坦治疗原发性高 血压在显效率,总有效率和无效率方面优于硝苯地平缓释片单用,不良反应与苯地平缓释片单用无明显差异,但远期疗效尚不清 楚,尚需更多高质量的随机双盲对照试验证实。     

Calcium Entry in Toxoplasma gondii and Its Enhancing Effect of Invasion-linked Traits

During invasion and egress from their host cells, Apicomplexan parasites face sharp changes in the surrounding calcium ion (Ca²⁺) concentration. Our work with Toxoplasma gondii provides evidence for Ca²⁺ influx from the extracellular milieu leading to cytosolic Ca²⁺ increase and enhancement of virulence traits, such as gliding motility, conoid extrusion, microneme secretion, and host cell invasion. Assays of Mn²⁺ and Ba²⁺ uptake do not support a canonical store-regulated Ca²⁺ entry mechanism. Ca²⁺ entry was blocked by the L-type Ca²⁺ channel inhibitor nifedipine and stimulated by the increase in cytosolic Ca²⁺ and by the specific L-type Ca²⁺ channel agonist Bay K-8644. Our results demonstrate that Ca²⁺ entry is critical for parasite virulence. We propose a regulated Ca²⁺ entry mechanism activated by cytosolic Ca²⁺ that has an enhancing effect on invasion-linked traits.     

Effects of nifedipine,verapamil, and diltiazem on tip growth inFunaria hygrometrica

Protonemata ofFunaria hygrometrica Sibth. were treated with nifedipine, verapamil, or diltiazem. Responses to each of the drugs were, on the one hand, reduction of growth rate and tip cell length and, on the other hand, formation of apical swellings in caulonema tip cells and of anomalously oriented separation walls between main filaments and young side branches. The first effect is regarded as a more general expression of inhibition while the second complex of effects is attributed to perturbations in directed vesicle transport. Replacement of drug-containing media by normal Knop agar demonstrated the reversibility of inhibitor action: growth parameters were comparable to those of control protonemata within a few hours. A fast reaction, the formation of subapical vacoules, occurred within minutes of drug application and was only observed with verapamil and diltiazem. In connection with this process, rapid migrations of chloroplasts took place, but examination of the microtubule cytoskeleton in such cells by indirect immunofluorescence with a monoclonal antibody against tubulin showed an intact microtubule network. callose deposits in tip cells treated with verapamil. They were polarly distributed and started to appear in cell apices about 2h after the beginning of verapamil application. Two mechanisms of action for the tested inhibitors are discussed: (i) perturbations of membrane permeability by interference with one or more of the cell's Ca²⁺-transport systems, and (ii) a more indirect mechanism affecting vesicle transport via the microfilament system.     

H+-ATPase-Mediated Cytoplasmic pH-Responses Associated with Elevation of Cytoplasmic Calcium in Cultured Rabbit Nonpigmented Ciliary Epithelium

Studies were conducted to test whether an increase of cytoplasmic calcium concentration influences H⁺-ATPase activity in cultured rabbit nonpigmented ciliary epithelium (NPE). Cytoplasmic calcium concentration or cytoplasmic pH was measured by a fluorescence ratio technique in cells loaded with either Fura-2 or BCECF. Cytoplasmic calcium was increased in three ways; by exposure to BAY K 8644 (1 μm), by exposure to a mixture of epinephrine (1 μm) + acetylcholine (10 μm) or by depolarization with potassium-rich solution. In each case cytoplasmic pH increased significantly. In all three cases 100 nm bafilomycin A₁, a specific H⁺-ATPase inhibitor, significantly inhibited the pH increase. These results suggest an increase of cytoplasmic calcium might initiate events that lead to activation of proton export from the cytoplasm by a mechanism involving H⁺-ATPase. This notion is supported by the observation that the pH increase was suppressed when either verapamil or nifedipine was used to prevent the cytoplasmic calcium increase in cells exposed to potassium-rich solution. Protein kinase C activation might also be involved in the mechanism of H⁺-ATPase stimulation since staurosporine suppressed the pH response to potassium-rich solution. A transient rise of cytoplasmic calcium concentration was observed when cytoplasmic acidification was induced by exposure to high pCO₂. This suggests a rise of cytoplasmic calcium might represent part of a physiological mechanism to stimulate H⁺-ATPase-mediated protein export under acid conditions. Received: 11 August 2000/Revised: 29 March 2001