Mechanisms of photosystem I activity stimulation in trypsin-treated pea chloroplast membranes

Trypsin-induced effects on the PSI-photochemical activity of pea chloroplast membranes have been measured under saturating light conditions. It was found that incubation of isolated chloroplasts with trypsin in concentration range of 20–60 μg trypsin per mg Chl leads to a linear increase of the rate of PSI-mediated electron transport, measured by O₂-uptake with methyl viologen as an electron acceptor and DCPIP·H₂ as electron donor. Low temperature (77 K) chlorophyll fluorescence measurements have indicated that a remarkable redistribution of excitation light energy in favor of PSI occurs under these conditions. The results are interpreted in terms of trypsin-induced lateral reorganization of the chlorophyll—protein complexes within the thylakoid membranes and specific alteration at the level of LHC a/b-PSII supramolecular organization.     

METHYLCELLULOSE FOR ENDOTHELIAL CELL PROTECTION

A randomised trial of three types of endothelial cell protection for patients undergoing posterior chamber intraocular lens implant is described. The results confirm the superiority of a viscoelastic fluid over air as a form of endothelial cell protection. No statistically significant difference was found between sodium hyaluronate and hydroxypropylmethykellulose (HPMC). As the cost of sodium haluronate is prohibitive, a manufacturing technique for HPMC is given.     

Spectrally weighted twisted projection imaging: Reducing T2 signal attenuation effects in fast three-dimensional sodium imaging

A scheme for the reduction of T₂ signal attenuation effects in three-dimensional twisted projection imaging is presented. By purposely reducing the sample density at the high spatial frequencies, a considerable reduction in readout time is achieved. The reduction in readout time leads to decreased T₂ signal attenuation which translates into improved signal-to-noise ratio (SNR). The SNR improvement is achieved without decreasing the image's resolution since the point spread function depends on the sample weighting as well as the T₂ attenuation. The results indicate that SNR improvements of up to 40% can be achieved using the proposed scheme.     

含金矿物的氰化浸取动力学

筛选了一种能强化金浸取反应速率的添加剂——间硝基苯磺酸钠(MS),并进行了浸取反应过程的动力学研究。讨论了MS和氰化钠浓度、温度、搅拌强度及矿物粒度等因素对浸取反应的影响。MS通过改变阴极反应体系强化了金的氰化浸取反应速率,且对浸取液中氰化物无破坏作用。采用收缩未反应芯模型较好地描述了金的浸取过程,金浸取的动力学过程受扩散控制。同时导出了宏观动力学方程。用黄铁矿焙渣在串联式池浸装置中进行工业化模拟试验的结果表明,含MS的浸取液,浸取金含量仅为0.94g/t的矿渣,具有较力满意的结果。     

双氯芬酸钠-β-环糊精包合物制备工艺的研究

本文采用正交试验法研究了β-环糊精对双氯芬酸的包合作用。以包合物的收率、含量作为考察指标，筛选出最佳包合条件为A1B3C3D2，即β-环糊精与双氯苯酸钠的摩尔比为1：1，包合温度为80℃，包合时间为5h，搅拌强度为中等。用IR、DSC证明包合物的形成。     

ACUTE LITHIUM ADMINISTRATION IMPAIRS THE ACTION OF PARATHYROID HORMONE ON RAT RENAL CALCIUM,MAGNESIUM AND PHOSPHATE TRANSPORT*

1. Chronic lithium (Li⁺) treatment commonly produces a state of hyperparathyroidism in humans and rat although the mechanism is unknown. 2. The present study evaluated the acute effect of Li⁺ on renal electrolyte transport, particularly Ca²⁺ and Mg²⁺ in thyroparathyroidectomized (TPTX) and intact rats. 3. The acute administration of Li⁺ significantly increased water, sodium, potassium and phosphate excretion in both TPTX and intact animals; however, Ca²⁺ and Mg²⁺ excretion was only increased in the intact group. Fractional excretion (FE) of Ca²⁺ and Mg²⁺ increased from 2.2±0.2 to 3.5±0.3% and 12±2 to 18±2%, respectively (P<0.01). 4. In further experiments in TPTX rats, Li⁺ administration inhibited the usual reduction in urine Ca²⁺ and Mg²⁺ excretion following parathyroid hormone (PTH) administration and inhibited the phosphaturia. However, supramaximal concentrations of PTH overcame this inhibitory effect. For example, an FE_Ca of 3.8±0.2% was reduced to 1.4±0.2% and 1.7±0.2% with maximal and supramaximal PTH concentrations, respectively, while in the presence of Li⁺ an FE_ca of 4.0±0.2 was decreased to 2.8±0.2 and then 1.9±0.3% with the same PTH concentrations. 5. The inhibitory effect of Li⁺ was reduced with a lower plasma Li⁺ concentration (0.7±0.2 vs 1.6–1.8 mmol/L). The FE_Mg results were comparable. 6. These results demonstrate that Li⁺ directly inhibits PTH-mediated renal reabsorption of Ca²⁺ and Mg²⁺ and also blunts PTH-mediated phosphaturia. Therefore, the hyperparathyroidism in humans following Li⁺ treatment may be a consequence of reduced renal Ca²⁺ reabsorption.     

Interactions between sodium balance, intrarenal dopamine synthesis, and sympathetic activity in HLA-identical kidney donors and recipients

Intrarenal dopamine (DA) synthesis, sympathetic activity andsodium homeostasis were studied in eight HLA-identical kidneyrecipient and donor pairs at 50, 150, and 300 mmol sodium intake.Trimethaphan was given intravenously (i.v.), to mimic acutedenervation, tyramine i.v. to induce noradrenaline (NE) release,and the DA precursor DOPA i.v. to study DOPA to DA conversion.Blood pressure was higher in the recipients (P<0.05) andwas not influenced by sodium intake. Cumulative sodium balanceswere not different between the groups. Sodium intake did notaffect DA excretion in either group. The recipients had higherDA (P<0.05) and DOPA (P<0.01) excretions and lower urinaryDA over DOPA ratio (U_DA/DOPA, P<0.01) and lower NE excretion(P<0.05) during the whole study. High sodium intake suppressedthe U_DA/DOPA in both groups (P<0.05). Trimetaphan decreasedrenal vascular resistance (RVR) and increased sodium excretiononly in the donors (P<0.05), while GFR increased in bothgroups. During HiSo tyramine increased RVR in the recipients(P<0.01) and U_DA/DOPA in the donors (P<0.05). DOPA infusionincreased DA excretion four to fivefold but did not change sodiumexcretion in either group. It is concluded that the recipientsmaintained sodium homeostasis well but seem to have an impairedfunctional innervation of the transplanted kidney. NE releaseseem to stimulate intrarenal DOPA to DA conversion. In bothgroups a direct relation between DA and sodium excretion waslacking.     

阿托品对兔局部脑缺血Ca2+积累和细胞水肿的作用

阿托品对兔局部脑缺血Ｃａ２＋积累和细胞水肿的作用吕爱刚胡香杰贾丹辉张贵卿可君（河南医科大学药理学教研室，郑州４５００５２）阿托品（ａｔｒｏｐｉｎｅ，Ａｔｒ）为一典型的Ｍ受体阻断剂，近年研究表明它可以选择性对抗ＫＣｌ和ＣａＣｌ２对兔基底动脉收缩作用，其...