Electrical and adaptive properties of rod photoreceptors in bufo marinus. I. Effects of altered extracellular Ca(2+) levels

The effects of altering extracellular Ca(2+) levels on the electrical and adaptive properties of toad rods have been examined. The retina was continually superfused in control (1.6 mM Ca(2+)) or test ringer’s solutions, and rod electrical activity was recorded intracellularly. Low-calcium ringer’s (10(-9)M Ca(2+)) superfused for up to 6 min caused a substantial depolarization of the resting membrane potential, an increase in light-evoked response amplitudes, and a change in the waveform of the light-evoked responses. High Ca(2+) ringer’s (3.2 mM) hyperpolarized the cell membrane and decreased response amplitudes. However, under conditions of either low or high Ca(2+) superfusion for up to 6 min, in both dark-adapted and partially light-adapted states, receptor sensitivity was virtually unaffected; i.e., the V-log I curve for the receptor potential was always located on the intensity scale at a position predicted by the prevailing light level, not by Ca(2+) concentration. Thus, we speculate that cytosol Ca(2+) concentration is capable of regulating membrane potential levels and light-evoked response amplitudes, but not the major component of rod sensitivity. Low Ca(2+) ringer’s also shortened the period of receptor response saturation after a bright but nonbleaching light flash, hence accelerating the onset of both membrane potential and sensitivity recovery during dark adaptation.

Exposure of the retina to low Ca(2+) (10(-9)M) ringer’s for long periods (7-15 min) caused dark-adapted rods to lose responsiveness. Response amplitudes gradually decreased, and the rods became desensitized. These severe conditions of low Ca(2+) caused changes in the dark-adapted rod that mimic those observed in rods during light adaptation. We suggest that loss of receptor sensitivity during prolonged exposure to low Ca(2+) ringer’s results from a decrease of intracellular (intradisk) stores of Ca(2+); i.e., less Ca(2+) is thereby released per quantum catch.

     

叶绿素结合蛋白CP24介导光照响应基因StRSM 1调控叶绿素积累

单MYB转录因子成员RSM(RADIALIS-like SANT/MYB)突变,倒置黑暗诱导的叶绿素减少,原因有待确定;为了揭示RSM如何调控叶绿素积累,本研究运用基因工程途径,获得了普通烟草和马铃薯体内抑制和过量表达StRSM 1阳性转化株系,测定了阳性转化株系的叶绿素积累等生理表型;结果显示,普通烟草和马铃薯体内抑制RSM 1表达,显著增加了叶绿素积累,叶色随之加深;RSM 1过量表达,显著减少叶绿素积累,叶色变浅。叶绿素代谢相关基因表达测定结果显示,StRSM 1过量表达增加了黑暗下叶绿素结合蛋白CP24基因的表达,改变了其表达模式。以上结果表明,转录因子StRSM 1响应光照反向调控叶绿素积累,叶绿素结合蛋白CP24参与了StRSM 1对叶绿素积累的调控。结果有助于进一步明确RSM 1如何响应光照和深刻理解RSM 1参与的光照响应。     

Using microwave irradiation in Marchi's method for demonstrating degenerated myelin

Conventional methods for histological preparation of degenerated myelin are time-consuming and difficult. The purpose of our study was to shorten the time required for the procedure and to obtain better quality results for light microscopic demonstration of degenerated myelin in the central and peripheral nervous systems by using microwave irradiation. Rat brain and sciatic nerve were used for the study. The middle cerebral artery was occluded and the sciatic nerve was cut to produce myelin degeneration. Marchi's method was used for staining degenerated myelin. Fixation for light microscopy that would take two days using the conventional procedure was completed in 16.5–18.5 min using microwave irradiation. While staining of degenerated myelin requires 10 days for the conventional Marchi method, we decreased it to 7 h for brain tissue and 1 h for sciatic nerve by using the microwave oven. Moreover, a better quality preparation was achieved in the groups stained under microwave irradiation than those prepared by the conventional method.     

Characterization of heterotypic interaction effects <Emphasis Type="Italic">in vitro</Emphasis> to deconvolute global gene expression profiles in cancer

Background  

Perturbations in cell-cell interactions are a key feature of cancer. However, little is known about the systematic effects of cell-cell interaction on global gene expression in cancer.     

Effects of bone morphogenic protein 4 (BMP4) and its inhibitor,Noggin, on <Emphasis Type="Italic">in vitro</Emphasis>maturation and culture of bovine preimplantation embryos

Background  

BMP4 is a member of the transforming growth factor beta (TGFbeta) superfamily and Noggin is a potent BMP inhibitor that exerts its function by binding to BMPs preventing interactions with its receptors. The aim of this work was to investigate the role of BMP4 and Noggin, on oocytes in vitro maturation (m experiments) and embryos in vitro development (c experiments) of bovine.     

Polypharmacy in the management of patients with schizophrenia on risperidone in a tertiary-care hospital in Malaysia

The present study was conducted primarily to determine the occurrence of polypharmacy in patients with schizophrenia on risperidone. The secondary aim was to ascertain the incidence of inappropriate prescribing with anticholinergics. A retrospective review of the medical records of all patients who were being followed up at the out-patient clinic of a tertiary-care hospital in Malaysia was conducted. Only patients who were being prescribed risperidone between 1 June 2008 and 31 December 2008 were included in the study. Demographic data such as patient’s age, gender and race were obtained from the patient’s medical records. In total, 113 patients met the selection criteria. Polypharmacy was found to occur in 34 patients (30.09%), with the majority (76.47%) being on two antipsychotics. In total, 27 patients (34.18%) on monotherapy with risperidone were prescribed an anticholinergic on scheduled dosing, while 19 patients (24.05%) were prescribed it on an as-needed basis. Of the patients on polypharmacy, 26 (76.47%) were on scheduled dosing of anticholinergics, while three (8.82%) were taking the medication on an as-needed basis. Polypharmacy should be avoided, and the use of anticholinergics should be closely reviewed. By adopting more efficient prescribing practices, costs can be reduced and financial resources can instead be channelled towards more beneficial areas for the patients.     

Reflooding the Faguibine floodplain system,northern Mali: potential benefits and challenges

The Faguibine system, northern Mali, consists of a series of interconnected floodplains of which the flooded surface area declined from about 1 000 km² in the late 19th century to only some 90 km² in 2010. Flood extent depends on the height of the Niger River flood peak at Diré. Satellite imagery analysis indicated that a phase shift may have occurred in the year 2000, probably as a delayed consequence of the Sahelian drought of the 1970s compounded by the collapse of societal controls on water use during recent civil conflict. An economic evaluation of the system in 2011 showed US$100 000 per year of net income per flooded km² in Lake Faguibine, allowing vulnerable people to practise recession agriculture, to fish and to graze livestock. An intensive investment phase, combined with an approach of rebuilding local governance systems and environmental management capacity, could yield net benefits to the user communities of the order of ten times the maintenance costs, contributing to human well-being. The system is currently threatened by the building of the Fomi Dam in Guinea and by the planned expansion of irrigation upstream. There is also a risk of the return of a prolonged drought linked to the Atlantic multi-decadal oscillation index.     

非酒精性脂肪肝大鼠脂质代谢及病理变化的动态观察

目的通过高脂饮食建立NAFLD大鼠模型,连续监测4～16周模型动物肝功能、脂质代谢、胰岛素抵抗及肝细胞凋亡在NAFLD进展过程中的变化情况及相互关系,为该模型在脂肪肝发病机制、脂肪肝治疗药物评价等方面的应用提供参考依据。方法 SD大鼠50只,除正常对照组外,其余动物饲喂高脂饲料,分别检测4,8,12,16周大鼠血清GLU、CHO、TG、HDL、LDL、GPT、GOT及胰岛素水平,肝脏组织切片进行病理学及细胞凋亡观察,进一步分析大鼠肝功能、脂质代谢、胰岛素抵抗及肝细胞凋亡对肝组织病理改变的影响。结果模型组大鼠4周后就出现肝功能损伤,脂质代谢紊乱、胰岛素抵抗,肝细胞凋亡8 W后明显增加,肝细胞脂变及炎症为肝组织病理变化的主要特征,且造模时间越长,病变程度越严重。结论经过高脂饲料的喂养,SD大鼠在4～16周内可形成病变程度逐步加重的NAFLD模型,肝功能损伤,脂质代谢紊乱及肝细胞凋亡是引起非酒精性脂肪肝中脂肪变性和炎症的重要因素,该模型可应用于脂肪肝治疗药物评价等方面。