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.

     

Different rewards in female and male flowers can explain the evolution of sexual dimorphism in plants

Insects use floral signals to find rewards in flowers, transferring pollen in the process. In unisexual plants, the general view is that staminate (male) and pistillate (female) flowers obtain conspecific pollen transfers by advertising their rewards with similar floral signals. For female plants lacking food rewards, this can lead to floral mimicry and pollination by deceit. In this study, we challenge this view by presenting evidence for different rewards offered by flowers on females and males, as a mechanism promoting sexual dimorphism in Leucadendron xanthoconus (Proteaceae), a clearly sexually dimorphic shrub. The tiny beetle pollinators Pria cinerascens (Nitidulidae) depend entirely on the plants they pollinate for survival and reproduction. Male flowers provide mating and egglaying sites, and food for adults and larvae. Female flowers lack nectar and function to shelter pollinators from rain. Their flower heads have cup‐shaped display leaves, and are more closed than are those in males. On rainy days, flowers on females received 30% more visits than did flowers on males, and 90% more than they did on sunny days. When we removed display leaves in females, intact flower heads received 14 times more P. cinerascens visits than did manipulated flower heads, indicating that the cup shape attracts the beetles. In both sexes, having many flowers increased the probability of visits and the number of P. cinerascens visiting a plant. In males, the number of larvae was positively correlated with floral‐display size, while in females, seed set (pollen transfers) showed no relationship with floral‐display size. Ninety‐five per cent of the ovules received pollen and 52% matured into seeds. We explain the sexual dimorphism in L. xanthoconus as a result of an intimate partnership with P. cinerascens pollinators, in conjunction with a rainy climate. Pollinators favour large male floral displays, because they offer a reliable food source for adults and larvae. Frequent rains drive the P. cinerascens to leave males in search of the protection offered by females. Because females offer shelter, an essential resource that is not offered by male plants, they receive sufficient pollen independent of their floral‐display size. This pollination system promotes the evolution of sexually dimorphic floral signals, guiding pollinators to different rewards in male and female flowers. © 2005 The Linnean Society of London, Biological Journal of the Linnean Society, 2005, 85 , 97–109.     

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。     

中国岩黄芪属(豆科)植物资料增补

根据对标本的研究及文献资料的整理,证实了西伯利亚岩黄芪在中国的分布;山竹岩黄芪在新疆的分布新记录。另外,还报道了地中海岩黄芪在陕西的栽培记录。     

内蒙古植被枯黄期变化及其与气候和植被生产力的关系

基于2001—2018年MODIS NDVI数据,采用累计归一化植被指数(NDVI)的Logistic曲线曲率极值法,识别内蒙古植被枯黄期及其时空变化特征,并在生态区尺度上分析枯黄期对气候因子和NDVI的响应特征。结果表明: 研究期间,内蒙古植被平均枯黄期主要集中在第260～280天。森林生态区枯黄期为第270～280天,从南向北推迟;草原生态区枯黄期最早,介于第257～273天,从东北向西南逐渐推迟;荒漠生态区枯黄期为第270～283天,东北向西南呈推迟态势。2001—2018年间,3个生态区植被枯黄期均呈不显著推迟趋势。植被生产力从东北向西南逐渐降低,在时间上呈增加趋势的面积大于呈减小趋势的面积。全内蒙古和各生态区植被枯黄期受季前2～3个月降水量的正面影响较大,与季前平均温度、最高温度和最低温度均呈正相关关系。全内蒙古和各生态区,8和9月植被生产力的增加(或减少)将推迟(或提前)植被枯黄期,而6和7月植被生产力的增加(或减少)将提前(或推迟)草原和荒漠生态区植被枯黄期。     

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.     

海洋浮游藻类细胞质膜氧化还原活性与细胞外CA活性的关系

海洋浮游藻类除通过吸收和释放分子与离子来改变其环境的化学成分外,还可通过细胞外表面一些酶的作用引起质膜外化学物质变化。在这方面,海洋浮游藻类一个主要的细胞外表面酶-碳酸酐酶(CA),在经胰蛋白酶处理从细胞质膜上释放出来后,仍保留其催化活性。当细胞外表面CA(简称细胞外CA)具活性时,可催化质膜外HCO_3~-与CO_2的相互转化,为Rubisco(磷酸核酮糖羧化酶)提供一稳定的CO_2流量环境,以维持正常的光合作用。     

海藻酸微囊替代DMSO和FBS的STO细胞冷冻保存研穷

目的：改进现有的细胞冷冻保存方法,建立一个不舍二甲基亚砜（DMSO）和血清（FBS）的高效冷冻保存方法,为细胞治疗等临床实践提供优质细胞。方法：海藻酸微囊包埋鼠胚成纤维细胞（STO细胞）后用不含DMSO和FBS的冷冻保存液进行冷冻保存。,设四个对照组：添加10％DMSO和20％FBS的组、仅添加10％DMSO的组、仅添加20％FBS、DMSO和FBS均不添加组。在冷冻前后对各实验组细胞用台盼兰染色,进行细胞计数,计算细胞存活率,同时利用溴乙锭的二聚物（EthD）、钙黄绿素-AM（Calcein—AM）进行染色观察细胞的形态,且进一步验证细胞存活率;解冻复苏后用MTT法评估细胞的增殖速度和生长活力。结果：冷冻保存30天后对各组的细胞数量、细胞存活率、细胞形态和解冻复苏后细胞的生长活力进行比较发现,海藻酸微囊包埋冷冻组的细胞数、细胞存活率、细胞形态和生长活力均与添加DMSO和FBS的组之间无显著性差异,而与其它三个对照组呈显著性差异。结论：使用海藻酸微囊替代DMSO和FBS保存STO细胞,能有效的维持细胞形态、数量、存活率,同时不影响细胞的生长活力,从而建立了一个不含DMS0和FBS的高效冷冻保存方法。     

利用双重PCR技术研究长爪沙鼠的微卫星结构

目的为了建立快速检测长爪沙鼠群体遗传多样性的方法及获得Z：ZCLA长爪沙鼠封闭群现用微卫星位点的结构。方法利用17个微卫星位点（9个来自长爪沙鼠,8个来自大小鼠）进行了PCR反应体系及反应条件的优化,组合了6组双重PCR及两个复合式点样,用上述8个组合对普通级Z：ZCLA长爪沙鼠封闭群43、444、5三个世代核心群各100只种鼠进行遗传检测。结果三个世代的300只种鼠的检测结果表明,9个长爪沙鼠位点均为微卫星,其中7个位点为完全型的微卫星,1个为复合型,1个为不完全型,多态性主要表现在核心序列的重复;来自大小鼠的8个微卫星位点,有7个在Z：ZCLA长爪沙鼠核心群中得到有效扩增,只有3个位点在三个世代中均有出现,对测序结果分析后发现,其核心序列均为小卫星。结论来自长爪沙鼠的位点,无论结构还是遗传方式均符合微卫星遗传标记的特点,可用作检测长爪沙鼠的群体遗传多样性。