Development of two types of calcium channels in cultured mammalian hippocampal neurons

Calcium influx through voltage-gated membrane channels plays a crucial role in a variety of neuronal processes, including long-term potentiation and epileptogenesis in the mammalian cortex. Recent studies indicate that calcium channels in some cell types are heterogeneous. This heterogeneity has now been shown for calcium channels in mammalian cortical neurons. When dissociated embryonic hippocampal neurons from rat were grown in culture they first had only low voltage-activated, fully inactivating somatic calcium channels. These channels were metabolically stable and conducted calcium better than barium. Appearing later in conjunction with neurite outgrowth and eventually predominating in the dendrites, were high voltage-activated, slowly inactivating calcium channels. These were metabolically labile and more selective to barium than to calcium. Both types of calcium currents were reduced by classical calcium channel antagonists, but the low voltage-activated channels were more strongly blocked by the anticonvulsant drug phenytoin. These findings demonstrate the development and coexistence of two distinct types of calcium channels in mammalian cortical neurons.     

Open channels in sea ice (leads) as ion sources

Open channels in sea ice may be acting as sources of atmospheric ions.     

Rapid chemically induced changes of PtdIns(4,5)P2 gate KCNQ ion channels

To resolve the controversy about messengers regulating KCNQ ion channels during phospholipase C-mediated suppression of current, we designed translocatable enzymes that quickly alter the phosphoinositide composition of the plasma membrane after application of a chemical cue. The KCNQ current falls rapidly to zero when phosphatidylinositol 4,5-bisphosphate [PtdIns(4,5)P2 or PI(4,5)P2] is depleted without changing Ca2+, diacylglycerol, or inositol 1,4,5-trisphosphate. Current rises by 30% when PI(4,5)P2 is overproduced and does not change when phosphatidylinositol 3,4,5-trisphosphate is raised. Hence, the depletion of PI(4,5)P2 suffices to suppress current fully, and other second messengers are not needed. Our approach is ideally suited to study biological signaling networks involving membrane phosphoinositides.     

Organization of ion channels in the myelinated nerve fiber

The functional organization of the mammalian myelinated nerve fiber is complex and elegant. In contrast to nonmyelinated axons, whose membranes have a relatively uniform structure, the mammalian myelinated axon exhibits a high degree of regional specialization that extends to the location of voltage-dependent ion channels within the axon membrane. Sodium and potassium channels are segregated into complementary membrane domains, with a distribution reflecting that of the overlying Schwann or glial cells. This complexity of organization has important implications for physiology and pathophysiology, particularly with respect to the development of myelinated fibers.     

Principles of selective ion transport in channels and pumps

The transport of ions across the membranes of cells and organelles is a prerequisite for many of life's processes. Transport often involves very precise selectivity for specific ions. Recently, atomic-resolution structures have been determined for channels or pumps that are selective for sodium, potassium, calcium, and chloride: four of the most abundant ions in biology. From these structures we can begin to understand the principles of selective ion transport in terms of the architecture and detailed chemistry of the ion conduction pathways.     

Immunoreactive dynorphin-(1-8) and corticotropin- releasing factor in subpopulation of hypothalamic neurons

Immunoreactive corticotropin-releasing factor (CRF) and dynorphin-(I-8) were visualized in rat hypothalamus by immunohistofluorescence with specific antibodies. In brains from colchicine-treated, adrenalectomized rats, neuronal perikarya with immunoreactive CRF were observed in the paraventricular nucleus of the hypothalamus. The CRF occurred together with the dynorphin-(1-8). However, the CRF immunoreactivity occurred only in a subpopulation of the dynorphin-(1-8) immunoreactive cells. These findings suggest that there may be a functional interrelationship of CRF with dynorphin-related opioid peptides and provide further evidence that neurons may contain more than one bioactive substance.     

The coupling of neurotransmitter receptors to ion channels in the brain

Recent studies on the action of neurotransmitters on hippocampal pyramidal cells indicate that different neurotransmitter receptors that use either the same or different coupling mechanisms converge onto the same ion channel. Conversely, virtually all of the neurotransmitters act on at least two distinct receptor subtypes coupled to different ion channels on the same cell. The existence of both convergence and divergence in the action of neurotransmitters results in a remarkable diversity in neuronal signaling.     

Genetic reconstitution of functional acetylcholine receptor channels in mouse fibroblasts

Foreign genes can be stably integrated into the genome of a cell by means of DNA-mediated gene transfer techniques, and large quantities of homogenous cells that continuously express these gene products can then be isolated. Such an expression system can be used to study the functional consequences of introducing specific mutations into genes and to study the expressed protein in the absence of cellular components with which it is normally in contact. All four Torpedo acetylcholine receptor (AChR) subunit complementary DNA's were introduced into the genome of a mouse fibroblast cell by DNA-mediated gene transfer. A clonal cell line that stably produced high concentrations of correctly assembled cell surface AChR's and formed proper ligand-gated ion channels was isolated. With this new expression system, recombinant DNA, biochemical, pharmacological, and electrophysiological techniques were combined to study Torpedo AChR's in a single intact system. The physiological and pharmacological profiles of Torpedo AChR's expressed in mouse fibroblast cells differ in some details from those described earlier, and may provide a more accurate reflection of the properties of this receptor in its natural environment.     

Metachromatic leukodystrophy (sulfatide lipidoses) cultured in vitro

Cerebral white matter from a patient with metachromatic leukodystrophly was successfully cultured in vitro. A luxuriant growth in Rose chambers and in roller tubes was apparent by the 14th day. The outgrown cells contained large numbers of granules which stained dark brown with cresyl violetacetic acid. The growth and metachromasia were maintained up to 80 days in vitro.     

脱落酸(Abscisic acid, ABA)对映异构体的生物活性比较

 采用新方法精制脱落酸(ABA)异构体试样,改变以往靠光学离析法分离racemic型(SR)-(±)-ABA,提高了(S)-(+)-ABA与(R)-(-)-ABA两镜像体纯度。抑制生长试验和残留量分析结果表明:天然型(S)-(+)-ABA活性,显着高于非天然型(R)-(-)-ABA或(SR)-(±)-ABA活性。抑制莴苣种子发芽50%的活性强度(S)-(+)-ABA约是(R)-(-)-ABA的5倍,(SR)-(±)-ABA介于二者之间。抑制萝卜下胚轴生长试验,最显着有效期2～6天,(6天后差异渐小,8日甚微),生理作用期约为一周,(S)-(+)-ABA活性是(R)-(-)-ABA的3.6倍。差异原因可能是两异构体分子立体结构不同所致。     

对双季晚稻粳籼(杂交)选型调向的初步探讨

针对目前对双季晚稻粳、籼(杂交)选型的热点问题,着重对粳型鄂宜105与籼型杂交稻4个组合与气候关联度较大的生育状况、产量构成因素进行了分析,结果表明在正常气候条件下,籼型杂交稻有明显的增产优势,现行双晚以粳型为主的状况应调向以籼型杂交稻为主的新格局。     

Steroid-dependent survival of identifiable neurons in cultured ganglia of the moth Manduca sexta

Adult emergence at the end of metamorphosis in the moth Manduca sexta is followed by the death of abdominal interneurons and motoneurons. Abdominal ganglia removed from insects before this period of naturally occurring cell death and maintained in vitro showed neuronal death confined to the same cells that normally die in vivo. Addition of physiological levels of the steroid 20-hydroxyecdysone to the culture system prevented the selective death of these motoneurons.     

低盐度地区集约化养殖的吉富罗非鱼的生长特性

对珠海低盐度地区(盐度2⁸)集约化养殖的吉富罗非鱼的生长特性进行了研究,试验共进行174d。结果表明:吉富罗非鱼在整个养殖期间体重增长速度较快,平均日增重5.58 g,最快可达13.25 g,平均日增重率为2.54%;养殖130 d后,平均体重可达600 g左右,其体长和体重的关系为W=0.0582×L2.89(R2=0.9968),体长生长方程为L=-0.0169t3+0.1911t2+2.3675t+0.7124(R2=0.9947);肥满度初期较高,最高为6.19,养殖中期有所下降,后期恢复到4.22;饵料系数平均为1.44。     

低盐度地区集约化养殖的吉富罗非鱼的生长特性

对珠海低盐度地区（盐度2—8）集约化养殖的吉富罗非鱼的生长特性进行了研究,试验共进行174d。结果表明：吉富罗非鱼在整个养殖期间体重增长速度较快,平均日增重5．58g,最快可达13．25g,平均日增重率为2．54％;养殖130d后,平均体重可达600g左右,其体长和体重的关系为W=0．0582×L^2.09（R^2=0．9968）,体长生长方程为L=-0．0169t^3＋0．1911t^2＋2．3675t＋0．7124（R^2=0．9947）;肥满度初期较高,最高为6．19,养殖中期有所下降,后期恢复到4．22;饵料系数平均为1．44。     

4-(N-叔丁氧羰基)氨甲基-1-(N-叔丁氧羰基)吡咯烷-3-醇的合成

[目的]改进4-(N-叔丁氧羰基)氨甲基-1-(N-叔丁氧羰基)吡咯烷-3-醇的合成工艺。[方法]以4-氰基-1-(N-叔丁氧羰基)吡咯烷-3-酮为原料,经硼氢化钠、漆原钴催化加氢还原、氨基保护"一锅法"制得目标化合物。[结果]改进的工艺采用漆原钴催化加氢代替原来的氢化铝锂还原,总收率由原来的75%提高至88%,结构经1HNMR确证。[结论]该工艺操作安全,适用于工业化生产。     

养殖中华绒鳌蟹风味品质比较研究

通过对江苏太湖、阳澄湖、滆湖、长荡湖、固城湖、洪泽湖、高宝湖、大纵湖八大养殖品牌河蟹测试分析,结果表明：平均体重120-200g的商品蟹,可食部分总指数〉30%,最高的太湖蟹达35.71%,最低的滆湖蟹为30.01%,各品牌河蟹之间差异不显著（p〉0.05）。肥满度以滆湖蟹最高,阳澄湖蟹最低,各品牌河蟹之间差异不显著（p〉0.05）。固城湖蟹的粗蛋白含量显著高于阳澄湖蟹（p〈0.05）,虽高于其它品牌河蟹,但差异不显著（p〉0.05）。可食部分17种氨基酸总量依次为：17.48、15.90、17.31、18.21、19.42、16.62、17.85、17.25;固城湖蟹与阳澄湖蟹的差异达极显著水平（p〈0.01）,与洪泽湖蟹的差异达显著水平（p〈0.05）,长荡湖蟹与阳澄湖蟹的差异达显著水平（p〈0.05）,其它品牌河蟹之间的差异不显著（p〉0.05）。固城湖蟹鲜味氨基酸含量显著高于阳澄湖蟹（p〈0.05）,其它品牌河蟹差异不显著（p〉0.05）。必需氨基酸指数依次为：77.29,75.80,83.12,78.73,77.33,70.55,75.91,73.93。必需氨基酸含量分别占总氨基酸的47.99%、47.80%、48.01%、43.95%、47.35%、48.23%、47.81%、49.47%,低于全鸡蛋白质模式,但均明显高于FAO/WHO模式。     

Localization and mobility of omega-conotoxin-sensitive Ca2+ channels in hippocampal CA1 neurons

Voltage-dependent Ca2+ channels (VDCCs) are modulators of synaptic plasticity, oscillatory behavior, and rhythmic firing in brain regions such as the hippocampus. The distribution and lateral mobility of VDCCs on CA1 hippocampal neurons have been determined with biologically active fluorescent and biotinylated derivatives of the selective probe omega-conotoxin in conjunction with circular dityndallism, digital fluorescence imaging, and photobleach recovery microscopy. On noninnervated cell bodies, VDCCs were found to be organized in multiple clusters, whereas after innervation the VDCCs were concentrated and immobilized at synaptic contact sites. On dendrites, VDCC distribution was punctate and was interrupted by extensive bare regions or abruptly terminated. More than 85% of the dendritic VDCCs were found to be immobile by fluorescence photobleach recovery. Thus, before synaptic contact, specific mechanisms target, segregate, and immobilize VDCCs to neuronal cell bodies and to specialized dendritic sites. Regulation of this distribution may be critical in determining the firing activity and integrative properties of hippocampal CA1 neurons.     

Histochemical and functional correlations in anterior horn neurons of the cat spinal cord

The histochemical reaction for phosphorylase is completely lost from anterior horn neurons rich in phosphorylase within 72 hours after proximal or distal axonal section. Using this new type of axonal reaction as a marking technique in the anterior horn of the seventh lumbar spinal cord segment of the cat, we demonstrated that (i) alpha motor neurons of slow twitch motor units, like those of fast twitch motor units, are rich in phosphorylase and poor in succinate dehydrogenase, and (ii) interneurons and Renshaw neurons are rich in succinate dehydrogenase and poor in phosphorylase. Gamma motor neurons, because of their small size, are considered to be rich in succinate dehydrogenase and poor in phosphorylase. Thus, anterior horn neurons capable of higher firing frequencies (Renshaw neurons, interneurons, and gamma motor neurons) are richer in mitochondrial oxidative enzyme activity as marked by succinate dehydrogenase. Those firing at lower frequencies (both types of alpha motor neurons) are richer in phosphorylase activity and glycogen content and, thus, apparently better equipped for anaerobic glycolysis.     

Regeneration of functional synapses between individual recognizable neurons in the lamprey spinal cord

In 4- to 5-year-old sea lamprey larvae that had recovered from complete transection of the spinal cord, pairs of giant interneurons on opposite sides of the scar were impaled with microelectrodes. In 4 of 30 pairs, stimulation of the caudal cell elicited a monosynaptic electrochemical excitatory postsynaptic potential in the rostral cell. Fifty percent of such pairs were synaptically linked in control lampreys without transections. These results show regeneration of functional synaptic connections between individual neurons in a vertebrate central nervous system.