Acetylcholine and GABA mediate opposing actions on neuronal chloride channels in crayfish

A central principle of neural integration is that excitatory and inhibitory neurotransmitters effect the opening of distinct classes of membrane ionic channels and that integration consists of the summation of the opposing ionic currents on the postsynaptic membrane. In tangential cells of crayfish optic lobes, a hyperpolarizing, biphasic synaptic potential is produced by the concurrent action of acetylcholine and gamma aminobutyric acid (GABA). Acetylcholine hyperpolarizes the cell and increases chlorine conductance. GABA depolarizes the cell by closing some of the same chloride channels. Therefore, in this case integration is achieved by the antagonistic actions of two transmitters on the same ionic channel.     

Shark pit organs: enhancement of mechanosensitivity by potassium ions

The mandibular pit organs of pelagic sharks, which respond sensitively to monovalent cations, often show neural discharges synchronized with respiratory gill movement. The mechanosensitivity of the organs is remarkably enhanced by application of potassium ions on the same end organ, respiratory movement remaining constant. In view of their michanosensitivity to an incr-ease of potassium ions in the cell environment, as well as their chemosensitivity,the pit organs of sarks, rather than the canal organs which have no chemosensitivity, may be designated as a better model of the inner ear of higher animals.     

Inhibition of sperm-egg interaction by specific antibody

Treatment of hamster ova, in vitro, with ovary specific antibody interferes with sperm-egg interaction by inhibiting sperm attachment to the zona pellucida and subsequent zona penetration. This inhibition results from precipitation of the zona by the specific antibody.     

K+及主要离子间交互作用对凡纳滨对虾存活、生长及体内ATP酶的影响

采取L16(215)正交设计试验,开展5周凡纳滨对虾养殖试验,分析养殖水体中K+及K+、盐度、Ca2+、Mg2+四因子间交互作用对凡纳滨对虾存活、生长及体内ATP酶的影响。结果表明:K+对凡纳滨对虾成活率、体长和体重增加及体内ATP酶活性均具有显著影响,K+浓度为150 mg/L时成活率最高,而K+浓度为50 mg/L时生长速度最快,Na+-K+-ATPase、Mg2+-ATPase、Ca2+-ATPase酶活也最高;K+、盐度、Ca2+、Mg2+四因子间交互作用对凡纳滨对虾存活、生长及体内ATP酶也具有显著影响。本试验因素水平组合中凡纳滨对虾成活率的最佳组合为盐度15、K+150 mg/L、Ca2+100 mg/L、Mg2+300 mg/L,生长速度的最佳组合为盐度15、K+50 mg/L、Ca2+100 mg/L、Mg2+100 mg/L,凡纳滨对虾体内Na+-K+-ATPase、Mg2+-ATPase、Ca2+-ATPase酶活的最佳组合为盐度5、K+50 mg/L、Ca2+100 mg/L、Mg2+100 mg/L。     

Activities of sodium and potassium ions in epithelial cells of small intestine

Intracellular molar Na(+) activity (a(Na)), measured with cation-selective glass microelectrodes, in epithelial cells of isolated bullfrog small intestine immersed at 26 degrees C in a sodium sulfate Ringer solution containing mannitol was 0.0144 +/- 0.0031 (average value plus or minus standard deviation). The corresponding K(+) activity (a(K)) was 0.0854 +/- 0.0060. Combination of these values with previous estimates of intracellular Na(+) and K(+) concentrations under identical conditions indicated that a substantial fraction of the cellular Na(+) is in an osmotically inactive state. When the cells were exposed to a Ringer solution in which 26 millimoles of mannitol per liter were replaced by 3-O-methyl glucose, highly significant decreases in a(K) and a(Na) were observed. The decrease in a(K) was proportionately larger than the corresponding decrease in a(Na).     

External calcium ions are required for potassium channel gating in squid neurons

The effects of calcium removal on the voltage-dependent potassium channels of isolated squid neurons were studied with whole cell patch-clamp techniques. When the calcium ion concentration was lowered from 10 to 0 millimolar (that is, no added calcium), potassium channel activity, identified from its characteristic time course, disappeared within a few seconds and there was a parallel increase in resting membrane conductance and in the holding current. The close temporal correlation of the changes in the three parameters suggests that potassium channels lose their ability to close in the absence of calcium and simultaneously lose their selectivity. If potassium channels were blocked by barium ion before calcium ion was removed, the increases in membrane conductance and holding current were delayed or prevented. Thus calcium is an essential cofactor in the gating of potassium channels in squid neurons.     

Potassium ion specific electrode with high selectivity for potassium over sodium

A new potassium electrode, made from valinomycin, which uses commercially available electrode configurations, responds to potassium ion concentrations from 1 mole per liter to below 10(-6) mole per liter. It is highly selective for potassium ion over sodium ion and divalent ions and can be used for the direct determination of potassium ion in human serumn. No significant complexing of potassiium appears to occur in normal seruin.     

Ionic basis of hyperpolarizing receptor potential in scallop eye: increase in permeability to potassium ions

Photoreceptors of the distal retina of the scallop respond to light with a large hyperpolarizing receptor potential which is caused by a selective increase in permeability to potassium ions.     

Regulation of myosin phosphatase by a specific interaction with cGMP- dependent protein kinase Ialpha

Contraction and relaxation of smooth muscle are regulated by myosin light-chain kinase and myosin phosphatase through phosphorylation and dephosphorylation of myosin light chains. Cyclic guanosine monophosphate (cGMP)-dependent protein kinase Ialpha (cGKIalpha) mediates physiologic relaxation of vascular smooth muscle in response to nitric oxide and cGMP. It is shown here that cGKIalpha is targeted to the smooth muscle cell contractile apparatus by a leucine zipper interaction with the myosin-binding subunit (MBS) of myosin phosphatase. Uncoupling of the cGKIalpha-MBS interaction prevents cGMP-dependent dephosphorylation of myosin light chain, demonstrating that this interaction is essential to the regulation of vascular smooth muscle cell tone.     

几种典型土壤中氮磷钾肥料交互作用对碱解氮的影响

采用河南封丘石灰性潮土、江苏常熟中性黄泥土及江西鹰潭红壤3种典型土壤,研究室内纯培养过程中碱解氮在土壤中的转化及其受磷钾影响的规律。结果表明,外源铵态氮在土壤中极易通过挥发、硝化、固定等途径而减少。不施氮条件下,随培养时间的延长有效氮呈轻微下降趋势,且磷钾对有效氮无明显影响。施氮条件下,随培养时间的延长有效氮显著下降,磷钾对有效氮的转化也有一定的影响,施钾比不施钾降低了黄泥土中碱解氮的含量,施磷处理的石灰性潮土中碱解氮高于不施磷处理。     

NaCl胁迫对苹果砧木K+和Na+吸收的影响及其与耐盐性的关系

试验以生根试管苗为材料,采用水培的方法,研究了小金海棠和M7两种苹果砧木在NaCl胁迫下的形态特征、叶片和根系中Na+和K+含量、叶面积扩展速率以及株高增长率的变化规律.试验结果表明小金海棠在各盐浓度下伤害程度均小于M7;两种砧木在盐胁迫下叶片和根系中Na+均随盐浓度的升高而迅速增加,但叶片中Na+增加幅度明显小于根系中的增加幅度,而K+含量变化则不明显.水培条件下表现耐盐性较强的小金海棠叶片中Na+增加幅度明显小于M7,而RSNa,K值显著高于M7.2种苹果砧木在盐胁迫下株高增长率和叶面积扩展率均随盐胁迫强度的增加而下降,但各盐浓度下小金海棠受抑程度均小于M7.     

氮、钾配施对强筋小麦产量和品质的影响及其交互作用的研究

采用盆栽试验方法研究了氮、钾配施对强筋小麦产量和品质的影响.结果表明,氮、钾配施对小麦产量和品质有明显的影响.适宜的氮、钾用量配比可提高小麦的穗数、株高、穗长、穗粒数和千粒重.小麦籽粒产量、蛋白质含量和产量、湿面筋含量及沉降值均表现出随氮、钾用量的增加而增加的趋势.氮、钾对强筋小麦产量和品质的提高有着明显的正交互作用.     

渭北苹果不同形态钾与水交互作用及品质效应研究

1997～ 1998年对渭北旱塬红富士苹果不同形态钾与水的交互作用、品质效应及耦合模型进行了研究。根据试验测定结果建立了红富士苹果产量、一级果占有率、>80 %果面红色果占有率、可溶性固形物浓度与KCl,K2 SO4 ,H2 O3因素之间的函数模型。通过主因素分析得出各因素对产量及品质的影响顺序为产量 (y1 ) :x3(H2 O) >x2 (K2 SO4 ) >x1 (KCl) ;一级果占有率 (y2 ) :x3(H2 O) >x2 (K2 SO4 ) >x1 (KCl) ;>80 %果面红色果占有率(y3) :x2 (K2 SO4 ) >x1 (KCl) >x3(H2 O) ;可溶性固形物浓度 (y4 ) :x2 (K2 SO4 ) >x1 (KCl) >x3(H2 O)。并对渭北旱塬红富士苹果不同形态钾与水交互作用及品质效应规律进行了综合研究