Generation of adrenergic and cholinergic potentials in sympathetic ganglion cells

Norepinephrine elicited a hyperpolarizing response, and acetylcholine (during nicotinic blockade) elicited a depolarizing one. Both responses showed no increase in membrane conductance. The norepinephrine response was suppressed by initial depolarization; the acetylcholine response (frog cells); by hyperpolarization. These neurotransmitters apparently can activate electrogenic mechanisms which do not involve movement of ions down their electrochemical gradients.     

Selective sensitivity to direction of movement in ganglion cells of the rabbit retina

Among the ganglion cells in the rabbit's retina there is a class that responds to movement of a stimulus in one direction, and does not respond to movement in the opposite direction. The same directional selectivity holds over the whole receptive field of one such cell, but the selected direction differs in different cells. The discharge is almost uninfluenced by the intensity of the stimulus spot, and the response occurs for the same direction of movement when a black spot is substituted for a light spot.     

Goldfish retina: sign of the rod input in opponent color ganglion cells

After light adaptation, all "on-center" ganglion cells in the dark became "red on-center," and all "off-center" cells turned into "red off-center" cells. On a chance basis, this similitude of effect between the rods and the red cones in opponent color cells was not expected. These findings indicate that in the goldfish there is some similarity between the connections of the rods and of the long-wavelength cones.     

北京鸭视网膜移动性无长突细胞的分布

利用视神经溃变试验和Nissl染色法研究了北京鸭视网膜移动性无长突细胞 (dACs)的形态、大小与密度分布。北京鸭dACs是位于视网膜节细胞层的小神经元 ,核深染 ,胞质很少 ,细胞体呈圆形或卵圆形 ,细胞大小均一 ,平均面积为 19～ 2 5 μm2 。在视网膜中央有一个dACs高密度区即中央高密度区 (CA ,386 0个·mm-2 ) ,dACs的密度由视网膜中央部向视网膜周边部逐渐降低 (TP ,约为 1780个·mm-2 ;NP ,约为 176 0个·mm-2 )。试验结果表明北京鸭视网膜中央部和周边部的dACs大小差异不明显 ,但dACs在节细胞层密度分布不均 ,呈现由视网膜中央部至周边部密度梯度递减的变化     

Response of Schwann cells to action potentials in development

Sensory axons become functional late in development when Schwann cells (SC) stop proliferating and differentiate into distinct phenotypes. We report that impulse activity in premyelinated axons can inhibit proliferation and differentiation of SCs. This neuron-glial signaling is mediated by adenosine triphosphate acting through P2 receptors on SCs and intracellular signaling pathways involving Ca2+, Ca2+/calmodulin kinase, mitogen-activated protein kinase, cyclic adenosine 3',5'-monophosphate response element binding protein, and expression of c-fos and Krox-24. Adenosine triphosphate arrests maturation of SCs in an immature morphological stage and prevents expression of O4, myelin basic protein, and the formation of myelin. Through this mechanism, functional activity in the developing nervous system could delay terminal differentiation of SCs until exposure to appropriate axon-derived signals.     

Transient morphological features of identified ganglion cells in living fetal and neonatal retina

The function and morphology of retinal ganglion cells in the adult mammalian visual system has been well studied, but little is known about how the adult state is achieved. To address this question, the morphological changes that retinal ganglion cells undergo during development were studied. Ganglion cells were first identified by retrograde labeling with rhodamine latex microspheres deposited in retinorecipient targets in fetal and early postnatal cats. The structure of ganglion cells was then revealed by intracellular injection of Lucifer yellow in living retinas removed and maintained in vitro. As early as 2 weeks before birth, a morphologically diverse assortment of ganglion cells is present, some of which resemble the alpha, beta, and gamma classes found in the adult. However, in contrast to the adult, developing ganglion cells exhibit several transient features, including excessive axonal and dendritic branching and exuberant somatic and dendritic spines. These morphological features indicate that there is a transient network of connectivity that could play an important role in the final determination of retinal ganglion cell form and function.     

Mechanism of fibrillation potentials in denervated mammalian skeletal muscle

This report concerns the origin and mechanism of fibrillation potentials. It is proposed that these potentials do not necessarily arise from degenerated endplate organs. The precursor is the rhythmic oscillations of the membrane potential. This mechanism may also occur in the case of epileptic discharges from epileptic cells in the cerebral cortex.     

GDF11 controls the timing of progenitor cell competence in developing retina

The orderly generation of cell types in the developing retina is thought to be regulated by changes in the competence of multipotent progenitors. Here, we show that a secreted factor, growth and differentiation factor 11 (GDF11), controls the numbers of retinal ganglion cells (RGCs), as well as amacrine and photoreceptor cells, that form during development. GDF11 does not affect proliferation of progenitors-a major mode of GDF11 action in other tissues-but instead controls duration of expression of Math5, a gene that confers competence for RGC genesis, in progenitor cells. Thus, GDF11 governs the temporal windows during which multipotent progenitors retain competence to produce distinct neural progeny.     

Corresponding spatial gradients of TOP molecules in the developing retina and optic tectum

The topographic map of cell position in the avian retina is inverted in its projection to the optic tectum. Dorsal retinal ganglion cell axons project to ventral tectum, and ventral retinal ganglion cells project to dorsal tectum. Topographic gradients of toponymic (TOP) cell surface molecules along the dorsoventral axes of retina and tectum also are inverted. TOP molecules are most abundant in dorsal retina and ventral tectum and least abundant in ventral retina and dorsal tectum during the period of initial retinal-tectal interaction. Thus, TOP molecules may be involved in orienting the retinotectal map.     

Differential shunting of EPSPs by action potentials

Neurons encode information and communicate via action potentials, which are generated following the summation of synaptic events. It is commonly assumed that action potentials reset the membrane potential completely, allowing another round of synaptic integration to begin. We show here that the conductances underlying the action potential act instead as a variable reset of synaptic integration. The strength of this reset is cell type-specific and depends on the kinetics, location, and timing of the synaptic input. As a consequence, distal synapses, as well as inputs mediated by N-methyl-d-aspartate receptor activation, can contribute disproportionately to synaptic integration during action potential firing.     

Hyperacuity in cat retinal ganglion cells

Cat X retinal ganglion cells that can resolve sine gratings of only 2.5 cycles per degree can nevertheless respond reliably to displacements of a grating of approximately 1 minute of arc. This is a form of hyperacuity comparable in magnitude to that seen in human vision. A theoretical analysis of this form of hyperacuity reveals it to be a result of the high gain and low noise of ganglion cells. The hyperacuity expected for the best retinal ganglion cells is substantially better than that observed in behavioral experiments. Thus the brain, rather than improving on the retinal signal-to-noise ratio by pooling signals from many ganglion cells, is unable to make use of all the hyperacuity information present in single ganglion cell responses.     

Miniature end plate potentials recorded from mammalian myoneural junction in vivo

Fibers of the cat soleus muscle had a mean resting potential of 87 millivolts as measured with an intracellular microelectrode. Miniature end plate potentials had a mean amplitude of 0.95 millivolt, a mean frequency of 1.01 per second, a mean duration of 4.44 milliseconds, and a mean rate of rise of 0.99 volt per second. Two populations of response could be discerned on the basis of rate of rise. Neither alpha-chloralose nor nerve section had any significant effect on the response pattern. The in vivo preparation appears to provide a superior representation of the physiology of the myoneural junction.     

Retinal stem cells in the adult mammalian eye

The mature mammalian retina is thought to lack regenerative capacity. Here, we report the identification of a stem cell in the adult mouse eye, which represents a possible substrate for retinal regeneration. Single pigmented ciliary margin cells clonally proliferate in vitro to form sphere colonies of cells that can differentiate into retinal-specific cell types, including rod photoreceptors, bipolar neurons, and Müller glia. Adult retinal stem cells are localized to the pigmented ciliary margin and not to the central and peripheral retinal pigmented epithelium, indicating that these cells may be homologous to those found in the eye germinal zone of other nonmammalian vertebrates.     

Distal initiation and active propagation of action potentials in interneuron dendrites

Fast and reliable activation of inhibitory interneurons is critical for the stability of cortical neuronal networks. Active conductances in dendrites may facilitate interneuron activation, but direct experimental evidence was unavailable. Patch-clamp recordings from dendrites of hippocampal oriens-alveus interneurons revealed high densities of voltage-gated sodium and potassium ion channels. Simultaneous recordings from dendrites and somata suggested that action potential initiation occurs preferentially in the axon with long threshold stimuli, but can be shifted to somatodendritic sites when brief stimuli are applied. After initiation, action potentials propagate over the somatodendritic domain with constant amplitude, high velocity, and reliability, even during high-frequency trains.     

Segregation of sister chromatids in mammalian cells

Segregation of sister chromatids in embryonic mouse cells in primary tissue culture is not random. In mitosis those chromatids replicated on a DNA template synthesized during the preceding division cycle are separated from those constructed on a template synthesized two division cycles previously. Segregation in cells of the Chinese hamster follows a similar, but less pronounced, pattern.     

Transmembrane action potentials from smooth muscle in turtle arteries and veins

Transmembrane potential and active tension were measured in isolated segments of turtle aorta and inferior vena cava. Changes in tension were associated with action potentials, but the potentials had a different pattern in the two tissues. When the frequency of the action potentials increased, the contractions summated, resulting in a steadily maintained contraction.     

Synaptic transmission between photoreceptors and horizontal cells in the turtle retina

Low calcium, high magnesium, and cobalt hyperpolarize the horizontal cell membrane and suppress the response to light, but only partially affect the response of receptor cells. These observations are consistent with the interpretation that a depolarizing transmitter is released by photoreceptors in darkness. The hyperpolarizing response to light of the horizontal cells would then result from a reduction in the amount of transmitter released.