Search results for "ganglion"
showing 10 items of 282 documents
The effects of the tricyclic antidepressants desipramine, doxepin and iprindole on the isolated perfused rabbit heart.
1974
1. The right sympathetic nerves of isolated perfused rabbit hearts were stimulated electrically (1 msec, supramaximal strength, 15 sec) with increasing frequencies (0.25–20 Hz) at 3 min intervals before and 20 min after starting perfusion with desipramine, doxepin or iprindole. Ventricular rate, right atrial and right ventricular tensions were recorded using the transverse method. 2. Sympathic nerve stimulation caused ventricular arrhythmias in the presence of desipramine (3.3 and 5.0 · 10−6 M) and doxepin (1.6−4.7×10−6 M) but failed to produce arrhythmias in hearts not exposed to drugs, or after iprindole, cocaine and atropine. 3. When desipramine or doxepin was added to Tyrode solution co…
Ex Vivo Retinal Explant Cultures to Study Angiogenic Responses
2012
The mouse retina has long been regarded as an easily accessible and advantageous system to investigate important questions of developmental angiogenesis. The protocol presented here profits from the suitability of the mouse retina as experimental model and describes an ex vivo culture technique of mouse retina explants that allows the quantitative assessment of angiogenic responses to pharmacological manipulations. The technique involves the extraction of the retina from the intact eye, the immediate flat mounting of the tissue on a hydrophilic membrane and the acute stimulation or inhibition of angiogenic processes of the developing vessels in their physiological context ex vivo. The numbe…
The Brain’s Camera. Optimal Algorithms for Wiring the Eye to the Brain Shape How We See
2016
The problem of sending information at long distances, without significant attenuation and at a low cost, is common to both artificial and natural environments. In the brain, a widespread strategy to solve the cost-efficiency trade off in long distance communication is the presence of convergent pathways, or bottlenecks. In the visual system, for example, to preserve resolution, information is acquired by a first layer with a large number of neurons (the photoreceptors in the retina) and then compressed into a much smaller number of units in the output layer (the retinal ganglion cells), to send that information to the brain at the lowest possible metabolic cost. Recently, we found experimen…
Sensitivity of a sensory process to short time delays: A study in pattern induced flicker colors (PIFCs)
1978
Pattern induced flicker colors (PIFCs) were generated by means of a modified version of Benham's top, the stimulus pattern of which could be varied continuously during stimulation by the human subjects. The sensitivity of the color sensation to small phase shifts between the periodic stimuli on neighboring retinal areas was recorded under several conditions of stimulus parameters. A mathematical model was developed to describe the influence of the stimulus parameters on the recorded sensory effect. Concerning the underlying neurophysiological processes, a hypothesis is advanced according to which the phase sensitive lateral interaction within the retina changes the spatial excitation distri…
Impaired formation of the inner retina in an AChE knockout mouse results in degeneration of all photoreceptors
2004
Blinding diseases can be assigned predominantly to genetic defects of the photoreceptor/pigmented epithelium complex. As an alternative, we show here for an acetylcholinesterase (AChE) knockout mouse that photoreceptor degeneration follows an impaired development of the inner retina. During the first 15 postnatal days of the AChE-/- retina, three major calretinin sublaminae of the inner plexiform layer (IPL) are disturbed. Thereby, processes of amacrine and ganglion cells diffusely criss-cross throughout the IPL. In contrast, parvalbumin cells present a nonlaminar IPL pattern in the wild-type, but in the AChE-/- mouse their processes become structured within two 'novel' sublaminae. During t…
Separate processing of “color” and “brightness” in goldfish
1991
Spectral sensitivity was measured under different adaptation levels using a behavioral training technique in which the fish had to discriminate between a dark test field and a test field illuminated with monochromatic light. Depending on which of the two test fields was used as training test field, two functions were obtained which differ (1) in absolute sensitivity and (2) in shape. When trained on the dark test field, the fish seems to discriminate on the basis of a "color" cue, but it uses a "brightness" cue when trained on the illuminated test field. This was concluded from measurements of wavelength discrimination. Under low levels of the adaptation light (1.5 and 0.2 lx instead of 20 …
Images perceived after chromatic or achromatic contrast sensitivity losses.
2010
Purpose. We simulate how subjects with losses in chromatic and achromatic contrast sensitivity perceive colored images by using the spatiochromatic corresponding pair algorithm. Methods. This is a generalized version of the algorithm by Capilla et al. (J Opt Soc Am (A) 2004;21:176 –186) for simulating color perception of color deviant subjects, which incorporates a simple spatial vision model, consisting of a linear filtering stage, with a band-pass achromatic filter and two low-pass chromatic ones, for the red-green and blue-yellow mechanisms. These filters, except for the global scaling, are the subject’s contrast sensitivity functions measured along the cardinal directions of the color s…
A new vicious cycle involving glutamate excitotoxicity, oxidative stress and mitochondrial dynamics
2011
Glutamate excitotoxicity leads to fragmented mitochondria in neurodegenerative diseases, mediated by nitric oxide and S-nitrosylation of dynamin-related protein 1, a mitochondrial outer membrane fission protein. Optic atrophy gene 1 (OPA1) is an inner membrane protein important for mitochondrial fusion. Autosomal dominant optic atrophy (ADOA), caused by mutations in OPA1, is a neurodegenerative disease affecting mainly retinal ganglion cells (RGCs). Here, we showed that OPA1 deficiency in an ADOA model influences N-methyl-D-aspartate (NMDA) receptor expression, which is involved in glutamate excitotoxicity and oxidative stress. Opa1enu/+mice show a slow progressive loss of RGCs, activation …
Connecting temporal identity to mitosis: the regulation of Hunchback in Drosophila neuroblast lineages.
2006
Both in vertebrates and invertebrates, neural stem cells generate different cell types at different times during development. It has been suggested that this process depends on temporal identity transitions of neural progenitors, but the underlying mechanism has not been resolved, yet. Recently, Drosophila neuroblasts (NBs) have been shown to be an excellent model system to investigate this subject. Here, changes in temporal identity are regulated by sequential and transient expression of transcription factors in the NB, such as Hunchback (Hb) and Kruppel (Kr). The temporal expression profile is maintained in the progeny. Hb is expressed first and thus defines the earliest identity in a giv…
PGC-1α signaling coordinates susceptibility to metabolic and oxidative injury in the inner retina.
2013
Retinal ganglion cells (RGCs), used as a common model of central nervous system injury, are particularly vulnerable to metabolic and oxidative damage. However, molecular mechanisms underlying this sensitivity have not been determined in vivo . PGC-1α (encoded by PPARGC1A ) regulates adaptive metabolism and oxidative stress responses in a tissue- and cell-specific manner. Aberrant PGC-1α signaling is implicated in neurodegeneration, but the mechanism underlying its role in central nervous system injury remains unclear. We provide evidence from a mouse model that PGC-1α expression and activity are induced in adult retina in response to metabolic and oxidative challenge. Deletion of Ppargc1a d…