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Results for “OPTIC PATHWAY”

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At least 811 records · Page 45Linked to original sources
PubMed2006

Bottom-up synthesis of optically active oligonaphthalenes: three different pathways for controlling axial chirality.

The oxidative homocoupling of optically active binaphthalenes 1a-d with a stoichiometric amount of CuCl2 and amines afforded quaternaphthalenes 2a-d in up to 93% de. The high diastereoselectivities were achieved through three different pathways (epimerization of the axis together with diastereoselective crystallization, thermodynamic, and kinetic control pathways). The type of side chains on the naphthalene influenced which pathway dominates. Three pathways were applicable to octinaphthalenes (8a-d) and hexadecanaphthalene 10a with 46-99% de. The absolute configuration of the newly formed axial bond was determined by (1) X-ray crystallographic analysis, (2) transformation to known compounds 15 and 16, (3) CD spectra of oligonaphthalenes with two pyrene rings as exciton parts, and (4) the shift values in 13C NMR spectra of 13C-enriched derivatives 29-31 toward chiral shift reagent Eu(+tfc)3.

Mass Spectrometry↗
PubMed1979

Descending pathways of the nucleus of the optic tract in the rat.

The descending pathways of the nucleus of the optic tract (pars lateralis) (NOTL) in the rat were examined in Nauta-Gygax impregnated sections and further confirmed by the horseradish peroxidase labeling technique. Following stereotactic lesions in the NOTL, visual cortex, and superior colliculus, projections which orginate in the NOTL were identified by elimination of the tectofugal and tectopetal fibers of the superior colliculus. The descending fibers from the NOTL appeared to be organized into three bundles. (1) The NOTL-contralateral NOTL fibers, which connect bilateral NOTLs through a part of the posterior commissure. (2) The NOTL-nucleus tegmenti pontis and inferior olivary nucleus fibers, which project to the ventromedial part of the nucleus tegmenti pontis and the dorsal cap of the inferior olivary nucleus, ipsilaterally to the NOTL. (3) The NOTL-pontine nuclei fibers, which terminate within the medial one-third of the pars lateralis of the ipsilateral pontine nuclei with topical relations.

Animals↗
PubMed1984

Cupping of the optic disc with compressive lesions of the anterior visual pathway.

Cupping of the optic nerve, classically a sign of glaucoma, was demonstrated in 16 patients with lesions compressing the anterior visual pathway. Color contrast determinations of the cup/disc ratio demonstrated a ratio greater than 0.49 in 31 eyes. Further evaluation by stereobiomicroscopy showed cavernous degeneration by contour changes in 25 of the optic nerves. None of the patients had intraocular pressures greater than 22, and seven had normal tonography. Visual fields demonstrated bitemporal field defects in most patients and none were typical of glaucoma. Snellen acuity loss, out of proportion to the extent of optic disc cupping was found in 12 patients. This study indicates that diseases other than glaucoma can cause significant cupping of the optic nerves. Detailed evaluation of the disc changes and the visual fields will prevent confusion between compressive lesions of the optic nerves or chiasm and glaucoma.

Adolescent↗
PubMed1993

Immunocytochemical and biochemical evidence for aromatase in neurons of the retina, optic tectum and retinotectal pathways in goldfish.

Using an animal model in which neural aromatase is apparently overexpressed (the goldfish, Carassius auratus) and an anti-human placental antibody which specifically crossreacts with goldfish brain aromatase, aromatase-immunoreactive neuronal cell bodies and fibers have been localized within the retina. These include a subset of horizontal cells, bipolar cells, and amacrine cells of the inner nuclear layer, some fibers of the outer and inner synaptic layers and certain cells of the ganglion cell layer; photoreceptors were never labeled. Some ganglion cell projections to the brain via the optic nerve and optic tract were aromatase-positive, as were small neurons of the stratum periventriculare (SPV) and fibers of two other strata of the optic tectum. Aromatase activity, as measured by [3H]androgen by tissue homogenates and cell cultures, confirmed the presence of aromatase in retina and in brain regions containing the optic tectum. This localization of the rate-limiting enzyme in estrogen biosynthesis suggests that neuroestrogen derived from circulating androgen m ay modulate transmission and integration of visual information important for reproduction in this species.

Animals↗
PubMed2004

Optical survey of neural circuit formation in the embryonic chick vagal pathway.

The multiple-site optical recording technique with a voltage-sensitive dye, NK2761, was used to survey functional organization of neural circuits related to the vagus nerve in the embryonic chick brainstem. When we stimulated the vagus nerve, in addition to the responses in the vagal sensory nucleus (nucleus of the tractus solitarius (NTS)) and motor nucleus (dorsal motor nucleus of the vagus nerve (DMNV)) on the stimulated side, another response area was discriminated at the level of the pons/rostral medulla on the contralateral side. Characteristics of the contralateral optical signals suggested that they correspond to the neural activity in the second/higher-ordered nucleus of the vagal pathway, possibly the parabrachial nucleus, which receives inputs from the NTS. Blockade of non-N-methyl-d-aspartate (NMDA) receptors abolished the responses on the contralateral side, together with the postsynaptic firing in the NTS, suggesting the significance of non-NMDA receptor function in sensory information transfer via the NTS. The responses on the contralateral side were first detected from the 7-day-old embryonic stage, when the glutamatergic excitatory postsynaptic potentials were first expressed in the NTS. The results suggest that the synaptic pathway from the NTS to the contralateral nucleus is already generated when the primary vagal afferents make functional synapses on NTS neurons.

6-Cyano-7-nitroquinoxaline-2,3-dione↗
PubMed1992

XeCl laser ablation of atherosclerotic aorta: optical properties and energy pathways.

The energetics of 308-nm excimer laser irradiation of human aorta were studied. The heat generation that occurred during laser irradiation of atherosclerotic aorta equaled the absorbed laser energy minus the fraction of energy for escaping fluorescence (0.8-1.6%) and photochemical decomposition (2%). The absorbed laser energy is equal to the total delivered light energy minus the energy lost as specular reflectance (2.4%, air/tissue) and diffuse reflectance (11.5-15.5%). Overall, about 79-83.5% of the delivered light energy was converted to heat. We conclude that the mechanism of XeCl laser ablation of soft tissue involves thermal overheating of the irradiated volume with subsequent explosive vaporization. The optical properties of normal wall of human aorta and fibrous plaque, both native and denatured were determined. The light scattering was significant and sufficient to cause a subsurface fluence (J/cm2) in native aorta that equaled 1.8 times the broad-beam radiant exposure, phi o (2.7 phi o for denatured aorta). An optical fiber must have a diameter of at least 800 microns to achieve a maximum light penetration (approximately 200 microns for phi o/e) in the aorta along the central axis of the beam.

Aorta↗
PubMed1981

Radiation therapy in and about the retina, optic nerve, and anterior visual pathway. Psychophysical assessment.

Visual changes may develop in patients receiving radiation therapy for malignant neoplasms in and about the optic nerve and anterior visual pathway. Cases have been studied using a series of psychophysical tests, including kinetic perimetry, increment threshold determinations, Flashing Repeat Static Test, and sustained- and transient-like functions. A characteristic time-dependent reduction in sensitivity has been identified in these patients. This finding, in addition to the presence of nerve fiber bundle defects, appears to place the pathologic changes in the axon of the ganglion cell posterior to the lamina cribrosa. Any change in the sustained- and transient-like functions, the organization of which appears to be in the neural retina, was seen only if a concomitant radiation retinopathy was identified.

Adenocarcinoma↗