1,721,053 research outputs found
Saffron supplement maintains morphology and function after exposure to damaging light in mammalian retina
No full textPURPOSE:
To test whether the saffron extract (Crocus sativus L.) given as a dietary supplement counteracts the effects of continuous light exposure in the albino rat retina.
METHODS:
Three experimental groups of Sprague-Dawley rats were used. Experimental animals were prefed either saffron or beta-carotene (1 mg extract/kg/d) before they were exposed to bright continuous light (BCL) for 24 hours. Flash electroretinograms (fERGs) were recorded in control and treated rats the day before and 1 week after light exposure. At the end of the second recording session, the animals were killed and the retinas were quickly removed, fixed, cryosectioned, and labeled so that the thickness of the outer nuclear layer (ONL) could be analyzed. Changes in protein level and cellular localization of fibroblast growth factor (FGF)2 were determined by Western blot analysis and retinal immunohistochemistry, respectively. In a second series of experiments, rats were killed at the end of light exposure, and the amount of apoptotic figures in the ONL was assessed by terminal transferase-mediated deoxyuridine triphosphate (d-UTP)-biotin nick-end labeling (TUNEL). BCL induced DNA fragmentation, characteristic of dying cells, almost exclusively in the photoreceptor layer. The rate of photoreceptor death induced by BCL is expressed as the frequency of TUNEL-positive profiles per millimeter.
RESULTS:
The photoreceptor layer was largely preserved in saffron-treated animals because it was the fERG response. In addition, the rate of photoreceptor death induced by BCL appeared drastically reduced in treated animals. In beta-carotene prefeeding experiments, morphologic analysis showed preservation of the ONL similar to that obtained with saffron prefeeding, whereas the fERG response was unrecordable. Western blot analysis showed that exposure to light induced a strong upregulation of FGF2 in control and beta-carotene-treated rats, but s no change was noted in saffron-treated rats.
CONCLUSIONS:
These results show that saffron may protect photoreceptors from retinal stress, maintaining both morphology and function and probably acting as a regulator of programmed cell death
Variations of the visual response of the superior colliculus in relation to the body roll
No full textA large percentage of the directional units of the superior colliculus of the curarized cat modify their response to a particular moving visual stimulus as a function of the position of rotation of the animal about its longitudinal axis
Blockade of glutamate-mediated activity in the developing retina perturbs functional segregation of ON and OFF pathways
Full text linkThe dendrites of ganglion cells initially ramify throughout the inner plexiform layer of the developing retina before becoming stratified into ON or OFF sublaminae. This ontogenetic event is thought to depend on glutamate-mediated afferent activity, because treating the developing retina with the glutamate analog 2-amino-4-phosphonobutyrate (APB), which hyperpolarizes ON cone bipolar cells and rod bipolar cells, thereby preventing their release of glutamate, effectively arrests the dendritic stratification process. To assess the functional consequences of this manipulation, extracellular recordings were made from single cells in the A laminae of the dorsal lateral geniculate nucleus and from the optic tract in mature cats that had received intraocular injections of APB during the first postnatal month. Such recordings revealed that stimulation of the APB-treated eye evoked both ON as well as OFF discharges in 37% of the cells tested. (As expected, when the normal eye was activated, virtually all cells yielded only ON or OFF responses.) The proportion of ON-OFF cells found here corresponds closely to the incidence of multistratified dendrites observed previously in anatomical studies of APB-treated cat retinas. This suggests that the ganglion cells with multistratified dendrites receive functional inputs from ON as well as OFF cone bipolar cells. This interpretation is further supported by the finding that the proportion of ON-OFF cells was very similar in the geniculate layer innervated by the treated eye and in the optic tract. The cells activated by the APB-treated eye were also found not to show response suppression when flashing stimuli of increasing size were used. This suggests that exposing the developing retina to APB perturbs the neural circuitry mediating the antagonistic center-surround organization found in normal receptive fields. The functional changes evident after treating the developing retina with APB suggest that it should now be feasible to assess how the segregation of ON and OFF retinal pathways relates to organizational features at higher levels of the visual system, such as orientation selectivity in cortical cells
Visuovestibular interactions in the cat superior colliculus
No full text1. Single-unit recording has been performed from the superficial layers of the superior colliculus of regionally anesthetized cats. The response of the collicular units to
a luminous bar moving in its receptive field has been analyzed as a function of the position of rotation of the animal about its longitudinal axis.
2. Forty-eight percent of collicular directional units altered their visual responses
with an approximately linear function of the body tilt.
3. Twenty-five percent of collicular nondirectional units changed their visual responses following body tilt. They showed no clear relation between amplitude of response and angle of tilt.
4. No variation in the preferred direction of stimulus movement of directionally selective collicular units was observed following body tilt.
5. Analysis of collicular responses after chronic section of the eighth nerves in five
cats strongly indicated that the vestibular system plays a major role in the modification of visual responses at collicular level
Type-1 and type-2 cannabinoid receptor signalling is involved in the neuroprotectiv eeffect of Saffron of rat retina
No full text
The impact of organic inhibitors of the hyperpolarization activated current (Ih) on the electroretinogram (ERG) of rodents
No full text
- …
