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At least 145 records · Page 8Linked to original sources
PubMed1984

Microspectrophotometry of vertebrate photoreceptors. A brief review.

Since the early 1960s, measurements of the absorbance spectra of both photosensitive and inert pigments within intact isolated visual receptor cells have been achieved in a great number of species, including representatives of all the vertebrate groups as well as some invertebrates, principally the insects. The technique has meant a rapid advance in our understanding of the basis of colour vision throughout the animal kingdom as well as increasing our knowledge of the behaviour of visual pigments in situ. A review of these advances, especially within the fish, birds and primates is presented with emphasis on the limitations of the technique, and the intriguing questions that microspectrophotometric analysis of the pigments of visual receptor cells has raised.

Amphibians↗
PubMed1986

Photoreceptor redox state monitored in vivo by transmission and fluorescence microspectrophotometry in blowfly compound eyes.

The transmission and fluorescence of the compound eye of living, intact blowflies Calliphora erythrocephala, mutant chalky, were studied microspectrophotometrically. Transmission spectra were recorded under four conditions. The fly was either in the normal air environment or in a nitrogen atmosphere, and in both cases the investigated eye was adapted to red and blue light, respectively. The absorbance difference spectra obtained from the two chromatic adapted conditions showed the clear characteristics of the main visual pigment; the difference spectra for the air and the N2 case were virtually identical. The absorbance difference spectrum obtained from the air vs N2 case was very similar to the redox difference spectrum of the pigments in the mitochondrial chain. The redox difference spectra obtained for the two photosteady states were essentially the same. The fluorescence emission spectra induced by UV and blue excitation were measured with the fly in air and in a nitrogen atmosphere, respectively. The UV-induced blue emission under hypoxia, whereas the blue-induced green emission dropped. The changes are typical for a reduction of mitochondrial NADH and flavoproteins, respectively. The transmission and fluorescence measurements corroborates each other and demonstrate mitochondrial activity in photoreceptors in vivo and non-invasively.

Adaptation, Ocular↗
PubMed1993

Stimulated release of acetylcholinesterase in rat striatum revealed by in vivo microspectrophotometry.

The microspectrophotometric technique allows a direct in vivo measurement of brain extracellular acetylcholinesterase. An optical probe associated with electrodes for stimulation was implanted in striatum of anaesthetized rats to determine the effects of neuronal excitation on the acetylcholinesterase activity. Electrical stimulations induced a reversible increase in acetylcholinesterase activity of about 30 to 50%, with a recovery to baseline occurring after 1 or 2 h. Furthermore, iterative electrical stimulation induced a progressive fading of this phenomenon. An enhancement of acetylcholinesterase activity was also observed by stimulations with potassium injections through a canal of the probe. These results suggest mainly an intracellular origin of the released enzyme and estimate its contribution at about 40% of the whole extracellular enzyme activity.

Acetylcholinesterase↗
PubMed1972

Microspectrophotometry of arthropod visual screening pigments.

Absorption spectra of visual screening pigments obtained in vitro with a microspectrophotometer using frozen sections are given for the insects Musca domestica, Phormia regina, Libellula luctuosa, Apis mellifera (worker honeybee only), Drosophila melanogaster (wild type only) and the arachnids Lycosa baltimoriana and Lycosa miami. The spectral range covered is 260-700 nm for Lycosa and Drosophila and 310-700 nm for the remainder of the arthropods. A complete description of the instrumentation is given. For the flies, Phormia and Musca, light absorption by the yellow and red pigments is high from 310 to about 610 nm. This implies that for these insects there should be no wavelength shift in electroretinogram (ERG) results due to light leakage among neighboring ommatidia for this wavelength range. The same comment applies to Calliphora erythrocephala, which is known to have similar screening pigments. For some of the insects studied a close correspondence is noted between screening pigment absorption spectra and spectral sensitivity curves for individual photoreceptors, available in the literature. In some cases the screening pigment absorption spectra can be related to chemical extraction results, with the general observation that some of the in vitro absorption peaks are shifted to the red. The Lycosa, Apis, and Libellula dark red pigments absorb strongly over a wide spectral range and therefore prevent chemical identification.

Animals↗
PubMed1983

Microspectrophotometry of single rhabdoms in the retina of the honeybee drone (Apis mellifera male).

The relative absorption spectra of the bistable photopigment of single rhabdoms from the dorsal region of the retina of the honeybee drone were obtained using slices of retina fixed in glutaraldehyde; less accurate measurements on unfixed tissue gave difference spectra that were similar to those for fixed retinae. The method used was based on measurements of absorbance changes during saturating adaptations of the visual pigment to different monochromatic lights. It is similar to previous methods based on measurements of difference spectra amplitudes, but is simpler to use and more accurate. The predominant pigment has states that absorb maximally at 446 (rhodopsin) and 505 nm (metarhodopsin). In addition, there is a small amount of another pigment whose two states absorb maximally at approximately 340 (UV) and 460 nm.

Animals↗
PubMed2006

Tracking X-ray-derived redox changes in crystals of a methylamine dehydrogenase/amicyanin complex using single-crystal UV/Vis microspectrophotometry.

X-ray exposure during crystallographic data collection can result in unintended redox changes in proteins containing functionally important redox centers. In order to directly monitor X-ray-derived redox changes in trapped oxidative half-reaction intermediates of Paracoccus denitrificans methylamine dehydrogenase, a commercially available single-crystal UV/Vis microspectrophotometer was installed on-line at the BioCARS beamline 14-BM-C at the Advanced Photon Source, Argonne, USA. Monitoring the redox state of the intermediates during X-ray exposure permitted the creation of a general multi-crystal data collection strategy to generate true structures of each redox intermediate.

Bacterial Proteins↗