An artificial heart with the right connection.

Led by Dr. Tofy Mussivand at the University of Ottawa Heart Institute, a team of Canadian medical scientists, engineers, economists, physicians and medical devices manufacturers is working to bring a prototype artificial heart closer to clinical trials. Key to this effort is the development of an electrical connector that can function for a long period in the harsh environment of the human body. Such a connector will enable various components of the artificial heart, such as the internal battery, to be replaced independently. As well as being of obvious benefit to people with end-stage heart disease, a Canadian-made artificial heart has export potential that should help to redress the country''s large trade deficit in medical devices.     

Fly visual pigments difference in visual pigments of blowfly and dronefly peripheral retinula cells

Journal of Comparative Physiology A - The visual pigments of peripheral retinula cells in fly eyes have been investigated by microspectrophotometry in vivo. Since flies have a pupil mechanism...     

Bleaching of visual pigment in steady illumination

The interaction of light and visual pigment is modeled in terms of a three component process, as in Leibovic and Kurtz (1974), but extended to continuous illumination. Based on the model, it is possible to deduce some of the rate constants from first principles and to derive a value for the empirically known light intensity to bleach half the pigment.     

Evolution of visual pigments in geckos

Most geckos are nocturnal forms and possess rod retinas, but some diurnal genera have pure-cone retinas. We isolated cDNAs encoding the diurnal gecko opsins, dg1 and dg2, similar to nocturnal gecko P521 and P467, respectively. Despite the large morphological differences between the diurnal and nocturnal gecko photoreceptor types, they express phylogenetically closely related opsins. These results provide molecular evidence for the reverse transmutation, that is, rods of an ancestral nocturnal gecko have backed into cones of diurnal geckos. The amino acid substitution rates of dgl and dg2 are higher than those of P521 and P467, respectively. Changes of behavior regarding photic environment may have contributed to acceleration of amino acid substitutions in the diurnal gecko opsins.     

Photoregeneration of visual pigments in a moth

Summary The spectral absorbance by the visual pigments in the compound eye of the mothDeilephila elpenor was determined by microphotometry. Two visual pigments and their photoproducts were demonstrated. The photoproducts are thermostable and are reconverted to the visual pigments by light. The concentrations of the visual pigments and the photoproducts at each wavelength are determined by their absorbance coefficients at this wavelength. P 525: The experimental recordings (difference spectra and spectral absorbance changes after exposure to monochromatic lights) were completely reproduced by calculations using nomograms for vertebrate rhodopsin. The identity between experimental recordings and calculations show: One visual pigment absorbs maximally at 525 nm (P 525). The resonance spectrum of the visual pigment is identical to that for a vertebrate rhodopsin (_max at 525 nm). The photoproduct of this pigment absorbs maximally at 480 nm (M 480). It is similar to the acid metarhodopsin in cephalopods. The relative absorbance of P 525 to that of M 480 is 11.75. The quantum efficiency for photoconversion of P 525 to M 480 is nearly equal to that for reconversion of M 480 to P 525. Wavelengths exceeding about 570 nm are absorbed only by P 525, i. e. P 525 is completely converted to M 480. Shorter wavelengths are absorbed both by P 525 and M 480. At these wavelengths a photoequilibrium between the two pigments is formed. Maximal concentration of P 525 is obtained at about 450 nm. P 350: A second visual pigment absorbs maximally at about 350 nm (P 350), and its photoproduct at 450 to 460 nm. In the region of spectral overlap a photoequilibrium between the two pigments is formed.The visual pigment and the photoproduct are similar to those in the neuropteran insectAscalaphus.The work reported in this article was supported by Deutsche Forschungsgemeinschaft, Schwerpunktsprogramm Rezeptorphysiologie Ha 258-10, and SFB 114, by the Swedish Medical Research Council (grant no B 73-04X-104-02B), by Karolinska Institutet, and by a grant (to G. Höglund) from Deutscher Akademischer Austauschdienst.     

Interspecific variation in the visual pigments of deep-sea fishes

Summary Visual pigments in the rods of 38 species of deep-sea fish were examined by microspectrophotometry. 33 species were found to have a single rhodopsin with a wavelength of maximum absorbance ( _max) in the range 470–495 nm. Such visual pigments have absorbance maxima close to the wavelengths of maximum spectral transmission of oceanic water. 5 species, however, did not conform to this pattern and visual pigments were found with _max values ranging from 451 nm to 539 nm. In 4 of these species two visual pigments were found located in two types of rod. Some 2-pigment species which have unusual red sensitivity, also have red-emitting photophores. These species have both rhodopsin and porphyropsin pigments in their retinae, which was confirmed by HPLC, and the two pigments are apparently located in separate rods in the same retinal area. In deep-sea fishes the occurrence of unusual visual pigments seems to be correlated with aspects of the species' depth ranges. In addition to ecological influences we present evidence, in the form of _max spectral clustering, that indicates the degree of molecular constraint imposed on the evolution of visual pigments in the deep-sea.     

The visual pigments of four deep-sea crustacean species

Summary The visual pigments of four mesopelagic crustacean species were studied at sea by means of microspectrophotometry. The absorbance maxima obtained for the visual pigments and their metarhodopsins, respectively, were: 493 nm and 481 nm (Systellaspis debilis), 485 nm and 480 nm (Acanthephyra curtirostris), 491 nm and 482 nm (A. smithi), and 495 nm and 487 nm (Sergestes tenuiremis). The spectral characteristics of the rhodopsins and metarhodopsins permit high photosensitivity and facilitate photoregeneration in a nearly monochromatic environment. Photic regeneration of rhodopsins from the deep-sea environment was demonstrated, and data were obtained which are consistent with the occurrence of dark regeneration. Specific optical density of the observed visual pigments was calculated for two species.     

The cone photoreceptors and visual pigments of chameleons

Visual pigments, oil droplets and photoreceptor types in the retinas of four species of true chameleons have been examined by microspectrophotometry. The species occupy different photic environments: two species of Chamaeleo are from Madagascar and two species of Furcifer are from Africa and the Arabian Peninsula. In addition to double cones, four spectrally distinct classes of single cone were identified. No rod photoreceptors were observed. The visual pigments appear to be mixtures of rhodopsins and porphyropsins. Double cones contained a pale oil droplet in the principle member and both outer segments contained a long-wave-sensitive visual pigment with a spectral maximum between about 555 nm and 610 nm, depending on the rhodopsin/porphyropsin mixture. Long-wave-sensitive single cones contained a visual pigment spectrally identical to the double cones, but combined with a yellow oil droplet. The other three classes of single cone contained visual pigments with maxima at about 480–505, 440–450 and 375–385 nm, combined with yellow, clear and transparent oil droplets respectively. The latter two classes were sparsely distributed. The transmission of the lens and cornea of C. dilepis was measured and found to be transparent throughout the visible and near ultraviolet, with a cut off at about 350 nm.     

Purification of cone visual pigments from chicken retina

A novel method for purification of chicken cone visual pigments was established by use of a 3-[(3-cholamidopropyl)dimethylammonio]-1- propanesulfonate-phosphatidylcholine (CHAPS-PC) mixture. Outer segment membranes isolated from chicken retinas were extracted with 0.75% CHAPS supplemented with 1.0 mg/mL phosphatidylcholine (CHAPS-PC system). After the extract was diluted to 0.6% CHAPS, it was loaded on a concanavalin A-Sepharose column. Elution from the column with different concentrations of methyl alpha-mannoside yielded three fractions: the first was composed of chicken violet, blue, and red in roughly equal amounts, the second predominantly contained chicken red, and the third was rhodopsin with a small amount of chicken green, which was separated from rhodopsin by DEAE-Sepharose column chromatography. Since CHAPS has little absorbance at both ultraviolet and visible regions, we could demonstrate the absolute absorption spectra of chicken red (92%) and rhodopsin (greater than 96%) in these regions. The maximum of the difference spectrum between either chicken red or rhodopsin and its photoproduct (all-trans-retinal oxime plus opsin) was determined to be 571 or 503 nm, respectively. Although chicken green was contaminated with a small amount of rhodopsin having a similar spectral shape, the maximum of its difference spectrum was located at 508 nm by taking advantage of the difference in susceptibility against hydroxylamine between these pigments. Although chicken blue and chicken violet were minor pigments present in the first fraction from the concanavalin A column, their maxima in the difference spectra were determined to be at 455 and 425 nm, respectively, by a partial bleaching method.(ABSTRACT TRUNCATED AT 250 WORDS)