Angular sensitivity of blowfly photoreceptors: intracellular measurements and wave-optical predictions

The angular sensitivity of blowfly photoreceptors was measured in detail at wavelengths λ = 355, 494 and 588 nm. The measured curves often showed numerous sidebands, indicating the importance of diffraction by the facet lens. The shape of the angular sensitivity profile is dependent on wavelength. The main peak of the angular sensitivities at the shorter wavelengths was flattened. This phenomenon as well as the overall shape of the main peak can be quantitatively described by a wave-optical theory using realistic values for the optical parameters of the lens-photoreceptor system. At a constant response level of 6 mV (almost dark adapted), the visual acuity of the peripheral cells R1-6 is at longer wavelengths mainly diffraction limited, while at shorter wavelengths the visual acuity is limited by the waveguide properties of the rhabdomere. Closure of the pupil narrows the angular sensitivity profile at the shorter wavelengths. This effect can be fully described by assuming that the intracellular pupil progressively absorbs light from the higher order modes. In light-adapted cells R1-6 the visual acuity is mainly diffraction limited at all wavelengths.

Metarhodopsin control by arrestin, light-filtering screening pigments, and visual pigment turnover in invertebrate microvillar photoreceptors

The visual pigments of most invertebrate photoreceptors have two thermostable photo-interconvertible states, the ground state rhodopsin and photo-activated metarhodopsin, which triggers the phototransduction cascade until it binds arrestin. The ratio of the two states in photoequilibrium is determined by their absorbance spectra and the effective spectral distribution of illumination. Calculations indicate that metarhodopsin levels in fly photoreceptors are maintained below ~35% in normal diurnal environments, due to the combination of a blue-green rhodopsin, an orange-absorbing metarhodopsin and red transparent screening pigments. Slow metarhodopsin degradation and rhodopsin regeneration processes further subserve visual pigment maintenance. In most insect eyes, where the majority of photoreceptors have green-absorbing rhodopsins and blue-absorbing metarhodopsins, natural illuminants are predicted to create metarhodopsin levels greater than 60% at high intensities. However, fast metarhodopsin decay and rhodopsin regeneration also play an important role in controlling metarhodopsin in green receptors, resulting in a high rhodopsin content at low light intensities and a reduced overall visual pigment content in bright light. A simple model for the visual pigment–arrestin cycle is used to illustrate the dependence of the visual pigment population states on light intensity, arrestin levels and pigment turnover

Deployment of a stand-alone hybrid renewable energy system in coastal areas as a reliable energy source

Solar and wind can be considered as sustainable environmentally friendly and omnipresent renewable energy sources for generating a part of required electrical energy for inhabitants of the remote areas in different countries. Accordingly, this study investigates the techno-economic evaluation for two-hybrid renewable energy systems for Bandar Dayyer. The findings of this study shows that using the HOMER software, the total amount of electricity production by these systems are equal to 470,176¿kW, of which 22,409¿kW is provided by PV-generic system and 447,767¿kW is supplied by PV-diesel-generic system. It should be mentioned that this area has an appropriate potential of wind speed and solar radiation; therefore, the area can be suitable for investing on a hybrid renewable energy site.Postprint (author's final draft

MicroRNAs in retinoblastoma: Potential diagnostic and therapeutic biomarkers

Retinoblastoma (Rb) is known as one of important childhood malignancies which due to inactivation of the RB gene (tumor suppressor gene in various patients). The early detection of Rb could provide better treatment for Rb patients. Imaging techniques (e.g., MRI and CT) are known as one of effective diagnosis approaches for detection of patients with Rb. It has been shown that utilization of imaging techniques is associated with some limitations. Hence, identification of new diagnosis approaches might provide a better treatment for Rb patients. Identification of new biomarkers could contribute to better understanding of pathogenesis events involved in Rb and provide new insights into design better treatment approaches for these patients. Among the various biomarkers, microRNAs (miRNAs) have emerged as attractive tools for Rb detection. miRNAs are one classes of small non-coding RNAs which could be involved in a variety of biological process via targeting sequence of cellular and molecular pathways. Deregulations of these molecules are associated with cancerous condition. Multiple lines of evidence indicated that deregulation of various miRNAs involved in various stages of Rb. Here, we summarized a variety of tissue-specific and circulating miRNAs involved in Rb pathogenesis which could be used as diagnostic, prognostic, and therapeutic biomarkers in Rb patients. © 2017 Wiley Periodicals, Inc