Comparison between Different Types of Sensors Used in the Real Operational Environment Based on Optical Scanning System.

The present paper describes the experimentation in a controlled environment and a real environment using different photosensors, such as infrared light emitting diode (IRLED-as receiver), photodiode, light dependent resistor (LDR), and blue LED for the purpose of selecting those devices, which can be employed in adverse conditions, such as sunlight or artificial sources. The experiments that are described in this paper confirmed that the blue LED and phototransistor could be used as a photosensor of an Optical Scanning System (OSS), because they were less sensitive to sunlight radiation. Moreover, they are appropriate as reference sources that are selected for the experiment (blue LED flashlight and light bulb). The best experimental results that were obtained contained a digital filter that was applied to the output of the photosensor, which reduced the standard deviation for the best case for the phototransistor LED from 100.26 to 0.15. For the best case, using the blue LED, the standard deviation was reduced from 86.08 to 0.11. Using these types of devices the cost of the Optical Scanning System can be reduced and a considerable increase in resolution and accuracy.

Light effects on the multicellular magnetotactic prokaryote 'Candidatus Magnetoglobus multicellularis' are cancelled by radiofrequency fields: the involvement of radical pair mechanisms.

'Candidatus Magnetoglobus multicellularis' is the most studied multicellular magnetotactic prokaryote. It presents a light-dependent photokinesis: green light decreases the translation velocity whereas red light increases it, in comparison to blue and white light. The present article shows that radio-frequency electromagnetic fields cancel the light effect on photokinesis. The frequency to cancel the light effect corresponds to the Zeeman resonance frequency (DC magnetic field of 4 Oe and radio-frequency of 11.5 MHz), indicating the involvement of a radical pair mechanism. An analysis of the orientation angle relative to the magnetic field direction shows that radio-frequency electromagnetic fields disturb the swimming orientation when the microorganisms are illuminated with red light. The analysis also shows that at low magnetic fields (1.6 Oe) the swimming orientation angles are well scattered around the magnetic field direction, showing that magnetotaxis is not efficiently in the swimming orientation to the geomagnetic field. The results do not support cryptochrome as being the responsible chromophore for the radical pair mechanism and perhaps two different chromophores are necessary to explain the radio-frequency effects.

Insulin-related signaling pathways elicited by light in photoreceptor nuclei from bovine retina.

Retina light stimulation triggers phototransduction events as well as different signaling mechanisms in outer segments (sensorial portion) of photoreceptor cells. We have recently reported a novel light-dependent activation of diacylglycerol kinase (DAGK) and protein kinase C (PKC) at the nuclear level of photoreceptor cells. The aim of the present study was to analyze whether ex-vivo light exposure of bovine retinas also modulates insulin-related signaling pathways in nuclei from photoreceptor cells. To this end, a nuclear fraction enriched in small nuclei from photoreceptor cells (PNF) was obtained using a modified nuclear isolation protocol. In PNF obtained from bovine retinas exposed to light or darkness, the presence of insulin receptor (IR) and phosphorylated insulin receptor (pIR), the activation of Akt, p38 and extracellular signal-regulated kinase (ERK1/2) and the local action of insulin on lipid kinases were studied. Immunofluorescence (IF) and Western blot (WB) studies revealed the presence of IR in photoreceptor nuclei. In PNF a light-dependent increase in IR total content was observed. The presence of activated IR (pIR) was also observed in PNF by WB, being its content higher in PNF from light than in to darkness. Light exposure also produced a significant increase in the content of p-Akt (3 fold) and p-p38 (60%) without changes in total Akt and p38. In addition, an increase in the content of total ERK1/2 (2 fold) was found without changes in p-ERK/total ERK ratio, indicating that light induces translocation of p-ERK to the nucleus. Polyphosphoinositide kinase and diacylglycerol kinase (DAGK) activities were measured in isolated nuclei from light-activated or darkness-adapted retinas through the formation of polyphosphoinositides (PPIs) and phosphatidic acid (PA) using nuclear lipid substrates and [γ-(32)P]ATP as radioactive substrate. A light-dependent increase in PPIs and PA formation was detected when isolated nuclei were exposed to 0.8 µM insulin plus 0.2 mM vanadate. WB studies revealed that retina's exposure to insulin under light condition increased nuclear IR content. In addition, PNF exposure to insulin increased ERK1/2 phosphorylation with no changes in total ERK1/2. Our results demonstrate the presence and the functional state of IR in the nucleus from photoreceptor cells. They also show that molecular signaling components linked to tyrosine kinase receptors and MAPK pathways, such as Akt and ERK1/2, respectively, are present in photoreceptor nuclei and are regulated by insulin and light.

A novel light-dependent activation of DAGK and PKC in bovine photoreceptor nuclei.

In this work, we describe a selective light-dependent distribution of the lipid kinase 1,2-diacylglycerol kinase (EC 2.7.1.107, DAGK) and the phosphorylated protein kinase C alpha (pPKCα) in a nuclear fraction of photoreceptor cells from bovine retinas. A nuclear fraction enriched in small nuclei from photoreceptor cells (PNF), was obtained when a modified nuclear isolation protocol developed by our laboratory was used. We measured and compared DAGK activity as phosphatidic acid (PA) formation in PNF obtained from retinas exposed to light and in retinas kept in darkness using [γ-(32)P]ATP or [(3)H]DAG. In the absence of exogenous substrates and detergents, no changes in DAGK activity were observed. However, when DAGK activity assays were performed in the presence of exogenous substrates, such as stearoyl arachidonoyl glycerol (SAG) or dioleoyl glycerol (DOG), and different detergents (used to make different DAGK isoforms evident), we observed significant light effects on DAGK activity, suggesting the presence of several DAGK isoforms in PNF. Under conditions favoring DAGKζ activity (DOG, Triton X-100, dioleoyl phosphatidylserine and R59022) we observed an increase in PA formation in PNF from retinas exposed to light with respect to those exposed to darkness. In contrast, under conditions favoring DAGKɛ (SAG, octylglucoside and R59022) we observed a decrease in its activity. These results suggest different physiological roles of the above-mentioned DAGK isoforms. Western blot analysis showed that whereas light stimulation of bovine retinas increases DAGKζ nuclear content, it decreases DAGKɛ and DAGKß content in PNF. The role of PIP2-phospholipase C in light-stimulated DAGK activity was demonstrated using U73122. Light was also observed to induce enhanced pPKCα content in PNF. The selective distribution of DAGKζ and ɛ in PNF could be a light-dependent mechanism that in vertebrate retina promotes selective DAG removal and PKC regulation.