Changes in electrophysiological properties of photoreceptors in Periplaneta americana associated with the loss of screening pigment

Abstract Absence of screening pigment in insect compound eyes has been linked to visual dysfunction. We investigated how its loss in a white-eyed mutant (W-E) alters the photoreceptor electrophysiological properties, opsin gene expression, and the behavior of the cockroach, Periplaneta americana. Whole-cell patch-clamp recordings of green-sensitive photoreceptors in W-E cockroaches gave reduced membrane capacitance, absolute sensitivity to light, and light-induced currents. Decreased low-pass filtering increased voltage-bump amplitudes in W-E photoreceptors. Intracellular recordings showed that angular sensitivity of W-E photoreceptors had two distinct components: a large narrow component with the same acceptance angle as wild type, plus a relatively small wide component. Information processing was evaluated using Gaussian white-noise modulated light stimulation. In bright light, W-E photoreceptors demonstrated higher signal gain and signal power than wild-type photoreceptors. Expression levels of the primary UV- and green-sensitive opsins were lower and the secondary green-sensitive opsin significantly higher in W-E than in wild-type retinae. In behavioral experiments, W-E cockroaches were significantly less active in dim green light, consistent with the relatively low light sensitivity of their photoreceptors. Overall, these differences can be related to the loss of screening pigment function and to a compensatory decrease in the rhabdomere size in W-E retinae

Fetal weight normograms for singleton pregnancies in a Jordanian population

<b>Background and Objectives</b> : Estimated intrauterine fetal weight (EIUFW) is important for reducing prenatal mortality and morbidity through early detection of faltering growth. Our objectives were to develop patterns of ultrasonically determined EIUFW by gestational age, for normal singleton pregnancies, and to assess the effect of a number of variables on EIUFW. <b> Methods</b> : Ultrasonically, EIUFW was obtained from 600 pregnant women who were at 20 to 42 weeks of gestation (WG). EIUFW was categorized into low weight and normal weight using the tenth and twentieth percentile as the cut-off points. Logistic regression was used to calculate the odds ratio and their 95&#x0025; confidence limits for a number of risk factors hypothesized to be associated with low fetal weight. EIUFW percentiles (twenty-fifth, fiftieth, and seventy-fifth), by gestational age and sex, were calculated for singleton pregnancies. <b> Results</b> : Up to 32 WG there was no statistically significant difference between male and female fetuses in EIUFW. Between 32 and 39 WG males had significantly (<i>P</i>&#60; .05) higher fetal weight than females. Charts of ultrasonically determined EIUFW by gestational age and sex for singleton pregnancies were created. A number of variables were significantly associated with EIUFW such as pregnancy weight gain, maternal hemoglobin level, frequency of antenatal visits, smoking status, and fetal sex. <b>Conclusion</b> : Weight gain during pregnancy should be encouraged for pregnant mothers who gain less than one kilogram per month in the second and third trimester. A prospective study on a national representative sample in Jordan is needed to generate our own standards for fetal growth

Binocular mirror-symmetric microsaccadic sampling enables Drosophila hyperacute 3D-vision

Neural mechanisms behind stereopsis, which requires simultaneous disparity inputs from two eyes, have remained mysterious. Here we show how ultrafast mirror-symmetric photomechanical contractions in the frontal forward-facing left and right eye photoreceptors give Drosophila super-resolution 3D-vision. By interlinking multiscale in vivo assays with multiscale simulations, we reveal how these photoreceptor microsaccades - by verging, diverging and narrowing the eyes’ overlapping receptive fields - channel depth information, as phasic binocular image motion disparity signals in time. We further show how peripherally, outside stereopsis, microsaccadic sampling tracks a flying fly’s optic flow field to better resolve the world in motion. These results change our understanding of how insect compound eyes work and suggest a general dynamic stereo-information sampling strategy for animals, robots and sensors