Retinal Topographic Maps: A Glimpse into the Animals’ Visual World

The vertebrates’ retina has a highly conserved laminar organization of 10 alternating nuclear and plexiform layers. Species differences in the retinal specializations, i.e., areas of higher cell density, among the species, represent specific regions of the visual field of higher importance for a better spatial resolution and indicate distinct evolutionary pressures on the structures of the visual system, which can be related to many aspects of the species evolutionary history. In this chapter, we analyzed the density and distribution of cells of the retinal ganglion cell layer (GCL) and estimated the upper limits of the spatial resolving power of 12 species of snakes from the Colubridae family, 6 diurnal and 6 nocturnal, which inhabit different habitats. Our results revealed lower visual acuity in nocturnal species, compared to diurnal, and we observed different types of retinal specialization, horizontal streak, area centralis, or scattered distribution, with higher cell density in different retinal regions, depending on the species. These variations may be related to ecological and behavioral features, such as daily activity pattern, habitat, and substrate preferentially occupied, hunting strategies and diet. This comparative study indicates the complexity of the adaptive strategies of the snakes’ visual system

Biparental origin of the chromosome set is required for a developing human being

Conception sometimes results in products that are not capable of developing into an embryo and fetus. This group, designated with the term gestational trophoblastic neoplasia, comprises the benign hydatidiform mole, the invasive mole (chorioadenoma destruens) and the frankly malignant variety, choriocarcinoma. Another type of atypical oocyte activation occurs in parthenogenesis. In the human, two types of tumors, dermoid cysts and teratomas, can result from this process. The authors of this paper aim to elucidate the mechanisms how these abnormal growths ensue and provide explanations why they cannot be regarded as human individuals or human beings. They conclude that it is not the exact number of chromosomes that is required for a form of human life to become a human being but rather the biparental origin of the chromosome set

Cycle scheduling for in vitro fertilization with oral contraceptive pills versus oral estradiol valerate: a randomized, controlled trial

BACKGROUND: Both oral contraceptive pills (OCPs) and estradiol (E(2)) valerate have been used to schedule gonadotropin-releasing hormone (GnRH) antagonist in vitro fertilization (IVF) cycles and, consequently, laboratory activities. However, there are no studies comparing treatment outcomes directly between these two pretreatment methods. This randomized controlled trial was aimed at finding differences in ongoing pregnancy rates between GnRH antagonist IVF cycles scheduled with OCPs or E(2) valerate. METHODS: Between January and May 2012, one hundred consecutive patients (nonobese, regularly cycling women 18–38 years with normal day 3 hormone levels and <3 previous IVF/ICSI attempts) undergoing IVF with the GnRH antagonist protocol were randomized to either the OCP or E(2) pretreatment arms, with no restrictions such as blocking or stratification. Authors involved in data collection and analysis were blinded to group assignment. Fifty patients received OCP (30 μg ethinyl E(2)/150 μg levonorgestrel) for 12–16 days from day 1 or 2, and stimulation was started 5 days after stopping OCP. Similarly, 50 patients received 4 mg/day oral E(2) valerate from day 20 for 5–12 days, until the day before starting stimulation. RESULTS: Pretreatment with OCP (mean±SD, 14.5±1.7 days) was significantly longer than with E(2) (7.8±1.9 days). Stimulation and embryological characteristics were similar. Ongoing pregnancy rates (46.0% vs. 44.0%; risk difference, –2.0% [95% CI –21.2% to 17.3%]), as well as implantation (43.5% vs. 47.4%), clinical pregnancy (50.0% vs. 48.0%), clinical miscarriage (7.1% vs. 7.7%), and live birth (42.0% vs. 40.0%) rates were comparable between groups. CONCLUSIONS: This is the first study to directly compare these two methods of cycle scheduling in GnRH antagonist cycles. Our results fail to show statistically significant differences in ongoing pregnancy rates between pretreatment with OCP and E(2) for IVF with the GnRH antagonist protocol. Although the study is limited by its sample size, our results may contribute to a future meta-analysis. An interesting future direction would be to extend our study to women with decreased ovarian reserve, as these are the patients in whom an increase in oocyte yield—due to the hypothetical beneficial effect of steroid pretreatment on follicular synchronization—could more easily be demonstrated. TRIAL REGISTRATION: ClinicalTrials.gov http://NCT01501448

Factors associated with failed treatment : an analysis of 121,744 women embarking on their first IVF cycles

Peer reviewedPublisher PD

Simultaneous expression of UV and violet SWS1 opsins expands the visual palette in a group of freshwater snakes

Snakes are known to express a rod visual opsin and two cone opsins, only (SWS1, LWS), a reduced palette resulting from their supposedly fossorial origins. Dipsadid snakes in the genus Helicops are highly visual predators that successfully invaded freshwater habitats from ancestral terrestrial-only habitats. Here we report the first case of multiple SWS1 visual pigments in a vertebrate, simultaneously expressed in different photoreceptors and conferring both UV and violet sensitivity to Helicops snakes. Molecular analysis and in vitro expression confirmed the presence of two functional SWS1 opsins, likely the result of recent gene duplication. Evolutionary analyses indicate that each sws1 variant has undergone different evolutionary paths, with strong purifying selection acting on the UV-sensitive copy and dN/dS ∼1 on the violet-sensitive copy. Site-directed mutagenesis points to the functional role of a single amino acid substitution, Phe86Val, in the large spectral shift between UV and violet opsins. In addition, higher densities of photoreceptors and SWS1 cones in the ventral retina suggest improved acuity in the upper visual field possibly correlated with visually-guided behaviors. The expanded visual opsin repertoire and specialized retinal architecture are likely to improve photon uptake in underwater and terrestrial environments, and provide the neural substrate for a gain in chromatic discrimination, potentially conferring unique color vision in the UV-violet range. Our findings highlight the innovative solutions undertaken by a highly specialized lineage to tackle the challenges imposed by the invasion of novel photic environments and the extraordinary diversity of evolutionary trajectories taken by visual opsin-based perception in vertebrates

The glycoprotein-hormones activin A and inhibin A interfere with dendritic cell maturation

<p>Abstract</p> <p>Background</p> <p>Pregnancy represents an exclusive situation in which the immune and the endocrine system cooperate to prevent rejection of the embryo by the maternal immune system. While immature dendritic cells (iDC) in the early pregnancy decidua presumably contribute to the establishment of peripheral tolerance, glycoprotein-hormones of the transforming growth factor beta (TGF-beta) family including activin A (ActA) and inhibin A (InA) are candidates that could direct the differentiation of DCs into a tolerance-inducing phenotype.</p> <p>Methods</p> <p>To test this hypothesis we generated iDCs from peripheral-blood-monocytes and exposed them to TGF-beta1, ActA, as well as InA and Dexamethasone (Dex) as controls.</p> <p>Results</p> <p>Both glycoprotein-hormones prevented up-regulation of HLA-DR during cytokine-induced DC maturation similar to Dex but did not influence the expression of CD 40, CD 83 and CD 86. Visualization of the F-actin cytoskeleton confirmed that the DCs retained a partially immature phenotype under these conditions. The T-cell stimulatory capacity of DCs was reduced after ActA and InA exposure while the secretion of cytokines and chemokines was unaffected.</p> <p>Conclusion</p> <p>These findings suggest that ActA and InA interfere with selected aspects of DC maturation and may thereby help preventing activation of allogenic T-cells by the embryo. Thus, we have identified two novel members of the TGF-beta superfamily that could promote the generation of tolerance-inducing DCs.</p

Effect of the Decrease in Luminance Noise Range on Color Discrimination of Dichromats and Trichromats

Color vision assessment can be done using pseudoisochromatic stimuli, which has a luminance noise to eliminate brightness differences between the target and background of the stimulus. It is not clear the influence of the luminance noise on color discrimination. We investigated the effect of change in the luminance noise limits on color discrimination. Eighteen trichromats and ten congenital dichromats (eight protans, two deutans) had their color vision evaluated by the Cambridge Colour Test, and were genetically tested for diagnostic confirmation. The stimuli were composed of a mosaic of circles in a 5° circular field. A subset of the circles differed in chromaticity from the remaining field, forming a letter C. Color discrimination was estimated in stimulus conditions differing in luminance noise range: (i) 6–20 cd/m2; (ii) 8–18 cd/m2; (iii) 10–16 cd/m2; and (iv) 12–14 cd/m2. Six equidistant luminance values were used within the luminance noise limits with the mean stimulus luminance maintained constant under all conditions. A four-alternative, forced-choice method was applied to feed a staircase procedure to estimate color discrimination thresholds along eight chromatic axes. An ellipse model was adjusted to the eight color discrimination thresholds. The parameters of performance were threshold vector lengths and the ellipse area. Results were compared using the Kruskal-Wallis test with a significance level of 5%. The linear function model was applied to analyze the dependence of the discrimination parameters on the noise luminance limits. The first derivative of linear function was used as an indicator of the rate of change in color discrimination as a function of luminance noise changes. The rate of change of the ellipse area as a function of the luminance range in dichromats was higher than in trichromats (p &lt; 0.05). Significant difference was also found for individual thresholds in half of the axes we tested. Luminance noise had a greater effect on color discrimination ability of dichromats than the trichromats, especially when the chromaticities were close to their protan and deutan color confusion lines

Spectral diversification and trans-species allelic polymorphism during the land-to-sea transition in snakes

Snakes are descended from highly visual lizards [1] , but have limited (probably dichromatic) colour vision attributed to a dim-light lifestyle of early snake ancestors [2–4]. The living species of front-fanged elapids, however, are ecologically very diverse, with ~300 terrestrial species (cobras, taipans, etc.) and ~60 fully marine sea snakes, plus eight independently marine, amphibious sea kraits [1]. Here, we investigate the evolution of spectral sensitivity in elapids by analyzing their opsin genes (which are responsible for sensitivity to UV and visible light), retinal photoreceptors, and ocular lenses. We found that sea snakes underwent rapid adaptive diversification of their visual pigments when compared with their terrestrial and amphibious relatives. The three opsins present in snakes (SWS1, LWS, RH1) have evolved under positive selection in elapids, and in sea snakes have undergone multiple shifts in spectral sensitivity towards the longer wavelengths that dominate below the sea surface. Several distantly related Hydrophis sea snakes are polymorphic for shortwave sensitive visual pigment encoded by alleles of SWS1. This spectral site polymorphism is expected to confer expanded ‘UV-Blue’ spectral sensitivity and is estimated to have persisted twice as long as the predicted survival time for selectively neutral nuclear alleles. We suggest that this polymorphism is adaptively maintained across Hydrophis species via balancing selection, similarly to the LWS polymorphism that confers allelic trichromacy in some primates. Diving sea snakes thus appear to share parallel mechanisms of color vision diversification with fruit-eating primates