Reptilian Heart Development And The Molecular Basis Of Cardiac Chamber Evolution

The emergence of terrestrial life witnessed the need for more sophisticated circulatory systems. This has evolved in birds, mammals and crocodilians into complete septation of the heart into left and right sides, allowing separate pulmonary and systemic circulatory systems, a key requirement for the evolution of endothermy(1-3). However, the evolution of the amniote heart is poorly understood. Reptilian hearts have been the subject of debate in the context of the evolution of cardiac septation: do they possess a single ventricular chamber or two incompletely septated ventricles(4-7)? Here we examine heart development in the red-eared slider turtle, Trachemys scripta elegans (a chelonian), and the green anole, Anolis carolinensis (a squamate), focusing on gene expression in the developing ventricles. Both reptiles initially form a ventricular chamber that homogenously expresses the T-box transcription factor gene Tbx5. In contrast, in birds and mammals, Tbx5 is restricted to left ventricle precursors(8,9). In later stages, Tbx5 expression in the turtle (but not anole) heart is gradually restricted to a distinct left ventricle, forming a left-right gradient. This suggests that Tbx5 expression was refined during evolution to pattern the ventricles. In support of this hypothesis, we show that loss of Tbx5 in the mouse ventricle results in a single chamber lacking distinct identity, indicating a requirement for Tbx5 in septation. Importantly, misexpression of Tbx5 throughout the developing myocardium to mimic the reptilian expression pattern also results in a single mispatterned ventricular chamber lacking septation. Thus ventricular septation is established by a steep and correctly positioned Tbx5 gradient. Our findings provide a molecular mechanism for the evolution of the amniote ventricle, and support the concept that altered expression of developmental regulators is a key mechanism of vertebrate evolution

Development of the Lacrimal Apparatus in the Rabbit (Oryctolagus cuniculus) and Its Potential Role as an Animal Model for Humans

Rabbits have been proposed as a model organism for the human lacrimal apparatus (LA), including the nasolacrimal duct (NLD), based principally on comparative studies of adult morphology; however, little is known about its development. The NLD first appears as an incomplete primordium in the subcutaneous region of the primordial eyelid and subsequently elongates to reach the naris. One posterior and three anterior orbital glands are present fetally although one of the anterior glands is soon lost. The NLD follows a tortuous path and passes through a bony canal consisting of lacrimal, maxilla, and maxilloturbinal bones at different regions. Although early developmental similarities exist to haplorhine primates, the narial opening of the NLD resembles strepsirrhines. This distinction, along with the ductal and glandular differences at the orbital end of the NLD, indicates that rabbits may be a poor model for LA drainage in primates, specifically humans

First description of a fossil chamaeleonid from Greece and its relevance for the European biogeographic history of the group

The fossil record of Chamaeleonidae is very scarce and any new specimen is therefore considered important for our understanding of the evolutionary and biogeographic history of the group. New specimens from the early Miocene of Aliveri (Evia Island), Greece constitute the only fossils of these lizards from southeastern Europe. Skull roofing material is tentatively attributed to the Czech species Chamaeleo cf. andrusovi, revealing a range extension for this taxon, whereas tooth-bearing elements are described as indeterminate chamaeleonids. The Aliveri fossils rank well among the oldest known reptiles from Greece, provide evidence for the dispersal routes of chameleons out of Africa towards the European continent and, additionally, imply strong affinities with coeval chamaeleonids from Central Europe

Designing and Building a Crew-Centric Mobile Scheduling and Planning Tool for Exploring Crew Autonomy Concepts Onboard the International Space Station

During 2015, as part of our ongoing research on crew autonomy, our team adapted and extended the plan viewing tool, Playbook, into a mobile tool for exploring crew autonomy onboard the International Space Station (ISS). This work enables crewmembers to intuitively re-plan and schedule on their own with limited input from mission control. Designed for ease of use, re-planning is composed of simple drag and drop interactions and learning the tool requires little to no training. Playbook was successfully uplinked onto ISS as a technology demonstration and completed its onboard ground and crew checkouts in August and September 2015, respectively. We will discuss and describe how Playbook was able to integrate with actual ISS operational plans and operational procedures without disrupting real mission operations. This work will also outline the design and technical constraints required to build a collaborative tool that allows multiple users to simultaneously self-schedule and synchronize during communication dropouts in the restricted networking and computing environment onboard ISS. Finally, we will explore the aspects of crew autonomy that this technology enables as well as discuss our next steps and possible extensions

Unveiling the Role of Guanidinium for Enhanced Charge Extraction in Inverted Perovskite Solar Cells

The incorporation of guanidinium (Gua) cations has significantly enhanced the optoelectronic properties of various perovskite compositions. When combined with other A-site cations in perovskite solar cells (PSCs), Gua cations not only enhance the power conversion efficiency of the solar cells but often improve their overall stability. While most studies examining the impact of Gua focus on PSCs with the n-i-p (conventional) structure, fewer have investigated its effects on the mechanism and performance of the p-i-n (inverted) structure. We investigate how partially substituting A-site cations with Gua affects the performance of PSCs and the associated charge carrier dynamics. Enhanced performance is observed in Gua-substituted inverted PSCs, primarily due to improved short-circuit current density and fill factor values. Our spectroscopic and microscopic analyses reveal that these enhancements stem from accelerated charge transport within the perovskite layer combined with inhibited ion migration following Gua incorporation, attributed to the reduction of localized inhomogeneities, which also notably enhance device stability. Our findings elucidate the role of Gua in inverted PSCs, showing negligible impact on open-circuit voltage but significant improvement in charge extraction efficiency. This contrasts with previous reports on conventional structures, where performance enhancement is primarily attributed to trap state reduction, resulting in higher open-circuit voltage

Chameleon radiation by oceanic dispersal

Historical biogeography is dominated by vicariance methods that search for a congruent pattern of fragmentation of ancestral distributions produced by shared Earth history(1-3). A focus of vicariant studies has been austral area relationships and the break-up of the supercontinent Gondwana(3-5). Chameleons are one of the few extant terrestrial vertebrates thought to have biogeographic patterns that are congruent with the Gondwanan break-up of Madagascar and Africa(6,7). Here we show, using molecular and morphological evidence for 52 chameleon taxa, support for a phylogeny and area cladogram that does not fit a simple vicariant history. Oceanic dispersal-not Gondwanan breakup-facilitated species radiation, and the most parsimonious biogeographic hypothesis supports a Madagascan origin for chameleons, with multiple 'out-of-Madagascar' dispersal events to Africa, the Seychelles, the Comoros archipelago, and possibly Reunion Island. Although dispersal is evident in other Indian Ocean terrestrial animal groups(8-16), our study finds substantial out-of-Madagascar species radiation, and further highlights the importance of oceanic dispersal as a potential precursor for speciation.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/62614/1/415784a.pd

Shaping Skeletal Growth by Modular Regulatory Elements in the Bmp5 Gene

Cartilage and bone are formed into a remarkable range of shapes and sizes that underlie many anatomical adaptations to different lifestyles in vertebrates. Although the morphological blueprints for individual cartilage and bony structures must somehow be encoded in the genome, we currently know little about the detailed genomic mechanisms that direct precise growth patterns for particular bones. We have carried out large-scale enhancer surveys to identify the regulatory architecture controlling developmental expression of the mouse Bmp5 gene, which encodes a secreted signaling molecule required for normal morphology of specific skeletal features. Although Bmp5 is expressed in many skeletal precursors, different enhancers control expression in individual bones. Remarkably, we show here that different enhancers also exist for highly restricted spatial subdomains along the surface of individual skeletal structures, including ribs and nasal cartilages. Transgenic, null, and regulatory mutations confirm that these anatomy-specific sequences are sufficient to trigger local changes in skeletal morphology and are required for establishing normal growth rates on separate bone surfaces. Our findings suggest that individual bones are composite structures whose detailed growth patterns are built from many smaller lineage and gene expression domains. Individual enhancers in BMP genes provide a genomic mechanism for controlling precise growth domains in particular cartilages and bones, making it possible to separately regulate skeletal anatomy at highly specific locations in the body

The differentiation within the genus Chamaeleo Laurenti, 1768

The main purpose of this study is to search for an explanation of the curious differentiation within the genus Chamaeleo. Since the species of this genus are rather doubtful units, I have studied the geograpical distribution of characters, not of the species, a method first used in botany (BAUR, ROTHMALER a.o.). I found that the number of characters is largest in east Afrika, gradually decreasing from this area to the periphery of the total range of the genus. East Africa proved to be still more important, as practically all the characters occur in it. This means that the chameleons in the other areas practically never possess characters that are not found in east Africa. This pattern of distribution fits in rather well with REINIG’S elimination theory (1938): „.. bei Einzelwanderungen wird nur ein Teil des gesamten Allelbestandes einer Art mitgeführt... eine durch Einzelwanderung entstandene Population weist eine geringere Zahl von Allelen auf als die Ausgangspopulation.” The existence of many parallel series of variation (meaning that several characters originated several times independently in different groups) led me to the conclusion that the mechanism described in REINIG’S theory as elimination, has consequences also for the genes predisposed to change into others. This reasoning gave a key to the reconstruction of the ancestral chameleon. By two different ways I arrived at the same conclusion, viz. the ancestral chameleon was probably an animal resembling mostly Chamaeleo chamaeleon s.l. (§ 21). As for this theoretical part of my study a survey of the species was needed, I first made an attempt at a natural system. I have divided the genus into groups of related species. For practical reasons the chameleons of Madagascar are treated separately. Their connections with the species of the African continent are examined in a special section (§ 11). As a result of my investigations I had to propose the following taxonomic changes: Ch. rhinoceratus var. lineatus + Ch. labordi + Ch. voeltzkowi + Ch. barbouri = Ch. rhinoceratus (§ 3), Ch. lambertoni = Ch. lateralis (§ 4), Ch. semicristatus = ♀ Ch. verrucosus (§ 5), Ch. guibei nov. spec. (§ 6), Ch. calcarifer = Ch. chamaeleon calcarifer, Ch. zeylanicus = Ch. chamaeleon zeylanicus, Ch. etiennei = Ch. gracilis etiennei (§ 12), Ch. anchietae vinkei + Ch. anchietae mertensi + Ch. marunguensis = Ch. anchietae (§ 13), Ch. unicornis = Ch. oweni unicornis (§ 14), Ch. pumilus = Ch. pumilus pumilus, Ch. melanocephalus = Ch. pumilus melanocephalus, Ch. gutturalis = Ch. pumilus gutturalis, Ch. ventralis = Ch. pumilus ventralis, Ch. ventralis occidentalis = Ch. pumilus occidentalis, Ch. ventralis karrooicus = Ch. pumilus karrooicus, Ch. damaranus = Ch. pumilus damaranus, Ch. caffer = Ch. pumilus caffer, Ch. taeniobronchus = Ch. pumilus taeniobronchus. (§ 16)