Reverse-engineering the locomotion of a stem amniote

Reconstructing the locomotion of extinct vertebrates offers insights into their palaeobiology and helps to conceptualize major transitions in vertebrate evolution. However, estimating the locomotor behaviour of a fossil species remains a challenge because of the limited information preserved and the lack of a direct correspondence between form and function. The evolution of advanced locomotion on land—that is, locomotion that is more erect, balanced and mechanically power-saving than is assumed of anamniote early tetrapods—has previously been linked to the terrestrialization and diversification of amniote lineages. To our knowledge, no reconstructions of the locomotor characteristics of stem amniotes based on multiple quantitative methods have previously been attempted: previous methods have relied on anatomical features alone, ambiguous locomotor information preserved in ichnofossils or unspecific modelling of locomotor dynamics. Here we quantitatively examine plausible gaits of the stem amniote Orobates pabsti, a species that is known from a complete body fossil preserved in association with trackways8. We reconstruct likely gaits that match the footprints, and investigate whether Orobates exhibited locomotor characteristics that have previously been linked to the diversification of crown amniotes. Our integrative methodology uses constraints derived from biomechanically relevant metrics, which also apply to extant tetrapods. The framework uses in vivo assessment of locomotor mechanics in four extant species to guide an anatomically informed kinematic simulation of Orobates, as well as dynamic simulations and robotics to filter the parameter space for plausible gaits. The approach was validated using two extant species that have different morphologies, gaits and footprints. Our metrics indicate that Orobates exhibited more advanced locomotion than has previously been assumed for earlier tetrapods, which suggests that advanced terrestrial locomotion preceded the diversification of crown amniotes. We provide an accompanying website for the exploration of the filters that constrain our simulations, which will allow revision of our approach using new data, assumptions or methods

From cineradiography to biorobots: an approach for designing robots to emulate and study animal locomotion

Robots are increasingly used as scientific tools to investigate animal locomotion. However, designing a robot that properly emulates the kinematic and dynamic properties of an animal is difficult because of the complexity of musculoskeletal systems and the limitations of current robotics technology. Here we propose a design process that combines high-speed cineradiography, optimization, dynamic scaling, 3D printing, high-end servomotors, and a tailored dry-suit to construct Pleurobot: a salamander-like robot that closely mimics its biological counterpart, Pleurodeles waltl. Our previous robots helped us test and confirm hypotheses on the interaction between the locomotor neuronal networks of the limbs and the spine to generate basic swimming and walking gaits. With Pleurobot, we demonstrate a design process that will enable studies of richer motor skills in salamanders. In particular, we are interested in how these richer motor skills can be obtained by extending our spinal cord models with the addition of more descending pathways and more detailed limb central pattern generators (CPG) networks. Pleurobot is a dynamically-scaled amphibious salamander robot with a large number of actuated degrees of freedom (27 in total). Because of our design process, the robot can capture most of the animal’s degrees of freedom and range of motion, especially at the limbs. We demonstrate the robot’s abilities by imposing raw kinematic data, extracted from X-ray videos, to the robot’s joints for basic locomotor behaviors in water and on land. The robot closely matches the behavior of the animal in terms of relative forward speeds and lateral displacements. Ground reaction forces during walking also resemble those of the animal. Based on our results we anticipate that future studies on richer motor skills in salamanders will highly benefit from Pleurobot’s design

Trackways Produced by Lungfish During Terrestrial Locomotion

Some primarily aquatic vertebrates make brief forays onto land, creating traces as they do. A lack of studies on aquatic trackmakers raises the possibility that such traces may be ignored or misidentified in the fossil record. Several terrestrial Actinopterygian and Sarcopterygian species have previously been proposed as possible models for ancestral tetrapod locomotion, despite extant fishes being quite distinct from Devonian fishes, both morphologically and phylogenetically. Although locomotion has been well-studied in some of these taxa, trackway production has not. We recorded terrestrial locomotion of a 35 cm African lungfish (Protopterus annectens; Dipnoi: Sarcopterygii) on compliant sediment. Terrestrial movement in the lungfish is accomplished by planting the head and then pivoting the trunk. Impressions are formed where the head impacts the substrate, while the body and fins produce few traces. The head leaves a series of alternating left-right impressions, where each impact can appear as two separate semi-circular impressions created by the upper and lower jaws, bearing some similarity to fossil traces interpreted as footprints. Further studies of trackways of extant terrestrial fishes are necessary to understand the behavioural repertoire that may be represented in the fossil track record

Relationship between antibodies to hepatitis C virus core+1 protein and treatment outcome

Background It has been suggested that hepatitis C virus (HCV) core+1 protein plays a crucial role in the viral life cycle, potentially affecting liver cirrhosis and the development of hepatocellular carcinoma. Methods To investigate its relationship with the outcome of HCV standard combination therapy with peginterferon-α plus ribavirin, we screened 139 consecutive HCV patients (119 with chronic HCV infection and 20 who spontaneously cleared HCV) for the presence of anti-core+1 antibodies (Abs). In addition, liver fibrosis was determined by FibroScan in all but one patients. Results Twenty-nine patients were cirrhotic (stiffness >12.5 kPa, F4 METAVIR), all of them with mild liver cirrhosis (Child-Pugh score A). Eighty-six of 139 patients were treatment-experienced with standard combination therapy. Fifty of them had achieved a sustained virological response, while 36 were non-responders. The prevalence of anti-core+1 Abs in patients with chronic HCV infection was 22.69% (27/119 patients): 18% (9/50 patients) in responders and 36.11% (13/36 patients) in non-responders (P=0.050). Five (17.24%) of the 29 cirrhotic patients and 22 (24.72%) of the 89 non-cirrhotic patients were positive for anti-core+1 Abs (P=0.405). Furthermore, the presence of anti-core+1 Abs correlated with the poor response interleukin (IL) 28B genotype TT (P=0.040). No correlation between spontaneous clearance and anti-core+1 Abs was observed (P=0.088). Conclusion The presence of anti-core+1 Abs might be correlated with the poor response IL28B TT genotype and may negatively affect the outcome of standard combination treatments in HCV patients, suggesting that core+1 may play a biological role in the course of HCV infection

Intergenotypic 2k/1b hepatitis C virus recombinants in the east macedonia and thrace region of Greece

Background Intergenotypic recombinant hepatitis C virus (HCV) strains emerge rarely during coinfection of the same individual with two HCV genotypes. Few recombinant HCV strains have been identified to date and only one, CRF01 2k/1b, has become a worldwide concern. This study reevaluated the genotyping of three HCV genotype 2 strains from a group of patients with an unusually low rate of sustained virological response after pegylated interferon/ribavirin treatment. In addition, genetic determinants of host interferon resistance were evaluated. Methods The HCV type 2 strains from the patients’ serum were subjected to partial sequencing of the core-E1, NS2, NS5A and NS5B regions by reverse transcription polymerase chain reaction. Furthermore, the IFNL3 rs12979860 and the IFNL4 rs368234815 single nucleotide polymorphisms were defined in two of the three patients. Results All three strains were phylogenetically related to the Russia-derived CRF01 2k/1b while they encompassed the exact same 2k/1b junction site within NS2. Conclusion This is the first report of HCV 2k/1b recombinants in Greece and the greater area of the Balkans

Chlorochlamys loop-like locomotion: combining crawling and climbing robotics

Summarization: Robotic prototypes for search and rescue operations tend to imitate crawling and swimming organisms such as snakes, salamanders, worms, and eels. The Chlorochlamys Chloroleucaria larvae move themselves by a unique form of loop-like body changes stabilized by their subterminal grasping tools; we call this kind of motion loop-like locomotion. By combining undulatory locomotion with loop-like locomotion, robotic prototypes may improve their efficiency and flexibility in moving through unstructured environments, while the climbing gaits may step up their gait repertoire. In our research we study the feasibility of robotic loop-like locomotion and we build robotic prototypes with the above capabilities. We model the Chlorochlamys Chloroleucaria as a multi-segment manipulator with grippers at both ends and we study the motion planning problem for loop-like locomotion under physical and environmental constraints. Extensive experimental studies demonstrate the feasibility and show the effectiveness of the proposed approach. Our robotic prototype is proposed as a testbed for realizing loop-like locomotion in the real world.Παρουσιάστηκε στο: 2007 IEEE International Conference on Robotics and Biomimetic

A main event and multiple introductions of SARS-CoV-2 initiated the COVID-19 epidemic in Greece

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a novel coronavirus responsible for the coronavirus disease 2019 (COVID-19) pandemic. Chains of infections starting from various countries worldwide seeded the outbreak of COVID-19 in Athens, capital city of Greece. A full-genome analysis of isolates from Athens' hospitals and other healthcare providers revealed the variety of SARS-CoV-2 that initiated the pandemic before lockdown and passenger flight restrictions. A dominant variant, encompassing the G614D amino acid substitution, spread through a major virus dispersal event, and sporadic introductions of rare variants characterized the local initiation of the epidemic. Mutations within the genome highlighted the genetic drift of the virus as rare variants emerged. An important variant contained a premature stop codon in orf7a leading to the truncation of a possibly important for viral pathogenesis domain. This study may serve as a reference for resolving future lines of infection in the area, especially after resumption of passenger flight connections to Athens and Greece during summer of 2020. © 2021 Wiley Periodicals LL