Echocardiographic analysis of a malfunctioning Davila-Sierra mitral valve

Although the Davila-Sierra mitral valve prosthesis was removed from the market nearly a decade ago, a number of patients still have this valve in place. We recently studied the echocardiographic features of a malfunctioning Davila-Sierra mitral valve prosthesis. Abnormalities that suggested improper functioning of the prosthesis included a markedly delayed poppet opening and an early diastolic hump believed to represent motion of the mitral annulus. Previously described echocardiographic indications of dys-function were not observed in our patient. We report the first known echocardiographic evaluation of a Davila-Sierra prosthesis.     

Evolutionary dynamics of SARS-CoV-2 circulating in Yogyakarta and Central Java,Indonesia: sequence analysis covering furin cleavage site (FCS) region of the spike protein

International Microbiology - Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a new virus responsible for the COVID-19 pandemic. The emergence of the new SARS-CoV-2 has been...     

Stable Vertical Takeoff of an Insect-Mimicking Flapping-Wing System Without Guide Implementing Inherent Pitching Stability

We briefly summarized how to design and fabricate an insect-mimicking flapping-wing system and demonstrate how to implement inherent pitching stability for stable vertical takeoff.The effect of relative locations of the Center of Gravity (CG) and the mean Aerodynamic Center (AC) on vertical flight was theoretically examined through static force balance consideration.We conducted a series of vertical takeoff tests in which the location of the mean AC was determined using an unsteady Blade Element Theory (BET) previously developed by the authors.Sequential images were captured during the takeoff tests using a high-speed camera.The results demonstrated that inherent pitching stability for vertical takeoff can be achieved by controlling the relative position between the CG and the mean AC of the flapping system.     

Comparative proteomics of Cannabis sativa plant tissues.

Comparative proteomics of leaves, flowers, and glands of Cannabis sativa have been used to identify specific tissue-expressed proteins. These tissues have significantly different levels of cannabinoids. Cannabinoids accumulate primarily in the glands but can also be found in flowers and leaves. Proteins extracted from glands, flowers, and leaves were separated using two-dimensional gel electrophoresis. Over 800 protein spots were reproducibly resolved in the two-dimensional gels from leaves and flowers. The patterns of the gels were different and little correlation among the proteins could be observed. Some proteins that were only expressed in flowers were chosen for identification by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and peptide mass fingerprint database searching. Flower and gland proteomes were also compared, with the finding that less then half of the proteins expressed in flowers were also expressed in glands. Some selected gland protein spots were identified: F1D9.26-unknown prot. (Arabidopsis thaliana), phospholipase D beta 1 isoform 1a (Gossypium hirsutum), and PG1 (Hordeum vulgare). Western blotting was employed to identify a polyketide synthase, an enzyme believed to be involved in cannabinoid biosynthesis, resulting in detection of a single protein.     

Three‐dimensional microscale modelling of CO2 transport and light propagation in tomato leaves enlightens photosynthesis

We present a combined three‐dimensional (3‐D) model of light propagation, CO₂ diffusion and photosynthesis in tomato (Solanum lycopersicum L.) leaves. The model incorporates a geometrical representation of the actual leaf microstructure that we obtained with synchrotron radiation X‐ray laminography, and was evaluated using measurements of gas exchange and leaf optical properties. The combination of the 3‐D microstructure of leaf tissue and chloroplast movement induced by changes in light intensity affects the simulated CO₂ transport within the leaf. The model predicts extensive reassimilation of CO₂ produced by respiration and photorespiration. Simulations also suggest that carbonic anhydrase could enhance photosynthesis at low CO₂ levels but had little impact on photosynthesis at high CO₂ levels. The model confirms that scaling of photosynthetic capacity with absorbed light would improve efficiency of CO₂ fixation in the leaf, especially at low light intensity.     

Large‐scale culture of a megakaryocytic progenitor cell line with a single‐use bioreactor system

The increasing application of regenerative medicine has generated a growing demand for stem cells and their derivatives. Single‐use bioreactors offer an attractive platform for stem cell expansion owing to their scalability for large‐scale production and feasibility of meeting clinical‐grade standards. The current work evaluated the capacity of a single‐use bioreactor system (1 L working volume) for expanding Meg01 cells, a megakaryocytic (MK) progenitor cell line. Oxygen supply was provided by surface aeration to minimize foaming and orbital shaking was used to promote oxygen transfer. Oxygen transfer rates (k_La) of shaking speeds 50, 100, and 125 rpm were estimated to be 0.39, 1.12, and 10.45 h^?1, respectively. Shaking speed was a critical factor for optimizing cell growth. At 50 rpm, Meg01 cells exhibited restricted growth due to insufficient mixing. A negative effect occurred when the shaking speed was increased to 125 rpm, likely caused by high hydrodynamic shear stress. The bioreactor culture achieved the highest growth profile when shaken at 100 rpm, achieving a total expansion rate up to 5.7‐fold with a total cell number of 1.2 ± 0.2 × 10⁹ cells L^?1. In addition, cells expanded using the bioreactor system could maintain their potency to differentiate following the MK lineage, as analyzed from specific surface protein and morphological similarity with the cells grown in the conventional culturing system. Our study reports the impact of operational variables such as shaking speed for growth profile and MK differentiation potential of a progenitor cell line in a single‐use bioreactor. © 2017 American Institute of Chemical Engineers Biotechnol. Prog., 34:362–369, 2018     

A Microscale Model for Combined CO2 Diffusion and Photosynthesis in Leaves

Transport of CO₂ in leaves was investigated by combining a 2-D, microscale CO₂ transport model with photosynthesis kinetics in wheat (Triticum aestivum L.) leaves. The biophysical microscale model for gas exchange featured an accurate geometric representation of the actual 2-D leaf tissue microstructure and accounted for diffusive mass exchange of CO_2. The resulting gas transport equations were coupled to the biochemical Farquhar-von Caemmerer-Berry model for photosynthesis. The combined model was evaluated using gas exchange and chlorophyll fluorescence measurements on wheat leaves. In general a good agreement between model predictions and measurements was obtained, but a discrepancy was observed for the mesophyll conductance at high CO₂ levels and low irradiance levels. This may indicate that some physiological processes related to photosynthesis are not incorporated in the model. The model provided detailed insight into the mechanisms of gas exchange and the effects of changes in ambient CO₂ concentration or photon flux density on stomatal and mesophyll conductance. It represents an important step forward to study CO₂ diffusion coupled to photosynthesis at the leaf tissue level, taking into account the leaf''s actual microstructure.     

A conserved tetrameric interaction of cry toxin helix α3 suggests a functional role for toxin oligomerization

Crystal (Cry) toxins are widely used for insect control, but their mechanism of toxicity is still uncertain. These toxins can form lytic pores in vitro, and water soluble tetrameric pre-pore intermediates have been reported. Even the precise oligomeric state of the toxin in membranes, trimeric or tetrameric, is still a debated issue. Based on previous reports, we have assumed that interactions between toxin monomers in solution are at least partly mediated by domain I, and we have analyzed in silico the homo-oligomerization tendencies of the domain I α-helices individually. Using many homologous sequences for each α-helix, our strategy allows selection of evolutionarily conserved interactions. These interactions appeared only in helices α3 and α5, but only α3 produced a suitably oriented or α-helical sample in lipid bilayers, forming homotetramers in C14-betaine, and allowing determination of its rotational orientation in lipid bilayers using site-specific infrared dichroism (SSID). The determined orientation in the tetrameric model is in agreement with only one of the evolutionarily conserved models. In addition mutation R99E, which was found to inhibit oligomerization experimentally, greatly destabilized the tetramer in molecular dynamic simulations. In this model, helix 3 is able to form inter-monomer interactions without significant rearrangements of domain I, which is compatible with the available crystal structure of Cry toxins in solution. The model presented here at least partially explains the reported tetrameric oligomerization of Cry toxins in solution and the inhibition of this oligomerization by a synthetic α3 peptide.