From Spheroids to Organoids: The Next Generation of Model Systems of Human Cardiac Regeneration in a Dish

Organoids are tiny, self-organized, three-dimensional tissue cultures that are derived from the differentiation of stem cells. The growing interest in the use of organoids arises from their ability to mimic the biology and physiology of specific tissue structures in vitro. Organoids indeed represent promising systems for the in vitro modeling of tissue morphogenesis and organogenesis, regenerative medicine and tissue engineering, drug therapy testing, toxicology screening, and disease modeling. Although 2D cell cultures have been used for more than 50 years, even for their simplicity and low-cost maintenance, recent years have witnessed a steep rise in the availability of organoid model systems. Exploiting the ability of cells to re-aggregate and reconstruct the original architecture of an organ makes it possible to overcome many limitations of 2D cell culture systems. In vitro replication of the cellular micro-environment of a specific tissue leads to reproducing the molecular, biochemical, and biomechanical mechanisms that directly influence cell behavior and fate within that specific tissue. Lineage-specific self-organizing organoids have now been generated for many organs. Currently, growing cardiac organoid (cardioids) from pluripotent stem cells and cardiac stem/progenitor cells remains an open challenge due to the complexity of the spreading, differentiation, and migration of cardiac muscle and vascular layers. Here, we summarize the evolution of biological model systems from the generation of 2D spheroids to 3D organoids by focusing on the generation of cardioids based on the currently available laboratory technologies and outline their high potential for cardiovascular research.     

Preparation and thermal behavior of random poly(butylene terephthalate/azelate) copolyesters

Poly(butylene terephthalate), poly(butylene azelate), and poly(butylene terephthalate/butylene azelate) random copolymers of various compositions were synthesized in bulk using the well‐known two‐stage polycondensation procedure, and characterized in terms of chemical structure and molecular weight. The thermal behavior was examined by thermogravimetric analysis and differential scanning calorimetry. As far as the thermal stability is concerned, it was found to be rather similar for all copolymers and homopolymers investigated. All the copolymers were found to be partially crystalline, and the main effect of copolymerization was a lowering in the amount of crystallinity and a decrease of melting temperature with respect to pure homopolymers. Flory's equation was found to describe the T_m–composition data and permitted to calculate the melting temperatures (T^°_m ) and the heats of fusion (ΔH_u) of both the completely crystalline homopolymers. Owing to the high crystallization rate, the glass transition was observable only for the copolymers containing from 30 to 70 mol % of the terephthalate units; even though the samples cannot be frozen in a completely amorphous state, the data obtained confirmed that the introduction of the aromatic units gave rise to an increase of T_g, due to a chain stiffening. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 2694–2702, 1999     

Refractive effects in coherent anti-Stokes Raman scattering microscopy

Coherent anti-Stokes Raman scattering (CARS) microscopy with high sensitivity and high three- dimensional resolution has been developed for the vibrational imaging of chemical species. Due to the coherent nature of the CARS emission, it has been reported that the detection of epi-CARS and forward-CARS (F-CARS) signals depends on the size and shape of the sample. We investigate theoretically and experimentally the effects on the CARS signal of refractive index mismatches between the sample and its surroundings. Backward-CARS and F-CARS signals are measured for different polystyrene bead diameters embedded in different refractive index solvents. We show that index mismatches result in a backward-reflected F-CARS signal that generally dominates the experimentally backward-detected signal. Simulations based on geometrical and wave optics comparing forward- and backward-detected signals for polystyrene beads embedded in different index solvents confirm our findings. Furthermore, we demonstrate that the maxima of forward- and backward-detected signals are generated at different positions along the optical axis in the sample if refractive index mismatches are present between the sample and its surroundings.     

Staphylococcus aureus growth and enterotoxin production during the manufacture of uncooked, semihard cheese from cows' raw milk

Staphylococcus aureus growth and enterotoxin production during the manufacture of model Saint-Nectaire, Registered Designation of Origin Saint-Nectaire, and Registered Designation of Origin Salers cheeses, three types of uncooked, semihard, raw milk cheese, were investigated. Coagulase-positive staphylococci (SC+) grew rapidly during the first 6 h. Between 6 and 24 h, counts increased by less than 0.5 log CFU/ml. Raw milk counts ranged from undetectable (<10 CFU/ml) to 3.03 log CFU/ml. Maximal levels reached in cheese on day 1 ranged from 2.82 to 6.84 log CFU/g. The level of SC+ after 24 h was mainly influenced by the milk baseline SC+ level (correlation coefficient, r > 0.80) but pH at 6 h influenced the SC+ growth observed between 6 and 24 h (r > 0.70). Thus, the initial level of SC+ in raw milk should be maintained below 100 CFU/ml and best below 40 CFU/ml. To limit growth, acidification should be managed to obtain pH values around or below 5.8 at 6 h in Saint-Nectaire cheeses and around or below 6.3 at 6 h in Salers cheeses. Enterotoxins were only detected in two Salers cheeses whose SC+ counts on day 1 were 5.55 log CFU/g and 5.06 log CFU/g, respectively, and whose pH values at 6 h were high (approximately 6.6 and 6.5, respectively).     

Chloroplastic glycolipids fuel aldehyde biosynthesis in the marine diatom Thalassiosira rotula

Enzymatic preparations and specialized analytical tools have shown that chloroplast-derived glycolipids are the main substrates for the biosynthetic pathway that produces antiproliferative polyunsaturated aldehydes in broken cells of the marine diatom Thalassiosira rotula. This process, which is associated with the formation of free fatty acids and lyso compounds from polar lipids but not triglycerides, is largely dependent on glycolipid hydrolytic activity, rather than phospholipase A(2) as previously suggested. Preliminary characterization of lipolytic enzymes has revealed protein bands of 40-45 kDa. Under native conditions these proteins seem to be associated with soluble aggregates that have an apparent molecular weight of approximately 200 kDa. The biochemical process, which is similar to that described in the algal-bloom forming diatom Skeletonema costatum, suggests a mechanism based on decompartmentalization and mixing of preexisting enzymes and substrates.     

A comparative study of voltage controllers for series active power filter

The series active power filter seems an ideal device to improve power quality. It allows to suppress and isolate voltage based distortion such as voltage unbalance, sag, interruption and voltage harmonics. In this paper, the determination of voltage references for series active power filter based on a robust three Phase digital Locked Loop system is analysed. Different control strategies are evaluated. In first hand, performances of two linear regulators: a polynomial controller based on a pole placement theory (called RST controller) and a Proportional Integral Derivative (PID) controller are studied and compared, in order to compensate different voltage perturbations in network. In second hand, a novel hysteresis band voltage control for a series active power filter is proposed to derive the switching signals and to improve the power quality. The study was carried on simulation via software Matlab/Simulink.     

Reflectance reduction of InP wafers after high-temperature annealing

Broadband reduction of light reflection from the surface of InP wafers after high-temperature annealing in air has been observed. In the transparency region of the material, the reflection drop is accompanied by increasing transmission of light through the wafer. The spectral position of a deep minimum of the reflection coefficient can be tuned, by varying the temperature and the time of annealing, in a wide spectral range from ultraviolet to infrared. The effect is due to formation of thermal oxide layers on the surfaces of the wafer with optical parameters favorable for antireflection.     

Effect of blend composition in BisEH-PFDTBT:PC70BM solar cells

The photovoltaic properties of bulk-heterojunction solar cells with an active layer made of an alternating fluorene copolymer, poly{[2,7-(9,9-bis-(2-ethylhexyl)-fluorene)]-alt-[5,5-(4,7-di-2′-thienyl-2,1,3-benzothiadiazole)]}, and [6,6]-phenyl-C₇₁-butyric acid methylester are investigated by varying the blend composition and the incident light power intensity. An efficient donor-acceptor intermixing is reached with donor to acceptor weight ratios of at least 1:3, while at lower acceptor content charge trapping effects are evidenced by the light intensity dependent study. Reverse bias analysis demonstrates that a major limiting factor for the performance of the investigated solar cells is represented by the poor ability of the generation of free charge carriers, attributed to the low hole mobility in the polymer phase.     

The role of income in energy consumption behaviour: Evidence from French households data

The main purpose of this paper is to characterise quantitatively the impact of income on household energy consumption in the residential and transport sectors. Starting from the data collected in a paper survey, we analyse the extent of the constraint experienced by households in terms of equipment purchasing behaviour and daily energy consumption. This analysis shows that the least well-off households are particularly constrained since the share of their budget represented by these energy services is very large (15–25%), and this corresponds to a level of energy service well below that of the better-off households. The case of space-heating shows a factor of 2 in terms of level of comfort achieved between the extreme 10-percentiles. These households also face a strong capital constraint for equipment purchases. This leads either to a large increase in the required rate of return or to a reduction in the proportion of households that are prepared to replace their equipment earlier. The least well-off households are thus doubly constrained, since it is more difficult for them to invest. In our opinion, it is crucial to take into account this observation in the context of political measures aimed at reducing households’CO₂ emissions.