The 20 winners of the 2022 "La preuve par l'image" (LPPI) competition

Glioblastoma is a brain tumour whose aggressive nature can be attributed to tumour stem cells. These cells, which are responsible for resistance to treatment, have the ability to form neurospheres and can enter neural differentiation pathways under certain culture conditions. Stem cells derived from human glioblastoma, clustered together in a neurosphere, can be seen in the image due to the labelling of the cell nuclei in blue. Through the action of growth factors, they adhere, migrate and…

Looking atthe living world, its shapes, materials and structures, can inspire the materials of tomorrow. Take this cuttlefish bone, whose unique features are revealed under the microscope. Its microstructure, arranged in layers, columns and undulations, gives it remarkable properties, such as a high degree of rigidity despite very low density – with porosity of around 93%. Rather than suddenly breaking when struck, cuttlefish bone, which is made up of the calcium carbonate mineral aragonite, is…

Choroid plexuses secrete the cerebrospinal fluid in which the brain is immersed. The cells that make them up form a barrier between the blood and the brain, preventing certain toxic molecules from entering it. The remarkable vascularisation of part of a choroid plexus, taken from a 9-day-old rat, can be seen here by means of green immunofluorescence. The researchers are investigating the ways in which immune cells can enter the brain in the event of infection, for example during childbirth…

The embryonic development of lymph nodes, small organs that are essential for the immune response, is now well understood. Using light-sheet microscopy, scientists were able to determinethe processes at work in this 13.5-day-old mouse embryo. Shown in blue are the lymphoid cells (LTi), derived from the haemogenic endothelium, a tissue specific to the embryo. They move into the liver where they multiply and then migrate to the rest of the body, where they give rise to the lymph nodes. The 3D…

This Cape fur seal has just given birth: the pink umbilical cord of her pup is still visible. She moves her baby by throwing it in the air in order to keep it away from other females in the colony, which might become very aggressive towards this little stranger if he came near them. A rather harsh, but necessary, start to life! The species forms huge, dense colonies in Namibia, where females give birth to a single pup that they nurse for 10 to 11 months. Throughout the lactation period, the…

In humans, Bethlem myopathy results from mutations in the gene encoding collagen VI, a component of the skeletal muscle extracellular matrix. This rare disease is characterised by muscle retractions and weakness, and a progressive worsening of symptoms, ranging from motor impairment to respiratory failure. The zebrafish is the only animal model that specifically reproduces one of the most common mutations found in patients. It is used to understand the functions of this collagen in the genesis…

Un plongeur scientifique prélève un tentacule sur des anémones blanchies par l’élévation de la température de l’océan à Moorea, en Polynésie. À quelques dixièmes de degrés près, le réchauffement provoque le blanchissement des coraux tropicaux et des anémones de mer : ils perdent les algues symbiotiques colorées, partenaires indispensables pour leur survie. Locataire de ces anémones, le poisson-clown en subit lui aussi les conséquences : vivre dans une anémone blanchie est un stress avec des…

How is it that small rocky planets such as Mercury or Ganymede, one of Jupiter’s moons, have a magnetic field? It could be due to to “snow” made up of flakes of iron. In the interior of these planets, the flakes, falling from the outer reaches of the liquid core to its centre, could cause turbulence that might potentially generate a magnetic field. To investigate this process, the researchers modelled iron snow in a tank of stratified salt water using glass beads – as fine as flour – to which…

The fact that a liquid rises in a capillary tube is well-known. This experiment attempts to take a fresh look at the phenomenon. For their laboratory bamboo grove, the scientists created a foam in a glass by bubbling air through a soap solution. Since the bubbles are at a higher pressure than the atmosphere, they readily rise up the glass tubes one by one, each forming a lamella. However, the more the bubbles accumulate, the slower each new one entering the tube goes up. The aim is to…

In both flies and humans, mortality increases with age. This is one of the possible definitions of “ageing”. However, the nature of this phenomenon, as well as its molecular or evolutionary origins, are still the subject of much debate. Both these female "Drosophila melanogaster" have the same chronological age and genotype. However, the life expectancy of the fly on the right is around three days, as compared to over twenty days for the one on the left. The former has reached the Smurf state,…

Rotors are used in many applications to exchange energy between a mechanical system (vehicle, turbine) and the surrounding fluid (such as air or water). This image shows the extreme deformations of a small rotor fitted with two flexible polyethylene blades when operating in water. Depending on the frequency of rotation, the speed of the incident flow and the inclination of the blades, largeamplitude deformations may appear in either direction, affecting its performance. In a liquid, this…

This bacterial spore is found, together with many of its conspecifics, in wheat straw cells in cow manure. When stored dry, it no longer forms a life-friendly environment, and some bacteria resist by going dormant and becoming spores, while waiting for more favourable conditions. Then, once the manure is rehydrated, the bacteria start breaking down organic matter again, thus helping to increase the fertility of the soil on which it is spread. Understanding the dynamics of microorganisms in soil…

Close-up view of a surface representing hyperbolic space and its boundary at infinity. The existence of such a surface was predicted by the mathematician John Nash in the 1950s. It has now actually been constructed, with the help of computers, by a team of scientists, who are attempting to visualise paradoxical mathematical objects. This surface, resulting from an infinite entanglement of corrugations (or folds), has an astonishing property: the shortest path between a point on its sinuous edge…

Autophagy is a survival pathway specific to the cell: it enables the destruction of intracellular pathogens, as well as access to a nutrient reserve through the recycling of the cell membranes. If this process is not well-balanced, it can cause the cell to die. The image shows the RUFY3 protein, which is involved in the autophagy mechanism, in a mouse macrophage – an immune system cell responsible for the phagocytosis of foreign bodies. The presence of these molecules is shown in blue,…

Although you’re more likely to come across "Podospora anserina" on herbivore dung, this version coloured in the Andy Warhol style could well end up in a museum. Forced here to grow in two dimensions, this microscopic filamentous fungus exhibits a network of hyphae (the filaments) extending over several tens of millimetres. Such a configuration, typical of this type of organism, is thought to enable it to optimise the transmission of information as well as the management of nearby reserves,…

Artificial intelligence can now be used to detect milk contamination quickly and easily. Certain bacteria such as "Pseudomonas fluorescens" can contaminate milk during the bottling process. As a result, the milk has to be incubated for several weeks to ensure that it is sterile before being sold. With Red One technology, microorganisms can be detected after only 48 hours of enrichment in the bottle. The sample is deposited and filtered automatically on a membrane. An algorithm is then used to…

Ostracods are microscopic crustaceans, most of them no larger than a grain of sand. This specimen of "Havanardia societatis" comes from a lagoon in French Polynesia and has valves with impressive lateral extensions that are specific to this species. It belongs to a major family that has lived for some 500 million years in marine environments ranging from coastal areas to the ocean depths. Fragile yet resilient, ostracods have survived the five mass extinctions that have punctuated the history…

If you think this picture looks a bit blurry, try putting on a pair of 3D glasses, and you’ll be able to see it in relief. The photograph was produced using the anaglyph method, in which two images are superimposed, one in red, the other in cyan: the slight offset between the two creates the impression of depth. Featured here are stacked copper nanostructures, a metal that is a promising candidate for converting the billions of tons of CO2 that we release into the atmosphere every year into…