Biology subjects

Mallet, C.

Publications and source records attributed to Mallet, C..

3 recordsLinked to original sources

bioRxiv2025

Temperature dependent response of microcystin-LR in acclimated Microcystis aeruginosa: highest content expected near the growth optimum

As climate change raises global temperatures and increases the frequency of cyanobacterial blooms, understanding how rising mean temperatures affect cyanotoxin content is crucial. However, no clear consensus exists, and the use of different methodologies, including different units of measurement and experimental conditions could significantly alter the yield of the relationship between temperature and toxins content. In this study, we assessed free microcystin content and cell volume in Microcystis aeruginosa PCC 7806 acclimated to seven temperatures spanning its entire thermal niche. This experimental design firstly highlighted the significant reduction in cell volume with rising temperatures between 17{degrees}C and 29{degrees}C. As a result, when the microcystin concentration was normalized by its cell volume, its temperature response was transformed from a negative correlation to a bell-shaped curve, with higher free MC-LR content measured at an estimated optimum temperature of 26.2{degrees}C, close to the thermal growth optimum of Microcystis aeruginosa. These findings provide new insights into the effects of climate warming on microcystin content. ImportanceMicrocystin-LR is a widespread cyanotoxin, originally known for its liver toxicity. In freshwater environments, cyanotoxins are an increasing concern as harmful cyanobacterial blooms become more frequent with rising global temperatures. Microcystis aeruginosa, a common bloom-forming species found worldwide, is a major producer of microcystin-LR. Understanding how environmental factors such as temperature influence toxin content in this species is essential for predicting bloom toxicity under future climate scenarios. However, current knowledge remains fragmented due to numerous factors that can influence its production and also to different way of measuring toxins and expressing their concentrations (cell or {micro}m3). Confirming that temperature greatly modifies biovolume of M. aeruginosa, this study offers new insights by highlighting the importance of considering cell volume when evaluating toxin content. Integrating changes in cell size helps reconcile earlier conflicting results and contributes to a more accurate understanding of how temperature affects toxin production in cyanobacteria. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=176 HEIGHT=200 SRC="FIGDIR/small/660678v1_ufig1.gif" ALT="Figure 1"> View larger version (31K): org.highwire.dtl.DTLVardef@7a591org.highwire.dtl.DTLVardef@6eb39org.highwire.dtl.DTLVardef@3d0f19org.highwire.dtl.DTLVardef@aa6be0_HPS_FORMAT_FIGEXP M_FIG C_FIG

microbiology↗

bioRxiv2022

Centrally expressed Cav3.2 T-type calcium channel is critical for the initiation and maintenance of neuropathic pain

Cav3.2 T-type calcium channel is a major molecular actor of neuropathic pain in peripheral sensory neurons, but its involvement at the supra-spinal level is almost unknown. In the Anterior Pretectum (APT), a hub of connectivity of the somatosensory system involved in pain perception, we show that Cav3.2 channels are expressed in a sub-population of GABAergic neurons co-expressing parvalbumin (PV). In these PV-expressing neurons, Cav3.2 channels contribute to a high frequency bursting activity, which is increased in the spared nerve injury model of neuropathy. Specific deletion of Cav3.2 channels in APT neurons reduced both the initiation and maintenance of mechanical and cold allodynia. These data are a direct demonstration that centrally expressed Cav3.2 channels also play a fundamental role in pain pathophysiology.

neuroscience↗

bioRxiv2019

Tooth Shape Adaptations in Aglyphous Colubrid Snakes Inferred from 3D Geometric Morphometrics and Finite Element Analysis

To date there are few detailed and quantitative studies investigating the evolution of the tooth shape and function in Aglyphous snakes in relation to diet. To study dental adaptations to diet, a lineage that is of particular interest due to its large range of adult body sizes, is the one including dwarfed snakes of the genus Eirenis and their immediate sister group, whip snakes of the genus Dolichophis. A considerable evolutionary decrease in the size is observed from a Dolichophis-like ancestor to the miniature Eirenis, coupled with a considerable shift in their diet from a regime consisting mainly of endotherms with endoskeleton to ectotherms bearing a hard exoskeleton. Maxilla, palatine, pterygoid and dentary teeth were examined in an adult and a juvenile of Dolichophis schmidti, one Eirenis punctolineatus and one Eirenis persicus. 3D Geometric Morphometrics comparison revealed maxilla and palatine teeth of the E. persicus are blunt and conical shape while those teeth are sharp and elongated in E. punctatolineatus as well as the adult and juvenile D. schmidti. A similar difference could be noted for the pterygoid teeth. In contrast, the dentary teeth are not as different among the examined snakes. Blunt and conically shaped teeth, as observed in E. persicus, seem to be more adapted for biting hard bodied, arthropod prey, while sharp and elongated teeth in Dolichophis and E. punctatolineatus, are specialized for puncturing endotherm prey. The results of a finite element analysis confirms that during biting a hard bodied prey, the generated stresses in E. persicus tooth is mostly confined to the tip of the tooth and mostly well below the von Mises yield criterion the tooth. In contrary, D. schmidti tooth appears less well suited for biting a hard prey since the generated stresses widely distribute across the tooth with values roughly 2 to 3 times higher than the von Mises yield criterion of the tooth. A lower degree of specialization that was observed among the dentary teeth in the examined snakes suggest a similar functional constraint in pushing the prey against the upper tooth rows.

evolutionary biology↗