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Clement, B.

Publications and source records attributed to Clement, B..

5 recordsLinked to original sources
bioRxiv2024

Avifauna composition in Rice plantations: effects of Harvesting Stage and Surrounding Vegetation. Insights from Weppa Farm, Agenebode.

Rice plantations provide important habitats for diverse avian communities which support both resident and migratory species. These ecosystems serve as breeding grounds, provide foraging resources and temporary habitats for various bird species, including waterbirds, shorebirds, and passerines. This study was conducted in Weppa Farm (total farm size [~]13000 hector), Agenebode, Etsako East local government area in Edo State, Nigeria to investigate the avifauna compositions in pre-harvested and post-harvested rice plantations and the influence of surrounding vegetation on avian abundance. Four line transects were surveyed around the rice plantation. The transects were 400m long and split into 4, 100m sections. Surveys were done on the rice field before harvest (Unharvested), during harvest (partially harvested) and post-harvest (harvested). Surveys were done in the morning (7:00-9:00 GMT) and repeated in the evening (16:00-18:00 GMT). Vegetation parameters were measured at the beginning of each section of the transect. A total of 48 different bird species from 6 feeding guilds were recorded. Granivorous birds were the most abundant feeding guild (n=599). The Unharvested rice plantation had the highest abundance (n=1453), highest richness (r=37) but not diversity (H=5.18), partially harvested farm had the least abundance (n=592) and least diversity (H=4.95). The surrounding vegetations had a significant effect on bird abundance. Granivores mainly weavers were the most abundant species. The were mainly observed foraging and using weeds as nesting material. Insectivorous birds were the second must abundant species and could serve as biocontrol for arthropod invasions on the farm. Surrounding vegetation influences the abundance of birds in a rice plantation. There was high bird abundance in areas that had trees and shrubs nearby.

ecology↗
bioRxiv2024

PPARgamma, a key modulator of metabolic reprogramming, stemness and chemoresistance associated with retrodifferentiation in human hepatocellular carcinomas

Human hepatocellular carcinomas (HCCs) with cancer stem cell (CSC) features are a subclass of therapeutically challenging cancers. We recently showed that retrodifferentiation of hepatic cancer cells into CSC-like cells leads to metabolic reprogramming and chemoresistance. The molecular mechanisms whereby differentiated cancer cells switch towards a CSC phenotype are poorly understood. By studying metabolic reprogramming associated with HCC cell plasticity, we identified an unsuspected role of peroxisome proliferator-activated receptor (PPAR){gamma} in hepatic CSC phenotype acquisition. Gene expression and metabolic analyses performed throughout cell differentiation/retrodifferentiation process of human HepaRG and HBG-BC2 HCC cells show that metabolic reprogramming in hepatic CSCs is associated with fragmented mitochondrial network, decreased respiration, de novo lipogenesis, fatty acid oxidation, but increased glycolysis and lipid storage. Mitochondrial genes downregulated in HepaRG-CSCs are also downregulated in the STEM HCC subclass. While PPAR is the main isoform in differentiated hepatic cells, we find high PPAR{gamma} expression in hepatic CSCs. Accordingly, nuclear localization of PPAR{gamma} is detected in human HCC tumors and PPAR{gamma}high/PPARlow expression is associated with the STEM HCC subclass and a poor outcome in human HCC cohorts. PPAR{gamma} silencing or/and inhibition of its target gene pyruvate dehydrogenase kinase 4 reactivates cell respiration, increases reactive oxygen species production and sensitizes hepatic CSCs to chemotherapy. Conversely, PPAR activation synergizes with chemotherapy to induce cell death. Targeting PPAR{gamma}, a key regulator of metabolic reprogramming and stemness in hepatic CSCs, or modulating the PPAR{gamma}/PPAR balance that finely tunes the differentiation/retrodifferentiation process in HCC deserves further investigation for antitumor therapy. Implications heading and statementPPAR{gamma}, a key regulator of metabolic reprogramming and stemness in hepatic CSC, reduces oxidative phosphorylation and reactive oxygen species production, therefore contributing to HCC chemoresistance.

cancer biology↗
bioRxiv2022

Chemical effects on ecological interactions within a model-experiment loop

We propose in this paper a method to assess the effects of a contaminant on a micro-ecosystem, integrating the population dynamics and the interactions between species. For that, we developed a dynamic model to describe the functioning of a microcosm exposed to a contaminant and to discriminate direct and indirect effects. Then, we get back from modelling to experimentation in order to identify which of the collected data have really been necessary and sufficient to estimate model parameters in order to propose a more efficient experimental design for further investigations. We illustrated our approach using a 2-L laboratory microcosm involving three species (the duckweed Lemna minor, the microalgae Pseudokirchneriella subcapitata and the daphnids Daphnia magna) exposed to cadmium contamination. We modelled the dynamics of the three species and their interactions using a mechanistic model based on coupled ordinary differential equations. The main processes occurring in this three-species microcosm were thus formalized, including growth and settling of algae, growth of duckweeds, interspecific competition between algae and duckweeds, growth, survival and grazing of daphnids, as well as cadmium effects. We estimated model parameters by Bayesian inference, using simultaneously all the data issued from multiple laboratory experiments specifically conducted for this study. Cadmium concentrations ranged between 0 and 50 g.L-1 . For all parameters of our model, we obtained biologically realistic values and reasonable uncertainties. The cascade of cadmium effects, both direct and indirect, was identified. Critical effect concentrations were provided for the life history traits of each species. An example of experimental design adapted to this kind a microcosm was also proposed. This approach appears promising when studying contaminant effects on ecosystem functioning.

ecology↗
bioRxiv2021

Topologically controlled circuits of human iPSC-derived neurons for electrophysiology recordings

Bottom-up neuroscience, which consists of building and studying controlled networks of neurons in vitro, is a promising method to investigate information processing at the neuronal level. However, in vitro studies tend to use cells of animal origin rather than human neurons, leading to conclusions that might not be generalizable to humans and limiting the possibilities for relevant studies on neurological disorders. Here we present a method to build arrays of topologically controlled circuits of human induced pluripotent stem cell (iPSC)-derived neurons. The circuits consist of 4 to 50 neurons with mostly unidirectional connections, confined by microfabricated polydimethylsiloxane (PDMS) membranes. Such circuits were characterized using optical imaging and microelectrode arrays (MEAs). Electrophysiology recordings were performed on circuits of human iPSC-derived neurons for at least 4.5 months. We believe that the capacity to build small and controlled circuits of human iPSC-derived neurons holds great promise to better understand the fundamental principles of information processing and storing in the brain.

neuroscience↗