Impact of trypsin on cell cytoplasm during detachment of cells studied by terahertz sensing

International audienc

Terahertz Spectroscopy Sheds Light on Real‐Time Exchange Kinetics Occurring through Plasma Membrane during Photodynamic Therapy Treatment

International audienceMethods to follow in real time complex processes occurring along living cell membranes such as cell permeabilization are rare. Here, the terahertz spectroscopy reveals early events in plasma membrane alteration generated during photodynamic therapy (PDT) protocol, events which are not observable in any other conventional biological techniques performed in parallel as comparison. Photodynamic process is examined in Madin-Darby canine kidney cells using Pheophorbide (Pheo) photosensitizer alone or alternatively encapsulated in poly(ethylene oxide)-block-poly(ε-caprolactone) micelles for drug delivery purpose. Terahertz spectroscopy (THz) reveals that plasma membrane permeabilization starts simultaneously with illumination and is stronger when photosensitizer is encapsulated. In parallel, the exchange of biological species is assessed. Over several hours, this conventional approach demonstrates significant differences between free and encapsulated Pheo, the latter leading to high penetration of propidium iodide, Na+ and Ca2+ ions, and a high level of leakage of K+, ATP, and lactate dehydrogenase. THz spectroscopy provides, in a single measurement, the relative number of defects per membrane surface created after PDT, which is not achieved by any other method, providing early, sensitive real-time information. THz spectroscopy is therefore a promising technique and can be applied to any biological topic requiring the examination of short-term plasma membrane permeabilization

EFFECT OF INSECTICIDE TREATMENT ON ARBOREAL ANT COMMUNITY STRUCTURE IN SMALL HOLDER COCOA FARM IN THE CENTRE REGION OF CAMEROON

To understand the effect of anthropogenic disturbances, mainly related to insecticide treatment on ant community structure, the present study was conducted on Cameroonian cocoa farms during two consecutive crop cycles. Ant sampling was based on chemical knock down in three smallholding cocoa farms selected in three different agro-ecological zones in the Centre Region of Cameroon. The C-score was used for null model analysis in order to detect deterministic factor of ant community structure and Spearman correlation test to screen relationship between pair species. Seven ant species were identified as a numerically dominant: Crematogaster clariventris, Crematogaster gabonensis, Crematogaster striatula, Camponotus vividus, Cataulacus guineensis, Tetramorium aculeatum and Oecophylla longinoda. Ant communities were structured by the competition and negative relationship were found between dominant species. Insecticide-treatments affected the ant community structure by favoring the acquisition of the dominant status by non-dominant species

Spatial pattern in arboreal ant community at Mfou suburban agglomeration around Yaoundé city, Cameroon

Ant community structure in natural and anthropogenic ecosystems depends on the combination of several factors not easy to elucidate according to the complexity of habitat structures and anthropogenic disturbances. We investigated the influence of tree distribution pattern on the spatial distribution of dominant ant species, and the spatial relationship between dominant and associated ant species in secondary forest, cocoa farms, and palm groves at Mfou around Yaoundé city. Nine plots of 30 × 30 m each were set up around the study area including three each from every habitat type. Each plot was mapped and the Cartesian coordinated of each tree was recorded. Ants were collected on the trees using a pitfall trap and visual catch. The spatial distribution pattern of the trees and numerical dominant species were analyzed using Besag’s function and spatial relationship between numerical dominant and associated ant species with pair correlation function. Trees distribution fits random models in cocoa farms and secondary forests, while in palm groves they fit regular models. Numerical dominant species also fit the same distribution pattern according to the distribution of the trees in the corresponding habitat. Spatial correlation analysis showed that the establishment of a positive or negative relationship between dominant and associated ant species depends on the distance which separates the nest of the colonies to the foraging area. Around the nest of the colonies, dominant ant species repulse all other ant species despite their territorial defensive behavior and created a safety cord intensively protected. Over this perimeter, the workers invest more in food searching than in the defense of territory and favor the establishment of a positive relationship