Gradual emergence followed by exponential spread of the SARS-CoV-2 Omicron variant in Africa.

The geographic and evolutionary origins of the SARS-CoV-2 Omicron variant (BA.1), which was first detected mid-November 2021 in Southern Africa, remain unknown. We tested 13,097 COVID-19 patients sampled between mid-2021 to early 2022 from 22 African countries for BA.1 by real-time RT-PCR. By November-December 2021, BA.1 had replaced the Delta variant in all African sub-regions following a South-North gradient, with a peak Rt of 4.1. Polymerase chain reaction and near-full genome sequencing data revealed genetically diverse Omicron ancestors already existed across Africa by August 2021. Mutations, altering viral tropism, replication and immune escape, gradually accumulated in the spike gene. Omicron ancestors were therefore present in several African countries months before Omicron dominated transmission. These data also indicate that travel bans are ineffective in the face of undetected and widespread infection

Retraction.

This is a retraction of 'Gradual emergence followed by exponential spread of the SARS-CoV-2 Omicron variant in Africa' 10.1126/science.add873

Perméabilités calciques modulant la différenciation neuronale in vitro chez l embryon de xénope (xenopus laevis)

L objectif de cette thèse a été d étudier le rôle des canaux calciques, des récepteurs nicotiniques et purinergiques ainsi que de l IGF-1 dans la différenciation neuronale (DN) chez l embryon de Xenopus laevis in vitro. Le calcium inhibe cette DN à tous les stades neurula étudiés (stades 13 à 20) et son action peut être partiellement reversée par des doses micromolaires de nickel, de lanthane et de gadolinium. Les canaux impliqués sont insensibles au potentiel de membrane et sont à identifier. Par ailleurs l action du calcium sur la DN est indépendante de son action sur la pousse neuritique (PN). L activation des canaux calciques voltage-dépendants de type N, des récepteurs nicotiniques et purinergiques de type P2X augmente la DN tandis que l activation des récepteurs purinergiques de types P2Y et P1 induit des effets opposés. L IGF-1 antagonise efficacement l action inhibitrice du calcium sur la DN et la PN in vitro. L ensemble de ces résultats montre que la voie d entrée du calcium dans la cellule détermine son effet spécifique sur l activité cellulaire.RENNES1-BU Sciences Philo (352382102) / SudocSudocFranceF

Anacardium Occidentale Linn. (Anacardiaceae) Stem Barks Extract Induces Hypotensive And Cardio-Inhibitory Effects In Experimental Animal Models

Anacardium occidentale Linn. (Anacardiaceae) is a plant largely used in Africa for the treatment of different diseases. In Côte d’Ivoire it’s commonly used for the treatment of hypertension. The present study was carried out in order to assess the effects of Anacardium occidentale extract (ANOE) on cardiovascular parameters in animal models. A mercury manometer kymograph of Ludwig was used to measure the blood pressure of normotensive rabbits in control conditions (normal physiological solution) and under the influence of ANOE. The contractile activity of an isolated rat heart was also measured in control conditions and under the influence of ANOE in different physiological media using a modified Langendhorff (1895) apparatus. The aqueous Anacardium occidentale (ANOE) bark extract applied intravenously in different doses (12, 40, 90, and 167 mg/kg b.w.), produced a significant dose-dependent decrease in blood pressure of previously normotensive rabbits (up to 89% vs control). Atropine (1 mg/ml) pre-treatment failed to reverse the hypotensive effects elicited by the extract. ANOE applied to isolated rat heart preparations in different concentrations (0.01, 0.1, 1.0, and 10 µg/ml) induced negative inotropic and chronotropic effects. Atropine pre-treatment of heart preparations (0.1 μg/ml) failed to reverse the negative effects induced by ANOE. The extract’s action on heart contractile activity studied in modified culture media further confirmed its cardio-inhibitory effects. ANOE induced strong hypotensive and cardio-inhibitory effects in animal models

Anacardium Occidentale Linn. (Anacardiaceae) Stem Bark Extract Induces Hypotensive and Cardio-Inhibitory Effects in Experimental Animal Models

Anacardium occidentale Linn. (Anacardiaceae) is a plant largely used in Africa for the treatment of different diseases. In Côte d'Ivoire it's commonly used for the treatment of hypertension. The present study was carried out in order to assess the effects of Anacardium occidentale extract (ANOE) on cardiovascular parameters in animal models. A mercury manometer kymograph of Ludwig was used to measure the blood pressure of normotensive rabbits in control conditions (normal physiological solution) and under the influence of ANOE. The contractile activity of an isolated rat heart was also measured in control conditions and under the influence of ANOE in different physiological media using a modified Langendhorff (1895) apparatus. The aqueous Anacardium occidentale (ANOE) bark extract applied intravenously in different doses (12, 40, 90, and 167 mg/kg b.w.), produced a significant dose-dependent decrease in blood pressure of previously normotensive rabbits (up to 89% vs control). Atropine (1 mg/ml) pre-treatment failed to reverse the hypotensive effects elicited by the extract. ANOE applied to isolated rat heart preparations in different concentrations (0.01, 0.1, 1.0, and 10 µg/ml) induced negative inotropic and chronotropic effects. Atropine pre-treatment of heart preparations (0.1 µg/ml) failed to reverse the negative effects induced by ANOE. The extract's action on heart contractile activity studied in modified culture media further confirmed its cardio-inhibitory effects. ANOE induced strong hypotensive and cardio-inhibitory effects in animal models