Long-term erosion rate in the SW Cameroon margin Ngapna, Moussa Nsangou; Owona, Sébastien; Mboudou, Germain Marie Monespérance ...
Environmental earth sciences,
04/2023, Volume:
82, Issue:
7
Journal Article
Peer reviewed
The SW Cameroon margin within the Gulf of Guinea (2°–5° N and 8°–13° E) displays a complex landscape and crosscut by three active pre- and syn-rift structures: the Sanaga Fault, Benue Triple Junction ...and Cameroon Volcanic Line (CVL). We evaluated the erosion activity on this margin using for the first time the erosion rate quantification (ERQ). From the Digital elevation model (DEM, 30 m), we extracted compound topographic attributes (CTA), areal morphometric parameters (Ar) and differential tectonic drainage system (DTD) which were combined with field data and the following results were obtained: CTA indicates the relationship between erosion rate variation and the different forms of landscape, runoff diversity and sediments transportation under lithostructural (Precambrian basement and Cretaceous to Recent volcano-sedimentary cover) control. Ar reveals a variable erosion activity triggering sedimentation, denudation and landsliding referring to specific lithostructural units and landscape types. DTD underlines the control of the erosion activity in South Cameroon Low Plateau-, West Cameroon Highlands-, Coastal Plain morphological units and associated lithostructural domains. The stream power index (SPI) and the topographic wetness index (TWI) outline the erosion heterogeneity/variability and represent the key indicators of the state of erosion within the lithostructural units and landscape types. The ERQ, therefore, demonstrates the complexity of the SW Cameroon margin landscape as a result of long-term heterogeneous erosion applicable to South American, Asian and Australian Precambrian to Recent terranes.
Ischemic and solid tumor tissues are less well perfused than normal tissue, leading to metabolic changes and chronic hypoxia, which in turn promotes angiogenesis. We identified human ...angiopoietin-like 4 (
angptl4
) as a gene with hypoxia-induced expression in endothelial cells. We showed that the levels of both mRNA and protein for ANGPTL4 increased in response to hypoxia. When tested in the chicken chorioallantoic membrane assay, ANGPTL4 induced a strong proangiogenic response, independently of vascular endothelial growth factor. In human pathology, ANGPTL4 mRNA is produced in ischemic tissues, in conditions such as critical leg ischemia. In tumors, ANGPTL4 is produced in the hypoxic areas surrounding necrotic regions. We observed particularly high levels of ANGPTL4 mRNA in tumor cells of conventional renal cell carcinoma. Other benign and malignant renal tumor cells do not produce ANGPTL4 mRNA. This molecule therefore seems to be a marker of conventional renal cell carcinoma. ANGPTL4, originally identified as a peroxisome proliferator-activated receptor α and γ target gene, has potential for use as a new diagnostic tool and a potential therapeutic target, modulating angiogenesis both in tumors and in ischemic tissues. This study also suggests that ANGPTL4 may provide a link between metabolic disorders and hypoxia-induced angiogenesis.
Reconstructing Northern Hemisphere ice-sheet oscillations and meltwater routing to the ocean is important to better understand the mechanisms behind abrupt climate changes. To date, research efforts ...have mainly focused on the North American (Laurentide) ice-sheets (LIS), leaving the potential role of the European Ice Sheet (EIS), and of the Scandinavian ice-sheet (SIS) in particular, largely unexplored. Using neodymium isotopes in detrital sediments deposited off the Channel River, we provide a continuous and well-dated record for the evolution of the EIS southern margin through the end of the last glacial period and during the deglaciation. Our results reveal that the evolution of EIS margins was accompanied with substantial ice recession (especially of the SIS) and simultaneous release of meltwater to the North Atlantic. These events occurred both in the course of the EIS to its LGM position (i.e., during Heinrich Stadial –HS– 3 and HS2; ∼31–29 ka and ∼26–23 ka, respectively) and during the deglaciation (i.e., at ∼22 ka, ∼20–19 ka and from 18.2 ± 0.2 to 16.7 ± 0.2 ka that corresponds to the first part of HS1). The deglaciation was discontinuous in character, and similar in timing to that of the southern LIS margin, with moderate ice-sheet retreat (from 22.5 ± 0.2 ka in the Baltic lowlands) as soon as the northern summer insolation increase (from ∼23 ka) and an acceleration of the margin retreat thereafter (from ∼20 ka). Importantly, our results show that EIS retreat events and release of meltwater to the North Atlantic during the deglaciation coincide with AMOC destabilisation and interhemispheric climate changes. They thus suggest that the EIS, together with the LIS, could have played a critical role in the climatic reorganization that accompanied the last deglaciation. Finally, our data suggest that meltwater discharges to the North Atlantic produced by large-scale recession of continental parts of Northern Hemisphere ice sheets during HS, could have been a possible source for the oceanic perturbations (i.e., AMOC shutdown) responsible for the marine-based ice stream purge cycle, or so-called HE's, that punctuate the last glacial period.
•Nd isotope evidence for sources of Channel River meltwater discharges.•Meltwater discharges caused by recession of the EIS into the North European Plain.•Timing of runoff pulses provide new insights into EIS history.•Temporal match between runoff pulses and AMOC shutdown reveals the role of the EIS in past global climate changes.
The medical staff is often powerless to treat patients affected by drug abuse or misuse and poisoning. In the case of envenomation, the treatment of choice remains horse sera administration that ...poses a wealth of other medical conditions and threats. Previously, we have demonstrated that DNA-based aptamers represent powerful neutralizing tools for lethal animal toxins of venomous origin. Herein, we further pursued our investigations in order to understand whether all toxin-interacting aptamers possessed equivalent potencies to neutralize αC-conotoxin PrXA in vitro and in vivo. We confirmed the high lethality in mice produced by αC-conotoxin PrXA regardless of the mode of injection and further characterized myoclonus produced by the toxin. We used high-throughput patch-clamp technology to assess the effect of αC-conotoxin PrXA on ACh-mediated responses in TE671 cells, responses that are carried by muscle-type nicotinic receptors. We show that 2 out of 4 aptamers reduce the affinity of the toxin for its receptor, most likely by interfering with the pharmacophore. In vivo, more complex responses on myoclonus and mice lethality are observed depending on the type of aptamer and mode of administration (concomitant or differed). Concomitant administration always works better than differed administration indicating the stability of the complex in vivo. The most remarkable conclusion is that an aptamer that has no or a limited efficacy in vitro may nevertheless be functional in vivo probably owing to an impact on the biodistribution or pharmacokinetics of the toxin in vivo. Overall, the results highlight that a blind selection of aptamers against toxins leads to efficient neutralizing compounds in vivo regardless of the mode of action. This opens the door to the use of aptamer mixtures as substitutes to horse sera for the neutralization of life-threatening animal venoms, an important WHO concern in tropical areas.
Remorins are a family of multigenic plasma membrane phosphoproteins involved in biotic and abiotic plant interaction mechanisms, partnering in molecular signaling cascades. Signaling activity of ...remorins depends on their phosphorylation states and subsequent clustering into nanosized membrane domains. The presence of a coiled-coil domain and a C-terminal domain is crucial to anchor remorins to negatively charged membrane domains; however, the exact role of the N-terminal intrinsically disordered domain (IDD) on protein clustering and lipid interactions is largely unknown. Here, we combine chemical biology and imaging approaches to study the partitioning of group 1 remorin into anionic model membranes mimicking the inner leaflet of the plant plasma membrane. Using reconstituted membranes containing a mix of saturated and unsaturated phosphatidylcholine, phosphatidylinositol phosphates, and sterol, we investigate the clustering of remorins to the membrane and monitor the formation of nanosized membrane domains. REM1.3 promoted membrane nanodomain organization on the exposed external leaflet of both spherical lipid vesicles and flat supported lipid bilayers. Our results reveal that REM1.3 drives a mechanism allowing lipid reorganization, leading to the formation of remorin-enriched nanodomains. Phosphorylation of the N-terminal IDD by the calcium protein kinase CPK3 influences this clustering and can lead to the formation of smaller and more disperse domains. Our work reveals the phosphate-dependent involvement of the N-terminal IDD in the remorin-membrane interaction process by driving structural rearrangements at lipid-water interfaces.
Angiopoietin-like 4 (ANGPTL4), a secreted protein of the angiopoietin-like family, is induced by hypoxia in both tumor and endothelial cells as well as in hypoxic perinecrotic areas of numerous ...cancers. Here, we investigated whether ANGPTL4 might affect tumor growth as well as metastasis. Metastatic 3LL cells were therefore xenografted into control mice and mice in which ANGPTL4 was expressed by using in vivo DNA electrotransfer. Whereas primary tumors grew at a similar rate in both groups, 3LL cells metastasized less efficiently to the lungs of mice that expressed ANGPTL4. Fewer 3LL emboli were observed in primary tumors, suggesting that intravasation of 3LL cells was inhibited by ANGPTL4. Furthermore, melanoma B16FO cells injected into the retro-orbital sinus also metastasized less efficiently in mice expressing ANGPTL4. Although B16FO cells were observed in lung vessels, they rarely invaded the parenchyma, suggesting that ANGPTL4 affects extravasation. In addition, recombinant B16FO cells that overexpress ANGPTL4 were generated, showing a lower capacity for in vitro migration, invasion, and adhesion than control cells. Expression of ANGPTL4 induced reorganization of the actin cytoskeleton through inhibition of actin stress fiber formation and vinculin localization at focal contacts. Together, these results show that ANGPTL4, through its action on both vascular and tumor compartments, prevents the metastatic process by inhibiting vascular activity as well as tumor cell motility and invasiveness.
Genetic improvement of feed efficiency is key to improve the economic and environmental sustainability of fish farming. However, it requires individual phenotypes of feed efficiency, which are ...difficult if not impossible to obtain when fish are reared in tanks or cages. Here, we applied and validated on gilthead sea bream a method to evaluate individual feed efficiency based on individual rearing of fish in aquariums under restricted feeding. We collected individual phenotypes of feed efficiency in aquariums on 538 sea bream (average weight = 54.50 g). Based on these individual phenotypes, fish (average weight = 174.6 g) were reared in groups of divergent phenotypes (high or low feed efficiency), validating that individual feed efficiency had an impact on group feed efficiency at a later stage. All 538 fish, their parents as well as 794 sibs reared in cages in a production environment, were genotyped on a 57k SNP array to estimate genomic heritability and correlations between traits. We showed that feed efficiency was heritable but did not find significant associated QTLs. We also showed that feed efficiency was negatively genetically correlated to viscera yield, indicating that the most efficient fish had less viscera than the least efficient ones. Altogether, these results support that measuring individual feed efficiency in aquariums under restricted feeding may be used as a reliable phenotyping method to genetically improve feed efficiency, despite the bias intrinsically linked to individual rearing.
•We phenotyped 538 sea bream for individual feed efficiency under restricted feeding in aquariums.•Individual feed efficiency is heritable and highly polygenic in sea bream.•The most efficient fish had lower viscera yield.•The most efficient fish in the aquariums were also more efficient in groups.
The Western Cameroon Highland margin (WCHM) within the West African margin displays an uneven high relief. Its evolutionary model in vogue suggests the tectonic activity of the Cameroon Volcanic Line ...(CVL). An evident question in this regard is whether there is any geomorphometric evidence in support of what is this widespread view? We evaluate this question using field controls and geomorphometric indices of active tectonics derived for 13 main river basins with the help of digital elevation model (DEM)‐30 m data. The WCHM is developed on Proterozoic granite‐gneissic basement and the Cretaceous to Recent volcano‐sedimentary cover and was affected by regional active tectonic features. It is marked by transient signs of different landscape evolutionary stages recorded by the relief and drainage network; shown by gradual adjustment of rivers to equilibrium stages; and cautioned by a greatest variation of DEM‐based geomorphic indices. These indices, hypsometric integral (HI = 0.10–0.35), topography relief (TR = 595–2,710), topography dissection (TD = 114–829), valley floor width to valley height ratio (Vf arg = 0.61–14.91), transverse topographic symmetric factor (T‐index = 0.18–0.49), and basin asymmetric factor (AF = 1.08–24.37) highlight elevated and roughness character of that margin, from the Benue Trough and culminating to the CVL. River longitudinal profiles reveal variably and deeply incised WCHM by the drainage network, reinforced by ongoing tectonic activities. Knickpoints (Kps), stream length‐gradient (SL), uplift (U = 1.17–2.0), and a variety of normalized steepness (Ksn = 11.63–635.16) evidence the diversity and preeminent tectonic controls. The above results show that the WCHM is widely considered to be the consequence of the mantle dynamisms and regional tectonics since Proterozoic, the CVL activities, and the erosional processes.
Active tectonics in the WCHM: (a) the Africa landform surface, (b) The Cameroon landform surface dissected by its main tectonic features, (c) Faults and epicentres of recorded earthquakes. (d) Catchments differential tectonic uplift and incisions shown by morphometric parameters. (e) Spatial distribution of the tilting river catchments of AF, T‐index, and Vf indices.
The Proterozoic metasedimentary rocks of the Yaounde Group on the northern edge of the Congo Shield in Central Africa were investigated to understand their provenance and depositional environment. ...Petrography, geochemistry, and field evidence helped to subdivide the metasediments into paragneiss, mica schist, chlorite schist, and quartzite which were derived from greywacke, shale, quartz arenite, litharenite protoliths. They are immature with some mature samples, moderately weathered and reworked Neo- and Post-Archean metasediments. Rare earth element signatures (Chondrite Eu/Eu* ≤ 1), enrichment of light rare earth elements over the heavy ones, and the La/Sc ratio (> 0.7) are compatible with those of the intermediate and felsic sources from the upper continental crust. These metasediments were deposited in the continental arc setting and have evolved during Proterozoic times according to the Wilson cycle to form the West Gondwana including NE Brazil.
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