Biology subjects

Lambert, C.

Publications and source records attributed to Lambert, C..

24 records · Page 2Linked to original sources

bioRxiv2021

Population monitoring of snow leopards using camera trapping in Naryn State Reserve, Kyrgyzstan, between 2016 and 2019

Four field seasons of snow leopard (Panthera uncia) camera trapping inside Naryn State Reserve, performed thanks to citizen science expeditions, allowed detecting a minimal population of five adults, caught every year with an equilibrated sex ratio (1.5:1), and reproduction: five cubs or subadults have been identified from three litters of two different females. Crossings were observed one to three times a year, in front of most camera traps, and several times a month in front of one of them. Overlap of adults territories was observed in front of several camera traps regardless of their sex. Significant snow leopard presence was detected in the buffer area and at Ulan, situated at the reserve border. To avoid poaching on this umbrella species and its preys, extending the more stringent protection measures of the core zone to both the Southern buffer area and land adjacent to Ulan is necessary.

ecology↗

bioRxiv2020

Ventralis intermedius nucleus anatomical variability assessment by MRI structural connectivity

The ventralis intermedius nucleus (Vim) is centrally placed in the dentato-thalamo-cortical pathway (DTCp) and is a key surgical target in the treatment of severe medically refractory tremor. It is not visible on conventional MRI sequences; consequently, stereotactic targeting currently relies on atlas-based coordinates. This fails to capture individual anatomical variability, which may lead to poor long-term clinical efficacy. Probabilistic tractography, combined with known anatomical connectivity, enables localisation of thalamic nuclei at an individual subject level. There are, however, a number of confounds associated with this technique that may influence results. Here we focused on an established method, using probabilistic tractography to reconstruct the DTCp, to identify the connectivity-defined Vim (cd-Vim) in vivo. Using 100 healthy individuals from the Human Connectome Project, our aim was to quantify cd-Vim variability across this population, measure the discrepancy with atlas-defined Vim (ad-Vim), and assess the influence of potential methodological confounds. We found no significant effect of any of the confounds. The mean cd-Vim coordinate was located within 1.9 mm (left) and 2.1 mm (right) of the average midpoint and 4.9 mm (left) and 5.4 mm (right) from the ad-Vim coordinates. cd-Vim location was more variable on the right, which reflects hemispheric asymmetries in the probabilistic DTCp reconstructed. The superior cerebellar peduncle was identified as a potential source of artificial variance. This work demonstrates significant individual anatomical variability of the cd-Vim that atlas-based approaches fail to capture. This variability was not related to any methodological confound tested. Lateralisation of cerebellar functions, such as speech, may contribute to the observed asymmetry. Tractography-based methods seem sensitive to individual anatomical variability that is missed by conventional neurosurgical targeting; These findings may form the basis for translational tools to improve efficacy and reduce side-effects of thalamic surgery for tremor. HighlightsO_LIConnectivity-based Vim position varied markedly between subjects and from atlas-defined coordinates. C_LIO_LIThis positional variability was not related to any methodological confound tested. C_LIO_LIHemispheric asymmetry was observed in connectivity-based Vim position. C_LIO_LIWe hypothesise lateralization of cerebellar functions, such as language, may contribute to asymmetry. C_LIO_LIKnowledge of Vim position variability could help inform neurosurgical planning in the management of tremor. C_LI

neuroscience↗

bioRxiv2019

The persistence in time of distributional patterns in mobile species: its impact for zonal conservation strategies

The main type of zonal conservation approach corresponds to Marine Protected Areas (MPAs), which are spatially defined and generally static entities aiming at the protection of some target populations by the implementation of a management plan. For highly mobile species the relevance of an MPA over time might be hampered by temporal variations in distributions or home ranges. In the present work, we used habitat model-based predicted distributions of cetaceans and seabirds within the Bay of Biscay from 2004 to 2017 to characterise the aggregation and persistence of mobile species distributional patterns and the relevance of the existing MPA network. We explored the relationship between population abundance and spatial extent of distribution to assess the aggregation level of species distribution. We used the smallest spatial extent including 75% of the population present in the Bay of Biscay to define specific core areas of distributions, and calculated their persistence over the 14 studied years. We inspected the relevance of the MPA network with respect to aggregation and persistence. We found that aggregation and persistence are two independent features of marine megafauna distributions. Indeed, strong persistence was shown in both aggregated (bottlenose dolphins, auks) and loosely distributed species (northern gannets), while some species with aggregated distributions also showed limited year-to-year persistence in their patterns (black-legged kittiwakes). We thus have demonstrated that both aggregation and persistence have potential impact on the amount of spatio-temporal distributional variability encompassed within static MPAs. Our results exemplified the need to have access to a minimal temporal depth in the species distribution data when aiming to designate new site boundaries for the conservation of mobile species.

ecology↗

bioRxiv2019

Streptococcus pyogenes infects human endometrium by limiting its immune response

Group A Streptococcus (GAS), a Gram-positive human-specific pathogen yields 517,000 deaths annually worldwide, including 163,000 due to invasive infections and among them puerperal fever. GAS is their most feared etiologic agent. Puerperal fever still accounts for more than 75,000 maternal deaths annually and before the introduction of efficient prophylactic measures 10% childbirths were followed by the mothers death. Yet little is known regarding GAS invasive infection establishment or GAS efficiency in causing postpartum infection. To characterize its early steps, we set up coordinated analyses of ex vivo infection of the human decidua, the puerperal fever portal of entry. We analyzed GAS behavior and the immune response triggered. We demonstrate that GAS (i) benefits from tissue secreted products to multiply; (ii) invades the tissue and leads to the death of half the cells within two hours via SpeB protease and Streptolysin O activities, respectively; (iii) impairs the tissue immune response. Immune impairment occurs both at the RNA level, with the induction of only a restricted immediate innate immune response, and at the protein level, in a SLO- and SpeB-dependent manner. Our study indicates that GAS efficient decidua invasion and immune response restraint favor its propensity to develop rapid invasive infections in a gynecological-obstetrical context.

microbiology↗

bioRxiv2019

Dynamics of chromosome replication and its relationship to predatory attack lifestyles in Bdellovibrio bacteriovorus

Bdellovibrio bacteriovorus is a small Gram-negative, an obligate predatory bacterium that is largely found in wet, aerobic environments (i.e. soil). This bacterium attacks and invades other Gram-negative bacteria, including animal and plant pathogens. The intriguing life cycle of B. bacteriovorus consists of two phases: a free-living non-replicative attack phase wherein the predatory bacterium searches for its prey, and a reproductive phase, in which B. bacteriovorus degrades a hosts macromolecules and reuses them for its own growth and chromosome replication. Although the cell biology of this predatory bacterium has gained considerable interest in recent years, we know almost nothing about the dynamics of chromosome replication in B. bacteriovorus. Here, we performed a real-time investigation into the subcellular localization of the replisome(s) in single cells of B. bacteriovorus. Our results confirm that in B. bacteriovorus chromosome replication fires only during the reproductive phase, and show for the first time that this predatory bacterium exhibits a novel spatiotemporal arrangement of chromosome replication. The replication process starts at the invasive pole of the predatory bacterium inside the prey cell and proceeds until several copies of the chromosome have been completely synthesized. This chromosome replication is not coincident with the predator-cell division, and it terminates shortly before synchronous predator-filament septation occurs. In addition, we demonstrate that if this lifecycle fails in some cells of B. bacteriovorus, they can instead use two prey cells sequentially to complete their life cycle.\n\nImportanceNew strategies are needed to combat multidrug-resistant bacterial infections. Application of the predatory bacterium, Bdellovibrio bacteriovorus, which kills other bacteria including pathogens, is considered promising for bacterial infections. The B. bacteriovorus life cycle consists of two phases, a free-living, invasive attack phase and an intracellular reproductive phase, in which this predatory bacterium degrades the hosts macromolecules and reuses them for its own growth. To understand the use of B. bacteriovorus as a living antibiotic, it is first necessary to dissect its life cycle including chromosome replication. Here, we present for the first time a real-time investigation into subcellular localization of chromosome replication in a single cells of B. bacteriovorus. This process initiates at the invasion pole of B. bacteriovorus and proceeds until several copies of the chromosome have been completely synthesized. Interestingly, we demonstrate that some cells of B. bacteriovorus require two prey cells sequentially to complete their life cycle.

microbiology↗

bioRxiv2018

A High-Quality De Novo Genome Assembly from a Single Mosquito using PacBio Sequencing

A high-quality reference genome is a fundamental resource for functional genetics, comparative genomics, and population genomics, and is increasingly important for conservation biology. PacBio Single Molecule, Real-Time (SMRT) sequencing generates long reads with uniform coverage and high consensus accuracy, making it a powerful technology for de novo genome assembly. Improvements in throughput and concomitant reductions in cost have made PacBio an attractive core technology for many large genome initiatives, however, relatively high DNA input requirements ([~]5 {micro}g for standard library protocol) have placed PacBio out of reach for many projects on small organisms that have lower DNA content, or on projects with limited input DNA for other reasons. Here we present a high-quality de novo genome assembly from a single Anopheles coluzzii mosquito. A modified SMRTbell library construction protocol without DNA shearing and size selection was used to generate a SMRTbell library from just 100 ng of starting genomic DNA. The sample was run on the Sequel System with chemistry 3.0 and software v6.0, generating, on average, 25 Gb of sequence per SMRT Cell with 20 hour movies, followed by diploid de novo genome assembly with FALCON-Unzip. The resulting curated assembly had high contiguity (contig N50 3.5 Mb) and completeness (more than 98% of conserved genes are present and full-length). In addition, this single-insect assembly now places 667 (>90%) of formerly unplaced genes into their appropriate chromosomal contexts in the AgamP4 PEST reference. We were also able to resolve maternal and paternal haplotypes for over 1/3 of the genome. By sequencing and assembling material from a single diploid individual, only two haplotypes are present, simplifying the assembly process compared to samples from multiple pooled individuals. The method presented here can be applied to samples with starting DNA amounts as low as 100 ng per 1 Gb genome size. This new low-input approach puts PacBio-based assemblies in reach for small highly heterozygous organisms that comprise much of the diversity of life.

genomics↗