Biology subjects

Howell, J.

Publications and source records attributed to Howell, J..

4 recordsLinked to original sources

bioRxiv2024

Impact of flagellated and elongated morphological phenotypes on the focusing behaviours of biological cells in inertial microfluidic devices

Inertial microfluidics has demonstrated tremendous potential to impact biological - and notably medical - fields, by offering a highly versatile, portable and cost-effective approach to cell focusing and sorting. While the range of applications of inertial devices spans medical diagnostics, bioprocessing or water engineering to mention a few, translation is still impeded by the lack of clear understanding of cell interactions in such devices. This often leads to bespoke designs that take years of development and characterisation for one targeted application, and limited tools for informed optimisation. A more fundamental knowledge of inertial behaviours is key to future translational works and impact, by enabling a deeper understanding of inertial forces in biological systems. Towards this goal, this paper focuses on high-throughput morphological phenotyping of the single-celled, flagellated parasite Leishmania mexicana to better understand how variations in cell body length, width and flagellated status impact the focusing patterns of highly non-spherical cells in curved inertial devices. Some of the key findings in this study include i) not all organelles, such as flagella, will alter focusing if the body shape is conserved, ii) the impact of cell shape is specific to a channel design and slight changes in e.g., cell confinement can completely change focusing patterns, iii) elongated prolate-like cells align in different orientations depending on their lateral position with a curved channel and iv) despite variabilities observed in focusing patterns for elongated versus rounder cell phenotypes, large morphological variations can be completely overcome at high Reynolds numbers so that all phenotypes tightly focus at a single position (here towards the channel outer wall). This last finding, in particular, may open new avenues for highly efficient cell enrichment processes, such as for the detection of pathogens in water.

bioengineering↗

bioRxiv2024

The collective application of shorebird tracking data to conservation

Addressing urgent conservation issues, like the drastic declines of North American migratory birds, requires creative, evidence-based, efficient, and collaborative approaches. Over 50% of monitored North American shorebird populations have lost over 50% of their abundance since 1980. To address these declines, we developed a partnership of scientists and practitioners called the Shorebird Science and Conservation Collective (hereinafter "the Collective"). Here, we present this successful case study as an example for others engaged in translational science. The Collective acts as an intermediary whereby dedicated staff collate and analyze data contributions from scientists to support knowledge requests from conservation practitioners. Data contributions from 74 organizations include over 6.7 million shorebird locations forming movement paths of 3,345 individuals representing 36 species tracked across the Americas. We describe the founding and structure of the Collective and conservation activities we supported in our first two years. As the volume of scientific data on animal movements continues to grow, groups like the Collective can be vital liaisons to rapidly integrate and interpret research to support conservation action.

ecology↗

bioRxiv2023

The use of imaging flow cytometry for rapid, high-throughput and automated analysis of the Leishmania mexicana promastigote cell cycle provides new insights into cell cycle events of short duration

Promastigote Leishmania mexicana have a complex cell division cycle characterised by the ordered replication of several single-copy organelles, a prolonged S phase and rapid G2 and cytokinesis phases, accompanied by cell cycle stage-associated morphological changes. Here we exploit these morphological changes to develop a high-throughput and semi-automated imaging flow cytometry (IFC) pipeline to analyse the cell cycle of L. mexicana in live cells. Firstly, we demonstrate that, unlike several other DNA stains, Vybrant DyeCycle Orange (DCO) is non-toxic and enables quantitative DNA imaging in live L. mexicana promastigotes. Secondly, by tagging the orphan spindle kinesin, KINF, with mNeonGreen, we describe KINFs cell cycle-dependent expression and localisation. Then, by combining manual gating of DCO DNA intensity profiles with automated masking and morphological measurements of parasite images, visual determination of the number of flagella per cell, and automated masking and analysis of mNG:KINF fluorescence, we provide a newly detailed description of L. mexicana promastigote cell cycle events that, for the first time, includes the durations of individual G2, mitosis and post-mitosis phases, and identifies G1 cells within the first 12 minutes of the new cell cycle. By applying IFC in this way, we were able, in minutes, to capture tens of thousands of high-quality brightfield and fluorescent images of live L. mexicana cells in solution, and to acquire quantitative data across multiple parameters for every image captured. Our custom-developed masking and gating scheme allowed us to identify elusive G2 cells and to demonstrate that the CDK-inhibitor, flavopiridol, arrests cells in G2 phase, rather than mitosis, providing proof-of-principle of the utility of IFC for drug mechanism-of-action studies. Further, the high-throughput nature of IFC allowed the close examination of promastigote cytokinesis, revealing considerable flexibility in both the timing of cytokinesis initiation and the direction of furrowing, in contrast to the related kinetoplastid parasite, Trypanosoma brucei. Significantly, our analysis demonstrate that the cleavage furrow can ingress unidirectionally from either pole of the cell, bidirectionally from both simultaneously or even commence internally along the anterior-posterior (A-P) axis. Our new pipeline offers many advantages over traditional methods of cell cycle analysis such as fluorescence microscopy and flow cytometry and paves the way for novel high-throughput analysis of Leishmania cell division. Author SummaryLeishmania mexicana is a single-celled parasite that is spread by sand flies and causes a spectrum of diseases called the leishmaniases in humans and animals. To cause disease, L. mexicana parasites must replicate and divide, and their cell division cycle has unusual and/or complex features, including that the parasite changes shape as it replicates. To aid analysis of the L. mexicana cell cycle, we developed a new quantitative DNA staining technique and also generated a fluorescent parasite cell line that highlighted when cells were dividing their DNA (mitosis) after replicating it. We then applied a high-throughput technique called imaging flow cytometry to capture images of tens of thousands of these parasites in just a few minutes. For each image, we were able to extract data about DNA replication, cell shape, whether the cells were in mitosis or not and how they divide. This provided new insights into how the parasites replicate and how long each stage of cell division takes as well as how the parasites split in two at the end of cell division. We were also able to use our analysis method to precisely determine the cell cycle stage at which a cell cycle inhibitor acts. More importantly, the imaging pipelines we have developed offer great advantages in terms of speed and depth over more traditional analysis techniques such as microscopy and should pave the way for increasingly detailed analyses of parasite cell biology in the future.

cell biology↗

bioRxiv2018

Race modifies default mode network connectivity in Alzheimer’s disease

ObjectiveTo determine if resting state functional MRI biomarkers of Alzheimers disease (AD) differ between older African Americans and Caucasians.\n\nMethodsWe analyzed MRI profiles from 78 individuals (31 African Americans, 47 Caucasians) with normal cognition (n=36) or mild cognitive impairment/mild AD dementia (MCI/AD, n=42). We compared AD-associated intra-network functional connectivity of the default mode network (DMN) according to race, and correlated domain-specific cognitive functions with functional connectivity which differed between the racial groups.\n\nResultsWe identified key differences in DMN functional connectivity associated with AD between the races. Whereas MCI/AD was associated with decreased functional connectivity within the midline core DMN subsystem in older Caucasians, MCI/AD was instead associated with increased functional connectivity within the same subsystem of older African Americans. This is despite decreased functional connectivity in the medial temporal lobe DMN subsystem in both races. Memory function was also positively associated with connectivity between the precuneus and the posterior cingulate/inferior parietal lobule within the midline core subsystem, in keeping with a less amnestic-profile in older African Americans with MCI/AD.\n\nConclusionsThese findings provide structural support that race modifies the AD phenotypes downstream from cerebral amyloid deposition, and suggests a rsf-MRI correlate of African Americans less amnestic neuropsychological profile in MCI/AD.

neuroscience↗