Neural coding in antennal olfactory cells of tsetse flies (Glossina spp.)

Spike trains from individual antennal olfactory cells of tsetse flies (Glossina spp.) obtained during steady-state conditions (spontaneous as well as during stimulation with 1-octen-3-ol) and dynamic stimulation with repetitive pulses of 1-octen-3-ol were investigated by studying the spike frequency and the temporal structure of the trains. In general, stimulation changes the intensity of the spike activity but leaves the underlying stochastic structure unaffected. This structure turns out to be a renewal process. The only independently varying parameter in this process is the mean interspike interval length, suggesting that olfactory cells of tsetse flies may transmit information via a frequency coding. In spike records with high firing rates, however, the stationary records had significant negative first- order serial correlation coefficients and were non-renewal. Some cells in this study were capable of precisely encoding the onset of the odour pulses at frequencies up to at least 3 Hz. Cells with a rapid return to pre-stimulus activity at the end of stimulation responded more adequately to pulsed stimuli than cells with a long increased spike frequency. While short-firing cells process information via a frequency code, long-firing cells responded with two distinctive phases: a phasic, non-renewal response and a tonic, renewal response which may function as a memory of previous stimulations.      

Properties of plant phospholipid-exchange proteins

Proteins able to stimulate the exchange of phospholipids between natural membranes (mitochondria and microsomal fractions) or between artificial (e.g. liposomes) and natural membranes were isolated from cytosols of plant tissues: potato tuber, cauliflower inflorescence and Jerusalem artichoke.     

In vitro granulopoiesis in oligoblastic leukaemia: prognostic value, characterization and serial cloning of bone marrow colony and cluster forming cells in agar culture

The colony and cluster forming capacity of bone marrow cells (BM CFC and CluFC) in agar culture, was studied from 20 oligoblastic patients. 13 patients had a leukemic growth pattern and 12 of these died within one year after diagnosis. 7 patients had no leukemic growth and 4 are alive 16 to 90 months after diagnosis. Both the determination of the proportion of abnormally light buoyant density of CFC and CluFC and the study of their suiciding index were used to characterize more precisely the leukemic or nonleukemic status of patients. Because of the small number of patients involved in the later preliminary study, the prognostic significance cannot be valuated. Serial studies of individual patients showed different types of evolution in the growth pattern of BM CFC and CluFC. Either the increase of BM CFC and CluFC paralleled that of the myeloblasts, or there was a change in the growth pattern before AML transformation suggesting clonal evolution.     

Centrosome defects cause microcephaly by activating the 53BP1‐USP28‐TP53 mitotic surveillance pathway

Mutations in centrosome genes deplete neural progenitor cells (NPCs) during brain development, causing microcephaly. While NPC attrition is linked to TP53‐mediated cell death in several microcephaly models, how TP53 is activated remains unclear. In cultured cells, mitotic delays resulting from centrosome loss prevent the growth of unfit daughter cells by activating a pathway involving 53BP1, USP28, and TP53, termed the mitotic surveillance pathway. Whether this pathway is active in the developing brain is unknown. Here, we show that the depletion of centrosome proteins in NPCs prolongs mitosis and increases TP53‐mediated apoptosis. Cell death after a delayed mitosis was rescued by inactivation of the mitotic surveillance pathway. Moreover, 53BP1 or USP28 deletion restored NPC proliferation and brain size without correcting the upstream centrosome defects or extended mitosis. By contrast, microcephaly caused by the loss of the non‐centrosomal protein SMC5 is also TP53‐dependent but is not rescued by loss of 53BP1 or USP28. Thus, we propose that mutations in centrosome genes cause microcephaly by delaying mitosis and pathologically activating the mitotic surveillance pathway in the developing brain.     

Three-dimensional cancer cell culture in high-yield multiscale scaffolds by shear spinning

Polymeric scaffolds comprising two size scales of microfibers and submicron fibers can better support three-dimensional (3D) cell growth in tissue engineering, making them an important class of healthcare material. However, a major manufacturing barrier hampers their translation into wider practical use: scalability. Traditional production of two-scale scaffolds by electrospinning is slow and costly. For day-to-day cell cultures, the scaffolds need to be affordable, made in high yield to drive down cost. Combining expertise from academia and industry from the United Kingdom and United States, this study uses a new series of high-yield, low-cost scaffolds made by shear spinning for tissue engineering. The scaffolds comprise interwoven submicron fibers and microfibers throughout as observed under scanning electron microscopy and demonstrate good capability to support cell culturing for tumor modeling. Three model human cancer cell lines (HEK293, A549 and MCF-7) with stable expression of GFP were cultured in the scaffolds and found to exhibit efficient cell attachment and sustained 3D growth and proliferation for 30 days. Cryosection and multiphoton fluorescence microscopy confirmed the formation of compact 3D cell clusters throughout the scaffolds. In addition, comparative growth curves of 2D and 3D cultures show significant cell-type-dependent differences. This work applies high-yield shear-spun scaffolds in mammalian tissue engineering and brings practical, affordable applications of multiscale scaffolds closer to reality. © 2018 American Institute of Chemical Engineers Biotechnol. Prog., 35: e2750, 2019.     

Fragmentation promotes the role of dispersal in determining 10 intermittent headwater stream metacommunities

1. Dispersal, defined as the movement of individuals among local communities in a landscape, is a central regional determinant of metacommunity dynamics in ecosystems. Whereas both natural and anthropogenic ecosystem fragmentations can limit dispersal, previous attempts to measure such limitations have faced considerable context dependency, due to a combination of spatial extent and associated environmental variability, the wide range of dispersal modes, and abilities of organisms or variation in network topologies. Therefore, the role dispersal plays compared to local environmental filtering in explaining metacommunity dynamics remains unclear in fragmented dendritic ecosystems.
2. We quantified α- and β-diversity components of invertebrate metacommunities across 10 fragmented headwater stream networks and tested the hypothesis that dispersal is the primary determinant of biodiversity organisation in these dynamic and spatially constrained ecosystems.
3. Alpha-diversity was much lower in intermittent than perennial reaches, even long after rewetting, indicating an overwhelming effect of drying including a legacy effect on local communities.
4. Beta-diversity was never correlated with environmental distances but predominantly explained by spatial distances accounting for river network fragmentation. The nestedness proportion of β-diversity was considerable and reflected compositional differences where communities from intermittent reaches were subsets of perennial reaches.
5. Altogether, these results indicate dispersal as the primary process shaping metacommunity dynamics in these 10 headwater stream networks, where local communities recurrently undergo extinction and recolonisation events. This challenges previous conceptual views that local environment filtering is the main driver of headwater stream metacommunities.
6. As river networks become increasingly fragmented due to global change, our results suggest that some freshwater ecosystems currently driven by local environment filtering could gradually become dispersal-limited. In this perspective, shifts from perennial to intermittent flow regimes represent ecological thresholds that should not be crossed to avoid jeopardising river biodiversity, functional integrity, and the ecosystem services they provide to society.

     

Quirks of dye nomenclature. 10. Eosin Y and its close relatives

The long history of eosin Y, eosin B and the methyl and ethyl eosins is recounted as well as their synthesis, the variety of their molecular species and some of the myriad applications of these dyes. Chromatographic techniques are described that reveal the purity or lack of it in commercial samples. Toxicological studies are discussed that suggest that the eosins are virtually non toxic, but efforts to remove them from the environment imply that there may be some risk.