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Recent Submissions
Toxicity of zinc to Schistosoma mansoni cercariae in a chemically defined water medium together with a note on the cercariophagic activity of Macrostomum gigas (Turbellaria: rhabdocoela)
Mecham, John Alvin (Virginia Tech, 1970-11)
A synthetic water medium has been found to support Schistosoma mansoni cercariae for approximately 50 hours, which is the normal life expectancy of cercariae in natural waters.
A partially enclosed slide chamber has proven to be effective in the study of schistosome cercariae where the close observation of a few individual cercariae in a large volume of water otherwise would be extremely difficult.
In low concentrations zinc has little lethal effect on cercariae of Schistosoma mansoni during that period of time in which the cer-cariae are most likely to be infective. Compared to the control groups, concentrations of zinc as low as 0.001 ppm were found to be toxic to schistosome cercariae. Concentrations as high as 57.6 ppm zinc were found to immobilize all cercariae tested within six hours.
A free living flatworm Macrostomum gigas was discovered to be a predator on Schistosoma mansoni cercariae.
Partial resistance to Schistosoma mansoni in mice inoculated with cercarial bodies
Mecham, John Alvin (Virginia Tech, 1972-07)
One group of mice was inoculated with Schistosorna mansoni cercarial bodies. Another group was inoculated with cercarial tails and a third group inoculated with cercarial bodies plus tails in an attempt to determine if schistosome cercarial parts elicit differing immune responses. The mice were then challenged with 100 viable cercariae as were control mice. At six weeks after infection, adult schistosomes were recovered by perfusion. The average worm burden for mice inoculated with cercarial bodies was 9.07 compared to 21.00 for mice inoculated with cercarial tails, 21.90 for mice inoculated with bodies plus tails, and 23.30 for control mice. The number of adults recovered from mice inoculated with cercarial bodies was significantly less than from mice inoculated with cercarial tails, or bodies plus tails, and control mice.
Two serodiagnosic tests, Cercarien-hullen Reaction (CHR) and immunodiffusion, were conducted with sera from experimental and control mice. CHR tests were positive for all experimental mice with strongest reactions occurring with infected mice and with mice inoculated with cercarial bodies. Precipitating antibodies against whole cercarial antigen were shown using anti-body, anti-body-plus-tail, and infected mouse serum. No precipitating antibodies were shown against whole cercarial antigen using anti-tail mouse serum.
The possibility of a cercarial body-tail interaction resulting in stimulation to develop or protection for the developing schistosomulum is indicated.
A late Precambrian resurgent cauldron in the Carolina slate belt of North Carolina, U.S.A.
Newton, Maury Claiborne III (Virginia Tech, 1983-04)
A resurgent cauldron, in the older part of the Carolina slate belt, is part of the lower greenschist-grade Hyco Volcanic-plutonic Group, dated between 620 and 650 Ma. The present dimensions of the cauldron are approximately 45 x 14 km.
The cauldron stratigraphy matches well Smith and Bailey's (1968) seven-stage resurgent cauldron mode!. During Stage (regional tumescence), the ring-fracture system developed, manifested by phreatic explosion breccias and a pre-Stage 11 porphyritic lava dome. The subaqueously-deposited terrane was arched to emergence prior to Stage 11 eruptions. Stage 11 (caldera-forming eruptions) is marked by subaerially-deposited dacitic to rhyolitic ignimbrites and air-fall tuffs. Strongly welded ash-flow tuffs have pumice-flattening ratios of 20-30: 1. Stage 111 (caldera collapse) took place while Stage 11 eruptions were continuing and is recorded by a vertical transition from subaerial pyroclastic facies to subaqueous pyroclastic and epiclastic facies. Stage IV (preresurgence volcanism and sedimentation) is marked by subaqueously-deposited low-Si dacitic to basaltic lavas and epiclastic rocks. Stage V ( resurgent doming), may be represented by a cupola of quartz gabbro to granodiorite that intruded the cauldron block and erupted to form amphibole crystal tuffs. Stage VI (major ring-fracture volcanism) was a second period of regional tumescence culminating in a second cycle of subaerially-deposited dacitic to rhyolitic ignimbrites. Concomitant with rhyolite extrusion, granodiorite to granite intruded the cauldron block. Stage VI I (terminal solfataric activity) resulted in the protoliths of economic pyrophyllite and andalusite deposits.
Stage I I-Stage IV volcanics may represent an inverted compositionally-layered magma chamber with a silicic top and a base of high-alumina basalt to low-Si andesite. Volcanics of the entire cauldron sequence are bimodal with basalt to low-Si andesite and dacite to rhyolite dominant over high-Si andesite. The bimodality suggests there is an apparent compositional gap in the range of high-Si andesite.
Single-cell atlases as meta-analytic compasses for developmental biology: a case study using the Arabidopsis root
Chen, Min; Kari, Saahithi; Szekely, Pablo; Bargmann, Bastiaan O. R.; Shahan, Rachel (2026-07-06)
Plant development requires coordinated execution of gene regulatory programs across diverse cell types. While classical genetic and genomic approaches have revealed many of the genes required for plant growth and patterning, these methods often average signals across heterogeneous tissues, thereby obscuring how regulatory programs operate within individual cells. Therefore, resolving gene expression at the cellular level is essential for understanding how developmental decisions are made, integrated, and propagated during organ growth. The Arabidopsis thaliana root, with its simple anatomy and invariant cell lineages, provides an ideal system for addressing these questions. Recent advances in single-cell and single-nucleus transcriptomics have enabled construction of comprehensive cellular atlases that capture gene expression dynamics across cell identities and developmental trajectories. In this Expert View article, we highlight recent conceptual and technical developments that illustrate how single-cell atlases have transformed studies of root development. We emphasize how these atlases serve as community resources to inform the interpretation of new datasets, including those generated from mutants and in response to perturbation, as well as provide a platform for meta-analysis to initiate new studies. Using auxin signaling as a meta-analysis case study, we demonstrate how legacy transcriptomic data can be reinterpreted within a cell lineage-resolved framework. Finally, we highlight how spatial transcriptomics and rigorous data-sharing practices will extend cellular atlases across tissues and species, thereby enabling increasingly precise strategies for understanding and engineering plant growth and resilience.
Hydro-Québec met en jeu sa réputation à Gull Island
Calder, Ryan S. D. (2026-08-27)