Distinct origins of adult and embryonic blood in Xenopus

Article Abstract:

Distinct origins of adult and embryonic blood in Xenopus are discussed based on a study into whether embryonic and adult blood derive from a single or dual origin, from a yolk sac, or a yolk sac/intraembryonic origin. In Xenopus the yolk sac (VBI) and intraembryonic DLP blood compartments come from distinct blastomeres in the 32-cell embryo. It is thought that the first adult hematopoietic stem cells form in association with the floor of the dorsal aorta. Using hematopoietic markers such aortic clusters were found in Xenopus.

Embryology, Experimental, Embryological research, Xenopus, Hematopoietic stem cells, Blood, Aorta

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Tomographic 3D reconstruction of quick-frozen, Ca(super.2+)-activated contracting insect flight muscle

Article Abstract:

Ca(super.2+)-activated contracting flight muscle of insects is discussed based on electron microscope (EM) tomographic 3D reconstruction using quick-frozen muscle. Results suggest the motor domain (MD) tilts and slews on actin from weak to strong binding. Swinging of the light chain domain (LCD) follows, through about a 35-degree axial angle for an about 13-nm interaction distance and an about 4-6-nm working stroke. A variety of structures are seen. A sequence of conformational changes brings on the generation of force.

United States, Germany, Usage, Observations, Insects, Electron microscopy, Actin, Muscle cells, Tomography, Myosin

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Control of organ asymmetry in flowers of Antirrhinum

Article Abstract:

Control of organ asymmetry in Antirrhinum (snapdragon) flowers, the asymmetry of which required cyc and dich gene activity, as do the component organs, is discussed. Organ asymmetry presumably evolved independently many times in many plants. Plant organ asymmetry can be shown to be able to arise through a series of steps in which early asymmetry in the developing meristem is built on progressively. Function and isolation of dich are described. The predicted DICH protein is closely related to CYC.

Plants, Physiological regulation, Biological control systems, Symmetry (Biology), Meristem, Flowers, Plant evolution, Snapdragons

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