In this paper, we introduce a set of methods for processing and analyzing long time series of 3D images representing embryo evolution. The images are obtained by in vivo scanning using a confocal microscope where one of the channels represents the cell nuclei and the other one the cell membranes. Our image processing chain consists of three steps: image filtering, object counting (center detection) and segmentation. The corresponding methods are based on numerical solution of nonlinear PDEs, namely the geodesic mean curvature flow model, flux-based level set center detection and generalized subjective surface equation. All three models have a similar character and therefore can be solved using a common approach. We explain in details our semi-implicit time discretization and finite volume space discretization. This part is concluded by a short description of parallelization of the algorithms. In the part devoted to experiments, we provide the experimental order of convergence of the numerical scheme, the validation of the methods and numerous experiments with the data representing an early developmental stage of a zebrafish embryo.
Over the past 40 years, much has been published on the ultrastructure and cellular development of embryonic structures in a wide range of cestodes. However, the literature contains many discrepancies in both terminology and interpretations because of the facts that these organisms are phylogenetically diverse within their respective orders and families, the habitats that affect embryonic envelope structure are diverse, and the work has been done in various laboratories around the world. This review and synthesis was initiated by a working group of biologists from around the world convened at the Fifth International Workshop on Cestode Systematics and Phylogeny in České Budĕjovice, at the Institute of Parasitology of the Biology Centre, Academy of Sciences of the Czech Republic. It brings together the data from published work and establishes a uniform terminology and interpretation based on the data as they are presented. A consensus was reached for standardised definitions of the oncosphere, hexacanth, coracidium, embryonic envelopes, outer envelope, inner envelope, embryophore, vitelline capsule, shell, and outer coat. All of these are defined as components of the embryo or its vitellocyte-derived or uterine-derived coatings.
Respiratory metabolism of developing eggs of Schistocerca gregaria has been individually monitored by means of scanning microrespirography. The freshly oviposited eggs consumed 7 nl of O2 /min./egg (50 µl O2/g/h) while the pharate 1st instar larvae shortly before hatching consumed 141 nl of O2/min./egg (550 µl O2/g/h), which shows 20-fold metabolic increase during the egg stage. The output of CO2 was also regular, without discontinuous bursts throughout the whole embryonic development. The amounts of CO2 produced were constantly close to R.Q. ratio of 0.7, suggesting that lipid was the main energetic source. The vermiform, pharate 1st instar larvae emerging from the eggs exhibited very high respiratory rates (up to 3,000 µl O2/g/h). During initial phases of the egg stage, O2 consumption steadily increased until day 6, which was associated with katatrepsis or blastokinesis stage of the embryo (61 nl of O2/egg/min. = 240 µl O2/g/h). Since blastokinesis, respiratory metabolism of the egg remained constant or decreased steadily until day 10, when it rose sharply again towards hatching. The temporary metabolic depression was closely correlated with endogenous peak in ecdysteroid concentration within the embryo. These results corroborate validity of the reciprocal, high ecdysteroid - low metabolism rule previously known from insect metamorphosis. They extend its application into the period of embryogenesis. Practical implications of certain physiological, morphological and evolutionary consequences of these findings are discussed with special emphasis on the connecting links between embryogenesis and metamorphosis.
We develop a method for counting number of cells and extraction of approximate cell centers in 2D and 3D images of early stages of the zebra-fish embryogenesis. The approximate cell centers give us the starting points for the subjective surface based cell segmentation. We move in the inner normal direction all level sets of nuclei and membranes images by a constant speed with slight regularization of this flow by the (mean) curvature. Such multi-scale evolutionary process is represented by a geometrical advection-diffusion equation which gives us at a certain scale the desired information on the number of cells. For solving the problems computationally we use flux-based finite volume level set method developed by Frolkovič and Mikula in \cite{FM1} and semi-implicit co-volume subjective surface method given in \cite{CMSSg, MSSg_CVS, MSSg_chapter}. Computational experiments on testing and real 2D and 3D embryogenesis images are presented and the results are discussed.