Engineering Support of Microgravity Life Science Research: Development of an Avian Development Facility
The Avian Development Facility (ADF) is designed to provide a 'window' for the study of embryogenesis in space. It allows researchers to determine and then to mitigate or nullify the forces of altered gravity upon embryos when leaving and re-entering the Earth's gravity. The ADF design will allow investigations to begin their incubation after their experiments have achieved orbit, and shut down the experiment and fix specimens before leaving orbit. In effect, the ADF makes every attempt to minimize launch and re-entry effects in order to isolate and preserve the effects of the experimental variable(s) of the space environment.
Avian biotechnology instrumentation as a mechanism for understanding human dysfunction in space
Gravitational biologists are recognizing the advantages and convenience the avian egg offers, as a biological model for examining developmental dysfunctions under microgravity conditions. The avian egg is a self-contained, individual development package with its own life-support system, requiring no additional food, water, or waste-removal systems. Since there is no dependence on a maternal host, embryos are unaffected by maternal responses to the microgravity environment. In addition, selected embryos can he manipulated without jeopardizing other members of .I the clutch, making selective collection of avian specimens in microgravity far easier than with most species. Thus, the avian model offers many research opportunities that can be structured for understanding human diseases, as well as those problems associated with adaptation to the weightless environment of space.
The system specifying body position in the early development of Xenopus, and its response to early perturbations.
Evidence is presented that the system setting up preliminary specifications for contributions to the axial body plan, across vegetal regions of the Xenopus embryo, acts in a widespread way at early stages. Mechanisms that regulate the spatial profile of this primary positional variable, and thus ensure the constancy and harmony of the body plans normally achieved, have lost this integrative ability by the 4-cell stage one hour after the plasm shifts that precede first cleavage and symmetrize the egg. Abnormal, partial or distorted profiles of the positional system across whole eggs or isolates, recorded by these times, are retained to give correspondingly partial or imbalanced mes/endodermal pattern at tailbud larval stages. There is evidence that subsequent 'back-up' positional interactions, which can heal gross positional discontinuities in isolated presumptive lateral half-eggs and so restore bilateral symmetry, also do this at the price of loss of complete pattern specification. This is probably because of an asymmetrical principle whereby relatively activated (dorsoanterior specified) material can raise the level of originally posterior material on contact, whereas the reverse interaction cannot occur. The observations are discussed in relation to apparently different behaviour in certain other amphibian embryos, and to our knowledge of other positional interactions, normal and also experimentally provoked, such as those that set up the germ layers.