Thinking of biology: toward a theory of cellularity--speculations on the nature of the living cell
No abstract available
NASA Discipline Plant Biology↗
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Results for “Plants/cytology”
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Real and simulated microgravity alters cellular processes: emergence of a new environmental frontier
No abstract available
NASA Discipline Number 40-40↗
Contemplating the plasmalemmal control center model
An abundant epidermal mechanosensory calcium-selective ion channel appears able not only to detect mechanical stimuli such as those that initiate gravitropism but also to detect thermal, electrical, and various chemical stimuli. Because it responds to multimodal input with a second messenger output, this channel system seems likely to be an integrator that can engage in feedbacks with many other systems of the cell--and feedback is the hallmark of regulation. In general, the mechanical tension required for channel activation is likely transmitted from the relatively rigid cell wall to the plasma membrane system via linkage or adhesion sites that display antigenicities recognized by antibodies to animal beta-1 integrin, vitronectin, and fibronectin and which have mechanical connections to the cytoskeleton. Thus, functionally, leverage exerted against any given adhesion site will tend to control channels within a surrounding domain. Reactions initiated by passage of calcium ions through the channels could presumably be more effectively regulated if channels within the domains were somewhat clustered and if appropriate receptors, kinases, porters, pumps, and some key cytoskeletal anchoring sites were in turn clustered about them. Accumulating evidence suggests not only that activity of clusters of channels may contribute to control of cytoskeletal architecture and of regulatory protein function within their domain, but also that both a variety of regulatory proteins and components of the cortical cytoskeleton may contribute to control of channel activity. The emerging capabilities of electronic optical microscopy are well suited for resolving the spatial distributions of many of these cytoskeletal and regulatory molecules in living cells, and for following some of their behaviors as channels are stimulated to open and cytosolic calcium builds in their vicinity. Such microscopy, coupled with biochemical and physiological probing, should help to establish the nature of the feedback loops putatively controlled by the linkage sites and their channel domains.
Review↗
Theories and models of the biology of the cell in space--an introduction
The World Space Congress 1992 took place after two Spacelab flights with important biological payloads on board, the SLS-1 (June 1991) and IML-1 (January 1992) missions respectively. Interesting experiments were carried out in 1991 also on the Shuttle middeck and on the sounding rocket MASER 4. The highlights of the investigations on these missions together with the results of relevant ground-based research were presented at the symposium.
NASA Discipline Cell Biology↗
Kinetics of determination in the differentiation of isolated mesophyll cells of Zinnia elegans to tracheary elements
Mechanically isolated mesophyll cells of Zinnia elegans L. cv Envy differentiate to tracheary elements when cultured in inductive medium containing 0.5 micromolar alpha-naphthaleneacetic acid and 0.5 micromolar benzyladenine. The cells do not differentiate when cultured in medium in which the concentration of auxin and/or cytokinin has been reduced to 0.005 micromolar. Cells require an initial 24-hour exposure to inductive cytokinin and 56-hour exposure to inductive auxin for differentiation at 72 hours of culture. Freshly isolated Zinnia cells can be maintained in medium having low concentrations of both auxin and cytokinin for only 1 day without significant loss of potential to differentiate upon transfer to inductive medium. Initial culture for up to 2 days in medium having high auxin and low cytokinin, or low auxin and high cytokinin, allows full differentiation on the third day after transfer to inductive medium and potentiates the early differentiation of some cells.
Non-NASA Center↗
Laser-assisted patch clamping: a methodology
Laser microsurgery can be used to perform both cell biological manipulations, such as targeted cell ablation, and molecular genetic manipulations, such as genetic transformation and chromosome dissection. In this report, we describe a laser microsurgical method that can be used either to ablate single cells or to ablate a small area (1-3 microns diameter) of the extracellular matrix. In plants and microorganisms, the extracellular matrix consists of the cell wall. While conventional patch clamping of these cells, as well as of many animal cells, requires enzymatic digestion of the extracellular matrix, we illustrate that laser microsurgery of a portion of the wall enables patch clamp access to the plasma membrane of higher plant cells remaining situated in their tissue environment. What follows is a detailed description of the construction and use of an economical laser microsurgery system, including procedures for single cell and targeted cell wall ablation. This methodology will be of interest to scientists wishing to perform cellular or subcellular ablation with a high degree of accuracy, or wishing to study how the extracellular matrix affects ion channel function.
Non-NASA Center↗