Eukaryotic cells and their cell bodies: Cell Theory revised

BACKGROUND: Cell Theory, also known as cell doctrine, states that all eukaryotic organisms are composed of cells, and that cells are the smallest independent units of life. This Cell Theory has been influential in shaping the biological sciences ever since, in 1838/1839, the botanist Matthias Schleiden and the zoologist Theodore Schwann stated the principle that cells represent the elements from which all plant and animal tissues are constructed. Some 20 years later, in a famous aphorism Omnis cellula e cellula, Rudolf Virchow annunciated that all cells arise only from pre-existing cells. General acceptance of Cell Theory was finally possible only when the cellular nature of brain tissues was confirmed at the end of the 20th century. Cell Theory then rapidly turned into a more dogmatic cell doctrine, and in this form survives up to the present day. In its current version, however, the generalized Cell Theory developed for both animals and plants is unable to accommodate the supracellular nature of higher plants, which is founded upon a super-symplasm of interconnected cells into which is woven apoplasm, symplasm and super-apoplasm. Furthermore, there are numerous examples of multinucleate coenocytes and syncytia found throughout the eukaryote superkingdom posing serious problems for the current version of Cell Theory. SCOPE: To cope with these problems, we here review data which conform to the original proposal of Daniel Mazia that the eukaryotic cell is composed of an elemental Cell Body whose structure is smaller than the cell and which is endowed with all the basic attributes of a living entity. A complement to the Cell Body is the Cell Periphery Apparatus, which consists of the plasma membrane associated with other periphery structures. Importantly, boundary structures of the Cell Periphery Apparatus, although capable of some self-assembly, are largely produced and maintained by Cell Body activities and can be produced from it de novo. These boundary structures serve not only as mechanical support for the Cell Bodies but they also protect them from the hostile external environment and from inappropriate interactions with adjacent Cell Bodies within the organism. CONCLUSIONS: From the evolutionary perspective, Cell Bodies of eukaryotes are proposed to represent vestiges of hypothetical, tubulin-based 'guest' proto-cells. After penetrating the equally hypothetical actin-based 'host' proto-cells, tubulin-based 'guests' became specialized for transcribing, storing and partitioning DNA molecules via the organization of microtubules. The Cell Periphery Apparatus, on the other hand, represents vestiges of the actin-based 'host' proto-cells which have become specialized for Cell Body protection, shape control, motility and for actin-mediated signalling across the plasma membrane.     

Forthcoming Meetings

Joint Meeting of the Cell Kinetics Society and the International Cell Cycle Society
17th Meeting of the European Study Group for Cell Proliferation
First International Congress on Very Ultra Low Dosage Bordeaux, France. 20-22 September 1990.     

Sensitivity of the mosquito Aedes aegypti (Culicidae) labral apical chemoreceptors to blood plasma components

The phagostimulants from the cellular fraction of blood induce gorging of Aedes aegypti (L.), and this process is enhanced by some plasma components. This project examines the responses of the labral apical chemoreceptors to plasma components enhancing phagostimulation. From the electrophysiological responses of the labral apical chemoreceptors four cells were identified by the waveform of their action potentials. Three of the cells (Cell 2, Cell 3 and Cell 4) responded in a dose dependent manner to NaCl. The responses of Cell 2 and Cell 3 to NaCl concentrations from 1 to 500 mmol/l can be described by a logarithmic equation. The response of Cell 2 to 150 mmol/l NaCl is modulated when a buffer is added. The magnitude of the modulation of the response is determined by the nature of the buffer: NaHCO(3) inhibits while Na(2)HPO(4) enhances the response. High osmotic pressure inhibits the response of Cell 4, regardless of how it is achieved. Cell 4 responds with a high frequency to the presence of L-alanine, the C-terminal amino acid of albumin, but shows a reduced response to the same concentration of albumin. From these results it can be concluded that labral apical chemoreceptors of A. aegypti are capable of detecting the plasma components involved in blood recognition.     

The pessimist's and optimist's views of adult neurogenesis

The reports by Bonaguidi et?al. (in this issue of Cell) and Encinas et?al. (in Cell Stem Cell) come to differing conclusions about whether and how the proliferation of radial glia-like stem cells of the adult hippocampus impacts their long-term potential for neurogenesis.     

Book reviews

Books review in this article:
The Regulation and Control of Cell Proliferation . Ed. By K. Lapis and A. Jeney.
Cell Kinetics and Cancer Therapy . By Juliana Denekamp. Charles C. Thomas
The Biology of Epithelial Cell Populations (2 Vol.). By N. Wright and M. Alison.     

Cell Cycle Regulation

Drosophila researchers met in sunny San Diego for the 49th annual meeting of The Genetics Society of America. It was cold outside and even colder inside. Like last year, ‘Mitosis, Meiosis and Cell Division’ was no longer a session. Instead, we searched out and covered talks and posters in ‘Cell Division and Growth Control’, ‘Gametogenesis’, ‘Cytoskeleton and Cell Biology’ and ‘Genome and Chromosome Structure’. We split up for maximal coverage and re-grouped later for the Workshop on Cell Cycle and Checkpoints. We apologize in advance for the brevity or omission of some reports.     

Recent advances in chemically induced reprogramming

Comment on: Zhu S, et al. Cell Stem Cell 2010; 7:651-5.     

Code breaking: The RNAPII modification code in pluripotency

Comment on: Brookes E, et al. Cell Stem Cell 2012; 10:157-70.     

Human pluripotency: A difficult state to make smart choices

Comment on: Hong SH, et al. Cell Stem Cell 2011; 9:24-36.     

A new role for microRNA-9 in human neural progenitor cells

Comment on: Delaloy C, et al. Cell Stem Cell 2010; 6:323–35     

Rescuing stalled replication forks: MMS22L-TONSL,a novel complex for DNA replication fork repair in human cells

Comment on: Piwko W, et al. EMBO J 2010; 29:4210-22, Duro E, et al. Mol Cell 2010; 40:632–44, O’Connell BC, et al. Mol Cell 2010; 40:645–57 and O’Donnell L, et al. Mol Cell 2010; 40:619–31.     

Through the looking-glass: Observing HSCs through the lens of infection reveals unexpected insights into HSC function

Comment on: Hall CJ, et al. Cell Stem Cell 2012; 10:198-209.     

Rejuvenating regeneration: Metformin activates endogenous adult stem cells

Comment on: Wang J, et al. Cell Stem Cell 2012; 11:23-35.     

The “X factor” in cellular reprogramming and proliferation

Comment on: Pomp O, et al. Cell Stem Cell 2011; 9:156-65.     

Hedgehog and hematopoietic stem cell differentiation: Don't believe the hype!

Comment on: Gao J, et al. Cell Stem Cell 2009; 4:548-58.     

Genetic instability in human induced pluripotent stem cells: Classification of causes and possible safeguards

Comment on: Mayshar Y, et al. Cell Stem Cell 2010; 7:521-31.     

MiRegulators in cancer stem cells of solid tumors

Comment on: Ma S, et al. Cell Stem Cell 2010; 7:694-707.     

Formins coming into focus

Two new crystal structures published in Cell and Molecular Cell provide the first clues about how fascinating proteins called formins interact with actin filaments.     

Single-cell microliter-droplet screening system (MISS Cell): An integrated platform for automated high-throughput microbial monoclonal cultivation and picking

Solid plates have been used for microbial monoclonal isolation, cultivation, and colony picking since 1881. However, the process is labor- and resource-intensive for high-throughput requirements. Currently, several instruments have been integrated for automated and high-throughput picking, but complicated and expensive. To address these issues, we report a novel integrated platform, the single-cell microliter-droplet screening system (MISS Cell), for automated, high-throughput microbial monoclonal colony cultivation and picking. We verified the monoclonality of droplet cultures in the MISS Cell and characterized culture performance. Compared with solid plates, the MISS Cell generated a larger number of monoclonal colonies with higher initial growth rates using fewer resources. Finally, we established a workflow for automated high-throughput screening of Corynebacterium glutamicum using the MISS Cell and identified high glutamate-producing strains. The MISS Cell can serve as a universal platform to efficiently produce monoclonal colonies in high-throughput applications, overcoming the limitations of solid plates to promote rapid development in biotechnology.