Cell theory

Summary

In biology, cell theory is a scientific theory first formulated in the mid-nineteenth century, that organisms are made up of cells, that they are the basic structural/organizational unit of all organisms, and that all cells come from pre-existing cells. Cells are the basic unit of structure in all organisms and also the basic unit of reproduction. The three tenets of the cell theory are:

All organisms are composed of one or more cells.

The cell is the basic unit of structure and organization in organisms.

Cells arise from pre-existing cells.

The theory was once universally accepted, but now some biologists consider non-cellular entities such as viruses living organisms, and thus disagree with the first tenet. As of 2021: "expert opinion remains divided roughly a third each between yes, no and don’t know". As there is no universally accepted definition of life, discussion still continues. History With continual improvements made to microscopes over time, magnificatio

Official source

https://en.wikipedia.org/wiki/Cell_theory

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Cell Seeding is a key factor for good regeneration in tissue engineering. In order to ensure uniform tissue regeneration, a system has to be found to distribute cells evenly within the scaffold that will carry them in the body. In this extent, this work try to find an accurate description of compression forced induced suction which is a seeding technique with reported satisfying seeding efficiency. This description will take the form of a numerical model with COMSOL Multiphysics and will allow us to maximize the seeding in terms of homogeneity. In order to find the best possible seeding, strains and velocities of the compression will be further analyzed. The scaffold material properties will also be examined in order to have the best possible material for that kind of applications.

2015

An Amidase_3 domain-containing N-acetylmuramyl-L-alanine amidase is required for mycobacterial cell division

Ashima Bhaskar, Neeraj Dhar, Dong Li

Mycobacteria possess a multi-layered cell wall that requires extensive remodelling during cell division. We investigated the role of an amidase_3 domain-containing N-acetylmuramyl-L-alanine amidase, a peptidoglycan remodelling enzyme implicated in cell division. We demonstrated that deletion of MSMEG_6281 (Ami1) in Mycobacterium smegmatis resulted in the formation of cellular chains, illustrative of cells that were unable to complete division. Suprisingly, viability in the Delta ami1 mutant was maintained through atypical lateral branching, the products of which proceeded to form viable daughter cells. We showed that these lateral buds resulted from mislocalization of DivIVA, a major determinant in facilitating polar elongation in mycobacterial cells. Failure of Delta ami1 mutant cells to separate also led to dysregulation of FtsZ ring bundling. Loss of Ami1 resulted in defects in septal peptidoglycan turnover with release of excess cell wall material from the septum or newly born cell poles. We noted signficant accumulation of 3-3 crosslinked muropeptides in the Delta ami1 mutant. We further demonstrated that deletion of ami1 leads to increased cell wall permeability and enhanced susceptiblity to cell wall targeting antibiotics. Collectively, these data provide novel insight on cell division in actinobacteria and highlights a new class of potential drug targets for mycobacterial diseases.

Nature Publishing Group2017

High-resolution cell outline segmentation and tracking from phase-contrast microscopy images

Mark Etienne Ambühl, Charles Brepsant, Jean-Jacques Meister

Accurate extraction of cell outlines from microscopy images is essential for analysing the dynamics of migrating cells. Phase-contrast microscopy is one of the most common and convenient imaging modalities for observing cell motility because it does not require exogenous labelling and uses only moderate light levels with generally negligible phototoxicity effects. Automatic extraction and tracking of high-resolution cell outlines from phase-contrast images, however, is difficult due to complex and non-uniform edge intensity. We present a novel image-processing method based on refined level-set segmentation for accurate extraction of cell outlines from high-resolution phase-contrast images. The algorithm is validated on synthetic images of defined noise levels and applied to real image sequences of polarizing and persistently migrating keratocyte cells. We demonstrate that the algorithm is able to reliably reveal fine features in the cell edge dynamics.

2012