This is the first animated computer simulation of cell proliferation in a living tissue. The program takes into account the long-neglected, although, well known fact that a living tissue represents an integral structure composed of interconnected cells and having a tissue-specific architectonics. In the program, the tissue is represented as a two-dimensional hexagonal lattice that can be curved and folded. Cell contacts within the lattice are permanent and are not broken by cell division. The program operates with two basic mechanisms: a) the division wave and b) the cell death (apoptosis) serving as an initiation point for cell division.
The program models cell proliferation, cell movement and cell growth in the crypt of intestinal epithelium. It can demonstrate the cell proliferation in a steady state, when cells are dividing, but the size of the crypt remains unchanged. It shows how the cells move along the crypt axis as a result of division waves propagating within the cell layer. In this process, the lattice undergoes peculiar transformations, rotating the direction of spiral rows of cells forming the crypt cylinder and changing the cell pattern but not the diameter of the cylinder.
The program allows modeling of other tissues with different structures. The rates of cell division and growth can be varied and the two processes can be uncoupled; this allows one to emulate certain cell patterns and shapes found in real tissues. Some structures will display growth and, in fact, will "develop" themselves, increasing their complexity. The model suggests a biological role of cell death (apoptosis). It also suggests proliferation patterns of stem cells that so far have escaped the attention of cell biologists.
This program can also serve as an excellent tool for classroom demonstration in Cell Biology.
The Annals PrePrint service provides rapid electronic publication of articles as they are received from the volume editors. PrePrint articles are fully reviewed and edited, and appear here in close to their final form. The final versions will be published in print and at Annals Online in the coming weeks.
Stem cells continue to be of enormous scientific and clinical interest, due to the myriad therapeutic possibilities promised by their use. The initial excitement generated by identification of novel stem cell populations has given way to more focused effort on methods to manipulate their differentiation and self-renewal capacities. A number of genome-scale studies are now underway to catalog stem cell gene expression profiles or generate mouse mutants in stem cell-control genes.
Meiosis is an important biological concept that all students should know and understand. Its basic function is important for genetic diversity and the continuation of life in all plants and animals. This tutorial was made to help simplify a somewhat confusing, but important process. Below is the AP Biology Laboratory Manual's Introduction to meiosis
The goal of this exercise is to introduce you to the kinds of cells that make up all living systems, and to contrast cells with viruses. You should be able to name the 6 Kingdoms, understand the differences between prokaryotes and eukaryotes, and be able to describe the basic functions of the eukaryotic cell organelles.
ClinicalTrials.gov provides regularly updated information about federally and privately supported clinical research in human volunteers. ClinicalTrials.gov gives you information about a trial's purpose, who may participate, locations, and phone numbers for more details.
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