Cell Growth

3 Key excerpts on "Cell Growth"

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  eBook - ePub

  Extreme Tissue Engineering

  Concepts and Strategies for Tissue Fabrication

  • Robert A. Brown(Author)
  • 2013(Publication Date)
  • Wiley-Blackwell

    (Publisher)

  In biology and medicine it tends to have a rather specific but also, to be honest, somewhat poorly understood series of meanings. In reality, it is more widely used to describe any form of geometric increase in size or proportion. For example, we like to think of children growing in height and salamanders growing new limbs after injury as rather special (i.e. biological). Yet the same word is used for both processes, even though they are clearly very different. Similarly, we are perfectly happy with the idea that the Eiffel Tower grew over a period of months (Figure 7.4) or that the Himalayas grew by seismic activity (as do tsunami waves on a different timescale!). Intriguingly, we even consider that a tunnel (i.e. tubular void) grows, although in this case as a result of excavators removing material. Figure 7.4 The Eiffel Tower grows in dimensions in images (a) to (c)—but this clearly is different to that growth which occurs between (b) and (d). Interestingly, (a) to (c) is analogous to soft tissue (interstitial) growth, but (b) to (d) better represents bone/hard tissue (appositional) growth. Equally interesting, (a) to (c) is a photo-trick which we cannot achieve by engineering. In other words, growth can be the appearance and extension of three-dimensional structure by almost any animate or inanimate means. As we shall see in the next chapter, the diversity of how we achieve growth may be at the very core of our thinking about how to engineer tissues. In particular, we shall wrestle with the tension between growth as a biological cell-driven process and growth of structure that we can achieve in the human world by routine engineering and fabrication. First, though, let us make the distinction we have used before between cell-rich and matrix-rich tissues. In effect, most of embryology and early mammalian development can be seen as a series of cell rich tissue organisations, template formation and growth processes, under relatively tight gene control

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  Bioenergetics Of Wild Herbivores

  • Robert J. Hudson(Author)
  • 2018(Publication Date)
  • CRC Press

    (Publisher)

  The homeostatic mechanisms of the body appear to be more weight- than time-oriented. Maximum positive growth rates are dictated by the maximum rate at which the body can assimilate nutrients and the maximum amount by which anabolism can exceed catabolism. Maximum negative growth rates are dictated by the maximum amount by which catabolism can exceed anabolism. Between these extremes, the body mechanisms attempt to ensure that each increment in body weight contains an appropriate proportion of each body component, regardless of how long it takes to achieve that increment. In practice, time can be of great importance because of its association with season and the changes including pho-toperiod that accompany changes in season in many locations. Since many ungulates are seasonal breeders and have seasonal changes in body composition, failure to achieve a particular body weight or condition in a particular time may be fatal. This places strong evolutionary pressure on appropriate adaptation.

  II. Principles of Growth

  Growth and development are directed, but not totally controlled, by the genetic code. Some of the rules controlling their progress are known, many are not. It is even possible to develop quite simple mathematical expressions describing growth and development. Nevertheless, these mathematical models will not apply under all circumstances, since the genetic code includes built-in adaptability which allows the growing animal to adapt to some particular environmental changes by apparently switching to “plan B” which may be outside the scope of the model proposed for that phase of growth.

  A. Organization

  1. Cellular Growth

  Growth can be studied at many levels, but a logical starting point is the cell. Cells have two ways of growing: they can increase in number (hyperplasia), or they can increase in size (hypertrophy). It is also possible for cells to accumulate noncellular material either around them (e.g., bone) or within themselves (e.g., fat). This process is called accretion.

  2. Tissue Growth

  Beds of cells make up tissues or organs, and each, depending on function and location, will exhibit a type of growth most appropriate to its needs. Most tissues increase in size interstitially (endogenously), meaning that the growth takes place throughout the tissue. Some tissues, bone for example, cannot grow this way, since the rigidity of the tissue itself prevents any internal growth. These tissues grow only at growth surfaces; this is called appositional (exogenous) growth.4

  FIGURE 1. Modes of growth within a tissue. In renewing, populations, cells are continually being lost or destroyed and replaced from mitotically active stem cells; in expanding cell populations, growth is by diffuse proliferation or cellular hyperplasia; in static cell populations, growth is by cellular hypertrophy. (From Goss, R. J., Adaptive Growth,

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  Basic Pathology

  An introduction to the mechanisms of disease

  • Sunil R. Lakhani, Caroline J. Finlayson, Susan A. Dilly, Mitesh Gandhi(Authors)
  • 2016(Publication Date)
  • CRC Press

    (Publisher)

  Pathological assessment of tissues has remained the lynchpin of diagnostic practice for over 100 years. It has become the core science of clinical medical practice, providing data for clinical management and a framework for future correlation of new markers and new therapies. With the current explosion of technology and data, it is important for pathologists and other clinical specialists to embrace and incorporate these changes into their training and practice. Molecular biologists will also benefit from a closer interaction with pathologists.

  This brings us to the end of this section on the cellular events involved in producing the cancer cell. Of course, we have a long way to go before we have full understanding, but our knowledge is advancing at an exciting pace, and a whole new language of tumour terminology is emerging. For the scientist, the battle is the biology; for the clinicians and students trying to understand and apply the new knowledge, it is often the terminology!

  The next question we need to address and one that will be in the forefront of the patient’s mind is: How will a given tumour behave? Passage contains an image

  CHAPTER 14

  THE BEHAVIOUR OF TUMOURS

  Tumour growth How do tumours spread? The biology of metastatic disease The role of the immune system

  The behaviour of a tumour can be considered under a number of headings covering how fast it will grow, whether it is likely to metastasise, which sites are affected, and what symptoms and complications the patient is likely to have.

  TUMOUR GROWTH

  It is often assumed that tumours grow faster than normal tissues because they expand to compress the surrounding structures. However, this does not mean that the cells are dividing more often, but that there is an imbalance between production and loss . The time taken for tumour cell division varies between 20 and 60 hours, with leukaemias having shorter cell cycles than solid tumours but, in general, tumour cells take longer

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