Biochemistry & Physiology: Open Access
Open Access

Cell; Phases; DNA; Synthesis

Introduction

Regulation and control of cell cycle: The regulation of the cell cycle must ensure that the events in each phase are complete before moving to the next. Thus checkpoints for monitoring the integrity of DNA are strategically placed in late G1 and at G2/M interface to prevent progression and propagation of mutated or damaged cells. G0 refers to cells that are quiescent (temporarily or permanently out of cycle). The normal cell is dependent on external stimuli (mitogens or growth factors) to move it out of 2 G0 and through the early part of G1.Cells have evolved many mechanisms that monitor various discrepancies occurring during their cell cycle, e.g. a fatal DNA damage. Because errors encoded in the genome may result in defective clones, close monitoring of the cell cycle for abnormal programming is mandatory.

The cells tend to remain in the cell cycle machinery are such alterations is mutation in the genes involved in cell cycle regulation. The hallmark of the transformed state (cancerous state) is incompetent checkpoint control, resulting in aberrant responses to cellular damage. For example, damage to DNA or the spindle apparatus normally triggers cell cycle arrest or apoptosis, depending on the degree of damage and the cellular context. Cell cycle arrest most frequently occurs at the G1/S or G2/M boundaries. When checkpoint arrest control is compromised, initiation of S phase or mitosis occurs despite cellular damage, and the ensuing genetic instability may lead to the eventual emergence of a cancerous clone.

Cell and tissue culture techniques

Study of any particular type of cell in its natural environment is generally not possible because of various constraints like growth of other organisms, temperature, pH etc. So, the necessity of cell culture came into picture that involves growing of cells in artificial condition, in vitro.

1. Tissue culture It is a very generic term involving the removal of cells, tissue or organs from animal/plant and subsequent incorporation into an artificial condition suitable for their growth. The liquid or semi liquid medium is supplied as the nutrients for their survival and growth.

2. Organ Culture involves the culture of whole organs or intact organ fragments with the aim of studying their function and development. When the cells are removed from the organ/tissue (thus disrupting their normal relationship with neighboring cells) and cultured in artificial condition, it is called Cell Culture.

There are two basic systems used for growing cells:

Suspension culture: cells divide and grow while floating in the culture medium 2. Monolayer culture: cells need the substratum for their growth and division.

Experimental Model System

Cell culture serves as a good model system for studying:

• The mechanism of basic cytological and biochemical processes taking place in any particular organism
• The host-pathogen interaction and its consequence
• Process of senescence
• Monoclonal antibodies
• Vaccines
• Hormones
• Other useful proteins

Maintenance

• Media and growth requirements
• Physiological parameters
• pH= 7.2-7.5
• osmolality of the medium must be maintained
• Temperature= 37oC
• Cells should be protected from direct light as it can produce toxic substances in the medium ii. Medium requirements:
• Na+, K+, Ca++, Mg++, Cl-, PO43-, HCO3- and CO2 • Fe, Zn, Se (Trace elements)
• Glucose
• 13 essential amino acids
• Vitamins
• Choline, Inositol Serum It contains various growth factors and hormones. Also, it neutralizes the adverse effect of trypsin and other proteases on the cells. Antibiotics - although not required for cell growth, antibiotics are often used to control the growth of unwanted bacterial and fungal contaminants.

Feeding – 2-3 times/week

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