Phosphate transistasis

Phosphate transistasis is the power or tendency of a living thing to keep changing its phosphate needs according to the transformation of circumstances; i.e., to reform its functions to maintain a meaningful condition, by means of multiple dynamic equilibrium adjustments, controlled by interrelated phosphate regulation mechanisms. Homeostasis and transistasis are needed to maintain stability and to survive.
Transistasis
An organism has to endure, adapt, and evolve to modifications of the environment. It does this by testing which way its variables should be adjusted, by being ultraflexible.
Negative feedback is a reaction in which the system responds in such a way as to reverse the direction of change. Since this tends to keep things constant, it allows the maintenance of homeostasis.
In positive feedback, the response is to amplify the change in the variable, allowing the maintenance of transistasis.
Cell growth and phosphate limitation
Mathematical modeling of the rate kinetics of growth and acid phosphatase formation under varying degrees of phosphate limitation is concerned with
# the time lag for exponential growth,
# the biphasic growth on a substrate (glucose) and its product,
# sustained growth on conservative phosphate, and
# the derepression of acid phosphatase.
The numerical calculations using appropriate parametric constants describe the variation in the cell mass, glucose, product, and inorganic phosphate concentrations, and the enzyme activity of acid phosphatase during aerobic growth under different conditions of phosphate starvation. Study by simulation revealed that the optimum initial phosphate concentration in the medium giving a high productivity of acid phosphate is 2.0 mg phosphorus/g glucose liter.
Regulation of phosphate transporters
The regulation of phosphate transporters by nutrient-responsive signaling pathways allows cells to tailor phosphate uptake to environmental conditions. Cells starved for phosphate activate positive and negative feedback loops in an interplay that leads to bistability in phosphate transporter usage. Expression of TF after thrombin and S1P stimulation activates the coagulation cascade leading to further generation of thrombin and S1P; hence, a positive feedback loop. The production of CD44 variants is stimulated by Ras/MAPK signaling (Ras-Raf-MEK-ERK) and regulated by splicing factors which promote the inclusion of CD44 variable exons, controlled by Ras/MAPK signaling, at least in part through modification of splicing factors at the level of phosphorylation. This small DNA sequence can initiate replication of itself unless kept in check by feedbacks.
In addition, there are many genomes that create phosphate reserves. Or, the particular genome needs to alter its phosphate budget, e.g., to create more structural phosphate, such as by mitosis, or more catalytic phosphate.
When any of these demands are placed on the current state of phosphate homeostasis, and the demand is not readily negated by negative feedback, a dynamic state of change occurs. A zygote, e.g., happily feeding and replicating itself in homeostatic bliss may eventually reach a polycellular situation when a phosphate reserve is needed. Endochondral ossification and intramembranous ossification are two processes resulting in the formation of normal, healthy bone tissue.
Several hypotheses have been proposed for how bone evolved as a structural element in vertebrates. One hypothesis is that bone developed from tissues that evolved to store minerals, such as hydroxyapatite. Up to fifty percent of bone is made up of a modified form of the inorganic mineral hydroxylapatite.
Or, specifically, calcium-based minerals were stored in cartilage and bone was an exaptation development from this calcified cartilage. However, other possibilities include bony tissue evolving as an osmotic barrier, or as a protective structure.
Then again, carbonated-calcium deficient hydroxyapatite is the main mineral of which bone, dental enamel and dentin are comprised.
Calcium oscillations
The major positive feedback loop for calcium concentration oscillations inside a cell is Ca stimulation of phospholipase C (PLC) to generate inositol 1,4,5-triphosphate (IP<sub>3</sub>), which releases more Ca if the internal cellular stores are sufficiently full. The dominant feedback mechanism appears to be Ca stimulation of phospholipase C once this enzyme has been activated by hormone receptors.<ref nameHarootunian/> The positive feedback fails when the Ca stare is mostly depleted.<ref nameHarootunian/> Diacylglycerol (DG) is produced when PLC generates IP<sub>3</sub>.<ref nameHarootunian/> Protein kinase C is not essential for the maintenance or timing of the oscillations.<ref nameHarootunian/>

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