Parathyroid hormone-related peptide directly increases adrenocorticotropic hormone secretion from the anterior pituitary in hens

Miller

2016

Front. Syst. Neurosci.

Hobson and Friston have hypothesized that the brain must actively dissipate heat in order to process information (Hobson et al., 2014). This physiologic trait is functionally homologous with the first instantation of life formed by lipids suspended in water forming micelles- allowing the reduction in entropy (heat dissipation). This circumvents the Second Law of Thermodynamics permitting the transfer of information between living entities, enabling them to perpetually glean information from the environment, that is felt by many to correspond to evolution per se. The next evolutionary milestone was the advent of cholesterol, embedded in the cell membranes of primordial eukaryotes, facilitating metabolism, oxygenation and locomotion, the triadic basis for vertebrate evolution. Lipids were key to homeostatic regulation of calcium, forming calcium channels. Cell membrane cholesterol also fostered metazoan evolution by forming lipid rafts for receptor-mediated cell-cell signaling, the origin of the endocrine system. The eukaryotic cell membrane exapted to all complex physiologic traits, including the lung and brain, which are molecularly homologous through the function of neuregulin, mediating both lung development and myelinization of neurons. That cooption later exapted as endothermy during the water-land transition (Torday, 2015a), perhaps being the functional homolog for brain heat dissipation and conscious/mindful information processing. The skin and brain similarly share molecular homologies through the “skin-brain” hypothesis, giving insight to the cellular-molecular “arc” of consciousness from its unicellular origins to integrated physiology. This perspective on the evolution of the central nervous system clarifies self-organization, reconciling thermodynamic and informational definitions of the underlying biophysical mechanisms, thereby elucidating relations between the predictive capabilities of the brain and self-organizational processes.

Section: On the Evolution Of Endothermymentioning

confidence: 99%

On the Evolution of the Mammalian Brain

Miller

2016

Front. Syst. Neurosci.

“…Another gene duplication that occurred during the vertebrate water-land transition was for the beta adrenergic receptor (βAR), which ultimately provided for the local pulmonary regulation of alveolar capillary blood pressure, necessitated by the constraints of the systemic blood pressure imposed on the alveolar capillary system [ 65 ]. That new physiologic trait may have evolved as a result of the coevolution of PTHrP signaling in the anterior pituitary [ 66 ], and in the adrenal cortex [ 67 ], increasing ACTH and glucocorticoid production, respectively, in adaptation to terrestrial physiologic stress. The resultant increased responsiveness to physiologic stress by the Pituitary-Adrenal Axis (PAA) would have amplified adrenalin production, since the corticoids produced in the adrenal cortex pass through the adrenal medulla, where they physiologically stimulate the rate-limiting step in adrenalin production, Catechol-O-Methyltransferase, or COMT [ 68 ].…”

Section: Homeostasis As the Consequence Of Developmental Mechanismentioning

confidence: 99%

“…More recently, it has been discovered that PTHrP is expressed in the pituitary [ 66 ], where it stimulates ACTH, and in the adrenal cortex [ 67 ] where it mediates the ACTH stimulation of corticoid synthesis. As a consequence, this pathway would have amplified the physiologic stress response by increasing adrenalin production by the adrenal medulla [ 78 ].…”

Section: The Role Of Pthrp Expression In Adrenal Corticoid Synthementioning

confidence: 99%

Homeostasis as the Mechanism of Evolution

2015

Biology

Homeostasis is conventionally thought of merely as a synchronic (same time) servo-mechanism that maintains the status quo for organismal physiology. However, when seen from the perspective of developmental physiology, homeostasis is a robust, dynamic, intergenerational, diachronic (across-time) mechanism for the maintenance, perpetuation and modification of physiologic structure and function. The integral relationships generated by cell-cell signaling for the mechanisms of embryogenesis, physiology and repair provide the needed insight to the scale-free universality of the homeostatic principle, offering a novel opportunity for a Systems approach to Biology. Starting with the inception of life itself, with the advent of reproduction during meiosis and mitosis, moving forward both ontogenetically and phylogenetically through the evolutionary steps involved in adaptation to an ever-changing environment, Biology and Evolution Theory need no longer default to teleology.

“…Shear stress within the renal vasculature could have given rise to PTHrP signaling for glomerular function—PTHrP-mesangium signaling for water and electrolyte flux. 67 Similarly, PTHrP is expressed in the pituitary 84 and adrenal cortex 85 of land vertebrates, making for a more robust physiologic stress “fight or flight” mechanism since the corticoids stimulate epinephrine secretion as they course their way from the adrenal cortex through the adrenal medulla. 86 But this amplified epinephrine response to stress is only applicable to amphibians and beyond phylogenetically since fish have an independent adrenal cortex and medulla.…”

Section: The Water-land Transition Pthrp Amplification and The Adapmentioning

confidence: 99%

What We Talk About When We Talk About Evolution

Cell Communication Insights

2015

Currently, the biologic sciences are a Tower of Babel, having become so highly specialized that one discipline cannot effectively communicate with another. A mechanism for evolution that integrates development and physiologic homeostasis phylogenetically has been identified—cell-cell interactions. By reducing this process to ligand-receptor interactions and their intermediate down-stream signaling partners, it is possible, for example, to envision the functional homologies between such seemingly disparate structures and functions as the lung alveolus and kidney glomerulus, the skin and brain, or the skin and lung. For example, by showing the continuum of the lung phenotype for gas exchange at the cell-molecular level, being selected for increased surface area by augmenting lung surfactant production and function in lowering surface tension, we have determined an unprecedented structural-functional continuum from proximate to ultimate causation in evolution. It is maintained that tracing the changes in structure and function that have occurred over both the short-term history of the organism (as ontogeny), and the long-term history of the organism (as phylogeny), and how the mechanisms shared in common can account for both biologic stability and novelty, will provide the key to understanding the mechanisms of evolution. We need to better understand evolution from its unicellular origins as the Big Bang of biology.