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Med Hypotheses. 2002 Apr;58(4):261-3.
Hormone-induced aberrations in electromagnetic adhesion signaling as a developmental factor of androgenetic alopecia.
Matilainen VA, Keinänen-Kiukaanniemi SM.
Source
Department of Public Health Science and General Practice, University of Oulu, Finland.
Abstract
In androgenetic alopecia, overactivation of the androgen hormone cascade in genetically predisposed persons leads to miniaturization of the dermal papilla of the hair follicle and to reduction in the number of papilla cells in the scalp, but the mechanisms explaining this miniaturization have remained unclear. According to our hypothesis, the increase of dihydrotestosterone (DHT) production in the overactive androgen state inhibits cell mitosis in the dermal papilla and contributes to the induction of programmed cell death (apoptosis). Normally, DNA molecules have a negative charge, which doubles in every cell mitosis. In the catagen and telogen phases, the sulphur-rich hair moves upwards, dehydrates and develops an increasing positive charge. In a normal hair-growth cycle, the epithelial column shortens and the secondary germ is formed and it invaginates the dermal papilla by electromagnetic attraction. In the mitotic inhibition state induced by DHT, the negative charge decreases, leading to a weakening of the electromagnetic adhesion forces and weaker electrical attraction between the undifferentiated germ cells and the dermal papilla. Insulin resistance has an additional pathogenic role in the excessive miniaturization of the hair follicle. The vasoactive substances associated with endothelial dysfunction in insulin resistance induce microcirculatory disturbance, perifollicular vasoconstriction and stimulation of smooth muscle cell proliferation in the vascular wall. This leads to microvascular insufficiency and local tissue hypoxia and progressive miniaturization of hair follicles.
- - - Updated - - -
The mechanism by which minoxidil promotes hair growth is not fully understood. Minoxidil contains the nitric oxide chemical moiety and may act as a nitric oxide agonist. Similarly, minoxidil is a potassium channel opener, causing hyperpolarization of cell membranes.
Hyperpolarization is a change in a cell's membrane potential that makes it more negative. It is the opposite of a depolarization.
- - - Updated - - -
[h=1]Effects of the inflammatory mediator prostaglandin D2 on submucosal neurons and secretion in guinea pig colon.[/h]Frieling T, Rupprecht C, Kroese AB, Schemann M.
[h=3]Source[/h]Department of Gastroenterology, University of Düsseldorf, Germany.
[h=3]Abstract[/h]Conventional flux chamber and intracellular recording methods were used to investigate the mode of action of prostaglandin D2 (PGD2) on ion transport in muscle-stripped segments of guinea pig colon and on colonic submucosal ganglion cells. Application of PGD2 resulted in a dose-dependent increase in short-circuit current that was reduced by serosal addition of bumetanide, tetrodotoxin, atropine, or piroxicam, but not hexamethonium. Application of PGD2 to submucosal neurons evoked a depolarization of the membrane potential that was associated with an enhanced spike discharge. In AH/type 2 neurons, postspike afterhyperpolarizations were reduced in amplitude and duration. The depolarizing responses to PGD2 were not affected by tetrodotoxin, indicative of a direct effect of PGD2 on the impaled neurons. Whereas fast excitatory postsynaptic potentials (EPSPs) were not affected by PGD2, slow EPSPs were reduced by a presynaptic effect, indicating presynaptic suppression of noncholinergic neurotransmitter release. The study demonstrates that PGD2 acts as a neuromodulator to evoke nerve-mediated chloride secretion, predominantly through activation of cholinergic submucosal neurons. The results further indicate that PGD2 released from lamina propria immune cells during antigenic stimulation may influence mucosal function by altering electrical behavior of submucosal neurons.
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[h=1]Acetyl-L-carnitine induces a sustained potentiation of the afterhyperpolarization.[/h]Lombardo P, Scuri R, Cataldo E, Calvani M, Nicolai R, Mosconi L, Brunelli M.
[h=3]Source[/h]Department of Physiology and Biochemistry G. Moruzzi, University of Pisa, Via S. Zeno 31, 56127, Italy.
[h=3]Abstract[/h]Acetyl-L-carnitine is known to improve many aspects of the neural activity even if its exact role in neurotransmission is still unknown. This study investigates the effects of acetyl-L-carnitine in T segmental sensory neurons of the leech Hirudo medicinalis. These neurons are involved in some forms of neural plasticity associated with learning processes. Their physiological firing is accompanied by a large afterhyperpolarization that is mainly due to the Na+/K+ ATPase activity and partially to a Ca2+ -dependent K+ current. A clear-cut hyperpolarization and a significant increase of the afterhyperpolarization have been recorded in T neurons of leeches injected with 2 mM acetyl-L-carnitine some days before. Acute treatments of 50 microM acetyl-L-carnitine induced similar effects in T cells of naive animals. In the presence of apamin, a pharmacological blocker of Ca2+ -dependent K+ channel, acetyl-L-carnitine still enhanced the residual afterhyperpolarization, suggesting an effect of the drug on the Na+/K+ATPase. Acetyl-L-carnitine also increased the hyperpolarization induced by intracellular injection of Na+ ions. Therefore, acetyl-L-carnitine seems to be able to exert a positive sustained effect on the Na+/K+ ATPase activity in leech T sensory neurons. Moreover, in these cells, widely arborized, the afterhyperpolarization seems to play an important role in determining the action potential transmission at neuritic bifurcations. A computational model of a T cell has been previously developed considering detailed data for geometry and the modulation of the pump current. Herein, we showed that to a larger afterhyperpolarization, due to the acetyl-L-carnitine-induced effects, corresponds a decrement in the number of action potentials reaching synaptic terminals.
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[h=1]Extracellular ATP induces hyperpolarization and motility stimulation of ciliary cells.[/h]Tarasiuk A, Bar-Shimon M, Gheber L, Korngreen A, Grossman Y, Priel Z.
[h=3]Source[/h]Faculty of Natural Sciences, Department of Chemistry, Ben-Gurion University of the Negev, Beer-Sheva, Israel.
[h=3]Abstract[/h]Cellular membrane potential and ciliary motility were examined in tissues cultures prepared from frog palate and esophagus epithelia. Addition of micromolar concentrations of extracellular ATP caused membrane hyperpolarization and enhanced the beat frequency. These two effects of ATP were 1) dose dependent, reaching a maximum at 10 microM ATP; 2) dependent on the presence of extracellular Ca2+ or Mg2+; 3) insensitive to inhibitors of voltage-gated calcium channels; 4) abolished after depleting the intracellular Ca2+ stores with thapsigargin; 5) attenuated by quinidine (1 mM), Cs+ (5-20 mM), and replacement of extracellular Na+ by K+; 6) insensitive to charybdotoxin (5-20 nM), TEA (1-20 microM), and apamin (0.1-1 microM); 7) independent of initial membrane potential; and 8) unaffected by amiloride. In addition, extracellular ATP induced an appreciable rise in intracellular Ca2+. Addition of thapsigargin caused an initial enhancement of the ciliary beat frequency and membrane hyperpolarization. These results strongly suggest the involvement of calcium-dependent potassium channels in the response to ATP. The results show that moderate hyperpolarization is closely associated with a sustained enhancement of ciliary beating by extracellular ATP.
Hormone-induced aberrations in electromagnetic adhesion signaling as a developmental factor of androgenetic alopecia.
Matilainen VA, Keinänen-Kiukaanniemi SM.
Source
Department of Public Health Science and General Practice, University of Oulu, Finland.
Abstract
In androgenetic alopecia, overactivation of the androgen hormone cascade in genetically predisposed persons leads to miniaturization of the dermal papilla of the hair follicle and to reduction in the number of papilla cells in the scalp, but the mechanisms explaining this miniaturization have remained unclear. According to our hypothesis, the increase of dihydrotestosterone (DHT) production in the overactive androgen state inhibits cell mitosis in the dermal papilla and contributes to the induction of programmed cell death (apoptosis). Normally, DNA molecules have a negative charge, which doubles in every cell mitosis. In the catagen and telogen phases, the sulphur-rich hair moves upwards, dehydrates and develops an increasing positive charge. In a normal hair-growth cycle, the epithelial column shortens and the secondary germ is formed and it invaginates the dermal papilla by electromagnetic attraction. In the mitotic inhibition state induced by DHT, the negative charge decreases, leading to a weakening of the electromagnetic adhesion forces and weaker electrical attraction between the undifferentiated germ cells and the dermal papilla. Insulin resistance has an additional pathogenic role in the excessive miniaturization of the hair follicle. The vasoactive substances associated with endothelial dysfunction in insulin resistance induce microcirculatory disturbance, perifollicular vasoconstriction and stimulation of smooth muscle cell proliferation in the vascular wall. This leads to microvascular insufficiency and local tissue hypoxia and progressive miniaturization of hair follicles.
- - - Updated - - -
The mechanism by which minoxidil promotes hair growth is not fully understood. Minoxidil contains the nitric oxide chemical moiety and may act as a nitric oxide agonist. Similarly, minoxidil is a potassium channel opener, causing hyperpolarization of cell membranes.
Hyperpolarization is a change in a cell's membrane potential that makes it more negative. It is the opposite of a depolarization.
- - - Updated - - -
[h=1]Effects of the inflammatory mediator prostaglandin D2 on submucosal neurons and secretion in guinea pig colon.[/h]Frieling T, Rupprecht C, Kroese AB, Schemann M.
[h=3]Source[/h]Department of Gastroenterology, University of Düsseldorf, Germany.
[h=3]Abstract[/h]Conventional flux chamber and intracellular recording methods were used to investigate the mode of action of prostaglandin D2 (PGD2) on ion transport in muscle-stripped segments of guinea pig colon and on colonic submucosal ganglion cells. Application of PGD2 resulted in a dose-dependent increase in short-circuit current that was reduced by serosal addition of bumetanide, tetrodotoxin, atropine, or piroxicam, but not hexamethonium. Application of PGD2 to submucosal neurons evoked a depolarization of the membrane potential that was associated with an enhanced spike discharge. In AH/type 2 neurons, postspike afterhyperpolarizations were reduced in amplitude and duration. The depolarizing responses to PGD2 were not affected by tetrodotoxin, indicative of a direct effect of PGD2 on the impaled neurons. Whereas fast excitatory postsynaptic potentials (EPSPs) were not affected by PGD2, slow EPSPs were reduced by a presynaptic effect, indicating presynaptic suppression of noncholinergic neurotransmitter release. The study demonstrates that PGD2 acts as a neuromodulator to evoke nerve-mediated chloride secretion, predominantly through activation of cholinergic submucosal neurons. The results further indicate that PGD2 released from lamina propria immune cells during antigenic stimulation may influence mucosal function by altering electrical behavior of submucosal neurons.
- - - Updated - - -
[h=1]Acetyl-L-carnitine induces a sustained potentiation of the afterhyperpolarization.[/h]Lombardo P, Scuri R, Cataldo E, Calvani M, Nicolai R, Mosconi L, Brunelli M.
[h=3]Source[/h]Department of Physiology and Biochemistry G. Moruzzi, University of Pisa, Via S. Zeno 31, 56127, Italy.
[h=3]Abstract[/h]Acetyl-L-carnitine is known to improve many aspects of the neural activity even if its exact role in neurotransmission is still unknown. This study investigates the effects of acetyl-L-carnitine in T segmental sensory neurons of the leech Hirudo medicinalis. These neurons are involved in some forms of neural plasticity associated with learning processes. Their physiological firing is accompanied by a large afterhyperpolarization that is mainly due to the Na+/K+ ATPase activity and partially to a Ca2+ -dependent K+ current. A clear-cut hyperpolarization and a significant increase of the afterhyperpolarization have been recorded in T neurons of leeches injected with 2 mM acetyl-L-carnitine some days before. Acute treatments of 50 microM acetyl-L-carnitine induced similar effects in T cells of naive animals. In the presence of apamin, a pharmacological blocker of Ca2+ -dependent K+ channel, acetyl-L-carnitine still enhanced the residual afterhyperpolarization, suggesting an effect of the drug on the Na+/K+ATPase. Acetyl-L-carnitine also increased the hyperpolarization induced by intracellular injection of Na+ ions. Therefore, acetyl-L-carnitine seems to be able to exert a positive sustained effect on the Na+/K+ ATPase activity in leech T sensory neurons. Moreover, in these cells, widely arborized, the afterhyperpolarization seems to play an important role in determining the action potential transmission at neuritic bifurcations. A computational model of a T cell has been previously developed considering detailed data for geometry and the modulation of the pump current. Herein, we showed that to a larger afterhyperpolarization, due to the acetyl-L-carnitine-induced effects, corresponds a decrement in the number of action potentials reaching synaptic terminals.
- - - Updated - - -
[h=1]Extracellular ATP induces hyperpolarization and motility stimulation of ciliary cells.[/h]Tarasiuk A, Bar-Shimon M, Gheber L, Korngreen A, Grossman Y, Priel Z.
[h=3]Source[/h]Faculty of Natural Sciences, Department of Chemistry, Ben-Gurion University of the Negev, Beer-Sheva, Israel.
[h=3]Abstract[/h]Cellular membrane potential and ciliary motility were examined in tissues cultures prepared from frog palate and esophagus epithelia. Addition of micromolar concentrations of extracellular ATP caused membrane hyperpolarization and enhanced the beat frequency. These two effects of ATP were 1) dose dependent, reaching a maximum at 10 microM ATP; 2) dependent on the presence of extracellular Ca2+ or Mg2+; 3) insensitive to inhibitors of voltage-gated calcium channels; 4) abolished after depleting the intracellular Ca2+ stores with thapsigargin; 5) attenuated by quinidine (1 mM), Cs+ (5-20 mM), and replacement of extracellular Na+ by K+; 6) insensitive to charybdotoxin (5-20 nM), TEA (1-20 microM), and apamin (0.1-1 microM); 7) independent of initial membrane potential; and 8) unaffected by amiloride. In addition, extracellular ATP induced an appreciable rise in intracellular Ca2+. Addition of thapsigargin caused an initial enhancement of the ciliary beat frequency and membrane hyperpolarization. These results strongly suggest the involvement of calcium-dependent potassium channels in the response to ATP. The results show that moderate hyperpolarization is closely associated with a sustained enhancement of ciliary beating by extracellular ATP.
