Luminescence in ophiuroids (Echinodermata) does not share a common nervous control in all species

2002 ◽  
Vol 205 (6) ◽  
pp. 799-806 ◽  
Author(s):  
Y. Dewael ◽  
J. Mallefet
Keyword(s):  
Amino Acids ◽  
Muscarinic Receptors ◽  
Nicotinic Receptors ◽  
Light Emission ◽  
Cholinergic Receptors ◽  
Common Mechanism ◽  
Control Mechanisms ◽  
Nervous Control ◽  
Amphipholis Squamata ◽  
Muscarinic And Nicotinic Receptors

SUMMARYStudy of the control mechanisms of light emission in invertebrates shows the involvement of several neurotransmitters. In ophiuroids, only one species (Amphipholis squamata) has so far been characterized for luminescence control, which seems to be cholinergic, with an influence of several excitatory and inhibitory neuromodulators (amino acids, catecholamines, neuropeptides S1 and S2, purines). The aim of this work is to investigate the nature of control mechanisms of light emission in three luminous ophiuroid species, A. filiformis, O. aranea and O. californica, in order to see whether or not they share common mechanisms. Luminescence induced by general depolarisation of tissues using KCl (200 mmol l–1) shows different patterns, according to species. Only A. filiformis emits light in response to acetylcholine. In this species, the involvement of both muscarinic and nicotinic receptors is proposed, since atropine and tubocurarine (at 10–3 mol l–1) inhibited 99 % and 71 %, respectively, of the light emitted. Study of the subtypes of cholinergic receptors involved in photogenesis revealed that several subtypes of muscarinic receptors might be involved. It was also clearly shown that ophiuroids did not share a common mechanism of nervous control of luminescence in all species.

scholarly journals Accumulation of amino acids by the perfused rat liver in the presence of ethanol

1973 ◽  
Vol 134 (3) ◽  
pp. 697-705 ◽  
Author(s):  
Hans A. Krebs ◽  
Reginald Hems ◽  
Patricia Lund
Keyword(s):  
Amino Acids ◽  
Rat Liver ◽  
Major Effect ◽  
Major Product ◽  
Control Mechanisms ◽  
Perfused Rat Liver ◽  
Carbamoyl Phosphate ◽  
Lactate Formation ◽  
Gluconeogenesis From Alanine ◽  
Almost All

1. The rate of gluconeogenesis from alanine in the perfused rat liver is affected by the presence of other metabolizable substances, especially fatty acids, ornithine and ethanol. Gluconeogenesis is accelerated by oleate and by ornithine. When both oleate and ornithine were present the acceleration was greater than expected on the basis of mere additive effects. 2. Much NH3 and some urea were formed from alanine when no ornithine was added. With ornithine almost all the nitrogen released from alanine appeared as urea. 3. Lactate was a major product of alanine metabolism. Addition of oleate, and especially of oleate plus ornithine, decreased lactate formation. 4. Ethanol had no major effect on gluconeogenesis from alanine when this was the sole added precursor. Gluconeogenesis was strongly inhibited (87%) when oleate was also added, but ethanol greatly accelerated gluconeogenesis when ornithine was added together with alanine. 5. In the absence of ethanol the alanine carbon and alanine nitrogen removed were essentially recovered in the form of glucose, lactate, pyruvate, NH3 and urea. 6. In the presence of ethanol the balance of both alanine carbon and alanine nitrogen showed substantial deficits. These deficits were largely accounted for by the formation of aspartate and glutamine, the formation of which was increased two- to three-fold. 7. When alanine was replaced by lactate plus NH4Cl, ethanol also caused a major accumulation of amino acids, especially of aspartate and alanine. 8. Earlier apparently discrepant results on the effects of ethanol on gluconeogenesis from alanine are explained by the fact that under well defined conditions ethanol can inhibit, or accelerate, or be without major effect on the rate of gluconeogenesis. 9. It is pointed out that in the synthesis of urea through the ornithine cycle half of the nitrogen must be supplied in the form of asparate and half in the form of carbamoyl phosphate. The accumulation of aspartate and other amino acids suggests that ethanol interferes with the control mechanisms which regulate the stoicheiometric formation of aspartate and carbamoyl phosphate.

scholarly journals Colocalization of muscarinic and nicotinic receptors in cholinoceptive neurons of the suprachiasmatic region in young and aged rats

1991 ◽  
Vol 542 (2) ◽  
pp. 348-352 ◽  
Author(s):  
E.A. van der Zee ◽  
C. Streefland ◽  
A.D. Strosberg ◽  
H. Schro¨der ◽  
P.G.M. Luiten
Keyword(s):  
Nicotinic Receptors ◽  
Aged Rats ◽  
Muscarinic And Nicotinic Receptors

scholarly journals The lantern shark's light switch: turning shallow water crypsis into midwater camouflage

2010 ◽  
Vol 6 (5) ◽  
pp. 685-687 ◽  
Author(s):  
Julien M. Claes ◽  
Jérôme Mallefet
Keyword(s):  
Shallow Water ◽  
Deep Sea ◽  
Light Emission ◽  
Colour Change ◽  
Hormonal Control ◽  
Nervous Control ◽  
Luminous Bacteria ◽  
Physiological Colour Change ◽  
Physiological Suppression

Bioluminescence is a common feature in the permanent darkness of the deep-sea. In fishes, light is emitted by organs containing either photogenic cells (intrinsic photophores), which are under direct nervous control, or symbiotic luminous bacteria (symbiotic photophores), whose light is controlled by secondary means such as mechanical occlusion or physiological suppression. The intrinsic photophores of the lantern shark Etmopterus spinax were recently shown as an exception to this rule since they appear to be under hormonal control. Here, we show that hormones operate what amounts to a unique light switch, by acting on a chromatophore iris, which regulates light emission by pigment translocation. This result strongly suggests that this shark's luminescence control originates from the mechanism for physiological colour change found in shallow water sharks that also involves hormonally controlled chromatophores: the lantern shark would have turned the initial shallow water crypsis mechanism into a midwater luminous camouflage, more efficient in the deep-sea environment.

Cardiac nicotinic receptors show β-subunit dependent compensatory changes

2021 ◽  
Author(s):  
Katarina Targosova ◽  
Matej Kucera ◽  
Zuzana Kilianova ◽  
Lubica Slobodova ◽  
Kristina Szmicsekova ◽  
...  
Keyword(s):  
Heart Rate ◽  
Muscarinic Receptors ◽  
Nicotinic Receptors ◽  
Isolated Heart ◽  
High Dose ◽  
Β Subunit ◽  
Adrenergic Stimulation ◽  
Relative Expression ◽  
Isolated Hearts ◽  
Heart Functions

Nicotinic receptors (NR) play an important role in the cholinergic regulation of heart functions, and converging evidence suggests a diverse repertoire of NR subunits in the heart. A recent hypothesis about the plasticity of β NR subunits suggests that β2 and β4 subunits may substitute for each other. In our study, we assessed the hypothetical β subunit interchangeability in the heart at the level of mRNA. Using two mutant mice strains lacking β2 or β4 NR subunits, we examined the relative expression of NR subunits and other key cholinergic molecules. We investigated the physiology of isolated hearts perfused by Langendorff's method at basal conditions and after cholinergic and/or adrenergic stimulation. Lack of β2 NR subunit was accompanied with decreased relative expression of β4 and α3 subunits. No other cholinergic changes were observed at the level of mRNA, except for increased M3 and decreased M4 muscarinic receptors. Isolated hearts lacking β2 NR subunit showed different dynamics in heart rate response to indirect cholinergic stimulation. In hearts lacking β4 NR subunit, increased levels of β2 subunits were observed together with decreased mRNA for acetylcholine-synthetizing enzyme and M1 and M4 muscarinic receptors. Changes in the expression levels in β4-/- hearts were associated with increased basal heart rate and impaired response to a high dose of acetylcholine upon adrenergic stimulation. In support of the proposed plasticity of cardiac NRs, our results confirmed subunit-dependent compensatory changes to missing cardiac NRs subunits with consequences on isolated heart physiology.

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