Adrenergic control of luminescence and cellular metabolism in Porichthys isolated luminous organs

1. Isolated photophores from the luminous fish Porichthys produce light in response to adrenaline and the metabolic inhibitors iodoacetic acid (IAA) or potassium cyanide (KCN).2. We attempted to analyse the interactions of cellular metabolism and adrenergic stimulation of the photogenic cells.3. Photophores were treated with IAA in the presence of pyruvate. In these conditions, IAA does inhibit glycolysis without inducing any luminescent activity of the cells.4. Similarly, other photophores were incubated with KCN in the presence of glucose, in order to inhibit cellular respiration while keeping the luminous system inactive.5. We observed that adrenergic stimulation of these photophores remained effective and induced a light emission, demonstrating that glycolytic and oxidative metabolism are not absolutely essential to the mechanism underlying adrenergic activation of the luminous system.6. The comparison of these luminescences with adrenergic responses of control photophores showed that the light emission to adrenaline was markedly inhibited by glycolysis blockade but potentiated by an inhibition of cellular respiration.7. As the inhibitory effect of IAA does not result from a direct action of IAA on the luminous system, these results suggest that adrenaline activation of adrenergic receptors might interact with glycolysis in photogenic cells.8. Glyceraldehyde 3-phosphate, or some derivatives, could be implicated in the glycolytic control of luminescence in the photophores.     

Pharmacomorphological study of denervation induced by 6-hydroxydopamine in Porichthys photophores

The effects of 6-hydroxydopamine (6-OHDA) on the bioluminescent response of Porichthys photophores were investigated as part of a pharmacological study of the neural control of luminescence in this fish. Subcutaneous injections of 6-OHDA induce a luminescent response similar to that of norepinephrine (NE), suggesting a sympathomimetic action. The luminescent response to electrical stimulation is almost completely and irreversibly abolished within 24 hours following low-dose treatment of the photophores with 6-OHDA, while the sensitivity of these organs to exogenous NE is increased significantly over the few days post-treatment. During this period the photophores continuously emitted a steady low-level glow. Electronmicroscopic studies of such photophores revealed progressive destruction of the nerve endings. Photophore luminescent sensitivity to NE subsequently became sub-normal, and at this stage electron microscopy revealed an increasingly larger number of damaged photocytes, supportive cells and, in one case, lens cells. From these results it is suggested that 6-OHDA initially impairs neuro-photocyte transmission by destroying catecholaminergic nerve endings. In turn, the transmitter reuptake mechanism is also impaired, thus accounting for development of supersensitive responses to exogenous NE. Subnormal luminescent responses to NE appear as a result of loss of photocyte competence due to structural deterioration. The latter are interpreted as the consequence of removal of trophic factors supplied by the photophore adrenergic innervation.Suppression of luminescent response to both electrical stimulation and exogenous NE in photophores treated with higher doses of 6-OHDA, may be due to a direct effect of this drug on the receptor sites of the photocytes.     

Early development of bioluminescence suggests camouflage by counter‐illumination in the velvet belly lantern shark Etmopterus spinax (Squaloidea: Etmopteridae)

The development of luminous structures and the acquisition of luminescence competence during the ontogeny of the velvet belly lantern shark Etmopterus spinax, a deep‐sea squalid species, were investigated. The sequential appearance of nine different luminous zones during shark embryogenesis were established, and a new terminology for them given. These zones form the complex luminous pattern observed in free‐swimming animals. The organogenesis of photophores (photogenic organs) from the different luminous zones was followed, and photophore maturation was marked by the appearance of green fluorescent vesicles inside the photocytes (photogenic cells). Peroxide‐induced light emissions as well as spontaneous luminescence analysis indicated that the ability of E. spinax to produce light was linked to the presence of these fluorescent vesicles and occured prior to birth. The size of photogenic organs, as well as the percentage of ventral body surface area occupied by the luminous pattern and covered by photophores increased sharply during embryogenesis but remained relatively stable in free‐swimming animals. All these results strongly suggest camouflage by counter‐illumination in juvenile E. spinax.     

Putatively luminous tissue in the abdominal pouch of a male dalatiine shark, Euprotomicroides zantedeschia Hulley & Penrith, 1966

The putatively luminous villous tissue in an abdominal pouch of a male specimen of the oceanic midwater shark Euprotomicroides zantedeschia is described. The epithelium within the pouch is probably stratified. The most conspicuous cell type is tall columnar cells, typically containing small cytoplasmic granules and a large inclusion. Cells with similar cytoplasmic characteristics, thought to be photogenic cells, are present in the epidermal skin photophores in other selachians which are known to be luminous.     

The morphology of photophores in the garrick,cyclothone braueri (Family: Gonostomatidae): an ultrastructure study

A contribution to the knowledge of the photophore structure of the mesopelagic fish Cyclothone braueri (Gonostomatidae) from the central Mediterranean Sea (Strait of Messina) is given by means of a structural and ultrastructural study, to better identify and classify the real anatomical structures costituing these luminous organs. The photocytes exhibit numerous secretory granules, of different electron density, embedded in an extremely developed rough endoplasmic reticulum. The lens appear to be composed of tightly contiguous polyhedral cells. The reflector is made up of cells rich in guanine crystals, embedded in an amorphous matrix and is surrounded by a layer of connective tissue containing melanocytes. Unlike the present knowledge, it is shown that the bioluminescence emitted from C. braueri light organs has glandular nature, with photophores similar to type α from Bassot classification. The phenomenon of adaptive convergence, documenting how the morphology and physiology of the light organs of teleosts is similar in different species despite their taxonomic distance, is confirmed also for C. braueri.     

Schistosoma mansoni: effects of bromolysergic acid diethylamide, verapamil, and Ca2+-free solution on the motor activity of the isolated male worm induced by electrical stimulation and oxamniquine

Electrical stimulation and oxamniquine effect the motor activity of isolated Schistosoma mansoni. Electrical stimulation produced contractions that increased with stimulus intensity. Oxamniquine (10(-4) M) produced an increase in basal tonus and in the frequency and amplitude of the worm's spontaneous contractions. Incubation in the absence of calcium produced a decrease in the basal tonus, abolished the spontaneous contractions of S. mansoni, and abolished the mechanical response induced by electrical stimulation and oxamniquine. The effects of electrical stimulation and oxamniquine were, respectively, significantly reduced and abolished by 10(-6) M verapamil (a calcium channel blocking agent). Bromolysergic acid diethylamide (3 X 10(-5) M), a serotonin blocking agent, reduced the motor response induced by high intensity electrical stimulation and blocked the response induced by oxamniquine. The effects of low intensity electrical stimulation were not modified in the presence of bromolysergic acid. We think that external Ca2+ is important for basal tonus, for spontaneous motor activity, and for motor responses of S. mansoni induced by electrical stimulation and oxamniquine. Serotonin may be important for mechanical responses induced by high intensity electrical stimulation and for responses induced by oxamniquine.     

Mechanical responses of the rat uterus, cervix, and bladder to stimulation of hypogastric and pelvic nerves in vivo

Mechanical activities of the uterus, cervix, and bladder were recorded in vivo in anesthetized rats during electrical stimulation of either the hypogastric or pelvic nerve. Ovariectomized controls and hormone-treated groups were used as well as pregnant and postpartum rats. Stimulation of either hypogastric or pelvic nerve produced voltage- and frequency-dependent contractions of the three organs with no evidence of apparent inhibition. All evoked responses were completely abolished by tetrodotoxin, suggesting that these nerves are common pathways of innervation to the three organs. Atropine abolished uterine and cervical responses to both hypogastric and pelvic nerve stimulation, whereas bladder responses were only partly reduced. Hexamethonium almost totally blocked the evoked responses of the uterus and cervix. Phentolamine partly blocked uterine and cervical responses, and propranolol or physostigmine enhanced uterine and cervical responses to both hypogastric and pelvic nerve stimulation. These results suggest that motor innervation to the rat uterus and cervix is predominantly postganglionic cholinergic, with some alpha- and beta-adrenergic components, and that the bladder is innervated by mainly cholinergic and also noncholinergic nerves. Estrogen and estrogen-plus-progesterone pretreatment significantly increased the responses of uterus and cervix but not bladder. Uterine and cervical responses to either hypogastric or pelvic nerve stimulation were markedly reduced late in pregnancy and reappeared within 7 days after delivery.     

Fast Simulation of Mechanical Heterogeneity in the Electrically Asynchronous Heart Using the MultiPatch Module

Cardiac electrical asynchrony occurs as a result of cardiac pacing or conduction disorders such as left bundle-branch block (LBBB). Electrically asynchronous activation causes myocardial contraction heterogeneity that can be detrimental for cardiac function. Computational models provide a tool for understanding pathological consequences of dyssynchronous contraction. Simulations of mechanical dyssynchrony within the heart are typically performed using the finite element method, whose computational intensity may present an obstacle to clinical deployment of patient-specific models. We present an alternative based on the CircAdapt lumped-parameter model of the heart and circulatory system, called the MultiPatch module. Cardiac walls are subdivided into an arbitrary number of patches of homogeneous tissue. Tissue properties and activation time can differ between patches. All patches within a wall share a common wall tension and curvature. Consequently, spatial location within the wall is not required to calculate deformation in a patch. We test the hypothesis that activation time is more important than tissue location for determining mechanical deformation in asynchronous hearts. We perform simulations representing an experimental study of myocardial deformation induced by ventricular pacing, and a patient with LBBB and heart failure using endocardial recordings of electrical activation, wall volumes, and end-diastolic volumes. Direct comparison between simulated and experimental strain patterns shows both qualitative and quantitative agreement between model fibre strain and experimental circumferential strain in terms of shortening and rebound stretch during ejection. Local myofibre strain in the patient simulation shows qualitative agreement with circumferential strain patterns observed in the patient using tagged MRI. We conclude that the MultiPatch module produces realistic regional deformation patterns in the asynchronous heart and that activation time is more important than tissue location within a wall for determining myocardial deformation. The CircAdapt model is therefore capable of fast and realistic simulations of dyssynchronous myocardial deformation embedded within the closed-loop cardiovascular system.     

Response of the isolated rat iris sphincter to cholinergic and adrenergic agents and electrical stimulation

In isolated rat iris sphincter muscle, there has been no attempt to measure mechanical tension changes, because of the small size of the preparation. In this study, responses of the isolated rat iris sphincter to some agents and electrical stimulation were examined. Acetylcholine and electrical stimulation produced powerful contractions of the iris sphincter. These contractile responses were suppressed by atropine and enhanced by physostigmine. 10 μM norepinephrine induced a weak contraction of the sphincter muscle and 1 mM isoproterenol induced a very weak relaxation. These responses were antagonized by phentolamine and propranolol, respectively. In the presence of 0.1 μM atropine, electrical stimulation produced a weak alpha-adrenergic contraction and a very weak beta-adrenergic relaxation. Electrically induced responses were abolished by tetrodotoxin. In conclusion, in the rat iris sphincter, powerful contraction is due to the activation of muscarinic receptors, and that there are weak alpha-adrenergic contraction and weak beta-adrenergic relaxation. Thus in rats, muscarinic contraction of the sphincter muscle plays major role in the regulation of pupil diameter.     

Electrosensitive polyacrylic acid/fibrin hydrogel facilitates cell seeding and alignment

Three-dimensional cell culture and conditioning is an effective means to guide cell distribution and patterning for tissue engineered constructs such as vascular grafts. Polyacrylic acid is known as an electroresponsive polymer, capable of transforming environmental stimuli like electrical energy to mechanical forces. In this study, we developed an electrosensitive and biocompatible hydrogel-based smart device composed of acrylic acid and fibrin as a tissue engineered construct to mechanically stimulate cells. Structural properties of the hydrogel were assessed by FTIR-ATR, scanning electron microscopy, prosimetry, and swelling measurement. Distribution and alignment of porcine smooth muscle cells (pSMCs) seeded on the surface of lyophilized hydrogels were evaluated and quantified by two-photon laser scanning microscopy. Smooth muscle cell tissue constructs exposed to 2 h of pulsatile electrical stimulation showed significantly enhanced cell penetration and alignment due to dynamic changes produced by alternative swelling and deswelling, in comparison with static samples. On the basis of the results, this hydrogel under electrical stimulation works as a mechanical pump, which can direct SMC alignment and facilitate infiltration and distribution of cells throughout the structure.     

Structural and ultrastructural comparison of photophores of two species of deep‐sea fishes: Argyropelecus hemigymnus and Maurolicus muelleri

The structure of the photophores (luminous organs) of two species of deep‐sea fishes from the Strait of Messina, Argyropelecus hemigymnus and Maurolicus muelleri , was examined. Although significant structural differences were identified between species, especially in photophore organization and distribution, ultrastructural comparisons indicated a marked similarity between them. The photocytes exhibited numerous secretory granules, of different electron density, embedded in an extremely developed rough endoplasmic reticulum. Numerous mitochondria were observed among the secretory granules. The lens appeared to be composed of tightly contiguous polyhedral cells. The reflector was made up of cells rich in guanine crystals embedded in an amorphous matrix and appeared to be surrounded by a layer of connective tissue full of melanocytes. Ventrally, every photophore was delimited by a thick cellular layer called the 'gelatinous layer' with dioptric properties. The results confirm that even though A. hemigymnus and M. muelleri differ widely phylogenetically, they exhibit adaptive convergence, involving similar morphology and physiology in these luminous structures.     

Determination by HPLC of adrenalin (E) and of noradrenalin (NE) in certain species of mesopelagic fish in the Strait of Messina

The presence of adrenalin (E) and noradrenalin (NE) was found by HPLC both in the photophores and at other tissue levels of numerous species of mesopelagic fish in The Strait of Messina, with the aim of determining the incidence of these catecholamines in photophores, in light transmission and the eventual presence at other tissue levels. © 1998 John Wiley & Sons, Ltd.     

It's all in the timing: Modeling isovolumic contraction through development and disease with a dynamic dual electromechanical bioreactor system

This commentary discusses the rationale behind our recently reported work entitled “Mimicking isovolumic contraction with combined electromechanical stimulation improves the development of engineered cardiac constructs,” introduces new data supporting our hypothesis, and discusses future applications of our bioreactor system. The ability to stimulate engineered cardiac tissue in a bioreactor system that combines both electrical and mechanical stimulation offers a unique opportunity to simulate the appropriate dynamics between stretch and contraction and model isovolumic contraction in vitro. Our previous study demonstrated that combined electromechanical stimulation that simulated the timing of isovolumic contraction in healthy tissue improved force generation via increased contractile and calcium handling protein expression and improved hypertrophic pathway activation. In new data presented here, we further demonstrate that modification of the timing between electrical and mechanical stimulation to mimic a non-physiological process negatively impacts the functionality of the engineered constructs. We close by exploring the various disease states that have altered timing between the electrical and mechanical stimulation signals as potential future directions for the use of this system.     

Aging does not affect voluntary activation of the ankle dorsiflexors during isometric, concentric, and eccentric contractions.

This study examines the age-related deficit in force of the ankle dorsiflexors during isometric (Iso), concentric (Con), and eccentric (Ecc) contractions. More specifically, the contribution of neural and muscular mechanisms to the loss of voluntary force was investigated in men and women. The torque produced by the dorsiflexors and the surface electromyogram (EMG) from the tibialis anterior and the soleus were recorded during maximal Iso contractions and during Con and Ecc contractions performed at constant angular velocities (5-100 degrees/s). Central activation was tested by the superimposed electrical stimulation method during maximal voluntary contraction and by computing the ratio between voluntary average EMG and compound muscle action potential (M wave) induced by electrical stimulation (average EMG/M wave). Contractile properties of the dorsiflexor muscles were investigated by recording the mechanical responses to single and paired maximal stimuli. The results showed that the age-related deficit in force (collapsed across genders and velocities) was greater for Iso (20.5%; P < 0.05) and Con (38.6%; P < 0.001) contractions compared with Ecc contractions (6.5%; P > 0.05). When the torque produced during Con and Ecc contractions was expressed relative to the maximal Iso torque, it was significantly reduced in Con contractions and increased in Ecc contractions with aging, with the latter effect being more pronounced for women. In both genders, voluntary activation was not significantly impaired in elderly adults and did not differ from young subjects. Similarly, coactivation was not changed with aging. In contrast, the mechanical responses to single and paired stimuli showed a general slowing of the muscle contractile kinetics with a slightly greater effect in women. It is concluded that the force deficit during Con and Iso contractions of the ankle dorsiflexors in advanced age cannot be explained by impaired voluntary activation or changes in coactivation. Instead, this age-related adaptation and the mechanisms that preserve force in Ecc contractions appeared to be located at the muscular level.     

Evidence for Synchronous Activation of Neurons Located in Different Layers of Primary Somatosensory Cortex

Although many studies have examined the columnar organization of primary somatosensory (SI) cortex, the functional relationship among neurons in different layers remains unclear. To understand how activity is coordinated among different cortical layers, the present investigation tested the hypothesis that the initial part of a peripheral stimulus produces a serial pattern of laminar activation in SI cortex. Extracellular discharges of 334 histologically recovered neurons were recorded from the medial bank of the coronal sulcus in nine anesthetized cats during electrical or cutaneous stimulation of the distal forelimb. Mean responses during the initial 50-msec period following stimulus onset were largest in layers IIIb or IV for both types of stimulation, but laminar differences in the magnitude of onset responses were not statistically significant. Among 175 neurons with responses exceeding 0.5 spikes per stimulus, electrical Stimulation consistently produced shorter response latencies than mechanical indentation in the extragranular (II, IIIa, V, VI), but not in the middle (IIIb, IV), cortical layers. The average minimum latencies for different cortical layers ranged from 7.4 to 10.1 msec for responses to electrical stimulation and from 10.3 to 11.6 msec for responses to mechanical indentations, but these laminar differences were not statistically significant. In some experiments, neurons in different layers of a cortical column were recorded simultaneously with dual-electrode assemblies; among 37 neuron pairs in which both neurons responded with more than 0.5 spikes per stimulus, response latencies were similar, even though the neurons were separated by several hundred microns. Cross-correlation analysis of the onset responses for neurons recorded simultaneously from different layers also indicated that many cells throughout a cortical column were activated nearly simultaneously by the initial phase of a peripheral stimulus. Results from the present study are compared with previous reports examining laminar patterns of activation.     

Uptake and release of [3H]-serotonin in photophores of the midshipman fish, Porichthys notatus

A kinetic analysis of [3H]-5-HT uptake in the photocytes of the photophores of Porichthys notatus revealed a high affinity (Km: 1.71 X 10(-7] and low affinity component (Km: 1.10 X 10(-5) M). The high affinity uptake was sodium- and potassium-dependent but largely insensitive to temperatures between 0 and 20 C. Ouabain (5 X 10(-3) M) and dinitrophenol (10(-3) M) reduced uptake significantly. DMI, imipramine and fluoxetine, in that order of potency, greatly inhibited [3H]-5-HT uptake. Noradrenaline and adrenaline reduced uptake in a non-competitive manner, while dopamine, tryptophan, 5-hydroxytryptophan and Cypridina luciferin had little or not effect on uptake. Non-facilitated luminescent responses to electrical stimulation were accompanied by release of [3H]-5-HT accumulated in the photocytes. Facilitatory luminescence excitation consistently failed to induce the release of [3H]-5-HT. Electrical and adrenaline (10(-5) M) stimulation of photophores after [3H]-5-HT release has occurred, failed to elicit any additional luminescent response. The photophores were responsive to KCN (10(-3) M) under these conditions. The results indicate that a specific carrier-mediated transport system is responsible for photocytic [3H]-5-HT uptake, and that release of photocytic [3H]-5-HT is stringently regulated and followed by inhibition of luminescence excitability.     

The comparative morphology of the photophores of the squid Pyroteuthis margaritifera (Cephalopoda: Enoploteuthidae)

Pyroteuthis margaritifera has morphologically distinctive photophores on the tentacles, eyeball and in the mantle cavity. The photogenic tissue in each photophore is identical, has a blue-green fluorescence and luminesces on treatment with dilute hydrogen peroxide. The photocytes frequently contain organized fibrillar material akin to that in the photocytes of certain other cephalopods. Several different types of blood vessel are present among the photocytes, including some, apparently restricted to the photophores, with a microvillous endothelium. Haemocyanin is present not only within identifiable blood vessels but also in some intercellular spaces.
On the basis of their characteristic optical systems the photophores can be separated into three types: (1) tentacular; (2) ocular and anal; (3) branchial and median abdominal. The tentacular photophores have collagenous reflector and light guide systems and the median ones are double organs. The ocular and anal organs do not have collagenous optical structures but an elaborate variety of reflective iridosomes. Those in the aperture of the photophores appear to act as interference filters. The branchial and abdominal organs have iridosomes as the major reflective tissue but collagenous fibrils function as light guides in the aperture of these organs and their emission is diffuse rather than collimated.     

The effect of indomethacin and adenosine 5'-triphosphate on the excitatory innervation of the rate urinary bladder

Adenosine 5'-triphosphate (ATP) (20-400 microM) contracted 48% of isolated rat urinary bladder preparations but induced no response in the remainder. The response to ATP never exceeded 25% of the response to electrical stimulation in the presence of indomethacin (50 microM) plus hyoscine (25 microM) and usually developed more slowly than that to electrical stimulation. Autoinhibition could be produced to ATP by incubating the tissue with ATP (200 microM) for 20 min. Incubation of the tissue with ATP (200 microM) for 60 min in the presence of indomethacin (50 microM) and either hyoscine (25 microM) or hemicholinium-3 (500 microM) reduced but failed to abolish responses to electrical stimulation. Responses to acetylcholine were not affected by ATP (200 microM) in the presence of indomethacin and the output of acetylcholine induced by neuronal stimulation at 10 Hz was not inhibited by ATP (200 microM) or by indomethacin (50 microM). The results suggest a possible modulatory role for ATP in the excitatory innervation of the rat urinary bladder.     

Changes in the activity of cells in the lateral geniculate nucleus by stimulation of the abducens nucleus area in rabbits

These investigations are aimed at studying the influence of the electrical stimulation of the VIth nucleus (abducens nucleus) on responses of lateral geniculate cells in rabbits. The animals were prepared in the usual fashion for single cell recordings at the lateral geniculate nucleus (LGN). Results show that: Electrical stimulation of the VIth nucleus always produced excitatory discharges whose latency varied from 30 to 400 ms. Interestingly, an electrical pulse applied to the abducens nucleus was capable of enhancing the light-evoked responses without altering the spontaneous rate of firing. It thus seems that the ascending influence of the VIth nucleus manifests itself when it coincides with light responses. Most cells which were sensitive to electrical activation of the abducens nucleus had their receptive field located peripherally (greater than 50 degrees). Histological reconstructions of recording electrode tracts suggest that cells which responded to electrical stimulation were located in a narrow band lying dorsally relative to the LGN. This area can be paralleled with the perigeniculate area observed in other mammals, although not identified in rabbits. It is suggested that these extraretinal impulses which reach the LGN and emerge from an area surrounding the VIth nucleus are associated with corollary discharges.     

Electrophysiological investigation of medullary neurons connected with lateral line organs of the catfish (Ictalurus nebulosus)

Unit responses in the acoustic-lateral region of the medulla to electrical and mechanical stimulation of the lateral line organs were investigated in acute experiments on curarized catfish. Of the total number of neurons 70% possessed spontaneous activity. An electrical stimulus evoked a tonic response both in spontaneously active and in "silent" cells. Three main types of firing pattern of the neurons were distinguished: fast-adapting, slow-adapting, and grouped. As regards the relation of the neurons to polarity of the stimulus they were subdivided into two groups. The thresholds of unit responses to electrical stimulation varied considerably: from 2.5·10^–9 to 5·10^–12 A/mm². The effect of intensity of the electrical stimulation on unit responses in the medulla is analyzed. The precise dependence of on- and off-responses of each neuron on stimulus intensity of any polarity was determined. The neurons were shown to be sensitive to both electrical and mechanical stimuli. It is postulated that this phenomenon is due to convergence of impulses from electrical and mechanical receptors of the lateral line on the neurons. The properties of the central neurons are compared with those of the peripheral electroreceptor system in catfish.I. P. Pavlov Institute of Physiology, Academy of Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 5, No. 2, pp. 156–163, March–April, 1973.