Serotonin or electrical optic nerve stimulation increases the photosensitivity of the Aplysia eye

• 1.1. Exposure of isolated Aplysia eyes to serotonin (10⁻⁷ M) produces large and long-lasting (hours) increases in the ERG recorded from the surface of the eye.
• 2.2. Dopamine, octopamine, or acetylcholine do not mimic the effect of 5-HT on the ERG.
• 3.3. Brief electrical optic nerve stimulation (2 Hz, 2 min) also increases the ERG and this effect also lasts a long period of time (0.5–2 hr).
• 4.4. Our results suggest that serotonin increases the response of photoreceptor cells to light and that efferent optic nerve activity may modulate photosensitivity through release of serotonin in the eye.

     

Effects of temperature and metabolic inhibitors on contraction of anterior byssus retractor muscle of Mytilus

• 1.1. Anterior byssus retractor muscle of Mytilus (ABRM) was stimulated to contract by ACh (acetylcholine) and effects of temperature (5–30°C), FDNB (1-fluoro 2,4 dinitro-benzene) and IAA (iodoacetic acid) on tension response were examined.
• 2.2. Isometric tension was highest at the temperature range of 10–20°C and decreased at higher and lower temperature than that range.
• 3.3. The rate of tension decay after washing of ACh was accelerated by the increase of temperature.
• 4.4. Tension redevelopment after release of 1 % during contraction was much smaller at 5°C than at 20°C.
• 5.5. Tension development by ACh and the rate of tension decay after washing of ACh were remarkably decreased by the treatment of FDNB or IAA.
• 6.6. The above results were discussed from the viewpoint that energy metabolism might be related to catch.

     

Biomines-stimulated phosphorylation and (Na+, K+-ATPase in the gills of the chinese crab,Eriocheir sinensis

• 1.1. Subcellular distribution of (NA⁺, K⁺-ATPase and ouabain-insensitive ATPase (Mg²⁺-ATPase) are compared in branchial tissues of the euryhaline crab, Eriocheir sinensis, acclimated to fresh water.
• 2.2. Both the anterior and posterior gills contain cAMP-dependent protein kinase and endogenous protein substrate for phosphorylation.
• 3.3. Phosphorylation occurs in both “particulate” and “soluble” subcellular fractions but its stimulation by cAMP is restricted to the “soluble” fraction.
• 4.4. serotonin (5-HT) and dopamine receptors are present only in the “light particulate” fraction isolated from the posterior gills.

• 1.(a) Serotonin and dopamine have no effect on the phosphorylation observed in a subcellular fraction alone.
• 2.(b) Activation of the phosphorylation by serotonin and dopamine is found when the soluble fraction (source of cAMP-dependent protein kinase) is added to the fraction P₃ from the posterior gills.
• 3.(c) No activation occurs with the fractions P₃ as well as P₁ or P₂ (not shown) from anterior gills of fresh water crab.
• 4.(d) Cyproheptadine, a serotonin receptor antagonist, inhibits the 5-HT dependent increase in phosphorylation.
• 5.(e) The dopamine receptor antagonist, chlorpromazine, inhibits dopamine-stimulated phosphorylation.
• 6.5. Ouabain mimics the effect of cyproheptadine on the serotonin-stimulated phosphorylation found in the posterior gills.

     

Immunochemical and immunohistochemical determination of ubiquitin in molluscan (Mytilus edulis) smooth muscle

• 1.1. Immunochemical and immunohistochemical distribution of ubiquitin in the anterior byssus retractor muscle (ABRM) of Mytilus edulis was investigated.
• 2.2. In immunostaining, specific ubiquitin immunoreactivity was observed in the cross-sectioned ABRM, and was uniformly localized in this section.
• 3.3. The amount of free ubiquitin in the ABRM homogenate was 130 ± 4.6 ng/mg protein by western blot analysis, and ubiquitin conjugates were found at about 25, 29 and 200–230 kDa.
• 4.4. These findings were similar to those obtained in the skeletal muscle of rat.

     

A dopamine- and octopamine-sensitive adenylate cyclase in the nervous system of Octopus vulgaris

• 1.1. Adenylate cyclase activity was assayed in the optic lobe of Octopus vulgaris.
• 2.2. Both octopamine and dopamine stimulate the octopus adenylate cyclase, apparently by competing with the same receptor site.
• 3.3. (±)-2-Amino-6,7-dihydroxy-1,2,3,4-tetrahydronaphthalene-HBr (6,7-ADTN) and a number of phenylethanolamine derivatives stimulate the octopus adenylate cyclase activity.
• 4.4. The dopamine D-1 antagonists R(+)-7-chloro-8-hydroxy-3-methyl-1-phenyl-2,3,4,5-tetrahydro-1H-3-benzazepine-HCl (SCH-23390) and (±)-7-bromo-8-hydroxy-3-methyl-1-phenyl-2,3,4,5-tetrahydro-1H-3-benzazepine-HCl (SKF-83566) are unable to antagonize the effects of dopamine and octopamine, and similarly ineffective is the agonist (±)-1-phenyl-2,3,4,5-tetrahydro-1H-3-benzazepine-7,8-diol-HCl (SKF-38393).
• 5.5. No detectable binding of labelled SCH-23390 occurs on membrane preparations from octopus optic lobe.

     

Oxygen binding by the hemocyanin of Busycon canaliculatum

• 1.1. This study examined the effect of the monoamines dopamine and octopamine, as well as tyrosine on the oxygen affinity and cooperativity of oxygen binding by the hemocyanin of the marine gastropod Busycon canaliculatum. The effect of temperature on hemocyanin oxygen affinity was also examined.
• 2.2. Freezing Busycon hemocyanin did not affect the binding of oxygen.
• 3.3. Dopamine, octopamine and tyrosine had no significant effect on the oxygen affinity or cooperativity of oxygen binding by the hemocyanin of B. canaliculatum.
• 4.4. It was concluded that Busycon hemocyanin either has no binding sites for the two monoamines or for tyrosine, or that binding of the molecules has no functional significance.
• 5.5. Both temperature sensitivity and affinity of hemocyanin-oxygen binding were similar to values previously reported for hemocyanin of Busycon from other localities.

     

Calcium binding by sarcoplasmic reticulum and mitochondria isolated from an annelid visceral muscle in relation to whole muscle calcium influx and efflux

• 1.1. Nereis pharangeal visceral muscle is composed of obliquely striated fibres with low mitochondrial density and moderately developed sarcoplasmic reticulum.
• 2.2. Isolated mitochondria and sarcoplasmic reticulum showed moderate passive calcium binding but only low ATP-promoted calcium binding which was inhibited by caffeine.
• 3.3. Whole fibres preloaded with Ca⁴⁵ showed a two compartment efflux. The slow, presumably intracellular, compartment accounted for only 10% of total Ca⁴⁵ activity.
• 4.4. Both acetylcholine and high KCl treatments stimulated calcium influx, causing contractures while calcium-free and EGTA treatments inhibited both these contractures and normal spontaneous contractions.
• 5.5. Lanthanum inhibited normal contractility and KCl contractures. Lanthanum also inhibited Ca⁴⁵ influx but was without effect on Ca⁴⁵ efflux.
• 6.6. It is concluded that there is little calcium storage capacity in these visceral muscle fibres and that normal contractions are strongly dependent upon extracellular calcium influx.

     

The action of the venom of Philanthus triangulum F. on an insect visceral muscle

• 1.1. Low concentrations (0.05−0.38 BU/ml) of a crude venom extract from P. triangulum F. potentiate nerve-evoked contractions of the locust hindgut, possibly due to contamination of the venom preparation with proctolin.
• 2.2. Higher venom concentrations inhibit nerve-evoked contractions to a dose-independent plateau level.
• 3.3. The venom has no effect on responses to bath-applied proctolin, but responses to bath-applied L-glutamate are inhibited.
• 4.4. Spontaneous contractions are unaffected by the venom.
• 5.5. It is concluded that the plateau contractions are the result of excitation by non-glutamatergic transmission, and are possibly the result of proctolin release.

     

Changes in cAMP and cGMP levels induced by relaxing drugs in acetylcholine- and potassium-treated molluscan smooth muscle

• 1.1. The changes of cAMP and cGMP levels in response to serotonin, dopamine, papaverine and Aspaminol were investigated in acetylcholine- and potassium-treated molluscan smooth muscle in accordance with the time course of contraction-relaxation process in mechanical response to acetylcholine and potassium.
• 2.2. Acetylcholine (10⁻⁵ M) and potassium (229 mM) had no influences on basal cAMP and cGMP levels.
• 3.3. Serotonin (10⁻⁶ M and 10⁻⁵ M) dose-dependently elevated cAMP level and serotonin (10⁻⁵ M) reduced cGMP level in acetylcholine-treated muscle.
• 4.4. Serotonin (10⁻⁵ M) elevated cAMP level and reduced cGMP level in potassium-treated muscle.
• 5.5. Dopamine (10⁻⁶M and 10⁻⁵M), papaverine (10⁻⁴M) and Aspaminol (10⁻⁴M) had no effect on cAMP and cGMP level in acetylcholine- and potassium-treated muscle.
• 6.6. Relaxing effect of serotonin may be associated with elevated cAMP level and reduced cGMP level at the pharmacological but not physiological level.

     

Time course of tension decay after stretch and unloaded shortening velocity in molluscan catch muscle at various physiological states

• 1.1. The anterior byssus retractor muscle of Mytilus was stimulated to contract with ACh, and the time courses of tension decay after an applied stretch (6% of l₀), as well as the unloaded shortening velocity, were examined at various states, i.e. (1) at the peak of initial tension development, (2) during the prolonged application of ACh, (3) after washout of ACh, (4) in the sucrose-hypertonic solution and (5) in the NaCl-hypertonic solution.
• 2.2. The tension decay after stretch was resolved into three exponential components.
• 3.3. The relationship between the amplitudes of three exponential components and the unloaded shortening velocity was examined in the above five states. It was shown that the intermediate component and the slow one were related to active and tonic contractions, respectively.

     

Stimulatory effect of amp on the copper ion dependent oxidation of adrenaline to adrenochrome

• 1.1. AMP markedly activated copper ion dependent oxidation of adrenaline to adrenochrome. It is proposed that a Cu(II)-AMP chelate forms a reactive complex with adrenaline.
• 2.2. AMP did not affect copper stimulated oxidation of noradrenaline, dopamine and l-dopa.

     

In situ phosphorylation of contractile proteins of a molluscan Mytilus edulis catch muscle in different functional states

• 1.1. The incorporation of ³²P into the contractile proteins of the anterior byssus retractor muscle of Mytilus edilus L. was analyzed during the different stages of a contraction-catch-relaxatin cycle.
• 2.2. The experiments were performed with saponin-skinned fibers preincubated with γ-³²P-ATP.
• 3.3. The total amount of ³²P incorporated into the fiber proteins was anlyzed by measuring the label of TCA-insoluble protein in a scintillation counter.
• 4.4. The dose incorporated was about twice as high during Ca²⁺ induced contraction and serotonin induced accelerated relaxation as during test and catch.
• 5.5. The molecular mass of the phosphorylated proteins was analyzed by autoradiography of the proteins separated by SDS-PAGE.
• 6.6. Up to 26 protein spots of different molecular masses were labelled, including such well characterized protein spe+cies as myosin heavy and light chains, paramyosin and tropomyosin.

     

Phosphofructokinase from the anterior byssus retractor muscle of Mytilvs edulis: Modification of the enzyme in anoxia and by endogenous protein kinases

• 1.1. Anoxia exposure resulted in a stable modification of the kinetic properties of 6-phosphofructo-1-kinase (PFK) from the anterior byssus retractor muscle (ABRM) of the sea mussel Mytilus edulis L.
• 2.2. Compared to the aerobic enzyme, the anoxic form of PFK. showed a reduced affinity for both substrates, fructose-6-phosphate (F6P) and ATP, and an increased sensitivity to inhibition by phosphoenolpyruvate.
• 3.3. To analyze the involvement of protein kinases in the modification of PFK, extracts from aerobic or anoxic muscle were incubated with ATP and Mg²⁺ plus protein kinase second messengers cyclic 3',5'-adenosine monophosphate (cAMP), cyclic 3',5'-guanosine monophosphate (cGMP) or Ca²⁺ plus phorbol 12-myristate 13-acetate (PMA).
• 4.4. Both forms of the enzyme responded to the presence of cAMP with a strong increase in affinity for F6P.
• 5.5. In response to cGMP affinity of the aerobic enzyme for F6P decreased whereas that of the anoxic enzyme form was not affected (at 0.5 mM ATP) or increased (at 3 mM ATP).
• 6.6. Incubation with Ca²⁺ + PMA had only a limited effect on PFK kinetics but appeared to enhance the response to cGMP when the three compounds were given together.
• 7.7. Treatment of PFK-aerobic with alkaline phosphatase resulted in a strong decrease in enzyme activity and affinity for F6P; subsequent treatment with cAMP reversed the effect on S_0.5 F6P.
• 8.8. The data indicate that PFK activity is altered during the aerobic-anaerobic transition by a change in the phosphorylation state of the enzyme and that cAMP and cGMP act oppositely to regulate PFK activity, and thereby alter glycolytic rate, during this transition.

     

Effects of hypoxia on resting potential and transmitter release at cercal afferent,giant interneurone synapses in the cockroach,Periplaneta americana L.

• 1.1. Studies of experimentally induced hypoxia were carried out on synapses in the isolated sixth abdominal (A6) ganglion of the cockroach using electrophysiological methods.
• 2.2. During a break of saline superfusion, oxygen tension (PO₂) decreased and depolarization of presynaptic and postsynaptic membranes was observed.
• 3.3. During hypoxia EPSP amplitude initially increased, but decreased after a few minutes.
• 4.4. Changes in the EPSP and membranes potential resulting from hypoxia were reversed when the saline superfusion was restarted.
• 5.5. Changes in the amplitude of both the EPSP and the depolarization induced by microiontophoretic injections of ACh indicated that ACh release initially increased during hypoxia and decreased during recovery from oxygen deprivation.

     

Monoamines and their metabolites in the amphibian (Ambystoma tigrinum) brain: Quantitative changes during metamorphosis and captivity

• 1.1. Monoamine neurotransmitters (epinephrine, norepinephrine, dopamine, serotonin and some of their metabolites (DOPEG, MHPG, DOPAC, 5-HIAA) were measured by HPLC in extracts from telencephalon (TEL) and diencephalon-midbrain (DM) before, during and at the end of metamorphosis.
• 2.2. During metamorphosis MHPG increased and 5-HIAA decreased in TEL and DM while DOPEG decreased only in DM.
• 3.3. Monoamine levels were greater in the TEL and a larger increase in MHPG occurred there.
• 4.4. Captivity without metamorphosis also caused a significant depression of 5-HIAA in TEL and depression of DOPEG, MHPG and DOPAC in DM.

     

Differential modulation of chemical and electrical components of mixed synapses in the lobster stomatogastric ganglion

1. Two pairs of neurons in the pyloric network of the spiny lobster, Panulirus interruptus, communicate through mixed graded chemical and rectifying electrical synapses. The anterior burster (AB) chemically inhibits and is electrically coupled to the ventricular dilator (VD); the lateral pyloric (LP) and pyloric (PY) neurons show reciprocal chemical inhibition and electrical coupling. We examined the effects of dopamine (DA), serotonin (5HT) and octopamine (Oct) on these mixed synapses to determine the plasticity possible with opposing modes of synaptic interaction.
2. Dopamine increased net inhibition at all three pyloric mixed synapses by both reducing electrical coupling and increasing chemical inhibition. This reversed the sign of the net synaptic interaction when electrotonic coupling dominated some mixed synapses, and activated silent chemical components of other mixed synapses.
3. Serofonin weakly enhanced LP → PY net inhibition, by reducing electrical coupling without altering chemical inhibition. Serotonin reduced AB→ VD electrical coupling, but variability in its effect on the chemical component made the net effect non-significant.
4. Octopamine enhanced LP→ PY and PY→ LP net inhibition by enhancing the chemical inhibitory component without altering electrical coupling.
5. Differential modulation of chemical and electrical components of mixed synapses markedly changes the net synaptic interactions. This contributes to the flexible outputs that modulators evoke from anatomically defined neural networks.

     

The association of changes in cerebral ganglion dopamine metabolism with ootheca development in Periplaneta americana

• 1.1. Dopamine levels and DOPA-decarboxylase activity were measured in cerebral ganglia and haemolymph of female Periplaneta americana.
• 2.2. Measurements were made at four points in the oothecal cycle of cockroaches known to drop oothecae at regular three day intervals.
• 3.3. Dopamine levels and DOPA-decarboxylase activity in haemocytes and plasma cycle in phase with ootheca formation; their levels in haemolymph are maximal when a half visible, untanned ootheca is present.
• 4.4. In the cerebral ganglia dopamine levels and DOPA-decarboxylase also cycle in phase with ootheca formation suggesting that cerebral ganglion dopamine metabolism is under the same controls as dopamine metabolism associated with oothecal tanning.

     

Serotonin,histamine and somatostatin modulation of PMA-stimulated phosphorylation of 130kDa Ca2+ pump-like protein from rat cerebellum synaptosomal membranes

• 1.1. Influence of some neurotransmitters and neuromodulators on the PMA-stimulated phosphorylation in vitro of calcium pump-like protein from rat cerebellum synaptosomal membranes was examined.
• 2.2. The prolonged time (up to 6 min) of synaptosomal membranes preincubation with 1 and 10 μM serotonin results in the increase of phosphorylation. The decrease of phosphorylation up to 80% of control value was observed for 100 μM serotonin.
• 3.3. The most stimulating effect on 130kDa protein phosphorylation was observed with 1μM of histamine (160% of control value).
• 4.4. 1 and 0.1 μM somatostatin triggered a short-time transient increase of 130 kDa phosphorylation (up to 135% of control value).

     

Purification and some properties of an atypical alkaline p-nitrophenylphosphate phosphatase activity from Halobacterium halobium

• 1.1. An alkaline p-nitrophenylphosphate phosphatase has been purified 440-fold from extracts of Hatobacterium halobium.
• 2.2. The enzyme has an apparent molecular weight of 24,000.
• 3.3. A K_m value for p-nitrophenylphosphate of 1.12mM has been found under optimal conditions.
• 4.4. The enzyme is selectively activated and stabilized by Mn²⁺.
• 5.5. It requires high salt concentrations for stability and maximum activity.
• 6.6. It displays an unusual restricted substrate specificity of 25 phosphate esters tested, only phosphotyrosine and casein were hydrolysed besides p-nitrophenylphosphate.

     

2-Deoxyglucose transport by the frog sartorius: Effects of electrical stimulation and N-carbobenzoxy-glycyl-l-phenylalaninamide

• 1.1. Studies characterizing glucose transport in the frog sartorius were performed.
• 2.2. For nonstimulated and stimulated muscles, intracellular 2-deoxyglucose exceeded 2-deoxyglucose-6-phosphate at 15 min, showed little further increase, and was maintained below the extracellular concentration for 2 hr.
• 3.3. Accumulated 2-deoxyglucose-6-phosphate did not inhibit glucose transport.
• 4.4. Unlike in adipocytes, basal and stimulated 2-deoxyglucose transport showed no difference in sensitivity to N-carbobenzoxy-glycyl-l-phenylalaninamide.
• 5.5. Phenylarsine oxide blocked contraction-enhanced 2-deoxyglucose uptake.
• 6.6. These results suggest that the glucose transporter of the sartorius exhibits auto-regulation, and that basal transport is not regulated by the same process as in adipocytes.