Pigment migration in fish erythrophores is controlled by alpha2-adrenoceptors

• 1.1. The aggregation of erythrosomes within erythrophores of the squirrel fish (Myripristis occidentalis; belonging to the family Holocentridae) was, on pharmacological grounds, shown to be mediated by alpha₂-adrenoceptors.
• 2.2. The erythrophores were shown to be controlled by adrenergic nerves activating the alpha₂-adrenoceptors.
• 3.3. The erythrophores themselves were found to possess a K⁺-sensitive mechanism of aggregation.
• 4.4. Some similarities and differences of the alpha₂-adrenoceptor-mediated chromatosome aggregation in melanophores and erythrophores are also discussed.

     

Identification and characterization of a third form (D3) of cyclic 3'5'-nucleotide phosphodiesterase from rhizobwm fredii

• 1.1. A third form (D3) of cyclic nucleotide phosphodiesterase from Rhizobiumfrediiv/as detected and characterized for the first time.
• 2.2. The enzyme could hydrolyse both cyclic AMP and cyclic GMP with apparent K_m for cyclic AMP of approx. 0.2 μM.
• 3.3. D3 cyclic nucleotide phosphodiesterase had a pH optimum of about 6.0 when hydrolysing cyclic AMP.
• 4.4. The enzyme lost almost all its activity when heated to 60°C for 20 min.
• 5.5. Gel filtration with Sephadex G-100 gave a mol. wt of approx. 42.5 kD for the native enzyme.

     

Binding proteins for cyclic AMP in mammalian tissues

• 1.1. The distribution and physicochemical properties of proteins known to bind cyclic AMP in vitro and methodological aspects of their interaction with ligands is reviewed.
• 2.2. The interaction between such proteins and cyclic AMP is discussed, the allosteric binding of the nucleotide to cyclic AMP dependent protein kinase type I being considered in detail.
• 3.3. The use of naturally occurring binding proteins in assays for cyclic AMP is briefly reviewed.
• 4.4. Finally, some aspects of the control of cyclic AMP binding in the intact cell are considered.

     

Soluble cyclic AMP-dependent protein kinases from chick kidney: Effects of ions and heat-stable modulator

• 1.1. Two cyclic nucleotide-dependent protein kinases have been isolated from chick kidney cytosol on DEAE cellulose.
• 2.2. Both have an apparent K_m ATP of 5 × 10⁻⁶ M, are stimulated half maximally by 1.8 × 10⁻⁸ M cyclic AMP, are inhibited half maximally by 5 × 10⁻³ M inorganic phosphate, and are inhibited slightly by Tris and chloride ions.
• 3.3. The heat-stable modulator of protein kinase inhibited both activities in the presence of cyclic AMP or cyclic GMP and histone, or cyclic AMP and casein, but with cyclic GMP and casein one kinase was stimulated and the other inhibited.

     

Purification and partial characterization of an AMP deaminase from the marine invertebrate Palaemon serratus

• 1.1. AMP deaminase from Palaemon serratus tail muscle was partially purified by chromatography on cellulose phosphate.
• 2.2. Muscle homogenates expressed very low enzyme activities and the presence of ATP was necessary to detect AMP deaminase. The specific activity and substrate affinity of the purified enzyme were also very low.
• 3.3. The purified prawn muscle AMP deaminase was contaminated by contractile proteins, one of the major contaminants being actin.
• 4.4. The enzyme displayed a very high affinity for actomyosin which was only partially abolished by pyrophosphate.

     

Ionic requirements for melanophore stimulating hormone (MSH) action on melanophores

• 1.1. Calcium is required for melanophore stimulating hormone (MSH) action on melanophores of the lizard, Anolis carolinensis, the toad, Scaphiopus couchi, and the frog Rana berlandieri forrei.
• 2.2. Ca²⁺ is required for an initial mechanism of MSH action, but not for melanosome dispersion per se, since melanophores respond to catecholamines, prostaglandins, theophylline or dibutyryl cyclic AMP in the absence of this cation.
• 3.3. Lithium, choline, rubidium and cesium, in the lizard and the toad, will replace the sodium and potassium of the Ringer medium and permit melanosome dispersion, but only if Ca²⁺ is present. These monovalent cations are irreversibly inhibitory to MSH action on melanophores of R. berlandieri and R. pipiens.
• 4.4. These results demonstrate that the Ca²⁺ is the only cation specifically required for MSH action on melanophores.

     

Soluble cyclic amp-dependent protein kinases from chick liver: Effects of NaCl and heat-stable modulator

• 1.1. Two cyclic AMP-dependent protein kinases—Fraction I and II—have been isolated from chick liver soluble preparation on DEAE-cellulose.
• 2.2. Both fractions have an apparent K_m for ATP of 2 × 10⁻⁶M, are stimulated maximally by 5 × 10⁻⁸ M cyclic AMP and phosphorylate mainly basic proteins—histone and protamine.
• 3.3. They exhibit various pH values for optimal activity and show differences with respect to both sensitivity to NaCl and substrate specificity.
• 4.4. The heat-stable protein modulator inhibits the cyclic AMP-dependent protein kinase activity of both fractions, but with cyclic GMP one kinase is stimulated and the other inhibited.
• 5.5. Slight differences in histone triggered holoenzyme dissociation as well as the lack of difference between their ability for subunit reassociation do not allow to classify these isozymes as protein kinases of Type I and II, according to Corbin et al. (1975).

     

A sensitive and specific binding assay for cyclic GMP-dependent and cyclic AMP-dependent protein kinases in rat liver

• 1.1. Sensitive and specific binding assays for cyclic GMP-dependent and cyclic AMP-dependent protein kinases have been developed for use in rat liver.
• 2.2. The addition of mixed histone to the binding mixture and the inclusion of ammonium sulfate in the termination and wash buffer enhanced the observed cyclic GMP- and cyclic AMP-binding activities markedly.
• 3.3. The principal effect of histone is to increase the binding of cyclic GMP and cyclic AMP to their respective protein kinases.
• 4.4. During filtration ammonium sulfate markedly increased the retention of the protein-bound cyclic nucleotides and markedly decreased the rapid dissociation component of cyclic GMP-binding.

     

Investigation of phycocyanin-membrane interaction: Promotion of membrane interactions

• 1.1. In a continuing investigation of phycocyanin-membrane surface interaction, fluorescence quenching experiments were performed with a mixture of two populations of fluorescence probe-encapsulated phospholipid bilayer vesicles in the presence and absence of phycocyanin.
• 2.2. These membrane vesicles were prepared with 1,2-dimyristoyl phosphatidylcholine (DMPC), cholesterol and a probe molecule.
• 3.3. A fluorophore was encapsulated in one population of membrane vesicles, while a quencher was encapsulated in another population of membrane vesicles.
• 4.4. The result was compared with those of experiments in the presence of other biomolecules, including albumin, cytochrome c, hemoglobin, myoglobin or RNA.
• 5.5. Interestingly, a one-third reduction of the fluorescence intensity was observed in the mixture of these two populations of membrane vesicles in phycocyanin's presence.
• 6.6. In contrast, the other biomolecules caused no significant reduction in the fluorescence intensity.
• 7.7. These findings were evidence of a phycocyanin-induced membrane perturbation.
• 8.8. This was further demonstrated by a phycocyanin-induced change in the thermotropic behavior of DMPC vesicles, as measured by differential scanning microcalorimetry.
• 9.9. Such a unique property of phycocyanin is believed to be associated with its known membrane surface-interacting character.
• 10.10. A possible phycocyanin-modulated membrane-membrane interaction was discussed.

     

Detergent solubilisation of rat liver particulate cyclic AMP phosphodiesterase

• 1.1. Detergent solubilisation of particulate rat liver low K_m cyclic AMP phosphodiesterase in the presence of protease inhibitors yields a form of the enzyme with a larger molecular weight than the form solubilised by protease treatment.
• 2.2. The detergent solubilised enzyme could be partially purified by anion exchange chromatography.
• 3.3. It displayed a marked tendency to precipitate from solution when detergent was removed.

     

Modulation of the ATP induced [Ca2+]c increase in as-30D hepatoma cells

• 1.1. The regulation of the increase in the cytosolic calcium concentration ([Ca²⁺]c) induced by extracellular ATP in AS-30D hepatoma cells was studied.
• 2.2. Homologous desensitization involving the refilling of intracellular calcium pools and the participation of protein kinase C was found.
• 3.3. Isoproterenol, forskolin and dibutyril-cyclic AMP also induced an increase in [Ca²⁺]c.
• 4.4. Interestingly, synergism was found for isoproterenol or forskolin and ATP.
• 5.5. The results suggest that there are two pathways for mobilizing [Ca²⁺] in AS-30D hepatoma cells; one is activated by ATP receptors and the other by cyclic AMP.

     

Cyclic AMP stimulation and prostaglandin inhibition of Na transport in freshwater mussels

• 1.1. Pondwater acclimated Carunculina texasensis and Ligumia subrostrata experienced a 230% increase in Na influx when injected with dibutyryl cyclic AMP (0.4mM/l blood).
• 2.2. Theophylline, a phosphodiesterase inhibitor, or indomethacin, an inhibitor of prostaglandin (PG) synthetase, caused a dose dependent stimulation of Na transport.
• 3.3. Prostaglandin E₂ injected into mussels caused an inhibition of Na influx. Arachidonic acid, the precursor of PGE₂, inhibited Na influx or stimulated Na efflux depending on the animal's acclimation conditions.
• 4.4. Chloride transport was unaffected by the drugs used in this study.

     

Comparative study on AMP deaminase in gill,muscle and blood of fish

• 1.1. High AMP deaminase activities were determined in the gill of one selachian, Scyliorhinus caniculus, and five teleosts, Anguilla anguilla, Cyprinus carpio, Salmo gairdneri, Perca fluviatilis and Esox lucius.
• 2.2. The highest activity was generally found in skeletal white muscle, except in A. anguilla and S. caniculus.
• 3.3. In s. caniculus a very high AMP deaminase activity was found in the blood where it was shown to be tightly regulated by inorganic phosphate.
• 4.4. Seasonal variations were observed for AMP deaminase activity in gill and white muscle, but also for blood Hb and protein concentration in the three tissues examined.

     

Cyclic nucleotides and other factors affecting the apparent activity of RNA polymerases solubilized from rat mammary gland nuclei

• 1.1. The apparent activity (counts/min per unit enzyme) of DNA-dependent RNA polymerase (E.C. 2.7.7.6) extracted from rat mammary gland nuclei, chromatographed on DEAE-Sephadex and incubated in the presence of cyclic AMP or cyclic GMP, was altered by intentional ‘contamination’ of nuclei with cytosol, or washing them with detergent before extraction of enzyme.
• 2.2. Addition of cytosol, different column fractions or theophyllin and cyclic AMP to aliquots of enzyme could also alter the activity of the polymerase.
• 3.3. While the mechanism(s) of these effects is not established, the presence within the same column fractions of specific RNA polymerases, ³H-cyclic AMP and ³H-cyclic GMP-binding proteins and protein kinases provides a number of sites at which such putative ‘regulatory’ events could occur.
• 4.4. Results of studies using sucrose gradient centrifugation were consistent with a close association between RNA polymerase II, ³H-cyclic AMP and the calf thymus DNA template, confirming previous observations of binding by cyclic AMP to proteins contained within column fractions of RNA polymerase II.

     

The pattern and influential factors of aquatic pharyngeal movements of Trionyx sinensis

• 1.1. The pharyngeal movements of Trionyx sinensis during submersion where recorded with physiological instruments.
• 2.2. Anoxia or hypercapnia caused a marked increase in breathing rate of tested turtles during voluntary diving, and in anoxia there was a significant increase in the frequency of aquatic pharyngeal movements while hypercapnia had a slight or no effect on the frequency of these movements.
• 3.3. During voluntary diving when turtles could easily extend their heads out of water to breathe air, the frequency of rhythmic pharyngeal movements was lower; but during forced submersion, the frequency was higher and the movements were continuous.
• 4.4. The frequency increased more rapidly and greatly when turtles were in forced submersion than when they dived freely and could easily surface to breathe in N₂.
• 5.5. The frequency of pharyngeal movements of T. sinensis during diving in an aquarium with water depth of 30 or 45 cm was markedly higher than that at a water depth of 15 cm. Disturbing stimuli also influenced the aquatic rhythmic pharyngeal movements of T. sinensis.

     

Nucleoside monophosphoramidate hydrolase from rat liver: Purification and characterization

• 1.1. Adenosine 5'-phosphoramidate hydrolase of 29 kDa was isolated from rat liver cytosol.
• 2.2. It consisted of two subunits of 14 kDa.
• 3.3. It hydrolyzed nucleoside 5'-monophosphoramidates into nucleoside 5'-monophosphates and ammonia, while it did not hydrolyze adenylyl phosphoramidate, adenylyl imidodiphosphate and N-phosphorylated compounds like phosphocreatine, N^ω-phosphoarginine, 6-phospholysine and 3-phosphohistidine.
• 4.4. Divalent cations and cyclic AMP had no effect on the hydrolytic activity.

     

Insulin,glucagon and catecholamine interactions in avian liver explants

• 1.1. A mechanical tissue chopper was used to obtain liver explants (35–75 mg) from 2- to 3-week-old chickens to determine both tissue sensitivity and metabolic effects of isoproterenol, avian insulin and glucagon.
• 2.2. Avian insulin had no effect on lipogenesis; however, lipogenesis was decreased by dibutyryl cyclic AMP. Insulin did not overcome a decrease in lipogenesis caused by catecholamines. Therefore, this control mechanisms is not modulated by insulin.
• 3.3. Preincubation in the presence of glucagon decreased in vitro lipogenesis. Preincubation in the presence of a 19–29 amino acid construct that approximated the radioimmune site for glucagon did not result in a similar effect. Therefore, this site does not relate to the biopotency of the hormone.
• 4.4. A previously noted catecholamine induced decrease in in vitro lipogenesis was verified, showing that points of in vitro regulation are under phosphorylation-dephosphorylation control.
• 5.5. Preincubation of slices (1 hr) with propranolol blocked the inhibition of lipogenesis caused by α and β adrenergic agonists (arterenol or isoproterenol) during a subsequent 2-hr incubation.
• 6.6. Preincubation of slices with either of these agonists decreased lipogenesis even following an extensive washout.
• 7.7. Inhibition could be overcome with propranolol, a β adrenergic antagonist.

     

The respiratory pigment of the serpulid polychaete,Serpula vermicularis L. Structure of its chlorocruorin and hemoglobin (erythrocruorin)

• 1.1. The respiratory pigment found in the vascular fluid of Serpula vermicularis appears to be homogeneous with respect to molecular weight (3 × 10⁶), charge (pl = 5.1) and high pH dissociation properties.
• 2.2. Serpula pigment contains one iron per 24,700 g protein with 60% of the iron present as chlorocruoroheme and 40% as heme. This ratio of chlorocruoroheme to heme was found in worms ranging in weight from about 50 to 500 mg.
• 3.3. The pigment is composed of at least three subunits with molecular weights in sodium dodecyl sulfate (SDS) of 13,300, 14,700 and 17,500. The amino acid composition of this pigment is similar to those of other annelid extracellular hemoglobins and chlorocruorins.
• 4.4. Preliminary oxygen equilibrium experiments show that the heme oxygen binding site may combine with oxygen in a manner different from the chlorocruoroheme oxygen binding site.
• 5.5. These results are discussed with respect to possible structures of S. vermicularis pigment, its relationships to other annelid pigments and its function.

     

Subcellular distribution of metals within the kidney of the bivalve Mercenaria mercenaria (L.)

• 1.1. The subcellular distribution of nine transition metals (plus four additional elements) was measured in the kidney tissue of the quahog, Mercenaria mercenaria.
• 2.2. Elemental analyses of the subcellular fractions indicated three main patterns of metal distribution within kidney cells.
• 3.3. Barium, iron, manganese and lead were associated primarily with kidney granules.
• 4.4. Cadmium, copper, potassium and magnesium were found mainly in the cytosolic fraction.
• 5.5. Calcium, phosphorus and zinc were found in all isolated fractions, probably reflecting the important roles that these elements play in bivalve metabolism.
• 6.6. The organelle composition of the isolated subcellular fractions was determined using marker enzyme assays and microscopic techniques.

     

Effect of ambient temperature on lipid metabolism in brown fat during the perinatal period

• 1.1. Norepinephrine-induced lipolysis, cyclic AMP production and glycerokinase activity were measured, in vitro, in the brown fat of rats born and reared at either 28° or 16°C during the first 3 weeks of life.
• 2.2. During the first two postnatal days, lipolytic activity in the tissue was lower than in the foetuses at both ambient temperatures At day 10, increased values of the parameters under consideration were similarly observed in both groups.
• 3.3. However, the hormonal regulation of lipolysis seemed to be quite different from that found in adult cold-acclimated rats.
• 4.4. At day 21, the cold-induced characteristics of lipid metabolism in brown fat were observed in the 16°C exposed rats, whereas a loss of tissue stimulation occurred in the 28°C exposed ones.