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At least 451 records · Page 25Linked to original sources
PubMed1987

Membrane-directed effects of the plant hormones abscisic acid, indole-3-acetic acid and 2,4-dichlorophenoxyacetic acid.

This study examines two ways plant hormones might influence membrane processes, effects on overall permeability and modifications of specific ion channels. Abscisic acid (ABA) and indole-3-acetic acid (IAA) greatly enhanced erythritol permeability in mixed egg lecithin bilayers. In single component dioleoylphosphatidylcholine bilayers ABA was less effective than IAA, while 2,4-dichlorophenoxyacetate (2,4-D) did not affect either system or alter their ABA response. In Myxicola axons ABA and IAA had no effect, while 2,4-D (10 uM) caused a depolarizing shift of voltage-dependent Na+ and K+ activation by 25 +/- 4 mV and 15 +/- 3 mV, consistent with internal negative surface charge changes of -0.002 e-/A2 and -0.0007 e-/A2. We conclude that both generalized and ion channel-directed effects may link plant hormones and intracellular regulation.

2,4-Dichlorophenoxyacetic Acid↗
PubMed1990

Presence in invertebrate genomes of sequences characterized by the repetition of the triplet CCPurine.

In Drosophila melanogaster (Dm), polypeptidic domains have been found in different morphogenetic genes. Two types of them are characterized by the repetition of nucleotidic triplets: the M repeat (CAX) and the paired repeat (CAXCCX). In this paper we described a third type of repeat isolated from the genome of a Polychaete annelid: Owenia fusiformis. This repeat is characterized by the repetition of the triplet CCPurine. Phylogenetic studies showed the presence of this repeat in all the invertebrate genomes tested (eight copies in Dm genome) while we failed to detect it in vertebrate genomes.

Amino Acid Sequence↗
PubMed1983

Bodian's silver method reveals molecular variation in the evolution of neurofilament proteins.

The recent demonstration that Bodian's silver method specifically stains mammalian neurofilament subunits (NFs), but not other intermediate filament proteins (IFs), provides a specific marker for the identification of neurofilament polypeptides. We have applied the Bodian stain to SDS-PAGE separated polypeptides in nervous tissues from 9 species, representing neuronal evolution in 4 major phyla: chordata, mollusca, arthropoda and annelida. Every species tested except the arthropod showed intense silver staining of a set of polypeptides, each subsequently identified as NFs by immunomethods. These results demonstrate that the affinity of NFs for Bodian's silver stain is conserved during the evolution of nervous systems in a diverse spectrum of animals. Further, considerable variation in the molecular weight of NF subunits was found among the 6 vertebrates studied. This variation suggests that the molecular weight of NFs has not been conserved during evolution, a quality which appears to be unusual for a structural protein.

Animals↗
PubMed1987

Zonisamide enhances slow sodium inactivation in Myxicola.

In voltage-clamped Myxicola giant axons Zonisamide (1,2-benzisoxazole-3-methanesulfonamide) caused a hyperpolarizing shift in the steady-state fast inactivation curve and retarded recovery from fast and slow Na+ inactivation. The effects of Zonisamide on steady-state fast inactivation could be described assuming a single binding site with a dissociation constant of 12 microM. Slow inactivation was significantly more sensitive, with a Kd of 1 microM from both steady-state and kinetic data. While these results account for anticonvulsant activity, the differential sensitivity suggests Zonisamide may also be useful in studies of the slow inactive state of the Na+ channel.

Animals↗
PubMed1984

Rise and fall of protein phosphorylation during meiotic maturation in oocytes of Sabellaria alveolata (polychaete annelid).

Incorporation of [32P]phosphate into proteins was monitored, in preloaded Sabellaria oocytes, during meiosis. After a fourfold increase during the transition from prophase to metaphase I, the incorporated radioactivity decreased steadily by 25% during completion of meiosis, while it slowly increased in metaphase I-blocked oocytes. Measurements of the amount and specific activity of nucleotide pools showed no variation, while total alkali-labile protein-bound phosphate was found to increase and then decrease during meiosis. Autoradiography of sodium dodecyl sulfate slabgels showed that some proteins have peculiar phosphorylation-dephosphorylation kinetics. The changes in the level of phosphorylation of proteins may be related to similar changes in maturation-promoting factor (MPF) activity.

Adenosine Triphosphate↗
PubMed1992

Regulation of M-phase progression in Chaetopterus oocytes by protein kinase C.

We have examined the presence of protein kinase C in oocytes of Chaetopterus pergamentaceus and its role in the initiation of germinal vesicle breakdown (GVBD). First, we demonstrated that the oocytes contain a phospholipid- and calcium-dependent protein kinase, protein kinase C (PKC). Since PKC is the primary intracellular receptor for phorbol esters, we tested the ability of phorbol 12,13-dibutyrate (PDBu) to induce GVBD and compared several critical events and processes involved in GVBD induced by PDBu to those induced normally (by seawater). Seawater and 100-200 nM PDBu induced chromosome condensation, spindle formation, and spindle migration over a similar time course. Both treatments induced similar alterations in the SDS-PAGE pattern of newly synthesized proteins. The synthesis of polypeptides of approximately 46 and 54 kDa increased specifically. Both treatments increased oocyte protein phosphorylation, especially of proteins of 22, 32, 46, 55, 64, and 84 kDa. Both treatments resulted in the activation of an M-phase-specific histone H1 kinase activity, which demonstrates the appearance of maturation-promoting factor. Staurosporine, a potent protein kinase C inhibitor, blocked GVBD and the activation of M-phase-specific H1 kinase, whereas HA1004, which preferentially antagonizes protein kinase A, had no effect. The results of this study demonstrate that protein kinase C can activate a wide spectrum of essential biochemical and morphological processes involved in GVBD. Further, these studies suggest that protein kinase C elicits GVBD by activating maturation-promoting factor and support the hypothesis that protein kinase C plays an essential role in oocyte maturation in this species.

Alkaloids↗
PubMed1987

Bepridil and valproate retard Na+ reactivation in Myxicola.

Two drugs were examined, each causing a similar specific modification of Na+ channel inactivation gating when internally applied to voltage-clamped Myxicola giant axons. Bepridil is an antianginal-antiarrhythmic agent with vasodilator and direct cardiac inotropic effects. Sodium valproate has anticonvulsant activity and causes use-dependent inhibition of repetitive firing in CNS neurons. Bepridil and sodium valproate caused a dose-dependent decrease in maximum Na+ conductance (KD = 25 microM for bepridil; KD = 0.5 mM for valproate). More importantly, at half-maximal blocking concentrations both drugs shifted steady state Na+ inactivation in the hyperpolarizing direction (by 30 mV for bepridil; 15 mV for valproate) and slowed the recovery of Na+ channels from inactivation (by 300% for bepridil; 60% for valproate). There was no effect on the K+ conductance, voltage-dependence of Na+ activation, or the time-dependence of inactivation of conducting channels. Neither produced non-inactivating Na+ current during long depolarizing steps.

Animals↗
PubMed1987

Selective modification of sodium channel gating by solvents and drugs.

In Myxicola heavy water (D2O) does not alter Na+ gating currents, but slows activation and inactivation. In this study, the solvent formamide (5-20% v/v) is shown to proportionately and reversibly block Na+ currents and charge movement, suggesting it may be useful for fractionating gating currents. Formamide- and prepulse-sensitive (inactivating) gating currents were identical, comprising 60-80% of total charge. Both had rising phases and decayed as single exponential functions. Formamide-insensitive and non-inactivating charge movements had no rising phases and decayed slowly with more complex kinetics. Another solvent, dimethylsulfoxide (1% v/v), had no effect on Na+ activation or charge movement, though it did affect inactivation. Amantadine (0.1 mM) did not change Na+ activation or charge movement, but slowed inactivation and shifted the foot of the steady state Na+ inactivation curve. Sotalol (0.1 mM) slowed inactivation, but also inhibited Na+ activation and gating current.

Amantadine↗
PubMed1985

Intercellular voltage gradient between oocyte and nurse cell in a polychaete.

In the polychaete Ophryotrocha labronica the oocyte is supported during vitellogenesis by a single nurse cell, which is cytoplasmically contiguous with the oocyte through an intercellular bridge. Our electrical measurements demonstrate a marked potential difference (22-32 mV) between the oocyte and the nurse cell in mid-vitellogenesis, suggesting an electrophoretically caused migration of nurse cell constituents into the oocyte. Possibly this potential gradient helps to create a developmental prepattern in the oocyte, a role postulated for similar gradients within the oocyte-nurse cell complex of the Cecropia moth.

Animals↗
PubMed1991

Primary structure of myohemerythrin from the annelid Nereis diversicolor.

The metal-free form of Nereis diversicolor myohemerythrin was purified from whole animal extracts by trichloroacetic acid precipitation and ion exchange chromatography. The amino acid sequence of myohemerythrin has been determined. The protein is composed of 120 residues, possesses an unblocked N-terminus and is devoid of cysteine residues. It bears 62% sequence identity with Themiste zostericola myohemerythrin, the only other member of this subfamily sequenced to date. Within the family of hemerythrins, homology is particularly high in the segments involved in the binding of the two iron atoms and in the beta-turn-rich N-terminal segment.

Amino Acid Sequence↗
PubMed1993

Anion-mediated lysine-arginine interaction. Evidence in Chaetopterus variopedatus sperm protamine.

Chaetopterus ariopedatus sperm protamine is a stable oligomer. Specific amino acid side chain modifications show that the oligomeric structure depends on anion-mediated lysine-arginine interactions. The occurrence of this type of interaction is confirmed by the finding that poly-L-arginine readily forms aggregates with poly-L-lysine or with the native but not with the protamine with carbamylated epsilon-amino groups.

Amino Acids↗