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At least 919 records · Page 51Linked to original sources
PubMed1993

Epitope mapping with ELISA of an antibody against oxytocin used for the characterization of an oxytocin-like epitope in the sex segmental ganglia of the leech Erpobdella octoculata.

1. Using direct, inhibiting and competitive enzyme-linked immunosorbent assay (ELISA), two steps were involved in the mapping of the recognition site of a polyclonal antibody against oxytocin (OT). 2. The percentage of cross-reactivity between OT and the N-terminal or the C-terminal fragment of OT demonstrated that the C-terminal fragment is the antigenic part of OT. 3. The percentage of cross-reactivity between OT and other molecules of the OT family indicated that the amino acid in the 8-position and the C-terminal amide of the OT molecule contribute to the recognition. 4. In the two sex segmental ganglia of the leech Erpobdella octoculata, where cells immunoreactive to the anti-OT are detected, the antibody has allowed to characterize an epitope close to the mammalian OT by its C-terminal part.

Amino Acid Sequence↗
PubMed1993

Potassium channels in growth cones of leech Retzius cells.

1. Potassium-selective channels were analysed in growth cones of cultured leech Retzius cells. 2. In the cell-attached mode and at physiological bath and pipette solution little channel activity was observed at resting membrane potential. The channel open probability (p(o)) increased with cell depolarization, and the slope conductance of the single K+ channel current was about 60 pS. 3. With symmetrical high KCl solution on both sides of the excised membrane patch three K(+)-selective channels could be discriminated. Two channels exhibited a linear current-voltage relation of about 18 pS and 106 pS, respectively. 4. The most frequently observed K+ channel showed a non-linear current-voltage relation and p(o) increased with increasing free cytoplasmic Ca2+ and during cell hyperpolarization.

Animals↗
PubMed1994

The bioenergetic costs of specific dynamic action and ammonia excretion in a freshwater predatory leech Nephelopsis obscura.

The energy utilized by the predatory freshwater leech for specific dynamic action (SDA) and exogenous excretion, and the proportion of absorbed energy available for growth and/or activity were determined at 5, 10, 15, 20 and 25 degrees C. SDA and exogenous ammonia excretion increased with increases in temperature to 20 degrees C but decreased at 25 degrees C. The duration of SDA decreased from 19 hr at 5 degrees C to 11 hr at 25 degrees C, while the duration of exogenous excretion decreased from 22 hr at 5 degrees C to 11 hr at 25 degrees C. The proportion of absorbed energy utilized for SDA and exogenous excretion decreased from 5 degrees C to 15 degrees C and increased at 25 degrees C; however the energy available for growth and activity increased from 7.4 J/day at 5 degrees C to a maximum of 32.6 J/day at 15 degrees C, decreasing to 12.7 J/day at 25 degrees C.

Ammonia↗
PubMed1990

RMI 12330A, an inhibitor of adenylate cyclase and cyclic AMP-phosphodiesterase activities in the segmental ganglia of the leech Hirudo medicinalis.

The effect of RMI 12330A, an inhibitor of basal as well as serotonin-stimulated adenylate cyclase in the segmental ganglia of the leech Hirudo medicinalis, has been tested on cyclic AMP-phosphodiesterase activity in the same tissue. The drug dose-dependently inhibits high and low affinity enzyme, an effect first evident at an RMI 12330A concentration of 0.5 mM. For both enzyme activities the drug reduces Vmax without substantially influencing Km values. Both basal and serotonin-stimulated adenylate cyclase as well as cyclic AMP-phosphodiesterase activities are inhibited by RMI 12330A in a non-competitive manner.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1993

FMRF-amide modulates the electrical activity of the leech Retzius cell.

The effect of the peptide FMRF-amide on the electrical activity of the leech Retzius (R) cell was investigated using electrophysiological techniques. FMRF-amide and six structurally related analogs increased the excitability of the R cell in several distinct ways that could act in concert to modulate transmitter release. 'Puffs' of FMRF-amide transiently depolarized the cell leading to a barrage of action potentials. This depolarization was followed by a phase of rhythmical bursting that appeared intrinsic to the neuron. FMRF-amide also broadened the plateau of the Ca(2+)-dependent action potential. The results suggest that the terminal Phe and Arg as well as the C-terminal amide are critical for the activity of these peptides.

Action Potentials↗
PubMed1991

Effect of phorbol ester on protein phosphorylation in the central nervous system of the leech Hirudo medicinalis: a two-dimensional electrophoretical analysis.

1. Proteins of different regions of the Hirudo medicinalis central nervous system have been analyzed by means of two-dimensional electrophoresis. 2. Subcellular distribution of phosphoproteins has been studied in leech segmental ganglia. 3. Phorbol 12,13-dibutyrate, a protein kinase C activator, stimulates the phosphorylation of a number of proteins whose isoelectric points and mol. wts are presented. 4. Putative roles for these phosphoproteins are discussed.

Animals↗
PubMed1995

Alterations in polyamine levels of nematode, earthworm, leech and planarian during regeneration, temperature and osmotic stresses.

Free-living nematodes, Caenorhabditis elegans and Dorylaimus fodori, contain putrescine and spermidine. Putrescine, spermidine and spermine occur in the parasitic Nematoda, Ascaris suum, Anisakis simplex and Dirofilaria immitis. Earthworms, Eisenia foetida, Tubifex hattai and Pheretima communissima and the leech, Hirudo nipponia (belonging to Annelida) and the planarian, Dugesia japonica (belonging to Platyhelminthes) contain homospermidine and spermine in addition to putrescine and spermidine. Regenerated heads of E. foetida and D. japonica are rich in putrescine indicating the stimulation of its synthesis during regeneration. Putrescine and spermidine levels temporarily increase after heat shock in C. elegans, E. foetida and D. japonica and cold shock and hypertonic osmotic shock treatments in D. japonica.

Animals↗
PubMed1995

Central and peripheral 5-HT receptors in the leech (Hirudo medicinalis) redefined.

1. 5-Hydroxytryptamine (5-HT) receptors in the Retzius neurones (R cells) and longitudinal body wall muscle strips of the leech H. medicinalis were studied using a range of selective agonists developed for mammalian receptors. 2. All agonists induced hyperpolarisation of R cells: the order of their potency was 5-HT > 5-CT > 2-Me 5HT > alpha-Me-5-HT > > CGS-12066B = 5MeOT > PAPP > Buspirone. This receptor is most like a mammalian 5-HT1C/2 receptor. 3. 5-HT induces relaxation of body wall strips, preceded at higher doses by contraction or an increase in spontaneous contractions. The relaxing effect was best mimicked by 5-CT and alpha-Me-5-HT, suggesting a 5-HT1C/2 receptor. The contractile effect was best mimicked by 5-MeOT suggesting a 5-HT4-like receptor. The overall potency of agonists on the body wall muscle was 5-MeOT > 5-CT > 5-HT > alpha-Me-5-HT > 2-Me 5-HT > PAPP > Buspirone > > CGS-12066B. 4. Results suggest that either the sites of 5-HT action possess several different receptors or the receptors themselves are more complex with multiple properties.

Animals↗
PubMed1995

Octopamine and Leydig cell stimulation depress the afterhyperpolarization in touch sensory neurons of the leech.

In touch sensory neurons of the leech, a train of spikes evoked by intracellular electrical stimulation leads to an afterhyperpolarization, mainly due to the activation of the Na+/K+ electrogenic pump and partly to a Ca(2+)-activated K+ conductance. It has been found that serotonin is able to reduce the afterhyperpolarization through the inhibition of the Na+/K+ electrogenic pump. We have investigated the possible modulation of the afterhyperpolarization by other endogenous neurotransmitters and we have found that octopamine is also able to reduce its amplitude. The electrical stimulation of the octopaminergic Leydig neurons mimics this effect. We have compared the actions of the two amines and found that the effect of serotonin is blocked by methysergide but not by high [Mg2+] or by phentolamine, and it is still present in touch cells isolated in culture. On the contrary, the octopamine modulation of the afterhyperpolarization does not occur in single touch cells in culture and it is blocked by all these treatments. These data suggest that while serotonin should act monosynaptically, octopamine should act through a serotonergic pathway.

Animals↗
PubMed1995

Enhancement of postsynaptic serotonin-activated Cl- currents by depolarization-induced Ca2+ entry into leech neurons.

Postsynaptic Ca2+ signals are a precondition for many types of synapse modification, including long-term potentiation. Here we describe a postsynaptic mechanism that augments synaptic currents at the serotonergic Retzius-P cell synapse of the leech. Depolarizations large enough to elicit Ca2+ currents evoked an increase in the amplitude of serotonin-activated Cl- currents in isolated embryonic neurons as well as at the Retzius-P cell synapse. The effect on embryonic whole cell currents lasted for up to one hour and was abolished in solutions containing Cd2+ as a Ca2+ channel blocker. Hence, Ca2+ influx into the postsynaptic neuron may be a common step regulating the plasticity of various vertebrate as well as invertebrate synapses.

Animals↗
PubMed1989

Cloning and expression of cDNA encoding antistasin, a leech-derived protein having anti-coagulant and anti-metastatic properties.

As a factor Xa inhibitor, antistasin is a potent anti-coagulant and anti-metastatic agent that is found in the salivary gland of the Mexican leech Haementaria officinalis. cDNA clones that encode antistasin have been isolated. Subsequent sequence analysis and comparison with the amino acid sequence of the mature protein indicates that antistasin is produced as a pre-protein containing a 17-amino acid signal peptide. Antistasin exists as at least two variants. By sequence analysis of multiple cDNA clones, we found two additional sites for amino acid substitutions, confirming variants that differ from each other by amino acid changes at a minimum of four residues. These sequence variations appear to be the result of allelic variation rather than gene duplication as deduced from DNA blot analyses. Sequence data suggest that antistasin may have evolved from a smaller ancestral gene by a duplication event giving rise to a two-fold structural homology between the N- and C-terminal halves of the molecule. Insect cells transfected with a recombinant baculovirus expressed antistasin which was biologically active and had an electrophoretic mobility identical to that of the native molecule.

Amino Acid Sequence↗
PubMed1991

Secretion of biologically active leech hirudin from baculovirus-infected insect cells.

The thrombin inhibitor, hirudin, from the leech Hirudo Medicinalis, is the most powerful natural anticoagulant known. It has been characterized as a polypeptide of 65 amino acids which exhibits its anticoagulant properties by binding tightly and specifically to alpha-thrombin. The potency and specificity of hirudin have generated interest on its possible use in the treatment or prophylaxis of various thrombotic diseases. We have used the baculovirus expression system to efficiently produce active hirudins in insect cells. The Autographa californica nuclear polyhedrosis virus has proved useful as a helper-independent viral expression vector for high-level production of recombinant proteins in cultured insect cells. Hirudin variants (HV1 and HV2) were produced in infected insect cells as secreted proteins by joining their coding sequences to the leader peptide sequence of the vescicular stomatitis virus G protein. The recombinant products were biologically active and, interestingly, N-terminal sequencing of HV1 revealed that the heterologous leader peptide is correctly removed.

Amino Acid Sequence↗
PubMed1984

Ultrastructural localization of [3H]dopamine in neurons of leech (Haemopis sanguisuga) abdominal ganglia.

Neurons in the cortex of the segmental ganglia of Haemopis sanguisuga accumulated [3H]DOPA in vitro. Electron microscopic autoradiography revealed deposits of silver grains over clusters of electron dense granules measuring 20-35 nM in diameter. [3H]Dopamine (DA) was localized in the giant glial cells. Dopaminergic terminals were labelled with both DOPA and dopamine and the morphology is similar to other DA synapses. The leech could be a useful model for the study of synaptic events at dopaminergic terminals.

Animals↗
PubMed1984

Action potential prolongation: an effect of physostigmine (eserine) upon Retzius cells in the leech C.N.S.

Physostigmine (PHY; eserine) prolongs the action potentials in the Retzius cells within leech ganglia to about 800 ms. The effect was reversible and occurred at concentrations of 1-10 mM which are several orders of magnitude greater than those required to inhibit cholinesterase. The prolonged action potentials showed an early, spike-like depolarization followed by a plateau. The initial depolarization exhibited a strong dependence on external Na+ while the amplitude of the plateau had somewhat less Na+ dependence: 52 and 24 mV/decade, respectively. The duration of the plateau was increased by elevating Na+ and decreased by elevating Ca2+. Increasing the action potential frequency, by intracellular stimulation, decreased both the duration and amplitude of the plateau. Neostigmine, di-isopropylphosphofluoridate, and acetylcholine did not prolong RZ action potentials. Thus, the membrane effects of physostigmine appear to be independent of any inhibition of cholinesterase or accumulation of acetylcholine.

Acetylcholine↗
PubMed1985

Effect of colchicine and vinblastine on identified leech neurons.

An identified neuron of the leech central nervous system is affected by the application of colchicine or vinblastine to its axon. It develops characteristic changes of membrane electrical properties, which are similar to those observed after surgical axotomy. The ionic mechanisms associated with the impulses induced by axotomy and colchicine treatment are not equivalent.

Animals↗
PubMed1985

A new approach to the analysis of complex dose-response relationships: a multivariate study of octopamine action on the leech Leydig neurone.

Octopamine (OA) hyperpolarizes leech Leydig neurones but response amplitudes and thresholds vary. Associations between response, OA dose and other variables [initial resting potential, action potential (AP) frequency and amplitude, temperature, microelectrode resistance, position of ganglion along nerve cord, animal, treatment order] were examined using canonical correlation. A complex response was expressed by summing changes in membrane potential and AP frequency over 2 min of OA treatment. Only dose and ganglion position influenced this response. One significant canonical variate related dose to immediate changes in membrane potential and summed changes in AP frequency throughout the OA effect. Response to OA was greater in cells in posterior ganglia.

Action Potentials↗
PubMed1988

Pharmacological control of the pattern of activity in leech Retzius neurones.

1. Changes in the activity pattern of leech Retzius (R) cells were investigated using intracellular recording. 2. The presence of an after-hyperpolarisation (AHP) is closely related to activity pattern; regular firing being associated with an AHP, bursting with its absence. 3. Increasing external calcium (Cao), cyclic AMP levels or activity of kinase A enhanced the AHP. 4. Bursting was induced by low Cao, EGTA, barium, cobalt or injection of phorbol ester. 5. Reduction of Cao to zero caused long paroxysmal depolarising shifts of potential which could be reversed to bursting by cobalt, IBMX or injection of kinase A catalytic subunit. 6. The possible roles of a calcium-activated potassium channel and protein phosphorylation in regulating the activity of the cell are discussed.

1-Methyl-3-isobutylxanthine↗
PubMed1988

Axon extension and retraction by leech neurons: severing early projections to peripheral targets prevents normal retraction of other projections.

During leech embryogenesis, interactions between homologous neurons in neighboring segments lead to the selective retraction of longitudinal axonal projections by midbody AP and AE neurons, which maintain lateral axonal projections to the periphery. Results of experiments reported here show that disconnecting the lateral projections from the periphery rescues the projections normally fated to retract. We propose that these neurons normally progress through two states during early development, one in which they are insensitive to interactions with their homologs (state A) and a second in which they are sensitive (state B). Establishment of lateral connections with their targets triggers the switch from state A to state B; cutting these projections puts neurons back to state A.

Animals↗