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PubMed2000

Steps in the formation of neurites and synapses studied in cultured leech neurons.

Leech neurons in culture have provided novel insights into the steps in the formation of neurite outgrowth patterns, target recognition and synapse formation. Identified adult neurons from the central nervous system of the leech can be removed individually and plated in culture under well-controlled conditions, where they retain their characteristic physiological properties, grow neurites and form specific chemical or electrical synapses. Different identified neurons develop distinctive outgrowth patterns that depend on their identities and on the molecular composition of the substrate. On native substrates, the patterns displayed by these neurons reproduce characteristics from the adult or the developing neurons. In addition, the substrate may induce selective directed growth between pairs of neurons that normally make contact in the ganglion. Upon contact, pairs of cultured leech neurons form chemical or electrical synapses, or both types depending on the neuronal identities. Anterograde and retrograde signals during membrane contact and synapse formation modify the distribution of synaptic terminals, calcium currents, and responses to 5-hydroxytryptamine.

Animals↗
PubMed2005

Cloning, expression and pharmacological characterization of a vasopressin-related receptor in an annelid, the leech Theromyzon tessulatum.

In annelids, it has been established that arginine-vasopressin (AVP)/oxytocin (OT) superfamily peptides are involved in the maintenance of water and electrolyte homeostasis as well as reproduction. At present, there is little information on their receptors. In this study, we report the characterization of a 1.7 kb cDNA for an AVP-related receptor from the leech Theromyzon tessulatum. The open reading frame encodes a 435-aminoacid transmembrane protein that displays seven segments of hydrophobic amino acids, typical of G-protein-coupled receptors. The overall predicted protein exhibits about 30% amino-acid identities to other invertebrate, as well as vertebrate, AVP/OT receptor family members, and displays conserved characteristic features belonging to the AVP/OT receptor superfamily. RT-PCR expression experiments showed that mRNA is expressed in the genital tract, the ovary and the brain. The receptor expression is stage specific, showing a weak expression after the two first blood meals, increasing dramatically after the last blood meal during the period of sexual maturation and disappearing after egg laying. Thus, the leech AVP-related receptor may mediate reproductive functions. When expressed in COS-7 cells, the receptor binds ligands with the following rank order of potency: AVP= Arg-vasotocin >Arg-conopressin >mesotocin = OT = Lys-conopressin=isotocin>annetocin. This shows an AVP-like pharmacological profile. The transfected receptor mediates AVP-induced accumulation of inositol phosphates, indicating that the leech AVP-related receptor is functional. This study describes the characterization of a novel AVP/OT superfamily receptor in annelids, which are considered the most distant group of coelomate metazoans possessing a functional AVP/OT-related endocrine system.

Amino Acid Sequence↗
PubMed1992

Biochemical characterisation of a pancreatic elastase inhibitor from the leech Hirudinaria manillensis.

The jawed leech, Hirudinaria manillensis is closely related to Hirudo medicinalis, both belonging to the same family Arhynchobdellida. From Hirudo, two potent peptide inhibitors, hirudin (a thrombin inhibitor) and eglin (an elastase/chymotrypsin inhibitor) have been characterised in detail. During our studies to isolate thrombin inhibitor from the leech Hirudinaria a potent inhibitor, analogous to eglin, was also detected. Results indicate that this inhibitor, which we have named 'GELIN', is significantly different from eglin. Gelin was isolated and purified to homogeneity by ion exchange chromatography and reverse phase HPLC. The isoelectric point of Gelin was estimated to be 4.55, in contrast to 6.45 for eglin. The molecular weight of Gelin was similar to eglin, as estimated by SDS-PAGE. Amino-terminal sequence analysis of the first 29 residues show no sequence homology with eglin or any other serine protease inhibitors. Circular dichroism studies showed that the secondary structure of Gelin has no helix, 58% beta sheets and 42% random structures compared to 19% helix, 56% beta sheets and 25% random structures in eglin. Like eglin, Gelin inhibits elastase, cathepsin G and chymotrypsin but has little or no activity towards plasmin, thrombin, pepsin and trypsin. These data suggest that the elastase inhibitors from these two species of leech are fundamentally different in structure, indicative of independent evolutionary origin.

Amino Acid Sequence↗
PubMed1996

A cysteine-rich serine protease inhibitor (Guamerin II) from the non-blood sucking leech Whitmania edentula: biochemical characterization and amino acid sequence analysis.

A cysteine-rich serine protease inhibitor (Guamerin II) was isolated from the non-blood sucking leech Whitmania edentula. The new inhibitor was identified as a low molecular weight (6,012 Da) polypeptide with some sequence similarities to antistasin, hirustasin and guamerin. The inhibitor contained 56 amino acid residues with 76.8% sequence similarity to guamerin, 48.2% to hirustasin and 28.6% to the first domain of antistasin. This new inhibitor was the first completely sequenced serine protease inhibitor from a non-blood sucking leech. Analysis of the inhibitor revealed that it was active against neutrophil elastase and chymotrypsin, but had no activity against a variety of other proteases. The P1 reactive site residue was identified as methionine and the residues surrounding the P1 site were hydrophobic amino acids. The primary structure of the inhibitor showed no similarity to well-known elastase inhibitors from leeches such as eglin.

Amino Acid Sequence↗
PubMed1999

Molecular cloning and characterization of LKv1, a novel voltage-gated potassium channel in leech.

We have cloned a novel voltage-gated K channel, LKv1, in two species of leech. The properties of LKv1 expressed in transiently transfected HEK293 cells is that of a delayed rectifier current. LKv1 may be a major modulator of excitability in leech neurons, since antibody localization studies show that LKv1 is expressed in the soma and axons of all neurons in both the central and peripheral nervous systems. Comparison of the biophysical and pharmacological properties of LKv1 with native voltage-gated conductances in leech neurons suggests that LKv1 may correspond to the previously characterized delayed rectifier current, I(K). Phylogenetic analysis of LKv1 shows that it is related to the Shaker subfamily of voltage-gated K channels although it occupies a separate branch from that of the monophyletic Shaker clade composed of the flatworm, Aplysia, Drosophila, and mammalian Shaker homologs as well as from that of two recently identified Shaker-related K channels in jellyfish. Thus, this analysis indicates that this group of voltage-gated K channels contains several evolutionarily divergent lineages.

Amino Acid Sequence↗
PubMed1999

Sensory feedback can coordinate the swimming activity of the leech.

Previous studies showed that sensory feedback from the body wall is important and sometimes critical for generating normal, robust swimming activity in leeches. In this paper, we evaluate the role of sensory feedback in intersegmental coordination using both behavioral and physiological measurements. We severed the ventral nerve cord of leeches in midbody and then made video and in situ extracellular recordings from swimming animals. Our electrophysiological recordings unequivocally demonstrate that active intersegmental coordination occurs in leeches with severed nerve cords, refuting earlier conclusions that sensory feedback cannot coordinate swimming activity. Intersegmental coordination can in fact be achieved by sensory feedback alone, without the intersegmental interactions conveyed by the nerve cord.

Animals↗
PubMed1999

Leech giant glial cell: functional role in a simple nervous system.

The giant glial cell in the central nervous system of the leech Hirudo medicinalis has been the subject of a series of studies trying to link its physiological properties with its role in neuron-glia interactions. Isolated ventral cord ganglia of this annelid offer several advantages for these studies. First, single giant glial cells can easily be identified and are quite accessible to electrophysiological and microfluorometric studies. Second, only two giant macroglial cells are located in the neuropil of each ganglion, rendering them well suited for studying neuron-glia interactions. Third, many neurons can be identified and are well known with respect to their physiology and their roles in controlling simple behaviors in the leech. This review briefly outlines the major recent findings gained by studying this preparation and its contributions to our knowledge of the functional role of glia in nervous systems. Emphasis is directed to glial responses during neuronal activity and to the analysis of intracellular Ca(2+) and H(+) transients mediated by neurotransmitter receptors and ion-driven carriers. Among its numerous properties, the leech giant glial cell prominently expresses a large K(+) conductance, voltage-dependent Ca(2+) channels, ionotropic non-NMDA glutamate receptors, and an electrogenic, reversible Na(+)-HCO(3)(-) cotransporter.

Animals↗
PubMed2000

Segmental control of midbody peristalsis during the consummatory phase of feeding in the medicinal leech, Hirudo medicinalis.

The ingestive behavior of the medicinal leech includes peristalsis-like movements of the midbody that are organized into both rostral-to-caudal and caudal-to-rostral waves (C. M. Lent, K. H. Fliegner, E. Freedman, & M. H. Dickenson, 1988). The neuronal control of this behavior is unknown. Using surgical manipulations and electromyograms, the authors show that (a) the head and tail ganglia are not necessary for this behavior; (b) the circuit is distributed, with components reiterated along the length of the leech; (c) excitatory signals transmitted from rostral segments via the nerve cord can initiate peristalsis in "empty" caudal segments; (d) inhibitory signals from caudal segments limit the frequency of peristalsis; and (e) stretch of the gut and/or body wall is sufficient to produce peristalsis in the absence of heat or chemical cues. These results are compared with peristalsis in the digestive tract of mammals. The leech may be a good model for studying peristalsis-like behaviors at the cellular level.

Animals↗
PubMed2000

Sensory modification of leech swimming: rhythmic activity of ventral stretch receptors can change intersegmental phase relationships.

For segmented animals to generate optimal locomotory movements, appropriate phase relationships between segmental oscillators are crucial. Using swimming leeches, we have investigated the role of sensory input in establishing such relationships. We found that the stretch receptors associated with ventral longitudinal muscles encode the information of muscle contraction during swimming via membrane potential oscillations, with amplitudes of up to 10 mV at our recording site. We subsequently modified the activity of ventral stretch receptors (VSRs) by injecting rhythmic current at different phases of the swim cycle and determined intersegmental phase lags by comparing the delay between the discharges of serially homologous motoneurons in three adjacent segments of isolated nerve cords. When no current was injected, the phase lag between neighboring segments was 8.6 +/- 0.8 degrees (mean +/- SEM; n = 20), with large phase variations from cycle to cycle, between different episodes, and between different preparations. When the phase of stretch receptor activity was set to 90-150 degrees by current injection, the phase of the motoneuron activity in the ganglion was consistently retarded by approximately 5 degrees. It was advanced by approximately 5 degrees when the VSR phase was set to 240-300 degrees. Therefore, the rhythmic activity of the ventral stretch receptor generated during swimming can change intersegmental phase lags of leech ganglia in a phase-dependent manner. These stretch receptors may set the optimal intersegmental phases during swimming movement in intact leeches.

Animals↗
PubMed1975

[Leeches in the respiratory system (author's transl)].

The leech as a foreign body and parasite in the human respiratory tract occurs principally in the Mediterranean countries, in Africa and Asia. It reaches the respiratory tract when water is drunk directly from rivers, lakes, etc. Ignorance of this fact may cause diagnostic difficulties leading to errors in treatment. Anaemia and respiratory obstruction due to leeches cause danger to health and life, especially in children. Fatalities have been known. Treatment consists of endoscopic removal of the parasite, which may be technically difficult, especially when the leech is in the region of the larynx and thus presents dramatic conditions for the procedure. A series of 120 cases treated in Algeria between 1962 and 1971 is presented.

Age Factors↗
PubMed2002

Highly variable spike trains underlie reproducible sensorimotor responses in the medicinal leech.

The nervous system of the leech is a particularly suitable model to investigate neural coding of sensorimotor responses because it allows both observation of behavior and the simultaneous measurement of a large fraction of its underlying neuronal activity. In this study, we used a combination of multielectrode recordings, videomicroscopy, and computation of the optical flow to investigate the reproducibility of the motor response caused by local mechanical stimulation of the leech skin. We analyzed variability at different levels of processing: mechanosensory neurons, motoneurons, muscle activation, and behavior. Spike trains in mechanosensory neurons were very reproducible, unlike those in motoneurons. The motor response, however, was reproducible because of two distinct biophysical mechanisms. First, leech muscles contract slowly and therefore are poorly sensitive to the jitter of motoneuron spikes. Second, the motor response results from the coactivation of a population of motoneurons firing in a statistically independent way, which reduces the variability of the population firing. These data show that reproducible spike trains are not required to sustain reproducible behaviors and illustrate how the nervous system can cope with unreliable components to produce reliable action.

Action Potentials↗
PubMedDate not supplied

[The effects of axotomy on the nociceptive neurons of the leech].

INTRODUCTION: It has been described several similarities between mammalian and invertebrate nociceptors. Lateral N neuron, in the segmental ganglion of the leech Hirudo medicinalis, behave like polimodal nociceptors in mammals, meanwhile medial N cells is similar to mechano nociceptors (Pastor, Soria, Belmonte 1996). The effects of axotomy in sensory neurons in leeches are poorly understood. OBJECTIVE: We have focused on the electrophysiological properties of leech nociceptive neurons after axotomy. RESULTS: In N lateral neurons, axotomy induced an increase in the total membrane capacitance, membrane time constant, decrease in the steady state/maximum hyperpolarization rate, increment in the time constant of voltage relaxation of inward rectifier, increase in action potential duration, dV/dtmax, dV/dtmin, and maximum amplitude and duration of after hyperpolarization; firing threshold (always in not axotomized) and an increment in adaptation spike frequency. In N medial cells, axotomy produced a slight depolarization and a decrease in Rinput, a rise in the time constant of voltage relaxation of inward rectifier, a decrement of action potential maximum amplitude, dV/dtmax, dV/dtmin, and after hyperpolarization maximum amplitude, with an increase in action potential and after hyperpolarization duration. Finally, firing threshold increased both in axotomized and not axotomized after axotomy. Axotomy not only induced changes in injured cells, but modified neurons whose axons did not run into the cutting nerves. CONCLUSION: axotomy induces different changes in N lateral and N medial nociceptive cells, and it is suggested some kind of communication between axotomized and not axotomized cells

Action Potentials↗
PubMed1998

Contact between identified leech neurones in culture prevents retraction of neurites following electrical activity.

Neurites of individual leech neurones in culture retract in response to electrical stimulation or K+ depolarisation. The aim of these experiments was to assess whether retraction of neurites is prevented by the establishment of cell-cell contacts. Retzius and anterior pagoda (AP) cells were isolated from leech ganglia and plated either as single cells or in pairs. A profusion of well-developed neurites was observed after 5-9 days in culture on laminin-rich leech extracellular matrix extract. Brief trains of action potentials in single cells caused neurites to retract reversibly by approximately 26% of their average length, confirming and extending and earlier results. In contrast, retraction after stimulation was significantly decreased in cultures of paired cells that had formed synapses or contacts between their processes. Even free neurites that had not made contact failed to retract; many neurites continued to elongate during and after electrical stimulation. These results indicate that the retraction of neurites induced by electrical stimulation is prevented by the establishment of intercellular contacts. By stabilising the neurites of neurones contacting potential target cells, the search for additional targets and the strengthening of connections that are being made can continue in the presence of electrical activity.

Animals↗
PubMed1992

An inhibitor of collagen-stimulated platelet activation from the salivary glands of the Haementeria officinalis leech. I. Identification, isolation, and characterization.

A protein that blocks collagen-stimulated platelet aggregation has been identified and isolated from the soluble fraction of salivary glands from Haementeria officinalis leeches. We have named this protein leech antiplatelet protein (LAPP). LAPP was isolated from soluble crude salivary gland extract by heparin-agarose, size exclusion, and C18 reverse phase high-performance chromatography. Its molecular weight is approximately 16,000 on sodium dodecyl sulfate-polyacrylamide gel electrophoresis under both reduced and nonreduced conditions. The sequences of peptides generated by V8 digestion of LAPP as well as its amino acid composition suggested no homology to other known proteins. The IC50 for LAPP to inhibit platelet aggregation was approximately 60 nM. This inhibitory activity is specific for collagen-induced aggregation. Platelet aggregation in response to ADP, arachidonic acid, U46619, thrombin, and ionophore A23187 was not inhibited by LAPP at a concentration that blocked platelet aggregation to collagen by 100%. In contrast, crude salivary gland-soluble extract contained activity(ies) which inhibited aggregation to all these agonists except thrombin at 1 unit/ml and 2 microM A23187. Thus, the H. officinalis leech has evolved multiple mechanisms to prevent hemostasis, including an inhibitor of collagen-stimulated platelet aggregation. The identification and isolation of LAPP demonstrates the existence of a new type of platelet inhibitor that should be useful to better understand the mechanism of collagen stimulation of platelets.

Amino Acids↗
PubMed1992

Alternative leech vectors for frog and turtle trypanosomes.

Trypanosoma pipientis infections were achieved by exposing laboratory-raised bullfrog tadpoles (Rana catesbeiana) to the leech Desserobdella picta that had fed on infected frogs. Likewise, a laboratory-raised snapping turtle (Chelydra serpentina) was infected with Trypanosoma chrysemydis following exposure to infected Placobdella ornata. Transmission of the trypanosomes by these leeches constitutes new vector records for the parasites. The biology of D. picta and P. ornata suggests that they are more important in transmitting these flagellates than the species of leech previously reported as vectors.

Animals↗
PubMedDate not supplied

Gastrointestinal bleed after leeching in a patient on aspirin therapy.

Leeches ( Hirudo medicinalis ) have been used in health care for their property of bloodletting. Bleed occurring from the site of leech attachment has been well documented. We report a 50-year-old man who was on aspirin therapy for coronary artery disease, and presented with GI bleed after leech treatment for his knee pain.

Aspirin↗
PubMedDate not supplied

[The medicinal leech Hirudo medicinalis: clinical use of the animal and therapeutic prospects of hirudin].

Blood sucking leech, Hirudo medicinalis, used in Medicine for very long, knew an intensive employment during early 18e century but its excess was responsible of the temporary disparition of the animal from the therapeutics. Leech has currently recovered a clinical use, especially in microsurgery. On the other hand, hirudin, main active compound isolated from leech extract and also known and used for long, offers interesting outlooks by its anticoagulant and antithrombic properties. This explains the great interest of hirudin preparation by molecular genetics.

Animals↗