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PubMed2006

Functions of the subesophageal ganglion in the medicinal leech revealed by ablation of neuromeres in embryos.

Two general trends in the evolution of the nervous system have been toward centralization of neuronal somata and cephalization of the central nervous system (CNS). These organizational trends are apparent in the nervous system of annelid worms, including leeches. To determine if the anterior brain of the leech serves functions similar to those of the brains of more complex organisms, including vertebrates, we ablated one of the two major regions of the cephalic brain--the subesophageal ganglion (SubEG). For anatomical reasons, ablations were performed in embryos, rather than in adults. At the end of embryonic development, we observed the leeches' spontaneous behaviour and their responses to moderate touch. We observed that, although the midbody ganglia of the leech CNS display a high degree of local autonomy, the cephalic brain provides generalized excitation to the rest of the CNS, is a source of selective inhibition that modulates behaviour, integrates sensory information from the head with signals from the rest of the body, and plays an important role in organizing at least some complicated whole-body behaviours. These roles of the leech cephalic brain are common features of brain function in many organisms, and our results are consistent with the hypothesis that they arose early in evolution and have been conserved in complex nervous systems.

Animals↗
PubMed1996

Olfaction and prey search in the carnivorous leech Haemopis marmorata

Haemopis marmorata, the green horse leech, is carnivorous and readily eats earthworms. Using a Y-maze with flowing water, we show that specimens of H. marmorata are attracted to live earthworms. Ablating the dorsal lip, the presumed site of the chemoreceptors that this species uses in prey search, disrupts the ability of the leeches to find the earthworms in the Y-maze. Earthworm wash, a preparation of the collagen coating of earthworm skin, shock-induced earthworm secretion, mammalian blood and a salt­arginine mixture are not attractive to the green horse leech. The tails of freshly killed earthworms are attractive to the leeches, but tails from worms killed 8­12 h previously and stored cold are not. Our conclusion is that the earthworms produce a metabolite that attracts the leeches.

Journal Article↗
PubMed2003

The return of the leech.

Medicinal leeches (Hirudo medicinalis) have been used in medicine for thousands of years to treat a wide range of ailments. Nowadays, leeches are used successfully for only a few conditions, notably in the field of reconstructive or microsurgery, to salvage tissue flaps and skin grafts whose viability is threatened by venous congestion. The anticoagulant properties of hirudin, contained in leech saliva, may lead to wider therapeutic applications in the prevention and treatment of thromboembolic disease. Optimal care is needed when applying leeches, because their use can be complicated by serious bacterial infections.

Animals↗
PubMed1988

Leeches. Objective monitoring of altered perfusion in congested flaps.

In plastic and reconstructive surgery, there has been new interest in the use of the medicinal leech (Hirudo medicinalis) for the treatment of venous congestion. To the best of our knowledge, no study has been performed to objectively demonstrate the benefits of leeching a congested flap. Doppler laser perfusion monitoring (DLPM) was used to record blood flow changes in pig rump flaps compromised by venous occlusion. With the application of leeches to nine congested pig rump flaps, significant increases in blood flow were demonstrated both clinically and by DLPM. It is concluded from this study that DLPM can demonstrate objective improvement in microcirculatory perfusion with leeching.

Animals↗
PubMed1996

Leech photoreceptors project their galectin-containing processes into the optic neuropils where they contact AP cells.

We characterized a subset of leech sensory afferents, the photoreceptors, in terms of their molecular composition, anatomical distribution, and candidate postsynaptic partners. For reagents, we used an antiserum generated against purified LL35, a 35 kD leech lactose-binding protein (galectin); monoclonal antibody (mAb) Lan3-2, which is specific for a mannose-containing epitope common to the full set of sensory afferents; and dye injections. Photoreceptors differ from other types of sensory afferents by their abundant expression of galectin. However, photoreceptors share in common with other sensory modalities the mannose-containing epitope recognized by mAb Lan3-2. Photoreceptors from a given segment project their axons directly into the CNS ganglion innervating the same segment. They assemble in a target region, the optic neuropil, which is separate from the target regions of other sensory modalities. They also extend their axons as an optic tract into the connective to innervate optic neuropils of other CNS ganglia, thereby providing extensive intersegmental innervation for the 33 CNS ganglia comprising the leech nerve cord. Because of its intimate contact with the optic neuropil, a central neuron, the AP effector cell, is a strong candidate second order visual neuron. In confocal images, the AP cell projects its primary axon for about 100 microns alongside the optic neuropil. In electron micrographs, spines emanating from the axon of the AP cell make contact with vesicle laden nerve terminals of photoreceptors. Leech photoreceptors and their second order visual neurons represent a simple visual system for studying the mechanisms of axonal targeting.

Animals↗
PubMed1999

Glutamate receptor 5/6/7-like and glutamate transporter-1-like immunoreactivity in the leech central nervous system.

Previous physiological and pharmacological evidence has suggested a neurotransmitter role for the excitatory amino acid glutamate in the leech central nervous system (CNS). In the present study, we sought to localize glutamate receptor (GluR) subunits (GluR 5/6/7, GluR 2/3 and N-methyl-D-aspartate receptor 1 [NMDAR 1]) and a glutamate transporter subtype [GLT-1] within the leech CNS using mono- and polyclonal antibodies. In whole-mounted tissue, small cells of the outer capsule and putative microglia labeled with both GluR 5/6/7 and GluR 2/3 but not NMDAR 1 subunit antisera. In general, GluR 5/6/7-like immunofluorescence was both more intense and more widespread than GluR 2/3-like immunolabeling. Cryostat-sectioned tissue revealed extensive GluR 5/6/7-like immunoreactivity throughout the neuropil as well as labeling within a few neuronal somata. GLT-1-like immunoreactivity localized to the inner capsule, which is the interface between neuronal somata and the neuropil and is deeply invested by processes of neuropil glia. These results complement previous physiological and pharmacological findings indicating that the leech CNS possesses the cellular machinery to respond to glutamate and to transport glutamate from extracellular spaces. Together, they provide further evidence for glutamate's role as a neurotransmitter within the leech CNS.

Animals↗
PubMed1989

Factors specifying cell lineages in the leech.

As in arthropods, several major organ systems in leeches, including body musculature, nervous system and nephridia, are organized into a fixed number of longitudinally iterated units called segments. Many cells, especially neurons, can be uniquely identified from segment to segment. Leech embryos comprise identified cells, which facilitates developmental analysis. So far as it is known, cell lineages in leech are largely determinate. Prior to first cleavage, cytoplasmic reorganization generates domains of yolk-deficient cytoplasm called teloplasm. In situ hybridization experiments suggest that teloplasm is enriched for polyadenylated RNAs. During the first three, unequal cell divisions, teloplasm is segregated to macromere D'; normally, this cell alone cleaves further to generate five bilateral pairs of embryonic stem cells, M, N, O/P and Q teloblasts. Centrifugation experiments have shown a causal link between inheritance of teloplasm and the cleavage pattern that generates teloblasts. Teloblasts undergo highly unequal divisions, generating a longitudinal array of segmental founder cells called m, n, o, p and q blast cells, from which the definitive segmental tissues arise via further stereotyped cell divisions. Microinjecting new-born teloblasts or their precursors with polyadenylic acid induces the formation of supernumerary teloblasts. This discovery permits further analyses of factors specifying the five cell lines generating segmental tissues of the leech.

Animals↗
PubMed2002

Distribution and development of dopamine- and octopamine-synthesizing neurons in the medicinal leech.

Although the medicinal leech is a well-studied system in which many neurons and circuits have been identified with precision, descriptions of the distributions of some of the major biogenic amines, such as dopamine (DA) and octopamine (OA), have yet to be completed. In the European medicinal leech Hirudo medicinalis and the American medicinal leech Macrobdella decora,we have presented the first immunohistochemical study of DA neurons in the entire central nervous system, and of OA-immunoreactive (ir) neurons in the head and tail brains. Dopaminergic neurons were identified using the glyoxylic acid method and antisera to DA and its rate-limiting synthetic enzyme tyrosine hydroxylase (TH). Octopaminergic neurons were recognized using a highly specific antiserum raised against OA. An antibody raised against DA-beta-hydroxylase (DbetaH), the mammalian enzyme that converts DA to norepinephrine (NE), was found to immunostain OA-ir neurons. This antibody appears to cross-react with the closely related invertebrate enzyme tyramine-beta-hydroxylase, which converts tyramine to OA, suggesting that the OA-ir cells are indeed octopaminergic, capable of synthesizing OA. Because the DbetaH antiserum selectively immunostained the OA-ir neurons, but not the DA-synthesizing cells, our results also indicate that the DA-ir neurons synthesize DA and not NE as their end product. The expression of TH immunoreactivity was found to emerge relatively early in development, on embryonic day 9 (47-48% of development). In contrast, OA expression remained absent as late as embryonic day 20. Higher order processes of some of the dopaminergic and octopaminergic neurons in the adult brain were observed to project to a region previously described as a neurohemal complex. Several TH-ir processes were also seen in the stomatogastric nerve ring, suggesting that DA may play a role in the regulation of biting behavior. By mapping the distributions and developmental expression pattern of DA and OA neurons in the leech, we aim to gain a better understanding of the functional roles of aminergic neurons and how they influence behavior.

Aging↗
PubMed1990

Carbohydrate epitopes involved in neural cell recognition are conserved between vertebrates and leech.

We are reporting on the evolutionary conservation of carbohydrate epitope families from vertebrate to leech. 1) The sulfated L2/HNK-1 carbohydrate epitope (Abo T, Balch CM (1981): J Immunol 127:1024-1029; Kruse J, Mailhammer R, Wernecke H, Faissner A, Timpl R, Schachner M (1984): Nature 311:153-155) is detected on glycoproteins of leech neurons using monoclonal antibodies (mAbs) L2 (336) and HNK-1. 2) Three rat mAbs, L3, L4, and L5, bind to leech nerve and muscle. The L3, L4, and L5 epitopes are localized to a group of mannosidic leech glycoproteins originally identified through mAbs Lan3-2 (Hogg N, Flaster M, Zipser B (1983): J Neurosci Res 9:445-457 and Laz6-189 (McRorie JW III, Zipser B (1988): "Cell Culture Approaches to Invertebrate Neuroscience." London: Academie Press, pp 33-52. MAb Lan3-2, which binds to a mannosidic epitope of the 130 kD sensory protein, has recently been shown to perturb the penetration of sensory afferents into the synaptic area of the central neuropile (Zipser B, Morell R, Bajt ML (1989): Neuron 3:621-630). The L3, L4, and L5 mAbs have been described to recognize different mannosidic epitopes on glycoproteins, some of which have been identified as neural cell adhesion molecules, and on astrocyte-specific proteoglycan from mouse brain (Kücherer A, Faissner A, Schachner M (1987): J Cell Biol 104:1597-1602; Fahrig T, Schmitz B, Weber D, Kücherer-Ehret A, Faissner A, Schachner M (1990): Eur J Neurosci 2:153-161; Streit A, Faissner A, Gehrig B, Schachner M (1990): J Neurochem In Press). The superposition of five different mannosidic epitopes on the axons of sensory afferents suggests complex, concerted participation of mannosidic epitopes in neuronal pathfinding and target recognition.

Animals↗
PubMed1994

Substrate-dependent interactions of leech microglial cells and neurons in culture.

The principal aim of the present experiments has been to analyze the properties of microglial cells and their role in nerve regeneration. In the leech, damage to the CNS has been shown to be followed by accumulation of laminin and microglial cells at the site of injury (Masuda-Nakagawa et al., 1990. Proc. R. Soc. Lond. B. 241:201-206; and 1993. Proc. Natl. Acad. Sci. USA 90:4966-4970). Procedures were devised for isolating these small, wandering cells from the CNS of the leech. In culture, they were reliably identified by their sizes, shapes, and phagocytotic activity. Their morphology, motility, and interactions with neurons were influenced by the substrate molecules on which they were plated. On the plant lectin concanavalin A (Con A) microglia had a rounded shape and remained stationary. By contrast on extracts of leech extracellular matrix (ECM) enriched with laminin the cells were mobile and spindle-shaped with long processes. On Con A, neuronal growth cones avoided microglial cells, whereas on ECM extract the presence of a microglial cell did not influence neurite growth. Microglial cells showed immunoreactivity on both substrates when stained with a monoclonal antibody against leech laminin. Together these results suggest that microglial cells are influenced in their properties by molecules in the environment and that they could contribute to neuronal outgrowth at the site of an injury.

Animals↗
PubMed1995

Neuronal control of leech swimming.

Leech swimming is produced by the antiphasic contractions of dorsal and ventral longitudinal muscles that travel rearward along the animal and propel it forward. Research over the past three decades has focused on identifying the underlying neuronal circuit and mechanisms that produce and control this coordinated movement pattern. Investigations have also tested whether leech swimming is modifiable, both by experience and by neuromodulators. One outcome has been the identification of several functional classes of neurons associated with swimming. Systematic analysis of the interactions between these neurons had led to the elucidation of a neuronal circuit that adequately accounts for the generation of the swim motor program cord. The swim motor program appears to be produced by a chain of coupled segmental oscillators whose intrinsic properties and intersegmental connections ensure the coordinated expression of swimming along the nerve cord. In addition, neurons identified in the head ganglion comprise two parallel, but opposite-acting, systems that control the initiation of swimming in response to sensory input. Also, the pathway by which body wall stimulation initiates swimming shows a simple form of learning, that is habituation. Repeatedly stroking the leech body wall decreases both the probability of initiating swimming and the length of elicited swim episodes. Finally, the biogenic amine serotonin, which is found in the nerve cord, affects leech swimming in a number of ways. Serotonin's modulation of swimming is due, in part, to its effect of the membrane properties of swim-initiating interneurons and several swim motor neurons.

Animals↗
PubMed1996

Identification and characterization of a hunchback orthologue, Lzf2, and its expression during leech embryogenesis.

Lzf1 and Lzf2 are leech zinc finger (Lzf) genes that are shown to be orthologues to the Drosophila gap gene hunchback (hb). Neither in situ hybridization nor RT-PCR detected Lzf1 transcripts in leech embryos or adults. Lzf2 expression was examined in leech embryos at various stages by in situ hybridization. Lzf2 is expressed continually throughout the early embryonic cleavage divisions, including the period during which the embryo forms stem cells that will give rise to the segmented tissues of the adult. At the time of segmental pattern formation, Lzf2 RNA is expressed uniformly along the length of the segmented trunk in both the ectodermal and mesodermal tissues. This is in contrast to the anteriorly restricted gradient of hb RNA shown to be critical to the normal anteroposterior (AP) patterning of the insect embryo. Thus, this leech orthologue of hb does not appear to play a comparable role in the patterning of the AP axis. In addition, Lzf2 is expressed during organogenesis in segmentally restricted patterns in the central nervous system, the gut, and epidermally derived structures. Lzf2 is the first hb orthologue to be characterized in detail outside of insects and its expression pattern suggests that hb may have acquired a gap gene function in arthropods or insects after their phyletic separation from the annelids.

Amino Acid Sequence↗
PubMed1995

The whole-body shortening reflex of the medicinal leech: motor pattern, sensory basis, and interneuronal pathways.

The leech whole-body shortening reflex consist of a rapid contraction of the body elicited by a mechanical stimulus to the anterior of the animal. We used a variety of reduced preparations - semi-intact, body wall, and isolated nerve cord - to begin to elucidate the neural basis of this reflex in the medicinal leech Hirudo medicinalis. The motor pattern of the reflex involved an activation of excitatory motor neurons innervating dorsal and ventral longitudinal muscles (dorsal excitors and ventral excitors respectively), as well as the L cell, a motor neuron innervating both dorsal and ventral longitudinal muscles. The sensory input for the reflex was provided primarily by the T (touch) and P (pressure) types of identified mechanosensory neuron. The S cell network, a set of electrically-coupled interneurons which makes up a 'fast conducting pathway' in the leech nerve cord, was active during shortening and accounted for the shortest-latency excitation of the L cells. Other, parallel, interneuronal pathways contributed to shortening as well. The whole-body shortening reflex was shown to be distinct from the previously described local shortening behavior of the leech in its sensory threshold, motor pattern, and (at least partially) in its interneuronal basis.

Animals↗
PubMed1994

Modulation of swimming behavior in the medicinal leech. III. Control of cellular properties in motor neurons by serotonin.

Expression of swimming in the medicinal leech (Hirudo medicinalis) is modulated by serotonin, a naturally occurring neurohormone. Exogenous application of serotonin engenders 'spontaneous' swimming activity in nerve-cord preparations. We examined whether this activity is due to enhanced participation of swim motor neurons (MNs) in generating the swimming rhythm. We found that depolarizing current injections into MNs during fictive swimming are more effective in shifting cycle phase in nerve cords following serotonin exposure. In such preparations, the dynamics of membrane potential excursions following current injection into neuronal somata are substantially altered. We observed: 1) a delayed outward rectification ('relaxation') during depolarizing current injection, most marked in inhibitory MNs; and 2) in excitor MNs, an enhancement of postinhibitory rebound (PIR) and afterhyperpolarizing potentials (AHPs) following hyperpolarizing and depolarizing current pulses, respectively. In contrast, we found little alteration in MN properties in leech nerve cords depleted of amines. We propose that enhanced expression of swimming activity in leeches exposed to elevated serotonin is due, partly, to enhancement of relaxation, PIR and AHP in MNs. We believe that as a consequence of alterations in cellular properties and synaptic interactions (subsequent paper) by serotonin, MNs are reconfigured to more effectively participate in generating and expressing the leech swimming rhythm.

Animals↗
PubMed1995

Parallel pathways coordinate crawling in the medicinal leech, Hirudo medicinalis.

Changes in the behavior of crawling leeches were investigated after various kinds of manipulations, including selective transection or inactivation of body parts, as well as partial or complete transection of the central nerve cord, using a frame-by-frame analysis of video tapes of the crawling animals. From these studies, we found that: 1. Leeches made rhythmic crawling cycles even after their suckers were prevented from contacting the substrate by covering them over with glue. Hence, engagement and disengagement of the suckers are not necessary links in the crawling cycle. 2. Cutting the small, medial connective (Faivre's nerve) had no influence on crawling, but contraction during the whole-body shortening reflex was interrupted. Thus two behaviors which use the same motor output (i.e., whole-body shortening and the contraction phase of crawling) are mediated by two different pathways. 3. Cutting all the connectives between two ganglia in the middle of the leech resulted in a loss of coordination between the parts of the animal on either side of the cut. Therefore, temporally coordinated sucker activity must be mediated through these connectives. 4. Pieces of leech bodies produced by complete transection produced rhythmic crawling cycles as long as the pieces included the head or tail plus 2-4 adjacent midbody segments. In all cases, the crawling movements progressed without delays as the movements reached the cut ends. Pieces of animals that included only midbody segments did not produce crawling movements. 5. These results can be explained by a model composed of intersegmental pathways for both elongation and contraction, circuits in the head and tail brains that switch between elongation and contraction, and both ascending and descending inhibitory influences that determine when the cycle switches from elongation to contraction and back again.

Animals↗
PubMed1995

Intracellular chloride activity of leech neurones and glial cells in physiological, low chloride saline.

Leech blood apparently contains considerably less chloride than generally used in physiological experiments. Instead of 85-130 mM Cl- used in experimental salines, leech blood contains around 40 mM Cl- and up to 45 mM organic anions, in particular malate. We have reinvestigated the distribution of Cl- across the cell membrane of identified glial cells and neurones in the central nervous system of the leech Hirudo medicinalis L., using double-barrelled Cl(-)- and pH-selective microelectrodes, in a conventional leech saline, and in a saline with a low Cl- concentration (40 mM), containing 40 mM malate. The interference of anions other than Cl- to the response of the ion-selective microelectrodes was estimated in Cl(-)-free salines (Cl- replaced by malate and/or gluconate). The results show that the absolute intracellular Cl- activities (aCli) in glial cells and neurones, but not the electrochemical gradients of Cl- across the glial and the neuronal cell membranes, are altered in the low Cl-, malate-based saline. In Retzius neurones, aCli is lower than expected from electrochemical equilibrium, while in pressure neurones and in neuropil glial cells, aCli is distributed close to its equilibrium in both salines, respectively. The steady-state intracellular pH values in the glial cells and Retzius neurones are little affected (< or = 0.1 pH units) in the low Cl-, malate-based saline.

Animals↗
PubMed1986

Chemosensory stimuli in feeding behavior of the leech Hirudo medicinalis.

The involvement of chemotherapy stimuli in the feeding behavior of the blood-sucking leech Hirudo medicinalis was investigated using a behavioral feeding test in which test solutions were encased in a highly permeable membrane and presented to the leech. Whole human blood or plasma at ambient temperature elicited the complete sequence of feeding behavior: probing, attachment, biting and ingestion. Spring water, 300 mM sucrose, or dialyzed plasma did not elicit any of these responses. Spring water warmed to 38 degrees C elicited probing and transient attachment but not ingestion. Thus, appropriate chemical stimuli were necessary for complete feeding behavior. A chemically defined artificial blood mix, containing the major components of low molecular weight found in blood, elicited all aspects of leech feeding behavior. Eliminating either NaCl or arginine from the mix resulted in complete loss of effectiveness. Moreover, a solution containing only NaCl (150 mM) and arginine (90 microM) was also an effective feeding stimulus. Thus, appropriate chemical stimuli are sufficient for complete feeding behavior. Neither NaCl nor arginine alone induced feeding although NaCl alone elicited probing. Sensory detection of blood was localized to a region of the dorsal lip that contains structures composed of ciliated, bipolar neurons, which are likely candidates as chemoreceptors. Surgical ablation of this region of the skin resulted in complete loss of ability to alert to, orient toward and ingest blood, while sham-operated controls fed normally. Substitution with other ions revealed specificity, with respect to both the cation and the anion, in the response to NaCl. Of the inorganic and organic cations tested, only Li+ substituted effectively for Na+. Of the inorganic and organic anions tested, only Br- was as effective as Cl-. Thus, the requirement for NaCl in leech feeding represents more than simply an ionic strength requirement or a requirement for Na+ ions and bears similarities to the chemosensory detection of NaCl in other species. Substitution with other amino acids and analogues for arginine revealed marked specificity in the feeding response to this compound as well. D-arginine at concentrations of up to 1000-fold greater than the effective threshold for L-arginine did not elicit ingestion, nor did other common L-amino acids, including the other basic amino acids histidine and lysine. Of the arginine analogues tested, only homoarginine and canavanine (in which all three functional groups of arginine are unchanged) were effective feeding stimulants.

Animals↗
PubMed1993

Studies on the host specificity of the medicinal blood leech Hirudo medicinalis L.

For the identification of host species of blood-sucking parasites, the suitability of disc-electrophoresis of the stomach contents was tested. Mammalian blood in the stomach of the medicinal blood leech Hirudo medicinalis gave satisfactory results. In the case of mixed blood samples from H. medicinalis, the identification of the host according to the electrophoretic patterns of the stomach contents failed as compared with an immunological method such as the Ouchterlony test. Medicinal blood leeches (H. medicinalis) collected in Istria Croatia, or bought in a pharmacy contained blood from cattle, horses, or frogs in their stomachs. Specimens of H. medicinalis from Lake Neusiedl or from the Seewinkel Austria, had sucked blood from mallards or frogs. Blood of cattle, mallards, and frogs was found in the stomachs of H. medicinalis coming from the National Park Kiskunsag Hungary. For the first time, horses were established as hosts for free-living specimens of H. medicinalis. A comparison of the weights of H. medicinalis bought in a pharmacy revealed that specimens containing frog blood in their stomachs weighed significantly less than those containing horse blood. These results confirmed the reports from Ssynewa (1944) concerning the breeding experiments. Probably, there is a change in hosts from the frog to warm-blooded animals during the life cycle of H. medicinalis. There were also significant differences in the weights of leeches as revealed by a comparison of the population from the Neusiedlersee with the leeches bought in the pharmacy.

Animals↗