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At least 253 records · Page 14Linked to original sources
PubMed1983

3H-GABA uptake selectively labels identifiable neurons in the leech central nervous system.

Segmental ganglia of the leech ventral nerve cord synthesize the neurotransmitter gamma-aminobutyric acid (GABA) when incubated in the presence of the precursor glutamate, suggesting that there may be GABA-ergic neurons in the leech nerve cord. GABA-accumulating neurons of the two taxonomically distant leech species, Haementeria ghilianii and Hirudo medicinalis, have been labeled by taking advantage of their high-affinity uptake system for the neurotransmitter. Autoradiography of sectioned segmental ganglia previously exposed to 3H-GABA reveals a reproducible pattern of about thirty 3H-GABA-labeled neuronal cell bodies per ganglion. The majority of 3H-GABA-labeled neuronal cell bodies are bilaterally paired, although some apparently unpaired cell bodies also accumulate label. Neuronal processes were reproducibly labeled by GABA uptake and could be traced in the neuropil through commissures and fiber tracts into the segmental nerve roots and interganglionic connectives, respectively.

Animals↗
PubMed1984

Monoclonal antibody identifies a 63,000 dalton antigen found in all central neuronal cell bodies but in only a subset of axons in the leech.

The monoclonal antibody Lan3-8 binds to all the neuronal cell bodies in midbody, head, tail, and supraesophageal ganglia in the mud leech (Haemopis marmorata) and the medicinal leech (Hirudo medicinalis). In contrast to the general distribution of the antigen in cell bodies it is only found in a subset of axons, where electron microscopy suggests that it may be associated with a cytoskeletal filament system. Immunoblotting shows that the antibody binds to a 63,000 dalton band that is protease-sensitive. The same 63 kilodalton (kd)-antigen is found in all regions of the central nervous system, in proteins isolated from connectives (axons alone), and from hand-dissected identified cell types. The molecular weight and electron microscopic localization raised the possibility that this antigen is the core neurofilament protein, but the antigen does not comigrate with 67-kd intense coomassie blue band that binds another anti-intermediate filament antibody. The supraesophageal ganglia are known to have a different developmental or origin from the other structures in the leech central nervous system. Two-dimensional gel electrophoresis and silver staining show that, like the 63-kd antigen, many other proteins are very similar in these developmentally distinct neural structures.

Animals↗
PubMed1987

Identification of motor neurons that contain a FMRFamidelike peptide and the effects of FMRFamide on longitudinal muscle in the medicinal leech, Hirudo medicinalis.

Excitatory motor neurons in the leech are cholinergic. By using a combination of intracellular Lucifer yellow injection and indirect immunofluorescence, we localized FMRFamidelike immunoreactivity to a number of the motor neurons innervating longitudinal and dorsoventral muscle in the leech. All excitatory motor neurons innervating longitudinal muscle (cells 3, 4, 5, 6, 8, L, 106, 107, 108) were labeled with an antiserum to FMRFamide, while the inhibitory motor neurons innervating longitudinal muscle (cells, 1, 2, 7, 9, 102) were not. The excitatory motor neuron innervating medial dorsoventral muscle (cell 117) was labeled, while the excitatory motor neuron innervating lateral dorsoventral muscle (cell 109) was not. The inhibitory motor neuron innervating dorsoventral muscle (cell 101) was also labeled. Nerve terminals along dorsoventral muscle were also labeled with the antiserum. FMRFamide was bath applied to strips of longitudinal muscle while recording tension, and the muscle's response was compared to its response to the previously identified neuromuscular transmitter ACh. Brief applications of FMRFamide caused a contraction approximately one-tenth as large as that caused by an equimolar amount of ACh. The muscle response to FMRFamide was unaffected by curare. During extended exposures, FMRFamide caused a maintained contraction in longitudinal muscle without any apparent desensitization of the FMRFamide receptors and occasionally triggered an irregular myogenic rhythm. This extended exposure to FMRFamide caused a post-exposure potentiation of the longitudinal muscle's response to ACh that shorter applications of FMRFamide did not. Thus FMRFamide may act as a transmitter or modulator in cholinergic motor neurons innervating longitudinal and dorsoventral muscles in the leech.

Acetylcholine↗
PubMed1990

Expression of surface glycoproteins early in leech neural development.

Cell migration and axon growth during neural development rely upon cell-cell and cell-matrix interactions mediated by surface glycoproteins. The surface glycoprotein recognized on leech neurons by monoclonal antibody Lan3-2 has previously been implicated in the process of axon fasciculation during regeneration in adults. In adult leeches, Lan3-2 binds to a carbohydrate epitope of a 130 kD protein. The present study demonstrates that in embryos the antibody binds to the same carbohydrate epitope of glycoproteins with molecular weights of 130 kD and higher. As a first step in evaluating a possible role of the Lan3-2 glycoprotein or the cells that express it during neural development, we determined its distribution in the developing nervous system of the leech Hirudo medicinalis. In embryos, Lan3-2 epitope is expressed on fasciculated sensory afferents and it appears on the cell bodies before neurite outgrowth. The sensory fibers appear rostrally by embryonic day 10, less than halfway through development. Earlier, by 7 days of development at 20 degrees C, Lan3-2 binds to previously undocumented cell types: (1) cells appearing along the embryonic midline and (2) a cluster of cells located at the rostral edge of the germinal plate. These cells only transiently express this antigen and are present at critical left-right and rostrocaudal boundaries during a period of cell proliferation, movement, and migration that produces the nervous system. Thus the Lan3-2 surface glycoprotein or the cells expressing it are candidates for involvement in axon fasciculation, cell migration, and directed axonal growth.

Animals↗
PubMed1990

Segregation of afferent projections in the central nervous system of the leech Hirudo medicinalis.

Sensory axons originating in peripheral tissues converge onto each segmental ganglion in the central nervous system (CNS) of the leech, where they segregate into well-defined regions of the synaptic neuropil. Here we report on several aspects of the molecular and anatomical organizations of these afferent projections that bear upon the hypothesis that surface markers are involved in organizing these axons as they grow into the CNS. First, we show that the distribution of some surface markers in the adult is restricted to axons of peripheral origin and is not present on the neighboring axons of central neurons. Second, we demonstrate that the number of afferents increases postembryonically as the leech increases in size, suggesting that at least some of the cues employed by afferent axons to grow to appropriate central targets must be present throughout the life of the animal. We then show, using anterograde axonal tracing and immunohistochemistry, that there is both convergence and divergence of afferent axons into highly specific regions of the neuropil. Lastly, we examine the distribution of surface markers present on different subsets of afferents and show that axons having one type of marker segregate from those having the second type. Our results, considered together with previous observations in this system, provide new clues about the organization of afferent projections in the nervous system of the leech. They also suggest how a relatively small number of molecular markers might mediate fiber-fiber interactions to organize afferent axons as they grow into the CNS.

Afferent Pathways↗
PubMed1989

Glial processes, identified through their glial-specific 130 kD surface glycoprotein, are juxtaposed to sites of neurogenesis in the leech germinal plate.

Glial processes, bearing a unique 130 kD surface protein, are located at key sites of morphogenic movement and neuronal differentiation in the leech germinal plate. A midline glial fascicle resides at the primary axis of embryonic symmetry, alongside which teloblasts move as they generate their bandlets of stem cells. The n-bandlets straddle the midline glia and are known to produce most of the central neuroblasts. The midline glia then defasciculates as neuroblasts begin to aggregate into neuromeres. The defasciculated processes expand into these neuromeres, molding the future central neuropile. Neuroblasts will initiate primary axons toward the midline glia. As the neuromeres mature, midline glial process thin out to demarcate the orientation of the future connectives, which are the major longitudinal axon tracts along the midline. Next, segmental but still primordial glia appear in the neuromeres. Initially, they also project longitudinally, then transversely, demarcating the other two major axonal pathways--the central commissures and peripheral roots. Finally, macroglial processes proliferate as massive axon growth invades the central and peripheral nervous system. Thus, glial processes with different developmental histories accompany different aspects of leech neurogenesis. In other systems, glia have been shown to promote the differentiation and the guidance of neurons. It remains to be seen whether the glial-specific 130 kD protein is a receptor mediating these typical glial functions in the leech germinal plate.

Animals↗
PubMed1995

Ca2+ influx into leech neuropile glial cells mediated by nicotinic acetylcholine receptors.

The effect of cholinergic agonists and antagonists on the intracellular free Ca2+ concentration ([Ca2+]i) of leech neuropile glial cells was investigated by use of iontophoretically injected fura-2. In neuropile glial cells, cholinergic agonists induced a marked increase in [Ca2+]i that was inhibited by d-tubocurarine, alpha-bungarotoxin, strychnine, and atropine. The efficacy of the various agonists and antagonists indicates that the [Ca2+]i increase is mediated by the nicotinic acetylcholine (ACh) receptors that have been characterized previously in these cells by using electrophysiological methods. In the presence of high agonist concentrations, [Ca2+]i partly recovered, suggesting that the ACh receptors desensitize. The [Ca2+]i increase induced by cholinergic agonists was abolished in Ca2(+)-free solution, which indicates that it is caused by Ca2+ influx from the external medium. The agonist-induced [Ca2+]i increase was partly preserved in Na(+)-free solution, whereas the agonist-induced membrane depolarization was strongly suppressed. The agonist-induced [Ca2+]i increase was also partly preserved in the presence of 5 mM Ni2+, which almost abolished the K(+)-induced [Ca2+]i increase mediated by voltage-dependent Ca2+ channels. It is concluded that at low agonist concentrations the [Ca2+]i increase in leech neuropile glial cells is mediated exclusively by the ion channels associated with the nicotinic ACh receptors. At high agonist concentrations, voltage-dependent [Ca2+]i increase in leech neuropile glial cells is mediated exclusively by the ion channels associated with the nicotinic ACh receptors. At high agonist concentrations, voltage-dependent Ca2+ channels activated by the concomitant membrane depolarization also contribute to the agonist-induced Ca2+ influx.

Animals↗
PubMed1992

Osmotic and ionic regulation during hypoxia in the medicinal leech, Hirudo medicinalis L.

The concentrations of inorganic and organic ions and osmolality in the blood of the medicinal leech, Hirudo medicinalis, were determined during normoxia and hypercapnic and hypocapnic hypoxia. In normoxic animals, the blood sodium concentration was 124.5 +/- 4.2 mmol/l and the total cation concentration was 132.2 +/- 4.3 mEq/l (mean +/- S.D.). Major anionic compounds were chloride (40.8 +/- 1.6 mmol/l), bicarbonate (8.4 +/- 1.3 mmol/l), and organic anions (42.5 +/- 2.3 mEq/l). Among the latter, malate accounts for 30.4 +/- 2.2 mEq/l. The nature of the remaining anion fraction, which balances cation and anion concentrations in leech blood, remains unknown. Within 96 h of hypercapnic hypoxia, the amount of organic osmolytes in leech tissue increased from the control level of 56.6 +/- 9.1 to 158.3 +/- 19.5 mumol/g dry weight. An even higher amount of organic acids was accumulated within 96 h of hypocapnic hypoxia (218.0 +/- 53.7 mumol/g dry weight). A possible reason for this is that lactate, which is a major end-product of hypocapnic hypoxia, cannot be excreted to the external medium as easily as propionate. The accumulation of blood organic acids generating osmotic stress in the animals was compensated by an equimolar decrease in sodium and chloride ion concentrations. In hypercapnic animals these changes resulted in a constant osmotic concentration of the blood (200 mosmol/kg H2O) during the experimental period. Between 24 and 96 h of hypocapnic hypoxia, however, the increase in the osmotic gradient between animal and medium was correlated with further net water uptake and the obvious deterioration of the volume- and ion-regulatory mechanisms in these animals.

Animals↗
PubMed1988

The cleavage pattern in the leech Theromyzon tessulatum (Hirudinea, Glossiphoniidae).

In order to evaluate the differences in the cleavage patterns of the glossiphoniid leeches Glossiphonia complanata and Theromyzon tessulatum, previously studied by Müller ('32) and Schmidt ('17, '41), the cleavage of Theromyzon tessulatum was reexamined. For the period of the first 29 hours of development embryos were observed, photographed, and serially sectioned for light microscopy at each developmental stage. The exact cell lineage until completion of teloblast formation is reported. Besides some other not previously reported features, we show that the mesoteloblast precursor cell in the glossiphoniid leeches, as probably in most Annelida, is not the cell 3D, but cell 4d formed by an additional division of cell 3D. The results further indicate that all glossiphoniid leeches likely share a common cleavage pattern, and that major differences between Glossiphonia complanata and Theromyzon tessulatum do not exist. A comparison between the cleavage patterns of some Oligochaeta and Hirudinea is made, and plesiomorphic characters in the cleavage of a clitellate ancestor species and their deviations in present day species are discussed.

Animals↗
PubMed1976

Tryptophan metabolism and the occurrence of amino acids and serotonin in the leech (Hirudo medicinalis) nervous system.

The occurrence and distribution of serotonin (5-HT) and amino acids along the central nerve chain of the leech, Hirudo medicinalis, was analyzed using dansyl-chloride in order to obtain information on the functional roles of amines and amino acids. There was no statistical variation in the occurrence of most of the amino acids or serotonin in the different parts of the dorsal nerve chain of the leech. A variation in the serotonin content was found during the year with the highest level occurring in winter. Leech ganglia also accumulated 3H-tryptophan and metabolized part of it to form 5-HTP, 5-HT, and 5-HIAA. The results are discussed from the point of view of 5-HT being a transmitter substance.

5-Hydroxytryptophan↗
PubMed1987

The macroglial cells of the leech are molecularly heterogeneous.

Monoclonal antibodies derived from fusions employing either whole leech nerve cords or fractionated proteins (gel bands) bind to the macroglial cells of the nerve cord. Three different antibodies bind to either one, two, or three of the four macroglial cell types in the leech CNS, serving as markers and showing that these four cell types, which differ primarily by anatomical position, all differ molecularly as well. Conventional microscopy confirms the existence of a novel macroglial cell type first noted because it binds antibody. Western (immunoblot) blot analyses demonstrate a polypeptide antigen of 77 kD in the macroglial cells of the connectives and a 130-kD polypeptide antigen associated with the macroglial cells of the connectives, of the root nerves, and of the ganglionic neuropil. The extensive molecular heterogeneity of leech neurons demonstrated by monoclonal antibody techniques is shared by macroglia.

Animals↗
PubMed1993

The medical leech: an old treatment revisited.

The treatment modality of choice for venous insufficiency after free tissue transfer or replantation remains surgical repair. When this is not technically possible, the use of medical leeches is a useful adjunct to treatment. This paper reviews the history of the use of leeches in medicine, the anatomy and physiology of Hirudo medicinalis, the techniques of leech therapy, and the complications and contraindications.

Adult↗
PubMed1994

Successful treatment of venous congestion in free skin flaps using medical leeches.

Of 74 patients with extensive skin loss of the upper and lower extremities who were treated with free skin flaps, 20 patients presented with venous insufficiency within the immediate 6 to 12 hours following surgery. In 17 of these patients, the venous congestion after free tissue transfer was successfully treated with medical leeches. The remaining three skin flaps did not survive, despite leeching, as well as exploration and revision of the venous anastomoses. The results from this small number of patients with free skin tissue transfer are encouraging, suggesting that in the presence of venous congestion, the use of medicinal leeches is a desirable modality of treatment.

Adolescent↗
PubMed2005

Ca2+ influx into identified leech neurons induced by 5-hydroxytryptamine.

The role of 5-hydroxytryptamine (5-HT, serotonin) in the control of leech behavior is well established and has been analyzed extensively on the cellular level; however, hitherto little is known about the effect of 5-HT on the cytosolic free calcium concentration ([Ca(2+)](i)) in leech neurons. As [Ca(2+)](i) plays a pivotal role in numerous cellular processes, we investigated the effect of 5-HT on [Ca(2+)](i) (measured by Fura-2) in identified leech neurons under different experimental conditions, such as changed extracellular ion composition and blockade of excitatory synaptic transmission. In pressure (P), lateral nociceptive (N1), and Leydig neurons, 5-HT induced a [Ca(2+)](i) increase which was predominantly due to Ca(2+) influx since it was abolished in Ca(2+)-free solution. The 5-HT-induced Ca(2+) influx occurred only if the cells depolarized sufficiently, indicating that it was mediated by voltage-dependent Ca(2+) channels. In P and N1 neurons, the membrane depolarization was due to Na(+) influx through cation channels coupled to 5-HT receptors, whereby the dose-dependency suggests an involvement in excitatory synaptic transmission. In Leydig neurons, 5-HT receptor-coupled cation channels seem to be absent. In these cells, the membrane depolarization activating the voltage-dependent Ca(2+) channels was evoked by 5-HT-triggered excitatory glutamatergic input. In Retzius, anterior pagoda (AP), annulus erector (AE), and median nociceptive (N2) neurons, 5-HT had no effect on [Ca(2+)](i).

Animals↗
PubMed1986

Control of leech swimming activity by the cephalic ganglia.

We investigated the role played by the cephalic nervous system in the control of swimming activity in the leech, Hirudo medicinalis, by comparing swimming activity in isolated leech nerve cords that included the head ganglia (supra- and subesophageal ganglia) with swimming activity in nerve cords from which these ganglia were removed. We found that the presence of these cephalic ganglia had an inhibitory influence on the reliability with which stimulation of peripheral (DP) nerves and intracellular stimulation of swim-initiating neurons initiated and maintained swimming activity. In addition, swimming activity recorded from both oscillator and motor neurons in preparations that included head ganglia frequently exhibited irregular bursting patterns consisting of missed, weak, or sustained bursts. Removal of the two head ganglia as well as the first segmental ganglion eliminated this irregular activity pattern. We also identified a pair of rhythmically active interneurons, SRN1, in the subesophageal ganglion that, when depolarized, could reset the swimming rhythm. Thus the cephalic ganglia and first segmental ganglion of the leech nerve cord are capable of exerting a tonic inhibitory influence as well as a modulatory effect on swimming activity in the segmental nerve cord.

Action Potentials↗
PubMed1995

In situ hybridization reveals transient laminin B-chain expression by individual glial and muscle cells in embryonic leech central nervous system.

Laminin, which strongly stimulates axon outgrowth in vitro, appears transiently within the central nervous system (CNS) in embryos. After CNS injury, laminin reportedly reappears along axonal pathways only in animal species in which central axon regeneration is successful, including the leech Hirudo medicinalis. Although glia have been suspected of making CNS laminin, in adult leeches glia are not required for laminin synthesis and evidently microglia, not present in the early embryo, produce laminin. To determine which embryonic cells make laminin, a 1.2 kb DNA fragment of leech laminin B1 chain, with homology to Drosophila, human, and mouse B1 laminins and rat S laminin, was isolated using reverse-transcription and degenerate polymerase chain reaction (PCR) cloning. In situ hybridization revealed that laminin expression began before embryonic day 8, and by days 8 and 9 it was seen in paired CNS muscle cells. By late day 9, the two neuropil glial cells began to express laminin. Lucifer Yellow dye was injected intracellularly and muscle cells stimulated to contract, confirming the identities of muscle and glial cells. Packet glial cells began to express B1 laminin by embryonic day 12. By day 15, the cells of the perineurial sheath expressed B1 laminin, whereas it was no longer detectable in CNS muscle and glia. The results agree with published immunohistochemistry showing laminin within the CNS among growing axons by day 8, and only later in the perineurial sheath, by which time laminin disappears from within the CNS. Therefore, different cells synthesize laminin in the embryo and during repair in adults.

Amino Acid Sequence↗
PubMed1995

Formation and specification of neurons during the development of the leech central nervous system.

In the leech embryo, neurogenesis takes place within the context of a stereotyped cell lineage. The prospective germ layers are formed during the early cleavage divisions by the reorganization and segregation of circumscribed domains within the cytoplasm of the fertilized egg. The majority of central neurons arise from the ectoderm, and central neuroblasts are distributed throughout both the length and width of each ectodermal hemisegment. Much of the segmental ganglion arises from medial neuroblasts, but there are also lateral ectodermal neuroblasts and mesodermal neuroblasts that migrate into the nascent ganglion from peripheral sites of origin. Some of these migratory cells are committed to neurogenesis prior to reaching their central destination. In addition, the leech embryo exhibits a secondary phase of neurogenesis that is restricted to the two sex segment ganglia. Secondary neurogenesis requires that a mitogenic or trophic signal be conveyed from the peripherally located male sex organ to a particular set of centrally located neuroblasts, apparently via already differentiated central neurons that innervate the sex organ. The differential specification of neuronal phenotypes within the leech central nervous system occurs in multiple steps. Some aspects of a neuron's identity are already specified at the time of its terminal cell division and would seem to involve the lineal inheritance of developmental commitments made by one of the neuron's progenitors. This lineage-based identity can then be modified by interactions between the postmitotic neuron and other neurons or non-neuronal target cells encountered during its terminal differentiation.

Animals↗
PubMed1995

Repair of the central nervous system: lessons from lesions in leeches.

In contrast to the limited repair observed in the mammalian central nervous system (CNS), injured neurons in the leech reliably regenerate synapses and restore function with remarkable accuracy at the level of individual neurons. New and recent results reveal important roles for microglial cells and extracellular matrix components, including laminin, in repair. Tissue culture experiments have permitted isolation of neurons and manipulation of their environment, providing insights into the influence of substrate, electrical activity, and other cells, including microglia, on axon growth and synapse formation. The results account for distinctive features of successful repair in the adult leech, where axonal sprouting and target selection can be influenced by unequal competition between neurons. Differences between the formation of connections during embryonic development and repair in the adult include dissimilarities in the roles of glia and microglia in adults and embryos, suggesting that axon growth during regeneration in the CNS is not simply a recapitulation of processes observed during embryonic development. It may be possible in the future to improve mammalian CNS regeneration by recruiting cells whose counterparts in the leech have been identified as instrumental in repair.

Animals↗