Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “LEECHES”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 415 records · Page 23Linked to original sources
PubMed1975

Axonal numbers and sizes in the connectives and peripheral nerves of the leech.

The present study is an electron microscopic analysis of the numbers and sizes of axons in the connectives and nerves of the medicinal leech. In either the right or left connectives for ganglia 14-18, there are approximately 2860 (+/- 294 S.D.) axons. Ninety-seven percent of these axons are less than one micron in diameter. The median connective, Faivre's nerve, contains 97 (+/- 3 S.D.) axons, and 94% of these fibers are smaller than one micron. In the peripheral nerve roots for ganglia 14-18, there are approximately 2351 (+/- 311 S.D.) axons. Ninety-eight percent of the axons in the nerves are less than one micron in diameter. Thus, there are approximately 20,000 axons associated with each of the segmental ganglia 14-18 in the leech, and the vast majority of these fibers are less than one micron in diameter.

Animals↗
PubMed1980

Number and distribution of neurons in leech segmental ganglia.

The number of neurons and their distribution were determined for specific segmental ganglia from the nerve cord of four different species of leech. Quantitative data were obtained by using computer-aided techniques for the analysis of nerve structure from serially sectioned or whole-mounted tissue. The species studied were Hirudo medicinalis, Macrobdella decora, Haemopis marmorata (family Hirudinidae), and Haementeria ghilianii (family Glossophoniidae). Two sets of ganglia were studied in each species: middle ganglia (9, 10, and 11) and sex ganglia (5 and 6). The middle ganglia, as well as the rest of the 21 segmental ganglia, except 5 and 6, are thought to be quite similar. The sex ganglia are associated with the sexual organs and appear to have more neurons. The data reported here indicate that: a) the number of neurons in a specified ganglion varies by one to two percent from animal to animal of a given species; b) the middle ganglia of a particular leech each have approximately the same number of neurons, with a variation also within two percent; c) the middle ganglia of Hirudo, Macrobdella, and Haemopis have nearly the same number of neurons (about 400), but those of Haementeria have some 20 fewer (about 380); d) the sex ganglia of Hirudo, Macrobdella, and Haemopis have a few hundred more neurons than their middle ganglia, with the exact number varying according to the species, but the sex ganglia in Haementeria have only about 20 more neurons than their middle ganglia; e) the distribution of neuronal somata among glial packets is not symmetric about the midsaggital plane of the animal, and the number of somata in each packet is variable; and f) the geometry of the glial packets is generally invariant, but occasionally packets are found in abnormal positions.

Animals↗
PubMed1984

Distribution and morphology of nociceptive cells in the CNS of three species of leeches.

The present study describes the segmental variation in the distribution and morphology of nociceptive neurons (N cells) in the central nervous system of the leech. N cells of midbody ganglia can be segregated into lateral and medial types. We show that monoclonal antibodies specific for N cells can distinguish between the two populations. The monoclonal antibodies were used to map the complete distribution of the cells along the nervous cord. There are two pairs of the medial and lateral nociceptive neurons in the midbody ganglia, one pair of the medial type in the sex ganglia (5 and 6), and a pair of the lateral type in ganglia 20 and 21. The caudal brain is without nociceptive neurons. This distribution was confirmed by electrophysiological means. The morphology of N cells in different parts of the nervous system was investigated by intracellular horseradish peroxidase (HRP) injections. In the terminal segmental ganglia the N cells showed extensive arborizations in the head and tail brains and, contrary to N cells in the midbody ganglia, their arborizations spanned more than three segments. N cells are absent in the tail brain, but the N cells of ganglia 20 and 21 were shown to innervate the entire caudal region. The basic morphology of all N-cell homologues was found to be very similar for three leech species. In the sex ganglia the pair of N-cell homologues were examined in Haemopis, Hirudo, and Macrobdella. The results showed a progressive modification in the three species of the cell's morphology, peripheral projections, and physiological responses, possibly correlated with the evolution and complexity of the sexual organs. HRP injections and monoclonal antibody staining revealed that a common feature of N-cell homologues is the presence of processes that tightly surround the cell soma of other cells. This suggests that N cells may have other functional properties in addition to being primary sensory neurons.

Animals↗
PubMed1985

Evidence for proctolin-like substances in the central nervous system of the leech Hirudo medicinalis.

The distribution of proctolin-like immunoreactive (PLI) cells was mapped in the central nervous system of the leech Hirudo medicinalis. In segmental ganglia, PLI cells can be divided into two groups: cells that stain repeatedly in every successive ganglion, and cells that stain only in specific segmental ganglia. The number of PLI cells, therefore, ranged from eight to 20 cells per ganglion. One bilateral pair of PLI cells (cells PLI-1) was further characterized morphologically by Lucifer yellow and horseradish peroxidase cell injections. Cell PLI-1 conforms in soma position, morphology, and physiological properties with cell 101, which has been previously classified as an inhibitory motoneuron to the flattener muscles. A locust bioassay (O'Shea and Adams, Science 213:567-569, 1981) was used to detect the presence of proctolin-like bioactivity. Extracts of leech ganglia when applied to the extensor tibialis muscle of the locust leg induced a proctolin-like response similar to the responses induced by proctolin standards. This work extends the finding of proctolin-like substances to the annelid phylum.

Animals↗
PubMed1987

Serotonin storage and uptake by identified neurons in the leech Haementeria ghilianii.

Characterization of serotonin-containing neurons in the glossiphoniid leech Haementeria ghilianii was undertaken to provide a reference for developmental studies of their differentiation and for comparative studies of their distribution and function. Five types of serotonin-containing neurons were identified with an antiserum against serotonin and by radioenzymatic assay of individual isolated somata. They contain high concentrations of serotonin (in some cases exceeding saturation in aqueous solution) and their serotonin content increases with growth of the animal. Each type is capable of taking serotonin up from the extracellular fluid, as demonstrated autoradiographically. They exhibit segment-specific, and on comparison with hirudinid leeches, species-specific, differences in distribution, morphology, and the expression of serotonin metabolism.

Animals↗
PubMed1993

Multimorphic growth cones in the embryonic medicinal leech: relationship between shape changes and outgrowth transitions.

Comparative studies of growth cone morphology may provide insight into the mechanisms underlying motility and navigation in vivo. Here we analyzed the morphology of a unique set of growth cones in the embryonic medicinal leech, Hirudo medicinalis. The comb or C-cell is a transient cell found as a bilateral pair in each midbody segment. Early in development, from embryonic day (E)7 to E11, each C-cell adds and orients about 70 parallel growth cones that remain relatively nonmotile until E12 when rapid process outgrowth is initiated. Individual C-cells from E10 to E14 were injected with Lucifer yellow and growth cones were traced with a camera lucida. Growth cone morphology was quantified from the drawings. Lamellar regions increased in area with age and change in extension rate. Young, relatively nonmotile growth cones had numerous short filopodia in many orientations, while at highly motile stages filopodial number decreased, length increased, and orientation became more restricted in the direction of outgrowth. Thus, while filopodia were distributed symmetrically, such that the average filopodial angle was predictive of the direction of outgrowth at all stages, younger (relatively nonmotile) growth cones project more filopodia in many directions than do older more motile growth cones. These results suggest that: (1) alterations in morphology may reflect developmentally regulated changes in extension and the local environment, (2) these growth cones maintain a large area for environmental sampling as they increase extension rate, even as filopodia become more restricted in orientation, and (3) C-cell growth cones might progressively alter their affinity for local cellular cues as they initiate rapid and directed outgrowth. The C-cell of embryonic leech may provide a relatively simple system in which to test these ideas experimentally.

Animals↗
PubMed2002

Characterization of a synaptiform transmission between a neuron and a glial cell in the leech central nervous system.

The cross-talk between neurons and glial cells is receiving increased attention because of its potential role in information processing in nervous systems. Stimulation of a single identifiable neuron, the neurosecretory Leydig interneuron in segmental ganglia of the leech Hirudo medicinalis, which modulates specific behaviors in the leech, evokes membrane hyperpolarization directly in the giant glial cell (Schmidt and Deitmer. Eur J Neurosci 11:3125-3133, 1999). We have studied the neuron-to-glia signal transmission in the voltage-clamped giant glial cell to determine whether this interaction exhibits properties of a chemical synapse. The glial response had a mean latency of 4.9 s and was dependent on the action potential frequency; the glial cell responded to as few as five Leydig neuron action potentials in 50% of the trials. The glial current was sustained for minutes during repetitive Leydig neuron activity without any sign of desensitization. The current was sensitive to tetraethylammonium, and its reversal potential of -78 mV shifted with the external K+ concentration. The glial response increased with the duration of the neuronal action potentials and was sensitive to the external Ca2+/Mg2+ concentration ratio. The results suggest that Leydig neuron activity leads to a Ca2+-dependent release of transmitter from the neuronal dendrites, evoking an K+ outward current in the giant glial cell, implying a synapse-like transmission between a neuron and a glial cell.

Action Potentials↗
PubMed1989

Glutamate and kainate increase intracellular sodium activity in leech neuropile glial cells.

Na+-selective, double-barrelled microelectrodes were used to measure intracellular Na+ activity (aiNa) and membrane potential (Em) in neuropile glial cells of isolated segmental ganglia in the leech Hirudo medicinalis. Bath application of glutamate (10(-3) M) resulted in membrane depolarizations of about 5 mV and a concomitant increase of aiNa by between 2 and 10 mM. Kainate (10(-4) M) elicited depolarizations of up to 40 mV amplitude followed by a prominent after hyperpolarization. During kainate, aiNa increased by 7 to 25 mM. In contrast to glutamate, an initial decrease of aiNa was detected during the action of kainate. N-methyl-D-aspartate (NMDA, 10(-5)-10(-3) M) had no effect of Em and aiNa. The results indicate that leech glial cells have a kainate-preferring non-NMDA glutamate receptor.

Animals↗
PubMed1989

Electrophysiological characterization of a nicotinic acetylcholine receptor on leech neuropile glial cells.

Ion-selective double-barrelled microelectrodes were used to measure the activities of intracellular K+, Na+, Cl-, and H+ (aiK, aiNa, aiCl, pHi) and membrane potential (Em) in neuropile glial cells as well as extracellular K+ activity (aeK) in the neuropile of the leech, Hirudo medicinalis, during bath application of carbachol. As measured with conventional single-barrelled microelectrodes, acetylcholine (ACh), nicotine, carbachol, tetramethylammonium (TMA), and choline elicited concentration-dependent (10(-6)-5 X 10(-3) M) transient membrane depolarizations of up to 60 mV amplitude whereas muscarine (10(-6)-10(-3) M) did not affect Em. alpha-Bungarotoxin (10(-7) M), decamethonium (10(-5) M), d-tubocurarine (5 X 10(-5) M), and strychnine (5 X 10(-5) M) blocked the carbachol depolarization by about 90%. Atropine (5 X 10(-5) M) blocked the response by about 75%, whereas hexamethonium was only effective at millimolar concentrations. Average baseline levels of aeK in the neuropile and of aiK, aiNa, and aiCl in the neuropile glial cells were about 3, 70, 10, and 7 mM, respectively. During the carbachol depolarization aeK and aiNa transiently increased, whereas aiK decreased. In contrast, a rise of aiK and a fall of aiNa were observed during glial depolarizations in solutions with elevated K+ concentration. aiCl increased during both the carbachol- and the K+-induced depolarization. During carbachol, pHi transiently fell by about 0.2 units from its average baseline level of 6.9, whereas an alkalinization of small amplitude was observed in high-K+ solutions. Bath-applied choline, TMA, and decamethonium rapidly accumulated in the neuropile glial cells as intracellularly monitored with double-barrelled microelectrodes filled with Corning K+ exchanger resin, which is highly selective for these agents. The results suggest that leech neuropile glial cells have a nicotinic ACh receptor coupled to a cation channel. It is hypothesized that this channel might also be permeable to choline, TMA, and decamethonium.

Animals↗
PubMed2005

Structure of the germinal vesicle during oogenesis in leech Glossiphonia heteroclita (Annelida, Hirudinea, Rhynchobdellida).

Oogenesis in the glossiphoniid leech Glossiphonia heteroclita (Hirudinea, Rhynchobdellida) is nutrimental, i.e., the growing oocyte is supported by specialized germline cells, the nurse cells. The main function of the nurse cells is to provide oocytes with cell organelles and RNAs (mainly rRNA). However, in studied leech species, irrespective of the nutrimental mode of oogenesis, the germinal vesicle (GV = oocyte nucleus) seems to be very active in rRNA production. As shown in the present study, during early previtellogenesis in the GV the meiotic chromosomes and prominent primary nucleoli occur. In late previtellogenesis the chromosomes condense and occupy a limited space of nucleoplasm in close vicinity to primary nucleolus, forming a karyosome. At the onset of vitellogenesis several prominent extrachromosomal DNA bodies appear in close association with the karyosome. At the same time, the primary nucleolus is no longer visible in the GV. As vitellogenesis proceeds the extrachromosomal DNA bodies undergo fragmentation and numerous spherical, RNA- and AgNOR-positive inclusions occur in the nucleoplasm. They are regarded as multiple nucleoli. Finally, in late oogenesis numerous accessory nuclei are formed in close proximity to the nuclear envelope. They usually contain one dense body, morphologically similar to multiple nucleoli. The amplification of rDNA genes, the occurrence of extrachromosomal DNA bodies, as well as the presence of multiple nucleoli and accessory nuclei are described for the first time in the phylum Annelida.

Animals↗
PubMed2007

Structure of the vector tissue in piscicolid leeches (Annelida, Hirudinea, Rhynchobdellida, Piscicolidae).

Hypodermic insemination occurs in piscicolid leeches (Hirudinea, Rhynchobdellida, Piscicolidae). The spermatophore is implanted in a specialized region of the leech body, the copulatory area. Just beneath the copulatory area, there is a specialized connective tissue (vector tissue) that is considered to guide the sperm toward the ovaries. In this study, we show that the vector tissue in the four species of the genus Piscicola is composed of a mass of cells located directly beneath the copulatory area, and two thin strands extend toward the ovaries. The ultrastructure of the vector tissue has been described for the first time. Four cell types were identified, constructing the vector tissue. The envelope of this tissue is made up of extracellular fibrous matrix and two types of cells: vesicular and flat envelope cells, which are embedded within the matrix. The rest of the tissue is formed of granular and plasmatic cells. Both of these last cell types have prominent cytoplasmic projections, filled with a filamentous material. However, only granular cells have numerous small electron-dense granules in their cytoplasm. The vector tissue was described prior, during and following copulation. Sperm passes within free spaces between the granular and plasmatic cells. Characteristic vector tissue cells also occur within the ovary wall and inside the ovary lumen. This supports earlier data, which postulated that the vector tissue appears to be an outgrowth of the ovary wall.

Animals↗
PubMed1987

Morphology of chemosensory organs required for feeding in the leech Hirudo medicinalis.

Sensilla that line the upper edge of the lip in the leech Hirudo medicinalis and that contain chemoreceptors required for feeding were examined in the scanning and transmission electron microscopes. The sensilla include two size-classes of ciliated button-like mounds--one about 35 microns in diameter and another about 10 microns in diameter. The larger sensilla are at the center of unpigmented patches of skin which are visible in the light microscope, while the smaller sensilla have not been previously described as distinct structures. Electron microscopy, though not light microscopy, shows that the lip sensilla differ markedly from the segmental sensilla of the leech, which have been shown to mediate mechanoreception and photoreception. In particular, the chemosensory lip sensilla contain multiciliated cells with cilia of a uniform length, whereas the segmental sensilla contain uniciliated cells with long, whip-like cilia, as well as multiciliated cells with short, stiff cilia. Thus, the two types of sensilla differ morphologically as well as functionally. In addition to the ciliated sensilla along the upper lip, structures consisting of a short, club-like process surrounded by granular material were observed inside the mouth. These structures may also be chemosensory organs.

Animals↗
PubMed1991

Mycoflora associated with five species of freshwater leeches.

Twenty-two species belonging to 11 genera of zoosporic fungi were collected from 10 freshwater sites and from five species of leeches on sesame and hemp seeds, maize grains and Pinus pollen grains as baits at 22 degrees C. Dictyuchus, Achlya, Pythium, Allomyces and Saprolegnia were the most common genera. The highest population of zoosporic fungi was estimated from Batracobdelloides tricarinata, the lowest from Barbronia assiuti. In addition fifty-three species and 1 variety representing 23 terrestrial fungal genera were identified on glucose (17 genera and 41 species) and cellulose (20 genera and 34 species + 1 variety) Czapek's Dox agar at 28 degrees C. The most common species on the two media were Aspergillus niger, A. fumigatus, A. flavus, Trichoderma harzianum, Gibberella fujikuroi and Penicillium chrysogenum. Some fungi were common only on cellulose agar medium such as Botryotrichum atrogriseum, Chaetomium bostrychodes, Dactylella alaskana and Drechslera halodes. Batracobdelloides tricarinata was the richest with terrestrial fungi whereas Salifa delicata was the poorest. Five leech species, namely Alboglossiphonia polypompholyx, Batracobdelloides tricarinata, Helobdella conifera, Barbronia assiuti and Salifa delicata were used during this investigation.

Animals↗
PubMed2003

Convergence of mechanosensory inputs onto neuromodulatory serotonergic neurons in the leech.

By the frequency-dependent release of serotonin, Retzius neurons in the leech modulate diverse behavioral responses of the animal. However, little is known about how their firing pattern is produced. Here we have analyzed the effects of mechanical stimulation of the skin and intracellular stimulation of mechanosensory neurons on the electrical activity of Retzius neurons. We recorded the electrical activity of neurons in ganglia attached to their corresponding skin segment by segmental nerve roots, or in isolated ganglia. Mechanosensory stimulation of the skin induced excitatory synaptic potentials (EPSPs) and action potentials in both Retzius neurons in a ganglion. The frequency and duration of responses depended on the strength and duration of the skin stimulation. Retzius cells responded after T and P cells, but before N cells, and their sustained responses correlated with the activity of P cells. Trains of five impulses at 10 Hz in every individual T, P, or N cell in isolated ganglia produced EPSPs and action potentials in Retzius neurons. Responses to T cell stimulation appeared after the first impulse. In contrast, the responses to P or N cell stimulation appeared after two or more presynaptic impulses and facilitated afterward. The polysynaptic nature of all the synaptic inputs was shown by blocking them with a high calcium/magnesium external solution. The rise time distribution of EPSPs produced by the different mechanosensory neurons suggested that several interneurons participate in this pathway. Our results suggest that sensory stimulation provides a mechanism for regulating serotonin-mediated modulation in the leech.

Action Potentials↗
PubMed2003

In vivo dynamics of CNS sensory arbor formation: a time-lapse study in the embryonic leech.

In the embryo of the leech Hirudo medicinalis, afferent projections of peripheral sensory neurons travel along common nerve tracts to the CNS, where they defasciculate, branch, and arborize into separate, modality-specific synaptic laminae. Previous studies have shown that this process requires, at least in part, the constitutive and then modality-specific glycosylations of tractin, a leech L1 homologue. We report here on the dynamics of growth of these projections as obtained by examining the morphology of single growing dye-filled sensory afferents as a function of time. Using 2-photon laser-scanning microscopy of the intact developing embryo, we obtained images of individual sensory projections at 3 to 30 min intervals, over several hours of growth, and at different stages of development. The time-lapse series of images revealed a highly dynamic and maturation-state-dependent pattern of growth. Upon entering the CNS, the growth cone-tipped primary axon sprouted numerous long filopodial processes, many of which appeared to undergo repeated cycles of extension and retraction. The growth cone was transformed into a sensory arbor through the formation of secondary branches that extended within the ganglionic neuropil along the anterior-posterior axis of the CNS. Numerous tertiary and quaternary processes grew from these branches and also displayed cycles of extension and retraction. The motility of these higher-order branches changed with age, with younger afferents displaying higher densities and greater motility than older, more mature sensory arbors. Finally, coincident with a reduction in higher order projections was the appearance of concavolar structures on the secondary processes. Rows of these indentations suggest the formation of presynaptic en-passant specializations accompanying the developmental onset of synapse formation.

Animals↗
PubMed2004

Leech filamin and Tractin: markers for muscle development and nerve formation.

The Lan3-14 and Laz10-1 monoclonal antibodies recognize a 400 kDa antigen that is specifically expressed by all muscle cells in leech. We show that the antigen recognized by both antibodies is a member of the filamin family of actin binding proteins. Leech filamin has two calponin homology domains and 35 filamin/ABP-repeat domains. In addition, we used the Laz10-1 antibody to characterize the development of the segmentally iterated dorsoventral flattener muscles. We demonstrate that the dorsoventral flattener muscle develops as three discrete bundles of myofibers and that CNS axons pioneering the DP nerve extend only along the middle bundle. Interestingly, the middle dorsoventral muscle anlage is associated with only non-neuronal expression of the L1-family cell adhesion molecule Tractin. This expression is transient and occurs at the precise developmental stages when DP nerve formation takes place. Based on these findings we propose that the middle dorsoventral muscle anlagen provides a substrate for early axonal outgrowth and nerve formation and that this function may be associated with differential expression of distinct cell adhesion molecules.

Animals↗
PubMed1976

A central inhibitory action of 5-hydroxytryptamine in the leech.

Previous studies indicated that 5-HT reduced the number of spontaneous excitatory junctional potentials (ejp's) that occurred in leech body wall muscle cells. The present study confirms these findings and shows that the ejp's arise from impulses in motoneuron L. This study further shows that 5-HT acts by hyperpolarizing and reducing the membrane resistance of neuron L, thus inhibiting the motoneuron and reducing the frequency of spontaneous ejp's on body wall muscle cells. These effects of 5-HT are not seen when the ganglion is bathed in a high magnesium solution, a finding that suggests that 5-HT does not act directly on the membrane of motoneuron L. This study demonstrates that 5-HT can have a central inhibitory effect on body wall muscle contractions. Previous studies provide evidence that 5-HT may act as a direct neuromuscular inhibitory transmitter and may also take part in peripheral presynaptic inhibition. Thus, if further studies confirm these suggestions, the well-known inhibitory effect of 5-HT on leech body wall muscle is a more complex process than was previously thought.

Action Potentials↗
PubMed1978

The caudal ganglion of the leech, with particular reference to homologues of segmental touch receptors.

The caudal ganglion of the leech, which provides sensory and motor innervation to the posterior sucker, represents the fusion of seven embryonic segmental ganglia. Although fused, each of the seven contributing ganglia ("subganglia") of the caudal ganglion can be distinguished morphologically and functionally. The roots from each subganglion carry the axons of mechanoreceptors homologous to "touch" cells found in the segmental ganglia and the subesophageal compound ganglion. The receptive fields supplied by the touch cells of the caudal ganglion are uniquely arranged and reveal the modified segmentation of the circular posterior sucker. Extensive overlap of sensory innervation occurs between adjacent segments of the sucker, beyond the overlap characteristic of the homologous cells of body segments. It thus appears that the touch receptors of the caudal ganglion are less restricted than receptors of the segmental ganglia with regard to their territories of innervation. The caudal ganglion has additional unique properties that establish it as a distinct integrative center of the leech CNS.

Animals↗