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At least 1,243 records · Page 69Linked to original sources
PubMed1981

Light microscopic analysis of contacts between pairs of identified leech neurons with combined use of horseradish peroxidase and lucifer yellow.

Intracellular injections of horseradish peroxidase (HRP) and Lucifer Yellow (LY) were used to determine the locations of possible synaptic contacts between pairs of identified leech neurons. The pairs studied were ipsilateral touch sensory neurons (T cells), T cells plus the large longitudinal motoneuron (L cell), and T cells plus the annulus erector motoneuron (AE cell). The joint use of epi-fluorescence and transmitted light permitted the simultaneous observation of the processes of the HRP- and LY-filled cells. Our results indicate that, within the resolution of the light microscope, (a) over 40% of the varicosities of a T cell are in contact with those of another ipsilateral T cell, (b) both ipsilateral and contralateral T cells make numerous contacts with the two motoneurons studied, and (c) T cell-motoneuron contacts are distributed widely within the region where the cells overlap in the neuropil and occur on both major and minor processes of the motoneurons.

Animals↗
PubMedDate not supplied

[Redox reaction of flavin and pyridine nucleotides of Hirudo medicinalis leech nerve cells].

On different Retzius cell preparations (cell in the whole leech, in part of the animal and in isolated ganglionic chain) it has been demonstrated that the process of preparation itself affects redox levels of flavoproteins and pyridine nucleotides in the intact cell, changes their redox response to oxygen and alters the direction of redox reaction of pyridine nucleotide to 5 mM oxaloacetate. Redox levels of flavin and pyridine nucleotides in the cell were evaluated by the intensity of its fluorescense in violet and green parts of the spectrum.

Animals↗
PubMed1995

The leech homeobox gene Lox4 may determine segmental differentiation of identified neurons.

We cloned and characterized a new leech homeobox gene, Lox4, a homolog of the Drosophila genes Ultrabithorax and abdominal-A. Lox4 has a complex and dynamic pattern of expression within a series of segmentally homologous neurons. These include a pair of specialized motor neurons of one segmental ganglion, the rostral penile evertors (RPEs), and their segmental homologs in other midbody ganglia. During gangliogenesis, Lox4 was expressed within this series of neurons in three different temporal patterns: (1) it was never expressed in the RPE homologs of ganglia 1-3; (2) it was expressed in the RPEs during gangliogenesis, but was turned off when these neurons started to differentiate after gangliogenesis; and (3) it was expressed in the RPE homologs of segments 4-5 and 7-21 during gangliogenesis and the subsequent period of axonogenesis. We found that these neurons have three distinct peripheral axonal morphologies that correlate with the three temporal patterns of expression. Our results suggest that the homeobox gene Lox4 may determine neuronal identities within this series of segmental homologs.

Amino Acid Sequence↗
PubMed1995

[Effects of leech and ground beetle powder on hemorheology and blood lipid of ischemic stroke].

In order to improve blood supply for the brain, restore the functions of the cerebral cells and the limbs, and increas the curative rate, the leech (Hirudo nipponica and ground beetle Eupolyphage sinensis), powder (LGBP) to the patients according to the principle of promoting the blood circulation to remove the stasis was administered, and the clinical observation and experimental study was conducted. Its effects were compared with those of Western medicines. The results showed that after medication of LGBP, the blood flow of brain significantly increased, the hypoxia was improved, blood viscosity and blood lipid were lowered and thrombosis was inhibited in vitro or in vivo. No toxic side-effects caused by LGBP was found.

Adult↗
PubMed1995

Acetylcholine-induced retraction of an identified axon in the developing leech embryo.

At early stages of embryonic development of the glossiphoniid leech, Theromyzon rude, a branch, termed MAC, of the axon of the segmentally iterated Retzius neuron extends into the anterior interganglionic connective nerve. At later stages, this branch disappears again in about 30% of the Retzius neurons in the standard midbody segments and in about 75% of the Retzius neurons in the two reproductive midbody segments. The frequency of disappearance of the MAC branch increases to about 85% in all Retzius neurons upon exposure of the embryos to culture media containing 1 mM acetylcholine (ACh) and 10 microM physostigmine during a sensitive period of axon outgrowth. This disappearance represents a retraction of the MAC branch to its point of origin, while other axon branches of the Retzius neuron remained unaffected. In later development, the retracted (medial) MAC branch was replaced by a new (lateral) branch termed LAC. The observations were made using confocal microscopy of fixed embryos stained with anti-5-HT antibody and confirmed by Lucifer yellow injection of individual Retzius neurons. The specific retraction of a single axon branch might be attributable to the local presence of extracellular matrix molecules in the ganglionic neuropil, which is contacted only by the MAC axon branch and could render this branch susceptible to growth-regulating signals. Since Retzius axon morphology in standard segments of ACh-treated embryos resembled that of reproductive segments in untreated embryos, it appears possible that ACh treatment may have simulated a process that contributes to the segmental differentiation of the Retzius neuron.

Acetylcholine↗
PubMed1994

First North American record of the marine leech Notostomum laeve (Annelida: Hirudinea).

The Arctic marine leech Notostomum laeve is reported for the first time from North America. A single, small specimen was collected in April 1990 on the external surface of 1 of 30 Greenland halibut Reinhardtius hippoglossoides from Cumberland Sound, Baffin Island, Northwest Territories, Canada. Total length of the specimen including suckers is 41 mm; maximum body width is 1.8 mm. The species is easily identified by the unusual suckers. The caudal sucker is divided into 2 lateral halves that appear to close somewhat like a clam shell; the oral sucker is very thick and muscular with a row of small, hard teeth-like papillae around the outer margin. On the basis of this report from northern Canada, N. laeve probably has a circumpolar distribution in the Arctic Ocean.

Animals↗
PubMed1993

Developmental regulation of segment-specific cholinergic receptors on Retzius neurons in the medicinal leech.

Retzius (Rz) neurons in the midbody ganglia of medicinal leeches responded to ACh, applied to their somata, in a manner that depended upon the neuron's segmental location: Rz neurons in ganglia from midbody segments 5 and 6 [Rz(5,6)] hyperpolarized, whereas Rz neurons from all other segments [Rz(X)] depolarized. Midbody segments 5 and 6 are notable because they contain the male and female reproductive organs. Both types of Rz neurons responded to ACh in a complex way, but the initial phase of each response appeared to be nicotinic because nicotinic agonists evoked the responses and nicotinic antagonists blocked them. The reversal potentials of the responses and the effects of changing the internal and external Cl- concentration indicated that the hyperpolarizing response of Rz(5,6) neurons depended upon Cl- whereas the depolarizing response of Rz(X) neurons did not. The segmentally characteristic responses of Rz neurons arose during embryonic development. Removing the reproductive ducts [the peripheral targets of Rz(5,6)] early in embryogenesis caused the Rz(5,6) neurons to depolarize in response to ACh rather than to hyperpolarize. This result indicates that development of the characteristic response of Rz neurons to ACh is strongly influenced by interactions between the neurons and their appropriate target tissues.

Acetylcholine↗
PubMed1993

Role of substrate and calcium in neurite retraction of leech neurons following depolarization.

The aim of these experiments was to analyze how depolarization influences neurite outgrowth in leech neurons and what role the substrate and Ca2+ play in this response. Neurons in culture were exposed to 60 mM extracellular K+ for 30 min, which induced retraction of a subset of neurites growing on extracellular matrix substrate (ECM), a response comparable to that observed after electrical stimulation (Grumbacher-Reinert and Nicholls, 1992). After normal medium had been restored, the neurites continued to retract for about 1 hr to approximately 80% of the total starting neurite length. Retraction was reversible and regrowth began after the cells had been in normal medium for about 3 hr. Similar depolarization-induced neurite retraction was observed in both Retzius and anterior pagoda cells. Retraction was inhibited by raised extracellular Mg2+, suggesting a mechanism dependent on calcium. The effect of high K+ on neurite outgrowth was also influenced by the substrate on which the cells were plated. Cells plated on concanavalin A (ConA) did not retract but continued to extend processes during exposure to high K+. To understand the different behavior of cells grown on ECM and ConA, the morphology of growth cones was analyzed by scanning electron microscopy. The growth cones of cells grown on ECM and exposed to high K+ revealed retraction of lamellipodial and filopodial structures. On ConA, however, no differences were observed between growth cones of cells exposed to high K+ and those of control cells. These results demonstrate the importance of substrate molecules in the responses of growth cones to depolarization and therefore in the differentiation of neurons.

Analysis of Variance↗
PubMed1977

Effects of spin labeled acetylcholine analogs on cholinergic receptors of the leech.

The spin labeled acetylcholine analog, SL-2, which is a potent, non-stimulating muscarinic antagonist on the isolated frog heart, is a potent agonist a low concentrations (3x10-5 M) and an antagonist at slightly higher concentrations (4.5x10-5 M) on the mixed cholinergic receptors of the leech. Ion the other hand, the spin labeled acetylcholine analog, SL-1, possesses no agonist activity while it retains the antagonist activity of SL-2. Furthermore, the spin labeled analog, SL-3, which causes hyperpolarization and a decrease in action potential frequency, exhibits neither agonist nor antagonist activity.

Acetylcholine↗
PubMed1993

Isolation, sequence analysis, and cloning of haemadin. An anticoagulant peptide from the Indian leech.

A slow, tight-binding inhibitor of thrombin with an apparent molecular mass of about 5 kDa has been isolated from Haemadipsa sylvestris, an Indian leech of the family of Haemadipsidae. The inhibitory activity, called haemadin, is thrombin specific since it does not inhibit other proteases like trypsin, chymotrypsin, factor Xa, or plasmin. NH2-terminal amino acid sequence analysis (residues 1-45) does not reveal any homology to known serine protease inhibitors, including the thrombin-specific inhibitor hirudin. The haemadin cDNA cloned by polymerase chain reaction techniques codes for a polypeptide of 57 amino acid residues preceded by 20 residues of a signal peptide sequence. A synthetic gene coding for the mature haemadin was expressed in Escherichia coli. Recombinant haemadin displays a similar inhibition constant and specific activity as its natural counterpart. Although there is no obvious sequence identity between haemadin and hirudin, both proteins seem to share common mechanisms for thrombin inhibition.

Amino Acid Sequence↗
PubMed1996

Modulation of conduction block in leech mechanosensory neurons.

Conduction block is a mechanism of activity-dependent neuronal plasticity, but little is known about its possible neuromodulation. Extensive activity in leech touch (T), pressure (P), and nociceptive (N) mechanosensory neurons results in conduction block of their minor receptive fields. We have examined whether the duration of conduction block could be modulated by the serotonergic Retzius neurons or by application of serotonin (5-HT). Activation of one Retzius cell reduced the duration of conduction block in T and P cell posterior fields, but their anterior fields and N cell fields were unaffected. Perfusion with 5-HT had stronger effects, reducing the duration of conduction block in T, P, and lateral N cells in the posterior fields and either reducing or more often enhancing the expression of conduction block in anterior fields. The effects of 5-HT on posterior fields were blocked by the nonspecific 5-HT antagonist methysergide and were partly suppressed by the 5-HT2 antagonist ketanserin. To determine the site of 5-HT action, the central ganglion or peripheral skin was perfused independently. T and to a greater extent P cells showed a preferential sensitivity to application of 5-HT onto the central ganglion. Interestingly, medial N cells exhibited a progressive decrease in the duration of conduction block during repeated trials ("wind-up") that was unaffected by 5-HT. We conclude that secretion of 5-HT by the Retzius cells has a central modulatory effect on the duration of conduction block in T, P, and lateral N cells.

Animals↗
PubMed1977

A calcium reversible action of barbiturates on the leech Retzius cell.

The Na salts of phenobarbital, barbital, pentobarbital, secobarbital, methohexital and thiopental in concentrations of 1 to 5 mM all caused prolonged action potentials in leech Retzius cells. The prolongation was favored by low Ca and was reversible by elevation of Ca. Barbiturate-prolonged action potentials were not affected by 50 micronm tetrodotoxin or replacement of Cl by propionate, but they were dependent on external Na. Their amplitudes were increased by steady hyperpolarization and input resistance was reduced during them. They were of shorter duration when elicited at a rapid rate. They were sometimes shortened by intracellular iontophoresis of Ca and by use of the ionophore X537A, but technical factors complicated the interpretation of both kinds of experiments. The results are consistent with the hypothesis that the barbiturates used blocked a voltage-dependent inward Ca current which activates a K conductance necessary for normal repolarization.

Action Potentials↗
PubMed1996

Activation of intrinsic and synaptic currents in leech heart interneurons by realistic waveforms.

Leech heart interneurons were voltage-clamped with realistic waveforms to investigate the currents underlying the oscillation in the cells. By estimating the leak current parameters in regions in which there was little contamination by voltage-gated currents, it was possible to measure the Ca2+ current, the persistent Na+ current, Ip, and the hyperpolarization-activated inward current, Ih. The experiments verified a prediction of a computer model of HN cells that the shape of the typical waveform was such that the low-threshold Ca2+ currents were partially inactivated during a slow up-ramp to a plateau potential. A step within the same range of the membrane potential as the realistic waveform produced > 4 times as much Ca2+ current. In two-cell voltage-clamp experiments, the step produced 20 times more graded inhibition than the normal presynaptic waveform. When the presynaptic heart interneuron oscillated with spikes, the graded inhibition was larger. The difference may arise from integration of a slowly decaying component of the spike-mediated inhibition. The persistent Na+ current had a very low threshold. During the most hyperpolarized phase of the waveform, Ip deactivated to 50% of its maximum conductance. A substantial part of Ip, therefore, was effectively contributing to the leak current in the HN cells. The h-current increased for waveforms that had longer periods, whereas increasing the h-current in the model reduced the period. The h-current thus provides negative feedback to perturbations that alter the period of the oscillation.

Action Potentials↗
PubMed1996

Dextran backfill tracers combined with Lucifer yellow injections for neuroanatomic studies of the leech head ganglion.

Several neuronal tracing substances were applied to the cut ends of leech cephalic nerves and the resulting backfills into the subesophageal ganglion (sbEG) were mapped. A 12 h incubation in 3 kDa dextrans conjugated either to a fluorochrome or to biotin (subsequently tagged with peroxidase) was satisfactory. In separate experiments, possible targets of cephalic nerve afferents (R3 Retzius neurons) were injected with Lucifer Yellow (LY) to visualize their projections. Comparison of the LY-R3 Retzius neuron map with that of the dextran-backfilled D1 nerve revealed extensive overlap in the sbEG. Experiments were performed combining the two protocols, confirming this observation. Moreover, confocal microscopy placed D1 nerve processes in close proximity to R3 Retzius neuron processes, suggesting that they could make synaptic contact with one another in the sbEG. With modifications, this method could be used to identify such contacts using electron microscopy.

Animals↗
PubMedDate not supplied

[Alteration of the electrophysiologic characteristics of the neurons of the great pseudo-equine leech after increasing the intracellular concentration of sodium ions].

Changes of membrane potential (MP), amplitude of action potential (AAP) and continuence of AP (CAP) of identified neurons of leech Haemopis sanguisuga have been investigated at high intracellular Na+ concentration. It has been shown that a moderate increase of intracellular Na+ concentration leads to hyperpolarization of the membrane to 15 mV and a certain increase of AAP and CAP. A further increase of [Na+]in leads to a sharp decrease of AAP and small decrease of CAP. Possible mechanisms of the phenomena described are discussed.

Action Potentials↗
PubMed1997

A slow outward current activated by FMRFamide in heart interneurons of the medicinal leech.

The endogenous neuropeptide FMRFamide (Phe-Met-Arg-Phe-NH2) can accelerate the oscillation of reciprocally inhibitory pairs of interneurons that pace heartbeat in the medicinal leech. A model based on all available biophysical data of a two-cell heart interneuron oscillator provides a theoretical basis for understanding this modulation. Previously observed modulation of K+ currents by FMRFamide cannot account for this acceleratory effect in the model. This observation prompted the present reexamination of K+ currents in heart interneurons. We devised better methods for separation of the various components of K+ current and more accurately measured their activation and deactivation kinetics. Moreover, we demonstrated that FMRFamide activates a previously undetected K+ current (IKF), which has very slow activation and deactivation kinetics. Addition of physiologically measured amounts of IKF to the model two-cell oscillator can account for the acceleratory effect of FMRFamide.

Animals↗
PubMed1997

Tridegin, a novel peptidic inhibitor of factor XIIIa from the leech, Haementeria ghilianii, enhances fibrinolysis in vitro.

Tridegin is a potent inhibitor of factor XIIIa from the leech, Haementeria ghilianii, which inhibits protein cross-linking. It modifies plasmin-mediated fibrin degradation as shown by the absence of D-dimer and approximately halves the time for fibrinolysis. Plasma clots formed in the presence of Tridegin lyse more rapidly when either streptokinase, tissue plasminogen activator or hementin is added 2 h after clot formation. The effect of Tridegin is markedly increased if clots are formed from platelet-rich plasma. Platelet-rich plasma clots are lysed much more slowly by the fibrinolytic enzymes used and if Tridegin is present, the rate of lysis returns almost to that of platelet-free clots. These studies indicate the important role of platelets in conferring resistance to commonly used fibrinolytic enzymes and suggest that protein cross-linking is an important step in this effect. Moreover they indicate that Tridegin, a small polypeptide, may have potential as an adjunct to thrombolytic therapy.

Animals↗