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At least 865 records · Page 48Linked to original sources
PubMed1986

Leydig cells: octopaminergic neurons in the leech.

Leydig cells are electrically-coupled neurons in the segmental ganglia of the leech. This study reports that they stain specifically with high concentrations (0.05 mg/ml) of the dye neutral red, and that they contain octopamine, as demonstrated by radioenzymatic assay. Individual cell bodies were pooled and found to contain 0.37 pmol octopamine/cell body, giving an approximate intracellular concentration of 7.75 mM. Leydig cell bodies contain approximately 75% of the octopamine content of a segmental ganglia. Intracellular injection of large amounts of Lucifer yellow, coupled with long diffusion times, revealed a previously-undescribed Leydig cell process. The probability that Leydig cells are octopaminergic neurosecretory cells is discussed.

Action Potentials↗
PubMed1987

Regeneration of afferent axons into discrete tracts within peripheral nerves in the leech.

We have analyzed the pathway followed by regenerating afferent axons in peripheral nerves of the leech Hirudo medicinalis by anterograde labeling with horseradish peroxidase. We show that axons are able to reestablish appropriate pathways following a lesion (crush) which greatly disrupts the organization of the nerves. Our results are consistent with a pathway selection mechanism involving axon surface markers which are retained on the distal stumps of crushed axons.

Animals↗
PubMed1987

A group of related surface glycoproteins distinguish sets and subsets of sensory afferents in the leech nervous system.

The distribution of 4 surface glycoproteins on axons of peripheral neurons was studied in the leech Hirudo medicinalis through monoclonal antibodies. All 4 glycoproteins have a similar molecular weight of 130 kDa. Immunohistochemical localization of these glycoproteins on tissue sections of nerves and neuropil reveals tracts of afferent axons organized as nested sets. Their distribution suggests a possible role for these molecules in mediating axon fasciculation.

Animals↗
PubMed1987

In situ patch-clamp recording of calcium-activated potassium channels from an identified leech neuron.

The paired anterior lateral giant cells of the leech Haementeria have only two active voltage gated ionic currents. We took advantage of this simple complement of ionic currents to investigate the single channel properties of this cells' calcium-activated K+ current (I(K,Ca) in situ. Cell-attached patch recordings showed large, bursting events with a conductance of approximately 90-100 pS which had extrapolated reversal potential consistent with K+ events. The channel open time distribution was well described by a single exponential process while the channel closed times were bi-exponentially distributed. The results show that the single channel properties of I(K,Ca) in annelids closely resemble those of similar currents described in vertebrates.

Animals↗
PubMed1988

The opiate receptor: a single 110 kDa recognition molecule appears to be conserved in Tetrahymena, leech, and rat.

We compared the molecular nature of the rat brain opiate receptor with that of the invertebrate leech, Haemopis marmorata, and the protozoan, Tetrahymena, in order to examine the issue of apparent receptor heterogeneity with respect to biochemical structure. A binding study with rat brain membrane verified that [125I]beta-endorphin [( 125I]beta E), a broad specificity ligand, is displaced by the antagonist (-)-naloxone, but not the inactive stereoisomer (+)-naloxone; agonists considered prototypes for mu, delta, and kappa opiate receptors all displayed stereospecific binding displacement. For SDS-PAGE analysis of the opiate receptor [125I]beta-endorphin was covalently affixed to its recognition molecule with the cross-linking reagent DSS. Primary reaction products occur at 110, 58/55, and 29 kDa. Cross-linking products of all 3 molecular weights are effectively reversed by opiate ligands, regardless of their mu, delta, or kappa specificities. Peptide mapping studies in SDS gels, using limited proteolysis, showed that the 110 kDa band can be digested into 58 and 29 kDa fragments and the 58 kDa band into a 29 kDa fragment. Additional smaller molecular weight fragments were generated from the 110, 58/55, and 29 kDa bands which shared their molecular weights. Two possible explanations for the extensive sequence homology between the three major cross-linking products are: (1) the 110 kDa species is the opiate receptor, and the 58 and 29 kDa species are proteolytic fragments; and (2) one of the lower molecular weight species is the opiate receptor, and adjacent receptors are aggregated into the 110 kDa complex through cross-linking.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Intracellular acidosis of identified leech neurones produced by substitution of external sodium.

The intracellular pH, pHi, of identified neurones of the central nervous system of the leech Hirudo medicinalis L. was measured with double-barrelled neutral carrier pH-sensitive microelectrodes. The active regulation of pHi of these neurons is due to amiloride-sensitive Na-H exchange and hence requires extracellular Na, Nao. We have measured a decrease of pHi following the removal of Nao. The rate of intracellular acidification in Na-free saline was similar to that in the presence of 2 mM amiloride suggesting that the acidification was due to inhibition of the Na-H exchange. The rate of intracellular acidification depended on the Na substitute chosen; it was 0.02 +/- 0.005 pH units/min (+/- S.D., n = 17) when Na was replaced by N-methyl-D-glucamine. A similar rate of acidification occurred with tris-hydroxymethyl-aminomethane (Tris) while the rate of acidification was higher with bis-2-hydroxymethyl-dimethylammonium (BDA, 0.033 +/- 0.016 pH units/min (+/- S.D., n = 7) and tetramethylammonium (TMA, 0.046 +/- 0.017 pH units/min (n = 3) as Na substitutes. A high, non-linear rate of intracellular acidification was observed, when Li, K or choline were used as Na substitute. The recovery of pHi from acidification upon readdition of Nao was fast, only when Li had replaced Na was the pHi recovery considerably delayed. In conclusion, in all experiments using different Na substitutes the removal of Nao caused a substantial intracellular acidification presumably due to inhibition of Na-H exchange. These changes in pHi might be relevant for results obtained by experiments in which Na-free solutions are used.

Animals↗
PubMed1989

Two types of K+ channels in excised patches of somatic membrane of the leech AP neuron.

The patch-clamp technique has been applied to the somatic membrane of the leech AP neurons. Ionic currents from single potassium channels were recorded in inside-out configuration. Two types of channels, sharing close values of conductance in symmetrical K+, were identified as distinct, according to their properties of rectification, Ca2+ sensitivity and voltage dependence. The channels designated as VCI exhibited an outward rectification and their gating was quite independent on changes of patch potential and of [Ca2+]i. The channels designated as VCD showed a linear I-V relationship and their activity was dependent on both the membrane potential and the intracellular [Ca2+].

Animals↗
PubMed1989

Localization of a leech inhibitory synapse by photo-ablation of individual dendrites.

An inhibitory motor neuron (cell 1) in the leech nervous system has a powerful inhibitory connection onto an excitatory motor neuron (cell 3) that is functionally important in behaviours such as swimming and local bending. The anatomical location of this connection was explored using focal ultraviolet irradiation of cell 3 dendrites filled with Lucifer yellow. Ablation of the main neurite of cell 3 in the middle of the ganglion eliminated 72% of the inhibitory postsynaptic potential (IPSP), showing that most of the synaptic contacts are in the dendritic field contralateral to the cell body. Ablation of a particular dendritic branch (d1), one of several that run anteriorly from the main neurite in the contralateral ganglion, eliminated 70% of the IPSP in some cases but only 4% in others. In these latter cases, subsequent ablation of a more distal dendrite (d2) eliminated from 41% to 83% of the IPSP. These findings suggest that the synapses onto cell 3 from cell 1 are primarily mediated by either one of these dendrites or the other, but not both. This synaptic specificity might be due to a developmental mechanism involving competition between dendrites for occupation of synaptic sites.

Action Potentials↗
PubMed1990

Stretch-activated cation channels with large unitary conductance in leech central neurons.

Stretch-activated cation channels were identified in the soma membrane of leech central neurons. These channels were almost silent under normal experimental conditions and were distinctly activated by application of negative pressure to the patch pipette. The channels exhibited a preferential selectivity for K+ and a slope conductance of about 200 pS, in symmetrical K+ solution. In cell-attached patches these cation channels were activated by cell swelling.

Animals↗
PubMed1990

Axotomy affects density but not properties of potassium leak channels, in the leech AP neurons.

Leech AP neurons react to axotomy by increasing excitability and resting potential of the cell body membrane. In a previous report we described single potassium channels contributing to the leak conductance in the soma membrane of AP cells. Here we compare both properties and density of single potassium leak channels in cell-free patches from normal and axotomized AP neurons. We show that properties such as single channel conductance, outward rectification, time constants of open and shut interval distributions and absence of inactivation do not significantly differ between normal and axotomized cells. On the other hand, we find that the number of channels per patch progressively increases with time after axotomy. We conclude that changes in density rather than alterations in properties of single channels can account for the increase in the resting potential, observed after axotomy.

Animals↗
PubMed1992

Preferential uptake of rubidium from extracellular space by glial cells compared to neurons in leech ganglia.

Glial cells play a significant role in maintaining extracellular space (ECS) potassium (K) by temporarily buffering or accumulating excess ECS K and then returning that K to neurons. Yet, little is known about the relative affinity of neurons or glial cells for K when both cells are simultaneously exposed to the same ECS K, in situ. Also, the process by which glial cells return K to neurons remains unknown. Therefore, electron probe X-ray microanalysis was used to measure rubidium (Rb) uptake, as a K tracer, into leech packet neurons and glial cells, and to measure the distribution of cell water content, K, Na and Cl. When ECS Rb was increased from 4 mM to 20 mM, there was a clear preferential Rb uptake into glial cells compared to neurons. At 4 mM extracellular Rb there was only a small difference between uptake velocity of neurons and glial cells (maximum mean uptake velocity at 4 mM Rb was 1.09 for glia, and 0.41 mmol Rb/kg dry wt/s for neurons), whereas at 20 mM extracellular Rb, glial uptake velocity was dramatically greater than of neurons (max. mean Rb uptake velocity for glia was 4.3 compared to 1.47 mmol Rb/kg dry wt/s for neurons). Glial Rb uptake velocity was enhanced by low temperature (max. mean Rb uptake velocity at 20 mM ECS Rb at 6 degrees C was 6.04 for glia compared to 0.78 mmol Rb/kg dry wt/s for neurons) and by substitution of Cl with isethionate (max. mean Rb uptake velocity was 10.6 for glia compared to 1.33 mmol Rb/kg dry wt/s for neurons).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Chloride-dependent pH regulation in connective glial cells of the leech nervous system.

We used double-barreled pH-sensitive microelectrodes to study the mechanisms by which the intracellular pH is regulated in the connective glial cells of the medicinal leech. The experiments indicate that a Cl(-)- and HCO3(-)-dependent mechanism mediates some recovery from intracellular alkalosis even in the absence of external Na+. This suggests the presence of Na(+)-independent Cl-/HCO3- exchange in the connective glial membrane. At alkaline pHi, this exchange most likely operates in the direction of net acid loading (i.e. HCO3- efflux).

Animals↗
PubMed1994

Protein phosphatase inhibitors prolong Ca(2+)-transients and divalent cation-dependent action potentials in leech Retzius cells.

Elevation of [K+]o for 30 s from 4 to 120 mM produced a fast and reversible depolarization and transient increase in [Ca2+]i in fura-2 loaded Retzius cells of the leech. The protein phosphatase inhibitor, okadaic acid, significantly slowed the return of [Ca2+]i toward baseline without affecting the amplitude of depolarization or rate of repolarization. Furthermore, okadaic acid and another phosphatase inhibitor, calyculin A, prolonged Ba(2+)-dependent action potentials. These results suggest that the kinetics of Ca2+ influx may be regulated by the activity of phosphatases PP-1 and/or PP-2A.

Action Potentials↗
PubMed1995

Effect of extracellular K+ on the intracellular free Ca2+ concentration in leech glial cells and Retzius neurones.

The effects of extracellular K+ on the intracellular free Ca2+ concentration ([Ca2+]i) of neuropile glial cells and Retzius neurones in intact segmental ganglia of the leech Hirudo medicinalis were investigated by using iontophoretically injected fura-2. In both cell types, an elevation of the extracellular K+ concentration ([K+]o) caused an increase in [Ca2+]i, which was blocked by Co2+, Ni2+ and menthol, whereas nicardipine, flunarizine, omega-conotoxin GVIA and omega-agatoxin IVA were ineffective. In Ca(2+)-free solution, the K(+)-induced [Ca2+]i increase was largely suppressed in neuropile glial cells and completely abolished in Retzius neurones. The results indicate that the K(+)-induced [Ca2+]i increase was mainly due to Ca2+ influx through voltage-dependent Ca2+ channels. The Ca2+ channels of the two cell types were activated at different membrane potentials but at the same [K+]o. In both cell types, the recovery from a K(+)-induced [Ca2+]i increase was unaltered in Na(+)-free solution, indicating that active Ca2+ transport across the plasma membrane is mediated by Na(+)-independent mechanisms.

Animals↗
PubMed1983

Avulsion of the scalp treated by microvascular repair: the use of leeches for post-operative decongestion.

A 28-year-old fitter and turner was scalped at work. The scalp was avulsed from the nuchal area to the eyebrows in one piece. It was successfully replanted by microvascular surgery. Leeches were used to decongest the flap when venous drainage appeared inadequate during the first week. Only a small part of the flap eventually failed to survive and normal hair growth returned in all other areas.

Accidents, Occupational↗
PubMed1983

Blastomere ablation and the developmental origin of identified monoamine-containing neurons in the leech.

Ablation of different identifiable blastomeres of the early embryo of the leech Helobdella triserialis was found to lead to the absence of different sets of segmentally iterated monoamine-containing neurons in subsequent development. Thus the ablation of one of the paired N ectoteloblasts leads to the absence of one member of each of the three bilateral pairs of serotonin-containing neurons (one of which is the Retzius cell) from each segmental ganglion. The ablation of one of the paired OP blastomeres (precursors of the paired O and P ectoteloblasts) leads to the absence of one member of each of the two bilateral pairs of lateral dopamine-containing neurons that lie in the body wall of each segment. And the ablation of one of the paired Q ectoteloblast leads to the absence of one member of the bilateral pair of medial dopamine-containing neurons that lie in the body wall of each segment. These results suggest that each of these sets of monoamine-containing neurons is derived from a particular blastomere. Upon ablation of that blastomere the set does not develop from any other source.

Animals↗
PubMed1984

Cell interactions in the developing epidermis of the leech Helobdella triserialis.

In embryonic development of the leech Helobdella triserialis, each of the four paired ectodermal teloblasts contributes some progeny to a characteristic dorsal or ventral territory of the epidermis. To ascertain the relative roles of cell lineage and cell interactions in generating the highly regular epidermal distribution pattern of the various ectodermal cell lines, a series of experiments was carried out in which the ablation of particular teloblasts was combined with the intracellular injection of cell lineage tracers. The results showed that, after the ablation of an OP proteloblast, or of an O, P, or Q teloblast, the epidermal progeny of the remaining ipsilateral and contralateral teloblasts spread into the territory normally occupied by the epidermal progeny of the ablated teloblast. In this spreading process, cells may cross the ventral midline but not the dorsal midline. The spread of epidermal progeny of one teloblast in response to ablation of another teloblast is contrasted with the failure of the neuronal progeny of one teloblast to replace any missing neural tissue. It appears, therefore, that all epidermal cell lines are of equal developmental potential, regardless of their teloblast of origin, with the eventual location of any epidermal cell in the body wall being governed by interactions between cells within the developing epidermis.

Animals↗