Functional rearrangements of the ultrastructure of the giant (Retzius') neuron of the medicinal leech and possible role of Ca++ ions in these processes

1985 ◽  
Vol 15 (4) ◽  
pp. 337-342
Author(s):  
V. F. Mashanskii ◽  
I. S. Bazanova ◽  
V. V. Kazanskii ◽  
O. S. Merkulova
Keyword(s):  
Medicinal Leech ◽  
Retzius Neuron ◽  
Ca Ions

Studies on the Pathogenesis of the Generalized Shwartzman Reaction

1964 ◽  
Vol 12 (02) ◽  
pp. 471-483 ◽  
Author(s):  
F Rodríguez-Erdmann
Keyword(s):  
Clotting Factor ◽  
Factor V ◽  
Clotting System ◽  
Platelet Factor ◽  
Trigger Mechanism ◽  
Haemorrhagic Diathesis ◽  
Shwartzman Reaction ◽  
Ca Ions

SummaryThe rôle of the clotting system in the pathogenesis of the generalized Shwartzman reaction (gSr) has been stressed in recent years. The clotting system is activated ubiquitously and as a result of it, fibrin is deposited intravascularly and a haemorrhagic diathesis develops. Evidence is presented herein, that endotoxin does not activate purified prothrombin, nor does endotoxin influence the convertion of prothrombin when it is activated in the presence of purified platelet-factor 3 (or caephalin) purified Ac-G (factor V) and Ca-ions.The trigger mechanism of the gSr also seems to be in the so-called prephase of clotting mechanism. Data are presented, which show that endotoxin activates the Hageman factor in vitro. The importance of this clotting factor and of platelet-factor 3 is discussed. Also the rôle played by the RES and cardiodynamic and vascular components are taken in consideration in the discussion.

Serotonin Mediates Learning-Induced Potentiation of Excitability

2005 ◽  
Vol 94 (6) ◽  
pp. 4002-4010 ◽  
Author(s):  
Brian D. Burrell ◽  
Christie L. Sahley
Keyword(s):  
Cell Activity ◽  
Medicinal Leech ◽  
Whole Body ◽  
Protein Inhibitor ◽  
Cell Excitability ◽  
Intracellular Injection ◽  
Camp Analogue ◽  
Bath Application ◽  
Serotonergic Modulation

Sensitization potentiates excitability in an interneuron, the S-cell, that is critical for this form of learning in the whole-body shortening reflex of the medicinal leech. Serotonin (5-HT) also increases S-cell excitability, and serotonergic modulation is known to be critical for sensitization of whole-body shortening, suggesting that 5-HT mediates learning-induced enhancement of S-cell excitability. In this paper, the role of 5-HT in mediating sensitization-induced potentiation of S-cell excitability was examined. Potentiation of S-cell excitability by 5-HT was blocked by the 5-HT receptor antagonist methysergide and by intracellular injection of the G-protein inhibitor GDP-β-S, indicating that a metabotropic 5-HT receptor was involved. Bath application of Rp-cAMP, an inhibitor of protein kinase A (PKA), blocked 5-HT-induced potentiation of excitability, whereas db-cAMP, a cAMP analogue that activates PKA, mimicked the potentiating effects of 5-HT on the S-cell. During sensitization of the shortening reflex in semi-intact preparations, methysergide and Rp-cAMP prevented learning-induced potentiation of S-cell excitability, as well as the increase in S-cell activity that normally occurs during sensitization. Furthermore, sensitization-induced increases in the shortening reflex did not occur in preparations treated with methysergide or Rp-cAMP. These results demonstrate that sensitization-induced enhancement of S-cell excitability is mediated by 5-HT and suggests that these changes may contribute to this form of learning.

Possible Role of Ca Ions in the Vestibular System

1988 ◽  
Vol 105 (sup460) ◽  
pp. 28-32 ◽  
Author(s):  
O. Sterkers ◽  
C. Bernard ◽  
E. Ferrary ◽  
I. Sziklai ◽  
P. Tran Ba Huy ◽  
...  
Keyword(s):  
Vestibular System ◽  
Ca Ions

Water - Compacted Na-Bentonite Interaction in Simulated Nuclear Fuel Disposal Conditions: the Role of Accessory Minerals

1993 ◽  
Vol 333 ◽  
Author(s):  
A. Melamed ◽  
P. Pitkänen
Keyword(s):  
Nuclear Fuel ◽  
Pore Space ◽  
Near Field ◽  
High Water ◽  
Exchange Processes ◽  
Water Ph ◽  
Ca Ions ◽  
Major Alteration ◽  
Granitic Groundwater

ABSTRACTIn an earlier laboratory study1, ion exchange processes and smectite alteration were investigated through the interaction between compacted Na-bentonite (Volclay MX-80) and simulated granitic groundwater solutions. The change of montmorillonite from Na- to Ca-rich was found to be the major alteration process in the bentonite. In the water, a concentration decrease in Ca, Mg and K, and an increase in Na, HCO3 and SO4 were recorded. The total amount of Ca available in the water, however, was found insufficient to account for the recorded formation of Ca-smectite, and it is therefore assumed that the accessory Ca-bearing minerals in the bentonite provide the fundamental source of these cations.X-ray powder diffraction analyses and microscope observations of the bentonite samples were re-conducted. Quartz, feldspars, pyrite, calcite and traces of gypsum were revealed as the primary accessories. In reacted samples, goethite and siderite are found as the secondary mineral products in association with corroded pyrite grains, while calcite and gypsum tend to disappear. From these results it is assumed that the oxygen present in the water and bentonite pore space promotes the oxidation of pyrite (dissolved) and the precipitation of goethite. The pore water pH decreases and calcite is partly dissolved. Through the dissolution, the bulk amount of Ca ions in addition to those arising by diffusion from the water is provided. Some of the reaction-released bicarbonate and Fe2+ re-precipitate in the bentonite as siderite, while the rest (as also SO4 ions) diffuse into the water.Though the relative oxygen content in the experiment may be considered higher than that of the repository concept for nuclear fuel disposal (interaction in a semi-closed system with high water/bentonite ratio), the near field geochemistry predictions imply limited oxidizing conditions, which will be characterized by the above-described processes in sulphide-bearing bentonite and occur for some time after the sealing of the repository.

The Role of Calcium on the Release of Tissue Factor (Thromboplastie) Activity from Leukocytes

1975 ◽  
Author(s):  
T. W. Muhlfelder ◽  
I. Khan ◽  
J. Niemetz
Keyword(s):  
Tissue Factor ◽  
Maximum Activity ◽  
Release Mechanism ◽  
Temperature Dependent ◽  
Cell Contractility ◽  
Thromboplastic Activity ◽  
Significant Release ◽  
Ca Ions ◽  
The One

It is now well established that leukocytes may generate tissue factor (thromboplastic) activity (TFa), particularly after “stimulation” with endotoxin. As these leukocytes have also a thrombogenic effect, it appeared desirable to study the conditions in which the TFa was released. Leukocytes were obtained from the peritoneal cavity of rabbits after 2 doses of endotoxin and prepared as described previously (Nature New Biol. 232, 247, 1971). The leukocytes were incubated in siotonic buffered solutions, for up to 30 min then sedimented by centrifugation and the supemate removed for testing. The TFa was tested by the one stage test and the 2 stage assay. Significant release of procoagulant activity occured only when the leukocytes were suspended in solutions containing calcium. 2 mM of calcium caused maximum release of TFa while lower or higher concentrations were less effective. Other bivalent cations (Mg, Mn Zn) could not replace Ca ions and caused no release, while Co caused only very slight release of TFa. The release was time and temperature dependent: maximum activity being released at 37°C and almost no activity released at 4° C. When the effect of pH was studied, maximum release of TFa occurcd at pH 6.5–7.5. Substances which affect cell contractility such as vincristine, colchicine, cytochalasin B, as well as ouabain which affects some ATPase’s had no effect on release. These data show tlrat leukocyte tissue factor activity can be released from the cell in the presence of calcium. This release mechanism may play a role in some pathological conditions.(Supported in part by NIH Grant 13155 and VA 6060–01.)

scholarly journals Calcium and Potassium Spectra in the EUV

Atoms ◽  
2020 ◽  
Vol 8 (4) ◽  
pp. 73
Author(s):  
Elmar Träbert
Keyword(s):  
Survey Data ◽  
Extreme Ultraviolet ◽  
Single Element ◽  
Data Bases ◽  
Online Data ◽  
Solar Observations ◽  
Multiply Charged ◽  
Ca Ions ◽  
Beam Foil

In online data bases, the entries on extreme ultraviolet (EUV) spectra of Ca are much more sparse than those of neighbouring elements such as Ar, K, Sc and Ti. This may be a result of experimental problems with Ca in the laboratory as well as of the limited role of multiply charged Ca ions in solar observations. Beam-foil EUV spectra of Ca and K are presented that provide survey data of a single element each.

The role of Ca ions in changes induced by excess Cu2+ in bean plants. Growth parameters

1998 ◽  
Vol 20 (4) ◽  
pp. 411-417 ◽  
Author(s):  
Waldemar Maksymiec ◽  
Tadeusz Baszyński
Keyword(s):  
Growth Parameters ◽  
Bean Plants ◽  
Ca Ions

Role of Na and Ca Ions in the Determination of Isometrically Developed Tension of Heart Muscle

1972 ◽  
Vol 80 (1) ◽  
pp. 121-132
Author(s):  
A. R. Mattiazzi ◽  
H. E. Cingolani ◽  
N. C. González ◽  
E. S. Blesa
Keyword(s):  
Heart Muscle ◽  
Ca Ions
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