Mn2+ Ions Pass Through Ca2+ Channels in Myoepithelial Cells

1979 ◽  
Vol 82 (1) ◽  
pp. 227-238
Author(s):  
M. ANDERSON
Keyword(s):  
Sea Water ◽  
Myoepithelial Cells ◽  
Fold Change ◽  
Applied Current ◽  
Bathing Medium ◽  
Current Pulses ◽  
Marine Polychaete ◽  
Intracellular Stimulation ◽  
Pass Through ◽  
Ca2 Channels

1. Intracellular recordings were made from the myoepithelial cells of the proventriculus of the marine polychaete worm Syllis spongiphila. Overshooting responses were elicited either by carbamylcholine added to the bathing medium or by directly applied intracellular current pulses. 2. In control artificial sea water (ASW) directly applied current pulses elicited regenerative responses of 68–119 mV in amplitude and 70–1800 ms in duration; these responses were associated with contractions of the myoepithelial cells. 3. Both pharmacologically and electrically elicited responses were reversibly abolished in Ca-free ASW and were unaffected by TTX or lowsodium solutions. Regenerative responses were elicited by direct intracellular stimulation in calcium-free ASW containing 1 mM-B2+ or 10 mM-Sr2+. Directly elicited responses were blocked reversibly in ASW containing calcium and 15-20 mM-Co2+ or 2.5-10 mM-Ni2+; they were blocked irreversibly in ASW containing calcium and 10 mM-La3+ or 100 μM-Zn2+. 4. Regenerative responses were elicited in Ca-free solutions containing 10-50 mM-Mn2+; these responses were not associated with contractions, were consistently of longer duration than responses elicited in control ASW, and were blocked by 20 mM-Co2+ or 10 mM-La3+. The overshoots of Mn2+ responses elicited in both Na-free and Na-containing, Ca-free solutions increased as the external concentration of Mn2+ was increased, with a slope of about 27 mV per 10-fold change in concentration of Mn2+. In Cacontaining solutions the slope was reduced to about 15mV per 10-fold change. 5. The results indicate that the myoepithelial cells generate Ca-spikes and that Mn2+ ions, in addition to Sr2+ and Ba2+ ions, pass through the Ca2+ channels of the myoepithelial cell membranes. Although Mn^ can replace Ca2+ in generating spikes, it apparently cannot replace Ca2+ in initiating contraction, and it many compete with Ca2+ in activating repolarization of the cell.

The effect of repetitive stimulation on the passive electrical properties of the presynaptic terminal of the squid giant synapse

1979 ◽  
Vol 206 (1164) ◽  
pp. 293-306 ◽  
Keyword(s):  
Electrical Properties ◽  
Transmitter Release ◽  
Sea Water ◽  
Presynaptic Terminal ◽  
Repetitive Stimulation ◽  
Constant Current ◽  
Current Pulses ◽  
Squid Giant Synapse ◽  
Giant Synapse ◽  
Passive Electrical Properties

The resting electrical properties of the presynaptic terminal of the squid giant synapse have been determined by using constant current pulses. After short periods of repetitive stimulation, the terminal resistance, time constant and capacitance are found to be increased. These changes are absent in terminals bathed in artificial sea water containing no calcium, and sea water containing 5 mM cobalt. It seems likely that these changes are associated with transmitter release.

scholarly journals Performance Evaluation of Shell-and-Tube Heat Exchanger with 3-Fluid Sets using CFD and NTU

2019 ◽  
Vol 9 (1) ◽  
pp. 1416-1420
Keyword(s):  
Heat Exchanger ◽  
Industrial Development ◽  
Cfd Simulation ◽  
Sea Water ◽  
Raw Water ◽  
Power Sector ◽  
Tube Heat Exchanger ◽  
Shell And Tube ◽  
Pass Through ◽  
Good Agreement

Energy generation to the present growing population is a crucial challenge for the power sector. Heat exchangers (HE) plays an important role in the industrial development. In this present work an attempt is made to develop a Shell-and- Tube Heat Exchanger (STHE) with segmental baffles using commercial CATIA V5 and Autodesk CFD Simulation Softwares. TEMA standards are considered for design of STHE with baffle-cut of 25%. 3-different sets of fluids are allowed to pass through the shell and tube sides i.e. Methanol - Sea Water (M-S), Distilled Water – Raw Water (D-R) and Kerosene- Crude Oil (K-C). The boundary conditions imposed for analysis are fluid inlet temperatures and velocities. ϵ-NTU is employed for the validation of simulation results and found good agreement between them. Results are plotted for temperature, pressure and velocity contours. The performance of the STHE is shown best for the K-C fluid set among other fluid sets.

Long-term Adaptations of Sabella Giant Axons to Hyposmotic Stress

1978 ◽  
Vol 75 (1) ◽  
pp. 253-263
Author(s):  
J. E. TREHERNE ◽  
Y. PICHON
Keyword(s):  
Sea Water ◽  
Potassium Concentration ◽  
Resting Potential ◽  
Sodium Permeability ◽  
Bathing Medium ◽  
Appreciable Change ◽  
Axon Membrane ◽  
Giant Axons

Reprint requests should be addressed to Dr Treherne. Sabella is a euryhaline osmoconformer which is killed by direct transfer to 50% sea water, but can adapt to this salinity with progressive dilution of the sea water. The giant axons were adapted to progressive dilution of the bathing medium (both in vivo and in vitro) and were able to function at hyposmotic dilutions (down to 50%) sufficient to induce conduction block in unadapted axons. Hyposmotic adaptation of the giant axon involves a decrease in intracellular potassium concentration which tends to maintain a relatively constant resting potential during adaptation despite the reduction in external potassium concentration. There is no appreciable change in the intracellular sodium concentration, but the relative sodium permeability of the active membrane increases during hyposmotic adaptation. This increase partially compensates for the reduction in sodium gradient across the axon membrane, during dilution of the bathing media, by increasing the overshoot of the action potentials recorded in hyposmotically adapted axons.

Bioelectric Regulation of Tentacle Movement in a Dinoflagellate

1967 ◽  
Vol 47 (3) ◽  
pp. 433-446
Author(s):  
ROGER ECKERT ◽  
TAKAO SIBAOKA
Keyword(s):  
Temporal Relationship ◽  
Sea Water ◽  
Outward Current ◽  
Wave Form ◽  
Applied Current ◽  
Inward Current ◽  
Wave Forms ◽  
Noctiluca Miliaris ◽  
Spike Wave ◽  
Peripheral Cytoplasm

1. Recurring extensions and flexions of the food-gathering tentacle of Noctiluca miliaris occur spontaneously. Identical movements can be evoked by appropriate electrical stimulation. 2. Spontaneous recurring potential wave forms (TRPs) were recorded from the vacuole of the luminescent form of Noctiluca during movements of the tentacle. The basic TRP wave form consists of a characteristic negative-going spike which arises at -20 to -30 mV. from the slowly redeveloping negativity of a pre-spike depolarization, and is followed by a quasi-stable post-spike d.c. level of relative vacuolar negativity (-45 to -60 mV.). 3. The TRP complex, similar in shape to that which occurs spontaneously, follows an intracellularly applied current pulse of either polarity if the vacuolar potential is at the post-spike level. The duration of the evoked pre-spike wave is related to the current intensity and duration. During the pre-spike state outward current is ineffective, although a TR spike occurs in response to inward current. 4. The TRP is distinct in its behaviour and wave form from the flash-triggering potential, which can be evoked in the same cell, even though both exhibit all-or-none spikes. 5. Simultaneous recordings of intracellular potentials and movements of the tentacle showed a consistent temporal relationship between potential changes and subsequent movement. Extension of the tentacle begins 1-2 sec. after the spike and flexion begins within 1 sec. after beginning of the pre-spike wave. 6. Tentacle movement ceased in Ca-free sea water even though the cyclic potential changes continued normally. 7. Electron micrographs of the tentacle showed longitudinal aggregations of microtubules near the outer surface of the peripheral cytoplasm. It is proposed that contraction of these microtubules is the immediate cause of tentacle movements.

I. Environmental Contamination and Biochemical Relationships

1975 ◽  
Vol 38 (5) ◽  
pp. 285-300 ◽  
Author(s):  
A. G. HUGUNIN ◽  
R. L. BRADLEY
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Methyl Mercury ◽  
Sea Water ◽  
Inorganic Mercury ◽  
Whole Body ◽  
Irreversible Damage ◽  
Mercury Compounds ◽  
The Central Nervous System ◽  
Pass Through

Mercury is naturally concentrated in geographical belts, but geological cycling has distributed the element in all strata of the earth. Natural concentrations of mercury are approximately 100 ppb in soil, 0.06 ppb in fresh water, 0.01–0.30 ppb in sea water, and 0.003–0.009 μg/m3 in air. Concentrations vary, being highest near mineral deposits. The concentration of mercury in some areas has been significantly increased by human carelessness. An epidemic among Japanese fishing families, death of Swedish wildlife, and discovery of elevated mercury levels in American fish focused attention on this problem. The discovery that certain species are capable of methylating inorganic mercury indicates pollution with any chemical form of mercury is dangerous. Alkylmercurials are the most dangerous form of mercury in the environment. Alkylmercurials are absorbed from the gastrointestinal tract, diffuse across the blood-brain carrier, and pass through the placental membrane in significantly higher proportions than other mercury compounds. The whole body half-life of methyl mercury in humans is 76 ± 3 days compared to half-lives of 37 ± 3 days for men and 48 ± 5 days for women observed for mercuric salts. Not readily broken down, sufficient concentrations of methyl mercury can cause irreversible damage to the central nervous system. Renal damage usually results from high levels of aryl- or alkoxyalkylmercurials and inorganic mercury; however, vapors of elemented mercury can damage the central nervous system. Organic mercury compounds cause chromosome changes, but the medical implications resulting from levels of mercury in food are unknown. The concentration of mercury in red blood cells and hair is indicative of the exposure to alkylmercurials. On a group basis, blood and urine concentrations of mercury may corrrelate with recent exposure to mercury.

scholarly journals Physiological Effects of a Hypotonic Environment

1940 ◽  
Vol 17 (3) ◽  
pp. 337-352
Author(s):  
G. P. WELLS ◽  
ISABEL C. LEDINGHAM
Keyword(s):  
Body Wall ◽  
Sea Water ◽  
Rapid Change ◽  
Natural Conditions ◽  
Bathing Medium ◽  
Nereis Diversicolor ◽  
Arenicola Marina ◽  
Lower Salinity ◽  
Hypotonic Fluid ◽  
Two Phases

1. The reactions of isolated rhythmic preparations from Arenicola marina, Nereis diversicolor and Perinereis cultrifera to hypotonic saliness are described. 2. The preparations used were (1) the "isolated extrovert" of all three species, (2) ventral longitudinal body-wall strips of the two last named. All these preparations are essentially alike in their reactions to dilution of the bathing medium. 3. On abruptly changing from sea water to a hypotonic fluid, responses of the following general type are seen: first, brief excitement; then a phase of more or less complete inhibition; finally, provide the hypotonic fluid is not below a lower salinity limit characteristic of the preparation, gradual return of activity as the preparation accommodates itself to the new medium. The first two phases are shock effects of sudden dilution. The inhibition phase may last for many hours. 4. Preparations were exposed to salinities which fell gradually at various speeds. From the results of these experiments it is inferred that shock effects of rapid change are unlikely to be evoked under natural conditions, at least in Arenicola and Nereis. 5. The lower salinity limits for spontaneous activity in the tissues of the various species are: Perinereis cultrifera, 20-25% sea water; Arenicola marina, 15-20%; Nereis diversicolor, 5-10%. The results are discussed with reference to the ability to live in brackish water. 6. On suddenly returning from a hypotonic fluid to normal the responses vary. There may be relatively slight excitation (Arenicola marina extrovert) or a cycle of excitation--inhibition--accommodation like that evoked by a sudden downward change (Nereis diversicolor body wall).

scholarly journals Physiological Effects of a Hypotonic Environment

1940 ◽  
Vol 17 (4) ◽  
pp. 378-385
Author(s):  
G. P. WELLS ◽  
ISABEL C. LEDINGHAM ◽  
MARY GREGORY
Keyword(s):  
Water Content ◽  
Sea Water ◽  
Mechanical Activity ◽  
Physiological Effects ◽  
Bathing Medium ◽  
Osmotic Equilibrium ◽  
Different Types

1. The cilia of Pleurobrachia, Mytilus and Arenicola show inhibition, followed by accommodation, as a result of sudden downward or upward changes in the salinity of the bathing medium. 2. Variations in sensitivity occur between different species, and between different types of cilia in the same species. 3. When Mytilus gills are suddenly transferred from 100 to 30% sea water, they take up water very rapidly. Accommodation, as indicated by the mechanical activity, continues long after osmotic equilibrium has been reached. Therefore, accommodation is not an adjustment of the water content of the cell. 4. The results are discussed, and compared with those obtained on other types of contractile tissues.

scholarly journals Giresun Sahilindeki Bazı Derelerin Denize Deşarj Olduğu Noktalardaki Su ve Sedimentte Ağır Metal Kirliliği

2015 ◽  
Vol 3 (9) ◽  
pp. 707
Author(s):  
Aysun Türkmen ◽  
Selin Akbulut
Keyword(s):  
Heavy Metal ◽  
Black Sea ◽  
Sea Water ◽  
Winter Season ◽  
City Center ◽  
Icp Ms ◽  
Metal Levels ◽  
Pass Through

Carrying between February 2012 and February 2013 as seasonal, the present study aims to determine heavy metal loads of five different creeks pass through Giresun city center and disembogue to Black Sea. Heavy metal analyses were performed from selected stations by ICP-MS instrument. Without seasonal and station differences, metal levels were found as follow; Cd: 0.129-5.113, Mn: 0.009-2.937, Fe: 0.007-1.985, Cu: 0.002-1.344, Zn: 0.002-1.901, Ni: 0.003-0.149, Pb: 0.009-21.22, Cr: 0.002-0.177, Co: 0.001-0.087 mg/L in water. Cd: 0.118-166.3, Pb: 5.62-398.9, Mn: 111.7-988.2, Fe: 2919-117973, Cu: 18.60-963.9, Zn: 11.09-2471, Ni: 11.29-813.1, Cr: 10.76-860.5, Co: 8.59-757.1 mg/kg in sediment. There were statistically significant differences between seasons in sea water. Statistically differences were found on Aksu, Güre, and Batlama stations. In sediment, statically differences in Cu, Zn, Ni, Co levels were found in winter season. The same elements were also statistically different on Güre station.

Neuronal diversity in the subiculum: correlations with the effects of somatostatin on intrinsic properties and on GABA-mediated IPSPs in vitro

1996 ◽  
Vol 76 (3) ◽  
pp. 1657-1666 ◽  
Author(s):  
J. R. Greene ◽  
A. Mason
Keyword(s):  
Cell Layer ◽  
Hippocampal Formation ◽  
Reversal Potential ◽  
Cell Types ◽  
Gamma Aminobutyric Acid ◽  
Cell Type ◽  
Bathing Medium ◽  
Current Pulses ◽  
Series Of Experiments

1. We used intracellular current-clamp techniques to record from 33 ventral subicular neurons in slices or rat hippocampal formation. Presumed pyramidal neurons were characterized by their responses to depolarizing current pulses as either intrinsically burst firing (IB) or regular spiking (RS). Within the subiculum, IB cells were encountered most frequently in the deep cell layer, whereas RS cells were encountered most frequently in the superficial cell layer. IB cells had more depolarized resting potentials, lower input resistances, and more sag in their voltage responses to hyperpolarizing current pulses. 2. Somatostatin (5 microM) applied in the bathing medium caused a hyperpolarization and reduction in input resistance. These effects were of greater magnitude in IB cells. Somatostatin had no effect on sag in either cell type. These effects of somatostatin were unchanged in the presence of gamma-aminobutyric acid (GABA) receptor antagonists. 3. In a series of experiments conducted in RS cells only, somatostatin reduced the amplitude of the late but not the early component of evoked biphasic inhibitory postsynaptic potentials (IPSPs). 4. A second series of experiments was conducted in RS and IB cells. Somatostatin reduced the amplitude of pharmacologically isolated GABAA IPSPS in both cell types. In IB cells but not RS cells there was a correlation between this effect and the somatostatin-induced hyperpolarization. Somatostatin also reduced the amplitude of isolated GABAB IPSPS in both cell types, but more so in IB cells. 5. Somatostatin had no effect on the reversal potential of either IPSP in either cell type and no effect on the GABAA-mediated conductance in either cell type. In contrast, the GABAB-mediated conductance was reduced, especially in IB cells. 6. The effects of somatostatin on GABAA IPSPS are principally a result of membrane shunting and reductions in ionic driving force, but these mechanisms do not account for the reduction in GABAB IPSPS. 7. We suggest that the combined effects of somatostatin are likely to alter the balance between fast and slow inhibition and to do so more in IB cells than in RS cells.

scholarly journals The Problem of Plastic Waste and Microplastics in the Seas and Oceans: Impact on Marine Organisms

2019 ◽  
Vol 77 (1) ◽  
pp. 51-56 ◽  
Author(s):  
Antonia Kurtela ◽  
Nenad Antolović
Keyword(s):  
Sea Water ◽  
Plastic Material ◽  
Chemical Compounds ◽  
Marine Organisms ◽  
Plastic Waste ◽  
Pathogenic Microorganisms ◽  
The Public ◽  
Plastic Materials ◽  
Pass Through ◽  
State Organizations

Abstract A global problem of today is the large amount of waste in the seas and oceans, primarily plastic waste. It is estimated that every year 1.25 to 2.41 million tons of plastic material is being carried by rivers into the seas and oceans. Waste is a major problem for marine organisms, causing entanglement, choking, strangulation, malnutrition and death. In 1972 the problems caused by microplastics, particles smaller than 5 mm, were first observed. Such particles bind pathogenic microorganisms on to their surface. Increasing quantities of microplastics have been found in the stomachs of fish, and also in shellfish that feed by filtering sea water. Ingested by marine organisms, such plastics may eventually pass through the food web and can end up ingested by humans. In addition, plastic releases chemical compounds whose effect on marine organisms and humans has still not been studied. Many international and state organizations offer solutions through recycling plastic waste, as well as reducing the production of plastic materials and informing the public about the problem.

Sign in / Sign up

Export Citation Format

Share Document