scholarly journals Studies on the Physiology of Arenicola Marina L.

1942 ◽  
Vol 19 (2) ◽  
pp. 176-185
Author(s):  
G. P. WELLS ◽  
I. C. LEDINGHAM
Keyword(s):  
Steady State ◽  
Sea Water ◽  
Potassium Concentration ◽  
Short Exposure ◽  
Simultaneous Increase ◽  
Distinctive Pattern ◽  
Bathing Medium ◽  
Arenicola Marina ◽  
Pattern Characteristic ◽  
Simultaneous Decrease

1. The effects on the isolated extrovert of Arenicola marina L. of varying the potassium concentration of the bathing medium are described. Data are also presented on K : Mg antagonism. Potassium and magnesium concentrations are given as multiples of their concentrations in artificial sea water, which was taken as the ‘normal’ starting fluid. 2. The extrovert normally shows a distinctive pattern of alternating periods of activity and rest, superposed on the more general properties of rhythm and tone. This pattern is very sensitive to changes in potassium concentration. Moderate changes produce modifications of the pattern. Severe changes abolish the pattern and produce effects on rhythm and tone resembling those shown by most rhythmic muscles under like conditions. 3. Moderate K excess (K 1.5-3.5) excites tone and rhythm. Accommodation occurs during long exposure. The effects resemble those of Mg deficit, and can be completely abolished by increasing the Mg concentration. 4. An increase of lever weight has effects on the rhythm resembling those of a moderate K excess or a moderate Mg deficit, but in this case there is no accommodation. It is suggested that the extrovert contains a steady state system such as k0kS↔A→ Bwhere S is a source and the performance of the extrovert depends, through B, on the rate of the process A→B. If change in the K : Mg balance acts on k, its result will be following automatically by accommodation. Change in tension can produce the same end-result, without accommodation, by acting on B. 5. Severe K excess (K 5-10) causes contracture and inhibition of the rhythm. The contracture is partly antagonized by simultaneous increase in Mg, but the inhibition is not antagonized. 6. Moderate K deficit (K 0.75-0.33) causes initial excitement, then a characteristically modified pattern, with widely spaced activity outbursts, and an occasional abnormally long outburst. These effects are not antagonized by simultaneous decrease in Mg. As, however, they are not seen in preparations exposed to sea water diluted to four times its volume, they are due to disturbance of a balance between K and some other constituent of the medium. 7. Severe K deficit (K 0.05 or 0.00) causes partial contracture with chaotic activity, which lasts for many hours. Neither effect can be antagonized by simultaneous decrease in Mg. With borderline deficits (K 0.25 or 0.20) the preparation reacts at first as if to severe deficit, then accommodates itself and gives the pattern characteristic of moderate deficit. 8. The potassium paradox occurs on returning to artificial sea water after severe deficit. With borderline deficits (K 0.25 or 0.20) it is seen after short exposure, but not after long.

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.

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).

Zellturgor und selektiver Ionentransport bei Chaetomorpha linum / Cell Turgor Pressure and Selective Ion Transport of Chaetomorpha linum

1971 ◽  
Vol 26 (12) ◽  
pp. 1276-1282 ◽  
Author(s):  
E. Steudle ◽  
U. Zimmermann
Keyword(s):  
Steady State ◽  
Ion Transport ◽  
Osmotic Pressure ◽  
Sea Water ◽  
Potassium Concentration ◽  
Turgor Pressure ◽  
Salt Content ◽  
Sodium Concentration ◽  
Cell Turgor ◽  
Chaetomorpha Linum

The littoral alga Chaetomorpha linum is especially able to maintain a constant turgor pressure in the cell by regulating the internal osmotic pressure, if the salt content of the sea water changes. Experiments in artificial isotonic sea water with a constant sodium concentration, but variable potassium concentrations (from 1 to 50 mMol/1) prove, that the decrease or increase of the potassium concentration in the medium (CKa) is an essential cause for this regulation of the turgor pressure besides the change of the osmotic pressure of the medium, which was thought to be the predominant cause till now. In the examined concentration range the ratio CKa to CK1 (potassium concentration in the cell) depends linear on CKa in the steady state. At low values of CKa (< 10 mMol/1) the decrease in CK1 is compensated by a reversible sodium uptake only in part, and this leads to partly high changes in the cell turgor pressure, although the osmotic pressure of the medium remains constant. The results are discussed on the basis of carrier models.

Studies on the mechanism of fluid secretion by isolated salivary glands of Calliphora

1976 ◽  
Vol 64 (2) ◽  
pp. 311-322
Author(s):  
M. J. Berridge ◽  
B. D. Lindley ◽  
W. T. Prince
Keyword(s):  
Salivary Glands ◽  
Apical Membrane ◽  
Potassium Concentration ◽  
Basal Membrane ◽  
Fluid Secretion ◽  
Sodium Permeability ◽  
Bathing Medium ◽  
Major Cation ◽  
Diuretic Agent ◽  
External Potassium

1. Potassium is the major cation in the secretion of the salivary glands of Calliphora and is necessary for full secretory rates. 2. Other ions (rubidium and sodium) can support secretion in the absence of potassium. 39. During stimulation with 5-HT a Nernst plot of the basal membrane potential has a slope of 53 mV for a tenfold change in external potassium concentration and the slope at rest deviates from this over the range I-20 mM external potassium. 4. Hyperpolarization of the basal membrane by 5-HT is abolished if the chloride in the bathing medium is replaced by isethionate. 5. The diuretic agent amiloride inhibits fluid secretion by a mechanism which may include a reduction in calcium entry in addition to its recognized effect on sodium permeability. 6. A model is proposed in which fluid secretion is driven by the active transport of potassium across the apical membrane with chloride following passively.

Effects of sodium intake on steady-state potassium excretion

1984 ◽  
Vol 246 (6) ◽  
pp. F772-F778 ◽  
Author(s):  
D. B. Young ◽  
T. E. Jackson ◽  
U. Tipayamontri ◽  
R. C. Scott
Keyword(s):  
Steady State ◽  
Potassium Concentration ◽  
Sodium Intake ◽  
Plasma Potassium ◽  
Potassium Excretion ◽  
Distal Nephron ◽  
Concentration Data ◽  
Potassium Intake ◽  
Independent Variable ◽  
The Relationship

The effects of changes in sodium intake on the steady-state relationship between plasma potassium concentration and potassium excretion were studied in 15 chronically adrenalectomized dogs. Throughout the experiments the dogs received aldosterone at a rate of 50 micrograms/day and methylprednisolone at 1 mg/day. The relationship between plasma potassium and steady-state potassium excretion was obtained by changing potassium intake from 10 to 30 to 100 meq/day, each level being maintained for 7-10 days. At the conclusion of each period at a given level of potassium intake, plasma potassium and excretion were measured and plotted, plasma potassium being the independent variable. Such a relationship was obtained while the dogs were on three different levels of sodium intake: 10, 100, and 200 meq/day. The curves from the data obtained at 100 and 200 meq/day sodium intake both were shifted to the left of the curve obtained at 10 meq/day (P less than 0.05), although the 100 and 200 meq/day curves were not different from each other. On the basis of these data one could predict that, at a plasma potassium concentration of 4.0 meq/liter, the animals would excrete potassium at a rate of 17 meq/day on a 10 meq/day sodium intake, 37 meq/day on a 100 meq/day sodium intake, and 47 meq/day on a 200 meq/day sodium intake. Urine flow and electrolyte concentration data are consistent with the hypothesis that the sodium intake effect on potassium excretion was mediated through increases in distal nephron flow rate and decreases in distal nephron potassium concentration.

Motility and energy-rich phosphorus compounds in spermatozoa of Octopus dofleini martini

1971 ◽  
Vol 178 (1051) ◽  
pp. 151-160 ◽  
Keyword(s):  
Sea Water ◽  
Phosphorus Compounds ◽  
Short Exposure ◽  
Motile Sperm ◽  
High Concentration ◽  
Irreversible Loss ◽  
Prolonged Incubation ◽  
The North ◽  
Sperm Suspension ◽  
The North Pacific

The spermatozoa of the giant octopus of the North Pacific, freshly removed from spermatophores, showed very little motility, but on dilution with sea-water or 2.7 % NaCl, followed by dialysis against either of these two media, they became intensely motile and remained so for several days at 2 to 10 °C. At higher temperatures, particularly above 25 °C, octopus spermatozoa lost their motility rapidly. At 35 °C, complete and irreversible loss of motility occurred within less than 1 min. The motility of octopus spermatozoa at 2 to 10 °C persisted under both anaerobic and aerobic conditions and did not require the presence of exogenous glycolysable sugar. The addition of spermatophoric plasma to a motile sperm suspension inhibited motility. Other inhibitors were sodium azide, 2, 4-dinitrophenol and ethylenediaminetetra-acetate, at 0.001 M concentrations. ATP, ADP and arginine phosphate have been identified and quantitatively measured in octopus spermatozoa. On prolonged incubation of motile sperm suspensions a t 3 °C, ATP and ADP did not decline appreciably, whilst arginine phosphate decreased considerably. The decrease was even more pronounced in sperm suspensions which had first been inactivated by short exposure to 35 °C, prior to prolonged incubation at 3 °C. Glycogen, the main carbohydrate store of octopus spermatozoa, remained at a high concentration even in sperm suspensions kept for 5 days at 3 °C, and there was no appreciable difference in that respect between a sample containing motile spermatozoa and one in which, at the outset of incubation, the spermatozoa were immobilized by heating to 35 °C.

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.

Ecotoxicity of contaminated sediments, a matter of bioavailability

1998 ◽  
Vol 37 (6-7) ◽  
pp. 225-231 ◽  
Author(s):  
N. H. B. M. Kaag ◽  
E. M. Foekema ◽  
M. C. Th. Scholten
Keyword(s):  
Dreissena Polymorpha ◽  
Sea Water ◽  
Feeding Habits ◽  
Macoma Balthica ◽  
Contaminated Sediments ◽  
Suspension Feeding ◽  
Simple Relationship ◽  
Filter Feeder ◽  
Arenicola Marina ◽  
The Baltic

Marine and freshwater mesocosm-scale experiments with contaminated sediments have shown that there is a direct relationship between the accumulated contaminant levels and the feeding habits of the organisms used. The highest levels of PAHs and PCBs were found in the sediment feeding lugworm Arenicola marina and in Tubifex worms. The levels of contaminants in the suspension feeding mussels Mytilus edulis and the zebra mussels, Dreissena polymorpha, were not influenced by the contaminant content of the sediments, but were related instead to the level of contaminants in the sea water above. Intermediate levels were found in the baltic tellin, Macoma balthica, which is a filter feeder as well as a deposit feeder, depending on the availability of food. These results show that there is no simple relationship between contaminant concentration in the sediments and bioavailability. Higher levels of contaminants do not necessarily lead to higher levels of these contaminants in Arenicola, due to differences in the sediment structure and the ageing of the contamination. On the other hand, toxic effects are related to the internal concentrations of certain chemicals. The internal concentrations observed in Arenicola may provide a good estimation of the true bioavailability of sedimentary contaminants and can also be used as an indicator for potential environmental effects.

scholarly journals On some Factors Limiting the Habitat of Arenicola marina

1929 ◽  
Vol 16 (1) ◽  
pp. 109-116 ◽  
Author(s):  
D. M. Reid
Keyword(s):  
Calcium Carbonate ◽  
Ferric Oxide ◽  
Sea Water ◽  
Amorphous State ◽  
Magnesium Carbonate ◽  
Arenicola Marina ◽  
Short Time ◽  
Clay Kaolin

SUMMARYIn the foregoing work it was found that: Arenicola marina was repelled and could not burrow in sand containing 20% of ferric oxide in the amorphous state.That 0·021% ferric oxide in suspension in sea-water was lethal owing to its forming with the mucus of the organism an envelope which prevented contact with the surrounding air-carrying water.That calcium carbonate, magnesium carbonate, Stourbridge clay, kaolin, and kieselguhr had the same effect as the ferric oxide in suspension.That although able to live for a short time in water of salinity 3·10%‰, Arenicola marina tended to become so turgid in water of 14·32%‰ as to be unable to burrow.

scholarly journals Lactic acid secretion by human neutrophils. Evidence for an H+ + lactate- cotransport system.

1992 ◽  
Vol 100 (2) ◽  
pp. 341-367 ◽  
Author(s):  
L Simchowitz ◽  
J A Textor
Keyword(s):  
Lactic Acid ◽  
Steady State ◽  
Ph Dependence ◽  
Transport Systems ◽  
Human Neutrophils ◽  
Bathing Medium ◽  
Monocarboxylate Transport ◽  
Cotransport System ◽  
Ph Stat ◽  
Transport In Mitochondria

The pathway by which L-lactate (Lac) crosses the plasma membrane of isolated human neutrophils was investigated. The influx of [14C]Lac from a 2 mM Lac, 145 mM Cl-, 5.6 mM glucose medium was approximately 1.5 meq/liter of cell water.min and was sensitive to the organomercurial agent mersalyl (apparent Ki approximately 20 microM), to alpha-cyano-4-hydroxycinnamate (CHC), the classical inhibitor of monocarboxylate transport in mitochondria, and to UK-5099 (apparent Ki approximately 40 microM), a more potent analogue of CHC. Transport was also strongly blocked (greater than 80%) by 1 mM of either 3,5-diiodosalicylic acid, MK-473 (an indanyloxyacetate derivative), or diphenyl-amine-2-carboxylate, and by 0.4 mM pentachlorophenol, but not by 1 mM ethacrynic acid, furosemide, or the disulfonic stilbenes SITS or H2DIDS. One-way [14C]Lac efflux from steady-state cells amounted to approximately 6 meq/liter.min and was likewise affected by the agents listed above. Influx, which was membrane potential insensitive and Na+ independent, displayed a strong pH dependence: extracellular acidification enhanced uptake while alkalinization inhibited the process (pK' approximately 5.7 at 2 mM external Lac). The rate of [14C]Lac influx was a saturable function of external Lac, the Km being approximately 7 mM. Steady-state cells exhibited an intracellular Lac content of approximately 5 mM and secreted lactic acid into the bathing medium a a rate of approximately 4 meq/liter.min. Secretion was completely suppressed by 1 mM mersalyl which inactivates the carrier, leading to an internal accumulation of Lac. That the Lac carrier truly mediates an H+ + Lac- cotransport (or formally equivalent Lac-/OH- exchange) was documented by pH-stat techniques wherein an alkalinization of poorly buffered medium could be detected upon the addition of Lac; these pH changes were sensitive to mersalyl. Thus, the Lac carrier of neutrophils possesses several features in common with other monocarboxylate transport systems in erythrocytes and epithelia.

Sign in / Sign up

Export Citation Format

Share Document