A Study of the Malpighian Tubules of the Pill Millipede, Glomeris marginata (Villers)

1974 ◽  
Vol 60 (1) ◽  
pp. 29-39
Author(s):  
PATRICIA ANNE FARQUHARSON
Keyword(s):  
Osmotic Pressure ◽  
Electrical Potential ◽  
Malpighian Tubules ◽  
Potassium Ions ◽  
Electrical Potential Difference ◽  
Ion Concentrations ◽  
Fluid Production ◽  
Tubule Fluid ◽  
Sodium And Potassium ◽  
Tubule Wall

1. Isolated Malpighian tubules of Glomeris produce fluid which is identical to the bathing media with respect to ion concentrations and osmotic pressure. 2. The tubules secrete normally in a potassium-free Ringer, but they cease to function in a sodium-free Ringer. 3. The rate of fluid production is dependent on the availability of sodium ions, but it is also inhibited by higher concentrations (25 mM/l of potassium ions. 4. Throughout a wide variation in concentrations of sodium and potassium ions in the bathing Ringer, the concentrations of these ions in the tubule fluid are the same as their concentrations in the Ringer. 5. Fluid production by the tubules of Glomeris is inhibited by ouabain at a concentration of 5x10-6M/l or greater. 6. The rate of fluid production varies inversely with the osmotic pressure, and the secreted fluid remains approximately isosmotic to the bathing media. 7. No electrical potential difference could be recorded across the tubule wall.

A Study of the Malpighian Tubules of the Pill Millipede, Glomeris marginata (Villers)

1974 ◽  
Vol 60 (1) ◽  
pp. 41-51
Author(s):  
PATRICIA ANNE FARQUHARSON
Keyword(s):  
Size Distribution ◽  
Fluid Transport ◽  
Molecular Size ◽  
Malpighian Tubules ◽  
Inverse Relation ◽  
Fluid Production ◽  
Molecular Size Distribution ◽  
Molecular Sieving ◽  
Tubule Fluid ◽  
Tubule Wall

1. Tubule fluid:medium ratios (TF/M) have been measured for inulin, glucose, LMWD and HMWD. These TF/M ratios were surprisingly high. 2. The tubule appears to act as a molecular filter; that is to say, molecules move through the tubule wall in inverse relation to their size. This is best illustrated using polyvinyl pyrrolidone as a tracer. The molecular size distribution of PVP fractions present in tubule fluid differs markedly from the molecular size distribution of PVP in the bathing Ringer. 3. No correlation can be made between the inulin and glucose TF/M and the rate of fluid production. However, the inverse relationship between TF/M and rate of fluid production for dextrans indicates a molecular sieving effect. 4. The significance of these results is discussed with reference to models of fluid transport.

Osmoregulation in the Larva of the Marine Caddis Fly, Philanisus Plebeius (Walk.) (Trichoptera)

1972 ◽  
Vol 57 (3) ◽  
pp. 821-838
Author(s):  
JOHN P. LEADER
Keyword(s):  
Sodium Chloride ◽  
Osmotic Pressure ◽  
Body Surface ◽  
Sea Water ◽  
Electrical Potential ◽  
Chloride Ion ◽  
Chloride Ions ◽  
The Body ◽  
Electrical Potential Difference ◽  
Caddis Fly

1. The larva of Philanisus plebeius is capable of surviving for at least 10 days in external salt concentrations from 90 mM/l sodium chloride (about 15 % sea water) to 900 mM/l sodium chloride (about 150 % sea water). 2. Over this range the osmotic pressure and the sodium and chloride ion concentrations of the haemolymph are strongly regulated. The osmotic pressure of the midgut fluid and rectal fluid is also strongly regulated. 3. The body surface of the larva is highly permeable to water and sodium ions. 4. In sea water the larva is exposed to a large osmotic flow of water outwards across the body surface. This loss is replaced by drinking the medium. 5. The rectal fluid of larvae in sea water, although hyperosmotic to the haemolymph, is hypo-osmotic to the medium, making it necessary to postulate an extra-renal site of salt excretion. 6. Measurements of electrical potential difference across the body wall of the larva suggest that in sea water this tissue actively transports sodium and chloride ions out of the body.

scholarly journals Quantum Electrochemical Equilibrium: Quantum Version of the Goldman–Hodgkin–Katz Equation

2020 ◽  
Vol 2 (2) ◽  
pp. 266-277
Author(s):  
Abdallah Barjas Qaswal
Keyword(s):  
Quantum Tunneling ◽  
Electrical Potential ◽  
Potential Gradient ◽  
Membrane Voltage ◽  
Potassium Ions ◽  
Excitable Cells ◽  
Quantum Version ◽  
Quantum Behavior ◽  
Sodium And Potassium ◽  
Electrochemical Equilibrium

The resting membrane voltage of excitable cells such as neurons and muscle cells is determined by the electrochemical equilibrium of potassium and sodium ions. This voltage is calculated by using the Goldman–Hodgkin–Katz equation. However, from the quantum perspective, ions with significant quantum tunneling through closed channels can interfere with the electrochemical equilibrium and affect the value of the membrane voltage. Hence, in this case the equilibrium becomes quantum electrochemical. Therefore, the model of quantum tunneling of ions is used in this study to modify the Goldman–Hodgkin–Katz equation in such a way to calculate the resting membrane voltage at the point of equilibrium. According to the present calculations, it is found that lithium—with its lower mass—shows a significant depolarizing shift in membrane voltage. In addition to this, when the free gating energy of the closed channels decreases, even sodium and potassium ions depolarize the resting membrane voltage via quantum tunneling. This study proposes the concept of quantum electrochemical equilibrium, at which the electrical potential gradient, the concentration gradient and the quantum gradient (due to quantum tunneling) are balanced. Additionally, this concept may be used to solve many issues and problems in which the quantum behavior becomes more influential.

Active Transport of Sulphate Ions by the Malpighian Tubules of Larvae of the Mosquito Aedes Campestris

1975 ◽  
Vol 62 (2) ◽  
pp. 367-378
Author(s):  
S. H. P. MADDRELL ◽  
J. E. PHILLIPS
Keyword(s):  
Active Transport ◽  
Concentration Gradient ◽  
Electrical Potential ◽  
Malpighian Tubules ◽  
Potential Difference ◽  
Electrical Potential Difference ◽  
Sulphate Content ◽  
Anal Papillae ◽  
Tracer Experiments

1. Larvae of Aedes campestris ingest and absorb into their haemolymph large quantities of the sulphate-rich water in which they live, yet they are able to maintain the sulphate content of the haemolymph well below that of the environment. 2. Tracer experiments showed that sulphate regulation was not achieved by deposition of precipitates in the tissues. 3. In vitro preparations of Malpighian tubules secrete sulphate ions actively against both a three times concentration gradient and an electrical potential difference of 20 mV. This transport is half saturated at about 10 mM. 4. The rate of sulphate secretion by the Malpighian tubules is sufficient to remove all of the sulphate ingested by larvae living in waters which contain less than 100 mM of this anion. At higher concentrations, sulphate ions are probably also excreted elsewhere, perhaps by the rectum or anal papillae.

scholarly journals Electrical potential difference and absorption of water, sodium, and potassium by the terminal ileum of ileostomy patients

Gut ◽  
1974 ◽  
Vol 15 (12) ◽  
pp. 977-981 ◽  
Author(s):  
J. P. P. De Moraes-Filho ◽  
C. Salas-Coll ◽  
L. Blendis ◽  
C. J. Edmonds
Keyword(s):  
Terminal Ileum ◽  
Electrical Potential ◽  
Potential Difference ◽  
Electrical Potential Difference ◽  
Sodium And Potassium

scholarly journals Active Transport of Potassium by the Malpighian Tubules of Insects

1953 ◽  
Vol 30 (3) ◽  
pp. 358-369 ◽  
Author(s):  
J. A. RAMSAY
Keyword(s):  
Active Transport ◽  
Electrical Potential ◽  
Passive Diffusion ◽  
Malpighian Tubules ◽  
The Difference ◽  
Sodium And Potassium

1. The concentrations of sodium and potassium in the haemolymph and in the urine have been measured in eight species of insect. 2. The concentration of potassium in the urine is always greater than in the haemolymph. The concentration of sodium in the urine is generally less than in the haemolymph. 3. In seven of the species the difference of electrical potential across the wall of the tubule has also been measured. 4. In these seven species the results lead to the conclusion that potassium is actively secreted into the tubule. It is very probable that the same is true in the eighth case. 5. It seems likely that the excretion of sodium can be brought about by passive diffusion into the tubule.

A Study of the Malpighian Tubules of the Pill Millipede, Glomeris marginata (Villers)

1974 ◽  
Vol 60 (1) ◽  
pp. 13-28
Author(s):  
PATRICIA ANNE FARQUHARSON
Keyword(s):  
Resistance Mechanism ◽  
Ringer Solution ◽  
Malpighian Tubules ◽  
Metabolic Inhibitors ◽  
Bathing Medium ◽  
Diuretic Hormone ◽  
Fluid Production ◽  
Tubule Fluid ◽  
Secretion Rates

1. The Malphigian tubules of the pill millipede, Glomeris marginata are described. 2. After the necessary analyses of the haemolymph had been carried out a Ringer solution was prepared which would support the secretion of tubule fluid in vitro. 3. The reasons for the variation and deterioration in the secretion rates of control tubules are discussed. The presence of various amino acids in the bathing medium appears to be essential for fluid production. 4. There would not appear to be a diuretic hormone involved in the control of secretion; and 5-HT, cylic AMP and theophylline will not stimulate fluid production. 5. Secretion is inhibited by the metabolic inhibitors 2,4-DNP, azide and cyanide. The relative insensitivity shown to the latter two compounds is probably associated with a resistance mechanism.

Aldosterone and thyroid hormone interaction on the sodium and potassium transport pathways of rat colonic epithelium

1990 ◽  
Vol 124 (1) ◽  
pp. 47-52 ◽  
Author(s):  
C. J. Edmonds ◽  
C. L. Willis
Keyword(s):  
Electrical Potential ◽  
Dry Weight ◽  
Potassium Transport ◽  
Plasma Sodium ◽  
Electrical Potential Difference ◽  
Stimulant Effect ◽  
Potassium Adaptation ◽  
Short Period ◽  
Potassium Secretion ◽  
Sodium And Potassium

ABSTRACT The effect of hypothyroidism on potassium adaptation (shown by increased potassium secretion in response to potassium loading) and on the action of aldosterone on potassium secretion and sodium fluxes was examined in the rat distal colon. Potassium adaptation, particularly the response to an acute potassium load, was impaired by hypothyroidism which also considerably reduced the rise of transepithelial electrical potential difference (p.d.) of total and transcellular (active) lumen-to-plasma sodium fluxes and of potassium secretion normally produced by aldosterone. These changes were, in part, corrected by a short period (3 days) of tri-iodothyronine replacement. Moreover in aldosterone-treated hypothyroid rats, amiloride in the lumen was considerably less effective in reducing the p.d. and sodium fluxes than in aldosterone-treated normal rats. The intracellular sodium transport pool was greater in the hypothyroid than in the normal rats (5·0± 1·1 (s.e.m.) nmol/mg dry weight compared with 2·9 ± 0·2 nmol/mg dry weight; P<0·02). Aldosterone increased the pool in the normal but not in the hypothyroid rats while amiloride had little effect on the pool in the aldosterone-treated hypothyroid rats but almost abolished it in aldosterone-treated normal rats. Aldosterone plays a major part in the adaptation of colonic sodium and potassium transport to sodium depletion or potassium excess; these adaptations were much impaired in hypothyroid animals. The present results are consistent with a deficiency in aldosterone induction of potassium- and amiloride-sensitive sodium pathways in the apical membrane of colonic epithelial cells in hypothyroid rats, a deficiency which limits the stimulant effect of aldosterone on sodium and potassium transport. Journal of Endocrinology (1990) 124, 47–52

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