Epidermal growth factor alters the electrolyte profile of lactating ewes Ovis aries

• 1.1. Lactating ewes were treated with mouse epidermal growth factor (EGF) at a dose rate of 0.5 mg/day for 4 days and its effects on the electrolyte profile were observed.
• 2.2. There was no effect of EGF on plasma concentrations of sodium or potassium, although urinary and total (in urine and milk) losses of both were reduced.
• 3.3. EGF-induced hypocalcaemia was associated with reduced milk calcium secretion and increased urinary calcium excretion whereas EGF-induced hypermagnesaemia was associated with reduced urinary and total magnesium losses.
• 4.4. Glomerular filtration rate was reduced during EGF infusion.
• 5.5. Chronic intravenous EGF infusion affects the electrolyte profile by altering electrolyte secretion by the mammary gland and renal electrolyte excretion.

     

The effect of osmotic and ion-osmotic stresses on the blood and urine composition and urine flow of rainbow trout (Salmo gairdneri)

• 1.1. Changes in urine and plasma concentrations (sodium, potassium, magnesium, calcium and total osmotic) and urine production were determined in fish exposed to various concentrations of an ionically active substance, sodium chloride, and a non-electrolyte, mannitol, as well as freshwater.
• 2.2. Responses occurred for the most part over a short crisis period preceeding establishment of new stable conditions.
• 3.3. It was shown that plasma homeostasis was not maintained in response to changing ion-osmotic and osmotic gradients.
• 4.4. Urinary osmotic and ionic concentrations were unaffected and urine production was shown to be inversely related to the external concentration.
• 5.5. It is suggested that ionic shifts between body compartments are an important aspect of ion-osmotic adaptation.

     

Renal function in migrating adult atlantic salmon,Salmo salar L.

• 1.1. Renal function in migrating adult Atlantic salmon was studied in sea-water (SW) and following abrupt transfer to fresh water (FW).
• 2.2. Urine flow rate of SW-adapted fish, 0.72 ml/kg/hr, increased 6.3-fold to 4.55 ml/kg/hr after 2–3 days in FW, later decreasing to around 1 ml/kg/hr.
• 3.3. Changes in glomerular filtration rate and ion filtration rates largely paralleled changes in urine flow. In SW-adapted salmon about 4% of excreted magnesium is filtered. Tubular magnesium secretion declined within 1 day of FW transfer.
• 4.4. During the period of maximum diuresis, urinary sodium loss is 77% of the branchial sodium uptake rate. This falls to less than 20% in FW-adapted fish.

     

In situ perfusion study of sodium transport across the nephridia of a marine invertebrate Sabella pavonia S. (Polychaeta; Annelida)

• 1.1. A suitable perfusion rate (0.110μl/min) was calculated after measuring nephridial volume and urine transit time.
• 2.2. Neither inulin nor albumin were found suitable as water movement markers for nephridia.
• 3.3. There was no net sodium flux through the nephridial wall.
• 4.4. Measurements of net nsodium flux through the nephridia showed that, in normal sea water, Sabella could not transport large amounts of sodium against a concentration gradient. A unidirectional sodium flux of about 10nequiv/min per cm crossed the nephridia.

     

Respiration in the eastern water dragon,Physignathus lesueurii (agamidae)

• 1.1. Some aspects of the gas exchange system of a diving lizard, Physignathus lesuewii were studied.
• 2.2. Breathing patterns were analysed.
• 3.3. Breathing rate increases logarithmically with temperature and Q₁₀ = 1.8. LogBR = −0.237 + 0.0256 T.
• 4.4. Gas tensions in lung air and arterial and venous blood were measured. Arterial pH declines with increasing temperature.
• 5.5. Temperature has a marked effect on oxygen affinity of the blood (ΔH = −10.1 kcal mol⁻). A Bohr effect was also noted.
• 6.6. CO₂ equilibrium curves were drawn.
• 7.7. The results are considered with a view to anticipating the efficiency of the gas exchange system of this species under conditions of variable temperature and during diving.

     

Ionic currents of an identifiable giant neurone,d-rpln,of an african giant snail (Achatina fulica férussac), measured under voltage clamping—i. inward currents

• 1.1. The ionic currents of d-RPLN (dorsal-right parietal large neurone), one of the largest neurones identified in the suboesophageal ganglia of an African giant snail (Achalina fulica Ferussac), were measured under voltage clamping.
• 2.2. The present study concerns the inward currents. The electrical properties of the d-RPLN neuromembrane were: −57.8 ± 0.84 mV for the resting membrane potential (N = 79) expressed as M ± SE,
• 3.2.57 ± 0.13 MΩ for the membrane resistance (N = 12) and 48.85 ± 2.96 nF for the membrane capacitance (N = 12).
• 4.3. The maximal peak values of the inward currents in the physiological state, obtained at the command voltage (Vc)= −10mV, were: −1.02±0.06μA at the holding voltage (Vh) = −50mV and −0.98 ± 0.06 μA. at Vh = −60 mV. The peak time values of the currents at Vc = −10 mV were about 3–4 msec.
• 5.4. The outward current blocking agents, quinine (Q), at a concentration of 1.0 mM, reduced the peak inward current values and delayed their peak time, whereas tetraethylammonium chloride (TEA) at 25.0 mM and 4-aminopyridine (4-AP) at 5.0 mM were quite ineffective. Q at 0.25 mM hardly affected the same currents at all.
• 6.5. With the perfusion of the solution containing TEA at 25 mM, 4-AP at 5 mM and Q at 0.25 mM, the outward currents were reduced so that they are much smaller; the maximal peak values of calcium current (Ica), sodium current (Ina) and total inward current (Iin), which would be the sum of Ica and Ina (all were N = 4), obtained at Vc = −10 mV, were: −0.92 ± 0.05 μA for Ica, −0.30 ± 0.03 μA for Ina and −1.27±0.17μA for Iin.
• 7.6. The ratio of the maximal peak values of Ica and Ina of the neurone was about 3 to 1.
• 8.7. Tetrodotoxin at 0.1 mM completely blocked Ina of d-RPLN, whereas this substance at the same concentration had no effect on Ica.

     

Porphyrin biosynthesis in Rhodopseudomonas palustris—IX. PBG-deaminase. Kinetic studies

• 1.1. PBG-Deaminase obtained from Rp. palustris exhibited classical Michaelis-Menten kinetics in the absence or presence of different ions.
• 2.2. Detailed kinetic studies were carried out in the presence of ammonium, phosphate and magnesium ions.
• 3.3. It has been found that the different effects observed are dependent on both the substrate and the ion concentration.

     

Adenosine triphosphate as a determinant of magnesium levels in cytoplasm

• 1.1. Levels of free magnesium ion in various tissues are reviewed.
• 2.2. Total magnesium and ATP levels in different tissues are correlated, due to the presence of MgATP.
• 3.3. Relationships between pH and temperature in poikilotherms are such as to keep constant the amount of magnesium bound by ATP.
• 4.4. ATP hydrolysis in vivo generally tends to release magnesium ions, but conditions in some muscle may be such as to minimize this release.

     

Preliminary studies on the characteristics of phenylalanine and β-methyl-glucoside transport in the tench intestine in vitro

• 1.1. The unidirectional transepithelial fluxes of L-phenylalanine, β-methyl-D-glucoside and sodium ions across emusculated sheets of tench mid-intestine were determined in flux chambers.
• 2.2. No net sodium flux was detectable, but phenylalanine was preferentially transferred from the mucosal to the serosal fluid.
• 3.3. There was also a net movement of β-methyl-glucoside towards the serosal medium, but it was much smaller than that of phenylalanine.
• 4.4. This transport was accompanied by an accumulation of each substrate from the mucosal medium into the tissue to a similar level and against a concentration gradient.
• 5.5. The poor transfer of the monosaccharide into the serosal medium could therefore be attributed to a low permeability of the baso-lateral membrane of the enterocyte for this substance.
• 6.6. The influx of L-phenylalanine and of β-methyl-d-glucoside into the epithelial cells of tench midintestine was examined by incubating slices of emusculated intestine in radioactively-labelled solutions of the substrate for 2 min.
• 7.7. The steady-state uptake was assessed after similar incubations lasting 45 min.
• 8.8. Phenylalanine influx obeys the Michaelis-Menten equation with a K_m of 2.9 mM and is dependent on the presence of sodium ions in the incubation medium.
• 9.9. β-Methyl-glucoside influx reveals the same characteristics with a K_m of 2.0 mM but a considerably lower V_max; in addition, it is inhibited by galactose.
• 10.10. The influx of both substrates is reduced by harmaline, which also inhibits the uptake of radioactive sodium by this preparation.
• 11.11. The steady-state uptake of β-methyl-glucoside is also inhibited by ouabain and by 2.4-dinitrophenol.
• 12.12. These results suggest that the mechanisms for sodium-dependent influx of monosaccharides and neutral amino-acids in the tench intestine are similar to those found in mammalian tissues.
• 13.13. The principal difference appears to involve the release of monosaccharides across the baso-lateral membrane of the enterocyte.

     

Sodium balance in adult atlantic salmon (Salmo salar L.) during migration into neutral and acid fresh water

• 1.1. In sea-water, adult salmon (S. salar) exchange an average of 12.6% of total body sodium/hr.
• 2.2. Following transfer to fresh water sodium uptake follows Michaelis-Menton kinetics. F_max = 2.40 mmol Na/1 ECF/hr, K_m = 0.26 mmol Na/1. The uptake system is fully activated immediately following transfer to fresh water.
• 3.3. Post smolts adapted to sea-water for 3 months take up sodium at only one third of the rate of adult fish following return to fresh water.
• 4.4. The concentration of prolactin in the plasma is low in sea-water adapted fish and does not rise during the first 8 hr in fresh water.
• 5.5. At pH 5 sodium uptake is reduced by almost 90%, even in the absence of aluminium, but recovers immediately on return to neutral water.
• 6.6. At pH 5 and 20 μmol Al/1 there is little further effect on sodium uptake but after 6 hr in aluminium the inhibition of sodium uptake continues after return to neutral aluminium fresh water and uptake is only 50% of normal 24 hr later.

     

The effect of eyestalk ablation on growth,haemolymph composition and gill Na+, K+-ATPase activity of Penaeus monodon juveniles

• 1.1. Eyestalk unablated and unilaterally ablated Penaeus monodon juveniles had survival rates after 5 months of 75–72.5 and 67.5–60%, respectively.
• 2.2. Unilaterally ablated shrimps had significantly higher (P < 0.05) growth rate than unablated shrimps.
• 3.3. Eyestalk-ablatement resulted in a decrease in the haemolymph sodium concentration and an increase in the potassium and calcium concentration of shrimps.
• 4.4. The osmolarity of haemolymph and total protein concentration of unablated shrimps were demonstrated to be higher than those of unilaterally ablated shrimps.
• 5.5. The eyestalk-ablated shrimps possess higher total ATPase and Na⁺,K⁺-ATPase activities in the gill than those of unablated shrimps.

     

Uptake of inorganic ions from the maternal circulation during development of the embryo of a viviparous lizard,Sphenomorphus quoyii

• 1.1. Inorganic ion content of developing follicles and of whole eggs and separated embryos and yolk sacs of the viviparous lizard, Sphenomorphus quoyii has been measured.
• 2.2. There is a net increase in calcium, sodium and potassium in whole eggs during gestation. Magnesium and phosphorus content remains constant.
• 3.3. The additional ions are incorporated into the developing embryo.
• 4.4. Calcium content of the yolk is compared with that of the fowl and other species of reptile.

     

Oxygen binding of intact coelomic cells and extracted hemoglobin of the echiuran Urechis caupo

• 1.1. The oxygen affinity of Urechis caupo coelomic cells is the same in normoxic and in hypoxic animals. There is no Bohr effect between pH 6.8 and 8.0.
• 2.2. The oxygen affinity of intact coelomic cells is the same as that of extracted, stripped hemoglobin. The oxygen binding properties of stripped hemoglobin are not affected by 1 mM ATP, IMP, or hydrogen ions between pH 6.8 and 8.0, nor do they clearly show cooperativity. The heat of oxygenation. ΔH, = −13.1 kcal/mol between 10 and 25 C.
• 3.3. Although U. caupo coelomic cell hemoglobin is tetrameric and intracellular, it apparently exhibits neither heterotropic nor homotropic interactions.

     

Anuran amphibia which are not acclimable to high salt,tolerate high plasma urea

• 1.1. The capacity of five anuran Amphibians (Bufo viridis B. regularis, Rana ridibunda, Hyla arborea and Pelobates syriacus) to acclimate to NaCl and urea solutions was investigated.
• 2.2. All species could be acclimated to relatively high concentrations of urea solutions, while only Bufo viridis and Hyla arborea could be acclimated to 500 mOsm/kg or higher NaCl solutions.
• 3.3. The plasma urea concentration in B. viridis and H. arborea was elevated to levels over 140 mmol/1.
• 4.4. The sum of plasma sodium and chloride concentrations did not increase over 400 mmol/l in any species.
• 5.5. Urine osmolality, which was normally low, increased, but never exceeded the plasma osmolality.
• 6.6. In the urea acclimation conditions, urine electrolytes diminished, similarly in all species in this study.
• 7.7. It is concluded that anuran Amphibians can tolerate high plasma urea concentrations, but only those species which can elevate it, either through retention or net synthesis, can be acclimated to high salt solutions.

     

Salt and water balance in selected crabs of madagascar

• 1.1. Salt and water regulation were studied in Cardisoma carnifex, Sesarma meinerti, Varuna litterata and Coenobita cavipes.
• 2.2. The brachyurans, Cardisoma, Sesarma and Varuna show strong osmoregulation in tap water or 150 per cent sea water, the antennary glands being ineffective in the process but able to concentrate magnesium in the urine independently of the magnesium influx from the medium.
• 3.3. The anomuran Coenobita was not studied in immersion experiments but was ssown to control its water balance on land by behavioral means.
• 4.4. When desiccated, Cardisoma can regain water against an osmotic gradient from sea water dampened sand.

     

The ionic mechanism responsible for L-glutamate excitation of leech Retzius cells

• 1.1. Intracellular recordings were made from the Retzius cells in the segmental ganglia of the leech, Hirudo medicinalis. L-Glutamate has a direct excitatory action on the neurons.
• 2.2. L-Glutamate causes an increase in the membrane conductance.
• 3.3. L-Glutamate causes conductance increase at the Retzius cell to both sodium and potassium ions but not to chloride ions.

     

Effects of angiotensin II and bladder condition on hydration behavior and water uptake in the toad,Bufo woodhousei

• 1.1. Water absorption response (WR) behavior and water weight gain were examined in hydrated toads, Bufo woodhousei, treated with angiotensin II (All) or with a control Ringer's solution. The effects of urinary bladder condition (ad lib. bladder urine or empty bladder) were examined concurrently.
• 2.2. Toads treated with All (100μg/100g body weight), spent more time in WR posture and absorbed more water than Ringer's-injected toads.
• 3.3. Toads with empty bladders maintained WR posture for longer periods of time and gained more weight than toads whose bladders were not emptied.
• 4.4. The effects of All and bladder urine on water absorption by B. woodhousei appear to be separate and additive.

     

O2-binding by the blood of the landhopper,Arcitalitrus dorrieni (Hunt) (Crustacea: Amphipoda)

• 1.1. The O₂-binding characteristics of the blood of the euterrestrial amphipod (landhopper) Arcitalitrus dorrieni have been studied.
• 2.2. The blood exhibited a low O₂ affinity, with a p₅₀ (at pH = 7.8) of 21.4 torr (10°C). Affinity decreased with an increase in temperature at constant pH (ΔH = − 79.4kJ/mol) but the Bohr factor (ΔlogP₅₀/Δ pH = −0.67) was unaffected.
• 3.3. The O₂-carrying capacity of the blood was moderate (1.51 ml/100 ml)
• 4.4. The results support the hypothesis that the blood of terrestrial amphipods is characterized by having a low affinity pigment.

     

Comparative study of hemoglobins from different Artemia populations. The influence of temperature on the oxygen equilibria

• 1.1. The P50 values of extracellular hemoglobin (Hb) of five Artemia populations from different geographical origin are affected by temperature.
• 2.2. The free oxygen binding energy is high for all the populations (ΔH between −34.7 and −56.2kj/mol).
• 3.3. A possible correlation between thermal sensitivity of Hb and the ambient temperature of the habitat must be considered very carefully.
• 4.4. The occurence of different quantities of Hb1 (αα chains) Hb2 (αβ chains) and Hb3 (ββ chains) in the different populations possibly influences thermal sensitivity.

     

Ionic regulation and salinity related changes in haemolymph protein in the semi-terrestrial beachflea Orchestia gammarellus (Pallas) (Crustacea: Amphipoda)

• 1.1. Orchestia gammarellus maintained in air and provided with food in the form of agar was found to be very tolerant of changes in the ionic content of the food and was shown to have well-developed powers of ionic regulation over the salinity range 5–40‰ at 10°C.
• 2.2. There was an inverse relationship between haemolymph protein and acclimation salinity.
• 3.3. The concentration of sodium and protein ions in the haemolymph of O. gammarellus from above high water mark (H.W.M.) was markedly different from animals collected below H.W.M. Individuals taken from above H.W.M. characteristically had low haemolymph sodium but elevated haemolymph protein concentrations.