Alkaline phosphatase from Basidiobolus haptosporosus: Comparison with alkaline phosphatases from rainbow lizard and man

• 1.1. DEAE-cellulose chromatography of mycelial alkaline phosphatase (orthophosphoric monoester phosphohydrolase, EC 3.1.3.1) from Basidiobolus haptosporosus, produced three iso-enzymes “A”, “B” and “C”.
• 2.2. Fraction “A” was further characterized and showed maximum activity at pH 10 in 0.1 M sodium carbonate-bicarbonate buffer.
• 3.3. The enzyme was stimulated by Mg²⁺, Co²⁺ and Mn²⁺ and inactivated by Zn²⁺, Cu²⁺, EDTA, citrate and tartrate.
• 4.4. Phosphate ions inhibited it competitively, phenylalanine uncompetitively and urea noncompetitively.
• 5.5. It was heat stable for 60 min at 37°C but labile above 55°C.
• 6.6. Its K_m with p-nitrophenylphosphate was 0.5 mM; its estimated molecular weight was 160,000.
• 7.7. The results are compared with the properties of alkaline phosphatases from the rainbow lizard and man and discussed in terms of a triadic association between the fungus, the lizard and man.

     

Partial purification and characterization of intestinal alkaline phosphatase of the rainbow lizard Agama agama

• 1.1. Alkaline phosphatase (orthophosphoric monoester phosphohydrolase EC 3.1.3.1.) was extracted from the small intestines of the rainbow lizard Agama agama, partially purified by DEAE-cellulose and Sephadex G-200 column chromatography and characterized.
• 2.2. The enzyme had an optimum pH at 9.5 in sodium carbonate/bicarbonate buffer: a K_m of 1.6 mM with p-nitrophenyl phosphate; a molecular weight of 132,000; was inhibited by Zn²⁺, EDTA, urea and phenylalanine; stimulated by Co²⁺, Mn²⁺ and Mg²⁺, but Ca²⁺ had little or no effect on the activity of the enzyme.
• 3.3. The inhibition by urea was non-competitive, that by phenylalanine was uncompetitive. The enzyme was heat-labile.

     

Calcium-dependent potassium conductance in the photoresponse of a nudibranch mollusk

• 1.1. The response to light of Hermissenda photoreceptors when recorded intracellularly without interference from synaptic and action potentials consisted of three phases: an early depolarization (ED) followed by hyperpolarization (dip) and subsequent depolarization (tail).
• 2.2. The ED and the dip were associated with increased membrane conductance while decreased membrane conductance was involved with the tail.
• 3.3. The dip reversal potential was − 82.1 ± 5.3 mV and its amplitude varied inversely with the log of [K⁺].
• 4.4. Perfusing with agents which block K⁺ current like 4AP, Quinine, Quinidine or injection of TEA eliminated the dip and its associated increased membrane conductance, thus further supporting the role of K⁺ conductance in producing the dip.
• 5.5. The dip was enhanced by increased [Ca²⁺]_o, reduced by decreased [Ca²⁺]_o and abolished together with its associated increased membrane conductance when perfused with either D600, Cd²⁺, Mg²⁺, Mn²⁺, or Co²⁺, which block transmembrane Ca²⁺ current.
• 6.6. The dip and its associated increased membrane conductance were abolished by intracellular injection of EGTA and enhanced by perfusion with Ruthenium red.
• 7.7. Intracellular injection of Ca²⁺ mimicked the dip: membrane conductance was increased and the cell hyperpolarized.
• 8.8. These results indicate that the increase in intracellular [Ca²⁺] is primarily responsible for the light-induced increase of K⁺ conductance during the dip. The possible source of the Ca²⁺ is, at least in part, extracellular due to activation of an inward Ca²⁺ current.

     

Phospholipase A activity of culture supernatants from Streptococcus mutans strain 6715

• 1.1. Phospholipase A activity was found in the culture broth of growing cultures of Streptococcus mutans strain 6715.
• 2.2. The amount of enzyme activity was proportional to the cell density of the cultures.
• 3.3. The enzyme had a pH optimum of 7.0 and was inactivated at temperatures greater than 45°C.
• 4.4. The enzyme was Ca²⁺-dependent, since both EDTA and EGTA were inhibitory and Ca²⁺ was stimulatory.
• 5.5. Analysis of the fatty acid products resulting from the enzyme's action on 1-palmitoyl-2-oleoyl phosphatidylcholine indicated the enzyme to be a phospholipase A₁, (EC 3.1.1.32).

     

Inhibitors of active Ca2+ uptake by fragments of the sarcoplasmic reticulum of lobster muscle

• 1.1. Vesicles from the sarcoplasmic reticulum of lobster muscle accumulate Ca²⁺ if supplied with ATP as an energy source. A search was undertaken for inhibitors of Ca²⁺ transport.
• 2.2. p-Hydroxymercuribenzoate can completely inhibit Ca²⁺ transport and ATP hydrolysis. 2–4 Dinitrophenol inhibits uptake but not hydrolysis.
• 3.3. Sr²⁺, Ba²⁺ and Zn²⁺ inhibit uptake, perhaps by competing with Ca²⁺ for a carrier.
• 4.4. The vesicles contain acetylcholinesterase. Anticholinesterases can reduce —but not abolish—Ca²⁺ uptake. Acetylcholine has no effect on the activity of the vesicles.
• 5.5. Ca²⁺ uptake is not affected by Mn²⁺, glutamate, pilocarpine, carnosine, caffeine, strophanthidin or tetraethylammonium.
• 6.6. K⁺ is needed for maximal activity of the uptake system but not for ATP hydrolysis. Apparently K⁺ enhances the coupling between the energy supply and the carrier mechanism.

     

The digestive enzymes of the pacific brown shrimp Penaeus californiensis.: I—Properties of amylase activity in the digestive tract

• 1.1. Crude extract of the whole digestive tract from the brown shrimp (P. californiensis) was investigated for digestive amylase activity.
• 2.2. Considerable amylase activity was found at pH 6.5–8.0, with optimum pH at around 7.5.
• 3.3. Optimum temperature was found between 30–40°C, similar to amylases from other crustaceans.
• 4.4. Amylase activity was highly halotolerant, having 50% maximum activity at 3 M NaCl.
• 5.5. Maximum amylase activity was found at 0.01 M NaCl.
• 6.6. Amylase activity was partially inhibited by the divalent ions Hg²⁺, Zn²⁺, Cu²⁺ and Cr²⁺.
• 7.7. Mg²⁺ and Ca²⁺ ions seemed to enhance amylase activity.

     

The participation of ionic strength and pH in the contraction induced in Vorticella by calcium and magnesium

• 1.1. Glycerinated stalks of Vorricella convallaria may be induced to contract by the application of either Ca²⁺ or Mg²⁺, and the contractions vary complexly as a function of pH.
• 2.2. The coiling that occurs in the presence of Mg²⁺ is atypical, and the effect of ionic strength is to prevent coiling.
• 3.3. The Ca²⁺ -contractions are typical of living vorticellid coiling, and those occurring at pH 6.8 and 7.0 are inhibited at low ionic strength and enhanced at high ionic strength.
• 4.4. High concentrations of Ca²⁺ abolish the ionic strength repression of contraction.

     

The possibility that Ca2+-ATPase from the plasma membrane-rich fraction of bovine parotid gland is ecto-Ca2+-dependent nucleoside triphosphatase

• 1.1. Parotid plasma membrane nonpump low-affinity Ca²⁺-ATPase, which possesses high-affinity (Ca²⁺ + Mg²⁺ )-ATPase activity, was characterized.
• 2.2. Purified Ca²⁺-ATPase hydrolyzed the nucleoside triphosphates, GTP, ITP, CTP, UTP, TTP (67–93% of ATP) and nucleoside diphosphates, ADP. GDP, IDP, CDP, TDP (12–40% of ATP) but not AMP and p-NPP.
• 3.3. The maximum activities of Ca²⁺- and (Ca²⁺ +Mg²⁺ )-ATPases were obtained in the presence of 1 mM and 0.13 μ M Ca²⁺, respectively.
• 4.4. The K_m values for Ca²⁺ in Ca²⁺- and (Ca²⁺+ Mg²⁺ )-ATPases were 0.2 mM and 22 nM. respectively.
• 5.5. The activities of both Ca²⁺- and (Ca²⁺ + Mg²⁺ )-ATPases were found in the right-side-out-vesicles obtained from the plasma membrane-rich fraction.
• 6.6. These features suggest that Ca²⁺-ATPase is an ecto-Ca²⁺-dependent nucleoside triphosphatase.

     

Ca2+-binding and protein-protein interaction domains of the sea urchin extraembryonic coat protein hyalin

• 1.1. As reported previously (Hopper and Robinson, 1990; Int. J. Biochem. 22, 1165–1170) the sea urchin extraembryonic coat protein hyalin undergoes a Ca²⁺-induced self-association into an insoluble gel (gelation) in the presence of Mg²⁺ and/or NaCl.
• 2.2. A 275 kDa peptide fragment, generated by limited tryptic digestion of hyalin, binds Ca²⁺+ but does not undergo gelation in the presence of Ca²⁺, Mg²⁺ and NaCl.
• 3.3. Comparisons between the capacities of hyalin and the 275 kDa peptide fragment to bind Ca²⁺ indicate that the latter binds 88% less Ca²⁺ than hyalin.
• 4.4. However, the presence of Ca²⁺ alone, at a concentration of 5 mM, protects the 275 kDa peptide fragment from further digestion by trypsin mimicking the effect of this cation in protecting hyalin.
• 5.5. Gel exclusion Chromatographie analyses of the 275 kDa peptide fragment, both in the presence and absence of 5 mM Ca²⁺, indicate that this cation does induce self-association of the fragment.
• 6.6. These results provide information on the organization of the functional domains on hyalin which are required for gel formation.

     

The exchange of radioactive cations by somatic and cardiac muscles of the crayfish

• 1.1. Intracellular concentrations of Na⁺, K⁺, Ca²⁺ and Mg²⁺ were measured in a somatic muscle and in the heart of the crayfish. The uptake and the efflux of Na²⁴, K⁴², Ca⁴⁵ and of Sr⁸⁹ were also measured.
• 2.2. The initial influx rates of the ions from van Harreveld's solution into resting somatic muscle (in μEq/g cell water/hr) are: K⁺ = 25; Na⁺ = 56; Ca²⁺ = 38. Similar figures were obtained for the heart muscle.
• 3.3. The calculated permeability constants (× 10⁸ cm/sec) are: P_K = 64; P_Na = 30 P_Ca = 10; P_Sr = 1·5.
• 4.4. The stimulation of the muscle fiber leads to an additional Ca²⁺ influx of about 2·8 pEq/cm² fiber surface. The additional Ca²⁺ uptake is sufficient to account for the change in potential on the membrane.
• 5.5. When muscles were immersed in Sr²⁺ solutions, no additional Sr⁸⁹ uptake was found with stimulation. However, there is a high resting Sr⁸⁹ uptake and the muscle in Sr²⁺ has a long refractory period, so a reasonable increase in Sr⁸⁹ uptake would not be detectable.
• 6.6. The results are discussed in relation to the divalent cation mechanism for generating action potentials and to the part played by Ca²⁺ in triggering contraction.

     

Comparative study of haemagglutination activity in the haemolymph of three tsetse fly Glossina species

• 1.1. Glossina morsitans morsitans (Gmm), G. palpalis gambiensis (Gpg) and G. tachinoides (Gt) haemolymph possessed multiple, glycoproteinaceous haemagglutinins (HGN).
• 2.2. Tsetse HGN bind to human erythrocyte surface glycoprotein/glycopeptide residues or, with Gmm and Gpg anti-0 activity, glycolipid moieties.
• 3.3. Variations in HGN physico-chemical properties occurred between the morsitans (Gmm) and palpalis (Gpg and Gt), and amongst the palpalis, groups of flies with respect to relative heat-lability, susceptibility to dithiothreitol reduction, resistance to γ-radiation exposure and sensitivity to urea treatment.
• 4.4. Gt and Gmm required acid and acid to neutral conditions respectively, and Ca²⁺ ion presence, for optimum agglutination activity whilst Gpg required neutral to alkaline pH and Mg²⁺ ions.
• 5.5. The findings reported here provide further information regarding HGN (lectin) properties in different species of the genus Glossina, member of the Diptera, a little studied order with respect to insect vector immunity.

     

The effects of heavy metal ions on Ca2+ ATPase extracted from fish gills

• 1.1. The gills of the freshwater fish Rutilus rutilus have been shown to contain a subcellular membrane fraction which is rich in the enzyme Ca²⁺ ATPase.
• 2.2. The enzyme is maximally activated by Ca²⁺ or Mg²⁺ ions at a concentration of about 2 mM but is not affected by Na⁺ or K⁺ ions or by ouabain.
• 3.3. In vitro the enzyme is inhibited by Cu²⁺, Pb²⁺, Zn²⁺ and Hg²⁺ ions at concentrations below 10 μM.
• 4.4. Copper ions at concentrations below 0.2 μM appear to induce the formation of additional enzyme units when applied to fish gills in vivo.

     

Influence of deionized water supplemented or not with different ions on prolactin cell activity and osmotic regulation in the goldfish

• 1.1. Goldfish were kept in deionized water (DW), DW + Na⁺ (0.35 mM), DW + K⁺ (0.05 mM), DW + Ca²⁺ (2mM) and DW + Mg²⁺ (0.2 mM). In Ca-free environments, prolactin cells appear unaffected. Stimulated calcium-sensitive cells (pars intermedia) may elaborate a hypercalcemic factor.
• 2.2. Fecal excretion, reduced in all groups, remains noticeable in DW + Ca²⁺
• 3.3. Ionic losses, very low in all groups, are minimal in DW. Supplementation with K⁺ increases Na⁺ loss.
• 4.4. Plasma Na⁺ Ca²⁺, and osmolarity decrease in DW, and still more in DW + K⁺. Ca²⁺' and Mg²⁺ partly suppress hyponatremia.
• 5.5. In goldfish kept in DW and subsequently in DW + Ca²⁺, calcemia increases.

     

Bioelectrical potentials across the mantle epithelium of Achatina fulica

• 1.1. The shell side of the mantle of Achatina fulica is several millivolts positive to the blood side in vitro.
• 2.2. The electrical potential does not depend on Na⁺, Ca²⁺, Mg²⁺, K⁺ or HCO₃⁻ but requires the presence of chloride on the shell side.
• 3.3. The potential difference and short-circuit current ranged from 3.0 to 30.0 mV and 15.0 to 75 μA/cm² with averages at 10m V and 50 μA/cm² respectively.
• 4.4. The electrical gradient is reduced by 2,4-dinitrophenol, thiocyanate and furosemide but not by ouabain, CO₂ or acetozolamide.
• 5.5. It is suggested that the nature and mechanism of electrogenesis in Achatina parallels that of the Helix mantle.

     

Synaptic transmission at high pressure: Effects of [Ca2+]o

• 1.1. The effects of pressure on synaptic currents were examined in crayfish abdominal muscles.
• 2.2. Helium pressure (10.1 MPa) considerably decreased extracellulariy-recorded excitatory junctional potentials associated with increased short-term facilitation.
• 3.3. These effects could be mimicked by a reduction of [Ca²⁺]_o, and partially compensated by an increase in [Ca²⁺]_o.
• 4.4. Pressure also reduced the amplitude of the extracellular nerve terminal potentials (ENTP) by up to 25%, and significantly increased synaptic delay in a [Ca²⁺]_o-dependent manner.
• 5.5. The interaction between compression and various [Ca²⁺]_o were analysed in terms of an existing model of transmitter release. The results were consistent with the hypothesis that high pressure decreases the maximal Ca²⁺ influx into nerve terminals.
• 6.6. The decreased ENTP and increased synaptic delay suggest that additional processes may be involved in pressure effects on synaptic transmission.

     

Crayfish retinular cells: Influence of extracellular sodium and calcium upon receptor potential

• 1.1. In crayfish, light stimulation of the retinular cells induces a depolarizing receptor potential.
• 2.2. Experiments were designed to determine the role of Na⁺ and Ca²⁺ on receptor potential during dark And light states.
• 3.3. Depolarization depends on Na⁺ and Ca²⁺ availability to the retinular cell.
• 4.4. Repolarization velocity and response duration depend on extracellular Ca²⁺ availability.
• 5.5. Light adaptation increases receptor potential dependence on calcium and sodium ions.
• 6.6. We analyse these results with respect to other invertebrate photoreceptors.

     

Erythrocyte membrane anion-sensitive Mg2+-ATPase—Identity with monovalent cation sensitive Ca2+-Mg2+-ATPase

• 1.1. Activation of Mg²⁺-ATPase of rabbit and guinea-pig erythrocyte membrane by bicarbonate or chloride could be completely abolished by ethylene-glycol-bis-(β-aminoethylether)-N,N'-tetraacetic acid. The anion stimulation was actually an activation of contaminating Ca²⁺ -stimulated Mg²⁺-ATPase by monovalent cations associated with the anions.
• 2.2. Guinea-pig red cell Ca²⁺-Mg²⁺-ATPase could be activated by both sodium and potassium while the rabbit enzyme was sensitive only to sodium. The concentrations of monovalent cations for half-maximal stimulation of Ca²⁺-Mg²⁺-ATPase are: k_na+ = 40.8 mM, k_k+ = 12.2 mM (guinea-pig); K_Na+ = 13.3mM (rabbit).
• 3.3. Potassium enhanced activation of rabbit erythrocyte membrane Ca²⁺-Mg²⁺-ATPase by red cell Ca²⁺-Mg²⁺-ATPase activator protein. With the guinea pig enzyme, neither sodium nor potassium enhanced activator stimulation of Ca²⁺-Mg²⁺-ATPase.
• 4.4. Ca²⁺-Mg²⁺-ATPase of aged rabbit erythrocyte membrane responded to sodium but not to activator protein.
• 5.5. Triton X-100 solubilized rabbit erythrocyte membrane Ca²⁺-Mg²⁺-ATPase has an apparent molecular weight of 371,000. It did not respond to the activator.
• 6.6. One major and three minor proteins, visualized by SDS-polyacrylamide gel electrophoresis, were extracted from rabbit erythrocyte membrane by 50 μM chlorpromazine.

     

A comparison of the effect of alternating current electronarcosis,rectified current electronarcosis and chemical anaesthesia on the blood physiology of the freshwater bream Oreochromis mossambicus (peters)—III. The effect on the plasma electrolytes Ca2+, Na+ and K+ and on the osmotic pressure of the blood

• 1.1. The effects of alternating current electronarcosis, rectified current electronarcosis and chemical anaesthesia (benzocaine hydrochloride) on plasma electrolytes and on the osmotic pressure of the blood of the freshwater bream Oreochromis mossambicus were evaluated.
• 2.2. Plasma Ca²⁺, Na⁺ and K⁺ concentrations and the osmotic pressure of the blood were monitored over a period of 7 days.
• 3.3. The results showed that the different electrolytes respond differently to the different techniques.
• 4.4. Chemical anaesthesia exhibited the least effects on the parameters studied.

     

Ionic selectivity of excitable neurone membrane: Are there any separate potential-dependent channels for Na+,Ca2+, Mg2+?

• 1.1. The dependence of the action potential overshoot and inward currents on ionic concentration has been studied on both intact and completely isolated neurones of Limnaea stagnalis.
• 2.2. The dependence of action potential on ion concentration in the medium is similar to that of intact ones.
• 3.3. The overshoot dependence on the log of Ca²⁺ Mg²⁺ and Na⁺ concentration in the medium is linear. This and the character of inward current dependence on ion concentration allow us to suppose the existence of separate channels for Ca, Na and Mg ions along which they move under the action of their own electrochemical potentials. Conductance of these channels depends slightly on ionic concentration in the medium.
• 4.4. If the medium contains both Ca and Sr ions the overshoot dependence on the log of their concentration is of a non-linear character. This indicates that both these kinds of ions pass through the same channel.
• 5.5. A physiological role of different ion mechanisms of action potential generation is discussed.

     

High-affinity Ca2+-Mg2+-ATPase in kidney of euryhaline Gillichthys mirabilis: kinetics,subcellular distribution and effects of salinity

• 1.1. Two components of Ca²⁺-Mg²⁺-ATPase are observed in kidneys of G. mirabilis. The high-affinity component has a K_0.5Ca of 0.23μM; the low-affinity activity K_0.5Ca is 90–110μM. The high-affinity activity requires Mg²⁺, displays Michaelis-Menten kinetics, has peak activity at 1.2 μM Ca²⁺, and is insensitive to ouabain and Na⁺ azide.
• 2.2. In subcellular fractions, the high-affinity component segregates with Na⁺-K⁺-ATPase and is localized predominantly in BLM. The low-affinity component is broadly distributed among membranous organelles, including brush border, and may be equivalent to alkaline phosphatase.
• 3.3. Specific activity of the high-affinity Ca²⁺-Mg²⁺-ATPase is modestly increased following adaptation of fish to FW, but total renal high-affinity activity is greatest in the hypertrophied kidneys of FW-adapted fish and is least in kidneys of fish adapted to 200% SW.
• 4.4. High-affinity Ca²⁺-Mg²⁺-ATPase may be associated with active Ca²⁺ transport or with regulation of intracellular Ca²⁺ concentration of tubular cells.