The effects of extremely alkaline water (pH 9·5) on rainbow trout gill function and morphology

Rainbow trout that were held under control conditions, at pH8·0, in moderately hard Hamilton tap water, had Cl^? and Na⁺ influx rates (J^CLin and J^Na, respectively) of 270 and 300 μmol kg^?1 h^?1, respectively. Exposure to pH 9·5 water led to an immediate 67% decline in J^CL_in and a 45% reduction in J^Na_in at 0–1 h. Influx rates declined further and by 4–5 h the net decreases in both J^CL_in and J^Na_in approximated 80%. By 24 h J^CL_in had recovered to rates not significantly different from those at pH 8·0; while J^Na_in only partially recovered and remained about 50% lower than control measurements through 72 h. The complete recovery of J^CL_in and partial recovery of J^Na_in may have been related to a fourfold greater branchial chloride cell (CC) fractional surface area observed in rainbow trout exposed to pH 9·5 for 72 h. Ammonia excretion (J_Amm) was about 170 μmol N kg^?1 h^?1 at pH 8·0 but was initially reduced by 90% over the first hour of high pH exposure. J_Amm rapidly recovered and by 24 h it had returned to pre-exposure levels. This recovery tended to parallel the partial recovery of J^Na_in. However, subsequent addition of amiloride (10^?4M) to the water at 75 h led to no change in J_Amm, despite a 50% reduction in J^Na_in. Thus, it does not appear that there is a linkage between Na⁺ influx and the recovery of ammonia excretion under highly alkaline conditions.     

Kinetics of chloride transport in the cyanobacterium Synechococcus R-2 (Anacystis nidulans, S. leopoliensis) PCC 7942

The kinetics of the light-driven Cl^? uptake pump of Synechococcus R-2 (PCC 7942) were investigated. The kinetics of Cl^? uptake were measured in BG-11 medium (pH_o, 7·5; [K⁺]_o, 0·35 mol m^?3; [Na⁺]_o, 18 mol m^?3; [Cl^?]_o, 0·508 mol m^?3) or modified media based on the above. Net³⁶Cl^? fluxes (?Cl^?_o,i) followed Michaelis-Menten kinetics and were stimulated by Na⁺ [18 mol m^?3 Na⁺ BG-11 ?Cl^?_max= 3·29±0·60 (49) nmol m^?2 s^?1 versus Na⁺-free BG-11 ?Cl^?_max= 1·02±0·13 (54) nmol m^?2 s^?1] but the Km was not significantly different in the presence or absence of Na⁺ at pH_o 10; the Km was lower, but not affected by the presence or absence of Na⁺ [Km = 22·3±3·54 (20) mmol m^?3]. Na⁺ is a non-competitive activator of net ?Cl^?_o,i. High [K⁺]_o (18 mol m^?3) did not stimulate net ?Cl^?_o,i or change the Km in Na⁺-free medium. High [K⁺]_o (18 mol m^?3) added to Na⁺ BG-11 medium decreased net ?Cl^?_o,i [18 mol m^?3K⁺ BG-11; ?Cl^?_max= 2·50±0·32 (20) nmol m^?2 s^?1 versus BG-11 medium; ?Cl^?_max= 3·35±0·56 (20) nmol m^?2 s^?1] but did not affect the Km 55·8±8·100 (40) mmol m^?3]. Na⁺-stimulation of net ?Cl^?_o,i followed Michaelis-Menten kinetics up to 2–5 mol m^?3 [Na⁺]_o but higher concentrations were inhibitory. The Km for Na⁺-stimulation of net ?Cl^?_o,i [K_1/2(Na⁺)] was different at 47 mmol m^?3 [Cl^?]_o (K_1/2[Na⁺] = 123±27 (37) mmol m^?3]. Li⁺ was only about one-third as effective as Na⁺ in stimulating Cl^? uptake but the activation constant was similar [K_1/2(Li⁺) = 88±46 (16) mmol m^?3]. Br^? was a competitive inhibitor of Cl^? uptake. The inhibition constant (Ki) was not significantly different in the presence and absence of Na⁺. The overall Ki was 297±23 (45) mmol m^?3. The discrimination ratio of Cl^? over Br^? (δCl^?/δBr^?) was 6·38±0·92 (df = 147). Synechococcus has a single Na⁺-stimulated Cl^? pump because the Km of the Cl^? transporter and its discrimination between Cl^? and Br^? are not significantly different in the presence and absence of Na⁺. The Cl^? pump is probably driven by ATP.     

Modelling the inhibitory effect of copper sulfate on the growth of Penicillium expansum and Botrytis cinerea

Aims: This study aimed to investigate the effect of copper sulfate (from 0 to 8 mmol kg^?1) on radial growth rate and lag time of two moulds responsible for vine grapes spoilage: Penicillium expansum strain 25·03 and Botrytis cinerea, strains BC1 and BC2. Methods and results: A new model was developed to describe tailing and shoulders in the inhibition curves. Because of tailing, the minimum inhibitory concentration (MIC), was not defined as the concentration at which no growth was observed, but as the concentration at which the lag time was infinite. The concentrations at which μ = μ_opt/2, (Cu₅₀), were in the range of 2·2–2·6 mmol kg^?1. Radial growth rate of P. expansum and the reciprocal of the lag time were linearly correlated (r = 0·84). In contrast, in the range 0–4 mmol kg^?1, an inhibition of growth of B. cinerea was observed whereas germination remained unaffected (i.e. the lag time was constant). In the range 4–8 mmol kg^?1, the radial growth rate of B. cinerea was almost constant (c. 1 mm day^?1), but germination was inhibited (i.e. the lag time was increased). Conclusions: The MIC values were 4·7 mmol kg^?1 for P. expansum, 8·2 and 7·3 mmol kg^?1 for B. cinerea strain BC1 and BC2, respectively, demonstrating that some isolates of these moulds are resistant to copper. Significance and Impact of the Study: Copper concentrations at 4 mmol kg^?1 would be sufficient to control the development of these isolates, but the toxicity of copper should be extended to other isolates and evaluated in vineyards.     

Characterization of sodium and proton flows in sub-bacterial particles of Halobacterium halobium in terms of nonequilibrium thermodynamics

A thermodynamic characterization of the Na⁺-H⁺ exchange system in Halobacterium halobium was carried out by evaluating the relevant phenomenological parameters derived from potential-jump measurements. The experiments were performed with sub-bacterial particles devoid of the purple membrane, in 1 M NaCl, 2 M KCl, and at pH 6.5–7.0. Jumps in either pH or pNa were brought about in the external medium, at zero electric potential difference across the membrane, and the resulting relaxation kinetics of protons and sodium flows were measured. It was found that the relaxation kinetics of the proton flow caused by a pH-jump follow a single exponential decay, and that the relaxation kinetics of both the proton and the sodium flows caused by a pNa-jump also follow single exponential decay patterns. In addition, it was found that the decay constants for the proton flow caused by a pH-jump and a pNa-jump have the same numerical value. The physical meaning of the decay constants has been elucidated in terms of the phenomenological coefficients (mobilities) and the buffering capacities of the system. The phenomenological coefficients for the Na⁺-H⁺ flows were determined as differential quantities. The value obtained for the total proton permeability through the particle membrane via all available channels, $\text{L}{}_{\mathrm{<mtext>H</mtext>}}\text{= (}\text{?J}{}_{\mathrm{<mtext>H\; +</mtext>}}\text{?Δ}\text{pH}\text{)}{}_{\mathrm{<mtext>\Delta \psi ,\Delta </mtext><mtext>pNa</mtext>}}$, was in the range of 850–1150 nmol H⁺·(mg protein)^?1·h^?1·(pH unit)^?1 for four different preparations; for the total Na⁺ permeability, $\text{L}{}_{\mathrm{<mtext>Na</mtext>}}\text{= (}\text{?J}{}_{\mathrm{<mtext>Na</mtext>}}{}^{\mathrm{+}}\text{?Δ}\text{pNa}\text{)}{}_{\mathrm{<mtext>\Delta \psi ,\Delta </mtext><mtext>pH</mtext>}}$, it was 1620–2500 nmol Na⁺·(mg protein)^?1·h^?1·(pNa unit)^?1; and for the proton ‘cross-permeability’, $\text{L}{}_{\mathrm{<mtext>HNa</mtext>}}\text{= (}\text{?J}{}_{\mathrm{<mtext>H</mtext>}}{}^{\mathrm{+}}\text{?Δ}\text{pNa}\text{)}{}_{\mathrm{<mtext>\Delta \psi ,\Delta </mtext><mtext>pH</mtext>}}$, it was 220–580 nmol H⁺·(mg protein)^?1·h^?1·(pNa unit)^?1, for different preparations. From the above phenomenological parameters, the following quantities have been calculated: the degree of coupling (q), the maximal efficiency of Na⁺-H⁺ exchange (η_max), the flow and force efficacies (?) of the above exchange, and the admissible range for the values of the molecular stoichiometry parameter (r). We found q ? 0.4; η_max ? 5%; 0.36 ? r ? 2; ?_JNa⁺ ? 1.3 · 10⁵μmol · (RT unit)^?1 at J_Na = 1 μmolNa⁺ · (mgprotein)^?1 · h^?1; and ?_ΔpNa ? 5 · 10⁴ ΔpNa · (mg protein) · h · (RT unit)^?1 at ΔpNa = 1 unit, for different preparations.     

Na+ uptake and extrusion in the cyanobacterium SynechocystisPCC6714 in response to hypersaline treatment. Evidence for transient changes in plasmalemma Na+ permeability

The kinetics of uptake and loss of Na⁺ have been studied using radioisotopic tracer techniques in cells of the cyanobacterium Synechocystis PCC6714 exposed to hyperosmotic stress. Cells transferred from a fresh-water-based medium to NaCl at 300–1000 mmol·dm⁻³ showed net Na⁺ uptake during the first 2 min following transfer, with the intracellular Na⁺ level at 2 min increasing as a direct function of the external NaCl concentration. Further incubation of cells in low-level hypersaline media (350–500 mmol · dm⁻³ NaCl) led to a marked reduction in cell Na⁺ within 20 min, indicating an efficient active Na⁺ extrusion system. In contrast, cells maintained in more extreme hypersaline media showed little (750 mmol · dm⁻³ NaCl) or no (1000 mmol · dm⁻³ NaCl) net Na⁺ extrusion following upshock. Cells grown in a saline medium (with NaCl at 500 mmol · dm⁻³ showed a greatly reduced net Na⁺ uptake after 2 min in media containing higher levels of NaCl. However, net Na⁺ uptake was also observed when these cells were downshocked to media containing 50–200 mmol · dm⁻³ NaCl. This is the first demonstration of downshock-induced Na⁺ accumulation in a microbial cell. Time-courses for Na⁺ extrusion in cells downshocked from 500 mmol · dm⁻³ to 100 mmol · dm⁻³ NaCl were similar to those for cells upshocked from freshwater to 500 mmol · dm⁻³ NaCl, requiring approximately 30 min to reach their lowest values. Net Na⁺ extrusion in upshocked cells was found to be markedly sensitive to the external K⁺ concentration, with limited net Na⁺ extrusion in the absence of external K⁺ and maximal reductions in cell Na⁺ in media containing K⁺ at 1–10 mmol · dm⁻³. Temperature was also shown to affect uptake and loss of cell Na⁺ during upshock: cells maintained at 5°C showed no capacity for net Na⁺ extrusion, while higher temperatures (up to 35°C) led to a progressive reduction in the amount of cell Na⁺ at 2 min following upshock and also in the rate of net Na⁺ extrusion after this time.     

Fine structure and motility of spermatozoa and composition of the seminal plasma in the perch

The fine structure and motility of spermatozoa and the composition of the seminal plasma of the perch Perca fluviatilis are investigated by electron microscopy, computer assisted cell motility analysis (CMA) and biochemical methods. The spermatozoon is asymmetrical as the flagellum inserts mediolateral on the nucleus. It lacks an acrosome, has an ovoid head and a small midpiece with one mitochondrion. Sperm motility–initiated in distilled water (10° C)–is characterized as follows: 85·0 ± 2·7% of the spermatozoa are motile, the main swimming type (10 ± 1 s after motility initiation) is the linear motion (61·4 ± 24·4%) and the average swimming velocity is 122·4 ± 21·9 μm s^–1. When motility is initiated with NaCl, glucose or sucrose solutions of 100 mosmol kg^–1 the percentage of motile spermatozoa and the swimming types are similar as in water, but the swimming velocity (174·0 ± 22·3 μm s^–1) is significantly higher. Motility is inhibited by high osmolality of the diluent: when increasing the osmolality of the saline solutions to 350 mosmol kg^–1 sperm motility is totally suppressed while potassium (10–40 mmol 1^–1) does not affect motility parameters. pH optimum for sperm motility is between pH 7·0 and 8·5. The seminal fluid contains 124·01 ± 21·68 mmol 1^–1 sodium, 10·22 ± 1·11 mmol 1^–1 potassium and 0·72 ± 0·26 mmol 1^–1 calcium. pH is 8·25 ± 0·09, and osmolality 283·90 ± 37·19 mosmol kg^–1. The following organic components were determined: monosaccharides (glucose 63 ± 19 μmol 1^–1, fructose 54 ± 28 μmol 1^–1, galactose 59 ± 25 μmol 1^–1), lipids (cholesterol 5·51 ± 6·42 μmol 1^–1, triglycerides 72 ± l00 μmol l^–1, cholesteryloleate 15–150 μmol 1^–1, phosphatidylcholine 26 · 31 μmol 1^–1, glycolipids 1–10 mg 100 m1^–1), lactate 108 ± 99 μmol 1^–1, hydroxybutyrate 102 ± 99 nmol 1^–1, choline 59 ± 159 μmol 1^–1, protein 344·75 ± 59·06 mg 100m1^–1, enzymes (β-d -glucuronidase l.4 ± 0.7 μmol h^–1 100 ml^–1, protease (caseolytic activity) 1·0 ± 0·6 μmol h^–1 100 ml^–1, alkaline phosphatase 2520·0 ± 861·0 μmol h^–1 100 ml^–1, acid phosphatase 44.0 ± 16.0 μmol h^–1 100 ml^–1, glucose-6-phosphate dehydrogenase 38·9 ± 86·9 μmol h^–1 100 ml^–1, lactate dehydrogenase 134·4 ± 69·6 μmol h^–1 100 ml^–1, butyrylcholine esterase 0·014 ± 0·010 μmol h^–1 100 ml^–1, adenosine triphosphatase 562·8 ± 665·4 μmol h ^–1 100 ml^–1).     

Effects of natural and artificially induced reduction on soil solution phosphorus in rice soils

The effect of natural and artificial reduction on P extractability from soils used for rice production and the relation of these values to response to fertilizer P were investigated. Soil solution P increased from a mean of 3.8 mg P·kg^?1 soil for naturally oxidized slurries of 28 soils to 19.8mg P·kg^?1 when the soils were naturally reduced. The mean values were further increased to 40.8 and 45.3 mg·kg^?1 when the soils were reduced with 0.1M Na₂S₂O₄ and 0.2M Na₂S₂O₄, respectively. These P-values compare with 18.2 mg kg^?1 when the dry soils were extracted with Bray No. 1 extractant. When the yields of rice were correlated with solution and extracted P, the R²'s for the quadratic relationships were 0.40^**, 0.31^*, 0.34^**, 0.30^*, and 0.55^** for the naturally oxidized, the naturally reduced, 0.1M Na₂S₂O₄, 0.2M Na₂S₂O₄ and Bray No. 1, respectively. The Cate-Nelson calculation confirmed the superiority of the weak acid Bray extractant and the critical value of 8.6 mg P·kg^?1 soil needed for satisfactory yields of rice. There was little response of rice to added fertilizer P on soils with solution P-values greater than 0.09 mg P·l^?1 in oxygenated soil slurries. Some soils with solution P of this order and high amounts of Bray No. 1 extractable P still gave modest responses to fertilizer P. Although natural or chemically induced reduction increased soil solution P, it did not improve prediction of yield response of rice to added fertilizer P.     

Sperm motility and seminal fluid composition in the burbot, Lota lota

Sperm motility and composition of the seminal fluid in Lota lota were investigated. Fives after motility initiation, 88.2 ± 12.4% of the spermatozoa were motile, their mean average path swimming velocity was 61.6 ± 16.3 μm s^?1 and their principal swimming type the linear motion (77.4 ± 20.9%). In distilled water the rate of motile spermatozoa decreased to 0% in 40s. In 25–50 mosmol kg^?1 electrolyte (NaCl) or non-electrolyte (glucose, sucrose) solutions, motility was prolonged for 10s and these solutions can therefore increase the efficiency of artificial fertilization when used for sperm motility activation. When semen was diluted in electrolyte or non-electrolyte solutions with osmolalities higher than 50 mosmol kg^?1, sperm motility rates and swimming velocities decreased, and at osmolalities of 400 mosmol kg^?1 motility was completely suppressed. In the seminal fluid with an osmolality of 290.08 ± 45.22 mosmol kg^?1, sodium levels of 139.86 ± 23.79 mmol × 1^?1, potassium levels of 11.59 ± 2.45 mmol × 1^?1 and calcium levels of 0.20 ± 0.08 mmol × 1^?1, sperm motility was inhibited. Under in vitro conditions, artificial saline solutions resembling the seminal plasma composition and 400 mosmol kg^?1 NaCl or glucose solutions were useful as motility inhibiting solutions for predilution of semen. Sperm motility was not affected by pH 7.5–9.0, but at pH 6 the motility rate and the swimming velocity were reduced; seminal fluid pH was 8.47 ± 0.02. Therefore buffering of the artificial saline solutions can provide more stabile conditions for semen during storage and activation. Temperature optimum of semen was between 2 and 5°C. At higher temperatures semen became spontaneously motile. Therefore, controlled temperature conditions are an important factor for handling of semen. The qualitative, organical composition of seminal fluid was similar as in other fresh water teleosts.     

Sulphydryl groups of (Na+ + K+)-ATPase from rectal glands of Squalus acanthias: Detection of ligand-induced conformational changes

1. Modification of the Class II sulphydryl groups on the (Na⁺ + K⁺)-ATPase from rectal glands of Squalus acanthias with N-ethylmaleimide has been used to detect conformational changes in the protein. The rates of inactivation of the enzyme and the incorporation of N-ethylmaleimide depend on the ligands present in the incubation medium. With 150 mM K⁺ the rate of inactivation is largest (k₁ = 1.73 mM^?1 · min^?1) and four SH groups per α-subunit are modified. The rate of inactivation in the presence of 150 mM Na⁺ is smaller (k₁ = 1.08 mM^?1 · min^-1) but the incorporation of N-ethylmaleimide is the same as with K⁺. 2. ATP in micromolar concentrations protects the Class II groups in the presence of Na⁺ (k₁ = 0.08 mM^?1 · min^?1 at saturating ATP) and the incorporation id drastically reduced. ATP in millimolar concentrations protects the Class II groups partially in the presence of K⁺ (k₁ = 1.08 mM^?1 · min^?1) and three SH groups are labelled per α subunit. 3. The K⁺ -dependent phosphatase is inhibited in parallel to the (Na⁺ + K⁺)-ATPase under all conditions, and the ligand-dependent incorporation of N-ethylmaleimide was on the α-subunit only. 4. It is shown that the difference between the Na⁺ and K⁺ conformations sensed with N-ethylmaleimide depends on the pH of the incubation medium. At pH 6 there is a very small difference between the rates of inactivation in the presence of Na⁺ and K⁺, but at higher pH the difference increases. It is also shown that the rate of inactivation has a minimum at pH 6.9, which suggests that the conformation of the enzyme changes with pH. 5. Modification of the Class III groups with N-ethylmaleimide-whereby the enzyme activity is reduced from about 16% to zero-shows that these groups are also sensitive to conformational changes. As with the Class II groups, ATP in micromolar concentrations protects in the presence of Na⁺ relative to Na⁺ or K⁺ alone. ATP in millimolar concentrations with K⁺ present increases the rate of inactivation relative to K⁺ alone, in contrast to the effect on the Class II groups. 6. Modification of the Class II groups with a maleimide spin label shows a difference between Class II groups labelled in the presence of Na⁺ (or K⁺) and Class II groups labelled in the presence of K + ATP, in agreement with the difference in incorporation of N-ethylmaleimide. The spectra suggest that the SH group protected by ATP in the presence of K⁺ is buried in the protein. 7. The results suggest that at least four different conformations of the (Na⁺ + K⁺)-ATPase can be sensed with N-ethylmaleimide: (i) a Na⁺ form of the enzyme with ATP bound to a high-affinity site (E₁-Na-ATP); (ii) a Na⁺ form without ATP bound (E₁-Na); (iii) a K⁺ form without ATP bound (E₂-K); and (iv) an enzyme form with ATP bound to a low-affinity site in the presence of K⁺, probably and E₁-K-ATP form.     

An ultramicro method for analysis of lithium and other biologically important cations

A new method for Li⁺ analysis by flameless atomic absorption spectroscopy is several orders of magnitude more sensitive than previous methods. Li⁺ quantities as small as 1·10^?12 mol, or Li⁺ concentrations as low as 1·10^?8 M, can be determined with a coefficient of variation of 2–4%. The same technique can determine approx. 1·10^?14 mol of Ca²⁺ and Mg²⁺, and approx. 1·10^?13 mol of Na⁺ and K⁺.     

Plant regeneration of the arsenic hyperaccumulator <Emphasis Type="Italic">Pteris vittata</Emphasis> L<Emphasis Type="Italic">.</Emphasis> from spores and identification of its tolerance and accumulation of arsenic and copper

An in vitro plant regeneration system was established from the spores of Pteris vittata and identification of its tolerance, and accumulation of gametophytes and callous, to arsenic (As) and copper (Cu) was investigated. The highest frequency (100%) of callus formation was achieved from gametophyte explants treated with 0.5 mg l^?1 6-benzylaminopurine (6-BA) + 0.5 mg l^?1 gibberellin acid (GA). Furthermore, sporophytes were differentiated from the callus tissue derived from gametophyte explants on MS medium supplemented with 0.5 mg l^?1 6-BA, 0.5–1.0 mg l^?1 GA and additional 300 mg l^?1 lactalbumin hydrolysate (LH) for 4 weeks. The optimum combination of ½ MS + 1.0 mg l^?1 GA + 0.5 mg l^?1 6-BA + 300 mg l^?1 LH promoted sporophyte formation on 75 ± 10% of the callus. Every callus derived from gametophyte explants could achieve 3–4 sporophytes. The in vitro growth of gametophyte and callus was accelerated in the medium containing Na₃AsO₄ lower than 0.5 mM, but this growth was inhibited with 2 mM Na₃AsO₄. And with the increase of Na₃AsO₄ in the culture medium from 0 to 2 mM, the As accumulation in gametophytes and callus increased and achieved a level of 763.3 and 315.4 mg kg^?1, respectively. Gametophytes and calluses transplanted to culture medium, supplemented with different concentrations of CuSO₄, are similar to those in Na₃AsO₄, and the Cu accumulation in gametophytes could achieve 7,940 mg kg^?1 when gametophytes were subcultured in medium containing 3 mM CuSO₄. These results suggested that the high efficiency propagation system could be a useful and rapid means to identify other heavy metal tolerance and accumulation. Further, the regeneration ability of callus made it possible for genetic transformation of this fern.     

Interactive effects of cadmium and carbon nanotubes on the growth and metal accumulation in a halophyte Spartina alterniflora (Poaceae)

A study quantifying the interactive effects of cadmium (Cd) and carbon nanotubes (CNTs) on plant growth and Cd accumulation of pot-cultured Spartina alterniflora was conducted. The experiment consisted of two Cd levels (50, 200 mg kg^?1) as well as two CNTs levels (800, 2,400 mg kg^?1). As expected, CNTs alleviated higher Cd stress (200 mg kg^?1) due to restored shoot growth reduction, retrieved water content and resumed plant height. Furthermore, CNTs mitigated the deleterious effects of Cd stress through improving K⁺ and Ca²⁺ contents, while reducing Na⁺/K⁺ and Na⁺/Ca²⁺ ratios, regardless of the level of Cd stress. The proline contents in combined Cd and CNTs treatments were lower than Cd alone, suggesting that CNTs could reduce production of organic solutes under Cd stress. The results also showed higher Cd accumulation in roots than shoots, and both were improved by CNTs, except inhibition in roots under higher Cd stress (200 mg kg^?1). It appears that CNTs may not significantly affect negative Cd effects on growth of S. alterniflora, but improve total Cd accumulation under lower Cd stress (50 mg kg^?1). However, under higher Cd stress (200 mg kg^?1), CNTs restored the reduced plant growth, improved and reduced Cd accumulation in shoots and roots, respectively. Therefore, the effects of CNTs on plant growth and Cd accumulation are different, and levels of Cd stress should be considered when evaluating the combined application of CNTs and S. alterniflora on phytoremediation of Cd pollution.     

Comparative coelomic fluid composition of sterlet sturgeon Acipenser ruthenus Linnaeus, 1758, Siberian sturgeon Acipenser baerii Brandt, 1869, and Russian sturgeon Acipenser gueldenstaedtii Brandt & Ratzeburg, 1833

The objectives of this study were to compare the physicochemical properties of coelomic fluid (CF) in three sturgeon species, sterlet sturgeon Acipenser ruthenus (age 5–8 years), Siberian sturgeon Acipenser baerii (age 15–20 years), and Russian sturgeon Acipenser gueldenstaedtii (age 13–18 years). For the study, CF was collected by plastic pipette from the eggs of mature female sterlet sturgeon (N = 10), Siberian sturgeon (N = 7) and Russian sturgeon (N = 4); osmolality, pH, ionic composition (Na⁺, K⁺, Ca²⁺, Mg²⁺, Cl^?), glucose, cholesterol and total protein of the CF were then analyzed. Mean concentration of K⁺ (4.4–6.11 mmol/L), Cl^? (89.8–98.0 mmol/L), Ca²⁺ (0.87–0.96 mmol/L), Mg²⁺ (0.57–0.67 mmol/L), cholesterol (0.13–0.16 mmol/L), total protein (2.41–3.57 g/L), pH (7.92–7.98), and osmolality (190–213 mOsm/kg) of CF were not significantly different among these three species. However, the mean concentration of Na⁺ was significantly lower in sterlet sturgeon (104.6 ± 7.7 mmol/L; p < .05) than in the Siberian (126.4 ± 6.2) and Russian (123.0 ± 5.9) sturgeon. For these three species, Na⁺, K⁺, Cl^?, and Mg²⁺ were the dominating ions; several significant correlations were observed among these ions and other physiochemical properties of CF. This is the first report on the ionic and biochemical composition of the CF of sterlet, Siberian and Russian sturgeon, which can be used as a reference point for further development of artificial media for the short‐term storage of unfertilized sturgeon eggs as well as for the standardization of the fertilization protocol for these species in controlled reproduction.     

Subcellular Localization and Kinetic Characterization of a Gill (Na+, K+)-ATPase from the Giant Freshwater Prawn Macrobrachium rosenbergii

The stimulation by Mg²⁺, Na⁺, K⁺, NH₄ ⁺, and ATP of (Na⁺, K⁺)-ATPase activity in a gill microsomal fraction from the freshwater prawn Macrobrachium rosenbergii was examined. Immunofluorescence labeling revealed that the (Na⁺, K⁺)-ATPase α-subunit is distributed predominantly within the intralamellar septum, while Western blotting revealed a single α-subunit isoform of about 108 kDa M _r. Under saturating Mg²⁺, Na⁺, and K⁺ concentrations, the enzyme hydrolyzed ATP, obeying cooperative kinetics with V _M = 115.0 ± 2.3 U mg^?1, K _0.5 = 0.10 ± 0.01 mmol L^?1. Stimulation by Na⁺ (V _M = 110.0 ± 3.3 U mg^?1, K _0.5 = 1.30 ± 0.03 mmol L^?1), Mg²⁺ (V _M = 115.0 ± 4.6 U mg^?1, K _0.5 = 0.96 ± 0.03 mmol L^?1), NH₄ ⁺ (V _M = 141.0 ± 5.6 U mg^?1, K _0.5 = 1.90 ± 0.04 mmol L^?1), and K⁺ (V _M = 120.0 ± 2.4 U mg^?1, K _M = 2.74 ± 0.08 mmol L^?1) followed single saturation curves and, except for K⁺, exhibited site–site interaction kinetics. Ouabain inhibited ATPase activity by around 73 % with K _I = 12.4 ± 1.3 mol L^?1. Complementary inhibition studies suggest the presence of F₀F₁–, Na⁺-, or K⁺-ATPases, but not V(H⁺)- or Ca²⁺-ATPases, in the gill microsomal preparation. K⁺ and NH₄ ⁺ synergistically stimulated enzyme activity (≈25 %), suggesting that these ions bind to different sites on the molecule. We propose a mechanism for the stimulation by both NH₄ ⁺, and K⁺ of the gill enzyme.     

Water and electrolyte balance in protoscoleces of Echinococcus granulosus incubated in vitro: general procedures for the determination of water,sodium, potassium and chloride in protoscoleces

Reisin I.L. and Rotunno C.A. 1981. Water and electrolyte balance in protoscoleces of Echimcoccus granulosus incubated in vitro: General procedures for the determination of water, sodium, potassium and chloride in protoscoleces. International Journal for Parasitology11: 399–404. Protoscoleces of E. granulosus (sheep strain) were incubated in vitro at 37°C in Ringer Krebs solution (RKS) for up to 3 h. When they were briefly washed in sucrose 0.3 M at 4°C, the water and electrolyte contents were: 1.768 ± 0.034 mlg^?1 d.w. for water content and 123 ± 2, 209 ± 2 and 78 ± 2 μmolg^?1 d.w. for Na⁺, K⁺ and Cl^? respectively. When protoscoleces were not washed in sucrose solution but were spun down from RKS, the K⁺ content suffered a very small change but larger values for Na⁺ and Cl⁺ contents were obtained. These higher Na⁺ and Cl^? contents are attributed to the RKS ions retained in the trapping space. The steady state distribution of Na⁺ and K⁺ in the protoscoleces incubated at 37°C indicates the activity of an active transport mechanism.     

The effect of pressure and the volume of activation on the monovalent cation and glucose permeabilities of liposomes of varying composition

Measurement of the cation permeability of phospholipid microvesicles as function of pressure confirmed that a single rate-determining step occured in each case.The volume of activation was 20 ml · mole^?1 for Na⁺ and K⁺, and about 40 ml · mole^?1 for valinomycin-mediated K⁺ permeability. It was virtually independent of membrane composition. The results were explained in terms of Träuble's theory of kink-substrate dissociation at the membrane interface involving possible 2g 1 and 2g 2 kink isomers.The volume of activation for d-glucose was 37 ml · mole^?1, which was not significantly different from that for any of the valinomycin-mediated K⁺ permeabilities. However, other data suggest that the rate-limiting steps for the sugar and cation permeabilities are not the same.     

Different mechanisms of ion homeostasis are dominant in the recretohalophyte <Emphasis Type="Italic">Tamarix ramosissima</Emphasis> under different soil salinity

Total ion (Na⁺, K⁺, Ca²⁺, SO₄ ^2? and Cl^?) accumulation by plants, ion contents in plant tissues and ion secretion by salt glands on the surface of shoots of Tamarix ramosissima adapted to different soil salinity, namely low (0.06 mmol Na⁺/g soil), moderate (3.14–4.85 mmol Na⁺/g soil) and strong (7.56 mmol Na⁺/g soil) were analyzed. There are two stages of interrelated and complementary regulation of ion homeostasis in whole T. ramosissima plants: (1) regulation of ion influx into the plant from the soil and (2) changing the secretion efficiency of salt glands on shoots. The secretion efficiency of salt glands was appraised by the ratio of ion secretion to tissue ion content. Independent of soil salinity, the accumulation of K⁺ and Ca²⁺ was higher than the contents of these ions in the soil. Furthermore, the accumulation of K⁺, Ca²⁺ and SO₄ ^2? ions by plants was maintained within a narrow range of values. Under low soil salinity, Na⁺ was accumulated, whereas under moderate and strong salinity, the influxes of Na⁺ were limited. However, under strong salinity, the accumulation of Na⁺ was threefold higher than that under low soil salinity. This led to a change in the Na⁺/K⁺ ratio (tenfold), an increase in the activity of salt glands (tenfold) and a reduction in plant growth (fivefold). An apparently high Na⁺/K⁺ ratio was the main factor determining over-active functioning of salt glands under strong salinity. Principal component analysis showed that K⁺ ions played a key role in ion homeostasis at all levels of salinity. Ca²⁺ played a significant role at low salinity, whereas Cl^? and interrelated regulatory components (K⁺ and proline) played a role under strong salinity. Proline, despite its low concentration under strong salinity, was involved in the regulation of secretion by salt glands. Different stages and mechanisms of ion homeostasis were dominant in T. ramosissima plants adapted to different levels of salinity. These mechanisms facilitated the accumulation of Na⁺ in plants under low soil salinity, the limitation of Na⁺ under moderate salinity and the over-activation of Na⁺ secretion by salt glands under strong salinity, which are all necessary for maintaining ion homeostasis and water potential in the whole plant.     

The cyanobacterium Synechococcus R-2 (Anacystis nidulans, S. leopoliensis) PCC 7942 has a sodium-dependent chloride transporter

Synechococcus R-2 (PCC 7942) actively accumulated Cl^? in the light and dark, under control conditions (BG-11 media: pH_o, 7·5; [Na⁺]_o, 18 mol m^?3; [Cl^?]_o, 0·508 molm^?3). In BG-11 medium [Cl^?], was 17·2±0·848 mol m^?3 (light), electrochemical potential of Cl^? (ΔμCl^?_i,o) =+211±2mV; [Cl^?]_i= 1·24±0·11 mol m^?3(dark), ΔμCl^?_i,o=+133±4mV. Cl^? fluxes, but not permeabilities, were much higher in the light: ?Cl^?_i,o= 4·01±5·4 nmol m^?2 s^?1, ^PCl^?_i,o= 47±5pm s^?1 (light); ?Cl^?_i,o= 0·395±0·071 nmol m^?2 s^?1, _PCl^?_i,o= 69±14 pm s^?1 (dark). Chloride fluxes are inhibited by acid pH_o (pH_o 5; ?Cl^?_i,o= 0·14±0·04 nmol m^?2 s^?1); optimal at pH_o 7·5 and not strongly inhibited by alkaline pH_o (pH_o 10; ?Cl^?1_i,o= 1·7±0·14 nmol m^?2 s^?1). A Cl^?_in/2H⁺_in coporter could not account for the accumulation of Cl^? alkaline pH_o. Permeability of Cl^? is very low, below 100pm s^?1 under all conditions used, and appears to be maximal at pH_o 7·5 (50–70 pm s^?1) and minimal in acid pH_o (20pm s^?1). DCCD (dicyclohexyl-carbodiimide) inhibited ?Cl^?_i,o in the light about 75% and [Cl^?]_i fell to 2·2±0·26 (4) mol m^?3. Valinomycin had no effect but monensin severely inhibited Cl^? uptake ([Cl^?]_i= 1·02±0·32 mol m^?3; ?Cl^?_i,o= 0·20±0·1 nmol m^?2 s^?1). Vanadate (200 mmol m^?3) accelerated the Cl^? flux (?Cl^?_i,o= 5·28±0·64 nmol m^?2 s^?1) but slightly decreased accumulation of Cl^? ([Cl^?], = 13·9±1·3 mol m^?3) in BG-11 medium but had no significant effect in Na⁺-free media. DCMU (dichlorophenyldimethylurea) did not reduce [Cl^?], or ?Cl^?_i,o to that found in the dark ([Cl^?]_i= 8·41±0·76 mol m^?3; ?Cl^?_i,o= 2·06±0·36 nmol m^?2 s^?1). Synechococcus also actively accumulated Cl^? in Na⁺-free media, [Cl^?]_i was lower but ΔΨ_i,o hyperpolarized in Na⁺-free media and so the ΔμCl^?_i,o was little changed ([Cl^?]_i= 7·98±0·698 mol m^?3; ΔμCl^?_i,o=+203±3 mV). Net Cl^? uptake was stimulated by Na⁺; Li⁺ acted as a partial analogue for Na⁺. Synechococcus has a Na⁺ activated Cl^? transporter which is probably a primary 2Cl^?/ATP pump. The Cl^? pump is voltage sensitive. ΔμCl^?_i,o is directly proportional to ΔΨ_i,o(P»0·01%): ΔμCl^?_i,o= -1·487 (±0·102) ×ΔΨ_i,o, r= -0·983, n= 31. The ΔμCl^?_i,o increased (more positive) as the Δμ_i,o became more negative. The ΔμCl^?_i,o has no known function, but might provide a driving force for the uptake of micronutrients.     

Regulation of proline accumulation in Arabidopsis thaliana (L.) Heynh during development and in response to desiccation

Significant differences were observed in the amount and proportion of free amino acids in different organs of Arabidopsis thaliana (L.) Heynh, ecotype Columbia. The most notable were found for proline, which formed 17–26% of the total free amino acid concentration in reproductive tissues (floret and seed), but only 1–3% of the total free amino acid concentration in vegetative tissues (rosette leaf and root). Proline accumulation was associated with tissues that had relatively low water contents. Tissues which displayed high water contents, such as rosette leaves, contained low levels of proline. A significant increase in the levels of proline accumulation occurred in plants subjected to experimentally induced low water potentials as compared to unstressed plants. For instance, an 8–10-fold increase in proline was observed in the presence of 120 mmol kg^?1 NaCl or KCl, and a 20-fold increase was stimulated by 60 mmol kg^?1 PEG. However, in addition to the accumulation of proline, massive accumulation of Na⁺, K⁺ and Cl^? ions occurred in tissues of plants stressed with salt. No significant differences were observed in mineral ions in plants stressed with PEG. Isotope tracer experiments with ¹⁴C compounds established that glutamate, ornithine and arginine are precursors of the proline biosynthesis induced by PEG in response to low water potentials in Arabidopsis thaliana. We conclude that the accumulation of proline in response to PEG occurs through increased biosynthesis.