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1.
By means of micro-dissection and injection Amœba proteus was treated with the chlorides of Na, K, Ca, and Mg alone, in combination, and with variations of pH. I. The Plasmalemma. 1. NaCl weakens and disrupts the surface membrane of the ameba. Tearing the membrane accelerates the disruption which spreads rapidly from the site of the tear. KCl has no disruptive effect on the membrane but renders it adhesive. 2. MgCl2 and CaCl2 have no appreciable effect on the integrity of the surface membrane of the ameba when applied on the outside. No spread of disruption occurs when the membrane is torn in these salts. When these salts are introduced into the ameba they render the pellicle of the involved region rigid. II. The Internal Protoplasm. 3. Injected water either diffuses through the protoplasm or becomes localized in a hyaline blister. Large amounts when rapidly injected produce a "rushing effect". 4. HCl at pH 1.8 solidifies the internal protoplasm and at pH 2.2 causes solidification only after several successive injections. The effect of the subsequent injections may be due to the neutralization of the cell-buffers by the first injection. 5. NaCl and KCl increase the fluidity of the internal protoplasm and induce quiescence. 6. CaCl2 and MgCl2 to a lesser extent solidify the internal protoplasm. With CaCl2 the solidification tends to be localized. With MgCl2 it tends to spread. The injection of CaCl2 accelerates movement in the regions not solidified whereas the injection of MgCl2 induces quiescence. III. Pinching-Off Reaction. 7. A hyaline blister produced by the injection of water may be pinched off. The pinched-off blister is a liquid sphere surrounded by a pellicle. 8. Pinching off always takes place with injections of HCl when the injected region is solidified. 9. The injection of CaCl2 usually results in the pinching off of the portion solidified. The rate of pinching off varies with the concentration of the salt. The injection of MgCl2 does not cause pinching off. IV. Reparability of Torn Surfaces. 10. The repair of a torn surface takes place readily in distilled water. In the different salt solutions, reparability varies specifically with each salt, with the concentration of the salt, and with the extent of the tear. In NaCl and in KCl repair occurs less readily than in water. In MgCl2 repair takes place with great difficulty. In CaCl2 a proper estimate of the process of repair is complicated by the pinching-off phenomenon. However, CaCl2 is the only salt found to increase the mobility of the plasmalemma, and this presumably enhances its reparability. 11. The repair of the surface is probably a function of the internal protoplasm and depends upon an interaction of the protoplasm with the surrounding medium. V. Permeability. 12. NaCl and KCl readily penetrate the ameba from the exterior. CaCl2 and MgCl2 do not. 13. All four salts when injected into an ameba readily diffuse through the internal protoplasm. In the case of CaCl2 the diffusion may be arrested by the pinching-off process. VI. Toxicity. 14. NaCl and KCl are more toxic to the exterior of the cell than to the interior, and the reverse is true for CaCl2 and MgCl2. 15. The relative non-toxicity of injected NaCl to the interior of the ameba is not necessarily due to its diffusion outward from the cell. 16. HCl is much more toxic to the exterior of a cell than to the interior; at pH 5.5 it is toxic to the surface whereas at pH 2.5 it is not toxic to the interior. NaOH to pH 9.8 is not toxic either to the surface or to the interior. VII. Antagonism. 17. The toxic effects of NaCl and of KCl on the exterior of the cell can be antagonized by CaCl2 and this antagonism occurs at the surface. Although the lethal effect of NaCl is thus antagonized, NaCl still penetrates but at a slower rate than if the ameba were immersed in a solution of this salt alone. 18. NaCl and HCl are mutually antagonistic in the interior of the ameba. No antagonism between the salts and HCl was found on the exterior of the ameba. No antagonism between the salts and NaOH was found on the interior or exterior of the ameba. 19. The pinching-off phenomenon can be antagonized by NaCl or by KCl, and the rate of the retardation of the pinching-off process varies with the concentration of the antagonizing salt. 20. The prevention of repair of a torn membrane by toxic solutions of NaCl or KCl can be antagonized by CaCl2. These experiments show directly the marked difference between the interior and the exterior of the cell in their behavior toward the chlorides of Na, K, Ca, and Mg. 相似文献
2.
Arthur Grollman 《The Journal of general physiology》1931,14(5):661-683
Data for the depression of vapour pressure are presented for the following aqueous solutions: NaCl (0.03 to 0.1 molar), KCl (0.03 to 0.1 molar), urea (0.05 to 0.5 molar), sucrose (0.05 to 0.10 molar), lactic and succinic acids, creatine, CaCl2 (0.05 molar), and mixtures of these substances with one another and with certain other solutions (gelatin, gum acacia, sea water, LiCl, etc.). The relation of the depression of vapour pressure of a mixed solution to that of solutions of the individual constituents was investigated in order to ascertain to what extent such studies may be used for the determination of the degree of hydration, or of the state of water, in solutions. Organic substances (urea, sucrose, etc.) showed anomalous results which were markedly affected and unpredictable in mixed solutions. They are, therefore, unsuited for the study of water binding. In the case of solutions of inorganic substances—LiCl and CaCl2—the principle of the additive nature of colligative properties is also only approximately true—except perhaps in very dilute solutions. The limitations of the colligative method for determining the degree of hydration have been defined in accord with the above findings.
Studies of the vapour pressures of mixtures of gelatin or gum acacia with NaCl or KCl demonstrated that hydration in gelatin is relatively small at pH = 7 and undetectable in gum acacia solutions. The view, therefore, that hydrophilic colloids are strongly hydrated has not been substantiated. The passage from the sol to the gel state also was not accompanied in gelatin or in blood by any appreciable change in the degree of hydration of the hydrophilic colloids present in these substances. 相似文献
3.
Paul Reznikoff 《The Journal of general physiology》1928,11(3):221-232
I. The Plasmalemma. 1. On the plasmalemma of amebæ CaCl2 antagonizes the toxic action of LiCl better than it does NaCl, and still better than it does KCl. MgCl2 antagonizes the toxic action of NaCl better than it does LiCl and still better than it does KCl. 2. CaCl2 antagonizes the toxic action of LiCl and of KCl better than does MgCl2: MgCl2 antagonizes NaCl better than does CaCl2. II. The Internal Protoplasm. 3. The antagonizing efficiency of CaCl2 and of MgCl2 are highest against the toxic action of KCl on the internal protoplasm, less against that of NaCl, and least against that of LiCl. 4. CaCl2 antagonizes the toxic action of LiCl better than does MgCl2: MgCl2 antagonizes the toxic action of NaCl and of KCl better than does CaCl2. 5. LiCl antagonizes the toxic action of MgCl2 on the internal protoplasm more effectively than do NaCl or KCl, which have an equal antagonizing effect on the MgCl2 action. III. The Nature of Antagonism. 6. When the concentration of an antagonizing salt is increased to a toxic value, it acts synergistically with a toxic salt. 7. No case was found in which a potentially antagonistic salt abolishes the toxic action of a salt unless it is present at the site (surface or interior) of toxic action. 8. Antagonistic actions of the salts used in these experiments are of differing effectiveness on the internal protoplasm and on the surface membrane. 相似文献
4.
Jacques Loeb 《The Journal of general physiology》1922,5(2):231-254
1. It is shown that NaCl acts like CaCl2 or LaCl3 in preventing the diffusion of strong acids through the membrane of the egg of Fundulus with this difference only that a M/8 solution of NaCl acts like a M/1,000 solution of CaCl2 and like a M/30,000 solution of LaCl3. 2. It is shown that these salts inhibit the diffusion of non-dissociated weak acid through the membrane of the Fundulus egg but slightly if at all. 3. Both NaCl and CaCl2 accelerate the diffusion of dissociated strong alkali through the egg membrane of Fundulus and CaCl2 is more efficient in this respect than NaCl. 4. It is shown that in moderate concentrations NaCl accelerates the rate of diffusion of KCl through the membrane of the egg of Fundulus while CaCl2 does not. 相似文献
5.
1. Permeability to water in unfertilized eggs of the sea urchin, Arbacia punctulata, is found to be greater in hypotonic solutions of dextrose, saccharose and glycocoll than in sea water of the same osmotic pressure. 2. The addition to dextrose solution of small amounts of CaCl2 or MgCl2 restores the permeability approximately to the value obtained in sea water. 3. This effect of CaCl2 and MgCl2 is antagonized by the further addition of NaCl or KCl. 4. It is concluded that the NaCl and KCl tend to increase the permeability of the cell to water, CaCl2 and MgCl2 to decrease it. 5. The method here employed can be used for quantitative study of salt antagonism. 相似文献
6.
In Nitella the substitution of KCl for NaCl changes the P.D. in a negative direction. In some cases this change is lessened by adding solid CaCl2 to the solution of KCl. This may be due to lessening the partition coefficient of KCl or to decreasing the solubility of an organic substance which sensitizes the cell to the action of KCl. Little or no correlation exists between this effect of calcium and its ordinary antagonistic action in producing a balanced solution which preserves the life of the cell indefinitely. CaCl2 is negative to NaCl but positive to KCl. The effects of mixtures of KCl, NaCl, and CaCl2 are discussed. The concentration effect of a mixture of KCl + CaCl2 shows certain peculiarities due to action currents: these resemble those found with pure KCl. These studies and others on Nitella, Valonia, and Halicystis indicate that mobilities and partition coefficients are variable and can be brought under experimental control. 相似文献
7.
Richard A. Fennell 《The Journal of general physiology》1944,27(4):339-354
1. Strychnine sulfate 0.000069 M decreased percentage attachment to the substratum by Amoeba proteus in 0.0029 M NaCl from 77.3 to 1.3, in 0.0029 M KCl from 40.8 to 2.5, in 0.002 M CaCl2 from 73.3 to 68.0, in 0.002 M MgCl2 from 85.5 to 83.3. 2. Frequency of ingestion of chilomonads by Amoeba proteus is increased by adding strychnine sulfate to solutions of NaCl, KCl, or CaCl2. Frequency of ingestion is increased in NaCl solution from 1.3 to 2.3, in KCl from 0.75 to 2.25, and in CaCl2 from 1.1 to 1.9 chilomonads per minute. Ingestion is not significantly increased by the addition of strychnine to MgCl2 solution. 3. Frequency of ingestion of food by Amoeba proteus is not closely correlated with attachment to the substratum in NaCl and KCl solutions to which strychnine sulfate is added. 4. Chilomonads adhere to the plasmalemma of Amoeba proteus in solutions of NaCl, KCl, or CaCl2 containing strychnine, but in MgCl2 plus strychnine only a few adhere to it. Strychnine appears to make the surface of the amebae and chilomonads sticky in the former but not in the latter. Frequency of ingestion is apparently correlated with adherence of chilomonads to the plasmalemma. 5. Attachment to the substratum and ingestion by Pelomyxa carolinensis is increased by dead Chilomonas, Colpidium, and Paramecium in aqueous solutions, by materials obtained from paramecia by alcoholic-ether extraction, and by solutions in which these organisms have lived. 6. Attachment to the substratum by Pelomyxa carolinensis is not closely correlated with kind or concentration of inorganic salts used in this study. 7. Materials were found in extracts of paramecia which had certain characteristics in common with choline esters. There is no reason to doubt that under certain conditions materials are present in aqueous and alcoholic extracts which are pharmacologically similar to choline and acetylcholine. 8. Aqueous suspensions of paramecia when subcutaneously injected into young mice for 21 days inhibit the gonadotropic luteinizing hormone of the pituitary. Ovaries from injected mice showed no corpora lutea, and the seminal vesicles from injected males were smaller and contained less fluid than those of the controls. 相似文献
8.
Henry S. Simms 《The Journal of general physiology》1929,12(6):783-792
The pH of a 0.01 molar solution of glycine, half neutralized with NaOH, is 9.685. Addition of only one of the salts NaCl, KCl, MgCl2, or CaCl2 will lower the pH of the solution (at least up to 1 µ). If a given amount of KCl is added to a glycine solution, the subsequent addition of increasing amounts of NaCl will first raise the pH (up to 0.007 M NaCl). Further addition of NaCl (up to 0.035 M NaCl) will lower the pH, and further additions slightly raise the pH. The same type of curve is obtained by adding NaCl to glycine solution containing MgCl2 or CaCl2 except that the first and second breaks occur at 0.015 M and 0.085 M NaCl, respectively. Addition of CaCl2 to a glycine solution containing MgCl2 gives the same phenomena with breaks at 0.005 M and 0.025 M CaCl; or at ionic strengths of 0.015 µCaCl2 and 0.075 µCaCl2. This indicates that the effect is a function of the ionic strength of the added salt. These effects are sharp and unmistakable. They are almost identical with the effects produced by the same salt mixtures on the pH of gelatin solutions. They are very suggestive of physiological antagonisms, and at the same time cannot be attributed to colloidal phenomena. 相似文献
9.
1. The question of the critical pore diameter for streaming potential is discussed. 2. The surface charge is calculated for cellulose in contact with solutions of K3PO4, K2CO3, K2SO4, KCl, and ThCl4. 3. The surface charge of cellulose in contact with a solution of 2 x 10–4
N NaCl is calculated as a function of temperature and is found to show a sharp break at 39°. This is interpreted in terms of the change of the specific heat of water. 4. A marked ion antagonism is found in NaCl:KCl, KCl:MgCl2, NaCl:MgCl2, NaCl:CaCl2, KCl:CaCl2, CaCl2:MgCl2 mixtures when the surface charge is calculated as a function of concentration. 相似文献
10.
Philip B. Armstrong 《The Journal of general physiology》1928,11(5):515-523
1. Developing Fundulus embryos react in much the same way to mixtures of acetic acid in salt solutions whether their membranes are removed or not. It is therefore not necessary to assume any specific rôle for the membrane. 2. The primary toxic effect of acetic acid is to kill the surface of the embryo; heart stoppage is due to penetration of the acid after the surface has been injured. 3. The salt (NaCl, KCl, CaCl2) antagonizes the acetic acid by slowing or preventing the killing of the surface of the embryo. 4. If embryos are immersed in certain KCl-acetic acid mixtures, the surface killing effect of the acid is antagonized but at the same time the KCl penetrates and stops the heart in the manner which is characteristic of a KCl solution alone. 相似文献
11.
Influence of Electrolytes on the Thicknesses of the Phospholipid Bilayers of Lamellar Lecithin Mesophases 总被引:1,自引:0,他引:1
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Over a wide range of water contents, aqueous lecithin-water mixtures are mesophases in which lecithin bilayers alternate with water layers. This paper reports on low-angle X-ray diffraction measurements of the effects of electrolytes, at 1.0 N concentration, on the thicknesses of the bilayers in mesophases formed by the synthetic lecithin: 1-octadec-9-enyl-2-hexadecylglycerophosphocholine. With solutions of LiCl, NaCl, Na2SO4, KCl, and CsCl, the bilayer thicknesses are less than with pure water. The maximum reduction in bilayer thickness with these electrolytes is about 10% and occurs with mesophases of high content of KCl and CsCl solutions. With HCl solutions the bilayer thicknesses are about 5% greater than with pure water, and with CaCl2 solutions the bilayer thicknesses are about the same as with pure water. The maximum amount of solution which can be mixed with lecithin before a second, purely aqueous phase is formed is also affected by electrolytes, the order for the various 1.0 N solutions being CsCl = KCl > NaCl > Na2SO4 > (pure water) = LiCl > CaCl2. 相似文献
12.
The conformational changes of poly-Nε-glutaryl-L -lysine (PGL) and poly-Nε-succinyl-L -lysine (PSL) in various salt solutions were studied by use of ORD and potentiometric titration measurements. The addition of alkali metal salts to the fully ionized PGL or PSL solution caused helix formation. The helical content of the polymers increases in the following sequences: at salt concentration 0–2 M, CsCl < KCl < LiCl < NaCl; and at 2–3 M, LiCl < CsCl < KCl ~ NaCl. The preferential binding of the solvent components with various alkali metal salts of PGL or PSL was measured in LiCl, NaCl, and KCl solutions by means of equilibrium dialysis and differential refractometry. It was found that with increasing salt concentration, the polymers were preferentially hydrated in NaCl and KCl soultions; however the salt was preferentially bound to the polymers in LiCl solution. Such preferential binding was suggested to be closely related to conformational change. The addition of CaCl2 to polymer solutions led to the stabilization of the helical structure of PGL or PSL. 相似文献
13.
1. Twenty-five solutions which contained KCl (0.0, 0.2, 0.4, 0.6, and 0.8 gm. per liter), in combination with CaCl2 (0.0, 0.2, 0.4, 0.6, and 0.8 gm. per liter), 10.0 gm. of NaCl, and 0.2 gm. of NaHCO3 per liter of solution were tested in order to determine satisfactory KCl/CaCl2 ratios in an insect physiological salt mixture for the maintenance of muscular activity by the isolated crop of the American roach. Satisfactory activity products (0.390 to 0.549) were obtained in seven mixtures with KCl/CaCl2 ratios of 0.2/0.2, 0.4/0.4, 0.6/0.6, 0.8/0.8, 0.2/0.4, 0.4/0.6, and 0.6/0.8, expressed as gram per liter. These ratios lie between 0.50 and 1.00. In solutions which contained calcium, but no potassium, approximately 50 per cent of the crops exhibited an initial tone increase and were arrested in rigor. See Fig. 2. In solutions which contained potassium, but no calcium, all crops showed an initial loss of tone and arrest in relaxation. See Fig. 2. 2. Seven KCl/CaCl2 ratios (see paragraph 1 above) were tested with eight NaCl concentrations (1.0, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, and 1.8 per cent) at a pH of 8.0. In these mixtures, the ones with KCl/CaCl2 ratios of less than 1.0 produced higher activity products than those with ratios equal to 1.00. The highest average activity product (0.849) was obtained in the solutions with 0.2 gm. of KCl and 0.4 gm. of CaCl2 per liter. 3. Four KCl/CaCl2 ratios (0.2/0.2, 0.4/0.4, 0.2/0.4, and 0.4/0.6 gm. per liter) were tested with 1.4, 1.5, and 1.6 per cent NaCl at a pH of 7.5. When analyzed with data from comparable solutions at a pH of 8.0, it was found that 1.4 per cent NaCl afforded an optimum environment for isolated crop activity. 4. Effects of hydrogen and hydroxyl ion concentrations were studied at pH values of 6.8, 7.5, 8.0, and 8.9. The highest average activity product, 1.011, was produced at a pH of about 8.0. 5. A satisfactory physiological salt solution for the isolated foregut of the American roach, Periplaneta americana, would contain 14.0 gm. of NaCl, 0.4 gm. of CaCl2, 0.2 gm. of KCl, and 0.2 gm. of NaHCO3 per liter of solution. This mixture should have a pH value between 7.8 and 8.2. 6. Durations of crop activity extending over periods as long as 25 hours were quite common, and several crops maintained contractions for more than 30 hours. The greatest longevity was for crop 814, from a female, which continued activity for slightly more than 47 hours. 7. A significant difference between the activity products of the crops from males and the crops from females was recorded. Although there was not a significant difference in the amount of food ingested by males and females, 12 hours after feeding there was more food in the females'' crops, and the food progressed more rapidly through the males'' crops than through the females''. In addition, crops from the two sexes reacted differently to the effects of day old solutions. This sex difference is apparently related to an inherently increased activity of the crop from the male roach. 相似文献
14.
Does Seed Priming Induce Changes in the Levels of Some Endogenous Plant Hormones in Hexaploid Wheat Plants Under Salt Stress? 总被引:8,自引:0,他引:8
Muhammad Iqbal Muhammad Ashraf Amer Jamil Shafiq-ur-Rehman 《植物学报(英文版)》2006,48(2):181-189
In order to assess whether salt tolerance could be Improved In spring wheat (Triticum aestivum L.), the present study was performed by soaking the seeds of two cultlvars, namely MH-97 (salt sensitive) and Inqlab-91 (salt tolerant), for 12 h In distilled water or 100 mol/m^3 CaCl2, KCI, or NaCI. Primed seeds from each treatment group and non-primed seeds were sown In a field In which NaCI salinity of 15 dS/m was developed. Priming of seeds with CaCl2, followed by priming with KCI and NaCI, was found to be effective In alleviating the adverse effects of salt stress on both wheat cultivars In terms of shoot fresh and dry weights and grain yield. Priming with CaCl2 alleviated the adverse effects of salt stress on hormonal balance In plants of both cultlvars. In MH-97 plants, CaCl2 pretreatment considerably reduced leaf absclslc acid (ABA) concentrations and Increased leaf free salicylic acid (SA) concentrations under both saline and non-saline conditions. In contrast, In the Inqlab-91 plant, CaCl2 Increased free Indoleacetic acid (IAA) and indolebutyrlc acid (IBA) content. However, priming of seeds with CaCl2 did not alter free polyamlne levels in either cultlvar, although spermldlne levels were considerably lower In plants raised from seeds treated with CaCl2 for both cultlvars under saline conditions. Priming with KCI Increased growth In Inqlab-91 plants, but not In MH-97 plants, under saline conditions. The salinity Induced reducUon In auxins (IAA and IBA) was alleviated by NaCI priming In both cultlvars under saline conditions. However, NaCI Increased leaf free ABA content and lowered leaf SA and putresclne levels In Inqlab-91 plants under saline conditions. In conclusion, although all three priming agents (I.e. CaCl2, KCI, and NaCI) were effective In alleviating the adverse effects of salt stress on wheat plants, their effects on altering the levels of different plant hormones were different In the two cuItlvars. 相似文献
15.
Matilda Moldenhauer Brooks 《Protoplasma》1927,2(1):420-427
Summary The penetration of the dye, dahlia, into the sap ofNitella has been determined in the presence of NaCl, KCl, MgCl2 and CaCl2 at various concentrations.NaCl is the least effective and MgCl2 was the most effective in preventing penetration of the dye.It was found that NaCl antagonizes the action of CaCl2 in certain proportions to a small degree but not sufficiently to permit the dye to penetrate at a normal rate.Published by permission of the Surgeon General. 相似文献
16.
Ana T.M. Viveiros Naiara C. Motta Ziara A. Isaú Izabella L.G. Almeida Marcelo C. Leal 《Zeitschrift fur angewandte Ichthyologie》2019,35(3):739-746
The aim of this study was to evaluate the effects of osmolality and the presence of ions on the activation of post‐thaw sperm motility of Brycon insignis. Sperm was frozen under a standardized methodology for this species. In experiment 1, 11 solutions were prepared with reverse osmosis (RO) water (~0 mOsm/kg) and glucose or NaCl adjusted to an osmolality of 50, 100, 150, 200 and 250 mOsm/kg. In experiment 2, six solutions were prepared with RO and adjusted to ~100 mOsm/kg with one of the following chemicals: NaHCO3, sodium citrate (Na3C6H5O7), NaCl, KCl, CaCl2 or glucose (as ion‐free control). Post‐thaw sperm of both experiments was evaluated for motility rate, velocities (curvilinear = VCL, among others) and beat‐cross frequency (BCF). In experiment 1, sperm motility rate and velocities were higher (p < 0.05) when triggered in solutions at osmolalities from 0 to 200 mOsm/kg (62–80% motility; 139–167 µm/s) than that at 250 mOsm/kg (36–44% motility; 94–99 µm/s VCL). BCF was not affected by osmolality and varied from 19 to 24 Hz in all samples. In experiment 2, samples activated in NaHCO3, citrate, NaCl and KCl solutions yielded higher motility rates (76–85%) and BCF (24–25 Hz) compared to those activated in CaCl2 (50%; 14 Hz). Samples activated in ion‐free control solution yielded higher motility rate (87%) than those activated in NaHCO3 and in CaCl2. Curvilinear velocity was higher in samples activated in NaHCO3, citrate, KCl and control solutions (144–160 µm/s) than in those activated in CaCl2 (104 µm/s); samples activated in NaCl yielded intermediate VCL values (127 µm/s). Post‐thaw sperm achieves maximum motility rate and velocities when activated in solutions composed of sodium citrate, NaCl, KCl or glucose. Thus, post‐thaw sperm motility of B. insignis can be triggered in ionic and non‐ionic solutions at osmolality between 0 and 200 mOsm/kg. The use of solutions containing calcium, however, should be avoided. 相似文献
17.
Abstract— Myelin fragments were isolated from bovine optic nerves and then exposed to solutions of NaCl, CaCl2, LaCl3 or to water. Measurements of the water content of myelin pellets and the hydrophobicity of myelin fragments indicated an apparent isoelectric point at about pH 4.0 which increased with increasing membrane counterion valence. The exposure of myelin to CaCl2 and LaCl3 solutions for 1 hr removed relatively more cholesterol and galactolipid than protein or phospholipid. The same changes were observed after 12 days of storage in all four solutions. Myelin ultrastructure was evaluated by electron microscopy after positive and negative staining. No pronounced changes in myelin ultra-structure were seen after exposure to any of these solutions although extensive beading of the lamellae was observed and the magnitude of the major period was greater than that reported for native myelin. While differences in the physical properties of myelin after exposure to Na+, Ca++, or La+++ ions could be explained by considering the fixed charge shielding capabilities of these cations, changes of state of the membrane infrastructure could not be ruled out. At pH values above 4.0 myelin fragments behaved like a cation exchange system. 相似文献
18.
The permeability of a psychrophilic Acbromobacter strain to the chlorides of Na, K, Mg and Ca was investigated with light-scattering technique. Comparisons, were made with cells of Escherichia coli B. Cells of both strains suspended in “water were plasmolyzed by 0.1 or 0.2 M solutions of MgCl2 or CaCl2 without subsequent deplasmolysis. NaCl or KCl also plasmolyzed the cells, but deplasmolysis followed.” When suspended in growth medium E. coli became completely de-plasmolyzed., whereas the psychrophile still excluded MgCl2 and CaCl2 to a great extent. The plasmolysis and deplasmolysis were reversible. Electron micrographs of the psychrophile exposed to CaCl2 confirmed the presence of plasrnolysis. 相似文献
19.
A. Zrig T. Tounekti H. BenMohamed H. Abdelgawad A. M. Vadel D. Valero H. Khemira 《Russian Journal of Plant Physiology》2016,63(1):143-151
It was examined how essential cations, Ca2+ and K+, can mitigate the toxic effects of NaCl on two different almond species (Prunus amygdalus Batsch) rootstocks, Garnem (GN15) and Bitter Almond. The tree growth parameters (water potential (Ψw), gas exchange, nutrient uptake) and leaf chlorophyll (Chl) content were measured in control and NaCl-treated plants with or without KCl or CaCl2 supplements. The addition of CaCl2 and KCl to Bitter Almond trees reduced their dry weight, shoot growth and leaf number although net photosynthetic assimilation rate (A) was not affected. These results indicated that changing of photo-assimilates flux to proline and/or soluble sugars synthesis may help to increase leaf Ψw. The Garnem trees also did not respond to the CaCl2 and KCl addition indicating that the plants are already getting enough of these two cations (Ca2+ and K+). In both rootstocks, NaCl in the medium reduced growth attributes, Ψw, A, stomatal conductance (gs), and leaf Chl content. When CaCl2 and KCl fertilizers were added together with NaCl to Bitter Almond trees, leaf K+ and Ca2+ contents increased while Na+ and Cl– decreased leading to higher Ca/Na and K/Na ratios, but shoot growth was not improved and even declined compared to NaCl-treated trees. It appears that the addition of salts further aggravated osmotic stress as indicated by the accumulation of proline and soluble sugars in leaf tissues. The addition of KCl or CaCl2 to NaCl-treated GN15 trees did not increase A, leaf Ψw, and shoot growth but improved ionic balances as indicated by higher Ca/Na and K/Na ratios. The reduction in A was mainly due to non-stomatal limitations in GN15, possibly due to the degradation of Chl a, unlike Bitter Almond, for which the reduction of A was due to stomata closure. The improvement in ionic balances and water status of Bitter Almond trees in response to addition of KCl or CaCl2 was apparently offset by a high sensitivity to Cl–; therefore, no-chloride salts should be the preferred forms of fertilizers for this rootstock. Both rootstocks were sensitive to soil salinity and cation supplements were of limited value in mitigating the effect of excessive salt concentrations. 相似文献
20.
1. In relatively low concentrations of NaCl, KCl, and CaCl2 the rate of respiration of Bacillus subtilis remains fairly constant for a period of several hours, while in the higher concentrations, there is a gradual decrease in the rate. 2. NaCl and KCl increase the rate of respiration of Bacillus subtilis somewhat at concentrations of 0.15 M and 0.2 M respectively; in sufficiently high concentrations they decrease the rate. CaCl2 increases the rate of respiration of Bacillus subtilis at a concentration of 0.05 M and decreases the rate at somewhat higher concentrations. 3. The effects of salts upon respiration show a well marked antagonism between NaCl and CaCl2, and between KCl and CaCl2. The antagonism between NaCl and KCl is slight and the antagonism curve shows two maxima. 相似文献