Excess KCl Research Articles

Mass transport in supported zinc halide solutions—II. Complexation and migration effects

Abstract The speciation of ZnCl 2 solutions, with or without conduction electrolyte (KCl), is analyzed. The complex ZnCl − 3 ion is the dominant zinc species in supported solutions. The complexation of zinc tends to cause a negative contribution to the limiting current in such solutions, since the migration flux of anionic species such as ZnCl − 3 (or ZnCl 2− 4 ) opposes the diffusional flux toward the cathode. Effective diffusivities of zinc, determined from limiting current measurements at a dropping mercury electrode, are corrected for this complex migration effect. The resultant corrected diffusivities are in good agreement with data reported in the literature for molecular diffusion of ZnCl 2 in the presence of excess KCl, eg from capillary diffusion and interferometric measurements.

Reciprocal effects of excess potassium salts in the culture medium on type I and type III collagen synthesis by human skin fibroblasts

By the addition of excess KCl or CH 3COOK in the culture medium of human skin fibroblasts, production of non-collagenous proteins and membrane transport of [ 3H]proline of the cells were activated, but collagen synthesis was not increased. Production of type I collagen was inhibited under these culture conditions but type III collagen synthesis was activated; thus the ratio of type I to type III collagen decreased from 10 to near 1, indicating that the regulation of these two types of collagen is independent in human skin fibroblasts.

Osmotic properties of the squid giant axon and their modifications.

Volume and morphological changes of the squid giant axons in response to hyper- and hypoosmotic media were examined. In hyperosmotic media, which were made by adding sucrose or sodium chloride to the artificial seawater, the axons behaved approximately as ideal osmometers. The fraction of the osmotically inactive volume was less than 0.05. In hypoosmotic media down to half the osmolality of the artificial seawater, intact squid axons did not show significant volume increases. However, following a combined treatment with hyaluronidase and collagenase, the volume of the squid axons increased in these hypoosmotic media. A wrinkled pattern appeared on the surface of the axons while they were in hyperosmotic media containing excess NaCl or KCl. Trypsin treatment prevented appearance of this surface pattern. Furthermore, no such patterns appeared in media which were made hyperosmotic by the addition of sucrose or sodium glutamate.

Activation of Barnea candida (mollusca, pelecypoda) oocytes by sperm or KCl, but not by NH 4Cl, requires a calcium influx

Artificial activation of Barnea candida oocytes by NH 4Cl and the addition of excess KCl are, respectively, independent and dependent upon external Ca 2+ concentration. The activating efficiency of NH 4Cl increases when external pH is raised which suggests that the proportion of unionized penetrating NH 3 is the key factor for activation under these conditions. The external Ca 2+-dependent period for KCl or sperm-induced activation does not exceed 3–4 min. The transmembrane Ca 2+ flux inhibitor D-600 reversibly inhibits KCl- or sperm-induced activation and the D-600-sensitive period closely corresponds to the Ca 2+-dependent period. Ca 2+ ions alone can also trigger activation provided external Mg 2+ concentration is lowered. Finally, a direct demonstration is presented for the existence of a D-600-sensitive Ca 2+ uptake following KCl- or sperm-induced activation, by using the radioactive tracer 45Ca. The significance of that Ca 2+ influx is discussed with respect to the possible involvement of an intracellular pH shift as a main factor in the activation of lamellibranch mollusc oocytes.

Chloroperoxidase-catalyzed halogenation of antipyrine, a drug substrate of liver microsomal cytochrome P-450

Chloroperoxidase catalyzes halogenation of antipyrine at the 4-position with stoichiometric H 2O 2, in the presence of excess KCl or KBr; the pH optima of these reactions, near pH 4.0, are characteristic of other halogenation activities of this enzyme. In the presence of KCl or KBr, antipyrine was an effective inhibitor of H 2O 2 decomposition catalyzed by chloroperoxidase. Under similar experimental conditions, 4-halogenation of antipyrine also occurred in the absence of chloroperoxidase with stoichiometric NaOCl, or enzymatically with horseradish peroxidase in the presence of H 2O 2 and excess KBr (but not KCl). As observed previously for chloroperoxidase, horseradish peroxidase catalyzed oxidation of Br − by H 2O 2 to Br 2, readily detected in the presence of excess Br − by the intense uv absorbance of Br 3 −. These nonenzymatic and enzymatic halogenating systems could also effect N-demethylation of antipyrine, with complete release of formal-dehyde requiring a severalfold molar excess of NaOCl or H 2O 2 respectively. These results and data obtained with 4-bromoantipyrine indicated that the methyl group is cleaved subsequent to halogenation. Since the halide anion was absolutely required for the enzymatic N-demethylation reactions, it appears that the enzymatically generated halogenating species is also responsible for N-demethylation, which is much less favorable than halogenation of antipyrine. These results parallel qualitatively the relative extents of 4-hydroxylation and N-demethylation of antipyrine catalyzed by liver microsomal cytochrome P-450 in vivo and in vitro and provide evidence for similar functions of chloroperoxidase and cytochrome P-450 as catalysts of: (1) dehydrogenation reactions and (2) insertion of an electonegative atom (Cl or 0) into an organic compound.

Inhibition of murine leukemia virus Pr65gag cleavage in vitro and in vivo by hypertonic medium.

Cleavage of murine leukemia virus Pr65gag is associated with the activity of a labile proteolytic factor found in virions. We have shown that the presence of 80 to 100 mM NaCl inhibits this cleavage activity in vitro by over 90%. Further, the addition of 80 to 100 mM excess NaCl in vivo to chronically infected cultures of MJD-54 mouse fibroblasts also caused inhibition of Pr65gag cleavage. Specifically, the excess salt added to cells: (i) caused a greater than 90% decrease in virus production; (ii) increased the Pr65gag/p30 ratio in virions produced by more than threefold; and (iii) in pulse-chase experiments, showed a 10-fold decrease in the amount of Pr65gag cleaved after 3 h. In contrast, during this chase interval there was only a slight diminution, i.e., about two fold, in the cleavage of env precursor polyprotein Pr80env, suggesting that cleavages of Pr65gag and Pr80env are differently controlled. Additionally, electron microscopic examination of the excess salt-treated cells showed a twofold increase in the number of associated immature particles, consistent with the observed higher than average Pr65gag/p30 ratio. The inhibitory effects were also found if excess KCl or MgCl2 was used instead of NaCl, suggesting that they are caused by the hypertonic state of the medium and are not dependent on the ionic species used.

Reversible loss of acetylcholine receptor clusters at the developing rat neuromuscular junction

Exposure of sternomastoid muscles excised from 16-day embryonic rats to medium depleted of Ca 2+ or containing high concentrations of KCl leads to extensive loss of aggregates of acetylcholine receptors newly formed at the motor end plate region. Upon restoration of Ca 2+ or removal of excess KCl, receptor accumulations reappear in the central regions of about one-third of the muscle fibers. This susceptibility of junctional AChR aggregates lasts only a short while during development of the neuromuscular junction. By the time of birth, end plate receptor aggregates have become resistant to these treatments.

Homoserine dehydrogenase: spontaneous reactivation by dissociation of p-mercuribenzoate from an inactive enzyme--p-mercuribenzoate complex.

Incubation of Rhodospirillum rubrum homoserine dehydrogenase (L-homoserine:NAD+ oxidoreductase, EC 1.1.1.3) with p-mercuribenzoate (PMB) in the presence of 0.2 M KCl and 2 mM L-threonine resulted in complete loss of enzyme activity. Upon removal of excess PMB, KCl, and L-threonine, a time-dependent recovery of enzyme activity was observed in 25 mM phosphate/I mM EDTA buffer, pH 7.5. Circular dichroism studies indicated that the transition from inactive to reactivated form of the enzyme was accompanied by a conformational change in the protein. Experiments with [14C]PMB revealed loss of enzyme-bound radioactivity during reactivation. Increase in ionic strength of the phosphate buffer and/or addition of L-threonine, leading to enzyme aggregation, decreased the rate of enzyme reactivation, aggregated enzyme that remained inactive retained [14C]PMB on the enzyme. Sulfhydryl titration of various forms of the enzyme suggested a preferential release of PMB from a sulfhydryl group essential to enzymic activity. We conclude that reactivation of the inactive enzyme is due to dissociation of PMB from an "active-site" sulfhydryl group and that changes in the protein structure influence the rate of dissociation of the enzyme-PMB complex.

A Respiratory Rhythm in Sea Anemones

ABSTRACT Continuous recording of the O2 content of sea water containing an Actinia equina or a Metridium senile has revealed the occurrence of periodic deflexions on most of the records obtained. The deflexions are probably caused by the release of coelenteric fluid via the mouth. The average period of the rhythm varied from 24 to 43 min (14−15 °C). The period increased in darkness, but was unaffected by feeding, brief mechanical or electrical stimulation, longitudinal bisection of the column and excess KCl or MgCl2; 1·6 mm-KCN abolished the rhythm. The O2 depletion rate did not increase when the anemone contracted in response to stimulation, but it did after feeding, exposure to darkness, or the application of MgCl2. It decreased in the presence of excess KCl. These changes may result from alterations in shape of the anemone. The mechanism for the release of coelenteric fluid has yet to be elucidated. Calculations indicate that from to of the total O2 requirement may enter the tissues from the coelenteron, the remainder being taken up via the ectoderm.

Growth of copper-treated corn roots as affected by EDTA, IAA, succinic acid-2,2-dimethyl hydrazide, vitamins and potassium

Corn roots were treated for 1 hr in a modified Hoagland's solution containing 8 mg/l Cu 2+ and either simultaneously or subsequently with various substances, in order to test theories of copper toxicity to roots. Post treatment with IAA, niacin amide, thiamin, or sucrose had no effect on subsequent growth. Addition of excess KCl and succinic acid-2,2-dimethyl hydrazide (an inhibitor of ethylene production) to the copper solution doubled average growth and increased recovery from 27 to 87%. A rinse with EDTA resulted in resumption of normal growth rates and 100% recovery if performed 1 hr after Cu treatment, but this effect was gradually lost in the following 6 to 12 hr. Copper toxicity was increasingly severe as pH of the Cu treating medium increased. Results are not consistent with any theory tested, but they do suggest there is an initial phase of copper-stress which lasts 3–6 hr, followed by plant reaction that results in irreversible cessation of growth.

The effect of Ca-transport inhibitors on the excitability of the pregnant and post partum rabbit uterus

To continue an earlier study, a total of 54 uterine strips were excised from 25 days pregnant and post partum rabbits. These muscles were examined under a variety of experimental conditions to further define functionally their “activator-Ca” (A-Ca) which couples excitation with contraction under these two extreme regulatory states of the uterus. As in earlier studies, increasing the stimulus strength in graded steps from 2 to 80 V/5 cm revealed two distinct “peaks” of excitability, one at ∼12 V/5 cm and another at ∼60 V/6 cm, separated by a zone of inhibition. Knowing that effective “first peak” stimulation demands intact membrane function and the availability of A-Ca, while the “second peak” stimulation probably bypasses the membrane process and activates the contractile system directly by mobilizing Ca bound to intracellular structures, the effects on the strength-tension curve of normal and Ca-free KRB, excess KCl, Verapamil, Ruthenium-red and MnCl 2 were examined. These studies exposed again the different states of the A-Ca in the uteri of pregnant and post partum rabbits, which partly explain the functional differences of the myometrium under these two extreme regulatory conditions.

The effect of adrenaline on the tension developed in contractures and twitches of the ventricle of the frog.

1. The effect of adrenaline on contracture and twitch tension in frog's ventricle has been examined, using the superfused preparation.2. In 1 mM-Ca Ringer, contractures induced with excess KCl concentrations from 50 to 200 mM, are reduced by 1 x 10(-6) g/ml. adrenaline to an average of 0.62 of control values, in marked contrast to the well known positive inotropic effect of adrenaline on the heart twitch. This effect of adrenaline is directly dose dependent. Increasing [Ca](o) diminishes the effect of adrenaline on contracture tension, and on the twitch tension.3. Adrenaline has a significantly greater effect on the KCl contracture tension than noradrenaline or isoprenaline.4. In 1 mM-Ca Ringer, Na-free contractures are reduced to 0.72 of controls by 1 x 10(-6) g/ml. adrenaline. Adrenaline also significantly reduces tension in contractures induced by 50 c/s alternating current.5. The action of adrenaline on contracture tension is largely complete in 1-2 min at various rates of stimulation and calcium concentrations. A similar time course has been found for the effect of adrenaline on membrane potential.6. Pronethalol blocks the action of adrenaline on both twitch and contracture. The action on the contracture can also be blocked by ouabain (1 x 10(-5)M), and exposure of the tissue to K-free or Na-free Ringer solution.7. Adrenaline hyperpolarizes the membrane potential with a range of [K](o) from 0 to 200 mM. This effect is blocked by pronethalol and ouabain. After exposure to ouabain, adrenaline causes a significant decrease in the membrane potential. This may be due to an increase in the sodium permeability.8. At low values of the [Ca]/[Na](2) ratio, adrenaline takes a relatively constant number of beats for full action, but at high values of the ratio the development of full effect is largely time dependent.9. The time course of the effect on the twitch of changing from 0.5 to 2 mM-Ca Ringer has been studied at various rates of stimulation. The equilibration time has been found to depend on the heart rate.10. The effect on the contracture suggests that adrenaline decreases the calcium permeability. It is further suggested that the development of twitch tension is not due to direct Ca entry but is due to the release of Ca from a local store within or between the cells. The inotropic action of adrenaline is explained in terms of this store.