Formation and Regeneration of Protoplasts of the Actinorhizal Nitrogen-Fixing Actinomycete Frankia

Procedures for forming and regenerating protoplasts of four Frankia strains are described. Cells obtained from growth medium containing 0.1% glycine were digested with lysozyme (250 μg/ml) in a medium containing 0.5 M sucrose, 5.0 mM CaCl₂, and 5.0 mM MgCl₂. Protoplasts were formed during 15 to 120 min of digestion at 25°C. Optimum conditions for protoplast regeneration involved placing protoplasts on a layer of complex growth medium containing 0.3 M sucrose, 5.0 mM CaCl₂, and 5.0 mM MgCl₂ which was overlaid with a layer of 0.8% low-melting-point agarose containing 0.5 M sucrose, 5.0 mM MgCl₂, and 5.0 mM CaCl₂. The maximum regeneration efficiency was 36.9% for strain CpI1, 1.3% for strain ACN1^AG, 27% for strain EAN1pec, and 20% for strain EuI1c.     

ELECTROKINETICS : XVII. SURFACE CHARGE AND ION ANTAGONISM

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.     

Survival and death of Chara internodal cells in electrolyte solutions and calcium release from the cell wall

Abstract. Survival and death of Chara internodal cells were investigated in one of the alkali metal salts KCl, some of the alkali earth metal salts CaCl₂, Ca(NO₃)₂, MgCl₂, Mg(NO₃)₂, SrCl₂, Sr(NO₃)₂, BaCl₂ and Ba(NO₃)₂, potassium phosphate pH buffer solution (pH 7.0), Tris-maleate pH buffer solution (pH 7.0), HEPES (N-2-hydroxyethylpiperazine-N′-2-ethanesulphonic acid)-KOH (pH 7.0) pH buffer solution, calcium buffer solutions, and deionized water. Most of the internodal cells died within a day or a few days in KCl, MgCl₂, Mg(NO₃)₂, BaCl₂ and Ba(NO₃)₂ solutions of higher concentrations, calcium buffer solutions of pCa 6.0, 10.0 mol m^-3 potassium phosphate pH buffer solution and 10.0 mol m^-3 Trismaleate pH buffer solution. However, all of the internodal cells survived more than 10 d in deionized water, 80.0 mol m^-3 CaCl₂, 80.0 mol m^-3 Ca(NO₃)₂, 80.0 mol m^-3 SrCl₂, 80.0 mol m^-3 Sr(NO₃)₂ calcium buffer solutions of pCa 4.0 and pCa 5.0, and 10.0 mol m^-3 HEPES-KOH (pH 7.0) pH buffer solution. Addition of Ca²⁺ or Sr²⁺ to K⁺, Mg²⁺ and Ba²⁺ salt solutions increased the survival rates of the internodal cells. Calcium release from the internodal cell wall was measured in deionized water, KCl, NaCl, MgCl₂, CaCl₂, SrCl₂ and BaCl₂ solutions. Except in deionized water and CaCl₂ solution, most of the calcium binding to the cell wall was released within one or a few hours in respective electrolyte solutions. Thus, survival and death of the internodal cells in the electrolyte solutions tested were interpreted in terms of the calcium release from the cell wall and the cell membrane, and intrinsic ability of Sr²⁺ to maintain the cell membrane normal.     

Coupling of excitation and cessation of cyclois in Nitella: role of divalent cations

The effect of external divalent cation salt solutions upon the association of an action potential and cessation of cytoplasmic streaming in Nitella was studied. Nitella cells remained excitable when immersed in solutions of CaCl₂, MgCl₂, BaCl₂, and SrCl₂. Cessation of streaming coincident with excitation occurred in solutions of CaCl₂ or SrCl₂ but not in solutions of MgCl₂ or BaCl₂. In cells exposed to solutions containing mixtures of MgCl₂ and CaCl₂, or MgCl₂ and SrCl₂, it was the [Ca]/[Mg] or [Sr]/[Mg] which determined the effect of an action potential upon the rate of streaming, rather than the absolute concentrations Ca⁺⁺ or Sr⁺⁺. The implications of these data are discussed with respect to the structure involved in the generation of cytoplasmic streaming and the relation of streaming to other types of biological motion.     

Ethylene and ethane production in response to salinity stress

Abstract Ethylene and ethane production in mung bean hypocotyl sections were evaluated as possible indicators of stress due to contact with four salts that are common in natural sites. Ethylene production decreased with increasing concentrations of applied NaCl and KCl. When CaCl₂ was applied, the ethylene evolution was greater. However, when MgCl₂ was applied, ethylene evolution remained high then decreased and at higher salt concentrations again showed an increase. NaCl (up to 0.1 kmol m^?1) and KCl (up to 0.5 kmol m^?3) caused a concentration-dependent increase in ethane production. The ethane production with CaCl₂ was the lowest among the salts tested and only a minute increase was noticed with the increase of concentration from 0.01 to 1 kmol m^?3. Ethane production showed a distinct maximum at 0.2 kmol m^?3 MgCl₂. The introduction of 0.01 kmol m^?3 CaCl₂, as well as anaerobic conditions obtained by purging vials with N₂, eliminated that high ethane production. Respiratory activity of the mung bean hypocotyl sections in MgCl₂ concentrations from 0 to 0.5 kmol m^?3 was correlated with ethane but not with ethylene production. The ethane/ethylene ratio showed three patterns for the four salts tested.     

Cajaninstilbene Acid Relaxes Rat Renal Arteries: Roles of Ca2+ Antagonism and Protein Kinase C-Dependent Mechanism

Cajaninstilbene acid (CSA) is a major active component present in the leaves of Cajanus cajan (L.) Millsp. The present study explores the underlying cellular mechanisms for CSA-induced relaxation in rat renal arteries. Vascular reactivity was examined in arterial rings that were suspended in a Multi Myograph System and the expression of signaling proteins was assessed by Western blotting method. CSA (0.1–10 µM) produced relaxations in rings pre-contracted by phenylephrine, serotonin, 9, 11-dideoxy-9α, 11α-epoxymethanoprostaglandin F_2α (U46619), and 60 mM KCl. CSA-induced relaxations did not show difference between genders and were unaffected by endothelium denudation, nor by treatment with N^G-nitro-L-arginine methyl ester, indomethacin, ICI-182780, tetraethylammonium ion, BaCl₂, glibenclamide, 4-aminopyridine or propranolol. CSA reduced contraction induced by CaCl₂ (0.01–5 mM) in Ca²⁺-free 60 mM KCl solution and by 30 nM (−)-Bay K8644 in 15 mM KCl solution. CSA inhibited 60 mM KCl-induced Ca²⁺ influx in smooth muscle of renal arteries. In addition, CSA inhibited contraction evoked by phorbol 12-myristate 13-acetate (PMA, protein kinase C agonist) in Ca²⁺-free Krebs solution. Moreover, CSA reduced the U46619- and PMA-induced phosphorylation of myosin light chain (MLC) at Ser19 and myosin phosphatase target subunit 1 (MYPT1) at Thr853 which was associated with vasoconstriction. CSA also lowered the phosphorylation of protein kinase C (PKCδ) at Thr505. In summary, the present results suggest that CSA relaxes renal arteries in vitro via multiple cellular mechanisms involving partial inhibition of calcium entry via nifedipine-sensitive calcium channels, protein kinase C and Rho kinase.     

CHEMICAL ANTAGONISM OF IONS : IV. EFFECT OF SALT MIXTURES ON GLYCINE ACTIVITY.

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.     

EFFECT OF SALINITY ON POLLEN I. POLLEN VIABILITY AS ALTERED BY INCREASING OSMOTIC PRESSURE WITH NaCl,MgCl2, and CaCl2

Petunia (Petunia hybrida Vilm. cv. ‘Snowstorm') plants were grown in saline solution (NaCl, MgCl₂, and/or CaCl₂) of 0, 1, 2, and 3 bars osmotic pressures. Pollen viability was tested by tetrazolium chloride staining and by germination (by the hanging drop method, using 15 % sucrose and 0.01 % boric acid as the nutrient medium, at 27 ± 1 C). Pollen viability decreased with increased salinity. Pollen from plants grown in single salt solutions of NaCl, MgCl₂, and CaCl₂ (each at 0, 1, 2, or 3 bars osmotic pressure) was germinated in base culture medium. Pollen viability decreased more with NaCl than with MgCl₂ or CaCl₂. In vitro studies of the effects of three salts, viz., NaCl, MgCl₂, and CaCl₂, on pollen germination and tube growth showed that NaCl inhibited germination and pollen tube growth more than did MgCl₂ or CaCl₂. MgCl₂ was least injurious, and even promoted tube growth at 0.5 and 0.75 bars osmotic pressure. Adding low concentrations of MgCl₂ reduced the toxic effect of NaCl and increased the percentage of germination. CaCl₂ reduced the effect of NaCl less than did MgCl₂. We conclude that specific ion effects were more important than osmotic pressure.     

Effects of addition of calcium and magnesium salts on ammonia volatilization during manure decomposition

Ammonia volatilization during aerobic decomposition of poultry manure was significantly reduced through additions of calcium and magnesium salts. The percentage reduction in ammonia loss decreased during the 48 day decomposition period from 85–100% in the first 2–3 weeks, to 23–52% at the end of the experiment. The maximum amount of ammonia which was retained (i.e. maximum reduction in ammonia loss) through addition of the chloride salts of Mg²⁺ or Ca²⁺ was independent of the type of cation. However, CaCl₂ released some of the ammonia initially retained as production of CO₂ and NH₃ from the manure decreased after 3 weeks of decomposition, whereas both MgCl₂ and MgSO₄ did not release any of the initially retained ammonia over the 7 week incubation period. Over the entire incubation period MgCl₂ therefore retained more ammonia than CaCl₂. Magnesium sulphate was considerably less effective in retaining ammonia than either chloride salts.     

Substrate Activation of beta-(1 --> 3) Glucan Synthetase and Its Effect on the Structure of beta-Glucan Obtained from UDP-d-glucose and Particulate Enzyme of Oat Coleoptiles

UDP-d-glucose, at a micromolar level in the presence of MgCl₂ and oat (Avena sativa) coleoptile particulate enzyme which contains both β-(1 → 3) and β-(1 → 4) glucan synthetases, produces glucan with mainly β-(1 → 4) glucosyl linkages. An activation of β-(1 → 3) glucan synthetase by UDP-d-glucose and a decrease in the formation of β-(1 → 3) glucan in the presence of MgCl₂ have been observed. However, at high substrate concentration (≥ 10⁻⁴m), the activation of β-(1 → 3) glucan synthetase is so pronounced that the formation of β-(1 → 3) glucosyl linkage predominates in synthesized glucan regardless of the presence of MgCl₂. These observations may explain the striking shift in the composition of glucan of particulate enzyme from a β-(1 → 4) to β-(1 → 3) glucosyl linkage when UDP-d-glucose concentration is raised from a low concentration (≤ 10⁻⁵m) to a higher concentration (≥ 10⁻⁴m).     

Oxidation-reduction potential of cytochrome C oxidase in mitochondria of yeast grown under various copper concentrations

The pore complex-lamina fraction obtained from nuclear envelope contains a protein phosphokinase activity capable of phosphorylating endogenous and exogenous protein substrates. Its specific activity in the presence of MgCl₂ is approximately twice that of intact nuclear envelope. However, when MgCl₂ is replaced by CoCl₂ in the reaction mixture, a 7 to 12-fold increase in incorporation of ³²P from γ-³²P-ATP into protein substrate occurs. This appears not to be due to an effect of the divalent cation on the substrate, or to inhibition of a phosphoprotein phosphatase activity. Substitution of CuCl₂, MnCl₂, CaCl₂, and ZnCl₂ for MgCl₂ results in a 20 to 30% decrease in incorporation of ³²P. Cyclic AMP and cyclic GMP at 1 μM were without apparent effect. Approximately 40% of the total protein phosphokinase activity of the nuclear envelope is associated with the pore complex-lamina fraction.     

A CD study of the role of metal ions in the conformation of poly(L-lysine)

The effect of LiCl, NaCl, and CsCl as univalent salts, and of CaCl₂, ZnCl₂, and MgCl₂ as divalent salts, on the α and antiparallel β-sheet, and random conformations of poly(L-lysine) (PLL), in water at room temperature were examined by means of CD and compared quantitatively on the basis of elliptical strength at the maximal peak. Changes in the α-helical and antiparallel β-sheet helical conformations of PLL were markedly dependent on the salt concentrations of LiCl, NaCl, and CsCl, which induced decreases in negative intensity in that order. The CD spectrum of the random conformation, the most disordered form, displayed positive cotton effect in concentrations of these salts up to 3.0M and a negative peak in concentrations of 6.0M. The effect of these salts on the random conformation of PLL was stronger than that on the α- and β-conformations in higher concentrations. The CD spectrum of the random conformation in the presence of CaCl₂, ZnCl₂, and MgCl₂, on the other hand, showed negative cotton effect in salt concentrations as low as 3.0M. It was impossible, however, to measure the effect on α- and β-conformations of ZnCl₂ and MgCl₂ above concentrations of 10 mM because of a solubility problem with salts in alkaline solution.     

The Thermodynamic Activity of Calcium Ion in Sodium Chloride-Calcium Chloride Electrolytes

Experimental data on the mean activity coefficient of CaCl₂ in NaCl-CaCl₂ mixtures at ionic strengths below 1 m have been used to prepare a table of activity coefficients for Ca⁺⁺ in solutions of physiological interest. The establishment of an empirical calcium ion activity scale is discussed, and a number of possible assumptions are examined. The assumption γ++ = (γ±)² is suggested as being the simplest with a theoretical basis.     

Electrodichroism of Purple Membrane: Ionic Strength Dependence

The dichroism of purple membrane suspension was measured in dc and ac electric fields. From these measurements three parameters can be obtained: the permanent dipole moment, μ, the electrical polarizability, α, and the retinal angle, δ, (relative to the membrane normal). The functional dependence of the dichroism on the electric field is analyzed. There is a small decrease (~2°) in retinal angle going from dark adapted to the light adapted form. No measurable difference in μ, α, and δ was found under the photocycle. The dichroism was measured in two different salt solutions (KCl and CaCl₂) in the range 0-10 mM. The retinal angle increases from 64° to 68° with increasing ionic strength going through a minimum. This is attributed to the changing (decreasing) inner electric field in the membrane. The polarizability, α, consists of two parts. One component is related to the polarization of the purple membrane and the second component to the ionic cloud. The second component decreases with ion concentration approximately as κ^-3 (κ is the Debye parameter) in agreement with a model calculation for the polarization of the ionic cloud. The origin of the slightly ionic strength dependent permanent dipole moment is not well understood.     

Raman dispersion spectroscopy probes heme distortions in deoxyHb-trout IV involved in its T-state Bohr effect

The depolarization ratios of heme protein Raman lines arising from vibrations of the heme group exhibit significant dependence on the excitation wavelength. From the analysis of this depolarization ratio dispersion, one obtains information about symmetry-lowering distortions δQ^Γ of the heme group that can be classified in terms of the symmetry races Γ = A_1g, B_1g, B_2g, and A_2g in D_4h symmetry. The heme-protein interaction can be changed by the protonation of distinct amino acid side chains (i.e., for instance the Bohr groups in hemoglobin derivates), which gives rise to specific static heme distortions for each protonation state. From the Raman dispersion data, it is possible to obtain parameters by fitting to a theoretical expression of the Raman tensor, which provide information on these static distortions and also about the pK values of the involved titrable side chains. We have applied this method to the ν₄ (1,355 cm^-1) and ν₁₀ (1,620 cm^-1) lines of deoxygenated hemoglobin of the fourth component of trout and have measured their depolarization ratio dispersion as a function of pH between 6 and 9. From the pH dependence of the thus derived parameters, we obtain pK values identical to those of the Bohr groups, which were earlier derived from the corresponding O₂-binding isotherms. These are pK_α1 = pK_α2 = 8.5 for the α and pK_β1 = 7.5, pK_β2 = 7.4 for the β chains. We also obtain the specific distortion parameters for each protonation state. As shown in earlier studies, the ν₄ mode mainly probes distortions from interactions between the proximal histidine and atoms of the heme core (i.e., the nitrogens and the C_α atoms of the pyrroles). Group theoretical argumentation allows us to relate specific changes of the imidazole geometry as determined by its tilt and azimuthal angle and the iron-out-of-plane displacement to distinct variations of the normal distortions δQ^Γ derived from the Raman dispersion data. Thus, we found that the pH dependence of the heme distortions δQ^A1g (totally symmetric) and δQ^B1g (asymmetric) is caused by variations of the azimuthal rather than the tilt angle of the Fe-His (F8) bond. In contrast to this, the ν₁₀ line mainly monitors changes resulting from the interaction between peripheral substituents of the porphyrin macrocycle (vinyl). From the pH dependence of the parameters, it is possible to separately identify distortions δQ^Γ affecting the hemes in the α and β chains, respectively. From this, we find that in the α subunit structural changes induced on protonation of the corresponding Bohr groups are mainly transferred via the Fe—N_ε bond and give rise to changes in the azimuthal angle. In the β subunit, however, in addition, structural changes of the heme pocket arise, which most probably result from protonation of the imidazole of the COOH-terminal His (HC3 β). This rearranges the net of H bonds between His HC3 β, Ser (F9 β), and Glu (F7 β).     

Effects of prostaglandins e(2) and f(2alpha) on the electrofusion of pea mesophyll protoplasts

The effects of prostaglandins E₂ and F_2α on the electrofusion of pea (Pisum sativum cv Ran 1) mesophyll protoplasts were examined. Prostaglandins E₂ and F_2α influenced electrofusion by lowering the threshold voltage necessary for fusion of dielectrophoretically arranged pairs of protoplasts. The direct current voltage threshold decreased with increasing Ca²⁺ concentration up to 0.1 millimolar CaCl₂ and the effects of prostaglandins E₂ and F_2α were more pronounced when CaCl₂ was present in the medium. Treatment with calcium channel blocker methoxy verapamil did not change the prostaglandin effects, while the addition of ethyleneglycol-bis (β-aminoethyl either)-N,N,N′,N′-tetraacetic acid, which binds free Ca²⁺, increased the threshold voltage. Influence of prostaglandins E₂ and F_2α and Ca²⁺ on the membrane fluidity was investigated by analysis of pyrene fluorescence spectra. The values of the ratio between the maximum fluorescence emission intensities of the excimer and the monomer forms (I_ex/I_mon) indicated that prostaglandins and Ca²⁺ decrease the membrane fluidity. It is proposed that electrically evoked displacement of plasmalemma components takes part in the fusion process (U Zimmermann 1982 Biochim Biophys Acta 694: 227-277). We suggest that prostaglandins E₂ and F_2α facilitate the electrofusion of pea mesophyll protoplasts by changing the fluidity of plasmalemma.     

Effects of calcium and kinetin on growth and cell wall composition of pea epicotyls

Kinetin and CaCl₂, in the presence of indoleacetic acid, promoted lateral expansion of epicotyls of decapitated and derooted Alaska pea seedlings (Pisum sativum L.) and inhibited their elongation. This growth response was correlated with the development of cell walls unusually rich in pectic uronic acids. Epicotyls in calcium-auxin solutions continued to enlarge and to add new wall material long after tissues in auxin only had stopped. Longitudinal enlargement, associated with the development of walls poor in pectic uronic acids, was favored by KCl, MgCl₂, and ethylenediaminetetraacetate. The last of these agents promoted the loss of ⁴⁵Ca from the epicotyls. Seedings grown in vermiculite moistened with CaCl₂, KCl, or MgCl₂ solutions did not differ in appearance or in the composition of their walls. They responded similarly to experimental treatment except that the decapitated epicotyls of the MgCl₂-grown plants suffered an absolute loss of pectic uronate when incubated in that salt.     

Electrophysiological responses to salts from antennal chaetoid taste sensilla of the ground beetle Pterostichus aethiops

Antennal gustatory sensilla of the ground beetle Pterostichus aethiops (Pz., 1797) (Coleoptera, Carabidae) respond to salts, the three sensory cells, A-, B- and C-cells, producing action potentials that are distinguished by differences in their shape, amplitude, duration and polarity of spikes. The B-cell (salt cell) was highly sensitive to both ionic composition and concentration of the tested nine salt solutions showing phasic-tonic type of reaction with a pronounced phasic component. The stimulating effect was dominated by the cations involved, and in most cases, monovalent cations were more effective stimuli than divalent cations. Salt concentration/response relations were tested with NaCl at 1, 10, 100 and 1000 mmol l⁻¹: mean firing rates increased from 0.8 to 44 spikes per first second of the response, respectively. The pH value of the stimulating solutions also influenced the B-cell rate of firing. By contrast, the pH level of stimulus solutions influenced the A-cells’ phasic-tonic response more than the ionic composition or concentration of these solutions. Compared to a standard 100 mmol l⁻¹ salt (NaCl) solution (pH 6.3), alkaline solutions of the salts NaCH₃COO, Na₂HPO₄ and Na₂B₄O₇ (pH 7.9, 8.5 and 9.3, respectively, all 100 mmol l⁻¹) induced remarkably stronger responses in the A-cell. On the other hand, the reaction to an acid solution of NaH₂PO₄ (pH 4.5, 100 mmol l⁻¹) was minimal. A-cell responses to neutral salts like NaCl, KCl, CaCl₂, MgCl₂ and C₅H₁₄NOCl (pH 6.1-6.5) varied largely in strength. Very low or no responses were observed with chlorides of divalent cations, CaCl₂ and MgCl₂, and choline chloride (C₅H₁₄NOCl), indicating that the ionic composition of the solutions also affected A-cell responses. Neural activity of the C-cell was not influenced by the salt solutions tested.     

Ca-stimulated secretion of alpha-amylase during development in barley aleurone protoplasts

The effects of gibberellic acid (GA₃) and Ca²⁺ on the synthesis and secretion of α-amylase from protoplasts of barley (Hordeum vulgare L. cv Himalaya) aleurone were studied. Protoplasts undergo dramatic morphological changes whether or not the incubation medium contains GA₃, CaCl₂, or both. Incubation of protoplasts in medium containing both GA₃ and Ca²⁺, however, causes an increase in the α-amylase activity of both incubation medium and tissue extract relative to controls incubated in GA₃ or Ca²⁺ alone. Isoelectric focusing shows that adding Ca²⁺ to incubation media containing GA₃ increases the levels of α-amylase isozymes having high isoelectric points (pI). In the presence of GA₃ alone, only isozymes with low pIs accumulate. The increase in α-amylase activity in the incubation medium begins after 36 hours of incubation, and secretion is complete after about 72 hours. Protoplasts require continuous exposure to Ca²⁺ to maintain elevated levels of α-amylase release. Immunoelectrophoresis shows that Ca²⁺ stimulates the release of low-pI α-amylase isozymes by 3-fold and high-pI isozymes by 30-fold over controls incubated in GA₃ alone. Immunochemical data also show that the half-maximum concentration for this response is between 5 and 10 millimolar CaCl₂. The response is not specific for Ca²⁺ since Sr²⁺ can substitute, although less effectively than Ca²⁺. Pulse-labeling experiments show that α-amylase isozymes produced by aleurone protoplasts in response to GA₃ and Ca²⁺ are newly synthesized. The effects of Ca²⁺ on the process of enzyme synthesis and secretion is not mediated via an effect of this ion on α-amylase stability or on protoplast viability. We conclude that Ca²⁺ directly affects the process of enzyme synthesis and transport. Experiments with protoplasts also argue against the direct involvement of the cell wall in Ca²⁺-stimulated enzyme release.     

THE RHEOLOGY OF THE BLOOD. III

The authors have confirmed the fact that blood serum and plasma behave rheologically like a true viscous liquid. It is true for whole blood only to a first approximation, but with this reservation they have studied the available data and extended the equation of Bingham and Durham to cover protein solutions of various concentrations and at various temperatures as well as mixtures of proteins and corpuscles present in whole blood. If Φ is the fluidity of whole blood, Φ₁ is the fluidity of water and ΔΦ = Φ – Φ₁, then ΔΦ = β₁ b ₁ + β₂ b ₂ + β₃ b ₃ + ··· where β₁, β₂, β₃, etc., are constants for the fluidity lowering of the salts, albumin, globulin, fibrinogen, and the corpuscles, etc., present in the whole blood. The conclusions from the data referred to are intended to buttress this simple equation (6).