Ce4+-stimulated ion fluxes are responsible for apoptosis and taxol biosynthesis in suspension cultures of Taxus cells

Ion fluxes across the plasma membrane activated by 1 mM Ce⁴⁺, cell apoptosis and taxol biosynthesis in suspension cultures ofTaxus cuspidata were studied. The extracellular pH sharply decreased upon the addition of 1 mM Ce⁴⁺, then increased gradually and exceeded the initial pH value over a time period of 12 h. The extracellular Ca²⁺ concentration decreased within the first 3 h after the addition of Ce⁴⁺, then gradually decreased to one third of initial value in control at about 72 h and remained unchanged afterwards. Experiments with an ion channel blocker and a Ca²⁺-channel blocker indicated that the dynamic changes in extracellular pH and the Ca²⁺ concentration resulted from the Ce⁴⁺-induced activation of H⁺ uptake and Ca²⁺ influx across the plasma membranevia ion channels. A pretreatment of the ion channel blocker initiated Ce⁴⁺-treated cells to undergo necrosis, and the prior addition of the Ca²⁺-channel blocker inhibited Ce⁴⁺-induced taxol biosynthesis and apoptosis. It is thus inferred that H⁺ uptake is necessary for cells to survive a Ce⁴⁺-caused acidic environment and is one of the mechanisms of Ce⁴-induced apoptosis. Furthermore, the Ca²⁺ influx across the plasma membrane mediated both the Ce⁴⁺-induced apoptosis and taxol biosynthesis.     

Prevention by Ce3+ of DNA destruction caused by Hg2+ in fish intestine

The interactions between Hg²⁺, Ce³⁺, and the mixuure of Ce³⁺ and Hg²⁺, and DNA from fish intestine in vitro were investigated by using absorption spectrum and fluorescence emission spectrum. The ultraviolet absorption spectra indicated that the addition of Hg²⁺, Ce³⁺, and the mixture of Ce³⁺ and Hg²⁺ to DNA generated an obviously hypochromic effect. Meanwhile, the peak of DNA at 205.2 nm blue-shifted and at 258.2 nm red-shifted. The size of the hypochromic effect and the peak shift of DNA by metal ion treatments was Hg²⁺>Hg²⁺+Ce³⁺>Ce³⁺. The fluorescence emission spectra showed that with the addition of Hg²⁺, Ce³⁺, and the mixture of Ce³⁺ and Hg²⁺ the emission peak at about 416.2 nm of DNA did not obviously change, but the intensity reduced gradually and the sequence was Hg²⁺>Hg²⁺+Ce²⁺>Ce³⁺. Hg²⁺, Ce³⁺, and the mixture of Ce³⁺ and Hg²⁺ had 1.12, 0.19, and 0.41 binding sites to DNA, respectively; the fluorescence quenching of DNA caused by the metal ions all attributed to static quenching. The binding constants (K _A ) of binding siees were 8.98×10⁴ L/mol and 1.02×10⁴ L/mol, 5.12×10⁴ L/mol and 1.10×10³ L/mol, 6.66×10⁴ L/mol and 2.36×10³ L/mol, respectively. The results showed that Ce³⁺ could relieve the destruction of Hg²⁺ on the DNA structure.     

Signal role for activation of caspase-3-like protease and burst of superoxide anions during Ce<Superscript>4+</Superscript>-induced apoptosis of cultured <Emphasis Type="Italic">Taxus cuspidata</Emphasis> cells

The signal events of 1 mM Ce⁴⁺ (Ce(NH₄)₂(NO₃)₆)-induced apoptosis of cultured Taxus cuspidata cells were investigated. The percentage of apoptotic cells increased from 0.82% to 51.32% within 6 days. Caspase-3-like protease activity became notable during the second day of Ce⁴⁺-treatment, and the maximum activity was 5-fold higher than that of control cells at the fourth day. When the experiment system was pretreated with acetyl-Asp-Glu-Val-Asp-aldehyde (Ac-DEVD-CHO) at 100 M, caspase-3-like activity resulted in distinct inhibition by 70% and 77.3% after 3 and 4 days of induction. Furthermore, 100 M Ac-DEVD-CHO partially reduced the apoptotic cells by 58.6% and 60.8% at day 4 and 5 respectively. Ce⁴⁺ induced superoxide anions (O₂·–) transient burst, and the first peak appeared at around 3.7–4 h, the second appeared at about 7 h. Both O₂·– burst and cell apoptosis were effectively suppressed by application of diphenyl iodonium (NADPH oxidase inhibitor). Inhibition of O₂·– production attenuated caspase-3-like activation by 49% and 53.6% during day 3 and 4 respectively. In addition, a total of 15 protein spots changed in response to caspase-3-like protease activation were identified by two-dimensional gel electrophoresis. These results suggest that Ce⁴⁺ of 1 mM induces apoptosis in suspension cultures of T. cuspidata through O₂·– burst as well as caspase-3-like protease activation. The burst of O₂·– exerts its activity as an upstream of caspase-3-like activation. Our results also implicate that other signal pathways independent of an O₂·– burst possibly participate in mediating caspase-3-like protease activation.     

Ce^3+和La^3+对人工老化沙葱种子活力及生理特性的影响

以未老化和人工老化后的沙葱(Allium mongolicum Regel.)种子为材料,采用氯化铈(Ce3+)和氯化镧(La3+)浸种,测定种子萌发和生理指标,探讨Ce3+和La3+浸种对种子萌发、老化种子活力和生理特性的影响。结果显示:(1)在老化0~5 h时,Ce3+和La3+处理可显著促进沙葱种子萌发,提高种子活力;在老化5 h后,Ce3+和La3+处理对种子萌发无明显促进作用。(2)在老化0~15 h时,Ce3+和La3+处理的沙葱种子中抗氧化酶活性和抗坏血酸(AsA)含量提高,其超氧阴离子自由基(O2-·)产生速率、过氧化氢(H2O2)含量和丙二醛(MDA)含量显著降低;在老化15 h后,Ce3+和La3+处理的种子抗氧化酶活性提高、AsA含量降低,O2-·产生速率和MDA含量提高。(3)在老化5 h时,沙葱种子呼吸速率发生跃变达到最大,Ce3+和La3+处理显著降低了种子呼吸速率。(4)Ce3+和La3+处理在老化0~5 h时提高了沙葱种子超弱发光(UWL)强度,但在老化5 h后沙葱种子的UWL强度降低。研究认为,在沙葱种子人工老化初期,Ce3+和La3+浸种处理可以诱导增强种子抗氧化酶活性和提高AsA含量,有效清除因老化产生积累的过量活性氧(ROS),减轻过氧化伤害,提高种子活力;种子老化中后期,其内部ROS产生与清除系统发生紊乱,加剧了ROS对种子结构的损伤,Ce3+和La3+浸种处理的缓解效应丧失。     

Lanthanide ions promote the hydrolysis of 2,3-Bisphosphoglycerate

The ³¹P NMR studies showed that lanthanide ions promote the site-specific hydrolysis of 2,3-Bisphosphoglycerate (BPG) at pH 7.4 by cleaving the 2 phosphomonoester bond. The effect of fourteen trivalent lanthanide ions and Sc³⁺, and Y³⁺ were compared by the percentage of hydrolysis obtained by determining the inorganic phosphate produced. All the trivalent lanthanide ions promote the hydrolysis, but Sc³⁺ not. Among them, Ce³⁺ affects the reaction mostly. This was mainly attributed to the autooxidation of Ce³⁺ to Ce⁴⁺, since the promoting effect of Ce³⁺ is related to the increasing Ce⁴⁺ amount in the solution and depressed by adding sulphite. Ce⁴⁺ promotes the hydrolysis more efficiently than Ce³⁺ do. The pseudo first-order rate constant for the hydrolysis of BPG by Ce(SO₄)₂ (18.7 mM) at pH 1 and pH 2, 37 °C is 3.1 h^–1 and 0.65 h^–1 respectively. A mechanism with a hydroxo species as reactive intermediate was proposed for the trivalent lanthanide ions. The site-specificity was explainable by this mechanism.     

Improved cell growth and total flavonoids of Saussurea medusa on solid culture medium supplemented with rare earth elements

Callus cultures of Saussurea medusa were cultivated on solid culture medium supplemented with either Ce³⁺, La³⁺, Nd³⁺ or a mixture of rare earth elements. Ce³⁺, 0.05 mM, gave the highest biomass (0.53 g dry wt per flask) and total flavonoids (27.5 mg per flask), which were, 70% and 100% higher than those without Ce³⁺ addition, respectively. Ce³⁺, 0.01–0.1 mM, or La³⁺, 0.05 mM, or the mixture of rare earth elements, 0.025–0.1 mM, can substitute for 6-benzyladenine, and 0.025 mM Ce³⁺ can partly substitute for naphthaleneacetic acid in promoting cell growth and biosynthesis of total flavonoids in S. medusa.     

Luminescent properties and energy transfer in the green phosphors LaBSiO5:Tb3+,Ce3+

LaBSiO₅ phosphors doped with Ce³⁺ and Tb³⁺ were synthesized using the conventional solid‐state method at 1100 °C. The phase purity and luminescent properties of these phosphors are investigated. LaBSiO₅:Tb³⁺ phosphors show intense green emission, and LaBSiO₅ phosphors doped with Ce³⁺ show blue–violet emission under UV light excitation. LaBSiO₅ phosphors co‐doped with Ce³⁺ and Tb³⁺ exhibit blue–violet and green emission under excitation by UV light. The blue–violet emission is due to the 5d–4f transition of Ce³⁺ and the green emission is ascribed to the ⁵D₄ → ⁷ F₅ transition of Tb³⁺. The spectral overlap between the excitation band of Tb³⁺ and the emission band of Ce³⁺ supports the occurrence of energy transfer from Ce³⁺ to Tb³⁺, and the energy transfer process was investigated. Copyright © 2014 John Wiley & Sons, Ltd.     

Dy(3+) and Mn(2+) emission in fluoride- and chloride-based Na(3) (SO(4) )X (X = F or Cl) phosphors

In the present study, Na₃(SO₄)X (X = F or Cl) halosulphate phosphors have been synthesized by the solid‐state diffusion method. The phase formation of the compounds Na₃(SO₄)F and Na₃(SO₄)Cl were confirmed by X‐ray powder diffraction (XRD) measurement. Photoluminescence (PL) excitation spectrum measurement of Na₃(SO₄)F:Ce³⁺ and Na₃(SO₄)Cl:Ce³⁺ shows this phosphor can be efficiently excited by near‐ultraviolet (UV) light and presents a dominant luminescence band centred at 341 nm for Ce³⁺, which is responsible for energy transfer to Dy³⁺and Mn²⁺ ions. The efficient Ce³⁺ → Dy³⁺ energy transfer in Na₃(SO₄)F and Na₃(SO₄)Cl under UV wavelength was observed due to ⁴ F_9/2 to ⁶H_15/2 and ⁶H_13/2 level, while Ce³⁺ → Mn²⁺ was observed due to ⁴ T₁ state to ⁶A₁. The purpose of the present study is to develop and understanding the photoluminescence properties of Ce³⁺‐, Dy³⁺‐ and Mn²⁺‐doped fluoride and chloride Na₃(SO₄)X (X = F or Cl) luminescent material, which can be the efficient phosphors in many applications, such as scintillation applications, TL dosimetry and the lamp industry, etc. Copyright © 2012 John Wiley & Sons, Ltd.     

In vitro selection and characterization of Ni-tolerant callus lines of Setaria italica L

Nickel tolerant callus lines of Setaria italica L. were developed from callus cultures grown on MS medium supplemented with 0.5 mg·dm⁻³ kinetin+2.0 mg·dm⁻³ 2,4-D+2.0 mg·dm⁻³ Ni⁺². Standard growth parameters such as callus fresh and dry weight, growth tolerance index were used as indicators of nickel toxicity. Measurements as early as 2 weeks after the beginning of the treatments did not yield consistent results. However, growth tolerance index at 4, and 8 weeks after the beginning of treatments yielded significant differences among the non-tolerant and tolerant calli. The tolerant calli has enhanced growth at 2.0 mg·dm⁻³ Ni⁺² while non-tolerant calli showed a reverse trend in growth in the presence of 2.0–2.5 mg·dm⁻³ of nickel. The tolerant calli differentiated into mass of embryogenic calli within 4 weeks of culture which could be maintained for prolonged period without loss of regenerative capacity.     

Luminescence and energy transfer in Ce3+, Mn2+‐doped K2AEP2O7 (AE = Ca,Sr) phosphor

Pyrophosphates K₂AEP₂O₇ (AE = Ca, Sr) prepared by the classical solid‐state technique and activated with Ce³⁺ are described. Intense emission was observed in K₂AEP₂O₇ (AE = Ca, Sr). The effect of Mn²⁺ co‐doping was studied. The broad emission peak of Mn²⁺ was observed at 534 nm in K₂SrP₂O₇:Ce³⁺ and at 539 nm in K₂CaP₂O₇:Ce³⁺, Mn²⁺. Mn²⁺ emission was greatly enhanced by addition of the sensitizer Ce³⁺ due to efficient energy transfer from Ce³⁺ to Mn²⁺. Copyright © 2015 John Wiley & Sons, Ltd.     

Photoluminescence of Dy3+ activator sensitized by Ce3+ in KNaSO4 microphosphor

The KNaSO₄ microphosphor doped with Ce or Ce and Dy prepared by a wet chemical method was studied by scanning electron microscopy (SEM) and characterized by photoluminescence (PL). KNaSO₄ has a 5‐µm particle size detected by SEM. The KNaSO₄:Ce³⁺ spectrum shows a single emission band at 327 nm for an excitation of 269 nm due to 5d → 4f transition of the Ce³⁺ ion, indicating weak spin orbiting coupling of the Ce³⁺ ground state. Efficient energy transfer takes place from Ce³⁺ → Dy³⁺ sublattices indicating that Ce³⁺ could effectively sensitize Dy³⁺ (orange emission) and that the Ce³⁺ emission weakens significantly in KNaSO₄. The powder form of prepared KNaSO₄ show negligible change in morphologies and hence no effect on the particle size. The characteristics of this powder could provide improved luminescence properties. The development and understanding of this photoluminescence and the effect of Dy³⁺ on KNaSO₄: Ce³⁺ are discussed. Copyright © 2014 John Wiley & Sons, Ltd.     

Energy transfer between Ce3+ → Gd3+ or Tb3+ in KNaSO4 microphosphor

KNaSO₄ microphosphor doped with Ce,Gd and Ce,Tb and prepared by a wet chemical method was studied using X‐ray diffraction (XRD), scanning electron microscopy (SEM) and photoluminescence (PL) characterization. KNaSO₄ has a 5‐µm particle size detected by SEM. KNaSO₄:Ce³⁺,Tb³⁺ showed blue and green emission (at 494 nm, 557 nm, 590 nm) of Tb³⁺ due to ⁵D₄ → ⁷F_J (J = 4, 5, 6) transitions. KNaSO₄:Ce³⁺,Gd³⁺ showed luminescence in the ultraviolet (UV) light region at 314 nm for an excitation at 271 nm wavelength. It was observed that efficient energy transfer took place from Ce³⁺ → Gd³⁺ and Ce³⁺ → Tb³⁺ sublattices indicating that Ce³⁺ could effectively sensitize Gd³⁺ or Tb³⁺ (green emission). Ce³⁺ emission weakened and Gd³⁺ or Tb³⁺ enhanced the emission significantly in KNaSO₄. This paper discusses the development and understanding of photoluminescence and the effect of Tb³⁺ and Gd³⁺ on KNaSO₄:Ce³⁺. Copyright © 2015 John Wiley & Sons, Ltd.     

Interaction of tert -butyl Hydroperoxide with Hypochlorous Acid. A Spin Trapping and Chemiluminescence Study

The formation of radical species during the reaction of tert-butyl hydroperoxide and hypochlorous acid has been investigated by spin trapping and chemiluminescence. A superposition of two signals appeared incubating tert-butyl hydroperoxide with hypochlorous acid in the presence of the spin trap &#102 -(4-pyridyl-1-oxide)-N-tert-butylnitrone (POBN). The first signal (a_N = 1.537mT, a^&#103_H = 0.148mT) was an oxidation product of POBN caused by the action of hypochlorous acid. The second spin adduct (a_N = 1.484mT, a^&#103_H = 0.233mT) was derived from a radical species that was formed in the result of reaction of tert-butyl hydroperoxide with hypochlorous acid. Similarly, a superposition of two signals was also obtained using the spin trap N-tert-butyl- &#102 -phenylnitrone (PBN). tert-Butyl hydroperoxide was also treated with Fe²⁺ or Ce⁴⁺ in the presence of POBN. Using Fe²⁺ a spin adduct with a _N= 1.633mT and a^&#103_H = 0.276mT was observed. The major spin adduct formed with Ce⁴⁺ was characterised by α_N = 1.480mT and a^&#103_H = 0.233mT. The reaction of tert-butyl hydroperoxide with hypochlorous acid was accompanied by a light emission, that time profile and intensity were identical to those emission using Ce⁴⁺. The addition of Fe²⁺ to tert-butyl hydroperoxide yielded a much smaller chemiluminescence. Thus, tert-butyl hydroperoxide yielded in its reaction with hypochlorous acid or Ce⁴⁺ the same spin adduct and the same luminescence profile. Because Ce⁴⁺ is known to oxidise organic hydroperoxides to peroxyl radical species, it can be concluded that a similar reaction takes place in the case of hypochlorous acid.     

Effect of pH on the stability of Pleurotus eryngii versatile peroxidase during heterologous production in Emericella nidulans

Complementary DNA (cDNA) encoding the new versatile peroxidase from the ligninolytic basidiomycete Pleurotus eryngii has been expressed in the ascomycete Emericella nidulans. In recombinant E. nidulans cultures, the pH reached values as high as 8.3, correlating with a sharp decrease in peroxidase activity. Peroxidase was rapidly inactivated at alkaline pH, but was comparatively stable at acidic pH. The peroxidase inactivation in alkaline buffer could be reversed by adding Ca²⁺ and lowering the pH. However, reactivation did not result after incubating the enzyme in non-buffered E. nidulans cultures that reached pH 7.5. To optimize recombinant peroxidase production, the effect of controlling the pH in E. nidulans bioreactor cultures was studied. An extended growth period, and a significant increase in the recombinant peroxidase level (5.3-fold higher activity than in the bioreactor without pH control) was obtained when the pH was maintained at 6.8, showing that culture pH is an important parameter for recombinant peroxidase production.     

Luminescence properties of Ce3+ in orthosilicate oxyapatite NaY9(SiO4)6O2

Ce³⁺‐doped orthosilicate oxyapatite NaY₉(SiO₄)₆O₂ phosphors NaY_9–x(SiO₄)₆O₂:xCe³⁺ were prepared by a conventional high‐temperature solid‐state reaction method, and their spectroscopic characteristics were systematically investigated. The occupancies of Ce³⁺ ions at two different sites (Wyckoff 6 h and 4f sites) in NaY₉(SiO₄)₆O₂ were determined. The influence of doping concentration on the emission intensity of Ce³⁺ was investigated and the critical distance Rc was estimated in terms of the concentration quenching data.     

The luminescent properties and crystal structure of Sr(1.5‐x)‐(1.5y)Mg0.5SiO4:xEu2+,yCe3+ blue phosphor synthesized by co‐precipitation method

In order to improve the luminescent performance of silicate blue phosphors, Sr_{(1.5‐x)‐(1.5y)}Mg_0.5SiO₄:xEu²⁺,yCe³⁺ phosphors were synthesized using one‐step calcination of a precursor prepared by chemical co‐precipitation. The crystal structure and luminescent properties of the phosphors were analyzed using X‐ray diffraction and fluorescence spectrophotometry, respectively. Because the activated ions (Eu²⁺) can occupy two different types of sites (Sr₁ and Sr₂), the emission spectrum of Eu²⁺ excited at 350 nm contains two single bands (EM₁ and EM₂) in the wavelength range 400–550 nm, centered at 463 nm, and the emission intensity first increases and then decreases with increasing concentrations of Eu²⁺ ions. Co‐doping of Ce³⁺ ions can greatly enhance the emission intensity of Eu²⁺ by transferring its excitation energy to Eu²⁺. Because of concentration quenching, a higher substitution concentration of Ce³⁺ can lead to a decrease in the intensity. Meanwhile, the quantum efficiency of the phosphor is improved after doping with Ce³⁺, and a blue shift phenomenon is observed in the CIE chromaticity diagram. The results indicate that Sr_{(1.5‐x)‐(1.5y)}Mg_0.5SiO₄:xEu²⁺,yCe³⁺ can be used as a potential new blue phosphor for white light‐emitting diodes.     

Sodium is required for nitrogenase activity in cyanobacteria

The cyanobacteriaAnabaena torulosa andAnabaena L-31 require sodium (Na⁺) for growth on N₂ but not in the presence of NH₄ ⁺. Na⁺-starved cultures show relatively little or no nitrogenase activity although they differentiate normal heterocysts. Nitrogenase activity appears rapidly on addition of Na⁺ to Na⁺-starved cultures. The time course of appearance of activity after addition of Na⁺ suggests that Na⁺ is involved in activation of the existing enzyme rather than in its de novo synthesis.     

Microcalorimetric Study on the Toxic Effect of Pb<Superscript>2+</Superscript> to <Emphasis Type="Italic">Tetrahymena</Emphasis>

The toxic effect of Pb²⁺ has been studied in eukaryotic cells by using Tetrahymena as a target. The maximum power (P _m) and the growth rate constant (k) were determined, which showed that values of P _m and k were linked to the concentration (C) of Pb²⁺. The addition of Pb²⁺ caused a decrease of the maximum heat production and growth rate constant, indicating that Tetrahymena growth was inhibited in the presence of Pb²⁺, and Pb²⁺ took part in the metabolism of cells. From micrographs, morphological changes of Tetrahymena were observed with addition of Pb²⁺, indicating that the toxic effect of Pb²⁺ derived from destroying the membrane of surface of Tetrahymena. According to the thermogenic curves and photos of Tetrahymena under different conditions, it is clear that metabolic mechanism of Halobacterium halobium R1 growth has been changed with the addition of Pb²⁺.     

K+-conductance and electrogenic Na+/K+ transport of cultured bovine pigmented ciliary epithelium

Summary Using intracellular microelectrode technique, we investigated the changes in membrane voltage (V) of cultured bovine pigmented ciliary epithelial cells induced by different extracellular solutions. (1)V in 213 cells under steady-state conditions averaged –46.1±0.6 mV (sem). (2) Increasing extracellular K⁺ concentration ([K⁺] _o ) depolarizedV. Addition of Ba²⁺ could diminish this response. (3) Depolarization on doubling [K⁺] _o was increased at higher [K⁺] _o (or low voltage). (4) Removing extracellular Ca²⁺ decreasedV and reduced theV amplitude on increasing [K⁺] _o . (5)V was pH sensitive. Extra-and intracellular acidification depolarizedV; alkalinization induced a hyperpolarization.V responses to high [K⁺] _o were reduced at acidic extracellular pH. (6) Removing K _o ⁺ depolarized, K _o ⁺ readdition after K⁺ depletion transiently hyperpolarizedV. These responses were insensitive to Ba²⁺ but were abolished in the presence of ouabain or in Na⁺-free medium. (7) Na⁺ readdition after Na⁺ depletion transiently hyperpolarizedV. This reaction was markedly reduced in the presence of ouabain or in K⁺-free solution but unchanged by Ba²⁺. It is concluded that in cultured bovine pigmented ciliary epithelial cells K⁺ conductance depends on Ca²⁺, pH and [K⁺] _o (or voltage). An electrogenic Na⁺/K⁺-transport is present, which is stimulated during recovery from K⁺ or Na⁺ depletion. This transport is inhibited by ouabain and in K⁺-or Na⁺-free medium.     

Elevation of Different Ion-Specific ATPase Activities by L-Thyroxine (T4) in Different Tissues of Tasar Silkworm, Antheraea mylitta (Lepidoptera: Saturniidae) during Developmental Stages

Tissue-specific age-dependent changes were observed in Na⁺K⁺-, Ca²⁺-, and Mg²⁺-ATPase activities in tropical tasar silkworm, Antheraea mylitta Drury. Maximum enzyme activity was recorded in all the tissues on day 12 (before spinning) in control group of animals. In testis, Na⁺K⁺-, Ca²⁺-, and Mg²⁺-ATPase activities gradually increased from day 2 to day 12 during fifth larval age and level was maintained up to adult eclosion while, in ovary, a marked decline was noted up to day of adult emergence. Further, a significant and sharp rise was found in ATPase activity in silk gland tissue up to day 12 and afterwards a drastic fall was noted on day 15 (end of spinning) during fifth larval age.Administration of T4 to fifth stage larvae (1 hr old) at doses 0.5–2.0 μg/g significantly elevated the Na⁺K⁺-, Ca²⁺-, and Mg²⁺-ATPase activities in larval and pupal gonads in a dose-dependent fashion. But, in moths, the enhancement was very much confined to Na⁺K⁺- and Ca²⁺-ATPase in testes and only Ca²⁺-ATPase in ovaries. Again, in silk glands thyroxine (0.5–2.0 μg/g) caused a significant rise in the all ion-dependent ATPase activities only during the fifth larval stage. Interestingly, higher doses of T4 (4.0 μg/g) caused a significant reduction in Na⁺K⁺-, Ca²⁺- and Mg²⁺-ATPase in all the tissues almost all the days studied so far. However, lower doses of T4 (0.1 and 0.25 μg/g) remained ineffective in altering the different ion-specific ATPase activities. This study suggests, that mammalian thyroxine has a metabolic influence showing biphasic nature of action in tasar silkworm ATPase system.