Tetrastischus howardi density and dispersal toward augmentation biological control of sugarcane borer.

The number of Tetrastischus howardi (Olliff) females to be released and their dispersion should be known, that way, used D. saccharalis pupae as sentinel host to measure parasitism as function of the release density of the parasitoid and its location in the field. Two sets of trials were run aiming first to define the number of parasitoids to be released and the dispersal of the parasitoid using plots in sugarcane commercial fields, respectively. Pieces of sugarcane stalk holding sentinel pupae were taken to the field and exposed to parasitism in both trials. The parasitoid was released at the rate of 20, 40, 80, and 160 females per sentinel pupa, except for the control plot without releasing. The parasitism rate was calculated based on the recovered pupae after 96 h of exposure time from releasing the parasitoids. The models estimated the best parasitism rate by releasing 102 parasitoids per pupa. In the second trial, sentinel pupae were arranged in five subsequent circles corresponding 4, 8, 12, 16, and 20 m around the central parasitoid releasing point at rate of 4, 8, 12, 16, and 18 pupae per circle. The mean estimated dispersal distance was 7.64 m, with a covering area of 80.07 m2. Based on these findings, release of T. howardi is recommended in 125 points per hectare of sugarcane at rate of 102 females per pupa of the pest aiming to achieve homogeneous distribution and parasitism.

Modulation of the induction of ornithine decarboxylase by some opioid receptor agonists in immune cells and cardiomyocytes.

The ability of natural and synthetic opioids to modulate the induction of ornithine decarboxylase (ODC) was investigated in immune cells and cardiomyocytes in culture. In particular, Leu-enkephalin, which shows preference for delta-receptors, enhanced ODC activity in both thymocytes and cardiomyocytes, whereas the effect of U-50488H, a synthetic kappa-selective agonist, was cell-specific. In thymocytes, U-50488H markedly inhibited the induction of the enzyme elicited by the mitogen concanavalin A (Con A) or by a combined treatment with PMA and A23187, and also reduced basal ODC activity. However the drug did not affect ODC induced by other stimuli. The inhibition of the induction of ODC activity was accompanied by a reduction of ODC mRNA level and an acceleration of ODC turnover. The action of U-50488H in thymocytes does not appear to be mediated by kappa or other classical opioid receptors lacking both stereospecificity and antagonist sensitivity, but may involve a pertussis toxin-sensitive G protein. Splenocytes also showed the ODC inhibiting effect of U-50488H, although they were less sensitive compared to thymocytes. In contrast, U-50488H enhanced ODC activity in cardiomyocytes and this effect was blocked by a specific kappa-antagonist. In conclusion, these results indicate that some opioid agonists can modulate ODC expression in non neural cells. In particular, kappa-opioid receptors may be involved in the U-50488H action in cardiomyocytes, and a distinct site, linked to inhibition of cell proliferation, may operate in immune cells.

Inhibition of the expression of ornithine decarboxylase and c-Myc by cell-permeant ceramide in difluoromethylornithine-resistant leukaemia cells.

Ceramide has emerged as a novel lipid mediator in cell growth and apoptosis. In difluoromethylornithine-resistant L1210 cells stimulated to growth from quiescence, the cell-permeant analogues of ceramide N-acetylsphingosine (C2-ceramide) and N-hexanoylsphingosine (C6-ceramide) inhibited the induction of ornithine decarboxylase (ODC) activity with IC50 of 8.3 and 1.5 microM respectively. This effect was strictly related to the ability to inhibit cell growth and [3H]thymidine incorporation. The suppression of cell growth was also associated with apoptosis. The addition of bacterial sphingomyelinase resulted in a significant, but limited, reduction of ODC induction and [3H]thymidine incorporation. Bacterial lipopolysaccharide, which may act as a ceramide analogue, also inhibited the induction of the enzyme. Moreover, C6-ceramide largely prevented the accumulation of ODC mRNA and its precursor, ODC heterogeneous nuclear RNA, that accompanied the induction of ODC activity. A slight increase in ODC turnover was also observed. The DNA-binding activity of some transcription factors known to bind and transactivate the ODC gene was investigated by gel mobility-shift assay under the same experimental conditions. However, only the binding of Myc/Max was negatively affected by the treatment with C6-ceramide. Furthermore, the amount of immunoreactive c-Myc, which increased after stimulation of the cells to growth, was strongly reduced by C6-ceramide. These results suggest that the inhibition of c-Myc and ODC expression may be early events in the response of leukaemia cells to ceramide.

ATP depletion inhibits glucocorticoid-induced thymocyte apoptosis.

In quiescent thymocytes, mitochondrial de-energization was not correlated to apoptotic death. In fact, thymocytes treated with oligomycin, a highly specific inhibitor of ATP synthase, alone or with atractyloside to block ATP translocation from the cytoplasm, were alive, even if their mitochondria were depolarized, as revealed by flow cytometry after Rhodamine 123 staining. Furthermore, oligomycin was a powerful inhibitor of apoptosis induced in rat thymocytes by dexamethasone and, to a lesser extent, by the calcium ionophore A23187 and etoposide, but was without effect when apoptosis was induced by staurosporine, and increased cell death in mitogen-treated thymocytes. The inhibition of apoptosis was confirmed by morphological criteria, inhibition of inter-nucleosomal DNA fragmentation and inhibition of the loss of membrane integrity. The anti-apoptotic effect of oligomycin in cells treated with A23187 or etoposide was correlated to the inhibition of protein synthesis, while inhibition of apoptosis induced by dexamethasone, already evident at an oligomycin concentration of 10 ng/ml, was instead strictly correlated to the effect exerted on the cellular ATP level. Thymocyte apoptosis triggered by dexamethasone was blocked or delayed by inhibitors of respiratory-chain uncouplers, inhibitors of ATP synthase and antioxidants: a lasting protection from dexamethasone-induced apoptosis was always correlated to a drastic and rapid reduction in ATP level (31-35% of control), while a delay in the death process was characterized by a moderate decrease in ATP (73-82% of control). Oligomycin inhibited the specific binding of radioactive corticosteroid to thymocyte nuclei, confirming the inhibitory effect of ATP depletion on glucocorticoid binding and suggesting that ATP depletion is a common mediator of the anti-apoptotic action of different effectors in glucocorticoid-induced apoptosis. In conclusion, the reported data indicate that ATP may act as a cellular modulator of some forms of apoptosis, depending on the death trigger, and that in quiescent cells the de-energization of mitochondria is not necessarily linked to apoptosis.

Inhibition of the expression of ornithine decarboxylase by haloperidol in difluoromethylornithine-resistant leukemia cells.

In difluoromethylornithine-resistant L1210 cells stimulated to grow from quiescence, haloperidol caused an early and dose-dependent inhibition of the induction of ornithine decarboxylase (ODC) activity, with an IC50 of 3.5 microM. This effect was accompanied by a reduction in the ODC mRNA level and inhibition of cell growth. Other sigma ligands of different chemical classes inhibited the induction of ODC activity, whereas sulpiride, a dopamine antagonist devoid of sigma-binding affinity, was ineffective. These results indicate that the inhibition of ODC expression may be an early event involved in the antiproliferative response of leukemia cells to haloperidol.

Inhibition of the expression of ornithine decarboxylase by some kappa-opioidergic receptor ligands in difluoromethylornithine-resistant L1210 cells.

In difluoromethylornithine resistant L1210 cells stimulated to growth from quiescence, the selective kappa-opioidergic agonist trans-(+/-)-3,4-dichloro-N-[2-(1-pyrrolidinyl)cyclohexyl]benzeneaceta mid e (U-50488H) caused a dose dependent inhibition of the induction of ODC activity, with a half-maximal effect at about 1 microM. U-50488H also provoked reduction of ODC mRNA level and increase of ODC turnover, as well as inhibition of cell growth. U-69593, another kappa-selective agonist, was only slightly effective. The action of U-50488H on ODC induction was not blocked by naloxone, beta-chlornaltrexamine or by the kappa-selective opioid antagonists Mr1452 and nor-binaltorphimine (nBNI). Actually Mr1452 and nBNI exerted some inhibitory effect. Furthermore, the separated enantiomers (+) and (-) of U-50488H were similarly effective. The (-)cis-(1S,2R)-U50488 stereoisomer, exhibiting low affinity for kappa and high affinity for sigma receptors and carbetapentane, another sigma ligand, also inhibited ODC induction, although less effectively than U-50488H. None of several other opioid ligands tested had significant effects on ODC induction. In conclusion, the inhibition of ODC expression by U-50488H does not involve classical, enantiospecific opioid receptors; rather, these results suggest the involvement of a distinct site of action linked to inhibition of lymphoid cell proliferation.

Oxygen tension influences DNA fragmentation and cell death in glucocorticoid-treated thymocytes.

Internucleosomal DNA fragmentation and cell death induced by dexamethasone in rat thymocytes were inhibited when cells were cultured in 95% N2/5% CO2 atmosphere, in which oxygen was rapidly reduced to under 0.5%. DNA fragmentation was delayed by a less severe hypoxia in 5% oxygen whilst in cell cultured in high oxygen atmosphere (95% O2) cell death was increased. On the other hand, prolonged oxygen deprivation caused an increase of spontaneous apoptotic cell death. Hypoxia also inhibited DNA fragmentation induced by calcium ionophore A23187, but not by topoisomerase inhibitor camptothecin. These data support the hypothesis of the involvement of oxygen reactive species in calcium-mediated apoptosis and suggest a complex role of oxygen in the modulation of programmed cell death.

Post-transcriptional inhibition of ornithine decarboxylase induction by zinc in a difluoromethylornithine resistant cell line.

Addition of Zn2+ to cell medium inhibited the induction of ornithine decarboxylase (ODC) activity in ODC overproducing L1210-DFMOr cells. A significant effect was observed at a concentration as low as 0.01 mM, however, a more marked inhibition was caused by the addition of 0.1 mM Zn2+. The inhibition of the induction of ODC activity was accompanied by a proportional decrease in the content of immunoreactive ODC protein, whereas the level of ODC mRNA, determined by a solution hybridization RNase protection assay, was not affected significantly. Instead, some acceleration of ODC turnover was observed. The addition of 0.1 mM Co2+ or Mn2+, but not of other divalent metal ions, also inhibited ODC induction; differently from Zn2+ however, these metals affected cell viability and/or cell growth. Removal of endogenous Zn2+ by a chelator also provoked a strong decrease of ODC induction, which was reversed by Zn2+. However, addition of Zn2+ in excess of the chelator proved to be markedly inhibitory. These results indicate that both a restricted Zn2+ availability and an enhanced presence of the metal can inhibit the induction of ODC in L1210-DFMOr cells.

Acylated proteins in Borrelia hermsii, Borrelia parkeri, Borrelia anserina, and Borrelia coriaceae.

Borrelia hermsii, Borrelia parkeri, Borrelia anserina, and Borrelia coriaceae produced several lipoproteins identified by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and fluorography of bacteria grown in [3H]palmitate. Five major acylated proteins were demonstrated by sequential alkaline and acid hydrolysis. High-pressure liquid chromatography of isolated proteins confirmed that covalently bound radioactivity was represented by fatty acids.

Zinc can influence ornithine decarboxylase activity in rat thymus cells.

The thymus of young rats contained a high basal activity of ornithine decarboxylase (ODC). Treatment with zinc sulphate caused a slight increase of thymic ODC activity within 6 hours and a more marked enhancement (three-fold) in the spleen 24 h after treatment. In spite of the high activity of thymic ODCin vivo, ODC was not detectable in primary cultures of rat thymocytes, but was early and largely induced after treatment with Concanavalin A (Con A). The presence of 0.1 mM zinc in the medium increased the response of ODC to Con A. This effect of zinc in mitogen activated thymocytes may be due to the stabilization of ODC, which was found to decay with a half life of 65 min after the block of protein synthesis with cycloheximide. On the contrary in absence of zinc the half life of the enzyme was 40 min, as in the rat thymus in vivo.Zinc alone, at 0.1 mM concentration, did not affect ODC activity in resting thymocytes during the early times, but the metal was able to cause an increase of the enzyme activity after 4-6 days of culture. Other heavy metals such as mercury, cadmium and copper provoked a late increase of ODC activity, but their action was evident only at dosages which were toxic for the cells.

Ornithine decarboxylase and ornithine decarboxylase-inhibiting activity in rat thymocytes.

Isolation of thymocytes from rat thymus resulted in the disappearance of the high activity of ornithine decarboxylase (ODC) that characterizes the thymus of young rats, together with the appearance of an antizyme-like ODC inhibiting activity, which showed a chromatographic profile that resembled that of dexamethasone-treated rat thymus. Omission of serum or addition of dexamethasone or spermidine did not affect appreciably the extent of the antizyme-like activity. On the other hand, a variety of hormonal effectors, i.e. insulin, glucagon, adrenalin and T3, as well as the phorbol ester, PMA or the mitogen, concanavalin A (Con A) induced ODC activity in cultured thymocytes together with the disappearance of the antizyme-like activity. A paradoxical, transient induction of ODC was caused by the transcriptional inhibitor, actinomycin D. Complexed ODC was detected in rat thymus, but not in thymocytes, either quiescent or stimulated by mitogens. These results indicate that thymic lymphocytes can express either ODC activity or its inhibitor depending on the hormonal and proliferative status of the cells.

[Coenzyme Q9 biosynthesis in the aging myocardium after ischemia and reperfusion]. / Biosintesi di coenzima Q9 nel miocardio senescente dopo ischemia e riperfusione.

The purpose of the present study was to evaluate the biosynthesis of coenzyme Q9 (CoQ9) in isolated and perfused young (6 months) and aged (24 months) rat hearts, either under aerobic perfusion condition or during postischemic reperfusion. The young and aged hearts have been divided into 2 groups: Group A, aerobic perfusion for 60 min with recirculating Krebs-Henseleit solution, containing 0.8 microM p-OH-[U-14C]benzoate plus 2.5 mM mevalonlactone; Group B, severe ischemic perfusion for 30 min, followed by 60 min of reperfusion under the same experimental condition of Group A. At the end of the reperfusion the mitochondrial content of CoQ9 was lower in young than aged rat hearts (p < 0.01). In Group A the incorporation of the labeled precursor into mitochondrial CoQ9 was greater in the hearts of aged than young rats (p < 0.01); on the contrary, in Group B this incorporation was significantly reduced in aged than in young rats (p < 0.05). Thus, it is possible that, in the aged rat heart, the higher activity of CoQ9 biosynthesis is related to an elevated turnover of the coenzyme due to the aging process; moreover, this activity is partially reduced by an ischemic-reperfusion stress.

Induction of ornithine decarboxylase by transcriptional inhibitors in quiescent thymocytes.

The transcriptional inhibitors actinomycin D and dichlororibofuranosylbenzimidazole induced ornithine decarboxylase activity in isolated, quiescent thymocytes, which otherwise did not show detectable levels of the enzyme. This paradoxical induction was transient and dependent on the presence of serum and continuous protein synthesis. However, alpha-amanitin, another inhibitor of transcription, did not affect ornithine decarboxylase activity. Dichlororibofuranosylbenzimidazole and actinomycin D were unable to enhance the activity of spermidine acetyltransferase or S-adenosyl-methionine decarboxylase, which are other inducible and short-lived enzymes involved in the metabolism of polyamines.

Effects of dexamethasone on spermidine N1-acetyltransferase and ornithine activities in rat spleen.

Treatment of rats with the glucocorticoid dexamethasone causes an increase in the activity of cytosolic spermidine N1-acetyltransferase both in the spleen and thymus, but not, however, in liver, kidney or lung. The induced spermidine N1-acetyltransferase activity in the spleen catalyses acetylation of spermidine as well as spermine and sym-norspermidine, but not of diamines and histones. The enzyme induction depends on the dose of dexamethasone, and is suppressed by cycloheximide, which suggests that de novo protein synthesis is required for the action of this glucocorticoid. N1-acetylspermidine accumulates in the spleen after dexamethasone treatment, while spermidine progressively decreases and is partly converted into putrescine, the content of which transiently increases. In accordance with previous reports, dexamethasone was found to cause a rapid and large fall in the activity of spleen ornithine decarboxylase which was effected via the appearance of an inhibitor of the enzyme. Glucocorticoids exert large catabolic effects on lymphoid tissues, and further selectively affect the activities of spermidine N1-acetyltransferase and ornithine decarboxylase in the thymus and spleen. These latter selective responses may represent an important early event in lymphoid tissue response to glucocorticoid hormones.

Accumulation of N1-acetylspermidine in heart and spleen of isoprenaline-treated rats.

N1-Acetylspermidine is not detectable in rat heart, but its content greatly increases after a single injection of isoprenaline (10 mg/kg), reaching a concentration of about 10 nmol/g of tissue 4 h after the treatment. Part of the accumulated N1-acetylspermidine was split to putrescine. Isoprenaline also caused an increase of N1-acetylspermidine in the spleen, where its concentration increased 3.5-fold 6 h after the catecholamine. The accumulation of N1-acetylspermidine was dependent on the dose of isoprenaline in both the heart and the spleen, and was strongly inhibited by beta-antagonists and inhibitors of protein synthesis.

Separation of N1- and N8-acetylspermidine isomers by reversed-phase column liquid chromatography after derivatization with dansyl chloride.

The separation of dansyl derivatives of N1- and N8-acetylspermidine by reversed-phase column liquid chromatography is reported. The influence of organic solvents on the retention of acetylspermidines was studied. Best resolutions were achieved using a C18 column and a ternary mobile phase composed of water, methanol and acetonitrile. The precolumn derivatization method permitted the detection of picomole quantities. A method for the determination of acetylspermidines in rat tissues is described.

Effect of adrenergic stimulation on ornithine decarboxylase activity in the rat spleen.

The effect of a single administration of catecholamines on ornithine decarboxylase activity and polyamine biosynthesis in the rat spleen was investigated. Isoproterenol elicited a dose-dependent increase in spleen ODC activity which reached a maximum 4 hr after the administration of the drug. Putrescine content was also found to increase within a few hours, whereas S-adenosylmethionine decarboxylase activity and spermidine and spermine levels did not change significantly. Adrenaline and noradrenaline proved to be even more effective in increasing splenic ODC activity than isoproterenol. alpha- and beta-adrenergic antagonists prevented the ODC increase by catecholamines to a different extent.