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At least 1,171 records · Page 65Linked to original sources
PubMed1997

Granulocyte colony-stimulating factor-induced activation of protein kinase-C in myeloid cells.

Granulocyte colony stimulating factor (G-CSF) regulates survival, proliferation, differentiation, and activation of myeloid cells. It binds to a high affinity receptor (G-CSF-R) expressed on myeloid cells, for which the signal transduction mechanisms other than protein tyrosine kinase (PTK) activation have not been completely identified. We explored the potential involvement of protein kinase-C (PKC) in G-CSF-R signal transduction. In this report, we provide direct evidence of PKC activation by G-CSF-R. G-CSF treatment of peripheral blood neutrophils, granulocytic cell lines (HL-60, NFS-60, KG-1), and monocytic cell lines (WEHI-3B,U-937) resulted in PKC activation. Chelerythrine chloride and HA-100, an isoquinolinesulfonamide derivative, the specific inhibitors of PKC, 1,2-Bis(2-aminophenoxy)ethane-N,N,N',N'-tetra-acetic acid (BAPTA), a chelator of intracellular calcium, and 3,4,5-trimethoxybenzoic acid 8-(diethylamino)-octyl ester (TMB-8), an inhibitor of intracellular calcium release, blocked G-CSF-induced PKC activation in HL-60 cells, and reduced CD11b upregulation in neutrophils, but did not affect ligand-binding or down-modulation of G-CSF-R. Methyl 2,5-dihydroxycinnamate (MDHC), a potent inhibitor of protein tyrosine kinases (PTK), also inhibited PKC activation in response to G-CSF treatment, suggesting that PKC activation may occur downstream of PTK activation. Our results demonstrate the involvement of PKC in G-CSF-R signal transduction, and suggest a common signaling pathway in myeloid cells of granulocytic and monocytic lineages.

Alkaloids↗
PubMed1996

Trypanosoma cruzi: involvement of intracellular calcium in multiplication and differentiation.

The possible role of intracellular Ca2+ level on Trypanosoma cruzi differentiation was explored. The addition to epimastigotes of a Triatoma infestans intestinal homogenate, which that triggers off the differentiation to the infective metacyclic form, induced a sudden rise in [Ca2+]i from the basal value, 94 +/- 28 to 584 +/- 43 nmole/liter. This increase was not affected by the presence of EGTA in the medium. Trypsin-treated intestinal homogenate did not alter the [Ca2+]i of epimastigotes. Calmodulin inhibitors (Calmidazolium, Trifluoperazine, and Chlorpromazine) blocked differentiation. Although the calcium ionophore ionomycin increased [Ca2+]i to 342 +/- 29 nmole/liter, it was unable to induce differentiation by itself. BAY K8644 and Methoxyverapamil (agonist and antagonist of Ca2+ channels, respectively) were unable to affect [Ca2+]i by themselves, or when added to stimulated parasites, and did not exert a stimulatory or inhibitory effect on morphogenesis. BAPTA/AM, a Ca2+ chelator, partially blocked the rise in [Ca2+]i and morphogenesis; this effect was reversed by ionomycin. The requirement of intracellular Ca2+ on epimastigote multiplication was also evaluated. The addition of EGTA to the culture medium led to a decrease in epimastigote multiplication till it practically ceased in the sixth passage. When such parasites were transferred to LIT they partially recovered the growth rate. Parasites from passages III, IV, and V in the Ca(2+)-depleted medium maintained their basal [Ca2+]i, but when treated with the intestinal homogenate, the rise in [Ca2+]i was abrogated. Accordingly, the differentiation percentages of such parasites dropped significantly compared with controls.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗
PubMed1991

Arxula adeninivorans, a yeast assimilating many nitrogenous and aromatic compounds.

A detailed description of the yeast species Arxula adeninivorans (syn. Trichosporon adeninovorans) was given. The yeast assimilated all the sugars, polyalcohols and organic acids used in the conventional carbon compound assimilation test rapidly, except for L-rhamnose, inulin, lactose, lactate and methanol. As nitrogen sources served all conventionally used compounds except creatine and creatinine. Several nitrogenous compounds, e.g. amino acids, purine derivatives, served as sole source of carbon, nitrogen and energy. This was also true of many primary n-alkylamines and terminal diamines, but of nitrogen-less analogous compounds such as alcohols, dialcohols, carboxylic acids and dicarboxylic acids only intermediates of general metabolism were assimilated. For observing growth at the expense of potentially toxic compounds the slant culture method was developed. In this test lactate was readily assimilated but proved to be toxic at the same time. Several aliphatic organic acids and their esters supported growth in this test, as was the case with several benzene compounds such as hydroquinone, 3- and 4-hydroxybenzoic acid, protocatechuic, gentisic, gallic and ferulic acids, 4-hydroxyacetophenone and 1-phenyl-n-dodecane.

Carbon↗
PubMed1990

Bacterial lipopolysaccharide enhances polymorphonuclear leukocyte function independent of changes in intracellular calcium.

Bacterial lipopolysaccharide (LPS) enhanced expression of C3bi receptors (CR3), phagocytosis of opsonized bacteria, and subsequent hydrogen peroxide (H2O2) production by human polymorphonuclear leukocytes (PMNs). The role of changes in intracellular calcium concentration ([Ca2+]i) in LPS-induced priming was examined by determining the effect of modulators of intracellular calcium on enhanced PMN function, determining the ability of calcium ionophores to reproduce the effects of LPS, and measuring PMN [Ca2+]i following addition of LPS. Inhibition of intracellular calcium-dependent processes with TMB-8 or quin-2 blocked all three measures of LPS-induced priming. LPS did not stimulate an increase in [Ca2+]i, and calcium ionophores failed to reproduce the effect of LPS. Maintenance of [Ca2+]i is necessary for LPS priming, but an increase in [Ca2+]i is not a component of the signal transduction pathway leading to PMN priming by LPS.

Aminoquinolines↗
PubMed2001

Ca++ regulation of paracellular permeability in the middle intestine of the eel, Anguilla anguilla.

The role of Ca++ on the regulation of the paracellular pathway permeability of the middle intestine of Anguilla anguilla was studied by measuring the transepithelial resistance and the dilution potential, generated when one half of NaCl in the mucosal solution was substituted iso-osmotically with mannitol, in various experimental conditions altering extracellular and/or intracellular calcium levels. We found that removal of Ca++ in the presence of ethylene glycol-bis(beta-aminoethyl ether) (EGTA) from both the mucosal and the serosal side, but not from one side only, reduced both the transepithelial resistance and the magnitude of the dilution potential. The irreversibility of this effect suggests a destruction of the organization of the junction in the nominal absence of Ca++. However a modulatory role of extracellular Ca++ cannot be excluded. The decrease of the intracellular Ca++ activity, produced by using verapamil to block the Ca++ entry into the cell, or by adding 3,4,5-trimethoxybenzoic acid 8-(diethylamino) octyl ester (hydrochloride) (TMB-8), an inhibitor of Ca++ release from the intracellular stores, reduced both the transepithelial resistance and the magnitude of the dilution potential, indicating a role of cytosolic Ca++ in the modulation of the paracellular permeability. However the rise of calcium activity produced by the Ca++ ionophore calcimycin (A23187) evoked an identical effect, suggesting that any change in physiological intracellular Ca++ activity alters the paracellular permeability.

Anguilla↗
PubMed1998

High protection by grape seed proanthocyanidins (GSPC) of polyunsaturated fatty acids against UV-C induced peroxidation.

The antioxidative effects of grape seed proanthocyanidins (GSPC) were studied in three in-vitro models in which polyunsaturated fatty acids (PUFAs) in aqueous solution and mice liver or brain microsomes were used as oxidative substrates, and UV-C irradiation as the pro-oxidant system. Analysis of UV-C induced lipid peroxidation was carried out by two methods: gas liquid chromatography of residual PUFAs and release of thiobarbituric acid-reactive substances (TBARs) measured by TBA reaction. Results indicate that PUFAs are more radiosensitive when incorporated in single component micelles than in mixed component micelles or microsomes. In every case, PUFA peroxidation was inhibited by low concentrations of GSPC (2 mg/L) while epigallocatecin (EGC) and epigallocatechin gallate (EGCG) monomers, at an equivalent level of epicatechin, exhibited no efficacy in our experimental conditions. This latter effect might be explained by a synergistic action of flavan-3-ol monomers, dimers and oligomers contained in the grape seed extract.

Animals↗
PubMed2000

Protection of dehydrated chicken meat by natural antioxidants as evaluated by electron spin resonance spectrometry.

Dehydrated chicken meat (a(w) = 0.20-0.35) made from mechanically deboned chicken necks can be protected against oxidative deterioration during storage by rosemary extract (at a sensory acceptable level of 1000 ppm, incorporated prior to drying). The efficiency of the rosemary extract was similar to that obtained by synthetic antioxidants in a reference product (70 ppm butylated hydroxyanisole and 70 ppm octyl gallate). Tea extract and coffee extract were less efficient than rosemary and synthetic antioxidants. Among the natural antioxidants tested, grape skin extract provided the least protection against oxidative changes in dehydrated chicken meat. Radicals in the product, quantified by direct measurement by electron spin resonance (ESR) spectrometry, developed similarly to headspace ethane, pentane, and hexanal, and to oxygen depletion both in unprotected and protected products. The ESR signal intensity and headspace hexanal both correlated with the sensory descriptor "rancidity" as evaluated by a trained sensory panel. Hexanal, as a secondary lipid oxidation product, showed an exponential dependence on the level of radicals in the product in agreement with a chain reaction mechanism for autoxidation, and direct ESR measurement may be used in quality control of dehydrated food products.

Animals↗
PubMed2004

Ex planta phytoremediation of trichlorophenol and phenolic allelochemicals via an engineered secretory laccase.

Plant roots release a range of enzymes capable of degrading chemical compounds in their immediate vicinity. We present a system of phytoremediation ex planta based on the overexpression of one such enzyme, a secretory laccase. Laccases catalyze the oxidation of a broad range of phenolic compounds, including polychlorinated phenols such as 2,4,6-trichlorophenol (TCP), that are among the most hazardous and recalcitrant pollutants in the environment. We isolated a secretory laccase cDNA of LAC1, which is specifically expressed in the roots of Gossypium arboreum (cotton). Transgenic Arabidopsis thaliana plants overexpressing LAC1 exhibited enhanced resistance to several phenolic allelochemicals and TCP. The secretory laccase activity in these plants was responsible for the conversion of sinapic acid into a mono-lactone type dimer and for the transformation of TCP.

Arabidopsis↗
PubMed2004

Production and analysis of organic acids in hairy-root cultures of Isatis indigotica Fort. (indigo woad).

Hairy roots were induced from both cotyledon and hypocotyl explants of Isatis indigotica Fort. (indigo woad) through transformation with Agrobaterium rhizogenes strain A4, R1601 and ATCC15834. The results showed that the cotyledons were the preferred explants to hypocotyls and A4 was the most suitable A. rhizogenes strain for the transformation and induction of hairy roots of I. indigotica. High-voltage paper electrophoresis (HVPE) analysis demonstrated the production of mannopine in hairy roots and confirmed the successful transfer of Ri T-DNA (root-inducing transferred DNA) of A. rhizogenes into the I. indigotica genome. Five organic acids, namely CPQ [3-(2-carboxyphenol)-4(3 H )-quinazolinone], syringic acid, salicylic acid, benzoic acid and 2-aminobenzoic acid, which were considered as main antiviral components of I. indigotica, were detected in natural roots, hairy roots and liquid media with high-performance capillary electrophoresis. The results showed CPQ production in hairy roots was significantly higher than that in natural roots. Our results also revealed that all the five organic acids could be excreted from hairy roots into liquid media, and the concentrations of organic acids in the liquid media paralleled those in hairy roots. The hairy roots of I. indigotica grew fast and showed an S-shaped growth curve that reached its apex on the day 24 of culture with a 20-fold increase in fresh weight compared with the starting inoculums. The accumulation of the two organic acids CPQ and syringic acid in liquid media paralleled the growth of hairy roots. MS [Murashige, T. and Skoog, F. (1962) Physiol. Plant. 15, 473-497] medium or half-strength MS medium supplemented with 30 g/l maltose was found to be best for hairy-root culture and accumulation of CPQ.

Benzoic Acid↗