Activity of cell wall-associated enzymes in ripening olive fruit

Enzymatically active cell wall isolaled from olive (Olea europaea) fruit was employed Hi investigate some hydrolytic enzymes bound to the cell wall and the changes in these during ripening. Seven glycosidases. β-glucosidase (EC 3.2.1.21) α-galactosidase (EC 3.2.1.22). β-galactosidase (EC 3.2.1.23). α-arabinosidase (EC 3.2.1.55), α-mannosidase (EC 3.2.1,24). β-xylosidase (EC 3.2.1.37) and β-N-acetylglucosamidase (EC 3.2.1.30). as well as Cx-cellulase (EC 3.2.1.4) and endo-polygalacturonase (EC 3.2.1.15). were identified in the cell wall preparation, at four stages of ripeness (mature green. changing colour, black and black-ripe). Activities of all these cell wall-associated enzymes fionicallv and covalently linked) were determined either by cell wall incubation with artificial substrate or after extraction from the cell wall with buffers of high salt concentration (Cx-cellulase). and were compared to those of forms solubilized from acetone powders with 500 nM citrate buffer (cytoplasmic and/or apoplastic plus ionically hound to cell wall) In general, the activities of low ionic strength buffer-soluble enzymes were found to be much higher than those of the bound enzymes. The bound enzymes are present in the fruit at the green colour stage, whereas the activities of the soluble enzymes only increased from the changing colour stage onwards. The tenacity of binding of enzymes to the wall was investigated by treating the walls with high salt and measuring residual activity. The nature of the ionic and covalent binding and the changes during ripening were also established for wall-hound glycosidase During ripening there was a marked change in the percentages of covalently- and tonically linked activities of β-glucosidase and β-galaclosidase: al the changing colour stages about 75–80% of the bound active in was present in high ionic strength buffer while al the black-ripe stage it was only 15–20. A possible role for these cell wall degradative enzymes in olive softening is discussed.     

Dexamethasone Up-Regulates a Constitutive Nitric Oxide Synthase in Cerebellar Astrocytes but Not in Granule Cells in Culture

Abstract: Treatment of rat cerebellar astrocyte-enriched primary cultures with dexamethasone enhances the nitric oxide-dependent cyclic GMP formation induced by noradrenaline in a time-(>6 h) and concentration-dependent manner (half-maximal effect at 1 n M ). Stimulation of cyclic GMP formation by the calcium ionophore A23187 is similarly enhanced. In contrast, cyclic GMP accumulation in cells treated with lipopolysaccharide is inhibited by dexamethasone. The potentiating effect of dexamethasone is prevented by the protein synthesis inhibitor cycloheximide and is not due to increased soluble guanylate cyclase activity. Agonist stimulation of [³H]arginine to [³H]citrulline conversion is enhanced by dexamethasone in astrocytes but not in cerebellar granule cells. These results indicate that glucocorticoids may up-regulate astroglial calcium-dependent nitric oxide synthase while preventing expression of inducible nitric oxide synthase and are the first report of a differential long-term regulation of the expression of neuronal and astroglial constitutive nitric oxide synthase activities.     

Preferential accumulation of [3H] corticosterone in chick brain during embryonic development

In the present study, we examined the distribution of [³H]corticosterone ([³H]B) in chick embryonic brain during development using two different routes of administration: intracerebral and intraocular. After injection of 1 Ci into the brain of 8-day embryos, [³H]B was preferentially accumulated in the retinas, whereas regions such as cerebral hemispheres, optic tecta, and midbrain showed lower amounts of [³H]B. In 14-day embryos, a slightly higher amount of [³H]B was found in retinas and midbrain in comparison with other regions of the brain. After injection into the eye, [³H]B seemed to easily diffuse to brain regions and to preferentially accumulate in the opposite eye and very slowly diffused to other brain areas. The accumulation of the hormone in the retina parallels the presence of hormone receptors reported by others. A correlation between the preferential accumulation of hormone and its action is proposed.     

Effects of corticosterone on brain cholinergic enzymes in chick embryos

The effects of corticosterone on the cholinergic enzymes, choline acetyltransferase (ChAT) and acetylcholinesterase (AChE) were studied in the chick embryonic brain. Chick embryos received either 0.25, 0.5, or 1.0 g of corticosterone via the air sac daily for three days during either embryonic days 6 through 8 (E6-E8), of cerebral neurogenesis, or days 10 through 12 (E10-E12), a period of cerebellar neurogenesis. Enzyme activities were determined in cerebral hemispheres, optic lobes, cerebellum and remaining brain at 10, 15, and 20 days of incubation. In embryos treated from E6 to E8, ChAT activity was generally higher at day 10 in cerebral hemispheres and optic lobes (cerebellum was not determined) while AChE activity was not affected. At day 20 ChAT activity of treated chick embryos was lower in the cerebral hemispheres and optic lobes, but not in the cerebellum; AChE activity was higher in the cerebral hemispheres, lower in the optic lobes, and not changed in the cerebellum as compared to controls. However, in embryos treated from E10 to E12 both cerebellar ChAT and AChE activities were higher at day 15 in comparison to controls. These data show that the hormonal effects were most prominent only in the brain areas undergoing neurogenesis during the period of hormonal treatment. Since AChE activity is also present in nonneuronal cells, the observed alterations caused by corticosterone may reflect glial cell responses to the hormone. Whether the hormone affects the final number and/or maturation of cholinergic neurons and/or glial cells remain to be investigated.     

Isolation and identification of a pepsitensin

1. From ox plasma incubated with pepsin a highly purified pepsitensin has been isolated by fractional precipitation, solvent extraction, column chromatography, countercurrent distribution and paper chromatography. 2. Comparison of the properties of this substance with those of synthetic valyl-5 angiotensin I showed: (a) the same specific pressor activity; (b) the same amino acid composition; (c) identical paper-electrophoretic mobilities at various pH values. 3. N- and C-Terminal studies carried out on the intact polypeptide and on the products of chymotrypsin digestion established the following sequence for the amino acids present in the molecule: Asp-Arg-Val-Tyr-Val-His-Pro-Phe-His-Leu. This structure is identical with that of valyl-5 angiotensin I.     

E-cadherin deregulation in breast cancer

E-cadherin protein (CDH1 gene) integrity is fundamental to the process of epithelial polarization and differentiation. Deregulation of the E-cadherin function plays a crucial role in breast cancer metastases, with worse prognosis and shorter overall survival. In this narrative review, we describe the inactivating mechanisms underlying CDH1 gene activity and its possible translation to clinical practice as a prognostic biomarker and as a potential targeted therapy.     

Arginine methylation: the promise of a ‘silver bullet’ for brain tumours?

Despite intense research efforts, our pharmaceutical repertoire against high-grade brain tumours has not been able to increase patient survival for a decade and life expectancy remains at less than 16 months after diagnosis, on average. Inhibitors of protein arginine methyltransferases (PRMTs) have been developed and investigated over the past 15 years and have now entered oncology clinical trials, including for brain tumours. This review collates recent advances in the understanding of the role of PRMTs and arginine methylation in brain tumours. We provide an up-to-date literature review on the mechanisms for PRMT regulation. These include endogenous modulators such as alternative splicing, miRNA, post-translational modifications and PRMT–protein interactions, and synthetic inhibitors. We discuss the relevance of PRMTs in brain tumours with a particular focus on PRMT1, -2, -5 and -8. Finally, we include a future perspective where we discuss possible routes for further research on arginine methylation and on the use of PRMT inhibitors in the context of brain tumours.

     

Morphological and Chemical Differentiation between Tunisian Populations of Pinus halepensis,Pinus brutia,and Pinus pinaster

The lipid fraction of seeds from different pine species and populations was studied regarding total lipid content, fatty acid profile and vitamin E composition. The investigated seeds contained a high percentage of lipid (13.6 to 31.5 %). Lipid fractions were found to be rich in vitamin E, which varied significantly among species and populations. P. halepensis (Ph−Hn) showed the highest content of vitamin E (256.3 mg/kg of seeds) and the uppermost content of α-tocopherol (44 mg/kg). However, P. halepensis (Ph−Kas) was the richest in γ-tocopherol (204.9 mg/kg). Lipid fractions had a low content of δ-tocopherol (1.2 to 3.6 mg/kg. The highest content of γ-tocotrienol (∼18 %) was determined for P. halepensis (Ph−Dc and Ph−Hn). Thirteen fatty acids were identified by GC-FID with significant variation between the investigated species. The linoleic acid was the major fatty acid followed by oleic acid and palmitic acid. The chemical differentiation among species for the composition of fatty acids and vitamin E was confirmed by PCA. Significant correlations were observed between the content of vitamin E and fatty acids and ecological parameters of P. halepensis populations.