Rapid changes in liver lipid composition and pancreatic islet K+ handling and secretory behaviour provoked by the intravenous administration of a medium-chain triglyceride: fish oil emulsion to long-chain polyunsaturated omega3 fatty acid-depleted rats.

Second generation rats depleted in long-chain polyunsaturated omega3 fatty acids are currently used as an animal model for the insufficient dietary supply of such fatty acids often prevailing in Western populations. The present study deals mainly with the effects of a novel medium-chain triglyceride: fish oil emulsion (MCT:FO), as compared to a control medium-chain triglyceride:olive oil emulsion (MCT: OO), administered as an intravenous bolus to the omega3-depleted rats 60-120 min before sacrifice upon selected biochemical and biophysical variables. The major findings consisted of a severe decrease of the omega3 fatty acid content of liver lipids in non-injected omega3-depleted rats and its partial correction after injection of the MCT:FO emulsion. The omega3-depleted rats also displayed liver steatosis, increased incorporation of long-chain polyunsaturated omega6 fatty acids in liver phospholipids and increased activity of liver Delta9-desaturase. As judged from the effects of ouabain upon 86Rb net uptake by isolated pancreatic islets, the activity of Na+,K+-ATPase was virtually abolished in the omega3-depleted rats. The latter defect was corrected by prior intravenous injection of the MCT:FO emulsion, this coinciding with suppression of the excessive secretory response to a number of insulin secretagogues otherwise observed in the islets of omega3-depleted rats injected or not with the MCT:OO emulsion.

Galectins and cancer.

The galectins are a family of proteins that are distributed widely in all living organisms. All of them share galactose-specificity. At present, 14 members of the family are characterized in mammals. The galectins have been implicated in many essential functions including development, differentiation, cell-cell adhesion, cell-matrix interaction, growth regulation, apoptosis, RNA splicing, and tumor metastasis. Although efforts have mostly focused on the possible function of galectins in tumor development and invasiveness, their precise role in this field is still debated. This review discusses the recent way in which the expression of galectins and galectin-binding sites may affect the behavior of a variety of human neoplastic tissues.

Galectin-1 modulates human glioblastoma cell migration into the brain through modifications to the actin cytoskeleton and levels of expression of small GTPases.

We show that high-grade astrocytic tumors with high levels of galectin-1 expression are associated with dismal prognoses. The immunohistochemical analysis of galectin-1 expression of human U87 and U373 glioblastoma xenografts from the brains of nude mice revealed a higher level of galectin-1 expression in invasive areas rather than non-invasive areas of the xenografts. Nude mice intracranially grafted with U87 or U373 cells constitutively expressing low levels of galectin-1 (by stable transfection of an expression vector containing the antisense mRNA of galectin-1) had longer survival periods than those grafted with U87 or U373 cells expressing normal levels of galectin-1. Galectin-1 added to the culture media markedly and specifically increased cell motility levels in human neoplastic astrocytes. These effects are related to marked modifications in the organization of the actin cytoskeleton and the increase in small GTPase RhoA expression. All the data obtained indicate that galectin-1 enhances the migratory capabilities of tumor astrocytes and, therefore, their biological aggressiveness.

Glucocorticoid-induced differential expression of the sialylated and nonsialylated Lewis(a) epitopes and respective binding sites in human nasal polyps maintained under ex vivo tissue culture conditions.

We characterized the anti-inflammatory effects of budesonide on the expression of adhesion molecules involving Lewis(a) (Le(a)) epitope, its sialylated derivative (sLe(a)), and their respective binding sites in human nasal polyposis. By computer-assisted microscopy, we quantitatively characterized the level of histochemical expression of L- and P-selectins, sialylated and nonsialylated Le(a) epitopes, and their respective binding sites in both surface epithelium and glandular epithelium of human nasal polyps obtained from surgical resection, maintained under ex vivo tissue culture conditions for 24 hours, and treated or not with budesonide. Intercellular adhesion molecule 1 (ICAM-1) and vascular cell adhesion molecule 1 (VCAM-1) were chosen as methodological controls, because data already published in the literature clearly indicated budesonide-mediated effects on ICAM-1 and VCAM-1 levels of expression. The present data show that budesonide significantly modified the levels of expression of ICAM-1 and VCAM-1, and to a lesser extent that of P-selectin, in the surface and glandular epithelia. Budesonide markedly decreased the levels of expression of the binding sites for both Le(a) and sLe(a), while those of Le(a) and sLe(a) remained globally unchanged. In conclusion, the present study documents that glucocorticoid-induced effects can encompass receptors for Le(a) epitopes different from E- and P-selectins on epithelial cells of human nasal polyps.

Improved methodology for the detection and quantification of the acrosome reaction in mouse spermatozoa.

This study evaluates the use of two fluorescein-labelled (FITC) plant lectins, Pisum sativum (edible pea) agglutinin (PSA) and Arachis hypogaea (peanut) agglutinin (PNA), in order to determine the most accurate and reliable method to experimentally detect and assess the acrosome reaction in mouse spermatozoa. PNA-FITC labelling was restricted to the acrosome and was not influenced by the fixation procedure; either absolute methanol or paraformaldehyde. In contrast, PSA-FITC not only labelled the acrosome, but also the whole head and the flagellum. This aspect was especially marked after methanol fixation. The cytoplasmic droplet, when present, was also stained by PSA-FITC. Incubation with the calcium ionophore ionomycin induced a concentration and time-dependent increase in the number of acrosome reactions. Compared to spotted preparations, smear samples exhibited a high proportion of spermatozoa with damaged acrosome. In conclusion, PNA-FITC labelling was more accurate than PSA-FITC labelling to detect the acrosome of mouse spermatozoa. The fixation method (methanol vs. paraformaldehyde) had no influence on the staining pattern of PNA-FITC labelling, but spotted preparations are recommended to avoid mechanical damage to the acrosome. Ionophore challenge confirmed the existence of a calcium-dependent acrosome reaction in mouse spermatozoa and validated the use of PNA-FITC to quantify this physiological process. The present study illustrates important methodological considerations which need to be taken into account in order to design a reliable and reproducible protocol for the study of the acrosome reaction.

Galectin-1 is overexpressed in nasal polyps under budesonide and inhibits eosinophil migration.

Because of the importance of galectins for various cellular activities, the influence of the glucocorticoid budesonide on the level of expression of galectins-1 and -3 was investigated in human nasal polyposis. Ten nasal polyps obtained from surgical resection were maintained for 24 hours in the presence of various concentrations of budesonide. As quantitatively demonstrated by means of computer-assisted microscopy, 250 ng/ml (the highest dose tested) induced a pronounced increase of galectin-1 expression. This feature was observed in nasal polyps from allergic patients but not in those from nonallergic patients. Since eosinophils represent the main inflammatory cell population in nasal polyps, we investigated the effect of galectin-1 on their migration levels by means of quantitative phase-contrast computer-assisted videomicroscopy. Our results show that galectin-1 (coated on plastic supports) markedly reduced the migration levels of eosinophils in comparison to P-selectin. On the cellular level, marked modifications in the polymerization/depolymerization dynamics of the actin cytoskeleton (as revealed by means of computer-assisted fluorescence microscopy) and, to a much lesser extent, an increase in the adhesiveness of eosinophils to tested substrata were detectable. The present study therefore reveals a new galectin-1-mediated mechanism of action for glucocorticoid-mediated anti-inflammatory effects.