Dermal nevus cells from congenital nevi cannot penetrate the dermis in skin reconstructs

Congenital nevi are composed of pigment cells bearing common features with melanocytes but showing altered differentiation which leads to nesting and dermal involvement. Using a dead de-epidermized dermis seeded with a combination of keratinocytes and various sources of pigment cells (normal melanocytes, dermal nevus cells from congenital nevi, Bowes melanoma cells), we have studied the formation of nests and the dermal migration of pigment cells together with their secretion profiles of matrix metalloproteinases (MMP). Dermal fibroblasts were also used as control cells in epidermal reconstructs. Besides their morphologic features, the absence of pigment donation to keratinocytes was the major characteristic of dermal nevus cells. A positive correlation was established between the increasing percentage of seeded nevus cells and the patchy pigmentation of reconstructs, as well as the clustering of cells in junctional nests. However, the presence of nevus cells in the dermis of reconstructs was never detected, whereas melanoma cells and dermal fibroblasts could invade the dermis during the time span of the experiments. MMP9 was never expressed in congenital dermal nevus cells but pro-MMP2 was constitutively expressed by all strains of congenital nevus cells and dermal fibroblasts. Melanocytes produced comparable amounts of both pro-MMP2 and pro-MMP9, and Bowes melanoma cells secreted a marginal level of pro-MMP2. In view of their three-dimensional behaviour and secretion of MMPs, we propose that dermal congenital nevus cells correspond to an intermediate status of differentiation between normal melanocytes and melanoma cells. Activation of MMPs by a cofactor or the activation of another signalling pathway seems necessary to induce the dermal passage of nevus cells.     

Mammary leptin synthesis,milk leptin and their putative physiological roles

This paper reviews data on mammary leptin and leptin receptor gene expression as well as on blood and milk leptin levels during the pregnancy-lactation cycle in humans, rodents and ruminants, with the aim of better understanding milk leptin origin and functions. The few published papers report that leptin may be produced by different cell types in the mammary tissue, and may act as a paracrine factor on mammary epithelial cell proliferation, differentiation and/or apoptosis via adipose-epithelial and/or myoepithelial-epithelial cellular interactions. In addition to leptin synthesis, epithelial cells may transfer leptin from the blood, and these two mechanisms may account for the presence of leptin in the milk. The respective parts of these two processes remain to be determined, as well as the true milk leptin levels. Indeed, reported concentrations for milk leptin vary strongly according to species and mainly according to the milk fractions and the assay methods used. If leptin levels in milk (and specially colostrum) are found to be significant, this hormone could be involved in neonate physiology.     

Arabidopsis glt1-T mutant defines a role for NADH-GOGAT in the non-photorespiratory ammonium assimilatory pathway

The physiological role of the NADH-dependent glutamine-2-oxoglutarate aminotransferase (NADH-GOGAT) enzyme was addressed in Arabidopsis using gene expression analysis and by the characterization of a knock-out T-DNA insertion mutant (glt1-T) in the single NADH-GOGAT GLT1 gene. The NADH-GOGAT GLT1 mRNA is expressed at higher levels in roots than in leaves. This expression pattern contrasts with GLU1, the major gene encoding Fd-GOGAT, which is most highly expressed in leaves and is involved in photorespiration. These distinct organ-specific expression patterns suggested a non-redundant physiological role for the NADH-GOGAT and Fd-GOGAT gene products. To test the in vivo function of NADH-GOGAT, we conducted molecular and physiological analysis of the glt1-T mutant, which is null for NADH-GOGAT, as judged by mRNA level and enzyme activity. Metabolic analysis showed that the glt1-T mutant has a specific defect in growth and glutamate biosynthesis when photorespiration was repressed by 1% CO2. Under these conditions, the glt1-T mutant displayed a 20% decrease in growth and a dramatic 70% reduction in glutamate levels. Herein, we discuss the significance of NADH-GOGAT in non-photorespiratory ammonium assimilation and in glutamate synthesis required for plant development.     

New N-pyridinyl(methyl)-indole-2- and 3-(alkyl)carboxamides and derivatives acting as systemic and topical inflammation inhibitors

A series of novel N-substituted-(indol-2-yl)carboxamides (12-18) and (indol-3-alkyl)carboxamides (25-31) were synthesized and evaluated as inhibitors of the inflammation process. Pharmacomodulation at the level of the amidic nitrogen by incorporation of the previously described pharmacophoric moieties 6-aminolutidine, beta-picolylamine, 4-aminopyridine and piperazine was investigated; only two compounds (12) and (31) exhibited significant (approximately 40%) inhibitory effect in the carrageenan-induced rat paw edema after oral administration of a dose of 0.1 mM kg(-1). Replacement of the indole core by indazole failed to increase activity. Incorporation of an alkyl chain spacer led to more efficient compounds (46-52) especially in the indolepropanamide sub-series. Determination of the efficiency of the most active compounds on topical inflammation, by measuring reduction of ear thickness in the acute tetradecanoyl phorbol acetate (TPA)-induced mouse ear swelling assay, confirmed the high potency of propanamides (49) and (51) after oral administration: ID50 = 0.041 +/- 0.013 and 0.042 +/- 0.016 mM kg(-1) respectively. The less toxic propanamide (51) exerted a high level of inhibitory activity after topical application of 2 x 100 microg/ear: 78 +/- 2%.     

Elaboration and characterization of whey protein beads by an emulsification/cold gelation process: application for the protection of retinol

Whey protein beads were successfully produced using a new emulsification/cold gelation method. The principle of this method is based on an emulsifying step followed by a Ca(2+)-induced gelation of pre-denatured (80 degreesC/30 min) whey protein. Beads are formed by the dropwise addition of the suspension into a calcium chloride (CaCl(2)) solution. IR results show that bead formation has a pronounced effect on the secondary structure of whey protein, which leads to the formation of intermolecular hydrogen-bonded beta-sheet structures. Their preparation conditions (CaCl(2) concentrations of 10, 15, and 20% (w/w)) influence their sphericity and homogeneity: an increase in CaCl(2) favors regular-shaped beads. The physicochemical and mechanical characterizations of beads were also carried out. Their properties, such as swelling, elasticity, deformability, and resistance at fracture, change according to pH levels (1.9, 4.5, and 7.5) and preparation conditions. Indeed, protein chain networks exhibit different behavior patterns with respect to their charge. Finally, bead degradation by enzymatic hydrolysis reveals that beads are gastroresistant and form good matrixes to protect fat-soluble bioactive molecules such as retinol, that have in vivo intestinal absorption sites. The experiment demonstrated the potential of whey protein beads to protect molecules sensitive (i.e., vitamins) to oxidation.     

Cholesterol-dependent insertion of glycosylphosphatidylinositol-anchored enzyme

Evidence is now accumulating that the plasma membrane is organized in different lipid and protein subdomains. Thus, glycosylphosphatidylinositol (GPI)-anchored proteins are proposed to be clustered in membrane microdomains enriched in cholesterol and sphingolipids, called rafts.By a detergent-mediated method, alkaline phosphatase, a GPI-anchored enzyme, was efficiently inserted into the membrane of sphingolipids- and cholesterol-rich liposomes as demonstrated by flotation in sucrose gradients. We have determined the enzyme extraluminal orientation. Using defined lipid components to assess the possible requirements for GPI-anchored protein insertion, we have demonstrated that insertion into membranes was cholesterol-dependent as the cholesterol addition increased the enzyme incorporation in simple phosphatidylcholine liposomes.     

Curly bare (cub), a new mouse mutation on chromosome 11 causing skin and hair abnormalities,and a modifier gene (mcub) on chromosome 5

In the outcrossing of a new recessive mouse mutation causing hair loss, a new wavy-coated phenotype appeared. The two distinct phenotypes were shown to be alternative manifestations of the same gene mutation and attributable to a single modifier locus. The new mutation, curly bare (cub), was mapped to distal Chr 11 and the modifier (mcub) was mapped to Chr 5. When homozygous for the recessive mcub allele, cub/cub mice appear hairless. A single copy of the dominant Mcub allele confers a full, curly coat in cub/cub mice. Reciprocal transfer of full-thickness skin grafts between mutant and control animals showed that the skin phenotype was tissue autonomous. The hairless cub/cub mcub/mcub mice show normal contact sensitivity responses to oxazolone. The similarity of the wavy coat phenotype to those of Tgfa and Egfr mutations and the map positions of cub and mcub suggest candidate genes that interact in the EGF receptor signal transduction pathway.     

Conformational changes of pediocin in an aqueous medium monitored by fourier transform infrared spectroscopy: a biological implication

Fourier transform infrared (FTIR) spectroscopy was used to investigate the secondary structure of pediocin PA-1 in different aqueous media in relation to its antimicrobial activity. The experiments were performed at pD (pH meter corrected for deuterium isotope effect) 6, 7, and 8 and during a heating-cooling cycle of 20-80 degrees C. At pD 6, (i.e. pediocin's most active form), the FTIR results show that pediocin adopts an unordered structure with a small contribution of beta-turn. After a heating-cooling cycle, thermally-induced changes in pediocin are reversed and its activity is maintained. Increasing the pD to 7 and 8 leads to a more ordered secondary structure. For these two pD values, an increase in temperature induces an irreversible aggregation of protein as revealed by the amide I' band. The analysis of the Tyr region provides more insight into the aggregation process. In fact, it appears to be a two-step process, involving first the C (carboxy)-terminus of pediocin and then the N (amino)-terminus. This study reveals two major points: (1) the preservation of pediocin flexibility is essential for maintaining its activity; and (2) the aggregation of its C-terminus is sufficient to induce a loss of activity, suggesting that this region plays an important role in the activity of pediocin.     

Heteroduplex mobility assay for the identification of Listeria sp and Listeria monocytogenes strains: application to characterisation of strains from sludge and food samples

One hundred and ten Listeria sp. isolates from sewage sludge were identified according to phenotypic and genotypic methods. The Listeria sp. strains isolated from five types of sludge from three sewage treatment plants in Angers (France) and the surrounding area included L. monocytogenes (55.5%), L. innocua (29.1%), L. seeligeri (13.6%) and L. welshimeri (1.8%). The majority of L. monocytogenes strains belonged to serotypes 4b, 1/2b and 1/2a. Moreover, a heteroduplex mobility assay based on the 16S rRNA sequences was tested for its ability to identify the six species of the genus Listeria. This study, performed on 283 Listeria sp. strains from human, food and sewage sludge samples, showed that all the species were distinguishable from one another. L. innocua and L. seeligeri showed respectively three and two distinct banding patterns. Within L. monocytogenes, four groups (I-IV) were defined. The majority of food and environmental isolates were clustered in group I and it is noteworthy that group IV clustered epidemiologic isolates and strains belonging to serotypes 4b, 1/2a and 1/2b.