María A. Castro

Structural changes in apple tissue during glucose and sucrose osmotic dehydration: shrinkage, porosity, density and microscopic features

Abstract Micro- and macrostructural changes in apple slices during osmotic dehydration were studied. Samples were immersed into 25.0% (w/w) glucose or 34.6% (w/w) sucrose aqueous solutions at 30 °C until water and solid contents were almost constant (≅350 min). They were removed after selected times, and examined for thickness, volume, bulk and solid–liquid densities, porosity, water activity, water loss, solids gain and microscopic aspects. At relatively short times, significant weight and volume losses were observed for both treatments arising from the fast water loss. The solid–liquid density of glucose or sucrose treated samples increased slowly along the process. However, the bulk density increased up to a certain value and then fluctuated with increasing time, showing in some cases another pronounced increase for long times of treatment. Fruit porosity values decreased in line with the increase in bulk density values. At the end of the osmotic treatments in glucose or sucrose solutions, there was a recovery in porosity, although the values were lower than for fresh fruit. The changes in bulk density, porosity and volume of apple tissue along osmotic process were closely supported by microstructural and structural observations (using light microscopy and environmental electron scanning microscopy) and explained by considering osmosis as a multicomponent diffusion process through porous media and due to the relaxation of the viscoelastic shrunken cell walls.

Air drying behaviour of apples as affected by blanching and glucose impregnation

The effect of blanching and/or glucose impregnation at atmospheric pressure or in vaccum on the kinetics of moisture transfer during the first falling rate period of air drying of apple was analyzed. The moisture diffusivity of water (Deff) was strongly decreased by glucose uptake during impregnation step as well as volume shrinking. Studies of the cell structure using transmission electron microscopy revealed that both pretreatments did not modify in a great extension the cell wall resistance to water flux.

Kinetics of moisture transfer during air drying of blanched and/or osmotically dehydrated mango

Abstract The effect of previous blanching and/or osmotic dehydration (at atmospheric pressure or in vacuum) with glucose syrups on the kinetics of water transport during the first falling rate period of air drying of mango at 60°C was investigated. Both pre-drying treatments decreased strongly the effective moisture diffusivity (Deff) calculated with Ficks second law. For osmotically concentrated fruit at atmospheric pressure, the increase in glucose concentration of the immersion solution decreased the drying rate. Deff values were similar for mangoes predehydrated to aw 0.97 by vacuum or atmospheric osmosis, but previous blanching slightly decreased the Deff value for vacuum treated slices compared with those osmotically dehydrated to the same aw at atmospheric pressure. The air drying behaviour of blanched and/or osmotically dehydrated mangoes was ascribed to glucose uptake during the impregnation step, volume shrinking, low modification of cell wall resistance to water flux by the pretreatments and/or gelatinization of starch and denaturation of protein – carbohydrate mucilage.

Cytokinin-induced changes of nitrogen remobilization and chloroplast ultrastructure in wheat (Triticum aestivum).

Nitrogen (N) remobilization in wheat (Triticum aestivum) plants is crucial because it determines the grain protein concentration and the baking quality of flour. In order to evaluate the influence of cytokinins on N remobilization during N starvation, we analyzed various N remobilization parameters in wheat plants that were watered with 6-benzylaminopurine (BAP) either with or without KNO(3). Besides, the effects of BAP on protein synthesis were evaluated, and the size and ultrastructure of chloroplasts of BAP-treated plants were studied. BAP supply inhibited N remobilization of plants independently of N supply as shown by the increase in protein, Rubisco, chlorophyll, sugar and starch concentrations in the older leaves, the decrease in amino acid and sugar export to the phloem, and the decrease in protein, Rubisco and chlorophyll concentrations in the younger leaves. Besides, BAP supply increased nitrate reductase activity and decreased nitrate concentration, thus suggesting an increased assimilatory capacity. The increase in protein concentration could be explained mainly by a significant decrease in protein degradation and, to a lesser extent, by an increase in protein synthesis. Finally, an increase both in the size of the chloroplast and in the plastoglobuli and starch contents in BAP-supplied plants was observed. We propose that cytokinins retain the sink activity of the older leaves by inhibiting amino acid and sugar export to the phloem and stimulating assimilate accumulation in the chloroplasts of the older leaves. Besides, BAP may increase protein concentration of the older leaves both by decreasing protein degradation and maintaining protein synthesis even under stress conditions.

Texture and structure of glucose-infused melon

The effect of glucose and calcium infusion on texture characteristics and ultrastructure of melon was studied using an Instron Universal Testing Machine and optical and transmission electron microscopy. Resistance to puncture was significantly greater when treatment was performed under vacuum or when Ca 2+ was present during atmospheric and vacuum glucose infusion. Atmospheric treatment produced a smaller resistance to puncture than the one shown by raw fruit. Processing reduced residual relaxation force and relaxation time, showing, the high internal fracture suffered by the fruit during treatment. There was a good correlation between textural changes detected through instrumental measurement and structural alterations of flesh tissues. Vacuum-treated samples showed cell walls with good optical density and a middle lamella still visible. Atmospheric impregnation caused very much reduced staining and disruption of cell walls as well as rupture of membranes. Addition of Ca 2+ during both infusion procedures resulted in more electron-dense cell walls as compared with those impregnated without Ca 2 + .

Anatomical Study of the Decay Caused by the White-Rot Fungus Trametes Trogii (Aphyllophorales) in Wood of Salix and Populus

Different stages of decay caused in vitro by Trametes trogii in Salix sp. and Populus sp. wood are described. Anatomical features are reported in three stages of this process. Decay progressed in a different pattern in both species studied. In Populus sp. T. trogii caused a combination of selective delignification and simultaneous decay within the same substrate. In advanced stages wood blocks exhibited large empty holes and a spongy structure. In Salix sp. a simultaneous white-rot decay took place. Only vessels remained and the residual white-rotted wood developed a stringy appearance.

Structure and ultrastructure of leaf and calyx glands in Galphimia brasiliensis (Malpighiaceae).

The present study describes the anatomical structure of calyx and leaf glands in Galphimia brasiliensis and analyzes the mechanism of secretion. The glands are marginal and suprabasal, cup-shaped, sessile, and scarcely visible with the naked eye. Light microscopy reveals the following features: a thin, smooth cuticle; unistratified secretory cells; subglandular parenchyma; and vascular bundle supply composed of phloem and xylem with abundant druses of calcium oxalate. Transmission electron microscopy reveals the presence of secretory cells with conspicuous nuclei, dense cytoplasm, lipid droplets, numerous vesicles, mitochondria, Golgi, rough endoplasmic reticulum (RER), and elongated plastids with osmiophilic contents. The secretion reaches the apoplastic space and accumulates beneath the cuticle. Finally, the viscous, translucent exudate is eliminated by mechanical rupture of the cuticle. Histochemical analysis confirms that lipids are the main constituent. Small amounts of polysaccharides were also identified.

Multifunctional Cytochrome c: Learning New Tricks from an Old Dog

Cytochrome c (cyt c) is a small soluble heme protein characterized by a relatively flexible structure, particularly in the ferric form, such that it is able to sample a broad conformational space. Depending on the specific conditions, interactions, and cellular localization, different conformations may be stabilized, which differ in structure, redox properties, binding affinities, and enzymatic activity. The primary function is electron shuttling in oxidative phosphorylation, and is exerted by the so-called native cyt c in the intermembrane mitochondrial space of healthy cells. Under pro-apoptotic conditions, however, cyt c gains cardiolipin peroxidase activity, translocates into the cytosol to engage in the intrinsic apoptotic pathway, and enters the nucleus where it impedes nucleosome assembly. Other reported functions include cytosolic redox sensing and involvement in the mitochondrial oxidative folding machinery. Moreover, post-translational modifications such as nitration, phosphorylation, and sulfoxidation of specific amino acids induce alternative conformations with differential properties, at least in vitro. Similar structural and functional alterations are elicited by biologically significant electric fields and by naturally occurring mutations of human cyt c that, along with mutations at the level of the maturation system, are associated with specific diseases. Here, we summarize current knowledge and recent advances in understanding the different structural, dynamic, and thermodynamic factors that regulate the primary electron transfer function, as well as alternative functions and conformations of cyt c. Finally, we present recent technological applications of this moonlighting protein.

Occurrence and phylogenetic significance of latex in the Malpighiaceae

Latex and laticifers are reported for the first time in the genera Galphimia and Verrucularia (Malpighiaceae), with description and illustration of the leaf and stem anatomy of both genera. Those genera and the other two in which latex is known (Lophanthera and Spachea) constitute a single tribe, Galphimieae, that is at or near the base of the familys phylogeny, which suggests that latex in the Malpighiaceae may indicate an ancestor shared with the Euphorbiaceae.

Pollution trends using bark of morus alba in the cities of buenos aires and mendoza (Argentina)

A comparative study of elements deposited on tree bark was carried out for urban and periurban areas of two of the most important cities in Argentina. The content of Fe, Mg, Al, Mn, Zn, Pb, Ba, Cr, Hg, Cu, Ni, Cd and Sb was determined by inductively coupled plasma atomic emission spectrometry (ICP-OES) in Morus alba tree bark collected in the cities of Buenos Aires and Mendoza. The main air pollutants detected in the Buenos Aires urban area were Ba, Cr, Cu and Ni and indicate significative difference from the Mendoza urban and periurban areas. Significantly, higher concentrations of Zn, Ba, Cr and Cu were recorded in the periurban area of the city of Buenos Aires than in Mendoza. Bark samples were strongly influenced by dust and show Al, Fe, Mg and other element accumulations that indicate that soil particles were carried out by wind. Elements like Ba and Zn, commonly linked to traffic emissions, showed the highest concentrations in the Buenos Aires metropolitan area, possibly due to more intensive vehicular traffic. Our results indicated that intensity of vehicular traffic and not city structure is responsible for air pollution.