Upregulation of group IB secreted phospholipase A(2) and its M-type receptor in rat ANTI-THY-1 glomerulonephritis

Treatment of rat glomerular mesangial cell (GMC) cultures with pancreatic secreted phospholipase A(2) (sPLA(2)-IB) results in an enhanced expression of sPLA(2)-IIA and COX-2, possibly via binding to its specific M-type sPLA(2) receptor. In the current study, we have investigated the expression and regulation of sPLA(2)-IB and its receptor during glomerulonephritis (GN). In vivo we used the well-established rat model of anti-Thy 1.1 GN (anti-Thy 1.1-GN) to study the expression of sPLA(2)-IB and the M-type sPLA(2) receptor by immunohistochemistry. In addition, in vitro we determined the interkeukin (IL)-1beta-regulated mRNA and protein expression in primary rat glomerular mesangial and endothelial cells as well as in rat peripheral blood leukocytes (PBLs). Shortly after induction of anti-Thy 1.1-GN, sPLA(2)-IB expression was markedly upregulated in the kidney at 6-24 h. Within glomeruli, the strongest sPLA(2)-IB protein expression was detected on infiltrated granulocytes and monocytes. However, at the same time, the M-type receptor was also markedly upregulated on resident glomerular cells. In vitro, the most prominent cytokine-stimulated secretion of sPLA(2)-IB was observed in monocytes isolated from rat PBLs. Treating glomerular endothelial cells (GECs) with cytokines elicited only weak sPLA(2)-IB expression, but treatment of these cells with exogenous sPLA(2)-IB resulted in a marked expression of the endogenous sPLA(2)-IB. Mesangial cells did not express sPLA(2)-IB at all. The M-type sPLA(2) receptor protein was markedly upregulated on cytokine-stimulated mesangial and endothelial cells as well as on lymphocytes and granulocytes. During anti-Thy 1.1 rat GN, sPLA(2)-IB and the M-type sPLA(2) receptor are induced as primary downstream genes stimulated by inflammatory cytokines. Subsequently, both sPLA(2)-IB and the M-type sPLA(2) receptor are involved in the autocrine and paracrine amplification of the inflammatory process in different resident and infiltrating cells.

Chemical characterization of sicilian prickly pear (Opuntia ficus indica) and perspectives for the storage of its juice

In this work, Sicilian cultivars of prickly pear (Opuntia ficus indica) were partially characterized from a chemical point of view, and the possibility of long-term storage of their juice was investigated. The acidity of the prickly pear juice turned out to be very low (0.02%) and the pH very high (6.4-6.5) if compared with values found in other common fruit juices. In the perspective of processing and storage conditions according to Italian law, the acidity has been corrected by adding the proper amount of tartaric and/or phosphoric acid. The sugar content (mainly glucose and fructose) is very high (11-12%), and also L-ascorbic acid is present in considerable amount (31-38 mg/100 g). Among the transition metals, a high content of manganese(II) (1.7-2.9 ppm) and good amounts of iron(III) (0.6-1.2 ppm) and zinc(II) (0.3-0.4 ppm) were found. In particular, such ions appear to be present mainly in the thick skin of the fruit or "trapped" inside the pulp. Pectin methylesterase (PME) seems to be present in very small amount and/or is not highly active. Furthermore, PME activity decreases considerably after the necessary adjustment of the pH and the thermal treatment requested for long-term storage. After approximately 2 months, none of the juices prepared was affected by noticeable sedimentation of the pulp. Finally, different samples of prickly pear juice were sensorially analyzed, employing descriptors such as color, aroma, viscosity, acidity, sweetness, and off-flavors. The results obtained can be considered very satisfactory, and the juice has been widely appreciated when compared with other products commonly available on the market such as pear and peach juices.

Trapping of megabase-sized DNA molecules during agarose gel electrophoresis

Megabase DNA molecules become trapped in agarose gels during electrophoresis if the electric field exceeds a few volts per cm. Fluorescence microscopy reveals that these molecules invariably arrest in U-shaped conformations. The field-vs.-size dependence for trapping indicates that a critical molecular tension is required for trapping. The size of unligated lambda-ladders, sheared during gel electrophoresis at a given field, coincides with the size of molecules trapped at that field, suggesting that both processes occur through nick melting near the vertex of the U-shape. Consistently, molecules nicked by exposure to UV radiation trap more readily than unexposed ones. The critical trapping tension at the vertex is estimated to be 15 pN, a force sufficient to melt nicks bent around gel fibers, and, according to our model, trap a molecule. Strategies to reduce molecular tension and avoid trapping are discussed.

Purification and staining of intact yeast DNA chromosomes and real-time observation of their migration during gel electrophoresis

In the past few years, fluorescence microscopy has been used successfully to characterize the motion of intermediate-size DNA molecules (50-500 kbp) during steady- and pulsed-field gel electrophoresis. However, experimental difficulties had prevented the application of this technique to the direct observation of longer DNA chromosomes (1-2 Mbp). In the present study a particular procedure was followed for the purification and staining of chromosomal yeast DNA to protect it from shear forces. Also, a new highly fluorescent DNA-labelling dye, YOYO-1, was employed to improve brightness and contrast. Finally, the motion of such long DNA molecules (1-2 Mbp) was characterized under steady-field electrophoresis conditions. An accurate description of the molecular mechanisms of motion of such long molecules should provide the basis for a detailed analysis of the mechanisms responsible for DNA trapping.

Direct visualization of individual DNA molecules by fluorescence microscopy: characterization of the factors affecting signal/background and optimization of imaging conditions using YOYO

A new series of high-affinity cyanine dyes was tested for the visualization of the dynamics of single DNA molecules through a fluorescence microscope. In particular, YOYO-1 (1,1'-(4,4,7,7-tetramethyl-4,7-diazaundecamethylene)- bis-4-[3-methyl-2,3-dihydro-(benzo-1,3-oxazole)- 2-methylidene]-quinolinium tetraiodide) forms a very stable, highly fluorescent complex with double-stranded DNA and dramatically improves the quality of the images. We have characterized the factors affecting the signal/background in the imaging of single DNA molecules by fluorescence microscopy and compared the results obtained using YOYO-1 with those obtained using standard fluorescent dyes like ethidium bromide or acridine orange.

Real-time imaging of the reorientation mechanisms of YOYO-labelled DNA molecules during 90 degrees and 120 degrees pulsed field gel electrophoresis

Pulsed field gel electrophoresis (PFGE) techniques have been developed to overcome the limitations of conventional electrophoresis and to increase the separation to DNA chromosomes of few megabase pairs in size. Despite of the large success of these techniques, the various separation protocols employed for PFGE experiments have been determined empirically. However, a deep understanding of the molecular mechanisms of motion responsible for DNA separation becomes necessary for the rational optimization of these techniques. This paper shows the first clear observations of individual molecules of DNA during the reorientation process in 90 degrees PFGE and 120 degrees PFGE. Real-time visualization of the DNA dynamics during PFGE was possible with the use of an epi-illumination fluorescence microscope specifically equipped to run these experiments and by staining the DNA with YOYO-1 (1,1'-(4,4,7,7-tetramethyl-4,7-diazaundecamethylene)-bis-4-[3-meth yl -2,3-dihydro-(benzo-1,3-oxazole)-2-methyl-idene]-quinolinium tetraiodide). This dye forms a very stable, highly fluorescent complex with double-stranded DNA and dramatically improves the quality of the DNA images. The results of computer simulations used to reproduce the molecular mechanisms of motion as well as the DNA separation features are also discussed.

Interaction of water-soluble porphyrins with single- and double-stranded polyribonucleotides

CD and uv-visible absorption studies with several tetracationic water-soluble porphyrin derivatives show that some of these species can serve as probes to discriminate between A- and B-conformational forms of single-stranded polynucleotides. It is also observed that these porphyrins can participate in the formation of double helices by forming transient intermediate complexes en-route to duplex formation.

Towards a molecular description of pulsed-field gel electrophoresis

An improved understanding of the molecular processes of migration and reorientation of DNA molecules undergoing conventional and pulsed-field gel electrophoresis (PFGE) should provide the basis for the rational optimization of these techniques. This review of common pulsed-field methods emphasizes the range of their applications as well as their current limitations. The molecular mechanisms involved in electrophoresis, as they are beginning to emerge from a combination of direct observations using a microscope and computer-modeling studies, are also discussed.

Imaging of kinked configurations of DNA molecules undergoing orthogonal field alternating gel electrophoresis by fluorescence microscopy

The dynamics of individual DNA molecules undergoing orthogonal field alternating gel electrophoresis (OFAGE) have been studied by use of T2 DNA molecules labeled with a dye and visualized with a fluorescence microscope. The mechanism of reorientation used by a molecule to align itself in the direction of the new orthogonal field depends on the degree of extension of the chain immediately before the application of this field. The formation of kinks is promoted when time is allowed between the application of the two orthogonal fields so that the molecule attains a partially relaxed configuration. In this case, the chain appears bunched up in domains moving along the contour of the molecule. These regions are found to be the locations where the kinks are formed upon application of the second field perpendicular to the chain. The formation of kinks provides a significant retardation of the reorientation of the molecules, relative to molecules that do not form kinks, and appears to play an important role in the fractionation attained with OFAGE. A classification of various reorientation mechanisms observed in molecules that form kinks is presented.

Calcium ion influence on thermotropic behaviour of dipalmitoylphosphatidylcholine-vitamin D3 systems

An analysis of Ca2+ influence on the thermotropic behaviour of different phosphatidylcholine-vitamin D3 mixtures was carried out by differential scanning calorimetry technique (DSC). A competitive effect between Ca2+ and vitamin D3 on the membrane fluidity was detected. The observed shifts of the gel-liquid crystal transition temperature were correlated with the mole fraction of vitamin D3 dissolved within the lipid bilayer as well as with the Ca2+ concentration in the surrounding medium. These shifts were rationalized on the ground of a simple microscopic model through the calculation of the internal pressure exerted by the adsorbed Ca2+ on the lipid matrix by the Clapeyron equation. The experimental results and the obtained equations accord with each other and support the idea of micro-domain formation richer in one lipid component. The extent of such lateral phase separation of the lipid components seems to be favoured by the adsorption of Ca2+ at the membrane-water interface.