Role of electrostatics in the binding of charged metallophthalocyanines to neutral and charged phospholipid membranes

Binding of the cationic tetra(tributylammoniomethyl)-substituted hydroxoaluminum phthalocyanine (AlPcN₄) to bilayer lipid membranes was studied by fluorescence correlation spectroscopy (FCS) and intramembrane field compensation (IFC) methods. With neutral phosphatidylcholine membranes, AlPcN₄ appeared to bind more effectively than the negatively charged tetrasulfonated aluminum phthalocyanine (AlPcS₄), which was attributed to the enhancement of the coordination interaction of aluminum with the phosphate moiety of phosphatidylcholine by the electric field created by positively charged groups of AlPcN₄. The inhibitory effect of fluoride ions on the membrane binding of both AlPcN₄ and AlPcS₄ supported the essential role of aluminum-phosphate coordination in the interaction of these phthalocyanines with phospholipids. The presence of negative or positive charges on the surface of lipid membranes modulated the binding of AlPcN₄ and AlPcS₄ in accord with the character (attraction or repulsion) of the electrostatic interaction, thus showing the significant contribution of the latter to the phthalocyanine adsorption on lipid bilayers. The data on the photodynamic activity of AlPcN₄ and AlPcS₄ as measured by sensitized photoinactivation of gramicidin channels in bilayer lipid membranes correlated well with the binding data obtained by FCS and IFC techniques. The reduced photodynamic activity of AlPcN₄ with neutral membranes violating this correlation was attributed to the concentration quenching of singlet excited states as proved by the data on the AlPcN₄ fluorescence quenching.     

Equine Pythiosis: Report in Crossed Bred (Criole Venezuelan) Horses

Pythium insidiosum is a pathogenic oomycete known since 1890 that causes pythiosis in mammals. In this report, seven P. insidiosum isolates were recovered from Venezuelan horses and were characterized. The strains were recovered from biopsied tissues and kunkers collected from granulomatous masses located on the hind limb and from a nodular lesion in the left upper eyelid, which decrease the ability of the horses to be used for working purposes. The methods used to identify P. insidiosum isolates were based on the production of sporangia and zoospores, histopathology and PCR assay. To further characterize these strains, portions of the 18S rRNA genes of the seven isolates were sequenced. The sequences showed high homology to previously described P. insidiosum DNA sequences available in GenBank. Similar studies based on the morphological, histological and molecular data identified the etiological agent in samples of granulomatous lesions in these equines as P. insidiosum. In America, the infection has been diagnosed more frequently in equines of Brazil, Colombia, Costa Rica and the United States of America.     

Identification of clusterin sequences mediating renal tubular cell interactions.

Expression of the glycoprotein clusterin is markedly increased following tissue injury. One function of clusterin is to promote cell interactions which are perturbed in these pathologic settings. Clusterin causes cell aggregation and adhesion in vitro yet the molecular mechanism for this effect is not known. In order to identify the active site(s) of clusterin, 34 peptides, each 15 amino acid residues in length, were synthesized from hydrophilic regions of human clusterin. When studied individually, none of the peptides caused aggregation of LLC-PK1 cells, a porcine renal epithelial cell line. However, two out of the 34 peptides inhibited clusterin-induced cell aggregation in a dose-dependent manner. Scrambled versions of these two 'active' peptides did not inhibit cell aggregation. Seven peptides promoted cell adhesion. In conclusion, these findings provide evidence for novel amino acid sequences mediating clusterin-induced renal cell interactions.     

Physiological responses of exercised-fatigued individuals exposed to wet-cold conditions.

Thirteen healthy and fit men [age = 27 +/- 8 (SD) yr, height = 177 +/- 5 cm, mass = 75 +/- 7 kg, body fat = 14 +/- 5%, maximal O2 consumption = 51 +/- 4 ml. kg-1. min-1] participated in an experiment designed to test their thermoregulatory response to a challenging cold exposure after 5 h of demanding mixed exercise during which only water was consumed. Subjects expended 7,314 +/- 741 kJ on cycling, rowing, and treadmill-walking machines, performed 8,403 +/- 1,401 kg. m of mechanical work during resistance exercises, and completed 120 inclined sit-ups. Subjects then assumed a seated position in a 10 degrees C air environment while wearing shorts, T-shirt, rain hat, and neoprene gloves and boots. After 30 min the subjects were showered continuously with cold water ( approximately 920 ml/min at 10 degrees C) on their backs accompanied by a 6 km/h wind for up to 4 h. Blood samples were taken from the nondominant arm every 30 min during the exposure and assayed for energy metabolites, hormones, indexes of hydration, and neurotransmitters. Counterbalanced control trials without prior exercise were also conducted. Blood insulin was higher during the control trial, whereas values of glycerol, nonesterified fatty acids, beta-hydroxybutyrate, lactate, cortisol, free triiodothyronine, and thyroxine were lower. Three subjects lasted the maximum duration of 4.5 h for control and fatigue trials, with final rectal temperatures of 36.43 +/- 0.21 and 36.08 +/- 0.49 degrees C, respectively. Overall, the duration of 172 +/- 68 (SD) min for the fatigue trial was not significantly different from that of the control trial (197 +/- 72 min) and, therefore, was not affected by the preexposure exercise. Although duration was positively correlated to body fatness and shivering intensity, the latter was not correlated to any physical characteristic or the fitness level of the individual.     

The role of the cysteine-rich region of the β2 integrin subunit in the leukocyte function-associated antigen-1 (LFA-1, αLβ2, CD11a/CD18) heterodimer formation and ligand binding

The cysteine-rich region (CRR) of the β2 integrin subunit was replaced by that of β1 to give the chimera β2NV1. β2NV1 can combine with αL to form a variant leukocyte-function-associated antigen (LFA)-1 on COS cell surface, suggesting that the specificity of the β2 interaction with αL does not lie in the CRR. Unlike those expressing wild-type LFA-1, COS cells expressing αLβ2NV1 are constitutively active in intercellular adhesion molecule (ICAM)-1 adhesion. These results suggest that activation of LFA-1 involves the release of an intramolecular constraint, which is maintained, in part, by the authentic β2 CRR.     

Identification of the structure of large-scale MHD perturbations in a tokamak from Mirnov signals

An algorithm is proposed that allows one to identify the MHD mode structure in toroidal plasmas by processing signals from Mirnov probes measuring plasma MHD activity. The algorithm differs fundamentally from the diagnostic methods presently used in tokamaks, being simpler and more efficient. The algorithm is based on constructing an analytic signal using the Hilbert transformation of the Mirnov signals at a given instant. The phase and amplitude dependences obtained take into account the toroidal effects and allow one to determine the number and amplitude of the excited MHD mode. The algorithm was approbated with both test signals and actual signals from MHD diagnostics in the T-10 tokamak. It is demonstrated that the algorithm can be used to analyze single-mode MHD instabilities in toroidal plasmas.     

Lung tissue mechanics and extracellular matrix composition in a murine model of silicosis.

The dynamic mechanical properties of lung tissue and its contents of collagen and elastic fibers were studied in strips prepared from mice instilled intratracheally with saline (C) or silica [15 (S15) and 30 days (S30) after instillation]. Resistance, elastance, and hysteresivity were studied during oscillations at different frequencies on S15 and S30. Elastance increased from C to silica groups but was similar between S15 and S30. Resistance was augmented from C to S15 and S30 and was greater in S30 than in S15 at higher frequencies. Hysteresivity was higher in S30 than in C and S15. Silica groups presented a greater amount of collagen than did C. Elastic fiber content increased progressively along time. This increment was related to the higher amount of oxytalan fibers at 15 and 30 days, whereas elaunin and fully developed elastic fibers were augmented only at 30 days. Silicosis led not only to pulmonary fibrosis but also to fibroelastosis, thus assigning a major role to the elastic system in the silicotic lung.     

Distribution of matter in the current-carrying plasma and dense core of the discharge channel formed upon electrical wire explosion

Distribution of matter in the discharge channel formed upon a nanosecond electrical explosion of a single wire in air and vacuum was studied experimentally. Simultaneous use of optical, UV, and X-ray diagnostics made it possible to distinguish qualitatively different regions of the discharge channel, such as the current-carrying layers and the region occupied by a weakly conducting cold plasma. Several series of experiments with 25-μm-diameter 12-mm-long wires made of different materials were performed. The charging voltage and the current amplitude were varied in the ranges of U ₀ = 10–20 kV and I _max ∼ 5–10 kA, respectively. Explosion regimes with a current pause and with and without current interruption, as well as with wire preheating in air and vacuum, were studied. Shadow and schlieren images of the discharge channel were obtained using optical probing at the second harmonic of a YAG: Nd⁺³ laser (λ = 0.532 μm, τ ∼ 10 ns). In the experiments carried out in vacuum, X-ray images of the discharge channel were also obtained using an X-pinch as a point source of probing radiation and UV images were recorded using a four-frame MCP camera.