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.     

Properties of aminoglycoside-3'-phosphotransferases determined by kanamycin transposones Tn 601 and Tn 5

Aminoglycoside-3'-phosphotransferase I and II (APT-3'-I and APT-3'-II) has been purified to homogenity from the cells of E. coli containing the plasmids R6 and JR67, respectively. The purification procedure involved competitive affinity chromatography on neomycin-sepharose and gel-filtration on Sephadex G-100. The specific activity of APT-3'-I with the substrates--lividomycin A, neomycin B, paromycin, ribostamycin, kanamycins A and B--are 4.3, 2.8, 2.1, 1.6, 0.9 and 0.8 mol/min. mg protein, respectively. The specific activity of APT-3'-II with the substrates--ribostamycin, paromycin, kanamycins A and B, neomycin B--are 8.0, 7.2, 4.0, 4.5 and 3.6, respectively. Mg2+ is required for the activity of both enzymes. Co2+, Zn2+ and Mn2+ are active in case of APT-3'-I; however, these cations are less active than Mg2+. The pH-optimum of APT-3'-I and APT-3'-II is 7.0--7.5. High ionic strength is required for the activity of both enzymes. The molecular weights of APT-3'-I and APT-3'-II are about 36 000 and 26 000, respectively. The amino acid composition of APT-3'-I and APT-3'-II was determined. Both enzymes contain tryptophane residues whose fluorescence intensity decreased when ATP, but not amino-glycoside antibiotics, is added. The interrelationship between the molecular weights of these enzymes and the sizes of the loops of transposones Tn 601 and Tn 5, encoding APT-3'-I and APT-3'-II, is discussed.     

A survey of histoplasmosis and blastomycosis in U.A.R. (Egyptian sector) a preliminary report

Summary A selected group of 525 individuals with pulmonary diseases, granulomas and other medical conditions was tested for histoplasmin and blastomycin dermal reactions. No positive results were observed. Few doubtful positive reactions were recorded (3 to histoplasmin and 7 to blastomycin). None of the patients with chronic cutaneous granulomas exhibited any reaction.Although the number of subjects studied is small, these preliminry findings suggest the probable absence of histoplasmosis and blastomycosis in Egypt.     

Intracellular Synthesis of Myxovirus Neuraminidase in Chick Embryo Cell Monolayer Culture I. Neuraminidase Activity, Hemagglutinin Synthesis, and Content of Cell-bound Sialic Acid in Newcastle Disease Virus-infected Cells

Neuraminidase (Nase) activity of chick embryo monolayer cell homogenates was determined by its rate of splitting of neuraminlactose, free neuraminic acid (NA) being determined by the thiobarbituric acid assay. Noninfected cells were found to have no detectable amount of Nase activity. Newcastle disease virus (NDV)-infected cells (multiplicity of infection, 20 to 75 plaque-forming units per cell) displayed a high level of Nase synthesis, the rate of synthesis being parallel to that of hemagglutinin (HA) synthesis (with a 1.5 hr delay in the latter). An "eclipse" of the Nase and HA activities associated with the virus that was adsorbed onto cells was observed. The data provide evidence that the Nase is not incorporated into the viral envelope from a pre-existing cell supply but that its synthesis is coded by the viral genome. The content of cell-bound sialic acid, determined simultaneously in infected-cell homogenates, showed characteristic features allowing certain conclusions concerning the renewal of NA-terminating cell receptors during the course of infection, and the intracellular action of the Nase of the virus introduced into cells by the inoculum and that of the newly synthesized Nase at different stages of infection.     

M protein (M1) of influenza virus: antigenic analysis and intracellular localization with monoclonal antibodies.

A panel of 16 monoclonal antibodies recognizing M protein (M1) of influenza virus was generated. Competition analyses resulted in localization of 14 monoclonal antibodies to three antigenic sites. Three monoclonal antibodies localized to site 1B recognized a peptide synthesized to M1 (residues 220 to 236) with enzyme-linked immunosorbent assay titers equivalent to or greater than that seen with purified M1; therefore, site 1B is located near the C terminus of M1. Sites 2 and 3 localize to the N-terminal half of M1. Antigenic variation of M proteins was seen when the monoclonal antibodies were tested against 14 strains of type A influenza viruses. Several monoclonal antibodies showed specific recognition of A/PR/8/34 and A/USSR/90/77 M proteins and little or no reactivity for all other strains tested. Immunofluorescence analysis with the monoclonal antibodies showed migration of M protein to the nucleus during the replicative cycle and demonstrated association of M protein with actin filaments in the cytoplasm. Use of a vaccinia virus recombinant containing the M-protein gene demonstrated migration of M protein to the nucleus in the absence of synthesis of gene products from other influenza virus RNA segments.     

Down's syndrome,Edwards' syndrome,Patau's syndrome —synthesis of glycosaminoglycans

Synthesis of glycosaminoglycans (GAGS) by fibroblasts derived from seven patients with Down's syndrome, five patients with Edwards' syndrome, and two patients with Patau's syndrome were studied in cell culture. The aneuploid strains were compared with diploid fibroblasts from age-matched controls. In terms of hyaluronic acid and sulfated GAG synthesis, the amount of synthesized hyaluronic acid was not significantly different between postnatal aneuploid strains and controls.     

Fractal properties of forest spatial structure

The definition of fractal dimension of natural objects, which enables to deal with scale dependence of fractal dimension is discussed. Abrupt changes of fractal dimension of spatial structure of terrestrial ecosystems are considered in the context of hierarchical paradigm. On this ground the procedure is proposed for segmentation of a territory, which takes into account the scale dependence of spatial variability of ecological parameters. Using remotely sensed data — normalized difference vegetation index (NDVI) and thermal radiation in the infrared band — fractal dimensions and critical scales are evaluated for different forest types with the help of software, developed for this purpose. The results obtained corroborate the potentialities of fractal approach in ecology. These methods and results can be used for discrimination of remotely sensed data; but further investigations, including detailed comparison of fractal characteristics of remotely sensed forest images with results of on-site field studies are necessary to validate them.     

Pan-Arctic soil moisture control on tundra carbon sequestration and plant productivity

Long-term atmospheric CO₂ concentration records have suggested a reduction in the positive effect of warming on high-latitude carbon uptake since the 1990s. A variety of mechanisms have been proposed to explain the reduced net carbon sink of northern ecosystems with increased air temperature, including water stress on vegetation and increased respiration over recent decades. However, the lack of consistent long-term carbon flux and in situ soil moisture data has severely limited our ability to identify the mechanisms responsible for the recent reduced carbon sink strength. In this study, we used a record of nearly 100 site-years of eddy covariance data from 11 continuous permafrost tundra sites distributed across the circumpolar Arctic to test the temperature (expressed as growing degree days, GDD) responses of gross primary production (GPP), net ecosystem exchange (NEE), and ecosystem respiration (ER) at different periods of the summer (early, peak, and late summer) including dominant tundra vegetation classes (graminoids and mosses, and shrubs). We further tested GPP, NEE, and ER relationships with soil moisture and vapor pressure deficit to identify potential moisture limitations on plant productivity and net carbon exchange. Our results show a decrease in GPP with rising GDD during the peak summer (July) for both vegetation classes, and a significant relationship between the peak summer GPP and soil moisture after statistically controlling for GDD in a partial correlation analysis. These results suggest that tundra ecosystems might not benefit from increased temperature as much as suggested by several terrestrial biosphere models, if decreased soil moisture limits the peak summer plant productivity, reducing the ability of these ecosystems to sequester carbon during the summer.     

Perspectives on the nanocarriers with miRNAs for targeting melanoma stemness through epigenetic regulation

Several research reports delineated the significant role of miRNAs in cancer proliferation, and their modulatory role in cancer mitigation, and drug resistance. Melanoma cells have been acquiring stemness to several chemotherapeutic agents through drug efflux proteins, epigenetic modulation, and DNA repair. miRNAs could be applied as novel therapeutic modalities for treating several kinds of cancers to modulate these mechanisms involved in stemness. Nanocarriers to carry these tumor-targeting miRNAs to modulate stemness are a prominent strategy to overcome their low penetrability, minimal stability, and nonspecificity. We have searched several public databases such as PubMed, Medline, Google scholar, and NLM and obtained the information pertinent to the miRNA-based nanocarrier systems to target stemness through epigenetic modulation in melanomas. This review delineates that various miRNAs can modulate the stemness in melanomas by specific intricate epigenetic signaling, and other cell-based signaling mechanisms. Specific nanocarrier formulations with specific miRNAs are optimal methods to deliver these miRNAs in order to achieve significant entrapment efficiency, loading efficiency, and stability. Furthermore, the combinatorial regimen of FDA-approved chemotherapeutic molecules with tumor-targeting miRNAs and chemotherapy combined with nanocarriers can efficiently deliver the utmost therapeutic window by targeting tumor matrix, invasion, metastasis, and angiogenesis in melanomas. Substantial research should focus on the clinical application of this gene therapy in melanomas using these low immunogenic, highly degradable, and biocompatible combinatorial nanotherapeutic regimens.     

Poleward increase in feeding efficiency of leafminer Stigmella lapponica (Lepidoptera: Nepticulidae) in a latitudinal gradient crossing a boreal forest zone

Damage to plant communities imposed by insect herbivores generally decreases from low to high latitudes. This decrease is routinely attributed to declines in herbivore abundance and/or diversity, whereas latitudinal changes in per capita food consumption remain virtually unknown. Here, we tested the hypothesis that the lifetime food consumption by a herbivore individual decreases from low to high latitudes due to a temperature-driven decrease in metabolic expenses. From 2016 to 2019, we explored latitudinal changes in multiple characteristics of linear (gallery) mines made by larvae of the pygmy moth, Stigmella lapponica, in leaves of downy birch, Betula pubescens. The mined leaves were larger than intact leaves at the southern end of our latitudinal gradient (at 60°N) but smaller than intact leaves at its northern end (at 69°N), suggesting that female oviposition preference changes with latitude. No latitudinal changes were observed in larval size, mine length or area, and in per capita food consumption, but the larval feeding efficiency (quantified as the ratio between larval size and mine size) increased with latitude. Consequently, S. lapponica larvae consumed less foliar biomass at higher latitudes than at lower latitudes to reach the same size. Based on space-for-time substitution, we suggest that climate warming will increase metabolic expenses of insect herbivores with uncertain consequences for plant–herbivore interactions.