Stimulation of monovalent cation fluxes by electron donors in the human red cell membrane

When human red cells are incubated at 37°C with the artificial electron donor system ascorbate + phenazine methosulphate the fluxes of Rb⁺ (K⁺) through the cell membrane are increased. The effect of this donor system is much stronger in energy-depleted than in normal cells. The same effects are produced by HS-glutathione, NADH or NADPH loaded into resealed ghosts, but these electron donors were ineffective when added to the incubation medium. The Rb⁺ (K⁺) fluxes induced by electron donors resemble closely those induced by an increase of intracellular Ca²⁺ (Gardos effect). The electron donors require the presence of intracellular Ca²⁺ to be effective, but at levels that do not stimulate by themselves the fluxes of K⁺. Flavoenzyme inhibitors (atebrin and chlorpromazine), oligomycin and quinine prevented the effects of both electron donors and Ca²⁺ alone; antimycin, uncouplers and ethacrynic acid inhibited them partially; ouabain, furosemide, and rotenone had no effect.The results could be explained if the effect of electron donors is to bring about a change in the redox state of some membrane component(s) that makes intracellular Ca²⁺ more effective to elicit rapid K⁺ movements. Plasma membrane oxidoreductase activities could be engaged in this change.     

IDENTIFICATION AND PHYSIOLOGICAL ASPECTS OF A NOVEL CAROTENOID‐ENRICHED,METAL‐RESISTANT MICROALGA ISOLATED FROM AN ACIDIC RIVER IN HUELVA (SPAIN)1

A heavy‐metal‐resistant, carotenoid‐enriched novel unicellular microalga was isolated from an acidic river in Huelva, Spain. The isolated ribosomal 18S subunit rDNA sequence showed homology with known sequences from green microalgae, the closest sequence (98% homology) belonging to the genus Coccomyxa. The isolated microalga therefore was an up to now uncultured microalga. The microalga was isolated from Tinto River area (Huelva, Spain), an acidic river that exhibits very low pH (1.7–3.1) with high concentrations of sulfuric acid and heavy metals, including Fe, Cu, Mn, Ni, and Al. Electron micrographs show that the microalga contains a large chloroplast with a presence of lipid droplets, an increased number of starch bodies as well as electron‐dense deposits and plastoglobules, the last observed only in iron‐exposed cells. Unlike other acidophile microalgae, the isolated microalga showed high growth rates when cultivated photoautotrophycally (up to 0.6 d^?1) in a suitable culture medium prepared at our laboratory. The growth was shown to be iron dependent. When the microalga is grown in fluidized bed reactors, the high growth rates resulted in unexpectedly high productivities for being a microalga that naturally grows in acidic environments (0.32 g·L^?1·d^?1). The microalga also grows optimally on reduced carbon sources, including glucose and urea, and at an optimal temperature of 35°C. The alga pigment profile is particularly rich in carotenoids, especially lutein, suggesting that the microalga might have potential for antioxidant production, namely, xanthophylls.     

Environmental characteristics around the household and their association with hookworm infection in rural communities from Bahir Dar,Amhara Region,Ethiopia

Soil-Transmitted Helminths (STH) are highly prevalent Neglected Tropical Disease in Ethiopia, an estimated 26 million are infected. Geographic Information Systems and Remote Sensing (RS) technologies assist data mapping and analysis, and the prediction of the spatial distribution of infection in relation to environmental variables. The influence of socioeconomic, environmental and soil characteristics on hookworm infection at the individual and household level is explored in order to identify spatial patterns of infection in rural villages from Zenzelema (Amhara region). Inhabitants greater than 5 years old were recruited in order to assess the presence of STH. Socioeconomic and hookworm infection variables at the household level and environmental variables and soil characteristics using RS were obtained. The dominant STH found was hookworm. Individuals which practiced open defecation and those without electricity had a significant higher number of hookworm eggs in their stool. Additionally, adults showed statistically higher hookworm egg counts than children. Nonetheless, the probability of hookworm infection was not determined by socioeconomic conditions but by environmental characteristics surrounding the households, including a combination of vigorous vegetation and bare soil, high temperatures, and compacted soils (high bulk density) with more acidic pH, given a pH of 6.0 is optimal for hatching of hookworm eggs. The identification of high-risk environmental areas provides a useful tool for planning, targeting and monitoring of control measures, including not only children but also adults when hookworm is concerned.     

Glycosaminoglycans of the fat globule membrane of cow milk

Membranes of fat globules of cow milk contained 163 μg/100 mg (dry weight) of glycosaminoglycans (expressed as uronic acid); 62.5% of the uronic acids corresponded to hyaluronic acid, the remaining consisted of sulfated glycosaminoglycans (chondroitin-4-(-6) sulfates, and dermatan and heparan sulfates) with different degrees of sulfation.     

A recombinant, arginine-glycine-aspartic acid (RGD) motif from foot-and-mouth disease virus binds mammalian cells through vitronectin and, to a lower extent, fibronectin receptors

The cell-binding abilities of a recombinant, RGD-containing peptide from foot-and-mouth disease virus (FMDV) have been characterized in HeLa and BHK cells. This peptide represents the aa sequence of the solvent-exposed G-H loop of protein VP1 which is involved in cell recognition and infection. The efficiency of the viral motif in promoting cell attachment and spreading is comparable to that shown by fibronectin or vitronectin. Cell binding is inhibited by a monoclonal antibody directed against a viral, RGD-involving B-cell epitope and also by sera against vitronectin (_Vβ₃/β₅) and fibronectin (₅β₁) receptors. In addition, a synthetic RGD peptide, which is a ligand for both integrins, prevents the cell binding mediated by the FMDV domain. These data demonstrate that the FMDV RGD motif is a potent ligand for cell-receptor integrins and sufficient to promote cell attachment to susceptible cells mainly through the vitronectin receptor.     

The pollen of Caesalpinia pyramidalis Tul. is toxic to honeybees (Apis mellifera)

Caesalpinia pyramidalis Tul. (syn. Caesalpinia gardneriana Benth.) is an endemic tree from northeastern Brazil whose flowers are visited by a number of bee species, including the honeybee (Apis mellifera). The present study aimed to determine whether the pollen of C. pyramidalis is toxic to honeybees. Pollen samples were collected, dried, and added to food at doses of 0 (control), 2.5, 5.0, and 10 %. Each dose of food was fed to 60 honeybees, which were observed daily until the last one died. Statistical comparison of the survival curves was performed using the log-rank test. The mean survival times of the bees fed with C. pyramidalis pollen were 6.40 ± 0.28 days for the 2.5 % group, 5.70 ± 0.18 days for the 5.0 % group, 5.72 ± 0.23 days for the 10.0 % group, and 13.7 ± 0.61 days for the control group. All the pollen concentrations of C. pyramidalis significantly (P < 0.0001) reduced the survival of honeybees in comparison with control group. In conclusion, the results of our study show that the pollen produced by C. pyramidalis is toxic to A. mellifera under laboratory conditions.     

Efficient plant regeneration from protoplasts of <Emphasis Type="Italic">Kalanchoe blossfeldiana</Emphasis> via organogenesis

A simple and efficient protocol for plant regeneration from protoplasts of the potted plant Kalanchoe blossfeldiana Poelln. is reported. Mesophyll protoplasts were isolated from axenic leaves after a preculture. The enzymatic digestion of the tissue with a solution containing 0.4% Cellulase Onozuka R-10 and 0.2% Driselase yielded 6.0 × 10⁵ protoplasts per gram fresh weight after density gradient purification. Protoplasts were cultured in the dark at an initial density of 1 × 10⁵ protoplasts per milliliter in a liquid medium with 320 mM mannitol, 130 mM sucrose, 2.3 μM 2,4-dichlorophenoxy acetic acid (2,4-D), 5.4 μM 1-naphthaleneacetic acid (NAA) and 2.2 μM 6-benzyladenine (BA). Cell wall regeneration was observed within 4 days of culture and cell division began after 5–7 days. When cultured in a liquid medium with 5.4 μM NAA and 8.9 μM BA, protoplast-derived colonies proliferated until small visible calli, and adventitious buds appeared after transfer to photoperiod conditions. Developed shoots were rooted on a solid medium supplemented with 0.6 μM indole-3-acetic acid (IAA) and successfully established under greenhouse conditions. The process required 4 months from isolation to rooted plants and the best conditions found gave a plant regeneration efficiency of 6.4 plants per 1 × 10⁵ protoplasts. This is the first protocol reported for plant regeneration from protoplasts for a Crassulaceae family species.     

Effects of redox agents on the Ca-activated K channel

The sensitivity to Ca²⁺ of the Ca²⁺-dependent K⁺ channel can be increased by the artificial electron donor system ascorbate + phenazine-methosulphate in a variety of animal cells. In the human erythrocyte the shift from the ‘low’ to the ‘high-affinity’ state seems to depend on the reduction of a membrane component accepting 2 electrons and with an standard redox potential (pH 7.5) of about 47 mV. The relevance of this redox modulation under physiological circumstances is unknown at the moment.