Two or more enteropathogens are associated with diarrhoea in Mexican children

Background

The Apicomplexa are a diverse group of obligate protozoan parasites infesting a wide range of invertebrate and vertebrate hosts including humans. These parasites are notoriously difficult to control and many species continue to evolve resistance to commercial antibiotics. In this study, we sought to find an effective chemotherapeutic treatment against arthropod gregarines (Apicomplexa), and to identify candidate compounds for testing against other groups of protozoan parasites.

Methods

We tested eleven commercial antibiotics against a gregarine parasite of Romalea microptera grasshoppers. Infected insects were fed daily, lettuce containing known amounts of specific antibiotics. On Days 15 or 20, we measured the number of gregarines remaining in the digestive tract of each grasshopper.

Results

Treatment with metronidazole and griseofulvin in host insects significantly reduced gregarine counts, whereas, gregarine counts of insects fed, albendazole, ampicillin, chloramphenicol, fumagillin, quinine, streptomycin, sulfadimethoxine, thiabendazole or tetracycline, were not significantly different from the controls. However, albendazole produced a strong, but non-significant reduction in gregarine count, and streptomycin exhibited a non-significant antagonistic trend.

Conclusion

Our results confirm that gregarine infections are difficult to control and suggest the possibility that streptomycin might aggravate gregarine infection. In addition, the insect system described here, provides a simple, inexpensive, and effective method for screening antibiotics.     

Thapsigargin-sensitive cationic current leads to membrane depolarization, calcium entry, and insulin secretion in rat pancreatic beta-cells

Glucose-induced insulin secretion by pancreatic beta-cells depends on membrane depolarization and [Ca2+]i increase. We correlated voltage- and current-clamp recordings, [Ca2+]i measurements, and insulin reverse hemolytic plaque assay to analyze the activity of a thapsigargin-sensitive cationic channel that can be important for membrane depolarization in single rat pancreatic beta-cells. We demonstrate the presence of a thapsigargin-sensitive cationic current, which is mainly carried by Na+. Moreover, in basal glucose concentration (5.6 mM), thapsigargin depolarizes the plasma membrane, producing electrical activity and increasing [Ca2+]i. The latter is prevented by nifedipine, indicating that Ca2+ enters the cell through L-type Ca2+ channels, which are activated by membrane depolarization. Thapsigargin also increased insulin secretion by increasing the percentage of cells secreting insulin and amplifying hormone secretion by individual beta-cells. Nifedipine blocked the increase completely in 5.6 mM glucose and partially in 15.6 mM glucose. We conclude that thapsigargin potentiates a cationic current that depolarizes the cell membrane. This, in turn, increases Ca2+ entry through L-type Ca2+ channels promoting insulin secretion.     

Variation of Transhexadecenoic Acid Content in Two Triazine Resistant Mutants of Chenopodium album and Their Susceptible Progenitor

Two atrazine resistant nutants of Chenopodium album L. and their susceptible progenitor were analyzed for lipid composition. In the phosphatidyldiacylglycerol the Δ3-trans-hexadecenoic acid (C16:1 trans) percentage was higher in the two resistant phenotypes. However, this difference appears later in the development of the leaves and is not clearly observed in young leaves and seedlings. Thus, the increase of the C16:1 trans during the leaf development of the resistant phenotypes is probably a secondary effect of the psbA mutation that arises in compensation for some photosynthesis deficiency. The significance of the lipid differences shown between the two resistant mutants is discussed in terms of whether they are responsible of the two different levels of herbicide resistance observed in the field.     

Chlorophyll a fluorescence responses of temperate Phaeophyceae under submersion and emersion regimes: a comparison of rapid and steady-state light curves

The potential of algae to acclimate to environmental stress is commonly assessed using chlorophyll a fluorescence, with changes in parameters of photosynthesis versus irradiance (P/E) curves measured either as rapid light curves (RLC) or steady-state light curves (LC). Here, effects of emersion on primary photosynthesis of four brown macroalgae (Ascophyllum nodosum, Fucus serratus, Sargassum muticum, Laminaria digitata) were compared by applying both RLC and LC. When LC were used, photosynthetic performance was enhanced during emersion in A. nodosum and F. serratus as shown by increases in q_P, rETR_max and E _k. By contrast, emersion had no impact on photosynthetic parameters of S. muticum and L. digitata. Relative changes in the NPQ?CrETR relationship were reduced in A. nodosum, F. serratus and S. muticum, but remained unaffected in L. digitata. As none of the species developed their potential NPQ_max, corresponding values could not be determined from RLC. Using RLC, observed photosynthetic performance of F. serratus and L. digitata was reduced upon emersion, whilst values for NPQ_max were enhanced. Only results derived from LC provide evidence for a potential physiological adaptation of brown macroalgae to their natural habitat; it is recommended using the LC protocol to detect environmental impacts on photosynthesis.     

46,XX,-12,+der(12),rcp(3;12)(p25.1;p13.31)pat karyotype in a girl. Probable subregional assignment of glyceraldehyde-3-phosphate dehydrogenase locus to 12p13.1----p13.31 by exclusion mapping

A female infant with partial trisomy 3p and a terminal deletion 12p, due to a paternal (3;12)(p25.1;p13.31) translocation is described. Normal glyceraldehyde-3-phosphate (GAPD) activity in the proposita tentatively excludes GAPD locus from the deleted segment. Therefore, the region for this locus is reduced to 12p13.1----p13.31.     

A simple rapid fluorescent assay for adenosine deaminase activity.

A simple, rapid (2 hours), fluorescent test for the activity of blood adenosine deaminase (ADA) is described. The test which can be performed on both heparinized and dried blood, is based on the conversion of adenosine to inosine and ammonium in the presence of ADA. The enzyme activity is visually estimated by the oxidation of NADH (fluorescent) to NAD+ (non-fluorescent) in a coupled reaction with glutamate dehydrogenase. The disappearance of fluorescence indicates ADA activity in the sample. The advantages are discussed of the use of this test for the study of the autosomal recessive severe combined immunodeficiency.     

Botulinum neurotoxin type B uses a distinct entry pathway mediated by CDC42 into intestinal cells versus neuronal cells

Botulinum neurotoxins (BoNTs) are responsible for severe flaccid paralysis by inhibiting the release of acetylcholine at the neuromuscular junctions. BoNT type B (BoNT/B) most often induces mild forms of botulism with predominant dysautonomic symptoms. In food borne botulism and botulism by intestinal colonisation such as infant botulism, which are the most frequent naturally acquired forms of botulism, the digestive tract is the main entry route of BoNTs into the organism. We previously showed that BoNT/B translocates through mouse intestinal barrier by an endocytosis‐dependent mechanism and subsequently targets neuronal cells, mainly cholinergic neurons, in the intestinal mucosa and musculosa. Here, we investigated the entry pathway of BoNT/B using fluorescent C‐terminal domain of the heavy chain (HcB), which is involved in the binding to specific receptor(s) and entry process into target cells. While the combination of gangliosides GD_1a/GD_1b/GT_1b and synaptotagmin I and to a greater extent synaptotagmin II constitutes the functional HcB receptor on NG108‐15 neuronal cells, HcB only uses the gangliosides GD_1a/GD_1b/GT_1b to efficiently bind to m‐IC_cl2 intestinal cells. HcB enters both cell types by a dynamin‐dependent endocytosis, which is efficiently prevented by Dynasore, a dynamin inhibitor, and reaches a common early endosomal compartment labeled by early endosome antigen (EEA1). In contrast to neuronal cells, HcB uses a Cdc42‐dependent pathway to enter intestinal cells. Then, HcB is transported to late endosomes in neuronal cells, whereas it exploits a nonacidified pathway from apical to basal lateral side of m‐IC_cl2 cells supporting a transcytotic route in epithelial intestinal cells.     

Mechanisms controlling choline transport and acetylcholine synthesis in motor nerve terminals during electrical stimulation

Electrical stimulation of the chick ciliary nerve leads to a frequency-dependent increase in the Na+-dependent high affinity uptake of [3H]choline (SDHACU) and its conversion to acetylcholine (ACh) in the nerve terminals innervating the iris muscle. The forces that drive this choline (Ch) uptake across the presynaptic membrane were evaluated. Depolarization with increased [K+] out or veratridine decreases Ch accumulation. In addition to the electrical driving force, energy is provided by the Na+ gradient. Inhibition of the Na,K-ATPase decreased the Ch taken up. Thus, changes in the rate of Ch transport are dependent on the electrochemical gradients for both Ch and Na+. Ch uptake and ACh synthesis were increased after a conditioning preincubation with high [K+] out or veratridine. As is the case for electrical stimulation, this acceleration of Ch uptake and ACh synthesis was strongly dependent on the presence of Ca++ in the incubation medium. Na+ influx through a TTX-sensitive channel also contributed to this acceleration. Inasmuch as membrane depolarization reduces the initial velocity of Ch uptake and ACh synthesis, their increases during electrical stimulation therefore cannot be the direct effect of the depolarization phase of the action potential. Instead they are the result of the ionic fluxes accompanying the presynaptic spike. It is concluded that stimulation of Ch uptake and ACh synthesis by nerve activity depends first, on the ACh release elicited by Ca++ influx after depolarization and second, on the activation of the Na,K-ATPase due to Na+ entry. Furthermore, it is suggested that the release of ACh after stimulation drives translocation of cytoplasmic ACh into a protected compartment (probably vesicular). This recompartmentation of intraterminal ACh stimulates ACh synthesis by mass action, allowing further accumulation of Ch.     

One-step synthesis of isomalto-oligosaccharide syrups and dextrans of controlled size using engineered dextransucrase

Isomalto-oligosaccharides and dextrans of controlled molecular weight of about 10 and 40 kDa were produced using a simple one-step process using engineered L. mesenteroides NRRL B-512F dextransucrase variants. Isomalto-oligosaccharides were produced in a 58% yield by the acceptor reaction with glucose, and reached a degree of polymerization of at least 27 glucosyl units. Reaction conditions for optimal synthesis of dextrans of controlled molecular weight were defined, in respect of initial sucrose concentration and reaction temperature. Thus, we achieved synthesis with impressive yields of 69 and 75% for the 40 and 10 kDa dextran species, respectively. These two dextran sizes are particularly suitable for clinical applications, and are of great industrial demand. Compared with the traditional processes based on chemical hydrolysis and fractionation, which achieve only low yields, the new enzymatic methods offer improvement in quantity, quality and efficiency.     

NATURAL REVEGETATION OF ALKALINE TAILING HEAPS AT TAXCO,GUERRERO, MEXICO

The aim of this research was to identify adapted native plant species with potential for use in phytoremediation of a metalliferous mine tailings heap in Guerrero, Mexico. Physico-chemical characterization, total, DTPA-extractable and fractionation of metals in rhizospheric and non-rhizopheric samples were carried out to gain information about their potential risks. Metal concentrations in plant and bioconcentration factors (BCF) were also determined. Organic matter (OM) and total N contents were higher in the rhizospheric samples, which could improve the conditions for plant establishment. Total Cu, Zn, and Pb concentration were above those for normal soils. The highest metals concentration was found in the residual and organic fractions. Eleven plant species were recorded at the site; three behaved as metal accumulator plants: Gnaphalium chartaceum (accumulator of Cu, Mn, Zn, and Pb), Wigandia urens and Senecio salignus (1027 and 2477 mg kg^?1 of Zn). These species and Brickellia sp. presented high Pb-BCF; they may be suitable for metals phytoextraction. Seven species behaved as excluder plants; Guardiola tulocarpus, Juniperus flaccida, and Ficus goldmanii, presented low BCFs. These species are well suited to cope with the toxic conditions, and they could be propagated for revegetation and stabilization of these residues and to decrease metal bioavailability.