Isolation of secondary metabolites of Aspergillus ochraceus by HPLC

A method is described for the isolation and purification of ochratoxin A, ochratoxin B, ochratoxin ß mellein, 4-hydroxymellein and penicillic acid produced byAspergillus ochraceus in a synthetic liquid medium. Ochratoxin α, which was not found in the culture medium, was obtained by acid hydrolysis of ochratoxin A. A high pressure liquid Chromatograph equipped with Lichrosorb 100 and Lichrosorb RP-18 columns and UV and/or Refractive Index detectors was used.     

Entamoeba histolytica: gene linkage groups and relevant features of its karyotype

We identified some gene linkage groups in Entamoeba histolytica using a 4-M urea improved transversal alternating field electrophoresis (TAFE) method. Complex rosette-structured DNA molecules were found trapped along the gel lanes, explaining the fuzziness of the patterns. Using several episomal probes, including 16 S, 5.8 S, and 25 S ribosomal (r)Dna genes, an autonomous replication sequence (ARS), and EhVR1, we identified a complete ribosomal episome linkage group (CELG) at the 1.2-Mb position. Three other incomplete groups were found: IELG-1, formed by EhVR1,16 S, 5.8 S, and 25 S genes; IELG-2 formed by EhVR1, 16 S and 25 S; and IELG-3 formed only by 5.8 S. Ehadh3, Ehpfo, and Ehredox genes migrated at the 1.8-Mb position, forming the non-ribosomal linkage group, NRLG-1.8, while the Ehenl-1 gene migrated at 1.6 Mb forming the NRLG-1.6 group. Ehhk was located at 1.2, 0.8, and 0.17 Mb in three different groups: NRLG-1.2, IELG-3-0.8, and NRLG-0.17. Putative lineal chromosomes were also identified using an heterologous telomeric probe. By in situ hybridization experiments, the rDNA and Ehhk genes were located in both nucleus and cytoplasm, while the Ehpfo and Ehredox genes were found mainly in the nucleus. We propose a model hypothezising that the 16 S and 25?S genes are in a linear molecule, duplicated in two inverted repeats, which may be looped out of the linear DNA to form an episome probably lacking or not the 5.8 S sequence, which could be added later by recombination.     

An Ustilago maydis Mutant Partially Blocked in P45014DM Activity Is Hypersensitive to Azole Fungicides

An Ustilago maydis ergosterol biosynthesis mutant (A14) which is partially blocked in sterol 14alpha-demethylase (P45014DM) activity is described. This mutant accumulated the abnormal 14alpha-methyl sterols, eburicol, 14alpha-methylfecosterol, and obtusifoliol, along with significant amounts of ergosterol. Although the A14 mutant grew nearly as well as the wild type, it was impaired in cell extension growth, which indicated a dysfunction in apical cell wall synthesis. The mutant was also found to be hypersensitive to the azole fungicides penconazole and tebuconazole.     

Hexazonium pararosaniline as a fixative for animal tissues

Hexazonium pararosaniline is a valuable reagent that has been used in enzyme activity histochemistry for 50 years. It is an aqueous solution containing the tris-diazonium ion derived from pararosaniline, an aminotriarylmethane dye, and it contains an excess of nitrous acid that was not consumed in the diazotization reaction. Other investigators have found that immersion for 2 min in an acidic (pH 3.5) 0.0015 M hexazonium pararosaniline solution can protect cryostat sections of unfixed animal tissues from the deleterious effects of aqueous reagents such as buffered solutions used in immunohistochemistry, while preserving specific affinities for antibodies. In the present investigation hexazonium pararosaniline protected lymphoid tissue and striated muscle against the damaging effects of water or saline. The same protection was conferred on unfixed sections treated with dilute nitrous or hydrochloric acid in concentrations similar to those in hexazonium pararosaniline solutions. Model tissues (solutions, gels or films containing gelatin and/or bovine albumin) responded predictably to well known cross-linking (formaldehyde) or coagulant (mercuric chloride) fixatives. Hexazonium pararosaniline solutions prevented the dissolution of protein gels in water only after 9 or more days of contact, during which time considerable swelling occurred. It is concluded that there is no evidence for a “fixative” action of hexazonium pararosaniline. The protective effect on frozen sections of unfixed tissue is attributable probably to the low pH of the solution.     

Major plant communities of North America's most arid region: The San Felipe Desert,Baja California,México

Abstract

This vegetation study describes the landscape of the San Felipe Desert (Baja California, México) based on the phytosociological analysis of its major plant associations, as determined by the Braun-Blanquet method and supported by cluster analysis. Four geomorphological or phytotopographical units were identified in the landscape of the San Felipe Desert (salt marshes, playas or sandy flats, bajadas or alluvial fans, and malpaíses or badlands), each characterized by its own plant communities. Two communities and eleven associations were identified, four of which are described and typified for the first time: Atriplici linearis-Frankenietum palmeri, Parkinsonio microphyllae-Olneyetum tesotae, Errazurizio megacarpae-Ephedretum trifurcae and Pachycereo schottii-Prosopidetum torreyanae. Ecological, phytogeographical, bioclimatic, syntaxonomical and floristic data are provided for each of these new associations.     

Microorganisms under high pressure — Adaptation,growth and biotechnological potential

Hydrostatic pressure is a well-known physical parameter which is now considered an important variable of life, since organisms have the ability to adapt to pressure changes, by the development of resistance against this variable. In the past decades a huge interest in high hydrostatic pressure (HHP) technology is increasingly emerging among food and biosciences researchers. Microbial specific stress responses to HHP are currently being investigated, through the evaluation of pressure effects on biomolecules, cell structure, metabolic behavior, growth and viability. The knowledge development in this field allows a better comprehension of pressure resistance mechanisms acquired at sub-lethal pressures. In addition, new applications of HHP could arise from these studies, particularly in what concerns to biotechnology. For instance, the modulation of microbial metabolic pathways, as a response to different pressure conditions, may lead to the production of novel compounds with potential biotechnological and industrial applications. Considering pressure as an extreme life condition, this review intends to present the main findings so far reported in the scientific literature, focusing on microorganisms with the ability to withstand and to grow in high pressure conditions, whether they have innated or acquired resistance, and show the potential of the application of HHP technology for microbial biotechnology.     

Economic evaluation of water loss saving due to the biological control of water hyacinth at New Year’s Dam,Eastern Cape province,South Africa

Water hyacinth Eichhornia crassipes is considered the most damaging aquatic weed in the world. However, few studies have quantified the impact of this weed economically and ecologically, and even fewer studies have quantified the benefits of its control. This paper focuses on water loss saving as the benefit derived from biological control of this plant between 1990 and 2013 at New Year’s Dam, Alicedale, Eastern Cape, South Africa. Estimates of water loss due to evapotranspiration from water hyacinth vary significantly; therefore, the study used three different rates, high, medium and low. A conservative raw agriculture value of R 0.26 per m³ was used to calculate the benefits derived by the water saved. The present benefit and cost values were determined using 10% and 5% discount rates. The benefit/cost ratio at the low evapotranspiration rate was less than one, implying that biological control was not economically viable but, at the higher evapotranspiration rates, the return justified the costs of biological control. However, at the marginal value product of water, the inclusion of the costs of damage to infrastructure, or the adverse effects of water hyacinth on biodiversity, would justify the use of biological control, even at the low transpiration rate.     

The Tau/A152T mutation,a risk factor for frontotemporal‐spectrum disorders,leads to NR2B receptor‐mediated excitotoxicity

We report on a novel transgenic mouse model expressing human full‐length Tau with the Tau mutation A152T (hTau^AT), a risk factor for FTD‐spectrum disorders including PSP and CBD. Brain neurons reveal pathological Tau conformation, hyperphosphorylation, mis‐sorting, aggregation, neuronal degeneration, and progressive loss, most prominently in area CA3 of the hippocampus. The mossy fiber pathway shows enhanced basal synaptic transmission without changes in short‐ or long‐term plasticity. In organotypic hippocampal slices, extracellular glutamate increases early above control levels, followed by a rise in neurotoxicity. These changes are normalized by inhibiting neurotransmitter release or by blocking voltage‐gated sodium channels. CA3 neurons show elevated intracellular calcium during rest and after activity induction which is sensitive to NR2B antagonizing drugs, demonstrating a pivotal role of extrasynaptic NMDA receptors. Slices show pronounced epileptiform activity and axonal sprouting of mossy fibers. Excitotoxic neuronal death is ameliorated by ceftriaxone, which stimulates astrocytic glutamate uptake via the transporter EAAT2/GLT1. In summary, hTau^AT causes excitotoxicity mediated by NR2B‐containing NMDA receptors due to enhanced extracellular glutamate.     

Effects of restricted nursing on milk production and collection, kid growth and plasma prolactin and growth hormone concentrations in dairy goats

The milk production of dairy goats under various regimes of mother-young contact from day 4 post partum were studied during the first 2 months of lactation, together with the prolactin (PRL) and growth hormone (GH) responses to udder stimulation. In the control group, 13 goats and their kids were left in permanent contact and did not undergo milking. In two additional groups, goats were machine milked once a day in the morning (at 0800 h) and kids were allowed 10 hours (from 1000 to 2000 h; 10H group, n = 11) or 5 h (from 1000 to 2000 h; 5H group, n = 11) of mother-young interaction per day. In the last group (MO, n = 10), mothers were permanently separated from their kids on day 4 post partum and milked once a day. Milk production during a 24-h period at 37 days post partum performed by controlled nursing and weighing of the kids (groups with kids) or by two machine milking 12 h apart (milking only group) revealed a higher production in the three groups with some mother-young contact than in the MO group. Total milk collected by milking over the 2 months of the study did not differ between the three groups that underwent milking. Kid weights at 2 months were 3.4 to 4.8 kg. lighter in the groups that underwent milking than in the control group. Hormonal profiles were significantly affected by restricted mother-young contact, with highest pre-stimulation concentrations of PRL and GH in the 5H group. Restricting mother-young contact from the first week postpartum can permit an early collection of milk without major effects on kid growth, when compared with one daily milking in goats totally separated from their young.