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.     

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.     

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.     

Macroalgae and nutrients promote algal turf growth in the absence of herbivores

Coral Reefs - Closely cropped algal turfs are characteristic of healthy coral reefs, but unchecked growth can cause transitions into long sediment-laden turfs, which may be an alternative degraded...     

Length of postpartum anestrus in goats in subtropical Mexico: effect of season of parturition and duration of nursing

The aim of this study was to determine whether season of birth and length of nursing affected the duration of postpartum anestrus in Creole female goats maintained on a constant plane of nutrition in subtropical Mexico. Three experiments were conducted in the Laguna region in the State of Coahuila, Mexico (26 degrees N). In the first experiment, 34 goats gave birth in January; in the second, 31 females gave birth in May; and in the third, 22 goats kidded in October. At parturition, females were allocated to 1 of 3 groups based on body weight and date of parturition: kids were weaned at 2, 30 or 90 d according to their group. After weaning, females were milked manually once a day until the end of the study. All animals were kept in a shed and were fed alfalfa ad libitum and given 200 g of concentrate daily. Starting 1 wk after parturition, estrous behavior was detected twice daily using an apron-bearing male, and blood samples were obtained twice weekly to determine ovarian activity from the plasma progesterone levels. A strong effect of month of parturition was found on the duration of postpartum anestrus (P < 0.0001), which was longer in females kidding in January (about 200 d) than in those kidding in May (about 100 d) or October (about 50 d). A tendency for an interaction between season of parturition and length of nursing was observed in the length of anovulation (P < 0.07): for parturition in October, anestrus was longer when kids were weaned after 90 d than after 2 or 30 d (P < 0.01). Season of parturition also affected dates of reinitiation of ovulatory and estrous activity (P < 0.001). Proportions of normal, short and long cycles and of associations between estrous and ovulations were not influenced by season of parturition or the age of weaning. These data demonstrate that in subtropical latitudes, season of parturition can dramatically influence the duration of postpartum anestrus independently of the availability of food.     

Zonobiomes, zonoecotones and azonal vegetation along the Pacific coast of North America

In this study of the Pacific coast of North America, from Baja California to Alaska, we evaluated the hypothesis that the floristic composition of azonal vegetation determines areas and distribution limits similar to those of the corresponding zonobiomes (ZB), and does so in response to the same macroclimatic changes occurring on the continental scale. To this end, 686 vascular plants of the different habitats found in 279 sites along this coastal strip were recorded. Using an objective classification system (Average Linkage Clustering) and factorial analysis, floristic data acquired in fieldwork were classified into groups, which were in turn related to regional macroclimates. Our main finding was that the azonal coastal vegetation follows a distribution model that is closely linked to the corresponding macroclimate. The four ZB of the northern Pacific coast show a flora and azonal vegetation characteristic to each zonobiome; the latitudinal limits of the azonal vegetation practically coinciding with those already established for the zonal vegetation. The Boreal and Temperate ZB show high percentages of broadly distributed elements. The floristically richest zonobiome in terms of endemic taxa is the Mediterranean zonobiome, whereas the flora of Baja California is characterized by a high number of taxa related to Neotropical flora, especially to those showing links with South America. Data on the geographical distribution and habitats of the 247 most significant coastal species are also provided.