Endomycopsis montevidensis n. sp.

A new species of the genusEndomycopsis is proposed. It was isolated from waste water, at Montevideo-Uruguay.By its morphological and biochemical proprieties it differs from allEndomycopsis previously described.

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Este trabajo fue desarrollado en el Laboratorio de Micologia de la Facultad de Química de Montevideo, Uruguay y en uso de una beca de la Universidad Federal de Pernambuco para perfecciobamiento en el estudio de las levaduras.     

Prions and lymphoid organs: Solved and remaining mysteries

Prion colonization of secondary lymphoid organs (SLOs) is a critical step preceding neuroinvasion in prion pathogenesis. Follicular dendritic cells (FDCs), which depend on both tumor necrosis factor receptor 1 (TNFR1) and lymphotoxin β receptor (LTβR) signaling for maintenance, are thought to be the primary sites of prion accumulation in SLOs. However, prion titers in RML-infected TNFR1^−/− lymph nodes and rates of neuroinvasion in TNFR1^−/− mice remain high despite the absence of mature FDCs. Recently, we discovered that TNFR1-independent prion accumulation in lymph nodes relies on LTβR signaling. Loss of LTβR signaling in TNFR1^−/− lymph nodes coincided with the de-differentiation of high endothelial venules (HEVs)—the primary sites of lymphocyte entry into lymph nodes. These findings suggest that HEVs are the sites through which prions initially invade lymph nodes from the bloodstream. Identification of HEVs as entry portals for prions clarifies a number of previous observations concerning peripheral prion pathogenesis. However, a number of questions still remain: What is the mechanism by which prions are taken up by HEVs? Which cells are responsible for delivering prions to lymph nodes? Are HEVs the main entry site for prions into lymph nodes or do alternative routes also exist? These questions and others are considered in this article.     

Phytochrome-mediated responses of cells and protoplasts of green calli obtained from the leaves of a CAM plant

Green callus obtained from leaves of the CAM-inducible plant Kalanchoe blossfeldiana cv. Montezuma has previously been shown to perform C₃-type photosynthesis under 16-h days and to shift to crassulacean acid metabolism (CAM) under 9-h days. The utilization of photoperiodic regimes (i.e. night interruptions by 30 min red light) established that CAM induction in the callus was under the control of phytochrome, as shown by measurements of CAM criteria: phosphoenolpyruvate carboxylase activity and malic acid pools. Short-term responsiveness of the callus cells to phytochrome modulations by monochromatic radiations was also established by the rapid changes observed in the diameter of the callus-derived protoplasts. These results provide further evidence that whole plant correlations are not necessary for phytochrome operativity.Abbreviations CAM crassulacean acid metabolism - PAL phenylalanine ammonia lyase (EC 4.3.1.5) - PAR photosynthetically active radiations - PEPC phosphoenolpyruvate carboxylase (EC 4.1.1. 31) - Rubisco ribulose 1,5 bisphosphate carboxylase (EC 4.1.1.39)     

Elutriation of human keratinocytes and melanocytes fromin vitro cultured epithelium

Summary Human epidermal keratinocytes grown in culture and at different stages of differentiation are shown to be viably separated by elutriation. A specific fraction enriched in melanocytes was obtained. Elutriation of cells obtained fromin vitro cultured epithlium could prove useful in studies concerning the biochemistry and molecular markers of cells isolated from normal epithelium and from different pathologies.     

Endomycopsis montevidensis n. sp.

A new species of the genusEndomycopsis is proposed. It was isolated from wast water, at Montevideo-Uruguay.By its morphological and biochemical proprieties it differs from allEndomycopsis previously described.Este trabajo fue desarrollado en el Laboratorio de Micologia de la Facultad de Quimica de Montevideo, Uruguay y en uso de una beca de la Universidad Federal de Pernambuco para perfeccio bamiento en el estudo de las levaduras.     

The effect of the plating medium on the recovery of nonsense suppressors in Saccharomyces cerevisiae

The recovery of nonsense suppressors in a strain of Saccharomyces cerevisiae carrying five ochre mutations, tr, hi, ly, ar, and ad, is affected by the plating medium. The highest frequency is observed on tryptophanless medium, while the lowest is observed on adenineless medium. Experiments showed that exogenous histidine inhibits suppressor expression and that exogenous adenine relieves this inhibition. In histidine-independent strains, mutation expression requires adenine. A model, based on the role of RNA in supersuppression and on the biosynthetic pathways of histidine and adenine, is proposed to account for the observed data. It cannot, however, account for the high frequency of suppressors on tryptophanless medium. The tentative conclusion is drawn either that mis-reading of the tryptophan nonsense codon by mutated tRNA is facilitated by the neighboring bases or that the type of acceptable amino acid is less rigorously limited in the mutated site of the tryptophan locus than in those of the other suppressible loci.This work was in part supported by the Calouste Gulbenkian Foundation and by the Medical Research Council (Grant No. G969/24/B).     

Evaluation of three herbaceous index plant species for bioavailability of soil cadmium, chromium, nickel and vanadium

Uncultivated plants growing on disturbed sites may be useful for assessing the bioavailability of some metals in soils, and thus the potential for metal mobilization up the terrestrial food chain, an important element in ecological risk assessment. A planted chicory cultivar (Cichorium intybus L. var. foliosum Hegi.) and the uncultivated plants horseweed (Canada fleabane) (Erigeron canadensis L.) and dogfennel (Eupatorium capillifolium (Lam.) Small) were evaluated for their ability to act as index plant species for soil Cd, Cr, Ni, and V at two field sites where these metals had been applied five yr previously to two highly weathered sandy Ultisols. Soil Cd was available to all analyzed plant tissues of all three plant species at both sites, particularly on the sandier Blanton soil. Chicory was an effective index plant for Cd on the finer textured Orangeburg soil but functioned as an indicator plant (toxicity symptoms were observed) on the sandier Blanton soil. Horseweed and dogfennel were effective index plants for Cd in both contaminated soils. Soil Cr, Ni, and V were less bioavailable than soil Cd and plant metal uptake was more sensitive to residual soil Cr, Ni, and V than was soil extraction with double acid. Horseweed and chicory may have potential as index plants for soil Cr. Chicory may have potential as a Ni index plant. Chicory and dogfennel may have potential as V index plants.     

Diet of the brown howler monkeyAlouatta fusca in a semi-deciduous forest fragment of southeastern Brazil

The diet of a group of six brown howlers was studied weekly during 12 months in a reserve of 250 ha of secondary, mesophytic, semi-deciduous forest. The phenology of 186 trees of 72 species and 29 families was monitored simultaneously. Scan sampling was used to record the diet from dawn until dusk on a total of 60 days of observation, yielding 718 hr of animal-observer contact and 2,943 feeding scans. The diet was composed of leaves (73%), flowers (12%), and fruits (5%), from 68 identified plant species.Celtis iguanae, Cassia ferruginea, andInga spp. were the main food sources, accounting for approximately 50% of the diet. Young leaves (59%) were preferred to mature leaves (31%), trees contributing 56% and lianas 41% of the leaf diet. The ingestion of young leaves was correlated to the availability of these items, however, the correlations were not significant for flowers and fruits. The diet was poorer in fruits and richer in young leaves of lianas in comparison to other howler monkey species studies, probably as a consequence of the liana abundance in this forest fragment.     

Trophic ecology of three stingrays (Myliobatoidei: Dasyatidae) off the Brazilian north-eastern coast: Habitat use and resource partitioning

Understanding the ecological role of species with overlapping distributions is central to inform ecosystem management. Here we describe the diet, trophic level and habitat use of three sympatric stingrays, Hypanus guttatus, H. marianae and H. berthalutzae, through combined stomach content and stable isotope (δ¹³C and δ¹⁵N) analyses. Our integrated approach revealed that H. guttatus is a mesopredator that feeds on a diverse diet of benthic and epibenthic marine and estuarine organisms, principally bivalve molluscs, Alpheus shrimp and teleost fishes. Isotopic data supported movement of this species between marine and estuarine environments. H. berthalutzae is also a marine generalist feeder, but feeds primarily on teleost fishes and cephalopods, and consequently occupies a higher trophic level. In contrast, H. marianae is a mesopredator specialized on shrimps and polychaetas occurring only in the marine environment and occupying a low niche breadth. While niche overlap occurred, the three stingrays utilized the same prey resources at different rates and occupied distinct trophic niches, potentially limiting competition for resources and promoting coexistence. These combined data demonstrate that these three mesopredators perform different ecological roles in the ecosystems they occupy, limiting functional redundancy.