High-Speed Cell Sorting of Infectious Trophic and Cystic Forms of Pneumocystis carinii

ABSTRACT. The separation of Pneumocystis carinii life-cycle stages while preserving infectivity is a hitherto unresolved challenge. We describe an original, reproducible, and efficient method for separating trophic from cystic forms of P. carinii using a high-speed cell sorter. The large amounts of highly purified (99.6±0.3%) infectious trophic and cystic forms can now be used to elucidate the poorly understood P. carinii life cycle.     

Genetic footprints of late Quaternary climate change in the diversity of Patagonian‐Fueguian rodents

Species are impacted by climate change at both ecological and evolutionary time scales. Studies in northern continents have provided abundant evidence of dramatic shifts in distributions of species subsequent to the last glacial maximum (LGM), particularly at high latitudes. However, little is known about the history of southern continents, especially at high latitudes. South America is the only continent, other than Antarctica, that extends beyond 40 °S. Genetic studies of a few Patagonian species have provided seemingly conflicting results, indicating either postglacial colonization from restricted glacial refugia or persistence through glacial cycles and in situ differentiation. Using mitochondrial DNA sequences of 14 species of sigmodontine rodents, a major faunal ensemble of Patagonia and Tierra del Fuego, we show that at least nine of these species bear genetic footprints of demographic expansion from single restricted sources. However, timing of demographic expansion precedes the LGM in most of these species. Four species are fragmented phylogeographically within the region. Our results indicate that (i) demographic instability in response to historical climate change has been widespread in the Patagonian‐Fueguian region, and is generally more pronounced at high latitudes in both southern and northern continents; (ii) colonization from lower latitudes is an important component of current Patagonian‐Fueguian diversity; but (iii) in situ differentiation has also contributed to species diversity.     

Intracellular phosphorylation of benzyladenosine is related to apoptosis induction in tobacco BY-2 cells

Treatment of tobacco BY‐2 cells with micromolar concentration of benzyladenosine ([9R]BA) resulted in the loss of cell viability in a time‐ and concentration‐dependent manner. Cell death induced by [9R]BA exhibited typical apoptotic hallmarks including cell shrinkage, chromatin condensation and degradation of nuclear DNA to characteristic high molecular weight (HMW) as well as nucleosomal size fragments. Externally added [9R]BA was very rapidly and almost quantitatively phosphorylated within BY‐2 cells. Accumulation of [9R]BA‐monophosphate was accompanied by massive production of endogenous reactive oxygen species (ROS), intracellular ATP depletion, and these events were followed by the loss of cell viability. Inhibition of intracellular phosphorylation of [9R]BA by adenosin kinase inhibitor, 5′‐amino‐5′‐deoxyadenosine (AdAs), diminished ROS production, ATP depletion, and consequently prevented cells from death. Selective inhibition of ROS production without restoring ATP production, however, did not provide any protection to cells. In contrast, even enhanced phosphorylation of [9R]BA caused by adenosine that simultaneously revived ATP synthesis reduced the number of dying cells. This is the first evidence of a direct relationship between intracellular phosphorylation of [9R]BA and apoptosis induction in BY‐2 cells. ATP depletion but not ROS production is the key secondary event that determines the cellular decision between life and death.     

A cyanobacterial bloom prevents fish trophic cascades

1. We experimentally compared the impacts of visually feeding zooplanktivorous fish and filter‐feeding omnivorous fish in shallow tropical Dakar Bango reservoir, Senegal. We provoked a cyanobacterial Anabaena bloom under mesotrophic to eutrophic N‐limited conditions in 18 enclosures assigned to six Nile tilapia life‐stage treatments, at typical biomasses: fishless control (C), zooplanktivorous fry (Z), omnivorous juveniles (O), herbivorous fingerlings (H) and two combinations (OZ, OH). 2. All fish grew well, but as prevalent inedible phytoplankton dampened fish effects, community‐level trophic cascades did not occur. Planktivore types acted independently and affected differentially the biomasses of total zooplankton, cyclopoids, nauplii, cladocerans, invertebrate carnivores, large herbivores, colonial cyanobacteria and Chlorophyta. They neither influenced the total biomass of phytoplankton, nor most water chemistry characteristics. Responses were apparently not fish‐biomass related. The bloom collapsed synchronously in all enclosures, coinciding with enrichment ending, with a return to clear water within 12 days. 3. Our results support the hypothesis that excess nutrients and prevalent inedible cyanobacteria inhibit the cascading effects of natural biomass levels of both visually feeding zooplanktivores and filter‐feeding omnivores. In N‐limited meso‐eutrophic shallow tropical lakes with predominantly small herbivorous zooplankton, neither the type nor the biomass of planktivorous fish present seems likely to prevent the transient outburst of cyanobacterial blooms. Such fragile ecosystems may thus not sustain a trophic state suitable for drinking water production, unless human impacts are restricted. The generality of restoration approaches based on ecological engineering should be further explored.     

Open Access to essential health care information

Open Access publishing is a valuable resource for the synthesis and distribution of essential health care information. This article discusses the potential benefits of Open Access, specifically in terms of Low and Middle Income (LAMI) countries in which there is currently a lack of informed health care providers - mainly a consequence of poor availability to information. We propose that without copyright restrictions, Open Access facilitates distribution of the most relevant research and health care information. Furthermore, we suggest that the technology and infrastructure that has been put in place for Open Access could be used to publish download-able manuals, guides or basic handbooks created by healthcare providers in LAMI countries.     

Ribosomal proteins from rabbit reticulocytes: number and molecular weights of proteins from ribosomal subunits.

The ribosomal proteins from 40 S and 60 S subunits of rabbit reticulocytes were separated by two-dimensional polyacrylamide gel electrophoresis. The protein spots stained with Coomassie brilliant blue were cut out and the proteins were extracted. The material extracted from each spot was mixed with proteins of known molecular weight and then analyzed by electrophoresis in polyacrylamide gels containing sodium dodecyl sulfate. Both the total number and the molecular weights of each of the proteins were determined by these procedures. Thirty-two proteins were identified in the 40 S subunits; their molecular weights ranged from 8000 to 39,000 (average mol. wt = 25,000). Thirty-nine proteins were identified in the 60 S subunit; their molecular weights ranged from 9000 to 58,000 (average mol. wt = 31,000). The sum of the molecular weights of the individual proteins from each subunit is in agreement with previous estimations, derived from physico-chemical measurements of the total protein in mammalian ribosomal subunits. The molecular weight distribution obtained for the isolated proteins was nearly identical to that derived from spectrophotometric analysis of polyacrylamide-sodium dodecyl sulfate gels of the total protein mixtures from each subunit stained with Coomassie brilliant blue. The results are consistent with the hypothesis that reticulocyte ribosomes contain one copy of most of their protein constituents.     

ZUR AUSLÖSUNG DER EIABLAGE BEI DER APHIDOPHAGEN GALLMÜCKE APHIDOLETES APHIDIMYZA (DIPTERA: CECIDOMYIIDAE)

Die Eiablage von Aphidoletes aphidimyza (Rond.) konnte im Experiment durch Honigtau oder durch tote Blattläuse (Myzus persicae, Aphis fabae und Acyrthosiphon pisum), jedoch wesentlich stärker durch beide zusammen ausgelöst werden. Siphonensekret von Acyrthosiphon pisum wurde ebenfalls belegt. Dagegen gelang es nicht, die Gallmücken durch klebrige Substanzen, deren Konsistenz der des Honigtaus ähnlich ist, zur Eiablage zu bringen. Während Exuvien der Erbsenblattlaus für sich allein fast keine Wirkung zeigten, lösten sie in Kombination mit Honigtau die Eiablage ebenso stark aus wie die toten Blattläuse mit Honigtau. Dagegen waren kleine Steinchen in Blattlaus-Größe anstelle der Exuvien unwirksam. Auch Duftstoffe von Blattläusen und Honigtau führten nicht zur Eiablage. Von den Bestandteilen des Honigtaus waren bestimmte Kohlehydrate und Aminosäuren schwach, andere, vor allem Fruktose und Arginin, besser wirksam; reproduzierbar war die Wirkung nur in Kombination mit getöteten Blattläusen.     

Crown Gall on Castor Bean Leaves: II. FORMATION OF SECONDARY TUMOURS

Secondary tumours were formed on the cotyledonary leaf petiole,the hypocotyl, and first true leaf of castor bean seedlingsafter inoculating the blades of the cotyledonary leaves withAgrobacterium tumefaciens. Depending on the strain of bacteriaemployed, 0 to 80 per cent of the plants developed secondarytumours. The ability of different strains to initiate secondarytumours was not obviously correlated with their relative effectivenessin initiating primary tumours. Though all produced primary tumours,five out of ten auxotrophic strains failed to yield secondarytumours, whereas only one out of 14 prototrophic strains failedto do so. Both the number of plants developing secondary tumoursand the frequency with which these tumours occurred on differentparts of the plant were positively correlated with the concentrationof the primary inoculum. Tumours also developed on the cotyledonaryleaf petiole and on the hypocotyl after vacuum infiltrationof A. tumefaciens into the blade of cotyledonary leaves. Inmost instances (9 out of 11 plants) no tumours were formed onthe blade of the infiltrated leaf. Thus, tumour formation equivalentto secondary tumours can occur in the absence of a primary tumouror an overt primary wound. Excision of inoculated leaves showedthat the stimulus for secondary tumour formation moves fromthe blade to the hypocotyl within 24 h. Attempts to demonstratethe presence of a sub-cellular tumour-initiating agent in homogenatesof inoculated leaves were unsuccessful. A. tumefaciens, however,was found in the petiole of the cotyledonary leaf and in thehypocotyl within 24 h of inoculation. The migrating agent responsiblefor secondary tumour formation in castor beans is concludedto be intact bacteria.