The effect of light levels on daily patterns of chlorophyll fluorescence and organic acid accumulation in the tropical CAM treeClusia hilariana

Sandy plains are characteristic of the coastal region of Brazil. We investigated the diel patterns of changes in organic acid levels, leaf conductance and chlorophylla fluorescence for sun-exposed and shaded plants ofClusia hilariana, one of the dominant woody species in the sandy coastal plains of northern Rio de Janeiro state. Both exposed and shaded plants showed a typical CAM pattern with considerable diel oscillations in organic acid levels. The degradation of both malic and citric acids during the midday stomatal closure period could lead to potential CO₂ fixation rates of 28 mol m^-2 s^-1 in exposed leaves. Moreover, exposed leaves exhibited large increases in total non-photochemical quenching (q_N) accompanied by a substantial decrease in effective quantum yield during the course of the day. However, these potential high rates of CO₂ fixation and the increases inqn of exposed plants were not enough to maintain the primary electron acceptor of photosystem II (q_A) in a low reduction state, similar to that of shaded plants. As a result, there was a moderate increase in the reduction state of q_A throughout the day. Most of the decline in photochemical efficiency of exposed leaves ofC. hilariana was reversible, as evidenced by the high levels of pre-dawn potential quantum yields (F_v/F_m) and their rapid recovery after sunset. However, the depletion of the organic acid pool in the afternoon resulted in an accentuated subsequent drop in F_v/F_m, suggesting that prolonged periods of water stress accompanied by high irradiance levels may expose plants ofC. hilariana in unprotected habitats to the danger of photoinhibition.     

Biodegradation of <Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis> diethylaniline in a contaminated aquifer: laboratory- and field-scale evidences

The effectiveness of biosparging to mitigate N,N diethylaniline in aquifer was evaluated by measuring the time course of decrease in concentration of the aforementioned compound in aerobic microcosm experiments. The first-order kinetic constant for N,N diethylaniline aerobic biodegradation was estimated from microcosm data (0.037 ± 0.004 d⁻¹), and the value was consistent with the best-fitting value in the transport and reaction model of the aquifer (0.020 d⁻¹). Furthermore, the biodegradability of the compound was evaluated under anaerobic condition in microcosm experiments, which was supported by field modelling. There was no significant degradation in the anaerobic microcosm experiments, confirming the recalcitrance of N,N diethyl aniline under the aforementioned aquifer condition.     

In search of specific cytotoxic T lymphocytes infiltrating or accompanying human ovarian carcinoma

Summary Lymphocytes infiltrating human ovarian carcinoma obtained directly from the tumour mass (tumour-infiltrating lymphocytes, TIL) or from the carcinomatous ascites (tumour-associated lymphocytes, TAL) were expanded in vitro in long-term cultures with interleukin-2 and tested for their specific cytolytic activity. Killing of the autologous tumour was detected only in a proportion of the patients, less frequently in TIL compared to TAL. In fact two out of ten TIL and four out of nine TAL cultures tested showed significant levels of lysis against the autologous tumour. This cytotoxic activity was not restricted to the autologous tumour, as other tumour cell lines, including non-ovarian ones, were lysed as well. The cultures that were not cytotoxic against the autologous tumour were in most cases able to lyse other tumour cell lines of ovarian or other histology. Cloning of TIL from one patient was performed: of 22 clones tested, 4 displayed higher cytotoxicity against the autologous tumour compared to the uncloned population and 3 out of these 4 did not kill an irrelevant carcinoma cell line. In order to stimulate the expansion of putative specific effectors we performed mixed lymphocyte/tumour cultures (MLTC) with autologous or allogeneic tumour cells. No stimulation of cytotoxicity against the autologous tumour was detected after MLTC in nine different TAL populations, using autologous or allogeneic tumours as stimulators. On the contrary, peripheral blood lymphocytes from two patients after MLTC with the autologous tumour showed increased killing of the autologous and decreased killing of an allogeneic target. In conclusion TIL and TAL from ovarian carcinoma expanded in vitro with interleukin-2 usually have non-MHC-restricted cytotoxicity and variable degrees of reactivity against the autologous tumour. A preferential killing for the autologous tumour was not observed even after MLTC. These results do not exclude the existence of tumour-specific cytotoxic T lymphocytes in ovarian carcinoma; nevertheless they suggest that putative specific effectors have very low frequency and that culture techniques for expanding their growth more selectively are still to be optimized.     

Neuronal assembly detection and cell membership specification by principal component analysis

In 1949, Donald Hebb postulated that assemblies of synchronously activated neurons are the elementary units of information processing in the brain. Despite being one of the most influential theories in neuroscience, Hebb's cell assembly hypothesis only started to become testable in the past two decades due to technological advances. However, while the technology for the simultaneous recording of large neuronal populations undergoes fast development, there is still a paucity of analytical methods that can properly detect and track the activity of cell assemblies. Here we describe a principal component-based method that is able to (1) identify all cell assemblies present in the neuronal population investigated, (2) determine the number of neurons involved in ensemble activity, (3) specify the precise identity of the neurons pertaining to each cell assembly, and (4) unravel the time course of the individual activity of multiple assemblies. Application of the method to multielectrode recordings of awake and behaving rats revealed that assemblies detected in the cerebral cortex and hippocampus typically contain overlapping neurons. The results indicate that the PCA method presented here is able to properly detect, track and specify neuronal assemblies, irrespective of overlapping membership.     

Characterization of a broad range antibacterial substance from a new <Emphasis Type="Italic">Bacillus</Emphasis> species isolated from Amazon basin

A Bacillus sp. strain producing a bacteriocin-like substance was characterized by biochemical profiling and 16S rDNA sequencing. The phylogenetic analysis indicated that this strain has low sequence similarity with most Bacillus spp., suggesting a new species was isolated. The antimicrobial activity was detected starting at the exponential growth phase, and maximum activity was observed at stationary phase. The substance was inhibitory to a broad range of indicator strains, incluing pathogenic and food spoilage bacteria such as Listeria monocytogenes, B. cereus, Aeromonas hydrophila, Erwinia carotovora, Pasteurella haemolytica, Salmonella Gallinarum, among other. The antibacterial substance was stable over a wide pH range, but it was sensitive to pronase E and lipase. The antibacterial substance was bactericidal and bacteriolytic to L. monocytogenes and B. cereus at 160 AU ml⁻¹. The identification of a broad range bacteriocin-like inhibitory substance active against L. monocytogenes addresses an important aspect of food protection against pathogens and spoilage microorganisms.     

Aerosols transmit prions to immunocompetent and immunodeficient mice

Prions, the agents causing transmissible spongiform encephalopathies, colonize the brain of hosts after oral, parenteral, intralingual, or even transdermal uptake. However, prions are not generally considered to be airborne. Here we report that inbred and crossbred wild-type mice, as well as tga20 transgenic mice overexpressing PrP(C), efficiently develop scrapie upon exposure to aerosolized prions. NSE-PrP transgenic mice, which express PrP(C) selectively in neurons, were also susceptible to airborne prions. Aerogenic infection occurred also in mice lacking B- and T-lymphocytes, NK-cells, follicular dendritic cells or complement components. Brains of diseased mice contained PrP(Sc) and transmitted scrapie when inoculated into further mice. We conclude that aerogenic exposure to prions is very efficacious and can lead to direct invasion of neural pathways without an obligatory replicative phase in lymphoid organs. This previously unappreciated risk for airborne prion transmission may warrant re-thinking on prion biosafety guidelines in research and diagnostic laboratories.     

Evolution, structure and function of mitochondrial carriers: a review with new insights

The mitochondrial carriers (MC) constitute a large family (MCF) of inner membrane transporters displaying different substrate specificities, patterns of gene expression and even non-mitochondrial organelle localization. In Arabidopsis thaliana 58 genes encode these six trans-membrane domain proteins. The number in other sequenced plant genomes varies from 37 to 125, thus being larger than that of Saccharomyces cerevisiae and comparable with that of Homo sapiens. In addition to displaying highly similar secondary structures, the proteins of the MCF can be subdivided into subfamilies on the basis of substrate specificity and the presence of specific symmetry-related amino acid triplets. We assessed the predictive power of these triplets by comparing predictions with experimentally determined data for Arabidopsis MCs, and applied these predictions to the not yet functionally characterized mitochondrial carriers of the grass, Brachypodium distachyon, and the alga, Ostreococcus lucimarinus. We additionally studied evolutionary aspects of the plant MCF by comparing sequence data of the Arabidopsis MCF with those of Saccharomyces cerevisiae and Homo sapiens, then with those of Brachypodium distachyon and Ostreococcus lucimarinus, employing intra- and inter-genome comparisons. Finally, we discussed the importance of the approaches of global gene expression analysis and in vivo characterizations in order to address the relevance of these vital carrier proteins.     

Lanfrediella amphicirrus gen. nov. sp. nov. Nematotaeniidae (Cestoda: Cyclophyllidea), a tapeworm parasite of Rhinella marina (Linnaeus, 1758) (Amphibia: Bufonidae)

The family Nematotaeniidae, tapeworms commonly found in the small intestines of amphibians and reptiles, includes 27 recognised species distributed among four genera: Bitegmen Jones, Cylindrotaenia Jewell, Distoichometra Dickey and Nematotaenia Lühe. The taxonomy of these cestodes is poorly defined, due in part to the difficulties of observing many anatomical traits. This study presents and describes a new genus and species of nematotaeniid parasite found in cane toads (Rhinella marina) from eastern Brazilian Amazonia. The cestodes were collected during the necropsy of 20 hosts captured in the urban area of Belém, Pará. The specimens were fixed and processed for light microscopy, scanning electron microscopy (SEM) and three-dimensional (3D) reconstruction. Samples were also collected for molecular analyses. The specimens presented a cylindrical body, two testes and paruterine organs. However, they could not be allocated to any of the four existing nematotaeniid genera due to the presence of two each of dorsal compact medullary testes, cirri, cirrus pouches, genital pores, ovaries and vitelline glands per mature segment. Lanfrediella amphicirrus gen. nov. sp. nov. is the first nematotaeniid studied using Historesin analysis, SEM and 3D reconstruction, and it is the second taxon for which molecular data have been deposited in GenBank.     

Invading parasites: spillover of an alien nematode reduces survival in a native species

Biological Invasions - It is widely assumed that spillover of alien parasites to native host species severely impacts naïve populations, ultimately conferring a competitive advantage to...