Evolution on a shaky piece of Gondwana: is local endemism recent in New Caledonia?

New Caledonia is well known as a hot spot of biodiversity whose origin as a land mass can be traced back to the Gondwanan supercontinent. The local flora and fauna, in addition to being remarkably rich and endemic, comprise many supposedly relictual groups. Does the New Caledonian biota date back to Gondwanan times, building up its richness and endemism over 100 Myr or does it result from recent diversifications after Tertiary geological catastrophic events? Here we use a molecular phylogenetic approach to answer this question with the study of the Neocaledonian cockroach genus Angustonicus belonging to the subfamily Tryonicinae from Australia and New Caledonia. Both geological and molecular dating show that the diversification of this group is less than two million years old, whatever the date of its origin itself. This dating is not consistent with hypotheses of Gondwanan richness and endemism in New Caledonian biota. In other terms, local richness and endemism at the specific level are not necessarily related to an old Gondwanan origin of the Neocaledonian groups. © The Willi Hennig Society 2005.     

Systematic analysis of FKBP inducible degradation domain tagging strategies for the human malaria parasite Plasmodium falciparum

Targeted regulation of protein levels is an important tool to gain insights into the role of proteins essential to cell function and development. In recent years, a method based on mutated forms of the human FKBP12 has been established and used to great effect in various cell types to explore protein function. The mutated FKBP protein, referred to as destabilization domain (DD) tag when fused with a native protein at the N- or C-terminus targets the protein for proteosomal degradation. Regulated expression is achieved via addition of a compound, Shld-1, that stabilizes the protein and prevents degradation. A limited number of studies have used this system to provide powerful insight into protein function in the human malaria parasite Plasmodium falciparum. In order to better understand the DD inducible system in P. falciparum, we studied the effect of Shld-1 on parasite growth, demonstrating that although development is not impaired, it is delayed, requiring the appropriate controls for phenotype interpretation. We explored the quantified regulation of reporter Green Fluorescent Protein (GFP) and luciferase constructs fused to three DD variants in parasite cells either via transient or stable transfection. The regulation obtained with the original FKBP derived DD domain was compared to two triple mutants DD24 and DD29, which had been described to provide better regulation for C-terminal tagging in other cell types. When cloned to the C-terminal of reporter proteins, DD24 provided the strongest regulation allowing reporter activity to be reduced to lower levels than DD and to restore the activity of stabilised proteins to higher levels than DD29. Importantly, DD24 has not previously been applied to regulate proteins in P. falciparum. The possibility of regulating an exported protein was addressed by targeting the Ring-Infected Erythrocyte Surface Antigen (RESA) at its C-terminus. The tagged protein demonstrated an important modulation of its expression.     

Acetaminophen is cardioprotective against H2O2-induced injury in vivo

Here we report our ongoing investigation of the cardiovascular effects of acetaminophen, with emphasis on oxidation-induced canine myocardial dysfunction. The objective of the current study was to investigate whether acetaminophen could attenuate exogenous H(2)O(2)-mediated myocardial dysfunction in vivo. Respiratory, metabolic, and hemodynamic indices such as left ventricular function (LVDP and +/-dP/dt(max)), and percent ectopy were measured in anesthetized, open-chest dogs during intravenous administration of 0.88 mM, 2.2 mM, 6.6 mM H(2)O(2). Following 6.6 mM H(2)O(2), tissue from the left ventricle was harvested for electron microscopy. Left ventricular function did not vary significantly between vehicle and acetaminophen groups under baseline conditions. Acetaminophen-treated dogs regained a significantly greater fraction of baseline function after high concentrations of H(2)O(2) than vehicle-treated dogs. Moreover, the incidence of H(2)O(2)-induced ventricular arrhythmias was significantly reduced in the acetaminophen-treated group. Percent ectopy following 6.6 mM concentrations of H(2)O(2) was 1 +/- 0.3 vs. 0.3 +/- 0.1 (P < 0.05) for vehicle- and acetaminophen-treated dogs, respectively. Additionally, electron micrograph images of left ventricular tissue confirmed preservation of tissue ultrastructure in acetaminophen-treated hearts when compared to vehicle. We conclude that, in the canine myocardium, acetaminophen is both functionally cardioprotective and antiarrhythmic against H(2)O(2)-induced oxidative injury.     

Antidepressants inhibit human acetylcholinesterase and butyrylcholinesterase activity

Magnesium deficiency in experimental animals leads to inflammation, exacerbated immune stress response and a decrease of specific immune response. It also results in a significant increase in free radical species and subsequent tissue injury. An accelerated thymus involution was observed in Mg-deficient rats in relation to enhanced apoptosis and enhanced susceptibility to oxidative stress. To examine the stress-inducing effects of low Mg status on thymocytes, cDNA arrays were used to evaluate changes in gene expression in weaning rats submitted to Mg deficiency of short duration (2 days). Several genes exhibited changes in their expression caused by Mg deficiency before any perceptible modification in cell integrity and functions. The up-regulated genes included cytochrome c oxidase, glutathione transferase, CuZn superoxide dismutase, genes associated with the stress response (HSP70 and HSP84) and a gene involved in DNA synthesis and repair (GADD45). The down-regulated genes included Na/P cotransporter 1. These findings are consistent with altered cell growth, modifications of ion fluxes and oxidative stress described during Mg deficiency. The observation of induction of genes involved in protection and repair in cells from Mg-deficient animals provides additional evidence of the role of oxidative stress in the pathobiology of this deficiency.     

Involvement of steroids in anti-inflammatory effects of peripheral benzodiazepine receptor ligands

Mouse paw oedema induced by carrageenan is used to determine if glucocorticoids are involved in the anti-inflammatory effects of peripheral benzodiazepine receptor ligands. The anti-inflammatory responses elicited by i.p. treatment with 1-(2-chlorophenyl)-N-methyl-N (1-methyl-propyl)-3-isoquinoline carboxamide (PK11195) and 7-chloro-5-(4-chlorophenyl)-1,3-dihydro-1-methyl-2-H-1, 4-benzodiazepin-2 (Ro5-4864) were reversed by aminoglutethimide, an inhibitor of steroidal synthesis. Intraplantar injection into the ipsilateral paw of Ro5-4864, but not PK11195, inhibited the formation of paw oedema and this effect was reversed by aminoglutethimide. These results suggest that glucocorticoids are involved in the systemic and local anti-inflammatory effects of Ro5-4864 and only in the systemic response to PK11195.     

The conservation-refugium value of small and disturbed Brazilian Atlantic forest fragments for the endemic ovoviviparous cockroach Monastria biguttata (Insecta: Dictyoptera, Blaberidae, Blaberinae)

The Brazilian Atlantic forest is a biodiversity hotspot and harbors many endemic species showing peculiar and unique traits. However, it has been reduced to less than 8% of its original surface and is distributed in scattered fragments, the great majority of which are smaller than 20 hectares and very disturbed, making it worth asking about their value for conservation. In this paper we assess the refugium value of small fragments to the conservation of one of the endemics of the Atlantic forest, the ovoviviparous cockroach Monastria biguttata. Our results showed that this species was ubiquitous in large and small forest fragments, but never present in plantations or pastures. The population age structure and sex ratio were balanced in every fragment, and total population size in the smallest fragments was at least several hundreds of individuals. Colony size, sex ratio, age structure, and density per piece of dead tree trunk indicated that populations from small fragments were not unbalanced or at risk of extinction. According to the analysis of resource availability, small fragments can provide suitable habitat for this species. In this situation, even very small forest fragments have a high refugium value for some endemic insect species. Considering their number in the landscape, these fragments should be considered with more attention in strategies of biodiversity conservation.