Toad radiation reveals into-India dispersal as a source of endemism in the Western Ghats-Sri Lanka biodiversity hotspot

Background  

High taxonomic level endemism in the Western Ghats-Sri Lanka biodiversity hotspot has been typically attributed to the subcontinent's geological history of long-term isolation. Subsequent out of – and into India dispersal of species after accretion to the Eurasian mainland is therefore often seen as a biogeographic factor that 'diluted' the composition of previously isolated Indian biota. However, few molecular studies have focussed on into-India dispersal as a possible source of endemism on the subcontinent. Using c. 6000 base pairs of mitochondrial and nuclear DNA, we investigated the evolutionary history and biogeography of true toads (Bufonidae), a group that colonized the Indian Subcontinent after the Indo-Asia collision.     

Methemoglobinemia and acidosis during the first week of life

Recently attention has been called on the possible role of acidosis in the increased methemoglobin formation in the erythrocyte of newborn infant. In the present paper the relations between acidosis and methemoglobin content in the red cells of newborns has been investigated. No significant differences between the percent of methemoglobin in the normal newborns and percent of methemoglobin in the newborns with acidosis has been found. In addition, no correlations between the base excess and percent of methemoglobin has been observed. On the contrary, two newborns with low glucose-6-phosphate dehydrogenase activity demonstrated a significantly increased methemoglobin content in their red cells. The results of our study do not confirm a key role of acidosis in the mechanism of methemoglobin formation in the neonate. It is likely than impairment of red cell metabolism should be the main factor in the formation of methemoglobin in the first days of life.     

Response of two parasitoid species (Hymenoptera: Braconidae,Figitidae) to tephritid host and host food substrate cues

The Neotropical‐native figitid Aganaspis pelleranoi (Brèthes) and the Asian braconid Diachasmimorpha longicaudata (Ashmead) are two parasitoids of Tephritidae fruit flies with long and recent, respectively, evolutionary histories in the Neotropics. Both species experienced a recent range of overlap. In Argentina, A. pelleranoi is a potential species in biological control programs against the pestiferous tephritid species, Anastrepha fraterculus (Wiedemann) and Ceratitis capitata (Wiedemann), whereas D. longicaudata is already used in open‐field releases against Medfly in central‐western Argentina. To characterize the host‐foraging strategies of A. pelleranoi and D. longicaudata, olfactometer experiments were conducted comparing responses to C. capitata and A. fraterculus larvae, in two kinds of food substrate: fruit and artificial larval medium. To control the possible influence of host larvae used for parasitoid rearing on olfactory response, two strains of both parasitoid species, reared on both tephrtid species, were studied. Volatiles directly emanating either from A. fraterculus or C. capitata larvae may be detected by both A. pelleranoi and D. longicaudata, although chemical stimuli originating from the combination of host larvae and the habitat of the host were preferred. However, olfactory cues associated with host larvae probably play a relevant role in host searching behaviour of A. pelleranoi, whereas for D. longicaudata, the host‐habitat olfactory stimuli would be highly essential in short‐range host location. The strain of the parasitoids did not affect host search ability on the two tephritid species evaluated. These evidences are relevant for mass production of both parasitoids and their impact following open‐field augmentative releases.     

Modeling the 3-D Structure of a Recombinant Laccase from Trametes trogii Active at a pH Close to Neutrality

A cDNA encoding a novel laccase from the white-rot fungus Trametes trogii was cloned and expressed in Pichia pastoris. The recombinant protein (Lcc2) exhibited kinetic parameters for both phenolic and non phenolic substrates that were different from the previously described Lcc1, the main laccase isoform expressed by T. trogii; in addition, the pH/activity profiles for phenolic substrates of Lcc2 were shifted upward by 1–1.5 pH units towards neutrality as compared to Lcc1. Comparative modeling of the two laccases (69.2% identity) showed that the overall fold of Lcc2 is very similar to Lcc1 and other laccases. The substrate cavity of Lcc2 contains the Asp residue which is thought to mediate the laccase activity at acidic pHs, whereas two hydrophobic residues (Phe, Ile) on the cavity orifice of Lcc2 replace the two polar residues (Thr, Ser) of Lcc1. These structural differences may be responsible for the unique kinetic performances of Lcc2.     

A Vesicular Stomatitis Virus-Based Hepatitis B Virus Vaccine Vector Provides Protection against Challenge in a Single Dose

As one of the world''s most common infectious diseases, hepatitis B virus (HBV) is a serious worldwide public health problem, with HBV-associated liver disease accounting for more than half a million deaths each year. Although there is an effective prophylactic vaccine currently available to prevent infection, it has a number of characteristics that are suboptimal: multiple doses are needed to induce long-lasting immunity, immunity declines over time, it does not elicit protection in some individuals, and it is not effective therapeutically. We produced a recombinant vesicular stomatitis virus (VSV)-based vaccine vector expressing the HBV middle envelope surface protein (MS) and found that this vector was able to efficiently generate a strong HBs-specific antibody response following a single immunization in mice. A single immunization with the VSV-MS vector also induced robust CD8 T-cell activation. The CD8 T-cell response was greater in magnitude and broader in specificity than the response generated by a vaccinia virus-based vaccine vector or by recombinant protein immunization. Furthermore, a single VSV-MS immunization provided protection against virus challenge in mice. Given the similar antibody titers and superior T-cell responses elicited from a single immunization, a VSV-based HBV vaccine may have advantages over the current recombinant protein vaccine.It is estimated that >2 billion people worldwide have been infected with hepatitis B virus (HBV), placing it among the world''s most common infectious diseases (44). HBV is a serious public health concern as regions of high endemicity, including Southeast Asia, and sub-Saharan Africa, consistently report a chronic carrier prevalence of 8 to 15% (28). Areas such as Taiwan and Thailand, however, have demonstrated that implementation of infant vaccination programs can have profound effects on lowering rates of infection and chronicity (7, 8). Nevertheless, in the United States alone, where the majority of states require HBV vaccination prior to enrollment in public schools (38), there are upwards of 2 million chronically infected individuals (12). Thus, there remains a need for continued development and evaluation of HBV vaccination programs and treatment options.Recombinant protein vaccines currently available for HBV are comprised of the small and/or large versions of the envelope surface glycoprotein (46). Despite their success, these vaccines have a number of characteristics that are suboptimal. The current vaccination protocol recommends two to three doses to induce long-lasting immunity (25). This may create delivery and compliance issues in areas lacking the appropriate medical infrastructure for administration, which includes some regions where HBV is highly endemic. Even after completion of the full HBV vaccine regimen, up to 10% of the population is unable generate a protective response to the virus (39). Furthermore, a waning antibody response following immunization may cause antibody to decline below protective titers (10 U/liter) in up to 60% of individuals who respond to vaccination (24). Due to the limitations of the current vaccine, alternative vaccination protocols continue to be explored. Generally, viral vaccine vectors efficiently express viral antigens and may be an effective strategy to enhance antigen presentation, thereby stimulating potent humoral and cell-mediated immune responses in a single dose (41). A number of viral vaccine platforms for HBV have been shown to generate protective antibody titers in animal models, including, most recently, modified vaccinia virus (VV) Ankara- and measles virus-based vaccines (21, 31).In the present study, we utilize the negative-strand RNA virus vesicular stomatitis virus (VSV), as it offers a variety of features that make it an ideal viral vaccine vector. The VSV genome is simple and more fully understood than other potential vaccine platforms, such as vaccinia virus, and can be grown to high titers in mammalian cell lines approved for vaccine production. Additionally, VSV infection in humans is rare, reducing the risk of preexisting immunity, which may interfere with vaccine efficacy (10). Despite the fact that neutralizing antibodies are generated against the VSV glycoprotein following a single vaccination, a variety of VSV serotypes are available if boosting is required (33). Finally, VSV vectors can be delivered intranasally in a needle-free manner. Recombinant VSV vectors have been developed for a variety of viruses, including HIV, influenza virus, and hepatitis C virus (HCV) (15, 32, 36). The majority of these vectors have provided protection against secondary challenge in animal models after a single dose. Taken together, the unique characteristics of VSV may lead to the development of a prophylactic vaccine that could be delivered in a single-dose and needle-free manner, which would provide certain advantages over the current vaccine. We have generated a VSV vector expressing HBV middle envelope surface protein (MS) antigen that is properly localized and secreted. Here we examine the potential of this vector as an alternative prophylactic HBV vaccine.     

Cellular activities during a mixed leucocyte reaction in the teleost sea bass Dicentrarchus labrax

In this investigation a number of "in vitro" activities of sea bass peripheral blood leucocytes (PBL) against allogeneic PBL inactivated by irradiation were studied. Stimulator PBL were cultured with inactivated allogeneic PBL, and direct counting of lymphocytes was done after 2 weeks by immunofluorescence and flow cytometry using mAbs DLT15 and DLIg3 specific for T-cells and B-cells, respectively. In a one-way mixed leucocyte reaction (MLR), results showed an increase of T lymphocytes, whereas B lymphocytes had values similar to those in control PBL. The increase of T-cells in MLR cultures was also confirmed using RT-PCR by analyzing the expression of the T-cell receptor (beta-subunit) mRNA. The addition of 5 microg/ml of cyclosporin A (CsA) to the MLR caused a significant decrease in T-cell proliferation. Leucocytes from MLR cultures displayed an enhanced cytotoxic activity against xenogeneic target cells with respect to control PBL, raising the possibility of the presence of cytotoxic-like T lymphocytes. Cellular activation of PBL was confirmed in 2 weeks MLR by measuring antibody-induced intracellular Ca(++) mobilization with Fura-2 AM. This work represents the first direct quantitative determination of an "in vitro" T-cell activity in a teleost species.     

A neuronal modeling paradigm in the presence of refractoriness

A mathematical characterization of the membrane potential as an instantaneous return process in the presence of refractoriness is investigated for diffusion models of single neuron's activity, assuming that the firing threshold acts as an elastic barrier. Steady-state probability densities and asymptotic moments of the neuronal membrane potential are explicitly obtained in a form that is suitable for quantitative evaluations. For the Ornstein-Uhlenbeck (OU) and Feller neuronal models, closed form expression are obtained for asymptotic mean and variance of the neuronal membrane potential and an analysis of the different features exhibited by the above mentioned models is performed.