Functional and Structural Properties of a Novel Protein and Virulence Factor (Protein sHIP) in Streptococcus pyogenes

Streptococcus pyogenes is a significant bacterial pathogen in the human population. The importance of virulence factors for the survival and colonization of S. pyogenes is well established, and many of these factors are exposed to the extracellular environment, enabling bacterial interactions with the host. In the present study, we quantitatively analyzed and compared S. pyogenes proteins in the growth medium of a strain that is virulent to mice with a non-virulent strain. Particularly, one of these proteins was present at significantly higher levels in stationary growth medium from the virulent strain. We determined the three-dimensional structure of the protein that showed a unique tetrameric organization composed of four helix-loop-helix motifs. Affinity pull-down mass spectrometry analysis in human plasma demonstrated that the protein interacts with histidine-rich glycoprotein (HRG), and the name sHIP (streptococcal histidine-rich glycoprotein-interacting protein) is therefore proposed. HRG has antibacterial activity, and when challenged by HRG, sHIP was found to rescue S. pyogenes bacteria. This and the finding that patients with invasive S. pyogenes infection respond with antibody production against sHIP suggest a role for the protein in S. pyogenes pathogenesis.     

Seasonal reliance on nectar by an insectivorous bat revealed by stable isotopes

Many animals have seasonally plastic diets to take advantage of seasonally abundant plant resources, such as fruit or nectar. Switches from insectivorous diets that are protein rich to fruits or nectar that are carbohydrate rich present physiological challenges, but are routinely done by insectivorous songbirds during migration. In contrast, insectivorous bat species are not known to switch diets to consume fruit or nectar. Here, we use carbon stable isotope ratios to establish the first known case of a temperate bat species consuming substantial quantities of nectar during spring. We show that pallid bats (Antrozous pallidus) switch from a diet indistinguishable from that of sympatric insectivorous bat species in winter (when no cactus nectar is present) to a diet intermediate between those of insectivorous bats and nectarivorous bats during the spring bloom of a bat-adapted cactus species. Combined with previous results that established that pallid bats are effective pollinators of the cardon cactus (Pachycereus pringlei), our results suggest that the interaction between pallid bats and cardon cacti represents the first-known plant-pollinator mutualism between a plant and a temperate bat. Diet plasticity in pallid bats raises questions about the degree of physiological adaptations of insectivorous bats for incorporation of carbohydrate-rich foods, such as nectar or fruit, into the diet.     

Colostrum from Cows Immunized with a Vaccine Associated with Bovine Neonatal Pancytopenia Contains Allo-Antibodies that Cross-React with Human MHC-I Molecules

In 2006, a new haemorrhagic syndrome affecting newborn calves, Bovine Neonatal Pancytopenia (BNP), was reported in southern Germany. It is characterized by severe bleeding, destruction of the red bone marrow, and a high case fatality rate. The syndrome is caused by alloreactive, maternal antibodies that are ingested by the calf with colostrum and result from a dam vaccination with one particular vaccine against Bovine-Viral-Diarrhoea-Virus. Because bovine colostrum is increasingly gaining interest as a dietary supplement for human consumption, the current study was initiated to elucidate whether BNP alloantibodies from BNP dams (i.e. animals that gave birth to a BNP-affected calf) cross-react with human cells, which could pose a health hazard for human consumers of colostral products. The present study clearly demonstrates that BNP alloantibodies cross-react with human lymphocytes in vitro. In agreement with previous reports on BNP, the cross-reactive antibodies are specific for MHC-I molecules, and sensitize opsonised human cells for in vitro complement lysis. Cross-reactive antibodies are present in serum and colostrum of individual BNP dams. They can be traced in commercial colostrum powder manufactured from cows immunized with the vaccine associated with BNP, but are absent from commercial powder manufactured from colostrum excluding such vaccinated cows. In humans alloreactive, MHC-I specific antibodies are generally not believed to cause severe symptoms. However, to minimize any theoretical risk for human consumers, manufacturers of bovine colostrum for human consumption should consider using only colostrum from animals that have not been exposed to the vaccine associated with BNP.     

Mentawai’s endemic,relictual fauna: is it evidence for Pleistocene extinctions on Sumatra?

Aim The four Mentawai islands, south‐west of Sumatra, have long been isolated from the remainder of Sundaland, resulting in a high level of endemism. We examined the distribution of 151 species of the Mentawai Islands in Sundaland and assessed various processes that may have resulted in the various biogeographical patterns. Location Southeast Asia, particularly the Mentawai Islands and nearby large landmasses (Sumatra, Java, Borneo and Peninsular Malaysia). Methods We compared the faunal composition of the Mentawai Islands for selected taxa (43 mammals, 92 reptiles and 16 amphibians) with that of the four nearby large landmasses of Sundaland using morphological comparisons and the most recent molecular phylogenetic analyses available in the literature. These comparisons yielded sister taxa, which were used to simulate species absence data for the four Sundaland landmasses under several scenarios to investigate how patterns of species absence could have arisen. Results In contrast to our expectations, several Mentawai species did not have their closest relatives on neighbouring Sumatra, but rather on the more distant Borneo, Java or Peninsular Malaysia. For mammals, the similarity between species from Mentawai and Borneo was greater than that observed between species from Mentawai and Sumatra. We conclude that the relationships represent traces of species historically distributed throughout Sundaland that became extinct in Sumatra during the Pleistocene. For reptiles and amphibians the observed pattern of species absences generally resembled the simulated pattern expected under the scenario of absence rates increasing with landmass isolation, whereas for mammals we observed more species than expected missing from Java and Sumatra, and fewer than expected from Borneo. Main conclusions The potential extinctions on Sumatra probably had two causes: changes of climate and vegetation during the Pleistocene and environmental impacts from the Toba supervolcanic eruption.     

Plasticity in the Rat Prefrontal Cortex: Linking Gene Expression and an Operant Learning with a Computational Theory

The plasticity in the medial Prefrontal Cortex (mPFC) of rodents or lateral prefrontal cortex in non human primates (lPFC), plays a key role neural circuits involved in learning and memory. Several genes, like brain-derived neurotrophic factor (BDNF), cAMP response element binding (CREB), Synapsin I, Calcium/calmodulin-dependent protein kinase II (CamKII), activity-regulated cytoskeleton-associated protein (Arc), c-jun and c-fos have been related to plasticity processes. We analysed differential expression of related plasticity genes and immediate early genes in the mPFC of rats during learning an operant conditioning task. Incompletely and completely trained animals were studied because of the distinct events predicted by our computational model at different learning stages. During learning an operant conditioning task, we measured changes in the mRNA levels by Real-Time RT-PCR during learning; expression of these markers associated to plasticity was incremented while learning and such increments began to decline when the task was learned. The plasticity changes in the lPFC during learning predicted by the model matched up with those of the representative gene BDNF. Herein, we showed for the first time that plasticity in the mPFC in rats during learning of an operant conditioning is higher while learning than when the task is learned, using an integrative approach of a computational model and gene expression.     

Semiautomated enzymic microassay for plasma L-alanine.

Plasma L-alanine is deaminated by bacterial alanine-dehydrogenase; the resulting ammonia is dialyzed out and measured by use of a continuous flow phenol-hypochlorite colorimetric microassay. Concentrations in the range of 10-1,000 mumol alanine/l can be determined in a 50-microliter sample. The optimal conditions for the assay are specified. Study of the analytical qualities of the technique shows high specificity, good reproducibility , and a detection limit of 6 mumol/l. Usual values in human plasma from arterial or venous blood are respectively 296 +/- 166 and 376 +/- 214 mumol alanine/l (x +/- 2 SD). The usual values in rats are close to those found in man.     

Protein H--a bacterial surface protein with affinity for both immunoglobulin and fibronectin type III domains.

Several bacterial species express surface proteins with affinity for the constant region (Fc) of immunoglobulin (Ig) G. The biological consequences of the interaction with IgG are poorly understood but it has been demonstrated that genes encoding different IgG Fc-binding proteins have undergone convergent evolution, suggesting that these surface molecules are connected with essential microbial functions. One of the molecules, protein H, is present in some strains of Streptococcus pyogenes, the most significant streptococcal species in clinical medicine. In contrast to other Ig-binding bacterial proteins tested, protein H was found to interact also with the neural cell adhesion molecule (N-CAM), a eukaryotic cell surface glycoprotein mediating homo- and heterophilic cell-cell interactions. The affinity for the interaction between protein H and N-CAM was 1.6 x 10(8)/M and the binding site on protein H was mapped to the NH2-terminal 80 amino acid residues. N-CAM and IgG are both members of the Ig superfamily and analogous to N-CAM, IgG binds to the NH2-terminal part of protein H. However, the binding sites for the two proteins were found to be separate, an unexpected result which was explained by the observation that the fibronectin type III (FNIII) domains and not the Ig-like domains of N-CAM are responsible for the interaction with protein H. Thus, the binding of N-CAM to protein H was blocked with fibronectin but not with IgG. Moreover, apart from fibronectin itself and N-CAM, fragments of fibronectin and the matrix protein cytotactin/tenascin containing FNIII domains also showed affinity for protein H.(ABSTRACT TRUNCATED AT 250 WORDS)     

Distinct roles for light-dependent NADPH:protochlorophyllide oxidoreductases (POR) A and B during greening in higher plants

Light-dependent NADPH:protochlorophyllide oxidoreductase (POR), a nuclear-encoded plastid-localized enzyme, catalyzes the photoreduction of protochlorophyllide (Pchlide) to chlorophyllide in higher plants, algae and cyanobacteria. Angiosperms require light for chlorophyll (Chl) biosynthesis and have recently been shown to contain two POR-encoding genes, PorA and PorB , that are differentially regulated by light and developmental state. PorA expression rapidly becomes undetectable after illumination of etiolated seedlings, whereas PorB expression persists throughout greening and in adult plants. In order to study the in vivo functions of Arabidopsis POR A and POR B we have abolished the expression of PorA through the use of the phytochrome A-mediated far-red high irradiance response. Wild-type seedlings grown in continuous far-red light (cFR) display the morphology of white light (WL)-grown seedlings, but contain only traces of Chl and do not green upon transfer to WL. This cFR-induced greening defect correlates with the absence of PorA mRNA, the putative POR A protein, phototransformable Pchlide-F₆₅₅, and with strongly reduced POR enzymatic activity in plant extracts. In contrast, a cFR-grown phyA mutant expresses the PorA gene, accumulates Chl and visibly greens in WL. Furthermore, constitutive overexpression of POR A in cFR-grown transgenic Arabidopsis wild-type seedlings restores Chl accumulation and WL-induced greening. These data demonstrate that POR A is required for greening and that the availability of POR A limits Chl accumulation during growth in cFR. POR B apparently provides a means to sustain light-dependent Chl biosynthesis in fully greened, mature plants in the absence of phototransformable Pchlide-F₆₅₅.