A "dock, lock, and latch" structural model for a staphylococcal adhesin binding to fibrinogen

Gram-positive pathogens such as staphylococci contain multiple cell wall-anchored proteins that serve as an interface between the microbe and its environment. Some of these proteins act as adhesins and mediate bacterial attachment to host tissues. SdrG is a cell wall-anchored adhesin from Staphylococcus epidermidis that binds to the Bbeta chain of human fibrinogen (Fg) and is necessary and sufficient for bacterial attachment to Fg-coated biomaterials. Here, we present the crystal structures of the ligand binding region of SdrG as an apoprotein and in complex with a synthetic peptide analogous to its binding site in Fg. Analysis of the crystal structures, along with mutational studies of both the protein and of the peptide, reveals that SdrG binds to its ligand with a dynamic "dock, lock, and latch" mechanism. We propose that this mechanism represents a general mode of ligand binding for structurally related cell wall-anchored proteins of gram-positive bacteria.     

Effect of exogenous melatonin on in vivo and in vitro prostaglandin secretion in Rasa Aragonesa ewes

The effect of exogenous melatonin on prostaglandin secretion was measured on Rasa Aragonesa ewes. Fourteen ewes received an 18 mg melatonin implant (M+) on 10 April and were compared with 13 control animals (without implants M-). Twenty days later, intravaginal pessaries were inserted in all animals to induce a synchronized oestrus (day 0). On day 14, ewes were injected, i.v., with 0.5 IU oxytocin. Plasma 15-ketodihydro-PGF(2alpha) (PGFM) concentrations were measured to assess uterine secretory responsiveness to oxytocin. After euthanasia, pieces of endometrium were collected to determine progesterone content and PGE(2) and PGF(2alpha) secretion in vitro, in the presence or absence of either 20 microg/ml recombinant ovine interferon-tau (roIFNt) or 1 nmol/l oxytocin in the medium. Endometrial progesterone content was similar in the two treatments (M+: 50.25+/-17.34 ng/mg tissue, M-: 43.08+/-11.21 ng/mg tissue). M+ ewes that responded to oxytocin had significantly higher plasma PGFM concentrations between 10 and 80 min after oxytocin administration, a higher mean PGFM peak (P<0.001), higher plasma PGFM levels after the challenge (P<0.05) and higher plasma progesterone concentrations (P<0.01) than control ewes. In the in vitro experiment, M+ and M- control samples secreted similar amounts of PGE(2). The presence of roIFNtau and oxytocin only stimulated PGE(2) production (P<0.05) in M- tissues. Control M+ tissues secreted higher amounts of PGF(2alpha) (P=0.07) and PGF(2alpha) secretion was significantly (P<0.01) stimulated by roIFNtau. Oxytocin produced this effect only in M- samples (P<0.01). In conclusion, although previous studies have demonstrated a positive effect of melatonin on lamb production, PGF(2alpha) secretion is higher in vitro and the PGE(2):PGF(2alpha) ratio is unfavourable in response to IFNtau, which could affect embryo survival. Whether or not these mechanisms are similar in pregnant ewes remains to be elucidated.     

Characterization of the RpoS status of clinical isolates of Salmonella enterica

The stationary-phase-inducible sigma factor, sigma(S) (RpoS), is the master regulator of the general stress response in Salmonella and is required for virulence in mice. rpoS mutants can frequently be isolated from highly passaged laboratory strains of Salmonella: We examined the rpoS status of 116 human clinical isolates of Salmonella, including 41 Salmonella enterica serotype Typhi strains isolated from blood, 38 S. enterica serotype Typhimurium strains isolated from blood, and 37 Salmonella serotype Typhimurium strains isolated from feces. We examined the abilities of these strains to produce the sigma(S) protein, to express RpoS-dependent catalase activity, and to resist to oxidative stress in the stationary phase of growth. We also carried out complementation experiments with a cloned wild-type rpoS gene. Our results showed that 15 of the 41 Salmonella serotype Typhi isolates were defective in RpoS. We sequenced the rpoS allele of 12 strains. This led to identification of small insertions, deletions, and point mutations resulting in premature stop codons or affecting regions 1 and 2 of sigma(S), showing that the rpoS mutations are not clonal. Thus, mutant rpoS alleles can be found in freshly isolated clinical strains of Salmonella serotype Typhi, and they may affect virulence properties. Interestingly however, no rpoS mutants were found among the 75 Salmonella serotype Typhimurium isolates. Strains that differed in catalase activity and resistance to hydrogen peroxide were found, but the differences were not linked to the rpoS status. This suggests that Salmonella serotype Typhimurium rpoS mutants are counterselected because rpoS plays a role in the pathogenesis of Salmonella serotype Typhimurium in humans or in the transmission cycle of the disease.     

ACE16k: a 128x128 focal plane analog processor with digital I/O

This paper presents a new generation 128x128 Focal-Plane Analog Programmable Array Processor -FPAPAP, from a system level perspective. It has been manufactured in a 0.35 microm standard digital 1P-5M CMOS technology. It has been designed to achieve the high-speed and moderate-accuracy -8b- requirements of most real time -early-vision applications. External data interchange and control are completely digital. The chip contains close to four million transistors, 90% of them working in analog mode. It achieves peak computing values of 0.33TeraOPS while keeping power consumption at reasonable limits -82.5GOPS/W. Preliminary experimental results are also provided in the paper.     

Oxidative DNA damage of mixed copper(II) complexes with sulfonamides and 1,10-phenanthroline. Crystal structure of [Cu(N-quinolin-8-yl-p-toluenesulfonamidate)2(1,10-phenanthroline)

Mixed coordination compounds of Cu(II) with sulfonamides and 1,10-phenanthroline as ligands have been prepared and characterised. Single crystal structural determination of the complex [Cu(N-quinolin-8-yl-p-toluenesulfonamidate)(2)(phen)] shows Cu(II) ions are located in a highly distorted octahedral environment, probably as a consequence of the Jahn-Teller effect. The FT-IR and electronic paramagnetic resonance (EPR) spectra are also discussed. The mixed complexes prepared undergo an extensive DNA cleavage in the presence of ascorbate and hydrogen peroxide. Two of the complexes have higher nucleolytic efficiency than the bis(o-phenanthroline)copper(II) complex.     

Synthesis and spectroscopic studies on the new Schiff base derived from the 1:2 condensation of 2,6-diformyl-4-methylphenol with 5-aminouracil (BDF5AU) and its transition metal complexes. Influence on biologically active peptides-regulating aminopeptidases

The synthesis, spectroscopic (IR, 1H and 13C NMR, UV-Vis-NIR, EPR), magnetic measurements and biological studies of a number of complexes of Co(II), Ni(II), Cu(II), Zn(II), Cd(II), Au(III) and Hg(II) of the Schiff base derived from the 1:2 condensation of 2,6-diformyl-4-methylphenol and 5-aminouracil, ((5-[[(3-[[(2,4-dioxopyrimidin-5(1H,3H)-yl)imino]methyl]-2-hydroxy-5-methylphenyl)methylene]amino]pyrimidine-2,4(1H,3H)-dione, hereafter denoted as BDF5AU) are reported. In all cases, the complexes appear to be monomeric. The deprotonated ligand in the phenolic oxygen atom shows a tridentate coordination mode through the two azomethine nitrogen atoms and the phenolic oxygen atom. The coordination of the neutral ligand takes place through the phenolic oxygen atom and one azomethine nitrogen atom and the carbonylic oxygen atom in fourth position of one uracil ring. The biological properties of some perchlorate complexes on the activity of some neutral, acid, basic and omega aminopeptidases (AP) are assayed, demonstrating a general inhibitory effect. Neutral and basic AP are mainly inhibited by Cu(II), Ni(II) and Cd(II) complexes, although tyrosyl-AP is activated by Zn(II) complex. Glutamyl-AP but not aspartyl-AP is inhibited by all the complexes assayed excepting Zn(II) complex. Finally, omega AP is inhibited by Ni(II) and Cd(II) complexes.     

Influence of the culture medium constituents and inoculum size on the accumulation of blue pigment and cell growth of Lavandula spica

The effects of the concentration of PO₄ ^3-, NO₃ ^–, Fe ²⁺, sucrose and inoculum size on the accumulation of blue pigment and growth of suspension cultures of Lavandula spica D.C. ( L. latifolia Vill.), were studied. The combination of 2.5 mM PO₄ ^3-, 14.1 mM NO₃ ^–, 1 mM Fe ²⁺, 30 g l^–1 sucrose and 10 g l^–1fresh weight of inoculum, promoted a 7-fold enhancement on the productivity of blue pigment in comparison to the control medium. Among all the culture medium constituents tested, phosphate exerted the highest beneficial effect and Fe²⁺ showed to be essential for the accumulation of the pigment. High levels of sucrose (60 or 90 g l^–1) did not stimulate the accumulation of blue pigment. In these conditions, cell growth and cell viability were drastically affected.     

Identification of species of Brucella using Fourier transform infrared spectroscopy

Fourier transform infrared spectroscopy (FTIR) is a technique that has been used over the years in chemical analysis for the identification of substances and is one that may be applied to the characterisation of microorganisms. The marked tendency of Brucella towards variation in the smooth rough phase, together with the laboriousness and risk involved in the methods used in their identification, make their classification difficult. We studied the type strains of the different species and biovars of Brucella and 11 isolates of human origin of Brucella melitensis, six corresponding to biovar 1, one to biovar 2 and five to biovar 3. The results of linear discriminant analysis performed using the data provide an above 95% likelihood of correct classification, over half of which are in fact above 99% for the vast majority of Brucella strains. Only one case of B. melitensis biovar 1 has been incorrectly classified. The rest of the microorganisms studied (Staphylococcus aureus, Strteptococcus pyogenes, Enterococcus faecalis, Corynebacterium pseudodiphtheriticum, Clostridium perfringens, Escherichia coli, Acinetobacter calcoaceticus and Pseudomonas aeruginosa) have been classified correctly in all cases to a likelihood of over 80%. In the graphic representation of the analysis, a grouping of these can be seen in clusters, which include the different species. One of these comprises B. melitensis, another Brucella abortus, and another wider one is made up of Brucella suis. The Brucella canis, Brucella ovis and Brucella neotomae strains appear separate from the previously described groups.     

Partial cloning and expression of the cyclin B gene in the ovary of the bullseye puffer (Sphoeroides annulatus)

The bullseye puffer is a marine fish species with great potential for aquaculture in Mexico, and the understanding of its reproductive physiology at every level of biological organization is essential in order to succeed. Several molecules orchestrate the complex process of oocyte maturation and spawning. One of these molecules is cyclin B, which is the regulatory subunit of the maturation-promoting factor. In this study, a fragment of the cyclin B gene was isolated from the ovary of the bullseye puffer using an RT-PCR approach. The gene fragment was homologous to the cyclin B2 gene of other vertebrate species. Similar levels of cyclin B gene expression were detected in ovaries at different developmental stages, except for atretic ovaries from captive fish which did not spawn. However, cyclin B gene expression was maintained in captive fish treated with LHRH-a to induce spawning, and appeared to be similar to the pattern observed in wild fish. It is possible that the reduced expression of cyclin B in atretic ovaries is the result of mRNA degradation during atresia. Alternatively, reduced gene expression could be a controlling factor in the process of oocyte reabsorption since cyclin B is required for final oocyte maturation and ovulation.