Mutations in the gerP locus of Bacillus subtilis and Bacillus cereus affect access of germinants to their targets in spores

The gerP1 transposon insertion mutation of Bacillus cereus is responsible for a defect in the germination response of spores to both L-alanine and inosine. The mutant is blocked at an early stage, before loss of heat resistance or release of dipicolinate, and the efficiency of colony formation on nutrient agar from spores is reduced fivefold. The protein profiles of alkaline-extracted spore coats and the spore cortex composition are unchanged in the mutant. Permeabilization of gerP mutant spores by coat extraction procedures removes the block in early stages of germination, although a consequence of the permeabilization procedure in both wild type and mutant is that late germination events are not complete. The complete hexacistronic operon that includes the site of insertion has been cloned and sequenced. Four small proteins encoded by the operon (GerPA, GerPD, GerPB, and GerPF) are related in sequence. A homologous operon (yisH-yisC) can be found in the Bacillus subtilis genome sequence; null mutations in yisD and yisF, constructed by integrational inactivation, result in a mutant phenotype similar to that seen in B. cereus, though somewhat less extreme and equally repairable by spore permeabilization. Normal rates of germination, as estimated by loss of heat resistance, are also restored to a gerP mutant by the introduction of a cotE mutation, which renders the spore coats permeable to lysozyme. The B. subtilis operon is expressed solely during sporulation, and is sigma K-inducible. We hypothesize that the GerP proteins are important as morphogenetic or structural components of the Bacillus spore, with a role in the establishment of normal spore coat structure and/or permeability, and that failure to synthesize these proteins during spore formation limits the opportunity for small hydrophilic organic molecules, like alanine or inosine, to gain access to their normal target, the germination receptor, in the spore.     

A novel series of positive modulators of the AMPA receptor: Structure-based lead optimization

Starting from lead compound 1, we demonstrate how X-ray structural data can be used to understand SAR and expediently optimize bioavailability in a novel series of AMPA receptor modulators, furnishing 5 with improved bioavailability and robust in vivo activity.     

Spatiotemporal and teratological analyses of diatom assemblages from sediments contaminated with industrial effluents in the St. Lawrence River near Cornwall (Ontario,Canada)

Hydrobiologia - Throughout the twentieth century, waterfront industries in Cornwall (Ontario, Canada) discharged significant quantities of mercury (Hg) and other industrial effluents to the St....     

Structure based evolution of a novel series of positive modulators of the AMPA receptor

Starting from compound 1, we utilized biostructural data to successfully evolve an existing series into a new chemotype with a promising overall profile, exemplified by 19.     

Anesthetic propofol attenuates the isoflurane-induced caspase-3 activation and Aβ oligomerization

Accumulation and deposition of β-amyloid protein (Aβ) are the hallmark features of Alzheimer''s disease. The inhalation anesthetic isoflurane has been shown to induce caspase activation and increase Aβ accumulation. In addition, recent studies suggest that isoflurane may directly promote the formation of cytotoxic soluble Aβ oligomers, which are thought to be the key pathological species in AD. In contrast, propofol, the most commonly used intravenous anesthetic, has been reported to have neuroprotective effects. We therefore set out to compare the effects of isoflurane and propofol alone and in combination on caspase-3 activation and Aβ oligomerization in vitro and in vivo. Naïve and stably-transfected H4 human neuroglioma cells that express human amyloid precursor protein, the precursor for Aβ; neonatal mice; and conditioned cell culture media containing secreted human Aβ40 or Aβ42 were treated with isoflurane and/or propofol. Here we show for the first time that propofol can attenuate isoflurane-induced caspase-3 activation in cultured cells and in the brain tissues of neonatal mice. Furthermore, propofol-mediated caspase inhibition occurred when there were elevated levels of Aβ. Finally, isoflurane alone induces Aβ42, but not Aβ40, oligomerization, and propofol can inhibit the isoflurane-mediated oligomerization of Aβ42. These data suggest that propofol may mitigate the caspase-3 activation by attenuating the isoflurane-induced Aβ42 oligomerization. Our findings provide novel insights into the possible mechanisms of isoflurane-induced neurotoxicity that may aid in the development of strategies to minimize potential adverse effects associated with the administration of anesthetics to patients.     

The influence of recovery duration on multiple sprint cycling performance

The purpose of this study was to examine the influence of recovery duration on various measures of multiple sprint cycling performance. Twenty-five physically active men completed 2 maximal multiple sprint (20 x 5 seconds) cycling tests with contrasting recovery periods (10 or 30 seconds). The mean +/- SD values for age, height, and body mass were 20.6 +/- 1.5 years, 177.2 +/- 5.4 cm, and 78.2 +/- 8.2 kg, respectively. All tests were conducted on a friction-braked cycle ergometer. Longer (30 seconds) recovery periods resulted in significantly (p < 0.05) higher measures of maximum (approximately 4%) and mean (approximately 26%) power output, the former appearing to result from a potentiation effect during the first few sprints. Thirty-second recovery periods also corresponded with significantly lower measures of fatigue (absolute difference: 16.1%; 95% likely range: 14.1-18.2%), heart rate, respiratory exchange ratio, and oxygen uptake. Blood lactate and ratings of perceived exertion (6-20 scale) increased progressively throughout both protocols and were significantly lower with 30-second recovery periods. The results of this study illustrate the considerable influence of recovery duration on various measures of multiple sprint work. Although the precise mechanisms of this response require further investigation, coaches and sport scientists should consider these findings when attempting to develop or evaluate the performance capabilities of athletes involved in multiple sprint sports.     

Accessibility of the distal heme face, rather than Fe-His bond strength, determines the heme-nitrosyl coordination number of cytochromes c': evidence from spectroscopic studies

The heme coordination chemistry and spectroscopic properties of Rhodobacter capsulatus cytochrome c' (RCCP) have been compared to data from Alcaligenes xylosoxidans (AXCP), with the aim of understanding the basis for their different reactivities with nitric oxide (NO). Whereas ferrous AXCP reacts with NO to form a predominantly five-coordinate heme-nitrosyl complex via a six-coordinate intermediate, RCCP forms an equilibrium mixture of six-coordinate and five-coordinate heme-nitrosyl species in approximately equal proportions. Ferrous RCCP and AXCP both exhibit high Fe-His stretching frequencies (227 and 231 cm(-)(1), respectively), suggesting that factors other than the Fe-His bond strength account for their differences in heme-nitrosyl coordination number. Resonance Raman spectra of ferrous-nitrosyl RCCP confirm the presence of both five-coordinate and six-coordinate heme-NO complexes. The six-coordinate heme-nitrosyl of RCCP exhibits a fairly typical Fe-NO stretching frequency (569 cm(-)(1)), in contrast to the relatively high value (579 cm(-)(1)) of the AXCP six-coordinate heme-nitrosyl intermediate. It is proposed that NO experiences greater steric hindrance in binding to the distal face of AXCP, as compared to RCCP, leading to a more distorted Fe-N-O geometry and an elevated Fe-NO stretching frequency. Evidence that RCCP has a more accessible distal coordination site than in AXCP stems from the fact that ferric RCCP readily forms a heme complex with exogenous imidazole, whereas AXCP does not. A model is proposed in which distal heme-face accessibility, rather than the proximal Fe-His bond strength, determines the heme-nitrosyl coordination number in cytochromes c'.     

Equivalence of multibreed animal models and hierarchical Bayes analysis for maternally influenced traits

Background

It has been argued that multibreed animal models should include a heterogeneous covariance structure. However, the estimation of the (co)variance components is not an easy task, because these parameters can not be factored out from the inverse of the additive genetic covariance matrix. An alternative model, based on the decomposition of the genetic covariance matrix by source of variability, provides a much simpler formulation. In this study, we formalize the equivalence between this alternative model and the one derived from the quantitative genetic theory. Further, we extend the model to include maternal effects and, in order to estimate the (co)variance components, we describe a hierarchical Bayes implementation. Finally, we implement the model to weaning weight data from an Angus × Hereford crossbred experiment.

Methods

Our argument is based on redefining the vectors of breeding values by breed origin such that they do not include individuals with null contributions. Next, we define matrices that retrieve the null-row and the null-column pattern and, by means of appropriate algebraic operations, we demonstrate the equivalence. The extension to include maternal effects and the estimation of the (co)variance components through the hierarchical Bayes analysis are then straightforward. A FORTRAN 90 Gibbs sampler was specifically programmed and executed to estimate the (co)variance components of the Angus × Hereford population.

Results

In general, genetic (co)variance components showed marginal posterior densities with a high degree of symmetry, except for the segregation components. Angus and Hereford breeds contributed with 50.26% and 41.73% of the total direct additive variance, and with 23.59% and 59.65% of the total maternal additive variance. In turn, the contribution of the segregation variance was not significant in either case, which suggests that the allelic frequencies in the two parental breeds were similar.

Conclusion

The multibreed maternal animal model introduced in this study simplifies the problem of estimating (co)variance components in the framework of a hierarchical Bayes analysis. Using this approach, we obtained for the first time estimates of the full set of genetic (co)variance components. It would be interesting to assess the performance of the procedure with field data, especially when interbreed information is limited.