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Biomedical subjects

Keith G Davies

Publications and source records attributed to Keith G Davies.

9 recordsLinked to original sources
PubMed2006

Exploitation of immunofluorescence for the quantification and characterization of small numbers of Pasteuria endospores.

The Pasteuria group of endospore-forming bacteria has been studied as a biocontrol agent of plant-parasitic nematodes. Techniques have been developed for its detection and quantification in soil samples, and these mainly focus on observations of endospore attachment to nematodes. Characterization of Pasteuria populations has recently been performed with DNA-based techniques, which usually require the extraction of large numbers of spores. We describe a simple immunological method for the quantification and characterization of Pasteuria populations. Bayesian statistics were used to determine an extraction efficiency of 43% and a threshold of detection of 210 endospores g(-1) sand. This provided a robust means of estimating numbers of endospores in small-volume samples from a natural system. Based on visual assessment of endospore fluorescence, a quantitative method was developed to characterize endospore populations, which were shown to vary according to their host.

Antibodies↗
PubMed2005

Scientific Citizenship and good governance: implications for biotechnology.

In the wake of public distrust regarding biotechnology, it has been suggested that the debate should be moved "upstream", whereby the public help to set research priorities. Although many scientists see this as an illogical reaction to a loss of faith in science, we argue that the boundaries between science and its technological applications have become blurred and this produces conflicts of interests that have led to this crisis of trust. Furthermore, this distrust is also a crisis in governance that calls for a new open and democratic approach to scientific research. We propose that the concept of Scientific Citizenship, based on good governance, will help to restore public trust and bridge the gap between science and the society that it serves. Integral to this is the suggestion that the governance of science forms part of the training for scientists.

Biotechnology↗
PubMed2005

Structural analysis of divalent metals binding to the Bacillus subtilis response regulator Spo0F: the possibility for in vitro metalloregulation in the initiation of sporulation.

The presence of a divalent metal ion in a negatively charged aspartic acid pocket is essential for phosphorylation of response regulator proteins. Here, we present metal binding studies of the Bacillus subtilis response regulator Spo0F using NMR and microESI-MS. NMR studies show that the divalent metals Ca(2+), Mg(2+) and Mn(2+) primarily bind, as expected, in the Asp pocket phosphorylation site. However, identical studies with Cu(2+) show distinct binding effects in three specific locations: (i) the Asp pocket, (ii) a grouping of charged residues at a site opposite of the Asp pocket, and (iii) on the beta 4-alpha 4 loop and the beta 5/alpha 5 interface, particularly around and including H101. microESI-MS studies stoichiometrically confirm the NMR studies and demonstrate that most divalent metal ions bind to Spo0F primarily in a 1:1 ratio. Again, in the case of Cu(2+), multiple metal-bound species are observed. Subsequent experiments reveal that Mg(2+) supports phosphotransfer between KinA and Spo0F, while Cu(2+) fails to support KinA phosphotransfer. Additionally, the presence of Cu(2+) at non-lethal concentrations in sporulation media for B. subtilis and the related organism Pasteuria penetrans was found to inhibit spore formation while continuing to permit vegetative growth. Depending on the type of divalent metal ion present, in vitro phosphorylation of Spo0F by its cognate kinase KinA can be inhibited.

Amino Acid Sequence↗
PubMed2005

Naming ability after tailored left temporal resection with extraoperative language mapping: increased risk of decline with later epilepsy onset age.

Standard temporal resection in the left hemisphere carries the risk of postoperative naming ability decline, especially with later epilepsy onset age/absence of hippocampal sclerosis. Language mapping has been performed routinely at some centers to minimize postoperative primary language impairment, but its effect on changes in naming performance has not been explored. This study examined naming outcome in 24 patients with nonlesional epilepsy who had left temporal resection after extraoperative language mapping. The mean decline in Boston Naming Test (BNT) score was 7.8, and 13 (54%) patients had a BNT decline greater than the Reliable Change Index. Simple correlations found significant relationships between BNT score decline and: later onset age, higher preoperative BNT score, and resection of isolated language sites. A multiple regression analysis showed that onset age was the best predictor of BNT decline. Although naming ability in patients with early onset age is stable with language mapping, there is still a risk of decline for those with later onset age.

Adolescent↗
PubMed2005

Phylogenetic analysis of Pasteuria penetrans by use of multiple genetic loci.

Pasteuria penetrans is a gram-positive, endospore-forming eubacterium that apparently is a member of the Bacillus-Clostridium clade. It is an obligate parasite of root knot nematodes (Meloidogyne spp.) and preferentially grows on the developing ovaries, inhibiting reproduction. Root knot nematodes are devastating root pests of economically important crop plants and are difficult to control. Consequently, P. penetrans has long been recognized as a potential biocontrol agent for root knot nematodes, but the fastidious life cycle and the obligate nature of parasitism have inhibited progress on mass culture and deployment. We are currently sequencing the genome of the Pasteuria bacterium and have performed amino acid level analyses of 33 bacterial species (including P. penetrans) using concatenation of 40 housekeeping genes, with and without insertions/deletions (indels) removed, and using each gene individually. By application of maximum-likelihood, maximum-parsimony, and Bayesian methods to the resulting data sets, P. penetrans was found to cluster tightly, with a high level of confidence, in the Bacillus class of the gram-positive, low-G+C-content eubacteria. Strikingly, our analyses identified P. penetrans as ancestral to Bacillus spp. Additionally, all analyses revealed that P. penetrans is surprisingly more closely related to the saprophytic extremophile Bacillus haladurans and Bacillus subtilis than to the pathogenic species Bacillus anthracis and Bacillus cereus. Collectively, these findings strongly imply that P. penetrans is an ancient member of the Bacillus group. We suggest that P. penetrans may have evolved from an ancient symbiotic bacterial associate of nematodes, possibly as the root knot nematode evolved to be a highly specialized parasite of plants.

Animals↗
PubMed2003

Interactions between bacteria and plant-parasitic nematodes: now and then.

Based on genome-to-genome analyses of gene sequences obtained from plant-parasitic, root-knot nematodes (Meloidogyne spp.), it seems likely that certain genes have been derived from bacteria by horizontal gene transfer. Strikingly, a common theme underpinning the function of these genes is their apparent direct relationship to the nematodes' parasitic lifestyle. Phylogenetic analyses implicate rhizobacteria as the predominant group of 'gene donor' bacteria. Root-knot nematodes and rhizobia occupy similar niches in the soil and in roots, and thus the opportunity for genetic exchange may be omnipresent. Further, both organisms establish intimate developmental interactions with host plants, and mounting evidence suggests that the mechanisms for these interactions are shared too. We propose that the origin of parasitism in Meloidogyne may have been facilitated by acquisition of genetic material from soil bacteria through horizontal transfer, and that such events represented key steps in speciation of plant-parasitic nematodes. To further understand the mechanisms of horizontal gene transfer, and also to provide experimental tools to manipulate this promising bio-control agent, we have initiated a genomic sequence of the bacterial hyper-parasite of plant parasitic nematodes, Pasteuria penetrans. Initial data have established that P. penetrans is closely related to Bacillus spp., to the extent that considerable genome synteny is apparent. Hence, Bacillus serves as a model for Pasteuria, and vice versa.

Animals↗
PubMed2003

Zones of inhibition: interactions between art and science.

It has been suggested that successful art helps to solve our emotional problems. Can it therefore help with our current crisis in the relationship between biological science and society? Art and science are activities that have seemingly different cultures; scientists are seen as objective and rational, artists as subjective and intuitive. Each inhabit cultures that are seen to be mutually exclusive, but this has not always been the case. For example, during the Renaissance, people were schooled across both art and science and there was no clear dividing line. Where did the split occur, and is their interaction important in the 21st century?

Biotechnology↗
PubMed2003

Amusia after right frontal resection for epilepsy with singing seizures: case report and review of the literature.

Although many authors consider aprosodia and amusia to be synonymous, they actually represent two distinct communication disorders. Amusia refers to a profound deficit involving musical abilities, whereas aprosodia refers to deficits regarding the emotional content of speech. Many authors have presumed a similar etiology and localization for these conditions and assumed that these disorders would not occur independently. We report the case of a 31-year-old choir director who developed amusia without aprosodia after a right frontal lobe resection for intractable seizures. His ictal onset manifested with rhythmic slapping of his thighs while communicating with melodic speech. Video EEG monitoring documented right hemispheric discharges that occurred simultaneously with this ictal behavior. While a right frontal lobe resection made him seizure-free, his postoperative amusia was so profound that he could no longer continue his occupation as a choir director. This case suggests that the right frontal cortex has different sites for musical ability distinct from the centers regarding prosody. Patients scheduled to undergo right frontal lobectomy ought to be counseled regarding the potential loss of musical abilities.

Adult↗