Evolution and medicine: the long reach of "Dr. Darwin"

In this review we consider the new science of Darwinian medicine. While it has often been said that evolutionary theory is the glue that holds the disparate branches of biological inquiry together and gives them direction and purpose, the links to biomedical inquiry have only recently been articulated in a coherent manner. Our aim in this review is to make clear first of all, how evolutionary theory is relevant to medicine; and secondly, how the biomedical sciences have enriched our understanding of evolutionary processes. We will conclude our review with some observations of the philosophical significance of this interplay between evolutionary theory and the biomedical sciences

Comparative genomics of Escherichia coli isolated from patients with inflammatory bowel disease

<p>Abstract</p> <p>Background</p> <p>Inflammatory bowel disease (IBD) is used to describe a state of idiopathic, chronic inflammation of the gastrointestinal tract. The two main phenotypes of IBD are Crohn's disease (CD) and ulcerative colitis (UC). The major cause of IBD-associated mortality is colorectal cancer. Although both host-genetic and exogenous factors have been found to be involved, the aetiology of IBD is still not well understood. In this study we characterized thirteen <it>Escherichia coli </it>strains from patients with IBD by comparative genomic hybridization employing a microarray based on 31 sequenced <it>E. coli </it>genomes from a wide range of commensal and pathogenic isolates.</p> <p>Results</p> <p>The IBD isolates, obtained from patients with UC and CD, displayed remarkably heterogeneous genomic profiles with little or no evidence of group-specific determinants. No IBD-specific genes were evident when compared with the prototypic CD isolate, LF82, suggesting that the IBD-inducing effect of the strains is multifactorial. Several of the IBD isolates carried a number of extraintestinal pathogenic <it>E. coli </it>(ExPEC)-related virulence determinants such as the <it>pap</it>, <it>sfa</it>, <it>cdt </it>and <it>hly </it>genes. The isolates were also found to carry genes of ExPEC-associated genomic islands.</p> <p>Conclusions</p> <p>Combined, these data suggest that <it>E. coli </it>isolates obtained from UC and CD patients represents a heterogeneous population of strains, with genomic profiles that are indistinguishable to those of ExPEC isolates. Our findings indicate that IBD-induction from <it>E. coli </it>strains is multifactorial and that a range of gene products may be involved in triggering the disease.</p

Modulation of Prey‐capture Behavior in Plethodon Cinereus (Green) (Amphibia: Caudata)

Many feeding kinematic studies do not identify sources of mechanical variation related to the type or size of prey. Studies of salamanders have concentrated on determining the morphological basis of feeding mechanics or on phylogenetic comparisons; few have examined variability within a species. A series of feeding trials was designed to test whether Plethodon cinereus of different age/size classes exhibits stereotypic patterns in capturing prey of differing type and size. Stopframe video analyses of feedings were made using 19 salamanders of varying body size and four prey types chosen to resemble items in the natural diet of the species. Five morphological features of each salamander, length and width of prey items, and 15 kinematic variables were used to describe each feeding trial. Statistical analyses of kinematic and morphological variables show that the feeding behavior of this species varies significantly with prey type. Effects of salamander size and prey size within prey types were a source of variation in some kinematic variables; among‐individual variation partitioned with salamander body size. Different feeding modes resulted from distinctive combinations of distances from prey, amount of tongue protrusion, body movements, and duration of mouth closure, which varied with the use of jaw prehension and lingual prey capture. Presence of a repertoire of behaviors, composed of versatile combinations of movements, suggests that Plethodon cinereus modulates feeding mechanics to capture different types of prey. Consideration of natural prey in experiments, and of prey type in comparisons made across taxa, are necessary to investigations of the evolution of feeding behaviors

Facultative Mobilization of Eggshell Calcium Promotes Embryonic Growth in an Oviparous Snake

The mineralized eggshell of Reptilia was a major innovation in the evolution of the amniotic egg. Inorganic components strengthen the eggshell and are a potential source of nutrients to developing embryos. Embryos of oviparous reptiles do extract calcium from eggshells but vary interspecifically in exploitation of this resource. The pattern of embryonic calcium nutrition of the corn snake, Pantherophis guttatus, is similar to a diversity of squamate species: embryos obtain most calcium from yolk, yet also mobilize calcium from the eggshell. We tested the hypothesis that embryonic development is not dependent on eggshell calcium by manipulating calcium availability. We peeled away the outer calcareous layer of the eggshell of recently oviposited eggs; control eggs were left intact. Eggs were sampled periodically and calcium content of egg compartments (embryo, yolk, eggshell) was measured. We also analyzed skeletal development and size of hatchlings. There was no difference in survivorship or length of incubation between treatments. However, hatchlings from intact eggs contained more calcium and were larger in mass and length than siblings from peeled eggs. There were no observable differences in ossification but hatchlings from intact eggs had larger skeletal elements (skull, vertebrae). Our results indicate that mobilization of eggshell calcium is not a requirement for embryonic development of P. guttatus and that embryos augment yolk calcium by extracting calcium from the eggshell. This pattern of embryonic calcium nutrition would favor embryos with a greater capacity to mobilize calcium from the eggshell by promoting growth and thereby potentially enhancing hatchling fitness

Teratogenic Potential of Atrazine and 2,4-D Using Fetax

The teratogenic potential of commercial formulations of atrazine (40.8%) and 2,4-D was evaluated using FETAX (frog embryo teratogenic assay--Xenopus). Because these herbicides have been detected in ground and surface water, this study was designed to determine the adverse effects in buffer and natural water for both herbicides. All treatments showed a significant concentration-response effect on exposed embryos, except for the 2,4-D natural water sample. Atrazine (solubility of the commercial formula used 70 mg/L at 20 degrees C), compared to 2,4-D (solubility = 311 mg/L at pH = 1 and 25 degrees C), had a significantly greater teratogenic effect in both the buffer (atrazine EC50 = 33 mg/L, LC50 = 100 mg/L, TI = 3.03; 2,4-D EC50 = 245 mg/L, LC50 = 254 mg/L, TI = 1.04) and natural water samples (atrazine EC50 \u3c 8 mg/L, LC50 = 126 mg/L; 2,4-D EC50 and LC50 \u3e 270 mg/L). The 2,4-D EC50 and LC50 values for the buffer were similar at 245 mg/L and 254 mg/L. These similar values and the teratogenic index (TI) of 1.04 suggested that 2,4-D was more embryotoxic than teratogenic to frog embryos at high concentrations. Atrazine in natural water demonstrated a significantly greater EC50 (100% abnormality at 8 mg/L, the lowest test concentration) to frog embryos than the buffer experiment (EC50 = 33 mg/L). The extrapolated lowest observable adverse effect concentration (LOAEC) for the natural water experiment was 1.1 mg/L. These results suggest that atrazine toxicity is enhanced by the synergistic or additive effects of some component of the water or atrazine was already present in the sample. In contrast to atrazine, 2,4-D was less toxic in natural water than buffer. These results suggest that both atrazine and 2,4-D pose little threat, since their embryotoxicity and teratogenicity to frog embryos occur at high concentrations approaching their maximum solubility levels in water