A general scenario of Hox gene inventory variation among major sarcopterygian lineages

<p>Abstract</p> <p>Background</p> <p><it>H</it>ox genes are known to play a key role in shaping the body plan of metazoans. Evolutionary dynamics of these genes is therefore essential in explaining patterns of evolutionary diversity. Among extant sarcopterygians comprising both lobe-finned fishes and tetrapods, our knowledge of the <it>Hox </it>genes and clusters has largely been restricted in several model organisms such as frogs, birds and mammals. Some evolutionary gaps still exist, especially for those groups with derived body morphology or occupying key positions on the tree of life, hindering our understanding of how <it>Hox </it>gene inventory varied along the sarcopterygian lineage.</p> <p>Results</p> <p>We determined the <it>Hox </it>gene inventory for six sarcopterygian groups: lungfishes, caecilians, salamanders, snakes, turtles and crocodiles by comprehensive PCR survey and genome walking. Variable <it>Hox </it>genes in each of the six sarcopterygian group representatives, compared to the human <it>Hox </it>gene inventory, were further validated for their presence/absence by PCR survey in a number of related species representing a broad evolutionary coverage of the group. Turtles, crocodiles, birds and placental mammals possess the same 39 <it>Hox </it>genes. <it>HoxD12 </it>is absent in snakes, amphibians and probably lungfishes. <it>HoxB13 </it>is lost in frogs and caecilians. Lobe-finned fishes, amphibians and squamate reptiles possess <it>HoxC3</it>. <it>HoxC1 </it>is only present in caecilians and lobe-finned fishes. Similar to coelacanths, lungfishes also possess <it>HoxA14</it>, which is only found in lobe-finned fishes to date. Our <it>Hox </it>gene variation data favor the lungfish-tetrapod, turtle-archosaur and frog-salamander relationships and imply that the loss of <it>HoxD12 </it>is not directly related to digit reduction.</p> <p>Conclusions</p> <p>Our newly determined <it>Hox </it>inventory data provide a more complete scenario for evolutionary dynamics of <it>Hox </it>genes along the sarcopterygian lineage. Limbless, worm-like caecilians and snakes possess similar <it>Hox </it>gene inventories to animals with less derived body morphology, suggesting changes to their body morphology are likely due to other modifications rather than changes to <it>Hox </it>gene numbers. Furthermore, our results provide basis for future sequencing of the entire <it>Hox </it>clusters of these animals.</p

Current and Historical Drivers of Landscape Genetic Structure Differ in Core and Peripheral Salamander Populations

With predicted decreases in genetic diversity and greater genetic differentiation at range peripheries relative to their cores, it can be difficult to distinguish between the roles of current disturbance versus historic processes in shaping contemporary genetic patterns. To address this problem, we test for differences in historic demography and landscape genetic structure of coastal giant salamanders (Dicamptodon tenebrosus) in two core regions (Washington State, United States) versus the species' northern peripheral region (British Columbia, Canada) where the species is listed as threatened. Coalescent-based demographic simulations were consistent with a pattern of post-glacial range expansion, with both ancestral and current estimates of effective population size being much larger within the core region relative to the periphery. However, contrary to predictions of recent human-induced population decline in the less genetically diverse peripheral region, there was no genetic signature of population size change. Effects of current demographic processes on genetic structure were evident using a resistance-based landscape genetics approach. Among core populations, genetic structure was best explained by length of the growing season and isolation by resistance (i.e. a ‘flat’ landscape), but at the periphery, topography (slope and elevation) had the greatest influence on genetic structure. Although reduced genetic variation at the range periphery of D. tenebrosus appears to be largely the result of biogeographical history rather than recent impacts, our analyses suggest that inherent landscape features act to alter dispersal pathways uniquely in different parts of the species' geographic range, with implications for habitat management

Multiple paternity in a viviparous toad with internal fertilisation

Anurans are renowned for a high diversity of reproductive modes, but less than 1% of species exhibit internal fertilisation followed by viviparity. In the live bearing West African Nimba toad (Nimbaphrynoides occidentalis), females produce yolk-poor eggs and internally nourish their young after fertilisation. Birth of fully developed juveniles takes place after nine months. In the present study, we used genetic markers (eight microsatellite loci) to assign the paternity of litters of 12 females comprising on average 9.7 juveniles. In nine out of twelve families (75%) a single sire was sufficient; in three families (25%) more than one sire was necessary to explain the observed genotypes in each family. These findings are backed up with field observations of male resource defence (underground cavities in which mating takes place) as well as coercive mating attempts, suggesting that the observed moderate level of multiple paternity in a species without distinct sperm storage organs is governed by a balance of female mate choice and male reproductive strategies

A randomised trial of oral versus intravenous opioids for treatment of pain after cardiac surgery

Background: Cardiac surgery and sternotomy are procedures accompanied by substantial postoperative pain which is challenging to treat. In general, intravenous (IV) opioids are used in the immediate postoperative phase, followed by oral opioids. Oral opioids are easier to use and generally less expensive. Our goal was thus to determine whether a new opioid preparation provides adequate analgesia after sternotomy. In particular, we tested the primary hypothesis that total opioid use (in morphine equivalents) is not greater with oral opioid compared with patient-controlled IV morphine. Our secondary hypothesis was that analgesic efficacy is similar with oral and IV opioids. Methods: A total of 51 patients having elective cardiac surgery were enrolled in this study. After rapid postoperative respiratory weaning, the patients were randomised into one of two groups receiving different types of analgesia: oral Targin (a combination of oxycodone–hydrochloride and the opioid antagonist naloxone hydrochloride-dihydrate) or patient-controlled IV morphine. Pain score (visual analogue scale), sedation (Ramsey score), respiratory rate and side effects were assessed at 3, 5, 7, 9 and 11 h after surgery, and every 6 h throughout the third postoperative evening. Results: The total opioid dose in morphine equivalent doses was significantly lower with oral opioid than with IV morphine (adjusted geometric means [95 % confidence interval]: 34 [29; 38] vs. 69 [61; 78] mg, respectively). Pain scores were similar in each group. Conclusions: Analgesic quality was comparable with oral and IV opioids, suggesting that postoperative pain even after very painful procedures can be sufficiently managed with oral opioids

A Multimodal Clinical Pathway Can Reduce Length of Stay After Total Knee Arthroplasty

Clinical pathways reduce length of stay which is critical for hospitals to remain financially sound. We sought to determine if a multimodal pathway focusing on pre-op discharge planning and pre-emptive pain and nausea management lead to reduced length of stay, better pain management, and more rapid functional gains without an increase in post-op complications. A multimodal pathway incorporating pre-op discharge planning and pre-emptive pain and nausea management was initiated in August of 2007. Physical therapy began the day of surgery. Two hundred eleven patients treated over a 3-month period with the new pathway were compared to 192 patients treated in the last 3 months of an older pathway. Length of stay, VAS scores for pain, and the incidence of nausea were compared. Length of time to achieve functional milestones while in hospital and the incidence of complications out to 6 months were compared. Average length of stay was reduced by 0.26 days. VAS scores for pain were lower. Several functional milestones were achieved earlier and complications were not increased. Efforts to control nausea were not successful and severe nausea was experienced in 40% of patients in both groups. This enhanced pathway can lead to an important reduction in length of stay. Although this reduction seems small, it can significantly increase patient throughput and increase hospital capacity. Post-op nausea continues to be an impediment in patient care after TKR