Molecular analysis of the sex chromosomes of the platyfish Xiphophorus maculatus: Towards the identification of a new type of master sexual regulator in vertebrates

In contrast to mammals and birds, fish display an amazing diversity of genetic sex determination systems, with frequent changes during evolution possibly associated with the emergence of new sex chromosomes and sex‐determining genes. To better understand the molecular and evolutionary mechanisms driving this diversity, several fish models are studied in parallel. Besides the medaka (Oryzias latipes Temminck and Schlegel, 1846) for which the master sex‐determination gene has been identified, one of the most advanced models for studying sex determination is the Southern platyfish (Xiphophorus maculatus, Günther 1966). Xiphophorus maculatus belongs to the Poeciliids, a family of live‐bearing freshwater fish, including platyfish, swordtails and guppies that perfectly illustrates the diversity of genetic sex‐determination mechanisms observed in teleosts. For X. maculatus, bacterial artificial chromosome contigs covering the sex‐determination region of the X and Y sex chromosomes have been constructed. Initial molecular analysis demonstrated that the sex‐determination region is very unstable and frequently undergoes duplications, deletions, inversions and other rearrangements. Eleven gene candidates linked to the master sex‐determining gene have been identified, some of them corresponding to pseudogenes. All putative genes are present on both the X and the Y chromosomes, suggesting a poor degree of differentiation and a young evolutionary age for platyfish sex chromosomes. When compared with other fish and tetrapod genomes, syntenies were detected only with autosomes. This observation supports an independent origin of sex chromosomes, not only in different vertebrate lineages but also between different fish species.     

Lameness prevalence and risk factors in organic and non-organic dairy herds in the United Kingdom

This study aimed to compare the prevalence of lameness on organic and non-organic dairy farms in the United Kingdom (UK) and to assess which cow and farm factors influenced lameness levels. Forty organic and 40 non-organic dairy farms across the UK were repeatedly visited over a 2.5 year period. On each visit all milking cows were locomotion scored, and information about farm housing, management and husbandry practices was recorded on-farm. Over the whole study, the mean herd lameness prevalence was 16.2%, 16.3% and 19.3% in the autumn, winter and spring observation periods, respectively. Lameness prevalence was lower (P=0.012) on organic farms compared to non-organic farms. Numerous specific factors were found to significantly influence the prevalence of lameness. This study provided evidence that organic management reduced herd lameness. It supported previous research which suggested that lameness is a serious problem on many farms in the UK and further emphasised the multi-factorial aetiology of lameness problems.     

A comparison of total calcium,corrected calcium,and ionized calcium concentrations as indicators of calcium homeostasis among hypoalbuminemic dogs requiring intensive care

Objective – (1) To evaluate whether total calcium (tCa) correlates with ionized calcium (iCa) in hypoalbuminemic dogs; (2) to evaluate whether calcium adjusted for albumin (Alb), or total protein (TP), or both accurately predict iCa concentrations and hence can be used to monitor calcium homeostasis in critically ill hypoalbuminemic dogs; and (3) to evaluate factors associated with any potential discrepancy in calcium classification between corrected total and ionized values. Design – Prospective observational clinical study. Setting – Small animal intensive care unit in a veterinary medical teaching hospital. Animals – Twenty‐eight client‐owned dogs with hypoalbuminemia. Interventions – None. Measurements and Main Results – iCa was determined using ion‐specific electrode methodology, on heparinized plasma. The tCa concentration was adjusted for Alb and TP using published equations. In total 29% (8/28) of the hypoalbuminemic, critically ill dogs in this study were hypocalcemic at intensive care unit admission, as determined by iCa measurement. Corrected calcium values failed to accurately classify calcium status in 67.9% and 64.3% of cases, according to whether the Alb‐adjusted or TP‐adjusted values, respectively, were used. The sensitivity and specificity of the tCa to evaluate hypocalcemia was 100% and 47%, respectively. The sensitivity and specificity of the correction formulae were 37.5% and 79% for the Alb‐adjusted values and 37.5% and 74% for TP‐adjusted values. tCa overestimated the presence of hypocalcemia and underestimated the presence of normocalcemia, while corrected calcium values overestimated the presence of normocalcemia and underestimated the presence of hypocalcemia. Conclusions – Calcium homeostasis in hypoalbuminemic critically ill dogs should be evaluated by iCa concentrations rather than tCa or calcium adjusted for Alb or TP. Given that tCa has 100% sensitivity for detecting hypocalcemia in this population it is recommended that all hypoalbuminemic and critically ill patients with low tCa should be evaluated with an iCa measurement.     

The genetic landscape of the childhood cancer medulloblastoma

Medulloblastoma (MB) is the most common malignant brain tumor of children. To identify the genetic alterations in this tumor type, we searched for copy number alterations using high-density microarrays and sequenced all known protein-coding genes and microRNA genes using Sanger sequencing in a set of 22 MBs. We found that, on average, each tumor had 11 gene alterations, fewer by a factor of 5 to 10 than in the adult solid tumors that have been sequenced to date. In addition to alterations in the Hedgehog and Wnt pathways, our analysis led to the discovery of genes not previously known to be altered in MBs. Most notably, inactivating mutations of the histone-lysine N-methyltransferase genes MLL2 or MLL3 were identified in 16% of MB patients. These results demonstrate key differences between the genetic landscapes of adult and childhood cancers, highlight dysregulation of developmental pathways as an important mechanism underlying MBs, and identify a role for a specific type of histone methylation in human tumorigenesis.     

Sediment and society: an approach for assessing management of contaminated sediments and stakeholder involvement in Norway

Introduction

Management options for large-scale contaminated sediment remediation projects can be challenging with regard to competing stakeholder interests. This has become apparent during the Oslofjord sediment remediation project (2005–2009) which caused considerable public discussion.

Background

To learn from this project, the ‘Sediment and society’ project was initiated to develop a collaborative approach that will incorporate local and scientific knowledge in order to achieve mutual gains, win-win outcomes for the stakeholders, in the management of contaminated marine sediments.

Method development

The project focuses on two Norwegian harbours: Oslo Harbour and Bergen Harbour. The Oslo Harbour case has been analysed ex-post, using elements of risk governance: participation, communication, information/knowledge and risk perception. The Bergen Harbour case is focused on the establishment of a citizens' jury as well as a stakeholder panel in Bergen Harbour.

Preliminary results and observations

Thus far, the results suggest three important commonalities or challenges for stakeholder involvement: (1) how to include people who have important management information and local knowledge, but not much influence in the decision-making process; (2) how to secure resources to ensure participation and (3) how to engage and motivate stakeholders to participate early in the sediment remediation planning process.     

Intravenous regional anesthesia in isoflurane anesthetized cats: lidocaine plasma concentrations and cardiovascular effects

Objective To determine if intravenous regional anesthesia (IVRA) can be used in cats without resulting in excessive plasma lidocaine concentrations or adverse cardiovascular effects. Study design Prospective, blinded crossover study. Animals Seven healthy male young adult cats weighing 3.96 ± 0.63 kg. Methods At 2.3% end‐tidal isoflurane concentration, lidocaine (L) 3 mg kg^?1 (1%) or saline (S) was injected in a distal cephalic venous catheter after application of two tourniquets to that forelimb which remained in place for 20 minutes. Heart and respiratory rates, arterial blood pressures and ECG were recorded every 5 minutes during tourniquet application and for 20 minutes following tourniquet removal. Lidocaine plasma concentrations were measured 5 minutes after injection and 0.5, 1, 2, 4, 8, 20 and 40 minutes after tourniquet removal. End tidal isoflurane concentrations were reduced to 1.5–2.0% to elicit a response to toe pinch (RTP) in the contralateral leg. The study was repeated similarly in the contralateral leg and RTP was graded for 40 minutes. Response was also tested in the leg previously injected, the differences between the two scores determined and those differences compared between the L and S treatments. The data were analyzed using anova for repeated measures comparing values to baseline. Significance was set at p < 0.005 using the Bonferroni method for multiple comparisons. Results There were no significant differences in physiologic parameters at either isoflurane concentration. Differences in RTP were significantly larger in the lidocaine treatment. The highest mean lidocaine concentrations were measured 0.5 minutes after tourniquet removal after both injections and were 2.79 ± 1.05 and 3.10 ± 1.11 µg mL^?1. The highest individual plasma concentration was 6.46 µg mL^?1. Conclusion No adverse hemodynamic effects were evident after IVRA lidocaine in any cat. The lidocaine dose studied inhibited a RTP until 20 minutes after tourniquet removal. Lidocaine concentrations varied and were measurable prior to tourniquet removal. Clinical relevance IVRA may be a suitable technique for cats undergoing surgery of the distal limbs.     

Explaining host–parasitoid interactions at the landscape scale: a new approach for calibration and sensitivity analysis of complex spatio-temporal models

Landscape Ecology - Linking spatial pattern and process is a difficult task in landscape ecology because spatial patterns of populations result from complex factors such as individual traits, the...