Climate change introduces threatened killer whale populations and conservation challenges to the Arctic.

The Arctic is the fastest-warming region on the planet, and the lengthening ice-free season is opening Arctic waters to sub-Arctic species such as the killer whale (Orcinus orca). As apex predators, killer whales can cause significant ecosystem-scale changes. Setting conservation priorities for killer whales and their Arctic prey species requires knowledge of their evolutionary history and demographic trajectory. Using whole-genome resequencing of 24 killer whales sampled in the northwest Atlantic, we first explored the population structure and demographic history of Arctic killer whales. To better understand the broader geographic relationship of these Arctic killer whales to other populations, we compared them to a globally sampled dataset. Finally, we assessed threats to Arctic killer whales due to anthropogenic harvest by reviewing the peer-reviewed and gray literature. We found that there are two highly genetically distinct, non-interbreeding populations of killer whales using the eastern Canadian Arctic. These populations appear to be as genetically different from each other as are ecotypes described elsewhere in the killer whale range; however, our data cannot speak to ecological differences between these populations. One population is newly identified as globally genetically distinct, and the second is genetically similar to individuals sampled from Greenland. The effective sizes of both populations recently declined, and both appear vulnerable to inbreeding and reduced adaptive potential. Our survey of human-caused mortalities suggests that harvest poses an ongoing threat to both populations. The dynamic Arctic environment complicates conservation and management efforts, with killer whales adding top-down pressure on Arctic food webs crucial to northern communities' social and economic well-being. While killer whales represent a conservation priority, they also complicate decisions surrounding wildlife conservation and resource management in the Arctic amid the effects of climate change.

Replication stress is a potent driver of functional decline in ageing haematopoietic stem cells.

Haematopoietic stem cells (HSCs) self-renew for life, thereby making them one of the few blood cells that truly age. Paradoxically, although HSCs numerically expand with age, their functional activity declines over time, resulting in degraded blood production and impaired engraftment following transplantation. While many drivers of HSC ageing have been proposed, the reason why HSC function degrades with age remains unknown. Here we show that cycling old HSCs in mice have heightened levels of replication stress associated with cell cycle defects and chromosome gaps or breaks, which are due to decreased expression of mini-chromosome maintenance (MCM) helicase components and altered dynamics of DNA replication forks. Nonetheless, old HSCs survive replication unless confronted with a strong replication challenge, such as transplantation. Moreover, once old HSCs re-establish quiescence, residual replication stress on ribosomal DNA (rDNA) genes leads to the formation of nucleolar-associated γH2AX signals, which persist owing to ineffective H2AX dephosphorylation by mislocalized PP4c phosphatase rather than ongoing DNA damage. Persistent nucleolar γH2AX also acts as a histone modification marking the transcriptional silencing of rDNA genes and decreased ribosome biogenesis in quiescent old HSCs. Our results identify replication stress as a potent driver of functional decline in old HSCs, and highlight the MCM DNA helicase as a potential molecular target for rejuvenation therapies.

Diagnostic assessment of tooth maturation of the mandibular second molars as a skeletal maturation indicator: A retrospective longitudinal study.

INTRODUCTION: Our aim was to analyze the correlation between growth status in height and chronological age, carpal maturation, cervical maturation, and dental maturation, and assess the diagnostic performance of Demirjian's dental maturation as an indicator of the pubertal growth spurt, through a retrospective longitudinal study. METHODS: Records of 60 Canadian patients obtained from the Burlington Growth Centre, which included height and weight charts and a set of x-rays at 6 points in time, were analyzed. The images at each point in time included 1 hand and wrist radiograph, a lateral cephalometric x-ray, and one 45° oblique cephalometric radiograph of each side, which were analyzed using the methods of Fishman, Baccetti, and Demirjian on the mandibular left and right second molars, respectively. The onset of the pubertal growth peak in height (distance to growth peak [DGP]) was identified, and the correlation between methods with DGP was assessed. RESULTS: High levels of correlation were obtained between the methods of Fishman, Baccetti, and Demirjian with DGP. The cutoff point between prepubertal and postpubertal stages was F stage for women and G stage for men, with statistically significant levels of sensitivity and specificity for the test. CONCLUSIONS: The use of the method of Demirjian applied to mandibular second molars is plausible as a predictor of the occurrence of the DGP for the studied population.

Haematopoietic stem cell niches: new insights inspire new questions.

Haematopoietic stem cell (HSC) niches provide an environment essential for life-long HSC function. Intense investigation of HSC niches both feed off and drive technology development to increase our capability to assay functionally defined cells with high resolution. A major driving force behind the desire to understand the basic biology of HSC niches is the clear implications for clinical therapies. Here, with particular emphasis on cell type-specific deletion of SCL and CXCL12, we focus on unresolved issues on HSC niches, framed around some very recent advances and novel discoveries on the extrinsic regulation of HSC maintenance. We also provide ideas for possible paths forward, some of which are clearly within reach while others will require both novel tools and vision.

Arctic marine mammal population status, sea ice habitat loss, and conservation recommendations for the 21st century.

Arctic marine mammals (AMMs) are icons of climate change, largely because of their close association with sea ice. However, neither a circumpolar assessment of AMM status nor a standardized metric of sea ice habitat change is available. We summarized available data on abundance and trend for each AMM species and recognized subpopulation. We also examined species diversity, the extent of human use, and temporal trends in sea ice habitat for 12 regions of the Arctic by calculating the dates of spring sea ice retreat and fall sea ice advance from satellite data (1979-2013). Estimates of AMM abundance varied greatly in quality, and few studies were long enough for trend analysis. Of the AMM subpopulations, 78% (61 of 78) are legally harvested for subsistence purposes. Changes in sea ice phenology have been profound. In all regions except the Bering Sea, the duration of the summer (i.e., reduced ice) period increased by 5-10 weeks and by >20 weeks in the Barents Sea between 1979 and 2013. In light of generally poor data, the importance of human use, and forecasted environmental changes in the 21st century, we recommend the following for effective AMM conservation: maintain and improve comanagement by local, federal, and international partners; recognize spatial and temporal variability in AMM subpopulation response to climate change; implement monitoring programs with clear goals; mitigate cumulative impacts of increased human activity; and recognize the limits of current protected species legislation.

Expression of the melanoma cell adhesion molecule in human mesenchymal stromal cells regulates proliferation, differentiation, and maintenance of hematopoietic stem and progenitor cells.

The melanoma cell adhesion molecule defines mesenchymal stromal cells in the human bone marrow that regenerate bone and establish a hematopoietic microenvironment in vivo. The role of the melanoma cell adhesion molecule in primary human mesenchymal stromal cells and the maintenance of hematopoietic stem and progenitor cells during ex vivo culture has not yet been demonstrated. We applied RNA interference or ectopic overexpression of the melanoma cell adhesion molecule in human mesenchymal stromal cells to evaluate the effect of the melanoma cell adhesion molecule on their proliferation and differentiation as well as its influence on co-cultivated hematopoietic stem and progenitor cells. Knockdown and overexpression of the melanoma cell adhesion molecule affected several characteristics of human mesenchymal stromal cells related to osteogenic differentiation, proliferation, and migration. Furthermore, knockdown of the melanoma cell adhesion molecule in human mesenchymal stromal cells stimulated the proliferation of hematopoietic stem and progenitor cells, and strongly reduced the formation of long-term culture-initiating cells. In contrast, melanoma cell adhesion molecule-overexpressing human mesenchymal stromal cells provided a supportive microenvironment for hematopoietic stem and progenitor cells. Expression of the melanoma cell adhesion molecule increased the adhesion of hematopoietic stem and progenitor cells to human mesenchymal stromal cells and their migration beneath the monolayer of human mesenchymal stromal cells. Our results demonstrate that the expression of the melanoma cell adhesion molecule in human mesenchymal stromal cells determines their fate and regulates the maintenance of hematopoietic stem and progenitor cells through direct cell-cell contact.

Glacial ice supports a distinct and undocumented polar bear subpopulation persisting in late 21st-century sea-ice conditions.

Polar bears are susceptible to climate warming because of their dependence on sea ice, which is declining rapidly. We present the first evidence for a genetically distinct and functionally isolated group of polar bears in Southeast Greenland. These bears occupy sea-ice conditions resembling those projected for the High Arctic in the late 21st century, with an annual ice-free period that is >100 days longer than the estimated fasting threshold for the species. Whereas polar bears in most of the Arctic depend on annual sea ice to catch seals, Southeast Greenland bears have a year-round hunting platform in the form of freshwater glacial mélange. This suggests that marine-terminating glaciers, although of limited availability, may serve as previously unrecognized climate refugia. Conservation of Southeast Greenland polar bears, which meet criteria for recognition as the world's 20th polar bear subpopulation, is necessary to preserve the genetic diversity and evolutionary potential of the species.

S1P(1) overexpression stimulates S1P-dependent chemotaxis of human CD34+ hematopoietic progenitor cells but strongly inhibits SDF-1/CXCR4-dependent migration and in vivo homing.

The CXC chemokine receptor 4 (CXCR4) and its ligand stromal derived factor 1 (SDF-1) regulate egress and homing of hematopoietic stem cells. Activation of sphingosine-1-phosphate (S1P) receptors (S1P(1-5)) modulates chemokine-induced migration of lymphocytes and hematopoietic stem cells. To analyze the influence of S1P(1) on SDF-1-dependent chemotaxis and trafficking, we overexpressed S1P(1) in CD34+ mobilized peripheral blood progenitor cells (PBPCs). Using a gamma-retroviral vector, transgene overexpression was achieved in more than 90% of target cells. S1P(1) transgene positive PBPCs showed enhanced chemotaxis towards S1P. S1P(1) overexpression resulted in reduced CXCR4 surface expression levels and strong inhibition of SDF-1-dependent ERK1/2 phosphorylation and Ca(2+) flux. Furthermore, SDF-1-dependent migration of S1P(1) overexpressing PBPCs or Jurkat cells was reduced up to 10-fold. Sublethally irradiated NOD/SCID mice were transplanted with 6-day cultured PBPCs overexpressing either S1P(1)-IRES-GFP or GFP alone. Screening for GFP positive human cells in the mouse bone marrow 20h after transplantation revealed an eightfold reduction in bone marrow homing of S1P(1) transgene expressing cells. Our data suggest that S1P(1) acts as an inhibitor of CXCR4-dependent migration of hematopoietic cells to sites of SDF-1 production.

Improving drug discovery using image-based multiparametric analysis of the epigenetic landscape.

High-content phenotypic screening has become the approach of choice for drug discovery due to its ability to extract drug-specific multi-layered data. In the field of epigenetics, such screening methods have suffered from a lack of tools sensitive to selective epigenetic perturbations. Here we describe a novel approach, Microscopic Imaging of Epigenetic Landscapes (MIEL), which captures the nuclear staining patterns of epigenetic marks and employs machine learning to accurately distinguish between such patterns. We validated the MIEL platform across multiple cells lines and using dose-response curves, to insure the fidelity and robustness of this approach for high content high throughput drug discovery. Focusing on noncytotoxic glioblastoma treatments, we demonstrated that MIEL can identify and classify epigenetically active drugs. Furthermore, we show MIEL was able to accurately rank candidate drugs by their ability to produce desired epigenetic alterations consistent with increased sensitivity to chemotherapeutic agents or with induction of glioblastoma differentiation.

Histone H3 Phosphorylation in Human Skin Histoculture as a Tool to Evaluate Patient's Response to Antiproliferative Drugs.

Evaluation of patient's response to chemotherapeutic drugs is often difficult and time consuming. Skin punch biopsies are easily accessible material that can be used for the evaluation of surrogate biomarkers of a patient's response to a drug. In this study, we hypothesized that assessment of phosphorylated histone H3 in human skin punch biopsies could be used as a pharmacodynamics biomarker of patient's response to the kinesin spindle protein inhibitor SCH2047069. To test this hypothesis, we used a human skin histoculture technique that allows culturing intact human skin in the presence of the drug. Human melanoma and skin histocultures were treated with SCH2047069, and the effect of the drug was assessed by increasing histone H3 phosphorylation using immunohistochemistry. Our results demonstrate that SCH2047069 has a significant effect on cell proliferation in human melanoma and skin histoculture and justify using human skin punch biopsies for evaluation of the pharmacodynamic changes induced by SCH2047069. ACRONYMS: Histone subunit H3 (H3), Kinesin spindle protein (KSP), 5-ethynyl-2'-deoxyuridine (EDU), Dimethyl sulfoxide (DMSO), Formalin-fixed paraffin embedded (FFPE).

Progressive Chromatin Condensation and H3K9 Methylation Regulate the Differentiation of Embryonic and Hematopoietic Stem Cells.

Epigenetic regulation serves as the basis for stem cell differentiation into distinct cell types, but it is unclear how global epigenetic changes are regulated during this process. Here, we tested the hypothesis that global chromatin organization affects the lineage potential of stem cells and that manipulation of chromatin dynamics influences stem cell function. Using nuclease sensitivity assays, we found a progressive decrease in chromatin digestion among pluripotent embryonic stem cells (ESCs), multipotent hematopoietic stem cells (HSCs), and mature hematopoietic cells. Quantitative high-resolution microscopy revealed that ESCs contain significantly more euchromatin than HSCs, with a further reduction in mature cells. Increased cellular maturation also led to heterochromatin localization to the nuclear periphery. Functionally, prevention of heterochromatin formation by inhibition of the histone methyltransferase G9A resulted in delayed HSC differentiation. Our results demonstrate global chromatin rearrangements during stem cell differentiation and that heterochromatin formation by H3K9 methylation regulates HSC differentiation.

Robo4 cooperates with CXCR4 to specify hematopoietic stem cell localization to bone marrow niches.

Specific bone marrow (BM) niches are critical for hematopoietic stem cell (HSC) function during both normal hematopoiesis and in stem cell transplantation therapy. We demonstrate that the guidance molecule Robo4 functions to specifically anchor HSCs to BM niches. Robo4-deficient HSCs displayed poor localization to BM niches and drastically reduced long-term reconstitution capability while retaining multilineage potential. Cxcr4, a critical regulator of HSC location, is upregulated in Robo4(-/-) HSCs to compensate for Robo4 loss. Robo4 deletion led to altered HSC mobilization efficiency, revealing that inhibition of both Cxcr4- and Robo4-mediated niche interactions are necessary for efficient HSC mobilization. Surprisingly, we found that WT HSCs express very low levels of Cxcr4 and respond poorly to Cxcr4 manipulation relative to other hematopoietic cells. We conclude that Robo4 cooperates with Cxcr4 to endow HSCs with competitive access to limited stem cell niches, and we propose Robo4 as a therapeutic target in HSC transplantation therapy.

Impact of CXCR4 inhibition on FLT3-ITD-positive human AML blasts.

OBJECTIVE: Internal tandem duplication (ITD) mutations of the FLT3 receptor are associated with a high incidence of relapse in acute myeloid leukemia (AML). Expression of the CXCR4 receptor in FLT3-ITD-positive AML is correlated with poor outcome, and inhibition of CXCR4 was shown to sensitize AML blasts toward chemotherapy. The aim of this study was to evaluate the impact of FLT3-ITD on cell proliferation and CXCR4-dependent migration in human hematopoietic progenitor cells and to investigate their response to CXCR4 inhibition. MATERIALS AND METHODS: We used primary blasts from patients with FLT3-ITD or FLT3 wild-type AML. In addition, human CD34(+) hematopoietic progenitor cells were transduced to >70% with retroviral vectors containing human FLT3-ITD. RESULTS: We found that FLT3-ITD transgene overexpressing human hematopoietic progenitor cells show strongly reduced migration toward stromal-derived factor-1 in vitro and display significantly reduced bone marrow homing in nonobese diabetic severe combined immunodeficient mice. Cocultivation of FLT3-ITD-positive AML blasts or hematopoietic progenitor cells on bone marrow stromal cells resulted in a strong proliferation advantage and increased early cobblestone area-forming cells compared to FLT3-wild-type AML blasts. Addition of the CXCR4 inhibitor AMD3100 to the coculture significantly reduced both cobblestone area-forming cells and proliferation of FLT3-ITD-positive cells, but did not affect FLT3-wild-type cells-highlighting the critical interaction between CXCR4 and FLT3-ITD. CONCLUSION: CXCR4 inhibition to decrease cell proliferation and to control the leukemic burden may provide a novel therapeutic strategy in patients with advanced FLT3-ITD-positive AML.

Notch signaling enhances osteogenic differentiation while inhibiting adipogenesis in primary human bone marrow stromal cells.

OBJECTIVE: The Notch signaling pathway has been shown to play a role in bone marrow-derived stromal cell differentiation, however, the precise outcome of Notch activation remains controversial. The aim of this study was to evaluate the effect of Notch signaling in primary human bone marrow-derived stromal cells (hBMSCs). MATERIALS AND METHODS: hBMSCs were transduced to >90% with lentiviral vectors containing either human notch1 intracellular domain (NICD), jagged1, or dominant negative mastermind1. Cells were exposed to adipogenic and osteogenic differentiation stimuli and differentiation was quantified by oil red or alizarin red staining, alkaline phosphatase liver/bone/kidney (ALPL) activity and expression of adipogenic or osteogenic marker genes. RESULTS: NICD and jagged1 transgene-expressing hBMSCs demonstrated enhanced mineralization, nodule formation, and ALPL activity in osteogenic differentiation media. These findings correlated with increased gene expression of bone morphogenetic protein 2 and ALPL. In contrast, NICD or jagged1 transgene expression strongly inhibited adipocyte formation and reduced peroxisome proliferator-activated receptor-gamma, fatty acid binding protein 4, and adiponectin precursor gene expression. Co-overexpression of dominant negative mastermind1 and NICD or jagged1 led to a partial rescue of the differentiation phenotypes. In addition, high endogenous jagged1 expression levels were observed in hBMSCs samples with strong ALPL activity compared to a group of samples with low ALPL activity. CONCLUSION: In summary, our data suggest that induction of Notch signaling enhances the osteogenic differentiation of hBMSCs while inhibiting the adipogenic fate.

mRNA transfection of CXCR4-GFP fusion--simply generated by PCR-results in efficient migration of primary human mesenchymal stem cells.

We present a general, entirely PCR-based strategy to construct mRNAs coding for green fluorescent protein (GFP) fusion proteins from a cDNA pool. We exemplify our approach for the chemokine receptor CXCR4. mRNA transfection of the PCR-generated fusion of CXCR4-GFP into K562 cells or primary mesenchymal stem cells (MSCs) resulted in excellent viability (> 90%) with more than 90% of target cells expressing easily detectable CXCR4-GFP for > 72 h. The fusion protein was localized in the plasma membrane and was rapidly internalized upon incubation with the CXCR4 ligand stromal cell-derived factor-1 (SDF-1). Transwell migration experiments showed significantly increased migration of CXCR4-GFP mRNA-transfected MSCs toward a gradient of SDF-1, demonstrating that mRNA-mediated chemokine receptor overexpression allows for transient initiation of chemotaxis. The presented strategy to construct a PCR-based fluorescent fusion protein can be generally applied to other genes of interest to study their function by simple overexpression and easy detection in primary cells.

Tratamiento ortodóncico de primera fase en un paciente con displasia dentinaria tipo I / First phase orthodontic treatment of a patient with dentin dysplasia type I

La displasia dentinaria (DD) es una condición autosómica dominante que afecta tanto los dientes temporales como los permanentes. En ella se observan piezas con defectos en la forma de sus raíces, parcial o completa obliteración de las cámaras pulpares, y predisposición para formar abscesos y quistes sin una causa previa. Se describe en la población en una proporción de 1 cada 100.000 pacientes. Esta anomalía fue descrita por primera vez en 1920, pero en 1939 se lo denominó como DD y luego, en 1957, Zellner se percató de su predisposición hereditaria por lo que consideró esta lesión como un síndrome de malformación mesodérmica. Histológicamente, el esmalte y la dentina de la corona aparecen normales, las cámaras pulpares se observan de forma semilunar y casi completamente obliteradas radiográficamente. En un artículo realizado se pudo concluir que su posible etiología sería un defecto en el componente epitelial, donde la invaginación de la vaina epitelial de Hertwig ocurre tempranamente, resultando en una raíz atrofiada con cámara y conductos radiculares obliterados.

Acoustic characteristics of underwater tail slaps used by Norwegian and Icelandic killer whales (Orcinus orca) to debilitate herring (Clupea harengus).

Norwegian killer whales debilitate prey by slapping their tails into herring schools. These underwater tail slaps produce a thud-like sound. It is unclear whether this sound is caused by cavitation and/or physical contact between herring and whale tail. Also the forces causing debilitation of the fish are not understood. Here we present an acoustic analysis of underwater tail slaps using a multi-channel wide (150 kHz) band recording system. Underwater tail slaps produced by Norwegian killer whales generated sounds consisting of multiple pulses with source levels of 186+/-5.4 dB (pp) re.1 microPa at 1 m (+/-1 s.d., N = 4). The -3 dB and 97% energy bandwidths were 36.8+/-22.5 kHz and 130.5+/-17.5 kHz (+/-1 s.d., N = 13), respectively, with a centre frequency of 46.1+/-22.3 kHz. The similarities between the acoustic properties of underwater tail slaps recorded from killer whales in Norway, and thud-like sounds recorded from killer whales in Iceland suggest that Norwegian and Icelandic killer whales use similar hunting techniques. The acoustic characteristics of sounds produced by underwater tail slaps were similar to the ones from other cavitation sound sources described in the literature, both in term of temporal and frequency features as well as in source level. We suggest that multiple factors generated by the tail slaps like particle fluctuations, turbulence, pressure changes and physical impact cause debilitation of herring.

Ethical aspects of sexual medicine.

INTRODUCTION: Ethics describe the ways in which moral life is understood. Morality comprises norms for human conduct, and addresses what is right and what is wrong. AIM: To provide a consensus-based summary of the ethical aspects of sexual medicine. METHODS: Over 200 multidisciplinary specialists from 60 countries were divided into 17 consultation committees as part of a process organized by an international consultation on sexual medicine held in Paris, June 28-July 1, 2003 in close alliance with several sexual medicine organizations. Embarking on a study on ethics in sexual medicine, 10 experts from eight countries assembled over a two-year period to develop this consensus-based summary. MAIN OUTCOME MEASURE: Although ethics are recognized as subjective, expert opinion was based on grading of evidence-based medical literature, in addition to cultural and ethical considerations. The process also involved extensive internal committee discussion, public presentation, and debate. RESULTS: Contemporary medical practitioners provide health care for patients from many different cultures from all around the world. Thus, it is recommended that all health professionals working in sexual medicine should above all be able to demonstrate respect, understanding, and tolerance toward the differing moral worldviews of their patients and colleagues, and the societies they represent. In sexual medicine, health professionals have an obligation to respect the autonomy of any individual that they treat, regardless of that individual's religious or socio-cultural tradition, race, gender, or sexual orientation. Sexual rights are a necessary condition for sexual health. Sexual health requires a positive and respectful approach to sexuality and sexual relationships as well as the possibility of having pleasurable and safe sexual experiences, free of coercion, discrimination, and violence. For sexual health to be attained and maintained, the sexual rights of all persons must be respected, protected, and fulfilled. CONCLUSIONS: Additional discussion and research on ethics in sexual medicine is needed.

Efectos de algunos fármacos e intervenciones quirúrgicas en la vida sexual / Effects of some pharmacos and surgical interventions in the sexual life

"Se presenta una revisión de las investigaciones acerca del efecto de algunos fármacos en las distintas fases de la respuesta sexual. Aunque existen numerosos reportes de los efectos adversos, en su mayoría son reportes de caso; y en muchos de ellos no se aclara cuál de estas fases estuvo alterada. Se aborda el tema separando los efectos de los medicamentos, empleados en la práctica diaria de la medicina, sobre cada una de las fases de la respuesta sexual. Hicimos mayor énfasis en los efectos de fármacos en la fase del deseo, ya que (hasta hace pocos años) es la que menos se había abordado en la literatura internacional. Se mencionan también algunos escritos relacionados con el efecto afrodisiaco de algunas sustancias, tema atractivo desde hace siglos hasta nuestros días, en donde no existen evidencias contundentes como se hubiera pensado. Sin duda los grupos de medicamentos que más comúnmente se vinculan con efectos colaterales en la sexualidad son las drogas de abuso, depresores de sistema nervioso central (SNC), los antihipertensivos, los antidepresivos, los compuestos hormonales, los neurolépticos, los quimoterapéuticos para cáncer y los empleados para cardiopatías crónicas. Aunque a lo largo de la exposición se presentan diversas hipótesis causales, no se ha establecido con precisión el mecanismo fisiopatológico de afectación de la respuesta sexual"