The impact of health and environmental factors on a population of Mekong River Irrawaddy dolphins (Orcaella brevirostris) in Cambodia

Background The critically endangered Mekong River Irrawaddy dolphin (MRID) (Orcaella brevirostris) population, estimated to comprise 85 individuals in 2010, is at risk of extirpation due to a high level of mortality, particularly in calves, and a very low recruitment level (<1%) into the population; however existing studies have failed to identify the causes of mortality in this population. In this study, a retrospective study was conducted to better understand the causes of mortality in different age classes, so that potentially mortality levels can be mitigated and recruitment rates improved. Methods Mortality data from 2001-2010 were analysed to identify mortality trends in 102 MRIDs. Samples were also collected from 41 necropsied dolphins and subjected to microbiological, histopathological, genetic and toxicological analyses to identify and quantify the threats to this population. Additionally, a study of skin lesions using photo-identification data of live MRIDs from 2007 to 2010 was conducted. Results In this study, significantly high levels of immuno-toxic pollutants, particularly DDT and mercury; genetic factors, specifically genetic drift and outbreeding depression; and disease and immunosuppression; were all contributing towards the population’s decline. Dead calves were 15 times (95%CI 2.4, 88.1, p=0.001) more likely to have a localised gangrenous, blue/black neck lesion than dead adult dolphins. These lesions were clinically, pathologically and microbiologically similar to necrotising fasciitis of humans. In contrast, adults were 17 times (95%CI of 1.8, 166.1, p=0.006) more likely to have evidence of interaction with fishery activities than juveniles and calves. The incidence of mortality in adults over a three year period when gillnets were used was 18.3% (95%CI 11.6, 26.9), and this reduced to 6.7% (95%CI 2.5, 14.1) when restrictions on the use of gillnets were introduced. The risk of dying during the three years with gillnets was 2.7 times (95%CI 1.1, 6.5) higher than the period when gillnet use was restricted (p=0.016). In contrast, there was no significant difference in mortality for calves for years with and without gillnet restrictions (p=0.39). Skin lesions were common in live MRIDs being detected in 35 of 84 individuals observed (41.6%; 95%CI 31.1, 52.2) over a three year period. However, the mean prevalence of MRIDs photographed with skin lesions during 11 surveys was 7% (95%CI 1.9, 16.7), with a significant difference found in the prevalence of skin lesions in MRIDs from pools 1 and 9 (Fisher’s exact test p=0.002). In necropsied MRIDs (n=8), significantly more calves 100% (95%CI 47.8, 100) had neck lesions and associated neck swelling with wet gangrenous musculature than adults (0%; 95%CI 0.0, 70.8) (p=0.018). The three most frequent bacteria cultured in 13 dolphins examined with neck lesions were Aeromonas hydrophila (54%, 95%CI 25.1, 80.8), Plesiomonas shigelloides (46%, 95%CI 19.2, 74.9), and ß-haemolytic Group C Streptococcus spp. (23%, 95%CI 5, 53.8). Toxicological analysis in a larger sample set (n=20), revealed that the levels of mercury (Hg) and methylmercury (MeHg) were significantly higher in the adult dolphins sampled than in calves (11.21μg/g vs. 1.51μg/g, p=0.019; 7.23μg/g vs. 0.72, p=0.033, respectively). In contrast, calves had significantly higher levels of liver copper (Cu) than adults (40.72μg/g vs. 3.49μg/g, p=0.0005). Adults also had a significantly higher level of Hg (11.21 μg/g vs. 0.91 μg/g, p=0.026) and MeHg (7.23 μg/g vs. 0.17 μg/g, p=0.006) than juveniles. The mean molar selenium:mercury ratio was significantly higher in calves (2.27, p=0.039) and juveniles (2.94, p=0.007) than in adults (0.95). The level of zinc (Zn) in the liver of adults with neck lesions (28.7μg/g) was significantly lower (p=0.049) than that of adults without evidence of neck lesions (65.17μg/g). The concentrations of organochlorines in the blubber of MRID decreased in the order of DDTs > PCBs > CHLs > HCB > PBDEs > Dioxins > OC. The level of ΣDioxins was significantly higher in adults (2.27TEQ) than in calves (1.15TEQ, p=0.004), and also significantly higher in juveniles (3.57TEQ) than in calves (p=0.0094). The levels of PCBs in adults (346.9ng/g) and in juveniles (705.4ng/g) were significantly higher than in calves (142.75ng/g) (p=0.019, p=0.012, respectively). Adult females had higher ΣDioxin levels (61.3pg/g; 2.27TEQ) than female (3.7pg/g, p=0.0017; 1.15 TEQ p=0.02) and male calves (2.8pg/g, p=0.003; 0.99 TEQ, p=0.01). Juvenile females had significantly higher ΣDioxins (3.57TEQ) and ΣPCBs (705.4ng/g) than female (1.15TEQ, p=0.02; 163.2ng/g, p=0.016) and male calves (0.99TEQ, p=0.01; 142.8ng/g, p=0.03) respectively. Adult males had significantly higher PCB levels (606.8ng/g) than female (163.2ng/g, p=0.01) and male calves (142.8 ng/g, p=0.03). The levels of ΣPBDE, ΣCHLDs, ΣDDT and ΣHCB were all significantly higher in MRIDs than in the Chilika Lake Irrawaddy dolphins from the study of Kannan et al. (2005) (p=0.0007). Phylogenetically the MRIDs appear to be an evolutionary significant unit (ESU), with six new haplotypes identified in this study. The average nucleotide diversity (π) was 0.001 ( SD 0.0001) and the average haplotype diversity (h) was 0.812 ( SD 0.333). 34% (n=11) of the necropsied MRIDs had Infrequent/Rare (I/R) alleles, with an excess found in the adults compared to the calves, indicating a strong likelihood of genetic drift occurring. Paternity tests suggested reproductive failure, as only a few dolphins were breeding in the population and breeding females were genetically related. Conclusions It is concluded that two principal factors are driving the population decline. Firstly, the interaction of adults with commercial fishery activities and secondly, necrotising fasciitis associated with neck lesions in the calves. Furthermore, reproductive failure is a major contributing factor limiting recruitment into the population and ultimately affecting the population stability. This study highlights the need for urgent attention to save this population from certain extirpation

Production and characterization of glass-ceramic materials for potential use in dental applications: thermal and mechanical properties, microstructure, and in vitro bioactivity

Multicomponent silicate glasses and their corresponding glass-ceramic derivatives were prepared and tested for potential applications in dentistry. The glasses were produced via a melting-quenching process, ground and sieved to obtain fine-grained powders that were pressed in the form of small cylinders and thermally treated to obtain sintered glass-ceramic samples. X-ray diffraction investigations were carried out on the materials before and after sintering to detect the presence of crystalline phases. Thermal analyses, mechanical characterizations (assessment of bending strength, Young’s modulus, Vickers hardness, fracture toughness), and in vitro bioactivity tests in simulated body fluid were performed. On the basis of the acquired results, different potential applications in the dental field were discussed for the proposed glass-ceramics. The use of such materials can be suggested for either restorative dentistry or dental implantology, mainly depending on their peculiar bioactive and mechanical properties. At the end of the work, the feasibility of a novel full-ceramic bilayered implant was explored and discussed. This implant, comprising a highly bioactive layer expected to promote osteointegration and another one mimicking the features of tooth enamel, can have an interesting potential for whole tooth substitution

Physical, Mechanical, and Biological Properties of PMMA-Based Composite Bone Cement Containing Silver-Doped Bioactive and Antibacterial Glass Particles with Different Particles Sizes

Abstract: In the present work, antibacterial composite bone cement was designed by introducing a bioactive and antibacterial glass into a commercial formulation. The effect of glass particles’ addition on the curing parameters of the polymeric matrix was evaluated; moreover, the influence of the glass particle size on the glass dispersion, compressive and bending strength, bioactivity, and antibacterial effect was estimated. The results evidence a delay in the polymerization kinetics of the composite cement, which nevertheless complies with the requirements of the ISO standard. Morphological characterization provides evidence of good dispersion of the glass in the polymeric matrix and its exposition on the cement surface. The different glass grain sizes do not affect the composites’ bioactivity and compressive strength, while a slight reduction in bending strength was observed for samples containing glass powders with greater dimensions. The size of the glass particles also appears to have an effect on the antibacterial properties, since the composites containing larger glass particles do not produce an inhibition halo towards the S. aureus strain. The obtained results demonstrate that, by carefully tailoring the glass amount and size, a multifunctional device for artificial joint fixing, temporary prostheses, or spinal surgery can be obtained

Sol-gel synthesis of spherical monodispersed bioactive glass nanoparticles co-doped with boron and copper

In this work, an optimized sol-gel process for the synthesis of spherical and monodispersed bioactive glass nanoparticles doped with boron and copper was developed, by investigating different synthesis parameters. The obtained glasses were characterized in terms of morphology, composition, dispersibility, structure and in vitro reactivity. The performed characterizations demonstrated that shape, dimension and dispersion can be tailored by acting on the timing of the addition of the catalyst and on the synthesis process, in particular the centrifugation step. The optimized glass particles showed a spherical shape, good ions incorporation and good dispersion. In vitro bioactivity test demonstrated that the boron and copper addition did not interfere with the glass ability to induce the precipitation of hydroxyapatite. The shape, dispersion, bioactive behavior and content of boron and copper of these novel bioactive glass particles make them very promising for both hard and soft tissue engineering applications

Bioactive glasses: from parent 45S5 composition to scaffold-assisted tissue-healing therapies

Nowadays, bioactive glasses (BGs) are mainly used to improve and support the healing process of osseous defects deriving from traumatic events, tumor removal, congenital pathologies, implant revisions, or infections. In the past, several approaches have been proposed in the replacement of extensive bone defects, each one with its own advantages and drawbacks. As a result, the need for synthetic bone grafts is still a remarkable clinical challenge since more than 1 million bone-graft surgical operations are annually performed worldwide. Moreover, recent studies show the effectiveness of BGs in the regeneration of soft tissues, too. Often, surgical criteria do not match the engineering ones and, thus, a compromise is required for getting closer to an ideal outcome in terms of good regeneration, mechanical support, and biocompatibility in contact with living tissues. The aim of the present review is providing a general overview of BGs, with particular reference to their use in clinics over the last decades and the latest synthesis/processing methods. Recent advances in the use of BGs in tissue engineering are outlined, where the use of porous scaffolds is gaining growing importance thanks to the new possibilities given by technological progress extended to both manufacturing processes and functionalization techniques

Por una Educación Física inclusiva en el marco del fracaso escolar : Aportes y reflexiones

La experiencia realizada forma parte de un proyecto de extensión. El objetivo del mismo es acompañar procesos de retención en tres escuelas medias en contextos con altos niveles de exclusión de S.C.de Bariloche. El fracaso escolar, cuestión preocupante y compleja, constituye uno de los problemas fundamentales de estas comunidades educativas. Desde la propuesta de intervención que fundamenta la extensión, la Educación Física, aborda la problemática, a través de actividades en el medio natural. De esta manera se brinda al adolescente y adulto estudiante, un espacio que le permite una auto percepción en otro ámbito, promoviendo de esta manera, la reconstrucción del autoconcepto y la autoestima, compartiendo con pares una experiencia, que favorece su inclusión grupal, la pertenencia a la institución y fortalece identidades al pensarse en sus procesos de aprendizaje (metacognición). La propuesta aborda contenidos disciplinares, interculturales, expresivos, ecológicos y de formación ciudadana. De esta manera se conceptualiza a la Educación Física como práctica social integrada al proceso educativo institucional y al contexto sociohistórico. Desde nuestra perspectiva esta propuesta pretende constituir una experiencia innovadora por integrar a la Educación Física a un proyecto institucional asociado con la retención y el fracaso; y posicionarla como espacio integrador de contenidos transversales.Panel "Educación e inclusión social".Departamento de Educación Físic