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[en] Although the normal adult human intervertebral disc is considered to be avascular, vascularised cellular fibrous tissue can be found in pathological conditions involving the disc such as disc herniation. Whether lymphatics vessels form a component of this reparative tissue is not known as the presence or absence of lymphatics in herniated and normal disc tissue is not known. We examined spinal tissues and discectomy specimens for the presence of lymphatics. The examination used immunohistochemistry to identify the specific lymphatic endothelial cell markers, podoplanin and LYVE1. Lymphatic vessels were not found in the nucleus pulposus or annulus fibrosus of intact, non-herniated lumbar and thoracic discs but were present in the surrounding ligaments. Ingrowth of fibrous tissue was seen in 73% of herniated disc specimens of which 36% contained LYVE1+/podoplanin + lymphatic vessels. Lymphatic vessels were not seen in the sacrum and coccyx or biopsies of four sacrococcygeal chordomas, but they were noted in surrounding extra-osseous fat and fibrous tissue at the edge of the infiltrating tumour. Our findings indicate that lymphatic vessels are not present in the normal adult intervertebral disc but that, when there is extrusion of disc material into surrounding soft tissue, there is ingrowth of reparative fibrous tissue containing lymphatic vessels. Our findings also indicate that chordoma, a tumour of notochordal origin, spreads to regional lymph nodes via lymphatics in para-spinal soft tissues. (orig.)
[en] Considerable information is available on the effects of radioactivity on adult and early life stages of organisms. The preponderance of data is on mortality after a single irradiation with relatively high doses. Unfortunately, because experiments were carried out under different conditions and for different time periods, the validity of comparing the results from different laxonomic groups is questionable. In general, the conclusions are that there is a relationship (1) between radioresistance to high doses of acute radiation and taxonomy of the organism, primitive forms being more radioresistant than complex vertebrates and (2) between radiosensitivity and developmental stage, early life stages being more sensitive than later stages. The first conclusion may be related to the capability of the organism to repopulate cells and to differentiate and redifferentiate them; the second to the rate of cellular division and to the degree of differentiation. In question, however, is the relevance of the responses from high levels of acute radiation to that of the responses to long-term exposure to low levels of radiation, which are ecologically of more interest. Data from studies of the effects of acute and chronic exposure on development of gametes and zygotes indicate that, for some fishes and invertebrates, responses at the cellular and molecular levels show effect levels comparable to those observed in some mammals. Acute doses between 0,05 and 0.5Cy and dose rates between 0.02 to 0.2mCy/h appear to define critical ranges in which detrimental effects on fertility are first observed in a variety of radiosensitive organisms. To better understand inherent radiosensitivity, we need more information on the ability of cells to repopulate and differentiate and to prevent or repair damage to biological critical molecules, such as DNA, because these factors may alter significantly organisms'' responses to radiation
[en] Fluctuations in population dynamics, like demographic expansions and invasions, are relatively common in ecosystems, and in certain cases may affect biodiversity and a suite of other ecological attributes. In this paper, we report the appearance and population explosion of the reef-building polychaete (Sabellariidae) Idanthyrsus cf. cretus in Gorgona Island (Eastern Tropical Pacific), describing some ecological characteristics (abundance and coverage). The survey was carried out in three study areas of Gorgona Island, located in the Colombian Pacific. Sampling was performed randomly at low, mid and high intertidal levels, in order to measure density and coverage. Density was measured randomly in three study areas at low, mid and high intertidal levels collecting samples (N=37) of 100 cm2 from the colony. Coverage was measured using random transects (N=21) per locality and intertidal levels (20 m length per 1 m width). A total of 1,904 I. cf. cretus were collected with a mean density of 73 ind./100 cm2. Coverage was statistically different between intertidal zones, with the highest values in the mid-intertidal level (11%). Differences in coverage of I. cf. cretus colonies among study areas are probably due to differing intertidal physical characteristics: the availability of adequate substrate and building materials in the study areas sediments, which in turn might affect abundance and colony size. Suitable substrate and construction material might have favored the rapid spreading and local invasion of this species.
[en] The immune system maintains the integrity of the organisms through a complex network of molecules, cells, and tissues that recognize internal or external antigenic substances to neutralized and eliminate them. The mechanisms of immune response have evolved in a modular fashion, where members of a given module interact strongly among them, but weakly with members of other modules, providing robustness and evolvability to the immune system. Ancestral modules are the raw material for the generation of new modules through evolution. Thus, the study of immune systems in basal metazoans such as cnidarians seeks to determine the basic tool kit from which the metazoans started to construct their immune systems. In addition, understanding the immune mechanisms in cnidarians contributes to decipher the etiopathology of coral diseases of infectious nature that are affecting coral reefs worldwide.
[en] Red wood ant (Formica rufa group) nests contain a highly diverse community of invertebrates, which is largely due to their abundant resources and regulated microclimatic conditions. Clear-felling, however, causes nest mounds to lose surface layer moisture, thus disrupting their inner stability. To study the effects of clear-felling on ant-associated beetles (myrmecophile and non-myrmecophile), 41 nests of Formica aquilonia Yarrow, 1955 located on three clear-fells and adjacent mature forest stands were sampled, and the beetle communities between these habitats were compared. We investigated how habitat type, nest surface moisture content, nest volume, and isolation affect the community composition, species richness, and abundance of beetles. Beetle community composition or species richness did not markedly differ between clearings and forests, although total abundance was higher in forests. Also, total species richness and abundance and myrmecophile abundance increased with increasing moisture content. Overall, nests with similar moisture content and volume had similar species compositions. Nest volume was negatively correlated with myrmecophile species richness. Nest isolation was not related to species richness or abundance. The lower abundances in clearings could be problematic in the long term, as small populations are more likely to become extinct. To ensure the survival of ants and their associates, small-scale clearings should be preferred. (author)
[en] The changes in algal and invertebrate communities resulting from the formation and operation of two water reservoirs in Saskatchewan were studied. Lake Diefenbaker was created in 1967 by flooding a river valley, whereas Buffalo Pound Lake was formed in 1952 by impounding the outflow of a shallow lake. Both lakes were studied using a multiple-indicator paleolimnological approach. Algal community composition is similar between the two reservoirs and biomass is distributed evenly among green algae, diatoms, chrysophyte, dinoflagellates, cryptophytes and cyanobacteria. Crustacean zooplankton are also similar between the two reservoirs. Sediment core was retrieved from both reservoirs and analyzed. It was shown that differences in reservoir formation and hydrological regime resulted in distinct patterns of aquatic community change even though the local geology, vegetation, soils, land use and climate were similar. Comparison of paleoecological records from both lakes have made it possible to compare the mechanisms that regulate community ontogeny and production following formation of reservoirs by novo flooding and lake inundation. It was determined that reservoir ontogeny does not inevitably lead to eutrophication. Fossil records have shown that oligotrophication can result from increased lake level stability, reduced erosion and complex ecological interactions among phytoplankton, grazers, and macrophyte populations. 49 refs., 2 tabs., 6 figs