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Chromosomal assignment of the human gene for endosarcomeric cytoskeletal M-protein (MYOM2) to 8p23.3
(1999)
Myomesin and M-Protein
(1999)
Na transport in sheep rumen is modulated by voltage-dependent cation conductance in apical membrane
(1999)
Changing functionality of surfaces by directed self-assembly using oligonucleotides - the oligo-tag
(1999)
Theoretical models indicate that natural populations may be structured in such a way that many individuals occur in habitats where reproduction is insufficient to balance mortality. The persistence of such 'sink' populations depends on immigration from neighboring 'source' habitats where local reproduction exceeds mortality. While source-sink dynamics has become a fundamental concept in ecological theory, there has been virtually no experimental test for the existence of sources and sinks in natural populations. This paper reports the results of a four-year study that was designed to experimentally test for source-sink population dynamics in desert annual communities. Based on evidence from a variety of desert ecosystems indicating that patchiness caused by the presence of shrubs is important in structuring desert annual communities, we distinguished between two types of habitats: areas beneath the canopy of shrubs and the open areas between the shrubs. If, as suggested in previous studies, source-sink dynamics is important in structuring such annual communities, one would expect that removal of populations from one habitat leads to extinction of some species in the other habitat. We tested this prediction using removal experiments. Specifically, we monitored density responses of annual populations inhabiting open areas to the repeated removal of conspecific populations from the shrubs and vice versa. Four years after establishment of the experiment, none of the studied 34 species responded to the removal treatments with habitat-specific extinction. Only one species exhibited a significant habitat-specific decrease in density in response to the removal of conspecific populations from the other habitat. These findings contradict our expectations and point to the importance of applying an experimental approach in studies of source-sink dynamics.
Sightings and migration patterns of 65 bean and 65 white-fronted geese are reported. These geese were tagged and serologically screened. 19 of the 53 birds sighted had serologic evidence of Newcastle Disease. The migration patterns of the wild geese provided further evidence that the main resting and wintering sites of migratory waterfowl are likely to be important for the inter- and intraspecies transmission of avian diseases.
Modulation of sarcomere assembly during embryonic stem cell-derived cardiomycyte differentiation.
(1999)
Modelling the competitiveness of clonal plants by complementary analytical and simulation approaches
(1999)
The C-protein (myosin binding protein C) family : regulators of contraction and sarcomere function?
(1999)
A shallow, saline lake (Rookery Lake) close to the sea and surrounded by a penguin rookery was investigated during the austral spring and summer of 1996/1997. The proximity to the sea means that the lake is likely to have been formed recently during isostatic uplift. Inputs of carbon and nutrients from the penguin rookery have rendered Rookery Lake eutrophic compared with other brackish and saline lakes in the Vestfold Hills. Chlorophyll a concentration, bacterioplankton, heterotrophic nanoflagellate and phototrophic nanoflagellate abundances were all significantly higher than in other non-enriched lakes. The high productivity created seasonal anoxia during winter and spring below ice cover. The ciliate community resembled the marine community, and was dissimilar to that seen in older saline lakes within the Vestfold Hills. Thus Rockery Lake provides valuable evidence of the impact of natural eutrophication on an Antarctic lake, as well as of the evolution of the typical microbial community which dominates the older lakes of the Vestfold Hills.
1. The plankton dynamics of Ace Lake, a saline, meromictic basin in the Vestfold Hills, eastern Antarctica was studied between December 1995 and February 1997. 2. The lake supported two distinct plankton communities; an aerobic microbial community in the upper oxygenated mixolimnion and an anaerobic microbial community in the lower anoxic monimolimnion. 3. Phytoplankton development was limited by nitrogen availability. Soluble reactive phosphorus was never limiting. Chlorophyll a concentrations in the mixolimnion ranged between 0.3 and 4.4 mu g L-1 during the study period and a deep chlorophyll maximum persisted throughout the year below the chemo/oxycline. 4. Bacterioplankton abundance showed considerable seasonal variation related to light and substrate availability. Autotrophic bacterial abundance ranged between 0.02 and 8.94 x 10(8) L-1 and heterotrophic bacterial abundance between 1.26 and 72.8 x 10(8) L-1 throughout the water column. 5. The mixolimnion phytoplankton was dominated by phytoflagellates, in particular Pyramimonas gelidicola. P. gelidicola remained active for most of the year by virtue of its mixotrophic behaviour. Photosynthetic dinoflagellates occurred during the austral summer, but the entire population encysted for the winter. 6. Two communities of heterotrophic flagellates were apparent; a community living in the upper monimolimnion and a community living in the aerobic mixolimnion. Both exhibited different seasonal dynamics. 7. The ciliate community was dominated by the autotroph Mesodinium rubrum. The abundance of M. rubrum peaked in summer. A proportion of the population encysted during winter. Only one other ciliate, Euplotes sp., occurred regularly. 8. Two species of Metazoa occurred in the mixolimnion; a calanoid copepod (Paralabidocera antarctica) and a rotifer (Notholca sp.). However, there was no evidence of grazing pressure on the microbial community. In common with most other Antarctic lakes, Ace Lake appears to be driven by 'bottom-up' forces.