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Adult mesenchymal stem cells (MSC) that are able to differentiate into various mesenchymal cell types are typically isolated from bone marrow, but their significant presence in human peripheral blood (PB) is controversial. Fibrin microbeads (FMB) that bind matrix-dependent cells were used to isolate MSC from the mononuclear fraction of mobilized PB of adult healthy human donors treated with a granulocyte colony-stimulating factor. Isolation by plastic adherence resulted in a negligible number of MSC in all samples tested, whereas FMB-based isolation yielded spindle-shaped cell samples that could further expand on plastic or on FMB in eight out of the 11 samples. The yield of these cells at days 17–18 after the harvest was ∼0.5% of the initial cell number. The isolated cells were grown on plastic and characterized by FACS analysis and immunohistochemistry for specific markers. Following culturing and first passage, the FMB-isolated cells stained positive for mesenchymal stromal cell markers CD90 and CD105, expressed vimentin and fibronectin and were negative for hematopoietic markers CD45 and CD34. These cells could differentiate into osteoblasts, adipocytes and chondrocytes. This study indicates that FMB may have special advantage in isolating MSC from sources such as mobilized PB, where the number of such cells is scarce.Bone Marrow Transplantation (2006) 37, 967–976. doi:10.1038/sj.bmt.1705358 [ABSTRACT FROM AUTHOR]

Algal and bacterial biomass and production were measured in the plankton, platelet ice and congelation ice communities at one station in McMurdo Sound, Antarctica during September and October 1986. Bacterial abundances and particulate organic carbon and nitrogen were 10 to 100 times greater in the plankton than in the sea ice, whereas the chlorophyll a concentrations in the plankton and sea ice microbial communities (SIMCO) were similar Rates of both light-limited and light-saturated photosynthesis and daily primary production were 2 to 6 times greater in the plankton than in the SIMCO. Bacterial growth rates ranges from 0.7 to 1.5 d in all three communities; however, because of the greater bacterial biomass in the plankton, bacterial production was 15 to 20 times higher there than in the SIMCO. These results suggest that during the early austral spring, planktonic production contributes significantly to total production in ice-covered environments. [ABSTRACT FROM AUTHOR]

Diel patterns of photosynthesis were measured for two polar diatoms ( Coscinodiscus sp. and Porosira pseudodenticulata) collected in September 1985 from McMurdo Sound, Antarctica, and four temperate dinoflagellates ( Gonyaulax hyalina, Gymnodinium splendens, Dinophysis caudata, and Glenodinium sp.) collected in July 1985 and January 1986 from the Southern California Bight, California, USA. For phytoplankton incubated under three combinations of photoperiod and irradiance, distinct diel patterns of light-saturated ( P) and light-limited ( P) photosynthesis were found for (i) different species isolated from the same environment, and (ii) polar diatoms and temperate dinoflagellates. The time of day when the maximum rate of P occurred was influenced by both irradiance and daylength for the polar diatoms but not by daylength for three out of four temperate dinoflagellates. The range of values of the ratio of maximum to minimum rates of photosynthesis ( P: P) was similar for polar diatoms and temperate dinoflagellates. The results of this study suggest that changes in irradiance or photoperiod could influence species-specific patterns of photosynthesis in nature. As a consequence, in light-limited environments differential reproductive success could result from these diel patterns, and ultimately be reflected in temporal and spatial differences in community structure. [ABSTRACT FROM AUTHOR]

The phosphorus metabolism of Pyrocystis noctiluca Murray (Schuett) 1886 has characteristics which may enhance its potential for success in orthophosphate impoverished waters. The steady-state phosphate uptake rates were equal in the light and dark, and were directly proportional to both the phosphorus cell quota and the cell division rate. In contrast, nutrient-saturated uptake rates were multiphasic, faster in the light than the dark, 2 to 4 orders of magnitude greater than steady-state rates, and were inversely proportional to both the phosphorus cell quota and the cell division rate. These uptake characteristics suggest that P. noctiluca may take up phosphate coincidently at their typically low ambient concentrations as well as to exploit episodic nutrient events in nature. Cell division rates were a hyperbolic function of the ambient orthophosphate concentration. The shortest doubling time was 8.7 d, the phosphate concentration at half the maximum division rate was 0.15 μ M and the threshold, concentration for cell division was ca 0.05 μ M PO. Division rates of P. noctiluca in the ocean are much faster than predicted from the measured ambient orthophosphate concentrations. Since this dinoflagellate has high naturally occurring alkaline phosphatase activities, and can utilize organic-P compounds, we suggest that organic-P can be as important as orthophosphate in supporting the observed division rates of P. noctiluca in the sea. [ABSTRACT FROM AUTHOR]

Vertical and horizontal distributions of 3 larval stages of the oyster Crassostrea virginica were measured concurrently with phytoplankton species compositions, phytoplankton size distributions and physical hydrographic parameters in tributaries of the Chesapeake Bay (USA) during the oyster spawning seasons of 1980 and 1981. The superposition of the biological distributions upon the physical hydrographic data provide instantaneous distributions of the entire system which are consistent with the upstream transport of oyster larvae. Oyster larvae distributions in the Choptank River and its Broad Creek and Tred Avon River tributaries can be described in terms of three contiguous regions: (1) a common spawning region, (2) an intermediate, upstream transport region and (3) a seed bed region where major spat set occurs. The phytoplankton species compositions and abundances in the size fraction less than 10 μm in the tributary system during the transport were sufficient to supply optimum growth requirements of developing larvae. The transport proposed can explain the 30 yr record of consistently higher spat set success in one tributary, Broad Creek, relative to an adjoining tributary, the Tred Avon River. This may be a general mechanism whereby oysters maintain reproductive success and emigrate to seed bed regions in the Chesapeake Bay. [ABSTRACT FROM AUTHOR]

In the Chesapeake Bay estuary there are persistent seasonal frontal and interfrontal regions that serve to deliver and retain different phytoplankton populations. The 'patchiness' of phytoplankton, both in total chlorophyll a concentrations and in species compositions and abundances, is shown to be causally related to density flow forcing which results in these frontal and interfrontal regions. The delineation of these regions by on-line, two-dimensional profiling of density isopleths serves to identify stations within these regions for biological and chemical sampling as opposed to sampling on an arbitrary geographical grid. It is possible, by superposition of nutrient and organism concentration isopleths upon salinity isopleths, to infer conservative and non-conservative features of the system. [ABSTRACT FROM AUTHOR]

Phosphate depleted Pyrocystis noctiluca (Murray) Schuett 1895 has at least one phosphomonoesterase (EC 3:1:3:1) which is triphasic between 0.1 and 222 μmol P. The enzyme has a broad temperature range with maximum activity at 50 °C and a Q of 1.4 to 1.5. A break in the Arrhenius plot at 35 °C implies the enzyme is membrane-bound. Cytological staining of whole cells and cell fractionation studies (showing 26 times higher specific activity in the particulate compared with the cytoplasmic fraction) suggest the enzyme is plasmalemma-bound. The enzyme has an absolute metal requirement which would be satisfied by Mg but not Mn, Zn, Fe, or Co at seawater concentrations. Alkaline phosphatase is a stable enzyme whose activity is not altered by inhibitors of protein synthesis. Orthophosphate inhibition of enzyme activity was largely eliminated in the presence of these inhibitors. Apparently, a protein induced by PO, rather than PO itself, inhibits alkaline phosphatase. Cell-free alkaline phosphatase can hydrolyze a variety of phosphate esters and linear polymers of inorganic phosphorus as well as disolved organic phosphorus from tropical oceanic waters. These same hydrolysable organic and inorganic phosphorus compounds support the axenic culture growth of P. noctiluca, suggesting that naturally occurring hydrolysable organic phosphorus compounds may also support the growth of this alga. [ABSTRACT FROM AUTHOR]