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21.
Long-term (millennial timescale) records of coral community structure can be developed from the analysis of corals preserved
in radiometrically dated reef cores. Here, we present such a record (based on six cores) from Lugger Shoal, a turbid zone,
nearshore reef on the inner-shelf of the central Great Barrier Reef. Lugger Shoal initiated growth ~800 cal yBP. It is constructed
of large in situ Porites bommies, between which a framework of coral rubble (dominated by Acropora pulchra, Montipora mollis, Galaxea fascicularis and Cyphastrea serailia) has accumulated. Reef accretion occurred under conditions of net long-term fine-grained, terrigenous sediment accumulation,
and with a coral community dominated throughout by a consistent, but low diversity, suite of coral taxa. This dataset supports
recent suggestions that nearshore coral communities that establish themselves under conditions that are already close to the
thresholds for coral survival may be resilient to water quality deteriorations associated with human activities. 相似文献
22.
Clegg J. A. and Smithers S. R., 1972. The effect of immune rhesus monkey serum on schistosomula of Schistosoma mansoni during cultivation in vitro. International journal for Parasitology2: 79–98. The sera of rhesus monkeys hyperimmunized by 2–4 exposures to S. mansoni cercariae contain an antibody lethal to schistosomula cultivated in vitro. The antibody (IgG) is dependent on labile factors in fresh monkey serum. It can be absorbed by adult worms cultivated in vitro and it is not the antibody responsible for CHR or COP reactions. A titre of lethal antibody sufficient to kill all schistosomula in vitro is maintained for 2–3 months following challenge: it then falls to a moderate level which may be retained for several years. After inactivation, hyperimmune serum inhibits the growth of cultured schistosomula but does not kill them. Following a small primary infection rhesus serum develops a marked growth-inhibiting property and a low titre of lethal antibody at about 4 months, i.e. the time when resistance to reinfection can first be reliably demonstrated. 相似文献
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Formyl phosphate, a putative enzyme-bound intermediate in the reaction catalyzed by formyltetrahydrofolate synthetase (EC 6.3.4.3), was synthesized from formyl fluoride and inorganic phosphate [Jaenicke, L. v., & Koch, J. (1963) Justus Liebigs Ann. Chem. 663, 50-58], and the product was characterized by 31P, 1H, and 13C nuclear magnetic resonance (NMR). Measurement of hydrolysis rates by 31P NMR indicates that formyl phosphate is particularly labile, with a half-life of 48 min in a buffered neutral solution at 20 degrees C. At pH 7, hydrolysis occurs with P-O bond cleavage, as demonstrated by 18O incorporation from H2(18)O into Pi, while at pH 1 and pH 13 hydrolysis occurs with C-O bond cleavage. The substrate activity of formyl phosphate was tested in the reaction catalyzed by formyltetrahydrofolate synthetase isolated from Clostridium cylindrosporum. Formyl phosphate supports the reaction in both the forward and reverse directions. Thus, N10-formyltetrahydrofolate is produced from tetrahydrofolate and formyl phosphate in a reaction mixture that contains enzyme, Mg(II), and ADP, and ATP is produced from formyl phosphate and ADP with enzyme, Mg(II), and tetrahydrofolate present. The requirements for ADP and for tetrahydrofolate as cofactors in these reactions are consistent with previous steady-state kinetic and isotope exchange studies, which demonstrated that all substrate subsites must be occupied prior to catalysis. The k cat values for both the forward and reverse directions, with formyl phosphate as the substrate, are much lower than those for the normal forward and reverse reactions. Kinetic analysis of the formyl phosphate supported reactions indicates that the low steady-state rates observed for the synthetic intermediate are most likely due to the sequential nature of the normal reaction. 相似文献
25.
D. W. Smithers 《BMJ (Clinical research ed.)》1949,2(4626):512-515
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28.
David A. Belford Mary-Louise Rogers Geoffrey O. Regester Geoffrey L. Francis Geoffrey W. Smithers Ingrid J. Liepe Ilka K. Priebe F. John Ballard 《In vitro cellular & developmental biology. Animal》1995,31(10):752-760
Summary We have investigated the response of several epithelial and fibroblastic cells to a mitogenic extract of bovine milk. Cation
exchange chromatography was used to produce a mitogen-rich fraction from an industrial whey source that, although comprising
only 0.5% of total whey protein, contained the bulk of the growth factor activity. This fraction was a source of potent growth
promoting activity for all mesodermal-derived cells tested, including human skin and embryonic lung fibroblasts, Balb/c 3T3
fibroblasts, and rat L6 myoblasts. Maximal growth of all these cell types exceeded that observed in 10% fetal bovine serum.
Feline kidney and baby hamster fibroblasts and Chinese hamster ovary cells were less responsive, achieving a maximal growth
response of 50–75% that observed in 10% fetal bovine serum. Maximal growth achieved in whey-extract-supplemented cultures
of Balb/c 3T3 and human skin fibroblasts, and L6 myoblast cultures exceeded that seen in response to recombinant acidic or
basic fibroblast growth factor, platelet-derived growth factor, insulin-like growth factor, or epidermal growth factor. Importantly,
addition of low concentrations of fetal bovine serum to the whey-derived mitogenic fraction produced an additive response.
However, concentrated milk-derived factors were found to be inhibitory to the growth of all epithelial lines tested, including
rat intestinal epithelial cells, canine kidney epithelial cells, and mink lung cells. It is concluded that industrial whey
extracted in this form constitutes an important source of potent growth-promoting agents for the supplementation of mesodermal-derived
cell cultures. 相似文献
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30.
Britten CJ; van den Eijnden DH; McDowell W; Kelly VA; Witham SJ; Edbrooke MR; Bird MI; de Vries T; Smithers N 《Glycobiology》1998,8(4):321-327
The alpha3 fucosyltransferase, FucT-VII, is one of the key
glycosyltransferases involved in the biosynthesis of the sialyl Lewis X
(sLex) antigen on human leukocytes. The sialyl Lewis X antigen
(NeuAcalpha(2-3)Galbeta(1-4)[Fucalpha(1-3)]GlcNAc-R) is an essential
component of the recruitment of leukocytes to sites of inflammation,
mediating the primary interaction between circulating leukocytes and
activated endothelium. In order to characterize the enzymatic properties of
the leukocyte alpha3 fucosyltransferase FucT-VII, the enzyme has been
expressed in Trichoplusia ni insect cells. The enzyme is capable of
synthesizing both sLexand sialyl-dimeric-Lexstructures in vitro , from
3'-sialyl-lacNAc and VIM-2 structures, respectively, with only low levels
of fucose transfer observed to neutral or 3'-sulfated acceptors. Studies
using fucosylated NeuAcalpha(2-3)-(Galbeta(1- 4)GlcNAc)3-Me acceptors
demonstrate that FucT-VII is able to synthesize both di-fucosylated and
tri-fucosylated structures from mono- fucosylated precursors, but
preferentially fucosylates the distal GlcNAc within a polylactosamine
chain. Furthermore, the rate of fucosylation of the internal GlcNAc
residues is reduced once fucose has been added to the distal GlcNAc. These
results indicate that FucT-VII is capable of generating complex selectin
ligands, in vitro , however the order of fucose addition to the lactosamine
chain affects the rate of selectin ligand synthesis.
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