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21.
Leaf anatomy of c(3)-c(4) species as related to evolution of c(4) photosynthesis 总被引:3,自引:2,他引:1
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This study was undertaken to examine the degree of Kranz anatomy development in the species intermediate to C3 and C4 types (C3-C4) in Panicum, Neurachne, Flaveria, and Moricandia. In each genus, C3 and/or C4 species were used for comparison. Leaf transections from each species were examined by light and transmission electron microscopy. The percentages of leaf photosynthetic cell profiles partitioned to bundle sheaths were higher in C4 than in C3 species, while C3-C4 species tended to be in between. However, percentages for C3-C4 species in Moricandia and some C3-C4Flaveria species were not greater than C3. When expressed on a cell profile area basis, C3-C4 species partitioned more photosynthetic tissue to bundle sheaths than C3 species in Moricandia, but not in Flaveria. Neurachne minor S. T. Blake (C3-C4) partitioned a very small portion of cell profile area to the inner bundle sheaths (5%) compared to Neurachne munroi F. Muell (C4) (21%). The percentage of organelles partitioned to bundle sheaths was much greater in C3-C4 than in C3 species. The average C3 percentages for mitochondria plus peroxisomes were 19, 8, and 19.5% for Neurachne, Flaveria, and Moricandia, respectively, compared to 41, 29, and 46.5% for the C3-C4 species. The CO2 compensation concentration was negatively related to the partitioning of tissue to bundle sheaths and to the percentage of organelles in bundle sheaths. It is concluded that all of the C3-C4 species examined have developed some degree of Kranz anatomy and that this altered anatomy is involved in their reduced apparent photorespiration. 相似文献
22.
Generation of osteoclasts from hemopoietic cells and a multipotential cell line in vitro 总被引:6,自引:0,他引:6
Osteoclasts are the cells that resorb bone. It is generally presumed, on the basis of indirect experiments, that they are derived from the hemopoietic stem cell. However, this origin has never been established. We have developed an assay for osteoclastic differentiation in which bone marrow cells are incubated in liquid culture on slices of cortical bone. The bone slices are inspected in the scanning electron microscope after incubation for the presence of excavations, which are characteristic of osteoclastic activity. We have now incubated bone marrow cells at low density, or a factor-dependent mouse hemopoietic cell line (FDCP-mix A4) with 1,25 dihydroxyvitamin D3 (a hormone which we have previously found induces osteoclastic differentiation) with and without murine bone marrow stromal cells, or with and without 3T3 cells, on bone slices. Neither the bone marrow cells nor the bone marrow stromal cells alone developed osteoclastic function even in the presence of 1,25 dihydroxyvitamin D3. However, extensive excavation of the bone surface was observed, only in the presence of 1,25 dihydroxyvitamin D3, on bone slices on which bone marrow stromal cells were cocultured with low-density bone marrow cells or the hemopoietic cell line. Similar results were obtained when the bone marrow stromal cells were killed by glutaraldehyde fixation; 3T3 cells were unable to substitute for stromal cells. These results are strong evidence that osteoclasts derive from the hemopoietic stem cell and suggest that although mature osteoclasts possess neither receptors for nor responsiveness to 1,25 dihydroxyvitamin D3, the hormone induces osteoclastic function through a direct effect on hemopoietic cells rather than through some accessory cell in the bone marrow stroma. The failure of 3T3 cells, which enable differentiation of other hemopoietic progeny from this cell line, to induce osteoclastic differentiation suggests that bone marrow stroma possesses additional characteristics distinct from those that induce differentiation of other hemopoietic cells that are specifically required for osteoclastic differentiation. 相似文献
23.
Macrophage colony stimulating factor (M-CSF) is essential for osteoclast formation in vitro 总被引:6,自引:0,他引:6
G Hattersley J Owens A M Flanagan T J Chambers 《Biochemical and biophysical research communications》1991,177(1):526-531
The op/op mouse, in which the M-CSF gene is mutated, has greatly reduced numbers of macrophages and osteoclasts. We assessed the ability of M-CSF to induce osteoclast and macrophage formation in op/op hemopoietic cells in vitro. Osteoclast production was undetectable in op/op cell cultures, but was restored by M-CSF at concentrations approximately an order of magnitude higher than those that induced macrophages. In normal hemopoietic tissue M-CSF similarly increased macrophage numbers, but inhibited osteoclast formation. Despite cure of the macrophage defect, neither interleukin 3 nor granulocyte-macrophage CSF were able to induce osteoclastic differentiation in op/op cells. The results suggest that M-CSF induces osteoclastic differentiation but that macrophages, which are also induced by M-CSF, suppress osteoclast differentiation. Macrophages induced by other cytokines seem unable to contribute to osteoclast-formation. 相似文献
24.
Unfolded ribonuclease A consists of 20% fast refolding (Uf) and 80% slow refolding material (Us). The latter consists of at least two different forms which refold at different rates. We have used absorbance and fluorescence spectrophotometry to compare the kinetics of refolding in aqueous and aqueous-methanol solutions. At 1 degree C and pH 3.0, the addition of increasing concentrations of methanol (to 50%, v/v) had negligible effect on the rates and amplitudes of the slow refolding Us states. The effect of temperature on the two slow phases of refolding was determined in 35 and 50% methanol. From Arrhenius plots the energies of activation were found to be in the vicinity of 20 kcal/mol for both processes. The results suggest that both slow phases correspond to proline isomerization, and that the presence of methanol does not significantly perturb the overall refolding process. It is possible that the faster of the slow refolding phases corresponds to the isomerization of a proline residue which is trans in the folded native state but which undergoes extensive isomerization to the cis conformation in the unfolded state. 相似文献
25.
Timothy M. Frayling Michael P. Bulman Maggie Appleton A. T. Hattersley Sian Ellard 《Human genetics》1997,101(3):351-354
Non-insulin dependent diabetes (NIDDM) is a polygenic heterogeneous disorder of glucose homeostasis. Maturity-onset diabetes
of the young (MODY) is a monogenic subtype of NIDDM characterised by early-onset (< 25 years) and autosomal dominant inheritance.
Mutations in the hepatocyte nuclear factor 1 alpha (HNF-1α) gene have recently been shown to cause MODY. The incidence of
mutations in this gene in MODY and late-onset NIDDM is not known. We have developed a rapid specific polymerase chain reaction
test for HNF-1α mutations; this test involves the use of fluorescently labelled forward primers and modified reverse primers
to detect length polymorphisms resulting from frameshift mutations. With this method, we have screened 102 MODY probands,
viz. 60 defined according to strict diagnostic criteria (autosomal dominant inheritance and at least one member diagnosed
age < 25 years) and 95 late-onset NIDDM probands (diagnosed 35–70 years with ≥ 1 affected relative), for the presence of 9
known HNF-1α frameshift mutations, including 6 that occur at two sites for recurring mutation (residues 291/292 and 379).
Mutations were detected in 11 of the strictly defined MODY probands and one mutation was also found in a single subject with
early-onset NIDDM but no family history of the disease. The HNF-1α frameshift mutations were not detected in any late-onset
NIDDM subjects, suggesting these mutations do not have a major role in the pathogenesis of NIDDM. Our results indicate that
the prevalence of the nine frameshift mutations in strictly defined UK MODY is 18%, with the P291fsinsC mutation alone having
a frequency of 13%.
Received: 13 May 1997 / Accepted: 13 August 1997 相似文献
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28.
Laura Johnson Cornelia H. M. van Jaarsveld Pauline M. Emmett Imogen S. Rogers Andy R. Ness Andrew T. Hattersley Nicholas J. Timpson George Davey Smith Susan A. Jebb 《PloS one》2009,4(3)
Background
Dietary energy density (DED) does not have a simple linear relationship to fat mass in children, which suggests that some children are more susceptible than others to the effects of DED. Children with the FTO (rs9939609) variant that increases the risk of obesity may have a higher susceptibility to the effects of DED because their internal appetite control system is compromised. We tested the relationship between DED and fat mass in early adolescence and its interaction with FTO variants.Methods and Findings
We carried out a prospective analysis on 2,275 children enrolled in the Avon Longitudinal Study of Parents and Children (ALSPAC). Diet was assessed at age 10 y using 3-day diet diaries. DED (kJ/g) was calculated excluding drinks. Children were genotyped for the FTO (rs9939609) variant. Fat mass was estimated at age 13 y using the Lunar Prodigy Dual-energy X-ray Absorptiometry scanner. There was no evidence of interaction between DED at age 10 y and the high risk A allele of the FTO gene in relation to fat mass at age 13 y (β = 0.005, p = 0.51), suggesting that the FTO gene has no effect on the relation between DED at 10 y and fat mass at 13 y. When DED at 10 y and the A allele of FTO were in the same model they were independently related to fat mass at 13 y. Each A allele of FTO was associated with 0.35±0.13 kg more fat mass at 13 y and each 1 kJ/g DED at 10 y was associated with 0.16±0.06 kg more fat mass at age 13 y, after controlling for misreporting of energy intake, gender, puberty, overweight status at 10 y, maternal education, TV watching, and physical activity.Conclusions
This study reveals the multi-factorial origin of obesity and indicates that although FTO may put some children at greater risk of obesity, encouraging a low dietary energy density may be an effective strategy to help all children avoid excessive fat gain. 相似文献29.
A novel BMP expressed in developing mouse limb, spinal cord, and tail bud is a potent mesoderm inducer in Xenopus embryos 总被引:6,自引:0,他引:6
Gamer LW Wolfman NM Celeste AJ Hattersley G Hewick R Rosen V 《Developmental biology》1999,208(1):222-232
The bone morphogenetic proteins (BMPs) play critical roles in patterning the early embryo and in the development of many organs and tissues. We have identified a new member of this multifunctional gene family, BMP-11, which is most closely related to GDF-8/myostatin. During mouse embryogenesis, BMP-11 is first detected at 9.5 dpc in the tail bud with expression becoming stronger as development proceeds. At 10.0 dpc, BMP-11 is expressed in the distal and posterior region of the limb bud and later localizes to the mesenchyme between the skeletal elements. BMP-11 is also expressed in the developing nervous system, in the dorsal root ganglia, and dorsal lateral region of the spinal cord. To assess the biological activity of BMP-11, we tested the protein in the Xenopus ectodermal explant (animal cap) assay. BMP-11 induced axial mesodermal tissue (muscle and notochord) in a dose-dependent fashion. At higher concentrations, BMP-11 also induced neural tissue. Interestingly, the activin antagonist, follistatin, but not noggin, an antagonist of BMPs 2 and 4, inhibited BMP-11 activity on animal caps. Our data suggest that in Xenopus embryos, BMP-11 acts more like activin, inducing dorsal mesoderm and neural tissue, and less like other family members such as BMPs 2, 4, and 7, which are ventralizing and anti-neuralizing signals. Taken together, these data suggest that during vertebrate embryogenesis, BMP-11 plays a unique role in patterning both mesodermal and neural tissues. 相似文献
30.
Relationships in the Drosophila obscura species group, inferred from mitochondrial cytochrome oxidase II sequences 总被引:2,自引:0,他引:2
We compare the sequences for the mitochondrial cytochrome oxidase II gene
of 13 species of the Drosophila obscura group. The survey includes six
members of the D. affinis subgroup, four of the D. pseudoobscura subgroup,
and three of the D. obscura subgroup. In all species, the gene is 688
nucleotides in length, encoding a protein of 229 amino acids plus the first
position T of the stop codon. The sequences show the typical
high-transition bias for closely related species, but that bias is
essentially eliminated for species pairs of > 5% sequence divergence.
The phylogenetic relationships in the species group are inferred using both
neighbor-joining and maximum parsimony. The two procedures give comparable
results, showing that the D. affinis and D. pseudoobscura subgroups are
monophyletic groupings that appear to have closer affinities to one another
than either has to the D. obscura subgroup. We use transversion distances
to estimate times of divergence, on the basis of three different estimates
of the time of separation of the D. obscura species group from the D.
melanogaster group. If that event occurred 35 Mya, then we can estimate the
origin of the nearctic forms at approximately 22 Mya and the separation of
the D. affinis and D. pseudoobscura subgroups at approximately 17 Mya.
相似文献