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151.
Developing taste buds in the anterior mandibular floor of perihatching
chicks were studied by high voltage electron microscopic autoradiography in
order to identify proliferating gemmal cell types. Montaged profiles of 29
taste buds in five cases euthanized between embryonic day 21 and
posthatching day 2 were analyzed after a single [3H]thymidine injection
administered on embryonic day 16, 17 or 18. Results showed that dark cells
comprised 55% of identified (n = 900 cells) and 62% of labeled (n = 568
cells) gemmal cells as compared with light, intermediate, basal or
perigemmal bud cells. Dark cells had both a greater (P < 0.05) number of
labeled cells and a greater amount of label (grains/nucleus) than the other
four bud cell types, irrespective of injection day. The nuclear area
(micron 2) of dark cells was not significantly larger (P > 0.05) than
that of the other gemmal cell types and therefore cannot account for the
greater amount for label in the dark cells. Interestingly, only dark cells
showed a positive correlation (P < 0.003) between amount of label and
nuclear area. Results suggest that, during the perihatching period of
robust cell proliferation, dividing dark cells may give rise primarily, but
not exclusively, to dark cell progeny.
相似文献
152.
Background
The methodologies we use both enable and help define our research. However, as experimental complexity has increased the choice of appropriate methodologies has become an increasingly difficult task. This makes it difficult to keep track of available bioinformatics software, let alone the most suitable protocols in a specific research area. To remedy this we present an approach for capturing methodology from literature in order to identify and, thus, define best practice within a field. 相似文献153.
The major rivers of the South African ‘Lowveld’ (low-latitude savanna) suffer numerous impacts from upstream economic activities. Whereas monitoring these rivers is required to detect biodiversity losses, record pollution events and devise mitigation strategies, current monitoring programmes are inadequate. In 2009, the South African Earth Observation Network initiated an intensive long-term research programme on the Lowveld reaches of the Olifants River. Physico-chemical parameters, aquatic macroinvertebrates and fish abundances were recorded at four Lowveld sites in the Olifants River. We review six years of this programme. The results suggest deterioration in the ecological condition of the Olifants River with no discernible improvement through protected areas. Trends could not be detected. The parameters measured, sampling methods and/or sampling frequency might be responsible for the limited trends observed, or alternatively the results simply reflect stable conditions despite on-going pollution. Real time monitoring and an expansion in the parameters monitored would add value to the monitoring programme. 相似文献
154.
17 alpha-Acetoxy-6-fluoro-16-methylene-(9 beta, 10 alpha)pregna-4,6-dien- 3,20-dione (DU41165), a retroprogestin (9 beta, 10 alpha) embodying a fluorine-substituted dienone system, has been prepared in high specific activity tritium-labeled form (4 Ci/mmol) and shown to be a high affinity ligand for the progesterone receptor (PgR) and a highly selective photoaffinity labeling reagent for PgR. The radiosynthesis involved conversion of DU41231 (the 17 alpha-hydroxy analog of DU41165) to DU41165 by treatment with tritium-labeled acetic anhydride. The binding affinity of DU41165 for PgR was determined by both a competitive binding assay and a direct binding assay (Scatchard analysis) to be 1.6-2.2-times higher than that of the high affinity synthetic progestin promegestone (R5020). In unlabeled form, DU41165 demonstrates photoinactivation of PgR to the extent of 60% at 60 min. In radiolabeled form [3H]DU41165 demonstrates specific covalent attachment with an efficiency of 5-7%. SDS-polyacrylamide gel electrophoresis of photoattached [3H]DU41165 confirms that there is covalent labeling of both the B subunit (Mr = 118,000), and the A subunit (Mr = 88,000) of PgR in a molar ratio of approximately 1:3. 相似文献