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排序方式: 共有340条查询结果,搜索用时 15 毫秒
331.
332.
Ontogeny of immune system organs in northern bluefin tuna (Thunnus orientalis, Temminck and Schlegel 1844) 总被引:4,自引:0,他引:4
Serial sections, prepared from 0.5 to 30 days posthatch (dph) larval and juvenile Thunnus orientalis (Temminck & Schlegel 1844), were stained with haematoxylin and eosin and examined by light microscopy for immune organ development. The early kidney was present at 0.5 dph, undifferentiated stem cells began to appear at 2 dph, and by 7 dph occasional small lymphocytes were present. The thymus was first obvious at 5 dph, located above the fourth branchial arch, small lymphocytes appeared at 7 dph, and by 15 dph an outer thymocytic zone and an inner epithelioid zone were visible. The progenitor spleen was present at 2 dph, located close to the gut, and by 12 dph it consisted of a mass of sinusoids filled with red blood cells, and remained mainly erythroid throughout the period studied. These results suggest that development of immune organs in this species is precocious relative to other marine teleosts. 相似文献
333.
Lack of efficient access to collections of synthetic compounds that have skeletal diversity is a key bottleneck in the small-molecule discovery process. We report a synthesis strategy that involves transforming substrates with different appendages that pre-encode skeletal information, named sigma elements, into products that have different skeletons with the use of common reaction conditions. With this approach, split-pool synthesis can be used to pre-encode skeletal diversity combinatorially and thereby generate such small molecules very efficiently. A split-pool synthesis of more than 1000 compounds produced overlapping, combinatorial matrices of molecular skeletons and appended building blocks in both enantiomeric and diastereomeric forms. 相似文献
334.
Lawrence CR Schneider DP Schmidt M Bennett CL Hewitt JN Burke BF Turner EL Gunn JE 《Science (New York, N.Y.)》1984,223(4631):46-49
A new gravitational lens system, the triple radio source MG2016+112, has been discovered. Five emission lines at a redshift of 3.2733+/-0.0014 have been identified in the spectra of two stellar objects of magnitude 22.5 coincident with radio components 3.4 arc seconds apart. The lines are the narrowest ever observed in objects at such a large redshift. The redshift of a 23rd-magnitude extended optical object coincident with the third radio component has not been determined spectroscopically, but its known optical properties are consistent with those of a giant elliptical galaxy with a redshift of about 0.8. 相似文献
335.
Matthew Burke Darryl M. Small Frank Antolasic Jeff G. Hughes Michelle J. S. Spencer Ewan W. Blanch Oliver A. H. Jones 《Cereal Chemistry》2016,93(5):444-449
Preharvest sprouting of grains causes significant losses to growers and buyers. The problem occurs throughout the world, and economic losses can be millions of dollars. Visual assessment of germination is ineffective because even grains showing no external signs (e.g., having a visible shoot) may still have germinated sufficiently so that it is no longer possible for high‐quality products to be made from them. Current procedures to determine whether a grain has germinated are based around measuring enzyme or starch levels. However, despite protracted efforts to develop enhanced ways to measure germination over the last 50 years, there are currently no sufficiently accurate or reliable approaches available. The present work assesses the potential for infrared spectroscopy‐based metabolomic profiling to assess the germination of barley and wheat. The results indicate that mid‐ and near‐infrared spectroscopy are able to determine if the grain has germinated and give an indication of how long the germination process has been occurring. Both techniques are already well established in the grain industry and have the potential to form the basis of a simple, fast dockside test that would allow segregation of sound and mildly sprouted grain. 相似文献
336.
337.
Burke BF 《Science (New York, N.Y.)》1990,250(4986):1365-1370
The surface of the moon would be an excellent location for astronomical telescopes, and, if a lunar base were to be established, the construction and maintenance of instruments would become feasible. The prospects are reviewed, with particular attention given to large optical aperturesynthesis instruments analogous to the Very Large Array of the National Radio Astronomy Observatory. Typical parameters for a particular system are presented. 相似文献
338.
Turrel JM McEntee MC Burke BP Page RL 《Journal of the American Veterinary Medical Association》2006,229(4):542-548
OBJECTIVE: To determine outcome for dogs with nonresectable thyroid carcinomas treated with sodium iodide I 131 and identify factors associated with outcome. DESIGN: Retrospective case series. Animals-39 dogs. PROCEDURES: A definitive or presumptive diagnosis of thyroid tumor was made on the basis of cytologic or histologic examination, abnormal accumulation of sodium pertechnetate Tc 99m during scintigraphy, or both, and dogs were treated with sodium iodide I 131. Dogs with cervical thyroid tumors were evaluated 3 to 6 weeks after 131I therapy, and residual tumor was resected when feasible. RESULTS: Prior to 131I therapy, 32 dogs had a solitary mass and 7 had metastases; 21 were hyperthyroid, 16 were euthyroid, and 2 were hypothyroid. Median survival time for dogs with local or regional tumors (ie, stage II or III) was significantly longer (839 days) than median survival time for dogs with metastasis (366 days). Tumor site (cervical vs ectopic), dose of sodium iodide I 131, age, body weight, treatment (131I therapy alone vs 131I therapy followed by surgery), and serum T4 concentration prior to 131I therapy were not significantly associated with survival time. Three dogs died of radioiodine-associated myelosuppression within 3 months after treatment, but no specific factor associated with development of toxicosis was identified. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggested that 131I therapy may result in prolonged survival times in dogs with nonresectable thyroid tumors, regardless of serum thyroxine concentration prior to treatment. Dogs undergoing 131I therapy should be monitored for signs of bone marrow suppression. 相似文献
339.
Distribution of thiobacillus ferrooxidans and leptospirillum ferrooxidans: implications for generation of acid mine drainage 总被引:1,自引:0,他引:1
MO Schrenk KJ Edwards RM Goodman RJ Hamers JF Banfield 《Science (New York, N.Y.)》1998,279(5356):1519-1522
Although Thiobacillus ferrooxidans and Leptospirillum ferrooxidans are widely considered to be the microorganisms that control the rate of generation of acid mine drainage, little is known about their natural distribution and abundance. Fluorescence in situ hybridization studies showed that at Iron Mountain, California, T. ferrooxidans occurs in peripheral slime-based communities (at pH over 1.3 and temperature under 30 degreesC) but not in important subsurface acid-forming environments (pH 0.3 to 0.7, temperature 30 degrees to 50 degreesC). Leptospirillum ferrooxidans is abundant in slimes and as a planktonic organism in environments with lower pH. Thiobacillus ferrooxidans affects the precipitation of ferric iron solids but plays a limited role in acid generation, and neither species controls direct catalysis at low pH at this site. 相似文献
340.
Anaemia is a common pathology associated with many infectious and non-infectious diseases. The effects of haemolytic anaemia
induced by i.p. injection of phenylhydrazine (PHZ) were studied in Atlantic cod. Phenylhydrazine injection (0.3 mg kg−1) in a DMSO and saline vehicle induced a reproducible and stable anaemia reducing haematocrit, (Hct) by 62% over 3 weeks.
Controls consisted of fish injected with saline and DMSO/saline vehicle with minimal effects on Hct or whole blood haemoglobin
(Hb). Although anaemia resulted in reduced blood lactate and glucose in PHZ injected fish, there were no effects of anaemia
on blood, sodium, chloride or potassium. Similarly, there were no changes in the relative proportions of leucocytes in the
blood although an increase in the number of immature erythrocytes was observed in the anaemic fish. Anaemic fish showed a
29 and 22% increase in cardiac somatic index (CSI) relative to saline and vehicle controls, respectively, although there were
no significant differences in the linear dimensions of the ventricle. Changes in cardiac somatic and ventricular somatic index
correlated positively and significantly with Hct but not with whole blood Hb concentration. Anaemic fish had significantly
reduced resting routine oxygen consumption compared with vehicle controls but were not able to increase oxygen consumption
following a bout of exhaustive exercise. Plasma lactate concentrations increased significantly after exercise to a greater
extent in anaemic fish compared with vehicle control fish. Phenylhydrazine is a useful model for studying haemolytic anaemia
in Atlantic cod with minimal effects on blood biochemistry and haematology and clearly reduces the aerobic capacity in Atlantic
cod. 相似文献