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991.
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993.
Dr. Victor Schiffner 《Plant Systematics and Evolution》1896,46(3):82-88
Ohne Zusammenfassung 相似文献
994.
Trevor J. Douglas Victor M. Villalobos Michael R. Thompson Trevor A. Thorpe 《Physiologia plantarum》1982,55(4):470-477
Cotyledon explants of radiata pine contain principally lipid and protein reserve materials, which decline during shoot initiation. This process was followed phytochemically and ultrastructurally. Fatty acid and sterol analyses indicated that there were both quantitative and qualitative changes in the different classes of lipid. The most pronounced changes were an increase in the linolenic acid content of the polar lipids and the appearance of stigmasterol during shoot initiation. There was also a continued increase in chlorophyll and carotenoid levels, which paralleled chloroplast development. It appears that the changes observed were similar to those that occur in cotyledons during normal seedling development. 相似文献
995.
Summary A new apparatus is described which permits pure cultivation of 110 l amounts of phototrophic organisms. Some data are given to prove its utility for mass production (kilogram amounts) of algae and photosynthetic bacteria. 相似文献
996.
Kenji Adachi Hajime Iizuka Kenneth M. Halprin Victor Levine 《Biochimica et Biophysica Acta (BBA)/General Subjects》1977,497(2):428-436
The cyclic AMP level in pig skin (epidermis) increases markedly after incubation with epinephrine, prostaglandin E, histamine or adenosine 5′-monophosphate. This increase is transient and “spiking” is the consistent response to these four stimulators. The “spiking” is due to a non-responsiveness or refractoriness which develops within minutes and is specific to any one stimulating hormone but not to the others. The addition of inhibitors of protein syntheses did not prevent the development of the refractoriness. Adenylate cyclase and phosphodiesterase activities measured in skin homogenates prepared from skin samples taken before, during and after the “spiking” did not change significantly. The hormone-induced refractoriness in this skin system appears to be due to a specific, localized loss of function of the adenylate cyclase system. 相似文献
997.
Latha Ramakrishnan Hélène Muller-Steffner Christophe Bosc Victor D. Vacquier Francis Schuber Marie-Jo Moutin Leslie Dale Sandip Patel 《The Journal of biological chemistry》2010,285(26):19900-19909
Cyclic ADP-ribose and nicotinic acid adenine dinucleotide phosphate are ubiquitous calcium-mobilizing messengers produced by the same family of multifunctional enzymes, the ADP-ribosyl cyclases. Not all ADP-ribosyl cyclases have been identified, and how production of different messengers is achieved is incompletely understood. Here, we report the cloning and characterization of a novel ADP-ribosyl cyclase (SpARC4) from the sea urchin, a key model organism for the study of calcium-signaling pathways. Like several other members of the ADP-ribosyl cyclase superfamily, SpARC4 is a glycoprotein targeted to the plasma membrane via a glycosylphosphatidylinositol anchor. However, unlike most other members, SpARC4 shows a remarkable preference for producing cyclic ADP-ribose over nicotinic acid adenine dinucleotide phosphate. Mutation of a single residue (tyrosine 142) within a noncanonical active site reversed this striking preference. Our data highlight further diversification of this unusual enzyme family, provide mechanistic insight into multifunctionality, and suggest that different ADP-ribosyl cyclases are fine-tuned to produce specific calcium-mobilizing messengers. 相似文献
998.
Asymmetric and Globular Forms of AChE in Slow and Fast Muscles of 129/ReJ Normal and Dystrophic Mice 总被引:3,自引:3,他引:0
Abstract: Acetylcholinesterase activities and molecular forms were studied in normal and dystrophic 129/ReJ mice, focusing on four predominantly fast-twitch muscles and the slow-twitch soleus. The asymmetric and globular forms were analyzed separately so that the effect of dystrophy on each form could be determined. This comparative study showed the following. (1) In the normal condition, each muscle exhibited a distinct distribution of the molecular forms. (2) The diversity among the fast muscles resulted mainly from variations in the proportions of the three globular forms; in contrast, these muscles showed a constant and precise A12 /A8 /A4 ratio. (3) The slow-twitch soleus clearly differed from the other muscles in its low acetylcholinesterase activity and distinct distribution of the molecular forms, characterized by a low level of G4 and a peculiar ratio among its asymmetric forms, resulting from a relative increase of the A8 and A4 forms. (4) In dystrophic mice, the diversity of the acetylcholin esterase distribution was lost; all the fast muscles displayed profiles exhibiting the characteristics typical of the soleus. The fast-twitch extensor digitorum longus, sternomastoid, and plantaris converged towards an identical set of acetylcholinesterase molecules. (5) In contrast, the acetylcholinesterase activity and molecular forms of the soleus were only slightly affected by the disease. These results reveal that the dystrophy modifies both categories of molecular forms of acetylcholinesterase in a very precise manner. Such complex changes, which are highly reproducible in a variety of different muscles, are unlikely to result from nonspecific reactions secondary to the disease. 相似文献
999.
Victor Chukwudi Osamor Ezekiel Femi Adebiyi Jelilli Olarenwaju Oyelade Seydou Doumbia 《PloS one》2012,7(12)
Traditional k-means and most k-means variants are still computationally expensive for large datasets, such as microarray data, which have large datasets with large dimension size d. In k-means clustering, we are given a set of n data points in d-dimensional space Rd and an integer k. The problem is to determine a set of k points in Rd, called centers, so as to minimize the mean squared distance from each data point to its nearest center. In this work, we develop a novel k-means algorithm, which is simple but more efficient than the traditional k-means and the recent enhanced k-means. Our new algorithm is based on the recently established relationship between principal component analysis and the k-means clustering. We provided the correctness proof for this algorithm. Results obtained from testing the algorithm on three biological data and six non-biological data (three of these data are real, while the other three are simulated) also indicate that our algorithm is empirically faster than other known k-means algorithms. We assessed the quality of our algorithm clusters against the clusters of a known structure using the Hubert-Arabie Adjusted Rand index (ARIHA). We found that when k is close to d, the quality is good (ARIHA>0.8) and when k is not close to d, the quality of our new k-means algorithm is excellent (ARIHA>0.9). In this paper, emphases are on the reduction of the time requirement of the k-means algorithm and its application to microarray data due to the desire to create a tool for clustering and malaria research. However, the new clustering algorithm can be used for other clustering needs as long as an appropriate measure of distance between the centroids and the members is used. This has been demonstrated in this work on six non-biological data. 相似文献
1000.