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981.
Spermiogenesis in Palaemon serratus is described. The mature sperm has an atypical form and is highly modified. In early stages of spermiogenesis mitochondria, golgi complexes, stacks of annulate lamellae and endoplasmic reticulum are present but disappear later in development. Two modified mitochondria are present in the mature sperm. This latter consists of a cup-shaped nucleus, a cross-striated “spike”, has a centriole and lacks an acrosome. The nucleus contains membrane-bounded vesicles which arise by pinocytosis. The “spike” may be a flexible posterior organ which suggests a mode of fertilization requiring limited mobility. 相似文献
982.
Raman modes from amorphous α-helical poly(L -alanine) in the low-frequency region < 150 cm?1 have been observed and assignments and values compared with mode-analysis calculations. The temperature dependence of the complete Raman spectrum of α-poly(L -Ala) is also reported. 相似文献
983.
Ferdinand Bohlmann Christa Zdero Harold Robinson Robert M. King 《Phytochemistry》1979,18(12):1993-1996
The investigation of the aerial part of B. scandens afforded a new ketone, a germacrene derivative. The aerial parts of B. tricuneata var. lineata yielded, in addition to known ent-clerodane derivatives, a malonate of a further diterpene of this type. The structures are elucidated by spectroscopic methods. 相似文献
984.
Background
Core histone genes are periodically expressed along the cell cycle and peak during S phase. Core histone gene expression is deeply evolutionarily conserved from the yeast Saccharomyces cerevisiae to human. 相似文献985.
986.
The authors would 相似文献
987.
Matthew Menke Jonathan King Bonnie Berger Lenore Cowen 《Journal of computational biology》2005,12(6):777-795
A method is presented that uses beta-strand interactions at both the sequence and the atomic level, to predict beta-structural motifs of protein sequences. A program called Wrap-and- Pack implements this method and is shown to recognize beta-trefoils, an important class of globular beta-structures, in the Protein Data Bank with 92% specificity and 92.3% sensitivity in cross-validation. It is demonstrated that Wrap-and-Pack learns each of the ten known SCOP beta-trefoil families, when trained primarily on beta-structures that are not beta-trefoils, together with three-dimensional structures of known beta-trefoils from outside the family. Wrap-and-Pack also predicts many proteins of unknown structure to be beta-trefoils. The computational method used here may generalize to other beta-structures for which strand topology and profiles of residue accessibility are well conserved. 相似文献
988.
E C Howell S J Armstrong G C Barker G H Jones G J King C D Ryder M J Kearsey 《Génome》2005,48(6):1093-1103
The close relationship between Brassica oleracea and Arabidopsis thaliana has been used to explore the genetic and physical collinearity of the two species, focusing on an inverted segmental chromosome duplication within linkage group O6 of B. oleracea. Genetic evidence suggests that these segments share a common origin with a region of Arabidopsis chromosome 1. Brassica oleracea and Arabidopsis bacterial artificial chromosome probes have been used for fluorescence in situ hybridization analysis of B. oleracea pachytene chromosomes to further characterize the inverted duplication. This has been highly effective in increasing the local resolution of the cytogenetic map. We have shown that the physical order of corresponding genetic markers is highly conserved between the duplicated regions in B. oleracea and the physical lengths of the regions at pachytene are similar, while the genetic distances are considerably different. The physical marker order is also well conserved between Arabidopsis and B. oleracea, with only one short inversion identified. Furthermore, the relative physical distances between the markers in one segment of B. oleracea and Arabidopsis have stayed approximately the same. The efficacy of using fluorescence in situ hybridization, together with other forms of physical and genetic mapping, for elucidating such issues relating to synteny is discussed. 相似文献
989.
Antonis P Stylianou Carl W Luchies David E Lerner Gregory W King 《Journal of electromyography and kinesiology》2005,15(5):437-443
Innovative applications of non-linear time series analysis have recently been used to investigate physiological phenomena. In this study, we investigated the feasibility of using the correlation integral to monitor the localized muscle fatigue process in the biceps brachii during sustained maximal efforts. The subjects performed isometric maximum contractions until failure in elbow flexion (90 degrees from neutral). The median and the 70th percentile frequency of the Surface electromyography (SEMG) power spectrum, the integrated SEMG, and the Correlation Integral (CI) were evaluated during the trials. The linear correlation between these variables and the elbow torque production was used to quantify the ability of a parameter to follow the fatiguing process. The CI had the highest linear correlation with torque (0.77 (0.12SD)), while the spectral indices correlations with torque were much lower. The decreasing trend of the torque production was followed by the spectral indices for only the beginning part of the contraction, while the CI increased sharply after the torque production fell to about 0.60 of the MVC. This suggests that the CI is sensitive to different changes of the SEMG signal during fatigue than the spectral variables. 相似文献
990.
Diversity and Structure of Bacterial Chemolithotrophic Communities in Pine Forest and Agroecosystem Soils 下载免费PDF全文
Obligate lithotrophs (e.g., ammonia oxidizers) and facultative lithotrophs (e.g., CO and hydrogen oxidizers) collectively comprise a phylogenetically diverse functional group that contributes significantly to carbon and nitrogen cycles in soils and plays important roles in trace gas dynamics (e.g., carbon monoxide and nitrous and nitric oxides) that affect tropospheric chemistry and radiative forcing. In spite of their diverse physiologies, facultative and obligate lithotrophs typically possess the Calvin-Benson-Bassham cycle enzyme, ribulose-1,5-bisphosphate carboxylase/oxygenase (rubisCO). In an effort designed to understand the structure of lithotrophic communities in soil, genomic DNA extracts from surface (0 to 2 cm) and subsurface (5 to 7 cm) soils have been obtained from two sites in a Georgia agroecosystem (peanut and cotton plots) and an unmanaged pine stand (>50 years old). The extracts have been used in PCR amplifications of the cbbL gene for the rubisCO large subunit protein. cbbL PCR products were cloned, sequenced, and subjected to phylogenetic and statistical analyses. Numerous novel lineages affiliated with the form IC clade (one of four form I rubisCO clades), which is typified by facultative lithotrophs, comprised lithotrophic communities from all soils. One of the form IC clone sequences clustered with a form IC clade of ammonia-oxidizing Nitrosospira. Distinct assemblages were obtained from each of the sites and from surface and subsurface soils. The results suggest that lithotrophic populations respond differentially to plant type and land use, perhaps forming characteristic associations. The paucity of clone sequences attributed to ammonia-oxidizing bacteria indicates that even though ammonia oxidation occurs in the various soils, the relevant populations are small compared to those of facultative lithotrophs. 相似文献