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Photo Wallahs Photo Wallahs, an encounter with photography in Mussoorie, a north Indian hill station. Directed by David and Judith MacDougall; camera: David MacDougall; sound: Judith MacDougall; editor: Dai Vaughan. Distributed by Fieldwork Films, 12 Meehan Gardens, Griffith, Canberra, A.C.T. 2603, Australia. 1991, 58 minutes, color, 16 mm. and PAL.  相似文献   

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The genome sequences completed so far contain more than 20 000 genes with unknown function and no similarity to genes in other genomes. The origin and evolution of the orphan genes is an enigma. Here, we discuss the suggestion that some orphan genes may represent pseudogenes or short fragments of genes that were functional in the genome of a common ancestor. These may be the remains of unsuccessful duplication or horizontal gene transfer events, in which the acquired sequences have entered the fragmentation process and thereby lost their similarity to genes in other species. This scenario is supported by a recent case study of orphan genes in several closely related species of Rickettsia, where full-length ancestral genes were reconstructed from sets of short, overlapping orphan genes. One of these was found to display similarity to genes encoding proteins with ankyrin-repeat domains.  相似文献   

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Dhiava: The Autumn Journey. 1997 (U.S. release date: 1999). 50 minutes, color. film by David Hope and Tim Salmon. For more information, please contact Documentary Educational Resources. 101 Morse Street. Watertown. MA 02472, (617) 926- 0491, (617) 926-9519 (fax).  相似文献   

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A. D. Kelly 《CMAJ》1963,88(3):150-151
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Claiming Power in Doctor-Patient Talk. Nancy Ainsworth-Vaughn. New York: Oxford University Press, 1998. xii. 212 pp.
From Doctor to Healer: The Transformative Journey. Robbie Davis-Floyd and Gloria St. John. New Brunswick: Rutgers University Press, 1998. xiv. 308 pp.  相似文献   

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BackgroundThe two-component signaling (TCS) system is an important signal transduction machinery in prokaryotes and eukaryotes, excluding animals, that uses a protein phosphorylation mechanism for signal transmission.ConclusionProkaryotes have a primitive type of TCS machinery, which mainly comprises a membrane-bound sensory histidine kinase (HK) and its cognate cytoplasmic response regulator (RR). Hence, it is sometimes referred to as two-step phosphorelay (TSP). Eukaryotes have more sophisticated signaling machinery, with an extra component - a histidine-containing phosphotransfer (HPT) protein that shuttles between HK and RR to communicate signal baggage. As a result, the TSP has evolved from a two-step phosphorelay (His–Asp) in simple prokaryotes to a multi-step phosphorelay (MSP) cascade (His–Asp–His–Asp) in complex eukaryotic organisms, such as plants, to mediate the signaling network. This molecular evolution is also reflected in the form of considerable structural modifications in the domain architecture of the individual components of the TCS system. In this review, we present TCS system''s evolutionary journey from the primitive TSP to advanced MSP type across the genera. This information will be highly useful in designing the future strategies of crop improvement based on the individual members of the TCS machinery.  相似文献   

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The peripheral axons of vertebrate tactile somatosensory neurons travel long distances from ganglia just outside the central nervous system to the skin. Once in the skin these axons form elaborate terminals whose organization must be regionally patterned to detect and accurately localize different kinds of touch stimuli. This review describes key studies that identified choice points for somatosensory axon growth cones and the extrinsic molecular cues that function at each of those steps. While much has been learned in the past 20 years about the guidance of these axons, there is still much to be learned about how the peripheral axons of different kinds of somatosensory neurons adopt different trajectories and form specific terminal structures.  相似文献   

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The Journey of Malaria Sporozoites in the Mosquito Salivary Gland   总被引:11,自引:0,他引:11  
The life cycle of malaria parasites in the mosquito vector is completed when the sporozoites infect the salivary gland and are ready to be injected into the vertebrate host. This paper describes the fine structure of the invasive process of mosquito salivary glands by malaria parasites. Plasmodium gallinaceum sporozoites start the invasion process by attaching to and crossing the basal lamina and then penetrating the host plasma membrane of the salivary cells. The penetration process appears to involve the formation of membrane junctions. Once inside the host cells, the sporozoites are seen within vacuoles attached by their anterior end to the vacuolar membrane. Mitochondria surround, and are closely associated with, the invading sporozoites. After the disruption of the membrane vacuole, the parasites traverse the cytoplasm, attach to, and invade the secretory cavity through the apical plasma membrane of the cells. Inside the secretory cavity, sporozoites are seen again inside vacuoles. Upon escaping from these vacuoles, sporozoites are positioned in parallel arrays forming large bundles attached by multilammelar membrane junctions. Several sporozoites are seen around and inside the secretory duct. Except for the penetration of the chitinous salivary duct, our observations have morphologically characterized the entire process of sporozoite passage through the salivary gland.  相似文献   

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