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91.
Florence W. L. Tsui Hing-Wo Tsui Samuel Mok Irena Mlinaric Neal G. Copeland Debra J. Gilbert Nancy A. Jenkins Katherine A. Siminovitch 《Genomics》1993,15(3)
Stefins or Type 1 cystatins belong to a large, evolutionarily conserved protein superfamily, the members of which inhibit the papain-like cysteine proteinases. We report here on the molecular cloning and chromosomal localization of three newly identified members of the murine stefin gene family. These genes, designated herein as mouse stefins 1, 2, and 3, were isolated on the basis of their relatively increased expression in moth-eaten viable compared to normal congenic mouse bone marrow cells. The open reading frames of the stefin cDNAs encode proteins of approximately 11.5 kDa that show between 50 and 92% identity to sequences of stefins isolated from various other species. Data from Southern analysis suggest that the murine stefin gene family encompasses at least 6 and possibly 10-20 members, all of which appear to be clustered in the genome. Analysis of interspecific backcross mice indicates that the genes encoding the three mouse stefins all map to mouse chromosome 16, a localization that is consistent with the recent assignment of the human stefin A gene to a region of conserved homology between human chromosome 3q and the proximal region of mouse chromosome 16. 相似文献
92.
Arpana Agrawal Sarah J. Brislin Kathleen K. Bucholz Danielle Dick Ronald P. Hart Emma C. Johnson Jacquelyn Meyers Jessica Salvatore Paul Slesinger COGA Collaborators Laura Almasy Tatiana Foroud Alison Goate Victor Hesselbrock John Kramer Samuel Kuperman Alison K. Merikangas John I. Nurnberger Jay Tischfield Howard J. Edenberg Bernice Porjesz 《Genes, Brain & Behavior》2023,22(5):e12864
93.
The inability of synaptic junctions to generate normalsized postsynaptic potentials under normal physiological conditions was studied at crayfish neuromuscular synapses. Synaptic repression in the superficial flexor muscle system of the crayfish was induced by surgery: the nerve was cut in the middle of the target field, and the lateral muscle fibers were removed. After this surgery, the remaining medial synapses were unable to generate normal-sized junction potentials (jp) over the medial muscle population. In an attempt to study the mechanism underlying this response, we varied the extracellular calcium concentration of the Ringers solution bathing the preparation, in both repressed and control animals, while monitoring the size of the same junction potential. The junction potential generated by the spontaneous activity of the nerve increased in size with increasing calcium concentrations in control animals, but failed to do so in repressed animals, that is, changes in external calcium concentrations did not affect repressed synapses. However, in the presence of the calcium ionophore A23187, control and repressed synapses both show an increase in the junction potential sizes they generate. Our data suggest that calcium is involved in the mechanisms that underlie synaptic repression in this crustacean neuromuscular system. © 1993 John Wiley & Sons, Inc. 相似文献
94.
AN ELECTRON MICROSCOPE STUDY OF THE EARLY ASSOCIATION BETWEEN TWO MAMMALIAN VIRUSES AND THEIR HOSTS 总被引:19,自引:4,他引:19 下载免费PDF全文
Samuel Dales 《The Journal of cell biology》1962,13(2):303-322
Early interaction between two animal viruses, vaccinia and adenovirus 7, which multiply readily in L strain and HeLa cells, respectively, was examined in both whole mount preparations and in thin sections. To observe the association at the surface, cells carrying adsorbed virus were swelled under controlled conditions and then "stained" with neutral phosphotungstate. Each particle of both virus types becomes attached to the cell by several capsomeres and is then ingested by phagocytosis. Within the cell, near the surface, single particles or small clumps of adenovirus are lodged within vesicles. Deeper in the cytoplasm this virus is packed in large, numerous inclusions, whereas very close to the nuclear envelope only free particles are found. Vaccinia, on the other hand, either free or in vesicles, is always found in the cytoplasm, at some distance from the nucleus (11). Adsorption and intracellular disposition of these two viruses is discussed in relation to the infectious process. 相似文献
95.
96.
A dynamic global vegetation model for use with climate models: concepts and description of simulated vegetation dynamics 总被引:14,自引:0,他引:14
Gordon B. Bonan Samuel Levis Stephen Sitch† Mariana Vertenstein Keith W. Oleson 《Global Change Biology》2003,9(11):1543-1566
Changes in vegetation structure and biogeography due to climate change feedback to alter climate by changing fluxes of energy, moisture, and momentum between land and atmosphere. While the current class of land process models used with climate models parameterizes these fluxes in detail, these models prescribe surface vegetation and leaf area from data sets. In this paper, we describe an approach in which ecological concepts from a global vegetation dynamics model are added to the land component of a climate model to grow plants interactively. The vegetation dynamics model is the Lund–Potsdam–Jena (LPJ) dynamic global vegetation model. The land model is the National Center for Atmospheric Research (NCAR) Land Surface Model (LSM). Vegetation is defined in terms of plant functional types. Each plant functional type is represented by an individual plant with the average biomass, crown area, height, and stem diameter (trees only) of its population, by the number of individuals in the population, and by the fractional cover in the grid cell. Three time‐scales (minutes, days, and years) govern the processes. Energy fluxes, the hydrologic cycle, and carbon assimilation, core processes in LSM, occur at a 20 min time step. Instantaneous net assimilated carbon is accumulated annually to update vegetation once a year. This is carried out with the addition of establishment, resource competition, growth, mortality, and fire parameterizations from LPJ. The leaf area index is updated daily based on prevailing environmental conditions, but the maximum value depends on the annual vegetation dynamics. The coupling approach is successful. The model simulates global biogeography, net primary production, and dynamics of tundra, boreal forest, northern hardwood forest, tropical rainforest, and savanna ecosystems, which are consistent with observations. This suggests that the model can be used with a climate model to study biogeophysical feedbacks in the climate system related to vegetation dynamics. 相似文献
97.
98.
Bonny Breckinridge DiNovo Richard Doan Roy B. Dyer Samuel Baron Norbert K. Herzog David W. Niesel 《FEMS immunology and medical microbiology》1996,15(2-3):149-158
Abstract Pathogenesis mediated by Shigella flexneri requires invasion of the gastrointestinal epithelium. It has been previously shown that HeLa cells challenged with S. flexneri show alterations in their phosphotyrosine-containing protein profile. In this report, we demonstrated that bacterial water extracts (WE) abrogated the invasion of HeLa cells by S. flexneri in a dose-dependent manner. A proteinaceous component of S. flexneri was shown to be responsible for this inhibitory activity. Proteins encoded on the 140-MDa plasmid were not responsible for the observed inhibition. WE from other Gram-negative bacteria also inhibited Shigella invasion of HeLa cells. HeLa cells pretreated with WE showed changes in the profile and the intensity of phosphotyrosine-containing protein bands. These data were consistent with a surface protein component in WE which initiated aberrant host cell signaling at the membrane which may account for the inhibition of bacterial entry. 相似文献
99.
The present study was undertaken to further characterize the nucleus reticularis gigantocellularis (NRGC) of the medulla oblongata in the central processing of nociceptive and cardiovascular signals, and its modulation by metenkephalin. In Sprague-Dawley rats anesthetized with pentobarbital sodium, we found that all 125 spontaneously active NRGC neurons that responded to noxious stimuli (tail clamp) also exhibited arterial pressure-relatedness. Forty neurons additionally manifested cardiac periodicity that persisted even during nociceptive responses. While maintaining their cardiovascular responsive characteristics, the nociception-related NRGC neuronal activity was blocked, naloxone-reversibly (0.5 mg/kg, i.v.), by morphine (5 mg/kg, i.v.). Microiontophoretically applied met-enkephalin suppressed the responsiveness of NRGC neurons to individually delivered tail clamp or transient hypertension induced by phenylephrine (5 µg/kg, i.v.). Interestingly, in NRGC neurons that manifested both nociception and arterial pressure relatedness, the preferential reduction in the response to noxious stimuli upon simultaneous elevation in systemic arterial pressure was reversed to one that favored nociception in the presence of met-enkephalin. All actions of met-enkephalin were discernibly blocked by the opioid receptor antagonist, naloxone. Our results suggest that individual NRGC neurons may participate in the processing of both nociceptive and cardiovascular information, or in the coordination of the necessary circulatory supports during nociception. In addition, neuropeptides such as met-enkephalin may exert differential modulation on neuronal responsiveness according to the prevailing physiologic status of the animal. They also showed that NRGC may be a central integrator for pain and cardiovascular-related functions. 相似文献
100.
Julie Gordon Robert Rumpf Samuel L. Shank Dawne Vernon C. William Birky 《Journal of phycology》1995,31(2):312-313
The nuclear Rrn18 gene coding for small-subunit ribosomal RNA was amplified from Chlamydomonas humicola and C. dysosmos. The sequences were identical, in agreement with the combination of these two species under the name C. applanata on morphological and physiological grounds by Ettl and Schlösser (1992). 相似文献