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1.
Murine Ia-associated invariant chain's processing to complex oligosaccharide forms and its dissociation from the I-Ak complex 总被引:5,自引:0,他引:5
G D Holt S J Swiedler J H Freed G W Hart 《Journal of immunology (Baltimore, Md. : 1950)》1985,135(1):399-407
The processing of murine invariant chain (Ii) to a cell surface form bearing complex N-linked oligosaccharides has been demonstrated in the B cell lymphoma, AKTB-1b. In addition, the rate of processing of pulse-labeled Ii has been determined relative to its rate of dissociation from the alpha/beta complex of I-Ak. Ii, alpha-, and beta-chains were immunoprecipitated with anti-I-Ak or anti-Ii monoclonal antibodies. The heretofore uncharacterized complex oligosaccharide form of Ii (Ii-c) was identified in gel-purified immunoprecipitates by peptide mapping with reverse-phase HPLC. Ii-c is resistant to deglycosylation by Endo H, which is specific for high-mannose N-linkages, but can be digested with Endo F, a glycosidase capable of cleaving both complex and high-mannose N-linked oligosaccharides. Immunoprecipitation of surface iodinated cells indicates that Ii-c is expressed on the plasma membrane. Pulse-chase metabolic labeling data show that the processing of Ii to Ii-c occurs with a t1/2 of about 120 min. In contrast, the processing of both alpha- and beta-chains of I-Ak to complex forms occurs with a t1/2 of 15 to 20 min. Our data show that Ii-hm begins to dissociate rapidly from the I-Ak complex after 100 to 120 min of chase. Only a small amount (less than 5% on a per mole basis) of Ii-c was found associated with the I-Ak complexes after 300 min of continuous metabolic labeling. These results are consistent with Ii serving as a carrier for Ia antigens as they are transported to the cell surface. In addition, they suggest that the processing of Ii to Ii-c, or a late processing event of the alpha- and beta-chains, such as their sialylation, may be a possible mechanism for inducing the dissociation of Ii from the I-Ak complex. 相似文献
2.
A sucrase gene from Leuconostoc mesenteroides was cloned and expressed in Escherichia coli. The cloned enzyme did not show dextransucrase or sucrose phosphorylase activity. HPLC and GC-MS analyses of the sucrase products indicated the presence of fructose and glucose in equimolar amounts. IPTG induction did not increase sucrase activity in E. coli indicating that the cloned gene may be transcribed from its own promoter. To our knowledge, this is the first sucrase cloned from L. mesenteroides that has invertase activity. 相似文献
3.
Elizabeth Holt 《Dialectical Anthropology》2005,29(3-4):387-396
In this paper, I read Leïla Sebbar’s staging in her novel Shérazade: 17 ans, brune, frisée, les yeux verts of the resistance by children of North African and other immigrants in the early 1980s to the French state’s cartographic modes and documents of control. The paper will consider the many uses to which the map was put by the French state in its colonization of North Africa and particularly Algeria, and later in its attempts to control the banlieues its policies of citizenship and cartographic control yielded on the margins of Paris. In this context, I will explore the ways in which the novel’s characters, living clandestinely in a squatt, simultaneously resist, put to use, and even supercede state documents of control as they disrupt everyday life and conduct heists across the city of Paris. The paper will explore unofficial cartographies of Paris, from those afforded by the radios libres and alternative publications such as Libération and Sans Frontièrez, to oral and almost proverbial networks of knowledge criss-crossing the city of Paris, while also tracing the uses to which supplemental cartographic sketches and counterfeit identity cards are put in the pages of the novel. The paper will be in dialogue with theoretical and critical formulations of space, cartography, and state control put forward by Michel de Certeau, Henri Lefebvre, Michel Foucault, and Tom Conley. The paper will conclude with a consideration of the means and limits of resistance by the novel’s characters in the context of this body of theory and criticism. 相似文献
4.
A P Weetman M E Holt A K Campbell R Hall A M McGregor 《BMJ (Clinical research ed.)》1984,288(6416):518-520
A study was conducted investigating the possibility that the immunosuppressive action of methimazole (the active metabolite of the antithyroid drug carbimazole) might be due to an effect on the production of oxygen radicals by monocytes. Techniques comprised measurement of luminol dependent chemoluminescence in monocytes and a spectrophotometric assay for production of hydrogen peroxide. The results showed definite inhibition of formation of oxygen radicals by resting and stimulated monocytes, which may explain the immunosuppressive action of the drug in Graves'' disease. The findings also suggest that the formation of oxygen radicals and the initiation of the immune response may be closely related. 相似文献
5.
T M Holt 《The American journal of anatomy》1975,144(2):169-195
Some question exists concerning the ability of the embryonic tongue to undergo reflex movements at the time of palatal closure (15.5 days of development). Functional motor endplates are prerequisite for such movements to occur. Light and ultrastructural cytochemical methods were employed to elucidate the morphology of neuromuscular relationships in the developing mouse tongue. The A/Jax mice used in the experiments demonstrated a 12-20% incidence (seasonal variation) of spontaneous cleft palate, allowing a correlation between normal and teratological processes. Organized myofibrils were first seen in tongues of normal and spontaneous cleft lip-cleft palate (SCL-CP) specimens at 14.5 days of development. The thiocholine technique of Karnovsky and Roots was used to demonstrate acetylcholinesterase (AChE) activity at the light microscope level. The Lewis and Schute method was used for ultrastructural localization of this enzyme. Tissues from normal and SCL-CP specimens from 12.5 to 20.5 days of gestation failed to show differences in amounts or distribution of AChE activity. AChE activity was seen as early as 14 day's gestation. Electron microscopic studies demonstrated reaction product in the endoplasmic reticulum and nuclear envelope of developing myoblasts. AChE activity at the developing neuromuscular junction and the occurrence of myofilaments preceded palatal closure by several days. Based on these morphological and histochemical findings the tongue of normal and SCL-CP embryos appears capable of responding to a neurogenic stimulus at the time of palatal closure. The findings suggest that the tongue of animals exhibiting a spontaneous cleft palate is not actively involved in the etiology of this condition. 相似文献
6.
Transmucosal transport rates for triolein in proximal and distal intestine were compared in unanesthetized rats. Emulsified [1-14-C] triolein together with bile and pancreatic juice from donor rats was infused for 6 hr into either the duodenum or the midpoint of the small intestine at such a rate that absorption was essentially complete in both regions of the intestine. Lymph was collected from the thoracic duct during triolein infusion and for an additional 6-hr period. The decrease in the rate of lymphatic output of labeled fat was found to follow a simple exponential function in all animals. This rate of decrease (decay rate) was used to calculate the half-times of lipid turnover through the intestinal wall and the fractional output rates. Distal intestine transported lipid 40% more slowly than proximal intestine, and the difference was associated with a greater accumulation of triglyceride in the distal intestinal wall. Chylomicron synthesis and/or release is the rate-limiting step for distal lymphatic fat transport in vivo, whereas fat uptake from the lumen is rate limiting for proximal intestine. 相似文献
7.
8.
Mutation response at the HGPRT locus has been compared in two differing cell lines: V79/4, an aneuploid Chinese-hamster fibroblast line with a complement of 20 chromosomes, and BHK21-C13, a diploid Syrian-hamster fibroblast line with a complement of 44 chromosomes. The data presented show that BHK is slightly more radiosensitive than V79/4; however, the toxicity curves and expression times are similar for both cell lines. If radiosensitivity is taken into account, a common line can be drawn for radiation mutagenesis. We conclude from the data that radiation-induced mutagenesis is broadly equivalent in the two cell lines examined, and is not dependent on the chromosome complement. 相似文献
9.
We found 8-azidoadenosine 5'-diphosphate to be a phosphoryl acceptor in the enzymatic conversion of 1,3-diphosphoglyceric acid to 3-phosphoglycerate. This has allowed us to synthesize in a single-step procedure carrier-free 8-azidoadenosine 5'-[gamma-32P]triphosphate, requiring no further purification of the end product. The synthesized 8-azidoadenosine 5'-[gamma-32P]triphosphate has been characterized and shown to meet all the criteria for a specific photoreactive ATP analogue. 相似文献
10.
J L Slonczewski T N Gonzalez F M Bartholomew N J Holt 《Journal of bacteriology》1987,169(7):3001-3006