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Bouillon M El Fakhry Y Girouard J Khalil H Thibodeau J Mourad W 《The Journal of biological chemistry》2003,278(9):7099-7107
Lipid rafts are plasma membrane microdomains that are highly enriched in signaling molecules and that act as signal transduction platforms for many immune receptors. The involvement of these microdomains in HLA-DR-induced signaling is less well defined. We examined the constitutive presence of HLA-DR molecules in lipid rafts, their possible recruitment into these microdomains, and the role of these microdomains in HLA-DR-induced responses. We detected significant amounts of HLA-DR molecules in the lipid rafts of EBV(+) and EBV(-) B cell lines, monocytic cell lines, transfected HeLa cells, tonsillar B cells, and human monocytes. Localization of HLA-DR in these microdomains was unaffected by the deletion of the cytoplasmic domain of both the alpha and beta chains. Ligation of HLA-DR with a bivalent, but not a monovalent, ligand resulted in rapid tyrosine phosphorylation of many substrates, especially Lyn, and activation of ERK1/2 MAP kinase. However, the treatment failed to induce further recruitment of HLA-DR molecules into lipid rafts. The HLA-DR-induced signaling events were accompanied by the induction of cell-cell adhesion that could be inhibited by PTK and Lyn but not ERK1/2 inhibitors. Disruption of lipid rafts by methyl-beta-cyclodextrin (MbetaCD) resulted in the loss of membrane raft association with HLA-DR molecules, inhibition of HLA-DR-mediated protein tyrosine phosphorylation and cell-cell adhesion. MbetaCD did not affect the activation of ERK1/2, which was absent from lipid rafts. These results indicate that although all the HLA-DR-induced events studied are dependent on HLA-DR dimerization, some require the presence of HLA-DR molecules in lipid rafts, whereas others do not. 相似文献
54.
An ectonucleoside triphosphate diphosphohydrolase 1 (NTPDase1) activity present in alkaline phosphatase-depleted rat osseous plate membranes, obtained 14 days after implantation of demineralized bone particles in the subcutaneous tissue of Wistar rats, was characterized. At pH 7.5, NTPDase1 hydrolyzed nucleotide triphosphates at rates 2.4-fold higher than those of nucleotide diphosphates, while the hydrolysis of nucleotide monophosphates and non-nucleotide phosphates was negligible. NTPDase 1 hydrolyzed ATP and ADP following Michaelis-Menten kinetics with V=1278.7+/-38.4 nmol Pi/min/mg and K(M)=83.3+/-2.5 microM and V=473.9+/-18.9 nmol Pi/min/mg and K(M)=150.6+/-6.0 microM, respectively, but in the absence of magnesium and calcium ions, ATP or ADP hydrolysis was negligible. The stimulation of the NTPDase1 by calcium (V=1084.7+/-32.5 nmol Pi/min/mg; and K(M)=377.8+/-11.3 microM) and magnesium (V=1367.2+/-41.0 nmol Pi/min/mg and K(M)=595.3+/-17.8 microM) ions suggested that each ion could replace the other during the catalytic cycle of the enzyme. Oligomycin, ouabain, bafilomycin A(1), theophylline, thapsigargin, ethacrynic acid, P(1),P(5)-(adenosine-5')-pentaphosphate and omeprazole had negligible effects on the hydrolysis of ATP and ADP by NTPDase1. However, suramin and sodium azide were effective inhibitors of ATP and ADP hydrolysis.To our knowledge this is the first report suggesting the presence of NTPDase1 in rat osseous plate membranes. Considering that the ectonucleoside triphosphate diphosphohydrolase family of enzymes participates in many regulatory functions, such as response to hormones, growth control, and cell differentiation, the present observations raise interesting questions about the participation of this activity in the calcification process. 相似文献
55.
dos Santos VM de Lima MA Cabrine-Santos M Marquez Dde S Reis Md Pereira Gde A Lages-Silva E Ramírez LE 《Experimental parasitology》2002,100(2):103-111
Hepatocytic metaplasia may be induced in hamsters by carcinogens, and associated with aging, diabetes or chronic pancreatitis. By means of histopathologic and immunohistochemic studies, we observed pancreatic hepatocytes in hamsters infected and reinfected with Trypanosoma cruzi. The change was seen in 18 (19%) out of 94 infected animals, and was not found among 53 controls, Normal islet cells were immunoreactive for neuron-specific enolase and not reactive for NCL-HAS. Metaplastic cells were immunoreactive for NCL-HAS and not reactive for islet hormones and enolase. No relationship was observed between number of inoculations and metaplasia; however, the intensity of the inflammatory process and sequels seems to favor the development of metaplastic cells. Hamsters infected with T. cruzi may be useful to study hepatocytic metaplasia, and contribute to clarify aspects of Chagas' disease and pancreatic changes. Our data indicate that aging, in addition to inflammation and atrophy, plays a role in this change. 相似文献
56.
Ribeiro KC Mariante RM Coutinho LL Benchimol M 《Biology of the cell / under the auspices of the European Cell Biology Organization》2002,94(4-5):289-301
We present observations on the fine structure and the division process of the nucleus in the protist Tritrichomonas foetus, parasite of the urogenital tract of cattle. The nucleus was followed by immunofluorescence and electron microscopy during interphase and mitosis. Conventional karyotyping coupled to image processing and bright field Panotic staining were used to follow nucleus modifications, chromosome number and condensation pattern along the whole cell cycle. Confocal laser scanning microscopy (CLSM) using DNA fluorescent probes, followed by image processing in the SURF-Driver program, produced three-dimensional reconstruction data of the mitotic nucleus under each phase of the division process. Immunocytochemistry in thin-sections revealed the chromosome spatial arrangement after bromodeoxyuridine incorporation and immunogold labeling using anti-DNA monoclonal antibodies. Our results indicate that: (1) the nucleus assumes different size and shapes along mitosis: it appears oval in interphase, becoming lobed or concave in prophase, then undergoing torsion and constriction, displaying an 'S' shape (metaphase). Next, it becomes elongated and it is finally separated in two nuclei at the transition of anaphase to telophase; (2) T. foetus nucleus harbors five chromosomes; (3) chromosomes become condensed in a pre-mitotic phase; (4) the nucleolus persists during the mitosis. 相似文献
57.
Ribeiro KC Pereira-Neves A Benchimol M 《Biology of the cell / under the auspices of the European Cell Biology Organization》2002,94(3):157-172
In the present work, we followed the several phases of Tritrichomonas foetus and Trichomonas vaginalis cell cycles using immunofluorescence, serial thin sections, three-dimensional (3D) reconstruction, and transmission electron microscopy. In motile trichomonad cells or in pseudocyst forms, the nuclear envelope persists throughout mitosis, and the spindle is extranuclear. We found three types of spindle microtubules: pole-to-nucleus microtubules which are attached to the nuclear envelope, pole-to-pole microtubules forming a cylindrical, cytoplasmic groove on the nuclear compartment in pseudocysts of T. foetus cells, and pole-to-cytosol microtubules which extend freely into the cytoplasm. We demonstrated that: (1) in T. foetus, the spindle is assembled from an MTOC located at the base of the costa, underneath one of the basal bodies; (2) the spindle presents an unusual arc shape during the initial phases of mitosis in motile trophozoites; (3) the spindle microtubules are glutamylated, but not acetylated; (4) several membranes similar to those of the endoplasmic reticulum follow the spindle microtubules; (5) finger-like projections extend from the nucleus towards the cell poles in pseudocysts and multinucleated cells; and (6) vesicles formed in between the two nuclear membranes are seen in the course of mitosis in both trophozoite and pseudocyst forms. 相似文献
58.
Recent interest has focused on immune response in an evolutionary context, with particular attention to disease resistance as a life-history trait, subject to trade-offs against other traits such as reproductive effort. Immune defense has several characteristics that complicate this approach, however; for example, because of the risk of autoimmunity, optimal immune defense is not necessarily maximum immune defense. Two important types of cost associated with immunity in the context of life history are resource costs, those related to the allocation of essential but limited resources, such as energy or nutrients, and option costs, those paid not in the currency of resources but in functional or structural components of the organism. Resource and option costs are likely to apply to different aspects of resistance. Recent investigations into possible trade-offs between reproductive effort, particularly sexual displays, and immunity have suggested interesting functional links between the two. Although all organisms balance the costs of immune defense against the requirements of reproduction, this balance works out differently for males than it does for females, creating sex differences in immune response that in turn are related to ecological factors such as the mating system. We conclude that immune response is indeed costly and that future work would do well to include invertebrates, which have sometimes been neglected in studies of the ecology of immune defense. 相似文献
59.
Kane AA Butman JA Mullick R Skopec M Choyke P 《Plastic and reconstructive surgery》2002,109(2):472-481
The purpose of this project was to assess the feasibility of imaging the velopharynx of adult volunteers during repetitive speech, using gated magnetic resonance imaging (MRI). Although a number of investigators have used conventional MRI in the study of the human vocal tract, the mismatch between the lengthy time necessary to acquire sufficiently detailed images and the rapidity of movement of the vocal tract during speech has forced investigators to acquire images either while the subject is at rest or during sustained utterances. The technique used here acquired a portion of each image during repetitive utterances, building the full image over multiple utterance cycles. The velopharyngeal portal was imaged on a 1.5-Tesla GE Signa LX 8.2 platform with gated fast spoiled gradient echo protocol. An external 1-Hertz trigger was fed to the cardiac gate. Subjects synchronized utterance of consonant-vowel syllables to a flashing light synchronized with the external trigger. Each acquisition of 30 phases per second at a single-slice location took 22 to 29 seconds. Four consonant-vowel syllables (/pa/, /ma/, /sa/, and /ka/) were evaluated. Subjects vocalized throughout the acquisition, beginning 5 to 6 seconds beforehand to establish a regular rhythm. Imaging of the velopharyngeal portal was performed for sagittal, velopharyngeal axial (aligned perpendicular to the "knee" of the velum), axial, and coronal planes. Volumes were obtained by sequential acquisition of six to 10 slices (each with 30 phases) in the axial or sagittal planes during repetition of the /pa/ syllable. Spatiotemporal volumes of the single-slice data were sectioned to provide time-motion images (analogous to M-mode echocardiograms). Three-dimensional dynamic volume renderings of palate motion were displayed interactively (Vortex; CieMed, Singapore). A method suitable for the collection and visualization of four-dimensional information regarding monosyllabic speech using gated MRI was developed. These techniques were applied to a population of adult volunteer subjects with no history of speech problems and two patients with a history of cleft lip and palate. The techniques allowed good real-time visualization of velopharyngeal anatomy during its entire range of motion and was also able to image pathology-specific anatomic differences in the subjects with cleft lip and cleft palate. These methods may be applicable to a wide spectrum of problems in speech physiology research and for clinical decision-making regarding surgery for speech and outcomes analysis. 相似文献
60.