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271.
Neural dynamics in a model of the thalamocortical system. I. Layers, loops and the emergence of fast synchronous rhythms 总被引:3,自引:2,他引:1
A large-scale computer model was constructed to gain insight into the
structural basis for the generation of fast synchronous rhythms (20-60 Hz)
in the thalamocortical system. The model consisted of 65,000 spiking
neurons organized topographically to represent sectors of a primary and
secondary area of mammalian visual cortex, and two associated regions of
the dorsal thalamus and the thalamic reticular nucleus. Cortical neurons,
both excitatory and inhibitory, were organized in supragranular layers,
infraganular layers and layer IV. Reciprocal intra- and interlaminar,
interareal, thalamocortical, corticothalamic and thalamoreticular
connections were set up based on known anatomical constraints. Simulations
of neuronal responses to visual input revealed sporadic epochs of
synchronous oscillations involving all levels of the model, similar to the
fast rhythms recorded in vivo. By systematically modifying physiological
and structural parameters in the model, specific network properties were
found to play a major role in the generation of this rhythmic activity. For
example, fast synchronous rhythms could be sustained autonomously by
lateral and interlaminar interactions within and among local cortical
circuits. In addition, these oscillations were propagated to the thalamus
and amplified by corticothalamocortical loops, including the thalamic
reticular complex. Finally, synchronous oscillations were differentially
affected by lesioning forward and backward interareal connections.
相似文献
272.
Twenty-four patients with aplastic anemia or acute leukemia were treated by marrow grafts from HLA-identical donors after conditioning with high doses of cyclophosphamide and/or today body irradiation. They were studied between 4 and 63 mo (median 14.2) after transplantation. Seventeen patients had chronic graft-versus-host disease (C-GVHD) and 7 were healthy. They were studied for defects in their T- and B-cell function using and indirect hemolytic plaque assay for Ig production after 6 days of culture in the presence of pokeweek mitogen. T or B cells from the patients with or without C-GVHD were cocultured with T or B cells from their HLA-identical marrow donors or unrelated normal controls. Intrinsic B-cell defects, lack of helper T-cell activity, and suppressor T-cell activity were more frequently found in patients with C-GVHD than in healthy patients. Fifteen of the 17 patients with C-GVHD showed on or more defects in their T-and B-cell function compared to only 3 of the 7 patients without C-GVHD. None of the healthy controls, including the marrow donors, showed defects in their T- and B-cell functions. These in vitro findings may be helpful in assessing the process of immune reconstitution and the immunologic aberration found after human marrow transplantation. 相似文献
273.
Fifty-four patients with severe aplastic anemia were treated with horse anti-human thymocyte globulin (ATG) and androgens. Thirty of these patients also received an infusion of HLA-haploidentical marrow cells. Only those patients having evidence of hematologic recovery within 3 mo after ATG therapy were considered responders to the immunosuppressive regimen. Of 53 patients evaluable for response, 21 had complete or partial responses and 7 had minimal improvement by defined criteria. The remaining patients did not respond or died. Factors correlated with response to therapy included a short duration of aplasia and a high admission granulocyte count. Thirty-six patients (66.7%) are surviving between 18 and 43 mo, and 18 have died. Deaths were due to hemorrhage and/or infection. Short duration of aplasia and high granulocyte counts also correlated with survival, as did younger age. Four patients with complete or partial responses had a recurrence of severe aplasia 6-17 mo after their first course of ATG. Three of these patients were retreated with ATG (and oxymetholone in two cases). All three had second responses to therapy, but two of the three have had second relapses. The fourth patient responded to oxymetholone alone, but died after a second relapse. Mismatched marrow infusion had no effect on the incidence of response or survival. 相似文献
274.
Epstein-Barr virus genomes are restricted to secondary neoplastic cells following bone marrow transplantation 总被引:1,自引:0,他引:1
DNA from mononuclear blood and tumor cells from 33 patients undergoing bone marrow transplantation for leukemia was examined for the presence of Epstein-Barr virus (EBV) genomes by blot hybridization. Four groups of patients were studied soon after engraftment, during long-term remission, after relapse of the original leukemia, and after development of secondary B cell neoplasms. Only the cells of patients with secondary neoplasms demonstrated EBV genomes, where all five adequately studied samples were positive. Samples from all other patient categories were negative for EBV genomes. We conclude that EBV genomes do not frequently persist in normal engrafted lymphocytes or in mononuclear cells of patients suffering recurrent leukemia. These results are consistent with EBV playing a role in the genesis of secondary B cell neoplasms following bone marrow transplantation. 相似文献
275.
Of the first 350 bases upstream of the ATG signal sequences were obtained representing the following HLA-A locus alleles: A*01, A*0102, A*02, A*0202, A*0206, A*0207, A*03, A*0302, A11.2, A11.1, A*68, A*68011, A*30, A*3002, A*23, A*24, A*26, A*2602, A*25, A*29, A*2902, A*31, A*31011, A*32, A*3201, A*33, A*3301, A*3303, A*34, A*6601, A*6602 A*74, A*80. We found 21 polymorphic positions of which a surprisingly large number (altogether 9) represent allele specific exchanges. For all 35 alleles tested of the HLA-A locus we found 16 different types of promoter. While all tested A2 subtypes, A*0201, A*0202, A*0206, A*0207 share the same promoter, there were in contrast several situations in which different subtypes of the same group have different promoters. This is true for HLA A*01, A*0102; A*03, A*0302; A*30, A*3002; A*6601, A*6602; A*32, A*3201; A*29, A*2902. Looking at the binding sites for nuclear factors, we observe that TATA-box, CAT-box, Enhancer B, the interferon response sequence and the Enhancer A (except HLA-A30 has one base exchange) are conserved within the HLA-A locus. The interferon response sequence shows for all A-locus alleles a double base pair exchange (TT for AC). In comparison with the promoter polymorphism of the HLA-B locus (Yao et al., 1995) we find a surprising diversity of the promoters in the HLA-A locus. While for the B-locus promoters large groups of sometimes strongly different alleles share the same promoter, in the HLA-A locus there is a private promoter for almost each allele and sometimes even each subtype. This lead to the conclusion that the promoter polymorphisms of the HLA-A and the HLA-B locus have been subjected to different selection pressure in evolution. 相似文献
276.
Accuracy of specific IgE in the prediction of asthma: development of a scoring formula for general practice 总被引:2,自引:0,他引:2
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Petra ED Eysink Gerben ter Riet Rob C Aalberse Wim MC van Aalderen Carel M Roos Jaring S van der Zee Patrick JE Bindels 《The British journal of general practice》2005,55(511):125-131
BACKGROUND: For the diagnosis of asthma in young children, GPs have to rely on history taking and physical examination, as spirometry is not possible. The additional diagnostic value of specific immunoglobulin E (IgE) to inhalent allergens remains unclear. AIM: To assess the predictive accuracy of specific IgE to cat, dog, and/or house dust mites in young children for the subsequent development of asthma at the age of 6 years. DESIGN OF STUDY: Prospective follow-up study. SETTING: Seventy-two general practices. METHOD: A total of 654 children, aged 1-4 years, visiting their GPs for persistent coughing (>/= 5 days), were tested for IgE antibodies by radio allergosorbent testing (RAST). Parents completed a questionnaire on potential risk indicators. Those children who showed an IgE-positive status (12.7%) and a random sample of those with an IgE-negative status (<0.5 U/ml) were followed up to the age of 6 years when the asthma status was established. The main outcome measure was asthma at the age of 6 years (combination of both symptoms and/or use of asthma medication, and impaired lung function). RESULTS: Addition of RAST results to a prediction model based on age, wheeze, and family history of pollen allergy increased the area under the receiver operating characteristic (ROC) curve from 0.76 to 0.87. Furthermore, RAST improved patient differentiation as indicated by a change in the range of asthma probabilities from 6-75% before the IgE test, to 1-95% after the IgE-test. CONCLUSION: Sensitisation to inhalant allergens in 1-4-year-olds, as shown by RAST, is a useful diagnostic indicator for the presence of asthma at the age of 6 years, even after a clinical history has been obtained. This model should preferably be validated in a new population before it can be applied in practice. 相似文献
277.
Severe aplastic anemia: a prospective study of the effect of early marrow transplantation on acute mortality 总被引:17,自引:5,他引:17
Camitta BM; Thomas ED; Nathan DG; Santos G; Gordon-Smith EC; Gale RP; Rappeport JM; Storb R 《Blood》1976,48(1):63-70
A prospective randomized trial of therapy for severe aplastic anemia was designed to compare early bone marrow transplantation with conventional treatments. All patients with a sibling matched at the major histocompatibility region were transplanted. Transplantation was performed with 17-100 (median 33) days of original diagnosis. Conventional treatments included transfusion support with or without androgens. Twenty-four of 36 patients intered on the transplant arm are alive after 4-20 (median 9) mo with full marrow reconstitution. Only two are limited by chronic graft-versus-host disease. In contrast only 12 of 31 conventionally treated patients are alive. Six of these survivors have improved, five incompletely. The 19 nontransplant deaths have occurred within 1-11 (median 3) mo of diagnosis. Compared to nontransplant regimens, early transplantation more effectively restores normal marrow function and decreases the acute mortality of severe marrow aplasia (p = 0.006). Pending longer follow-up, early marrow transplantation appears to be the most effective available treatment for severe aplastic anemia. 相似文献
278.
Role of endothelial cells in human hematopoiesis: modulation of mixed colony growth in vitro 总被引:10,自引:1,他引:10
The identification of clonal human multipotent hematopoietic progenitors has permitted an analysis of the growth factor requirements for these cells. Human endothelial cell cultures were used to examine the effects of media conditioned by the endothelial cells on human multipotent (CFU-mix) and committed erythroid (BFU-E, CFU-E) and myeloid (CFU-GM) precursors. These studies demonstrate that endothelial cells produce proteins of approximately 30,000 daltons, with isoelectric focusing points of 4.5 and 7.2, which stimulate the growth of human BFU-E and CFU-mix. A heat-labile protein(s) of 30,000 and 15,000 daltons stimulated the proliferation and differentiation of granulocyte-macrophage (CFU-GM) colonies. No erythropoietin was detected in endothelial cell supernatants. This suggests that endothelial cells, a normal component of marrow stroma, play an active role in the modulation of human hematopoietic stem cell growth. 相似文献
279.
Stauder R; Van Driel M; Schwarzler C; Thaler J; Lokhorst HM; Kreuser ED; Bloem AC; Gunthert U; Eisterer W 《Blood》1996,88(8):3101-3108
280.
Singer JW; Keating A; Ramberg R; McGuffin R; Sanders JE; Sale G; Fialkow PJ; Thomas ED 《Blood》1983,62(4):869-872
This article describes the course of a patient who received an allogeneic marrow graft from his HLA-identical sister for acute lymphoblastic leukemia in second remission. In the second month after grafting, marrow aspirates showed the presence of 7%-10% lymphoblasts. In addition, cytogenetic examination indicated the persistence of host cells. Thereafter, the patient had morphologically normal marrow examinations, with no evidence for recurrent leukemia. In addition, stable hematopoietic chimerism in both the lymphoid and myeloid cell lines has persisted for over 5 yr. Between 20% and 50% of phytohemagglutinin-stimulated peripheral blood mononuclear cells were host-derived on repeated studies. A marrow sample 4 yr after transplantation was established in long-term culture and produced 2% host granulocyte-macrophage colonies at its inception, but 24% host colonies by week 4. Despite this persistent chimerism, no in vitro or in vivo abnormalities of hematopoiesis have been detected. 相似文献