Temperature-Mediated Interaction of Tetanus Toxin with Cerebral Neuron Cultures: Characterization of a Neuraminidase-Insensitive Toxin-Receptor Complex

Abstract: Energy-dependent internalization of ¹²⁵I-labeled tetanus toxin into cultured neural cells is shown to follow an energy-independent binding process. A three-step model, involving receptor-mediated binding followed by sequestration and internalization is proposed. In the first step, binding of toxin is enhanced in appearance under low ionic strength medium, at 0–4°C; it is suppressed, however, with increasing incubation temperature under physiological salt concentrations. Cell-bound toxin is displaced by approximately 35.5% when high-salt medium (physiological concentrations) is added to cells at 0–4°C; the effect is further amplified at 37°C. Addition of disialoganglioside G_D1b (1–5 μg/ml) also lowers the amount of cell-associated toxin. The fraction of ¹²⁵I-labeled toxin retained by the cells after exposure to high-salt medium at 0–4°C or after addition of G_D1b is operationally defined as sequestered toxin. This second step, characterized by a stable association of the toxin with the neural cells, is affected by both physiological salt and by 37°C conditions. Lastly, an energy-dependent phenomenon of firm association of tetanus toxin with neural cells, compatible with internalization, is described. The toxin residing in this fraction is bioactive and cannot be removed by salts, gangliosides, or by treatment with protease or neuraminidase. Binding, sequestration, and internalization are mutually dependent, as they are all blocked by pretreatment of cells with neuraminidase and by an enhanced energy-independent sequestration event, which results in enhanced tetanus toxin internalization by an energy-dependent process.     

Antigen-binding receptors on T cells from long-term MLR. Evidence of binding sites for allogeneic and self-MHC products

Antibody inhibition of radiolabelled stimulator membrane vesicle binding by T blasts activated in the mixed lymphocyte reaction (MLR) was used to identify responder-cell determinants involved in the binding phenomenon. Antisera or monoclonal antibodies against Thy-1, Lyt-1, Lyt-2 and Ly-6 antigens were not inhibitory. However, antibodies against heavy-chain V region (V_H) determinants strongly inhibited vesicle binding by both primary and longterm MLR blasts. Anti-Ia (both alloantisera and monoclonal reagents) caused inhibition of antigen binding by primary MLR blasts only. T blasts from long-term MLR lines were neither Ia-positive, nor susceptible to blocking of antigen binding with anti-Ia. However, these cells were capable of specifically absorbing soluble syngeneic Ia material, with the concomitant appearance of vesiclebinding inhibition with anti-Ia sera. Acquisition of syngeneic Ia by T blasts was effectively blocked with the anti-V_H reagent. Passively bound self-Ia did not interfere with vesicle binding in the absence of anti-Ia. These results strongly suggest the existance of specific self-Ia acceptor sites closely linked to the receptors for stimulator alloantigens on T cells proliferating in MLR. A receptor model based on these findings is briefly discussed.Abbreviations used in this paper B10 C57BL/10 - Con A concanavalin A - FcR Fc receptor - FCS fetal calf serum - H heavy chain - Ia I-region associated antigen - Ig immunoglobulin - LPS lipopolysaccharide - Lyt T-lymphocyte differentiation antigen - MHC major histocompatibility complex - MLR mixed lymphocyte reaction - PM plasma membrane - T thymus derived - Tcr T-cell receptor - V variable region of Ig     

Antigen-binding receptors on T cells from long-term MLR. evidence of binding sites for allogeneic and self-MHC products

Antibody inhibition of radiolabelled stimulator membrane vesicle binding by T blasts activated in the mixed lymphocyte reaction (MLR) was used to identify responder-cell determinants involved in the binding phenomenon. Antisera or monoclonal antibodies against Thy-1, Lyt-1, Lyt-2 and Ly-6 antigens were not inhibitory. However, antibodies against heavy-chain V region (VH) determinants strongly inhibited vesicle binding by both primary and long-term MLR blasts. Anti-Ia (both alloantisera and monoclonal reagents) caused inhibition of antigen binding by primary MLR blasts only. T blasts from long-term MLR lines were neither Ia-positive, nor susceptible to blocking of antigen binding with anti-Ia. However, these cells were capable of specifically absorbing soluble syngeneic Ia material, with the concomitant appearance of vesicle-binding inhibition with anti-Ia sera. Acquisition of syngeneic Ia by T blasts was effectivelly blocked with the anti-VH reagent. Passively bound self-Ia did not interfere with vesicle binding in the absence of anti-Ia. These results strongly suggest the existance of specific self-Ia acceptor sites closely linked to the receptors for stimulator alloantigens on T cells proliferating in MLR. A receptor model based on these findings is briefly discussed.     

DNA ploidy as a prognostic factor in rhabdomyosarcoma. Analysis of 35 cases with image cytometry

OBJECTIVE: To correlate DNA ploidy in rhabdomyosarcoma (RMS) with other prognostic factors and patient survival and to search for possible reasons for inconsistent conclusions in similar, published studies. STUDY DESIGN: DNA content was measured in archival specimens obtained from 35 patients (23 children and 12 adults) with RMS. Cell suspensions were prepared by the modified Hedley technique, stained by the modified Feulgen-thionin method and analyzed by automated high-resolution image cytometry. DNA ploidy was assessed on the basis of DNA index values. We used the chi 2 test to correlate DNA ploidy with other prognostic factors, Kaplan-Meier procedure to estimate overall survival in terms of individual prognostic factors, log-rank test to calculate differences in survival between groups and Cox multivariate regression analysis to determine the independence of variables in relation to survival. RESULTS: A statistically significant correlation was found only between DNA ploidy and histologic subtype of RMS, patient sex and patient age. A hyperdiploid DNA pattern predominated among patients with embryonal RMS, and a tetraploid pattern dominated among patients with alveolar RMS. The highest 5-year survival rate was seen among patients with hyperdiploid RMS, followed by those with diploid, tetraploid and hypertetraploid RMS. Although DNA ploidy was a significant prognostic factor in univariate analysis, it did not retain its independent prognostic value in multivariate analysis, in which patient age, tumor size and histologic subtype were the only significant factors. We found 12 articles reporting on the association between DNA ploidy and survival of patients with RMS: 6 found a correlation, and 6 did not. The main reasons for the discrepancies seem to be the inclusion of chemotherapy-treated and nontreated patients, low number of patients and differences in grouping DNA histograms. CONCLUSION: The precise prognostic value of DNA ploidy in RMS remains equivocal. Larger, cooperative studies could give statistically more reliable results.     

mTOR generates an auto-amplification loop by triggering the βTrCP- and CK1α-dependent degradation of DEPTOR

DEPTOR is a recently identified inhibitor of the mTOR?kinase that is highly regulated at the posttranslational level. In response to mitogens, we found that DEPTOR was rapidly phosphorylated on three serines in a conserved degron, facilitating binding and ubiquitylation by the F box protein βTrCP, with consequent proteasomal degradation of DEPTOR. Phosphorylation of the βTrCP degron in DEPTOR is executed by CK1α after a priming phosphorylation event mediated by either the mTORC1 or mTORC2 complexes. Blocking the βTrCP-dependent degradation of DEPTOR via βTrCP knockdown or expression of a stable DEPTOR mutant that is unable to bind βTrCP results in mTOR inhibition. Our findings reveal that mTOR cooperates with CK1α and βTrCP to generate an auto-amplification loop to promote its own full activation. Moreover, our results suggest that pharmacologic inhibition of CK1 may be?a viable therapeutic option for the treatment of cancers characterized by activation of mTOR-signaling pathways.     

Chromosome aberration and environmental physical activity: Down syndrome and solar and cosmic ray activity, Israel, 1990–2000

The possibility that environmental effects are associated with chromosome aberrations and various congenital pathologies has been discussed previously. Recent advances in the collection and computerization of data make studying these potential associations more feasible. The aim of this study was to investigate a possible link between the number of Down syndrome (DS) cases detected prenatally or at birth yearly in Israel over a 10-year period compared with the levels of solar and cosmic ray activity 1 year before the detection or birth of each affected child. Information about 1,108,449 births was collected for the years 1990–2000, excluding 1991, when data were unavailable. A total of 1,310 cases of DS were detected prenatally or at birth—138 in the non-Jewish community and 1,172 in the Jewish population. Solar activity indices—sunspot number and solar radio flux 2,800 MHz at 10.7 cm wavelength for 1989–1999—were compared with the number of DS cases detected. Pearson correlation coefficients (r) and their probabilities (P) were established for the percentage of DS cases in the whole population. There was a significant inverse correlation between the indices of solar activity and the number of cases of DS detected—r=–0.78, P=0.008 for sunspot number and r=–0.76, P=0.01 for solar flux. The possibility that cosmophysical factors inversely related to solar activity play a role in the pathogenesis of chromosome aberrations should be considered. We have confirmed a strong trend towards an association between the cosmic ray activity level and the incidence of DS.