A functional spiking-neuron model of activity-silent working memory in humans based on calcium-mediated short-term synaptic plasticity

In this paper, we present a functional spiking-neuron model of human working memory (WM). This model combines neural firing for encoding of information with activity-silent maintenance. While it used to be widely assumed that information in WM is maintained through persistent recurrent activity, recent studies have shown that information can be maintained without persistent firing; instead, information can be stored in activity-silent states. A candidate mechanism underlying this type of storage is short-term synaptic plasticity (STSP), by which the strength of connections between neurons rapidly changes to encode new information. To demonstrate that STSP can lead to functional behavior, we integrated STSP by means of calcium-mediated synaptic facilitation in a large-scale spiking-neuron model and added a decision mechanism. The model was used to simulate a recent study that measured behavior and EEG activity of participants in three delayed-response tasks. In these tasks, one or two visual gratings had to be maintained in WM, and compared to subsequent probes. The original study demonstrated that WM contents and its priority status could be decoded from neural activity elicited by a task-irrelevant stimulus displayed during the activity-silent maintenance period. In support of our model, we show that it can perform these tasks, and that both its behavior as well as its neural representations are in agreement with the human data. We conclude that information in WM can be effectively maintained in activity-silent states by means of calcium-mediated STSP

Variation in gene copy number and polymorphism of the human salivary amylase isoenzyme system in Caucasians

The polymorphic patterns of human salivary amylase of a large number of individuals of Caucasian origin were determined by using isoelectric focusing and polyacrylamide gel electrophoresis. Nine different salivary amylase protein variants were found; three of them are recorded for the first time and their heredity is shown. Some of the variants are encoded by haplotypes expressing three allozymes. Most variants display low frequencies. Analysis of the relative intensities of variant-specific isozyme bands, combined with segregation analysis, show that extensive quantitative variation is present in the population. The numbers of salivary amylase genes in some families showing quantitative variation at the protein level have been estimated by the polymerase chain reaction. We present evidence that quantitative variations in amylase protein patterns do not always reflect variations in gene copy number but that other mechanisms are also involved. © 1992 Springer-Verlag

Histopathological Features of Early Onset Indonesian Breast Cancer Pointing to Brca1/2 Germline Mutations

Background: Breast cancer under 40 years concerns a relatively small subgroup of cases that tend to display a more aggressive phenotype. Compatible with this, early age of onset has been known as one of clinical characteristic of hereditary breast cancers associated with germline BRCA1 or BRCA1 mutations. As early onset breast cancer is frequent in Indonesia, we investigated the histopathological and immunohistochemical characteristics of early onset (< 40 years) Indonesian breast cancer patients, as such features can be used to distinguish between BRCA and non-BRCA germline mutation carriers among these young women.Method: Thirty-five formalin-fixed and paraffin-embedded tissue sections of young women (mean 36 years, range 22-40 years) who underwent surgical resection at the Department of Surgery of the Sardjito Hospital Yogyakarta were examined for pathological features, estrogen and progesterone receptor status, proliferation as determined by Ki67 labeling, EGFR and CK5/6 and the presence of HER-2/neu and p53 protein. Additionally, mutation analysis for BRCA1 and BRCA2 was performed in 30 young women. The control group consisted ofcarcinomas from women above 50 years (mean 59.02, range 50-80 years).Result: Carcinomas occurring in women aged below 40 years were more often advanced stage and higher proliferating (p=0.006). Among the early onset breast cancer patients, ductal type, grade 3, ER and HER-2/neu negativity, high Ki67 index and CK5/6 and EGFR positivity were typical for BRCA1 patients. Unfortunately, there were no typical phenotypical features for BRCA2 carriers. However, grade I and lobular cases were never BRCA1/2 germline mutated.Conclusion: Early onset Indonesian breast cancer shows increased proliferation compared to late onset patients. Within the early onset group, the strongest features pointing to a sporadic cancer seem to be grade I and lobular differentiation. Features increasing the chance of a germline BRCA1/2 mutation are CK5/6 and EGFR expression, p53 accumulation and high proliferation as measured by Ki67 labeling. This is potentially useful to optimize selection of early onset breast cancer patients for BRCA1/2 mutation testing

Histopathological Features of Early Onset Indonesian Breast Cancer Pointing to Brca1/2 Germline Mutations

Background: Breast cancer under 40 years concerns a relatively small subgroup of cases that tend to display a more aggressive phenotype. Compatible with this, early age of onset has been known as one of clinical characteristic of hereditary breast cancers associated with germline BRCA1 or BRCA1 mutations. As early onset breast cancer is frequent in Indonesia, we investigated the histopathological and immunohistochemical characteristics of early onset (< 40 years) Indonesian breast cancer patients, as such features can be used to distinguish between BRCA and non-BRCA germline mutation carriers among these young women.Method: Thirty-five formalin-fixed and paraffin-embedded tissue sections of young women (mean 36 years, range 22-40 years) who underwent surgical resection at the Department of Surgery of the Sardjito Hospital Yogyakarta were examined for pathological features, estrogen and progesterone receptor status, proliferation as determined by Ki67 labeling, EGFR and CK5/6 and the presence of HER-2/neu and p53 protein. Additionally, mutation analysis for BRCA1 and BRCA2 was performed in 30 young women. The control group consisted ofcarcinomas from women above 50 years (mean 59.02, range 50-80 years).Result: Carcinomas occurring in women aged below 40 years were more often advanced stage and higher proliferating (p=0.006). Among the early onset breast cancer patients, ductal type, grade 3, ER and HER-2/neu negativity, high Ki67 index and CK5/6 and EGFR positivity were typical for BRCA1 patients. Unfortunately, there were no typical phenotypical features for BRCA2 carriers. However, grade I and lobular cases were never BRCA1/2 germline mutated.Conclusion: Early onset Indonesian breast cancer shows increased proliferation compared to late onset patients. Within the early onset group, the strongest features pointing to a sporadic cancer seem to be grade I and lobular differentiation. Features increasing the chance of a germline BRCA1/2 mutation are CK5/6 and EGFR expression, p53 accumulation and high proliferation as measured by Ki67 labeling. This is potentially useful to optimize selection of early onset breast cancer patients for BRCA1/2 mutation testing.Keywords: breast cancer, early onset, histopathology, immunohistochemistry, BRCA1, BRCA

Level statistics of XXZ spin chains with a random magnetic field

The level-spacing distribution of a spin 1/2 XXZ chain is numerically studied under random magnetic field. We show explicitly how the level statistics depends on the lattice size L, the anisotropy parameter $\Delta$, and the mean amplitude of the random magnetic field h. In the energy spectrum, quantum integrability competes with nonintegrability derived from the randomness, where the XXZ interaction is modified by the parameter $\Delta$. When $\Delta \ne 0$, the level-spacing distribution mostly shows Wigner-like behavior, while when $\Delta$=0, Poisson-like behavior appears although the system is nonintegrable due to randomness. Poisson-like behavior also appears for $\Delta \ne 0$ in the large h limit. Furthermore, the level-spacing distribution depends on the lattice size L, particularly when the random field is weak.Comment: 4 pages, 3 figures, to be published in Phys. Rev.

Allosuppressor and allohelper T cells in acute and chronic graft-vs.-host disease. II. F1 recipients carrying mutations at H-2K and/or I-A.

By induction of a graft-vs.-host reaction (GVHR) in nonirradiated H-2-different F1 mice, one can induce stimulatory pathological symptoms, such as lymphadenopathy and hypergammaglobulinemia, combined with the production of autoantibodies characteristic of systemic lupus erythematosus (SLE). Alternatively, the GVHR can lead to the suppressive pathological symptoms, such as pancytopenia and hypogammaglobulinemia, characteristic of acute GVH disease (GVHD). Whether stimulatory or suppressive symptoms are induced by a GVHR depends, in our view (2-4), on the functional subset of donor T cells activated in the F1 host. The purpose of the present study was to investigate whether class I and/or class II H-2 alloantigens can selectively trigger, out of a pool of unselected donor T cells, those subpopulations of T cells responsible for the stimulatory and suppressive GVH symptoms, respectively. For the induction of the GVHR, 10(8) lymphoid cells from C57BL/6 (B6) donors were injected into three kinds of F1 hybrid mice, which had been bred from H-2 mutant strains on a B6 background. Whereas the I-A-disparate (B6 X bm12)F1 recipients exclusively developed stimulatory GVH symptoms, including SLE-like autoantibodies and immune complex glomerulonephritis, the K locus-disparate (B6 X bm1)F1 recipients showed neither clearly stimulatory nor clearly suppressive GVH symptoms. In marked contrast, the (bm1 X bm12)F1 recipients, which differ from the B6 donor strain by mutations at both K and I-A locus, initially developed stimulatory GVH symptoms, but rapidly thereafter showed the suppressive pathological symptoms of acute GVHD and died. Moreover, spleen cells obtained from (B6 X bm12)F1 mice injected with B6 donor cells helped the primary anti-sheep erythrocyte (SRBC) response of normal (B6 X bm12)F1 spleen cells in vitro, whereas spleen cells (bm1 X bm12)F1 mice injected with B6 donor cells strongly suppressed the primary anti-SRBC response of normal (bm1 X bm12)F1 spleen cells. Spleen cells from the K locus-disparate (B6 X bm1)F1 recipients also suppressed the primary anti-SRBC of normal (B6 X bm1)F1 spleen cells; this suppression, however, was weak when compared with the suppression induced by spleen cells from GVH (bm1 X bm12)F1 mice. Taken together, these findings indicate that a small class II (I-A) antigenic difference suffices to trigger the alloreactive donor T helper cells causing SLE-like GVHD. In contrast, both class I (H-2K) and class II (I-A) differences are required to trigger the subsets of donor T cells responsible for acute GVHD. It appears that alloreactive donor T helper cells induce the alloreactive T suppressor cells, which then act as the suppressor effector cells causing the pancytopenia of acute GVHD. These findings may help to understand the variability of GVH-like diseases caused by a given etiologic agent, their cellular pathogenesis, and association with certain HLA loc

Unexpected non-Wigner behavior in level-spacing distributions of next-nearest-neighbor coupled XXZ spin chains

The level-spacing distributions of XXZ spin chains with next-nearest-neighbor couplings are studied under periodic boundary conditions. We confirm that integrable XXZ spin chains mostly have the Poisson distribution as expected. On the contrary, the level-spacing distributions of next-nearest-neighbor coupled XXZ chains are given by non-Wigner distributions. It is against the expectations, since the models are nonintegrable.Comment: 4 pages, 4 figures, to be published in Physical Review

Among B cell non-Hodgkin's lymphomas, MALT lymphomas express a unique antibody repertoire with frequent rheumatoid factor reactivity

We analyzed the structure of antigen receptors of a comprehensive panel of mature B non-Hodgkin's lymphomas (B-NHLs) by comparing, at the amino acid level, their immunoglobulin (Ig)VH-CDR3s with CDR3 sequences present in GenBank. Follicular lymphomas, diffuse large B cell lymphomas, Burkitt's lymphomas, and myelomas expressed a CDR3 repertoire comparable to that of normal B cells. Mantle cell lymphomas and B cell chronic lymphocytic leukemias (B-CLLs) expressed clearly restricted albeit different CDR3 repertoires. Lymphomas of mucosa-associated lymphoid tissues (MALTs) were unique as 8 out of 45 (18%) of gastric- and 13 out of 32 (41%) of salivary gland-MALT lymphomas expressed B cell antigen receptors with strong CDR3 homology to rheumatoid factors (RFs). Of note, the RF-CDR3 homology without exception included N-region–encoded residues in the hypermutated IgVH genes, indicating that they were stringently selected for reactivity with auto-IgG. By in vitro binding studies with 10 MALT lymphoma–derived antibodies, we showed that seven of these cases, of which four with RF-CDR3 homology, indeed possessed strong RF reactivity. Of one MALT lymphoma, functional proof for selection of subclones with high RF affinity was obtained. Interestingly, RF-CDR3 homology and t(11;18) appeared to be mutually exclusive features and RF-CDR3 homology was not encountered in any of the 19 pulmonary MALT lymphomas studied