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Measurements of Hall coefficients, thermoelectric power, and optical conductivity spectra were done for single crystals of La 2Ϫx Sr x NiO 4 (xϭ0.27Ϫ0.50) showing prototypical charge ordering. We found that the character of the carriers in the charge-ordered state changes from electronlike to holelike when the hole concentration p crosses 1/3, and that the correlation gap in the optical spectrum for pϭ1/3 is collapsed when p is away from 1/3. These results indicate that the deviation of p from 1/3 can be regarded as electron or hole doping into the commensurate charge-ordered state at pϭ1/3. ͓S0163-1829͑99͒50732-7͔Charge ordering is a generic phenomenon for the strongly correlated electron system whose band filling deviates away from integer value. In this state, doped carriers are localized and order periodically ͑usually accompanied by spin order-ing͒ at low temperature. Recent studies on transition metal oxides have shown a variety of examples of charge ordering for two-dimensional ͑2D͒ nickelates ͑with K 2 NiF 4 structure͒, 1-5 2D and 3D ͑perovskite͒ manganites, 6-8 and perovskite ferrates. 9 Among them, La 2Ϫx Sr x NiO 4 is a prototypical example of charge ordering. In this compound, charge and spin ordering occurs over a wide holeconcentration ͑p͒ range (0Ͻpр0.5), and the wave vectors of the charge ordering, (Ϯ⑀,Ϯ⑀), and spin ordering, ( 1 2 Ϯ⑀/2, 1 2 Ϯ⑀/2), vary continuously with p, almost following the trend that ⑀ϳp. 1-4 These results suggest a picture in which doped holes in this 2D nickelate line up along the diagonal direction of the Ni square lattice, and the period of these ''charge stripes'' varies continuously in accordance with the hole concentration. 5 It should be noted that similar variations of the charge-stripes period with carrier concentration are also observed in perovskite manganites, 7 and that several theoretical studies 10,11 can reproduce this phenomenon and the relation of ⑀ϭp.Concerning such charge ordering over a wide carrierconcentration range, it is an interesting issue whether the commensurability effect exists for a specific carrier concentration. In fact, a previous study 12 reported an anomaly at p ϭ1/3, where the resistivity jumps most clearly at the transition temperature of the charge ordering (T co ), compared with other hole concentrations. This suggests the importance of the commensurate vs incommensurate issue in the charge and spin ordering of 2D nickelates. In this paper, we demonstrate that pϭ1/3 is a special hole concentration for this system and transport properties and electronic structures are critically affected by the deviation of the hole concentration from this value. We propose a picture in which the commensurate charge-ordered state for pϭ1/3 is analogous to a Mott insulator, and the deviation from pϭ1/3 (pϾ1/3 or p Ͻ1/3) can be regarded as hole or electron doping, respectively, into such a Mott insulator.All the samples studied in this work are single crystals grown by a floating-zone method. Taking account of the oxygen of stoichiometry (␦) in the sampl...

While the use of polymerase chain reaction (PCR)-based clonality analysis of formalin-fixed paraffin-embedded (FFPE) tissue has recently become widespread, the detection sensitivity for lymphoma subtypes using FFPE samples is not well known. Here, we analyzed T-cell receptor γ chain (TCRG) gene rearrangement clonality in 100 cases of T- or natural killer (NK)/T-cell lymphoma and examined detection sensitivity according to lymphoma subtype. Clonality was detected in approximately 80% of the major T-cell lymphoma subtypes: peripheral T-cell lymphoma, not otherwise specified, 84% (21/25 cases); angioimmunoblastic T-cell lymphoma, 71% (15/21 cases); and adult T-cell leukemia/lymphoma, 80% (8/10 cases). The number of clonal peaks differed according to subtype. TCRG gene rearrangement was not detected in 63 cases of B-cell lymphoma or reactive lesions. Thus, clonality analysis can effectively and reliably detect TCRG gene rearrangement in T-cell lymphoma cases and could, therefore, be a useful diagnostic tool in routine practice.

A T cell activation antigen, Ly6C, is considered to be involved in the autoimmunity of some autoimmune-prone mice; however, the function of Ly6C remains largely unknown. We prepared a rat anti-mouse Ly6C monoclonal antibody (mAb) (S14) that inhibits the proliferation of peripheral T cells stimulated with anti-CD3 mAb in vitro. S14 mAb, the specificity of which is confirmed by a cDNA transfectant, recognizes Ly6C antigen preferentially expressed on a part of CD8+ T cells in peripheral lymphoid organs. The immunohistochemical analysis demonstrates that Ly6C appears on CD8+ T cells in the conventional T cell-associated area of BALB/c but not of nonobese diabetic (NOD) mice, confirming the absence of Ly6C+ T cells in NOD mice. Addition of soluble S14 mAb to the culture does not influence the proliferation of T cells in vitro; however, the S14 mAb coated on the plate clearly inhibits the proliferation and IL-2 production of anti-CD3-stimulated peripheral T cells. The T cells are arrested at the transitional stage from G0/G1 to S+G2/M phases, but they are not induced to undergo apoptotic changes in vitro. This inhibitory signal provided through the Ly6C molecule inhibited IL-2 secretion in a subpopulation of the activated CD4+ T cells. Ly6C is expressed on T cell clones of both Th1 and Th2 cells, but the cytokine secretion from Th1 clones is preferentially inhibited. These results suggest that Ly6C mediates an inhibitory signal for secretion of cytokines from Th1 CD4+ T cells, potentially causing the inhibition of immune response in peripheral lymphoid tissues.

Abstract. The effects of calyculin-A (CL-A), a phosphatase inhibitor, on 20a-hydroxysteroid dehydrogenase (20a-HSD) activity were studied in rat luteal cell cultures to examine whether protein phosphatases were involved in the regulation of the enzyme activity. Luteal cells were harvested from the rats on day 6 of pseudopregnancy.In the absence of prolactin (PRL), the stimulatory effect of CL-A (10-9M) on 20x-HSD activity was observed during the first 3 h period of the culture, but was not discernible thereafter. Since the enzyme activity of luteal cells during pseudopregnancy is known to be suppressed by PRL, the results suggest that this effect of CL-A could be manifested only as long as the effect of endogenous PRL was remained. On the other hand, CL-A enhanced the 20cr-HSD activity of the cells cultured for 24 h, where a spontaneous increase in 20a-HSD activity was blocked by exogenously supplementing the culture medium with PRL. These results suggest that a CL-A sensitive phosphatase(s) may be involved in the action of PRL in suppressing the increase in 20a HSD activity in rat luteal cells.