Re-evaluation of the probabilities for productive rearrangements on the κ andλloci

V-J rearrangements at Ig light chain (IgL) genes occur in resting small pre-B cells. In the absence of cell division, the probability of productive κ and λ rearrangements is proportional to the output of κ+ B and λ+ B cells in bone marrow. The kinetics and probability of productive κ or λ rearrangements was assessed in three groups of mice carrying two (wild-type), one or no intact Ig gene, and the following conclusion are drawn,κ and λ rearrangements occur independently at different kinetics, and rearrangements are initiated at a time when κ rearrangements are stopping. The probability of productive κ and λ rearrangements per chromosome is calculated to be −60 and −20% respectively. Thus, a κ gene can attempt rearrangements up to three times per chromosome during B cell development. These findings explain that the observed ratio of κ+ B/λ+ B cell production in wild-type mice is 95/

Evaluation of radiograph signs for the diagnosis of solitary peripheral pulmonary nodules less than 3 cm.

Ten radiograph signs were assessed by two experts for their usefulness in the diagnosis of small solitary peripheral pulmonary nodules less than 3 cm. The ten categories included notching, spicula formation, pleural indentation, vascular convergence, contour, paleness, homogeneity, cavitation, air bronchogram, and calcification. The cases included 134 lung cancers and 44 benign lung lesions resected between 1972 and 1988 at the Second Department of Surgery, Okayama University Medical School. Notching, spicula formation, pleural indentation, vascular convergence, contour, and air bronchogram were useful signs in differentiating lung cancer from benign lung lesions. However, since the radiograph signs exhibited great variation in both lung cancer and benign lung lesions, a diagnostic operation is sometimes inevitable.</p

Distorted antibody repertoire developed in the absence of pre-B cell receptor formation

The pre-B cell receptor (pre-BCR), consisting of the μ heavy chain (μHC) and the surrogate light chain (SLC, Vpre-B and λ5), plays important roles during B cell development. The formation of the pre-BCR, which enables the nascent immunoglobulin HC to associate with the SLC, is considered a prerequisite for B cell development. However, a significant number of peripheral mature (leaky) B cells exist in SLC-deficient mice. These leaky B cells develop in the absence of pre-BCR and do not undergo the pre-BCR checkpoint. The antibody repertoires of leaky B cells thus reflect the absence of pre-BCR function. To investigate how the absence of the pre-BCR is circumvented by these leaky-B cells and examine the effect of the pre-BCR checkpoint on the antibody system, we analyzed the antibody repertoires of λ5-deficient (λ5−/−) mice using next-generation sequencing. In λ5−/− mice, spleen B cells displayed different patterns of VDJ-usage, relative to those in wild-type (WT) mice. Moreover, leaky B cells were neither derived from unusual B2 cells, characterized by particular LC gene rearrangements in the absence of pre-BCR signaling, nor from B1 cells, originating from different B cell progenitors. Analysis of the CDR-H3 amino acid sequences of μ-chain repertoires revealed that certain bone marrow B cells with particular CDR-H3 profiles undergo clonal expansion in λ5−/− mice. Part of these CDR-H3s contain arginine(s) in the middle of the CDR-H3 loop in λ5−/− mice, whereas few arginine(s) exist in this middle loop in WT CDR-H3s in the absence of clonal expansion. This CDR-H3 feature in λ5−/− mice presumably reflects the role of the pre-BCR in autoantibody regulation, since arginine(s) are often found in the antigen-binding site of autoantibodies. Here, we present a unique viewpoint on the role of pre-BCR, by assessing the whole antibody repertoire formed in SLC-deficient mice

Molecular dynamics simulation of rubbing phenomena in ultra-precision abrasive machining

This study aims to clarify the friction and wear phenomena, which are of great importance in abrasive machining with atomic-scale material removal, such as polishing of magnetic disk substrates and CMP of semiconductor substrates. Various phenomena that occurred when a well-defined copper surface rubbed by an extremely fine rigid diamond abrasive, such asthe sliding without removal and the atomic-scale wear, were analyzed using a molecular dynamics model, in which the abrasive grain was connected to a three-dimensional spring and the holding rigidity of the abrasive grain was taken into account. A series of simulations using different indentation depths clarified that the one- or two-dimensional atomic-scale stick-slip phenomenon in proportion to the period of atomic arrays of workpiece surface occurred in the sliding processes without atomic removal. The results also demonstrated that the period and amplitude of the fundamental stick-slip wave varied when accompanied with atomic removal due to the increase in normal load. © (2010) Trans Tech Publications, Switzerland

MHC Class II Molecules Are Not Required for Survival of Newly Generated CD4+ T Cells, but Affect Their Long-Term Life Span

AbstractWe grafted fetal thymi from wild-type mice into immunodeficient RAG-2−/− or class II−/−RAG-2−/− (class II MHC−) recipients and followed the fate of naive CD4+ T cells derived from the grafts. In both types of recipients, newly generated CD4+ T cells proliferated to the same extent in the periphery and rapidly filled the empty T cell compartment. However, CD4+ T cells in class II− recipients gradually decreased in number over 6 months. These results show that interactions between the TCR and class II molecules are not required for newly generated CD4+ T cells to survive and proliferate, but are necessary to maintain the size of the peripheral T cell pool for extended periods