Radiocarbon Production Events and their Potential Relationship with the Schwabe Cycle.

Extreme cosmic radiation events occurred in the years 774/5 and 993/4 CE, as revealed by anomalies in the concentration of radiocarbon in known-age tree-rings. Most hypotheses point towards intense solar storms as the cause for these events, although little direct experimental support for this claim has thus far come to light. In this study, we perform very high-precision accelerator mass spectrometry (AMS) measurements on dendrochronological tree-rings spanning the years of the events of interest, as well as the Carrington Event of 1859 CE, which is recognized as an extreme solar storm even though it did not generate an anomalous radiocarbon signature. Our data, comprising 169 new and previously published measurements, appear to delineate the modulation of radiocarbon production due to the Schwabe (11-year) solar cycle. Moreover, they suggest that all three events occurred around the maximum of the solar cycle, adding experimental support for a common solar origin.

Rare mutations in XRCC2 increase the risk of breast cancer.

An exome-sequencing study of families with multiple breast-cancer-affected individuals identified two families with XRCC2 mutations, one with a protein-truncating mutation and one with a probably deleterious missense mutation. We performed a population-based case-control mutation-screening study that identified six probably pathogenic coding variants in 1,308 cases with early-onset breast cancer and no variants in 1,120 controls (the severity grading was p < 0.02). We also performed additional mutation screening in 689 multiple-case families. We identified ten breast-cancer-affected families with protein-truncating or probably deleterious rare missense variants in XRCC2. Our identification of XRCC2 as a breast cancer susceptibility gene thus increases the proportion of breast cancers that are associated with homologous recombination-DNA-repair dysfunction and Fanconi anemia and could therefore benefit from specific targeted treatments such as PARP (poly ADP ribose polymerase) inhibitors. This study demonstrates the power of massively parallel sequencing for discovering susceptibility genes for common, complex diseases.

Space and time in the nucleus: developmental control of replication timing and chromosome architecture.

All eukaryotic cells replicate segments of their genomes in a defined temporal sequence. In multicellular organisms, at least half of the genome is subject to changes in this temporal sequence during development. We now know that this temporal sequence and its developmentally regulated changes are conserved across distantly related species, suggesting that it either represents or reflects something biologically important. However, both the mechanism and the significance of this program remain unknown. We recently demonstrated a remarkably strong genome-wide correlation between replication timing and chromatin interaction maps, stronger than any other chromosomal property analyzed to date, indicating that sequences localized close to one another replicate at similar times. This provides molecular confirmation of long-standing cytogenetic evidence for spatial compartmentalization of early- and late-replicating DNA and supports our earlier model that replication timing is reestablished in each G(1) phase, coincident with the anchorage of chromosomal segments at specific locations within the nucleus (timing decision point [TDP]). Here, we review the evidence linking the replication program to the three-dimensional architecture of chromatin in the nucleus and discuss what such a link might mean for the mechanism and significance of a developmentally regulated replication program.

CMRF44+ dendritic cells from peripheral blood stem cell harvests of patients with myeloma as potential cellular vectors for idiotype vaccination.

The optimal conditions required to harvest dendritic cells (DC) for immunotherapy were investigated in a series of preliminary investigations using peripheral blood stem cell (PBSC) harvests and blood from patients with myeloma. There was no difference in the number of DC (CMRF44+, CD19-, CD14-) in PBSC mobilized with G-CSF (mean 0.28%, n = 7) compared with GM-CSF (mean 0.24%, n = 6) and apheresis itself did not concentrate DC. In longitudinal studies (n = 10), the peak DC count (day 12 post PBSC harvest) did not correlate with the peak CD34+ cell count or white cell count. A simple affinity purification of DC resulted in a mean 63-fold purification. Affinity enriched suspensions from normal blood contained more DC (mean = 18.8%; n = 5) than those from patients with myeloma (mean = 9.9%; n = 13). The percentage of DC with a lymphoid phenotype (CD11c-, CDw123hi+) was significantly higher in G-CSF mobilized PBSC harvests (22.7%; n = 6) than in peripheral blood samples from patients with myeloma (7.0%; n = 13; p = 0.01). DC endocytosis was normal and did not change throughout the course of the disease. Neither DC numbers nor subsets changed significantly between days 1 and 3 of culture. Current mobilization procedures, optimized for PBSC, need to be altered when harvesting DC.

Aggregation of proteins with expanded glutamine and alanine repeats of the glutamine-rich and asparagine-rich domains of Sup35 and of the amyloid beta-peptide of amyloid plaques.

The exon-1 peptide of huntingtin has 51 Gln repeats and produces the symptoms of Huntington's disease in transgenic mice. Aggregation of the yeast Sup35 protein into prions has been attributed to its glutamine-rich and asparagine-rich domain. Here, we show that poly-L-asparagine forms polar zippers similar to those of poly-L-glutamine. In solution at acid pH, the glutamine-rich and asparagine-rich 18-residue Sup35 peptide, rendered soluble by the addition of two aspartates at the amino end and two lysines at the carboxyl end, gives a beta-sheet CD spectrum; it aggregates at neutral pH. A poly-alanine peptide D(2)A(10)K(2) gives an alpha-helical CD spectrum at all pHs and does not aggregate; a peptide with the sequence of the C-terminal helix of the alpha-chain of human hemoglobin, preceded by two aspartates and followed by two lysines, exhibits a random coil spectrum and does not aggregate either. Alignment of several beta-strands with the sequence of the 42-residue Alzheimer's amyloid beta-peptide shows that they can be linked together by a network of salt bridges. We also asked why single amino acid replacements can so destabilize the native structures of proteins that they unfold and form amyloids. The difference in free energy of a protein molecule between its native, fully ordered structure and an amorphous mixture of randomly coiled chains is only of the order of 10 kcal/mol. Theory shows that destabilization of the native structure by no more than 2 kcal/mol can increase the probability of nucleation of disordered aggregates from which amyloids could grow 130,000-fold.

Dendritic cells from patients with myeloma are numerically normal but functionally defective as they fail to up-regulate CD80 (B7-1) expression after huCD40LT stimulation because of inhibition by transforming growth factor-beta1 and interleukin-10.

Limited response to idiotype vaccination in patients with myeloma suggests that there is a need to develop better immunotherapy strategies. It has been determined that the number of high-potency CMRF44+CD14-CD19- dendritic cells (DCs) in the blood of patients with myeloma (range, 0.03%-0.8% of mononuclear cells [MNCs]; n = 26) was not significantly different from that in controls (range, 0.05%-0.8% of MNCs; n = 13). Expression of the costimulatory molecules CD80 and CD86 on DCs from these patients (mean, 29%+/-17% of MNCs and 85%+/-10% of MNCs, respectively) was also normal (mean, 29%+/-17% and 86%+/-16% of MNCs, respectively). Up-regulation of CD80 expression in response to stimulation by human huCD40LT + interleukin (IL)-2 was significantly reduced on the DCs of patients with myeloma during stable disease (n = 9) and was absent during progressive stages (n = 7) of disease. Similar effects were seen on B cells but not on monocytes of the same group of patients. CD86 expression on DCs was high before (86%) and after (89%) stimulation. Inhibition of CD80 up-regulation was neutralized by either anti-transforming growth factor (TGF)-beta1 or anti-IL-10. Up-regulation of CD80 on DCs of controls was inhibited by rTGF-beta1 in a dose-dependent manner. Serum TGF-beta1 and IL-10 levels were normal in most patients studied. Cytoplasmic TGF-beta1 was increased in plasma cells during progressive disease. Thus patients with myeloma have normal numbers of DCs, but CD80 expression may fail to be up-regulated in the presence of huCD40LT because of tumor-derived TGF-beta1 or IL-10. Autologous high-potency DCs may have to be tested for CD80 up-regulation and biologically modified ex vivo before idiotype priming for immunotherapy.

Actin bound to the heterogeneous nuclear ribonucleoprotein hrp36 is associated with Balbiani ring mRNA from the gene to polysomes.

In the salivary glands of the dipteran Chironomus tentans, a specific messenger ribonucleoprotein (mRNP) particle, the Balbiani ring (BR) granule, can be visualized during its assembly on the gene and during its nucleocytoplasmic transport. We now show with immunoelectron microscopy that actin becomes associated with the BR particle concomitantly with transcription and is present in the particle in the nucleoplasm. DNase I affinity chromatography experiments with extracts from tissue culture cells indicate that both nuclear and cytoplasmic actin are bound to the heterogeneous RNP (hnRNP) protein hrp36, but not to the hnRNP proteins hrp23 and hrp45. The interaction is likely to be direct as purified actin binds to recombinant hrp36 in vitro. Furthermore, it is demonstrated by cross linking that nuclear as well as cytoplasmic actin are bound to hrp36 in vivo. It is known that hrp36 is added cotranscriptionally along the BR mRNA molecule and accompanies the RNA through the nuclear pores and into polysomes. We conclude that actin is likely to be bound to the BR transcript via hrp36 during the transfer of the mRNA from the gene all the way into polysomes.

Assessment of clinical partner violence screening tools.

OBJECTIVE: To compare the Women's Experience with Battering Scale (WEB) with the Index of Spouse Abuse-Physical Scale (ISA-P) as screening tools to identify intimate partner violence (IPV). METHODS: We conducted a large cross-sectional survey of women age 18 to 65 attending one of two family practice clinics from 1997 to 1998. All women completed both the WEB and the ISA-P and a telephone interview. We figured agreement estimates between the two tools, used stratified analyses to evaluate attributes of those more likely to screen as battered or physically assaulted, and compared associations between the WEB and ISA-P and a range of mental and physical health indicators known to be associated with IPV. RESULTS: 18% of 1152 eligible women surveyed had experienced IPV in a current or most recent intimate relationship with a male partner; 17% had been battered (WEB+), and 10% had been physically assaulted (ISA-P+). Had we used the ISA-P alone to assess IPV, we would have missed almost 45% of IPV. As anticipated, the ISA-P was more strongly associated with IPV-associated injuries and number of physician visits in the last year. The WEB was more strongly associated with self-perceived mental health, anxiety, depression, drug abuse, and low social support. CONCLUSION: Clinicians need validated screening tools to rapidly and reliably screen patients for IPV. Most screening tools assess physical violence and injury without considering the more chronic experience of battering and the psychological terror associated with this violence. The WEB may identify more abused women than tools measuring physical assaults.

The C-terminal tail of UNC-60B (actin depolymerizing factor/cofilin) is critical for maintaining its stable association with F-actin and is implicated in the second actin-binding site.

Actin depolymerizing factor (ADF)/cofilin changes the twist of actin filaments by binding two longitudinally associated actin subunits. In the absence of an atomic model of the ADF/cofilin-F-actin complex, we have identified residues in ADF/cofilin that are essential for filament binding. Here, we have characterized the C-terminal tail of UNC-60B (a nematode ADF/cofilin isoform) as a novel determinant for its association with F-actin. Removal of the C-terminal isoleucine (Ile152) by carboxypeptidase A or truncation by mutagenesis eliminated F-actin binding activity but strongly enhanced actin depolymerizing activity. Replacement of Ile152 by Ala had a similar but less marked effect; F-actin binding was weakened and depolymerizing activity slightly enhanced. Truncation of both Arg151 and Ile152 or replacement of Arg151 with Ala also abolished F-actin binding and enhanced depolymerizing activity. Loss of F-actin binding in these mutants was accompanied by loss or greatly decreased severing activity. All of the variants of UNC-60B interacted with G-actin in an indistinguishable manner from wild type. Cryoelectron microscopy showed that UNC-60B changed the twist of F-actin to a similar extent to vertebrate ADF/cofilins. Helical reconstruction and structural modeling of UNC-60B-F-actin complex reveal how the C terminus of UNC-60B might be involved in one of the two actin-binding sites.

B7-2-positive myeloma: incidence, clinical characteristics, prognostic significance, and implications for tumor immunotherapy.

Deficiencies in B7:CD28 costimulation are considered to be one of the major causes of the failure to generate a tumor-specific immune response. Up-regulating the expression of the B7 molecules on malignant B cells has been shown to stimulate cytotoxic T cells. Plasma cells from patients with myeloma express a tumor-specific idiotype but lack CD80 (B7-1) and have a variable expression of CD86 (B7-2). This study has identified the incidence and clinical significance of high CD86 expression on plasma cells at diagnosis and studied the ability of trimeric human CD40 ligand (huCD40LT) to up-regulate the expression of the B7 family on malignant plasma cells. CD86 expression on plasma cells was increased in 54% of the patients studied at diagnosis (n = 35) and was associated with a significantly shorter survival (median, 28 versus 57 months; chi(2) = 4.6; P =.03) and a higher tumor load (patients with more than 50% bone marrow plasma cells, 47% versus 6%; chi(2) = 7.2; P =.005). CD86 expression was highest on immature and primitive plasma cells (CD38(++), CD45(+)) of both patients and controls and was associated with a CD40(+), CD20(+), CD19(-), CD138(+) phenotype. The shortened survival was associated with high CD86 only on mature (CD38(++), CD45(-)) plasma cells (chi(2) = 7.6; P =.006). There was no significant correlation between high CD86 and other known prognostic markers, including serum beta(2)-microglobulin, serum thymidine kinase, and labeling index. The addition of huCD40LT to short-term cultures up-regulated both CD80 and CD86 expression on B cells (CD19(+)) and CD80 on plasma cells (CD38(++)), but did not up-regulate CD86 expression on plasma cells. Thus, B7-2-positive myeloma consists of a subgroup of patients with a relatively poor prognosis, and CD40LT may be useful in immunotherapy protocols because it up-regulates CD80 expression on malignant plasma cells without inducing B7-2-positive myeloma. (Blood. 2000;96:1274-1279)

T-cell expansions in patients with multiple myeloma have a phenotype of cytotoxic T cells.

The presence of T-cell clones in peripheral blood has been previously shown to be associated with a survival advantage in patients with multiple myeloma and suggests that the expanded T-cell populations may be involved in an anti-tumour response. We studied the T-cell receptor (TCR) repertoire of 38 patients with myeloma to identify and characterize the expanded T-cell populations by flow cytometry. T-cell expansions were found in 79% of the patients. The expansions occurred randomly among the 21 variable regions of the TCR beta chain (Vbeta) studied, representing 62% of the V-beta repertoire, and were stable during an 18-month follow-up. The phenotype of the expanded V-beta populations was predominantly CD8+, CD57+, CD28- and perforin+, which differed significantly from the other non-expanded Vbeta populations. The expression of the apoptosis markers Fas (CD95) and bcl-2 were similar between the expanded and non-expanded Vbeta populations. In conclusion, expanded T-cell populations were frequent in patients with myeloma, they remained unchanged during follow-up and had phenotypic characteristics of cytotoxic T cells. These data add further support to the concept that the T-cell expansions may have an immunoregulatory role in myeloma.

Uncoupling actin filament fragmentation by cofilin from increased subunit turnover.

The actin depolymerizing factor (ADF)/cofilin family of proteins interact with actin monomers and filaments in a pH-sensitive manner. When ADF/cofilin binds F-actin it induces a change in the helical twist and fragmentation; it also accelerates the dissociation of subunits from the pointed ends of filaments, thereby increasing treadmilling or depolymerization. Using site-directed mutagenesis we characterized the two actin-binding sites on human cofilin. One target site was chosen because we previously showed that the villin head piece competes with ADF for binding to F-actin. Limited sequence homology between ADF/cofilin and the part of the villin headpiece essential for actin binding suggested an actin-binding site on cofilin involving a structural loop at the opposite end of the molecule to the alpha-helix already implicated in actin binding. Binding through the alpha-helix is primarily to monomeric actin, whereas the loop region is specifically involved in filament association. We have characterized the actin binding properties of each site independently of the other. Mutation of a single lysine residue in the loop region abolishes binding to filaments, but not to monomers. Using the mutation analogous to the phosphorylated form of cofilin (S3D), we show that filament binding is inhibited at physiological ionic strength but not under low salt conditions. At low ionic strength, this mutant induces both the twist change and fragmentation characteristic of wild-type cofilin, but does not activate subunit dissociation. The results suggest a two-site binding to filaments, initiated by association through the loop site, followed by interaction with the adjacent subunit through the "helix" site at the opposite end of the molecule. Together, these interactions induce twist and fragmentation of filaments, but the twist change itself is not responsible for the enhanced rate of actin subunit release from filaments.

The bone marrow plasma cell labeling index by flow cytometry.

The bone marrow plasma cell labeling index is the most important prognostic indicator for patients with multiple myeloma. Traditionally, this test has been performed as a two color immunofluorescent microscope technique which is time consuming and requires a degree of subjectivity in its interpretation. We have assessed various adaptations of this method to flow cytometry. A bromodeoxyuridine method has been compared with a propidium iodide DNA method to detect cells in S phase and CD38-FITC has been compared with CD38-FITC + CD138-FITC and CD38-biotin + streptavidin FITC to identify plasma cells. The mean channel fluorescent intensity of the plasma cell peaks for each of these markers was 12. 7, 17.4 and 35.3 respectively demonstrating the superiority of CD38-biotin + streptavidin FITC. Analysis after propidium iodide staining provided a good correlation with the slide technique (r = 0. 71; P < 0.0001) but the bromodeoxyuridine method did not correlate with the slide method (r = 0.09; P = NS). The labeling index values obtained from either of the flow methods were greater than the microscopic method. Thus a labeling index of >4% will replace the traditional >1% threshold for identifying patients with a significantly increased labeling index. The advantages of the new method are that it takes less time to perform, is more objective and provides additional data on ploidy and cell cycle status.

Strand displacement amplification and homogeneous real-time detection incorporated in a second-generation DNA probe system, BDProbeTecET.

BACKGROUND: Amplified DNA probes provide powerful tools for the detection of infectious diseases, cancer, and genetic diseases. Commercially available amplification systems suffer from low throughput and require decontamination schemes, significant hands-on time, and specially trained laboratory staff. Our objective was to develop a DNA probe system to overcome these limitations. METHODS: We developed a DNA probe system, the BDProbeTecTMET, based on simultaneous strand displacement amplification and real-time fluorescence detection. The system uses sealed microwells to minimize the release of amplicons to the environment. To avoid the need for specially trained labor, the system uses a simple workflow with predispensed reagent devices; a programmable, expandable-spacing pipettor; and the 96-microwell format. Amplification and detection time was 1 h, with potential throughput up to 564 patient results per shift. We tested 122 total patient specimens obtained from a family practice clinic with the BD ProbeTecET and the Abbott LCx(R) amplified system for the detection of Chlamydia trachomatis and Neisseria gonorrhoeae. RESULTS: Based on reportable results, the BDProbeTecET results for both organisms were 100% sensitive and 100% specific relative to the LCx. CONCLUSIONS: The BDProbeTecET is an easy-to-use, high-throughput, closed amplification system for the detection of nucleic acid from C. trachomatis and N. gonorrhoeae and other organisms.

Wild-type p53 protein shows calcium-dependent binding to F-actin.

Nuclear localization of p53 is required for p53 to detect and respond to DNA strand abnormalities and breaks following DNA damage. This leads to activation of the tumour suppressive functions of p53 resulting in either cell cycle arrest and DNA repair; or apoptosis. Critical functional changes in DNA which require strand breaks, including gene rearrangement, may transiently mimic DNA damage: here it is important not to trigger a p53 response. The fine control of p53 in these different circumstances is unknown but may include transient sequestering of p53 in the cytoplasm. Reversible nuclear-cytoplasmic shuttling is an intrinsic property of p53 (Middeler et al., 1997) associated with cell cycle-related changes in p53's subcellular distribution. Takahashi and Suzuki (1994) described p53 inactivation by shuttling to the cytoplasm and Katsumoto et al. (1995) found wild-type p53 to be closely associated with cytoplasmic actin filaments during DNA synthesis. Here we show that, in the presence of free calcium ions, p53 binds directly to F-actin with a dissocation constant of about 10 microM. Thus, part of the regulatory machinery in normal cell cycling may involve p53-actin interactions regulated by calcium fluxes and the dynamic turnover of F-actin.