Hypoxia induces HIF1α-dependent epigenetic vulnerability in triple negative breast cancer to confer immune effector dysfunction and resistance to anti-PD-1 immunotherapy

The hypoxic tumor microenvironment has been implicated in immune escape, but the underlying mechanism remains elusive. Using an in vitro culture system modeling human T cell dysfunction and exhaustion in triple-negative breast cancer (TNBC), we find that hypoxia suppresses immune effector gene expression, including in T and NK cells, resulting in immune effector cell dysfunction and resistance to immunotherapy. We demonstrate that hypoxia-induced factor 1α (HIF1α) interaction with HDAC1 and concurrent PRC2 dependency causes chromatin remolding resulting in epigenetic suppression of effector genes and subsequent immune dysfunction. Targeting HIF1α and the associated epigenetic machinery can reverse the immune effector dysfunction and overcome resistance to PD-1 blockade, as demonstrated both in vitro and in vivo using syngeneic and humanized mice models. These findings identify a HIF1α-mediated epigenetic mechanism in immune dysfunction and provide a potential strategy to overcome immune resistance in TNBC.

Hypoxia can promote tumor escape from immune surveillance and immunotherapy. Here, the authors show that hypoxia induces T and NK cell dysfunction through HIF1α-mediated epigenetic suppression of effector gene expression, conferring resistance to anti-PD1 blockade in triple negative breast cancer models.

Cross-cultural adaptation of Cantonese (Hong Kong) Oswestry Disability Index version 2.1b

PURPOSE

Oswestry Disability Index (ODI) was established by Fairbank in 1989 to assess functional disabilities in low back pain (LBP). It was last updated in 2019 as ODI version 2.1b (ODI AU_2.1b). ODI was first translated into Simplified Chinese Oswestry Disability Index (CODI) in 2008 by Lue. The construct validity, internal consistency, level of agreement and the floor and ceiling effects of CODI were found unclear by Yao in 2016. This study will verify how well the adapted Cantonese-Hong Kong Oswestry Disability Index version 2.1b (HKCODI) aligns with ODI AU_2.1b in the Southern Chinese population.

METHODS

The translation of ODI AU_2.1b was performed according to guidelines from MAPI Research Trust and American Association of Orthopaedic Surgeons. Psychometric properties of HKCODI were tested statistically by Pearson's correlation, Cronbach's Alpha and Intraclass  Correlation  Coefficient (ICC).

RESULTS

A total of 200 subjects (109 males, 91 females) aged from 15 to 85 (mean age = 58.91) with LBP scored from 3/10 to 10/10 in the Visual Analogue Scale (VAS) were recruited in the Occupational Therapy Department of a tertiary referral center. HKCODI demonstrated strong construct validity in comparing with Hong Kong Roland-Morris Disability Questionnaire (HKRMDQ) (r = 0.666, p = 0.000), Short Form Health Survey (SF-36)  Physical Composite Summary (- 0.700, p = 0.000) and VAS (0.487, p = 0.000). Excellent internal consistency and test-retest reliability were confirmed with Cronbach's Alpha of 0.997 and ICC of 0.993 at 95% confidence level.

CONCLUSION

Cross-cultural adaptation of ODI AU_2.1b has been translated and validated as   HKCODI and Item-8 (Sex Life) was suggested to skip for patient older than 60. HKCODI is a fully self-administered and highly reliable tool in assessing the functional disability of patients with LBP in the Southern Chinese population.

EZH2-mediated PP2A inactivation confers resistance to HER2-targeted breast cancer therapy

HER2-targeted therapy has yielded a significant clinical benefit in patients with HER2+ breast cancer, yet disease relapse due to intrinsic or acquired resistance remains a significant challenge in the clinic. Here, we show that the protein phosphatase 2A (PP2A) regulatory subunit PPP2R2B is a crucial determinant of anti-HER2 response. PPP2R2B is downregulated in a substantial subset of HER2+ breast cancers, which correlates with poor clinical outcome and resistance to HER2-targeted therapies. EZH2-mediated histone modification accounts for the PPP2R2B downregulation, resulting in sustained phosphorylation of PP2A targets p70S6K and 4EBP1 which leads to resistance to inhibition by anti-HER2 treatments. Genetic depletion or inhibition of EZH2 by a clinically-available EZH2 inhibitor restores PPP2R2B expression, abolishes the residual phosphorylation of p70S6K and 4EBP1, and resensitizes HER2+ breast cancer cells to anti-HER2 treatments both in vitro and in vivo. Furthermore, the same epigenetic mechanism also contributes to the development of acquired resistance through clonal selection. These findings identify EZH2-dependent PPP2R2B suppression as an epigenetic control of anti-HER2 resistance, potentially providing an opportunity to mitigate anti-HER2 resistance with EZH2 inhibitors.

KDM4B-regulated unfolded protein response as a therapeutic vulnerability in PTEN-deficient breast cancer

Wang et al. report an unexpected role of demethylase KDM4B in regulating unfolded protein response (UPR). A stepwise hyperactivation of UPR by co-targeting the KDM4B and PI3K pathway uncovers a therapeutic vulnerability of PTEN-deficient TNBC that otherwise would be resistant to PI3K inhibition.

PTEN deficiency in breast cancer leads to resistance to PI3K–AKT inhibitor treatment despite aberrant activation of this signaling pathway. Here, we report that genetic depletion or small molecule inhibition of KDM4B histone demethylase activates the unfolded protein response (UPR) pathway and results in preferential apoptosis in PTEN-deficient triple-negative breast cancers (TNBCs). Intriguingly, this function of KDM4B on UPR requires its demethylase activity but is independent of its canonical role in histone modification, and acts through its cytoplasmic interaction with eIF2α, a crucial component of UPR signaling, resulting in reduced phosphorylation of this component. Targeting KDM4B in combination with PI3K inhibition induces further activation of UPR, leading to robust synergy in apoptosis. These findings identify KDM4B as a therapeutic vulnerability in PTEN-deficient TNBC that otherwise would be resistant to PI3K inhibition.

KDM6B Counteracts EZH2-Mediated Suppression of IGFBP5 to Confer Resistance to PI3K/AKT Inhibitor Treatment in Breast Cancer

Despite showing promise against PIK3CA-mutant breast cancers in preclinical studies, PI3K/AKT pathway inhibitors demonstrate limited clinical efficacy as monotherapy. Here, we found that histone H3K27me3 demethylase KDM6B-targeted IGFBP5 expression provides a protective mechanism for PI3K/AKT inhibitor-induced apoptosis in breast cancer cells. We found that overexpression of KDM6B and IGFBP5 in luminal breast cancer are positively associated with poorer disease outcomes. Mechanistically, KDM6B promotes IGFBP5 expression by antagonizing EZH2-mediated repression, and pharmacologic inhibition of KDM6B augments apoptotic response to PI3K/AKT inhibitor treatment. Moreover, the IGFBP5 expression is upregulated upon acquired resistance to the PI3K inhibitor GDC-0941, which is associated with an epigenetic switch from H3K27me3 to H3K27Ac at the IGFBP5 gene promoter. Intriguingly, GDC-0941-resistant breast cancer cells remained sensitive to KDM6B or IGFBP5 inhibition, indicating the dependency on the KDM6B-IGFBP5 axis to confer the survival advantage in GDC-0941-resistant cells. Our study reveals an epigenetic mechanism associated with resistance to targeted therapy and demonstrates that therapeutic targeting of KDM6B-mediated IGFBP5 expression may provide a useful approach to mitigate both intrinsic and acquired resistance to the PI3K inhibitor in breast cancer. Mol Cancer Ther; 17(9); 1973-83. ©2018 AACR.

Abstract B039: KDM4B inhibition confers suseptibility to PI3K inhibitor in PTEN-deficient TNBC through overactivating UPR pathway

Triple-negative breast cancer (TNBC) is among the most lethal cancers in females. Up to 35% of TNBC show PTEN mutation or PTEN loss (PTEN deficiency). Although PTEN deficiency leads to aberrant activation of PI3K/AKT signaling, therapeutic targeting of PI3K/AKT pathway has yielded very limited clinical benefit. The effective therapeutic targets for PTEN-deficient cancers are in urgent need of identifying common vulnerabilities of this important pathway. To identify additional chemical drugs that target PTEN-deficient TNBC, we performed a drug screening together with a series of in vitro and in vivo validation. Here, we show that PTEN deficiency confers vulnerability to inhibition of histone demethylase KDM4B, resulting from perturbation of endoplasmic reticulum (ER) homeostasis through activating eIF2α/ATF4 unfolded protein response (UPR) pathway. Mechanistically, KDM4B suppresses UPR pathway by interacting with and inhibiting eIF2α activation, and this function requires its demethylase activity but is independent of histone modification. Consistent with the sensitivity, PTEN-deficient cells and samples from PTEN-deficient patients show constitutively activation of UPR, which usually confers survival advantage but induces cell death once it is further activated and prolonged by KDM4B inhibition. More importantly, targeting KDM4B can robustly synergize with PI3K inhibitor to induce cell death in PTEN-deficient TNBC. This synergistic killing is caused by "overactivating" the UPR pathway resulting from transcriptional activation of UPR genes by ATF4 and FoxO1. Collectively, our study thus identifies a novel cytoplasmic function of KDM4B in regulating cellular stress and provides a new therapeutic approach to treat PTEN-deficient TNBC.

Citation Format: Wenyu Wang, Gokce Oguz, Puay Leng Lee, Siti Maryam Yatim, Qiang Yu. KDM4B inhibition confers suseptibility to PI3K inhibitor in PTEN-deficient TNBC through overactivating UPR pathway [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2017 Oct 26-30; Philadelphia, PA. Philadelphia (PA): AACR; Mol Cancer Ther 2018;17(1 Suppl):Abstract nr B039.

IRAK1 is a therapeutic target that drives breast cancer metastasis and resistance to paclitaxel

Metastatic tumour recurrence due to failed treatments remains a major challenge of breast cancer clinical management. Here we report that interleukin-1 receptor-associated kinase 1 (IRAK1) is overexpressed in a subset of breast cancers, in particular triple-negative breast cancer (TNBC), where it acts to drive aggressive growth, metastasis and acquired resistance to paclitaxel treatment. We show that IRAK1 overexpression confers TNBC growth advantage through NF-κB-related cytokine secretion and metastatic TNBC cells exhibit gain of IRAK1 dependency, resulting in high susceptibility to genetic and pharmacologic inhibition of IRAK1. Importantly, paclitaxel treatment induces strong IRAK1 phosphorylation, an increase in inflammatory cytokine expression, enrichment of cancer stem cells and acquired resistance to paclitaxel treatment. Pharmacologic inhibition of IRAK1 is able to reverse paclitaxel resistance by triggering massive apoptosis at least in part through inhibiting p38-MCL1 pro-survival pathway. Our study thus demonstrates IRAK1 as a promising therapeutic target for TNBC metastasis and paclitaxel resistance.

Triple negative breast cancer (TNBC) patients often acquire resistant to chemotherapy. In this study, the authors identify the IRAK1 as the crucial driver of NF-κB-related cytokine secretion involved in TNBC metastasis and therapy resistance.

3-Deazaneplanocin A and neplanocin A analogues and their effects on apoptotic cell death

3-Deazaneplanocin A (DzNep) is a potential epigenetic drug for the treatment of various cancers. DzNep has been reported to deplete histone methylations, including oncogenic EZH2 complex, giving rise to epigenetic modifications that reactivate many silenced tumor suppressors in cancer cells. Despite its promise as an anticancer drug, little is known about the structure-activity relationships of DzNep in the context of epigenetic modifications and apoptosis induction. In this study, a number of analogues of DzNep were examined for DzNep-like ability to induce synergistic apoptosis in cancer cells in combination with trichostatin A, a known histone deacetylase (HDAC) inhibitor. The structure-activity relationship data thus obtained provide valuable information on the structural requirements for biological activity. The studies identified three compounds that show similar activities to DzNep. Two of these compounds show good pharmacokinetics and safety profiles. Attempts to correlate the observed synergistic apoptotic activities with measured S-adenosylhomocysteine hydrolase (SAHH) inhibitory activities suggest that the apoptotic activity of DzNep might not be directly due to its inhibition of SAHH.

EZH2-mediated inactivation of IFN-γ-JAK-STAT1 signaling is an effective therapeutic target in MYC-driven prostate cancer

Although small-molecule targeting of EZH2 appears to be effective in lymphomas carrying EZH2 activating mutations, finding similar approaches to target EZH2-overexpressing epithelial tumors remains challenging. In MYC-driven, but not PI3K-driven prostate cancer, we show that interferon-γ receptor 1 (IFNGR1) is directly repressed by EZH2 in a MYC-dependent manner and is downregulated in a subset of metastatic prostate cancers. EZH2 knockdown restored the expression of IFNGR1 and, when combined with IFN-γ treatment, led to strong activation of IFN-JAK-STAT1 tumor-suppressor signaling and robust apoptosis. Pharmacologic depletion of EZH2 by the histone-methylation inhibitor DZNep mimicked the effects of EZH2 knockdown on IFNGR1 induction and delivered a remarkable synergistic antitumor effect with IFN-γ. In contrast, although they efficiently depleted histone Lysine 27 trimethylation, EZH2 catalytic inhibitors failed to mimic EZH2 depletion. Thus, EZH2-inactivated IFN signaling may represent a therapeutic target, and patients with advanced prostate cancer driven by MYC may benefit from the combination of EZH2 and IFN-γ-targeted therapy.

exomeSuite: Whole exome sequence variant filtering tool for rapid identification of putative disease causing SNVs/indels

Exome and whole-genome analyses powered by next-generation sequencing (NGS) have become invaluable tools in identifying causal mutations responsible for Mendelian disorders. Given that individual exomes contain several thousand single nucleotide variants and insertions/deletions, it remains a challenge to analyze large numbers of variants from multiple exomes to identify causal alleles associated with inherited conditions. To this end, we have developed user-friendly software that analyzes variant calls from multiple individuals to facilitate identification of causal mutations. The software, termed exomeSuite, filters for putative causative variants of monogenic diseases inherited in one of three forms: dominant, recessive caused by a homozygous variant, or recessive caused by two compound heterozygous variants. In addition, exomeSuite can perform homozygosity mapping and analyze the variant data of multiple unrelated individuals. Here we demonstrate that filtering of variants with exomeSuite reduces datasets to a fraction of a percent of their original size. To the best of our knowledge this is the first freely available software developed to analyze variant data from multiple individuals that rapidly assimilates and filters large data sets based on pattern of inheritance.

PDK1 signaling toward PLK1-MYC activation confers oncogenic transformation, tumor-initiating cell activation, and resistance to mTOR-targeted therapy

Although 3-phosphoinositide-dependent protein kinase-1 (PDK1) has been predominately linked to the phosphoinositide 3-kinase (PI3K)-AKT pathway, it may also evoke additional signaling outputs to promote tumorigenesis. Here, we report that PDK1 directly induces phosphorylation of Polo-like kinase 1 (PLK1), which in turn induces MYC phosphorylation and protein accumulation. We show that PDK1-PLK1-MYC signaling is critical for cancer cell growth and survival, and small-molecule inhibition of PDK1/PLK1 provides an effective approach for therapeutic targeting of MYC dependency. Intriguingly, PDK1-PLK1-MYC signaling induces an embryonic stem cell-like gene signature associated with aggressive tumor behaviors and is a robust signaling axis driving cancer stem cell (CSC) self-renewal. Finally, we show that a PLK1 inhibitor synergizes with an mTOR inhibitor to induce synergistic antitumor effects in colorectal cancer by antagonizing compensatory MYC induction. These findings identify a novel pathway in human cancer and CSC activation and provide a therapeutic strategy for targeting MYC-associated tumorigenesis and therapeutic resistance.

SIGNIFICANCE

This work identifies PDK1–PLK1-MYC signaling as a new oncogenic pathway driving oncogenic transformation and CSC self-renewal. Targeted inhibition of PDK1/PLK1 is robust in targeting MYC dependency in cancer cells. Thus, our findings provide important insights into cancer and CSC biology and have significant therapeutic implications.

B55β-associated PP2A complex controls PDK1-directed myc signaling and modulates rapamycin sensitivity in colorectal cancer

The PP2A serine/threonine protein phosphatase serves as a critical cellular regulator of cell growth, proliferation, and survival. However, how this pathway is altered in human cancer to confer growth advantage is largely unknown. Here, we show that PPP2R2B, encoding the B55β regulatory subunit of the PP2A complex, is epigenetically inactivated by DNA hypermethylation in colorectal cancer. B55β-associated PP2A interacts with PDK1 and modulates its activity toward Myc phosphorylation. On loss of PPP2R2B, mTORC1 inhibitor rapamycin triggers a compensatory Myc phosphorylation in PDK1-dependent, but PI3K and AKT-independent manner, resulting in resistance. Reexpression of PPP2R2B, genetic ablation of PDK1 or pharmacologic inhibition of PDK1 abrogates the rapamycin-induced Myc phosphorylation, leading to rapamycin sensitization. Thus, PP2A-B55β antagonizes PDK1-Myc signaling and modulates rapamycin sensitivity.

Polymorphisms and mutations of human TMPRSS6 in iron deficiency anemia

Male subjects with iron deficiency from the general population were examined for polymorphisms or sporadic mutations in TMPRSS6 to identify genetic risk factors for iron deficiency anemia. Three uncommon non-synonymous polymorphisms were identified, G228D, R446W, and V795I (allele frequencies 0.0074, 0.023 and 0.0074 respectively), of which the R446W polymorphism appeared to be overrepresented in the anemic population. In addition, three children with iron refractory iron deficiency anemia, and one sibling with iron responsive iron deficiency anemia were also examined for polymorphisms or sporadic mutations in TMPRSS6. Two children (family 1) were compound heterozygotes for a L674F mutation and a previously described splicing defect predicted to cause skipping of exon 13 (IVS13+1 G>A). One child from the second family was homozygous for a deletion (497T) causing a frameshift (L166X+36) and premature termination. The sibling and mother from the second family were compound heterozygotes for the L166X mutation and the uncommon R446W polymorphism. Although in vitro expression studies demonstrated that the R446W isoform was biologically similar to wildtype Tmprss6, clinical data indicate that the R446W produces a milder disease when carried in trans with severe mutation in Tmprss6. The four children carrying mutations in TMPRSS6 all exhibited inappropriately high urinary hepcidin levels for the degree of iron deficiency.

DACT3 is an epigenetic regulator of Wnt/beta-catenin signaling in colorectal cancer and is a therapeutic target of histone modifications

Genetic and epigenetic defects in Wnt/beta-catenin signaling play important roles in colorectal cancer progression. Here we identify DACT3, a member of the DACT (Dpr/Frodo) gene family, as a negative regulator of Wnt/beta-catenin signaling that is transcriptionally repressed in colorectal cancer. Unlike other Wnt signaling inhibitors that are silenced by DNA methylation, DACT3 repression is associated with bivalent histone modifications. Remarkably, DACT3 expression can be robustly derepressed by a pharmacological combination that simultaneously targets both histone methylation and deacetylation, leading to strong inhibition of Dishevelled (Dvl)-mediated Wnt/beta-catenin signaling and massive apoptosis of colorectal cancer cells. Our study identifies DACT3 as an important regulator of Wnt/beta-catenin signaling in colorectal cancer and suggests a potential strategy for therapeutic control of Wnt/beta-catenin signaling in colorectal cancer.

Early age-of-onset iron overload and homozygosity for the novel hemojuvelin mutation HJV R54X (exon 3; c.160A-->T) in an African American male of West Indies descent

An African American male of West Indies descent was diagnosed to have elevated transferrin saturation, hyperferritinemia, severe iron deposition in hepatocytes, and hepatic cirrhosis at age 4. He was treated with serial phlebotomy to maintain a normal serum ferritin concentration thereafter. We evaluated him at age 23 and confirmed that he had normal serum ferritin levels, severe iron deposition in hepatocytes, hepatic cirrhosis, and portal hypertension. He did not have endocrinopathy, cardiomyopathy, or arthropathy. He was homozygous for the novel hemojuvelin (HJV) premature stop-codon mutation R54X (exon 3; c.160A-->T). He did not have either HFE C282Y, H63D, or S65C, or deleterious coding region mutations of SLC40A1, TFR2, or HAMP. His erythrocyte measures and hemoglobin electrophoresis were consistent with alpha-thalassemia trait. We conclude that homozygosity for HJV R54X accounts for his severe, early age-of-onset hemochromatosis; his phenotype was probably modified by serial phlebotomy therapy.

Zero thermal expansion in a nanostructured inorganic-organic hybrid crystal

There are very few materials that exhibit zero thermal expansion (ZTE), and of these even fewer are appropriate for electronic and optoelectronic applications. We find that a multifunctional crystalline hybrid inorganic-organic semiconductor, beta-ZnTe(en)(0.5) (en denotes ethylenediamine), shows uniaxial ZTE in a very broad temperature range of 4-400 K, and concurrently possesses superior electronic and optical properties. The ZTE behavior is a result of compensation of contraction and expansion of different segments along the inorganic-organic stacking axis. This work suggests an alternative route to designing materials in a nanoscopic scale with ZTE or any desired positive or negative thermal expansion (PTE or NTE), which is supported by preliminary data for ZnTe(pda)(0.5) (pda denotes 1,3-propanediamine) with a larger molecule.

Pharmacologic disruption of Polycomb-repressive complex 2-mediated gene repression selectively induces apoptosis in cancer cells

Polycomb-repressive complex 2 (PRC2)-mediated histone methylation plays an important role in aberrant cancer gene silencing and is a potential target for cancer therapy. Here we show that S-adenosylhomocysteine hydrolase inhibitor 3-Deazaneplanocin A (DZNep) induces efficient apoptotic cell death in cancer cells but not in normal cells. We found that DZNep effectively depleted cellular levels of PRC2 components EZH2, SUZ12, and EED and inhibited associated histone H3 Lys 27 methylation (but not H3 Lys 9 methylation). By integrating RNA interference (RNAi), genome-wide expression analysis, and chromatin immunoprecipitation (ChIP) studies, we have identified a prominent set of genes selectively repressed by PRC2 in breast cancer that can be reactivated by DZNep. We further demonstrate that the preferential reactivation of a set of these genes by DZNep, including a novel apoptosis affector, FBXO32, contributes to DZNep-induced apoptosis in breast cancer cells. Our results demonstrate the unique feature of DZNep as a novel chromatin remodeling compound and suggest that pharmacologic reversal of PRC2-mediated gene repression by DZNep may constitute a novel approach for cancer therapy.

Polyamorphism in a metallic glass

A metal, or an alloy, can often exist in more than one crystal structure. The face-centred-cubic and body-centred-cubic forms of iron (or steel) are a familiar example of such polymorphism. When metallic materials are made in the amorphous form, is a parallel 'polyamorphism' possible? So far, polyamorphic phase transitions in the glassy state have been observed only in glasses involving directional and open (such as tetrahedral) coordination environments. Here, we report an in situ X-ray diffraction observation of a pressure-induced transition between two distinct amorphous polymorphs in a Ce(55)Al(45) metallic glass. The large density difference observed between the two polyamorphs is attributed to their different electronic and atomic structures, in particular the bond shortening revealed by ab initio modelling of the effects of f-electron delocalization. This discovery offers a new perspective of the amorphous state of metals, and has implications for understanding the structure, evolution and properties of metallic glasses and related liquids. Our work also opens a new avenue towards technologically useful amorphous alloys that are compositionally identical but with different thermodynamic, functional and rheological properties due to different bonding and structural characteristics.

Effects of vitamin E supplementation on bone metabolism in nicotine-treated rats

INTRODUCTION

Nicotine has been shown to exert negative effects on bone. This study determined whether vitamin E supplementation is able to repair the nicotine-induced adverse effects in bone.

METHODS

24 male rats were divided into three groups. The fi rst group was the baseline control and killed untreated at the beginning of the study. Groups 2 and 3 received nicotine at 7 mg per kg for three months but during the second and third months, group 2 was supplemented with alpha-tocopherol (N+ATF) while group 3 was given palm tocotrienol mixture (N+TT). Serum interleukin-1 (IL-1), serum interleukin-6 (IL-6), serum osteocalcin, urine deoxypyridinoline (DPD) and bone calcium content were measured.

RESULTS

Palm tocotrienol mixture was able to prevent the increment of IL-1 and IL- 6 due to nicotine treatment. No changes were seen in the osteocalcin levels, but the N+ATF group had lower urine DPD levels after treatment. However, bone-remodelling index revealed no significant changes. No significant differences were seen in the femoral bone calcium content results, although the fourth lumbar bone calcium content was reduced in both groups with 66.5 percent reduction in the N+ATF group and 59.6 percent reduction in the N+TT group.

CONCLUSION

Palm tocotrienol mixture was better than alpha-tocopherol in reversing the effects of nicotine on IL-1 and IL-6. Both forms of vitamin E were not able to restore the nicotine-induced bone calcium loss, but the N+ATF group suffered a greater loss. Tocotrienol seemed to be superior to alpha-tocopherol in combating against the adverse effect of nicotine.

MR Spectroscopic Changes in the Rat Hippocampus following Proton Radiosurgery

PURPOSE

To identify MR spectroscopic changes in the rat hippocampus following proton radiosurgery.

METHODS AND MATERIALS

A group of 12 rats were treated with Bragg peak proton beam irradiation involving the right hippocampus. Single doses of 30 CGE, 50 CGE, 70 CGE, 90 CGE were delivered to groups of 3 animals using single fraction technique. Animals were imaged using a standard 3 T GE Signa MRI at 4 months following treatment. An untreated animal was also studied. A 3'' surface coil was employed to obtain T1 weighted coronal pre- and post-gadolinium images (TR 600 and TE 30) and dual echo T2 weighted coronal images (TR 3000, TE 30/90). Volumetric analysis with custom software was done to evaluate areas of increased signal on T2 weighted images and the development of hydrocephalus was examined. Animals were sacrificed and specimens of the treated hippocampus were harvested for High Resolution Magic Angle Spinning MR Spectroscopy (HRMAS) followed by histopathology of the tissue samples. Peak values of choline, creatine, N-acetyl aspartate and lipids were evaluated and compared.

RESULTS

Peak tissue injury occurred in the surviving 90 CGE animal by both T2 weighted and post-gadolinium imaging. Gadolinium enhancement was seen in decreasing volumes of tissue at dosage levels from 90 to 50 CGE. Hydrocephalus was seen on the untreated side in the 90 CGE animal likely because of mass effect, while it was seen in small degrees in the side of treatment in the 70 and 50 CGE animals. Histopathology showed changes at 90 and 70 CGE, but not at 50 or 30 CGE at this time point using H and E stains. HRMAS showed spectroscopic changes in the surviving 90 and 70 CGE animals but not in the 50 and 30 CGE animals. Statistical significance was not reached because of the small sample size.

CONCLUSIONS

Following single dose proton radiosurgery of rat hippocampus, HRMAS is able to identify metabolic changes induced by radiation. Studies built on these principles may help develop non-invasive MR spectroscopic methods to distinguish radiation changes from tumor recurrence.

Modeling a potential atmospheric release from a waste disposal facility at the savannah river site as an area source

The Saltstone Facility was designed at the Savannah River Site (SRS) to treat and dispose of certain low-level liquid radioactive wastes. The final product of Saltstone is several large concrete vaults. As part of the performance assessment for Saltstone, reduction of dose to receptors downwind of the vaults have been estimated for treating the vaults as an area atmospheric source as opposed to a point source. The CAP88 model has the ability to handle area sources, but the methods are not appropriate for receptors close to the source such as those modeled at 100 m. Use of the area source as opposed to the point source can reduce the dose by as much as a factor of 5 depending on vault size. A method for quickly assessing the dose from an area source for near-in exposures is demonstrated here.

On the structure of aragonite

High-resolution synchrotron powder diffraction measurements were carried out at the 32-ID beamline of the Advanced Photon Source of Argonne National Laboratory in order to clarify the structure of geological aragonite, a widely abundant polymorph of CaCO3. The investigated crystals were practically free of impurity atoms, as measured by wavelength-dispersive X-ray spectroscopy in scanning electron microscopy. A superior quality of diffraction data was achieved by using the 11-channel 111 Si multi-analyzer of the diffracted beam. Applying the Rietveld refinement procedure to the high-resolution diffraction spectra, we were able to extract the aragonite lattice parameters with an accuracy of about 20 p.p.m. The data obtained unambiguously confirm that pure aragonite crystals have orthorhombic symmetry.

A multicenter in vivo proton-MRS study of HIV-associated dementia and its relationship to age

OBJECTIVE

Differences in diagnostic criteria and methods have led to mixed results regarding the metabolite pattern of HIV-associated brain injury in relation to neurocognitive impairment. Therefore, a multicenter MRS consortium was formed to evaluate the neurometabolites in HIV patients with or without cognitive impairment.

METHODS

Proton magnetic resonance spectroscopy (MRS) at short-echo time (30 ms) was assessed in the frontal white matter, basal ganglia, and parietal cortex of 100 HIV patients [61 with AIDS dementia complex (ADC) and 39 neuroasymptomatic (NAS)] and 37 seronegative (SN) controls.

RESULTS

Compared to SN, NAS had higher glial marker myoinositol-to-creatine ratio (MI/Cr) in the white matter (multivariate analyses, adjusted P=0.001), while ADC showed further increased MI/Cr in the white matter and basal ganglia (both P<0.001), and increased choline compounds (Cho)/Cr in white matter (P=0.04) and basal ganglia (P<0.001). Compared to NAS, ADC showed a reduction in the neuronal marker N-acetyl compound (NA)/Cr in the frontal white matter (P=0.007). CSF, but not plasma, viral load correlated with MI/Cr and Cho/Cr in white matter and NAA/Cr in parietal cortex. HIV infection and aging had additive effects on Cho/Cr and MI/Cr in the basal ganglia and white matter.

CONCLUSIONS

The results suggest that glial activation occurs during the NAS stages of HIV infection, whereas further inflammatory activity in the basal ganglia and neuronal injury in the white matter is associated with the development of cognitive impairment. Aging may further exacerbate brain metabolites associated with inflammation in HIV patient and thereby increase the risk for cognitive impairment.

A previously undescribed frameshift deletion mutation of HFE (c.del277; G93fs) associated with hemochromatosis and iron overload in a C282Y heterozygote

A 62-year-old white man with a hemochromatosis phenotype was found to be heterozygous for the C282Y mutation of the HFE gene. The H63D and S65C mutations of HFE were not present. As most C282Y heterozygotes do not develop a hemochromatosis phenotype, the coding region of the patient's HFE gene was sequenced and a previously undescribed frameshift mutation was identified in exon 2 (c.del277; G93fs) that resulted in a premature stop-codon. There were no coding region mutations of the ferroportin gene (FPN1). We performed human leukocyte antigen (HLA) typing of the patient and his brother who was heterozygous for the C282Y HFE mutation unassociated with a hemochromatosis phenotype. They shared only C282Y and the HLA haplotype A*03, B*14; hence, the c.del277 mutation was linked to the HLA haplotype A*02, B*44 and therefore not on the same chromosome as the C282Y mutation. Thus, the present patient's only intact HFE protein is C282Y, and this may explain his hemochromatosis phenotype.

Comparative study on conventional and low-flow nebulizers for arsenic speciation by means of microbore liquid chromatography with inductively coupled plasma mass spectrometry

The performance of conventional and low-flow nebulizer systems with liquid chromatography in differentiating four arsenic species in urine was evaluated. Two low-flow (DIN and MCN) chamber assemblies and a conventional (CFN) nebulizer-spray chamber assembly were compared in the hyphenation of anion-exchange microbore liquid chromatography with inductively coupled plasma mass spectrometry. Under optimal analytical conditions, the detection limits of the four arsenic species were 0.2-0.6 ng ml(-1) for all the nebulizer systems tested. The chromatographic resolution was best in the case of DIN due to its minimal off-column dead volume and superior transport efficiency. Four arsenic species were determined in the certified reference materials NIST SRM 2670E and 2670N.

Patient mortality of active pulmonary tuberculosis requiring mechanical ventilation

Mortality remains high among patients with pulmonary tuberculosis requiring mechanical ventilation (TBMV). This study was carried out to establish the mortality rates of TBMV and to identify factors that contribute to in-hospital mortality. From January 1996-April 2001, there were 825 patients with active pulmonary tuberculosis at the National Taiwan University Hospital, Taipei, Taiwan. Of these, 41 suffered acute respiratory failure and required mechanical ventilation in the intensive care unit (ICU). Of these 41 patients, 38 were followed up for 180 days. In-hospital deaths were documented in the medical records and all possible parameters contributing to mortality were collected. Of the 41 patients, 27 died in the hospital and 14 were discharged alive (in-hospital mortality rate 65.9%), with (mean +/- SD) 40.7 +/- 35.4 admission days before death. Of the 27 that died, 25 died during ICU admission and two died after being transferred to the ward. The mortality rate for the 180-day monitoring period was 79%. Factors contributing to in-hospital mortality included consolidations on chest radiographs and multiple organ failure. The mortality rate in the patients with pulmonary tuberculosis requiring mechanical ventilation is very high, with two factors affecting in-hospital mortality. These factors were multiple organ failure and consolidation on chest radiographs.

High-energy diffuse scattering on the 1-ID beamline at the advanced photon source

This paper reports on experiments in which high-energy (65.35 keV) X-rays were used to record the detailed diffuse diffraction patterns of a number of ceramic materials. The methodology has enabled a greater q-range to be explored (up to sintheta/lambda approximately 0.97) than is possible with laboratory-based experiments, with better q-space resolution and increased sensitivity, thus allowing previously unseen detail in diffraction patterns to be recorded. In all, 11 sections of data have been collected for Ca-CSZ, eight for Y-CSZ and six for wüstite.

Cryogenically cooled bent double-Laue monochromator for high-energy undulator X-rays (50-200 keV)

A liquid-nitrogen-cooled monochromator for high-energy X-rays consisting of two bent Si(111) Laue crystals adjusted to sequential Rowland conditions has been in operation for over two years at the SRI-CAT sector 1 undulator beamline of the Advanced Photon Source (APS). It delivers over ten times more flux than a flat-crystal monochromator does at high energies, without any increase in energy width (DeltaE/E approximately 10(-3)). Cryogenic cooling permits optimal flux, avoiding a sacrifice from the often employed alternative technique of filtration - a technique less effective at sources like the 7 GeV APS, where considerable heat loads can be deposited by high-energy photons, especially at closed undulator gaps. The fixed-offset geometry provides a fully tunable in-line monochromatic beam. In addition to presenting the optics performance, unique crystal design and stable bending mechanism for a cryogenically cooled crystal under high heat load, the bending radii adjustment procedures are described.

Magnetic resonance spectroscopy: an in vivo tool for monitoring cerebral injury in SIV-infected macaques

The purpose of our study was to demonstrate the feasibility of using in vivo proton Magnetic Resonance Spectroscopy (MRS) to monitor the brain manifestations of SIV infection in the macaque model of AIDS. Previous spectroscopy work on macaque brain tissue and in vivo work in humans is reviewed to provide the motivation and context for this study. We collected 34 MRS data sets on 14 uninfected rhesus macaques. From this data, we demonstrate that we are capable of detecting changes similar to those observed in human MRS studies for most metabolites using less than 10 animals. The juvenile macaques utilized in this study demonstrate age-related changes in the levels of N-acetyl aspartate (NAA), a neuronal marker. The quantity and distribution of neurochemicals in the macaque are found to be slightly, but significantly, different than in the human.

Human transferrin G277S mutation: a risk factor for iron deficiency anaemia

Numerous polymorphisms of the transferrin gene result in a range of electrophoretic variants. We show that one of these mutations has a functional consequence. A G-->A mutation at cDNA nucleotide 829 (G277S) was associated with a reduction in total iron binding capacity (TIBC). In menstruating white women, the G277S genotype was a risk factor for iron deficiency anaemia: iron deficiency anaemia was present in 27% of homozygous G277S/G277S women, 10% of G277G/G277S heterozygous women and 5% of homozygous wild-type G277G/G277G women.

Hospital-based management of acute asthmatic exacerbation: an assessment of physicians' behavior in Taiwan

This retrospective study was conducted to assess Taiwanese emergency physicians for their preference in management and adherence to guidelines in treating patients with acute exacerbation of asthma. One hundred twenty patients from hospitals of three different levels were evaluated by reviewing their medical records. Our study revealed that physicians from medical centers and regional hospitals assessed patients more often with arterial blood gas or pulse oximetry; prescribed more doses of beta2-agonist nebulizers; administered more doses of beta2-agonist nebulizers before administering parenteral aminophylline; and prescribed ipratropium nebulizers more often as adjunctive therapy. On the other hand, physicians from district hospitals more frequently prescribed parenteral aminophylline as the first-line medication and more often prescribed only a single dose of beta2-agonist nebulizer. Most emergency physicians in Taiwan did not adhere to guidelines. Specifically, these included omission of peak expiratory flow as the means to assess the severity of asthma exacerbation and response to treatment; suboptimal use of inhaled bronchodilators, such as beta2-agonists and ipratropium; and inappropriate use of parenteral aminophylline as the first-line medication.

A study of genes that may modulate the expression of hereditary hemochromatosis: transferrin receptor-1, ferroportin, ceruloplasmin, ferritin light and heavy chains, iron regulatory proteins (IRP)-1 and -2, and hepcidin

We have examined transferrin receptor-1, ferroportin, ceruloplasmin, ferritin light and heavy chains, iron regulatory proteins (IRP)-1 and -2, and hepcidin for mutations that might modulate the iron burden of individuals harboring the common mutant hemochromatosis HFE genotype C282Y/C282Y or cause hemochromatosis independent of mutations in the HFE gene. In a group of white, Asian, and African-American normal and iron-overloaded individuals, the coding and flanking regions of these genes were completely sequenced. Numerous coding region and promoter polymorphisms were detected. These were further examined for association with differences in iron accumulation as measured by plasma transferrin saturation and ferritin levels, but no such association could be documented.

Observation of the 22.5-keV resonance in (149)Sm by the nuclear lighthouse effect

We have observed coherent nuclear resonant scattering of synchrotron radiation at the 22.5-keV resonance of (149)Sm. High-speed rotational sample motion led to an angular deflection of the resonantly scattered radiation off the nonresonant primary beam. This allowed us to determine the resonance energy of the first excited nuclear level of (149)Sm to be 22496(4) eV. Because of the angular deflection of the resonant photons, time spectra of coherent nuclear resonant scattering can be recorded as a function of a spatial coordinate. Time resolutions of a few 10 ps can be expected, which are beyond the limits of existing x-ray detection schemes.

Microsatellite variation in the yellowhammer Emberiza citrinella: population structure of a declining farmland bird

In recent years, there has been much concern in the UK about population declines of widespread species in agricultural habitats. Conservation-orientated research on declining birds has focused on vital rates of survival and productivity. However, the environmental factors which may influence movements between populations of widespread species is poorly understood. Population genetic structure is an indirect description of dispersal between groups of individuals. To attempt to develop an understanding of genetic structuring in a widespread, but declining, farmland bird, we therefore investigated the yellowhammer, Emberiza citrinella, population in England and Wales using microsatellite data. Our first aim was to investigate whether there was genetic substructuring in the population. A second aim was to investigate if there was a relationship between genetic distances and various environmental variables. Finally, we analysed the microsatellite data for evidence of loss of genetic variation due to population decline. Our data showed a slight but significant structure within the yellowhammer population. This therefore cannot be considered a panmictic population. Our example from South Cumbria implies that high-altitude barriers may have a slight influence on population structure. However, on the whole, genetic distances between sample sites were not significantly correlated with geographical distances, degrees of population connectivity, high altitudes, or differences in precipitation between sites. Finally, we detected departures from mutation-drift equilibrium (excess heterozygosity), which is indicative of a loss of genetic variation through recent decline.

SOS mutator DNA polymerase IV functions in adaptive mutation and not adaptive amplification

Adaptive point mutation and amplification are induced responses to environmental stress, promoting genetic changes that can enhance survival. A specialized adaptive mutation mechanism has been documented in one Escherichia coli assay, but its enzymatic basis remained unclear. We report that the SOS-inducible, error-prone DNA polymerase (pol) IV, encoded by dinB, is required for adaptive point mutation in the E. coli lac operon. A nonpolar dinB mutation reduces adaptive mutation frequencies by 85% but does not affect adaptive amplification, growth-dependent mutation, or survival after oxidative or UV damage. We show that pol IV, together with the major replicase, pol III, can account for all adaptive point mutations at lac. The results identify a role for pol IV in inducible genetic change.

Polymorphisms in the transferrin 5' flanking region associated with differences in total iron binding capacity: possible implications in iron homeostasis

We have identified five single nucleotide polymorphisms (SNPs) upstream (5') of the transferrin coding region. One polymorphism is in the 5' UTR at nt +49, and four are in the promoter region at nt -34, -551, -617, and -739, numbering from the start of transcription. The -34 and -617 SNPs are tightly but not completely linked. The -34 polymorphism lies between a conserved Sp1 site and the TATA box. The -617 polymorphism is within the DRII enhancer region. Five haplotypes have been defined from these SNPs by the identification of at least one homozygous individual, and two other haplotypes were deduced from heterozygous individuals. The total iron-binding capacity associated with each transferrin haplotype was haplotype 2 > 1 > 4 > 3. Transferrin promoter haplotype 2 had a significantly higher mean TIBC and haplotype 3 had a significantly lower mean TIBC than the more common haplotype 1. Persons with haplotype 4, which includes the -34T and -617A minor alleles, have a lower mean TIBC but the difference was not statistically significant. In normal individuals, the differences in the haplotypes were not found to be associated with differences in transferrin saturation and ferritin levels. There was no difference in the extent of increase in the mean TIBC levels in individuals with iron deficiency anemia in regard to their haplotype. Furthermore, there was no difference in the relative frequencies of the transferrin haplotypes in the iron-deficient population. In hemochromatosis patients who were homozygous for the C282Y HFE mutation, no particular haplotype was associated with a significant difference in transferrin saturation or ferritin levels. In White patients with Parkinson's disease, a disorder in which there is abnormal iron deposition in the brain, the presence of transferrin haplotype 3 was in slight excess over the normal White population.

Mutation Analysis of the Transferrin Receptor-2 Gene in Patients with Iron Overload

Three mutations in the transferrin receptor-2 gene have recently been identified in four Sicilian families with iron overload who had a normal hemochromatosis gene, HFE (C. Camaschella, personal communication). To determine the extent to which mutations in the transferrin receptor-2 gene occur in other populations with iron overload, we have completely sequenced this gene in 17 whites, 10 Asians, and 8 African Americans with iron overload and a C282C/C282C HFE genotype, as well as 4 subjects without iron overload and homozygous for the mutant HFE C282Y genotype, 5 patients with iron overload and homozygous for the mutant HFE C282Y genotype, and 5 normal individuals. None of the individuals exhibited the Sicilian mutations, Y250X in exon 6, M172K in exon 4, and E60X in exon 2. One iron-overloaded individual of Asian descent exhibited a I238M mutation which was subsequently found to be a polymorphism present in the Asian population at a frequency of 0.0192. The presence of the I238M mutation was not associated with an increase in ferritin or transferrin saturation levels. Three silent polymorphisms were also identified, nt 1770 (D590D) and nt 1851 (A617A) and a polymorphism at nt 2255 in the 3' UTR. Thus, mutations in the transferrin receptor-2 gene were not responsible for the iron overload seen in our subjects.

Improved common carotid elasticity and intima-media thickness measurements from computer analysis of sequential ultrasound frames

B-mode ultrasound has gained popularity as a non-invasive method for direct visualization of superficial vessels. With B-mode ultrasound, arterial stiffness can be directly measured since image acquisition of the arterial wall thickness and vessel diameter can be obtained simultaneously in a dynamic fashion throughout the cardiac cycle. Recently, a method was developed to measure carotid arterial diameter and intima-media thickness (IMT) from B-mode images that utilizes computerized edge tracking-multiframe image processing that automatically measures arterial diameter and IMT in multiple sequential frames spanning several cardiac cycles. To evaluate this method, replicate B-mode common carotid artery ultrasound examinations and blood pressure measurements were obtained in 24 subjects 1-2 weeks apart. Approximately 80 sequential frames spanning two cardiac cycles were analyzed from each ultrasound examination to obtain maximum arterial diameter (D(max)), minimum arterial diameter (D(min)), and IMT using a computerized edge detection method. The intraclass correlations of D(max), D(min), and IMT were 0.97-0.99 and the mean absolute difference for these measurements were 0.03-0.11 mm. The coefficient of variation for D(max) and D(min) were 1.28 and 1.18%, respectively. The intraclass correlation for several standard arterial stiffness indices, Peterson's elastic modulus, Young's modulus, arterial distensibility, compliance, and the beta stiffness index ranged between 0.84 and 0.89. Additionally, it was determined that averaging IMT over five frames centered at D(min) reduced single frame IMT measurement variability by 27% (P=0.005) compared with IMT measured from a single frame corresponding to D(min). Comparison of the phasic relationship of D(max) and D(min) measured from the B-mode ultrasound image with the simultaneously recorded electrocardiogram (ECG) signal in the 24 subjects, provided a more accurate method of frame selection for arterial diameter extrema independent of the ECG signal. The method of computerized edge detection-sequential multiframe image processing presented in this paper represents a technological advance for image analysis of B-mode ultrasound images of common carotid arterial dimensions that is highly reproducible and directly applicable to noninvasive imaging of atherosclerosis.

Early brain injury in the SIV-macaque model of AIDS

OBJECTIVE

To specify the type and severity of cellular damage in the central nervous system soon after infection and at later stages of disease in the SIV-macaque model of AIDS.

DESIGN AND METHODS

Adjacent samples of frontal cortical gray matter were taken from three groups of macaques: uninfected controls (n = 4), acute (14 days post-infection; n = 4), and chronic (mean 2 years post-infection; n = 7). In vitro high resolution magnetic resonance spectroscopy of snap frozen intact tissue and quantitative neuropathology measurements of synaptophysin, calbindin, and glial fibrillary acidic protein (GFAP) in formalin-fixed tissue were performed.

RESULTS

Losses in n-acetylaspartate and calbindin (indicating neuronal injury and/or death) and decreases in synaptophysin immunoreactivity (indicating synaptodendritic injury) were detected along with increases in GFAP (indicating reactive gliosis). Cellular injury worsened progressively with increased time after infection.

CONCLUSIONS

These results are the first direct evidence that neuronal injury occurs soon after infection. The exacerbation of injury with time suggests a connection between the early response of the central nervous system and dementia, which occurs late in the course of infection. This connection may have broad implications for the study of and the development of therapies for damage of the central nervous system by HIV.

Dobutamine-induced increase of right ventricular contractility without increased stroke volume in adolescent patients with transposition of the great arteries: evaluation with magnetic resonance imaging

OBJECTIVE

Prognosis in patients with surgically corrected (Senning or Mustard) transposition of the great arteries (TGA) depends mainly on right ventricular (RV) function and RV functional reserve. We examined the role of dobutamine stress in the early detection of RV dysfunction in asymptomatic or slightly symptomatic patients with TGA using magnetic resonance imaging (MRI).

DESIGN AND PATIENTS

Twelve asymptomatic or slightly symptomatic patients with chronic RV pressure overload, surgically corrected (Mustard or Senning) TGA (age 22.8 (+/- 3.4) years; New York Heart Association (NYHA) class I/II) and nine age matched healthy volunteers (age 27.3 (+/- 4.4) years) were included. MRI was applied both at baseline and during dobutamine stress (start dose 5 microg/kg/min to maximum dose 15 microg/kg/min) to determine RV and left ventricular (LV) stroke volumes (SV) and ejection fraction (EF).

RESULTS

At baseline only RVEF was significantly higher in controls than in patients (71 (+/- 9) vs. 57 (+/- 10)%, p < 0.001), other RV parameters were not significantly different between the two examined groups: RVSV (86 (+/- 21) vs. 72 (+/- 27) ml, p = ns), RV end-diastolic volume (EDV) (123 (+/- 37) vs. 123 (+/- 33) ml, p = ns), and heart rate (61 (+/- 10) vs. 69 (+/- 14) bpm, p = ns), respectively. During dobutamine stress RVEF increased significantly both in controls and patients (20 (+/- 16) vs. 17 (+/- 18)%, p < 0.01 and p < 0.02 vs. rest, respectively), but stress RVEF was significantly higher in controls than in patients (85 (+/- 3) vs. 66 (+/- 7)%, p < 0.0001). RVSV increased significantly in controls (22 (+/- 19)%, p < 0.02), and there was no significant increase in RVSV in patients (-10 (+/- 28)%, p = ns). The controls showed no change in RVEDV (2 (+/- 17)%, p = ns), but in patients a significant decrease in RVEDV (-24 (+/- 15)%, p < 0.001) was observed. Maximal heart rate was significantly higher in patients than in controls (122 (+/- 20) vs. 101 (+/- 14) bpm, p < 0.02).

CONCLUSION

In asymptomatic or slightly symptomatic patients with surgically corrected TGA dobutamine had a positive inotropic effect on RV, but the increased contractility was not accompanied by an appropriate increase in SV. Our data suggest inadequate RV filling in this category of patients, possibly due to rigid atrial baffles and compromised atrial function or decreased compliance due to RV hypertrophy.

The SOS response regulates adaptive mutation

Upon starvation some Escherichia coli cells undergo a transient, genome-wide hypermutation (called adaptive mutation) that is recombination-dependent and appears to be a response to a stressful environment. Adaptive mutation may reflect an inducible mechanism that generates genetic variability in times of stress. Previously, however, the regulatory components and signal transduction pathways controlling adaptive mutation were unknown. Here we show that adaptive mutation is regulated by the SOS response, a complex, graded response to DNA damage that includes induction of gene products blocking cell division and promoting mutation, recombination, and DNA repair. We find that SOS-induced levels of proteins other than RecA are needed for adaptive mutation. We report a requirement of RecF for efficient adaptive mutation and provide evidence that the role of RecF in mutation is to allow SOS induction. We also report the discovery of an SOS-controlled inhibitor of adaptive mutation, PsiB. These results indicate that adaptive mutation is a tightly regulated response, controlled both positively and negatively by the SOS system.

NADH-ferric reductase activity associated with dihydropteridine reductase

In mammals dietary ferric iron is reduced to ferrous iron for more efficient absorption by the intestine. Analysis of a pig duodenal membrane fraction revealed two NADH-dependent ferric reductase activities, one associated with a b-type cytochrome and the other not. Purification and characterization of the non-cytochrome ferric reductase identified a 31 kDa protein. MALDI-MS analysis and amino acid sequencing identified the ferric reductase as being related to the 26 kDa liver NADH-dependent quinoid dihydropteridine reductase (DHPR). The NADH-dependent DHPR ferric reductase activity was found to be pteridine-independent since exhaustive dialysis did not reduce activity and heat-inactivation destroyed activity. In intestinal Caco-2 cells, DHPR mRNA levels were found to be regulated by iron. Thus, DHPR appears to be a dual function enzyme, a NADH-dependent dihydopteridine reductase and an iron-regulated, NADH-dependent, pteridine-independent ferric reductase.

Magnetic resonance spectroscopy of brain tumors

Magnetic resonance spectroscopy provides metabolic information about brain tumors beyond what can be obtained from anatomic images. In contrast to other metabolism-based imaging techniques such as single photon emission computed tomography and positron-emission tomography, magnetic resonance spectroscopy yields multiparametric data, does not require radio-labeled tracers or ionizing radiation, and can be performed in conjunction with other magnetic resonance imaging studies. Magnetic resonance spectral patterns have been shown to be distinct for different tumor types and grades. Response to radiation therapy is also reflected by magnetic resonance spectral patterns. Although there are quantitative issues still to be addressed, correlation of in vivo spectral patterns with ex vivo spectral patterns obtained from actual biopsy samples indicates that magnetic resonance spectroscopy is a fundamentally valid tool for monitoring disease progression and therapeutic response in patients with brain tumors.

A new high-speed beam chopper for time-resolved X-ray studies

A new high-speed X-ray beam chopper, which can be phase locked to the temporal structure of the Advanced Photon Source (APS) storage ring, has been developed and tested. The open window time of the chopper is 2450 ns, which corresponds to approximately 67% of the revolution time of the APS storage ring. By phase locking the rotation of the beam chopper to the storage-ring orbital frequency, any portion of the storage-ring fill pattern can be positioned within the beam-chopper transmission-time window.

The effect of transferrin polymorphisms on iron metabolism

The effect of five different transferrin variants (TFv1, TFv2, TFv3, TFv4, and TFv5) on the hemoglobin level, mean corpuscular volume (MCV), ferritin level, percent transferrin saturation (%TS), and the unsaturated iron binding capacity (UIBC) was investigated in subjects with defined HFE haplotypes, 919 persons undergoing health screening and 113 patients with clinical hemochromatosis. The most common variant is TFv4; the population distribution of this variant was also studied. None of the variants were found to have an effect on any of the parameters of iron metabolism that were investigated. Moreover, the frequency of these variants in patients with clinically significant hemochromatosis was no different from that in the general population. We conclude that these polymorphisms in transferrin do not play a role in the expression of hemochromatosis, nor do they produce any other significant changes in iron metabolism.

Echoplanar chemical shift imaging

A novel method of chemical shift imaging utilizing echoplanar imaging (EPI) has been developed for the purpose of improving the spatial resolution of metabolite images for the specific goal of high spatial resolution mapping of neuronal content. An EPI sequence was modified to allow temporal offsets of the 180 degree refocusing pulse that encode the chemical shift information into the phase of the signal. Implementation of this method on 1.5 and 3 T human imagers has resulted in images of N-acetyl aspartate in humans with spatial resolution of 360 microl and signal-to-noise ratio approximately 7:1 in less than 13 min.