An IR-Selected Galaxy Cluster at z=1.27

We report the discovery of a galaxy cluster at z=1.27. ClG J0848+4453 was found in a near-IR field survey as a high density region of objects with very red J-K colors. Optical spectroscopy of a limited number of 24 < R < 25 objects in the area shows that 6 galaxies within a 90 arcsec (0.49/h Mpc, q_O = 0.1) diameter region lie at z=1.273 +/- 0.002. Most of these 6 member galaxies have broad-band colors consistent with the expected spectral energy distribution of a passively-evolving elliptical galaxy formed at high redshift. An additional 2 galaxies located ~2 arcmin from the cluster center are also at z=1.27. Using all 8 of these spectroscopic members, we estimate the velocity dispersion is 700 +/- 180 km/s, similar to that of Abell R=1 clusters in the present epoch. A deep Rosat PSPC observation detects X-ray emission at the 5 sigma level coincident with the nominal cluster center. Assuming that the X-ray flux is emitted by hot gas trapped in the potential well of a collapsed system (no AGN is known to exist in the area), the resulting X-ray luminosity in the rest frame 0.1-2.4 keV band of L_x = 1.5 x 10^44 ergs/s suggests the presence of a moderately large mass. ClG J0848+4453 is the highest redshift cluster found without targetting a central active galaxy.Comment: Accepted for publication in The Astronomical Journal; 22 pages, 6 figures; corrected titl

Discovery of a Color-Selected Quasar at z=5.50

We present observations of RD J030117+002025, a quasar at z=5.50 discovered from deep, multi-color, ground-based observations covering 74 square arcmin. This is the most distant quasar or AGN currently known. The object was targeted as an R-band dropout, with R(AB)>26.3 (3-sigma limit in a 3 arcsec diameter region), I(AB)=23.8, and z(AB)=23.4. The Keck/LRIS spectrum shows broad Lyman-alpha/NV emission and sharp absorption decrements from the highly-redshifted hydrogen forests. The fractional continuum depression due to the Lyman-alpha forest is D(A)=0.90. RD J030117+002025 is the least luminous, high-redshift quasar known (M(B)~-22.7).Comment: 9 pages, 2 figures; to appear in the The Astrophysical Journal Letter

Mediterranean Diet and Alzheimer Disease Mortality

BACKGROUND: We previously reported that the Mediterranean diet (MeDi) is related to lower risk for Alzheimer disease (AD). Whether MeDi is associated with subsequent AD course and outcomes has not been investigated. OBJECTIVES: To examine the association between MeDi and mortality in patients with AD. METHODS: A total of 192 community-based individuals in New York who were diagnosed with AD were prospectively followed every 1.5 years. Adherence to the MeDi (0- to 9-point scale with higher scores indicating higher adherence) was the main predictor of mortality in Cox models that were adjusted for period of recruitment, age, gender, ethnicity, education, APOE genotype, caloric intake, smoking, and body mass index. RESULTS: Eighty-five patients with AD (44%) died during the course of 4.4 (+/-3.6, 0.2 to 13.6) years of follow-up. In unadjusted models, higher adherence to MeDi was associated with lower mortality risk (for each additional MeDi point hazard ratio 0.79; 95% CI 0.69 to 0.91; p = 0.001). This result remained significant after controlling for all covariates (0.76; 0.65 to 0.89; p = 0.001). In adjusted models, as compared with AD patients at the lowest MeDi adherence tertile, those at the middle tertile had lower mortality risk (0.65; 0.38 to 1.09; 1.33 years' longer survival), whereas subjects at the highest tertile had an even lower risk (0.27; 0.10 to 0.69; 3.91 years' longer survival; p for trend = 0.003). CONCLUSION: Adherence to the Mediterranean diet (MeDi) may affect not only risk for Alzheimer disease (AD) but also subsequent disease course: Higher adherence to the MeDi is associated with lower mortality in AD. The gradual reduction in mortality risk for higher MeDi adherence tertiles suggests a possible dose-response effect

Selective Decline in Memory Function among Healthy Elderly

Objective: To use longitudinally acquired data to establish whether aging is associated with memory decline. Background: Memory loss is one of the most frequent complaints among the elderly. Nevertheless, age-related memory decline remains controversial in large part because it has been established with cross-sectional studies. Methods: A total of 212 community-based healthy people were followed prospectively and evaluated annually with a neuropsychological battery testing memory and other cognitive domains. To control for the learning effect—the improvement in test performance associated with repeated exposure—longitudinal performance was compared between two age groups. Results: The older age group displayed a relative decline in memory performance with time. In contrast to memory, a relative age-related decline was not observed in tests of language, visuospatial ability, and abstract reasoning. Furthermore, within the memory domain, age-related decline was restricted to a specific aspect of memory, manifesting only in a measure sensitive to the acquisition and early retrieval of new information, and not in a measure of memory retention. This profile of age-related cognitive decline anatomically localizes to the hippocampal formation. Conclusion: This study establishes age-related memory decline using longitudinal data, and shows that this decline does not occur diffusely across multiple cognitive domains. Both early AD as well as non-AD processes likely contribute to age-related memory decline, and continued follow-up may reveal distinguishing features between these two

Gray-Matter Degeneration in Presenile Alzheimer's Disease

Previous comparisons between presenile Alzheimer's disease (AD) and senile dementia of the Alzheimer type (SDAT) did not control for disease severity and duration. In the current study, 18 patients with each diagnosis were matched for disease duration, cognitive dysfunction, and behavioral symptoms (using the modified Mini-Mental Status [mMMS] examination and the Blessed Dementia Rating Scale [BDRS]). Regional cerebral blood flow (rCBF) was quantified by the 133xenon inhalation technique, and several indices of tissue perfusion were examined. The two variables of primary interest were relative gray-matter weight and a gray-matter perfusion index, the initial slope index. Presenile onset was associated with loss of gray-matter relative weight (35% in presenile patients versus 39% in senile patients and healthy control subjects, p = 0.006), with neither perfusion nor disease severity differences between the two dementia samples. This loss of gray matter was significantly related to both severity and duration of disease in the patients with presenile AD, but not in patients with SDAT. These findings lend support to previous suggestions of greater degenerative process in presenile AD and confirm the need to examine and control age of onset in future investigations of AD. Further, correlation analysis suggests greater proportion of common variance among clinical and physiological indices in presenile AD

Mediterranean Diet and Risk for Alzheimer's Disease

OBJECTIVE: Previous research in Alzheimer's disease (AD) has focused on individual dietary components. There is converging evidence that composite dietary patterns such as the Mediterranean diet (MeDi) is related to lower risk for cardiovascular disease, several forms of cancer, and overall mortality. We sought to investigate the association between MeDi and risk for AD. METHODS: A total of 2,258 community-based nondemented individuals in New York were prospectively evaluated every 1.5 years. Adherence to the MeDi (zero- to nine-point scale with higher scores indicating higher adherence) was the main predictor in models that were adjusted for cohort, age, sex, ethnicity, education, apolipoprotein E genotype, caloric intake, smoking, medical comorbidity index, and body mass index. RESULTS: There were 262 incident AD cases during the course of 4 (+/-3.0; range, 0.2-13.9) years of follow-up. Higher adherence to the MeDi was associated with lower risk for AD (hazard ratio, 0.91; 95% confidence interval, 0.83-0.98; p = 0.015). Compared with subjects in the lowest MeDi tertile, subjects in the middle MeDi tertile had a hazard ratio of 0.85 (95% confidence interval, 0.63-1.16) and those at the highest tertile had a hazard ratio of 0.60 (95% confidence interval, 0.42-0.87) for AD (p for trend = 0.007). INTERPRETATION: We conclude that higher adherence to the MeDi is associated with a reduction in risk for AD. Ann Neurol 2006

SPICES II. Optical and Near-Infrared Identifications of Faint X-Ray Sources from Deep Chandra Observations of Lynx

We present our first results on field X-ray sources detected in a deep, 184.7 ks observation with the ACIS-I camera on Chandra. The observations target the Lynx field of SPICES, and contains three known X-ray-emitting clusters out to z=1.27. Not including the known clusters, in the 17'x17' ACIS-I field we detect 132 sources in the 0.5-2 keV (soft) X-ray band down to a limiting flux of \~1.7e-16 erg/cm2/s and 111 sources in the 2-10 keV (hard) X-ray band down to a limiting flux of ~1.3e-15 erg/cm2/s. The combined catalog contains a total of 153 sources, of which 42 are detected only in the soft band and 21 are detected only in the hard band. Confirming previous Chandra results, we find that the fainter sources have harder X-ray spectra, providing a consistent solution to the long-standing `spectral paradox'. From deep optical and near-infrared follow-up data, 77% of the X-ray sources have optical counterparts to I=24 and 71% of the X-ray sources have near-infrared counterparts to K=20. Four of the 24 sources in the near-IR field are associated with extremely red objects (EROs; I-K>4). We have obtained spectroscopic redshifts with the Keck telescopes of 18 of the Lynx Chandra sources. These sources comprise a mix of broad-lined active galaxies, apparently normal galaxies, and two late-type Galactic dwarfs. Intriguingly, one Galactic source is identified with an M7 dwarf exhibiting non-transient, hard X-ray emission. We review non-AGN mechanisms to produce X-ray emission and discuss properties of the Lynx Chandra sample in relation to other samples of X-ray and non-X-ray sources.Comment: 42 pages, 16 figures. Accepted for publication in the May 2002 Astronomical Journa

Differential Regional Dysfunction of the Hippocampal Formation among Elderly with Memory Decline and Alzheimer's Disease

The hippocampal formation is composed of separate anatomical regions interconnected to form a circuit, and investigating abnormal hippocampal function is most revealing at the level of these regions. Until recently, regional analysis of the hippocampal formation could be performed only in animals or in human postmortem tissue. Here, we report a method using functional magnetic resonance imaging that evaluates the hippocampal regions in vivo, and we use this method to study elderly with normal memory, with isolated memory decline, and with probable Alzheimer's disease (AD). Although age-related memory decline occurs commonly, the cause of this decline remains unknown, with disagreement as to whether this decline represents one or more etiologies. Analysis revealed two distinct patterns of regional dysfunction among elderly with isolated memory decline--one pattern similar to that found in elders with AD, involving all hippocampal regions, and a second pattern with dysfunction restricted to only one hippocampal region, the subiculum. These results offer direct evidence of hippocampal dysfunction associated with memory decline in the elderly, and implicate both predementia AD and non-AD processes as possible underlying cause

Primary Care Expenditures before the Onset of Alzheimer's Disease

Objective: To investigate primary care expenditures in the period before diagnosis of AD. Methods: In a population-based sample of Medicare enrollees in New York City, person-level 1996 Medicare claims, summed over primary care encounters, were examined for people who developed AD in 1997 to 1998 and those who did not. Results: People who developed AD were more likely to use Medicare outpatient and ambulatory care 1 to 2 years before diagnosis. Compared with respondents who did not develop AD, the excess cost for men was $1,167 (85$239 (26% higher). Among elderly people ≥75 years in the United States, the prodromal period of AD was associated with an excess Medicare-based primary care cost of $128.5 to$194.7 million. Conclusion: In addition to huge costs associated with AD after diagnosis, prediagnosis costs are an unrecognized source of expenditures related to the disease

Transition-Transversion Bias Is Not Universal: A Counter Example from Grasshopper Pseudogenes

Comparisons of the DNA sequences of metazoa show an excess of transitional over transversional substitutions. Part of this bias is due to the relatively high rate of mutation of methylated cytosines to thymine. Postmutation processes also introduce a bias, particularly selection for codon-usage bias in coding regions. It is generally assumed, however, that there is a universal bias in favour of transitions over transversions, possibly as a result of the underlying chemistry of mutation. Surprisingly, this underlying trend has been evaluated only in two types of metazoan, namely Drosophila and the Mammalia. Here, we investigate a third group, and find no such bias. We characterize the point substitution spectrum in Podisma pedestris, a grasshopper species with a very large genome. The accumulation of mutations was surveyed in two pseudogene families, nuclear mitochondrial and ribosomal DNA sequences. The cytosine-guanine (CpG) dinucleotides exhibit the high transition frequencies expected of methylated sites. The transition rate at other cytosine residues is significantly lower. After accounting for this methylation effect, there is no significant difference between transition and transversion rates. These results contrast with reports from other taxa and lead us to reject the hypothesis of a universal transition/transversion bias. Instead we suggest fundamental interspecific differences in point substitution processes