No abstract

The magnesium-to-calcium (Mg/Ca) ratio of coral skeletons from Ishigaki Island, Ryukyu Islands, Japan, closely tracked sea surface temperature (SST) over an 8-year period. Measurements were made with the fast technique of inductively coupled plasma-atomic emission spectrometry. The variation of the coral Mg/Ca ratio with SST change is about four times that of the current, widely used coral strontium-to-calcium ratio. The temporal and geographic variation of the seawater Mg2+/Ca2+ ratio probably has little influence on coral Mg/Ca variation. Results indicate that the coral Mg/Ca ratio has the potential to provide fast, precise, high-resolution proxies for past tropical SSTs.

MRI studies using the manual tracing method have shown a smaller-than-normal hippocampal volume in patients with posttraumatic stress disorder (PTSD). However, these studies have yielded inconsistent results, and brain structures other than the hippocampus have not been well investigated. A recently developed, fully automated method called voxel-based morphometry enables an exploration of structural changes throughout the brain by applying statistical parametric mapping to high-resolution MRI. Here we first used this technology in patients with PTSD. Participants were 9 victims of the Tokyo subway sarin attack with PTSD and 16 matched victims of the same traumatic event without PTSD. The voxel-based morphometry showed a significant gray-matter volume reduction in the left anterior cingulate cortex (ACC) in trauma survivors with PTSD compared with those without PTSD. The severity of the disorder was negatively correlated with the gray-matter volume of the left ACC in PTSD subjects. There were no significant differences in other gray-matter regions or any of the white-matter regions between two groups. The present study demonstrates evidence for structural abnormalities of ACC in patients with PTSD. Together with previous functional neuroimaging studies showing a dysfunction of this region, the present findings provide further support for the important role of ACC, which is pivotally involved in attention, emotional regulation, and conditioned fear, in the pathology of PTSD.F indings from neuroimaging studies of patients with posttraumatic stress disorder (PTSD) have suggested that some brain pathology plays an important role in the disorder (1, 2). Six structural MRI studies have shown that combat-related or childhood physically and͞or sexually abused subjects with PTSD have a smaller-than-normal hippocampal volume (3-8). However, almost the same number of studies failed to show reduced hippocampal volume in chronically maltreated children (9-11), survivors of acute traumatic events (12), nonalcoholic combat veterans (13), and alcoholic patients (14) with PTSD. In contrast, brain structures other than the hippocampus have received less attention, although a few studies have reported whole-brain volume reduction (9), reduced total white-matter volume (7), smaller corpus callosum (9), larger superior temporal gyrus gray-matter volume (15), and attenuation of frontal lobe asymmetry (11). Therefore, it is unclear whether structural abnormality in brain structures other than the hippocampus exists in patients with PTSD.In contrast to the emphasis on the hippocampus in previous structural MRI studies, symptom-provocation and cognitiveactivation studies using functional neuroimaging have revealed greater activation of the amygdala, anterior paralimbic structures, Broca's region, and other neocortical regions and a failure of activation of anterior cingulate cortex (ACC) in response to trauma-related stimuli in individuals with PTSD (1, 2, 16). Furthermore, one study (17) showed a reduced N-acetylaspartate͞creatine ratio...

No abstract

Identifying both the commonalities and differences in brain structures among psychiatric disorders is important for understanding the pathophysiology. Recently, the ENIGMA-Schizophrenia DTI Working Group performed a large-scale meta-analysis and reported widespread white matter microstructural alterations in schizophrenia; however, no similar crossdisorder study has been carried out to date. Here, we conducted mega-analyses comparing white matter microstructural differences between healthy comparison subjects (HCS; N = 1506) and patients with schizophrenia (N = 696), bipolar disorder (N = 211), autism spectrum disorder (N = 126), or major depressive disorder (N = 398; total N = 2937 from 12 sites). In comparison with HCS, we found that schizophrenia, bipolar disorder, and autism spectrum disorder share similar white matter microstructural differences in the body of the corpus callosum; schizophrenia and bipolar disorder featured comparable changes in the limbic system, such as the fornix and cingulum. By comparison, alterations in tracts connecting neocortical areas, such as the uncinate fasciculus, were observed only in schizophrenia. No significant difference was found in major depressive disorder. In a direct comparison between schizophrenia and bipolar disorder, there were no significant differences. Significant differences between schizophrenia/bipolar disorder and major depressive disorder were found in the limbic system, which were similar to the differences in schizophrenia and bipolar disorder relative to HCS. While schizophrenia and bipolar disorder may have similar pathological characteristics, the biological characteristics of major depressive disorder may be close to those of HCS. Our findings provide insights into nosology and encourage further investigations of shared and unique pathophysiology of psychiatric disorders.

No abstract

Daily precipitation samples for stable isotope analysis were collected throughout 2003 at Dome Fuji Station, inland East Antarctica. Stable isotopes show significantly depleted values with a large seasonal variability, which have never been obtained. Temporal changes in δ‐T relation and d‐excess are consistent with those found in geographical distribution. Precipitation was obtained almost everyday, though the amounts were quite small (27.6 mm water equivalent (w.e.) annual total and 0.08 mm w.e. daily average). Half of the annual precipitation was accumulated by only 11 events (18 days) without seasonality. Since the precipitation events occurred under warmer circumstances, the precipitation‐weighted temperature, which should be related directly to the isotopes, was significantly warmer than the mean annual surface temperature, which has usually been adopted as isotopic thermometer. This study provides significant information to understand present‐day seasonality of precipitation and its isotopic composition in inland Antarctica.

An FA value of about 0.20 was found to be the optimal trackability threshold.