Thermokarst lakes as a source of atmospheric CH4 during the last deglaciation

Polar ice-core records suggest that an arctic or boreal source was responsible for more than 30% of the large increase in global atmospheric methane (CH4) concentration during deglacial climate warming; however, specific sources of that CH4 are still debated. Here we present an estimate of past CH4 flux during deglaciation from bubbling from thermokarst (thaw) lakes. Based on high rates of CH4 bubbling from contemporary arctic thermokarst lakes, high CH4 production potentials of organic matter from Pleistocene-aged frozen sediments, and estimates of the changing extent of these deposits as thermokarst lakes developed during deglaciation, we find that CH4 bubbling from newly forming thermokarst lakes comprised 33 to 87% of the high-latitude increase in atmospheric methane concentration and, in turn, contributed to the climate warming at the Pleistocene-Holocene transition.     

Magnesium interaction with the surface of calcite in seawater

Magnesian calcite overgrowth containing 4 (+/- 2) mole percent magnesium carbonate forms on calcite exposed to natural seawater near the ocean surface. This magnesian calcite is approximately 30 percent less soluble in seawater than pure calcite. The formation of the magnesian calcite of reduced solubility may have a major influence on calcite accumulation in deep sea sediments.     

Brain dopamine and serotonin receptor sites revealed by digital subtraction autoradiography

Autoradiography combined with image analysis permitted quantitative visualization of dopamine (D2) and serotonin (S2) binding sites in rat brain. Forebrain sections were incubated with tritiated spiroperidol alone or with tritiated spiroperidol plus unlabeled compounds that saturated the D2 or S2 sites. By subtracting the digitized image of an autoradiograph derived from the latter sections from that of the former, the D2 or S2 sites were specifically revealed. The resulting quantitative images demonstrate the differing anatomical distributions of these sites. The D2 site is largely restricted to the striatal complex (caudate-putamen, nucleus accumbens septi, and olfactory tubercle), whereas the S2 site is enriched in layer 5 of motor cortex, the perirhinal and cingulate cortices, and the claustrum.     

8-Arginine]-vasopressinoic acid: an inhibitor of rabbit kidney adenyl cyclase

Neurohypophyseal hormnones and several synthetic analogs stimulate adenyl cyclase prepared from rabbit kidney medullary tissue. [8-Arginine]-vasopressinoic acid inhibits the stimulation of medullary adenyl cyclase by neurohypophyseal peptides but does not influence the action of parathyroid hormone on adenyl cyclase from kidiney cortex.     

Deep mantle cycling of oceanic crust: evidence from diamonds and their mineral inclusions

A primary consequence of plate tectonics is that basaltic oceanic crust subducts with lithospheric slabs into the mantle. Seismological studies extend this process to the lower mantle, and geochemical observations indicate return of oceanic crust to the upper mantle in plumes. There has been no direct petrologic evidence, however, of the return of subducted oceanic crustal components from the lower mantle. We analyzed superdeep diamonds from Juina-5 kimberlite, Brazil, which host inclusions with compositions comprising the entire phase assemblage expected to crystallize from basalt under lower-mantle conditions. The inclusion mineralogies require exhumation from the lower to upper mantle. Because the diamond hosts have carbon isotope signatures consistent with surface-derived carbon, we conclude that the deep carbon cycle extends into the lower mantle.     

Stress control of deep rift intrusion at Mauna Loa volcano, Hawaii

Mauna Loa volcano, Hawaii, deforms by a combination of shallow dike intrusions in the rift zones and earthquakes along the base of the volcano, but it is not known how the spreading is accommodated in the lower part of the volcanic edifice. We present evidence from interferometric synthetic aperture radar data for secular inflation of a dike-like magma body at intermediate depth in the southwest rift zone during 2002 to 2005. Magma accumulation occurred in a section of the rift zone that was unclamped by previous dikes and earthquakes, suggesting that stress transfer plays an important role in controlling subsurface magma accumulation.     

Plasma Corticosteroids: Changes in Concentration after Stimulation of Hippocampus and Amygdala

Plasma 17-OH corticosteroid levels were determined before stimulation and at various intervals after stimulation in these limbic sites in patients in whom implanted electrodes had been placed during evaluation for surgical treatment of psychomotor epilepsy. Stimulation of the amygdala was followed by an elevation of plasma 17-hydroxycorticosteroids. Hippocampal stimulation resulted in a decreased corticosteroid level, followed in two instances by a secondary elevation.