The channels mediating most of the somatodendritic A-type K super(+) current in neurons are thought to be ternary complexes of Kv4 pore-forming subunits and two types of auxiliary subunits, the K ...super(+) channel interacting proteins (KChIPs) and dipeptidyl-peptidase-like (DPPL) proteins. The channels expressed in heterologous expression systems by mixtures of Kv4.2, KChIP1 and DPP6-S resemble in many properties the A-type current in hippocampal CA1 pyramidal neurons and cerebellar granule cells, neurons with prominent A-type K super(+) currents. However, the native currents have faster kinetics. Moreover, the A-type currents in neurons in intermediary layers of the superior colliculus have even faster inactivating rates. We have characterized a new DPP6 spliced isoform, DPP6-E, that produces in heterologous cells ternary Kv4 channels with very fast kinetics. DPP6-E is selectively expressed in a few neuronal populations in brain including cerebellar granule neurons, hippocampal pyramidal cells and neurons in intermediary layers of the superior colliculus. The effects of DPP6-E explain past discrepancies between reconstituted and native Kv4 channels in some neurons, and contributes to the diversity of A-type K super(+) currents in neurons.
Geochemical analyses of various components (foraminifera, coccoliths and siliciclastic fractions) of limestone and marl samples from the marine Trubi Formation (Early Pliocene) of southern Italy ...revealed subtle diagenetic contamination. The coccolith fraction is altered from its original value both in its trace element (Sr/Ca, Mg/Ca, Fe/Ca, Mn/Ca, Na/Ca all were higher) and isotopic (
87
Sr
/
86
Sr
,
δ
18
O
,
δ
13C) composition. Coccolith
87
Sr
/
86
Sr
values (limestones 0.709010; marls 0.708951) are lower than those of coeval Early Pliocene seawater (0.709025–60 Farrell, J.W., Clemens, S.C., Gromet, L.P., 1995. Improved chronostratigraphic reference curve of Late Neogene seawater
87
Sr
/
86
Sr
. Geology 23, 403–406) and similar to the
87
Sr
/
86
Sr
values of Messinian evaporites (0.70887 to 0.70896 Müller, D.W., Mueller, P.A., 1991. Origin and age of the Mediterranean Messinian evaporites: implications from Sr isotopes. Earth Planet. Sci. Lett. 107, 1-12). Foraminiferal calcite is unaltered and retains its elemental and isotopic composition, with
87
Sr
/
86
Sr
values (0.709052) within the range for Early Pliocene seawater. However, unaltered
87
Sr
/
86
Sr
values were obtained only when the foraminifera were cleaned in acid to remove all contaminating coccoliths. Simple hand-picking and ultrasonic cleaning in water is inadequate to remove adhering coccoliths and may result in erroneous
87
Sr
/
86
Sr
values being quoted.
Intrusion-related gold deposits at the Clear Creek, Scheelite Dome and Dublin Gulch properties of the Tombstone Gold Belt (TGB), Yukon Territory have dominantly E-striking, steeply dipping, ...auriferous quartz extension veins within intrusions. In adjacent metasedimentary rocks gold is hosted in subvertical NW- to NNW-striking sinistral faults as veins and breccias, in E-striking extension veins and locally in E- to ENE-striking fault veins. These structural relationships indicate low magnitude, broadly E–W-directed shortening and N–S extension during stock emplacement and gold mineralisation at ∼92 Ma.
The lack of any deviation or deflection of the extension vein orientations in the country rocks, with respect to their orientation within the stocks, indicates consistent stress trajectories in both rock types. These TGB deposits formed at 5–8 km depth, where mean and differential stresses may be greater in magnitude than in shallower porphyry environments. Many porphyry systems feature magmatic-related stresses that dominated the local stress field, with more variable vein orientations the result. Conversely, orogenic gold systems usually exhibit strong dimensionality in vein orientations. Fault-hosted mineralisation in metasedimentary rocks of the TGB deposits in this study is comparable in geometry, but generally smaller in size than in many orogenic gold systems. Intrusion-related systems of the TGB exhibit intermediate structural styles of mineralisation that provide a useful bridge in understanding the diversity of mechanically controlled structural styles in otherwise mostly unrelated gold deposit types.
Integration of foraminiferal biostratigraphy,
87
Sr/
86
Sr isotope stratigraphy, and traditional physical stratigraphy has provided a refined age control of a poorly known Oligocene-to-Pleistocene ...sedimentary sequence nonconformably covering the crystalline basement complex of the Calabrian microplate, a continental block which rifted off the southern margin of the European plate during Neogene time. In spite of the fossil-poor content of the sequence, the simultaneous use of paleontological and geochemical techniques have resulted in the following conclusions. 1) The age of an unnamed, thin calcarenite unit locally present at the base of the sequence, previously considered Rupelian to early Aquitanian in age, has been refined to Chattian (27.8–24.8 Ma). This calcarenite was considered a basal, conformable member of the overlying Stilo-Capo d'Orlando Formation. However, this study indicates that it is separated from the Stilo-Capo d'Orlando Formation either by an angular unconformity or by a disconformity representing a significant time interval. 2) The Stilo-Capo d'Orlando Formation has a latest Chattian–earliest Aquitanian to Burdigalian age. Previously published reports suggested deposition over a much longer time span, ranging from late Rupelian to Langhian. 3) An unnamed deep-marine siliciclastic unit mostly composed of conglomerate and sandstone and previously considered Tortonian in age is, in fact, Serravallian to Tortonian. 4) The depositional interval of the “trubi,” fine-grained marine deposits, has been independently confirmed to span the Pliocene-Pleistocene.
The results of this study provide a framework for future sequence–stratigraphic and paleotectonic studies in the area, and prove the effectiveness of an integrated paleontological and geochemical (
87
Sr/
86
Sr) approach in the study of fossil-poor sedimentary sequences.
Integration of foraminiferal biostratigraphy, 87Sr/86Sr isotope stratigraphy, and traditional physical stratigraphy has provided a refined age control of a poorly known Oligocene-to-Pleistocene ...sedimentary sequence nonconformably covering the crystalline basement complex of the Calabrian microplate, a continental block which rifted off the southern margin of the European plate during Neogene time. In spite of the fossil-poor content of the sequence, the simultaneous use of paleontological and geochemical techniques have resulted in the following conclusions. 1) The age of an unnamed, thin calcarenite unit locally present at the base of the sequence, previously considered Rupelian to early Aquitanian in age, has been refined to Chattian (27.8–24.8 Ma). This calcarenite was considered a basal, conformable member of the overlying Stilo-Capo d'Orlando Formation. However, this study indicates that it is separated from the Stilo-Capo d'Orlando Formation either by an angular unconformity or by a disconformity representing a significant time interval. 2) The Stilo-Capo d'Orlando Formation has a latest Chattian–earliest Aquitanian to Burdigalian age. Previously published reports suggested deposition over a much longer time span, ranging from late Rupelian to Langhian. 3) An unnamed deep-marine siliciclastic unit mostly composed of conglomerate and sandstone and previously considered Tortonian in age is, in fact, Serravallian to Tortonian. 4) The depositional interval of the “trubi,” fine-grained marine deposits, has been independently confirmed to span the Pliocene-Pleistocene. The results of this study provide a framework for future sequence–stratigraphic and paleotectonic studies in the area, and prove the effectiveness of an integrated paleontological and geochemical (87Sr/86Sr) approach in the study of fossil-poor sedimentary sequences.
Tortaguttus stiloensis, a new species of benthic unilocular foraminifera of the suborder Lagenina, is described from Middle Pleistocene marine sediments of Calabria, Italy. This species is ...characterized by radiating elevated costae on the surface of a double marginal carinae connected by numerous cross-struts. Previously known occurrences of Tortaguttus are restricted to the Pacific rim. However, the occurrence of Tortaguttus stiloensis in the Mediteranean region indicates that this genus is cosmopolitan in neritic-depth waters. The widespread distribution of species referable to Tortaguttus so soon after its appearance in the Quaternary indicates either a highly efficient dispersal mechanism or that the genus has a much longer and yet unrecorded fossil record.
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