bluuebunny/crossref_metadata_2025 huggingface dataset:
Identification of CD46 Binding Sites within the Adenovirus Serotype 35 Fiber Knob
Authors: Wang Hongjie , Liaw Yen-Chywan , Stone Daniel , Kalyuzhniy Oleksandr , Amiraslanov Imameddin , Tuve Sebastian , Verlinde Christophe L. M. J. , Shayakhmetov Dmitry , Stehle Thilo , Roffler Steve , Lieber André
Published: September 2007

Species B human adenoviruses (Ads) are often associated with fatal illnesses in immunocompromised individuals. Recently, species B Ads, most of which use the ubiquitously expressed complement regulatory protein CD46 as a primary attachment receptor, have gained interest for use as gene therapy vectors. In this study, we focused on species B Ad serotype 35 (Ad35), whose trimeric fiber knob domain binds to three CD46 molecules with a

K
D

(equilibrium dissociation constant) of 15.5 nM. To study the Ad35 knob-CD46 interaction, we generated an expression library of Ad35 knobs with random mutations and screened it for CD46 binding. We identified four critical residues (Phe242, Arg279, Ser282, and Glu302) which, when mutated, ablated Ad35 knob binding to CD46 without affecting knob trimerization. The functional importance of the identified residues was validated in surface plasmon resonance and competition binding studies. To model the Ad35 knob-CD46 interaction, we resolved the Ad35 knob structure at 2-Å resolution by X-ray crystallography and overlaid it onto the existing structure for Ad11-CD46 interaction. According to our model, all identified Ad35 residues are in regions that interact with CD46, whereby one CD46 molecule binds between two knob monomers. This mode of interaction might have potential consequences for CD46 signaling and intracellular trafficking of Ad35. Our findings are also fundamental for better characterization of species B Ads and design of antiviral drugs, as well as for application of species B Ads as in vivo and in vitro gene transfer vectors.
Characterization of a waaF mutant of Helicobacter pylori strain 26695 provides evidence that an extended lipopolysaccharide structure has a limited role in the invasion of gastric cancer cells
Authors: Chandan Vandana , Logan Susan M. , Harrison Blair A. , Vinogradov Evgenii , Aubry Annie , Stupak Jacek , Li Jianjun , Altman Eleonora
Published: September 2007

An ld-heptosyltransferase gene, HP1191 (waaF), involved in biosynthesis of the inner-core region of Helicobacter pylori strain 26695 lipopolysaccharide (LPS), has been cloned and its function established by complementation of Salmonella enterica serovar Typhimurium waaF mutant strain, strain 3789. Insertional inactivation of the HP1191 open reading frame in strain 26695 resulted in the formation of a deeply truncated LPS molecule, as observed using SDS–PAGE. Subsequent compositional and fatty acid analyses, followed by capillary electrophoresis – mass spectrometry and nuclear magnetic resonance studies established its structure as the following: PE→7)-l-α-d-Hepp-(1→5)-α-Kdop-(2→6)-Lipid A, where PE represents a phosphoethanolamine group, ld-Hep represents l-glycero-d-manno-heptose, and Kdo represents 3-deoxy-d-manno-oct-2-ulosonic acid. This structural analysis identifies the activity of HP1191 as a heptosyltransferase and a waaF homolog. In vitro invasion assays using human cultured gastric adenocarcinoma cells as a host cell model confirmed that the level of invasion was unaffected for an H. pylori HP1191::Kan deep-rough mutant strain compared with the wild-type strain 26695 expressing the O-chain polysaccharide, providing evidence that LPS is not a critical factor for invasion.
Expression of the selectable marker gene bsrm in BALB/MK cells induces apoptosis by overproduction of hydrogen peroxide
Authors: Takeshita Daniela , Bento Fernanda Mara , Chammas Roger , Belizário José Ernesto , Carmona Adriana Karaoglanovic , Konno Katsuhiro , Lopes de Melo Robson , Molina Gustavo , Lisboa Bianca Cristina Garcia , Han Sang Won
Published: September 2007

Transduction of the retroviral vector LBmSN, which expresses the blasticidin S resistance gene bsrm in the murine keratinocyte cell line BALB/MK, induces death in these cells. Cell death is caused by a factor called DOKEB (death factor obtained from keratinocytes expressing bsrm), which is released before the cells' death. In this report we describe and discuss the purification and characterization of DOKEB. Our results were as follows. (i) The 5-day-old medium from the modified BALB/MK cells with LBmSN was used for purification and characterization by filtration and chromatography: DOKEB was a stable and highly hydrophilic compound, with a molecular mass less than that of 1 amino acid. (ii) The conditioned medium containing DOKEB was reactive against thiobarbituric acid and dichlorofluorescein diacetate. (iii) DOKEB activity was neutralized by the incubation of the conditioned medium with catalase. Therefore, our conclusion is that the BALB/MK cells expressing bsrm produce a large amount of hydrogen peroxide, which catalyzes the process of apoptosis of those cells.
Reversal of P-glycoprotein-mediated multidrug resistance by cholesterol derived from low density lipoprotein in a vinblastine-resistant human lymphoblastic leukemia cell line
Authors: Shu Yu , Liu Hu
Published: September 2007

P-glycoprotein (P-gp) is believed to be one of the most common causes of multidrug resistance (MDR) in chemotherapy. Studies have shown that the biosynthesis of cholesterol and cholesterol esters interfere with the function of P-gp. Since low density lipoprotein (LDL) carries a large amount of cholesterol, we investigated the effect of cholesterol derived from LDL on a line of human lymphoblastic leukemia MDR cells, CEM/VLB. Our results demonstrated that, in addition to increased cytotoxicity, the uptake of vinblastine in CEM/VLB cells increased, and LDL subsequently increased the intracellular vinblastine concentrations retained by CEM/VLB cells. The cholesterol levels in the membrane of the MDR cells were restored, while LDL significantly decreased the P-gp-associated ATPase activity. Current studies have shown that LDL leads to the resensitization of CEM/VLB cells to cytotoxic agents, likely through the restoration of cholesterol and reduction of P-gp-associated ATPase in the cell membrane.
Comparative evaluation of atenolol and metoprolol on cardiovascular complications associated with streptozotocin-induced diabetic rats
Authors: Bhadada Shraddha V. , Goyal Ramesh K.
Published: September 2007

Recently, various clinical studies have indicated that lipophilic β-blockers reduce the coronary mortality in diabetic patients; however, systematic studies have not been reported. The objective of the present investigation was to compare the effects of chronic treatment with metoprolol and atenolol on cardiovascular complications in streptozotocin (STZ)-induced diabetic rats. Injection of STZ produced hyperglycemia, hypoinsulinemia, hyperlipidemia, increased blood pressure, cardiac hypertrophy, reduction in heart rate, and structural alterations in cardiac tissues. Metoprolol and atenolol effectively prevented the development of hypertension in diabetic rats. Metoprolol treatment produced a slight but significant reduction in serum glucose levels with elevation in serum insulin levels, while atenolol produced a slight increase in glucose levels but no effect on insulin levels. Moreover, neither metoprolol nor atenolol treatment reduced the elevated cholesterol levels in diabetic rats. Metoprolol treatment significantly prevented STZ-induced increase in triglyceride levels, but atenolol failed to produce this effect. Metoprolol exhibited a minimal improvement in STZ-induced bradycardia, whereas atenolol produced a further reduction in heart rate. Histological examination showed metoprolol treatment also prevented STZ-induced hypertrophy and some of the alterations in cardiomyocytes. In conclusion, our data suggest that metoprolol has some beneficial effects over atenolol with respect to cardiovascular complications associated with diabetes mellitus.
Effects of chronic coffee consumption on glucose kinetics in the conscious rat
Authors: Shearer J. , Sellars E.A. , Farah A. , Graham T.E. , Wasserman D.H.
Published: September 2007

Epidemiological studies indicate that regular coffee consumption reduces the risk of developing type 2 diabetes. Despite these findings, the biological mechanisms by which coffee consumption exerts these effects are unknown. The aim of this study was twofold: to develop a rat model that would further delineate the effects of regular coffee consumption on glucose kinetics, and to determine whether coffee, with or without caffeine, alters the actions of insulin on glucose kinetics in vivo. Male Sprague–Dawley rats were fed a high-fat diet for 4 weeks in combination with one of the following: (i) drinking water as placebo (PL), (ii) decaffeinated coffee (2 g/100 mL) (DC), or (iii) alkaloid caffeine (20 mg/100 mL) added to decaffeinated coffee (2 g/100 mL) (CAF). Catheters were chronically implanted in a carotid artery and jugular vein for sampling and infusions, respectively. Recovered animals (5 days postoperative) were fasted for 5 h before hyperinsulinemic-euglycemic clamps (2 mU·kg–1·min–1). Glucose was clamped at 6 mmol/L and isotopes (2-deoxy-[14C]glucose and [3-3H]glucose) were administered to obtain indices of whole-body and tissue-specific glucose kinetics. Glucose infusion rates and measures of whole-body metabolic clearance were greater in DC than in PL or CAF, indicating increased whole-body insulin sensitivity. As the only difference between DC and CAF was the addition of alkaloid caffeine, it can be concluded that caffeine antagonizes the beneficial effects of DC. Given these findings, decaffeinated coffee may represent a nutritional means of combating insulin resistance.
Kappa opioids modulate the arterial baroreflex control of heart rate in conscious young sheep
Authors: Qi Wei , Smith Francine G.
Published: September 2007

The present study tested the hypothesis that κ-opioids modulate the arterial baroreflex control of heart rate in conscious young sheep. Various parameters governing the arterial baroreflex control of heart rate were assessed before and after activation of κ-opiate receptors (KOR) by i.v. administration of the specific KOR agonist U-50488H (experiment 1) or vehicle (experiment 2) to conscious, chronically instrumented lambs aged 42 ± 2 days (n = 6). The 2 experiments were administered in random order at minimum intervals of 48 h. Thirty min after U-50488H treatment, there was an increase in diastolic and mean arterial pressure and in heart rate, returning to control levels by 90 min. A significant increase in the arterial pressure at the midpoint of the baroreflex range and in the minimum heart rate as well as a significant decrease in the heart rate range over which the arterial baroreflex operates were also seen at 30 min after U-50488H, gradually returning to control levels over 120 min. Vehicle had no effect on any of the parameters governing the arterial baroreflex control of heart rate. These data provide the first direct evidence that under physiological conditions in young lambs, the arterial baroreflex control of heart rate is altered after administration of the specific KOR agonist U-50488H, revealing a previously unidentified role for this opioid receptor.
INTEGRATED INNOVATION BETWEEN TECHNOLOGY AND ORGANIZATION
Authors: GUAN JIANCHENG , LIU JIANYAN
Published: September 2007

A framework for technological and organizational capability audits is proposed, and the relevance of integrating technology and organization and product competitiveness of Chinese firms is then examined. Empirical data were acquired through a recent study of innovative firms from Beijing, China. An organization-technology map and statistical analyses are used to verify five hypotheses in order to identify the relationship amongst product competitiveness and integration of technology and organization. The results effectively verify the positive relationship among technological innovation, organizational innovation and product competitiveness. The findings also reveal that integrated innovation between technology and organization is critical for the improvement of product competitiveness of Chinese firms.
KNOWLEDGE FLOW FROM THE SCIENTIFIC SECTOR TO PRIVATE FIRMS: A REVIEW ON THE POLICY OF TECHNOLOGY TRANSFERS IN JAPAN
Authors: NAGATA AKIYA
Published: September 2007

This paper investigates the stylized facts for Japan's policy of cooperation between industry and the academic sector with experiential data. The results of the analysis make it apparent that the importance of intellectual property as a medium of knowledge flow is limited by nature in Japan. Furthermore, the results indicate that one future issue for the policy in Japan is to support the informal information exchange between industry and the academic sector and to convert "invisible" cooperation arising from such exchange into a more "visible" cooperation.
Uranium–thorium–lead age-determinations with respect to the phanerozoic time-scale
Authors: Darnley A. G.
Published: September 2007

Topics discussed in this short review are: the physical basis of the method, common lead ages, calculation of results, the significance of discordant results, and the selection of material for analysis. It is stressed that all aspects of the geology of an area, including its mineralogy and geochemistry, must be studied before age-determinations on material can be properly evaluated.
Potassium—argon methods with special reference to basic igneous rocks
Authors: Miller John Alfred , Fitch Frank John
Published: September 2007

The theory, analytical method, and experimental errors of potassium–argon radiometric age-determination are briefly reviewed. The choice of suitable material for analysis and the application of the method to basic igneous and other rocks using whole-rock samples are described. ‘Discrepancy’ in potassium-argon age-determination is defined; geological factors that control the accuracy of potassium-argon ages, and must be taken into consideration in their interpretation, are discussed. It is asserted that, in favourable circumstances, potassium-argon age studies can provide a wide variety of alternative information of geological significance as well as, or instead of, indicating the initial age of consolidation of a rock: in particular, that it is possible to define the dates of subsequent cleavage, metasomatism, or metamorphism from a consideration of the discrepantly low ages obtained from older rocks.
The Tertiary period
Authors: Funnell Brian Michael
Published: September 2007

A time-scale for the Tertiary period is suggested which is based on radiometric age-determinations published by March 1964. The principal boundaries are dated as follows:

Comparison with time-scales published previously (Holmes 1959; Evernden
et al.
1961; Kulp 1961) shows a number of differences in detail, but none of any magnitude. The date attributed to the Mio-Pliocene boundary is, however, rather younger than those given previously.
The Ordovician period
Authors: Whittington H. B. , Williams A.
Published: September 2007

Stratigraphical and palaeontological evidence for the location of the boundaries of the Ordovician System is examined and considered to be less important than historical priority, so that the Tremadoc is excluded from the system. Reasons are also given for reverting to the twofold subsystemic division advocated by Lapworth in which the base of the
Nema-graptus gracilis
Zone (or its correlatives) is taken as the lower limit of the Upper Ordovician. The only reliable radiometric age-determination is that of 445 m.y. for the early Upper Ordovician; an estimate of 500 m.y. for the base of the Ordovician appears reasonable.
Analytic Procedure and Results of an Isotope Geochemical Surface Survey in an Area of the British North Sea
Authors: Faber E. , Stahl W.
Published: September 2007

A sample preparation system for the determination of stable carbon isotope ratios in hydrocarbons, which are adsorbed in sediment samples, has been developed. The system consists of: (1) a degassing line, (2) a hydrocarbon separation and oxidation unit, and (3) an isotope mass spectrometer.

As little as 25 µl CH
4
desorbed from a sediment sample is sufficient to achieve an accuracy of ± 1 parts/10
18
for δ
13
C determinations. Typical methane yields are 20 µl CH
4
200 g
−1
sediment in the investigated area. Approximately 200 g sample material are routinely introduced into the degassing procedure. Natural degassing during or after sampling decreases the yields (i.e. the amount of hydrocarbons) at the samples. Laboratory experiments indicate that these effects can be minimized if the samples are rapidly degassed in a laboratory at the sampling site or quickly brought to low temperatures (≤ −80°C) immediately after sampling.

As an example of the application of the method, the results of a geochemical reconnaissance surface survey covering the area of the Forties Field in the North Sea are discussed. Some 24 sediment cores have been taken from an area of about 5500 km
2
. Sediment samples from the lowermost part of the cores (≤2 m long) have been degassed and the amounts of methane, the molecular composition of the hydrocarbons, and the
13
C/
12
C-isotope ratios of the methane have been determined. The geochemical data of the sediment gases, especially the δ
12
C
1
and the C
1
-yield data, favour that area for petroleum prospection, in which the large oil field is situated. The results indicate that methane migrates from deep source rocks to the surface and can be used as a guide to generating hydrocarbon source rocks and reservoirs.
Applications of Geochemistry to Sandstone Reservoir Studies
Authors: Irwin Hilary , Hurst Andrew
Published: September 2007

The mineralogy and chemical composition of reservoir sandstones can be easily and quickly determined. Our knowledge of the chemical and physical properties of each mineral (both detrital and authigenic) allows us to define environmental limits within which each mineral is stable. This information is useful in establishing the burial history of the reservoir sediments and in the anticipation of production problems.

Examples are discussed to illustrate how a detailed sequence of diagenetic events can be established from petrographic analysis of only a wide selection of core samples. The evolution of pore fluid with time and the source of pore fluid can be deduced using the geochemistry of the mineral assemblage. Carbonate cements can preserve evidence of diagenetic events which is obscured or removed from more porous and permeable parts of a sandstone sequence.

Stable isotope geochemistry can be used to establish the source of carbonate cement which is characterized by the carbon isotopes. In addition, the stable isotope composition of oxygen from carbonate and silicate cements details changes in pore fluid with time and can indicate the depth at which cement precipitation occurred. This information is invaluable in reconstructuring the burial history of a sandstone sequence.

Geochemistry, integrated with sedimentology should be applied to understanding cementation controls. This will allow models of the distribution of cement to be constructed and enable more accurate modelling of fluid movement in the reservoir. This should be especially useful in achieving better reservoir simulation and better prediction of the effects of stimulation and enhancement techniques.
Organofacies and Early Maturation Effects in Upper Jurassic Sediments From the Inner Moray Firth Basin, North Sea
Authors: Pearson M. J. , Watkins D.
Published: September 2007

A study of oil source rock characteristics and the degree of organic maturity has been carried out on a thick succession of Upper Jurassic sediments from the inner part of the Moray Firth Basin. The sequence, which attains a thickness of up to 1000 m, consists of organic-rich mudstones and silty shales with periodic intercalations of turbidite sands. Samples representative of finer grained lithologies covering a range of present burial depths from 800 to 2400 m were selected from four exploration wells, one each in Blocks 12/21 to 12/24, immediately northeast of the Beatrice Oil Field.

Kerogen preparations from all samples are dominated by amorphous algal sapropel, but contain appreciable coarsely particulate terrigenous material originating from vascular plants and probably introduced into the restricted marine basin of deposition by distal turbidity currents. This organofacies is highly rated as a potential oil source, but maturation levels are consistently low within the drilled wells. Independent maturation-specific parameters, including vitrinite reflectance, sporomorph colour, solvent extract and extractable hydrocarbon:organic carbon ratios and the carbon preference index of nC
21
-nC
33
alkanes indicate immature organic matter at depths above 2000 m. A pronounced increase in extract ratios below 2000 m indicates approach to the oil generation threshold at the base of the deepest section. Initially high CPI values in the uppermost samples (except where migrated oil is present in Block 12/23-1) decrease steadily with burial.

Significant amounts of steranes and triterpanes are present in the sediment extracts and have been identified by combined gas chromatography-mass spectrometry (GC/MS). A C
28
pentacyclic triterpane (17αH,18αH,21βH-28,30-bisnorhopane) was identified in unusual abundance. Isomerization occurs at one or more chiral centres in the steranes, rearranged steranes and hopane type pentacyclic triterpanes in response to increased burial and temperature (Mackenzie
et al.
1980). These changes have been assessed in terms of relative abundances of certain specific isomers and compared with abundances in other basinal sequences with known maturational trends. A consideration of all parameters places the onset of intense oil generation somewhat below the base of the deepest section (Block 12/24-1) and sets limits on the maximum relative uplift experienced by the other sections.
Oil Potential of Coals: A Geochemical Approach
Authors: Durand B. , Paratte M.
Published: September 2007

Rock-Eval and pyrolysis GC data show that coals from various origins generate on thermal cracking up to 30% weight in form of hydrocarbons. Most of them consist of oil-type components (C
6
+ hydrocarbons) up to about 1.5% vitrinite reflectance maturity. Therefore fair quantities of oil should be generated during maturation of such samples. Paradoxically, coal-rich sediments contain only minute amounts of oil, whatever their maturity rank. This is interpreted by an easy expulsion of hydrocarbons from coals during burial. Moreover, trapping of oil in the ‘microporosity’ of coals, or due to their ‘plastic’ behaviour is unlikely.

Therefore coals should have a fair potential for oil generation and expulsion and the observed poor association between coal measures and oil pools is due to geological reasons rather than to geochemical ones.

Distributions and yields of the generated hydrocarbons may be quite different from one sample to another. For instance, North Sea coals do not resemble coals from Tertiary deltas.
Use of Porphyrins as a Maturity Parameter for Oils and Sediments
Authors: Barwise A. J. G.
Published: September 2007

There is considerable interest at present in the use of biological markers, both as maturity parameters for oils and sediments, and oil-oil and oil-source rock correlations. Earlier work on biomarkers concentrated on the distribution of steranes and triterpanes; but with new analytical techniques becoming available other biomarker classes are under investigation, such as aromatics, sulphur compounds and porphyrins.

Porphyrins in oils and sediments are probably derived from chlorophylls in algae or photosynthetic bacteria. Until recently, little was known about the structure of geological porphyrins, but now several compounds have been isolated, purified and characterized. Two main types of porphyrins are present, DPEP and ETIO, and it has been shown that with increasing thermal maturity the relative concentration of ETIO-porphyrins increases with respect to DPEP-porphyrins.

Thus a measure of ratio (1) in sediments and oils should reveal the thermal maturity of these samples. A suite of oils and related source rocks have been examined, and their porphyrin distributions recorded. Porphyrins show large changes in ratio (1), ranging from 0.8, in the least mature oils, to zero in the most mature oils. Changes in molecular distribution were similar in the sediment extracts, and porphyrins seem to be useful maturation parameters in the range %Ro 0.3 to 0.8; after which they are thermally destroyed.
The Compilation of an Earth Science Bibliography for the North Sea and Adjacent Areas
Authors: McKay D. J.
Published: September 2007

This paper acts as an introduction to the bibliography of the North Sea and adjacent areas that is being compiled by the Exploration Division Library of Britoil. The paper gives an overview of Earth Science literature. Considerable attention is paid to the use of on-line information retrieval, which was the primary method of data collection for the bibliography. The bibliography itself will be available separately, and it is emphasised that it contains references only to publications that are publicly available.
Evaluation of exhumation mechanisms for coherent blueschists in western Baja California, Mexico
Authors: Sedlock Richard L.
Published: September 2007

Structural data and field observations from Franciscan-type coherent blueschists in western Baja California, Mexico, are used to test proposed mechanisms for exhumation of these high-pressure, low-temperature (high
P/T
) metamorphic rocks. Analysis of specific observations that are predicted by, consistent with, or inconsistent with specific mechanisms supports extension and normal faulting as the dominant mechanism in Baja. Erosion and strike-slip faulting may have been active, but their contributions cannot be documented and are inferred to be minor. Buoyancy forces and ductile flow probably played a negligible role. Extension and exhumation probably occurred in Late Cretaceous and Paleogene time, while subduction continued at the convergent margin west of North America. Blueschists probably were exhumed to shallow crustal levels by 30 Ma, and possibly before a decrease in convergence rate at about 40 Ma. Coherent blueschists lie in the footwalls of major normal fault zones that contain serpentinite-matrix mélange with exotic blocks of greenschist, amphibolite, eclogite, and blueschist. Mélange probably formed before normal slip on the fault zones. Most mélange components are consistent with tectonic thinning of the mantle wedge and adjacent parts of the accretionary prism that once lay structurally higher than the lower-plate blueschists. Many of these findings may be applicable to similar rocks in California, including Franciscan blueschists.
Ductile deformation and mass loss in the Franciscan Subduction Complex: implications for exhumation processes in accretionary wedges
Authors: Ring Uwe , Brandon Mark T.
Published: September 2007

Deformation measurements from 64 sandstone samples collected in three study areas from the Eastern Belt of the Franciscan Complex are used to evaluate how the high-pressure metamorphic interior of the Franciscan wedge was exhumed. Pressure estimates indicate 25–30 km of exhumation in this part of the Franciscan Complex. Much of the Eastern Belt has a semi-penetrative cleavage that formed by solution mass transfer (SMT) while the rocks were moving through the wedge. Individual samples have absolute principal stretches ofSX= 1.00–1.52,SY= 0.60–1.21, andSZ= 0.33–0.81. Strain magnitudes and directions are quite variable at the local scale. The deformation at the regional scale is estimated by calculating tensor averages for groups of measurements. The three study areas, which are spaced over a distance ofc.500 km along the Franciscan margin, give remarkably similar averages, which indicates that the deformation of the Eastern Belt is consistent at the regional scale. The tensor average for all data indicates a nearly verticalZdirection withSX= 0.96,SY= 0.92, andSZ= 0.70.SXandSYare near one because at the local scale, theXandYdirections vary considerably in orientation, which means that their stretch contributions are averaged out at the regional scale. This unusual strain type, consisting of both plane strain and uniaxial shortening, results from the fact that shortening inZwas balanced by a pervasive mass-loss volume strain, averaging about 38%. The geometry of directed fibre overgrowths was used to measure internal rotations. These data indicate that in sandstones, SMT deformation was nearly coaxial (mean kinematic vorticity number is 0.05 at the regional scale and generally <0.4 for individual samples). A simple one-dimensional steady-state model indicates that ductile thinning accounted for onlyc.10% of the overall exhumation. Ductile shortening across the Franciscan wedge was very slow, at rates <8 × 10−17s−1(<0.3% Ma−1). Assuming that this strain was active in an across-strike zone <200 km wide, we estimate that horizontal ductile flow would have accounted for <0.25% of the total convergence across the Franciscan margin. We conclude that the SMT mechanism operated slowly as a background deformation process, and that the dislocation glide mechanism was completely inactive down to depths of 25–30 km. Thus, the stability of the Franciscan wedge was probably better defined by the Coulomb wedge criterion than by a viscous wedge criterion. No definitive normal faults have been found in or adjacent to the Eastern Belt. Therefore, we infer that wedge taper was mainly controlled by deep accretion and erosion of an emergent forearc high.
Miocene high-pressure metamorphic rocks of Crete, Greece: rapid exhumation by buoyant escape
Authors: Thomson Stuart N. , Stöckhert Bernhard , Brix Manfred R.
Published: September 2007

The pre-Neogene thrust sheets of Crete, Greece, accreted during Oligocene and Early Miocene time, can be divided into two main groups juxtaposed by a Miocene extensional detachment. Oligo-Miocene high pressure-low temperature (HP-LT) metamorphic rocks crop out in the lower plate to the detachment, and rocks that show no evidence of Tertiary metamorphism in the upper plate. Detailed pressure, temperature and structural information from the HP-LT metamorphic rocks combined with new fission-track data from the upper plate reveal that the lower plate rocks were subducted, then pervasively deformed and metamorphosed at their maximum depth of burial (30–35 km, 300–400°C) between
c.
24 and 19 Ma and then exhumed to less than 10 km depth at rates >4 km Ma
−1
before
c.
17 Ma. Microstructural studies reveal that during exhumation the lower plate acted as a coherent block, with deformation and retrograde metamorphism localized along the extensional detachment. The rocks of the upper plate can be shown to have remained in the upper 4–7 km of the crust since at least Eocene time. After cessation of movement along the main extensional detachment, both the upper and lower plates were subjected to brittle extension and increased erosion initiated at
c.
16–17 Ma. These boundary conditions imply continuous subduction retreat since at least Eocene time along the Aegean segment of the Hellenic convergent plate boundary. A tectonic model is presented where exhumation is driven by positive buoyancy of the subducted continental crust following lithospheric delamination. We propose that the subducted microcontinent was exhumed by a process of ‘oblique buoyant escape’ and entered the space created by the retreating subducting oceanic slab.
Spatial and temporal variations in exhumation of the central Swiss Alps and implications for exhumation mechanisms
Authors: Schlunegger Fritz , Willett Sean
Published: September 2007

Information about the structural and thermal evolution of the Alps, interpreted through thermal and mechanical models, provides an improved understanding of the processes that led to the exhumation of the Alps. We synthesize published thermochronometric data, analyse these data in terms of cooling rates and interpret the spatial and temporal patterns of cooling. Cooling rates are interpreted in terms of exhumation rates, aided by the use of a one-dimensional thermal model. Our study reveals that rapid exhumation of the Lepontine core occurred during the interval of 35-20 Ma. Existing data cannot determine whether this was by rapid erosion at rates exceeding 1 km Ma
−1
or by a relatively brief period of tectonic exhumation, although the correlation between extensional fault motion and high cooling rates supports the tectonic exhaumation hypothesis. Peripheral regions of the Alps cooled at rates consistent with low to moderate exhumation rates of 400–500 m Ma
−1
, initiating later than cooling of the Lepontine core, consistent with outward growth of the orogen. Outward growth of the orogen is potentially the result of either lower exhumation rates or higher rates of crustal accretion as demonstrated by a two-dimensional, coupled erosion-deformation model. In particular, the growth of the Southern Alps after
c.
20 Ma is evidence for a decrease in the exhumation rate relative to the crustal accretion rate. This could represent a decrease in exhumation rate after cessation of normal faulting, or it could reflect initiation of accretion of a larger fraction of the European crust.
Exhumation of migmatites in two collapsed orogens: Canadian Cordillera and French Variscides
Authors: Vanderhaeghe Olivier , Burg Jean-Pierre , Teyssier Christian
Published: September 2007

The Shuswap Metamorphic Core Complex in the Canadian Cordillera and the Velay Dome in the French Massif Central are examples of metamorphic core complexes formed in the hinterland of collapsed orogens. They display structural sections which allow the assessment of the efficiency of various exhumation mechanisms at different crustal levels. Erosion affected the relief generated during crustal thickening and redistributed the upper level of the mountain belt into nearby extensional basins or larger foreland basins. Faulting accommodated horizontal extension and laterla sliding of the upper crust. A detachment zone separates the upper brittle crust from ductilely deformed lower crust and achieved mechanical decoupling between these two major crustal layers. Below the detachment zone, the major fabric of high-grade rocks developed in the presence of melt and indicates vertical thinning along with horizontal extension. The lowest structural level exposed consists of migmatites which rose during crustal-scale boudinage of the overlying units and appear in the cores of dome-shaped culminations. The combination of these various exhumation mechanisms within a period of a few million years brought into close proximity migmatites which formed at depth of about 20–25 km and sediments deposited at the surface.
Geological and geochronological constraints on the exhumation of a high-pressure metamorphic terrane, Oman
Authors: Miller J. McL. , Gregory R. T. , Gray D. R. , Foster D. A.
Published: September 2007

New
40
Ar-
39
Ar age data from high-pressure former continental shelf rocks, now structurally beneath the Samail ophiolite, support a two-stage exhumation process for these rocks. High-
P
rocks occur as stacked fold-nappes within a less deformed upper plate and a strong to intensely deformed lower plate separated by a major, ductile, crustal discontinuity. The highest-grade lower plate rocks yield
40
Ar-
39
Ar ages that range from 82 to 131 Ma. The majority of these ages are inferred to represent cooling by the progressive emplacement of colder units during convergent margin tectonism, before emplacement to higher structural levels. In the lower plate, 82–79 Ma
40
Ar-
39
Ar ages are associated with lower-grade assemblages defining both transposition fabrics and C’-type shear bands which overprint the high-
P
assemblages during a NE-directed shearing event. Partial exhumation of these lower plate sequences resulted in the formation of regional closures by folding and transposition of earlier high-pressure fabrics. The lower plate closures are truncated by the structural break separating the two plates. Emplacement of the lower plate units to shallower crustal levels may have occurred before, or synchronously with, peak metamorphism of the upper plate units. The lower plate
40
Ar-
39
Ar cooling(?) ages are older than mica crystallization ages of 76–70 Ma from the upper plate. These upper plate micas grew in axial surface fabrics associated with regional-scale fold-nappes which formed during the exhumation of the upper plate units and their transport over the higher-grade lower plate units. This nappe-forming event was possibly synchronous with structurally higher low-angle normal faulting and/or rapid erosion of the nappe pile before the deposition of Maastrichtian autochthonous units at
c.
67–68 Ma.
Quantifying tectonic exhumation in an extensional orogen with thermochronology: examples from the southern Basin and Range Province
Authors: Foster David A. , John Barbara E.
Published: September 2007

The Colorado River extensional corridor is a region of large-scale crustal attenuation, where the integration of thermochronological techniques illuminates processes of extension and exhumation. Biotite and K-feldspar
40
Ar-
39
Ar, and zircon and apatite fission-track ages from metamorphic core complexes in the corridor consistently young in the displacement directions of detachment faults. The onset of rapid extension is denoted by an abrupt change, at
c.
22–21 Ma, in cooling rate derived from age-closure temperature plots, and in slope of age-distance gradients in footwalls. Linear age-distance trends with slopes of
c.
3–8 km Ma
−1
, for low-temperature thermochronometers, give time-averaged displacement rates on detachment faults. Gradients of mineral age across thick tilted hanging wall fault blocks reveal palaeotemperature gradients when the angle of tilting is known. Pre-extensional thermal gradients for tilted blocks in the southern Basin and Range province were
c.
20–25°C km
−1
, 17° ± 5°C km
−1
, and
c.
20–24°C km
−1
. Thermochronological data from the footwall of the Chemehuevi detachment fault reveal a trend of increasing temperature, in the known slip direction, from ≤200° to 350–400°C over an exposed distance of 23 km, at the onset of extension. The gradual increase in temperature constrains the Chemehuevi detachment fault to have had an original dip of
c.
15–30°, within the brittle upper crust.
The kinematics of back-arc basins, examples from the Tyrrhenian, Aegean and Japan Seas
Authors: Jolivet Laurent , Faccenna Claudio , D’Agostino Nicola , Fournier Marc , Worrall Dan
Published: September 2007

Three classical examples of marginal basins are explored to show the respective contributions of body forces and far-field stresses to the extension mechanism. Extensional stresses can be provided by: (1) the slab-pull force, which induces a retreat of the slab and which originates in the density contrast between the subducting slab (oceanic or continental) and the asthenosphere; (2) by lateral density contrasts within the crust (due to crustal thickening), which induce crustal spreading; and (3) by far-field stresses due to intra-continental deformation (continent-continent collision, for example). Slab pull is probably the most efficient extensional force to provide but its effects are modulated by the contributions of the two other forces. The Japan Sea opened along the eastern margin of the Eurasian continent because extensional boundary conditions were provided by the retreating Pacific subduction zone. The opening stopped as soon as the central Japan triple junction was established in its present position which resulted in a more efficient coupling between the Pacific and Eurasian Plates through the Philippine Sea Plate. The geometry of opening was further controlled by large-scale dextral strike-slip faults that run oblique to the subduction zone along >2500 km, and which are far-field effects of the India-Asia collision. The Northern Tyrrhenian Sea opened because of the retreat of the Adriatic continental slab. The strong slab-pull force is probably due to phase changes within the subducting lower crust. Crustal delamination leads to a warm lower crust which localizes the extensional strain. This extending domain migrated with time from west to east as the delamination and slab retreat proceeded. Upper crustal units incorporated in the Apennines accretionary wedge were later exhumed in the collapsing back-arc domain where their deformation andP-Thistory can now be observed. A similar history with an outward migration can be proposed for the Aegean Sea with, however, a stronger influence of crustal collapse over a larger domain. Here too continental collision (the Arabia-Eurasia collision) controlled the geometry of opening through the westward propogation of the North Anatolian Fault.
Taconian seismogenic deformation in the Appalachian Orogen and the North American Craton
Authors: Rast Nicholas , Ettensohn Frank R. , Rast Diana E.
Published: September 2007

Originally the paradigm of plate tectonics was largely based on seismological interpretation of earthquakes. It therefore behoves that geological literature should pay more attention to the detection of seismic activity in ancient rocks. The effects of earthquakes on relatively young Tertiary and Holocene deposits have been recognized, commonly in the context of engineering works. In this paper, observational evidence for seismogenic structures in the Lower Palaeozoic carbonate belt of E. North America is presented. The structures range from minor faults and liquefaction effects to breccias and melanges. It is sometimes possible to suggest the dynamics of faults on which earthquakes occurred. Although most of the deformation happened at the margins of the craton and the growing orogenic belt, intracratonic faulting, earthquakes and synsedimentary deformation also took place.
The Northern Sacramento Mountains, southwest United States. Part I: Structural profile through a crustal extensional detachment system
Authors: Pease V. , Argent J.
Published: September 2007

Miocene exhumation of the Sacramento Mountains metamorphic core complex in the Colorado River extensional corridor, southwest United States, produced a range of deformational fabrics: pervasive, synthetic ductile deformation (with associated syntectonic intrusion) occurred at depth, discrete antithetic ductile through to brittle extensional shear zones developed at intermediate crustal levels and brittle cataclasis occurred at upper crustal levels. The region divides into three structural domains on the basis of these fabrics: (1) the eastern domain is dominated by a penetrative, ductile fabric with a consistent mineral alignment and stretching lineation, and sense of shear synthethic with detachment fault motion (top-to-northeast); (2) the central domain is characterized by a continuum of overprinting ductile through to brittle extensional shear zones with motion antithetic (topto-southwest) to detachment faulting; and (3) the western domain, where deformation occurred entirely by brittle cataclasis. Structural and petrofabric data from the Sacramento Mountains suggest that increasing structural depth/temperature is exposed in the direction of tectonic transport (N60E), consistent with detachment faulting. This region is interpreted as a profile through a crustal-scale shear zone in which the central domain of discrete antithetic shear zones formed in response to a combination of non-coaxial shear and vertical shortening, and represents an exhumed brittle-ductile transition. Rapid uplift and cooling of the northern Sacramento Mountains in the Miocene facilitated the preservation of this relatively transient regime.
Structural and magmatic segmentation of the Tertiary East Greenland Volcanic Rifted Margin
Authors: Karson Jeffrey A. , Brooks C. Kent
Published: September 2007

The Tertiary East Greenland Volcanic Rifted Margin is characterized by massive magmatic construction that produced a distinctive crustal architecture including: (1) a thick pile of flood basalts continuing offshore as seismically imaged ‘seaward-dipping reflector sequences’; (2) an extensive margin-parallel mafic dyke swarm; and (3) shallow crustal gabbroic plutons and deeper crustal ‘underplated’ material. These igneous units developed in the framework of an asymmetrical, crustal-scale fold, or ‘flexure’, that accommodated major subsidence along the continent-ocean transition. Extensive exposures along the margin reveal that the flexure and associated igneous structures define rift segments separated by various types of structural discontinuities. First-order segments occur between major triple-rift junctions as at Kangerlussuaq. At an intermediate scale, second-order accommodation zones bound margin segments
c.
100 km in length with long-lived structural and/or magmatic expressions. Third-order discontinuities, spaced at tens of kilometres, correspond to smaller accommodation zones at abrupt along-strike changes fault or magmatic structures. Outcrop-scale transfer and transform faults occur at still smaller scales. Some of the larger accommodation zones appear to be related to pre-existing Precambrian structures and may have helped localize relatively late, post-flexure alkalic intrusions. The style of segmentation provides a link between similar segmentation patterns in continental rifts and mid-ocean ridge spreading centres that persist long after continental separation.
Rodent intestinal folate transporters (SLC46A1): secondary structure, functional properties, and response to dietary folate restriction
Authors: Qiu Andong , Min Sang Hee , Jansen Michaela , Malhotra Usha , Tsai Eugenia , Cabelof Diane C. , Matherly Larry H. , Zhao Rongbao , Akabas Myles H. , Goldman I. David
Published: September 2007

This laboratory recently identified a human gene that encodes a novel folate transporter [ Homo sapiens proton-coupled folate transporter ( HsPCFT); SLC46A1] required for intestinal folate absorption. This study focused on mouse ( Mus musculus) PCFT ( MmPCFT) and rat ( Rattus norvegicus) PCFT ( RnPCFT) and addresses their secondary structure, specificity, tissue expression, and regulation by dietary folates. Both rodent PCFT proteins traffic to the cell membrane with the NH2- and COOH-termini accessible to antibodies targeted to these domains only in permeabilized HeLa cells. This, together with computer-based topological analyses, is consistent with a model in which rodent PCFT proteins likely contain 12 transmembrane domains. Transport of [3H]folates was optimal at pH 5.5 and decreased with increasing pH due to an increase in Km and a decrease in Vmax. At pH 7.0, folic acid and methotrexate influx was negligible, but there was residual (6 S)5-methyltetrahydrofolate transport. Uptake of folates in PCFT-injected Xenopus oocytes was electrogenic and pH dependent. Folic acid influx Km values of MmPCFT and RnPCFT, assessed electrophysiologically, were 0.7 and 0.3 μM at pH 5.5 and 1.1 and 0.8 μM at pH 6.5, respectively. Rodent PCFTs were highly specific for monoglutamyl but not polyglutamyl methotrexate. MmPCFT mRNA was highly expressed in the duodenum, proximal jejunum, liver, and kidney with lesser expression in the brain and other tissues. MmPCFT protein was localized to the apical brush-border membrane of the duodenum and proximal jejunum. MmPCFT mRNA levels increased ∼13-fold in the proximal small intestine in mice fed a folate-deficient vesus folate-replete diet, consistent with the critical role that PCFT plays in intestinal folate absorption.