Synorogenic extension: Quantitative constraints on the age and displacement of the Zanskar shear zone (northwest Himalaya)

subsequent extension-induced exhumation. Geochronological dating of various Structural, thermobarometric, and geochronological data place limits on the age and tectonic displacement along the Zanskar shear zone, a major north-dipping synorogenic extensional structure separating the high-grade metamorphic sequence of the High Himalayan Crystalline Sequence from the overlying low-grade sedimentary rocks of the Tethyan Himalaya, A complete Barrovian metamorphic succession, from kyanite to biotite zone mineral assemblages, occurs within the I-km-thick Zanskar shear zone. Thermobarometric data indicate a difference In equilibration depths of 12 +/- 3 km between the lower kyanite zone and the garnet zone, which is Interpreted as a minimum estimate for the finite vertical displacement accommodated by the Zanskar shear zone. For the present-day dip of the structure (20 degrees), a simple geometrical model shows that a net slip of 35 +/- 9 km is required to regroup these samples to the same structural level. Because the kyanite to garnet zone rocks represent only part of the Zanskar shear zone, and because its original dip may have been less than the present-day dip, these estimates fur the finite displacement represent minimum values. Field relations and petrographic data suggest that migmatization and associated leucogranite intrusion in the footwall of the Zanskar shear zone occurred as a continuous profess starting at the Barrovian metamorphic peak and lasting throughout the subsequent extension-induced exhumation. Geochronological dataing of various leucogranitic plutons and dikes in the Zanskar shear zone footwall indicates that the main ductile shearing along the structure ended by 19.8 Ma and that extension most likely initiated shortly before 22.2 Ma.

Differential reactivity of TCR Vbeta10 alleles to a mouse mammary tumor virus superantigen.

Mouse mammary tumor virus (MMTV) expresses a superantigen (SAg) which plays a critical role in the viral life cycle. We have recently described the new infectious MMTV (SIM) encoding a Vbeta4-specific SAg in mice with a TCR-Vbeta(b) haplotype. We have now compared the SAg activity of this virus in BALB/c mice harboring the TCR-Vbeta(a), TCR-Vbeta(b) or TCR-Vbeta(c) haplotypes which differ by a central deletion in the TCR-Vbeta(a) and TCR-Vbeta(c) locus and by mutations in some of the remaining Vbeta elements. Injection of MMTV (SIM) led to a strong stimulation of Vbeta4+ CD4+ T cells in TCR-Vbeta(b) mice, but only to a weak stimulation of these cells in TCR-Vbeta(a) or TCR-Vbeta(c) mice. A large increase in the percentage of Vbeta10+ cells was observed among CD4+ T cells in mice with the Vbeta(a) or Vbeta(c), but not the Vbeta(b) TCR-Vbeta haplotype. Vbeta10+ cells dominated the response when Vbeta10(a/c) and Vbeta4 subsets were present together. This is the first report of a viral SAg interacting with murine Vbeta10+ cells. Six amino acid differences between Vbeta10(a/c) and Vbeta10(b) could account for the gain of reactivity of Vbeta10(a/c) to the MMTV(SIM) SAg. No mutations were found in the hypervariable region 4 (HV4) of the TCR. Mutations at positions 22 and 28 introduce into Vbeta10(a/c) the same amino acids which are found at these positions in the MMTV(SIM)-reactive Vbeta4. Tridimensional models indicated that these amino acids lie close to HV4 and are likely to be important for the interaction of the SAg with the TCR.

Large calcite and bulk-rock volume loss in metacarbonate xenoliths from the Qu,rigut massif (French Pyrenees)

Chemical mass transfer was quantified in a metacarbonate xenolith enclosed within the granodiorite of the Qu,rigut massif (Pyrenees, France). Mass balance calculations suggest a strong decrease of CaO, SrO and CO(2) contents (up to -90%), correlated with a decrease of modal calcite content as the contact is approached. Most other chemical elements behave immobile during metasomatism. They are therefore passively enriched. Only a small increase of SiO(2), Al(2)O(3) and Fe(2)O(3) contents occurs in the immediate vicinity of the contact. Hence, in this study, skarn formation is characterized by the lack of large chemical element influx from the granitoid protolith. A large decrease of the initial carbonate volume (up to -86%) resulted from a combination of decarbonation reactions and loss of CaO and CO(2). The resulting volume change has potentially important consequences for the interpretation of stable isotope profiles: the isotope alteration could have occured over greater distances than those observed today.

NMR and LC-MSn characterisation of two minor saponins from Ilex paraguariensis.

Two minor saponins obtained from the methanolic extract of the leaves of Ilex paraguariensis have been characterised by 13C-NMR, 1H-NMR, API-MS and chemical hydrolysis as oleanolic acid-3-O-(beta-D-glucopyranosyl-(1-->3)-alpha-L-arabinopyranosyl)-(28-->1)- beta-D-glucopyranosyl ester (guaiacin B) and oleanolic acid-3-O-(beta-D-glucopyranosyl-(1-->3)-(alpha-L-rhamnopyranosyl- (1-->2))-alpha-L-arabinopyranosyl)-(28-->1)-beta-D-glucopyranosyl ester (nudicaucin C). Both are isomeric forms of the known matesaponins 1 (MSP 1) and 2 (MSP 2) and differ only by the nature of the aglycone: they have oleanolic acid instead of ursolic acid, as found in the matesaponins. These minor saponins have not been fully separated from their major isomers MSP 1 and 2 and were characterised by in-mixture NMR analysis, LC-MS and LC-MSn experiments.

Mesozoic sequence of Fuerteventura (Canary Islands): Witness of Early Jurassic sea-floor spreading in the central Atlantic

The Fuerteventura Jurassic sedimentary succession consists of oceanic and elastic deposits, the latter derived from the southwestern Moroccan continental margin. Normal mid-oceanic-ridge basalt (N-MORB) flows and breccias are found at the base of the sequence and witness sea-floor spreading events in the central Atlantic. These basalts were extruded in a postrift environment (post-late Pliensbachian), We propose a Toarcian age for the Atlantic oceanic floor in this region, on the basis of the presence higher up in the sequence of the Bositra buchi filament microfacies (Aalenian-Bajocian) and of elastic deposits reflecting tectono-eustatic events (e.g,, late Toarcian to mid-Callovian erosion of the rift shoulder). The S-l sea-floor oceanic magnetic anomaly west of Fuerteventura is therefore at least Toarcian in age. The remaining sequence records Atlantic-Tethyan basinal facies (e.g., Callovian-Oxfordian red clays, Aptian-Albian black shales) alternating with elastic deposits (e.g., Kimmeridgian-Berriasian periplatform calciturbidites and a Lower Cretaceous deep-sea fan system). The Fuerteventura N-MORB outcrops represent the only Early Jurassic oceanic basement described so far in the central Atlantic. They are covered by a 1600 m, nearly continuous sedimentary sequence which extends to Upper Cretaceous facies.

Impact of free-range pigs on mountain pastures in the Swiss Jura

The consequences of foraging by free-range pigs on the vegetation of mountain pastures was investigated. 25 pigs (15 week-old, mean weight 50 kg) were enclosed from June to mid-September in a 2 ha-enclosure in Jura Mountains (Switzerland), fed with a mixture of lactoserum and cereals. The enclosure contained five different plant communities. Eutrophic pastures on deep soil were strongly overturned, but the recolonisation was quick and dominated by the original species. Mesotrophic pastures were less damaged on stony soil but completely destroyed on deep soil, and the recovery was slow, characterised by a shift of plant species in a more eutrophic direction. Four years were not sufficient for complete recovery. Oligotrophic calcareous pastures on shallow stony soil were not damaged. Extensive breeding of pigs in mountain pastures might be harmful to plant species and vegetation, and ought to be restricted to the less sensitive plant communities, with a rotation on two to three different sites.

Effect of added dead space on sleep disordered breathing at high altitude.

OBJECTIVE: Sleep disordered breathing with central apnea or hypopnea frequently occurs at high altitude and is thought to be caused by a decrease in blood CO(2) level. The aim of this study was to assess the effects of added respiratory dead space on sleep disordered breathing.¦METHODS: Full polysomnographies were performed on 12 unacclimatized swiss mountaineers (11 males, 1 female, mean age 39±12 y.o.) in Leh, Ladakh (3500m). In random order, half of the night was spent with a 500ml increase in dead space through a custom designed full face mask and the other half without it.¦RESULTS: Baseline data revealed two clearly distinct groups: one with severe sleep disordered breathing (n=5, AHI>30) and the other with moderate to no disordered breathing (n=7, AHI<30). DS markedly improved breathing in the first group (baseline vs DS): apnea hypopnea index (AHI) 70.3±25.8 vs 29.4±6.9 (p=0.013), oxygen desaturation index (ODI): 72.9±24.1/h vs 42.5±14.4 (p=0.031), whereas it had no significant effect in the second group or in the total population. Respiratory events were almost exclusively central apnea or hypopnea. Microarousal index, sleep efficiency, and sleep architecture remained unchanged with DS. A minor increase in mean PtcCO(2) (n=3) was observed with DS.¦CONCLUSION: A 500ml increase in dead space through a fitted mask may improve nocturnal breathing in mountaineers with severe altitude-induced sleep disordered breathing.

Expression of B220 on activated T cell blasts precedes apoptosis.

Superantigens are bacterial or viral products that polyclonally activate T cells bearing certain TCR beta chain variable elements. For instance, Vbeta8+ T cells proliferate in response to staphylococcal enterotoxin B (SEB) in vivo and then undergo Fas- and/or TNF-mediated apoptosis. We have recently shown that apoptotic SEB-reactive T cells express the B cell marker B220. Here we report the identification of a novel subset of CD4+ B220+ T cell blasts that are the precursors of these apoptotic cells in SEB-immunized mice. Moreover, we show that the CD4- CD8- B220+ T cells that accumulate in the lymphoid organs of Fas ligand-defective gld mice stably express a form of the B220 molecule which exhibits biochemical similarities to that expressed by activated wild-type T cells, but is distinct from that displayed on the surface of B cells. Surprisingly, we also find a population of CD4+ B220+ pre-apoptotic T cells in FasL-defective gld mice, arguing that these cells can be generated in a Fas-independent fashion. Collectively, our data support a general model whereby upon activation, T cells up-regulate B220 before undergoing apoptosis. When the apoptotic mechanisms are defective, T cells presumably down-regulate their coreceptor molecules but retain expression of B220 as they accumulate in lymphoid organs.

A regulatory network for the efficient control of transgene expression.

BACKGROUND: Expression of heterologous genes in mammalian cells or organisms for therapeutic or experimental purposes often requires tight control of transgene expression. Specifically, the following criteria should be met: no background gene activity in the off-state, high gene expression in the on-state, regulated expression over an extended period, and multiple switching between on- and off-states. METHODS: Here, we describe a genetic switch system for controlled transgene transcription using chimeric repressor and activator proteins functioning in a novel regulatory network. In the off-state, the target transgene is actively silenced by a chimeric protein consisting of multimerized eukaryotic transcriptional repression domains fused to the DNA-binding tetracycline repressor. In the on-state, the inducer drug doxycycline affects both the derepression of the target gene promoter and activation by the GAL4-VP16 transactivator, which in turn is under the control of an autoregulatory feedback loop. RESULTS: The hallmark of this new system is the efficient transgene silencing in the off-state, as demonstrated by the tightly controlled expression of the highly cytotoxic diphtheria toxin A gene. Addition of the inducer drug allows robust activation of transgene expression. In stably transfected cells, this control is still observed after months of repeated cycling between the repressed and activated states of the target genes. CONCLUSIONS: This system permits tight long-term regulation when stably introduced into cell lines. The underlying principles of this network system should have general applications in biotechnology and gene therapy.

Physiological traits affecting the distribution and wintering strategy of the bat Tadarida teniotis

The ability to enter torpor at low ambient temperature, which enables insectivorous bats to survive seasonal food shortage, is often seen as a prerequisite for colonizing cold environments. Free-tailed bats (Molossidae) show a distribution with a maximum latitudinal extension that appears to be intermediate between truly tropical and temperate-zone bat families. We therefore tested the hypothesis that Tadarida teniotis, the molossid species reaching the highest latitude worldwide (46 degrees N), lacks the extreme physiological adaptations to cold that enable other sympatric bats to enter further into the temperate zone. We studied the metabolism of individuals subjected to various ambient temperatures in the laboratory by respirometry, and we monitored the body temperature of free-ranging individuals in winter and early spring in the Swiss Alps using temperature-sensitive radio-tags. For comparison, metabolic data were obtained from Nyctalus noctula, a typically hibernating vespertilionid bat of similar body size and convergent foraging tactics. The metabolic data support the hypothesis that T. teniotis cannot experience such low ambient temperatures as sympatric temperate-zone vespertilionid bats without incurring much higher energetic costs for thermogenesis. The minimum rate of metabolism in torpor was obtained at 7.5 degrees-10 degrees C in T. teniotis, as compared to 2.5 degrees-5 degrees C in N. noctula. Field data showed that T. teniotis behaves as a classic thermo-conforming hibernator in the Alps, with torpor bouts lasting up to 8 d. This contradicts the widely accepted opinion that Molossidae are nonhibernating bars. However, average body temperature (10 degrees-13 degrees C) and mean arousal frequency (3.4 d in one bat in January) appear to be markedly higher than in other temperate-zone bat species. At the northern border of its range T. teniotis selects relatively warm roosts (crevices in tall, south-exposed limestone cliffs) in winter where temperatures oscillate around 10 degrees C. By this means, T. teniotis apparently avoids the risk of prolonged exposure to energetically critical ambient temperatures in torpor (<6.5 degrees-7.5 degrees C) during cold spells. Possibly shared by other Molossidae, the physiological pattern observed in T. teniotis may clearly be linked to the intermediate latitudinal extension of this bat family.

A fast 3D approach for coronary MRA.

Two-dimensional (2D)-breath-hold coronary magnetic resonance angiography (MRA) has been shown to be a fast and reliable method to depict the proximal coronary arteries. Recent developments, however, allow for free-breathing navigator gated and navigator corrected three-dimensional (3D) coronary MRA. These 3D approaches have potential for improved signal-to-noise ratio (SNR) and allow for the acquisition of adjacent thin slices without the misregistration problems known from 2D approaches. Still, a major impediment of a 3D acquisition is the increased scan time. The purpose of this study was the implementation of a free-breathing navigator gated and corrected ultra-fast 3D coronary MRA technique, which allows for scan times of less than 5 minutes. Twelve healthy adult subjects were examined in the supine position using a navigator gated and corrected ECG triggered ultra-fast 3D interleaved gradient echo planar imaging sequence (TFE-EPI). A 3D slab, consisting of 20 slices with a reconstructed slice thickness of 1.5 mm, was acquired with free-breathing. The diastolic TFE-EPI acquisition block was preceded by a T2prep pre-pulse, a diaphragmatic navigator pulse, and a fat suppression pre-pulse. With a TR of 19 ms and an effective TE of 5.4 ms, the duration of the data acquisition window duration was 38 ms. The in-plane spatial resolution was 1.0-1.3 mm*1.5-1.9 mm. In all cases, the entire left main (LM) and extensive portions of the left anterior descending (LAD) and right coronary artery (RCA) could be visualized with an average scan time for the entire 3D-volume data set of 2:57 +/- 0:51 minutes. Average contiguous vessel length visualized was 53 +/- 11 mm (range: 42 to 75 mm) for the LAD and 84 +/- 14 mm (range: 62 to 112 mm) for the RCA. Contrast-to-noise between coronary blood and myocardium was 5.0 +/- 2.3 for the LM/LAD and 8.0 +/- 2.9 for the RCA, resulting in an excellent suppression of myocardium. We present a new approach for free-breathing 3D coronary MRA, which allows for scan times superior to corresponding 2D coronary MRA approaches, and which takes advantage of the enhanced SNR of 3D acquisitions and the post-processing benefits of thin adjacent slices. The robust image quality and the short average scanning time suggest that this approach may be useful for screening the major coronary arteries or identification of anomalous coronary arteries. J. Magn. Reson. Imaging 1999;10:821-825.

Effect of bicarbonate and lactate buffer on glucose and lactate metabolism during hemodiafiltration in patients with multiple organ failure.

OBJECTIVE: To compare the effects of sodium bicarbonate and lactate for continuous veno-venous hemodiafiltration (CVVHDF) in critically ill patients. DESIGN AND SETTINGS: Prospective crossed-over controlled trial in the surgical and medical ICUs of a university hospital. PATIENTS: Eight patients with multiple organ dysfunction syndrome (MODS) requiring CVVHDF. INTERVENTION: Each patient received the two buffers in a randomized sequence over two consecutive days. MEASUREMENTS AND RESULTS: The following variables were determined: acid-base parameters, lactate production and utilization ((13)C lactate infusion), glucose turnover (6,6(2)H(2)-glucose), gas exchange (indirect calorimetry). No side effect was observed during lactate administration. Baseline arterial acid-base variables were equal with the two buffers. Arterial lactate (2.9 versus 1.5 mmol/l), glycemia (+18%) and glucose turnover (+23%) were higher in the lactate period. Bicarbonate and glucose losses in CVVHDF were substantial, but not lactate elimination. Infusing (13)C lactate increased plasma lactate levels equally with the two buffers. Lactate clearance (7.8+/-0.8 vs 7.5+/-0.8 ml/kg per min in the bicarbonate and lactate periods) and endogenous production rates (14.0+/-2.6 vs 13.6+/-2.6 mmol/kg per min) were similar. (13)C lactate was used as a metabolic substrate, as shown by (13)CO(2) excretion. Glycemia and metabolic rate increased significantly and similarly during the two periods during lactate infusion. CONCLUSION: Lactate was rapidly cleared from the blood of critically ill patients without acute liver failure requiring CVVHDF, being transformed into glucose or oxidized. Lactate did not exert undesirable effects, except moderate hyperglycemia, and achieved comparable effects on acid-base balance to bicarbonate.

Fluid evolution at the Variscan front in the vicinity of the Aachen thrust

Quartz-carbonate-chlorite veins were studied in borehole samples of the RWTH-1 well in Aachen. Veins formed in Devonian rocks in the footwall of the Aachen thrust during Variscan deformation and associated fluid flow. Primary fluid inclusions indicate subsolvus unmixing of a homogenous H(2)O-CO(2)-CH(4)-(N(2))-Na-(K)-Cl fluid into a H(2)O-Na-(K)-Cl solution and a vapour-rich CO(2)-(H(2)O, CH(4), N(2)) fluid. The aqueous end-member composition resembles that of metamorphic fluids of the Variscan front zone with salinities ranging from 4 to 7% NaCl equiv. and maximum homogenisation temperatures of close to 400A degrees C. Pressure estimates indicate a burial depth between 4,500 and 8,000 m at geothermal gradients between 50 and 75A degrees C/26 MPa, but pressure decrease to sublithostatic conditions is also indicated, probably as a consequence of fracture opening during episodic seismic activity. A second fluid system, mainly preserved in pseudo-secondary and secondary fluid inclusions, is characterised by fluid temperatures between 200 and 250A degrees C and salinities of < 5% NaCl equiv. Bulk stable isotope analyses of fluids released from vein quartz, calcite, and dolomite by decrepitation yielded delta D(H2O) values from -89 to -113 aEuro degrees, delta(13)C(CH4) from -26.9 to -28.9aEuro degrees (VPDB) and delta(13)C(CO2) from -12.8 to -23.3aEuro degrees (VPDB). The low delta D and delta(13)C range of the fluids is considered to be due to interaction with cracked hydrocarbons. The second fluid influx caused partial isotope exchange and disequilibrium. It is envisaged that an initial short lived flux of hot metamorphic fluids expelled from the epizonal metamorphic domains of the Stavelot-Venn massif. The metamorphic fluid was focused along major thrust faults of the Variscan front zone such as the Aachen thrust. A second fluid influx was introduced from formation waters in the footwall of the Aachen thrust as a consequence of progressive deformation. Mixing of the cooler and lower salinity formation water with the hot metamorphic fluid during episodic fluid trapping resulted in an evolving range of physicochemical fluid inclusion characteristics.