bluuebunny/crossref_metadata_2025 huggingface dataset:
Development of angiotensin (1‐7) as an agent to accelerate dermal repair
Authors: Rodgers Kathleen , Xiong Shiquan , Felix Juan , Roda Norma , Espinoza Theresa , Maldonado Sonia , Dizerega Gere
Published: March 2003

Angiotensin II has been shown to be a potent agent in the acceleration of wound repair. Angiotensin (1‐7), a fragment of angiotensin II that is not hypertensive, was found to be comparable to angiotensin II in accelerating dermal healing. This activity was evaluated in four models: rat and diabetic mouse full‐thickness excisional wounds; rat random flap; and guinea pig partial thickness thermal injury. In all models, angiotensin (1‐7) was comparable to angiotensin II. Angiotensin (1‐7) accelerated the closure of wounds in diabetic mice and rats. In diabetic mice the resultant tissue at day 25 after injury was more comparable to normal tissue than the fibrotic scar observed in placebo‐treated wounds. In the random flap model, angiotensin (1‐7) was comparable to angiotensin II in maintaining flap viability (approximately 82%) and flap survival (40%). Finally, angiotensin (1‐7) increased proliferation in the hair follicles at the edge of the wound and site of thermal injury, and the number of patent blood vessels on day 7 after partial thickness thermal injury. These data may be partially explained by the effect of angiotensin II and angiotensin (1‐7) on keratinocyte proliferation. While platelet‐derived growth factor had no effect on keratinocyte proliferation, angiotensin II and angiotensin (1‐7) significantly increased keratinocyte proliferation. These data show that angiotensin(1‐7) is comparable to angiotensin II in accelerating skin repair. Furthermore, the hypertensive and wound healing effects can be separated within the family of angiotensin peptides.
Modeling the effects of transforming growth factor‐β on extracellular matrix alignment in dermal wound repair
Authors: Dallon John C. , Sherratt Jonathan A. , Maini Philip K.
Published: March 2003

We present a novel mathematical model for collagen deposition and alignment during dermal wound healing, focusing on the regulatory effects of transforming growth factor‐β (TGFβ.) Our work extends a previously developed model which considers the interactions between fibroblasts and an extracellular matrix composed of collagen and a fibrin based blood clot, by allowing fibroblasts to orient the collagen matrix, and produce and degrade the extracellular matrix, while the matrix directs the fibroblasts and control their speed. Here we extend the model by allowing a time varying concentration of TGFβ to alter the properties of the fibroblasts. Thus we are able to simulate experiments which alter the TGFβ profile. Within this model framework we find that most of the known effects of TGFβ, i.e., changes in cell motility, cell proliferation and collagen production, are of minor importance to matrix alignment and cannot explain the anti‐scarring properties of TGFβ. However, we find that by changing fibroblast reorientation rates, consistent with experimental evidence, the alignment of the regenerated tissue can be significantly altered. These data provide an explanation for the experimentally observed influence of TGFβ on scarring.
Calcium: a potential central regulator in wound healing in the skin
Authors: Lansdown Alan B. G.
Published: March 2003

Calcium has an established role in the normal homeostasis of mammalian skin and serves as a modulator in keratinocyte proliferation and differentiation. Gradients of calcium concentration increasing from 0.5 mM in the basal layer to > 1.4 mM in the stratum granulosum are consistent with migration patterns in response to minor abrasion (normal wear). Dermal fibroblasts require calcium but are approximately 100 times less sensitive than keratinocytes. Normal calcium metabolism in the skin is dependent on cell membrane and cytosolic calcium binding proteins (calmodulin, cadherins, etc.), but their modulation through parathyroid hormone, vitamin D or growth factors in normal or damaged tissue is not well documented. In wound repair, calcium is predominantly involved as Factor IV in the hemostatic phase, but it is expected to be required in epidermal cell migration and regeneration patterns in later stages of healing. Calcium alginate dressings are designed to liberate calcium early in the acute phase to promote hemostasis, but it is presently unclear whether the supplementary calcium influences the intracellular environment at later stages of wound repair, notably during the remodeling phase. Although experimental studies suggest that control of calcium is obligatory in wound management, we know very little as to how calcium in the wound bed is modulated through hormones, vitamin D, or various growth factors. Also, there is limited information as to how calcium released either from dressings, platelets, or from the circulation through the action of parathyroid hormone, growth factors or other modulators influences cell migration and remodeling in skin wounds, although experimental models suggest that management of calcium is essential in wound management. (WOUND REP REG 2002;10:271–285)
Persistent wound infection delays epidermal maturation and increases scarring in thermal burns
Authors: Singer Adam J. , McClain Steve A.
Published: March 2003

We developed a reliable scale measuring epidermal maturation during wound healing and determined the effects of persistent infection on epidermal maturation and dermal scarring after cutaneous burns. A secondary analysis of data from 80 contaminated burns collected during a randomized experiment comparing four topical burn therapies in a contaminated porcine burn model was performed. Persistent infection was defined histologically as the presence of intradermal neutrophils containing bacteria at 14 days. Epidermal maturation at 14 days was classified into one of five categories from least (0) to most (4) mature using strictly defined criteria. Dermal scarring was classified as none, superficial, or deep. The epidermal classification system was highly reliable (ρ = 0.97). At 14 days, 18% of burns were infected. Most infected wounds (79%) had an immature epidermis (types 0–2) while most noninfected wounds (75%) had a mature epidermis (types 3 or 4); χ2 and χ2 for linearity both p < 0.001. Deep scars were more common in infected (93%) than noninfected wounds (29%), p < 0.001. We conclude that our scale is reliable and that persistence of infection 14 days after thermal injury is associated with delayed epidermal maturation and deep scarring. (WOUND REP REG 2002;10:372–377)
Organization of corneal collagen fibrils during the healing of trephined wounds in rabbits
Authors: Connon Che J. , Meek Keith M.
Published: March 2003

The purpose of this study was to investigate the structure and organization of collagen during the healing of penetrating rabbit corneal wounds. Full‐thickness wounds were produced in both corneas of six New Zealand White rabbits with a 2‐mm trephine. After 5, 10, and 16 months, wounds were examined using transmission electron microscopy and wide‐angle synchrotron X‐ray diffraction, which allowed the quantification of the relative amount of collagen and fibril orientation in different parts of the cornea. The intensity of the diffraction patterns taken from the wound edge was much higher than patterns collected at the wound center, indicating a greater amount of collagen near the wound edge. This collagen was shown to have a preferred orientation, forming a circular pattern around the wound. As the wounds healed, the amount of preferentially aligned collagen decreased and lamella formation and ordered fibrillar arrangement increased as shown by electron microscopy. The orientation of collagen fibrils in healing penetrating corneal wounds is not random. Instead, fibrils tend to be circularly arranged within and without the wound, gradually becoming more normal over time. We speculate that collagen is artefactually displaced during trephination, resulting in an abnormal alignment of the fibrils surrounding the wound edge, and that this influences the wound healing process. (WOUND REP REG 2003;11:71–78)
Human plasma fibronectin potentiates the mitogenic activity of platelet‐derived growth factor and complements its wound healing effects
Authors: Larivière Benoît , Rouleau Michèle , Picard Sylvain , Beaulieu André D.
Published: March 2003

Integrin‐mediated cell adhesion and growth factor stimuli are both required for optimal control of cell proliferation. In the context of skin injury, cell‐derived fibronectin and platelet‐derived growth factor play important roles in the stimulation of cell proliferation and migration, activities that are crucial to the healing process. To assess the ability of exogenously supplied plasma‐derived fibronectin to stimulate wound repair and to study its ability to cooperate with platelet‐derived growth factor‐BB during healing, we devised a novel topical delivery formulation that allows the controlled release of both molecules to a wound. Using this topical formulation and the rabbit ear model of dermal wound healing, we show that plasma fibronectin is a potent stimulator of the wound healing process. We also show that administration of fibronectin and platelet‐derived growth factor‐BB in combination has additive wound healing effects. Finally, we report novel findings on the ability of soluble plasma fibronectin to potentiate the mitogenic effects of platelet‐derived growth factor‐BB in vitro. These findings not only show that optimal concentrations of exogenous fibronectin administered using an effective delivery system stimulate wound healing; they also suggest that PDGF‐BB should be administered with fibronectin to achieve optimal therapeutic stimulation of wound healing. (WOUND REP REG 2003;11:79–89)
Textural evolution in the transition from subsolidus annealing to melting process, Velay Dome, French Massif Central
Authors: Dallain  , Schulmann  , Ledru
Published: March 2003

Petrographic analysis is a useful, but underused tool to aid in distinguishing between subsolidus and anatetic‐related textures in migmatites. This study focuses on assessing the relative contributions of these two processes in the development of migmatitic orthogneiss textures in the Velay Massif, French Massif Central. The results of this study show that subsolidus processes are more important in the development of migmatitic textures in the orthogneiss than anatectic leucosome development. Four textural stages are identified from the mylonitic non‐anatectic orthogneiss, annealed, migmatitic orthogneiss to diatexite. The monomineralic K‐feldspar and plagioclase–muscovite banding was transformed with increasing temperature to polymineralic plagioclase–quartz–muscovite and K‐feldspar–quartz–muscovite layers by the wetting of feldspar boundaries during heterogeneous nucleation of quartz from a fluid phase at high surface energy triple points. A further increase of temperature led to the growth of K‐feldspar probably related to production of small amounts of melt in plagioclase rich aggregates, controlled by muscovite abundance. Solid state annealing processes in conjunction with incipient anatexis resulted in the formation of apparent granitic‐like textures in plagioclase dominated aggregates. By contrast, in K‐feldspar dominated aggregates exclusively subsolidus processes prevail, leading to the development of coarse grained leucosome. With the onset of biotite dehydration melting the plagioclase‐dominated aggregates are destroyed by the melt whereas the K‐feldspar aggregates may be preserved.
Calculated mineral equilibria for eclogites in CaO–Na2O–FeO–MgO–Al2O3–SiO2–H2O: application to the Pouébo Terrane, Pam Peninsula, New Caledonia
Authors: Carson  , Powell  , Clarke
Published: March 2003

The high‐P, medium‐T  Pouébo terrane of the Pam Peninsula, northern New Caledonia includes barroisite‐ and glaucophane‐bearing eclogite and variably rehydrated equivalents. The metamorphic evolution of the Pouébo terrane is inferred from calculated P–T  and
P–T –XH2O pseudosections for bulk compositions appropriate to these rocks in the model system CaO–Na2O–FeO–MgO–Al2O3–SiO2–H2O. The eclogites experienced a clockwise P–T  path that reached P≈19 kbar and T ≈600 °C. The eclogitic mineral assemblages are preserved because reaction consequent upon decompression consumed the rocks’ fluid. Extensive reaction occurred only in rocks with fluid influx during decompression of the Pouébo terrane.
Humite‐ and scapolite‐bearing assemblages in marbles and calcsilicates of Dronning Maud Land, Antarctica: new data for Gondwana reconstructions
Authors: Piazolo  , Markl
Published: March 2003

This study investigates marbles and calcsilicates in Central Dronning Maud Land (CDML), East Antarctica. The paleogeographic positioning of CDML as part of Gondwana is still unclear; however, rock types, mineral assemblages, textures andP–T conditions observed in this study are remarkably similar to the Kerala Khondalite Belt in India. The CDML marbles and calcsilicates experienced a Pan‐African granulite facies metamorphism atc. 570 Ma and an amphibolite facies retrogression atc. 520 Ma. The highest grade assemblage in marbles is forsterite+spinel+calcite+dolomite, in calcsilicates the assemblages are diopside+spinel, diopside+garnet, scapolite+wollastonite+clinopyroxene±quartz, scapolite±anorthite±calcite+clinopyroxene+wollastonite. These assemblages constrain the peak metamorphic conditions to 830±20 °C, 6.8±0.5 kbar andXCO2>0.46. During retrogression, highly fluoric humite‐group minerals (humite, clinohumite, chondrodite) replaced forsterite, and garnet rims formed at the expense of scapolite during reactions with wollastonite, calcite or clinopyroxene but without involvement of anorthite. Metamorphic conditions were about 650 °C, 4.5±0.7 kbar, 0.2<XCO2fluid<0.36, and the co‐existence of garnet, clinopyroxene, wollastonite and quartz constrainsfO2to FMQ‐1.5 log units. Mineral textures indicate a very limited influx of H2O‐rich fluid during amphibolite facies retrogression and point to significant variations of fluid composition in mm‐sized areas of the rock. Gypsum was observed in two samples; it probably replaced metamorphic anhydrite which appears to have formed under amphibolite facies conditions. The observed extensive anorogenic magmatism (anorthosites, A‐type granitoids) and the character of metamorphism between 610 and 510 Ma suggest that the crustal thermal structure was characterized by a long‐lived (50–100 Ma) rise of the crustal geotherm probably caused by magmatic underplating.
Origin and metamorphism of ultrabasic rocks associated with a subducted continental margin, Naxos (Cyclades, Greece)
Authors: KATZIR  , AVIGAD  , MATTHEWS  , GARFUNKEL  , EVANS
Published: March 2003

Meta‐peridotites outcropping at different structural levels within the Alpine metamorphic complex of the Cycladic island of Naxos were studied to re‐examine their metamorphic evolution and possible tectonic mechanisms for emplacement of mantle material into the continental crust. The continental margin section exposed on Naxos, consisting of pre‐Alpine basement and c. 7 km thick Mesozoic platform cover, has undergone intense metamorphism of Alpine age, comprising an Eocene (M1) blueschist event strongly overprinted by a Miocene Barrovian‐type event (M2). Structural concordance with the country rocks and metasomatic zonation at the contact with the felsic host rocks indicate that the meta‐peridotites have experienced the M2 metamorphism. This conclusion is supported by the similarity between metamorphic temperatures of the ultrabasic rocks and those of the host rocks. Maximum temperatures of 730–760 °C were calculated for the upper‐amphibolite facies meta‐peridotites (Fo–En–Hbl–Chl–Spl), associated with sillimanite gneisses and migmatites. Relict phases in ultrabasics of different structural levels indicate two distinct pre‐M2 histories: whereas the cover‐associated horizons have been affected by low‐grade serpentinization prior to metamorphism, the basement‐ associated meta‐peridotites show no signs of serpentinization and instead preserve some of their original mantle assemblage. The geochemical affinities of the two groups are also different. The basement‐associated meta‐peridotites retain their original composition indicating derivation by fractional partial melting of primitive lherzolite, whereas serpentinization has led to almost complete Ca‐loss in the second group. The cover‐associated ultrabasics are interpreted as remnants of an ophiolite sequence obducted on the adjacent continental shelf early in the Alpine orogenesis. In contrast, the basement‐associated meta‐peridotites were tectonically interleaved with the Naxos section at great depth during the Alpine collision and high P/T  metamorphism. Their emplacement at the base of the orogenic wedge is inferred to have involved isobaric cooling from temperatures of c. 1050 °C within the spinel lherzolite field to eclogite facies temperatures of c. 600 °C.
Cr‐rich magnesiochloritoid eclogites from the Monviso ophiolites (Western Alps, Italy)
Authors: MESSIGA  , KIENAST  , REBAY  , RICCARDI  , TRIBUZIO
Published: March 2003

Cr‐rich magnesiochloritoid in the eclogitized ophiolites of the Monviso massif occurs in the least differentiated rocks of the gabbroic sequence (troctolites to melatroctolites). Chloritoid (XMg=0.63–0.85; Cr≤0.55, atoms) co‐exists with omphacite, talc and garnet. Minor, syn‐eclogitic minerals are chromite, rutile and sometimes magnesite and Cr–Ti oxides.

Coronitic textures, indicative of a static recrystallization, characterize the analysed samples. Layers of variable mineral composition develop among igneous plagioclase, olivine, clinopyroxene and spinel. The minerals in the coronitic layers display sharp compositional zonings. The igneous minerals are commonly not preserved; their presence in the original assemblage is inferred from the mineralogical composition of the pseudomorphs.

Syn‐eclogitic volatile components are indicated by the development of OH‐bearing minerals (e.g. chloritoid & talc) and carbonates (e.g. magnesite), and supported by the presence of coarse‐grained and fibrous mineral growths. The complex pseudomorphic replacements of igneous minerals suggest that these rocks changed their mineralogical composition prior to the eclogite facies recrystallization, most likely during ocean‐floor metamorphism. It is suggested that syn‐eclogitic fluids formed by breakdown reactions of pre‐eclogitic volatile‐bearing minerals.

Geothermobarometry indicates that the investigated rocks recrystallized at a depth corresponding to 2.4 GPa and temperatures of 620±50 °C. The attainment of high‐pressure conditions is supported by the presence of magnesiochloritoid, magnesite and garnet with high pyrope content (up to 58 mol%). P–T  estimates point to a very low thermal gradient (about 9 °C km−1), comparable to that deduced in the adjacent Dora‐Maira ultra‐high pressure unit.
Regional high‐pressure metamorphism during intracratonic deformation: the Petermann Orogeny, central Australia
Authors: Scrimgeour  , Close
Published: March 2003

The Petermann Orogeny is a late Neoproterozoic to Cambrian (c. 560–520 Ma) intracratonic event that affected the Musgrave Block and south‐western Amadeus Basin in central Australia. In the Mann Ranges, within the central Musgrave Block, Mesoproterozoic granulite facies gneisses, granites and mafic dykes have been substantially reworked by deep crustal non‐coaxial strain of late Neoproterozoic to early Cambrian age. Dolerite dykes have recrystallized to garnet granulite facies assemblages, associated with the development of a mylonitic fabric at P=12–13 kbar and T =700–750 °C. Migmatization is restricted to discrete shear zones, which represent conduits for hydrous fluids during metamorphism. Peak metamorphism was followed by decompression to c. 7 kbar, reflecting exhumation of the terrane along the south‐dipping Woodroffe Thrust. In scattered outcrops north of the Mann Ranges, peak metamorphism occurred at P=9–10 kbar and T =c. 700 °C. The Woodroffe Thrust separates these deep crustal mylonites from granites that were metamorphosed during the Petermann Orogeny at P=c. 6–7 kbar and T =c. 650 °C. The similarity in peak temperatures at different crustal levels implies an unusual thermal regime during this event. The existence of a relatively elevated geotherm corresponding with Th‐ and K‐enriched granites that were in the mid‐crust during the Petermann Orogeny suggests that radiogenic heat production may have substantially contributed to the thermal regime during metamorphism. This potentially has implications for the mechanisms by which intra‐plate strain was localized during this event.
The geometry and timing of orogenic extension: an example from the Western Italian Alps
Authors: Reddy  , Wheeler  , Cliff
Published: March 2003

Contacts between rocks recording large differences in metamorphic grade are indicative of major tectonic displacements. Low‐P upon high‐P contacts are commonly interpreted as extensional (i.e. material points on either side of the contact moved apart relative to the palaeo‐horizontal), but dating of deformation and metamorphism is essential in testing such models. In the Western Alps, the Piemonte Ophiolite consists of eclogites (T ≈550–600 °C and P≈18–20 kbar) structurally beneath greenschist facies rocks (T ≈400 °C and P≈9 kbar). Mapping shows that the latter form a kilometre‐wide shear zone (the Gressoney Shear Zone, GSZ) dominated by top‐SE movement related to crustal extension. Rb–Sr data from micas within different GSZ fabrics, which dynamically recrystallized below their blocking temperature, are interpreted as deformation ages. Ages from different samples within the same fabric are reproducible and are consistent with the relative chronology derived from mapping. They show that the GSZ had an extensional deformation history over a period of c. 9 Myr between c. 45–36 Ma. This overlaps in time with the eclogite facies metamorphism. The GSZ operated over the entire period during which the footwall evolved from eclogite to greenschist facies and was therefore responsible for eclogite exhumation. The discrete contact zone between eclogite and greenschist facies rocks is the last active part of the GSZ and truncates greenschist facies folds in the footwall. These final movements were therefore not a major component of eclogite exhumation. Pressure estimates associated with old and young fabrics within the GSZ are comparable, indicating that during extensional deformation there was no significant unroofing of the hangingwall. Since there are no known extensional structures younger than 36 Ma at higher levels in this part of the Alps, exhumation since the final juxtaposition of the two units (at 36 Ma) seems to have been dominated by erosion.

Key words: deformation age, eclogite, exhumation, Rb–Sr dating, tectonic.
Hydration of eclogite, Pam Peninsula, New Caledonia
Authors: Carson  , Clarke  , Powell
Published: March 2003

Garnet glaucophanite and greenschist facies assemblages were formed by the recrystallization of barroisite‐bearing eclogite facies metabasites in northern New Caledonia. The mineralogical evolution can be modelled by calculated P–T and
P–XH2O diagrams for appropriate bulk rock compositions in the model system CaO–Na2O–FeO–MgO–Al2O3–SiO2–H2O. The eclogites, having developed in a clockwise P–T path that reached P≈19 kbar and T ≈590 °C, underwent decompression with the consumption of free H2O as the volume of hydrous minerals increased. Eclogite is preserved in domains that experienced no fluid influx following the loss of this fluid. Garnet glaucophanite formed at P≈16 kbar during semi‐pervasive fluid influx. Fluid influx, after further isothermal decompression, was focused in shear zones, and resulted in chlorite–albite‐bearing greenschist facies mineral assemblages that reflect P≈9 kbar.
The garnet–clinopyroxene Fe2+–Mg geothermometer: an updated calibration
Authors: Krogh Ravna
Published: March 2003

Multiple regression analysis on an extended dataset has been performed to refine the relationship between temperature, pressure, composition and the Fe–Mg distribution between garnet and clinopyroxene. In addition to a significant dependence between the distribution coefficientKDandXGrtCaandXGrtMg#, as shown by the experimental data, the effect ofXGrtMnhas also been incorporated using data from natural Mn‐rich garnet–clinopyroxene pairs. Multiple regression of data (n=360) covering a large span in pressure, temperature and composition from 27 experimental datasets, combined with 49 natural high‐Mn granulites from Ruby Range, Montana, USA, and Karnataka, India, yields theP–T –compositional relationship (r2=0.98):

whereKD=(Fe2+/Mg)Grt/(Fe2+/Mg)Cpx,XGrtCa=Ca/(Ca+Mn+Fe2++Mg) in garnet,XGrtMn= Mn/(Ca+Mn+Fe2++Mg) in garnet, andXGrtMg#=Mg/(Mg+Fe2+) in garnet. The Fe2+–Mg equilibrium between garnet and clinopyroxene does not seem to be affected by variations in the sodic content of the co‐existing clinopyroxene in the rangeXCpxNa=0–0.51. Comparisons between the new and former calibrations of the garnet–clinopyroxene Fe2+–Mg geothermometer clearly demonstrate how the various parameters in each case affect the calculated temperatures. Application of the new expression gives reasonable results for natural garnet–clinopyroxene pairs from various rock types and settings, and should be preferred to previous formulations. Using the new calibration to the self‐consistent dataset of Pattison & Newton (Contributions to Mineralogy and Petrology, 1989,101,87–103) suggests a systematic deviation with regard to both temperature and composition between their dataset and the datasets used in the present calibration.
A general model for the intrusion and evolution of ‘mantle’ garnet peridotites in high‐pressure and ultra‐high‐pressure metamorphic terranes
Authors: Brueckner  , Medaris
Published: March 2003

Garnet‐bearing peridotite lenses are minor but significant components of most metamorphic terranes characterized by high‐temperature eclogite facies assemblages. Most peridotite intrudes when slabs of continental crust are subducted deeply (60–120 km) into the mantle, usually by following oceanic lithosphere down an established subduction zone. Peridotite is transferred from the resulting mantle wedge into the crustal footwall through brittle and/or ductile mechanisms. These ‘mantle’ peridotites vary petrographically, chemically, isotopically, chronologically and thermobarometrically from orogen to orogen, within orogens and even within individual terranes. The variations reflect: (1) derivation from different mantle sources (oceanic or continental lithosphere, asthenosphere); (2) perturbations while the mantle wedges were above subducting oceanic lithosphere; and (3) changes within the host crustal slabs during intrusion, subduction and exhumation. Peridotite caught within mantle wedges above oceanic subduction zones will tend to recrystallize and be contaminated by fluids derived from the subducting oceanic crust. These ‘subduction zone peridotites’ intrude during the subsequent subduction of continental crust. Low‐pressure protoliths introduced at shallow (serpentinite, plagioclase peridotite) and intermediate (spinel peridotite) mantle depths (20–50 km) may be carried to deeper levels within the host slab and undergo high‐pressure metamorphism along with the enclosing rocks. If subducted deeply enough, the peridotites will develop garnet‐bearing assemblages that are isofacial with, and give the same recrystallization ages as, the eclogite facies country rocks. Peridotites introduced at deeper levels (50–120 km) may already contain garnet when they intrude and will not necessarily be isofacial or isochronous with the enclosing crustal rocks. Some garnet peridotites recrystallize from spinel peridotite precursors at very high temperatures (c. 1200 °C) and may derive ultimately from the asthenosphere. Other peridotites are from old (>1 Ga), cold (c. 850 °C), subcontinental mantle (‘relict peridotites’) and seem to require the development of major intra‐cratonic faults to effect their intrusion.
Super‐silicic garnet microstructures from an orogenic garnet peridotite, evidence for an ultra‐deep (>6 GPa) origin
Authors: Van Roermund  , Drury  , Barnhoorn  , De Ronde
Published: March 2003

We report the field, petrographic and mineral chemical characteristics of relict super‐silicic (=majoritic) garnet microstructures from the Otrøy peridotites in the Western Gneiss Region, Norway. The evidence for the former existence of super‐silicic garnet consists of two‐pyroxene exsolution microstructures from garnet. Estimates of the initial composition of the super‐silicic garnet imply pressures of 6–6.5 GPa, indicating that the Otrøy garnet peridotites were derived from depths >185 km. The garnet peridotites consist of inter‐banded variable compositions with c. 50% garnet peridotite and 50% garnet‐free peridotite. Two distinct garnet types were identified: (a) normal matrix garnet, grain‐size ≤4 mm, and (b) large isolated single garnet crystals and/or (polycrystalline) garnet nodules up to 10 cm in size. Large garnet nodules occur only within limited bands within the garnet peridotites. The relicts of super‐silicic garnet were exclusively found in some (not all) of the larger garnet nodules. Petrographic observations revealed that the microstructure of nodular garnet consists of the following four characteristic elements. (1) Individual garnet nodules are polycrystalline, with grain sizes of 2–8 mm. Garnet grain boundaries are straight with well‐defined triple junctions. (2) Some garnet triple junctions and garnet grain boundaries are decorated by interstitial orthopyroxene. (3) Cores of larger polycrystalline garnet contain two‐pyroxene exsolution microstructures. (4) Precipitation‐free rims (2 mm thick) surround garnet cores containing the exsolved pyroxene microstructure. Pyroxene exsolution from super‐silicic garnet was subsequently followed by brittle–ductile deformation of garnet. Both exsolved pyroxene needles and laths become undulous or truncated by fractures. Simultaneous garnet plasticity is indicated by the occurrence of high densities of naturally decorated dislocations. Transmission electron microscopy observations indicate that decoration is due to Ti‐oxide precipitation. Estimates of the P–T  conditions for mineral chemical equilibration were obtained from geothermobarometry. The mineral compositions equilibrated at mantle conditions around 805±40 °C and 3.2±0.2 GPa. These P–T  estimates correspond to cold continental lithosphere conditions at depths of around 105 km. From a combination of both depth estimates it can be concluded that the microstructural memory of the rock extends backwards to twice as great a depth range as obtained by thermobarometric methods. Available geochronological and geochemical data of Norwegian garnet peridotites suggest a multi‐stage, multi‐orogenic exhumation history.
The effect of TiO2 and Fe2O3 on metapelitic assemblages at greenschist and amphibolite facies conditions: mineral equilibria calculations in the system K2O–FeO–MgO–Al2O3–SiO2–H2O–TiO2–Fe2O3
Authors: White  , Powell  , Holland  , Worley
Published: March 2003

Mineral equilibria calculations in the system K2O–FeO–MgO–Al2O3–SiO2–H2O–TiO2–Fe2O3 (KFMASHTO) using thermocalc and its internally consistent thermodynamic dataset constrain the effect of TiO2 and Fe2O3 on greenschist and amphibolite facies mineral equilibria in metapelites. The end‐member data and activity–composition relationships for biotite and chloritoid, calibrated with natural rock data, and activity–composition data for garnet, calibrated using experimental data, provide new constraints on the effects of TiO2 and Fe2O3 on the stability of these minerals. Thermodynamic models for ilmenite–hematite and magnetite–ulvospinel solid solutions accounting for order–disorder in these phases allow the distribution of TiO2 and Fe2O3 between oxide minerals and silicate minerals to be calculated. The calculations indicate that small to moderate amounts of TiO2 and Fe2O3 in typical metapelitic bulk compositions have little effect on silicate mineral equilibria in metapelites at greenschist to amphibolite facies, compared with those calculated in KFMASH. The addition of large amounts of TiO2 to typical pelitic bulk compositions has little effect on the stability of silicate assemblages; in contrast, rocks rich in Fe2O3 develop a markedly different metamorphic succession from that of common Barrovian sequences. In particular, Fe2O3‐rich metapelites show a marked reduction in the stability fields of staurolite and garnet to higher pressures, in comparison to those predicted by KFMASH grids.
Metamorphism and microstructures along a high‐temperature metamorphic field gradient: the north–eastern boundary of the Královský hvozd unit (Bohemian Massif, Czech Republic)
Authors: Scheuvens D.
Published: March 2003

A metamorphic field gradient has been investigated in the Moldanubian zone of the central European Variscides encompassing, from base to the top, a staurolite–kyanite zone, a muscovite–sillimanite zone, a K‐feldspar–sillimanite zone, and a K‐feldspar–cordierite zone, respectively. The observed reaction textures in the anatectic metapsammopelites of the higher grade zones are fully compatible with experimental data and petrogenetic grids that are based on fluid‐absent melting reactions. From structural and microstructural observations it can be concluded that the boundary between the kyanite–staurolite zone and the muscovite‐ and K‐feldspar–sillimanite zones coincides with an important switch in deformation mechanism(s). Besides minor syn‐anatectic shearing (melt‐enhanced deformation), microstructural criteria point (a) to a switch in deformation mechanism from rotation recrystallization (climb‐accommodated dislocation creep) to prism  slip and high‐temperature (fast) grain boundary migration in quartz (b) to the activity of diffusion creep in quartz–feldspar layers, and (c) to accommodation of strain by intense shearing in fibrolite–biotite layers. It is suggested that any combination of these deformation mechanisms will profoundly affect the rheological characteristics of high‐grade metamorphic rocks and significantly lower rock strength. Hence, the boundary between these zones marks a major rheological barrier in the investigated cross section and probably also in other low‐ to medium‐pressure/high‐temperature areas. At still higher metamorphic grades (K‐feldspar‐cordierite zone), where the rheologically critical melt percentage is reached, rock rheology is mainly governed by the melt and other deformation mechanisms are of minor importance. In the study area, the switch in deformation mechanism(s) is responsible for large‐scale strain partitioning and concentration of deformation within the higher‐temperature hanging wall during top‐to‐the‐S thrusting, thus preserving a more complete petrostructural record within the rocks of the footwall including indications for a ?Devonian high‐ to medium‐pressure/medium‐temperature metamorphic event. Thrusting is accompanied by diapiric ascent of diatexites of the K‐feldspar‐cordierite zone and infolding of the footwall, suggesting local crustal overturn in this part of the Moldanubian zone.
Discovery of eclogite facies carbonate rocks from the Lindås Nappe, Caledonides, Western Norway
Authors: Boundy T. M. , Donohue C. L. , Essene E. J. , Mezger K. , Austrheim H.
Published: March 2003

Eclogite facies carbonate rocks have been discovered associated with the granulite–eclogite transitional rocks within Bergen Arc system, Caledonian Orogen of western Norway. The local occurrences of marbles and calc‐silicates are found subparallel to the mafic eclogite facies shear zones on Holsnøy Island. Marbles contain the assemblage calcite (Ca0.99Sr0.01CO3), calcian strontianite (Ca0.18−0.44Sr0.53−0.84CO3), clinopyroxene (Jd7−32), epidote/allanite (Ps0−33), titanite, garnet (Alm52−56Grs28−33Pyp11−16), barite (Ba0.90−0.99Sr0.01−0.10SO4), celestine (Sr0.67−0.98Ba0.01−0.23Ca0.01−0.11SO4), and one apparently homogeneous grain of intermediate composition (Ba0.49Ca0.01Sr0.50SO4). Adjacent eclogites have clinopyroxene with similar jadeite contents (Jd14−34) and similar garnet (Alm51−60Grs26−36Pyp8−14) compositions. The marbles have high contents of Sr (9500–11000 p.p.m) and Y (115–130 p.p.m). However, low concentrations of some key trace elements (110–160 p.p.m. Ba and <5 p.p.m. Nb) appear to indicate that the marble is not a metamorphosed carbonatite. The 87Sr/86Sr ratios range from 0.7051 to 0.7059. Field and petrological relationships suggest that metasomatic reactions and fluids played a significant role in producing and/or modifying the marbles. The breakdown of scapolite in the granulite into carbonates and sulphates during eclogite facies metamorphism may have contributed to the metasomatic formation of the marbles along shear zones.

Fluids involved during subduction are an important catalyst for metamorphism and are recognized to have played a critical role in the localized transformation from granulite to eclogite in the Holsnøy Island area. Thermobarometry indicates 640–690 °C and 18–20 kbar for adjacent eclogites and temperatures of 580–650 °C for the calc‐silicates. The marble assemblages are consistent with fluid that is dominantly comprised of H2O (XCO2 < 0.03) under high‐pressure conditions. Phase equilibria of the marbles constrain the fO2 of the fluids and imply oxidizing conditions of the deep crustal fluids. At present the source of the fluids remains unresolved. The results provide additional insights into the variable and evolving nature of fluids related to subduction and high‐pressure metamorphism.
The Tertiary collision‐related thermal history of the NW Himalaya
Authors: Foster G. , Vance D. , Argles T. , Harris N.
Published: March 2003

Garnet‐whole rock Sm‐Nd data are presented for several samples from the Indian plate in the NW Himalaya. These dates, when combined with the P‐T evolution of the Indian plate rocks, allow a thorough reconstruction of the prograde thermal evolution of this region (including the Nanga Parbat Haramosh Massif) during the early Cenozoic. Combining these data with Rb‐Sr mineral separate ages, enables us to constrain the post‐peak cooling history of this region of the Himalaya.

The data presented here indicate that the upper structural levels of the cover rocks of the Nanga Parbat Haramosh Massif, and similar rocks in the Kaghan Valley to the south‐west, were buried to pressures of c. 10 kbar and heated to temperatures of c. 650 °C at 46–41 Ma. The burial of the lower structural levels of the cover rocks of the Nanga Parbat Haramosh Massif, to similar depths but at higher temperatures of c. 700 °C, occurred slightly later at 40–36 Ma, synchronous with the imbrication and exhumation of the amphibolite‐ and eclogite‐grade rocks of the Kaghan Valley. In contrast, the cover rocks of the Nanga Parbat Haramosh Massif were not imbricated or exhumed at this time, remaining buried beneath the Kohistan‐Ladakh Island Arc until the syntaxis‐forming event that occurred in the last 10 Myr. The timing of tectonic events in the north‐western Himalaya differs from that experienced by the rocks of the Central Himalaya in that the earliest stage of burial in the NW Himalaya predates that of the Central Himalaya by c. 6 Myr. This difference may result from the diachronous nature of the Indo‐Asian collision or may simply be a reflection of differing timing at different structural levels.
Petrological and geochronological constraints on high pressure, high temperature metamorphism in the Snowbird tectonic zone, Canada
Authors: Baldwin J. A. , Bowring S. A. , Williams M. L.
Published: March 2003

The upper deck of the East Athabasca mylonite triangle (EAmt), northern Saskatchewan, Canada, contains mafic granulites that have undergone high P–T metamorphism at conditions ranging from 1.3 to 1.9 GPa, 890–960 °C. Coronitic textures in these mafic granulites indicate a near‐isothermal decompression path to 0.9 GPa, 800 °C. The Godfrey granite occurs to the north adjacent to the upper deck high P–T domain. Well‐preserved corona textures in the Godfrey granite constrain igneous crystallization and early metamorphism in the intermediate‐pressure granulite field (Opx + Pl) at 1.0 GPa, 775 °C followed by metamorphism in the high pressure granulite field (Grt + Cpx + Pl) at 1.2 GPa, 860 °C. U–Pb geochronology of zircon in upper deck mafic granulite yields evidence for events at both c. 2.5 Ga and c. 1.9 Ga. The oldest zircon dates are interpreted to constrain a minimum age for crystallization or early metamorphism of the protolith. A population of 1.9 Ga zircon in one mafic granulite is interpreted to constrain the timing of high P–T metamorphism. Titanite from the mafic granulites yields dates ranging from 1900 to 1894 Ma, and is interpreted to have grown along the decompression path, but still above its closure temperature, indicating cooling following the high P–T metamorphism from c. 960–650 °C in 4–10 Myr. Zircon dates from the Godfrey granite indicate a minimum crystallization age of 2.61 Ga, without any evidence for 1.9 Ga overgrowths. The data indicate that an early granulite facies event occurred at c. 2.55–2.52 Ga in the lower crust (c. 1.0 GPa), but at 1.9 Ga the upper deck underwent high P–T metamorphism, then decompressed to 0.9–1.0 GPa. Juxtaposition of the upper deck and Godfrey granite would have occurred after or been related to this decompression. In this model, the high P–T rocks are exhumed quickly following the high pressure metamorphism. This type of metamorphism is typically associated with collisional orogenesis, which has important implications for the Snowbird tectonic zone as a fundamental boundary in the Canadian Shield.
Ethical Issues in Dialysis, Series Editor: Aaron Spital,: Profit‐Making in the Treatment of Chronic Kidney Disease: Truth and Consequences
Authors: Garg Pushkal P. , Powe Neil R.
Published: March 2003

Many have speculated that the quality of dialysis care differs for patients treated in for‐profit and not‐for‐profit facilities. In 1999 we published a study that demonstrated poorer survival and lower rates of listing for renal transplant for patients in for‐profit rather than not‐for‐profit, freestanding centers. While these findings generated substantial discussion, few have commented on their implications. In this article we first discuss potential sources of bias that could impact on the study's results and place the findings in context. We conclude that these disparities are likely to be real, as they are consistent with theorized differences between for‐profit and not‐for‐profit health care organizations and with other evaluations of dialysis facility ownership. We then discuss several policy options for addressing the quality differences we identified. Reducing the outcome discrepancies will not be easy. Upon considering several policy alternatives, we conclude that a widespread effort to link processes of dialysis care to patient outcomes is best suited to reduce the quality differences between for‐profit and not‐for‐profit dialysis units and improve outcomes in both types of facilities.
Editorials: Dialysis Access Failure: An Indication for Immediate Kidney Transplantation
Authors: Laskow David A. , Ahsan Nasimul
Published: March 2003

In the United States, presently there are more than 50,000 patients with end‐stage renal disease (ESRD) awaiting a cadaveric kidney and each year less than a quarter receive kidney transplantation. Although the real incidence in unknown, a significant number of these patients die due to lack of dialysis access. While various medical necessities are indications for emergent transplantation of other organs, the current kidney allocation system of the United Network for Organ Sharing (UNOS) makes no room for those ESRD patients whose death is imminent due to lack of vascular access. Local organ procurement organizations (OPOs) are allowed to make decisions based on arbitrary policies (or no policies at all) which often falter and fail to deal appropriately with a largely ignored issue. The growing wait for cadaveric kidneys makes the problem of ESRD patients dying due to lack of dialysis access increasingly important and one that must be addressed through a revision of the UNOS kidney allocation system.
Intradialytic Hypotension: An Overview of Recent, Unresolved and Overlooked Issues
Authors: Sherman Richard A.
Published: March 2003

The etiology and management of intradialytic hypotension has become an increasingly complex issue. Volume depletion due to ultrafiltration remains the predominant underlying etiologic factor. However, patients vary markedly in their hemodynamic tolerance to fluid removal. While many risk factors have been identified, the issues of sodium and thermal balance and variability in left ventricular filling have not been adequately emphasized or investigated.
Epidemiology and Demographic Aspects of Treated End‐Stage Renal Disease in the Elderly
Authors: Krishnan Murali , Lok Charmaine E. , Jassal Sarbjit V.
Published: March 2003

Over the last 10 years an increasing number of patients worldwide have started dialysis or had transplantation. Many are elderly with complex comorbid conditions. Registries across the world all show a rapid and dramatic increase in the number of older patients accepted for renal replacement therapy. In addition, the number of patients who grow old on dialysis is increasing, leading to a marked change in the demographics of the renal population. Changes over time and across registries are discussed with reference to patient characteristics, survival statistics, and the trends seen with transplantation in the elderly.
Nutrition in Elderly Dialysis Patients
Authors: Wolfson Marsha
Published: March 2003

The end‐stage renal disease (ESRD) population is aging, and currently approximately 50% of patients treated with maintenance dialysis are more than 65 years old. With advancing age comes challenges to maintaining the nutritional status of these patients. As patients get older, purchasing and preparing food may become more difficult. In addition, appetite may decrease, the occurrence of intercurrent illnesses may become more frequent, and nutrient requirements change. Mobility may decline, as well as cognitive function, and the combination of several of these factors may result in malnutrition. Since malnutrition has been demonstrated to impact survival in dialysis patients of all ages, appropriate attention to nutritional status and its management is essential for the elderly dialysis patient. This article reviews the issues associated with the maintenance of good nutrition in the elderly dialysis patient and describes the potential causes of malnutrition in these patients. It also reviews the nutrient requirements for older dialysis patients (which differ somewhat from those of younger patients), as well as the assessment of their nutritional status. Finally, recommendations for management of nutrition in the elderly dialysis patient are discussed.
Congestive Heart Failure Due to Systolic Dysfunction: The Cinderella of Cardiovascular Management in Dialysis Patients
Authors: Ritz Eberhard , Dikow Ralf , Adamzcak Marcin , Zeier Martin
Published: March 2003

Cardiac disease is common in dialysis patients. Survival is poorest in the subgroup with systolic dysfunction (pump failure). Audits show that cardiovascular management of dialysis patients in general, and treatment of congestive heart failure (CHF) specifically, is generally not in agreement with recommendations based on evidence obtained from controlled trials, admittedly in nonrenal patients. The pathophysiology underlying CHF and the rationale underlying interventions are discussed in an effort to heighten awareness of this important clinical problem in the dialysis community.