Abstract
Arc lavas display elevated Fe
3+
/ΣFe ratios relative to MORB. One mechanism to explain this is the mobilization and transfer of oxidized or oxidizing components from the subducting slab to ...the mantle wedge. Here we use iron and zinc isotopes, which are fractionated upon complexation by sulfide, chloride, and carbonate ligands, to remark on the chemistry and oxidation state of fluids released during prograde metamorphism of subducted oceanic crust. We present data for metagabbros and metabasalts from the Chenaillet massif, Queyras complex, and the Zermatt‐Saas ophiolite (Western European Alps), which have been metamorphosed at typical subduction zone
P‐T
conditions and preserve their prograde metamorphic history. There is no systematic, detectable fractionation of either Fe or Zn isotopes across metamorphic facies, rather the isotope composition of the eclogites overlaps with published data for MORB. The lack of resolvable Fe isotope fractionation with increasing prograde metamorphism likely reflects the mass balance of the system, and in this scenario Fe mobility is not traceable with Fe isotopes. Given that Zn isotopes are fractionated by S‐bearing and C‐bearing fluids, this suggests that relatively small amounts of Zn are mobilized from the mafic lithologies in within these types of dehydration fluids. Conversely, metagabbros from the Queyras that are in proximity to metasediments display a significant Fe isotope fractionation. The covariation of δ
56
Fe of these samples with selected fluid mobile elements suggests the infiltration of sediment derived fluids with an isotopically light signature during subduction.
Key Points
Iron and zinc stable isotope and elemental data are presented for a prograde suite of metabasalts and metagabbros from Western Alpine ophiolite complexes
Bulk rock δ
56
Fe and δ
66
Zn do not vary across metamorphic facies and the eclogitic samples show a MORB‐like isotope composition
Blueschist facies metagabbros preserve evidence for infiltration of sediment derived fluids that impart a light δ
56
Fe isotope composition to the gabbro
Between 6-20% of the cellular proteome is under circadian control and tunes mammalian cell function with daily environmental cycles. For cell viability, and to maintain volume within narrow limits, ...the daily variation in osmotic potential exerted by changes in the soluble proteome must be counterbalanced. The mechanisms and consequences of this osmotic compensation have not been investigated before. In cultured cells and in tissue we find that compensation involves electroneutral active transport of Na
, K
, and Cl
through differential activity of SLC12A family cotransporters. In cardiomyocytes ex vivo and in vivo, compensatory ion fluxes confer daily variation in electrical activity. Perturbation of soluble protein abundance has commensurate effects on ion composition and cellular function across the circadian cycle. Thus, circadian regulation of the proteome impacts ion homeostasis with substantial consequences for the physiology of electrically active cells such as cardiomyocytes.
Multiple system atrophy is a sporadic, progressive, neurodegenerative disease characterized by an oligodendroglial accumulation of alpha-synuclein (α-syn). The mechanisms underlying the ...oligodendroglial accumulation of α-syn in the brains of patients with multiple system atrophy have attracted a great deal of interest, given the primarily neuronal role reported for this protein. We examined the interactions between neuronal and oligodendroglial α-syn in the progeny of crosses between parental transgenic (tg) mouse lines that express α-syn either under the oligodendroglial-specific myelin-basic protein promoter (MBP1-hα-syn tg) or under the neuronal platelet-derived growth factor promoter (PDGF-hα-syn tg). Our results demonstrate that progeny from the cross hα-syn double (dbl) tg mice displayed a robust redistribution of α-syn accumulation, with a relocalization from a neuronal or a mixed neuronal/oligodendroglial α-syn expression to a more oligodendroglial pattern in both the neocortex and the basal ganglia that closely resembled the parental MBP-hα-syn tg line. The hα-syn dbl tg mice also displayed motor deficits, concomitant with reduced levels of tyrosine hydroxylase and augmented neuropathological alterations in the basal ganglia. These results suggest that the central nervous system milieu in the hα-syn dbl tg mice favors an oligodendroglial accumulation of α-syn. This model represents an important tool to examine the interactions between neuronal and oligodendrocytic α-syn in diseases such as multiple system atrophy.
Multiple systems atrophy (MSA) is a neurodegenerative disorder characterized by oligodendrocytic accumulations of alpha-synuclein (alphasyn). Oxidative stress is a key mechanism proposed to underlie ...MSA pathology. To address the role of alphasyn modifications, over and above general oxidative modifications, this study examined the effects of 3-nitropropionic acid (3NP) administration, a technique used to model MSA, in knock-out mice lacking alphasyn (alphasynKO). Although susceptible to 3NP-induced oxidative stress, alphasynKO mice display reduced neuronal loss and dendritic pathology. The alphasynKO mice are resistant to 3NP-induced motor deficits and display attenuated loss of tyrosine hydroxylase and dopamine transporter striatal immunoreactivity. The results suggest that deficits in MSA are not due to general oxidative protein modification but in addition may be related to specific alphasyn modifications.
In most filamentous fungi, telomere-associated sequences (TASs) are polymorphic, and the presence of restriction fragment length polymorphisms (RFLPs) may permit the number of chromosome ends to be ...estimated from the number of telomeric bands obtained by restriction digestion. Here, we describe strains of Metarhizium, Gliocladium and Paecilomyces species in which only one or a few telomeric bands of unequal intensity are detectable by Southern hybridization, indicating that interchromosomal TAS exchange occurs. We also studied an anomalous strain of Metarhizium anisopliae, which produces polymorphic telomeric bands larger than 8 kb upon digestion of genomic DNA with XhoI. In this case, the first XhoI site in from the chromosome end must lie beyond the presumed monomorphic region. Cloned telomeres from this strain comprise 18-26 TTAGGG repeats, followed at the internal end of the telomere tract by five repeats of the telomere-like sequence TAAACGCTGG. An 8.1-kb TAS clone also contains a gene for a RecQ-like helicase, designated TAH1, suggesting that this TAS is analogous to the Y' elements in yeast and the subtelomeric helicase ORFs of Ustilago maydis (UTASRecQ) and Magnaporthe grisea (TLH1). The TAS in the anomalous strain of M. anisopliae, however, appears distinct from these in that it is found at most telomeres and its predicted protein product possesses a significantly longer N-terminal region in comparison to the M. grisea and U. maydis helicases. Hybridization analyses showed that TAH1 homologues are present in all other anomalous M. anisopliae strains studied, as well as in some other polymorphic strains, where the recQ-like gene also appears to be telomere-associated.
Domoic acid (DA) is a naturally occurring neurotoxin harmful to marine animals and humans. California sea lions exposed to DA in prey during algal blooms along the Pacific coast exhibit significant ...neurological symptoms, including epilepsy with hippocampal atrophy.
Here the authors describe a xenotransplantation procedure to deliver interneuron progenitor cells into the damaged hippocampus of an epileptic sea lion with suspected DA toxicosis. The sea lion has had no evidence of seizures after the procedure, and clinical measures of well-being, including weight and feeding habits, have stabilized.
These preliminary results suggest xenotransplantation has improved the quality of life for this animal and holds tremendous therapeutic promise.
One hundred eight GUEPAR knee arthroplasties have been studied with a follow-up of one year on 41; 2 years on 22 and 3 years on 45 knees. Overall results were 17% excellent, 44% good, 10% fair and ...29% poor. Excellent results were comparatively fewer in rheumatoid arthritis. There was a deterioration in the quality of results of arthroplasty with longer follow-up. The incidence of deep infection was 11%. There was a significant correlation between early wound drainage and deep infection. More than half of the infected knees have not required intervenition as yet. One knee was revised and 3 had attempted arthrodesis with one successful fusion. Two patients died with septicemia. Axle migration occurred in 8 knees and femoral stem breakage in 2 knees. Loosening was found in 27% of the knees with progressive reduction in quality of the arthroplasty. Incomplete cementing predisposed to loosening. Patellar symptoms were present in 28% of the knees. Patellar subluxation and dislocation occurred in 49% of the knees. More than half of these were symptomatic. With normal patellofemoral alignment, pain was more common in the osteoarthritic knee. Use of a patellar implant with GUEPAR knee prostesis should be restricted to severely disabled patients with major fixed deformities. Mechanical failure can be minimized by proper positioning of the implant, correct alignment of the extensor mechanism and adequate cement around the entire stem.
Discectomy is the surgery of choice for the lumbosacral radicular syndrome. Previous studies on the postsurgical management of these cases compare one exercise regime to another. This study compares ...an exercise-based group with a control group involving no formal exercise or rehabilitation.
The outcomes of a formal postsurgical exercise-based rehabilitation when compared with the usual rehabilitative surgical advice were evaluated.
A randomized clinical trial comparing management regimes after lumbar discectomies.
Ninety-three lumbar discectomy patients were randomized to two groups.
The following postoperative outcomes were used: levels of pain; levels of function; psychological well-being; time off work; levels of medication; and number of doctor/therapist visits.
Ninety-three lumbar discectomy patients were randomized to two groups. The treatment group undertook a 6-month supervised nonaggravating exercise program. The control group followed the usual surgical advice to resume normal activities as soon as the pain allowed. Both groups were followed for 1 year by using validated outcome measures.
The results are based on an intention-to-treat analysis. Patients in both groups improved during the 1-year follow-up (p=.001). There was no statistical significance between the groups at the clinical endpoint. The treatment group returned to work 7 days earlier and had fewer days off work in the 1-year follow-up period.
There was no statistical advantage gained by the group that performed the 6-month supervised nonaggravating exercise program at 1-year follow-up. They did, however, have fewer days off work.
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