326 research outputs found
Pyrimidine Pathway-Dependent and -Independent Functions of the Toxoplasma gondii Mitochondrial Dihydroorotate Dehydrogenase
Dihydroorotate dehydrogenase (DHODH) mediates the fourth step of de novo pyrimidine biosynthesis and is a proven drug target for inducing immunosuppression in therapy of human disease as well as a rapidly emerging drug target for treatment of malaria. In Toxoplasma gondii, disruption of the first, fifth, or sixth step of de novo pyrimidine biosynthesis induced uracil aux- otrophy. However, previous attempts to generate uracil auxotrophy by genetically deleting the mitochondrion-associated DHODH of T. gondii (Tg DHODH) failed. To further address the essentiality of Tg DHODH, mutant gene alleles deficient in Tg DHODH activity were designed to ablate the enzyme activity. Replacement of the endogenous DHODH gene with catalytically deficient DHODH gene alleles induced uracil auxotrophy. Catalytically deficient Tg DHODH localized to the mitochondria, and parasites retained mitochondrial membrane potential. These results show that Tg DHODH is essential for the synthesis of pyrimidines and suggest that Tg DHODH is required for a second essential function independent of its role in pyrimidine biosynthesis
A potential mouse model for the erosive vitreoretinopathy of Wagner disease
Patients with the very rare eye pathology Wagner disease (OMIM #143200) present with an abnormal (empty) vitreous, retinal detachment and altered electroretinogram (ERG). The disease is progressive and can eventually lead to blindness. No therapy can be offered to date. The genetic basis is the presence of mutations in the VCAN gene, encoding the large extracellular matrix molecule versican, which is a component of the vitreous. All identified mutations map to the canonical splice sites flanking exon 8, resulting in low number of aberrant splice products and a severe increase in two (V2, V3) of the four naturally occurring splice variants. The pathomechanism of Wagner's disease is poorly understood and a mouse model may afford further insight. The hdf -/- mice, named for their initial phenotype of heart defects, carry a null allele for Vcan that leads to embryonic lethality when homozygous, but heterozygote animals are viable. Here we investigated a possible eye phenotype in the heterozygous animals. While the overall morphology of retina and ciliary body appears to be normal, older (17 months) mutant animals show a decrease in ERG signaling profiles affecting the a-, b- and c-waves. This aspect of altered ERG profile demonstrates similarities to the human disease manifestation and underlines the suitability of heterozygous hdf+/- mice as a model for Wagner disease
Hjort i Hedmark: Resultater fra GPS-merking 2002â2011
Prosjektet Hjort i Hedmark var en del av samarbeidsprosjektet HjortAreal, som undersĂžkte hjortens arealbruk,
Ăžkologisk bĂŠrekraft og hjort som nĂŠring i MĂžre & Romsdal og SĂžr-TrĂžndelag, Sogn i Hordaland, Buskerud,
Haugalandet i Rogaland/Hordaland og Hedmark. StudieomrÄdet i Hedmark hadde en unik posisjon i prosjektet fordi
det representerte et ytterpunkt i forhold til klima, landskapsstruktur og tetthet av elg (Alces alces). Vi undersĂžkte
Hedmarkshjortens trekkmĂžnster og habitatbruk og da spesielt bruken av innmark og foringsplasser. Hjortemerking
med GPS radiosendere begynte i Hedmark i 2002 og ble avsluttet vinteren 2011. Det ble totalt merket 51 hinder og
vi fikk bra nok data fra 48 hinder.
Sammenlignet med de andre studieomrÄdene i HjortAreal-prosjektet var andelen trekkdyr hÞyest i Hedmark, der hele
96 % av hjortehindene var trekkdyr, og kun 4 % stasjonÊre. OgsÄ trekkavstandene var lengst i Hedmark. Hjorten
trakk i gjennomsnitt 36.7 ± 7.5 km (2 SE) og tre av hjortene hadde sine respektive sommeromrÄder rundt 100 km
i luftlinje fra merkeplassen. Trekktidene er noksÄ sammenlignbare over hele SÞr-Norge, med vÄrtrekket i lÞpet av
april-mai og hĂžsttrekket i august-september.
Det var stor variasjon pÄ stÞrrelse av bÄde vinter- og sommeromrÄde. Gjennomsnittlig var vinteromrÄde og
sommeromrĂ„de pĂ„ henholdsvis 18.8 km2ÂŹ (minst â stĂžrst 1.9â83.0 km2) og 22.9 km2 (1.7â98.0 km2). Avhengig av
hvor hindene hadde sine vinteromrÄder trakk de enten til hÞyereliggende eller lavereliggende sommeromrÄde, eller
vinter- og sommeromrÄdene overlappet hverandre.
Hjortens omrÄdebruk ble styrt av menneskeskapte matressurser. Hele 10.5 % av posisjonene var knyttet til
menneskeskapte konsentrasjoner av mat, enten de var innen 100 m av nÊrmeste foringsplass (3.1 %), eller pÄ
innmark (7.4 %). I mÄnedsskifte februar-mars var en tredjedel av alle GPS-posisjonene knyttet til foringsplasser.
NĂ„r bruken av foringsplasser avtok utover vinteren, fikk innmark mer og mer betydning. Innmarksarealet dekket
gjennomsnittlig 3.4 ± 1.3 % (2 SE) av sommerleveomrÄdene, og tilgangen varierte sterkt mellom hindene og
omrÄdene. Hindene oppholdt seg lenger enn forventet pÄ innmark nattestid mens de brukte mindre tid enn forventet
pÄ innmark pÄ dagtid.
Samtlige foringsplasser i hoveddalfĂžret langs Glomma i Stor-Elvdal og Rendalen kommuner hadde spor etter hjort,
men ingen av foringsplassene hadde hÞye tettheter av bÄde elg og hjort. Vi kan kun spekulere hvorvidt foring av elg
har vĂŠrt en medvirkende Ă„rsak for den nylige Ăžkningen i hjortebestanden i Hedmark.
Vi har diskutert bÄde plantefenologi-, konkurranse-, sosial barriere- og antipredator-hypotesen som en forklaring for
Hedmarkhjortens trekkatferd med lange avstander og stor andel av trekkende dyr. Det kan tenkes et samspill av flere
av disse hypotesene som grunnlag for at andel trekkdyr er hĂžyest og trekkrutene er lengst i Hedmark sammenlignet
med de andre studieomrÄdene.
Som delvis trekkende art kan hjorten utfordre forvaltningen. Fordi hjorten stort sett er tilbake pÄ vinteromrÄdene til
jaktstart, kan kommune eller jaktvald vĂŠre tilstrekkelig forvaltningsenhet, men ved en mer helthetlig forvaltning som
tar hensyn til biologisk mangfold, vern av kalvingsomrÄder og tiltak mot viltulykker, bÞr den romlige forvaltningsenheten
vÊre pÄ regionalt nivÄ
Hjortens trekkmĂžnster skaper forvaltningsutfordringer i Hedmark
Jaktstatistikken fra Hedmark fylke tilsier at hjorten er tilbake for godt i
Hedmark og befinner seg i en sterk vekstfase. Med det fĂžlger mange forvaltningsutfordringer.
Vi har studert hjortens forflytningsmĂžnster og
trekkatferd ved Ä merke 51 hinder med GPS pÄ fire merkeplasser i henholdsvis
Rendalen, Stor-Elvdal, Ă
mot og Stange kommune. De aller fleste
hindene oppholdt seg i et sommeromrÄde som var atskilt fra vinteromrÄdet.
Avstanden mellom de to omrÄdene var gjennomsnittlig lenger enn
for hinder merket pÄ Vest- og SÞrlandet. For tre av hindene var avstanden
rundt 100 km. PĂ„ trekkruten var hindene innom forskjellige kommuner,
og totalt ble vÄrt studieomrÄde utvidet fra de fire vinterkommunene til
29 kommuner for hele Ă„ret. Vi anbefaler derfor en mer regional forvaltning
av hjorten enn dagens forvaltning pÄ eiendoms- eller kommunenivÄ.
Innmark og fĂŽringsplasser ble flittig brukt av hindene, og da spesielt
nattestid.
OvervÄkning av fÎringsplasser for elg som opprinnelig ble
etablert for Ă„ redusere trafikkulykker og beiteskader i skogen, viste at
hjorten var til stede pÄ samtlige plasser langs Glommas hoveddalfÞre i
Stor-Elvdal og Rendalen kommuner. Mye tyder pÄ at hjorten har tatt over flere plasser, og at elg og hjort til en viss grad unngikk hverandre i tid og
rom. Det kan tenkes at hjorten kan minske den Ăžnskede effekten av vinterfĂŽring
av elg. Hvis vinterfĂŽring skal fortsette, anbefaler vi Ă„ legge ut
flere siloballer samtidig per fĂŽringsplass for Ă„ sikre elgens tilgang til fĂŽr
Low aerobic mitochondrial energy metabolism in poorly- or undifferentiated neuroblastoma
<p>Abstract</p> <p>Background</p> <p>Succinate dehydrogenase (SDH) has been associated with carcinogenesis in pheochromocytoma and paraganglioma. In the present study we investigated components of the oxidative phosphorylation system in human neuroblastoma tissue samples.</p> <p>Methods</p> <p>Spectrophotometric measurements, immunohistochemical analysis and Western blot analysis were used to characterize the aerobic mitochondrial energy metabolism in neuroblastomas (NB).</p> <p>Results</p> <p>Compared to mitochondrial citrate synthase, SDH activity was severely reduced in NB (n = 14) versus kidney tissue. However no pathogenic mutations could be identified in any of the four subunits of SDH. Furthermore, no genetic alterations could be identified in the two novel SDH assembly factors SDHAF1 and SDH5. Alterations in genes encoding nfs-1, frataxin and isd-11 that could lead to a diminished SDH activity have not been detected in NB.</p> <p>Conclusion</p> <p>Because downregulation of other complexes of the oxidative phosphorylation system was also observed, a more generalized reduction of mitochondrial respiration seems to be present in neuroblastoma in contrast to the single enzyme defect found in hereditary pheochromocytomas.</p
Selective Attenuation of Norepinephrine Release and Stress-Induced Heart Rate Increase by Partial Adenosine A1 Agonism
The release of the neurotransmitter norepinephrine (NE) is modulated by presynaptic adenosine receptors. In the present study we investigated the effect of a partial activation of this feedback mechanism. We hypothesized that partial agonism would have differential effects on NE release in isolated hearts as well as on heart rate in vivo depending on the genetic background and baseline sympathetic activity. In isolated perfused hearts of Wistar and Spontaneously Hypertensive Rats (SHR), NE release was induced by electrical stimulation under control conditions (S1), and with capadenoson 6 · 10â8 M (30 ”g/l), 6 · 10â7 M (300 ”g/l) or 2-chloro-N6-cyclopentyladenosine (CCPA) 10â6 M (S2). Under control conditions (S1), NE release was significantly higher in SHR hearts compared to Wistar (766+/â87 pmol/g vs. 173+/â18 pmol/g, p<0.01). Capadenoson led to a concentration-dependent decrease of the stimulationâinduced NE release in SHR (S2/S1â=â0.90±0.08 with capadenoson 6 · 10â8 M, 0.54±0.02 with 6 · 10â7 M), but not in Wistar hearts (S2/S1â=â1.05±0.12 with 6 · 10â8 M, 1.03±0.09 with 6 · 10â7 M). CCPA reduced NE release to a similar degree in hearts from both strains. In vivo capadenoson did not alter resting heart rate in Wistar rats or SHR. Restraint stress induced a significantly greater increase of heart rate in SHR than in Wistar rats. Capadenoson blunted this stress-induced tachycardia by 45% in SHR, but not in Wistar rats. Using a [35S]GTPÎłS assay we demonstrated that capadenoson is a partial agonist compared to the full agonist CCPA (74+/â2% A1-receptor stimulation). These results suggest that partial adenosine A1-agonism dampens stress-induced tachycardia selectively in rats susceptible to strong increases in sympathetic activity, most likely due to a presynaptic attenuation of NE release
Measurement of the cosmic ray spectrum above eV using inclined events detected with the Pierre Auger Observatory
A measurement of the cosmic-ray spectrum for energies exceeding
eV is presented, which is based on the analysis of showers
with zenith angles greater than detected with the Pierre Auger
Observatory between 1 January 2004 and 31 December 2013. The measured spectrum
confirms a flux suppression at the highest energies. Above
eV, the "ankle", the flux can be described by a power law with
index followed by
a smooth suppression region. For the energy () at which the
spectral flux has fallen to one-half of its extrapolated value in the absence
of suppression, we find
eV.Comment: Replaced with published version. Added journal reference and DO
Energy Estimation of Cosmic Rays with the Engineering Radio Array of the Pierre Auger Observatory
The Auger Engineering Radio Array (AERA) is part of the Pierre Auger
Observatory and is used to detect the radio emission of cosmic-ray air showers.
These observations are compared to the data of the surface detector stations of
the Observatory, which provide well-calibrated information on the cosmic-ray
energies and arrival directions. The response of the radio stations in the 30
to 80 MHz regime has been thoroughly calibrated to enable the reconstruction of
the incoming electric field. For the latter, the energy deposit per area is
determined from the radio pulses at each observer position and is interpolated
using a two-dimensional function that takes into account signal asymmetries due
to interference between the geomagnetic and charge-excess emission components.
The spatial integral over the signal distribution gives a direct measurement of
the energy transferred from the primary cosmic ray into radio emission in the
AERA frequency range. We measure 15.8 MeV of radiation energy for a 1 EeV air
shower arriving perpendicularly to the geomagnetic field. This radiation energy
-- corrected for geometrical effects -- is used as a cosmic-ray energy
estimator. Performing an absolute energy calibration against the
surface-detector information, we observe that this radio-energy estimator
scales quadratically with the cosmic-ray energy as expected for coherent
emission. We find an energy resolution of the radio reconstruction of 22% for
the data set and 17% for a high-quality subset containing only events with at
least five radio stations with signal.Comment: Replaced with published version. Added journal reference and DO
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