1,023 research outputs found
Characterization of iodothyronine sulfotransferase activity in rat liver
Sulfation is an important pathway in the metabolism of thyroid hormone
because it strongly facilitates the degradation of the hormone by the type
I iodothyronine deiodinase. However, little is known about the properties
and possible regulation of the sulfotransferase(s) involved in the
sulfation of thyroid hormone. We have developed a convenient method for
the analysis of iodothyronine sulfotransferase activity in tissue
cytosolic fractions, using radioiodinated 3,3'-diiodothyronine (3,3'-T2)
as the preferred substrate, unlabeled
3'-phosphoadenosine-5'-phosphosulfate (PAPS) as the sulfate donor, and
Sephadex LH-20 minicolomns for separation of the products. We found that
iodothyronine sulfotransferase activity in rat liver cytosol is 1) higher
in male than in female rats; 2) optimal at pH 8.0; 3) characterized (at 50
microM PAPS and pH 7.2) by apparent Michaelis-Menton (Km) values for
3,3'-T2 of 1.77 and 4.19 microM, and Vmax values of 1.94 and 1.45 nmol/min
per mg protein in male and female rats, respectively; 4) characterized (at
1 microM 3,3'-T2 and pH 7.2) by apparent Km values for PAPS of 4.92 and
3.80 microM and Vmax values of 0.72 and 0.31 nmol/min per mg protein, in
males and females, respectively; 5) little affected by hyperthyroidism in
both male and female rats, but significantly decreased by hypothyroidism
in males but not in females; and 6) not affected by short-term (3 days)
fasting in both male and female rats, but significantly decreased by
long-term (3 weeks) food restriction to one-third of normal intake in
males but not in females. It is suggested that the higher hepatic
iodothyronine sulfotransferase activity in male vs. female rats, as well
as the decreases induced in males by hypothyroidism and long-term food
restriction, represents differences in the expression of the male-dominant
isoenzyme rSULT1C1
Chandra observations of the bursting X-ray transient SAX J1747.0-2853 during low-level accretion activity
We present Chandra/ACIS observations of the bursting X-ray transient SAX
J1747.0-2853 performed on 18 July 2001. We detected a bright source at the
position of R.A = 17^h 47^m 02.60^s and Dec. = -28 52' 58.9'' (J2000.0; with a
1 sigma error of ~0.7 arcseconds), consistent with the BeppoSAX and ASCA
positions of SAX J1747.0-2853 and with the Ariel V position of the transient GX
+0.2,-0.2, which was active during the 1970's. The 0.5-10 keV luminosity of the
source during our observations was ~3 x 10^{35} erg/s (assuming a distance of 9
kpc) demonstrating that the source was in a low-level accretion state. We also
report on the long-term light curve of the source as observed with the all sky
monitor aboard the Rossi X-ray Timing Explorer. After the initial 1998
outburst, two more outbursts (in 2000 and 2001) were detected with peak
luminosities about two orders of magnitude larger than our Chandra luminosity.
Our Chandra observation falls in-between those two outbursts, making the
outburst history for SAX J1747.0-2853 complex. Those bright 2000 and 2001
outbursts combined with the likely extended period of low level activity
in-between those outbursts strongly suggest that the classification of SAX
J1747.0-2853 as a faint X-ray transient was premature. It might be possible
that the other faint X-ray transients also can exhibit bright, extended
outbursts which would eliminate the need for a separate sub-class of X-ray
transients. We discuss our results also in the context of the behavior of X-ray
binaries accreting at low levels with luminosities around 10^{35} erg/s, a
poorly studied accretion rate regime.Comment: Accepte for publication in ApJ, 11 July 200
Leiderschap in ethiek
Het goede doen met de goede redenen. Dat is waar ethiek over gaat.
Wat betekent dat in de praktijk? Het raakt aan de waarden waar een
bedrijf of persoon voor staat en ook aan waardengedreven ondernemerschap.
En dus raakt het aan de essentie van ondernemen.
In deze publicatie vindt u inspirerende voorbeelden van ondernemers die
werk maken van ethiek, zowel vanuit grote bedrijven als vanuit het MKB.
Zij creëren een bedrijfscultuur waarin duidelijk is vanuit welke waarden
het bedrijf opereert. Een cultuur waarin mensen elkaar aanspreken op
hun handelen en elkaar inspireren om stappen voorwaarts te zetten.
Ook wordt ingegaan op leiderschap in ethiek waarbij een nieuwe norm
wordt gesteld waarin anderen meegaan. Maar hoe doe je dat en wat
levert het op? U leest er in deze publicatie meer over met handreikingen
om zelf mee aan de slag te gaan en stof voor reflectie
BeppoSAX measurements of the bright gamma-ray burst 010222
We analyze the BeppoSAX measurements of the prompt and afterglow emission of
the gamma-ray burst GRB010222. Among 45 GRBs detected with the Wide Field
Cameras on BeppoSAX, the 40-700 keV fluence of (9.3+/-0.3)E-5 erg cm-2 is only
surpassed by GRB990123. In terms of the isotropic 20-2000 keV energy output of
7.8E53 erg, it ranks third of all GRBs with measured distances. Since this
burst is so bright, the data provide complete and valuable coverage up to 65 hr
after the event, except for a gap between 3.5 and 8.0 hr. The 2-10 keV flux
history shows clear signs of a break which is consistent with a break seen in
the optical, and provides supporting evidence for the achromatic nature of the
break. An explanation for the break in the context of a collimated expansion is
not straightforward. Rather, a model is favored whereby the fireball is braked
to the non-relativistic regime quickly (within a fraction of day) by a dense
1E6 cm-3 circumburst medium. This implies that, after a mild beaming
correction, GRB010222 may be the most energetic burst observed thus far. The
X-ray decay index after the break is 1.33+/-0.04, the spectral index
0.97+/-0.05. The decay is, with unprecedented accuracy, identical to that
observed in the optical.Comment: Accepted on June 6 for publication in ApJ part I. Publication due in
October 2001. Accepted version has only minor modification
Influence of spin 1/2 hetero-nuclei on spin relaxation and polarization transfer among strongly coupled protons
Effects of spin-spin interactions on the nuclear magnetic relaxation
dispersion (NMRD) of protons were studied in a situation where spin ½ hetero-
nuclei are present in the molecule. As in earlier works [K. L. Ivanov, A. V.
Yurkovskaya, and H.-M. Vieth, J. Chem. Phys.129, 234513
(2008)10.1063/1.3040272;S. E. Korchak, K. L. Ivanov, A. V. Yurkovskaya, and
H.-M. Vieth, J. Chem. Phys.133, 194502 (2010)10.1063/1.3495988], spin-spin
interactions have a pronounced effect on the relaxivity tending to equalize
the longitudinal relaxation times once the spins become strongly coupled at a
sufficiently low magnetic field. In addition, we have found influence of 19F
nuclei on the proton NMRD, although in the whole field range, studied protons
and fluorine spins were only weakly coupled. In particular, pronounced
features in the proton NMRD were found; but each feature was predominantly
observed only for particular spin states of the hetero-nuclei. The features
are explained theoretically; it is shown that hetero-nuclei can affect the
proton NMRD even in the limit of weak coupling when (i) protons are coupled
strongly and (ii) have spin-spin interactions of different strengths with the
hetero-nuclei. We also show that by choosing the proper magnetic field
strength, one can selectively transfer proton spin magnetization between
spectral components of choice
Thyroid function and deiodinase activities in rats with marginal iodine deficiency
The hypothesis tested was whether marginal iodine deficiency for a period of 6 wk affects iodothyronine deiodinase activities in liver and brain of rats. Male rats were fed purified diets either deficient or sufficient in iodine; the diets were fed on a restricted basis (60% of ad libitum intake). Body weight gain of the two groups was comparable. Iodine deficiency was evidenced by increased thyroid weight (26%), reduced urinary iodine excretion (80%), and reduced plasma T4 concentrations (22%). Activities of liver type I and brain type III deiodinase were unchanged, but the activity of type II deiodinase in brain was increased (28%) in the iodine-deficient rats. Food restriction per se significantly lowered T3 (30%) and T4 (22%) concentrations in plasma and decreased type III deiodinase activity in brain (30%). These results indicate that in marginal iodine deficiency the activities of hepatic type I deiodinase and brain type III deiodinase are unchanged, whereas that of brain type II deiodinase is increased
Isotopic analysis of Solenopsis geminata diets in invaded Indonesian savanna.
OBJECTIVE: To examine the extent to which smokers express negative statements about quitting and the extent to which these statements influence general practitioners' (GPs') and practice nurses' (PNs') (dis)continuation of guideline-recommended smoking cessation care. METHODS: Fifty-two video-consultations were observed (GP-consultations: 2007-2008; PN-consultations: 2010-2011). Dialogues were transcribed verbatim and professionals' and patients' speech units were coded and analysed using sequential analyses (n=1424 speech units). RESULTS: GPs focused on asking about smoking (GPs: 42.4% versus PNs: 26.2%, p=0.011) and advising them to quit (GPs: 15.3% versus PNs: 3.5%, p<0.001), whereas PNs focused on assisting them with quitting (GPs: 25.4% versus PNs: 55.2%, p<0.001). Overall, patients expressed more negative statements about quitting than positive statements (negative: 25.3% versus positive: 11.9%, p<0.001), especially when PNs assessed their willingness to quit (OR 3.61, 95% CI 1.44-9.01) or assisted them with quitting (OR 2.23, 95% CI 1.43-3.48). PRACTICE IMPLICATIONS: An alternative approach to smoking cessation care is proposed in which GPs' tasks are limited to asking, advising, and arranging follow-up. This approach seems the least likely to evoke negative statements of patients about quitting during dialogues with GPs and is compatible with the tasks and skills of PNs who could, subsequently, assist smokers with quitting
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