1,455 research outputs found
Long-term low-dose ketoconazole treatment in bilateral macronodular adrenal hyperplasia
Medical therapy for Cushing's syndrome due to bilateral macronodular adrenal hyperplasia (BMAH) is generally administered for a limited time before surgery. Aberrant receptors antagonists show inconsistent efficacy in the long run to prevent adrenalectomy. We present a patient with BMAH, treated for 10 years with low doses of ketoconazole to control cortisol secretion. A 48-year-old woman presented with headaches and hypertension. Investigations showed the following: no clinical signs of Cushing's syndrome; enlarged lobulated adrenals; normal creatinine, potassium, and aldosterone; normal urinary aldosterone and metanephrines; elevated urinary free cortisol and steroid metabolites; and suppressed plasma renin activity and ACTH. A screening protocol for aberrant adrenal receptors failed to show any illegitimate hormone dependence. Ketoconazole caused rapid normalisation of cortisol and ACTH that persists over 10 years on treatment, while adrenals show no change in shape or size. Ketoconazole decreases cortisol in patients with Cushing's syndrome, and may prevent adrenal overgrowth. Steroid secretion in BMAH is inefficient as compared with normal adrenals or secreting tumours and can be controlled with low, well-tolerated doses of ketoconazole, as an alternative to surgery.
LEARNING POINTS: Enlarged, macronodular adrenals are often incidentally found during the investigation of hypertension in patients harboring BMAH. Although laboratory findings include low ACTH and elevated cortisol, the majority of patients do not display cushingoid features.Bilateral adrenalectomy, followed by life-long steroid replacement, is the usual treatment of this benign condition, and alternative medical therapy is sought. Therapy based on aberrant adrenal receptors gives disappointing results, and inhibitors of steroidogenesis are not always well tolerated.However, ketoconazole at low, well-tolerated doses appeared appropriate to control adrenal steroid secretion indefinitely, while preventing adrenal overgrowth. This treatment probably constitutes the most convenient long-term alternative to surgery
Fluctuations in the Irreversible Decay of Turbulent Energy
A fluctuation law of the energy in freely-decaying, homogeneous and isotropic
turbulence is derived within standard closure hypotheses for 3D incompressible
flow. In particular, a fluctuation-dissipation relation is derived which
relates the strength of a stochastic backscatter term in the energy decay
equation to the mean of the energy dissipation rate. The theory is based on the
so-called ``effective action'' of the energy history and illustrates a
Rayleigh-Ritz method recently developed to evaluate the effective action
approximately within probability density-function (PDF) closures. These
effective actions generalize the Onsager-Machlup action of nonequilibrium
statistical mechanics to turbulent flow. They yield detailed, concrete
predictions for fluctuations, such as multi-time correlation functions of
arbitrary order, which cannot be obtained by direct PDF methods. They also
characterize the mean histories by a variational principle.Comment: 26 pages, Latex Version 2.09, plus seceq.sty, a stylefile for
sequential numbering of equations by section. This version includes new
discussion of the physical interpretation of the formal Rayleigh-Ritz
approximation. The title is also change
Excitonic BCS-BEC crossover at finite temperature: Effects of repulsion and electron-hole mass difference
The BCS to Bose-Einstein condensation (BEC) crossover of electron-hole (e-h)
pairs in optically excited semiconductors is studied using the two-band Hubbard
model with both repulsive and attractive interactions. Applying the
self-consistent t-matrix approximation combined with a local approximation, we
examine the properties of a normal phase and an excitonic instability. The
transition temperature from the normal phase to an e-h pair condensed one is
studied to clarify the crossover from an e-h BCS-like state to an excitonic
Bose-Einstein condensation, which takes place on increasing the e-h attraction
strength. To investigate effects of the repulsive interaction and the e-h mass
difference, we calculate the transition temperature for various parameters of
the interaction strengths, the e-h particle density, and the mass difference.
While the transition temperature in the e-h BCS regime is sufficiently
suppressed by the repulsive interaction, that of the excitonic BEC is largely
insensitive to it. We also show quantitatively that in the whole regime the
mass difference leads to large suppression of the transition temperature.Comment: 8 pages, 7 figures, to be published in Phys. Rev.
The Physical Conditions and Dynamics of the Interstellar Medium in the Nucleus of M83: Observations of CO and CI
This paper presents CI, CO J=4-3, and CO J=3-2 maps of the barred spiral
galaxy M83 taken at the James Clerk Maxwell Telescope. Observations indicate a
double peaked structure which is consistent with gas inflow along the bar
collecting at the inner Lindblad resonance. This structure suggests that
nuclear starbursts can occur even in galaxies where this inflow/collection
occurs, in contrast to previous studies of barred spiral galaxies. However, the
observations also suggest that the double peaked emission may be the result of
a rotating molecular ring oriented nearly perpendicular to the main disk of the
galaxy. The CO J=4-3 data indicate the presence of warm gas in the nucleus that
is not apparent in the lower-J CO observations, which suggests that CO J=1-0
emission may not be a reliable tracer of molecular gas in starburst galaxies.
The twelve CI/CO J=4-3 line ratios in the inner 24'' x 24'' are uniform at the
2 sigma level, which indicates that the CO J=4-3 emission is originating in the
same hot photon-dominated regions as the CI emission. The CO J=4-3/J=3-2 line
ratios vary significantly within the nucleus with the higher line ratios
occurring away from peaks of emission along an arc of active star forming
regions. These high line ratios (>1) likely indicate optically thin gas created
by the high temperatures caused by star forming regions in the nucleus of this
starburst galaxy.Comment: 15 pages with 10 figures. To appear in the August 10 1998 issue of
The Astrophysical Journa
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