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•TPO inhibitors MMI and amitrole elicit similar disruptions of the thyroid hormone system.•MMI and amitrole perturb thyroid hormone dependent rat brain development via TPO ...inhibition.•MMI and amitrole reduce expression of thyroid hormone-sensitive genes in cerebral cortex.•MMI and amitrole alter motor activity of perinatally exposed rat offspring.
Disruption of the thyroid hormone system during development can impair brain development and cause irreversible damage. Some thyroid hormone system disruptors act by inhibiting the thyroperoxidase (TPO) enzyme, which is key to thyroid hormone synthesis. For the potent TPO-inhibiting drug propylthiouracil (PTU) this has been shown to result in thyroid hormone system disruption and altered brain development in animal studies. However, an outstanding question is which chemicals beside PTU can cause similar effects on brain development and to what degree thyroid hormone insufficiency must be induced to be able to measure adverse effects in rats and their offspring. To start answering these questions, we performed a perinatal exposure study in pregnant rats with two TPO-inhibitors: the drug methimazole (MMI) and the triazole herbicide amitrole. The study involved maternal exposure from gestational day 7 through to postnatal day 22, to MMI (8 and 16 mg/kg body weight/day) or amitrole (25 and 50 mg/kg body weight/day). Both MMI and amitrole reduced serum T4 concentrations in a dose-dependent manner in dams and offspring, with a strong activation of the hypothalamic-pituitary-thyroid axis. This reduction in serum T4 led to decreased thyroid hormone-mediated gene expression in the offspring’s brains and caused adverse effects on brain function, seen as hyperactivity and decreased habituation in preweaning pups. These dose-dependent effects induced by MMI and amitrole are largely the same as those observed with PTU. This demonstrates that potent TPO-inhibitors can induce effects on brain development in rats and that these effects are driven by T4 deficiency. This knowledge will aid the identification of TPO-inhibiting thyroid hormone system disruptors in a regulatory context and can serve as a starting point in search of more sensitive markers of developmental thyroid hormone system disruption.
Thyroid hormone transport across the plasma membrane depends on transmembrane transport proteins, including monocarboxylate transporter 8 (MCT8). Mutations in MCT8 (or SLC16A2) lead to a severe form ...of X-linked psychomotor retardation, which is characterised by elevated plasma triiodothyronine (T(3)) and low/normal thyroxine (T(4)). MCT8 contributes to hormone release from the thyroid gland.
To characterise the potential impact of MCT8-deficiency on thyroid morphology in a patient and in Mct8-deficient mice.
Thyroid morphology in a patient carrying the A224V mutation was followed by ultrasound imaging for over 10 years. After thyroidectomy, a histopathological analysis was carried out. The findings were compared with histological analyses of mouse thyroids from the Mct8(-/y) model.
We show that an inactivating mutation in MCT8 leads to a unique, progressive thyroid follicular pathology in a patient. After thyroidectomy, histological analysis revealed gross morphological changes, including several hyperplastic nodules, microfollicular areas with stromal fibrosis and a small focus of microfollicular structures with nuclear features reminiscent of papillary thyroid carcinoma (PTC). These findings are supported by an Mct8-null mouse model in which we found massive papillary hyperplasia in 6- to 12-month-old mice and nuclear features consistent with PTC in almost 2-year-old animals. After complete thyroidectomy and substitution with levothyroxine (l-T(4)), the preoperative, inadequately low T(4) and free T(4) remained, while increasing the l-T(4) dosage led to T(3) serum concentrations above the normal range.
Our results implicate peripheral deiodination in the peculiar hormonal constellation of MCT8-deficient patients. Other MCT8-deficient patients should be closely monitored for potential thyroid abnormalities.
Visceral adipose tissue (VAT) could affect Crohn's disease (CD); however, no prospective clinical studies have explored the issue.
We measured VAT with magnetic resonance imaging and total fat mass ...(FM) with air-displacement plethysmography in 31 women with CD in remission and 19 matched control women. We assessed the VAT/FM ratio as index of VAT accumulation, measured cytokines, and monitored clinical features (duration of remission, disease behavior, and outcome) in patients with CD retrospectively and prospectively. We also tested whether ultrasound could provide a surrogate marker of VAT in patients with CD.
Patients with CD had higher percentage of FM (37 ± 10% versus 31 ± 10%, P = 0.03), VAT (1885 ± 1403 mL versus 941 ± 988 mL, P = 0.02), and VAT/FM ratio (65 ± 24 mL/kg versus 37 ± 25 mL/kg, P = 0.004) than control women. In patients with CD, VAT/FM ratio was associated with leptin (P = 0.009) and interleukin 6 (P = 0.032) concentrations, and higher in short-term than in long-term remission (72.6 ± 27.1 mL/kg versus 54.8 ± 16.1 mL/kg, P = 0.079). Patients with CD with stricturing/fistulizing disease had a higher VAT/FM ratio than patients with nonstricturing/nonfistulizing behavior (79 ± 0.15 mL/kg versus 63 ± 28 mL/kg, P = 0.067). A higher baseline VAT/FM ratio was associated with an increased disease activity at follow-up (P = 0.029). The ultrasound-determined thickness between the abdominal wall and the aorta was strongly associated with VAT as measured by magnetic resonance imaging (P < 0.001).
VAT accumulation could be a prospective risk factor for increased disease activity in CD.
AVE0118 is a novel blocker of the K(+) channels K(v)1.5 and K(v)4.3 which are the molecular basis for the human cardiac ultrarapid delayed rectifier potassium current (I(Kur)) and the transient ...outward current (I(to)). The objective of this study was to investigate the effect of AVE0118 on atrial refractoriness (ERP), left atrial vulnerability (LAV) and on left atrial monophasic action potentials (MAP) in pentobarbital anesthetized pigs in comparison to the selective I(Kr) blocker dofetilide in order to assess the therapeutic potential of the novel K(+) channel blocker for atrial fibrillation.
Atrial ERP was determined with the S1-S2-stimulus method in the free walls of left and right atrium at 240, 300 and 400 ms basic cycle length (BCL). The inducibility of mostly nonsustained atrial tachyarrhythmias by the premature S2 extrastimulus, which is very high in the left pig atrium and referred to as LAV, was evaluated before and after drugs. Left atrial epicardial MAP was recorded to study the influence of the potassium channel blockers on the time course of repolarization. Left ventricular epicardial MAP, ERP and QT interval were measured to investigate a possible effect of AVE0118 on ventricular repolarization.
ERPs determined at 240, 300 and 400 ms BCL were significantly shorter in the left vs. right atrium (99+/-3, 106+/-4 and 113+/-3 ms vs. 133+/-4 ms, 142+/-4 and 149+/-5, respectively; p<0.001; n=21). AVE0118 administered i.v. dose-dependently prolonged the atrial ERP independent from rate and inhibited LAV (100% at 0.5 and 1 mg/kg) while having no effect at all on the corrected QT (QTc) interval. At 1 mg/kg (n=5) AVE0118 prolonged left vs. right atrial ERP by 49.6+/-4.1 ms vs. 37.7+/-9.7 ms (means+/-SEM of changes at 240, 300, and 400 ms BCL), respectively, corresponding to a relative increase of 53.2+/-6.2% vs. 27.6+/-6.8% (p<0.05 for percent increase of left vs. right atrial ERP). In a separate group of pigs (n=5) AVE0118 had no effect on left ventricular ERP at 333, 400 and 500 ms BCL and no effect on MAP duration and QT at 600 ms BCL. After 1 mg/kg of AVE0118 the atrial MAP was significantly prolonged already at 10% repolarization (P<0.05; n=7) reaching the maximum at 40% repolarization. In contrast to AVE0118 the effect of dofetilide (10 microg/kg) on atrial MAP started to become significant only at 60% repolarization (n=6) with a maximum increase at 90%. Dofetilide, which prolonged the QTc interval by 16.9% (P<0.001), had a significantly stronger effect on right (34.7+/-5 ms) vs. left atrial ERP (23.5+/-7 ms) at 300 ms BCL, respectively, but did not significantly inhibit LAV (14%; n=6).
The novel K(+) channel blocker AVE0118 prolonged atrial ERP and showed strong atrial antiarrhythmic efficacy with no apparent effect on ventricular repolarization in pigs in vivo.
Tertiary hospital in Gaborone, Botswana.
To examine whether exposure to wood smoke worsens outcomes of childhood pneumonia.
Prospective cohort study of children aged 1-23 months meeting clinical ...criteria for pneumonia. Household use of wood as a cooking fuel was assessed during a face-to-face questionnaire with care givers. We estimated crude and adjusted risk ratios (RRs) and 95% confidence intervals (CIs) for treatment failure at 48 h by household use of wood as a cooking fuel. We assessed for effect modification by age (1-5 vs. 6-23 months) and malnutrition (none vs. moderate vs. severe).
The median age of the 284 enrolled children was 5.9 months; 17% had moderate or severe malnutrition. Ninety-nine (35%) children failed treatment at 48 h and 17 (6%) died. In multivariable analyses, household use of wood as a cooking fuel increased the risk of treatment failure at 48 h (RR 1.44, 95%CI 1.09-1.92, P = 0.01). This association differed by child nutritional status (P = 0.02), with a detrimental effect observed only among children with no or moderate malnutrition.
Exposure to wood smoke worsens outcomes for childhood pneumonia. Efforts to prevent exposure to smoke from unprocessed fuels may improve pneumonia outcomes among children.
The annular fluidized bed is a new technology consisting of a large central nozzle surrounded by a stationary fluidized bed. Due to the moderate primary gas fluidization of the annulus, the solids ...overflow at the upper edge of the central nozzle is mixed into the high upward velocity central secondary gas stream and transported into the mixing chamber. With this geometrical configuration, the process combines the advantages of the stationary fluidized bed (long solids residence time) and of the circulating fluidized bed (good heat and mass transfer).
This paper presents the determination of the operating range of the system and the characterization of the solids mixing behaviour above the central nozzle in order to develop scale-up rules for the industrial application of the annular fluidized bed. The local radial solids concentration, velocity and mass flux profiles are investigated by capacitance probe measurements in a laboratory rig and a pilot plant of inside diameter 0.19 m and 0.74 m, respectively. The geometric and operating parameters varied are the diameter of the central nozzle, the gas velocity in the annulus and in the central nozzle and the pressure drop in the mixing chamber.
The annular fluidized bed combines a long solids residence time to a good heat and mass transfer. The influence of the plant diameter on its flow pattern is presented. The interaction between the ratio of bubble to central nozzle diameter and the central gas velocity regulates the occurrence of a “saturation” point regarding the solids concentration into the jet.
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