Three‐dimensional inversion recovery manganese‐enhanced MRI of mouse brain using super‐resolution reconstruction to visualize nuclei involved in higher brain function

The visualization of activity in mouse brain using inversion recovery spin echo (IR‐SE) manganese‐enhanced MRI (MEMRI) provides unique contrast, but suffers from poor resolution in the slice‐encoding direction. Super‐resolution reconstruction (SRR) is a resolution‐enhancing post‐processing technique in which multiple low‐resolution slice stacks are combined into a single volume of high isotropic resolution using computational methods. In this study, we investigated, first, whether SRR can improve the three‐dimensional resolution of IR‐SE MEMRI in the slice selection direction, whilst maintaining or improving the contrast‐to‐noise ratio of the two‐dimensional slice stacks. Second, the contrast‐to‐noise ratio of SRR IR‐SE MEMRI was compared with a conventional three‐dimensional gradient echo (GE) acquisition. Quantitative experiments were performed on a phantom containing compartments of various manganese concentrations. The results showed that, with comparable scan times, the signal‐to‐noise ratio of three‐dimensional GE acquisition is higher than that of SRR IR‐SE MEMRI. However, the contrast‐to‐noise ratio between different compartments can be superior with SRR IR‐SE MEMRI, depending on the chosen inversion time. In vivo experiments were performed in mice receiving manganese using an implanted osmotic pump. The results showed that SRR works well as a resolution‐enhancing technique in IR‐SE MEMRI experiments. In addition, the SRR image also shows a number of brain structures that are more clearly discernible from the surrounding tissues than in three‐dimensional GE acquisition, including a number of nuclei with specific higher brain functions, such as memory, stress, anxiety and reward behavior. Copyright © 2014 John Wiley & Sons, Ltd.     

Confounder selection in environmental epidemiology: assessment of health effects of prenatal mercury exposure

PURPOSE: The purpose of the study is to compare different approaches to the identification of confounders needed for analyzing observational data. Whereas standard analysis usually is conducted as if the confounders were known a priori, selection uncertainty also must be taken into account. METHODS: Confounders were selected by using backward elimination (BE), change in estimate (CIE) method, Akaike information criterion, Bayesian information criterion (BIC), and an empirical approach using a priori information. A modified ridge regression estimator, which shrinks effects of confounders toward zero, also was considered. For each criterion, uncertainty in the estimated exposure effect was assessed by using bootstrap simulations for which confounders were selected in each sample. These methods were illustrated by using data for mercury neurotoxicity in Faroe Islands children. Point estimates and standard errors of mercury effects on confounder-sensitive neurobehavioral outcomes were calculated for each selection procedure. RESULTS: The full model and the empirical a priori model showed approximately the same precision, and these methods were (slightly) inferior to only modified ridge regression. Lower precisions were obtained by using BE with a low cutoff level, BIC, and CIE. CONCLUSIONS: Standard analysis ignores model selection uncertainty and is likely to yield overoptimistic inferences. Thus, the traditional BE procedure with p = 5% should be avoided. If data-dependent procedures are required for confounder identification, we recommend that inferences be based on bootstrap statistics to describe the selection process.     

Serum ghrelin levels are increased in hypothyroid patients and become normalized by L-thyroxine treatment

CONTEXT: An interaction between ghrelin, which is implicated in the regulation of short- and long-term energy balance, and thyroid function has been reported in hyperthyroidism in which ghrelin levels are reversibly suppressed. We measured serum ghrelin levels and metabolic indices in hypothyroid patients before and after L-thyroxine replacement. PATIENTS AND METHODS: Eleven patients were examined twice: 1) in the hypothyroid state and 2) after at least 2 months of euthyroidism. Ten healthy subjects served as a control group. Ghrelin was measured in conjunction with indirect calorimetry and a hyperinsulinemic euglycemic clamp. RESULTS: Serum ghrelin levels were increased by 32% under basal conditions in the hypothyroid state (PRE) as compared with posttreatment (POST) (picograms per milliliter): 976.4 +/- 80.8 vs. 736.8 +/- 67.1 (P < 0.001). This difference prevailed during the clamp, but a decline was observed in both states: 641.4 +/- 82.2 vs. 444.3 +/- 66.8 microg/ml (P = 0.005). The hypothyroid state was associated with decreased resting energy expenditure, increased respiratory quotient, and insulin resistance. Serum ghrelin levels as well as the metabolic aberrations became normalized after L-thyroxine replacement as compared with the control subjects. CONCLUSION: Serum ghrelin levels are reversibly increased in hypothyroid patients. It remains to be investigated whether this represents a direct effect of iodothyronines on ghrelin secretion or clearance or a compensatory response to the abnormal energy metabolism in hypothyroid patients.     

Acute coronary artery thrombosis and a giant coronary artery aneurysm: an atypical combination and an unconventional catheter-based intervention.

Coronary artery aneurysm is an unusual finding at coronary arteriography. We present a case of acute myocardial infarction and a giant aneurysm of the left circumflex coronary artery (CX) in a 70-year-old male with hypertension. The culprit lesion was a thrombus occupying the aneurysm and the distal CX. By an unconventional manoeuvre the thrombus was aspirated via the 7 French guiding catheter. After stent implantation in the distal CX a thrombolysis in myocardial infarction 3 flow was achieved and still present at 2-month follow-up. The patient was prescribed aspirin and clopidogrel as a life-long therapy.     

Impaired aortic distensibility and elevated central blood pressure in Turner Syndrome: a cardiovascular magnetic resonance study

Background

Women with Turner Syndrome have an increased risk for aortic dissection. Arterial stiffening is a risk factor for aortic dilatation and dissection. Here we investigate if arterial stiffening can be observed in Turner Syndrome patients and is an initial step in the development of aortic dilatation and subsequent dissection.

Methods

Fifty-seven women with Turner Syndrome (48 years [29–66]) and thirty-six age- and sex-matched controls (49 years [26–68]) were included. Distensibility, blood pressure, carotid-femoral pulse wave velocity (PWV), the augmentation index (Aix) and central blood pressure were determined using cardiovascular magnetic resonance, a 24-h blood pressure measurement and applanation tonometry. Aortic distensibility was determined at three locations: ascending aorta, transverse aortic arch, and descending aorta.

Results

Mean aortic distensibility in the descending aorta was significantly lower in Turner Syndrome compared to healthy controls (P =?0.02), however, this was due to a much lower distensibility among Turner Syndrome with coarctation, while Turner Syndrome without coarctation had similar distensibility as controls. Both the mean heart rate adjusted Aix (31.4% vs. 24.4%; P?=?0.02) and central diastolic blood pressure (78.8 mmHg vs. 73.7 mmHg; P?=?0.02) were higher in Turner Syndrome compared to controls, and these indices correlated significantly with ambulatory night-time diastolic blood pressure. The presence of aortic coarctation (r = ??0.44, P =?0.005) and a higher central systolic blood pressure (r = ??0.34, P =?0.03), age and presence of diabetes were inversely correlated with aortic distensibility in TS.

Conclusion

Aortic wall function in the descending aorta is impaired in Turner Syndrome with lower distensibility among those with coarctation of the aorta, and among all Turner Syndrome higher Aix, and elevated central diastolic blood pressure when compared to sex- and age-matched controls.

Trial registration

The study was registered at ClinicalTrials.gov (#NCT01678274) on September 3, 2012.

     

A novel HPLC method for the measurement of thiobarbituric acid reactive substances (TBARS). A comparison with a commercially available kit

OBJECTIVES: Malondialdehyde (MDA) as a part of thiobarbituric acid reacting substances (TBARS) is frequently used as an indicator of lipid peroxidation. Most methods for the measurement of TBARS require long derivatization time and addition of antioxidants in the samples. Furthermore, comparison of these methods with commercially available HPLC kits is lacking. DESIGN AND METHODS: We investigated column performance of five different columns, tested eight different acids for the hydrolysis of the samples, and estimated stability of derivatized plasma samples with different anticoagulants. The samples were derivatized with TBA. The peak for the TBA(2)-MDA adduct was separated and detected by HPLC. RESULTS: Performance of the Phenomenex Gemini column was best. PCA at the concentration of 0.1125 N was used in this method. Coefficient of variation (CV %) within the run and between the run was 4.1% and 6.7%, and analytical recovery was 90-94%. The retention time of the TBA(2)-MDA peak was 1.8 min. Reference intervals for TBARS in serum from 250 individuals were 0.53 and 2.1 micromol/l using our HPLC method and 0.07 and 0.24 micromol/l using the Chromsystems assay. Linear regression with log converted values revealed weak relationship between the two methods (r(2) = 0.064). CONCLUSIONS: Our HPLC method for the analysis of TBARS in serum and plasma is fast and accurate and therefore can be used in clinical studies.     

Osteopontin Mediates Citrobacter rodentium-Induced Colonic Epithelial Cell Hyperplasia and Attaching-Effacing Lesions

Although osteopontin (OPN) is up-regulated in inflammatory bowel diseases, its role in disease pathogenesis remains controversial. The objective of this study was to determine the role of OPN in host responses to a non-invasive bacterial pathogen, Citrobacter rodentium, which serves as a murine infectious model of colitis. OPN gene knockout and wild-type mice were infected orogastrically with either C. rodentium or Luria-Bertani (LB) broth. Mouse-derived OPN^+/+ and OPN^−/− fibroblasts were incubated with C. rodentium and attaching-effacing lesions were demonstrated using transmission electron microscopy and immunofluorescence. Colonic expression of OPN was increased by C. rodentium infection of wild-type mice. Furthermore, colonic epithelial cell hyperplasia, the hallmark of C. rodentium infection, was reduced in OPN^−/− mice, and spleen enlargement by infection was absent in OPN^−/− mice. Rectal administration of OPN to OPN^−/− mice restored these effects. There was an 8- to 17-fold reduction in bacterial colonization in OPN^−/− mice, compared with wild-type mice, which was accompanied by reduced attaching–effacing lesions, both in infected OPN^−/− mice and OPN^−/− mouse fibroblasts. Moreover, adhesion pedestals were restored in OPN^−/− cells complemented with human OPN. Therefore, lack of OPN results in decreased pedestal formation, colonization, and colonic epithelial cell hyperplasia responses to C. rodentium infection, indicating that OPN impacts disease pathogenesis through bacterial attachment and altered host immune responses.Osteopontin (OPN) is a multifunctional glycophosphoprotein involved in a variety of cellular functions, including stimulation of T helper(_H)1 cytokines and adhesion through binding to integrins and CD44 receptors on cell surfaces. This cytokine is highly expressed in chronic inflammatory and autoimmune diseases¹ and is localized in and around inflammatory cells.² OPN is believed to exacerbate inflammation in a variety of settings, including infectious diseases.¹ It is involved in recruiting inflammatory cells to sites of injury, as indicated by a decrease in macrophage infiltration in ischemic kidneys in OPN-deficient (OPN^−/−) mice.¹ OPN is also involved in controlling expression of inflammatory mediators, such as down-regulation of the anti-inflammatory cytokine interleukin (IL)-10 and an increase in levels of the T_H1 cytokine interferon (IFN)γ.³Accumulating evidence indicates that defects in the dynamic balance between organisms in the commensal intestinal microbiota and host innate defensive responses at the intestinal mucosal surface results in the induction of inflammatory bowel diseases (IBD).⁴ An association between luminal bacteria and IBD is further supported by animal models,⁵ including the use of Citrobacter rodentium infection. C. rodentium is the causative agent of transmissible murine colonic epithelial cell hyperplasia that harbors a locus of enterocyte effacement pathogenicity island, similar to enterohemorrhagic Escherichia coli (EHEC) O157:H7, and is capable of forming dense F-actin bacterial attachment pedestals, known as attaching–effacing (A/E) lesions, in mouse colon.⁶ The resulting T_H1 response and accompanying pathological changes represent findings observed in patients with IBD.⁷ As a result, C. rodentium serves as a relevant animal model to study potential infectious mechanisms of IBD.⁸An association between OPN and IBD was recently assessed using dextran sodium sulfate (DSS) to induce colitis in wild-type and OPN^−/− mice. However, the results arising were contradictory. One study suggested that lack of OPN has a protective effect,⁹ whereas others reported a detrimental outcome during the acute phase^10,11,12 and protection from chronic exposure to DSS.¹¹ This controversy prompted us to study an association between OPN and gut inflammation, using C. rodentium as a model of infectious colitis, to provide insight regarding the role of OPN in the pathogenesis of IBD.Herein, we describe the attenuation of C. rodentium-induced colonic epithelial cell hyperplasia and a reduction in bacterial colonization in OPN^−/− mice. In addition, we demonstrate dependence of adhesion pedestal formation in response to C. rodentium on the presence of OPN. Taken together, these findings contribute to an improved understanding of the role of OPN in response to intestinal infection.