Anatomical and functional assessment of brown adipose tissue by magnetic resonance imaging

Brown adipose tissue (BAT) is the primary tissue responsible for nonshivering thermogenesis in mammals. The amount of BAT and its level of activation help regulate the utilization of excessive calories for thermogenesis as opposed to storage in white adipose tissue (WAT) which would lead to weight gain. Over the past several years, BAT activity in vivo has been primarily assessed by positron emission tomography-computed tomography (PET-CT) scan using 2-[18F]-fluoro-2-deoxy-D-glucose (18F-FDG) to measure glucose utilization associated with BAT mitochondrial respiration. In this study, we demonstrate the feasibility of mapping and estimating BAT volume and metabolic function in vivo in rats at a 9.4T magnetic resonance imaging (MRI) scanner using sequences available from clinical MR scanners. Based on the morphological characteristics of BAT, we measured the volume distribution of BAT with MRI sequences that have strong fat-water contrast. We also investigated BAT volume by utilizing spin-echo MRI sequences. The in vivo MRI-estimated BAT volumes were correlated with direct measurement of BAT mass from dissected samples. Using MRI, we also were able to map hemodynamic responses to changes in BAT metabolism induced pharmacologically by β3-adrenergic receptor agonist, CL-316,243 and compare this to BAT activity in response to CL-316,243 assessed by PET 18F-FDG. In conclusion, we demonstrate the feasibility of measuring BAT volume and function in vivo using routine MRI sequences. The MRI measurement of BAT volume is consistent with quantitative measurement of the tissue ex vivo.     

Evaluation of APOE polymorphisms and the risk for age-related macular degeneration in a Southeastern Brazilian population

This study aimed to evaluate the role of APOE polymorphisms (rs429358 and rs7412) in the risk of age-related macular degeneration in a sample of the Southeastern Brazilian population. Seven hundred and five unrelated individuals were analyzed, 334 with age-related macular degeneration (case group), and 371 without the disease (control group). In the case group, patients were further stratified according to disease phenotypes, divided into dry and wet age-related macular degeneration, and non-advanced and advanced age-related macular degeneration. APOE polymorphisms (rs429358 and rs7412) were evaluated through polymerase chain reaction and direct sequencing. In the comparison of cases vs. controls, none of the associations reached statistical significance, considering the Bonferroni-adjusted P-value, although there was a suggestive protection for the E3/E4 genotype (OR = 0.626; P-value = 0.037) and E4 carriers (OR = 0.6515; P-value = 0.047). Statistically significant protection for both the E3/E4 genotype and E4 carriers was observed in the comparisons: advanced age-related macular degeneration vs. controls (OR = 0.3665, P-value = 0.491 × 10⁻³ and OR = 0.4031, P-value = 0.814 × 10⁻³, respectively), advanced age-related macular degeneration vs. non-advanced age-related macular degeneration (OR = 0.2529, P-value = 0.659 × 10⁻⁴ and OR = 0.2692, P-value = 0.631 × 10⁻⁴, respectively). In the comparison of wet age-related macular degeneration vs. control, protection was statistically significant only for E3/E4 (OR = 0.4052, P-value = 0.001). None of the comparisons demonstrated any significant association for E2 genotypes or E2 carriers in age-related macular degeneration risk in this study. Findings suggest a protective role of the E4 haplotype in the APOE gene in the risk for advanced and wet forms of age-related macular degeneration, in a sample of the Brazilian population. To our knowledge, this is the first Brazilian study to show the association between APOE polymorphisms and age-related macular degeneration.     

Some Effects of Sodium on Nitrate Assimilation and N(2) Fixation in Anabaena cylindrica

Anabaena cylindrica grown with nitrate required higher levels of sodium (0.4 meq/l NaCl) to prevent chlorosis than when grown without combined nitrogen (0.004 meq/l NaCl). Nitrite accumulated in sodium-deficient cultures containing nitrate. Amounts of nitrite similar to those found in deficient cultures when added to normal cultures resulted in a chlorosis of the cells. Thus loss of chlorophyll was caused by nitrite toxicity.     

Hedgehog signaling regulates the generation of ameloblast progenitors in the continuously growing mouse incisor

In many organ systems such as the skin, gastrointestinal tract and hematopoietic system, homeostasis is dependent on the continuous generation of differentiated progeny from stem cells. The rodent incisor, unlike human teeth, grows throughout the life of the animal and provides a prime example of an organ that rapidly deteriorates if newly differentiated cells cease to form from adult stem cells. Hedgehog (Hh) signaling has been proposed to regulate self-renewal, survival, proliferation and/or differentiation of stem cells in several systems, but to date there is little evidence supporting a role for Hh signaling in adult stem cells. We used in vivo genetic lineage tracing to identify Hh-responsive stem cells in the mouse incisor and we show that sonic hedgehog (SHH), which is produced by the differentiating progeny of the stem cells, signals to several regions of the incisor. Using a hedgehog pathway inhibitor (HPI), we demonstrate that Hh signaling is not required for stem cell survival but is essential for the generation of ameloblasts, one of the major differentiated cell types in the tooth, from the stem cells. These results therefore reveal the existence of a positive-feedback loop in which differentiating progeny produce the signal that in turn allows them to be generated from stem cells.     

Calcium regulation of inositol 1,4,5-trisphosphate receptors

Ca2+ exerts both a stimulatory and inhibitory effect on type-I IP3R channel activity. However, the structural determinants of Ca2+ sensing in IP3Rs are not fully understood. Previous studies by others have identified eight domains of the type-I IP3R that bind 45Ca2+ when expressed as GST-fusion proteins. We have mutated six highly conserved acidic residues within the second of these domains (aa378-450) in the full-length IP3R and measured the Ca2+ regulation of IP3-mediated Ca2+ release in COS-7 cells. 45Ca2+ flux assays measured with a maximal [IP3] (1 microM) indicate that one of the mutants retained a Ca2+ sensitivity that was not significantly different from control (E411Q), three of the mutants show an enhanced Ca2+ inhibition (D426N, E428Q and E439Q) and two of the mutants were relatively insensitive to Ca2+ inhibition (D442N and D444N). IP3 dose-response relationships indicated that the sensitivity to Ca2+ inhibition and affinity for IP3 were correlated for three of the constructs. Other mutants with enhanced IP3 sensitivity (e.g. R441Q and a type-II/I IP3R chimera) were also less sensitive to Ca2+ inhibition. We conclude that the acidic residues within the aa378-450 segment are unlikely to represent a single functional Ca2+ binding domain and do not contribute to Ca2+ activation of the receptor. The different effects of the mutations may be related to their location within two clusters of acidic residues identified in the crystal structure of the ligand-binding domain [I. Bosanac, J.R. Alattia, T.K. Mal, et al., Structure of the inositol 1,4,5-trisphosphate receptor binding core in complex with its ligand, Nature 420 (2002) 696-700]. The data support the view that all IP3R isoforms may display a range of Ca2+ sensitivities that are determined by multiple sites within the protein and markedly influenced by the affinity of the receptor for IP3.     

Effect of membrane mechanics on charge transfer by the membrane protein prestin

Prestin was found in the membrane of outer hair cells (OHCs) located in the cochlea of the mammalian inner ear. These cells convert changes in the membrane potential into dimensional changes and (if constrained) to an active electromechanical force. The OHCs provide the ear with the mechanism of amplification and frequency selectivity that is effective up to tens of kHz. Prestin is a crucial part of the motor complex driving OHCs. Other cells transfected with prestin acquire electromechanical properties similar to those in the native cell. While the mechanism of prestin has yet to be fully understood, the charge transfer is its critical component. Here we investigate the effect of the mechanics of the surrounding membrane on electric charge transfer by prestin. We simulate changes in the membrane mechanics via the corresponding changes in the free energy of the prestin system. The free energy gradient enters a Fokker-Planck equation that describes charge transfer in our model. We analyze the effects of changes in the membrane tension and membrane elastic moduli. In the case of OHC, we simulate changes in the longitudinal and/or circumferential stiffness of the cell’s orthotropic composite membrane. In the case of cells transfected with prestin, we vary the membrane areal modulus. As a result, we show the effects of the membrane mechanics on the probabilistic characteristics of prestin-associated charge transfer for both stationary and high-frequency conditions. We compare our computational results with the available experimental data and find good agreement with the experiment.     

Application of microbial source tracking methods in a Gulf of Mexico field setting

Aims:  Microbial water quality and possible human sources of faecal pollution were assessed in a Florida estuary that serves shellfishing and recreational activities.
Methods and Results:  Indicator organisms (IO), including faecal coliforms, Escherichia coli and enterococci, were quantified from marine and river waters, sediments and oysters. Florida recreational water standards were infrequently exceeded (6–10% of samples); however, shellfishing standards were more frequently exceeded (28%). IO concentrations in oysters and overlaying waters were significantly correlated, but oyster and sediment IO concentrations were uncorrelated. The human-associated esp gene of Enterococcus faecium was detected in marine and fresh waters at sites with suspected human sewage contamination. Lagrangian drifters, used to determine the pathways of bacterial transport and deposition, suggested that sediment deposition from the Ochlockonee River contributes to frequent detection of esp at a Gulf of Mexico beach.
Conclusions:  These data indicate that human faecal pollution affects water quality in Wakulla County and that local topography and hydrology play a role in bacterial transport and deposition.
Significance and Impact of the Study:  A combination of IO enumeration, microbial source tracking methods and regional hydrological study can reliably inform regulatory agencies of IO sources, improving risk assessment and pollution mitigation in impaired waters.     

Confronting and coping with weight stigma: an investigation of overweight and obese adults

Objective: This study examined experiences of weight stigmatization, sources of stigma, coping strategies, psychological functioning, and eating behaviors in a sample of 2671 overweight and obese adults. Research Methods and Procedures: The total sample was partitioned into two subsamples for investigation. Sample I was comprised of 2449 adult women, and Sample II was a matched sample of adult men and women (N = 222) that was disaggregated to investigate gender differences. Both samples completed an online battery of self‐report questionnaires measuring frequency of weight stigmatization and coping responses to deal with bias, the most common sources of the bias, symptoms of depression, self‐esteem, attitudes about weight and obesity, and binge eating behaviors. Results: Experiences of weight stigmatization, in many forms and across multiple occasions, was common in both samples. A variety of coping strategies were used in response. More frequent exposure to stigma was related to more attempts to cope and higher BMI. Physicians and family members were the most frequent sources of weight bias reported. No gender differences were observed in types or frequency of stigmatization. Frequency of stigmatization was not related to current psychological functioning, although coping responses were associated with emotional well‐being. Discussion: These findings raise questions about the relationship between stigma and psychological functioning and have important implications for obesity treatment and stigma reduction intervention efforts, both of which are discussed.