Improvements in parallel imaging accelerated functional MRI using multiecho echo‐planar imaging

Multiecho echo‐planar imaging (EPI) was implemented for blood‐oxygenation‐level‐dependent functional MRI at 1.5 T and compared to single‐echo EPI with and without parallel imaging acceleration. A time‐normalized breath‐hold task using a block design functional MRI protocol was carried out in combination with up to four echo trains per excitation and parallel imaging acceleration factors R = 1–3. Experiments were conducted in five human subjects, each scanned in three sessions. Across all reduction factors, both signal‐to‐fluctuation‐noise ratio and the total number of activated voxels were significantly lower using a single‐echo EPI pulse sequence compared with the multiecho approach. Signal‐to‐fluctuation‐noise ratio and total number of activated voxels were also considerably reduced for nonaccelerated conventional single‐echo EPI when compared to three‐echo measurements with R = 2. Parallel imaging accelerated multiecho EPI reduced geometric distortions and signal dropout, while it increased blood‐oxygenation‐level‐dependent signal sensitivity all over the brain, particularly in regions with short underlying T*₂. Thus, the presented method showed multiple advantages over conventional single‐echo EPI for standard blood‐oxygenation‐level‐dependent functional MRI experiments. Magn Reson Med 63:959–969, 2010. © 2010 Wiley‐Liss, Inc.     

Use of psychoactive substances among private school children]

A study was carried out in 1988, using a random sample of 1,441 pupils attending the elementary and high schools of the Federal District, Brazil, with the purpose of determining the frequency of the use of alcohol, tobacco and other drugs. A self-administered questionnaire, adapted by the World Health Organization for this type of survey, was applied. The prevalence of general usage (covering everything from experimental to daily use) showed rates of 67.2% for alcohol, 28.7% for tobacco, 13.9% for inhalants, 6.1% for marijuana and 1.8% for cocaine. The use of the majority of drugs increases with age. As regards sex, the illegal drugs were mostly frequently used by boys.     

Ciliary neurotrophic factor and leptin induce distinct patterns of immediate early gene expression in the brain

Ciliary neurotrophic factor (CNTF) and leptin decrease food intake and body weight. Lipopolysaccharide (LPS) is a potent exogenous pyrogen and produces anorexia via cytokine production. CNTF-, leptin-, and LPS-induced cytokines all act on type I cytokine receptors. However, it is not known if these cytokines engage similar central nervous system (CNS) pathways to exert their effects. To assess mechanisms by which these cytokines act, we examined the patterns of immediate early gene expression (SOCS-3, c-fos, and tis-11) in the brain following intravenous administration. CNTF and LPS induced gene expression in circumventricular organs; ependymal cells of the ventricles, meninges, and choroid plexus; and the arcuate nucleus of the hypothalamus. CNTF administration also induced fever and cyclooxygenase-2 mRNA expression. In contrast, we found no evidence of leptin-induced inflammation. CNTF and leptin are being assessed as potential therapeutic anti-obesity agents, and both potently reduce food intake. Our findings support the hypothesis that CNTF and leptin engage distinct CNS sites and CNTF possesses inflammatory properties distinct from leptin.     

Reperfusion arrhythmia: a marker of restoration of antegrade flow during intracoronary thrombolysis for acute myocardial infarction

We studied the effects of coronary recanalization on arrhythmogenesis in patients undergoing intracoronary thrombolysis during the early hours of myocardial infarction. Catheterization, ventriculography, coronary angiography, and intracoronary streptokinase infusion were performed in 22 patients. Twenty-one of 22 had thrombotic total occlusion of the infarct-related transient thrombolysis with reocclusion by the end of the procedure. In 12 of these 17 patients, restoration of antegrade coronary flow was accompanied by transient arrhythmia. In these 12 patients coronary angiography within seconds of onset of arrhythmia showed vessel patency in a previously totally occluded coronary artery. Two additional patients developed arrhythmias during streptokinase infusion but after reperfusion had already been established. Accelerated idioventricular rhythm was most often noted. Sinus bradycardia and atrioventricular block with hypotension occurred during restoration of flow in arteries supplying the inferoposterior left ventricle. These arrhythmias may be useful noninvasive markers of successful reperfusion during thrombolytic therapy in acute myocardial infarction.     

T2* measurement of the knee articular cartilage in osteoarthritis at 3T

Purpose:

To measure reproducibility, longitudinal and cross‐sectional differences in T2* maps at 3 Tesla (T) in the articular cartilage of the knee in subjects with osteoarthritis (OA) and healthy matched controls.

Materials and Methods:

MRI data and standing radiographs were acquired from 33 subjects with OA and 21 healthy controls matched for age and gender. Reproducibility was determined by two sessions in the same day, while longitudinal and cross‐sectional group differences used visits at baseline, 3 and 6 months. Each visit contained symptomological assessments and an MRI session consisting of high resolution three‐dimensional double‐echo‐steady‐state (DESS) and co‐registered T2* maps of the most diseased knee. A blinded reader delineated the articular cartilage on the DESS images and median T2* values were reported.

Results:

T2* values showed an intra‐visit reproducibility of 2.0% over the whole cartilage. No longitudinal effects were measured in either group over 6 months. T2* maps revealed a 5.8% longer T2* in the medial tibial cartilage and 7.6% and 6.5% shorter T2* in the patellar and lateral tibial cartilage, respectively, in OA subjects versus controls (P < 0.02).

Conclusion:

T2* mapping is a repeatable process that showed differences between the OA subject and control groups. J. Magn. Reson. Imaging 2012;35:1422–1429. © 2012 Wiley Periodicals Inc.     

Profile of the navrongo health and demographic surveillance system

Located in the Kassena-Nankana districts of northern Ghana, the Navrongo health and demographic surveillance system (NHDSS) was established in 1992 by the Navrongo health research centre (NHRC). The NHRC is one of three research centres of the Ghana health service. The activities and potential of the NHDSS for collaborative research are described. The NHDSS monitors health and demographic dynamics of the two Kassena-Nankana districts of northern Ghana and facilitates evaluation of the morbidity and mortality impact of health and social interventions. The total population currently under surveillance is 152 000 residing in 32 000 households. Events monitored routinely include pregnancies, births, morbidity, deaths, migration, marriages and vaccination coverage. Data updates are done every 4 months by trained fieldworkers. The NHRC also undertakes biomedical and socio-economic studies. Additional features of the NHDSS include the community key informant system where trained volunteers routinely report key events, such as births and deaths as they occur in their locality and the verbal autopsy (VA) system for determining the probable causes of deaths that occur at the community level. Data from the NHDSS are shared with funders and collaborators and partners in the INDEPTH Network. The Director of the NHDSS is the contact person for potential collaboration with the NHDSS and the use of its data.     

Neuroendocrine profiles associated with energy intake, sleep, and stress in the night eating syndrome

CONTEXT: Night eating syndrome (NES) is characterized by evening hyperphagia and frequent awakenings with ingestion of food. It is associated with obesity and depressed mood. Greater understanding of hormonal influences on NES is desirable. OBJECTIVE: Our objective was to evaluate 25-h profiles of hormones involved in energy balance, sleep, and stress in NES. DESIGN: Blood assays for glucose, insulin, ghrelin, leptin, melatonin, cortisol, TSH, and prolactin were sampled repeatedly among NES and control subjects. Food intake and depressive symptoms were assessed. SETTING AND PARTICIPANTS: Fifteen NES and 14 matched control participants stayed three nights in a General Clinical Research Center. MAIN OUTCOME MEASURES: We assessed differences between NES and control participants in the 25-h profiles of eight hormones. RESULTS: Nocturnal food intake was higher among NES participants, although their daily calorie intake was similar to that of controls. Reflecting their increased nocturnal intake, insulin (P < 0.001) and glucose levels (P = 0.07) among NES participants were higher than those of controls. Ghrelin levels were significantly lower in NES participants than in controls from 0100-0900 h (P = 0.003). Levels of plasma cortisol, melatonin, leptin, and prolactin did not differ between groups, but there was a trend for TSH levels (P = 0.07) to be higher during the 25 h in NES. NES participants had greater depressive symptoms than controls (P < 0.001). The differences in the levels of glucose, insulin, and ghrelin between NES and controls are closely associated with nocturnal food intake.     

Intermittent altitude exposures reduce acute mountain sickness at 4300 m

Acute mountain sickness (AMS) commonly occurs at altitudes exceeding 2000-2500 m and usually resolves after acclimatization induced by a few days of chronic residence at the same altitude. Increased ventilation and diuresis may contribute to the reduction in AMS with altitude acclimatization. The aim of the present study was to examine the effects of intermittent altitude exposures (IAE), in combination with rest and exercise training, on the incidence and severity of AMS, resting ventilation and 24-h urine volume at 4300 m. Six lowlanders (age, 23 +/- 2 years; body weight, 77 +/- 6 kg; values are means +/- S.E.M.) completed an Environmental Symptoms Questionnaire (ESQ) and Lake Louise AMS Scoring System (LLS), a resting end-tidal partial pressure of CO2 ( PETCO2) test and a 24-h urine volume collection at sea level (SL) and during a 30 h exposure to 4300 m altitude-equivalent (barometric pressure=446 mmHg) once before (PreIAE) and once after (PostIAE) a 3-week period of IAE (4 h.day(-1), 5 days.week(-1), 4300 m). The previously validated factor score, AMS cerebral score, was calculated from the ESQ and the self-report score was calculated from the LLS at 24 h of altitude exposure to assess the incidence and severity of AMS. During each IAE, three subjects cycled for 45-60 min.day(-1) at 60-70% of maximal O2 uptake (VO2 max) and three subjects rested. Cycle training during each IAE did not affect any of the measured variables, so data from all six subjects were combined. The results showed that the incidence of AMS (%), determined from both the ESQ and LLS, increased (P<0.05) from SL (0 +/- 0) to PreIAE (50 +/- 22) at 24 h of altitude exposure and decreased (P<0.05) from PreIAE to PostIAE (0 +/- 0). The severity of AMS (i.e. AMS cerebral symptom and LLS self-report scores) increased (P<0.05) from SL (0.02 +/- 0.02 and 0.17 +/- 0.17 respectively) to PreIAE (0.49 +/- 0.18 and 4.17 +/- 0.94 respectively) at 24 h of altitude exposure, and decreased (P<0.05) from PreIAE to PostIAE (0.03 +/- 0.02 and 0.83 +/- 0.31 respectively). Resting PETCO2 (mmHg) decreased (i.e. increase in ventilation; P<0.05) from SL (38 +/- 1) to PreIAE (32 +/- 1) at 24 h of altitude exposure and decreased further (P<0.05) from PreIAE to PostIAE (28 +/- 1). In addition, 24-h urine volumes were similar at SL, PreIAE and PostIAE. In conclusion, our findings suggest that 3 weeks of IAE provide an effective alternative to chronic altitude residence for increasing resting ventilation and reducing the incidence and severity of AMS.     

Adipocytokine changes caused by low-carbohydrate compared to conventional diets in obesity

Modest weight loss causing a decrease in insulin resistance has been linked to favorable changes in the adipocyte cytokines leptin, adiponectin, and tumor necrosis factor-alpha (TNF-alpha), three emerging risk factors of cardiovascular disease. We previously observed a significant reduction in insulin resistance with weight loss in obese subjects on a low-carbohydrate diet. Based on these previous findings, we hypothesize that a low-carbohydrate diet would be more beneficial in changing leptin, TNF-alpha, and adiponectin than a conventional diet. A total of 75 severely obese (body mass index >/=35 kg/m(2)) subjects were randomized to instruction of 6 months of a low-carbohydrate diet or a conventional calorie-restricted diet. Serum levels of leptin, TNF-alpha, TNF-alpha-soluble receptor 1 (TNF-alpha SR1), and adiponectin were measured at baseline and after 6 months of dietary intervention. Subjects on low-carbohydrate diets experienced a greater decrease in leptin when compared to conventional dieters (p < 0.001). TNF-alpha increased significantly in nondiabetic subjects on conventional vs. low-carbohydrate diets (p = 0.003). Adiponectin and TNF-alpha SR1 change were not significantly different between diets. This is the first study to report the effects of dietary macronutrient alterations on serum adipocytokines in a randomized controlled trial. The greater reduction in insulin resistance and weight on a low-carbohydrate diet, in the short term, translates into greater improvement in leptin but with no significant improvements in TNF-alpha or adiponectin in patients with moderate to severe obesity after 6 months of dietary intervention.     

Leptin activates distinct projections from the dorsomedial and ventromedial hypothalamic nuclei

Leptin has profound effects on feeding, metabolism, and neuroendocrine status. Evidence indicates that the hypothalamus coordinates these responses, though the specific brain pathways engaged by leptin remain obscure. The paraventricular nucleus of the hypothalamus (PVH) regulates pituitary gland function and feeding, and innervates autonomic preganglionic neurons, making it a candidate to regulate many of the responses to leptin. The subparaventricular zone, an anterior hypothalamic region receiving dense innervation from the suprachiasmatic nucleus, is thought to integrate circadian and metabolic information. We investigated the distribution of neurons in the rat brain activated by leptin administration that also project to the PVH or the subparaventricular zone by coupling immunohistochemistry for Fos with retrograde transport of cholera toxin-b. Intravenous leptin characteristically activated several cell groups including the ventromedial hypothalamic nucleus, the dorsomedial hypothalamic nucleus (DMH), and the PVH. When tracer injections were centered in the subparaventricular zone, many double-labeled cells were observed in the dorsomedial subdivision of the ventromedial hypothalamic nucleus. This projection may provide an anatomic substrate for integration of metabolic and circadian information to regulate the hypothalamo-pituitary axis. When cholera toxin-b injections were centered in the PVH, many double-labeled cells were found within the caudal DMH. Hence, activation of specific neuroendocrine and autonomic elements of the PVH may be triggered by leptin-activated afferents arising in the DMH. Our results demonstrate that a discrete set of hypothalamic pathways may underlie leptin’s autonomic, endocrine, and behavioral effects.