Diurnal cortisol and obesity in adolescents with and without Down syndrome.

BACKGROUND: The prevalence of obesity in adolescents with Down syndrome (DS) far exceeds that in the general population. Cortisol, an adrenal hormone, can be obesogenic when dysregulated. However, the diurnal patterns of this hormone have not been examined among individuals with DS. Variations in adiposity may also mediate cortisol regulation. This study sought to examine diurnal cortisol patterns in adolescents with DS as well as associations between cortisol function and obesity. METHOD: A total of 32 adolescents, including 16 with DS and 16 controls with typical development (TD) of similar sex, age and Tanner pubertal stage (P > 0.05), participated in this preliminary study. Participants completed a dual-energy X-ray absorptiometry scan to measure body composition and collected saliva samples for cortisol measurements in the morning, afternoon and night. Linear mixed models with random intercepts and repeated measures were used to examine the daily trajectory of log-transformed cortisol concentrations between adolescents with and without DS. A second model examined the interaction between DS and presence of elevated body fatness. RESULTS: Adolescents with DS had higher morning cortisol concentrations (intercept = 0.37 µg/dL), but this was not significantly different than in TD (0.35 µg/dL, P = 0.16). Cortisol significantly declined across hours (b = -0.026 µg/dL/h, P < 0.001), but this decline also did not differ from that observed in TD (b = -0.024 µg/dL/h, P = 0.43). While cortisol levels were slightly higher among adolescents with elevated body fatness, this difference was not statistically significant (P > 0.05; d = 0.30). CONCLUSIONS: This study is the first to examine diurnal cortisol in DS but is limited in sample size. These preliminary findings suggest that diurnal cortisol patterns are not significantly different between adolescents with DS and TD and that cortisol levels are not associated with adiposity in this population. Despite these non-significant differences, youth with DS continue to be an 'at-risk' population for paediatric obesity in need of clinical intervention.

Insulin sensitivity and brain reward activation in overweight Hispanic girls: a pilot study.

BACKGROUND: Insulin resistance is a link between obesity and the associated disease risk. In addition to its role as an energy regulatory signal to the hypothalamus, insulin also modulates food reward. OBJECTIVE: To examine the relationship of insulin sensitivity (SI) and fasting insulin with cerebral activation in response to food and non-food cues in children. METHODS: Twelve overweight Hispanic girls (age: 8-11) participated in two study visits, a frequently sampled intravenous glucose tolerance test and a functional neuroimaging session (GE HDxt 3.0Tesla) with visual stimulation tasks. Blocks of images (high calorie [HC], low calorie [LC] and non-food [NF]) were presented in randomized order. RESULTS: Comparing HC with NF, SI was inversely associated with activation in the anterior cingulate (r(2) = 0.65; P < 0.05), the insula (r(2) = 0.69; P < 0.05), the orbitofrontal cortex (r(2) = 0.74; P < 0.05), and the frontal and rolandic operculum (r(2) = 0.76; P < 0.001). Associations remained significant after adjustment for body mass index. Association of fasting insulin and cerebral activation disappeared after adjustment for waist circumference. CONCLUSION: In addition to weight loss, insulin sensitivity may pose an important target to regulate neural responses to food cues in the prevention of excessive weight gain.

Overt and hidden forms of chronic malnutrition in the rat and their relevance to man.

We have examined the physiological weight changes seen in rat dams and their offspring as sequelae of either an overt or a hidden form of chronic protein malnutrition. In the overt model, which was produced by feeding dams a very low protein diet (6% casein) starting 5 weeks prior to conception and continued through lactation, the females showed significant weight losses at all ages compared to dams maintained on a normal diet (25% casein). This caused the malnourished 6% dams to have offspring that were categorized as small-for-date at birth in terms of their weight indices and peripheral metabolic profiles. Also, the inadequate milk production of these dams resulted in their pups displaying the almost total failure of growth (greater than 60% decreases in body weights) and peripheral imbalances characteristic of infantile marasmus by day 8 of lactation. Consequently, at all times examined the 6% dams and pups showed most of the typical responses seen in the more severe forms of in utero and lactational malnutrition of mankind. In contrast, the hidden form of malnutrition produced by feeding dams a somewhat higher protein diet (8% casein) throughout the same time periods caused no marked weight losses by these females during their pregnancy compared to the normal dams. Although the 8% pups had the same birth weight indices as the normal offspring, previous data from our group have indicated that the 8% progeny show many metabolic imbalances at birth which are indicators of severe gestational malnutrition in humans. Moreover, while the 8% dams displayed lactational insufficiencies as noted by their pups retarded postnatal growth, nursing of these offspring by 25% dams allowed them to maintain a normal lactational growth curve. However, not only was this cross-fostering unable to rehabilitate most of the prenatally determined biochemical alterations affecting the 8% pups but, additionally, this form of malnutrition will remain undetected if weight indices alone are used as assessors of normalcy. Thus, it appears that the 8% rats may serve as a useful model for the hidden forms of malnutrition in man.

Adrenalectomy: its effects on systemic tryptophan metabolism in normal and protein malnourished rats.

Rats born to dams fed either a low protein diet (8% casein) or a normal diet (25% casein) started 5 weeks prior to conception and continued through lactation were bilaterally adrenalectomized or received a sham-operation at 30 days of age. At 60 days of age, the systemic tryptophan metabolism of th 8% and 25% adrenalectomized rats was compared to the sham-operated controls of each diet group. While adrenal ablation produced significant decreases in the brain serotonin and metabolite concentrations and marked increases in brain tryptophan concentrations for both diet groups compared to their respective controls, these substances remained significant higher in all malnourished rats than in the well-nourished groups. Also, the major modulator of the peripheral metabolic pathways which regulates the availability of free plasma tryptophan (total tryptophan, albumin, and nonesterified fatty acid concentrations) was the nutritional status of the rats rather than their treatment condition. Only plasma corticosterone concentrations showed changes (significantly decreases) as a consequence of adrenal ablation for either diet group. Overall, the data indicated that under physiological conditions the adrenal cortex has an important function in determining brain tryptophan utilization, whereas its role in regulating peripheral tryptophan metabolism is minimal.

Identification of discrete regions of activity using correlation coefficient scanning of distributed current maps.

Biomagnetic measurements of the brain are often analysed in terms of a number of discrete primary generators. In this paper we describe an objective method of identifying the number of approximate location of such generators. The method is based on the matching of an instrument-independent representation of the data with a template whose pattern is characteristic of a localized primary source. The method is shown to be insensitive to severe noise and to be capable of resolving closely spaced generators.

A systematic review of physical activity interventions among African American adults: evidence from 2009 to 2013.

This review extends findings from four previous reviews of physical activity (PA) interventions among African Americans (AA) and includes papers published between January 2009 and August 2013. Eligible papers were retrieved using strategies employed in previous reviews. Overall, 16 relevant papers were identified, including four pilot studies and 12 full trials. Interventions were based on a variety of behavioural sciences theories. The most common setting for interventions was churches. Most interventions lasted >6 months; few interventions included >6 months of post-intervention follow-up. Overall, studies identified within-group differences showing positive improvements in PA, and most studies showed statistically significant between-group differences in at least one measure of PA. A quality score was used to rate various elements of the studies and provide a numerical assessment of each paper; scores ranged from 3 to 10 out of 13 possible points. The current review indicates a continued need for studies that use objective PA measures, assess long-term intervention impact, provide specific PA goals for interventions, include more attention to strategies that can increase retention and adherence among AA study participants, include AA men and determine the independent and synergistic effects of individual and environmental (socio-cultural and built) change strategies.

Compensatory responses to insulin resistance in obese African-American and Latina girls.

PURPOSE: Insulin responses to oral and intravenous glucose markedly differ by ethnicity. This study examined whether ethnic differences in pancreatic insulin secretion, hepatic insulin extraction and clearance explain these disparate findings in 35 obese African-American and 41 Latina girls (Tanner Stages: IV-V; ages: 14-18; body mass index percentile: 85.9-99.8%). METHODS: Pancreatic insulin secretion, hepatic insulin extraction and clearance were estimated by C-peptide and insulin modeling during an oral glucose tolerance test. Insulin sensitivity (SI), acute insulin response to glucose (AIRG ) and disposition index were derived from a frequently sampled intravenous glucose tolerance test. RESULTS: Compared to Latinas, obese African-American adolescents had lower pancreatic insulin secretion (21.3%; P < 0.01), glucose incremental area under the curve (IAUC) (41.7%, P = 0.02), C-peptide IAUC (25.1%, P < 0.01) and SI (33.7%; P < 0.01). There were no ethnic differences in hepatic insulin extraction and clearance (P's > 0.05). CONCLUSIONS: Compensatory mechanisms to insulin resistance do not appear to explain the ethnic differences in insulin responses to oral and intravenous glucose in obese African-American and Latina girls.

Effects of a randomized maintenance intervention on adiposity and metabolic risk factors in overweight minority adolescents.

OBJECTIVE: The objective of this study was to assess the effects of a maintenance programme (monthly newsletters vs. monthly group classes and telephone behavioural sessions) on obesity and metabolic disease risk at 1 year in overweight minority adolescents. METHODS: After a 4-month nutrition and strength training intervention, 53 overweight Latino and African-American adolescents (15.4 ± 1.1 years) were randomized into one of two maintenance groups for 8 months: monthly newsletters (n = 23) or group classes (n = 30; monthly classes + individualized behavioural telephone sessions). The following outcomes were measured at months 4 (immediately following the intense intervention) and 12: height, weight, blood pressure, body composition via BodPod™ (Life Measurement Instruments, Concord, CA, USA), lipids and glucose/insulin indices via frequently sampled intravenous glucose tolerance test. RESULTS: There were no significant group by time interactions for any of the health outcomes. There were significant time effects in several outcomes for both groups from months 4 to 12: bench press and leg press decreased by 5% and 14%, respectively (P = 0.004 & P = 0.01), fasting insulin and acute insulin response decreased by 26% and 16%, respectively (P < 0.001 & P = 0.046); while high-density lipoprotein cholesterol and insulin sensitivity improved by 5% and 14% (P = 0.042 & P = 0.039). CONCLUSIONS: Newsletters as opposed to group classes may suffice as follow-up maintenance programmes to decrease type 2 diabetes and cardiovascular risk in overweight minority adolescents.

[Optic microscope observations on changes in enamel and dentin induced by laser beams]. / Observations en microscopie optique des modifications de l'émail et de la dentine induites par le rayonnement laser.

By a laser beam, enamel and dentin are changed into an identical crystalline structure observed in reflected light and described as recrystallisation after fusion. The Vickers pyramidal numbers of these areas are the same as the mature enamel surface (590 VPN). The theoretical calculation proved that after irradiation in enamel there is an elevation of temperature about 2,5 degrees C through 3 mm. These observations suggest that new operative techniques might be possible.

Treatment of dental decay by CO2 laser beam: preliminary results.

Results obtained from two clinical cases, representative of 1,140 human teeth treated by CO2 laser beam during 3 years, announce a new conception of treatment of dental caries. The beam (P = 4 - 5 W, energy density of 9 to 25 kw/cm2) causes a dentin healing which becomes sterile, chemically and physically more resistant than pathological dentin. In addition, this exposure leads to an activation of the dentinogenesis supported by X-ray, confirming histo-pathological results obtained from experiments performed on animals.

Electron-beam computed tomographic detection of coronary calcification in patients undergoing percutaneous transluminal coronary angioplasty: predictability of restenosis. A preliminary report.

Coronary artery calcification is a recognized marker for coronary atherosclerosis; however, the relationship between calcification and the success of balloon angioplasty at a calcification site has not been determined. The purpose of this study was to evaluate whether the presence of coronary artery calcification, as detected by electron bean computed tomography (EBCT), was predictive of restenosis after percutaneous transluminal coronary angioplasty (PTCA). Site- specific coronary calcification was determined by EBCT in 20 patients with 24 lesions before, immediately after, and 2 to 18 month after PTCA. Calcification was scored using >130 Hounsfield units and >1.02-mm2 area criteria. Coronary calcium at the PTCA site was significantly greater in restenosed versus nonrestenosed patients (109.16 +/- 198.16 mm2 v 4.39 +/- 9.50 mm2) (P < .025). The amount of coronary calcium did not change as a result of the PTCA procedure (+2.72 +/- 22.31 mm2 v -4.81 +/- 7.82 mm2) (P = NS). The rate of progression of calcification was not greater in restenosed versus nonrestenosed patients (1.78 +/- 3.32 mm2/month v 0.09 +/- 0.19 mm2/mo) (P = NS). Site-specific coronary calcification as determined by EBCT appeared to be predictive of patients with an increased likelihood to restenose after PTCA. Further studies are needed to verify these observations in a considerably larger patient population.

Magnetic field tomography of coherent thalamocortical 40-Hz oscillations in humans.

This paper introduces the use of magnetic field tomography (MFT), a noninvasive technique based on distributed source analysis of magnetoencephalography data, which makes possible the three-dimensional reconstruction of dynamic brain activity in humans. MFT has a temporal resolution better than 1 msec and a spatial accuracy of 2-5 mm at the cortical level, which deteriorates to 1-3 cm at depths of 6 cm or more. MFT is used here to visualize the origin of a spatiotemporally organized pattern of coherent 40-Hz electrical activity. This coherence, initially observed during auditory input, was proposed to be generated by recurrent corticothalamic oscillation. In support of this hypothesis, we illustrate well-defined 40-Hz coherence between cortical-subcortical sites with a time shift that is consistent with thalamocortical conduction times. Studies on Alzheimer patients indicate that, while a similar activity pattern is present, the cortical component is reduced in these subjects.

Comparison of single current dipole and magnetic field tomography analyses of the cortical response to auditory stimuli.

Measurements of the magnetic field elicited by a 50 ms long auditory stimulus, from three normal subjects and one head injured subject, are used to estimate the three dimensional distribution of generators in the brain. The resulting images are compared with point source solutions obtained with the usual single current dipole fitting procedures, over a latency range which includes the extrema in the (average) measured signal. In all cases considered, 100 or so epochs time-locked to the stimulus were magnetically recorded. These were averaged, and then analyzed using two techniques; a new distributed current model known as Magnetic Field Tomography (MFT), and the standard single current dipole (SCD) model. Both methods provide estimates of the current generators in the brain. In two of the normal subjects, the MFT solutions are super-imposed onto Magnetic Resonance Images (MRI) of the relevant cortical area. The results show that when the SCD model provides a reasonable description of the data, the MFT estimate shows one dominant localized region in agreement with the current dipole position. In the MFT sequence of solutions the activity evolves smoothly; multiple areas of activity often arise as the focal activity in one region declines while focal activity in another region grows. In contrast the SCD solutions during these intermediate periods fit the data poorly, and may move erratically from one locale to another. We conclude that MFT seems to provide a reasonable description of the activity through cortical and subcortical regions. The evolution of activity, as derived from the average signal, can be traced continuously from the onset of the stimulus, not just at the peaks.(ABSTRACT TRUNCATED AT 250 WORDS)