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At least 757 records · Page 42Linked to original sources
PubMed2005

Effects of day-length and food availability on food caching, mass and fat reserves in black-capped chickadees (Poecile atricapillus).

Many animals seasonally change energy stores such as food caches and fat deposits. Two factors that potentially influence energy stores are changes in day-length and food availability. We investigated food storing and fat levels in black-capped chickadees to determine how they are affected by changes in duration of light period and duration of food availability. Because previous studies have confounded the effects of photoperiod and the effects of duration of access to food we manipulated these variables independently. Birds were exposed to either long days (15 h light with 15 h of food availability), long day light exposure with short day food availability (15 h light, 9 h food), or short days (9 h light, 9 h food). We measured mass, body fat and the number of sunflower seeds stored in 1-h test sessions for 2 weeks prior and 3 weeks following this manipulation. Neither photoperiod nor food availability had an effect on food storing behavior. Fat and body mass transiently increased in both groups exposed to short duration of food availability, regardless of photoperiod, but did not increase in birds exposed to long days with long duration food availability. These results indicate that duration of time to feed may affect seasonal changes in energy reserves in addition to any effects of photoperiod.

Adipose Tissue↗
PubMed1999

Bone mineral density testing and osteoporosis education improve lifestyle behaviors in premenopausal women: a prospective study.

One way to decrease the risk of osteoporosis is to maximize peak bone mass. Peak bone mass may be moderately influenced by lifestyle behaviors: increasing calcium and exercise, decreasing alcohol intake and smoking may increase peak bone mass. We examined the effects of osteoporosis education and bone mineral density (BMD) testing on self-reported lifestyle behaviors in 669 premenopausal women enrolled in a prospective study to assess determinants of peak bone mass. Study participants completed a questionnaire that assessed lifestyle behaviors, received pamphlets about osteoporosis, and had BMD testing. One year later, the women completed a similar questionnaire. After education about osteoporosis and BMD testing, women reported that they were less likely to smoke (odds ratio [OR] = 0.55; 95% confidence interval [95% CI]: 0.28-1.0), consume alcohol (OR = 0.13; 95% CI: 0.04-0.34), and caffeinated beverages (OR = 0. 43; 95% CI: 0.27-0.68). Women were more likely to use calcium supplements (OR = 4.3; 95% CI: 3.04-6.2), vitamin D supplements (OR = 12.6; 95% CI: 7.4-22.9), and drink at least one glass of milk a day (OR = 13.3; 95% CI: 7.8-23.9). Further, women with low bone mass were more likely to use calcium supplements (OR = 1.7; 95% CI: 1.2-2.3) and vitamin D supplements (OR = 1.6; 95% CI:1.1-2.2) compared with women who had normal bone mass. Thus, our intervention improved self-reported lifestyle behaviors in premenopausal women. Such behaviors may ultimately increase peak bone mass and decrease the risk of developing osteoporosis.

Adult↗
PubMedDate not supplied

The eating and physical activity habits of inner-city adolescents.

INTRODUCTION: The purposes of this study were to (a) analyze the body mass index (BMI) percentile and eating and physical activity habits of adolescents, viewing them by sex, ethnicity, household type, and foreign-born or born in the United States, and (b) evaluate diet and activity analysis software for use by practitioners and adolescent clients. METHOD: A descriptive-correlational study of 74 adolescents from low-income households completed a 24-hour recall of their foods, drinks, and activities, which were analyzed using MyPyramidTracker software. Data were analyzed using parametric and nonparametric methods to test associations and conduct between-group comparisons. RESULTS: Girls, Hispanics, adolescents living with single-parent mothers, and those who were foreign born had the highest mean BMI percentiles and the least healthy eating and physical activity habits. BMI percentile fell as daily calorie expenditure rose. MyPyramidTracker software is suitable for use by adolescents and their family members. DISCUSSION: To contribute to the reversal of national trends of increasing overweight status among adolescents, practitioners can focus their teaching, counseling, and advocacy on adolescents in these groups.

Adolescent↗
PubMed2005

Influence of the labeling group on ionization and fragmentation of carbohydrates in mass spectrometry.

The ionization and fragmentation behaviors of carbohydrate derivatives prepared by reaction with 2-aminobenzamide (AB), 1-phenyl-3-methyl-5-pyrazolone (PMP), and phenylhydrazine (PHN) were compared under identical mass spectrometric conditions. It has been shown that the intensities of signals in MS spectra depend on the kind of saccharides investigated and reducing end labels used. PMP sialyllactose, when ionized by ESI/MALDI, produced a mixture of [M + H]+, [M + Na]+, [M - H + 2Na]+ ions in the positive mode and [M - H]-, [M + Na - 2H]- ions in the negative mode. The AB and PHN derivatives formed abundant [M + H]+ and [M - H]- ions in ESI, and by matrix-assisted laser desorption/ionization (MALDI) produced abundant [M + Na]+ ions. PMP- and reduced AB-sialyllactose produced only Y-type fragment ions under both MS/MS sources. In the electrospray ionization (ESI)-MS/MS spectrum of PHN-sialyllactose, abundant ions corresponded to B, Z cleavages and in its MALDI-MS/MS spectrum, the abundant ions were consistent with Y glycosidic cleavages with the concurrence of B, C, and cross-ring fragment ions. In the MALDI-MS spectra of oligosaccharides acquired immediately after derivatization, it was possible to detect only PHN derivatives. After purification, spectra of all three types of derivatives showed high signal-to-noise ratios with the most abundant ions observed for AB reduced saccharides. [M + Na]+ ions were the dominant products and their fragmentation patterns were influenced by the type of the labeling and the kind of oligosaccharide considered. In the MALDI-PSD and -MS/MS spectra of AB-derivatized glycans, higher m/z fragment ions corresponded to B and Y cleavages and the loss of bisecting GlcNAc appeared as a weak signal or was not detected at all. Fragmentation patterns observed in the spectra of hybrid/complex PHN and PMP glycans were more comparable-higher m/z fragments corresponded to B and C glycosidic cleavages. For PHN glycans, the abundance of ions resulting from the loss of bisecting GlcNAc depended on the number of residues linked to the 6-positioned mannose. Also, PHN and PMP derivatives produced cross-ring cleavages with abundances higher than observed in the spectra of AB derivatized oligosaccharides. For high-mannose glycans, the most informative cleavages were provided by AB and PHN type of labeling. Here, PMP produced dominant Y-cleavages from the chitobiose while other ions produced weak signals.

Antipyrine↗
PubMed2000

Theoretical and numerical analysis of the behavior of ions injected into a quadrupole ion trap mass spectrometer

A numerical simulation method has been developed for the analysis of trapping ions injected into an ion trap mass spectrometer. This method was applied to clarify the effects of the following parameters on trapping efficiencies: (1) initial phase of the radio frequency (RF) drive voltage, (2) ion injection energy, and (3) RF peak voltage while injecting ions. The following conclusions were obtained by theoretical and simulation approaches. 1. The second and third dominant oscillations contribute significantly to the trapping mechanism of the injected ions, even for low q values. 2. A formula relating the operating parameters, which gives the maximum trapping efficiency, is derived. 3. Based on the above-mentioned formula, an advanced injection method is proposed, in which the RF peak voltage is decreased while injecting ions. The ability of this method to solve the problem of unequal sensitivity among different ion species is indicated by numerical simulation. Copyright 2000 John Wiley & Sons, Ltd.

Journal Article↗
PubMed1996

RNA partitioning accompanied by adsorption: high-molecular-mass RNA adsorbed at the interface like a particle.

In a potassium phosphate-poly(ethylene glycol) (PEG) system. RNA partitioning was accompanied by adsorption at the interface, depending on the molecular mass. Low-molecular-mass RNA showed the typical partition behavior of a soluble substance. Conversely, high-molecular-mass RNA was significantly adsorbed at the interface in the potassium phosphate-PEG1500 system. The adsorbed amount was proportional to the added amount, regardless of the phase volume ratio. The partitioning of high-molecular-mass RNA showed an amount-ratio-dependent distribution like that of a particle.

Adsorption↗
PubMed2003

Blunted stress responses in delayed type hypersensitivity in mice lacking the neuronal isoform of nitric oxide synthase.

Nitric oxide (NO) is implicated in inflammation and hypothalamic-pituitary responses to immune stimuli; however, the specific role of NO from neurons during stress-induced immune responses remains unspecified. We measured antigen-specific delayed-type-hypersensitivity (DTH) responses in the skin of wild-type (WT) and neuronal nitric oxide synthase knockout (nNOS(-/-)) mice at baseline and after 2 h of restraint. Baseline corticosterone concentrations were higher in nNOS(-/-) than WT mice. However, stress-induced increases in corticosterone were dampened in nNOS(-/-) mice, and restraint suppressed DTH only in WT animals. Furthermore, WT mice lost more body mass after stress, and exhibited more anxiety-like behavior in the open field, than nNOS(-/-) mice. Neuronal NO appears to be involved in the neuroendocrine-immune response to stress, perhaps via glucocorticoid regulation.

Animals↗
PubMed2006

Detecting gas hydrate behavior in crude oil using NMR.

Because of the associated experimental difficulties, natural gas hydrate behavior in black oil is poorly understood despite its grave importance in deep-water flow assurance. Since the hydrate cannot be visually observed in black oil, traditional methods often rely on gas pressure changes to monitor hydrate formation and dissociation. Because gases have to diffuse through the liquid phase for hydrate behavior to create pressure responses, the complication of gas mass transfer is involved and hydrate behavior is only indirectly observed. This pressure monitoring technique encounters difficulties when the oil phase is too viscous, the amount of water is too small, or the gas phase is absent. In this work we employ proton nuclear magnetic resonance (NMR) spectroscopy to observe directly the liquid-to-solid conversion of the water component in black oil emulsions. The technique relies on two facts. The first, well-known, is that water becomes essentially invisible to liquid state NMR as it becomes immobile, as in hydrate or ice formation. The second, our recent finding, is that in high magnetic fields of sufficient homogeneity, it is possible to distinguish water from black oil spectrally by their chemical shifts. By following changes in the area of the water peak, the process of hydrate conversion can be measured, and, at lower temperatures, the formation of ice. Taking only seconds to accomplish, this measurement is nearly direct in contrast to conventional techniques that measure the pressure changes of the whole system and assume these changes represent formation or dissociation of hydrates - rather than simply changes in solubility. This new technique clearly can provide accurate hydrate thermodynamic data in black oils. Because the technique measures the total mobile water with rapidity, extensions should prove valuable in studying the dynamics of phase transitions in emulsions.

Journal Article↗
PubMed2003

Scaling of impact fragmentation near the critical point.

We investigated two-dimensional brittle fragmentation with a flat impact experimentally, focusing on the low-impact-energy region near the fragmentation-critical point. We found that the universality class of fragmentation transition disagreed with that of percolation. However, the weighted mean mass of the fragments could be scaled using the pseudo-control-parameter multiplicity. The data for highly fragmented samples included a cumulative fragment mass distribution that clearly obeyed a power law. The exponent of this power law was 0.5 and it was independent of sample size. The fragment mass distributions in this regime seemed to collapse into a unified scaling function using weighted mean fragment mass scaling. We also examined the behavior of higher-order moments of the fragment mass distributions, and obtained multiscaling exponents that agreed with those of the simple biased cascade model.

Journal Article↗
PubMed2006

Alcohol consumption and risk for coronary heart disease in men with healthy lifestyles.

BACKGROUND: Although moderate alcohol intake is associated with lower risk for myocardial infarction (MI), guidelines generally suggest that adults seek other lifestyle measures to reduce cardiovascular risk. We studied whether alcohol consumption is inversely associated with risk for coronary heart disease in men who report consistently favorable lifestyle behaviors. METHODS: From 51 529 male participants of the Health Professionals Follow-up Study who have reported diet and other lifestyle factors in biennial questionnaires since 1986, we defined a cohort of 8867 men free of major illness to participate in a prospective study. All participants reported 4 healthy lifestyle behaviors, including a body mass index (calculated as weight in kilograms divided by height in meters squared) of less than 25, moderate to vigorous activity for 30 minutes or more per day, abstention from smoking, and a summary diet score in the top 50% for men. High dietary scores reflected a high intake of vegetables, fruits, cereal fiber, fish, chicken, nuts, soy, and polyunsaturated fat; low consumption of trans-fat, and red and processed meats; and multivitamin use. We ascertained the incidence of nonfatal MI and fatal coronary heart disease according to reported intake of beer, wine, and liquor every 4 years. RESULTS: During 16 years of follow-up, we documented 106 incident cases of MI. Compared with abstention, the hazard ratios for MI were 0.98 (95% confidence interval, 0.55-1.74) for alcohol intake of 0.1 to 4.9 g/d, 0.59 (95% confidence interval, 0.33-1.07) for alcohol intake of 5.0 to 14.9 g/d, 0.38 (95% confidence interval, 0.16-0.89) for alcohol intake of 15.0 to 29.9 g/d, and 0.86 (95% confidence interval, 0.36-2.05) for alcohol intake of 30.0 g/d or more. In men who met 3 criteria, the lower risk associated with alcohol intake of 5.0 to 29.9 g/d tended to be similar to the lower risk associated with the remaining healthy lifestyle behavior. CONCLUSION: Even in men already at low risk on the basis of body mass index, physical activity, smoking, and diet, moderate alcohol intake is associated with lower risk for MI.

Alcohol Drinking↗
PubMed2005

Effects of fusion-bone stiffness on the mechanical behavior of the lumbar spine after vertebral body replacement.

BACKGROUND: Implants for vertebral body replacement are often inserted together with an additional stabilizing implant, e.g. an internal fixation device. During implantation bone grafts or milled bone is normally added to the anterior implant. Little is known about the stiffening effect of this fusion-bone mass on the mechanical behavior of the corresponding bone region, including the load distribution between the different parts. METHODS: A three-dimensional finite element model of the lumbar spine was created with a vertebral body replacement at L3, a paired internal fixation device between L2 and L4, and left anterolateral fusion bone. The elastic modulus of fusion bone was varied in discrete steps between 0 MPa and 10,000 MPa. The model was loaded to simulate standing, 20 degrees flexion, 15 degrees extension and 6 degrees axial rotation in the lumbar spine. FINDINGS: The elastic modulus of fusion bone has a considerable effect on the compressive force on vertebral body replacement and fusion bone for all loading cases studied. For extension, it also affects intersegmental rotation, the force in the erector spinae muscle, the compressive force on the internal fixator and intradiscal pressure in the adjacent discs. The elastic modulus most strongly affects the different parameters at values between 0 MPa and 500 MPa. INTERPRETATION: Adding bone mass during vertebral body replacement reduces the loads on the ventral implant for all loading cases studied but extension when the fusion-bone stiffens. This protects the implant from fatigue. The load on the fusion bone increases with increasing elastic modulus. Thus bone grafts should be used whenever possible.

Biomechanical Phenomena↗
PubMedDate not supplied

Embedding health messages into entertainment television: effect on gay men's response to a syphilis outbreak.

The entertainment education (EE) approach seeks to impact audiences' health behavior by embedding messages in mass media productions, storylines, and characters that appeal strongly to them. Effect on behavioral intentions was examined following a storyline about syphilis in men who have sex with men (MSM) presented in a popular dramatic series. Five hundred and one MSM drawn from gay Internet chat rooms completed the questionnaire. Differences in item responses between those who did and did not view the syphilis storyline were calculated, and linear regression was used to examine predictors of intentions to take action. Those who viewed the syphilis storyline were more likely to report intention to get screened and to tell others to get screened for syphilis. Seeing the episode was a predictor of these intentions. Education was also a predictor of intention to tell others to get screened. Results suggest that exposure to a storyline about syphilis in gay men had a positive public health outcome on users of Internet chat rooms for MSM. Further studies are warranted to examine the extent to which and how the EE approach can produce health-relevant outcomes for U.S. populations, just as the approach has done in the developing world.

Adolescent↗
PubMed2006

Tandem mass spectra of ammonium adducts of monosaccharides: differentiation of diastereomers.

Tandem mass spectra of ammonium adducts of monosaccharides gave characteristic fragmentation patterns involving elimination of NH3/H2O followed by multiple eliminations of H2O and cross ring cleavages. Tandem mass spectra were examined over a range of collision energies (1-20 eV) on a triple-quadrupole mass spectrometer. The breakdown behavior of the ammonium adducts revealed patterns that could differentiate diastereomers of monosaccharides.

Glucose↗
PubMed1991

Application of the split-peak effect to study the adsorption kinetics of human serum albumin on a reversed-phase support.

The adsorption step of human serum albumin on a reversed-phase support was analyzed by studying the "split-peak" effect in mass-overload conditions. This behavior is characterized by the occurrence of a first non-retained fraction and is described by an analytical expression in the case of a Langmuirian adsorption isotherm. The method was applied to determine the column loading capacity, the number of mass-transfer units and the apparent adsorption rate constant measured at a given flow-rate. The nature of the organic modifier influences the split-peak effect: it increases with the eluotropic strength of the organic solvent added to the buffer. Compared to the results with pure buffer, it is the association of two effects, the decrease of the column loading capacity and that of the apparent adsorption rate constant, which increases the split-peak effects observed when methanol and 2-propanol are added to the eluent. These results allow us to gain a better understanding of the role of the organic solvent in the elution behavior of proteins in reversed-phase high-performance liquid chromatography.

1-Propanol↗
PubMed2006

Bifurcation analysis of Jansen's neural mass model.

We present a mathematical model of a neural mass developed by a number of people, including Lopes da Silva and Jansen. This model features three interacting populations of cortical neurons and is described by a six-dimensional nonlinear dynamical system. We address some aspects of its behavior through a bifurcation analysis with respect to the input parameter of the system. This leads to a compact description of the oscillatory behaviors observed in Jansen and Rit (1995) (alpha activity) and Wendling, Bellanger, Bartolomei, and Chauvel (2000) (spike-like epileptic activity). In the case of small or slow variation of the input, the model can even be described as a binary unit. Again using the bifurcation framework, we discuss the influence of other parameters of the system on the behavior of the neural mass model.

Action Potentials↗
PubMed1998

Satellites as probes of the masses of spiral galaxies.

We present atomic hydrogen (HI) observations and analyses of the kinematics of satellite-primary galaxy pairs. Two estimates for the masses of the primaries are available, one from their rotation curves and one from the orbital properties of the satellites. Defining chi as the ratio of these two mass estimates, it is a measure of the presence, or absence, of a significant halo. The chi distribution is presented and the selection effects are discussed. We show that our data, compared with the more numerous pairs identified by Zaritsky et al., have similar distributions for projected separations of less than 200 kpc, even though the selection criteria employed were quite different. Observational biases have a negligible effect; the biased and unbiased distributions are essentially identical. N-body calculations were executed to simulate the dynamical behavior of relatively low mass satellites orbiting primary disk galaxies with and without extended halos. In addition, we made a partially analytical analysis of the behavior of orbits in a logarithmic potential. We find that a "generic" model, characterized by a single disk-halo combination, cannot reproduce the observed P(chi) distribution. However, a simple two-component population of galaxies, composed of not more than 60% with halos and 40% without halos, is successful, if galaxies have dimensions of order 200 kpc. If galaxies are considerably larger with sizes extending to 400 kpc or more, no generic model can describe the full range of the observed P(chi), particularly if the distribution for r(p) < 200 kpc is compared with that for r(p) > 200 kpc. Regardless of the mix of orbital eccentricities, neither pure halo, nor canonical models (disk and halo masses are comparable within the disk radius) will work. A multicomponent approximation can be constructed; the canonical model must be mixed with a small fraction of systems essentially devoid of a massive dark halo. Only by including these complexities can the full range of P(chi) be modeled with any degree of success over all radial extents. We show that dynamical friction cannot be ignored in these explorations and that the average mass of a galaxy is in the range of (1-5) x 10(12) M, with a mass-to-luminosity ratio of at most a few hundred. This is insufficient to close the Universe.

Journal Article↗