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At least 37 records · Page 2Linked to original sources
PubMed1999

Basal and stress-induced corticosterone levels in olive ridley sea turtles (Lepidochelys olivacea) in relation to their mass nesting behavior.

Adrenocortical responsiveness to turning stress was examined in wild, reproductively-active olive ridley sea turtles (Lepidochelys olivacea) in relation to their mass nesting (arribada) behavior. We hypothesized that the high sensitivity threshold (HST) observed in ovipositing sea turtles is associated with a diminished sensitivity of the hypothalamo-pituitary-adrenal (HPA) axis to stressful stimuli in arribada females. We tested this hypothesis by determining whether arribada females exhibited an increased activation threshold of the HPA axis to an imposed stressor (turning stress). Mean basal corticosterone (B) and glucose levels were below 1.0 ng/ml and 60 mg/dl, respectively. Basal B remained unchanged throughout a 24-hr period in basking females. Most animals responded to turning stress with elevated mean B levels (up to 6.5 ng/ml after 6 hr) and no increase in circulating glucose. Nearly 50% of females (and none of the males) were refractory to the stimulation. Males exhibited the most rapid response, with B levels significantly elevated by 20 min over basal levels. Among females, arribada and solitary nesters exhibited a slower rate of response than basking, non-nesting animals. These results demonstrate that olive ridleys exhibit stress-induced changes in circulating B which are slower than those observed in most reptilian and in mammalian, avian, and piscine species. Furthermore, the presence of refractory females and the relatively slower increase in B in arribada and solitary nesters indicate a hyporesponsiveness of the HPA axis to turning stress in nesting olive ridleys. The hyporesponsiveness may be part of a mechanism to facilitate arribada nesting. J. Exp. Zool. 284:652-662, 1999.

Animals↗
PubMed2002

Observations of anomalous mass-loss behavior in SRM coals and cokes on drying.

The determination of moisture content in coal and coke is required for the accurate reporting of physical and chemical constituents on a dry mass basis. Interlaboratory comparisons are reported on a dry mass basis and require reproducible assessments of moisture content to minimize differences among laboratories. Comparability between laboratories is necessary to ensure equity in trade and to avoid costly disputes between buyer and seller. Moisture loss was measured as mass (M) loss as a function of time (t) at constant temperature in a dynamic inert nitrogen atmosphere on 10 SRM coals (7 bituminous and 3 subbituminous) and 4 SRM cokes. Three different patterns of mass-loss were observed-ideal (dM/dt = 0), and two anomalous behaviors, negative deviation (dM/ dt < 0) and positive deviation (dM/dt > 0). Bituminous coals with lower moisture (1-4%) and volatile content (33-38%) tend to display either ideal or positive behavior while subbituminous coals with higher moisture (12-17%) and volatile content (41-47%) display negative behavior. The identification of these different mass-loss patterns demonstrates the potential for method bias depending on the drying end-point definition (ASTM and LECO) used.

Journal Article↗
PubMed1997

Synthesis and mass spectrometric behavior of some new nucleosides as potential anti-HIV agents.

The electron-impact (EI) mass spectrometric behaviour of a series of 8-aza-purines derivatized with hydroxymethylcyclopentane and exhibiting cis-trans isomerization in the cyclopentane ring has been studied in detail with the aid of metastable-ion data. Specific fragmentation processes, present in both EI and mass analysed ion kinetic energy spectra of molecular species, allow characterization of the different pairs of stereoisomers. Contrary to what is observed in the case of purine analogs, the presence of a nitrogen atom in position 8 strongly inhibits fragmentation processes related to the heterocycle.

Anti-HIV Agents↗
PubMed1999

Stereochemical effects on the mass spectrometric behavior of native and derivatized trisaccharide isomers: comparisons with results from molecular modeling.

Differentiation of oligosaccharide isomers by mass spectrometry (MS) is a challenging task. For native, permethylated and peracetylated trisaccharides, matrix-assisted laser desorption/ionization time-of-flight (MALDI/TOF) MS and liquid secondary ionization (LSI) MS experiments can produce complementary results that are useful for molecular mass and sugar sequence determination and isomer differentiation. Linear MALDI/TOF-MS analysis of native and derivatized oligosaccharides usually produces cationized molecular ions. Characterization by LSI-MS and tandem mass spectrometry (LSI-MS/MS) typically may yield only low-abundance protonated molecular ions but produces dominant B-type ions by elimination of ROH (R = Me, Ac) from the C-1 position at the reducing end and distinctive sequence-related fragments. Results for four milk trisaccharides, two neutral (fucosyllactoses) and two sialylated (sialyllactoses), are presented to demonstrate the utility of microscale permethylation and gas-to-solid phase peracetylation for high sensitivity structural elucidation. For the pairs of carbohydrates investigated in this study by LSI-MS, LSI-MS/MS and linear MALDI/TOF-MS, the fragmentation patterns of the native, permethylated and peracetylated isomer pairs are shown to differ markedly as a consequence of their limited dissimilarities. In addition, the tendency of sialylated carbohydrates to form lactones upon peracetylation has been exploited to take advantage of the variation in the extent of lactonization with orientation of the sialic acid moiety relative to the adjacent sugar rings. Lactone formation is favored for 3'-sialyllactose compared with its 6'-isomer; Hyperchem was employed to indicate the relative stabilities of the molecular and fragment ions and to visualize the molecules in 3D (rather than to obtain absolute conformational energy values). The relative conformational energies of lactonized and non-lactonized ions were calculated using the Hyperchem software; their values support the trends observed by MS.

Carbohydrate Conformation↗
PubMed1991

Age, time since menopause, and body parameters as determinants of female spinal bone mass: a mathematical model.

The study of mathematical models to describe bone mass behavior throughout life is a possibility for assessing the main factors of peak bone mass and bone loss. We developed a mathematical model to predict spinal bone mass behavior on a sample of 181 healthy Italian women whose lumbar bone mineral content was determined by Gd-153 dual photon absorptiometry. This model proved to be both efficient, showing the best fit (r = 0.7 on spinal bone mineral content) when compared to other previously suggested models, and also reliable as its fit remained the best when applied to a subsequent sample of 519 women whose lumbar spine was measured by dual X-ray photon absorptiometry. This model suggests that body height and body weight (but not age) are determinants of bone mass in premenopausal women. In postmenopausal women, an accelerated phase of bone loss starting at menopause is dependent on age and time since menopause, whereas body mass index acts as a protective factor. This model confirms the influence on spinal bone mass not only of age and time since menopause but also of body size parameters.

Absorptiometry, Photon↗
PubMed2006

Effects of intrathecally administered nociceptin/orphanin FQ in monkeys: behavioral and mass spectrometric studies.

Nociceptin/orphanin FQ (N/OFQ) is a heptadecapeptide that is an endogenous ligand for the N/OFQ peptide (NOP) receptor. The aim of this study was to investigate the behavioral responses of N/OFQ and its major fragment N/OFQ(2-17) in monkeys following i.t. administration. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) was used to quantify the amounts of N/OFQ and N/OFQ(2-17) in the cerebrospinal fluid at specific time points when effects of i.t. N/OFQ were sustained and disappeared. Intrathecal administration of N/OFQ dose dependently (10-100 nmol) produced long-lasting antinociception against a noxious stimulus, 50 degrees C water, and did not elicit itch/scratching responses in monkeys. Subcutaneous pretreatment with a selective NOP receptor antagonist, (+)J-113397 [(1-[3R,4R)-1-cyclooctymethyl-3-hydroxymethyl-4-piperidyl]-3-ethyl-1,3,-dihydro-2H-benzimidazol-2-one] (0.1 mg/kg), completely blocked i.t. N/OFQ (100 nmol)-induced antinociception. In contrast, a classic opioid receptor antagonist, naltrexone (0.01 and 1 mg/kg), failed to reverse i.t. N/OFQ-induced antinociception. MALDI-TOF-MS showed that the amount of N/OFQ(2-17) was 4-fold higher than that of N/OFQ at 1.5 h after i.t. administration of 100 nmol N/OFQ. Intrathecal N/OFQ-induced antinociception disappeared at 4.5 h, which corresponded to nearly undetectable cerebrospinal fluid levels of N/OFQ. No other metabolite of N/OFQ was detected at appreciable levels at either the 1.5- or 4.5-h time points. Although significant amounts of N/OFQ(2-17) were detected at the 1.5- and 4.5-h time points, 100 nmol N/OFQ(2-17) i.t. was inactive in changing the monkeys' nociceptive threshold. These results provide the first functional evidence of spinal N/OFQ-induced antinociception in primates and indicate that activation of spinal NOP receptors may be a potential target for spinal analgesics.

Analgesics↗
PubMed1995

Behavioral economics and behavioral momentum.

Some relations between elasticity of demand and the conditions of reinforcement are reanalyzed in terms of resistance to change, in ways suggested by the metaphor of behavioral momentum; some relations between resistance to change and the conditions of reinforcement are reanalyzed in terms of elasticity of demand, in ways suggested by behavioral economics. In addition, some data on labor supply in relation to variable-ratio schedules and alternative reinforcement are reanalyzed in terms of resistance to change and compared with steady-state resistance data for performance on multiple and concurrent interval schedules. The results of these studies can be summarized by two functions based on the behavioral momentum approach, relating relative behavioral mass to relative reinforcement per response or per unit time. The former is a relation between relative unit price and relative behavioral mass, suggesting the possibility of convergent measurement of a theoretical construct common to both approaches. However, the momentum and economic approaches differ fundamentally on whether it is preferable to construe discriminated operant behavior as selected and strengthened by its consequences or as part of a behavior-consequence bundle that maximizes utility.

Journal Article↗
PubMed1996

Experimental and theoretical study of the adsorption behavior and mass transfer kinetics of propranolol enantiomers on cellulase protein as the selector.

The thermodynamics and mass transfer kinetics of the retention of the R and S enantiomers of propranolol were investigated on a system comprising an acetic acid buffer solution as the mobile phase and the protein cellobiohydrolase I immobilized on silica as the stationary phase. The bi-Langmuir isotherm model fitted best to each set of single-component isotherm data. The monolayer capacity of the nonchiral type of adsorption sites was 22.9 mM. For the chiral type of sites, it was 0.24 mM for the R enantiomer and 0.64 mM for the S enantiomer. Peak tailing was observed, even at very low concentrations allowing operation of the low-capacity chiral sites under linear conditions. This tailing can be explained on the basis of heterogeneous mass transfer kinetics. At higher concentrations, which are often used in analytical applications, the isotherms on the chiral sites no longer have a linear behavior, and peak tailing is consequently more pronounced. Under those conditions, peak tailing originates from the combined effect of heterogeneous thermodynamics and heterogeneous mass transfer kinetics. These complex phenomena are explained and modeled using the transport-dispersive model with a solid film linear driving force model modified to account for heterogeneous mass transfer kinetics. The rate coefficient of the mass transfer kinetics was found to be concentration dependent.

Adsorption↗
PubMed2005

Intriguing mass spectrometric behavior of guanosine under low energy collision-induced dissociation: H2O adduct formation and gas-phase reactions in the collision cell.

An in-depth study of the fragmentation pathway of guanosine was conducted by using an in-source collision-induced dissociation high-mass accuracy tandem mass spectrometry experiment. The equivalent of MS4 data, a level of information normally achieved on ion trap instruments, was obtained on a Q-TOF mass spectrometer. The combination of the features of high-resolution, accuracy, and in-source CID permitted the unambiguous elucidation of the different fragmentation pathways. Furthermore the elemental compositions of the product ions generated were assigned and their mutual genealogical relationships established. Formerly proposed dissociation pathways of guanosine were revisited and elaborated on more deeply. Furthermore, the presence of H2O in the collision cell of several tandem MS instruments was demonstrated and its effect on the product ion spectra investigated. The neutral gain of H2O by particular fragments of guanosine was experimentally proven by using argon, saturated with H2(18)O, as the collision gas. Data indicating the occurrence of more complex reactions in the collision cell as a result of the presence of H2O were produced, specifically relating to neutral gain/neutral loss sequences. In silico calculations supported the experimental observation of neutral gain by guanosine fragments and predicted a similar behavior for adenosine. The latter was subsequently experimentally confirmed.

Argon↗
PubMed2003

Throwing behavior and mass distribution of stone selection in tufted capuchin monkeys (Cebus apella).

Cannell [Journal of Archaeological Science 29:335-339, 2002] argued that sex-based differences among humans in terms of the mass of chosen throwing stones could be used to infer body mass and patterns of sexual dimorphism in early hominids from Olduvai and Koobi Fora by examining the mass distributions of unaltered stone tools at those sites. We examined this hypothesis in tufted capuchin monkeys using a comparative approach, by investigating the relationships among body mass, sex, stone weight preference, and accuracy in a throwing task. The subject sample consisted of nine monkeys trained to perform an aimed-throwing task in which a food reward could be obtained by throwing a stone into a bucket. We found that 1) the subjects showed a strong mean stone mass preference; 2) the females chose heavier stones than the males, in terms of absolute mean selected stone mass and selected stone mass relative to body mass; 3) subjects threw more accurately when they used stones of preferred mass vs. stones of nonpreferred mass; and 4) overall, the males were more accurate in the throwing task than the females. We conclude that capuchins are highly selective when choosing throwing stones, and that this confers an advantage for throwing accuracy. Our results indicate that the sexually dimorphic pattern in stone mass preference observed among humans does not generalize to Cebus apella. We suggest that researchers examining this pattern in humans in an attempt to explain early hominid patterns of dimorphism and behavior should take into account not only stone weight preference, but also its adaptive advantage.

Animals↗
PubMed2002

Stress-related eating and drinking behavior and body mass index and predictors of this behavior.

BACKGROUND: Earlier studies on stress and obesity have not considered coping in situations involving stress. This study examines the associations between stress-related eating and drinking and obesity and the factors predicting this behavior. Predictive factors include risk factors for adult obesity, longitudinal socioeconomic status, and perceived social support. METHODS: A longitudinal, population-based study of 2,359 men and 2,791 women born in 1966 in Northern Finland was conducted. RESULTS: The body mass index at 31 years was highest among stress-driven eaters and drinkers, especially among women. Stress-driven eaters tended to eat sausages, hamburgers and pizza, and chocolate more frequently than other people. Stress-driven eaters consumed more alcohol than other people. The best predictors of stress-related eating and drinking among men age 31 years were being single or divorced, a long history of unemployment, an academic degree, and a low level of occupational education. Among women, the best predictor was a lack of emotional support. CONCLUSION: Programs aimed at preventing and treating obesity should cover the way in which people deal with emotions, ways of achieving greater emotional support, and strategies for handling stress caused by unemployment or work.

Adaptation, Psychological↗
PubMedDate not supplied

Mass spectral behavior and HPLC of some unusual molecular phospholipid species.

The molecular species of the major phospholipids from the marine sponges Parasperella psila and Microciona prolifera were studied using chemical hydrolysis, enzymatic degradation and capillary gas chromatography (GC), high performance liquid chromatography (HPLC), desorption chemical ionization (DCI), fast atom bombardment (FAB) combined with collisionally activated decomposition (CAD) mass spectrometry. Two new solvent systems were developed for the isolation of these species from the sponges. Our investigations indicated the existence of unusual symmetrical phospholipids as major components. 1,2-Di-(5Z,9Z)-5,9-hexacosadienoyl-sn-glycero-3-phosph oethanolamine was found in both organisms, while 1,2-di(5Z,9Z,19Z)-5,9,19-hexacosatrienoyl-sn-gly cero-3-phosphoethanolamine was present in M. prolifera, 1,2-Di-(4Z,7Z,10Z,13Z,16Z,19Z)-4,7,1 0,13,16,19-docosahexaenoyl-sn-glycero-3- phosphocholine was the major molecular species in the PC fraction of M. prolifera.

Animals↗
PubMed2002

Measuring behavioral momentum.

The metaphor of behavioral momentum proposes that when ongoing operant behavior is disrupted, changes in response rate are directly related to a force-like aspect of the disruptor and inversely proportional to behavioral mass. Several data sets suggest that differential resistance to change between the components of a multiple schedule satisfies the requirements of a ratio scale and is additive when different disruptors and different dimensions of reinforcement are combined. Differential resistance also provides a basis for scaling force in relation to rate of food presentation between components as a disruptor, and for scaling mass in relation to food rate within a component as a reinforcer. Preference in concurrent chains with terminal links identical to multiple-schedule components also meets the requirements of ratio-scale measurement, is additive when different dimensions of reinforcement are combined, and provides convergent measurement of behavioral mass.

Journal Article↗
PubMed2006

Exogenously triggered, enzymatic degradation of photopolymerized hydrogels with polycaprolactone subunits: experimental observation and modeling of mass loss behavior.

Degradation plays an important role in the evolution of the extracellular matrix secreted by chondrocytes encapsulated in PEG-based hydrogels. For this study, macromonomers were synthesized by methacrylating both ends of polycaprolactone-b-poly(ethylene glycol)-b-polycaprolactone (PEG-CAP) tri-block copolymers. These divinyl molecules were photopolymerized to form hydrogels with PEG-CAP crosslinks that were subsequently degraded upon exogenous addition of a lipase enzyme. The rate of degradation and subsequent mass loss depends on both the length of the polycaprolactone units and the concentration of enzyme. Control gels that did not receive lipase did not significantly degrade on the time scale of these experiments. A model was developed to predict mass loss using enzyme kinetics and a previously described statistical treatment of bulk network degradation. The model was used to predict mass loss profiles at the specific conditions used, and also to demonstrate the importance of potential changes in reaction rate and enzyme stability on temporal mass loss.

Hydrogels↗
PubMedDate not supplied

Influence of glycosaminoglycan content of mass transfer behavior of porcine artery wall. Part 1. Diffusive transport of 45Ca2+ and 3HHO.

The diffusion coefficients of Ca2+ and H2O in in vitro porcine arterial tissue were determined to provide a measure of vascular permeability. The effect of anatomical location and diet on the magnitude of that permeability was evaluated. The diffusion coefficient of calcium was found to vary focally and, in addition, pulmonary artery was much more permeable than thoracic aorta. Four months feeding of a high lipid diet did not affect diffusive transport.

Animals↗