bluuebunny/crossref_metadata_2025_split huggingface dataset:
Hypermethylation of Adenosine Triphosphate-Binding Cassette Transporter Genes in Primary Hyperparathyroidism and Its Effect on Sestamibi Imaging
Authors: Takeuchi Hiroya , Greep Nancy C. , Hoon Dave S. B. , Giuliano Armando E. , Hansen Nora M. , Umetani Naoyuki , Singer Frederick R. 
Published: February 2007

Abstract
Context: Retention of technetium-99m-sestamibi (99mTc-sestamibi) by parathyroid adenomas appears to be due to the loss of at least one membrane transporter, multidrug resistance 1 (MDR1), and possibly another, multidrug resistance-associated protein 1 (MRP1).
Objective: The objective was to determine whether hypermethylation of either gene plays a role in their expression and 99mTc-sestamibi retention.
Design: This was a retrospective study on a convenience sample of paraffin-embedded parathyroid glands.
Setting: The study was performed at the John Wayne Cancer Institute at Saint John’s Health Center (Santa Monica, CA).
Patients: Forty-eight patients with primary hyperparathyroidism and five patients without parathyroid disease undergoing thyroid surgery provided 27 adenomatous, 10 hyperplastic, and 16 normal parathyroid glands.
Intervention: We performed immunohistochemistry, real-time quantitative RT-PCR, and methylation-specific PCR for MDR1 and MRP1 on archival parathyroid tissue and correlated these results with the patient’s 99mTc-sestamibi scan.
Main Outcome Measure: The main outcome measure was to determine whether hypermethylation of the genes for either transporter is associated with loss of their expression and with a positive 99mTc-sestamibi scan.
Results: The MDR1 gene was methylated in none of 12 normal glands, 19 of 27 adenomas, and three of 10 hyperplastic glands. Methylation of the MRP1 gene was uncommon (five of 48 tested glands). Methylation of the gene affected the transcript level only for MDR1. Among all glands, hypermethylation for MDR1 was more likely in 99mTc-sestamibi-positive scans (P &lt; 0.001).
Conclusion: In parathyroid tissue, hypermethylation of the MDR1 gene decreases its expression and is associated with increased detection of parathyroid adenomas by 99mTc-sestamibi parathyroid scans.
Dexmedetomidine: An Updated Review
Authors: Gerlach Anthony T , Dasta Joseph F 
Published: February 2007

Objective: To review recent literature on the safety and efficacy of dexmedetomidine. Data Sources: Articles were identified through searches of MEDLINE (1966–January 2007). Key words included dexmedetomidine, medetomidine, α2-agonist, and sedation. References from selected articles were reviewed for additional references. Study Selection and Data Extraction: Experimental and observational studies that focused on the safety and efficacy of dexmedetomidine in humans were selected. Data Synthesis: Dexmedetomidine is an α2-agonist for short-term sedation in critically ill patients. In postoperative patients, dexmedetomidine produced similar levels of sedation and times to extubation, with less opioid requirements compared with propofol. Dexmedetomidine has also been studied for sedation in critically ill medical and pediatric patients, as adjunct to anesthesia, and for procedural sedation. Hypotension, hypertension, and bradycardia are common adverse effects. Although dexmedetomidine is labeled only for sedation less than 24 hours, it has been administered for longer than 24 hours without apparent development of rebound hypertension and tachycardia. Conclusions: Dexmedetomidine is a safe and effective agent for sedation in critically ill patients. Further, well designed studies are needed to define its role as a sedative for critically ill medical, neurosurgical, and pediatric patients, as an adjunct to anesthesia, and as a sedative during procedures.
The preservational fidelity of evenness in molluscan death assemblages
Authors: Olszewski Thomas D. , Kidwell Susan M. 
Published: February 2007

The richness (number of species) and evenness (uniformity of species abundances) of death assemblages can differ from corresponding living communities due to processes such as between-habitat transport, environmental condensation, and differential taphonomic destruction. Analysis of 132 single-census live-dead comparisons of benthic molluscs from a variety of soft-bottom marine settings indicates thaton averageevenness does not differ greatly between live and dead assemblages, regardless of the particular depositional setting or grain size of associated sediment. However,individualdeath assemblages can deviate quite substantially from their corresponding living assemblages, especially if processed using a fine mesh. In addition, death assemblages collected using sieves with 2 mm mesh or coarser showed consistently and significantly greater evenness than corresponding living assemblages. These results are encouraging for broad-scale assessments of evenness in the fossil record based on the comparison ofaveragevalues (rather than for individual assemblages) and wheretrendsin evenness are the aim of the study.Our live-dead comparisons of richness sample-size corrected by rarefaction revealed that death assemblages were on average ~1.45 times richer than the corresponding living assemblages regardless of rarefied size. In 63.6% of death assemblages both dead richness and dead evenness were greater than live, suggesting sufficient time-averaging to catch significant random or directional changes in the living community and/or introduction of individuals from outside the sampled habitat. In 12.9% of collections both dead richness and dead evenness were less than live, suggesting either rapid loss of dead shells so that dead diversity is depressed below the local living community or selective loss of taphonomically vulnerable taxa. In 18.2% of data sets dead richness was elevated but dead evenness was depressed relative to live: these are interpreted to reflect the addition of low-evenness allochthonous material. The remaining 4.5% of data sets had elevated dead evenness but depressed dead richness, suggesting that live and dead in this case may not be closely related.In seven available time series, temporal volatility in living communities over 6–24 months was considerable but could not account for observed (mostly higher) evenness values in corresponding death assemblages, whose evenness and composition were quite stable in the few examined studies. A densely sampled spatial transect shows that changes in living-assemblage evenness along an environmental gradient were preserved in the corresponding death assemblages, although dead evenness at any location on the gradient was substantially higher than living evenness.
A quantitative null model of additive diversity partitioning: examining the response of beta diversity to extinction
Authors: Layou Karen M. 
Published: February 2007

Paleobiological diversity is often expressed as α (within-sample), β (among-sample), and γ (total) diversities. However, when studying the effects of extinction on diversity patterns, only variations in α and γ diversities are typically addressed. A null model that examines changes in β diversity as a function of percent extinction is presented here.The model examines diversity in the context of a hierarchical sampling strategy that allows for the additive partitioning of γ diversity into mean α and β diversities at varying scales. Here, the sampling hierarchy has four levels: samples, beds, facies, and region; thus, there are four levels of α diversity (α1, α2, α3, α4) and three levels of β diversity (β1, β2, and β3). Taxa are randomly assigned to samples within the hierarchy according to probability of occurrence, and initial mean α and β values are calculated. A regional extinction is imposed, and the hierarchy is resampled from the remaining extant taxa. Post-extinction mean α and β values are then calculated.Both non-selective and selective extinctions with respect to taxon abundance yield decreases in α, β, and γ diversities. Non-selective extinction with respect to taxon abundance shows little effect on diversity partitioning except at the highest extinction magnitudes (above 75% extinction), where the contribution of α1 to total γ increases at the expense of β3, with β1 and β2 varying little with increasing extinction magnitude. The pre-extinction contribution of α1 to total diversity increases with increased probabilities of taxon occurrence and the number of shared taxa between facies. Both β1 and β2 contribute equally to total diversity at low occurrence probabilities, but β2 is negligible at high probabilities, because individual samples preserve all the taxonomic variation present within a facies. Selective extinction with respect to rare taxa indicates a constant increase in α1 and constant decrease in β3 with increasing extinction magnitudes, whereas selective extinction with respect to abundant taxa yields the opposite pattern of an initial decrease in α1 and increase in β3. Both β1 and β2 remain constant with increasing extinction for both cases of selectivity. By comparing diversity partitioning before and after an extinction event, it may be possible to determine whether the extinction was selective with respect to taxon abundances, and if so, whether that selectivity was against rare or abundant taxa.Field data were collected across a Late Ordovician regional extinction in the Nashville Dome of Tennessee, with sampling hierarchy similar to that of the model. These data agree with the abundant-selective model, showing declines in α, β, and γ diversities, and a decrease in α1 and increase in β3, which suggests this extinction may have targeted abundant taxa.
A model of wear in curved mammal teeth: controls on occlusal morphology and the evolution of hypsodonty in lagomorphs
Authors: Bair Andrea R. 
Published: February 2007

Cheek teeth of some mammalian herbivores exhibit pronounced changes in occlusal size and shape through wear, purportedly caused by strong curvature. Such changes are extreme in the upper cheek teeth of extinct, dentally archaic lagomorphs. Morphologic and taxonomic turnover in lagomorphs suggests that these dentally archaic forms may have been unable to develop hypselodont (ever-growing) cheek teeth. This study investigates how the interaction of tooth shape and wear can cause occlusal size and shape changes, and potentially impose structural constraints on crown height. These constraints may help explain extinction of mammals with teeth like archaic lagomorphs, evolution and diversification of other mammalian herbivores during the late Miocene, and the relative paucity of hypsodont cheek tooth shapes in extant mammals.I first quantify two-dimensional curvature accounting for shape differences observed in hypsodont teeth, P4s of the archaic lagomorphsRussellagusandHesperolagomys, which exhibit pronounced change with wear, andOndatralower incisors, which show minimal change with wear. Using this quantification, I generate theoretical curvature morphologies and describe a geometric model of tooth wear that generates values for qualitative and quantitative aspects of the occlusal surface at different wear stages. Modeled results of wear surface topography and dimensions closely correspond to observed patterns inRussellagus, Hesperolagomys, andOndatra. Model results on wear in theoretical tooth morphologies identify two major shape factors influencing wear: orientation of the wear surface (incisor-like or cheek-tooth-like), and tooth curvature (“concentric” or “nonconcentric”). Modeled wear also suggests two geometric constraints on crown height. Teeth with nonconcentric curvatures can have crown height limited by potential tooth area. “Incomplete wear” in any tooth can present severe constraints on increasing crown height, causing structurally untenable morphologies in very tall-crowned to hypselodont teeth.
Polychlorinated biphenyl contamination of the spider crab (Maja brachydactyla): Influence of physiological and ecological processes
Authors: Bodin Nathalie , Caisey Xavier , Abarnou Alain , Loizeau Véronique , Latrouite Daniel , Guellec Anne-Marie Le , Guillou Monique 
Published: February 2007

Abstract
Maja brachydactyla is a decapod crustacean widely distributed along the Northeast Atlantic coasts. The main objective of this work was to establish the influence of ontogenic factors, such as growth, aging, seasonal migrations, and reproduction, on the contamination of this species by polychlorinated biphenyls (PCBs). Two populations were studied: One in the Seine Bay (Eastern English Channel), which is exposed to greatly contaminated discharges from the Seine River, and one in the Iroise Sea (Western Brittany), which is little contaminated by such man-made compounds. At both sampling areas, PCB analysis revealed concentrations in hepatopancreas that were 10- and 50-fold higher than concentrations in gonads and muscle, respectively. Levels of 2,2′,4,4′,5,5′-hexachlorobiphenyl (CB153) increased with the age of the spider crabs, whereas their seasonal migrations had no direct effect. No significant sex effect was observed with regards to CB153 levels, but adult females exhibited PCB fingerprints different from those of males, probably because of the influence of the reproductive cycle on enzymatic system activity. Finally, spawning gave rise to a higher CB153 decontamination of female body burdens for specimens from the Iroise Sea than for those from the Seine Bay.
Desorption kinetics of hydrophobic organic chemicals from sediment to water: A review of data and models
Authors: Birdwell Justin , Cook Robert L. , Thibodeaux Louis J. 
Published: February 2007

Abstract
Resuspension of contaminated sediment can lead to the release of toxic compounds to surface waters where they are more bioavailable and mobile. Because the timeframe of particle resettling during such events is shorter than that needed to reach equilibrium, a kinetic approach is required for modeling the release process. Due to the current inability of common theoretical approaches to predict site-specific release rates, empirical algorithms incorporating the phenomenological assumption of biphasic, or fast and slow, release dominate the descriptions of nonpolar organic chemical release in the literature. Two first-order rate constants and one fraction are sufficient to characterize practically all of the data sets studied. These rate constants were compared to theoretical model parameters and functionalities, including chemical properties of the contaminants and physical properties of the sorbents, to determine if the trends incorporated into the hindered diffusion model are consistent with the parameters used in curve fitting. The results did not correspond to the parameter dependence of the hindered diffusion model. No trend in desorption rate constants, for either fast or slow release, was observed to be dependent on KOC or aqueous solubility for six and seven orders of magnitude, respectively. The same was observed for aqueous diffusivity and sediment fraction organic carbon. The distribution of kinetic rate constant values was approximately log-normal, ranging from 0.1 to 50 d−1 for the fast release (average ∼5 d−1) and 0.0001 to 0.1 d−1 for the slow release (average ∼0.03 d−1). The implications of these findings with regard to laboratory studies, theoretical desorption process mechanisms, and water quality modeling needs are presented and discussed.
Competition among zinc, manganese, and cadmium uptake in the freshwater alga Scenedesmus vacuolatus
Authors: Töpperwien Stefanie , Behra Renata , Sigg Laura 
Published: February 2007

Abstract
In the present study, Zn and Mn competition with Cd uptake was investigated in the freshwater alga Scenedesmus vacuolatus. Scenedesmus vacuolatus was exposed to experimental media with Cd and either Zn or Mn in short-term experiments; long-term experiments were undertaken to investigate the effect of growth on Cd accumulation. Cadmium accumulation in S. vacuolatus could be detected at very low exposure concentrations (free Cd2+, 2 × 10−14 to 1 × 10−11 M), and uptake was proportional to the free-Cd2+ concentration. Zinc was an effective competitive inhibitor of Cd uptake when the Zn2+ to Cd2+ ratio was greater than 14 in the exposure medium, whereas Mn competed with Cd for uptake above a Mn2+ to Cd2+ ratio of greater than 10,000. Binding constants for Cd and Zn affinity to the transport sites were determined (KZn and KCd). Values for KZn were slightly higher (log K = 9.4–9.8) than values for KCd (log K = 8.9–9.8). In contrast, Cd seemed not to compete with the Mn-binding sites for uptake over the Mn concentration range from 1 × 10−10 to 1 × 10−8 M. Determined values for the binding constants of Zn and Cd show that a simple model can be applied to predict Cd uptake at known Zn and Cd concentrations. The environmental implications of these results are discussed with respect to potential Cd toxicity for aquatic organisms.
Availability of polycyclic aromatic hydrocarbons from lampblack-impacted soils at former oil-gas plant sites in California, USA
Authors: Hong Lei , Luthy Richard G. 
Published: February 2007

Abstract
Lampblack-impacted soils at former oil-gas plant sites in California, USA, were characterized to assess the sorption of polycyclic aromatic hydrocarbons (PAHs) and the concentration-dependent effects of a residual oil tar phase on sorption mechanism and availability of PAHs. Nuclear magnetic resonance spectroscopy demonstrated similar aromaticity for both lampblack carbon and the oil tar phase, with pronounced resonance signals in the range of 100 to 150 ppm. Scanning-electron microscopic images revealed a physically distinct oil tar phase, especially at high concentrations in lampblack, which resulted in an organic-like film structure when lampblack particles became saturated with the oil tar. Sorption experiments were conducted on a series of laboratory-prepared lampblack samples to systematically evaluate influences of an oil tar phase on PAH sorption to lampblack. Results indicate that the sorption of PAHs to lampblack exhibits a competition among sorption phases at low oil tar contents when micro- and mesopores are accessible. When the oil tar content increases to more than 5 to 10% by weight, this tar phase fills small pores, reduces surface area, and dominates PAH sorption on lampblack surface. A new PAH partitioning model, Kd = KLB-C(1-ftar)° + ftarKtar (α = empirical exponent), incorporates these effects in which the control of PAH partitioning transits from being dominated by sorption in lampblack (KLB-C) to absorption in oil tar (Ktar), depending on the fraction of tar (ftar). This study illustrates the importance of understanding interactions among PAHs, oil tar, and lampblack for explaining the differences in availability of PAHs among site soils and, consequently, for refining site-specific risk assessment and establishing soil cleanup levels.
Cadmium uptake byCeriodaphnia dubiafrom different exposures: Relevance to body burden and toxicity
Authors: Sofyan Agus , Rosita Gina , Price David J. , Birge Wesley J. 
Published: February 2007

AbstractUptake of cadmium from water by freshwater animals has been well documented. However, little attention has been given to the importance of dietary and combined exposure as the source for uptake. In the present study, we compared cadmium uptake from waterborne (water-only), dietary (food-only), and combined (water plus food) exposures on the freshwater cladoceran Ceriodaphnia dubia. Major test end points included cadmium whole-body burdens, feeding rate, and reproduction. The C. dubia three-brood reproduction tests were conducted according to U.S. Environmental Protection Agency methods. The results indicated that cadmium was accumulated from both water and diet. Whereas the results showed that uptake from water was more rapid than uptake from diet, both uptakes occurred independently, and cadmium concentrations in C. dubia were additive from both sources. Furthermore, the present study found cadmium trophic transfer between primary producers (i.e., Pseudokirchneriella subcapitata) and primary consumers (i.e., C. dubia). Feeding rate was reduced from all avenues of exposure. Feeding reduction in combined exposure was affected additively by waterborne and dietary cadmium. Also, reductions in neonate production were observed after exposure to all three exposure types. Both body burden and reduced feeding affected C. dubia reproduction. These results indicate the importance of both waterborne and dietary cadmium exposures as the sources for metal uptake and toxicity.
Predicting survival of grass shrimp (Palaemonetes pugio) during ethylnaphthalene, dimethylnaphthalene, and phenanthrene exposures differing in concentration and duration
Authors: Unger Michael A. , Newman Michael C. , Vadas George G. 
Published: February 2007

AbstractBoth exposure duration and concentration determine the lethal consequences of polycyclic aromatic hydrocarbons (PAHs) released during oil spills. Many factors, such as weathering, tidal transport, and addition of surfactants, can change the composition of individual dissolved compounds and the duration over which an individual is exposed. Conventional toxicity testing methods produce effect metrics, such as the median lethal concentration (LC50), that are not applicable to predicting mortality at all toxicant exposure durations that are likely to occur during a spill. In the present study, survival time models were developed that explicitly include toxicant exposure duration and concentration to predict time-to-death for grass shrimp (Palaemonetes pugio) exposed to three PAHs (1-ethylnaphthalene, 2,6-dimethylnaphthalene, and phenanthrene) commonly found in the water-soluble fraction derived from oil. Conventional 48-h LC50s also were calculated for the compounds (ethylnaphthalene, 295 μg/L; dimethylnaphthalene, 500 μg/L; and phenanthrene, 360 μg/L). In contrast to LC50s, survival models and associated response surfaces can be used to predict the proportions of shrimp that will die at various times throughout the exposure period.
Integrated assessment of multilevel biomarker responses and chemical analysis in mussels from São Sebastião, São Paulo, Brazil
Authors: Pereira Camilo Dias Seabra , de Souza Abessa Denis Moledo , Bainy Afonso Celso Dias , Zaroni Letícia Pires , Gasparro Márcia Regina , Bicego Márcia Caruso , Taniguchi Satie , Furley Tatiana Heid , de Sousa Eduinetty Ceci Pereira Moreira 
Published: February 2007

Abstract
The aim of the present study was to investigate the presence of contaminants in the mussel Perna perna from São Sebastião Channel, São Paulo, Brazil, and to evaluate the effects of these contaminants on these organisms at biochemical (catalase [CAT], glutathione-S-transferase [GST], and cholinesterase [ChE]), cellular (neutral red retention time [NRRT] assay), and physiological (cardiac monitoring) levels. Two sampling surveys were performed (winter of 2001 and summer of 2002) at six stations along the channel: Cigarras, station 1; Iate Clube de Ilhabela, station 2; Oil Terminal, station 3; Toque Toque, station 4; Ponta da Sela, station 5 (reference station); and Taubaté, station 6. Differences in CAT activity were observed between mussels from stations 3 and 5 during the winter, but no differences were detected in the summer. No differences in GST activity were found among stations during the winter, although animals from station 3 showed higher activity during the summer. The ChE activity was significantly higher in the mussels from stations 1 and 2 during the winter and from stations 1 and 3 during the summer. Organisms from stations 1 through 4 showed statistically lower NRRT in both seasons. Similar heart rates were observed in the mussels from all stations. Hydrocarbons were detected in organisms from all the stations in both seasons. During the winter, higher polycyclic aromatic hydrocarbon (PAH) levels were observed in organisms from station 3, whereas during the summer, higher levels of metals were found in organisms from stations 1,3, and 4. The multivariate analyses showed a strong influence of PAHs on the winter biological results, but metals showed higher influence on these responses in the summer, indicating multiple contaminant sources.