bluuebunny/crossref_metadata_2025 huggingface dataset:
Association of the type 2 deiodinase Thr92Ala polymorphism with type 2 diabetes: case–control study and meta-analysis
Authors: Dora José Miguel , Machado Walter Escouto , Rheinheimer Jakeline , Crispim Daisy , Maia Ana Luiza
Published: June 2010

Objective

The type 2 deiodinase (D2) is a key enzyme for intracellular triiodothyronine (T3) generation. A single-nucleotide polymorphism in D2 (Thr92Ala) has been associated with increased insulin resistance in nondiabetic and type 2 diabetes (DM2) subjects. Our aim was to evaluate whether the D2 Thr92Ala polymorphism is associated with increased risk for DM2.

Design and methods

A case–control study with 1057 DM2 and 516 nondiabetic subjects was performed. All participants underwent genotyping of the D2 Thr92Ala polymorphism. Additionally, systematic review and meta-analysis of the literature for genetic association studies of D2 Thr92Ala polymorphism and DM2 were performed in Medline, Embase, LiLacs, and SciELO, and major meeting databases using the terms ‘rs225014’ odds ratio (OR) ‘thr92ala’ OR ‘T92A’ OR ‘dio2 a/g’.

Results

In the case–control study, the frequencies of D2 Ala92Ala homozygous were 16.4% (n=173) versus 12.0% (n=62) in DM2 versus controls respectively resulting in an adjusted OR of 1.41 (95% confidence intervals (CI) 1.03–1.94, P=0.03). The literature search identified three studies that analyzed the association of the D2 Thr92Ala polymorphism with DM2, with the following effect estimates: Mentuccia (OR 1.40 (95% CI 0.78–2.51)), Grarup (OR 1.09 (95% CI 0.92–1.29)), and Maia (OR 1.22 (95% CI 0.78–1.92)). The pooled effect of the four studies resulted in an OR 1.18 (95% CI 1.03–1.36, P=0.02).

Conclusions

Our results indicate that in a case–control study, the homozygosity for D2 Thr92Ala polymorphism is associated with increased risk for DM2. These results were confirmed by a meta-analysis including 11 033 individuals, and support a role for intracellular T3 concentration in skeletal muscle on DM2 pathogenesis.
Prolonged and Exclusive Breastfeeding Reduces the Risk of Infectious Diseases in Infancy
Authors: Duijts Liesbeth , Jaddoe Vincent W. V. , Hofman Albert , Moll Henriëtte A.
Published: June 2010

OBJECTIVE:

To examine the associations of duration of exclusive breastfeeding with infections in the upper respiratory (URTI), lower respiratory (LRTI), and gastrointestinal tracts (GI) in infancy.

METHODS:

This study was embedded in the Generation R Study, a population-based prospective cohort study from fetal life onward in the Netherlands. Rates of breastfeeding during the first 6 months (never; partial for <4 months, not thereafter; partial for 4–6 months; exclusive for 4 months, not thereafter; exclusive for 4 months, partial thereafter; and exclusive for 6 months) and doctor-attended infections in the URTI, LRTI, and GI until the age of 12 months were assessed by questionnaires and available for 4164 subjects.

RESULTS:

Compared with never-breastfed infants, those who were breastfed exclusively until the age of 4 months and partially thereafter had lower risks of infections in the URTI, LRTI, and GI until the age of 6 months (adjusted odds ratio [aOR]: 0.65 [95% confidence interval (CI): 0.51–0.83]; aOR: 0.50 [CI: 0.32–0.79]; and aOR: 0.41 [CI: 0.26–0.64], respectively) and of LRTI infections between the ages of 7 and 12 months (aOR: 0.46 [CI: 0.31–0.69]). Similar tendencies were observed for infants who were exclusively breastfed for 6 months or longer. Partial breastfeeding, even for 6 months, did not result in significantly lower risks of these infections.

CONCLUSIONS:

Exclusive breastfeeding until the age of 4 months and partially thereafter was associated with a significant reduction of respiratory and gastrointestinal morbidity in infants. Our findings support health-policy strategies to promote exclusive breastfeeding for at least 4 months, but preferably 6 months, in industrialized countries.
Yield of Lumbar Puncture Among Children Who Present With Their First Complex Febrile Seizure
Authors: Kimia Amir , Ben-Joseph Elana Pearl , Rudloe Tiffany , Capraro Andrew , Sarco Dean , Hummel David , Johnston Patrick , Harper Marvin B.
Published: June 2010

OBJECTIVE:

To assess the rate of acute bacterial meningitis (ABM) among children who present with their first complex febrile seizure (CFS).

DESIGN AND METHODS:

This study was a retrospective, cohort review of patients aged 6 to 60 months who were evaluated in a pediatric emergency department (ED) between 1995 and 2008 for their first CFS. Cases were identified by using a computerized text search followed by a manual chart review. Exclusion criteria included prior history of nonfebrile seizures, an immunocompromised state, an underlying illness associated with seizures or altered mental status, or trauma. Data extracted included age, gender, seizure features, the number of previous simple febrile seizures, temperature, a family history of seizures, findings on physical examination, laboratory and imaging study results, and ED diagnosis and disposition.

RESULTS:

We identified 526 patients. The median age was 17 months (interquartile range: 13–24), and 44% were female. Ninety patients (17%) had a previous history of simple febrile seizures. Of the patients, 340 (64%) had a lumbar puncture (LP). The patients' median white blood cell count during a CFS was 1 cell per μL (interquartile range: 1–2), and 14 patients had CSF pleocytosis (2.7% [95% confidence interval [CI]: 1.5–4.5]). Three patients had ABM (0.9% [95% CI: 0.2–2.8]). Two had Streptococcus pneumoniae in a culture of their cerebrospinal fluid. Among these 2 patients, 1 was nonresponsive during presentation, and the other had a bulging fontanel and apnea. The third child appeared well; however, her blood culture grew S pneumoniae and failed the LP test. None of the patients for whom an LP was not attempted subsequently returned to the hospital with a diagnosis of ABM (0% [95% CI: 0, 0.9]).

CONCLUSION:

Few patients who experienced a CFS had ABM in the absence of other signs or symptoms.
Effect of Hypothermia on Amplitude-Integrated Electroencephalogram in Infants With Asphyxia
Authors: Thoresen Marianne , Hellström-Westas Lena , Liu Xun , de Vries Linda S.
Published: June 2010

OBJECTIVES:

Amplitude-integrated electroencephalogram (aEEG) at <6 hours is the best single outcome predictor in term infants with perinatal asphyxia at normothermia. Hypothermia has been used to treat those infants and proved to improve their outcome. The objectives of this study were to compare the predictive value of aEEG at <6 hours on outcomes in normothermia- and hypothermia-treated infants and to investigate the best outcome predictor (time to normal trace or sleep–wake cycling [SWC]) in normothermia- and hypothermia-treated infants.

METHODS:

Seventy-four infants were recruited by using the CoolCap entry criteria, and their outcomes were assessed by using the Bayley Scales of Infant Development II at 18 months. The aEEG was recorded for 72 hours. Patterns and voltages of aEEG backgrounds were assessed.

RESULTS:

The positive predictive value of an abnormal aEEG pattern at the age of 3 to 6 hours was 84% for normothermia and 59% for hypothermia. Moderate abnormal voltage background at 3 to 6 hours of age did not predict outcome. The recovery time to normal background pattern was the best predictor of poor outcome (96.2% in hypothermia, 90.9% in normothermia). Never developing SWC always predicted poor outcome. Time to SWC was a better outcome predictor for infants who were treated with hypothermia (88.5%) than with normothermia (63.6%).

CONCLUSIONS:

Early aEEG patterns can be used to predict outcome for infants treated with normothermia but not hypothermia. Infants with good outcome had normalized background pattern by 24 hours when treated with normothermia and by 48 hours when treated with hypothermia.
Procession to Pediatric Bacteremia and Sepsis: Covert Operations and Failures in Diplomacy
Authors: Bateman Stacey L. , Seed Patrick C.
Published: June 2010

Despite advances in diagnosis and treatment, bacterial sepsis remains a major cause of pediatric morbidity and mortality, particularly among neonates, the critically ill, and the growing immunocompromised patient population. Sepsis is the end point of a complex and dynamic series of events in which both host and microbial factors drive high morbidity and potentially lethal physiologic alterations. In this article we provide a succinct overview of the events that lead to pediatric bloodstream infections (BSIs) and sepsis, with a focus on the molecular mechanisms used by bacteria to subvert host barriers and local immunity to gain access to and persist within the systemic circulation. In the events preceding and during BSI and sepsis, Gram-positive and Gram-negative pathogens use a battery of factors for translocation, inhibition of immunity, molecular mimicry, intracellular survival, and nutrient scavenging. Gaps in understanding the molecular pathogenesis of bacterial BSIs and sepsis are highlighted as opportunities to identify and develop new therapeutics.
Errors of Diagnosis in Pediatric Practice: A Multisite Survey
Authors: Singh Hardeep , Thomas Eric J. , Wilson Lindsey , Kelly P. Adam , Pietz Kenneth , Elkeeb Dena , Singhal Geeta
Published: June 2010

OBJECTIVE:

We surveyed pediatricians to elicit their perceptions regarding frequency, contributing factors, and potential system- and provider-based solutions to address diagnostic errors.

METHODS:

Academic, community, and trainee pediatricians (N = 1362) at 3 tertiary care institutions and 109 affiliated clinics were invited to complete the survey anonymously through an Internet survey administration service between November 2008 and May 2009.

RESULTS:

The overall response rate was 53% (N = 726). More than one-half (54%) of respondents reported that they made a diagnostic error at least once or twice per month; this frequency was markedly higher (77%) among trainees. Almost one-half (45%) of respondents reported diagnostic errors that harmed patients at least once or twice per year. Failure to gather information through history, physical examination, or chart review was the most-commonly reported process breakdown, whereas inadequate care coordination and teamwork was the most-commonly reported system factor. Viral illnesses being diagnosed as bacterial illnesses was the most-commonly reported diagnostic error, followed by misdiagnosis of medication side effects, psychiatric disorders, and appendicitis. Physicians ranked access to electronic health records and close follow-up of patients as strategies most likely to be effective in preventing diagnostic errors.

CONCLUSION:

Pediatricians reported making diagnostic errors relatively frequently, and patient harm from these errors was not uncommon.
Influence of Licensed Characters on Children's Taste and Snack Preferences
Authors: Roberto Christina A. , Baik Jenny , Harris Jennifer L. , Brownell Kelly D.
Published: June 2010

OBJECTIVE:

The goal was to study how popular licensed cartoon characters appearing on food packaging affect young children's taste and snack preferences.

METHODS:

Forty 4- to 6-year-old children tasted 3 pairs of identical foods (graham crackers, gummy fruit snacks, and carrots) presented in packages either with or without a popular cartoon character. Children tasted both food items in each pair and indicated whether the 2 foods tasted the same or one tasted better. Children then selected which of the food items they would prefer to eat for a snack.

RESULTS:

Children significantly preferred the taste of foods that had popular cartoon characters on the packaging, compared with the same foods without characters. The majority of children selected the food sample with a licensed character on it for their snack, but the effects were weaker for carrots than for gummy fruit snacks and graham crackers.

CONCLUSIONS:

Branding food packages with licensed characters substantially influences young children's taste preferences and snack selection and does so most strongly for energy-dense, nutrient-poor foods. These findings suggest that the use of licensed characters to advertise junk food to children should be restricted.
Measurement Issues in Trials of Pediatric Acute Diarrheal Diseases: A Systematic Review
Authors: Johnston Bradley C. , Shamseer Larissa , da Costa Bruno R. , Tsuyuki Ross T. , Vohra Sunita
Published: June 2010

BACKGROUND:

Worldwide, diarrheal diseases rank second among conditions that afflict children. Despite the disease burden, there is limited consensus on how to define and measure pediatric acute diarrhea in trials.

OBJECTIVES:

In RCTs of children involving acute diarrhea as the primary outcome, we documented (1) how acute diarrhea and its resolution were defined, (2) all primary outcomes, (3) the psychometric properties of instruments used to measure acute diarrhea and (4) the methodologic quality of included trials, as reported.

METHODS:

We searched CENTRAL, Embase, Global Health, and Medline from inception to February 2009. English-language RCTs of children younger than 19 years that measured acute diarrhea as a primary outcome were chosen.

RESULTS:

We identified 138 RCTs reporting on 1 or more primary outcomes related to pediatric acute diarrhea/diseases. Included trials used 64 unique definitions of diarrhea, 69 unique definitions of diarrhea resolution, and 46 unique primary outcomes. The majority of included trials evaluated short-term clinical disease activity (incidence and duration of diarrhea), laboratory outcomes, or a composite of these end points. Thirty-two trials used instruments (eg, single and multidomain scoring systems) to support assessment of disease activity. Of these, 3 trials stated that their instrument was valid; however, none of the trials (or their citations) reported evidence of this validity. The overall methodologic quality of included trials was good.

CONCLUSIONS:

Even in what would be considered methodologically sound clinical trials, definitions of diarrhea, primary outcomes, and instruments employed in RCTs of pediatric acute diarrhea are heterogeneous, lack evidence of validity, and focus on indices that may not be important to participants.
N-carbamylglutamate Augments Ureagenesis and Reduces Ammonia and Glutamine in Propionic Acidemia
Authors: Mew Nicholas Ah , McCarter Robert , Daikhin Yevgeny , Nissim Itzhak , Yudkoff Marc , Tuchman Mendel
Published: June 2010

OBJECTIVES:

The objective of this study was to determine whether N-carbamylglutamate (NCG) reduces plasma levels of ammonia and glutamine and increases the rate of ureagenesis in patients with propionic acidemia (PA).

METHODS:

Identical 4-hour studies were performed before and immediately after a 3-day trial of oral NCG in 7 patients with PA. An oral bolus of [13C]sodium acetate was administered at the start of each study, and sequential blood samples were obtained to measure [13C]urea, ammonia, urea, and amino acids.

RESULTS:

With longitudinal mixed-effects linear regression, peak [13C]urea increased after treatment with NCG (from 2.2 to 3.8 μM; P < .0005). There were concomitant decreases in mean plasma ammonia (59–43 μM; P < .018) and glutamine (552–331 μM; P < .0005).

CONCLUSIONS:

NCG augments ureagenesis and decreases plasma ammonia and glutamine in patients with PA. The drug may serve as an important therapeutic adjunct in the treatment of acute hyperammonemia in this disorder.
Foot morphology and substrate adhesion in the Madagascan hissing cockroach, Gromphadorhina portentosa
Authors: van Casteren Adam , Codd Jonathan R.
Published: June 2010

Insects are successful terrestrial organisms able to locomote over a wide range of obstacles and substrates. This study investigated how foot morphology (tarsal structure) correlates with substrate adhesion and ecological niche in the Madagascan hissing cockroach, Gromphadorhina portentosa Schaum (Blattaria: Blaberidae). Using light and scanning electron microscopy, the morphology of the different structures of the tarsus of G. portentosa was analysed. Using an Instron® universal testing machine, a series of peak force experiments were then conducted to record the force required to lift the cockroaches off different substrates. G. portentosa was pulled off 10 different substrates, which consisted of smooth Perspex; Perspex scored at 1cm intervals; Perspex hatched at 1 cm, 0.5 cm, and 1 mm intervals; Perspex abraded with fine grade sandpaper; Perspex abraded with coarse grade sandpaper; wood; glass; and Teflon. A clear relationship was seen where an increase in scoring on the Perspex caused a decrease in adhesive ability of G. portentosa. This may be due to there being adequate contact area for the attachment of the pads and to allow the claws to engage. The results obtained suggest that to achieve the greatest adhesion to substrates, G. portentosa uses a combined effect of both adhesive pads and pretarsal claws. Adhesion to a wide range of substrates appears to be an adaptation to life as a wingless forest floor dweller.
MEN1 in pancreatic endocrine tumors: analysis of gene and protein status in 169 sporadic neoplasms reveals alterations in the vast majority of cases
Authors: Corbo Vincenzo , Dalai Irene , Scardoni Maria , Barbi Stefano , Beghelli Stefania , Bersani Samantha , Albarello Luca , Doglioni Claudio , Schott Christina , Capelli Paola , Chilosi Marco , Boninsegna Letizia , Becker Karl-Friedrich , Falconi Massimo , Scarpa Aldo
Published: June 2010

Pancreatic endocrine tumors (PETs) may be part of hereditary multiple endocrine neoplasia type 1 (MEN1) syndrome. While MEN1 gene mutation is the only ascertained genetic anomaly described in PETs, no data exist on the cellular localization of MEN1-encoded protein, menin, in normal pancreas and PETs. A total of 169 PETs were used to assess the i) MEN1 gene mutational status in 100 clinically sporadic PETs by direct DNA sequencing, ii) immunohistochemical expression of menin in normal pancreas and 140 PETs, including 71 cases screened for gene mutations, and iii) correlation of these findings with clinical–pathological parameters. Twenty-seven PETs showed mutations that were somatic in 25 patients and revealed to be germline in 2 patients. Menin immunostaining showed strong nuclear and very faint cytoplasmic signal in normal islet cells, whereas it displayed abnormal location and expression levels in 80% of tumors. PETs harboring MEN1 truncating mutations lacked nuclear protein, and most PETs with MEN1 missense mutations showed a strong cytoplasmic positivity for menin. Menin was also misplaced in a significant number of cases lacking MEN1 mutations. In conclusion, the vast majority of PETs showed qualitative and/or quantitative alterations in menin localization. In 30% of cases, this was associated with MEN1 mutations affecting sequences involved in nuclear localization or protein–protein interaction. In cases lacking MEN1 mutations, the alteration of one of the menin interactors may have prevented its proper localization, as suggested by recent data showing that menin protein shuttles between the nucleus and cytoplasm and also affects the subcellular localization of its interactors.
Macrophage migration inhibitory factor deficiency leads to age-dependent impairment of glucose homeostasis in mice
Authors: Serre-Beinier Véronique , Toso Christian , Morel Philippe , Gonelle-Gispert Carmen , Veyrat-Durebex Christelle , Rohner-Jeanrenaud Françoise , Calandra Thierry , Roger Thierry , James Richard W , Montet Xavier , Bühler Léo , Bosco Domenico , Berney Thierry
Published: June 2010

Macrophage migration inhibitory factor (MIF) is a proinflammatory cytokine produced by many cells and tissues including pancreatic β-cells, liver, skeletal muscle, and adipocytes. This study investigates the potential role of MIF in carbohydrate homeostasis in a physiological setting outside of severe inflammation, utilizing Mif knockout (MIF−/−) mice. Compared with wild-type (WT) mice, MIF−/− mice had a lower body weight, from birth until 4 months of age, but subsequently gained weight faster, resulting in a higher body weight at 12 months of age. The lower weight in young mice was related to a higher energy expenditure, and the higher weight in older mice was related to an increased food intake and a higher fat mass. Fasting blood insulin level was higher in MIF−/− mice compared with WT mice at any age. After i.p. glucose injection, the elevation of blood insulin level was higher in MIF−/− mice compared with WT mice, at 2 months of age, but was lower in 12-month-old MIF−/− mice. As a result, the glucose clearance during intraperitoneal glucose tolerance tests was higher in MIF−/− mice compared with WT mice until 4 months of age, and was lower in 12-month-old MIF−/− mice. Insulin resistance was estimated (euglycemic–hyperinsulinemic clamp tests), and the phosphorylation activity of AKT was similar in MIF−/− mice and WT mice. In conclusion, this mouse model provides evidence for the role of MIF in the control of glucose homeostasis.
Meta‐analyses and mega‐mistakes: calling time on meta‐analysis of the species richness–productivity relationship
Authors: Whittaker Robert J.
Published: June 2010

The form of the species richness–productivity relationship (SRPR) is both theoretically important and contentious. In an effort to distill general patterns, ecologists have undertaken meta‐analyses, within which each SRPR data set is first classified into one of five alternative forms: positive, humped (unimodal), negative, U‐shaped (unimodal), and no relationship. Herein, I first provide a critique of this approach, based on 68 plant data sets/studies used in three meta‐analyses published in Ecology. The meta‐analyses are shown to have resulted in highly divergent outcomes, inconsistent and often highly inappropriate classification of data sets, and the introduction and multiplication of errors from one meta‐analysis to the next. I therefore call on the ecological community at large to adopt a far more rigorous and critical attitude to the use of meta‐analysis. Second, I develop the argument that the literature on the SRPR continues to be bedeviled by a common failing to appreciate the fundamental importance of the scale of analysis, beginning with the confusion evident between concepts of grain, focus, and extent. I postulate that variation in the form of the SRPR at fine scales of analysis owes much to artifacts of the sampling regime adopted. An improved understanding may emerge from combining sampling theory with an understanding of the factors controlling the form of species abundance distributions and species accumulation curves.
Responses of benthic macroinvertebrates to environmental changes associated with urbanization in nine metropolitan areas
Authors: Cuffney Thomas F. , Brightbill Robin A. , May Jason T. , Waite Ian R.
Published: June 2010

Responses of benthic macroinvertebrates along gradients of urban intensity were investigated in nine metropolitan areas across the United States. Invertebrate assemblages in metropolitan areas where forests or shrublands were being converted to urban land were strongly related to urban intensity. In metropolitan areas where agriculture and grazing lands were being converted to urban land, invertebrate assemblages showed much weaker or nonsignificant relations with urban intensity because sites with low urban intensity were already degraded by agriculture. Ordination scores, the number of EPT taxa, and the mean pollution‐tolerance value of organisms at a site were the best indicators of changes in assemblage condition. Diversity indices, functional groups, behavior, and dominance metrics were not good indicators of urbanization. Richness metrics were better indicators of urban effects than were abundance metrics, and qualitative samples collected from multiple habitats gave similar results to those of single habitat quantitative samples (riffles or woody snags) in all metropolitan areas. Changes in urban intensity were strongly correlated with a set of landscape variables that was consistent across all metropolitan areas. In contrast, the instream environmental variables that were strongly correlated with urbanization and invertebrate responses varied among metropolitan areas. The natural environmental setting determined the biological, chemical, and physical instream conditions upon which urbanization acts and dictated the differences in responses to urbanization among metropolitan areas. Threshold analysis showed little evidence for an initial period of resistance to urbanization. Instead, assemblages were degraded at very low levels of urbanization, and response rates were either similar across the gradient or higher at low levels of urbanization. Levels of impervious cover that have been suggested as protective of streams (5–10%) were associated with significant assemblage degradation and were not protective.
Land‐use controls on sources and processing of nitrate in small watersheds: insights from dual isotopic analysis
Authors: Barnes Rebecca T. , Raymond Peter A.
Published: June 2010

Studies have repeatedly shown that agricultural and urban areas export considerably more nitrogen to streams than forested counterparts, yet it is difficult to identify and quantify nitrogen sources to streams due to complications associated with terrestrial and in‐stream biogeochemical processes. In this study, we used the isotopic composition of nitrate (δ15N‐NO3− and δ18O‐NO3−) in conjunction with a simple numerical model to examine the spatial and temporal variability of nitrate (NO3−) export across a land‐use gradient and how agricultural and urban development affects net removal mechanisms. In an effort to isolate the effects of land use, we chose small headwater systems in close proximity to each other, limiting the variation in geology, surficial materials, and climate between sites. The δ15N and δ18O of stream NO3− varied significantly between urban, agricultural, and forested watersheds, indicating that nitrogen sources are the primary determinant of the δ15N‐NO3−, while the δ18O‐NO3− was found to reflect biogeochemical processes. The greatest NO3− concentrations corresponded with the highest stream δ15N‐NO3− values due to the enriched nature of two dominant anthropogenic sources, septic and manure, within the urban and agricultural watersheds, respectively. On average, net removal of the available NO3− pool within urban and agricultural catchments was estimated at 45%. The variation in the estimated net removal of NO3− from developed watersheds was related to both drainage area and the availability of organic carbon. The determination of differentiated isotopic land‐use signatures and dominant seasonal mechanisms illustrates the usefulness of this approach in examining the sources and processing of excess nitrogen within headwater catchments.
Wetland response to sedimentation and nitrogen loading: diversification and inhibition of nitrogen‐fixing microbes
Authors: Moseman-Valtierra S. M. , Armaiz-Nolla K. , Levin L. A.
Published: June 2010

Anthropogenic inputs of nutrients and sediment simultaneously impact coastal ecosystems, such as wetlands, especially during storms. Independent and combined effects of sediment and ammonium nitrate loading on nitrogen fixation rates and diversity of microbes that fix nitrogen (diazotrophs) were tested via field manipulations inSpartina foliosaand unvegetated zones at Tijuana Estuary (California, USA). This estuary is subject to episodic nitrogen enrichment and sedimentation associated with rain‐driven flooding and slope instabilities, the latter of which may worsen as the Triple Border Fence is constructed along the U.S.–Mexico border. Responses of diazotrophs were assessed over 17 days using acetylene reduction assays and genetic fingerprinting (terminal restriction fragment length polymorphism [T‐RFLP]) ofnifH, which codes for dinitrogenase reductase. Sulfate‐reducing bacteria performed ~70% of nitrogen fixation inSpartina foliosarhizospheres in the absence of nitrogen loading, based on sodium molybdate inhibitions in the laboratory. Following nutrient additions, richness (number of T‐RFs [terminal restriction fragments]) and evenness (relative T‐RF fluorescence) of diazotrophs in surface sediments increased, but nitrogen fixation rates decreased significantly within 17 days. These responses illustrate, within a microbial community, conformance to a more general ecological pattern of high function among assemblages of low diversity. Diazotroph community composition (T‐RF profiles) and rhizosphere diversity were not affected. Pore water ammonium concentrations were higher and more persistent for 17 days in plots receiving sediment additions (1 cm deep), suggesting that recovery of diazotroph functions may be delayed by the combination of sediment and nutrient inputs. Nitrogen fixation constitutes a mechanism for rapid transfer of fixed N toS. foliosaroots and a variety of primary consumers (within 3 and 8 days, respectively), as determined via15N2enrichment studies with in situ microcosms of intact marsh sediment. Thus, long‐term declines in nitrogen fixation rates in response to increasingly frequent nutrient loading and sedimentation may potentially alter nitrogen sources for vascular plants as well as trophic pathways in wetland ecosystems.
On the differential advantages of evergreenness and deciduousness in mediterranean oak woodlands: a flux perspective
Authors: Baldocchi Dennis D. , Ma Siyan , Rambal Serge , Misson Laurent , Ourcival Jean-Marc , Limousin Jean-Marc , Pereira Joao , Papale Dario
Published: June 2010

We assessed the differential advantages of deciduousness and evergreenness by examining 26 site‐years of carbon dioxide, water vapor, and energy flux measurements from five comparable oak woodlands in France, Italy, Portugal, and California (USA). On average, the evergreen and deciduous oak woodlands assimilated and respired similar amounts of carbon while using similar amounts of water. These results suggest that evergreen and deciduous woodlands have specific, and similar, ecological costs in mediterranean climates, and that both leaf habits are able to meet these costs.

What are the mechanisms behind these findings? Deciduous oaks compensated for having a shorter growing season by attaining a greater capacity to assimilate carbon for a given amount of intercepted solar radiation during the well‐watered spring period; at saturating light levels, deciduous oaks gained carbon at six times the rate of evergreen oaks. Otherwise, the two leaf habits experienced similar efficiencies in carbon use (the change in carbon respired per change in carbon assimilated), water use (the change in carbon assimilation per change in water evaporated), and rainfall use (the change in evaporation per change in rainfall).

Overall, leaf area index, rather than leaf habit, was the significant factor in determining the absolute magnitude of carbon gained and water lost by each evergreen and deciduous oak woodland over an annual interval; the closed canopies assimilated and respired more carbon and transpired more water than the open canopies.

Both deciduous and evergreen mediterranean oaks survive in their seasonally hot/dry, wet/cool native range by ensuring that actual evaporation is less than the supply of water. This feat is accomplished by adjusting the leaf area index to reduce total water loss at the landscape scale, by down‐regulating photosynthesis, respiration, and stomatal conductance with progressive seasonal soil water deficits, and by extending their root systems to tap groundwater.
Phosphorus mobilization in rewetted fens: the effect of altered peat properties and implications for their restoration
Authors: Zak Dominik , Wagner Carola , Payer Brian , Augustin Jürgen , Gelbrecht Jörg
Published: June 2010

Rewetting of drained fens is necessary to stop further soil degradation and to reestablish important ecological functions. However, substantial changes of peat characteristics in the upper soil layers, due to drainage and land use, could counteract their recovery as nutrient‐poor systems for an unknown period. We assessed the importance of altered peat properties, such as the degree of peat decomposition and the amount of redox‐sensitive phosphorus (P) compounds, for P mobilization in different degraded fens. An experimental design involving 63 intact peat cores from fens with varying drainage and land‐use histories was developed to quantify the mobilization of P, as well as that of iron (Fe), ammonium, carbon dioxide, and methane, all indicators of organic‐matter decomposition and/or P‐releasing processes. We found that net P release rates in peat cores with highly decomposed peat (range: 0.1–52.3 mg P·m−2·d−1) were significantly correlated to the amount of P bound to redox‐sensitive compounds and the molar Fe:P as well as Al:P ratios of peat. We conclude that the following general rules apply for P mobilization in rewetted fens: (1) elevated levels of P release rates and P concentrations in pore water up to three orders of magnitude larger than under natural reference conditions can only be expected for rewetted fens whose surface soil layers consist of highly decomposed peat; (2) peat characteristics, such as the amount of P bound to redox‐sensitive Fe(III) compounds (positive correlation) and molar ratios of Fe:P or Al:P (negative correlations), explain the high range of P release rates; and (3) a critical P export to adjacent lakes or rivers can only be expected if molar Fe:P ratios of highly decomposed peat are less than 10.
Favorable fragmentation: river reservoirs can impede downstream expansion of riparian weeds
Authors: Rood Stewart B. , Braatne Jeffrey H. , Goater Lori A.
Published: June 2010

River valleys represent biologically rich corridors characterized by natural disturbances that create moist and barren sites suitable for colonization by native riparian plants, and also by weeds. Dams and reservoirs interrupt the longitudinal corridors and we hypothesized that this could restrict downstream weed expansion. To consider this “reservoir impediment” hypothesis we assessed the occurrences and abundances of weeds along a 315‐km river valley corridor that commenced with an unimpounded reach of the Snake River and extended through Brownlee, Oxbow, and Hells Canyon reservoirs and dams, and downstream along the Snake River. Sampling along 206 belt transects with 3610 quadrats revealed 16 noxious and four invasive weed species. Ten weeds were upland plants, with Canada thistle (Cirsium arvense) restricted to the upstream reaches, where field morning glory (Convolvulus arvensis) was also more common. In contrast, St. John's wort (Hypericum perforatum) was more abundant below the dams, and medusahead wildrye (Taeniatherum caput‐medusae) occurred primarily along the reservoirs. All seven riparian species were abundant in the upstream zones but sparse or absent below the dams. This pattern was observed for the facultative riparian species, poison hemlock (Conium maculatum) and perennial pepperweed (Lepidium latifolium), the obligate riparian, yellow nut sedge (Cyperus esculentus), the invasive perennial, reed canary grass (Phalaris arundinacea), and three invasive riparian trees, Russian olive (Elaeagnus angustifolia), false indigo (Amorpha fruticosa), and tamarisk (Tamarix spp.). The hydrophyte purple loosestrife (Lythrum salicaria) was also restricted to the upstream zone. These longitudinal patterns indicate that the reservoirs have impeded the downstream expansion of riparian weeds, and this may especially result from the repetitive draw‐down and refilling of Brownlee Reservoir that imposes a lethal combination of drought and flood stress. The dams and reservoirs may also interrupt hydrochory, the downstream flow of seeds and clonal fragments. We thus conclude that with some operational patterns, dams and reservoirs can impede the downstream expansion of riparian weeds.
Bat reproduction declines when conditions mimic climate change projections for western North America
Authors: Adams Rick A.
Published: June 2010

Climate change models predict that much of western North America is becoming significantly warmer and drier, resulting in overall reductions in availability of water for ecosystems. Herein, I demonstrate that significant declines in the reproductive success of female insectivorous bats occur in years when annual environmental conditions mimic the long‐term predictions of regional climate change models. Using a data set gathered on bat populations from 1996 through 2008 along the Front Range of Colorado, I compare trends in population numbers and reproductive outcomes of six species of vespertilionid bats with data on mean annual high temperature, precipitation, snow pack, and stream discharge rates. I show that levels of precipitation and flow rates of small streams near maternity colonies is fundamentally tied to successful reproduction in female bats, particularly during the lactation phase. Across years that experienced greater than average mean temperatures with less than average precipitation and stream flow, bat populations responded by slight to profound reductions in reproductive output depending on the severity of drought conditions. In particular, reproductive outputs showed profound declines (32–51%) when discharge rates of the largest stream in the field area dropped below 7 m3/s, indicating a threshold response. Such sensitivity to environmental change portends severe impacts to regional bat populations if current scenarios for climate change in western North America are accurate. In addition, bats act as early‐warning indicators of large‐scale ecological effects resulting from further regional warming and drying trends currently at play in western North America.
The relationship between maternal phenotype and offspring quality: Do older mothers really produce the best offspring?
Authors: Marshall Dustin J. , Heppell Selina S. , Munch Stephan B. , Warner Robert R.
Published: June 2010

Maternal effects are increasingly recognized as important drivers of population dynamics and determinants of evolutionary trajectories. Recently, there has been a proliferation of studies finding or citing a positive relationship between maternal size/age and offspring size or offspring quality. The relationship between maternal phenotype and offspring size is intriguing in that it is unclear why young mothers should produce offspring of inferior quality or fitness. Here we evaluate the underlying evolutionary pressures that may lead to a maternal size/age–offspring size correlation and consider the likelihood that such a correlation results in a positive relationship between the age or size of mothers and the fitness of their offspring. We find that, while there are a number of reasons why selection may favor the production of larger offspring by larger mothers, this change in size is more likely due to associated changes in the maternal phenotype that affect the offspring size–performance relationship. We did not find evidence that the offspring of older females should have intrinsically higher fitness. When we explored this issue theoretically, the only instance in which smaller mothers produce suboptimal offspring sizes is when a (largely unsupported) constraint on maximum offspring size is introduced into the model. It is clear that larger offspring fare better than smaller offspring when reared in the same environment, but this misses a critical point:differentenvironments elicit selection for different optimal sizes of young. We suggest that caution should be exercised when interpreting the outcome of offspring‐size experiments when offspring from different mothers are reared in a common environment, because this approach may remove the source of selection (e.g., reproducing in different context) that induced a shift in offspring size in the first place. It has been suggested that fish stocks should be managed to preserve these older age classes because larger mothers produce offspring with a greater chance of survival and subsequent recruitment. Overall, we suggest that, while there are clear and compelling reasons for preserving older females in exploited populations, there is little theoretical justification or evidence that older mothers produce offspring with higher per capita fitness than do younger mothers.
Tigers on trails: occupancy modeling for cluster sampling
Authors: Hines J. E. , Nichols J. D. , Royle J. A. , MacKenzie D. I. , Gopalaswamy A. M. , Kumar N. Samba , Karanth K. U.
Published: June 2010

Occupancy modeling focuses on inference about the distribution of organisms over space, using temporal or spatial replication to allow inference about the detection process. Inference based on spatial replication strictly requires that replicates be selected randomly and with replacement, but the importance of these design requirements is not well understood. This paper focuses on an increasingly popular sampling design based on spatial replicates that are not selected randomly and that are expected to exhibit Markovian dependence. We develop two new occupancy models for data collected under this sort of design, one based on an underlying Markov model for spatial dependence and the other based on a trap response model with Markovian detections. We then simulated data under the model for Markovian spatial dependence and fit the data to standard occupancy models and to the two new models. Bias of occupancy estimates was substantial for the standard models, smaller for the new trap response model, and negligible for the new spatial process model. We also fit these models to data from a large‐scale tiger occupancy survey recently conducted in Karnataka State, southwestern India. In addition to providing evidence of a positive relationship between tiger occupancy and habitat, model selection statistics and estimates strongly supported the use of the model with Markovian spatial dependence. This new model provides another tool for the decomposition of the detection process, which is sometimes needed for proper estimation and which may also permit interesting biological inferences. In addition to designs employing spatial replication, we note the likely existence of temporal Markovian dependence in many designs using temporal replication. The models developed here will be useful either directly, or with minor extensions, for these designs as well. We believe that these new models represent important additions to the suite of modeling tools now available for occupancy estimation in conservation monitoring. More generally, this work represents a contribution to the topic of cluster sampling for situations in which there is a need for specific modeling (e.g., reflecting dependence) for the distribution of the variable(s) of interest among subunits.
Estimating the impacts of fishing on dependent predators: a case study in the California Current
Authors: Field J. C. , MacCall A. D. , Bradley R. W. , Sydeman W. J.
Published: June 2010

Juvenile rockfish (Sebastes spp.) are important prey to seabirds in the California Current System, particularly during the breeding season. Both seabird breeding success and the abundance of pelagic juvenile rockfish show high interannual variability. This covariation is largely a response to variable ocean conditions; however, fishing on adult rockfish may have had consequences for seabird productivity (e.g., the number of chicks fledged per breeding pair) by reducing the availability of juvenile rockfish to provisioning seabird parents. We tested the hypothesis that fishing has decreased juvenile rockfish availability and thereby limited seabird productivity over the past 30 years. We quantified relationships between observed juvenile rockfish relative abundance and seabird productivity, used fisheries stock assessment approaches to estimate the relative abundance of juvenile rockfish in the absence of fishing, and compared the differences in seabird productivity that would have resulted without rockfish fisheries. We examined the abundance of juvenile rockfish and the corresponding productivity of three seabird species breeding on Southeast Farallon Island (near San Francisco, California, USA) from the early 1980s to the present. Results show that while the relative abundance of juvenile rockfish has declined to ∼50% of the estimated unfished biomass, seabirds achieved 75–95% of the estimated un‐impacted levels of productivity, depending upon the species of bird and various model assumptions. These results primarily reflect seabirds with “conservative” life histories (one egg laid per year) and may be different for species with more flexible life history strategies (greater reproductive effort). Our results are consistent with the premise that the impacts of local rockfish fisheries on seabird productivity are less than impacts that have occurred to the prey resources themselves due to ocean climate and the ability of seabirds to buffer against changes in prey availability through prey‐switching and other behavioral mechanisms.
Simulations show decreasing carbon stocks and potential for carbon emissions in Rocky Mountain forests over the next century
Authors: Boisvenue Céline , Running Steven W.
Published: June 2010

Climate change has altered the environment in which forests grow, and climate change models predict more severe alterations to come. Forests have already responded to these changes, and the future temperature and precipitation scenarios are of foremost concern, especially in the mountainous western United States, where forests occur in the dry environments that interface with grasslands. The objective of this study was to understand the trade‐offs between temperature and water controls on these forested sites in the context of available climate projections. Three temperature and precipitation scenarios from IPCC AR4 AOGCMs ranging in precipitation levels were input to the process model Biome‐BGC for key forested sites in the northern U.S. Rocky Mountains. Despite the omission of natural and human‐caused disturbances in our simulations, our results show consequential effects from these conservative future temperature and precipitation scenarios. According to these projections, if future precipitation and temperatures are similar to or drier than the dry scenario depicted here, high‐elevation forests on both the drier and wetter sites, which have in the absence of disturbance accumulated carbon, will reduce their carbon accumulation. Under the marginally drier climate projections, most forests became carbon sources by the end of the simulation horizon (2089). Under all three scenarios, growing season lengthened, the number of days with snow on the ground decreased, peak snow occurred earlier, and water stress increased through the projection horizon (1950–2089) for all sites, which represent the temperature and precipitation spectrum of forests in this region. The quantity, form, and timing of precipitation ultimately drive the carbon accumulation trajectory of forests in this region.