bluuebunny/crossref_metadata_2025 huggingface dataset:
Surgical-Site Infections Following Cesarean Section in an Estonian University Hospital: Postdischarge Surveillance and analysis of Risk Factors
Authors: Mitt Piret , Lang Katrin , Peri Aira , Maimets Matti
Published: April 2006

Objectives:

To evaluate a multi-method approach to postdischarge surveillance of surgical-site infections (SSIs) and to identify infection rates and risk factors associated with SSI following cesarean section.

Design:

Cross-sectional survey.

Setting:

Academic tertiary-care obstetric and gynecology center with 54 beds.

Patients:

All women who delivered by cesarean section in Tartu University Women's Clinic during 2002.

Methods:

Infections were identified during hospital stay or by postdischarge survey using a combination of telephone calls, healthcare worker questionnaire, and outpatient medical records review. SSI was diagnosed according to the criteria of the Centers for Disease Control and Prevention National Nosocomial Infections Surveillance System.

Results:

The multi-method approach gave a follow-up rate of 94.8%. Of 305 patients, 19 (6.2%; 95% confidence interval [CI95)], 3.8-9.6) had SSIs. Forty-two percent of these SSIs were detected during postdischarge surveillance. We found three variables associated with increased risk for developing SSI: internal fetal monitoring (odds ratio [OR], 16.6; CI95, 2.2-125.8; P = .007), chorioamnionitis (OR, 8.8; CI95, 1.1-69.6; P = .04), and surgical wound classes III and IV (OR, 3.8; CI95, 1.2-11.8; P=.02).

Conclusions:

The high response rate validated the effectiveness of this kind of surveillance method and was most suitable in current circumstances. A challenge exists to decrease the frequency of internal fetal monitoring and to treat chorioamnionitis as soon as possible (Infect Control Hosp Epidemiol 2005;26:449-454).
Incidence of and Risk Factors for Surgical-Site Infections in a Peruvian Hospital
Authors: Hernandez Katherine , Ramos Elizabeth , Seas Carlos , Henostroza German , Gotuzzo Eduardo
Published: April 2006

Objective:

To determine the incidence of and risk factors for surgical-site infections (SSIs) after abdominal surgery.

Design:

A cohort study was conducted from January to June 1998. CDC criteria for SSI and the NNIS System risk index were used.

Setting:

A tertiary-care hospital in Peru.

Patients:

Adult patients undergoing abdominal surgery who consented were enrolled and observed until 30 days after surgery. Patients who had undergone surgery at another hospital or who died or were transferred to another hospital within 24 hours after surgery were excluded.

Results:

Four hundred sixty-eight patients were enrolled. Their mean age was 37.2 years. One hundred twenty-five patients developed SSIs, 18% of which were identified after discharge. The overall incidence rate (IR) was 26.7%. The IR was 13.9% for clean, 15.9% for clean-contaminated, 13.5% for contaminated, and 47.2% for dirty interventions. The IR was 3.6% for NNIS System risk index 0 and 60% for index 3. Risk factors for SSI on logistic regression analysis were dirty or infected wound (RR, 3.8; CI95, 1.7-8.4), drain use longer than 9 days (RR, 6.0; CI95, 2.5-12.5), and length of surgery greater than the 75th percentile (RR, 2.1; CI95, 1.0-4.4). Patients with SSI had a longer hospital stay than did non-infected patients (14.0 vs 6.1 days; P < .001).

Conclusions:

SSI is a major problem in this hospital, which has a higher IR (especially for clean interventions) than those of developed countries. In developing countries, prevention of SSI should include active surveillance and interventions targeting modifiable risk factors.
Peracetic Acid in the Disinfection of a Hospital Water System Contaminated With Legionella Species
Authors: Ditommaso Savina , Biasin Cinzia , Giacomuzzi Monica , Zotti Carla Maria , Cavanna Alberto , Moiraghi Angela Ruggenini
Published: April 2006

Objective:

To assess the efficacy of an alternative disinfection method for hospital water distribution systems contaminated with Legionella.

Methods:

Disinfection with peracetic acid was performed in a small hospital contaminated with L. pneumophila serotype 1. The disinfectant was used at concentrations of 50 ppm (first three surveillance phases) and 1,000 ppm (fourth surveillance phase) for 30 minutes.

Results:

Environmental monitoring revealed that disinfection was maintained 1 week after treatment; however, levels of recontamination surpassing baseline values were detected after approximately 1 month. Comparison of water temperatures measured at the distal outlets showed a statistically significant association between temperature and bacterial load. The circulating water temperature was found to be lower in the two wards farthest away from the hot water production plant than in other wards. It was thought that the lower water temperature in the two wards promoted the bacterial growth even after disinfection.

Conclusion:

Peracetic acid may be useful in emergency situations, but does not provide definitive protection even if used monthly.
Duration of Virus Shedding After Trivalent Intranasal Live Attenuated Influenza Vaccination in Adults
Authors: Talbot Thomas R. , Crocker Deidre D. , Peters Jody , Doersam Jennifer K. , Ikizler Mine R. , Sannella Edith , Wright Peter F. , Edwards Kathryn M.
Published: April 2006

Objective:

To characterize the probability and duration of viral shedding among adults given trivalent live attenuated influenza vaccine (LATV).

Design:

Prospective surveillance study.

Methods:

Nasal wash samples were collected from adult volunteers at baseline and on days 3, 7, and 10 and between days 17 and 21 following intranasal LAIV vaccination. The presence, titer, and identification of each specific strain of influenza virus shed were determined by standard methodology.

Results:

Twenty subjects received LATV. No samples were positive for influenza virus at baseline. After LAIV vaccination, influenza virus was recovered from 10 of 20 vaccinees on day 3, from 1 of 18 vaccinees on day 7, and from none of the samples on days 10 or 17 through 21. Vaccinees who shed vaccine virus were significantly younger than those who did not (mean age, 26.4 vs 38.6 years;P< .01). Although the presence of specific mucosal immunoglobulin A to influenza B was associated with significantly less shedding of influenza B after vaccination (P= .02), associations of shedding with other measures of immunity were not detected.

Conclusion:

The duration of shedding of vaccine virus after LAIV in adults is limited and may be associated with an individual's prior influenza vaccination history.
Clinical Outcomes and Costs Due toStaphylococcus aureusBacteremia Among Patients Receiving Long-Term Hemodialysis
Authors: Engemann John J. , Friedman Joëlle Y. , Reed Shelby D. , Griffiths Robert I. , Szczech Lynda A. , Kaye Keith S. , Stryjewski Martin E. , Reller L. Barth , Schulman Kevin A. , Corey G. Ralph , Fowler Vance G.
Published: April 2006

Objective:

To examine the clinical outcomes and costs associated withStaphylococcus aureusbacteremia among hemodialysis-dependent patients.

Design:

Prospectively identified cohort study.

Setting:

A tertiary-care university medical center in North Carolina.

Patients:

Two hundred ten hemodialysis-dependent adults with end-stage renal disease hospitalized withS. aureusbacteremia.

Results:

The majority of the patients (117; 55.7%) underwent dialysis via tunneled catheters, and 29.5% (62) underwent dialysis via synthetic arteriovenous fistulas. Vascular access was the suspected source of bacteremia in 185 patients (88.1%). Complications occurred in 31.0% (65), and the overall 12-week mortality rate was 19.0% (40). The mean cost of treatingS. aureusbacteremia, including readmissions and outpatient costs, was $24,034 per episode. The mean initial hospitalization cost was significantly greater for patients with complicated versus uncomplicatedS. aureusbacteremia ($32,462 vs $17,011;P= .002).

Conclusion:

Interventions to decrease the rate of S.aureusbacteremia are needed in this high-risk, hemodialysis-dependent population (Infect Control Hosp Epidemiol2005;26:534-539).
Secular Trends of Candidemia in a Large Tertiary-Care Hospital From 1988 to 2000: Emergence ofCandida parapsilosis
Authors: Miguel Lucía García San , Cobo Javier , Otheo Enrique , Sánchez-Sousa Aurora , Abraira Victor , Moreno Santiago
Published: April 2006

Objective:

To analyze the secular trends of candidemia in a large tertiary-care hospital to determine the overall incidence, as well as the incidence by ward and by species, and to detect the occurrence of outbreaks.

Design:

Retrospective descriptive analysis. Secular trends were calculated using the Mantel-Haenszel test.

Setting:

A large tertiary-care referral center in Spain with a pediatric intensive care unit (ICU) to which more than 500 children with congenital cardiac disease are admitted annually.

Patients:

All patients with candidemia occurring from 1988 to 2000 were included. Cases were identified from laboratory records of blood cultures.

Results:

There were 331 episodes of candidemia. The overall incidence of nosocomial candidemia was 0.6 episode per 1,000 admissions and remained stable throughout the study period (P= .925). The species most frequently isolated wasCandida albicans, but the incidence ofC. parapsilosiscandidemia increased (P= .035). In the pediatric ICU, the incidence ofC. parapsilosiswas 5.6 episodes per 1,000 admissions and it was the predominant species. Outbreaks occurred occasionally in the pediatric ICU, suggesting nosocomial transmission.

Conclusions:

During this 13-year period, the incidence of candidemia remained stable in this hospital, butC. parapsilosisincreased in frequency. Occasional outbreaks of candidemia suggested nosocomial transmission ofCandidaspecies (Infect Control Hosp Epidemiol2005;26:548-552).
Determining the Clinical Significance of Coagulase-Negative Staphylococci Isolated From Blood Cultures
Authors: Beekmann Susan E. , Diekema Daniel J. , Doern Gary V.
Published: April 2006

Background and Objective:

Coagulase-negative staphylococci are both an important cause of nosocomial bloodstream infections and the most common contaminants of blood cultures. Judging the clinical significance of coagulase-negative staphylococci is vital but often difficult and can have a profound impact on an institution's bloodstream infection rates. Our objective was to develop an algorithm to assist in determining the clinical significance of coagulase-negative staphylococci.

Design:

A single experienced reviewer examined the medical records of 960 consecutive patients with positive blood cultures in a tertiary-care referral teaching hospital. Four hundred five of the cultures contained coagulase-negative staphylococci. A determination of clinical significance was made and the performances of various published algorithms that contained readily available clinical and laboratory data were compared.

Results:

Eighty-nine (22%) of the episodes were considered significant, whereas 316 were contaminants. Patients with bacteremia were significantly more likely to be neutropenic and exhibit signs of sepsis syndrome. The algorithm with the best combined sensitivity (62%) and specificity (91%) for determining the clinical significance of coagulase-negative staphylococci was defined as at least two blood cultures positive for coagulase-negative staphylococci within 5 days, or one positive blood culture plus clinical evidence of infection, which includes abnormal white blood cell count and temperature or blood pressure.

Conclusion:

Use of this algorithm could potentially reduce misclassification of nosocomial bloodstream infections and inappropriate use of vancomycin for positive blood cultures likely to represent contamination (Infect Control Hosp Epidemiol2005;26:559-566).
VizStruct for visualization of genome-wide SNP analyses
Authors: Bhasi Kavitha , Zhang Li , Brazeau Daniel , Zhang Aidong , Ramanathan Murali
Published: April 2006

Motivation: The size, dimensionality and the limited range of the data values make visualization of single nucleotide polymorphism (SNP) datasets challenging. The purpose of this study is to evaluate the usefulness of 3D VizStruct, a novel multi-dimensional data visualization technique for analyzing patterns in SNP datasets.

Results: VizStruct is an interactive visualization technique that reduces multi-dimensional data to two dimensions using the complex-valued harmonics of the discrete Fourier transform (DFT). In the 3D VizStruct extension, the multi-dimensional SNP data vectors are reduced to three dimensions using a combination of the DFT and the Kullback–Leibler divergence. The performance of 3D VizStruct was challenged with several biologically relevant published datasets that included human Chromosome 21, the human lipoprotein lipase (LPL) gene locus and the multi-locus genotypes of coral populations. In every case, the 3D VizStruct mapping provided an intuitive visual description of the key characteristics of the underlying multi-dimensional genotype.

Availability: Excel and MATLAB code are available at

Contact:  murali@Buffalo.edu
The influence of phenotypic and genetic effects on maternal provisioning and offspring weight gain in mice
Authors: Hager Reinmar , Johnstone Rufus A
Published: April 2006

Close interactions between mother and offspring are said to result in a coevolution of parental and offspring genotypes such that offspring are adapted in their solicitation behaviour to obtain maternal provisioning that maximizes their fitness. Few empirical studies have been conducted in this field and it remains unclear whether maternal provisioning and offspring weight gain are influenced by the same set of maternal and offspring phenotypic and genotypic factors. Using a cross-foster, split-litter design in mice, we found that overall maternal provisioning and offspring weight gain are significantly correlated but are affected by a different set of parameters, except for the effect of maternal bodyweight. While the level of maternal provisioning was influenced by both offspring and foster mother genotype, offspring weight gain was only affected by the number of males in the mixed litter. We suggest that this disparity may hint at the inefficiency of offspring solicitation behaviour or effects of sibling competition.
Local differentiation in the presence of gene flow in the citril finchSerinus citrinella
Authors: Senar Juan Carlos , Borras Antoni , Cabrera Josep , Cabrera Toni , Björklund Mats
Published: April 2006

It is well known theoretically that gene flow can impede genetic differentiation between populations. In this study, we show that in a highly mobile bird species, where dispersal is well documented, there is a strong genetic and morphological differentiation over a very short geographical scale (less than 5 km). Allocation tests revealed that birds caught in one area were assigned genetically to the same area with a very high probability, in spite of current gene flow. Populations were also morphologically differentiated. The results suggest that the relationship between gene flow and differentiation can be rather complicated and non-intuitive.
Flows in large, self-similar tree networks and their control
Authors: Franco Walfre , Sen Mihir , Yang K.T
Published: April 2006

We consider flow in large, regular networks configured in the form of a self-similar branching tree, in which each branch of the tree splits into two with a constant diameter and length ratio. Where appropriate, the limit of an infinite network is also considered. The laminar or turbulent nature of the flow at the inlet may be different from that at the outlet as a consequence of the change in Reynolds number from one generation to the next. A steady flow is shown to be globally stable for a friction law that is non-decreasing with respect to the flow rate. A difference between critical Reynolds numbers for transition and relaminarization may cause the flow in the entire network to oscillate. Control of branch flow rates and junction pressures is investigated using valves and pumps as the input variables. Fault detection due to blockage is discussed. The network hydrodynamics are only partially controllable if individual pumps are used to control the pressure at the junctions.
Weed seed resources for birds in fields with contrasting conventional and genetically modified herbicide-tolerant crops
Authors: Gibbons David W , Bohan David A , Rothery Peter , Stuart Rick C , Haughton Alison J , Scott Rod J , Wilson Jeremy D , Perry Joe N , Clark Suzanne J , Dawson Robert J.G , Firbank Les G
Published: April 2006

The UK Farm Scale Evaluations (FSEs) have shown that the use of broad spectrum herbicides on genetically modified herbicide-tolerant (GMHT) crops can have dramatic effects on weed seed production compared to management of conventional varieties. Here, we use FSE data and information on bird diets to determine how GMHT cropping might change the food resources available to farmland birds. More than 60 fields of each of four crops, spring- and winter-sown oilseed rape, beet and maize, were split, one half being sown with a conventional variety, the other with a GMHT variety. Seed rain from weeds known to be important in the diets of 17 granivorous farmland bird species was measured under the two treatments. In beet and spring oilseed rape, rain of weed seeds important in the diets of 16 bird species was significantly reduced in GMHT compared to conventional halves; for no species did it increase. In winter oilseed rape, rain of weed seeds important in the diets of 10 species was significantly reduced in GMHT halves; for only one species did it increase significantly. By contrast, in maize, rain of weed seeds important in the diets of seven species was significantly greater in GMHT halves; for no species was it reduced. Treatment effects for the total weed seed energy available to each bird species were very similar to those for seed rain alone. Measuring the effects on individual bird species was outside the scope of this study. Despite this, these results suggest that should beet, spring and winter rape crops in the UK be largely replaced by GMHT varieties and managed as in the FSEs, this would markedly reduce important food resources for farmland birds, many of which declined during the last quarter of the twentieth century. By contrast, GMHT maize would be beneficial to farmland birds.
The coexistence of hybrid and parentalDaphnia: the role of parasites
Authors: Wolinska Justyna , Bittner Kerstin , Ebert Dieter , Spaak Piet
Published: April 2006

Parasite driven time-lagged negative frequency-dependent selection of hosts has been studied in natural populations by following changes in host genotype frequencies over time. However, such dynamics have not been considered at higher taxonomic levels, for example, between parental species and their hybrids. In a field study on aDaphniahybrid system, we observed that oneDaphniataxon first was relatively under-infected, but became over-infected after a strong increase in frequency. This finding is consistent with the idea of parasite evolution towards the most frequent host taxon. In two experiments, we investigated whether the assumptions made by a model of negative frequency-dependent selection apply to our host taxa system. First, we showed that the parasite can change the outcome of taxa competition and secondly, we confirmed that the over-infection of one host taxon observed in the field has a genetic basis. Our results indicate that the incorporation of host–parasite interactions at the species level may allow us to gain a more complete picture of forces driving dynamic taxa coexistence inDaphniahybrid systems. More generally, we suggest that if hybrids coexist in sympatry with parental taxa, the infection patterns as observed under natural conditions may be rather temporal and unstable.
Origin of mitochondria by intracellular enslavement of a photosynthetic purple bacterium
Authors: Cavalier-Smith Thomas
Published: April 2006

Mitochondria originated by permanent enslavement of purple non-sulphur bacteria. These endosymbionts became organelles through the origin of complex protein-import machinery and insertion into their inner membranes of protein carriers for extracting energy for the host. A chicken-and-egg problem exists: selective advantages for evolving import machinery were absent until inner membrane carriers were present, but this very machinery is now required for carrier insertion. I argue here that this problem was probably circumvented by conversion of the symbiont protein-export machinery into protein-import machinery, in three phases. I suggest that the first carrier entered the periplasmic space via pre-existing β-barrel proteins in the bacterial outer membrane that later became Tom40, and inserted into the inner membrane probably helped by a pre-existing inner membrane protein, thereby immediately providing the protoeukaryote host with photosynthesate. This would have created a powerful selective advantage for evolving more efficient carrier import by inserting Tom70 receptors. Massive gene transfer to the nucleus inevitably occurred by mutation pressure. Finally, pressure from harmful, non-selected gene transfer to the nucleus probably caused evolution of the presequence mechanism, and photosynthesis was lost.
A noisy transform predicts saccadic and manual reaction times to changes in contrast
Authors: Taylor M. J. , Carpenter R. H. S. , Anderson A. J.
Published: April 2006

One of the most important factors affecting the time taken to respond to a visual stimulus is contrast, and studies of reaction time can provide precise, quantitative information about the underlying signal processing. In this study we measured both saccadic and manual reaction times to step increments in target contrast. Our results over a range of initial contrasts are consistent with a simple model consisting of a noisy logarithmic transducer followed by a rise‐to‐threshold accumulator. A systematic comparison with previous contrast‐processing models also shows that the commonly used method of linear regression may not be a particularly sensitive tool in deciding between them. We found similar parameters for the contrast processor in both saccadic and manual reaction times, as might be expected if a common target detection stage precedes each type of reaction.
cAMP sensor Epac as a determinant of ATP‐sensitive potassium channel activity in human pancreatic β cells and rat INS‐1 cells
Authors: Kang Guoxin , Chepurny Oleg G. , Malester Brian , Rindler Michael J. , Rehmann Holger , Bos Johannes L. , Schwede Frank , Coetzee William A. , Holz George G.
Published: April 2006

The Epac family of cAMP‐regulated guanine nucleotide exchange factors (cAMPGEFs, also known as Epac1 and Epac2) mediate stimulatory actions of the second messenger cAMP on insulin secretion from pancreatic β cells. Because Epac2 is reported to interact in vitro with the isolated nucleotide‐binding fold‐1 (NBF‐1) of the β‐cell sulphonylurea receptor‐1 (SUR1), we hypothesized that cAMP might act via Epac1 and/or Epac2 to inhibit β‐cell ATP‐sensitive K+ channels (KATP channels; a hetero‐octomer of SUR1 and Kir6.2). If so, Epac‐mediated inhibition of KATP channels might explain prior reports that cAMP‐elevating agents promote β‐cell depolarization, Ca2+ influx and insulin secretion. Here we report that Epac‐selective cAMP analogues (2′‐O‐Me‐cAMP; 8‐pCPT‐2′‐O‐Me‐cAMP; 8‐pMeOPT‐2′‐O‐Me‐cAMP), but not a cGMP analogue (2′‐O‐Me‐cGMP), inhibit the function of KATP channels in human β cells and rat INS‐1 insulin‐secreting cells. Inhibition of KATP channels is also observed when cAMP, itself, is administered intracellularly, whereas no such effect is observed upon administration N6‐Bnz‐cAMP, a cAMP analogue that activates protein kinase A (PKA) but not Epac. The inhibitory actions of Epac‐selective cAMP analogues at KATP channels are mimicked by a cAMP agonist (8‐Bromoadenosine‐3′, 5′‐cyclic monophosphorothioate, Sp‐isomer, Sp‐8‐Br‐cAMPS), but not a cAMP antagonist (8‐Bromoadenosine‐3′, 5′‐cyclic monophosphorothioate, Rp‐isomer, Rp‐8‐Br‐cAMPS), and are abrogated following transfection of INS‐1 cells with a dominant‐negative Epac1 that fails to bind cAMP. Because both Epac1 and Epac2 coimmunoprecipitate with full‐length SUR1 in HEK cell lysates, such findings delineate a novel mechanism of second messenger signal transduction in which cAMP acts via Epac to modulate ion channel function, an effect measurable as the inhibition of KATP channel activity in pancreatic β cells.
The influence of intracellular lactate and H+ on cell volume in amphibian skeletal muscle
Authors: Usher‐Smith Juliet A. , Fraser James A. , Bailey Peter S. J. , Griffin Julian L. , Huang Christopher L.‐H.
Published: April 2006

The combined effects of intracellular lactate and proton accumulation on cell volume, Vc, were investigated in resting Rana temporaria striated muscle fibres. Intracellular lactate and H+ concentrations were simultaneously increased by exposing resting muscle fibres to extracellular solutions that contained 20–80 mm sodium lactate. Cellular H+ and lactate entry was confirmed using pH‐sensitive electrodes and 1H‐NMR, respectively, and effects on Vc were measured using confocal microscope xz‐scanning. Exposure to extracellular lactate up to 80 mm produced significant changes in pH and intracellular lactate (from a pH of 7.24 ± 0.03, n= 8, and 4.65 ± 1.07 mm, n= 6, respectively, in control fibres, to 6.59 ± 0.03, n= 4, and 26.41 ± 0.92 mm, n= 3, respectively) that were comparable to those observed following fatiguing stimulation (6.30–6.70 and 18.04 ± 1.78 mm, n= 6, respectively). Yet, the increase in intracellular osmolarity expected from such an increase in intracellular lactate did not significantly alter Vc. Simulation of these experimental results, modified from the charge difference model of Fraser & Huang, demonstrated that such experimental manoeuvres produced changes in intracellular [H+] and [lactate] comparable to those observed during muscle fatigue, and accounted for this paradoxical conservation of Vc through balancing negative osmotic effects resulting from the net cation efflux that would follow a titration of intracellular membrane‐impermeant anions by the intracellular accumulation of protons. It demonstrated that with established physiological values for intracellular buffering capacity and the permeability ratio of lactic acid and anionic lactate, PLacH: PLac−, this would provide a mechanism that precisely balanced any effect on cell volume resulting from lactate accumulation during exercise.
AMPK and cell proliferation – AMPK as a therapeutic target for atherosclerosis and cancer
Authors: Motoshima Hiroyuki , Goldstein Barry J. , Igata Motoyuki , Araki Eiichi
Published: April 2006

AMPK is a serine/threonine protein kinase, which serves as an energy sensor in all eukaryotic cell types. Published studies indicate that AMPK activation strongly suppresses cell proliferation in non‐malignant cells as well as in tumour cells. These actions of AMPK appear to be mediated through multiple mechanisms including regulation of the cell cycle and inhibition of protein synthesis, de novo fatty acid synthesis, specifically the generation of mevalonate as well as other products downstream of mevalonate in the cholesterol synthesis pathway. Cell cycle regulation by AMPK is mediated by up‐regulation of the p53–p21 axis as well as regulation of TSC2–mTOR (mammalian target of rapamycin) pathway. The AMPK signalling network contains a number of tumour suppressor genes including LKB1, p53, TSC1 and TSC2, and overcomes growth factor signalling from a variety of stimuli (via growth factors and by abnormal regulation of cellular proto‐oncogenes including PI3K, Akt and ERK). These observations suggest that AMPK activation is a logical therapeutic target for diseases rooted in cellular proliferation, including atherosclerosis and cancer. In this review, we discuss about exciting recent advances indicating that AMPK functions as a suppressor of cell proliferation by controlling a variety of cellular events in normal cells as well as in tumour cells.
Subthalamic stimulation evokes complex EPSCs in the rat substantia nigra pars reticulata in vitro
Authors: Shen Ke‐Zhong , Johnson Steven W.
Published: April 2006

The subthalamic nucleus (STN) plays an important role in movement control by exerting its excitatory influence on the substantia nigra pars reticulata (SNR), a major output structure of the basal ganglia. Moreover, excessive burst firing of SNR neurons seen in Parkinson's disease has been attributed to excessive transmission in the subthalamonigral pathway. Using the ‘blind’ whole‐cell patch clamp recording technique in rat brain slices, we found that focal electrical stimulation of the STN evoked complex, long‐duration excitatory postsynaptic currents (EPSCs) in SNR neurons. Complex EPSCs lasted 200–500 ms and consisted of an initial monosynaptic EPSC followed by a series of late EPSCs superimposed on a slow inward shift in holding current. Focal stimulation of regions outside the STN failed to evoke complex EPSCs. The late component of complex EPSCs was markedly reduced by ionotropic glutamate receptor antagonists (2‐amino‐5‐phosphonopentanoic acid and 6‐cyano‐7‐nitro‐quinoxalone) and by a GABAA receptor agonist (isoguvacine) when these agents were applied directly to the STN using a fast‐flow microapplicator. Moreover, the complex EPSC was greatly enhanced by bath application of the GABAA receptor antagonists picrotoxin or bicuculline. These data suggest that recurrent glutamate synapses in the STN generate polysynaptic, complex EPSCs that are under tonic inhibition by GABA. Because complex EPSCs are expected to generate bursts of action potentials in SNR neurons, we suggest that complex EPSCs may contribute to the pathological burst firing that is associated with the symptoms of Parkinson's disease.
Confined one-dimensional harmonic oscillator as a two-mode system
Authors: Gueorguiev V. G. , Rau A. R. P. , Draayer J. P.
Published: April 2006

The one-dimensional harmonic oscillator in a box is possibly the simplest example of a two-mode system. This system has two exactly solvable limits, the harmonic oscillator and a particle in a (one-dimensional) box. Each of the limits has a characteristic spectral structure describing the two different excitation modes of the system. Near these limits perturbation theory can be used to find an accurate description of the eigenstates. Away from the limits it is necessary to do a matrix diagonalization because the basis-state mixing that occurs is typically large. An alternative to formulating the problem in terms of one or the other basis set is to use an “oblique” basis that uses both sets. We study this alternative for the example system and then discuss the applicability of this approach for more complex systems, such as the study of complex nuclei where oblique-basis calculations have been successful.
Using classical probability functions to illuminate the relation between classical and quantum physics
Authors: Yoder G.
Published: April 2006

The classical and quantum mechanical solutions to three simple physical systems are directly compared by using the classical equations of motion to determine a probability density function. This function is compared to the probability density function for the quantum mechanical stationary state with the same energy. The nonclassical behavior of the quantum mechanical systems is thus made more distinct. This comparison allows students to gain experience using probability functions to describe physical systems and to see how the quantum mechanical solutions reduce to classical behavior in the high-energy/short-wavelength limit.
Testing the test: Item response curves and test quality
Authors: Morris Gary A. , Branum-Martin Lee , Harshman Nathan , Baker Stephen D. , Mazur Eric , Dutta Suvendra , Mzoughi Taha , McCauley Veronica
Published: April 2006

We present a simple technique for evaluating multiple-choice questions and their answers beyond the usual measures of difficulty and the effectiveness of distractors. The technique involves the construction and qualitative consideration of item response curves and is based on item response theory from the field of education measurement. To demonstrate the technique, we apply item response curve analysis to three questions from the Force Concept Inventory. Item response curve analysis allows us to characterize qualitatively whether these questions are efficient, where efficient is defined in terms of the construction, performance, and discrimination of a question and its answer choices. This technique can be used to develop future multiple-choice examination questions and a better understanding of results from existing diagnostic instruments.
Comments on the motion of magnetic field lines
Authors: Fälthammar Carl-Gunne
Published: April 2006

Belcher and Olbert recently showed that the concept of the motion of magnetic field lines can be helpful in teaching classical electromagnetism. Although this concept holds in many situations, it has important limitations. It is shown that the most common definition, v=E×B∕B2, which is the one used by Belcher and Olbert, is not appropriate when an electrostatic field is present, unless the field satisfies special conditions. In an infinitely conducting medium where the electric field has no component parallel to the magnetic field, E×B∕B2 is still a meaningful definition of the motion of magnetic field lines (which follow the plasma motion as if “frozen-in”). It used to be assumed that space plasmas could be treated as infinitely conducting and therefore the concept of magnetic field line motion was used extensively. But local nonvanishing values of E∙B can “cut” magnetic field lines and invalidate the frozen-in condition.
Bruchpilot Promotes Active Zone Assembly, Ca
2+
Channel Clustering, and Vesicle Release
Authors: Kittel Robert J. , Wichmann Carolin , Rasse Tobias M. , Fouquet Wernher , Schmidt Manuela , Schmid Andreas , Wagh Dhananjay A. , Pawlu Christian , Kellner Robert R. , Willig Katrin I. , Hell Stefan W. , Buchner Erich , Heckmann Manfred , Sigrist Stephan J.
Published: April 2006

The molecular organization of presynaptic active zones during calcium influx–triggered neurotransmitter release is the focus of intense investigation. The
Drosophila
coiled-coil domain protein Bruchpilot (BRP) was observed in donut-shaped structures centered at active zones of neuromuscular synapses by using subdiffraction resolution STED (stimulated emission depletion) fluorescence microscopy. At
brp
mutant active zones, electron-dense projections (T-bars) were entirely lost, Ca
2+
channels were reduced in density, evoked vesicle release was depressed, and short-term plasticity was altered. BRP-like proteins seem to establish proximity between Ca
2+
channels and vesicles to allow efficient transmitter release and patterned synaptic plasticity.
An SNP Caused Loss of Seed Shattering During Rice Domestication
Authors: Konishi Saeko , Izawa Takeshi , Lin Shao Yang , Ebana Kaworu , Fukuta Yoshimichi , Sasaki Takuji , Yano Masahiro
Published: April 2006

Loss of seed shattering was a key event in the domestication of major cereals. We revealed that the
qSH1
gene, a major quantitative trait locus of seed shattering in rice, encodes a BEL1-type homeobox gene and demonstrated that a single-nucleotide polymorphism (SNP) in the 5′ regulatory region of the
qSH1
gene caused loss of seed shattering owing to the absence of abscission layer formation. Haplotype analysis and association analysis in various rice collections revealed that the SNP was highly associated with shattering among
japonica
subspecies of rice, implying that it was a target of artificial selection during rice domestication.
Cyclopropenylidenes: From Interstellar Space to an Isolated Derivative in the Laboratory
Authors: Lavallo Vincent , Canac Yves , Donnadieu Bruno , Schoeller Wolfgang W. , Bertrand Guy
Published: April 2006

Like many of the molecular species that have been detected in the interstellar medium, the singlet carbene cyclopropenylidene (C
3
H
2
) has been presumed to be too unstable to isolate in the laboratory. However, by appending π-electron–donating amino groups to the triangular skeleton, we prepared a cyclopropenylidene derivative that is stable at room temperature. In contrast to previously isolated carbenes, this compound does not require a heteroatom adjacent to the electron-deficient carbon to confer stability. Despite the presence of amino groups, the geometric parameters of the cyclic skeleton, revealed by x-ray crystallography, are only slightly perturbed relative to those of the calculated structure of unsubstituted cyclopropenylidene. Stable cyclopropenylidene derivatives might thus serve as models for a better understanding of the formation of carbon-bearing molecules in the interstellar medium.
Engineered early embryonic cardiac tissue retains proliferative and contractile properties of developing embryonic myocardium
Authors: Tobita Kimimasa , Liu Li J. , Janczewski Andrzej M. , Tinney Joseph P. , Nonemaker Jill M. , Augustine Serena , Stolz Donna B. , Shroff Sanjeev G. , Keller Bradley B.
Published: April 2006

Embryonic myocardium has a high rate of cell proliferation and regulates cellular proliferation, contractile function, and myocardial architecture in response to changes in external mechanical loads. However, the small and complex three-dimensional (3D) structure of the embryonic myocardium limits our ability to directly investigate detailed relationships between mechanical load, contractile function, and cardiomyocyte proliferation. We developed a novel 3D engineered early embryonic cardiac tissue (EEECT) from early embryonic ventricular cells to test the hypothesis that EEECT retains the proliferative and contractile properties of embryonic myocardium. We combined freshly isolated White Leghorn chicken embryonic ventricular cells at Hamburger-Hamilton (HH) stage 31 ( day 7 of a 46-stage, 21-day incubation period), collagen type I, and matrix factors to construct cylindrical-shaped EEECTs. We studied tissue architecture, cell proliferation patterns, and contractile function. We then generated engineered fetal cardiac tissue (EFCT) from HH stage 40 ( day 14) fetal ventricular cells for direct comparison with EEECT. Tissue architecture was similar in EEECT and EFCT. EEECT maintained high cell proliferation patterns by culture day 12, whereas EFCT decreased cell proliferation rate by culture day 9 ( P < 0.05). EEECT increased active contractile force from culture day 7 to day 12. The culture day 12 EEECT contractile response to the β-adrenergic stimulation was less than culture day 9 EFCT ( P < 0.05). Cyclic mechanical stretch stimulation induced myocardial hyperplasia in EEECT. Results indicate that EEECT retains the proliferative and contractile properties of developing embryonic myocardium and shows potential as a robust in vitro model of developing embryonic myocardium.
Intrauterine ethanol exposure results in hypothalamic oxidative stress and neuroendocrine alterations in adult rat offspring
Authors: Dembele Korami , Yao Xing-Hai , Chen Li , Nyomba B. L. Grégoire
Published: April 2006

Prenatal ethanol (EtOH) exposure is associated with low birth weight, followed by increased appetite, catch-up growth, insulin resistance, and impaired glucose tolerance in the rat offspring. Because EtOH can induce oxidative stress, which is a putative mechanism of insulin resistance, and because of the central role of the hypothalamus in the regulation of energy homeostasis and insulin action, we investigated whether prenatal EtOH exposure causes oxidative damage to the hypothalamus, which may alter its function. Female rats were given EtOH by gavage throughout pregnancy. At birth, their offspring were smaller than those of non-EtOH rats. Markers of oxidative stress and expression of neuropeptide Y and proopiomelanocortin (POMC) were determined in hypothalami of postnatal day 7 (PD7) and 3-mo-old (adult) rat offspring. In both PD7 and adult rats, prenatal EtOH exposure was associated with decreased levels of glutathione and increased expression of MnSOD. The concentrations of lipid peroxides and protein carbonyls were normal in PD7 EtOH-exposed offspring, but were increased in adult EtOH-exposed offspring. Both PD7 and adult EtOH-exposed offspring had normal neuropeptide Y and POMC mRNA levels, but the adult offspring had reduced POMC protein concentration. Thus only adult offspring preexposed to EtOH had increased hypothalamic tissue damage and decreased levels of POMC, which could impair melanocortin signaling. We conclude that prenatal EtOH exposure causes hypothalamic oxidative stress, which persists into adult life and alters melanocortin action during adulthood. These neuroendocrine alterations may explain weight gain and insulin resistance in rats exposed to EtOH early in life.
Thermal effects of whole head submersion in cold water on nonshivering humans
Authors: Pretorius Thea , Bristow Gerald K. , Steinman Alan M. , Giesbrecht Gordon G.
Published: April 2006

This study isolated the effect of whole head submersion in cold water, on surface heat loss and body core cooling, when the confounding effect of shivering heat production was pharmacologically eliminated. Eight healthy male subjects were studied in 17°C water under four conditions: the body was either insulated or uninsulated, with the head either above the water or completely submersed in each body-insulation subcondition. Shivering was abolished with buspirone (30 mg) and meperidine (2.5 mg/kg), and subjects breathed compressed air throughout all trials. Over the first 30 min of immersion, exposure of the head increased core cooling both in the body-insulated conditions (head out: 0.47 ± 0.2°C, head in: 0.77 ± 0.2°C; P < 0.05) and the body-exposed conditions (head out: 0.84 ± 0.2°C and head in: 1.17 ± 0.5°C; P < 0.02). Submersion of the head (7% of the body surface area) in the body-exposed conditions increased total heat loss by only 10%. In both body-exposed and body-insulated conditions, head submersion increased core cooling rate much more (average of 42%) than it increased total heat loss. This may be explained by a redistribution of blood flow in response to stimulation of thermosensitive and/or trigeminal receptors in the scalp, neck and face, where a given amount of heat loss would have a greater cooling effect on a smaller perfused body mass. In 17°C water, the head does not contribute relatively more than the rest of the body to surface heat loss; however, a cold-induced reduction of perfused body mass may allow this small increase in heat loss to cause a relatively larger cooling of the body core.
Single muscle fiber adaptations with marathon training
Authors: Trappe Scott , Harber Matthew , Creer Andrew , Gallagher Philip , Slivka Dustin , Minchev Kiril , Whitsett David
Published: April 2006

The purpose of this investigation was to characterize the effects of marathon training on single muscle fiber contractile function in a group of recreational runners. Muscle biopsies were obtained from the gastrocnemius muscle of seven individuals (22 ± 1 yr, 177 ± 3 cm, and 68 ± 2 kg) before, after 13 wk of run training, and after 3 wk of taper. Slow-twitch myosin heavy chain [(MHC) I] and fast-twitch (MHC IIa) muscle fibers were analyzed for size, strength (Po), speed ( Vo), and power. The run training program led to the successful completion of a marathon (range 3 h 56 min to 5 h 35 min). Oxygen uptake during submaximal running and citrate synthase activity were improved ( P < 0.05) with the training program. Muscle fiber size declined ( P < 0.05) by ∼20% in both fiber types after training. Po was maintained in both fiber types with training and increased ( P < 0.05) by 18% in the MHC IIa fibers after taper. This resulted in >60% increase ( P < 0.05) in force per cross-sectional area in both fiber types. Fiber Vo increased ( P < 0.05) by 28% in MHC I fibers with training and was unchanged in MHC IIa fibers. Peak power increased ( P < 0.05) in MHC I and IIa fibers after training with a further increase ( P < 0.05) in MHC IIa fiber power after taper. These data show that marathon training decreased slow-twitch and fast-twitch muscle fiber size but that it maintained or improved the functional profile of these fibers. A taper period before the marathon further improved the functional profile of the muscle, which was targeted to the fast-twitch muscle fibers.
Strain-dependent pulmonary gene expression profiles of a cystic fibrosis mouse model
Authors: Haston Christina K. , Cory Sean , Lafontaine Laurie , Dorion Geneviève , Hallett Michael T.
Published: April 2006

Cystic fibrosis (CF) lung disease severity is influenced by unknown genetic factors apart from the disease causative gene, cystic fibrosis transmembrane conductance regulator ( CFTR). Previous studies have shown the C57BL/6J congenic Cftr−/− (B6 CF) mouse to develop a fibrotic lung disease compared with both CF mice of the BALB/c background and wild-type animals. In this report, gene expression profiling with microarrays was used to identify genes differentially expressed in the lungs of B6 and BALB CF mice compared with non-CF littermates. Seven hundred two genes or expressed sequence tags (ESTs) were identified to be differentially expressed between the B6 CF and non-CF control lungs ( P < 0.05), and, by Gene Ontology classification, the B6 CF response included the cell proliferation categories of DNA metabolism and mitosis. In the response of BALB mice to nonfunctional Cftr, 943 genes/ESTs were differentially expressed compared with controls. The biological processes of apoptosis and T and B cell proliferation were prominent in the gene list of the BALB CF strain. In support of this strain difference, increased T lymphocyte infiltration was evident in the lungs of BALB CF mice, through immunohistochemical staining, compared with the lungs from both B6 CF and non-CF control mice. Four hundred forty-four genes/ESTs were differentially expressed between B6 CF and BALB CF mice ( P < 0.05, fold >2), including 56 that map to previously identified linkage intervals. These results suggest that the variable severity of CF lung disease in this mouse model is controlled by multiple genetic factors, including those of an immune response.
Hyperinsulinemia Is Associated With Increased Production Rate of Intestinal Apolipoprotein B-48–Containing Lipoproteins in Humans
Authors: Duez Hélène , Lamarche Benoît , Uffelman Kristine D. , Valero René , Cohn Jeffrey S. , Lewis Gary F.
Published: April 2006

Objectives—

Whereas postprandial hyperlipidemia is a well-described feature of insulin-resistant states and type 2 diabetes, no previous studies have examined intestinal lipoprotein production rates (PRs) in relation to hyperinsulinemia or insulin resistance in humans.

Methods and Results—

Apolipoprotein B-48 (apoB-48)–containing lipoprotein metabolism was examined in the steady-state fed condition with a 15-hour primed constant infusion of [D3]-
l
-leucine in 14 nondiabetic men with a broad range of body mass index (BMI) and insulin sensitivity. To examine the relationship between indices of insulin resistance and intestinal lipoprotein PR data were analyzed in 2 ways: by correlation and by comparing apoB-48 PRs in those whose fasting plasma insulin concentrations were above or below the median for the 14 subjects studied (60 pmol/L). ApoB-48 PR was significantly higher in hyperinsulinemic, insulin-resistant subjects (1.73±0.39 versus 0.88±0.13 mg/kg per day;
P
<0.05) and correlated with fasting plasma insulin concentrations (
r
=0.558;
P
=0.038), despite great heterogeneity in apoB-48 kinetic parameters, particularly among the obese subjects. There was no significant difference in clearance of apoB-48 between the 2 groups, nor was there a significant correlation between apoB-48 fractional clearance rate and fasting insulin or homeostasis model assessment-insulin resistance.

Conclusions—

These are the first human data to conclusively demonstrate that intestinal apoB-48–containing triglyceride-rich lipoprotein PR is increased in hyperinsulinemic, insulin-resistant humans. Intestinal lipoprotein particle overproduction is a newly described feature of insulin resistance in humans.