bluuebunny/crossref_metadata_2025 huggingface dataset:
Adiponectin, Leptin, and Erythrocyte Sodium/Lithium Countertransport Activity, But Not Resistin, Are Related to Glucose Metabolism in Growth Hormone-Deficient Adults
Authors: Svensson Johan , Herlitz Hans , Lundberg Per-Arne , Johannsson Gudmundur
Published: April 2005

In a randomized, placebo-controlled, crossover study under metabolic ward conditions, 10 GH-deficient adults received 1-wk GH replacement therapy (9.5 μg/kg·d). The effect of this treatment on the erythrocyte sodium/lithium countertransport (SLC) activity and on serum levels of adiponectin, resistin, leptin, IGF binding protein-1 (IGFBP-1) and IL-6 was determined.

The 1-wk GH replacement impaired glucose homeostasis determined from an oral glucose tolerance test. The other measured variables in serum were unchanged by GH replacement. At baseline, serum adiponectin level was inversely correlated and serum leptin level was positively correlated with measures of glucose tolerance and insulin sensitivity. The changes in serum leptin level and erythrocyte SLC activity were positively correlated, and the change in serum IGFBP-1 level was negatively correlated, correlated with changes in measures of glucose metabolism.

In conclusion, short-term GH treatment induced glucose intolerance but did not significantly change the erythrocyte SLC activity and the serum levels of adipokines, arguing against direct effects of GH on these measures. However, baseline values or changes in erythrocyte SLC activity, adiponectin, leptin, and IGFBP-1 correlated with glucose metabolism. This suggests that these factors are of importance for glucose homeostasis in GH-deficient adults, most likely through GH-independent mechanisms.
Delayed Diagnosis of Congenital Adrenal Hyperplasia with Salt Wasting Due to Type II 3β-Hydroxysteroid Dehydrogenase Deficiency
Authors: Johannsen Trine H. , Mallet Delphine , Dige-Petersen Harriet , Müller Jørn , Main Katharina M. , Morel Yves , Forest Maguelone G.
Published: April 2005

Classical 3β-hydroxysteroid dehydrogenase (3β-HSD) deficiency is a rare cause of congenital adrenal hyperplasia. We report two sisters presenting with delayed diagnoses of classical 3β-HSD, despite salt wasting (SW) episodes in infancy. Sibling 1 was referred for premature pubarche, slight growth acceleration, and advanced bone age, whereas sibling 2 had no signs of virilization.

At referral, increased 17α-hydroxyprogesterone associated with premature pubarche at first suggested a nonclassical 21-hydroxylase deficiency. Sequencing of the CYP21 gene showed both girls only heterozygotes (V281L mutation). This result, combined with SW in infancy, suggested a 3β-HSD deficiency because of increased dehydroepiandrosterone sulfate levels. Further hormonal studies showed markedly elevated Δ5-steroids, in particular 17α-hydroxypregnenolone greater than 100 nmol/liter (the clue to the diagnosis) and elevated Δ5-/Δ4-steroid ratios. Sequencing of the type II 3β-HSD gene documented that both girls were compound heterozygotes for T181I and 1105delA mutations. Retrospectively, elevated levels of 17α-hydroxyprogesterone were found on blood spots from Guthrie’s test.

There is no previous report of the combination of SW and premature pubarche due to mutations in the type II 3β-HSD gene. Because neonatal diagnosis could have prevented life-threatening crises in these girls, this report further supports the benefits for neonatal screening for congenital adrenal hyperplasia whatever the etiology.
Effect of Thiazolidinedione Treatment on Progression of Subclinical Atherosclerosis in Premenopausal Women at High Risk for Type 2 Diabetes
Authors: Xiang Anny H. , Peters Ruth K. , Kjos Siri L. , Ochoa Cesar , Marroquin Aura , Goico Jose , Tan Sylvia , Wang Chengwei , Azen Stanley P. , Liu Chao-ran , Liu Ci-hua , Hodis Howard N. , Buchanan Thomas A.
Published: April 2005

We tested the effects of treatment with a thiazolidinedione drug on rates of progression of carotid intima-media thickness (CIMT) and some putative determinants of CIMT in young women at high risk for type 2 diabetes. A total of 266 nondiabetic, Hispanic women with recent gestational diabetes were randomized to placebo or troglitazone. CIMT measurements were made at baseline, annually, and at study end, together with measurements of obesity, serum lipids, and glucose and insulin levels during oral glucose tolerance tests. Insulin sensitivity (minimal model analysis) was measured at baseline and 3 months later. Data were analyzed to compare CIMT progression rates between treatment groups and investigate potential determinants of differences in CIMT progression.

One hundred ninety-two women had a CIMT measurement at baseline and at least one follow-up visit. The mean rate of CIMT change was 31% lower in women assigned to troglitazone (P = 0.048). This intergroup difference was not explained by baseline or on-trial differences in obesity, lipids, glucose, or insulin. The reduction in CIMT progression developed gradually, occurred only in women who had an increase in insulin sensitivity, and was unrelated to the presence of the metabolic syndrome at baseline.

Troglitazone reduced the progression of subclinical atherosclerosis via a mechanism that involved unmeasured mediators of atherosclerosis, either in the circulation or directly in the arterial wall.
Monocyte Chemoattractant Protein-1 Release Is Higher in Visceral than Subcutaneous Human Adipose Tissue (AT): Implication of Macrophages Resident in the AT
Authors: Bruun Jens M. , Lihn Aina S. , Pedersen Steen B. , Richelsen Bjørn
Published: April 2005

Human adipose tissue (AT) produces several adipokines including monocyte chemoattractant protein (MCP)-1, involved in the pathogenesis of atherosclerosis.

Objective: Human AT cultures, isolated adipocytes, and stromal-vascular cells were used to investigate the relationship among AT-resident macrophages, MCP-1, and adiposity and the regulation of MCP-1.

Results: mRNA levels of specific macrophage markers (CD68 and CD14) are correlated with adiposity in sc AT and visceral AT (P < 0.05). MCP-1 production is higher in stromal-vascular cells vs. adipocytes (P < 0.01) and correlates with macrophage markers in both AT compartments (P < 0.05). MCP-1 release is higher in obese subjects (P < 0.05) and in VAT (P < 0.01), but after adjusting for AT-resident macrophages, the differences disappear. MCP-1 is stimulated by IL-1β, TNF-α, IL-8, IL-4, and IL-6 + IL-6-soluble receptor and is decreased by dexamethasone, IL-10, metformin, and thiazolidinediones.

Discussion: MCP-1 is correlated with specific macrophage markers, adiposity, and AT localization, but the relationship seems to be related to the number of AT-resident macrophages. Despite this, MCP-1 may be involved in obesity-related health complications, and the decrease of MCP-1 by metformin and thiazolidinediones suggests that these antidiabetic compounds have antiinflammatory properties improving the low-grade inflammatory state observed in obesity.
Thyrotropin Receptor/Thyroglobulin Messenger Ribonucleic Acid in Peripheral Blood and Fine-Needle Aspiration Cytology: Diagnostic Synergy for Detecting Thyroid Cancer
Authors: Wagner Kristin , Arciaga Rosemarie , Siperstein Allan , Milas Mira , Warshawsky Ilka , Sethu S. , Reddy K. , Gupta Manjula K.
Published: April 2005

RT-PCR for thyroglobulin (Tg) and TSH receptor (TSHR) mRNA has been used to detect circulating thyroid cancer cells. Little is known, however, regarding the preoperative sensitivity of this test to detect cancer. Seventy-two patients with thyroid disease (36 with malignancy and 36 with benign disease) were evaluated preoperatively. TSHR and Tg mRNA transcripts were detected by RT-PCR assays, previously determined to be specific for cancer cells. There was 100% concordance between TSHR and Tg mRNA RT-PCR results. Of 36 cancer patients, 11 had recurrent disease, and all were positive by RT-PCR. Among 25 patients with no prior thyroid surgery, 18 tested positive preoperatively (sensitivity 72%). Seven of 36 patients with benign disease tested positive (specificity 80%). The overall preoperative diagnostic accuracy was 77%. Preoperative fine-needle aspiration (FNA) biopsy was performed on 46 of 61 patients with no prior thyroid surgery. FNA was diagnostic in 28 (61%) patients. Preoperative cytology was adequate but not diagnostic in 18 (39%) patients. RT-PCR correctly classified 14 of these 18 patients with indeterminate FNA, and the test detected three of four cancer patients as positive (75% sensitive) and 11 of 14 patients (78% specific) with benign disease as negative. The combined diagnostic performance characteristics for RT-PCR and FNA cytology were sensitivity = 95%, specificity = 83%, and diagnostic accuracy = 89%, with positive and negative predictive values of 84 and 95%, respectively. Our results suggest that the molecular detection of circulating thyroid cancer cells by RT-PCR for TSHR/Tg mRNA complements FNA cytology in the preoperative differentiation of benign from malignant thyroid disease and their combined use may save unnecessary surgeries.
Effect of L-000845704, an αVβ3 Integrin Antagonist, on Markers of Bone Turnover and Bone Mineral Density in Postmenopausal Osteoporotic Women
Authors: Murphy M. G. , Cerchio K. , Stoch S. A. , Gottesdiener K. , Wu M. , Recker R.
Published: April 2005

The αVβ3 integrin (vitronectin receptor) plays a pivotal role in bone resorption. We hypothesized that L-000845704, an αVβ3 integrin antagonist, would potently inhibit bone resorption, thereby increasing bone mass as assessed by bone mineral density (BMD) in women with postmenopausal osteoporosis. In a multicenter, randomized, double-blind, placebo-controlled, 12-month study, 227 women (average 63 yr) with low lumbar spine or femoral neck BMD were randomly assigned to receive 100 or 400 mg L-000845704 once daily (qd), 200 mg L-000845704 twice daily (bid), or placebo. L-000845704 increased lumbar spine BMD (2.1, 3.1, and 3.5% for the 100-mg-qd, 400-mg-qd, and 200-mg-bid treatment groups, respectively, vs. −0.1% for placebo; P < 0.01 all treatments vs. placebo). Only 200 mg L-000845704 bid significantly increased BMD at the hip (1.7 vs. 0.3% for placebo; P < 0.03) and femoral neck (2.4 vs. 0.7% for placebo; P < 0.05). No L-000845704 group increased total body BMD. All doses of L-000845704 resulted in a similar approximately 42% decrease from baseline of N-telopeptide cross-links (P < 0.001 vs. placebo). L-000845704 was generally well tolerated; adverse events resulting in discontinuation from the study were relatively infrequent.

In conclusion, the antiresorptive effect of the αVβ3 integrin antagonist L-000845704 translated into significant increases in lumbar spine BMD. Furthermore, 200 mg L-000845704 bid provided efficacy at the hip sites. These data suggest that the αVβ3 integrin antagonist L-000845704 could be developed as an effective therapeutic agent for osteoporosis.
Ocular surface epithelia contain ABCG2-dependent side population cells exhibiting features associated with stem cells
Authors: Budak Murat T. , Alpdogan Onder S. , Zhou Mingyuan , Lavker Robert M. , Akinci M.A. Murat , Wolosin J. Mario
Published: April 2005

When cell populations are incubated with the DNA-binding dye Hoechst 33342 and subjected to flow cytometry analysis for Hoechst 33342 emissions, active efflux of the dye by the ABCG2/BCRP1 transporter causes certain cells to appear as a segregated cohort, known as a side population (SP). Stem cells from several tissues have been shown to possess the SP phenotype. As the lack of specific surface markers has hindered the isolation and subsequent biochemical characterization of epithelial stem cells this study sought to determine the existence of SP cells and expression of ABCG2 in the epithelia of the ocular surface and evaluate whether such SP cells had features associated with epithelial stem cells. Human and rabbit limbal-corneal and conjunctival epithelial cells were incubated with Hoechst 33342, and analyzed and sorted by flow cytometry. Sorted cells were subjected to several tests to determine whether the isolated SP cells displayed features consistent with the stem cell phenotype. Side populations amounting to <1% of total cells, which were sensitive to the ABCG2-inhibitor fumitremorgin C, were found in the conjunctival and limbal epithelia, but were absent from the stem cell-free corneal epithelium. Immunohistochemistry was used to establish the spatial expression pattern of ABCG2. The antigen was detected in clusters of conjunctival and limbal epithelia basal cells but was not present in the corneal epithelium. SP cells were characterized by extremely low light side scattering and contained a high percentage of cells that: showed slow cycling prior to tissue collection; exhibited an initial delay in proliferation after culturing; and displayed clonogenic capacity and resistance to phorbol-induced differentiation; all features that are consistent with a stem cell phenotype.
Multi-lineage potential of fetal cells in maternal tissue: a legacy in reverse
Authors: Khosrotehrani Kiarash , Bianchi Diana W.
Published: April 2005

Fetal cells circulate in pregnant women and persist in blood and tissue for decades post-partum. The mother thus becomes chimeric. Factors that may influence such fetal cell microchimerism include histocompatibility, fetal or placental abnormalities, or a reproductive history that includes miscarriage or elective termination. Fetal cell microchimerism is associated with some maternal autoimmune diseases, such as systemic sclerosis. Moreover, a novel population of fetal cells, the pregnancy-associated progenitor cells (PAPCs), appears to differentiate in diseased or injured maternal tissue. The cellular origin of these cells is at present unknown but could be a hematopoietic stem cell, a mesenchymal stem cell, or a novel cell type. Pregnancy therefore results in the acquisition of cells with stem-cell-like properties that may influence maternal health post-partum. Rather than triggering disease, these cells may instead combat it.
Digital robust preview control of path tracking
Authors: Tan Y G , Liu D K , Liu F , Zhou Z D
Published: April 2005

A robust optimal preview control method is presented in this paper for path tracking control problems to improve robustness and tracking precision of path tracking control systems. The known path information is used as reference input signals. Simulation results show that this method is valid not only for improving the performance of highly accurate trajectory control but also for improving system stabilization.
STP: Skills, tactics, and plays for multi-robot control in adversarial environments
Authors: Browning B , Bruce J , Bowling M , Veloso M
Published: April 2005

In an adversarial multi-robot task, such as playing robot soccer, decisions for team and single-robot behaviour must be made quickly to take advantage of short-term fortuitous events. When no such opportunities exist, the team must execute sequences of coordinated team action that increases the likelihood of future opportunities. A hierarchical architecture, called STP, has been developed to control an autonomous team of robots operating in an adversarial environment. STP consists of skills for executing the low-level actions that make up robot behaviour, tactics for determining what skills to execute, and plays for coordinating synchronized activity among team members. The STP architecture combines each of these components to achieve autonomous team control. Moreover, the STP hierarchy allows for fast team response in adversarial environments while carrying out actions with longer goals. This article presents the STP architecture for controlling an autonomous robot team in a dynamic adversarial task that allows for coordinated team activity towards long-term goals, with the ability to respond rapidly to dynamic events. Secondly, the subcomponent of skills and tactics is presented as a generalized single-robot control hierarchy for hierarchical problem decomposition with flexible control policy implementation and reuse. Thirdly, the play techniques contribute as a generalized method for encoding and synchronizing team behaviour, providing multiple competing team responses, and for supporting effective strategy adaptation against opponent teams. STP has been fully implemented on a robot platform and thoroughly tested against a variety of unknown opponent teams in a number of RoboCup robot soccer competitions. These competition results are presented as a mechanism to analyse the performance of STP in a real setting.
Kripke modelling of multiple robots with decentralized cooperation specified with temporal logic
Authors: Jeyaraman S , Tsourdos A , Zbikowski R , White B A
Published: April 2005

Kripke models are used to formalize decentralized cooperation of a group of robots, to propose temporal logic specification of the cooperation, and to verify the correctness of the specification by checking the models. The focus is on implementing this mathematical formalism under minimalist communication and under constrained motion of the robots. Kripke models consist of, firstly, a of possible worlds (system configurations), secondly, an accessibility relation in the (transitions between the worlds), and, thirdly, a labelling function (which logical statements are true in each world). This approach represents continuous dynamics and discrete decision making of the robots in a unified way. Desirable properties of cooperation can be precisely expressed using temporal logic statements defining safety, liveness, etc. Whether a group of robots, whose behaviour is formalized with Kripke models, possesses such properties is then verified using automated model checking tools. The scenarios considered include path planning of a group of three robots moving in an obstacle-free environment, without and with communication among group members. The results show that for each scenario the mathematical formalism of Kripke models expresses the group behaviour in a transparent and tractable way. Finally, desirable properties of the decentralized cooperation, specified with temporal logic, can be verified on the Kripke models by automatic model checking software. Hence, guaranteed performance of cooperating autonomous robots can be assured in a formal, precise, and clear way.
Dynamic characteristics of squeeze-type mount using magnetorheological fluid
Authors: Ahn Y K , Ha J-Y , Kim Y-H , Yang B-S , Ahmadian M , Ahn K K , Morishita S
Published: April 2005

This paper presents an analytical and experimental analysis of the characteristics of a squeeze-type magnetorheological (MR) mount which can be used for various vibration isolation areas. The concept of the squeeze-type mount and details of the design of a squeeze-type MR mount are discussed. These are followed by a detailed description of the test set-up for evaluating the dynamic behaviour of the mount. A series of tests was conducted on the prototype mount built for this study, in order to characterize the changes occurring as a result of changing electrical current to the mount. The results of this study show that increasing electrical current to the mount, which increases the yield stress of the MR fluid, will result in an increase in both stiffness and damping of the mount. The results also show that the mount hysteresis increases with increase in current to the MR fluid, causing changes in stiffness and damping at different input frequencies.
Forced response of translating media with variable length and tension: Application to high-speed elevators
Authors: Zhu W D , Chen Y
Published: April 2005

The lateral response of vertically translating media with variable length and tension, subjected to general initial conditions and external excitation, are determined. The translating media are modelled as a taut string and tensioned beams with pinned and fixed boundaries. In each model a rigid body is attached to the lower end of the medium and has a prescribed displacement along the horizontal direction. The rate of change in the energy of the translating medium is analysed from the control volume and system viewpoints. The models are used to predict the forced response of a moving cable in a high-speed elevator. Three spatial discretization schemes are used to calculate the response and shown to yield the same results. The convergence of the solution for each model is investigated. The approximate solution for the string model with constant tension is compared with its exact solution from the wave method.
Impact-induced vibration in vehicular driveline systems: Theoretical and experimental investigations
Authors: Gnanakumarr M , Theodossiades S , Rahnejat H , Menday M
Published: April 2005

The paper investigates the conditions leading to the emergence and persistence of an acute metallic noise in light-truck drivelines. Sudden demands in torque in the presence of lash zones give rise to this phenomenon, which is onomatopoeically referred to as clonk. The study of clonk requires combined rigid multi-body dynamics and flexible body oscillations. The results show high-frequency contributions in the driveline vibrational response of certain structural modes of the driveshaft pieces, which are induced by remote impact of meshing transmission teeth through backlash. The numerically predicted spectrum of vibration shows good correlation with experimental measurements of radiated noise from a dynamic drivetrain rig.
A new non-linear approach to analysing the dynamic behaviour of tank vehicles subjected to liquid sloshing
Authors: Dai L , Xu L , Setiawan B
Published: April 2005

This research presents a new approach to investigating the non-linear dynamic behaviour of partially filled tank vehicles under large-amplitude liquid sloshing. A non-linear impact model for liquid sloshing in partially filled liquid tank vehicles is established for investigating the longitudinal dynamic characteristics of tank vehicles under typical driving conditions. The dynamic fluid motion within the tank is modelled by utilizing an analogy system together with an impact subsystem for longitudinal oscillations. The forces on the fifth wheel and the axles of the vehicle are determined in considering the effects of the liquid sloshing in the tank. The non-linear dynamic behaviours of the tank vehicle subjected to liquid sloshing and the excitations generated by rough roads are analysed and compared with those of linear models. Numerical simulation of the tank vehicle under typical rough road conditions is performed.
Chaotic response of a Galerkin shell to constant load and periodic excitation
Authors: Dai L , Han Q , Dong M
Published: April 2005

This study intends to investigate the dynamic behaviour of a non-linear elastic shallow shell of large deflection subjected to constant boundary loading and harmonic lateral excitation. The general governing equation for the shell is established using the Galerkin Principle. Three types of dynamic equation of the shell are developed, corresponding to certain geometry and loading conditions. Melnikov functions are considered for each type. Non-linear responses of the shell to the loads are analysed theoretically. Centre points, saddle points, and homoclinic orbits are determined and analysed on the basis of the governing equations established. The critical conditions for chaos to occur are provided for the vibrations of the shell. Numerical analysis is also performed for the non-linear elastic shell. Chaotic and regular vibrations of the shell are analysed with presentations of time history plots, phase diagrams, and Poincaré maps.
Elastodynamic transient analysis of a four-cylinder valvetrain system with camshaft flexibility
Authors: Teodorescu M , Kushwaha M , Rahnejat H , Taraza D
Published: April 2005

This paper presents an analysis of a line of valvetrains in a four-cylinder, four-stroke in-line diesel engine. The method highlighted in this paper predicts the vibration signature together with the prevailing contact conditions and frictional characteristics exhibited in the valvetrain system. This integrated dynamic and tribological investigation provides a practical approach that can be used during the design or the evaluation phase of automotive valvetrain systems.
Non-linear characteristics of a cracked rotor-journal bearing system
Authors: Yang B , Suh C S
Published: April 2005

A model rotor-journal bearing system incorporating translational and rotational inertia, bending stiffness, gyroscopic moment, shear deformation, and disc imbalance is developed for investigating the various rotor-dynamic instabilities induced by the simultaneous exertion of crack breathing and bearing fluid film forces. Rich and complex non-linear behaviours displayed at different rotor speeds, relative flexibility (embodying the extent of surface crack development), and film clearances are studied employing the fundamental concept of instantaneous frequency. Acquired results show that the model system responds differently to two sources of non-linearity than to only one. The presence of surface fatigue cracks generates various prominent effects at low speeds and dominates non-linear instability response at high speeds. In addition, smaller bearing clearances are seen not only to induce smaller rotor vibration amplitude subject to cracking opening but also to bring about more bifurcations.
The symmetry of steady-state solutions of non-smooth dynamical systems with two constraints
Authors: Luo A C J
Published: April 2005

In this paper, the symmetry of steady-state solutions in non-smooth dynamical systems with two symmetrical constraints are investigated to obtain all possible stable and unstable motions. An invariant transformation exists in regular and chaotic motions relative to skew-symmetrical mapping pairs in symmetrical systems with harmonic excitations. This investigation provides a mathematical foundation for the symmetry of solutions in this class of non-smooth dynamical systems. The group structure of mapping combinations should be further investigated.
Analytical modal analysis of thin-film flat lenses
Authors: Hamidzadeh H R , Moxey L
Published: April 2005

The free vibrations of circular and elliptical thin-film lens are investigated. In particular, linear closed-form solutions for free vibrations of these structures were achieved and modal analysis was performed. The vibration response of the thin-film membranes were mathematically modelled using the Mathieu equation. Numerical results for various nodal diameters were computed. For the limited case, when an elliptical lens becomes circular, an excellent comparison was established with the available analytical solution. Experimental analyses were conducted to determine the effects of various parameters, such as material properties, membrane pre-strain rate, and the geometry, on natural frequency and mode shapes of these structures. The comparison verified the adequacy of linear solutions to predict the dynamic response of thin-film lenses.
tRNA m7G methyltransferase Trm8p/Trm82p: Evidence linking activity to a growth phenotype and implicating Trm82p in maintaining levels of active Trm8p
Authors: ALEXANDROV ANDREI , GRAYHACK ELIZABETH J. , PHIZICKY ERIC M.
Published: April 2005

We show that Saccharomyces cerevisiae strains lacking Trm8p/Trm82p tRNA m7G methyltransferase are temperature-sensitive in synthetic media containing glycerol. Bacterial TRM8 orthologs complement the growth defect of trm8-Δ, trm82-Δ, and trm8-Δ trm82-Δ double mutants, suggesting that bacteria employ a single subunit for Trm8p/Trm82p function. The growth phenotype of trm8 mutants correlates with lack of tRNA m7G methyltransferase activity in vitro and in vivo, based on analysis of 10 mutant alleles of trm8 and bacterial orthologs, and suggests that m7G modification is the cellular function important for growth. Initial examination of the roles of the yeast subunits shows that Trm8p has most of the functions required to effect m7G modification, and that a major role of Trm82p is to maintain cellular levels of Trm8p. Trm8p efficiently cross-links to pre-tRNAPhe in vitro in the presence or absence of Trm82p, in addition to its known residual tRNA m7G modification activity and its SAM-binding domain. Surprisingly, the levels of Trm8p, but not its mRNA, are severely reduced in a trm82-Δ strain. Although Trm8p can be produced in the absence of Trm82p by deliberate overproduction, the resulting protein is inactive, suggesting that a second role of Trm82p is to stabilize Trm8p in an active conformation.
Molecular dynamics simulations and free energy calculations of base flipping in dsRNA
Authors: HART KATARINA , NYSTRÖM BOEL , ÖHMAN MARIE , NILSSON LENNART
Published: April 2005

The family of adenosine deaminases acting on RNA (ADARs) targets adenosines in RNA that is mainly double stranded. Some substrates are promiscuously deaminated whereas others, such as the mammalian glutamate receptor B (gluR-B) pre-mRNA, are more selectively deaminated. Many DNA/RNA-base modification enzymes use a base flipping mechanism to be able to reach their target base and it is believed that ADARs function in a similar way. In this study we used molecular dynamics (MD) simulations to describe two sites on the gluR-B pre-mRNA, the selectively targeted R/G site and the nontargeted 46 site, in an attempt to explain the substrate specificity. We used regular MD and also a forced base flipping method with umbrella sampling to calculate the free energy of base opening. Spontaneous opening of the mismatched adenosine was observed for the R/G site but not for the 46 site.
Nonbridging phosphate oxygens in 16S rRNA important for 30S subunit assembly and association with the 50S ribosomal subunit
Authors: GHOSH SRIKANTA , JOSEPH SIMPSON
Published: April 2005

Ribosomes are composed of RNA and protein molecules that associate together to form a supramolecular machine responsible for protein biosynthesis. Detailed information about the structure of the ribosome has come from the recent X-ray crystal structures of the ribosome and the ribosomal subunits. However, the molecular interactions between the rRNAs and the r-proteins that occur during the intermediate steps of ribosome assembly are poorly understood. Here we describe a modification-interference approach to identify nonbridging phosphate oxygens within 16S rRNA that are important for the in vitro assembly of the Escherichia coli 30S small ribosomal subunit and for its association with the 50S large ribosomal subunit. The 30S small subunit was reconstituted from phosphorothioate-substituted 16S rRNA and small subunit proteins. Active 30S subunits were selected by their ability to bind to the 50S large subunit and form 70S ribosomes. Analysis of the selected population shows that phosphate oxygens at specific positions in the 16S rRNA are important for either subunit assembly or for binding to the 50S subunit. The X-ray crystallographic structures of the 30S subunit suggest that some of these phosphate oxygens participate in r-protein binding, coordination of metal ions, or for the formation of intersubunit bridges in the mature 30S subunit. Interestingly, however, several of the phosphate oxygens identified in this study do not participate in any interaction in the mature 30S subunit, suggesting that they play a role in the early steps of the 30S subunit assembly.
UTP-dependent turnover of Trypanosoma brucei mitochondrial mRNA requires UTP polymerization and involves the RET1 TUTase
Authors: RYAN CHRISTOPHER M. , READ LAURIE K.
Published: April 2005

Trypanosoma brucei mitochondria possess a unique RNA decay pathway in which rapid degradation of polyadenylated mRNAs is dependent on the addition of UTP, as measured by in organello pulse chase assays. To determine the mechanism by which UTP stimulates the degradation of polyadenylated RNAs, we performed in organello pulse chase assays under different conditions. Treatment of mitochondria with proteinase K revealed that UTP does not act through a receptor on the surface of the mitochondria. To determine if the UTP-stimulated RNA decay pathway is triggered by the mitochondrial energy state or ATP:UTP ratio, increasing ATP was added to a constant amount of UTP during the chase period of the assay. Results indicate that rapid turnover is responsive to UTP and not the ATP:UTP ratio. Experiments using UTP analogs demonstrate that UTP polymerization into RNAs is necessary for UTP-dependent degradation. Furthermore, experiments performed with RNAi cells indicate that the RET1 terminal uridylyl transferase (TUTase) is required for UTP-dependent decay of polyadenylated RNAs. Overall, these results show that degradation of polyadenylated RNAs in T. brucei mitochondria can occur through a unique mechanism that requires the polymerization of UTP into RNAs, presumably by the RET1 TUTase.
Transfer-messenger RNA unfolds as it transits the ribosome
Authors: WOWER IWONA K. , ZWIEB CHRISTIAN , WOWER JACEK
Published: April 2005

In bacteria, translation of mRNAs lacking stop codons produces truncated polypeptides and traps ribosomes in unproductive complexes. Potentially harmful truncated proteins are tagged with short peptides encoded by the mRNA-like domain of tmRNA and targeted for digestion by housekeeping proteases. We show that altered Escherichia coli transfer-messenger RNAs (tmRNAs) produce in vivo fusion proteins with peptide tags that extend far beyond the conventional termination signal of the wild-type tmRNA. Regions of tmRNA capable of serving as templates for protein synthesis include helix 5, as well as pseudoknots 2, 3, and 4. The removal of all six in-frame stop codons negatively affects tmRNA processing, thereby preventing translation of the 3′ portion of the tRNA-like domain. These findings provide evidence that trans-translation can be accompanied by the unfolding of significant portions of the tmRNA molecule. Many of these conformational changes are likely to be required during trans-translation to maintain the ribosomal subunits in close proximity to the tmRNA for monitoring its transit.
The contributions of dsRNA structure to Dicer specificity and efficiency
Authors: VERMEULEN ANNALEEN , BEHLEN LINDA , REYNOLDS ANGELA , WOLFSON ALEXEY , MARSHALL WILLIAM S. , KARPILOW JON , KHVOROVA ANASTASIA
Published: April 2005

Dicer processes long double-stranded RNA (dsRNA) and pre-microRNAs to generate the functional intermediates (short interfering RNAs and microRNAs) of the RNA interference pathway. Here we identify features of RNA structure that affect Dicer specificity and efficiency. The data presented show that various attributes of the 3′ end structure, including overhang length and sequence composition, play a primary role in determining the position of Dicer cleavage in both dsRNA and unimolecular, short hairpin RNA (shRNA). We also demonstrate that siRNA end structure affects overall silencing functionality. Awareness of these new features of Dicer cleavage specificity as it is related to siRNA functionality provides a more detailed understanding of the RNAi mechanism and can shape the development of hairpins with enhanced functionality.
Co-evolution of tRNA 3′ trailer sequences with 3′ processing enzymes in bacteria
Authors: LI ZHONGWEI , GONG XIN , JOSHI VEDANG H. , LI MUXIN
Published: April 2005

Maturation of the tRNA 3′ terminus is a complicated process in bacteria. Usually, it is initiated by an endonucleolytic cleavage carried out by RNase E and Z in different bacteria. In Escherichia coli, RNase E cleaves AU-rich sequences downstream of tRNA, producing processing intermediates with a few extra residues at the 3′ end; these are then removed by exoribonuclease trimming to generate the mature 3′ end. Here we show that essentially all E. coli tRNA precursors contain a potential RNase E cleavage site, the AU-rich sequence element (AUE), in the 3′ trailer. This suggests that RNase E cleavage and exonucleolytic trimming is a general pathway for tRNA maturation in this organism. Remarkably, the AUE immediately downstream of each tRNA is selectively conserved in bacteria having RNase E and tRNA-specific exoribonucleases, suggesting that this pathway for tRNA processing is also commonly used in these bacteria. Two types of RNase E-like proteins are identified in actinobacteria and the α-subdivision of proteobacteria. The tRNA 3′ proximal AUE is conserved in bacteria with only one type of E-like protein. Selective conservation of the AUE is usually not observed in bacteria without RNase E. These results demonstrate a novel example of co-evolution of RNA sequences with processing activities.
Initializing Concordance in Frail Elderly Patients via a Medicines Organizer
Authors: Ryan-Woolley Bernadette M , Rees Judith A
Published: April 2005

BACKGROUND:

Concordance, which involves prescribing with rather than for patients, should result in less drug wastage (non-use), but is proving hard to put into practice. One possible way of easing elderly people and prescribers toward concordance is to use a medicines organizer (MO).

OBJECTIVE:

To document medication wastage, using a pharmacy-prepared reusable MO, and explore, using a qualitative approach, use of this information on communication of individuals' drug regimens.

METHODS:

Sixty-two sheltered housing residents, aged ⩾60 years, participated in an exploratory controlled, matched study. The intervention group received medication in the MO, and the control group continued with standard packaging. Community pharmacists recorded details of wasted drugs returned during the 3-month study and, for the intervention group, 6, 9, and 12 months after the study. Medicines management data were collected from participants. Qualitative interviews were conducted with a sample of general practitioners (GPs) and community pharmacists to explore views on the role of the MO.

RESULTS:

Intervention group wastage was reduced from 18.1% (prestudy) to 1% at 12 months. No data on wastage were collected for the control group after the prestudy assessment. Sixty-one percent more prescription changes, including significant decreases in the number of prescribed drugs and dosages, were reported for the intervention group. GPs and pharmacists reported improvements in communication concerning medication-related dialog.

CONCLUSIONS:

This small exploratory study has shown that a pharmacy-prepared reusable MO provided visual, objective insights into medication wastage. This resulted in improved communication of drug needs and reduced wastage—the foundation for concordance.
High-Dose Insulin Therapy for Calcium-Channel Blocker Overdose
Authors: Shepherd Greene , Klein-Schwartz Wendy
Published: April 2005

OBJECTIVE:

To evaluate the evidence for using high-dose insulin therapy with supplemental dextrose and potassium in calcium-channel blocker (CCB) overdose.

DATA SOURCES:

Evidence of efficacy for high-dose insulin therapy with supplemental dextrose and potassium was sought by performing a search of MEDLINE and Toxline between 1966 and July 2004 using combinations of the terms calcium-channel blocker, overdose, poisoning, antidote, and insulin. Abstracts from the North American Congress of Clinical Toxicology for the years 1996–2003 were also reviewed.

STUDY SELECTION AND DATA EXTRACTION:

Identified articles, including animal studies, case reports, and case series, were evaluated for this review. No clinical trials were available.

DATA SYNTHESIS:

Animal models of CCB overdose demonstrate that high-dose insulin with supplemental dextrose and potassium was a more effective therapy than calcium, glucagon, or catecholamines. High-dose insulin appears to enhance cardiac carbohydrate metabolism and has direct inotropic effects. Published clinical experience is limited to 13 case reports where insulin was used after other therapies were failing; 12 of these patients survived. High-dose insulin therapy was beneficial for CCB-induced hypotension, hyperglycemia, and metabolic acidosis. Bradycardia and heart block resolved in some patients, but persisted in others.

CONCLUSIONS:

Based on animal data and limited human experience, as well as the inadequacies of available alternatives for patients with significant poisoning, high-dose insulin therapy warrants further study and judicious use in patients with life-threatening CCB poisoning.
Intrathecal Colistin and Sterilization of Resistant Pseudomonas Aeruginosa Shunt Infection
Authors: Quinn Andrea L , Parada Jorge P , Belmares Jaime , O'Keefe J Paul
Published: April 2005

OBJECTIVE:

To report 2 cases of multidrug-resistant (MDR) Pseudomonas aeruginosa meningitis and ventriculo-peritoneal shunt (VPS) infection successfully sterilized with intrathecal colistin 10 mg/day after development of nephrotoxicity associated with intravenous administration.

CASE SUMMARIES:

Case 1. A 69-year-old African American woman with a history of subarachnoid hemorrhage and hydrocephalus requiring VPS placement was admitted with VPS infection and meningitis. Cerebrospinal fluid (CSF) cultures revealed MDR P. aeruginosa susceptible only to colistin. Intravenous colistin was initiated but rapidly discontinued due to development of renal dysfunction. Intravenous colistin was the probable cause of the adverse effect. Intrathecal colistin was initiated via an externalized VPS, with subsequent improvement in white blood cell counts in the CSF. Follow-up CSF cultures remained sterile and renal function returned to baseline. Case 2. A 69-year-old white woman with a history of subarachnoid hemorrhage, hydrocephalus, and VPS was transferred from an extended-care facility for management of a VPS infection. CSF cultures revealed MDR P. aeruginosa susceptible only to colistin. Intravenous colistin was initiated but subsequently discontinued due to worsening renal function that, as with the first case, probably correlated with colistin administration and persisted despite dose adjustment. Therapy was changed to intrathecal administration, with subsequent normalization of her CSF white blood cell counts and sterilization of cultures.

DISCUSSION:

The limited availability of antibiotics for treatment of highly resistant or MDR gram-negative organisms has prompted clinicians to reconsider the use of older drugs. Prior reports have suggested that intravenous colistin is a potential alternative for treating highly resistant gram-negative central nervous system infections, specifically Acinetobacter, but its use is limited by nephrotoxicity. Our experience suggests that intrathecal colistin is a potentially curative intervention for the treatment of severe MDR P. aeruginosa meningitis and VPS infections in patients in whom intravenous colistin is not an option.

CONCLUSIONS:

Intrathecal use of colistin is a potentially safe, effective, and viable treatment option for MDR P. aeruginosa central nervous system infections when intravenous administration is not feasible.
Pheochromocytoma Unmasked by Amisulpride and Tiapride
Authors: Henry Agnès , Charpiat Bruno , Vial Thierry , Franchini Serge , Cuilleret François J , Milon Hugues
Published: April 2005

OBJECTIVE:

To describe the unmasking of pheochromocytoma in a patient treated with amisulpride and tiapride.

CASE SUMMARY:

A 42-year-old white man developed acute hypertension with severe headache and vomiting 2 hours after the first doses of amisulpride 100 mg and tiapride 100 mg. Both drugs were immediately discontinued, and the patient recovered after subsequent nicardipine and verapamil treatment. Abdominal ultrasound showed an adrenal mass, and postoperative histologic examination confirmed the diagnosis of pheochromocytoma.

DISCUSSION:

Drug-induced symptoms of pheochromocytoma are often associated with the use of substituted benzamide drugs, but the underlying mechanism is unknown. In our case, use of the Naranjo probability scale indicated a possible relationship between the hypertensive crisis and amisulpride and tiapride therapy.

CONCLUSIONS:

As of March 24, 2005, this is the first reported case of amisulpride- and tiapride-induced hypertensive crisis in a patient with pheochromocytoma. Physicians and other healthcare professionals should be aware of this potential adverse effect of tiapride and amisulpride.
What is New with the β2-Agonists: Issues in the Management of Asthma
Authors: Kelly H William
Published: April 2005

OBJECTIVE:

To review the more recent literature addressing the issue of whether β2-agonists can worsen asthma and/or increase the risk of severe exacerbations and death from asthma.

DATA SOURCES:

PubMed was searched (2001–December 2004), along with the Food and Drug Administration and Cochrane Library Web sites. In addition, the bibliographies of recent reviews of the subject were assessed.

STUDY SELECTION AND DATA EXTRACTION:

Randomized clinical trials, retrospective and prospective cohort studies, and meta-analyses published in the past 3 years were reviewed. Studies assessing the potential for β2-agonists to worsen outcomes in asthma as well as long-term studies assessing asthma outcomes that included an arm with regular administration of short- or long-acting inhaled β2-agonists (LABAs) were selected. Worsening asthma was defined as a decline in lung function, an increase in bronchial hyperresponsiveness, exacerbations, or death. Studies older than 3 years selected from the bibliographies of the primary articles that addressed background perspective were also included where appropriate.

DATA SYNTHESIS:

The studies fell into 3 primary categories with some overlap: those assessing toxicity of the S-enantiomer of albuterol, those evaluating the risk of specific genotypes regarding worsening asthma, and those assessing asthma outcomes with LABA therapy.

CONCLUSIONS:

The current data on the use of β2-agonists continue to support the national and international guidelines for the treatment of asthma. That is, short-acting inhaled β2-agonists should only be used as needed for symptoms and prevention of exercise-induced bronchospasm, and LABAs should only be used regularly as adjunctive therapy with inhaled corticosteroids in patients whose asthma is not controlled with low to medium doses of the inhaled corticosteroid.
Hydrogen Leak Detection Using Laser-Induced Breakdown Spectroscopy
Authors: Ball A. J. , Hohreiter V. , Hahn D. W.
Published: April 2005

Laser-induced breakdown spectroscopy (LIBS) is investigated as a technique for real-time monitoring of hydrogen gas. Two methodologies were examined: The use of a 100 mJ laser pulse to create a laser-induced breakdown directly in a sample gas stream, and the use of a 55 mJ laser pulse to create a laser-induced plasma on a solid substrate surface, with the expanding plasma sampling the gas stream. Various metals were analyzed as candidate substrate surfaces, including aluminum, copper, molybdenum, stainless steel, titanium, and tungsten. Stainless steel was selected, and a detailed analysis of hydrogen detection in binary mixtures of nitrogen and hydrogen at atmospheric pressure was performed. Both the gaseous plasma and the plasma initiated on the stainless steel surface generated comparable hydrogen emission signals, using the 656.28 Hα emission line, and exhibited excellent signal linearity. The limit of detection is about 20 ppm (mass) as determined for both methodologies, with the solid-initiated plasma yielding a slightly better value. Overall, LIBS is concluded to be a viable candidate for hydrogen sensing, offering a combination of high sensitivity with a technique that is well suited to implementation in field environments.