bluuebunny/crossref_metadata_2025 huggingface dataset:
DYNAMICS IN ONE-DIMENSIONAL SPIN SYSTEMS – DENSITY MATRIX RENORMALIZATION GROUP STUDY
Authors: NISHIMOTO S. , ARIKAWA M.
Published: July 2007

We study the one-dimensional S = 1/2 Heisenberg model with an uniform and a staggered magnetic fields, using the dynamical density-matrix renormalization group (DDMRG) technique. The DDMRG enables us to investigate the dynamical properties of chain with lengths up to a few hundreds, and the results are numerically exact in the same sense as 'exact diagonalization' results are. Thus, we can analyze the low-energy spectrum almost in the thermodynamic limit. In this work, we calculate the dynamical spin structure factor and demonstrate the performance of the DDMRG method applying the open-end boundary conditions as well as the periodic boundary conditions.
SUPERCONDUCTING ORDER PARAMETERS IN THE EXTENDED HUBBARD MODEL: A SIMPLE MEAN-FIELD STUDY
Authors: THAKUR J. S. , DAS M. P.
Published: July 2007

The extended Hubbard model with nearest neighbor hopping and intersite interaction for a 2D square lattice has been studied within the frame work of a simple mean-field formalism. The self-consistent solutions of superconducting order parameters have been obtained for various fillings. The results indicate that superconducting pairing occurs on doping for the repulsive on-site U and attractive nearest neighbor V.
PAIRING OF STRONGLY CORRELATED NUCLEONS
Authors: DICKHOFF W. H.
Published: July 2007

Pairing properties of infinite matter are surveyed that are obtained from self-consistent Green's function calculations. A complete treatment of off-shell propagation that incorporates the effects of short-range correlations is included. Mean-field calculations based on the BCS approach are superseded by the present results, which resolve a long-standing puzzle associated with 3S1-3D1 (proton-neutron) pairing in symmetric nuclear matter. Results for 1S0 pairing in pure neutron matter are in agreement with recent Monte-Carlo calculations for this system. The possibility of proton pairing in finite nuclei, as a result of increasing proton correlations with increasing nucleon asymmetry, is pointed out.
SHORT RANGE CORRELATIONS IN RELATIVISTIC NUCLEAR MODELS
Authors: PANDA PRAFULLA K. , PROVIDÊNCIA C. , DA PROVIDÊNCIA J.
Published: July 2007

Short range correlations are introduced using the unitary operator method in a relativistic theory of nuclear matter based on the Hartree-Fock approximation. Pion exchange, including the tensor contribution, is taken into account. It is found that both the tensor contribution of pion exchange and short range correlations soften the equation of state. The neutron matter equation of state is also discussed.
ALPHA-ALPHA AND ALPHA-NUCLEUS POTENTIALS: AN ENERGY-DENSITY FUNCTIONAL APPROACH
Authors: SHEHADEH Z. F. , BASAK A. K. , ABDULLAH M. N. A. , UDDIN M. A. , REICHSTEIN I. , SABRA M. S. , MALIK F. B.
Published: July 2007

The real parts of the alpha-alpha and alpha-nucleus potential, particularly for40,44,48Ca and58Ni targets are determined from a realistic two-nucleon potential using an energy-density functional approach and are found to be non-monotonic with a short range repulsion in their functional forms that are similar to those needed in accounting for elastic scattering data. The deduced alpha-alpha potential has no bound states and the calculated decay width of8Be of about 6.4 eV at about 200 keV energy is in agreement with the measurement.
DYNAMICS OF METAL CLUSTERS IN RARE GAS CLUSTERS
Authors: BAER M. , BOUSQUET G. , DINH P. M. , FEHRER F. , REINHARD P.-G. , SURAUD E.
Published: July 2007

We investigate the dynamics of Na clusters embedded in Ar matrices. We use a hierarchical approach, accounting microscopically for the cluster's degrees of freedom and more coarsely for the matrix. The dynamical polarizability of the Ar atoms and the strong Pauli-repulsion exerted by the Ar -electrons are taken into account. We discuss the impact of the matrix on the cluster gross properties and on its optical response. We then consider a realistic case of irradiation by a moderately intense laser and discuss the impact of the matrix on the hindrance of the explosion, as well as a possible pump probe scenario for analyzing dynamical responses.
FROM THERMODYNAMICS TO MAXENT
Authors: PLASTINO A. , CURADO E. M. F.
Published: July 2007

The maximum entropy principle (MaxEnt) is one of the most powerful approaches in the theorist arsenal. It has been used in many areas of science, and, in particular, in both statistical mechanics and the quantum many body problem. Here we show how to derive MaxEnt from the laws of thermodynamics.
PERIPHERALLY SPECIFIED HOMOMORPHS OF LINK GROUPS
Authors: KURLIN V. , LINES D.
Published: July 2007

Johnson and Livingston have characterized peripheral structures in homomorphs of knot groups. We extend their approach to the case of links. The main result is an algebraic characterization of all possible peripheral structures in certain homomorphic images of link groups.
ON THE GROUP-LIKE BEHAVIOR OF THE LE–MURAKAMI–OHTSUKI INVARIANT
Authors: JACKSON DAVID M. , MOFFATT IAIN , MORALES ALEJANDRO
Published: July 2007

We study the effect of Feynman integration and diagrammatic differential operators on the structure of group-like elements in the algebra generated by colored vertex-oriented uni-trivalent graphs. We provide applications of our results to the study of the LMO invariant, a quantum invariant of manifolds. We also indicate further situations in which our results apply and may prove useful. The enumerative approach that we adopt has a clarity that has enabled us to perceive a number of generalizations.
MATRICES AND FINITE ALEXANDER QUANDLES
Authors: MURILLO GABRIEL , NELSON SAM , THOMPSON ANTHONY
Published: July 2007

We study the question of whether a finite quandle specified by a matrix is isomorphic to an Alexander quandle. We first collect some necessary conditions for a finite quandle to be Alexander. We then describe an algorithm for determining finding all possible Alexander presentations of a finite quandle given its matrix and provide a URL for Maple code implementing this algorithm.
TOPOLOGICAL QUANDLES AND INVARIANTS OF LINKS
Authors: RUBINSZTEIN RYSZARD L.
Published: July 2007

We introduce a notion of topological quandle. Given a topological quandle Q we associate to every classical link L in ℝ3 an invariant JQ(L) which is a topological space (defined up to a homeomorphism). The space JQ(L) can be interpreted as a space of colorings of a diagram of the link L with colors from the quandle Q.
SOME RESULTS ON INTRINSICALLY KNOTTED GRAPHS
Authors: BLAIN PAUL , BOWLIN GARRY , FLEMING THOMAS , FOISY JOEL , HENDRICKS JACOB , LACOMBE JASON
Published: July 2007

We show that graphs of the form G * K2 are intrinsically knotted if and only if G is nonplanar. This can be extended to show that G * K5m+1 is intrinsically (m + 2)-linked when G is nonplanar. We also apply this result to classify all complete n-partite graphs with respect to intrinsic knotting and show that this family does not produce any new minor-minimal examples. Finally, we categorize all minor-minimal intrinsically knotted graphs on 8 or fewer vertices.
ENDOSCOPE DAMAGED DURING ENDOSCOPIC CARPAL TUNNEL RELEASE — THE SOLUTION METHOD
Authors: Wu Wing-Cheung
Published: July 2007

An unusual problem occurred during the endoscopic carpal tunnel release procedure of a patient with carpal tunnel syndrome. The endoscope was damaged because of inadequate knowledge in handling the instruments. The procedure was completed smoothly with a knee arthroscope.
ARTHROSCOPIC EVALUATION AND TREATMENT BY TENDON INTERPOSITIONAL ARTHROPLASTY OF FIRST CARPOMETACARPAL JOINT ARTHRITIS
Authors: Pegoli L. , Parolo C. , Ogawa T. , Toh S. , Pajardi G.
Published: July 2007

Basal joint arthritis of the thumb is usually seen in females beginning from the fourth and fifth decades. In the last two decades, arthroscopic techniques have brought new chances of diagnosis and treatment for this condition. In this paper, the authors describe the indications and their experience concerning arthroscopic hemitrapezectomy and tendon interposition using the palmaris longus tendon. A series of 16 patients with a maximum follow-up of 12 months is analysed. All of the 16 patients were followed and assessed with grasp strength, pinch strength, DASH and MAYO evaluation score both pre- and post-operatively at 12 months follow-up. According to the MAYO score, there were six excellent results, six good, three fair and one poor. No complications occurred. According to our preliminary results, this procedure with the proper indications gives a valid option for the treatment of thumb carpometacarpal joint arthritis in stages I and II according to Eaton's classification.
CLINICAL ANATOMICAL STUDY OF PEDICLED VASCULARISED SCAPULAR BONE GRAFT USING THE ANGULAR BRANCH
Authors: Satomi Yoshiaki , Shimizu Hiroyuki , Beppu Moroe , Hirata Kazuaki , Takahashi Tsuneo
Published: July 2007

This study is an anatomical investigation of the angular branch of thoracodorsal artery, and examines the possible range of clinical targets for pedicled vascularised scapular bone graft.

Forty-six cadavers were studied. The blood vessel length was calculated, and the distance required to reach the distal humerus from the lower end of the articular surface of the humeral head as reference point was compared with bone length.

The length from reference point was an average of 121.7 mm. It was thought that the maximum distance to arrive in reference point to the distal humerus was a total of blood vessel length and transplantation bone length, which was an average of 246.3 mm. This was longer than the average of 240.8 mm of bone length from reference point to humeral medial condyle.

This study had confirmed that a pedicled vascularised scapular bone graft using the angular branch could be transplanted to the distal humerus.
ON THE PIECEWISE SMOOTHNESS OF ENTROPY SOLUTIONS TO SCALAR CONSERVATION LAWS FOR A LARGER CLASS OF INITIAL DATA
Authors: TANG TAO , WANG JINGHUA , ZHAO YINCHUAN
Published: July 2007

We prove that if the initial data do not belong to a certain subset of Ck, then the solutions of scalar conservation laws are piecewise Cksmooth. In particular, our initial data allow centered compression waves, which was the case not covered by Dafermos (1974) and Schaeffer (1973). More precisely, we are concerned with the structure of the solutions in some neighborhood of the point at which only a Ck+1shock is generated. It is also shown that there are finitely many shocks for smooth initial data (in the Schwartz space) except for a certain subset of 𝒮(ℝ) of the first category. It should be pointed out that this subset is smaller than those used in previous works. We point out that Thom's theory of catastrophes, which plays a key role in Schaeffer (1973), cannot be used to analyze the larger class of initial data considered in this paper.
EXISTENCE OF TRAVELLING WAVES IN NON-ISOTHERMAL PHASE DYNAMICS
Authors: ZHANG SHU-YI
Published: July 2007

We study travelling wave solutions describing non-isothermal subsonic phase transitions in a van der Waals fluid. We apply the center manifold method and establish the existence of viscosity-capillarity profiles for small viscosity, large heat conduction, and large heat capacity.
SYSTEMS OF HYPERBOLIC CONSERVATION LAWS WITH MEMORY
Authors: CHRISTOFOROU CLEOPATRA
Published: July 2007

Global weak solutions of bounded variation to systems of balance laws with non-local source are constructed by the method of vanishing viscosity. Suitable dissipativeness assumptions are imposed on the source terms to assure convergence of the method. Under these hypotheses, the total variation remains uniformly bounded and integrable in time, the vanishing viscosity solutions are uniformly stable in L1with respect to the initial data and converge to equilibrium as t → ∞. The motivation to study these systems is the observation that conservations laws with fading memory can be written in such form under appropriate conditions on the flux.
OCCURRENCE AND NON-APPEARANCE OF SHOCKS IN FRACTAL BURGERS EQUATIONS
Authors: ALIBAUD NATHAËL , DRONIOU JÉRÔME , VOVELLE JULIEN
Published: July 2007

We consider the fractal Burgers equation (that is to say the Burgers equation to which is added a fractional power of the Laplacian) and we prove that, if the power of the Laplacian involved is lower than 1/2, then the equation does not regularize the initial condition: on the contrary to what happens if the power of the Laplacian is greater than 1/2, discontinuities in the initial data can persist in the solution and shocks can develop even for smooth initial data. We also prove that the creation of shocks can occur only for sufficiently "large" initial conditions, by giving a result which states that, for smooth "small" initial data, the solution remains at least Lipschitz continuous.
MECHANISMS FOR ERROR PROPAGATION AND CANCELLATION IN GLIMM'S SCHEME WITHOUT RAREFACTIONS
Authors: LAFOREST M.
Published: July 2007

We derive an a posteriori error bound for Glimm's approximate solutions to convex scalar conservation laws containing only shock waves. Using Liu's wave-tracing method, we show that the L1 norm of the error is bounded by a sum of residuals containing independent contributions from each wave in the approximate solution. We introduce a framework, similar to the method of characteristics, for the analysis of the local errors generated by wave interactions. The analysis allows for explicit cancellation among the errors created by a single wave and for error propagation along discontinuities.
Effects of high-intensity training on MCT1, MCT4, and NBC expressions in rat skeletal muscles: influence of chronic metabolic alkalosis
Authors: Thomas Claire , Bishop David , Moore-Morris Tom , Mercier Jacques
Published: July 2007

This study investigated the effects of high-intensity training, with or without induced metabolic alkalosis, on lactate transporter (MCT1 and MCT4) and sodium bicarbonate cotransporter (NBC) content in rat skeletal muscles. Male Wistar rats performed high-intensity training on a treadmill 5 times/wk for 5 wk, receiving either sodium bicarbonate (ALK-T) or a placebo (PLA-T) prior to each training session, and were compared with a group of control rats (CON). MCT1, MCT4, and NBC content was measured by Western blotting in soleus and extensor digitorum longus (EDL) skeletal muscles. Citrate synthase (CS) and phosphofructokinase (PFK) activities and muscle buffer capacity (βm) were also evaluated. Following training, CS and PFK activities were significantly higher in the soleus only ( P < 0.05), whereas βm was significantly higher in both soleus and EDL ( P < 0.05). MCT1 (PLA-T: 30%; ALK-T: 23%) and NBC contents (PLA-T: 85%; ALK-T: 60%) increased significantly only in the soleus following training ( P < 0.01). MCT4 content in the soleus was significantly greater in ALK-T (115%) but not PLA-T compared with CON. There was no significant change in protein content in the EDL. Finally, NBC content was related only to MCT1 content in soleus ( r = 0.50, P < 0.01). In conclusion, these results suggest that MCT1, MCT4, and NBC undergo fiber-specific adaptive changes in response to high-intensity training and that induced alkalosis has a positive effect on training-induced changes in MCT4 content. The correlation between MCT1 and NBC expression suggests that lactate transport may be facilitated by NBC in oxidative skeletal muscle, which may in turn favor better muscle pH regulation.
Adipocyte triglyceride lipase expression in human obesity
Authors: Steinberg Gregory R. , Kemp Bruce E. , Watt Matthew J.
Published: July 2007

We have investigated the gene and protein expression of adipose triglyceride lipase (ATGL) and triglyceride (TG) lipase activity from subcutaneous and visceral adipose tissue of lean and obese subjects. Visceral and subcutaneous adipose tissue was obtained from 16 age-matched lean and obese subjects during abdominal surgery. Tissues were analyzed for mRNA expression of lipolytic enzymes by real-time quantitative PCR. ATGL protein content was assessed by Western blot and TG lipase activity by radiometric assessment. Subcutaneous and visceral adipose tissue of obese subjects had elevated mRNA expression of PNPLA2 (ATGL) and other lipases including PNPLA3, PNPLA4, CES1, and LYPLAL1 ( P < 0.05). Surprisingly, ATGL protein expression and TG lipase activity were reduced in subcutaneous adipose tissue of obese subjects. Immunoprecipitation of ATGL reduced total TG lipase activity in adipose lysates by 70% in obese and 83% in lean subjects. No significant differences in the ATGL activator CGI-58 mRNA levels ( ABHD5) were associated with obesity. These data demonstrate that ATGL is important for efficient TG lipase activity in humans. They also demonstrate reduced ATGL protein expression and TG lipase activity despite increased mRNA expression of ATGL and other novel lipolytic enzymes in obesity. The lack of correlation between ATGL protein content and in vitro TG lipase activity indicates that small decrements in ATGL protein expression are not responsible for the reduction in TG lipase activity observed here in obesity, and that posttranslational modifications may be important.
Reduction of hepatic insulin clearance after oral glucose ingestion is not mediated by glucagon-like peptide 1 or gastric inhibitory polypeptide in humans
Authors: Meier Juris J. , Holst Jens J. , Schmidt Wolfgang E. , Nauck Michael A.
Published: July 2007

Changes in hepatic insulin clearance can occur after oral glucose or meal ingestion. This has been attributed to the secretion and action of gastric inhibitory polypeptide (GIP) and glucagon-like peptide (GLP)−1. Given the recent availability of drugs based on incretin hormones, such clearance effects may be important for the future treatment of type 2 diabetes. Therefore, we determined insulin clearance in response to endogenously secreted and exogenously administered GIP and GLP-1. Insulin clearance was estimated from the molar C-peptide-to-insulin ratio calculated at basal conditions and from the respective areas under the curve after glucose, GIP, or GLP-1 administration. Oral glucose administration led to an ∼60% reduction in the C-peptide-to-insulin ratio ( P < 0.0001), whereas intravenous glucose administration had no effect ( P = 0.09). The endogenous secretion of GIP or GLP-1 was unrelated to the changes in insulin clearance. The C-peptide-to-insulin ratio was unchanged after the intravenous administration of GIP or GLP-1 in the fasting state ( P = 0.27 and P = 0.35, respectively). Likewise, infusing GLP-1 during a meal course did not alter insulin clearance ( P = 0.87). An inverse nonlinear relationship was found between the C-peptide-to-insulin ratio and the integrated insulin levels after oral and during intravenous glucose administration. Insulin clearance is reduced by oral but not by intravenous glucose administration. Neither GIP nor GLP-1 has significant effects on insulin extraction. An inverse relationship between insulin concentrations and insulin clearance suggests that the secretion of insulin itself determines the rate of hepatic insulin clearance.
Cold-induced alterations of phospholipid fatty acyl composition in brown adipose tissue mitochondria are independent of uncoupling protein-1
Authors: Ocloo Augustine , Shabalina Irina G. , Nedergaard Jan , Brand Martin D.
Published: July 2007

The recruitment process induced by acclimation of mammals to cold includes a marked alteration in the acyl composition of the phospholipids of mitochondria from brown adipose tissue: increases in 18:0, 18:2( n–6), and 20:4( n–6) and decreases in 16:0, 16:1, 18:1, and 22:6( n–3). A basic question is whether these alterations are caused by changes in the concentration of uncoupling protein-1 (UCP1) or the thermogenesis it mediates—implying that they are secondary effects—or whether they are an integrated, independent part of the recruitment process. This question was addressed here using wild-type and UCP1-ablated C57BL/6 mice acclimated to 24°C or 4°C. In wild-type mice, the phospholipid fatty acyl composition of mitochondria from brown adipose tissue showed the changes in response to cold that were expected from observations in other species and strains. The changes were specific, as different changes occurred in skeletal muscle mitochondria. In UCP1-ablated mice, cold acclimation induced acyl alterations in brown adipose tissue that were qualitatively identical and quantitatively similar to those in wild-type mice. Therefore, neither the increased content of UCP1 nor mitochondrial uncoupling altered the effect of cold on acyl composition. Cold acclimation in wild-type mice had little effect on phospholipid acyl composition in muscle mitochondria, but cold-acclimation in UCP1-ablated mice caused significant alterations, probably due to sustained shivering. Thus, the alterations in brown adipose tissue phospholipid acyl composition are revealed to be an independent part of the recruitment process, and their functional significance for thermogenesis should be elucidated.
p21-Activated kinase-1 and its role in integrated regulation of cardiac contractility
Authors: Sheehan Katherine A. , Ke Yunbo , Solaro R. John
Published: July 2007

We review here a novel concept in the regulation of cardiac contractility involving variations in the activity of the multifunctional enzyme, p21-activated kinase 1 (Pak1), a member of a family of proteins in the small G protein-signaling pathway that is activated by Cdc42 and Rac1. There is a large body of evidence from studies in noncardiac tissue that Pak1 activity is key in regulation of a number of cellular functions, including cytoskeletal dynamics, cell motility, growth, and proliferation. Although of significant potential impact, the role of Pak1 in regulation of the heart has been investigated in only a few laboratories. In this review, we discuss the structure of Pak1 and its sites of posttranslational modification and molecular interactions. We assemble an overview of the current data on Pak1 signaling in noncardiac tissues relative to similar signaling pathways in the heart, and we identify potential roles of Pak1 in cardiac regulation. Finally, we discuss the current state of Pak1 research in the heart in regard to regulation of contractility through functional myofilament and Ca2+-flux modification. An important aspect of this regulation is the modulation of kinase and phosphatase activity. We have focused on Pak1 regulation of protein phosphatase 2A (PP2A), which is abundant in cardiac muscle, thereby mediating dephosphorylation of sarcomeric proteins and sensitizing the myofilaments to Ca2+. We present a model for Pak1 signaling that provides a mechanism for specifically affecting cardiac cellular processes in which regulation of protein phosphorylation states by PP2A dephosphorylation predominates.
Determinants of blood oxygenation during pregnancy in Andean and European residents of high altitude
Authors: Vargas Marco , Vargas Enrique , Julian Colleen G. , Armaza J. Fernando , Rodriguez Armando , Tellez Wilma , Niermeyer Susan , Wilson Megan , Parra Esteban , Shriver Mark , Moore Lorna G.
Published: July 2007

High altitude decreases birth weight, but this effect is diminished in long vs. short-resident, high-altitude populations. We asked whether women from long vs. short-resident, high-altitude populations had higher arterial oxygenation levels by comparing 42 Andean and 26 European residents of La Paz, Bolivia (3,600 m), serially during pregnancy ( weeks 20, 30, and 36) and again 4 mo postpartum. Pregnancy raised hypoxic ventilatory sensitivity threefold, resting ventilation (V̇e), and arterial O2saturation (SaO2) in both groups. Ancestry, as identified using 81 genetic markers, correlated with respiratory pattern, such that greater Andean ancestry was associated with higher respiratory frequency and lower tidal volume. Pregnancy increased total blood and plasma volume ∼40% in both groups without changing red blood cell mass relative to body weight; hence, hemoglobin fell. The hemoglobin decline was compensated for by the rise in V̇e and SaO2with the result that arterial O2content (CaO2) was maintained near nonpregnant levels in both groups. Birth weights were similar for all Andean and European babies, but after adjusting for variation in gestational age, maternal height and parity, Andeans weighed 209 g more than Europeans. Babies with heavier birth weights and greater ponderal indices were born to Andean women with higher V̇e during pregnancy. We concluded that while maternal V̇e and arterial oxygenation were important, some factor other than higher CaO2was responsible for protecting Andeans from altitude-associated reductions in fetal growth.
Compensatory paracrine mechanisms that define the urothelial response to injury in partial bladder outlet obstruction
Authors: Lendvay Thomas S. , Sweet Robert , Han Chang-Hee , Soygur Tarkan , Cheng Jan-Fan , Plaire J. Chadwick , Charleston Jay S. , Charleston Lynne B. , Bagai Shelly , Cochrane Kimberly , Rubio Eric , Bassuk James A.
Published: July 2007

Diseases and conditions affecting the lower urinary tract are a leading cause of dysfunctional sexual health, incontinence, infection, and kidney failure. The growth, differentiation, and repair of the bladder's epithelial lining are regulated, in part, by fibroblast growth factor (FGF)-7 and -10 via a paracrine cascade originating in the mesenchyme (lamina propria) and targeting the receptor for FGF-7 and -10 within the transitional epithelium (urothelium). The FGF-7 gene is located at the 15q15-q21.1 locus on chromosome 15 and four exons generate a 3.852-kb mRNA. Five duplicated FGF-7 gene sequences that localized to chromosome 9 were predicted not to generate functional protein products, thus validating the use of FGF-7-null mice as an experimental model. Recombinant FGF-7 and -10 induced proliferation of human urothelial cells in vitro and transitional epithelium of wild-type and FGF-7-null mice in vivo. To determine the extent that induction of urothelial cell proliferation during the bladder response to injury is dependent on FGF-7, an animal model of partial bladder outlet obstruction was developed. Unbiased stereology was used to measure the percentage of proliferating urothelial cells between obstructed groups of wild-type and FGF-7-null mice. The stereological analysis indicated that a statistical significant difference did not exist between the two groups, suggesting that FGF-7 is not essential for urothelial cell proliferation in response to partial outlet obstruction. In contrast, a significant increase in FGF-10 expression was observed in the obstructed FGF-7-null group, indicating that the compensatory pathway that functions in this model results in urothelial repair.
Hypoxia and podocyte-specificVhlhdeletion confer risk of glomerular disease
Authors: Brukamp Kirsten , Jim Belinda , Moeller Marcus J. , Haase Volker H.
Published: July 2007

Hypoxia is a potent regulator of a multitude of cellular processes, including metabolism and cell survival. The transcriptional response to oxygen deprivation is mainly mediated by hypoxia-inducible factors (HIFs), which are targeted for proteasomal degradation by the von Hippel-Lindau tumor suppressor protein (pVHL) under normoxia. Podocytes, as part of the glomerular filtration barrier, are prone to hypoxic injury during diseases affecting the glomerulus. VHL and HIF1 were functional in mature murine podocytes in vivo and in vitro, with HIF1 protein stabilization and target gene transcription under both hypoxia and VHL deficiency. Podocyte-specific Vhlh gene loss, mimicking podocyte hypoxia, in young mice of mixed background led to glomerulomegaly and occasional glomerulosclerosis, despite preserved glomerular development. In parallel, hypoxia effects on podocytes in cell culture included increased susceptibility to apoptosis, associated with nuclear translocation of apoptosis-inducing factor (AIF). Similarly, Vhlh gene inactivation in podocytes in vitro resulted in a significant survival disadvantage, particularly in conjunction with additional proapoptotic stimuli. Evaluation of the global transcriptional response to hypoxia in podocytes by microarray analysis revealed a typical upregulation of HIF target genes as well as the induction of genes relevant for stress response, cell-cell, and cell-extracellular matrix interaction. While the lack of a prominent phenotype in young mice with VHL-deficient podocytes is consistent with the absence of specific glomerular manifestations in human VHL disease, a low-oxygen environment of podocytes may contribute to the progression of glomerular disease by altering cellular metabolism and survival.
The Pathophysiology of Constipation
Authors: Milla Peter J.
Published: July 2007

Constipation is an extremely common disorder in childhood and is responsible for up to 25% of all pediatric gastroenterological consultations and 3% of all pediatric outpatient visits. In 90% of the cases the disorder is functional in origin and in only 10% is there an underlying organic disorder. Common organic causes of childhood constipation include: congenital defects of the gut; neurologic disease especially cerebral palsy, spinal cord disorders and hypotonia; endocrine and metabolic disorders (hypothyroidism, cystic fibrosis, hypercalcemia, diabetes mellitus, renal acidosis), and the use of constipating drugs such as some antacids, sucralfate, iron, codeine-containing medications, imipramine, phenytoin, etc. The commonest of the congenital defects is Hirschsprung’s disease, which has an incidence of 1 in 4,500 live births compared to 1 in 7,000 live births with anorectal malformations, and 1 in 40,000 with other enteric neuromuscular disorders. Fewer than 5% of children presenting for the first time with constipation have demonstrable organic disease.
Current Treatment of Childhood Constipation
Authors: Liem Olivia , Di Lorenzo Carlo , Taminiau Jan A.J.M. , Mousa Hayat M. , Benninga Marc A.
Published: July 2007

Childhood constipation is a worldwide problem. It is one of the more common complaints presented to both general pediatricians and pediatric gastroenterologists. Treatment for chronic constipation is challenging and often requires long-term follow-up and medication use. Despite its high prevalence, few randomized trials have been performed to investigate the efficacy of different interventions used to treat this condition. In this review we will discuss current treatment options for childhood constipation and address some of the most frequently asked questions and misconceptions among parents and physicians.
Functional Fecal Incontinence in Children
Authors: Bongers Marloes E.J. , Benninga Marc A.
Published: July 2007

Fecal incontinence is defined as the passage of stools in an inappropriate place. This frustrating symptom is a source of considerable distress and embarrassment for the child and his/her family. Pediatric fecal incontinence can be divided into 2 main categories: (1) organic fecal incontinence, e.g., resulting from anorectal malformations or neurogenic abnormalities, and (2) functional fecal incontinence. This review will only address functional fecal incontinence in children, and the definition, epidemiology, pathophysiology and recent updates on the clinical and diagnostic aspects of functional fecal incontinence will be discussed.
Applications of Carbon Nanotubes in Neurobiology
Authors: Malarkey Erik B. , Parpura Vladimir
Published: July 2007

Background: Carbon nanotubes are one of the most promising materials for the electronics, computer and aerospace industries. There are numerous properties of carbon nanotubes that make them attractive for applications in neurobiology: small size, flexibility, strength, inertness, electrical conductivity and ease of modification with biological compounds. Objective/Methods: Here, we discuss the current applications of carbon nanotubes in neuroscience. Results: Carbon nanotubes and their derivatives can be used as substrates/scaffolds for neural cell growth. The chemical properties of carbon nanotubes can be systematically varied by attaching different functional groups; manipulation of the charge carried by functionalized carbon nanotubes can be used to control the outgrowth and branching pattern of neuronal processes. The ease with which carbon nanotubes can be patterned makes them attractive for studying the organization of neural networks and the electrical conductivity of nanotubes can provide a mechanism to monitor or stimulate neurons through the substrate itself. However, it is important to recognize that carbon nanotubes themselves can affect neuronal function, most likely by interaction with ion channels. Conclusion: The use of carbon nanotubes in neurobiology is a promising application that has the potential to develop new methods and techniques to advance the study of neuroscience.
The Role of Noninvasive Cellular Imaging in Developing Cell-Based Therapies for Neurodegenerative Disorders
Authors: Walczak Piotr , Bulte Jeff W.M.
Published: July 2007

Stem and progenitor cells from various sources are currently recognized as entities with potential for the treatment of numerous neurodegenerative diseases. It has been observed in many animal models that transplantation of stem cells induces functional improvement. As a result of these findings, the first clinical cell transplantation trials were initiated, including those for Parkinson’s disease and cerebral ischemia patients. However, in many patients, although modest improvements have been observed, these improvements were not sufficient to warrant invasive and possibly risky cell therapy. Thus, it is apparent that therapeutic success requires a better understanding of the mechanisms of action and the ability to control these mechanisms that underlie functional improvements, permitting amplification of the therapeutic effect. Considering the complexity of the nervous system, the task of repairing damaged or dysfunctional brain tissue with naïve cellular elements that require spatially and temporally accurate governance may seem daunting. However, the hope for faster and more inclusive progress in this field arises from recent developments in medical biotechnology that offers scientists increasingly sophisticated tools to study and control biological processes. One such technology with great potential for neurotransplantation is noninvasive cellular imaging. This tool allows real-time ‘supervision’ of grafted cells, as well as monitoring biodistribution and development. In this review, we highlight the current challenges in the field of cell-based therapy for neurodegenerative disorders and outline the role and capabilities of different cellular imaging techniques in addressing those issues.
Magnetic Resonance Imaging as a Tool for Monitoring Stem Cell Migration
Authors: Magnitsky S. , Walton R.M. , Wolfe J.H. , Poptani H.
Published: July 2007

Noninvasive monitoring of stem cells is an important step in developing stem-cell-based therapies. Among several imaging techniques available, magnetic resonance imaging (MRI) provides an effective way to detect implanted stem cells in live animals. In this mini-review, we discuss the available MRI contrast agents and different cell-labeling strategies used for detection of stem cell migration in the brain. The potential effects of MRI contrast agents on stem cell viability and differentiation are also discussed.
Gene Duplication and the Evolution of Vertebrate Skeletal Mineralization
Authors: Kawasaki Kazuhiko , Buchanan Anne V. , Weiss Kenneth M.
Published: July 2007

The mineralized skeleton is a critical innovation that evolved early in vertebrate history. The tissues found in dermal skeletons of ancient vertebrates are similar to the dental tissues of modern vertebrates; both consist of a highly mineralized surface hard tissue, enamel or enameloid, more resilient body dentin, and basal bone. Many proteins regulating mineralization of these tissues are evolutionarily related and form the secretory calcium-binding phosphoprotein (SCPP) family. We hypothesize here the duplication histories of SCPP genes and their common ancestors, SPARC and SPARCL1. At around the same time that Paleozoic jawless vertebrates first evolved mineralized skeleton, SPARCL1 arose from SPARC by whole genome duplication. Then both before and after the split of ray-finned fish and lobe-finned fish, tandem gene duplication created two types of SCPP genes, each residing on the opposite side of SPARCL1. One type was subsequently used in surface tissue and the other in body tissue. In tetrapods, these two types of SCPP genes were separated by intrachromosomal rearrangement. While new SCPP genes arose by duplication, some old genes were eliminated from the genome. As a consequence, phenogenetic drift occurred: while mineralized skeleton is maintained by natural selection, the underlying genetic basis has changed.
The Origin and Evolution of Enamel Mineralization Genes
Authors: Sire Jean-Yves , Davit-Béal Tiphaine , Delgado Sidney , Gu Xun
Published: July 2007

Background/Aims: Enamel and enameloid were identified in early jawless vertebrates, about 500 million years ago (MYA). This suggests that enamel matrix proteins (EMPs) have at least the same age. We review the current data on the origin, evolution and relationships of enamel mineralization genes. Methods and Results: Three EMPs are secreted by ameloblasts during enamel formation: amelogenin (AMEL), ameloblastin (AMBN) and enamelin (ENAM). Recently, two new genes, amelotin (AMTN) and odontogenic ameloblast associated (ODAM), were found to be expressed by ameloblasts during maturation, increasing the group of ameloblast-secreted proteins to five members. The evolutionary analysis of these five genes indicates that they are related: AMEL is derived from AMBN, AMTN and ODAM are sister genes, and all are derived from ENAM. Using molecular dating, we showed that AMBN/AMEL duplication occurred >600 MYA. The large sequence dataset available for mammals and reptiles was used to study AMEL evolution. In the N- and C-terminal regions, numerous residues were unchanged during >200 million years, suggesting that they are important for the proper function of the protein. Conclusion: The evolutionary analysis of AMEL led to propose a dataset that will be useful to validate AMEL mutations leading to X- linked AI.
Enamel Formation and Amelogenesis Imperfecta
Authors: Hu Jan C.-C. , Chun Yong-Hee P. , Al Hazzazzi Turki , Simmer James P.
Published: July 2007

Dental enamel is the epithelial-derived hard tissue covering the crowns of teeth. It is the most highly mineralized and hardest tissue in the body. Dental enamel is acellular and has no physiological means of repair outside of the protective and remineralization potential provided by saliva. Enamel is comprised of highly organized hydroxyapatite crystals that form in a defined extracellular space, the contents of which are supplied and regulated by ameloblasts. The entire process is under genetic instruction. The genetic control of amelogenesis is poorly understood, but requires the activities of multiple components that are uniquely important for dental enamel formation. Amelogenesis imperfecta (AI) is a collective designation for the variety of inherited conditions displaying isolated enamel malformations, but the designation is also used to indicate the presence of an enamel phenotype in syndromes. Recently, genetic studies have demonstrated the importance of genes encoding enamel matrix proteins in the etiology of isolated AI. Here we review the essential elements of dental enamel formation and the results of genetic analyses that have identified disease-causing mutations in genes encoding enamel matrix proteins. In addition, we provide a fresh perspective on the roles matrix proteins play in catalyzing the biomineralization of dental enamel.
The Molecular Control of and Clinical Variations in Root Formation
Authors: Wright Tim
Published: July 2007

Roots of teeth perform critical functions to anchor the teeth in the jaws and transmit the masticatory forces in such a way as to minimize fracture and wear of the dentition. Tooth root development involves a variety of cell types, epithelial-mesenchymal interactions, the enumeration of specialized extracellular matrices, processing of these matrices and strict control over the microenvironment to allow the cementum and dentin to mineralize. While many of the specific molecular mechanisms involved in root formation remain poorly understood, our knowledge of these events and pathways has advanced markedly over the past decade. The molecular bases of many hereditary conditions having associated dental root anomalies are now known. Therapeutic approaches based on the molecular biology of root formation have and will continue to emerge and be translated into improved clinical care. The purpose of this study was to review our knowledge regarding developmental defects of root formation, the molecular mechanisms involved, and the impact of root variants on clinical dentistry.
Endocardial Endothelium-Dependent Positive Inotropy by Ca2+ Pump Inhibitors: Possible Involvement of Store-Operated Ca2+ Entry
Authors: Nishimaru Kazuhide , Fujiki Shinpei , Tanaka Yoshio , Tanaka Hikaru , Shigenobu Koki
Published: July 2007

Positive inotropy by sarcoplasmic/endoplasmic reticulum Ca2+ pump inhibitors was found and its mechanisms were analyzed pharmacologically. Thapsigargin and cyclopiazonic acid produced positive inotropy in isolated mouse left atria. The responses were inhibited by pretreatment of the endocardial surface with Triton X-100 or by indomethacin, which suggests that the inotropic responses were mediated by prostaglandin(s) released from the endocardial endothelium as well as acetylcholine-induced positive inotropy. The thapsigargin- and acetylcholine-induced positive inotropy was significantly inhibited by Gd3+, La3+ and lavendustin A, a tyrosine kinase inhibitor, but not by Ni2+ and LOE908, a non-selective cation channel inhibitor. Gd3+ and lavendustin A had no effect on the exogenously applied PGF2α-induced positive inotropy. In addition, acetylcholine did not induce any positive inotropy when applied after the application of thapsigargin. These results strongly suggest that thapsigargin- as well as acetylcholine-induced prostaglandin release from endocardial endothelium is mediated by store-operated Ca2+ entry through Gd3+-sensitive channels and activation of tyrosine kinase.
Induction of Apoptosis and Inhibition of Cell Migration and Tube-Like Formation by Dihydroartemisinin in Murine Lymphatic Endothelial Cells
Authors: Wang Jun , Guo Yan , Zhang Bi-Cheng , Chen Zheng-Tang , Gao Jian-Fei
Published: July 2007

Dihydroartemisinin (DHA) is a semisynthesized agent from the artemisinin first extracted from the Chinese plant Artemisia annua. Previous studies have shown that artemisinin derivates, apart from their antimalarial activity, possess antitumor, antiangiogenic, and anti-inflammatory effects. In the present investigation, DHA was found to have a potent ability in influencing lymphatic endothelial cells (LECs) behavior. Murine LECs were isolated from benign lymphangiomas induced by intraperitoneal injection of incomplete Freund’s adjuvant and identified by indirect immunofluorescence assay and fluorescence-activated cell sorting analysis to examine the expression of the specific marker VEGFR-3/Flt-4. When LECs were treated with DHA at 10 µg/ml, the growth of LECs was inhibited, and LECs showed typical apoptotic morphological features, with a higher apoptotic rate as compared with the controls. DHA also exerted a significant inhibitory effect on migration and tube-like formation of LECs in a dose-dependent manner. Quantitative RT-PCR further showed thatDHA remarkably downregulated the expression of antiapoptotic bcl-2 mRNA, but upregulated that of the proapoptotic gene bax mRNA. In addition, DHA could strongly attenuate the mRNA and protein levels of VEGFR-3/Flt-4. In summary, these findings indicate that DHA may be useful as a potential lymphangiogenesis inhibitor under induction of cell apoptosis, inhibition of the migration, and formation of tube-like structures in LECs.
Skeletal Muscle Morphology in Patients with Restless Legs Syndrome
Authors: Wåhlin Larsson Britta , Kadi Fawzi , Ulfberg Jan , Piehl Aulin Karin
Published: July 2007

Aim: The aim of the study was to assess the cellular and structural properties of skeletal muscle in restless legs syndrome (RLS). Method: Twenty patients and 16 controls were included. Aerobic performance was assessed using a submaximal test. On muscle biopsies taken from the tibialis anterior, fiber distribution and fiber area were analyzed together with parameters surveying the microvascularization, especially the tortuosity, which is expressed as a percent of muscle fiber perimeter in contact with the wall of the microvessel, length of capillary/perimeter of fiber (LC/PF) index. Results: The RLS group had significantly lower predicted maximal oxygen uptake (p = 0.01) and significantly higher LC/PF index (p = 0.01) compared to the controls. Conclusion: The higher capillary tortuosity in RLS patients indicates the occurrence of significant remodeling in capillary geometry in RLS.
Botulinum Toxin Injection into Riolan’s Muscle: Somatosensory ‘Trick’
Authors: Inoue Ken , Rogers John D.
Published: July 2007

We studied the effect of injecting botulinum toxin A (BTX-A) into the pars ciliaris – also known as Riolan’s muscle – of patients with eyelid apraxia (ELA). Six patients with ELA were treated with injections of BTX-A into the region of Riolan’s muscle at the medial and lateral portions of the upper and lower pretarsal orbicularis oculi. Clinical benefit was seen in all 6 patients, 2 of whom had previously been treated with conventional pretarsal injections of BTX-A and had not improved. BTX-A injections into Riolan’s muscle are effective as treatment for ELA. The proposed mechanism is not that of muscle relaxation but rather modulation of the somatosensory cortex, similar to that of a ‘sensory trick’ in patients with dystonia.
Gait Apraxia: Further Clues to Localization
Authors: Nadeau Stephen E.
Published: July 2007

Background/Aims: Gait apraxia characterized primarily by gait ignition failure has been linked to lesions involving the dorsomedial frontal lobes, but the precise locus within this general region has not been determined. It has previously been hypothesized by Thompson and Marsden that disease, disconnection, or dysfunction of supplementary motor area (SMA) may account for the similarities in the gait disorders observed in Binswanger’s disease, hydrocephalus, frontal lobe lesions, and Parkinson’s disease. We reevaluate this hypothesis. Methods: Clinical description and MRI of 2 subjects with gait apraxia characterized primarily by gait ignition failure. Results: Both subjects had incapacitating gait disorders characterized by particular difficulty with initiating gait and making turns. Both had MRI-demonstrated lesions of the SMA region, parasagittal convexity premotor cortex, or subjacent white matter bilaterally, one due to primary CNS lymphoma, one due to a lobar atrophy. Conclusions: In both these cases, the lesions were substantially more limited and focal than any reported heretofore in the literature on gait apraxia or freezing of gait. The clinicopathologic correlation in these cases provides partial support for the Thompson and Marsden hypothesis, but also may implicate parasagittal convexity premotor cortex in the genesis of gait apraxia.