bluuebunny/crossref_metadata_2025 huggingface dataset:
Mitochondria are morphologically heterogeneous within cells
Authors: Collins Tony J. , Bootman Martin D.
Published: May 2003

Mitochondria play key roles in the life and death of cells. We investigated whether mitochondria represent morphologically continuous entities within single intact cells. Physical continuity of mitochondria was determined by three-dimensional reconstruction of fluorescence from mitochondrially targeted DsRed1 or tetra-methyl rhodamine ethyl ester (TMRE). The mitochondria of pancreatic acinar, porcine aortic endothelial (PAE) cells, COS-7 cells and SH-SY5Y cells and neocortical astrocytes all displayed heterogeneous distributions and were of varying sizes. In general, there was a denser aggregation of mitochondria in perinuclear positions than in the cell periphery, where individual isolated mitochondria could clearly be seen. DsRed1 was found to be highly mobile within the matrix of individual mitochondria, with an estimated linear diffusion rate of 1μm s-1. High-intensity irradiation of subcellular regions bleached the fluorescence of mitochondrially targeted DsRed1, but did not cause the mitochondria to depolarise or fragment. A lack of rapid fluorescence-recovery-after-photobleaching (FRAP) of DsRed1 indicated lumenal discontinuity between mitochondria. We observed a slow (half-time approx. 20 min) recovery of DsRed1 fluorescence within the irradiated area that was attributed to mitochondrial movement or fusion of unbleached and bleached organelles. Mitochondria were not electrically coupled, since typically only individual mitochondria were observed to depolarise following irradiation of TMRE-loaded cells. Our data indicate that the mitochondria within individual cells are morphologically heterogeneous and unconnected, thus allowing them to have distinct functional properties.
Mitochondrial movement and positioning in axons: the role of growth factor signaling
Authors: Chada Sonita R. , Hollenbeck Peter J.
Published: May 2003

The extreme length of axonal processes requires that aerobic ATP production and Ca2+ homeostasis are non-uniformly organized in the cytoplasm. As a result, the transport and positioning of mitochondria along axons is essential for neuronal homeostasis. Mitochondria undergo rapid but intermittent transport in both the anterograde and retrograde directions in axons. We have shown that in chick embryonic sensory neurons, the transport of mitochondria responds to physiological changes in the cell and, particularly,to growth cone activity. When an axon is actively elongating, mitochondria move preferentially anterograde and then become stationary, accumulating in the region of the active growth cone. When axonal elongation ceases,mitochondria in the distal axon resume movement but undergo net retrograde transport and become uniformly distributed along the axon. This redistribution of mitochondria is achieved in two ways: there is a transition between motile and stationary mitochondria and a large up- and downregulation of their anterograde, but not retrograde, motor activity. Mitochondrial transport does not respond to the experimentally induced elongation of axons in the absence of an active growth cone, implying that signals from the active growth cone regulate transport. To determine the nature of these signals, we have focally stimulated the shafts of sensory axons in culture with nerve growth factor(NGF) covalently conjugated to polystyrene beads. We find that mitochondria accumulate at regions of focal NGF stimulation. This response is specific to mitochondria and does not result from general disruption of the cytoskeleton in the region of stimulation. Disruption of the phosphoinositide 3-kinase (PI 3-kinase) pathway, one of the signaling pathways downstream from NGF–receptor binding, completely eliminates NGF effects on mitochondrial behavior in axons. We propose that mitochondrial transport and/or docking are regulated in part via NGF/TrkA/PI 3-kinase signaling.
Four-dimensional organization of protein kinase signaling cascades: the roles of diffusion, endocytosis and molecular motors
Authors: Kholodenko Boris N
Published: May 2003

Extracellular signals received by membrane receptors are processed, encoded and transferred to the nucleus via phosphorylation and spatial relocation of protein members of multiple component pathways, such as mitogen activated protein kinase (MAPK) cascades. The receptor-induced membrane recruitment of the cytoplasmic protein SOS results in the activation of the Ras/MAPK cascade. It has been suggested that the membrane recruitment of signaling proteins causes an increase in the diffusion-limited rates. We have recently shown that this increase is too small to be responsible for enhanced signal transduction. Instead we demonstrate that the function of membrane localization is to increase the number (or average lifetime) of complexes between signaling partners. A hallmark of signaling pathways is the spatial separation of activation and deactivation mechanisms; e.g. a protein can be phosphorylated at the cell surface by a membrane-bound kinase and dephosphorylated in the cytosol by a cytosolic phosphatase. Given the measured values of protein diffusion coefficients and of phosphatase and kinase activities, the spatial separation is shown to result in precipitous phospho-protein gradients. When information transfer is hampered by slow protein diffusion and rapid dephosphorylation, phospho-protein trafficking within endocytic vesicles may be an efficient way to deliver messages to physiologically relevant locations. The proposed mechanism explains recent observations that various inhibitors of endocytosis can inhibit MAPK activation. Additional mechanisms facilitating the relay of signals from cell-surface receptors to the nucleus can involve the assembly of protein kinases on a scaffolding protein and active transport of signaling complexes by molecular motors. We also discuss long-range signaling within a cell, such as survival signaling in neurons. We hypothesize that ligand-independent waves of receptor activation or/and traveling waves of phosphorylated kinases emerge to spread the signals over long distances.
The caveolar nitric oxide synthase/arginine regeneration system for NO production in endothelial cells
Authors: Solomonson Larry P. , Flam Brenda R. , Pendleton Laura C. , Goodwin Bonnie L. , Eichler Duane C.
Published: May 2003

The enzyme endothelial nitric oxide synthase (eNOS) catalyzes the conversion of arginine, oxygen and NADPH to NO and citrulline. Previous results suggest an efficient, compartmentalized system for recycling of citrulline to arginine utilized for NO production. In support of this hypothesis, the recycling enzymes, argininosuccinate synthase (AS) and argininosuccinate lyase (AL), have been shown to colocalize with eNOS in caveolae, a subcompartment of the plasma membrane. Under unstimulated conditions, the degree of recycling is minimal. Upon stimulation of NO production by bradykinin, however, recycling is co-stimulated to the extent that more than 80% of the citrulline produced is recycled to arginine. These results suggest an efficient caveolar recycling complex that supports the receptor-mediated stimulation of endothelial NO production. To investigate the molecular basis for the unique location and function of endothelial AS and AL,endothelial AS mRNA was compared with liver AS mRNA. No differences were found in the coding region of the mRNA species, but significant differences were found in the 5′-untranslated region (5′-UTR). The results of these studies suggest that sequence in the endothelial AS-encoding gene, represented by position -92 nt to -43 nt from the translation start site in the extended AS mRNA 5′-UTRs, plays an important role in differential and tissue-specific expression. Overall, a strong evidential case has been developed supporting the proposal that arginine availability, governed by a caveolar-localized arginine regeneration system, plays a key role in receptor-mediated endothelial NO production.
Shaken and stirred: muscle structure and metabolism
Authors: Suarez Raul K.
Published: May 2003

Muscles are ideal models with which to examine the relationship between structure and metabolism because they are some of the most highly structured cells, and are capable of the largest and most rapid metabolic transitions as well as the highest metabolic rates known. Studies of metabolism have traditionally been conducted within what can considered as the kinetic paradigm provided by `solution biochemistry'; i.e. the rates of enzymatic reactions are studied in terms of their regulation by mass-action and allosteric effectors and, most recently, metabolic control analysis of pathways. This approach has served biology well and continues to be useful. Here, we consider the diffusion of small and large molecules in muscles and energy metabolism in the context of intracellular space. We find that in attempting to explain certain phenomena, a purely kinetic paradigm appears insufficient. Instead, phenomena such as the `shuttling' of high-energy phosphate donors and acceptors and the binding of metabolic enzymes to intracellular structures or to each other are better understood when metabolic rates and their regulation are considered in the context of intracellular compartments, distances, gradients and diffusion. As in all of biology,however, complexity dominates, and to such a degree that one pathway may consist of several reactions that each behave according to different rules.`Soluble' creatine kinase operates at or near equilibrium, while mitochondrial and myofibrillar creatine kinases directly channel substrate to (or from) the adenine nucleotide translocase and actomyosin-ATPase, their operation being thus displaced from equilibrium. Hexose 6-phosphate metabolism appears to obey the rules of solution biochemistry, e.g. phosphoglucoisomerase behaves as Haldane would have predicted in 1930. In contrast, given low steady-state substrate and product concentrations and high flux rates, a number of glycolytic reactions further downstream must be catalyzed by enzymes localized in close proximity to each other. Metabolites may be channeled within these complexes. When observed, mechanistic differences between species in the same steps or processes should not be surprising, considering how animals vary so much in structures, mechanical properties, mitochondrial contents and metabolic rates. This analysis suggests that declarations of the triumph of one mechanism or paradigm over all others, as well as calls for the abandonment of solution biochemistry, are unwarranted. Rather, metabolic biochemistry would seem better served by reconciling the old and the new.
Analysis of glycolytic enzyme co-localization in Drosophilaflight muscle
Authors: Sullivan David T. , MacIntyre R. , Fuda N. , Fiori J. , Barrilla J. , Ramizel L.
Published: May 2003

In Drosophila flight muscles, glycolytic enzymes are co-localized along sarcomeres at M-lines and Z-discs and co-localization is required for normal flight. We have extended our analysis of this phenomenon to include a set of six glycolytic enzymes that catalyze consecutive reactions along the glycolytic pathway: aldolase, glycerol-3-phosphate dehydrogenase (GPDH),glyceraldehyde-3-phosphate dehydrogenase (GAPDH), triose phosphate isomerase,phosphoglycerate kinase and phosphoglycerol mutase (PGLYM). Each of these enzymes has an identical pattern of localization. In mutants null for GPDH,localization of none of the other enzymes occurs and therefore is interdependent. In optimally fixed preparations of myofibrils, accumulation of the enzymes at M-lines is much greater than at Z-discs. However, localization at M-lines is more labile, as shown by loss of localization when fixation is delayed. We have begun to analyze the protein—protein interaction involved in glycolytic enzyme co-localization using the yeast two-hybrid system. We have identified two pair-wise interactions. One is between GPDH and GAPDH and another is between GPDH and PGLYM.
Body size as a latent variable in a structural equation model: thermal acclimation and energetics of the leaf-eared mouse
Authors: Nespolo Roberto F. , Arim Matías , Bozinovic Francisco
Published: May 2003

Body size is one of the most important determinants of energy metabolism in mammals. However, the usual physiological variables measured to characterize energy metabolism and heat dissipation in endotherms are strongly affected by thermal acclimation, and are also correlated among themselves. In addition to choosing the appropriate measurement of body size, these problems create additional complications when analyzing the relationships among physiological variables such as basal metabolism, non-shivering thermogenesis,thermoregulatory maximum metabolic rate and minimum thermal conductance, body size dependence, and the effect of thermal acclimation on them.

We measured these variables in Phyllotis darwini, a murid rodent from central Chile, under conditions of warm and cold acclimation. In addition to standard statistical analyses to determine the effect of thermal acclimation on each variable and the body-mass-controlled correlation among them, we performed a Structural Equation Modeling analysis to evaluate the effects of three different measurements of body size (body mass, mb; body length, Lb and foot length, Lf) on energy metabolism and thermal conductance. We found that thermal acclimation changed the correlation among physiological variables. Only cold-acclimated animals supported our a priori path models, and mb appeared to be the best descriptor of body size (compared with Lb and Lf) when dealing with energy metabolism and thermal conductance. However, while mb appeared to be the strongest determinant of energy metabolism, there was an important and significant contribution of Lb (but not Lf) to thermal conductance. This study demonstrates how additional information can be drawn from physiological ecology and general organismal studies by applying Structural Equation Modeling when multiple variables are measured in the same individuals.
Occlusable corneas in toadfishes: light transmission, movement and ultrastruture of pigment during light- and dark-adaptation
Authors: Siebeck Ulrike E. , Collin Shaun P. , Ghoddusi Majid , Marshall N. Justin
Published: May 2003

The toadfishes Tetractenos hamiltoni and Torquigener pleurogramma (Tetraodontidae) possess occlusable yellow corneas. We examine the light transmission and location of the yellow/orange pigment throughout the cornea, the temporal properties of pigment migration and the ultrastructure of the pigmented processes during light- and dark-adaptation. Each species was dark-adapted during the day and light-adapted during the night and then exposed to either sun illumination or darkness for different lengths of time (0–70 min). Movement of corneal pigment could be induced in both species regardless of time of day or night. The pigment was able to migrate in a dorsal or ventral direction and changed from minimal to maximal pigmentation within 60 min. Three types of transmission curves were found with varying degrees of transmission in the 400–500 nm waveband, indicating that the pigment distribution is not uniform across the cornea; some areas of the cornea transmit near UV light, while others absorb blue light. The gradual change of the transmission characteristics in different areas of the cornea indicates the presence of different concentrations of a single type of pigment. Ultrastructural examination of the corneas showed that the layer containing the pigment is situated within the scleral cornea either surrounding (T. pleurogramma) or abutting (T. hamiltoni) an iridescent layer. Long sheet-like processes or chromatophores extending centrally from dorsal and ventral reservoirs are filled with pigment during the light-adapted state but empty in the dark-adapted state.
Intracellular convection, homeostasis and metabolic regulation
Authors: Hochachka P. W.
Published: May 2003

Two views currently dominate experimental approaches to metabolic regulation. The first, let us call it Model 1, assumes that cells behave like a watery bag of enzymes. The alternative Model 2, however, assumes that 3-dimensional order and structure constrain metabolite behavior. A major problem in cell metabolism is determining why essentially all metabolite concentrations are remarkably stable (homeostatic) over large changes in pathway fluxes–for convenience, this is termed the [s] stability paradox. During large-scale transitions from maintenance metabolic rates to maximally activated work, contrasting demands of intracellular homeostasis versus metabolic regulation obviously arise. Data accumulated over the last 3–4 decades now make it clear that the demands of homeostasis prevail: during rest–work transitions, metabolites such as ATP and O2 are notably and rigorously homeostatic; other intermediates usually do not vary by more than 0.5- to threefold over the resting condition. This impressive homeostasis is maintained despite changes in pathway fluxes that can exceed two orders of magnitude. Classical or Model 1 approaches to this problem can explain metabolite homeostasis, but the mechanisms for each metabolite, each enzyme locus, are necessarily specific. Thus Model 1 approaches basically do not provide a global explanation for the [s] stability paradox. Model 2 takes a different tack and assumes that an intracellular convection system acts as an over-riding `assist' mechanism for facilitating enzyme–substrate encounter. Model 2 postulates that intracellular movement and convection are powered by macromolecular motors (unconventional myosins, dyneins, kinesin) running on actin or tubulin tracks. For fast and slow muscle fibers, microfilaments are concentrated near the periphery (where convection may be most important), but also extend throughout the actomyosin contractile apparatus both in horizontal and vertical dimensions. To this point in the development of the field, Model 1 and Model 2 approaches have operated as `two solitudes', each considering the other incompatible with its own experimental modus operandi. In order to finally assemble a model that can sensibly explain a realistic working range of metabolic systems,opening of channels of communication between the above two very differing views of metabolic regulation would seem to be the requirement for the future.
Phosphotransfer networks and cellular energetics
Authors: Dzeja Petras P. , Terzic Andre
Published: May 2003

Precise coupling of spatially separated intracellular ATP-producing and ATP-consuming processes is fundamental to the bioenergetics of living organisms, ensuring a fail-safe operation of the energetic system over a broad range of cellular functional activities. Here, we provide an overview of the role of spatially arranged enzymatic networks, catalyzed by creatine kinase,adenylate kinase, carbonic anhydrase and glycolytic enzymes, in efficient high-energy phosphoryl transfer and signal communication in the cell. Studies of transgenic creatine kinase and adenylate kinase deficient mice, along with pharmacological targeting of individual enzymes, have revealed the importance of near-equilibrium reactions in the dissipation of metabolite gradients and communication of energetic signals to distinct intracellular compartments,including the cell nucleus and membrane metabolic sensors. Enzymatic capacities, isoform distribution and the dynamics of net phosphoryl flux through the integrated phosphotransfer systems tightly correlate with cellular functions, indicating a critical role of such networks in efficient energy transfer and distribution, thereby securing the cellular economy and energetic homeostasis under stress.
Modelling plasticity using strain nuclei: Discretization of the dislocation field by uniform triangles
Authors: McKellar D. K , Hills D A , Sackfield A
Published: May 2003

The solution is given for the state of stress induced in an infinite plane by a uniform distribution of edge dislocations present over a general triangle. This provides the basis of a ‘perturbation element’ for modelling macroscopic plastic flow, providing a systematic and internally consistent way of developing a plasticity solution from an underlying elasticity solution to a problem.
Theoretical stress concentration factors for short shouldered plates subjected to uniform tension
Authors: Troyani N , Marín A , García H , Rodríguez F , Rodríguez S , Gomes C
Published: May 2003

The values of the theoretical stress concentration factors for a variety of geometries and loads are available in a number of well-known publications. It is shown in this work that the reported existing results neglect the length of the members in the direction of the applied loads, and it is also shown that shorter lengths may have very significant effects on the magnitudes of the stress concentration factors. The finite element determined in-plane theoretical stress concentration factors for uniform thickness short shouldered plates subjected to uniform tension at the wide end and held longitudinally at the narrow end, for practical ranges of the fillet radius values, are reported and are presented in the standard graphical form. For completeness, other types of boundary condition have also been examined in this work. The value of the transition length between long and short plates is reported as well.
A self-powered damage detection sensor
Authors: Elvin N , Elvin A , Choi D. H
Published: May 2003

All existing methods of embedded damage-detecting sensors require an external power source and a means of transmitting the data to a central processor. This paper presents a novel self-powered strain sensor capable of transmitting data wirelessly to a remote receiver. This paper illustrates the performance of the sensor through the theoretical and experimental analysis of a simple damaged beam. The results show that a sensor powered through the conversion of mechanical to electrical energy is viable for detecting damage. The potential benefits of this sensor include ease of implementation during manufacture of the structure, and the use of an environmentally safe and renewable power source.
Interpretation of damage mechanics behaviour of two-bar structures for the life extension of high-temperature components
Authors: Tu S-T , Ling X
Published: May 2003

The creep damage behaviour of two-bar structures of different dimensions and materials is studied in terms of continuum damage theory. The basic model is used to interpret the effectiveness of life extension measures for complicated structures. It is found that replacement of the more damaged component prior to rupture will result in an optimized life extension efficiency, depending on the geometric or material difference between the damaged and less damaged components. This has potential to provide guidance on the effectiveness of life extension repairs in high-temperature plants.
Fretting fatigue analysis of aluminium conductor wires near the suspension clamp: Metallurgical and fracture mechanics analysis
Authors: Ouaki B , Goudreau S , Cardou A , Fiset M
Published: May 2003

Fretting fatigue is the main phenomenon inducing reduction of fatigue strength in overhead transmission conductor lines which are subjected to aeolian vibrations. Using the Bersfort ACSR 48/7 conductor, fatigue tests were conducted under several traction forces and relative vibration amplitudes. By metallographic examinations it has been observed that fretting induces microcracks which are mainly located between the keeper edge (KE) and the last point of the contact (LPC) of the conductor at the mouth of the suspension clamp.

Under the fatigue tests conditions, several cross-sections of wires in the external layer of the conductor were instrumented using strain gauges. Wire strains recorded near to the suspension clamp show that the alternating strains were predominantly traction strains near the KE and that bending alternating strains become significant near the LPC.

On the basis of fatigue tests results and assuming some simplified hypothesis, stress intensity factors were computed at the tip of cracks. The computed stress intensity factors take into account the combined effect of fretting behaviour at the contact points and both traction and bending stresses. The computed stress intensity factor ranges for low fatigue bending vibration amplitudes show good agreement with the endurance limit of the conductor.
Comparison of white metal and resin socket terminations for wire ropes
Authors: Bradon J. E , Ridge I. M. L
Published: May 2003

Previously the authors have presented both theoretical and experimental work discussing the operating mechanism of a wire rope held in a tapered socket by means of a cast resin cone. The work reported here extends the investigation to address the question of whether the same socket fabricated with white metal operates in the same manner. To date, previous investigations have compared the operational efficiency of resin and white metal in terms of both strength and/or fatigue endurance. Some other work has analysed the operation of resin sockets or specific cast metal terminations. This paper seeks to draw the results from this work together, and, in addition to a theoretical analysis, presents experimental data obtained from a direct comparison of the operation mechanism for the same sockets filled with resin or white metal. Results show that white metal terminations have a very different distribution of stresses along the length of the socket basket from resin terminations, and a smaller but still significant amount of socket draw. For both types of termination the socket draw develops high frictional gripping forces which can transfer the load from the rope to the socket. The different stress distributions mean that the consequences of termination fabrication defects may not be the same for resin and white metal terminations.
Computation of stresses and deformations for a two-dimensional sliding contact between an elastic layer and a rigid indenter with a rounded profile
Authors: Jaffar M. J
Published: May 2003

The two-dimensional indentation problem of an elastic layer by either a wedge with a rounded tip or a flat punch with rounded corners in the presence of friction is investigated numerically. Contact stresses and deformations are presented when the layer is either bonded or resting without friction on a rigid foundation. Moreover, a set of asymptotic solutions for the contact pressure is obtained for an unbonded thin layer (the contact width is significantly larger than the layer thickness). The effects of several parameters on the results are examined.
Elimination of fold defects in the radial extrusion of tubular components using an elastic support ring
Authors: Lin F. C , Lin S. Y
Published: May 2003

The production of tubular flanged parts by traditional radial extrusion is limited to components having a low ratio of the flange thickness to the wall thickness of the tube. In this study, the concept of a one-step technique is introduced using an elastic ring which is placed outside around the specimen to overcome the formability limits. The elastic ring with suitable Young's modulus is used as a spring restraint to retard the workpiece material from flowing outwards and on the contrary to increase the material flowing inwards, which improves the geometrical shape and results in avoidance of residual fold defects. A finite element based methodology is utilized to investigate the effects of various ratios of Young's modulus of the elastic ring to that of the specimen on the deformation characteristics. It is shown that the addition of an elastic ring can facilitate the radial extrusion process more efficiently and effectively in the production of tubular flanged parts.
Force stream function method
Authors: Wu X , Genin J
Published: May 2003

A new stress analysis procedure, the force stream function method, is introduced. A general relationship between a fluid stream function and a force stream function is established. Simultaneously, the relationship between an Airy stress function and the force stream function is also presented. Classic elasticity problems, such as a simple tension plate with a circular hole in it and torsional problems are revisited using the method.
An Amino Acid Co-catalyzed Asymmetric Aldol Reaction
Authors: Gao Ming Z , Gao Jian , Lane Benjamin S , Zingaro Ralph A
Published: May 2003

A series of chiral amino acids were found to be effective catalysts in an asymmetric aldol reaction between 4-nitrobenzaldehyde and acetone. Lewis acids and bases were found to effectively promote this reaction. Enantioselectivities greater than 74% (ee) and product yields over 85% were achieved under optimum conditions.
Iodo(etiohemiporphycenato)iron(III). Unexpected Difference in Magnetic Behavior in Solution and Solid
Authors: Ohgo Yoshiki , Neya Saburo , Takahashi Masashi , Takeda Masuo , Funasaki Noriaki , Nakamura Mikio
Published: May 2003

Although iodo(etiohemiporphycenato)iron(III) showed an admixed intermediate-spin state (S = 3/2, 5/2) with a major contribution of S = 3/2 in solution, the same complex exhibited the high-spin state (S = 5/2) in the solid phase. Importance of the crystal packing has been pointed out for the formation of the high-spin complex in the solid.
Polypyrrole Fibrils Synthesized on ITO Electrode in the Presence of Polyacrylic Acid
Authors: Wang Jixiao , Ge Dongtao , Wang Shichang
Published: May 2003

In the presence of polyacrylic acid (PAA), oriented growth of polypyrrole (Ppy) was achieved on tin-doped indium oxide (ITO) electrode by electropolymerization. The resulting Ppy exhibits unusual fibrillar morphology. The possible mechanism responsible for the formation of Ppy fibrils was discussed.
Separation of Lanthanides by Ion Chromatography with Imprinted Polymers
Authors: Vigneau Olivier , Pinel Catherine , Lemaire Marc
Published: May 2003

Several lanthanides were separated by ion chromatography with blank and imprinted polymers; the best resolutions were achieved over the latter one.
Mechanism of Oscillatory Electrodeposition of Zinc, Revealed by Microscopic Inspection of Dendritic Deposits during the Oscillation
Authors: Fukami Kazuhiro , Nakanishi Shuji , Sakai Sho-ichiro , Nakato Yoshihiro
Published: May 2003

Electrodeposition of Zn shows a potential oscillation in a diffusion-limited current region, accompanied by dendritic deposits. Detailed microscopic investigations of the deposits during one cycle of the oscillation have revealed a new mechanism including autocatalytic Zn growth, which is closely related to Mullins-Sekerka instability.
“Molecular Magic”. Formation of a Self-inclusion Complex from a Dumbbell-shaped Permethylated β-Cyclodextrin Derivative
Authors: Yamada Takashi , Fukuhara Gaku , Kaneda Takahiro
Published: May 2003

Hermaphroditic permethylated β-cyclodextrins 1f and 2f and the relevant dumbbell-shaped CD dimers 3f and 4 were synthesized and their intramolecular complexation was examined by 1H NMR methods. The dumbbell 3f was found to isomerize to a self-inclusion complex 3c at room temperature in CD3OD, but not 4. The isomerization was explained by means of a “somersault mechanism,” which involves turning the glucose bearing the internal guest through 360°.
Synthesis and Characterization of the First Pair of an Unlocked and a Locked Self-inclusion Complex from a Permethylated α-Cyclodextrin Derivative
Authors: Fukuhara Gaku , Fujimoto Tatsuhiko , Kaneda Takahiro
Published: May 2003

To examine self-inclusion phenomena, we intentionally synthesized the first pair of an unlocked and a locked self-inclusion complex, 3h and 4h, from a permethylated α-cyclodextrin-azobenzene dyad through an m-xylylene spacer. A d2-labeled complex 4d was also prepared for decisive 1H NMR spectral assignments. In both complexes, the guests were bound in the CD cavities in a similar manner, whereas the mutual orientation of the spacer and the nearest benzene ring was unexpectedly different.
Pentane Isomerization over Molybdenum Oxide Prepared by H2 Reduction of a Hydrogen Molybdenum Bronze
Authors: Matsuda Takeshi , Asano Yoko , Sakagami Hirotoshi , Takahashi Nobuo
Published: May 2003

Physical and catalytic properties of hydrogen molybdenum bronze, H1.55MoO3 varied markedly with H2 reduction. The surface area was enlarged from 10 m2/g to 250 m2/g by H2 reduction at 673–723 K. H1.55MoO3 became an active and selective catalyst for pentane isomerization after reduction. H2-reduced H1.55MoO3 exhibited a comparable isomerization activity to H2-reduced Pt/MoO3.
Ubiquinone: cholesterol's reclusive cousin
Authors: Hargreaves Iain P
Published: May 2003

Coenzyme Q10 (CoQ10) is the predominant form of ubiquinone in man. CoQ10 functions as an electron carrier in the mitochondrial respiratory chain as well as serving as an important intracellular antioxidant. Lowered blood and tissue concentrations of CoQ10 have been reported in a number of diseases, although whether this deficiency is the cause or an effect of the disease remains largely unresolved. Some studies have reported lowered plasma CoQ10 concentrations after statin drug treatment of hypercholesterolaemic patients. However, a deficiency in CoQ10 status has yet to be demonstrated in patients experiencing the rare myotoxic side-effects of these drugs.

Most clinical investigations assessing the therapeutic potential of CoQ10 have focused on cardiovascular disease, specifically congestive heart failure. Although a number of studies have reported clinical improvement in congestive heart failure patients after CoQ10 supplementation to standard therapy, concerns about the design of these studies coupled to the small number of patients involved have limited their acceptance.

Assessment of CoQ10 status is generally based on plasma measurements. As plasma concentrations are influenced by a number of physiological factors and may not represent cellular concentrations, platelets, lymphocytes and fibroblasts may provide suitable alternatives for these measurements.
Urinary PC-1 activity in patients with type 1 diabetes mellitus
Authors: Stefanovicć V , Rajicć M , Anticć S , Miticć-Zlatkovicć M , Stojiljkovicć S , Ivicĭ MA , Vlahovicć P
Published: May 2003

Background: Insulin resistance characterizes type 1 diabetes mellitus with nephropathy. The molecular mechanisms of insulin resistance are not completely understood. Recently some advances have been made in identification of transmembrane glycoprotein PC-1 as a potential factor of insulin resistance.

Methods: We measured urinary excretion of PC-1 (alkaline phosphodiesterase I), a potential factor of insulin resistance, and N-acetyl-β-D-glucosaminidase (NAGA) in 62 type 1 diabetic patients with different damage to the kidney.

Results: In newly detected type 1 diabetes patients, before insulin therapy, urine PC-1 excretion was significantly increased (P<0·05) over the control level. However, in patients after 12·4 years of therapy, urinary PC-1 was significantly decreased (P<0·05). Decreased urine PC-1 activity (P<0·05) was found also in type 1 diabetes patients with microalbuminuria and manifest nephropathy, including those with renal failure. Urinary NAGA excretion was found to be significantly increased (P=0·001) in all but the group of type 1 diabetes patients without nephropathy.

Conclusion: This study of urinary PC-1 in patients with type 1 diabetes shows increased excretion in newly detected patients with poor glycaemic control, but decreased excretion in patients with micro-/macroalbuminuria as well as in those without apparent kidney damage. In patients with primary glomerulonephritis, urinary excretion of PC-1 was significantly decreased and that of NAGA significantly increased compared with the excretion in healthy controls.
An audit of the laboratory interpretation of growth hormone response to insulin-induced hypoglycaemia in the assessment of short stature in children
Authors: Ellis Andrew , Seth John , Al-Sadie Ruth , Barth Julian H
Published: May 2003

Introduction: Measurement of serum growth hormone (GH) concentration in response to insulin-induced hypoglycaemia remains an important investigation in the assessment of pituitary disease.

Methods In this audit, laboratories were presented with aliquots of sera with GH concentrations likely to be found in an insulin stress test (IST). They were invited to analyse the specimens for GH and comment on their results.

Results and discussion: A number of laboratories appeared to be using out-of-consensus cut-off concentrations that sometimes were unrelated to the bias of their GH assay. The specimens were chosen to mimic those seen in an IST that was clearly not indicative of GH deficiency, so there was reasonable consensus in the interpretation of results. However, five laboratories (9·6%) did indicate that their results were equivocal.
Comparison of perfusate activities of glutathione S-transferase, alanine aminopeptidase and fatty acid binding protein in the assessment of non-heart-beating donor kidneys
Authors: Gok Muhammed A , Pelsers Maurice , Glatz Jan FC , Bhatti Aftab A , Shenton Brian K , Peaston Robert , Cornell Chris , Mantle Dave , Talbot David
Published: May 2003

Background: With a universal shortage of donor organs, screening and selection of marginal kidneys from non-heart-beating donors (NHBDs) provides a valuable source for transplantation. Pre-transplant viability assessment is based on a combination of flow characteristics and assessment of ischaemic tissue injury during NHBD kidney machine perfusion by measurement of total glutathione S-transferase (GST) activity. Successful viability screening has facilitated 69 renal transplants from 60 NHBDs within our transplant centre since 1998, with a first-year graft survival of 90·5%.

Methods: We have investigated alanine aminopeptidase (Ala-AP) and fatty acid binding protein (FABP) as alternative biochemical markers to GST for pre-transplantation viability assessment. They were measured, together with GST, in tissue perfusate samples from machine-perfused kidneys from controlled and uncontrolled NHBDs.

Results: During machine perfusion, a parallel response was seen for each of the three markers in the perfusates of controlled and uncontrolled NHBD kidneys over the 4-h perfusion. A highly significant correlation was obtained between GST and Ala-AP activities (P<0·0001) and between GST activity and FABP concentration (P<0·0001) in corresponding samples.

Conclusion: In this study, GST, Ala-AP and FABP represent equivalent biochemical markers in terms of their ability to quantitate renal tissue injury in human NHBD kidneys. However, there may be some advantage in using all three analytes to provide complementary information on kidney allograft viability.
A novel method for measuring serum ornithine carbamoyltransferase
Authors: Ishikawa Hiroaki , Matsuzawa Takeo , Ohashi Koji , Nagamura Yoichi
Published: May 2003

Background: Serum ornithine carbamoyltransferase is a diagnostic marker of hepatic disorders due to its localization in periportal mitochondria.

Methods: We have developed a new method for the determination of serum ornithine carbamoyltransferase. It is based on the reverse reaction of ornithine carbamoyltransferase, using ornithine-ketoacid aminotransferase, ∆1-pyrroline-5-carboxylate dehydrogenase and glutamate dehydrogenase, which together convert citrulline through ornithine to glutamate. The glutamate is then quantitatively measured using glutamate oxidase and Trinder's reagent.

Results: The results obtained by this method agreed well with those obtained using the diacetylmonoxime method as a gold standard [correlation coefficient (r) = 0·973 P<0·001]. The endogenous amino acids sensitive to this method in serum (glutamate, ornithine and ∆1-pyrroline-5-carboxylate) were eliminated by the initial futile reaction. The new method appears to be more accurate at low levels of ornithine carbamoyltransferase activity than the diacetylmonoxime method.

Conclusions: Here we report a new method for serum ornithine carbamoyl-transferase assay which might be useful for clinical diagnosis of hepatic disorders, including hepatic cancer.
Retrospective analysis of abnormal 24-h urinary free catecholamine concentration in screening for phaeochromocytoma
Authors: Idris Iskandar R , Hill Robert , Sands Keith A , Thomson George A
Published: May 2003

Background: Patients with hypertension often have increased 24-h excretion of urinary free catecholamines (UFCA) compared with normotensive patients, but the extent to which β-blockade and other antihypertensive agents affect 24-h UFCA concentrations remains unclear. Consequently, many patients with slightly elevated 24-h UFCA concentrations are not adequately investigated for the presence of phaeochromocytoma.

Method: We undertook a retrospective study on patients with at least one abnormal 24-h urinary collection of adrenaline (Adr), noradrenaline (NA) or dopamine (DA) between July 1997 and December 1999 to assess these issues.

Results: Of the 168 patients identified with raised 24-h UFCA concentrations, 106 with hospital notes were audited. Of the 46 patients whose values were more than twice the upper reference limit, 24 had their result confirmed with a repeat sample and only 10 underwent computed tomography or m-iodobenzylguanidine scanning. Two patients of these 10 had a phaeochromocytoma. We observed that hypertension correlated with significantly increased NA excretion compared with normotensive patients (median value 490±222 nmol per 24 h versus 304±229 nmol per 24 h, P<0·005). Patients on β-blockers showed a trend towards significantly increased NA excretion (P=0·08).

Conclusions: Many patients with abnormal 24-h UFCA excretion are not thoroughly investigated for the presence of phaeochromocytoma. NA concentration is significantly raised above the reference limit for patients with hypertension, and the use of β-blockers showed a trend towards a further elevation in NA concentrations. Care must therefore be taken when interpreting abnormal NA concentrations in patients with hypertension or in those taking β-blockers.
Comparison of lipid and non-lipid markers of atherosclerosis in arterial versus venous blood
Authors: Palmer Bruce , Watson Linley E , Riggs Mark W , Lawrence Mark , Baisden Clinton E , McNeal Catherine J , Macfarlane Ronald D
Published: May 2003

Background: Early studies have suggested that there may be differences in the concentration of lipoprotein particles and their associated apolipoproteins in arterial and venous blood and that this gradient might explain a proclivity to develop atherosclerotic lesions. The aim of this study was to use current methods of analysis to determine levels of these components, including particle densities and several common inflammatory markers in arterial and venous blood.

Methods: Samples of arterial and venous blood were obtained nearly simultaneously in 26 patients undergoing right and left heart catheterization. Analyses were performed using enzymatic, immunoturbidimetric and ultracentrifugation assays.

Results: Data obtained for total cholesterol, triglyceride, HDL-cholesterol, LDL-cholesterol, HDL and LDL particle density, high sensitivity C-reactive protein, serum amyloid-A and apoprotein B-100 concentrations in arterial and venous blood did not demonstrate any significant difference in the means.

Conclusion: Arterial and venous blood can be used interchangeably to study the effect of blood concentrations of common soluble surrogate markers of atherosclerosis.
Vitamin A deficiency presenting as night blindness during pregnancy
Authors: Livingstone Callum , Davis Joy , Marvin Vanessa , Morton Karen
Published: May 2003

We describe a patient with a 6-year history of pancreatic malabsorption following surgical subtotal pancreatectomy. She presented at 33 weeks of pregnancy with night blindness as a result of vitamin A deficiency. She had had two successful pregnancies 9 and 8 years previously, giving birth to a healthy baby boy on each occasion. We suggest that patients with long-term malabsorption due to intestinal or pancreatic disease should have vitamin A status checked prior to and during pregnancy so that prompt supplementation can be commenced if necessary. The possibility that vitamin A deficiency may be contributing to anaemia present in pregnancy should also be considered.
Severe hypercalcaemia secondary to isolated adrenocorticotrophic hormone deficiency and subacute thyroiditis
Authors: Strachan Mark WJ , Walker James D , Patrick Alan W
Published: May 2003

Severe hypercalcaemia is usually due to either neoplastic disease or primary hyperparathyroidism. Rarer causes do exist, and exceptionally these may occur concomitantly. We describe the case of a 45-year-old man who presented in a debilitated state with severe hypercalcaemia (total serum calcium 3·56 mmol/L, albumin 35 g/L) and suppressed serum parathyroid hormone concentration. It was initially suspected that he had neoplastic disease, but routine thyroid function tests demonstrated evidence of thyrotoxicosis [thyroid-stimulating hormone <0·05 mU/L (0·15-3·5); free thyroxine 75 pmol/L (8-27); total tri-iodothyronine 7·0 nmol/L (1·0-2·6)], which was probably secondary to a silent or subacute thyroiditis. After extensive investigation, it was established that the patient also had isolated adrenocorticotrophic hormone deficiency, presumably secondary to lymphocytic hypophysitis. Glucocorticoid therapy resulted in a dramatic improvement in the patient's clinical state and 1 year later he remained euthyroid and normocalcaemic.
Physicochemical and Catalytic Properties of Vanadia/Titania Catalysts. V. Selective Catalytic Reduction of NO with NH3
Authors: El-Nabarawy Th. , Alaya M.N. , Ahmed S.A. Sayed , Youssef A.M.
Published: May 2003

Vanadia/titania catalysts were prepared containing 6.0 or 8.0 wt% V2O5 via the impregnation method. The samples as prepared were calcined at 400°C or 600°C, respectively. Selective catalytic reduction (SCR) of NO with NH3 was carried out at 257°C over the prepared catalysts. NO conversion as a function of time was followed and the stationary conversion versus the amount of catalyst employed was also investigated.

It was found that the vanadia/titania catalysts calcined at 400°C were more active in the SCR of NO with NH3 relative to those calcined at 600°C. This was attributed to such catalysts possessing complete monolayer coverage of vanadia on the titania substrate. It was established that V5+ was not the active vanadia species but V4+ and V3+ may act as such for the SCR of NO with NH3.
The Jäntti Approach to Adsorption with Increasing Gas Pressure
Authors: Poulis Johannes A. , Massen Carel H. , Robens Erich
Published: May 2003

Jäntti introduced a method of calculating equilibrium adsorption from measurements where the pressure of the gas was varied in a stepwise manner. His aim was to shorten the time necessary for a given measurement. The method was applied to gas/solid systems in which simple adsorption processes occurred and where the number of adsorption sites was infinite.

The present paper discusses the case where no adsorption is possible on an already occupied site (Langmuir isotherm) while the number of positions available for adsorption is considered limited. The advantages of using a gas pressure that increases linearly with time are evident for studies with this limitation. It is shown that such measurements can also be speeded up using Jäntti's method.
Adsorption of Argon on Six Microporous Solids
Authors: Wojsz Roman
Published: May 2003

An analysis of the function characterizing the structural heterogeneity of microporous adsorbents was presented. The micropore distribution functions f(x), where x is the micropore half-width, were calculated assuming a slit-like model for the micropores and applied to the adsorption of argon on four active carbons, one carbon fibre and one zeolite at 77.3 K.