bluuebunny/crossref_metadata_2025_split huggingface dataset:
Intracellular convection, homeostasis and metabolic regulation
Authors: Hochachka P. W. 
Published: May 2003

SUMMARYTwo 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

SUMMARYPrecise 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.
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.
An Amino Acid Co-catalyzed Asymmetric Aldol Reaction
Authors: Gao Ming Z , Gao Jian , Lane Benjamin S , Zingaro Ralph A 
Published: May 2003

Abstract
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

Abstract
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

Abstract
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.
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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.
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.
Solid Acids from Persulphated and Perchlorated Physical Mixtures of Zirconium and Titanium Hydroxides
Authors: Shafei Gamal M.S. El , Philip Christine A. 
Published: May 2003

Calcination at 650°C of a physical mixture of zirconium and titanium hydroxides led to the formation of the corresponding oxides, monoclinic zirconia and anatase. The adsorption of perchlorate or persulphate anions (as 0.05, 0.1, 0.2 or 0.4 M aqueous solutions) before calcination did not inhibit crystallization; however, perchlorate anions activated the formation of rutile in addition to the predominant anatase phase. Indeed, the adsorption of perchlorated anions prior to calcination allowed the thermodynamically less stable tetragonal phase of zirconia to be detected in addition to monoclinic zirconia at ambient temperature. In contrast, the adsorption of persulphate anions before calcination stabilized the tetragonal phase with no rutile phase being detected in this case. Infrared spectroscopy showed that adsorbed S2O82– anions were held more strongly by the solid than ClO4− anions which tended to decompose when the solid was calcined. The acidities of the solid acids produced because of S2O82– or ClO4−anion adsorption were studied via the adsorption of pyridine (pKa = 5.3) from cyclohexane solution. The amounts and strengths of the acid sites formed during persulphate treatment were higher than those resulting from perchlorate adsorption. The strength of the acid sites formed on samples calcined before loading with S2O82– or ClO4− anions showed no significant differences. Variations detected in the structural aspects arising from S2O82– or ClO4− anion adsorption were reflected in the texture as assessed by nitrogen adsorption at −196°C.