bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of sodium butyrate on the transfer of arachidonic acid to phosphatidylcholine in a clonal oligodendrocyte cell line (CB‐II)
Authors: Sun Synthia H. , Chen Kuo‐Chi , Chen Yue‐Wen
Published: March 2007

The effect of sodium butyrate on membrane phospholipid metabolism in a neonate rat cerebellum derived clonal oligodendrocyte cell line (CB‐II) was investigated. Sodium butyrate is an agent known to induce cell differentiation and morphological transformations. A comparison of thein vivo phospholipid labeling patterns obtained by incubating CB‐II cells with [3H]choline, [14C]myristic acid or [3H]arachidonic acid indicated that butyrate altered the route of acylation‐deacylation in phosphatidylcholine (PC) biosynthesis. Using anin vitro incubation system containing homogenates of CB‐II cells, the largest proportion of radioactivity was found in PC, and addition of sodium butyrate resulted in a further increase in the transfer of arachidonic acid to PC, but not to phosphatidylinositol. Similar results were obtained when thisin vitro acylation activity was tested using homogenates from sodium butyrate pretreated cells. The butyrate effect was observed regardless of whether or not exogenous lysophosphatidylcholine (LPC) was added to the incubation system. Addition of butyrate did not result in a change in the activity of LPC:acyl‐CoA (coenzyme A) acyltransferase (EC 2.3.1.23) in CB‐II cells upon incubating cell homogenates with [1‐14C]arachidonoyl‐CoA and LPC. However, when cell homogenates were incubated with [3H]arachidonic acid in the presence of 2.5–10 mM sodium butyrate, arachidonoyl‐CoA synthesis was stimulated. A time course study demonstrated that significant stimulation occurred after three minutes. Taken together, the results suggest that in CB‐II cells, sodium butyrate stimulates the transfer of arachidonic acid into PC and that this effect is at least partially due to a stimulation of arachidonoyl‐CoA ligase (EC 6.2.1.3).
Stimulation of phosphatidylglycerolphosphate phosphatase activity by unsaturated fatty acids in rat heart
Authors: Cao Shu Guang , Hatch Grant M.
Published: March 2007

Phosphatidylglycerolphosphate (PGP) synthase and PGP phosphatase catalyze the sequential synthesis of phosphatidylglycerol from cytidine‐5′‐diphosphate 1,2‐diacyl‐sn‐glycerol (CDP‐DG) and glycerol‐3‐phosphate. PGP synthase and PGP phosphatase activities were characterized in rat heart mitochondrial fractions, and the effect of fatty acids on the activity of these enzymes was determined. PGP synthase was observed to be a heat labile enzyme that exhibited apparent Km values for CDP‐PG and glycerol‐3‐phosphate of 46 and 20 μM, respectively. The addition of exogenous oleic acid to the assay mixture did not affect PGP synthase activity. PGP phosphatase was observed to be a heat labile enzyme, and addition of oleic acid to the assay mixture caused a concentration‐dependent stimulation of PGP phosphatase activity. Maximum stimulation (1.9‐fold) of enzyme activity was observed in the presence of 0.5 mM oleic acid, but the stimulation was slightly attenuated by the presence of albumin in the assay. The presence of oleic acid in the assay mixture caused the inactivation of PGP phosphatase activity to be retarded at 55°C. Stimulation of PGP phosphatase activity was also observed with arachidonic acid, whereas taurocholic, stearic and palmitic acids did not significantly affect PGP phosphatase activity. The activity of mitochondrial phosphatidic acid phosphohydrolase was not affected by inclusion of oleic acid in the incubation mixture. We postulate that unsaturated fatty acids stimulate PGP phosphatase activity in rat heart.
Synthesis and Properties of 1,1‐bis{[3‐(N,N‐Dimethylamino)propyl]amido}alkane‐di‐N‐oxides
Authors: Piasecki Andrzej , Karczewski Sławomir , Maliszewska Irena
Published: March 2007

A homologous series of new surface‐active 1,1‐bis{[3‐(N,N‐dimethylamino)propyl]amido}alkane‐di‐N‐oxides were synthesized in the reaction of an appropriate diethyl 2‐alkylmalonate with N,N‐dimethylamino‐1,3‐propanediamine followed by oxidation with aqueous hydrogen peroxide. The adsorption isotherms of their aqueous solutions were measured and evaluated to obtain adsorption parameters: critical micelle concentration (CMC), surface excess concentration (ΓCMC), equilibrium surface tension at the CMC (γCMC), cross‐sectional area of the adsorbed surfactant molecule (ACMC), efficiency of surface adsorption (pC20), standard free energies of adsorption (ΔG°ads), and micellization (ΔG°CMC). All investigated di‐amidoamines and di‐N‐oxides were practically non‐toxic to selected bacteria and yeasts. These compounds are readily biodegradable in the Closed Bottle Test inoculated with activated sludge. Surface and biological properties showed that this group of N‐oxide‐type compounds has high surface activity and fulfills requirements for environmental acceptance.
Nearly time optimal stabilizing patchy feedbacks
Authors: Ancona Fabio , Bressan Alberto
Published: March 2007

We consider the time optimal stabilization problem for a nonlinear control system

\.{x} = f(x,u)

. Let

T(y)

be the minimum time needed to steer the system from the state

y∊\mathbb{R}^{n}

to the origin, and call

\mathcal{A}(\tau )

the set of initial states that can be steered to the origin in time

T(y)⩽\tau

. Given any

ɛ > 0

, in this paper we construct a patchy feedback

u = U(x)

such that every solution of

\.{x} = f(x,U(x))

,

x(0) = y\in \mathcal{A}(\tau )

reaches an

ɛ

-neighborhood of the origin within time

T(y) + ɛ

.

On considère un problème de stabilization en temps optimal pour un système de commandé non-linéaire du type

\.{x} = f(x,u)

. Notons par

T(y)

le temps minimal nécessaire pour aller de

y∊\mathbb{R}^{n}

à l'origine, et par

\mathcal{A}(\tau )

l'ensemble des

y\in \mathbb{R}^{n}

tels que

T(y)⩽\tau

. Pour chaque

ɛ > 0

, on construit un feedback

u = U(x)

de type patchy tel que toutes les solutions de

\.{x} = f(x,U(x))

,

x(0) = y\in \mathcal{A}(\tau )

atteignent un

ɛ

-voisinage de l'origine en temps au plus

T(y) + ɛ

.
Anthocyanin-rich purple potato flake extract has antioxidant capacity and improves antioxidant potential in rats
Authors: Han Kyu-Ho , Sekikawa Mitsuo , Shimada Ken-ichiro , Hashimoto Makoto , Hashimoto Naoto , Noda Takahiro , Tanaka Hisashi , Fukushima Michihiro
Published: March 2007

Anthocyanins from various vegetables and fruits have antioxidant activities, however, the bioactivities of coloured potato anthocyanins are not well studied. We examined the antioxidant capacities of pigmented fractions from purple potato flakes in vitro, and the antioxidant potentials of purple potato flakes in vivo. 1,1-Diphenyl-2-picrylhydrazyl radical scavenging activity of the pigmented fraction from Hokkai no. 92 (H92) potato flakes was higher than that from Kitamurasaki (KM) potato flakes. Extracts equivalent to 600 μg pigmented fractions from KM and H92 potato flakes inhibited linoleic acid oxidation in the order trolox>H92 ≥ KM>control. Rats were fed 25 % KM or H92 potato flake diets for 4 weeks. The major anthocyanin was identified as petanin. Control rats were fed a diet with cornstarch instead of potato flakes for 4 weeks. The serum antioxidant potential level in the H92 group was significantly higher than that in the control group. The degree of hepatic lipid peroxidation in the H92 group was significantly lower than that in the control group. Hepatic Cu/Zn-superoxide dismutase (SOD), Mn-SOD and glutathione peroxidase (GSH-Px) mRNA levels in the H92 group were significantly higher than those in the control group. Similar significant differences in Cu/Zn-SOD and Mn-SOD mRNA levels between the KM and control groups were found. The present results suggest that purple potato flakes have antioxidant functions with regard to radical scavenging activity and inhibition of linoleic acid oxidation, and that they improve the antioxidant potentials in rats by enhancing hepatic Mn-SOD, Cu/Zn-SOD and GSH-Px mRNA expression.
Parental feeding style, energy intake and weight status in young Scottish children
Authors: Montgomery Colette , Jackson Diane M. , Kelly Louise A. , Reilly John J.
Published: March 2007

Parental feeding style, as measured by the Child Feeding Questionnaire (CFQ), may be an important influence on child feeding behaviour and weight status in early to mid childhood, but more evidence on parental feeding style is required from samples outside the USA. We aimed to use the CFQ in a sample of 117 Scottish children (boysn53, girlsn64 mean age 4·6 (sd0·5) years) to: characterise gender differences and changes over time (in forty of the 117 children studied over 2 years); test associations between parental feeding style, free-living energy intake (measured over 3 days using the multiple pass 24-h recall), and weight status (BMIsdscore). No dimensions of parental feeding style changed significantly over 2 years in the longitudinal study (P>0·05 in all cases). No aspects of parental feeding style as measured by the CFQ differed significantly between the sexes (P>0·05 in all cases). Parental perceptions of child weight status were generally significantly positively correlated with child weight status as measured by the BMIsdscore. In this sample and setting, measures of parental control over child feeding were generally not associated with child energy intake or weight status.
Plasma phylloquinone (vitamin K1) concentration and its relationship to intake in British adults aged 19–64 years
Authors: Thane Christopher W. , Wang Laura Y. , Coward W. Andy
Published: March 2007

Plasma phylloquinone (vitamin K1) concentration from non-fasted blood samples was examined by season, smoking status, socio-demographic factors and phylloquinone intake in a nationally representative sample of 1154 British individuals aged 19–64 years from the 2000–1 National Diet and Nutrition Survey. Geometric mean plasma phylloquinone concentration was 0·94 (95 % CI 0·88, 1·00) nmol/l, with 95 % of values in the range 0·10–8·72 nmol/l. Plasma phylloquinone concentrations of 530 men were significantly higher than those of 624 women (1·13 (95 % CI 1·04, 1·22) v. 0·81 (95 % CI 0·74, 0·88) nmol/l; P < 0·001), independent of other factors. Women aged 19–34 years had significantly lower plasma phylloquinone concentration than their older counterparts. Women were also found to have lower plasma phylloquinone concentrations during summer compared with winter and spring (each P < 0·01). In contrast, plasma phylloquinone concentration in men did not vary significantly by season or any of the socio-demographic or lifestyle factors. Plasma phylloquinone concentrations were positively correlated with phylloquinone intake in men and women (r 0·26 and 0·32 respectively; each P < 0·001). Overall, forward stepwise multiple regression analysis revealed that 8 % of the variation in plasma phylloquinone concentration was explained by phylloquinone intake, with a further 10 % of its variation explained by plasma concentrations of γ-tocopherol (6 %) and retinyl palmitate (4 %). After adjustment for age and corresponding nutrient intakes, plasma phylloquinone concentration was significantly associated (each P < 0·01) with plasma concentrations of total and LDL-cholesterol, α- and γ-tocopherols, retinyl palmitate, β-carotene, lycopene and lutein plus zeaxanthin in men and women.
EPIDEMIOLOGICAL FEATURES OF HIV INFECTION AMONG PREGNANT WOMEN IN MAKURDI, BENUE STATE, NIGERIA
Authors: UTULU S. N. , LAWOYIN T. O.
Published: March 2007

Women in Benue State have for years had the highest HIV rate in the country, but because the sentinel surveys are anonymized and unlinked, not much is known about the socio-demographic, behavioural and other risk factors that predispose these women to the disease. The HIV/AIDS epidemic in Nigeria does not appear to be a single epidemic but rather multiple epidemics of varying magnitude and trends. This cross-sectional study was therefore carried out to identify the risk factors for HIV/AIDS among these women. A total of 404 consecutive consenting mothers enrolled at the booking clinic were followed up until delivery of their babies. They were interviewed using a semi-structured questionnaire and tested for HIV infection using an ELISA-based kit after obtaining informed consent. Mean age of the mothers was 26±6·1 years, 94·8% were married while 50·5% had at least secondary level education. Sixty-one (15·1%) mothers were HIV positive with mothers aged 15–24 years being responsible for 50·8% of all infection. Following bivariate analysis, being single, having a partner with low level of formal education, living in a rural location, being in a polygamous/multiple partner union, being a higher order polygamous wife, being married more than once and reporting a history of a sexually transmitted infection were significantly associated with HIV infection. Monogamous women who lived apart from their partners and women who had ever had blood transfusion were also more likely to be HIV positive. Following multivariate logistic regression, a young age of 15–24 years (multivariate OR=3·3, 95% CI=1·2–8·4, p=0·02); ever had other STIs (OR=1·6, 95% CI 1·1–2·3, p=0·009); no formal maternal education (OR=0·6, 95% CI 0·4–0·9, p=0·021) and having one lifetime sexual partner (OR=0·4, 95% CI 0·3–0·5, p<0·00001) were significantly associated with HIV infection in the study population. Appropriate interventions must be directed at young people and should include STI control and abstinence education. Blood safety must be ensured as well as a general improvement in the level of formal and health education in this community.
Which variables matter in smell tests in the clinic?
Authors: Philpott C M , Wolstenholme C R , Goodenough P C , Clark A , Murty G E
Published: March 2007

Background: Testing of olfactory thresholds in the clinic is becoming more common, with commercially produced tests now available. The effect of common potential variables in the clinic setting on these results is unclear. If many variables must be controlled, tests become more complex and a universally accepted olfactory test becomes less likely.

Objectives: The aim of this study was to determine which potential variables the clinician needs to consider when testing olfaction in the out-patient clinic.

Methods: The study was conducted in a clinic setting at a university hospital, using 103 normal volunteers, comprising staff members and patients and relatives from the ENT clinic waiting room. The subjects recruited had no active rhinological complaints, were not taking any medications and were aged between 16 and 70 years. An olfactory threshold was established for each subject for the odour eucalyptol. Gender, smoking status, age, peak nasal inspiratory flow, ambient temperature and relative humidity were all recorded.

Results: For eucalyptol, the distribution of values for olfactory thresholds in the normal population lies around the concentration 10−3 log vol/vol. There was no significant effect of smoking status, tester, ambient temperature or humidity on the thresholds obtained.

Conclusions: The above variables do not have a significant effect on olfactory thresholds elicited in the clinic. The clinician therefore need not attempt to control these factors when testing olfaction in the out-patient setting. These findings bring the implementation of a universal, reliable and easily administered measurement of olfaction a step closer.
Frequent allelic loss at the FRA3B site in endemic nasopharyngeal carcinoma: association with clinical features and Epstein–Barr virus infection
Authors: Deng Y F , Zhou D N , Lu Y D
Published: March 2007

In this study, we aimed to precisely define the patterns of allelic loss at the FRA3B site in endemic nasopharyngeal carcinoma and to determine whether an association exists between allelic loss, clinicopathological features and Epstein–Barr virus infection.

We examined the loss of heterozygosity in 40 cases of nasopharyngeal carcinoma from an endemic area in southern China, using eight high dense, polymorphic, microsatellite markers within or flanking the FRA3B site.

Loss of heterozygosity at the FRA3B region was shown in 31 (77.5 per cent) primary tumours. Loss of heterozygosity was found most frequently at the D3S1300 (55.6 per cent) and D3S2757 (50.0 per cent) loci. The common area of deletion was located between the D3S4103 and D3S4260 loci. In nasopharyngeal carcinoma, loss of heterozygosity at the FRA3B/fragile histidine triad locus correlated with the following clinicopathological parameters: tumour T-stage, lymph node status, clinical stage, tumour differentiation and serum antibody titres of immunoglobulin (Ig) A against Epstein–Barr virus capsid antigen. Significantly frequent loss of heterozygosity was observed in nasopharyngeal carcinoma with tumour stages T3 and T4, lymph node metastasis and advanced tumour–node–metastasis staging (III and IV). Very frequent loss of heterozygosity was also observed to correlate with World Health Organization type III nasopharyngeal carcinoma histopathology. We also found that nasopharyngeal carcinoma patients with high titres of IgA against Epstein–Barr virus capsid antigen showed very frequent loss of heterozygosity.

Allelic loss at the FRA3B site occurs significantly more commonly in endemic nasopharyngeal carcinoma patients. This suggests that the region between D3S4103 and D3S4260 may represent a preferential molecular target in nasopharyngeal carcinogenesis.
Long time convergence of magnetohydrodynamic flows to alfvénic states
Authors: NÚÑEZ MANUEL
Published: March 2007

Alfvénic states of a plasma, where velocity and magnetic field coincide, form a particular simple class of ideal equilibria and are also found in certain astrophysical phenomena. While transient processes of alignment in turbulent plasmas are well known and due to preferential spectral transfer, the possible long-term evolution of a magnetohydrodynamic plasma towards an alfvénic state has been rarely studied. It is shown that this tendency does not exist: neither specific ideal alfvénic equilibria nor the whole set of such states attract trajectories in any functional sense. Another possibility is that the perturbations of a static equilibrium could tend to become alfvénic, such as the classical Alfvén waves. We find that if these equilibria are current free, when a perturbation approaches an alfvénic state it immediately bounces away from it.
Whistler wave emission by a modulated electron beam injected into a plasma column surrounded by a uniform medium
Authors: KRAFFT C. , ZABORONKOVA T. M.
Published: March 2007

The efficiency of whistler wave radiation by a density modulated and thin electron beam of finite length injected parallel with respect to the constant ambient magnetic field into a cylindrical plasma column surrounded by a uniform isotropic medium and aligned along the magnetic field is studied. A rigorous analytical derivation of the wave fields excited by the beam in the plasma column is presented. The time-averaged power radiated by the beam at the modulation frequency is determined. In particular, numerical calculations performed for physical conditions relevant to laboratory magnetized discharge plasmas show that, in the presence of a plasma column, the power lost by the modulated beam can be efficiently enhanced owing to resonant Cherenkov excitation of guided whistler modes at the beam modulation frequency.
Ethnic difference in the relationship between acute inflammation and serum ferritin in US adult males
Authors: PAN Y. , JACKSON R. T.
Published: March 2007

This study examined the ethnic difference in the association between increased serum ferritin (SF) (>300 μg/l) and acute inflammation (AI) (C-reactive protein ⩾1·0 mg/dl) between black and white males aged ⩾20 years. Using data from the third National Health and Nutrition Examination Survey (NHANES III), we determined the risk for having elevated SF in black males (n=164) and white males (n=325) with AI present as well as black males (n=1731) and white males (n=2877) with AI absent. Black subjects with AI present were 1·71 times (95% CI 1·18–2·49), and 1·87 times (95% CI 1·46–2·40) more likely to have increased SF than AI absent blacks and AI present whites, respectively. Furthermore, with AI present, every increment of C-reactive protein, white blood cell count, serum albumin, lymphocyte count and platelet count was associated with higher odds of having elevations in SF in blacks than whites. Regardless of AI status, blacks were more likely to have elevations in SF than whites, and the prevalence of elevated SF was significantly higher in blacks than whites. This finding suggested that black males may respond to inflammation with a more aggressive rise in SF compared to white males. Future research is needed to investigate the underlying mechanisms.
Failure to detect infection by oral polio vaccine virus following natural exposure among inactivated polio vaccine recipients
Authors: GARY H. E. , SMITH B. , JENKS J. , RUIZ J. , SESSIONS W. , VINJE J. , SOBSEY M.
Published: March 2007

While oral polio vaccine (OPV) has been shown to be safe and effective, it has been observed that it can circulate within a susceptible population and revert to a virulent form. Inactivated polio vaccine (IPV) confers protection from paralytic disease, but provides limited protection against infection. It is possible, then, that an IPV-immunized population, when exposed to OPV, could sustain undetected circulation of vaccine-derived poliovirus. This study examines the possibility of polio vaccine virus circulating within the United States (highly IPV-immunized) population that borders Mexico (OPV-immunized). A total of 653 stool and 20 sewage samples collected on the US side of the border were tested for the presence of poliovirus. All samples were found to be negative. These results suggest that the risk of circulating vaccine-derived poliovirus is low in fully immunized IPV-using populations in developed countries that border OPV-using populations.
Gravitational effects on bed load transport at low Shields stress: Experimental observations
Authors: Francalanci S. , Solari L.
Published: March 2007

In the present study we investigate the bed load transport mechanism due to the action of a free surface water flow when the transversal and longitudinal slopes of the bed are not negligible and in the case of low values of the applied Shields stress. Such a problem, which has been recently tackled by Parker et al. (2003) by means of a theoretical formulation, does not appear to be fully addressed in the literature from an experimental point of view. To this aim, average motion characteristics and transport dynamics of bed particles over an arbitrarily inclined nonerodible bed are studied by means of an experimental activity based on different techniques. A laser Doppler and an image‐based technique are developed here and employed to study the average properties of saltating particles, while volumetric sampling is applied to estimate the average bed load transport intensity at equilibrium. Results show the intensity and direction of average particle velocity and average bed load transport as a function of the applied Shields stress for various bed inclinations. It appears that the intensity of bed load transport increases with the applied Shields stress much faster than predicted by the linear formulations on horizontal beds, while its direction may largely deviate from the direction of the applied shear stress at the bed when the bed is transversally tilted. Experimental results are compared with the theoretical results of Parker et al. (2003) and show a good agreement.
Oceanic distributions and emissions of short‐lived halocarbons
Authors: Butler James H. , King Daniel B. , Lobert Jürgen M. , Montzka Stephen A. , Yvon‐Lewis Shari A. , Hall Bradley D. , Warwick Nicola J. , Mondeel Debra J. , Aydin Murat , Elkins James W.
Published: March 2007

Using data from seven cruises over a 10‐year span, we report marine boundary layer mixing ratios (i.e., dry mole fractions as pmol mol−1 or ppt), degrees of surface seawater saturation, and air‐sea fluxes of three short‐lived halocarbons that are significant in tropospheric and potentially stratospheric chemistry. CHBr3, CH2Br2, and CH3I were all highly supersaturated almost everywhere, all the time. Highest saturations of the two polybrominated gases were observed in coastal waters and areas of upwelling, such as those near the equator and along ocean fronts. CH3I distributions reflected the different chemistry and cycling of this gas in both the water and the atmosphere. Seasonal variations in fluxes were apparent where cruises overlapped and were consistent among oceans. Undersaturations of these gases were noted at some locations in the Southern Ocean, owing to mixing of surface and subsurface waters, not necessarily biological or chemical sinks. The Pacific Ocean appears to be a much stronger source of CHBr3 to the marine boundary layer than the Atlantic. The high supersaturations, fluxes, and marine boundary layer mixing ratios in the tropics are consistent with the suggestion that tropical convection could deliver some portion of these gases and their breakdown products to the upper troposphere and lower stratosphere.
Emergence of coherent flow structures over a gravel surface: A numerical experiment
Authors: Hardy Richard J. , Lane Stuart N. , Ferguson Robert I. , Parsons Daniel R.
Published: March 2007

Gravel bed rivers have complex, porous, and irregular surfaces, characterized by a range of morphological forms. These topographical structures determine the flow structures that develop over the river bed, primarily by the shedding of vortices in the downstream wake of protruding clasts. Previous research into these flow structures has come from experimental studies, which have used either flow visualization or single‐point measurements techniques. Here we present a numerical experiment where large‐eddy simulation (LES) is used to study the generation, evolution, and destruction of these flow structures over a naturally water worked gravel surface. The numerical simulations reported in this paper show that there are two distinct scales of boundary influence upon the shallow flow and emphasize that the measured flow variability at any one point in a natural river will contain both locally derived and upstream‐inherited flow structures, according to the range of scales of bed topography present.
Cloning of rat amelotin and localization of the protein to the basal lamina of maturation stage ameloblasts and junctional epithelium
Authors: Moffatt Pierre , Smith Charles E. , St-Arnaud René , Simmons Darrin , Wright J. Timothy , Nanci Antonio
Published: March 2007

Formation of tooth enamel is a very complex process in which a specific set of proteins secreted by ameloblasts play a primordial role. As part of a screening procedure to identify novel proteins secreted by EO (enamel organ) cells of rat incisors, we isolated a partial cDNA fragment (EO-017) that is the homologue of the recently described mouse Amtn (amelotin) gene [Iwasaki, Bajenova, Somogyi-Ganss, Miller, Nguyen, Nourkeyhani, Gao, Wendel and Ganss (2005) J. Dent. Res. 84, 1127–1132]. Presented herein is the cloning of rat and pig full-length cDNAs with their deduced protein sequences. Detailed expression profiling by Northern-blot analysis and RT (reverse transcriptase)–PCR on rat and mouse tissues revealed highest expression in the mandible, more specifically in the maturation stage of the EO. Among all tissues tested, low expression was detected only in periodontal ligament, lung, thymus and gingiva. In silico analyses revealed that the Amtn gene is highly conserved in seven other mammals, but is absent from fish, birds and amphibians. The Amtn protein is enriched in proline, leucine, glutamine and threonine (52% of total) and contains a perfectly conserved protein kinase CK2 phosphorylation site. Transient transfection experiments in HEK-293 cells (human embryonic kidney cells) showed that secreted Amtn is post-translationally modified possibly through O-linked oligosaccharides on threonine residues. In concordance with its predominant expression site, immunofluorescence localization within the rat and mouse mandibles revealed Amtn localized to the basal lamina of maturation stage ameloblasts of incisors and unerupted molars. Intense Amtn protein expression was also detected in the internal basal lamina of junctional epithelium in molars. The peculiar and unique cellular localization of Amtn suggests a role in cell adhesion.
Different redox states of metallothionein/thionein in biological tissue
Authors: Krężel Artur , Maret Wolfgang
Published: March 2007

Mammalian metallothioneins are redox-active metalloproteins. In the case of zinc metallothioneins, the redox activity resides in the cysteine sulfur ligands of zinc. Oxidation releases zinc, whereas reduction re-generates zinc-binding capacity. Attempts to demonstrate the presence of the apoprotein (thionein) and the oxidized protein (thionin) in tissues posed tremendous analytical challenges. One emerging strategy is differential chemical modification of cysteine residues in the protein. Chemical modification distinguishes three states of the cysteine ligands (reduced, oxidized and metal-bound) based on (i) quenched reactivity of the thiolates when bound to metal ions and restoration of thiol reactivity in the presence of metal-ion-chelating agents, and (ii) modification of free thiols with alkylating agents and subsequent reduction of disulfides to yield reactive thiols. Under normal physiological conditions, metallothionein exists in three states in rat liver and in cell lines. Ras-mediated oncogenic transformation of normal HOSE (human ovarian surface epithelial) cells induces oxidative stress and increases the amount of thionin and the availability of cellular zinc. These experiments support the notion that metallothionein is a dynamic protein in terms of its redox state and metal content and functions at a juncture of redox and zinc metabolism. Thus redox control of zinc availability from this protein establishes multiple methods of zinc-dependent cellular regulation, while the presence of both oxidized and reduced states of the apoprotein suggest that they serve as a redox couple, the generation of which is controlled by metal ion release from metallothionein.
Kinetic analysis of GTP hydrolysis catalysed by the Arf1-GTP–ASAP1 complex
Authors: Luo Ruibai , Ahvazi Bijan , Amariei Diana , Shroder Deborah , Burrola Beatriz , Losert Wolfgang , Randazzo Paul A.
Published: March 2007

Arf (ADP-ribosylation factor) GAPs (GTPase-activating proteins) are enzymes that catalyse the hydrolysis of GTP bound to the small GTP-binding protein Arf. They have also been proposed to function as Arf effectors and oncogenes. We have set out to characterize the kinetics of the GAP-induced GTP hydrolysis using a truncated form of ASAP1 [Arf GAP with SH3 (Src homology 3) domain, ankyrin repeats and PH (pleckstrin homology) domains 1] as a model. We found that ASAP1 used Arf1-GTP as a substrate with a kcat of 57±5 s−1 and a Km of 2.2±0.5 μM determined by steady-state kinetics and a kcat of 56±7 s−1 determined by single-turnover kinetics. Tetrafluoroaluminate (AlF4−), which stabilizes complexes of other Ras family members with their cognate GAPs, also stabilized a complex of Arf1-GDP with ASAP1. As anticipated, mutation of Arg-497 to a lysine residue affected kcat to a much greater extent than Km. Changing Trp-479, Iso-490, Arg-505, Leu-511 or Asp-512 was predicted, based on previous studies, to affect affinity for Arf1-GTP. Instead, these mutations primarily affected the kcat. Mutants that lacked activity in vitro similarly lacked activity in an in vivo assay of ASAP1 function, the inhibition of dorsal ruffle formation. Our results support the conclusion that the Arf GAP ASAP1 functions in binary complex with Arf1-GTP to induce a transition state towards GTP hydrolysis. The results have led us to speculate that Arf1-GTP–ASAP1 undergoes a significant conformational change when transitioning from the ground to catalytically active state. The ramifications for the putative effector function of ASAP1 are discussed.
An active site tyrosine residue is essential for amidohydrolase but not for esterase activity of a class 2 histone deacetylase-like bacterial enzyme
Authors: Moreth Kristin , Riester Daniel , Hildmann Christian , Hempel René , Wegener Dennis , Schober Andreas , Schwienhorst Andreas
Published: March 2007

HDACs (histone deacetylases) are considered to be among the most important enzymes that regulate gene expression in eukaryotic cells acting through deacetylation of ϵ-acetyl-lysine residues within the N-terminal tail of core histones. In addition, both eukaryotic HDACs as well as their bacterial counterparts were reported to also act on non-histone targets. However, we are still far from a comprehensive understanding of the biological activities of this ancient class of enzymes. In the present paper, we studied in more detail the esterase activity of HDACs, focussing on the HDAH (histone deacetylase-like amidohydrolase) from Bordetella/Alcaligenes strain FB188. This enzyme was classified as a class 2 HDAC based on sequence comparison as well as functional data. Using chromogenic and fluorogenic ester substrates we show that HDACs such as FB188 HDAH indeed have esterase activity that is comparable with those of known esterases. Similar results were obtained for human HDAC1, 3 and 8. Standard HDAC inhibitors were able to block both activities with similar IC50 values. Interestingly, HDAC inhibitors such as suberoylanilide hydroxamic acid (SAHA) also showed inhibitory activity against porcine liver esterase and Pseudomonas fluorescens lipase. The esterase and the amidohydrolase activity of FB188 HDAH both appear to have the same substrate specificity concerning the acyl moiety. Interestingly, a Y312F mutation in the active site of HDAH obstructed amidohydrolase activity but significantly improved esterase activity, indicating subtle differences in the mechanism of both catalytic activities. Our results suggest that, in principle, HDACs may have other biological roles besides acting as protein deacetylases. Furthermore, data on HDAC inhibitors affecting known esterases indicate that these molecules, which are currently among the most promising drug candidates in cancer therapy, may have a broader target profile requiring further exploration.
The role of the synergistic phosphate anion in iron transport by the periplasmic iron-binding protein from Haemophilus influenzae
Authors: Khan Ali G. , Shouldice Stephen R. , Tari Leslie W. , Schryvers Anthony B.
Published: March 2007

The acquisition of iron from transferrin by Gram-negative bacterial pathogens is dependent on a periplasmic ferric-ion-binding protein, FbpA. FbpA shuttles iron from the outer membrane to an inner membrane transport complex. A bound phosphate anion completes the iron co-ordination shell of FbpA and kinetic studies demonstrate that the anion plays a critical role in iron binding and release in vitro. The present study was initiated to directly address the hypothesis that the synergistic anion is required for transport of iron in intact cells. A series of site-directed mutants in the anion-binding amino acids of the Haemophilus influenzae FbpA (Gln-58, Asn-175 and Asn-193) were prepared to provide proteins defective in binding of the phosphate anion. Crystal structures of various mutants have revealed that alteration of the C-terminal domain ligands (Asn-175 or Asn-193) but not the N-terminal domain ligand (Gln-58) abrogated binding of the phosphate anion. The mutant proteins were introduced into H. influenzae to evaluate their ability to mediate iron transport. All of the single site-directed mutants (Q58L, N175L and N193L) were capable of mediating iron acquisition from transferrin and from limiting concentrations of ferric citrate. The results suggest that the transport of iron by FbpA is not dependent on binding of phosphate in the synergistic anion-binding site.
Immunopathogenesis in hepatitis C virus cirrhosis
Authors: Spengler Ulrich , Nattermann Jacob
Published: March 2007

HCV (hepatitis C virus) has a high propensity to persist and to cause chronic hepatitis C, eventually leading to cirrhosis. Since HCV itself is not cytopathic, liver damage in chronic hepatitis C is commonly attributed to immune-mediated mechanisms. HCV proteins interact with several pathways in the host's immune response and disrupt pathogen-associated pattern recognition pathways, interfere with cellular immunoregulation via CD81 binding and subvert the activity of NK (natural killer) cells as well as CD4+ and CD8+ T-cells. Finally, HCV-specific T-cells become increasingly unresponsive and apparently disappear, owing to several possible mechanisms, such as escape mutations in critical viral epitopes, lack of sufficient help, clonal anergy or expansion of regulatory T-cells. The role of neutralizing antibodies remains uncertain, although it is still possible that humoral immunity contributes to bystander damage of virally coated cells via antibody-dependent cellular cytotoxicity. Cytotoxic lymphocytes kill HCV-infected cells via the perforin/granzyme pathway, but also release Fas ligand and inflammatory cytokines such as IFNγ (interferon γ). Release of soluble effector molecules helps to control HCV infection, but may also destroy uninfected liver cells and can attract further lymphocytes without HCV specificity to invade the liver. Bystander damage of these non-specific inflammatory cells will expand the tissue damage triggered by HCV infection and ultimately activate fibrogenesis. A clear understanding of these processes will eventually help to develop novel treatment strategies for HCV liver disease, independent from direct inhibition of HCV replication.
Vasoactive drugs enhance pancreatic islet blood flow, augment insulin secretion and improve glucose tolerance in female rats
Authors: Huang Zhen , Jansson Leif , Sjöholm Åke
Published: March 2007

Pravastatin, irbesartan and captopril are frequently used in the treatment of patients with Type 2 diabetes. These drugs also exert beneficial metabolic effects, causing an improved glucose tolerance in patients, but the precise mechanisms by which this is achieved remain elusive. To this end, we have studied whether these drugs influence insulin secretion in vivo through effects on islet blood perfusion. Captopril (3 mg/kg of body weight), irbesartan (3 mg/kg of body weight) and pravastatin (0.5 mg/kg of body weight) were injected intravenously into anaesthetized female Wistar rats. Blood flow rates were determined by a microsphere technique. Blood glucose concentrations were measured with test reagent strips and serum insulin concentrations were measured by ELISA. Pancreatic blood flow was markedly increased by pravastatin (P<0.001), captopril (P<0.05) and irbesartan (P<0.01). Pancreatic islet blood flow was significantly and preferentially enhanced after the administration of captopril (P<0.01), irbesartan (P<0.01) and pravastatin (P<0.001). Kidney blood flow was enhanced significantly by pravastatin (P<0.01), irbesartan (P<0.05) and captopril (P<0.01). Captopril and pravastatin also enhanced late-phase insulin secretion and positively influenced glycaemia in intraperitoneal glucose tolerance tests. In conclusion, the present study suggests that a local pancreatic renin–angiotensin system and pravastatin treatment may be selectively controlling pancreatic islet blood flow, augmenting insulin secretion and thereby improving glucose tolerance. Our findings indicate significant gender-related differences in the vascular response to these agents. Since statins and renin–angiotensin system inhibitors are frequently used by diabetic patients, the antidiabetic actions of these drugs reported previously might occur, in part, through the beneficial direct islet effects shown in the present study.
Linear-scaling implementation of molecular electronic self-consistent field theory
Authors: Sałek Paweł , Høst Stinne , Thøgersen Lea , Jørgensen Poul , Manninen Pekka , Olsen Jeppe , Jansík Branislav , Reine Simen , Pawłowski Filip , Tellgren Erik , Helgaker Trygve , Coriani Sonia
Published: March 2007

A linear-scaling implementation of Hartree-Fock and Kohn-Sham self-consistent field (SCF) theories is presented and illustrated with applications to molecules consisting of more than 1000 atoms. The diagonalization bottleneck of traditional SCF methods is avoided by carrying out a minimization of the Roothaan-Hall (RH) energy function and solving the Newton equations using the preconditioned conjugate-gradient (PCG) method. For rapid PCG convergence, the Löwdin orthogonal atomic orbital basis is used. The resulting linear-scaling trust-region Roothaan-Hall (LS-TRRH) method works by the introduction of a level-shift parameter in the RH Newton equations. A great advantage of the LS-TRRH method is that the optimal level shift can be determined at no extra cost, ensuring fast and robust convergence of both the SCF iterations and the level-shifted Newton equations. For density averaging, the authors use the trust-region density-subspace minimization (TRDSM) method, which, unlike the traditional direct inversion in the iterative subspace (DIIS) scheme, is firmly based on the principle of energy minimization. When combined with a linear-scaling evaluation of the Fock/Kohn-Sham matrix (including a boxed fitting of the electron density), LS-TRRH and TRDSM methods constitute the linear-scaling trust-region SCF (LS-TRSCF) method. The LS-TRSCF method compares favorably with the traditional SCF/DIIS scheme, converging smoothly and reliably in cases where the latter method fails. In one case where the LS-TRSCF method converges smoothly to a minimum, the SCF/DIIS method converges to a saddle point.
Spectroscopic studies on methyl torsional behavior in 1-methyl-2(1H)-pyridone, 1-methyl-2(1H)-pyridinimine, and 3-methyl-2(1H)-pyridone. I. Excited state
Authors: Sinha Rajeev K. , Pradhan B. , Wategaonkar S. , Singh Bhanu P. , Kundu T.
Published: March 2007

The laser induced fluorescence excitation and dispersed fluorescence spectra of three nitrogen heterocyclic molecules 1-methyl-2(1H)pyridone (1MPY), 1-methyl-2(1H)pyridinimine (1MPI), and 3-methyl-2(1H)pyridone (3MPY) have been studied under supersonic jet cooled condition. The methyl torsional and some low frequency vibrational transitions in the fluorescence excitation spectrum were assigned for 1MPY. These new assignments modify the potential parameters to the methyl torsion reported earlier. Some striking similarities exist between the torsional and vibrational transitions in the fluorescence excitation spectra of 1MPY and 1MPI. Apart from pure torsional transitions, a progression of vibration-torsion combination bands was observed for both these molecules. The excitation spectrum of 3MPY resembles the spectrum of its parent molecule, 2-pyridone. The barrier height of the methyl torsion in the excited state of 3MPY is highest amongst all these molecules, whereas the barrier in 1MPI is higher than that of 1MPY. To get an insight into the methyl torsional barrier for these molecules, results of the ab initio calculations were compared with the experimental results. It was found that the conformation of the methyl group undergoes a 60° rotation in the excited state in all these molecules with respect to their ground state conformation. This phase shift of the excited state potential is attributed to the π*-σ* hyperconjugation between the out-of-plane hydrogen of the methyl group and the molecular frame. It has been inferred that the change in lowest unoccupied molecular orbital energy plays the dominant role in the excited state barrier formation.
Electronic structures and electron detachment energies of halogen substituted acetate anions, XCH2COO− (X=F,Cl,Br)
Authors: Yu Wenbo , Lin Zijing , Ding Chuanfan
Published: March 2007

The electronic structures and the halogen inductive effects on the acetate anion were investigated in XCH2COO− (X=F,Cl,Br) by photoelectron spectroscopy (PES) and ab initio calculations. The PES spectra indicated that the electron binding energies increased in the order of F<Cl<Br, contradictory to the known electron affinities of the halogen atoms. The measured adiabatic detachment energies (ADEs) are 3.80, 3.93, and 3.97eV and the vertical detachment energies (VDEs) are 3.96, 4.10, and 4.13eV for the F-, Cl-, and Br-substituted species, respectively. Structures of these anions and their neutral species were obtained by full geometry optimizations at the CCSD(T)/aug-cc-pVDZ level of theory, and final energies were calculated at the CCSD(T)/aug-cc-pVTZ level. The calculated ADEs (3.76, 3.88, and 3.91eV for F, Cl, Br, respectively) and VDEs (4.14, 4.29, and 4.32eV, respectively) are in good agreement with the corresponding experimental results. Theoretical analysis shows that the increase of ADE/VDE from F to Cl to Br is related to that the matching of the p orbital energy of X with the COO− group is better for Br than that of Cl and F. For comparison, additional calculations were carried out to include halogen substituted ethanol, XCH2CH2OH. Similar trend on electron binding energies was also found. In contrast, the ionization potentials (IPs) of both XCH2COOH and XCH2CH2OH decrease in the order of F>Cl>Br. These systematic changes of detachment energy and IPs were explained by examining the charge redistributions upon detaching electrons.
Effect of magnetic field on dislocation-oxygen impurity interaction in silicon
Authors: Yonenaga I. , Takahashi K.
Published: March 2007

Dislocation-oxygen impurity interaction in Czochralski-grown silicon crystals was influenced by treatments at temperature of 650°C under a magnetic field up to 8T. It was found that the critical stress for dislocation generation from a surface scratch varies with an intensity of the applied magnetic field and duration of the magnetic treatment. The generation of dislocations was effectively suppressed under certain conditions of the magnetic treatments. Such phenomena could not be detected in float-zone-grown silicon crystals. The results were discussed in terms of spin-dependent solid-state reaction in atomic bindings with impurity atoms around dislocation core, causing immobilization of dislocations in their macroscopic generation process.
(
In
,
Ga
)
N
∕
Ga
N
microcavities with double dielectric mirrors fabricated by selective removal of an (Al,In)N sacrificial layer
Authors: Rizzi F. , Edwards P. R. , Bejtka K. , Semond F. , Kang X. N. , Zhang G. Y. , Gu E. , Dawson M. D. , Watson I. M. , Martin R. W.
Published: March 2007

Comparable microcavities with 3λ∕2 (∼240nm) active regions containing distributed (In,Ga)N quantum wells, grown on GaN substrates and bounded by two dielectric mirrors, have been fabricated by two different routes: one using laser lift-off to process structures grown on GaN-on-sapphire templates and the second using freestanding GaN substrates, which are initially processed by mechanical thinning. Both exploit the properties of an Al0.83In0.17N layer, lattice matched to the GaN substrate and spacer layers. In both cases cavity quality factors >400 are demonstrated by measurements of the cavity-filtered room-temperature excitonic emission near 410nm.
Experimental demonstration of bending and splitting of self-collimated beams in two-dimensional photonic crystals
Authors: Kim Myeong-Woo , Lee Sun-Goo , Kim Teun-Teun , Kim Jae-Eun , Park Hae Yong , Kee Chul-Sik
Published: March 2007

The authors have experimentally demonstrated the bending and splitting phenomena of self-collimated microwave beams in a two-dimensional square lattice photonic crystal composed of alumina rods. The bending and splitting were achieved by introducing a line defect in the photonic crystal. The power ratio of two split beams can be controlled by varying the radii of rods in the line defect.