bluuebunny/crossref_metadata_2025 huggingface dataset:
The influence of country-rock assimilation and silicate to sulfide ratios (R factor) on the genesis of the Dunka Road Cu – Ni – platinum-group element deposit, Duluth Complex, Minnesota
Authors: Thériault Robert D. , Barnes Sarah-Jane , Severson Mark J.
Published: December 2009

The Dunka Road deposit is one of several Cu – Ni – platinum-group element (PGE) sulfide occurrences found along the northwestern margin of the Duluth Complex, where the host troctolitic rocks are in contact with metasedimentary rocks of the Animikie Group. Magma contamination through assimilation of sulfidic argillaceous country rocks is generally recognized as having played a key role in the genesis of the mineralization. Three main types of disseminated sulfide mineralization have been identified within the Dunka Road deposit: (i) norite-hosted sulfides, (ii) troctolite-hosted sulfides, and (iii) PGE-rich sulfide horizons. The norite-hosted sulfides are found either adjacent to country-rock xenoliths or near the basal contact. The troctolite-hosted sulfides form the bulk of the deposit, and occur throughout the lower 250 m of the intrusion. The PGE-rich sulfide horizons are typically localized directly beneath ultramafic layers. The composition of the different types of sulfide occurrences is modelled using Cu/Pd ratios. It is shown that each type results from the interplay of two main parameters, namely the degree of magma contamination and the silicate magma to sulfide melt ratio (R factor). The norite-hosted sulfides formed at low R factors and high degrees of contamination, as expressed by their PGE-depleted nature, low Se/S ratios, and elevated content in pyrrhotite and arsenide minerals. The troctolite-hosted sulfides formed at moderate R factors and small degrees of contamination, as shown by their moderate PGE content and mantle-like Se/S ratios. Finally, the PGE-rich sulfide horizons are modelled using elevated R factors from an uncontaminated parental magma, which is substantiated by their elevated noble metal content and Se/S ratios, and low pyrrhotite to precious metal sulfide ratio.
Geochronology of the North American Midcontinent rift in western Lake Superior and implications for its geodynamic evolution
Authors: Davis D. W. , Green J. C.
Published: December 2009

Volcanism in the Midcontinent rift system lasted between 1108 and 1086 Ma. Rates of flood-basalt eruption and subsidence in the western Lake Superior region appear to have been greatest at the beginning of recorded activity (estimated 5 km/Ma subsidence rate at 1108 Ma) and rapidly waned over a period of 1–3 Ma during a magnetically reversed period. The age of the paleomagnetic polarity reversal is now constrained to be between 1105 ± 2 and 1102 ± 2 Ma. A resurgence of intense volcanism began at 1100 ± 2 Ma in the North Shore Volcanic Group and lasted until 1097 ± 2 Ma. This group contains a ca. 7 Ma time gap between magnetically reversed and normal volcanic sequences. A similar disconformity appears to exist in the upper part of the Powder Mill Group. The average subsidence rate during this period was approximately 3.7 km/Ma. Latitude variations measured from paleomagnetism on dated sequences indicate that the North American plate was drifting at a minimum rate of 22 cm/year during the early history of the Midcontinent rift. An abrupt slowdown to approximately 8 cm/year occurred at ca. 1095 Ma. These data support a mantle-plume origin for Midcontinent rift volcanism, with the plume head attached to and drifting with the continental lithosphere. Resurgence of flood-basalt magmatism at 1100 Ma may have been caused by extension of the superheated lithosphere following continental collision within the Grenville Orogen to the east.
Re-Os isotopic compositions of Midcontinent rift system picrites: implications for plume – lithosphere interaction and enriched mantle sources
Authors: Shirey Steven B.
Published: December 2009

Picrites and tholeiites from the Mamainse Point Formation, a 5.3 km thick section of Keweenawan (1100 Ma) volcanic and sedimentary fill on the eastern flank of the central portion of the Midcontinent rift system, contain a nearly continuous record of rift magmatic activity. Picrites occur primarily in the lowermost two units of the formation. In this study, they are compared to rarely exposed, slightly older Keweenawan basalts from the North Shore Volcanic Group and the Powder Mill Group to constrain mantle source compositions during early phases of rift magmatic activity. The most primitive picrites analyzed have low Re content (0.069–0.18 ppb), high Os content (0.8–2.1 ppb), and low 187Re/188Os (0.28–1.18). A Re–Os isochron with an age of 1128 ± 54 Ma and an initial 187Os/188Os of 0.1267 ± 0.0013 (γOs = +5.7) was obtained from a 24-point isochron on all but two analyzed samples. The Re–Os data, regressed separately for the older basalts, and the groups 1 and 2 samples from the Mamainse Point Formation, have barely resolvable initial 187Os/188Os that decrease up-stratigraphy from initial γOs(1100) of +12.2 to +6.2 and +4.2, respectively, and couple with changes in initial Nd isotopic composition. These data can be explained by mixing of melts of an enriched mantle plume and unradiogenic continental lithospheric mantle. A radiogenic initial Os isotopic composition (γOs of +8 or higher) for the Keweenawan plume marks the first known appearance of demonstrably radiogenic plume-derived magmas on Earth. Plume-derived magmas with radiogenic Os signatures are more common later. The radiogenic Os signatures of Keweenawan plume magmas may mark the appearance of melts derived from mantle containing recycled slab components from late Archean subduction.
Rift-wide correlation of 1.1 Ga Midcontinent rift system basalts: implications for multiple mantle sources during rift development
Authors: Nicholson Suzanne W. , Schulz Klaus J. , Shirey Steven B. , Green John C.
Published: December 2009

Magmatism that accompanied the 1.1 Ga Midcontinent rift system (MRS) is attributed to the upwelling and decompression melting of a mantle plume beneath North America. Five distinctive flood-basalt compositions are recognized in the rift-related basalt succession along the south shore of western Lake Superior, based on stratigraphically correlated major element, trace element, and Nd isotopic analyses. These distinctive compositions can be correlated with equivalent basalt types in comparable stratigraphic positions in other MRS localities around western Lake Superior. Four of these compositions are also recognized at Mamainse Point more than 200 km away in eastern Lake Superior. These regionally correlative basalt compositions provide the basis for determining the sequential contribution of various mantle sources to flood-basalt magmatism during rift development, extending a model originally developed for eastern Lake Superior. In this refined model, the earliest basalts were derived from small degrees of partial melting at great depth of an enriched, ocean-island-type plume mantle source (εNd(1100) value of about 0), followed by magmas representing melts from this plume source and interaction with another mantle source, most likely continental lithospheric mantle (εNd(1100) < 0). The relative contribution of this second mantle source diminished with time as larger degree partial melts of the plume became the dominant source for the voluminous younger basalts (εNd(1100) value of about 0). Towards the end of magmatism, mixtures of melts from the plume and a depleted asthenospheric mantle source became dominant (εNd(1100) = 0 to +3).
Proterozoic reactivation of the southern Superior Province and its role in the evolution of the Midcontinent rift
Authors: Manson Matthew L. , Halls Henry C.
Published: December 2009

Major reverse faults associated with the late compressional phase of the 1.1 Ga Midcontinent rift in the western Lake Superior region appear to cut across the rift at the eastern end of the lake and join with reverse faults on the eastern shoreline, defined on the basis of geological and potential field data. The continuation of the faults across eastern Lake Superior is inferred on evidence drawn from nearshore shipborne magnetic surveys together with new interpretations of published bathymetric and GLIMPCE aeromagnetic data. In the Archean Superior Province about 100 km east of Lake Superior, paleomagnetic and petrographic data from the 2.45 Ga Matachewan dyke swarm show that the Kapuskasing Zone, a narrow belt of uplifted crust, can be extended to within 50 km of the Lake Superior shoreline and has bounding reverse faults that are almost continuous with two faults of similar dip and sense of displacement that define the inversion of the Midcontinent rift in the central and western parts of the lake. Since the Kapuskasing Zone is dominantly a Paleoproterozoic (about 1.9 Ga) structure, the continuity suggests that the Lake Superior faults, whose last major activity was during the Grenville Orogen, may represent reactivation of much older faults that were part of an extended Kapuskasing structure. Within the Superior Province to the north and east of Lake Superior, published radiometric data on biotites suggest a series of alternating crustal blocks of varying tectonic stability, separated by northeast-trending faults. The Lake Superior segment of the Midcontinent rift developed within the most unstable block, bounded by the Gravel River fault to the northwest and the Ivanhoe Lake fault (the eastern margin of the Kapuskasing Zone) to the southeast.
Trunk muscle activation during moderate- and high-intensity running
Authors: Behm David G. , Cappa Dario , Power Geoffrey A.
Published: December 2009

Time constraints are cited as a barrier to regular exercise. If particular exercises can achieve multiple training functions, the number of exercises and the time needed to achieve a training goal may be decreased. It was the objective of this study to compare the extent of trunk muscle electromyographic (EMG) activity during running and callisthenic activities. EMG activity of the external obliques, lower abdominals (LA), upper lumbar erector spinae (ULES), and lumbosacral erector spinae (LSES) was monitored while triathletes and active nonrunners ran on a treadmill for 30 min at 60% and 80% of their maximum heart rate (HR) reserve, as well as during 30 repetitions of a partial curl-up and 3 min of a modified Biering-Sørensen back extension exercise. The mean root mean square (RMS) amplitude of the EMG signal was monitored over 10-s periods with measures normalized to a maximum voluntary contraction rotating curl-up (external obliques), hollowing exercise (LA), or back extension (ULES and LSES). A main effect for group was that triathletes had greater overall activation of the external obliques (p < 0.05), LA (p = 0.01), and LSES (p < 0.05) than did nonrunners. Main effects for exercise type showed that the external obliques had less EMG activity during 60% and 80% runs, respectively, than with the curl-ups (p = 0.001). The back extension exercise provided less ULES (p = 0.009) and LSES (p = 0.0001) EMG activity than the 60% and 80% runs, respectively. In conclusion, triathletes had greater trunk activation than nonrunners did while running, which could have contributed to their better performance. Back-stabilizing muscles can be activated more effectively with running than with a prolonged back extension activity. Running can be considered as an efficient, multifunctional exercise combining cardiovascular and trunk endurance benefits.
Moderate and heavy oxygen uptake kinetics in postmenopausal women
Authors: Stathokostas Liza , Kowalchuk John M. , Petrella Robert J. , Paterson Donald H.
Published: December 2009

The lack of estrogen in postmenopausal women not using hormone replacement therapy (HRT), compared with those using HRT, may reduce submaximal blood flow during exercise and result in an oxygen delivery limitation constraining oxygen uptake (VO2) kinetics. The adaptation of pulmonary VO2 (VO2p) during the transition to exercise in older women was examined in this study. Thirty-one healthy postmenopausal women (mean age, 61 ± 6 years), 15 not using HRT and 16 using HRT, performed repeated exercise transitions (6 min) on a cycle, to work rates corresponding to 80% of estimated ventilatory threshold (moderate-intensity exercise) and to Δ50 (heavy-intensity exercise). There was no difference in moderate-intensity τVO2p between non-HRT (40 ± 9 s) and HRT (41 ± 9 s) women. Similarly, there was no difference in heavy-intensity τVO2p between non-HRT (44 ± 8 s) and HRT (45 ± 8 s) women. Thus, HRT did not affect the slowing of VO2 kinetics of older women.
Repeated-sprint ability in professional and amateur soccer players
Authors: Rampinini Ermanno , Sassi Aldo , Morelli Andrea , Mazzoni Stefano , Fanchini Maurizio , Coutts Aaron J.
Published: December 2009

This study investigated the repeated-sprint ability (RSA) physiological responses to a standardized, high-intensity, intermittent running test (HIT), maximal oxygen uptake (VO2 max), and oxygen uptake (VO2) kinetics in male soccer players (professional (N = 12) and amateur (N = 11)) of different playing standards. The relationships between each of these factors and RSA performance were determined. Mean RSA time (RSAmean) and RSA decrement were related to the physiological responses to HIT (blood lactate concentration ([La–]), r = 0.66 and 0.77; blood bicarbonate concentration ([HCO3–]), r = –0.71 and –0.75; and blood hydrogen ion concentration ([H+]),r = 0.61 and 0.73; all p < 0.05), VO2 max (r = –0.45 and –0.65, p < 0.05), and time constant (τ) in VO2 kinetics (r = 0.62 and 0.62, p < 0.05). VO2 max was not different between playing standards (58.5 ± 4.0 vs. 56.3 ± 4.5 mL·kg–1·min–1; p = 0.227); however, the professional players demonstrated better RSAmean (7.17 ± 0.09 vs. 7.41 ± 0.19 s; p = 0.001), lower [La–] (5.7 ± 1.5 vs. 8.2 ± 2.2 mmol·L–1; p = 0.004), lower [H+] (46.5 ± 5.3 vs. 52.2 ± 3.4 mmol·L–1; p = 0.007), and higher [HCO3–] (20.1 ± 2.1 vs. 17.7 ± 1.7 mmol·L–1; p = 0.006) after the HIT, and a shorter τ in VO2 kinetics (27.2 ± 3.5 vs. 32.3 ± 6.0 s; p = 0.019). These results show that RSA performance, the physiological response to the HIT, and τ differentiate between professional- and amateur-standard soccer players. Our results also show that RSA performance is related to VO2 max, τ, and selected physiological responses to a standardized, high-intensity, intermittent exercise.
High-intensity interval training attenuates the exercise-induced increase in plasma IL-6 in response to acute exercise
Authors: Croft Louise , Bartlett Jonathan D. , MacLaren Don P.M. , Reilly Thomas , Evans Louise , Mattey Derek L. , Nixon Nicola B. , Drust Barry , Morton James P.
Published: December 2009

This aims of this study were to investigate the effects of carbohydrate availability during endurance training on the plasma interleukin (IL)-6, IL-8, and tumor necrosis factor (TNF)-α response to a subsequent acute bout of high-intensity interval exercise. Three groups of recreationally active males performed 6 weeks of high-intensity interval running. Groups 1 (LOW+GLU) and 2 (LOW+PLA) trained twice per day, 2 days per week, and consumed a 6.4% glucose or placebo solution, respectively, before every second training session and at regular intervals throughout exercise. Group 3 (NORM) trained once per day, 4 days per week, and consumed no beverage during training. Each group performed 50 min of high-intensity interval running at the same absolute workloads before and after training. Muscle glycogen utilization in the gastrocnemius muscle during acute exercise was reduced (p < 0.05) in all groups following training, although this was not affected by training condition. Plasma IL-6 concentration increased (p < 0.05) after acute exercise in all groups before and after training. Furthermore, the magnitude of increase was reduced (p < 0.05) following training. This training-induced attenuation in plasma IL-6 increase was similar among groups. Plasma IL-8 concentration increased (p < 0.05) after acute exercise in all groups, although the magnitude of increase was not affected (p > 0.05) by training. Acute exercise did not increase (p > 0.05) plasma TNF-α when undertaken before or after training. Data demonstrate that the exercise-induced increase in plasma IL-6 concentration in response to customary exercise is attenuated by previous exercise training, and that this attenuation appears to occur independent of carbohydrate availability during training.
Bioscrubbing as a treatment for a complex mixture of volatile organic compounds: influence of the absorption column characteristics on performanceThis article is one of a selection of papers published in this Special Issue on Biological Air Treatment.
Authors: Malhautier Luc , Lalanne Franck , Fanlo Jean-Louis
Published: December 2009

A semi-industrial bioscrubber was developed to treat a complex mixture of volatile organic compounds (VOCs), including oxygenated, aromatic, and chlorinated compounds. Packed and atomizing columns were used for the bioscrubber. For an applied inlet load of around 850–870 g VOCs·m–3 packing material·h–1, the various performances of the bioscrubber were equivalent (around 50%), regardless of the selected absorption column. Only the removal efficiency of oxygenated compounds was found to be reasonable, close to 80%–85%. For the bioscrubber equipped with an atomizing column, a doubling of the inlet load involved a decrease in the removal efficiency of the VOC mixture (35%) and oxygenated compounds (from 80% to 55%). As the transferred compounds were biodegraded, the limits could be explained by the hydrodynamic characteristics of the atomizing column. Furthermore, these results demonstrate the necessity of optimizing the gas–liquid mass transfer step. Two-phase partitioning bioreactors seem to represent an attractive option, even though knowledge of the transfer of compounds and biodegradation mechanisms is required prior to scale-up and industrial use.
Treatment of air polluted with methanol vapours in biofilters with and without percolationThis article is one of a selection of papers published in this Special Issue on Biological Air Treatment.
Authors: Avalos Ramirez Antonio , Bénard Sandrine , Giroir-Fendler Anne , Jones J. Peter , Heitz Michèle
Published: December 2009

Air polluted with methanol vapours was treated in a biofilter and a biotrickling filter, both packed with inert materials. The effects of the nitrogen concentration present in the nutrient solution, the empty bed residence time, and the methanol inlet load, on the biofilter and biotrickling filter performance were all examined and compared. The elimination capacity, the biomass and the carbon dioxide production rates all increased with the increase of the parameters tested. The maximum elimination capacity for the biotrickling filter was 240 g·m–3·h–1 with corresponding removal efficiency of 75% and carbon dioxide production rate of 10 g·m–3·h–1, whereas the maximum elimination capacity for the biofilter was 80 g·m–3·h–1 with corresponding removal efficiency of 35% and carbon dioxide production rate of 70 g·m–3·h–1. The biomass production rate was similar for both the biofilter and the biotrickling filter. The carbon dioxide production rate was higher by a factor of 2 to 9 for the biofilter compared to the biotrickling filter.
Biofiltration of methane using an inorganic filter bed: Influence of inlet load and nitrogen concentrationThis article is one of a selection of papers published in this Special Issue on Biological Air Treatment.
Authors: Nikiema Josiane , Girard Matthieu , Brzezinski Ryszard , Heitz Michèle
Published: December 2009

An upflow lab-scale biofilter was operated with an inorganic filter material to control methane emissions. The influence of the inlet load on methane removal was investigated and the maximum elimination capacity obtained was 36 g/(m3·h) for an inlet load of 95 g/(m3·h). The influence of the nitrogen concentration, which was provided in the form of nitrate through a nutrient solution, was also determined. We established that the optimum nitrogen concentration required for biofilter operation decreases with the methane inlet load. In fact, it was around 0.75 g/L for inlet loads comprised between 55 and 95 g/(m3·h) and of 0.50 g/L when the inlet load was comprised between 20 and 55 g/(m3·h). During this study, a nitrogen concentration of 1.00 g/L inhibited methane removal in the biofilter. In addition, the use of a nitrogen concentration superior to its optimum level can cause, in the long-term run, severe damages to the biofilter performance.
Characterization and substrate specificity of fumarylacetoacetate fumarylhydrolase
Authors: Mahuran D. J. , Angus Ronald H. , Braun Carl V. , Sim S. S. , Schmidt Jr. Donald E.
Published: December 2009

The molecular weight of fumarylacetoacetate fumarylhydrolase (EC 3.7.1.2) is 86 000 ± 10 000, as determined by gel filtration. The enzyme appears to be a dimer with a monomer molecular weight of 38 000 – 43 000, as determined by gel electrophoresis, gel filtration in guanidine–hydrochloride, and ultracentrifugation. The subunits appear to be identical, as only one band is seen in gel electrophoresis, only one protein peak is detected in gel filtration in guanidine–hydrochloride, and only one amino-terminal amino acid (proline) is detected. Three free sulfhydryl groups per denatured monomer are detected by reaction with 5,5′-dithiobis(2-nitrobenzoic acid), while for the active enzyme only two sulfhydryl groups react with this reagent. The extinction coefficients at 260 and 280 nm, the amino acid composition, and the isoelectric point (6.7) of the enzyme are also reported.The enzyme catalyzes the hydrolysis of six 2,4-diketo acids and three 3,5-diketo acids tested. The Km of the substrates is similar but V varies by a factor of 120. The pH optimum is 7.3. The enzyme did not catalyze the hydrolysis of a number of esters tested.
Electron-microscopic visualization of transcriptionally active and less active chromatin fractions from the rat ventral prostate and their content of histones
Authors: Shirley M. A. , Anderson K. M.
Published: December 2009

The content of histones in transcriptionally active (euchromatin-like (E)) and transcriptionally less active (heterochromatin-like (H)) fractions from the rat ventral prostate was determined. The absolute amount of total histone was less in the E fraction, which contained relatively more stained histone F2b and F3 and less histone F1 than either the H fraction or unfractionated chromatin.The phosphotungstic-acid-stained E fraction was composed predominantly of shorter (50–500 nm) and thinner (5–15 nm) structures. In some preparations, pieces estimated to be 500–1000 + nm in length were present. Spherical structures, from 10 to 20 nm in diameter, some of which were present as 'dimers,' trimers,' or higher-ordered ensembles were seen in the shadow-cast E fraction. The stained or shadow-cast H fraction contained longer (200–2000 + nm) and thicker [Formula: see text] fragments with a more complex substructure. When the shadow-cast H fraction was sufficiently dispersed, it had a nodular or 'beaded' appearance.
The occurrence and seasonal variation of gigartinine and L-citrullinyl-L-arginine in Chondrus crispus Stackh
Authors: Laycock M. V. , Craigie J. S.
Published: December 2009

Gigartinine, 5-(3-amidinoureido)-2-aminovaleric acid, and L-citrullinyl-L-arginine were islated from aqueous extracts of Chondrus crispus (Rhodophyceae). Their identifications were confirmed by chemical procedures, and 1H and 13C nuclear magnetic resonance and infrared spectroscopic methods. Citrullinylarginine, gigartinine, taurine, citrulline, and glutamic acid were the predominant free amino compounds. Citrullinylarginine showed the most pronounced change in concentration. This occurred during the winter months when it reached a maximum (in March) of 58 μmol/g fresh weight, a value 10 times greater than that of any of the free amino acids and equal to 50% of the total organic nitrogen in the plant. All of these compounds were depleted to a minimum of about 1 μmol/g fresh weight in October. Both gigartinine and citrullinylarginine were detected in Ahnfeltia plicata, Gracilaria sp. Petrocelis middendorfii, Polyides rotundus, Polysiphonia lanosa, and Rhodomela confervoides.
Steroid β-D-glucosidase in steer liver and kidney
Authors: Williamson Denis G. , Gwilliam Cynthia , Layne Donald S.
Published: December 2009

Homogenates of liver and kidney tissue from young steers had β-D-glucosidase (EC 3.2.1.21) activity toward 17α-estradiol-3-glucoside, 17β-estradiol-3-glucoside, 17α-estradiol-17-glucoside, and deoxycorticosterone-21-glucoside. The activity towards the phenolic 3-glucosides was largely present in the 100 000 × g supernatant, while that towards 17α-estradiol-17-glucoside was concentrated in the microsomes. The use of beef liver preparations for the hydrolysis of steroid 'glucuronide' fractions could result in hydrolysis of other steroid glycosides which might be present.
Investigation of the quaternary structure of Neurospora pyruvate kinase by cross-linking with bifunctional reagents: the effect of substrates and allosteric ligands
Authors: Kapoor M. , O'Brien M. D.
Published: December 2009

Pyruvate kinase (EC 2.7.1.40) of Neurospora, a tetramer composed of apparently identical subunits, has been shown to be a dimer of dimers by interprotomeric cross-linking experiments in which bifunctional reagents were used. An analysis of the polyacrylamide gel profiles of the enzyme after cross-linking with glutaraldehyde, dimethyl suberimidate, and dimethyl adipimidate shows that the extent of intersubunit cross-linking is influenced markedly by the ligand bound to the enzyme. Bifunctional cross-linking reagents with a shorter distance between the two functional groups form cross-links effectively in the unliganded enzyme. In the FDP – pyruvate kinase complex, cross-linking was observed over longer distances compared with the unliganded enzyme. It is demonstrated that covalent cross-linkers can be used as sensitive indicators of conformational changes induced in pyruvate kinase by substrates and allosteric ligands.
Radioactive conversion products of intramuscularly injected [4-14C]formononetin including sulfates in the urine of hens
Authors: Chang Herbert Hang-Shing , Robinson Arthur Robin , Chan Albert Hon-Hang , Common Robert Haddon
Published: December 2009

The phytoestrogen formononetin was injected intramuscularly as [4-14C]formononetin into two adult hens. Radioactive materials in the urine for the succeeding 14 days (hen 1) or 16 days (hen 2) were fractionated on DEAE-Sephadex-25 columns by elution with a gradient of NaCl; the four major fractions thus separated were examined by solvent partition, thin-layer chromatography, and enzymic cleavage. The following seven radioactive components were identified in the urine, the average proportions of each being given in terms of percentage of total 14C recovered from the urine: [14C]formononetin (4.3%); [14C]daidzein (11.4%); [14C]equol (6.8%); [14C]daidzein monosulfate (30.4%); [14C]equol monosulfate (5.8%); [14C]daidzein disulfate (19.8%); and [14C]equol disulfate (6.5%). Small proportions of sulfates of unidentified radioactive phenols were present. Tests for presence of glucosiduronates of 14C-labelled material gave negative results. Radioactive formononetin sulfate was not detected in the urine of either hen.
The effect of chronic iron deficiency on adrenal tyrosine hydroxylase activity
Authors: Quik Maryka , Sourkes Theodore L.
Published: December 2009

Chronic nutritional iron deficiency of 2 to 5 weeks duration reduced the blood hemoglobin content to 30–50% of control values and resulted in an increase in rat adrenal tyrosine hydroxylase (TH) (EC 1.14.16.2) activity. Kinetic and mixing experiments indicated that this increase was due to an increase in enzyme protein. The body weight of iron-deficient rats ranged from 60 to 80% of control; this factor, however, was not responsible for the increase in adrenal TH as enzyme activity was directly proportional to final body weight. To determine whether the increase in adrenal TH in iron-deficient rats was due to increased sympathetic activity to the adrenal medulla, the splanchnic nerve was cut. The increased TH was still observed after adrenal denervation; this indicates that the mechanism of response to iron deficiency lies within the adrenal itself. Age of the rats is important in determining whether the increase in TH activity will occur.
Synthesis and solution conformation of [Trp1, Val5]-angiotensin II
Authors: Schiller Peter W.
Published: December 2009

[Trp1, Val5]-Angiotensin II was synthesized by the solid-phase method and purified by partition chromatography on Sephadex G-25 and by ion-exchange chromatography on Sephadex SP-25. Relative to [Val5]-angiotensin II, the analog displayed 36% smooth muscle activity in a preparation of the superior mesenteric artery. Conformational aspects of the analog were revealed by fluorescence techniques. The fluorescence emission maximum at 350 nm suggests a completely aqueous environment for the tryptophanyl residue in [Trp1, Val5]-angiotensin II. Singlet–singlet resonance energy transfer between Tyr in position 4 and Trp in position 1 was evaluated for a calculation of the intramolecular distance between these two residues on the basis of the Förster equation. From the relative increase of tryptophan fluorescence a transfer efficiency of > 0.9 was obtained, which is compatible with the observed complete quenching of tyrosine fluorescence in the analog. The computed average intramolecular distance of < 8 Å precludes an extended conformation for the N-terminal sequence encompassing residues 1 through 4 at neutral pH and suggests the existence of a loop in this part of the molecule. The results are discussed in relation to the various models proposed for the solution conformation of angiotensin II.
Inhibitory action of the adenine analog, 4-aminopyrazolo(3,4-d)pyrimidine, in Crithidia fasciculata
Authors: Dewey Virginia C. , Kidder G. W.
Published: December 2009

The adenine analog 4-aminopyrazolo(3,4-d)pyrimidine inhibits the growth of the kinetoplastid (trypanosomatid) flagellate Crithidia fasciculata. This inhibition is partially overcome only by adenine (of a number of purines tested), with an inhibition index of 0.025. More effective reversal of inhibition is obtained with any of a number of naturally occurring pyrimidine compounds, up to a concentration of 0.18 mM. Higher concentrations of pyrimidines or addition of guanine, as well as adenine and uracil, to the medium increases inhibition. The analog (presumably as the ribonucleotide) was found not to be inhibitory to any enzyme of the pyrimidine biosynthetic pathway that could be tested. It is suggested that the analog competes with adenine for adenine phosphoribosyltransferase (AMP:pyrophosphate phosphoribosyltransferase, EC 2.4.2.7), is converted to a ribonucleotide, and is incorporated into nucleic acid.
D-Glucose uptake and insulin binding by the human adipose cell plasma membrane as a function of its polypeptide composition
Authors: Brenner Bluma G. , Ozaki Shiro , Kalant Norman , Kahlenberg Arthur
Published: December 2009

A preparation of plasma membranes isolated from human omental lipocytes is composed of about 15 major polypeptide components including three major glycoproteins with an apparent molecular weight range from 100 000 to 23 000, as determined by sodium dodecyl sulfate – polyacrylamide gel electrophoresis. Extraction of this membrane preparation with sodium iodide or 2,3-dimethylmaleic anhydride solubilized 50 and 70% of the membrane protein, respectively, resulting from the extensive extraction of protein from all but two of the major membrane polypeptide components. This removal of protein did not affect the membrane's stereospecific D-glucose-uptake activity but did reduce its total specific [l25I]insulin-binding activity by 46–67%. The binding of [125I]insulin to its specific receptor on lipocyte plasma membranes was detected at physiologic concentrations of the hormone and could be competitively displaced by increasing concentrations of native insulin. The kinetic behaviour of this reaction was approximated by Scatchard analysis, and both the affinity and binding capacity of the plasma membrane for insulin were increased at lower temperatures.These results suggest that D-glucose transport in human adipose tissue is mediated by an intrinsic component of the hydrophobic structure of the lipocyte plasma membrane, and represent a partial purification of this component. In addition, these studies demonstrate and characterize the binding of insulin to the plasma membrane isolated from human lipocytes. A quantitative study of this binding reaction may provide further understanding of the mechanisms underlying the decreased insulin responsiveness characteristic of human diabetes.
Characterization of the interaction between chymotrypsin and heparin
Authors: Twining Sally S. , Brecher Arthur S.
Published: December 2009

Heparin forms a complex with chymotrypsin which is active towards glutaryl-L-phenylalanine-p-nitroanilide (GPANA) and glutaryl-L-phenylalanine-β-naphthylamide (GPNA) at pH 7.6. The activity of chymotrypsin towards GPANA at pH 7.6 is enhanced in the presence of heparin. Heparin does not bind at the active site of the enzyme since proflavin is not displaced from the active site of chymotrypsin upon complex formation. The heparin–chymotrypsin complex migrates under basic polyacrylamide disc gel electrophoresis conditions to a position intermediate between heparin and free chymotrypsin. The complex is dissociable under acidic polyacrylamide gel electrophoresis conditions. It is estimated that one to three molecules of heparin can bind to each chymotrypsin molecule on the basis of electrophoretic and enzymic activity data.
The β-glucosidases of porcine kidney
Authors: Kanfer Julian N. , Mumford Richard A. , Raghavan Srinivasa S.
Published: December 2009

Some of the properties of a partially purified particle bound and soluble β-glucosidase (EC 3.2.1.21) from pig kidney were compared. The soluble β-glucosidase (1) hydrolyzed 4-methylumbelliferyl-β-D-glucoside (4-MU-β-D-glucoside) 17α-estradiol 3β-glucoside, 17α-estradiol 17β-glucoside, and salicin, but not glucosylceramide, (2) possessed a broad pH optimum (5.5–7.0), (3) had an isoelectric point of 4.9, and (4) was inhibited by Triton X-100. Several compounds were found to be competitive inhibitors of its hydrolytic activity, gluconolactam and estrone β-glucoside being the most effective. In contrast, a particulate β-glucosidase purified from the same tissue (1) had an acidic pH optimum (5.0), (2) was stimulated by sodium taurocholate and 'Gaucher's factor' for the hydrolysis of both 4-MU-β-glucoside and glucosylceramide, and (3) was capable of catalyzing a transglucosylation reaction employing 4-MU-β-D-glucoside or glucosylceramide as the glucosyl donor, and [l4C]ceramide as acceptor.
Isolation and properties of a ferredoxin from leaves of Sambucus racemosa L.
Authors: Altosaar I. , Bohm B. A. , Taylor I. E. P.
Published: December 2009

Ferredoxin was isolated in good yield from leaves of Sambucus racemosa L. by the following procedure: (1) homogenization in buffered acetone–water (1:1,v/v); (2) ion-exchange chromatography on several columns of DEAE-cellulose; and (3) purification by gel filtration with Sephadex G-75. The ultraviolet and visible spectrum showed maxima at 277, 331, 423, and 466 nm. The electron paramagnetic resonance spectrum was centered around g = 1.957. The protein sustained an initial photoreduction rate of 86 μmol NADP per milligram chlorophyll per hour. The amino acid composition was found to be Lys5, His2, Arg1 Asx11, Thr5, Ser7, Glx17, Pro6, Gly7, Ala6–7, Cys4, Val8, Ile5, Leu7, Tyr3, Phe2, and Trp1 The molecule had a molecular weight of 10 700 and contained two atoms of iron. The amino-terminal residue was alanine. These properties are highly similar to those of other angiosperm ferredoxins. Sambucus ferredoxin was found to be most closely related to that of Leucaena.
Temperature-induced changes in lecithin model membranes detected by novel covalent spin-labelled phospholipids
Authors: Stuhne-Sekalec L. , Stanacev N. Z.
Published: December 2009

Several spin-labelled phospholipids carrying covalently bound 5-doxylstearic acid (2-(3-carboxydecyl)-2-hexyl-4,4-dimethyl-3-oxazolidinoxyl) were intercalated in liposomes of saturated and unsaturated lecithins. Temperature-induced changes of these liposomes, detected by the spin-labelled phospholipids, were found to be in agreement with the previously described transitions of hydrocarbon chains of host lecithins detected by different probes and different techniques, establishing that spin-labelled phosopholipids are sensitive probes for the detection of temperature-induced changes in lecithin model membranes. In addition to the detection of already-known transitions in lecithin liposomes, the coexistence of two distinctly different environments was observed above the characteristic transition temperature. This phenomenon was tentatively attributed to the influence of the lecithin polar group on the fluidity of fatty acyl chains near the polar group. Combined with other results from the literature, the coexistence of two environments could be associated with the coexistence of two conformational isomers of lecithin, differing in the orientation of the polar head group with respect to the plane of bilayer. These findings have been discussed in view of the present state of knowledge regarding temperature-induced changes in model membranes.
Activity of purified and chromatin-associated mouse TLT hepatoma RNA polymerases on homologous whole chromatin and euchromatin-enriched segments isolated from homologous chromatin
Authors: Smith Ralph J. , Duerksen Jacob D.
Published: December 2009

The RNA polymerase (EC 2.7.7.6) activity of mouse TLT hepatoma nuclei is separable into three forms, I, IIA, and IIB; each of these partially purified enzymes demonstrates characteristics generally similar to those reported for these enzymes of other systems. All three forms of TLT hepatoma RNA polymerase show a considerable preference for single-stranded DNA. The full expression of the endogenous RNA polymerase activity of mouse TLT hepatoma chromatin is dependent on the salt concentration. No additional template activity to added RNA polymerase I or II is available. Physical shearing decreased endogenous RNA polymerase activity and increased template capacity to the added enzymes. Glycerol-gradient fractionation of physically sheared chromatin gave a fairly diffuse distribution of the endogenous RNA polymerase activity to the marginally euchromatin-enriched fractions. However, enzymatic shearing of TLT hepatoma chromatin by Mg,Ca-dependent autodigestion results in a distribution of endogenous RNA polymerase activity to the highly euchromatin-enriched fractions similar to that obtained for nascent RNA (Paul, I. J. &Duerksen, J. D. (1976) Biochem. Biophys. Res. Commun. 68, 97–105). The distribution patterns of template capacity determined with added RNA polymerase I and II differed somewhat from the above distributions and varied with the length of autodigestion. Shearing by autodigestion is preferred, and followed by glycerol-gradient centrifugation permits a considerable enrichment for euchromatic segments.
Evidence from rotatory measurements for an intermediate state in the guanidine hydrochloride denaturation of β-lactoglobulin
Authors: Ananthanarayanan V. S. , Ahmad F.
Published: December 2009

We present here the results of our studies on the ultraviolet rotatory characteristics of β-lactoglobulin in the native as well as in the heat- and guanidine-hydrochloride-denatured states. In comparison to the native protein, the ellipticity at 220 nm, [θ]220, is more negative for the heat-denatured state but more positive for the guanidine-hydrochloride-denatured state. On the basis of other evidence, the heat-denatured state is known to have less ordered structure than the native protein but not as completely disordered as the guanidine-hydrochloride-denatured state. Taking this into account, the observed changes in [θ]220 on denaturation have been interpreted in terms of anomalous effects that could arise from the exposure, during denaturation, of asymmetrically-placed aromatic residues or of β structure regions situated in a hydrophobic environment in the native protein molecule. During the transition from the native to the guanidine-hydrochloride-denatured state, [θ]220 is found to go through a change towards more negative values at lower concentrations of guanidine hydrochloride (< 2.3 M) before changing to more positive values at higher concentrations of the denaturant. This, in conjunction with the noncoincidence of the transition profiles obtained by [θ]220 on the one hand and the ellipticity or difference absorbance at 290 nm on the other, provides evidence for the presence of an intermediate state in the early stages of the denaturation of β-lactoglobulin by guanidine hydrochloride.
The role of carbohydrate in the glycoenzyme invertase of Neurospora crassa
Authors: Tashiro Yuji , Trevithick John R.
Published: December 2009

Data obtained concerning the carbohydrate moieties of the glycoenzyme invertase (EC 3.2.1.26, β-D-fructofuranoside fructohydrolase) from Neurospora crassa were consistent with a linkage of some carbohydrate chains by O-glycosidic bonds to serine and threonine residues; the possibility of N-glycosylamine linkage of some of the carbohydrate to the amide group of asparagine is also indicated. The invertase was remarkably stable on storage at low temperatures. Oxidation of the carbohydrate residues in the enzyme by sodium periodate markedly affected the heat-stability of the enzyme. It is suggested that the carbohydrate moieties function as stabilizers of the tertiary structure of the glycoenzyme.
γ-L-Glutamyl-L-cysteine: its isolation and identification from wheat germ
Authors: Tkachuk Russell , Mellish V. J.
Published: December 2009

γ-L-Glutamyl-L-cysteine was isolated from wheat germ as the S-[2-14C]carboxymethyl derivative. Identity of the peptide was established by amino acid analysis, N-terminal procedures and mass spectroscopy.
Glutathione–insulin transhydrogenase activity in pregnant mouse mammary gland: hormonal influences studied in tissue culture
Authors: Ferrier B. M. , Hendrie J. M. , Cardy C. A.
Published: December 2009

Glutathione–insulin transhydrogenase (GIT) activity has been shown to be stimulated in culture of explants of pregnant mouse mammary gland by a mixture of insulin, cortisol, and prolactin. Since this hormone mixture stimulates lactogenesis in vitro it is possible that the increase in GIT activity is functionally related to one of the processes of milk secretion or ejection. Oxytocin is degraded by GIT and the interaction of this hormone with its mammary gland receptors may be influenced by the change in enzyme activity. The increase in GIT activity caused by insulin, cortisol, and prolactin in vitro can be prevented by the addition of progesterone or oxytocin to the culture medium.
Histone 5 from carp erythrocytes
Authors: Miki B. L. A. , Neelin J. M.
Published: December 2009

Histone 5 (H5) has been isolated from carp (Cyprinus carpio) erythrocytes and identified by its amino acid composition. It was found in very small relative amounts, despite the use of either 50 mM sodium bisulfite or 1.0 mM phenylmethylsulfonyl fluoride to inhibit endogenous protease activity. Carp H5 differed significantly from H5's of other lower vertebrates in its amino acid composition, position of elution from Amberlite CG-50 ion-exchange columns, and its unusually high electrophoretic mobility. The extensive quantitative and qualitative variability of H5 from different species must be reconciled with the presumed functional homology of these cells.
Synthesis of soluble dextran–hemoglobin complexes of different molecular sizes
Authors: Chang Jian E. , Wong J. Tze-Fei
Published: December 2009

Experimental conditions were defined that determined the synthesis of dextran–hemoglobin complexes through the alkylation of hemoglobin by N-bromoacetylaminoethylaminodextran. Using appropriate concentrations of the two reactants, over 90% yield of dextran–hemoglobin was obtained for dextrans of average molecular weight of 200 000, 110 000, 70 000, 40 000, and 20 000. Extensive viscosity increase due to crosslinking could be avoided, and a large molar excess of dextran over hemoglobin made unnecessary, under the optimal conditions.
The interactions between cytochrome c and cytochrome oxidase that determine the conformation of the oxidized oxidase
Authors: Kornblatt Jack A.
Published: December 2009

1. Cytochrome c2+ increases the rate at which cytochrome oxidase (EC 1.9.3.1) λmax428 nm) converts to its conformational isomer (λmax418–423 nm) but cytochrome c3+ has little effect on the conversion rate.2. Interactions between reduced cytochrome oxidase and cytochrome c were studied in the absence of electron flow using anaerobic Sephadex columns.3. Oxidase that is reduced by cytochrome c2+ or other reductant forms the 418- to 423-nm isomer if its last contact, before oxidation, is with cytochrome c3+. If the reduced oxidase contacts cytochrome c2+, before oxidation, the 428-nm oxidase forms.
Mechanism of action of Zn2+ and Mg2+ on rat placenta alkaline phosphatase. II. Studies on membrane-bound phosphatase in tissue sections and in whole placenta
Authors: PetitClerc Claude , Fecteau Claude
Published: December 2009

Alkaline phosphatase (EC 3.1.3.1) bound to trophoblastic cells in rat placenta is activated by Mg2+ and inhibited by Zn2+ in the same way as is found with partially purified soluble alkaline phosphatase in the same tissue (PetitClerc, C., Delisle, M., Martel, M., Fecteau, C. &Brière, N. (1975) Can. J. Biochem. 53, 1089–1100). In studies done with tissue sections (6–10 μm), it is shown that alkaline phosphatase activity and labelling of active sites by orthophosphate are lost during incubation with ethanolamine at pH 9.0. Addition of Mg2+ causes total recovery of catalytic activity and active sites labelling. Zn2+ displaces and replaces at the Mg2+ binding sites. The affinity for both ions is similar, and dissociation of Zn2+ from the enzyme is a very slow process, even in the presence of Mg2+. The Zn2+–alkaline phosphatase and Mg2+–alkaline phosphatase, which only differ by the ion bound to an apparent modulator site, have the same catalytic activity at pH <7.0, but the Zn2+ species has little activity at alkaline pH. Phosphorylation of the enzyme by orthophosphate indicates that with both enzyme species phosphoryl intermediate does not accumulate at alkaline pH. These results suggest that with orthophosphate, the phosphorylation step is rate determining for both enzymes, and that Zn2+ affects this step to a much greater extent. It is proposed that Zn2+ and Mg2+ regulate alkaline phosphatase in rat placenta. The concentration of both ions in maternal serum and placenta suggest that such a mechanism could exist in vivo.
N-terminal amino acid sequences of acid proteases: acid proteases from Penicillium roqueforti and Rhizopus chinensis and alignment with penicillopepsin and mammalian proteases
Authors: Gripon Jean-Claude , Rhee Sung H. , Hofmann Theo
Published: December 2009

The amino-terminal sequence (33 residues) of the acid protease from Penicillium roqueforti has been determined with an automated sequencer. The amino-terminal sequence of Rhizopus pepsin (published by Sepulveda, P., Jackson, K. W. &Tang, J. (1975) Biochem. Biophys. Res. Commun. 63, 1106–1112) has been extended from 27 residues to 39 residues. Also, it was found that two forms of Rhizopus pepsin differ in position 15, where Rhizopus pepsin I has an isoleucine and Rhizopus pepsin II a valine residue. The new sequences have been aligned with the amino-terminal sequences of penicillopepsin (EC 3.4.23.7), pig pepsin (EC 3.4.23.1), calf chymosin (EC 3.4.23.4), human pepsin (EC 3.4.23.2), human gastricsin (EC 3.4.23.3), and cow pepsin (EC 3.4.23.1). Residues 31–35 (numbering based on pig pepsin, Tang, J., Sepulveda, P., Marciniszyn, Jr., J., Chen, K.S.C., Huang. W.-Y., Tao, N., Liu, D. &Lanier, P. (1973) Proc. Natl. Acad. Sci. U.S.A. 70, 3437–3439) are identical in all enzymes. This section contains one of the two aspartic acids (Asp-32) implicated in the active site. The similarity of the sequences provides strong evidence for the homology of these acid proteases.