bluuebunny/crossref_metadata_2025 huggingface dataset:
Evidence for mantle heterogeneity from platinum-group-element abundances in Indian Ocean basalts
Authors: Fryer Brian J. , Greenough John D.
Published: December 2009

Oceanic-island tholeiitic basalts recovered from four sunken oceanic islands along the Reunion hot-spot trace show trace-element and mineralogical characteristics ranging from typical oceanic-island tholeiites to incompatible-element-depleted tholeiites resembling mid-ocean-ridge basalts. There are also variable degrees of magma evolution at each island. Noble metal (Au, Pd, Pt, Rh, Ru, Ir) abundances tend to decrease with magma evolution and with magma "alkalinity", indicating that the metals behave as compatible elements during crystal fractionation processes and during mantle melting processes. Palladium-to-iridium ratios also decrease with increasing alkalinity. Absolute abundances of elements such as Pd are higher than those in typical mid-ocean-ridge basalts, by factors up to 30, despite many major-element similarities with the latter. Comparison with other types of mafic rocks shows that Pd/Ir ratios increase with decreasing alkalinity in basaltic rocks but plunge to alkali-basalt values in komatiites. A model involving retention of low-melting-point Au, Pd, and Rh in mantle sulphides, which completely dissolve by intermediate percentages of melting, and the high-melting-point metals Ir and Ru in late-melting mantle alloys explains increasing Pd/Ir ratios with decreasing alkalinity (increasing melting percentages) in oceanic basalts and the low Pd/Ir ratios of high-percentage melt komatiites.The high noble metal concentrations in Indian Ocean basalts compared with basalts from many other ocean basins are most easily explained by higher concentrations in their source regions. This may be related to incomplete mixing of a post-core-formation meteoritic component of the upper mantle, or deep mantle plume-derived blebs of core material that either failed to reach the core, during core–mantle differentiation, or were plucked from the core by a convecting lower mantle. The latter is tentatively favoured due to the apparently higher noble metal concentrations in oceanic-island (plume) basalts.
A seismic reflection study of northern Baffin Bay: implication for tectonic evolution
Authors: Jackson H. Ruth , Dickie Kate , Marillier François
Published: December 2009

Reflection profiles offshore of Baffin Island, south of Lancaster Sound, reveal coast-parallel half-grabens containing flat-lying sedimentary sections typical of a rifted margin. In northernmost Baffin Bay, adjacent to Devon and southern Ellesmere islands, four sedimentary basins are identified. In these basins the sedimentary sections are faulted, folded, and laterally discontinuous. The basement shows linear trends, steep faults, and abrupt variations in depth. In one basin a 50 km long and 10 km wide "flower structure" is observed. A transpressive tectonic regime is suggested to explain the uplifted sedimentary and basement section and the change in depth to basement across it. A 150 km long paleoshelf, buried by a thickening sedimentary wedge, is present offshore of Devon Island. Because strike-slip and compressional features are observed on seismic profiles north of Lancaster Sound and extensional features are observed to the south, differences in the plate tectonic development are inferred. The interpretations of the seismic reflection records are shown to be compatible with plate motions determined by matching magnetic anomalies in the North Atlantic, the Labrador Sea, the Norwegian and Greenland seas, and the Eurasia Basin. In addition, the onshore geology of Baffin Island, Labrador, and Greenland is consistent with the predrift position of the plates.
A Glacier Peak and Mount Saint Helens J volcanic ash couplet and the timing of deglaciation in the Colville Valley area, Washington
Authors: Carrara Paul E. , Trimble Deborah A.
Published: December 2009

A Late Pleistocene volcanic ash couplet consisting of a Glacier Peak ash layer and an underlying Mount Saint Helens J ash layer has been identified at three sites in the Colville Valley area of northeastern Washington. This ash couplet has been reported as far east as northwestern Montana and therefore appears to have widespread distribution south of the International Boundary. Because areas covered by the Cordilleran Ice Sheet, as well as by local mountain glaciers and icefields, were undergoing extensive deglaciation when these ash layers were deposited, about 11 200 BP, the ash couplet is an important time-stratigraphic marker, and its identification at a site provides information about the extent of deglaciation at that time.The ash couplet is easily recognized in the study area. Distinguishing characteristics include (i) the medium-sand-size (0.2–0.4 mm) rounded glass fragments and abundant mafic crystals in the fine-sand fraction of the Glacier Peak ash, a white layer 5–10 mm thick; (ii) the fine sandy silt and mafic-crystal-poor Mount Saint Helens J ash, also a white layer 5–10 mm thick, below the Glacier Peak ash; and (iii) the stratigraphic position of the couplet beneath the much younger Mazama ash.The presence of the Glacier Peak and Mount Saint Helens J ash couplet in the Colville Valley, about 50 km north (upglacier) from the Late Wisconsin terminal moraine near the town of Springdale, indicates that the active margin of the Colville sublobe of the Cordilleran Ice Sheet had retreated at least that distance by 11 200 BP.
Bracketing ages for the formation of the Ring Creek lava flow, Mount Garibaldi volcanic field, southwestern British Columbia
Authors: Brooks Gregory R. , Friele Pierre A.
Published: December 2009

The Ring Creek lava flow, extending from Opal Cone, generally is considered to be the youngest volcanic feature in the southern section of the Mount Garibaldi volcanic field, southwestern British Columbia. An in situ stump dated 10 650 ± 70 BP (Beta 43865) obtained from a raised delta partially overridden by the lava flow indicates that the lava was extruded after ca. 10.7 ka. At the Skookum Creek and Mamquam River confluence, sediments eroded from the Ring Creek lava flow form an alluvial fan that contains charcoal dated 9360 ± 160 BP (Beta 38914), which indicates that the extrusion probably occurred before ca. 9.3 ka. Thus these radiocarbon ages bracket the age of the Ring Creek lava flow and indicate that volcanic activity in the southern section of the Mount Garibaldi volcanic field has been dormant since at least ca. 9.3 ka.
Orogen parallel and transverse shearing in the Opatica belt, Quebec: implications for the structure of the Abitibi Subprovince
Authors: Benn Keith , Sawyer Edward W. , Bouchez Jean-Luc
Published: December 2009

The late Archean Opatica granitoid-gneiss belt is situated within the northern Abitibi Subprovince, along the northern margin of the Abitibi greenstone belt. Approximately 200 km of structural section was mapped along three traverses within the previously unstudied Opatica belt. The earliest preserved structures are penetrative foliations and stretching and mineral lineations recording regional ductile shearing (D1). Late-D1 deformation was concentrated into kilometre-scale ductile fault zones, typically with L > S tectonite fabrics. Two families of lineations are associated with D1, indicating shearing both parallel and transverse to the east-northeast trend of the belt. Lineations trending east-northeast or northwest–southeast tend to be dominant within domains separated by major fault zones. In light of the abundant evidence for early north–south compression documented throughout southern Superior Province, including the Abitibi greenstone belt, D1 is interpreted in terms of mid-crustal thrusting, probably resulting in considerable crustal thickening. Movement-sense indicators suggest that thrusting was dominantly southward vergent. D2 deformation resulted in the development of vertical, regional-scale dextral and sinistral transcurrent fault zones and open to tight upright horizontal folds of D1 fabrics. In the context of late Archean orogenesis in southern Superior Province, the tectonic histories of the Abitibi and Opatica belts should not be considered separately. The Opatica belt may correlate with the present-day mid-crustal levels of the Abitibi greenstone belt, and to crystalline complexes within the Abitibi belt. It is suggested that the Abitibi Subprovince should be viewed, at the regional scale, as a dominantly southward-vergent orogenic belt. This work demonstrates that structural study of granitoid-gneiss belts adjacent to greenstone belts can shed considerable light on the regional structure and structural evolution of late Archean terranes.
Caractérisation, genèse et évolution géodynamique du terrain de Guerrero (Mexique occidental)
Authors: Lapierre H. , Tardy M. , Coulon C. , Hernandez E. Ortiz , Bourdier J.-L. , Reyes J. Martínez , Freydier C.
Published: December 2009

The Guerrero terrane (western Mexico) is composed of Late Jurassic – Early Cretaceous plutono-volcanic and volcano-sedimentary sequences of the Alisitos–Teloloapan arc that accreted to the North American craton at the end of the Early Cretaceous. The geodynamic evolution of the Guerrero terrane is that of the Alisitos–Teloloapan intraoceanic arc, partly built on continental crust and partly on oceanic crust. The growth of the arc was likely linked to the subduction of the Arperos and Olvidada basins fringing the North American borderland. The subduction was dipping west-south-west.The continent-based segment of the arc, which is presently exposed mainly in northwestern Mexico, is composed of aerial and submarine K-rich calc-alkaline basalts, andesites, and rhyolites and of siliceous pyroclastic rocks interbedded with Aptian–Albian bioclastic carbonates or red beds bearing dinosaurus foot prints. The calc-alkaline basalts and andesites show light rare earth elements enriched patterns and high concentrations in large ion lithophile elements. The siliceous andesites and rhyodacites display low contents in Y and heavy rare earth elements, uncommon for such calc-alkaline SiO2-saturated rocks. This depletion is likely linked to amphibole fractionation and to the presence of sphene and zircon, minerals known to concentrate the heavy rare earth elements.In contrast, the magmatic arc sequences built on oceanic crust, that crops out in central-southern areas of the Guerrero terrane, show an evolution with time. The activity of the arc began with depleted tholeiitic igneous rocks, followed first by mature tholeiitic basalts, then by calc-alkaline olivine basalts interbedded with micritic limestones and radiolarian oozes of Early Cretaceous age (Neocomian). At the end of the arc development, in Late Aptian–Albian, calc-alkaline pillow basalts and andesites erupted at the volcanic front whereas shoshonitic basalts emitted backwards. In the late Early Cretaceous, the arc drifted towards the north and collided with the craton. Arc tholeiites are characterized by flat rare earth element patterns or slightly depleted in light rare earth elements and by high εNd ratios. The calc-alkaline plutonic and volcanic rocks show light rare earth elements enriched patterns and their εNd ratios decrease with time. This decrease of the εNd ratios suggests that either the mantle source of the calc-alkaline rocks was contaminated by subducted terrigenous sediments derived from an old continental crust (North American craton) or that these calc-alkaline rocks derive from the partial melt of an oceanic island basalt source present in the mantle wedge. The shoshonitic features of the basalts are marked by the presence of sanidine in the groundmass and the high levels of K2O, Ba, and Sr of the unaltered rocks.
Interactions of the 18.5-kDa isoform of myelin basic protein with Ca2+-calmodulin: in vitro studies using fluorescence microscopy and spectroscopy
Authors: Libich David S , Harauz George
Published: December 2009

The interactions of the 18.5-kDa isoform of myelin basic protein (MBP) with calmodulin (CaM) in vitro have been investigated using fluorescence microscopy and spectroscopy. Two forms of MBP were used: the natural bovine C1 charge isomer (bMBP/C1) and a hexahistidine-tagged recombinant murine product (rmMBP), with only minor differences in behaviour being observed. Fragments of each protein generated by digestion with cathepsin D (EC 3.4.23.5) were also evaluated. Using fluorescence microscopy, it was shown that MBP and CaM interacted in the presence of Ca2+under a variety of conditions, including high urea and salt concentrations, indicating that the interaction was specific and not merely electrostatic in nature. Using cathepsin D digestion fragments of MBP, it was further shown that the carboxyl-terminal domain of MBP interacted with Ca2+-CaM, consistent with our theoretical prediction. Spectroscopy of the intrinsic fluorescence of the sole Trp residue of MBP showed that binding was cooperative in nature. The dissociation constants for formation of a 1:1 MBP-Ca2+-CaM complex were determined to be 2.1 ± 0.1 and 2.0 ± 0.2 μM for bMBP/C1 and rmMBP, respectively. Fluorescence spectroscopy using cathepsin D digestion fragments indicated also that the carboxyl-terminal region of each protein interacted with Ca2+-CaM, with dissociation constants of 1.8 ± 0.2 and 2.8 ± 0.9 μM for the bMBP/C1 and rmMBP fragments, respectively. These values show a roughly 1000-fold lower affinity of MBP for CaM than other CaM-binding peptides, such as myristoylated alanine-rich C-kinase substrate, that are involved in signal transduction. Key words: myelin basic protein, Ca2+-calmodulin, intrinsic Trp fluorescence, MARCKS, cathepsin D.
NOTEExpression of prolactin receptors and regulation of cell proliferation by prolactin, corticotropin-releasing factor, and corticosterone in a neuroblastoma cell line
Authors: Mohammad Y N , Perone M , Wang L , Ingleton P M , Castro M G , Lovejoy D A
Published: December 2009

The aetiology of neuroblastoma remains obscure, although a number of neuropeptides have been implicated in its pathogenesis. Using the mouse neuroblastoma cell line Neuro2a as a model, we have investigated the mitogenic actions of prolactin (PRL) and two hypothalamopituitaryadrenal stress axis hormones, corticotropin-releasing factor (CRF) and corticosterone. Using established polyclonal PRL receptor antisera with immunofluorescence cytochemistry, we show that the Neuro2a cells possess immunoreactive forms of both the long and short forms of the receptor. PRL and CRF were effective as mitogens in Neuro2a cell cultures, where a 107M concentration of PRL or CRF elicited a two-fold increase in the numbers of cells after 72 h (p < 0.0001). Corticosterone, however, attenuated their proliferation. These data suggest that prolactin may act to increase the proliferation and regulation of neuroblastomas and that the effects of PRL may be modified by hypothalamopituitaryadrenal hormones.Key words: cell proliferation, mitogens, neuroblasts, stress, cancer.
Enzymes of guanine nucleotide metabolism and the diurnal cycle in cGMP content of the chick pineal gland
Authors: Wainwright S. D. , Wainwright Lillian K.
Published: December 2009

Levels of cGMP phosphodiesterase, guanylate cyclase, and GTPase activities were determined in homogenates of chick pineal glands. Only small variations in vivo were observed with glands removed at different times of the day from birds under a standard cycle of illumination. Glands cultured under the cycle of illumination from late in the photoperiod showed a progressive loss of about half the phosphodiesterase activity in 24 h, and an increase of roughly 75% in GTPase activity within 12 h. No simple correlations were found between variations in levels of enzyme activity and the diurnal cycles in pineal content of cGMP and level of serotonin N-acetyltransferase (NAT) activity. However, onset of rapid increases in 3′, 5′-cyclic GMP (cGMP) content and NAT activity was correlated with a transient decrease of about 30% in the phosphodiesterase activity, both in vivo and in culture. Further, known inhibitors of phosphodiesterase activity previously shown to elicit increase of cGMP content and marked elevation of NAT activity in cultured glands only inhibited phosphodiesterase activity of homogenates by 25–30%. It was therefore concluded that the transient decrease in level of phosphodiesterase may facilitate onset of increase in pineal cGMP content. However, it seems improbable that changes in pineal content of enzymes of guanine nucleotide metabolism are essential to regulation of diurnal cycles in cGMP content or level of NAT activity.
The specific capsular polysaccharide of Streptococcus pneumoniae type 20
Authors: Richards James C. , Perry Malcolm B. , Carlo Dennis J.
Published: December 2009

The specific capsular polysaccharide produced by Streptococcus pneumoniae type 20 is composed of D-glucose (three parts), D-galactose (two parts), 2-acetarnido-2-deoxy-D-glucose (one part), phosphate (one part), and O-acetyl (approximately two parts). Methylation, periodate oxidation, optical rotation, nuclear magnetic resonance, partial and enzymic hydrolyses, and chromatographic studies showed that the polysaccharide is a high molecular weight polymer of partially O-acetylated hexasaccharide repeating units linked by monophosphate, having the structure indicated below:[Formula: see text]
Ontogeny of some enzymes of glycogen metabolism in rabbit fetal heart, lungs, and liver
Authors: Bhavnani Bhagu R.
Published: December 2009

Optimum conditions were established for the assay of glycogen, glycogen synthase, glycogen phosphorylase, phosphoglucomutase, and glucose-6-phosphatase in rabbit fetal heart, lung, and liver. Using these methods, the pattern of appearance of glycogen and the above four enzymes was established from day 18 of gestation to day 8 after birth. The results indicate that total tissue glycogen reaches maximum levels between days 22 and 24 in the heart, days 24 and 26 in the lung, and days 30 and 31 in the liver. In all three tissues, the rapid rise or depletion of glycogen is coincident with a corresponding increase in glycogen synthase and glycogen phosphorylase activities. However, substantial amounts of glycogen synthase are present both prior to and after the accumulation of glycogen. Similarly, considerable amounts of glycogen phosphorylase are present early in gestation, yet deposition of glycogen occurs. Both the I and D forms of glycogen synthase are present in the three tissues, the major being the physiologically inactive D form. Similarly both the a and b forms of glycogen phosphorylase are present, with the a form (active form) making up about 30–60% of the total phosphorylase activity. Glucose-6-phosphatase was absent in fetal heart and lung throughout the period of gestation investigated. Low levels of this enzyme were detectable in fetal liver near term. The phosphoglucomutase activity increased progressively from day 22 of gestation in all three tissues and continues to increase after birth. The disappearance of fetal lung glycogen occurs between days 27 and 28 at a time when surfactant phospholipids first appear. These findings indicate that the breakdown of glycogen is providing the fetal lung cells with energy necessary for surfactant phospholipid biosynthesis.
Plasma and liver carnitine (free and esterified) levels and their interrelationships in moderately hypercholesterolemic monkeys (Macaca arctoides)
Authors: Bell Frank P. , DeLucia Anthony J.
Published: December 2009

The level of carnitine and its esters was measured in plasma and liver in 20 male stump-tailed monkeys (Macaca arctoides) that were fed a moderately hypercholesterolemic diet. Plasma total carnitine was 60 ± 3 nmol/mL (30% esterified) and liver total carnitine was 254 ± 15 nmol/g wet weight (16% esterified) or 1.28 ± 0.07 nmol/mg noncollagen protein. The plasma concentration of total carnitine was positively correlated with the total carnitine concentration of the livers (r = 0.71, p < 0.001). Additionally, there was a positive correlation between plasma esterified carnitine and liver esterified carnitine (r = 0.92, p < 0.001) as well as between plasma esterified carnitine and plasma β-hydroxybutyrate (r = 0.92, p < 0.001), which together suggest that plasma esterified carnitine in the monkeys was largely of hepatic origin. There was no significant correlation between plasma carnitine (total, free, or esterified) and body mass, plasma triglycerides, or plasma cholesterol.
Further evidence for enhanced phospholipid synthesis by rat jejunal villus cells during fat absorption
Authors: Shaikh N. A. , Kuksis A.
Published: December 2009

The effect of fat absorption on the phospholipid turnover of rat intestinal mucosa was determined in animals receiving single fatty meals by stomach tube or multiple meals in the form of corn-oil-soaked laboratory chow diet. The specific activity and relative specific activity of the total phospholipids and of individual phospholipid classes were measured in the isolated jejunal villus cells of fasting and fat-fed animals following an injection of radioactive inorganic phosphate 0.5–31 h prior to sacrifice, which was scheduled to coincide with the peak of fat absorption (2.5–3 h after the last meal). It was shown that the relative specific activity of the fat-absorbing cells increased by about 33% when the samples were taken 0.5 h after intravenous injection of radioactive phosphate. Samples taken 11 and 31 h after the introduction of the radioactive phosphate showed about 16% decrease in the relative specific activity of the phospholipids of the fat-absorbing cells when compared with the fasting controls. These changes in the relative specific activity of the total phospholipids included all phospholipid classes and corresponded to the recently described expansion of the cellular phospholipid pool owing partly to increased de novo synthesis of the membrane phospholipids. The present results are consistent with the known biochemical and physiological changes taking place in the mucosal cells during fat absorption and transport and find support in various less direct biochemical and morphometric measurements.
Effect of heat shock on synthesis and phosphorylation of nuclear and cytoplasmic proteins in the fungus Achlya
Authors: Silver Julie C. , Andrews Diane R. , Pekkala David
Published: December 2009

Heat shock induced by an increase in temperature from 28 to 37 °C led to changes in synthesis and phosphorylation of cytoplasmic and nuclear proteins in the aquatic fungus Achlya. In the cytoplasmic fraction a marked increase in [35S] methionine labelling of proteins in the molecular weight range of 96 000, 85 000, 74 000, and 70 000 was observed. Two-dimensional electrophoresis resolved each of these classes of proteins into several components. Major changes in the nuclear fraction included the increased [35S]methionine labelling of 43 000 and 28 000 – 23 000 proteins. A marked decline in the synthesis of many other proteins was also evident. The heat-shock-induced changes in labelling patterns became evident as early as 20 to 60 min after treatment, but they were transient. With continued incubation at the heat-shock temperature, the cells appeared to adapt to the new temperature conditions. Both cytoplasmic and nuclear proteins returned to nearly normal labelling patterns within 100 to 140 min at 37 °C. Changes in phosphorylation of histone and nonhistone nuclear proteins were also noted. Achlya histone H3 and the putative oomycete-specific histone "α" appeared highly phosphorylated after heat shock. Since phosphorylation of histone H3 is primarily associated with chromatin condensation, it is possible that rapid chromatin condensation is an initial response to heat shock in Achlya.
Cold- and heat-shock induction of new gene expression in cultured amphibian cells
Authors: Ketola-Pirie C. A. , Atkinson Burr G.
Published: December 2009

Exposing primary epidermal cell cultures from the American bullfrog Rana catesbeiana to elevated (≥ 32 °C; heat shock) or depressed (≤ 5 °C; cold shock) temperatures for a short time results in the new and (or) enhanced synthesis of a 65 000 dalton (isoelectric point (pI) 6.7–6.9) polypeptide. With increasing temperature, a marked decrease in the synthesis of polypeptides observed at the control temperature (22 °C) and the new and (or) enhanced synthesis of another polypeptide with a relative mass of 25 000 and a pI of 6.7–6.9 is noted. Following a 1-h incubation at 34 °C, at least 4 h of recovery (at 22 °C) is required for primary epidermal cultures to resume their preinduction pattern of protein synthesis. Similar studies using an established adult kidney epithelial cell line from the African claw-toed frog Xenopus laevis demonstrate that cells from this organism respond to heat shock but do not respond to cold shock. Xenopus cells respond to heat shock by the new and (or) enhanced synthesis of at least five polypeptides. In vitro translation of the mRNAs from heat-shocked Xenopus cells suggests that the heat-shock mRNAs from these cells are preferentially transcribed and translated during thermal stress.
The major heat-shock protein (hsp70) gene family: related sequences in mouse, Drosophila, and yeast
Authors: Moran L. A. , Chauvin M. , Kennedy M. E. , Korri M. , Lowe D. G. , Nicholson R. C. , Perry M. D.
Published: December 2009

Heat shock induces the synthesis of a 70-kdalton protein in Escherichia coli, Drosophila, yeast, and mouse. We show that the genes for this heat-shock protein in mouse, yeast, and Drosophila share extensive sequence homology as determined by heteroduplex formation at different stringencies. We calculate that the heat-shock gene homology is 74% between yeast and Drosophila and 85% between mouse and Drosophila. The organization of the six copies of the Drosophila gene for the 70-kdalton heat-shock protein at two separate loci is summarized and evidence is presented that the yeast and mouse genomes each contain multiple copies of sequences related to the Drosophila gene for the 70-kdalton heat-shock protein. These results demonstrate that not only the sequence but also the repetitive organization of the major heat-shock genes is conserved.
Adenylate cyclase activity in Y1 mouse adrenocortical tumor cells: some properties of the enzyme associated with purified plasma membrane fractions
Authors: Schimmer Bernard P.
Published: December 2009

Fractions enriched in plasma membranes were prepared from the Y1 mouse adrenocortical tumor cell line and were characterized with respect to adenylate cyclase activity. Optimal requirements of the adenylate cyclase system for guanyl nucleotides, Mg2+, ATP, and corticotropin (ACTH) were determined. The sensitivity of the adenylate cyclase system to ACTH1–24 in plasma membrane fractions was comparable with that observed in isolated intact cells. Polycations such as poly-L-arginine and histone competitively inhibited the action of ACTH1–24, supporting the view that the affinity of ACTH for the adenylate cyclase system is determined by the basic core of amino acids at residues 15–18. ACTH1–24 was at least one order of magnitude more potent than ACTH1–39 in stimulating adenylate cyclase activity in plasma membrane fractions.
Hormonal influences on formation of plasminogen activator by cultured testis tubule segments at defined stages of the cycle of the seminiferous epithelium
Authors: Fritz Irving B. , Karmally Katherine
Published: December 2009

We confirm that basal rates of formation of plasminogen activator by cells in cultured tubule segments at stages of the cycle associated with spermiation (stages VII and VIII) are higher than those by cells in tubule segments at any other stages of the cycle of the seminiferous epithelium. We demonstrate that addition of cAMP derivatives or follicle-stimulating hormone in the presence of a phosphodiesterase inhibitor results in a large stimulation of plasminogen activator formation by tubule segments at all stages of the cycle. The greatest percentage increase (approximately 100-fold) is observed in cells in tubule segments having lowest basal rates of plasminogen activator formation (stages IX–VI). Even under stimulated conditions, however, the amounts of plasminogen activator produced by cultured tubule segments at stages VII and VIII remain greater than those produced by cultured tubule segments at other stages of the cycle, and these differences persist during organ culture for 48 h. Insulin and testosterone do not alter rates of formation of plasminogen activator. We conclude that Sertoli cells, the primary source of formation of plasminogen activator in the testis, are metabolically heterogeneous in the seminiferous tubule and that the germ cell association patterns in various stages of the cycle modulate Sertoli cell functions. We discuss the data in relation to the tissue restructuring within the seminiferous tubule which occurs during spermatogenesis and the possible role of plasminogen activator in these processes.
The interactive effects of fluoride and N-formyl-L-methionyl-L-leucyl-L-phenylalanine on superoxide production and cAMP levels in human neutrophils
Authors: Wong Kenneth
Published: December 2009

The kinetics of superoxide (O2−) production and intracellular cAMP levels were monitored in human neutrophils incubated in vitro with sodium fluoride and the chemotactic peptide N-formyl-L-methionyl-L-leucyl-L-phenylalanine (FMLP). F− activation of both the O2−-generating system, NAD(P)H oxidase, and adenylate cyclase was characterized by a prolonged lag period of 8 to 10 min at 37 °C. Adenylate cyclase agonists or cAMP analogues which inhibited FMLP-induced O2− bursts did not affect O2− production of F−-activated cells. Prior treatment of cells with F− suppressed the short rapid burst elicited by FMLP but not the binding of the tripeptide. FMLP reciprocally decreased the lag period of the F−-induced burst by 40 to 50% and, in the case of cells incubated at temperatures below 37 °C, increased the rate of O2− production. A similar potentiating effect of FMLP on F−-induced elevation of intracellular cAMP levels was observed.
Isolation, analysis of structure, synthesis, and biological actions of urotensin I neuropeptides
Authors: Lederis K. , Letter A. , McMaster D. , Ichikawa T. , MacCannell K. L. , Kobayashi Y. , Rivier J. , Rivier C. , Vale W. , Fryer J.
Published: December 2009

The 41-residue neuropeptide urotensin I (UI), from the urophyses of two teleost fish species (Cyprinus carpio and Catostomus commersoni), was isolated and purified, and its amino acid sequence was determined and confirmed by synthesis of a fully active peptide. The UI peptide was found to be a close structural and biological homologue of the ovine hypothalamic corticotropin-releasing factor (CRF) and the frog skin peptide sauvagine; UI is, therefore, a phylogenetic prototype of this group of peptides. Extraction of urophyses in hot acetic or hydrochloric acid cleaves an amino terminal tripeptide yielding a fully active UI(4–41). The UI peptides are equipotent with the other two naturally occurring peptides (CRF and sauvagine) in the release of mammalian pituitary corticotropin (ACTH), but UI is several times more potent than the mammalian homologue in the stimulation of release of fish pituitary ACTH. The UI peptide and its mammalian or amphibian homologues have a long-lasting hypotensive action in mammals, via a uniquely selective vasodilatation in the superior (anterior) mesenteric vascular bed only. The significantly lower hypotensive vasodilatory action of the mammalian homologue (CRF) suggests a change in the unknown physiological role of the haemodynamic actions of the UI peptides in the mammalian gastrointestinal tract during phylogenetic progression from fishes to mammals.
Receptors, acceptors, and the action of polypeptide hormones: illustrative studies with epidermal growth factor (urogastrone)
Authors: O'Connor-McCourt M. , Hollenberg M. D.
Published: December 2009

The action of polypeptide hormones is discussed in the context of observations made both with receptors, like the ones for epidermal growth factor (urogastrone) (EGF-URO), insulin, and gonadotropin-releasing hormone (GnRH), and with acceptors, like the ones that participate in the adsorptive pinocytosis of substances like cholesterol (low density lipoprotein acceptor), cobalamin (transcobalamin-II acceptor), and asialoglycoproteins (galactose acceptor). The overall processes that both pharmacologic receptors and acceptors undergo subsequent to ligand binding comprise (a) microclustering; (b) aggregation at both coated ("coated pits") and uncoated plasma membrane regions; (c) internalization, with the formation of endocytic vesicles (endosomes or receptosomes); and (d) either recycling of endosomes (receptosomes) to the plasma membrane or fusion of endosomes (receptosomes) with lysosomes, accompanied by proteolytic degradation of the internalized ligand–receptor complex. The relevance of these processes to hormone action is discussed. Further, illustrative studies with EGF-URO are used to highlight general mechanisms that are thought to participate in the action of a variety of peptide hormones. The microclustering event and the concomitant receptor-regulated membrane phosphorylation reactions are emphasized as key plasma-membrane-localized processes that are very likely involved in the rapid (minutes to tens of minutes) actions of many peptide hormones. For the delayed actions of hormones (hours to tens of hours; e.g., DNA synthesis), the potential importance of nonlysosomal receptor processing, mediated by SH-requiring proteases that generate intracellular receptor fragments, is pointed out. A scheme for the action of EGF-URO is outlined and a model for peptide hormone action is presented that illustrates how multiple chemical mediators of hormone action may result from the combination of a single hormone with its unique receptor.
Cholesterol metabolism in the rat adrenal cortex: acute temporal changes following stress
Authors: Alfano Josephine , Pedersen Robert C. , Kramer Robert E. , Brownie Alexander C.
Published: December 2009

Adrenal and serum corticosterone concentrations, cholesterol association with adrenal cortical cytochrome P-450scc (the cytochrome P-450 catalyzing the conversion of cholesterol to pregnenolone), and adrenal cortical activities of cholesteryl ester hydrolase, acyl-CoA:cholesterol acyltransferase, and cholesterol side-chain cleavage have been determined at various times following stress in female rats. The paramount importance of cholesterol side-chain cleavage activation in the response to stress at the low point of the circadian rhythm is confirmed. At the high point of the circadian rhythm, there is evidence that the provision of free cholesterol for the cytochrome P-450scc enzyme system may also be controlled. The data support a coordinate action of ACTH and pro-γ-melanotropin in controlling cholesterol metabolism in the adrenal cortex following stress.
Rat prostatic acid phosphatase: androgenic control of isoelectric focusing patterns
Authors: Downey J. , Mahan D. , Flynn T. G. , Bird C. E. , Clark A. F.
Published: December 2009

To further characterize the androgen dependence of prostatic acid phosphatase (AP), the isoelectric focusing patterns of enzyme activity have been examined for normal and castrated adult rats and for rats receiving androgen injections. Isoelectric focusing was performed in polyacrylamide gels over the pH range 4–8. Naphthyl phosphate was used as substrate for staining. For normal rats there was a single lysosomal band (isoelectric point (pI) = 7.35 ± 0.04), four closely migrating secretory bands (pI = 5.96–5.63), and an androgen-dependent band (pI = 6.37 ± 0.05) which as yet has not been identified as either lysosomal or secretory. Following castration the secretory bands decreased significantly in staining intensity, the androgen-dependent band disappeared, and two new lysosomal bands (pI's = 7.13 ± 0.03 and 7.00 ± 0.03) appeared. With androgen replacement the latter two bands disappeared, the androgen-dependent band reappeared, and the secretory bands increased in staining intensity but with the most anodic of the four appearing before the others. This suggests that it could be a precursor to the others. The isoelectric focusing patterns of AP activity appear to be a better method of assessing the androgen status of the prostate than are the previously used parameters, namely, enzyme specific activity, degree of inhibition by tartrate, and polyacrylamide gel electrophoretic pattern.
Studies of the nuclear 5α-reductase of human prostatic tissue: comparison of enzyme activites in hyperplastic, malignant, and normal tissues
Authors: Hudson Robert W. , Moffitt Patricia M. , Owens Wendy A.
Published: December 2009

The nuclear conversion of testosterone (T) to dihydrotestosterone (DHT) was compared in hyperplastic (n = 40), malignant (n = 20), and normal (n = 3) prostatic tissues. Standard assay conditions were 2 μM testosterone, 2.0 mM EDTA, 1.0 mM NADPH, and the nuclear fraction equivalent to 200 mg of prostatic tissue, in 0.1 M N-2-hydroxyethylpiperazine-N′-2-ethanesulfonic acid buffer (pH 7.4). The Km values were 0.6, 0.5, and 0.3 μM, respectively, for the enzymes in hyperplastic, malignant, and normal tissues. The Vmax values were 42 ± 17, 4.2 ± 1.8, and 3.9 ± 0.9 pmol/mg protein per 30 min of incubation, respectively, for the hyperplastic, malignant, and normal tissues. When DHT formation was measured at T concentrations equivalent to reported endogenous levels, it was found that enzyme activity in the hyperplastic tissue was still greater than that in the other two tissues. The enzyme in the malignant prostate was less efficient than the enzyme in normal tissue in converting T to DHT. These results would suggest that differences in the conversion of T to DHT may explain, at least in part, the higher DHT levels seen in hyperplastic tissue than in either the normal or the malignant prostate and the higher T levels seen in the malignant prostate than in the other two tissues.
The formation of unconjugated and sulfoconjugated estrogens by Leydig cells of the boar testis
Authors: Raeside J. I.
Published: December 2009

The metabolism of radioactive androstenedione (A) and estrone (E1) was examined in preparations of enzyme-dispersed cells from testicular interstitial tissue of the boar. Incubations were made with two-cell populations from a discontinuous density gradient (10–90% Percoll). Products were separated into unconjugated and "conjugated" (water-soluble) fractions by countercurrent distribution (CCD) using an ether-water partition. As much as 75% of A and 20–25% of E1 appeared in the aqueous phase. Unconjugated and solvolyzed steroids were separated similarly into neutral and phenolic fractions by CCD with a system of toluene –1 N NaOH. Radioactivity was found to be approximately equal in the two phases for each CCD. Partition chromatography on Celite columns for unconjugated and sulfoconjugated estrogens showed the presence of E1, estradiol, estrone sulfate, and estradiol sulfate from both radioactive substrates. Further identification of the estrogens was obtained from high performance liquid chromatography. The study included radioimmunoassays for estrogens in the media of cell preparations incubated without radiolabelled substrates. The results are in accord with the known high level of estrogen secretion by the testes of the mature male domestic pig and support the view of steroid sulfate secretion by the Leydig cells.
Isolation of tremerogens A-9291-I and A-9291-II, novel sex hormones of Tremella brasiliensis
Authors: Ishibashi Yoshihiro , Sakagami Youji , Isogai Akira , Suzuki Akinori , Bandoni Robert J.
Published: December 2009

Two hormones, tremerogens A-9291-I and A-9291-II, that induce conjugation tube formation in a-type cells of Tremella brasiliensis were isolated from the culture filtrate of A-type cells. Both hormones are peptides and they have similar amino acid compositions. The N-terminal amino acids of these peptides are aspartic acid or asparagine.
The triterpenoid carotenoids and related terpenoids in Staphylococcus aureus 209P
Authors: Taylor Richard F. , Davies Brian H.
Published: December 2009

The carotenoids of Staphylococcus aureus 209P have been identified as triterpenoid (C30) carotenoids. The pigments include members of a carotene dehydrogenation sequence with C30 analogs of phytoene, phytofluene, ζ-carotene, and neurosporene. The major xanthophyll present under the cultural conditions used is a carotenoic acid derived from the C30 analog of neurosporene. A cis-isomer of this major xanthophyll has also been characterized, as have four other xanthophylls. Of the latter xanthophylls, two have been identified as the hydroxy and glycosyloxy derivatives of the major xanthophyll, while the remaining two xanthophylls are carotenoid esters. Squalene and menaquinone MK-8 have also been identified in the bacterium.
Enzymatic carboxyl methylation of calcium-binding proteins
Authors: Gagnon Claude
Published: December 2009

The enzymes protein-carboxyl methylase and protein methylesterase reversibly modify the charge and structure of proteins by adding and removing methyl groups on free carboxyl groups of proteins. Since this posttranslational system has been implicated in biological processes that required calcium, the carboxyl methylation of calmodulin was investigated. Calmodulin was an excellent substrate for both protein-carboxyl methylase and protein methylesterase. Carboxyl methylation of calmodulin resulted in inactivation, since methylated calmodulin was less capable of activating cyclic nucleotide phosphodiesterase. To determine whether the carboxyl methylation of calmodulin was simply a test tube reaction or a biochemical reaction normally occurring in intact cells, two different cell lines were labeled with [methyl-3H]methionine. Calmodulin was isolated by affinity chromatography and was found to be carboxyl methylated. Finally, calcineurin was also an excellent substrate for the methylase, suggesting that other calcium-binding proteins may be affected by protein methylation–demethylation.
Phosphorylation of spore coat proteins of Dictyostelium discoideum
Authors: Akalehiywot Teshome , Siu Chi-Hung
Published: December 2009

Phosphorylation of cellular proteins was studied during development of Dictyostelium discoideum. In the second half of the developmental cycle, two heavily phosphorylated proteins were observed together with a limited number of minor phosphorylated proteins. The electrophoretic mobility of these two phosphoproteins corresponded to two of the major spore coat glycoproteins, with apparent molecular weights of 103 000 and 80 000. They were found to be externalized and associated with the spore coat during spore formation. Phosphoserine was the predominant phosphoamino acid in both cases. These two phosphoproteins thus serve as excellent markers for the differentiation of prespore cells in D. discoideum.
Distribution and metabolism of dolichol and dolichyl phosphate in rat liver
Authors: Rip Jack W. , Chaudhary Nilabh , Carroll Kenneth K.
Published: December 2009

The dolichol and dolichyl phosphate (Dol-P) content of various tissues and liver subcellular fractions obtained from rats have been measured directly using high pressure liquid chromatographic methods developed in this laboratory. Spleen contained the highest concentration of dolichol, while other tissues including serum had smaller amounts. Although considerable differences in homologue distribution patterns were observed among the tissues examined, a number of purified subcellular fractions obtained from liver (nuclei, mitochondria, cytosol, and microsomes) exhibited a single common pattern. Only some 5% of liver dolichol appeared in the microsomal compartment of the cell where glycoprotein formation occurs, while 50% of the dolichol in this tissue was found in a lysosome-enriched fraction. The concentrations of dolichol present in liver nuclei, mitochondria, whole microsomes (also rough and smooth, endoplasmic recticulum (RER and SER, respectively), and cytosol were considerably lower (on a protein basis) than those present in whole liver. Besides the lysosome-enriched fraction, only plasma membranes and Golgi contained dolichol at concentrations equal to or greater than those present in liver homogenates. The low concentrations of dolichol found in microsomes suggest that the amounts of dolichol available for Dol-P formation via the CTP-dependent kinase reaction may be rate limiting. Most of the Dol-P in liver could be recovered in the microsomal fraction. Dol-P accounted for 4 and 40% of the sum of alcohol + dolichyl fatty acyl ester + Dol-P forms present in whole liver and in microsomes, respectively. The RER, SER, and Golgi all contained substantial amounts of Dol-P, supporting the idea that Dol-P may be involved in the movement of sugars used in glycoprotein formation from a cytosolic to a luminal membrane orientation. The relative activities of dolichol kinase and dolichyl phosphate phosphatase observed in RER, SER, and Golgi suggested that RER and SER favour the formation of Dol-P from dolichol, while Golgi membranes favour the dephosphorylation of Dol-P.
Key role of dolichol phosphate in glycoprotein biosynthesis
Authors: Mookerjea Sailen , Coolbear Timothy , Sarkar Mohan Lal
Published: December 2009

Studies on the developmental changes in oviducts of hormone-treated chicks and embryos of sea urchins have indicated that the level of dolichol phosphate in the tissues may serve as a control for asparagine-linked glycoprotein biosynthesis. Acute-phase reactant glycoprotein biosynthesis is greatly increased in inflamed rats given a single injection of turpentine. As most of the serum glycoproteins are synthesized via the dolichol pathway, the rate of synthesis of mannosyl and glucosyl dolichol monophosphate and of glucosyl dolichol pyrophosphoryl oligosaccharide, CTP-dependent doiichol phosphokinase, and the level of dolichol phosphate were measured in the livers of inflamed rats. The activities of the glycosyltransferases were increased at least twofold as a result of inflammation. It was also observed that dexamethasone treatment reversed the inflammation-induced increase of mannosyl and glucosyl transfer to dolichol monophosphate. The endogenous level of dolichol phosphate and dolichol kinase activity were increased in microsomes 24 h after inflammation. With exogenous dolichol added to the microsome assay, increased kinase activity was observed as early as 6 h after turpentine injection. The increase of dolichol phosphate in inflammation is most likely due to both greater availability of dolichol and an increase in the level of CTP-dependent dolichol kinase. Studies with purified subcellular fractions showed that dolichol kinase activity is primarily localized in the rough endoplasmic reticular fraction. Since this is the major site of dolichol-phosphate-linked N-glycosylation reactions, a key role of dolichol phosphokinase activity in rough microsomes to initiate the first steps of N-glycoprotein synthesis seems plausible.