bluuebunny/crossref_metadata_2025 huggingface dataset:
U–Pb evidence of late Archean tectono-thermal activity in the southern São Francisco shield, Brazil
Authors: Machado N. , Carneiro M.
Published: December 2009

The São Francisco craton in eastern Brazil is one of the major shield areas in South America. In the Quadrilátero Ferrífero area (southern sector of the craton) the Archean Rio das Velhas greenstone belt is surrounded by granite–gneiss terrane and is overlain by Proterozoic sedimentary successions. The Bonfim Metamorphic Complex is the only area of the granite–gneiss terrane adjacent to the greenstone belt that has been mapped. It comprises two gneissic units, tonalites, and late granitic dykes, which crosscut the regional north–south shear fabric. Samples of gneiss, two tonalites and a granitic dyke were dated by U–Pb. A zircon core from the Alberto Flores gneiss yielded a minimum age of 2920 Ma, whereas the overgrowth is concordant at 2772 ± 6 Ma. Two tonalites from the vicinity of Serra da Moeda are [Formula: see text] old, and a late dyke yielded an age of [Formula: see text]. These data, together with previously published U–Pb ages, show that (i) greenstone belt volcanism was coeval with granitoid intrusion and with metamorphism of older units in the granite–gneiss terrane at ca. 2780 Ma and (ii) the main crust-forming event in the Quadrilátero Ferrífero area is about 2780 Ma old. Clear evidence is now available indicating that older magmatism is 2.8–3.2 Ga old. In addition, the last Archean deformation must have occurred in the interval 2780–2703 Ma. Finally, the presence of 2774 ± 6 Ma titanite in the tonalites indicates that the metamorphism associated with the Trans-Amazonian orogeny (ca. 2.0 Ga) did not reach amphibolite facies in the study area.
The sedimentary record and Neoglacial history of Tide Lake, northwestern British Columbia
Authors: Clague John J. , Mathews William H.
Published: December 2009

Tide Lake was the largest glacier-dammed lake in British Columbia before its demise in the early twentieth century. Situated in the northern Coast Mountains, the lake was impounded by Frank Mackie Glacier and its Neoglacial end moraine. A study of Tide Lake has provided information on styles of glaciolacustrine sedimentation and the chronology of the Neoglacial interval.Much of the sediment underlying the floor of Tide Lake was transported by subglacial and proglacial meltwater streams flowing from nearby glaciers. During the last phase of the lake, large subaqueous fans were built in front of Berendon and Frank Mackie glaciers, and deltas formed on the east side of the basin. Rhythmically bedded fine sediments, which cover much of the lake floor but are almost completely lacking on the slopes above, were deposited from underflows originating on deltas and subaqueous fans and by fallout from interflows and overflows.Three major and one minor lake phases are recognized from stratigraphic, geomorphic, radiocarbon, and dendrochronological data: the earliest phase is undated, but older than 3000 BP (1300 B.C.); the second phase has yielded radiocarbon ages of 2600–2700 BP (800–1000 B.C.); a third, minor phase, during which Tide Lake was restricted to the northern part of the basin, began before 1600 BP (A.D. 350–550) and probably ended a few hundred years later; the last phase may have begun as early as 1000 BP (A.D. 1000–1150), peaked in the seventeenth century, and ended in the early twentieth century. During each of the four phases, Tide Lake fluctuated in a complex fashion and at times was empty. The second phase corresponds to a widely recognized middle Neoglacial advance in western North America; the last phase is coincident with the Little Ice Age. Outburst floods from Tide Lake in the nineteenth and early twentieth centuries devastated Bowser River valley as far downstream as Bowser Lake. The last of the floods occurred around A.D. 1930 when the Frank Mackie moraine was breached and the lake emptied for the last time.
Tectonic implications of 40Ar/39Ar mineral ages from late Precambrian – Cambrian plutons, Avalon composite terrane, southern New Brunswick, Canada
Authors: Dallmeyer R. David , Nance R. Damian
Published: December 2009

Within the Avalon composite terrane exposed in southern New Brunswick, late Precambrian, low-grade volcanic–sedimentary sequences are juxtaposed against late Precambrian gneisses (Brookville Gneiss) and older platformal metasedimentary rocks (Green Head Group) along the Caledonia Fault. Both assemblages host petrographically similar suites of calc-alkalic dioritic and granodioritic plutons. Those intruding volcanic–sedimentary sequences (Caledonia terrane) record ca. 615–625 Ma crystallization ages typical of arc-related magmatism throughout the Avalon composite terrane. However, 40Ar/39Ar age data from stocks intruding gneisses and platformal metasedimentary rocks (Brookville terrane) suggest significantly younger crystallization ages.36Ar/40Ar versus 39Ar/40Ar isotope correlation ages recorded by hornblende are interpreted to closely date postmagmatic cooling within six plutons: Fairville Granite (547 ± 1 Ma); French Village Quartz Diorite (539 ± 2 and 537 ± 1 Ma); Rockwood Park Granodiorite (529 ± 2 and 523 ± 3.5 Ma); Musquash Granite (526 ± 2 Ma); Milkish Head Granite (Red Bridge pluton, 520 ± 1.5 Ma); Lepreau Diorite (Talbot Road pluton, 519 ± 2 Ma and Hansen Stream pluton, 518 ± 1.5 Ma. A hornblende isotope correlation age of 530 ± 2 Ma from penetratively foliated amphibolite within the French Village Quartz Diorite suggests that the magmatic activity was locally accompanied by ductile shear. Muscovite within granitic pegmatite in the Brookville Gneiss records a 40Ar/39Ar plateau age of 510 ± 1 Ma interpreted to date final phases of associated magmatic activity.Arc-related magmatism extending into the Cambrian contrasts with the characteristic tectono-stratigraphic record in the Avalon composite terrane where late Precambrian igneous rocks are overstepped by Cambrian–Ordovician shallow-marine strata with only a local and minor record of rift-related volcanic activity. Although the Brookville terrane shows affinities with the Avalon composite terrane during the late Precambrian, the 40Ar/39Ar age data suggest that it was isolated as a distinct tectono-stratigraphic element by the Early Cambrian.
Age of emplacement and basement character of the Cache Creek terrane as constrained by new isotopic and geochemical data
Authors: Mihalynuk Mitchell G. , Smith Moira T. , Gabites Janet E. , Runkle Dita , Lefebure David
Published: December 2009

New U–Pb and Rb–Sr isotopic and major and trace element geochemical data are reported for Late Triassic to Eocene granite bodies that intrude the Cache Creek and Stikine terranes in the Atlin–Bennett area of northwestern British Columbia. The U–Pb isotopic age data help constrain closure of the Cache Creek ocean and obduction of the Cache Creek terrane to before 172 Ma (Middle Jurassic). Low 87Sr/86Sr initial ratios (0.7037–0.7046) and lack of evidence for inheritance in zircons suggest that rocks underlying the Cache Creek terrane are largely primitive in nature, with derivation of intrusive rocks predominantly from unevolved sources.A genetic link between Late Triassic granitic plutons and Stuhini arc volcanics of Stikinia is supported by trace and rare-earth element data which indicate generation of magma in a volcanic-arc setting. Geochemical patterns for postaccretion Middle Jurassic and Late Cretaceous to early Tertiary age plutons are similar to those of the Late Triassic, indicating that Middle Jurassic and younger plutons could be derived from the same source area as the Late Triassic plutons.These data do not support recent theories proposing that the Cache Creek and Stikine terranes are klippe overlying a thick section of deformed, Proterozoic and lower Paleozoic continental-margin strata and attenuated cratonal basement. Rather, they are consistent with models in which remnants of Cache Creek ocean basin are placed over the Stikine arc in the Early to Middle Jurassic. Both terranes in turn overlie mainly late Paleozoic to early Mesozoic juvenile crustal material or the upper mantle.
Racklan Orogen
Authors: Cook Frederick A.
Published: December 2009

The term Racklan Orogen is applied to an extensive region of deformed rocks that underlies northwestern Canada. At least one period of deformation predated extrusion of the ca. 1267–1270 Ma basalt of the Coppermine River Group, and at least two periods of deformation postdated extrusion of the Coppermine basalt. Limits on the age of deformation can be confidently placed between 1663 Ma (the age of the Narakay volcanic complex that postdates uppermost strata of the Hornby Bay Group) and 1100–800 Ma (the maximum age of the Mackenzie Mountains Supergroup).
MammalianEGLNgenes have distinct patterns of mRNA expression and regulation
Authors: Lieb Mark E , Menzies Keon , Moschella Maria C , Ni Rujing , Taubman Mark B
Published: December 2009

The mammalian EGLN family contains three paralagous genes (EGLN1, EGLN2, and EGLN3) encoding prolyl hydroxylase isoforms that mediate the oxygen-dependent targeting of the transcription factor hypoxia inducible factor alpha to the proteosome. The rat orthologue of EGLN3 (SM-20) exhibits tissue-restricted expression, is induced by growth factors in cultured vascular smooth muscle, and is up-regulated during myogenesis. To determine if all three EGLN genes are coordinately regulated, we examined their mRNA expression in murine tissues and in cultured cells. We now report that the three murine EGLN mRNAs have unique but overlapping patterns of tissue expression. The most striking differences were in the heart, where EGLN3 had its highest levels of expression, and the testis, where EGLN2 was the only isoform expressed. In cultured vascular smooth muscle cells, serum treatment led to up-regulation of EGLN1 and EGLN3, but not EGLN2, and only EGLN3 was superinduced by cyclohexamide. In cultured C2C12 myocytes, EGLN3 was up-regulated during differentiation, whereas EGLN1 andEGLN2 were constitutively expressed. The abundance of EGLN3 mRNA in the heart, its induction by growth factors in vascular smooth muscle, and its regulation during C2C12 differentiation suggest a unique role for EGLN3 and might justify the development of isoform-specific inhibitors.Key words: EGLN, SM-20, vascular smooth muscle, C2C12, prolyl hydroxylase.
Hepatitis B viral core protein activates the hepatitis B viral enhancer II/pregenomic promoter through the nuclear factor κB binding site
Authors: Kwon Jin Ah , Rho Hyune Mo
Published: December 2009

We here demonstrated that the hepatitis B viral (HBV) core protein (HBc) functions as a transcriptional activator on the pregenomic promoter of HBV. Detailed analyses on the HBV pregenomic promoter by serial deletion, mutation, and heterologous promoter system showed that the site responsible for activation was the nuclear factor κB (NF-κB) binding site (GGGACGTACT, nucleotides 1408-1417) upstream of the enhancer II/pregenomic promoter. The electrophoretic mobility shift assay using the HBc-transfected HepG2 nuclear extracts showed that the HBc enhanced the NF-κB DNA-binding ability. These results suggest that the HBc functions as a positive regulator, which may enhance viral replication in hepatocytes.Key words: hepatitis B viral core protein (HBc), transcriptional activation, EnII/Cp, NF-κB.
Purification and properties of the Proteus mirabilis catalase
Authors: Jouve Hélène M. , Tessier Sylvie , Pelmont Jean
Published: December 2009

The purification of catalase from Proteus mirabilis has been described. The protein had four subunits of equal apparent molecular weight (MW 62 000). The enzyme was found to be slightly heterogenous after electrofocusing, the main fraction having an isoelectric pH of 4.8. No detectable peroxidatic activity was observed in physiological conditions. The absorbance spectrum and the effects of pH and temperature on catalase have also been described.
Enzymatic sulfation of steroids. XVIII. Study of the specific estradiol-17β sulfotransferase of rat liver cytosol, that converts the estrogen to its 3-sulfate, and some elements of the endocrine control of its production
Authors: Green Jacalyn M. , Singer Sanford S.
Published: December 2009

A radioisotopic assay for cytoplasmic estradiol-17β sulfotransferase activity in rat liver was developed. Routine enzyme assays used 120 μM [3H]estradiol-17β, 240 μM 3′-phosphoadenosine-5′-phosphosulfate, and enzyme samples containing up to 0.60 mg of cytosol protein. Livers from males and females sulfated 934 ± 231 and 861 ± 266 nmol estradiol-17β∙h−1∙g−1. DEAE-Sephadex A-50 chromatography showed that most of the cytoplasmic enzyme activity eluted as one peak that was well separated from glucocorticoid and 3β-hydroxysteroid sulfotransferases. Pooled column fractions containing this estradiol-17β sulfotransferase exhibited kinetic properties similar to the enzyme activity in cytosol, but gave slightly greater activity with 180 μM estradiol-17β and 360 μM 3′-phosphoadenosine-5′-phosphosulfate. Apparent Km's for the steroid and the coenzyme were 71–85 and 80–93 μM, respectively. The pH optimum for the enzyme reaction was 7.75 ± 0.25. The enzyme sulfated estradiol-17β at all concentrations tested between 10 and 180 μM. It did not sulfate estrone, testosterone, dehydroepiandrosterone, or cortisol well at any test concentration between 10 and 120 μM. The sulfation product was estra-1,3,5-triene-17β-ol-3-sulfate. The molecular weight of the enzyme was 54 500 ± 2300 by Sephadex G-100 chromatography. The estradiol-17β sulfotransferase was inhibited strongly by phenols, but not by corticosterone, deoxycorticosterone, dehydroepiandrosterone, estrone, progesterone, or testosterone. Adrenalectomy diminished the estradiol-17β sulfotransferase activity greatly, owing to decreases of the specific estradiol-17β sulfotransferase concentration. The possible relationships between the specific estradiol-17β sulfotransferase and other sulfotransferases in rat liver are discussed.
Primary structures of four novel small ribosomal RNAs from Crithidia fasciculata
Authors: Schnare Murray N. , Spencer David F. , Gray Michael W.
Published: December 2009

We report here the complete primary structures of four novel small RNA species (designated e, f, g, and j) found in the large ribosomal subunit of Crithidia fasciculata, a trypanosomatid protozoan. These RNAs, which are distinct from Crithidia 5S (species h) and 5.8S (species i) rRNAs, do not have counterparts in the more conventional eukaryotic ribosomes characterized to date. The small RNAs are 212 (e), 183 (f), 135–136 (g), and 72–73 (j) nucleotides long, with g and j displaying 5′-terminal heterogeneity. All have unique sequences and all contain 5′-monophosphorylated and 3′-unphosphorylated termini. In their basic structural features, therefore, species e, f, g, and j are indistinguishable from other RNAs (including 5S and 5.8S) that are recognized components of eukaryotic ribosomes, although they are unrelated to 5S or 5.8S rRNA in sequence. Since previous work from this laboratory has ruled out the possibility that these small RNAs are generated by quantitative and highly specific (albeit artifactual) RNase cleavage of large rRNAs during isolation, we conclude that species e, f, g, and j are native components of the Crithidia ribosome. With the exception of e, which appears to contain a single pseudouridine residue, all of these novel RNA species are devoid of modified nucleosides. In connection with primary sequence analysis, we present a simple modification of the standard G-specific chemical sequencing reaction which in our hands yields reproducible and unambiguous results using commercially available dimethyl sulfate.
Purification and characterization of exo-β-1,3-glucanase from a hatching supernatant of Strongylocentrotus intermedius
Authors: Takeuchi Kiyoshi
Published: December 2009

Exo-β-1,3-glucanase from the sea urchin embryos was purified 114-fold from the initial hatching supernatant by the following procedures: (a) gel filtration on Sephadex G-100; (b) hydrophobic chromatography on 4-phenylbutylamine-Sepharose (PBA-Sepharose); (c) two ion-exchange chromatographic steps on DEAE-cellulose; (d) gel filtration on Ultrogel AcA 34; (e) gel filtration on Sephadex G-100. The purified enzyme contained 2.2% carbohydrate and gave a single protein band corresponding to a molecular weight of 136 000 following electrophoresis on sodium dodecyl sulfate (SDS) – urea – polyacrylamide gel. Gel filtration on Ultrogel AcA 34 with a nondenaturing solvent gave a molecular weight of 130 000 ± 6000. The enzyme displayed an optimum pH at 5.0–5.5 and hydrolysed laminarin and PS(curdlan)-beads at the nonreducing ends, releasing glucose. Although activity of the purified enzyme was not affected by SDS, urea, some divalent ions, and 2-mercaptoethanol, both dithiothreitol and Hg2+ were markedly inhibitory.
Extracellular effect of calcium on compound 48/80 stimulated mast cells
Authors: Ranadive Narendranath S. , Lewis Rubina
Published: December 2009

The effects of changes in the extracellular concentration of calcium on activation of rat mast cells by compound 48/80 were studied. The intracellular exchangeable Ca2+ pools at various concentrations of extracellular Ca2+ were determined by equilibration of the cells with 45Ca2+. The cells stimulated by compound 48/80 in the presence of 2.5 μM and 1.6 mM extracellular Ca2+ released comparable amounts of histamine. However, the intracellular Ca2+ pool was doubled in 2.5 μM Ca2+ and was increased sixfold in 1.6 mM Ca2+. In 14.4 mM extracellular Ca2+, there was neither release of histamine nor uptake of Ca2+ which suggested an impairment in activation. The kinetics of Ca2+ influx in the presence of 2.5 μM Ca2+ did not reveal intracellular mobilization of calcium. The cells activated in 1.6 mM Ca2+ at 0 °C when allowed to stand in 14.4 mM extracellular Ca2+ released decreased amounts of histamine upon warming to 37 °C. The inhibition of the release progressively increased with time of standing at 0 °C. The decrease in histamine release was not seen with the cells standing in 1.6 mM Ca2+ at 0 °C. The effect of 14.4 mM Ca2+ added prior to the challenge with compound 48/80 did not depend on the time of incubation. The data presented in this paper suggest that the high concentration of Ca2+ inhibits the histamine release from mast cells by interfering with membrane-associated phenomena.
Synthesis of two photoreactive heterobifunctional reagents derived from hexanoic acid
Authors: Dupuis Gilles , Radwan Farouk
Published: December 2009

The synthesis of two photoreactive heterobifunctional reagents derived from hexanoic acid is described. The compounds are succinimido 6-N-(4-azidobenzoyl)aminohexanoate (1c) and succinimido 6-mercapto-S-(4-azidothiophenyl)hexanoate (2c). Compound 1c was synthesized from benzyloxycarbonyl 4-aminobenzoic acid and 6-aminohexanoic acid benzyl ester. Compound 2c was obtained by disulfide exchange of dithiobis-4-aminobenzene with 6-mercaptohexanoic acid. The azido function was introduced by displacement of the corresponding diazonium salt and the active ester, by the mixed anhydride method. Both compounds were decomposed by ultraviolet irradiation. Phytohemagglutinin was modified by reaction with reagent 1c or 2c. Irradiation afforded polymeric lectin derivatives resulting from intermolecular cross-linking. Sodium dodecyl sulfate – polyacrylamide gel electrophoretic analyses revealed the presence of Coomassie-positive bands of molecular weight 33 000, 67 000, 120 000,144 000, and higher. Polymeric structures resulting from irradiation of phytohemagglutinin modified with compound 2c were cleaved by reduction with 2-mercaptoethanol or with dithiothreitol. Phytohemagglutinin modified by reaction with compound 1c or 2c retained its ability to stimulate pig spleen lymphocytes in vitro. Whereas the lectin treated with reagent 2c was as active as the unmodified protein, the lectin treated with compound 1c was more active than unmodified lectin at nearly all the concentrations tested.
An electron spin resonance spectral study of the dynamics of spin-labelled fatty acids bound to oxidoreductases
Authors: Thewalt Jenifer , Viswanathan Tenkasi S. , Cushley Robert J.
Published: December 2009

Electron spin resonance (ESR) spectra have been recorded for 5-doxylstearate (I) and 16-doxylstearate (II) in the presence of bacterial luciferase and soybean lipoxygenase. The acids are inhibitors of the enzymes (Kd ≈ 2 × 10−5 M for II bound to luciferase). Using theoretical computer simulations of the ESR line shapes, an effective correlation time of τeff ≈ 3.7 × 10−9 ± 0.5 × 10−9 s is found for the motion of spin label I bound to luciferase. Concentration-dependent sedimentation velocity experiments indicate luciferase is anisotropic and, assuming a prolate ellipsoid of axial ratio ≤ 9, a correlation time of τa ≈ 7.7 × 10−9 s is predicted for rotation about the luciferase long axis. The tightly bound spin-labelled inhibitors, therefore, are proposed to give rise to ESR spectra chiefly reflecting luciferase long axis rotation. The ESR spectra of I and II, bound to lipoxygenase and to luciferase, appear similar.
A novel phosphoprotein dependent on the bacterial phosphoenolpyruvate–sugar phosphotransferase system
Authors: Waygood E. Bruce , Mattoo Roshan L.
Published: December 2009

A protein has been found by isoelectricfocusing and autoradiography in Escherichia coli and Salmonella typhimurium which was phosphorylated by enzyme I and an histidine-containing phosphocarrier protein (HPr) of the phosphoenolpyruvate–sugar phosphotransferase system (PTS). This protein was not factor IIIglc nor was it specifically induced by fructose. Its presence in soluble crude extracts was dependent upon growth conditions; however, the two bacteria had different patterns and amounts in respect to this novel protein. The protein was present in S. typhimurium SB2950 which has an extensive deletion through the pts operon, thus indicating that it must be coded for elsewhere on the genome.
Differences in the effects of pH on the hydrolytic and transgalactosylic reactions of β-galactosidase (Escherichia coli)
Authors: Huber R. E. , Gaunt M. T. , Sept R. L. , Babiak M. J.
Published: December 2009

Steady-state kinetic studies with β-galactosidase and various substrates were carried out to determine why the ratio of transgalactosylis to hydrolysis increased as a function of pH from 7.0 to 10.0. The rate constant [Formula: see text] for the formation of galactose (hydrolytic reaction) decreased whereas the rate constant (k4) for the transgalactosylic reaction (i.e., the formation of allolactose) remained constant. The equilibrium constant for acceptor dissociation from the galactosyl form of the enzyme was also unaffected by pH in the range studied; this was true whether the acceptor was glucose, sucrose, or glycerol. These results suggest that there is a group of high pKa at, or of influence at, the enzyme's active site which affects hydrolysis but not transgalactosylis. A further finding was that the rate constant for the breakage of the glycosidic bond decreased with pH in a manner different from the change observed for the hydrolytic rate constant (pKa 9.4 for glycosidic breakage as compared with 8.6 for hydrolysis). This could explain why the pH optimum for (β-galactosidase activity varies with substrate; different steps are rate limiting for different substrates.
Release of prostaglandins from intact fetal lamb ductus arteriosus
Authors: Pace-Asciak C. R. , Rangaraj G.
Published: December 2009

Intact rings and slices of ductus arteriosus from fetal lambs near term (130–143 days gestation) were incubated with [14C]arachidonic acid and the fate of the label in the incubation fluid and tissue was followed by thin-layer radiochromatography (TLC). Prostaglandins formed from endogenous stores of arachidonic acid were assayed by capillary gas chromatography with electron-capture detection. In additional experiments, the prelabelled tissue was incubated with various drugs (e.g., angiotensin II, bradykinin, and calcium ionophore) to determine their effects on the release of 14C-labelled prostaglandins. Results indicate that the ductus arteriosus is oriented towards forming prostaglandin (PG) I2, with PGE2 being formed to a minor extent in all studies. While radiochromatographic studies (TLC) suggested a considerable complexity mostly because of overlapping products (PGs and metabolites), this was resolved using gas chromatography where a complete resolution of PGs from these metabolites was observed. In the tissue-labelling experiments most of the radioactivity remained in the incubation fluid and was recovered as unchanged arachidonic acid, although a small but significant proportion of label was observed in a mixture of prostaglandins (4.2 ± 0.6%, n = 16) with 6-keto PGF1α being the major product. The ductus tissue incorporated a small amount of label (3.4 ± 0.4%, n = 19) of which 49.7 ± 4.9% (n = 13) was found in the tissue phospholipids. Hydrolysis of tissue-bound [14C]arachidonic acid, which appeared in the perfusing medium together with 14C-labelled prostaglandins, was in the range of 28.0 ± 2.7% (n = 9) of total tissue radioactivity per experiment. Although 42.2 ± 2.5% (n = 18) of the radioactivity released by each of the drugs represented a mixture of prostaglandins and their metabolites (the rest recovered as arachidonic acid), no appreciable selectivity by any of the drugs was found for either the stimulation of phospholipase activity in this tissue or for the rerouting of the prostaglandin synthetic system to form prostaglandin E2 instead of I2. We conclude that prostaglandin I2 rather than E2 is probably of physiological importance in this unique fetal blood vessel.
Primary structure determination of Escherichia coli heat-stable enterotoxin of porcine origin
Authors: Lazure Claude , Seidah Nabil G. , Chrétien Michel , Lallier Réal , St-Pierre Serge
Published: December 2009

The chemical characterization of Escherichia coli heat-stable enterotoxin (ST) is described. The toxin was isolated and purified to homogeneity from the E. coli strain F11 (PI55) of porcine origin. Following quantitative amino acid analysis, the enterotoxin was found to contain 18 amino acids including 6 cysteines, but was devoid of Ser, Val, Met, Ile, Lys, His, and Arg residues. All cysteine residues were found to be involved in disulfide bridges, even though their positions could not be localized. The enterotoxin thus has a molecular weight of 1979 and was shown to be an octadecapeptide with the following sequence: H2N-Asn-Thr-Phe-Tyr-Cys-Cys-Glu-Leu-Cys-Cys-Asn-Pro-Ala-Cys-Ala-Gly-Cys-Tyr-COOH. Its relationship to other known enterotoxins is discussed.
Effect of Ca2+ ions on liver cell plasma membrane polypeptides
Authors: Yousef Ibrahim M.
Published: December 2009

Plasma membrane fractions, microsomes, and mitochondrial membrane were prepared from rat liver. The effects of incubation of these membranes in various ionic strengths (1–12 mM) of NaHCO3 (pH 7.4) on the polypeptide patterns were studied in the absence or the presence of various concentrations of CaCl2 (1–12 mM). Many polypeptides were extracted from each of the membranes in the low ionic strength buffers (1 mM); these polypeptides were essentially similar to those remaining in the membrane after incubation. The extraction of these polypeptides continued when concentration of NaHCO3 increased. However, the presence of CaCl2 at a concentration of 4 mM or higher stabilized the membrane proteins and reduced the continuous loss of the polypeptides, and only low molecular weight polypeptides were affected. These data suggest that the organization of proteins in liver cell membranes may depend on the nature of their interaction with other membrane components (i.e., phospholipids), which could be affected by Ca2+ ions.
Aspects of hepatic cholesterol metabolism in normal and dystrophic chicken embryos
Authors: Kuhn D. E. , Logan D. M.
Published: December 2009

Several aspects of hepatic cholesterol metabolism have been studied in normal and dystrophic chicken embryos (12 days in ovo). Dystrophic embryo livers weigh the same and have the same total protein content as their normal counterparts. However, the total cholesterol content of dystrophic embryo livers is significantly decreased compared with the content of normal embryo livers. This decrease in total cholesterol is due mainly to a large decrease in the amount of cholesterol esters, although the free cholesterol content is also decreased. The proportions of free cholesterol and cholesterol esters are 43 and 57%, respectively, in normal embryo livers, but this proportion is essentially reversed in dystrophic embryo livers (i.e., 56 and 44%). The decreased total cholesterol content of dystrophic embryo livers is not apparently due to a decrease in the rate of free cholesterol de novo biosynthesis or to a decrease in the rate of free cholesterol esterification. However, the decrease in cholesterol ester content may be due to an increase in the rate of its hydrolysis, as a result of increased levels of sterol ester hydrolase in dystrophic livers. These data are consistent with the proposal that membranes in dystrophic tissues are altered as a result of altered cholesterol metabolism and utilization.
Genetic regulation during heat shock and function of heat-shock proteins: a review
Authors: Tanguay R. M.
Published: December 2009

The induction by thermal stress of certain specific genes (heat-shock genes) first described in Drosophila has recently been observed in a wide variety of unicellular and multicellular organisms, emphasizing the basic importance of this ubiquitous response. Recent data dealing with the molecular mechanisms involved in the intensive transcriptional and posttranscriptional regulation during heat shock is reviewed with emphasis on the induction of the response and the putative function of the heat-shock proteins. A model showing the various interactions of cellular regulatory mechanisms operating in the heat-shocked cell is presented. While the list of agents or treatments inducing heat-shock proteins (hsp's) in various organisms is increasing, the identification of a hypothetical common inducing factor is elusive. The recently described reorganization of some cytoskeletal elements upon heat shock is discussed both in terms of its potential involvement in transcriptional and (or) translational regulation and of its putative relation with the cellular localization of the hsp's. Studies on the cellular localization of hsp's in various organisms do not show a clear uniform pattern which could help in elucidating the function of hsp's. On the other hand, studies on the thermal resistance of various cells types show a strong correlation between the induction of hsp's and the development of transitory thermotolerance. Such a protective function for hsp's can probably be extended to other types of cellular aggression.
Regulation of gene expression in corn (Zea mays L.) by heat shock. II. In vitro analysis of RNAs from heat-shocked seedlings
Authors: Baszczynski Chris L. , Walden David B. , Atkinson Burr G.
Published: December 2009

Five-day-old maize seedlings subjected to heat shock exhibit a dramatic enhancement in the synthesis of a small group of polypeptides. Isolation of total RNA from control and heat-shocked maize plumules, fractionation of poly(A)+ mRNA by oligo(dT)-cellulose chromatography, and in vitro translations of the RNAs in both the rabbit reticulocyte and the wheat germ systems indicates that there is remarkable fidelity of the mRNA pool obtained from heat-shocked plumules to reproduce in vitro those same polypeptides whose synthesis is greatly elevated in the intact, heat-shocked plumule. Moreover, these heat-shock polypeptides with molecular masses of 108 000, 89 000, 84 000, 73 000, and 18 000 are translated from polyadenylated mRNAs. The absence of a 76 000 dalton heat-shock polypeptide (HSP) and the presence of fewer isoelectric point variants of the 89 000 and 84 000 dalton HSPs among the in vitro translation products suggests that translational and (or) posttranslational regulatory mechanisms might be operative in determining the final spectrum of the maize heat-shock proteins.
Characterization of the synthesis and accumulation of a 71-kilodalton protein induced in rat tissues after hyperthermia
Authors: Currie R. William , White Fredric P.
Published: December 2009

Tissues of rats subjected to brief hyperthermic shock were examined by two-dimensional gel electrophoresis for the synthesis and accumulation of a 71-kdalton stress-induced protein (P71). Tissues of 6-week-old rats, killed immediately or 30 min after hyperthermic shock, contained little or no P71. However, in all tissues tested, synthesis and accumulation of P71 was easily detected as early as 2.5 h after hyperthermic shock. The synthesis of P71 was markedly reduced by 1 and 2 days postshock, while the concentration of P71 in all tissues remained high up to 2 days postshock. After 4 days, P71 accumulation was not detected in brain and was reduced in other tissues; at 8 and 16 days after hyperthermic shock, P71 was still detectable but at ever diminishing amounts in heart, lung, liver, spleen, adrenals, and bladder. The subcellular distribution of P71 in brain and liver was determined 2.5 h and 1 and 2 days after hyperthermic shock. The soluble fractions of brain and liver had the greatest enrichment of P71 at each of these times. These results indicate that P71 is a soluble protein which may be present in at least some tissues of unstressed rats and that relatively high concentrations of P71 are found in most tissues after trauma. The increased synthesis of P71 is transient (persisting for less than 24 h after induction), suggesting that P71 is only slowly degraded in these tissues.
Alterations in the pattern of gene expression following heat shock in the nematode Caenorhabditis elegans
Authors: Snutch Terry P. , Baillie David L.
Published: December 2009

Exposure of the nematode Caenorhabditis elegans to elevated temperatures induces the preferential synthesis of eight major polypeptides of approximate molecular weights 81 000, 70 000, 41 000, 38 000, 29 000, 19 000, 18 000, and 16 000. In pulse-labelled worms these peptides first appear at 29 °C and continue to be synthesized up to lethal temperatures. They are heat inducible at every stage of development. While temperature elevation induces the synthesis of the heat-shock polypeptides, the in vivo synthesis of most other proteins present before heat shock is suppressed. In contrast, in vitro translation of mRNA from heat-shocked worms shows no alteration from the pattern of normal 20 °C mRNAs except for the appearance of the heat-shock mRNAs. An in vitro study of RNA from control and heat-shocked dauer larvae shows that this developmental variant possesses little translatable mRNA but, upon heat shock, synthesizes a set of messages corresponding to the heat-shock polypeptides. The low background of this system will be especially useful in the analysis and purification of heat-shock mRNA for molecular cloning experiments. Extensive similarities between the Drosophila and C. elegans heat-shock responses are shown, including homology between the 70-kdalton heat-shock genes of the two organisms.
Changes in characteristics of rat adrenal glomerulosa cells under acute and chronic treatment with ACTH
Authors: Legros François , Lehoux Jean-Guy
Published: December 2009

Groups of Long Evans rats were treated with 15 IU ACTH/day for 1–9 days and sacrificed at different intervals during and after treatment. Aldosterone and corticosterone plasma levels were increased above control values for the entire duration of treatment and were decreased to control values as early as 3 days posttreatment. The uptake of [125I]angiotensin II ([125I]AII) by adrenocortical glomerulosa cell suspensions was diminished by 71% at day 9 of treatment and this [125I]AII-uptake capacity slowly returned to control values after cessation of treatment (66.0% of control at day +19). The association constants at equilibrium (Ka) for AII receptors were similar in both treated (0.19 × 109 M−1 at day 9) and control (0.12 × 109 M−1) rats, whereas the number of AII-binding sites was lowered in the glomerulosa cells of treated (Nmax = 6 fmol/50 000 cells) compared with control (29 fmol) animals. In vitro cell suspensions from treated rats had, compared with controls, a lowered basal aldosterone and an increased corticosterone output. Addition of ACTH (10−8 M) to these cell suspensions showed no effect on the aldosterone or corticosterone output, whereas a significant stimulation was observed for cells obtained from control animals. Studies on rats treated 9 days and sacrificed 19 days after cessation of treatment demonstrated that the basal aldosterone and corticosterone output from zona glomerulosa cell suspensions was comparable with that of control rats; the steroid output of these cells could be further stimulated in vitro by addition of ACTH. It is concluded that the chronic ACTH treatment produced (i) a loss of AII receptor of adrenal zona glomerulosa cells, a phenomenon that was reversible 3–4 weeks posttreatment; (ii) a decreased capacity of glomerulosa cells to further respond to ACTH stimuli in vitro, suggesting either a loss of ACTH receptor by these cells or a decrease in activity of enzymes responsible for steroidogenesis, or a lack of endogenous precursor; (iii) a diminution of the thickness of the zona glomerulosa accompanied by an enlargement of the zonae fasciculate–reticularis, resulting in high circulating plasma corticosterone. This high plasma corticosterone level might well be the source of the precursor used in vivo by the zona glomerulosa to maintain the observed high plasma aldosterone level, despite the lowered overall steroidogenic capacities of these cells demonstrated by our in vitro studies.
Peptide neurohormones: their role in thermoregulation and fever
Authors: Ruwe W. D. , Veale W. L. , Cooper K. E.
Published: December 2009

The neural elements of the rostral diencephalon in the mammal have been implicated in the regulation of body temperature. Moreover, it may be the neural elements within this region of the brain which activate the febrile mechanisms in response to pyrogen. Is it possible that the neuropeptides located within this area of the brain serve as neurochemical intermediaries involved in temperature regulation, fever, and (or) antipyresis? Central administration of several neuropeptides can elicit marked changes in the core temperature of an animal. Although most of these purative neuroregulators exert only a very minor influence on thermoregulation, a small number of the neuropeptides have been shown to have a profound effect on the system controlling this basic vegetative function. One of these peptides, arginine vasopressin (AVP) may play a role as an endogenous antipyretic. The neuroanatomical localization of this peptide, as well as its axonal projections, are consistent with such a role for this neurohypophyseal peptide in the mediation of antipyresis. In addition, current evidence suggests that AVP does function as a neurotransmitter. Examination of the febrile response to pyrogen in both the periparturient animal and the neonate indicates that an elevation in plasma levels of AVP is closely correlated with the diminution in the febrile response. Also, when AVP is perfused into punctate regions of the brain, a pyrogen-induced fever may be markedly suppressed. AVP appears to act primarily within the septal area, 2- to 3-mm rostral to the anterior commissure. During the development of fever, the release of AVP is altered within these same loci. As body temperature decreases during the febrile state, there is a concomitant increase in the amount of AVP released into the extracellular fluid of these septal sites. Very recent findings suggest that AVP may have additional central neurochemical functions. For example, this peptide may be involved in the etiology of some forms of convulsive disorders. The precise manner in which body temperature is regulated by the central nervous system normally and during fever is not well understood. In particular, the central mechanism of action of AVP in these processes remains to be determined. Currently, it is clear that the critical central mechanisms which are active in thermoregulation and fever are quite complex and will require many more years of investigation before the exact role of each can be enunciated.
Immunologic similarity of insulin receptors in Golgi and plasma membranes from rat liver
Authors: Patel B. A. , Posner B. I.
Published: December 2009

Insulin receptor antibodies (IRA) have been shown to inhibit 125I-labeled insulin binding to plasmalemma and whole cells. An earlier study claimed that IRA was less able to inhibit 125I-labeled insulin binding to intracellular receptors than plasmalemma of rat liver. We have examined the effect of IRA serum from a patient with insulin-resistant diabetes mellitus on 125I-labeled insulin binding to plasmalemma and Golgi fractions prepared from female rat liver. Maximum inhibitions of 125I-labeled insulin binding were 44, 48, 55, and 51% for plasmalemma, Golgi light, Golgi intermediate, and Golgi heavy, respectively, and these were maintained at a serum dilution of up to 1:100. Half-maximal inhibition occurred at a serum dilution of 1:900. The IRA serum had no inhibitory effect on 125I-labeled ILAs and ovine prolactin (oPRL) binding to either plasma membrane or Golgi fractions. Analysis of the effect of the IRA serum showed that its inhibition of 125I-labeled insulin binding linearized the Scatchard plot, with abolition of the high affinity portion of the curve, and reduced the number of low affinity sites. The affinity of binding to Golgi but not plasmalemma insulin receptors was decreased. We conclude that there is immunologic similarity between intracellular and cell surface insulin receptors of rat liver. This is compatible with a fairly rapid equilibration between these two receptor populations, as expected with an active membrane recycling process.
Estrogen–androgeri interaction: selective inhibition of estrogen-induced uterine peroxidase by testosterone and 5α-dihydrotestosterone
Authors: Jellinck Peter H. , Affleck Andrew , Newcombe Anne-Marie
Published: December 2009

The effect of testosterone (T) and dihydrotestosterone (DHT) on the induction of peroxidase and glucose-6-phosphate dehydrogenase (G6PDH) in the immature rat uterus by estradiol (E2) was investigated. T (0.5–12.5 mg/rat) given on 3 successive days produced a large increase in uterine weight but, in contrast to E2, did not induce peroxidase or significantly augment uterine G6PDH. However, this androgen, even at a very low dose (50 μg/rat three times), inhibited the induction of peroxidase without a corresponding effect on G6PDH when given concurrently with E2 and was more effective than DHT. Inhibition by androgen was also observed when diethylstilbestrol was used to stimulate uterine growth. Combined treatment with E2 (3 μg/rat) and T (3 mg/rat) produced a cytosolic and nuclear estrogen receptor pattern in the uterus similar to that observed with E2 alone after various time intervals. The results speak against a direct inhibitory action or T on E2-induced uterine peroxidase via the estrogen receptor and confirm the lack of aromatization of T to E2 in the immature rat. Possible mechanisms for modifying the action of estrogens by androgens are discussed, particularly in the light of E2-induced eosinophilia. It is proposed that steroid hormones can interact in several ways and that uterine peroxidase provides a useful indicator to study steroid hormone action.
Identification and characterization of estrogen-responsive gene products in the liver of rainbow trout
Authors: Chen Thomas T.
Published: December 2009

Injection of male rainbow trout with estradiol induced the production of a major serum protein, vitellogenin (VG), of molecular weight (MW) 170 000. This protein is immunoprecipitable by an antiserum raised against lipovitellin from the eggs. Labelling by incubation of liver cubes of estradiol-treated fish with [35S]methionine and analysis of immunospecific products showed incorporation into two polypeptides of MW 170 000 and 160 000. The peptide patterns generated from these two polypeptides by Staphylococcus aureus V8 protease digestion were identical. Cytoplasmic poly(A)+ RNA of estradiol-treated male liver directs the synthesis of a polypeptide of 160 000 daltons in the reticulocyte cell-free protein-synthesizing system or in Xenopus oocytes. This polypeptide is chemically, immunologically, and electrophoretically identical to the authentic VG polypeptide of 160 000 daltons. Changes in mRNA populations in the liver of male fish following estradiol treatment were detected on gels and by hybridization. On methylmercuric hydroxide gels, a polyadenylated RNA species of about 6300 nucleotides was found in estradiol-treated fish which was absent from the control fish. Data from R0t analysis revealed the presence of at least two mRNA sequences of the high frequency class in the RNA of hormone-induced fish and their sizes were determined by Northern blot analysis to be 6300 and 1800 nucleotides, respectively. These observations are consistent with the induction of vitellogenins and at least another estrogen-responsive gene product by estradiol as reported in other egg-laying vertebrates.
Juvenile hormone increases ouabain-binding capacity of microsomal preparations from vitellogenic follicle cells
Authors: Ilenchuk T. T. , Davey K. G.
Published: December 2009

A comparison has been made of the effects of juvenile hormone (JH) on the binding characteristics for ouabain of microsomes prepared from brain and from cells of the follicular epithelium surrounding previtellogenic or vitellogenic oocytes in Rhodnius. JH has no effect on the binding of ouabain to brain microsomes and decreases the Kd, but does not alter the Bmax for previtellogenic follicle cells. For vitellogenic follicle cells, Scatchard analysis reveals a curvilinear relationship, which is interpreted as indicating that a new population of JH-sensitive ouabain-binding sites develops as the follicle cell enters vitellogenesis. These results are related to earlier data obtained on the effect of JH on ATPase activity, volume changes in isolated follicle cells, and the development of spaces between the cells of the follicular epithelium.
Removal of O-acetylated sialic acids from rat colonic epithelial glycoproteins by cell-free extracts of rat faeces
Authors: Poon H. , Reid P. E. , Ramey C. W. , Dunn W. L. , Clay M. G.
Published: December 2009

Sterile, cell-free, extracts of freshly defaecated Wistar rat faeces in a pH 7.0 "minimal medium" contain neuraminidase(s), capable of removing sialic acids both with and without side-chain substituents from bovine submandibular mucin and rat colonic epithelial glycoproteins, and an esterase which removes O-acetyl substituents from the side chain of sialic acid residues. Studies of the removal of sialic acids from bovine submandibular mucin and rat colonic epithelial glycoproteins indicated that (i) the faecal enzymes removed a greater proportion of the sialic acid of both the de-O-acetylated and native glycoproteins than was removed with Vibrio cholera neuraminidase, (ii) sialic acids were removed more rapidly from de-O-acetylated glycoproteins, and (iii) the resistance to removal of sialic acids was apparently dependent at least in part upon the O-acetyl sialic acid content of the substrate.