bluuebunny/crossref_metadata_2025_split huggingface dataset:
Glycoprotein VI/Fc receptor γ chain-independent tyrosine phosphorylation and activation of murine platelets by collagen
Authors: JARVIS Gavin E. , BEST Denise , WATSON Steve P. 
Published: October 2004

We have investigated the ability of collagen to induce signalling and functional responses in suspensions of murine platelets deficient in the FcRγ (Fc receptor γ) chain, which lack the collagen receptor GPVI (glycoprotein VI). In the absence of the FcRγ chain, collagen induced a unique pattern of tyrosine phosphorylation which was potentiated by the thromboxane analogue U46619. Immunoprecipitation studies indicated that neither collagen alone nor the combination of collagen plus U46619 induced phosphorylation of the GPVI-regulated proteins Syk and SLP-76 (Src homology 2-containing leucocyte protein of 76 kDa). A low level of tyrosine phosphorylation of phospholipase Cγ2 was observed, which was increased in the presence of U46619, although the degree of phosphorylation remained well below that observed in wild-type platelets (∼10%). By contrast, collagen-induced phosphorylation of the adapter ADAP (adhesion- and degranulation-promoting adapter protein) was substantially potentiated by U46619 to levels equivalent to those observed in wild-type platelets. Collagen plus U46619 also induced significant phosphorylation of FAK (focal adhesion kinase). The functional significance of collagen-induced non-GPVI signals was highlighted by the ability of U46619 and collagen to induce the secretion of ATP in FcRγ chain-deficient platelets, even though neither agonist was effective alone. Protein tyrosine phosphorylation and the release of ATP were abolished by the anti-(α2 integrin) antibodies Ha1/29 and HMα2, but not by blockade of αIIbβ3. These results illustrate a novel mechanism of platelet activation by collagen which is independent of the GPVI–FcRγ chain complex, and is facilitated by binding of collagen to integrin α2β1.
Cathepsin K: a cysteine protease with unique kinin-degrading properties
Authors: GODAT Emmanuel , LECAILLE Fabien , DESMAZES Claire , DUCHÊNE Sophie , WEIDAUER Enrico , SAFTIG Paul , BRÖMME Dieter , VANDIER Christophe , LALMANACH Gilles 
Published: October 2004

Taking into account a previous report of an unidentified enzyme from macrophages acting as a kininase, the ability of cysteine proteases to degrade kinins has been investigated. Wild-type fibroblast lysates from mice, by contrast with cathepsin K-deficient lysates, hydrolysed BK (bradykinin), and released two metabolites, BK-(1–4) and BK-(5–9). Cathepsin K, but not cathepsins B, H, L and S, cleaved kinins at the Gly4–Phe5 bond and the bradykinin-mimicking substrate Abz (o-aminobenzoic acid)-RPPGFSPFR-3-NO2-Tyr (3-nitrotyrosine) more efficiently (pH 6.0: kcat/Km=12500 mM−1·s−1; pH 7.4: kcat/Km=6930 mM−1·s−1) than angiotensin-converting enzyme hydrolysed BK. Conversely Abz-RPPGFSPFR-3-NO2-Tyr was not cleaved by the Y67L (Tyr67→Leu)/L205A (Leu205→Ala) cathepsin K mutant, indicating that kinin degradation mostly depends on the S2 substrate specificity. Kininase activity was further evaluated on bronchial smooth muscles. BK, but not its metabolites BK(1-4) and BK(5-9), induced a dose-dependent contraction, which was abolished by Hoe140, a B2-type receptor antagonist. Cathepsin K impaired BK-dependent contraction of normal and chronic hypoxic rats, whereas cathepsins B and L did not. Taking together vasoactive properties of kinins and the potency of cathepsin K to modulate BK-dependent contraction of smooth muscles, the present data support the notion that cathepsin K may act as a kininase, a unique property among mammalian cysteine proteases.
Sulpho-conjugation of ethanol in humans in vivo and by individual sulphotransferase forms in vitro
Authors: SCHNEIDER Heiko , GLATT Hansruedi 
Published: October 2004

We studied whether ethanol is sulphonated in humans with the perspective of using the urinary excretion of ethyl sulphate after ethanol consumption as a biomarker for SULT (sulphotransferase) activity. We developed a sensitive and selective HPLC–MS/MS method for determining ethyl sulphate in urine. Ten volunteers received a low dose of ethanol (0.1 g/kg of body mass). In general, excretion of ethyl sulphate was maximal in the first or second hour after dosage. Within 8 h, 2.5–6.8 μmol of ethyl sulphate was excreted. A 5-fold increase in the dose of ethanol led to an increase in the amount of ethyl sulphate excreted within 8 h (28–95 μmol) and the presence of this metabolite in urine for at least 24 h. Since ethyl sulphate was still being excreted for a substantial period after the elimination of ethanol, it might be used as a medium-time biomarker for preceding ethanol consumption. We have expressed previously all human SULT forms identified in Salmonella typhimurium. Ethanol sulphonation was studied in cytosolic preparations of these strains. The highest activities were observed with SULT1A2, 1B1 and 1C2, followed by 1A3. Activities were markedly lower with SULT1E1, 1A1 and 2A1, and were negligible with SULT1C1, 2B1a, 2B1b and 4A1. If the expression levels in tissues are additionally taken into account, SULT1A3 might be the predominant form for the sulphonation of ethanol in vivo, although a robust estimate requires further studies. With this limitation, urinary ethyl sulphate excretion appears very promising as a biomarker for SULT activity in vivo.
B-group vitamin supplementation mitigates oxidative damage after acute ischaemic stroke
Authors: ULLEGADDI Rajesh , POWERS Hilary J. , GARIBALLA Salah E. 
Published: October 2004

Evidence shows that there is a rapid increase in the production of markers of oxidative damage immediately following acute stroke and that endogenous antioxidant defences are rapidly depleted, thus permitting further tissue damage. Several studies point to an antioxidant effect of B-group vitamins and a pro-oxidant effect of elevated plasma tHcy (total homocysteine). In the present study, we assessed whether supplementary B-group vitamins during this critical period will enhance antioxidant capacity and mitigate oxidative damage. Forty-eight patients with acute ischaemic stroke within 12 h of symptom onset were assigned to receive daily oral supplements of B-group vitamins comprising 5 mg of folate, 5 mg of vitamin B2, 50 mg of vitamin B6 and 0.4 mg of vitamin B12 (n=24) or no supplements (n=24) for 14 days. The treatment group and controls were matched for stroke subtype and age. Blood samples were obtained before intervention and also at 7 and 14 days post-recruitment for measurement of the following biomarkers: red cell folate (whole blood folate corrected with haematocrit), erythrocyte glutathione reductase activity coefficient (EGRAC; measure of vitamin B2 status), plasma pyridoxal phosphate (vitamin B6 status), plasma vitamin B12, plasma α-tocopherol, plasma ascorbic acid, plasma TAOC (total antioxidant capacity), plasma MDA (malondialdehyde), plasma tHcy and CRP (C-reactive protein). Supplementation for 14 days with B-group vitamins significantly increased the plasma concentrations of pyridoxal phosphate and red blood cell folate and improved a measure of B2 status compared with the control group (P&lt;0.05). Plasma tHcy decreased in both groups albeit less in the control group, but differences in cumulative changes were not significant. There was, however, a decrease in plasma MDA concentration in the treatment group, in contrast with the increase seen in the control group and these differences were significant (P=0.05). CRP concentration, a marker of tissue inflammation, was significantly lower in the treatment group compared with controls (P&lt;0.05). In conclusion, B-group vitamin supplementation immediately post-infarct may have antioxidant and anti-inflammatory effects in stroke disease independent of a homocysteine-lowering effect.
Inflammatory and redox responses to ischaemia/reperfusion in human skeletal muscle
Authors: HUDA Ruksana , SOLANKI Daneshvari R. , MATHRU Mali 
Published: October 2004

The objective of this study was to identify cellular and plasma marker(s) of post-I/R (ischaemia/reperfusion) in patients undergoing elective knee surgery where a tourniquet was used to facilitate a bloodless surgical field. We evaluated the inflammatory and redox response by measuring the mRNA levels of ICAM-1 (intercellular cell-adhesion molecule-1), MnSOD (manganese superoxide dismutase), GST-μ (glutathione transferase-μ) and Cu/ZnSOD (copper/zinc superoxide dismutase) in the operated muscle and blood cells pre-operatively (pre-tourniquet) and at various times after reperfusion (tourniquet release). We also measured plasma concentrations of IL (interleukin)-6, IL-8, sICAM-1 (soluble ICAM-1), IL-1β and TNF-α (tumour necrosis factor-α) using ELISA. Our results show a strong induction of MnSOD and GST-μ in granulocytes (but not in mononuclear cells or muscle) after reperfusion (2 and 4 h). There was no change in the mRNA level of Cu/ZnSOD after reperfusion. An up-regulation of membrane ICAM-1 in muscle and a decrease in sICAM-1 in plasma were detected after reperfusion. Plasma IL-6 and IL-8 levels (but not TNF-α or IL-1β) increased significantly over baseline at 2 and 4 h after reperfusion. Elevated expression of ICAM-1 in muscle, MnSOD and GST-μ in granulocytes and increased levels of plasma IL-6 and IL-8 may be considered as phase- and cell-specific markers of post-I/R of skeletal muscle in humans.
South American palaeobotany and the origins of neotropical rainforests
Authors: Burnham Robyn J. , Johnson Kirk R. 
Published: October 2004

Extant neotropical rainforest biomes are characterized by a high diversity and abundance of angiosperm trees and vines, high proportions of entire–margined leaves, high proportions of large leaves (larger than 4500 mm2), high abundance of drip tips and a suite of characteristic dominant families: Sapotaceae, Lauraceae, Leguminosae (Fabaceae), Melastomataceae and Palmae (Arecaceae). Our aim is to define parameters of extant rainforests that will allow their recognition in the fossil record of South America and to evaluate all known South American plant fossil assemblages for first evidence and continued presence of those parameters. We ask when did these critical rainforest characters arise? When did vegetative parameters reach the level of abundance that we see in neotropical forests? Also, when do specific lineages become common in neotropical forests?Our review indicates that evidence of neotropical rainforest is exceedingly rare and equivocal before the Palaeocene. Even in the Palaeocene, the only evidence for tropical rainforest in South America is the appearance of moderately high pollen diversity. By contrast, North American sites provide evidence that rainforest leaf physiognomy was established early in the Palaeocene. By the Eocene in South America, several lines of evidence suggest that neotropical rainforests were diverse, physiognomically recognizable as rainforest and taxonomically allied to modern neotropical rainforests. A mismatch of evidence regarding the age of origin between sites of palaeobotanical high diversity and sites of predicted tropical climates should be reconciled with intensified collecting efforts in South America. We identify several lines of promising research that will help to coalesce previously disparate approaches to the origin, longevity and maintenance of high diversity floras of South America.
ISOLATION AND CHARACTERIZATION OF NATIVE PIGMENT‐PROTEIN COMPLEXES FROM TWO EUSTIGMATOPHYCEAE1
Authors: Arsalane Wafa , Rousseau Bernard , Thomas J. C. 
Published: October 2004

ABSTRACTPigment‐protein complexes were isolated from two species of Eustigmatophyceae, Monodus subterraneus Peterson and Vischeria punctata Vischer, by digitonin treatment followed by density gradient centrifugation. Absorption and fluorescence spectra of the samples were monitored at various steps of preparation, and pigment composition was analyzed by reverse phase HPLC. Although the fluorescence emission spectra were very different in the two species, the absorption spectra were similar, and each exhibited an absorption band with a maximum at 487 nm attributable to violaxanthin and vaucheriaxanthin ester (the molar concentration of these pigments in Monodus was, respectively, 28 and 10 per 100 Chl a). The light‐harvesting role of these xanthophylls was ascertained by fluorescence excitation spectra. The light‐harvesting fractions (LH) collected in the upper part of the gradient were depleted in β‐carotene, whereas their xanthophyll/chlorophyll ratio was almost the same as in whole cells. This is consistent with the presence in these algae of large LH antennae and relatively small core antennae in the photosystems. In Monodus, a polypeptide of 23 kDa, immunologically related to the major LH polypeptide of brown algae, constituted the majority of the LH protein moiety.
STRUCTURE OF EXTRACELLULAR POLYSACCHARIDES PRODUCED BY A SOIL CRYPTOMONAS SP. (CRYPTOPHYCEAE)1
Authors: Paulsen Berit Smestad , Vieira Armando Augusta Henriques , Klaveness Dag 
Published: October 2004

ABSTRACTThe Hindak strain of a Cryptomonas species (Cryptophyceae) produces extracellular polysaccharides. Because there is no information on the structure of these compounds in the Cryptophyceae we conducted structural studies. Gas–liquid chromatographic analyses showed that the polysaccharide is composed of fucose, rhamnose, xylose, mannose, glucose, galactose, galacturonic acid, glucuronic acid, and traces of 3‐O‐methyl galactose. The polysaccharide was separated into two subtractions by ion‐exchange chromatography. Fraction A consisted mainly of 1,3‐linked galactose units and 1,4‐linked galacturonic acid. Unlike fraction B, fraction A did not have xylose, 3‐O‐methyl galactose, or glucuronic acid. Also, its degree of branching was low compared to that of fraction B. Only traces of sulfate were present infraction A, but fraction B was 10–15% sulfated. Protein was approximately 1% in both fractions. These polysaccharides appear to be a novel type of polymer in algae.
ULTRASTRUCTURE OF THE FEEDING APPARATUS AND MYONEMAL SYSTEM OF THE HETEROTROPHIC DINOFLAGELLATE PROTOPERIDINIUM SPINULOSUM1
Authors: Jacobson Dean M. , Anderson Donald M. 
Published: October 2004

ABSTRACTThe feeding veil or pallium of the thecate heterotrophic dinoflagellate Protoperidinium spinulosum Schiller is a highly vesiculate membranous sac containing several arched, sometimes bifurcated microtubular ribbons. It originates from an internal microtubular basket, passes through a sphincter‐like osmiophilic ring located inside the posterior flagellar pore, and emerges from the cell at that pore. The osmiophilic ring is part of an interconnected myonemal system (composed of two striated collars and several striated connectives) that is anchored to the pore plate and to two inward protrusions composed of minute sulcal plates. A related species, Protoperidinium punctulatum (Paulsen) Balech, also possesses a microtubular basket/osmiophilic ring complex. Elongate electron‐dense bodies within the basket resemble digestive secretory granules found in other protists. Granular, electron‐lucent microbodies clustered at the anterior end of the basket may also have a role in prey digestion. Dense membranous whorls observed within a P. spinulosum cell presented as it was preparing to initiate feeding indicate a condensed storage site for pallium membranes. A narrow microtubule‐strengthened pseudopodal appendage found in two non‐feeding cells constitutes the tow filament that serves as the initial linkage between the dinoflagellate and its food. The structures that constitute the pallium and pallium precursors, described here for the first time, are unlike those of other known protists, although some similarities with the dinoflagellate peduncle are evident. The existence of this unique system of organelles may have important ramifications in the search for evolutionary relationships among protists.
COMPARISON OF CHLOROPLAST DNA AND ALLOZYME VARIATION IN WINTER STRAINS OF THE MARINE DIATOM SKELETONEMA COSTATUM(BACILLARIOPHYTA)1
Authors: Stabile Joseph E. , Wurtzel Eleanore T. , Gallagher Jane C. 
Published: October 2004

ABSTRACTRestriction fragment length polymorphisms (RFLPs) were examined in 12 winter strains of the marine diatom Skeletonema costatum (Grev.) Cleve using homologous chloroplast gene probes. The winter strains included eight different allozyme genotypes exhibiting physiological differences. These 12 winter strains were representative of the least diverse genetic group present in Narragansett Bay populations. Five chloroplast DNA probes and four different restriction enzymes were used to analyze the 12 Narragansett Bay strains and a reference strain “Skel.” A total of 46 restriction fragments were identified. All 12 of the winter strains had identical patterns. Strain Skel exhibited two RFLPs in comparison to the Narragansett Bay strains. Calculated diversity within the winter strain group was 0.0 and 0.85 for the chloroplast DNA and allozyme data, respectively. The chloroplast DNA polymorphisms revealed by this study are expected to represent a minimum level of the chloroplast DNA diversity present in Narragansett Bay seasonal populations.
OBSERVATIONS ON THE MORPHOLOGY AND SEXUAL REPRODUCTION OFCOOLIA MONOTIS(DINOPHYCEAE)1
Authors: Maria A. Faust 
Published: October 2004

ABSTRACTThe surface morphology of the dinoflagellateCoolia monotisMeunier was compared with the surface morphologyof Ostreopsis, The apical pore ofC. monotisis similar in architecture to that ofOstreopsisbut considerably longer (12 μm) than inO. heptagona(8–9 μm) andO. ovata(6–7 μm). A ventral pore inC. monotisis located on the right ventral margin between apical plate l′ and precingular plate 6″ and is similar in appearance and location to the ventral pore ofO. ovata.The longitudinal flagellum (20 μm) inC. monotisis longer than inO. ovata(12 μ). AlthoughCooliaandOstreopsisappear to be distinctly different and should remain as two separate genera, they appear to be related.Cells ofC. monotisdivided by binary fission. Doubling time was 3–4 days in the logarithmic phase of growth at 23°C, 12:12 h L:D, 30–90 μE‐m−2·s−1, and a salinity of 36%. Cultures reached cell densities of 2.5 × 103cells·L−1after 15 days of growth.The sexual process inC. monotisoccurred in Erdschreiber's medium when Danish soil extract was substituted with mangrove sediment extract under the culture conditions described above. Gamete fusion produced large biflagellated planozygotes (70–75 μm diam). Planozygote maturation involved cytoplasmic reorganization, loss of motility, development of a spherical shape (80–90 μm diam), and two to three orange accumulation bodies. The cells at this stage appeared to be thin‐walled cysts. Further development included reorganization of cyst contents, emergence of non‐motile gametes, and development of chloroplasts, sulcus, and girdle. The nucleus of the newly formed cells occupied 50% or more of the total cell volume. Meiosis occurred in the cyst, but nuclear cyclosis was not observed. Four daughter cells were produced within 36–48 h, and motile gametes developed. The gametes exhibited sexuality for 2 months and completed the sexual life cycle by going through a thin‐walled cyst stage.
SCALED CHRYSOPHYTES (CHRYSOPHYCEAE AND SYNUROPHYCEAE) FROM ADIRONDACK DRAINAGE LAKES AND THEIR RELATIONSHIP TO ENVIRONMENTAL VARIABLES1
Authors: Cumming Brian F. , Smol John P. , Birks H. John B. 
Published: October 2004

ABSTRACTThe relationships between 23 scaled chrysophyte taxa (Chrysophyceae and Synurophyceae) and measured limnological variables in 62 Adirondack, New York, drainage lakes were examined by canonical correspondence analysis (CCA). The major proportion of variation in chrysophyte species distributions was strongly related to total monomeric Al (Alm) and Mg concentrations, and their close correlates pH, Na, Ca, and acid‐neutralizing capacity (ANC). Total monomeric Al concentrations explain a greater proportion of species variation than pH, suggesting that Alm concentrations may be more important in governing the distribution of chrysophyte taxa in these lakes. Gaussian logit (GL) and linear logit (LL) regressions of the relative percentages of individual chrysophyte taxa to lakewater pH and Alm concentrations and the examination of pH–Alm response surfaces show that many chrysophyte taxa exhibit unique responses to these environmental gradients; taxa can be characterized as alkaline, circumneutral, acidic, and pH indifferent. Within each of these groups, taxa can be characterized further based upon their optima and tolerances to Alm concentrations. Chrysophyte indicator species (i.e. a taxon with a strong statistical relationship to the environmental variable of interest, a well‐defined optimum, and a narrow tolerance to the variable of interest) for pH include Mallomonas hindonii, M. crassisquama, M. pseudocoronata, and Synura uvella; M. hindonii, M. crassisquama, M. pseudocoronata, S. petersenii, and S. spinosa are good indicators of Alm concentrations. Highly significant predictive models were developed to infer lakewater pH and Alm concentrations from the relative percentages of chrysophyte scales in the study lakes. Model evaluation was based on their correlation coefficients and the root‐mean‐squared error of prediction (RMSE) derived from bootstrapping. Weighted averaging regression and calibration with tolerance down‐weighting (i.e. weighting taxa inversely to their variance) produced superior results when compared to the computationally and data‐demanding maximum likelihood methods and to simple weighted averaging regression and calibration.
PHOTOSYNTHESIS‐IRRADIANCE RELATIONSHIPS IN PHYTOPLANKTON FROM THE PHYSICALLY STABLE WATER COLUMN OF A PERENNIALLY ICE‐COVERED LAKE (LAKE BONNEY, ANTARCTICA)1
Authors: Lizotte Michael P. , Priscu John C. 
Published: October 2004

ABSTRACTThe perennially ice‐covered lakes of Antarctica have hydrodynamically stable water columns with a number of vertically distinct phytoplankton populations. We examined the photosynthesis‐irradiance characteristics of phytoplankton from four depths of Lake Bonney to determine their physiological condition relative to vertical gradients in irradiance and temperature. All populations studied showed evidence of extreme shade adaptation, including low Ik values (15–45 μE · m−2· s−1) and extremely low maximal photosynthetic rates (PBm less than 0.3 μg C ·μg chl a−1· h−1). Photosynthetic rates were controlled by temperature as well as light variations with depth. Lake Bonney has an inverted temperature profile within the trophogenic zone that increased from 0° C at the ice‐water interface to 6° C from 10 to 18 m. Deeper phytoplankton (10 m and 17 m) were found to have photosynthetic capacities (PBm) and efficiences (α) three to five times higher than those at the ice‐water interface. However, Q10 values were only ca. 2 for PBm (no temperature dependence was evident for α), suggesting that a simple temperature response cannot explain all the differences between populations. Lake Bonney phytoplankton (primarily cryptophytes and chlorophytes) had photosynthetic characteristics similar to diatoms from other physically stable environments (e.g. sea ice, benthos) and may be ecologically analogous to multiple deep chlorophyll maxima.