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At least 703 records · Page 39Linked to original sources
PubMed1985

Four methods for determining total protein compared by using purified protein fractions from human serum.

The proportional bias of four methods frequently used for determining low concentrations of protein was evaluated with human serum protein fractions (Cohn Fractions II, III, IV, and V). Each fraction was assigned a protein concentration value as determined by the biuret method, calibrated with purified human serum albumin monomer. All four methods (Coomassie Brilliant Blue dye-binding, the method of Lowry et al., ultraviolet absorption, and immunonephelometry gave acceptable results for Fraction V (albumin). The ultraviolet absorption and the Lowry methods overestimated the three globulin fractions (II, III, and IV), whereas the other two methods underestimated these fractions. The method of Lowry et al. gave the least proportional bias for the globulin fractions.

Blood Proteins↗
PubMed1984

Inhibition of DNA polymerase alpha activity by ammonium 21-tungsto-9-antimoniate (HPA23).

Ammonium 21-tungsto-9-antimoniate (HPA23), an inorganic condensed ion, was shown to be a potent inhibitor for DNA polymerase alpha but not for beta. It inhibited the activity of mammalian DNA polymerase alpha in noncompetitive fashion with respect to either of deoxynucleotide substrate and template X primer, indicating the presence of a specific binding site for HPA23 on DNA polymerase alpha molecule. The Ki of the alpha polymerase for HPA23 was 24 nM. A possible interaction of HPA23 with DNA polymerase alpha is discussed.

Animals↗
PubMed1983

[Scanning electron microscopy study of the effect of steel and tungsten carbide burs on dental tissues].

The effects of steel and tungsten carbide burs have been studied under the scanning electron microscope on human enamel and dentin during preparation of mesio-occluso-distal cavities in vitro with cutting speeds varying from 5 000 to 120 000 r.p.m. All the cavities presented clean and regular walls. However, the final quality of the cavity borders, and in particular the cavo-surface angles of the box walls, was directly related to the speed and rotation direction of the bur. The cavo-surface angles at the gingival planes showed in all cases fractures of the superficial prisms. The cutting character displayed in dentine surfaces were mainly dependent on the orientation of the tubules in relation to the surface of the cavity preparation and the degree of sclerosed dentine. The cavities prepared in the absence of water and air showed the presence of tissue debris nd cracks; their number increased with increasing rotational speed.

Adolescent↗
PubMed1983

Automated characterization of particles extracted from human lungs: three cases of tungsten carbide exposure.

An automated scanning electron microscope-energy dispersive x-ray analysis-image analysis system was used to characterize particles extracted from three human lung samples which had suspected occupationally-induced lung disease. The particles were isolated from the lung tissues by low temperature ashing and deposited on Nuclepore filters. Particles in randomly selected fields of view for each filter were automatically sized, analyzed for 32 elements, and classified according to their chemistry by the system. For each of the three lung specimens, large numbers of particles were found which indicated exposure to cemented tungsten carbide products. The particle analysis data was collected at a rate of 200 particles per hour which is considerably faster than the rate at which manual, in situ analyses can be performed.

Adult↗
PubMed1984

[Diffuse interstitial pneumopathy related to tungsten carbide, confirmed by bronchoalveolar lavage, and responding to corticotherapy].

The authors report a case of severe diffuse interstitial hard metal lung disease responding to corticosteroid therapy. They point out that the course of this disease may be regressive and emphasise that analysis of broncho-alveolar washings showed no abnormality in the differential cell count. Mineralogical study of the same material confirmed exposure.

Adrenal Cortex Hormones↗
PubMed1983

[Determination of protein in cerebrospinal fluid: comparison of the Coomassie-Blue method and the Cu-Folin differential test].

Comparison of within-run and between-day imprecision of protein assays using CSF controls as well as 96 random CSF samples from the routine laboratory shows that the Cu-Folin differential test and the Coomassie-Brilliant-Blue method from Bio-Rad are equally suited to total protein determination in cerebrospinal fluid. Problems possibly arising with very low concentrations of CSF or urine protein and the influence of some drugs often used in the neurological clinic are presented and discussed.

Cerebrospinal Fluid Proteins↗
PubMed1980

Facilitation of tungstic acid gel-induced cortical epilepsy in rats by depression of the reticular formation.

The experiments were performed electroencephalographically (EEG) on intact and decerebrated (cerveau isolé) rats with cortical foci induced by application of tungstic acid gel. In both preparations, the gel applied cortically (15 microliter) caused generalized seizures (GS) which often recurred with a stable interictal period approximately 1 hr later. The amplitude of GS and its high frequency components induced in decerebrated animals were more pronounced than those in intact ones. The duration of GS was prolonged up to 232% as compared with that in intact ones. Administration of chlorpromazine or biperiden in intact animals enhanced GS at the doses depressing EEG arousal response induced by electrical stimulation of the sciatic nerve, but did not enhance GS in decerebrated animals. The anticonvulsive effect of phenobarbital and diazepam in decerebrated animals was stronger than that in intact ones, while the effect of diphenylhydantoin and dipropylacetate was the same in both preparations. It is suggested in the gel-induced epilepsy that either impairment or depression of the reticular formation enhances GS.

Acids↗
PubMed1995

Measurement of phosphotyrosine phosphatase activity using the Folin-Ciocalteu phenol reaction.

An assay for the estimation of phosphotyrosine phosphatase using the Folin-Ciocalteu phenol reaction to monitor enzyme activity is presented. The method is based on the property of the substrate phosphotyrosine not to react as a phenol until it is dephosphorylated. The method is sensitive, there is no interference from the use of detergents and it does not rely on special laboratory equipment to distinguish tyrosine from phosphotyrosine.

Amino Acid Sequence↗
PubMed1994

[Pleural fibroma: a case of a patient exposed to tungsten carbide and asbestos].

We report here a case of localized fibrous pleural mesothelioma diagnosed in a sixty-year old patient, who had been exposed to tungsten carbide and asbestos dust for almost twenty years. He first consulted because of enduring lateral chest pains combined with progressive and increasing dyspnea on exertion. The initial diagnosis, after both pulmonary radiograph and computerised tomography, was confirmed by a histology which revealed fusiform cells of fibroblastic origin. After simple and total excision of the tumor, symptoms improved.

Asbestos↗
PubMed1994

Evidence for a H+ nitrate symporter in Aspergillus nidulans.

Nitrate transport in Aspergillus nidulans was dependent upon a consistent proton motive force (delta p) across the cell membrane which was maintained in a range of 105 (+/- 6.7) to 131 (+/- 3.4) mV over an external pH span of 5.5 to 7.5. The membrane potential (delta psi) measured by uptake of [3H]-tetra-phenylphosphonium bromide and the transmembrane pH difference (delta pH) measured by the distribution of 3H2O and [14C]- salicylic acid were used to compute the delta p present during transport of nitrate. Energy dependent accumulation of nitrate was measured in actively assimilating and tungstate inhibited cells. A delta G for nitrate of 14 kJ mol-1 was computed from the results. Cells induced for nitrate transport maintained internal nitrate levels of 6 to 8 mM based on an internal volume of 2.6 microliters/mg dry wt as determined by a conventional dual label procedure. A fivefold higher level of cellular nitrate was observed in tungstate inhibited cells. Nitrate accumulation was dependent upon a H+ gradient which was dissipated by treatment with 2-butanol, the ionophores valinomycin and gramicidin and the proton conductors carbonyl cyanide m-chlorophenyl hydrazone and N,N'-dicyclo-hexylcarbodiimide. Significant ATP and nitrate efflux occurred in cells treated with the above agents. The results suggest that nitrate is transported by symport with H+ on a carrier which is functionally linked to a H+ ATPase pump.

Aspergillus nidulans↗
PubMed1994

Insulin-like actions of tungstate in diabetic rats. Normalization of hepatic glucose metabolism.

Oral administration of tungstate for 15 days normalized glycemia in streptozotocin-induced diabetic rats. Simultaneously, the alterations in hepatic glucose metabolism due to diabetes were almost completely counteracted by this treatment. Thus, 6-phosphofructo-2-kinase, L-pyruvate kinase, and glycogen phosphorylase alpha activities reached levels similar to those observed in healthy animals. Hepatic levels of fructose 2,6-bisphosphate and glycogen also recovered. However, the recovery of glucokinase activity and hepatic levels of glucose 6-phosphate was only partial. The total activity of glycogen synthase increased, although the activation state was not recovered. Moreover, mRNA levels of hepatic glucokinase, glycogen phosphorylase, and phosphoenolpyruvate carboxykinase were also normalized. Tungstate administration in healthy animals also affected all these parameters, although to a much lesser extent. All these effects were similar to those previously reported for vanadate, suggesting a common mechanism of action in vivo.

Animals↗
PubMed1994

Crystal structure of human protein tyrosine phosphatase 1B.

Protein tyrosine phosphatases (PTPs) constitute a family of receptor-like and cytoplasmic signal transducing enzymes that catalyze the dephosphorylation of phosphotyrosine residues and are characterized by homologous catalytic domains. The crystal structure of a representative member of this family, the 37-kilodalton form (residues 1 to 321) of PTP1B, has been determined at 2.8 A resolution. The enzyme consists of a single domain with the catalytic site located at the base of a shallow cleft. The phosphate recognition site is created from a loop that is located at the amino-terminus of an alpha helix. This site is formed from an 11-residue sequence motif that is diagnostic of PTPs and the dual specificity phosphatases, and that contains the catalytically essential cysteine and arginine residues. The position of the invariant cysteine residue within the phosphate binding site is consistent with its role as a nucleophile in the catalytic reaction. The structure of PTP1B should serve as a model for other members of the PTP family and as a framework for understanding the mechanism of tyrosine dephosphorylation.

Amino Acid Sequence↗