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PubMed1990

Mercury in the Swedish chloralkali industry--an evaluation of the exposure and preventive measures over 40 years.

The monitoring of exposure to mercury in the Swedish chloralkali industry started in 1946 and became common in the 1960s. During the 1970s both urinary and blood mercury (U-Hg, B-Hg) concentrations decreased substantially. The mean (geometric) U-Hg was 500-700 nmol l.-1 in the 1960s as compared with 150 nmol l.-1 today. During the 1970s the mean (geometric) B-Hg declined from about 100 to 40 nmol l.-1. Nowadays high values, U-Hg greater than 1500 nmol l.-1 or B-Hg greater than 600 nmol l.-1, are very rare whereas in the 1950s and the 1960s such peak values were found among 30% of the workers. The most effective measures taken were the reduction of the hydrogen discharges from the process and the replacement of graphite anodes by dimensionally stable anodes which require less frequent maintenance. Today efficient cleaning and continuous monitoring make it possible to keep the exposure levels low. The use of respiratory protection equipment is, however, still necessary during certain maintenance operations.

Air Pollutants↗
PubMed1992

Alteration of the curved helical structure located in the upstream region of the beta-lactamase promoter of plasmid pUC19 and its effect on transcription.

The region preceding the beta-lactamase promoter of Escherichia coli plasmid pUC19 has a curved DNA (bent DNA) structure. The center of the curvature was revealed to exist around nucleotide position 2580 of the plasmid, which is just beside RNA polymerase binding region. It was indicated that the identified region is curved even at 60 degrees C. The gross geometry of the curvature was altered by inserting synthetic double-stranded oligonucleotides between positions 2585 and 2586. Effect of the alteration on strength of the promoter was not detected in vitro. However, in vivo analyses showed that the promoter strength is apparently dependent, in part, on the gross geometry of the curvature. Insertions of 4 and 16 bp, both of which altered the gross geometry of the curvature greatly, caused considerable reductions of in vivo level of beta-lactamase mRNA. In vivo, overall three-dimensional structure of the region covering the promoter and the curvature seems to play some significant role in transcription of the gene.

Base Sequence↗
PubMed2002

DNA-PCR and RT-PCR for the 18-kDa gene of Mycobacterium leprae to assess the efficacy of multi-drug therapy for leprosy.

DNA-PCR and reverse transcription (RT)-PCR for the 18-kDa protein of Mycobacterium leprae were used to examine the efficacy of multi-drug therapy (MDT) in leprosy. MDT was administered for 0-24 months. Fourteen (63.6%) of 22 patients showed positive PCR results after treatment for 12 months and the positive results decreased to 30% after 24 months of MDT. These results did not correlate with the bacterial index (BI) or the IgM antibody titre for the phenolic glycolipid (PGL)-1. One-dimensional densitometric analysis of agarose gels from PCR from the longitudinal study showed a gradual reduction of the 360-bp band after 12-24 months of MDT. RT-PCR for mRNA of the 18-kDa protein successfully tracked bacterial RNA changes in the biopsies and confirmed a decrease in the RNA of M. leprae in patients after MDT for 12 months. Thus, DNA- and RT-PCR for the 18-kDa protein of M. leprae are effective in assessing the efficacy of MDT for leprosy.

Animals↗
PubMed2002

Angular momentum and cross sections for fusion with weakly bound nuclei: breakup, a coherent effect.

Results for the cross section and average angular momentum for complete fusion at energies around the Coulomb barrier are presented for 7Li with 165Ho. Comparison of the cross sections with a one-dimensional barrier penetration model, using a potential consistent with the measured elastic scattering, showed a reduction above the barrier and an enhancement below it. An increase in the measured average angular momentum, , above the barrier and its consistency with that obtained from the fusion excitation function for weakly bound nuclei, is reported. These results together with a reanalysis of existing data conclusively demonstrate that the effect of breakup on fusion is coherent, like coupling to any nonelastic channel.

Journal Article↗
PubMed2005

High temperature ferromagnetism in GaAs-based heterostructures with Mn delta doping.

We show that suitably designed magnetic semiconductor heterostructures consisting of Mn delta (delta)-doped GaAs and p-type AlGaAs layers, in which the locally high concentration of magnetic moments of Mn atoms are controllably overlapped with the two-dimensional hole gas wave function, realized remarkably high ferromagnetic transition temperatures (T(C)). A significant reduction of compensative Mn interstitials by varying the growth sequence of the structures followed by low-temperature annealing led to high T(C) up to 250 K. The heterostructure with high T(C) exhibited peculiar anomalous Hall effect behavior, whose sign depends on temperature.

Journal Article↗
PubMed2001

Bulk modulus and non-uniform compression of Nb3Te4 and InxNb3Te4 (x < 1) channel compounds.

The crystal structures of Nb3Te4 and InxNb3Te4 [x = 0.539 (4)] are reported for a series of pressures between 0 and 40 GPa. Both compounds crystallize in space group P6(3)/m with a = b = 10.671 and c = 3.6468 A for Nb3Te4, and a = b = 10.677 and c = 3.6566 A for InxNb3Te4 at ambient conditions. Phase transitions were not observed. High-pressure X-ray powder diffraction was measured using a diamond anvil cell and synchrotron radiation. Full Rietveld refinements provided the values of the lattice parameters and the values of the atomic coordinates at each pressure. The bulk modulus is found as K(0) = 70 (5) GPa for Nb3Te4 and as K(0) = 73 (4) GPa for InxNb3Te4. The analysis of the pressure dependences of the detailed crystal structures shows that the compression along c involves the folding up of the quasi-one-dimensional zigzag chains of Nb. The compression perpendicular to c is entirely due to the reduction of the diameter of the channels. The presence of intercalated In atoms is found to have hardly any influence on the compression behaviour up to 40 GPa.

Journal Article↗
PubMed2004

Collection of reciprocal space maps using imaging plates at the Australian National Beamline Facility at the Photon Factory.

Weissenberg screens and a translating cassette have been employed to allow an imaging plate to collect 30 scans per readout. In this configuration the imaging plate functions as a curved one-dimensional position-sensitive detector and, by changing the sample angle for each of the scans, two-dimensional images were produced in reciprocal space. This method of data collection leads to a reduction in scan time compared with methods based on a scintillation detector, particularly for asymmetric reflections. The data-collection method was tested using InGaN/GaN/AlN multilayers on sapphire substrates, since these exhibit broad features in reciprocal space. The geometry of the scans in reciprocal space required the data to be interpolated onto a Cartesian grid. Several interpolation schemes were investigated, with the results compared with the reciprocal space maps collected using a triple-axis scheme with a point detector. The quality of the interpolated reciprocal space maps depends upon the size and shape of the feature in reciprocal space, the interpolation method used, and the step size of the sample rotation. The method can be extended to three dimensions without an increase in data-collection time.

Journal Article↗
PubMed2001

CBIT--context-based image transmission.

Few networks offer sufficient bandwidth for the transmission of high resolution two- and three-dimensional medical image sets without incurring significant latency. Traditional compression methods achieve bit-rate reduction based on pixel statistics and ignore visual cues that are important in identifying visually informative regions. This paper describes an approach to managing image transmission in which spatial regions are selected and prioritized for transmission so that visually informative data is received in a timely manner. This context-based image transmission (CBIT) scheme is a lossless form of progressive image transmission (PIT) in which gross structure, represented by an approximate iconic image, is transmitted first. Each part of this iconic image is progressively updated, using a simple set of rules that take into account viewing requirements. CBIT is realized using knowledge about image composition to segment, label, prioritize, and fit geometric models to regions of an image. Tests, using neurological images, show that, with CBIT, a valuable transmitted image is received with a latency that is about one-tenth that of traditional PIT schemes. Frequently, the necessary regions of the image are transmitted in about half the time taken to transmit the full image.

Artificial Intelligence↗
PubMed1981

Electrophoretic polymorphism of human C4 is due to charge differences in the alpha chain, presumably in the C4d fragment.

Various common C4 gene products were isolated from serum by immunoprecipitation. After reduction the C4 alpha-, beta-, and gamma-polypeptide chains were studied by two-dimensional electrophoresis. Isoelectrofocusing was performed in the first dimension and sodium dodecyl sulphate polyacrylamide gradient gel electrophoresis in the second. The charge differences behind the electrophoretic C4 polymorphism were shown to reside in the 95,000-u (atomic mass units) alpha-chain. Charge variation closely mirroring the alpha-chain differences were also found in a 49,000-u fragment of the alpha-chain, most probably C4d. The basic beta-chain could not be studied in detail, but no differences were observed with regard to molecular weight or charge of the gamma-chains of the different C4 gene products.

Complement C4↗
PubMed2000

Stent appearance at contrast-enhanced MR angiography: in vitro examination with 14 stents.

PURPOSE: To evaluate signal intensity changes influencing assessment of stent patency at contrast material-enhanced magnetic resonance (MR) angiography. MATERIALS AND METHODS: By using an in vitro model, 14 stents-nine nitinol, one tantalum, two stainless steel, and two cobalt alloy-were investigated regarding their appearance at MR imaging. A vascular phantom consisting of tubes filled with 2.00 mmol/L gadopentetate dimeglumine in saline solution was studied in different orientations within the magnetic field. Imaging was performed with a fast three-dimensional gradient-echo sequence (4. 70/1.89 [repetition time msec/echo time msec]). Relative signal intensity reduction within the stents and the degree of artificial narrowing of the stent lumen were calculated. RESULTS: The stent lumen was visible within 13 stents. A total signal void inside the stent lumen appeared in only one cobalt alloy stent. Artificial narrowing of the diameter was less than 33% in 10 of 14 stents. The tantalum stent and four nitinol stents seemed best suited for contrast-enhanced MR angiography. A bandlike artifact occurred at the ends of the stents when positioned along the readout direction. CONCLUSION: To differentiate between artifacts and stenoses, knowledge of the degree of signal intensity reduction and artificial lumen narrowing within vascular stents is essential. Stent geometry, relative orientation to the magnetic field, and alloy composition influence signal intensity alteration within the stent lumen.

Contrast Media↗
PubMed2004

A modified equivalent annulus model for the hollow fiber hemodialyzer.

Experimental approaches to optimize hollow fiber hemodialyzer design are expensive and time-consuming. Computer modeling is an effective way to study mass transfer in the hemodialyzer because a substantial reduction in experimental time and cost can be achieved. This paper presents a two-dimensional modified "equivalent annulus" model, which employs Navier-Stokes (N-S) equations to describe blood and dialysate flow, and Kedem-Katchalsky (K-K) equations to calculate transmembrane flow. N-S equations and K-K equations must be coupled together in the process of computing. The corresponding experiments were designed to validate this model, and experimental results agreed well with numerical results. The distribution of velocity, pressure and solute concentration were investigated in detail, presenting a clear insight into dialyzer mass transfer. This model can be applied to help optimize hemodialyzer design.

Algorithms↗
PubMed2000

PET measures of benzodiazepine receptors in progressive supranuclear palsy.

OBJECTIVE: To evaluate the integrity of neurons containing benzodiazepine receptors in metabolically affected regions of the brain in patients with clinically diagnosed progressive supranuclear palsy (PSP). METHODS: The cerebral distribution of [11C]flumazenil (FMZ), a ligand that binds to the gamma-aminobutyric acid A (GABAA) receptor, and [18F]fluorodeoxyglucose (FDG), a measure of local cerebral glucose metabolism, was determined with PET in 12 patients with PSP and 10 normal control subjects. Tracer kinetic analysis was applied to quantify data and analysis was performed using three-dimensional stereotactic surface projections and stereotactically determined volumes of interest. RESULTS: There was a global reduction in FMZ binding of 13%, with a reduction in the anterior cingulate gyrus of 20% (p = 0.004), where glucose metabolic rates also showed the greatest reduction. CONCLUSIONS: PSP causes loss of benzodiazepine receptors in the cerebral cortex. Consistent with postmortem studies, the authors did not find significant changes in FMZ binding in subcortical nuclei that exhibit the most pathologic change. This study suggests that both loss of intrinsic neurons containing benzodiazepine receptors and deafferentation of the cerebral cortex from distant brain regions contribute to cerebral cortical hypometabolism in PSP.

Aged↗
PubMedDate not supplied

Regulation of redox-sensitive exofacial protein thiols in CHO cells.

Thiols affect a variety of cell functions, an effect known as redox regulation, largely attributed to modification of transcription factors and intracellular signaling mechanisms. Since exofacial protein thiols are more exposed to redox-acting molecules used in cell culture and may represent sensors of the redox state of the environment, we investigated their susceptibility to redox regulation. Exofacial protein thiols were measured using cell-impermeable Ellman's reagent [5,5'-dithiobis(2-nitrobenzoic acid), DTNB]. For quantification, we also set up an ELISA assay based on the cell-impermeable biotinylated SH reagent, N-(biotinoyl)-N-(iodoacetyl) ethylendiamine (BIAM). Exposure of CHO cells to H(2)O(2) induces oxidation of surface thiols at concentrations not affecting intracellular GSH. Depletion (50%) of GSH decreases surface thiols by 88%. Surface thiols are also highly sensitive to thiol antioxidants, since exposure to 5 mM N-acetyl-L-cysteine (NAC) for 2 h augmented their expression without increasing GSH levels. Using BIAM labeling and two-dimensional gel electrophoresis, we show that this increase in surface thiols is due to the reduction of specific membrane proteins. Peptide mass fingerprinting by MALDI mass spectrometry allowed us to identify two of these proteins as Erp57 and vimentin.

Animals↗
PubMed1995

Oxygen and xenobiotic reductase activities of cytochrome P450.

The oxygen reductase and xenobiotic reductase activities of cytochrome P450 (P450) are reviewed. During the oxygen reductase activity of P450, molecular oxygen is reduced to superoxide anion radicals (O2-.) most likely by autooxidation of a P450 ferric-dioxyanion complex. The formation of reactive oxygen species (O2-., hydrogen peroxide, and, notably, hydroxyl free radicals) presents a potential toxication pathway, particularly when effective means of detoxication are lacking. Under anaerobic conditions, P450 may also be involved in the reduction of xenobiotics. During the xenobiotic reductase activity of P450, xenobiotics are reduced by the ferrous xenobiotic complex. After xenobiotic reduction by P450, xenobiotic free radicals are formed that are often capable of reacting directly with tissue macromolecules. Unfortunately, the compounds that are reductively activated by P450 have little structural similarity. The precise molecular mechanism underlying the xenobiotic reductase activity of P450 is, therefore, not yet fully understood. Moreover, description of the molecular mechanisms of xenobiotic and oxygen reduction reactions by P450 is limited by the lack of knowledge of the three-dimensional (3D) structure of the mammalian P450 proteins.

Animals↗
PubMed2003

Perceptual disturbances predicted in zero-g through three-dimensional modeling.

Perceptual disturbances in zero-g and 1-g differ. For example, the vestibular coriolis (or "cross-coupled") effect is weaker in zero-g. In 1-g, blindfolded subjects rotating on-axis experience perceptual disturbances upon head tilt, but the effects diminish in zero-g. Head tilts during centrifugation in zero-g and 1-g are investigated here by means of three-dimensional modeling, using a model that was previously used to explain the zero-g reduction of the on-axis vestibular coriolis effect. The model's foundation comprises the laws of physics, including linear-angular interactions in three dimensions. Addressed is the question: In zero-g, will the vestibular coriolis effect be as weak during centrifugation as during on-axis rotation? Centrifugation in 1-g was simulated first, with the subject supine, head toward center. The most noticeable result concerned direction of head yaw. For clockwise centrifuge rotation, greater perceptual effects arose in simulations during yaw counterclockwise (as viewed from the top of the head) than for yaw clockwise. Centrifugation in zero-g was then simulated with the same "supine" orientation. The result: In zero-g the simulated vestibular coriolis effect was greater during centrifugation than during on-axis rotation. In addition, clockwise-counterclockwise differences did not appear in zero-g, in contrast to the differences that appear in 1-g.

Centrifugation↗
PubMed1992

Foamy transformed Gaucher cells.

Two cases of Gaucher's disease (Types I and III) are described with a substantial part of the storage cell population in several organs (liver, adrenal cortex) intensively vacuolized and transformed into non-specific foam cells. The transformation process encompassed massive three-dimensional distension of the lysosomal system filled with typical lipid tubules as well as severe reduction of the intervening cytoplasm and decrease or disappearance of histochemically detectable enzyme activities, high in typical Gaucher cell (GC). Such an extensive GC foamy transformation may cause diagnostic embarrassment in microscopic interpretation especially of liver biopsies.

Adrenal Cortex↗
PubMed1986

Ultrastructural evidence for fibril-to-fibril associations in articular cartilage and their functional implication.

This study presents ultrastructural evidence for the presence of a variety of fibril-to-fibril interactions or associations in the architecture of the general matrix of articular cartilage. These interactions are believed to serve a higher purpose of repeatedly constraining an overall radial arrangement of fibrils into an array of oblique interconnecting segments thus creating a three dimensional meshwork within which the hydrated ground substance is constrained. It is argued that any reduction in these interfibrillar interactions will allow the oblique fibril segments to revert to a low energy radial configuration, thus explaining the presence of such arrays prominent in various degenerate forms of articular cartilage.

Animals↗
PubMed1996

Resistance to etoposide in human leukemia HL-60 cells: reduction in drug-induced DNA cleavage associated with hypophosphorylation of topoisomerase II phosphopeptides.

Tumor cell resistance to anthracyclines and epipodophyllotoxins can be due to reduced drug accumulation and/or alterations in the activity of topoisomerase II (TOPO II). HL-60 cells selected in 0.05 micrograms/ml doxorubicin (DOX) are 10-fold and > 20-fold resistant to DOX and etoposide (VP-16), respectively. The accumulation of [3H]VP-16 was 2-3-fold lower in the resistant cells (HL-60/DOX 0.05) than in similarly treated parent-sensitive cells (HL-60/S). However, compared with HL-60/S cells, the HL-60/DOX 0.05 cells required > 20-fold higher concentrations of VP-16 to produce equivalent damage to DNA. The reduced formation of VP-16-stabilized DNA cleavable complex in the HL-60/DOX 0.05 cells was not due to differences in the amount of 170-kDa TOPO (alpha) II protein or enzyme catalytic activity between HL-60/S and HL-60/DOX 0.05 cells. Metabolic labeling with [32P]orthophosphoric acid and immunoprecipitation indicated that the level of phosphorylated 170-kDa TOPO II alpha protein in the HL-60-/S cells was 2.2 +/- 0.4-fold higher than that in HL-60/DOX 0.05 cells. Hypophosphorylation (3-fold) of 170-kDa TOPO II protein in HL-60/S cells treated with the calcium chelator 1,2-bis-(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid acetoxymethyl ester produced a > 2-fold reduction in VP-16-induced TOPO II-mediated DNA cleavable complex formation. Two-dimensional mapping of phosphopeptides in complete tryptic digests demonstrated that the reduced phosphorylation of the 170-kDa TOPO II alpha in HL-60/DOX 0.05 cells was due to the hypophosphorylation of at least three phosphopeptides characteristic of HL-60/S cells. Thus, the attenuated ability of TOPO II to form drug-stabilized DNA cleavable complex is related to the phosphorylated state of 170-kDa TOPO II, and in HL-60/DOX 0.05 cells, resistance may be related to hypophosphorylation of three phosphopeptides characteristic of HL-60/S cells.

Antineoplastic Agents, Phytogenic↗