Parallel Loss Research Articles

Decreased stability of the M54 isoform of paraoxonase as a contributory factor to variations in human serum paraoxonase concentrations

There are considerable variations in serum concentrations of the high density lipoprotein (HDL)-associated enzyme, paraoxonase (PON), which is an important determinant of the antioxidant capacity of HDL. The present study examined the hypothesis that differences in the stability of isoforms arising from the coding region L54M polymorphism could contribute to such variations. A model system was developed using transfected Chinese hamster ovary cells to secrete recombinant PON corresponding to human L or M isoforms. The recombinant peptides exhibited the molecular properties of human serum PON. They formed complexes with lipoproteins in culture medium, notably binding to apolipoprotein A-I-containing particles. The enzymatic properties of the recombinant isoforms were comparable to those of human serum PON. The recombinant M isoform lost activity more rapidly and to a greater extent than the recombinant L isoform [26.0 +/- 3.0% vs. 14.0 +/- 1.0% (phenylacetate substrate) and 36.1 +/- 2.0% vs. 19.3 +/- 2.0% (paraoxon substrate) over 96 h (P < 0.01)] in medium containing fetal calf serum or PON-free human serum. Addition of a protease inhibitor resulted in retention of activity by both isoforms. Parallel results were obtained in incubation studies of human serum from donors homozygous LL or MM for the L54M polymorphism. Enzyme activity was lost more rapidly and to a greater extent from MM than LL sera (P < 0.01). A parallel loss of PON peptide mass was also observed, with a significantly greater loss from MM homozygotes (P < 0.001). It corresponded to the appearance of a smaller molecular mass band on SDS-PAGE analysis. Direct analysis of the proteolytic effect using HDL isolated from homozygotes and incubated with purified kallikrein confirmed the greater loss of activity from MM homozygotes and the protective effect of proteolysis inhibitor. The results provide evidence for lesser stability of the M54 isoform of PON, apparently involving greater susceptibility to proteolysis. It provides one mechanism to explain variations in serum levels of PON and has implications for the antioxidant capacity of HDL.

Endometrial carcinoma: association of steroid hormone receptor expression with low angiogenesis and bcl-2 expression

In endometrial tissues, malignant change may be accompanied by a loss of hormone dependence which is, usually, reflected in a parallel loss of oestrogen and progesterone receptors (ER and PR). In this study, the steroid receptor status of 164 endometrial carcinomas was related to intratumoural angiogenesis and the apoptotic proteins bcl-2 and p53. Relationships to conventional histopathological features and patient survival were also sought. Immunohistochemistry was performed on formalin-fixed, paraffin-embedded tissues. The mean follow-up was 55 months (range 19-167 months). Specific nuclear staining for ER and PR was detected in 35% and 32% of endometrial carcinomas, respectively, and was very commonly co-expressed (P<0.0001). The failure of demonstrating a steroid receptor complement in endometrial neoplasms was, in general terms, an adverse prognostic sign. Thus, ER or PR loss was significantly associated with non-endometrioid carcinomas (ER P=0.01; PR P=0.004) and with deep myometrial invasion (ER P<0.0002), high intratumoural angiogenesis (PR P<0.01) and the absence of bcl-2 expression (PR P<0.005). There was a trend for patients with ER or simultaneous ER/PR expression to have an improved survival, but this association did not reach the level of statistical significance. In multivariate analysis (all stages), tumour cell type (endometrioid versus non-endometrioid carcinomas) and stage of disease were the only variables associated with prognosis (P=0.01 and P<0.0001, respectively), with tumour cell type retaining its independent prognostic value and within stage-I endometrial carcinomas (P=0.02). It is suggested that the loss of steroid hormone receptors in endometrial carcinomas is associated with a more aggressive phenotype and the switching-on of angiogenic pathways.

Development and characterization of Bi-2223 conductors for HTS transformer applications

Multifilamentary Bi-2223 tapes for AC applications in HTS transformers are studied. By twisting the filaments in tapes with AgMg sheath and Ag matrix the parallel field AC loss at power frequencies is lowered by more the 50% for the optimum twist length of 10 mm. The critical current density of these conductors corresponds to >80% of the non-twisted tape. In order to achieve a larger loss reduction tapes with Ag-alloys and ceramic barriers are studied.

Many parallel losses of infA from chloroplast DNA during angiosperm evolution with multiple independent transfers to the nucleus.

We used DNA sequencing and gel blot surveys to assess the integrity of the chloroplast gene infA, which codes for translation initiation factor 1, in >300 diverse angiosperms. Whereas most angiosperms appear to contain an intact chloroplast infA gene, the gene has repeatedly become defunct in approximately 24 separate lineages of angiosperms, including almost all rosid species. In four species in which chloroplast infA is defunct, transferred and expressed copies of the gene were found in the nucleus, complete with putative chloroplast transit peptide sequences. The transit peptide sequences of the nuclear infA genes from soybean and Arabidopsis were shown to be functional by their ability to target green fluorescent protein to chloroplasts in vivo. Phylogenetic analysis of infA sequences and assessment of transit peptide homology indicate that the four nuclear infA genes are probably derived from four independent gene transfers from chloroplast to nuclear DNA during angiosperm evolution. Considering this and the many separate losses of infA from chloroplast DNA, the gene has probably been transferred many more times, making infA by far the most mobile chloroplast gene known in plants.

Many Parallel Losses of infA from Chloroplast DNA during Angiosperm Evolution with Multiple Independent Transfers to the Nucleus

Many Parallel Losses of infA from Chloroplast DNA during Angiosperm Evolution with Multiple Independent Transfers to the Nucleus

Phylogenetic Implications of the Multiple Losses of the Mitochondrial coxII.i3 Intron in the Angiosperms

Previous studies have shown that the mitochondrial coxII.i3 intron is absent in all rosids examined, in Philadelphus (Hydrangeaceae, Cornales), and in Catharanthus and Vinca (Apocynaceae, Gentianales). We surveyed for the presence or absence of this intron in 177 species representing all orders of angiosperms, where it is primitively present. The intron appears to have been lost independently in Gnetales, Laurales, Zingiberales, Ranunculales, Saxifragales, rosids, Santalales, Caryophyllales, Ericales, Cornales, Gentianales, Lamiales, Boraginales, Aquifoliales, Asterales, Dipsacales, as well as in the genus Escallonia. Depending upon the phylogenies used to interpret the losses, and due to lack of resolution in some groups, the intron could have been lost up to 27 times in the angiosperms (excluding the loss in Gnetales). The losses sometimes corroborate the monophyly of groups (rosids and Lamiales) or of subgroups within orders (in the Ranunculales, Caryophyllales, Cornales, Gentianales, and Asterales). In other groups, such as the Saxifragales, Ericales, and Dipsacales, the patterns of losses are more complex and would require further study. The presence or absence of the coxII.i3 mitochondrial intron seems a useful phylogenetic marker in some groups, but caution in interpretation is needed as multiple parallel losses have occurred throughout the angiosperms.

Independent Regulation of Lymphocytic Choriomeningitis Virus-Specific T Cell Memory Pools: Relative Stability of CD4 Memory Under Conditions of CD8 Memory T Cell Loss

Infection of mice with a series of heterologous viruses causes a reduction of memory CD8(+) T cells specific to viruses from earlier infections, but the fate of the virus-specific memory CD4(+) T cell pool following multiple virus infections has been unknown. We have previously reported that the virus-specific CD4(+) Th precursor (Thp) frequency remains stable into long-term immunity following lymphocytic choriomeningitis virus (LCMV) infection. In this study, we questioned whether heterologous virus infections or injection with soluble protein CD4 Ags would impact this stable LCMV-specific CD4(+) Thp memory pool. Limiting dilution analyses for IL-2-producing cells and intracellular cytokine staining for IFN-gamma revealed that the LCMV-specific CD4(+) Thp frequency remains relatively stable following multiple heterologous virus infections or protein Ag immunizations, even under conditions that dramatically reduce the LCMV-specific CD8(+) CTL precursor frequency. These data indicate that the CD4(+) and CD8(+) memory T cell pools are regulated independently and that the loss in CD8(+) T cell memory following heterologous virus infections is not a consequence of a parallel loss in the memory CD4(+) T cell population.

Reaction of magnesium boride particles in mechanically alloyed Ti-4wt%MgB2

A Ti-4wt%MgB2 alloy was produced by mechanical alloying (MA) Ti and MgB2 powders for 48 hours in a Spex 8000 mill. TEM analysis of the alloy showed it to consist of a nanocrystalline (10–20 nm) Ti matrix, which enclosed 20–300 nm MgB2 particles. Following heat treatments at 600°C, plate like structures of a previously unknown compound were observed to have extended into the crystals. Convergent beam electron diffraction (CBED) confirmed the new phase to have the same basic arrangement of atom sites as in the NiAs structure. Parallel electron energy loss spectroscopy (PEELS) and energy dispersive X-ray analysis (EDX) measurements identified the elements Ti, Mg and B within these plates. However, the exact proportions of these elements and their distribution within the unit cell could not be determined.

Synthesis, HRTEM and electron diffraction studies of B/N-doped C and BN nanotubes

Large-scale synthesis of multi-walled BN and single-walled B/N-doped C nanotubes (NT) from C nanotube templates was carried out. The NTs were produced through heating of C templates with B2O3 in a flowing N2 atmosphere at 1503-1773 K. The NTs were analyzed by means of a JEM-3000F high-resolution field emission transmission electron microscope operated at 300 kV and equipped with a parallel detection electron energy loss spectrometer. Particular attention was given to the effects of C template morphology, synthesis temperature and metal oxide promoters on the yield and chemical composition of NTs. Ropes consisting of tens of multi-walled BN NTs were synthesized at 1773 K using MoO3 and PbO promoters. Ropes of single-walled B/N-doped C NTs were produced at high yields by synthesis at 1553 K. Packing of NTs in the ropes and nanotube helicities were studied by electron diffraction. B/N-doped C and BN NT morphologies, formation mechanism and atomic structures are discussed in this paper.

Silicide Formation by Pulsed Excimer Laser Annealing

AbstractSilicide formation may occur at the interface of metal and a-Si films upon annealing with a pulsed excimer laser (XeCl 308 nm; 30 ns). During laser-induced melting, the melt front reaches the Si/metal interface, where liquid phase kinetics allow reaction to occur to form a silicide, despite the &lt;100 ns time-scale. It is thought that silicide reaction would occur if TM, metal ≍ TM, a-Si (1480 ± 50K). The a-Si/metal film stacks that have been investigated include a-Si/Al/Cr, a-Si/Ti, and a-Si/W on thermally oxidized Si. Samples were laser-annealed at varying energy densities in order to determine the onset of melt, and the fluence at which Si/metal interface reaction and film ablation occurs. Rutherford backscattering (RBS), optical inspection, cross-sectional scanning transmission electron microscopy (STEM), as well as parallel and serial electron energy loss spectroscopy (EELS) were used to analyze the films. For the a-Si/Al/Cr and a-Si/W films, no reaction is observed at the Si/metal interface. With a-Si/Ti, intermixing of Si and Ti at the interface is observed, as indicated by RBS and parallel EELS analysis. Laser annealing at higher fluences and further characterization is needed to determine if this mechanism does allow for silicide reaction to take place.

Senescence of foveal and parafoveal cone sensitivities and their relations to macular pigment density.

Foveal and parafoveal increment thresholds were measured for 50 observers (12-88 years of age) under conditions that isolated retinal mechanisms dominated by short- (S-), middle- (M-), or long- (L-) wave-sensitive cones. Thresholds were obtained on the plateau of the threshold-versus-intensity function of each isolated mechanism and were referred to the retina by using individual measurements of ocular media and macular pigment density. Age-related increases in foveal thresholds, specified at the retina, were found for all three cone mechanisms. Parallel sensitivity losses for each cone mechanism were also observed at 4 degrees and 8 degrees in the temporal retina. A significant positive correlation was found between foveal macular pigment density and the S-cone, but not the M- and L-cone, log sensitivity difference (0 degrees-8 degrees) specified at the retina. This relation is expected from the hypothesis that the macular pigment protects the photoreceptors from senescent losses in sensitivity. However, because this result is independent of age, it is interpreted as being due to local gain changes resulting from differential filtering of incident light by the macular pigment between the fovea and the parafovea.

Involvement of the ceramide signaling pathway in modulating the differentiated state of porcine thyroid cells.

Neutral sphingomyelinase (Smase) is a cell membrane-associated phospholipase that hydrolyzes sphingomyelin to phosphocholine and ceramide, a lipid second messenger involved in cell differentiation and/or apoptosis. We first evidenced that porcine cultured thyroid cells could express neutral Smase activity even if thyrotropin (TStH), an essential hormone in thyroid cell differentiation, was found to induce a 1.7-fold decrease in Smase activity. Triggering the ceramide pathway by exogenous addition of neutral bacterial Smase (0.1 U/mL for 48 h), which transiently increased ceramide level by fourfold, drastically modified thyroid cell morphology. The follicle-like structures generated by TSH were disrupted, and the Smase-induced cell spreading was accompanied by a parallel loss of cell ability to iodinate proteins as well as a decrease of the adenylate cyclase system response. These inhibitory effects have been reproduced using short-chain exogenous ceramide analogs (C2-ceramides). Overall these data showed that ceramides emerged as potential mediators of dedifferentiation in thyroid cells.

Complex heterogeneous precipitation in titanium–niobium microalloyed Al-killed HSLA steels—II. Non-titanium based particles

An analytical electron microscopical investigation of three Ti–Nb Al deoxidized steels with different N:Ti ratios has been undertaken. In each steel, a large number of small (<10 nm) particles were observed. Parallel electron energy loss spectroscopy (PEELS) showed that their compositions in the three steels were consistent with those reported for the caps on the TiN cores in the equivalent steels in Part I, i.e. NbC 0.7N 0.3, NbC and (Nb 0.7Ti 0.3)C, respectively. The Nb incorporated in these caps added to that dissolved in the TiN cores results in a significant reduction in the number of small particles which give effective dispersion hardening. The size of this reduction depends on a number of competing factors. AlN precipitation also occurred in the as-rolled steel with highest N content and in the normalized steels with the two higher N contents. AlN is usually expected to control the austenite grain growth. NbC-based material grew on the AlN. A dendritic complex based on the iso-structural compounds MnSiN 2 and AlN was observed in the high N steel.

Evolution and Phylogenetic Information Content of Mitochondrial Genomic Structural Features Illustrated with Acrodont Lizards

DNA sequences from 195 squamate reptiles indicate that mitochondrial gene order is the most reliable phylogenetic character establishing monophyly of acrodont lizards and of the snake families Boidae, Colubridae, and Viperidae. Gene order shows no evidence of evolutionary parallelisms or reversals in these taxa. Derived secondary structures of mitochondrial tRNAs also prove to be useful phylogenetic characters showing no reversals. Parallelisms for secondary structures of tRNAs are restricted to deep lineages that are separated by at least 200 million years of independent evolution. Presence of a stem-and-loop structure between the genes encoding tRNA(Asn) and tRNA(Cys), where the replication origin for light-strand synthesis is typically located in vertebrate mitochondrial genomes, is found to undergo at least three and possibly as many as seven evolutionary shifts, most likely parallel losses. This character is therefore a less desirable phylogenetic marker than the other structural changes examined. Sequencing regions that contain multiple genes, including tRNA genes, may be preferable to the common practice of obtaining single-gene fragments for phylogenetic inference because it permits observation of major structural changes in the mitochondrial genome. Such characters may occasionally provide phylogenetic information on relatively short internal branches for which base substitutional changes are expected to be relatively uninformative.

Soft tissue body composition differences in monozygotic twins discordant for spinal cord injury.

To determine the effect of paralysis on body composition, eight pairs of male monozygotic twins, one twin in each pair with paraplegia, were studied by dual-energy X-ray absorptiometry. Significant loss of total body lean tissue mass was found in the paralyzed twins compared with their able-bodied co-twins: 47.5 +/- 6. 7 vs. 60.1 +/- 7.8 (SD) kg (P < 0.005). Regionally, arm lean tissue mass was not different between the twin pairs, whereas trunk and leg lean tissue masses were significantly lower in the paralyzed twins: -3.0 +/- 3.3 kg (P < 0.05) and -10.1 +/- 4.0 kg (P < 0.0005), respectively. Bone mineral content of the total body and legs was significantly related to lean tissue mass in the able-bodied twins (R = 0.88 and 0.98, respectively) but not in the paralyzed twins. However, the intrapair difference scores for bone and lean tissue mass were significantly related (R = 0.80 and 0.81, respectively). The paralyzed twins had significantly more total body fat mass and percent fat per unit body mass index than the able-bodied twins: 4.8 kg (P < 0.05) and 7 +/- 2% (P < 0.01). In the paralyzed twins, total body lean tissue was significantly lost (mostly from the trunk and legs), independent of age, at a rate of 3.9 +/- 0.2 kg per 5-yr period of paralysis (R = 0.87, P < 0.005). Extreme disuse from paralysis appears to contribute to a parallel loss of bone with loss of lean tissue in the legs. The continuous lean tissue loss may represent a form of sarcopenia that is progressive and accelerated compared with that in ambulatory individuals.

Theory of edge plasma in a spheromak

Properties of the edge plasma in the SSPX spheromak during the plasma formation and sustainment phases are discussed. For the breakdown and formation phase, the main emphasis is on the analysis of possible plasma contamination by impurities from the electrodes of the plasma gun (helicity injector). The issue of an azimuthally uniform breakdown initiation is also discussed. After the plasma settles down in the main vacuum chamber, one has to sustain the current between the electrodes, in order to continuously inject helicity. We discuss properties of the plasma on the field lines intersecting the electrodes. We conclude that the thermal balance of this plasma is maintained by Joule heating competing with parallel heat losses to the electrodes. The resulting plasma temperature is in the range 15–30 eV. Under the expected operational conditions, the `current' velocity of the electrons is only slightly below their thermal velocity. Implications of this observation are briefly discussed.

Loss of Cholinergic Phenotype in Basal Forebrain Coincides with Cognitive Decline in a Mouse Model of Down's Syndrome

Mice with segmental trisomy of chromosome 16 (Ts65Dn) have been used as a model for Down's syndrome. These mice are born with a normal density of basal forebrain cholinergic neurons but, like patients with Down's syndrome, undergo a significant deterioration of these neurons later in life. The time course for this degeneration of cholinergic neurons has not been studied, nor is it known if it correlates with the progressive memory and learning deficits described. Ts65Dn mice that were 4, 6, 8, and 10 months old were sacrificed for evaluation of basal forebrain morphology. Separate groups of mice were tested on visual or spatial discrimination learning and reversal. We found no alterations in cholinergic markers in 4-month-old Ts65Dn mice, but thereafter a progressive decline in density of cholinergic neurons, as well as significant shrinkage of cell body size, was seen. A parallel loss of staining for the high-affinity nerve growth factor receptor, trkA, was observed at all time points, suggesting a biological mechanism for the cell loss involving this growth factor. Other than transient difficulty in learning the task requirements, there was no impairment of trisomic mice on visual discrimination learning and reversal, whereas spatial learning and reversal showed significant deficits, particularly in the mice over 6 months of age. Thus, the loss of ChAT-immunoreactive neurons in the basal forebrain was coupled with simultaneous deficits in behavioral flexibility on a spatial task occurring for the first time around 6 months of age. These findings suggest that the loss of cholinergic function and the simultaneous decrease in trkA immunoreactivity in basal forebrain may directly correlate with cognitive impairment in the Ts65Dn mouse

RAMAN AND PEELS STUDIES ON MAGNETRON SPUTTERED a-C

Amorphous carbon coatings (a-C, a-C:H) of less than 100 nm thick were deposited on KBr pellets and silicon wafer substrate via magnetron sputtering of graphite target in argon, argon/hydrogen and argon/nitrogen atmosphere. Parallel electron energy loss spectroscopy (PEELS) analysis was used to quantify the sp 2/ sp 3 bonding in carbon films. Stand-alone films of amorphous carbon were produced by sputtering onto compressed KBr pellets and then floating off is distilled water for PEELS study. Raman spectroscopy was used to measure the peak intensity ratio of D-band to that of the G-band (IdIg). It shows that higher sp 3 fraction often associates with lower Raman peak ratio (IdIg). At the same time, G-band peak position P g decreases while sp 3 fraction increases.

The effect of reactive oxygen species generated from the mitochondrial electron transport chain on the cytochrome c oxidase activity and on the cardiolipin content in bovine heart submitochondrial particles

The effect of reactive oxygen species (ROS), produced by the mitochondrial respiratory chain, on the activity of cytochrome c oxidase and on the cardiolipin content in bovine heart submitochondrial particles (SMP) was studied. ROS were produced by treatment of succinate-respiring SMP with antimycin A. This treatment resulted in a large production of superoxide anion, measured by epinephrine method, which was blocked by superoxide dismutase (SOD). Exposure of SMP to mitochondrial mediated ROS generation, led to a marked loss of cytochrome c oxidase activity and to a parallel loss of cardiolipin content. Both these effects were completely abolished by SOD+catalase. Added cardiolipin was able to almost completely restore the ROS-induced loss of cytochrome c oxidase activity. No restoration was obtained with peroxidized cardiolipin. These results demonstrate that mitochondrial mediated ROS generation affects the activity of cytochrome c oxidase via peroxidation of cardiolipin which is needed for the optimal functioning of this enzyme complex. These results may prove useful in probing molecular mechanism of ROS-induced peroxidative damage to mitochondria which have been proposed to contribute to aging, ischemia/reperfusion and chronic degenerative diseases.

Senescent Changes in Color Discrimination and Color Appearance

Age-related anatomical and physiological changes in the human visual system have been reported such as an increase in the density of the lens, a reduction of pupil size and loss of retinal ganglion cells. Although the retinal stimulus and neural signals are strongly affected by such age-related changes, color appearance is stable throughout the life-span because of parallel losses of cone sensitivities and other compensation mechanisms related to color constancy. On the other hand, there is a loss of sensitivity in color discrimination due, in part, to the reduction of retinal illuminance. The results of recent experimental studies by the author and colleagues indicate that this loss in discrimination is not only caused by the reduction of retinal illuminance, but also by a decrease in the signal-to-noise (S/N) ratio in neural pathways processing signals from S-cones and antagonistic signals from L- and M-cones. This change can be considered as a sort of a trade-off between maintaining a constant signal level from the cones through the life-span and decreasing the signal-to-noise ratio in the human visual system. These results suggest some possible methods for making safer and more comfortable visual environments for the elderly.