Participation of proteinase yscA in the in vitro formation of the smaller subunit of glycogen phosphorylase in extracts of Saccharomyces cerevisiae.

Analyses by sodium dodecyl sulphate-polyacrylamide gradient-gel electrophoresis and Western blotting of the proteins from boiled cell samples from all growth phases of yeast cultures, and from all stages of extract preparation indicate that the smaller subunit (s-monomer), which is found in purified glycogen phosphorylase (EC 2.4.1.1) from baker's yeast, is not present in the living cell. It is observed in extracts of Saccharomyces carlsbergensis and S. cerevisiae after incubation at ambient temperatures or even after storage in the frozen state at -25 degrees C. Its formation is sensitive towards pepstatin A, and it is absent from extracts of several mutants of S. cerevisiae that do not contain active proteinase yscA (EC 3.4.33.6). When purified proteinase yscA is added to the extracts of these mutants, the formation of s-monomer is restored. When the proteinase yscA-deficient strains are grown with a reduced amount of complex nitrogen compounds, the slightly smaller sc-monomer is formed in their extracts. This event must be attributed to a different proteinase, since it is sensitive towards p-hydroxymercuriphenylsulphonate, but not towards pepstatin A. The N-terminal amino acid of the sc-monomer was found to be blocked, as in the case of the native l-monomer, but not the s-monomer.     

Restricted inflammatory reaction in the CNS: a key impediment to axonal regeneration?

Axons in the central nervous system (CNS) of adult mammals do not regenerate after injury. Mammalian CNS differs in this respect from other mammalian tissues, including the peripheral nervous system (PNS), and from the CNS of lower vertebrates. In most parts of the body, including the nervous system, injury triggers an inflammatory reaction involving macrophages. This reaction is needed for tissue healing; when it is delayed or insufficient, healing is incomplete. The CNS, although needing an efficient inflammatory reaction resembling that in the periphery for tissue healing, appears to have lost the ability to supply it. We suggest that restricted CNS recruitment and activation of macrophages are linked to regeneration failure and might reflect the immune privilege that characterizes the mammalian CNS. As macrophages play a critical role in tissue restoration, and because their recruitment and activation are among the most upstream of the events leading to tissue healing, overcoming the deficiencies in these steps might trigger a self-repair processing leading to recovery after CNS injury.     

Behavior of 60Co and 134Cs in a Canadian Shield lake over 5 years

Radionuclides were added to the anoxic hypolimnion of a Canadian Shield lake to simulate the nuclear fuel waste disposal scenario where radionuclides might enter the bottom waters of a lake. The radionuclides remained in the hypolimnion until lake mixing at autumn turnover after which 60Co was rapidly lost and 134Cs was slowly lost from the water. Only 0.4% of the 60Co and 0.6% of the 134Cs remained in the water at year 5. Highest concentrations occurred in periphyton and filter feeders, Holopedium gibberum and clams (Anodonata grandis grandis). From maximum annual concentrations in clam tissues, it was estimated that the availability of 60Co for uptake had a half-time (t1/2) of 835 days in the lake, whereas that for 134Cs was 780 days. Loss rate coefficients, k, for the radionuclides from taxa ranged from 0.0008 to 0.0043 day-1 (t1/2 = 161-866 days) for 60Co and from 0.0009 to 0.005 day-1 (t1/2 = 139-770 days) for 134Cs. Cobalt-60 concentrations in forage fish were low, whereas 134Cs concentrations increased over the first year or two, then slowly declined. On the basis of k values measured for forage fish, the biological half-time of 134Cs in forage fish ranged from 428 to 630 days. Maximum 134Cs concentrations in forage fish were higher following hypolimnetic addition than epilimnetic addition. Relatively high 134Cs concentrations in periphyton at year 5 point to the importance of benthic pathways in the recycling of contaminants to higher trophic levels. The presence of 134Cs in biota 5 years after the addition, long after concentrations were no longer detectable in surface waters, is evidence of the persistence of Cs in aquatic systems. The k values (or t1/2 values) for the loss of 60Co and 134Cs from water and their uptake and loss from biota can be used to establish parameter values for assessment models. The results demonstrate that assessment models should account for the release of radionuclides from sediment and their subsequent recycling in the food chain when modeling over the long term after the end of a radionuclide release to the environment.     

Measured propagation characteristics of coplanar waveguide on semi-insulating 4H-SiC through 800 K

Wireless sensors for high temperature industrial applications and jet engines require RF transmission lines and RF integrated circuits (RFICs) on wide bandgap semiconductors such as SiC. In this paper, the complex propagation constant of coplanar waveguide fabricated on semi-insulating 4H-SiC has been measured through 813 K. It is shown that the attenuation increases 3.4 dB/cm at 50 GHz as the SiC temperature is increased from 300 K to 813 K. Above 500 K, the major contribution to loss is the decrease in SiC resistivity. The effective permittivity of the same line increases by approximately 5% at microwave frequencies and 20% at 1 GHz.     

mRNA instability elements in the human papillomavirus type 16 L2 coding region

Human papillomavirus capsid proteins L1 and L2 are detected only in terminally differentiated cells, indicating that expression of the L1 and L2 genes is blocked in dividing cells. The results presented here establish that the human papillomavirus type 16 L2 coding region contains cis-acting inhibitory sequences. When placed downstream of a reporter gene, the human papillomavirus type 16 L2 sequence reduced both mRNA and protein levels in an orientation-dependent manner. Deletion analysis revealed that the L2 sequence contains two cis-acting inhibitory RNA regions. We identified an inhibitory region in the 5'-most 845 nucleotides of L2 that acted by reducing cytoplasmic mRNA stability and a second, weaker inhibitory region in the 3' end of L2. In contrast, human papillomavirus type 1 L1 and L2 genes did not encode strong inhibitory sequences. This result is consistent with observations of high virus production in human papillomavirus type 1-infected tissue, whereas only low levels of human papillomavirus type 16 virions are detectable in infected epithelium. The presence of inhibitory sequences in the L1 and L2 mRNAs may aid the virus in avoiding the host immunosurveillance and in establishing persistent infections.     

Urban appalachian girls and writing: institutional and 'other/ed' identities

This study addresses urban Appalachian girls and identities as constructed within and outside of the written discourses of the institution known as school. Drawing on poststructuralist (Weedon, 1997) and sociocultural (Gee, 1996) perspectives of language, identities and discourses (Gee, 1996), and on the feminist philosopher Griffiths (1995), it is argued that girls' identities are dependent upon consent given to particular relationships available in various discourses.     

Frequent detection of tumor cells in hematopoietic grafts in neuroblastoma and Ewing's sarcoma

Many poor-risk neuroblastomas and tumours of the Ewing's sarcoma family (ET) recur despite autologous transplants. Recurrence may be due to tumor cells contained in the BM harvests or PBSC harvests. The objectives of this prospective study were to: (1) determine the incidence and degree of tumor cell contamination in paired BM and PBSC harvests; and (2) determine the efficacy of tumor cell purging by immunomagnetic CD34+ cell selection. 198 samples from 11 consecutive patients with neuroblastoma or Ewing's sarcoma were analyzed. We assayed tumor contamination by RT-PCR assay for PGP 9.5, plus immunohistochemistry for neuroblastoma-specific antigens (the latter in neuroblastoma only). None of these patients had tumor cells detected in their BM by clinical histology immediately before BM or PBSC harvests. However, 82% of PBSC and 89% of backup BM harvests were contaminated with tumor by RT-PCR and/or immunocytochemistry assays. Unselected PBSC and BM harvests contained similar quantities of tumor cells (median, approximately 200000 cells). Cyclophosphamide plus G-CSF mobilization did not affect the incidence or level of contamination in PBSC harvests, as compared to blood obtained before mobilization. Immunomagnetic CD34+ cell selection depleted tumor cells by a median of 3.0 logs for PBSC, and 2.6 logs for BM harvests.     

Optimization of a Slow-Release Tablet Formulation Containing Sodium Sulfathiazole and a Montmorillonite Clay

A slow-release tablet formulation containing high levels of a montomorillonite clay, Veegum F®, was initially developed by trial and error. The present study was undertaken to utilize an approach involving statistics with the aid of computer science to develop a formula with desired characteristics. An experimental design for five factors was employed. The five factors consisted of levels of various components and the amount of compressional force applied while tableting. The response or dependent variables included tablet weight uniformity, hardness and friability; and percent drug in solution after 3 hours of dissolution testing. The response variables were fitted to a second-order polynomial with the five formulation factors as the independent variables. The resulting equations were used to optimize the formulation with respect to the response variables. The results indicated that a formulation with the desired characteristics could be predicted by the technique.     

Photoinduced ordering of block copolymers

Photoinduced ordering of disordered block copolymers (BCPs) would provide an on-demand, nonintrusive route for formation of well-ordered nanostructures in arbitrarily defined regions of an otherwise disordered material. Here we achieve this objective using a rapid and simple approach in which photoconversion of an additive blended with the BCP introduces strong interactions between the additive and one of the chain segments and induces strong order in the BCP blend. The strategy is generally applicable to block copolymers containing chain segments capable of hydrogen bonding with the additive.     

Efficient Organic Tandem Solar Cells based on Small Molecules

In this paper, two vacuum processed single heterojunction organic solar cells with complementary absorption are described and the construction and optimization of tandem solar cells based on the combination of these heterojunctions demonstrated. The red‐absorbing heterojunction consists of C₆₀ and a fluorinated zinc phthalocyanine derivative (F4‐ZnPc) that leads to a 0.1–0.15 V higher open circuit voltage V_oc than the commonly used ZnPc. The second heterojunction incorporates C₆₀ and a dicyanovinyl‐capped sexithiophene derivative (DCV6T) that mainly absorbs in the green. The combination of both heterojunctions into one tandem solar cell leads to an absorption over the whole visible range of the sun spectrum. Thickness variations of the transparent p‐doped optical spacer between both subcells in the tandem solar cell is shown to lead to a significant change in short circuit current density j_sc due to optical interference effects, whereas V_oc and fill factor are hardly affected. The maximum efficiency η of about 5.6% is found for a spacer thickness of 150‐165 nm. Based on the optimized 165nm thick spacer, effects of intensity and angle of illumination, and temperature on a tandem device are investigated. Variations in illumination intensity lead to a linear change in j_sc over three orders of magnitude and a nearly constant η in the range of 30 to 310 mW cm^?2. Despite the stacked heterojunctions, the performance of the tandem device is robust against different illumination angles: j_sc and η closely follow a cosine behavior between 0° and 70°. Investigations of the temperature behavior of the tandem device show an increase in η of 0.016 percentage points per Kelvin between ?20 °C and 25 °C followed by a plateau up to 50 °C. Finally, further optimization of the tandem stack results in a certified η of (6.07 ± 0.24)% on (1.9893 ± 0.0060)cm² (Fraunhofer ISE), i.e., areas large enough to be of relevance for modules.