Cutting edge: antigen-dependent regulation of telomerase activity in murine T cells

Telomeres, structures on the ends of linear chromosomes, function to maintain chromosomal integrity. Telomere shortening occurs with cell division and provides a mechanism for limiting the replicative potential of normal human somatic cells. Telomerase, a ribonucleoprotein enzyme, synthesizes telomeric repeats on chromosomal termini, potentially extending the capacity for cell division. The present study demonstrates that resting T cells express little/no activity, and optimal Ag-specific induction of telomerase activity in vitro requires both TCR and CD28-B7 costimulatory signals. Regulation of telomerase in T cells during in vivo Ag-dependent activation was also assessed by adoptive transfer of TCR transgenic T cells and subsequent Ag challenge. Under these conditions, telomerase was induced in transgenic T cells coincident with a phase of extensive clonal expansion. These findings suggest that telomerase may represent an adoptive response that functions to preserve replicative potential in Ag-reactive lymphocytes.     

Evaluation of serum inhibin A as a surveillance marker after conservative management of tubal pregnancy

Tubal pregnancy is now commonly managed by laparoscopic salpingostomy or systemic methotrexate. A disadvantage of such conservative management is the need for appropriate follow-up, with serial measurement of serum concentrations of human chorionic gonadotrophin (HCG), to exclude persistent ectopic pregnancy (PEP). Concentrations of inhibin A, also a placental product, are significantly increased during pregnancy and the half-life of inhibin A is significantly shorter than that of HCG. To assess the suitability of inhibin A as a marker of PEP, we studied 16 women who had undergone surgery for a tubal pregnancy, measuring HCG and inhibin during follow-up. The mean +/- SEM time taken to achieve non-pregnant concentrations of inhibin A was significantly shorter than for HCG (4.2 +/- 0.8 days versus 21.6 +/- 4.4 days respectively; P < 0.001 Wilcoxon signed rank test). However, in all women the inhibin A concentration increased rapidly after reaching a nadir, reflecting the return of ovarian function, complicating the interpretation of results. In four women inhibin A was almost undetectable preoperatively, while the corresponding HCG concentration was high. These data suggest that inhibin A will not be a useful marker for PEP but that it may provide a more accurate preoperative assessment of trophoblast viability than HCG, thereby improving management.     

Formation of Silicon Nanoclusters in Disproportionation of Silicon Monoxide

Semiconductors - The processes of the disproportionation of solid-phase silicon monoxide, accompanied by the formation of nanocrystalline silicon precipitates in the medium of amorphous suboxide...     

Oxygen Nitrogen Mixture Effect on Aluminum Nitride Synthesis by Reactive Ion Plasma Deposition

In the work we investigate synthesis of aluminum nitride films using reactive ion plasma deposition in oxygen/nitrogen gas mixture for application as optical elements for power semiconductor lasers. The experimental refractive index of synthesized AlNO films is dependent on oxygen composition and is decreasing in diapason from 1.76 to 2.035 at elevation of the oxygen fraction.It is shown that the AlN films synthesized by pure nitrogen plasma are polycrystalline and textured. The oxygen presence in discharging gas results to growth of amorphous phase of the AlNO film.     

Reserve mobilisation in mesquite (Prosopis juliflora) seed (Leguminosae)

The seeds of Prosopis juliflora (mesquite) have a water barrier composed of the palisade layer present in the seed tegument and galactomannans in the endosperm. Changes in the morphological and physiological states of seeds are usually accompanied by changes in their metabolism. The aim of this study was to detect and characterise the main reserves and their mobilisation during and following germination of P. juliflora seeds. Sections of seeds 0, 24, 48 and 72 h after the onset of the imbibing process were evaluated by light microscopy, and seed reserves were extracted and quantified. Polysaccharides were isolated and characterised by ¹H nuclear magnetic resonance (NMR) spectroscopy. In mesquite seeds a well‐developed endosperm, consisting largely of the storage carbohydrate (galactomannans), lies between the seed coat and the cotyledons. Germination was complete after 24 h of imbibition. At this time, morphological changes were observed in stained protein bodies. Chemical analysis showed a decrease in protein levels until 48 h. After 48 h, globular structures were observed in the cotyledon cells, but after 72 h these grains were smaller and their content was reduced. Polarisation microscopy confirmed that this material was composed of starch grains. The ¹H NMR spectrum of P. juliflora seeds showed that sucrose was used following germination. Apparently, sucrose is the transport sugar mobilised from reserve stocks for seedling growth. Parallel to endosperm galactomannan degradation, starch is produced transitorily in the cotyledon. Copyright © 2007 Society of Chemical Industry