Biochemical Markers of Lymphocyte Maturation

Abstract KováfiÛ H., F. KováfiÛ, A. Fi‰erová, P. Zelníãková, E. Matalová: Biochemical Markers of Lymphocyte Maturation. Acta Vet Brno 2002, 71: 503-508. We studied maturation-associated changes of cell membrane Na + , K + -and Mg 2+ -ATPase activities and gamma-glutamyltranspeptidase activity (GGT) during prenatal and postnatal development of lymphocytes in pig thymus and lymph nodes, i.e. primary or secondary lymphoid organs. Furthermore, we analyzed the developmental changes in expression of alpha subunits (Gs, Gq/11) of membrane heterotrimeric GTP-binding proteins. We demonstrated marked developmental decrease of both Na + , K + -and Mg 2+ -ATPase activities in thymus and lymph node lymphocytes. On the other hand, we found elevated membrane gammaglutamyltranspeptidase (GGT) activity as a function of age in lymph node lymphocytes in contrast to declined GGT in thymus. These findings are probably associated with antibody formation related to antigenic pressure during postnatal development. Finally, we assayed developmental changes of G alpha (s) and G alpha q/11 subunits in thymus and lymph nodes. There were ontogenetic specifities in expression of G alpha (s) or G alpha q/11 and appropriate effector enzyme systems generating of 2 nd messengers cAMP or 1,4,5 IP 3 , respectively, in cell signal transduction. The results of this study contribute to our understanding of the dynamic changes of both enzymes and G alpha subunit profiles at the level lymphocyte cell surface linked to maturation events in ontogenetic development

Study of coupling loss on bi-columnar BSCCO/Ag tapes by a.c. susceptibility measurements

Coupling losses were studied in composite tapes containing superconducting material in the form of two separate stacks of densely packed filaments embedded in a metallic matrix of Ag or Ag alloy. This kind of sample geometry is quite favorable for studying the coupling currents and in particular the role of superconducting bridges between filaments. By using a.c. susceptibility technique, the electromagnetic losses as function of a.c. magnetic field amplitude and frequency were measured at the temperature T = 77 K for two tapes with different matrix composition. The length of samples was varied by subsequent cutting in order to investigate its influence on the dynamics of magnetic flux penetration. The geometrical factor $\chi_0$ which takes into account the demagnetizing effects was established from a.c. susceptibility data at low amplitudes. Losses vs frequency dependencies have been found to agree nicely with the theoretical model developed for round multifilamentary wires. Applying this model, the effective resistivity of the matrix was determined for each tape, by using only measured quantities. For the tape with pure silver matrix its value was found to be larger than what predicted by the theory for given metal resistivity and filamentary architecture. On the contrary, in the sample with a Ag/Mg alloy matrix, an effective resistivity much lower than expected was determined. We explain these discrepancies by taking into account the properties of the electrical contact of the interface between the superconducting filaments and the normal matrix. In the case of soft matrix of pure Ag, this is of poor quality, while the properties of alloy matrix seem to provoke an extensive creation of intergrowths which can be actually observed in this kind of samples.Comment: 20 pages 11 figure, submitted to Superconductor Science and Technolog

Multifilamentary, in-situ Route, Cu-stabilized MgB2 Strands

Transport critical current densities and n-values were measured at 4.2 K in fields up to 15 T on 7, 19, and 37-stack multifilamentary MgB2 strands made using an in-situ route. Some strands included SiC additions (particle size 30 nm), while in others Mg-rich compositions were used. Two basic multifilamentary variants were measured, the first had Nb filamentary barriers, the second had Fe filamentary barriers. All samples incorporated stabilizer in the form of Cu 101. Simple, one-step heat treatments were used, with temperatures ranging from 700-800C, and times from 10-30 minutes. Transport critical current densities of 1.75 x 105 A/cm2 were seen at 4.2 K and 5 T in 37 stack strands.Comment: 10 pages, 3 figs, 2 table

Ionophore A23187 induced reductions in toad urinary bladder epithelial cell oxidative phosphorylation and viability

The divalent cation ionophore A23187 increased oxygen consumption by isolated epithelial cells from toad urinary bladder, an increase similar to that seen with 2,4-dinitrophenol, a classic uncoupler of mitochondrial oxidative phosphorylation. This respiratory stimulation was not seen in calcium-free incubation media. That this A23187 induced rise in cell oxygen consumption was due to a primary uncoupling action on mitochondrial oxidative phosphorylation rather than secondary to stimulation of cellular transport processes and mediated via increased cellular ADP levels was suggested by the ability of A23187 to release the inhibition of cellular respiration by oligomycin, an inhibitor of the mitochondrial proton ATPase which blocks the stimulation of mitochondrial respiration by ADP. Since active transepithelial ion transport and cellular energy production are closely linked processes, the uncoupling action of A23187 in the presence of extracellular calcium is sufficient to account for an acute decline in active ion transport across epithelia without invoking other calcium-mediated processes. Furthermore, isolated epithelial cells exposed to A23187 for 90 min had greater than 50% loss of viability, as measured by failure of Trypan blue exclusion. The subacute A23187 induced declines in transepithelial transport, therefore, may be secondary to its non-specific effects on cell viability.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47447/1/424_2004_Article_BF00658484.pd

Geographical and temporal distribution of SARS-CoV-2 clades in the WHO European Region, January to June 2020

We show the distribution of SARS-CoV-2 genetic clades over time and between countries and outline potential genomic surveillance objectives. We applied three available genomic nomenclature systems for SARS-CoV-2 to all sequence data from the WHO European Region available during the COVID-19 pandemic until 10 July 2020. We highlight the importance of real-time sequencing and data dissemination in a pandemic situation. We provide a comparison of the nomenclatures and lay a foundation for future European genomic surveillance of SARS-CoV-2.Peer reviewe

CHEMICAL OXYGEN-IODINE LASER IN PERIODICALLY-PULSED REGIME OF GENERATION

A periodically-pulsed regime of generation in an originally CW chemical oxygen-iodine laser (COIL) using magnetic modulation of gain is presented. An experimental verification of feasibility of a direct magnetic gain switching in the active zone of COIL utilizing the Zeeman effect is demonstrated