Heterogeneity of signal requirements in T cell activation within a panel of human proliferative T cell clones

Activation of T lymphocytes is initiated by receptor ligand interactions at the cell surface leading to the transduction of intracellular signals followed by the de novo synthesis and expression of T cell activation markers (including receptors for interleukin 2 (IL 2) and transferrin), production of lymphokines, and T cell proliferation. This requisite first step for activation of T lymphocytes can be mimicked in certain situations with a variety of stimuli. These include antibodies to certain integral membrane proteins, phorbol esters, and plant lectins that act as mitogens. In this paper, we report that at least two classes of human T cell clones can be distinguished based upon signal requirements necessary to induce proliferation. Although all clones analyzed expressed IL 2 receptors and secreted IL 2 after non-antigenic activation, one subset of clones did not proliferate in response to the same non-antigenic signals. In that subset, complete activation leading to proliferation required interaction of the T cell with specific antigen. The ability to subset these T cell clones into two groups did not correlate with phenotypic differences, source of the clone, nor with magnitude of intracellular calcium mobilization. By studying the stimulation requirements of these two subsets of human T cell clones through the use of specific antigen or antigen-independent stimuli, it was possible to demonstrate that different stimuli varied in their ability to induce steps of T cell activation. Analysis of reactivity of these clones to suboptimal stimulation allowed the definition of intermediate stages of T cell activation. Such intermediate stages might reflect a diversity of intracellular signaling pathways or a complexity of regulatory mechanisms distal to the events that allow intracellular calcium mobilization. Thus for the first time, it has been possible to study ordered events of T cell activation in non-transformed, antigen-dependent human T lymphocytes. The data presented in this paper suggest that T cell activation is not an all or nothing phenomenon, and there is an ordered sequence of events that can be differentiated based upon signal requirements at the T cell membrane.     

A non-alphoid repetitive DNA sequence from human chromosome 21

Summary A non-alphoid repetitive DNA from human chromosome 22, consisting of a 48-bp motif, shows homology to both G-group chromosomes in the gorilla, thus indicating the presence of additional repeat family members on further human chromosomes. Therefore, we screened a chromosome-21-specific cosmid library using this repetitive sequence from chromosome 22 (D22Z3). Some 40–50 cosmid clones were positive in tests for hybridization. One of the clones giving the strongest signals was digested with EcoRI/PstI, which we knew to cut frequently within the repeats; this resulted in fragments containing repeat units only. The fragments were subcloned into plasmid vector pTZ 19. Sequence-analysis of a 500-bp insert showed ten copies of a 48-bp repeat similar to D22Z3, with about 15% sequence deviation from the chromosome 22 consensus sequence. In situ hybridization of the newly isolated recombinant established its chromosome 21 specifity at high stringency. Physical mapping by pulsed field gel electrophoresis placed this new repeat in close vicinity to the chromosome 21 alphoid repeat. No cross-hybridization with other mammalian genomes except for those of apes was observed. The locus has been designated D21Z2 by the Genome Data Base. A gel mobility shift assay indicated that this repetitive motif has protein-binding properties.     

Technetium and rhenium complexes of mercapto-containing peptides 1. Tc(V) and Re(V) complexes with mercaptoacetyl diglycine (MAG2) and X-ray structure of AsPh4[TcO(MAG2)]·C2H5OH

The reaction of mercaptoacetyl diglycine (MAG₂) with technetium(V) gluconate in aqueous solution produced [TcO(MAG₂)]⁻. A single X-ray structure determination was carried out for the tetraphenylarsonium salt. The dark brown crystals are monoclinic, space group P2(1)/n, with a=12.478(5), b=14.922(5), c=17.183(9) Å and Z=4. The [TcO(MAG₂)]⁻ ion has a square pyramidal geometry with the technetium atom displaced by 0.756 Å towards the oxo ligand from the plane formed by the equatorial S,N,N,O atoms. The rhenium complex AsPh₄[ReO(MAG₂)] was prepared analogously starting from Re(V) gluconate and characterized.     

Teaching life cycle assessment in higher education

The International Journal of Life Cycle Assessment - Scientific Life Cycle Assessment (LCA) literature provides some examples of LCA teaching in higher education, but not a structured overview of...     

Heart Rate Variability and Blood Pressure during Dynamic and Static Exercise at Similar Heart Rate Levels

Aim was to elucidate autonomic responses to dynamic and static (isometric) exercise of the lower limbs eliciting the same moderate heart rate (HR) response. Method: 23 males performed two kinds of voluntary exercise in a supine position at similar heart rates: static exercise (SE) of the lower limbs (static leg press) and dynamic exercise (DE) of the lower limbs (cycling). Subjective effort, systolic (SBP) and diastolic blood pressure (DBP), mean arterial pressure (MAP), rate pressure product (RPP) and the time between consecutive heart beats (RR-intervals) were measured. Time-domain (SDNN, RMSSD), frequency-domain (power in the low and high frequency band (LFP, HFP)) and geometric measures (SD1, SD2) as well as non-linear measures of regularity (approximate entropy (ApEn), sample entropy (SampEn) and correlation dimension D2) were calculated. Results: Although HR was similar during both exercise conditions (88±10 bpm), subjective effort, SBP, DBP, MAP and RPP were significantly enhanced during SE. HRV indicators representing overall variability (SDNN, SD 2) and vagal modulated variability (RMSSD, HFP, SD 1) were increased. LFP, thought to be modulated by both autonomic branches, tended to be higher during SE. ApEn and SampEn were decreased whereas D₂ was enhanced during SE. It can be concluded that autonomic control processes during SE and DE were qualitatively different despite similar heart rate levels. The differences were reflected by blood pressure and HRV indices. HRV-measures indicated a stronger vagal cardiac activity during SE, while blood pressure response indicated a stronger sympathetic efferent activity to the vessels. The elevated vagal cardiac activity during SE might be a response mechanism, compensating a possible co-activation of sympathetic cardiac efferents, as HR and LF/HF was similar and LFP tended to be higher. However, this conclusion must be drawn cautiously as there is no HRV-marker reflecting “pure” sympathetic cardiac activity.     

1.2 Å X-ray Structure of the Renal Potassium Channel Kv1.3 T1 Domain

Here we present the structure of the T1 domain derived from the voltage-dependent potassium channel K_v1.3 of Homo sapiens sapiens at 1.2 Å resolution crystallized under near-physiological conditions. The crystals were grown without precipitant in 150 mM KP_i, pH 6.25. The crystals show I4 symmetry typical of the natural occurring tetrameric assembly of the single subunits. The obtained structural model is based on the highest resolution currently achieved for tetramerization domains of voltage-gated potassium channels. We identified an identical fold of the monomer but inside the tetramer the single monomers show a significant rotation which leads to a different orientation of the tetramer compared to other known structures. Such a rotational movement inside the tetrameric assembly might influence the gating properties of the channel. In addition we see two distinct side chain configurations for amino acids located in the top layer proximal to the membrane (Tyr109, Arg116, Ser129, Glu140, Met142, Arg146), and amino acids in the bottom layer of the T1-domain distal from the membrane (Val55, Ile56, Leu77, Arg86). The relative populations of these two states are ranging from 50:50 for Val55, Tyr109, Arg116, Ser129, Glu140, 60:40 for Met142, 65:35 for Arg86, 70:30 for Arg146, and 80:20 for Ile56 and Leu77. The data suggest that in solution these amino acids are involved in an equilibrium of conformational states that may be coupled to the functional states of the whole potassium channel.