The avidity spectrum of T cell receptor interactions accounts for T cell anergy in a double transgenic model

The mechanism of self-tolerance in the CD4(+) T cell compartment was examined in a double transgenic (Tg) model in which T cell receptor (TCR)-alpha/beta Tg mice with specificity for the COOH-terminal peptide of moth cytochrome c in association with I-Ek were crossed with antigen Tg mice. Partial deletion of cytochrome-reactive T cells in the thymus allowed some self-specific CD4(+) T cells to be selected into the peripheral T cell pool. Upon restimulation with peptide in vitro, these cells upregulated interleukin (IL)-2 receptor but showed substantially lower cytokine production and proliferation than cells from TCR Tg controls. Proliferation and cytokine production were restored to control levels by addition of saturating concentrations of IL-2, consistent with the original in vitro definition of T cell anergy. However, the response of double Tg cells to superantigen stimulation in the absence of exogenous IL-2 was indistinguishable from that of TCR Tg controls, indicating that these self-reactive cells were not intrinsically hyporesponsive. Measurement of surface expression of Tg-encoded TCR alpha and beta chains revealed that cells from double Tg mice expressed the same amount of TCR-beta as cells from TCR Tg controls, but only 50% of TCR-alpha, implying expression of more than one alpha chain. Naive CD4(+) T cells expressing both Tg-encoded and endogenous alpha chains also manifested an anergic phenotype upon primary stimulation with cytochrome c in vitro, suggesting that low avidity for antigen can produce an anergic phenotype in naive cells. The carboxyfluorescein diacetate succinimidyl ester cell division profiles in response to titered peptide +/- IL-2 indicated that expression of IL-2 receptor correlated with peptide concentration but not TCR level, whereas IL-2 production was profoundly affected by the twofold decrease in specific TCR expression. Addition of exogenous IL-2 recruited double Tg cells into division, resulting in a pattern of cell division indistinguishable from that of controls. Thus, in this experimental model, cells expressing more than one alpha chain escaped negative selection to a soluble self-protein in the thymus and had an anergic phenotype indistinguishable from that of low avidity naive cells. The data are consistent with the notion that avidity-mediated selection for self-reactivity in the thymus may lead to the appearance of anergy within the peripheral, self-reactive T cell repertoire, without invoking the induction of hyporesponsiveness to TCR-mediated signals.     

Unusual effects of ammonium ligno-sulphonate on the electrochemical behaviour of lead, lead-calcium, and lead-antimony alloys

Ammonium ligno-sulphonate (ALS), is used as a negative plate additive in lead/acid batteries. This compound exerts beneficial effects on lead/acid battery performance by producing a porous film that enhances the reactant and product transport. However, from electrochemical studies conducted in this laboratory, it is shown that the beneficial effects of ALS are restricted to conditions when prior hydrogen evolution did not take place during charging.     

Community action for health promotion: a review of methods and outcomes 1990-1995

Five repeated cross-sectional serological surveys of 790 dairy cattle in 4 dairy herds between December 1985 and February 1987 provided an opportunity to study the changes in the seroprevalence of Haemophilus somnus across the 5 surveys and with respect to some demographic and disease variables. The demographic variables included were age (heifers or cows) and farm, representing two groups of herds (two herds in each group, located in the Central and Northern Valleys of California). The serological status of cattle as either negative or positive against H. somnus, Campylobacter fetus and Leptospira hardjo were determined with enzyme linked-immunosorbent assays. Logistic regression analysis was used to compute maximum likelihood estimates of adjusted odds ratios and their respective 95% confidence intervals. The baseline risk of being H. somnus seropositive in the cattle observed at first sampling did not vary significantly during the study period after adjustment for the effects of covariates. Only at first sampling were cows about twice as likely to be H. somnus seropositive than heifers. At samplings 1 and 3, but not at 2 and 5, being in the herds of the Central Valley appeared protective. In contrast, at sampling 4 the cattle in herds in the Central Valley were about 7 times more likely to be H. somnus seropositive. C. fetus-positive cattle were about 3 times more likely to be H. somnus seropositive at sampling 1 only. The relationship between H. somnus status and L. hardjo was not significant during the study period.     

Nickel and iron nano-particles in natural rubber composites

In this work, the mechanical, electrical, and magnetic properties of natural rubber (NR) composites containing iron or nickel nanoparticles at different percentage varying from 0 to 120 phr (part of magnetic particle per hundred rubber) have been investigated at room temperature. It was found that the optimum concentration of magnetic fillers in NR is 30 phr, which improve the rheometric characteristics and physico-mechanical properties. Magnetic properties of the rubber composites have been investigated using vibrating sample magnetometer (VSM) at room temperature. The magnetic measurements show superparamagnetic behavior for all Ni and Fe nanoparticles percentage. The electrical measurements show a strong dependency of the conductivity on the percentage of magnetic nanoparticles.     

Simplified quantitative stress-induced leakage current (SILC) model for MOS devices

A simplified quantitative model for the steady-state component of stress-induced leakage current (SILC) in MOS capacitors with ultrathin oxide layers has been developed by assuming a two-step inelastic trap-assisted tunneling (ITAT) process as the conduction mechanism. By using our model, we reduced the time of numerical calculations of SILC to 17% of the standard method while maintaining a high accuracy of the results. We also confirmed that the SILC component must not be neglected when calculating the gate current in modern devices, especially at low fields. Our simplified model helped us to investigate the dependence of SILC on the oxide field and the oxide thickness. We also shed some light on the reasons that cause the peak in the SILC–oxide thickness relation.     

Fault location on a transmission line using synchronized Voltage measurements

Many methods for fault location using synchronized phasor measurement have been reported in literature. Most of these methods use voltage and current measurements at one or both ends of a transmission line. Accuracy of current measurement is limited by the accuracy of the current transformers (CT) used. This paper describes a fault-location method for transmission lines using only synchronized voltage measurements at both ends of the line, eliminating the inherent error due to CT. The method can be applied to transposed and untransposed lines. The method is tested using results from a steady state fault-analysis program and EMTP.     

Effect of phase composition on the binding characteristics of unfired stable dolomite refractories

Three batches of stable dolomite cements with different mineral compositions and fineness were prepared. The hydraulic properties of each sample were measured after curing at 100% relative humidity for 1, 3, 7 and 28 days. The results were interpreted in the light of the phase composition, fineness and curing time. The cement with the highest hydraulic properties was used as a binder for the preparation of unfired stable dolomite bodies. The changes in properties of the prepared bodies at temperatures up to 1550°C were correlated with the phase compositions.     

Lesser known Nigerian edible oils and fats. I.—Characteristics of melon seed oils

Some of the characteristics of a melon seed oil, which is shown to be of the semi-drying type containing mainly linoleic and oleic acids, are described.     

Linoleic Acid Oxidation Catalysed by Various Amino Acids and Cupric Ions in Non-Aqueous Media

The effect of amino acids under the present investigation on linoleic acid oxidation in non-aqueous media has shown feature of an autocatalytic chain reaction and possessed minor antioxidant behaviour except cysteine. The antioxidant effect might be attributed to the absence of protonated amino nitrogen. Linoleic acid alone had an induction period of 15 hr and on the addition of various α-amino acids, the systems had an induction period ranged from 16–19 hr. This increase did not exhibit any specific function for the studied amino acids. Cysteine exceptionally possessed pro-oxidant effect and that was due to the role of HS-group. The addition of copper at concentrations of 10^?5 M and 10^?3 M to the model systems composed of linoleic acid and various α-amino acids in non-aqueous media have shown to exhibit minor and highly pro-oxidant effects respectively. The pro-oxidant effect of these amino acids in the presence of copper might be due to amino acids-copper complexes.     

Porosity Development in Carbons Derived from Olive Oil Mill Residue Under Steam Pyrolysis

Activated carbons were obtained from olive oil mill wastes (OMW) by a single-step steam pyrolysis process, under different conditions of heat treatment temperature (HTT = 873–1073 K) and duration of reaction (15–120 min). Porosity characteristics were determined from N₂ adsorption isotherms and subsequent analysis by the BET-and _s -methods. Development in the texture parameters was found to depend on both experimental variables. A two-step rate process of reaction is proposed to govern carbon activation: a slow external steam-carbon reaction (under mild conditions) removing disorganized material and is associated with considerable weight loss but with low generation of porosity. A second bulk gasification process dominates at high temperature, and/or prolonged duration, and leads to considerable evolution of porosity with minor change in burn-off. Pyrolysis/carbonization under the flow of steam is suggested to enhance removal of low molecular volatiles, retards decomposition of high molecular products, initiates controlled gasification at lower temperatures, and prevents shrinkage of the produced carbon skeleton. OMW seems to need severe conditions of temperature and duration to obtain good adsorbing carbons, or requires pretreatment to remove skin, flesh and seed contaminants.