Inhibition of smoking-related information in smokers and nonsmokers.

Twenty-four smokers and 24 nonsmokers performed a modified version of M. A. Gernsbacher, K. R. Varner, and M. E. Faust's (1990) suppression task, involving presentations of sentences on a computer screen. Each sentence was followed by a word that either was or was not related to the meaning of the sentence. Participants judged whether the word was related to the sentence by pressing either a "yes" or "no" key on a button box. In the experimental sentences, the test word was related to one meaning of the final word of the sentence, but this was not necessarily the meaning intended in the sentence. In half of the experimental sentences, the last word was a smoking-related word (e.g., tar or ashes). Smokers had relatively longer response latencies and lower accuracy scores than nonsmokers when the final word was smoking related, whereas both groups performed similarly on items unrelated to smoking, suggesting that smokers had more difficulty than nonsmokers inhibiting task-irrelevant, smoking-related information but that they did not have a general inability to inhibit irrelevant information.

Smoking urges affect language processing.

We examined the hypothesis that cigarette smoking urges take up working memory resources and interfere with language comprehension. Thirty-six smokers and 36 nonsmokers participated in the experiment. Eighteen members of each group were exposed to an imagery script that was intended to elicit a smoking urge in smokers, and the other 18 were exposed to a neutral script. The participants then performed a sentence comprehension task. The results showed that the urge script had a detrimental effect on the smokers' comprehension accuracy. As expected, there was no urge effect for the nonsmokers. Furthermore, smokers read the sentences significantly faster than nonsmokers. The results are discussed with reference to cognitive theories of urges and a capacity model of language processing.

Characterization of anti-mouse IL-12 monoclonal antibodies and measurement of mouse IL-12 by ELISA.

Enzyme-linked immunosorbent assays (ELISAs) capable of quantitatively measuring pg/ml amounts of mouse IL-12 (moIL-12) were developed as an alternative to the current bioassay procedure used for the measurement of moIL-12. A panel of 40 rat anti-moIL-12 monoclonal antibodies were identified and tested for their ability to bind 125I-moIL-12. Two of the MAbs, 2B5 and 9A5, were able to capture 125I-moIL-12 in the presence of unlabelled moIL-12 p35 and moIL-12 p40, suggesting specificity for the moIL-12 p75 heterodimer. Western blot analysis confirmed that MAb 9A5 specifically recognized only moIL-12 p75. Using MAb 9A5, and an additional anti-moIL-12 p40 MAb 5D9, we developed quantitative ELISAs for the specific detection of moIL-12 p75 and p40, respectively. These ELISAs detect moIL-12 with a sensitivity of 40 pg/ml. Whereas the p40 ELISA detected three forms of moIL-12 (p40 monomer, p40 homodimer, and the heterodimer), the p75 ELISA only detected moIL-12 heterodimer. Neither of these assays crossreacted with a panel of additional cytokines. The levels of moIL-12 measured by the p75 ELISA and the bioassay were directly compared and found to correlate well. Therefore, the p75 ELISA represents an alternative to the bioassay for the measurement of moIL-12.

Expression cloning of a human IL-12 receptor component. A new member of the cytokine receptor superfamily with strong homology to gp130.

A cDNA encoding a human IL-12R subunit was isolated by expression cloning. This subunit is a 662 amino acid type I transmembrane protein with an extracellular domain of 516 amino acids and a cytoplasmic domain of 91 amino acids. It is a member of the hemopoietin receptor superfamily and is most closely related over its entire length to gp130 and the receptors for granulocyte-CSF (G-CSF) and leukemia-inhibitory factor. When expressed in COS cells, this IL-12R subunit binds both human and murine IL-12 with an apparent affinity of 2 to 5 nM. The transfected COS cells express both monomers and disulfide-linked dimers or oligomers of the IL-12R subunit on their surface. However, unlike the IL-6-induced dimerization of gp130, the oligomerization of the IL-12R subunit is not dependent on binding of IL-12. Only the IL-12R subunit dimers/oligomers but not the monomers bind IL-12 with an affinity of 2 to 5 nM. A polyclonal antiserum raised against this receptor subunit specifically inhibits IL-12-induced proliferation of PHA-activated PBMC. The data are consistent with the hypotheses that 1) a dimer/oligomer of the cloned IL-12R subunit (IL-12R-beta) represents the low affinity IL-12 binding site identified on human lymphoblasts, 2) the cloned receptor subunit is involved in IL-12 signal transduction, and 3) an additional, as of yet unidentified subunit is required to generate a high affinity IL-12R complex.