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The use of peer interviewers with privileged access to a particular population group, which is difficult to reach via more conventional methods, has been acknowledged in recent research. This paper explores a number of key issues relating to the employment of peer interviewers by reflecting on a project designed to explore the views and experiences of parents who use illegal drugs. The project presented the research team with a number of challenges. These included the need to provide on‐going support for the interviewers, a sense of distance felt by the researchers from the raw data they collected, and the difficulties of gaining from the skills and experiences of peer interviewers without exploiting their labour. The paper also explores the advantages of involving peer interviewers closely in research work and reflects on the nature and boundaries of expert knowledge that can become evident in such collaborations. The need for a certain amount of flexibility over the roles and domains of control that lay experts and researchers traditionally inhabit is suggested. In conclusion, it is argued that the involvement of peer interviewers in research can be a valuable means of enhancing our knowledge and understanding of a variety of population groups who tend to live beyond the gaze of more orthodox researchers.

The G protein ␤ subunit, G␤ 5 , is predominantly expressed in the central nervous system. In rodent brain, G␤ 5 is expressed as a protein with an apparent molecular mass of 39,000 daltons (39 kDa). We have identified an additional G␤ 5 immunoreactive protein of apparent size 44 kDa in the vertebrate retina. Molecular cloning and sequencing of polymerase chain reaction products revealed that the cDNA encoding the larger species of G␤ 5 (G␤ 5L ) was identical to the shorter form with the addition of 126 base pairs of 5 DNA sequence potentially encoding an in-frame 42-amino acid extension. Sequencing of mouse G␤ 5 genomic clones demonstrated that the 126-base pair of retinal-specific coding material is derived from a hitherto undetected 5 exon. During sucrose density gradient fractionation of bovine retinas, the 44-kDa G␤ 5L protein co-purified with rod outer segment membranes. Incubation of rod outer segment membranes with the nonhydrolyzable guanine nucleotide, GTP␥S (guanosine 5-3-O-(thio)triphosphate), which released the G␤ subunit of transducin (G␤ 1 ), failed to remove G␤ 5L . The 39-kDa G␤ 5 protein displayed differential association with retinal and brain membranes. In the retina, G␤ 5 was present as a soluble protein and was undetectable in the membrane fraction, whereas in the brain approximately 70% of G␤ 5 was associated with cellular membranes. In transient COS-7 cell expression experiments, G␤ 5L formed functional G␤␥ dimers and G␣␤␥ heterotrimers, and activated phosphoinositide-specific phospholipase C␤ 2 in a manner indistinguishable from the 39-kDa G␤ 5 protein. The cloning of the retinal-specific G␤ 5L cDNA suggests the existence of potentially novel G protein-mediated signaling cascades in photoreception.In eukaryotic cells, a family of signal-transducing guaninenucleotide binding proteins (G proteins) 1 orchestrates many physiological processes by coupling activated cell surface receptors to intracellular second messenger systems. G protein-coupled receptors (GPCRs), which possess a stereotypical seventransmembrane-spanning domain architecture, bind and mediate the signaling of a variety of molecules, including hormones, neurotransmitters, odorants, and light. To date, several hundred GPCRs have been cloned or characterized (1). In contrast, the number of heterotrimeric G proteins, as well as the number of G protein-regulated effectors, is much more limited.G proteins are heterotrimeric, composed of ␣, ␤, and ␥ subunits (G␣, G␤, G␥). Activation of a GPCR by ligand binding stimulates the exchange of bound GDP for GTP on the G␣ subunit and results in the dissociation of the G␣ subunit from a tightly complexed G␤␥ dimer. The released G␣ and G␤␥ subunits in turn regulate the activity of effector proteins, the better characterized of which include cGMP phosphodiesterase, adenylyl cyclases, phosphoinositide-specific phospholipase C ␤ enzymes, and ion channels. In addition, the dimeric G␤␥ subunits are involved in GPCR desensitization by recruitment of receptor kinases to the plasma membrane, and in ...

Thrombin stimulation of 1321N1 astrocytoma cells leads to Ras-dependent AP-1-mediated transcriptional activation and to DNA replication. In contrast to what has been observed in most cell systems, in 1321N1 cells these responses are pertussis toxin-insensitive. The pertussis toxin-insensitive G-protein G12 has been implicated in cell growth and transformation in different cell systems. We have examined the potential role of this protein in AP-1-mediated transcriptional activation and DNA synthesis in 1321N1 cells. Transient expression of an activated (GTPase-deficient) mutant of G alpha 12 increased AP-1-dependent gene expression. This response was inhibited by co-expression of a dominant negative Ala-15 Ras protein. To determine whether the pertussis toxin-insensitive G12 protein is involved in the thrombin-stimulated DNA synthesis, an inhibitory antibody against the C-terminal sequence of G alpha 12 subunit was microinjected into 1321N1 cells. Microinjection of the anti-G alpha 12 resulted in a concentration-dependent inhibition of thrombin-stimulated DNA synthesis. In contrast, microinjection of nonimmune IgG or an antibody directed against the C terminus of G alpha o did not reduce the mitogenic response to thrombin. Furthermore, microinjection of the anti-G alpha 12 antibody had no effect on fibroblast growth factor-stimulated DNA synthesis. These results demonstrate a specific role for G alpha 12 in the mitogenic response to thrombin in human astroglial cells.

A cDNA clone encoding a rabbit ileal villus cell Na+/H+ exchanger was isolated and its complete nucleotide sequence was determined. The cDNA is 4 kb long and contains 322 bp of 5′‐untranslated region, 2451 bp of open reading frame and 1163 bp of 3′‐untranslated area, with 70%, 91% and 40% identity to the human sequence, respectively. Amino acid sequence deduced from the longest open reading frame indicated a protein of 816 residues (predicted Mr 90,716) which exhibits 95% amino acid identity to the human Na+/H+ exchanger. The two putative glycosylation sites in the human Na+/H+ exchanger are conserved in this protein, suggesting that it is a glycoprotein. Stable transfection of the cDNA into an Na+/H+ exchanger deficient fibroblast cell line, established Na+/H+ exchange. The Na+/H+ exchanger was stimulated by serum and a phorbol ester but not by 8‐Br‐cAMP. In Northern blot analysis, the cDNA hybridized to a 4.8 kb message in rabbit ileal villus cells, kidney cortex, kidney medulla, adrenal gland, brain and descending colon and to a 5.2 kb message in cultured human colonic cancer cell lines, HT29‐18 and Caco‐2. In immunoblotting, a polyclonal antibody raised against a fusion protein of beta‐galactosidase and the C‐terminal 158 amino acids of the human Na+/H+ exchanger identified a rabbit ileal basolateral membrane protein of 94 kd and only weakly interacted with the ileal brush border membrane. In immunocytochemical studies using ileal villus and crypt epithelial cells, the same antibody identified basolateral and not brush border epitopes. Restriction analysis of genomic DNA with a 462 bp PstI‐AccI fragment of the rabbit Na+/H+ exchanger strongly suggests the existence of closely related Na+/H+ exchanger genes. The near identity of the basolateral Na+/H+ exchanger and the human Na+/H+ exchanger plus the ubiquitous expression of this message suggests that the ileal basolateral Na+/H+ exchanger is the ‘housekeeping’ Na+/H+ exchanger.