We have constructed infectious retroviral vectors, derived from Moloney murine leukemia virus, that efficiently transduce the polyoma virus tumor (T) antigens individually. The parental vector we have chosen [pZIP-NeoSV(X)l] expresses a dominant selectable marker for neomycin resistance and is a shuttle vector capable of propagation in both eukaryotic and prokaryotic cells, thus facilitating its use in structure-function studies. To address the relationship between polyoma T-antigen tumorigenesis and the effects of individual T antigens on growth control and differentiation, we used these vectors to introduce and stably express large, middle-sized, or small T antigens into mouse fibroblasts and preadipocytes. All cDNAs introduced into the vector are expressed stably even in the absence of selective pressure. The stable expression of small T antigen is noted particularly because cell lines expressing small T antigen have not been readily available prior to the use of retroviral vectors. Small T antigen-induced increase in saturation density of NIH 3T3 cells can be scored on the basis of the morphology of drug-resistant colonies. Middle-sized T antigen eliminates the growth requirement of NIH 3T3 cells for epidermal growth factor in a defined medium and permits growth in platelet-poor plasma, indicating elimination of the platelet-derived growth factor requirement as well. Large T antigen suppresses mouse preadipocyte (3T3-F442A) differentiation. These vectors and these functional assays of T-antigen activity permit genetic analysis of the relationship between tumorigenesis by T antigens and the alteration of cellular growth and differentiation.The role of the individual polyoma tumor (T) antigens in tumorigenesis and in the polyoma virus replication cycle is currently the subject of intense study. Large T antigen (LTAg) is a nuclear protein with origin-specific DNA binding properties, and it is essential for viral DNA replication (1). In addition, this protein also negatively regulates early viral transcription (1) and is both necessary and sufficient to immortalize primary rodent fibroblasts (2). Middle-sized T antigen (MTAg) is sufficient to transform immortalized cell lines to form foci in monolayer cultures and colonies in soft agar and to become tumorigenic (3). MTAg immunoprecipitates contain tyrosine kinase activity (4), and recent results indicate that the tyrosine kinase activity in MTAg immunoprecipitates is pp60'csrc (5). An activity in MTAg immunoprecipitates will also phosphorylate the membrane phospholipid phosphatidylinositol (6), leading to the generation of two potent second messengers, diacylglycerol and inositol trisphosphate, which are important signals in normal cellular regulation (7) and may be important in MTAg transformation (8). Unlike LTAg and MTAg, small T antigen (STAg) has no known intrinsic or associated biochemical activity. Bastin and coworkers (9) have shown, however, that either STAg or LTAg must complement MTAg to cause tumor formation in newborn rats. In addition, Benj...

No abstract

No abstract

Aims: The aim of this article is to assess what goes on in treatment sessions in courtmandated drug treatment in the UK. Methods: The study used a case note audit involving interviews with drug workers about each of their active cases, assessing client characteristics and their reports on what activities had taken place in treatment sessions. Findings: The average session lasts just under 30 minutes and typically at least three different types of worker-led activity are engaged in per session, often including time spent on compliance with treatment, with prescriptions and with the testing requirements of the court mandate. The amount of time dedicated to evidenced psychosocial interventions is typically less than 10 minutes. Conclusions: The tensions reported elsewhere for drug workers engaged in criminal justice services are evidenced in the study given the range of tasks (potentially conflicting) that drug workers are required to engage in and the limited opportunity for them to engage in effective psychosocial drug treatment.