In vitro selection of dopamine RNA ligands

RNA aptamers that specifically bind dopamine have been isolated by in vitro selection from a pool of 3.4 x 10(14) different RNA molecules. One aptamer (dopa2), which dominated the selected pool, has been characterized and binds to the dopamine affinity column with a dissociation constant of 2.8 microM. The specificity of binding has been determined by studying binding properties of a number of dopamine-related molecules, showing that the interaction with the RNA might be mediated by the hydroxyl group at position 3 and the proximal aliphatic chain in the dopamine molecule. The binding domain was initially localized by boundary experiments. Further definition of the dopamine binding site was obtained by secondary selection on a pool of sequences derived from a partial randomization of the dopa2 molecule. Sequence comparison of a large panel of selected variants revealed a structural consensus motif among the active aptamers. The dopamine binding pocket is built up by a tertiary interaction between two stem and loop motifs, creating a stable framework in which five invariant nucleotides are precisely arrayed. Minimal active sequence and key nucleotides have been confirmed by the design of small functional aptamers and mutational analysis. Enzymatic probing suggests that the RNA might undergo a conformational change upon ligand binding that stabilizes the proposed tertiary structure.     

Transgenic models of Huntington's disease

CAG/polyglutamine expansion has been shown to form the molecular basis of an increasing number of inherited neurodegenerative diseases. The mutation is likely to act by a dominant gain of function but the mechanism by which it leads to neuronal dysfunction and cell death is unknown. The proteins harbouring these polyglutamine tracts are unrelated and without exception are widely expressed with extensively overlapping expression patterns. The factors governing the cell specific nature of the neurodegeneration have yet to be understood. Upon a certain size threshold, expanded CAG repeats become unstable on transmission and a modest degree of somatic mosaicism is apparent. Similarly, the molecular basis of the instability and its tissue specificity has yet to be unravelled. Recent reports describing the first mouse models of CAG/polyglutamine disorders indicate that it will be possible to model both the pathogenic mechanism and the CAG repeat instability in the mouse. This has great potential and promise for uncovering the molecular basis of these diseases and developing therapeutic interventions.     

Prospects for a vaccine to prevent Lyme disease in humans

Vaccination with recombinant outer-surface protein A (OspA) preparations has been highly successful in protecting laboratory animals against challenge by strains of Borrelia burgdorferi closely related to the one from which the OspA was derived. Humoral immunity is sufficient for protection. Against natural infection introduced by ticks, the vaccine-induced immune response may begin to take effect in the tick itself--i.e., before the spirochete enters the host--and may extend to a broader spectrum of strains of B. burgdorferi than are represented in the vaccine. Single recombinant OspA vaccine preparations are currently being evaluated in two large-scale efficacy trials in adults in the United States. Greater heterogeneity among B. burgdorferi strains in Europe than among those in the United States will likely necessitate the development of a vaccine containing antigens from multiple strains; a multivalent vaccine may or may not be needed in the United States.     

Transgenic A1 adenosine receptor overexpression increases myocardial resistance to ischemia

Activation of myocardial A1 adenosine receptors (A1AR) protects the heart from ischemic injury. In this study transgenic mice were created using the cardiac-specific alpha-myosin heavy chain promoter and rat A1AR cDNA. Heart membranes from two transgene positive lines displayed approximately 1,000-fold overexpression of A1AR (6,574 +/- 965 and 10,691 +/- 1,002 fmol per mg of protein vs. 8 +/- 5 fmol per mg of protein in control hearts). Compared with control hearts, transgenic Langendorff-perfused hearts had a significantly lower intrinsic heart rate (248 beats per min vs. 318 beats per min, P < 0. 05), lower developed tension (1.2 g vs. 1.6 g, P < 0.05), and similar coronary resistance. The difference in developed tension was eliminated by pacing. Injury of control hearts during global ischemia, indexed by time-to-ischemic contracture, was accelerated by blocking adenosine receptors with 50 microM 8-(p-sulfophenyl) theophylline but was unaffected by addition of 20 nM N6-cyclopentyladenosine, an A1AR agonist. Thus A1ARs in ischemic myocardium are presumably saturated by endogenous adenosine. Overexpressing myocardial A1ARs increased time-to-ischemic contracture and improved functional recovery during reperfusion. The data indicate that A1AR activation by endogenous adenosine affords protection during ischemia, but that the response is limited by A1AR number in murine myocardium. Overexpression of A1AR affords additional protection. These data support the concept that genetic manipulation of A1AR expression may improve myocardial tolerance to ischemia.     

The growth and maturation of the National Cancer Data Base

BACKGROUND: The National Cancer Data Base (NCDB), a joint project of the Commission on Cancer of the American College of Surgeons and the American Cancer Society, is a cancer management and outcomes data base for health care organizations. It provides a comparative summary of patient care that is used by communities and participating hospitals for self-assessment. The most current (1994) data are described here. METHODS: Six calls for data have yielded a total of 4,580,000 cases for the years 1985-1994. A total of 1735 hospital cancer registries have each participated in at least one of the calls for data. RESULTS: Summing the last year's report from each of the 1227 hospitals that participated in 1994, the cases represent the equivalent of 57% of the estimated 1994 U.S. cancer cases. These data were received from all six regions of the country, including all 50 states. Ninety-seven percent of patients received all or part of their treatment at the reporting hospital. The four most common cancers are carcinomas of the breast (15.7%), lung (14.3%), prostate (13.1%), and colon (7.7%), and collectively they comprise a majority of new cases. CONCLUSIONS: The NCDB is a cancer management and outcomes data base for health care organizations that currently provides data on 57% of the estimated new cases in the U.S. Past data have been used extensively to assess patterns of care and outcomes.