Time-of-flight Laue fiber diffraction studies of perdeuterated DNA

The diffractometer SXD at the Rutherford Appleton Laboratory ISIS pulsed neutron source has been used to record high resolution time-of-flight Laue fiber diffraction data from DNA. These experiments, which are the first of their kind, were undertaken using fibers of DNA in the A conformation and prepared using deuterated DNA in order to minimise incoherent background scattering. These studies complement previous experiments on instrument D19 at the Institut Laue Langevin using monochromatic neutrons. Sample preparation involved drawing large numbers of these deuterated DNA fibers and mounting them in a parallel array. The strategy of data collection is discussed in terms of camera design, sample environment and data collection. The methods used to correct the recorded time-of-flight data and map it into the final reciprocal space fiber diffraction dataset are also discussed. Difference Fourier maps showing the distribution of water around A-DNA calculated on the basis of these data are compared with results obtained using data recorded from hydrogenated A-DNA on D19. Since the methods used for sample preparation, data collection and data processing are fundamentally different for the monochromatic and Laue techniques, the results of these experiments also afford a valuable opportunity to independently test the data reduction and analysis techniques used in the two methods.

DNA hydration studied by neutron fiber diffraction

The development of neutron high angle fiber diffraction to investigate the location of water around the deoxyribonucleic acid (DNA) double-helix is described. The power of the technique is illustrated by its application to the D and A conformations of DNA using the single crystal diffractometer, D19, at the Institut Laue-Langevin. Grenoble and the time of flight diffractometer, SXD, at the Rutherford Appleton ISIS Spallation Neutron Source. These studies show the existence of bound water closely associated with the DNA. The patterns of hydration in these two DNA conformations are quite distinct and are compared to those observed in X-ray single crystal studies of two-stranded oligodeoxynucleotides. Information on the location of water around the DNA double-helix from the neutron fiber diffraction studies is combined with that on the location of alkali metal cations from complementary X-ray high angle fiber diffraction studies at the Daresbury Laboratory SRS using synchrotron radiation. These analyses emphasize the importance of viewing DNA, water and ions as a single system with specific interactions between the three components and provide a basis for understanding the effect of changes in the concentration of water and ions in inducing conformational transitions in the DNA double-helix.

The joint operating company: an innovative approach to collaboration

Hospitals interested in horizontal integration often run into difficulties. In spite of otherwise sound business logic for two organizations to merge, there may be political, legal or financial reasons why a merger option cannot be pursued. Increasingly, enterprises are turning to a joint operating company structure as the solution to their needs. Scott A. Mason and Donald W. Seymour, partners with consulting firm National Health Advisors, explore situations where a JOC model of collaboration may be appropriate.

Young, scarred children and their mothers--a short-term investigation into the practical, psychological and social implications of thermal injury to the preschool child. Part I: Implications for the mother

A short-term, prospective study, using both quantitative and qualitative methods, was designed to determine the practical, psychological and social implications of thermal injury resulting in scarring, for the mothers of thermally injured children, during the 6 months following the child's discharge from hospital. Mothers of 57 thermally injured children under 5 years of age were interviewed whilst the child was in hospital and at home, at 1 week, 2 months and 6 months following hospital discharge. Thermal injuries ranged from 1 to 41 per cent of body surface area and all required skin grafting. Qualitative analysis of interview transcripts resulted in the development of a model of the mother's response--The Maternal Thermal Injury Response Pattern (MTIRP)--which describes a phasic pattern of general response categories. The mothers' psychiatric morbidity was measured using Goldberg's (1978) 60-item General Health Questionnaire (GHQ). The mean of the mothers' total GHQ scores was 2.42 for the retrospective, pre-injury score, 24.5 at the hospital interview and 5.96 at 6 months following the child's discharge from hospital. In conclusion, the mother is a neglected victim of a young child's thermal injury. Use of the MTIRP as an educational tool for carers would promote increased understanding and, thus, more appropriate support.

Site-directed mutagenesis of the phosphorylation sites in the mouse glucocorticoid receptor

The functional significance of receptor phosphorylation in mediating the actions of glucocorticoids remains undefined. The identification of seven phosphorylation sites in the mouse glucocorticoid receptor (Bodwell, J. E., Orti, E., Coull, J. M., Pappin, D. J. C., Smith, L. I., and Swift, F. (1991) J. Biol. Chem. 266, 7549-7555) permits a direct examination of the potential regulatory role of glucocorticoid receptor phosphorylation in transactivation. Using oligonucleotide-directed mutagenesis of the mouse glucocorticoid receptor cDNA, we have substituted alanine or aspartate for the residues phosphorylated in this ligand-dependent transcription factor. COS-1 cells were cotransfected with mutant receptor cDNA expression vectors and a reporter plasmid containing the glucocorticoid-inducible mouse mammary tumor virus promoter linked to chloramphenicol acetyltransferase in order to characterize the effect of these substitutions on receptor-mediated gene expression. Substitution of alanine or aspartate at single phosphorylation sites does not prevent receptor transactivation. Receptors containing multiple substitutions of alanine or aspartate at the major phosphorylation sites in the acidic domain elicit levels of hormone-induced reporter gene expression that are comparable to wild-type receptors. Mutant receptors substituted with alanine at the five phosphorylation sites conserved among the rat, human, and mouse receptors exhibit a 22% decrease in transcriptional activity. Receptors mutated at all seven sites display a similar modest reduction. These results demonstrate that receptor phosphorylation at these seven identified residues is not a major determinant in glucocorticoid receptor transcriptional activity at the mouse mammary tumor virus promoter.

Employing quantitative and qualitative methods in one study

There is an apparent lack of epistemological rigour when quantitative and qualitative methods are combined in the same study, because they reflect opposing positivist and interpretive perspectives. When and how to use methodological pluralism is discussed in this article.

A high angle neutron fibre diffraction study of the hydration of the A conformation of the DNA double helix

A high angle neutron fibre diffraction study of the distribution of water around the A-form of DNA has been performed using the diffractometer D19 at the Institut Laue-Langevin, Grenoble. These experiments have exploited the ability to replace H2O surrounding the DNA by D2O so that isotopic difference Fourier maps can be computed in which peaks are identified with the distribution of water in the unit cell. All peaks of significant height have been accounted for by four families of water molecules whose positions and occupancies have been determined using least squares refinement. The coordinates of the water peaks making up each family do not deviate significantly from a regular helical arrangement with the same parameters as the DNA. Two of these families are of particular interest. The first consists of water molecules in the major groove linking successive charged phosphate oxygens along the polynucleotide chains. The second is associated with bases in the major groove and forms a central core of density along the helix axis. These two families provide a layer of hydration lining the interior wall of the major groove leaving a central channel to accommodate cations. The relationship between these observations and conformational stability is discussed.

Network integration. A new vision for Catholic healthcare systems in the 1990s

The 1990s will be the decade of network integration for many of the nation's healthcare organizations. Catholic healthcare systems will have to refocus on local and regional healthcare delivery. To succeed in local and regional markets, the systems will have to offer various levels of care through numerous types of providers, share services among facilities, cooperate with secular organizations, and build stronger affiliations with local parishes. Managing this change (from offering fragmented healthcare services to offering integrated services) will be a major challenge facing organizations in the decade ahead. They must develop a clearly articulated vision to provide stability during this time of rapid change. To meet the challenges of the 1990s, Catholic healthcare systems will have to determine the types of functional sharing that will be beneficial at the local level, divest and transfer sponsorship of facilities that burden the system's mission, and expand the activities of the laity.

Artifactual effects of sensory-integrative therapy on self-injurious behavior

Three individuals who exhibited self-injurious behavior (SIB) were exposed to sensory-integrative therapy. Prior to treatment, a functional analysis baseline was conducted to identify the motivational features of their SIB. One subject's SIB appeared to be an attention-getting response (maintained by positive reinforcement), which varied subsequently as a function of attention being either withheld or provided noncontingently during sensory-integration sessions. The 2nd subject displayed a pattern of responding suggestive of stereotypic SIB (maintained by automatic reinforcement), which paradoxically increased during sensory-integration sessions. The 3rd subject's SIB appeared to function as an escape response (maintained by negative reinforcement), and his behavior during sensory-integration sessions was similar to that observed during baseline sessions in which demands were not present. The SIB of all 3 subjects later was reduced when behavior interventions were applied. The data presented raise questions about the active components of sensory-integrative therapy and the functional types of SIB for which it might be appropriate.

Neutron fibre diffraction study of DNA hydration

Interactions with water are crucial to the conformation assumed by the DNA double helix. The location of water around the D conformation has been investigated in a neutron fibre diffraction study which shows that water is ordered in the minor groove of the DNA. The D conformation is important since its occurrence is limited to specific DNA base pair sequences which have been identified as functionally significant. This study is of particular interest because the D conformation has not been reported in single crystal studies of oligonucleotides.

A practical strategy for ongoing reinforcer assessment

There is a need for practical methods of reinforcer assessment that systematically track ongoing changes in clients' preferences. In this study, the effects of a time-efficient reinforcer assessment package were evaluated in a multiple baseline across 3 preschoolers with autism, comparing individualized item selections by experienced teachers with children's presession preferences for items of various sensory qualities. Systematic assessment of children's reinforcers for correct responding virtually eliminated nontargeted maladaptive behaviors, as well as yielding expected improvements in accuracy. The powerful side-effects of potent reinforcers underline the importance of increased attention to reinforcer assessment in research and practice.

Study of ethanol-lysozyme interactions using neutron diffraction

Single-crystal neutron diffraction has been used to observe the interactions between deuterated ethanol (CD3CD2OH) and lysozyme in triclinic crystals of hen egg white lysozyme soaked in 25% (v/v) ethanol solutions. A total of 6047 observed reflections to a resolution of 2 A were used, and 13 possible ethanol sites were identified. The three highest occupied sites are close to locations for bromoethanol found in an earlier study by Yonath et al. [Yonath, A., Podjarny, A., Honig, B., Traub, W., Sielecki, A., Herzberg, O., & Moult, J. (1978) Biophys. Struct. Mech. 4, 27-36]. Structure refinements including a model for the flat solvent lead to a final crystallographic agreement factor of 0.097. Comparison with earlier neutron studies on triclinic lysozyme showed that neither the molecular structure nor the thermal motions were affected significantly by the ethanol. A detailed analysis of the ethanol-lysozyme contacts showed 61% of these to be with hydrophobic sites, in agreement with the dominant hydrophobic nature of ethanol. This, together with the fact that the molecular structure of lysozyme is not perturbed, suggests a model for denaturation of lysozyme by alcohol, which proceeds via a dehydration of the protein at high alcohol concentration.

Exchange of individual hydrogens for a protein in a crystal and in solution

A preliminary comparison of the solvent exchange of individual hydrogens of a protein in solution and in a crystal has been possible by using data for lysozyme from 1H nuclear magnetic resonance and neutron diffraction studies. It is suggested that this approach enables a direct comparison of local dynamical behaviour in the two states. The results indicate markedly similar behaviour for many residues, but significant differences are indicated in several regions of the protein.