The MRC machine-usable dictionary contains 150,837 words and up 26 linguistic and psycholinguistic attributes for each. The attributes are from sources that are publicly available but are difficult to obtain and structure into a single dictionary, Three utility programs are described that permit the selection of words defined by a set of specified attribute values and the selection of attribute values for a set of specified words. These programs permit the construction of word sets for psycholinguistic experiments that control for the attributes specified in the dictionary. The dictionary may also be of use to researchers in artificial intelligence and computer science who require psychological and linguistic descriptions of words.Those wishing to construct word sets as stimuli for psycholinguistic experiments must take into account a large number of characteristics of the words (see Cutler, 1981;Whaley, 1978). The Medical Research Council (MRC) Psycholinguistic Database, version 1, was provided as an on-line service (see Coltheart, 1981a; this paper describes an update) to provide control in selecting word sets. The service made available three files and several access programs. The first file was a dictionary of words; the second and third files were sets of word-association norms from the Edinburgh thesaurus (Kiss, Armstrong, Milroy, & Piper, 1973). The service has been discontinued.The second version of the MRC Psycholinguistic Database is being provided as a computer-usable resource rather than as a service. An updated version of the dictionary file from the database is being provided for public research purposes along with some programs that can be used either to access the dictionary or as examples on which to model programs that match users' specific needs. The changes from the first version of the database include the addition of 52,299 new entries, the inclusion of data on written word capitalization and spoken word frequency, and an expansion of the categorizations used for several properties. Corrections have also been made to erroneous entries discovered during the use of version 1.I am gratefulto Professor Coltheart, PhilipQuinlan, and Roger Mitton for makingavailabletheir version of the MRC database(produced under grant SPG 977/912 from the MedicalResearch Council) and to those who constructedeach of the data sets included in the present version. Copies of the dictionary, full documentation, and the utility programs are availablefor research purposeson magnetictape in a variety of formats (anyof: BOO, 1600,6250BPIdensities; ISO/ASCII, EBCDIC, BCD character codes; labeled for ANSI, ICL VME, none; formatted as fixed, variable, formatted). A modestcharge will be made to cover mailing and the cost of the tape. The database can be obtained from Oxford Text Archive, Oxford UniversityComputingService, 13 Banbury Rd., Oxford 0X2 6NN, England.The author's mailing addressis Informatics Division, Science and EngineeringResearch Council, Rutherford Appleton Laboratory,Chilton, Didcot, Oxon OXli OQX, U.K.Copyr...

Background and Objective: Some oral bacteria are susceptible to killing by red light after their sensitization with toluidine blue 0 (TBO). The photochemotherapy of periodontal disease in vivo would require a therapeutic window where bacteria could be killed without adjacent normal tissue damage. Study DesignIMaterials and Methods: The laser-induced effects of TBO on normal human gingival keratinocytes and fibroblasts have been studied in vitro. For the assessment of viability, the CellTiter 96 Tv AQueous Non-Radioactive Cell Proliferation Assay was used. Results: TBO was cytotoxic at low concentrations (5.0 pg/ml). Sensitization of keratinocytes and fibroblasts with 2 and 5.0 pglml TBO, respectively, for 5 min and exposure to light from a 7.3 mW HeliundNeon (HeNe) laser for up to 2 min (0.8765) did not reduce cell viability. However, killing of Streptococcus sanguis was achieved following exposure to HeNe light for 75 sec (0.5475) in the presence of TBO at a concentration of 2.5 pg/ml. Conclusion: The development of a system for the lethal photosensitization of bacteria responsible for periodontal disease may be possible. o 19% Wiley-Liss, Inc.

The purpose of the study was to determine the distribution of the photosensitizer toluidine blue O (TBO) within Porphyromonas gingivalis and the possible mechanism(s) involved in the lethal photosensitization of this organism. The distribution of TBO was determined by incubating P. gingivalis with tritiated TBO (3H-TBO) and fractionating the cells into outer membrane (OM), plasma membrane (PM), cytoplasmic proteins, other cytoplasmic constituents and DNA. The percentage of TBO in each of the fractions was found to be, 86.7, 5.4, 1.9, 5.7 and 0.3%, respectively. The involvement of cytotoxic species in the lethal photosensitization induced by light from a heliumneon (HeNe) laser and TBO was investigated by using deuterium oxide (D2O), which prolongs the lifetime of singlet oxygen, and the free radical and signlet oxygen scavenger L-tryptophan. There were 9.0 log10 and 2 log10 reductions in the presence of D2O and H2O (saline solutions), respectively, at a light dose of 0.44 J (energy density = 0.22 J/cm2), suggesting the involvement of singlet oxygen. Decreased kills were attained in the presence of increasing concentrations of L-tryptophan. The effect of lethal photosensitization on whole cell proteins was determined by measuring tryptophan fluorescence, which decreased by 30% using 4.3 J (energy density = 4.3 J/cm2) of light. Effects on the OM and PM proteins were determined by sodium dodecyl sulfate polyacrylamide gel electrophoresis. There was evidence of change in the molecular masses of several PM proteins and OM proteins compared to controls. There was evidence of damage to the DNA obtained from irradiated cells. Scanning electron microscopic studies showed that there was coaggregation of P. gingivalis cells when sensitized and then exposed to laser light. These results suggest that lethal photosensitization of P. gingivalis may involve changes in OM and/or PM proteins and DNA damage mediated by singlet oxygen.

The purpose of this study was to develop an understanding of the current state of scientific data sharing that stakeholders could use to develop and implement effective data sharing strategies and policies. The study developed a conceptual model to describe the process of data sharing, and the drivers, barriers, and enablers that determine stakeholder engagement. The conceptual model was used as a framework to structure discussions and interviews with key members of all stakeholder groups. Analysis of data obtained from interviewees identified a number of themes that highlight key requirements for the development of a mature data sharing culture.