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Biomedical subjects

J B Best

Publications and source records attributed to J B Best.

At least 19 recordsLinked to original sources
PubMed1990

Knowledge acquisition and strategic action in "Mastermind" problems.

In two experiments, the strategies used by subjects playing the logical-deduction game, Mastermind, were examined. In the first experiment, subjects showed improvement resulting from the continued use of a particular strategic action, and the data suggested that the subjects learned the strategy from their transactions with the task. In the second experiment, the question of changes in underlying strategic knowledge of Mastermind was examined. The accuracy and complexity of the subjects' deductions and their use of the previously identified strategy were used to generate a model of the cognitive operations involved in Mastermind. Although there were improvements in the accuracy and complexity of the subjects' deductions resulting from continued play, these improvements were unrelated to the use of the strategy. Moreover, the likelihood of making accurate and complex deductions was well accounted for by a Markovian model, suggesting that the deployment of the strategy was not driven by any change in the subject's underlying knowledge structures. Rather, the subjects seemed to use the strategy to create Mastermind situations whose interpretation was fairly easy. The implications for previous work on the issue of Mastermind strategies and the development of logical-deduction strategies are discussed.

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PubMed1987

Photoperiodic modulation of cephalic melatonin in planarians.

Endogenous melatonin was detected by high-performance liquid chromatography (HPLC) with electrochemical detection (EC) in the head of the planarian Dugesia dorotocephala. The identity of this elution peak was further confirmed by radioimmunoassay. In groups of planarians adapted to either normal or reversed photoperiods, the melatonin levels were always higher in those heads collected in the dark period than in those collected in the light period. This indicates that primitive animals such as planarians have already evolved a melatonin-metabolizing system that is photically driven in a manner suggestive of the way melatonin synthesis is influenced by light and dark cycles in vertebrates.

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PubMed1986

Neoplastic transformation in the planarian: I. Cocarcinogenesis and histopathology.

Although several investigators have reported that exposure to mammalian carcinogens induces abnormal tumorlike growths and teratogenic remodeling in planarians, there is no general agreement that these, or comparable responses in any other invertebrates, model mammalian carcinogenesis. To investigate this question, freshwater planarians of the species Dugesia dorotocephala were exposed to culture water containing an initiator and a promoter, either alone or in combination. Cadmium, a potent carcinogen, was used as an initiator in the protocol. Treatment with sublethal concentrations of cadmium sulfate produced a benign, but persistent, tumor in a small percentage of the planarians. The addition of 12-O-tetradecanoylphorbol-13-acetate (TPA), a phorbol ester and well-known promoter, to the cadmium-containing solutions resulted in the induction of a progressive, potentially lethal, transplantable tumor in a large proportion of the treated flatworms. Light and electron microscopy revealed this particular tumor to be composed both of immature cells and of a single mature cell type: newly differentiated, but transformed, reticular cells. Further examination of the infiltrating tissue formations elucidated the profile of differentiation, from a population of mitotically active transformed stem cells through the transitional stages in the associated reticuloma. These results suggest that 1) the freshwater planarian displays the major phenomenology of mammalian cocarcinogenesis and that 2) the planarian reticuloma models several important features of a neoplastic stem cell disease.

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PubMed1986

Neoplastic transformation in the planarian: II. Ultrastructure of malignant reticuloma.

Cadmium and phorbol ester induced tumorigenesis in the planarian, Dugesia dorotocephala, develops as a cocarcinogenic process involving initiation and promotion in the progression of neoplastic disease. Treatment of intact planarians with sublethal concentrations of cadmium sulfate and 12-O-tetradecanoylphorbol-13-acetate (TPA) induced a type of infiltrating tumor that proved to be potentially lethal. Surgical transplantation of such tumorous tissues into otherwise healthy planarians resulted in the same histopathological progression to lethality, which confirmed the metastatic nature of the neoplasia. Electron microscopic studies revealed that both the chemically-induced and the transplantation-based tumors involved, exclusively, the proliferation and differentiation of abnormal reticular cells, referred to as reticuloma cells. Reticular cells normally are ameboid, phagocytic, and are thought to provide the planarian with a phylogenetic predecessor of an immune surveillance system. A considerable incidence of mitosis was observed within the tumor areas; and the sequence of differentiation, from transformed stem cells to mature but nonfunctional reticuloma cells, was elucidated. This profile of differentiation supports the concept of cellular derivation via stem cell dynamics as opposed to dedifferentiation. A variety of ultrastructural abnormalities were characterized: several of which tend to substantiate the anaplastic quality of the reticuloma, while others are more specifically diagnostic for malignancy. These findings further extend the potential usefulness of the planarian malignant reticuloma as a model system for the study of neoplastic stem cell diseases.

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PubMed1986

The perception of empathy in alcoholism counselors.

Alcoholic inpatients evaluated the level of empathy demonstrated by a purported alcoholism counselor. Forty-two detoxified subjects viewed a 15-min videotape of a simulated alcoholism counseling session. Subjects had been randomly assigned to one of two groups: Group 1 was told that the counselor they were about to see was a recovering alcoholic whose empathy they were to evaluate. The subjects in Group 2 were given the same instructions; however, the information concerning the counselor's drinking history was omitted. A form of the Barrett-Lennard Relationship Inventory (BLRI) was administered immediately after the viewing. No statistical differences between group means on the empathy subscale of the BLRI were found. This finding does not support the contention that a history of drinking and rehabilitation enhances the perception of counselor empathy among alcoholics.

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PubMed1978

Early Childhood Development Programme--early detection.

The Early Childhood Development Programme has four main objectives. These are: 1. To foster child development in families with young children largely through personal involvement of the family in an education context. 2. To provide enrichment programmes to enrich the social, emotional and physical environment and to ensure that children with special needs have these needs met optimally. 3. To provide for the early detection of children who are more vulnerable because of the presence of a condition which may tend to limit optimal development and make the child more open to adverse influence of social or cultural pressures; that is a health assessment programme. 4. To provide a family support service for families of children with special needs to enable these families to foster and to fulfil themselves in the society in which they live. This family support service is seen as providing a structure for home centred parent/infant habilitation aimed at keeping the family in the main stream insofar as education and health are concerned.

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PubMed1975

Cephalic mechanism for social control of fissioning in planarians: III. Central nervous system centers of facilitation and inhibition.

Previous studies have indicated that asexual reproduction (fissioning) in the planarian Dugesia dorotocephala is socially controlled through a cephalic mechanism: Isolation releases fissioning; grouping inhibits it; decapitation, at the level of the auricles, releases it even in grouped subjects. The brain is not necessary for programming the actual events of fissioning; these are orchestrated by the segmental plexus fissioning (SPF) system. Various surgical cuts were made to ablate selected portions of the central nervous system of isolated and grouped planarians in order to ascertain the inhibitory or facilitatory effects of these in the physiological mediation of such control on the SPF system. These results were synthesized into a model of this control system; the anterior lobes and optic regions of the brain inhibit the SPF system, and the anterior and caudal segmental plexuses facilitate it. These influences are partially tonic and partially contingent upon social stimulation.

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