Rethinking infant knowledge: toward an adaptive process account of successes and failures in object permanence tasks

Infants seem sensitive to hidden objects in habituation tasks at 3.5 months but fail to retrieve hidden objects until 8 months. The authors first consider principle-based accounts of these successes and failures, in which early successes imply knowledge of principles and failures are attributed to ancillary deficits. One account is that infants younger than 8 months have the object permanence principle but lack means-ends abilities. To test this, 7-month-olds were trained on means-ends behaviors and were tested on retrieval of visible and occluded toys. Means-ends demands were the same, yet infants made more toy-guided retrievals in the visible case. The authors offer an adaptive process account in which knowledge is graded and embedded in specific behavioral processes. Simulation models that learn gradually to represent occluded objects show how this approach can account for success and failure in object permanence tasks without assuming principles and ancillary deficits.     

Recall of Descriptive Information: The Roles of Presentation Format, Annotation Strategy, and Individual Differences

The benefits of using a comprehensive annotation strategy (employing underlining/circling, making connections, asking questions, and making comments) with knowledge maps (spatial/verbal arrays) and traditional, linear text to improve free recall scores for learners with individual differences in vocabulary and comprehension ability were examined. Types and frequencies of annotations generated were also examined for each stimulus format condition. Multiple regression analyses indicate that the frequency of use of two component annotation strategies, asking questions and making connections, were significant predictors of recall scores, while frequency of underlining/circling and generating elaborations failed to predict recall scores. Text users generated more underlining/circling, while knowledge map users generated more connections between ideas, suggesting that knowledge maps may facilitate the application of more productive annotation strategies. Also examined were the interrelationships between vocabulary ability, comprehension ability, and free recall scores. Copyright 1997Academic Press     

The murine Tcl1 oncogene: embryonic and lymphoid cell expression

In human leukemias and lymphomas nonrandom chromosomal rearrangements cause changes in cell growth and/or survival in such a way as to promote malignancy. The detailed study of the biochemical and genetic pathways altered in human cancer requires the identification or development of models to allow the study and manipulation of cancer gene function. Recently, the breakpoint gene TCL1, involved in chromosome translocations observed mostly in mature T-cell proliferations and chronic lymphocytic leukemias (CLL), was isolated and characterized, and showed to be part of a new gene family of proteins involved in these tumors. The murine Tcl1 gene, is similar in sequence to the murine and human MTCP1 gene also involved in T cell leukemias. The murine Tcl1 gene was shown to reside on mouse chromosome 12 in a region syntenic to human chromosome 14. Furthermore, we show that the murine Tcl1 gene is expressed early in mouse embryonic development and demonstrates expression in fetal hematopoietic organs as well as in immature T and B cells. Characterization of the murine Tcl1 gene will help in developing a mouse model of CLL and would provide the best opportunity to study and decipher the role of TCL1 in malignant transformation.     

Application of flow injection analysis in trace element determination of body fluids

Nucleophiles activated the catalytic actions of beta-galactosidases with neutral or positively charged substitutions for Glu-461. Aliphatic carboxylic acids increased the rate of hydrolysis of o-nitrophenyl beta-D-galactopyranoside if the pKa values of the carboxyl groups were > approximately 3.5. Amino compounds activated if their pKa values were < approximately 8.5. Imidazole, azide, and 2-mercaptoethanol also activated. Nucleophiles with high pKa values were able to activate the catalysis if the pH was high, and this showed that the lack of activation at pH 7.0 was because of protonation. Kinetic analysis showed that most of the nucleophiles that activated were bound to the active site, since the activation followed Michaelis-Menten type saturation kinetics. The binding seemed to be dependent upon the hydrophobicity; the longer the aliphatic chain, the stronger the binding. Gas-liquid chromatographic analysis showed that adducts of some type were formed during the reactions in the presence of many of the nucleophiles. Three of these adducts were purified and the nucleophiles were found beta-linked to D-galactose. This indicates that if an intermediate covalent bond is formed in the mechanism of beta-galactosidase action and if the nucleophile reacts to displace it, the intermediate covalent bond must have the alpha configuration and involve a group other than Glu-461.