Expression of alpha-D-mannosidase in man-hamster somatic cell hybrids

Two types of alpha-D-mannosidase isozymes are present in human white blood cells, human diploid fibroblasts, and HeLa cells. One of these (the S isozyme) constitutes the major alpha-D-mannosidase of the human cells, has a pH optimum of 4.4, and is associated with lysosomes. The other (the F isozyme) is most active at pH 6, is acid labile, and is located in the soluble portion of the cytoplasm. The expression of human lysosomal alpha-D-mannosidase was examined in man-hamster hybrid clones, and was found to be concordant with that of phosphohexose isomerase in 54 of 55 primary clones. A locus specifying human lysosomal alpha-D-mannosidase has therfore been assigned to chromosome 19.     

Contemporary theories of depression: critique and comparison

Three theoretical viewpoints have dominated the recent empirically oriented literature on depression: A. Beck's (see PA, Vol 53:7512) cognitive view, M. Seligman's (see PA, Vol 53:7618) helplessness model, and P. M. Lewinsohn's (see PA, Vol 53:7587) theory implicating a low rate of response-contingent reinforcement. In this paper, each theory is evaluated individually in terms of its empirical support and adequacy as a theory, and the theories are contrasted and compared with one another. Special attention is given to recent studies not discussed in the theorists' major summary papers and to empirical findings whose relevance to a particular theory has not previously been noted. Although there is reason to believe that any or all of the elements suggested by the three theorists—perception, control, and rate of reinforcement—are of import in depression, none has been proven to be a necessary antecedent of depressive episodes. (3 p ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Role of nerve growth factor in the development of rat sympathetic neurons in vitro. III. Effect on acetylcholine production

The effect of nerve growth factor (NGF) on the development of cholinergic sympathetic neurons was studied in cultures grown either on monolayers of dissociated rat heart cells or in medium conditioned by them. In the presence of rat heart cells the absolute requirement of neurons for exogenous NGF was partially spared. The ability of heart cells to support neuronal survival was due at least in part to production of a diffusable NGF-like substance into the medium. Although some neurons survived on the heart cell monolayer without added NGF, increased levels of exogenous NGF increased neuronal survival until saturation was achieved at 0.5 microgram/ml 7S NGF. The ability of neurons to produce acetylcholine (ACh) from choline was also dependent on the level of exogenous NGF. In mixed neuron-heart cell cultures, NGF increased both ACh and catecholamine (CA) production per neuron to the same extent; saturation occurred at 1 microgram/ml 7S NGF. As cholinergic neurons developed in culture, they became less dependent on NGF for survival and ACh production, but even in older cultures approximately 40% of the neurons died when NGF was withdrawn. Thus, NGF is as necessary for survival, growth, and differentiation of sympathetic neurons when the neurons express cholinergic functions as when the neurons express adrenergic functions (4, 5).     

Numerical evaluation of cytologic data. VI. Multivariate distributions and matrix notation

To represent multivariate data, matrix notation is required. Its equivalence to the arithmetic notation is shown with a bivariate example. With matrix notation one can then readily represent and evaluate multivariate data sets; however, most multivariate procedures require that one find that inverse of the variance-covariance matrix. This is shown using the Cholesky factorization with a numerical example.     

A plea for consideration of ecological validity in the experimental psychology of mental retardation: a guest editorial

The point was raised that, despite considerable experimental effort, laboratory research concerning learning, memory, and cognition, more generally, has not produced a very remarkable increase in our understanding of retarded behavior. Our principal contention in this paper is that the experimental psychology of mental retardation, while basically seeking causal relations between theoretical constructs and retarded behavior, is suffering from some metatheoretical and methodological shortcomings. These include, basically, a prevalent failure to consider the ecological aspects of the phenomenon of mental retardation. Implications of ecological validity are important with respect to the basis upon which subjects are selected for experimentation, the rationale underlying manipulation of independent variables, the choice of dependent variables, and the definition of the boundaries that limit generalizations. Some suggestions were offered for the purpose of guiding experimental research toward more meaningful and socially relevant goals.