Book reviews

Environmental Biology of Fishes -     

Block by phencyclidine of acetylcholine and barium induced adrenal catecholamine secretion

Activation of the sympathetic system by phencyclidine (PCP) should result in catecholamine release from the adrenals. However, adrenalectomy does not reduce PCP-induced hypertension. In an attempt to rectify this inconsistency, the direct effects of PCP on the bovine adrenal medulla were examined. At (3×10^?6M), PCP reduced the acetylcholine-(ACh)-induced catecholamine release by 50%. Surprisingly, barium-induced secretion of catecholamines was also reduced by PCP. ACh-induced catecholamine release was not altered by 10^?3M 4-aminopyridine (4 AP), the potassium channel blocker. Thus, calcium antagonist actions of PCP and consequent block of catecholamine secretion from adrenal medulla may explain the lack of effect of adrenalectomy on PCP-induced hypertension. Possible contributions of calcium and/or potassium channel blockade to other manifestations of PCP overdosage are discussed.     

Is group progressive relaxation training as effective with hyperactive children as individual EMG biofeedback treatment?

This study examined whether group progressive relaxation training was as effective as individual EMG biofeedback training in facilitating the academic achievement and self-control of 45 hyperactive elementary school children. Academic achievement was assessed with the Gates-MacGinities Reading Tests, and self-control was measured with the Nowicki-Strickland and the Teacher Rating scales. Eight sessions were scheduled at weekly intervals. Progressive relaxation was conducted in groups of seven or eight and was induced with a commercial audiocassette program. EMG training augmented frontalis biofeedback with those taped exercises. A placebo group listened to taped children's stories. Multivariate analysis of variance indicated no significant differences among the three contrast groups when all dependent variables were considered together. However, univariate F values and discriminant analysis disclosed locus of control to be significantly more internal for the progressive relaxation condition. Also, differences between the two relaxation and the placebo groups, though not statistically significant, were all in the expected direction. While the relative efficacy of group progressive relaxation could not be established conclusively, the data appeared sufficiently positive to warrant further investigation of this cost-effective prospective intervention.The opinions expressed by the authors are not necessarily those of their respective institutions.     

ON RHODOPSIN IN SOLUTION

1. The properties of rhodopsin in solution have been examined in preparations from marine fishes, frogs, and mammals. 2. The bleaching of neutral rhodopsin in solution includes a photic and at least three thermal ("dark") processes. Thermal reactions account for approximately half the total fall in extinction at 500 mµ. 3. Bleaching has been investigated at various pH''s from 3.9 to about 11. With increase in pH the velocity of the thermal components increases rapidly. Though the spectrum of rhodopsin itself is scarcely affected by change in pH, the spectra of all product-mixtures following irradiation are highly pH-labile. 4. The spectrum of pure rhodopsin—or of the rhodopsin chromophore—is fixed within narrow limits. The extinction at 400 mµ lies between 0.20 to 0.32 of that at the maximum. 5. Within the limitations of available data, the spectrum of pure rhodopsin corresponds in form and position with the spectral sensitivity of human rod vision, computed at the retinal surface. 6. The nature of bleaching of rhodopsin in solution, its kinetics, and its significance in the retinal cycle are discussed.     

Normal thymic cortical epithelial cells developmentally regulate the expression of a B-lineage transformation-associated antigen

Nonlymphoid, stromal cells in the mouse thymus are believed to be important in T cell maturation and have been proposed to play a central role in the acquisition of major histocompatibility complex (MHC) restriction and self-tolerance by maturing thymocytes. Both cortical and medullary epithelial cells in the thymus express high levels of class II (A) major histocompatibility antigens (MHC Ags). We show here that a specific subset of these A^– epithelial cells express a transformation-associated antigen (6C3Ag) found previously on the surfaces of Abelson murine leukemia virus-transformed pre-B cells and on those bone marrow-derived stromal cell clones which support normal and preneoplastic pre-B cell proliferation. Among solid lymphoid organs, only the thymus contains 6C3Ag¹ cells and within the thymus, this antigen is found exclusively on A^– epithelial cells in cortical regions. It is striking that the expression of the 6C3Ag on thymic epithelium is developmentally regulated, suggesting a role for this lymphostromal antigen in the maturation of the thymic microenvironment.     

THE EVOLUTION OF GENETIC CORRELATIONS: AN ANALYSIS OF PATTERNS

The genetic correlation is a central parameter of quantitative genetics, providing a measure of the rate at which traits respond to indirect selection (i.e., selection that does not act upon the traits under study, but some other trait with which they have genes in common). In this paper, I review the pattern of variation among four combinations of traits: life history × life history (L × L), morphological × morphological (M × M), life history × morphological (L × M), and behavioral × behavioral (B × B). A few other combinations were investigated, but insufficient data were obtained for separate analysis. A total of 1798 correlations, distributed over 51 different animal and plant species, were analyzed. The analysis was conducted at two levels: first by dividing the data set solely by trait combination, and second by blocking the data by trait combination and species. Because selection will tend to fix alleles that show positive correlations with fitness traits faster than those that are negative and because the latter are expected to arise more frequently by mutation, correlations between life-history traits are predicted to be more often negative than those between morphological traits. This prediction was supported, with the ranking in decreasing proportion of negative correlations being: L × L > L × M > B × B > M × M. The mean magnitude of the genetic correlation shows little variation among morphological and life-history combinations, and the distribution of values is remarkably flat. However, the estimated standard errors and the coefficient of variation (SE/r_G) are large, making it difficult to separate biological factors influencing the pattern of dispersion from experimental error. Analysis of the phenotypic and genetic correlations suggest that for the combinations M × M and L × M, but not L × L or B × B, the phenotypic correlation is an adequate estimate of the genetic correlation.