Dark-adaptation of the human rod system: A new hypothesis

Following a long, full bleach, rod dark-adaptation curves from two normal trichromats were obtained with test fields of various size, exposure time and retinal eccentricity. The results show that there is a substantial region of threshold recovery with an approximately constant, linear slope of about 0.27 log per minute of dark-adaptation, which is independent of the test variables. It is suggested that the increase in sensitivity during this constant, linear slope is completely determined by changes in the concentration of bleached rhodopsin. The relationship between change of relative threshold (T) and fraction of bleached rhodopsin ( B ) is given by T=B ^3,7. This exponential law is well described by the displacement of the equilibrium between the active and inactive states of an allosteric enzyme built as a tetrarner.     

Mechanisms of long-term dark adaptation

It has previously been suggested that long-term dark adaptation is controlled by bleaching signals that regulate the activity of an allosteric, positively cooperative protein (Stabell et al., 1986a, b). Recent biochemical evidence strongly supports this assumption, indicating that the primary regulator of the light-sensitive channels in the plasma membrane of the outer segments of the photoreceptors is a homo-oligomeric, allosteric, positively cooperative protein. In this report, we discuss the possibility that signals from bleached photopigments may control the dark-adaptation process through the allosteric protein of the plasma membrane. It is suggested that the concentrations of the bleached photopigment and of the allosteric effector are reciprocal quantities.     

The factor structure of the Maslach Burnout Inventory in two Swedish human service organizations

The Maslach Burnout Inventory, MBI, is a well established measure of burnout. Its validity outside the USA is, however, uncertain. The aim of the present study was therefore to apply the MBI on personnel in two Swedish human service organizations, comparing factor solutions and scoring norms to the original results. The population consisted of 5730 employees in the Social Insurance Organization (SIO) and the Individual and Family Care section (IFC) of the social welfare agencies. Principal components analysis, principal axes and alpha factor analyses were performed, all with varimax rotation. The suggested three factor solution showed to be remarkably stable irrespective of type of analysis. Score levels were somewhat lower on two subscales in the Swedish population. The conclusion is that the psychometric properties of the MBI seem to be very satisfactory and stable, at least in comparison between Sweden and USA. It is suggested that the dimensionality of MBI is rather invariant, but that the score levels covary with national, cultural, or professional contexts within the human services.     

Executive processing differences between learning-disabled,mildly retarded,and normal achieving children

This study examined possible executive processing differences between mildly retarded, learning-disabled, and normal achieving children. To this end, the groups were compared as to their ability to recall central and secondary words from base and elaborative sentences under conditions of high and low encoding effort. Executive processing was inferred from the children's ability to maintain optimal recall performance for central and secondary words. Groups were comparable in central recall, but differences in secondary recall occurred for the high- effort encoding condition. Qualitative differences related to the prioritizing of resources (as reflected in the correlation between central and secondary recall) and monitoring the transfer of information (as reflected from central and secondary recall insertions) were found between groups. The results were discussed in terms of an executive processing frame-work that views retarded children as suffering from inefficiencies related to the sharing of resources, whereas the learning-disabled children's inefficiencies were related to the discrimination of resources.The author is indebted to Karl Schemdli, Director of Special Education and Susan Swaim, Research Director, University of Northern Colorado Laboratory School, for their administration assistance in providing children for this study. The author is indebted to Dr. Jim Nicholes for his assistance in the data collection.     

Research as a family therapy intervention technique

The utilization of the research process as an intervention has recently been described in the family therapy literature. However, it is important to draw a distinction between research as intervention and research as a unique family therapy intervention technique. From a family systems perspective, research as an intervention technique may make therapy more palatable for some families. A case study is presented in which this technique created the context for change for a family involved in a chronic illness research project.The author would like to thank Dr. Wendy L. Watson for her participation as a member of the clinical team and Drs. Fabie Duhamel and Wendy L. Watson for their helpful critiques on earlier drafts of this paper.Supported by a grant from the Albert Foundation for Nursing Research.     

Effects of novelty and familiarity on illness-induced aversions to food and place cues in coyotes (Canis latrans)

Two experiments investigated the effects of novelty and familiarity on illness-induced aversions to taste and place cues in coyotes (Canis latrans). Coyotes were made ill on familiar food laced with lithium chloride in a novel place and then received preference tests. In Experiment 1, coyotes avoided the previously poisoned familiar food in the novel treatment place but readily ate the same familiar food in a familiar safe place. In Experiment 2, the results of Experiment 1 were replicated, and it was found that coyotes would eat a different familiar food in the novel treatment place. On the basis of the results of this and other studies, a model for averting animals from places where they are not wanted is presented.     

Scotopic contrast hues displaced toward blue

Abstract.— Pre-stimulation with a neutral white light, in a dark-adapted state, produced a disposition for a scotopic hue of violet of about 463 nm. The observation may be explained on the basis of Helmholtz's theory of complementary negative afterimages, provided that (1) the assumption that neutral white is observed when the three types of cone receptors are activated to about the same degree, is rejected, and (2) the origin of the scotopic contrast hues is assumed to be located centrally to the photochemical systems of the receptors.     

The effect of stimulus preexposure upon the context effect in taste-aversion learning in noradrenaline-depleted rats

The present investigation was designed to study the effect of preexposure to a saccharin plus noisy bottle stimulus compound, or to each element by itself, upon the extinction-dependent "context effects" (due to the presencelabsence of the noisy bottle contextual cue) in taste-aversion learning, following noradrenaline (NA) depletion via a single systemic DSP4 injection. Since contextual manipulations have provided a reliable means of studying selective attentional processes the current theorising on the role of noradrenaline can be effectively accommodated. It was found that, under the No Preexposure and Noisy Bottle Preexposure conditions, the "context effect" during the saccharin preference tests, after reinstatement of the noisy bottles for all groups, was totally absent for the NA-depleted rats; in the Saccharin plus Noisy Bottle Preexposure condition the "context effect" was partially blocked for the NA depleted rats and in the Saccharin Preexposure condition it was at least as strong as in the control condition, These findings may be interpreted as supporting our conclusions, concerning NA-depleted rats derived from several different investigations, i.e. that following NA loss rats fail to attend sufficiently to contextual cues in taste-neophobia and taste-aversion situations. Thus, the attentional deficit may be described as an inability to attend to all aspects of the taste stimulus plus exteroceptive context stimulus compound. Although the selective attentional hypothesis of noradrenaline function requires a good deal of alteration, it remains the most parsimonious account that can be described at present.     

A Civil Art: The Persuasive Moral Voice of Oscar Romero

When moral or religious teachings have public and political effects, analysis usually focuses on the message, but attention to the manner in which the teachings are communicated is equally important in understanding their power to influence the course of events. Oscar Romero's particular style of moral discourse was remarkably effective for three reasons: First, his moral reasoning resonated with Salvadoran identity. It was intelligible within those reigning assumptions about national history and territory that could actually move a public to action. Second, his moral judgments were timely. Romero sought to discern what was possible for the Salvadoran public at a given moment. Third, Romero had integrity as public figure. He lived in such a way that his life, and especially his death, became an exemplary embodiment of the larger religious narrative that both grounded his ethics and gave meaning to the nation.