Contrast sensitivity through hybrid diffractive, Fresnel, and refractive prisms.

BACKGROUND: Fresnel and wedge-shaped refractive prisms are used diagnostically and therapeutically in clinical practice. This article extends the study on the effect of prisms on visual acuity to the effect on contrast sensitivity by membrane Fresnel (F), refractive (R), and newly designed hybrid diffractive (C) prisms (ComPrisms), which combine a wedge-shaped refractive prism with a diffractive element. METHODS: Vistech contrast sensitivity function (CSF) Charts A, B, and C were used to measure the monocular and binocular contrast sensitivity of 21 and 20 subjects, respectively. CSF was measured without prisms (U), through the hybrid diffractive prisms, membrane Fresnel prisms, and acrylic refractive prisms in powers of 20delta, 30delta, and 40delta. RESULTS: Repeated measures analysis of variance calculations resulted in significant main effects in contrast sensitivity across prism types, prism powers, and between monocular and binocular measurements. Results of the Scheffé test for all possible contrast sensitivity comparisons between spatial frequencies are provided. It was found that as prism power increased from 20delta to 40delta, the rate of reduction in area under the CSF curve of ComPrisms became half that of the refractive and Fresnel prisms. CONCLUSIONS: Although all three prism types reduced contrast sensitivity with respect to the unaided condition, the ComPrisms at all powers provided significantly better contrast sensitivity than the refractive or Fresnel prisms of equivalent power. Significant binocular summations in contrast sensitivity were found without prisms and across all prism types and powers.     

Hypnotic medication in the treatment of chronic insomnia: non nocere! Doesn't anyone care?

Chronic primary insomnia is a recurrent condition that negatively effects the daily functioning of patients, diminishing the quality of their lives. It is associated with, and in some situations, is a risk factor in both psychiatric (depression) and physical (cardiovascular) illness. Treatment effectiveness has been shown in the short term for both drug (benzodiazepine and benzodiazepine agonists) and behavioral treatment. Expert opinion has strongly advised against long-term drug treatment because of concerns about residual sedative effects, memory impairment, falls, respiratory depression, rebound insomnia, medication abuse, dose escalation, dependency and withdrawal difficulties, and an increased risk of death possibly associated with the current hypnotic medications. Many of these concerns could be made against using these agents at all. Worries about these potential problems are challenged by the widespread clinical practice of using hypnotic drugs long-term without any of these difficulties developing and with patients who feel their sleep and daily function function is improved with the nightly use of their sleeping pill. The ability to mount a randomized, placebo-controlled, parallel group, double-blind trial of hypnotic medication in primary insomnia may not be possible. We may have to develop large systematic clinical databases, a number of case series in effect, to monitor both emergent symptoms and possible clinical effectiveness. There is the additional concern that there is a reluctance to examine the long-term drug treatment of insomnia. This reluctance may reflect a negative moral judgement about treating primary insomnia with drugs, a sort of , rather than just a data based judiciousness.     

Crystal structures of thrombin and thrombin complexes as a framework for antithrombotic drug design

Summary The wealth of structural information now available on thrombin, its precursors, its substrates and its inhibitors allows a rationalization of its many roles. -Thrombin exhibits an unusually deep and narrow active-site cleft, formed by loop insertions that are characteristic of thrombin. This canyon structure is one of the prime causes for the narrow specificity of thrombin. As a result of the conjunction of amino acid residues with similar properties such as charge or hydrophobicity, thrombin can be divided up into a number of functional regions. The apposition of the active site to a hydrophobic pocket (the apolar binding site) on one side and a basic patch (the fibrinogen recognition exosite) on the other allows for a fine-tuning of enzymatic activity, as seen for fibrinogen. These two sites are also optimally used by the leech-derived inhibitor hirudin, allowing the very tight binding observed; thrombin inhibition is effected by blocking access to the active site. Interactions with antithrombin III are tightened with the help of heparin, which binds to a second basic site (the heparin binding site). Non-proteolytic cellular properties are attributed to the rigid insertion loop at Tyr^60A. The observed rigidity of the thrombin molecule in its complexes makes thrombin ideal for structure-based drug design. Thrombin can be inhibited either at the active site or at the fibrinogen recognition exosite, or both. Structural information shows that binding at the former is enhanced by good fit of aromatic moieties to the aryl and S2 binding sites (the apolar binding site). Binding at the fibrinogen recognition exosite is facilitated by negatively charged groups. The unpredictable nature of inhibitor binding underlines the importance of experimental monitoring of structures of thrombin inhibitors in the drug design process.     

Antibody levels to parainfluenza,rubella, measles,and influenza a virus in children with polymyositis

The CF and HI antibody titers to rubella and measles viruses, the CF titers to influenza A, and the HI titers to parainfluenza 1, 2, and 3 were carried out on the sera of 20 patients with childhood polymyositis and their matched controls. The titers for measles, parainfluenza 1, and influenza A were slightly higher for patients than for controls. The control group had antibody titers to rubella and parainfluenza 2 and 3 higher than or similar to those of patients. Strong patterns or significant differences for a given virus or virus group were not encountered.     

Preface

Nine patients (4F, 5M) aged 12-17 years with “fear of obesity” were studied with a sequential stimulation test utilizing insulin, LRH, TRH, and L-dopa. The comparative groups were nine female with classic anorexia nervosa, five males with undifferentiated nutritional dwarfing, and nine children (1F, 8M) with constitutional growth delay. The serum TSH, glucose, cortisol, somatotropin, prolactin, LH, and FSH were sampled periodically over 2 hours. Basal T3, T4, transferrin, and Somatomedin-C levels were also obtained. The “fear of obesity” patients did not have any pituitary function changes that were unique. These patients, as well as the comparison groups, revealed a delayed TSH response in proportion to the weight deficit which, when expressed as an integrated response, correlated well to the weight deficit for height (P less than 0.001) and to the ability to recover from hypoglycemia (p less than 0.001). The Somatomedin-C level was low and correlated to the T3 level (p less than 0.05) and not correlated to the elevated Somatotropin levels. The pituitary response to combined stimulation in patients with fear of obesity was determined to be a component of the spectrum starting at normal and proceeding to the extreme undernutrition of anorexia nervosa. Pituitary responsiveness, therefore, changes not as a function of the etiology of the malnutrition, but simply as a function of its severity.     

Toward a model of person-environment congruence: Development of the EPPIS

The Person Environment (P-E) Congruence model represents an approach to understanding the impact of the environment on the well-being and adjustment of the elderly which may also provide information for the development of intervention programs at individual, group and/or institutional levels. Assessment of P-E congruence, or fit between the person and his/her environment, was operationalized in two studies through the development of the Environmental Perception, Preference and Importance Scale (EPPIS). The EPPIS provides scales to assess environmental perceptions, individual environmental preferences and the important or salience of the environment on 15 empirically derived, commensurate dimensions. In a third study, the four-month test-retest reliability of the overall P-E congruence score of the EPPIS, defined as the absolute difference between the perceived and preferred environment weighted by importance, was 78 while the unweighted model reliability was 76. Also, the 15 dimensions of the EPPIS were observed to be significant predictors of well-being. It was proposed that the EPPIS may be used both to determine areas of intervention which the elderly themselves feel are important and as a means to evaluate the effectiveness of interventions intended to reduce P-E incongruence and increase psychological well-being.     

Resident and staff perceptions of latitude of choice in elderly institutionalized men

Ninety-nine elderly institutionalized males, selected equally from three decades, completed measures of: their personal, perceived latitude of choice (LOC) in activities of daily living; self-concept; and life satisfaction. One hundred staff, of both sexes, estimated how the typical or “average” V.A. domiciliary resident would respond to the LOC meaure. Mean resident LOC scores were found to be significantly related to life satisfaction but not to self-concept. This supports the thesis that latitude of choice, or personal autonomy, is related to well-being and that the LOC measure may be a useful tool in the development and evaluation of interventions aimed at improving resident well-being. Significant relationships between resident age and the importance of daily activities, self-concept and life satisfaction were also observed although there were no age differences in the resident data for the LOC, importance or choice measures. In comparing staff attributed and resident perceived latitude of choice, significant differences were found. Examination of response patterns to the specifically listed activities of daily living also revealed significant staff-resident differences. Therefore, any attempt to intervene in the environment to increase the personal autonomy or control of residents, and hence their well-being, must deal with such staff-resident differences and with staff misperceptions of what is and is not important to residents. Interventions should be targeted at specific activities viewed by a majority of residents as restricted and insofar as practical, interventions should be individually tailored.