Showing papers by "University of Connecticut published in 1981"

Process Analysis: Estimating Mediation in Treatment Evaluations

Abstract: This article presents the rationale and procedures for conducting a process analysis in evaluation research. Such an analysis attempts to identify the process that mediates the effects of some treatment, by estimating the parameters of a causal chain between the treatment and some outcome variable. Two different procedures for estimating mediation are discussed. In addition we present procedures for examining whether a treatment exerts its effects, in part, by altering the mediating process that produces the outcome. Finally, the benefits of process analysis in evaluation research are underlined.

Role of osteoblasts in hormonal control of bone resorption - a hypothesis

Abstract: The following hypothesis attempts to explain the puzzling fact that osteoblasts--the bone-forming cells--seem to be the target cells of parathyroid hormone (PTH), the prostaglandins, and 1,25-dihydroxyvitamin D3 (1,25(OH)2D3), the bone-resorbing hormones. This hypothesis combines some old and new physiological, biochemical, and morphological data, and ascribes to the osteoblasts a pivotal role in bone resorption. PTH has been shown to have a large number of effects on osteoblasts or \"osteoblast-like\" cells including: (a) stimulation of adenylate cyclase activity resulting in a cyclic AMP (cAMP) surge [1, 2]; (b) rapid activation of cyclic AMP-dependent protein kinase [3]; (c) inhibition of collagen synthesis [4]; (d) inhibition of alkaline phosphatase activity [1, 5]; (e) stimulation of calcium uptake [6, 7]; and (f) production of cell shape changes resulting in less tight packing of the cells, observed both in calvaria and in culture [8, 9]. On the other hand, there is little evidence so far that osteoclasts possess PTH receptors or respond to PTH directly. There is accumulating evidence that circulating mononuclear cells (monocytes) are osteoclast precursors and can resorb devitalized bone in culture [10, 12], but PTH has no effect on the chemotactic migration or the resorbing activity of these cells. Moreover, PTH does not seem tO be essential for normal osteoclastic activity and bone remodeling since these functions are retained in parathyroidectomized newborn rats [13]. Furthermore, no PTH-related defect can be implicated in osteoclast malfunctions associated with osteopetrosis [14]. Other bone-resorbing humoral factors have osteoblasts as their targets. Prostaglandins stimulate cyclic AMP accumulation in osteoblast-like cells, and there is a remarkably close correlation between

Hemispheric laterality in animals and the effects of early experience

Abstract: A review of research with chicks, songbirds, rodents, and nonhuman primates indicates that the brain is lateralized for a number of behavioral functions. These findings can be understood in terms of three hypothetical brain processes derived from a brain model based on general systems theory: hemispheric activation, interhemispheric inhibition, and interhemispheric coupling.Left-hemisphere activation occurs in songbirds and nonhuman primates in response to salient auditory or visual input, or when a communicative output is required. The right hemisphere is activated in rats when spatial performance is required, and in chicks when they are placed in an emotion-provoking situation. In rats and chicks interhemispheric activation and inhibition occur when there is an affective component in the environment (novelty, aversive conditioning) or when an emotional response is emitted (copulation, attack, killing). An interhemispheric coupling (correlation) found in rats and rabbits implies that the hemispheres are two major components in a control system with a negative feedback loop. Early-experience variables in rats can induce laterality in a symmetric brain or facilitate its development in an already biased brain.It is predicted that functional lateralization, when present, will be similar across species: the left hemisphere will tend to be involved in communicative functions while the right hemisphere will respond to spatial and affective information; both hemispheres will often interact via activation-inhibition mechanisms when affective or emotional processes are involved. Homologous brain areas and their connecting callosal fibers must be intact at birth and must remain intact throughout development for lateralization to reach its maximum level. Injury to any portion of this unit will result in hemispheric redundancy rather than specialization. One major function of early experience is to provide stimulation during development, which acts to enhance the growth and development of the corpus callosum, thereby giving rise to a more specialized brain.

On the track-to-track correlation problem

Abstract: The testing of the hypothesis whether two tracks represent the same target is considered. Previous works in the literature assumed that the estimates of the same target's state from two track files are uncorrelated. A test that includes their correlation is presented.

Patterns of human interlimb coordination emerge from the properties of non-linear, limit cycle oscillatory processes.

Abstract: The present article represents an initial attempt to offer a principled solution to a fundamental problem of movement identified by Bernstein (1967), namely, how the degrees of freedom of the motor system are regulated. Conventional views of movement control focus on motor programs or closed-loop devices and have little or nothing to say on this matter. As an appropriate conceptual framework we offer Iberall and his colleagues’ physical theory of homeokinetics first elaborated for movement by Kugler, Kelso, and Turvey (1980). Homeokinetic theory characterizes biological systems as ensembles of non-linear, limit cycle oscillatory processes coupled and mutually entrained at all levels of organization. Patterns of interlimb coordination may be predicted from the properties of non-linear, limit cycle oscillators. In a set of experiments and formal demonstrations we show that cyclical, two-handed movements maintain fixed amplitude and frequency (a stable limit cycle organization) under the following conditions...

A cross validation study of the Maslach Burnout Inventory.

Abstract: The Maslach Burnout Inventory (MBI) was designed to assess the frequency and intensity of perceived burnout among persons in the helping professions in general. This study examined the reliability ...

In vivo damage of rat lungs by oxygen metabolites.

Abstract: The intrapulmonary instillation into rat lung of enzymes that generate oxygen metabolites results in acute lung injury. The injection of xanthine oxidase and xanthine produces acute lung injury that, in the presence of superoxide dismutase, but not in the presence of catalase, can be significantly diminished, suggesting that O2- has the capacity to injure the lung. Instillation of a generator of H2O2, namely glucose oxidase, will, in sufficient quantities, produce acute injury that is not neutrophil-dependent. When either a low dose of glucose oxidase alone or lactoperoxidase alone is employed, little lung injury occurs. However, instilling the combination of the two enzymes produces severe, acute injury that can be blocked in a dose-dependent manner by catalase, but not by superoxide dismutase. Purified human leukocytic myeloperoxidase, but not horseradish peroxidase, will substitute for lactoperoxidase in the model of lung injury. The lung damaging effects of these enzymes cannot be attributed to the presence of contaminating proteases. Acute lung injury produced by the instillation of glucose oxidase and lactoperioxidase progresses to interstitial fibrosis. These studies represent a direct application of generators of oxygen metabolites to the in vivo induction of lung injury. The data suggest that rat lung is susceptible to injury by a variety of oxygen metabolites, including O2-, H2O2 and its lactoperoxidase or myeloperoxidase-produced derivatives. The studies also indicate that lung injury produced by oxygen metabolites can result in interstitial pulmonary fibrosis.

Limited wrist arthrodesis. Part II: Intercarpal and radiocarpal combinations

Abstract: Fusion of selected bones of the carpus occasionally combined with the radius or metacarpal bases, has been used to treat a wide variety of serious pathologic conditons of the wrist. Indications include severe localized degenerative arthritis and posttraumatic changes secondary to subluxation, dislocation, or residual instability resulting in significant pain. The procedure was performed on 28 wrists in 26 patients. There were three failures to obtain union initially, two of which united after secondary grafting procedures. All patients had less pain and most had functional, though limited, ranges of wrist motion. Limited wrist arthrodesis provides a workable alternative to complete wrist fusion and Silastic wrist arthroplasty for many wrists with localized destruction.

Effect of Warfarin on Survival in Small Cell Carcinoma of the Lung: Veterans Administration Study No. 75

Abstract: In a controlled, randomized study, survival of patients with small cell carcinoma of the lung (SCCL) was prolonged on addition of warfarin sodium to combination chemotherapy plus radiation therapy. Median survival for 25 control patients was 24 weeks and for 25 warfarin-treated patients was 50 weeks. This difference could not be accounted for by differences between groups in performance status, extent of disease, age, or sex. The survival advantage associated with warfarin administration was observed both for patients with extensive disease and for those who failed to achieve complete or partial remission. The warfarin-treated group also demonstrated a significantly increased time to first evidence of disease progression. These results suggest that warfarin may be useful in the treatment of SCCL and also support the hypothesis that the blood coagulation mechanism may be involved in the growth and spread of cancer in man. ( JAMA 1981;245:831-835)

The effect of various finish line preparations on the marginal seal and occlusal seat of full crown preparations

Abstract: The influences of the marginal design of a full crown on the occlusal seat and marginal seal of a cemented full crown restoration was examined. Under the conditions of the study, the featheredge and parallel bevel preparations demonstrated the best marginal seal, followed in order by the full shoulder, 45-degree shoulder, and finally the 90-degree shoulders with 30-degree and 45-degree bevels. With regard to seating of the restoration, the 90-degree full shoulder demonstrated the best seat, followed in order by the 45-degree shoulder, 90-degree shoulder with 45-degree bevel, featheredge, 90-degree shoulder with 30-degree bevel, chamfer with parallel bevel, and finally 90-degree shoulder with parallel bevel.

Matrix control of protein diffusion in biological membranes

Abstract: Lateral diffusion coefficients of fluorescently labeled lipids and integral membrane proteins were determined in the membranes of normal and spectrin-deficient spherocytic mouse erythrocytes by the technique of fluorescence redistribution after photobleaching The results were used to generate a mathematical description of a matrix-control model of membrane protein diffusion In the spherocytic cells, which lack the principal components of the cytoskeletal matrix of normal cells, the diffusion coefficients of lipid (15 +/- 05 X 10(-8) cm2/s) and protein (25 +/- 06 X 10(-9) cm2/s) differ only by a factor of 6, close to the difference predicted on the basis of size by the two-dimensional bilayer continuum model of Saffman and Delbruck [Saffman, P G l& Delbruck, M (1975) Proc Natl Acad Sci USA 72, 3111-3113] In contrast, the membranes of normal cells show a lipid diffusion coefficient (14 +/- 05 X 10(-8) cm2/s) that is some 300-fold greater than that of the membrane proteins (45 +/- 08 X 10(-11) cm2/s) Analysis of these results, based on the hypothesis that protein diffusion in normal membranes is sterically hindered by a labile matrix, yields an effective matrix surface viscosity consistent with the viscoelastic mechanical properties of the membranes Thus, a relationship is established between the deformation characteristics of the membrane and the lateral mobility of proteins suspended in the membrane

Melanotic neuroectodermal tumor of infancy: An ultrastructural study, literature review, and reevaluation

Abstract: Two cases of melanotic neuroectodermal tumor of infancy were examined by electron microscopy and an extensive review of the literature was performed. Ultrastructural examination revealed several features not previously described for this lesion. Three different types of melanin granule formation were observed, many cells had a single cilium, and cell junctions of the "close" or "modified-tight" type were seen, but no desmosomes were found. The morphologic data were consistent with the concept that the tumor arises from neural crest cells. The review of the literature indicated that there have been 158 reported cases of this lesion, including the two reported here. There were five cases of malignant tumor reported for a rate of 3.2%. This rate of malignancy is very high in view of the fact that the tumor has been described as universally benign. The significance of this finding is discussed with regard to melanin-producing lesions of the oral cavity.

Plateaued Versus Nonplateaued Managers: Career Patterns, Attitudes, and Path Potential

Abstract: This study compared both effectively and ineffectively plateaued managers with nonplateaued managers by investigating (1) career movement histories, (2) career attitudes central to a plateaued care...

The microbiology of ligature-induced periodontitis in the cynomolgus monkey

Abstract: The cultivable subgingival microflora in the cynomolgus monkey, Macaca fascicularis, was monitored during the ligature-induced progression of naturally occurring gingivitis to periodontitis. Clinical and microbiological observations were divided into four stages. Stage I, prior to ligature placement, was characterized clinically by chronic generalized gingivitis and microbiologically by Gram-positive cocci and rods with B. melaninogenicus ss. intermedius the dominant Gram-negative organism. Stage II, 1 to 3 weeks following ligature placement, exhibited slightly greater gingival inflammation but no clinical evidence of attachment loss. The subgingival flora showed a significant increase in motile and surface translocating Gram-negative rods, primarily Capnocytophaga species and Campylobacter sputorum. Stage III, 4 to 7 weeks following ligature placement, revealed increased pocket depth and radiographic evidence of alveolar bone loss. This stage was characterized by a Gram-negative anaerobic flora with B. asaccharolyticus as the dominant cultivable organism. Stage IV encompassed the remainder of the experimental period, 8 to 17 weeks, during which time no further change in the clinical parameters occurred and levels of B. asaccharolyticus decreased. The subgingival microflora of ligature induced periodontitis in Macaca fascicularis closely resembled that reported for human periodontal disease and the episodic clinical pattern of attachment loss was associated with levels of Gram-negative anaerobes, primarily B. asaccharolyticus.

Cellular responses to stress: Comparison of a family of 71–73-kilodalton proteins rapidly synthesized in rat tissue slices and canavanine-treated cells in culture

Abstract: Cultured rat embryo cells exposed to the L-arginine analogue L-canavanine rapidly accumulated a major 71 kilodalton polypeptide and several minor ones (110, 95, 88, and 78 kilodaltons). Canavanine-treated cultures contained elevated levels of translatable mRNA encoding P71, and the stimulated synthesis of this protein was blocked by actinomycin D, suggesting that P71 is inducible. Rat embryo cells maintained under routine culture conditions synthesized only trace amounts of P71; however, they accumulated an abundant 73 kilodalton protein that was closely related to P71. No kinetic evidence of a precursor-product relationship between P73 and P71 was found. The peptide map of P71 from cultured cells was identical to the map of proteins with the same electrophoretic mobility isolated from incubated slices of rat telencephalon. Previous studies (White, ′80a, b, c) have shown that the latter proteins are rapidly synthesized by cells associated with cerebral microvessels in incubated brain slices, but are not detectable in vivo. Herein we present evidence that the synthesis of P71 is not unique to brain slices. Incubated slices of heart, lung, thymus, kidney, spleen, and liver all accumulated an abundant 71 kilodalton size class. The peptide maps of P71 obtained from brain, heart, lung, and thymus tissue were similar. The stimulated synthesis of P71 in brain, heart, and lung slices was inhibited strongly by the addition of actinomycin D at the start of incubation. The 71–73 kilodalton proteins of canavanine-treated rat embryo cells and incubated slices from seven different organs were compared in detail on two-dimensional poly-acrylamide gels. Eight charge variants were detected in extracts of lung, spleen, and thymus tissue, four in liver and heart, three in kidney, and two different pairs of variants in extracts of brain tissue and cultured cells. The possible significance of the rapid synthesis of a similar small set of proteins in tissue slices and cultured cells in response to a variety of physical, chemical, and biological stimuli is discussed in terms of cellular responses to traumatic injury and metabolic stress.

Stochastic dynamic programming: Caution and probing

Abstract: The purpose of this paper is to unify the concepts of caution and probing put forth by Feldbaum [14] with the mathematical technique of stochastic dynamic programming originated by Bellman [5]. The decomposition of the expected cost in a stochastic control problem, recently developed in [8], is used to assess quantitatively the caution and probing effects of the system uncertainties on the control. It is shown how in some problems, because of the uncertainties, the control becomes cautious (less aggressive) while in other problems it will probe (by becoming more aggressive) in order to enhance the estimation/identification while controlling the system. Following this a classification of stochastic control problems according to the dominant effect is discussed. This is then used to point out which are the stochastic control problems where substantial improvements can be expected from using a sophisticated algorithm versus a simple one.

The factor VIII complex: structure and function.

Abstract: Normal human plasma contains a complex of two proteins that are important in hemostasis and coagulation. The factor VIII procoagulant protein (antihemophilic factor) and the factor VIII-related protein (von Willebrand factor) are under separate genetic control, have distinct biochemical properties, and have unique and essential physiologic properties. While the nature of their interaction and the details of their biochemical structure remain to be determined, the information now available permits a preliminary understanding of the molecular defects in the factor VIII deficiency disease.

Standardization in Causal Analysis

Abstract: In comparative study, it is argued that (1) the standardization of variables and scales should be separated from the habitual use of standardized coefficients; (2) the use of standardized coefficie...

Alternative Estimation Methods for Conjoint Analysis: A Monté Carlo Study:

Abstract: Conjoint analysis has been applied in a large number of commercial projects as well as in many noncommercial studies. Often MONANOVA, a nonmetric technique, is applied to a preference rank order ob...