Showing papers by "University of Missouri published in 1993"

A Review and an Integration of Research on Job Burnout

Abstract: Burnout is a unique type of stress syndrome, characterized by emotional exhaustion, depersonalization, and diminished personal accomplishment. Although burnout has been shown to be potentially very costly in the helping professions, such as nursing, education, and social work, little work has been done thus far to establish its generalizability to industry. This article reviews the literature on burnout and provides a conceptual framework designed to improve the understanding of burnout. Propositions are presented that are aimed at clarifying the dynamics of burnout, including determinants of and interrelationships among the three burnout components.

A possibilistic approach to clustering

Abstract: The clustering problem is cast in the framework of possibility theory. The approach differs from the existing clustering methods in that the resulting partition of the data can be interpreted as a possibilistic partition, and the membership values can be interpreted as degrees of possibility of the points belonging to the classes, i.e., the compatibilities of the points with the class prototypes. An appropriate objective function whose minimum will characterize a good possibilistic partition of the data is constructed, and the membership and prototype update equations are derived from necessary conditions for minimization of the criterion function. The advantages of the resulting family of possibilistic algorithms are illustrated by several examples. >

Board of director involvement in restructuring: The effects of board versus managerial controls and characteristics

Abstract: Board of director involvement in restructuring reveals whether restructuring is brought on as an action by the board in its central oversight role or whether managers are purusing positive strategic action or correction Therefore, based on an integration of organization economics (agency theory and market for corporate control) and strategic management theory (internal control and strategic leadership contingencies), this research examines board involvement in restructuring Board involvement is hypothesized to be contingent on the governance mechanisms used by the board to monitor top management, control emphasis used by managers to process strategic information and board and managerial characteristics The basic premise of the paper is that, due to their oversight role, board members (especially outside directors) become involved in restructuring only when managerial strategy implementation appears to be deficient Top management team equity stakes are found to be negatively related to board involvement in restructuring, while outside director ownership is found to be positively related Emphasis on strategic controls by managers was found to be negatively related to board involvement in restructuring Top management team tenure and top management organizational tenure are negatively related to board involvement Outsider representation on the board is positively related to board involvement in restructuring, while board tenure was found to be unrelated Results imply that incentives to monitor (ownership) and emphasis on strategic controls reinforced by higher top management team tenure result in less board involvement in restructuring However, restructuring may be initiated by outsiders on the board when other governance and control mechanisms fail This implies a substitution process between governance tactics (ownership vs board monitoring) and internal controls (managerial vigilance)

Does problem-based learning work? A meta-analysis of evaluative research.

Abstract: The purpose of this review is to synthesize all available evaluative research from 1970 through 1992 that compares problem-based learning (PBL) with more traditional methods of medical education. Five separate meta-analyses were performed on 35 studies representing 19 institutions. For 22 of the studies (representing 14 institutions), both effect-size and supplementary vote-count analyses could be performed; otherwise, only supplementary analyses were performed. PBL was found to be significantly superior with respect to students' program evaluations (i.e., students' attitudes and opinions about their programs)--dw (standardized differences between means, weighted by sample size) = +.55, CI.95 = +.40 to +.70 - and measures of students' clinical performance (dw = +.28, CI.95 = +.16 to +.40). PBL and traditional methods did not differ on miscellaneous tests of factual knowledge (dw = -.09, CI.95 = +.06 to -.24) and tests of clinical knowledge (dw = +.08, CI.95 = -.05 to +.21). Traditional students performed significantly better than their PBL counterparts on the National Board of Medical Examiners Part I examination--NBME I (dw = -.18, CI.95 = -.10 to -.26). However, the NBME I data displayed significant overall heterogeneity (Qt = 192.23, p < .001) and significant differences among programs (Qb = 59.09, p < .001), which casts doubt on the generality of the findings across programs. The comparative value of PBL is also supported by data on outcomes that have been studied less frequently, i.e., faculty attitudes, student mood, class attendance, academic process variables, and measures of humanism. In conclusion, the results generally support the superiority of the PBL approach over more traditional methods. Acad. Med. 68 (1993):550-563.

Noise enhancement of information transfer in crayfish mechanoreceptors by stochastic resonance

Abstract: IN linear information theory, electrical engineering and neurobiology, random noise has traditionally been viewed as a detriment to information transmission. Stochastic resonance (SR) is a nonlinear, statistical dynamics whereby information flow in a multistate system is enhanced by the presence of optimized, random noise1–4. A major consequence of SR for signal reception is that it makes possible substantial improvements in the detection of weak periodic signals. Although SR has recently been demonstrated in several artificial physical systems5,6, it may also occur naturally, and an intriguing possibility is that biological systems have evolved the capability to exploit SR by optimizing endogenous sources of noise. Sensory systems are an obvious place to look for SR, as they excel at detecting weak signals in a noisy environment. Here we demonstrate SR using external noise applied to crayfish mechanoreceptor cells. Our results show that individual neurons can provide a physiological substrate for SR in sensory systems.

Libraries of peptides and proteins displayed on filamentous phage

Abstract: Publisher Summary A fusion phage is a filamentous virion displaying on its surface a foreign peptide fused to a coat protein and harboring the gene for the fusion protein within its genome This chapter emphasizes an application for which these surface expression vectors are particularly well suited: construction of epitope libraries In such a library—the kind so far constructed—the phages display random foreign peptides encoded by degenerate synthetic oligonucleotides spliced into the coat protein gene, the library as a whole representing up to billions of peptide sequences Affinity purified phages are eluted without destroying their infectivity, and the peptide sequences responsible for binding are easily ascertained by infecting the eluted phages into bacteria, propagating the resulting phage clones, and sequencing the relevant part of their viral DNAs The number of peptides that can be accommodated with this technology exceeds by a factor of 100–1,000 the number that can be screened with conventional expression systems, in which the epitope is not displayed as part of the propagatable unit that encodes it It also discusses more complex libraries, in which the displayed ligands are whole folded domains

Construct validity of an objective (entropy) categorical measure of diversification strategy

Abstract: This study measures the construct validity of an objective (entropy) approach to measurement of diversification strategy. Results indicate strong convergent, discriminant and criterion-related validity for the entropy measure of diversification. In particular, support for the entropy measure of diversification strategy was demonstrated through associations with the Rumelt subjective measure of diversification (convergent validity); size, debt and RD and accounting and market-based performance (criterion-related validity). Using structural equations modeling, the study reports strong standardized validity coefficients with a diversification factor (0.87 for the entropy and 0.94 for Rumelt's measures). The objective (SIC count) measure exhibits a low standardized validity coefficient (0.44) with the diversification factor. In a discriminant validity test, 70 percent of the variance in the entropy measure is unique to diversification while only 2.8 percent and 7.6 percent are unique to leverage and size, respectively. However, only 6.3 percent of the variance in the SIC count measure is unique to diversification. The study suggests that it may be more appropriate to use the diversification factor with both the entropy and Rumelt subjective measures for maximum accuracy (however, using either alone would be acceptable). Also, the results suggest that the SIC measure may be appropriate in more limited circumstances.

Effect of prenatal ultrasound screening on perinatal outcome. RADIUS Study Group.

Abstract: Background Many clinicians advocate routine ultrasound screening during pregnancy to detect congenital anomalies, multiple-gestation pregnancies, fetal growth disorders, placental abnormalities, and errors in the estimation of gestational age. However, it is not known whether the detection of these conditions through screening leads to interventions that improve perinatal outcome. Methods We conducted a randomized trial involving 15,151 pregnant women at low risk for perinatal problems to determine whether ultrasound screening decreased the frequency of adverse perinatal outcomes. The women randomly assigned to the ultrasound-screening group underwent one sonographic examination at 15 to 22 weeks of gestation and another at 31 to 35 weeks. The women in the control group underwent ultrasonography only for medical indications, as identified by their physicians. Adverse perinatal outcome was defined as fetal death, neonatal death, or neonatal morbidity such as intraventricular hemorrhage. Results The mean nu...

Retinal age pigments generated by self-assembling lysosomotropic detergents

Abstract: A universal biomarker of cellular ageing in eukaryotic postmitotic cells is the appearance over time of autofluorescent lysosomal residual bodies called age pigments or lipofuscin granules. Their role in the process of cellular ageing has been debated without resolution. Neither the identity nor mechanism of formation of the fluorophores has been definitively determined. A postmitotic cell type that accumulates large quantities of age pigments is the ocular retinal pigment epithelium. We have now identified the major orange-emitting fluorophore of these pigments using fast-atom bombardment tandem mass spectrometry with collisional activation analysis. It is an amphoteric quaternary amine that arises as a Schiff base reaction product of retinaldehyde and ethanolamine. This compound should display lysosomotropic detergent behaviour which would help explain many of the age-related changes shown in this cell. These results suggest a new role for Schiff base reaction products as lysosomotropic amines in the genesis of cellular age pigments.

The daf-4 gene encodes a bone morphogenetic protein receptor controlling C. elegans dauer larva development

Abstract: THE bone morphogenetic protein (BMP) family is a conserved group of signalling molecules within the transforming growth fact-or-β (TGF-β) superfamily1,2. This group, including theDrosophila decapentaplegic (dpp) protein and the mammalian BMPs, mediates cellular interactions and tissue differentiation during development3,4. Here we show that a homologue of human BMPs controls a developmental switch in the life cycle of the free-living soil nematode Caenorhabditis elegans. Starvation and overcrowding induce C. elegans to form a developmentally arrested, third-stage dauer larva5. The daf-4 gene, which acts to inhibit dauer larva formation and promote growth, encodes a receptor protein kinase similar to the daf-1, activin and TGF-β receptor serine/ threonine kinases. When expressed in monkey COS cells, thedaf-4receptor binds human BMP-2 and BMP-4. The daf-4 receptor is the first to be identified for any growth factor in the BMP family.

Uroguanylin: structure and activity of a second endogenous peptide that stimulates intestinal guanylate cyclase

Abstract: The intestinal hormone guanylin and bacterial heat-stable enterotoxins (STs) are members of a peptide family that activates intestinal membrane guanylate cyclase. Two different peptides that activate the human intestinal T84 cell guanylate cyclase have been purified from urine and intestinal mucosa of opossums (Didelphis virginiana). The highly acidic peptide, QEDCELCINVACTGC, was named uroguanylin because it was isolated from urine and shares 53% identity with guanylin. A second peptide, SHTCEICAFAACAGC, was purified from urine and intestinal mucosa. This alanine-rich peptide was 47% identical to uroguanylin and 73% identical to human guanylin, suggesting that it may be an opossum homologue of guanylin. Synthetic uroguanylin-(2-15) (i.e., EDCELCINVACTGC) was 10-fold more potent than synthetic rat guanylin, but both peptides were less potent than Escherichia coli ST in the T84 cell cGMP bioassay. Uroguanylin-(2-15) and guanylin inhibited 125I-ST binding to T84 cell receptors in competitive radioligand binding assays. Transepithelial Cl- secretion was stimulated by 1 microM uroguanylin, indicated by an increase in the short circuit current of T84 cells. Thus, uroguanylin is another paracrine hormone in the emerging peptide family that activates intestinal membrane guanylate cyclase. The second peptide may be the opossum form of guanylin, or perhaps, it is still another member of this peptide family. The presence of uroguanylin and guanylin in urine and receptors in proximal tubules suggests that these peptides may also originate from renal tissue and may regulate kidney function.

Diagnostic Issues in Self-Mutilation

Abstract: Objective: Pathological self-mutilation-the deliberate alteration or destruction of body tissue without conscious suicidal intent-was examined both as a symptom of mental disorders and as a distinct syndrome. Methods: Data from more than 250 articles and books were reviewed, as well as data obtained by the authors from their extensive clinical experience in treating self-mutilating patients. Results and conclusions: The diverse behaviors that constitute pathological self-mutilation can be categorized into three basic types: major-infrequent acts that result in significant tissue damage, usually associated with psychoses and acute intoxications; stereotypic-fixed, rhythmic behavior seemingly devoid of symbolism, commonly associated with mental retardation; and superficial or moderate-behavior such as skin cutting, burning, and scratching associated with a variety of mental disorders. The authors propose that a syndrome of repetitive superficial or moderate self-mutilation should be regarded as an axis I im...

Development of a core RFLP map in maize using an immortalized F2 population.

Abstract: A map derived from restriction fragment length polymorphisms (RFLPs) in maize (Zea mays L.) is presented. The map was constructed in an immortalized Tx303 x CO159 F2 mapping population that allowed for an unlimited number of markers to be mapped and pooled F3 seed to be distributed to other laboratories. A total of 215 markers consisting of 159 genomic clones, 16 isozymes and 35 cloned genes of defined function have been placed on 10 chromosomes. An examination of segregation data has revealed several genomic regions with aberrant segregation ratios favoring either parent or the heterozygote. Mapping of cloned genes and isozymes that have been previously mapped by functional criteria has provided 29 points of alignment with the classical maize genetic map. Screening of all mapped RFLP probes against a collection of U.S. Corn Belt germplasm using EcoRI, HindIII and EcoRV has resulted in a set of 97 core markers being defined. The designation of a set of core markers allows the maize genome to be subdivided into a series of bins which serve as the backbone for maize genetic information and database boundaries. The merits and applications of core markers and bins are discussed.

Apoptosis during luteal regression in cattle

Abstract: The present studies were conducted to evaluate whether apoptosis occurs during spontaneous and prostaglandin F2 alpha (PGF2 alpha)-induced luteolysis and, if so, to determine the relationship between the onset of luteolysis and oligonucleosome formation (a characteristic of apoptosis). In the first study, nine normally cycling heifers were ovariectomized (ovx) during the midluteal phase (day 10 or 15; day 0 = estrus) or after luteal regression (day 19; n = 3/time point). While there was no evidence of oligonucleosome formation in DNA from corpora lutea (CL) collected on days 10 and 15, each CL collected on day 19 exhibited DNA fragmentation, represented by distinct bands of DNA in approximately 185-basepair multiples. In the second study, heifers were ovx (n = 5; controls) or given 25 mg PGF2 alpha 15-16 days after estrus. Heifers receiving PGF2 alpha were subsequently ovx 4, 8, 12, 24, or 48 h (n = 5/time point) after the injection of PGF2 alpha. The concentration of progesterone in venous sera collected at ovx was not different (P > 0.20) in control and 4 h groups, but was decreased (P 0.10) from 0 h (controls) to 24 h after injection (range, 3.2 +/- 0.5 to 4.1 +/- 0.6), but decreased (P < 0.06) to 2.0 +/- 0.3 at 48 h. With ethidium bromide (EtBr) staining, no oligonucleosome formation was detected in CL collected from 0-12 h after PGF2 alpha injection. However, pronounced oligonucleosome formation was observed in all 10 CL collected 24 and 48 h after the injection of PGF2 alpha. The absence of oligonucleosomes in 0 and 4 h samples was confirmed by the more sensitive technique of 3'-end labeling of DNA fragments. Some samples in both the 8 and 12 h groups had slight oligonucleosome formation, while all samples in the 24 and 48 h groups showed evidence of intense oligonucleosome formation. Histological analysis of tissue sections indicated an increase (P < 0.001) in the percentage of degenerated luteal cells in the 24 and 48 h groups compared to that in the 0-12 h groups. These data indicate that apoptosis occurs during both spontaneous and PGF2 alpha-induced luteal regression in cattle; however, apoptosis, as indicated by oligonucleosome formation, is not apparent until after serum progesterone concentrations have begun to decrease.(ABSTRACT TRUNCATED AT 400 WORDS)

Effects of endothelins on collagen turnover in cardiac fibroblasts.

Abstract: Objectives: Endothelins (ET-1 and ET-3) may be promoters of tissue remodelling, including fibrillar collagen accumulation. The hypothesis that ET-1 and ET-3 each modify cardiac fibroblast collagen turnover was tested. Methods: Confluent adult rat cardiac fibroblasts were maintained for 24 hours in medium with 0.4% fetal call serum, and varying concentrations of ET-1 or ET-3. Collagen synthesis was measured by 3H-proline incorporation. The synthesis of type I and III collagens was measured by enzyme linked immunosorbent assay (ELISA). The effects of endothelins on collagenase activity were estimated by zymography. Results: ET-1 and ET-3 increased collagen synthesis in a concentration-dependent manner with a maximal 1.7-fold increase (p < 0.001 v control cells). The effects of ET-1 or ET-3 on collagen synthesis were not blocked by PED-3512-PI (10−6 M). an ETA receptor antagonist. ET-1 and ET-3 each significantly (p < 0.01) increased the synthesis of both type I and III collagens. ET-1 caused a 5.8-fold decrease in collagenase activity (p<0.01 v control), and this effect was blocked by PED-3512-PI (10−6 M). ET-3 did not alter collagenase activity. Conclusion: ET-1 and ET-3 increased the synthesis of type I and III collagens, whereas ET-1. but not ET-3, reduced collagenase activity. The effects of endothelins on collagen synthesis in cardiac fibroblasts seem to be mediated through ETA and ETB receptors, whereas their effects on collagenase seem to be mediated by ETA receptors. Cardiovascular Research 1993: 27 : 2130-2134

Psychometric properties of the Problem Solving Inventory in a group of Turkish university students

Abstract: The Problem Solving Inventory (PSI; Heppner & Petersen, 1982) is a widely used self-report measure of applied problem solving in the United States. This study examined the psychometric properties of the PSI in a Turkish cultural context, specifically with regard to normative, reliability, and validity information. Subjects were 244 Turkish university students (153 women, 71 men) who completed the Turkish version of the PSI, Beck Depression Inventory, and the State-Trait Anxiety Inventory. The Turkish data provide additional psychometric support for the PSI and enhance the generalizability of some of the previous findings based on U.S. samples. Moreover, the Turkish data also suggest that the psychological construct of problem-solving appraisal may have some utility in understanding applied problem solving in the Turkish culture. Finally, the study provides cross-cultural information that increases our knowledge about the utility of problem-solving constructs across diverse environments, particularly with regard to an approach/avoidance dimension across problem-solving strategies.

Microentrapment of Lactobacilli in Calcium Alginate Gels

Abstract: A procedure was developed to entrap culture bacteria using a two-phase (water/oil) system. It consisted of 3% sodium alginate mixed with microbial cells and suspended in an oil bath containing 0.2% Tween 80. While stirring at 200 rpm, calcium chloride (O.OSM) solution was added to break the water/oil emulsion and form calcium alginate gel. The calcium alginate beads containing microbial cells had mean diameters of 25–35 μm (range S-100 μm). The entrapped microbial cells were released completely from the drop shaped beads by gentle shaking in 0.lM phosphate solution (pH 7.5) for 10 min. About 40% more lactobacilli survived freezing of ice milk when they were entrapped in calcium alginate than when they were not entrapped.

Maize anthocyanin regulatory gene pl is a duplicate of c1 that functions in the plant.

Abstract: Genetic studies in maize have identified several regulatory genes that control the tissue-specific synthesis of purple anthocyanin pigments in the plant. c1 regulates pigmentation in the aleurone layer of the kernel, whereas pigmentation in the vegetative and floral tissues of the plant body depends on pl. c1 encodes a protein with the structural features of eukaryotic transcription factors and functions to control the accumulation of transcripts for the anthocyanin biosynthetic genes. Previous genetic and molecular observations have prompted the hypothesis that c1 and pl are functionally duplicate, in that they control the same set of anthocyanin structural genes but in distinct parts of the plant. Here, we show that this proposed functional similarity is reflected by DNA sequence homology between c1 and pl. Using a c1 DNA fragment as a hybridization probe, genomic and cDNA clones for pl were isolated. Comparison of pl and c1 cDNA sequences revealed that the genes encode proteins with 90% or more amino acid identity in the amino- and carboxyl-terminal domains that are known to be important for the regulatory function of the C1 protein. Consistent with the idea that the pl gene product also acts as a transcriptional activator is our finding that a functional pl allele is required for the transcription of at least three structural genes in the anthocyanin biosynthetic pathway.

Antifibrotic effects of spironolactone in preventing myocardial fibrosis in systemic arterial hypertension.

Abstract: Activation of the renin-angiotensin-aldosterone system in arterial hypertension can lead to remodeling of the myocardial collagen network, with progressive collagen accumulation in the cardiac interstitium. This reactive myocardial fibrosis, which is not secondary to myocyte necrosis, appears to be an important determinant of diastolic dysfunction and thus of pathologic hypertrophy. To examine the effects of the aldosterone antagonist spironolactone on myocardial fibrosis, we analyzed interstitial fibrosis in 7 different models of arterial hypertension in rats: 2 kidney, 1 clip model of renovascular hypertension (RHT); continuous subcutaneous aldosterone (0.75 micrograms/hr) infusion; RHT and aldosterone models treated with 20 mg/kg per day of subcutaneous spironolactone; uninephrectomized rats on a high sodium diet; and age- and sex-matched controls with or without spironolactone treatment. Systolic arterial pressure was comparably elevated in RHT and aldosterone models; it was modestly lowered but not normalized by 8 weeks of spironolactone treatment at the low doses used. Such treatment also failed to prevent left ventricular hypertrophy (LVH) in all experimental groups with hypertension. Spironolactone, however, was able to prevent myocardial fibrosis in RHT and aldosterone models of acquired arterial hypertension irrespective of the development of LVH and the presence of hypertension. These findings provide further evidence that elevated aldosterone levels play an important role in the adverse remodeling of the myocardium in arterial hypertension. The antifibrotic effects of spironolactone, if confirmed in human studies, may be a valuable strategy in treating hypertensive heart disease.

Activation, attention, and short-term memory

Abstract: The premise of this paper is that the popular term "short-term memory" (STM) is vague because it is used to refer to either (1) the set of representations from long-term memory currently in a state of heightened activation or (2) the focus of attention or content of awareness. A more coherent conception of STM is hierarchical, with the focus of attention depicted as a subset of the activated portion of long-term memory. Research issues are discussed to illustrate that this simple conception of STM leads to testable predictions and useful lines of inquiry.

Exercise training alters endothelium-dependent vasoreactivity of rat abdominal aorta

Abstract: We tested the hypothesis that adaptations in peripheral arterial vasoreactivity are induced by exercise training. Male rats were trained to run on a treadmill at 30 m/min (15 degrees incline) for 1...

Fundamentals of environmental chemistry

Abstract: Introduction to Chemistry and Green Chemistry Matter and Materials Atoms and Elements Chemical Bonds, Molecules, and Compounds Chemical Reactions, Equations, and Stoichiometry Acids, Bases, and Salts Solutions and Solvents Chemistry and Electricity Organic Chemistry Biological Chemistry Water and the Hydrosphere Environmental Chemistry and Pollution of the Hydrosphere Sustaining the Hydrosphere: Keeping Water Green The Atmosphere: A Protective Blanket Around Us Atmospheric Chemistry Blue Skies for a Green Earth The Geosphere and Geochemistry Soil, Agriculture, and Food Production Sustaining the Geosphere The Biosphere and Biospeheric Resource Toxicological Chemistry The Anthrosphere and Technology Green Chemistry and Industrial Ecology The Anthrosphere and Wastes Green Chemistry and Industrial Ecology in Waste Management Sustainable Energy: The Key to Everything Fundamentals of Analytical Chemistry Environmental and Xenobiotics Analysis Literature Cited Supplementary References Questions and Problems Index