Showing papers by "Vanderbilt University published in 1998"
TL;DR: In this article, the authors examined the relation between stock returns, measures of risk, and several non-risk security characteristics, including the book-to-market ratio, firm size, the stock price, the dividend yield, and lagged returns.
1,552 citations
TL;DR: In this paper, a multidimensional measure for Leader-Member Exchange (LMX) was developed and validated through item analysis and criterion-related validation using 249 employees representing two organizations.
1,547 citations
TL;DR: The National Science Education Standards as discussed by the authors provide a vision teaching and learning science for the science education system and criteria to measure progress toward that vision, including content, teaching, assessment, three major levers of change identified by policy analysts.
Abstract: The National Science Education Standards provides a vision teaching and learning science for the science education system and criteria to measure progress toward that vision. The document contains standards for content, teaching, assessment, three major levers of change identified by policy analysts. The Standards also include program standards for schools and districts and system standards. This article describes how the Standards were developed within a political context, through a process with political aspects and includes political intents. It closes with recommendations about why and how science education researchers might engage in the political process. © 1998 John Wiley & Sons, Inc. J Res Sci Teach 35: 711–727, 1998.
1,375 citations
01 Jan 1998
1,238 citations
TL;DR: An approach to designing, implementing, and evaluating problemand project-based curricula that has emerged from a long-term collaboration with teachers is shared and 4 design principles that appear to be especially important are identified.
Abstract: (1998). Doing With Understanding: Lessons From Research on Problem- and Project-Based Learning. Journal of the Learning Sciences: Vol. 7, No. 3-4, pp. 271-311.
1,193 citations
Journal Article•
TL;DR: It is reported that PGE2 treatment of human colon cancer cells leads to increased clonogenicity of HCA-7, but not HCT-116 cells, which may help to explain a component of the mechanism by which COX inhibitors prevent colorectal cancer in humans.
Abstract: Previously, we have shown that forced expression of prostaglandin endoperoxide synthase-2 [also called cyclooxygenase (COX) 2] leads to inhibition of programmed cell death in intestinal epithelial cells. More recently, we have demonstrated that growth of human colonic cancer xenografts is inhibited by treatment with a highly selective COX-2 inhibitor in tumors that express COX-2 (HCA-7) but not in those that lack COX-2 expression (HCT-116). To explore the biochemical mechanisms involved in these effects, we have evaluated the role of COX-2-derived eicosanoid products on programmed cell death in human colon cancer cells. Here we report that PGE2 treatment of human colon cancer cells leads to increased clonogenicity of HCA-7, but not HCT-116 cells. Treatment with a highly selective COX-2 inhibitor (SC-58125) decreases colony formation in monolayer culture and this growth inhibition was reversed by treatment with PGE2. Additionally, PGE2 inhibits programmed cell death caused by SC-58125 and induces Bcl-2 expression, but did not affect Bcl-x or Bax expression in human colon cancer (HCA-7) cells. Therefore, decreased cell death caused by PGE2 would enhance the tumorigenic potential of intestinal epithelial cells. Thus, these results may help to explain a component of the mechanism by which COX inhibitors prevent colorectal cancer in humans.
1,151 citations
TL;DR: Compared with men, women were more expressive, did not differ in reports of experienced emotion, and demonstrated different patterns of skin conductance responding, and gender role characteristics and family expressiveness moderated the relationship between sex and expressivity.
Abstract: Although previous studies of emotional responding have found that women are more emotionally expressive than men, it remains unclear whether men and women differ in other domains of emotional response. We assessed the expressive, experiential, and physiological emotional responses of men and women in 2 studies. In Study 1, undergraduates viewed emotional films. Compared with men, women were more expressive, did not differ in reports of experienced emotion, and demonstrated different patterns of skin conductance responding. In Study 2, undergraduate men and women viewed emotional films and completed self-report scales of expressivity, gender role characteristics, and family expressiveness. Results replicated those from Study 1, and gender role characteristics and family expressiveness moderated the relationship between sex and expressivity.
1,142 citations
TL;DR: In this paper, the authors examined the relation among ownership structure, investment, and corporate value, focusing on whether ownership structure affects investment and showed that the endogeneity of ownership may affect these inferences, suggesting that investment affects corporate value which, in turn, affects ownership structure.
1,095 citations
TL;DR: It is demonstrated that P-glycoprotein limits the oral bioavailability and penetration of these agents into the brain and raises the possibility that higher HIV-1 protease inhibitor concentrations may be obtained by targeted pharmacologic inhibition of P- glycoprotein transport activity.
Abstract: Currently available HIV-1 protease inhibitors are potent agents in the therapy of HIV-1 infection. However, limited oral absorption and variable tissue distribution, both of which are largely unexplained, complicate their use. We tested the hypothesis that P-glycoprotein is an important transporter for these agents. We studied the vectorial transport characteristics of indinavir, nelfinavir, and saquinavir in vitro using the model P-glycoprotein expressing cell lines L-MDR1 and Caco-2 cells, and in vivo after intravenous and oral administration of these agents to mice with a disrupted mdr1a gene. All three compounds were found to be transported by P-glycoprotein in vitro. After oral administration, plasma concentrations were elevated 2-5-fold in mdr1a (-/-) mice and with intravenous administration, brain concentrations were elevated 7-36-fold. These data demonstrate that P-glycoprotein limits the oral bioavailability and penetration of these agents into the brain. This raises the possibility that higher HIV-1 protease inhibitor concentrations may be obtained by targeted pharmacologic inhibition of P-glycoprotein transport activity.
1,075 citations
TL;DR: Two new expressions for estimating registration accuracy of point-based guidance systems and a surprising conclusion that expected registration accuracy (TRE) is worst near the fiducials that are most closely aligned are presented.
Abstract: Guidance systems designed for neurosurgery, hip surgery, and spine surgery, and for approaches to other anatomy that is relatively rigid can use rigid-body transformations to accomplish image registration. These systems often rely on point-based registration to determine the transformation, and many such systems use attached fiducial markers to establish accurate fiducial points for the registration, the points being established by some fiducial localization process. Accuracy is important to these systems, as is knowledge of the level of that accuracy. An advantage of marker-based systems, particularly those in which the markers are bone-implanted, is that registration error depends only on the fiducial localization error (FLE) and is thus to a large extent independent of the particular object being registered. Thus, it should be possible to predict the clinical accuracy of marker-based systems on the basis of experimental measurements made with phantoms or previous patients. This paper presents two new expressions for estimating registration accuracy of such systems and points out a danger in using a traditional measure of registration accuracy. The new expressions represent fundamental theoretical results with regard to the relationship between localization error and registration error in rigid-body, point-based registration. Rigid-body, point-based registration is achieved by finding the rigid transformation that minimizes "fiducial registration error" (FRE), which is the root mean square distance between homologous fiducials after registration. Closed form solutions have been known since 1966. The expected value (FRE/sup 2/) depends on the number N of fiducials and expected squared value of FLE, (FLE/sup 2/), but in 1979 it was shown that (FRE/sup 2/) is approximately independent of the fiducial configuration C. The importance of this surprising result seems not yet to have been appreciated by the registration community: Poor registrations caused by poor fiducial configurations may appear to be good due to a small FRE value. A more critical and direct measure of registration error is the "target registration error" (TRE), which is the distance between homologous points other than the centroids of fiducials. Efforts to characterize its behavior have been made since 1989. Published numerical simulations have shown that (TRE/sup 2/) is roughly proportional to (FLE/sup 2/)/N and, unlike (FRE/sup 2/), does depend in some way on C. Thus, FRE, which is often used as feedback to the surgeon using a point-based guidance system, is in fact an unreliable indicator of registration-accuracy. In this work the authors derive approximate expressions for (TRE/sup 2/), and for the expected squared alignment error of an individual fiducial. They validate both approximations through numerical simulations. The former expression can be used to provide reliable feedback to the surgeon during surgery and to guide the placement of markers before surgery, or at least to warn the surgeon of potentially dangerous fiducial placements; the latter expression leads to a surprising conclusion: Expected registration accuracy (TRE) is worst near the fiducials that are most closely aligned! This revelation should be of particular concern to surgeons who may at present be relying on fiducial alignment as an indicator of the accuracy of their point-based guidance systems.
1,055 citations
TL;DR: It is shown that co-expression of the mutant ß1 subunit with a brain Na+-channel ß subunit in Xenopus laevis oocytes demonstrates that the mutation interferes with the ability of the subunit to modulate channel-gating kinetics consistent with a loss-of-function allele, developing the theme that idiopathic epilepsies are a family of channelopathies.
Abstract: Febrile seizures affect approximately 3% of all children under six years of age and are by far the most common seizure disorder. A small proportion of children with febrile seizures later develop ongoing epilepsy with afebrile seizures. Segregation analysis suggests the majority of cases have complex inheritance but rare families show apparent autosomal dominant inheritance. Two putative loci have been mapped (FEB1 and FEB2), but specific genes have not yet been identified. We recently described a clinical subset, termed generalized epilepsy with febrile seizures plus (GEFS+), in which many family members have seizures with fever that may persist beyond six years of age or be associated with afebrile generalized seizures. We now report linkage, in another large GEFS+ family, to chromosome region 19q13.1 and identification of a mutation in the voltage-gated sodium (Na+)-channel beta1 subunit gene (SCN1B). The mutation changes a conserved cysteine residue disrupting a putative disulfide bridge which normally maintains an extracellular immunoglobulin-like fold. Co-expression of the mutant beta1 subunit with a brain Na+-channel alpha subunit in Xenopus laevis oocytes demonstrates that the mutation interferes with the ability of the subunit to modulate channel-gating kinetics consistent with a loss-of-function allele. This observation develops the theme that idiopathic epilepsies are a family of channelopathies and raises the possibility of involvement of other Na+-channel subunit genes in febrile seizures and generalized epilepsies with complex inheritance patterns.
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TL;DR: The authors found that analyzing contrasting cases can help learners generate the differentiated knowledge structures that enable them to understand a text deeply, and that analyzing the contrasting cases increased students' abilities to distinguish specific features that differentiated classes of psychological phenomena, much as a botanist can distinguish subspecies of a given flower.
Abstract: Suggestions for improving text understanding often prescribe activating prior knowledge, a prescription that may be problematic if students do not have the relevant prior knowledge to begin with. In this article, we describe research about a method for developing prior knowledge that prepares students to learn from a text or lecture. We propose that analyzing contrasting cases can help learners generate the differentiated knowledge structures that enable them to understand a text deeply. Noticing the distinctions between contrasting cases creates a "time for telling"; learners are prepared to be told the significance of the distinctions they have discovered. In 3 classroom studies, college students analyzed contrasting cases that consisted of simplified experimental designs and data from classic psychology experiments. They then received a lecture or text on the psychological phenomena highlighted in the experiments. Approximately 1 week later, the students predicted outcomes for a hypothetical experiment that could be interpreted in light of the concepts they had studied. Generating the distinctions between contrasting cases and then reading a text or hearing a lecture led to more accurate predictions than the control treatments of (a) reading about the distinctions between the cases and hearing alecture, (b) summarizing a relevant text and hearing a lecture, and (c) analyzing the contrasting cases twice without receiving a lecture. We argue that analyzing the contrasting cases increased students' abilities to discern specific features that differentiated classes of psychological phenomena, much as a botanist can distinguish subspecies of a given flower. This differentiated knowledge prepared the students to understand deeply an explanation of the relevant psychological principles when it was presented to them. These results can inform constructivist models of instruction as they apply to classroom activities and learning from verbal materials. In particular, the results indicate that there is a place for lectures and readings in the classroom if students have sufficiently differentiated domain knowledge to use the expository materials in a generative manner.
TL;DR: Differences in the time course of activation across the dorsal and ventral streams provide important temporal constraints on theories of visual processing.
Abstract: Schmolesky, Matthew T., Youngchang Wang, Doug P. Hanes, Kirk G. Thompson, Stefan Leutgeb, Jeffrey D. Schall, and Audie G. Leventhal. Signal timing across the macaque visual system. J. Neurophysiol....
TL;DR: The data suggest that VEGF, at pathologically relevant concentrations in vivo, may exert effects on pluripotent stem cells that result in blocked DC development as well as affect many other hematopoietic lineages.
TL;DR: This article presents methods for sample size and power calculations for studies involving linear regression, applicable to clinical trials designed to detect a regression slope of a given magnitude or to studies that test whether the slopes or intercepts of two independent regression lines differ by a given amount.
TL;DR: The history of the development of one of the first identified topoisomerase II inhibitors, etoposide, is reviewed and critical developments in etopose's mechanism of action, pharmacology and administration schedule are summarised.
TL;DR: Cytochrome P4503A (CYP3A) is importantly involved in the metabolism of many chemically diverse drugs administered to humans and makes it a major contributor to presystemic elimination following oral drug administration.
Abstract: Cytochrome P4503A (CYP3A) is importantly involved in the metabolism of many chemically diverse drugs administered to humans. Moreover, its localization in high amounts both in the small intestinal epithelium and liver makes it a major contributor to presystemic elimination following oral drug administration. Drug interactions involving enzyme inhibition or induction are common following the coadministration of two or more CYP3A substrates. Studies using in vitro preparations are useful in identifying such potential interactions and possibly permitting extrapolation of in vitro findings to the likely in vivo situation. Even if accurate quantitative predictions cannot be made, several classes of drugs can be expected to result in a drug interaction based on clinical experience. In many instances, the extent of such drug interactions is sufficiently pronounced to contraindicate the therapeutic use of the involved drugs.
TL;DR: It is concluded that any single VAS score in the immediate postoperative period should be considered to have an imprecision of +/- 20 mm, and the visual analog scale was developed for assessing chronic pain but is often used in studies of postoperative pain.
Abstract: The visual analog scale (VAS) has been used to assess the efficacy of pain management regimens in patients with acute postoperative pain, but its usefulness has not been confirmed in postoperative pain studies. We studied 60 subjects in the immediate postoperative period. The specific data collected were: VAS scores versus an 11-point numeric pain scale; repeatability in VAS scores over a short time interval; and change in VAS scores from one assessment period to the next versus a verbal report of change in pain. The correlation coefficients for VAS scores with the 11-point pain scale were 0.94, 0.91, and 0.95. The repeatability coefficients were 17.6, 23.0, and 13.5 mm. Of the 56 patients who completed all three assessments, only 16 (29%) had repeatability within 5 mm on all three. Some of the changes in VAS scores between assessments were in the direction opposite the verbally reported changes in pain (31%); however, most (92%) were within 20 mm. There was no correlation between the level of sedation, previous pain experience, anxiety, or anticipated pain with consistency in VAS scores. We conclude that any single VAS score in the immediate postoperative period should be considered to have an imprecision of +/- 20 mm. Implications The visual analog scale was developed for assessing chronic pain but is often used in studies of postoperative pain. This study finds that the visual analog scale correlates well with a verbal 11-point scale but that any individual determination has an imprecision of +/- 20 mm.
TL;DR: A negative feedback control of kaiC expression by KaiC generates a circadian oscillation in cyanobacteria, and KaiA sustains the oscillation by enhancing kaiA expression.
Abstract: Cyanobacteria are the simplest organisms known to have a circadian clock. A circadian clock gene cluster kaiABC was cloned from the cyanobacterium Synechococcus. Nineteen clock mutations were mapped to the three kai genes. Promoter activities upstream of the kaiA and kaiB genes showed circadian rhythms of expression, and both kaiA and kaiBC messenger RNAs displayed circadian cycling. Inactivation of any single kai gene abolished these rhythms and reduced kaiBC-promoter activity. Continuous kaiC overexpression repressed the kaiBC promoter, whereas kaiA overexpression enhanced it. Temporal kaiC overexpression reset the phase of the rhythms. Thus, a negative feedback control of kaiC expression by KaiC generates a circadian oscillation in cyanobacteria, and KaiA sustains the oscillation by enhancing kaiC expression.
TL;DR: This work tested the adaptive significance of circadian programming by measuring the relative fitness under competition between various strains of cyanobacteria expressing different circadian periods and found strains that had a circadian period similar to that of the light/dark cycle were favored under competition in a manner that indicates the action of soft selection.
Abstract: In some organisms longevity, growth, and developmental rate are improved when they are maintained on a light/dark cycle, the period of which “resonates” optimally with the period of the endogenous circadian clock. However, to our knowledge no studies have demonstrated that reproductive fitness per se is improved by resonance between the endogenous clock and the environmental cycle. We tested the adaptive significance of circadian programming by measuring the relative fitness under competition between various strains of cyanobacteria expressing different circadian periods. Strains that had a circadian period similar to that of the light/dark cycle were favored under competition in a manner that indicates the action of soft selection.
TL;DR: It is suggested that changes in the production of the pro-inflammatory cytokines, TNF-alpha, IL-6 and IFN-gamma, and negative immunoregulatory cytokine,IL-10 and IL-4, take part in the homeostatic responses to psychological stress and that stress-induced anxiety is related to a T-helper-1-like response.
TL;DR: In this article, the authors outline relations between the social functions of emotion and four psychological disorders, i.e., depression, anxiety, depression, and suicidal ideation, and conclude that emotion function and emotional disorders complement one another.
Abstract: The studies of emotion function and emotional disorders complement one another. In this article, the authors outline relations between the social functions of emotion and four psychological disorde...
TL;DR: The data suggest that, out of every 10,000 women in their third trimester without other identified risk factors who experience an average influenza season of 2.5 months, 25 will be hospitalized with influenza-related morbidity.
Abstract: This study sought to quantify influenza-related serious morbidity in pregnant women, as measured by hospitalizations for or death from selected acute cardiopulmonary conditions during predefined influenza seasons. The study population included women aged 15-44 years who were enrolled in the Tennessee Medicaid program for at least 180 days between 1974 and 1993. In a nested case-control study, 4,369 women with a first study event during influenza season were compared with 21,845 population controls. The odds ratios associated with study events increased from 1.44 (95% confidence interval (CI) 0.97-2.15) for women at 14-20 weeks' gestation to 4.67 (95% CI 3.42-6.39) for those at 37-42 weeks in comparison with postpartum women. A retrospective cohort analysis, which controlled for risk factors identified in the case-control study, identified 22,824 study events during 1,393,166 women-years of follow-up. Women in their third trimester without other identified risk factors for influenza morbidity had an event rate of 21.7 per 10,000 women-months during influenza season. Approximately half of this morbidity, 10.5 (95% CI 6.7-14.3) events per 10,000 women-months, was attributable to influenza. Influenza-attributable risks in comparable nonpregnant and postpartum women were 1.91 (95% CI 1.51-2.31) and 1.16 (95% CI -0.09 to 2.42) per 10,000 women-months, respectively. The data suggest that, out of every 10,000 women in their third trimester without other identified risk factors who experience an average influenza season of 2.5 months, 25 will be hospitalized with influenza-related morbidity.
TL;DR: The discovery of the isoprostanes as lipid peroxidation products which can be measured by gas chromatography mass spectrometry or immunoassay has opened a new avenue by which to quantify lipid per oxidation in vivo, and will be discussed in detail.
Abstract: Lipid peroxidation results in the formation of conjugated dienes, lipid hydroperoxides and degradation products such as alkanes, aldehydes and isoprostanes. The approach to the quantitative assessment of lipid peroxidation depends on whether the samples involve complex biological material obtained in vivo, or whether the samples involve relatively simple mixtures obtained in vitro. Samples obtained in vivo contain a large number of products which themselves may undergo metabolism. The measurement of conjugated diene formation is generally applied as a dynamic quantitation e.g. during the oxidation of LDL, and is not generally applied to samples obtained in vivo. Lipid hydroperoxides readily decompose, but can be measured directly and indirectly by a variety of techniques. The measurement of MDA by the TBAR assay is non-specific, and is generally poor when applied to biological samples. More recent assays based on the measurement of MDA or HNE-lysine adducts are likely to be more applicable to biological samples, since adducts of these reactive aldehydes are relatively stable. The discovery of the isoprostanes as lipid peroxidation products which can be measured by gas chromatography mass spectrometry or immunoassay has opened a new avenue by which to quantify lipid peroxidation in vivo, and will be discussed in detail.
TL;DR: Evidence was found that individual differences in externalizing behavior problems were stable over time and were related to individual risk factors as well as the number of risk factors present, and there were multiple clusters of risks that led to similar outcomes.
Abstract: The aim of this study was to test whether individual risk factors as well as the number of risk factors (cumulative risk) predicted children's externalizing behaviors over middle childhood. A sample of 466 European American and 100 African American boys and girls from a broad range of socioeconomic levels was followed from age 5 to 10 years. Twenty risk variables from four domains (child, sociocultural, parenting, and peer-related) were measured using in-home interviews at the beginning of the study, and annual assessments of externalizing behaviors were conducted. Consistent with past research, individual differences in externalizing behavior problems were stable over time and were related to individual risk factors as well as the number of risk factors present. Particular risks accounted for 36% to 45% of the variance, and the number of risks present (cumulative risk status) accounted for 19% to 32% of the variance, in externalizing outcomes. Cumulative risk was related to subsequent externalizing even after initial levels of externalizing had been statistically controlled. All four domains of risk variables made significant unique contributions to this statistical prediction, and there were multiple clusters of risks that led to similar outcomes. There was also evidence that this prediction was moderated by ethnic group status, most of the prediction of externalizing being found for European American children. However, this moderation effect varied depending on the predictor and outcome variables included in the model.
TL;DR: Progress toward understanding mechanisms underlying torsades de pointes and identifying patients at risk would go a long way to rationalizing therapy with currently available antiarrhythmic drugs and perhaps directing development of new agents.
Abstract: Adverse reactions to drug therapy are the hane of the practitioner, and all the more so when they occur in an idiosyncratic, or apparently unpredictable, fashion. The occurrence of torsades de pointes during treatment with action potential prolonging drugs has long fallen into this category. Progress toward understanding mechanisms underlying torsades de pointes and identifying patients at risk would go a long way to rationalizing therapy with currently available antiarrhythmic drugs and perhaps directing development of new agents.
01 Jan 1998
TL;DR: Current knowledge about the clinical, epidemiological, pathogenetic, and laboratory aspects of campylobacter-associated Guillain-Barre syndrome is summarized.
Abstract: Since the eradication of polio in most parts of the world, Guillain-Barre syndrome (GBS) has become the most common cause of acute flaccid paralysis. GBS is an autoimmune disorder of the peripheral nervous system characterized by weakness, usually symmetrical, evolving over a period of several days or more. Since laboratories began to isolate Campylobacter species from stool specimens some 20 years ago, there have been many reports of GBS following Campylobacter infection. Only during the past few years has strong evidence supporting this association developed. Campylobacter infection is now known as the single most identifiable antecedent infection associated with the development of GBS. Campylobacter is thought to cause this autoimmune disease through a mechanism called molecular mimicry, whereby Campylobacter contains ganglioside-like epitopes in the lipopolysaccharide moiety that elicit autoantibodies reacting with peripheral nerve targets. Campylobacter is associated with several pathologic forms of GBS, including the demyelinating (acute inflammatory demyelinating polyneuropathy) and axonal (acute motor axonal neuropathy) forms. Different strains of Campylobacter as well as host factors likely play an important role in determining who develops GBS as well as the nerve targets for the host immune attack of peripheral nerves. The purpose of this review is to summarize our current knowledge about the clinical, epidemiological, pathogenetic, and laboratory aspects of campylobacter-associated GBS.
TL;DR: Data indicate that Ang II induces Ca2+-dependent transactivation of the EGF receptor which serves as a scaffold for pre-activated c-Src and for downstream adaptors, leading to MAPK activation in VSMC.
TL;DR: In this paper, the authors provided estimates of the potential benefits from "saving" a high-risk youth, by estimating the lifetime costs associated with the typical career criminal, drug abuser, and high-school dropout.
Abstract: Programs targeted at high-risk youth are designed to prevent high-school dropout, crime, drug abuse, and other forms of delinquency. Even if shown to be successful in reducing one or more social ill, a key policy question is whether the cost to society from that intervention program exceeds its benefits. Although the costs of intervention programs are often available, the benefits are more illusive. This paper provides estimates of the potential benefits from "saving" a high-risk youth, by estimating the lifetime costs associated with the typical career criminal, drug abuser, and high-school dropout. In the absence of controlled experimental data on the number of career criminals averted, one can ask the reverse question—How many career criminals must be prevented before the program "pays for itself?" Based on a 2% discount rate, the typical career criminal causes $1.3$1.5 million in external costs; a heavy drug user, $370,000 to $970,000; and a high-school dropout, $243,000 to $388,000. Eliminating duplication between crimes committed by individuals who are both heavy drug users and career criminals results in an overall estimate of the "monetary value of saving a high-risk youth" of $1.7 to $2.3 million.