Showing papers by "Tulane University published in 1997"

Range of antinuclear antibodies in "healthy" individuals

Abstract: Objective. To determine the range of antinuclear antibodies (ANA) in “healthy” individuals compared with that in patients with systemic lupus erythematosus (SLE), systemic sclerosis (SSc; scleroderma), Sjogren's syndrome (SS), rheumatoid arthritis (RA), or soft tissue rheumatism (STR). Methods. Fifteen international laboratories experienced in performing tests for ANA by indirect immunofluorescence participated in analyzing coded sera from healthy individuals and from patients in the 5 different disease groups described above. Except for the stipulation that HEp-2 cells should be used as substrate, each laboratory used its own in-house methodology so that the data might be expected to reflect the output of a cross-section of worldwide ANA reference laboratories. The sera were analyzed at 4 dilutions: 1:40, 1:80, 1:160, and 1:320. Results. In healthy individuals, the frequency of ANA did not differ significantly across the 4 age subgroups spanning 20–60 years of age. This putatively normal population was ANA positive in 31.7% of individuals at 1:40 serum dilution, 13.3% at 1:80, 5.0% at 1:160, and 3.3% at 1:320. In comparison with the findings among the disease groups, a low cutoff point at 1:40 serum dilution (high sensitivity, low specificity) could have diagnostic value, since it would classify virtually all patients with SLE, SSc, or SS as ANA positive. Conversely, a high positive cutoff at 1:160 serum dilution (high specificity, low sensitivity) would be useful to confirm the presence of disease in only a portion of cases, but would be likely to exclude 95% of normal individuals. Conclusion. It is recommended that laboratories performing immunofluorescent ANA tests should report results at both the 1:40 and 1:160 dilutions, and should supply information on the percentage of normal individuals who are positive at these dilutions. A low-titer ANA is not necessarily insignificant and might depend on at least 4 specific factors. ANA assays can be a useful discriminant in recognizing certain disease conditions, but can create misunderstanding when the limitations are not fully appreciated.

Reading the wind: how middle managers assess the context for selling issues to top managers

Abstract: Issue selling is an important mechanism for creating change initiatives in organizations. This paper presents two studies that examine what middle managers think about as they decide whether or not to sell strategic issues to top management. In Study 1 middle managers identify themes that indicate a favorable or unfavorable context for issue selling. Top management’s willingness to listen and a supportive culture were the most often named contributors to context favorability, while fear of negative consequences, downsizing conditions and uncertainty were thought to signal that a context was unfavorable for issue selling. Study 2 identifies factors that middle managers associate with image risk in the context of issue selling. Violating norms for issue selling, selling in a politically vulnerable way and having a distant relationship with top management were regarded as major contributors to a middle manager’s level of image risk. Both studies enrich our understanding of the social psychological mechanisms that undergird the strategic change process.© 1997 by John Wiley & Sons, Ltd.

Traveling Waves in a Convolution Model for Phase Transitions

Abstract: The existence, uniqueness, stability and regularity properties of traveling-wave solutions of a bistable nonlinear integrodifferential equation are established, as well as their global asymptotic stability in the case of zero-velocity continuous waves. This equation is a direct analog of the more familiar bistable nonlinear diffusion equation, and shares many of its properties. It governs gradient flows for free-energy functionals with general nonlocal interaction integrals penalizing spatial nonuniformity.

BECOMING MOTHERS AND FATHERS Parenthood, Gender, and the Division of Labor

Abstract: This study used two waves of the National Survey of Families and Households (1987 to 1988 and 1992 to 1994) to examine the effect of the transition to parenthood on the division of labor among married couples, hypothesizing that parenthood would produce a more differentiated gender division of labor, but that attitudes and preparental division of labor would moderate parenthood. There were no effects of parenthood nor direct or moderating effects of gender attitudes on husbands' employment or housework hours, with the exception that fathering more than one child results in slightly longer employment hours. Motherhood increases wives' housework hours and reduces employment hours. Wives' traditional gender attitudes reduce their employment, but not their housework. Women married to full-time breadwinners have the largest reductions in employment after motherhood. Last, wives' initial economic dependency increases wives' subsequent housework and husbands' employment. Parenthood crystallizes a gendered divisi...

The use of isotope tracers for identifying populations of migratory birds

Abstract: To determine whether stable isotopes can be used for identifying the geographic origins of migratory bird populations, we examined the isotopic composition of hydrogen (deuterium, δD), carbon (δ13C), and strontium (δ87Sr) in tissues of a migratory passerine, the black-throated blue warbler (Dendroica caerulescens), throughout its breeding range in eastern North America. δD and δ13C values in feathers, which are grown in the breeding area, varied systematically along a latitudinal gradient, being highest in samples from the southern end of the species’ breeding range in Georgia and lowest in southern Canada. In addition, δD decreased from east to west across the northern part of the breeding range, from New Brunswick to Michigan. δ87Sr ratios were highest in the Appalachian Mountains, and decreased towards the west. These patterns are consistent with geographical variation in the isotopic composition of the natural environment, i.e., with that of precipitation, plants, and soils for δD, δ13C, and δ87Sr, respectively. Preliminary analyses of the δD and δ13C composition of feathers collected from warblers in their Caribbean winter grounds indicate that these individuals were mostly from northern breeding populations. Furthermore, variances in isotope ratios in samples from local areas in winter tended to be larger than those in summer, suggesting that individuals from different breeding localities may mix in winter habitats. These isotope markers, therefore, have the potential for locating the breeding origins of migratory species on their winter areas, for quantifying the degree of mixing of breeding populations on migratory and wintering sites, and for documenting other aspects of the population structure migratory animals – information needed for studies of year-round ecology of these species as well as for their conservation. Combining information from several stable isotopes will help to increase the resolution for determining the geographic origins of individuals in such highly vagile populations.

Influences of Organizational Culture and Climate on Individual Creativity.

Abstract: This paper provides a framework for conceptualizing and reviewing the literature on the influences of organizational culture and climate on individual creativity. Although often treated interchangeably, culture and climate are distinct constructs operating at different levels of meaning; yet at the same time, they are closely interrelated. Culture is the beliefs and values held by management and communicated to employees through norms, stories, socialization processes, and observations of managerial responses to critical events. The beliefs and values that typify a culture for creativity become manifested in organizational structures, practices, and policies. In turn, these structures, practices, and policies guide and shape individual creativity by creating a climate that communicates both the organization's goals regarding creativity and the means to achieve those goals. The paper concludes with a discussion of issues relating to the development of cultures and climates for creativity and potential new directions for future research.

Site-dependent regulation of population size:a new synthesis

Abstract: The nature and extent of population regulation remains a principal unanswered question for many types of organisms, despite extensive research. In this paper, we provide a new synthesis of theoretical and empirical evidence that elucidates and extends a mechanism of population regulation for species whose individuals preemptively use sites that differ in suitability. The sites may be territories, refuges from predation, oviposition sites, etc. The mechanism, which we call site dependence, is not an alternative to density dependence; rather, site dependence is one of several mechanisms that potentially generate the negative feedback required for regulation. Site dependence has two major features: (1) environmentally caused heterogeneity among sites in suitability for reproduction and/or survival; and (2) preemptive site occupancy, with the tendency for individuals to move to sites of higher quality as they become available. Simulation modeling shows that these two features, acting in concert, generate nega...

Comment on ``Significance of the highest occupied Kohn-Sham eigenvalue''

Abstract: With more explanation than usual and without appeal to Janak's theorem, we review the statement and proof of the ionization potential theorems for the exact Kohn-Sham density-functional theory of a many-electron system: (1) For any average electron number $N$ between the integers $Z\ensuremath{-}1$ and $Z,$ and thus for $N\ensuremath{\rightarrow}Z$ from below, the highest occupied or partly occupied Kohn-Sham orbital energy is minus the ionization energy of the $Z$-electron system. (2) For $Z\ensuremath{-}1lNlZ,$ the exact Kohn-Sham effective potential ${v}_{s}(\mathbf{r})$ tends to zero as $|\mathbf{r}|\ensuremath{\rightarrow}\ensuremath{\infty}.$ We then argue that an objection to these theorems. [L. Kleinman, Phys. Rev. B 56, 12 042 (1997)] overlooks a crucial step in the proof of theorem (2): The asymptotic exponential decay of the exact electron density of the $Z$-electron system is controlled by the exact ionization energy, but the decay of an approximate density is not controlled by the approximate ionization energy. We review relevant evidence from the numerical construction of the exact Kohn-Sham potential. In particular, we point out a model two-electron problem for which the ionization potential theorems are exactly confirmed. Finally, we comment on related issues: the self-interaction correction, the discontinuity of the exact Kohn-Sham potential as $N$ passes through the integer $Z,$ and the generalized sum rule on the exchange-correlation hole.

Cooperative search and rescue with a team of mobile robots

Abstract: We present an implemented algorithm for a distributed team of autonomous mobile robots to search for an object. When one robot finds it, they all gather around it, and then manipulate ("rescue") it. The algorithm exploits parallelism, with all robots searching concurrently, and also teamwork, because the manipulation is performed cooperatively. Our algorithm is fully distributed; the robots communicate with each other, and there is no central server or supervisor. Applications include hazardous waste cleanup, bomb detection and removal, materials delivery, and eventually the rescue of survivors of accidents or disasters. The search and rescue program was written using MOVER, a programming system for distributed tasks. The system provides high-level programming constructs for task distribution across robots. Finally, MOVER encourages code re-use because the task distribution mechanism can synchronize any set of procedures (without rewriting), allowing the programmer of a distributed task to access libraries of robot software written for single-robot tasks.

Peroxynitrite inhibits leukocyte-endothelial cell interactions and protects against ischemia-reperfusion injury in rats.

Abstract: Peroxynitrite (ONOO-) anion, formed by the interaction of superoxide with nitric oxide (NO), has previously been implicated as a cytotoxic agent. However, the effects of this free radical species on neutrophil (PMN)-endothelial cell interactions is largely unknown. We investigated the direct actions of ONOO- on PMN adhesion to endothelial cells in vitro and in vivo, as well as the effects of ONOO- on PMN-mediated myocardial ischemia-reperfusion injury. In vitro, peroxynitrite (100-1,000 nM) inhibited the adhesion of rat PMNs to the endothelium of isolated thrombin- or H2O2-stimulated rat mesenteric artery (P < 0.01 vs. thrombin or H2O2 alone). In vivo, in the rat mesentery, thrombin (0.5 U/ml) or N(G)-nitro-L-arginine-methyl ester (50 microM) significantly increased venular leukocyte rolling and adherence, which were also significantly (P < 0.01) attenuated by ONOO (800 nM) accompanied by reduced P-selectin expression on the endothelial cell surface. Isolated perfused rat hearts were subjected to global ischemia and reperfusion with rat PMNs (10(8) cells), which resulted in profound cardiac depression (i.e., a marked reduction in left ventricular developed pressure and maximal rate of development of left ventricular pressure). Infusion of ONOO- reversed the myocardial contractile dysfunction of ischemic-reperfused rat hearts to near baseline levels, and markedly attenuated the accumulation of PMNs in the postischemic heart. The present study provides strong evidence that nanomolar concentrations of ONOO- both inhibit leukocyte-endothelial cell interactions and exert cytoprotective effects in myocardial ischemia-reperfusion injury. Furthermore, our results suggest that the inhibition of P-selectin expression by peroxynitrite is a key mechanism of the modulatory actions of ONOO- on leukocyte-endothelial cell interactions.

Promoting clinical involvement in hospital quality improvement efforts: the effects of top management, board, and physician leadership.

Abstract: STUDY QUESTION: An examination of the effects of top management, board, and physician leadership for quality on the extent of clinical involvement in hospital CQI/TQM efforts. DATA SOURCES: A sample of 2,193 acute care community hospitals, created by merging data from a 1989 national survey on hospital governance and a 1993 national survey on hospital quality improvement efforts. STUDY DESIGN: Hypotheses were tested using Heckman's two-stage modeling approach. Four dimensions of clinical involvement in CQI/TQM were examined: physician participation in formal QI training, physician participation in QI teams, clinical departments with formally organized QA/QI project teams, and clinical conditions and procedures for which quality of care data are used by formally organized QA/QI project teams. Leadership measures included CEO involvement in CQI/TQM, board quality monitoring, board activity in quality improvement, active-staff physician involvement in governance, and physician-at-large involvement in governance. Relevant control variables were included in the analysis. PRINCIPAL FINDINGS: Measures of top management leadership for quality and board leadership for quality showed significant, positive relationships with measures of clinical involvement in CQI/TQM. Active-staff physician involvement in governance showed positive, significant relationships with clinical involvement measures, while physician-at-large involvement in governance showed significant, negative relationships. CONCLUSIONS: Study results suggest that leadership from the top promotes clinical involvement in CQI/TQM. Further, results indicate that leadership for quality in healthcare settings may issue from several sources, including managers, boards, and physician leaders.

Immunohistochemical localization of ANG II AT1 receptor in adult rat kidney using a monoclonal antibody

Abstract: Molecular and functional studies have suggested that AT1 receptors are present in most nephron segments, yet direct demonstration of AT1 at these sites is lacking. The present study was performed to determine the intrarenal localization of the AT1 receptor utilizing a monoclonal anti-peptide (amino acid residues 8-17) antibody (6313/G2) in adult male Sprague-Dawley rats. Western blot analysis of kidney protein extracts showed a predominant 41-kDa immunoreactive band corresponding to the molecular weight of the deduced cDNA sequence. To determine optimal fixation conditions, kidney tissues were immersion fixed in Bouin's solution, 10% buffered Formalin, or 4% paraformaldehyde. Specificity of immunostaining was documented by preadsorption of the antibody with the immunogenic peptide sequence. Prominent AT1 immunostaining was visualized in the proximal tubule brush-border and basolateral membranes. In addition, distal tubules, cortical and medullary collecting ducts, and the renal arterial vasculature exhibited specific immunoreactivity. Glomerular staining for AT1 was observed in mesangial cells and podocytes. Macula densa cells stained positively. Similar localization of the AT1 receptor was obtained using the three tissue fixation methods, although the intensity of vascular and glomerular staining was highest in Bouin-fixed tissues. The present study demonstrates that the AT1 receptor is more widely distributed along the nephron than previously described and includes renal vascular smooth muscle and proximal and distal epithelial sites.

Parenting Styles, Adolescent Substance Use, and Academic Achievement:

Abstract: This article investigates how children and their parents rate their parenting styles, and how this rating is associated with academic achievement, alcohol, and tobacco use. We surveyed students and their parents in two public school districts. A total of 386 matched parent-child pairs from eighth- and ninth-grade students were analyzed for parent and student classification of parents as authoritative, authoritarian, permissive, or mixed parenting styles. Agreement on parenting styles between parents and children was poor. Students perceived parents as less authoritative, less permissive and more authoritarian than parents considered themselves. High grades were associated with child and parent perception of higher authoritativeness, lower permissiveness, and lower authoritarianism. Child tobacco and alcohol use was associated with child perception of lower authoritativeness, and higher permissiveness while parent perception of parenting style was not associated with child substance use. This study provides further evidence that parenting styles and adolescents' perceptions of them are associated with child achievement and substance use. While we cannot determine whether child or parent perception of parenting style is more accurate, child perception is more strongly associated with grades and substance use than is parent perception. It is likely that parents would benefit from understanding how they are perceived by their children.

Differential utilization of CCR5 by macrophage and T cell tropic simian immunodeficiency virus strains

Abstract: Certain chemokine receptors serve as cofactors for HIV type 1 envelope (env)-mediated cell-cell fusion and virus infection of CD4-positive cells. Macrophage tropic (M-tropic) HIV-1 isolates use CCR5, and T cell tropic (T-tropic) strains use CXCR4. To investigate the cofactors used by simian immunodeficiency viruses (SIV), we tested four T-tropic and two M-tropic SIV env proteins for their ability to mediate cell-cell fusion with cells expressing CD4 and either human or nonhuman primate chemokine receptors. Unlike HIV-1, both M- and T-tropic SIV envs used CCR5 but not CXCR4 or the other chemokine receptors tested. However, by testing a panel of CCR5/CCR2b chimeras, we found that the structural requirements for CCR5 utilization by M-tropic and T-tropic SIV strains were different. T-tropic SIV strains required the second extracellular loop of CCR5 whereas a closely related M-tropic SIV strain could, like M-tropic HIV-1 strains, use the amino-terminal domain of CCR5. As few as two amino acid changes in the SIV env V3 domain affected the regions of CCR5 that were critical for fusogenic activity. Receptor signaling was not required for either fusion or infection. Our results suggest that viral tropism may be influenced not only by the coreceptors used by a given virus strain but also by how a given coreceptor is used.

Review—The Transient Equation of Motion for Particles, Bubbles, and Droplets

Abstract: The development, form, and engineering applications of the transient equation of motion of rigid particles, bubbles, and droplets are presented. Some of the early work on the equation of motion, as well as recent advances, are exposed. Particular emphasis is placed on the semiempirical forms of the equation, which are widely used in engineering practice. The creeping flow assumption, on which most of the known applications are based, is critically examined and its limitations are pointed out. Recent results on particle flow, which include the effect of the advection of a downstream wake and are applicable to finite (but small) Reynolds numbers are also presented. The form of the history (Basset) term is discussed, in the light of recent work and its effect on the integrated results of the equation of motion is examined. Recommendations are given on the appearance, importance, and significance of the history and added mass terms for those who may use the semiempirical form of the transient equation of spheres in a differential or integrated form.

Clinical Assessment of Swallowing and Prediction of Dysphagia Severity

Abstract: Dysphagia with aspiration is prevalent in acute stroke; however, noninvasive clinical screening assessments to identify patients at risk of developing aspiration are limited. This study was underta...

Longitudinal Changes in Cardiovascular Risk From Childhood to Young Adulthood in Offspring of Parents With Coronary Artery Disease: The Bogalusa Heart Study

Abstract: Context. —Although the association between parental coronary artery disease (CAD) and its risk factors in the offspring is known, the timing and the course of development of risk factors from childhood to adulthood in the offspring is not known. Objective. —To examine the association between parental CAD and longitudinal changes in risk factor profile from childhood to young adulthood in offspring. Design. —Cohort study. Setting. —Bogalusa, La, a semirural, biracial community. Participants. —Individuals with clinically verified parental history of CAD (n=271) vs those without such a history (n=1253) Mean age at first CAD event was 50 years for fathers and 52 years for mothers. Main Outcome Measures. —Body mass index, subscapular skinfolds, blood pressure, and triglyceride, cholesterol (total, very low-density lipoprotein [VLDL-C], low-density lipoprotein [LDL-C], and high-density lipoprotein [HDL-C] cholesterols), glucose, and insulin levels. Reslts. —The offspring of parents with CAD were consistently overweight beginning in childhood. Their levels of total serum cholesterol, LDL-C, plasma glucose, and insulin became significantly higher at older ages, because of a higher rate of increase in these risk factors over time. In adulthood, the offspring with a positive parental history had a higher prevalence of obesity (body mass index >85th percentile in the National Health and Nutrition Examination Survey I, 35% vs 26%,P=.01), elevated total cholesterol (>6.2 mmol/L [240 mg/dL], 8.4% vs 4.8%,P=.05) and LDL-C levels (>4.1 mmol/L [160 mg/dL], 12.4% vs 4.7%,P=.05), and hyperglycemia (glucose, >6.6 mmol/L, 2.7% vs 0.4%,P Conclusions. —Offspring of parents with early CAD were overweight beginning in childhood and developed an adverse cardiovascular risk factor profile at an increased rate. These observations have important implications for prevention and intervention.

Bacterial persistence and expression of disease.

Abstract: A considerable body of experimental and clinical evidence supports the concept that difficult-to-culture and dormant bacteria are involved in latency of infection and that these persistent bacteria may be pathogenic. This review includes details on the diverse forms and functions of individual bacteria and attempts to make this information relevant to the care of patients. A series of experimental studies involving host-bacterium interactions illustrates the probability that most bacteria exposed to a deleterious host environment can assume a form quite different from that of a free-living bacterium. A hypothesis is offered for a kind of reproductive cycle of morphologically aberrant bacteria as a means to relate their diverse tissue forms to each other. Data on the basic biology of persistent bacteria are correlated with expression of disease and particularly the mechanisms of both latency and chronicity that typify certain infections. For example, in certain streptococcal and nocardial infections, it has been clearly established that wall-defective forms can be induced in a suitable host. These organisms can survive and persist in a latent state within the host, and they can cause pathologic responses compatible with disease. A series of cases illustrating idiopathic conditions in which cryptic bacteria have been implicated in the expression of disease is presented. These conditions include nephritis, rheumatic fever, aphthous stomatitis, idiopathic hematuria, Crohn's disease, and mycobacterial infections. By utilizing PCR, previously nonculturable bacilli have been identified in patients with Whipple's disease and bacillary angiomatosis. Koch's postulates may have to be redefined in terms of molecular data when dormant and nonculturable bacteria are implicated as causative agents of mysterious diseases.