Showing papers by "University of Illinois at Chicago published in 1996"

A Comparison of Continuous Intravenous Epoprostenol (Prostacyclin) with Conventional Therapy for Primary Pulmonary Hypertension

Abstract: Background Primary pulmonary hypertension is a progressive disease for which no treatment has been shown in a prospective, randomized trial to improve survival. Methods We conducted a 12-week prospective, randomized, multicenter open trial comparing the effects of the continuous intravenous infusion of epoprostenol (formerly called prostacyclin) plus conventional therapy with those of conventional therapy alone in 81 patients with severe primary pulmonary hypertension (New York Heart Association functional class III or IV). Results Exercise capacity was improved in the 41 patients treated with epoprostenol (median distance walked in six minutes, 362 m at 12 weeks vs. 315 m at base line), but it decreased in the 40 patients treated with conventional therapy alone (204 m at 12 weeks vs. 270 m at base line; P<0.002 for the comparison of the treatment groups). Indexes of the quality of life were improved only in the epoprostenol group (P<0.01). Hemodynamics improved at 12 weeks in the epoprostenol-treated pat...

Social Exchange in Organizations: Perceived Organizational Support, Leader-Member Exchange, and Employee Reciprocity

Abstract: Whether Leader-Member Exchange (LMX) is a unidimensional or a multidimensional construct was assessed through the development and validation of a multidimensional measure. Item analysis involving 302 working students, followed by construct and criterion-related validation using 249 employees representing two organizations resulted in a multidimensional LMX scale. The results provided support for the affect, loyalty, and contribution dimensions identified by Dienesch and Liden (1986), as well as a fourth dimension, professional respect.

Ubiquitin-dependent protein degradation

Abstract: ▪ Abstract A growing number of cellular regulatory mechanisms are being linked to protein modification by the polypeptide ubiquitin. These include key transitions in the cell cycle, class I antigen processing, signal transduction pathways, and receptor-mediated endocytosis. In most, but not all, of these examples, ubiquitination of a protein leads to its degradation by the 26S proteasome. Following attachment of ubiquitin to a substrate and binding of the ubiquitinated protein to the proteasome, the bound substrate must be unfolded (and eventually deubiquitinated) and translocated through a narrow set of channels that leads to the proteasome interior, where the polypeptide is cleaved into short peptides. Protein ubiquitination and deubiquitination are both mediated by large enzyme families, and the proteasome itself comprises a family of related but functionally distinct particles. This diversity underlies both the high substrate specificity of the ubiquitin system and the variety of regulatory mechanisms...

BACTERIAL HEAVY METAL RESISTANCE: New Surprises

Abstract: Bacterial plasmids encode resistance systems for toxic metal ions including Ag+, AsO2-, AsO4(3-), Cd2+, CO2+, CrO4(2-), Cu2+, Hg2+, Ni2+, Pb2+, Sb3+, TeO3(2-), Tl+, and Zn2+. In addition to understanding of the molecular genetics and environmental roles of these resistances, studies during the last few years have provided surprises and new biochemical mechanisms. Chromosomal determinants of toxic metal resistances are known, and the distinction between plasmid resistances and those from chromosomal genes has blurred, because for some metals (notably mercury and arsenic), the plasmid and chromosomal determinants are basically the same. Other systems, such as copper transport ATPases and metallothionein cation-binding proteins, are only known from chromosomal genes. The largest group of metal resistance systems function by energy-dependent efflux of toxic ions. Some of the efflux systems are ATPases and others are chemiosmotic cation/proton antiporters. The CadA cadmium resistance ATPase of gram-positive bacteria and the CopB copper efflux system of Enterococcus hirae are homologous to P-type ATPases of animals and plants. The CadA ATPase protein has been labeled with 32P from gamma-32P-ATP and drives ATP-dependent Cd2+ uptake by inside-out membrane vesicles. Recently isolated genes defective in the human hereditary diseases of copper metabolism, Menkes syndrome and Wilson's disease, encode P-type ATPases that are more similar to the bacterial CadA and CopB ATPases than to eukaryote ATPases that pump different cations. The arsenic resistance efflux system transports arsenite, using alternatively either a two-component (ArsA and ArsB) ATPase or a single polypeptide (ArsB) functioning as a chemiosmotic transporter. The third gene in the arsenic resistance system, arsC, encodes an enzyme that converts intracellular arsenate [As (V)] to arsenite [As (III)], the substrate of the efflux system. The three-component Czc (Cd2+, Zn2+, and CO2+) chemiosmotic efflux pump of soil microbes consists of inner membrane (CzcA), outer membrane (CzcC), and membrane-spanning (CzcB) proteins that together transport cations from the cytoplasm across the periplasmic space to the outside of the cell. Finally, the first bacterial metallothionein (which by definition is a small protein that binds metal cations by means of numerous cysteine thiolates) has been characterized in cyanobacteria.

The 2.0 Å crystal structure of a heterotrimeric G protein

Abstract: The structure of a heterotrimeric G protein reveals the mechanism of the nucleotide-dependent engagement of the alpha and beta gamma subunits that regulates their interaction with receptor and effector molecules. The interaction involves two distinct interfaces and dramatically alters the conformation of the alpha but not of the beta gamma subunits. The location of the known sites for post-translational modification and receptor coupling suggest a plausible orientation with respect to the membrane surface and an activated heptahelical receptor.

Appetite-suppressant drugs and the risk of primary pulmonary hypertension. International Primary Pulmonary Hypertension Study Group

Abstract: Background Recently in France, primary pulmonary hypertension developed in a cluster of patients exposed to derivatives of fenfluramine in appetite suppressants (anorexic agents), which are used for weight control. We investigated the potential role of anorexic agents and other suspected risk factors for primary pulmonary hypertension. Methods In a case–control study, we assessed 95 patients with primary pulmonary hypertension from 35 centers in France, Belgium, the United Kingdom, and the Netherlands and 355 controls recruited from general practices and matched to the patients' sex and age. Results The use of anorexic drugs (mainly derivatives of fenfluramine) was associated with an increased risk of primary pulmonary hypertension (odds ratio with any anorexic-drug use, 6.3; 95 percent confidence interval, 3.0 to 13.2). For the use of anorexic agents in the preceding year, the odds ratio was 10.1 (95 percent confidence interval, 3.4 to 29.9). When anorexic drugs were used for a total of more than three m...

Spectroscopic evidence for a pseudogap in the normal state of underdoped high- T c superconductors

Abstract: IT is well known that BCS mean-field theory is remarkably successful in describing conventional superconductors. A central concept of BCS theory is the energy gap in the electronic excitation spectrum below the superconducting transition temperature, Tc. The gap also serves as the order parameter: quite generally, long-range phase coherence and a non-zero gap go hand-in-hand1. But in underdoped high-Tc superconductors there is considerable evidence that a pseudogap (a suppression of spectral weight) is already formed in the normal state above Tc—first, from studies of the spin excitation spectrum2–5,24, which measure a 'spin gap', and later from a variety of other probes6–10. Here we present a study of underdoped Bi2Sr2CaCu2O8+δ (Bi2212) using angle-resolved photoemission spectroscopy (ARPES), which directly measures the momentum-resolved electron excitation spectrum of the CuO2 planes. We find that a pseudogap with d-wave symmetry opens up in the normal state below a temperature T* > Tc, and develops into the d-wave superconducting gap once phase coherence is established below Tc.

First-Generation College Students: Characteristics, Experiences, and Cognitive Development.

Abstract: This study sought answers to three questions: (1) Do the precollege characteristics of first-generation students differ from those of traditional students? (2) Do first-generation students' college experiences differ from those of other students? (3) What are the educational consequences of any differences on first-year gains in students' reading, math, and critical thinking abilities? Answers come from 2,685 students (825 first-generation and 1,860 traditional students) who entered 23 diverse institutions nationwide in Fall 1992 and who completed one year of study. First-generation students differ from their traditional peers in both entering characteristics and college experiences. Although traditional students make greater net gains in reading during their first year, the two groups gain to about the same degree in math and critical thinking skills. Those gains, however, appear to result from somewhat different experiences.

Effects of gender and age on the levels and circadian rhythmicity of plasma cortisol.

Abstract: Data from rodent studies indicate that cumulative stress exposure may accelerate senescence and offer a theory to explain differences in the rate of aging. Cumulative exposure to glucocorticoids causes hippocampal defects, resulting in an impairment of the ability to terminate glucocorticoid secretion at the end of stress and, therefore, in increased exposure to glucocorticoids which, in turn, further decreases the ability of the hypothalamo-pituitary-adrenal axis to recover from a challenge. However, the consensus emerging from reviews of human studies is that basal corticotropic function is unaffected by aging, suggesting that the negative interaction of stress and aging does not occur in man. In the present study, a total of 177 temporal profiles of plasma cortisol from 90 normal men and 87 women, aged 18-83 yr, were collected from 7 laboratories and reanalyzed. Twelve parameters quantifying mean levels, value and timing of morning maximum and nocturnal nadir, circadian rhythm amplitude, and start and end of quiescent period were calculated for each individual profile. In both men and women, mean cortisol levels increased by 20-50% between 20-80 yr of age. Premenopausal women had slightly lower mean levels than men in the same age range, primarily because of lower morning maxima. The level of the nocturnal nadir increased progressively with aging in both sexes. An age-related elevation in the morning acrophase occurred in women, but not in men. The diurnal rhythmicity of cortisol secretion was preserved in old age, but the relative amplitude was dampened, and the timing of the circadian elevation was advanced. We conclude that there are marked gender-specific effects of aging on the levels and diurnal variation of human adrenocorticotropic activity, consistent with the hypothesis of the "wear and tear" of lifelong exposure to stress. The alterations in circadian amplitude and phase could be involved in the etiology of sleep disorders in the elderly.

Superoxide production in rat hippocampal neurons: selective imaging with hydroethidine

Abstract: Digital-imaging microfluorimetry of the oxidation of hydroethidine (HEt) to ethidium can be used to monitor superoxide (O2-) production selectively within individual rat hippocampal pyramidal neurons in culture and in brain slices. Under assay conditions, oxidation was not accomplished by hydroxyl radical, singlet O2, H2O2, or nitrogen radicals. Neuronal O2- production varied with metabolic activity and age. O2- generation increased after treatment with AMPA, kainic acid, and NMDA, and the mitochondrial uncoupler carbonylcyanide p-(trifluoromethoxy)phenyl hydrazone, but usually not after depolarization (50 mM K+). O2- concentrations were sensitive to scavengers and nitric oxide. HEt oxidation was higher in Ca(2+)-containing versus Ca(2+)-free saline. However, Ca2+ ionophores did not increase oxidation greatly. H2O2 application produced a secondary increase in O2-. The major source of O2- under basal and stimulated conditions appeared to be the mitochondria. Consistent with this, ethidium staining in dendrites was punctate, colocalized with mitochondria, and blocked by CN-.

CTLA-4 ligation blocks CD28-dependent T cell activation.

Abstract: CTLA-4 is a CD28 homologue believed to be a negative regulator of T cell function. However, the mechanism of this downregulatory activity is not well understood. The present study was designed to examine the effect of CTLA-4 ligation on cytokine production, cell survival, and cell cycle progression. The results demonstrate that the primary effect of CTLA-4 ligation is not the induction of apoptosis. Instead, CTLA-4 signaling blocks IL-2 production, IL-2 receptor expression, and cell cycle progression of activated T cells. Moreover, the effect of CTLA-4 signaling was manifested after initial T cell activation. Inhibition of IL-2 receptor expression and cell cycle progression was more pronounced at late (72 h) time points after initial activation. The effects of anti-CTLA-4 mAbs were most apparent in the presence of optimal CD28-mediated costimulation consistent with the finding that CTLA-4 upregulation was CD28-dependent. Finally, the addition of exogenous IL-2 to the cultures restored IL-2 receptor expression and T cell proliferation. These results suggest that CTLA-4 signaling does not regulate cell survival or responsiveness to IL-2, but does inhibit CD28-dependent IL-2 production.

The Role of Perceptions of Prejudice and Discrimination on the Adjustment of Minority Students to College

Abstract: College participation by minority students declined in the middle 1980s following a period of sustained growth [21]. This trend was particularly evident among African Americans and Hispanics [46] who exhibited both the lowest participation rates as well as the highest propensity to drop out from college. Porter's [45] analyses of the high-school senior class of 1980, for instance, revealed that Hispanic college students were 13 percent more prone to withdraw from college than were white students, whereas African American college students were 22 percent more likely to drop out than their white counterparts over a six-year period. These low persistence rates (even over extended periods of enrollment in college) are particularly troublesome from a policy perspective given the relationship that the attainment of a bachelor's degree has on subsequent occupational and economic attainment [44]. Several reasons have been advanced to account for these trends. Hauser and Anderson [21] explored the extent to which declines in college participation rates could be attributed to changes in college aspirations as well as to changes in high-school completion rates among African Americans. After analyzing college aspiration trends for both minorities and nonminorities over a period of thirty years and taking into account high-school completion rates and indicators of socioeconomic status, Hauser and Anderson could not find support for this hypothesis. Other researchers have speculated that the decline could be attributed to changes in the composition of federal assistance and to patterns of financing higher education exhibited by minority students. Porter [45] noted that declines in minorities' college participation rates correlated with the growth of student loans at the expense of grants. Olivas [41], Mortenson and Wu [31], and Mortenson [30] observed that African American and Hispanic students were less willing to go into debt to finance their college education than were white students. Moreover, Ekstrom [19] helped to establish and test the proposition that students willing to go into debt to finance their education were more likely to enroll and persist in college. An alternative explanation to the role of finances in the persistence process has stressed the influence of academic preparation for college. Tinto [56] argued that overall differences in persistence rates between minorities and nonminorities were primarily due to differences in their academic preparedness rather than differences in their socioeconomic backgrounds. Tinto further contended that these ability differences arise from prior educational experiences at the elementary and secondary educational levels which tend to favor the educational achievement of nonminorities relative to minorities. Some degree of support has been given to this hypothesis. St. John, Kirshstein, and Noell [50], for instance, reported that the effects of ethnicity disappeared once academic preparation for college was taken into account for the high-school class of 1980. The proposition that a lack of adjustment to predominantly white institutions and that perceptions of prejudice (racial climate) may lower the quality of college experiences of minority students has emerged as a competing explanation for the differences in persistence rates between minority and nonminority college students [for example, 1, 18, 23, 24, 28, 34, 35, 36, 53]. Fleming [18], in particular, has argued that adjustment problems with the curriculum, lack of support services, financial problems and the nature of interpersonal relationships with faculty, peers and academic staff are some of the experiences that negatively impact minority students attending predominantly white institutions. Likewise, Tracey and Sedlacek [57, 58, 59] have contended that noncognitive factors (that is, self-concept, an understanding of racism, and the ability to cope with it) play a more critical role in shaping academic performance in college and persistence decisions among minority students than do cognitive factors such as academic ability and study habits. …

Exploring the Limits of the New Institutionalism: The Causes and Consequences of Illegitimate Organizational Change

Abstract: While the new institutionalism has emerged as a dominant theory of organization-environment relations, very little research has examined its possible limits. Under what circumstances might the neoinstitutional predictions regarding organizational inertia, institutional isomorphism, the legitimacy imperative, and other fundamental beliefs be overshadowed by more traditional sociological theories accentuating organizational adaptation, variation, and the role of specific global and local technical environmental demands? We analyze longitudinal data from 1971 to 1986 for 631 private liberal arts colleges facing strong institutional and increasingly strong technical environments. Our findings reveal surprisingly little support for neoinstitutional predictions: (1) Many liberal arts colleges changed in ways contrary to institutional demands by professionalizing or vocationalizing their curricula; (2) global and local technical environmental conditions, such as changes in consumers' preferences and local economic and demographic differences, were strong predictors of the changes observed; (3) schools became less, rather than more, homogeneous over time; (4) schools generally did not mimic their most prestigious counterparts; (5) the illegitimate changes had no negative (and often had positive) performance consequences for enrollment and survival. Our results suggest that current research on organization-environment relations may underestimate the power of traditional adaptation-based explanations in organizational sociology

Crystal structure of a G-protein beta gamma dimer at 2.1A resolution

Abstract: Many signalling cascades use seven-helical transmembrane receptors coupled to heterotrimeric G proteins (G alpha beta gamma) to convert extracellular signals into intracellular responses. Upon nucleotide exchange catalysed by activated receptors, heterotrimers dissociate into GTP-bound G alpha subunits and G beta gamma dimers, either of which can modulate many downstream effectors. Here we use multiwavelength anomalous diffraction data to solve the crystal structure of the beta gamma dimer of the G protein transducin. The beta-subunit is primarily a seven-bladed beta-propeller that is partially encircled by an extended gamma-subunit. The beta-propeller, which contains seven structurally similar WD repeats, defines the stereochemistry of the WD repeat and the probable architecture of all WD-repeat-containing domains. The structure details interactions between G protein beta- and gamma-subunits and highlights regions implicated in effector modulation for the conserved family of G protein beta gamma dimers.

Prevalence of Psychiatric Disorders Among Incarcerated Women: I. Pretrial Jail Detainees

Abstract: Background: There are little epidemiologic data on psychiatric disorders of women in jails. Accurate data on female jail detainees are critical because of their increasing numbers and their unique treatment needs. Methods: Using the Diagnostic Interview Schedule, independent interviewers assessed a randomly selected, stratified sample of 1272 female jail detainees awaiting trial in Chicago, Ill. We tabulated lifetime and 6-month prevalence rates of disorders by race or ethnicity (African American, non-Hispanic white, Hispanic), age, and education and compared the jail rates with general population rates for women in the Epidemiologic Catchment Area program. We also examined whether or not psychiatric disorder was associated with the severity of the detainee's current arrest charges. Results: Over 80% of the sample met criteria for one or more lifetime psychiatric disorders; 70% were symptomatic within 6 months of the interview. The most common disorders were drug abuse or dependence, alcohol abuse or dependence, and post-traumatic stress disorder. Major depressive episode was the most prevalent major mental disorder. Rates were generally highest among non-Hispanic whites and among older detainees. Rates for all disorders were significantly higher than general population rates, except for schizophrenia. Most detainees with psychiatric disorders were arrested for nonviolent crimes. Conclusion: These results suggest substantial psychiatric morbidity among female jail detainees.

Immune responses to transgene–encoded proteins limit the stability of gene expression after injection of replication–defective adenovirus vectors

Abstract: The use of replication–defective adenoviruses (RDAd) for human gene therapy has been limited by host immune responses that result in transient recombinant gene expression in vivo. It remained unclear whether these immune responses were directed predominantly against viral proteins or, alternatively, against foreign transgene–encoded proteins. In this report, we have compared the stability of recombinant gene expression in adult immunocompetent mice following intramuscular (i.m.) injection with identical RDAd encoding self (murine) or foreign (human) erythropoietin. Our results demonstrate that immune responses directed against foreign transgene–encoded proteins are the major determinants of the stability of gene expression following i.m. injection of RDAd. Moreover, we demonstrate long–term recombinant gene expression in immunocompetent animals following a single i.m. injection of RDAd encoding a self protein. These findings are important for the design of future preclinical and clinical gene therapy trials.

Geometric categories and o-minimal structures

Abstract: The theory of subanalytic sets is an excellent tool in various analytic-geometric contexts; see, for example, Bierstone and Milman [1]. Regrettably, certain “nice” sets—like { (x, x) : x > 0 } for positive irrational r, and { (x, e−1/x) : x > 0 }—are not subanalytic (at the origin) in R. Here we make available an extension of the category of subanalytic sets that has these sets among its objects, and that behaves much like the category of subanalytic sets. The possibility of doing this emerged in 1991 when Wilkie [27] proved that the real exponential field is “model complete”, followed soon by work of Ressayre, Macintyre, Marker and the authors; see [21], [5], [7] and [19]. However, there are two obstructions to the use by geometers of this development: (i) while the proofs in these articles make essential use of model theory, many results are also stated there (efficiently, but unnecessarily) in model-theoretic terms; (ii) the results of these papers apply directly only to the cartesian spaces R, and not to arbitrary real analytic manifolds. Consequently, in order to carry out our goal we recast here some results in those papers—as well as many of their consequences—in more familiar terms, with emphasis on results of a geometric nature, and allowing arbitrary (real analytic) manifolds as ambient spaces. We thank W. Schmid and K. Vilonen for their suggestion that this would be a useful undertaking; indeed, they gave us a “wish list” (inspired by Chapters 8 and 9 of Kashiwara and Schapira [12]; see also §10 of [22]) which strongly influenced the form and content of this paper. We axiomatize in Section 1 the notion of “behaving like the category of subanalytic sets” by introducing the notion of “analytic-geometric category”. (The category Can of subanalytic sets is the “smallest” analytic-geometric category.) We also state in Section 1 a number of properties shared by all analytic-geometric categories. Proofs of the more difficult results of this nature, like the Whitney-stratifiability of sets and maps in such a category, often involve the use of charts to reduce to the case of subsets of R. For subsets of R, there already exists the theory of “o-minimal structures on the real field” (defined in Section 2); this subject is developed in detail in [4] and is an abstraction of

National Culture and New Product Development: An Integrative Review:

Abstract: The increasing globalization of markets and businesses and the criticality of new products to business performance make the relationship between national culture and new product development an impo...

Prevalence Rates and Correlates of Psychiatric Disorders among Preschool Children

Abstract: Objective To determine the prevalence and correlates of psychiatric disorders among preschool children in a primary care pediatric sample. Method In a two-stage design, 3,860 preschool children were screened; 510 received fuller evaluations. Results For quantitative assessment of disorder (90th percentile), prevalence of behavior problems was 8.3%. "Probable" occurrence of an Axis I DSM-III-R disorder was 21.4% (9.1%, severe). Logistic regression analyses indicated significant demographic correlates for quantitative outcomes (older age, minority status, male sex, low socioeconomic status, father absence, small family size) but not for DSM-III-R diagnoses. Maternal and family characteristics were generally not significant. Child correlates included activity level, timidity, persistence, and IQ. Conclusions Overall prevalence of disorder was consistent with rates for older children; correlates varied by approach used for classification.

Ceramics in dentistry: historical roots and current perspectives

Abstract: This article presents a brief history of dental ceramics and offers perspectives on recent research aimed at the further development of ceramics for clinical use, at their evaluation and selection, and very importantly, their clinical performance. Innovative ceramic materials and ceramics processing strategies that were introduced to restorative dentistry since the early 1980s are discussed. Notable research is highlighted regarding (1) wear of ceramics and opposing enamel, (2) polishability of porcelains, (3) influence of firing history on the thermal expansion of porcelains for metal ceramics, (4) machining and CAD/CAM as fabrication methods for clinical restorations, (5) fit of ceramic restorations, (6) clinical failure mechanisms of all-ceramic prostheses, (7) chemical and thermal strengthening of dental ceramics, (8) intraoral porcelain repair, and (9) criteria for selection of the various ceramics available. It is found that strong scientific and collaborative foundations exist for the continued understanding and improvement of dental ceramic systems.

Dietary soybean protein prevents bone loss in an ovariectomized rat model of osteoporosis

Abstract: The purpose of this study was to examine whether soybean protein isolate prevents bone loss induced by ovarian hormone deficiency. Thirty-two 95-d-old Sprague-Dawley rats were randomly assigned to four treatment groups [sham-operated (sham); ovariectomized (ovx); ovx+soybean; ovx + 17 beta-estradiol (E2)] and killed after 30 d. Rats in the sham, ovx and ovx + 17 beta-estradiol groups were fed a casein-based diet, and the soybean group was fed soybean protein isolate instead of casein; the diets were otherwise comparable. Rats in the ovx group had significantly lower densities of the right femur (P < 0.001) and the fourth lumbar vertebra (P < 0.05) than rats in the sham group. These lower bone densities were not observed in animals receiving 17 beta-estradiol or fed soybean. The ovx group also had significantly (P < 0.01) greater serum concentrations of 1,25-dihydroxycholecalciferol than the other three groups. Our findings suggest that dietary soybean protein is effective in preventing bone loss due to ovarian hormone deficiency. Because serum activities of both alkaline phosphatase and tartrate-resistant acid phosphatase were significantly greater in the ovx group and in the ovx + soybean group but not in the group receiving 17 beta-estradiol, compared with sham animals, this confirms that ovariectomy enhances and 17 beta-estradiol suppresses the rate of bone turnover. Despite the higher rate of bone turnover in the soybean-fed animals, the vertebral and femoral bone densities of these rats were significantly greater than those of rats in the ovx group, suggesting that formation exceeded resorption. Further studies are needed to clarify whether this protective effect on bone is due to the protein itself or to the presence of isoflavones in soybean protein.

Genesis and Variability of [ PSI ] Prion Factors in Saccharomyces cerevisiae

Abstract: We have previously shown that multicopy plasmids containing the complete SUP35 gene are able to induce the appearance of the non-Mendelian factor [ PSI ]. This result was later interpreted by others as a crucial piece of evidence for a model postulating that [ PSI ] is a self-modified, prion-like conformational derivative of the Sup35 protein. Here we support this interpretation by proving that it is the overproduction of Sup35 protein, and not the excess of SUP35 DNA or mRNA that causes the appearance of [ PSI ]. We also show that the “prion-inducing domain” of Sup35p is in the N-terminal region, which, like the “prion-inducing domain” of another yeast prion, Ure2p, was previously shown to be distinct from the functional domain of the protein. This suggests that such a chimeric organization may be a common pattern of some prion elements. Finally, we find that [ PSI ] factors of different efficiencies and different mitotic stabilities are induced in the same yeast strain by overproduction of the identical Sup35 protein. We suggest that the different [ PSI ]-containing derivatives are analogous to the mysterious mammalian prion strains and result from different conformational variants of Sup35p.

Lacunarity analysis: A general technique for the analysis of spatial patterns

Abstract: Lacunarity analysis is a multiscaled method for describing patterns of spatial dispersion. It can be used with both binary and quantitative data in one, two, and three dimensions. Although originally developed for fractal objects, the method is more general and can be readily used to describe nonfractal and multifractal patterns. Lacunarity analysis is broadly applicable to many data sets used in the natural sciences; we illustrate its application to both geological and ecological data. {copyright} {ital 1996 The American Physical Society.}

Influences on students' openness to diversity and challenge in the first year of college

Abstract: It appears clear that diversity comprises a central aspect of America's future. According to a 1989 Census Bureau projection, during the next four decades (1990-2030), the white population of the United States will grow by about 25 percent. During that same 40-year period, the African-American population will increase by 68 percent, the Asian-American, Pacific Island-American, and American Indian populations will grow by 79 percent, and the Latino or Hispanic population of the United States will leap by 187 percent.... The Population Reference Bureau has projected that, by the year 2080, the United States of America may well be 24 percent Latino, 15 percent African-American, and 12 percent Asian American--more than half of the nation's population [15]. If the trends projected above represent the country's future demographic reality, then it is likely that future college graduates will be challenged by a society that is increasingly diverse in terms of race, culture, and values. It seems reasonable, therefore, to be concerned with identifying the ways in which American postsecondary institutions engender in students a greater openness to racial, cultural, and value diversity. A substantial amount of inquiry has addressed the issue of the impact of college on attitudes, values, and the ways in which individuals relate to their external world. While only indirectly related to openness to racial, cultural, and value diversity, the weight of evidence from this research suggests that during college, students tend to change in the direction of greater openness and tolerance. From freshman to senior year, students become less authoritarian, dogmatic, and ethnocentric [7, 8, 10, 11, 13, 16, 17, 18, 20, 23, 26, 27, 28, 31, 40].They also demonstrate statistically significant shifts in the direction of greater social, racial, ethnic, and political tolerance and greater support for individual rights [5, 6, 9, 21, 22, 24, 25, 29, 30, 38, 39, 41, 43]. Moreover, as Pascarella and Terenzini [35] point out in their synthesis of the literature on college impact, the evidence is reasonably clear that on most of the above dimensions a statistically significant part of the change observed can be attributed to college attendance itself, above and beyond that attributable to normal maturation or to societal changes. Another line of inquiry has attempted to identify the specific college experiences that influence changes in values, attitudes, and the ways in which individuals relate to their external world. Perhaps the clearest generalization that can be made from this evidence is that it is the student's interpersonal environment (for example, the frequency and nature of his or her interactions with peers and faculty) that has the greatest impact on value, attitudinal and psychosocial change during college [for example, 4, 12, 19, 35]. Of course, a major shortcoming of the existing body of evidence is that it fails to address directly the impact of specific dimensions of the college experience on students' appreciation and acceptance of cultural, racial, and value diversity. What research does exist has investigated the extent to which diversity and multiculturalism on campus influence other outcomes of college. This work was conducted by Astin [3, 4] in his analysis of 25,000 students attending 217 four-year colleges and universities between 1985 and 1989. Controlling for important precollege characteristics and other potential confounding influences, he found that three different measures of diversity (institutional diversity emphasis, faculty diversity emphasis, and direct student experience with diversity) had significant positive impacts on a number of salient college outcomes. For example, the extent to which an institution emphasized and supported racial and multicultural diversity among faculty and students had a positive impact on an individual student's commitment to promoting racial understanding. …

Ultrafast Computed Tomography as a Diagnostic Modality in the Detection of Coronary Artery Disease A Multicenter Study

Abstract: Background Ultrafast computed tomography (CT), by acquiring images of the proximal coronary arteries, detects coronary calcifications and has been demonstrated to be highly sensitive for the detection of coronary artery disease in many small studies. The aim of this study was to determine the relationship between ultrafast CT scanning and coronary angiography in a large number of symptomatic patients. Methods and Results The study population consisted of 710 patients from six participating centers. A multivariate logistic regression model was used to evaluate the individual contributions of age, number of calcified vessels, and the calcium score for the probability of angiographically significant disease. Of the 710 patients enrolled, 427 patients had significant angiographic disease, and coronary calcification was detected in 404, yielding a sensitivity of 95%. Of the 23 patients without calcifications, 19 (83%) had single-vessel disease at angiography. Of the 283 patients without angiographically signif...

Naturally Occurring Truncated trkB Receptors Have Dominant Inhibitory Effects on Brain-Derived Neurotrophic Factor Signaling

Abstract: trkB encodes a receptor tyrosine kinase activated by three neurotrophins--brain-derived neurotrophic factor (BDNF), neurotrophin-3, and neurotrophin-4/5. In vivo, three isoforms of the receptor are generated by differential splicing--gp145trkB or the full-length trkB receptor, and trkB.T1 and trkB.T2, two cytoplasmically truncated receptors that lack kinases, but contain unique C termini. Although the truncated receptors appear to be precisely regulated during nervous system development and regeneration, their role in neurotrophin signaling has not been directly tested. In this paper, we studied the signaling properties and interactions of gp145trkB, trkB.T1, and trkB.T2 by expressing the receptors in a Xenopus oocyte microinjection assay. We found that oocytes expressing gp145trkB, but not trkB.T1 or trkB.T2, were capable of eliciting 45Ca efflux responses (a phospholipase C-gamma-mediated mechanism) after stimulation by BDNF. When trkB.T1 and trkB.T2 were coexpressed with gp145trkB, they acted as dominant negative receptors, inhibiting the BDNF signal by forming nonfunctional heterodimers with the full-length receptors. An ATP-binding mutant of gp145trkB had similar dominant inhibitory effects. Our data suggest that naturally occurring truncated trkB receptors function as inhibitory modulators of neurotrophin responsiveness. Furthermore, the homodimerization of gp145trkB appears to be an essential step in activation of the BDNF signaling cascade.