Showing papers by "New York University published in 1991"

Survival in Patients with Primary Pulmonary Hypertension: Results from a National Prospective Registry

Abstract: Objective To characterize mortality in persons diagnosed with primary pulmonary hypertension and to investigate factors associated with survival. Design Registry with prospective follow-up. Setting Thirty-two clinical centers in the United States participating in the Patient Registry for the Characterization of Primary Pulmonary Hypertension supported by the National Heart, Lung, and Blood Institute. Patients Patients (194) diagnosed at clinical centers between 1 July 1981 and 31 December 1985 and followed through 8 August 1988. Measurements At diagnosis, measurements of hemodynamic variables, pulmonary function, and gas exchange variables were taken in addition to information on demographic variables, medical history, and life-style. Patients were followed for survival at 6-month intervals. Main results The estimated median survival of these patients was 2.8 years (95% Cl, 1.9 to 3.7 years). Estimated single-year survival rates were as follows: at 1 year, 68% (Cl, 61% to 75%); at 3 years, 48% (Cl, 41% to 55%); and at 5 years, 34% (Cl, 24% to 44%). Variables associated with poor survival included a New York Heart Association (NYHA) functional class of III or IV, presence of Raynaud phenomenon, elevated mean right atrial pressure, elevated mean pulmonary artery pressure, decreased cardiac index, and decreased diffusing capacity for carbon monoxide (DLCO). Drug therapy at entry or discharge was not associated with survival duration. Conclusions Mortality was most closely associated with right ventricular hemodynamic function and can be characterized by means of an equation using three variables: mean pulmonary artery pressure, mean right atrial pressure, and cardiac index. Such an equation, once validated prospectively, could be used as an adjunct in planning treatment strategies and allocating medical resources.

Democracy and the Market: Political and Economic Reforms in Eastern Europe and Latin America

Abstract: The quest for freedom from hunger and repression has triggered in recent years a dramatic, worldwide reform of political and economic systems. Never have so many people enjoyed, or at least experimented with democratic institutions. However, many strategies for economic development in Eastern Europe and Latin America have failed with the result that entire economic systems on both continents are being transformed. This major book analyzes recent transitions to democracy and market-oriented economic reforms in Eastern Europe and Latin America. Drawing in a quite distinctive way on models derived from political philosophy, economics, and game theory, Professor Przeworski also considers specific data on individual countries. Among the questions raised by the book are: What should we expect from these experiments in democracy and market economy? What new economic systems will emerge? Will these transitions result in new democracies or old dictatorships?

The Limits of the State: Beyond Statist Approaches and their Critics

Abstract: The state has always been difficult to define. Its boundary with society appears elusive, porous, and mobile. I argue that this elusiveness should not be overcome by sharper definitions, but explored as a clue to the state's nature. Analysis of the literature shows that neither rejecting the state in favor of such concepts as the political system, nor “bringing it back in,” has dealt with this boundary problem. The former approach founders on it, the latter avoids it by a narrow idealism that construes the state-society distinction as an external relation between subjective and objective entities. A third approach, presented here, can account for both the salience of the state and its elusiveness. Reanalyzing evidence presented by recent theorists, state-society boundaries are shown to be distinctions erected internally, as an aspect of more complex power relations. Their appearance can be historically traced to technical innovations of the modern social order, whereby methods of organization and control internal to the social processes they govern create the effect of a state structure external to those processes.

Photonic band structure: The face-centered-cubic case employing nonspherical atoms.

Abstract: We introduce a practical, new, face-centered-cubic dielectric structure which simultaneously solves two of the outstanding problems in photonic band structure. In this new ``photonic crystal'' the atoms are nonspherical, lifting the degeneracy at the W point of the Brillouin zone, and permitting a full photonic band gap rather than a pseudogap. Furthermore, this fully three-dimensional fcc structure lends itself readily to microfabrication on the scale of optical wavelengths. It is created by simply drilling three sets of holes 35.26\ifmmode^\circ\else\textdegree\fi{} off vertical into the top surface of a solid slab or wafer, as can be done, for example, by chemical-beam-assisted ion etching.

Synthesis from DNA of a molecule with the connectivity of a cube

Abstract: A principal goal of biotechnology is the assembly of novel biomaterials for analytical, industrial and therapeutic purposes. The advent of stable immobile nucleic acid branched junctions makes DNA a good candidate for building frameworks to which proteins or other functional molecules can be attached and thereby juxtaposed. The addition of single-stranded 'sticky' ends to branched DNA molecules converts them into macromolecular valence clusters that can be ligated together. The edges of these frameworks are double-helical DNA, and the vertices correspond to the branch points of junctions. Here, we report the construction from DNA of a covalently closed cube-like molecular complex containing twelve equal-length double-helical edges arranged about eight vertices. Each of the six 'faces' of the object is a single-stranded cyclic molecule, doubly catenated to four neighbouring strands, and each vertex is connected by an edge to three others. Each edge contains a unique restriction site for analytical purposes. This is the first construction of a closed polyhedral object from DNA.

Some differences make a difference: Individual dissimilarity and group heterogeneity as correlates of recruitment, promotions, and turnover.

Abstract: Schneider's (1987) attraction-selection-attrition model and Pfeffer's (1983) organization demography model were used to generate individual-level and group-level hypotheses relating interpersonal context to recruitment, promotion, and turnover patterns. Interpersonal context was operationalized as personal dissimilarity and group heterogeneity with respect to age, tenure, education level, curriculum, alma mater, military service, and career experiences. For 93 top management teams in bank holding companies examined over a 4-yr period, turnover rate was predicted by group heterogeneity. For individuals, turnover was predicted by dissimilarity to other group members, but promotion was not. Team heterogeneity was a relatively strong predictor of team turnover rates. Furthermore, reliance on internal recruitment predicted subsequent team homogeneity.

Mild cognitive impairment in the elderly: predictors of dementia.

Abstract: We conducted full diagnostic evaluations, including a comprehensive cognitive assessment battery, of a group of 32 elderly subjects with a clinically identified mild cognitive impairment and a group of 32 age-matched and education-matched normal subjects. The mildly impaired subjects performed significantly more poorly than the controls on tests of recent memory, remote memory, language function, concept formation, and visuospatial praxis. Follow-up evaluations of cognitive status 2 years later revealed clinically detectable cognitive decline relative baseline in 23 (72%) of the mildly impaired subjects. Several of the objective psychological tests accurately discriminated at baseline between the decliners and nondecliners in the mildly impaired group. Among the 20 mildly impaired subjects with no complicating conditions, 16 exhibited cognitive deterioration between baseline and follow-up. These results suggest that most elderly subjects with mild cognitive deficits, as determined by clinical evaluation and objective psychological testing, will manifest the progressive mental deterioration characteristic of dementia and that psychometric predictors can be used to distinguish between benign and more significant underlying disorders in mildly impaired elderly subjects.

Zero-crossings of a wavelet transform

Abstract: The completeness, stability, and application to pattern recognition of a multiscale representation based on zero-crossings is discussed. An alternative projection algorithm is described that reconstructs a signal from a zero-crossing representation, which is stabilized by keeping the value of the wavelet transform integral between each pair of consecutive zero-crossings. The reconstruction algorithm has a fast convergence and each iteration requires O(N log/sup 2/ (N)) computation for a signal of N samples. The zero-crossings of a wavelet transform define a representation which is particularly well adapted for solving pattern recognition problems. As an example, the implementation and results of a coarse-to-fine stereo-matching algorithm are described. >

Promoting systematic processing in low-motivation settings: effect of incongruent information on processing and judgment.

Abstract: Ss received consensus information that was either congruent or incongruent with the valence of persuasive message content. In Experiment 1 Ss believed that their processing task was either important or unimportant whereas in Experiment 2 all Ss believed that their task was unimportant. In accord with the heuristic-systematic model's sufficiency principle, high-task-importance Ss exhibited a great deal of systematic processing regardless of congruency, whereas low-importance Ss processed systematically only when they received incongruent messages; in the congruent conditions heuristic processing dominated. Attitude data generally reflected these processing differences and confirmed the additivity and attenuation assumptions of the model. The utility of the sufficiency principle for understanding motivation for elaborative processing and the relevance of the findings to understanding the processing and judgmental effects of expectancy disconfirmation are discussed.

On the method of moving planes and the sliding method

Abstract: The method of moving planes and the sliding method are used in proving mono- tonicity or symmetry in, say, the zl direction "for solutions of nonlinear elliptic equations F(x, u, Du, D~u) = 0 in a bounded domain (2 in R n which is convex in the Zl direction. Here we present a much simplified approach to these methods; at the same time it yields improved results. For example, for the Dirichlet problem, no regularity of the boundary is assumed. The new approach relies on improved forms of the Maximum Principle in "narrow domains". Several results are also presented in cylindrical domains -- under more general boundary conditions.

The Summary Informativeness of Stock Trades: An Econometric Analysis

Abstract: In a security market with asymmetrically informed participants, trades are signals of private information. In this article, new measures of trade informativeness are proposed based on a decomposition of the variance of changes in the efficient price into trade-correlated and -uncorrelated components. The trade-correlated component has a natural interpretation as an absolute measure of trade informativeness. The ratio of this component to the total variance is a relative measure (i.e., a proportion normalized with respect to the total public information). For a sample NYSE-listed companies, trade are found to be more informative for small firms in both absolute and relative senses. From an analysis of intraday patterns, it appears that trades are in absolute terms more informative at the beginning of trading, but slightly less informative in relative terms. Article published by Oxford University Press on behalf of the Society for Financial Studies in its journal, The Review of Financial Studies.

Methylation-sensitive sequence-specific DNA binding by the c-Myc basic region.

Abstract: The function of the c-Myc oncoprotein and its role in cell growth control is unclear. A basic region of c-Myc is structurally related to the basic motifs of helix-loop-helix (HLH) and leucine zipper proteins, which provide sequence-specific DNA binding function. The c-Myc basic region was tested for its ability to bind DNA by attaching it to the HLH dimerization interface of the E12 enhancer binding factor. Dimers of the chimeric protein, termed E6, specifically bound an E box element (GGCCACGTGACC) recognized by other HLH proteins in a manner dependent on the integrity of the c-Myc basic motif. Methylation of the core CpG in the E box recognition site specifically inhibited binding by E6, but not by two other HLH proteins. Expression of E6 (but not an E6 DNA binding mutant) suppressed the ability of c-myc to cooperate with H-ras in a rat embryo fibroblast transformation assay, suggesting that the DNA recognition specificity of E6 is related to that of c-Myc in vivo.

Tetracyclines inhibit connective tissue breakdown: new therapeutic implications for an old family of drugs.

Abstract: Tetracyclines have long been considered useful adjuncts in peridontal therapy based on their antimicrobial efficacy against putative periodontopathogens. However, recently these drugs were found to inhibit mammalian collagenases and several other matrix metalloproteinases (MMPs) by a mechanism independent of their antimicrobial activity. Evidence is presented that this property may be therapeutically useful in retarding pathologic connective tissue breakdown, including bone resorption. The experiments leading to this discovery are described and possible mechanisms are addressed, including the specificity of tetracyclines' anti-collagenase activity, the role of the drugs' metal ion (Zn2+, Ca2+)- binding capacity, and the site on the tetracycline molecule responsible for this nonantimicrobial property. Of extreme interest, the tetracycline molecule has been chemically modified in multiple ways, generating a new family of compounds called CMTs (chemically modified tetracyclines) that lack antimicrobial but s...

In vitro neurons in mammalian cortical layer 4 exhibit intrinsic oscillatory activity in the 10- to 50-Hz frequency range.

Abstract: We report here the presence of fast subthreshold oscillatory potentials recorded in vitro from neurons within layer 4 of the guinea pig frontal cortex. Two types of oscillatory neurons were recorded: (i) One type exhibited subthreshold oscillations whose frequency increased with membrane depolarization and encompassed a range of 10-45 Hz. Action potentials in this type of neuron demonstrated clear after-hyperpolarizations. (ii) The second type of neuron was characterized by narrow-frequency oscillations near 35-50 Hz. These oscillations often outlasted the initiating depolarizing stimulus. No calcium component could be identified in their action potential. In both types of cell the subthreshold oscillations were tetrodotoxin-sensitive, indicating that the depolarizing phase of the oscillation was generated by a voltage-dependent sodium conductance. The initial depolarizing phase was followed by a potassium conductance responsible for the falling phase of the oscillatory wave. In both types of cell, the subthreshold oscillation could trigger spikes at the oscillatory frequency, if the membrane was sufficiently depolarized. Combining intracellular recordings with Lucifer yellow staining showed that the narrow-frequency oscillatory activity was produced by a sparsely spinous interneuron located in layer 4 of the cortex. This neuron has extensive local axonal collaterals that ramify in layers 3 and 4 such that they may contribute to the columnar synchronization of activity in the 40- to 50-Hz range. Cortical activity in this frequency range has been proposed as the basis for the "conjunctive properties" of central nervous system networks.

Cellular activation of latent transforming growth factor beta requires binding to the cation-independent mannose 6-phosphate/insulin-like growth factor type II receptor.

Abstract: The activation of latent transforming growth factor beta (LTGF-beta) normally seen in cocultures of bovine aortic endothelial and bovine smooth muscle cells can be inhibited by coculturing the cells with either mannose 6-phosphate (Man-6-P) or antibodies directed against the cation-independent Man-6-P/insulin-like growth factor type II receptor (anti-Man-6-PR). This result was established by measuring the ability of coculture conditioned medium (formed with or without Man-6-P or anti-Man-6-PR) to suppress bovine aortic endothelial cell migration and protease production, activities previously shown to be related to transforming growth factor beta activity. The inhibition by Man-6-P is dose dependent, with maximal inhibition seen at 100 microM and is specific because mannose 1-phosphate and glucose 6-phosphate do not interfere with activation of LTGF-beta. The inhibitory effect of anti-Man-6-PR is also specific and dose dependent; maximal inhibition of activation occurs at 400 micrograms/ml. Control experiments indicate that Man-6-P and anti-Man-6-PR do not interfere with the basal level of migration of bovine aortic endothelial cells, the migration observed when exogenous transforming growth factor beta is added, the activation of transforming growth factor beta by plasmin or transient acidification, and the release of LTGF-beta. Thus, binding to the cation-independent Man-6-P/insulin-like growth factor type II receptor appears to be a requirement for activation of LTGF-beta.

Secured Lending and Default Risk: Equilibrium Analysis, Policy Implications and Empirical Results

Abstract: The authors examine collateral in a competitive equilibrium in which borrowers can choose hidden actions and may additionally possess hidden knowledge. Apart from explaining the widespread use of collateral despite deadweight costs, they show that an increase in the riskless interest rate causes equilibrium loan rates and collateral requirements to increase, a decline in the deadweight costs of collateral reduces the equilibrium collateral use under moral hazard, and an increase in the borrower's project size reduces equilibrium collateral use under moral hazard. Some of these predictions are tested and found to be supported by the data. Copyright 1991 by Royal Economic Society.

The Significance of Technical Trading-Rule Profits in the Foreign Exchange Market: a Bootstrap Approach

Abstract: In this paper, we present new evidence on the profitability and statistical significance of technical trading rules in the foreign exchange market. We utilize a new data base, currency futures contracts for the period 1976-1990, and we implement a new testing procedure based on bootstrap methodology. Using this approach, we generate thousands of new exchange rate series constructed by random reordering of each original series. We then measure the profitability of the technical rules for each new series. The significance of the profits in the original series is assessed by comparison to the empirical distribution of results derived from the thousands of randomly generated series. Overall, our results suggest that simple technical trading rules have very often led to profits that are highly unusual. Splitting the entire 15-year sample period into three 5-year periods reveals that on average the profitability of some trading rules declined in the 1986-1990 period although profits remained positive (on average) and significant in many cases.

Comorbidity of psychiatric diagnoses in anorexia nervosa.

Abstract: • The comorbidity of psychiatric diagnoses was examined with the Diagnostic Interview Schedule in 62 women who participated in a 10-year follow-up study of anorexia nervosa. Sixty-two age- and sex-matched controls, their parents, and parents of the anorectic probands were also interviewed with the Diagnostic Interview Schedule. There was a statistically significant comorbidity of the affective and anxiety disorders with anorexia nervosa. The first-degree relatives of the anorectic probands had significantly more alcoholism and total number of psychiatric diagnoses compared with the first-degree relatives of controls. There were two mothers with bulimia nervosa, two cases of anorexia nervosa and two of bulimia nervosa in other first-degree relatives of anorectic probands, and no cases of eating disorders in the first-degree relatives of controls.

A new vascularized bone graft for scaphoid nonunion

Abstract: Nonunion and avascular necrosis after scaphoid fractures continue to be problem sequelae because of unrecognized injuries, inadequate immobilization techniques, or insufficient treatment time. Screw fixation and inlay bone grafting techniques remain the options of choice, with successful union reported in approximately 90% of patients. However, prolonged immobilization with plaster up to 4 to 6 months is required with conventional techniques. With the use of standard latex injection techniques with vascular filling of vessels to less than 0.1 mm diameter in ten fresh cadaver dissections, we discovered a consistent vascularized bone graft source from the distal dorsoradial radius. We have used this vascularized bone graft source with good results in eleven patients with long-standing nonunion of the scaphoid. It is technically easy and seemingly offers the advantages of a decreased period of immobilization and a higher union rate.

Magnetic field tomography of coherent thalamocortical 40-Hz oscillations in humans

Abstract: This paper introduces the use of magnetic field tomography (MFT), a noninvasive technique based on distributed source analysis of magnetoencephalography data, which makes possible the three-dimensional reconstruction of dynamic brain activity in humans. MFT has a temporal resolution better than 1 msec and a spatial accuracy of 2-5 mm at the cortical level, which deteriorates to 1-3 cm at depths of 6 cm or more. MFT is used here to visualize the origin of a spatiotemporally organized pattern of coherent 40-Hz electrical activity. This coherence, initially observed during auditory input, was proposed to be generated by recurrent corticothalamic oscillation. In support of this hypothesis, we illustrate well-defined 40-Hz coherence between cortical-subcortical sites with a time shift that is consistent with thalamocortical conduction times. Studies on Alzheimer patients indicate that, while a similar activity pattern is present, the cortical component is reduced in these subjects.

A tyrosine-phosphorylated carboxy-terminal peptide of the fibroblast growth factor receptor (Flg) is a binding site for the SH2 domain of phospholipase C-gamma 1.

Abstract: Phospholipase C-gamma (PLC-gamma) is a substrate of the fibroblast growth factor receptor (FGFR; encoded by the flg gene) and other receptors with tyrosine kinase activity. It has been demonstrated that the src homology region 2 (SH2 domain) of PLC-gamma and of other signalling molecules such as GTPase-activating protein and phosphatidylinositol 3-kinase-associated p85 direct their binding toward tyrosine-autophosphorylated regions of the epidermal growth factor or platelet-derived growth factor receptor. In this report, we describe the identification of Tyr-766 as an autophosphorylation site of flg-encoded FGFR by direct sequencing of a tyrosine-phosphorylated tryptic peptide isolated from the cytoplasmic domain of FGFR expressed in Escherichia coli. The same phosphopeptide was found in wild-type FGFR phosphorylated either in vitro or in living cells. Like other growth factor receptors, tyrosine-phosphorylated wild-type FGFR or its cytoplasmic domain becomes associated with intact PLC-gamma or with a fusion protein containing the SH2 domain of PLC-gamma. To delineate the site of association, we have examined the capacity of a 28-amino-acid tryptic peptide containing phosphorylated Tyr-766 to bind to various constructs containing SH2 and other domains of PLC-gamma. It is demonstrated that the tyrosine-phosphorylated peptide binds specifically to the SH2 domain but not to the SH3 domain or other regions of PLC-gamma. Hence, Tyr-766 and its flanking sequences represent a major binding site in FGFR for PLC-gamma. Alignment of the amino acid sequences surrounding Tyr-766 with corresponding regions of other FGFRs revealed conserved tyrosine residues in all known members of the FGFR family. We propose that homologous tyrosine-phosphorylated regions in other FGFRs also function as binding sites for PLC-gamma and therefore are involved in coupling to phosphatidylinositol breakdown.