Showing papers by "New York University published in 1989"

A theory for multiresolution signal decomposition: the wavelet representation

Abstract: Multiresolution representations are effective for analyzing the information content of images. The properties of the operator which approximates a signal at a given resolution were studied. It is shown that the difference of information between the approximation of a signal at the resolutions 2/sup j+1/ and 2/sup j/ (where j is an integer) can be extracted by decomposing this signal on a wavelet orthonormal basis of L/sup 2/(R/sup n/), the vector space of measurable, square-integrable n-dimensional functions. In L/sup 2/(R), a wavelet orthonormal basis is a family of functions which is built by dilating and translating a unique function psi (x). This decomposition defines an orthogonal multiresolution representation called a wavelet representation. It is computed with a pyramidal algorithm based on convolutions with quadrature mirror filters. Wavelet representation lies between the spatial and Fourier domains. For images, the wavelet representation differentiates several spatial orientations. The application of this representation to data compression in image coding, texture discrimination and fractal analysis is discussed. >

Regression and time series model selection in small samples

Abstract: SUMMARY A bias correction to the Akaike information criterion, AIC, is derived for regression and autoregressive time series models. The correction is of particular use when the sample size is small, or when the number of fitted parameters is a moderate to large fraction of the sample size. The corrected method, called AICC, is asymptotically efficient if the true model is infinite dimensional. Furthermore, when the true model is of finite dimension, AICC is found to provide better model order choices than any other asymptotically efficient method. Applications to nonstationary autoregressive and mixed autoregressive moving average time series models are also discussed.

Top management and innovations in banking: Does the composition of the top team make a difference?

Abstract: The relationship between the social composition of top management teams and innovation adoptions was examined in a sample of 199 banks. The following characteristics of top management teams were examined: average age, average tenure in the firm, education level, and heterogeneity with respect to age, tenure, educational background, and functional background. In addition, the effects of bank size, location (state of operation), and team size were assessed. Results indicate that more innovative banks are managed by more educated teams who are diverse with respect to their functional areas of expertise. These relationships remain significant when organizational size, team size, and location are controlled for.

Multifrequency channel decompositions of images and wavelet models

Abstract: The author reviews recent multichannel models developed in psychophysiology, computer vision, and image processing. In psychophysiology, multichannel models have been particularly successful in explaining some low-level processing in the visual cortex. The expansion of a function into several frequency channels provides a representation which is intermediate between a spatial and a Fourier representation. The author describes the mathematical properties of such decompositions and introduces the wavelet transform. He reviews the classical multiresolution pyramidal transforms developed in computer vision and shows how they relate to the decomposition of an image into a wavelet orthonormal basis. He discusses the properties of the zero crossings of multifrequency channels. Zero-crossing representations are particularly well adapted for pattern recognition in computer vision. >

Simple fast algorithms for the editing distance between trees and related problems

Abstract: Ordered labeled trees are trees in which the left-to-right order among siblings is significant. The distance between two ordered trees is considered to be the weighted number of edit operations (in...

A randomized trial comparing ticlopidine hydrochloride with aspirin for the prevention of stroke in high-risk patients. Ticlopidine Aspirin Stroke Study Group.

Abstract: We report the results of the Ticlopidine Aspirin Stroke Study, a blinded trial at 56 North American centers that compared the effects of ticlopidine hydrochloride (500 mg daily) with those of aspirin (1300 mg daily) on the risk of stroke or death. The medications were randomly assigned to 3069 patients with recent transient or mild persistent focal cerebral or retinal ischemia. Follow-up lasted for two to six years. The three-year event rate for nonfatal stroke or death from any cause was 17 percent for ticlopidine and 19 percent for aspirin--a 12 percent risk reduction (95 percent confidence interval, -2 to 26 percent) with ticlopidine (P = 0.048 for cumulative Kaplan-Meier estimates). The rates of fatal and nonfatal stroke at three years were 10 percent for ticlopidine and 13 percent for aspirin--a 21 percent risk reduction (95 percent confidence interval, 4 to 38 percent) with ticlopidine (P = 0.024 for cumulative Kaplan-Meier estimates). Ticlopidine was more effective than aspirin in both sexes. The adverse effects of aspirin included diarrhea (10 percent), rash (5.5 percent), peptic ulceration (3 percent), gastritis (2 percent), and gastrointestinal bleeding (1 percent). With ticlopidine, diarrhea (20 percent), skin rash (14 percent), and severe but reversible neutropenia (less than 1 percent) were noted. The mean increase in total cholesterol level was 9 percent with ticlopidine and 2 percent with aspirin (P less than 0.01). The ratios of high-density lipoprotein and low-density lipoprotein to total cholesterol were similar in both treatment groups. We conclude that ticlopidine was somewhat more effective than aspirin in preventing strokes in this population, although the risks of side effects were greater.

Recent developments in the cell biology of basic fibroblast growth factor.

Abstract: Revue sur les connaissances actuelles concernant la biologie des facteurs de croissance basiques: biosynthese, localisation, activites biologiques, proteines associees, potentiel transformant, recepteurs, liberation, interactions avec les matrices

Inhibition of endothelial cell movement by pericytes and smooth muscle cells: activation of a latent transforming growth factor-beta 1-like molecule by plasmin during co-culture.

Abstract: When a confluent monolayer of bovine aortic endothelial (BAE) cells is wounded with a razor blade, endothelial cells (ECs) spontaneously move into the denuded area. If bovine pericytes or smooth muscle cells (SMCs) are plated into the denuded area at low density, they block the movement of the ECs. This effect is dependent upon the number of cells plated into the wound area and contact between ECs and the plated cells. Antibodies to transforming growth factor-beta 1 (TGF-beta 1) abrogate the inhibition of BAE cell movement by pericytes or SMCs. TGF-beta 1, if added to wounded BAE cell monolayers, also inhibits cell movement. When cultured separately, BAE cells, pericytes, and SMCs each produce an inactive TGF-beta 1-like molecule which is activated in BAE cell-pericyte or BAE cell-SMC co-cultures. The activation appears to be mediated by plasmin as the inhibitory effect on cell movement in co-cultures of BAE cells and pericytes is blocked by the inclusion of inhibitors of plasmin in the culture medium.

Organizational Characteristics as Predictors of Personnel Practices.

Abstract: This study investigated the relationship between organizational context characteristics and personnel practices. The following organizational characteristics were hypothesized to influence personnel practices: industry sector, the pursuit of innovation as a competitive strategy, manufacturing technology, and organizational structure. In addition, organizational size and unionization were examined. Results based upon data obtained from 267 organizations provided support for the general hypothesis that personnel practices vary as a function of organizational characteristics. In addition to interorganizational differences in personnel practices, this study illustrates that large intraorganiza-tional differences exist with respect to the practices used for managerial and hourly employees. Implications and future research needs are described.

Has anything changed? Current characterizations of men, women, and managers.

Abstract: Replication et extension de la recherche de Schein (1973) sur la description des hommes, des femmes, en tant que tels ou comme managers ou managers a succes, par 268 managers utilisant un inventaire d'attributs a 92 items pour evaluer un des sept groupes cibles. La proximite de l'image de manager avec celle de chaque role sexuel est en particulier commentee

DNA topoisomerase I--targeted chemotherapy of human colon cancer in xenografts

Abstract: Drug development is needed to improve chemotherapy of patients with locally advanced or metastatic colon carcinoma, who otherwise have an unfavorable prognosis. DNA topoisomerase I, a nuclear enzyme important for solving topological problems arising during DNA replication and for other cellular functions, has been identified as a principal target of a plant alkaloid 20(S)-camptothecin. Significantly increased concentrations of this enzyme, compared to that in normal colonic mucosa, were found in advanced stages of human colon adenocarcinoma and in xenografts of colon cancer carried by immunodeficient mice. Several synthetic analogs of camptothecin, selected by tests with the purified enzyme and tissue-culture screens, were evaluated in the xenograft model. Unlike other anticancer drugs tested, 20(RS)-9-amino-camptothecin (9-AC) induced disease-free remissions. The overall drug toxicity was low and allowed for repeated courses of treatment.

IL-6 inhibits lipopolysaccharide-induced tumor necrosis factor production in cultured human monocytes, U937 cells, and in mice.

Abstract: Incubation of the human U937 histiocytic lymphoma cell line with granulocyte-macrophage colony stimulating factor (GM-CSF) rendered the cells responsive to induction of TNF by LPS. Treatment with IL-6 reduced TNF production in GM-CSF-primed U937 cells. The inhibitory effect was most pronounced (approximately equal to 80%) when IL-6 was added either along with GM-CSF or within the first 3 h of GM-CSF treatment. Both GM-CSF or IL-6 inhibited [3H]TdR uptake in U937 cells, and simultaneous treatment with GM-CSF and IL-6 resulted in an additive inhibitory effect on cell proliferation. However, the inhibition of TNF production could not be explained by the inhibitory effect of IL-6 on cell growth, nor was it due to a reduction in cell viability. An inhibition of TNF production by IL-6 was also demonstrated in cultured human peripheral blood monocytes. Treatment with IL-6 also resulted in a dose-dependent reduction of the 17-kDa TNF band revealed by SDS-PAGE after labeling monocytes with [35S]cysteine and immunoprecipitation with anti-TNF mAb. In addition, treatment with IL-6 resulted in a reduction of monocyte in vitro cytotoxicity for tumor target cells. Finally, in mice sensitized by the administration of Bacillus Calmette-Guerin, the injection of IL-6 significantly reduced the levels of TNF found in the serum upon challenge with LPS. Inasmuch as TNF is known to be an inducer of IL-6, the inhibitory action of IL-6 on TNF production may represent the negative arm of a regulatory circuit. The inhibitory action of IL-6 on TNF production is consistent with a predominantly antiinflammatory role of IL-6 in the intact organism.

Self-discrepancy theory: What patterns of self-beliefs cause people to suffer?

Abstract: Publisher Summary The basic premise of self-discrepancy theory is that it is the relations between and among different types of self-beliefs or self-state representations that produce emotional vulnerabilities rather than the particular content or nature of the actual self or of any other individual self-belief. To distinguish among different types of self-state representations, self-discrepancy theory proposes two psychological parameters: the domains of the self and the standpoints on the self. The chapter presents the reports of associations between particular types of discrepant self-beliefs and particular kinds of discomfort that are generally consistent with the predictions of self-discrepancy theory. However, the effect of the magnitude of different types of self-discrepancies on the intensity of different kinds of discomfort has been tested. For the vulnerability associated with a particular self-belief pattern to eventuate in an episode—that is, an occurrence of suffering—the self-belief pattern must be activated. The chapter explains the various factors that can increase the likelihood that a stored construct will be activated. One source of activation is the applicability of the construct to a stimulus event. According to self-discrepancy theory, the interrelations among attributes constituting an actual/ownself-guide discrepancy represent, as a whole, a negative psychological situation that functions as a construct. Thus, the negative psychological situation represented by such a discrepancy and the emotional-motivational state associated with it are more likely to be activated when the negative psychological situation is applicable to a stimulus event than when it is nonapplicable.

Blocking and isolation of a calcium channel from neurons in mammals and cephalopods utilizing a toxin fraction (FTX) from funnel-web spider poison

Abstract: A Ca2+-channel blocker derived from funnel-web spider toxin (FTX) has made it possible to define and study the ionic channels responsible for the Ca2+ conductance in mammalian Purkinje cell neurons and the preterminal in squid giant synapse. In cerebellar slices, FTX blocked Ca2+-dependent spikes in Purkinje cells, reduced the spike afterpotential hyperpolarization, and increased the Na+-dependent plateau potential. In the squid giant synapse, FTX blocked synaptic transmission without affecting the presynaptic action potential. Presynaptic voltage-clamp results show blockage of the inward Ca2+ current and of transmitter release. FTX was used to isolate channels from cerebellum and squid optic lobe. The isolated product was incorporated into black lipid membranes and was analyzed by using patch-clamp techniques. The channel from cerebellum exhibited a 10- to 12-pS conductance in 80 mM Ba2+ and 5-8 pS in 100 mM Ca2+ with voltage-dependent open probabilities and kinetics. High Ba2+ concentrations at the cytoplasmic side of the channel increased the average open time from 1 to 3 msec to more than 1 sec. A similar channel was also isolated from squid optic lobe. However, its conductance was higher in Ba2+, and the maximum opening probability was about half of that derived from cerebellar tissue and also was sensitive to high cytoplasmic Ba2+. Both channels were blocked by FTX, Cd2+, and Co2+ but were not blocked by omega-conotoxin or dihydropyridines. These results suggest that one of the main Ca2+ conductances in mammalian neurons and in the squid preterminal represents the activation of a previously undefined class of Ca2+ channel. We propose that it be termed the "P" channel, as it was first described in Purkinje cells.

The P450 Superfamily: Updated Listing of All Genes and Recommended Nomenclature for the Chromosomal Loci

Abstract: In this update we provide a list of the 71 P450 genes and the four P450 pseudogenes that have been characterized as of September 30, 1988. The chromosomal locations of many of these genes are also summarized. A modest revision of the initially proposed nomenclature of the P450 superfamily (Nebert et al., DNA 6, 1–11, 1987) is described specifically for the human and mouse chromosomal loci. The motivation for this revision is to conform to the rules of nomenclature for human and mouse genes. Recommendations for the naming of chromosomal loci include the root symbol "CYP" for human ("Cyp" for mouse), denoting "cytochrome P450." We recommend that this root also be used for other organisms. For a chromosomal locus, the root symbol is followed by an Arabic numeral designating the P450 family, a letter indicating the sub-family, and an Arabic numeral representing the individual gene within the family or subfamily. Numbers of the individual genes usually will be assigned in the order the genes are ident...

Cognitive-Emotional Interactions in the Brain

Abstract: Emotion and cognition are mediated by separate but interacting systems of the brain. The core of the emotional system is a network that evaluates (computes) the biological significance of stimuli, including stimuli from the external or internal environment or from within the brain (thoughts, images, memories). The computation of stimulus significance takes place prior to and independent of conscious awareness, with only the computational products reaching awareness, and only in some instances. The amygdala may be a focal structure in the affective network. By way of neural interactions between the amygdala and brain areas involved in cognition (particularly the neocortex and hippocampus), affect can influence cognition and cognition can influence affect. Emotional experiences, it is proposed, result when stimulus representations, affect representations, and self representations coincide in working memory.

Subthreshold Na + -dependent theta-like rhythmicity in stellate cells of entorhinal cortex layer II

Abstract: THE oscillation of membrane potential in mammalian central neurons is of interest because it relates to the role of oscillations in brain function. It has been proposed that the entorhinal cortex (EC), particularly the stellate cells of layer II (ECIIscs), plays an important part in the genesis of the theta rhythm1–3. These neurons occupy a key position in the neocortex-hippocampus-neocortex circuit, a crucial crossroad in memory functions4,5. Neuronal oscillations typically rely on the activation of voltage-dependent Ca2+ conductances and the Ca2+-dependent K+ conductance that usually follows6,7, as seen in other limbic subcortical structures generating theta rhymicity8–10. Here we report, however, that similar oscillations are generated in ECIIscs by a Na+ conductance. The finding of a subthreshold, voltage-gated, Na+-dependent rhythmic membrane oscillation in mammalian neurons indicates that rhythmicity in heterogeneous neuronal networks may be supported by different sets of intrinsic ionic mechanisms in each of the neuronal elements involved.

Cloned cytotoxic T cells recognize an epitope in the circumsporozoite protein and protect against malaria

Abstract: PROTECTIVE immunity against malaria is induced by vaccination of hosts with irradiation-attenuated sporozoites. This immunity is mediated in part by neutralizing antibodies that are directed mainly against the repeat domain of the circumsporozoite protein1–4. Early experiments showed, however, that B-cell-depleted mice that are immunized with sporozoites can resist challenge, indicating that T-cell effector mechanisms may also have a role in protection5. This idea was supported by the recent observation that protective immunity also requires T-cells expressing the CDS antigen (CD8+ T cells) 6,7, whose target is probably the developing liver-stage parasites8–10. Moreover, an oral Salmonella vaccine that expresses the circumsporozoite protein is able to protect against murine malaria in the absence of antibodies11. Here we report the identification of an epitope contained within amino acids 249–260 of the Plasmodium berghei circumsporozoite protein that is recognized by H–2Kd-restricted cytotoxic T cells12,13. Passive transfer into mice of cytotoxic-T-cell clones that recognize this epitope conferred a high degree of protection against challenge. These results provide the first direct evidence that CD8+ T cells that are specific for a defined epitope can confer protection against a parasitic infection.

Transformation of biphasic calcium phosphate ceramics in vivo: ultrastructural and physicochemical characterization.

Abstract: Specially prepared biphasic calcium phosphate (BCP) macroporous ceramics consisting of an intimate association of beta tricalcium phosphate (beta-TCP) and hydroxyapatite (HA) with beta-TCP/HA weight ratios of 15/85, 35/65, and 85/15 were implanted in surgically created periodontal osseous defects in dogs and recovered after 6 months. A decrease in average size of crystals in BCP ceramics and an increase in the size of microporosities in the surface and at the core of the ceramic after implantation were observed, indicating that in vivo dissolution has taken place. The resorbability (reflecting in vivo dissolution) of BCP ceramics depended on their beta-TCP/HA ratios, the higher the ratio, the greater the resorbability. The formation of microcrystals with crystallographic properties and Ca/P ratio similar to those of bone apatite crystals were also observed. The abundance of these crystals were directly related to the beta-TCP/HA ratio of the BCP ceramic before implantation. The formation of the bone apatite-like crystals may be due to the precipitation of calcium and phosphate ions released from the dissolving ceramic crystals (the beta-TCP component dissolving preferentially to the HA component). Results from this study suggested that one of the means of controlling resorbability (in vivo dissolution) of BCP ceramic is by varying its beta-TCP/HA ratio.

In vitro angiogenesis on the human amniotic membrane: requirement for basic fibroblast growth factor-induced proteinases.

Abstract: The role of basic fibroblast growth factor-(bFGF) induced proteinases in basement membrane (BM) invasion by bovine capillary endothelial (BCE) cells was studied using a quantitative in vitro assay previously described (Mignatti et al., 1986). 125I-iododeoxyuridine-labeled BCE cells were grown for 72 h on the human amnion BM, and cell invasion was determined by measuring the radioactivity associated with the tissue after removal of the noninvasive cell layer. BCE cells were noninvasive under normal conditions. Addition of human bFGF to either the BM or to the stromal aspect of the amnion induced BCE cell invasion with a dose-dependent response. This effect was maximal in the presence of 70 ng/ml bFGF, and was inhibited by anti-FGF antibody. Transforming growth factor beta, as well as plasmin inhibitors and anti-tissue type plasminogen activator antibody inhibited BCE cell invasion. The tissue inhibitor of metalloproteinases, 1-10 phenanthroline, anti-type IV and anti-interstitial collagenase antibodies had the same effect. On the contrary, anti-stromelysin antibody and Eglin, an inhibitor of elastase, were ineffective. The results obtained show that both the plasminogen activator-plasmin system and specific collagenases are involved in the invasive process occurring during angiogenesis.

Cytoplasmic activation of ISGF3, the positive regulator of interferon-alpha-stimulated transcription, reconstituted in vitro.

Abstract: The signal transduction pathway through which interferon-alpha (IFN alpha) stimulates transcription of a defined set of genes involves activation of DNA-binding factors specific for the IFN alpha-stimulated response element (ISRE). IFN-stimulated gene factor-3 (ISGF3), the positive regulator of transcription, was derived in response to IFN alpha treatment from preexisting protein components that were activated first in the cell cytoplasm prior to appearance in the nucleus. Nuclear translocation of ISGF3 required several minutes and could be inhibited by NaF. Formation of active ISGF3 was mimicked in vitro by mixing cytoplasmic extracts from IFN alpha-stimulated cells with extracts of cells treated to contain high amounts of the unactivated factor. Active ISGF3 was found to be formed from association of two latent polypeptide precursors that were distinguished biochemically by differential sensitivity to N-ethyl maleimide. One precursor was modified in response to IFN alpha occupation of its cell-surface receptor, thus enabling association with the second subunit. The resulting complex then was competent for nuclear translocation and binding to ISRE. Cytoplasmically localized transcription factor precursors thus serve as second messengers to translate directly an extracellular signal into specific transcriptional activity in the nucleus.

Regime Types and International Conflict, 1816-1976

Abstract: This study replicates and extends previous inquiries on the relations between regime type and conflict involvement of states. It examines the robustness of previous findings with respect to various regime attributes, various conflict involvement measures, and units of analysis. Using two comprehensive datasets on polity characteristics and militarized interstate disputes, the empirical analyses reveal: (1) There are no relations between regime type and conflict involvement measures when the unit of analysis is the individual polity (i.e., a state characterized by a certain regime type over a given time span); this finding is robust in that it holds over most regime characteristics and conflict involvement measures. (2) There is a significant relationship between the regime characteristics of a dyad and the probability of conflict involvement of that dyad: Democracies rarely clash with one another, and never fight one another in war. (3) Both the proportion of democratic dyads and the proportion of autocra...

The mechanisms of action of nonsteroidal antiinflammatory drugs.

Abstract: In mammalian species and in the oldest of multicellular animal forms, NSAIDs inhibit cell activation, apparently in the absence of effects on PG biosynthesis. Thus, an alternative hypothesis can be proposed to account for the antiinflammatory effects of these drugs. Clearly, at low doses aspirin and most of the newer NSAIDs inhibit the biosynthesis of PGs from arachidonic acid, and stable PGs have been shown to mediate fever, hyperalgesia, vasodilation (edema), and several interleukin-1-dependent responses. At high doses, however, aspirin, sodium salicylate, and the newer NSAIDs (at antiinflammatory doses) inhibit non-PG-dependent processes, such as the activity of a variety of enzymes, proteoglycan synthesis by chondrocytes, transmembrane ion fluxes, and chemoattractant binding. These effects are most likely due to the capacity of aspirin-like drugs to insert into the lipid bilayer of plasma membranes, where they disrupt normal signaling events and protein-protein interactions. The ability of NSAIDs to thereby inhibit the activation of inflammatory cells such as the neutrophil may contribute to the antiinflammatory properties of this class of drugs.