Showing papers by "University of Southern California published in 1991"

Identification of FAP locus genes from chromosome 5q21

Abstract: Recent studies suggest that one or more genes on chromosome 5q21 are important for the development of colorectal cancers, particularly those associated with familial adenomatous polyposis (FAP). To facilitate the identification of genes from this locus, a portion of the region that is tightly linked to FAP was cloned. Six contiguous stretches of sequence (contigs) containing approximately 5.5 Mb of DNA were isolated. Subclones from these contigs were used to identify and position six genes, all of which were expressed in normal colonic mucosa. Two of these genes (APC and MCC) are likely to contribute to colorectal tumorigenesis. The MCC gene had previously been identified by virtue of its mutation in human colorectal tumors. The APC gene was identified in a contig initiated from the MCC gene and was found to encode an unusually large protein. These two closely spaced genes encode proteins predicted to contain coiled-coil regions. Both genes were also expressed in a wide variety of tissues. Further studies of MCC and APC and their potential interaction should prove useful for understanding colorectal neoplasia.

neural networks and fuzzy systems a dynamical systems approach to machine intelligence

Abstract: This work combines neural networks and fuzzy systems, presenting neural networks as trainable dynamical systems and developing mechanisms and principles of adaption, self-organization, convergence and global stability. It includes the new geometric theory of fuzzy sets, systems and associated memories, and shows how to apply fuzzy set theory to adaptive control and how to generate structured fuzzy systems with unsupervised neural techniques.

Object modeling by registration of multiple range images

Abstract: The problem of creating a complete model of a physical object is studied. Although this may be possible using intensity images, the authors use range images which directly provide access to three-dimensional information. The first problem that needs to be solved is to find the transformation between the different views. Previous approaches have either assumed this transformation to be known (which is extremely difficult for a complete model) or computed it with feature matching (which is not accurate enough for integration. The authors propose an approach that works on range data directly and registers successive views with enough overlapping area to get an accurate transformation between views. This is performed by minimizing a functional that does not require point-to-point matches. Details are given of the registration method and modeling procedure, and they are illustrated on range images of complex objects. >

Effect of Oral Milrinone on Mortality in Severe Chronic Heart Failure

Abstract: Background. Milrinone, a phosphodiesterase inhibitor, enhances cardiac contractility by increasing intracellular levels of cyclic AMP, but the long-term effect of this type of positive inotropic agent on the survival of patients with chronic heart failure has not been determined. Methods. We randomly assigned 1088 patients with severe chronic heart failure (New York Heart Association class III or IV) and advanced left ventricular dysfunction to double-blind treatment with 40 mg of oral milrinone daily (561 patients) or placebo (527 patients). In addition, all patients received conventional therapy with digoxin, diuretics, and a converting-enzyme inhibitor throughout the trial. The median period of follow-up was 6.1 months (range, 1 day to 20 months). Results. As compared with placebo, milrinone therapy was associated with a 28 percent increase in mortality from all causes (95 percent confidence interval, 1 to 61 percent; P = 0.038) and a 34 percent increase in cardiovascular mortality (95 percent...

The SPQ: A Scale for the Assessment of Schizotypal Personality Based on DSM-III-R Criteria

Abstract: Existing self-report measures of schizotypal personality assess only one to three of the nine traits of schizotypal personality disorder. This study describes the development of the Schizotypal Personality Questionnaire (SPQ), a self-report scale modeled on DSM-III-R criteria for schizotypal personality disorder and containing subscales for all nine schizotypal traits. Two samples of normal subjects (w •= 302 and n = 195) were used to test replicability of findings. The SPQ was found to have high sampling validity, high internal reliability (0.91), test-retest reliability (0.82), convergent validity (0.59 to 0.81), discriminant validity, and criterion validity (0.63, 0.68), findings which were replicated across samples. Fifty-five percent of subjects scoring in the top 10 percent of SPQ scores had a clinical diagnosis of schizotypal personality disorder. Thus, the SPQ may be useful in screening for schizotypal personality disorder in the general population and also in researching the correlates of individual schizotypal traits.

Tutorial on higher-order statistics (spectra) in signal processing and system theory: theoretical results and some applications

Abstract: A compendium of recent theoretical results associated with using higher-order statistics in signal processing and system theory is provided, and the utility of applying higher-order statistics to practical problems is demonstrated. Most of the results are given for one-dimensional processes, but some extensions to vector processes and multichannel systems are discussed. The topics covered include cumulant-polyspectra formulas; impulse response formulas; autoregressive (AR) coefficients; relationships between second-order and higher-order statistics for linear systems; double C(q,k) formulas for extracting autoregressive moving average (ARMA) coefficients; bicepstral formulas; multichannel formulas; harmonic processes; estimates of cumulants; and applications to identification of various systems, including the identification of systems from just output measurements, identification of AR systems, identification of moving-average systems, and identification of ARMA systems. >

Tuberculosis in Patients with Human Immunodeficiency Virus Infection

Abstract: Tuberculosis remains an important problem in patients with human immunodeficiency virus (HIV) infection in the United States, with an estimated 6000 to 9000 new cases annually.1 The case rates are extraordinarily high among indigent patients and substance abusers, and one third of these patients are also infected with HIV.2 Much has been learned about the pathogenesis, clinical presentation, treatment, and prevention of tuberculosis in HIV-infected persons over the past several years. We summarize recent developments in these areas, as well as the effects of new antiretroviral therapies on antituberculosis regimens. HIV Infection and Susceptibility to Tuberculosis HIV-infected persons are at . . .

Abrupt deep-sea warming, palaeoceanographic changes and benthic extinctions at the end of the Palaeocene

Abstract: A remarkable oxygen and carbon isotope excursion occurred in Antarctic waters near the end of the Palaeocene (~57.33 Myr ago), indicating rapid global warming and oceanographic changes that caused one of the largest deep-sea benthic extinctions of the past 90 million years. In contrast, the oceanic plankton were largely unaffected, implying a decoupling of the deep and shallow ecosystems. The data suggest that for a few thousand years, ocean circulation underwent fundamental changes producing a transient state that, although brief, had long-term effects on environmental and biotic evolution.

Defining protective responses to pathogens: cytokine profiles in leprosy lesions

Abstract: The immunological mechanisms required to engender resistance have been defined in few infectious diseases of man, and the role of specific cytokines is unclear. Leprosy presents clinically as a spectrum in which resistance correlates with cell-mediated immunity to the pathogen. To assess in situ cytokine patterns, messenger RNA extracted from leprosy skin biopsy specimens was amplified by the polymerase chain reaction with 14 cytokine-specific primers. In lesions of the resistant form of the disease, messenger RNAs coding for interleukin-2 and interferon-gamma were most evident. In contrast, messenger RNAs for interleukin-4, interleukin-5, and interleukin-10 predominated in the multibacillary form. Thus, resistance and susceptibility were correlated with distinct patterns of cytokine production.

A Single Intravenous Infusion of Gamma Globulin as Compared with Four Infusions in the Treatment of Acute Kawasaki Syndrome

Abstract: Background. Treatment of acute Kawasaki syndrome with a four-day course of intravenous gamma globulin, together with aspirin, has been demonstrated to be safe and effective in preventing coronary-artery lesions and reducing systemic inflammation. We hypothesized that therapy with a single, very high dose of gamma globulin would be at least as effective as the standard regimen. Methods. We conducted a multicenter, randomized, controlled trial involving 549 children with acute Kawasaki syndrome. The children were assigned to receive gamma globulin either as a single infusion of 2 g per kilogram of body weight over 10 hours or as daily infusions of 400 mg per kilogram for four consecutive days. Both treatment groups received aspirin (100 mg per kilogram per day through the 14th day of illness, then 3 to 5 mg per kilogram per day). Results. The relative prevalence of coronary abnormalities, adjusted for age and sex, among patients treated with the four-day regimen, as compared with those treated with...

Now out of Never: The Element of Surprise in the East European Revolution of 1989

Abstract: Like many major revolutions in history, the East European Revolution of 1989 caught its leaders, participants, victims, and observers by surprise. This paper offers an explanation whose crucial feature is a distinction between private and public preferences. By suppressing their antipathies to the political status quo, the East Europeans misled everyone, including themselves, as to the possibility of a successful uprising. In effect, they conferred on their privately despised governments an aura of invincibility. Under the circumstances, public opposition was poised to grow explosively if ever enough people lost their fear of exposing their private preferences. The currently popular theories of revolution do not make clear why uprisings easily explained in retrospect may not have been anticipated. The theory developed here fills this void. Among its predictions is that political revolutions will inevitably continue to catch the world by surprise.

Identification of p53 gene mutations in bladder cancers and urine samples

Abstract: Although bladder cancers are very common, little is known about their molecular pathogenesis. In this study, invasive bladder cancers were evaluated for the presence of gene mutations in the p53 suppressor gene. Of 18 tumors evaluated, 11 (61 percent) were found to have genetic alterations of p53. The alterations included ten point mutations resulting in single amino acid substitutions, and one 24-base pair deletion. In all but one case, the mutations were associated with chromosome 17p allelic deletions, leaving the cells with only mutant forms of the p53 gene products. Through the use of the polymerase chain reaction and oligomer-specific hybridization, p53 mutations were identified in 1 to 7 percent of the cells within the urine sediment of each of three patients tested. The p53 mutations are the first genetic alterations demonstrated to occur in a high proportion of primary invasive bladder cancers. Detection of such mutations ex vivo has clinical implications for monitoring individuals whose tumor cells are shed extracorporeally.

The Use of Influence Strategies in Interfirm Relationships in Industrial Product Channels

Abstract: The authors seek to extend theory and empirical findings on interfirm influence strategies by examining their use in channel relationships between suppliers and distributors of industrial products....

Multimarket Trading and Market Liquidity

Abstract: When a security trades at multiple locations simultaneously, an informed trader has several avenues in which to exploit his private information. The greater the proportion of liquidity trading by "large" traders who can split their trades across markets, the larger is the correlation between volume in different markets and the smaller is the informativeness of prices. We show that one of the markets emerges as the dominant location for trading in that security. When informed traders can use their information for more than one trading period, the timely release of price information by market makers at one location adversely affects the profits informed traders expect to make subsequently at other locations. Market makers, competing to offer the lowest cost of trading at their location, consequently deter informed trading be voluntarily making the price information public and by "cracking down" on insider trading. Article published by Oxford University Press on behalf of the Society for Financial Studies in its journal, The Review of Financial Studies.

Promotion of central cholinergic and dopaminergic neuron differentiation by brain-derived neurotrophic factor but not neurotrophin 3.

Abstract: Recombinant human brain-derived neurotrophic factor (rhBDNF) and neurotrophin 3 (rhNT-3), two recently cloned molecules closely related to nerve growth factor (NGF), were produced from human cDNA expressed in human embryonic kidney cells. The recombinant proteins were tested in cultures of dissociated fetal rat brain cells containing basal forebrain cholinergic neurons. rhBDNF stimulated the differentiation of the cholinergic neurons, similar to NGF, which is well established as a neurotrophic factor for these cells. However, rhBDNF was particularly effective during the first few days in vitro, whereas the stimulatory action of rhNGF was more pronounced later in the development of the cultures. This finding indicates the existence of different time periods of responsiveness of the cholinergic neurons to BDNF and NGF. To assess the selectivity of the effect of rhBDNF on cholinergic neurons, its actions were tested in cultures of ventral mesencephalon containing dopaminergic cells. In contrast to NGF, which does not affect central dopaminergic neurons, rhBDNF increased dopamine uptake activity. The findings suggest that BDNF stimulates survival or differentiation of other cells besides the cholinergic neurons.

Decreased Mortality in Users of Estrogen Replacement Therapy

Abstract: In a prospective study of 8881 postmenopausal female residents of a retirement community in southern California, we evaluated in detail the relationship between estrogen use and overall mortality. After 71/2 years of follow-up, there had been 1447 deaths. Women with a history of estrogen use had 20% lower age-adjusted, all-cause mortality than lifetime nonusers (95% confidence interval, 0.70 to 0.87). Mortality decreased with increasing duration of use and was lower among current users than among women who used estrogens only in the distant past. Current users with more than 15 years of estrogen use had a 40% reduction in their overall mortality. Among oral estrogen users, relative risks of death could not be distinguished by specific dosages of the oral estrogen taken for the longest time. Women who had used estrogen replacement therapy had a reduced mortality from all categories of acute and chronic arteriosclerotic disease and cerebrovascular disease. This group of women had a reduced mortality from cancer, although this reduction was not statistically significant. The mortality from all remaining causes combined was the same in estrogen users and lifetime nonusers. (Arch Intern Med.1991;151:75-78)

Narrative and Self-Concept

Abstract: When the self is thought of as a narrative or story, rather than a substance or thing, the temporal and dramatic dimension of human existence is emphasized. The operation of narrative "emplotment" (Ricoeur, 1983/1984) can configure the diverse events and actions of one's life into a meaningful whole. One's self-concept or self-identity is fashioned by adaptation of plots from one's cul-tural stock of stories and myths. Stories of personal identity differ from literary productions in that they are constructed within an unfolding autobiography and incorporate the accidental events and unintended consequences of actions. Under stressful conditions, a self-narrative may decompose, producing the anxiety and depression of meaninglessness. One function of psychotherapy is to assist in the reconstruction of a meaning-giving narrative of self-identity. (Psychology)

Stock Price Clustering and Discreteness

Abstract: Stock prices cluster on round fractions. Clustering increases with price level and volatility, and decreases with capitalization and transaction frequency. Clustering is pervasive. Price clustering will occur if traders use discrete price sets to simplify their negotiations. Exchange regulations require that most stocks be traded on eighths. Clustering on larger fractions will occur if traders choose to use discrete price sets based on quarters, halves, or whole numbers. An econometric model of clustering is derived and estimated. Projections from the results suggest that traders would frequently use odd sixteenths when trading low-price stocks, if exchange regulations permitted trading on sixteenths. Article published by Oxford University Press on behalf of the Society for Financial Studies in its journal, The Review of Financial Studies.

Scaled test statistics and robust standard errors for non-normal data in covariance structure analysis: a Monte Carlo study.

Abstract: Research studying robustness of maximum likelihood (ML) statistics in covariance structure analysis has concluded that test statistics and standard errors are biased under severe non-normality. An estimation procedure known as asymptotic distribution free (ADF), making no distributional assumption, has been suggested to avoid these biases. Corrections to the normal theory statistics to yield more adequate performance have also been proposed. This study compares the performance of a scaled test statistic and robust standard errors for two models under several non-normal conditions and also compares these with the results from ML and ADF methods. Both ML and ADF test statistics performed rather well in one model and considerably worse in the other. In general, the scaled test statistic seemed to behave better than the ML test statistic and the ADF statistic performed the worst. The robust and ADF standard errors yielded more appropriate estimates of sampling variability than the ML standard errors, which were usually downward biased, in both models under most of the non-normal conditions. ML test statistics and standard errors were found to be quite robust to the violation of the normality assumption when data had either symmetric and platykurtic distributions, or non-symmetric and zero kurtotic distributions.

Second neoplasms after acute lymphoblastic leukemia in childhood.

Abstract: Background. Effective forms of treatment for acute lymphoblastic leukemia (ALL) in childhood now result in survival rates above 70 percent at five years, but the treatments are potentially carcinogenic. To determine the magnitude of this risk and identify possible risk factors for the development of second neoplasms, we studied a large cohort of children treated for ALL. Methods and Results. We undertook a retrospective cohort study of 9720 children who had been given a diagnosis of ALL between June 1972 and August 1988 and had been treated according to the therapeutic protocols of the Children's Cancer Study Group. The median follow-up was 4.7 years (range, 2 months to 16 years). We found that 43 second neoplasms occurred among the children in the cohort, including 24 neoplasms of the central nervous system, 10 new leukemias and lymphomas, and 9 other neoplasms. This represented a 7-fold excess of all cancers and a 22-fold excess of neoplasms of the central nervous system. The estimated cumulati...

Organizational Learning Curves: A Method for Investigating Intra-Plant Transfer of Knowledge Acquired Through Learning by Doing

Abstract: This paper illustrates how a learning-curve model can be generalized to investigate potential explanations of organizational learning. The paper examines the hypothesis that knowledge acquired through by learning by doing is embodied in an organization's technology by analyzing the amount of transfer that occurs across shifts within a plant. If knowledge becomes completely embodied in technology, transfer across shifts should be complete since both shifts use the same technology. Methods that can be used for studying intra-plant transfer of knowledge are presented. The methods are illustrated by analyzing data from a plant that began production with one shift and then added a second shift several months into the production program. Three aspects of transfer are analyzed: 1 carry forward of knowledge when the plant makes the transition from one to two shifts, 2 transfer across shifts after both shifts are operating, and 3 transfer across time. Results indicate that substantial, but less than complete, transfer of knowledge occurred when the second shift was introduced. Once both shifts were operating, partial transfer across them occurred. Implications of the results for a theory of organizational learning and practical applications are discussed.