Showing papers by "Johns Hopkins University published in 1988"
TL;DR: This article discusses extensions of generalized linear models for the analysis of longitudinal data in which heterogeneity in regression parameters is explicitly modelled and uses a generalized estimating equation approach to fit both classes of models for discrete and continuous outcomes.
Abstract: This article discusses extensions of generalized linear models for the analysis of longitudinal data. Two approaches are considered: subject-specific (SS) models in which heterogeneity in regression parameters is explicitly modelled; and population-averaged (PA) models in which the aggregate response for the population is the focus. We use a generalized estimating equation approach to fit both classes of models for discrete and continuous outcomes. When the subject-specific parameters are assumed to follow a Gaussian distribution, simple relationships between the PA and SS parameters are available. The methods are illustrated with an analysis of data on mother's smoking and children's respiratory disease.
4,303 citations
TL;DR: In this paper, a self-reported measure of pubertal status was used to assess the transition from childhood to adolescence in a longitudinal study of 335 young adolescent boys and girls.
Abstract: Puberty is a central process in the complex set of changes that constitutes the transition from childhood to adolescence. Research on the role of pubertal change in this transition has been impeded by the difficulty of assessing puberty in ways acceptable to young adolescents and others involved. Addressing this problem, this paper describes and presents norms for a selfreport measure of pubertal status. The measure was used twice annually over a period of three years in a longitudinal study of 335 young adolescent boys and girls. Data on a longitudinal subsample of 253 subjects are reported. The scale shows good reliability, as indicated by coefficient alpha. In addition, several sources of data suggest that these reports are valid. The availability of such a measure is important for studies, such as those based in schools, in which more direct measures of puberty may not be possible.
2,602 citations
TL;DR: It was found that self-reported psychological job demands, work control, and co-worker social support combined greater then multiplicatively in relation to CVD prevalence.
Abstract: This cross-sectional study investigates the relationship between the psychosocial work environment and cardiovascular disease (CVD) prevalence in a randomly selected, representative sample of 13,779 Swedish male and female workers. It was found that self-reported psychological job demands, work control, and co-worker social support combined greater then multiplicatively in relation to CVD prevalence. An age-adjusted prevalence ratio (PR) of 2.17 (95% CI-1.32, 3.56) was observed among workers with high demands, low control, and low social support compared to a low demand, high control, and high social support reference group. PRs of approximately 2.00 were observed in this group after consecutively controlling for the effects of age together with 11 other potential confounding factors. The magnitude of the age-adjusted PRs was greatest for blue collar males. Due to the cross-sectional nature of the study design, causal inferences cannot be made. The limitations of design and measurement are discussed in th...
2,451 citations
TL;DR: Specified regions of the myocardium can be labeled in magnetic resonance (MR) imaging to serve as markers during contraction, thus permitting sampling of the entire contractile phase of the cardiac cycle.
Abstract: Specified regions of the myocardium can be labeled in magnetic resonance (MR) imaging to serve as markers during contraction. The technique is based on locally perturbing the magnetization of the myocardium with selective radio-frequency (RF) saturation of multiple, thin tag planes during diastole followed by conventional, orthogonal-plane imaging during systole. The technique was implemented on a 0.38-T imager and tested on phantoms and volunteers. In humans, tags could be seen 60-450 msec after RF saturation, thus permitting sampling of the entire contractile phase of the cardiac cycle. Tagged regions appear as hypointense stripes, and their patterns of displacement reflect intervening cardiac motion. In addition to simple translation and rotation, complex motions such as cardiac twist can be demonstrated. The effects of RF pulse angle, relaxation times, and heart rate on depiction of the tagged region are discussed.
1,506 citations
TL;DR: It is concluded from computational experiments on real and artificial structures that no method based solely on local information in the protein sequence is likely to produce significantly better results for non-homologous proteins.
1,237 citations
Journal Article•
1,217 citations
TL;DR: A neural network learning procedure has been applied to the classification of sonar returns from two undersea targets, a metal cylinder and a similarly shaped rock, and network performance and classification strategy was comparable to that of trained human listeners.
1,146 citations
TL;DR: In this article, a method for measuring correlation functions without interpolating in the temporal domain is proposed which provides an assumption-free representation of the correlation measured in the data and allows meaningful error estimates.
Abstract: A method for measuring correlation functions without interpolating in the temporal domain is proposed which provides an assumption-free representation of the correlation measured in the data and allows meaningful error estimates. Physical interpretation of the cross-correlation function of two series believed to be related by a convolution is shown to require knowledge of the input function's fluctuation power spectrum. Application of the method to two systems reveals no correlation for the optical data of Akn 120, but a strong correlation for the UV data of NGC 4151, placing bounds of between 1.2 and 20 light days on the size of the line-emitting region.
1,139 citations
TL;DR: This article summarizes the results of 41 independent studies containing correlates of objectively measured provider behaviors in medical encounters grouped a priori into the process categories of information giving, questions, competence, partnership building, and socioemotional behavior.
Abstract: This article summarizes the results of 41 independent studies containing correlates of objectively measured provider behaviors in medical encounters. Provider behaviors were grouped a priori into the process categories of information giving, questions, competence, partnership building, and socioemotional behavior. Total amount of communication was also included. All correlations between variables within these categories and external variables (patient outcome variables or patient and provider background variables) were extracted. The most frequently occurring outcome variables were satisfaction, recall, and compliance, and the most frequently occurring background variables were the patient's gender, age, and social class. Average correlations and combined significance levels were calculated for each combination of process category and external variable. Results showed significant relations of small to moderate average magnitude between these external variables and almost all of the provider behavior categories. A theory of provider-patient reciprocation is proposed to account for the pattern of results.
1,070 citations
TL;DR: It is shown that a nonlinear array of coupled waveguides can exhibit discrete self-focusing that in the continuum approximation obeys the so-called nonlinear Schrödinger equation.
Abstract: We show that a nonlinear array of coupled waveguides can exhibit discrete self-focusing that in the continuum approximation obeys the so-called nonlinear Schrodinger equation. This process has much in common with the biophysical model of Davydov.
998 citations
TL;DR: Experiments are reported investigating whether abrupt onset is simply one member of a large class of stimulus characteristics, all of which are capable of capturing attention, and whether these also could elicit shifts of attention.
Abstract: Yantis and Jonides (1984) demonstrated that the detection of a target in visual search was markedly enhanced when the target was presented as an abruptly onset character embedded among other characters whose presentation was not characterized by abrupt onset. This effect was attributed to a shift of attention caused by abrupt onset. In the present article, we report experiments investigating whether abrupt onset is simply one member of a large class of stimulus characteristics, all of which are capable of capturing attention. To test this possibility, we compared abrupt onset with differences in stimulus luminance and hue to determine whether these also could elicit shifts of attention. They could not.
Journal Article•
TL;DR: The results suggest that camptothecin interferes with DNA topoisomerase I both in cultured mammalian cells and in the purified system by trapping a reversible enzyme-DNA cleavable complex.
Abstract: Camptothecin, a plant alkaloid with antitumor activity, has been shown to be a potent inhibitor of nucleic acid synthesis and a strong inducer of DNA strand breaks in mammalian cells. Previous studies have shown that camptothecin inhibits purified mammalian DNA topoisomerase I by trapping a reversible enzyme-DNA "cleavable complex" (Hsiang et al., J. Biol. Chem., 260: 14873-14878, 1985). Our present studies, using L1210 cells and SV40-infected monkey cells, have shown that camptothecin-induced strand breaks are protein linked. The linked protein is most likely DNA topoisomerase I as revealed by immunoblot analysis, using antibodies against purified mammalian DNA topoisomerase I. Brief heating of camptothecin-treated cells to 65 degrees C resulted in a rapid reduction of the number of protein-linked DNA breaks. Reversal of the camptothecin-induced topoisomerase I-DNA complex by heat was also observed in an in vitro system by using purified mammalian DNA topoisomerase I. Our results suggest that camptothecin interferes with DNA topoisomerase I both in cultured mammalian cells and in the purified system by trapping a reversible enzyme-DNA cleavable complex.
TL;DR: In this article, the authors provide a formalism for the macroscopic study of kinetic and physical processes affecting crystallization, within which the explicit affect of chemical and physical process on the CSD can be analytically tested.
Abstract: Crystal-size in crystalline rocks is a fundamental measure of growth rate and age. And if nucleation spawns crystals over a span of time, a broad range of crystal sizes is possible during crystallization. A population balance based on the number density of crystals of each size generally predicts a log-linear distribution with increasing size. The negative slope of such a distribution is a measure of the product of overall population growth rate and mean age and the zero size intercept is nucleation density. Crystal size distributions (CSDs) observed for many lavas are smooth and regular, if not actually linear, when so plotted and can be interpreted using the theory of CSDs developed in chemical engineering by Randolph and Larson (1971). Nucleation density, nucleation and growth rates, and orders of kinetic reactions can be estimated from such data, and physical processes affecting the CSD (e.g. crystal fractionation and accumulation, mixing of populations, annealing in metamorphic and plutonic rocks, and nuclei destruction) can be gauged through analytical modeling. CSD theory provides a formalism for the macroscopic study of kinetic and physical processes affecting crystallization, within which the explicit affect of chemical and physical processes on the CSD can be analytically tested. It is a means by which petrographic information can be quantitatively linked to the kinetics of crystallization, and on these grounds CSDs furnish essential information supplemental to laboratory kinetic studies. In this three part series of papers, Part I provides the general CSD theory in a geological context, while applications to igneous and metamorphic rocks are given, respectively, in Parts II and III.
TL;DR: Flow cytometric analysis of nuclear DNA content demonstrated that each day after castration, a subpopulation of androgen-dependent cells in rat ventral prostate fragmented all of their genomic DNA, as opposed to the whole population of cells fragmenting an increasing portion of their DNA daily.
Abstract: The rapid involution of the rat ventral prostate after castration is an active process initiated by removal of the inhibitory effects of androgen on prostatic cell death. The present studies demonstrate that after castration-induced androgen deprivation a series of temporally discrete biochemical events are activated which result in the rapid programmed death of the subset of androgen-dependent cells within the rat ventral prostate. These biochemical steps involve 1) rapid loss of nuclear androgen receptor retention; by 12 h after castration, androgen receptors are no longer detectable in ventral prostatic nuclei; 2) an initial fragmentation of nuclear DNA into low mol wt (less than 1000 basepairs) nucleosomal oligomers which lack intranucleosomal break points; and 3) eventual complete digestion of these nucleosomal oligomers into component nucleotides. Additional studies demonstrate that activation of a Ca2+-Mg2+-dependent endonuclease is associated with this DNA fragmentation. By 4 days after castration, maximal DNA fragmentation is obtained, with 15% of the total nuclear DNA extractable as low mol wt fragments. Proteolytic enzymes are apparently not involved initially in this process, suggesting that DNA fragmentation is a discrete event in, rather than a result of, cell death. Flow cytometric analysis of nuclear DNA content demonstrated that each day after castration, a subpopulation of androgen-dependent cells in rat ventral prostate fragmented all of their genomic DNA, as opposed to the whole population of cells fragmenting an increasing portion of their DNA daily.
TL;DR: It is concluded that there is an association between exposure to ultraviolet B radiation and cataract formation, which supports the need for ocular protection from ultraviolet B.
Abstract: To investigate the relation of ultraviolet radiation and cataract formation, we undertook an epidemiologc survey of 838 watermen (mean age, 53 years) who worked on Chesapeake Bay. The annual ocular exposure was calculated from the age of 16 for each waterman by combining a detailed occupational history with laboratory and field measurements of sun exposure. Cataracts were graded by ophthalmologic examination for both type and severity. Some degree of cortical cataract was found in 111 of the watermen (13 percent), and some degree of nuclear cataract in 229 (27 percent). Logistic regression analysis showed that high cumulative levels of ultraviolet B exposure significantly increased the risk of cortical cataract (regression coefficient, 0.70; P = 0.04). A doubling of cumulative exposure increased the risk of cortical cataract by a factor of 1.60 (95 percent confidence interval, 1.01 to 2.64). Those whose annual average exposure was in the upper quartile had a risk increased by 3.30 (confidence int...
Journal Article•
TL;DR: La prueba tiene un puntaje total de 30 puntos en ítems que evalúan el rendimiento en orientación, memoria inmediata, atención y cálculo, lenguaje y praxis constructiva, y se obtiene sumando los puntajes asignados en cada ítem.
Abstract: B a c k g r o u n d . Occupational therapists are increasingly involved in the diagnostic process of cognitive impairment in the elderly. Purpose. Three tools designed to facilitate the evaluation process were examined in order to document their diagnostic qualities and the nature of the association between their results : the Mini-Mental State Examination (MMSE), the Protocole d’examen cognitif de la personne âgée (PECPA-2r) and the Système de mesure de l’autonomie fonctionnelle (SMAF). M e t h o d s . A crosssectional correlative study was used in order to document the association between the results obtained with the three tools when they were used with aging adults referred to the project by their attending physician. R e s u l t s . Fifty-two older adults with a suspected cognitive impairment participated in the study. The results of the study indicate that a strong correlation exists between the scores obtained with the three evaluation tools. The MMSE scores would be an excellent predictor of the PECPA-2r and the SMAF scores. The degree of cognitive impairment would be a good predictor of the degree of impairment of the autonomy. Practice implications. Referring physicians found some of the evaluators’ observations made during the administration of the PECPA-2r and the SMAF particularly useful for their subsequent diagnostic processes. The shorter administration time for the MMSE did not provide for such observations, while the PECPA-2r and the SMAF allowed more time for these kinds of observations. Occupational therapists are invited to examine carefully their intentions when choosing their evaluation tools. Résumé D e s c r i p t i o n . Les ergothérapeutes sont de plus en plus sollicités dans la démarche diagnostique des atteintes cognitives chez la personne âgée. B u t . Trois outils pouvant aider au processus d’évaluation ont été étudiés pour documenter leurs qualités diagnostiques et la nature de l’association de leurs résultats : le Mini-Mental State Examination (MMSE), le Protocole d’examen cognitif de la personne âgée (PECPA-2r) et le Système de mesure de l’autonomie fonctionnelle (SMAF). Méthodologie. Une étude corrélationnelle transversale a permis de documenter l’association entre les résultats obtenus avec les trois outils alors qu’ils étaient utilisés auprès de personnes âgées référées au projet par leur médecin traitant. R é s u l t a t s . Les résultats de l’étude, réalisée auprès de 52 personnes âgées chez qui une atteinte cognitive était soupçonnée, ont montré qu’une corrélation très forte existe entre les scores obtenus aux trois outils d’évaluation. Les scores au MMSE seraient d’excellents prédicteurs des scores au PECPA-2r et au SMAF. La sévérité de l’atteinte cognitive serait un bon prédicteur du niveau d’atteinte de l’autonomie. Conséquences pour la pratique. Certaines observations faites par les évaluateurs lors de l’administration des PECPA-2r et SMAF se sont révélées particulièrement utiles à la démarche diagnostique ultérieure faite par le médecin traitant. Le court temps d’administration du MMSE ne permettait pas de telles observations alors que les PECPA-2r et SMAF offraient ce temps propice à l’observation. Les ergothérapeutes sont invités à examiner avec attention leurs intentions cliniques alors qu’ils choisissent leurs outils d’évaluation.
TL;DR: The results indicate that the state of supercoiling of bacterial DNA is strongly modulated by transcription, and that DNA topoisomerases are normally involved in the elongation step of transcription.
TL;DR: In this paper, the authors reported that the cDNA (clone 268) derived from one of these immediate early genes (zif/268) encodes a protein with three tandem "zinc finger" sequences typical of a class of eukaryotic transcription factors.
Abstract: We have recently identified by cDNA cloning a set of genes that are rapidly activated in mouse 3T3 cells by serum or purified growth factors. Here we report that the cDNA (clone 268) derived from one of these immediate early genes (zif/268) encodes a protein with three tandem "zinc finger" sequences typical of a class of eukaryotic transcription factors. The mRNA of zif/268 is present in many organs and tissues of the mouse and is especially abundant in the brain and thymus tissue. The 5' genomic flanking sequence of zif/268 has sequences related to binding sites for known regulatory proteins, including four sequences that resemble the core of the serum response elements (SREs) upstream of the c-fos and actin genes. The SRE-like sequences could be responsible for the coordinate activation of zif/268 and fos after serum stimulation of 3T3 cells.
TL;DR: The findings suggest that there is a jun family of genes encoding related transcriptional regulatory proteins and that the jun-B protein, and perhaps other members of the jun family, may play a role in regulating the genomic response to growth factors.
Abstract: We have recently identified by cDNA cloning a set of genes that are rapidly activated in cultured mouse cells by protein growth factors. Here we report that the nucleotide sequence of a cDNA (clone 465) derived from one of these immediate early genes (hereafter called jun-B) encodes a protein homologous to that encoded by the avian sarcoma virus 17 oncogene v-jun. Homology between the jun-B and v-jun proteins is in two regions: one near the N terminus and the other at the C terminus. The latter sequence was shown by Vogt et al. [Vogt, P. K., Bos, T. J. & Doolittle, R. F. (1987) Proc. Natl. Acad. Sci. USA 84, 3316-3319] to have regions of sequence similarity to the DNA-binding domain of the yeast transcriptional regulatory protein GCN4 and to the oncogenic protein fos. Southern blots of human, mouse, and chicken DNA demonstrate that jun-B and c-jun are different genes and that there may be other vertebrate genes related to jun-B and c-jun. These findings suggest that there is a jun family of genes encoding related transcriptional regulatory proteins. The jun-B protein, and perhaps other members of the jun family, may play a role in regulating the genomic response to growth factors.
TL;DR: The current view of EUKARYOTIC Chemotaxis is viewed as a continuum of human evolution, with an emphasis on the role of the immune system.
Abstract: OVERVIEW 649 FEATURES OF CHEMOTACTIC BEHAVIOR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 650 HOW DO CELLS ACCOMPLISH CHEMOTAXIS? 652 Critical Questions . 652 Hypothetical Schemes for Chemotaxis 652 RESPONSES INDUCED BY ADDITION OF CHEMOATTRACTANTS . . . . . . . . . . . . . . . . . . . ....... . . . . . . . 656 Physiological Responses 656 Underlying Biochemistry .659 CHEMOATTRACTANT-INDUCED DESENSITIZATION ......... 669 Receptor Alterations 669 Additional Desensitization Mechanisms 670 CURRENT VIEW OF EUKARYOTIC CHEMOTAXIS . . . . . . . . . . ......... . . . . . . . . . .. ...... . ........ . . . . . . ...... . . . . . . . . 672 Biochemical Events Essential for Chemotaxis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 672 Working Modelfor Chemotaxis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 672
TL;DR: These studies suggest that superoxide derived .OH and R. free radicals are generated in the reperfused heart via Fenton chemistry, and appear to be key mediators of myocardial reperfusion injury.
TL;DR: In this paper, the internal state of the clouds and their size distribution function are examined, and it is shown that the Jeans mass scale results in clouds which are individually sufficiently opaque to block out the nucleus.
Abstract: The principal properties of the tori of gas which surround Seyfert nuclei are discussed. The internal state of the clouds and their size distribution function are examined, and it is shown that the Jeans mass scale results in clouds which are individually sufficiently opaque to block out the nucleus, and that the balance of processes which controls their size distribution function also forces the covering factor to be of the order of or greater than unity. Where the gravitational potential is dominated by stars, cloud-cloud collisions keep the molecular clouds close to the equatorial plane. Stirring by stellar processes is never strong enough to compete with collisional losses. The position of the inner edge of the torus is determined by a balance between the inward flow of clouds and the rate at which the nuclear continuum can evaporate them.
TL;DR: It was found that within the class of morphologically legal nonwords performance was affected by the type of relationship that obtained between the morphemes that comprised a stimulus item.
TL;DR: In this paper, the development of an instrument measuring a variable that represents a synthesis of the concepts of psychological sense of community, attractionto-neighborhood, and social interaction within a neighborhood is reported.
Abstract: The development of an instrument measuring a variable that represents a synthesis of the concepts of psychological sense of community, attractionto-neighborhood, and social interaction within a neighborhood is reported. When this individual-level variable (termed "sense of community/cohesion") is assessed in a random sample of residents in a geographically bounded neighborhood, the mean value forms a measure of the neighborhood's cohesiveness. The stages of instrument conceptualization, development, and testing are outlined. In administration to 206 residents in three separate neighborhoods the instrument demonstrated good internal consistency and testretest stability at the individual-level of analysis. When evaluated at the neighborhood-level of analysis the Neighborhood Cohesion Instrument exhibited good discriminatory power and evidenced criterion-related validity in the assessment of neighborhood cohesion.
TL;DR: In this paper, electron paramagnetic resonance measurements with the spin trap 5,5'-dimethyl-1-pyrroline-N-oxide (DMPO) demonstrate that bovine endothelial cells subjected to anoxia and reoxygenation become potent generators of superoxide and hydroxyl free radicals.
Abstract: Oxygen free radicals have been demonstrated to be important mediators of postischemic reperfusion injury in a broad variety of tissues; however, the cellular source of free radical generation is still unknown. In this study, electron paramagnetic resonance measurements with the spin trap 5,5'-dimethyl-1-pyrroline-N-oxide (DMPO) demonstrate that bovine endothelial cells subjected to anoxia and reoxygenation become potent generators of superoxide and hydroxyl free radicals. A prominent DMPO-OH signal aN = aH = 14.9 G is observed on reoxygenation after 45 min of anoxic incubation. Quantitative measurements of this free radical generation and the time course of radical generation are performed. Both superoxide dismutase and catalase totally abolish this radical signal, suggesting that O2 is sequentially reduced from O2-. to H2O2 to OH.. Addition of ethanol resulted in trapping of the ethoxy radical, further confirming the generation of OH.. Endothelial radical generation was shown to cause cell death, as evidenced by trypan blue uptake. Radical generation was partially inhibited and partially scavenged by the xanthine oxidase inhibitor allopurinol. Marked inhibition of radical generation was observed with the potent xanthine oxidase inhibitor oxypurinol. These studies demonstrate that endothelial cells subjected to anoxia and reoxygenation, conditions observed in ischemic and reperfused tissues, generate a burst of superoxide-derived hydroxyl free radicals that in turn cause cell injury and cell death. Most of this free radical generation appears to be from the enzyme xanthine oxidase. Thus, endothelial cell free radical generation may be a central mechanism of cellular injury in postischemic tissues.
TL;DR: 2 patients with a treatable, immune‐mediated motor polyneuropathy associated with antibodies to defined neural antigens, initially diagnosed as having lower motor neuron forms of amyotrophic lateral sclerosis are reported.
Abstract: We report 2 patients with a treatable, immune-mediated motor polyneuropathy associated with antibodies to defined neural antigens. In these patients asymmetrical weakness developed in one arm and progressed over 2 to 3 years to involve the other arm, legs, and trunk. Both patients were initially diagnosed as having lower motor neuron forms of amyotrophic lateral sclerosis. However, repeated electrophysiological testing eventually showed multifocal conduction blocks in motor but not sensory fibers compatible with patchy selective demyelination. Serum testing by thin-layer chromatography and enzyme-linked immunosorbent assay revealed that both patients had high titers of antibody directed against GM1 and other gangliosides. Initial therapeutic trials of prednisone (100 mg daily for 4 to 6 months) and plasmapheresis were unsuccessful. Treatment with cyclophosphamide, however, was followed by Marchked improvement in strength in both patients.
TL;DR: In this paper, a model for regression analysis with a time series of counts is presented, where correlation is assumed to arise from an unobservable process added to the linear predictor in a log linear model.
Abstract: SUMMARY This paper discusses a model for regression analysis with a time series of counts. Correlation is assumed to arise from an unobservable process added to the linear predictor in a log linear model. An estimating equation approach used for parameter estimation leads to an iterative weighted and filtered least-squares algorithm. Asymptotic properties for the regression coefficients are presented. We illustrate the technique with an analysis of trends in U.S. polio incidence since 1970.
TL;DR: The hypothesis that maternal dengue antibodies play a dual role by first protecting and later increasing the risk of development of d Dengue hemorrhagic fever/dengue shock syndrome in infants who become infected by denge 2 virus is consistent.
Abstract: To establish the role of maternal dengue-specific antibodies in the development of dengue hemorrhagic fever and dengue shock syndrome caused by dengue 2 virus in infants, we examined sera from mothers of infants and toddlers with dengue hemorrhagic fever or dengue shock syndrome and mothers of infants with pyrexia of unknown origin. The mean titers of hemagglutination inhibition, neutralization, and infection-enhancing activities against dengue 2 virus were not statistically different among the three groups. However, among infants who developed dengue hemorrhagic fever/dengue shock syndrome there was a strong correlation between the mothers' dengue 2 neutralizing titers and infant age at the time of onset of severe illness, where no such correlation was found among the other two groups. Furthermore, the actual age at which dengue hemorrhagic fever/dengue shock syndrome occurred in each infant correlated with the age at which maximum enhancing activity for dengue 2 infection in mononuclear phagocytes was predicted. This critical time for the occurrence of dengue hemorrhagic fever/dengue shock syndrome was observed to be approximately 2 months after the time calculated for maternal dengue 2 neutralizing antibodies to degrade below a protective level. In addition, sera of mothers of infants with dengue hemorrhagic fever/dengue shock syndrome enhanced dengue 2 virus infection to a slightly greater degree than did sera from mothers of infants with pyrexia of unknown origin and toddlers with dengue hemorrhagic fever/dengue shock syndrome. These data are consistent with the hypothesis that maternal dengue antibodies play a dual role by first protecting and later increasing the risk of development of dengue hemorrhagic fever/dengue shock syndrome in infants who become infected by dengue 2 virus.