20 results on '"Silverman MR"'
Search Results
2. Current and future practices in hospital foodservice.
- Author
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Silverman MR, Gregoire MB, Lafferty LJ, and Dowling RA
- Published
- 2000
- Full Text
- View/download PDF
3. Parental Factors That Confer Risk and Resilience for Remote Learning Outcomes During the COVID-19 Pandemic Among Children With and Without Attention-Deficit/Hyperactivity Disorder.
- Author
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Silverman MR, Stadterman J, Lorenzi D, Feuerstahler L, Hirsch E, and Roy AK
- Subjects
- Adolescent, Child, Humans, Male, Pandemics, Parenting psychology, Parents psychology, Attention Deficit Disorder with Hyperactivity psychology, COVID-19
- Abstract
Objective: To test whether parental factors including internalizing symptoms, parenting style, and confidence in assisting with remote learning conferred risk/resilience for children with/without ADHD's learning and emotional outcomes during the COVID-19 pandemic., Method: 291 parents of children (ages 6-13; n = 180 males) with ( n = 148) and without ADHD completed questionnaires online (April-July 2020)., Results: Structural equation modeling identified parental risk/resilience factors. Across groups, risk predicted greater difficulties with learning, internalizing and externalizing symptoms, while parent confidence in educating their child predicted better outcomes. A positive association was observed between parental involvement and child difficulties, which was stronger in families of children with ADHD. Children with/without ADHD did not differ in remote learning difficulties., Conclusion: Parent factors impacted child emotional and learning outcomes during the pandemic. With increases in remote learning practices, there is a need for improved understanding of how parent factors impact outcomes of children with/without ADHD.
- Published
- 2022
- Full Text
- View/download PDF
4. Measuring Emotion Dysregulation in Children With Attention-Deficit/Hyperactivity Disorder: Revisiting the Factor Structure of the Emotion Regulation Checklist.
- Author
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Silverman MR, Bennett R, Feuerstahler L, Stadterman J, Dick AS, Graziano P, and Roy AK
- Subjects
- Adolescent, Affective Symptoms complications, Affective Symptoms psychology, Attention Deficit and Disruptive Behavior Disorders, Checklist, Child, Emotions physiology, Humans, Attention Deficit Disorder with Hyperactivity psychology, Emotional Regulation
- Abstract
Emotion dysregulation (ED) is prevalent among youth with Attention-Deficit/Hyperactivity Disorder (ADHD) and significantly impacts functioning. Nuanced measurement of ED is central to understanding its role in this disorder and informing treatment approaches. The present study examined the factor structure of the Emotion Regulation Checklist (ERC) among children with ADHD with and without Oppositional Defiant Disorder (ODD). Exploratory factor analysis (EFA) conducted in a sample of 328 youth (mean age = 6.08) with ADHD indicated a four-factor solution, comprised of the following factors: Negative Emotion Lability, Positive Emotion Lability, Socially Appropriate Affect, and Socially Incongruent Affect. The Negative and Positive Emotion Lability subscales assess the reactivity of negatively and positively valenced emotions, respectively. The Socially Appropriate and Socially Incongruent Affect subscales provide an assessment of social-emotional functioning. All subscales discriminated between children with ADHD only and ADHD with co-morbid ODD, such that children with ODD had greater emotional lability and social-emotional difficulties. This revised factor structure of the ERC facilitates a uniquely brief, yet multifaceted and specific, assessment of emotional difficulties in children with ADHD that can inform treatment planning and operationalize emotional reactivity and social-emotional functioning in future research efforts., (Copyright © 2021. Published by Elsevier Ltd.)
- Published
- 2022
- Full Text
- View/download PDF
5. Detection of eye contact with deep neural networks is as accurate as human experts.
- Author
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Chong E, Clark-Whitney E, Southerland A, Stubbs E, Miller C, Ajodan EL, Silverman MR, Lord C, Rozga A, Jones RM, and Rehg JM
- Subjects
- Autism Spectrum Disorder, Child, Preschool, Female, Hand, Humans, Infant, Machine Learning, Male, Models, Theoretical, Communication, Deep Learning, Eye, Neural Networks, Computer
- Abstract
Eye contact is among the most primary means of social communication used by humans. Quantification of eye contact is valuable as a part of the analysis of social roles and communication skills, and for clinical screening. Estimating a subject's looking direction is a challenging task, but eye contact can be effectively captured by a wearable point-of-view camera which provides a unique viewpoint. While moments of eye contact from this viewpoint can be hand-coded, such a process tends to be laborious and subjective. In this work, we develop a deep neural network model to automatically detect eye contact in egocentric video. It is the first to achieve accuracy equivalent to that of human experts. We train a deep convolutional network using a dataset of 4,339,879 annotated images, consisting of 103 subjects with diverse demographic backgrounds. 57 subjects have a diagnosis of Autism Spectrum Disorder. The network achieves overall precision of 0.936 and recall of 0.943 on 18 validation subjects, and its performance is on par with 10 trained human coders with a mean precision 0.918 and recall 0.946. Our method will be instrumental in gaze behavior analysis by serving as a scalable, objective, and accessible tool for clinicians and researchers.
- Published
- 2020
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- View/download PDF
6. Adolescent-Specific Motivation Deficits in Autism Versus Typical Development.
- Author
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Bos DJ, Silver BM, Barnes ED, Ajodan EL, Silverman MR, Clark-Whitney E, Tarpey T, and Jones RM
- Subjects
- Adolescent, Adult, Child, Cross-Sectional Studies, Cues, Female, Humans, Linear Models, Male, Orientation, Task Performance and Analysis, Young Adult, Adolescent Development, Attention, Autistic Disorder psychology, Motivation
- Abstract
Differences in motivation during adolescence relative to childhood and adulthood in autism was tested in a cross-sectional study. 156 Typically developing individuals and 79 individuals with autism ages 10-30 years of age completed a go/nogo task with social and non-social cues. To assess age effects, linear and quadratic models were used. Consistent with prior studies, typically developing adolescents and young adults demonstrated more false alarms for positive relative to neutral social cues. In autism, there were no changes in attention across age for social or non-social cues. Findings suggest reduced orienting to motivating cues during late adolescence and early adulthood in autism. The findings provide a unique perspective to explain the challenges for adolescents with autism transitioning to adulthood.
- Published
- 2020
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7. Rigidity coincides with reduced cognitive control to affective cues in children with autism.
- Author
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Bos DJ, Silverman MR, Ajodan EL, Martin C, Silver BM, Brouwer GJ, Di Martino A, and Jones RM
- Subjects
- Child, Female, Humans, Male, Autism Spectrum Disorder physiopathology, Cues, Emotions physiology, Executive Function physiology
- Abstract
The present study tested whether salient affective cues would negatively influence cognitive control in children with and without autism spectrum disorder (ASD). One hundred children aged 6-12 years who were either typically developing or had ASD performed a novel go/no-go task to cues of their interest versus cues of noninterest. Linear mixed-effects (LME) models for hit rate, false alarms, and the sensitivity index d ' were used to test for group differences. Caregivers completed the Repetitive Behavior Scale-Revised to test associations between repetitive behaviors and task performance. Children with ASD had reduced cognitive control toward their interests compared with typically developing children. Further, children with ASD showed reduced cognitive control to interests compared with noninterests, a pattern not observed in typically developing children. Decreased cognitive control toward interests was associated with higher insistence on sameness behavior in ASD, but there was no association between sameness behavior and cognitive control for noninterests. Together, children with ASD demonstrated decreased cognitive flexibility in the context of increased affective salience related to interests. These results provide a mechanism for how salient affective cues, such as interests, interfere with daily functioning and social communication in ASD. Further, the findings have broader clinical implications for understanding how affective cues can drive interactions between restricted patterns of behavior and cognitive control. (PsycINFO Database Record (c) 2019 APA, all rights reserved).
- Published
- 2019
- Full Text
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8. Customized head molds reduce motion during resting state fMRI scans.
- Author
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Power JD, Silver BM, Silverman MR, Ajodan EL, Bos DJ, and Jones RM
- Subjects
- Adolescent, Adult, Child, Equipment Design standards, Female, Humans, Male, Polystyrenes, Young Adult, Functional Neuroimaging standards, Head Movements, Magnetic Resonance Imaging standards, Restraint, Physical instrumentation
- Abstract
Head motion causes artifacts in functional magnetic resonance imaging (fMRI) scans, a problem especially relevant for task-free resting state paradigms and for developmental, aging, and clinical populations. In a cohort spanning 7-28 years old (mean age 15) we produced customized head-anatomy-specific Styrofoam molds for each subject that inserted into an MRI head coil. We scanned these subjects under two conditions: using our standard procedure of packing the head coil with foam padding about the head to reduce head motion, and using the customized molds to reduce head motion. In 12 of 13 subjects, the molds reduced head motion throughout the scan and reduced the fraction of a scan with substantial motion (i.e., volumes with motion notably above baseline levels of motion). Motion was reduced in all 6 head position estimates, especially in rotational, left-right, and superior-inferior directions. Motion was reduced throughout the full age range studied, including children, adolescents, and young adults. In terms of the fMRI data itself, quality indices improved with the head mold on, scrubbing analyses detected less distance-dependent artifact in scans with the head mold on, and distant-dependent artifact was less evident in both the entire scan and also during only low-motion volumes. Subjects found the molds comfortable. Head molds are thus effective tools for reducing head motion, and motion artifacts, during fMRI scans., (Copyright © 2019 Elsevier Inc. All rights reserved.)
- Published
- 2019
- Full Text
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9. How effective is LENA in detecting speech vocalizations and language produced by children and adolescents with ASD in different contexts?
- Author
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Jones RM, Plesa Skwerer D, Pawar R, Hamo A, Carberry C, Ajodan EL, Caulley D, Silverman MR, McAdoo S, Meyer S, Yoder A, Clements M, Lord C, and Tager-Flusberg H
- Subjects
- Adolescent, Child, Child, Preschool, Female, Humans, Language Development Disorders physiopathology, Male, Reproducibility of Results, Software, Algorithms, Autism Spectrum Disorder complications, Autism Spectrum Disorder physiopathology, Language Development Disorders complications, Language Development Disorders diagnosis, Speech physiology
- Abstract
The LENA system was designed and validated to provide information about the language environment in children 0 to 4 years of age and its use has been expanded to populations with a number of communication profiles. Its utility in children 5 years of age and older is not yet known. The present study used acoustic data from two samples of children with autism spectrum disorders (ASD) to evaluate the reliability of LENA automated analyses for detecting speech utterances in older, school age children, and adolescents with ASD, in clinic and home environments. Participants between 5 and 18 years old who were minimally verbal (study 1) or had a range of verbal abilities (study 2) completed standardized assessments in the clinic (study 1 and 2) and in the home (study 2) while speech was recorded from a LENA device. We compared LENA segment labels with manual ground truth coding by human transcribers using two different methods. We found that the automated LENA algorithms were not successful (<50% reliable) in detecting vocalizations from older children and adolescents with ASD, and that the proportion of speaker misclassifications by the automated system increased significantly with the target-child's age. The findings in children and adolescents with ASD suggest possibly misleading results when expanding the use of LENA beyond the age ranges for which it was developed and highlight the need to develop novel automated methods that are more appropriate for older children. Autism Research 2019, 12: 628-635. © 2019 International Society for Autism Research, Wiley Periodicals, Inc. LAY SUMMARY: Current commercially available speech detection algorithms (LENA system) were previously validated in toddlers and children up to 48 months of age, and it is not known whether they are reliable in older children and adolescents. Our data suggest that LENA does not adequately capture speech in school age children and adolescents with autism and highlights the need to develop new automated methods for older children., (© 2019 International Society for Autism Research, Wiley Periodicals, Inc.)
- Published
- 2019
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- View/download PDF
10. Neural correlates of preferred activities: development of an interest-specific go/nogo task.
- Author
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Bos DJ, Ajodan EL, Silverman MR, Dyke JP, Durston S, Power JD, and Jones RM
- Subjects
- Adolescent, Adult, Attention Deficit Disorder with Hyperactivity psychology, Autism Spectrum Disorder psychology, Cognition, Cues, Facial Expression, Female, Frontal Lobe physiology, Hobbies psychology, Humans, Magnetic Resonance Imaging, Male, Neostriatum physiology, Neural Pathways physiology, Neuropsychological Tests, Photic Stimulation, Reproducibility of Results, Young Adult, Impulsive Behavior, Leisure Activities psychology
- Abstract
The activities we choose to spend our leisure time with are intrinsically motivating and vary across individuals. Yet it is unknown how impulse control or neural activity changes when processing a preferred stimulus related to a hobby or interest. Developing a task that assesses the response to preferred interests is of importance as it would be relevant to a range of psychiatric disorders that have hyper- or hypo-arousal to such cues. During functional Magnetic Resonance Imaging (fMRI), 39 healthy adults completed a novel task to test approach behavior and cognitive control to cues that were personalized to the participants' interests compared to stimuli the participants identified as being of non-interest and colored shapes. fMRI results showed that cues of one's interest elicited activation in the anterior insula compared to colored shapes. Interests did not change inhibition compared to non-interests and colored shapes and all stimuli equally engaged a frontostriatal circuit. Together the results suggest that adults were sensitive to their interests but were effective at regulating their impulses towards these cues, a skill that is critical for navigating the temptations and distractions in our daily environment., (© The Author (2017). Published by Oxford University Press.)
- Published
- 2017
- Full Text
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11. Patients with bulimia nervosa do not show typical neurodevelopment of cognitive control under emotional influences.
- Author
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Dreyfuss MFW, Riegel ML, Pedersen GA, Cohen AO, Silverman MR, Dyke JP, Mayer LES, Walsh BT, Casey BJ, and Broft AI
- Subjects
- Adolescent, Adult, Female, Humans, Male, Prefrontal Cortex diagnostic imaging, Young Adult, Bulimia Nervosa physiopathology, Emotions physiology, Executive Function physiology, Magnetic Resonance Imaging methods, Prefrontal Cortex physiopathology, Self-Control psychology
- Abstract
Bulimia nervosa (BN) emerges in the late teen years and is characterized by binge eating and related compensatory behaviors. These behaviors often co-occur with periods of negative affect suggesting an association between emotions and control over eating behavior. In the current study, we examined how cognitive control and neural processes change under emotional states of arousal in 46 participants with (n=19) and without (n=27) BN from the ages of 18-33 years. Participants performed a go/nogo task consisting of brief negative, positive and neutral emotional cues and sustained negative, positive and neutral emotional states of arousal during functional magnetic resonance imaging (fMRI). Overall task performance improved with age for healthy participants, but not for patients with BN. These age-dependent behavioral effects were paralleled by diminished recruitment of prefrontal control circuitry in patients with BN with age. Although patients with BN showed no difference in performance on the experimental manipulations of negative emotions, sustained positive emotions related to improved performance among patients with BN. Together the findings highlight a neurodevelopmental approach towards understanding markers of psychopathology and suggest that sustained positive affect may have potential therapeutic effects on maintaining behavioral control in BN., (Copyright © 2017 Elsevier Ireland Ltd. All rights reserved.)
- Published
- 2017
- Full Text
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12. When Is an Adolescent an Adult? Assessing Cognitive Control in Emotional and Nonemotional Contexts.
- Author
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Cohen AO, Breiner K, Steinberg L, Bonnie RJ, Scott ES, Taylor-Thompson KA, Rudolph MD, Chein J, Richeson JA, Heller AS, Silverman MR, Dellarco DV, Fair DA, Galván A, and Casey BJ
- Subjects
- Adolescent, Adult, Brain Mapping methods, Female, Humans, Image Processing, Computer-Assisted methods, Los Angeles, Magnetic Resonance Imaging, Male, New York City, Reaction Time, Young Adult, Arousal, Brain diagnostic imaging, Cognition, Emotions, Nerve Net diagnostic imaging
- Abstract
An individual is typically considered an adult at age 18, although the age of adulthood varies for different legal and social policies. A key question is how cognitive capacities relevant to these policies change with development. The current study used an emotional go/no-go paradigm and functional neuroimaging to assess cognitive control under sustained states of negative and positive arousal in a community sample of one hundred ten 13- to 25-year-olds from New York City and Los Angeles. The results showed diminished cognitive performance under brief and prolonged negative emotional arousal in 18- to 21-year-olds relative to adults over 21. This reduction in performance was paralleled by decreased activity in fronto-parietal circuitry, implicated in cognitive control, and increased sustained activity in the ventromedial prefrontal cortex, involved in emotional processes. The findings suggest a developmental shift in cognitive capacity in emotional situations that coincides with dynamic changes in prefrontal circuitry. These findings may inform age-related social policies., (© The Author(s) 2016.)
- Published
- 2016
- Full Text
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13. HSF-1 activates the ubiquitin proteasome system to promote non-apoptotic developmental cell death in C. elegans.
- Author
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Kinet MJ, Malin JA, Abraham MC, Blum ES, Silverman MR, Lu Y, and Shaham S
- Subjects
- Animals, Gene Expression Regulation, Developmental, Signal Transduction, Caenorhabditis elegans growth & development, Caenorhabditis elegans Proteins metabolism, Cell Death, Proteasome Endopeptidase Complex metabolism, Transcription Factors metabolism, Ubiquitin metabolism
- Abstract
Apoptosis is a prominent metazoan cell death form. Yet, mutations in apoptosis regulators cause only minor defects in vertebrate development, suggesting that another developmental cell death mechanism exists. While some non-apoptotic programs have been molecularly characterized, none appear to control developmental cell culling. Linker-cell-type death (LCD) is a morphologically conserved non-apoptotic cell death process operating in Caenorhabditis elegans and vertebrate development, and is therefore a compelling candidate process complementing apoptosis. However, the details of LCD execution are not known. Here we delineate a molecular-genetic pathway governing LCD in C. elegans. Redundant activities of antagonistic Wnt signals, a temporal control pathway, and mitogen-activated protein kinase kinase signaling control heat shock factor 1 (HSF-1), a conserved stress-activated transcription factor. Rather than protecting cells, HSF-1 promotes their demise by activating components of the ubiquitin proteasome system, including the E2 ligase LET-70/UBE2D2 functioning with E3 components CUL-3, RBX-1, BTBD-2, and SIAH-1. Our studies uncover design similarities between LCD and developmental apoptosis, and provide testable predictions for analyzing LCD in vertebrates.
- Published
- 2016
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14. Multiple signalling systems controlling expression of luminescence in Vibrio harveyi: sequence and function of genes encoding a second sensory pathway.
- Author
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Bassler BL, Wright M, and Silverman MR
- Subjects
- 4-Butyrolactone analogs & derivatives, 4-Butyrolactone metabolism, Amino Acid Sequence, Bacterial Proteins biosynthesis, Bacterial Proteins genetics, Base Sequence, Models, Biological, Molecular Sequence Data, Mutagenesis, Insertional, Phenotype, Phosphorylation, Protein Kinases biosynthesis, Protein Kinases genetics, Protein Processing, Post-Translational, Repressor Proteins genetics, Repressor Proteins physiology, Sequence Alignment, Sequence Homology, Amino Acid, Transcription Factors genetics, Transcription Factors physiology, Vibrio genetics, Bacterial Proteins physiology, Gene Expression Regulation, Bacterial, Luminescent Measurements, Phosphotransferases, Protein Kinases physiology, Signal Transduction physiology, Trans-Activators, Vibrio physiology
- Abstract
Density-dependent expression of luminescence in Vibrio harveyi is regulated by the concentration of extracellular signal molecules (autoinducers) in the culture medium. One signal-response system is encoded by the luxL,M,N locus. The luxL and luxM genes are required for the production of an autoinducer (probably beta-hydroxybutyl homoserine lactone), and the luxN gene is required for the response to that autoinducer. Analysis of the phenotypes of LuxL,M and N mutants indicated that an additional signal-response system also controls density sensing. We report here the identification, cloning and analysis of luxP and luxQ, which encode functions required for a second density-sensing system. Mutants with defects in luxP and luxQ are defective in response to a second autoinducer substance. LuxQ, like LuxN, is similar to members of the family of two-component, signal transduction proteins and contains both a histidine protein kinase and a response regulator domain. Analysis of signalling mutant phenotypes indicates that there are at least two separate signal-response pathways which converge to regulate expression of luminescence in V. harveyi.
- Published
- 1994
- Full Text
- View/download PDF
15. Sequence and function of LuxO, a negative regulator of luminescence in Vibrio harveyi.
- Author
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Bassler BL, Wright M, and Silverman MR
- Subjects
- Amino Acid Sequence, Base Sequence, Gene Expression Regulation, Bacterial, Models, Genetic, Molecular Sequence Data, Mutagenesis, Insertional, Recombinant Proteins, Sequence Analysis, DNA, Sequence Homology, Amino Acid, Signal Transduction genetics, Vibrio growth & development, Bacterial Proteins genetics, Genes, Bacterial genetics, Genes, Regulator genetics, Luminescent Measurements, Repressor Proteins genetics, Transcription Factors, Vibrio genetics
- Abstract
Density-dependent expression of luminescence in Vibrio harveyi is regulated by the concentration of extracellular signal molecules (autoinducers) in the culture medium. A recombinant clone that restored function to one class of spontaneous dim mutants was found to encode a function required for the density-dependent response. Transposon Tn5 insertions in the recombinant clone were isolated, and the mutations were transferred to the genome of V. harveyi for examination of mutant phenotypes. Expression of luminescence in V. harveyi strains with transposon insertions in one locus, luxO, was independent of the density of the culture and was similar in intensity to the maximal level observed in wild-type bacteria. Sequence analysis of luxO revealed one open reading frame that encoded a protein, LuxO, similar in amino acid sequence to the response regulator domain of the family of two-component, signal transduction proteins. The constitutive phenotype of LuxO- mutants indicates that LuxO acts negatively to control expression of luminescence, and relief of repression by LuxO in the wild type could result from interactions with other components in the Lux signalling system.
- Published
- 1994
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16. Intercellular signalling in Vibrio harveyi: sequence and function of genes regulating expression of luminescence.
- Author
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Bassler BL, Wright M, Showalter RE, and Silverman MR
- Subjects
- Amino Acid Sequence, Bacterial Proteins metabolism, Base Sequence, Cloning, Molecular, Consensus Sequence, Homoserine analogs & derivatives, Homoserine biosynthesis, Molecular Sequence Data, Mutagenesis, Insertional, Open Reading Frames, Phenotype, Recombinant Proteins metabolism, Sequence Alignment, Sequence Homology, Amino Acid, Vibrio genetics, Aldehyde Oxidoreductases genetics, Bacterial Proteins genetics, Gene Expression Regulation, Bacterial, Genes, Bacterial, Luciferases genetics, Luminescent Measurements, Operon, Protein Kinases, Repressor Proteins, Signal Transduction, Trans-Activators, Transcription Factors, Vibrio physiology
- Abstract
Density-dependent expression of luminescence in Vibrio harveyi is regulated by the concentration of an extracellular signal molecule (autoinducer) in the culture medium. A recombinant clone that restored function to one class of spontaneous dim mutants was found to encode functions necessary for the synthesis of, and response to, a signal molecule. Sequence analysis of the region encoding these functions revealed three open reading frames, two (luxL and luxM) that are required for production of an autoinducer substance and a third (luxN) that is required for response to this signal substance. The LuxL and LuxM proteins are not similar in amino acid sequence to other proteins in the database, but the LuxN protein contains regions of sequence resembling both the histidine protein kinase and the response regulator domains of the family of two-component, signal transduction proteins. The phenotypes of mutants with luxL, luxM and luxN defects indicated that an additional signal-response system controlling density-dependent expression of luminescence remains to be identified.
- Published
- 1993
- Full Text
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17. Nucleotide sequence of a gene, hpt, for hypoxanthine phosphoribosyltransferase from Vibrio harveyi.
- Author
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Showalter RE and Silverman MR
- Subjects
- Amino Acid Sequence, Base Sequence, DNA, Bacterial genetics, Genes, Bacterial, Humans, Molecular Sequence Data, Sequence Homology, Nucleic Acid, Vibrio enzymology, Hypoxanthine Phosphoribosyltransferase genetics, Vibrio genetics
- Published
- 1990
- Full Text
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18. Cloning and nucleotide sequence of luxR, a regulatory gene controlling bioluminescence in Vibrio harveyi.
- Author
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Showalter RE, Martin MO, and Silverman MR
- Subjects
- Base Sequence, DNA Transposable Elements, Luciferases genetics, Luminescent Measurements, Molecular Sequence Data, Mutation, Recombination, Genetic, Cloning, Molecular, DNA, Bacterial analysis, Genes, Bacterial, Genes, Regulator, Vibrio genetics
- Abstract
Mutagenesis with transposon mini-Mulac was used previously to identify a regulatory locus necessary for expression of bioluminescence genes, lux, in Vibrio harveyi (M. Martin, R. Showalter, and M. Silverman, J. Bacteriol. 171:2406-2414, 1989). Mutants with transposon insertions in this regulatory locus were used to construct a hybridization probe which was used in this study to detect recombinants in a cosmid library containing the homologous DNA. Recombinant cosmids with this DNA stimulated expression of the genes encoding enzymes for luminescence, i.e., the luxCDABE operon, which were positioned in trans on a compatible replicon in Escherichia coli. Transposon mutagenesis and analysis of the DNA sequence of the cloned DNA indicated that regulatory function resided in a single gene of about 0.6-kilobases named luxR. Expression of bioluminescence in V. harveyi and in the fish light-organ symbiont Vibrio fischeri is controlled by density-sensing mechanisms involving the accumulation of small signal molecules called autoinducers, but similarity of the two luminescence systems at the molecular level was not apparent in this study. The amino acid sequence of the LuxR product of V. harveyi, which indicates a structural relationship to some DNA-binding proteins, is not similar to the sequence of the protein that regulates expression of luminescence in V. fischeri. In addition, reconstitution of autoinducer-controlled luminescence in recombinant E. coli, already achieved with lux genes cloned from V. fischeri, was not accomplished with the isolation of luxR from V. harveyi, suggesting a requirement for an additional regulatory component.
- Published
- 1990
- Full Text
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19. Departmental computer systems--reevaluating the issues of control.
- Author
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Silverman MR
- Subjects
- United States, Computers, Hospital Departments organization & administration, Information Systems organization & administration, Management Information Systems organization & administration
- Published
- 1986
20. Flagellar assembly mutants in Escherichia coli.
- Author
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Silverman MR and Simon MI
- Subjects
- Alkanesulfonates, Amino Acids analysis, Animals, Antigens, Bacterial analysis, Bacterial Proteins analysis, Binding Sites, Antibody, Complement Fixation Tests, Culture Media, Electrophoresis, Polyacrylamide Gel, Escherichia coli analysis, Escherichia coli growth & development, Escherichia coli immunology, Immune Sera, Microscopy, Electron, Mutagens, Phosphotungstic Acid, Rabbits immunology, Recombination, Genetic, Staining and Labeling, Transduction, Genetic, Escherichia coli cytology, Flagella analysis, Flagella immunology, Mutation
- Abstract
Genetic and biochemical analysis of mutants defective in the synthesis of flagella in Escherichia coli revealed an unusual class of mutants. These mutants were found to produce short, curly, flagella-like filaments with low amplitude ( approximately 0.06 mum). The filaments were connected to characteristic flagellar basal caps and extended for 1 to 2 mum from the bacterial surface. The mutations in these strains were all members of one complementation group, group E, which is located between his and uvrC. The structural, serological, and chemical properties of the filament derived from the mutants closely resemble those of the flagellar hook structure. On the basis of these properties, it is suggested that these filaments are "polyhooks", i.e., repeated end-to-end polymers of the hook portion of the flagellum. Polyhooks are presumed to be the result of a defective cistron which normally functions to control the length of the hook region of the flagellum.
- Published
- 1972
- Full Text
- View/download PDF
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