Your browser doesn't support javascript.
loading
Show: 20 | 50 | 100
Results 1 - 20 de 22
Filter
1.
J Health Econ ; 95: 102877, 2024 May.
Article in English | MEDLINE | ID: mdl-38581749

ABSTRACT

Medicaid spends nearly 100 billion dollars annually on home and community-based care for the disabled. Much of this care is provided by personal care aides, few of whom have received training related to the services they provide. We conducted a randomized controlled trial to estimate their demand for training. We find that 13 percent of these caregivers complete training without an incentive. Paying the caregivers four times their hourly wage increases training completion by roughly nine percentage points. Additional experimental variation suggests that among individuals confirmed to be aware of the training, the financial incentive increases completion from 35 to 58 percent. Demand curves based on these results suggest that while many caregivers value the opportunity to train, policies aimed at universal take up require large financial incentives.


Subject(s)
Medicaid , Humans , United States , Female , Male , Home Care Services , Home Health Aides/education , Caregivers , Middle Aged , Adult
2.
Cureus ; 16(2): e54355, 2024 Feb.
Article in English | MEDLINE | ID: mdl-38500945

ABSTRACT

Eosinophilic enteritis is an inflammatory condition characterized by eosinophilic infiltration of the gastrointestinal tract. This case report highlights a unique presentation of eosinophilic enteritis as a cause of recurrent small bowel obstruction. The diagnosis was elusive despite extensive abdominal imaging. A histopathologic examination of a full-thickness bowel segment showing extensive eosinophilic infiltration in the muscularis propria was vital in establishing the diagnosis. This report underscores the diagnostic complexities associated with eosinophilic enteritis and the need to consider this condition as a potential cause of recurrent abdominal pain and small bowel obstruction.

3.
Lung Cancer Manag ; 12(1): LMT58, 2023 Mar.
Article in English | MEDLINE | ID: mdl-37283858

ABSTRACT

Aim: Adjuvant chemotherapy in NSCLC is associated with modest benefits and significant toxicity. We sought to evaluate the toxicity of adjuvant chemotherapy and disease-specific outcomes in a real-world population. Methods: We performed a retrospective analysis of patients undergoing adjuvant chemotherapy for NSCLC in an Irish center over a 7-year period. We described treatment-associated toxicity, recurrence-free survival and overall survival. Results: 62 patients underwent adjuvant chemotherapy. Treatment-associated hospitalisation occurred in 29% of patients. Relapse was recorded in 56% of patients and median recurrence-free survival was 27 months. Conclusion: High rates of disease recurrence and treatment-associated morbidity were observed in patients receiving adjuvant chemotherapy for NSCLC. Novel therapeutic strategies are required to improve outcomes in this population.


Early NSCLC is primarily managed with lung cancer surgery. Chemotherapy is offered to some patients with early NSCLC after surgery depending on the size of the tumor and lymph node involvement. The benefit of post-surgery (adjuvant) chemotherapy in reducing the chance of cancer recurrence has been shown to be relatively small in previous studies. Large studies of post-surgery chemotherapy in NSCLC have included limited numbers of older patients, and patients with significant medical issues. This study looked to evaluate the safety and treatment-associated side effects of adjuvant chemotherapy in a group of patients more reflective of everyday clinical practice, and to assess the rates of cancer recurrence in these patients. In our study of 62 patients who underwent adjuvant chemotherapy for NSCLC, nearly 1 in 3 patients required hospital admission due to treatment-associated side effects. Almost 40% of patients experienced significant blood test abnormalities (including anaemia, reduced platelets, and reduced white blood cells). Approximately 1 in 4 patients required a reduction in the doses of their treatment due to treatment-associated side effects. More than half of the patients in our study experienced a recurrence of their cancer. Our study demonstrates the significant side effects associated with adjuvant chemotherapy in NSCLC and highlights the need for better-tolerated treatment strategies to reduce cancer recurrence in early NSCLC.

4.
J Health Econ ; 82: 102592, 2022 03.
Article in English | MEDLINE | ID: mdl-35104669

ABSTRACT

The COVID-19 pandemic in the US has been particularly devastating for nursing home residents. A key question is how have some nursing homes been able to effectively protect their residents, while others have not? Using data on the universe of US nursing homes, we examine whether establishment quality is predictive of COVID-19 mortality. Higher-quality nursing homes, as measured by CMS overall five-star rating, have substantially lower COVID-19 mortality through September of 2020. Quality does not predict the ability to prevent any COVID-19 resident or staff cases, but higher-quality establishments prevent the spread of resident infections conditional on having one. Preventing COVID-19 cases and deaths may come at some cost, as high-quality homes have substantially higher non-COVID deaths. The positive correlation between establishment quality and non-COVID mortality is strong enough that high-quality homes also have more total deaths than their low-quality counterparts and this relationship has grown with time. As of late April 2021, five-star homes have experienced 8.4 percent more total deaths than one-star homes.


Subject(s)
COVID-19 , Humans , Nursing Homes , Pandemics , Skilled Nursing Facilities
5.
Front Med (Lausanne) ; 9: 1070828, 2022.
Article in English | MEDLINE | ID: mdl-36619621

ABSTRACT

BRAF V600E oncogene mutations have been reported in multiple central nervous system (CNS) tumor types, and emerging evidence supports the use of targeted therapy in BRAF-mutated gliomas. BRAF oncogene mutations have been recently identified in Rosai-Dorfman disease (RDD)-a rare non-Langerhans cell histiocytosis. This series describes three patients from two neurosurgical centers in Ireland with BRAF V600E-mutated CNS tumors. The study participants include a 19-year-old male patient with ganglioglioma with anaplastic features, a 21-year-old male patient with CNS involvement of RDD, and a 28-year-old female patient with ganglioglioma with anaplastic features. Two patients received radiation with concurrent temozolomide before BRAF-targeted therapy. This case series describes clinical and radiological responses to BRAF-targeted therapy in BRAF V600E-mutated gliomas across multiple tumor grades and is only the second published report of response to targeted therapy in BRAF-mutated RDD. The durability of disease control with BRAF-targeted therapy was generally superior to that achieved with chemoradiation; one patient has experienced ongoing disease control for 5 years. The reported case of treatment response in BRAF-mutated RDD supports the strategy of genotyping and utilization of targeted therapy in this rare disease. The optimal sequencing of BRAF-targeted therapy in BRAF-mutated gliomas/glioneuronal tumors remains unclear, and further prospective studies are required to guide the use of genome-matched therapy in this patient population.

6.
Proc Natl Acad Sci U S A ; 118(39)2021 09 28.
Article in English | MEDLINE | ID: mdl-34544858

ABSTRACT

The 2020 US mortality totaled 2.8 million after early March, which is 17.3% higher than age-population-weighted mortality over the same time interval in 2017 to 2019, for a total excess death count of 413,592. We use data on weekly death counts by cause, as well as life tables, to quantify excess mortality and life years lost from both COVID-19 and non-COVID-19 causes by race/ethnicity, age, and gender/sex. Excess mortality from non-COVID-19 causes is substantial and much more heavily concentrated among males and minorities, especially Black, non-Hispanic males, than COVID-19 deaths. Thirty-four percent of the excess life years lost for males is from non-COVID-19 causes. While minorities represent 36% of COVID-19 deaths, they represent 70% of non-COVID-19 related excess deaths and 58% of non-COVID-19 excess life years lost. Black, non-Hispanic males represent only 6.9% of the population, but they are responsible for 8.9% of COVID-19 deaths and 28% of 2020 excess deaths from non-COVID-19 causes. For this group, nearly half of the excess life years lost in 2020 are due to non-COVID-19 causes.


Subject(s)
COVID-19/mortality , Cause of Death , Health Status Disparities , Minority Groups , Adolescent , Adult , Black or African American/genetics , Age Factors , Aged , Aged, 80 and over , COVID-19/genetics , COVID-19/virology , Child , Child, Preschool , Ethnicity/genetics , Female , Hispanic or Latino/genetics , Humans , Infant , Infant, Newborn , Male , Middle Aged , Racial Groups/genetics , SARS-CoV-2/pathogenicity , Sex Characteristics , United States/epidemiology , White People/genetics , Young Adult
7.
J Health Econ ; 79: 102497, 2021 09.
Article in English | MEDLINE | ID: mdl-34325285

ABSTRACT

We examine the impact of early state and local COVID-19 policies to encourage social distancing. Outcomes are daily foot traffic at establishments spanning ten key industries, across which transmission risk varies substantially. Policies include state of emergency declarations, blunt general restrictions such as stay-at-home (SAH) orders, and targeted rules such as restrictions on bars, restaurants, entertainment venues, and schools. Exploiting variation in the timing of policies in difference-in-difference models, we show that much of the decline in foot traffic early in the pandemic was due to private precautionary behavior. SAH orders explain almost none of the foot traffic decline in industries with high risk of virus transmission, but they do explain a substantial share of the decline in moderate- to low-risk industries such as outdoor sports and visits to parks. Targeted restrictions tend to impact intended industries, as well as complementary ones. We show that the impact of targeted restrictions is largest in counties with no SAH restrictions, suggesting that better targeting of public restrictions can have important efficiency gains.


Subject(s)
COVID-19 , Physical Distancing , Health Promotion , Humans , Pandemics , Policy , SARS-CoV-2
8.
J Health Econ ; 73: 102348, 2020 09.
Article in English | MEDLINE | ID: mdl-32615362

ABSTRACT

Public policies aimed at improving health may have indirect effects on outcomes such as education and employment. We study the labor market effects of the US Food and Drug Administration's 2007 expanded black box warning on antidepressants. Our difference-in-differences estimates imply that the warning reduced employment by 6.1 percent among women aged 35-49 with a history of depression. We explore potential mechanisms and find that antidepressant and psychotherapy use among women aged 35-49 decreased after the warning. Our analysis suggests that the 2007 warning reduced US labor force participation by 0.23 percentage points, leading to $11.8 billion in lost wages.


Subject(s)
Antidepressive Agents , Drug Labeling , Antidepressive Agents/adverse effects , Employment , Female , Health Policy , Humans , United States , United States Food and Drug Administration
9.
Nature ; 568(7751): 235-239, 2019 04.
Article in English | MEDLINE | ID: mdl-30911168

ABSTRACT

Imaging the transcriptome in situ with high accuracy has been a major challenge in single-cell biology, which is particularly hindered by the limits of optical resolution and the density of transcripts in single cells1-5. Here we demonstrate an evolution of sequential fluorescence in situ hybridization (seqFISH+). We show that seqFISH+ can image mRNAs for 10,000 genes in single cells-with high accuracy and sub-diffraction-limit resolution-in the cortex, subventricular zone and olfactory bulb of mouse brain, using a standard confocal microscope. The transcriptome-level profiling of seqFISH+ allows unbiased identification of cell classes and their spatial organization in tissues. In addition, seqFISH+ reveals subcellular mRNA localization patterns in cells and ligand-receptor pairs across neighbouring cells. This technology demonstrates the ability to generate spatial cell atlases and to perform discovery-driven studies of biological processes in situ.


Subject(s)
Brain/anatomy & histology , Brain/metabolism , In Situ Hybridization, Fluorescence/methods , RNA, Messenger/analysis , RNA, Messenger/genetics , Single-Cell Analysis/methods , Transcriptome/genetics , 3T3 Cells , Animals , Brain/cytology , Dopaminergic Neurons/metabolism , Endothelial Cells/metabolism , Female , Gene Expression Profiling , Ligands , Male , Mice , Microglia/metabolism , Organ Specificity
10.
J Appl Econ (Chichester Engl) ; 34(7): 1102-1120, 2019.
Article in English | MEDLINE | ID: mdl-32153316

ABSTRACT

We use individual-level health facility choice data from urban Senegal to estimate consumer preferences for facility characteristics related to maternal health services. We find that consumers consider a large number of quality related facility characteristics, as well as travel costs, when making their health facility choice. In contrast to the typical assumption in the literature, our findings indicate that individuals frequently bypass the facility nearest their home. In light of this, we show that the mismeasured data used commonly in the literature produces biased preference estimates; most notably, the literature likely overestimates consumer distaste for travel.

11.
Cell ; 174(2): 363-376.e16, 2018 07 12.
Article in English | MEDLINE | ID: mdl-29887381

ABSTRACT

Visualization of the transcriptome and the nuclear organization in situ has been challenging for single-cell analysis. Here, we demonstrate a multiplexed single-molecule in situ method, intron seqFISH, that allows imaging of 10,421 genes at their nascent transcription active sites in single cells, followed by mRNA and lncRNA seqFISH and immunofluorescence. This nascent transcriptome-profiling method can identify different cell types and states with mouse embryonic stem cells and fibroblasts. The nascent sites of RNA synthesis tend to be localized on the surfaces of chromosome territories, and their organization in individual cells is highly variable. Surprisingly, the global nascent transcription oscillated asynchronously in individual cells with a period of 2 hr in mouse embryonic stem cells, as well as in fibroblasts. Together, spatial genomics of the nascent transcriptome by intron seqFISH reveals nuclear organizational principles and fast dynamics in single cells that are otherwise obscured.


Subject(s)
In Situ Hybridization, Fluorescence/methods , Transcriptome , Animals , Catalytic Domain , Cell Line , Chromosomes/metabolism , Fibroblasts/cytology , Fibroblasts/metabolism , Introns , Mice , Microscopy, Fluorescence , Microscopy, Video , Mouse Embryonic Stem Cells/cytology , Mouse Embryonic Stem Cells/metabolism , RNA Polymerase II/genetics , RNA Polymerase II/metabolism , RNA, Long Noncoding/genetics , RNA, Messenger/genetics , Single-Cell Analysis
12.
Health Econ ; 27(3): 576-591, 2018 03.
Article in English | MEDLINE | ID: mdl-29094775

ABSTRACT

Research in developing countries is rarely focused on examining how supply side factors affect family planning decisions due to a lack of facility-level data. When these data exist, analyses tend to focus on rural environments. In this paper, we study the effects that health facility access and quality have on contraceptive use and desired number of children for women in urban Senegal. Unlike related studies focusing on rural environments, we find no evidence that greater access to health facilities and pharmacies increases contraceptive use among urban women. However, we do find that contraceptive use among urban women is higher with greater facility quality. For example, we find that increasing the proportion of pharmacies employing multiple pharmacists from 0% to 50% would increase contraceptive use by 6.0 percentage points, and increasing the proportion of facilities with family planning guidelines/protocols from 50% to 100% would increase use by 2.1 percentage points.


Subject(s)
Family Planning Services/statistics & numerical data , Health Services Accessibility/statistics & numerical data , Quality of Health Care/statistics & numerical data , Urban Population , Adult , Community Pharmacy Services/statistics & numerical data , Contraception Behavior , Developing Countries , Family Planning Services/standards , Female , Health Services Accessibility/standards , Humans , Models, Statistical , Quality of Health Care/standards , Senegal , Socioeconomic Factors , Young Adult
13.
J Vis Exp ; (125)2017 07 13.
Article in English | MEDLINE | ID: mdl-28745641

ABSTRACT

The nematode, Caenorhabditis elegans' compact nervous system of only 302 neurons underlies a diverse repertoire of behaviors. To facilitate the dissection of the neural circuits underlying these behaviors, the development of robust and reproducible behavioral assays is necessary. Previous C. elegans behavioral studies have used variations of a "drop test", a "chemotaxis assay", and a "retention assay" to investigate the response of C. elegans to soluble compounds. The method described in this article seeks to combine the complementary strengths of the three aforementioned assays. Briefly, a small circle in the middle of each assay plate is divided into four quadrants with the control and experimental solutions alternately placed. After the addition of the worms, the assay plates are loaded into a behavior chamber where microscope cameras record the worms' encounters with the treated regions. Automated video analysis is then performed and a preference index (PI) value for each video is generated. The video acquisition and automated analysis features of this method minimizes the experimenter's involvement and any associated errors. Furthermore, minute amounts of the experimental compound are used per assay and the behavior chamber's multi-camera setup increases experimental throughput. This method is particularly useful for conducting behavioral screens of genetic mutants and novel chemical compounds. However, this method is not appropriate for studying stimulus gradient navigation due to the close proximity of the control and experimental solution regions. It should also not be used when only a small population of worms is available. While suitable for assaying responses only to soluble compounds in its current form, this method can be easily modified to accommodate multimodal sensory interaction and optogenetic studies. This method can also be adapted to assay the chemosensory responses of other nematode species.


Subject(s)
Biological Assay , Caenorhabditis elegans/physiology , Animals , Automation , Behavior, Animal/drug effects , Caenorhabditis elegans/drug effects , Chemotaxis/drug effects , Copper/pharmacology , Microscopy , Solutions/chemistry , Video Recording
14.
Econ Hum Biol ; 24: 164-183, 2017 02.
Article in English | MEDLINE | ID: mdl-28038413

ABSTRACT

This paper examines how a single female's investment in healthy body weight is affected by the quality of single males in her marriage market. A principle concern in estimation is the presence of market-level unobserved heterogeneity that may be correlated with changes in single male quality, measured as earning potential. To address this concern, we employ a differencing strategy that normalizes the exercise behaviors of single women to those of their married counterparts. Our main results suggest that when potential mate quality in a marriage market decreases, single black women invest less in healthy body weight. For example, we find that a 10 percentage point increase in the proportion of low quality single black males leads to a 5-10% decrease in vigorous exercise taken by single black females. Results for single white women are qualitatively similar, but not consistent across specifications. These results highlight the relationship between male and female human capital acquisition that is driven by participation in the marriage market. Our results suggest that programs designed to improve the economic prospects of single males may yield positive externalities in the form of improved health behaviors, such as more exercise, particularly for single black females.


Subject(s)
Body Weight/ethnology , Employment/economics , Healthy Lifestyle , Marriage/psychology , Obesity/ethnology , Single Person/psychology , Social Class , Adult , Black or African American/psychology , Black or African American/statistics & numerical data , Behavioral Risk Factor Surveillance System , Body Weight/physiology , Cross-Sectional Studies , Employment/classification , Exercise/physiology , Exercise/psychology , Female , Humans , Incidence , Income , Marriage/ethnology , Marriage/statistics & numerical data , Motivation , Obesity/economics , Obesity/psychology , Regression Analysis , United States/epidemiology , White People/psychology , White People/statistics & numerical data
15.
Environ Entomol ; 43(1): 146-56, 2014 Feb.
Article in English | MEDLINE | ID: mdl-24472207

ABSTRACT

Invasive mole cricket species in the genus Scapteriscus have become significant agricultural pests and are continuing to expand their range in North America. Though largely subterranean, adults of some species, such as Scapteriscus borellii Giglio-Tos 1894, are capable of long dispersive flights and phonotaxis to male calling songs to find suitable habitats and mates. Mole crickets in the genus Scapteriscus are known to be attracted to and can be caught by audio lure traps that broadcast synthesized or recorded calling songs. We report improvements in the design and production of electronic controllers for the automation of semipermanent mole cricket trap lures as well as highly portable audio trap collection designs. Using these improved audio lure traps, we collected the first reported individuals of the pest mole cricket S. borellii in California. We describe several characteristic features of the calling song of the California population including that the pulse rate is a function of soil temperature, similar to Florida populations of S. borellii. Further, we show that other calling song characteristics (carrier frequency, intensity, and pulse rate) are significantly different between the populations.


Subject(s)
Animal Communication , Entomology/instrumentation , Gryllidae , Animal Distribution , Animals , California , Female , Male
16.
Proc Natl Acad Sci U S A ; 110(29): 11940-5, 2013 Jul 16.
Article in English | MEDLINE | ID: mdl-23818641

ABSTRACT

Genetic screens have been widely applied to uncover genetic mechanisms of movement disorders. However, most screens rely on human observations of qualitative differences. Here we demonstrate the application of an automatic imaging system to conduct a quantitative screen for genes regulating the locomotive behavior in Caenorhabditis elegans. Two hundred twenty-seven neuronal signaling genes with viable homozygous mutants were selected for this study. We tracked and recorded each animal for 4 min and analyzed over 4,400 animals of 239 genotypes to obtain a quantitative, 10-parameter behavioral profile for each genotype. We discovered 87 genes whose inactivation causes movement defects, including 50 genes that had never been associated with locomotive defects. Computational analysis of the high-content behavioral profiles predicted 370 genetic interactions among these genes. Network partition revealed several functional modules regulating locomotive behaviors, including sensory genes that detect environmental conditions, genes that function in multiple types of excitable cells, and genes in the signaling pathway of the G protein Gαq, a protein that is essential for animal life and behavior. We developed quantitative epistasis analysis methods to analyze the locomotive profiles and validated the prediction of the γ isoform of phospholipase C as a component in the Gαq pathway. These results provided a system-level understanding of how neuronal signaling genes coordinate locomotive behaviors. This study also demonstrated the power of quantitative approaches in genetic studies.


Subject(s)
Caenorhabditis elegans/physiology , Epistasis, Genetic/physiology , GTP-Binding Protein alpha Subunits, Gq-G11/metabolism , Locomotion/physiology , Neurons/metabolism , Signal Transduction/physiology , Animals , Caenorhabditis elegans/genetics , Epistasis, Genetic/genetics , Gene Expression Profiling/methods , Locomotion/genetics , RNA Interference , Signal Transduction/genetics
17.
J Comput Neurosci ; 24(3): 253-76, 2008 Jun.
Article in English | MEDLINE | ID: mdl-17768672

ABSTRACT

To establish the relationship between locomotory behavior and dynamics of neural circuits in the nematode C. elegans we combined molecular and theoretical approaches. In particular, we quantitatively analyzed the motion of C. elegans with defective synaptic GABA and acetylcholine transmission, defective muscle calcium signaling, and defective muscles and cuticle structures, and compared the data with our systems level circuit model. The major experimental findings are: (1) anterior-to-posterior gradients of body bending flex for almost all strains both for forward and backward motion, and for neuronal mutants, also analogous weak gradients of undulatory frequency, (2) existence of some form of neuromuscular (stretch receptor) feedback, (3) invariance of neuromuscular wavelength, (4) biphasic dependence of frequency on synaptic signaling, and (5) decrease of frequency with increase of the muscle time constant. Based on (1) we hypothesize that the Central Pattern Generator (CPG) is located in the head both for forward and backward motion. Points (1) and (2) are the starting assumptions for our theoretical model, whose dynamical patterns are qualitatively insensitive to the details of the CPG design if stretch receptor feedback is sufficiently strong and slow. The model reveals that stretch receptor coupling in the body wall is critical for generation of the neuromuscular wave. Our model agrees with our behavioral data (3), (4), and (5), and with other pertinent published data, e.g., that frequency is an increasing function of muscle gap-junction coupling.


Subject(s)
Caenorhabditis elegans/physiology , Locomotion/physiology , Motor Activity/physiology , Animals , Caenorhabditis elegans/genetics , Locomotion/genetics , Mechanoreceptors/physiology , Models, Biological , Models, Genetic , Mutation , Signal Transduction , Synapses/physiology
18.
Methods Mol Biol ; 351: 241-51, 2006.
Article in English | MEDLINE | ID: mdl-16988438

ABSTRACT

Automated systems for recording and analyzing behavior have many applications for the study of neurobiology in Caenorhabditis elegans. In particular, machine-based approaches allow for precise quantitative definitions of behavioral phenotypes that have traditionally been subjectively described by individual observers. Automated systems also facilitate the analysis of behaviors that occur over long time scales or are difficult to detect by eye. Here we describe the detailed methodology for the use of one recently described automated tracking system for C. elegans. These protocols make it possible to measure a wide range of parameters related to the morphology, body posture, and locomotion patterns of individual wild-type and mutant nematodes.


Subject(s)
Algorithms , Behavior, Animal/physiology , Caenorhabditis elegans/physiology , Image Interpretation, Computer-Assisted , Motor Activity/physiology , Software , Animals , Image Interpretation, Computer-Assisted/methods , Locomotion/physiology , Microscopy, Video/methods , Mutation
19.
J Theor Biol ; 242(3): 652-69, 2006 Oct 07.
Article in English | MEDLINE | ID: mdl-16759670

ABSTRACT

Undulatory locomotion is common to nematodes as well as to limbless vertebrates, but its control is not understood in spite of the identification of hundred of genes involved in Caenorhabditis elegans locomotion. To reveal the mechanisms of nematode undulatory locomotion, we quantitatively analysed the movement of C. elegans with genetic perturbations to neurons, muscles, and skeleton (cuticle). We also compared locomotion of different Caenorhabditis species. We constructed a theoretical model that combines mechanics and biophysics, and that is constrained by the observations of propulsion and muscular velocities, as well as wavelength and amplitude of undulations. We find that normalized wavelength is a conserved quantity among wild-type C. elegans individuals, across mutants, and across different species. The velocity of forward propulsion scales linearly with the velocity of the muscular wave and the corresponding slope is also a conserved quantity and almost optimal; the exceptions are in some mutants affecting cuticle structure. In theoretical terms, the optimality of the slope is equivalent to the exact balance between muscular and visco-elastic body reaction bending moments. We find that the amplitude and frequency of undulations are inversely correlated and provide a theoretical explanation for this fact. These experimental results are valid both for young adults and for all larval stages of wild-type C. elegans. In particular, during development, the amplitude scales linearly with the wavelength, consistent with our theory. We also investigated the influence of substrate firmness on motion parameters, and found that it does not affect the above invariants. In general, our biomechanical model can explain the observed robustness of the mechanisms controlling nematode undulatory locomotion.


Subject(s)
Caenorhabditis elegans/physiology , Genes, Helminth , Locomotion/genetics , Models, Neurological , Animals , Biomechanical Phenomena , Caenorhabditis elegans/genetics , Caenorhabditis elegans Proteins/genetics , Caenorhabditis elegans Proteins/physiology , Motor Neurons/physiology , Muscles/physiology , Skin Physiological Phenomena
20.
BMC Genet ; 6: 5, 2005 Feb 07.
Article in English | MEDLINE | ID: mdl-15698479

ABSTRACT

BACKGROUND: Nematode sinusoidal movement has been used as a phenotype in many studies of C. elegans development, behavior and physiology. A thorough understanding of the ways in which genes control these aspects of biology depends, in part, on the accuracy of phenotypic analysis. While worms that move poorly are relatively easy to describe, description of hyperactive movement and movement modulation presents more of a challenge. An enhanced capability to analyze all the complexities of nematode movement will thus help our understanding of how genes control behavior. RESULTS: We have developed a user-friendly system to analyze nematode movement in an automated and quantitative manner. In this system nematodes are automatically recognized and a computer-controlled microscope stage ensures that the nematode is kept within the camera field of view while video images from the camera are stored on videotape. In a second step, the images from the videotapes are processed to recognize the worm and to extract its changing position and posture over time. From this information, a variety of movement parameters are calculated. These parameters include the velocity of the worm's centroid, the velocity of the worm along its track, the extent and frequency of body bending, the amplitude and wavelength of the sinusoidal movement, and the propagation of the contraction wave along the body. The length of the worm is also determined and used to normalize the amplitude and wavelength measurements. To demonstrate the utility of this system, we report here a comparison of movement parameters for a small set of mutants affecting the Go/Gq mediated signaling network that controls acetylcholine release at the neuromuscular junction. The system allows comparison of distinct genotypes that affect movement similarly (activation of Gq-alpha versus loss of Go-alpha function), as well as of different mutant alleles at a single locus (null and dominant negative alleles of the goa-1 gene, which encodes Go-alpha). We also demonstrate the use of this system for analyzing the effects of toxic agents. Concentration-response curves for the toxicants arsenite and aldicarb, both of which affect motility, were determined for wild-type and several mutant strains, identifying P-glycoprotein mutants as not significantly more sensitive to either compound, while cat-4 mutants are more sensitive to arsenite but not aldicarb. CONCLUSIONS: Automated analysis of nematode movement facilitates a broad spectrum of experiments. Detailed genetic analysis of multiple alleles and of distinct genes in a regulatory network is now possible. These studies will facilitate quantitative modeling of C. elegans movement, as well as a comparison of gene function. Concentration-response curves will allow rigorous analysis of toxic agents as well as of pharmacological agents. This type of system thus represents a powerful analytical tool that can be readily coupled with the molecular genetics of nematodes.


Subject(s)
Caenorhabditis elegans/genetics , Caenorhabditis elegans/physiology , Movement , Acetylcholine/metabolism , Animals , Automation , GTP-Binding Protein alpha Subunits, Gi-Go/genetics , GTP-Binding Protein alpha Subunits, Gq-G11/genetics , Methods , Microscopy, Video , Mutation , Nematoda/genetics , Nematoda/physiology , Signal Transduction/genetics
SELECTION OF CITATIONS
SEARCH DETAIL
...