Biomedical subjects

Laura E Jones

Publications and source records attributed to Laura E Jones.

16 recordsLinked to original sources

PubMed2006

Prey evolution on the time scale of predator-prey dynamics revealed by allele-specific quantitative PCR.

Using rotifer-algal microcosms, we tracked rapid evolution resulting from temporally changing natural selection in ecological predator-prey dynamics. We previously demonstrated that predator-prey oscillations in rotifer-algal laboratory microcosms are qualitatively altered by the presence of genetic variation within the prey. In that study, changes in algal gene frequencies were inferred from their effects on population dynamics but not observed directly. Here, we document rapid prey evolution in this system by directly observing changes in Chlorella vulgaris genotype frequencies as the abundances of these algae and their consumer, Brachionus calyciflorus, change through time. We isolated a group of algal clones that we could distinguish by using microsatellite-DNA markers, and developed an allele-specific quantitative PCR technique (AsQ-PCR) to quantify the frequencies of pairs of clones in mixed culture. We showed that two of these genotypes exhibited a fitness tradeoff in which one was more resistant to predation (more digestion-resistant), and the other had faster population growth under limiting nitrogen concentrations. A fully specified mathematical model for the rotifer-algal population and evolutionary dynamics predicted that these two clones would undergo a single oscillation in clonal frequencies followed by asymptotic fixation of the more resistant clone, rather than the recurrent oscillations previously observed with other algal clones. We used AsQ-PCR to confirm this prediction: the superior competitor dominated initially, but as rotifer densities increased, the more predator-resistant clone predominated.

Alleles↗

PubMed2006

Ecology: mechanisms for consumer diversity.

A variety of mechanisms can theoretically produce competitive coexistence in nature, making it hard to identify a single explanation for the maintenance of diversity in any particular system. Based on laboratory experiments with a consumer-resource system of crustacean Daphnia eating algae, Nelson et al. suggest that maintenance of genetic diversity in the consumer populations they studied depends only on the dynamics of the population structure of the consumer. We suggest that the differences in Daphnia genetic diversity that they find for different experimental treatments could equally be explained by a simple, well known mechanism: the number of coexisting competitors cannot exceed the number of shared resources. Here we confirm this possibility by using a simple mathematical model and suggest that more than one mechanism may account for the maintenance of genetic diversity observed by Nelson et al. in their system.

Aging↗

PubMed2006

The influence of type and severity of mental illness on receipt of screening mammography.

BACKGROUND: Women with mental illness may be at risk for failure to receive recommended preventive services such as mammography. Little is known about whether the type or severity of mental illness influences receipt of preventive services. OBJECTIVE: To measure the influence of type and severity of mental illness on receipt of mammography. DESIGN: Retrospective study of administrative claims data, 1996 to 2001. SUBJECTS: Privately insured women age 40 to 64 years, with and without claims for mental illness, and who were eligible for mammography between 1996 and 2001. MEASUREMENT: Odds ratios (OR) for receipt of screening mammography, any mammography, and follow-up mammography, adjusted for age, rural location, utilization of nonmental health services, and severity and type of the mental disorder. Severity measures were based on utilization of outpatient and inpatient mental health services and presence of comorbid substance use disorder. RESULTS: Women with any mental disorder were significantly less likely to receive mammography than controls. This was strongly influenced by severity of mental illness (any mammography: moderate severity OR 0.62; confidence interval [CI] 0.59 to 0.66: high severity OR 0.38; CI 0.33 to 0.43). Whereas severity contributed to lower receipt of mammography among women with mood and anxiety disorders, women with psychotic, alcohol, and substance abuse disorders had decreased odds for receipt of mammography regardless of severity. CONCLUSIONS: Women with mental disorders are at risk for failure to receive mammography, a recommended preventive service. Women with severe mental illness or psychotic and substance abuse disorders should be targeted to ensure delivery of mammography.

Adult↗

PubMed2006

Nonadherence to depression treatment guidelines among veterans with diabetes mellitus.

OBJECTIVE: To assess the adequacy of antidepressant dosage and duration among veterans with and without diabetes mellitus (DM), as well as provider-level and patient-level predictors of depression care quality, based on Veterans Health Administration (VHA) evidence-based clinical practice guidelines. STUDY DESIGN: Retrospective (1997-2005) cohort study of administrative, clinical, and pharmacy data from a midwestern VHA facility. METHODS: The sample included 2332 subjects (773 with DM) who had a new episode of depression, received antidepressant therapy, and had neither schizophrenia nor bipolar disorder. Antidepressant dosage and duration were evaluated in the acute and continuation phases. Dosage was adequate if the treatment dosage met the minimum therapeutic dosage specified in VHA guidelines. Treatment duration was adequate if the medication possession ratio was at least 80%. Multivariate logistic regression analysis was used to calculate odds ratios (ORs), adjusted for demographic, clinical, and healthcare utilization characteristics. RESULTS: Most subjects received an adequate dosage during the acute (88%) and continuation (58%) phases. Subjects with DM were 1.51-fold more likely to receive adequate dosage during the acute phase but were similarly likely (OR, 1.15) to receive adequate dosage during the continuation phase. Few subjects (<10%) received adequate treatment duration. Diabetes mellitus was not associated with less adequate duration during the acute phase (OR, 1.14). Few factors were identified as significant predictors of both antidepressant dosage and duration. CONCLUSIONS: Diabetes mellitus did not adversely affect depression care quality. Adequate antidepressant dosages were prescribed, but treatment duration fell short of guideline recommendations. Strategies to more effectively manage depression treatment are needed.

Adult↗

PubMed2005

Opportunistic infection as a cause of transient viremia in chronically infected HIV patients under treatment with HAART.

When highly active antiretroviral therapy is administered for long periods of time to HIV-1 infected patients, most patients achieve viral loads that are "undetectable" by standard assay (i.e., HIV -1 RNA<50 copies/ml). Yet despite exhibiting sustained viral loads below the level of detection, a number of these patients experience unexplained episodes of transient viremia or viral "blips". We propose here that transient activation of the immune system by opportunistic infection may explain these episodes of viremia. Indeed, immune activation by opportunistic infection may spur HIV replication, replenish viral reservoirs and contribute to accelerated disease progression. In order to investigate the effects of intercurrent infection on chronically infected HIV patients under treatment with highly active antiretroviral therapy (HAART), we extend a simple dynamic model of the effects of vaccination on HIV infection [Jones, L.E., Perelson, A.S., 2002. Modeling the effects of vaccination on chronically infected HIV-positive patients. JAIDS 31, 369-377] to include growing pathogens. We then propose a more realistic model for immune cell expansion in the presence of pathogen, and include this in a set of competing models that allow low baseline viral loads in the presence of drug treatment. Programmed expansion of immune cells upon exposure to antigen is a feature not previously included in HIV models, and one that is especially important to consider when simulating an immune response to opportunistic infection. Using these models we show that viral blips with realistic duration and amplitude can be generated by intercurrent infections in HAART treated patients.

AIDS-Related Opportunistic Infections↗

PubMed2004

Evolutionary tradeoff and equilibrium in an aquatic predator-prey system.

Due to the conventional distinction between ecological (rapid) and evolutionary (slow) timescales, ecological and population models have typically ignored the effects of evolution. Yet the potential for rapid evolutionary change has been recently established and may be critical to understanding how populations persist in changing environments. In this paper we examine the relationship between ecological and evolutionary dynamics, focusing on a well-studied experimental aquatic predator-prey system (Fussmann et al., 2000, Science, 290, 1358-1360; Shertzer et al., 2002, J. Anim. Ecol., 71, 802-815; Yoshida et al., 2003, Nature, 424, 303-306). Major properties of predator-prey cycles in this system are determined by ongoing evolutionary dynamics in the prey population. Under some conditions, however, the populations tend to apparently stable steady-state densities. These are the subject of the present paper. We examine a previously developed model for the system, to determine how evolution shapes properties of the equilibria, in particular the number and identity of coexisting prey genotypes. We then apply these results to explore how evolutionary dynamics can shape the responses of the system to 'management': externally imposed alterations in conditions. Specifically, we compare the behavior of the system including evolutionary dynamics, with predictions that would be made if the potential for rapid evolutionary change is neglected. Finally, we posit some simple experiments to verify our prediction that evolution can have significant qualitative effects on observed population-level responses to changing conditions.

Animals↗

PubMed2004

Monarch butterfly spatially discrete advection model.

We study the population cycles of the Monarch butterfly using one of the simplest systems incorporating both migration and local dynamics. The annual migration of the Monarch involves four generations. Members of Generations 1-3 (occasionally 4) migrate from the over-wintering site in Central Mexico to breeding grounds that extend as far north as the Northern United States and Southern Canada. A portion of the Generation 3 and all members of the Generation 4 butterflies begin their return to the over-wintering grounds in August through October where they enter reproductive diapause for several months. We developed a simple discrete-time island chain model in which different fecundity functions are used to model the reproductive strategies of each generation. The fecundity functions are selected from broad classes of functions that capture the effects of either contest or scramble intraspecific competition in the Monarch population. The objectives of our research are multiple and include the study of the generationally dependent intraspecific competition and its effect on the pool size of migrants as well as the persistence of the overall butterfly populations. The stage structure used in modeling the Monarch butterfly dynamics and their generationally dependent reproductive strategies naturally support fluctuating patterns and multiple attractors. The implications of these fluctuations and attractors on the long-term survival of the Monarch butterfly population are explored.

Animal Migration↗

PubMed2004

Receipt of diabetes services by insured adults with and without claims for mental disorders.

OBJECTIVES: We sought to determine whether receipt of the American Diabetes Association's recommended clinical services was similar among insured subjects with and without mental disorders during the period of 1996 to 2001. RESEARCH DESIGN: Our study was a retrospective analysis of Blue Cross/Blue Shield of Iowa administrative claims data, 1996-2001. SUBJECTS: We studied 26,020 adults with diabetes; 6,627 (25%) had a coexisting mental disorder. MEASURES: Service receipt included hemoglobin A1c (HbA1c) testing, dilated eye examination, cholesterol measurement, and urine protein testing. We used Cox regression to calculate hazard ratios (HRs) for service receipt after adjusting for demographic, disease, and utilization factors. RESULTS: Mental disorder subjects were more likely to be younger, women, urban residents, have diabetes complications and comorbidity, and to have increased healthcare utilization. Although they received more services (mean, 2.6) than subjects without mental disorders (mean, 2.3), they were less likely to have received a HbA1c test (HR 0.92; 99.9% confidence interval [CI] 0.87-0.97) and a cholesterol measurement (HR 0.92; 99.9% CI 0.86-0.98). Receipt of a dilated eye examination (HR 0.96; 99.9% CI 0.89-1.04) and urine protein test (HR 0.98; 99.9% CI 0.92-1.04) was similar. Service receipt varied by specific mental disorder categorization. Few subjects (< 6%) strictly adhered to the guidelines of the American Diabetes Association. CONCLUSIONS: Receipt of clinical preventive services for both populations was suboptimal. Importantly, subjects with mental disorders were more likely to have diabetic complications, even when controlling for utilization of healthcare services, possibly because of poorer receipt of HbA1c testing. Persons with mental disorders should be more aggressively educated about blood sugar control, given the high rate of complications in this population. Medical care directed at persons with comorbid medical and psychiatric disorders may be beneficial.

Adolescent↗

PubMed2003

Rapid evolution drives ecological dynamics in a predator-prey system.

Ecological and evolutionary dynamics can occur on similar timescales. However, theoretical predictions of how rapid evolution can affect ecological dynamics are inconclusive and often depend on untested model assumptions. Here we report that rapid prey evolution in response to oscillating predator density affects predator-prey (rotifer-algal) cycles in laboratory microcosms. Our experiments tested explicit predictions from a model for our system that allows prey evolution. We verified the predicted existence of an evolutionary tradeoff between algal competitive ability and defence against consumption, and examined its effects on cycle dynamics by manipulating the evolutionary potential of the prey population. Single-clone algal cultures (lacking genetic variability) produced short cycle periods and typical quarter-period phase lags between prey and predator densities, whereas multi-clonal (genetically variable) algal cultures produced long cycles with prey and predator densities nearly out of phase, exactly as predicted. These results confirm that prey evolution can substantially alter predator-prey dynamics, and therefore that attempts to understand population oscillations in nature cannot neglect potential effects from ongoing rapid evolution.

Animals↗

PubMed2002

Modeling the effects of vaccination on chronically infected HIV-positive patients.

T-cell activation plays a critical role in the initiation and propagation of HIV-1 infection and yet transient activation of the immune system is a normal response to immunization. While it is now considered wise to vaccinate HIV-1-positive patients, it is crucial to anticipate any lasting effects of vaccination on plasma HIV-1 RNA levels and on infected T-cell populations. We extend a simple dynamic model of HIV infection to include T-cell activation by vaccination. We show that the model can reproduce many but not all of the features of the post-tetanus immunization rise in viral load observed and reported on by Stanley et al. in 1966 ( 334:1222-1230). Amplitudes and approximate timing of postimmunization peak viral loads were matched in 10 of 12 cases; in patients with double postimmunization peaks of nearly equal amplitude the later peaks were matched. Furthermore, our simulations suggest that productively infected cell populations track postvaccination increases in plasma viral load, rising and falling in concert over a period of about 4 weeks, whereas chronically infected cells peak later and remain elevated over baseline levels for up to 6 weeks postvaccination.

AIDS Vaccines↗

PubMedDate not supplied

Inadequate follow-up care for depression and its impact on antidepressant treatment duration among veterans with and without diabetes mellitus in the Veterans Health Administration.

OBJECTIVE: Our objective was to describe the adequacy of follow-up care for depression and its association with antidepressant treatment duration among veterans with and without diabetes mellitus (DM). METHOD: This was a retrospective study (1997-2005) of 2178 veterans (33% with DM) in a Midwestern Veterans Health Administration facility who had a new episode of unipolar depression. Adequate follow-up care was defined by a health care visit within 7 and 14 days, and >/=3 visits following antidepressant treatment initiation. Adequate treatment duration was defined by a medication possession ratio of >/=80%. Multivariate logistic regression was used to calculate odds ratios (ORs) adjusted for demographic, clinical and health care utilization characteristics. RESULTS: Only 27% received >/=3 follow-up visits within 12 weeks, and <23% received follow-up within 2 weeks of antidepressant initiation. Subjects with DM were 1.36-fold more likely [95% confidence interval (95% CI)=1.05-1.75] to have received >/=3 visits but were similarly likely to have received follow-up within 7 days (OR=1.02; 95% CI=0.74-1.41) or 14 days (OR=1.08; 95% CI=0.83-1.40) of antidepressant initiation. Adequate follow-up care was the most important predictor of adequate treatment duration (OR=2.10; 95% CI=1.54-2.88). CONCLUSION: DM had little influence on the adequacy of follow-up care for depression, with few exceptions. Follow-up care for depression is underutilized and has a significant impact on antidepressant treatment duration. Strategies to more effectively manage depression treatment are required.

Adult↗

PubMedDate not supplied

Increased risk for metabolic syndrome in persons seeking care for mental disorders.

BACKGROUND: An increased risk for metabolic syndrome has been described for persons with psychotic and mood disorders. Our objectives were to determine whether the odds for metabolic syndrome (MetSyn) were increased among insured adults with and without mental illness, and to determine whether this risk extends beyond psychotic and affective disorders. METHOD: This was a retrospective analysis of a 100% sample of Blue Cross/Blue Shield of Iowa claims data. Three definitions of MetSyn were examined: 1) presence of any 3 or more components of MetSyn (obesity, hypertriglyceridemia, hypercholesterolemia, hypertension, and glucose intolerance/diabetes mellitus), 2) criteria #1 and/or claim for glucose intolerance/diabetes mellitus, and 3) criteria #1, criteria #2, and/or claim for obesity. ICD-9 codes were used to define obesity, hypertriglyceridemia, hypercholesterolemia, hypertension, and glucose intolerance/diabetes mellitus. Multivariate logistic regression was used to investigate the association between mental illness and MetSyn. RESULTS: Prevalence of MetSyn for subjects with any mental illness as compared to those without was 4.9% vs. 2.0% (criteria #1), 8.1% vs. 4.2% (criteria #2), and 13.2% vs. 6.2% (criteria #3). MetSyn was more common (OR = 1.3-1.5) for subjects with any mental illness as compared to those without, regardless of which definition of MetSyn was used. Subjects with sexual disorders (OR = 1.7-1.8), sleep disorders (OR = 1.2-1.7), and mood disorders (OR = 1.3-1.6) had significantly higher odds of MetSyn compared to those without claims for mental disorders, regardless of which definition of MetSyn was used. CONCLUSIONS: These results suggest that MetSyn is not only problematic among persons with psychosis and affective disorders, but that it also affects patients with other forms of mental illness. Clinicians should have a heightened awareness of metabolic risk factors, particularly when mental illness is present.

Adult↗

PubMedDate not supplied

Mental disorders and revascularization procedures in a commercially insured sample.

OBJECTIVE: The objective of this study was to determine if receipt of revascularization was similar among commercially insured adults with mental disorders compared with people without mental disorders. METHODS: This was a retrospective analysis of a 100% sample of Blue Cross/Blue Shield of Iowa administrative claims data, 1996 to 2001. Logistic regression was used to calculate unadjusted and adjusted odds ratios (OR) for receipt of angioplasty (PTCA) and bypass graft surgery (CABG) within 30 days of discharge. RESULTS: A total of 3368 adults, aged 18 to 64 years, were hospitalized for myocardial infarction (MI) and 40% (n = 1342) had a mental disorder. Subjects with mental disorders were more likely to be younger, female, urban residents, and to have increased cardiovascular and medical comorbidity. They were similarly likely as subjects without mental disorders to have received PTCA (OR, 1.10; 95% confidence interval [CI], 0.95-1.29) and CABG (OR, 0.89; 95% CI, 0.71-1.11) in analyses adjusted for demographic and clinical characteristics. Revascularization rates did not differ by mental disorder type, with few exceptions. CONCLUSIONS: Receipt of revascularization was similar for patients with and without mental disorders. Our results may differ from previous findings as a result of the younger population studied and increased comorbidity in people with mental disorders, which may have resulted in a contraindication for surgical intervention. Conversely, the increased burden of comorbidity could suggest that these patients should have received PTCA at higher rates because of the better prognosis associated with revascularization as compared with medical management. Prospective analyses with review of clinical data and behavioral risk factors are necessary to determine why some patients with mental illness may be less likely to receive cardiac interventions.

Angioplasty, Balloon, Coronary↗

PubMedDate not supplied

Medical comorbidity in women and men with bipolar disorders: a population-based controlled study.

OBJECTIVE: Rarely has validated information on chronic medical comorbidity been presented for persons with bipolar disorder. To deliver appropriate health services, it is important to understand the prevalence of chronic medical conditions in this population. This study examines chronic medical comorbidity using validated methodology in persons with bipolar disorder. METHODS: This is a retrospective study of a 100% sample of administrative claims (1996-2001) from Wellmark Blue Cross Blue Shield. Three thousand five hundred fifty-seven subjects had bipolar I disorder and did not have claims for schizophrenia or schizoaffective disorder. Controls had no documented claims for psychiatric conditions. Using validated methodology, inpatient and outpatient claims were used to determine prevalence of 44 chronic medical conditions. Odds ratios (ORs) were adjusted for age, gender, residence, and nonmental healthcare utilization. RESULTS: Persons with bipolar disorder were young (mean age, 38.8 years) and significantly more likely to have medical comorbidity, including three or more chronic conditions (41% versus 12%, p < .001) compared with controls. Elevated ORs were found for conditions spanning all organ systems. Hyperlipidemia, lymphoma, and metastatic cancer were the only conditions less likely to occur in persons with bipolar disorder. CONCLUSION: Bipolar disorders are associated with substantial chronic medical burden. Familiarity with conditions affecting this population may assist in programs aimed at providing medical care for the chronically mentally ill.

Accidents↗

PubMedDate not supplied

Psychiatric sequelae following breast cancer chemotherapy: a pilot study using claims data.

Despite attention to depression and cognitive disorders, the prevalence of other mental disorders following breast cancer chemotherapy has not been well described. The authors undertook a pilot study using insurance claims data to compare the prevalence of mental disorders other than depression in a population of breast cancer surgery patients who did versus did not receive postsurgical chemotherapy treatment. Women receiving chemotherapy in addition to surgery were more likely to be diagnosed with adjustment disorders (odds ratio=2.01, 95% CI=1.04-3.87). Prevalence of depression, anxiety, cognitive, and sleep disorders were not dependent on receipt of post-surgical chemotherapy treatment. These findings support the need for heightened awareness for mental conditions following chemotherapy.

Adjustment Disorders↗

PubMedDate not supplied

Prevalence and correlates of illness worry in the general population.

The prevalence and correlates of illness worry in the general population were investigated in a representative sample. The authors screened residents of the United States by telephone, and more detailed interviews were conducted with 123 respondents who reported at least 1 month of worry about serious illness in the past 12 months and an equal number of randomly selected persons without such worry. Data on demographic characteristics, medical and psychiatric conditions, functional impairment, and health care utilization were collected. At least 1 month of worry was endorsed by 13.1% of the screened population. Correlates of worry included a cluster of psychiatric conditions (major depressive episode, panic attacks, and generalized anxiety disorder) and three clusters of physical conditions (heart disease, cancer, and other diseases). Worry about serious illness was associated with functional impairment and health care utilization.

Adolescent↗