Your browser doesn't support javascript.
loading
Show: 20 | 50 | 100
Results 1 - 20 de 36
Filter
1.
Insects ; 14(3)2023 Mar 07.
Article in English | MEDLINE | ID: mdl-36975947

ABSTRACT

After resistance is first detected, continued resistance monitoring can inform decisions on how to effectively manage resistant populations. We monitored for resistance to Cry1Ac (2018 and 2019) and Cry2Ab2 (2019) from southeastern USA populations of Helicoverpa zea. We collected larvae from various plant hosts, sib-mated the adults, and tested neonates using diet-overlay bioassays and compared them to susceptible populations for resistance estimates. We also compared LC50 values with larval survival, weight and larval inhibition at the highest dose tested using regression, and found that LC50 values were negatively correlated with survival for both proteins. Finally, we compared resistance rations between Cry1Ac and Cry2Ab2 during 2019. Some populations were resistant to Cry1Ac, and most were resistant to CryAb2; Cry1Ac resistance ratios were lower than Cry2Ab2 during 2019. Survival was positively correlated with larval weight inhibition for Cry2Ab. This contrasts with other studies in both the mid-southern and southeastern USA, where resistance to Cry1Ac, Cry1A.105, and Cry2Ab2 increased over time and was found in a majority of populations. This indicates that cotton expressing Cry proteins in the southeastern USA was at variable risk for damage in this region.

2.
J Neurooncol ; 162(1): 15-23, 2023 Mar.
Article in English | MEDLINE | ID: mdl-36853489

ABSTRACT

PURPSOSE: Cerebral radiation necrosis (RN) is often a delayed phenomenon occurring several months to years after the completion of radiation treatment. Differentiating RN from tumor recurrence presents a diagnostic challenge on standard MRI. To date, no evidence-based guidelines exist regarding imaging modalities best suited for this purpose. We aim to review the current literature and perform a diagnostic meta-analysis comparing various imaging modalities that have been studied to differentiate tumor recurrence and RN. METHODS: A systematic search adherent to PRISMA guidelines was performed using Scopus, PubMed/MEDLINE, and Embase. Pooled sensitivities and specificities were determined using a random-effects or fixed-effects proportional meta-analysis based on heterogeneity. Using diagnostic odds ratios, a diagnostic frequentist random-effects network meta-analysis was performed, and studies were ranked using P-score hierarchical ranking. RESULTS: The analysis included 127 studies with a total of 220 imaging datasets, including the following imaging modalities: MRI (n = 10), MR Spectroscopy (MRS) (n = 28), dynamic contrast-enhanced MRI (n = 7), dynamic susceptibility contrast MRI (n = 36), MR arterial spin labeling (n = 5), diffusion-weighted imaging (n = 13), diffusion tensor imaging (DTI) (n = 2), PET (n = 89), and single photon emission computed tomography (SPECT) (n = 30). MRS had the highest pooled sensitivity (90.7%). DTI had the highest pooled specificity (90.5%). Our hierarchical ranking ranked SPECT and MRS as most preferable, and MRI was ranked as least preferable. CONCLUSION: These findings suggest SPECT and MRS carry greater utility than standard MRI in distinguishing RN from tumor recurrence.


Subject(s)
Diffusion Tensor Imaging , Neoplasm Recurrence, Local , Humans , Magnetic Resonance Imaging/methods , Necrosis/diagnostic imaging , Neoplasm Recurrence, Local/diagnostic imaging , Sensitivity and Specificity , Tomography, Emission-Computed, Single-Photon/methods
3.
J Gastrointest Cancer ; 54(3): 846-854, 2023 Sep.
Article in English | MEDLINE | ID: mdl-36251211

ABSTRACT

PURPOSE: Historically, reported incidence of brain metastasis secondary to esophageal carcinoma is low. We sought to determine the incidence of brain metastasis in a contemporary cohort of patients with carcinoma of the esophagus. METHODS: Data from patients with localized esophageal carcinoma prospectively enrolled on three curative intent Alliance treatment trials (N0044, N0342, N044E) were reviewed including time to diagnosis of first progression event (brain versus other site) and overall survival. RESULTS: Eighty-five patients comprised the cohort of which 85% were male and 86% had adenocarcinoma primary tumor histology. Thirty-nine of the 85 patients had documented progression to any site, and of those, brain metastasis occurred as the first event in 15% (6 of 39). Adenocarcinoma was the primary histology in all 6 patients and tumor grade was high (3 or 4) in 5 of the 6 patients (one not documented). Median time to brain metastasis (9.6 months) versus non-brain metastasis (12.4 months) and median survival after first progression (5.4 months versus 8.1 months, respectively) were not statistically different. CONCLUSION: In this prospective cohort of patients with esophageal carcinoma, those with high-grade adenocarcinoma appear to have a higher incidence of brain metastasis than historically reported. The pattern of brain metastases corroborates recent findings in terms of incidence, predominance of adenocarcinoma primary tumor histology, timing after diagnosis, and overall survival. Further study to confirm these findings, as well as the value of baseline, restaging and follow-up cranial imaging for brain metastasis is recommended. GOV IDENTIFIERS: NCT00022139 (NCCTG N0044), NCT00100945 (NCCTG N0342), and NCT00100945 (NCCTG N044E).


Subject(s)
Adenocarcinoma , Brain Neoplasms , Carcinoma , Esophageal Neoplasms , Humans , Male , Female , Incidence , Prospective Studies , Adenocarcinoma/epidemiology , Adenocarcinoma/therapy , Esophageal Neoplasms/epidemiology , Esophageal Neoplasms/therapy , Esophageal Neoplasms/pathology , Brain Neoplasms/epidemiology , Brain Neoplasms/therapy , Brain Neoplasms/secondary
5.
Health Econ ; 29(7): 748-765, 2020 07.
Article in English | MEDLINE | ID: mdl-32301244

ABSTRACT

This paper offers an approach to assessing quality of life, based on Sen's (1985) theory, which it uses to understand loss in quality of life due to mobility impairment. Specifically, it provides a novel theoretical analysis that is able to account for the possibility that some functionings may increase when a person's capabilities decrease, if substitution effects are large enough. We then develop new data consistent with our theoretical framework that permits comparison of quality of life between those with a disability (mobility impairment) and those without. Empirical results show that mobility impairment has widespread rather than concentrated impacts on capabilities and is associated with high psychological costs. We also find evidence that a small number of functionings are higher for those with a disability, as our theory allows. The paper concludes by discussing possible implications for policy and health assessment methods.


Subject(s)
Disabled Persons , Quality of Life , Health Status , Humans , Income
6.
Lancet ; 391 Suppl 2: S37, 2018 Feb 21.
Article in English | MEDLINE | ID: mdl-29553436

ABSTRACT

BACKGROUND: Siege, a process of political domination aimed at isolating an entire population, is a unique threat to health-care provision. The aim of this study was to qualitatively examine the effects of the Israeli siege on the practices and systems that underlie health in the Gaza Strip. METHODS: Data were from participant observation between 2009 and 2017, including 20 interviews with doctors and health administrators in non-governmental organisations (NGO), government, and UN sectors. All participants were provided with a description of the study and provided written consent to participate. The study was approved through the Human Subjects Review process at Bucknell University and the University of Washington. The data were analysed using a critical political economic framework, based on the concepts of primitive accumulation, accumulation by dispossession, surplus populations, and de-development. These analytical frames are further developed to interpret neoliberal trends in health-care systems organising and financing as they apply in the distorted social and economic context of siege. FINDINGS: The elimination of political sovereignty through the twin processes of occupation and siege are the primary impediments to the successful promotion of public health in the Gaza Strip. Findings indicate that siege impinges on effective health-care provision by withholding materials and resources and undermining the health care at a systems level. These strains pose considerable threats to health care, within the ministry of health and among other entities in the Gaza Strip that deliver care. Gazan society is divested of the underpinnings necessary for a well functioning sovereign health-care infrastructure. Instead of a self-governing, independent system, this analysis reveals a system that is comprised of captive clients who are entirely dependent on Israel, international bodies, and the aid industry for goods and services, with no means of independent development. INTERPRETATION: The siege represents a totalising social determinant of public health in the Gaza Strip, and it has significant and deliberate deleterious effects on the provision of medical care and exacerbates problems in overstretched medical services. These findings point to the importance of foregrounding the geopolitical context for analysis of medical service delivery within conflict settings. The data indicate formative trends in health-care provision in the Gaza Strip. Although the siege creates a seemingly unique economic context for analysis of health-care provision, critical analyses that deconstruct the depredations of neoliberalism in the health-care setting provide a useful framework for analysis of the failings of the health-care sector. Indeed, health-care providers are in an impossible position of attempting to provide quality care without the ability to coordinate with their colleagues in other sectors, and without substantial support from the international community. The final analysis also highlights the importance of advocating for sovereignty and self-determination as related to health systems, and it suggests that successful health-care provision is impossible without a strong analysis of the political and economic context. FUNDING: Bucknell University.

7.
Pest Manag Sci ; 72(10): 1934-45, 2016 Oct.
Article in English | MEDLINE | ID: mdl-26775623

ABSTRACT

BACKGROUND: Over the past two decades, neonicotinoid seed treatments have become the primary method to manage tobacco thrips, Frankliniella fusca Hinds, on seedling cotton. Because this insect is highly polyphagous and the window of insecticide exposure is short, neonicotinoid resistance was expected to pose a minimal risk. However, reports of higher than expected F. fusca seedling damage in seed-treated cotton fields throughout the Mid-South and Southeast US production regions suggested neonicotinoid resistance had developed. To document this change, F. fusca populations from 86 different locations in the eastern United States were assayed in 2014 and 2015 for imidacloprid and thiamethoxam resistance to determine the extent of the issue in the region. RESULTS: Approximately 57 and 65% of the F. fusca populations surveyed had reduced imidacloprid and thiamethoxam sensitivity respectively. Survivorship in diagnostic bioassays was significantly different at both the state and regional scales. Multiple-dose bioassays conducted on 37 of the populations documented up to 55- and 39-fold resistance ratios for imidacloprid and thiamethoxam respectively. CONCLUSION: Estimates of neonicotinoid resistance indicate an emerging issue for management of F. fusca in the eastern United States. Significant variation in survivorship within states and regions indicated that finer-scale surveys were needed to determine factors (genetic, insecticide use) driving resistance evolution. © 2016 Society of Chemical Industry.


Subject(s)
Insecticide Resistance , Insecticides , Thysanoptera/genetics , Animals , Gossypium/parasitology , Imidazoles , Neonicotinoids , Nitro Compounds , Oxazines , Seeds/parasitology , Thiamethoxam , Thiazoles , United States
8.
Environ Res ; 144(Pt B): 15-26, 2016 Jan.
Article in English | MEDLINE | ID: mdl-26597639

ABSTRACT

An integrated methodology, based on linking Bayesian belief networks (BBN) with GIS, is proposed for combining available evidence to help forest managers evaluate implications and trade-offs between forest production and conservation measures to preserve biodiversity in forested habitats. A Bayesian belief network is a probabilistic graphical model that represents variables and their dependencies through specifying probabilistic relationships. In spatially explicit decision problems where it is difficult to choose appropriate combinations of interventions, the proposed integration of a BBN with GIS helped to facilitate shared understanding of the human-landscape relationships, while fostering collective management that can be incorporated into landscape planning processes. Trades-offs become more and more relevant in these landscape contexts where the participation of many and varied stakeholder groups is indispensable. With these challenges in mind, our integrated approach incorporates GIS-based data with expert knowledge to consider two different land use interests - biodiversity value for conservation and timber production potential - with the focus on a complex mountain landscape in the French Alps. The spatial models produced provided different alternatives of suitable sites that can be used by policy makers in order to support conservation priorities while addressing management options. The approach provided provide a common reasoning language among different experts from different backgrounds while helped to identify spatially explicit conflictive areas.


Subject(s)
Biodiversity , Conservation of Natural Resources/methods , Decision Making , Ecology/methods , Forests , Bayes Theorem , Conservation of Natural Resources/economics , Ecology/economics , France , Planning Techniques
9.
Soc Sci Med ; 146: 332-40, 2015 Dec.
Article in English | MEDLINE | ID: mdl-26603311

ABSTRACT

Siege, a process of political domination aimed at isolating an entire population, represents a unique threat to healthcare provision. This study is a qualitative examination of the impacts of siege on the practices and systems that underlie health in Gaza. Data are from participant observation conducted over a period of six years (2009-2014), along over 20 interviews with doctors and health administrators in the Non-Governmental Organisation (NGO), Governmental, and United Nations sectors. Analyses were informed by two connected theories. First, the theory of surplus population was used, an idea that builds on Marx's conception of primitive accumulation and Harvey's accumulation by dispossession. Second, Roy's theory of de-development was used, particularly as it is connected to neoliberal trends in healthcare systems organizing and financing. Findings indicate that siege impinges on effective healthcare provision through two central, intertwined processes: withholding materials and resources and undermining healthcare at a systems level. These strains pose considerable threats to healthcare, particularly within the Ministry of Health but also within and among other entities in Gaza that deliver care. The strategies of de-development described by participants reflect the ways the population that is codified as a surplus population. Gazan society is continually divested of any of the underpinnings necessary for a well-functioning sovereign health care infrastructure. Instead of a self-governing, independent system, this analysis of health care structures in Gaza reveals a system that is continually at risk of being comprised entirely of captive consumers who are entirely dependent on Israel, international bodies, and the aid industry for goods and services. This study points to the importance of foregrounding the geopolitical context for analysis of medical service delivery within conflict settings. Findings also highlight the importance of advocating for sovereignty and self-determination as related to health systems.


Subject(s)
Armed Conflicts , Health Services Accessibility , Healthcare Disparities , Politics , Female , Human Rights Abuses , Humans , Interdisciplinary Studies , Israel , Male , Middle East , Resource Allocation
11.
Nanomedicine (Lond) ; 8(10): 1577-86, 2013 Oct.
Article in English | MEDLINE | ID: mdl-23432340

ABSTRACT

AIM: The aim of this study was to investigate in vitro the utility of biologically compatible, nontoxic and cell-specific targetable hydrogel nanoparticles (NPs), which have Coomassie® Brilliant Blue G dye (Sigma-Aldrich, MO, USA) covalently linked into their polyacrylamide matrix, as candidates for photothermal therapy (PTT) of cancer cells. MATERIALS & METHODS: Hydrogel NPs with Coomassie Brilliant Blue G dye covalently linked into their polyacrylamide matrix were fabricated using a reverse micelle microemulsion polymerization method and were found to be 80-95 nm in diameter, with an absorbance value of 0.52. PTT-induced hyperthermia/thermolysis was achieved at 37°C using an inexpensive, portable, light-emitting diode array light source (590 nm, 25 mW/cm(2)). RESULTS & CONCLUSION: Hydrogel NPs with Coomassie Brilliant Blue G dye linked into their polyacrylamide matrix are effective in causing PTT-induced thermolysis in immortalized human cervical cancer cell line (HeLa) cells for varying NP concentrations and treatment times. These multifunctional particles have previously been used in cancer studies to enable delineation, for glioma surgery and in photoacoustic imaging studies. The addition of the PTT function would enable a three-pronged theranostic approach to cancer medicine, such as guided tumor surgery with intra-operative photoacoustic imaging and intra-operative PTT.


Subject(s)
Hydrogels/administration & dosage , Nanoparticles/administration & dosage , Phototherapy , Uterine Cervical Neoplasms/therapy , Acrylic Resins/administration & dosage , Acrylic Resins/chemistry , Female , HeLa Cells , Humans , Hydrogels/chemistry , Nanoparticles/chemistry , Rosaniline Dyes/administration & dosage , Rosaniline Dyes/chemistry , Uterine Cervical Neoplasms/pathology
12.
World J Gastroenterol ; 17(19): 2407-10, 2011 May 21.
Article in English | MEDLINE | ID: mdl-21633640

ABSTRACT

AIM: To determine the incidence of brain metastasis in a contemporary group of patients with carcinoma of the esophagus. METHODS: Retrospective analysis of 53 patients with esophageal carcinoma who received radiotherapy as a component of treatment between 1998 and 2007, including patient and tumor characteristics, and subsequent diagnosis of brain metastasis. The association between the histological type of esophageal cancer and the incidence of brain metastasis was assessed using Fisher's exact test. RESULTS: Forty-four of the fifty-three patients in this study had adenocarcinoma and nine had squamous cell carcinoma, ranging from stage IIA-IVB. Primary treatment was surgery with neoadjuvant chemoradiotherapy (trimodality therapy) in 19% of patients; chemoradiotherapy in 42%; and surgery and adjuvant radiotherapy in 7%. Twenty-five percent of patients in this study received palliative radiotherapy. The overall incidence of brain metastasis in this cohort was 13%. Adenocarcinoma was the primary tumor histology in all of the patients who developed brain metastasis, representing an incidence of 16% in this subgroup. No patients with squamous cell carcinoma received trimodality therapy. The association between histology and brain metastasis was not statistically significant. CONCLUSION: The incidence of brain metastasis in this contemporary cohort of patients with esophageal carcinoma is higher than previously reported and was confined to those with adenocarcinoma.


Subject(s)
Adenocarcinoma/epidemiology , Adenocarcinoma/secondary , Brain Neoplasms/epidemiology , Brain Neoplasms/secondary , Esophageal Neoplasms/pathology , Adenocarcinoma/therapy , Adult , Aged , Aged, 80 and over , Brain Neoplasms/therapy , Carcinoma, Squamous Cell/epidemiology , Carcinoma, Squamous Cell/secondary , Carcinoma, Squamous Cell/therapy , Combined Modality Therapy , Female , Humans , Incidence , Male , Middle Aged , Minnesota/epidemiology , Neoplasm Staging , Retrospective Studies , Survival Analysis , Treatment Outcome
13.
Chem Commun (Camb) ; 46(36): 6777-9, 2010 Sep 28.
Article in English | MEDLINE | ID: mdl-20820505

ABSTRACT

A sizeable negative magnetoresistance (MR) has been observed for oxypnictides LnOMnAs (Ln = La,Nd). MR up to -24% is observed at 200 K for LaOMnAs which is unprecedented for divalent Mn(2+). Both materials are weak ferromagnets with transition temperatures above room temperature.

14.
PDA J Pharm Sci Technol ; 64(4): 356-63, 2010.
Article in English | MEDLINE | ID: mdl-21502036

ABSTRACT

Two sterility test methods, the ScanRDI® rapid sterility test and the United States Pharmacopeia/European Pharmacopoeia/Japanese Pharmacopoeia (USP/EP/JP) compendial sterility test, were compared with respect to the limits of detection for the presence of viable microorganisms in aqueous solutions at low inoculation levels. The ScanRDI® system employs a combination of direct fluorescent labeling techniques and solid-phase laser scanning cytometry to rapidly enumerate viable microorganisms from aqueous samples, whereas the compendial sterility test is a qualitative, growth-based method that uses a visual assessment of turbidity to indicate microbial contamination. Eight microorganisms were evaluated, seven compendial microorganisms (Clostridium sporogenes, Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, Bacillus subtilis, Aspergillus niger, Candida albicans) and the Gram-positive anaerobe Propionibacterium acnes. The number of viable organisms was estimated using the ScanRDI® method and the conventional sterility test method using most probable number methodology. The mean difference between the methods was computed and 95% confidence intervals around the mean difference were estimated. The ScanRDI® method was found to be numerically superior and statistically non-inferior to the compendial (USP/EP/JP) sterility test with respect to the limits of detection for all organisms tested.


Subject(s)
Limit of Detection , Staphylococcus aureus , Aspergillus niger , Bacillus subtilis , Bacteria , Clostridium , Escherichia coli , Infertility , Pseudomonas aeruginosa
15.
J Strength Cond Res ; 23(9): 2555-9, 2009 Dec.
Article in English | MEDLINE | ID: mdl-19910819

ABSTRACT

The purpose of this study was to examine changes in various aerobic and anaerobic physical performance measures in male National Collegiate Athletic Association (NCAA) Division III soccer players during the competitive soccer season. Twelve starters of the men's soccer team (mean +/- SD; age = 20.0 +/- 0.9 years, height = 175.7 +/- 8.1 cm, body mass = 73.9 +/- 11.00 kg, body mass index [BMI] 24.0 +/- 3.0 kg.m2, and percent body fat = 10.6 +/- 5.4%) were tested at the beginning (PRS) and the end (POS) of the collegiate soccer season. Each experimental trial included a maximal aerobic capacity test (VO2max); 10-, 30-, and 40-m sprints; pro-agility test; and the Wingate anaerobic power test (WAnT). From PRS to POS, VO2max significantly increased (51.05 +/- 5.97 vs. 54.64 +/- 4.90 ml.kg-1.min-1), and the 10- and 30-m sprint were significantly lower (2.03 +/- 0.15 vs. 1.96 +/- 0.11 seconds and 4.72 +/- 0.26 vs. 4.51 +/- 0.24 seconds, respectively). Anthropometric measures, 40-m sprint, pro-agility test, and WAnT were not significantly different between PRS and POS. The results of this study indicate that NCAA Division III male soccer players appear to improve aerobic and anaerobic performance measures during the competitive soccer season. It is arguable that these performance improvements may represent a poor preseason conditioning level that may result in a competitive disadvantage during the early stages of the season. An ongoing process of recruiting better-quality players that may closely follow the off-season training regimen may partially remedy this problem.


Subject(s)
Anaerobic Threshold/physiology , Athletic Performance/physiology , Oxygen Consumption/physiology , Running/physiology , Seasons , Soccer/physiology , Adult , Anthropometry , Body Composition , Body Mass Index , Competitive Behavior , Exercise Test , Exercise Tolerance/physiology , Humans , Male , Muscle Fatigue/physiology , North Carolina , Physical Fitness , Skinfold Thickness , United States , Universities
16.
Inorg Chem ; 48(12): 5216-23, 2009 Jun 15.
Article in English | MEDLINE | ID: mdl-19432467

ABSTRACT

Neutron diffraction experiments and Korringa-Kohn-Rostoker with coherent potential approximation electronic band structure calculations as well as electrical resistivity measurements have been performed on polycrystalline Mo(3-x)Ru(x)Sb(7) samples for 0 < or = x < or = 1. Neutron diffraction studies have been undertaken at room temperature and extended down to 4 K to get a better understanding of the crystalline structure modifications as the Ru content increases. Both structural and chemical characterizations have unambiguously revealed a solubility limit of the Ru atoms close to 0.8. Electronic band structure calculations have provided theoretical evidence of a progressive transition from a metalliclike state (x = 0) toward a semiconducting-like character as x = 1 is approached, although the solubility limit of Ru precludes a crossover to a semiconducting behavior. The theoretical prediction has been experimentally confirmed by low-temperature electrical resistivity measurements from 2 up to 350 K.

17.
Heart Surg Forum ; 12(1): E59-60, 2009 Jan.
Article in English | MEDLINE | ID: mdl-19233769

ABSTRACT

Elevated pulmonary vascular resistance in a transplantation candidate should be viewed as potentially reversible, and there are several options for therapy. We describe a young patient with congenital restrictive cardiomyopathy and a markedly elevated pulmonary artery pressure. The patient underwent successful orthotopic heart transplantation after pharmacologic lowering of the pulmonary artery pressure with a new drug combination of milrinone and nesiritide. The length of therapy can be extended to 3 days to allow for determining the pulmonary vascular responsiveness.


Subject(s)
Cardiomyopathies/complications , Cardiomyopathies/surgery , Heart Failure/etiology , Heart Failure/prevention & control , Heart Transplantation/methods , Hypertension/complications , Hypertension/surgery , Noonan Syndrome/surgery , Adolescent , Contraindications , Humans , Male , Noonan Syndrome/complications , Treatment Outcome
18.
Article in English | MEDLINE | ID: mdl-20098636

ABSTRACT

Nanoparticle sensors have been developed for real-time imaging and dynamic monitoring, both in live cells and in vivo, of molecular and ionic components, constructs, forces, and dynamics observed during biological, chemical, and physical processes. With their biocompatible small size and inert matrix, nanoparticle sensors have been successfully applied to noninvasive real-time measurements of analytes and fields in cells and in rodents, with spatial, temporal, physical, and chemical resolution. This review describes the diverse designs of nanoparticle sensors for ions and small molecules, physical fields, and biological features, as well as the characterization, properties, and applications of these nanosensors to in vitro and in vivo measurements. Their floating as well as localization abilities in biological media are captured by the acronym PEBBLE: photonic explorer for bioanalysis with biologically localized embedding.


Subject(s)
Biosensing Techniques/methods , Nanoparticles/chemistry , Animals , Humans , Nanotechnology
19.
J Chem Phys ; 128(15): 154706, 2008 Apr 21.
Article in English | MEDLINE | ID: mdl-18433257

ABSTRACT

Previously we have demonstrated that several structural features are crucial for the functionality of molecular field-effect transistors. The effect of additional structural aspects of molecular wires is explored. These include the type of, the thiol binding location on, and the chemical substitutions of a conjugated system. Pentacene, porphyrin, and the Tour-Reed devices are utilized as model systems. The thiol binding location is shown to have a varied effect on the transmission of a system depending on the molecular orbitals involved. Substitution by electron withdrawing and donating groups is illustrated to have a substantial effect on the transmission of single molecule devices. The substitution effect is either a simple energy shifting effect or a more complicated resonance effect, and can be used to effectively tune the electronic behavior of a single molecule field effect transistor.

20.
J Pharmacol Exp Ther ; 320(1): 180-93, 2007 Jan.
Article in English | MEDLINE | ID: mdl-17050784

ABSTRACT

The present study characterized nicotine intake, circadian patterns of food and water intake, precipitated somatic signs of withdrawal, and extinction of nicotine-seeking behavior in rats with 23-h access to intravenous self-administration (IVSA). Separate groups of animals were allowed access to nicotine IVSA (0.015, n = 9; 0.03, n = 14; 0.06, n = 16; mg/kg/0.1 ml infusion/s; fixed ratio 1) and trained to nosepoke for food and water 23 h/day for 40 consecutive days. Somatic signs of nicotine withdrawal were examined following saline or mecamylamine administration (1.5 mg/kg i.p.), and extinction of nicotine-seeking behavior was assessed. A dose-dependent decrease in lever responding and an increase in nicotine intake were observed, with the highest nicotine dose producing the lowest amount of lever responding and the highest amount of nicotine intake. Nicotine acutely reduced diurnal and nocturnal food intake, producing smaller and fewer meals, and an increased rate of eating. Differences in rate of nicotine intake between the light and dark phase decreased significantly, especially in rats receiving higher unit nicotine doses (0.03 and 0.06 mg/kg), along with long-term decreases in the circadian profile and amplitude of feeding. Mecamylamine precipitated robust withdrawal signs, the magnitude of which was positively correlated with the total amount of self-administered nicotine. Extinction of nicotine-seeking behavior was observed and was facilitated by removal of nicotine-associated cues. The results demonstrate that rats will self-administer nicotine to the point of producing dependence, as measured by somatic signs, resistance to extinction, and measures of food intake.


Subject(s)
Circadian Rhythm , Extinction, Psychological/drug effects , Nicotine/administration & dosage , Self Administration , Substance Withdrawal Syndrome/etiology , Tobacco Use Disorder/etiology , Animals , Eating , Male , Mecamylamine/pharmacology , Rats , Rats, Wistar
SELECTION OF CITATIONS
SEARCH DETAIL
...