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1.
Phys Rev Lett ; 131(18): 185101, 2023 Nov 03.
Artículo en Inglés | MEDLINE | ID: mdl-37977609

RESUMEN

High-performance fusion plasmas, requiring high pressure ß, are not well understood in stellarator-type experiments. Here, the effect of ß on ion-temperature-gradient-driven (ITG) turbulence is studied in Wendelstein 7-X (W7-X), showing that subdominant kinetic ballooning modes (KBMs) are unstable well below the ideal MHD threshold and get strongly excited in the turbulence. By zonal-flow erosion, these subthreshold KBMs (stKBMs) affect ITG saturation and enable higher heat fluxes. Controlling stKBMs will be essential to allow W7-X and future stellarators to achieve maximum performance.

2.
Neurobiol Learn Mem ; 144: 136-146, 2017 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-28720405

RESUMEN

While thepsychoactive inhalant toluene causes behavioral effects similarto those produced by other drugs of abuse, the persistent behavioral and anatomical abnormalities induced by toluene exposure are not well known. To mimic human "binge-like" inhalant intoxication, adolescent, male Sprague-Dawley rats were exposed to toluene vapor (5700ppm) twice daily for five consecutive days. These rats remained in their home cages until adulthood (P60), when they were trained in operant boxes to respond to a palatable food reward and then challenged with several different cognitive tasks. Rats that experienced chronic exposure to toluene plus abstinence ("CTA") showed enhanced performance in a strategy set-shifting task using a between-session, but not a within-session test design. CTA also blunted operant and classical conditioning without affecting responding during a progressive ratio task. While CTA rats displayed normal latent inhibition, previous exposure to a non-reinforced cue enhanced extinction of classically conditioned approach behavior of these animals compared to air controls. To determine whether CTA alters the structural plasticity of brain areas involved in set-shifting and appetitive behaviors, we quantified basal dendritic spine morphology in DiI-labeled pyramidal neurons in layer 5 of the medial prefrontal cortex (mPFC) and medium spiny neurons in the nucleus accumbens (NAc). There were no changes in dendritic spine density or subtype in the mPFC of CTA rats while NAc spine density was significantly increased due to an enhanced prevalence of long-thin spines. Together, these findings suggest that the persistent effects of CTA on cognition are related to learning and memory consolidation/recall, but not mPFC-dependent behavioral flexibility.


Asunto(s)
Cognición/efectos de los fármacos , Aprendizaje/efectos de los fármacos , Núcleo Accumbens/efectos de los fármacos , Corteza Prefrontal/efectos de los fármacos , Tolueno/administración & dosificación , Animales , Condicionamiento Clásico/efectos de los fármacos , Condicionamiento Operante/efectos de los fármacos , Espinas Dendríticas/efectos de los fármacos , Espinas Dendríticas/patología , Extinción Psicológica/efectos de los fármacos , Masculino , Núcleo Accumbens/patología , Corteza Prefrontal/patología , Ratas Sprague-Dawley
3.
Br J Cancer ; 109(4): 827-35, 2013 Aug 20.
Artículo en Inglés | MEDLINE | ID: mdl-23887607

RESUMEN

Next-generation sequencing (NGS) of cancer genomes promises to revolutionise oncology, with the ability to design and use targeted drugs, to predict outcome and response, and to classify tumours. It is continually becoming cheaper, faster and more reliable, with the capability to identify rare yet clinically important somatic mutations. Technical challenges include sequencing samples of low quality and/or quantity, reliable identification of structural and copy number variation, and assessment of intratumour heterogeneity. Once these problems are overcome, the use of the data to guide clinical decision making is not straightforward, and there is a risk of premature use of molecular changes to guide patient management in the absence of supporting evidence. Paradoxically, NGS may simply move the bottleneck of personalised medicine from data acquisition to the identification of reliable biomarkers. Standardised cancer NGS data collection on an international scale would be a significant step towards optimising patient care.


Asunto(s)
Neoplasias/genética , Genoma , Humanos , Técnicas de Diagnóstico Molecular , Mutación , Neoplasias/diagnóstico , Medicina de Precisión , Análisis de Secuencia de ADN
4.
Science ; 292(5514): 86-90, 2001 Apr 06.
Artículo en Inglés | MEDLINE | ID: mdl-11292868

RESUMEN

A comparative (15)N-tracer study of nitrogen dynamics in headwater streams from biomes throughout North America demonstrates that streams exert control over nutrient exports to rivers, lakes, and estuaries. The most rapid uptake and transformation of inorganic nitrogen occurred in the smallest streams. Ammonium entering these streams was removed from the water within a few tens to hundreds of meters. Nitrate was also removed from stream water but traveled a distance 5 to 10 times as long, on average, as ammonium. Despite low ammonium concentration in stream water, nitrification rates were high, indicating that small streams are potentially important sources of atmospheric nitrous oxide. During seasons of high biological activity, the reaches of headwater streams typically export downstream less than half of the input of dissolved inorganic nitrogen from their watersheds.


Asunto(s)
Ecosistema , Agua Dulce , Nitrógeno/metabolismo , Absorción , Animales , Bacterias/metabolismo , Biopelículas , Eucariontes/metabolismo , Hongos/metabolismo , Sedimentos Geológicos , Nitratos/metabolismo , Oxidación-Reducción , Fotosíntesis , Compuestos de Amonio Cuaternario/metabolismo , Estaciones del Año , Estados Unidos
5.
Neuroscience ; 151(2): 419-27, 2008 Jan 24.
Artículo en Inglés | MEDLINE | ID: mdl-18055129

RESUMEN

NMDA receptors bidirectionally modulate extracellular signal-regulated kinase (ERK) through the coupling of synaptic NMDA receptors to an ERK activation pathway that is opposed by a dominant ERK shutoff pathway thought to be coupled to extrasynaptic NMDA receptors. In the present study, synaptic NMDA receptor activation of ERK in rat cortical cultures was partially inhibited by the highly selective NR2B antagonist Ro25-6981 (Ro) and the less selective NR2A antagonist NVP-AAM077 (NVP). When Ro and NVP were added together, inhibition appeared additive and equal to that observed with the NMDA open-channel blocker MK-801. Consistent with a selective coupling of extrasynaptic NMDA receptors to the dominant ERK shutoff pathway, pre-block of synaptic NMDA receptors with MK-801 did not alter the inhibitory effect of bath-applied NMDA on ERK activity. Lastly, in contrast to a complete block of synaptic NMDA receptor activation of ERK by extrasynaptic NMDA receptors, activation of extrasynaptic NMDA receptors had no effect upon ERK activation by brain-derived neurotrophic factor. These results suggest that the synaptic NMDA receptor ERK activation pathway is coupled to both NR2A and NR2B containing receptors, and that the extrasynaptic NMDA receptor ERK inhibitory pathway is not a non-selective global ERK shutoff.


Asunto(s)
Factor Neurotrófico Derivado del Encéfalo/fisiología , Quinasas MAP Reguladas por Señal Extracelular/metabolismo , Receptores de N-Metil-D-Aspartato/fisiología , Transducción de Señal/efectos de los fármacos , Animales , Western Blotting , Factor Neurotrófico Derivado del Encéfalo/efectos de los fármacos , Células Cultivadas , Corteza Cerebral/citología , Corteza Cerebral/efectos de los fármacos , Proteína de Unión a Elemento de Respuesta al AMP Cíclico/biosíntesis , Proteína de Unión a Elemento de Respuesta al AMP Cíclico/genética , Maleato de Dizocilpina , Activación Enzimática/efectos de los fármacos , Antagonistas de Aminoácidos Excitadores , Potenciales Postsinápticos Excitadores/efectos de los fármacos , Espacio Extracelular/efectos de los fármacos , Espacio Extracelular/metabolismo , N-Metilaspartato , Neuronas/efectos de los fármacos , Neuronas/metabolismo , Técnicas de Placa-Clamp , Fenoles/farmacología , Piperidinas/farmacología , Quinoxalinas/farmacología , Ratas , Ratas Sprague-Dawley , Receptores de N-Metil-D-Aspartato/antagonistas & inhibidores
6.
Ecology ; 89(12): 3515-27, 2008 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-19137956

RESUMEN

Allochthonous inputs act as resource subsidies to many ecosystems, where they exert strong influences on metabolism and material cycling. At the same time, metabolic theory proposes endogenous thermal control independent of resource supply. To address the relative importance of exogenous and endogenous influences, we quantified spatial and temporal variation in ecosystem metabolism and nitrogen (N) uptake using seasonal releases of 15N as nitrate in six streams differing in riparian-stream interaction and metabolic character. Nitrate removal was quantified using a nutrient spiraling approach based on measurements of downstream decline in 15N flux. Respiration (R) and gross primary production (GPP) were measured with whole-stream diel oxygen budgets. Uptake and metabolism metrics were addressed as z scores relative to site means to assess temporal variation. In open-canopied streams, areal uptake (U; microg N x m(-2) x s(-1)) was closely related to GPP, metabolic rates increased with temperature, and R was accurately predicted by metabolic scaling relationships. In forested streams, N spiraling was not related to GPP; instead, uptake velocity (v(f); mm/s) was closely related to R. In contrast to open-canopied streams, N uptake and metabolic activity were negatively correlated to temperature and poorly described by scaling laws. We contend that streams differ along a gradient of exogenous and endogenous control that relates to the relative influences of resource subsidies and in-stream energetics as determinants of seasonal patterns of metabolism and N cycling. Our research suggests that temporal variation in the propagation of ecological influence between adjacent systems generates phases when ecosystems are alternatively characterized as endogenously and exogenously controlled.


Asunto(s)
Ecosistema , Monitoreo del Ambiente/métodos , Agua Dulce/química , Nitrógeno/análisis , Nitrógeno/metabolismo , Carbono/análisis , Carbono/metabolismo , Isótopos de Nitrógeno , Ríos , Estaciones del Año
7.
Clin Oncol (R Coll Radiol) ; 28(10): 622-626, 2016 10.
Artículo en Inglés | MEDLINE | ID: mdl-27169593

RESUMEN

The median survival in glioblastoma is just over a year, with no standard second-line therapy. Ipilimumab is an immune checkpoint inhibitor that activates the anti-tumour immune response by cytotoxic T-lymphocyte antigen-4 blockade. There is significant evidence supporting its role in the treatment of malignant melanoma, including in patients with brain metastases. The addition of the anti-angiogenesis agent, bevacizumab, seems to offer additional benefit and limit the immune-related side-effects of ipilimumab in melanoma. To date there have been no clinical trials investigating this combination in glioblastoma. In this single practice case series, 20 patients with glioblastoma were consented for and treated with ipilimumab and bevacizumab in combination. Safety, tolerability and the response to treatment were reviewed for all patients. Three patients were treated after palliative first-line radiotherapy, one patient after first-line chemoradiation and 16 patients were treated with recurrent disease. Sixty-five per cent of patients completed four cycles of 3 weekly ipilimumab therapy, administered with 2 weekly bevacizumab. Radiographic responses for patients with recurrent disease were evaluated by Response Assessment in Neuro-oncology (RANO) criteria; 31% of patients showed a partial response, 31% had stable disease and 38% had disease progression. The treatment combination was well tolerated, with treatment terminated before completion due to adverse events in two patients. Autoimmune toxicity was manageable with systemic corticosteroid therapy. Ipilimumab and bevacizumab in combination show promising activity with a predictable and manageable toxicity profile, warranting further clinical studies.


Asunto(s)
Inhibidores de la Angiogénesis/uso terapéutico , Anticuerpos Monoclonales Humanizados/uso terapéutico , Anticuerpos Monoclonales/uso terapéutico , Bevacizumab/uso terapéutico , Neoplasias Encefálicas/tratamiento farmacológico , Glioblastoma/tratamiento farmacológico , Adulto , Anciano , Inhibidores de la Angiogénesis/efectos adversos , Anticuerpos Monoclonales/efectos adversos , Anticuerpos Monoclonales Humanizados/efectos adversos , Protocolos de Quimioterapia Combinada Antineoplásica , Bevacizumab/efectos adversos , Neoplasias Encefálicas/patología , Terapia Combinada , Femenino , Humanos , Ipilimumab , Masculino , Melanoma , Persona de Mediana Edad , Recurrencia Local de Neoplasia/patología , Neoplasias Cutáneas , Resultado del Tratamiento , Adulto Joven , Melanoma Cutáneo Maligno
8.
J Clin Oncol ; 18(4): 854-9, 2000 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-10673528

RESUMEN

PURPOSE: To evaluate the results of etoposide, cisplatin/etoposide, methotrexate, and actinomycin D (EP/EMA) chemotherapy in patients with gestational trophoblastic tumors (GTTs), who have relapsed after or who have become refractory to EMA/cyclophosphamide and vincristine (CO) chemotherapy, and in patients presenting with metastatic placental site trophoblastic tumors (PSTTs). PATIENTS AND METHODS: We have treated a total of 34 patients with GTT and eight patients with metastatic PSTT with the EP/EMA chemotherapy schedule. RESULTS: Twenty-two patients received EP/EMA because of apparent drug resistance to EMA/CO, and because the human chorionic gonadotropin (hCG) was near normal, they were not assessable for response. Twenty-one of these patients (95%) are alive and in remission. In the group where the hCG was high enough to confirm a response (greater than one log fall in hCG) to EP/EMA, all 12 patients responded and nine of these patients (75%) are alive and in remission. We have treated three patients with PSTT where the interval from antecedent pregnancy was less than 2 years, and all patients (100%) are alive and in remission. We have treated five patients where the interval from antecedent pregnancy was greater than 2 years and one fifth (20%) remain in remission. The survival for patients with GTT is 30 (88%) out of 34 patients and four (50%) out of eight patients for PSTT, giving an overall survival for these two cohorts of 34 (81%) out of 42 patients. The toxicity of this schedule is significant, with grade 3 or 4 toxicity (National Cancer Institute common toxicity criteria) recorded in hemoglobin (21%), WBC (68%), and platelets (40%). The role of surgery in this group of patients is important and contributed to sustained remission in five patients (23%) and possibly helped an additional seven patients (32%). CONCLUSION: EP/EMA is an effective but moderately toxic regimen for patients with high-risk GTT who become refractory to or relapse from EMA/CO chemotherapy. Also, EP/EMA clearly has activity in patients with metastatic PSTT.


Asunto(s)
Protocolos de Quimioterapia Combinada Antineoplásica/uso terapéutico , Neoplasias Trofoblásticas/tratamiento farmacológico , Neoplasias Uterinas/tratamiento farmacológico , Adolescente , Adulto , Antibióticos Antineoplásicos/administración & dosificación , Antibióticos Antineoplásicos/efectos adversos , Antimetabolitos Antineoplásicos/administración & dosificación , Antimetabolitos Antineoplásicos/efectos adversos , Antineoplásicos/administración & dosificación , Antineoplásicos/efectos adversos , Antineoplásicos Alquilantes/administración & dosificación , Antineoplásicos Alquilantes/efectos adversos , Antineoplásicos Fitogénicos/administración & dosificación , Antineoplásicos Fitogénicos/efectos adversos , Protocolos de Quimioterapia Combinada Antineoplásica/efectos adversos , Gonadotropina Coriónica/sangre , Cisplatino/administración & dosificación , Cisplatino/efectos adversos , Estudios de Cohortes , Ciclofosfamida/administración & dosificación , Ciclofosfamida/efectos adversos , Dactinomicina/administración & dosificación , Dactinomicina/efectos adversos , Resistencia a Antineoplásicos , Etopósido/administración & dosificación , Etopósido/efectos adversos , Femenino , Humanos , Metotrexato/administración & dosificación , Metotrexato/efectos adversos , Persona de Mediana Edad , Recurrencia Local de Neoplasia/patología , Placenta/patología , Embarazo , Inducción de Remisión , Factores de Riesgo , Tasa de Supervivencia , Neoplasias Trofoblásticas/secundario , Neoplasias Trofoblásticas/cirugía , Neoplasias Uterinas/cirugía
9.
J Clin Oncol ; 21(21): 4009-15, 2003 Nov 01.
Artículo en Inglés | MEDLINE | ID: mdl-14581424

RESUMEN

PURPOSE: Squamous cell carcinoma of the esophagus remains an aggressive disease with a poor prognosis, even after curative-intent surgery. This article analyzes the impact of preoperative chemotherapy with mitomycin, ifosfamide, and cisplatin (MIC) on a cohort of 68 patients. PATIENTS AND METHODS: From 1988 to 1994, 68 patients with potentially operable squamous cell carcinoma of the esophagus were entered onto two phase II trials of neoadjuvant chemotherapy with mitomycin 6 mg/m2, ifosfamide 3 g/m2, and cisplatin 50 mg/m2 and received between two and four cycles of treatment at 3-weekly intervals. Two patients were removed from the analysis when they were found to have malignancy other than squamous cell carcinoma of the esophagus. RESULTS: Forty (61%) of 66 patients had a radiologic response to chemotherapy (18 complete responses and 22 partial responses), and 52 (79%) of 66 patients went on to have the primary tumor resected. There were nine pathologic complete responders, seven of whom remain fit and well after at least 60 months of follow-up. The overall median survival was 12.4 months (95% confidence interval, 9.6 to 18.8 months). The complete response and node-negative patients survived significantly longer than those in other categories (log-rank chi2 = 18.8; P <.001): on average 13 months longer than the node-positive or nonresected category (22.0 v 9.4 months). The toxicity of the regimen was low. CONCLUSION: MIC is an easily administered, well-tolerated, and efficacious regimen as neoadjuvant therapy for patients with squamous cell carcinoma of the esophagus. These results warrant further investigation.


Asunto(s)
Protocolos de Quimioterapia Combinada Antineoplásica/uso terapéutico , Carcinoma de Células Escamosas/tratamiento farmacológico , Carcinoma de Células Escamosas/cirugía , Neoplasias Esofágicas/tratamiento farmacológico , Neoplasias Esofágicas/cirugía , Terapia Neoadyuvante , Adulto , Anciano , Protocolos de Quimioterapia Combinada Antineoplásica/administración & dosificación , Carcinoma de Células Escamosas/diagnóstico por imagen , Carcinoma de Células Escamosas/mortalidad , Carcinoma de Células Escamosas/patología , Cisplatino/administración & dosificación , Estudios de Cohortes , Terapia Combinada , Esquema de Medicación , Neoplasias Esofágicas/diagnóstico por imagen , Neoplasias Esofágicas/mortalidad , Neoplasias Esofágicas/patología , Esofagectomía , Femenino , Humanos , Ifosfamida/administración & dosificación , Masculino , Persona de Mediana Edad , Mitomicina/administración & dosificación , Recurrencia Local de Neoplasia/diagnóstico por imagen , Recurrencia Local de Neoplasia/mortalidad , Recurrencia Local de Neoplasia/patología , Irlanda del Norte , Radiografía , Análisis de Supervivencia , Resultado del Tratamiento
10.
Neuroscience ; 136(1): 259-67, 2005.
Artículo en Inglés | MEDLINE | ID: mdl-16182452

RESUMEN

Many patients display elevated levels of serum cortisol following acute ischemic stroke. Given that glucocorticoids may potentiate some forms of insult, these studies examined the effects of corticosterone or dexamethasone exposure on cytotoxicity following oxygen-glucose deprivation in the cerebellum, a brain region susceptible to stroke. In organotypic cerebellar slice cultures prepared from neonatal rat pups, 90-min of oxygen-glucose deprivation at 15 days in vitro resulted in significant cytotoxicity at 24-, 48-, and 72-h post-oxygen-glucose deprivation, as measured by uptake of propidium iodide. Exposure of cultures following oxygen-glucose deprivation to the antioxidant trolox (500 microM), but not to the glucocorticoid receptor antagonist RU486 (10 microM), completely blocked oxygen-glucose deprivation-induced cytotoxicity. Corticosterone (1 microM) or dexamethasone (10 microM) exposure alone did not significantly increase propidium iodide uptake above levels observed in control cultures. However, corticosterone or dexamethasone exposure after oxygen-glucose deprivation potentiated oxygen-glucose deprivation-mediated propidium iodide uptake at each time point. Trolox, as well as RU486, co-exposure of cultures to corticosterone or dexamethasone after oxygen-glucose deprivation abolished all cytotoxicity. In conclusion, these data demonstrated that glucocorticoid exposure modulated oxygen-glucose deprivation-mediated propidium iodide uptake, which likely involved glucocorticoid receptor activation and pro-oxidant effects.


Asunto(s)
Cerebelo/efectos de los fármacos , Cerebelo/fisiopatología , Corticosterona/farmacología , Dexametasona/farmacología , Glucosa/deficiencia , Hipoxia/fisiopatología , Animales , Antioxidantes/farmacología , Muerte Celular/efectos de los fármacos , Cerebelo/metabolismo , Cromanos/farmacología , Sinergismo Farmacológico , Femenino , Técnicas In Vitro , Masculino , Mifepristona/farmacología , Propidio/farmacocinética , Ratas , Ratas Sprague-Dawley
11.
Neuroscience ; 135(4): 1129-39, 2005.
Artículo en Inglés | MEDLINE | ID: mdl-16165302

RESUMEN

Nutritional deficiencies associated with long-term ethanol consumption may cause neuronal damage in ethanol-dependent individuals. Thiamine deficiency, in particular, is thought to contribute to ethanol-associated cerebellar degeneration, although damage may occur in adequately nourished alcoholics. Thus, the present study examined the effects of thiamine depletion and ethanol exposure on cytotoxicity in rat cerebellum. Organotypic cerebellar slice cultures were treated starting at 25 days in vitro with 100 mM ethanol for 11 days or 10 days followed by a 24-h withdrawal period. This exposure paradigm has previously been shown in hippocampal slice cultures to result in spontaneous cytotoxicity upon ethanol withdrawal. Additional cerebellar cultures were exposed to the thiamine depleting agent pyrithiamine (10-500 microM) for 10 or 11 days, some in the presence of ethanol exposure or withdrawal. Other cultures were co-exposed to thiamine (1-100 microM), 500 microM pyrithiamine, and ethanol for 10 or 11 days. The results demonstrated that neither 11-day ethanol treatment nor withdrawal from 10-day exposure significantly increased cerebellar cytotoxicity, as measured by propidium iodide fluorescence. The 11-day treatment with 100 or 500 microM pyrithiamine significantly increased propidium iodide fluorescence approximately 21% above levels observed in control tissue. Cultures treated with both ethanol (11 days or 10 days plus withdrawal) and 500 microM pyrithiamine displayed a marked increase in cytotoxicity approximately 60-90% above levels observed in control cultures. Pyrithiamine and ethanol-induced cytotoxicity was prevented in cultures co-exposed to thiamine (10-100 microM) for the duration of pyrithiamine treatment. Findings from this report suggest that the cerebellum may be more sensitive to the toxic effects of thiamine deficiency, as compared with alcohol withdrawal, associated with alcohol dependence.


Asunto(s)
Depresores del Sistema Nervioso Central/toxicidad , Cerebelo/efectos de los fármacos , Cerebelo/patología , Etanol/toxicidad , Deficiencia de Tiamina/fisiopatología , Animales , Femenino , Masculino , Técnicas de Cultivo de Órganos , Piritiamina/farmacología , Ratas , Ratas Sprague-Dawley , Síndrome de Abstinencia a Sustancias/fisiopatología , Deficiencia de Tiamina/inducido químicamente
12.
Neuroscience ; 125(3): 671-82, 2004.
Artículo en Inglés | MEDLINE | ID: mdl-15099681

RESUMEN

Hypercortisolemia, long-term exposure of the brain to high concentrations of stress hormones (i.e. cortisol), may occur in patients suffering from depression, alcoholism, and other disorders. This has been suggested to produce neuropathological effects, in part, via increased function or sensitivity of N-methyl-d-aspartate (NMDA)-type glutamate receptors. Given that cigarette smoking is highly prevalent in some of these patient groups and nicotine has been shown to reduce toxic consequences of NMDA receptor function, it may be suggested that nicotine intake may attenuate the neurotoxic effects of hypercortisolemia. To investigate this possibility, organotypic hippocampal slice cultures derived from rat were pre-treated with corticosterone (0.001-1 microM) alone or in combination with selective glucocorticoid receptor antagonists for 72-h prior to a brief (1-h) NMDA exposure (5 microM). Pre-treatment with corticosterone (0.001-1 microM) alone did not cause hippocampal damage, while NMDA exposure produced significant cellular damage in the cornu ammonis (CA)1 subregion. No significant damage was observed in the dentate gyrus or CA3 regions following NMDA exposure. Pre-treatment of cultures with corticosterone (0.1-1 microM) markedly exacerbated NMDA-induced CA1 and dentate gyrus region damage. This effect in the CA1 region was prevented by co-administration of the glucocorticoid receptor antagonist RU486 (>or=1 microM), but not spironolactone (1-10 microM), a mineralocorticoid receptor antagonist. In a second series of studies, both acute and pre-exposure of cultures to (-)-nicotine (1-10 microM) significantly reduced NMDA toxicity in the CA1 region. Co-administration of cultures to (-)-nicotine (1-10 microM) with 100 nM corticosterone prevented corticosterone's exacerbation of subsequent CA1 insult. This protective effect of (-)-nicotine was not altered by co-exposure of cultures to 10 microM dihydro-beta-erythroidine but was blocked by co-exposure to 100 nM methyllycaconitine, suggesting the involvement of nicotinic acetylcholine receptors possessing the alpha7* subunit. The present studies suggest a role for hypercortisolemia in sensitizing the hippocampal NMDA receptor system to pathological activation and indicate that prolonged nicotine exposure attenuates this sensitization. Thus, it is possible that one consequence of heavy smoking in those suffering from hypercortisolemia may be a reduction of neuronal injury and sparing of cellular function.


Asunto(s)
Aconitina/análogos & derivados , Corticosterona/antagonistas & inhibidores , Hipocampo/efectos de los fármacos , Neuronas/efectos de los fármacos , Nicotina/farmacología , Receptores de N-Metil-D-Aspartato/metabolismo , Aconitina/farmacología , Animales , Supervivencia Celular/efectos de los fármacos , Corticosterona/farmacología , Modelos Animales de Enfermedad , Interacciones Farmacológicas/fisiología , Hipocampo/metabolismo , Hipocampo/patología , Técnicas In Vitro , Masculino , Mifepristona/farmacología , N-Metilaspartato/toxicidad , Neuronas/metabolismo , Neuronas/patología , Fármacos Neuroprotectores/farmacología , Neurotoxinas/toxicidad , Antagonistas Nicotínicos/farmacología , Ratas , Ratas Sprague-Dawley , Receptores de Glucocorticoides/antagonistas & inhibidores , Receptores de Glucocorticoides/metabolismo , Receptores de N-Metil-D-Aspartato/efectos de los fármacos , Receptores Nicotínicos/efectos de los fármacos , Receptores Nicotínicos/metabolismo , Receptor Nicotínico de Acetilcolina alfa 7
13.
Oecologia ; 98(1): 40-47, 1994 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-28312794

RESUMEN

The effect of periphyton biomass on hydraulic characteristics and nutrient cycling was studied in laboratory streams with and without snail herbivores. Hydraulic characteristics, such as average water velocity, dispersion coefficients, and relative volume of transient storage zones (zones of stationary water), were quantified by performing short-term injections of a conservative tracer and fitting an advection-dispersion model to the conservative tracer concentration profile downstream from the injection site. Nutrient cycling was quantified by measuring two indices: (1) uptake rate of phosphorus from stream water normalized to gross primary production (GPP), a surrogate measure of total P demand, and (2) turnover rate of phosphorus in the periphyton matrix. These measures indicate the importance of internal cycling (within the periphyton matrix) in meeting the P demands of periphyton. Dense growths of filamentous diatoms and blue-green algae accumulated in the streams with no snails (high-biomass streams), whereas the periphyton communities in streams with snails consisted almost entirely of a thin layer of basal cells of Stigeoclonium sp. (low-biomass streams). Dispersion coefficients were significantly greater and transient storage zones were significantly larger in the high-biomass streams compared to the low-biomass streams. Rates of GPP-normalized P uptake from water and rates of P turnover in periphyton were significantly lower in high biomass than in low biomass periphyton communities, suggesting that a greater fraction of the P demand was met by recycling in the high biomass communities. Increases in streamwater P concentration significantly increased GPP-normalized P uptake in high biomass communities, suggesting diffusion limitation of nutrient transfer from stream water to algal cells in these communities. Our results demonstrate that accumulations of periphyton biomass can alter the hydraulic characteristics of streams, particularly by increasing transient storage zones, and can increase internal nutrient cycling. They suggest a close coupling of hydraulic characteristics and nutrient cycling processes in stream ecosystems.

14.
Oecologia ; 66(2): 199-206, 1985 May.
Artículo en Inglés | MEDLINE | ID: mdl-28311590

RESUMEN

The effect of invertebrate shredders on organic matter dynamics and phosphorus spiralling was studied over a 30-week period in laboratory streams. The streams were fed by groundwater, layered with cobble and gravel from a natural stream, covered with opaque material to eliminate algal growth, and initially contained 195 g/m2 of autumn-shed leaves. Four weeks after leaf addition, leaf-shredding snails (Goniobasis clavaeformis) were added to each of three streams in densities of 75, 220, and 800/m2. A fourth stream contained no snails and served as a control.Presence of snails increased the loss rates of coarse particulate organic matter (CPOM) and total organic matter (TOM), primarily by increasing leaf fragmentation and seston export. Although snail feeding increased specific metabolism of microbes associated with CPOM and cobble surfaces, it was not enough to compensate for reduction in bacterial cell numbers per unit surface area and in stream TOM. Consequently mineralization of detritus and whole stream phosphorus utilization rate were maximum in the stream with no snails and decreased with increasing snail density. From previous simulations of a stream model based on the nutrient spiralling concept, we predicted that there should be an intermediate shredder density which would minimize phosphorus spiralling length (maximize phosphorus utilization) in a natural stream nearby. Our current results conflict with the model-based predictions primarily because the increase in microbial metabolism was less important than reduction in bacterial cell numbers and total benthic organic matter resulting from snail feeding. Although our results indicate macroinvertebrate shredders reduce phosphorus utilization in headwater streams, shreders may increase nutrient utilization downstream where riparian inputs are lower, thus linking low- and high-order streams.

15.
Clin Oncol (R Coll Radiol) ; 13(3): 164-9, 2001.
Artículo en Inglés | MEDLINE | ID: mdl-11527288

RESUMEN

Adenocarcinoma of the oesophagus is a systemic disease at presentation in the majority of patients. This article analyses the impact of preoperative chemotherapy on a cohort of 68 patients. From 1990 to 1996, 68 patients with potentially operable adenocarcinoma of the oesophagus were entered into three sequential Phase II trials of neoadjuvant chemotherapy with cisplatin/mitomycin C/ifosfamide, cisplatin/5-fluorouracil (5-FU) and mitomycin C/cisplatin/5-FU. Twenty-four (35%) patients had a radiological (4 complete; 20 partial) response to chemotherapy, and 52 (76%) went on to have the primary tumour resected. There was only one pathological complete responder. The overall median survival was 13 months (95% confidence interval (CI) 9-16). Survival for the 28 N(0) patients was 34 months (95% CI 14-60). The pattern of failure for resected patients was predominantly systemic (16/17). These results indicate that neoadjuvant chemotherapy followed by surgery for adenocarcinoma of the oesophagus achieves excellent local control. The dominance, however, of distant recurrence after surgery underlines the fact that, in the majority of patients, the only hope of improving results in the future is to develop better systemic therapies.


Asunto(s)
Adenocarcinoma/tratamiento farmacológico , Protocolos de Quimioterapia Combinada Antineoplásica/uso terapéutico , Neoplasias Esofágicas/tratamiento farmacológico , Terapia Neoadyuvante , Recurrencia Local de Neoplasia , Adenocarcinoma/cirugía , Adulto , Anciano , Anciano de 80 o más Años , Cisplatino/administración & dosificación , Neoplasias Esofágicas/cirugía , Femenino , Fluorouracilo/administración & dosificación , Estudios de Seguimiento , Humanos , Ifosfamida/administración & dosificación , Masculino , Persona de Mediana Edad , Mitomicina/administración & dosificación , Análisis de Supervivencia , Resultado del Tratamiento
16.
J Hum Lact ; 10(1): 25-30, 1994 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-7619243

RESUMEN

This study compares the attitudes toward breastfeeding of high-school students in Japan and the United States. The study was conducted as a cross-sectional survey with a convenience sample (N = 329). Data were collected in 1989 and 1990 at two private, girls-only high schools (Tokyo, Japan and Farmington, Michigan). Retrieval rates were 100 percent (Tokyo) and 78 percent (Michigan) respectively. Responses were compared by the chi-square (chi 2) test with Yate's correction and factor analyses. Tokyo students perceived that their mothers talked positively about breastfeeding (54 percent), while only 17 percent of Michigan students reported that their mothers did so (< .001). Less than five percent of the Tokyo students felt that breastfeeding disturbs family life, whereas nearly 98 percent of the Michigan students felt so (p < .001). Tokyo students scored significantly higher on the 'family' factor, while the Michigan students scored significantly higher on the 'self' factor. Overall, this study indicates that high school students in Japan have more positive attitudes toward breastfeeding than students in the United States; however, teenagers in the United States are more interested than their Japanese age-mates in gaining information about breastfeeding.


Asunto(s)
Actitud Frente a la Salud/etnología , Lactancia Materna , Estudiantes/psicología , Adolescente , Comparación Transcultural , Estudios Transversales , Características Culturales , Femenino , Humanos , Japón , Estados Unidos
17.
ScientificWorldJournal ; 1 Suppl 2: 623-31, 2001 Nov 09.
Artículo en Inglés | MEDLINE | ID: mdl-12805817

RESUMEN

Groundwater-surface water (GW-SW) interaction lengthens hydraulic residence times, increases contact between solutes and biologically active surfaces, and often creates a gradient of redox conditions conducive to an array of biogeochemical processes. As such, the interaction of hydraulic patterns and biogeochemical activity is suspected to be an important determinant of elemental spiraling in streams. Hydrologic interactions may be particularly important in headwater streams, where the extent of the GW-SW mixing environment (i.e., hyporheic zone) is proportionately greater than in larger streams. From our current understanding of stream ecosystem function, we discuss nitrogen (N) spiraling, present a conceptual model of N retention in streams, and use both of these issues to generate specific research questions and testable hypotheses regarding N dynamics in streams.


Asunto(s)
Ecosistema , Agua Dulce/química , Nitrógeno/análisis , Modelos Teóricos , Nitrógeno/metabolismo , Fijación del Nitrógeno , América del Norte , Oxidación-Reducción , Ríos/química , Solventes/química , Árboles
19.
Oncogenesis ; 2: e41, 2013 Apr 01.
Artículo en Inglés | MEDLINE | ID: mdl-23545860

RESUMEN

Despite an improved understanding of the molecular aberrations that occur in glioblastoma, the use of molecularly targeted therapies have so far been disappointing. We present a patient with three different brain tumours: astrocytoma, glioblastoma and gliosarcoma. Genetic analysis showed that the three different brain tumours were derived from a common origin but had each developed unique genetic aberrations. Included in these, the glioblastoma had PDGFRA amplification, whereas the gliosarcoma had MYC amplification. We propose that genetic heterogeneity contributes to treatment failure and requires comprehensive assessment in the era of personalised medicine.

20.
OA Alcohol ; 1(1): 2, 2013 Feb 01.
Artículo en Inglés | MEDLINE | ID: mdl-24432188

RESUMEN

Alcohol use disorders (AUDs) are a major public health issue and have an enormous social and economic burden in developed, developing, and third-world countries. Current pharmacotherapies for treating AUDs suffer from deleterious side effects and are only effective in preventing relapse in a subset of individuals. This signifies an essential need for improved medications to reduce heavy episodic drinking and alcohol-related problems. Growing literature has provided support for the use of anticonvulsants in suppressing symptoms induced by alcohol withdrawal. Emerging clinical and preclinical evidence suggests that a number of well-tolerated anticonvulsants may also decrease alcohol drinking. This review will focus on recent evidence supporting the efficacy of novel anticonvulsants in reducing voluntary alcohol consumption in rodent models. The data demonstrate that anticonvulsants reduce drinking in standard home cage two-bottle choice paradigms, self-administration of alcohol in operant chambers, and cue- and stress-induced reinstatement of alcohol seeking behaviors in rats and mice. This review also highlights evidence that some anticonvulsants were only moderately effective in reducing drinking in select strains of rodents or models. This suggests that genetics, possible neuroadaptations, or the pharmacological target affect the ability of anticonvulsants to attenuate alcohol consumption. Nonetheless, anticonvulsants are relatively safe, have little abuse potential, and can work in combination with other drugs. The results from these preclinical and clinical studies provide compelling evidence that anticonvulsants are a promising class of medication for the treatment of AUDs.

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