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1.
J Environ Manage ; 357: 120685, 2024 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-38552519

RESUMEN

Fisheries social-ecological systems (SES) in the North Sea region confront multifaceted challenges stemming from environmental changes, offshore wind farm expansion, and marine protected area establishment. In this paper, we demonstrate the utility of a Bayesian Belief Network (BN) approach in comprehensively capturing and assessing the intricate spatial dynamics within the German plaice-related fisheries SES. The BN integrates ecological, economic, and socio-cultural factors to generate high-resolution maps of profitability and adaptive capacity potential (ACP) as prospective management targets. Our analysis of future scenarios, delineating changes in spatial constraints, economics, and socio-cultural aspects, identifies factors that will exert significant influence on this fisheries SES in the near future. These include the loss of fishing grounds due to the installation of offshore wind farms and marine protected areas, as well as reduced plaice landings due to climate change. The identified ACP hotspots hold the potential to guide the development of localized management strategies and sustainable planning efforts by highlighting the consequences of management decisions. Our findings emphasize the need to consider detailed spatial dynamics of fisheries SES within marine spatial planning (MSP) and illustrate how this information may assist decision-makers and practitioners in area prioritization. We, therefore, propose adopting the concept of fisheries SES within broader integrated management approaches to foster sustainable development of inherently dynamic SES in a rapidly evolving marine environment.


Asunto(s)
Explotaciones Pesqueras , Lenguado , Animales , Mar del Norte , Estudios Prospectivos , Teorema de Bayes , Fuentes Generadoras de Energía , Conservación de los Recursos Naturales , Viento , Ecosistema
2.
J Environ Manage ; 278(Pt 2): 111545, 2021 Jan 15.
Artículo en Inglés | MEDLINE | ID: mdl-33202370

RESUMEN

Marine spatial planning (MSP) has rapidly become the most widely used integrated, place-based management approach in the marine environment. Monitoring and evaluation of MSP is key to inform best practices, adaptive management and plan iteration. While standardised evaluation frameworks cannot be readily applied, accounting for evaluation essentials such as the definition of evaluation objectives, indicators and stakeholder engagement of stakeholders is a prerequisite for meaningful evaluation outcomes. By way of a literature review and eleven practical MSP case studies, we analysed present day trends in evaluation approaches and unravelled the adoption of evaluation essentials for three categories for monitoring and evaluation for plan making, plan outcomes, and policy implementation. We found that at a global scale the focus of MSP evaluation has shifted over the past decade from evaluating predominantly plan outcomes towards the evaluation of plan making. Independent of the scope of the evaluation, evaluation approaches varied greatly from formal and structured processes, building for instance on MSP goals and objectives, to informal processes based on stakeholder interviews. We noted a trend in the adoption of formalised approaches where MSP evaluations have increasingly become linked to MSP policy goals and objectives. However, the enhanced use of MSP objectives and indicators did not result in a more straightforward reporting of outcomes, e.g. such as the achievement of specific MSP objectives. Overall, we found weak linkages between defined MSP objectives, indicators and available monitoring data. While the apparent shift towards a focus on objectives is promising, we highlight the need of fit-for-purpose monitoring data to enable effective evaluation of those objectives. Hence, effective MSP and adaptive management processes require customised and concurrent monitoring and evaluation strategies and procedures. We argue that evaluation processes would also benefit from a better understanding of the general environmental, socio-economic and socio-cultural effects of MSP. Therefore, to understand better environmental effects of MSP, we praise that forthcoming MSP processes need to deepen the understanding and considerations of cause-effect pathways between human activities and changes of ecosystem state through the adoption of targeted cumulative effects assessments.


Asunto(s)
Conservación de los Recursos Naturales , Ecosistema , Actividades Humanas , Humanos
3.
Nat Genet ; 17(1): 88-91, 1997 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-9288104

RESUMEN

Individuals inheriting the same mutation predisposing to cancer may show very different outcomes, ranging from early aggressive cancer to disease-free survival. Experimental mouse models can provide a powerful tool to identify factors in the environment and genetic background that account for such modifications. The Min mouse strain, in which the ApcMin mutation disrupts the mouse homologue of the human familial polyposis gene, develops intestinal neoplasms whose multiplicity is strongly affected by genetic background. We previously mapped a strong modifier locus, Mom1 (modifier of Min-1), to a 4-cM region on mouse chromosome 4 containing a candidate gene Pla2g2a encoding a secretory phospholipase. Here, we report that a cosmid transgene overexpressing Pla2g2a caused a reduction in tumour multiplicity and size, comparable to that conferred by a single copy of the resistance allele of Mom1. These results offer strong evidence that this secretory phospholipase can provide active tumour resistance. The association of Pla2g2a with Mom1 thus withstands a strong functional test and is likely to represent the successful identification of a polymorphic quantitative trait locus in mammals.


Asunto(s)
Mapeo Cromosómico , Genes Supresores de Tumor , Neoplasias Intestinales/genética , Fosfolipasas A/genética , Poliposis Adenomatosa del Colon/genética , Animales , Secuencia de Bases , Cartilla de ADN , Genes APC , Genotipo , Humanos , Inmunidad Innata , Ratones , Ratones Endogámicos AKR , Ratones Transgénicos , Datos de Secuencia Molecular , Fosfolipasas A/análisis , Fosfolipasas A/biosíntesis , Reacción en Cadena de la Polimerasa
4.
Sci Total Environ ; 705: 135838, 2020 Feb 25.
Artículo en Inglés | MEDLINE | ID: mdl-31855803

RESUMEN

Sustainability in the provision of ecosystem services requires understanding of the vulnerability of social-ecological systems (SES) to tipping points (TPs). Assessing SES vulnerability to abrupt ecosystem state changes remains challenging, however, because frameworks do not operationally link ecological, socio-economic and cultural elements of the SES. We conducted a targeted literature review on empirical assessments of SES and TPs in the marine realm and their use in ecosystem-based management. Our results revealed a plurality of terminologies, definitions and concepts that hampers practical operationalisation of these concepts. Furthermore, we found a striking lack of socio-cultural aspects in SES vulnerability assessments, possibly because of a lack of involvement of stakeholders and interest groups. We propose guiding principles for assessing vulnerability to TPs that build on participative approaches and prioritise the connectivity between SES components by accounting for component linkages, cascading effects and feedback processes.

5.
Neuron ; 10(5): 907-19, 1993 May.
Artículo en Inglés | MEDLINE | ID: mdl-8098611

RESUMEN

Protocols that induce long-term potentiation (LTP) typically involve afferent stimulation. We tested the hypothesis that LTP induction does not require presynaptic activity. The significance of this hypothesis is underscored by results suggesting that LTP expression may involve activity-dependent presynaptic changes. An induction protocol using glutamate iontophoresis was developed that reliably induced LTP in hippocampal slices without afferent stimulation. Iontophoresis LTP was Ca2+ dependent, was blocked by MK-801, and occluded tetanus-induced LTP. Iontophoresis LTP was induced when excitatory postsynaptic potentials were completely blocked by adenosine plus tetrodotoxin. Our results suggest constraints on the involvement of presynaptic mechanisms and putative retrograde messengers in LTP induction and expression; namely, these processes must function without many forms of activity-dependent presynaptic processes.


Asunto(s)
Glutamatos/farmacología , Hipocampo/fisiología , Iontoforesis , Sinapsis/fisiología , Potenciales de Acción/efectos de los fármacos , Adenosina/farmacología , Animales , Calcio/farmacología , Maleato de Dizocilpina/farmacología , Ácido Egtácico/farmacología , Glutamatos/administración & dosificación , Ácido Glutámico , Hipocampo/efectos de los fármacos , Masculino , Neurotransmisores/antagonistas & inhibidores , Neurotransmisores/metabolismo , Ratas , Ratas Sprague-Dawley , Cloruro de Sodio/farmacología , Sinapsis/efectos de los fármacos , Transmisión Sináptica/efectos de los fármacos , Tetrodotoxina/farmacología
6.
Cancer Sci ; 99(11): 2113-9, 2008 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-19037975

RESUMEN

Goblet cell depletion and down-regulation of MUC2 expression are observed in a significant percentage of human non-mucinous colorectal adenocarcinomas. Direct evidence for the role of MUC2 in gastrointestinal tumor formation was demonstrated by a knockout of Muc2 in mice that resulted in the development of adenocarcinomas in the small and large intestine. The secretory phospholipase Pla2g2a is a protein that confers resistance to Apc(Min/+)-induced intestinal tumorigenesis. Like Muc2, in the large intestine Pla2g2a is exclusively expressed by the goblet cells and Pla2g2a's tumor resistance is also strongest in the large intestine. Possible genetic interactions between Muc2 and Pla2g2a were examined by creating C57BL/6-Muc2(-/-)Pla2g2a transgenic mice. Expression of a Pla2g2a transgene reduced tumorigenesis in the large intestine by 90% in male Muc2(-/-) mice and by nearly 100% in female Muc2(-/-) mice. Expression of Pla2g2a also inhibited tumor progression. Microarray gene expression studies revealed Pla2g2a target genes that modulate intestinal energy metabolism, differentiation, inflammation, immune responses and proliferation. Overall, results of the present study demonstrate an Apc-independent role for Pla2g2a in tumor resistance and indicate that Pla2g2a plays an important role, along with Muc2, in protection of the intestinal mucosa.


Asunto(s)
Transformación Celular Neoplásica/genética , Fosfolipasas A2 Grupo II/genética , Mucina 2/genética , Animales , Femenino , Expresión Génica , Fosfolipasas A2 Grupo II/metabolismo , Inmunohistoquímica , Masculino , Ratones , Ratones Endogámicos C57BL , Ratones Transgénicos , Mucina 2/metabolismo , Análisis de Secuencia por Matrices de Oligonucleótidos
7.
Phys Rev E Stat Nonlin Soft Matter Phys ; 75(4 Pt 1): 041802, 2007 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-17500914

RESUMEN

We here develop a theory for the effect of shearing flow on residual proton dipole-dipole interactions for polymer melts. The model is based on the use of correlation functions which derive from the return to origin probability for polymers reptating in the tube of surrounding constraints. Using Doi-Edwards theory we calculate the spin-echo response under equilibrium conditions and then consider the effect of a shearing flow which deforms the tube, finding that there exists a strong dependence of transverse relaxation on Weissenberg number. The results are compared with NMR measurements of shear-perturbed proton T2 relaxation in 494kDa poly (dimethylsiloxane).

8.
Mar Pollut Bull ; 118(1-2): 27-40, 2017 May 15.
Artículo en Inglés | MEDLINE | ID: mdl-28396077

RESUMEN

The marine environment is a complex system formed by interactions between ecological structure and functioning, physico-chemical processes and socio-economic systems. An increase in competing marine uses and users requires a holistic approach to marine management which considers the environmental, economic and societal impacts of all activities. If managed sustainably, the marine environment will deliver a range of ecosystem services which lead to benefits for society. In order to understand the complexity of the system, the DPSIR (Driver-Pressure-State-Impact-Response) approach has long been a valuable problem-structuring framework used to assess the causes, consequences and responses to change in a holistic way. Despite DPSIR being used for a long time, there is still confusion over the definition of its terms and so to be appropriate for current marine management, we contend that this confusion needs to be addressed. Our viewpoint advocates that DPSIR should be extended to DAPSI(W)R(M) (pronounced dap-see-worm) in which Drivers of basic human needs require Activities which lead to Pressures. The Pressures are the mechanisms of State change on the natural system which then leads to Impacts (on human Welfare). Those then require Responses (as Measures). Furthermore, because of the complexity of any managed sea area in terms of multiple Activities, there is the need for a linked-DAPSI(W)R(M) framework, and then the connectivity between marine ecosystems and ecosystems in the catchment and further at sea, requires an interlinked, nested-DAPSI(W)R(M) framework to reflect the continuum between adjacent ecosystems. Finally, the unifying framework for integrated marine management is completed by encompassing ecosystem structure and functioning, ecosystem services and societal benefits. Hence, DAPSI(W)R(M) links the socio-ecological system of the effects of changes to the natural system on the human uses and benefits of the marine system. However, to deliver these sustainably in the light of human activities requires a Risk Assessment and Risk Management framework; the ISO-compliant Bow-Tie method is used here as an example. Finally, to secure ecosystem health and economic benefits such as Blue Growth, successful, adaptive and sustainable marine management Responses (as Measures) are delivered using the 10-tenets, a set of facets covering all management disciplines and approaches.


Asunto(s)
Conservación de los Recursos Naturales/métodos , Ecología , Ecosistema , Actividades Humanas , Humanos , Océanos y Mares , Medición de Riesgo , Gestión de Riesgos
10.
Neuroscience ; 140(3): 889-95, 2006 Jul 07.
Artículo en Inglés | MEDLINE | ID: mdl-16581195

RESUMEN

Glucose transporters play a critical role in mammalian brain energy metabolism because glucose is the principal brain energy source and these transporters promote glucose movement into neural cells. When glucose is unavailable, fructose can serve as an alternative energy source. Using real-time polymerase chain reaction and actin as a reference mRNA, we investigated the impact of fructose feeding on rat brain and other tissue mRNA expression of glucose transporter 5 which has high affinity for fructose. Brain mRNA levels of glucose transporter 5 increased 1.5-fold in 35-day old rats after 7 days of fructose feeding compared with controls, whereas it increased 2.5-fold in jejunum. Semi-quantitative analysis of protein expression by immunofluorescence of glucose transporter 5 in rat hippocampi indicated a 2.4-fold increase. We demonstrated the specificity of fructose feeding on glucose transporter 5 expression by showing that the expression of the neuronal glucose transporter 3 and insulin-regulated glucose transporter 4 were unaffected. In addition, the expression of glucose transporter 5 increased in fructose fed older adult rats (8-months and 12-months old) when compared with controls. These results suggest that short-term fructose feeding increases the expression of glucose transporter 5 in both young and aging adult rats. Increased brain expression of glucose transporter 5 is likely to be important in the role of fructose as an alternative energy source.


Asunto(s)
Encéfalo/metabolismo , Metabolismo Energético/fisiología , Fructosa/metabolismo , Transportador de Glucosa de Tipo 5/genética , ARN Mensajero/metabolismo , Regulación hacia Arriba/fisiología , Factores de Edad , Envejecimiento/fisiología , Animales , Técnica del Anticuerpo Fluorescente , Alimentos Formulados , Glucosa/metabolismo , Transportador de Glucosa de Tipo 3/genética , Transportador de Glucosa de Tipo 4/genética , Hipocampo/metabolismo , Insulina/metabolismo , Masculino , Ratas , Ratas Sprague-Dawley
11.
Cancer Res ; 60(14): 3965-70, 2000 Jul 15.
Artículo en Inglés | MEDLINE | ID: mdl-10919675

RESUMEN

Altered patterns of the 5-cytosine methylation of genomic DNA are associated with the development of a wide range of human cancers. We have studied the mechanisms and genetic pathways by which a targeted heterozygous deficiency in the murine 5-cytosine DNA methyltransferase gene (Dnmt1(N/+)) diminishes intestinal tumorigenesis in C57BL/6-multiple intestinal neoplasia (Min)/+ mice. We found that Dnmt1(N/+) retards the net growth rate of intestinal adenomas and reduces tumor multiplicity by approximately 50%. This tumor resistance affects the entire intestinal tract and is independent of the status of modifier of Min 1 and p53, two loci that have been found to confer strong resistance to Min-induced neoplasia Interestingly, Dnmt/(N/+) and modifier of Min 1 resistance interact synergistically, together virtually eliminating tumor incidence. This finding may provide an insight into potential combinatorial therapeutic approaches for treating human colon cancer.


Asunto(s)
Adenoma/tratamiento farmacológico , ADN (Citosina-5-)-Metiltransferasas/genética , Genes p53/genética , Neoplasias Intestinales/tratamiento farmacológico , Adenoma/genética , Adenoma/patología , Factores de Edad , Alelos , Animales , Apoptosis/genética , Bromodesoxiuridina/metabolismo , División Celular/efectos de los fármacos , ADN (Citosina-5-)-Metiltransferasa 1 , ADN (Citosina-5-)-Metiltransferasas/fisiología , Metilación de ADN , Replicación del ADN/genética , Femenino , Genotipo , Mutación de Línea Germinal , Neoplasias Intestinales/genética , Neoplasias Intestinales/patología , Masculino , Ratones , Ratones Endogámicos C57BL , Ratones Mutantes , Mitosis/genética , Mutagénesis Sitio-Dirigida , Neoplasias Experimentales/tratamiento farmacológico , Neoplasias Experimentales/genética , Neoplasias Experimentales/patología
12.
Oncogene ; 35(32): 4179-87, 2016 08 11.
Artículo en Inglés | MEDLINE | ID: mdl-26751771

RESUMEN

CFTR, the cystic fibrosis (CF) gene, encodes for the CFTR protein that plays an essential role in anion regulation and tissue homeostasis of various epithelia. In the gastrointestinal (GI) tract CFTR promotes chloride and bicarbonate secretion, playing an essential role in ion and acid-base homeostasis. Cftr has been identified as a candidate driver gene for colorectal cancer (CRC) in several Sleeping Beauty DNA transposon-based forward genetic screens in mice. Further, recent epidemiological and clinical studies indicate that CF patients are at high risk for developing tumors in the colon. To investigate the effects of CFTR dysregulation on GI cancer, we generated Apc(Min) mice that carried an intestinal-specific knockout of Cftr. Our results indicate that Cftr is a tumor suppressor gene in the intestinal tract as Cftr mutant mice developed significantly more tumors in the colon and the entire small intestine. In Apc(+/+) mice aged to ~1 year, Cftr deficiency alone caused the development of intestinal tumors in >60% of mice. Colon organoid formation was significantly increased in organoids created from Cftr mutant mice compared with wild-type controls, suggesting a potential role of Cftr in regulating the intestinal stem cell compartment. Microarray data from the Cftr-deficient colon and the small intestine identified dysregulated genes that belong to groups of immune response, ion channel, intestinal stem cell and other growth signaling regulators. These associated clusters of genes were confirmed by pathway analysis using Ingenuity Pathway Analysis and gene set enrichment analysis (GSEA). We also conducted RNA Seq analysis of tumors from Apc(+/+) Cftr knockout mice and identified sets of genes dysregulated in tumors including altered Wnt ß-catenin target genes. Finally we analyzed expression of CFTR in early stage human CRC patients stratified by risk of recurrence and found that loss of expression of CFTR was significantly associated with poor disease-free survival.


Asunto(s)
Neoplasias Colorrectales/genética , Regulador de Conductancia de Transmembrana de Fibrosis Quística/genética , Genes Supresores de Tumor , Animales , Colon/metabolismo , Colon/patología , Neoplasias Colorrectales/patología , Supervivencia sin Enfermedad , Eliminación de Gen , Regulación Neoplásica de la Expresión Génica , Humanos , Ratones , Mutación , Transducción de Señal
13.
Oncogene ; 19(28): 3182-92, 2000 Jun 29.
Artículo en Inglés | MEDLINE | ID: mdl-10918573

RESUMEN

The Mom1 (Modifier of Min-1) region of distal chromosome 4 was identified during a screen for polymorphic modifiers of intestinal tumorigenesis in ApcMin/+ mice. Here, we demonstrate that the Mom1AKR allele consists of two genetic components. These include the secretory phospholipase Pla2g2a, whose candidacy as a Mom1 resistance modifier has now been tested with several transgenic lines. A second region, distal to Pla2g2a, has also been identified using fine structure recombinants. Pla2g2aAKR transgenic mice demonstrate a modest resistance to tumorigenesis in the small intestine and a very robust resistance in the large intestine. Moreover, the tumor resistance in the colon of Pla2g2aAKR animals is dosage-dependent, a finding that is consistent with our observation that Pla2g2a is expressed in goblet cells. By contrast, mice carrying the distal Mom1 modifier demonstrate a modest tumor resistance that is confined to the small intestine. Thus, the phenotypes of these two modifier loci are complementary, both in their quantitative and regional effects. The additive effects and tight linkage of these modifiers may have been necessary for the initial identification of the Mom1 region.


Asunto(s)
Poliposis Adenomatosa del Colon/genética , Proteínas del Citoesqueleto/genética , Fosfolipasas A/genética , Proteína de la Poliposis Adenomatosa del Colon , Animales , Femenino , Células Caliciformes/patología , Humanos , Inmunidad Innata/genética , Intestinos/patología , Masculino , Ratones , Ratones Endogámicos AKR , Ratones Endogámicos C57BL , Ratones Transgénicos , Fosfolipasas A/biosíntesis
14.
J Neurosci ; 20(9): 3147-56, 2000 May 01.
Artículo en Inglés | MEDLINE | ID: mdl-10777778

RESUMEN

Neurotransmitters can have both toxic and trophic functions in addition to their role in neural signaling. Surprisingly, chronic blockade of GABA(A) receptor activity for 5-8 d in vitro enhanced survival of hippocampal neurons, suggesting that GABA(A) receptor overactivation may be neurotoxic. Potentiating GABA(A) receptor activity by chronic treatment with the endogenous neurosteroid (3alpha,5alpha)-3-hydroxypregnan-20-one caused massive cell loss over 1 week in culture. Other potentiators of GABA(A) receptors, including benzodiazepines, mimicked the cell loss, suggesting that potentiating endogenous GABA activity is sufficient to produce neuronal death. Neurosteroid-treated neurons had lower resting intracellular calcium levels than control cells and produced smaller calcium rises in response to depolarizing challenges. Manipulating intracellular calcium levels with chronic elevated extracellular potassium or with the calcium channel agonist Bay K 8644 protected neurons. The results may have implications for the mechanisms of programmed cell death in the developing CNS as well as implications for the long-term consequences of chronic GABAmimetic drug use during development.


Asunto(s)
Calcio/metabolismo , Muerte Celular/fisiología , Antagonistas del GABA/farmacología , Moduladores del GABA/farmacología , Neuronas/fisiología , Receptores de GABA-A/efectos de los fármacos , Ácido gamma-Aminobutírico/efectos de los fármacos , Ácido 3-piridinacarboxílico, 1,4-dihidro-2,6-dimetil-5-nitro-4-(2-(trifluorometil)fenil)-, Éster Metílico/farmacología , Animales , Agonistas de los Canales de Calcio/farmacología , Muerte Celular/efectos de los fármacos , Células Cultivadas , Agonistas de Aminoácidos Excitadores/farmacología , Hipocampo/efectos de los fármacos , Hipocampo/metabolismo , N-Metilaspartato/farmacología , Cloruro de Potasio/farmacología , Ratas , Receptores de GABA-A/fisiología , Ácido gamma-Aminobutírico/metabolismo , Ácido gamma-Aminobutírico/farmacología
15.
Neuroscience ; 131(2): 349-58, 2005.
Artículo en Inglés | MEDLINE | ID: mdl-15708478

RESUMEN

We investigated conditions that promote basal and activity-dependent neuronal apoptosis in postnatal rat hippocampal cultures. Low-density mixed cultures of astrocytes and neurons exhibited lower sensitivity than high-density cultures to basal neuronal death and activity-sensitive neuronal death, induced with glutamate receptor blockers, sodium channel blockers, or calcium channel blockers. Although elevations of [Ca(2+)](i) protect neurons from apoptosis, low-density microcultures and mass cultures exhibited only minor differences in resting [Ca(2+)](i) and Ca(2+) current density, suggesting that these variables are unlikely to explain differences in susceptibility. Astrocytes, rather than neurons, were implicated in the neuronal loss. Several candidate molecules implicated in other astrocyte-dependent neurotoxicity models were excluded, but heat inactivation experiments suggested that a heat-labile factor is critically involved. In sum, our results suggest the surprising result that astrocytes can be negative modulators of neuronal survival during development and when the immature nervous system is challenged with drugs that dampen electrical excitability.


Asunto(s)
Apoptosis/fisiología , Astrocitos/fisiología , Hipocampo/fisiología , Animales , Animales Recién Nacidos , Apoptosis/efectos de los fármacos , Astrocitos/citología , Astrocitos/efectos de los fármacos , Supervivencia Celular/efectos de los fármacos , Supervivencia Celular/fisiología , Células Cultivadas , Ácido Glutámico/farmacología , Hipocampo/citología , Hipocampo/efectos de los fármacos , Nifedipino/farmacología , Ratas
16.
J Magn Reson ; 172(1): 91-7, 2005 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-15589412

RESUMEN

We consider the problem of performing NMR spectroscopy under conditions of flow, a central issue in Rheo-NMR. By way of example, the effects of rotational motion on the deuterium NMR spectrum are considered for Couette cell experiments involving deformation of polymers under shearing conditions. The polymer was modelled as a power law fluid and for each streamline, the spin Hamiltonian evolved to allow for flow reorientation. The gap-integral spectra are compared with the 'ideal' spectra for a polymer under shear, but without reorientation. It is found that flow does affect the shape of the deuterium spectra, as well as slightly perturbing the splittings.


Asunto(s)
Espectroscopía de Resonancia Magnética/métodos , Polímeros/química , Reología , Deuterio , Diseño de Equipo , Espectroscopía de Resonancia Magnética/instrumentación , Procesamiento de Señales Asistido por Computador , Factores de Tiempo
17.
Am J Surg ; 153(1): 80-5, 1987 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-3799896

RESUMEN

Patients with cirrhosis who had undergone the distal splenorenal shunt were grouped based on preoperative to early postoperative changes in hepatic portal perfusion and corrected sinusoidal pressure. Early and late postoperative morbidity and mortality rates were determined for each hemodynamic group. Morbidity was least when both hepatic portal perfusion and sinusoidal pressure were maintained near preoperative levels (Group 1). Survival for this group was significantly better than for patients who lost portal flow to the liver during the early postoperative interval (Group 4). Patients with absent hepatic portal perfusion had the worst survival and greatest morbidity. Intermediate results were achieved for the two groups of patients that had postoperative preservation of portal perfusion but significant preoperative to postoperative alterations in sinusoidal pressure. Although survival curves for these two groups were not significantly different from Group 1, morbidity was greater, especially for patients with an increase in sinusoidal pressure (Group 2).


Asunto(s)
Hemodinámica , Circulación Hepática , Derivación Portosistémica Quirúrgica , Derivación Esplenorrenal Quirúrgica , Várices Esofágicas y Gástricas/cirugía , Humanos , Cirrosis Hepática Alcohólica/fisiopatología , Cirrosis Hepática Alcohólica/cirugía , Persona de Mediana Edad , Sistema Porta , Periodo Posoperatorio
18.
Am J Surg ; 147(1): 89-96, 1984 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-6606992

RESUMEN

Since 1978, the operation chosen for patients with variceal hemorrhage has been based on preoperative hemodynamic and clinical factors. One hundred sixteen consecutive patients were managed with the following operations: distal splenorenal shunt (75 patients), nonselective shunts (33 patients), and nonshunting operation (8 patients). Emergency surgery was required in 19 percent of patients. The selection criteria used resulted in the majority of high risk patients receiving nonselective shunts. This selective operative approach resulted in an overall operative mortality of 12 percent, a median survival of 3 years, and postoperative encephalopathy, ascites, and recurrent variceal hemorrhage in 20, 23, and 11 percent of patients, respectively. Operative mortality for the total group was closely related to Child's class. Whereas encephalopathy was most frequent after nonselective shunts, ascites was more common after the distal splenorenal shunt. Recurrent hemorrhage rarely occurred after a shunting procedure, but was a frequent complication of nonshunting operations. Neither the type of procedure selected nor the cause of liver disease influenced long-term survival.


Asunto(s)
Várices Esofágicas y Gástricas/cirugía , Derivación Portosistémica Quirúrgica , Derivación Esplenorrenal Quirúrgica , Adulto , Várices Esofágicas y Gástricas/mortalidad , Várices Esofágicas y Gástricas/fisiopatología , Femenino , Hemorragia Gastrointestinal/mortalidad , Hemorragia Gastrointestinal/fisiopatología , Hemorragia Gastrointestinal/cirugía , Hemodinámica , Humanos , Masculino , Persona de Mediana Edad , Complicaciones Posoperatorias
19.
Am J Surg ; 165(1): 27-32; discussion 32-3, 1993 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-8418700

RESUMEN

Between September 1982 and April 1988, 60 cirrhotic patients with prior variceal hemorrhage were randomized to undergo the placement of an elective shunt (distal splenorenal: 26; nonselective: 4) or long-term endoscopic sclerotherapy (n = 30). Eighty-six percent of patients had alcoholic cirrhosis, and 33% were classified as Child's class C. After a mean follow-up of 87 months, 60% of patients undergoing sclerotherapy and 17% of shunt patients experienced rebleeding (p < 0.001). Shunt patients have survived longer than those who had sclerotherapy (6-year survival rates of 53% and 26%, respectively; p < 0.05). In part because of the wide geographic distribution of patients, only 4 of 13 patients in whom sclerotherapy failed (31%) could undergo salvage by shunt surgery. Although hepatic portal perfusion was better maintained after sclerotherapy, there were no major differences between the groups in terms of post-therapy hepatic or psychoneurologic function. In a predominantly alcoholic cirrhotic patient population (half non-urban), the results of elective shunt surgery were superior to those of chronic endoscopic sclerotherapy with respect to the prevention of recurrent variceal hemorrhage and survival.


Asunto(s)
Várices Esofágicas y Gástricas/terapia , Hemorragia Gastrointestinal/terapia , Escleroterapia , Derivación Esplenorrenal Quirúrgica , Várices Esofágicas y Gástricas/etiología , Várices Esofágicas y Gástricas/mortalidad , Estudios de Seguimiento , Hemorragia Gastrointestinal/etiología , Hemorragia Gastrointestinal/mortalidad , Humanos , Cirrosis Hepática Alcohólica/complicaciones , Análisis de Supervivencia , Factores de Tiempo
20.
Respir Med ; 92(3): 588-92, 1998 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-9692128

RESUMEN

Methacholine chloride bronchoprovocation challenges are performed for the diagnosis and investigation of hyperreactive airways. Over the last 20 yrs various formulations and pH values for the preparation of solutions of methacholine have been described. To determine the stability of methacholine chloride solutions prepared in a variety of buffers with differing pH values and under varying storage temperatures, we measured methacholine concentrations at intervals from 1 to 5 weeks. It was found that methacholine chloride solutions rapidly decompose if the pH is greater than 6 and that decomposition is more rapid as the pH is raised; solutions at pH 9, i.e. bicarbonate buffer, and stored at 27 degrees C have degradation up to 36% after only one week. Solutions of the same pH but prepared in different buffers can have both varied rates of deterioration and different absolute amounts of methacholine hydrolysed, e.g. solutions prepared in pH 9 borate buffer and stored at 27 degrees C have up to 60% degradation after 1 week. Solutions prepared in saline are stable probably because methacholine solutions are weakly acidic. The results emphasise the importance of preparing methacholine chloride in the proper buffers for use in the accurate assessment of airway responsiveness.


Asunto(s)
Broncoconstrictores/química , Cloruro de Metacolina/química , Estabilidad de Medicamentos , Concentración de Iones de Hidrógeno
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