920 resultados para half-life measurement


Relevância:

80.00% 80.00%

Publicador:

Resumo:

Because of the short half-life of NO, previous studies implicating NO in central nervous system pathology during infection had to rely on the demonstration of elevated levels of NO synthase mRNA or enzyme expression or NO metabolites such as nitrate and nitrite in the infected brain. To more definitively investigate the potential causative role of NO in lesions of the central nervous system in animals infected with neurotropic viruses or suffering from experimental allergic encephalitis, we have determined directly the levels of NO present in the central nervous system of such animals. Using spin trapping of NO and electron paramagnetic resonance spectroscopy, we confirm here that copious amounts of NO (up to 30-fold more than control) are elaborated in the brains of rats infected with rabies virus or borna disease virus, as well as in the spinal cords of rats that had received myelin basic protein-specific T cells.

Relevância:

80.00% 80.00%

Publicador:

Resumo:

The heat shock response in Escherichia coli is governed by the concentration of the highly unstable sigma factor sigma 32. The essential protein HflB (FtsH), known to control proteolysis of the phage lambda cII protein, also governs sigma 32 degradation: an HflB-depleted strain accumulated sigma 32 and induced the heat shock response, and the half-life of sigma 32 increased by a factor up to 12 in mutants with reduced HflB function and decreased by a factor of 1.8 in a strain overexpressing HflB. The hflB gene is in the ftsJ-hflB operon, one promoter of which is positively regulated by heat shock and sigma 32. The lambda cIII protein, which stabilizes sigma 32 and lambda cII, appears to inhibit the HflB-governed protease. The E. coli HflB protein controls the stability of two master regulators, lambda cII and sigma 32, responsible for the lysis-lysogeny decision of phage lambda and the heat shock response of the host.

Relevância:

80.00% 80.00%

Publicador:

Resumo:

The levels in Sn-129 populated from the beta(-) decay of In-129 isomers were investigated at the ISOLDE facility of CERN using the newly commissioned ISOLDE Decay Station (IDS). The lowest 1/2(+) state and the 3/2(+) ground state in 129Sn are expected to have configurations dominated by the neutron s(1/2) (l = 0) and d(3/2) (l = 2) single-particle states, respectively. Consequently, these states should be connected by a somewhat slow l-forbidden M1 transition. Using fast-timing spectroscopy we havemeasured the half-life of the 1/2(+) 315.3-keV state, T-1/2 = 19(10) ps, which corresponds to a moderately fast M1 transition. Shell-model calculations using the CD-Bonn effective interaction, with standard effective charges and g factors, predict a 4-ns half-life for this level. We can reconcile the shell-model calculations to the measured T-1/2 value by the renormalization of the M1 effective operator for neutron holes.

Relevância:

80.00% 80.00%

Publicador:

Resumo:

Com o objetivo de se avaliar a importância do \"clearance\" do dietilenotriamino-pentacetato marcado com Tecnécio 99m (DTPA-Tecnécio-99m) em portadores de pneumopatia por amiodarona foram estudados 40 indivíduos, em quatro grupos. Grupo I: 10 voluntários normais, assintomáticos e não fumantes (8 homens e 2 mulheres), com média de idade de 56,80 anos. Grupo II: 10 voluntários normais, assintomáticos e fumantes (6 homens e 4 mulheres ), com média de idade de 27,50 anos. Grupo III: 10 pacientes não fumantes ( 4 homens e 5 mulheres ), com média de idade de 52,90 anos. Todos faziam uso crônico de amiodarona por via oral. Grupo IV: 10 pacientes portadores de pneumopatia por amiodarona, quatro ex-fumantes, dois fumantes e quatro não fumantes ( 8 homens e 2 mulheres) com média de idade de 52,90 anos. Todos faziam uso de amiodarona por via oral e nenhum fumou nas 4 semanas que precederam o estudo. Após espirometria que constou do registro da curva volume-tempo, todos inalaram 4 ml de solução salina contendo 740 MBq de DTPA Tecnécio-99m, durante cinco minutos. Através de uma c~mara de cintilação computadorizada foram obtidas imagens pulmonares, definindo-se 9 áreas de interesse. Para cada região escolhida foi determinada uma curva de \"clearance\" extraindo-se o valor de meia-vida biológica em minu- tos ( T 1/2 ) e a taxa percentual de \" clearance\" alvéolo capilar do radioaerossol por minuto (K%/min). Observamos que, das variáveis espirométricas consideradas, a capacidade vital forçada (CVF) e o volume expiratório forçado no 1 segundo (VEF1) mostraram diferenças significantes entre os grupos I e IV. A contagem total de radioatividade de ambos os pulmões não mostrou relação com a CVF e o VEF1. O \" clearance \" pulmonar do DTPA Tecnécio-99m foi maior nos grupos 11 e IV, porém não permitindo sua diferenciação. Estes resultados permitem concluir: Os pacientes portadores de pneumonite por amiodaro- na apresentam\" clearance \" alvéolo-capilar de DTPA Tecnécio-99m significativamente maior que os indivíduos do grupo de normais não fumantes. Este fato também se verificou em relação aos pacientes em uso crônico de amiodarona mas sem evidências de pneumopatia. Não é possível diferenciar os fumantes dos portadores de pneumonite por amiodarona através da análise da integridade da barreira alvéolo-epitelial com DTPA Tecnécio-99m. Comparativamente, o estudo da integridade alvéolo-epitelial pelo \"clearance\" pulmonar de DTPA Tecnécio-99m é mais sensível que a espirometria na avaliação da pneumonite por amiodarona, permitindo diferenciar estes pacientes dos que fazem uso crônico da droga

Relevância:

80.00% 80.00%

Publicador:

Resumo:

Introducción: La obesidad en la población infantil y juvenil en España se sitúa actualmente en el 13,9%, y el sobrepeso se encuentra en el 26,3%. Esto hace que sea fundamental la adopción en los primeros años de vida de unos hábitos alimentarios correctos, donde la educación alimentaria y nutricional, desarrollada dentro de los programas de educación para la salud en el medio escolar, juega un papel fundamental. El objetivo del presente trabajo fue analizar, mediante revisión bibliométrica, la producción científica existente sobre programas o intervenciones de educación alimentaria y nutricional desarrollados en el medio escolar en España que muestran influencia en la salud y/o en los hábitos alimentarios de los escolares. Material y Métodos: Estudio descriptivo transversal de los resultados obtenidos en la búsqueda bibliográfica de las bases de datos Medline, Cochrane Library Plus en Español, Cuiden, Excelencia clínica, IBECS, Scielo, CSIC (ICYT, ISOC e IME), Lilacs, Cuidatge y Teseo. Se estudiaron indicadores bibliométricos: bases de datos, revistas, documentos publicados, idiomas, autoría, Índice de colaboración y grado de obsolescencia (Semiperíodo de Burton y Kebler e Índice de Price), entre otros. Resultados: La búsqueda proporcionó un total de 148 registros. La tasa final de artículos pertinentes fue de 49 (33,11%). La base de datos que más registros pertinentes proporcionó fue Medline con 24 (48,98%). 42 de los registros seleccionados (85,71%) pertenecían a artículos originales. La revista Nutrición Hospitalaria fue la que presentó mayor número de publicaciones, con 11 (22,45%). El Semiperíodo de Burton y Kebler fue de 6 años y el Índice de Price fue de 42,86%. Conclusiones: Existe una gran producción de artículos científicos relacionados con programas de educación alimentaria y nutricional en el medio escolar en España, lo cual es un indicador de la importancia de la adquisición de hábitos alimentarios saludables en la población infantil y juvenil y del interés que despiertan.

Relevância:

80.00% 80.00%

Publicador:

Resumo:

A pollen profile from the highest known peatbog in the Alps is presented. The peatbog started to grow about 8000 years ago and over the last 5000 years. The influence of man on the vegetation is documented. Before the beginning of the bronze age pasturing started.

Relevância:

80.00% 80.00%

Publicador:

Resumo:

"Contract AT(30-1)2101."

Relevância:

80.00% 80.00%

Publicador:

Resumo:

Thesis (Ph.D.)--University of Washington, 2016-06

Relevância:

80.00% 80.00%

Publicador:

Resumo:

Thesis (Master's)--University of Washington, 2016-06

Relevância:

80.00% 80.00%

Publicador:

Resumo:

Objective To determine the pharmacokinetics of carboplatin in sulphur-crested cockatoos, so that its use in clinical studies in birds can be considered. Design A pharmacokinetic study of carboplatin, following a single intravenous (IV) or intraosseus (10) infusion over 3 min, was performed in six healthy sulphur-crested cockatoos (Cacatua galerita). Procedure Birds were anaesthetised and a jugular vein cannulated for blood collection. Carboplatin (5 mg/kg) was infused over 3 min by the IV route in four birds via the contralateral jugular vein, and by the 10 route in two birds via the ulna. Serial blood samples were collected for 96 h after initiation of the infusion. Tissue samples from 11 organs were obtained at necropsy, 96 h after carboplatin administration. Total Pt and filterable Pt in plasma and tissue Pt concentrations were assayed by inductively coupled plasma-mass spectrometry. A noncompartmental pharmacokinetic analysis was performed on the plasma data. Results The mean +/- SD for the C-max of filterable Pt was 27.3 +/- 4.06 mg/L and in all six birds occurred at the end of the 3 min infusion, thenceforth declining exponentially over the next 6 h to an average concentration of 0.128 +/- 0.065 mg/L. The terminal half-life (T-1/2) was 1.0 +/- 0.17 h, the systemic clearance (CI) was 5.50 +/- 1.06 mL/min/kg and the volume of distribution (Vss) was 0.378 +/- 0.073 L/kg. The extrapolated area under the curve (AUC(0-x)) was 0.903 +/- 0.127 mg/mL.min; the area extrapolated past the last (6 h) data point to infinite time averaged only 1.25% of the total AUC(0-x). The kidneys had the greatest accumulation of Pt (7.04 +/- 3.006 mug/g), followed by the liver (3.08 +/- 1.785 mug/g DM). Conclusions and clinical relevance Carboplatin infusion in sulphur-crested cockatoos produced mild, transient alimentary tract signs and the Pt plasma concentration was similar whether carboplatin was given intravenously or intraosseously. Filterable plasma Pt concentrations for carboplatin persisted longer than for cisplatin, due mostly to the difference in systemic clearance between these drugs in sulphur-crested cockatoos. The distribution of tissue Pt after carboplatin administration was similar to that reported for cisplatin in sulphur-crested cockatoos. Despite anatomical, physiological and biochemical differences among animal species, the pharmacokinetic disposition of filterable Pt in the sulphur-crested cockatoo shares some features with the kinetics reported previously in other animals and human beings.

Relevância:

80.00% 80.00%

Publicador:

Resumo:

The prevalence of obesity in the western world is dramatically rising, with many of these individuals requiring therapeutic intervention for a variety of disease states. Despite the growing prevalence of obesity there is a paucity of information describing how doses should be adjusted, or indeed whether they need to be adjusted, in the clinical setting. This review is aimed at identifying which descriptors of body size provide the most information about the relationship between dose and concentration in the obese. The size descriptors, weight, lean body weight, ideal body weight, body surface area, body mass index, fat-free mass, percent ideal body weight, adjusted body weight and predicted normal body weight were considered as potential size descriptors. We conducted an extensive review of the literature to identify studies that have assessed the quantitative relationship between the parameters clearance (CL) and volume of distribution (V) and these descriptors of body size. Surprisingly few studies have addressed the relationship between obesity and CL or V in a quantitative manner. Despite the lack of studies there were consistent findings: (i) most studies found total body weight to be the best descriptor of V. A further analysis of the studies that have addressed V found that total body weight or another descriptor that incorporated fat mass was the preferred descriptor for drugs that have high lipophilicity; (ii) in contrast, CL was best described by lean body mass and no apparent relationship between lipophilicity or clearance mechanism and preference for body size descriptor was found. In conclusion, no single descriptor described the influence of body size on both CL and V equally well. For drugs that are dosed chronically, and therefore CL is of primary concern, dosing for obese patients should not be based on their total weight. If a weight-based dose individualization is required then we would suggest that chronic drug dosing in the obese subject should be based on lean body weight, at least until a more robust size descriptor becomes available.

Relevância:

80.00% 80.00%

Publicador:

Resumo:

Objective To determine the pharmacokinetics of doxorubicin in sulphur-crested cockatoos, so that its use in clinical studies in birds can be considered. Design A pharmacokinetic study of doxorubicin, following a single intravenous (IV) infusion over 20 min, was performed in four healthy sulphur-crested cockatoos (Cacatua galerita). Procedure Birds were anaesthetised and both jugular veins were cannulated, one for doxorubicin infusion and the other for blood collection. Doxorubicin hydrochloride (2 mg/kg) in normal saline was infused IV over 20 min at a constant rate. Serial blood samples were collected for 96 h after initiation of the infusion. Plasma doxorubicin concentrations were assayed using an HPLC method involving ethyl acetate extraction, reverse-phase chromatography and fluorescence detection. The limit of quantification was 20 ng/mL. Established non-parametric methods were used for the analysis of plasma doxorubicin data. Results During the infusion the mean +/- SD for the C-max of doxorubicin was 4037 +/- 2577 ng/mL. Plasma concentrations declined biexponentially immediately after the infusion was ceased. There was considerable intersubject variability in all pharmacokinetic variables. The terminal (beta-phase) half-life was 41.4 +/- 18.5 min, the systemic clearance (Cl) was 45.7 +/- 18.0 mL/min/kg, the mean residence time (MRT) was 4.8 +/- 1.4 min, and the volume of distribution at steady state (V-SS) was 238 131 mL/kg. The extrapolated area under the curve (AUC(0-infinity)) was 950 +/- 677 ng/mL.h. The reduced metabolite, doxorubicinol, was detected in the plasma of all four parrots but could be quantified in only one bird with the profile suggesting formation rate-limited pharmacokinetics of doxorubicinol. Conclusions and clinical relevance Doxorubicin infusion in sulphur-crested cockatoos produced mild, transient inappetence. The volume of distribution per kilogram and terminal half-life were considerably smaller, but the clearance per kilogram was similar to or larger than reported in the dog, rat and humans. Traces of doxorubicinol, a metabolite of doxorubicin, were detected in the plasma.

Relevância:

80.00% 80.00%

Publicador:

Resumo:

The development of resistance to sulfadoxine-pyrimethamine by Plasmodium parasites is a major problem for the effective treatment of malaria, especially P. falciparum malaria. Although the molecular basis for parasite resistance is known, the factors promoting the development and transmission of these resistant parasites are less clear. This paper reports the results of a quantitative comparison of factors previously hypothesized as important for the development of drug resistance, drug dosage, time of treatment, and drug elimination half-life, with an in-host dynamics model of P. falciparum malaria in a malaria-naive host. The results indicate that the development of drug resistance can be categorized into three stages. The first is the selection of existing parasites with genetic mutations in the dihydrofolate reductase or dihydropteroate synthetase gene. This selection is driven by the long half-life of the sulfadoxine-pyrimethamine combination. The second stage involves the selection of parasites with allelic types of higher resistance within the host during an infection. The timing of treatment relative to initiation of a specific anti-P. falciparum EMP1 immune response is an important factor during this stage, as is the treatment dosage. During the third stage, clinical treatment failure becomes prevalent as the parasites develop sufficient resistance mutations to survive therapeutic doses of the drug combination. Therefore, the model output reaffirms the importance of correct treatment of confirmed malaria cases in slowing the development of parasite resistance to sulfadoxine-pyrimethamine.

Relevância:

80.00% 80.00%

Publicador:

Resumo:

By establishing mouse primary keratinocytes (KCs) in culture, we were able, for the first time, to express papillomavirus major capsid (L1) proteins by transient transfection of authentic or codon-modified L1 gene expression plasmids. We demonstrate in vitro and in vivo that gene codon composition is in part responsible for differentiation-dependent expression of L1 protein in KCs. L1 mRNA was present in similar amounts in differentiated and undifferentiated KCs transfected with authentic or codon-modified L1 genes and had a similar half-life, demonstrating that L1 protein production is posttranscriptionally regulated. We demonstrate further that KCs substantially change their tRNA profiles upon differentiation. Aminoacyl-tRNAs from differentiated KCs but not undifferentiated KCs enhanced the translation of authentic L1 mRNA, suggesting that differentiation-associated change to tRNA profiles enhances L1 expression in differentiated KCs. Thus, our data reveal a novel mechanism for regulation of gene expression utilized by a virus to direct viral capsid protein expression to the site of virion assembly in mature KCs. Analysis of two structural proteins of KCs, involucrin and keratin 14, suggests that translation of their mRNAs is also regulated, in association with KC differentiation in vitro, by a similar mechanism

Relevância:

80.00% 80.00%

Publicador:

Resumo:

Pesticides in soil are subject to a number of processes that result in transformation and biodegradation, sorption to and desorption from soil components, and diffusion and leaching. Pesticides leaching through a soil profile will be exposed to changing environmental conditions as different horizons with distinct physical, chemical and biological properties are encountered. The many ways in which soil properties influence pesticide retention and degradation need to be addressed to allow accurate predictions of environmental fate and the potential for groundwater pollution. Degradation and sorption processes were investigated in a long-term (100 days) study of the chloroacetanilide herbicide, acetochlor. Soil cores were collected from a clay soil profile and samples taken from 0-30cm (surface), 1.0-1.3m (mid) and 2.7-3.0m (deep) and treated with acetochlor (2.5, 1.25, 0.67 mu g acetochlor g(-1) dry wt soil, respectively). In sterile and non-sterile conditions, acetochlor concentration in the aqueous phase declined rapidly from the surface and subsoil layers, predominantly through nonextractable residue (NER) formation on soil surfaces, but also through biodegradation and biotic transformation. Abiotic transformation was also evident in the sterile soils. Several metabolites were produced, including acetochlor-ethane sulphonic acid and acetochlor-oxanilic acid. Transformation was principally microbial in origin, as shown by the differences between non-sterile and sterile soils. NER formation increased rapidly over the first 21 days in all soils and was mainly associated with the macroaggregate (> 2000 mu m diameter) size fractions. It is likely that acetochlor is incorporated into the macroaggregates through oxidative coupling, as humification of particulate organic matter progresses. The dissipation (ie total loss of acetochlor) half-life values were 9.3 (surface), 12.3 (mid) and 12.6 days (deep) in the non-sterile soils, compared with 20.9 [surface], 23.5 [mid], and 24 days [deep] in the sterile soils, demonstrating the importance of microbially driven processes in the rapid dissipation of acetochlor in soil.