RESUMO
The Sea-viewing Wide Field-of-view Sensor (SeaWiFS) provides global monthly measurements of both oceanic phytoplankton chlorophyll biomass and light harvesting by land plants. These measurements allowed the comparison of simultaneous ocean and land net primary production (NPP) responses to a major El Niño to La Niña transition. Between September 1997 and August 2000, biospheric NPP varied by 6 petagrams of carbon per year (from 111 to 117 petagrams of carbon per year). Increases in ocean NPP were pronounced in tropical regions where El Niño-Southern Oscillation (ENSO) impacts on upwelling and nutrient availability were greatest. Globally, land NPP did not exhibit a clear ENSO response, although regional changes were substantial.
Assuntos
Biomassa , Clorofila/análise , Clima , Fotossíntese , Fitoplâncton/metabolismo , Plantas/metabolismo , Luz , Oceanos e Mares , Fitoplâncton/crescimento & desenvolvimento , Desenvolvimento Vegetal , Estações do Ano , Água do Mar , AstronaveRESUMO
The mechanistic relationship of the inhibition of gap junctional intercellular communication (GJIC) to other toxicological phenomena was explored using a recently developed method that models the properties of a large population of molecules chosen to represent the 'universe of chemicals'. The analyses indicate that inhibition of GJIC is strongly linked to the carcinogenic process in rodents, to cellular but not systemic toxicity, to biological phenomena that may involve inflammatory processes and to development effects. The inhibition of GJIC appears not to be associated with genotoxic mechanisms. With respect to cancer causation, integration of the analyses suggests that inhibition of GJIC is involved in non-genotoxic cancer induction or in the non-genotoxic phases of the carcinogenic process (such as inflammation, cell toxicity, cell proliferation, inhibition of cell differentiation and apoptosis).
Assuntos
Comunicação Celular/efeitos dos fármacos , Junções Comunicantes/efeitos dos fármacos , Animais , Carcinógenos/toxicidade , DNA/efeitos dos fármacos , Modelos Biológicos , Relação Estrutura-AtividadeRESUMO
The CASE/MULTICASE structure-activity relationship (SAR) system was used to assess a new procedure to investigate the mechanistic relatedness of various toxicological endpoints. The method consisted of predicting the activity of 10,000 randomly selected chemicals using validated and characterized SAR models from a variety of biological and toxicological endpoints. The prevalence of chemicals predicted to possess the ability to induce two or more toxicological effects simultaneously should provide a measure of the mechanistic relatedness of these phenomena. Eight toxicological endpoints were predicted and the results were compared to predictions based on an eye irritation SAR model. Allergic contact dermatitis demonstrated a 29.6% greater than expected overlap between expected and observed results (p < 0.001). Similar results were seen for respiratory hypersensitivity (33.1%), sensory irritation (28.9%), cell toxicity (25.9%), and Ah receptor binding (19.8%). A lesser degree of overlap was seen between eye irritation and Salmonella mutagenicity (11.5%) and the inhibition of gap junction intercellular communication (6.7%). Moreover, a negative overlap, suggesting possibly an antagonistic phenomena, was observed between eye irritation and alpha 2 mu-induced nephropathy. These results indicate that this method can provide a useful tool to investigate mechanistic relatedness between diverse toxicological endpoints.
Assuntos
Dermatite de Contato/etiologia , Irritantes/química , Xenobióticos/química , Xenobióticos/toxicidade , Animais , Hipersensibilidade a Drogas , Olho/efeitos dos fármacos , Humanos , Irritantes/toxicidade , Valor Preditivo dos Testes , Coelhos , Valores de Referência , Reprodutibilidade dos Testes , Salmonella , Relação Estrutura-Atividade , Testes de Toxicidade/métodosRESUMO
Alveolar epithelial cell (AEC) injury and repair are important in the pathogenesis of oxidant-induced lung damage. Keratinocyte growth factor (KGF) prevents lung damage and mortality in animals exposed to various forms of oxidant stress, but the protective mechanisms are not yet established. Because DNA strand break (DNA-SB) formation is one of the earliest cellular changes that occurs after cells are exposed to an oxidant stress, we determined whether KGF reduces H2O2-induced pulmonary toxicity by attenuating AEC DNA damage. KGF (10-100 ng/ml) decreased H2O2 (0.05-0.5 mM)-induced DNA-SB formation in cultured A549 and rat alveolar type II cells measured by an alkaline unwinding, ethidium bromide fluorometric technique. The protective effects of KGF were independent of alterations in catalase, glutathione (GSH), or the expression of bcl-2 and bax, two protooncogenes known to regulate oxidant-induced apoptosis. Actinomycin D and cycloheximide abrogated protective effects of KGF. Furthermore, protection by KGF was completely blocked by 1) genistein, a tyrosine kinase inhibitor; 2) staurosporine and calphostin C, protein kinase C (PKC) inhibitors; and 3) aphidicolin, butylphenyl dGTP, and 2',3'-dideoxythymidine 5'-triphosphate, inhibitors of DNA polymerase. We conclude that KGF attenuates H2O2-induced DNA-SB formation in cultured AECs by mechanisms that involve tyrosine kinase, PKC, and DNA polymerases. These data suggest that the ability of KGF to protect against oxidant-induced lung injury is partly due to enhanced AEC DNA repair.
Assuntos
Dano ao DNA , Reparo do DNA/efeitos dos fármacos , Inibidores Enzimáticos/farmacologia , Fatores de Crescimento de Fibroblastos , Substâncias de Crescimento/farmacologia , Peróxido de Hidrogênio/toxicidade , Alvéolos Pulmonares/fisiologia , Animais , Afidicolina/farmacologia , Morte Celular/efeitos dos fármacos , Cicloeximida/farmacologia , Dactinomicina/farmacologia , Fator 10 de Crescimento de Fibroblastos , Fator 7 de Crescimento de Fibroblastos , Genisteína/farmacologia , Substâncias de Crescimento/fisiologia , Humanos , Cinética , Neoplasias Pulmonares , Naftalenos/farmacologia , Proteína Quinase C/antagonistas & inibidores , Proteínas Tirosina Quinases/antagonistas & inibidores , Alvéolos Pulmonares/citologia , Alvéolos Pulmonares/efeitos dos fármacos , Ratos , Estaurosporina/farmacologia , Células Tumorais CultivadasRESUMO
As their profession changes, dietitians are constantly breaking stereotypes. Gone are the days when all dietitians wore lab coats and worked in hospitals. Expanding knowledge, increased community support and new technology all present dietitians with more and more career opportunities. Here's what some of your peers had to say about the expanding world of dietetics.
Assuntos
Atitude do Pessoal de Saúde , Mobilidade Ocupacional , Dietética/tendências , Humanos , Mudança Social , Estados Unidos , Recursos HumanosRESUMO
A survey of 108 major teaching institutions in the United States regarding the utilization of the McRoberts maneuver for shoulder dystocia was conducted. Only 40% taught the procedure but 64% reported being familiar with its use. Among users, only 32% used it as the initial step. Surprisingly, only 40% thought it reduced fetal trauma.