RESUMO

BACKGROUND: Hepatocellular carcinoma (HCC) is a primary liver cancer with a high mortality rate. It has been reported that circular RNA hsa_circ_0091579 (circ_0091579) is involved in HCC progression. Nevertheless, the molecular mechanism by which circ_0091579 modulates HCC advancement is indistinct. METHODS: The expression of circ_0091579, microRNA (miR)-624, and H3 histone family member 3B (H3F3B) mRNA was evaluated by quantitative real-time polymerase chain reaction (qRT-PCR). The extracellular acidification rate (ECAR) and oxygen consumption rate (OCR) of HCC cells were analyzed using an extracellular flux analyzer. Adenosine triphosphate (ATP) level was evaluated using a commercial kit. Cell migration, invasion, and apoptosis were assessed by wound-healing, transwell, or flow cytometry assay. The relationship between miR-624 and circ_0091579 or H3F3B was verified using luciferase reporter assay and/or RNA immunoprecipitation (RIP) assay. H3F3B protein level was detected by western blotting. RESULTS: Circ_0091579 was upregulated in HCC tissues and cells. Circ_0091579 inhibition decreased xenograft tumor growth in vivo and repressed Warburg effect, migration, invasion, and induced apoptosis of HCC cells in vitro. MiR-624 was downregulated, while H3F3B was upregulated in HCC tissues and cells. Circ_0091579 acted as a miR-624 sponge and regulated H3F3B expression by adsorbing miR-624. MiR-624 inhibitor reversed circ_0091579 downregulation-mediated effects on the Warburg effect and malignant behaviors of HCC cells. H3F3B overexpression reversed the repressive impact of miR-624 mimic on the Warburg effect and malignancy of HCC cells. CONCLUSIONS: Circ_0091579 accelerated Warburg effect and tumor growth via upregulating H3F3B via adsorbing miR-624 in HCC, providing evidence to support the involvement of circ_0091579 in the progression of HCC.

Assuntos

Carcinoma Hepatocelular/metabolismo , Histonas/metabolismo , Neoplasias Hepáticas/metabolismo , MicroRNAs/metabolismo , RNA Circular/metabolismo , RNA Mensageiro/metabolismo , Efeito Warburg em Oncologia , Trifosfato de Adenosina/análise , Trifosfato de Adenosina/metabolismo , Animais , Apoptose , Carcinoma Hepatocelular/genética , Carcinoma Hepatocelular/patologia , Linhagem Celular Tumoral , Movimento Celular , Progressão da Doença , Regulação para Baixo , Humanos , Imunoprecipitação/métodos , Neoplasias Hepáticas/genética , Neoplasias Hepáticas/patologia , Camundongos , Camundongos Nus , MicroRNAs/antagonistas & inibidores , Invasividade Neoplásica , Transplante de Neoplasias , Consumo de Oxigênio , RNA Circular/antagonistas & inibidores , Regulação para Cima

RESUMO

OBJECTIVE: To study the clinical significance of serum epidermal growth factor receptor (EGFR) gene mutation and serum tumor markers in the prediction of tyrosine kinase inhibitor (TKI) efficacy in patients with lung adenocarcinoma. METHODS: Ninety patients with pathologically diagnosed lung adenocarcinoma were enrolled. Further, 51 out of 90 patients received the EGFR-TKI therapy, oral gefitinib. The correlations among serum EGFR gene mutations in exons 18-21, serum tumor markers such as carcinoembryonic antigen (CEA), carbohydrate antigen 24-2 (CA24-2), carbohydrate antigen 125, carbohydrate antigen 15-3 as well as carbohydrate antigen 19-9 (CA19-9) levels, and EGFR-TKI efficacy were determined. RESULTS: There was a high consistency of EGFR gene mutation rate between serum and tissue samples. The serum EGFR gene mutation rate in female patients or non-smokers was significantly higher than that in male patients or smokers, respectively. Serum CA19-9, CA24-2, and CEA levels were significantly correlated with serum EGFR mutation. After receiving gefitinib, the progression-free survivals (PFSs) of patients with high serum CEA level, high serum CA19-9 level, or serum EGFR gene mutation were significantly higher than those of normal patients, respectively. The PFSs were significantly prolonged in patients with EGFR gene mutation and high serum CEA level or patients with EGFR gene mutation and high serum CA19-9 level compared with those in patients with one abnormal biomarker and normal patients. CONCLUSION: Combined detection of EGFR gene mutations as well as CA19-9 and CEA levels in peripheral blood can predict the efficacy of EGFR-TKI in the treatment of patients with lung adenocarcinoma.

Assuntos

Adenocarcinoma de Pulmão/patologia , Biomarcadores Tumorais/sangue , Biomarcadores Tumorais/genética , Gefitinibe/uso terapêutico , Neoplasias Pulmonares/patologia , Mutação , Adenocarcinoma/sangue , Adenocarcinoma/tratamento farmacológico , Adenocarcinoma/genética , Adenocarcinoma/patologia , Adenocarcinoma de Pulmão/sangue , Adenocarcinoma de Pulmão/tratamento farmacológico , Adenocarcinoma de Pulmão/genética , Adulto , Idoso , Receptores ErbB/sangue , Receptores ErbB/genética , Feminino , Seguimentos , Humanos , Neoplasias Pulmonares/sangue , Neoplasias Pulmonares/tratamento farmacológico , Neoplasias Pulmonares/genética , Masculino , Pessoa de Meia-Idade , Prognóstico , Inibidores de Proteínas Quinases/uso terapêutico , Taxa de Sobrevida

RESUMO

Isoflurane can induce widespread cytotoxicity. We hypothesized that isoflurane induces apoptosis partly by causing excessive calcium release from the endoplasmic reticulum (ER) via direct activation of inositol 1,4,5-trisphosphate receptors (IP3R). Rat pheochromocytoma cells cultured for seven days with nerve growth factor were divided into four groups: control group (C), IP3R antagonist group (X), isoflurane group (I) and isoflurane + IP3R antagonist group (I+X). Groups I and I+X were treated with 1 MAC isoflurane for 12 h. Groups X and I+X were pretreated with IP3R antagonist. Annexin V/PI apoptosis and TUNEL assays were performed to evaluate cell apoptosis. TEM was used to observe changes in cell ultrastructure. Changes in calcium concentration ([Ca(2+)]i) in the cytoplasm were measured by flow cytometry. RT-PCR was performed to evaluate IP3R mRNA expression. TEM showed that isoflurane treatment altered cell ultrastructure. Compared to group C, cell apoptosis rate and [Ca(2+)]i increased in groups I and I+X (P < 0.05). Compared to group C, IP3R mRNA expression was lower in group X and higher in group I (P < 0.05). Compared to group X, cell apoptosis rate, [Ca(2+)]i and IP3R mRNA expression increased in groups I and I+X (P < 0.05). Compared to group I, cell apoptosis rate, [Ca(2+)]i and IP3R mRNA expression decreased in group I+X (P < 0.05). These results suggest that exposure to 1 MAC isoflurane for 12 h causes excessive calcium release partly by direct activation of IP3R on the ER membrane and triggers cell apoptosis.

Assuntos

Anestésicos Inalatórios/toxicidade , Cálcio/metabolismo , Receptores de Inositol 1,4,5-Trifosfato/metabolismo , Isoflurano/toxicidade , RNA Mensageiro/metabolismo , Animais , Anexina A5/metabolismo , Apoptose/efeitos dos fármacos , Retículo Endoplasmático/efeitos dos fármacos , Retículo Endoplasmático/metabolismo , Expressão Gênica , Marcação In Situ das Extremidades Cortadas , Receptores de Inositol 1,4,5-Trifosfato/agonistas , Receptores de Inositol 1,4,5-Trifosfato/antagonistas & inibidores , Receptores de Inositol 1,4,5-Trifosfato/genética , Transporte de Íons , Compostos Macrocíclicos/farmacologia , Fator de Crescimento Neural/farmacologia , Oxazóis/farmacologia , Células PC12 , RNA Mensageiro/agonistas , RNA Mensageiro/antagonistas & inibidores , RNA Mensageiro/genética , Ratos

RESUMO

BACKGROUNDS: As for intrahepatic cholangiocarcinoma, the most frequent site of failure after curative intent resection is the liver. We identified the risk factors for locoregional recurrence after curative intent resection for intrahepatic cholangiocarcinoma. METHODS: Medical records of 115 patients treated with surgical resection alone for intrahepatic cholangiocarcinoma from November 2000 to December 2010 were retrospectively reviewed. Locoregional failure was defined as recurrence within 20 mm from resection margin or regional lymph node. Overall survival and locoregional recurrence rates were analyzed using Kaplan-Meier methods, and the prognostic factors were analyzed using Cox proportional hazards model. RESULTS: Median follow-up duration of surviving patients was 61 months (range 8-139). Sixty-six patients had recurrence, and 45 of 66 patients (68 %) had locoregional recurrence. The 5-year overall survival and locoregional control rates were 49.1 and 51.6 %, respectively. ≥ T2b disease and R1 resection were associated with locoregional recurrence in multivariate analysis. Patients were divided into two groups whether these risk factors exist or not. The 5-year locoregional control rates of low (no risk factor n = 64) and high (1 or 2 risk factors n = 51) risk groups were 62.5 and 34.7 %, respectively (P = 0.001). CONCLUSIONS: After curative intent resection, locoregional control and survival of patients with intrahepatic cholangiocarcinoma were far from satisfactory. Further studies are needed to evaluate the potential benefit of adjuvant locoregional treatment such as radiotherapy for patients with high-risk factors (≥ T2b disease or R1 resection).

Assuntos

Neoplasias dos Ductos Biliares/cirurgia , Ductos Biliares Intra-Hepáticos/cirurgia , Colangiocarcinoma/cirurgia , Hepatectomia , Recidiva Local de Neoplasia/epidemiologia , Adulto , Idoso , Idoso de 80 Anos ou mais , Neoplasias dos Ductos Biliares/patologia , Ductos Biliares Intra-Hepáticos/patologia , Colangiocarcinoma/patologia , Feminino , Humanos , Estimativa de Kaplan-Meier , Masculino , Pessoa de Meia-Idade , Análise Multivariada , Estadiamento de Neoplasias , Modelos de Riscos Proporcionais , Radioterapia Adjuvante , Estudos Retrospectivos , Fatores de Risco , Taxa de Sobrevida , Resultado do Tratamento

RESUMO

This study investigated the Asian pear transcriptome using the RNA-Seq normalized fruit cDNA library to create a transcriptomic resource for unigene and marker discovery. Following the removal of lowquality reads, 127,085,054 trimmed reads were assembled de novo to yield 37,649 non-redundant unigenes with an average length of 599 bp. Alternative splicing events were detected in 4121 contigs. A total of 30,560 single nucleotide polymorphisms (SNPs) and 7443 simple sequence repeat (SSR) makers were obtained. Approximately 21,449 (56.9%) unigenes were categorized into three gene ontology groups; 3682 (9.8%) were classified into 25 cluster of orthologous groups; and 10,451 (27.8%) were assigned to six Kyoto Encyclopedia of Genes and Genomes pathways. Differentially expressed genes were investigated using the reads per kilobase of the exon model per million reads methodology. A total of 546 unigenes showed significant differences in expression levels at different fruit developmental stages. Gene ontology categories associated with various aspects, including carbohydrate metabolic processes, transmembrane transport, and signal transduction, were enriched with genes with divergent expressions. These Pyrus pyrifolia transcriptome data provide a rich resource for the discovery and identification of new genes. Furthermore, the numerous putative SSRs and SNPs detected in this study will be important resources for the future development of a linkage map or of marker-assisted breeding programs for the Asian pear.

Assuntos

Perfilação da Expressão Gênica , Marcadores Genéticos , Pyrus/genética , Transcriptoma , Análise por Conglomerados , Biologia Computacional/métodos , Bases de Dados Genéticas , Frutas/genética , Regulação da Expressão Gênica de Plantas , Ontologia Genética , Sequenciamento de Nucleotídeos em Larga Escala , Repetições de Microssatélites , Anotação de Sequência Molecular , Polimorfismo de Nucleotídeo Único

RESUMO

The aim of this study was to compare the effects and indications of minimally invasive plate osteosynthesis (MIPO) and limited open reduction (LOR) for managing distal tibial shaft fractures. A total of 79 cases of distal tibial shaft fractures were treated surgically in our trauma center. The 79 fracture cases were classified into type A, B, and C (C1) according to the Arbeitsgemeinschaft für Osteosynthesefragen (AO) classification, with 28, 32, and 19 cases, respectively. Among the 79 fracture cases, 52 were closed fractures and 27 were open fractures (GUSTILO, I-II). After adequate preparation, 48 cases were treated with LOR and 31 cases were treated with MIPO. All cases were followed up for 12 to 18 months, with an average of 16.4 months. During the follow-up period, 76 fracture cases were healed in the first stage, whereas the 3 cases that developed non-union were treated by changing the fixation device and autografting. For types A, B, and some of C simple fractures (C1), LOR accelerated the fracture healing and lowered the non-union rate. One case suffered from regional soft tissue infection, which was controlled by wound dressing and intravenous antibiotics. Another case that developed local skin necrosis underwent local flap transplant. LOR promoted bone healing and lowered the non-union rate of several simple-distal tibial shaft fractures. Thereafter, the incidence of soft tissue complication was not significantly increased. However, for complex and comminuted fractures, MIPO was the preferred method for correcting bone alignment and protecting soft tissue, leading to functional recovery.

Assuntos

Fixação Interna de Fraturas/métodos , Consolidação da Fratura/fisiologia , Tíbia/cirurgia , Fraturas da Tíbia/cirurgia , Adolescente , Adulto , Idoso , Placas Ósseas , Feminino , Seguimentos , Fixação Interna de Fraturas/instrumentação , Humanos , Masculino , Pessoa de Meia-Idade , Recuperação de Função Fisiológica , Tíbia/lesões , Fraturas da Tíbia/reabilitação

RESUMO

This study aimed to investigate the inhibition of vascular endothelial growth factor (VEGF) by small hairpin RNA (shRNA) interference combined with radiotherapy on the growth of cervical cancer SiHa cell xenografts in nude mice. The effective pVEGF-shRNA plasmid was screened by reverse transcription-polymerase chain reaction (RT-PCR), and the cell apoptosis rate was estimated by flow cytometry. A nude mouse cervical xenograft model was established and all models were divided into four groups: blank control, VEGF shRNA, radiotherapy, and combined treatment. We calculated the tumor growth curve and the inhibitory rate. The histopathological changes of the microvascular density and VEGF protein expression were observed by immunohistochemistry. The expressions of VEGF and hypoxia inducible factor-1α (HIF-1α) proteins in the tumor tissue were analyzed via Western blot. VEGF shRNA interference inhibited the expression of radiation-induced VEGF (P < 0.05), induced apoptosis (P < 0.05), downregulated the HIF-1α protein, and reduced angiogenesis. Compared with the other three groups, the combined treatment group showed the most significant effects (P < 0.01). VEGF shRNA interference combined with radiotherapy promotes the radiosensitivity of tumors via improvement of the hypoxic microenvironment.

Assuntos

RNA Interferente Pequeno/genética , Neoplasias do Colo do Útero/genética , Neoplasias do Colo do Útero/terapia , Fator A de Crescimento do Endotélio Vascular/antagonistas & inibidores , Animais , Apoptose , Terapia Combinada , Progressão da Doença , Feminino , Raios gama , Expressão Gênica , Terapia Genética , Humanos , Subunidade alfa do Fator 1 Induzível por Hipóxia/genética , Subunidade alfa do Fator 1 Induzível por Hipóxia/metabolismo , Camundongos , Camundongos Nus , Transplante de Neoplasias , Neovascularização Patológica , RNA Interferente Pequeno/metabolismo , Transplante Heterólogo , Carga Tumoral , Neoplasias do Colo do Útero/irrigação sanguínea , Neoplasias do Colo do Útero/patologia , Fator A de Crescimento do Endotélio Vascular/genética , Fator A de Crescimento do Endotélio Vascular/metabolismo

RESUMO

The genomic expression profile of the super-hybrid rice Liangyoupeijiu female parent Pei'ai 64S in different tissues at different developmental stages under low temperature, drought, and high temperature stresses were detected using an Affymetrix GeneChip Rice Genome Array to screen upregulated and downregulated genes. In this study, we screened the drought-resistant gene OsRCI2-5, after which a constitutive OsRCI2-5 construct was created and transferred into Nipponbare. After polyethylene glycol-6000 and drought treatment, we found that the OsRCI2-5 gene improved the drought resistance of Nipponbare. Gene expression profiling showed that the OsRCI2-5 gene was expressed in the rice leaves, stems, and flower organs. Subcellular localization revealed that the gene was located in the membranes, and hence, we can deduce that a membrane signal peptide was responsible for signal transduction.

Assuntos

Regulação da Expressão Gênica de Plantas , Oryza/genética , Transdução de Sinais/genética , Secas , Genoma de Planta/genética , Folhas de Planta/metabolismo , Estresse Fisiológico/genética , Temperatura

RESUMO

The activity-regulated cytoskeletal associated protein (Arc/Arg3.1) has been implicated in experience-dependent synaptic plasticity and memory formation. However, information regarding its coding gene in buffalo remains scarce. In this study, the full-length of Arc/Arg3.1 was isolated and characterized (accession No. JX491649) and genetic variations of six river buffalo and eight swamp buffalo were investigated. A tissue expression profile was obtained using semi-quantitative reverse transcription-polymerase chain reaction. The coding region sequence of Arc/Arg3.1 contained 1191 nucleotides encoding a putative protein of 396 amino acids with a theoretical isoelectric point (pI) and molecular weight (Mw) of 5.4 and 45.2 kDa, respectively. Four polymorphisms (c.63T>C, c.228T>C, c.558G>A, and c.625G>C) were found in buffalo; however, only substitution c.625G>C was non-synonymous, leading to an amino acid change from Val to Leu at the 209th position of the Arc/Arg3.1 protein sequence. Bioinformatics analysis revealed that this substitution had no significant effect on Arc/Arg3.1 function (subPSEC = -1.4039, Pdeleterious = 0.1685), which indicated that Arc/Arg3.1 was highly conserved and functionally important in buffalo. Phylogenetic analysis revealed that the gene is closely related to that of Bos taurus and Bos grunniens. The gene was moderately expressed in the hypophysis and the placenta; it was weakly expressed in the kidney, milk, mammary gland, cerebrum, lung, heart, rumen, fat, and uterus; and it was almost silent in the muscle, liver, and skin. These findings will provide further insights into the structure and function of the immediate-early gene in buffalo.

Assuntos

Búfalos/genética , Proteínas do Citoesqueleto/genética , Perfilação da Expressão Gênica , Genes Precoces , Proteínas do Tecido Nervoso/genética , Polimorfismo Genético , Sequência de Aminoácidos , Animais , Sequência de Bases , Búfalos/classificação , Bovinos , Proteínas do Citoesqueleto/química , Evolução Molecular , MicroRNAs/genética , Dados de Sequência Molecular , Proteínas do Tecido Nervoso/química , Especificidade de Órgãos/genética , Filogenia , Polimorfismo de Nucleotídeo Único , Interferência de RNA , RNA Mensageiro/genética , Alinhamento de Sequência , Análise de Sequência de DNA

RESUMO

OBJECTIVES: To investigate the relationship of the MTHFR polymorphisms (C677T) and the risk of CRC by meta-analysis. METHODS: Relevant literatures concerning the association between the MTHFR C677T polymorphism and the risk of CRC were searched using the electronic database PubMed, EMBASE, Cochrane and China National Knowledge Infrastructure (CNKI). Odds ratio (ORs) and 95 % confidence intervals (CIs) were determined to assess the gene-disease association using fixed or random effect models, according to the heterogeneity among included studies. RESULTS: The study shows that the MTHFR 677 TT homozygous genotype significantly decreases the risk of CRC in Asians (TT vs. CC: OR = 0.82, 95 % CI 0.73-0.92; TT vs. CT: OR = 0.84, 95 % CI 0.75-0.94; TT vs. CC+TT: OR = 0.83, 95 % CI 0.75-0.93). CONCLUSION: This meta-analysis indicated that the MTHFR 677 TT homozygous genotype decreased the risk of CRC in Asians, while the MTHFR 677 CT heterozygous genotype did not contribute to CRC susceptibility.

Assuntos

Povo Asiático/genética , Neoplasias Colorretais/genética , Predisposição Genética para Doença/genética , Metilenotetra-Hidrofolato Redutase (NADPH2)/genética , Polimorfismo de Nucleotídeo Único/genética , Humanos , Fatores de Risco

RESUMO

Several 1-acylglycerol-3-phosphate-O-acyltransferases (AGPATs) can acylate lysophosphatidic acid to produce phosphatidic acid. Of the eight AGPAT isoforms, AGPAT6 is a crucial enzyme for glycerolipids and triacylglycerol biosynthesis in some mammalian tissues. We amplified and identified the complete coding sequence (CDS) of the water buffalo AGPAT6 gene by using the reverse transcription-polymerase chain reaction, based on the conversed sequence information of the cattle or expressed sequence tags of other Bovidae species. This novel gene was deposited in the NCBI database (accession No. JX518941). Sequence analysis revealed that the CDS of this AGPAT6 encodes a 456-amino acid enzyme (molecular mass = 52 kDa; pI = 9.34). Water buffalo AGPAT6 contains three hydrophobic transmembrane regions and a signal 37-amino acid peptide, localized in the cytoplasm. The deduced amino acid sequences share 99, 98, 98, 97, 98, 98, 97 and 95% identity with their homologous sequences from cattle, horse, human, mouse, orangutan, pig, rat, and chicken, respectively. The phylogenetic tree analysis based on the AGPAT6 CDS showed that water buffalo has a closer genetic relationship with cattle than with other species. Tissue expression profile analysis shows that this gene is highly expressed in the mammary gland, moderately expressed in the heart, muscle, liver, and brain; weakly expressed in the pituitary gland, spleen, and lung; and almost silently expressed in the small intestine, skin, kidney, and adipose tissues. Four predicted microRNA target sites are found in the water buffalo AGPAT6 CDS. These results will establish a foundation for further insights into this novel water buffalo gene.

Assuntos

Búfalos/genética , Glicerol-3-Fosfato O-Aciltransferase/genética , Sequência de Aminoácidos , Animais , Sequência de Bases , Búfalos/metabolismo , Clonagem Molecular , Sequência Conservada , Feminino , Expressão Gênica , Perfilação da Expressão Gênica , Glicerol-3-Fosfato O-Aciltransferase/metabolismo , Interações Hidrofóbicas e Hidrofílicas , Glândulas Mamárias Animais/enzimologia , Dados de Sequência Molecular , Especificidade de Órgãos , Filogenia , Análise de Sequência de DNA

RESUMO

The effect of temperature and pH on the zeta potential of alpha-Al2O3 and adsorption of fluoride ions at the alpha-Al2O3/aqueous solution interface has been investigated through electrophoretic mobility measurements and adsorption studies, to delineate mechanisms involved in the removal of fluoride ions from water using alumina as adsorbent. When the temperature increases from 10 to 40 degrees C, the pH of the point of zero charge (pH(pzc)) shifts to smaller values, indicating proton desorption from the alumina surface. The pH(pzc) increases linearly with 1/T, which allowed estimation of the standard enthalpy change for the surface-deprotonation process. Fluoride ion adsorption follows a Langmuir-type adsorption isotherm and is affected by the electric charge at the alpha-Al2O3/aqueous solution interface and the surface density of hydroxyl groups. Such adsorption occurs through an exchange between fluoride ions and surface-hydroxyl groups and it depends on temperature, pH, and initial fluoride ion concentration. At 25 and 40 degrees C, maximum fluoride adsorption density takes place between pH 5 and 6. Increasing the temperature from 25 to 40 degrees C lowers the adsorption density of fluoride.

RESUMO

Arsenic removal from high-arsenic water in a mine drainage system has been studied through an enhanced coagulation process with ferric ions and coarse calcite (38-74 microm) in this work. The experimental results have shown that arsenic-borne coagulates produced by coagulation with ferric ions alone were very fine, so micro-filtration (membrane as filter medium) was needed to remove the coagulates from water. In the presence of coarse calcite, small arsenic-borne coagulates coated on coarse calcite surfaces, leading the settling rate of the coagulates to considerably increase. The enhanced coagulation followed by conventional filtration (filter paper as filter medium) achieved a very high arsenic removal (over 99%) from high-arsenic water (5mg/l arsenic concentration), producing a cleaned water with the residual arsenic concentration of 13 microg/l. It has been found that the mechanism by which coarse calcite enhanced the coagulation of high-arsenic water might be due to attractive electrical double layer interaction between small arsenic-borne coagulates and calcite particles, which leads to non-existence of a potential energy barrier between the heterogeneous particles.

Assuntos

Arsênio/isolamento & purificação , Poluentes da Água/isolamento & purificação , Purificação da Água/métodos , Arsênio/química , Carbonato de Cálcio/química , Filtração , Ferro/química , Mineração

RESUMO

The northwestern Gulf of Mexico shelf has been nicknamed "The Dead Zone" due to annual summertime (May-September) bottom-water hypoxia (dissolved oxygen < or =2 mg L(-1)) that can be extensive (>20 000 km2) and last for several months. Hypoxia has been attributed to eutrophication caused by increasing nitrogen loads, although directly linking hypoxia to nitrogen is difficult. While the areal extent of hypoxia has been shown to increase with Mississippi River flow, it is unclear whether this increase results from enhanced vertical water-column stratification or from eutrophication caused by river-borne nutrients. Disentangling the relative contributions of eutrophication versus stratification has important management consequences. Our analysis indicates that the top:bottom salinity difference is an important predictor of hypoxia, exhibiting a threshold, where the probability of hypoxia increases rapidly, at approximately 4.1 ppt. Using a Bayesian change-point model, we show that this stratification threshold decreased from 1982 to 2002, indicating the degree of stratification needed to induce hypoxia has gone down. Although this declining threshold does not link hypoxia and nitrogen, it does implicate a long-term factor transcending yearly flow-induced stratification differences. Concurrently, we show that surface temperature increased, while surface dissolved oxygen decreased, suggesting that factors in addition to nitrogen may be influencing the incidence of hypoxia in the bottom water.

Assuntos

Modelos Teóricos , Oxigênio/análise , Água do Mar/química , Oceano Atlântico , Teorema de Bayes , Monitoramento Ambiental , Estações do Ano , Movimentos da Água

RESUMO

The most important factor in the electrodialysis (ED) process is the permselectivity of the ion exchange membranes, which permit not only the separation of cations and anions in a solution, but also the separation of ions with the same sign but different valences. In this work, the mechanism of the permselectivity has been studied through the measurement of the potentials at different planes of the membrane. The experimental results have shown that there was a secondary potential inside ion exchange membranes in an electrodialysis process. At the membrane side touched with dilute solution, this secondary potential enhanced the external electrical field, and thus speeded up the passage of the corresponding ions in the dilute solution through the membranes; at the membrane side touched with concentrated solution, the secondary potential was contrary to the external electrical field and thus counteracted it, which could be very helpful by preventing the ions in the concentrated solution from entering the membranes. Obviously, the existence of the secondary potential might play an important role in the permselectivity of ion exchange membranes in ED processes.

RESUMO

The adsorption of ethyl and amyl xanthate ions on galena and sphalerite fines has been studied using electrophoretic light-scattering (ELS) measurements. It was performed on galena and sphalerite (<2&mgr;m) in aqueous solution at different potassium ethyl xanthate (PEX) and potassium amyl xanthate (PAX) concentrations. It has been observed that the presence of PEX or PAX caused the isoelectric points (IEP) of galena and sphalerite fines to shift and the electrophoretic mobility to reverse in sign, indicating that the xanthate ions chemisorbed on galena and sphalerite surfaces. This adsorption markedly broadened the electrophoretic mobility distribution of the mineral fines, suggesting that the populations of the particles have quite different adsorption densities of xanthate ions, and therefore the particle hydrophobicity was different. This phenomenon might be attributable to the effect of the hemimicelle adsorption of the xanthate ions on the minerals, the nonuniform distribution of active sites and their degree of activity, the effect of particle size and shape, etc. The nonuniform adsorption has been found to increase with increasing PEX or PAX concentration, reaching a maximum at a medium concentration followed by a decline. Also, experimental results have demonstrated that the nonuniform adsorption of the xanthate ions is much stronger on sphalerite than on galena, which may explain why sphalerite has a worse flotation response than galena when alkyl xanthates are used as collectors in flotation systems. Copyright 2001 Academic Press.

RESUMO

Computations based on the extended DLVO theory are carried out on the potential energies of interactions between air bubbles and talc particles covered by nonpolar oil. It is shown that the major role of nonpolar oil in this system is to greatly increase the depth of the primary energy valley, giving rise to a much stronger bubble-particle aggregate that can support greater aggregate-rupture force fields from turbulent flows. Also, due to nonpolar oil involvement, the energy barrier between bubbles and mineral particles sharply collapses down and further separates, indicative of a greater probability of attachment of mineral particles to air bubbles. A linear relationship is found between the primary energy valley and the contact angles of oil or bubbles, and thus a simple and approximate formula is presented to evaluate the depth of the primary energy valley. In addition, it is found that the primary energy valley and the energy barrier are directly proportional to the effective particle radius, but the barrier location is independent of the effective particle radius. Copyright 1999 Academic Press.

Assuntos

Insuficiência Cardíaca/tratamento farmacológico , Coração/efeitos dos fármacos , Vasodilatadores/uso terapêutico , Débito Cardíaco/efeitos dos fármacos , Insuficiência Cardíaca/fisiopatologia , Hemodinâmica/efeitos dos fármacos , Humanos

RESUMO

La respuesta hemodinamica obtenida de la administracion de agentes vasodilatadores a pacientes con fallo congestivo cardiaco va a depender de su efecto relativo en las arteriolas y venas. Aquellos vasodilatadores que predominantemente causan dilatacion arteriolar, aumentan el debito cardiaco sin cambios significativos en la presion de cuna pulmonar. Aquellos que son vasodilatadores venosos disminuyen la presion de cuna pulmonar sin causar cambios significativos en el debito cardiaco. Los efectos hemodinamicos en pacientes con infarto agudo del miocardio y decompensacion cardiaca van a depender del valor o nivel inicial de la presion telediastolica del ventriculo izquierdo. El rastreo hemodinamico es indispensable en situaciones agudas, para determinar los efectos hemodinamicos de este tipo de terapia

Assuntos

Insuficiência Cardíaca , Vasodilatadores , Hemodinâmica