Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 19 de 19
Filtrar
1.
Earth Space Sci ; 8(11): e2021EA001941, 2021 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-34820483

RESUMO

Following extreme drought during the 2019-2020 bushfire summer, the eastern part of Australia suffered from a week-long intense rainfall and extensive flooding in March 2021. Understanding how much water storage changes in response to these climate extremes is critical for developing timely water management strategies. To quantify prompt water storage changes associated with the 2021 March flooding, we processed the low-latency (1-3 days), high-precision intersatellite laser ranging measurements from GRACE Follow-On spacecraft and determined instantaneous gravity changes along spacecraft orbital passes. Such new data processing detected an abrupt surge of water storage approaching 60-70 trillion liters (km3 of water) over a week in the region, which concurrently caused land subsidence of ∼5 mm measured by a network of ground GPS stations. This was the highest speed of ground water recharge ever recorded in the region over the last two decades. Compared to the condition in February 2020, the amount of recharged water was similar but the recharge speed was much faster in March 2021. While these two events together replenished the region up to ∼80% of the maximum storage over the last two decades, the wet antecedent condition of soils in 2021 was distinctly different from the dry conditions in 2020 and led to generating extensive runoff and flooding in 2021.

2.
Proc Natl Acad Sci U S A ; 118(47)2021 11 23.
Artigo em Inglês | MEDLINE | ID: mdl-34785594

RESUMO

The overall size and timing of monsoon floods in Bangladesh are challenging to measure. The inundated area is extensive in low-lying Bangladesh, and observations of water storage are key to understanding floods. Laser-ranging instruments on Gravity Recovery and Climate Experiment (GRACE) Follow-On spacecraft detected the peak water storage anomaly of 75 gigatons across Bangladesh in late July 2020. This is in addition to, and three times larger than, the maximum storage anomaly in soil layers during the same period. A flood propagation model suggested that the water mass, as shown in satellite observations, is largely influenced by slow floodplain and groundwater flow processes. Independent global positioning system measurements confirmed the timing and total volume of the flood water estimates. According to land surface models, the soils were saturated a month earlier than the timing of the peak floodplain storage observed by GRACE Follow-On. The cyclone Amphan replenished soils with rainfall just before the monsoon rains started, and consequently, excessive runoff was produced and led to the early onset of the 2020 flooding. This study demonstrated how antecedent soil moisture conditions can influence the magnitude and duration of flooding. Continuous monitoring of storage change from GRACE Follow-On gravity measurements provides important information complementary to river gauges and well levels for enhancing hydrologic flood forecasting models and assisting surface water management.

3.
Environ Entomol ; 50(4): 821-831, 2021 08 12.
Artigo em Inglês | MEDLINE | ID: mdl-33899083

RESUMO

Pollination provided by bees is a critical ecosystem service for agricultural production. However, bee populations are at risk from stressors such as habitat loss, pesticides, and disease. On-farm wildflower plantings is one mitigation strategy to provide habitat and resources for bees. In many instances, government programs can subsidize the installation of these plantings for private landowners. Semi-natural habitat (SNH) in the landscape is also important for bee conservation and may alter the effectiveness of wildflower plantings. In this study, we tested the effectiveness of wildflower plantings and interactions with SNH in the landscape for promoting bee abundance and richness. Bee surveys were conducted over 2 yr at 22 sites in eastern Virginia and Maryland. Wildflower plantings, averaging 0.22 ha in size, were installed and maintained by cooperators at 10 of the sites. In total, 5,122 bees were identified from 85 species. Wildflower plantings did not alter bee communities independently, but bee abundance was greater on farms with plantings and 20-30% SNH in the landscape. Bee abundance and richness had nonlinear responses to increasing SNH in the landscape. The positive effects for richness and abundance peaked when SNH was approximately 40% of the landscape. Similar to predictions of the intermediate-landscape complexity hypothesis, increases in bee abundance at wildflower sites were only detected in simplified landscapes. Results indicate that small wildflower plantings in the Mid-Atlantic U.S. only provided conservation benefits to bee communities under specific circumstances on the scale studied, and that conserving SNH across the landscape may be a more important strategy.


Assuntos
Ecossistema , Polinização , Agricultura , Animais , Abelhas , Fazendas , Maryland
4.
Insects ; 11(9)2020 Sep 09.
Artigo em Inglês | MEDLINE | ID: mdl-32917048

RESUMO

Planting wildflowers is a commonly suggested measure to conserve pollinators. While beneficial for pollinators, plots of wildflowers may be inadvertently performing an ecosystem disservice by providing a suitable habitat for arthropod disease vectors like ticks. The lone star tick, Amblyomma americanum (L.), is a medically important tick species that might be able to utilize wildflower plantings as a suitable habitat. In this two-year study, ticks were sampled using dry ice baited traps from wildflower plots, weedy field margins, and forested areas to determine if wildflower plantings were increasing the on-farm abundance of A. americanum. Abiotic and biotic environmental variables were also measured to better understand which factors affect A. americanum abundance. We found no more A. americanum in wildflower plots than in weedy field margins. Forested areas harbored the greatest number of A. americanum sampled. The height of the vegetation in the sampled habitats was a significant factor in determining A. americanum abundance. Depending on the sampled habitat and life stage, this relationship can be positive or negative. The relationship with vegetation height may be related to the behavior of the white-tailed deer and the questing success of A. americanum. Overall, wildflower plots do not pose an increased risk of exposure to A. americanum on farms.

5.
J Insect Sci ; 19(4)2019 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-31268545

RESUMO

The 2018 student debates of the Entomological Society of America were held at the Joint Annual Meeting for the Entomological Societies of America, Canada, and British Columbia in Vancouver, BC. Three unbiased introductory speakers and six debate teams discussed and debated topics under the theme 'Entomology in the 21st Century: Tackling Insect Invasions, Promoting Advancements in Technology, and Using Effective Science Communication'. This year's debate topics included: 1) What is the most harmful invasive insect species in the world? 2) How can scientists diffuse the stigma or scare factor surrounding issues that become controversial such as genetically modified organisms, agricultural biotechnological developments, or pesticide chemicals? 3) What new/emerging technologies have the potential to revolutionize entomology (other than Clustered Regularly Interspaced Short Palindromic Repeats)? Introductory speakers and debate teams spent approximately 9 mo preparing their statements and arguments and had the opportunity to share this at the Joint Annual Meeting with an engaged audience.


Assuntos
Entomologia/tendências , Insetos , Animais , Biotecnologia , Espécies Introduzidas
6.
Sci Rep ; 7(1): 16159, 2017 11 23.
Artigo em Inglês | MEDLINE | ID: mdl-29170516

RESUMO

The new oncologic paradigm of precision medicine is focused on identifying metabolic, proteomic, transcriptomic and genomic variabilities in tumors that can be exploited to tailor treatments and improve patient outcomes. Metabolic changes are a hallmark of cancer, and inhibition of metabolic pathways is now a major strategy in medicinal chemistry for targeting cancers. However, non-invasive biomarkers to categorize metabolic subtypes are in short supply. The purpose of this study was to characterize the intracellular and extracellular metabolic profiles of four prostate cancer cell lines with varying degrees of aggressiveness. We observed metabolic differences between the aggressive prostate cancer cell line PC3 and the even more aggressive, metastatic subline PC3M assessed by hyperpolarized in vivo pyruvate studies, nuclear magnetic resonance spectroscopy, and carbon-13 feeding studies. On further examination of the differences between these two cell lines, we found increased glutamine utilization in the metastatic PC3M subline that led directly to sensitivity to glutaminase inhibitor CB-839. Our study supports the theory that metastatic progression increases glutamine utilization and the inhibition of glutaminolysis could have clinical implications.


Assuntos
Glutamina/metabolismo , Neoplasias da Próstata/metabolismo , Benzenoacetamidas/farmacologia , Linhagem Celular Tumoral , Glutaminase/antagonistas & inibidores , Glutaminase/metabolismo , Humanos , Masculino , Ressonância Magnética Nuclear Biomolecular , Tiadiazóis/farmacologia
7.
BMC Cancer ; 16(1): 824, 2016 10 26.
Artigo em Inglês | MEDLINE | ID: mdl-27784287

RESUMO

BACKGROUND: Autophagy is a bulk catabolic process that modulates tumorigenesis, therapeutic resistance, and dormancy. The tumor suppressor ARHI (DIRAS3) is a potent inducer of autophagy and its expression results in necroptotic cell death in vitro and tumor dormancy in vivo. ARHI is down-regulated or lost in over 60 % of primary ovarian tumors yet is dramatically up-regulated in metastatic disease. The metabolic changes that occur during ARHI induction and their role in modulating death and dormancy are unknown. METHODS: We employed Nuclear Magnetic Resonance (NMR)-based metabolomic strategies to characterize changes in key metabolic pathways in both cell culture and xenograft models of ARHI expression and autophagy. These pathways were further interrogated by cell-based immunofluorescence imaging, tracer uptake studies, targeted metabolic inhibition, and in vivo PET/CT imaging. RESULTS: Induction of ARHI in cell culture models resulted in an autophagy-dependent increase in lactate production along with increased glucose uptake and enhanced sensitivity to glycolytic inhibitors. Increased uptake of glutamine was also dependent on autophagy and dramatically sensitized cultured ARHI-expressing ovarian cancer cell lines to glutaminase inhibition. Induction of ARHI resulted in a reduction in mitochondrial respiration, decreased mitochondrial membrane potential, and decreased Tom20 staining suggesting an ARHI-dependent loss of mitochondrial function. ARHI induction in mouse xenograft models resulted in an increase in free amino acids, a transient increase in [18F]-FDG uptake, and significantly altered choline metabolism. CONCLUSIONS: ARHI expression has previously been shown to trigger autophagy-associated necroptosis in cell culture. In this study, we have demonstrated that ARHI expression results in decreased cellular ATP/ADP, increased oxidative stress, and decreased mitochondrial function. While this bioenergetic shock is consistent with programmed necrosis, our data indicates that the accompanying up-regulation of glycolysis and glutaminolysis is autophagy-dependent and serves to support cell viability rather than facilitate necroptotic cell death. While the mechanistic basis for metabolic up-regulation following ARHI induction is unknown, our preliminary data suggest that decreased mitochondrial function and increased metabolic demand may play a role. These alterations in fundamental metabolic pathways during autophagy-associated necroptosis may provide the basis for new therapeutic strategies for the treatment of dormant ovarian tumors.


Assuntos
Autofagia , Redes e Vias Metabólicas , Neoplasias Ovarianas/metabolismo , Neoplasias Ovarianas/patologia , Proteínas rho de Ligação ao GTP/metabolismo , Animais , Linhagem Celular Tumoral , Modelos Animais de Doenças , Feminino , Glucose/metabolismo , Glutamatos/metabolismo , Glutamina/metabolismo , Glicólise , Xenoenxertos , Humanos , Potencial da Membrana Mitocondrial , Camundongos , Mitocôndrias/metabolismo , Neoplasias Ovarianas/diagnóstico por imagem , Estresse Oxidativo , Tomografia por Emissão de Pósitrons combinada à Tomografia Computadorizada
8.
J Mol Imaging Dyn ; 6(1)2016 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-27547490

RESUMO

PURPOSE: The energy-yielding mitochondrial Krebs cycle has been shown in many cancers and other diseases to be inhibited or mutated. In most cells, the Krebs cycle with oxidative phosphorylation generates approximately 90% of the adenosine triphosphate in the cell. We designed and hyperpolarized carbon-13 labeled succinate (SUC) and its derivative diethyl succinate (DES) to interrogate the Krebs cycle in real-time in cancer animal models. PROCEDURES: Using Parahydrogen Induced Polarization (PHIP), we generated hyperpolarized SUC and DES by hydrogenating their respective fumarate precursors. DES and SUC metabolism was studied in five cancer allograft animal models: breast (4T1), Renal Cell Carcinoma (RENCA), colon (CT26), lymphoma NSO, and lymphoma A20. RESULTS: The extent of hyperpolarization was 8 ± 2% for SUC and 2.1 ± 0.6% for DES. The metabolism of DES and SUC in the Krebs cycle could be followed in animals 5 s after tail vein injection. The biodistribution of the compounds was observed using 13C FISP imaging. We observed significant differences in uptake and conversion of both compounds in different cell types both in vivo and in vitro. CONCLUSION: With hyperpolarized DES and SUC, we are able to meet many of the requirements for a useable in vivo metabolic imaging compound - high polarization, relatively long T1 values, low toxicity and high water solubility. However, succinate and its derivative DES are metabolized robustly by RENCA but not by the other cancer models. Our results underscore the heterogeneity of cancer cells and the role cellular uptake plays in hyperpolarized metabolic spectroscopy.

9.
J Natl Cancer Inst ; 108(6): djv426, 2016 Jan 26.
Artigo em Inglês | MEDLINE | ID: mdl-26819345

RESUMO

BACKGROUND: The clinical and biological effects of metabolic alterations in cancer are not fully understood. METHODS: In high-grade serous ovarian cancer (HGSOC) samples (n = 101), over 170 metabolites were profiled and compared with normal ovarian tissues (n = 15). To determine NAT8L gene expression across different cancer types, we analyzed the RNA expression of cancer types using RNASeqV2 data available from the open access The Cancer Genome Atlas (TCGA) website (http://www.cbioportal.org/public-portal/). Using NAT8L siRNA, molecular techniques and histological analysis, we determined cancer cell viability, proliferation, apoptosis, and tumor growth in in vitro and in vivo (n = 6-10 mice/group) settings. Data were analyzed with the Student's t test and Kaplan-Meier analysis. Statistical tests were two-sided. RESULTS: Patients with high levels of tumoral NAA and its biosynthetic enzyme, aspartate N-acetyltransferase (NAT8L), had worse overall survival than patients with low levels of NAA and NAT8L. The overall survival duration of patients with higher-than-median NAA levels (3.6 years) was lower than that of patients with lower-than-median NAA levels (5.1 years, P = .03). High NAT8L gene expression in other cancers (melanoma, renal cell, breast, colon, and uterine cancers) was associated with worse overall survival. NAT8L silencing reduced cancer cell viability (HEYA8: control siRNA 90.61% ± 2.53, NAT8L siRNA 39.43% ± 3.00, P < .001; A2780: control siRNA 90.59% ± 2.53, NAT8L siRNA 7.44% ± 1.71, P < .001) and proliferation (HEYA8: control siRNA 74.83% ± 0.92, NAT8L siRNA 55.70% ± 1.54, P < .001; A2780: control siRNA 50.17% ± 4.13, NAT8L siRNA 26.52% ± 3.70, P < .001), which was rescued by addition of NAA. In orthotopic mouse models (ovarian cancer and melanoma), NAT8L silencing reduced tumor growth statistically significantly (A2780: control siRNA 0.52 g ± 0.15, NAT8L siRNA 0.08 g ± 0.17, P < .001; HEYA8: control siRNA 0.79 g ± 0.42, NAT8L siRNA 0.24 g ± 0.18, P = .008, A375-SM: control siRNA 0.55 g ± 0.22, NAT8L siRNA 0.21 g ± 0.17 g, P = .001). NAT8L silencing downregulated the anti-apoptotic pathway, which was mediated through FOXM1. CONCLUSION: These findings indicate that the NAA pathway has a prominent role in promoting tumor growth and represents a valuable target for anticancer therapy.Altered energy metabolism is a hallmark of cancer (1). Proliferating cancer cells have much greater metabolic requirements than nonproliferating differentiated cells (2,3). Moreover, altered cancer metabolism elevates unique metabolic intermediates, which can promote cancer survival and progression (4,5). Furthermore, emerging evidence suggests that proliferating cancer cells exploit alternative metabolic pathways to meet their high demand for energy and to accumulate biomass (6-8).


Assuntos
Acetiltransferases/metabolismo , Ácido Aspártico/análogos & derivados , Biomarcadores Tumorais/metabolismo , Cistadenocarcinoma Seroso/metabolismo , Neoplasias Ovarianas/metabolismo , Ovário/metabolismo , Animais , Apoptose , Ácido Aspártico/metabolismo , Linhagem Celular Tumoral , Proliferação de Células , Sobrevivência Celular , Cromatografia Líquida de Alta Pressão , Cistadenocarcinoma Seroso/patologia , Feminino , Regulação Enzimológica da Expressão Gênica , Regulação Neoplásica da Expressão Gênica , Humanos , Estimativa de Kaplan-Meier , Camundongos , Gradação de Tumores , Neoplasias Ovarianas/patologia , Espectrometria de Massas em Tandem
10.
Bioorg Med Chem ; 22(1): 303-10, 2014 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-24315190

RESUMO

Various estrogen analogs were synthesized and tested for binding to human ERα using a fluorescence polarization displacement assay. Binding affinity and orientation were also predicted using docking calculations. Docking was able to accurately predict relative binding affinity and orientation for estradiol, but only if a tightly bound water molecule bridging Arg394/Glu353 is present. Di-hydroxyl compounds sometimes bind in two orientations, which are flipped in terms of relative positioning of their hydroxyl groups. Di-hydroxyl compounds were predicted to bind with their aliphatic hydroxyl group interacting with His524 in ERα. One nonsteroid-based dihdroxyl compound was 1000-fold specific for ERß over ERα, and was also 25-fold specific for agonist ERß versus antagonist activity. Docking predictions suggest this specificity may be due to interaction of the aliphatic hydroxyl with His475 in the agonist form of ERß, versus with Thr299 in the antagonist form. But, the presence of this aliphatic hydroxyl is not required in all compounds, since mono-hydroxyl (phenolic) compounds bind ERα with high affinity, via hydroxyl hydrogen bonding interactions with the ERα Arg394/Glu353/water triad, and van der Waals interactions with the rest of the molecule.


Assuntos
Estradiol/química , Receptor alfa de Estrogênio/química , Radical Hidroxila/síntese química , Feminino , Humanos , Radical Hidroxila/química , Relação Estrutura-Atividade
11.
Methods Mol Biol ; 987: 51-9, 2013.
Artigo em Inglês | MEDLINE | ID: mdl-23475666

RESUMO

The cytochromes P450 (CYPs) play a central role in a variety of important biological oxidations, such as steroid synthesis and the metabolism of xenobiotic compounds, including most drugs. Because CYPs are frequently assayed as drug targets or as anti-targets, tools that provide confirmation of active-site binding and information on binding orientation would be of great utility. Of greatest value are assays that are reasonably high throughput. Other heme proteins, too-such as the nitric oxide synthases (NOSs), with their importance in signaling, regulation of blood pressure, and involvement in the immune response-often display critical roles in the complex functions of many higher organisms, and also require improved assay methods. To this end, we have developed an analog of cyanide, with a (13)CH3-reporter group attached to make methyl isocyanide. We describe the synthesis and use of (13)C-methyl isocyanide as a probe of both bacterial (P450cam) and membrane-bound mammalian (CYP2B4) CYPs. The (13)C-methyl isocyanide probe can be used in a relatively high-throughput 1-D experiment to identify binders, but it can also be used to detect structural changes in the active site based on chemical shift changes, and potentially nuclear Overhauser effects between probe and inhibitor.


Assuntos
Domínio Catalítico , Hemeproteínas/química , Hemeproteínas/metabolismo , Sondas Moleculares/química , Sondas Moleculares/síntese química , Nitrilas/química , Nitrilas/síntese química , Isótopos de Carbono , Técnicas de Química Sintética , Espectroscopia de Ressonância Magnética , Modelos Moleculares , Conformação Molecular
12.
PLoS One ; 7(7): e33958, 2012.
Artigo em Inglês | MEDLINE | ID: mdl-22815674

RESUMO

In influenza, the envelope protein hemagglutinin (HA) plays a critical role in viral entry by first binding to sialic acid receptors on the cell surface and subsequently mediating fusion of the viral and target membranes. In this work, the receptor binding properties of influenza A HA from different subtypes (H1 A/California/04/09, H5 A/Vietnam/1205/04, H5 A/bar-headed goose/Qinghai/1A/05, and H9 A/Hong Kong/1073/99) have been characterized by NMR spectroscopy. Using saturation transfer difference (STD) NMR, we find that all HAs bind to the receptor analogs 2,3-sialyllactose and 2,6-sialyllactose, with subtle differences in the binding mode. Using competition STD NMR, we determine the receptor preferences for the HA subtypes. We find that H5-Qinghai and H9-Hong Kong HA bind to both receptor analogs with similar affinity. On the other hand, H1 exhibits a clear preference for 2,6-sialyllactose while H5-Vietnam exhibits a clear preference for 2,3-sialyllactose. Together, these results are interpreted within the context of differences in both the amino acid sequence and structures of HA from the different subtypes in determining receptor preference.


Assuntos
Glicoproteínas de Hemaglutininação de Vírus da Influenza/metabolismo , Vírus da Influenza A , Ácido N-Acetilneuramínico/metabolismo , Ressonância Magnética Nuclear Biomolecular , Sequência de Aminoácidos , Glicoproteínas de Hemaglutininação de Vírus da Influenza/química , Lactose/análogos & derivados , Lactose/metabolismo , Modelos Moleculares , Dados de Sequência Molecular , Ácido N-Acetilneuramínico/análogos & derivados , Ligação Proteica , Conformação Proteica , Especificidade da Espécie , Especificidade por Substrato
13.
J Virol ; 86(8): 4455-62, 2012 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-22301136

RESUMO

Influenza A virus glycoprotein hemagglutinin (HA) binds to host cell surface sialic acid (SA)-terminated sugars in glycoproteins to initiate viral entry. It is thought that avian influenza viruses preferentially bind to N-acetylneuraminic acid α3 (NeuAcα3) sugars, while human influenza viruses exhibit a preference for NeuAcα6-containing sugars. Thus, species-specific SA(s) is one of the determinants in viral host tropism. The SA binding pocket of the HA1 subunit has been extensively studied, and a number of residues important for receptor binding have been identified. In this study, we examined the potential roles of seven highly conserved HA surface-located amino acid residues in receptor binding and viral entry using an H5 subtype. Among them, mutant Y161A showed cell-type-dependent viral entry without obvious defects in HA protein expression or viral incorporation. This mutant also displayed dramatically different ability in agglutinating different animal erythrocytes. Oligosaccharide binding analysis showed that substituting alanine at Y161 of HA changed the SA binding preference from NeuAc to N-glycolylneuraminic acid (NeuGc). Rescued mutant Y161A viruses demonstrated a 5- to 10-fold growth defect, but they were robust in viral replication and plaque forming ability. Our results demonstrate that Y161 is a critical residue involved in recognition of different SA species. This residue may play a role in determining influenza virus host tropism.


Assuntos
Substituição de Aminoácidos , Glicoproteínas de Hemaglutininação de Vírus da Influenza/química , Glicoproteínas de Hemaglutininação de Vírus da Influenza/genética , Especificidade de Hospedeiro , Virus da Influenza A Subtipo H5N1/fisiologia , Ácido N-Acetilneuramínico/metabolismo , Sequência de Aminoácidos , Animais , Linhagem Celular , Cães , Testes de Hemaglutinação , Glicoproteínas de Hemaglutininação de Vírus da Influenza/metabolismo , Humanos , Virus da Influenza A Subtipo H5N1/genética , Virus da Influenza A Subtipo H5N1/crescimento & desenvolvimento , Dados de Sequência Molecular , Mutação , Ligação Proteica , Alinhamento de Sequência , Internalização do Vírus
14.
J Biomol NMR ; 43(3): 171-8, 2009 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-19199046

RESUMO

The cytochromes P450 (CYPs) play a central role in many biologically important oxidation reactions, including the metabolism of drugs and other xenobiotic compounds. Because they are often assayed as both drug targets and anti-targets, any tools that provide: (a) confirmation of active site binding and (b) structural data, would be of great utility, especially if data could be obtained in reasonably high throughput. To this end, we have developed an analog of the promiscuous heme ligand, cyanide, with a (13)CH(3)-reporter attached. This (13)C-methyl isocyanide ligand binds to bacterial (P450cam) and membrane-bound mammalian (CYP2B4) CYPs. It can be used in a rapid 1D experiment to identify binders, and provides a qualitative measure of structural changes in the active site.


Assuntos
Hidrocarboneto de Aril Hidroxilases/química , Cânfora 5-Mono-Oxigenase/química , Domínio Catalítico , Nitrilas , Ressonância Magnética Nuclear Biomolecular/métodos , Animais , Hidrocarboneto de Aril Hidroxilases/genética , Hidrocarboneto de Aril Hidroxilases/metabolismo , Proteínas de Bactérias/química , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Cânfora 5-Mono-Oxigenase/genética , Cânfora 5-Mono-Oxigenase/metabolismo , Isótopos de Carbono/química , Isótopos de Carbono/metabolismo , Família 2 do Citocromo P450 , Escherichia coli/genética , Escherichia coli/metabolismo , Nitrilas/química , Nitrilas/metabolismo , Pseudomonas putida/genética , Coelhos , Proteínas Recombinantes/química , Proteínas Recombinantes/metabolismo
15.
Methods Cell Biol ; 90: 327-64, 2008.
Artigo em Inglês | MEDLINE | ID: mdl-19195557

RESUMO

Human high-density lipoproteins (HDL) are protein/lipid particles of nanometer sizes. These nano particles are critical for transportation of the "bad cholesterol" from peripheral tissues back to the liver for clearance. An inverse correlation has been observed between the plasma HDL concentration and atherosclerosis. Furthermore, the HDL particle has also been utilized as a vehicle for drug delivery and for intracellular cell biology studies of membrane proteins. The structural basis of HDL formation and assembly, however, is poorly understood. Using high-resolution structural approaches, the formation and assembly of the HDL particle is being examined at atomic resolution, which is reviewed in this chapter. We will mainly focus on our own NMR studies of different apoAI conformations with a brief summary of previously published work by other laboratories.


Assuntos
Lipoproteínas HDL/química , Lipoproteínas HDL/metabolismo , Nanotecnologia/métodos , Sequência de Aminoácidos , Animais , Apolipoproteína A-I/química , Apolipoproteína A-I/metabolismo , Dicroísmo Circular , Lipoproteínas de Alta Densidade Pré-beta/química , Lipoproteínas de Alta Densidade Pré-beta/metabolismo , Humanos , Lipoproteínas HDL/ultraestrutura , Espectroscopia de Ressonância Magnética , Camundongos , Modelos Biológicos , Dados de Sequência Molecular , Peso Molecular , Conformação Proteica , Ultracentrifugação
16.
Proteins ; 69(1): 125-38, 2007 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-17598143

RESUMO

P450cam has long served as a prototype for the cytochrome P450 (CYP) gene family. But, little is known about how substrate enters its active site pocket, and how access is achieved in a way that minimizes exposure of the reactive heme. We hypothesize that P450cam may first bind substrate transiently near the mobile F-G helix that covers the active site pocket. Such a two-step binding process is kinetically required if P450cam rarely populates an open conformation-as suggested by previous literature and the inability to obtain a crystal structure of P450cam in an open conformation. Such a mechanism would minimize exposure of the heme by allowing P450cam to stay in a closed conformation as long as possible, since only brief flexing into an open conformation would be required to allow substrate entry. To test this model, we have attempted to dock a second camphor molecule into the crystal structure of camphor-bound P450cam. The docking identified only one potential entry site pocket, a well-defined cavity on the F-helix side of the F-G flap, 16 A from the heme iron. Location of this entry site pocket is consistent with our NMR T1 relaxation-based measurements of distances for a camphor that binds in fast exchange (active site camphor is known to bind in slow exchange). Presence of a second camphor binding site is also confirmed with [(1)H-(13)C] HSQC titrations of (13)CH3-threonine labeled P450cam. To confirm that camphor can bind outside of the active site pocket, (13)CH3-S-pyridine was bound to the heme iron to physically block the active site, and to serve as an NMR chemical shift probe. Titration of this P450cam-pyridine complex confirms that camphor can bind to a site outside the active site pocket, with an estimated Kd of 43 microM. The two-site binding model that is proposed based on these data is analogous to that recently proposed for CYP3A4, and is consistent with recent crystal structures of P450cam bound to tethered-substrates, which force a partially opened conformation.


Assuntos
Cânfora 5-Mono-Oxigenase/química , Cânfora 5-Mono-Oxigenase/metabolismo , Cânfora/metabolismo , Modelos Moleculares , Sítios de Ligação , Cânfora 5-Mono-Oxigenase/isolamento & purificação , Cristalografia por Raios X , Cinética , Ressonância Magnética Nuclear Biomolecular , Conformação Proteica , Estrutura Terciária de Proteína , Especificidade por Substrato
17.
Transpl Int ; 15(11): 563-9, 2002 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-12461661

RESUMO

Several laboratories have resorted to flow-cytometric crossmatch (FCXM) in an effort to prevent hyperacute and accelerated renal allograft rejections. The currently employed FCXM has problems with both false-positive and -negative reactions, largely as a result of irrelevant IgG binding to Fc IgG receptors. In 1980, we circumvented this problem by digesting Fc IgG receptors with pronase, and demonstrated that, with immunofluorescence microscopy (IF), detection of IgG anti-HLA antibodies was highly sensitive and specific. In 1995, we introduced the pronase technique to FCXM and showed that this enzyme did not decrease HLA expression. We present herein a prospective study at our institution to determine whether FCXM using pronase-digested (PD) lymphocytes is as sensitive and more specific than FCXM with undigested (UD) lymphocytes when compared with the highly sensitive and specific IF assay. In analyzing the 186 donor-specific pre-renal-transplant crossmatches, we found that PD FCXM was as sensitive and specific as IF and was able to detect weak IgG anti-HLA antibodies that bound to B cells. Fourteen of these patients would have been denied transplants if one were to have relied on UD FCXM. The data clearly indicate that PD FCXM can reliably be used to detect weak IgG anti-HLA antibodies before renal transplantation.


Assuntos
Teste de Histocompatibilidade/métodos , Transplante de Rim , Linfócitos/efeitos dos fármacos , Pronase/farmacologia , Anticorpos/análise , Imunofluorescência , Antígenos HLA/imunologia , Humanos , Imunoglobulina G/análise , Estudos Prospectivos , Sensibilidade e Especificidade
18.
Clin Transplant ; 16 Suppl 7: 62-8, 2002.
Artigo em Inglês | MEDLINE | ID: mdl-12372047

RESUMO

In order to define current issues and outcomes of living kidney donation, 100 consecutive living donors operated on between July 1996 and March 2001 were evaluated. The 64 women and 36 men ranged in age from 19 to 72 yr (mean 42.5 yr), and 65 were related to the recipient while 35 were unrelated donors. Hospital admission the morning of surgery and use of a minimal open approach to the donor kidney were standard, as were post-operative epidural pain control and plans for short hospital stay. The 100 donors were hospitalized for 2 (25), 3 (48), 4 (18), 5 (8), or 6 (1) days, with an average length of stay of 3.12 d (range 2-6 d). The mean charge for kidney donor hospitalization was 14,470 dollars (range 9671-22,808 dollars). There were no major intra or immediate post-operative complications. Six rehospitalizations occurred for post-donation nausea, vomiting, dehydration (n = 2); spinal headache; pneumonia and wound haematoma; and late wound reexploration (one hernia and one nerve entrapment). All donors returned to pre-operative functional status within 6 d to 6 wk of donation. All kidneys functioned immediately in the 100 recipients (50 women, 50 men) who averaged 46.6 yr of age (range 17-69 yr); recipient length of stay averaged 3.81 d (range 2-15 d). All donors survived in excellent health; recipient graft and patient survival, respectively, are 87 and 90% through the entire 5-yr period. Excellent long-term outcomes for living kidney donors may be accomplished using minimal open surgical technique, post-operative epidural pain control and plans for a brief hospitalization. Expansion of living donor resources in renal transplant programs may grow as unrelated kidney donation and non-directed donation as well as minimally invasive (open and laparoscopic) techniques evolve.


Assuntos
Transplante de Rim , Doadores Vivos , Adulto , Idoso , Feminino , Humanos , Imunossupressores/uso terapêutico , Transplante de Rim/efeitos adversos , Transplante de Rim/economia , Tempo de Internação , Doadores Vivos/estatística & dados numéricos , Masculino , Pessoa de Meia-Idade
19.
London; Martin Dunitz; 1990. 359 p. ilus.
Monografia em Inglês | Sec. Munic. Saúde SP, AHM-Acervo, TATUAPE-Acervo | ID: sms-11081
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA