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1.
J Viral Hepat ; 23(1): 15-22, 2016 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-26192022

RESUMO

Hepatitis B immunoprophylaxis failure is linked to high maternal viraemia. There is limited North American data on hepatitis B outcomes in pregnancy. Pregnant hepatitis B carriers were enrolled January 2011-December 2014 and offered tenofovir in the 3rd trimester if hepatitis B virus (HBV)-DNA was >7-log IU/mL. Outcomes were determined in treated vs untreated patients. In total, 161 women with 169 pregnancies (one twin, 170 infants; median age 32 years), 18% (29/161) HBeAg+ and median HBV-DNA 2.51 log IU/mL (IQR 1.66-3.65; range 0.8-8.1) were studied. 14.3% (23/161) received tenofovir due to high viral load (16/23, median 74 days, IQR 59-110) or due to liver disease (7/23). In 10/16 treated due to high viraemia, with confirmed adherence, follow-up HBV-DNA showed a 5.49 log decline (P = 0.003). In treatment naïve mothers, median alanine aminotransferase (ALT) increased from 17 IU/L (IQR 12-24) to 29 (IQR 18-36) post-partum (P = 1.5e-7). In seven highly viraemic mothers who declined therapy (HBV-DNA >8-log IU/mL); median ALT increased ~3X from baseline (P < 0.01). 26% (44/169) had Caesarean section with no difference in treated vs untreated subjects. No tenofovir-treated mothers had renal dysfunction. Data were available on 167/170 infants; in 50.8% (85/167) who completed immunoprophylaxis, 98.8% (84/85, including 12 exposed to tenofovir in utero) were HBV immune. One infant born to an HBeAg+ mother with HBV-DNA >8-log IU/mL failed immunoprophylaxis. In this prospective Canadian cohort study, most untreated mothers experienced mild HBV flares. Tenofovir in pregnancy is well tolerated and reduces viral load prior to parturition.


Assuntos
Antivirais/uso terapêutico , Vacinas contra Hepatite B/uso terapêutico , Hepatite B Crônica/tratamento farmacológico , Transmissão Vertical de Doenças Infecciosas/prevenção & controle , Complicações Infecciosas na Gravidez/prevenção & controle , Tenofovir/uso terapêutico , Viremia/tratamento farmacológico , Adulto , Alanina Transaminase/sangue , Canadá , Estudos de Coortes , Feminino , Antígenos de Superfície da Hepatite B/sangue , Vírus da Hepatite B/imunologia , Vírus da Hepatite B/isolamento & purificação , Hepatite B Crônica/prevenção & controle , Hepatite B Crônica/transmissão , Hepatite B Crônica/virologia , Humanos , Lactente , Recém-Nascido , Gravidez , Complicações Infecciosas na Gravidez/virologia , Estudos Prospectivos , Resultado do Tratamento , Carga Viral/efeitos dos fármacos , Viremia/virologia
2.
Int J Pediatr Otorhinolaryngol ; 79(12): 2170-3, 2015 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-26514928

RESUMO

OBJECTIVE: Tympanostomy tube insertion is the most common pediatric surgery, but it typically requires general anesthesia. To facilitate in-office tube placement without general anesthesia, two complementary technologies have recently been developed comprising an iontophoresis system for delivering local anesthesia and an integrated tube delivery system. The purpose of this study was to evaluate behavioral support techniques used during a clinical study of the new technology for pediatric in-office tube placement without general anesthesia or physical restraints. METHODS: As part of an IRB-approved, prospective, nine-center clinical study, pediatric patients requiring tube insertion underwent in-office treatment using the new procedure. The behavior management techniques included preparation, distraction, coaching, and reinforcement for cooperation. The entire procedure was videotaped and two independent coders used the validated FLACC (Face, Legs, Activity, Cry, Consolability) scale to code behavioral distress across five procedural phases. RESULTS: Seventy pediatric patients aged 8 months to 17 years (M=7.0 years; 51% female) were enrolled in the study and 68 had video recordings available for analysis. Of the 68 recordings analyzed, 63 patients completed the procedure and had tubes placed without sedation. Mean FLACC scores ranged from 0.05 to 2.38 (M=1.25, SD=0.82) and median FLACC scores ranged from 0 to 1 (Mdn=0, IQR=0.05), which indicate "mild" distress. During iontophoresis, eardrum tap (anesthesia assessment), and tube delivery, older children displayed lower distress and girls had higher FLACC scores during the eardrum tap procedural phase. CONCLUSION: When combined with the evidence-based behavioral techniques, office-based local anesthesia and tube delivery resulted in minimal distress, suggesting that the new procedure may be a viable method of conducting tympanostomy tube placement in children without having to use general anesthesia. Clinicaltrials.gov identifier: NCT01496287.


Assuntos
Assistência Ambulatorial , Comportamento Infantil , Ventilação da Orelha Média/métodos , Adolescente , Comportamento do Adolescente , Criança , Pré-Escolar , Feminino , Humanos , Lactente , Masculino , Dor/prevenção & controle , Medição da Dor , Estudos Prospectivos
3.
Ultrasound Obstet Gynecol ; 43(2): 165-9, 2014 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-23703927

RESUMO

OBJECTIVES: To compare the role of two nomograms to classify large-for-gestational age (LGA) neonates in women with pre-eclampsia and to determine the frequency of placental vascular lesions according to the timing of delivery. METHOD: This cohort study included 118 consecutive women with pre-eclampsia delivering between 23 and 41 weeks' gestation. The frequencies of LGA neonates according to customized growth curves and a national birth weight (BW) chart were compared. Similarly, the frequencies of LGA neonates and histological placental vascular lesions were compared between pre-eclamptic women delivering at <34 weeks (n=40) and those delivering later (n=78). RESULTS: Customized growth curves allowed classification of a higher proportion of LGA neonates than did BW curves (18.6% (22/118) vs 10.2% (12/118); P=0.002). Among pre-eclamptic women delivering at ≥34 weeks, but not earlier, the proportion of neonates classified as LGA by customized growth curves was higher than that classified by BW curves (26.9% (21/78) vs 15.4% (12/78); P=0.004). Placental vascular lesions were less frequent in pre-eclamptic women delivering at ≥34 weeks than in those delivering earlier (41% (32/78) vs 62.5% (25/40); P=0.03). CONCLUSIONS: Customized growth curves allow classification of a higher proportion of LGA neonates than do population birth weight curves among women with pre-eclampsia delivering at ≥34 weeks. Pre-eclamptic women delivering at ≥34 weeks have fewer placental vascular lesions than do those delivering earlier.


Assuntos
Idade Gestacional , Pré-Eclâmpsia/epidemiologia , Peso ao Nascer , Estudos de Coortes , Feminino , Humanos , Recém-Nascido
5.
Plant Cell Rep ; 32(8): 1243-9, 2013 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-23539290

RESUMO

KEY MESSAGE: Sensitivity to Erysiphe in Noccaea praecox with low metal supply is related to the failure in enhancing SA. Cadmium protects against fungal-infection by direct toxicity and/or enhanced fungal-induced JA signaling. Metal-based defense against biotic stress is an attractive hypothesis on evolutionary advantages of plant metal hyperaccumulation. Metals may compensate for a defect in biotic stress signaling in hyperaccumulators (metal-therapy) by either or both direct toxicity to pathogens and by metal-induced alternative signaling pathways. Jasmonic acid (JA) and salicylic acid (SA) are well-established components of stress signaling pathways. However, few studies evaluate the influence of metals on endogenous concentrations of these defense-related hormones. Even less data are available for metal hyperaccumulators. To further test the metal-therapy hypothesis we analyzed endogenous SA and JA concentrations in Noccaea praecox, a cadmium (Cd) hyperaccumulator. Plants treated or not with Cd, were exposed to mechanical wounding, expected to enhance JA signaling, and/or to infection by biotrophic fungus Erysiphe cruciferarum for triggering SA. JA and SA were analyzed in leaf extracts using LC-ESI(-)-MS/MS. Plants without Cd were more susceptible to fungal attack than plants receiving Cd. Cadmium alone tended to increase leaf SA but not JA. Either or both fungal attack and mechanical wounding decreased SA levels and enhanced JA in the Cd-rich leaves of plants exposed to Cd. High leaf Cd in N. praecox seems to hamper biotic-stress-induced SA, while triggering JA signaling in response to fungal attack and wounding. To the best of our knowledge, this is the first report on the endogenous JA and SA levels in a Cd-hyperaccumulator exposed to different biotic and abiotic stresses. Our results support the view of a defect in SA stress signaling in Cd hyperaccumulating N. praecox.


Assuntos
Ascomicetos/fisiologia , Cádmio/metabolismo , Ciclopentanos/metabolismo , Oxilipinas/metabolismo , Ácido Salicílico/metabolismo , Estresse Mecânico , Thlaspi/metabolismo , Thlaspi/microbiologia , Biomassa , Doenças das Plantas/microbiologia , Raízes de Plantas/crescimento & desenvolvimento , Raízes de Plantas/metabolismo , Raízes de Plantas/microbiologia , Brotos de Planta/crescimento & desenvolvimento , Brotos de Planta/metabolismo , Brotos de Planta/microbiologia
6.
Vaccine ; 27(45): 6317-23, 2009 Oct 23.
Artigo em Inglês | MEDLINE | ID: mdl-19840667

RESUMO

Oseltamivir, one of the two anti-neuraminidase drugs, is currently the most widely used drug against influenza. Resistance to the drug has occurred infrequently among different viruses in response to drug treatment, including A H5N1 viruses, but most notably has emerged among recently circulating A H1N1 viruses and has spread throughout the population in the absence of drug use. Crystal structures of enzyme-drug complexes, together with enzymatic properties, of mutants of H5N1 neuraminidase have provided explanations for high level oseltamivir resistance due to the common H275Y mutation, with retention of zanamivir susceptibility, and intermediate level resistance due to the N295S mutation. Complementation of enhanced NA activity due to a D344N mutation by the H275Y mutation suggests an explanation for the recent emergence and predominance of oseltamivir-resistant influenza A H1N1 viruses.


Assuntos
Farmacorresistência Viral , Vírus da Influenza A Subtipo H1N1/efeitos dos fármacos , Virus da Influenza A Subtipo H5N1/efeitos dos fármacos , Neuraminidase/genética , Oseltamivir/química , Oseltamivir/farmacologia , Proteínas Virais/genética , Vírus da Influenza A Subtipo H1N1/genética , Virus da Influenza A Subtipo H5N1/genética , Modelos Moleculares , Mutação , Estrutura Terciária de Proteína
7.
8.
Astrobiology ; 9(1): 1-22, 2009.
Artigo em Inglês | MEDLINE | ID: mdl-19203238

RESUMO

The discovery of extrasolar planets is one of the greatest achievements of modern astronomy. The detection of planets that vary widely in mass demonstrates that extrasolar planets of low mass exist. In this paper, we describe a mission, called Darwin, whose primary goal is the search for, and characterization of, terrestrial extrasolar planets and the search for life. Accomplishing the mission objectives will require collaborative science across disciplines, including astrophysics, planetary sciences, chemistry, and microbiology. Darwin is designed to detect rocky planets similar to Earth and perform spectroscopic analysis at mid-infrared wavelengths (6-20 mum), where an advantageous contrast ratio between star and planet occurs. The baseline mission is projected to last 5 years and consists of approximately 200 individual target stars. Among these, 25-50 planetary systems can be studied spectroscopically, which will include the search for gases such as CO(2), H(2)O, CH(4), and O(3). Many of the key technologies required for the construction of Darwin have already been demonstrated, and the remainder are estimated to be mature in the near future. Darwin is a mission that will ignite intense interest in both the research community and the wider public.


Assuntos
Exobiologia/métodos , Meio Ambiente Extraterreno , Origem da Vida , Planetas , Voo Espacial , Astronomia , Teorema de Bayes , Processamento de Imagem Assistida por Computador , Astronave , Espectrofotometria Infravermelho , Astros Celestes
9.
Appl Opt ; 47(31): 5728-35, 2008 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-19122712

RESUMO

We demonstrate the modal filtering properties of newly developed single mode silver halide fibers for use at midinfrared wavelengths, centered at 10.5 microm. The goal was to achieve a suppression of nonfundamental modes greater than a factor of 300 to enable the detection and characterization of Earthlike exoplanets with a space-based nulling interferometer. Fiber segments of 4.5 cm, 10.5 cm, 15 cm, and 20 cm lengths were tested. We find that the performance of the fiber was limited not by the modal filtering properties of the core but by the unsuppressed cladding modes present at the output of the fiber. In 10.5 cm and longer sections, this effect can be alleviated by properly aperturing the output. Exclusive of coupling losses, the fiber segments of 10.5-20 cm length can provide power suppression of undesirable components of the input field by a factor of 15,000 at least. The demonstrated performance thus far surpasses our requirements, such that even very short sections of fiber provide adequate modal filtering for exoplanet characterization.

10.
Nucleic Acids Res ; 35(Database issue): D476-9, 2007 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-17090595

RESUMO

BeetleBase (http://www.bioinformatics.ksu.edu/BeetleBase/) is an integrated resource for the Tribolium research community. The red flour beetle (Tribolium castaneum) is an important model organism for genetics, developmental biology, toxicology and comparative genomics, the genome of which has recently been sequenced. BeetleBase is constructed to integrate the genomic sequence data with information about genes, mutants, genetic markers, expressed sequence tags and publications. BeetleBase uses the Chado data model and software components developed by the Generic Model Organism Database (GMOD) project. This strategy not only reduces the time required to develop the database query tools but also makes the data structure of BeetleBase compatible with that of other model organism databases. BeetleBase will be useful to the Tribolium research community for genome annotation as well as comparative genomics.


Assuntos
Bases de Dados Genéticas , Genoma de Inseto , Tribolium/genética , Animais , Genômica , Internet , Modelos Biológicos , Software , Interface Usuário-Computador
11.
Pediatr Transplant ; 8(3): 273-83, 2004 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-15176966

RESUMO

Studies of Pediatric Liver Transplantation (SPLIT) is a cooperative research network comprising 38 pediatric liver transplant centers in North America. Data from the 1092 patients who have received a first liver transplant since 1995 were analyzed for factors influencing patient survival, graft survival and acute rejection. The 3, 12, 24 and 36 month Kaplan-Meier estimates of patient/graft survival were 90.9/85.5, 86.3/80.2, 84.3/76.0, and 83.8/75.3% respectively. Univariate analysis identified initial diagnosis, type of graft (whole vs. living and cadaveric technical variant), growth failure and continuous hospitalization or ICU admission prior to transplantation as significantly influencing patient and graft survival. Subsequent multivariate analysis identified as risk factors for death: fulminant liver failure (RR = 3.05, p < 0.05), cadaveric technical variant grafts (RR = 1.95, p < 0.05), continuous hospitalization pre-transplant (RR = 1.79, p < 0.05), height deficit >2 s.d. from mean (RR = 3.22, p < 0.05). Risk factors for graft loss included: fulminant liver failure (RR = 2.27, p < 0.05), cadaveric technical variant grafts, (RR = 1.97, p < 0.05). Eleven percent of the 1092 patients were re-transplanted; vascular complications, particularly hepatic artery thrombosis (8.3% overall; 36.3% of graft failures), were responsible for the majority of re-transplants. Infection was the single most important cause of death (40 of 141, 28.4%) and was a contributing cause in 55 (39%), particularly with bacterial or fungal organisms. The cumulative Kaplan-Meier estimates of first rejection at 3, 12, 24 and 36 months were 44.8, 52.9, 59.1, and 60.3%. Initial immunosuppression with tacrolimus reduced the probability of rejection (RR = 0.62, p < 0.05). Eleven percent of rejections were steroid-resistant; chronic rejection led to 7 of 121 (5.8%) re-transplants. The SPLIT registry, in compiling data from a large number of centers, reflects the current outcomes for pediatric liver transplants in North America.


Assuntos
Rejeição de Enxerto/epidemiologia , Sobrevivência de Enxerto , Transplante de Fígado/mortalidade , Adolescente , Canadá/epidemiologia , Causas de Morte , Criança , Pré-Escolar , Feminino , Humanos , Lactente , Transplante de Fígado/estatística & dados numéricos , Masculino , Análise Multivariada , Fatores de Risco , Análise de Sobrevida , Taxa de Sobrevida , Estados Unidos/epidemiologia
12.
Biochemistry ; 42(35): 10437-44, 2003 Sep 09.
Artigo em Inglês | MEDLINE | ID: mdl-12950170

RESUMO

Fragile X syndrome, the most common cause of inherited mental retardation, is caused by the absence of the fragile X mental retardation protein (FMRP). The emerging picture is that FMRP is involved in repression of translation through a complex network of protein-protein and protein-RNA interactions. Very little structural information is, however, available for FMRP that could help to understand its function. In particular, no structural studies are available about the N-terminus of the protein, a highly conserved region which is involved in several molecular interactions. Here, we explore systematically the ability of the FMRP N-terminus to form independently folded units (domains). We produced deletion mutants and tested their fold and functional properties by mutually complementary biophysical and biochemical techniques. On the basis of our data, we conclude that the N-terminus contains a domain, that we named NDF, comprising the first 134 amino acids. Most interestingly, NDF comprises two copies of a newly identified Agenet motif. NDF is thermally stable and has a high content of beta structure. In addition to being able to bind to RNA and to recognize some of the FMRP interacting proteins, NDF forms stable dimers and is able to interact, although weakly, with the full-length protein. Our data provide conclusive evidence that NDF is a novel motif for protein-protein and protein-RNA interactions and contains a previously unidentified dimerization site.


Assuntos
Proteínas do Tecido Nervoso/metabolismo , Estrutura Terciária de Proteína , Proteínas de Ligação a RNA/metabolismo , RNA/metabolismo , Sequência de Aminoácidos , Dimerização , Proteína do X Frágil da Deficiência Intelectual , Síndrome do Cromossomo X Frágil/genética , Síndrome do Cromossomo X Frágil/metabolismo , Humanos , Dados de Sequência Molecular , Mutação , Proteínas do Tecido Nervoso/química , Proteínas do Tecido Nervoso/genética , Dobramento de Proteína , Estrutura Secundária de Proteína , Proteínas de Ligação a RNA/genética , Alinhamento de Sequência
13.
Biochemistry ; 40(20): 5906-13, 2001 May 22.
Artigo em Inglês | MEDLINE | ID: mdl-11352725

RESUMO

Proteins involved in DNA repair, or its coordination with DNA replication and mitosis through cell cycle checkpoints, are vital in the concerted cellular response to DNA damage that maintains the integrity of the genome. The "BRCT" domain (BRCA1 carboxy terminal) was noted as a putative protein-protein interaction motif in the breast cancer suppressor gene, BRCA1, and subsequently identified in over 50 proteins involved in DNA repair, recombination, or cell cycle control. The heterodimer of the DNA repair proteins, XRCC1 and DNA ligase III, was the first example of a functional interaction via BRCT modules. The only three-dimensional crystal structure of a BRCT domain was solved for this region of XRCC1. Key amino acid residues mediating the interaction with DNA ligase III were identified here by targeted mutagenesis of the XRCC1 BRCT domain. The consequences of these mutations on protein folding were assessed. A structural model of the DNA ligase III BRCT domain was constructed and similarly tested by mutation of corresponding residues required for the interaction with XRCC1. These data identify the XRCC1-DNA ligase III heterodimer interface and provide the first demonstration of the surface contacts coordinating a functional BRCT-BRCT protein interaction.


Assuntos
Proteína BRCA1/metabolismo , DNA Ligases/metabolismo , Reparo do DNA , Proteínas de Ligação a DNA/metabolismo , Substituição de Aminoácidos/genética , Proteína BRCA1/química , Proteína BRCA1/genética , Dicroísmo Circular , DNA Ligase Dependente de ATP , DNA Ligases/química , Proteínas de Ligação a DNA/química , Dimerização , Humanos , Modelos Moleculares , Mutagênese Sítio-Dirigida , Fragmentos de Peptídeos/química , Fragmentos de Peptídeos/genética , Fragmentos de Peptídeos/metabolismo , Proteínas de Ligação a Poli-ADP-Ribose , Ligação Proteica/genética , Estrutura Secundária de Proteína/genética , Estrutura Terciária de Proteína/genética , Termodinâmica , Triptofano/genética , Proteína 1 Complementadora Cruzada de Reparo de Raio-X , Proteínas de Xenopus
14.
Blood ; 97(9): 2574-9, 2001 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-11313244

RESUMO

Standard allogeneic stem cell transplant (allo-SCT) regimens have been associated with a high transplant-related mortality (TRM) in multiple myeloma (MM). Nonmyeloablative therapy can establish stable engraftment after allo-SCT and maintain the antitumor effect with less toxicity, which is important in heavily pretreated and elderly patients. We report on 16 poor-risk MM patients receiving allo-SCT from an HLA-matched (n = 14) or mismatched (n = 2) sibling following conditioning with melphalan 100 mg/m(2) (MEL-100). Ten patients had refractory relapse, 4 responsive relapse, and 2 patients were in near complete remission (nCR) with poor-prognosis disease. Patients had received 1 (n = 9) or 2 (n = 7) prior autotransplants. Donor lymphocyte infusions (DLIs) were given to 14 patients with no clinical evidence of graft versus host disease (GVHD) either to attain full donor chimerism (n = 4) or to eradicate residual disease (n = 10). Fifteen patients showed myeloid engraftment, and 12 patients were full donor chimeras at day +21. No TRM was observed during the first 100 days. Acute GVHD developed in 10 patients; 1 had fatal grade IV GVHD. Seven progressed to chronic GVHD, limited in 3 and extensive in 4 patients. At a median follow-up of 1 year, 5 patients achieved and sustained CR, 3 nCR, and 4 partial remission. Of 4 patients progressing after transplantation, 3 achieved a remission following further chemotherapy and DLI. Remarkable graft versus myeloma responses were seen in chemotherapy-refractory patients. Two patients died of progressive disease, and 3 died of GVHD complications without active disease. GVHD remains a major problem with this procedure.


Assuntos
Transplante de Células-Tronco Hematopoéticas , Transfusão de Linfócitos , Mieloma Múltiplo/terapia , Adulto , Idoso , Feminino , Mobilização de Células-Tronco Hematopoéticas , Humanos , Masculino , Pessoa de Meia-Idade , Mieloma Múltiplo/patologia , Agonistas Mieloablativos/uso terapêutico , Transplante Homólogo , Resultado do Tratamento
15.
Drug Metab Dispos ; 29(5): 693-700, 2001 May.
Artigo em Inglês | MEDLINE | ID: mdl-11302936

RESUMO

Flavin-containing monooxygenase (FMO) metabolizes a wide variety of nitrogen, sulfur, and phosphorous-containing xenobiotics. FMO2 is highly expressed in the lung of most mammals examined, but the protein has only recently been detected in humans, presumably due to a premature stop codon at AA472 in most individuals. In this study, full-length (mFMO2-535) and 3'-truncated (mFMO2-471) monkey FMO2 protein, produced by cDNA-mediated baculovirus expression, were characterized and compared with baculovirus-expressed rabbit FMO2 (rFMO2-535). Although baculovirus-expressed mFMO2-535 had properties similar to FMO in monkey lung microsomes and had catalytic properties similar to rFMO2-535, the expressed proteins differed in a number of properties in S-oxidation assays. Both enzymes had the same pH optima (pH 9.5); however, mFMO2-535 quickly lost activity at higher pH values whereas rFMO2-535 retained the majority of its activity. Also, mFMO2-535 was significantly less stable at elevated temperatures and in the presence of cholic acid but had greater activity in the presence of magnesium. mFMO2-535 had higher apparent K(m) and V(max)/K(m) values than rFMO2-535 did in N-oxygenation assays. mFMO2-471 was correctly targeted to the membrane fraction, but N- and S-oxygenation was not detected. Since the AA sequence identity of mFMO2 and human FMO2 is 97%, our results with mFMO2-535 suggest that individuals carrying the allele encoding full-length FMO2 are likely to have in vivo FMO2 activity. Such activity could result in marked differences in the metabolism, efficacy, and/or toxicity of drugs and xenobiotics for which lung is a portal of entry or target organ.


Assuntos
Oxigenases/metabolismo , Animais , Catálise , Clonagem Molecular , Macaca mulatta , Oxigenases/química , Oxigenases/genética
16.
Biochemistry ; 40(16): 4957-65, 2001 Apr 24.
Artigo em Inglês | MEDLINE | ID: mdl-11305911

RESUMO

Titin and alpha-actinin, two modular muscle proteins, are with actin the major components of the Z-band in vertebrate striated muscles where they serve to organize the antiparallel actin filament arrays in adjacent sarcomeres and to transmit tension between sarcomeres during activation. Interactions between titin and alpha-actinin have been mainly localized in a 45-amino acid multiple motif (Z-repeat) in the N-terminal region of titin and the C-terminal region of alpha-actinin. In this study, we provide the first quantitative characterization of alpha-actinin-Z-repeat recognition and dissect the interaction to its minimal units. Different complementary techniques, such as circular dichroism, calorimetry, and nuclear magnetic spectroscopy, were used. Two overlapping alpha-actinin constructs (Act-EF34 and Act-EF1234) containing two and four EF-hand motifs, respectively, were produced, and their folding properties were examined. Complex formation of Act-EF34 and Act-EF1234 with single- and double-Z-repeat constructs was studied. Act-EF34 was shown quantitatively to be necessary and sufficient for binding to Z-repeats, excluding the presence of additional high-affinity binding sites in the remaining part of the domain. The binding affinities of the different Z-repeats for Act-EF34 range from micromolar to millimolar values. The strongest of these interactions are comparable to those observed in troponin C-troponin I complexes. The binding affinities for Act-EF34 are maximal for Zr1 and Zr7, the two highly homologous sequences present in all muscle isoforms. No cooperative or additional contributions to the interaction were observed for Z-repeat double constructs. These findings have direct relevance for evaluating current models of Z-disk assembly.


Assuntos
Actinina/química , Proteínas Musculares/química , Fragmentos de Peptídeos/química , Proteínas Quinases/química , Sequências Repetitivas de Aminoácidos , Actinina/genética , Actinina/metabolismo , Sequência de Aminoácidos , Animais , Calorimetria , Dicroísmo Circular , Conectina , Motivos EF Hand/genética , Escherichia coli/genética , Humanos , Espectroscopia de Ressonância Magnética , Dados de Sequência Molecular , Proteínas Musculares/metabolismo , Fragmentos de Peptídeos/genética , Ligação Proteica/genética , Dobramento de Proteína , Proteínas Quinases/metabolismo , Estrutura Secundária de Proteína , Estrutura Terciária de Proteína/genética , Coelhos , Proteínas Recombinantes de Fusão/química , Proteínas Recombinantes de Fusão/metabolismo , Sequências Repetitivas de Aminoácidos/genética , Relação Estrutura-Atividade
17.
Biochemistry ; 39(51): 15920-31, 2000 Dec 26.
Artigo em Inglês | MEDLINE | ID: mdl-11123919

RESUMO

The Ca(2+) titration of the (15)N-labeled mutant V136G calmodulin has been monitored using (1)H-(15)N HSQC NMR spectra. Up to a [Ca(2+)]/[CaM] ratio of 2, the Ca(2+) ions bind predominantly to sites I and II on the N-domain in contrast with the behavior of the wild-type calmodulin where the C-terminal domain has the higher affinity for Ca(2+). Surprisingly, the Ca(2+)-binding affinity for the N-domain in the mutant calmodulin is greater than that for the N-domain in the wild-type protein. The mutated C-domain is observed as a mixture of unfolded, partially folded (site III occupied), and native-like folded (sites III and IV occupied) conformations, with relative populations dependent on the [Ca(2+)]/[CaM] ratio. The occupancy of site III independently of site IV in this mutant shows that the cooperativity of Ca(2+) binding in the C-domain is mediated by the integrity of the domain structure. Several NH signals from residues in the Ca(2+)-bound N-domain appear as two signals during the Ca(2+) titration indicating separate species in slow exchange, and it can be deduced that these result from the presence and absence of interdomain interactions in the mutant. It is proposed that an unfolded part of the mutated C-domain interacts with sites on the N-domain that normally bind to target proteins. This would also account for the increase in the Ca(2+) affinity for the N-domain in the mutant compared with the wild-type calmodulin. The results therefore show the wide-ranging effects of a point mutation in a single Ca(2+)-binding site, providing details of the involvement of individual residues in the calcium-induced folding reactions.


Assuntos
Cálcio/química , Calmodulina/química , Calmodulina/genética , Glicina/genética , Valina/genética , Substituição de Aminoácidos/genética , Animais , Sítios de Ligação/genética , Cálcio/metabolismo , Calmodulina/metabolismo , Drosophila melanogaster , Motivos EF Hand/genética , Glicina/química , Substâncias Macromoleculares , Músculo Liso/enzimologia , Quinase de Cadeia Leve de Miosina/química , Isótopos de Nitrogênio , Ressonância Magnética Nuclear Biomolecular/métodos , Conformação Proteica , Dobramento de Proteína , Estrutura Terciária de Proteína/genética , Prótons , Proteínas Recombinantes/química , Proteínas Recombinantes/metabolismo , Soluções , Termodinâmica , Valina/química
18.
Protein Sci ; 9(8): 1519-29, 2000 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-10975573

RESUMO

Chemical and thermal denaturation of calmodulin has been monitored spectroscopically to determine the stability for the intact protein and its two isolated domains as a function of binding of Ca2+ or Mg2+. The reversible urea unfolding of either isolated apo-domain follows a two-state mechanism with relatively low deltaG(o)20 values of approximately 2.7 (N-domain) and approximately 1.9 kcal/mol (C-domain). The apo-C-domain is significantly unfolded at normal temperatures (20-25 degrees C). The greater affinity of the C-domain for Ca2+ causes it to be more stable than the N-domain at [Ca2+] > or = 0.3 mM. By contrast, Mg2+ causes a greater stabilization of the N- rather than the C-domain, consistent with measured Mg2+ affinities. For the intact protein (+/-Ca2+), the bimodal denaturation profiles can be analyzed to give two deltaG(o)20 values, which differ significantly from those of the isolated domains, with one domain being less stable and one domain more stable. The observed stability of the domains is strongly dependent on solution conditions such as ionic strength, as well as specific effects due to metal ion binding. In the intact protein, different folding intermediates are observed, depending on the ionic composition. The results illustrate that a protein of low intrinsic stability is liable to major perturbation of its unfolding properties by environmental conditions and liganding processes and, by extension, mutation. Hence, the observed stability of an isolated domain may differ significantly from the stability of the same structure in a multidomain protein. These results address questions involved in manipulating the stability of a protein or its domains by site directed mutagenesis and protein engineering.


Assuntos
Cálcio/metabolismo , Calmodulina/metabolismo , Magnésio/metabolismo , Animais , Sítios de Ligação , Calmodulina/química , Dicroísmo Circular , Drosophila/química , Escherichia coli/enzimologia , Fluorescência , Ligantes , Espectrometria de Massas , Conformação Proteica , Desnaturação Proteica , Espectrofotometria Ultravioleta , Termodinâmica , Tirosina/química , Ureia/química
19.
J Parasitol ; 86(4): 846-9, 2000 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-10958469

RESUMO

Archeological deposits from the 19th century company town of Fayette, Michigan were analyzed for evidence of endoparasitic infection in the human population residing in the town between 1867 and 1891. Three privies were associated with upper-income and middle-income neighborhoods; 2 household refuse disposal areas were found in a predominately lower-income immigrant working class neighborhood. Sediment samples from 2 privies associated with dwellings in the middle-income neighborhood were positive for eggs of the human whipworm Trichuris trichiura. The parasite was probably also present among residents of the lower income neighborhood, but the shallow nature of the refuse deposits in that locality precluded preservation of the eggs. Contemporary epidemiologic studies of helminth infections support the belief that T. trichiura may have been a common parasite of 19th century school-age children given the natural inclination of young children to defecate indiscriminately, play freely in the dirt, and eat without washing their hands.


Assuntos
Tricuríase/história , Animais , Fezes/parasitologia , História do Século XIX , Humanos , Michigan , Fatores Socioeconômicos , Banheiros/história , Trichuris/isolamento & purificação
20.
Am J Kidney Dis ; 35(6): 1089-95, 2000 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-10845822

RESUMO

We recently showed that a single low graft blood-flow measurement (Qa) does not accurately predict graft thrombosis. In this study, we prospectively determined whether percentage of decrease in Qa (DeltaQa) or adjustment of Qa for mean arterial pressure (Qa/MAP; Delta(Qa/MAP)) provides greater predictive accuracy than a single Qa. We monitored 83 grafts from 80 patients for thrombosis over periods up to 12 months. Qa (by ultrasound dilution) and MAP were measured monthly during the study. Receiver operating characteristic curves were used to determine whether Qa, DeltaQa, Qa/MAP, or Delta(Qa/MAP) provided the combination of high sensitivity (>80%) and low false-positive rate (FPR; <20%) needed for clinical use. This level of predictive accuracy requires an area under the curve (AUC) of approximately 0.90. We analyzed the four predictors by a number of criteria and found that all AUCs were less than 0.90 and adjustment for MAP reduced the AUC. In predicting thrombosis within 1 month, for example, AUCs for Qa and net DeltaQa (over 3 months) were 0.84 and 0.82, respectively, whereas AUCs for Qa/MAP and net Delta(Qa/MAP) were 0.78 and 0.75, respectively. At a sensitivity of 80%, FPRs for all predictors were at least 30%. Thus, a high sensitivity always required a high FPR. These results show that DeltaQa and adjustment for MAP are not more accurate than a single low Qa in predicting thrombosis. None of these predictors provide enough predictive accuracy to be the sole criterion for clinical decision making. A successful monitoring and intervention program will likely require the inclusion of other predictors that, together with Qa, may provide the needed accuracy.


Assuntos
Derivação Arteriovenosa Cirúrgica/instrumentação , Prótese Vascular , Oclusão de Enxerto Vascular/etiologia , Diálise Renal/instrumentação , Trombose/etiologia , Área Sob a Curva , Pressão Sanguínea/fisiologia , Reações Falso-Positivas , Feminino , Seguimentos , Previsões , Oclusão de Enxerto Vascular/diagnóstico por imagem , Oclusão de Enxerto Vascular/prevenção & controle , Humanos , Masculino , Pessoa de Meia-Idade , Politetrafluoretileno , Estudos Prospectivos , Curva ROC , Fluxo Sanguíneo Regional/fisiologia , Fatores de Risco , Sensibilidade e Especificidade , Trombose/diagnóstico por imagem , Trombose/prevenção & controle , Ultrassonografia
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