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The evidence base for the performance and effectiveness of non-structural measures to manage stormwater pollution in industrial areas is relatively underdeveloped, despite their increased use in practice. This study aims to advance stormwater management practice and research by presenting a detailed case study of the development, implementation and evaluation of a targeted behaviour change trial that engaged small to medium industrial businesses in stormwater pollution prevention. Utilising a combination of different behaviour change strategies - including capacity building, social norms and commitment - a number of preventative stormwater pollution behaviours were changed in participating businesses. Our study provides a practice model for tackling stormwater pollution from a behavioural perspective that can be further developed by both practitioners and researchers to create effective and long-lasting change.
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Poluição Ambiental/prevenção & controle , Monitoramento Ambiental , Indústrias/normas , ChuvaRESUMO
Mixing of materials is fundamental to many natural phenomena and engineering applications. The presence of discontinuous deformations-such as shear banding or wall slip-creates new mechanisms for mixing and transport beyond those predicted by classical dynamical systems theory. Here, we show how a novel mixing mechanism combining stretching with cutting and shuffling yields exponential mixing rates, quantified by a positive Lyapunov exponent, an impossibility for systems with cutting and shuffling alone or bounded systems with stretching alone, and demonstrate it in a fluid flow. While dynamical systems theory provides a framework for understanding mixing in smoothly deforming media, a theory of discontinuous mixing is yet to be fully developed. New methods are needed to systematize, explain, and extrapolate measurements on systems with discontinuous deformations. Here, we investigate "webs" of Lagrangian discontinuities and show that they provide a template for the overall transport dynamics. Considering slip deformations as the asymptotic limit of increasingly localised smooth shear, we also demonstrate exactly how some of the new structures introduced by discontinuous deformations are analogous to structures in smoothly deforming systems.
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Modelos Teóricos , Reologia , Dinâmica não LinearRESUMO
Analysis of the periodic points of a conservative periodic dynamical system uncovers the basic kinematic structure of the transport dynamics and identifies regions of local stability or chaos. While elliptic and hyperbolic points typically govern such behaviour in 3D systems, degenerate (parabolic) points also play an important role. These points represent a bifurcation in local stability and Lagrangian topology. In this study, we consider the ramifications of the two types of degenerate periodic points that occur in a model 3D fluid flow. (1) Period-tripling bifurcations occur when the local rotation angle associated with elliptic points is reversed, creating a reversal in the orientation of associated Lagrangian structures. Even though a single unstable point is created, the bifurcation in local stability has a large influence on local transport and the global arrangement of manifolds as the unstable degenerate point has three stable and three unstable directions, similar to hyperbolic points, and occurs at the intersection of three hyperbolic periodic lines. The presence of period-tripling bifurcation points indicates regions of both chaos and confinement, with the extent of each depending on the nature of the associated manifold intersections. (2) The second type of bifurcation occurs when periodic lines become tangent to local or global invariant surfaces. This bifurcation creates both saddle-centre bifurcations which can create both chaotic and stable regions, and period-doubling bifurcations which are a common route to chaos in 2D systems. We provide conditions for the occurrence of these tangent bifurcations in 3D conservative systems, as well as constraints on the possible types of tangent bifurcation that can occur based on topological considerations.
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As corticosteroid-sparing protocols are increasingly utilized in kidney transplant recipients, it is crucial to understand potential drug interactions between tacrolimus (TAC) and the effect of corticosteroid withdrawal as well as to characterize dose adjustments of mycophenolate mofetil (MMF) in this setting. This prospective, multicenter, randomized, double-blind study included 397 patients who were randomized on posttransplant day 8 to receive either placebo (CSWD) or corticosteroid continuance (CCS). TAC trough levels at week two posttransplant were significantly greater in the CSWD group whereas TAC doses were comparable to the CCS group. This interaction was not observed in the African American subgroup. Higher serum creatinine and potassium levels were also observed in the CSWD group. MMF dose was significantly reduced in the CSWD group by the investigators because of decreased WBC counts, mostly outside of study protocol criteria, despite similar incidence of neutropenia and reported cytomegalovirus infection. Understanding TAC and MMF exposure in the context of corticosteroid-sparing protocols should allow for improved dosing of immunosuppressants and better management of posttransplant patients.
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Corticosteroides/uso terapêutico , Transplante de Rim/métodos , Ácido Micofenólico/análogos & derivados , Insuficiência Renal/terapia , Tacrolimo/administração & dosagem , Adulto , Negro ou Afro-Americano , Índice de Massa Corporal , Método Duplo-Cego , Feminino , Humanos , Hiperpotassemia/metabolismo , Masculino , Pessoa de Meia-Idade , Ácido Micofenólico/administração & dosagem , Estudos Prospectivos , Insuficiência Renal/etnologiaRESUMO
Background: The primary aim of this study was to determine the epidemiology of lateral-end clavicle fractures in adolescents. The secondary aim was to assess the outcome following non-operative management. Methods: A retrospective review of all adolescent clavicle fractures over a 10-year period was undertaken. Fracture classification, demographics, management, and complications were analysed. Functional outcomes were undertaken with the Quick Disabilities of Arm, Shoulder and Hand and EuroQol five-dimension at mean 8.8 years post-injury. Results: In total, 677 clavicle fractures were analysed, 8.7% were lateral-end fractures (n = 59/677). The median age was 14.6 (range: 13-17) and 92% were male (n = 54/59). The incidence was 0.17 per 100,000 per year. All displaced physeal fractures (Neer IV n = 14) were managed non-operatively and of the six followed-up, all united with good outcomes. The adult type displaced fracture (Neer II) occurred in fifteen fractures, five underwent operative fixation and ten were managed non-operatively with one subsequent nonunion (n = 1/10). Those patients that underwent non-operative management (response n = 5/10, 50%) reported a median Quick Disabilities of Arm, Shoulder and Hand of 2.3 but approximately 40% reported cosmetic and outcome dissatisfaction at long-term follow-up. Conclusion: Displaced Neer II lateral-end clavicle fractures are rare in the adolescent population. Although nonunion is rare, some dissatisfaction with cosmesis persists at long-term follow-up despite good functional outcomes with non-operative management.
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BACKGROUND: Knowing a young woman with newly diagnosed breast cancer has a germline BRCA1 mutation informs her clinical management and that of her relatives. We sought an optimal strategy for identifying carriers using family history, breast cancer morphology and hormone receptor status data. METHODS: We studied a population-based sample of 452 Australian women with invasive breast cancer diagnosed before age 40 years for whom we conducted extensive germline mutation testing (29 carried a BRCA1 mutation) and a systematic pathology review, and collected three-generational family history and tumour ER and PR status. Predictors of mutation status were identified using multiple logistic regression. Areas under receiver operator characteristic (ROC) curves were estimated using five-fold stratified cross-validation. RESULTS: The probability of being a BRCA1 mutation carrier increased with number of selected histology features even after adjusting for family history and ER and PR status (P<0.0001). From the most parsimonious multivariate model, the odds ratio for being a carrier were: 9.7 (95% confidence interval: 2.6-47.0) for trabecular growth pattern (P=0.001); 7.8 (2.7-25.7) for mitotic index over 50 mitoses per 10 high-powered field (P=0.0003); and 2.7 (1.3-5.9) for each first-degree relative with breast cancer diagnosed before age 60 years (P=0.01).The area under the ROC curve was 0.87 (0.83-0.90). CONCLUSION: Pathology review, with attention to a few specific morphological features of invasive breast cancers, can identify almost all BRCA1 germline mutation carriers among women with early-onset breast cancer without taking into account family history.
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Neoplasias da Mama/genética , Neoplasias da Mama/patologia , Carcinoma/genética , Carcinoma/patologia , Genes BRCA1 , Mutação em Linhagem Germinativa , Adulto , Fatores Etários , Neoplasias da Mama/diagnóstico , Carcinoma/diagnóstico , Análise Mutacional de DNA , Saúde da Família , Feminino , Estudo de Associação Genômica Ampla , Heterozigoto , Humanos , Prognóstico , Sistema de Registros , Estudos Retrospectivos , Carga Tumoral , MulheresRESUMO
Background Emergency "Anesthesia Stat!" (AS!) calls remain a common practice in medical centers even when advanced communication infrastructures are available. We hypothesize that the analysis of post-procedure "AS!" calls will lead to actionable insights which may enhance patient safety. Methods After institutional review board approval, we prospectively collected data from April 2015 through May 2018 on "AS!" calls throughout the pediatric operating rooms (OR), off-site locations, and post-anesthesia care unit (PACU) at a tertiary university medical center. Data recorded included demographic information, location, time of the event, event duration, vital signs, medications, anesthesia staff, attending anesthesiologist, and staff responding to the call. A narrative account of the event was also documented. Results A total of 82 "AS!" calls occurred, with ages ranging from 11 days old to 17 years old. Forty-nine of the 82 calls (60%) occurred at emergence. Seventy-one of the 82 calls (87%) were solely respiratory-related. Thirty-five of 49 emergence calls (71%) occurred in the PACU. Further, 34 of 35 PACU calls (97%) were respiratory-related, with 30 of 35 PACU calls (86%) associated with desaturation requiring intervention by anesthesia staff. Finally, 31 of 35 PACU calls (89%) occurred within 30 minutes of patient arrival to PACU. Conclusion Analysis of "AS!" events from our PACU continues to support the need for the prompt and continuous availability of at least one staff member with advanced airway management skills. Further, pediatric patients undergoing general anesthesia and surgery should likely be monitored for a minimum of 30 minutes following arrival in the PACU.
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OBJECTIVE: Chromosomal loss within the region of 18q and loss of SMAD4 expression have been reported to be frequent somatic events during colorectal cancer tumour progression; however, their associations with age at onset have not been widely studied. METHOD: We analysed 109 tumours from a population-based case-family study based on colorectal cancers diagnosed before the age of 45 years. These patients with early-onset colorectal cancer had been previously screened for germ-line mismatch repair gene mutations, microsatellite instability (that included the mononucleotide repeat in TGFbetaRII) and somatic k-ras mutations. We measured SMAD4 protein expression using immunohistochemistry and SMAD4 copy number using quantitative real-time PCR. RESULTS: Loss of SMAD4 protein expression was observed in 27/109 (25%) of cancers tested and was more commonly observed in rectal tumours (15/41, 36%) when compared with tumours arising in the colon (11/66, 17%) (P = 0.04). There was no association between SMAD4 protein expression and TGFbetaR11 mutation status, SMAD4 copy number, family history, MSI status, tumour stage or grade. CONCLUSION: Loss of SMAD4 expression is a common feature of early-onset colorectal tumours as it is in colorectal cancers diagnosed in other age-groups. Taken together, the molecular pathways (genetic and epigenetic) now known to be involved in early-onset colorectal cancer only explain a small proportion of the disease and require further exploration.
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Adenocarcinoma/metabolismo , Neoplasias Colorretais/metabolismo , Proteína Smad4/metabolismo , Adenocarcinoma/genética , Adolescente , Adulto , Neoplasias Colorretais/genética , Variações do Número de Cópias de DNA , Feminino , Humanos , Masculino , Proteína Smad4/genética , Adulto JovemRESUMO
The activity of a cytoplasmic factor (MPF), capable of inducing nuclear membrane breakdown (germinal vesicle breakdown) when injected into amphibian oocytes, has been studied during the course of early cleavage in amphibian embryos. Mature egg cytoplasm was found to contain high levels of this activity, but this was quickly lost after fertilization or artificial activation. MPF activity later reappeared in the egg cytoplasm and started to cycle with time. The peak of embryonic MPF activity during each cycle coincided with the time the embryonic nuclei were entering the G2-M transition, i.e., mitosis. However, in colchicine-arrested embryos, this activity remained at an elevated level and no longer oscillated. The timing of the appearance and disappearance of this activity appeared to be under the control of the cytoplasm because such behavior was still observed in enucleated eggs. Continued protein synthesis in the embryo was required for the reappearance, but not for the disappearance, of this activity. MPF, previously thought to be restricted to oocyte maturation, may play a more general role in controlling nuclear membrane breakdown during mitosis as well as meiosis.
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Núcleo Celular/metabolismo , Mitose , Oócitos/ultraestrutura , Óvulo/ultraestrutura , Zigoto/ultraestrutura , Animais , Citoplasma , Feminino , Biossíntese de Proteínas , Rana pipiens , Fatores de Tempo , XenopusRESUMO
The calcium-binding protein, calmodulin, has been purified from Xenopus laevis oocytes. This 18,500-dalton protein, pl 4.3, has two high-affinity calcium-binding sites per mole protein having a dissociation constant of 2.8 x 10(-6) M. Full-grown Xenopus oocytes, arrested in late G2 of the meiotic cell cycle, resumed meiosis when microinjected with 60-80 ng (3-4 pmol) of calmodulin in the form of a calcium-calmodulin complex. The timing of the meiotic events in these recipient oocytes was the same as that normally induced by progesterone. Xenopus ovarian calmodulin stimulated bovine brain phosphodiesterase (PDE) 3- to 10-fold in a calcium-dependent manner, but it had no apparent effect on ovarian PDE activity. A calcium-calmodulin-dependent protein kinase has been isolated from Xenopus oocytes using a calmodulin-Sepharose 4B affinity column. The possible role for this kinase in regulating the G2-M transition in oocytes has been discussed.
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Proteínas de Ligação ao Cálcio/farmacologia , Calmodulina/farmacologia , Meiose/efeitos dos fármacos , Oócitos/efeitos dos fármacos , Óvulo/efeitos dos fármacos , Animais , Encéfalo/enzimologia , Cromatografia de Afinidade , Feminino , Oócitos/enzimologia , Diester Fosfórico Hidrolases/metabolismo , Proteínas Quinases/isolamento & purificação , Xenopus laevisRESUMO
Maize storage proteins synthesized in oocytes were compartmentalized in membrane vesicles because they were resistant to hydrolysis by protease, unless detergent was present. The site of storage protein deposition within the oocyte was determined by subcellular fractionation. Optimal separation of oocyte membranes and organelles was obtained when EDTA and high concentrations of NaCl were included in the homogenization and gradient buffers. Under these conditions, fractions in sucrose gradients containing a heterogeneous mixture of smooth membranes (presumably endoplasmic reticulum, Golgi apparatus, and plasma membrane, density = 1.10-1.12 g/cm3), mitochondria (densities = 1.14 and 1.16 g/cm3), yolk platelets (density = 1.21 g/cm3), and a dense matrix material (density = 1.22 g/cm3) could be separated. Some zein proteins were recovered in the mixed membrane fraction, but the majority occurred in vesicles sedimenting with yolk platelets and granular material at a density of approximately 1.22 g/cm3. When metrizamide was included in the gradient to increase the density, little of the dense matrix material was isolated, and vesicles containing zein proteins were separated from other oocyte components. These vesicles were similar to protein bodies in maize endosperm because they were of identical density and contained the same group of polypeptides.
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Oócitos/fisiologia , Óvulo/fisiologia , Zeína/metabolismo , Animais , Compartimento Celular , Fracionamento Celular/métodos , Centrifugação Isopícnica , Feminino , Membranas Intracelulares/metabolismo , Ponto Isoelétrico , Proteínas de Membrana/metabolismo , Peso Molecular , Oócitos/ultraestrutura , RNA Mensageiro/metabolismo , Zeína/genéticaRESUMO
Crabs grown experimentally on fully shelled prey developed larger and stronger claws than those raised on nutritionally equivalent unshelled prey. When one claw was immobilized, claws also became asymmetrical. These use-induced changes differ from skeletal remodelling in vertebrates and many invertebrates because changes in the rigid exoskeleton can occur only after molting, and claw muscle mass must be reduced substantially before the molt. Such short-term adaptive responses to environmental stimuli, if heritable, could yield long-term evolutionary changes in claw size and, if combined with behavioral biases toward one side (handedness), could also promote the evolution of claw dimorphism.
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Kinetics of protein synthesis were measured in oocytes of Rana pipiens enucleated at various times during and following pituitary-induced maturation. These enucleated oocytes were capable of the same rate of protein synthesis as nucleated controls, even when rates were measured many hours after enucleation.
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Células Germinativas/metabolismo , Óvulo , Biossíntese de Proteínas , Animais , Anuros , Núcleo Celular , Feminino , Técnicas In Vitro , Cinética , Leucina/metabolismo , Meiose , Hipófise/fisiologia , Cloreto de Potássio/farmacologia , TrítioRESUMO
Information on the potential ecological value of offshore oil and gas infrastructure is required as it reaches the end of its operational life and decisions must be made regarding the best practice option for decommissioning. This study uses baited remote underwater stereo-video systems to assess fish assemblages along an offshore subsea pipeline and in adjacent natural seabed habitats at â¼140â¯m depth on the North West Shelf of Western Australia. A total of 955 fish from 40 species and 25 families were recorded. Species richness was, on average 25% higher on the pipeline (6.48⯱â¯0.37 SE) than off (4.81⯱â¯0.28 SE) while relative abundance of fish was nearly double on the pipeline (20.38⯱â¯2.81 SE) than in adjacent natural habitats (10.97⯱â¯1.02 SE). The pipeline was characterised by large, commercially important species known to associate with complex epibenthic habitat and, as such, possessed a biomass of commercial fish ca 7.5 × higher and catch value ca. 8.6 × ($65.11⯱â¯$11.14 SE) than in adjacent natural habitats ($7.57⯱â¯$2.41 SE). This study has added to the knowledge of fish assemblage associations with subsea infrastructure and provides a greater understanding of the ecological and fisheries implications of decommissioning, helping to better inform decision-making on the fate of infrastructure.
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Pesqueiros , Peixes , Campos de Petróleo e Gás , Animais , Ecossistema , Biologia Marinha , Austrália OcidentalRESUMO
Women diagnosed with breast cancer before the age of 40 years who have a strong family history of breast and/or ovarian cancer were selected from an Australian population-based case-control-family study for large deletion screening within the BRCA1 promoter. Deletions within the BRCA1 promoter region are usually not detected by the methods applied in routine clinical mutation detection strategies. Fifty-one of the 66 women (77%) who met our inclusion criteria were tested for promoter deletions using linkage disequilibrium analysis of two BRCA1 polymorphic sites (C/G1802 and Pro871Leu) and multiplex ligation-dependent probe amplification. Two cases of BRCA1 promoter deletion involving exons 1A-2 and exons 1A-23 were detected. The morphology of the breast cancers arising in these women with BRCA1 promoter deletions was consistent with the morphology associated with other germline BRCA1 mutations. Large genomic deletions that involve the promoter regions of BRCA1 make up 20% (2/10) of all known BRCA1 mutations in this group of young women with a strong family history of breast and ovarian cancer. Our data support the inclusion of testing for large genomic alterations in the BRCA1 promoter region in routine clinical mutation detection within BRCA1.
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Neoplasias da Mama/genética , Deleção de Genes , Genes BRCA1 , Regiões Promotoras Genéticas/genética , Adulto , Feminino , Predisposição Genética para Doença/genética , Genótipo , Humanos , LinhagemRESUMO
The regulation of adenovirus type 5 gene expression by the E1a gene product was examined in microinjected Xenopus laevis oocytes. Chimeric genes were constructed which included the promoter region of early adenovirus type 5 gene 3 and the structural sequence which codes for the bacterial enzyme chloramphenicol-3-O-acetyltransferase (CAT). A plasmid containing this chimeric gene as well as plasmids containing the E1a gene were coinjected into oocyte nuclei. The presence of the E1a gene was shown to increase CAT activity by up to 8.5-fold over basal levels. Synthesis of the functional product from the E1a gene requires the removal of intron sequences by RNA splicing. The E1a gene and a derivative that precisely lacks the intron were equally effective in increasing CAT activity, suggesting that splicing of the primary E1a transcript is efficiently accomplished in the oocyte nucleus. This was confirmed by directly examining the E1a mRNAs by the S1 mapping procedure. A protein extract from adenovirus type 5-infected HeLa cells enriched for the E1a protein may supplant the E1a plasmid in enhancing CAT activity. Synthesis of the CAT enzyme after gene injection is invariant in oocytes from the same frog, but oocytes from different frogs show a high degree of variability in their ability to synthesize the CAT enzyme. Microinjected X. laevis oocytes appear to be an extremely useful system to study the effects of protein elements on transcription.
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Acetiltransferases/genética , Adenovírus Humanos/genética , Genes Virais , Genes , Oócitos/metabolismo , Transcrição Gênica , Adenovírus Humanos/enzimologia , Animais , Sequência de Bases , Cloranfenicol O-Acetiltransferase , Enzimas de Restrição do DNA , Feminino , Cinética , Microinjeções , Plasmídeos , XenopusRESUMO
Clinical and electrophysiologic findings on 136 patients (39 women and 97 men; mean age = 33.2 years) with traumatic peripheral nerve injuries were reviewed. Motor vehicular collisions (MVCs) caused 39.7% and gunshot wounds (GSWs) produced 32.4% of the nerve injuries studied. Other factors such as falls, lacerations, work-related injuries, knife wounds, and blunt traumas produced the remaining 27.9% of the nerve injuries in the study group. Peripheral nerves of the upper limbs (79.6%) were disproportionately damaged in MVCs compared with those of the lower limbs (20.4 %). In MVCs, the brachial plexus was involved in 37.0% and radial nerve in 22.2% of the cases. Patients with GSWs were predominantly men (88.6%) and slightly younger (mean age = 28.7 years). The frequencies of peripheral nerve injuries to the upper extremities (52.3%) and lower extremities (45.5%) were nearly similar in GSWs. The sciatic nerve was involved in 34.1% of GSWs, followed by the ulnar nerve (22.7%).
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Traumatismos dos Nervos Periféricos , Acidentes de Trabalho , Acidentes de Trânsito , Adolescente , Adulto , Idoso , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Neurofisiologia , Ferimentos não Penetrantes/complicações , Ferimentos Penetrantes/complicaçõesRESUMO
Activities of the adenine purine nucleotide cycle enzymes, i.e., adenylosuccinate (SAMP) synthetase, SAMP lyase, and adenosine 5'-monophosphate deaminse, were determined in hepatic tissue of rats fed and/or given injections of 3'-methyl-4-dimethylaminoazobenzene, 4'-methyl-4-dimethylaminoazobenzene, thioacetamide, ethionine, or 2-acetylaminofluorene. SAMP lyase activity showed an early increase in all regimens containing hepatocarcinogens. Adenosine 5'-monophosphate deaminse showed increases with 3'-methyl-4-dimethylaminoazobenzene and thioacetamide but not with ethionine or 2-acetylaminofluorene. SAMP synthetase either was nonresponsive or else showed inhibition to the carcinogens. Increase in SAMP lyase activity was noted as early as 48 to 72 hr following i.p. injections of these carcinogens. The response of SAMP lyase was not duplicated by analogs of carcinogens such as 4'-methyl-4-dimethylaminoazobenzene or methionine. These data imply interaction of active carcinogens with SAMP lyase and to some extent adenosine 5'-monophosphate deaminse or to some mechanism responsible for their synthesis and/or release. This interaction may be a significant component of the initiation phase of carcinogenesis.
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AMP Desaminase/metabolismo , Adenilossuccinato Liase/metabolismo , Adenilossuccinato Sintase/metabolismo , Carcinógenos/toxicidade , Ligases/metabolismo , Neoplasias Hepáticas Experimentais/metabolismo , Liases/metabolismo , Nucleotídeo Desaminases/metabolismo , Lesões Pré-Cancerosas/metabolismo , 2-Acetilaminofluoreno/toxicidade , Animais , Ativação Enzimática/efeitos dos fármacos , Etionina/toxicidade , Feminino , Metildimetilaminoazobenzeno/toxicidade , Ratos , Tioacetamida/toxicidade , Fatores de TempoRESUMO
Tetracycline induces transcription of the Tn10 tetracycline resistance gene (tetA) by binding to the tet repressor, thereby reducing the repressor's affinity for two operator sites that overlap the tet promoters. We characterized mutations in the tet repressor (tetRs mutations) that interfere with induction of tetA expression. The mutations were isolated on multicopy Tn10 tet plasmids by selecting for resistance to the inducer 5a,6-anhydrotetracycline. Under these conditions, maximal induction of tetA expression inhibits the growth of Escherichia coli K-12. DNA sequence analysis of 25 spontaneous tetRs mutations identified amino acid changes at 13 different positions clustered near the middle of the 207 amino acid residue sequence of tet repressor. This region (residues 64 to 107) is distinct from the bihelical DNA-binding motif of tet repressor (residues 26 to 47). The capacity of tetRs repressors to bind tet operator DNA and to respond to inducer was examined in vivo in tetA-lacZ fusion strains. In three cases, the capacity of tetRs repressors to bind tetracycline was examined in vitro using cell extracts enriched in repressor. Mutations 64Y (His64----Tyr) and 82H (Asn82----His) reduce the repressor's affinity for tetracycline more than 1000-fold and more than 100-fold, respectively, suggesting that His64 and Asn82 may be part of the inducer-binding site or directly involved in maintaining its conformation. Mutation 103I (Thr103----Ile) reduces the repressor's affinity for tetracycline less than tenfold, yet it interferes with induction to a greater extent than either 64Y or 82H, suggesting that 103I may also reduce the repressor's capacity to undergo a conformational change required for induction. The properties of tetRs mutants suggest that the region of amino acid residues 64 to 107 is involved in inducer binding and in signalling between the inducer-binding and operator-binding domains of the repressor.
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Proteínas de Bactérias/genética , Regulação da Expressão Gênica , Genes Bacterianos , Proteínas Repressoras/genética , Tetraciclina/metabolismo , Fatores de Transcrição/genética , Bacteriófagos , Sítios de Ligação , Escherichia coli , Óperon Lac , Mutação , Plasmídeos , Resistência a Tetraciclina/genéticaRESUMO
The poly(A) RNA of the Xenopus oocytes has been shown to include both single copy and interspersed transcripts. Interspersed maternal poly(A) RNAs contain repetitive sequence elements distributed within regions transcribed from single copy sequences. When renatured these RNAs form partially double-stranded RNA networks, and as shown earlier this can be utilized for preparative separation of interspersed maternal transcripts from maternal transcripts that remain single-stranded after renaturation (Anderson et al., 1982). The translational activity of these RNA fractions was tested in vitro, in wheat germ and reticulocyte systems. While the single-stranded fractions supported protein synthesis, the interspersed oocyte RNAs displayed little translational activity. Translational activity was measured in vivo by injection into the Xenopus oocyte. Oocytes previously injected with globin mRNA were injected with increasing amounts of single-stranded, double-stranded, or denatured double-stranded RNA fractions, and the amount of globin synthesis was determined. It was found that single-stranded RNA competes with globin mRNA for the limited translational apparatus of the oocyte, as manifested by a quantitative reduction of globin synthesis. However, globin synthesis was not affected when double-stranded RNA, either in renatured or denatured form, was injected. We conclude that the interspersed RNAs are not translated within the oocyte. The amount of single and double-stranded RNAs loaded onto polysomes in the injected oocytes was also determined. Sixty seven per cent of radio-iodinated single-stranded RNA pelleted with polysomes in injected oocytes, whereas less than 20% of similarly labeled double-stranded RNA pelleted with polysomes. This value is similar to that obtained when partially hydrolyzed RNA is injected, suggesting again that essentially none of the interspersed RNA is translated in vivo. The significance of these findings in relation to translational regulation during oogenesis and early development is discussed.