RESUMO
Prognosis of feline gastrointestinal mast cell tumours (FGIMCT), based on limited available literature, is described as guarded to poor, which may influence treatment recommendations and patient outcome. The purpose of this study is to describe the clinical findings, treatment response, and outcome of FGIMCT. Medical records of 31 cats diagnosed with and treated for FGIMCT were retrospectively reviewed. Data collected included signalment, method of diagnosis, tumour location (including metastatic sites), treatment type, cause of death and survival time. Mean age was 12.9 y. Diagnosis was made via cytology (n = 15), histopathology (n = 13) or both (n = 3). Metastatic sites included abdominal lymph node (n = 10), abdominal viscera (n = 4) and both (n = 2). Therapeutic approaches included chemotherapy alone (n = 15), surgery and chemotherapy (n = 7), glucocorticoid only (n = 6) and surgery and glucocorticoid (n = 3). Lomustine (n = 15) and chlorambucil (n = 12) were the most commonly used chemotherapy drugs. Overall median survival time was 531 d (95% confidence interval 334, 982). Gastrointestinal location, diagnosis of additional cancers, and treatment type did not significantly affect survival time. Cause of death was tumour-related or unknown (n = 12) and unrelated (n = 8) in the 20 cats dead at the time of analysis. The prognosis for cats with FGIMCT may be better than previously reported, with 26% of cats deceased from an unrelated cause. Surgical and medical treatments (including prednisolone alone) were both associated with prolonged survival times. Treatment other than prednisolone may not be necessary in some cats. Continued research into prognostic factors and most effective treatment strategies are needed.
Assuntos
Doenças do Gato/patologia , Doenças do Gato/terapia , Neoplasias Gastrointestinais/terapia , Neoplasias Gastrointestinais/veterinária , Sarcoma de Mastócitos/veterinária , Animais , Antineoplásicos/uso terapêutico , Gatos , Bases de Dados Factuais , Feminino , Neoplasias Gastrointestinais/patologia , Hospitais Veterinários , Estimativa de Kaplan-Meier , Masculino , Mastócitos/efeitos dos fármacos , Mastócitos/patologia , Sarcoma de Mastócitos/patologia , Sarcoma de Mastócitos/terapia , Estadiamento de Neoplasias , Estudos Retrospectivos , Faculdades de Medicina Veterinária , Sobrevida , Resultado do Tratamento , Estados UnidosRESUMO
The purpose of this study was to provide an initial assessment of the potential biologic activity of toceranib phosphate (Palladia®, Pfizer Animal Health, Madison, NJ, USA) in select solid tumours in dogs. Cases in which toceranib was used to treat dogs with apocrine gland anal sac adenocarcinoma (AGASACA), metastatic osteosarcoma (OSA), thyroid carcinoma, head and neck carcinoma and nasal carcinoma were included. Clinical benefit (CB) was observed in 63/85 (74%) dogs including 28/32 AGASACA [8 partial response (PR), 20 stable disease (SD)], 11/23 OSAs (1 PR and 10 SD), 12/15 thyroid carcinomas (4 PR and 8 SD), 7/8 head and neck carcinomas [1 complete response (CR), 5 PR and 1 SD] and 5/7 (1 CR and 4 SD) nasal carcinomas. For dogs experiencing CB, the median dose of toceranib was 2.8 mg kg(-1) , 36/63 (58.7%) were dosed on a Monday/Wednesday/Friday basis and 47/63 (74.6%) were treated 4 months or longer. Although these data provide preliminary evidence that toceranib exhibits CB in dogs with certain solid tumours, future prospective studies are necessary to define its true activity.
Assuntos
Antineoplásicos/uso terapêutico , Doenças do Cão/tratamento farmacológico , Indóis/uso terapêutico , Neoplasias/veterinária , Pirróis/uso terapêutico , Receptores Proteína Tirosina Quinases/antagonistas & inibidores , Adenocarcinoma/tratamento farmacológico , Adenocarcinoma/veterinária , Neoplasias das Glândulas Anais/tratamento farmacológico , Sacos Anais , Animais , Glândulas Apócrinas , Neoplasias Ósseas/tratamento farmacológico , Neoplasias Ósseas/veterinária , Carcinoma/tratamento farmacológico , Carcinoma/veterinária , Cães , Feminino , Neoplasias de Cabeça e Pescoço/tratamento farmacológico , Neoplasias de Cabeça e Pescoço/veterinária , Indóis/farmacologia , Masculino , Neoplasias/tratamento farmacológico , Neoplasias Nasais/tratamento farmacológico , Neoplasias Nasais/veterinária , Osteossarcoma/tratamento farmacológico , Osteossarcoma/veterinária , Pirróis/farmacologia , Neoplasias Cutâneas/tratamento farmacológico , Neoplasias Cutâneas/veterinária , Neoplasias da Glândula Tireoide/tratamento farmacológico , Neoplasias da Glândula Tireoide/veterináriaRESUMO
BACKGROUND: Mast cell tumors (MCT) are common cutaneous tumors in dogs and when not amenable to surgical excision can present a therapeutic challenge. New treatment protocols for unresectable MCT are needed. HYPOTHESIS: The combination of toceranib, prednisone, and hypofractionated radiation treatment (RT) will be well tolerated and efficacious. ANIMALS: Seventeen client-owned dogs with measurable MCT amenable to RT. METHODS: Prospective clinical trial. All dogs received prednisone, omeprazole, diphenhydramine, and toceranib. Toceranib was administered for 1 week before initiating RT, consisting of 24 Gy delivered in 3 or 4 fractions. RESULTS: On an intent-to-treat basis, the overall response rate was 76.4%, with 58.8% of dogs achieving a complete response and 17.6% a partial response. The median time to best response was 32 days, and the median progression-free interval was 316 days. The overall median survival time was not reached with a median follow-up of 374 days. The most common toxicoses were gastrointestinal and hepatic. CONCLUSIONS AND CLINICAL IMPORTANCE: The combination of hypofractionated RT, toceranib, and prednisone was tolerated and efficacious in the majority of dogs. Response rates and durations were higher than those reported for toceranib as a single-agent treatment for MCT. This combination is a viable treatment option for unresectable MCT.
Assuntos
Protocolos de Quimioterapia Combinada Antineoplásica/uso terapêutico , Doenças do Cão/tratamento farmacológico , Doenças do Cão/radioterapia , Sarcoma de Mastócitos/veterinária , Neoplasias Cutâneas/veterinária , Animais , DNA de Neoplasias/química , DNA de Neoplasias/genética , Intervalo Livre de Doença , Doenças do Cão/patologia , Cães , Feminino , Indóis/administração & dosagem , Estimativa de Kaplan-Meier , Masculino , Sarcoma de Mastócitos/tratamento farmacológico , Sarcoma de Mastócitos/patologia , Sarcoma de Mastócitos/radioterapia , Reação em Cadeia da Polimerase/veterinária , Prednisona/administração & dosagem , Estudos Prospectivos , Proteínas Proto-Oncogênicas c-kit/genética , Pirróis/administração & dosagem , Radiografia , Neoplasias Cutâneas/diagnóstico por imagem , Neoplasias Cutâneas/tratamento farmacológico , Neoplasias Cutâneas/patologiaRESUMO
BACKGROUND: Feline nasal lymphoma (NLSA) is a condition for which no standard of care exists. HYPOTHESIS: There is no difference in survival times of cats with NLSA treated with single or multimodality therapy. ANIMALS: Records from 97 cats diagnosed with NLSA were examined. METHODS: The purpose of this retrospective study was to compare the survival times of cats with NLSA treated with radiation therapy (RT) alone, chemotherapy alone, or RT + chemotherapy and identify potential prognostic variables that affected survival. Cats were grouped according to therapy: RT + chemotherapy (n = 60), RT alone (n = 19), or chemotherapy alone (n = 18). RESULTS: Survival was calculated with 2 methods. The 1st survival analysis (method A) included all cats, but counted only deaths caused by progressive NLSA. The median survival time (MST), regardless of therapy modality, was 536 days. The 2nd survival analysis (method B) also included all cats and counted all deaths, regardless of cause, as events. The overall MST calculated for all deaths was 172 days. A negative independent prognostic variable identified was anemia (P < .001), and positive independent prognostic variables were a complete response to therapy (P < .001) and total radiation dose >32 Gy (P= .03). CONCLUSIONS AND CLINICAL IMPORTANCE: There were no significant differences in survival times among the 3 treatment groups but these results suggest that the addition of higher doses of RT to a cat's treatment protocol may control local disease and therefore influence survival.
Assuntos
Doenças do Gato/mortalidade , Linfoma/veterinária , Neoplasias Nasais/veterinária , Animais , Doenças do Gato/tratamento farmacológico , Doenças do Gato/radioterapia , Gatos , Terapia Combinada/veterinária , Feminino , Linfoma/tratamento farmacológico , Linfoma/mortalidade , Linfoma/radioterapia , Masculino , Neoplasias Nasais/tratamento farmacológico , Neoplasias Nasais/mortalidade , Neoplasias Nasais/radioterapia , Estudos Retrospectivos , Taxa de Sobrevida , Resultado do TratamentoRESUMO
The purpose of this retrospective study was to compare Rottweilers diagnosed with osteosarcoma (OSA) with other breeds to determine whether Rottweilers experienced a more aggressive form of the disease. Two hundred and fifty-eight dogs were evaluated (102 clinical and 156 necropsy cases). In the necropsy population, Rottweilers had a younger mean age at death (7.3 versus 9 years, P = 0.006). There were no significant differences between Rottweilers and other breeds in age at diagnosis, median disease-free interval or survival time. However, Rottweilers were more likely to have metastasis to the brain (7 versus 0%, P = 0.03). These results suggest that OSA in Rottweilers may have a different biological behaviour, but this study did not confirm that these differences were associated with a worse outcome.
RESUMO
The advent of transcription profiling technologies has provided researchers with an unprecedented ability to study biological processes. Accordingly, a custom-made Affymetrix GeneChip, constituting >86% of the Staphylococcus aureus genome, was used to identify open reading frames that are regulated by agr and/or SarA, the two best-studied regulators of the organism's virulence response. RNA extracted from wild-type cells and agr, sarA, and agr sarA mutant cells in the early-, mid-, and late-log and stationary phases of growth was analyzed. Open reading frames with transcription patterns expected of genes either up- or downregulated in an agr- and/or SarA-dependent manner were identified. Oligonucleotide microarray and Northern blot analyses confirmed that the transcription of several known virulence genes, including hla (alpha-toxin) and spa (protein A), is regulated by each effector and provided insights about the regulatory cascades involved in both alpha-hemolysin and protein A expression. Several putative virulence factors were also identified as regulated by agr and/or SarA. In addition, genes that are involved in several biological processes but which are difficult to reconcile as playing a direct role in the organism's pathogenesis also appeared to be regulated by each effector, suggesting that products of both the agr and the sarA locus are more-global transcription regulators than previously realized.
Assuntos
Proteínas de Bactérias/metabolismo , Proteínas de Ligação a DNA/metabolismo , Genes Bacterianos , Staphylococcus aureus/genética , Transativadores , Fatores de Transcrição/metabolismo , Toxinas Bacterianas/genética , Regulação para Baixo , Perfilação da Expressão Gênica , Regulação Bacteriana da Expressão Gênica , Proteínas Hemolisinas/genética , Análise de Sequência com Séries de Oligonucleotídeos , Fases de Leitura Aberta , Proteína Estafilocócica A/genética , Staphylococcus aureus/patogenicidade , Regulação para Cima , Virulência/genéticaRESUMO
We show that co-expression of rat Galphas together with type I, II, IV, or VI mammalian adenylyl cyclase (AC) can suppress the growth defect of cyr1 strains of Saccharomyces cerevisiae, which lack a functional endogenous AC. Complemention of cvr1 is not observed in the absence of Galphas, indicating that the mammalian ACs retain their normal regulatory behavior in yeast. Selection for Galphas-independent growth of (cyr1 strains expressing type IV AC yielded several ACIV mutants with enhanced basal activity, each of which had a single amino acid substitution in the conserved C1a or C2a region of the protein. Expression of two of the mutant ACs in HEK293 cells resulted in increased levels of cAMP and elevated adenylyl cyclase activity. Further selection for reverting mutations in one of these constitutively active AC mutants yielded three independent intragenic suppressor mutations. The distribution of the activating and suppressor mutations throughout both C1a and C2a is consistent with a model in which the enhanced basal activity results from an increase in the affinity between C1a and C2a. These results demonstrate the utility of Saccharomyces as a tool for the identification of informative mutant forms of mammalian ACs.
Assuntos
Adenilil Ciclases/genética , Adenilil Ciclases/metabolismo , Saccharomyces cerevisiae/genética , Adenilil Ciclases/química , Sequência de Aminoácidos , Animais , Linhagem Celular , Genes Reporter , Teste de Complementação Genética , Guanosina Trifosfato/metabolismo , Proteínas Heterotriméricas de Ligação ao GTP/genética , Proteínas Heterotriméricas de Ligação ao GTP/metabolismo , Humanos , Isoenzimas/genética , Isoenzimas/metabolismo , Mamíferos , Modelos Moleculares , Dados de Sequência Molecular , Conformação Proteica , Ratos , Proteínas Recombinantes/química , Proteínas Recombinantes/metabolismo , Saccharomyces cerevisiae/enzimologia , Saccharomyces cerevisiae/crescimento & desenvolvimento , Homologia de Sequência de Aminoácidos , Transfecção , beta-Galactosidase/genética , beta-Galactosidase/metabolismoRESUMO
Short-interval scanning of patients offers a detailed understanding of the natural progression of tumor tissue, as revealed through imaging markers such as contrast enhancement and edema, prior to therapy. Following treatment, short-interval scanning can also provide evidence of attenuation of growth rates. We present a longitudinal imaging study of a patient with glioblastoma multiforme (GBM) scanned 15 times in 104 days on a 3 T MR scanner. Images were analyzed independently by two automated algorithms capable of creating detailed maps of tumor changes as well as volumetric analysis. The algorithms, a nearest-neighbor-based tissue segmentation and a surface-modeling algorithm, tracked the patient's response to temozolomide, showing an attenuation of growth. The need for surrogate imaging end-points, of which growth rates are an example, is discussed. Further, the strengths of these algorithms, the insight gained by short-interval scanning, and the need for a better understanding of imaging markers are also described.
Assuntos
Algoritmos , Neoplasias Encefálicas/patologia , Glioblastoma/patologia , Progressão da Doença , Humanos , Estudos Longitudinais , Imageamento por Ressonância Magnética , Masculino , Pessoa de Meia-Idade , Fatores de TempoRESUMO
Cac3p/Msi1p, the Saccharomyces cerevisiae homolog of retinoblastoma-associated protein 48 (RbAp48), is a component of chromatin assembly factor I (CAF-I), a complex that assembles histones H3 and H4 onto replicated DNA. CAC3 overexpression also suppresses the RAS/cyclic AMP (cAMP) signal transduction pathway by an unknown mechanism. We investigated this mechanism and found that CAC3 suppression of RAS/cAMP signal transduction was independent of either CAC1 or CAC2, subunits required for CAF-I function. CAC3 suppression was also independent of other chromatin-modifying activities, indicating that Cac3p has at least two distinct, separable functions, one in chromatin assembly and one in regulating RAS function. Unlike Cac1p, which localizes primarily to the nucleus, Cac3p localizes to both the nucleus and the cytoplasm. In addition, Cac3p associates with Npr1p, a cytoplasmic kinase that stablizes several nutrient transporters by antagonizing a ubiquitin-mediated protein degradation pathway. Deletion of NPR1, like overexpression of Cac3p, suppressed the RAS/cAMP pathway. Furthermore, NPR1 overexpression interfered with the ability of CAC3 to suppress the RAS/cAMP pathway, indicating that extra Cac3p suppresses the RAS/cAMP pathway by sequestering Npr1p. Deletion of NPR1 did not affect the quantity, phosphorylation state, or localization of Ras2p. Consistent with the idea that Npr1p exerts its effect on the RAS/cAMP pathway by antagonizing a ubiquitin-mediated process, excess ubiquitin suppressed both the heat shock sensitivity and the sporulation defects caused by constitutive activation of the RAS/cAMP pathway. Thus, CAC3/MSI1 regulates the RAS/cAMP pathway via a chromatin-independent mechanism that involves the sequestration of Npr1p and may be due to the increased ubiquitination of an Npr1p substrate.
Assuntos
Proteínas Cromossômicas não Histona , Proteínas de Ligação a DNA/metabolismo , Proteínas Fúngicas/metabolismo , Proteínas Quinases , Proteínas de Saccharomyces cerevisiae , Supressão Genética , Proteínas ras/genética , Alelos , Núcleo Celular/metabolismo , Fator 1 de Modelagem da Cromatina , AMP Cíclico/metabolismo , Citoplasma/metabolismo , DNA/metabolismo , Proteínas Fúngicas/genética , Proteínas Fúngicas/fisiologia , Galactose/metabolismo , Genótipo , Glucose/metabolismo , Proteínas de Fluorescência Verde , Temperatura Alta , Proteínas Luminescentes/metabolismo , Fenótipo , Plasmídeos/metabolismo , Testes de Precipitina , Ligação Proteica , Proteínas Recombinantes de Fusão/metabolismo , Transdução de Sinais , Fatores de Tempo , Técnicas do Sistema de Duplo-Híbrido , Proteínas ras/metabolismo , Proteínas ras/fisiologiaRESUMO
The recruitment of ZipA to the septum by FtsZ is an early, essential step in cell division in Escherichia coli. We have used polymerase chain reaction-mediated random mutagenesis in the yeast two-hybrid system to analyze this interaction and have identified residues within a highly conserved sequence at the C terminus of FtsZ as the ZipA binding site. A search for suppressors of a mutation that causes a loss of interaction (ftsZ(D373G)) identified eight different changes at two residues within this sequence. In vitro, wild type FtsZ interacted with ZipA with a high affinity in an enzyme-linked immunosorbent assay, whereas FtsZ(D373G) failed to interact. Two mutant proteins examined restored this interaction significantly. In vivo, the alleles tested are significantly more toxic than the wild type ftsZ and cannot complement a deletion. We have shown that a fusion, which encodes the last 70 residues of FtsZ in the two-hybrid system, is sufficient for the interaction with FtsA and ZipA. However, when the wild type sequence is compared with one that encodes FtsZ(D373G), no interaction was seen with either protein. Mutations surrounding Asp-373 differentially affected the interactions of FtsZ with ZipA and FtsA, indicating that these proteins bind the C terminus of FtsZ differently.
Assuntos
Proteínas de Bactérias/metabolismo , Proteínas de Transporte/metabolismo , Proteínas de Ciclo Celular/metabolismo , Proteínas do Citoesqueleto , Proteínas de Escherichia coli , Escherichia coli/metabolismo , Sequência de Aminoácidos , Proteínas de Bactérias/química , Proteínas de Bactérias/genética , Proteínas de Transporte/química , Proteínas de Transporte/genética , Proteínas de Ciclo Celular/química , Proteínas de Ciclo Celular/genética , Divisão Celular/genética , Escherichia coli/genética , Modelos Moleculares , Conformação Molecular , Dados de Sequência Molecular , Mutagênese Sítio-Dirigida , Fenótipo , Reação em Cadeia da Polimerase , Ligação Proteica , Saccharomyces cerevisiae/genética , Técnicas do Sistema de Duplo-HíbridoRESUMO
BACKGROUND AND PURPOSE: Two 3D image analysis algorithms, nearest-neighbor tissue segmentation and surface modeling, were applied separately to serial MR images in patients with glioblastoma multiforme (GBM). Rates of volumetric change were tracked for contrast-enhancing tumor tissue. Our purpose was to compare the two image analysis algorithms in their ability to track tumor volume relative to a manually defined standard of reference. METHODS: Three-dimensional T2-weighted and contrast-enhanced T1-weighted spoiled gradient-echo MR volumes were acquired in 10 patients with GBM. One of two protocols was observed: 1) a nearest-neighbor algorithm, which used manually determined or propagated tags and automatically segmented tissues into specific classes to determine tissue volume; or 2) a surface modeling algorithm, which used operator-defined contrast-enhancing boundaries to convert traced points into a parametric mesh model. Volumes were automatically calculated from the mesh models. Volumes determined by each algorithm were compared with the standard of reference, generated by manual segmentation of contrast-enhancing tissue in each cross section of a scan. RESULTS: Nearest-neighbor algorithm enhancement volumes were highly correlated with manually segmented volumes, as were growth rates, which were measured in terms of halving and doubling times. Enhancement volumes generated by the surface modeling algorithm were also highly correlated with the standard of reference, although growth rates were not. CONCLUSION: The nearest-neighbor tissue segmentation algorithm provides significant power in quantifying tumor volume and in tracking growth rates of contrast-enhancing tissue in patients with GBM. The surface modeling algorithm is able to quantify tumor volume reliably as well.
Assuntos
Algoritmos , Neoplasias Encefálicas/diagnóstico , Glioma/diagnóstico , Imageamento por Ressonância Magnética , Adolescente , Adulto , Idoso , Idoso de 80 Anos ou mais , Neoplasias Encefálicas/patologia , Divisão Celular , Criança , Pré-Escolar , Glioma/patologia , Humanos , Processamento de Imagem Assistida por Computador , Imageamento Tridimensional , Pessoa de Meia-Idade , Estudos ProspectivosRESUMO
In Escherichia coli, FtsZ, a homologue of eukaryotic tubulins, and ZipA, a membrane-anchored protein that binds to FtsZ, are two essential components of the septal ring structure that mediates cell division. Recent data indicate that ZipA is involved in the assembly of the ring by linking FtsZ to the cytoplasmic membrane and that the ZipA-FtsZ interaction is mediated by their C-terminal domains. We present the X-ray crystal structures of the C-terminal FtsZ-binding domain of ZipA and a complex between this domain and a C-terminal fragment of FtsZ. The ZipA domain is a six-stranded beta-sheet packed against three alpha-helices and contains the split beta-alpha-beta motif found in many RNA-binding proteins. The uncovered side of the sheet incorporates a shallow hydrophobic cavity exposed to solvent. In the complex, the 17-residue FtsZ fragment occupies this entire cavity of ZipA and binds as an extended beta-strand followed by alpha-helix. An alanine-scanning mutagenesis analysis of the FtsZ fragment was also performed, which shows that only a small cluster of the buried FtsZ side chains is critical in binding to ZipA.
Assuntos
Proteínas de Bactérias/metabolismo , Proteínas de Transporte/metabolismo , Proteínas de Ciclo Celular/metabolismo , Proteínas do Citoesqueleto , Proteínas de Escherichia coli , Fragmentos de Peptídeos/metabolismo , Sequência de Aminoácidos , Proteínas de Bactérias/química , Proteínas de Transporte/química , Proteínas de Ciclo Celular/química , Cristalografia por Raios X , Escherichia coli/metabolismo , Modelos Moleculares , Dados de Sequência Molecular , Fragmentos de Peptídeos/química , Conformação Proteica , Homologia de Sequência de AminoácidosRESUMO
PURPOSE: To describe and compare the intra- and interexaminer reliability of three length measurement techniques and to determine if the three measurement techniques yield significantly different measurements. METHOD: Two experienced, mother-baby nurses each obtained length measurements using the supine, paper barrier, and Auto-length measurement techniques twice each from 48 healthy term infants. The nurses were blind to their own and to each other's measurements. The order of the nurses and the order of the measurement techniques were randomized. RESULTS: For intraexaminer reliability, RN-1 had smaller mean absolute differences for the Auto-length measurements. RN-2 had similar mean absolute differences for all three measurement techniques. The percentage of differences < or = 1 cm were smallest for the supine measurements for RN-1 and not remarkably different between the measurement techniques for RN-2. For interexaminer reliability, the mean absolute differences between the pairs of measurements were smallest for the Auto-length measurements for Set-1 and for the paper-barrier measurements for Set-2. The percentage of differences < or = 1 cm between the pairs of measurements for Set-1 were not remarkably different and were lowest for the supine measurements for Set-2. The mean measurements obtained by the supine, paper-barrier, and the Auto-length measurements were respectively: 50.88, 50.33, and 49.67 cm. The differences between the means were statistically significant (X2 = 56.56, p = .0000). CONCLUSIONS: The differences between length measurements by individual examiners and pairs of examiners are relatively large. Clinicians should be aware of the magnitude of error in length measurements and should interpret length measurements with caution. These findings also demonstrate that all clinicians in any setting should use the same technique to obtain length measurements.
Assuntos
Antropometria/métodos , Estatura , Recém-Nascido , Viés , Humanos , Avaliação em Enfermagem/métodos , Variações Dependentes do Observador , Reprodutibilidade dos Testes , Método Simples-Cego , Decúbito DorsalRESUMO
This in vitro study investigated the temperature changes experienced during electric welding of titanium to determine if the welding heat presented a potential danger to pulpal vitality. Welds were applied to cast titanium simulations of a three-unit fixed partial denture containing two thermocouples measuring temperature changes. Mean maximal temperature changes were 127.4 degrees F near the weld and 68.6 F degrees at the axial wall. The mean times for the temperature to drop to within 10.0 degrees F of the starting temperature ranged from 84.1 to 133.7 seconds. The relatively low temperatures recorded in this study suggest that further investigation is warranted into the use of the welder intraorally.
Assuntos
Titânio , Soldagem/métodos , Técnica de Fundição Odontológica , Prótese Parcial Fixa , Estudos de Avaliação como Assunto , Humanos , Técnicas In Vitro , Temperatura , Condutividade Térmica , Soldagem/instrumentação , Soldagem/estatística & dados numéricosRESUMO
In Saccharomyces cerevisiae, adenylate cyclase activity is controlled by Ras1p and Ras2p. Activation of the Ras proteins is in turn controlled by the GTPase-activating proteins (GAPs), Ira1p and Ira2p, and the guanine nucleotide exchange factor (GNEF), Cdc25p. We have characterized Cdc25p enzymologically in order to gain information about the mechanism of Cdc25p-mediated guanine nucleotide exchange and to appreciate how the activity of a GNEF is integrated as a part of a basic molecular switch module consisting of Ras, GNEF, and GAP. Using Ras2p and a catalytic fragment of Cdc25p, both expressed in and purified from Escherichia coli, we determined that Cdc25p has a Km for Ras2p-GDP of 160 nM and a maximal rate of 0.20 s-1. The Km of Cdc25p for Ras2p complexed to GTP is 3-fold greater than that for Ras2p complexed to GDP. The Km of free GDP is about 2-fold higher than the Km of free GTP. This suggests that Cdc25p activates Ras2p primarily by equilibrating Ras2p with the pool of free guanine nucleotides in the cell rather than by driving Ras2p inexorably into the activated state. This renders Ras activation potentially subject to energy charge fluctuations in the cell. The free guanine nucleotide affects kcat, indicating that the rate-limiting step is nucleotide association. Finally, we demonstrated that dominant negative alleles of Ras2p are potent competitive inhibitors of Cdc25p. These data, in conjunction with the kinetic data, are consistent with the hypothesis that Cdc25p catalyzes guanine nucleotide exchange by stabilizing a nucleotide-free intermediate of Ras.
Assuntos
Proteínas de Ciclo Celular , Proteínas Fúngicas/metabolismo , Proteínas de Ligação ao GTP/metabolismo , Guanosina Difosfato/metabolismo , Guanosina Trifosfato/metabolismo , Saccharomyces cerevisiae/metabolismo , Proteínas ras , ras-GRF1 , Cromatografia de Afinidade , Clonagem Molecular , Eletroforese em Gel de Poliacrilamida , Escherichia coli , Proteínas Fúngicas/isolamento & purificação , Cinética , Proteínas Recombinantes/isolamento & purificação , Proteínas Recombinantes/metabolismo , Proteínas de Saccharomyces cerevisiaeRESUMO
A prototype high-speed tape target transport is constructed for use in a high-repetition-rate laser plasma source. To reduce plasma debris, a 1000-5000-A-thick film of target material is supported by thin Mylar tape backing. Tape is transported to the laser focal volume at a maximum velocity of 356 cm/s, a rate sufficient to accommodate laser repetition rates of 1 kHz. The transport is fully vacuum compatible and can be retracted and then isolated from the laser plasma vacuum enclosure during tape reel replacement. The operating characteristics of the transport are described.
RESUMO
Soft-x-ray projection imaging is demonstrated by the use of 14-nm radiation from a laser plasma source and a single-surface multilayer-coated ellipsoidal condenser. Aberrations in the condenser and the Schwarzschild imaging objective are characterized and correlated with imaging performance. A new Schwarzschild housing, designed for improved alignment stability, is described.
RESUMO
We investigated the relationship between two regulatory genes, livR and lrp, that map near min 20 on the Escherichia coli chromosome. livR was identified earlier as a regulatory gene affecting high-affinity transport of branched-chain amino acids through the LIV-I and LS transport systems, encoded by the livJ and livKHMGF operons. lrp was characterized more recently as a regulatory gene of a regulon that includes operons involved in isoleucine-valine biosynthesis, oligopeptide transport, and serine and threonine catabolism. The expression of each of these livR- and lrp-regulated operons is altered in cells when leucine is added to their growth medium. The following results demonstrate that livR and lrp are the same gene. The lrp gene from a livR1-containing strain was cloned and shown to contain two single-base-pair substitutions in comparison with the wild-type strain. Mutations in livR affected the regulation of ilvIH, an operon known to be controlled by lrp, and mutations in lrp affected the regulation of the LIV-I and LS transport systems. Lrp from a wild-type strain bound specifically to several sites upstream of the ilvIH operon, whereas binding by Lrp from a livR1-containing strain was barely detectable. In a strain containing a Tn10 insertion in lrp, high-affinity leucine transport occurred at a high, constitutive level, as did expression from the livJ and livK promoters as measured by lacZ reporter gene expression. Taken together, these results suggest that Lrp acts directly or indirectly to repress livJ and livK expression and that leucine is required for this repression. This pattern of regulation is unusual for operons that are controlled by Lrp.
Assuntos
Aminoácidos de Cadeia Ramificada/metabolismo , Escherichia coli/metabolismo , Leucina/metabolismo , Aminoácidos de Cadeia Ramificada/genética , Transporte Biológico , Clonagem Molecular , Escherichia coli/genética , Regulação Bacteriana da Expressão Gênica , Teste de Complementação Genética , Óperon Lac , Leucina/genética , Óperon , Plasmídeos , Regiões Promotoras Genéticas , Proteínas Recombinantes de FusãoRESUMO
Projection imaging of 0.1-microm lines and spaces is demonstrated with a Mo/Si multilayer coated Schwarzschild objective and 14-nm illumination from a laser plasma source. This structure has been etched into a silicon wafer by using a trilevel resist and reactive ion etching. Low-contrast modulation at 0.05-microm lines and spaces is observed in polymethylmethacrylate.