Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 144
Filtrar
1.
J Med Entomol ; 59(6): 2013-2021, 2022 11 16.
Artigo em Inglês | MEDLINE | ID: mdl-36130183

RESUMO

Knowledge of the hibernation site preferences and the factors which influence winter survival in these hibernation sites may enhance understanding of mosquito population dynamics after winter and how arboviruses persist in temperate regions. Our study quantified the number of adult overwintering mosquitoes in cellars and aboveground constructions and analyzed survival rates in relation to the environmental conditions in these sites. During the winters 2016/2017 and 2018/2019, 149 different constructions in Northwest Germany were sampled for mosquitoes. Mosquitoes were detected in 44% of the cellars and in 33% of the aboveground constructions. Culex p. pipiens Linnaeus was the most abundant species in cellars, whereas high numbers of Anopheles messeae Falleroni were collected from a single barn. Subsequently, an enclosure study was conducted during 2019/2020. Overwintering field-collected Cx. p. pipiens and An. messeae were divided into groups with or without fructose availability, and placed in cages with different man-made hibernations sites, where temperature and relative humidity were recorded hourly. For both species, increasing mean temperatures (5-16°C) but not mean relative humidity (58-94%) were correlated with winter mortality rates of the mosquitoes. The lipid measurements were greater and mortality rates were lower when both species were provided fructose. Larger specimens (determined by wing length) stored more lipids, and in Cx. p pipiens, but not in An. messeae, survival probability of large specimens was significantly greater than for small females. Mosquitoes showed a distinct pattern in the selection of overwintering sites, while temperature was an important driver for survival.


Assuntos
Anopheles , Culex , Culicidae , Hibernação , Feminino , Animais , Temperatura , Umidade , Frutose
2.
Med Vet Entomol ; 35(3): 379-388, 2021 09.
Artigo em Inglês | MEDLINE | ID: mdl-33394505

RESUMO

Mosquitoes (Diptera: Culicidae) use certain resting sites during their inactive phase. The microclimatic conditions of these resting sites might affect their physiology and vectorial capacity. In this study, we combined a field and a laboratory study to investigate the natural resting site and temperature preferences of mosquitoes. The field study was conducted at a forest close to Oldenburg (Lower Saxony, Germany) from May to October 2018. Mosquitoes were collected in five different natural habitats with seven replicates each. Temperature was recorded hourly at each site. Significantly more mosquitoes were collected in deadwood (predominantly Culiseta morsitans/fumipennis) and shaded herb layer (predominantly Aedes species) compared to unshaded herb layer or broadleaf and coniferous trees. GLMMs revealed resting site habitats as the best predictor to explain the observed preference patterns, but microclimatic conditions are also involved in mosquito resting site selection. Most mosquitoes were collected at resting sites with relatively colder and more stable temperatures. In concert, laboratory choice experiments with a thermal gradient ring demonstrated that Cs. morsitans/fumipennis avoid temperatures over 30 °C. Understanding the small-scaled resting site preferences and the related microclimatic conditions can improve mosquito collection techniques and refine the prediction of mosquito-borne pathogen transmission.


Assuntos
Aedes , Culicidae , Animais , Ecossistema , Alemanha , Microclima , Temperatura
3.
Sci Rep ; 10(1): 17613, 2020 10 19.
Artigo em Inglês | MEDLINE | ID: mdl-33077803

RESUMO

Accurate species identification is the prerequisite to assess the relevance of mosquito specimens, but is often hindered by missing or damaged morphological features. The present study analyses the applicability of wing geometric morphometrics as a low-cost and practical alternative to identify native mosquitoes in Germany. Wing pictures were collected for 502 female mosquitoes of five genera and 19 species from 80 sampling sites. The reliable species identification based on interspecific wing geometry of 18 landmarks per specimen was tested. Leave-one-out cross validation revealed an overall accuracy of 99% for the genus and 90% for the species identification. Misidentifications were mainly due to three pairings of Aedes species: Aedes annulipes vs. Aedes cantans, Aedes cinereus vs. Aedes rossicus and Aedes communis vs. Aedes punctor. Cytochrome oxidase subunit I (COI) gene region was sequenced to validate the morphological and morphometric identification. Similar to the results of the morphometric analysis, the same problematic three Aedes-pairs clustered, but most other species could be well separated. Overall, our study underpins that morphometric wing analysis is a robust tool for reliable mosquito identification, which reach the accuracy of COI barcoding.


Assuntos
Culicidae/anatomia & histologia , Asas de Animais/anatomia & histologia , Aedes/anatomia & histologia , Aedes/genética , Animais , Culicidae/genética , Código de Barras de DNA Taxonômico , Complexo IV da Cadeia de Transporte de Elétrons/genética , Feminino , Alemanha
4.
Domest Anim Endocrinol ; 72: 106445, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-32247992

RESUMO

The aim of the present study was to measure salivary cortisol concentrations of horses before and after hypothalamic-pituitary-adrenal (HPA) axis stimulation by means of liquid chromatography-tandem-mass spectrometry (LC-MS/MS) and an immunoassay (cELISA) for method comparison. Nine clinically healthy horses participated in the study. An ACTH stimulation test was performed. Saliva samples were collected before (T0) and 60 (T60) min after intravenous injection of 1 µg/kg BW synthetic ACTH1-24. LC-MS/MS was assessed for the determination of equine salivary cortisol. The results of these measurements were then compared to the results obtained by a cELISA, which has previously been validated for use in horses. The Pearson correlation coefficient was calculated and showed no correlation at T0 (r = -0.2452; P = 0.5249) and significantly correlated results at T60 (r = 0.8334; P = 0.0053). Bland-Altman-Plots of T60 revealed that immunoassay measurements led to higher outcome values than LC-MS/MS. On average, immunoassay results were 2.3 times higher. Poor agreement between both methods at T0 is potentially a consequence of inaccuracy in the very low measuring range of the immunoassay, and to a smaller extent, structurally similar cross-reacting agents and matrix effects, which might bias the results. Overestimation of immunoassay results at T60 might be due to different standardization of both methods, non-avoidable matrix effects on the antigen-antibody interaction in the ELISA, and possibly cross-reactions of other steroids. While immunoassay measurements of equine salivary cortisol yielded higher but reasonably correlated results for elevated cortisol concentrations after stimulation of the HPA axis, LC-MS/MS provided more accurate results, particularly for baseline cortisol concentrations close to the limit of detection of the ELISA.


Assuntos
Cromatografia Líquida/veterinária , Ensaio de Imunoadsorção Enzimática/veterinária , Cavalos/metabolismo , Hidrocortisona/química , Hidrocortisona/metabolismo , Saliva/química , Espectrometria de Massas em Tandem/veterinária , Hormônio Adrenocorticotrópico/farmacologia , Animais , Sensibilidade e Especificidade
5.
Domest Anim Endocrinol ; 72: 106419, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-31958644

RESUMO

This study describes steroid profiles in equine plasma before and after ACTH stimulation. In human medicine, other steroids have been shown to have a more pronounced reaction to an ACTH stimulation test than cortisol. This study aimed to determine if the same was true for the horse. A total of 11 clinically healthy horses were selected for this study. Ethylenediaminetetraacetic acid plasma samples were taken before and 60 min after stimulation with 1 µg/kg BW of synthetic ACTH administered intravenously. The samples were analyzed for cortisol, 11-deoxycortisol, 21-deoxycortisol, cortisone, corticosterone, 11-deoxycorticosterone, androstenedione, 17-OH-progesterone, progesterone, and testosterone with a liquid chromatography-tandem mass spectrometry (LC-MS/MS). Cortisol, 11-deoxycortisol, cortisone, corticosterone, and 11-deoxycorticosterone showed a significant increase after ACTH stimulation. In conclusion, the LC-MS/MS represents a viable method to measure glucocorticoids and related precursors or metabolites in equine plasma samples. In addition, we were able to show a more pronounced increase of 11-deoxycorticosterone, 11-deoxycortisol, and corticosterone compared with cortisol. These 3 metabolites could potentially serve as more sensitive biomarkers for stress in horses than cortisol.


Assuntos
Hormônio Adrenocorticotrópico/farmacologia , Cavalos/sangue , Esteroides/sangue , Bem-Estar do Animal , Animais , Feminino , Masculino
6.
Unfallchirurg ; 118(5): 476-8, 2015 May.
Artigo em Alemão | MEDLINE | ID: mdl-25277729

RESUMO

Psychogenic polydipsia leading to severe hyponatremia is well documented in the literature. This electrolyte disorder can result in encephalopathy, cerebral edema and epileptic seizures. Another rare effect is rhabdomyolysis with all its well known complications (e.g. renal failure, hyperkalemia and cardiac arrhythmia) and even resulting in compartment syndrome due to severe muscle edema. We present the case of a patient with severe hyponatremia caused by psychogenic polydipsia leading to rhabdomyolysis and compartment syndrome.


Assuntos
Síndromes Compartimentais/etiologia , Síndromes Compartimentais/prevenção & controle , Polidipsia Psicogênica/complicações , Polidipsia Psicogênica/terapia , Rabdomiólise/etiologia , Rabdomiólise/prevenção & controle , Adulto , Terapia Combinada/métodos , Síndromes Compartimentais/diagnóstico , Descompressão Cirúrgica/métodos , Diagnóstico Diferencial , Hidratação/métodos , Humanos , Masculino , Polidipsia Psicogênica/diagnóstico , Rabdomiólise/diagnóstico , Resultado do Tratamento
7.
Rev. bras. mastologia ; 20(2): 61-65, abr.-jun. 2010. tab
Artigo em Português | LILACS | ID: lil-605110

RESUMO

O estadiamento TNMuicc classifica a neoplasia mamária de acordo com o tamanho tumoral, comprometimento linfonodal e metástases à distância. O tratamento da neoplasia mamária é influenciado por esses parâmetros, porém, também é necessário conhecimento sobre uma série de outros fatores. Na realidade, o tratamento eficaz depende da extensão da doença, do status dos receptores hormonais e de outras características biológicas do câncer. Nós propomos uma nova classificação(TNM), que não apenas inclui características biológicas relevantes e amplia o estadiamento para incluir outros fatores quando validados, mas também especifica o tamanho exato do tumor (T2,3 indica um tumor com diâmetro maior que 2,3 cm), fornece mais dados sobre o envolvimento linfonodal e especifica sítio(s) de metástases a distância. Propomos também abolir o termo "carcinoma" quando se trata de condição neoplásica não-invasiva e o termo "infiltrante" para carcinomas. A nova classificação é suficientemente similar à classificação TNMuicc para permitir comparações válidas entre pacientes classificados por ambos os sistemas, porém é mais lógica, fornece informações úteis para guiar a terapia e é flexivel o suficiente para satisfazer as necessidades de pesquisas no presente e no futuro.


The TNMuicc classification of breast cancer categorizes tumor size, regional lymph node involvement, and distant metastases. Treatment is influenced by these characteristics, but requires knowledge of several other factors. In fact, effective treatment is dependent on disease extent, hormone receptor status, and other biologic characteristics of the cancer. We propose a new classification (tumor node metastasis, TNM), that not only includes relevant biologic characteristics and can expand to include others as they are validated but also specifies tumor size exactly (T2,3 indicates a cancer of maximum diameter 2,3 cm), provides more information on regional lymph node involvement, and specifies the site(s) of distant metastases. We also propose abolishing the term "carcinoma" for non-invasive neoplastic conditions and the term "infiltrating" for carcinomas. The new classification is sufficiently similar to the TNMuicc classification to permit valid comparison of patients classified by both systems, but is more logical, provides useful information for guiding therapy, and is flexible enough to satisfy present and future clinical and research needs.


Assuntos
Estadiamento de Neoplasias/classificação , Neoplasias da Mama/classificação , Terminologia como Assunto
8.
Biosens Bioelectron ; 24(5): 1512-7, 2009 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-18809309

RESUMO

A proteoheparan sulfate coated, hydrophobic silica surface serves as lipoprotein receptor at which the Ca(2+)-driven arteriosclerotic nanoplaque formation can be pursued by laser-based ellipsometry. Any lipoprotein from human blood can be very sensitively tested for its atherogenic properties. From the same blood sample, it is possible to determine the concentration and activity of a series of interacting biomarker molecules which, through a pattern analysis, allow to assess the state of health with respect to cardiovascular diseases. These two interlinked and complementary biosensors make a prospective cardio-cerebro-vascular risk stratification feasible, especially the sequelae of an underlying arteriosclerotic disease. Based on these diagnostic tools, an optimized therapy decision for the patient can be taken and the necessary preventive measures for the still healthy person.


Assuntos
Aterosclerose/diagnóstico , Aterosclerose/metabolismo , Técnicas Biossensoriais/instrumentação , Lipoproteínas/análise , Nanotecnologia/instrumentação , Reconhecimento Automatizado de Padrão/métodos , Refratometria/instrumentação , Biomarcadores/análise , Técnicas Biossensoriais/métodos , Desenho de Equipamento , Análise de Falha de Equipamento , Humanos , Reprodutibilidade dos Testes , Medição de Risco/métodos , Fatores de Risco , Sensibilidade e Especificidade
9.
Phys Rev Lett ; 100(23): 233003, 2008 Jun 13.
Artigo em Inglês | MEDLINE | ID: mdl-18643493

RESUMO

We demonstrate the photoassociation of ultracold rubidium dimers using coherent femtosecond pulses. Starting from a cloud of ultracold rubidium atoms, electronically excited rubidium molecules are formed with shaped photoassociation pump pulses. The excited state molecules are projected with a time-delayed probe pulse onto molecular ion states which are detected in a mass spectrometer. Coherent transient oscillations of the excited state population are observed in the wings of the pump pulse, in agreement with the time-dependent solution of the Schrödinger equation of the excitation process.

11.
Rofo ; 175(3): 418-21, 2003 Mar.
Artigo em Alemão | MEDLINE | ID: mdl-12635021

RESUMO

PURPOSE: To discuss the technical details of a head mounted display with an augmented reality (AR) system and to describe a first pre-clinical evaluation in interventional MRI. METHOD: The AR system consists of a video-see-through head mounted display (HMD), mounted with a mini video camera for tracking and a stereo pair of mini cameras that capture live images of the scene. The live video view of the phantom/patient is augmented with graphical representations of anatomical structures from MRI image data and is displayed on the HMD. The application of the AR system with interventional MRI was tested using a MRI data set of the head and a head phantom. RESULTS: The HMD enables the user to move around and observe the scene dynamically from various viewpoints. Within a short time the natural hand-eye coordination can easily be adapted to the slightly different view. The 3D perception is based on stereo and kinetic depth cues. A circular target with a diameter of 0.5 square centimeter was hit in 19 of 20 attempts. In a first evaluation the MRI image data augmented reality scene of a head phantom allowed good planning and precise simulation of a puncture. CONCLUSION: The HMD in combination with AR provides a direct, intuitive guidance for interventional MR procedures.


Assuntos
Gráficos por Computador , Processamento de Imagem Assistida por Computador , Imageamento por Ressonância Magnética/métodos , Imagens de Fantasmas , Simulação por Computador , Cabeça , Humanos , Modelos Anatômicos , Punções , Interface Usuário-Computador , Gravação em Vídeo
12.
Genome Biol ; 5(1): R3, 2003.
Artigo em Inglês | MEDLINE | ID: mdl-14709175

RESUMO

BACKGROUND: While the genome sequences for a variety of organisms are now available, the precise number of the genes encoded is still a matter of debate. For the human genome several stringent annotation approaches have resulted in the same number of potential genes, but a careful comparison revealed only limited overlap. This indicates that only the combination of different computational prediction methods and experimental evaluation of such in silico data will provide more complete genome annotations. In order to get a more complete gene content of the Drosophila melanogaster genome, we based our new D. melanogaster whole-transcriptome microarray, the Heidelberg FlyArray, on the combination of the Berkeley Drosophila Genome Project (BDGP) annotation and a novel ab initio gene prediction of lower stringency using the Fgenesh software. RESULTS: Here we provide evidence for the transcription of approximately 2,600 additional genes predicted by Fgenesh. Validation of the developmental profiling data by RT-PCR and in situ hybridization indicates a lower limit of 2,000 novel annotations, thus substantially raising the number of genes that make a fly. CONCLUSIONS: The successful design and application of this novel Drosophila microarray on the basis of our integrated in silico/wet biology approach confirms our expectation that in silico approaches alone will always tend to be incomplete. The identification of at least 2,000 novel genes highlights the importance of gathering experimental evidence to discover all genes within a genome. Moreover, as such an approach is independent of homology criteria, it will allow the discovery of novel genes unrelated to known protein families or those that have not been strictly conserved between species.


Assuntos
Drosophila melanogaster/genética , Perfilação da Expressão Gênica/métodos , Genes de Insetos/fisiologia , Genoma , Análise de Sequência com Séries de Oligonucleotídeos/métodos , Animais , Análise por Conglomerados , Biologia Computacional/métodos , Biologia Computacional/estatística & dados numéricos , Perfilação da Expressão Gênica/estatística & dados numéricos , Hibridização In Situ/métodos , Modelos Genéticos , Dados de Sequência Molecular , Análise de Sequência com Séries de Oligonucleotídeos/estatística & dados numéricos , Valor Preditivo dos Testes , Pseudogenes/genética , Interferência de RNA/fisiologia , Reação em Cadeia da Polimerase Via Transcriptase Reversa/métodos
13.
Swiss Surg ; 8(4): 176-80, 2002.
Artigo em Alemão | MEDLINE | ID: mdl-12227111

RESUMO

BACKGROUND: Extracorporeal shockwave therapy (ESWT) is recommended as an alternative treatment for lateral epicondylitis (LE). An influence on the blood perfusion is considered to be one possible effect. Infrared thermography is used in this trial to measure effects of ESWT on the thermal regulation in the target area. METHODS: 33 patients with chronic LE were examined in a prospective, placebo-controlled single blind study with an independent observer. 3 x 2000 impulses of an energy flux density ED+ 0.22 mJ/mm2 were applied under local anaesthesia as verum-ESWT. Placebo-ESWT was performed under the same conditions. One elbow was treated, the other served as control. Before and after each shockwave application and after 12 weeks skin temperature was measured on both elbows at three predefined points by infrared thermography. RESULTS: While a significant decrease in the skin temperature was found on the treated and sham-treated sides opposed to the contralateral side, there was no difference between the real shockwave treatment and placebo therapy. Responder and Non-responder to the treatment could not be distinguished during the therapy. DISCUSSION: Infrared thermography was proved to be a valuable additional technical instrument for diagnosis of LE, but is not an appropriate instrument to predict the clinical outcome in patients treated with ESWT. A noted reduction of skin temperature on the treated side is not due to specific effects of the shockwaves. It is unlikely that ESWT as applied has an influence on thermal regulation in the target area. These findings are supported by negative results of experimental and clinical trials.


Assuntos
Articulação do Cotovelo/irrigação sanguínea , Litotripsia , Temperatura Cutânea/fisiologia , Cotovelo de Tenista/terapia , Termografia , Adulto , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Estudos Prospectivos , Fluxo Sanguíneo Regional/fisiologia , Método Simples-Cego , Cotovelo de Tenista/fisiopatologia
14.
J Cell Sci ; 114(Pt 16): 2895-902, 2001 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-11686293

RESUMO

Activation of RNA-polymerase-II-dependent transcription involves conversion of signals provided by gene-specific activator proteins into the synthesis of messenger RNA. This conversion requires dynamic structural changes in chromatin and assembly of general transcription factors (GTFs) and RNA polymerase II at core promoter sequence elements surrounding the transcription start site of genes. One hallmark of transcriptional activation is the interaction of DNA-bound activators with coactivators such as the TATA-box binding protein (TBP)-associated factors (TAF(II)s) within the GTF TFIID. TAF(II)250 possesses a variety of activities that are likely to contribute to the initial steps of RNA polymerase II transcription. TAF(II)250 is a scaffold for assembly of other TAF(II)s and TBP into TFIID, TAF(II)250 binds activators to recruit TFIID to particular promoters, TAF(II)250 regulates binding of TBP to DNA, TAF(II)250 binds core promoter initiator elements, TAF(II)250 binds acetylated lysine residues in core histones, and TAF(II)250 possesses protein kinase, ubiquitin-activating/conjugating and acetylase activities that modify histones and GTFs. We speculate that these activities achieve two goals--(1) they aid in positioning and stabilizing TFIID at particular promoters, and (2) they alter chromatin structure at the promoter to allow assembly of GTFs--and we propose a model for how TAF(II)250 converts activation signals into active transcription.


Assuntos
Proteínas de Ligação a DNA/metabolismo , Proteínas Nucleares/metabolismo , Fatores Associados à Proteína de Ligação a TATA , Transcrição Gênica , Animais , Glucosiltransferases/metabolismo , Histona Acetiltransferases , Histonas/metabolismo , Humanos , Processamento de Proteína Pós-Traducional , RNA Polimerase II/metabolismo , Proteína de Ligação a TATA-Box , Transativadores/metabolismo , Fator de Transcrição TFIID , Fatores de Transcrição/metabolismo , Fatores de Transcrição TFII/metabolismo
15.
Anesth Analg ; 92(4): 842-7, 2001 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-11273912

RESUMO

UNLABELLED: We studied whether inhaled nitric oxide (NO) would improve arterial oxygen tension (PaO(2)) and reduce the occurrence of oxygen saturation of hemoglobin (O(2)Hb) < 90% during one-lung ventilation (OLV). One-hundred-fifty-two patients were ventilated either with or without NO (20 ppm) with an inspired fraction of oxygen (FIO(2)) of either 0.3, 0.5, or 1.0 during OLV. Anesthesia was induced and maintained with propofol, remifentanil, and rocuronium IV, and lung separation was achieved with a double-lumen tube. During OLV, we set positive end-expiratory pressure at 5 cm H(2)O, peak pressure at 30 cm H(2)O, and end-tidal CO(2) at 30 mm Hg. The nonventilated lung was opened to room air and collapsed. During OLV, three consecutive measurements were performed every 10 min. The operated lung was temporarily ventilated if pulse oximetric saturation (SpO(2)) decreased to < 91%. SpO(2) <9 1% occurred in 2 of the 152 patients. SpO(2) overestimated O(2)Hb by 2.9% +/- 0.1%. NO failed to improve oxygenation or alter occurrence of O(2)Hb < 90% during OLV across all time points and all levels of FIO(2). Increasing FIO(2) increased oxygenation and decreased occurrence of O(2)Hb < 90% (P: < 0.001). At FIO(2) = 1, PaO(2) was higher (P < 0.01) and O(2)Hb < 90% rate tended to be lower (P = 0.1) during right versus left lung ventilation. PaO(2) was higher in patients undergoing pneumonectomy and lobectomy than in those undergoing metastasectomy or video-assisted operations (P < 0.05). IMPLICATIONS: Inhaled nitric oxide failed to improve oxygenation during one-lung ventilation. Oxygenation during one-lung ventilation was improved with increasing levels of FIO(2) during ventilation of the right versus the left lung and with increasing pathology of the nonventilated lung.


Assuntos
Óxido Nítrico/farmacologia , Oxigenoterapia , Oxigênio/sangue , Respiração Artificial , Adulto , Idoso , Idoso de 80 Anos ou mais , Dióxido de Carbono/sangue , Feminino , Hemodinâmica/efeitos dos fármacos , Hemoglobinas/metabolismo , Humanos , Unidades de Terapia Intensiva , Masculino , Pessoa de Meia-Idade , Óxido Nítrico/administração & dosagem , Oximetria
16.
Lancet Infect Dis ; 1(2): 125-7, 2001 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-11871463

RESUMO

Approaches towards the public-health prevention of bioterrorism are too little, and too late. New information-based approaches could yield better homeland protection. An internet civil defence is presented where millions of eyes could help to identify suspected cases of bioterrorism, with the internet used to report, confirm, and prevent outbreaks.


Assuntos
Bioterrorismo/prevenção & controle , Defesa Civil/métodos , Internet , Saúde Pública , Humanos , Reino Unido , Estados Unidos
18.
IEEE Trans Med Imaging ; 19(5): 361-75, 2000 May.
Artigo em Inglês | MEDLINE | ID: mdl-11021680

RESUMO

This paper addresses the long object problem in helical cone-beam computed tomography. We present the PHI-method, a new algorithm for the exact reconstruction of a region-of-interest (ROI) of a long object from axially truncated data extending only slightly beyond the ROI. The PHI-method is an extension of the Radon-method, published by Kudo, Noo, and Defrise in issue 43 of journal Physics in Medicine and Biology. The key novelty of the PHI-method is the introduction of a virtual object fpsi(x) for each value of the azimuthal angle psi in the image space, with each virtual object having the property of being equal to the true object f(x) in some ROI omegam. We show that, for each psi, one can calculate exact Radon data corresponding to the two-dimensional (2-D) parallel-beam projection of fpsi(x) onto the meridian plane of angle psi. Given an angular range of length pi of such parallel-beam projections, the ROI omegam can be exactly reconstructed because f(x) is identical to fpsi(x) in Omegam. Simulation results are given for both the Radon-method and the PHI-method indicating that 1) for the case of short objects, the Radon- and PHI-methods produce comparable image quality, 2) for the case of long objects, the PHI-method delivers the same image quality as in the short object case, while the Radon-method fails, and 3) the image quality produced by the PHI-method is similar for a large range of pitch values.


Assuntos
Algoritmos , Processamento de Imagem Assistida por Computador , Tomografia Computadorizada por Raios X/métodos , Humanos , Processamento de Imagem Assistida por Computador/instrumentação , Processamento de Imagem Assistida por Computador/métodos , Modelos Teóricos , Imagens de Fantasmas , Radônio , Tomografia Computadorizada por Raios X/instrumentação
19.
IEEE Trans Med Imaging ; 19(5): 376-83, 2000 May.
Artigo em Inglês | MEDLINE | ID: mdl-11021681

RESUMO

We present a (spiral + circles) scan cone beam reconstruction algorithm in which image reconstruction proceeds via backprojection in the object space. In principle, the algorithm can reconstruct sectional region-of-interest (ROI) in a long object. The approach is a generalization of the cone beam backprojection technique developed by Kudo and Saito in two aspects: the resource-demanding normalization step in the Kudo and Saito's algorithm is eliminated through the technique of data combination that we published earlier, and the elimination of the restriction that the detector be big enough to capture the entire cone beam projection of the ROI. Restricting the projection data to the appropriate angular range required by data combination can be accomplished by a masking process. Because of the simplification resulting from the elimination of the normalization step, the most time-consuming operations of the algorithm can be approximated by the efficient step of line-by-line ramp filtering the cone beam image in the direction of the scan path, plus a correction image. The correction image, which can be computed exactly, is needed because data combination is not properly matched at the mask boundary when ramp filtering is involved. Empirical two-dimensional (2-D) point spread function (PSF) is developed to improve matching with the correction image which is computed with finite samplings. The use of transition region to further improve matching is introduced. The results of testing the algorithm on simulated phantoms are presented.


Assuntos
Algoritmos , Processamento de Imagem Assistida por Computador/métodos , Tomografia Computadorizada por Raios X/métodos , Humanos , Processamento de Imagem Assistida por Computador/instrumentação , Modelos Teóricos , Imagens de Fantasmas , Radônio , Tomografia Computadorizada por Raios X/instrumentação
20.
Curr Opin Struct Biol ; 10(5): 548-56, 2000 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-11042452

RESUMO

Bacterial pili assembled by the chaperone-usher pathway can mediate microbial attachment, an early step in the establishment of an infection, by binding specifically to sugars present in host tissues. Recent work has begun to reveal the structural basis both of chaperone function in the biogenesis of these pili and of bacterial attachment.


Assuntos
Adesinas de Escherichia coli , Aderência Bacteriana , Proteínas de Fímbrias , Fímbrias Bacterianas/metabolismo , Chaperonas Moleculares/metabolismo , Adesinas Bacterianas/metabolismo , Chaperonas Moleculares/química , Organelas/metabolismo , Ligação Proteica , Conformação Proteica , Dobramento de Proteína
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA