1,720,993 research outputs found
Molekulare Systematik und Evolution der Spezies der Familie Arthrodermataceae (Dermatophyten)
Get PDFDermatophyten sind keratinophile Pilze, d.h. sie besiedeln und infizieren die Haut und ihre Anhangsgebilde (Haare, Nägel) bei Mensch und Tier. Die derzeit häufigsten durch Dermatophyten hervorgerufenen Infektionen sind die Onychomykose, Tinea pedis, Tinea capitis und Tinea corporis. Da Antimykotika nicht bei alle Erregern von Dermatophytosen gleich wirksam sind, sollte im Vordergrund einer Behandlung zunächst die korrekte Erregerdifferenzierung stehen. Konventionell erfolgt diese Differenzierung über morphologische Merkmale wie Form und Farbe der auf dem Nährmedium gewachsenen Pilzkolonie, charakteristische mikromorphologische Elemente (Konidien) und biochemische Eigenschaften. Diese Merkmale werden jedoch oftmals nicht exprimiert. Damit ist in diesen Fällen keine Speziesdiagnose möglich. Eine zuverlässige Diagnostik sollte zudem das natürliche Klassifizierungssystem direkt reflektieren. Die Studien zur molekularen Biodiversität innerhalb der Dermatophyten sollten deshalb zur Klärung evolutionärer, taxonomischer und populationsgenetischer Zusammenhänge bei den verschiedenen Spezies der Gattungen Arthroderma, Trichophyton, Microsporum und Epidermophyten beitragen und helfen, geeignete DNA-Marker für die Anwendung in der medizinischen Diagnostik zu finden und einzusetzen. Dazu wurden verschiedene Methoden und Zielsequenzen genutzt, wie die Sequezierung der internal transcribed spacer (ITS) Region der ribosomalen DNA, das PCR-Fingerprinting, single strand conformation polymorphism (SSCP) und amplified fragment length polymorphism (AFLP)-Analyse. Es wurden weit über 200 Stämme, die bisher ca. 100 verschiedenen Taxa zuzuordnen waren, analysiert. Die molekularen Studien zeigen, dass die phylogenetisch ältesten Dermatophytenspezies geophil sind und sich die wärmeliebenden, zoophilen Arten erst später durch Koevolution mit warmblütigen Tieren entwickelt haben. Die anthropophilen scheinen dagegen erst mit Entstehung des Menschen evolviert und demzufolge am jüngsten zu sein. Damit kann man ihre geringe Biodiversität und ihr verändertes pathogenetisches Verhalten erklären. Es konnte gezeigt werden, dass die molekularen Phylogenie der Spezies besser mit ihrer Ökologie und dem Krankheitsbild als mit morphologischen Eigenschaften übereinstimmt und dass etliche Dermatophytenspezies überklassifiziert sind. Aus diesem Grunde wurde eine neue Systematik vorgeschlagen. Für den Nachweis des häufigsten Erreger, Trichophyton rubrum wurde eine Gensonde entwickelt, die in der medizinischen Diagnostik einsetzbar ist.Dermatophytes are keratinophilic fungi which colonise and infect skin, hair and nails of man and animals. The most common infections caused by dermatophytes are onychomycosis, tinea pedis, tinea capitis and tinea corporis. Antimycotics may have different spectra of activity even in related dermatophyte species. Therefore a correct species identification is necessary before onset of antifungal therapy. Conventionally, the identification of dermatophytes is performed by the use of morphological features, such as shape and colour of the colony, micromorphological characteristics (conidia) and biochemical properties. However, these characters may not be expressed and then identification down to the species level is frequently impossible. Reliable diagnostics directly reflects the natural system. Studies of biodiversity in dermatophytes should therefore focus on elucidation of the connection of evolution, taxonomy and population genetics of the species of the genera Arthroderma, Trichophyton, Microsporum and Epidermophyten and thus contribute to development of stable DNA markers to be applied in routine diagnostics. Several methods and targets were applied such as sequencing of the internal transcribed spacer region (ITS) of the ribosomal DNA, PCR fingerprinting, single strand conformation polymor phism (SSCP) and amplified fragment length polymorphism (AFLP) analysis. More than 200 strains belonging to about 100 dermatophyte taxa were analysed. Phylogenetically, the molecular data show the oldest dermatophyte species to be geophilic and subsequently co-evolved as zoophilic dermatophytes with warm blooded animals. In contrast, the anthropophilic dermatophytes are much younger as they evolved in association with humans. This hypothesis is supported by their low biodiversity and changing pathogenicity. The molecular data show correspondence between phylogeny of species and their ecology and clinical picture, rather than with morphological features. Many dermatophyte species were shown to be overclassified. A new systematic system was proposed. For the identification of Trichophyton rubrum, the most common dermatophyte species, an oligonucleotide probe was developed which is applicable in medical routine diagnostics
Identifizerung von Candia-Spezies und -Stämmen durch den Nachweis von polymorphen DNA-Regionen in der PCR
Get PDFFür die Identifizierung bzw. Differenzierung von Candida- Spezies und -Stämmen sowie für die Bestimmung der genetischen und epidemiologischen Verwandtschaft von Stämmen der gleichen Spezies wurde eine PCR-Fingerprint-Technik und eine RFLP-Analyse der amplifizierten ITS-Region angewandt. Das PCR-Fingerprinting amplifiziert anonyme Sequenzen in der chromosomalen DNA, die über das gesamte Genom verteilt sind. Die ITS-Region ist Bestandteil des ribosomalen Operons, welches in ca. 50-100 Kopien/Zelle vorhanden ist. 1.a. Beide molekularbiologischen Verfahren wurden zur Unterscheidung von routinemäßig schwer differenzierbaren klinischen Candida famata und Candida guilliermondii-Isolaten genutzt. Von insgesamt 37 fraglichen Stämmen konnten 31 als C. guilliermondii und 3 als C. famata identifiziert werden, die drei verbliebenen Stämme waren mit diesen Techniken nicht identifizierbar. Mit der Biochemotypie gelang nur die Zuordnung eines der 3 C. famata-Isolate sowie von 23 der 31 C. guilliermondii-Isolate. 14 Isolate wurden mit den konventionellen Methoden gar nicht oder falsch identifiziert. 1b. Mit dem PCR-Fingerprinting wurde auch die Spezieszugehörigkeit phänotypisch veränderter Candida albicans-Isolate überprüft. Alle atypischen Stämme, bei denen solche für C.albicans charakteristischen Merkmale wie die Bildung von Chlamydosporen, die Verwertung der Aminozucker Glukosamin und N-Acetylglukosamin sowie die Assimilation von 2-Ketogluconat und Xylose nicht ausgeprägt waren, wiesen die für C. albicans typischen Fingerprintmuster auf. Unsere Studie zeigte, daß die biochemische Typisierung an Grenzen stößt, wenn typische Stoffwechselreaktionen nicht nachgewiesen werden können. 2. Bei 6 verschiedenen C. albicans-Populationen aus Angola, Madagaskar, Deutschland und Portugal wurde die Variabilität phänotypischer und genotypischer Merkmale untersucht, wobei in diese Analyse auch atypische Stämme miteinbezogen wurden. Während die phänotypischen Eigenschaften, bis auf die der atypischen Stämme, kaum variierten, wurden für die insgesamt 212 C. albicans-Isolate 87 unterschiedliche PCR-Fingerprint-Genotypen nachgewiesen. Eine Analyse der Beziehungen zwischen den Fingerprint-Genotypen wurde mit der UPGMA-Distanz-Methode durchgeführt. 3. Weiterhin wurden Candida-Vaginalisolate von Patientinnen mit rezidivierenden Episoden von Candida-Vaginitis mit Stämmen verglichen, die aus anderen Körperregionen stammten bzw. bei ihren Partnern isoliert wurden. Es konnte gezeigt werden, daß Stammaustausche zwischen den Partnern vorkommen, ein Stamm ohne oder mit geringfügigen genotypischen Veränderungen trotz Therapie persistieren kann und daß eine Reinfektion auch durch einen neuen Stamm möglich ist. Das Problem der Erregeridentifizierung in der mykologischen Labordiagnostik ist sowohl klinisch als auch epidemiologisch relevant. Molekularbiologische Methoden sollen gut funktionierende konventionelle Methoden zur Erregeridentifizierung nicht ersetzen, können aber bei Problemfällen eine wertvolle Ergänzung für die mykologische Diagnostik vorzugsweise in fachständigen Referenzlaboratorien darstellen.A PCR fingerprinting approach and a RFLP analysis of the amplified ITS region were used to differentiate Candida species and strains as well as to assess genetic and epidemiological relationships of strains belonging to the same species. The PCR fingerprinting amplifies anonymous DNA sequences sampled throughout the whole genome. The ITS region is part of the ribosomal operon which occurs in tandem arrays of nearly 50-100 copies in one cell. 1.a. Both methods were used to identify clinical isolates of C. famata and C. guilliermondii which were difficult to differentiate with routine methods. Out of 37 ambiguous isolates 31 could be identified as C. guilliermondii, 3 as C. famata and the other 3 were not identifiable. Biochemical typing (Api 32 C V.1) identified only 23 out of 31 C. guilliermondii and 1 out of 3 C. famata whereas 14 isolates were misidentified or not identified at all. 1.b. By using the PCR fingerprinting technique strains of C. albicans with altered phenotypes could be identified at species level. Atypical isolates which did not express those characteristics which are thought to be typical for C.albicans like the formation of clamydospores, the ability to metabolise the amino sugars glucosamine and N-acetylglucosamine as the sole carbon source or to assimilate 2-ketogluconate and xylose showed the PCR patterns typical for C.albicans. Our study revealed that biochemical and morphological methods of species identification are limited if some of the key reactions fail. 2. We investigated the variability of phenotypic and genotypic properties of 6 different C. albicans populations from different countries (Angola, Madagascar, Portugal and Germany) including atypical strains. Except for the atypical strains only very little phenotypical variation was observed. However, 87 different genotypes were found among the 212 strains. The relatedness of the fingerprint-genotypes were analysed by measuring genetic distances with the UPGMA method. 3. Vaginal isolates of Candida spp. obtained from patients with recurrent episodes of vaginitis were compared with isolates from different body locations of the women and from their male partners. It has been shown that strain exchanges between the partners occur, that the original strain with or without minor genotypic changes can persist despite of the therapy, but also that reinfection by a new strain is possible. The identification of an ethiological agent by the mycological diagnostic laboratory is of clinical and epidemiological importance. Molecular biological methods should not replace well established conventional methods but they can supplement the identification of fungal pathogens in specialised reference laboratories if diagnosis cannot be achieved easily by conventional diagnostic procedures
Lipid flow phenomena between liposomes, lipoproteins and cell membranes; application in drug delivery
No full textThe bilayer structure making up the physical boundary of the liposome bears a strong resemblance to the biological membranes forming the boundaries of cells and subcellular particles. Similarly, the extracellular lipid layers in the stratum corneum of the skin basically possess this bimolecular leaflet structure. Essentially half such a bilayer is found at the interface at the air-water interface in the lung and at the lipid-water interface of the surface of lipoprotein particles. In contrast to the bilayer, which separates two aqueous phases, these monolayers constitute the boundary between an aqueous and an air phase or an aqueous and a lipid phase, respectively. A fundamental difference between artificial (phospho)lipid membranes such as in liposomes and biological membranes is the presence in the latter of a host of membrane-spanning integral proteins as well as more loosely associated peripheral proteins. Proteins are likely to play an important role in interactions between biological membranes. Such interactions may, for example, lead to the induction of membrane fusion and lipid or protein exchange phenomena. During the interaction of liposomes with the membranous structures of the skin similar phenomena may be involved. In this paper observations will be discussed which have been made in our laboratories over the past few years and which may bear relevance to the understanding of such phenomena in which transfer of lipids between membranes plays a role
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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