367 research outputs found
The Role of Scanning Electron Microscopy in Periodontal Research
During recent years a great amount of research has led to a better understanding of the etiology, pathogenesis and pattern of progression of periodontal diseases. Scanning electron microscopy (SEM) has contributed to this improvement, mainly with respect to histology of periodontal tissues, the description of the morphology and distribution of bacteria on the exposed root surface, analysis of the host-parasite interactions on the gingival pocket wall, and morphological evaluation of root treatment. This review deals with all these topics. Unusual types of SEM research are also described and discussed. Uncommon sample preparation techniques for SEM in periodontal research are described. SEM in periodontal research should be of great application in the near future. Cathodoluminescence, backscattered emission and immunolabelling techniques will be formidable tools in this field of dentistry
Precambrian isotopic sources of the Anti-Atlas, Morocco
The isotopic data stored in detrital and magmatic zircons are crucial for assessing magma
sources, terrane correlation, paleogeography and plate reconstructions. In many cases the
comparison of the zircon age and isotope signature of a terrane of unknown provenance with
the signature of possible sources, generally old cratonic areas, can resolve questions of origin
and paleoposition. Obviously, a precise knowledge of the zircon characteristics of these old
areas is essential for reliable comparisons.
One of the major sources of sediments of the peri-Gondwanan terranes and of the European
Variscan Belt is the West African craton. The northern boundary of this craton is the Pan-
African Anti-Atlas belt, which is therefore an ideal place to better constrain the zircon isotopic
features of sediments sourced from it. With that aim, we obtained LA-ICM-MS U-Pb and Hf
isotopic data of more than 600 zircons separated from six samples of siliciclastic sedimentary
rocks from the main Neoproterozoic stratigraphic units of the Anti-Atlas belt, from the Sirwa
and Zenaga inliers.
The data suggest that the north part of the West African craton formed during three cycles of
juvenile crust formation, with variable amount of reworking of older crust. The youngest group
of zircons, with a main population clustering around 610 Ma, has a predominantly juvenile
character and evidence of moderate mixing with Paleoproterozoic crust, suggesting that the
igneous and metamorphic rocks in which the zircons originally crystallized were formed in
an ensialic magmatic arc environment. A group of zircons with ages in the range 1.79–2.3
Ga corresponds to the major crust forming event in the West African craton: the Eburnian-
Birimian orogeny. The isotopic data indicate that the provenance area should represent a crustal
domain that separated from a mantle reservoir at ∼2050–2300 Ma, and further evolved with
a time-integrated 176Lu/177Hf of ∼0.013, characteristic of continental crust. The evolution
of the Eburnian orogeny is apparently dominated by new crust formation in a magmatic arc
environment. The Lower Paleoproterozoic and Neoarchean evolution (2.3–2.75 Ga) involves a
group of detrital zircon ages that has not been identified up to now in the igneous or metamorphic
rocks of the north West African craton basement. Their Hf isotopic signature points to reworking
of juvenile crust mixed with moderate amounts of Archean crust. The significance of these ages
is uncertain: they could represent a tectonothermal event not discovered yet in the Reguibat
Shield or the zircons can be far-travelled from an unknown source.Peer Reviewe
Use of Preputial Skin as Cutaneous Graft after Nevus Excision
We report a four-year-old boy with a nevus covering all the plantar side of his second finger on the left foot. He was also affected by congenital phimosis. Surgical excision of the nevus was indicated, but the skin defect would have been too large to be directly closed. The foreskin was taken as a full-thickness skin graft to cover the cutaneous defect of the finger. The graft intake was favourable and provided a functional repair with good aesthetic characteristic
Modelización del equilibrio de fases en el sistema KFMASH para mostrar la evolución metamórfica de los Esquistos de Ceán (Unidad de Malpica-Tui, NW del Macizo Ibérico)
Para complementar los resultados obtenidos mediante termobarometría convencional (termómetro granatemoscovita
y barómetros GRIPS y GASP) en los Esquistos de Ceán (López-Carmona et al., 2008) se ha
construido una pseudosección P-T en el sistema químico KFMASH para una composición media de estas
metapelitas [SiO2:71.42; Al2O3:13.42; MgO:4.78; FeO:7.04; K2O:3.34]. Adicionalmente, la proyección
de isopletas que reflejan el contenido en sílice de las fengitas en los diferentes campos de estabilidad de la
pseudoseción, proporciona otro barómetro muy fiable. En base a los resultados obtenidos, y de acuerdo
principalmente con las paragénesis naturales preservadas en los esquistos, las condiciones P-T obtenidas
para el pico metamórfico son P=23-24 Kb y T=530-540 ºC, mientras que para un segundo evento
metamórfico se obtuvieron valores de P=20-23 Kb y T=550-560 ºC. Los resultados proporcionados por
la termobarometría convencional indican P=19-21 Kb y T=430-500 ºC para el pico y P=16-19 Kb y
T=440-515 ºC cuando se emplean las composiciones de los minerales del segundo evento metamórfic
Lixiviação de íons potássio, cálcio e magnésio para determinação do vigor em sementes de milho doce.
O teste de lixiviação de íons de potássio, cálcio e magnésio é baseado na integridade das membranas celulares das sementes, sendo considerado um procedimento rápido para a avaliação do vigor em sementes de várias espécies. Porém, para sementes de milho doce não se têm informações necessárias para a validação deste procedimento. Com isso, o trabalho teve como objetivo obter informações que permitam o aperfeiçoamento dos testes de lixiviação de potássio, cálcio e magnésio para a avaliação do vigor em sementes de milho doce. Foram utilizados 14 lotes de sementes de milho doce de duas cultivares, BR-401 e BR-402. O delineamento utilizado foi inteiramente casualizado com três repetições. A qualidade fisiológica das sementes foi avaliada por meio dos testes de germinação, condutividade elétrica, emergência a campo, lixiviação de potássio, de cálcio e de magnésio. Os testes de lixiviação de potássio e magnésio foram eficientes na avaliação do vigor em sementes de milho doce. A condutividade elétrica apresentou correlação negativa com a emergência de plântulas e positiva com a lixiviação de íons de potássio e magnésio
In vitro models of multiple system atrophy from primary cells to induced pluripotent stem cells
Multiple system atrophy (MSA) is a rare neurodegenerative disease with a fatal outcome. Nowadays, only symptomatic treatment is available for MSA patients. The hallmarks of the disease are glial cytoplasmic inclusions (GCIs), proteinaceous aggregates mainly composed of alpha-synuclein, which accumulate in oligodendrocytes. However, despite the extensive research efforts, little is known about the pathogenesis of MSA. Early myelin dysfunction and alpha-synuclein deposition are thought to play a major role, but the origin of the aggregates and the causes of misfolding are obscure. One of the reasons for this is the lack of a reliable model of the disease. Recently, the development of induced pluripotent stem cell (iPSC) technology opened up the possibility of elucidating disease mechanisms in neurodegenerative diseases including MSA. Patient specific iPSC can be differentiated in glia and neurons, the cells involved in MSA, providing a useful human disease model. Here, we firstly review the progress made in MSA modelling with primary cell cultures. Subsequently, we focus on the first iPSC-based model of MSA, which showed that alpha-synuclein is expressed in oligodendrocyte progenitors, whereas its production decreases in mature oligodendrocytes. We then highlight the opportunities offered by iPSC in studying disease mechanisms and providing innovative models for testing therapeutic strategies, and we discuss the challenges connected with this technique
Seedling emergence and yield performance of wheat cultivars depending on seed vigor and sowing density.
Título em português: Emergência de plântulas e desempenho produtivo de cultivares de trigo em função do vigor de sementes e densidades de semeadura
Assessing Mn as an antioxidant agent in bioactive glasses by quantification of catalase and superoxide dismutase enzymatic mimetic activities
The antioxidant activity of Mn as additive in a 45S5 type glass system with and without P2O5 was studied by mimicking the activity of catalase (CMA) and superoxide dismutase (SOD) enzymes. Glasses were melted either under oxidizing or reducing atmosphere (N2/H2) to compare the processing influence on the Mn oxidation state. Thermal (DTA) and optical (UV–Vis) characterizations of the glass powders were carried out to obtain further insight into the structural role of Mn. A correlation of in vitro apatite formation between Tris buffer solution and Simulated Body Fluid (SBF) was performed to optimise Mn substitution, where a decrease in apatite formation was observed by increasing Mn content. Despite this, glasses with up to 1.0 mol% MnO did not show any delay in apatite formation and maintained their CMA and SOD activity. The antioxidant effect of Mn can be attributed to the interconversion Mn2+ ↔ Mn3+ occurring on the glass surface through a heterogeneous catalysis. P2O5 plays an important role in the antioxidant effect of the glass, possibly by charge balancing Mn ions and forming more stable units compared to those formed with Ca and Na. The amount of Mn2+ is predominant in the glass network with respect to Mn3+ in all synthetized glasses. Moreover, glass melting in a reducing atmosphere further avoided Mn oxidation
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