Cutting artefacts and cutting process in vitreous sections for cryo-electron microscopy.

Cryo-electron microscopy of vitreous sections (CEMOVIS) has recently been shown to provide images of biological specimens with unprecedented quality and resolution. Cutting the sections remains however the major difficulty. Here, we examine the parameters influencing the quality of the sections and analyse the resulting artefacts. They are in particular: knife marks, compression, crevasses, and chatter. We propose a model taking into account the interplay between viscous flow and fracture. We confirm that crevasses are formed on only one side of the section, and define conditions by which they can be avoided. Chatter is an effect of irregular compression due to friction of the section of the knife edge and conditions to prevent this are also explored. In absence of crevasses and chatter, the bulk of the section is compressed approximately homogeneously. Within this approximation, it is possible to correct for compression by a simple linear transformation for the bulk of the section. A research program is proposed to test and refine our understanding of the sectioning process.

Morphological study of the eggs and nymphs of Triatoma dimidiata (Latreille, 1811) observed by light and scanning electron microscopy (Hemiptera: Reduviidae: Triatominae)

Eggs and nymphs of Triatoma dimidiata were described using both light and scanning electron microscopy. The egg body and operculum have an exochorion formed by irregular juxtaposed polygonal cells; these cells are without sculpture and the majority of them are hexagonal in shape. The five instars of T. dimidiatacan be distinguished from each other by characteristics of the pre, meso and metanotum. The number of setiferous tubercles increases progressively among instars. The sulcus stridulatorium of 1st instar nymphs is amorphous, showing median parallel grooves; from the 2nd instar on the sulcus is, progressively, elongate, deep and posteriorly pointed with stretched parallel grooves. All instars have a trichobothrium on the apical 1/3 of segment II of the antenna. The opening of the Brindley's gland is on the mesopleura. Fifth instar nymphs have an apical ctenidium on the ventral surface of the fore tibia. Dorsal glabrous patches are found on the lateral 1/3 of abdomen. Bright oval patches are found on the ventral median line of the abdomen, from segment IV-VI; 1st instar nymphs lack these patches. Abdominal dorsal plates are present from the 1st-5th instars; the 1st instar also contains a rectangular plate in segment IX. From the 2nd instar on, variably-shaped plates are present on segments VII to IX. Morphometric data were also obtained and proved to be useful for distinguishing T. dimidiata instars.

Le taux de détresse respiratoire du nouveau-né augmente, celui des césariennes aussi: et si ce n'était pas un hasard? [Respiratory distress of the neonate and the rate of caesarean section have increased over the last 30 years. Is there a link?]

Ces trente dernières années, on note en Suisse une augmentation significative de l'incidence du syndrome de détresse respiratoire (SDR) chez le nouveau-né (NN), touchant particulièrement les enfants avec un poids de naissance >2500 g. En même temps, le taux des césariennes (CS) s'est aussi accru. Une explication pour une éventuelle corrélation entre les deux évolutions est une augmentation en particulier des CS électives qui ont tendance à être planifiées à un terme précoce pour éviter la mise en travail spontanée. Suite à cela, le foetus est privé de différents mécanismes qui favorisent l'adaptation pulmonaire périnatale. Les bénéfices réels de la CS sur la morbidité tant foetale que maternelle ne doivent pas faire oublier que la CS est un facteur de risque pour le SDR du NN. Ce risque peut être diminué efficacement en planifiant une CS élective après 39 semaines révolues. In Switzerland, the rate of respiratory distress in neonates needing hospitalization has doubled over the last thirty years, concerning in particular babies weighing more than 2500 g. In the same time, the rate of Caesarean section (CS) has also multiplied. We suppose that a link between the two evolutions might be the increase of elective CS. They tend to be planned early at term to avoid the onset of spontaneous labour As a consequence, the foetus is deprived of different mechanisms helping pulmonary transition around birth. The potential benefits of CS regarding morbidity of foetus and mother should not overshadow that CS is a significant risk factor for respiratory problems of the neonate. This risk could be dramatically decreased by planning elective CS only after completed 39 weeks of gestation

Suture repair of umbilical hernia during caesarean section: a case-control study.

PURPOSE: The objective of this study was to investigate the additional burdens in terms of pain, prolongation of surgery and morbidity which is added to elective caesarean section if umbilical hernia suture repair is performed simultaneously. Secondly, patient's satisfaction and hernia recurrence rate were assessed. METHODS: Consecutive women with symptomatic umbilical hernia undergoing internal or external suture repair during elective caesarean were included in this retrospective cohort-control study. Data on post-operative pain, duration of surgery and morbidity of a combined procedure were collected. These patients were matched 1:10 to women undergoing caesarean section only. Additionally, two subgroups were assessed separately: external and internal suture hernia repair. These subgroups were compared for patient's satisfaction, cosmesis, body image and recurrence rate. RESULTS: Fourteen patients with a mean age of 37 years were analysed. Internal suture repair (n = 7) prolonged caesarean section by 20 min (p = 0.001) and external suture repair (n = 7) by 34 min (p < 0.0001). Suture repair did not increase morphine use (0.38 ± 0.2 vs. 0.4 ± 02 mg/kg body weight), had no procedure-related morbidity and prolonged hospitalization by 0.5 days (p = 0.01). At a median follow-up of 37 (5-125) months, two recurrences in each surgical technique, internal and external suture repair, occurred (28 %). Body image and cosmesis score showed a higher level of functioning in internal suture repair (p = 0.02; p = 0.04). DISCUSSION: Despite a high recurrence rate, internal suture repair of a symptomatic umbilical hernia during elective caesarean section should be offered to women if requested. No additional morbidity or scar is added to caesarean section. Internal repair is faster, and cosmetic results are better, additional skin or fascia dissection is avoided, and it seems to be as effective as an external approach. Yet, women must be informed on the high recurrence rate.

Redescription of Anopheles (Nyssorhynchus) antunesi Galvão & Amaral and description of a new species of the Myzorhynchella Section (Diptera: Culicidae) from Serra da Mantiqueira, Brazil

Anopheles (Nyssorhynchus) pristinus Nagaki & Sallum, n. sp. of the Myzorhynchella Section is described based on morphological characters of adult females, males, fourth-instar larvae, pupae and male genitalia. Anopheles (Nyssorhynchus) antunesi Galvão & Amaral is characterized to fix its identity and distinguish it from An. pristinus. The eggs of An. antunesi are described for the first time. Molecular characterization employing sequences of the COI mitochondrial gene and the ITS2 region of ribosomal DNA are provided for each species. An. antunesi and An. pristinus are compared with morphologically similar species of the Myzorhynchella Section. The results of the present study suggest that the new species has been misidentified as both An. antunesi and Anopheles lutzii Cruz. An. antunesi and An. pristinus are sympatric, occurring at high altitudes in Serra da Mantiqueira, Southeastern Brazil.

Magma generation at the easternmost section of the Hellenic arc: Hf, Nd, Pb and Sr isotope geochemistry of Nisyros and Yali volcanoes (Greece)

Geochemical and petrographical studies of lavas and ignimbrites from the Quaternary Nisyros-Yali volcanic system in the easternmost part of the Hellenic arc (Greece) reveal insight into magma generating processes. A compositional gap between 61 and 68 wt.% SiO2 is recognized that coincides with the stratigraphic distinction between pre-caldera and postcaldera volcanic units. Trace element systematics support the subdivision of Nisyros and Yali volcanic units into two distinct suites of rocks. The variation of Nd and Hf present day isotope data and the fact that they are distinct from the isotope compositions of MORB rule out an origin by pure differentiation and require assimilation of a crustal component. Lead isotope ratios of Nisyros and Yali volcanic rocks support mixing of mantle material with a lower crust equivalent. However, Sr-87/Sr-86 ratios of 0.7036-0.7048 are incompatible with a simple binary mixing scenario and give low depleted mantle extraction ages (< 0.1 Ga), in contrast with Pb model ages of 0.3 Ga and Hf and Nd model ages of ca. 0.8 Ga. The budget of fluid-mobile elements Sr and Pb is likely to be dominated by abundant hydrous fluids characterised by mantle-like Sr isotope ratios. Late stage fluids probably were enriched in CO2, needed to explain the high Th concentrations. The occurrence of hydrated minerals (e.g., amphibole) in the first post-caldera unit with the lowermost Sr-87/Sr-86 ratio of 0.7036 +/- 2 can be interpreted as the result of the increased water activity in the source. The presence of two different plagioclase phenocryst generations in the first lava subsequent to the caldera-causing event is indicative for a longer storage time of this magma at a shallower level. A model capable of explaining these observations involves three evolutionary stages. First stage, assimilation of lower crustal material by a primitive magma of mantle origin (as modelled by Nd-Hf isotope systematics). This stage ended by an interruption in replenishment that led to an increase of crystallization and, hence, an increase in viscosity, suppressing eruption. During this time gap, differentiation by fractional crystallization led to enrichment of incompatible species, especially aqueous fluids, to silica depolymerisation and to a decrease in viscosity, finally enabling eruption again in the third stage. (c) 2005 Elsevier B.V. All rights reserved.

Molecular phylogeny of the Myzorhynchella Section of Anopheles (Nyssorhynchus) (Diptera: Culicidae): genetic support for recently described and resurrected species

Phylogenetic relationships among species of the Myzorhynchella Section of Anopheles (Nyssorhynchus) were investigated using the nuclear ribosomal DNA second internal transcribed spacer (ITS2), the nuclear whitegene and mitochondrial cytochrome oxidase subunit I (COI) regions. The recently described Anopheles pristinus and resurrected Anopheles guarani were also included in the study. Bayesian phylogenetic analyses found Anopheles parvus to be the most distantly related species within the Section, a finding that is consistent with morphology. An. pristinus and An. guarani were clearly resolved from Anopheles antunesi and Anopheles lutzii, respectively. An. lutzii collected in the same mountain range as the type locality were found within a strongly supported clade, whereas individuals from the southern state of Rio Grande do Sul, tentatively identified as An. lutzii based on adult female external morphology, were distinct from An. lutzii, An. antunesi and from each other, and may therefore represent two new sympatric species. A more detailed examination of An. lutzii sensu latoalong its known geographic range is recommended to resolve these anomalous relationships.

Non-invasive prenatal diagnosis of multiple endocrine neoplasia type 2A using COLD-PCR combined with HRM genotyping analysis from maternal serum.

The multiple endocrine neoplasia type 2A (MEN2A) is a monogenic disorder characterized by an autosomal dominant pattern of inheritance which is characterized by high risk of medullary thyroid carcinoma in all mutation carriers. Although this disorder is classified as a rare disease, the patients affected have a low life quality and a very expensive and continuous treatment. At present, MEN2A is diagnosed by gene sequencing after birth, thus trying to start an early treatment and by reduction of morbidity and mortality. We first evaluated the presence of MEN2A mutation (C634Y) in serum of 25 patients, previously diagnosed by sequencing in peripheral blood leucocytes, using HRM genotyping analysis. In a second step, we used a COLD-PCR approach followed by HRM genotyping analysis for non-invasive prenatal diagnosis of a pregnant woman carrying a fetus with a C634Y mutation. HRM analysis revealed differences in melting curve shapes that correlated with patients diagnosed for MEN2A by gene sequencing analysis with 100% accuracy. Moreover, the pregnant woman carrying the fetus with the C634Y mutation revealed a melting curve shape in agreement with the positive controls in the COLD-PCR study. The mutation was confirmed by sequencing of the COLD-PCR amplification product. In conclusion, we have established a HRM analysis in serum samples as a new primary diagnosis method suitable for the detection of C634Y mutations in MEN2A patients. Simultaneously, we have applied the increase of sensitivity of COLD-PCR assay approach combined with HRM analysis for the non-invasive prenatal diagnosis of C634Y fetal mutations using pregnant women serum.