Application d'une méthode d'extraction des lipides aux parois des blastospores de Candida albicans

Résumé Une méthode d'extraction physico-chimique des lipides a été appliquée à des blastospores entières de C. albicans, préalablement à leur étude en microscopie électronique à transmission. Les résultats permettent de supposer une localisation très superficielle des lipides liés à d'autres composants, en particulier peptidopolysaccharidiques, ce qui est en accord avec les données de la littérature. La méthode à également permis l'observation de structures microfibrillaires pariétales. Il s'agit surtout, d'une part, de fibrilles d'environ 50 Å de diamètre, situées dans les couches moyennes, également observables, après mise en oeuvre d'une technique d'extraction de polysaccharides sur cellules entières, et qui ont été assimilées à des fibrilles de ß 1–3 glucanes; d'autre part de fibrilles de 120 À de diamètre, situées au centre du septum de la cicatrice de bourgeonnement et qui ont été assimilées à des fibrilles de chitine.

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A chemical method for lipid extraction has been applied to Candida albicans blastospores previously to their examination by transmission electron microscopy. The results led to the concept of a superficial location of lipids bounded to the peptidopolysaccharidic matrix of the cell wall. This lipid extraction also allowed us to describe cell wall microfibrillar structures. Two types of microfibrills have been particularly identified: (1) microfibrils of approximately 50 Å in diameter, involved in a network of the cell wall intermediate layers and supposed to correspond to ß 1–3 glucans; (2) fibrillar structures of 120 Å in diameter, similar to chitin microfibrils, observed in the bud scar septum.

     

The mycelial wall of Trichophyton mentagrophytes; ultrastructural study of its constitutive layers following the use of a method to demonstrate polysaccharides]

The ultrastructure of T. mentagrophytes hyphal walls was studied after the use of a cytochemical reaction for polysaccharides. The sections showed a wall composed of 3 layers viz: an external, poorly reactive one with a microfibrillary structure; a medium, fairly reactive one, with a periodic structure and an internal, intensivly stained layer, not observed in old cells. Other observations suggested that the septal medium layer should be differentiated from those cited above. The results are compared with previous data and a synthetic scheme of the Trichophyton mentagrophytes hyphal wall is proposed.     

Superb Lyrebird Menura novaehollandiae mycophagy,truffles and soil disturbance

We observed foraging behaviour and collected 18 faecal samples of Superb Lyrebirds Menura novaehollandiae at two National Park locations in high‐elevation Nothofagus forests in the New England Tablelands of New South Wales, Australia. Based on microscopic examination of faecal samples, we provide the first report of mycophagy by this bird species. We hypothesize that this association is representative of a much more widespread relation between ground‐foraging birds and fungi. We apply methods not typically used by ornithologists to demonstrate the potential prevalence of mycophagy among ground‐foraging birds and its possible nutritional value. We additionally show the ecological significance that this and associated bird–fungus interactions have in the dispersal of symbiotic fungi.     

Similar hypotensive responses to resistance exercise with and without blood flow restriction

Low intensity resistance exercise (RE) with blood flow restriction (BFR) has gained attention in the literature due to the beneficial effects on functional and morphological variables, similar to those observed during traditional RE without BFR, while the effects of BFR on post-exercise hypotension remain unclear. The aim of the present study was to compare the blood pressure (BP) response of trained normotensive individuals to RE with and without BFR. In this cross-over randomized trial, eight male subjects (23.8 ± 4 years, 74 ± 3 kg, 174 ± 4 cm) completed two exercise protocols: traditional RE (3 x 10 repetitions at 70% one-repetition maximum [1-RM]) and low intensity RE (3 x 15 repetitions at 20% 1-RM) with BFR. Blood pressure measurements were performed after 15 min of seated rest (0), immediately after and 10 min, 20 min, 30 min, 40 min, 50 min and 60 min after the experimental sessions. Similar hypotensive effects for systolic BP (SBP) were observed for both protocols (P < 0.05) after exercise, with no differences between groups (P > 0.05) and no statistically significant difference for diastolic BP (P > 0.05). These results suggest that in normotensive trained individuals, both traditional RE and RE with BFR induce hypotension for SBP, which is important to prevent cardiovascular disturbances.     

Long-term treadmill exercise improves spatial memory of male APPswe/PS1dE9 mice by regulation of BDNF expression and microglia activation

Increasing evidence suggests that physical activity could delay or attenuate the symptoms of Alzheimer''s disease (AD). But the underlying mechanisms are still not fully understood. To investigate the effect of long-term treadmill exercise on the spatial memory of AD mice and the possible role of β-amyloid, brain-derived neurotrophic factor (BDNF) and microglia in the effect, male APPswe/PS1dE9 AD mice aged 4 months were subjected to treadmill exercise for 5 months with 6 sessions per week and gradually increased load. A Morris water maze was used to evaluate the spatial memory. Expression levels of β-amyloid, BDNF and Iba-1 (a microglia marker) in brain tissue were detected by immunohistochemistry. Sedentary AD mice and wildtype C57BL/6J mice served as controls. The results showed that 5-month treadmill exercise significantly decreased the escape latencies (P < 0.01 on the 4th day) and improved the spatial memory of the AD mice in the water maze test. Meanwhile, treadmill exercise significantly increased the number of BDNF-positive cells and decreased the ratios of activated microglia in both the cerebral cortex and the hippocampus. However, treadmill exercise did not significantly alleviate the accumulation of β-amyloid in either the cerebral cortex or the hippocampus of the AD mice (P > 0.05). The study suggested that long-term treadmill exercise could improve the spatial memory of the male APPswe/PS1dE9 AD mice. The increase in BDNF-positive cells and decrease in activated microglia might underpin the beneficial effect.     

Habitat correlates of the red panda in the temperate forests of Bhutan

Anthropogenic activities and associated global climate change are threatening the biodiversity in the Himalayas against a backdrop of poor knowledge of the region's threatened species. The red panda (Ailurus fulgens) is a threatened mammal confined to the eastern Himalayas, and because of Bhutan's central location in the distributional range of red pandas, its forests are integral to the long-term viability of wild populations. Detailed habitat requirements of the red panda are largely speculative, and there is virtually no ecological information available on this species in Bhutan. Between 2007 and 2009, we established 615 presence/absence plots in a systematic sampling of resident habitat types within Jigme Dorji and Thrumshingla National Parks, Bhutan, to investigate broad and fine-scale red panda habitat associations. Additional locality records of red pandas were obtained from interviewing 664 park residents. Red pandas were generally confined to cool broadleaf and conifer forests from 2,110-4,389 m above sea level (asl), with the majority of records between 2,400-3,700 m asl on south and east-facing slopes. At a finer scale, multivariate analysis revealed that red pandas were strongly associated with old growth Bhutan Fir (Abies densa) forest dominated by a dense cover of Yushania and Arundanaria bamboo with a high density of fallen logs and tree stumps at ground level; a high density of trees, dead snags, and rhododendron shrubs in the mid-storey; and locations that were close to water. Because Bhutan's temperate forests that encompass prime red panda habitat are also integral to human subsistence and socio-economic development, there exists an inadvertent conflict between the needs of people and red pandas. As such, careful sustainable management of Bhutan's temperate forests is necessary if a balance is to be met between the socioeconomic needs of people and the conservation goals for red pandas.