Evaluation of Organelle Changes in Promastigotes of Unresponsive Leishmania Tropica to Meglumine Antimoniate in Comparison with Sensitive and Standard Isolates by Electron Microscopy.

BACKGROUND: The control of leishmaniasis faces serious challenges because of resistance to the first-line antimonial drugs. We aimed to evaluate the differences in organelle changes of cultivated promastigotes obtained from skin lesions of sensitive and unresponsive isolates to meglumine antimoniate (Glucantime) by electron microscopy. MATERIAL AND METHODS: This study was done in Bam city, southeastern Iran, in which the incidence of disease has sharply increased since the earthquake in 2003. The samples were taken from 66 patients who were referred to the cutaneous leishmaniasis (CL) treatment center in Bam. A questionnaire was completed for each individual, recording their demographic characteristics and CL status. The scraping smears provided from the edge of active lesions with sterile blades were fixed with methanol, stained by Giemsa, and examined under a compound light microscope for amastigote form simultaneously. To prepare the specimens for transmission electron imaging, promastigotes were centrifuged and resuspened. RESULTS: Transmission electron microscopic study of the cultivated promastigotes revealed that there were alterations in the organelles and structures of sensitive isolates compared with unresponsive and standard ones. Organelles and structures such as mitochondria, kinetoplast, microtubules, cytoplasmic vacuoles, plasma membrane and vesicles were studied. The alterations such as disintegration of kinetoplast into thin filaments and condensation of kinetoplast DNA core, changes in size, number and location of vesicles and microtubules were observed. We noted intense cytoplasmic vacuolization, and considerable swelling of mitochondria. CONCLUSION: The significance and relevance of these changes might help understand drug resistance patterns and help localize the best target site for inactivating the organism.

Electron Microscopy Reconstruction of Brain Structure Using Sparse Representations Over Learned Dictionaries.

A central problem in neuroscience is reconstructing neuronal circuits on the synapse level. Due to a wide range of scales in brain architecture such reconstruction requires imaging that is both high-resolution and high-throughput. Existing electron microscopy (EM) techniques possess required resolution in the lateral plane and either high-throughput or high depth resolution but not both. Here, we exploit recent advances in unsupervised learning and signal processing to obtain high depth-resolution EM images computationally without sacrificing throughput. First, we show that the brain tissue can be represented as a sparse linear combination of localized basis functions that are learned using high-resolution datasets. We then develop compressive sensing-inspired techniques that can reconstruct the brain tissue from very few (typically five) tomographic views of each section. This enables tracing of neuronal processes and, hence, high throughput reconstruction of neural circuits on the level of individual synapses.

On the production of X-rays by low energy ion beams.

Although electron beams with energies of a few keV can excite fluorescent X-ray production from solids, ion beams of comparable energy cannot do so. The reason for this situation is that it is the velocity of the incident particle, rather than its energy, which determines whether an ionization event can be generated.