Paula Macedo

Ultrastructure of Bacilli and the Bacillary Origin of the Macrophagic Inclusions in Whipple's Disease

An electron microscopic and cytochemical study of the Whipple bacillus in jejunal biopsies from three untreated patients was made using fixation procedures developed for the satisfactory preservation of bacterial ultrastructure. The envelopes of the normal-looking bacilli present free in the lamina propria consisted of the following layers. (i) A cytoplasmic membrane with a triple-layered profile and a mean thickness (peak-to-peak distance) of 6.08 nm. (ii) A thick (20 nm) cell wall containing peptidoglycan; the wall had a hitherto undescribed inner layer that contained polysaccharides, possibly teichoic acids. (iii) Surrounding the cell wall, a surface membrane with a symmetric profile and a mean peak-to-peak distance of 4.74 nm. The ultrastructural pattern of the Whipple bacillus wall corresponds to that of Gram-positive bacteria, but with an additional surface membrane. This membrane is different from the outer membrane of Gram-negative bacteria because it has a symmetric profile, is thinner and has no periodic acid-Schiff (PAS)-positive components. Normal-looking bacilli were seen very rarely inside jejunal macrophages, but degenerating bacteria were abundant in these phagocytes. Electron microscopy and ultrastructural cytochemistry of Whipple bacilli inside jejunal macrophages of the three untreated patients showed that the degenerative process is a sequence that leads to the loss of bacillary forms and to the accumulation of bacterial remnants resistant to degradation by the macrophage. These remnants correspond to the innermost, polysaccharide-containing portion of the bacillus wall. The progressive accumulation of these PAS-positive wall remnants is the origin of the intramacrophagic inclusions that are important in the histological diagnosis of Whipples disease. The reported results indicate that in the three patients studied, the Whipple bacillus multiplies extracellularly, the bacteria that are phagocytosed by macrophages being degraded.

Ultrastructural Characterization of Normal and Damaged Membranes of Mycobacterium leprae and of Cultivable Mycobacteria

Microdensitometry showed that the membrane profiles of normal cultivable mycobacteria were very asymmetric (outer layer denser and thicker than the inner layer), while the profiles of normal-looking M. leprae in lepromatous patients, in experimentally infected armadillos and in nude mice were approximately symmetric; moreover, the membrane of M. leprae was thicker than that of cultivable species. Using two cytochemical methods for the ultrastructural detection of periodic acid-Schiff (PAS)-positive molecules (the Thiéry procedure, and staining with phosphotungstic acid at low pH) we found that the membrane of cultivable mycobacteria, growing in vitro or in vivo, had PAS-positive components exclusively in the outer layer, while the normal-looking M. leprae in patients and in armadillos had membranes with PAS-positive components in both layers. The membranes of damaged cultivable mycobacteria, in vivo or in vitro, and of damaged M. leprae, in patients or armadillos, were PAS-negative.

Cytochemical and ultrastructural study of anoikis and secondary necrosis in enterocytes detached in vivo.

Detachment-induced apoptosis of enterocytes (anoikis) has not been investigated in vivo. Here we describe anoikis of fish enterocytes following detachment in a septicemia by Photobacterium damselae subsp. piscicida, or following injection of its exotoxin. The in vivo study was complemented with an ex vivo time-lapse analysis using conditions duplicating the in vivo situation. Linings of enterocytes detached from intestine mucosa dissociate into isolated enterocytes which undergo caspase 3-mediated anoikis with cell rounding, loss of polarization, condensation of chromatin and fragmentation of the nuclear envelope, early swelling of mitochondria with rupture of the outer membrane, and brush border disappearance. One mechanism for brush border loss was shedding of apoptotic bodies incorporating the apical part of the enterocyte. Brush border disappearance was also associated with disassembly of the F-actin microvillar core and involved re-absorption into the cell, or expansion and vesiculation followed by shedding of microvillar fragments. The enterocyte anoikis terminates by secondary necrosis and lysis due to lack of elimination by phagocytosis of apoptosing enterocytes. The conditions prevailing in vivo in the gut lumen accelerate enterocyte secondary necrosis. Our results underscore the importance of analyzing anoikis under conditions similar to those occurring in vivo.

Acquisition of autoimmunity genes by New Zealand mice is associated with natural resistance to infection by mycobacteria.

New Zealand (NZ) mouse strains comprise both autoimmune and non-autoimmune animals: NZ black (NZB) mice and the F1 hybrid (NZB/W) of NZB and NZ white (NZW) mice show spontaneous autoimmune disease by 6 months of age and die before the first year of age from renal disease, while NZW mice do not show autoimmune disorders. We investigated whether the autoimmunity-prone NZ animals (NZB and NZB/W) differ from the non-autoimmune NZW mice in susceptibility/resistance to mycobacterial infection. The three groups of NZ mice were infected by intraperitoneal inoculation of 10(8) colony forming units (cfu) of Mycobacterium avium. The M. avium infection was induced in 3-month-old mice (i.e., before NZB and NZB/W mice develop autoimmune disease) and studied for 4 months. Infected NZB and NZB/W mice showed evidence of renal disease at 2 and 4 months of infection (but not at 1 month). The non-autoimmune NZW mice were found to be susceptible to M. avium since they allowed massive proliferation (4-5 log growth) of the bacilli in liver and spleen. In contrast, both groups of autoimmunity-prone mice (NZB and NZB/W) were resistant to M. avium since their mycobacterial loads remained below the value of the initial inoculum. We conclude that in NZ mice the acquisition of autoimmunity genes is associated with expression of natural resistance to mycobacterial infection. This is consistent with the view that autoimmunity genes may have been evolutionarily selected because of their association with increased resistance of the host to infections by intracellular parasites.

Oral Health in Down Syndrome

Oral health in Down Syndrome (DS) individuals has some peculiar aspects that must be considered in the follow up of these patients. In this chapter, we will focus on the oral and maxillofacial morphological alteration, the most prevalent oral pathologies as well as preventive measures and strategies for pathologies management in this population. Also, future research on oral health of DS will be discussed.

Medicine and Social Media - Ethical Challenges of the 21st Century

Introduction: With the huge growth of social networks, their use is increasing in hospitals and clinics and by physicians. However, health professionals are not always aware of the risks inherent to the use of these tools. The aim of this study is to analyse the problems associated with the use of social media in doctor-patient communication, as well as some rules that may help overcoming the potential risks of this situation. Methodology: Searches were conducted on Google Scholar, Google and Medline and limited to articles published in English, between 2004 and 2014. Twenty-three articles were selected out of 52. Boudreaux’s social media governance website was also used to identify institutional policies on social media. The articles were analysed through thematic coding using template analysis. Discussion and Conclusion: The control of the published information, the regular review of the privacy settings and the limiting access to personal information is of great interest not only for the physician but also for the profession he/she represents. To ensure that health professionals are Mini-review Article