Exosomes are a heterogeneous group of cell-derived membranous structures, which mediate crosstalk interaction between cells. Recent studies have revealed a close relationship between exosomes and bone homeostasis. It is suggested that bone cells can spontaneously secret exosomes containing proteins, lipids and nucleic acids, which then to regulate osteoclastogenesis and osteogenesis. However, the network of regulatory activities of exosomes in bone homeostasis as well as their therapeutic potential in bone injury remain largely unknown. This review will detail and discuss the characteristics of exosomes, the regulatory activities of exosomes in bone homeostasis as well as the clinical potential of exosomes in bone injury.

The histopathological features of the acute infection by Candida albicans in susceptible CBA/H mice, as well as its dissemination in various organs has been examined. The brain, in which the localization of blastospores is minimal, is the organ most severely affected. A significant deposition of blastospores occurs in lungs, liver, spleen and kidney, but of these organs, only in the kidneys is infection established. A transient myocarditis follows the minor blastospore deposition that occurs in the heart. Infection in the affected organs is characterized by abscess formation while in the brain the process is complicated by the development of hydrocephalus and a pachymeningitis that erodes the petrous temporal and involves the vestibular apparatus. There is also infection of the retinae with an accompanying endophthalmitis.

Summary The pathogenesis of Candida albicans infection was compared in three inbred strains of mice—CBA/H; C57B1/6J and BALB/c. CBA/H mice developed the most severe lesions, and also showed the weakest inflammatory responses in the popliteal lymph node after challenge with live organisms in the footpad. Nevertheless, this strain cleared Candida from the spleen more efficiently than either C57BI/6J or BALB/c mice. This apparently excludes a defect in phagocytosis as the basis for the increased susceptibility. The gene(s) determining susceptibility in CBA/H mice are located outside the major histocompatibility complex (MHC).

Macrophages are large mononuclear phagocytes that represent the major differentiated elements of the mononuclear phagocytic system. They arise from distinct progenitors in the bone marrow, and their immediate precursors, the monocytes, emigrate from the vascular compartment into many tissues and organs where they develop into mature macrophages. The latter display diverse morphological and functional characteristics, depending on the environmental stimuli that they receive. This phenotypic heterogeneity is, therefore, the final consequence of a series of down-regulation of some cellular processes and the up-regulation of others. The kinetics of the production of macrophages and their participation in various physiological and pathological phenomena is the subject of this review.

Summary Candida alhicans infections were established in eight inbred strains of mice. Using established histological criteria, only two strains (AKR and CBA/CaH) were found to exhibit severe lesions. The remainder showed only mild tissue damage. Deaths occurred in three strains: CBA/CaH, A/J and DBA/2. The last two strains lack the important complement component C5. Colony counts in the brain varied widely between strains and showed no correlation with the extent or severity of tissue destruction. However, strains lacking C5 had a significantly greater fungal burden in the brain than C5-sufficient mice. The data are discussed in relation to concepts of susceptibility and resistance to C. albicans in experimental infections in mice.

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This study was designed to define the precise anatomical location of Strongyloides ratti in the intestinal mucosa of the mouse. Light microscopy showed adult worms in vacuoles in close relationship with the columnar epithelium. Serial sections indicated that the adults wound their way circuitously through the mucosa, usually close to the crypts. Portions of worms were sometimes seen in the intestinal lumen. Electron microscopy demonstrated that adult worms were situated between the epithelial cells. They were never observed to penetrate the basement lamina and enter the lamina propria. Enterocytes were in close proximity to the cephalic end of worms, suggesting that the head of the moving worm forced the cells apart. More posteriorly along the worm, a fluid-filled vacuole surrounded the nematode. The surrounding epithelial cells were compressed and distorted but there was never any evidence of syncytial cell formation. The external cortical layer of worms was seen in some vacuoles, suggesting that ecdysis may occur in tunnels in the epithelium. It appears that S. ratti may create epithelial tunnels through which it moves, moults and deposits eggs. Since S. ratti is a mucosal-dwelling parasite, it is susceptible to attack by cellular elements of the host's defences.

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