Intracellular distribution of iron (and associated elements) in various cell types of larvae and juveniles of the sea lamprey (Petromyzon marinus).

The intracellular distribution of iron and other elements was examined in various cell types in larvae and juveniles of the sea lamprey (Petromyzon marinus) using transmission electron microscopy and energy dispersive x-ray microanalysis. The objective was to establish whether there are cell-type specific relationships between iron and other elements in the iron-rich organs and tissues (adipose tissue, opisthonephric kidneys, dorsal integument, fat column, liver, and posterior intestine) of these two life cycle periods. Iron was localized within either dense bodies (presumptive lysosomes, siderosomes) or in the cytoplasmic matrix of many cell types where it was viewed as haemosiderin/ferritin and ferritin, respectively. Presumptive lysosomes of adipocytes of the nephric folds, dorsal integument, and fat column possessed iron and sulphur and this elemental association was also prevalent in the epithelia of the larval proximal tubules and in the posterior intestine and epidermis of both life periods. Macrophages of the larval haemopoietic tissue (posterior intestine) and of the juvenile opisthonephros, which were described as melanomacrophages because of their granules, possessed iron, sulphur, and calcium. This elemental association was also noted in the presumptive lysosomes of the iron-loaded hepatocytes of the juvenile liver while no elements could be detected in these cells in the larval organ. The variations and similarities in elemental associations between the cell types in each life period and at different life periods is discussed in the context of specific cell functions related to the prevention of iron toxicity. These functions are sequestration of iron and storage as the less toxic haemosiderin (larval adipocytes, macrophages, juvenile hepatocytes) or as part of a process of elimination of excesses of this metal (posterior intestine, dorsal epidermal cells). Due to its unique ability to deal with copious amounts of iron at all periods of the life cycle, the lamprey serves as an important model for studies of iron loading in vertebrates.

"Floating thumb metacarpal" or complete dislocation of the thumb metacarpal: a case report and review of the literature.

We present a case of a patient with a simultaneous dislocation of the metacarpophalangeal (MP) and the carpometacarpal (CMC) joint of the thumb as an isolated injury, and we review the relevant literature. We found only three previous reports in the literature, two reports as an isolated injury and another similar injury combined with a carpometacarpal fracture-dislocation of all four fingers. A closed reduction of both joints followed by an open repair of the torn ulnar collateral ligament of the MP joint and Kirschner-wire (K-wire) stabilization of the CMC joint led to a good result at 1 year. This rare injury has been described as a "complete dislocation of the thumb metacarpal" or as a "simultaneous dislocation of the MP and CMC joints of the thumb". We suggest it is a "floating thumb metacarpal".