Calcium pathway through a mineralizing epithelium in the crustacean Orchestia in pre-molt: Ultrastructural cytochemistry and X-ray microanalysis

During the pre-exuvial period of the terrestrial crustacean Orchestia, the calcium of the old cuticle is almost entirely reabsorbed and stored as calcareous concretions in the lumen of the midgut posterior caeca. The elaboration of these concretions is due to transport by the caecal epithelium. With ultrastructural cytochemistry controlled by X-ray microanalysis, it can be demonstrated that the main sites of ionized or ionizable calcium are the apical microvilli and an extracellular (lateral and basal) network of channels. Direct precipitating cytochemical methods, using potassium pyroantimonate or pyrophosphate, potassium oxalate or oxalic acid, sodium fluoride, sodium tungstate, and indirect substitution methods, using lead acetate or nitrate and cobalt nitrate were comparatively used. The results are interpreted in favour of the hypothesis of an extracellular transport pathway for calcium through the lateral smooth septate junctions, in conjunction with a more classical apical transport through the microvilli.     

Uptake of fetal proteins by Trypanosoma cruzi immunofluorescence and ultrastructural studies

Isolated proteins from fetal calf serum needed for trypanosomal growth were labelled with I¹²⁵, colloidal gold and fluorochrome tagged specific antibodies. The proteins were localized in the membranes and cytoplasm of parasites cutured in vitro in a defined liquid medium.     

Clinical interest of cutaneous models reproducedin vitro for severe burn treatment: histopathological and ultrastructural study

The healing of minimal skin lesions is usually obtained by epidermal migration and proliferation from peripheral wound margins. However, cutaneous grafts or reconstituted skin are necessary for severe injuries. Various models have recently been reproduced for this purpose. The aim of this work is to report the histopathologic evolution of burn lesions treated two years ago by autologous epidermis (Genzyme Tissue Repair, Boston, USA). Fifteen patients with severe burns (more than 80% of surface) have been treated. These observations have been based exclusively on biopsies of grafted wounds. Cultured epidermis is rapidly fully differentiated after grafting with temporary hyperplasia and normal strata. At 18 months, rete ridges formation is present only in young patients. Melanocytes and Langerhans' cells repopulated grafts rapidly. The use of cultured epidermis nowadays represents an important improvement in burn treatment.Abbreviations CEA cultured epidermal autologous sheets - TBSA total burn surface area     

Changes in the Ultrastructure of Prasiola crispa ssp. antarctica under Salinity Stress

The supralittoral green alga Prasiola crispa, collected in Antarctica, was grown at salinities ranging from 0.35 %o to 175 %o. Its ultrastructure was examined by electron microscopy and compared with the ultrastructure of plants grown under standard conditions (35 %o). The thalli had very thick cell walls, making up approximately 50% of the thallus volume. Most of the protoplast was occupied by a single chloroplast. Numerous starch granules in the chloroplast were enlarged under hypo-osmotic conditions and reduced in volume when subjected to hyperosmotic stress indicating a metabolic shift towards low molecular weight organic osmolytes under the latter conditions. Whilst vacuoles were lacking in plants cultured at salinities between 0.35 %o and 35 %o, they developed under hyperosmotic conditions and possibly may serve as compartments accumulating inorganic ions. Growth, photosynthesis and dark respiration were strongly inhibited under higher salinities, whilst they remained almost unaffected under lower salinities (Jacob et al., 1991).