Iron is essential for normal brain function and its uptake in the developing rat brain peaks during the first two weeks after birth, prior to the formation of the blood–brain barrier (BBB). The first step of iron transport from the blood to the brain is transferrin receptor (TfR)-mediated endocytosis in the capillary endothelial cells. However, the subsequent step from the endothelium into interstitium has not been fully described. The goal of this study was to examine the expression of iron transport proteins by immunodetection and RT–PCR in the developing rat brain. Tf and TfR are transiently expressed in perivascular NG2+ cells of the capillary wall during the early postnatal weeks in the rat brain. However, MTP-1 and hephaestin were expressed in endothelial cells, but not in the NG2+ perivascular cells. Immunoblot analysis for these iron transfer proteins in the developing brain generally confirmed the immunochemical findings. Furthermore, the expression of Tf and TfR in the blood vessels precedes its expression in oligodendrocytes, the main iron-storing cells in the vertebrate brain. RT–PCR analysis for the primary culture of endothelial cells and pericytes revealed that Tf and TfR were highly expressed in the pericytes while MTP-1 and hephaestin were expressed in the endothelial cells. The specific expression of Tf and TfR in brain perivascular cells and MTP-1 and hephaestin in endothelial cells suggest the possibility that trafficking of elemental iron through perivascular cells may be instrumental in the distribution of iron in the developing central nervous system.

In a previous paper(1) t,he mechanism of external respiration in certain acridian species of Orthoptera was described. I n these species it was shown that the exchange of gases between the tracheal system and the outside air does not occur by an alternate influx and efflux of air through all of the spiracles. Instead, there is a circulation through the tracheal system, air being inspired through the anterior four pairs of spiracles and expired through the posterior six pairs. Of these expiratory spiracles, the tenth ones are the most efficient.As opportunities have permitted, further observations have been made in other species of Acrididae and in representative species of the other families of Orthoptera. These species and families were Mecostethus lineatus and Hippiscus tuberculatus of the family Acrididae ; Blatta orientalis and Periplaneta americana of the family Blattidae ; Stagmomantis Carolina of the family Mantidae ; Diapheromera femorata of the family Phasmidae ; Scudderia texensis, Microcentrum laurifolium, and Neoconocephalus ensiger of the family Locnstidae ; Gryllus abbreviatus of the family Gryllidae. This list includes representatives of all of the families of the Orthoptera, unless the Forficulidae are considered as belonging to the order.The methods used were the same as those reported previously(l), and the observations made were the same. Although only one species of the Phasmidae and one of the Mantidae were studied, it is believed that a general statement 319