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A carbonated simulated inorganic plasma CSIP physiologically buffered with carbonate-hydrogencarbonate, where a flow of CO2at controlled partial pressure enables pH control between 7.3–7.4 while maintaining a constant HCO−3concentration within the plasmatic range 24 to 27 mmol dm−3, was previously developed and reported1by the authors. The present work represents a step forward, by introducing albumin in this solution, to produce albumin-containing CSIP CSIPA. Mineralisation studies were performed on three materials two calcium phosphate ceramics and a glass of the Si-Ca-Mg-P system in CSIPA, and compared with those performed in traditional Tris-buffered Kokubo's SBF containing albumin SBFA. It was found that the formation of apatite deposits in CSIPA is favoured when compared not only with SBFA, but also with albumin-free CSIP. The results indicate that the presence of HCO−3in physiological concentration andor the absence of TrisHCl buffer may alter the role of albumin in the mineralising medium. The results also suggest that CSIPA-simulated plasma not only mimics in vivobiomineralisation more closely than traditional SBF, but may also be a suitable medium for biomimetic deposition of apatite.

The ultrastructural changes induced in the cells of the young rat adrenal zona fasciculata by cycloheximide are studied. Thirty minutes after administration of doses producing inhibition of protein synthesis (1.5 and 4.5 mg/kg body weight) there was a significant increase in the relative volume of the nucleolus, as shown by stereologic methods, which was accompanied by extensive perinucleolar chromatin caps. In the cytoplasm, membranous whorls were observed in several organelles and the background cytoplasm, but the volume fractions of the organelles were not significantly altered. Nucleolar changes were interpreted as suggesting that the inhibition of cytoplasmic protein synthesis may be accompanied by an enhanced formation of nucleolar proteins.

The sites of RNA synthesis, processing and migration were studied with light and electron microscope radioautography in adrenal zona fasciculata cells of the young rat. Animals were injected iv with [3H]uridine and sacrificed at various time intervals. A marked radioactive peak was found in blood at the 20 min interval, later time intervals being considered as chase periods. Labelling was high over nucleoli of fasciculata cells at 1 h, with the silver grains concentrated over the fibrillar component. Simultaneous though lower peaks occurred over the condensed chromatin and the interchromatin space. Nucleolar and extranucleolar values were decreased at 8 and 24 h, most silver grains overlaying the cytoplasm at this time period. At 8 h, the granular component of the nucleolus was more heavily labelled than the fibrillar component.This sequence of events suggests a relatively slow uptake of the labelled nucleotides and slow formation of pre-rRNA molecules in the fibrillar component of the nucleolus, with the processing into smaller subunits occurring in the granular component during initial chase. Extranucleolar RNAs were synthesized simultaneously but in a smaller rate. Most nucleolar RNA was finally transferred to the cytoplasm. This pattern will serve as a basis for studying the effects of ACTH on the different steps of RNA synthesis and transport in adrenal cortex cells.

Abstract. The effect of ACTH on the RNA synthesis in adrenal zona fasciculata cells of the young rat were studied by light and electron microscope radioautography. Two units of ACTH were administered scto animals and immediately followed by an iv injection of [3H]uridine. ACTH-injected and control rats, which received the isotope alone, were sacrificed at various time intervals. Labelling over extranucleolar areas was higher in the ACTH-treated animals at 20 min, then becoming lower than in the controls at 60 min and 24 h. Nucleolar radioactivity, however, was consistently decreased by ACTH at all experimental times. Apart from these changes in the rate of synthesis, the over-all curves of labelling were similar to those in the control animals with a striking peak at 1 h. The short-term increase in extranucleolar RNA synthesis observed after ACTH injection was considered to be consistent with the hypothesis that an enhanced extranucleolar synthesis of mRNA takes place early in stimulated animals and is associated with the synthesis of steroidogenic proteins. On the other hand, the relatively decreased uridine uptake of the label by the nucleolus in ACTH-treated animals, suggests an inhibition of nucleolar transcription with diminished pre-rRNA formation in treated animals.