Rapid separation of rat peritoneal mast cells with Percoll

Rat peritoneal mast cells were separated by using density gradients of PVP-coated silica particles (Percoll). Mast cells were either isolated on preformed Percoll gradients or cell separation was made simultaneously with the gradient formation. Both procedures resulted in mast cell suspensions of 95 to 99 per cent purity. As tested by Ruthenium red staining and electron microscopy, the isolated mast cells showed a very good preservation of cell structure and reacted easily to the degranulating agent Compound 48/80. Practically all mast cells could be recovered from the peritoneal cell suspension. Percoll was found to be superior to earlier isolation procedures by giving a practically pure and intact mast cell suspension and by avoiding cell aggregation.     

The choline transport system of erythrocytes. Distribution of the free carrier in the membrane

A method is described, based on the kinetics of transport, for determining the equilibrium distribution of the carrier site on the inner and outer surfaces of the cell membrane, and this method is applied to the choline carrier of human erythrocytes. This method depends on measurement of flux ratios for both entry and exit, i.e., the transport rates of a low concentration of labeled substrate into a solution which contains either no substrate or a saturating concentration of unlabeled substrate. The concentrations of inward-facing and outward-facing carrier are found to be nearly equal, and therefore the 5-fold difference in choline affinity on the inner and outer surfaces of the membrane cannot be explained by an unequal carrier distribution. It is also shown that both reorientation and dissociation of the carrier-substrate complex are far more rapid than reorientation of the free carrier.     

Utilization of exogenous sugars by excised maize embryos in culture

Sucrose was markedly superior to fructose and glucose in promoting growth of plantlets from immature maize embryos. The elongation of roots is shown to be more sucrose dependent than that of shoots. On the other hand, the exogenous sucrose was less effective than fructose as substrate for carbohydrate catabolism and for the synthesis of alcohol-insoluble compounds at the beginning of embryo cultivation. The absorbed fructose was found to be rapidly converted to sucrose and the level of endogenous sucrose derived from sugar supplied to the medium was higher in fructosethan in sucrose-fed embryos. The preferential utilization of fructose over sucrose, however, declined with the progress of germination which may be related to the decrease in proportion of scutellum in total mass and physiological activity of the embryo.     

Isolation of 3-(2-carboxyethyl)thymine following in vitro reaction of β-propiolactone with calf thymus DNA

3-(2-Carboxyethyl)thymine (3-CET) was synthesized from β-propiolactone (BPL) and dThd5′P at pH 9.0–9.5 via the intermediate 3-(2-carboxyethyl)thymidine-5′-monophosphoric acid (3-CEdThd5′P). 3-CEdThd5′P was converted to 3-CET by hydrolysis in 1.5 N HCl at 100°C for 2 h. The structure of 3-CET was assigned on the basis of UV spectra, electron impact (EI) and isobutane chemical ionization mass spectra and the EI mass spectrum of a trimethylsilyl derivative of 3-CET. BPL was reacted in vitro with calf thymus DNA at pH 7.5. 100 A units of BPL-reacted DNA yielded, following perchloric acid hydrolysis and preparative paper chromatography, 3 A units of 3-CET. Reaction of BPL with the phosphodiester thymidylyl-(3′-5′)thymidine gave 3-(2-carboxyethyl)thymidylyl-(3′-5′)-3-(2-carboxyethyl)thymidine (～3%). Phosphotriester formation was not detected.     

Sialyl-transferase mitochondriale

A sialyl transferase activity is found in purified mitochondria. It is not due to residual contamination and this enzymatic system is located in the outer mitochondrial membrane. This proves mitochondrial autonomy in regard to glycoconjugate sialylation.     

Occurrence of subcutaneous zygomycosis (Entomophthoromycosis Basidiobolae) caused by Basidiobolus haptosporus with pulmonary involvement

A case of a two-year-old boy with multiple subcutaneous lesions caused by Basidiobolus haptosporus is presented.The child had also a non-toxic familial goiter and clinical and radiological features of a pulmonary illness. The pulmonary manifestations only disappeared with the treatment with potassium iodide. The authors think that the pulmonary lesions must have arisen by direct spread of the fungus from the subcutaneous lesions of the chest.     

Fine structure of early previtellogenic oocytes in Mugil (Liza) auratus Risso, 1810 (Teleostei,Mugilidae)

Summary Sequential cytological events at the onset of previtellogenesis were studied in oocytes from 12 m to 70 m in diameter of golden grey mullet. The main cytological changes observed (increase in size of cell, nucleus, nucleolus and increase in number of nucleoli, RNP particles, nuage and mitochondria) provide evidence for important synthetic processes in an early preparatory phase of oocyte development.Somatic cells (pre-follicle, follicle and thecal) are also described.