it is a very short time that the quaternaries period in geology and physical geography's knowledge has occupied a very important place. during this period, the earth has suffered consecutive freezing that has been accompanied by tides and alternate erosion and sedimentation. sedimentary successions have recorded valuable evidence of changes with very accurate details. the study of these sedimen...

Cryopreservation procedures of living cells involve the use of organic solvents against fiwzing damage. An eff~ient cryopnwection might be achieved by obtaining a cytoplasmic gel able to reduce water flux and avoid crystallizarion. Small angle X-ray scattering experiments were performed at LURE (Orsay. France) to investigate the effects of 1.2propawdiot and glycerol on the struchne of auin, a m...

Gangliosides are a complex group of acid glycolipids characterized by the presence of sialic acid residues (Klenk, 1942). 'Ihey are present in high concentrations in neuronal tissue and appear to be concentrated in nerve endings (Pert et al., 1974). As such, they may be important in the process of neurotransmission (McIlwain, 1961) or may be involved in membrane receptors (Cuatrecasas, 1974) wh...

The aim of this study was to evaluate the effect of ovarian tissue fragmentation before preservation at 4C in MEM on the morphology, apoptosis, and growth of ovine preantral follicles. After collection, the ovaries were divided into two halves, being one divided into two fragments (1/4 of the ovary). One fragment was subdivided into two fragments (1/8), being one fixed for histology (fresh cont...

Triacylglycerol synthesis in plants occurs via the classical Kennedy pathway [1,2]. The quality and physical properties of the triaqlglycerol products are determined by the substrate specificities of the acyltransferases involved [2]. The initial step is catalysed by glycerol 3-phosphate acyltransferase and involves the acylation of the sn-1 position of lycerol 3-phosphate to form lysophosphati...

Protein synthesis is very active in cardiac muscle, and the isolated perfused rat heart has been shown to be sensitive to hormone administration (Morgan et al., 1971; Mowbray er al., 1975). We describe here a preparation of purified ribosomes in improved yield and in which the effects of insulin pretreatment have been preserved. Preparations of Flyribosomes from muscle generally involve attempt...

plant growth is greatly influenced by environmental stresses including water deficit, salinity and extreme temperatures. hence, the identification of genes especially regulatory ones whose expression enables plants to adapt to or to tolerate these abiotic stresses, is very essential. myb proteins are a superfamily of transcription factors that play regulatory roles in developmental processes an...