Goffredo Cognetti

Synthesis of histones during sea urchin oogenesis.

Abstract Oocytes at the stage of vitellogenesis were isolated from sea urchin gonads and incubated in vitro with labelled lysine. The synthesis of arginine-rich and some other histone fraction was detected by column chromatography and electrophoresis. An attempt to calculate the absolute rate of histone synthesis is also reported.

Studies on protein synthesis during sea urchin oogenesis. I. Synthesis of histone F2b.

Basic proteins were extracted from sea urchin oocytes previously incubated with 3H-lysine and then were analyzed by electrophoresis. A very radioactive band, which showed the same mobility as histone F2b, was analyzed for its amino acid composition. The results show an identity between this protein and histones F2b. In addition, an improved method of isolating large amounts of sea urchin oocytes is described.

A molecular approach to the taxonomy and biogeography of African parrots

Abstract Random amplified polymorphic DNA analysis of blood samples from eight African parrot species was performed to study the genetic relationship within the genus Poicephalus and among Poi‐cephalus and the two other main African parrot genuses, Agapornis and Psittacus. To this end, DNA from six Poicephalus species, one species, of the Agapornis group and the single Psittacus species was analysed. The amplification pattern was then converted into a binary matrix and scored by the unweighted pair‐group method algorithm. The resulting dendrogram showed a neat separation of all the Poicephalus on one side, from Psittacus‐Agapornis on the other side. Among the six analysed species of Poicephalus, two larger clusters occurred, one containing four species belonging to the P. meyeri superspecies and the other one containing the two species pertaining to the P. robustus superspecies. The larger one of these is further subdivided in two smaller clusters, each one containing two species, that is P. meyeri‐P. cryptoxanthus and P. senegalus‐P. rufiventris, respectively. These results are consistent with the hypothesis that the genus Poicephalus is a natural assemblage that, after undergoing a very early separation from Psittacus and Agapornis, was subsequently affected by a number of discrete speciation events, especially during episodes of aridity resulting in fragmentation of forest habitats.

Studies of protein synthesis during sea urchin oogenesis. II. Synthesis of tubulin.

Sea urchin oocytes were incubated in vitro with [14C]lysine. Tubulin synthesis was demonstrated by gel filtration and/or electrophoresis of the colchicine-tubulin complex precipitated by vinblastine. The incorporation of [14C]lysine into tubulin represented about 12% of the incorporation into the total proteins at vitellogenesis.

Unusual properties of sea urchin unfertilized egg chromatin

A typical nucleosomal pattern is not detected by electrophoretic analysis of sea urchin mature egg chromatin, following digestion with micrococcal nuclease. Moreover, at least 80% of the egg nuclear DNA is resistant to nuclease attack. These unusual features of unfertilized egg chromatin, not shared by oocytes or sperms, are discussed in view of the unique properties and fate of mature female germ cells.

Block of Histone Synthesis in Isolated Sea Urchin Cells Actively Synthesizing DNA

Abstract The synthesis of DNA and histones are normally coupled. Only a few exceptions have been found. Dissociated cells from sea urchin embryos stop DNA synthesis, but resume it after trypsin treatment. It was of interest, therefore, to examine whether the synthesis of histones is similarly affected. Sea urchin embryos were dissociated from swimming blastulae and the cells so obtained were divided into two batches, one of which was treated with trypsin. Normal embryos from the same culture were used as controls. It was found that, in the dissociated cells, histone synthesis ceases, but unlike DNA, its synthesis is not resumed after treatment with trypsin.

Two proteases from nuclei of rat testis cells. I: Isolation

Abstract Two proteases, assayed with fluorogenic peptides and tentatively designated Rc and Kc, have been isolated from nuclei of rat testis cells by differential extraction with acetic acid, removal of some proteins at pH 4.5, and polyacrylamide gel electrophoresis followed by electroblotting onto nitrocellulose paper. Protease R hydrolyzes t‐Butyl‐oxycarbonyl‐Val‐Pro‐Arg‐7‐amino‐4‐methyl‐coumarin and other peptides in which arginine is joined to 7‐amino‐4‐methyl‐coumarin by amide linkage. Protease Kc has a preference for peptides terminating in lysine‐7‐amino‐4‐methylcoumarin amide. Neither of these proteases is active against Glu‐Phe‐7‐amino‐4‐methyl‐coumarin amide or Carbobenzoxy‐Arg‐7‐amino‐4‐methyl‐coumarin. Proteases Rc and Kc partially hydrolyze [3H] methyl ‐labeled histones H3 + H4 to trichloroacetic acid ‐ soluble peptides. Activities similar to proteases Rc and Kc are also found in cytoplas‐mic fractions of testis homogenates.

Microevolution in the sicilian shrew crocidura sicula (Mammalia, Soricidae) tested by RAPD‐PCR fingerprinting

Abstract Genetic variation in samples of the endemic Crocidura sicula living in Sicily and in two surrounding small islands, Marettimo and Ustica, was analysed by Random Amplified Polymorphic DNA fingerprinting (RAPD) and compared to morphometrics and external phenotypes. Molecular variation in the random sample of 99 DNA fragments of the Ustica shrews, showing.a melanic fur and a size‐shape variation in skull morphometrics, is of comparable size to that of the of northwestern and northeastern samples Sicily (Tufanio and Madonie). In the Marettimo shrews, bicoloured (grey and white) animals like those coming from Sicily and presenting a significant reduction in body‐size and skull morphometrics, molecular differentiation is higher than in those of the other locations, and characterizes this geographic population. Considering the paleogeographic records, it is hypothesized that the Marettimo shrews must have been isolated longer from the mother‐island; whereas for the Ustica shrews, a more recent arrival/i...

Fingerprinting ofCaprinae ancient genomic DNA: A preliminary note for studying the history of domestication in sicily

Oligonucleotide primers representing promoter and protein motifs in rats and mice were assayed for PCR amplification of ancient DNA from two sheep and one goat. We show preliminary evidence that this type of primers can be used for genomic fingerprinting of ancient DNA at interspecific level and can help in solving some paleoecological promlems.

Cell fractionation and RNA synthesis in yeast protoplasts

Abstract A new method is presented for obtaining purified nuclei and mitochondria from yeast. In addition, it has been observed that yeast protoplast incorporates 32P-phosphate into RNA and that RNA synthesis is inhibited by concentrations of actinomycin D equal or superior to 50 μg/ml.