Silvio Ranzi

The proteins in the cells and in embryonic development

A viscosimetric method allowing one to recognize the shape of protein particles in solution has been devised. The method is based on the differences in behaviour of the different kinds of proteins upon denaturation s . Two samples are prepared from a protein solution. In the first, KSCN is added up to 0 .05-0 .1m final concentration. In the second (the control) the same amount of KC1 is added. To 10 ml of protein solution (from 0.01% to 0.1%) 0.6 ml of 1 m KSCN are added. 10 ml of the same solution plus 0.6 ml of 1 m KC1 are used as controD. After standing 4 hours at 10°-20 ° C (or overnight at 0°C) the viscosity was measured in an Ostwald viscosimeter. Owing to the low concentrations used in our experiments, determination of density is not necessary. In a protein solution with fibrillar particles, the

Sul meccanismo di azione delle sostanze che modificano lo sviluppo embrionale

The lithium chloride and the substances, which are capable of producing a similar effect on the embryo development, increase the viscosity of proteins from the Amphibian embryo. The sodium thiocyanate, the sodium iodide and the pyocyanine lower it. The proteins fractions which can appear in elongated particles are those which feel the action of the thiocyanate and of the pyocyanine.

Sintesi di mRNA di β-tubulina durante ľinduzione e ľorientamento specifico neurale

Ľibridazionein situ condotta su embrioni diXenopus laevis con cDNA di β-tubulina ha dimostrato un forte incremento nelle cellule della piastra neurale e delľectoderma laterale dopo la gastrulazione, quando il cordomesoderma viene a contatto con ľectoderma. Esperimenti condotti su espianti di ectoderma neurale presuntivo eseguiti prima e dopo ľinduzione neurale suggeriscono che le cellule abbiano gia un orientamento specifico in senso neurale allo stadio di blastula. prima che ľinduzione avvenga.In situ hybridization experiments carried out with β-tubulin cDNA onXenopus laevis embryos showed a marked increase in β-tubulin mRNA in neural plate and lateral ectoderm after gastrulation, when chordomesoderm and ectoderm come in contact. Experiments with fragments of presumptive neural ectoderm explanted before and after neural induction suggest that the cells are already specified in neural sense at the blastula stage, long before the neural induction.RiassuntoĽibridazionein situ condotta su embrioni diXenopus laevis con cDNA di β-tubulina ha dimostrato un forte incremento nelle cellule della piastra neurale e delľectoderma laterale dopo la gastrulazione, quando il cordomesoderma viene a contatto con ľectoderma. Esperimenti condotti su espianti di ectoderma neurale presuntivo eseguiti prima e dopo ľinduzione neurale suggeriscono che le cellule abbiano già un orientamento specifico in senso neurale allo stadio di blastula. prima che ľinduzione avvenga.

Induction of Somites by Myosin mRNA

The effects of the messenger for myosin heavy chain (26S mRNA) on postnodal explants of chick embryo blastoderm were studied. Somites do not differentiate in the postnodal explants of chick embryo cultivated by News method. They are induced when postnodal pieces are cultivated in the presence of a 26S mRNA extracted from chick leg muscles or in the presence of myosin. 26S mRNA plus actinomycin D induces small somites. 26S mRNA of duck, rabbit, or trout induce somite structures often built up of cells separated by large spaces and joined around a large myocele. Crayfish 26S mRNA or chick myosin light chain induce columnar cells connected around a cavity. Liver or kidney mRNA do not induce. The induction process can be summarized as follows: 26S mRNA codes for myosin (heavy chain) and the myosin (heavy chain) induces the somites. Induction of somites by mRNA can occur in the presence of actinomycin D but not when there is mRNA plus puromycin. It does occur when myosin acts in the presence of puromycin. Myosin and its heavy chain are present in chick blastoderm before the appearance of somites. Induced somites are able to induce neural plates. We conclude that in normal development somites are induced by myosin.

Espressione genica e induzione neurale

Abstractβ-tubulin cDNA has been used as molecular marker to study the expression of β-tubulin-mRNA during neural induction by dot blot andin situ hybridization. The results show that a marked increase in β-tubulin mRNA levels occurs during gastrulation, when chordomesoderm and ectoderm come in contact.In situ hybridization experiments with fragments of presumptive neural plate explanted before and after neural induction suggest that neural ectoderm is already specified before neural induction.RiassuntoII cDNA di β-tubulina è stato utilizzato come marcatore molecolare per studiare ľespressione del mRNA di β-tubulina durante ľinduzione neurale. I risultati ottenuti con le tecniche della ibridazione su filtro (dot blot) e delľibridazionein situ mostrano un notevole incremento della quamità di mRNA di β-tubulina durante la gastrulazione, quando il mesoderma cordale si dispone al di sotto delľTectoderma. I risultati delle ibridazioniin situ eseguite sulla piastra neurale espiantata prima e dopo ľinduzione neurale suggeriscono ľipotesi che ľectoderma neurale sia già pre-determinato.