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Biomedical subjects

F D Barbieri

Publications and source records attributed to F D Barbieri.

At least 19 recordsLinked to original sources
PubMed1989

The origin of Metazoa and Weismann's germ line theory.

Weismann's theory asserts that the continuity of germ cells throughout the entire life cycle is insured by the protection of the somatic cells which represent a distinct lineage. On the basis of embryological data and the organization pattern displayed by some highly differentiated unicellular organisms, it is postulated that the soma of multicellular animals has probably arisen as an accessory structure for an initially unicellular system.

Animals↗
PubMed1988

Extracellular materials and determination of neuroectoblast in amphibian gastrula.

The biological activity of the extracellular material (ECM) located in the dorsal and ventral regions of Bufo arenarum is assayed. Ectoblast cells were isolated and cultured with ECM taken from the embryonal regions. The epiblastic cells treated with dorsal ECM, mainly located at the interphase between the invaginating blastoporal lip and the overlying ectoblast differentiated morphologically into neural, mesenchyme and pigment cells. In contrast, control epiplastic cells, cultured either in salt solution or in ventral region ECM, differentiated into ciliated and secretory cell types. The results reported here provide evidence that the dorsal region ECM of the embryo can induce neural differentiation in indeterminate epiblastic cells.

Animals↗
PubMed1983

Newly synthesized extracellular ribonucleic acids in the amphibian gastrula.

The possible synthesis of RNA located in the extracellular compartment of Bufo arenarum gastrula was studied using a biochemical method. [3H]adenosine was microinjected into the blastocoel of late blastulae or early gastrulae, which were then dissociated at advanced gastrula stage. RNA was extracted from both, the cellular supernatant and the disaggregated cells, by the Kirby-phenol procedure. Most of the ethanol-precipitable radioactivity was sensitive to RNase and alkaline treatment. The partial characterization of these molecules indicate that the radioactive pattern of total RNA, found in sucrose gradients, the ratio Poly(A)+RNA/Poly(A)-RNA as well as the radioactive pattern of Poly(A) fraction in acrylamide gels were different in samples from cellular and from extracellular origin. Although not conclusive, these results are proposed as a new argument for the existence of an extracellular RNA in the amphibian embryo.

Animals↗
PubMed1980

Changes in lectin-mediated agglutinability during primary embryonic induction in the amphibian embryo.

The present study was undertaken to investigate structural alterations at the surface of presumptive neural cells after primary embryonic induction. For this purpose, plant lectin-mediated agglutinability of dissociated cells from the epiblast of Bufo arenarum gastrulae was tested. Two fragments of epiblast were excised from the same mid-gastrula: one from the dorsal side of the egg, making contact with the invaginating chordamesoblast and assumed to be composed of determined cells and the other from the ventral region of the egg, facing the blastocoele cavity and assumed to be composed of undetermined cells. Cells of the pooled fragments were dissociated in calcium-free Holtfreter's solution with potassium oxalate and incubated in the presence of different concentrations of phytohemagglutinin and concanavalin A. Epiblast cells overlying the archenteron roof are less agglutinated with both lectins than undetermined cells. On the other hand, when egg fragments were removed from the dorsal and ventral regions of early gastrulae before the archenteron was formed, no significant difference in lectin-mediated agglutinability was observed, even after having been cultured in vitro in absence of inducing tissue. These results suggest that the target of the inducing signal generated in the mesoblast is likely to be located on the surface of epiblast cells. Additional experiments showed that cells pretreated with colchicine, cytochalasin B or colchicine and cytochalasin B simultaneously exhibit no significant variation in agglutinability, suggesting that the cytoskeleton was not be involved in the cell surface alteration here described. Treatment of whole embryos or sandwich explants with concanavalin A or phytohemagglutinin has no effect on neural tube formation, suggesting that the carbohydrate-containing binding sites for these lectins are not involved in primary embryonic induction. Changes in cell agglutinability described in this paper are to be interpreted thus as a secondary expression of structural alterations in the cell surface concomitant with neural determination.

Animals↗
PubMed1978

A trypsin-like oviducal proteinase involved in Bufo arenarum fertilization.

When the jelly-less eggs removed from the most cephalic region of the oviduct (pars recta) of the toad Bufo arenarum were inseminated at a high sperm concentration, high frequencies of fertilization were obtained. On the other hand, control eggs removed from the pleuroperitoneal cavity (coelomic eggs)) were neither fertilized upon insemination under identical conditions, nor with the water extract of the jelly. Under these inseminating conditions, however, a high frequency of fertilization was obtained when coelomic eggs were preincubated in the presence of the fluid secreted by the epithelium of the pars recta or of an extract prepared from pars recta homogenate. Experimental evidence is presented showing that the component responsible for this effect acts on the vitelline envelope of the egg, increasing its susceptibility to sperm lysin. It is probable, therefore, that it induces successful fertilization of coelomic eggs by making the vitelline envelope more easily penetrable by sperm. The active factor was partially purified by Sephadex chromatography. The product obtained was of high activity and, as judged by its inhibition with soybean trypsin inhibitor and lima-bean trypsin inhibitor, it is likely to be a trypsin-like enzyme. The molecular weight of the factor was estimated to be 47000 by Sephadex chromatography. Secretion of the pars recta factor is hypophysis-dependent and its activity is not influenced by pH within the range testes (6.0--8.4).

Animals↗
PubMed1977

Properties and isolation of the diffusible factor involved in Bufo arenarum fertilization.

Earlier studies have shown that a substance(s) released from the egg jelly of the toad Bufo arenarum is required for fertilization. In this paper some properties of this diffusible factor were further examined, and a procedure was designed for its isolation from crude egg extracts. The active component is soluble in water and ethanol, and insoluble in chloroform, ether and n-butanol. The biological activity is stable to liophylization and to heat, and remains unaffected after trypsin treatment. In contrast, it is impaired after treatment with ethyl acetate, 0.1 N HCl or chloroform, and is completely destroyed after converting the diffusible factor into ash. Data are presented showing that the recovery of fertilizability of extracted eggs in the bioassay system as carried out under present conditions, cannot be ascribed to a pH alteration of the insemination medium. This lends further support to the view that diffusible factor activity is not mediated through a pH effect. The factor was purified by gel chromatography coupled with desalting and paper chromatography. The active molecule is of low molecular weight and appears associated with a high pH ninhydrin-positive fraction.

Animals↗
PubMed1976

Diffusible factors in anuran fertilization.

Anuran eggs are shed surrounded by a jelly material which is deposited by the oviduct as they descend through it. As soon as they come in contact with water, some components are released from the jelly coats into the inseminating inedium. The present review summarizes the information bearing on the problem of these diffusible factor involvement in fertilization. Evidence exists indicating that they are likely to exert some specific as well as protective influence on the spermatozoon. Their activity is discussed in connection to the acrosome reaction and the role of the jelly in the fertilization process. Attention is also drawn to some adaptive features of anuran fetrillization, suggesting that they would represent a transitional form between typically external and internal fertilization.

Acrosome↗