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Biomedical subjects

E Tosti

Publications and source records attributed to E Tosti.

33 records · Page 2Linked to original sources
PubMed1993

Inositol tri-phosphate inhuman and ascidian spermatozoa.

Using a specific protein binding assay we have shown that a spermatozoon of the ascidian Ciona intestinalis contains 1.58 +/- 0.74 x 10(-19) moles of inositol 1,4,5-tri-phosphate (InsP3), while a human spermatozoon contains 6.4 +/- 0.14 x 10(-19) moles. Induction of the acrosome reaction (AR) in both species, by exposure to the calcium ionophore A23187, does not significantly alter levels of InsP3, suggesting that phosphatidylinositol (PI) turnover is not necessary for the calcium ionophore induced AR. Furthermore, PI turnover in ascidian spermatozoa appears to be insensitive to lithium and phorbol ester. The high intracellular concentration of InsP3 in spermatozoa, corresponding to 50-200 microM, suggests it may play a role in egg activation.

Acrosome↗
PubMed1993

Activation currents, sperm entry and surface contractions in ascidian eggs.

Spermatozoa from the mollusc Ostrea edulis are capable of fusing to and entering de-chorionated ascidian eggs. During interaction they generate activation currents, comparable to the fertilisation currents induced by homologous spermatozoa. Activation currents are inward at -80 mV, with a mean initial slope of 111 +/- 124 pA/s for Ciona intestinalis eggs and 47 +/- 25 pA/s for Phallusia mammillata eggs, while the mean peak currents are 2782 +/- 1132 pA and 1523 +/- 1668 pA, respectively. The fertilisation and activation currents reverse at a holding potential of 0 mV to + 20 mV, suggesting that oyster sperm and ascidian sperm gate the same channel precursor, a non-specific, large conductance channel described previously (Dale & DeFelice, 1984). In contrast to homologous fertilisation, the activation current is not followed by a polarised contraction of the egg surface, nor other signs of egg activation. Staining eggs with Hoechst 33342 after insemination shows the female nucleus and a single oyster sperm nucleus at the antipode. This suggests a specialised predetermined site at the vegetal pole for sperm entry. Homologous and heterologous spermatozoa delivered, in a large pipette, to localised areas of the egg surface generate fast inward currents of 200-2000 pA, but do not induce contraction of the egg surface. This shows that although channel precursors are located globally over the egg surface, channel activation does not necessarily trigger the contraction wave. Subsequent induction of both a fertilisation current and a contraction by homologous sperm added to the bath, implies a regionalised activation site with an accumulation of channel precursors and a 'pacemaker' for the initiation of the contraction wave.

Action Potentials↗
PubMed1991

Intercellular communication in the early human embryo.

A preliminary study on intercellular communicative devices in the early human embryo has been made using dye-coupling techniques and electron microscopy (EM). Lucifer yellow injected into single blastomeres of embryos at the 4-cell stage up to the late morula stage did not spread to neighbouring cells, indicating that gap junctions and cytoplasmic bridges are not significant pathways for information transfer. Dye spread was first observed in the blastocyst stage, where trophectoderm cells and inner mass cells were shown to be in communication through gap junctions. Studies at the EM level confirmed this finding. Tight junctions and desmosome-like structures, apparent from the 6-cell stage onward, were located both peripherally and centrally and were initially nonzonular. The role of intercellular devices in the primary differentiation of the human embryo is discussed.

Blastocyst↗
PubMed1991

Gap-junctional permeability in early and cleavage-arrested ascidian embryos.

Using the whole-cell voltage clamp technique, we have studied junctional conductance (Gj), and Lucifer Yellow (LY) coupling in 2-cell and 32-cell ascidian embryos. Gj ranges from 17.5 to 35.3 nS in the 2-cell embryo where there is no passage of LY, and from 3.5 to 12.2 nS in the later embryo where LY dye spread is extensive. In both cases, Gj is independent of the transjunctional potential (Vj). Manually apposed 2-cell or 32-cell embryos established a junctional conductance of up to 10 nS within 30 min of contact. Furthermore, since we did not observe any significant number of cytoplasmic bridges at the EM and Gj is sensitive to octanol, it is probable that blastomeres in the 2-cell and 32-cell embryos are in communication by gap junctions. In order to compare Gj in the two stages and to circumvent problems of cell size, movement and spatial location, we used cytochalasin B to arrest cleavage. Gj in cleavage-arrested 2-cell embryos ranged from 25.0 to 38.0 nS and remained constant over a period of 2.5 h. LY injected into a blastomere of these arrested embryos did not spread to the neighbour cell until they attained the developmental age of a 32- to 64-cell control embryo. Our experiments indicate a change in selectivity of gap junctions at the 32-cell stage that is not reflected by a macroscopic change in ionic permeability.

Animals↗
PubMed1988

Water hygiene of two swimming pools: microbial indicators.

The microbiological quality of the water of two swimming pools was evaluated to determine which organisms might be the best indicators of pollution. Membrane filtration gave low numbers of the common indicators of faecal pollution but high counts of the indigenous skin bacteria. As illnesses normally contracted in a swimming pool are mostly those of the skin rather than intestinal, it is suggested that the best indicators of the hygienic condition of water in a swimming pool are staphylococci because of their resistance to disinfection, high numbers in the environment, and ease of recovery.

Bacteria↗
PubMed1984

Incubation temperature and faecal streptococci recovery from marine sediments.

A comparative work was carried out on two different incubation temperatures that may be used for faecal streptococci recovery. Analyses were made on sediments samples collected in the bay of Naples in a larger survey of environmental pollution detection. Results showed a selective effect of 44 degrees C temperature on the isolation of the Streptococcus faecalis, Streptococcus faecium and Streptococcus durans species that may be considered properly faecal streptococci.

Animals↗
PubMed1982

The hemolytic activity of suberitine.

1. The hemolytic activity of suberitine, a neurotoxic protein isolated from Suberites domuncula, has been examined. 2. The toxin has no phospholipase A activity. 3. The hemolytic activity of suberitine does not exhibit the induction period and is completely inhibited by sucrose. 4. A study of the effect of temperature on the rate of hemolysis shows that suberitine has two values of the critical thermal increment. The optimum pH for the hemolytic activity was 6.0. 5. There was a correlation between the hemolytic and toxic activity.

Animals↗
PubMed1982

Hygienic condition of marine waters and sediments in the Gulf of Naples.

Faecal indicators of pollution were analysed in water and sediment samples which were collected in stations located in the gulf of Naples. Results showed the generalised build-up capacity typical of the sediments. Analyses stressed the extent of the pollution in the gulf: sediments might be polluted also in zones where the overlying waters remained faecally uncontaminated.

Feces↗
PubMed1979

Shellfish quality standards.

Total coliforms, faecal coliforms, enterococci and heterotrophic bacteria were determined in shellfish samples collected both in the marine environment (at Bacoli and Coroglio in the Bay of Naples) and from the local market. The same bacteriological analyses were carried out on water samples obtained from the shellfish growing areas. The results are considered in relation to standards applied in Italy and elsewhere to shellfish and shellfish cultures.

Animals↗