Search PubMed⌕ Search

Biomedical subjects

M Grattarola

Publications and source records attributed to M Grattarola.

At least 37 records · Page 2Linked to original sources
PubMed1994

Scanning force microscopy on live cultured cells: imaging and force-versus-distance investigations.

Extensive measurements with the scanning force microscope on living cells in their native liquid environment are described with the purpose of critically assessing the extent of the interaction between the SFM tip and the (soft) cell materials and the effect of such interaction on topographic information. Images are obtained under various force conditions and systematically correlated with force-versus-distance curves. As a result, detailed indications about tip indentation are given, thickness estimates deduced and identification of submembranous cytoplasmic structures suggested.

Animals↗
PubMed1993

Modeling the neuron-microtransducer junction: from extracellular to patch recording.

This paper is devoted to a detailed characterization of the neuron-to-microtransducer junction, based on the equivalent electric-circuit approach. As a result, recording of action potentials can be simulated with the general-purpose network-analysis program SPICE. Both noble-metal microelectrodes and insulated-gate FET's are considered. The responses of such devices are characterized as functions of several parameters, e.g., sealing impedance, density of ionic currents in the cell membrane, and spatial discontinuities of the adhesion process. It is shown that the various signal shapes reported in the literature can be reproduced and interpreted in terms of time derivatives of the action potential. In this way, the shape of any experimental signal can be interpreted on the basis of a specific sealing condition. Possible future improvements in microtransducer design, based on the proposed approach, are also suggested.

Action Potentials↗
PubMed1993

Images of cultured neurons: morphological and functional information.

The in vitro culture of neuronal cells is a useful tool for studying, in a controlled way, neurobiological and neuropharmacological phenomena. A first step towards the understanding of these phenomena is described. Effects of simulated excitatory/inhibitory synapses, artificially positioned along the digitized image of neural arborizations, are presented.

Animals↗
PubMed1993

Early detection of cell metabolism with a silicon microsensor.

A silicon microsensor (ISFET--Ion Sensitive Field Effect Transistor) has been used to detect the metabolism of a cell population cultured on a coverslip and positioned close to the sensor surface. The system output is analyzed as a function of cell density.

Animals↗
PubMed1988

Cell adhesion to silicon substrata: characterization by means of optical and acoustic cytometric techniques.

The adhesion and growth of cells on silicon dioxide substrata are analysed. The adhesion of human red blood cells to silicon dioxide layers of different depth and doping compares well with that to glass. Rat pheochromocytoma cells also grow on the same substrata. The adhesion of these two biological systems is characterized at the microscopic level by using the quite new technique of scanning reflection acoustic microscopy. Possible future developments towards the functional coupling of living cells to microelectronic integrated circuits are briefly discussed.

Adrenal Gland Neoplasms↗
PubMed1987

Effects of low-intensity pulsed electromagnetic fields on the early development of sea urchins.

The effects of weak electromagnetic signals on the early development of the sea urchin Paracentrotus lividus have been studied. The duration and repetition of the pulses were similar to those used for bone healing in clinical practice. A sequence of pulses, applied for a time ranging from 2 to 4 h, accelerates the cleavages of sea urchin embryo cells. This effect can be quantitatively assessed by determining the time shifts induced by the applied electromagnetic field on the completion of the first and second cleavages in a population of fertilized eggs. The exposed embryos were allowed to develop up to the pluteus stage, showing no abnormalities.

Animals↗
PubMed1985

Laser flow measurements of scattering and fluorescence from cell nuclei in the presence of increasing Mg++ concentrations.

The effects of Mg++ on the spatial organization of nuclei from rat hepatocytes are analyzed in the range 0-60 mM, in the presence of suitable concentrations of KCl to reproduce physiological conditions. It is shown that the scatter-signal distribution measured by means of a flow microfluorimeter is greatly affected by this range of Mg concentrations. By coupling this result to phase-contrast-automated image analysis, it is possible to identify a shrinking process induced by Mg++ in the range 0-2.5 mM, which reaches a plateau in the range 5-20 mM and is followed by a swelling process in the range 30-60 mM. The same Mg ranges are shown to affect the intercalation of the fluorochrome acridine orange into chromatin, suggesting that the shrinking-swelling phenomenon has also a molecular correspondence at the genome level. Possible implications in terms of the influence of Mg++ on the organization of chromatin inside intact cells are briefly discussed.

Acridine Orange↗
PubMed1984

Interaction between electromagnetic fields and cells: microelectrophoretic effect on ligands and surface receptors.

The aggregation between lectins and lymphocyte surface receptors can be affected strongly by a low-level electric field induced in the cell suspension by a time-varying magnetic field. One of the possible mechanisms is the microelectrophoretic effect due to the electric field, which influences the distance (in the mean square sense) between charged ligands and receptors when they are about to separate. On a purely theoretical basis, it is shown that, at low frequencies, an externally induced periodic electric field always decreases the mean lifetime of ligand-receptor complexes. As a consequence, the mitogenic gain obtained by lectin addition to cell suspension is decreased. These results suggest that such a mechanism, if effective, reduces the lectin mitogenic capability and offers a way of handling similar phenomena which have been described for other biological systems.

Electromagnetic Fields↗
PubMed1982

Early effects of chemical carcinogens as compared to induced cell proliferation. II. Automated image analysis.

Static automated image analysis was applied to study early variations of chromatin structure in Feulgen-stained liver nuclei from rats injected i.p. with a single dose of dimethylnitrosamine (DMNA), a well known hepatocarcinogen. An increase of nuclear area and a correspondent decrease of average optical density (integrated optical density/area) was observed, as compared with controls, in nuclei from rats treated with 5.4 mg/kg of DMNA. These findings, which were comparable with those induced by partial hepatectomy, indicate the existence in DMNA-treated cells of a chromatin DNA relaxation similar to the G0-G1 transition previously described for human diploid fibroblasts stimulated to proliferate. Because similar results were independently obtained by flow microfluorimetry, it seems reasonable to hypothesize that chromatin decondensation could be a prerequisite for cancer induction.

Animals↗
PubMed1982

Early effects of chemical carcinogens as compared to induced cell proliferation. I. Flow microfluorimetry.

Acridine orange-stained rat liver cells have been analyzed by flow microfluorimetry either after i.p. injection of 0.6 and 5.4 mg/kg of dimethylnitrosamine or 18 hr after partial hepatectomy. Treatment with dimethylnitrosamine induced a marked increase in the fraction of cells with higher green fluorescence intensity which can be related to a greater number of chromatin primary binding sites, and a decrease in the fraction of cells with higher red fluorescence intensity corresponding to a lower amount of cellular RNA. Contrary to the carcinogen-induced early changes towards a more relaxed uncoiled structure, as well as an apparent uncoupling between chromatin-DNA structural alterations and total RNA synthesis, could be first events in the carcinogenetic process.

Acridine Orange↗
PubMed1981

Correlation between Barr body and overall chromatin decondensation in vitro.

Geometric and densitometric properties of the Barr body of early and late phase II confluent human fibroblasts are analysed by the automated image analyser Quantimet 720 D. In cells with the same 2C DNA content, the state of condensation of the Barr body varies proportionally wih the state of condensation of the entire nucleus yielding a correlation between nuclear and Barr body area. In light of these results, indicating the participation of the Barr body in the overall process of chromatin condensation and decondensation, a definitive "'static" separation between dense ("heterochromatic") and dispersed ("euchromatic") regions of chromatin seems to be arbitrary. The implications of these results in terms of a possible attachment of interphase chromatin to the nuclear envelope are briefly discussed.

Cell Nucleus↗
PubMed1980

FPi analysis. II. Use of the method to monitor the in vivo kinetics of cell populations perturbed by hydroxyurea.

In a previous report, we described a new method called FPi analysis to analyze time sequences of DNA histograms taken from a perturbed population of cells. In this paper we utilize the method to analyze the in vivo kinetic response of bone marrow and of lung metastases of the B16 tumor to various chemotherapeutic agents. We show that the technique allows useful kinetic data to be obtained with minimal processing of the raw histograms, thus allowing fast analysis of the data. We also show that, in order to monitor the kinetic response of living tissues, it is essential to collect multiparameter distributions; to monitor only the one dimensional fluorescence histogram can give rise to misleading results. Using these multiparameter histograms, we are also able to monitor the growth fraction of the lung metastases during treatment, allowing discrimination between cell synchrony and cell recruitment from the resting compartment.

Animals↗