Biomedical subjects

A Diaspro

Publications and source records attributed to A Diaspro.

46 records · Page 3Linked to original sources

PubMed1989

Analysis of three-dimensional cell imaging obtained with optical microscopy techniques based on defocusing.

The properties of an optical microscope are analyzed and analytically evaluated with a simple and effective model in order to understand the true meaning, limitations, and real capabilities of a defocusing technique. Major emphasis is given to the applications related to microscopic objects of biological interest using fluorescence and absorption light microscopy. A procedure for three-dimensional viewing is analyzed and discussed.

Cytological Techniques↗

PubMed1988

Native chromatin and damage induced by nuclease.

Differential scanning calorimetry, gel electrophoresis and polarized light scattering of chromatin prepared by different methods have been carried out at low and high ionic strength, before and after shearing. These noninvasive studies, when compared to the ones similarly conducted in the corresponding native nuclei, conclusively point to the artefactual nature of chromatin prepared by limited nuclease digestion, which has no resemblence with the in situ chromatin-DNA structure being instead preserved by lysis of native nuclei and by subsequent sedimentation and suspension of the viscous chromatin mass. Native nucleofilaments appear longer than 200 nucleosomes and yield, from thermodynamic and optical standpoints, a tight quaternary structure maintained even at 0.01 M.

Animals↗

PubMed1988

Nuclear architecture, intranuclear DNA distribution, and nuclease digestion.

G0, G1, and mammalian cells and nuclei were shortly digested with either micrococcal nuclease or DNAse I, both before and after mild fixation, either before (G0) or after (G1) partial hepatectomy. Cells were Feulgen stained and examined by high resolution light microscopy. In metabolically active G1 nuclei, intranuclear DNA appears organized at least in two distinct domains, whereby the highly dispersed one is large enough to be detected at the resolution of the light microscope and appears preferentially attacked by limited DNAse I digestion. The action of the enzyme is readily apparent only in the nuclei that are first digested and then fixed. Spectroscopic characterization of the same nuclei reveals that the fixation causes a sizeable removal of proteins, mostly in the soluble chromatin subfraction. Results are discussed in terms of two control levels for gene expression and for higher order DNA structure.

Animals↗

PubMed1987

Circular intensity differential scattering and chromatin-DNA structure. A combined theoretical approach.

Circular intensity differential scattering (CIDS) has been proven a powerful method in determining the higher-order structure of large biopolymers, such as chromatin. Theoretical predictions of the expected differential light scattering of circularly polarized light have previously been made for chromatin, either within the Born approximation, treating nucleosomes as noninteracting, oblate ellipsoids, or within a multiple dipole approximation, treating nucleosomes as interacting spheres. In order to conduct a meaningful interpretation of the CIDS signal in terms of given geometric parameters of the chiral structure, we have in this paper combined the two approaches considering the mutual interactions of ellipsoidal nucleosomes. In the process we have also found a confirmation for the validity of the Born approximation itself.

Chromatin↗

PubMedDate not supplied

Computer acquisition and analysis of thermal profiles from differential scanning calorimeter.

In this paper we describe a computerized system for data recovery from differential scanning calorimetry of mammalian cells and their biopolymers. The 'in-house'-designed preamplifier, digital acquisition, control card and its real-time software provide us with a powerful workstation to acquire and analyze large quantities of data on-line and off-line. The final data are obtained after eliminating noise interference using both hardware and software filters. Fourier analysis is also performed for a more refined thermodynamic characterization. All software is written in Basic and Fortran 77 under the DOS 3.10 operating system on a personal computer.

Algorithms↗

PubMedDate not supplied

IMAGO: a complete system for acquisition, processing, two/three-dimensional and temporal display of microscopic bio-images.

This work describes IMAGO, an integrated bio-imaging system developed in our laboratory. The whole system consists of a personal computer, a commercially available frame grabber directly plugged into a personal computer, video input/output modules, specific hardware for z-axis movement and light shuttering, and a software package. IMAGO is user-friendly, menu driven and enables one to perform image acquisition with different methods: optical sectioning, flashing epifluorescence, transmitted and phase contrast microscopy. It makes various functions possible, including: image transfer, gray scale processing, conventional and advanced filtering, logical operations, look-up table management, three-dimensional (3D) editing, 3D representation and auto-correlation techniques. More than 100 image processing functions have been implemented and can be easily managed through IMAGO. Examples are given in the area of biophysical research, like 3D representation of nuclei and of electron microscopic images, in situ microscopy of living cells. IMAGO processes information in an x, y, z, t space.

Image Processing, Computer-Assisted↗

PubMedDate not supplied