Primo Coltelli

A procedure for the extraction of object features in microscope images.

A program for a detailed and fast feature extraction procedure on objects from a digitized microscope image is presented. The single-pass algorithm labels the pixels of the image that are above a selected threshold, and connects those which belong to the same object. A data structure addressable as an associative memory is created, thus avoiding the use of any recursive procedures. A detailed description of the procedure, which extracts features such as integrated optical density, area and baricenter coordinates, is presented.

A digital microscope for real time detection of moving microorganisms

Abstract A digital microscope which can store time sequences in order to analyse moving objects, without the aid of a videorecorder, is described. This digital microscope can also be used to highlight moving microorganisms, such as protozoa, by suppressing the images of any stationary object, such as particles of dirt, dead or immobile cells. This microscope which operates in real time, is equipped with such standard devices as a TV-camera and a digital frame grabber with hardware facilities (Zoom, Pan, Scroll).

Automatic and real time recognition of microalgae by means of pigment signature and shape

Microalgae are unicellular photoautotrophic organisms that grow in any habitat such as fresh and salt water bodies, hot springs, ice, air, and in or on other organisms and substrates. Massive growth of microalgae may produce harmful effects on the marine and freshwater ecological environment and fishery resources. Therefore, rapid and accurate recognition and classification of microalgae is one of the most important issues in water resource management. In this paper, a new methodology for automatic and real time identification of microalgae by means of microscopy image analysis is presented. This methodology is based on segmentation, shape features extraction, and characteristic colour (i.e. pigment signature) determination. A classifier algorithm based on the minimum distance criterion was used for microalgae grouping according to the measured features. 96.6% accuracy from a set of 3423 images of 24 different microalgae representing the major algal phyla was achieved by this methodology.

The World of Algae

In the following sections of this chapter we will try to give an outline of some algae characteristics and general information on their classification, distribution, structure, nutrition and reproduction. In the last paragraph a short account on the origin of eukaryotic algae is set out.

Oddities and Curiosities in the Algal World

The term algae refers to a polyphyletic, non-cohesive and artificial assemblage, of O2-evolving, photosynthetic organisms. The profound diversity of size, shape, habitat, metabolic traits and growth strategies makes this heterogeneous assemblage of both prokaryotic and eukaryotic species an almost unlimited source of curious and unusual features. Algae display an incredible adaptability to most environments, and provide an excellent system for testing hypotheses concerning the evolution of ecological tolerance. In fact, they are not limited to temperate waters, but can survive at very low depth and very low irradiance, and thrive beneath polar ice sheets. Upon adaptation to life on land, algae have colonized such surprising places, as catacombs, tree trunks, hot springs, and can also resist desiccation in the desert regions of the world. Moreover, relations between them and other organisms, which include competition within and between species for space, light, nutrient or any limiting source, are based on a variety of associations, which includes epiphytism, parasitism, and symbiosis. Algae can share their life with animals, growing on sloth hair, inside the jelly capsule of amphibian eggs, upon the carapaces of turtles or shells of mollusks, camouflaging the dorsal scute of harvestmen. They can also light up the sea at night, and cause infections in animals and humans.

Computer processing of optical microscope images

Abstract Our paper describes the possibilities offered by connecting a computer to a traditional microscope. In particular it refers to the pictorial improvement of the microscope field, and to the enhancement and extraction of such features as perimeters, areas and countours.

In Vivo Absorption Spectra of the Two Stable States of the Euglena Photoreceptor Photocycle

Euglena gracilis possesses a simple but sophisticated light detecting system, consisting of an eyespot formed by carotenoids globules and a photoreceptor. The photoreceptor of Euglena is characterized by optical bistability, with two stable states. In order to provide important and discriminating information on the series of structural changes that Euglena photoreceptive protein(s) undergoes inside the photoreceptor in response to light, we measured the in vivo absorption spectra of the two stable states A and B of photoreceptor photocycle. Data were collected using two different devices, i.e. a microspectrophotometer and a digital microscope. Our results show that the photocycle and the absorption spectra of the photoreceptor possess strong spectroscopic similarities with a rhodopsin‐like protein. Moreover, the analysis of the absorption spectra of the two stable states of the photoreceptor and the absorption spectrum of the eyespot suggests an intriguing hypothesis for the orientation of microalgae toward light.

Low-resolution characterization of the 3D structure of the Euglena gracilis photoreceptor.

This paper deals with the first characterization of the structure of the photoreceptive organelle of the unicellular alga Euglena gracilis (Euglenophyta). This organelle has a three-dimensional organization consisting of up to 50 closely stacked membrane lamellae. Ionically induced unstacking of the photoreceptor lamellae revealed ordered arrays well suited to structural analysis by electron microscopy and image analysis, which ultimately yielded a low-resolution picture of the structure. Each lamella is formed by the photoreceptive membrane protein of the cell assembled within the membrane layer in a hexagonal lattice. The first order diffraction spots in the calculated Fourier transform reveals the presence of 6-fold symmetrized topography (better resolution about 90A). The 2D and 3D structural data are very similar with those recently published on proteorodopsin, a membrane protein used by marine bacterio-plankton as light-driven proton pump. In our opinion these similarity indicate that a photoreceptive protein belonging to the same superfamily of proteorodopsin could form the Euglena photoreceptor.

An image-processing system, motion analysis oriented (IPS-100), applied to microscopy.

This paper describes a real-time video image processing system, suitable for image analysis of stationary and moving images. It consists of a high-quality microscope, a general-purpose personal computer, a commercially available image-processing hardware module plugged into the computer bus, a b/w TV-camera, video monitors and a software package. The structure and the capability of this system are explained. The software is menu-driven and performs real-time image enhancements, real-time mathematical and morphological filters, image segmentation and labelling, real-time identification of moving objects, and real-time analysis of their movements. The program is available in listing form.

Reconstruction of the absorption spectrum of an object spot from the colour values of the corresponding pixel(s) in its digital image: the challenge of algal colours.

A novel procedure for deriving the absorption spectrum of an object spot from the colour values of the corresponding pixel(s) in its image is presented. Any digital image acquired by a microscope can be used; typical applications are the analysis of cellular/subcellular metabolic processes under physiological conditions and in response to environmental stressors (e.g. heavy metals), and the measurement of chromophore composition, distribution and concentration in cells. In this paper, we challenged the procedure with images of algae, acquired by means of a CCD camera mounted onto a microscope. The many colours algae display result from the combinations of chromophores whose spectroscopic information is limited to organic solvents extracts that suffers from displacements, amplifications, and contraction/dilatation respect to spectra recorded inside the cell. Hence, preliminary processing is necessary, which consists of in vivo measurement of the absorption spectra of photosynthetic compartments of algal cells and determination of spectra of the single chromophores inside the cell. The final step of the procedure consists in the reconstruction of the absorption spectrum of the cell spot from the colour values of the corresponding pixel(s) in its digital image by minimization of a system of transcendental equations based on the absorption spectra of the chromophores under physiological conditions.