Paolo Gualtieri

A complex photoreceptive structure in the cyanobacterium Leptolyngbya sp.

Among the terrestrial epilithic cyanobacteria isolated from Roman hypogea at extremely low light intensity, a non-heterocystous strain, belonging to the genus Leptolyngbya, showed a marked photobehavior. These red cyanobacteria possess an orange spot at the tip of the apical cell. Micro-spectrophotometric analysis of this tip showed an absorption spectrum with two bands, centered at 456 and 504 nm, respectively. Experiments on photo-orientation impairment of these cells, and micro-spectrophotometric analysis of the tip of impaired trichomes showed that a rhodopsin-like protein might be present in this structure. All these data could support the hypothesis of the presence of a complex photoreceptive system in this prokaryote.

Photoreceptor morphology and visual pigment content in the pineal organ and in the retina of juvenile and adult trout, Salmo irideus

Abstract We performed microspectrophotometric measurements on isolated retinal and pineal photoreceptors of the trout Salmo irideus. Retinal rods contain a visual pigment with λmax at 512 nm. In adult trout the retinal cone system consists of single and double cones with pigments having peaks at 453 nm (single cones and one member of double cones), 530 nm (single cones and one member of double cones) and 598 nm (one member of double cones). Juvenile fish possess an additional type of single cone absorbing maximally at 400 nm. Scanning electron microscopy analysis of the cone mosaic shows a square pattern of double cones with a central single cone and corner single cones in yearling trout, and a similar pattern without corner single cones in two-year-old trout. Our data on the pineal organ reveal two different kinds of cells showing two distinct types of pigments, the former having its λmax at 463 nm and the latter with its maximum at 561 nm.

Identification of retinal in higher plants: Is a rhodopsinlike protein the blue light receptor?

Abstract We here report the purification and identification of all- trans -retinal by column chromatography, HPLC and GC-MS in a tomato mutant ( Lycopersion esculentum Mill. aurea mutant). Since retinal, wherever present, is almost exclusively associated to an opsin to form a light-sensitive complex (rhodopsin-like proteins), this finding suggests that a rhodopsin-like protein could function as a blue light photoreceptor in higher plants.

A Rhodopsin-like Protein in the Plasma Membrane of Silvetia compressa Eggs ¶

Unidirectional blue light directs the rhizoid–thallus axis in the apolar zygote of the brown alga, Silvetia compressa. This effect is mediated by an increase in the intracellular concentration of guanosine 3′, 5′‐cyclic monophosphate. In this study we show the identification of a rhodopsin‐like protein, by means of antibody reaction, in the plasma membrane of Silvetia eggs. This new result suggests a role for opsins in Silvetia photopolarity.

Atomic Force Microscopy Study on the Pellicle of the Alga Euglena gracilis

AFM technique was used to investigate the organization of the pellicle complex of Euglena gracilis. These results mainly validate data obtained by our group using SEM and TEM investigations. In this chapter particular attention has been given to the surface characteristic of Euglena such as the muciferous canals and pores.

Time as the Fifth Dimension in Microscopy

This paper describes an image processing system, suitable for real time image understanding and the analysis of moving objects under the optical microscope, such as microorganisms orienting toward a source of light. The system consists of an optical microscope, a desktop computer, a commercially available image-processing hardware module plugged in the computer bus, a b/w TV-camera, video monitors, and special software developed for the use. The structure and the capability of this system are explained.

Wavelength as the Fourth Dimension in Light Microscopy

This paper describes a microspectroscopic instrumentation suitable for performing absorption and fluorescence spectra of cellular compartments inside their functional environment. The system consists of an optical microscope, measuring diaphragms, diffraction gratings, and photodetectors. A personal computer acquires the signals from the photodetectors and handles the diffraction gratings. In this chapter the absorption and fluorescent spectra of Euglena gracilis photoreceptor and chloroplast are presented.

An algorithm comparing the two mononuclear curves of choice reaction times in pigeons

A simple and fast algorithm allowing the matching between frequency distributions is developed. The procedure consists in a class by class mapping of two distributional curves in order to derive a class transformation function that specifies how a class from one distribution is modified to produce a class in another distribution. Being interested in investigating the equivalence between the eyes, we have compared left and right monocular curves of choice reaction times to three different visual discrimination tasks in intact and surgically manipulated pigeons by means of the present technique of analysis. The results indicate that RTs distributions of the eyes belong to the same family of functions. It is possible, however, to demonstrate a difference in the range of time responses between the two monocular curves during one of the three visual discriminations used, particularly in the lesioned group.