Phototaxis action spectra have been determined in three different types of Euglena gracilis; green and dark-bleached cells containing the stigma and streptomycin-treated white mutant with an absorptionless stigma. In all three types of microorganisms the flavin containing paraflagellar body is present. The shape of the action spectrum is the same for the three types of cells and proportional to the absorption spectrum of flavoproteins. It has been shown that the structure of the action spectrum does not depend on the presence of screening organelles, on which, instead, depends the direction of the response to the light stimulus. It is concluded that the flavin chromophores present in the photoreceptor are the pigments responsible for phototaxis in Euglena gracilis.

No abstract

This is a cross-sectional survey on the health conditions of railways workers active in 258 interconnection and conversion substations all over Italy. Measurements performed in both kinds of substations operating at 220 kV have shown that maximum levels of the electric field strength and of the magnetic flux density at 50 Hz are of the order of 5 kV/m and 15 microT, respectively. Three subject groups, differently exposed (1, 10, 20 h/week), and an unexposed control group, for a total number of 627 workers, constitute the population at study. All subjects underwent a general medical examination, laboratory investigations, and a series of selected examinations relative to three systems (nervous, cardiovascular, and haematopoietic) considered at higher risk. No differences have been found between the exposed and the control groups. It is concluded that workers exposed to ELF electromagnetic fields of moderate strength do not show the presence of clear effects on their state of health.

After a short description of the motile physiology of Euglena gracilis the responses to light stimulation are analyzed and a new nomenclature is proposed concerning flagellar motility variations. A discussion follows about the characteristics of the photoreceptive system of Euglena and about the flavinic nature of its phototactic pigments.

Abstract— It has been shown that green cells of Euglena gracilis accumulate under red light. The action spectrum of this response has been determined. Its shape and the results of regreening experiments clearly indicate a role of chlorophyll. The quenching effect of chlorophenyl–dimethylurea and NH2OH demonstrate that this cell accumulation is not directly light‐induced, as in the case of phototaxis, but is due to an effect of oxygen, the evolution of which is stimulated by light.