Prevention of hand-arm vibration hazards: from laboratory to practice.

Many studies were made throughout the world regarding the medical and technical aspects of hand-arm vibration since the first description by Loriga in 1911 of the vibration syndrome. Despite that the protection of operators against vibration hazards had progressed very slowly in practice with one notable exception, the case of chain saw users for whom several countries developed a comprehensive programme to eradicate the diseases successfully; regulations, antivibration tools, medical screening, preventive treatment. If all these actions are not carried out simultaneously in an industrial sector the transmission of knowledge from the laboratory to practice may be a failure or very costly in money, time and energy, as this article will show it in the case of suspended rammers and breakers.

Elaboration of a standard procedure for the measurement of vibration emitted by percussive tools--application to breakers.

The Association Française de Normalisation (AFNOR) is preparing a standard on the exposure assessment of vibration from percussive tools. Therefore, a test code was developed for the measurement of vibration from percussive tools under laboratory conditions. The handle vibration from six different breakers, among which three tools were of "antivibration design," was measured with the following energy absorption methods: hydraulic base, steel shot, actual breaking of concrete, AFNOR concrete block, pointed chisel embedded in concrete. The last four methods were applied with breakers held by three successive operators. In addition, the first two were used with tools mounted in a rig which held them vertically and loaded them with a vertical downforce. The results indicated that the steel shot method was preferable although it gave 20% lower vibration results than those recorded for the actual breaking of concrete. It has the advantages of yielding consistent results with low scatter and being simple and cheap. Since difficulties have been experienced during the use of a pneumatic rig with breakers of antivibration design conception, the shot method should be applied with human operators.

Ultrastructural modifications of the glandular epithelium of the receptaculum seminis in Thermobia domestica (Insectica: Thysanura) during the moulting period.

The wall of the receptaculum seminis of Thermobia domestica is composed of numerous glandular units, each with four enveloping cells (denoted 1 to 4) separated by ordinary epithelial cells and associated with a cuticular apparatus. During the moulting periods, which continue to occur in the adult stage, these cells undergo a series of transformations. Just before apolysis there is a dedifferentiation of numerous cytoplasmic organelles, but no mitosis has been observed. When the intima lifts off, the apical system of each glandular unit, i.e. the distal parts of the C2 and C3 cells surrounding the end apparatus, is also eliminated. Then at the apex of each glandular unit, a new ductule is formed in the cavity of which a long ciliary process grows up from cell C1. Finally comes the phase of cuticle formation, i.e., epicuticle for the ductules, epi- and endocuticle for the intima lining the central cavity of the receptaculum. Various cell types participate in secretion of cuticle, the ciliary cells (C1) being responsible for the formation of the porous end apparatus. At ecdysis almost all of the new intima has been secreted and the apical systems are once more differentiated. These transformations are compared with those recently described in other exocrine glands of arthropods, e.g., tegumentary glands and accessory glands of the genital ducts.

Ultrastructure of pheromone-producing eversible vesicles in males of Chrysopa perla L. (Insecta, Neuroptera).

During courtship, males of Chrysopa perla extrude from the genital aperture two eversible vesicles that bear approximately 50 sclerotized tubercles with a long, apical hair. Ultrastructural study reveals within each tubercle two juxtaposed subunits: a sensory subunit formed by a mechanoreceptor neuron, a glial cell, two enveloping cells, and a glandular subunit consisting of a glandular cell provided with an extracellular reservoir, a duct cell and an enveloping cell. The glandular-cell cytoplasm is characterized by extensive RER, a large amount of SER, probably involved in lipid elaboration, and voluminous myeloid bodies encircling the reservoir. The secretion is released to the outside by a cuticular duct that opens into the side of the tubercle. The function of the mechanoreceptor associated with the glandular subunit is discussed.