Antonio Quaglia

Studies on the role of neurosecretion in the induction of sexuality in a planarian agamic strain

Previous research work showed that in agamic strains of Dugesia gonocephala sensu lato (sl) inhibition of agamic reproduction by fission and development of a hermaphrodite genital apparatus could be induced by feeding the planarian species, Polycelis nigra, in which fission never occurs. In the present work, to isolate the sexualizing substance, 1200 specimens of P. nigra were homogenized and separated into four fractions by differential centrifugation. The fractions were: the 800g pellet, the 18 000g pellet, the 105 000g pellet, and the final 105 000g supernatant. Four groups of five specimens each of D. gonocephala were separately fed once a week for 10 weeks with the four fractions. Only the first and second fractions inhibited the agamic reproduction by fission and induced a sexual state. Ultrastructural examination of the four fractions showed structures that can be considered as neurosecretosomes only in the first and second fractions.

Ultrastructural localization of alkaline phosphatase in cultures of nervous tissuein vitro

SummaryThe fine localization of alkaline phosphatase in culturesin vitro of chick embryo spinal cord, explanted at early stages of development, was studied. Enzyme localization was found to vary in the different areas of the culture. In the central region, the reaction product was present only on the membranes of non-nervous cells and fibres directly in contact with the culture medium, while in the migration area the reaction product was also localized on membranes of deeper cells and fibres and on all membranes at the periphery of the culture. However, the membranes of nerve cells and their processes showed no evidence of reaction product when they were in direct contact with the medium. These observations are compared with data on the distribution of alkaline phosphatase in nervous tissue during embryonic development and in adults, and in relation to the possible role of alkaline phosphatase at the level of the haematoencephalic barrier. The hypothesis is considered that selective trophic mechanisms characteristic of nervous tissuein vivo may also occur in cultures.

The development of NADPH-diaphorase and nitric oxide synthase in the visual system of the cichlid fish, Tilapia mariae

The pattern of NADPH-diaphorase expression was studied in the retina and optic tectum of the cichlid fish Tilapia mariae during the first developmental stages. NADPH-diaphorase activity was seen early, at hatching. In the retina a few cell bodies of the retinal inner nuclear layer showed a faint labeling. Scattered labeled cells were found in the stratum periventriculare of the optic tectum, while the optic nerve was unlabeled. Two days after hatching, the number of labeled neurons increased in the inner nuclear layer and a few stained cell bodies were also scattered in the ganglion cell layer. Both the inner and outer plexiform layers showed a diffuse staining and the optic nerve was devoid of labeling. In the optic tectum several positive cells in the periventricular layer, with their dendritic trees extending in the superficial fibrous layer, were found. In 1-month-old Tilapia, NADPH-diaphorase staining and nitric oxide synthase immunoreactivity were found to overlap in both the retina and optic tectum. The density of NADPH-diaphorase labeled neurons in the inner nuclear layer of the retina and in the stratum periventriculare of the optic tectum was largely reduced in comparison with 2 days posthatching embryos. These findings indicated an early and transient production of nitric oxide in the retina and optic tectum of Tilapia, suggesting a functional role for nitric oxide in the development of visual structures in aquatic vertebrates.

Fine structure of undifferentiated gonads in Rana dalmatina tadpoles

Abstract The ultrastructure of Rana dalmatina tadpoles’ gonads is described during two early stages of development: the primary and the secondary undifferentiated condition. The gonadal bud structure in the first stage of differentiation is characterized, and it is clearly demonstrated that the cortex and the medulla are lined by an uninterrupted basal lamina along the margin adjacent to the primary cavity. The basal lamina that lines the cortex is a continuation of the one delimiting the somatopleura. In the second stage, it is shown that the medulla delaminates to form a secondary gonadal cavity known as the ovarian pocket, and that the cortex contains early germ cells, both isolated and undergoing mitotic division, corresponding to a germinal epithelium. In addition the diplotenic oocytes form a distinct layer within the primary gonadal cavity between the cortex and medulla. Each of the three layers (germinal epithelium, diplotenic oocytes, and hollow medulla) is delimited by its own basal lamina. The ultrastructure of the different germ and somatic cells is described.

Telencephalo-habenulo-interpeduncular connections in the brain of the shark Chiloscyllium arabicum.

The telencephalo-habenulo-interpeduncular connections have been studied in the brain of the cartilaginous fish Chiloscyllium arabicum. In addition to telencephalic and diencephalic projections to the habenula and to habenulo-interpeduncular projection, the presence of a direct telencephalo-interpeduncular connection confirmed some homologies of this system in cartilaginous fishes with actinopterigian fishes and land vertebrates.

The fine localization of ATPases in culturesin vitro of chick embryo spinal cord

SummaryA histochemical study of the ultrastructural localization of ATPases in cultures of chick embryo spinal cord has been carried out. The localization of Ca2+ and Mg2+ activated membrane ATPases appears similar: both enzyme activities are localized on the outer surfaces of plasma membranes of all kinds of cell present in the cultures, with the exception of the membranes in direct contact with the culture medium. The results are discussed in relation to data concerning the localization and function of ATPasesin vivo and in relation to the possible establishment of mechanisms of nutrient uptake and transfer in cultures of nervous tissue.

The muscular system of coelenterates

Abstract Though coelenterate muscle fibres develop as a part of epithelial cells, yet they seem to have the main morpho-functional features of muscle in the higher Metazoa. In fact, these fibres contain thick and thin myofilaments which may function as a sliding system. In addition, they may be smooth or cross-striated depending on the movement involved. Finally, they are connected by synapses with the nervous system.

Ultrastructural and morphometric studies on the axial muscles of the Grey mullet Mugil cephalus L. (Pisces Perciformes)

Abstract White and red axial muscle fibres of the grey mullet were studied by electron microscopy and morphometry. No significant difference was found between white and red fibers in their percentage of sarcoplasmic reticulum and T system, in location of triads and also in myofibril organization. However, red fibres were found to be richer in mitochondria and energy reserves than white fibres and this supports the view that these two fibre types play different roles in swimming locomotion.