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Biomedical subjects

R Romand

Publications and source records attributed to R Romand.

78 records · Page 5Linked to original sources
PubMedDate not supplied

Reinvestigation of spermatic flagella structure: the teleostean Cyprinodontidae.

The study of 7 genera and 15 species of teleostean fishes belonging to the family Cyprinodontidae shows a similar morphology of mobile spermatozoa and a wide diversity of structure of the spermatic flagellum. The flagellar membrane has one, two, or three lateral expansions depending on the species. Peripheral doublets of axonema show only the external arm, except for two species that completely lack them. Intratubular differentiations (ITD) are present in A or B tubules of peripheral doublets as in central tubules of some species, whereas others are totally devoid of them. The ITD can affect all doublets or preferentially doublets 1, 5, and 6. These variations may be due to neutral mutations.

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PubMedDate not supplied

Early stages of myelination in the spiral ganglion cells of the kitten during development.

Myelinated cell bodies of spiral ganglion in kittens during development can first be distinguished by light microscopic observation at the end of the first postnatal week. By mean of electron microscopic observation, the first signs of myelinated perikarya can be observed around the time of birth. Myelination is preceded by the ensheathment of the ganglion cell body by two or three layers of Schwann cell cytoplasmic processes. At birth, the first sign of myelination is visible at the basal part of the cochlea with thin thickenings which contain two or three major dense lines. At this stage, these thickenings cover only a small perikaryal area. Later on, the thickness and the number of thickenings increase and cover the major part of the cell body. The onset of myelination of the processes seems to precede the perikaryal myelination.

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PubMedDate not supplied

The ontogenesis of pseudomonopolar cells in spiral ganglion of cat and rat.

The ontogenesis of type II ganglion cells (T II cell) in the spiral ganglion in the cat and in the rat was studied by light microscopy and by electron microscopy. In the cat, typical pseudomonopolar T II cells with light-coloured cytoplasm containing abundant neurofilaments are observed at birth in the basal part of the cochlea. No T II cells are observed in more immature areas such as the third turn. A constant number of T II cells is present and no typical sign of degenerative ganglion cells is observed throughout postnatal development. In the rat, T II cells can be recognized with confidence at the 6th day post partum. It is suggested that T II cells represent a population of normal cells in the spiral ganglion that can be seen late during ontogenesis.

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PubMedDate not supplied

The ultrastructure of spiral ganglion cells in the mouse.

In the adult mouse, three types of spiral ganglion cells can be distinguished on an ultrastructural basis. The first type, TI cells, corresponds to the most commonly encountered cells in the ganglion, which represents 92 to 94% of the whole population. This type of cell is characterized by numerous cytoplasmic organelles that give a dark and a granular appearance, while the nucleus is more lightly coloured. Moreover, the perikaryon is surrounded by a myelin sheath composed of several myelin lamellae that can be either loose or compact. The periodicity of compact myelin around the perikaryon is larger than that found in nerve fibres. The T II ganglion cells, corresponding to the second type, are less numerous and represent only 6 to 8% of the cell population. They present a clear perikaryon with few cytoplasmic organelles and large areas composed of filamentous structures. The perikaryon is not surrounded by a myelin sheath, although several Schwann cell processes can be observed. The third type is composed of few ganglion cells that are ultrastructurally very close to T I cells, but without a myelin sheath. Desmosome-like junctions have been observed between myelin lamellae and between myelin lamellae and the plasmalemma, but no synaptic contacts have been observed between auditory nerve fibres and ganglion cells.

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