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Microglia of teleosts: facing a challenge in neurobiology
Full text linkThis review is concerned with recent literature on teleost fish CNS microglia. It covers not only various aspects of these cells, notably comparing them with mammalian microglia, but also points out the several potentialities neural tissue of teleosts exhibits in neurobiological research. The relationships between neurons and glial cells are considered in fish, aiming at an integrated picture of the complex ways neurons and glia communicate and collaborate in normal and injured neural tissues. In addition, attention has been paid to different teleost models according to their availability, easy maintenance in experimental conditions, possibilities of embryos manipulation and sequenced genome. The recent setting up of successful protocols for fish glia and mixed neuron-glia cultures, together with the molecular facilities offered from genome knowledge, should provide a new boost to studies about microglia and neuron-microglia relationships
Fish take their revenge: alternative models for modern neurobiology.
No full textThe last decade witnessed an “explosion” in neurobiological research. Part of this success is due to the rapid development of molecular biology techniques which gave a substantial contribution, becoming an extraordinarily powerful tool in researcher’s hands and opening new perspectives unimaginable before. The increasing interest about neurobiology significantly derives from facing serious pathologies, such as multiple sclerosis, Parkinson’s and Alzheimer’s disease, and brain injury. Undoubtedly, this challenge gave a huge impulse to studies performed on mammalian models, seen as privileged points of reference for humans. Nevertheless, vertebrate models other than mammalian ones, were already known and successfully utilized as simpler, but complete, experimental materials
Morphological, cytochemical, and cytofluorimetric features of supramedullary neurons of the fish Solea ocellata
No full textVarious teleost species belonging to different orders possess a particular neuronal system, formed by giant supramedullary neurons (SNs). In some species SNs are scattered along the spinal cord, while in others SNs are organized in a compacted and well-defined cluster located at the boundary between the medulla oblongata and spinal cord. Besides many morphological, physiological and histochemical studies performed both in vivo and in vitro by several authors since the end of the 19th century, quantitative microfluorometric evaluation of the DNA content of SNs showed that clustered SNs but not aligned SNs have a DNA content much greater than normal 2C. Such a high DNA content is exceptional for vertebrate neurons. In the present study, we extend this analysis of SNs to the fish Solea ocellata. Our results show that the organization of SNs of S. ocellata are neither strictly aligned or clustered SNs, but somewhere in between, in both their morphological characteristics and DNA content values. Interspecific differences in the distribution and morphology of SNs may reflect functional differences, possibly related to environmental and/or behavioral differences among species. Furthermore, some possible functional significance of endoreplication in SNs is discussed
Use of citometry for the “reproductive model” assessment of the shrimp Palaemon serratus (Pennant, 1777)
No full textThe reproductive biology of the shrimp Palaemon serratus (Crustacea, Decapoda), fisheries resources, has been scarcely studied, especially in the marine habitats of Italian waters. For this purpose, in the present study, monthly samples were taken in brackish waters of the Po River Delta in the North Adriatic Sea. The annual maturative cycle of the ovary was assessed both qualitative, on the basis of histological findings, and quantitative terms, by cytometry. The ovaries feature a proliferative centre from which maturing oocytes branch out in a centrifugal direction. The reproductive period falls between March and June. During the non-reproductive period oocyte diameter ranged from 24 to 153 ?m, whilst during the reproductive period ranged from 24 to 733 ?m. The oviposition pattern may be described as “fractioned”, since it is recurrent. In fact, histological and cytometric findings of the Spring catch revealed that the females had both issued eggs that were still attached to the abdomen, as well as oocytes in all stages of vitellogenesis. The size at first maturity was around 51 mm of length.
In conclusion, the histo-cytological approach applied throughout the ovary maturation cycle is a good “reproductive model” assessment and an environmental test because the gonadal maturation is closely dependent on enviromental conditions
USE OF CYTOMETRY FOR THE “REPRODUCTIVE MODEL” ASSESSMENT OF THE SHRIMP PALAEMON SERRATUS (PENNANT, 1777).
No full textDNA endoreplication: what you did not expect from neurons
No full textEndoreplication has been repeatedly found in eukaryotes. In particular, endoreplicative or endoduplicative mechanisms have been reported in protists, plants, arthropods, molluscs, fishes and mammals. The same studies indicated that cells possessing endoreplicated genome are generally large-sized and highly metabolically active, suggesting that endoreplication could have a functional significance. Neurons are typically considered as fully differentiated, non-dividing cells containing normally a diploid DNA amount, and endoreplication has not been historically reported in neuronal cells. Despite this general rule, some papers questioned the validity of this finding and indicated that giant neurons in molluscs, supramedullary and hypothalamic magnocellular neurons in fishes and Purkinje cells in vertebrate (prevalently mammal) cerebellum present DNA contents greater than 2C. Quantitative microfluorometric evaluation of DNA content in nerve cells of the gastropod molluscs Planorbarius corneus, Aplysia californica and Lymnaea stagnalis indicated that neuronal DNA contents are scattered between 2C and 200.000C values. This increase in DNA content is given in account mostly to whole-genome duplications, whereas in P. corneus an endoreplication mainly of GC-rich sequences occurs. The second example of endoreplicated neurons was highlighted in the large clustered neurons, located at the boundary between the medulla oblongata and spinal cord, of the fishes Lophius piscatorius and Diodon holacanthus. The DNA content of these neurons, evaluated by microfluorimetric methods, results ranging from a minimum of 4C in the smaller to over 5000C in the larger neurons. Further experiments with AT and GC specific fluorochromes showed that the increase in DNA content is due to an amplification involving GC-rich DNAs in L. piscatorius, whereas a whole-genome endoduplication occurs in D. holacanthus. Subsequent quantitative evaluation revealed that also L. piscatorius hypothalamic magnocellular neurons, located in the preoptic and tuberal complexes, largely exceed 2C DNA content. The last example is represented by nuclei of vertebrate Purkinje cells isolated from cerebellum. These results have been debated for several years, since contrasting data are present in literature. Up till now, the dilemma remains unsolved, but it is not possible to exclude that a small percentage of Purkinje neurons contains hyperdiploid and tetraploid nuclei, might be due to an extra DNA synthesis. In order to go in depth in the understanding of this topic, we revised in the present review the available data about endoreplication in invertebrate and vertebrate giant neurons and considered the possible molecular mechanisms responsible for endoreplication. Furthermore, some possible functional significances of neuron endoploidy are discussed
Occurrence of DNA endoreplication in neurons.
No full textDNA endoreplication has been repeatedly reported in protists, plants, arthropods, molluscs, fish and mammals. The same studies indicated that cells possessing endoreplicated genome are generally large-sized and highly metabolically active, suggesting that endoreplication could have a functional significance. Neurons are typically considered as fully differentiated, non-dividing cells containing a diploid genome. Despite this general rule, some papers questioned the validity of this statement and indicated that giant neurons in molluscs, supramedullary and hypothalamic magnocellular neurons in fish and Purkinje cells in vertebrate (predominantly mammalian) cerebellum present DNA contents larger than 2C. Quantitative microfluorimetric evaluation of DNA content in nerve cells of the gastropod molluscs Planorbarius corneus, Aplysia californica and Lymnaea stagnalis indicated that neuronal DNA contents range between 2C and 200.000C values. This increase in DNA content generally concerns whole-genome duplications, whereas in P. corneus endoreplication mainly applies to GC-rich sequences. The second example of endoreplicated neurons is highlighted by the large, clustered neurons located at the boundary between the medulla oblongata and spinal cord in the fish Lophius piscatorius and Diodon holacanthus. The DNA content of these neurons, evaluated by microfluorimetric methods, range from 4C in small to over 5000C in large neurons. Further experiments with AT and GC specific fluorochromes showed that the increase in DNA content is due to an amplification involving GC-rich DNAs in L. piscatorius, whereas a whole-genome endoduplication occurs in D. holacanthus. Subsequent quantitative evaluation revealed that also L. piscatorius hypothalamic magnocellular neurons, located in the preoptic and tuberal areas, largely exceed 2C. The third example is represented by nuclei of Purkinje cells isolated from the cerebellum. These results have been debated for several years, since contrasting data are present in literature. Up till now, the dilemma remains unsolved, but it is not possible to exclude that a small percentage of Purkinje neurons contain hyperdiploid and tetraploid nuclei, due to additional DNA synthesis. In order to study this topic into more detail, we here review the available data about endoreplication in invertebrate and vertebrate giant neurons and consider the possible molecular mechanisms responsible for endoreplication. Furthermore, some possible functional significances of neuron endoploidy are discussed
Cytometry of supramedullary neurons in Solea ocellata
No full textThe supramedullary neurons (SN) are a noradrenergic automic system of giant cells, dorsally grouped in a cluster at the boundary between medulla oblongata and spinal cord in some orders of fish and aligned one by one along the spinal cord in others
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