Cephalopod Olfaction

Within the Phylum Mollusca, cephalopods encompass a small and complex group of exclusively marine animals that live in all the oceans of the world with the exception of the Black and Caspian seas. They are distributed from shallow waters down into the deep sea, occupying a wide range of ecological niches. They are dominant predators and themselves prey with high visual capability and well-developed vestibular, auditory, and tactile systems. Nevertheless, their perceptions are chemically facilitated, so that water-soluble and volatile odorants are the key mediators of many physiological and behavioral events. For cephalopods as well as the other aquatic animals, chemical cues convey a remarkable amount of information critical to social interaction, habitat selection, defense, prey localization, courtship and mating, affecting not only individual behavior and population-level processes, but also community organization and ecosystem function. Cephalopods possess chemosensory systems that have anatomical similarities to the olfactory systems of land-based animals, but the molecules perceived from distance are different because their water solubility is of importance. Many insoluble molecules that are detected from distance on land must, in an aquatic system, be perceived by direct contact with the odour source. Most of the studies regarding olfaction in cephalopods have been performed considering only waterborne molecules detected by the “olfactory organs.” However cephalopods are also equipped with “gustatory systems” consisting of receptors distributed on the arm suckers in octopods, buccal lips in decapods, and tentacles in nautiluses. To date, what is known about the olfactory organ in cephalopods comes from studies on nautiloids and coleoids (decapods and octopods). In the nautiloid’s olfactory system, there is a pair of rhinophores located below each eye and open to the environment with a tiny pore, whereas in coleoids a small pit of ciliated cells is present on either side of the head below the eyes close to the mantle edge

The use of mice deficient in MCT8 to identify a mechanism regulating thyroid hormone secretion

The mechanism of thyroid hormone (TH) secretion from the thyroid gland into the bloodstream is still unknown. The aim of my thesis has been to investigate the role of monocarboxylate transporter 8 (MCT8) in this process. To accomplish the goal, we used the Mct8 deficient mice (Mct8KO), generated by homologous recombination. MCT8 is a specific transporter of TH across the cell membrane, active in both uptake and efflux. Mutations of MCT8 gene cause in human severe psychomotor retardation and thyroid function test abnormalities. The Mct8KO mice faithfully replicate the endocrine aberrances observed in humans, including a low concentration of serum thyroxine (T4). This latter finding cannot be fully explained by increased deiodination. Here, we have shown that Mct8 is localized at the basolateral membrane of thyrocytes and that the serum TH concentration is reduced in Mct8KO mice early after being taken off a treatment that almost completely depleted the thyroid gland of TH. Furthermore, thyroid glands in Mct8KO mice contained 2.3-fold and 1.5-fold more non thyroglobulin associated T4 and triiodothyronine (T3), respectively, than did those in wild-type (Wt) mice. This was independent of deiodination, as comparable increases were also found in Mct8KO mice which lacked the types 1 and 2 deiodinases. In addition, depletion of thyroidal TH content was slower during iodine deficiency. After administration of 125I, the rate of both its secretion from the thyroid gland and its appearance in the serum as trichloroacetic acid-precipitable radioactivity were greatly reduced in Mct8KO mice. Similarly, the secretion of T4 induced by injection of thyrotropin was reduced in Mct8KO in which endogenous TSH and T4 were suppressed by administration of T3. This study is the first to demonstrate that Mct8 is involved in the secretion of TH from the thyroid gland. The defect in the efflux contributes, in part, to the low serum T4 level observed in Mct8 deficiency

A novel approach to primary cell culture for Octopus vulgaris neurons

Octopus vulgaris is a unique model system for studying complex behaviours in animals. It has a large and centralized nervous system made up of lobes that are involved in controlling various sophisticated behaviours. As such, it may be considered as a model organism for untangling the neuronal mechanisms underlying behaviours – including learning and memory. However, despite considerable efforts, Octopus lags behind its other counterparts vis-à-vis its utility in deciphering the cellular, molecular and synaptic mechanisms underlying various behaviours. This study represents a novel approach designed to establish a neuronal cell culture protocol that makes this species amenable to further exploitation as a model system. Here we developed a protocol that enables dissociation of neurons from two specific Octopus’ brain regions, the vertical-superior frontal system and the optic lobes, which are involved in memory, learning, sensory integration and adult neurogenesis. In particular, cells dissociated with enzyme papain and cultured on Poly-D-Lysine-coated dishes with L15-medium and fetal bovine serum yielded high neuronal survival, axon growth, and re-growth after injury. This model was also explored to define optimal culture conditions and to demonstrate the regenerative capabilities of adult Octopus neurons after axotomy. This study thus further underscores the importance of Octopus neurons as a model system for deciphering fundamental molecular and cellular mechanism of complex brain function and underlying behaviours

Roe enhancement of Paracentrotus lividus: Nutritional effects of fresh and formulated diets

Sea urchin gonads are exploited both for gastronomic and scientific purposes; thus, the production of large and mature gonads is essential. Natural populations of the Mediterranean Sea urchin Paracentrotus lividus are subject to increasing fishing ef- forts, due to continuous intensification of consumptions. Aquaculture practices may represent an answer, but the availability of artificial feeds accelerating the produc- tion of high-quality gonads in terms of size, taste, colour, firmness, maturity and via- bility of gametes is critical to boost the productions. The accessibility of cheap and effective feeds promoting the fattening of gonads and the quality of gametes is still a bottleneck slowing down the expansion of echinoculture practices. This investiga- tion is aimed at enabling the development of this strategic sector, by comparing the dietetic effects of fresh foods and a commercial feed for aquaculture, to four newly formulated feeds. The protein contents of diets were strongly related to the GSIs. The abundance of fatty acids appeared inversely related to the viability of embryos and abnormalities of larvae. The features of an ideal diet for this sea urchin were defined, based on the results of experimental trials, and the need for increasing levels of plant-derived proteins during the grow-out period was demonstrated

Tubulin nitration in human gliomas

Immunohistochem. and biochem. investigations showed that significant protein nitration occurs in human gliomas, esp. in grade IV glioblastomas at the level of astrocytes and oligodendrocytes and neurons. Enhanced alpha-tubulin immunoreactivity was co-present in the same elements in the glioblastomas. Proteomic methodologies were employed to identify a nitrated protein band at 55 kDa as alpha-tubulin. Peptide mass fingerprinting procedures demonstrated that tubulin is nitrated at Tyr224 in grade IV tumor samples but is unmodified in grade I samples and in non-cancerous brain tissue. These results provide the first characterization of endogenously nitrated tubulin from human tumor samples