Les marsupiaux naissent très immatures, mais doivent atteindre une tétine, sans aide de la mère, à laquelle ils s’attachent pour poursuivre leur développement. Des informations sensorielles sont nécessaires pour s’orienter vers la tétine, la trouver, et s’y attacher. Le système vestibulaire, associé au sens de l’équilibre, a été proposé comme pouvant guider les petits marsupiaux vers la tétine en agissant sur les réseaux moteurs spinaux. Diverses études des marsupiaux suggèrent que le développement de ce système pourrait être suffisamment avancé pour influencer les comportements moteurs chez les nouveau-nés, mais son fonctionnement n’a jamais été testé. Pour le faire, nous avons soumis des opossums âgés de P0 (jour de la naissance; postnatal 0) à P21 à des stimulations vestibulaires et traité les tissus de la tête par immunohistochimie pour révéler c-Fos, utilisé comme indicateur d’activité neuronale. Du marquage dans les noyaux vestibulaires a été observé seulement à partir de P15. Pour confirmer ces résultats, nous avons effectué deux types d’expériences de stimulation sur des préparations in vitro d’opossums et enregistré les réponses motrices induites. Ainsi, des élévations de la tête n’ont pas permis de déceler de réponse suite aux stimulations aux âges étudiés (P4-P12). Par contraste, des pressions mécaniques directement appliquées sur le labyrinthe afin de stimuler les organes vestibulaires ont entrainé des réponses à tous les âges testés (P1-P9). Nos résultats suggèrent que la fonction du système vestibulaire est limitée par la maturité de ses organes sensoriels, et qu’il n’influence pas la motricité des nouveau-nés d’opossum en conditions physiologiques avant environ la fin de la 2e semaine de vie, même si les voies nerveuses entre les organes vestibulaires et la moelle épinière semblent déjà établies à la naissance. / Marsupials are born very immature, but must nevertheless find a teat, unaided by the mother, to which they attach to pursue their development. Sensory inputs are necessary to find the teat and attach to it, but the senses involved are still under discussion. The vestibular system, responsible for the sense of balance, was proposed as influencing motor behavior of newborns in various marsupial species by an action on spinal motor networks. Studies in the opossum Monodelphis domestica suggest that the development of the vestibular system could be advanced enough to influence locomotion at birth but its functionality has never been tested. To do that, we subjected intact opossums aged P0 (Postnatal day 0 ; day of birth) to P21 to vestibular stimulations and immunohistochemically processed their brain tissues to reveal c-Fos, used as a marker of neuronal activity. Immunoreactivity of neurons in the vestibular nuclei was observed only from P15 onwards. To confirm those results, we performed two series of experiments on in vitro preparations of newborn opossums, using stimulation of the vestibular apparatus and physiological recording of the induced motor responses Thus, vertical head tilts did not induce motor response at any of the ages studied (P4-P12). In contrast, mechanical pressure applied on the labyrinth to stimulate the vestibular organs induced motor responses at all ages studied (P1-P9). Our results suggest that the vestibular system’s function is limited by the maturity of its sensory organs and that it can’t influence motor activity in physiological condition before the end of the 2nd postnatal week, even if functional pathways from the labyrinth to the spinal cord seem to be already in place at birth.

Master of Science / Department of Animal Sciences and Industry / Timothy G. Rozell / Follicle stimulating hormone (FSH) is known as the key hormone capable of causing proliferation of granulosa cells in the ovary. The classical receptor belongs to the G protein-coupled superfamily and is designated FSHR-1. A variant in the FSH receptor has been shown to be functional in mouse ovaries. The variant receptor is designated as FSHR-3, and when bound by FSH activates a pathway that shares similar characteristics to the growth factor type I receptor pathway, with no increase in cAMP. The FSHR-3 variant activates MAPK upon binding to FSH, and causes proliferation of cells on which it is known to be expressed. For example ID8 mouse ovarian surface epithelium cells (MOSEC), a cell line that when introduced in immunocompetent mice causes tumors similar to human ovarian cancer and which also express FSHR-3, proliferated in response to FSH. The present study explored the potential for decreasing expression of FSHR-3 protein. The RNA interference (RNAi) technique was used to insert small inhibitory RNA(siRNA) segments corresponding specifically to the R3 variant of the FSH receptor in ID8 MOSEC. Transfected cells were lysed and FSHR-3 protein was visualized using SDS Page and Western blotting analysis. A reduction in expression of FSHR-3 was observed in two of the transfection groups, with the greatest down-regulation of FSHR-3 being 30.1%. From these preliminary results we conclude that the FSHR-3 is expressed on ID8 cells, and that siRNA may be useful to reduce its expression. Thus, it may be possible to slow the growth of FSH-responsive tumors using siRNA to target the FSHR-3 receptor.

Master of Science / Department of Clinical Sciences / Daniel U. Thomson / Bovine respiratory disease complex (BRDC) is the most common, and costly, disease in feed yard cattle. A review of the literature shows a correlation between the diagnosis of BRDC ante-mortem and respiratory lesions at slaughter. The objectives of the studies reported here were to: 1) validate a thoracic auscultation scoring system by correlating ante-mortem lung sounds with post-mortem lung lesions and 2) evaluate thoracic auscultation and rectal temperature as diagnostic tools to predict case outcome in the feeder cattle treated for BRDC. First, a prospective cohort study involving thirty four head of cattle that had been realized from commercial cattle feeding operations were used to validate the use of a lung auscultation scoring system to identify cattle suffering from BRDC. Ante-mortem auscultation scores were compared to post-mortem lung lesions evaluated using a previously described scoring system. There was a positive correlation (P < .0001) between ante-mortem lung auscultation scores and post-mortem lung lesion scores in the population of feeder cattle that were tested. Subsequently, a retrospective cohort study was conducted using data obtained from three commercial feed yards. Cattle enrolled in the study (n = 4,341 head) were treated for BRDC between January 2007 to October 2007 by trained feed yard personnel. Data recorded included animal identification, rectal temperature, lung score, and antibiotic therapy at first treatment. Treatment outcome data were recorded by feed yard personnel utilizing an animal health computer. The outcome data tracked for this study included subsequent BRDC treatment or death of the animal. Our findings indicated that as lung auscultation score (P < .0001) or rectal temperature (P < .0001) increased there was an increased risk for cattle to require a second BRDC treatment. Also, we observed an increased risk for death loss in cattle with higher lung auscultation scores (P < .0001) or higher rectal temperature (P < .0001) at the time of treatment for BRDC. We have demonstrated that lung auscultation score and rectal temperature can be used as tools to predict treatment outcome in cattle treated for BRDC. Future research with these tools could be used to develop more precise therapeutic protocols for BRDC in feeder cattle.

The Asian elephant (Elephas maximus), a charismatic ‘flagship species’, is threatened by extinction in the wild, and the development of self-sustainable captive populations is a key conservation challenge. A third of the Asian elephant population is presently in captivity and information on the reproductive status, especially in females, is still lacking to a large extent. The onset of estrus in female Asian elephants is not associated with any visible physical signs, thus making the assessment of the reproductive status rather difficult. One approach to understanding reproductive cyclicity of animals is through generating profiles of reproductive hormones in blood (Wiseman et al. 1983; Brown et al. 1999, 2004). Profiles of reproductive hormones such as progesterone (P4), estrogen, luteinizing hormone and follicle stimulating hormone have already being demonstrated in Asian elephants (Brown et al. 1999, 2004; Brown 2000). In these studies, the reproductive status of females, maintained in zoos/captivity, was characterized based on circulating levels of hormones in blood samples. This is difficult to implement in the case of semi-captive or wild populations of elephants due to practical, legal and ethical considerations. In order to overcome this problem and to better understand the estrous status of female elephants, it is important to develop and validate non-invasive methods to monitor the reproductive status of female Asian elephants. An alternative approach to evaluating the reproductive status of females is to consider behavioral responses shown by males towards chemical signals produced by females to advertise their reproductive status. In order to understand the reproductive status of the individual belonging to the opposite sex, studies have shown that elephants rely on a variety of chemical signals produced in biological fluids such as urine, temporal gland secretion, inter-digital gland secretion, etc. (Krishnan 1972; Rasmussen & Schulte 1998). Chemical signaling is one of the prominent modes of communication in elephants, especially with respect to locating potential mates (Sukumar 2003). Thus, in most cases, elephants usually employ specific behavioral responses, for example sniff, check and place behaviors of trunk, for investigating the reproductive status of the conspecific individual, belonging either to the same or the opposite sex (Rasmussen et al. 1996; Schulte & Rasmussen 1999; Bagley et al. 2006). The objectives of the thesis are two-fold. First, to develop a non-invasive method of reproductive monitoring from fecal hormonal metabolites and also to understand the possible role of feces as an inter-sexual signal. The main body of thesis is divided into four chapters. 1) Development and validation of a non-invasive method to estimate progesterone metabolite in feces, to monitor the reproductive cyclicity of female elephants (Chapter 2). 2)Generation and characterization of progesterone and its metabolite, 5α-P-3-OH, profiles of semi-captive females using the developed non-invasive method to measure fecal metabolites (Chapter 3). 3) Validation of developed methodology and assay systems to a wild-population of female elephants (Chapter 4). 4) Feces as a potential source for inter-sexual chemical signaling in Asian elephants (Chapter 5). The above studies were carried out on semi-captive male and female elephants maintained in the forest camps of Mudumalai Wildlife Sanctuary (MWLS), Tamil Nadu and Bandipur National Park (BNP), Karnataka, India (Chapters 2, 3 and 5). For Chapter-4, free-ranging females of the MWLS were examined. 1. Development and validation of a non-invasive method to estimate progesterone metabolite in feces, to monitor the reproductive cyclicity of female elephants Niemuller et al. (1993) generated a profile of the progesterone metabolite, 5βpregnanetriol, to assess the estrous phase of Asian elephants based on non-invasive urine sampling. However, the collection of urine is difficult and to some extent impossible in the case of semi-captive and as well as that of wild elephants. Thus, the method of choice in this study was the development and validation of a non-invasive approach to measure fecal progesterone metabolites to assess reproductive status of females. Sampling was carried out at monthly intervals on three female elephants at the MWLS forest camp, while three other females maintained at the BNP forest camp were sampled fortnightly. An enzyme linked immuno-sorbent assay was developed to measure the concentration of the progesterone metabolite, 5α-P-3OH in the fecal samples of the semi-captive females. Using varying concentrations of the hapten (5α-P3OH), from low (0.1 mM) to high (1 mM), a standard curve was first generated, which had a linear range between 0.25 mM to 62.5 mM, with an EC50 of 1.37 mM. The linear range was then used to detect the concentrations of 5α-P-3OH in the fecal samples of females examined. The non-invasive method was further validated as there existed a positive correlation (p<0.1) between the levels of fecal 5α-P-3OH and that of concentration of circulating P4, measured in blood samples. This is the first valid documentation of a non-invasive method based on fecal progesterone metabolite pattern in order to assess the reproductive status of the female Asian elephants. 2. Generation and characterization of reproductive hormone profiles of semi-captive females using the developed non-invasive method to measure fecal metabolites With the establishment of a non-invasive method to understand occurrence of estrus in female elephants (described in Chapter 2), attempts were made to generate hormonal profiles over a longer time interval through more frequent sampling. Based on sampling at weekly intervals, the concentrations of both fecal 5α-P-3OH and that of native P4 hormone in the blood were determined, and the females were then identified as belonging to different reproductive states of hormonal cycling (follicular and luteal phases), non-cycling and pregnant categories. Of the 7 females sampled at both MWLS and BNP, three distinct categories of hormone-metabolite profiles emerged. The first category included four females that showed regular cyclicity throughout the sampling period, as monitored through the measurement of fecal 5α-P-3OH and serum P4 levels. The estrous cycle of all the four females was divided into two phases (follicular and luteal), based on the patterns of fecal 5α-P-3OH and serum P4 concentrations. The follicular phase of the estrous cycle was assigned when the values of both fecal 5α-P-3OH and serum P4 remained below 0.3 µg/gm and 0.3 ng/ml, respectively, for a considerable time period (viz. >2 wk). However, the luteal phase was characterized, when the levels of fecal 5α-P-3OH and serum P4 remained at or above 0.3 µg/gm and 0.3 ng/ml respectively, over a period of more than 2 - 3 wk. The second category had two females showing a ‘flat-lining pattern’ for the levels of fecal 5α-P-3OH and serum P4 concentrations, without any peak or dip in their concentrations. Since the reproductive pattern for both these females was flat-lined throughout their sampling period (51 wk), maintaining the levels of fecal 5α-P-3OH and serum P4 below 0.3 µg/gm and 0.3 ng/ml respectively, the females were considered to be non-cycling or anestrus. The third category had one female in which the levels of both fecal 5α-P-3OH and serum P4 measured were consistently high throughout the entire sampling period (26 wk). The levels of both fecal -P-3OH and serum P4 were above 0.3 µg/gm and 0.3 ng/ml, respectively. At the end of the sampling period, this female delivered a male calf; thus, the measured concentrations of fecal 5α-P-3OH and serum P4 signified the levels maintained during the gestational phase of this female. Sampling and hormonal analyses were also carried out for a male in the MWLS forest camps to investigate the baseline concentrations of fecal 5α-P-3OH and serum P4. The male showed consistently low concentrations of both fecal 5α-P-3OH and serum P4 throughout the sampling period (16 wk), below the margin of 0.3 µg/gm and 0.3 ng/ml, respectively. In this part of the study, it was confirmed that the reproductive status of a female elephant can be correctly assessed on the basis of measurements of fecal 5α-P-3OH alone, with repeated sampling of the female over a longer time scale. It was also shown that the strength of the positive correlation between the concentrations of the fecal 5α-P3OH and the serum P4 increased (p<0.01) for a larger sample size than that obtained for a comparatively smaller sample (described in Chapter 2). 3. Validation of developed methodology and assay systems to wild-population of female elephants So far, the non-invasive method to estimate fecal progesterone metabolite in order to predict occurrence of estrus of elephants was largely applied to semi-captive females (described in Chapters 2, 3). However, the necessity of such a method is being recognized for assessing the reproductive status of free-ranging females. Several findings have described differences in the rate and type of steroid metabolite excretion among individuals maintained under different diet regimes (Wasser et al. 1993; Smith et al. 2006). For instance, female elephants in the forest camps are provided with supplementary diet consisting of sugarcane, rice and millets. This diet is strikingly different from the feeding materials consumed by wild/free-ranging elephants (Sukumar 2003). Therefore, differences in dietary components can potentially influence the fecal steroid metabolites’ excretory patterns shown by semi-captive vis-a-vis wild females, which can affect the validity of measuring fecal 5α-P-3OH to predict females’ reproductive status. In order to examine this problem, the non-invasive method was applied to the population of wild elephants in the forests of MWLS, through random one time sampling of 30 individual female elephants. The steroid extraction efficiency (73 ± 11.0%, mean ± S.D., n =30) determined for the fecal samples collected from the wild females was not significantly different from the coefficient calculated in the case of the semi-captive females (80 ± 4.3%, mean ± S.D., n = 38). This indicated that dietary differences between wild and captive elephants did not influence levels of fecal hormonal metabolites in feces, unlike earlier observations on baboons (Wasser et al. 1993), old world primates (Wasser et al. 1988) and sheep (Smith et al. 2006). The values of the fecal allopregnanolone determined in the case of the wild females, ranged from as low as 0.06 µg/gm to as high as 23µg/gm of the sample, thus showing the heterogeneity of the samples, indicating that the females may be belonging to different reproductive phases. However, since sampling was carried out randomly, with an adult female being sampled just once, at this stage, it is not possible to identify or elaborate on the reproductive phase of the females. This is the first study reporting the values of the fecal progesterone metabolite in female Asian elephants in the wild. Further studies may be required to carry out long term monitoring of the wild females, through repeated collection of fecal samples over time from particular female. 4. Feces as a potential source for inter-sexual chemical signaling in Asian elephants In this Chapter-5, behavioral trials were conducted on male elephants to understand the role of fecal matter in conveying inter-sexual chemical signals. This was demonstrated by analyses of specific chemosensory behavioral responses shown by males towards the fecal samples of females that were strangers and belonging to different reproductive stages. Males showed four prominent behavioral responses namely ‘distant sniff’, ‘close sniff’, ‘check’ and ‘place’ towards the fecal samples of females. The sum of frequencies of these four responses (distant sniff, close sniff, check and place) was much higher for samples of the follicular (pre-ovulatory) phase females as compared to those of the luteal (post-ovulatory) phase females (p<0.005). Thus, for the first time, it was shown that male elephants are able to discriminate the different reproductive phases of females based on their specific behavioral response towards the fecal samples of the opposite sex. In conclusion, the thesis has focused on understanding and providing new insights regarding the reproductive biology of the female Asian elephants. This has been achieved through the development of the non-invasive method based on measuring the concentrations of the fecal progesterone metabolite and through the analyses of the chemosensory responses performed by the males towards the fecal samples of strange females. These methods can potentially be applied to the populations of both wild and captive/semi-captive female elephants in order to evaluate their reproductive status, through non-invasive measures. The information derived from the application of such methods will help in understanding the reproductive potential of the wild elephants under various environmental and ecological conditions. Further, the non-invasive measurement of reproductive hormones will help in monitoring the reproductive state of the individuals and thus aid in planning strategies for the welfare and management of the elephants maintained in captive or semi-captive conditions.

Ao avaliar parâmetros de qualidade de carne de peito de frango com a intenção de verificar se são afetados pelo estresse térmico severo pré-abate (35&#176;C, 75% umidade relativa, por 2 horas), observou-se que o gasto intenso de energia do animal, no momento do estresse, resultou em pequena extensão da glicólise, gerando como respostas na carne, principalmente, características de escurecimento e alto valor de pH. O uso da marinação com o objetivo de restaurar carnes com propriedades funcionais prejudicadas pelo estresse resultou na padronização da aparência e em pH igualado entre os tratamentos (carnes de animais &#34;estressados&#34; e &#34;não estressados&#34;). No capítulo referente à classificação de carnes pelo uso da cor, foi possível observar a existência de alta correlação entre a luminosidade e outros atributos de qualidade e que o valor L* pode ser usado como uma ferramenta de classificação (com nota de corte L*=53, mensurada 24 horas post mortem). Com relação ao processo de marinação, observou-se que a técnica restaura parcialmente a qualidade da carne pálida, promovendo uma melhora visual da cor, contudo, sem corrigir a funcionalidade das proteínas em reter água ao nível de carnes normais. / In evaluating the quality of chicken breast meat regarding the effects of pre-slaughter severe heat stress (35&#176;C, 75% relative humidity, for 2 hours), it was observed that the intense energy expenditure of the animal at the moment of stress resulted in a slight extension of glicolysis, generating as a consequence, mainly, characteristics of darkening and high levels of pH, on the meat. The use of marination in an attempt to restore meat with damaged functional properties due to stress resulted in the standardization of appearance and in leveling of pH between the treatments (stressed and non-stressed animal meat). In the last chapter, it was possible to observe the existence of strong correlation between the color and the other quality attributes and that the lightness can be used as a classification tool (minimum level L*=53, measured 24 hours postmortem). As for the marination process, it was observed that the technique partly restores the quality of pale meat, promoting a visual improvement of the color, however, it does not correct the proteins functionality to retain water at the same level of normal meat.

Les changements climatiques ont un impact sur quasiment toutes formes de vie. Des augmentations des moyennes de température ainsi que desfluctuations peuvent causer un stress, particulièrement chez les ectothermes aquatiques sessiles tels que les moules d’eau douce. Cependant, certaines espèces semblent mieux faire face à ces températures stressantes que d’autres. La tolérance au stress thermique peut par exemple expliquer le succès de certaines espèces envahissantes. Il est connu que les mitochondries peuvent jouer un rôle clé dans l’établissement de la thermo-tolérance des ectothermes. Dans cette étude, nous avons visé à caractériser la thermo-tolérance mitochondriale chez des moules d’eau douce endémiques et invasives. À travers l’utilisation de la respirométrie à haute résolution, nous avons analysé la respiration mitochondriale de deux espèces de moules d’eau douce exposées à plusieurs températures différentes. Nous avons remarqué que la moule invasive Dreissena bugensis possédait un métabolisme mitochondrial moins thermo-tolérant que la moule endémique Elliptio complanata. Cette lacune au niveau de la tolérance a été liée à une dépression métabolique aérobique plus marquée à des températures élevées. Ces résultats pourraient potentiellement être associées avec les traits de caractéristiques de vie de ces espèces, car D. bugensis est plus adaptée à des environnements instables dans lesquels les pressions de sélection pour des adaptations de résistance sont réduites. Nos résultats s’ajoutent à la littérature grandissante qui caractérise le métabolisme mitochondrial de plusieurs espèces aquatiques face aux changements climatiques / Climate change is impacting many, if not all, forms of life. Increases in extreme temperature fluctuations and average temperatures can cause stress, particularly in aquatic sessile ectotherms such as freshwater mussels. However, some species seem to thrive more than others in face of temperature-related stressors. Thermal tolerance may for example explain invasive species success. It is also known that mitochondria can play a key role in setting an ectothermic species’ thermal tolerance. In this study, we aimed to characterize the mitochondrial thermo-tolerance in invasive and endemic freshwater mussels. With the use of high-resolution respirometry, we analyzed the mitochondrial respiration of two freshwater bivalve species exposed to a broad range of temperatures. We noticed that the invasive dreissenid Dreissena bugensis displayed a less thermo-tolerant mitochondrial metabolism than the endemic unionid Elliptio complanata. This lack of tolerance was linked with a more noticeable depression of aerobic metabolism at elevated temperatures. These findings may be associated with the life history traits of both species, as D. bugensis is more adapted to unstable habitats, where selection pressures for resistance adaptations are reduced. Our findings add to the growing body of literature characterizing the mitochondrial metabolism of many aquatic ectotherms in the context of climate change.

Les mitochondries et leur génome, l'ADN mitochondrial (ADNmt), sont généralement transmis uniquement par la mère aux fils et aux filles chez les métazoaires (transmission strictement maternelle, SMI). Une exception à la règle générale de la SMI se trouve dans environ 100 espèces de bivalves, qui se caractérise par une double transmission uniparentale (DUI) des mitochondries. Chez les espèces DUI, deux lignées d'ADNmt très divergentes et liées au sexe coexistent. Une lignée mitochondriale maternelle (type F), présente dans les ovocytes et les tissus somatiques des individus femelles et males, et une lignée paternelle (type M), présente dans les spermatozoïdes. Dans les tissus somatiques mâles, les deux lignées coexistent parfois, une condition appelée hétéroplasmie. En sachant que les variations génétiques dans l’ADNmt peuvent avoir un impact sur les fonctions mitochondriales, et en donnant l'association stricte des ADNmt de type M et F avec différents gamètes, il est imaginable que la forte divergence entre les deux lignées DUI puisse entraîner des adaptations bioénergétiques avec répercussion sur la reproduction. Le système DUI apporte également la nécessité pour les mitochondries paternelles de préserver leur propre intégrité génétique, ainsi que pour les cellules somatiques de faire face à l'hétéroplasmie. L'objectif de ma thèse était de lier le génotype mitochondrial des espèces bivalves DUI et SMI au phénotype. Plus précisément, j'ai exploré l'impact des variations de l'ADN mitochondrial spécifiques au sexe sur un large éventail de traits phénotypiques, allant de la bioénergétique mitochondriale et cellulaire à la performance des spermatozoïdes, en étudiant la valeur adaptative du système DUI à la lumière du fitness reproductif, de la sélection et de la transmission mitochondriales. Les résultats issus de ce projet de thèse ont révélé une nette divergence phénotypique entre les espèces DUI et SMI, reflétant peut-être les différentes pressions sélectives agissant sur les deux lignées mitochondriales. Contrairement aux espèces SMI, l'évolution sexo-spécifique des variants d'ADNmt DUI entraîne l'expression de différents phénotypes bioénergétiques mâles et femelles. Au niveau de la fonctionnalité mitochondriale, les mitochondries DUI de type M présentent une phosphorylation oxydative (OXPHOS) remodelée, caractérisée par un contrôle respiratoire inhabituel à l'extrémité de la chaîne respiratoire. La réorganisation générale de la bioénergétique des spermes DUI entraîne également une variation de l'équilibre entre les principales voies de production d'énergie, incluant la glycolyse, la glycolyse anaérobique, le métabolisme des acides gras, le cycle de l'acide tricarboxylique, l'OXPHOS, ainsi que la capacité antioxydante. Enfin, les spermatozoïdes DUI comptent entièrement sur l'énergie produite par OXPHOS pour maintenir une motilité inhabituelle caractérisée par une vitesse lente et une trajectoire plus curviligne, traits potentiellement associés à un plus grand succès de reproduction chez les organismes marins sessiles. Aussi, ils conservent la capacité de passer à une stratégie de production d'énergie mixte (aérobique et anaérobie) après la détection des ovocytes. Dans l'ensemble, ces résultats suggèrent que la variation de l'ADNmt dans les espèces DUI pourrait être adaptative, incluant adaptation bioénergétique sexo-spécifiques avec un effet en aval sur la performance des spermatozoïdes, la capacité de reproduction, la sélection et transmission des mitochondries paternelles. / Mitochondria and their genome, the mitochondrial DNA (mtDNA), are usually transmitted only by the mother to both sons and daughters in metazoan (i.e. strict maternal inheritance, SMI). An exception to the general rule of SMI is found in around 100 species of bivalves, which are characterized by a doubly uniparental inheritance (DUI) of mitochondria. In DUI species, two highly divergent and sex-linked mtDNA lineages coexist. One mitochondrial lineage is maternally inherited (F-type) and is present in oocytes and somatic tissues of both female and male individuals. The other lineage is paternally inherited (M-type) and is present in sperm. In male somatic tissues both lineages sometimes coexist, a condition named heteroplasmy. Knowing that variations in mitochondrially-encoded genes might impact mitochondrial functions, and giving the strict association of M and F-type mtDNAs with different gametes, it is conceivable that the variation between the two DUI lineages might result in sex-specific bioenergetic adaptations with repercussion on reproduction. Despite providing an unprecedented opportunity for the mtDNA to evolve for male functions, the DUI system also brings the need for sperm mitochondria to preserve their genetic integrity, as well as for somatic cells to deal with heteroplasmy. The objective of my PhD was to link the mitochondrial genotype of DUI and SMI bivalve species to the phenotype. I explored the impact of sex-specific mtDNA variations upon a wide set of phenotypic traits, ranging from mitochondrial and cellular bioenergetics to sperm performance, investigating the adaptive value of DUI system in the light of reproductive fitness, mitochondrial selection, preservation and transmission. The results stemming from this PhD project revealed a clear phenotypic divergence between DUI and SMI species, possibly reflecting the different selective pressures acting on their mitochondria as a result of their different mode of mitochondria transmission. Conversely to SMI species, the sex-specific evolution of DUI mtDNA variants results in the expression of different male and female bioenergetic phenotypes. At the level of mitochondrial functionality, M-type mitochondria exhibit a remodelled OXPHOS characterized by unusual respiratory control at the terminus of the respiratory chain. The general reorganization of DUI sperm bioenergetics also entails variation in the balance between the main energy producing pathways, including glycolysis, anaerobic glycolysis, fatty acid metabolism, tricarboxylic acid cycle, OXPHOS, as well as the antioxidant capacity. Finally, DUI sperm exhibit an unusual motility phenotype characterized by slow speed and high curvilinear trajectory, traits potentially associated with a higher reproductive success in sessile broadcast spawning marine organisms. They also completely rely on the energy produced by OXPHOS to sustain their performance, although maintaining the ability to switch to a more combined aerobic/anaerobic strategy of energy production after oocyte detection. Altogether, these results suggest that the mtDNA variation in DUI species might be adaptive, resulting in the expression of sex-specific bioenergetic adaptation with downstream effect on sperm performance, reproductive fitness, paternal mitochondria selection, preservation and transmission. The results also suggest that heteroplasmy has an impact onto the bioenergetics of male soma, and that a functional compensation between genomes might minimize any potential deleterious outcome.

Chez les primates, le raffinement des mouvements de la main est associé à l’apparition d’aires prémotrices corticales additionnelles. Chacune de ces aires prémotrices semble avoir une fonction spécialisée dans le contrôle moteur de la main, appuyant l’idée qu’elles sont apparues au cours de l’évolution afin de soutenir un répertoire comportemental accru. Afin de participer à l’exécution de ce vaste répertoire, il est suggéré que les aires prémotrices modulent les efférences du cortex moteur primaire (M1), une aire corticale jouant un rôle clé dans la production des mouvements volontaires. En effet, grâce à leurs nombreuses projections cortico-corticales vers M1 ainsi que leurs projections vers des structures sous-corticales qui sont également innervées par M1, les aires prémotrices se trouvent dans une position idéale pour moduler les efférences motrices de M1. Néanmoins, la contribution de ces projections anatomiques à la production des mouvements de la main demeure peu comprise. La fonction de ces projections est toutefois importante à investiguer afin de mieux comprendre les interactions corticales qui sous-tendent l’augmentation du répertoire des mouvements de la main chez les primates. S’intégrant dans ce contexte de recherche, les expériences présentées dans cette thèse visent à caractériser les interactions corticales entre les aires prémotrices et M1 qui sont impliquées dans les mouvements de la main chez le singe capucin. Dans une première étude, les effets modulateurs du cortex prémoteur ventral (PMv) sur les efférences de M1 ont été investigués (Chapitre I). Dans une seconde étude, les effets modulateurs du cortex prémoteur dorsal (PMd) ont été étudiés et comparés à ceux de PMv (Chapitre II). Finalement, dans une troisième étude, les effets modulateurs de l’aire supplémentaire motrice (SMA) ont été examinés et comparés à ceux de PMv et de PMd (Chapitre III). En résumé, les résultats présentés dans cette thèse offrent une nouvelle perspective quant aux interactions corticales liant les aires prémotrices à M1. Il est démontré que chaque aire prémotrice influence les efférences de M1 de manière unique. Ceci appuie l’idée que chaque aire prémotrice joue un rôle spécialisé dans le contrôle moteur de la main et est en mesure d’accomplir cette fonction, entre autres, à travers sa modulation des efférences motrices de M1. Ces résultats contribuent à une meilleure compréhension des interactions corticales qui sous-tendent le raffinement des mouvements de la main accompagnant l’évolution du système moteur. / In primates, the refinement of hand movements is associated with the appearance of additional cortical premotor areas. Each of these premotor areas appears to have a specialized function in the motor control of the hand, supporting the idea that they have appeared during evolution to support an increased behavioral repertoire. In order to participate in the execution of this vast repertoire, it is suggested that the premotor areas modulate the motor outputs of the primary motor cortex (M1), a cortical area that plays a key role in the production of voluntary movements. Indeed, thanks to their numerous cortico-cortical projections to M1 as well as their projections to sub-cortical structures also innervated by M1, premotor areas are in an ideal position to modulate the motor outputs of M1. Nevertheless, the contribution of these anatomical projections to the production of hand movements is still unclear. The function of these projections, however, is important to investigate in order to better understand the cortical interactions that underlie the increased motor repertoire of primates. As an integral part of this research context, the experiments presented in this thesis aim to characterize the cortical interactions between the premotor areas and M1 involved in hand movements in the capuchin monkey. In a first study, the modulatory effects of ventral premotor cortex (PMv) on M1 outputs were investigated (Chapter I). In a second study, the modulatory effects of the dorsal premotor cortex (PMd) were studied and compared to those of PMv (Chapter II). Lastly, in a third study, the modulatory effects of the supplementary motor area (SMA) were examined and compared to those of PMv and PMd (Chapter III). In summary, the results presented in this thesis offer a new perspective on the cortical interactions linking the premotor areas to M1. It is shown that each premotor area influences the outputs of M1 in a unique way. This supports the idea that each premotor area plays a specialized role in the motor control of the hand and is able to accomplish this function, in part, through its modulation of M1 outputs. These results contribute to a better understanding of the cortical interactions that underlie the refinement of hand movements accompanying the evolution of the motor system.

La cécité précoce induit des changements comportementaux souvent accompagnés par des changements fonctionnels et neuroanatomiques au niveau du cerveau. Alors que les modifications dans les modalités tactiles et auditives ont été largement étudiées, les changements touchant l’olfaction et la douleur chez les aveugles sont restés moins explorés. Chez l’humain aveugle précoce, certaines études ont rapporté une amélioration de la fonction olfactive alors que d’autres n’ont pas réussi à démontrer de tels effets. Chez l’humain, des études récentes ont mis en évidence une hypersensibilité à la douleur aiguë chez les aveugles précoces. Cependant, les mécanismes sous-jacents sont restés inconnus. Afin d’étudier les changements olfactifs et nociceptifs induits par la cécité précoce ainsi que la plasticité fonctionnelle et neuroanatomique qui les accompagne, nous avons développé un modèle de souris de cécité précoce appelé ZRDBA. Dans cette souche, en croisant un parent homozygote pour le gène Rax/Rx (gène responsable de l’anophtalmie) avec un parent hétérozygote, dans une même portée la moitié des souris naissent anophtalmes alors que l’autre moitié a une vue normale. Cette souche nous permet d’examiner les modifications comportementales et cérébrales induites par la cécité chez deux groupes de souris ayant la même base génétique. Le premier objectif de cette thèse était d’évaluer les changements comportementaux olfactifs induits par la cécité chez les souris ZRDBA et d’examiner si ces changements sont accompagnés de plasticité anatomique dans les régions cérébrales impliquées dans le traitement olfactif. Trois tests comportementaux ont été menés : le test de recherche de nourriture, le test du seuil olfactif et le test de performance olfactive. Les résultats ont révélé des meilleures performances olfactives chez les aveugles dans le test de recherche de nourriture ainsi que dans le test de performance olfactive, mais pas dans le test du seuil olfactif. Ces résultats indiquent une amélioration de la discrimination et identification des odeurs chez les souris aveugles. La plasticité cérébrale dans les structures olfactives a été examinée par des analyses histologiques et analyses IRM. Les résultats des mesures histologiques ont révélé une augmentation du volume des bulbes olfactifs, premier relais de traitement des informations olfactives, chez les souris aveugles. Les analyses IRM ont révélé une augmentation du volume dans les couches granulaires et glomérulaires des bulbes olfactifs ainsi que dans d’autres régions impliquées dans ii le traitement olfactif, notamment, le cortex orbitofrontal et le cortex piriforme. Ces résultats suggèrent que l’amélioration de la fonction olfactive chez les souris aveugles peut être expliquée par la plasticité anatomique mise en évidence dans les structures olfactives. Le deuxiéme objectif de cette thèse était d’évaluer la sensibilité à la douleur chez les souris aveugles ZRDBA. Quatre tests nociceptifs ont été réalisés : le test de formaline (sensibilité chimique), le test de Von Frey (sensibilité mécanique), le test d’acétone (sensibilité au froid) et le test de tail-flick dans l’eau (sensibilité au chaud). Les souris aveugles, lorsque comparées à leurs congénères voyantes, ont montré une hypersensibilité à la douleur dans tous les tests. Afin d’examiner les mécanismes sous-jacents de cette hypersensibilité, nous avons investigué par le biais d’analyses immunohistologiques la plasticité fonctionnelle et anatomique dans l’amygdale, structure clé pour la modulation et traitement de la douleur. Les résultats ont montré une augmentation de l’activité c-fos induite par l’injection de la formaline dans le noyau central de l’amygdale et dans toute l’amygdale chez les souris aveugles. Les analyses histologiques ont également montré une augmentation du volume de l’amygdale chez les souris aveugles. Ces résultats suggèrent la contribution de l’amygdale dans l’hypersensibilité à la douleur mise en évidence chez les souris aveugles. Finalement, dans la troisième partie de cette thèse, nous avons voulu investiguer l’impact de la cécité sur la plasticité dans l’ensemble du cerveau à l’aide d’analyses IRM et d’analyses histologiques. Les résultats de cette étude ont révélé une atrophie de la plupart des structures visuelles, notamment, le corps géniculé latéral, le cortex visuel primaire, le cortex visuel secondaire ainsi que les collicules supérieurs. En outre, les analyses histologiques ont révélé une atrophie de la couche IV dans le cortex visuel primaire et dans le cortex visuel secondaire ainsi qu’une atrophie des couches visuelles superficielles des collicules supérieurs chez les souris aveugles expliquant la réduction du volume observée dans ces régions. Dans les autres structures non visuelles, les analyses ont révélé une augmentation du volume dans l’amygdale, impliquée dans la douleur ainsi que dans plusieurs régions olfactives comme les bulbes olfactifs, le cortex piriforme et le cortex orbitofronal chez les souris aveugles. Ces résultats permettent de faire le parallèle avec les études réalisées chez l’humain et ouvrent la porte pour plus d’investigations des mécanismes sous-jacents de la plasticité cérébrale observée chez les aveugles. / Early blindness induces behavioral changes often accompanied by functional and neuroanatomical changes in the brain. While changes in tactile and hearing modalities have been largely investigated, changes in olfaction and pain in the blind remained less explored. While some studies reported an improvement in olfactory function in early blind humans, others failed to demonstrate such effects. In addition, recent studies evidenced hypersensitivity to acute pain in early blind humans. However, the underlying mechanisms remained unknown. In order to study changes induced by early blindness in olfactory function and as well as the underlying functional and neuroanatomical plasticity, we developed a mouse model of early blindness called ZRDBA. In the unique ZRDBA strain, half of the mice homozygous for the Rax / Rx gene (gene responsible for anophthalmia) are born anophthalmic while the other half heterozygous are born sighted. This ZRDBA mice allow investigation of the behavioral and cerebral changes impacts of early blindness without worrying about strain differences. The first aim of this thesis was to assess olfactory changes induced by blindness in ZRDBA mice and examine whether these changes are accompanied by anatomical plasticity in brain regions involved in olfactory processing. Three behavioral tests were conducted: the buried food test, the odor detection threshold test (sensitivity measure) and the olfactory performance test (three-odor discrimination measure). The results revealed better olfactory performance of blind mice the buried food test as well as in the olfactory performance test but not in the olfactory threshold test. These results indicate an improvement in olfactory discrimination and identification in blind mice. Brain plasticity in olfactory structures was examined by histological and MRI analyses. The results of the histological measurements revealed a larger volume of the olfactory bulbs, the first site for processing olfactory information, in blind mice. MRI analysis revealed a larger volume in the granular and glomerular layers of the olfactory bulbs as well as in other regions involved in olfactory processing, namely, the orbitofrontal cortex and the piriform cortex. These results suggest that plasticity in the olfactory structures may explain the improved olfactory function in blind mice. The second aim of this thesis was to assess pain sensitivity in the blind ZRDBA mice. Four nociceptive tests were carried out: the formalin test (chemical sensitivity), the Von Frey iv test (mechanical sensitivity), the acetone test (cold sensitivity) and the water tail-flick test (hot pain sensitivity). Blind mice showed hypersensitivity to pain in all tests. In order to examine the underlying mechanisms of this pain hypersensitivity, we investigated the functional and anatomical plasticity in the amygdala, a key structure for the modulation and treatment of pain using immunohistological analyses. The results revealed an increase of c-Fos activity induced by the injection of formalin in the central nucleus of the amygdala as well as the whole amygdaloid complex in blind mice. Histological measurement also revealed a larger volume of the amygdala in blind mice. These results suggest the contribution of the amygdala in pain hypersensitivity evidenced in blind mice. Finally, in the third part of this thesis, we wanted to investigate the impact of blindness on anatomical plasticity in the whole brain using MRI and histological analyses. The results of this study revealed atrophy of most of the visual structures, in particular, the lateral geniculate nucleus, the primary visual cortex, the secondary visual cortex as well as the superior colliculi. Moreover, histological analyses revealed an atrophy of layer IV of the primary visual cortex and the secondary visual cortex as well as atrophy of the superficial visual layers of the superior colliculus in blind mice explaining the volumetric reduction observed in these regions. In the non-visual structures, analyses revealed a larger volume in the amygdala, as well as in several olfactory structures such as the olfactory bulbs, the piriform cortex and the orbitofronal cortex in blind mice. These results clarify the impact of early blindness on brain plasticity and opens the door for further investigation of its underlying mechanisms.

<p>Sea urchins are fascinating marine creatures belonging to the phylum Echinodermata that serve as an essential ecological component and hold promise as a prospective source of therapeutics. However, sudden environmental changes, such as global warming and marine pollution, are placing significant stress on these organisms. To maintain natural resources and exploit sea urchins commercially, researchers are investigating aquaculture as a solution.</p> <p>This investigation discloses the physiological and immunological effects of physical and chemical stressors on one of the most common edible species of sea urchin, <em>Arbacia punctulata</em>. The study employed an elevated temperature as a physical stressor (1°C/day), lipopolysaccharides (LPS) inoculation as a chemical stressor (4µg/ml/day), and a combination of both LPS and elevated temperature as combined stressors. The results demonstrated a significant alteration in the total and differential coelomocyte count in the LPS-stressed group (p<0.05) and combined stressed group (p<0.05) followed by abnormal behavioral activity compared to those of control. Additionally, exposure to acute LPS exposure (at day 1 and day 3) and combined stressors led to an increase in phagocytic capacity (p<0.05) and lysozyme activity (p<0.05). Chronic exposure to LPS and combined stressors resulted in a decrease in gonadosomatic index (p<0.05, at day 10) and lysozyme activity (at day 7). A significant increase in coelomic fluid (CF) protein (p<0.05)was observed in the temperature-stressed group on days 5 and 10, while the combined stressed group had significantly more CF protein on days 1, 5, 7, and 10. An upregulation of Nf-kB gene expression was also observed (p>0.05) in temperature stressed group.  </p> <p>The study also revealed that sea urchins contain bioactive compounds that protect against external and internal injury, cell death, and body wall extract of sea urchin exhibited high antioxidant activity(p<0.05). Furthermore, it confirmed the antibacterial activity (p<0.05) of sea urchin (<em>Arbacia punctulata </em>and<em> Lytechinus variegatus</em>) body wall and coelomic fluid (cell-free plasma) extracts against ten pathogenic bacteria. The ethyl acetate body wall extract of both sea urchin species demonstrated higher inhibitory activity against the pathogenic bacteria tested. Overall sea urchin has potentials to meet the demand of food and medicine. </p>