Few PET isotopes are suitable for antibody labelling since immunoPET requires that the PET isotope can be attached to the mAb with high in-vivo stability and the decay half-life of the isotope should match the pharmacokinetics of the mAb (Phelps 2004). Both 124I (t½ = 4.2 d) and 89Zr (t½ = 3.3 d) have a near ideal half-life for anti-body-based imaging, but there are several ad-vantages of using 89Zr over 124I. For 124I, the high energy of its positrons (2.13 MeV), results in a relatively low PET image resolution and the possible dehalogenation in vivo can lead to significant radioactivity uptake in non-targeted organs. In comparison, for 89Zr the low energy of its positron (395.5 keV), results in a PET images with a higher spatial resolution and furthermore, 89Zr is a residualizing isotope, which is trapped inside the target cell after internalization of the mAb. One disadvantage of 89Zr is its abundant high energy gamma-ray (909 keV), which may limit the radioactive dose that can be administered to the patients. The most popular reaction to produce 89Zr is the 89Y(p,n)89Zr nuclear reaction (Sahar et al., 1966; Link et al., 1986). A proton beam with 14-16MeV energy is used to bombard inexpensive high-purity 89Y metal target (99.9%), avoiding cumbersome recycling of the target material. The yttrium targets could be either a foil (Dejesus and Nickels, 1990), sputtered onto a copper support (Meijs et al., 1994) or Y2O3 pellets (S. A. Kandil, B. Scholten, 2007). Although 89Zr is currently commercially available, its price is prohibitive for routine clinical applications of 89Zr immuno-PET. The motivation of the present work was the fully automated production of small quantities of 89Zr using commercially available automated systems. We also describe a newly designed and tested platinum cradle, capable of holding a metallic foil and being directly transferable/compatible between the IBA NIRTA target and IBA Pinctada Metal dissolution/purification module. Material and Methods The solid target infrastructure used for 89Zr production was identical to the implementation reported earlier for production of 64Cu and 124I (S. Poniger et al. 2012). The commercially avail-able Nirta Solid Target from IBA was coupled to our 18/9 IBA cyclotron using a 2-meter external beam line. A fully automated pneumatic solid target transfer system (STTS) designed by TEMA Sinergie was used to deliver the irradiated tar-gets to a dedicated hotcell. The newly designed platinum cradle holding the yttrium foil (0.127 mm thick, 8 mm d) is shown in FIG. 1. Typical irradiation parameters were 14.9 MeV at 20 μA for 1.5 hours (90o angle of incidence). The irradiated cradle, containing the 89Zr target is then loaded directly into the IBA Pinctada Metal module (see FIG. 2) for dissolution/purification without disassembly. We used the dissolution/purification method described by Holland et al. 2009, without modification (Purification of 89Zr from 89Y, 88Y and other radionuclidic impurities using a hydroxamate column, with 89Zr eluted with 1.0M Oxalic acid). Radionuclidic purities were evaluated by gamma spectroscopy and traces of metallic impurities were determined by ICP-MS. Results and Conclusion FIGURE 3 shows the gamma spectrum of the purified 89Zr solution. Since yttrium has one stable isotope only, relatively pure 89Zr is produced at low energy (14.9 MeV). In these preliminary non-optimized cyclotron productions, average purified 89Zr yield of 0.34 mCi/μAh was achieved, in comparison to values of 1.5 mCi/μAh found in the literature (10° angle of incidence). In these preliminary experiments, no deformation of the foil was observed at 20 μA beam current and higher currents are under investigation.

Thesis (Ph.D.) - James Cook University, 2004. / Typescript (photocopy) Appendices: leaves 136-141. Bibliography: leaves 119-135.

Les coquilles d’huitres perlières (Pinctada margaritifera) en élevage sont abondamment colonisées par des peuplements épibiontes (ie biofouling). Ces communautés d’épibiontes représentent des contraintes de gestion coûteuses pour les perliculteurs (manutention, traitements). Leur rôle dans le fonctionnement des élevages, à la fois sur les espèces cultivées et sur l'environnement, est cependant encore très mal connu. La majorité des épibiontes sont des organismes filtreurs, potentiels compétiteurs des huitres perlières pour la ressource. Alors qu’une telle compétition pourrait compromettre la production, les interactions trophiques entre les huitres perlières et les épibiontes ont été très peu étudiées en Polynésie française. Plus largement, l’activité des épibiontes, ajoutée à celle des huitres perlières, pourrait également avoir des conséquences sur le fonctionnement de l’écosystème lagonaire. Au cours de ce travail de thèse, le biofouling a été étudié au travers d’une approche globale, considéré simultanément comme une contrainte pour la perliculture et comme un forçage biologique pour l’écosystème. Plusieurs expérimentations ont été réalisées dans 4 lagons de Polynésie française : Ahe, Mangareva, Rangiroa et Tahiti. Les communautés d’épibiontes ont été décrites, leur influence sur les fonctions physiologiques des huitres perlières (nutrition, croissance, reproduction) évaluée et finalement, leur rôle dans les interactions entre les élevages d’huitres perlières et l'environnement a été quantifié. Alors qu’aucun effet négatif du biofouling n’a été décelé sur la production des huitres perlières, son importance dans les processus à l’échelle de l’écosystème a été démontrée. / Reared pearl oysters support a host of epibiont communities (ie biofouling). Biofouling control results in additional costs for farmers (handling, treatment). However, the impact of epibionts on pearl oysters and on environment remains poorly known. Epibiont communities are dominated by filter-feeder organisms, which may compete for food with pearl oysters. Although such competition could alter the commercial production, very few studies have been conducted concerning the trophic interactions between pearl oysters and epibionts in French Polynesia. Otherwise, epibionts could reinforce the influence already induced by pearl oysters on the ecosystem. During this thesis, the problem of biofouling was addressed using a holistic approach, considering it as a constraint for pearl farming and a biological forcing for the ecosystem. Several experiments have been conducted in 4 lagoons of French Polynesia: Ahe, Mangareva, Rangiroa and Tahiti. Biofouling communities have been described, their impact on pearl oysters (feeding, growth, reproduction) assessed and finally we quantified their influence in the interactions between pearl oysters’ rearing and environment. While no negative impact of biofouling was observed on pearl oysters, its importance on the ecosystem processes have been demonstrated.

Few PET isotopes are suitable for antibody labelling since immunoPET requires that the PET isotope can be attached to the mAb with high in-vivo stability and the decay half-life of the isotope should match the pharmacokinetics of the mAb (Phelps 2004). Both 124I (t½ = 4.2 d) and 89Zr (t½ = 3.3 d) have a near ideal half-life for anti-body-based imaging, but there are several ad-vantages of using 89Zr over 124I. For 124I, the high energy of its positrons (2.13 MeV), results in a relatively low PET image resolution and the possible dehalogenation in vivo can lead to significant radioactivity uptake in non-targeted organs. In comparison, for 89Zr the low energy of its positron (395.5 keV), results in a PET images with a higher spatial resolution and furthermore, 89Zr is a residualizing isotope, which is trapped inside the target cell after internalization of the mAb. One disadvantage of 89Zr is its abundant high energy gamma-ray (909 keV), which may limit the radioactive dose that can be administered to the patients. The most popular reaction to produce 89Zr is the 89Y(p,n)89Zr nuclear reaction (Sahar et al., 1966; Link et al., 1986). A proton beam with 14-16MeV energy is used to bombard inexpensive high-purity 89Y metal target (99.9%), avoiding cumbersome recycling of the target material. The yttrium targets could be either a foil (Dejesus and Nickels, 1990), sputtered onto a copper support (Meijs et al., 1994) or Y2O3 pellets (S. A. Kandil, B. Scholten, 2007). Although 89Zr is currently commercially available, its price is prohibitive for routine clinical applications of 89Zr immuno-PET. The motivation of the present work was the fully automated production of small quantities of 89Zr using commercially available automated systems. We also describe a newly designed and tested platinum cradle, capable of holding a metallic foil and being directly transferable/compatible between the IBA NIRTA target and IBA Pinctada Metal dissolution/purification module. Material and Methods The solid target infrastructure used for 89Zr production was identical to the implementation reported earlier for production of 64Cu and 124I (S. Poniger et al. 2012). The commercially avail-able Nirta Solid Target from IBA was coupled to our 18/9 IBA cyclotron using a 2-meter external beam line. A fully automated pneumatic solid target transfer system (STTS) designed by TEMA Sinergie was used to deliver the irradiated tar-gets to a dedicated hotcell. The newly designed platinum cradle holding the yttrium foil (0.127 mm thick, 8 mm d) is shown in FIG. 1. Typical irradiation parameters were 14.9 MeV at 20 μA for 1.5 hours (90o angle of incidence). The irradiated cradle, containing the 89Zr target is then loaded directly into the IBA Pinctada Metal module (see FIG. 2) for dissolution/purification without disassembly. We used the dissolution/purification method described by Holland et al. 2009, without modification (Purification of 89Zr from 89Y, 88Y and other radionuclidic impurities using a hydroxamate column, with 89Zr eluted with 1.0M Oxalic acid). Radionuclidic purities were evaluated by gamma spectroscopy and traces of metallic impurities were determined by ICP-MS. Results and Conclusion FIGURE 3 shows the gamma spectrum of the purified 89Zr solution. Since yttrium has one stable isotope only, relatively pure 89Zr is produced at low energy (14.9 MeV). In these preliminary non-optimized cyclotron productions, average purified 89Zr yield of 0.34 mCi/μAh was achieved, in comparison to values of 1.5 mCi/μAh found in the literature (10° angle of incidence). In these preliminary experiments, no deformation of the foil was observed at 20 μA beam current and higher currents are under investigation.

Thesis (Ph.D.) - James Cook University, 2004. / Typescript (photocopy) Bibliography: leaves 194-210.

La production de perle de culture par l’huître perlière Pinctada margaritifera représente la seconde ressource économique après le tourisme en Polynésie Française. L’une des voies d’amélioration privilégiée de la qualité de production passe par la voie de la sélection génétique. Dans ce contexte, le déterminisme génétique des caractères d’intérêt perlicole et leurs variations à différentes échelles phénotypiques a été étudié. Les rôles respectifs de l’huître donneuse et de la receveuse, au travers de greffes expérimentales, ont révélées une corrélation positive entre les paramètres de croissance des coquilles de receveuses et la taille des perles, ainsi qu’un effet donneuse sur la qualité de la perle. Les analyses d'expressions de huit biomarqueurs de biominéralisation, codant des protéines des couches aragonitiques ou prismatiques, ont révélé une corrélation entre l’expression de ces gènes au niveau du sac perlier avec à la fois les paramètres de qualité des perles et de croissance des receveuses. L’âge de l’huître donneuse de greffon semble jouer un rôle déterminant aussi bien au niveau des phénotypes de la taille que pour le grade et les défauts de surface de la perle. Enfin, les valeurs d'héritabilité des phénotypes ont été estimées pour la première fois chez l'espèce, au travers de modèle animal utilisant des familles produites en écloserie. Globalement, les résultats montrent une transmission génétique linéaire et schématiquement on peut dire que les receveuses contrôlent principalement la croissance et la taille des perles, alors que les donneuses influencent leur qualité. / Cultured pearl production in the pearl oyster Pinctada margaritifera represents the second largest source of revenue after tourism, and it is the top export industry in French Polynesia. One of pearl farming industry’s greatest challenges is to “produce fewer but better pearls” through genetic improvement. To address this challenge, the genetic determinism of pearl quality traits and how they vary at different phenotypic scales was studied. The respective roles of donors and recipients was explored through uniform experimental grafts and revealed a positive correlation between recipient shell biometric parameters and pearl size, and a donor effect on pearl quality traits. Gene expression analyses of 8 biomineralisation biomarkers, encoding aragonitic and prismatic proteins, highlights a correlation between pearl sac gene expression with pearl quality traits and recipient shell biometric parameters. The age of the donor oyster also played a determining role with respect to the size phenotype and for grade and surface defects of the pearl. Finally, the heritability values of the phenotype were estimated for the first time for this species using an animal model on a family produced in a hatchery setting. Results show a linear genetic transmission and overall, suggest that the recipient oyster primarily controls the size of the pearls while the donor oyster influences the quality.

French Polynesia relies solely on the collection of wild Pinctada margaritifera spat for pearl oyster culture. This was developed to help protect the wild populations from overexploitation, but it is feared that massive spat collection could lead to erosion of genetic diversity both in farmed and wild stocks. Wild and farmed collections of P. margaritifera from four atolls in French Polynesia were genotyped at eight microsatellite loci to determine whether there was a loss of genetic diversity from the wild to adjacent farmed aggregations. The average allelic richness for wild samples was not significantly different from that seen for farmed samples, but there was a significant effect of atoll and locus. Pair-wise genetic differentiation (FST) was not significant between adjacent wild and farmed collections or across atolls. Overall there was no evidence for a loss of genetic variability in farmed oysters. Both farmed and wild individuals analyzed here were adults and could have originated from multiple spawning events in time and space. This could have masked genetic processes linked to recruitment happening at a finer scale. P. margaritifera demonstrates high recruitment variability, but the number of parents contributing to a successful cohort of juveniles recruited on collectors is unknown. Low effective number of breeders and variable recruitment are assumed to be responsible for the genetic patchiness that has been observed at a small spatial scale for this species and this could lead to a loss of genetic diversity in both the farmed and wild stocks. The genetic diversity and family make-up of three groups of 1.5 year old oysters were assessed using 13 microsatellite markers. These individuals were harvested on collectors in three closely located sites of the Takapoto atoll. Higher recruitment density and higher allelic richness was observed in one zone compared to the other two. Significant genetic differentiation was also observed at a small spatial scale. Pair-wise FST estimates between collectors within zone were not significant, but were generally significant across zones. Estimates of effective population size and number of families present for these individuals were larger than expected and suggested that the numbers of parents contributing to the recruits on these collector lines were not limited. Similar results were obtained when assessing monthly cohorts of recruits collected in Takapoto over 5 months with 11 microsatellites. Levels of allelic richness were not significantly different among monthly cohorts, and were comparable to the levels observed in the adult samples above. Small but significant temporal genetic differentiation was observed between the monthly cohorts. Again, there was no evidence for low effective population size or for significant family structuring and it did not appear that a limited number of parents produced these temporal cohorts. Patchy genetic structure was observed, but recruitment on collectors does not seem to be driven by a limited number of successful parents. It does not appear that the current pearl culture practices are negatively impacting the local farmed and wild stocks of P. margaritifera in French Polynesia by reducing their levels of genetic diversity.

Biomineralization is a process encompassing all mineral containing tissues produced within an organism. The most dynamic example of this process is the formation of the mollusk shell, comprising a variety of crystal phases and microstructures. The organic component incorporated within the shell is said to dictate this remarkable architecture. Subsequently, for the past decade considerable research have been undertaken to identify and characterize the protein components involved in biomineralization. Despite these efforts the general understanding of the process remains ambiguous. This study employs a novel molecular approach to further the elucidation of the shell biomineralization. A microarray platform has been custom generated (PmaxArray 1.0) from the pearl oyster Pinctada maxima. PmaxArray 1.0 consists of 4992 expressed sequence tags (ESTs) originating from the mantle, an organ involved in shell formation. This microarray has been used as the primary tool for three separate investigations in an effort to associate transcriptional gene expression from P. maxima to the process of shell biomineralization. The first investigation analyzes the spatial expression of ESTs throughout the mantle organ. The mantle was dissected into five discrete regions and each analyzed for gene expression with PmaxArray 1.0. Over 2000 ESTs were differentially expressed among the tissue sections, identifying five major expression regions. Three of these regions have been proposed to have shell formation functions belonging to nacre, prismatic calcite and periostracum. The spatial gene expression map was confirmed by in situ hybridization, localizing a subset of ESTs from each expression region to the same mantle area. Comparative sequence analysis of ESTs expressed in the proposed shell formation regions with the BLAST tool, revealed a number of the transcripts were novel while others showed significant sequence similarities to previously characterized shell formation genes. The second investigation correlates temporal EST expression during P. maxima larval ontogeny with transitions in shell mineralization during the same period. A timeline documenting the morphologicat microstructural and mineralogical shell characteristics of P. maxima throughout larval ontogeny has been established. Three different shell types were noted based on the physical characters and termed, prodissoconch I, prodissoconch 11 and dissoconch. PmaxArray 1.0 analyzed ESTs expression of animals throughout the larval development of P. maxima, noting up-regulation of 359 ESTs in association with the shell transitions from prodissoconch 1 to prodissoconch 11 to dissoconch. Comparative sequence analysis of these ESTs indicates a number of the transcripts are novel as well as showing significant sequence similarities between ESTs and known shell matrix associated genes and proteins. These ESTs are discussed in relation to the shell characters associated with their temporal expression. The third investigation uses PmaxArray 1.0 to analyze gene expression in the mantle tissue of P. maxima specimens exposed to sub-lethal concentrations of a shell-deforming toxin, tributyltin (TBT). The shell specific effects of TBT are used in this investigation to interpret differential expression of ESTs with respect to shell formation functions. A lethal and sublethal TBT concentration range was established for P. maxima, noting a concentration of 50 ng L- 1 TBT as sub-lethal over a 21 day period. Mantle tissue from P. maxima animals treated with 50 ng L- 1 TBT was assessed for differential EST expression with untreated control animals. A total of 102 ESTs were identified as differentially expressed in association with TBT exposure, comparative sequence identities included an up-regulation of immunity and detoxification related genes and down-regulation of several shell matrix genes. A number of transcripts encoding novel peptides were additionally identified. The potential actions of these genes are discussed with reference to TBT toxicity and shell biomineralization. This thesis has used a microarray platform to analyze gene expression in spatial, temporal and toxicity investigations, revealing the involvement of numerous gene transcripts in specific shell formation functions. Investigation of thousands of transcripts simultaneously has provided a holistic interpretation of the organic components regulating shell biomineralization.

Depuis plusieurs années il est devenu essentiel de comprendre le déterminisme sexuel des espèces à fort intérêt économique afin d’optimiser leur production au sein d’écloseries émergentes.L’objectif principal de cette thèse était de mettre en évidence les mécanismes impliqués dans la détermination et la différenciation sexuelle, et notamment du sexe femelle, chez l’huître perlière P. margaritifera, espèce hermaphrodite protandre et espèce clé de la perliculture, la seconde ressource économique pour la Polynésie française. Pour atteindre cet objectif, deux approches ont été menées : une approche transcriptomique visant à étudier les mécanismes moléculaires du déterminisme et de la différenciation sexuelle, et une approche expérimentale visant à comprendre le phénomène de la sexualisation par des forçages environnementaux et hormonaux en s’intéressant plus particulièrement au déterminisme et à la différenciation sexuelle femelle.Dans l’approche transcriptomique, le transcriptome de la gonade de P. margaritifera a été séquencé à partir de plusieurs échantillons gonadiques d’huîtres de sexe mâle et femelle à différents stades de développement. Après le séquençage Illumina et l'assemblage du transcriptome, 70 147 contigs ont été obtenus. L’analyse fonctionnelle de ces 70 147contigs, a permis d’identifier des gènes d’intérêt et ainsi de constituer un catalogue de 87 ARNm codant pour 67 protéines impliquées dans la détermination, la différenciation sexuelle et/ou la gamétogenèse. Ensuite une analyse stricte des données de quantification RNAseq a révélé 1 937 contigs exprimés de manière différentielle entre les catégories histologiques des gonades. À partir de l’analyse de leurs profils d’expression au sein de chaque échantillon, un nouveau modèle de la reproduction de P. margaritifera, basé sur une double approche analytique, eg. histo-moléculaire, a été proposé. Ce modèle révèle notamment que le déterminisme sexuel de P. margaritifera chez l’adulte se produirait durant une phase de régression de la gonade. Considérant ainsi les nouveaux stades définis par ce modèle, 9 gènes biomarqueurs de la voie sexuelle femelle ont pu être identifiés révélant un modèle prédictif de la voie sexuelle basé sur 3 rapports d’expressions de gènes impliquant 2 gènes inconnus pmarg-c43476 et pmarg-c54338 et 2 gènes connus pmarg-foxl2 et pmarg-fem1-like. Ce deuxième modèle suggère fortement l'implication de pmarg-foxl2 et pmarg-fem1-like dans le déterminisme du sexe de P. margaritifera. Dans l’approche expérimentale, deux expérimentations séparées ont été réalisées pour mettre en évidence l’effet i) de plusieurs combinaisons de température et de niveau trophique, et ii) de l’œstradiol-17β administré par injection directe dans la gonade ; sur le sexe, la gamétogenèse et l’expression des neuf gènes biomarqueurs de la voie sexuelle femelle identifiés précédemment. Les résultats ont montré que la condition combinant la température de 28°C et la concentration en algues de 40 000 cellules mL-1 était la plus favorable non seulement à la maturation des gonades mâles et femelles mais aussi au maintien du sexe femelle. Ce serait dans cette condition environnementale qu’il serait possible d’induire un changement de sexe de mâle vers femelle. Dans la seconde expérimentation, il a été clairement démontré que la reproduction de P. margaritifera pouvait être régulée par les hormones œstrogènes. Les résultats montrent un effet négatif de l’œstradiol sur le développement et la différenciation mâle. Enfin les résultats du modèle prédictif de la voie sexuelle de P. margaritifera, suggèrent une programmation génétique du sexe femelle qui toutefois resterait soumise aux conditions environnementales validant ainsi l’hypothèse d’un mode de détermination mixte du sexe chez P. margaritifera. / For several years it has become essential to understand sex determination of species with high economic interest to maximize their production in emerging hatcheries.The main objective of this thesis was to identify the mechanisms involved in sex determination and sex differentiation, and particularly in female sex, in the pearl oyster P. margaritifera, a protandrous hermaphrodite species and the key species of the pearl farming, the second economic resource for French Polynesia. To achieve this goal, two approaches were undertaken: a transcriptomic approach to investigate the molecular mechanisms of sex determinism and sex differentiation, and an experimental approach to understand the phenomenon of sexualization by environmental and hormonal forcing focusing especially on female sex determinism and female sex differentiation.In the transcriptomic approach, the gonad transcriptome of P. margaritifera was sequenced from several samples of male and female oyster gonads at different stages of development. After Illumina sequencing and assembly of the transcriptome, 70,147 contigs were obtained. Functional analysis of these 70,147 contigs identified genes of interest and allowed the constitution of a catalog of 87 mRNAs encoding 67 proteins involved in sex determination, sex differentiation and/or gametogenesis. Then a strict analysis of RNAseq quantification data revealed 1,937 contigs differentially expressed between the histological categories of gonad. From the analysis of their expression profiles in each sample, a new model of reproduction of P. margaritifera, based on dual analytical approach, i.e. histo-molecular, has been proposed. This model shows that sex determination of adult P. margaritifera pearl oysters occur during a regression phase of the gonad. And considering the new stages defined on this model, 9 biomarkers genes of the female sexual pathway have been identified revealing a 3-gene-pair expression ratio based model, which makes it possible to predict the sexual pathway in this hermaphrodite species. This predictive model involves two unknown genes pmarg-c43476 and pmarg-c54338 and 2 known genes pmarg-foxl2 and pmarg-fem1-like, and strongly suggests the involvement of pmarg-foxl2 and pmarg-fem1-like in sex determinism in P. margaritifera.In the experimental approach, two separated experiments were conducted to demonstrate the effect of i) various combinations of temperature and trophic level, and ii) 17β-estradiol administered by direct injection into the gonad; on sex, gametogenesis and expression of the nine biomarkers genes of the female sexual pathway previously identified. The results showed that the condition combining a temperature of 28 °C and a concentration of 40 000 cells of algae mL-1 was the most favorable not only for the maturation of the male and female gonads but also for the maintenance of the female sex. It would be in this environmental condition that it would be possible to induce a sex change from male to female. In the second experiment, it was clearly demonstrated that the reproduction of P. margaritifera could be regulated by estrogen hormones. The results show a negative effect of estradiol on male development and differentiation. Finally the results of the predictive model of the sexual pathway of P. margaritifera, suggest a genetic programming of the female sex, which however remain subject to environmental conditions, thus validating the hypothesis of a mixed sex determinism mode in P. margaritifera.

Le développement considérable réalisé ces dix dernières années dans les techniques de<br />diffraction sur des échantillons sous forme de poudre même très texturés (temps<br />d'enregistrement raisonnable et très bonne résolution) et les progrès fascinants des moyens de<br />calcul sur des machines individuelles rendent possible l'accès à des informations précises et<br />avec des temps de calcul raisonnablement courts. Dans ce travail, nous avons appliqué<br />l'analyse combinée basée sur la méthode de Rietveld pour étudier des échantillons de<br />carbonates de calcium naturels de coquilles de certaines espèces de mollusques (structure,<br />texture, tailles anisotropes...etc.) et synthétiques par biomimétisme dans le but de comprendre<br />l'influence des différents facteurs intervenants dans la croissance et la forme des grains des<br />différents polymorphes de CaCO3. Dans les échantillons naturels, nous avons clairement mis<br />en évidence l'existence de déformations de mailles cristallines dues à la présence des<br />macromolécules intra-cristallines et extra-cristallines, en complément d'études du même<br />genre réalisées sur des échantillons broyés. Dans les échantillons synthétiques obtenus par une<br />méthode de synthèse simple, nous avons analysé l'effet de l'ajout d'acide polyacrylique, en<br />termes de modulateur de croissance des polymorphes de CaCO3. La simulation des<br />digrammes de diffraction anisotropes réalisée sur ces deux types d'échantillons nous a permis<br />d'accéder aux informations pertinentes de façon précise (tailles anisotropes des cristallites,<br />structure, texture, proportion volumique des polymorphes).