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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
21

Análise morfométrica mandibular por meio de tomografia volumétrica visando a melhor forma de fixação interna da osteotomia sagital do ramo mandibular / Morphometrical examinations of the ramus mandibular for the indication stable internal fixation to sagittal ramus split osteotomy : a cone beam computer tomography study

Oliveira, Marcelo Vinicius de, 1963- 18 August 2018 (has links)
Orientador: José Ricardo de Albergaria Barbosa / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Odontologia de Piracicaba / Made available in DSpace on 2018-08-18T23:46:45Z (GMT). No. of bitstreams: 1 Oliveira_MarceloViniciusde_D.pdf: 1959101 bytes, checksum: 50a4cad57e9f79f74fc52cba91fd5fc7 (MD5) Previous issue date: 2011 / Resumo: A osteotomia sagital do ramo mandibular (OSRM) como descrito por Obwegeser e Dal-Pont é atualmente um procedimento comum e de sucesso na cirurgia oral e maxilo-facial no tratamento de certas discrepâncias mandibulares. Em cirurgia ortognática, entre muitas diferentes propostas de osteotomia para correções de deformidades dento-faciais na mandíbula, é evidente que a osteotomia sagital da mandíbula (OSRM) é a mais utilizada pelos cirurgiões buco-maxilo-faciais. Este fato, devido a várias razões, principalmente a estabilidade alcançada pelo contato osso grande entre os segmentos, sem a necessidade de enxerto ósseo, função mandibular precoce; estabilidade no tratamento em longo prazo e fixação fácil. Diferentes métodos para fixação interna foram utilizados para permitir a mobilização precoce e funções após a OSRM. A introdução dispositivos de fixação interna, como miniplacas e parafusos diminui substancialmente a duração do bloqueio maxilo-mandibular ou mesmo o elimina completamente. A espessura da cortical óssea mandibular tem demonstrado ser um dos muitos fatores que levam a falha de afrouxamento de parafuso e, conseqüentemente, o poder de fixação do parafuso. Mensurações da morfologia mandibular utilizando métodos convencionais têm sido relatadas na literatura. Até o momento, apenas um estudo foi publicado em que analisa a espessura do osso cortical no ramo mandibular relacionando-a com fixação interna na osteotomia sagital do ramo mandibular. O objetivo deste estudo foi quantificar a espessura do osso cortical do ramo mandibular para determinar as condições relacionadas com a osteotomia sagital do ramo e colocação de parafusos. A amostra foi composta por 44 pacientes de pacientes, com idades variando de 46 a 52 (idade média de 49 anos). Tomografias computadorizada Cone-Beam foram realizadas fazendo três cortes; na área de terceiro molar (seção A), posterior 5mm (seção B) e 5 milímetros posterior a este último (seção C). Foram realizadas as medidas das corticais em nível superior e inferior relacionada com o canal mandibular além das medições relacionadas com a largura total da mandíbula. Coeficiente de correlação intra classe com p <0,05 foi usado. O resultado mostrou que as corticais vestibular e lingual não apresentaram diferenças estatísticas e seu menor valor foi 1,5 milímetros para cada um. Corticais ósseas superior e inferior não apresentaram diferenças e a largura total da mandíbula foi entre 15,9 milímetros a 8,5 milímetros na região anterior, entre os 17,4 milímetros a 12,8 milímetros na área intermediária e 18mm de 8,8 milímetros na região posterior. A distância superiormente ao canal mandibular apresentou um desvio padrão mínimo com uma média de 8,5 milímetros na região anterior, 10,6 milímetros para a região intermediária e 12,5 milímetros na região posterior. Em conclusão, a espessura cortical do ramo mandibular é particularmente forte e oferece um bom ancoradouro para SSRO osteossíntese com parafusos de fixação independente do tipo de disposição / Abstract: The sagittal split ramus osteotomy (SSRO) as described by Obwegeser and Dai­Pont is now a standard, common and successful procedure in oral and maxillofacial surgery for the treatment for certain mandibular discrepancies. In orthognathic surgery, among many different designs proposed osteotomy for correction of dental­facial deformities in the jaw, it is clear that the sagittal osteotomy of the mandibular (OSRM) is the most commonly used by surgeons maxillofacial. This fact due to several reasons, mainly the stability achieved by the large bone contact between the segments, without the need for bone grafts, early jaw function; stability in long-term treatment and easy fixation. Different methods for internal fixation have been used to allow early mobilization and functions after the common use of the SSRO. The introduction of modern devices for internal fixation such as miniplates or lag screws substantially shortens the duration of intermaxillary fixation (IMF) or even obviates it completely. Cortical bone thickness has been shown to be one of many factors affecting screw pullout strength and, consequently, the holding power of the screw. Measurement of mandibular ramus morphology using conventional methods has been reported in the literature28, but surgeons have found that further investigatio of the anatomical relationship is needed. To date, only one study have been publi hed in which the thickness of cortical bone at the mandibular ramus relates to stable internal fixation of SSRO. The objective of this study was to quantify the cortical bone thickness of the mandibular ramus to determine conditions related to sagittal split ramus osteotomy and placement of screws. The patient sample comprised 44 patients, ages ranging. from 46 to 52 (mean age, 49 years). The cone beam computed tomography were periormed and realized three cuts in third molar area (section A), 5 mm posterior (section B) and 5mm posterior to the latter (section C). Was executed measurement in cortical areas of superior and inferior level related to mandibular canal and measurement related to total width of mandible. Intra class Correlation Coefficient with p<0.05 was used. The result showed that buccal and lingual cortical zone was not present sta1istical differences and his minor value was 1.5mm for each one. Superior and inferior cortical bone was not present differences and the total width of mandible was between 15.9mm to 8.5mm in the anterior area, between 17.4mm to 12.8mm in the meddle area and 18mm to 8.8 mm in the posterior area. The distance superiorly to mandible canal presented a minimal standard deviation with a mean of 8.5mm in the anterior region, 10.6 mm for meddle region and 12.5mm in the posterior region. In conclusion, the cortical thickness of the mandibular ramus is particularly strong and offers a good anchorage for SSRO using osteosynthesis screws independently of disposition fixation type / Doutorado / Cirurgia e Traumatologia Buco-Maxilo-Faciais / Doutor em Clínica Odontológica
22

Performance reprodutiva e avaliação morfofisiológica cardíaca materna, e desenvolvimento embriofetal de ratas normais e com sobrepeso expostas à sibutramina / Maternal reproductive performance and cardiac morphophysiological evaluation, and embryofetal development of normal and overweight female rats exposed to sibutramine

Francia-Farje, Luis Alberto Domingo 16 August 2018 (has links)
Orientadores: Wilma De Grava Kempinas, Jair de Campos Soares / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Biologia / Made available in DSpace on 2018-08-16T17:23:07Z (GMT). No. of bitstreams: 1 Francia-Farje_LuisAlbertoDomingo_D.pdf: 5269408 bytes, checksum: 9fcbeacc2566c4c907be21de0f818627 (MD5) Previous issue date: 2010 / Resumo: A ação anorexígena e termogênica da sibutramina é bem conhecida e tem com efeitos colaterrais principalmente o aumento da pressão arterial e da frequência cardíaca. Entretanto, seus efeitos sobre a performance reprodutiva e sobre os fetos de mulheres que receberam sibutramina durante a gestação nõa é bem conhecido. Assim, os trabalhos mostrados nesta tese têm o bojetivo de avaliar os possíveis efeitos da sibutramina na pergormance reprodutiva de ratas prenhes, assim como seu possível efeito teratogêncio na prole de ratas tratadas durante a prenheze sua possível influência na morfofisiologia cardíaca das mães...Observação: O resumo, na íntegra poderá ser visualizado no texto completo da tese digital / Abstract: The anorexigenic and thermogenic action of sibutramine is well-knownand its side effects are mainly the increase of arterial pressure and cardiac frequency. However, its effects on the reproductive performance and on the fetuses of women who had sibutramine during pregnancy are not well known. Thus, the studies in this thesis aimed to evaluate possible effects of sibutramine on the reproductive performance of pregnant rats as well as its possible teratogenic effect on the pups of rats treated during pregnancy and its possible influence on the cardiac morpho physiology of the mothers...Note: The complete abstract is available with the full electronic digital thesis or dissertations / Doutorado / Anatomia / Doutor em Biologia Celular e Estrutural
23

Using haptic modelling for spinal implant design

Campbell, R.I., Lo-Sapio, M., Martorelli, M. January 2009 (has links)
Published Article / The link from medical scan images through data manipulation to additive manufacturing is well established. Various types of software are used to deliver the required .STL file(s). Often, the data manipulation will require the generation of new shapes around existing geometry, e.g. an implant that will replace missing bone tissue. This paper reports exploratory work undertaken to assess the feasibility of using haptic modelling and "virtual sculpting" software to generate novel designs of vertebrae implants for correction of spinal curvature. .STL data of several vertebrae, originating from CT scans, was imported into the Freeform system from SensAble technologies. It was used to create immutable "bucks" around which the user "sculpted" three-dimensional implant geometries. It must be noted that the designs have not been medically assessed and were for demonstration purposes only. However, the process route followed did prove to be feasible and offered some particular advantages, e.g. a precise fit between the implant and the vertebra and the possibility of enabling the direct intervention of medics in the implant design process.
24

Dopady tanečního sportu na pohybový aparát jedince / Effects of dance sport in the musculoskeletal system of the individual

Křivohlávek, Jakub January 2013 (has links)
Title: Effects of dance sport in the musculoskeletal system of the individual Objectives: The goal is to musculoskeletal examination of selected individuals and evaluation the effect of dance sport on examined status. The results should be the basis for further research in this area. Methods: Kinesiology analysis, bioimpedance analysis and X-ray were used for scrutiny of the musculoskeletal system. Primary and secondary data were analyzed afterwards. Results: Findings of struktural deformities: flat feet (both), both sided hallux valgus with incipient degenerative changes of I. MTP joint (male), limit angle of I. MTP joint of left leg (female). These deviations are related to the using of dance shoes. Muscle imbalance upper thoracic region and lateral imbalance of tested people are the result of the prescribed holding and leading used in dance. Keywords: dance sport, musculoskeletal system, muscle imbalances, feet deformities
25

Mouthpart deformities of Chironomid larvae as an indicator of heavy metal polluted water

Lindström Jonsson, Tim January 2019 (has links)
Freshwater ecosystems are under increasing pressure from a variety of contaminants, including heavy metals from mining operations, which can have complex effects that are difficult to evaluate. To detect early warnings from elevated concentrations of metals, organisms are sought to be used as monitoring tools. For example, mouthpart deformities in Chironomid larvae have been proposed as a bioindicator of stress in aquatic environments. However, the frequency and cause of these deformations, and their sensitivity to different stressors remain uncertain. In this study, I evaluated the usefulness of mouthpart deformities as a tool to monitor the effects of heavy metals from mining in northern Sweden. To do this, the mouthparts of 3789 Chironomid individuals analyzed from 17 sites closely located to mining operations and tested against concentrations of metals and DOC in the water chemistry of lakes and rivers. The frequency of deformities ranged from 0.00 – 4.79 % across all sites. Metal concentrations ranged from ‘very low’ to ‘low’ based on biological effect risk assessments. Of these, copper (R2 = 0.73) and cobalt (R2 = 0.66) were found to be significantly correlated with frequency of deformities. Additionally, the occurrence of deformities declined with DOC concentration, this was a nonlinear relationship. Frequencies of deformities observed in this study were lower than what have been reported to similar studies. The result from this study, together with other studies, suggest that deformities in Chironomid larvae are sensitive to even low levels of certain metals and could potentially be a good biomonitoring tool for early warnings of contamination in freshwater environments.
26

Evolução da órtese Anel em Oito Articulado (AOA) / Evolution of the articulated eight-shaped ring orthosis (AOA)

Masalskas, Ellen Cristina 25 October 2018 (has links)
A deformidade em pescoço de cisne é uma postura anormal do dedo caracterizada por hiperextensão da articulação interfalangeana proximal juntamente com a flexão da interfalangeana distal, que pode causar dor e incapacidade funcional. Na prática clínica, as órteses são amplamente aplicadas no tratamento conservador da deformidade, sendo indicados modelos adquiridos comercialmente ou confeccionados sob medida pelos terapeutas. Trabalhos anteriores do grupo de pesquisa propuseram um modelo de órtese articulada para correção da deformidade pescoço de cisne denominada AOA (Anel em Oito Articulado) que teve sua funcionalidade aprovada pelos voluntários da pesquisa. O presente trabalho objetiva a evolução deste projeto na busca de um modelo mais anatômico (maior conforto), mais funcional e melhorar a compreensão acerca da relação entre materiais, manufatura e custo da órtese. Para isto, foram utilizados os processos de Manufatura Aditiva (MA) ou impressão 3D e parametrização, que permite o redezenhar automaticamente a órtese. A metodologia aplicada foi baseada no desenvolvimento de produtos e otimização integrada entre a técnica e a participação de adultos, atendidos nos ambulatórios do HCFMRP-USP, que apresentam a deformidade a fim de identificar sua percepção acerca da experimentação. A metodologia foi dividida didaticamente em duas etapas. Na primeira, foram realizadas as medidas antropométricas de dedos com a deformidade, além da definição das medidas de referência para parametrização através de medidas das mãos dos pesquisadores e de clientes; na segunda etapa, foi realizada a otimização e a parametrização do desenho, foi testada a manufatura da órtese com diferentes materiais, teste de usabilidade, por teste de bancada com os pesquisadores e após aprovação foram experimentadas por dois clientes para avaliar a opinião e na sequencia, foi feita análise descritiva dos dados. As principais alterações do projeto atual sobre o original foram a substituição dos diâmetros das seções dos dedos pela altura e largura que as aproximou de formatos elípticos; aumentos e reposicionamentos dos apoios ao dedo; reposicionamento do eixo de rotação da articulação; alteração do ângulo de bloqueio segundo recomendação do terapeuta pela avaliação da deformidade; modelagem paramétrica e manufatura aditiva em resina de alta resistência. Foram realizados também ensaios mecânicos para avaliação das propriedades das resinas curadas e teste com sensor de força, para conhecimento da distribuição de pressão da órtese no dedo. O presente modelo possibilitou aos usuários um ganho em funcionalidade e conforto e através do desenho paramétrico e manufatura aditiva direta possibilitou a dispensação da órtese personalizada com maior agilidade, em poucas horas. A evolução da AOA foi considerada promissora pois apresenta uma ferramenta inovadora muito próxima da aplicação comercial para a resolução de um problema de saúde crônico. / The swan neck deformity is an abnormal posture of the finger characterized by the hyperextension of the proximal interphalangeal joint with distal interphalangeal flexion, which can cause pain and lead to functional disability. In clinical practice, the orthosis is widely recommended in the conservative treatment of the deformity, and both commercially-acquirable models and on demand models made by therapists can be indicated. The previous work of the research group proposed an articulated orthosis model for the correction of swan neck deformity called AOA (Articulated Eight-shape Ring) that had its functionality approved by the research volunteers. The present work aims to further develop this project by searching for a more anatomical and functional model, providing greater comfort, and seeking a compromise among materials, manufacture and cost of the orthosis. For this, the processes of Additive Manufacturing (MA) or 3D printing and parameterization were used, which allows the automatic redesign of the orthosis The applied methodology was based on the product development and the integrated optimization between the technique and the feedback of adult patients who were affected by the deformity and treated at the HCFMRP-USP ambulatories. The methodology was divided into two steps: firstly, the anthropometric measurements of the fingers with the deformity were carried out, and the reference measurements for parameterization were defined through the measurement of the researchers\' and the patients\' hands; secondly, the optimization and parameterization of the design was performed, followed by the manufacturing of the orthosis with different materials that were submitted to usability tests and a bench test with the researchers. After approval, the orthosis were tested by two patients in order to obtain their opinion, and subsequently, the descriptive analysis of collected data was established. When comparing the current design to the original one, the main changes were the replacement of the diameters of fingers sections by slightly elliptical formats, the enlargement and repositioning of the finger supports, the repositioning of the rotation axis of the joint, the alteration of the blockage angle according to the recommendation of the therapist to evaluate the evolution of the deformity, and the parametric modelling and additive manufacture in high strength resin. Mechanical tests were also carried out to evaluate the properties of the cured resins as well as load sensor tests to identify the pressure distribution from the orthosis to the finger. The present model provided the users with greater functionality and comfort. Moreover, the personalized orthosis can be fabricated in matter of a few hours due to the parametric design and direct additive manufacture. The evolution of AOA was considered promising as it presents an innovative tool very close to the commercial application for the resolution of a chronic health issue.
27

Avaliação ultrassonográfica da reparação do tendão calcâneo após secção percutânea para a correção do equino residual do pé torto congênito idiopático / Ultrasonographic evaluation of Achilles tendon repair after percutaneous sectioning for the correction of congenital clubfoot residual equinus

Maranho, Daniel Augusto Carvalho 14 August 2009 (has links)
A maioria dos casos de pé torto congênito tratados pelo método de Ponseti requer a secção do tendão calcâneo para correção do equino residual. Evidências clínicas sugerem que há completa cicatrização entre os cotos tendíneos, mas este processo reparativo ainda não foi suficientemente estudado. Esta investigação teve como objetivo avaliar o processo de reparação que ocorre após a secção percutânea do tendão calcâneo para a correção do equino residual no pé torto congênito idiopático tratado pelo método de Ponseti. Por meio de estudo prospectivo, foram analisadas 37 tenotomias em 26 pacientes com pé torto congênito idiopático tratados pelo método de Ponseti, com seguimento mínimo de um ano após a secção. A tenotomia foi realizada percutaneamente com agulha biselada de grosso calibre, sob sedação e anestesia local. O exame ultrassonográfico foi feito logo após a secção tendínea para assegurar que ela tenha sido completa e mensurar o afastamento entre os cotos. A reparação foi estudada por meio da ultrassonografia realizada três semanas, seis meses e um ano após a tenotomia. A ultrassonografia, realizada imediatamente após o procedimento, mostrou que, em alguns casos, feixes tendíneos residuais persistiam entre os cotos, mas foram completamente seccionados, em seguida, sob controle ultrassonográfico. Houve afastamento médio de 5,65 mm ± 2,26 (2,3 a 11,0 mm) entre os cotos tendíneos logo após a secção. Em um caso ocorreu sangramento maior que o habitual, que foi controlado com pressão local e não provocou interferência no tratamento. Após três semanas, a ultrassonografia mostrou regeneração tendínea com preenchimento do espaçamento entre os cotos por tecido hipoecoico com ecotextura irregular e com restituição da continuidade entre os cotos demonstrada dinamicamente pela transmissão de movimentos do músculo tríceps sural para o calcanhar. Seis meses após a tenotomia, o exame ultrassonográfico evidenciou que o tecido de reparação apresentava ecotextura de aspecto fibrilar e, quando comparado ao tendão normal, havia leve ou moderada hipoecogenicidade e espessamento cicatricial. Um ano após a tenotomia, o exame ultrassonográfico mostrou estrutura fibrilar na região de reparação, com ecogenicidade semelhante ao tendão normal, mas ainda apresentando espessamento tendíneo cicatricial. Em termos gerais, ocorreu rápida cicatrização após a secção percutânea do tendão calcâneo, que restabeleceu a continuidade entre os cotos. Ao final do período de observação, o tecido de reparação tendínea apresentou aspecto ultrassonográfico semelhante ao lado normal, exceto por leve espessamento, o que sugere um mecanismo de reparação predominantemente intrínseco. / Most cases of congenital clubfoot treated by the Ponseti technique require percutaneous Achilles tenotomy in order to correct the residual equinus. Clinical evidences suggest that complete healing occurs between the cut tendon stumps, but there have not yet been any detailed studies investigating this reparative process. This study was performed to assess the Achilles tendon repair after percutaneous sectioning to correct the residual equinus of clubfoot treated by the Ponseti method. A prospective study analyzed 37 tenotomies in 26 patients with clubfoot treated by the Ponseti technique, with a minimum follow-up of one year after the section. The tenotomy was performed percutaneously with a large-bore needle bevel with patient sedation and local anesthesia. Ultrasonographic scanning was performed after section to ascertain that the tenotomy had been completed and to measure the stump separation. In the follow-up period, the reparative process was followed ultrasonographically at three weeks, six months and one year post-tenotomy. The ultrasonography performed immediately after the procedure showed that in some cases, residual strands between the tendon ends persisted, and these were completely sectioned under ultrasound control. A mean retraction of 5.65 mm ± 2.26 (range, 2.3 to 11.0 mm) between tendon stumps after section was observed. Unusual bleeding occurred in one case and was controlled by digital pressure, with no interference with the final treatment. After three weeks, ultrasonography showed tendon repair with the tendon gap filled with irregular hypoechoic tissue, and also with transmission of muscle motion to the heel. Six months after tenotomy, there was structural filling with a fibrillar aspect, mild or moderate hypoechogenicity, and tendon scar thickening when compared to a normal tendon. One year after tenotomy, ultrasound showed a fibrillar structure and the echogenicity at the repair site that was similar to a normal tendon, but with persistent mild tendon scarring thickness. It was observed that there was a fast reparative process after Achilles tendon percutaneous sectioning that reestablished continuity between stumps. The reparative tissue evolved to tendon tissue with a normal ultrasonographic appearance except for mild thickening, suggesting a predominantly intrinsic repair mechanism
28

Development of a novel balance assessment tool to study postural instability and fall risk

Paliwal, Monica 01 May 2015 (has links)
Balance disorders and falls are prevalent among multiple pathologies that affect the musculoskeletal or sensorineural systems. Annually, fall-related injuries put excessive economic burden on society and yet, current clinical balance assessment tools based on functional tests are inaccurate and have limited association with fall risk. Therefore, there is a growing need of an accurate balance and fall risk assessment tool for clinical use. The primary purpose of this research was to develop an accurate Center of Pressure (COP) based balance assessment tool to study postural instability and fall risk. Chapter 1 aimed at development of the COP based tool using cost effective equipment- a Wii Balance Board (WBB) and testing its accuracy and errors. The result of this study indicated that the WBB tool is reliable in assessing balance and the linearity and hysteresis errors in WBB tool are higher than force plates but it compares well in terms of cost, portability and availability. Chapter 2 aimed at assessing the relation between the radiographic parameters of balance, COP metrics, and health related quality of life in adults with spinal deformities. The results of this investigation revealed that just like radiographic parameters, COP metrics could help explain some variability in symptoms in patients with comparable extent of deformity. Chapter 3 attempted to establish a threshold value of COP metrics for binary classification of fall risk in patients with multiple sclerosis (MS). The findings of this study highlighted path length as an excellent predictor of future falls with high test accuracy, sensitivity and specificity. This dissertation concludes that the WBB tool has the potential to revolutionize balance and fall risk assessment in clinical fields such as geriatrics, rehabilitation, neurology, and orthopedics.
29

Respiratory disturbances in congenital heart disease

Davies, Hywel January 1965 (has links)
The work described in this thesis has been carried out over the period 1958-1965, having been begun during the tenure of a residency at the University of Colorado, Denver, U.S.A. At this time, surgery for the closure of septal defects was being actively carried out, and interest was aroused, in two clinical features which were apparent from close contact with this programme. The first was the nature of the chest deformities associated with septal defects; the second, the striking alleviation of symptoms which followed successful closure of these defects. The reasons for these phenomena were by no means clear and the subsequent work has been concerned with an attempt to understand them.
30

Επίδραση των διατροφικών επιπέδων βιταμίνης Α στην οστεολογική ανάπτυξη του λαβρακιού, Dicentrarchus labrax (Linnaeus, 1758)

Γλυνάτση, Νομική 23 October 2008 (has links)
Στην παρούσα εργασία μελετήθηκε η επίδραση των διατροφικών επιπέδων βιταμίνης Α στην ανάπτυξη των σκελετικών δυσπλασιών και των μεριστικών χαρακτήρων του λαβρακιού. Εφαρμόσθηκαν 7 διαφορετικά διατροφικά επίπεδα ρετινόλης (0, 5, 10, 15, 25, 35 και 70 mg ρετινόλης ανά Kg ξηράς τροφής) σε 21 νυμφικούς πληθυσμούς λαβρακιού (3 επαναλήψεις ανά διατροφική ομάδα). Η εφαρμογή των διαφορετικών συνθηκών έλαβε χώρα στο διάστημα των πρώτων 45 ημερών ανάπτυξης. Συνολικά μελετήθηκαν 1098 νύμφες και 1053 ιχθύδια. Τα αποτελέσματα έδειξαν πως οι διαφορετικές συγκεντρώσεις της βιταμίνης Α επιδρούν σημαντικά στην ανάπτυξη σκελετικών παραμορφώσεων στις νύμφες και τα ιχθύδια του λαβρακιού, καθώς επίσης και στους μεριστικούς χαρακτήρες. Οι διάφορες σκελετικές δομές δεν παρουσίασαν την ίδια ευαισθησία στη βιταμίνη Α. Σημαντικά επηρεάστηκαν δομές του κρανίου όπως οι βραγχιοστεγείς ακτίνες, το υοειδές τόξο και οι γνάθοι, καθώς και τα σκελετικά στοιχεία των πτερυγίων. Τα βέλτιστα επίπεδα των εξεταζόμενων συγκεντρώσεων βιταμίνης Α στα οποία παρατηρούνται οι μικρότερες συχνότητες εμφάνισης δυσπλασιών διαφοροποιήθηκαν σημαντικά, ανάλογα με την εξεταζόμενη ανατομική περιοχή. Εντούτοις, η συγκέντρωση 5-10 mg Kg-1 παρατηρήθηκε σε πολλές περιπτώσεις να αντιστοιχεί στο βέλτιστο. Στο εύρος αυτό της συγκέντρωσης ρετινόλης παρατηρήθηκε και η μεγιστοποίηση του ρυθμού σωματικής αύξησης των ατόμων, όπως αυτή εκτιμήθηκε από το ολικός μήκος σώματος στην ηλικία των 45 ημερών μετά την εκκόλαψη. Όσον αφορά στους μεριστικούς χαρακτήρες, αυξανομένης της συγκέντρωσης της ρετινόλης οι προ-αιματικοί σπόνδυλοι τείνουν να αυξηθούν ενώ ο αριθμός των ραχιαίων στοιχείων όπως και των δερματοτρίχιων φαίνεται να μειώνεται. Τα αποτελέσματα συζητούνται ως προς τα αποτελέσματα παρόμοιων εργασιών για άλλα είδη ψαριών, ως προς τους πιθανούς μηχανισμούς δράσης της ρετινόλης, καθώς και ως προς την υπόθεση της αλλαγής των διατροφικών προτιμήσεων του λαβρακιού κατά τη διάρκεια της οντογένεσης. / The goal of the current MSc Thesis was to examine the effect of Vitamin A both on the development of skeletal deformities and of the meristic characters in European sea bass. The experimental design involved 7 different dietary levels of retinol (0, 5, 10, 15, 25, 35, 70 mg retinol kg-1 of dry food) and included 3 repetitions. Due to the fact that both the meristic characters and the skeletal deformities develop during early developmental stages, the application of the experimental dietary levels took place during the first 45 days post hatching. In total 1098 larvae and 1053 juveniles were examined. Results demonstrated that the different dietary levels of Vitamin A significantly affected the development of skeletal deformities in both the larval and juvenile stage, as well the meristic characters. The different anatomical areas exhibited different sensitivity in Vitamin A. There was a significant effect on cephalic structures such as the branchiostegal rays, hyoid arch and the jaws and on the internal skeletal elements of the fins. The optimum levels of dietary Vitamin A where the lowest frequencies of skeletal deformities were observed differed between the different anatomical areas. However, the dietary level of 5-10 mg Kg-1 was identified as the common optimum. In this range of dietary retinol the growth rate was maximized, as it was estimated by the body fork length at the age of 45 days post hatching. As far as the meristic characters are concerned, the number of pre-haemal vertebra tended to increase whereas the number of dorsal elements and caudal dermatotrichia to decrease at elevated retinol levels. The results are discussed in respect to similar studies for other fish species, the presumable molecular mechanisms of retinol action, as well as the hypothesis of switching dietary preferences of sea bass during ontogeny.

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