Recent studies have demonstrated the omnipresence of antibacterial agents in the aquatic environment due to high usage and widespread applications of these compounds in medicine and agriculture, raising concerns over proliferation of antibiotic-resistant bacteria and other adverse health effects. Tetracyclines (TCs) are among the most widely used antibiotics and their fate and transformation in the soil-water environment are not yet well understood. Based on TCs' strong tendency to interact with metals, their environmental fate and transport are expected to be greatly influenced by metal species commonly present in waters and soils and thus the focus of this study. The study results show that TCs are highly susceptible to oxidative transformation mediated by dissolved Mn(II) and Cu(II) ions and manganese dioxide under environmentally relevant conditions. The oxidative transformation can occur via different TC structural moieties and reaction pathways when different metal species are involved, leading to complicated product formation patterns. It was also found that Al oxide surfaces can promote the acid-catalyzed isomeration and dehydration of TCs. To better evaluate the surface reactions of Mn oxide with TCs and other compounds, a new kinetic model was successfully developed to describe the complex reaction kinetics based on the experimental results with TCs and three other classes of antibacterial agents. Overall, this work significantly advances the fundamental understanding of the reaction mechanisms of TC compounds and provides the knowledge basis for better risk assessment of these compounds in the environment.

Listeria monocytogenes is a foodborne pathogen with a high mortality rate in susceptible populations and is of great public health concern with regard to food safety. The ability to grow at refrigeration temperatures during storage and at low pH levels during food processing has enabled the species to establish and sustain growth on processed food. Some food products particularly at risk of contamination by L. monocytogenes are deli or processed meat products, seafood, processed vegetables, dairy products and other food that do not require heating or reheating before consumption. The aims of this study are therefore to investigate firstly the prevalence rates of the species in high risk food products and a food processing plant in Brisbane. Secondly, to determine whether food isolates are better than environmental isolates at surviving the stress factors in food processing environments, or if their lineage groupings are a better indicator of their survival. Thirdly, to compare the survival of food and environmental isolates under temperature stress in co-cultures. A survey of more than 100 high-risk food products at supermarkets was carried out to investigate the prevalence of L. monocytogenes and other Listeria species in food. Isolates were also obtained from a food processing plant during routine tests. This study has found a low prevalence rate (under 10%) of L. monocytogenes in the processed vegetables and meat products tested. Other products tested included processed and raw seafood and processed fresh fruit. More L. monocytogenes isolates were isolated from the food processing plant (101) than from the food survey (25). Listeria grayi (73 isolates), a non-pathogenic species, was more frequently isolated from the food survey. The characterisation of those isolates has revealed their lineage groupings and REP-PCR profiles, which did not appear to be related to their sources. A selected group of 25 isolates were also serotyped for further identification. A larger number of lineage II isolates (70) were found compared to lineage I isolates (25), and were more common in food than the environments; while some (7) produced inconclusive results in the lineage PCR. The REP-PCR did not separate isolates of different sources, lineages or serotypes. In order to investigate the survival fitness of L. monocytogenes isolates whilst under environmental stress relevant to food safety, ten isolates from the food survey and food processing plant were chosen. Five isolates each from lineages I and II were subjected to temperatures ranging from 4ºC to 30ºC and pH levels from 4.0 to 6.0 for two weeks continuously, with their growth monitored by either optical density or plate counts. It was found that the isolates were most susceptible at the combination of pH 4.0 and 4ºC, where the growth of the isolates was completely inhibited. Again no relationship was observed between the lineage or the sources and the survival fitness of the chosen isolates. Due to the frequency of L. monocytogenes being co-isolated with other Listeria species as well as other food-borne pathogens, the relative competitive fitness of four of the isolates from the survival fitness experiment were compared in co-cultures at 4ºC and 30ºC at pH 7.4 in a small-scale preliminary study. The four isolates from food and environments were grown in broth cultures in pairs with the plate counts performed on antibiotic-supplemented selective TSA agar. The isolates were distinguished on agar supplemented with tetracycline which the isolates had acquired resistance to for this purpose. No significant difference (P>0.05) was observed between the lineages or the sources and the competitive fitness of the isolates in this study. The isolates always produced slightly more colonies in the antibioticresistant form compared to the wildtype form but did not seem to relate to the competitive fitness of the isolates. It would seemed that within the scope of this study, neither the lineage, serotype nor source of the isolates indicated any isolate with a better ability of survival while at low temperatures and low pH levels in pure and mixed cultures. However, other classifying groups such as serotypes, RAPD profiles may reveal possible co-relations, as well as a wider isolate pool. Furthermore, different stress factors could be included as part of an investigation on the survival of L. monocytogenes, as this study focused on food safety during processing.

Listeria monocytogenes is a foodborne pathogen with a high mortality rate in susceptible populations and is of great public health concern with regard to food safety. The ability to grow at refrigeration temperatures during storage and at low pH levels during food processing has enabled the species to establish and sustain growth on processed food. Some food products particularly at risk of contamination by L. monocytogenes are deli or processed meat products, seafood, processed vegetables, dairy products and other food that do not require heating or reheating before consumption. The aims of this study are therefore to investigate firstly the prevalence rates of the species in high risk food products and a food processing plant in Brisbane. Secondly, to determine whether food isolates are better than environmental isolates at surviving the stress factors in food processing environments, or if their lineage groupings are a better indicator of their survival. Thirdly, to compare the survival of food and environmental isolates under temperature stress in co-cultures. A survey of more than 100 high-risk food products at supermarkets was carried out to investigate the prevalence of L. monocytogenes and other Listeria species in food. Isolates were also obtained from a food processing plant during routine tests. This study has found a low prevalence rate (under 10%) of L. monocytogenes in the processed vegetables and meat products tested. Other products tested included processed and raw seafood and processed fresh fruit. More L. monocytogenes isolates were isolated from the food processing plant (101) than from the food survey (25). Listeria grayi (73 isolates), a non-pathogenic species, was more frequently isolated from the food survey. The characterisation of those isolates has revealed their lineage groupings and REP-PCR profiles, which did not appear to be related to their sources. A selected group of 25 isolates were also serotyped for further identification. A larger number of lineage II isolates (70) were found compared to lineage I isolates (25), and were more common in food than the environments; while some (7) produced inconclusive results in the lineage PCR. The REP-PCR did not separate isolates of different sources, lineages or serotypes. In order to investigate the survival fitness of L. monocytogenes isolates whilst under environmental stress relevant to food safety, ten isolates from the food survey and food processing plant were chosen. Five isolates each from lineages I and II were subjected to temperatures ranging from 4ºC to 30ºC and pH levels from 4.0 to 6.0 for two weeks continuously, with their growth monitored by either optical density or plate counts. It was found that the isolates were most susceptible at the combination of pH 4.0 and 4ºC, where the growth of the isolates was completely inhibited. Again no relationship was observed between the lineage or the sources and the survival fitness of the chosen isolates. Due to the frequency of L. monocytogenes being co-isolated with other Listeria species as well as other food-borne pathogens, the relative competitive fitness of four of the isolates from the survival fitness experiment were compared in co-cultures at 4ºC and 30ºC at pH 7.4 in a small-scale preliminary study. The four isolates from food and environments were grown in broth cultures in pairs with the plate counts performed on antibiotic-supplemented selective TSA agar. The isolates were distinguished on agar supplemented with tetracycline which the isolates had acquired resistance to for this purpose. No significant difference (P>0.05) was observed between the lineages or the sources and the competitive fitness of the isolates in this study. The isolates always produced slightly more colonies in the antibioticresistant form compared to the wildtype form but did not seem to relate to the competitive fitness of the isolates. It would seemed that within the scope of this study, neither the lineage, serotype nor source of the isolates indicated any isolate with a better ability of survival while at low temperatures and low pH levels in pure and mixed cultures. However, other classifying groups such as serotypes, RAPD profiles may reveal possible co-relations, as well as a wider isolate pool. Furthermore, different stress factors could be included as part of an investigation on the survival of L. monocytogenes, as this study focused on food safety during processing.

Listeria monocytogenes is a foodborne pathogen with a high mortality rate in susceptible populations and is of great public health concern with regard to food safety. The ability to grow at refrigeration temperatures during storage and at low pH levels during food processing has enabled the species to establish and sustain growth on processed food. Some food products particularly at risk of contamination by L. monocytogenes are deli or processed meat products, seafood, processed vegetables, dairy products and other food that do not require heating or reheating before consumption. The aims of this study are therefore to investigate firstly the prevalence rates of the species in high risk food products and a food processing plant in Brisbane. Secondly, to determine whether food isolates are better than environmental isolates at surviving the stress factors in food processing environments, or if their lineage groupings are a better indicator of their survival. Thirdly, to compare the survival of food and environmental isolates under temperature stress in co-cultures. A survey of more than 100 high-risk food products at supermarkets was carried out to investigate the prevalence of L. monocytogenes and other Listeria species in food. Isolates were also obtained from a food processing plant during routine tests. This study has found a low prevalence rate (under 10%) of L. monocytogenes in the processed vegetables and meat products tested. Other products tested included processed and raw seafood and processed fresh fruit. More L. monocytogenes isolates were isolated from the food processing plant (101) than from the food survey (25). Listeria grayi (73 isolates), a non-pathogenic species, was more frequently isolated from the food survey. The characterisation of those isolates has revealed their lineage groupings and REP-PCR profiles, which did not appear to be related to their sources. A selected group of 25 isolates were also serotyped for further identification. A larger number of lineage II isolates (70) were found compared to lineage I isolates (25), and were more common in food than the environments; while some (7) produced inconclusive results in the lineage PCR. The REP-PCR did not separate isolates of different sources, lineages or serotypes. In order to investigate the survival fitness of L. monocytogenes isolates whilst under environmental stress relevant to food safety, ten isolates from the food survey and food processing plant were chosen. Five isolates each from lineages I and II were subjected to temperatures ranging from 4ºC to 30ºC and pH levels from 4.0 to 6.0 for two weeks continuously, with their growth monitored by either optical density or plate counts. It was found that the isolates were most susceptible at the combination of pH 4.0 and 4ºC, where the growth of the isolates was completely inhibited. Again no relationship was observed between the lineage or the sources and the survival fitness of the chosen isolates. Due to the frequency of L. monocytogenes being co-isolated with other Listeria species as well as other food-borne pathogens, the relative competitive fitness of four of the isolates from the survival fitness experiment were compared in co-cultures at 4ºC and 30ºC at pH 7.4 in a small-scale preliminary study. The four isolates from food and environments were grown in broth cultures in pairs with the plate counts performed on antibiotic-supplemented selective TSA agar. The isolates were distinguished on agar supplemented with tetracycline which the isolates had acquired resistance to for this purpose. No significant difference (P>0.05) was observed between the lineages or the sources and the competitive fitness of the isolates in this study. The isolates always produced slightly more colonies in the antibioticresistant form compared to the wildtype form but did not seem to relate to the competitive fitness of the isolates. It would seemed that within the scope of this study, neither the lineage, serotype nor source of the isolates indicated any isolate with a better ability of survival while at low temperatures and low pH levels in pure and mixed cultures. However, other classifying groups such as serotypes, RAPD profiles may reveal possible co-relations, as well as a wider isolate pool. Furthermore, different stress factors could be included as part of an investigation on the survival of L. monocytogenes, as this study focused on food safety during processing.

Thesis (Ph. D.)--University of Washington, 1999. / Vita. Includes bibliographical references (leaves 112-144).

The objective of the field of Synthetic Biology is to implement novel functionalities in a biological context or redesign existing biological systems. To achieve this, it employs tried and tested engineering principles, such as standardisation and the design-build-test cycle. A crucial part of this process is the convergence of modelling and experiment. The aim of this thesis is to improve the design principles employed by Synthetic Biology in the context of Gene Regulatory Networks (GRNs). Small Ribonucleic Acids (sRNAs), in particular, are focussed on as a mechanism for post-transcriptional expression regulation, as they present great potential as a tool to be harnessed in GRNs. Modelling sRNA regulation and its interaction with its associated chaperone Host-Factor of Bacteriophage Qβ (Hfq) is investigated. Inclusion of Hfq is found to be necessary in stochastic models, but not in deterministic models. Secondly, feedback is core to the thesis, as it presents a means to scale-up designed systems. A linear design framework for GRNs is then presented, focussing on Transcription Factor (TF) interactions. Such frameworks are powerful as they facilitate the design of feedback. The framework supplies a block diagram methodology for visualisation and analysis of the designed circuit. In this context, phase lead and lag controllers, well-known in the context of Control Engineering, are presented as genetic motifs. A design example, employing the genetic phase lag controller, is then presented, demonstrating how the developed framework can be used to design a genetic circuit. The framework is then extended to include sRNA regulation. Four GRNs, demonstrating the simplest forms of genetic feedback, are then modelled and implemented. The feedback occurs at three different levels: autoregulation, through an sRNA and through another TF. The models of these GRNs are inspired by the implemented biological topologies, focussing on steady state behaviour and various setups. Both deterministic and stochastic models are studied. Dynamic responses of the circuits are also briefly compared. Data is presented, showing good qualitative agreement between models and experiment. Both culture level data and cell population data is presented. The latter of these is particularly useful as the moments of the distributions can be calculated and compared to results from stochastic simulation. The fit of a deterministic model to data is attempted, which results in a suggested extension of the model. The conclusion summarises the thesis, stating that modelling and experiment are in good qualitative agreement. The required next step is to be able to predict behaviour quantitatively.

This master thesis is focused on the role of horizontal gene transfer in disseminating tetracycline resistance among bacteria in farm soils. In the experimental part, plasmids carrying antibiotic resistance, were exogenously isolated in biparental matings with cattle manure and Escherichia coli K-12 CV601 gfp recipients.

Due to the growing problem of water scarcity, as well as the need to preserve the environment, studies have been conducted aiming at the reuse of agroindustrial waste so that biofuels can be produced to promote the reuse of wastewater in crop irrigation as well as used in the removal of emerging micropollutants in wastewater. The bioadsorption arouses great interest in the research of new materials that can be used as adsorbents, because it presents a promising, efficient, economically viable and ecologically sustainable proposal when compared to other decontamination methods. In this context, the present study was based on the production of a biochar from the orange bagasse at 550oC to compose a tertiary treatment in the tetracycline retention as well as the use of the effluent in the irrigation of the radish culture. Samples of in natura orange pomace, biochar and activated commercial charcoal were characterized. The samples were characterized by thermogravimetry, surface area and porosity measurements, scanning electron microscopy and X-ray diffraction. Irrigation with the filtered effluent with activated charcoal and biocarbon did not influence representatively the agronomic variables of the culture, the physical- chemical properties of water and effluents were met by the aforementioned resolution and / or work on the subject. He observed the risk of salinization and sodification of the soil by the practice. The Langmuir model was the one that best adapted to the biochar, configuring adsorption of physical nature, beneficial to the desorption process. The kinetic model that fitted the most was the pseudo-second order and the estimated equilibrium time for the biochar was eight minutes. The spectrophotometric method was safe, economical and feasible in all the analyzes used. The biocarbon had a capacity of 100% tetracycline adsorption in domestic wastewater and the efficiency of the filtration with biochar was on average 25% higher than with the commercial coal. In view of the above, the possibility of converting a waste from the low-value agro-industry and without appropriate destination to a value-added product, orange marc bagasse, to be used as a tertiary treatment for reuse of effluent in irrigation and as adsorbent for the removal of tetracycline in domestic wastewater. / Devido ao crescente problema de escassez de água, bem como pela necessidade da preservação do meio ambiente, estudos têm sido conduzidos visando o reaproveitamento de resíduos da agroindústria para que possam ser produzidos biocarvões para a promoção do reuso de águas residuárias na irrigação de culturas, bem como utilizados na remoção de micropoluentes emergentes em águas residuárias. A bioadsorção desperta elevado interesse em relação à pesquisa de novos materiais que possam ser utilizados como adsorventes, por apresentar uma proposta promissora, eficiente, economicamente viável e ecologicamente sustentável quando comparado aos demais métodos de descontaminação. Neste contexto, o estudo do presente trabalho se baseou na produção de um biocarvão a partir do bagaço da laranja a 550oC para compor um tratamento terciário na retenção da tetraciclina bem como a utilização do efluente na irrigação da cultura do rabanete. Foram caracterizadas amostras do bagaço de laranja in natura, o biocarvão e o carvão comercial ativado. As amostras foram caracterizadas por termogravimetria, medidas de área superficial e porosidade, microscopia eletrônica de varredura e difração de raios X. A irrigação com o efluente filtrado com o biocarvão e carvão comercial ativado não influenciaram representativamente nas variáveis agronômicas da cultura, nas análises físico-químicas da água e efluentes foram atendidos pela referida Resolução e/ou trabalhos sobre a temática. Observou o risco de salinização e sodificação do solo pela prática. O modelo de Langmuir foi o que melhor se adaptou ao biocarvão, configurando adsorção de natureza física, benéficas para a processo de dessorção. O modelo cinético que mais se ajustou foi o de pseudo-segunda ordem e o tempo de equilíbrio estimado para o biocarvão foi de oito minutos. O método espectofotométrico apresentou-se seguro, econômico e viável em todas as análises utilizadas. O biocarvão teve capacidade de adsorção da tetraciclina de 100% em águas residuárias domésticas e a eficiência da filtração com biocarvão foi em média 25% maior do que com o carvão comercial. Diante do exposto conclui-se a possibilidade de conversão de um resíduo da agroindústria de baixo valor e sem destinação apropriada, a um produto de valor agregado, o biocarvão do bagaço da laranja, a ser utilizado como tratamento terciário para o reuso de efluentes na irrigação de culturas e como adsorvente para remoção da tetraciclina em águas residuárias domésticas. / São Cristóvão, SE

Submitted by Edineia Teixeira (edineia.teixeira@unioeste.br) on 2017-09-01T19:28:20Z No. of bitstreams: 2 NATHALIE_KESSLER2017.pdf: 1449397 bytes, checksum: c331e85586f45bd807a7022916c9e272 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2017-09-01T19:28:20Z (GMT). No. of bitstreams: 2 NATHALIE_KESSLER2017.pdf: 1449397 bytes, checksum: c331e85586f45bd807a7022916c9e272 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2017-02-08 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Antibiotics are added to animals’ diet to increase zootechnical development rates in livestock production. Thus, tetracycline class drugs are the most frequently used ones, mainly in swine breeding. It is known that these compounds are not completely digested by the animals’ metabolism, consequently, they take part of wastewater, and eventually, they can reach the soil and change all the dynamics of microorganisms. Thus, this trial aimed at evaluating the effect of tetracycline associated with swine wastewater on enzymatic activity of soil regarding biogeochemical cycle of nutrients under two applications, in different seasons. The experiment was carried out in soil-containing pots, which received, once in summertime, and again in the autumn, doses of swine wastewater (0.2 and 0.3 L) with or without tetracycline doses (35 μg L-1), chlortetracycline (40.9 μg L-1) and doxycycline (14.9 μg L-1). Soil samples were collected at 2, 4, 8, 15, 30, 45 and 75 days after each application of the treatments in order to determine dehydrogenase, β-glucosidase, acid phosphatase and urease enzymes activity. It was observed an increase in the activity of all the studied enzymes when submitted to swine wastewater. And, a decrease of their activity when in antibiotics presence, applied in both experimental periods. There was also a decrease in nutrients bioavailability in soil, which reduces soil quality and fertility / Antibióticos são adicionados à dieta dos animais com objetivo de aumentar os índices de desenvolvimento zootécnico na produção pecuária. Desses, os medicamentos da classe das tetraciclinas são os mais frequentemente utilizados, principalmente na suinocultura. Sabe-se que estes compostos não são completamente digeridos pelo metabolismo dos animais, vindo a compor as águas residuárias e, eventualmente, chegam aos solos e alteram toda dinâmica dos microrganismos. Nesse sentido, o presente trabalho teve como objetivo avaliar o efeito das tetraciclinas associadas à agua residuária de suinocultura sobre a atividade enzimática do solo, relacionada ao ciclo biogeoquímico dos nutrientes sob duas aplicações, em diferentes estações do ano. O experimento foi conduzido em vasos contendo solo, os quais receberam, uma vez no verão e novamente no outono, doses de água residuária da suinocultura (0,2 e 0,3 L), combinadas ou não, com doses de tetraciclina (35 μg L-1), clortetraciclina (40,9 μg L-1) e doxiciclina (14,9 μg L-1). Amostras de solo foram coletadas aos 2, 4, 8, 15, 30, 45 e 75 dias, após cada aplicação dos tratamentos, para determinação da atividade das enzimas desidrogenase, β-glicosidase, fosfatase ácida e urease. Foi verificado aumento da atividade de todas as enzimas na presença de água residuária da suinocultura, e redução da atividade na presença dos antibióticos aplicados em ambos os períodos experimentais. Também foi observada redução na biodisponibilidade de nutrientes no solo, o que reduz a qualidade e fertilidade do solo.

A remodelação óssea pode ser estimulada por forças mecânicas presentes nas atividades físicas normais. Mas, a diminuição dos estímulos mecânicos, observada em vôos espaciais (exposição dos astronautas ao ambiente de microgravidade), nas imobilizações ortopédicas e na permanência prolongada de pacientes no leito, pode causar danos significativos na estrutura óssea. Neste caso, aumenta o risco de fraturas, não durante o período de sub-carregamento, mas no retorno às atividades físicas normais. A contra medida mais estudada para evitar danos ou promover a recuperação da estrutura óssea, é o exercício físico. Portanto, um dos objetivos desta pesquisa surgiu do interesse em analisar mecanicamente e microscopicamente fêmures de ratos submetidos à hipocinesia e posterior treinamento em esteira. Outro objetivo surgiu da necessidade de desenvolver metodologias mais precisas de análises mecânicas em ossos longos de ratos. Foram utilizadas 66 ratas da raça Wistar. Os animais foram criados até a idade de 90 dias, para o início dos procedimentos experimentais. Eles foram divididos em cinco grupos, sendo dois controles e três experimentais. Os animais do grupo Cont I foram criados até completarem 118 dias de idade e serviu de controle para o grupo S (suspenso), que consistiu em suspender os animais pela cauda por 28 dias. Já no grupo Cont II os animais foram criados até 139 dias e foi o controle para os grupos S-L (suspenso e liberado) e S-T (suspenso e treinado). No grupo S-L os animais foram liberados por 21 dias, após o período de suspensão pela cauda. No grupo S-T os animais passaram por um protocolo de treinamento em esteira por 21 dias após a suspensão pela cauda. Foram analisadas algumas propriedades mecânicas do terço proximal do fêmur esquerdo e da diáfise do fêmur direito. Outra análise realizada foi a microscópica, por meio de fluorescência óssea da região do terço proximal do fêmur direito e da região da diáfise do fêmur esquerdo. A suspensão pela cauda provocou diminuição das propriedades mecânicas do terço proximal do fêmur dos animais, apesar de não apresentar diferença visível na análise microscópica. A liberação após a suspensão causou alterações no núcleo de ossificação, na esfericidade da cabeça e na placa de crescimento do terço proximal do fêmur, sem alterar o comportamento mecânico desta região. E o treinamento conservou o núcleo de ossificação e a esfericidade da cabeça após a suspensão, e também, não alterou o comportamento mecânico. A ossificação periosteal na diáfise do fêmur dos animais suspensos diminuiu, no grupo S-L foi mais acentuada no endósteo e, no grupo S-T o treinamento promoveu a recuperação do balanço osteogênico. A liberação promoveu a recuperação parcial do comportamento mecânico do osso cortical da diáfise do fêmur do rato e, o treinamento recuperou as propriedades e estimulou a formação de osso novo. / Bone remodeling can be stimulated by the mechanical solicitation from normal physical activities. Consequently, decreasing of mechanical stimuli as occurring during spatial flights, prolonged bed rest and orthopedic immobilization may cause significant weakening of the bone structure. In such cases there is an increased risk of fractures when the normal physical activities are resumed. Physical exercises are a way to try to strengthen the bone structure. Therefore, in the present research we investigated the mechanical behavior and microscopy analysis of long bones from rats that were previously maintained in tail suspension and later, submitted to physical exercise in a treadmill. An additional aim came up from the necessity to develop more precise technologies that mechanical testing in long bones of rats. Sixty-six Wistar rats were used. Firstly, the animals were raised until the age of ninety days and the divided into five groups (two controls and three experimental). The animals allocated to control I were killed at 118 days of age. In the groups S, the animals were tail suspended during 28 days. In the control group II the animals were killed at 139 days of age. In group S-R (suspended and released) the rats were keep free for 21 days after the tail suspension. In group S-T (suspended and trained) after the tail suspension period the rats were trained in treadmill during 21 days. The mechanical properties of the whole proximal third of the femur were analyzed in flexion-compression on one side and from the opposite side femur bone samples were harnested for three-point bending tests. Furthermore, the osteogeneses in different groups were studied at the mid-diaphysis of the femur and at the proximal femoral epiphysis with oxitetracycline. The suspension caused a decrease of the mechanical properties of the proximal femur. Resuming free activities in cage after the suspension period caused flattening of the femoral head and earlier closure of the growth plate, but no difference of the mechanical behavior was detected. Conversely, the treadmill training caused no alteration in the femoral head shape, but the mechanical properties did not change. The fluorescence studies showed that there was a decrease of the osteogenic activity at the subperiosteal level in suspended animals, but for suspended-released rats the diminished activity occurred at the endosteal level. The treadmill training caused recovering of the osteogenic balance. The post-suspension released in cage promoted partial recovery of the mechanical properties of the diaphyseal bone and the treadmill training besides recovering the normal mechanical properties did stimulate the new-bone formation.