Στην παρούσα διδακτορική διατριβή εκθέτονται η χλωρίδα των Βαρδουσίων ορέων καθώς και τα δεδομένα που προκύπτουν από την διερεύνηση – ανάλυσή της. Στο πεδίο της βλάστησης (φυτοκοινωνιολογία), έχει επιβεβαιωθεί σχεδόν το σύνολο των προηγούμενων αναφορών και έχει συμπληρωθεί με νέα δεδομένα όσο αφορά τις φυτοκοινωνιολογικές ομαδοποιήσεις. Συγχρόνως δικαιολογήθηκε και εξηγήθηκε η ύπαρξη των φυτοκοινωνιολογικών μονάδων σε σχέση με το σύνολο των οικολογικών παραγόντων που ήταν δυνατό να ληφθούν υπόψη (μικροκλίμα, εδαφικοί παράγοντες, γεωλογικό - πετρολογικό υπόστρωμα), συμβάλλοντας έτσι στην συνοικολογική προσέγγιση του θέματος. Επίσης όπου ήταν δυνατό έγινε προσπάθεια να διερευνηθεί η δυναμική εξέλιξης των περισσότερων φυτοκοινωνιολογικών ομάδων, όπως αυτή διαμορφώνεται κάτω από την επίδραση των περιβαλλοντικών μεταβλητών. Πιο κάτω ακολουθεί μια συνοπτική περιγραφή των σημαντικότερων σημείων της διδακτορικής διατριβής, καθώς και τα συμπεράσματα που μπορούν να διατυπωθούν από τα αποτελέσματα της ερευνητικής αυτής προσπάθειας. / In the present doctoral thesis the flora of Mt. Vardousia, as well as the data that have resulted from its analysis are presented. From a vegetation (plant sociology) point of view, almost all the previous reports on the mountain have been confirmed and have been enriched with new data as far as phytosociological groups are concerned. Additionally, the existence of certain phytosociological units was justified and explained based on the ecological factors that were possible to be measured (microclimate, soil, geology, geological substrate), contributing in this way to the synecological approach of the subject. Also, where feasible, an effort was done to study the dynamics of succession of most of the phytosociological groups, as they depend on various environmental variables. A concise description of the most important points of the doctoral thesis, as well as the conclusions that can be extracted from the results of this research follow.

The thesis focuses on the qualitative analysis of a general class of SEIRS models in periodic and non-periodic environments. The classical SEIRS model, with standard incidence function, is, first of all, extended to incorporate multiple infectious stages. Using Lyapunov function theory and LaSalle's Invariance Principle, the disease-free equilibrium (DFE) of the resulting SEIⁿRS model is shown to be globally-asymptotically stable whenever the associated reproduction number is less than unity. Furthermore, this model has a unique endemic equilibrium point (EEP), which is shown (using a non-linear Lyapunov function of Goh-Volterra type) to be globally-asymptotically stable for a special case. The SEIⁿRS model is further extended to incorporate arbitrary number of latent stages. A notable feature of the resulting SE^mIⁿRS model is that it uses gamma distribution assumptions for the average waiting times in the latent (m) and infectious (n) stages. Like in the case of the SEIⁿRS model, the SE^mIⁿRS model also has a globally-asymptotically stable DFE when its associated reproduction threshold is less than unity, and it has a unique EEP (which is globally-stable for a special case) when the threshold exceeds unity. The SE^mIⁿRS model is further extended to incorporate the effect of periodicity on the disease transmission dynamics. The resulting non-autonomous SE^mIⁿRS model is shown to have a globally-stable disease-free solution when the associated reproduction ratio is less than unity. Furthermore, the non-autonomous model has at least one positive (non-trivial) periodic solution when the reproduction ratio exceeds unity. It is shown (using persistence theory) that, for the non-autonomous model, the disease will always persist in the population whenever the reproduction ratio is greater than unity. One of the main mathematical contributions of this thesis is that it shows that adding multiple latent and infectious stages, gamma distribution assumptions (for the average waiting times in these stages) and periodicity to the classical SEIRS model (with standard incidence) does not alter the main qualitative dynamics (pertaining to the persistence or elimination of the disease from the population) of the SEIRS model.

The thesis focuses on the qualitative analysis of a general class of SEIRS models in periodic and non-periodic environments. The classical SEIRS model, with standard incidence function, is, first of all, extended to incorporate multiple infectious stages. Using Lyapunov function theory and LaSalle's Invariance Principle, the disease-free equilibrium (DFE) of the resulting SEIⁿRS model is shown to be globally-asymptotically stable whenever the associated reproduction number is less than unity. Furthermore, this model has a unique endemic equilibrium point (EEP), which is shown (using a non-linear Lyapunov function of Goh-Volterra type) to be globally-asymptotically stable for a special case. The SEIⁿRS model is further extended to incorporate arbitrary number of latent stages. A notable feature of the resulting SE^mIⁿRS model is that it uses gamma distribution assumptions for the average waiting times in the latent (m) and infectious (n) stages. Like in the case of the SEIⁿRS model, the SE^mIⁿRS model also has a globally-asymptotically stable DFE when its associated reproduction threshold is less than unity, and it has a unique EEP (which is globally-stable for a special case) when the threshold exceeds unity. The SE^mIⁿRS model is further extended to incorporate the effect of periodicity on the disease transmission dynamics. The resulting non-autonomous SE^mIⁿRS model is shown to have a globally-stable disease-free solution when the associated reproduction ratio is less than unity. Furthermore, the non-autonomous model has at least one positive (non-trivial) periodic solution when the reproduction ratio exceeds unity. It is shown (using persistence theory) that, for the non-autonomous model, the disease will always persist in the population whenever the reproduction ratio is greater than unity. One of the main mathematical contributions of this thesis is that it shows that adding multiple latent and infectious stages, gamma distribution assumptions (for the average waiting times in these stages) and periodicity to the classical SEIRS model (with standard incidence) does not alter the main qualitative dynamics (pertaining to the persistence or elimination of the disease from the population) of the SEIRS model.

Introduction This thesis concerns the mosquito-borne arbovirus Ross River (RR) virus. The main objectives were to determine the vector associations, the incidence, costs and natural history of disease, and behavioural and environmental risks for infection in tropical Queensland. 1. Literature review On the basis of the literature review there is strong evidence that Aedes vigilax, Ae. camptorhynchus and Culex annulirostris are important vectors in Australia. Aedes camptorhychus does not occur in Queensland. There is evidence that two peri-domestic container-breeding mosquitoes, Ae. notoscriptus and Ae. aegypti, may be vectors of the virus. The virus has been isolated from many other species but the role of most of these is unclear. It is unclear which vertebrate species are the major reservoirs for human infection. Studies are inconsistent with regard to the prevalence, duration and severity of symptoms and debility during RR virus disease. Nearly all epidemiological studies of RR virus have been descriptive. Therefore one can only surmise what the risks for human infection might be. Epidemiological studies to determine the associations between exposures and risk for disease do not exist. 2. Virus isolation from mosquitoes During 1996-1998 61,619 mosquitoes were processed for virus isolation. Thirty-three isolates of RR virus were made. The largest number (14) were from Ae. carmenti. The minimum infection rate (MIR) per 1,000 was 2.4. Isolates were also made from Ae. imprimens (1 isolate, MIR 10.3), Ae. kochi (2, 0.2), Ae. lineatus (1, 0.2), Ae. notoscriptus (1, 1.6), Ae. vigilax (1, 0.3), Cx. annulirostris (9, 0.3), Cx. vicinus (1, 4.0) and Mansonia septempunctata (3, 5.8). Ross River virus has been isolated from Cx. annulirostris, Ae. vigilax, Ae. notoscriputus and Ae. kochi but not from the other species. Ross River virus was not isolated from Ae. aegypti. Twenty-six isolates came from in or near a colony of 15,000 spectacled flying-fox, Pteropus conspicillatus. The proportion of RR virus positive pools from within 1 km. of this colony was significantly greater than elsewhere for all species combined and for Cx. annulirostris but not for Ae. carmenti. 3. The incidence and costs of Ross River virus disease Unpublished data on National, State and Territory notifications was collected. Crude incidence rates using census figures for denominator data were calculated. The same was done for the areas in which the other studies described in the thesis were carried out. An estimate of the cost of Ross River virus disease in Australia was made. During the period 1991-1998 of the States and Territories the Northern Territory (NT) had the highest and the Australian Capital Territory (ACT) the lowest notification incidences. These were 62-281 and 0-3 per 100,000 per annum, respectively. During this period the notification incidence for Queensland ranged from 70 to 149 per 100,000 per annum. For the local government areas of Cairns and Mareeba, where the majority of cases of RR virus disease for the studies described in this thesis were recruited, the notification incidences were between 74 and 267, and 28 and 200, respectively. On the basis of an average of 4,800 cases per annum in Australia the cost of serological testing and medical consultations were estimated at $443,520 and $105,600. Lost earnings were estimated at $1,798,560. The total cost for medical consultations, serological testing and lost earnings will therefore be over $2 million in an average year. 4. The natural history of Ross River virus disease In 1998 incident cases of RR virus disease were ascertained. Fifty-seven eligible cases were recruited but only 47 could be reviewed on 3 occasions and data on these were analysed. Cases were followed for up to 197 days. Review included history, examination and the administration of the Clinical Health Assessment Questionnaire (CLINHAQ) and Short Form-36 (SF-36) . On initial review the 3 most common symptoms were arthralgia, joint stiffness and myalgia affecting 97.9, 89.4 and 59.6% of cases, respectively. The joint types most commonly affected by pain at the initial review were the ankles, wrists, interphalangeal joints of the fingers, knees and metacarpophalangeal joints. Objective signs of joint inflammation were rare. The prevalence of signs of inflammation decreased and the prevalence of normal joints on examination increased through the reviews. The prevalence of use of NSAIDs decreased through the reviews. On the basis of CLINHAQ items regarding work performance functioning at work improved through the course of the reviews. Linear regression with days since symptom onset as the independent variable was performed for some variables. The 8 dimensions of the SF-36 were standardized to the Queensland population and analyzed longitudinally . Analyses of the CLINHAQ functional disability index (FDI) and the visual analogue scales (VASs) for pain, global severity, fatigue, gastrointestinal complaints and sleep, and the depression and anxiety scales were also performed. The slopes of all fitted regressions except the SF-36 general health dimension were significantly different from zero. All measures of disease severity returned to normal by 8 months from onset, many in a shorter period. 5. Behavioural and environmental risks for infection Fifty-five incident cases of RR virus disease were recruited and formed the basis of a case-control study of behavioural and environmental risks. They were matched to 85 controls. In the year prior to symptom onset the only leisure exposure that significantly altered risk was camping [Odds ratio (OR) = 2.15; 95% confidence interval (CI) = 1.07-4.35]. No peri-domestic activities in the year prior to onset significantly altered disease risk. Leisure exposures were also assessed in a 3-week exposure period ending 4 days prior to symptom onset. None significantly altered risk. No peri-domestic activity in this period significantly altered risk and nor did exposure to vertebrates or mosquitoes. Containers and vegetation around the subject's dwelling did not significantly increase risk. The presence of ice cream containers and buckets was significantly protective when assessed by questionnaire, however this was also assessed by inspection and was found to increase risk though not significantly so. It was concluded that the former finding was due to differential misclassification of exposure status. The premise condition index (PCI) was measured. A low PCI for the subject's house was associated with a significantly increased risk (3-4 relative to 7-9 as reference category: OR = 3.15, 95% CI = 1.07-9.25). Window screening did not alter disease risk and air-conditioning in the house or the bedroom decreased risk but not significantly so. Use of protective measures, except bed nets, in the year prior to onset was found to decrease disease risk. Personal repellents, mosquito coils and citronella candles significantly decreased risk. A dose response was shown for the number of protective measures from personal repellents, aerosol and surface sprays, mosquito coils, citronella candles and mosquito "zappers" used in the year prior to symptom onset. Pet ownership and proximity of dwelling to horses did not significantly alter risk. A preference for light coloured clothing was significantly protective (0.37, 0.15-0.89). Stratification by gender, date of symptom onset and geographical area was performed. Stratification by geographical area included a coastal and tablelands stratum. There were differences between the stratum-specific odds ratios for camping in the year prior to symptom onset, the presence of bromeliads in the subject's garden and a preference for light coloured clothing. Multivariate analysis demonstrated confounding by use of personal repellents, mosquito coils and citronella candles. When modeled together these were found to cause confounding among themselves. They also caused significant confounding of camping, outdoor work and the presence of banana trees in the subject's yard. Multivariate analysis of the association between PCI and disease risk failed to demonstrate confounding by use of protective measures or time between symptom onset and review. 6. Synthesis and conclusions The three research Chapters form a coherent body of public health research on the epidemiology (Chapters 5 and 6) and ecology (Chapters 4 and 7) of RR virus, and the natural history of RR virus disease (Chapter 6) in tropical Queensland. Conclusions are drawn from the research in the thesis. A set of priorities for future public health research on RR virus is suggested, and a pilot control program for Ross River virus disease in tropical Queensland is recommended.

>Magister Scientiae - MSc / In this thesis, we investigate the HIV/AIDS epidemic in a population which experiences a significant flow of immigrants. We derive and analyse a math- ematical model that describes the dynamics of HIV infection among the im- migrant youths and intervention that can minimize or prevent the spread of the disease in the population. In particular, we are interested in the effects of public-health education and of parental care.We consider existing models of public-health education in HIV/AIDS epidemi-ology, and provide some new insights on these. In this regard we focus atten-tion on the papers [b] and [c], expanding those researches by adding sensitivity analysis and optimal control problems with their solutions.Our main emphasis will be on the effect of parental care on HIV/AIDS epidemi-ology. In this regard we introduce a new model. Firstly, we analyse the model without parental care and investigate its stability and sensitivity behaviour.We conduct both qualitative and quantitative analyses. It is observed that in the absence of infected youths, disease-free equilibrium is achievable and is asymptotically stable. Further, we use optimal control methods to determine the necessary conditions for the optimality of intervention, and for disease eradication or control. Using Pontryagin’s Maximum Principle to check the effects of screening control and parental care on the spread of HIV/AIDS, we observe that parental care is more effective than screening control. However, the most efficient control strategy is in fact a combination of parental care and screening control. The results form the central theme of this thesis, and are included in the manuscript [a] which is now being reviewed for publication. Finally, numerical simulations are performed to illustrate the analytical results.

Background: Access to safe water and sanitation are universal need and basic human right, but the provision of quality water and improved sanitation remains a challenge in many African countries including Ethiopia. Objectives: The study investigated drinking water quality, sanitation-hygiene practices and the potential of Moringa stenopetala seed powder for the purification of water in Bale Zone, Southeast Ethiopia. Methodology: A community-based cross-sectional study was conducted among 422 randomly selected households in Robe and Ginnir Towns. Data were collected by interviewer-administered structured questionnaires from June 2012 to August 2013. An observation checklist was used to observe the sanitary condition of water sources. A total of 71 water samples were collected using sterile glass bottles in accordance with the standard method of American Public Health Association APHA. The physicochemical and bacteriological water quality analyses were done in Addis Ababa Environmental protection and Oromia water and Energy laboratories. The efficiency of Moringa stenopetala seed powder for removal of turbidity, hardness, and nitrate was evaluated. Data were analyzed SPSS Version 21.0 for the window. Descriptive analysis was done for appropriate variables. Logistic regression was used to identify the factors associated with under-five diarrhea. The results were presented using adjusted odds ratio and P-value of < 0.05 was used to declare significance association. Results: From the total sample, 401 respondents participated making a response rate of 95%. More than one third (37.9%) of the respondents were found to use pipe water. Two hundred and eighty (69.8%) of households wash storage containers before refilling and 325 (81%) of households were using separate containers for water storage. Two hundred seventy (67.3%) of the households had pit latrine. Prevalence of childhood diarrhea was found to be 50.1%. From the logistic regression model, those households having access to clean water source are 68% less likely to have under-five diarrhea, the households having clean storage of drinking water are 45% less likely to have under-five diarrhea in their home, and those households having poor latrine sanitation are 68% more likely to have under-five diarrhea in their home. Seed powder of 200mg/l Moringa stenopetala reduced the Nitrate concentration doses from 5.49mg/l to 8.18mg/l, a 75mg/l was reduced the turbidity from 4.49NTU to 1.07 NTU. A total hardness of 427 was reduced by 7.8% after treatment with powder seed of Moringa stenopetala. Conclusion: Prevalence of childhood diarrhea was high and it is associated with lack of access to a clean water source, poor sanitation of drinking water storage and latrine. Prevalence of open field defecation was remarkably high. The iron content of drinking water was above the range of World Health Organization standards. Moringa stenopetala seed powder has efficiency in the reduction of total and faecal coliform, turbidity, hardness and nitrate level in drinking water Recommendation: Health education on water handling, sanitation and low-cost effective water treatment methods like Using Moringa stenopetala seed should be practiced at the household level. / Environmental Sciences / Ph. D. (Environmental Science)

Text in Afrikaans / Die tydruimtelike variasie in die fluoriedinhoud vannatuurlike drinkwater en in die voorkoms van tandfluorose, die verband tussen hierdie veranderlikes asook hulle kovariasie is op 'n hoe resolusievlak in geselekteerde endemiese gebiede ondersoek. Die drie studiegebiede verskil grootliks van mekaar wat sommige fisies- en menslik-geografiese kenmerke betref, maar ondergrondse water was oral die belangrikste bron van drinkwater. Ioonspesifieke analise en laboratoriumtegnieke is gebruik om die fluoriedinhoud van die drinkwater uit 517 bronne te bepaal. Die tande van 3 068 kinders is klinies en fotografies ondersoek. Die erkende Tooth Fluorosis Index en die indeks van Dean is gebruik om die voorkoms van fluorose te beskryf. Grafiese tegnieke, beskrywende statistieke en nieparametriese analise van variansietoetse is gebruik om die voorkoms en tydruimtelike variasiepatrone van die sleutelveranderlikes in elke studiegebied, asook die verskillende ruimtelike eenhede binne die studiegebiede, te beskryf. Die verband tussen die sleutelveranderlikes asook hul intra- en interareale kovariasie is ontleed. Daar is gevind dat die fluoriedinhoud van die ondergrondse water in die Pilanesberg- en Hammanskraal-studiegebied relatief hoog tot hoog is en die in die Vrystaat-studiegebied relatief laag. Ruimtelike veranderlikheid met groot verskille oor klein afstande kenmerk die fluoriedinhoud van ondergrondse water ongeag die gesteentes waaruit dit onttrek word. Middelwaardes bied ontoereikende beskrywings van die fluoriedgehalte van die drinkwater. Die skep van nuwe drinkwaterbronne veroorsaak langtermynvariasie in die fluoriedinhoud van die beskikbare drinkwater. Fluoroseprevalensie in die studiegebiede bet van 62% tot 87% gewissel, met meer ernstige aantasting in die Pilanesberg- en Hammanskraal-gebied as in die Suid-Vrystaat. Beduidende intra-areale ruimtelike variasie is 'n wesenlike kenmerk van die voorkoms van fluorose in al drie studiegebiede. In alle gevalle het die variasiepatroon in die fluoriedinhoud van die drinkwater die in die voorkoms van fluorose slegs gedeeltelik verklaar. Sporadiese en/of periodieke kortstondige blootstelling aan hoe fluoriedkonsentrasies lei tot emstige aantasting ten spyte van die gereelde gebruik van water met 'n laefluoriedinhoud. Ligte fluorose ontwikkel geredelik in assosiasie met <0,5 mgF-/l en matige fluorose in assossiasie met 0,5-0,7 mgF-/l, die optimum konsentrasieinterval vir fluoridasie in Suid-Afrika. / The spatiotemporal variation in the fluoride content of natural drinking water and the occurrence of dental fluorosis, the relation between these variables as well as their covariation were investigated at a high resolution level in selected endemic areas. Groundwater was the most important source of drinking water in all three study areas, but they differed markedly in respect of some physical and human geographical characteristics. Ion specific analysis and laboratory techniques were used to determine the fluoride content of the water from 517 sources. The teeth of 3 068 children were examined clinically and photographically. The fluorosis was scored according to the Tooth Fluorosis Index and Dean's classification. Graphical techniques, descriptive statistics and nonparametric analysis of variance were used to describe the occurrence and variation patterns of the key variables in the different spatial units is each study area. The relation between the variables as well as their intra and interareal covariation were analysed. The fluoride content of the groundwater in the Pilanesberg and Hammanskraal areas was relatively high to high; in the southern Free State it was relatively low. Spatial variability and significant differences over small distances typify the fluoride content of the groundwater, irrespective of the aquifer. Central statistics inadequately describe the fluoride quality of the natural drinking water. The development of new water sources causes long term variation in the fluoride content of the available drinking water. Fluorosis prevalence varied form 62% to 87%, with more severe fluorosis in Pilanesberg and Hammanskraal than in the southern Free State. Significant intra-areal spatial variation is an attribute of fluorosis in all three study areas. In all cases the variation pattern in the fluoride content of the drinking water partly explained the spatial pattern in the occurrence of fluorosis. Sporadic and/or periodic brief exposure to high fluoride concentrations leads to severe fluorosis despite regul~ usage of water with a low fluoride content. Mild fluorosis readily develops in association with <0,5 mgF-1~ and medium fluorosis in association with 0,5-0,7 mgF-/l, the optimum concentration interval for fluoridation in South Africa. / Geography / D. Phil. (Geografie)

Made available in DSpace on 2014-12-17T14:02:01Z (GMT). No. of bitstreams: 1 WallaceSN_DISSERT.pdf: 4760466 bytes, checksum: 02e9f4b160af4472ebf0590033624755 (MD5) Previous issue date: 2010-06-18 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico / The Caatinga biome is rich in endemic fish species fauna. The present study the results of fish faunal surveys conducted in the hydrographic basin of Piranhas-Assu of the Brazilian Caatinga biome. The fish samples collected were distributed in four orders (Characiformes, Perciformes, Siluriformes and Synbranchiformes), 11 families (Characidae, Curimatidae, Auchenipteridae, Anostomidae, Prochilodontidae, Erythrinidae, Cichlidae, Sciaenidae, Heptapteridae, Loricariidae, Synbranchidae) and 22 species, of which 17 are endemic and five have been introduced from other basins. The order Characiformes was the most representative in number of species (46,35% ) followed by Perciformes (35,38%), Siluriformes (17,44%) and Synbranchiformes (0,5%). The Nile tilapia, Oreochomis niloticus, the only exotic species, was most expressive in number of individuals (24.92%) followed by the native species piau preto, Leporinus piau (18,77 %). Considering the relative frequency of occurrence of the 22 species, 13 were constant, five were accessory and four were occasional. This study investigated the reproductive ecology of an endemic fish black piau, Leporinus piau from the Marechal Dutra reservoir, Acari, Rio Grande do Norte. Samplings were done on a monthly basis from January to December 2009, and a total of 211 specimens were captured. The environmental parameters such as rainfall, temperature, pH, electrical conductivity and dissolved oxygen of water were recorded. The sampled population showed a slight predominance of males (55%), however females were larger and heavier. Both sexes of L. piau showed positive allometric growth, indicating a higher increase of weight than length. The first sexual maturation of males occurred at smaller size, with 16.5 cm in total length than females (20.5 cm). During the reproductive period, the condition factor and gonadosomatic index (GSI) of L. piau were negatively correlated. This species has large oocytes with a high mean fecundity of 54.966 with synchronous oocyte development and total spawning / O bioma Caatinga ? rico em v?rias esp?cies end?micas da ictiofauna. O presente trabalho teve como objetivo verificar a diversidade da ictiofauna da bacia do Rio Piranhas-Assu, RN inserida no bioma Caatinga, alem de verificar os aspectos reprodutivos de uma esp?cie de peixe nativa, piau preto, Leporinus piau (Osteichthyes: Anostomidae). Foram realizadas amostragens mensais entre setembro de 2008 a dezembro de 2009. Foram capturados 602 peixes, distribu?dos em quatro ordens (Characiformes, Perciformes, Siluriformes e Synbranchiformes), 11 fam?lias (Characidae, Curimatidae, Auchenipteridae, Anostomidae, Prochilodontidae, Erythrinidae, Cichlidae, Sciaenidae, Heptapteridae, Loricariidae, Synbranchidae), e 22 esp?cies, sendo 17 end?micas, quatro introduzidas de outras bacias e uma ex?tica. A ordem Characiformes foi mais representativa em n?mero de esp?cies (46,35%) seguidas por Perciformes (35,38%), Siluriformes (17,44%) e Synbranchiformes (0,5%). A til?pia do Nilo, Oreochomis niloticus, a ?nica esp?cie ex?tica registrada foi mais expressiva em n?mero de indiv?duos (24,92%) seguida pela esp?cie nativa o piau-preto, Leporinus piau (18,77 %). Quando considerado a freq??ncia relativa de ocorr?ncia das 22 esp?cies, 13 foram constantes, cinco acess?rias e quatro raras. Medidas de gest?o ambiental devem ser tomadas para conserva??o das esp?cies end?micas da bacia do Rio Piranhas-Assu do bioma Caatinga. Para investigar os aspectos reprodutivos de peixe nativo piau preto, L. piau, foi capturado um total de 211 exemplares. Os par?metros ambientais, como pluviosidade, temperatura, pH, condutividade el?trica e oxig?nio dissolvido da ?gua foram registradas. A popula??o amostrada mostrou uma leve predomin?ncia de machos (55%) e as f?meas foram maiores em comprimento e mais pesadas. Ambos os sexos de L. piau apresentaram um crescimento alom?trico positivo, indicando um maior incremento de peso do que comprimento. A primeira matura??o sexual dos machos ocorreu mais em tamanho menor, com 16,5cm de comprimento total, do que as f?meas (20,5cm). Durante o per?odo reprodutivo, o fator de condi??o e ?ndice gonadossom?tico (IGS) de L. piau foram correlacionadas negativamente. A esp?cie apresenta ov?citos grandes com uma alta fecundidade (54,966 em m?dia), com desenvolvimento ovocit?rio sincr?nico e desova total

The most recent surveys in South Africa estimate that invasions are still increasing, despite substantial clearing efforts. Riparian systems in South Africa are particularly vulnerable to invasion by woody IAPs. This thesis addresses the restoration of alien‐invaded riparian systems, by investigating the factors that facilitate or constrain spontaneous recovery and influence the trajectories of succession. These factors include invasion history and management history, especially the use of fire. A seedling emergence approach was used to test the presence of a viable pre‐fire seedbank, and the effect of fire on the seed bank. The efficacy of some active restoration interventions was also tested, with the aim to return invasion‐resistant, indigenous vegetation with a structure and function representative of uninvaded sites. The findings of this study indicated the presence of a viable and persistent riparian soil seed bank, even after 30 years of intermtittent invasion as well as two fire cycles under invasion. It shows that the management practice of fell‐and‐burn resulted in high soil temperatures, and that this reduced the indigenous soil seed bank density, especially in the upper soil layer. Clear germination sequences and patterns of emergence over time for different species were observed during this study, with many species exhibiting delayed emergence relative to the timing of the fire event. It is proposed that manipulation of the season of fire could be used to selectively optimise the order of arrival and therefore superior recruitment of some species over others in the Eastern Cape fynbos, and thus alter the trajectories of recovery of vegetation towards a more desired state. Active restoration in the form of indigenous seed and plant additions resulted in a significantly higher indigenous cover after seven months, compared to a control (passive restoration) or restoring with grass. Indigenous cover and composition was also strongly influenced by lateral zonation, and some key guilds and species were missing or present in much lower densities compared to reference sites. Grass restoration significantly suppressed the regeneration of A. longifolia, as well as the regeneration of indigenous species. Biotic resistance can thus be achieved through restoration, and it could be a powerful tool in the management of IAPs, although the deliberate introduction of grass after clearing in fynbos also reduces biodiversity and could have unforeseen consequences to riparian function.

<p align="justify"><i>Note des Bibliothèques :la thèse du Dr Vanderpas a été défendue en 1991 mais il n'est techniquement pas possible d'indiquer cette date dans le logiciel Bictel/e.</i></p><p><p><p align="justify"><u>Première partie</u> :Fonction thyroïdienne de la naissance à 7 ans chez les enfants d’un essai clinique de supplémentation d’huile iodée versus placebo à la femme enceinte.</p><p><p><p align="justify">L’endémie goitreuse du Nord-Congo (République démocratique, ex-Zaïre) a fait l’objet d’un programme de santé publique de prévention du goitre et du crétinisme dans le cadre du Centre d’Etudes Médicales de l’Université Libre de Bruxelles pour les actions de coopération de 1974 à 1995. Le partenaire congolais était l’Institut de Recherche Scientifique et le Bureau National des Troubles dus à la Carence Iodée.</p><p><p><p align="justify">Le présente travail s’inscrit dans ce contexte et analyse plus particulièrement la fonction thyroïdienne chez l’enfant de zéro à sept ans, dans la continuité d’un suivi d’un essai clinique pharmacologique randomisé et contrôlé (RCT, Randomised Clinical Trial) de phase 2 consistant à administrer une huile iodée (Lipiodol®) à des femmes enceintes se présentant à la maternité de Karawa. Cette cohorte de femmes enceintes a été précédemment étudiée par le Professeur Claude-Hector Thilly*.</p><p><p><p align="justify">Chez les enfants nés de mères non supplémentées en iode, l’histoire fonction thyroïdienne se caractérise comme suit :<p><li>Une fonction thyroïdienne relativement stable au ours de la première année de vie par rapport aux valeurs de TSH et de T4 sériques du sang de cordon ;les moyennes de ces marqueurs biologiques sont clairement indicateurs d’un niveau de carence iodée par rapport aux normes d’une population d’enfants belges d’âge comparable (T4 sérique abaissée et TSH sérique élevée) ;</li><p><li>Une aggravation des altérations de la TSH et de la T4 sériques au cours de la deuxième année de vie, aggravation qui se poursuit jusqu’à la quatrième année ;</li><p><li>Un maintien de marqueurs biologiques de TSH et T4 sérique fortement altérés au moins jusqu’à l’âge de 7 ans (étendue d’âge étudiée).</li></p><p><p><p align="justify">Dans cette région, le manioc est connu pour son rôle goitrogène, au travers de son contenu en glucosides cyanogènes, et il avait été précédemment démontré que le thiocyanate élevé des mères passait librement la barrière placentaire. Au cours de la première année de vie, lorsque les nourrissons sont essentiellement alimentés au sein, le thiocyanate sérique diminue fortement et se rapproche de valeurs observées chez des enfants d’autres régions non exposés au manioc. La dégradation de la fonction thyroïdienne au cours de la deuxième année de vie coïncide avec l’introduction du manioc dans l’alimentation. Pour une valeur de concentration urinaire en iode stable au cours des 7 premières années de vie, la prévalence de goitre et les variations de T4 et TSH sériques suivent celles du thiocyanate sérique. Cela est confirmé au travers d’une analyse multi-variée qui met en évidence l’association entre les valeurs moyennes de TSH et T4 et les concentrations urinaires en iode et en thiocyanate.</p> <p><p><p align="justify">L’administration intra-musculaire d’huile iodée prévient les altérations de la fonction thyroïdienne chez la mère (Thilly 1978), et cette protection s’étend chez l’enfant jusqu’à 24 mois, c’est-à-dire jusqu’à ce que l’allaitement maternel reste le principal apport nutritionnel. Au-delà de 24 mois, des altérations de la fonction thyroïdienne apparaissent chez certains de ces enfants (Elévation de la TSH et abaissement de la T4), et au-delà de 4 ans, la fréquence des altérations de la fonction thyroïdienne est aussi fréquente chez les enfants de mères traitées que chez les enfants de mères non traitées.</p><p><p><p align="justify">Au vu de la fréquence fort élevée d’altérations de la fonction thyroïdienne entre 4 et 7 ans (2/3 ont une TSH anormalement élevée > 10 mU/L), seuls certains enfants présentent les stigmates d’une hypothyroïdie prolongée depuis le début de l’existence. Il apparaît qu’il y a lieu de distinguer des hypothyroïdies juvéniles de durée, de sévérité, et de timing différents. Si l’hypothyroïdie juvénile est aussi fréquente au-delà de 4 ans dans les deux groupes de l’étude, les stigmates cliniques d’hypothyroïdie persistante sont plus fréquemment observés chez les enfants nés de mères non supplémentées en iode que chez les autres. De plus, la sévérité des stigmates cliniques (degré d’arriération mentale ;importance du retard de développement statural) démontre que l’hypothyroïdie persistante s’est installée plus précocement chez ertains enfants nés de mères non supplémentées en iode que chez les autres. Dans les formes les plus sévères, l’évolution staturale et le niveau d’intelligence de ces enfants avec hypothyroïdie persistante sont compatibles avec le tableau clinique de crétinisme myxédémateux endémique décrits chez le sujet adulte par les Professeurs François Delange et Jacques Dumont.</p><p><p><p><p align="justify"><u>Deuxième partie</u>: étude du métabolisme iodé chez les enfants hypothyroïdiens et mise en évidence de la carence combinée en iode et en sélénium.</p> <p><p><p align="justify">Certains enfants hypothyroïdiens le sont depuis longtemps (depuis la naissance, éventuellement), d’autres le sont transitoirement, sans que leur hypothyroïdie passagère ne laisse de séquelles évidentes en termes de retard statural ou d’arriération mentale.</p><p><p><p align="justify">Ceux qui sont en hypothyroïdie persistante au-delà de 4 ans ont une fonction thyroïdienne altérée :lorsqu’on leur administre de l’iode, leur glande ne répond pas à cette correction de carence iodée, et ils demeurent profondément hypothyroïdiens. Ce phénomène de non réponse à la correction de la carence iodée n’estpas observé chez les enfants hypothyroïdiens plus jeunes :cela démontre qu’il y a, chez certains enfants, une perte progressive de la capacité fonctionnelle de la thyroïde à répondre à la supplémentation iodée. Ces sujets développent le tableau clinique de crétin myxédémateux endémique.</p><p><p><p align="justify">On constate que l’hypothyroïdie juvénile recouvre un vaste spectre depuis les cas d’hypothyroïdie transitoire jusqu’aux cas d’hypothyroïdie irréversible, même après correction de la carence iodée.</p><p><p><p align="justify">Sur base d’hypothèse physiopathologique de cette perte de capacité fonctionnelle de la thyroïde chez certains jeunes enfants, il a été proposé qu’une carence combinée en iode et en sélénium pourrait expliquer ce processus. Une telle carence combinée a été décrite dans notre travail dans la région goitreuse du Nord-Congo, et pas dans d’autres régions non goitreuses du même pays ou dans d’autres endémies goitreuses avec peu de crétinisme myxédémateux endémique (Soudan, Sénégal).</p> <p><p><p align="justify"><FONT size=1>*Thilly Claude-Hector, Delange François, Lagasse Raphael, Bourdoux Pierre, Ramioul L, Berquist Helen, Ermans André-Marie. Fetal hypothyroidism and maternal thyroid status in severe endemic goiter. Journal of Clinical Endocrinology and Metabolism.</FONT></P><p><p> / Agrégation de l'enseignement supérieur, Orientation médecine / info:eu-repo/semantics/nonPublished