The work described in the preceding chapters was undertaken to determine whether the tadpole of Xenopus laevis is a suitable test-animal for measuring TSH in biological fluids. It was intended that the assay should be applicable on a routine basis for use in investigation of thyroid disorders and the findings were assessed accordingly. Studies using a histometric technique demonstrated that this method reaches the required standards of sensitivity and reliability when large test-groups are employed; accordingly, it has been used to estimate the concentration of TSH in serum. The limiting factor, where clinical application of the method is concerned, was found to be the time and labour involved in completing the estimation. An attempt was made to overcome this difficulty by application of a projection technique whereby the time required to make cell-height measurements was reduced and the method made more objective. Although, from the point of view of technical simplicity, the histometric method does not complete with either of the radiometric techniques described, it has a lower limit of sensitivity of 0.1 imu/ml. of TSH and has yielded meaningful results in assays on serum. It may be concluded, therefore, that the histometric method can be employed in this type of work provided that the time required to complete an estimation is not of major importance. The factors influencing thyroidal iodine accumulation were investigated with the aim of developing an assay method based on estimation of -uptake by the glands. A considerable individual variability in iodine uptake was demonstrated in both Xenopus larvae, reared under artificial conditions, and in larvae of the common toad, collected from their natural surroundings. Although neither diet nor temperature was found to influence this variability greatly, pretreatment with a dilute solution of potassium iodide was found to be effective to a united extent. In animals pretreated with potassium iodide it was possible to demonstrate an increase in 131I-uptake in response to administration of TSH at a concentration of 10 imu/ml. Administration of TSH was also shown to have an effect on discharge of as demonstrated by increase in the radioactivity released into the water in which the animals are immersed. This method of measuring thyroid stimulation is indirect and probably less accurate than direct determination of the activity present in the glands. It is further complicated by the presence of comparatively large amounts of iodine retained in the extrathyroidal tissues. Improvement in the sensitivity of the radiometric techniques is entirely dependent on control of individual variability in iodine uptake. In their present form, however, both the 131I-uptake method and the 131I-discharge method are suitable for application where the concentration of is 10 imu/ml. or more, and where very little material is available. Such a situation arises in comparative work on vertebrate endocrinology where small quantities of pituitary material are available in which the expected concentration of TSH would be high as compared with that in serum samples.

Various potential nutrient deficiencies associated with the vegan diet have been thoroughly investigated, but limited research has been undertaken to assess the iodine intake of vegans. Moreover, such research may be considered unreliable. Therefore, the aims of the current work were to firstly ascertain the main sources of iodine in the vegan diet, both dietary and pharmacological, and their frequency of consumption. Secondly, it was intended, by way of a prospective cross-sectional study, to determine the iodine intake of vegans consuming their habitual diet, and their iodine status. The current sources of iodine in the vegan diet and the frequency of consumption were assessed in 378 replies to a questionnaire advertised in 'The Vegan' - the official magazine of the Vegan Society. The main sources of iodine were identified as seaweed and seaweed products, iodised salt and iodine supplements. Over 1 in 4 of the volunteers were not consuming any of these sources and 54% were consuming only one source. Conversely, 19% were consuming at least two of the three identified sources. The preliminary findings suggested that vegans may be at risk of both iodine deficiency and toxicity and that iodine consumption was largely dependent on the iodine content of the food, the portion size and the frequency of consumption. Thirty 'healthy' vegans were recruited to the prospective study. Duplicate portions and 24 hour urine specimens were collected concurrently over four consecutive days and the iodine intake and status determined by chemical analysis. Dietary intake was also recorded and iodine intakes were determined by Comp-Eat, a computerised nutritional analysis program, to assess the reliability of this dietary survey technique. The iodine intake of the majority of the subjects was below the RNI and even below the LRNI. Moreover, the iodine status of the majority of the group investigated was low. Conversely iodine intakes of those who consumed seaweed approached levels which may be considered toxic. These findings indicate that iodine intakes may be low, however it is uncertain as to whether or not the body is able to adapt to such intakes. Furthermore, the potential effect on thyroid function of possibly toxic, but infrequent, intakes of the trace element is unclear. Finally, the study exposed a need for the availability of reliable information on iodine for vegans.

No description available.

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Orientador: Sergio de Toledo / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Odontologia de Piracicaba / Made available in DSpace on 2018-08-14T07:05:31Z (GMT). No. of bitstreams: 1 Feitosa_DanieladaSilva_D.pdf: 1363613 bytes, checksum: b80d15e19efde386402b0bd9f3d1ac8f (MD5) Previous issue date: 2009 / Resumo: Os hormônios tireoidianos desempenham um papel crítico no metabolismo ósseo. Entretanto, dados relacionados ao efeito das alterações nos níveis destes hormônios na densidade mineral óssea mandibular e na progressão da doença periodontal são limitados. O objetivo do presente estudo foi avaliar, em ratos, a influência de diferentes níveis séricos dos hormônios tireoidianos: (1) na densidade radiográfica e na proporção dos componentes cortical e medular na mandíbula em comparação com a tíbia; e (2) na taxa de perda óssea resultante da periodontite induzida e na qualidade do osso alveolar, bem como no número de células com capacidade de reabsorção em sítios inflamados e não-inflamados por meio de análise histológica. Trinta e seis ratos Wistar machos foram aleatoriamente designados para os seguintes grupos: G1 (n=12) - controle saudável; G2 (n=12) - hipotireoidismo (1 g propiltiouracil / 1 l água); G3 (n=12) - hipertireoidismo (800 µg T4 e 180 µg T3 / 1 l água). Três meses após o início da indução das disfunções tireoidianas, as alterações nos níveis séricos de T3 e T4 total foram confirmadas por radioimunoensaio. Para indução da periodontite, as ligaduras foram posicionadas em um dos primeiros molares inferiores e, após 30 dias, os animais foram sacrificados. Radiografias digitais de uma hemimandíbula e uma tíbia por animal foram realizadas imediatamente e, em seguida, as hemimandíbulas foram processadas rotineiramente para obtenção de cortes descalcificados seriados. Os parâmetros radiográficos acessados foram: densidade da tíbia e da mandíbula e a proporção dos componentes cortical e medular destes ossos. Adicionalmente, os parâmetros histológicos avaliados foram: perda óssea induzida pela periodontite, densidade do osso alveolar e número de células positivas para fosfatase ácida tartarato resistente (TRAP), um marcador fenotípico de reabsorção óssea. A análise dos dados radiográficos demonstrou que a densidade óssea (p<0,05) e a proporção de osso cortical (p<0,01) foram influenciados na tíbia quando condições hormonais distintas foram comparadas, com diminuição significativa nos parâmetros para o hipotireoidismo. Entretanto, na mandíbula não houve diferenças significativas entre os grupos para ambos parâmetros (p>0,05). Com relação aos dados histológicos, nos sítios com ligadura, o hipotireoidismo aumentou significativamente a perda óssea induzida pela periodontite (p<0,05) e o número de células TRAP-positivas na superfície linear da crista óssea (p=0,01). Não foram detectadas diferenças significantes entre os grupos na densidade óssea alveolar (p>0,05). Portanto, dentro dos limites do presente estudo, pode-se concluir que o osso mandibular parece ser menos sensível que a tíbia a mudanças radiográficas induzidas por alterações nos hormônios tireoidianos. Além disso, hipotireoidismo parece aumentar a perda óssea relacionada à periodontite experimental, em função do aumento no número de células com capacidade de reabsorção óssea. / Abstract: Thyroid hormones play a critical role on bone metabolism. However, data regarding the effect of thyroid hormones alterations on mandibular bone density and on the progression of periodontal disease are limited. The aim of the present study was to evaluate, in rats, the influence of different serum levels of thyroid hormones on: (1) the bone mineral density and the proportion of cortical and cancellous components in mandibles compared to tibia by radiographic evaluation; and (2) the rate of periodontal bone loss resulting from ligature placement and on the quality of tooth-supporting alveolar bone, as well as on the number of resorbing cells on inflamed and non-inflamed sites by histologic analysis. Thirty-six male Wistar rats were randomly assigned to the following groups: G1 (n=12) - healthy (control); G2 (n=12) - hypothyroidism (1 g propylthiouracil / 1 l drinking water); G3 (n=12) - hyperthyroidism (800 µg T4 and 180 µg T3 / 1 l drinking water). Three months after the beggining of the induction of thyroid dysfunctions, total serum levels of T3 and T4 alterations were confirmed by radioimmunoassay. For periodontitis induction, ligatures were randomly placed around one of the first mandibular molars and, thirty days later, the animals were sacrificed. Digital radiographs were immediately taken from one tibiae and one hemimandible of each animal and, subsequently, the hemimandibles were routinely processed for serial decalcified sections. The radiographic parameters assessed were tibiae and mandibular bone density and the proportion of cortical and cancellous components in both bone types were assessed. In addition, the histologic parameter analyzed were periodontitis-related bone loss, quality of tooth-supporting alveolar bone, and the number of tartrate-resistant acid phosphatase (TRAP)-positive cells. Radiographic data analyses demonstrated that bone density (p<0.05) and the proportion of cortical bone (p<0.01) were influenced in the tibiae when distinct hormonal conditions were compared, with a significant decrease in the parameters for hypothyroidism. However, in the mandibles, there were no significant differences among the groups neither for bone density nor for the proportion of cortical/cancellous components (p>0.05). Regarding histologic data, in the ligated sites, hypothyroidism significantly increased the bone loss resulting from ligatureinduced periodontitis (p<0.05) and the number of TRAP-positive cells on the linear surface of bone crest (p<0.05). In addition, no significant differences were detected regarding the alveolar bone density (p>0.05). Therefore, within the limits of the present study it may be concluded that bone density and the proportion of cortical/cancellous bone in the mandibles seem to be less sensitive than tibia to the hormones' changes. Moreover, decreased serum levels of thyroid hormones may enhance periodontitis-related bone loss, as a function of an increased number of resorbing cells. / Doutorado / Periodontia / Mestre em Clínica Odontológica

Temperature resistance was measured in goldfish which had been maintained under controlled photoperiods during different seasons over a twelve month period. A consistently higher heat resistance was found in fish which had been kept under the longer photoperiod. The cold resistance of short-day fish was greater than that of long-day fish in the fall and winter, but in the spring and summer the relationship seemed to be reversed. Thyroid uptake of radioiodine was determined in fish which had been subjected to the same photoperiod treatment. Short-day fish showed a consistently higher uptake of I¹³¹ , although the differences were not statistically significant. Photoperiodically adapted fish treated with thyroxine or TSH showed increased resistance to cold. Thiouracil caused the reverse effect, but thiourea caused increased resistance in the long-day group. Tissue cholesterol analyses were carried out on fish treated with thyroid materials. Gonad weight/body weight relationships were compared in fish maintained under the two photoperiods to determine possible correlations between the state of sexual maturity and thermal resistance. / Science, Faculty of / Zoology, Department of / Graduate

Changes in serum protein-bound iodine (PBI) levels were estimated in pregnant and non-pregnant mature ewes during the months from August to March. The PBI levels in ewes appeared to be elevated by low temperature (P < 0.001) and depressed by high temperature. The estrous cycle affected the PBI levels in ewes. The peak of PBI level was within 48 hours of estrus period. Breed differences played an important part on PBI levels; the Dorset breed generally had a higher PBI level than the Suffolk crossbred animal. The PBI levels in pregnant ewes became significantly higher (P < 0.05) than in the control after the third week of pregnancy. This increase in PBI level was followed by a significant increase (P < 0.05) in body weight gain at the seventh week of pregnancy. Toward the end of pregnancy (last seven weeks) the ewes with twin lambs had a significantly higher PBI level than the ewes with single lambs. The higher PBI levels remain elevated after parturition until the end of the lactation period. The PBI levels of lambs implanted with 3 and 6 mg diethystilbestroi (DES) were determined. Female lambs had a higher PBI level than mature ewes. Ten days after DES implantation, a significant (P < 0.001) increase in PBI levels was observed. This was followed by an increase in body weight gain over the control of 35% and 37% for 3 and 6 mg DES implants respectively during the remaining part of the experiment. There was a difference in the response to DES treatment between sexes. The wethers grew faster than the female lambs; this difference in growth rate can be reduced by treating the ewes with a larger dose of DES. Iodinated casein (protamone trade name, 1% thyroid activity) fed at 0, 0.25, 0.5 and 1 gm and also in combination with 1.75 mg DES were fed daily to growing lambs. The results showed that Protamone feeding to lambs as well as in combination with DES, caused a significant increase in PBI levels over the controls (P < 0.001). Blood glucose measurements showed a parallel with PBI in fluctuation. The blood sugar levels of lambs were found to be higher than those of mature ewes. DES and Protamone feeding caused an increase rate of gain over the control (DES 13.2 lb; 0.25 gm Protamone 8.7 lb)and improved feed efficiency (DES 1:3.4; Protamone 1:3.9 and control 1:5.6). / Land and Food Systems, Faculty of / Graduate