The effects of 98 day foetal thyroidectomy on brain development in the sheep

McIntosh, Graeme H.; Potter, Brian J.; Hetzel, Basil S.; Hua, Chaoyang; Cragg, B.G.

doi:10.1016/0021-9975(82)90012-3

Cited by 16 publications

(14 citation statements)

References 8 publications

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“…In an elegant series of experiments it has been shown that fetal and maternal thyroidectomy in the sheep gives rise to more severe brain defects than fetal thyroidectomy alone (Mclntosh, Potter, Hetzel et al 1982;Mclntosh, Potter, Mano et al 1983). Calmodulin (CaM) and calcineurin, a CaMregulated phosphatase (CaM-Pase), are highly con¬ centrated in the brain and CaM abounds in the nerve endings of the developing brain (Cáceres, Bender, Snavely et al 1983).…”

Section: Introductionmentioning

confidence: 99%

Effect of maternal hypothyroxinaemia during fetal life on the calmodulin-regulated phosphatase activity in the brain of the adult progeny in the rat

Elvira¹,

Sinha²,

Pickard³

et al. 1989

Journal of Endocrinology

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Calmodulin-regulated phosphatase activity was measured in the brain of 2-month-old rats born from hypothyroid and normal dams, using a fluorometric enzyme assay developed for this purpose. Calmodulin content was measured in the same brain regions by radioimmunoassay. Significant differences between groups in weight and protein content, basal phosphatase and calmodulin-regulated phosphatase activity were found. The brain region most affected was the cerebellum, where basal and calmodulin-regulated phosphatase activities, and protein content were increased. The data point towards a lasting effect of maternal hypothyroxinaemia on the brain function of the progeny.

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Section: Introductionmentioning

confidence: 99%

Effect of maternal hypothyroxinaemia during fetal life on the calmodulin-regulated phosphatase activity in the brain of the adult progeny in the rat

Elvira¹,

Sinha²,

Pickard³

et al. 1989

Journal of Endocrinology

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“…The (Erenberg & Fisher, 1973;Hollingsworth et al, 1975). Thyroidectomy of the foetus and of the ewe has been performed to reproduce the effect of a lack of thyroid hormones on brain development (Hua et al, 1980;Bhakthavathsalan et al, 1981;Mcintosh et aL, 1982Mcintosh et aL, , 1983. Therefore, nutritional experiments with an ovine model could be a reliable way of studying the disturbance in thyroid status induced by an I deficiency.…”

Section: Introductionmentioning

confidence: 99%

Iodine nutrition in ewes : effects of low to high iodine intake on iodine content of biological fluids in pregnant and lactating ewes

Aumont¹,

Lamand²,

Tressol³

1989

Reprod. Nutr. Dévelop.

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Summary ― In a first experiment, 2 groups of 46 and 47 multiparous ewes received diets which provided an iodine intake of 0.36 and 0.26 mg/kg dry matter (group C) and, 2.01 and 1.94 mg/kg (group D), respectively, for pregnancy and lactation. In a second experiment, 3 groups of 10 nulliparous ewes received diets which provided an I intake of 0.13 and 0.12 mg/kg dry matter (group A), 0.22 and 0.20 mg/kg dry matter (group B), and 10.77 and 8.88 mg/kg dry matter (group E), respectively, for pregnancy and lactation. Observations and sampling were carried out on the ewes from the first third of pregnancy to the 2nd and the 6th week of lactation.The diets provided adequate nutrition for pregnant and lactating ewes. Dietary I content had no effect on the dry matter intake, the size or the weight of the litter and the length of pregnancy.Plasma inorganic iodine (Pit) was less affected by the I intake during lactation than during pregnancy. The excretion of I in milk induced a decrease in Pll between pregnancy and lactation. The I in urine expressed as I1g I/g creatinine was largely affected by the I intake. Colostrum I was 6.7, 4.0, 1.2, 1.3 and 1.5 times higher in groups A, B, C, D and E than the I in milk collected 1 week postpartum. Milk iodine (MI) content and the ratio MI/PII were markedly dependent on the I intake. During pregnancy, plasma T4 concentration decreased for each group. Plasma T4 concentration remained low during lactation in the low I intake group, whereas it increased at the same time in the other groups. The plasma T3 concentration decreased at the 6th week of lactation in the highest I intake group.Experimental values showed that 0.12 mg I/kg dry matter induced depletion in the I stocks of pregnant and lactating ewes, whereas an I intake above 10 mg I/mg dry matter disturbed the metabolism of thyroid hormones.dietary iodine -ewes ― plasma inorganic iodine -milk iodine -thyroxine

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“…The rat is an altricial species, born with a relatively undeveloped brain and with the thyroid-pituitary-hypothalamic axis not yet fully matured. Whereas there is evidence of a role for thyroid hormone in brain maturation during the intrauterine period in human (13)(14)(15) and sheep (16,17), this is not yet clearly established in the rat. Development of the ovine thyroid-pituitary axis is nearly complete at birth (10).…”

Section: A Species Specificitymentioning

confidence: 99%

“…We recently observed that injection of large doses of T 4 into pregnant rats on gestational day 15, sufficient to raise the fetal brain T 3 to adult levels for the remainder of pregnancy failed to elicit premature expression of the Pcp-2, calmodulin kinase IV, and myelin basic protein genes (151). In the sheep, thyroidectomy in utero leads to major deficiencies in morphogenesis (16,17). These findings suggest that yet-to-be defined cellular processes render the cells responsive to thyroid hormone action in the postnatal period.…”

Section: Theories and Speculationsmentioning

confidence: 99%