Genetic predisposition to Hashimoto's thyroiditis is suggested by its striking aggregation in families and its occurrence in twins. The manifestations range from overt clinical and biochemical hypothyroidism to the detection of thyroid autoantibodies in healthy, symptom-free individuals and their relatives. So far as the authors are aware, the finding of Hashimoto's thyroiditis in identical triplets has not previously been reported and they therefore present the cases of Faith, Hope and Charity, 63-year-old triplet sisters.
In three experiments, the nature of the interaction between multiple memory systems in rats solving a variation of a spatial task in the water maze was investigated. Throughout training rats were able to find a submerged platform at a fixed distance and direction from an intramaze landmark by learning a landmark-goal vector. Extramaze cues were also available for standard place learning, or “cognitive mapping,” but these cues were valid only within each session, as the position of the platform moved around the pool between sessions together with the intramaze landmark. Animals could therefore learn the position of the platform by taking the consistent vector from the landmark across sessions or by rapidly encoding the new platform position on each session with reference to the extramaze cues. Excitotoxic lesions of the dorsolateral striatum impaired vector-based learning but facilitated cognitive map-based rapid place learning when the extramaze cues were relatively poor (Experiment 1) but not when they were more salient (Experiments 2 and 3). The way the lesion effects interacted with cue availability is consistent with the idea that the memory systems involved in the current navigation task are functionally cooperative yet associatively competitive in nature.
A high prevalence of postpartum thyroid dysfunction has been reported in several countries, but there have been no systematic studies of its prevalence in Britain. Among a group of 901 consecutive, unselected pregnant women thyroid autoantibodies were detected in 117 (13%) at booking. The clinical course of postpartum thyroid dysfunction, factors associated with its development, and its likely prevalence were defined in 100 of these women with thyroid antibodies and 120 women with no such antibodies who were matched for age. None of the women had a history of autoimmune thyroid disease. Normal reference ranges for thyroid function during pregnancy and post partum were established in the 120 women negative for thyroid antibodies. On the basis of these observations postpartum thyroid dysfunction was observed in 49 (22%) of the 220 women studied, and the prevalence in the total group of 901 women was estimated to be 16·7%. Thyroid dysfunction, mainly occurring in the first six months post partum, was usually transient and included both destruction induced hyperthyroidism and hypothyroidism. The development of the syndrome was significantly related to smoking more than 20 cigarettes a day and the presence of thyroid microsomal autoantibodies at booking. Of the 16 women with a family history of thyroid disease in whom thyroid microsomal autoantibody activity was detectable at booking, 11 developed thyroid dysfunction. Age, parity, presence of goitre at presentation, duration of breast feeding, and the sex and birth weight of the infant were not associated with the development of postpartum thyroid dysfunction. The mood changes experienced by women post partum may in part be associated with altered thyroid function during this time.
Despite cardiac failure being a well recognised complication ofthyrotoxicosis, systolic function has generally been reported as maintained or enhanced. In this study, left ventricular diastolic function was assessed in 16 thyrotoxic patients and 18 age-matched controls by pulsed-Doppler echocardiography. Patients were re-studied after 3 and 12 months of treatment. Prior to treatment all standard Doppler-;derived indices of diastolic function were significantly different to control (isovolumic relaxation time (IVRT) 63±18.9 vs 84.0±14.8 ms, peak early filling velocity (Emax) 79.2±15.2 vs 61.9±10.7 cm . s−1, peak atrial filling velocity (Amax) 68.2±17.9 vs42.2±9.4 cm . s−1, deceleration of early filling (E/F slope) 6.1±1.8 vs3.7±1.1 m . s−1, thyrotoxic vs control). However, these filling abnormalities appear likely to reflect the tachycardia and reduced systemic vascular resistance (SVR) found in the patients (heart rate 102±15 vs 76 ± 9, SVR 874 ± 207 vs 1293 ± 362 dynes .s−1. cm−5, both P<0.001). After 3 months of treatment haemodynamics were similar in the two groups but filling remained abnormal in patients with a pattern suggesting increased transmitral pressure gradients (Emax 73.1 ± 15.1 cm.s−1, Amax 55.8 ± 19.2cm.s−1, E/F slope 4.9 ± 2.0m . s−1, all P<0.05 compared to controls). After 12 months of treatment most parameters had returned to normal but the atrial contribution to left ventricular filling remained high (Amax54.7 ± 13.9 vs control 42.2 ± 9.4 cm . s−1 .flow velocity integral of atrial filling 4.7 ± 1.3 vs 3.6±11 control, both P0.01). Left ventricular filling is therefore highly abnormal before and during the treatment ofthyrotoxicosis. However, these changes appear unlikely to reflect an intrinsic thyrotoxic cardiomyopathy and are more likely to represent a combination of prolonged increases in left ventricular filling pressures along with abnormalities of left atrial function. The abnormal Doppler parameters emphasise the importance of sinus rhythm in maintaining left ventricular filling in thyrotoxicosis and may explain why marked haemodynamic deterioration may result from the development of atrial fibrillation in these patients.
We have investigated the role of the spleen in the humoral and cellular immune response of rats with experimental autoimmune thyroiditis (EAT) induced by immunization with thyroglobulin and Freund's complete adjuvant. Animals subjected to splenectomy within 4 days of immunization developed lower thyroglobulin antibody levels and less severe thyroiditis compared to sham operated controls. There was no impairment in the ability of the animals to recover spontaneously from the disease after splenectomy. Together with the results obtained using splenocyte infusions, this suggests that suppressor cell production within the spleen plays only a small part in the normal immunological control which is presumably responsible for spontaneous regression of the disease.
Abstract The original provocative formulation of the ‘geometric module’ hypothesis was based on a working-memory task in rats which suggested that spontaneous reorientation behavior is based solely on the environmental geometry and is impervious to featural cues. Here, we retested that claim by returning to a spontaneous navigation task with rats and domestic chicks, using a single prominent featural cue (a striped wall) within a rectangular arena. Experiments 1 and 2 tested the influence of geometry and features separately. In Experiment 1, we found that both rats and chicks used environmental geometry to compute locations in a plain rectangular arena. In Experiment 2, while chicks failed to spontaneously use a striped wall in a square arena, rats showed a modest influence of the featural cue as a local marker to the goal. The critical third experiment tested the striped wall inside the rectangular arena. We found that although chicks solely relied on geometry, rats navigated based on both environmental geometry and the featural cue. While our findings with rats are contrary to classic claims of an impervious geometric module, they are consistent with the hypothesis that navigation by boundaries and features may involve distinct underlying cognitive computations. We conclude by discussing the similarities and differences in feature-use across tasks and species.
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