Cortical modulation of spindle afferent discharge patterns in the pyramidal cat.
Explore the source record for details and available documents.
Action Potentials↗
Biomedical subjects
R W Piwonka
Publications and source records attributed to R W Piwonka.
Amiodarone and thyroid function.
Amiodarone blocks the action of thyroid hormone by the inhibition of 5'-deiodinase which reduces production of T3 in peripheral tissues and possibly by blocking nuclear binding of T3. Since the drug inhibits peripheral conversion of T4 to T3, many patients taking amiodarone have abnormal thyroid function studies (increased T4 and rT3; decreased T3) despite being euthyroid. Treatment of patients with amiodarone generates an iodine excess, which contributes greatly to the significant incidence of altered thyroid status in this population. The diagnosis of hyperthyroidism and hypothyroidism can be difficult. However, using the overall clinical picture and the tolerance limits of hormone levels determined for patients remaining euthyroid on amiodarone therapy, the accurate diagnosis of clinically significant thyroid dysfunction can almost always be made. To screen for thyroid disease, thyroid function should be assessed before initiating therapy, semiannually during therapy or whenever clinical features of thyroid dysfunction occur. Subclinical hypothyroidism as denoted by modest increases in TSH levels do not require treatment or the discontinuation of amiodarone therapy. An appreciation of the mechanism of the interaction between amiodarone and thyroid hormone metabolism allows the clinician to recognize thyroid dysfunction at an early stage and initiate appropriate therapy, thereby minimizing the morbidity associated with forms of amiodarone toxicity.
Amiodarone↗
Intrathecal tolerance of metrizamide in chloralose anesthetized cats.
The water soluble radiopaque medium, metrizamide (Amipaque) was introduced into the lumbar subarachnoid space in chloralose anesthetized cats at a standard volume of 0.35 cc/kg in concentrations of 300 mgI/cc to 500 mgI/cc during EMG recording. These animals did not differ from controls which received cerebrospinal fluid under otherwise identical conditions; both groups usually showed some mild and occasional muscle fasciculations or mild spasms. Treatment with metrizamide appeared to be a less deleterious procedure than that using hyperosmotic sucrose (1.32 M) as judged from EMG records. In contrast, equivalent amounts of neglumine iothalamate produced frank convulsions in 7 of 15 cases and a range of hyperirritability in the remaining 8.
Anesthesia↗