Biomedical subjects
Publications and source records attributed to R P Spears.
Benign ectopic thyroid tissue is a rare entity. The etiology is related to the embryological development and maturation of the thyroid gland. It is important to consider metastatic thyroid carcinoma when ectopic thyroid tissue is identified. We present two cases of nonmalignant ectopic thyroid tissue.
Heart rate, mean arterial pressure, and vascular conductance response to intravenous nitroprusside were compared in conscious, unrestrained portal vein-stenosed and sham-operated rats chronically instrumented for pulsed Doppler flowmetry. Ten to twelve days after portal vein stenosis, portal venous pressures were elevated and resting heart rates were greater. Portal vein-stenosed animals' depressor responses to nitroprusside were similar to those of sham-operated animals, despite a 41% reduction in their tachycardic response to arterial hypotension. Skeletal muscle vascular bed reflex responses to nitroprusside-induced hypotension were significantly attenuated in the portal vein-stenosed group, whereas their renal artery and superior mesenteric artery responses resembled that of the sham-operated group. After ganglionic blockade, tachycardic responses to hypotension were abolished, but portal vein-stenosed rats' heart rates remained greater than sham-operated rats. Comparisons of arterial pressure changes, renal artery, abdominal aorta, and superior mesenteric artery vascular conductance changes after ganglionic blockade revealed no differences in neurogenic vascular tone between groups. Ganglionic blockade enhanced nitroprusside depressor responses and increased vascular conductance responses to nitroprusside in both treatment groups while abolishing the between group difference in the skeletal muscle baroreflex response. These findings indicate that chronic prehepatic portal vein stenosis with portal venous hypertension results in reduced reflex tachycardic and skeletal muscle baroreflex responses to nitroprusside-induced hypotension.
Heart rate, mean arterial pressure (MAP), and vascular conductance responses to graded phenylephrine (PE) infusions were compared in conscious, unrestrained portal vein-stenosed (PS), and sham-operated (SO) rats chronically instrumented for pulsed Doppler flowmetry. Ten days after stenosis, MAP was lower in PS than in SO, and PS heart rates were higher. Pressor sensitivity to PE was attenuated 70%, and bradycardic responses to increases in MAP were 47% greater in PS. Abdominal aorta vascular bed conductance sensitivity was reduced 84%, and renal artery sensitivity was reduced 29% in PS compared with SO, whereas the superior mesenteric artery conductance response was unaffected by portal vein stenosis. After ganglionic blockade, the heart rate of PS remained greater than that of SO, and comparisons of renal artery, abdominal aorta, and superior mesenteric artery vascular conductances revealed no significant differences in neurogenic vascular tone. Differences between PS and SO pressor responses were abolished by ganglionic blockade, as were differences in vascular bed conductance responses. These findings suggest that a greater bradycardic response and greater baroreflex-mediated withdrawal of sympathetic tone from skeletal muscle and renal vascular beds were responsible for the decreased pressor sensitivity observed in PS animals.