pituitrin and araldite

To investigate the origin of posterior pituitary high intensity (PPHI) seen on T1-weighted magnetic resonance (MR) images.. Six rabbits, including four rabbits deprived of drinking water for 4 days and two control rabbits, were examined by MR imaging. Plasma vasopressin levels were sequentially measured by radioimmunoassay. Pituitary glands were immunostained with guinea pig anti-rabbit vasopressin antibody, and ultrathin sections of Epon/Araldite-embedded specimens were observed with a transmission electron microscope.. In control rabbits, PPHI was noted on T1-weighted MR images, and the posterior pituitary lobe was positively immunostained with anti-vasopressin antibody. At the ultrastructural level, nerve terminals contained numerous neurosecretory granules bearing vasopressin. Conversely, plasma vasopressin levels gradually increased and PPHI was absent in 4-day dehydrated rabbits. The posterior lobe was scarcely stained with anti-vasopressin antibody, and neurosecretory granules were rarely observed. However, a number of small dispersed vesicles, possibly derived from the fragmentation of neurosecretory granule envelopes, were seen in the nerve terminal.. Posterior pituitary high signal seen on T1-weighted MR images is attributed to neurosecretory granules bearing vasopressin.

Topics: Animals; Cytoplasmic Granules; Dehydration; Epoxy Resins; Image Enhancement; Immunohistochemistry; Magnetic Resonance Imaging; Male; Microscopy, Electron; Nerve Endings; Neurosecretion; Phthalic Anhydrides; Pituitary Gland, Posterior; Plastic Embedding; Rabbits; Radioimmunoassay; Vasopressins