Studies on the site of action of vasopressin in inducing adrenocorticotropin secretion.

Hypophysectomized rats bearing three transplanted pituitaries under the kidney capsule responded to synthetic lysine vasopressin or pitressin with a significant elevation of plasma corticosterone, whereas hypophysectomized rats with no grafts did not. This response was completely abolished by pretreatment of animals with dexamethasone but was unaltered by central hypothalamic destruction. Corticotropin-releasing factor content of the hypothalamic median eminence, hypophyseal stal-, or pars nervosa of the posterior pituitary of intact rats was unchanged 5 or 10 min after ip injection of vasopressin compared to the basal level. We conclude that vasopressin and dexamethasone act directly on the adenohypophysis in vivo to exert their stimulatory or inhibitory effect on ACTH secretion.

Evidence that the pars intermedia and pars nervosa of the pituitary do not secrete functionally significant quantities of ACTH.

We have compared the capacity to secrete ACTH in response to stress or adrenalectomy in control rats and in those with total hypophysectomy (H), adenohypophysectomy (AH) with preservation of the intermediate and the neural lobes, neurohypophysectomy (NH) with removal of the pars nervosa and all or part of the pars intermedia with preservation of the adenohypophysis, or incomplete adenohypophysectomy (IAH) in which a portion of the adenohypophysis and all of the pars intermedia and pars nervosa were left intact. Plasma ACTH measured with an N-terminal antibody that reacts on an equimolar basis with ACTH and alpha-MSH but not with other known pituitary hormones was elevated after ether or tourniquet stress in all except the H group. Three weeks after adrenalectomy there was an elevated basal plasma ACTH and an augmented ACTH response to stress in intact and IAH but not in AH rats. When a more specific alpha11-24 ACTH antibody was used there was a high plasma ACTH after ether stress in the IAH, NH, and intact groups but not in the AH or H groups. Adrenal weight and plasma corticosterone after tourniquet or ether stress were indistinguishable in the AH and H groups and were much higher and nearly identical in the intact, NH and IAH groups. We conclude that only the adenohypophysis secretes functionally significant amounts of ACTH. Plasma ACTH detected by the N-terminal antibody in the AH group is probably related to alpha-MSH or similar peptides and is incapable of maintaining adrenal weight or stimulating corticosterone secretion.

Distribution of corticotrophin releasing factor activity within the hypothalamic-pituitary complex of rats and cattle.

An assay system involving cultured rat adenohypophysial cells from either intact or adrenalectomized donors was used to study the distribution of corticotrophin releasing factor (CRF) activity in the hypothalamic-pituitary complex of rats and cattle. In the rat hypothalamus, CRF activity was most concentrated in the median eminence, but CRF was present in the stalk and the posterior pituitary gland in much higher concentrations than in the median eminence in both species. The dose--response slopes for the median eminence, stalk and pars nervosa of the posterior pituitary gland were parallel to each other, suggesting a qualitative similarity between the CRF activity in these tissues. Rat posterior pituitary glands may also contain another CRF component which has a much flatter dose--response curve, but is detectable in smaller quantities of posterior pituitary tissue than is the other type of CRF.

Surgical management of subluxed posterior-chamber intraocular lenses.

OBJECTIVE: To formulate a systematic approach to the surgical management of subluxed posterior-chamber intraocular lenses (IOLs). DESIGN: We reviewed the records of 31 consecutive patients who underwent anterior-segment surgery for IOL subluxation. Presumed anatomic causes of IOL subluxation were identified in 28 cases (90%). Three surgical procedures were used to correct the implant subluxation: modified McCannel sutures (19 eyes), IOL exchange (eight eyes), or IOL rotation (four eyes). RESULTS: Twenty-nine (94%) of the 31 patients obtained a postoperative visual acuity of 20/40 or better. Surgical complications included persistent vitreous in the anterior chamber (three cases), progressive capsular opacification (two cases), and anterior chamber and vitreous hemorrhage (one case). CONCLUSIONS: Our results show that, by implementing a planned surgical approach, subluxed posterior-chamber IOLs can be safely and effectively managed.

The effect of iodine deficiency on thyroid function in the infant rat.

We have studied rats born to severely iodine-deficient mothers and subsequently maintained on a low-iodine diet (LID) from birth to 41 days. They were compared with controls born to mothers fed a high-iodine diet (HID). LID babies from birth on had large goiters, high thyroid labeled MIT/DIT ratios and radioiodine uptakes, high plasma TSH and low plasma T4 in comparison to HID controls. Thyroid labeled T3/T4 ratios were low in all babies at birth but were higher in the LID than HID babies from day 5 on and were greater than 1 after day 10, approximating the T3/T4 of the mothers. Coupling efficiency, as indicated by thyroid labeled (T3 + T4)/(MIT + DIT), was relatively low for the first 4 postnatal days for both the HID and LID babies and was associated with a lower plasma T4 than at later intervals. Injection of 0.05 mug 127I- simultaneously with 131I- caused an acute increase in labeled T4 and decrease in MIT formation in LID babies of all ages, but did not affect T3 synthesis. Doses of 127I- 20 times as large had no effect on labeled iodoamino acid synthesis in HID babies. Thyroid organic radioiodine content in newborn LID rats was 65% lower at 24 hr than at 4 hr after 131I injection, indicating that thyroid secretion was occurring. A few of the LID pups were "runts" approximately 60% the size of HID babies the same age. However, the overwhelming majority of LID babies maintained the same weight as HID controls from birth until weaning. After weaning, the LID babies grew at a slower rate than the HID controls. Relative thyroid weight, radioiodine metabolism and plasma TSH were no different in runts of various ages or in their mothers than in the "normal" LID controls. Adaptation was apparently adequate in the LID babies to maintain a nearly euthyroid state. We suggest that the low labeled T3/T4 ratio in the first few days of life in the LID babies may be due to a coupling deficiency in newborn rats resulting in a proportionately greater formation of iodotyrosines than of iodothyronines compared to older animals. This results in a greater intrathyroidal retention of iodine during intracellular thyroglobulin proteolysis and a more highly iodinated thyroglobulin in the LID babies than after normal coupling is achieved.

Long-term follow-up of leiske closed-loop anterior chamber intraocular lenses.

PURPOSE: To provide long-term follow-up on the rates of endothelial cell loss in eyes with retained closed-loop anterior chamber intraocular lenses (IOLs). SETTING: Private practices, Chicago, Illinois, USA. METHODS: In 1980 to 1982, 3 surgeons performed 587 intracapsular cataract extractions with implantation of Leiske closed-loop anterior chamber IOLs. During the prospective part of the study from 1991 to 1996, 59 patients with 83 eligible eyes were followed using specular microscopy and pachymetry. The mean follow-up of the prospective study was 41.9 months, or 12.9 years from the original cataract surgery. RESULTS: No specific preoperative or postoperative factor except the behavior of the fellow eye (P =.022) predicted the rate of endothelial cell loss. During the prospective study, 6 patients required IOL exchange and corneal transplantation. The rate of corneal decompensation was heavily dependent on the initial measurement of endothelial cell density. Corneas with initial endothelial cell counts greater than 1000 cells/mm(2) had a decompensation rate of 1.5%, and corneas with counts of 500 cells/mm(2) or less had a decompensation rate of 57.1% (P <.01). CONCLUSIONS: Clinical examination and serial measurements of endothelial cell density provide the most reliable methods for monitoring patients with closed-loop anterior chamber IOLs. Endothelial cell counts can predict the rate of corneal decompensation. Patients with endothelial cell counts greater than 1000 cells/mm(2) usually do not require an IOL exchange.

Studies on iodine concentration in psammoma bodies in the thyroids of chronically iodine-deficient rats: effect of iodine repletion.

Thyroids of rats fed an iodine-deficient diet for several months contain small psammoma bodies within the follicular lumens which concentrate radioactive iodine. If the iodine-deficient rats are fed a high-iodine diet to produce a "colloid goiter" with reaccumulation of PAS-positive colloid around the psammoma bodies before administering radioactive iodine, the radioactivity is present in follicular cells, around the psammoma bodies and in the colloid 24 hours after radioactive iodine administration. Propylthiouracil (PTU) causes radioactivity to disappear from the cells and colloid but does not produce any appreciable discharge of radioactivity from the psammoma bodies. If radioactive iodine is given to the iodine-deficient rats before feeding a high-iodine diet, radioactivity is initially present chiefly in the cells and psammoma bodies and gradually accumulates in the PAS-positive colloid as this becomes deposited under the influence of the increased dietary iodine. If such rats are fed PTU for 4 days before the high-iodine diet is instituted, radioactivity remains limited almost entirely to the psammoma bodies and does not appear in the accumulating colloid. It is concluded that the psammoma bodies are iodinated directly, rather than forming a nidus for condensation of intrafollicular thyroglobulin after it is iodinated. Although iodine is readily bound to the psammoma bodies, it apparently is not easily removed from these structures under in vivo conditions.