Transport of estrogen-induced oxytocin receptors in the ventromedial hypothalamus.

The modulation of oxytocin (OT) receptors (OTRs) by estrogen was investigated in the ventromedial hypothalamus by in vitro receptor autoradiography. Treatment of ovariectomized and adrenalectomized rats with various doses of estradiol benzoate (EB) increased OTR binding not only in the ventromedial nuclei of the hypothalamus (VMN), but also in the area lateral to the nuclei (IVMN). After a single injection of EB, OTRs first were induced within the ventrolateral parts of the VMN, and only hours later they appeared in the IVMN. This is consistent with the interpretation that OTRs are first induced within the estrogen-sensitive neurons of the ventrolateral VMN and then are transported laterally out of the nuclei. Two additional experiments confirmed this interpretation. First, local infusion of a low dose (10 micrograms) of the neuronal transport inhibitor vinblastine blocked the appearance of OTRs in the IVMN but did not prevent the induction of OTRs by EB within the nuclei. Second, a knife cut placed lateral to the VMN prevented the spread of OTRs out of the nuclei. However, even after treatment with a high dose of EB (2 x 10 micrograms), progesterone (P) was required for a maximal extension of the area covered by OTRs. Thus, the OTR is an estrogen-induced neurotransmitter receptor that is transported to its site of action, the lateral ventromedial hypothalamus, where it is modulated by P and where estrogen-induced OT immunoreactivity is found.     

Objective morphological assessment of macular hole surgery by scanning laser tomography

AIM—To assess the morphological change in retinal topography using a scanning laser tomographer following macular hole surgery. To compare the results of scanning laser tomography with clinical evaluation and visual function assessment.
METHODS—The sample for this pilot study comprised four eyes exhibiting different stages of macular hole formation preoperatively. Subjects were assessed preoperatively and at 1 and 3 months postoperatively. Each assessment included visual acuity, letter contrast sensitivity, clinical examination (including automated static perimetry), and scanning laser tomography. The Heidelberg retina tomograph (HRT) was used to acquire digitised scanning laser tomography images of the macula (10° and 20° fields). Surgery essentially comprised vitrectomy, peeling of the posterior hyaloid face, if still attached, and intraocular gas tamponade. The magnitude and significance of topographic change were determined postoperatively using the HRT topographic difference facility.
RESULTS—Topographic difference analysis of the right and left eyes of case 1 showed a significant reduction in the height of the retina postoperatively. Topographic difference analysis of case 2 showed no significant change in topography. Topographic difference analysis of case 3 showed a significant increase in the height of the retina postoperatively. Scanning laser tomography agreed with clinical assessment based upon fundus biomicroscopy in three of the four eyes studied; the postoperative closure of the stage 2 macular hole (as noted by clinical assessment) proved to be too small to reach statistical significance. Scanning laser tomography agreed with the assessment of visual function in two eyes; the agreement between scanning laser tomography and visual function depends, in part, on the stage of development of the macular hole.
CONCLUSION—Scanning laser tomography provides an objective evaluation of the outcome of macular hole surgery. Studies employing larger sample sizes are required to fully determine the clinical worth of the technique.

     

Estrogen synthesis by osteoblast cell lines.

Estrogens play a central role in modulating bone turnover and in the postmenopausal female are formed almost exclusively by peripheral conversion of sex steroid precursors derived from the adrenals. In this study we have demonstrated that three human osteoblastic cell lines [HOS, U20S (HTB96) and MG63] possess the enzymes necessary for estrogen synthesis and metabolism. Aromatase, estradiol 17 beta-hydroxysteroid dehydrogenase (reductive and oxidative) and estrone sulfatase activities were measured in whole cell monolayers over a 20 h period by isotopic assay techniques. Significant aromatase activity was detected in all three cell lines ranging from 1.8 +/- 0.2 fmol/20 h/10(6) cells (mean +/- S.D., n = 3) for MG63 cells to 51 +/- 1.5 fmol/20 h/10(6) cells for HOS cells. The specific aromatase inhibitor, 4-hydroxyandrostenedione (1 mumol/L) completely inhibited aromatase activity in these cells. Two of the cell lines, HOS and MG63, had significant estradiol 17 beta-hydroxysteroid dehydrogenase activity with oxidative (32.7 +/- 1.9 and 1068.4 +/- 40.2 fmol/20 h/10(6) cells respectively) predominant over reductive activity (1.6 +/- 0.4 and 38.7 +/- 1.8 fmol/20 h/10(6) cells). All three cell lines were able to hydrolyse estrone sulfate to estrone with activities ranging from 13.3 +/- 1.5 fmol/20 h/10(6) cells for U20S cells to 482.2 +/- 3.7 fmol/20 h/10(6) cells for MG63 cells. Since estrogen has been implicated as a critical factor in the modulation of bone resorption and formation, the regulation of skeletal estrogen production, particularly at the time of the menopause, is likely to be an important mechanism by which bone volume is determined in physiological and pathological states.