Are receptor-associated nuclear proteins associated with the earliest effects of steroid hormones?

Dark field electron microscopy has been used for the study of the structure of individual macromolecules with a resolution to at least the 5Å level. The use of this technique has been extended to the investigation of structure of interacting molecules, particularly the interaction between DNA and fish protamine, a class of basic nuclear proteins of molecular weight 4,000 daltons.Protamine, which is synthesized during spermatogenesis, binds to chromatin, displaces the somatic histones and wraps up the DNA to fit into the small volume of the sperm head. It has been proposed that protamine, existing as an extended polypeptide, winds around the minor groove of the DNA double helix, with protamine's positively-charged arginines lining up with the negatively-charged phosphates of DNA. However, viewing protamine as an extended protein is inconsistent with the results obtained in our laboratory.

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Ultrastructural Cytopiasmic Changes of Adrenal Cortex During Pregnancy

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100063408 ◽

1969 ◽

Vol 27 ◽

pp. 298-299

Author(s):

T. M. Murad ◽

Karen Israel ◽

Jack C. Geer

Keyword(s):

Adrenal Gland ◽

Steroid Hormones ◽

Adrenal Cortex ◽

Lipid Droplets ◽

Plasma Cholesterol ◽

Adrenal Steroids ◽

Dynamic Changes ◽

Cortical Cells ◽

Acetyl Coenzyme A ◽

Adrenal Cortical Cells

Adrenal steroids are normally synthesized from acetyl coenzyme A via cholesterol. Cholesterol is also shown to enter the adrenal gland and to be localized in the lipid droplets of the adrenal cortical cells. Both pregnenolone and progesterone act as intermediates in the conversion of cholesterol into steroid hormones. During pregnancy an increased level of plasma cholesterol is known to be associated with an increase of the adrenal corticoid and progesterone. The present study is designed to demonstrate whether the adrenal cortical cells show any dynamic changes during pregnancy.

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Smooth endoplasmic reticulum in perfusion and immersion-fixed Leydig cells

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100157954 ◽

1990 ◽

Vol 48 (3) ◽

pp. 82-83

Author(s):

R.T.F. Bernard ◽

R.H.M. Cross

Keyword(s):

Endoplasmic Reticulum ◽

Electron Microscope ◽

Steroid Hormones ◽

Transmission Electron Microscope ◽

Leydig Cells ◽

Smooth Endoplasmic Reticulum ◽

Random Mixture ◽

Transmission Electron

Smooth endoplasmic reticulum (SER) is involved in the biosynthesis of steroid hormones, and changes in the organisation and abundance of this organelle are regularly used as indicators of changes in the level of steroidogenesis. SER is typically arranged as a meshwork of anastomosing tubules which, with the transmission electron microscope, appear as a random mixture of cross, oblique and longitudinal sections. Less commonly the SER appears as swollen vesicles and it is generally suggested that this is an artefact caused during immersion fixation or during immersion of poorly-perfused tissue.During a previous study of the Leydig cells of a seasonally reproducing bat, in which tissue was fixed by immersion, we noted that tubular SER and vesicular SER often occured in adjacent cells and sometimes in the same cell, and that the abundance of the two types of SER changed seasonally. We came to doubt the widelyheld dogma that vesicular SER was an artefact of immersion fixation and set out to test the hypothesis that the method of fixation does not modify the ultrastructure of the SER.

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