Morphological manifestations of the functional activity of the menstrual corpus luteum

A histomorphological investigation of the corpus luteum has been performed in 60 women with an unchanged menstrual cycle. Physiological changes of the corpus luteum are reliably reflected in the karyometry results, in correlation between immature, mature and distrophic luteocytes, their mitotic activity and in total thickness of the parenchymatous layer. The parameters taken into account are united into a total index of the corpus luteum activity, its functional significance is proved when a parallel estimation of microelements content (zinc and copper) is performed in the corpus luteum tissues. The morphometric indices used demonstrate that the menstrual corpus luteum is mainly formed at the expense of a combined hypertrophy of granulous and theca-lutein cells and maturation of the preceding cellular forms. Regressive changes are characterized by a decreasing volume of the nuclei and distrophic changes of luteocytes, which are especially manifested at the end of the menstrual cycle.     

Fine structure of the corpus luteum of the autografted ovary in the rat

Summary The rat ovary has been transplanted successfully to subcutaneous tissue areas by several investigators. Light microscopy has revealed that corpora lutea in ovarian autografts are formed by luteinization of intact follicles and contain entrapped ova. In the present study, corpora lutea from autografted ovaries in castrate rats were obtained at metestrus and examined electron microscopically to determine whether their cellular morphology correlated with the normal progesterone levels in these animals. Cellular features usually accepted as regressive were apparent. The findings suggest either structural luteolysis is occurring before functional luteolysis or that the adrenal has increased steroidogenic activity in the castrate with ovarian autografts to account for the normal progesterone levels.Supported in part by USPHS Grant T01-DE00241-04The authors wish to thank J. Canale and Y. Tablada for technical, G. Kerimian for photographic, and M.A. Anderson for secretarial assistance     

A quantitative study of changes in the human corpus luteum microvasculature during the menstrual cycle

Endothelial cells are the most abundant cell type in the corpus luteum (CL), and changes in blood vessels have been proposed to play a pivotal role in CL regression. We have studied quantitatively the changes in the human granulosa-luteal microvasculature in CL of various ages: young (Days 17-19 of the cycle), mature (Days 20-24), old (Days 25-27), early regressing (follicular phase of the following cycle), and late regressing (luteal phase of the following cycle). Blood vessels were identified by immunohistochemical staining for the endothelial cell marker CD34. Because of the anisotropy of blood vessels, both vertical and transverse sections of the granulosa-lutein layer (GLL) were used to estimate relative (volume, surface, and length densities) and absolute (mean cross-sectional area) vascular variables. Full luteinization from young to mature CL was accompanied by a 61% increase in the mean cross-sectional area of vascular profiles and a 52% increase in the mean volume of granulosa-lutein cells, as an estimator of changes in the volume of the GLL. In old and early regressing CL, there was a progressive increase in relative structural vascular variables, due to the shrinkage of the GLL, whereas the mean cross-sectional area of capillaries showed a 53% decrease from mature to old CL. Finally, in late regressing CL, there was a decrease in most relative structural variables, in spite of the increasingly shrunken GLL. The decrease in the capillary diameter found at the late luteal phase most likely leads to a decreased blood flow, and early changes in blood vessels could initiate and/or accelerate CL regression.     

Fine structure of the corpus luteum of pregnancy in the gerbil (Meriones unguiculatus)

Summary Corpora lutea from gerbils on days 1, 4, 8, 12, 16, 20 and 24 of pregnancy were studied electron microscopically. Similarly, luteal tissue from animals on the day of parturition and one day postpartum was studied (gestation: 24 days ± 8–24h). Agranular endoplasmic reticulum increases in quantity through day 16 and thereafter is somewhat reduced. Granular endoplasmic reticulum and a population of small granules (type I) become abundant during late pregnancy and their possible role in the production and storage of relaxin is discussed. Luteal tissue undergoes a relatively rapid regression which begins on the day of parturition. Conspicuous in the regressing luteal tissue are large (type II) granules (possibly lysosomes), lipid droplets, leucocytic elements and macrophages. Functional correlates of these morphological findings are discussed.The author would like to thank Mrs. Yvis Tablada, Miss Mary Ann Anderson and Mr. Garbis Kerimian for their technical, secretarial and photographic assistance, respectively     

Effect of enucleation of the corpus luteum at different stages of the luteal phase of the human menstrual cycle on subsequent follicular development

To investigate the mechanism of suppression of follicular development during the luteal phase of the human menstrual cycle, the corpus luteum was enucleated surgically from 10 women at various times after ovulation. In the 24 h after CL enucleation there was an immediate and rapid fall in the concentration of oestradiol and progesterone and a temporary decline in the concentration of FSH and LH. Within 3 days, however, all 10 women showed evidence of renewed follicular activity as indicated by a progressive rise in the concentration of oestradiol. This rise was preceded by a rise in the concentration of FSH and LH, and ovulation, as indicated by a mid-cycle surge in LH and rise in the concentration of plasma progesterone, occurred 16-19 days after enucleation. There was no significant difference in the time to ovulation following enucleation at different times of the luteal phase. The post-operative follicular phase, measured from the time of enucleation, was 3 days longer than that observed pre-operatively from the first day of menstrual bleeding. In the follicular phase of post-operative cycles the concentration of FSH was higher and that of oestradiol lower than the corresponding values before surgery. These results indicate that the absence of healthy antral follicles in the luteal phase of the cycle is due to the inhibitory effects of the corpus luteum. The fact that, after CL enucleation, emergence of the dominant follicle was always preceded by a rise in the concentration of FSH and LH suggests that suppression of gonadotrophins by ovarian steroids secreted by the corpus luteum is responsible for the inhibition of follicular development during the luteal phase of the cycle.     

Rescue of the corpus luteum in human pregnancy

Rescue of the corpus luteum from its programmed senescence maintains progesterone production required for pregnancy. In primates, chorionic gonadotropin produced by the developing conceptus acts as the primary luteotrophic signal. The purpose of this research was to assess corpus luteum rescue by examining changes in daily urinary progesterone metabolite levels during the first week after implantation. We determined the variability in progesterone metabolite profiles and evaluated its relationship to early pregnancy loss in 120 naturally conceived human pregnancies, including 43 early pregnancy losses. In other primates, an abrupt increase in the progesterone metabolite occurs at the time of implantation. This pattern occurred in an estimated 45% of the pregnancies in the present study. In the remaining pregnancies, there was a delayed rise (18%), neither a rise or decline (22%), or a decline (15%) during the week after implantation. The estimated rate of early pregnancy loss increased across these categories (from 5% loss with an abrupt rise at implantation to 100% loss with progesterone metabolite decline). Low urinary hCG levels in early pregnancy were significant determinants of a decline in postimplantation progesterone metabolite. However, preimplantation steroid metabolite levels were not significant, suggesting no inherent problem with the corpus luteum. Examination of individual progesterone metabolite profiles in relation to hCG profiles also indicated that few losses were caused by corpus luteum failure. Delineating the functional importance of an abrupt progesterone rise at the time of implantation may provide new strategies for promoting successful implantation in assisted reproduction.     

The fine structure of the corpus luteum in Hyrax

Summary Hyrax possess luteal cells with many ultrastructural features similar to those described in other mammalian species. The process of luteinization is gradual. Cells with increasing amounts of smooth endoplasmic reticulum become predominant in the developing gland. The luteal cells of Procavia and Heterohyrax show many ultrastructural similarities. In both species the corpus luteum persists throughout pregnancy.     

Fine structure of the human ovum in the pronuclear stage

A penetrated ovum was recovered from the oviduct of a 33 year old surgical patient who had had sexual intercourse 26 hr before the operation. The ovum was in the pronuclear stage. The ooplasmic organelles were mainly represented by mitochondria, endoplasmic reticulum components, and Golgi elements. Small vesicles were found in the space between the two sheets of the pronuclear envelope. These vesicles appeared to be morphologically similar to the ER vesicles in the ooplasm and were considered to be involved in pronuclear development. Numerous annulate lamellae were seen in the ooplasm as well as in the pronuclei. Ooplasmic crystalloids were also observed. These were thought to represent cytoplasmic yolk. Remnants of the penetrating spermatozoon were found in close relation to one of the pronuclei. The fine structure of the first and second polar body is also described. The nuclear complement of the first polar body consisted of isolated chromosomes, whereas the second polar body contained a membrane-bounded nucleus. In consideration of the possibility that polar body fertilization may take place, these differences in nuclear organization could be of importance. Other recognizable differences between the two polar bodies were presence of dense cortical granules and microvilli in the first polar body, and absence of these structures in the second. These dissimilarities were considered to be related to the organization of the egg cytoplasm at the time of polar body separation.     

Fine structural localization of 3beta-hydroxysteroid dehydrogenase in rat corpus luteum

Synopsis A procedure for the ultracytochemical demonstration of 3-hydroxysteroid dehydrogenase (3-HSD) is described and the results for the localization of this enzyme in the lutein cells of the rat corpus luteum are presented.The procedure involved pre-fixation with aldehydes and incubation of small blocks. Short fixation (maximum 30 min) in 0.1% glutaraldehyde, 2% depolymerized paraformaldehyde or in 6.25% hydroxyadipaldehyde was found to be the best compromise for the preservation of both 3-HSD activity and fine structure. The method utilizes 3-hydroxy-5-androstan-17-one as substrate, tetranitro blue tetrazolium as a final electron acceptor, and phenazine methosulphate or menadione as an intermediate electron carrier to bypass the NADH₂-diaphorase. Control and inhibitor (cyano-ketone) experiments provide evidence for the specificity of the cytochemical reaction.Results showed that 3-HSD activity is localized on or in membranes of smooth endoplasmic reticulum, in outer compartments of mitochondria, and possibly within smooth endoplasmic reticulum cisternae and intracristal spaces of mitochondria.Localization of NADH₂-diaphorase activity in the same tissue was also examined. With the ferricyanide techniques, the reaction product was found to be associated mainly with the mitochondria.     

3D ultrasound imaging of the human corpus luteum

The aim of this article was to present the extent to which the state-of-the art ultrasonographic imaging can be used to visualize the features of the human corpus luteum (CL). In the late 1970s, the first ultrasonographic images of human CLs were published. The advent of transvaginal, high-resolution transducers has greatly improved the quality of imaging as did the subsequent introduction of color Doppler and 3D ultrasonography. In the present technical note, the examples of the various technical and imaging modalities used to examine the human CLs are shown. CL is a short-lived structure with a highly variable morphological appearance and the 3D ultrasonographic technique is an ideal tool to perform standardized measurements on the CL. The introduction of new imaging techniques in clinical reproductive medicine can only be successful if operators are properly trained.     

Isolation and characterization of cell subpopulations from the monkey corpus luteum of the menstrual cycle

This study was designed to test the hypothesis that the corpus luteum of primate species consists of cell subpopulations that differ in physical characteristics, function, and regulation by endocrine and paracrine factors. The corpus luteum (n = 25) was removed from rhesus monkeys at the mid-luteal phase of the menstrual cycle (Days 7-8 after the surge of luteinizing hormone, LH) and enzymatically dispersed. Freshly dispersed cells were analyzed and sorted on the basis of their forward and 90 degrees light scatter (FLS and 90LS, respectively) properties using an EPICS C flow cytometer. Freshly dispersed and sorted cells were fixed, stained histochemically for the presence of 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD), and measured to determine their diameters. Freshly dispersed (MIX) and sorted cells from corpora lutea during the early (Days 4-5 after the LH surge; n = 4) and mid-luteal phases of the cycle were incubated in vitro and steroid production was assessed. The size distribution of dispersed cells revealed four peaks that corresponded to small (10-15 microns in diameter) 3 beta-HSD-negative, and small, medium (16-20 microns), and large (greater than 20 microns) 3 beta-HSD-positive cells. Analysis of dispersed cells for FLS and 90LS demonstrated two continua (C alpha and C beta). C alpha contained single cells and cell clusters; 99.7 +/- 0.3% (n = 3) of the cells were less than or equal to 15 microns in diameter and 96.7 +/- 0.3% were 3 beta-HSD-negative. C alpha cells produced low levels of progesterone (0.2 +/- 0.1 ng/ml per 5 x 10(4) cells; n = 3) in vitro under basal conditions. C beta consisted of single cells from 10 microns to 40 microns in diameter and contained the lipid-filled and 3 beta-HSD-positive cells. Two regions (R1 and R3) of C beta were defined and their cells separated. In R1, 96 +/- 2% (n = 3) of the cells had diameters of less than or equal to 15 microns, whereas 82 +/- 4% (n = 3) of those in R3 were greater than or equal to 20 microns. Basal progesterone production by R3 cells from early luteal phase of the cycle was 12 times greater than that by R1 cells (n = 3 per group).(ABSTRACT TRUNCATED AT 400 WORDS)     

Localization of relaxin in human gestational corpus luteum

Summary Corpora lutea from 12 pregnant women were prepared for immunohistochemical localization of relaxin using a highly specific antiserum. A positive response is given by luteal cells that are diffusely distributed throughout the corpus luteum. These cells do not form a distinctive group in any particular area. A negative response is seen in the adjacent ovarian tissue, and also in nongestational corpora lutea in an early luteal phase.