The endometrial cycle: the expression of a secretory component correlated with the luteinizing hormone peak

Keratan sulfate, an electrosensory neurosentient bioresponsive cell instructive glycosaminoglycan

The roles of keratan sulfate (KS) as a proton detection glycosaminoglycan in neurosensory processes in the central and peripheral nervous systems is reviewed. The functional properties of the KS-proteoglycans aggrecan, phosphacan, podocalyxcin as components of perineuronal nets in neurosensory processes in neuronal plasticity, cognitive learning and memory are also discussed. KS-glycoconjugate neurosensory gels used in electrolocation in elasmobranch fish species and KS substituted mucin like conjugates in some tissue contexts in mammals need to be considered in sensory signalling. Parallels are drawn between KS's roles in elasmobranch fish neurosensory processes and its roles in mammalian electro mechanical transduction of acoustic liquid displacement signals in the cochlea by the tectorial membrane and stereocilia of sensory inner and outer hair cells into neural signals for sound interpretation. The sophisticated structural and functional proteins which maintain the unique high precision physical properties of stereocilia in the detection, transmittance and interpretation of acoustic signals in the hearing process are important. The maintenance of the material properties of stereocilia are essential in sound transmission processes. Specific, emerging roles for low sulfation KS in sensory bioregulation are contrasted with the properties of high charge density KS isoforms. Some speculations are made on how the molecular and electrical properties of KS may be of potential application in futuristic nanoelectronic, memristor technology in advanced ultrafast computing devices with low energy requirements in nanomachines, nanobots or molecular switches which could be potentially useful in artificial synapse development. Application of KS in such innovative areas in bioregulation are eagerly awaited.

Keratan Sulphate in the Tumour Environment

Keratan sulphate (KS) is a bioactive glycosaminoglycan (GAG) of some complexity composed of the repeat disaccharide D-galactose β1→4 glycosidically linked to N-acetyl glucosamine. During the biosynthesis of KS, a family of glycosyltransferase and sulphotransferase enzymes act sequentially and in a coordinated fashion to add D-galactose (D-Gal) then N-acetyl glucosamine (GlcNAc) to a GlcNAc acceptor residue at the reducing terminus of a nascent KS chain to effect chain elongation. D-Gal and GlcNAc can both undergo sulphation at C6 but this occurs more frequently on GlcNAc than D-Gal. Sulphation along the developing KS chain is not uniform and contains regions of variable length where no sulphation occurs, regions which are monosulphated mainly on GlcNAc and further regions of high sulphation where both of the repeat disaccharides are sulphated. Each of these respective regions in the KS chain can be of variable length leading to KS complexity in terms of chain length and charge localization along the KS chain. Like other GAGs, it is these variably sulphated regions in KS which define its interactive properties with ligands such as growth factors, morphogens and cytokines and which determine the functional properties of tissues containing KS. Further adding to KS complexity is the identification of three different linkage structures in KS to asparagine (N-linked) or to threonine or serine residues (O-linked) in proteoglycan core proteins which has allowed the categorization of KS into three types, namely KS-I (corneal KS, N-linked), KS-II (skeletal KS, O-linked) or KS-III (brain KS, O-linked). KS-I to -III are also subject to variable addition of L-fucose and sialic acid groups. Furthermore, the GlcNAc residues of some members of the mucin-like glycoprotein family can also act as acceptor molecules for the addition of D-Gal and GlcNAc residues which can also be sulphated leading to small low sulphation glycoforms of KS. These differ from the more heavily sulphated KS chains found on proteoglycans. Like other GAGs, KS has evolved molecular recognition and information transfer properties over hundreds of millions of years of vertebrate and invertebrate evolution which equips them with cell mediatory properties in normal cellular processes and in aberrant pathological situations such as in tumourogenesis. Two KS-proteoglycans in particular, podocalyxin and lumican, are cell membrane, intracellular or stromal tissue-associated components with roles in the promotion or regulation of tumour development, mucin-like KS glycoproteins may also contribute to tumourogenesis. A greater understanding of the biology of KS may allow better methodology to be developed to more effectively combat tumourogenic processes.

Keratan sulfate, a complex glycosaminoglycan with unique functional capability

From an evolutionary perspective keratan sulfate (KS) is the newest glycosaminoglycan (GAG) but the least understood. KS is a sophisticated molecule with a diverse structure, and unique functional roles continue to be uncovered for this GAG. The cornea is the richest tissue source of KS in the human body but the central and peripheral nervous systems also contain significant levels of KS and a diverse range of KS-proteoglycans with essential functional roles. KS also displays important cell regulatory properties in epithelial and mesenchymal tissues and in bone and in tumor development of diagnostic and prognostic utility. Corneal KS-I displays variable degrees of sulfation along the KS chain ranging from non-sulfated polylactosamine, mono-sulfated and disulfated disaccharide regions. Skeletal KS-II is almost completely sulfated consisting of disulfated disaccharides interrupted by occasional mono-sulfated N-acetyllactosamine residues. KS-III also contains highly sulfated KS disaccharides but differs from KS-I and KS-II through 2-O-mannose linkage to serine or threonine core protein residues on proteoglycans such as phosphacan and abakan in brain tissue. Historically, the major emphasis on the biology of KS has focused on its sulfated regions for good reason. The sulfation motifs on KS convey important molecular recognition information and direct cell behavior through a number of interactive proteins. Emerging evidence also suggest functional roles for the poly-N-acetyllactosamine regions of KS requiring further investigation. Thus further research is warranted to better understand the complexities of KS.

The human endometrium expresses the glycoprotein mucin-1 and shows positive correlation for Thomsen-Friedenreich epitope expression and galectin-1 binding

Mucin 1 (MUC1) is a glycoprotein in human endometrium and is abundant at the luminal epithelial surface in the receptive phase. It has a highly glycosylated ecto-domain that contains keratan sulfate chains, that disappears at the time of implantation. In addition, the glycoforms on MUC1 differ in fertile and infertile women. Therefore the aims of this study were investigations on glycosylation of MUC1 with the Thomsen-Friedenreich (TF) epitope on normal human endometrium throughout the menstrual cycle and binding of galectin-1 on the TF epitope in the endometrium and the expression of galectin-1 on the human oocyte. Human endometrial tissue was obtained from 54 premenopausal patients and was immunohistochemically analyzed with monoclonal antibodies against MUC1, TF epitope, galectin-1, and biotinylated galectin-1. In addition, human oocytes were analyzed for TF, galectin-1 expression, and galectin-1 binding. We identified a significant upregulation of MUC1 and TF epitope and, in addition, galectin-1 binding in glandular epithelium and epithelial apical surface tissue from proliferative to secretory phase. With double staining experiments, we identified a coexpression of TF and MUC1 in the early secretory phase and galectin-1 binding to TF during the same period of time. In addition we identified TF epitope and galectin-1 expression plus binding on the human oocyte and irregularly fertilized oocytes. Upregulation of TF epitope on the glandular epithelium and epithelial apical surface tissue in the secretory phase and binding of galectin-1 at the same time show the possibility of galectin-1-mediated trophectoderm binding to the endometrium within the window of implantation.

Differential expression of MUC genes in endometrial and cervical tissues and tumors

Background

Mucin glycoprotein's are major components of mucus and are considered an important class of tumor associated antigens. The objective of this study was to investigate the expression of human MUC genes (MUC1, MUC2, MUC5B, MUC5AC and MUC8) in human endometrium and cervix, and to compare and quantitate the expression of MUC genes in normal and cancerous tissues.

Methods

Slot blot techniques were used to study the MUC gene expression and quantitation.

Results

Of the five-mucin genes studied, MUC1, MUC5B and MUC8 showed high expression levels in the normal and cancerous endometrial and cervical tissues, MUC2 and MUC5AC showed considerably lower expression. Statistically, higher levels of MUC1, MUC5B and MUC8 were observed in endometrial adenocarcinomas compared to normal tissues. In contrast, only MUC1 levels increased with no significant changes in expression of MUC5B and MUC8 in cervical tumors over normal cervical tissues.

Conclusion

Endometrial tumors showed increased expression of MUC1, MUC5B and MUC8 over normal tissues. Only MUC1 appears to be increase, in cervical tumors. All the studied tissues showed high and consistent expression of MUC8 mRNA. Low to neglible levels of MUC2 and MUC5AC were observed in all studied endometrial and cervical tissues.

The cell biological basis of human implantation

Understanding the cellular basis of implantation and placental development depends on a combination of the limited morphological evidence in the human with data from other primates, separate studies of pre-implantation embryos and endometrium and in vitro models. There is increasing evidence of a dialogue between embryo and endometrium that begins prior to implantation and evolves rapidly through the successive epithelial and stromal/vascular phases. This includes paracrine signals passing to endometrial tissue from the embryo, and vice versa. The production and timing of these signals by endometrium, and its ability to respond to signals from the blastocyst, are dependent on steroidal sensitization. A complex cascade of cell adhesion mechanisms and local tissue remodelling are required for the establishment of a stable haemochorial interface.

Sialyl-Lewis x and Sialyl-Lewis a are associated with MUC1 in human endometrium

Endometrial epithelial cells express MUC1 with increased abundance in the secretory phase of the menstrual cycle, when embryo implantation occurs. MUC1 is associated with the apical surface of epithelial cells and is also secreted, being detectable in uterine fluid at elevated levels in the implantation phase. However, its physiological role is uncertain; it may either inhibit intercellular adhesion by steric hindrance or carry carbohydrate recognition structures capable of mediating cell-cell interaction. Here we show that endometrial epithelium expresses both Sialyl-Lewis x (SLex) and Sialyl-Lewis a (SLea), with a distribution and pattern of menstrual cycle regulation similar to that of MUC1. Using Western blotting and double determinant ELISA of uterine flushings, we demonstrate that SLex is associated with MUC1 core protein. The endometrial carcinoma cell lines HEC1A and HEC1B are shown to express MUC1 in a mosaic pattern, while three other cell lines express much lower amounts. HEC1A expresses both SLex and SLea while HEC1B expresses SLea only. Immunoprecipitation has been used to demonstrate that SLea is associated with MUC1 in HEC1B cells, and both SLex and SLea are associated with MUC1 in HEC1A cells.

MUC1 as a cell surface and secretory component of endometrial epithelium: reduced levels in recurrent miscarriage

The mucin MUC1 is a large, highly glycosylated, hormonally regulated product of endometrial glandular and luminal epithelium with both cell surface-associated and secreted isoforms. The abundance of mRNA coding for MUC1 increases about sixfold from the proliferative to the early secretory phase (Hey et al., J. Clin. Endocrinol. Metab. 78:337-342, 1994). Immunohistochemical studies show intracellular deposits accumulating in the early secretory phase followed by the release of MUC1 into gland lumens. The apical surface of luminal epithelium is strongly immunopositive in the early secretory phase. We have used a two site ELISA to measure MUC1 in uterine flushings as a function of time after the luteinising hormone (LH) peak. Low levels of secretory MUC1 are observed before day LH+7, while values on days LH+7-LH+13 are much higher. Using semi-quantitative immunohistochemical methods we have shown that in women suffering recurrent spontaneous miscarriage, mid secretory phase levels of MUC1 core protein and mucin-associated glycans are reduced (Serle et al., Fertil. Steril. 62:989-996, 1994). Similarly, lower core protein levels are observed in uterine flushings after day LH+7 in these women. Reduced epithelial secretory function and a resultant change in uterine fluid composition are features of endometrium from recurrent miscarriage patients.

Endometrial differentiation in the peri-implantation phase of women with recurrent miscarriage: a morphological and immunohistochemical study

OBJECTIVES

To study endometrial differentiation in the peri-implantation phase of women with recurrent miscarriage and to compare the results with endometrium of normal fertile women.

DESIGN

A prospective study of endometrial specimens precisely timed from the LH surge, using traditional histologic dating (Noyes' criteria), quantitative histologic measurement (morphometric analysis), and immunohistochemical techniques.

RESULTS

Fifteen of 25 (60%) subjects in the recurrent miscarriage group had retarded endometrial development in the peri-implantation period as monitored by morphometry. The recurrent miscarriage group showed reduced levels of four mucin-related secretory epitopes, and greater reductions were associated with morphological retardation. Normal differentiation was observed in all of the 14 subjects in the control group.

CONCLUSIONS

Women with idiopathic recurrent pregnancy loss may be divided into two distinct subgroups on the basis of their endometrial response in the peri-implantation period. Precisely timed endometrial biopsy should be incorporated in the investigation of recurrent miscarriage.

The endometrial cell surface and implantation. Expression of the polymorphic mucin MUC-1 and adhesion molecules during the endometrial cycle

The cell surface mucin MUC-1 is present in endometrial epithelial cells and their associated apical glycocalyx and is also released into gland lumens as a secretory product. MUC-1 mRNA and core protein are found at low levels in the proliferative phase of the cycle, but their abundance increases after ovulation. Endometrial MUC-1 has been found to carry sialokeratan sulphate chains and these show a dramatically increased abundance in cells and secretions in the post-ovulatory phase of the cycle, reaching a maximum in secretions 6-7 days after the LH peak. The apical epithelium also contains adhesion receptor molecules of the integrin and CD44 families. MUC-1 is large and highly glycosylated and probably extends farther from the cell surface than these 'conventional' glycoprotein receptors. It has the potential to inhibit sterically receptor-mediated cell-cell adhesion. However, it is also possible that MUC-1 displays specific (e.g., glycan) recognition structures for the initial attachment of the blastocyst or that the embryo may create a specialised microenvironment in which to implant.

Morphology of the human endometrium in the peri-implantation period

Although the histology and ultrastructure of the human endometrium are well documented, it is clear that morphometry can reveal subtle changes in cellular biology, especially when combined with suitable sampling and dating of the specimen. These changes reflect functional events, such as protein secretion, which may be studied using the endometrial flushing technique. Although it is likely that further insights into the basic cell physiology of the reproductive tract will result from the use of appropriate in vitro models, the role of endometrial biopsy for clinical monitoring remains essential.

Immunohistochemical markers of uterine receptivity in the human endometrium

The factors responsible for the initial interaction between maternal and fetal epithelium leading to the establishment of pregnancy remain poorly understood. Temporal and spatial expression of specific endometrial peptides in response to ovarian steroids is thought to contribute to the development of a period of uterine receptivity, whereby the endometrium becomes hospitable to the implanting blastocyst. The failure to establish receptivity may account for a significant percentage of the cases of infertility in the female, especially affecting women with luteal phase deficiency, leiomyomata uteri, endometriosis, habitual abortion, and unexplained infertility. In addition, despite increasing global experience with advanced reproductive technologies, the majority of In Vitro Fertilization (IVF) attempts remain unsuccessful, most likely on the basis of implantation failure. In this article, we review the concepts involved in the study of uterine receptivity in the human, highlight potential immunohistochemical (IHC) markers that have recently been discovered, and discuss how IHC assessment of the endometrium is a potentially valuable method for the evaluation of the receptive endometrial state. Using this approach we have examined several new potential markers of uterine receptivity. Endometrial progesterone receptors and one of the integrin cell adhesion molecules appear to undergo changes in expression around the time of implantation, and may be sensitive indicators of the receptive state. Further, these markers are delayed in women with infertility and luteal phase deficiency. These studies illustrate the utility of IHC diagnosis for the evaluation of endometrial function.

Concentration of endometrial protein PP14 in uterine flushings throughout the menstrual cycle in normal, fertile women

OBJECTIVE

To determine the variation in concentration of endometrial protein PP14 in uterine flushings throughout the menstrual cycle comparing this to concentrations in plasma samples.

DESIGN

Precise timing of all samples by the luteinising hormone surge.

SETTING

Jessop Hospital for Women, Sheffield.

SUBJECTS

Twenty-three regularly cycling, previously fertile volunteer women.

INTERVENTIONS

Observational study; 10 ml of physiological saline was used to flush the uterine cavity once or serially in the cycle of the study.

MAIN OUTCOME MEASURES

The measurement of PP14 levels by radioimmunoassay in uterine flushings and plasma samples.

RESULTS

In uterine flushing, PP14 levels were not detectable in significant amounts in the proliferative phase and the early luteal phase; after day LH + 6, the concentration rises rapidly with a doubling time of only 6.6 to 14.6 h in the midluteal phase. In the late luteal phase, the concentrations in uterine flushing were over a hundred times higher than the corresponding plasma samples.

CONCLUSIONS

The measurement of PP14 in uterine flushings is likely to be of greater value than the measurement in plasma samples; it may provide a valuable alternative to the evaluation of endometrial function.

Endometrial responses in artificial cycles: a prospective study comparing four different oestrogen dosages

OBJECTIVE

To examine the endometrial response to four different regimens of oestrogen.

DESIGN

A prospective, randomized cross-over study.

SETTING

Jessop Hospital for Women, Sheffield.

SUBJECTS

Twenty one women with premature ovarian failure divided into three equal groups.

INTERVENTIONS

Four different regimens of hormone replacement therapy: variable, fixed 1 mg, fixed 2 mg and fixed 4 mg oestrogen dosages. Each woman received the variable dosage regimen in one cycle and crossed over to receive one of the three fixed dose regimens (1 mg, Group 1; 2 mg, Group 2; 4 mg Group 3) in another cycle.

MAIN OUTCOME MEASURE

Ultrasonographic measurement of endometrial thickness and outpatient endometrial biopsy on day 19 of the artificial cycle; analysis of endometrial specimens by three separate methods: traditional histological criteria, morphometry and immunohistochemistry.

RESULTS

The endometrial response was similar in those treated with the variable and the fixed 2 mg or 4 mg dosage regimens. The response was suboptimal in those treated with the fixed 1 mg dosage regimen.

CONCLUSIONS

Normal endometrial development requires adequate priming of the endometrium by oestrogen, which may be administered in a sequential, variable dosage fashion, or simply by a fixed daily dosage regimen. However, the minimum daily dose required is likely to be 2 mg of oestradiol valerate. No adverse effect on the endometrium was observed at a daily dose of 4 mg oestradiol valerate, which produced plasma levels of oestradiol above the reference ranges of the natural cycle.

Structure of premenstrual endometrium in HMG + HCG induced anovulatory women

In this study structural alterations were tested on anovulatory infertile women who had undergone treatment of HMG + HCG to induce ovulation and subsequently to achieve pregnancy. For this purpose, a single premenstrual endometrial fundal biopsy was performed and evaluated using light and electron microscopy. The aim of the study was to evaluate the biopsies with respect to 'in-phase' or 'out-of-phase' at light microscopic level, in which a series of strict criteria were chosen, and then to detect the additional structural abnormalities at electron microscopic level, if present. Only one of the women in our study who had an in-phase endometrium became pregnant after proper treatment protocol individually adjusted and consequently terminated by an early abortion. Histologic features of the biopsies revealed that about half were normal while the rest had various types of structural abnormalities in the transformation of the secretory endometrium detected by light and/or electron microscopy. At the electron microscopic level, multiple alterations were seen in cellular and intercellular components even in those diagnosed as normal by light microscopy. As a result of the above data it was concluded that the cause of inconceivability might arise from some fine structural alterations which may affect the endometrial receptivity of an implanting embryo.

The effects of the antiprogesterone RU486 (Mifepristone) on an endometrial secretory glycan: an immunocytochemical study

OBJECTIVE

To examine the effects of progesterone (P) receptor blockade by RU486 (Mifepristone; Roussel-Uclaf, Paris, France) on a secretory endometrial glycan recognized by monoclonal antibody D9B1.

DESIGN

Retrospective comparison of endometrial biopsies from treated and untreated women from 2 to 8 days after the luteinizing peak (LH) peak.

SETTING

Infertility clinic, Jessop Hospital for Women, Sheffield.

PATIENTS

Twenty-two normal fertile women received the RU486. A control group of 44 normal fertile women were also assessed.

INTERVENTIONS

RU486 was administered to 22 normal women during the first half of the luteal phase and an endometrial biopsy examined 3 days later.

MAIN OUTCOME MEASURES

Immunohistochemistry was used to assess the production and secretion of the D9B1 epitope.

RESULTS

When the drug was given 2 days after the LH peak, it prevented appearance of the epitope. When RU486 was administered 5 days after the LH peak, epitope already present in gland cells was subsequently secreted.

CONCLUSIONS

These data suggest that production of the sialo-oligosaccharide is P-dependent, but secretion through established intracellular pathways is P-independent.

Role of embryonic factors in implantation: recent developments

The embryonic factors influencing implantation have been studied extensively in laboratory and domestic animals, but not in primates, including humans. Species differences make extrapolation inadvisable. Embryonic factors affecting implantation include intrinsic features of the embryo, such as its genetic constitution, morphology and hatching. Abnormal genetic constitutions or unsuccessful transitions from maternal to embryonic transcription could account for many failures of early embryonic growth and implantation. Morphology per se does not greatly influence implantation, except when it reflects an abnormal genetic constitution, e.g. in severe fragmentation, although subtle effects may be detected as experimental techniques are refined. The initiation of differentiation and intraembryonic communication between cells and cell types has been studied in animal embryos. Signals must be exchanged between the embryo and the mother to ensure satisfactory implantation. These could include platelet activating factor, prostaglandins, histamine related factors, steroids, proteins, metabolic products and immune-active factors. No one factor seems to be totally responsible for alerting the mother to the presence of an embryo, and a concerted action of these and other agents is probably responsible. The process of implantation itself is poorly understood because of a lack of adequate experimental models. The expression of complementary proteins and the role of specific enzymes and markers of endometrial and embryonic competence are factors well worthy of further study. Knowledge about human implantation is increasing because of recent developments in assisted reproductive technology, and concepts arising from many years of research in animals should find clinical applications in understanding and controlling human reproduction.

A quantitative study of endometrial development in the luteal phase: comparison between women with unexplained infertility and normal fertility

This study compared endometrial development in the luteal phase of women with unexplained infertility (n = 30) with that in women with normal fertility (n = 70) by the use of quantitative histological techniques (morphometric analysis) on endometrial specimens which were precisely timed from the luteinizing hormone surge. When overall endometrial development (histological dating) was considered, the proportion of women with unexplained infertility who had retarded endometrial development (20%) was found to be significantly higher than for women with normal fertility (3%) (P less than 0.01). When individual histological features were considered, women with unexplained infertility were found to have significant deviation from the normal range established from fertile women in only five of the 14 histological features measured. All of these five features related to the glandular but not to the stromal component of the endometrium; four of these five features are related to glandular secretory activity.

An endometrial factor in unexplained infertility

OBJECTIVE

To study a group of women with unexplained infertility to see whether they have a defect that is intrinsic to the endometrium.

DESIGN

Evaluation of the functional response of the endometrium by examining endometrial biopsy specimens using immunohistochemical methods in a group of women with unexplained infertility and in a control group of women with normal fertility.

PATIENTS

27 Women with unexplained infertility (average age 33.2); median duration of infertility five years. A control group of 44 women with normal fertility (average age 33.8) who were requesting sterilisation or reversal of sterilisation.

SETTING

Infertility clinic, Jessop Hospital for Women, Sheffield.

INTERVENTION

Secretory phase endometrial biopsy specimens were taken, with informed consent, as an outpatient procedure.

MAIN OUTCOME MEASURES

Immunohistochemistry with monoclonal antibody D9B1, was used to assess the production and secretion of an oligosaccharide epitope produced by endometrial gland cells between two and seven days after the luteinising hormone surge. A reflected light measuring system was used to assess the amount of epitope within the gland cells, and in the gland lumen.

RESULTS

In the control group of women, mean reflected light measurements at the cell base and cell apex peaked at three and five days after the luteinising hormone surge respectively, and in the gland lumen the epitope accumulated rapidly from three days, reaching a peak at seven days. In the women with infertility the peaks of epitope at the cell base and cell apex were lower, broader, and delayed in onset, and the build up of epitope in the gland lumen was retarded. The synthesis and secretion of the epitope in the women with infertility was therefore significantly reduced and delayed, even in the presence of normal concentrations of circulating progesterone.

CONCLUSIONS

The results suggest that a primary dysfunction of the endometrium might be associated with hitherto unexplained infertility.

Menstrual-cycle-dependent expression of keratan sulphate in human endometrium

Immunochemical methods have been used to detect and characterize two classes of polypeptide-associated keratan sulphate (KS) in epithelial secretions from human endometrium. Monoclonal antibody D9B1 binds to a hormonally regulated sialylated epitope associated with KS in a high relative molecular mass (250,000-350,000) component that bands as a doublet in SDS/PAGE. These KS chain(s) are sensitive to keratanase, endo-beta-galactosidase and N-glycanase. A second, more highly sulphated, type of KS is also present, that is resistant to all three enzymes. This can be detected using monoclonal antibody 5D4. It is present throughout the menstrual cycle and is associated principally with a component of Mr 140,000. Thus secretory KS contributes to the environment of the implanting embryo, may be used as a molecular index of endometrial function and could be important in the establishment of pregnancy.

The effect of the intrauterine contraceptive device on endometrial secretory function: a possible mode of action

The effect of the intrauterine contraceptive device (IUD) on the composition of endometrial secretion has been studied using the monoclonal antibody D9B1. The antibody binds to a polypeptide-associated oligosaccharide epitope that is secreted by endometrial epithelium in the secretory phase with a maximum around the time of implantation. In endometria affected by the IUD in situ, a significant reduction in epitope expression has been observed using immunohistochemistry. This defect can occur against a background of normal secretory differentiation and in the expectation of normal ovarian stimulus. The data provide new insight into the contraceptive mechanisms of action of the IUD.

The effects of steroids on the fine structure of the endometrium

This brief review illustrates the lack of ultrastructural studies on human endometrium, particularly on well-dated material from normal, fertile women. The glandular epithelium, with its triad of unusual organelles in the early luteal phase, poses fascinating problems in cell biology and, probably for this reason, has attracted the most work. Many problems in reproductive biology, in uterine pathology and in the study of unexplained infertility are crying out for detailed study of the luminal epithelium, the stroma and the blood vessels. If this review, by highlighting the gaps in our knowledge, stimulates research into these areas, it will have been successful.