Attachment of blastocysts to lens capsule: A model system for trophoblast-epithelial cell interaction on a natural basement membrane

Summary The bovine lens capsule has previously been shown to provide an optimal surface for the examination of epithelial cell interaction with a basement membrane. This native substrate has been used to investigate some initial aspects of attachment of mouse blastocysts and trophoblastic cellular outgrowth. Mouse blastocysts were presented to the cell-free humoral side of the anterior lens capsule, incubated for 72 h, and examined by scanning and transmission electron microscopy. Blastocysts hatch and attach from their zonae pellucidae by 30 h. Trophoblastic cells proliferate rapidly in a coronal direction, display extensive surface microvilli, and advance by the extension of numerous filipodia, many of which terminate with bulbous projections. These projections were shown by transmission electron microscopy to contain numerous vacuoles and polysomes. To simulate further the initial blastocyst-uterine interaction, a suspension of lens epithelial cells was introduced to the capsule and permitted to form a monolayer prior to the addition of the blastocysts. At 72 h the monolayer of lens cells remained intact. We observed that: a) lens cells appear to recede from the advancing trophoblastic cells, and b) trophoblastic cells extend beneath the monolayer of lens cells and thereby dislodge the cells from the lens capsule substrate. No infiltration of the capsule by the advancing trophoblastic cells was observed. The lens capsule appears to offer a promising system for the study of trophoblast-epithelial cell interaction on a natural basement membrane.     

Stimulator of interferon genes (STING): A “new chapter” in virus-associated cancer research. Lessons from wild-derived mouse models of innate immunity

Thanks to the numerous studies that have been carried out recently in the field of cytosolic DNA sensing, STING (Stimulator of Interferon Genes) is now recognized as a key mediator of innate immune signaling. A substantial body of evidence derived from in vivo mouse models demonstrates that STING-regulated pathways underlie the pathogenesis of many diseases including infectious diseases and cancers. It has also become evident from these studies that STING is a promising therapeutic target for the treatment of cancer. However, mouse strains commonly used for modelling innate immune response against infections or tumors do not allow investigators to accurately reproduce certain specific characteristics of immune response observed in human cells. In this review, we will discuss recent data demonstrating that the use of wild-derived genetically distinct inbred mice as a model for investigation into the innate immunity signaling networks may provide valuable insight into the STING-regulated pathways specific for human cells. The maximum complexity of STING-mediated mechanisms can probably be seen in case of DNA virus-induced carcinogenesis in which STING may perform unexpected biological activities. Therefore, in another part of this review we will summarize emerging data on the role of STING in human DNA virus-related oncopathologies, with particular attention to HPV-associated cervical cancer, aiming to demonstrate that STING indeed “starts a new chapter” in research on this issue and that wild-derived mouse models of STING-mediated response to infections will probably be helpful in finding out molecular basis for clinical observations.     

Comparison of the relative sensitivity of human lymphocytes and mouse splenocytes to two spindle poisons

Aneugenic compounds act on non-DNA targets to exert genotoxicity via an indirect mechanism. In contrast to DNA-binding agents, these compounds are expected to possess threshold levels of activity. Therefore, the risk for adverse effects following human exposure to an aneugen could be minimal, if the threshold of activity has been clearly determined in vivo and in vitro and providing the human exposure level is below this threshold. Thus, the development of a single-cell model to allow comparisons between in vitro and in vivo threshold values for aneugenic compounds is of importance.The in vivo micronucleus test is one of the main assays used in genetic toxicology, and is often performed in the mouse. Thus, an extensive database is available in the literature. However, there are only few data concerning the in vitro micronucleus assay using mouse cells, as the majority of in vitro micronucleus assays have been performed using human lymphocytes. In addition, there is a lack of data concerning thresholds for any compound using this model.First, we evaluated whether the use of mouse splenocytes would be an acceptable alternative to that of human lymphocytes to identify aneugens. To allow valid comparisons, the two protocols were first harmonized. Thus, phytohemagglutinin (PHA) and concanavalin A were used as specific mitogens for human lymphocytes and mouse splenocytes, respectively, in order to achieve similar cell-proliferation rates. To achieve similar and sufficient numbers of binucleated cells, cytochalasin B was added 44 and 56 h after culture initiation of the human and mouse cells, respectively.Second, we compared the sensitivity of the mouse protocol with that of the human protocol by exposing the cells to the aneugens nocodazole and paclitaxel.There was good reproducibility of the cytotoxic/genotoxic responses of the two cell models following exposure to the aneugens. The sensitivity of the mouse splenocytes to paclitaxel was higher than that of the human lymphocytes. The two cell types were equally sensitive to nocodazole.     

Biology and regulation of ectoplasmic specialization, an atypical adherens junction type, in the testis

Anchoring junctions are cell adhesion apparatus present in all epithelia and endothelia. They are found at the cell-cell interface (adherens junction (AJ) and desmosome) and cell-matrix interface (focal contact and hemidesmosome). In this review, we focus our discussion on AJ in particular the dynamic changes and regulation of this junction type in normal epithelia using testis as a model. There are extensive restructuring of AJ (e.g., ectoplasmic specialization, ES, a testis-specific AJ) at the Sertoli-Sertoli cell interface (basal ES) and Sertoli-elongating spermatid interface (apical ES) during the seminiferous epithelial cycle of spermatogenesis to facilitate the migration of developing germ cells across the seminiferous epithelium. Furthermore, recent findings have shown that ES also confers cell orientation and polarity in the seminiferous epithelium, illustrating that some of the functions initially ascribed to tight junctions (TJ), such as conferring cell polarity, are also part of the inherent properties of the AJ (e.g., apical ES) in the testis. The biology and regulation based on recent studies in the testis are of interest to cell biologists in the field, in particular their regulation, which perhaps is applicable to tumorigenesis.     

Establishment of cellulolytic bacteria in the digestive tract of conventionally reared young mice: effect of the dietary cellulose content in the adult

Cellulolytic bacteria became established 12 days after birth in the caecum and colon of conventionally-reared mice fed a diet containing 5 p. 100 crude cellulose (Weende). Their population reached a level between 10(6) and 10(7) bacteria per gram of digestive contents in 25-day-old animals. However, variations between animals were very large; 20 to 50% of the individuals were free of cellulolytic bacteria. A low cellulolytic population was observed in adult mice fed a cellulose-free diet. The amount of cellulose in the diet and its nature (crude or pure cellulose) affected the number of cellulolytic bacteria: the higher the percentage of cellulose in the diet, the higher the number of cellulolytic bacteria, in particular with crude cellulose-containing diet.     

Horseradish peroxidase: a reliable or a misleading tool for the investigations on the origin of the proteins of the aqueous humor?

The concept of the blood-aqueous barrier is largely based on the use of horseradish peroxidase (HRP). The present investigation was designed to check its reliability as a macromolecular tracer, especially with regard to the transport of plasma proteins. Rabbits were killed 5 min to 24 h after being intravenously injected with HRP. The tracer diffused rapidly, reaching the aqueous humor of the eye in 3 min or less and was detected at high concentration in the narrow space between the outer epithelial layer of the ciliary epithelium and the wall of the pervious capillaries in the stroma of the processes. HRP appeared to migrate from the blood to the posterior chamber, permeating the tight junctions, viz., the anatomical basis of the blood-aqueous barrier. It was detected at higher concentration at the anterior surface of the iris, at short time intervals; this was interpreted as penetration of the tracer from the aqueous humor of the anterior chamber. The choroid was also labeled in continuation with the reaction in the stroma of the pars plana of the ciliary body which, in turn, sometimes reached the iris root. Therefore, the pervious blood vessels of the choroid could be a source of macromolecules for the iris root. HRP also induced the formation of lysosomes in the ciliary epithelium. This can hardly be accepted as the way in which plasma proteins are physiologically transported to the aqueous humor. However, the pathway of HRP migration over short time intervals seems to be in agreement with previous research indicating that the entrance of serum albumin into the posterior chamber is the first step of its incorporation into the aqueous humor. Received: 7 June 1996 / Accepted: 15 January 1997